Aluminium casting by David Gaskell

Aluminium Casting Alloys

Content

Introduction

Recycled aluminium

Melt quality and melt cleaning 24

Surface treatment: corrosion 48

•

Avoiding impurities

and corrosion protection

•

Melt testing and

Technology and service

inspection procedure

for our customers

•

Quality Management

•

Work safety and health

protection •

Information on physical data, 50 30

strength calculations •

Pressure die casting

process 9

strength properties and

Selecting the casting process 31

Environmental protection

Aluminium and aluminium

Thermal analysis

Notes on the casting

alloy tables

•

Gravity die casting process

•

Sand casting process

Casting-compliant design

Solidification simulation

casting alloys

Overview: Aluminium casting 52 alloys by alloy group

•

Aluminium – Material properties

•

Recycling of aluminium

•

Shaping by casting

Eutectic aluminium-silicon 10

casting alloys

and thermography Product range and

form of delivery •

Technical consultancy

Near-eutectic wheel Avoiding casting defects

casting alloys

Heat treatment of

The 10 per cent aluminium-

service

aluminium castings Selecting aluminium

•

casting alloys •

Criteria for the selection of

Influence of the

Metallurgy –

•

Solution annealing

•

Quenching

•

Ageing

The 7 and 5 per cent 41

elements on aluminium

Mechanical machining of

casting alloys

aluminium castings Welding and joining

microstructural formation of

aluminium castings

•

Suitability and behaviour

•

Applications in the

•

Grain refinement

•

Modification of AlSi eutectic 21

•

Refinement of primary silicon

Aluminium Casting Alloys

20 23

Welding processes

•

Weld preparation

•

Weld filler materials

aluminium-silicon

42 Al SiCu casting alloys

AlMg casting alloys

Casting alloys for special

applications

aluminium sector •

casting alloys

most important alloying

Influencing the

silicon casting alloys

fundamental principles

aluminium casting alloys •

Introduction

Many of you have most certainly worked

In the second part, all technical aspects

casting alloys a clear, well laid-out com-

with the “old“ Aluminium Casting Alloys

which have to be taken into account in

panion for practical application. Should

Catalogue – over the years in thousands

the selection of an aluminium casting al-

you have any questions concerning the

of workplaces in the aluminium indus-

loy are explained in detail. All details are

selection and use of aluminium casting

try, it has become a standard reference

based on the DIN EN 1676: 2010 standard.

alloys, please contact our foundry con-

book, a reliable source of advice about

sultants or our sales staff.

all matters relating to the selection and

The third part begins with notes on the

processing of aluminium casting alloys.

physical data, tensile strength charac-

You can also refer to www.aleris.com.

teristics and strength calculations of Even if you are holding this Aluminium

aluminium casting alloys. Subsequently,

We would be pleased to advise

Casting Alloys Catalogue in your hands

all standardised aluminium casting alloys

you and wish you every success

for the first time, you will quickly find your

in accordance with DIN EN 1676 as well

in your dealings with aluminium

way around with the help of the following

as common, non-standardised casting

casting alloys!

notes and the catalogue‘s detailed index.

alloys are depicted in a summary table together with their casting/technical and

How is this Aluminium Casting Alloys

other typical similarities in “alloy families”.

Catalogue structured? The catalogue consists of three separate parts. In the

The aim of this new, revised and rede-

first part, we provide details on our com-

signed Aluminium Casting Alloys Cata-

pany – a proven supplier of aluminium

logue is to give the user of aluminium

casting alloys.

Aluminium Casting Alloys

Recycled aluminium Technology and service for our customers

Employing approx. 600 people, Aleris

Its properties are not impaired when

from oxidising while binding contami-

Recycling produces high-quality cast-

used in products. The metallic value is

nants (salt slag). Modern processing and

ing and wrought alloys from recycled

retained which represents a huge eco-

melting plants at Aleris Recycling enable

aluminium. The company‘s headquar-

nomic incentive to collect, treat and melt

efficient yet environmentally-friendly re-

ters are represented by the “Erftwerk”

the metal in order to reuse it at the end

cycling of aluminium scrap and dross.

in Grevenbroich near Düsseldorf which

of its useful life.

The technology used is largely based on

is also the largest production facility in

our own developments and – in terms of

the group. Other production facilities

For this reason, casting alloys from Aleris

yield and melt quality – works significantly

in Germany (Deizisau, Töging), Norway

Recycling can be used for manufacturing

more efficiently than fixed axis rotary

(Eidsväg, Raudsand) and Great Britain

new high-quality cast products such as

furnaces and hearth furnaces. The melt

(Swansea) are managed from here. With

crankcases, cylinder heads or aluminium

gleaned from these furnaces has a very

up to 550,000 mt, Aleris Recycling avails

wheels while wrought materials can be

low gas content thanks to the special gas

of the largest production capacities in

used for manufacturing rolled and pressed

purging technique we use as well as

Europe and is also one of the world‘s

products, for example. Key industries

being homogeneous and largely free of

leading suppliers of technology and

supplied include:

oxide inclusions and/or contaminants.

services relating to aluminium casting

The resulting high quality of Aleris alloys

alloys. Aleris Recycling also offers a wide

•

Rolling mills and extrusion plants

enables our customers to open up an in-

range of high-quality magnesium alloys.

•

Automotive industry

creasing number of possible applications.

•

Transport sector

Aluminium recycled from scrap and

•

Packaging industry

All management processes and the en-

dross has developed to become a

•

Engineering

tire process chain from procurement

highly-complex technical market of the

•

Building and construction

through production to sale are subject to

future. This is attributable to the steady

•

Electronics industry

systematic Quality Management. Com-

increase in demand for raw materials,

•

as well as other companies in the

bined with Quality Management certified

Aleris Group.

to ISO/TS 16949 and DIN EN ISO 9001,

the sustainability issue, increased environmental awareness among producers

this guarantees that our clients‘ maximum

and consumers alike and, not least, the

State-of-the-art production facilities and

requirements and increasing demands

necessity to keep production costs as

an extensive range of products made of

can be fulfilled.

low as possible.

aluminium in the form of scrap, chips or dross are collected and treated by Aleris

The product range offered by Aleris Re-

This is where aluminium offers some es-

Recycling before melting in tilting rotary

cycling comprises more than 250 differ-

sential advantages. Recycled aluminium

furnaces with melting salt, for example,

ent casting and wrought alloys. They can

can be generated at only a fraction of the

whereby the salt prevents the aluminium

be supplied as ingots with unit weights

energy costs (approx. 5%) compared to

of approx. 6 kg (in stacks of up to 1,300

primary aluminium manufactured from

kg) as well as pigs of up to 1,400 kg or

bauxite with the result that it makes a

as liquid metal. Based on our sophisti-

significant contribution towards reduc-

cated crucible technology and optimised

ing CO emissions. This light-alloy metal

transport logistics, Aleris Recycling sup-

can be recycled any number of times

plies customers with liquid aluminium in

and good segregation even guarantees

a just-in-time process and at the appro-

no quality losses.

priate temperature.

Aluminium Casting Alloys

Due to its future-oriented corporate

Quality Management

structure, Aleris Recycling supplies the

The principle of avoiding errors is paramount in all our individual procedures and

market with an increasing number of

We believe that our most important cor-

regulations. In other words, our priority

applications involving high-quality sec-

porate goal is to meet in full our custom-

is to strive to achieve a zero-error target.

ondary aluminium. This service is not re-

ersâ&#x20AC;&#x2DC; requirements and expectations in

By effectively combating the sources of

stricted to the area of casting alloys but

terms of providing them with products

errors, we create the right conditions for

also applies for 3000- and 5000-grade

and services of consistent quality. In or-

reliability and high quality standards.

wrought alloys, for example. Aleris Re-

der to meet this goal, our guidelines and

cycling is also capable of offering some

integrated management system specifi-

We have also established a comprehen-

6000-grade secondary aluminium alloys

cations outline rules and regulations that

sive process of continuous improvement

largely required by the automotive sector.

are binding for all staff.

(PMO, Best Practice, Six Sigma etc.) in

For this so-called upgrade, Aleris applies

our plants in response to the demands

special production technologies when

As a manufacturer of aluminium casting

being placed on our company by the

it comes to manufacturing high-quality

alloys, we are certified according to ISO/

increasing trend towards business glo-

alloys from scrap.

TS 16949. In addition, we operate ac-

balisation. This creates the right cli-

cording to DIN EN ISO 9001 standards.

mate for creative thinking and action.

Recycled aluminium is increasingly be-

All members of staff, within their own

coming a complex range at the interface

area of responsibility, endeavour to en-

between high-tech production, trade and

sure that operational procedures are

service. In addition, customers demand

constantly improved, even if in small,

intensive consulting as well as individual

gradual stages, with a clear focus on

service. Aleris Recycling enjoys an ex-

our customersâ&#x20AC;&#x2DC; needs.

cellent position in this regard. At its various locations, the company units offer a high degree of recycling expertise, manufacturing competence and delivery reliability for its customers. With the result that Aleris Recycling guarantees its customers a high level of efficiency and added value while supporting their success on the market.

Aluminium Casting Alloys

Work safety and health protection

Environmental protection

Our staff are our most valuable asset. Work

Following the validation of our environ-

protection of water bodies, noise and

safety and health protection, therefore,

mental management system in conformity

waste are checked at regular intervals.

have top priority for us, and also make

with EMAS II and certification to DIN EN

By modifying procedures, reusing mate-

a valuable contribution to the success

ISO 14001, we have undertaken not only

rials and recycling residues, we optimise

of our company. Our â&#x20AC;&#x153;Work safety and

to meet all the required environmental

the use of raw materials and energy in

health protectionâ&#x20AC;? programme is geared

standards, but also to work towards a

order to conserve resources as efficiently

towards achieving a zero accident rate,

fundamental, systematic and continual

as possible.

and towards avoiding occupational ill-

improvement in the level of environmental

nesses. Depending on the respective

protection within the company.

The environmental impacts of our company operations in terms of air purity,

location, we are certified to OHSAS 18001 or OHRIS.

We pursue a policy of open information and provide interested members of the

Our management system and environ-

public with comprehensive details of

mental policy are documented in the

the companyâ&#x20AC;&#x2DC;s activities in a particu-

All management members and staff are

company manual which describes all

lar location, and an explanation of the

obliged to comply with legal regulations

the elements of the system in easily

environmental issues involved. For us,

and company rules at all times, to pro-

understood terms, while serving as a

open dialogue with the general pub-

tect their own health and the health of

reference for all regulations concerning

lic, our suppliers, customers and other

other members of staff and, when en-

the environment.

contractual partners is as much a part

gaged in any company operations, to

of routine operations as reliable co-op-

do their utmost to ensure that accidents

eration with the relevant authorities and

and work-related illnesses are avoided,

trade associations.

as well as anything that might have a negative impact on the general company

Likewise, ecological standards are in-

environment. Management provides the

corporated in development and planning

appropriate level of resources required

processes for new products and produc-

to achieve these goals.

tion processes, as are other standards required by the market or society at large.

There are regular internal and external training seminars on the topic of work

Our staff is fully conscious of all environ-

safety, and detailed programmes to im-

mental protection issues and is keen to

prove health protection. These help to

ensure that the environmental policy is

maintain our comparatively low accident

reliably implemented in day-to-day op-

and illness rates.

erations within the company.

Aluminium Casting Alloys

Aluminium and aluminium casting alloys

Aluminium – Material properties

•

Aluminium is light; its specific weight

Recycling of aluminium

is substantially lower than other Aluminium has become the most widely

common metals and, at the same

Long before the term “recycling” became

used non-ferrous metal. It is used in the

time, it is so strong that it can with

popular, recycling circuits already exist-

transport sector, construction, the pack-

stand high stress.

ed in the aluminium sector. Used parts

aging industry, mechanical engineering,

Aluminium is very corrosion-

made from aluminium or aluminium alloys

electrical engineering and design. New

resistant and durable. A thin,

as well as aluminium residue materials

fields of application are constantly open-

natural oxide layer protects

arising from production and fabrication

ing up as the advantages of this material

aluminium against decomposition

are far too valuable to end up as land-

from oxygen, water or chemicals.

fill. One of the great advantages of this

Aluminium is an excellent

metal, and an added plus for its use as a

conductor of electricity,

construction material, is that aluminium

heat and cold.

parts, no matter the type, are extremely

Aluminium is non-toxic, hygienic

well suited to remelting.

•

speak for themselves: •

•

and physiologically harmless. •

The energy savings made in

•

Aluminium is non-magnetic.

•

Aluminium is decorative and

recycling aluminium are

displays high reflectivity.

considerable. Remelting requires

Aluminium has outstanding

only about 5 % of the energy

formability and can be

initially required to produce

processed in a variety of ways.

primary aluminium.

•

Aluminium alloys are easy to cast

•

retains the value added to the

casting processes.

metal. Aluminium can be recycled

Aluminium alloys are

to the same quality level as the

distinguished by an excellent degree of homogeneity. • •

•

As a rule, aluminium recycling

as well as being suitable for all known

original metal. •

Aluminium recycling safeguards

Aluminium and aluminium

and supplements the supply of

alloys are easy to machine.

raw materials while saving

Castings made from aluminium

resources, protecting the

alloys can be given an artificial,

environment and conserving

wear-resistant oxide layer

energy. Recycling is therefore also

using the ELOXAL process.

a dictate of economic reason.

Aluminium is an outstanding recycling material.

Aluminium Casting Alloys

The experience accumulated over ma-

Shaping by casting

ny decades, the use of state-of-the-art

The variety of modern casting processes makes it possible to face up to the

technology in scrap preparation, remelt-

Casting represents the shortest route

economic realities, i.e. the optimisation

ing and exhaust gas cleaning as well

from raw materials to finished parts â&#x20AC;&#x201C; a

of investment expenditure and costs

as our constant efforts to develop new,

fact which has been known for five thou-

in relation to the number of units. With

environmentally-sound manufactur-

sand years. Through continuous further

casting, the variable weighting of pro-

ing technology puts us in a position to

development and, in part, by a selective

duction costs and quality requirements

achieve the best possible and efficient

return to classic methods such as the

are also possible.

recycling rates. At the same time, they

lost-form process, casting has remained

also help us to make the most efficient

at the forefront of technical progress.

When designing the shape of the casting, further possibilities arise from the

use of energy and auxiliary materials. The most important advantage of the

use of inserts and/or from joining the

casting process is that the possibilities

part to other castings or workpieces.

of shaping the part are practically limitless. Castings are, therefore, easier and

In the last decade, aluminium has at-

cheaper to produce than machined and/

tained a leading position among cast

or joined components. The general waiv-

metals because, in addition to its other

ing of subsequent machining not only

positive material properties, this light

results in a good density and path of

metal offers the greatest possible variety

force lines but also in high form strength.

of casting and joining processes.

Furthermore, waste is also avoided. As a rule, the casting surface displays a tight, fine-grained structure and, consequently, is also resistant to wear and corrosion.

10 Aluminium Casting Alloys

Product range and form of delivery

As ecological and economic trends sen-

Our casting alloys are delivered in the

sibly move towards the development of

form of ingots with a unit weight of ap-

closed material circuits, the clear dividing

prox. 6 kg or as liquid metal.

lines between the three classic quality grades of aluminium casting alloys are

We distinguish between ingots cast in

ever-decreasing. In future, people will

open moulds and horizontal continu-

simply talk about “casting alloys”. In

ously cast ingots (so-called HGM). In-

practice, this is already the case. Metal

gots are dispatched in bundles of up to

from used parts is converted back into

approx. 1,300 kg.

the same field of application. The DIN EN 1676 and 1706 standards with their

The delivery of liquid or molten metal is

rather fluid quality transitions take this

useful and economic when large quanti-

trend into account.

ties of one homogeneous casting alloy are required and the equipment for tapping

Aleris is one of only a few companies

and holding the molten metal containers

to produce a wide range of aluminium

is available. Supplying molten metal can

alloys; our product spectrum extends

lead to a substantial reduction in costs

from classic secondary alloys to high-

as a result of saving melting costs and

purity alloys for special applications.

a reduction in melting losses. The sup-

Production is in full compliance with

ply of liquid metal also provides a viable

the European DIN EN 1676 standard

alternative in cases where new melting

or international standards and in many

capacities need to be built to comply

cases, manufactured to specific cus-

with emission standards or where space

tomer requirements. We have also been

is a problem.

offering several aluminium casting alloys as protected brand-name alloys for many years, e.g. Silumin®®, Pantal®® and Autodur ®.

Aluminium Casting Alloys 11

Technical consultancy service

Technical consultants also provide assistance in evaluating casting defects or

The technical consultancy service is

surface flaws and offer suggestions with

the address for questions relating to

regard to eliminating defects. They sup-

foundry technology. We provide assis-

ply advice on the design of castings, the

tance in clarifying aluminium casting alloy

construction of dies, the casting system

designations as stated in German and

and the configuration of feeders.

international standards or the temper conditions for castings. We also offer

Technical consultants also provide tech-

advice on the selection of alloys and can

nical support to aluminium foundries in

provide aluminium foundries or users of

the preparation of chemical analyses,

castings with information on:

microsections and structural analyses. Customer feedback coupled with exten-

•

Aluminium casting alloys

sive experience in the foundry sector fa-

•

Chemical and physical properties

cilitates the continuous optimisation and

Casting and solidification

quality improvement of our aluminium

behaviour

casting alloys.

• • •

•

Casting processes and details regarding foundry technology

In co-operation with our customers, we

Melt treatment possibilities, such as

are working on gaining wider acceptance

cleaning, degassing, modification

of our aluminium casting alloys in new

or grain refinement

fields of application.

Possibilities of influencing the strength of castings by means

Where required and especially where

of alloying elements or heat

fundamental problems arise, we arrange

treatment

contracts with leading research institutes

Questions relating to surface

in Europe and North America.

finish and surface protection.

12 Aluminium Casting Alloys

Selecting aluminium casting alloys

To supplement and provide greater depth

In the European DIN EN 1676 and DIN

As far as possible, the use of common

to our technical explanations, we refer

EN 1706 standards, the most important

aluminium casting alloys is recommended.

you to standard works on aluminium

aluminium casting alloys have been col-

These involve well-known and proven

and aluminium casting alloys. Further

lated in a version which is valid Europe-

casting alloys and we stand fully behind

details on other specialist literature are

wide. Consequently, there are already

the quality properties of these casting

available and can be requested at any

more than 41 standard aluminium casting

alloys which are often manufactured in

time. We would be delighted to advise

alloys available.

large quantities, are more cost-effective than special alloys and, in most cases,

you in such matters. Aluminium foundries should – according Should you have any queries or com-

to their respective structure – limit them-

ments, which are always welcome,

selves to as small a number of casting

please contact our technical service.

alloys as possible in order to use their

Standard works on aluminium and alu-

melting equipment economically, to keep

minium casting alloys:

inventories as low as possible and to re-

•

duce the risk of mixing alloys.

“Aluminium-Taschenbuch”, Verlag

can be delivered at short notice.

Beuth, Düsseldorf •

“Aluminium viewed from within -

With regard to the quality of a casting,

Profile of a modern metal”, Prof.

it is more sensible to process a casting

Dr. D. G. Altenpohl, Verlag Beuth,

alloy which is operational in use than one

Düsseldorf.

which displays slightly better properties on paper but is actually more difficult to

Once the requirements of a casting

process. The quality potential of a cast-

have been determined, the selection of

ing alloy is only exploited in a casting if

the correct casting alloy from the mul-

the cast piece is as free as possible of

titude of possibilities often represents

casting defects and is suitable for subse-

a problem for the designer and also for

quent process steps (e.g. heat treatment).

the foundryman. In this case, the “Aluminium-Taschenbuch” can be of great

Our sales team and technicians are on

assistance.

hand to provide foundries and users of castings with assistance in selecting the correct aluminium casting alloy.

Aluminium Casting Alloys 13

Table 1

Criteria for the selection of

Classification of casting alloys acc. to strength properties 1)

aluminium casting alloys

Casting alloy

Temper

In the following section, we provide an insight into the chemical and physical

Tensile strength Rm [MPa]

Elongation Brinell hardness A5 [%] HB

Strong and ductile

Al Cu4Ti Silumin-Beta Al Si10Mg(a)

T6 T6 T6

330 290 260

7 4 1

95 90 90

Hard

Al Si8Cu3 Al Si18CuNiMg

F F

170 180

1 1

75 90

establish whether a casting alloy is suit-

Ductile

Silumin

170

able for the specific demands placed

Other

Al Mg3

150

on a casting.

1) Typical values for permanent mould casting, established on separately-cast test bars.

potentials of aluminium casting alloys by describing their various properties. The standardisation provided here helps to

Degree of purity One important selection criteria is the de-

Casting alloys made from scrap are,

different casting alloys are compared.

gree of purity of a casting alloy. With the

with regard to ductility and corrosion

These casting alloys are used for high-

increasing purity of a casting alloy family,

resistance, inferior to other casting alloy

grade construction components, espe-

the corrosion resistance and ductility of

groups due to their lower purity. They are,

cially for critical parts.

the as-cast structure also increase; the

however, widely applicable and meet the

selection of pure feedstock for making

set performance requirements.

“hard” The casting alloys of this group must

casting alloys, however, will necessarily

display a certain tensile strength and

cause costs to rise. Strength properties The increasing importance of the closed-

hardness without particular requirements being placed on the metal‘s elongation.

circuit economy means that, for the pro-

Strength properties should be discussed

First of all, Al SiCu alloys belong to this

ducer of aluminium casting alloys, the

as a further selection criterion (Table 1).

group. Due to their Cu, Mg and Zn con-

transition between the previous quality

A rough subdivision into four groups is

tent, these casting alloys experience a

grades for aluminium casting alloys is

practical:

certain amount of self-hardening after

becoming ever more fluid.

casting (approx. 1 week). These alloys “strong and ductile”

are particularly important for pressure

Due to their high purity, casting alloys

The most important age-hardenable

die casting since it is in pressure die

made from primary aluminium display the

casting alloys belong to this group. By

casting – except for special processes

best corrosion resistance as well as high

means of different kinds of heat treat-

such as vacuum die casting – that pro-

ductility. By way of example, Silumin-Beta

ment, their properties can be adjusted

cess-induced structural defects occur,

with max. 0.15 % Fe, max. 0.03 % Cu

either in favour of high tensile strength

preventing high elongation values. Due

and max. 0.07 % Zn can be mentioned.

or high elongation. In Table 1, the typi-

to its particularly strong self-hardening

In many countries, the Silumin trademark

cal combinations of Rm and A values for

characteristics, the Autodur casting al-

has already become a synonym for aluminium-silicon casting alloys.

14 Aluminium Casting Alloys

Table 2

Classification of casting alloys acc. to casting properties Fluidity

High

Thermal Casting alloy crack susceptibility

Type of solidification

Low

Exogenous-shell forming

Silumin

Casting properties Further selection criteria comprise casting properties such as the fluidity or solidification behaviour which sets the

Al Si12 Al S12(Cu)

Exogenous-rough wall

Al Si10Mg

Endogenous-dendritic

foundryman certain limits. Not every ideally-shaped casting can be cast in every casting alloy.

Silumin-Beta Al Si8Cu3

A simplified summary of the casting prop-

Pantal 7

erties associated with the most impor-

Al Si5Mg

tant casting alloys is shown in Table 2.

Al Cu4Ti

Low

High

Al Mg3

Endogenous-globular

Al Mg5

Mushy

Co-operation between the technical designer and an experienced foundryman works to great advantage when looking for the optimum casting alloy for a par-

loy represents a special case allowing

“ductile”

hardness values of approx. 100 HB and

Casting alloys which display particu-

a corresponding strength – albeit at very

larly high ductility, e.g. Silumin-Kappa

Given constant conditions, the fluidity

low ductility – in all casting processes.

(Al Si11Mg), come under this general

of a metallic melt is established by de-

heading. This casting alloy is frequently

termining the flow length of a test piece.

Hypereutectic AlSi casting alloys such

used for the manufacture of automobile

Theoretically, low fluidity can be offset

as Al Si18CuNiMg and Al Si17Cu4Mg,

wheels.

by a higher casting temperature; this is,

ticular application.

however, linked with disadvantages such

for example, which display particularly high wear resistance due to their high

In this particular application, a high elon-

as oxidation and hydrogen absorption as

silicon content, can also be classified

gation value is required for safety reasons.

well as increased mould wear. Eutectic

in this group.

AlSi casting alloys such as Silumin or “other”

Al Si12 display high fluidity. Hypoeutectic

Casting alloys for more decorative pur-

AlSi casting alloys such as Pantal 7 have

poses with lower strength properties, e.g.

medium values. AlCu and AlMg casting

Al Mg3, belong to this category.

alloys display low fluidity. Hypereutectic AlSi casting alloys such as Al Si17Cu4Mg occupy a special position. In their case, very long flow paths are observed. This does not however necessarily lead to a drop in the melt temperature since primary silicon crystals already form in the melt. The melt still flows well because the latent heat of solidification of the primary silicon

Aluminium Casting Alloys 15

Table 3

Selection criteria for aluminium casting alloys Casting properties

Strength characteristics

Shrinkage formation

Fluidity

Thermal crack susceptibility

Coarse

High

Low

High strength and ductile (T6)

Strong and ductile

Corrosion resistance* Ductile

Hard

Silumin Silumin-Kappa Silumin-Delta Al Si12 Al Si12(Cu)

Al Si12CuNiMg Al Si17Cu4Mg Al Si18CuNiMg Autodur

Silumin-Beta Al Si10Mg Al Si10Mg(Cu) Al Si8Cu3 Pantal 7 Al Cu4Ti Al Mg3Si Al Mg3 Al Mg5 Fine

Low

High

Al Mg9

* Analogue to DIN EN 1706

heats up the remainder of the melt. The

solidification, e.g. under the influence of

age cavities and porosity, for example,

already solidified silicon, however, causes

shrinkage or other tensions which can

or other defects in the cast structure

increased mould wear and very uneven

be transmitted via the casting moulds.

as it determines the distribution of the

distribution in the castings. In these

volume deficit in the casting. To curb

casting alloys, high melting and holding

The cracks or tears arising can be healed

the aforementioned casting defects,

temperatures are necessary so that a

by, among other things, the feeding of

casting/technical measures need to be

casting temperature of at least 720 째C

residual melt. Eutectic and near-eutectic

taken: e.g. by making adjustments to

for pressure die casting and 740 째C

AlSi casting alloys also behave particularly

the sprue system, the thermal balance

for sand and gravity die casting has to

well in this case, while AlCu and AlMg

of the mould or by controlling the gas

be attained.

casting alloys behave particularly badly.

content of the melt. A volume deficit

The susceptibility to hot tearing is almost

In practice, there are mixed forms and

solid state. This is quite small in high

the opposite of fluidity (Tables 2 and 3).

transitional forms of these solidification

silicon casting alloys since the silicon

By hot tearing, we mean a separation of

modes. The solidification behaviour is

increases in volume during solidification.

the already crystallised phases during

responsible for the formation of shrink-

In any case, the volume deficit incurred

occurs during transition from liquid to

16 Aluminium Casting Alloys

needs to be offset as far as possible by

ture of Types D and E (“mushy” or “shell-

which should be extensively pore-free –

casting/technical means (see also the

forming”). The remaining casting alloys

as well as pressure-tight – the preferred

section on “Avoiding casting defects”).

also represent intermediate types. At high

casting alloys are to be found at the top

solidification speeds, the solidification

of Table 3.

Figure 1 indicates the main types of so-

types move upwards, i.e. in the direction

lidification; each type is shown at two

of “exogenous-rough wall”.

For complex castings whose geometry

successive points in time. With regard

does not allow each material accumu-

to aluminium, only high-purity aluminium

Shell-forming casting alloys with “smooth-

lation to be achieved with a feeder, the

belongs to Solidification Type A (“exog-

wall” or “rough-wall” solidification are sus-

casting alloys listed in Table 3 offer ad-

enous-shell forming”). The only casting

ceptible to the formation of macroshrink-

vantages provided that a certain amount

alloy which corresponds to this type is

age which can only be prevented to a

of microporosity is taken into account.

the eutectic silicon alloy or Al Si12 with

limited extent by feeding. Casting alloys

approx. 13 % silicon.

of a spongy-mushy type are susceptible to shrinkage porosity which can only be

The hypoeutectic AlSi casting alloys

avoided to a limited extent by feeding.

solidify according to Type C (“spongy”),

In castings which demand feeding by

AlMg casting alloys according to a mix-

material accumulation in particular and

Exogenous solidification types A Smooth wall

B Rough wall

Picture 1 C Spongy

Endogenous solidification types D Mushy

E Shell forming

Mould Fluid Strong

Aluminium Casting Alloys 17

i S Fe Influence of the most important

Copper

Nickel

alloying elements on aluminium

•

increases the strength, also at

high temperatures (high-

casting alloys

increases high-temperature strength.

temperature strength) Silicon

•

produces age-hardenability

Titanium

•

improves the casting properties

•

impairs corrosion resistance

•

produces age-hardenability in

•

in binary AlCu casting alloys, the

•

combination with magnesium but

large solidification range needs to

causes a grey colour during anodi-

be taken into account from a

sation

casting/technical point of view.

in pure AlCu casting alloys (e.g. Al Cu4Ti), silicon is a harmful im-

Manganese

purity and leads to hot tearing

•

partially offsets iron‘s negative effect on ductility when iron

susceptibility.

content is > 0.15 % Iron •

•

above, has a decidedly negative

segregates in combination with iron and chromium

at a content of approx. 0.2 % and •

reduces the tendency to stickiness in pressure die casting.

influence on the ductility (elongation at fracture); this results in a

•

very brittle AlFe(Si) compound in

Magnesium

the form of plates which appear in

•

produces age-hardenability in

micrographs as “needles”; these

combination with silicon,

plates act like large-scale micro-

copper or zinc; with zinc also

structural separations and lead to

self-hardening

fracture when the slightest strain

•

improves corrosion resistance

is applied

•

increases the tendency towards

at a content of approx. 0.4 % and

oxidation and hydrogen

above, reduces the tendency to

absorption

stickiness in pressure die casting.

•

binary AlMg casting alloys are difficult to cast owing to their large solidification range.

Zinc • •

increases strength produces (self) age-hardenability in conjunction with magnesium.

18 Aluminium Casting Alloys

increases strength (solid-solution hardening)

•

produces grain refinement on its own and together with boron.

Influencing the microstructural formation of aluminium castings

Measures influencing microstructural

Common treatment measures include:

The marked areas in Figure 1 denote

formation are aimed at improving the

•

grain refinement of the solid

where it makes sense to carry out the

solution with Ti and/or B

respective types of treatment on AlSi

transformation of the eutectic Si

casting alloys.

mechanical and casting properties. In practice, apart from varying the cool-

•

ing speed by means of different mould materials, additions to the melt are usu-

from lamellar into granular form •

ally used. •

modification of the eutectic Si

Some of these measures are explained

with Na or Sr

in more detail in the following section.

refinement of the eutectic Si with Sb

•

refinement of the Si primary phase with P or Sb.

Types of treatment to influence grain structure

Figure 1

Temperature [°C] 700 Melt Melt + Al 660 °C

600

Melt + Si Eutectic temperature 577 C°

Al + Si

500

400 0

Silicon [wt. – %] Primary Si refinement Grain refinement Modification

Al Si5

Al Si7

Al Si9

Al Si12

Al Si18

Aluminium Casting Alloys 19

Figure 2

Grain refinement

Effect of silicon content on grain refinement with Al Ti5B1 master alloy

The solidification of many aluminium

Mean grain diameter [µm]

casting alloys begins with the formation

Casting temperature 720 °C holding time 5 min

1400

of aluminium-rich dendritic or equiaxed crystals. In the beginning, these solidified

1200

crystallites are surrounded by the remaining melt and, starting from nucleation sites, grow on all sides until they touch

1000 800

the neighbouring grain or the mould wall. 600

The characterisation of a grain is the equiaxed spatial arrangement on the lattice level. For casting/technical or

400 200

optical/decorative reasons as well as for reasons of chemical resistance, it is

often desirable to set the size of these

grains as uniformly as possible or as finely

Silicon [%]

as technically possible. To achieve this, Columnar and equiaxed crystals

so-called grain refinement is frequently

Without grain refinement

With grain refinement Al Ti5B1: 2,0 kg/mt

carried out. The idea is to offer the solidifying aluminium as many nucleating agents as possible. Since grain refinement only affects the

We pre-treat the appropriate casting al-

Since every alloying operation means

α-solid solution, it is more effective when

loys when producing the alloys so that

more contaminants in the melt, grain

the casting alloy contains little silicon,

grain refinement in the foundry is either

refinement should only be carried out

i.e. a lower fraction of eutectic (Figure 2).

unnecessary or only needs a freshen-

for the reasons referred to above.

Grain refinement is particularly important

up. The latter can be done in the form of

in AlMg and AlCu casting alloys in order

salts, pellets or preferably with titanium

To make a qualitative assessment of a

to reduce their tendency to hot tearing.

master alloy wire, following the manu-

particular grain refinement treatment,

facturer’s instructions.

thermal analysis can be carried out (see

From a technical and smelting perspec-

section on “Melt testing and inspection

tive, grain refinement mostly takes place

procedure”).

by adding special Al TiB master alloys.

20 Aluminium Casting Alloys

Modification of AlSi eutectic

Figures 3 and 4 depict the formation of

or elongation. When higher elongation is

(refinement)

microstructural conditions or the degree

required in a workpiece, aluminium cast-

of modification as a result of interaction

ing alloys containing approx. 7 to 13 %

By â&#x20AC;&#x153;modificationâ&#x20AC;?, we mean the use

between sodium and strontium and the

silicon will thus be modified by adding

of a specific melt treatment to set a

phosphorous element. It can be ascer-

approx. 0.0040 to 0.0100 % sodium (40

fine-grained eutectic silicon in the cast

tained that the disruption of modification

to 100 ppm).

structure which improves the mechanical

due to small amounts of phosphorous

properties (and elongation in particular)

is relatively slight. In Sr modification, a

In casting alloys with approx. 11 % silicon,

as well as the casting properties in many

high phosphorous content can be offset

particularly for use in low-pressure die

cases. As a general rule, modification

by an increased amount of modifying

casting, strontium can also be used as a

is carried out by adding small amounts

agent. In aluminium casting alloys with a

long-term modifier since the melting loss

of sodium or strontium. To facilitate an

silicon content exceeding 7 %, eutectic,

behaviour of this element is substantially

understanding of the possible forms of

silicon takes up a larger part of the area

better than that of sodium. In this case,

eutectic silicon, these are depicted in

of a metallographic specimen. From a

the recommended addition is approx.

Figure 2 (a-e) for Al Si11 with a varying

silicon content of approx. 7 to 13 %,

0.014 to 0.04 % Sr (140 to 400 ppm).

Na content:

the type of eutectic formation, e.g.

With suitable casting alloys, the required

a) The lamellar condition only

grained or modified, thus plays a key

amount of strontium can be added

appears in casting alloys which

role in determining the performance

during alloy manufacture so that, as

are virtually free of phosphorous

characteristics, especially the ductility

a rule, the modification process step

or modification agents, e.g. Na or Sr. b) In granular condition which

Types of grain structure

Picture 2

appears in the presence of phosphorous without Na or Sr, the silicon crystals exist in the form of coarse grains or plates. c) In undermodified and d) to a great extent in fully-modified microstructural condition, e.g. by adding Na or Sr, they are

a) Lamellar

b) Granular

d) Modified

e) Overmodified

c) Undermodified

significantly reduced in size, rounded and evenly distributed which has a particularly positive effect on elongation. e) In the case of overmodification with sodium, vein-like bands with coarse Si crystals appear. Overmodification can therefore mean deterioration as regards mechanical properties.

Aluminium Casting Alloys 21

Figure 3

Figure 4

Microstructural formation in relation to the content of phosphorous and sodium Al Si7Mg

Microstructural formation in relation to the content of phosphorous and strontium Al Si7Mg

Sodium [ppm]

Strontium [ppm]

Sand casting cooling rate 0.1 K/s

Gravity die casting gravity die cast test bar cooling rate 2.5 K/s

140 450 120 400 100 350 80 300 60 250 40 200 20 150 0 100 0

Phosphorous [ppm] Overmodified

Modified

Granular

Lamellar

Undermodified

60 50 0 0

100

Phosphorous [ppm] Modified

Undermodified

Granular

Lamellar

can be omitted in the foundry. At low

can be offset by adding Sr master alloy

cation must take place in the foundry

cooling rates, strontium modification is

wire in accordance with the respective

at regular intervals. In melts modified

less effective so that it is not advisable

manufacturerâ&#x20AC;&#x2DC;s instructions. At the right

with sodium, any requested cleaning

to use this in sand casting processes.

temperature, the addition of sodium to

and degassing should be carried out

the melt is best done by charging stand-

with chlorine-free compounds only

To avoid the burn-off of strontium, any

ard portions. For easy handling, storage

(argon or nitrogen). A certain amount

cleaning and degassing of Sr-modified

and proportioning, the manufacturerâ&#x20AC;&#x2DC;s

of sodium burn-off is to be reckoned

melts should be carried out with chlorine-

recommendations and safety instruc-

with, however, and needs to be taken

free preparations only, preferably using

tions should be followed.

into account in the subsequent addition

argon or nitrogen. Strontium modifica-

of sodium. When absolutely necessary,

tion is not greatly impaired even when

Since sodium burns off from the melt

the melt can be treated with chlorine-

remelting revert material. Larger losses

relatively quickly, subsequent modifi-

releasing compounds long before the

22 Aluminium Casting Alloys

Figure 5

first addition of sodium. If such treatment is carried out after adding sodium or strontium, chlorine may react with these elements and remove them from

Influence of antimony and phosphorous content on the form of the eutectic silicon of Al Si7Mg Antimony [%]

High-purity base

0.30

the melt, thereby preventing any further modification. Modification with sodium or strontium

0.20 Coarse-lamellar

increases the tendency to gas absorption in the melt. As a result of the reaction of the precipitating hydrogen with

0.10

the rapidly-forming oxides, defects can

Acceptable

Coarse-lamellar to granular

occur in the casting, especially cumulant microporosity. In many practical cases,

0.00

this potential for micropore formation 0

is even desirable. Then, the purpose

of modification is also to offset the

Phosphorous [ppm]

expected macroshrinkage by forming many micropores. An accurate assessment of the effects of modification can only be made by

A Sb content of at least 0.1 % is required.

means of metallographic examination.

This treatment, however, only produces

As a quick test, thermal analysis can be

a finer formation of the lamellar eutec-

In hypereutectic AlSi casting alloys

carried out if it is possible to establish by

tic silicon and is not really modification

(e.g. Al Si18CuNiMg), the silicon-rich,

means of a preliminary metallographic

in the traditional sense. The danger of

polygonal primary crystals solidify first.

examination which depression value is

contamination of other melts by closed-

To produce as many fine crystals as pos-

necessary to attain a sufficiently-modi-

circuit material containing Sb exists as

sible in the as-cast structure, nucleating

fied grain structure (for more information

even a Sb content of approx. 100 ppm

agents need to be provided.

on thermal analysis, please refer to the

can disturb normal sodium or strontium

section on “Methods for monitoring the

modification. What‘s more, refinement

This is done with the aid of prepara-

melt”). Under the same conditions, rapid

with antimony can be easily disturbed

tions or master alloys which contain

determination of the modified condition

by only a low level of phosphorous (a

phosphorous-aluminium compounds.

is also possible by measuring the elec-

few ppm) (Figure 5). In contrast to modi-

This treatment can also be carried out

trical conductance of a sample.

fication, refinement with antimony can

when the alloy is being manufactured

not be checked by means of thermal

and, in most cases, the foundryman

analysis of a melt sample.

does not need to repeat the process.

In aluminium casting alloys of the type

Refinement of primary silicon

Al Si7Mg, a refinement of the eutectic

If required, the quality of such primary

silicon with antimony (Sb) is possible.

refinement can be checked by means of thermal analysis.

Aluminium Casting Alloys 23

Melt quality and melt cleaning

All factors which come under the general term of “melt quality” have a direct effect on the quality of the casting to be produced. Inversely, according to DIN EN

Critical melting temperatures in relation to the segregation factor

Figure 6

Temperature [°C] 650

1706, the cast samples play a valuable role in checking the quality of the melt.

640

Most problems in casting are caused by

630

two natural properties of liquid melts, i.e.

620

their marked tendency to form oxides and their tendency towards hydrogen

610

absorption. Furthermore, other insoluble impurities, such as Al-carbides or refractory particles as well as impurities

600 590

with iron, play an important role. 0.8

1.2

1.4

1.6

Al Si8Cu3

Al Si6Cu4

Al Si12(Cu)

separation in the microstructure and, consequently, to a reduction in the loadbearing cross-section of the casting. The solubility of hydrogen in aluminium decreases discontinuously during the

To achieve good melt quality, the for-

transition from liquid to solid so that as

mation of oxides and the absorption

solidification takes place, precipitating

of hydrogen have to be suppressed as

gaseous hydrogen reacting with exist-

much as possible on the one hand, while

ing oxides can cause voids which can

other hydrogen and oxides have to be

in turn take various forms ranging from

removed from the melt as far as pos-

large pipe-like blisters to finely-distrib-

sible on the other, although this is only

uted micro-porosity.

possible to a certain extent.

24 Aluminium Casting Alloys

1.8

Segregation factor [(Fe)+2(Mn)+3(Cr)]

As mentioned in other sections, the larger oxide film can lead to a material

1.0

2.0

2.2

Avoiding impurities

Melting

Melting temperature

Ingot quality

When melting ingots or revert material,

The temperature of the melt must be set

it must be ensured that the metal is not

individually for each alloy.

An essential prerequisite for a good

exposed unnecessarily to the flame or

casting is good ingot quality. The metal

furnace atmosphere. The pieces of metal

Too low melting temperatures lead to

should be cleaned effectively and the in-

should be melted down swiftly, i.e. follow-

longer residence times and, as a result,

gots should display neither metallic nor

ing short preheating, immersed directly

to greater oxidation of the pieces jut-

non-metallic inclusions. The ingots must

in the liquid melt.

ting out of the melt. The melt becomes homogeneous too slowly, i.e. local un-

be dry (there is a risk of explosion when damp) and no oil or paint residue should

Large-volume hearth or crucible furnaces

dercooling allows segregation to take

be present on their surface. When using

are best suited to melting. Furnaces with

place, even as far as tenacious gravity

revert material, this should be in lumps,

melting bridges are oxide producers and

segregation of the FeMnCrSi type phases.

if possible, and well cleaned.

they lead to expensive, unnecessary and

The mathematical interrelationship for

irretrievable metal losses.

the segregation of heavy intermetallic phases is depicted in Figure 6.

The type and state of the melt in contact with refractory materials are of particular

Furthermore, at too low temperatures,

importance in the melting and holding

autopurification of the melt (oxides ris-

of aluminium.

ing) can not take place.

Aluminium and aluminium casting alloys

When the temperature of the melt is too

in a molten state are very aggressive, es-

high, increased oxide formation and

pecially when AlSi melts contain sodium

gassing can occur. Lighter alloying ele-

or strontium as modifying agents. With

ments, e.g. magnesium, are subject to

an eye to quality, reactions, adherences,

burn-off in any case; this must be off-

infiltrations, abrasive wear and decompo-

set by appropriate additions. Too high

sition have to be kept within limits when

melting temperatures aggravate this loss

using melting crucibles and refractory

by burning.

materials as well as during subsequent processing. The care and maintenance as well as cleanliness of equipment are equally important. Adhering materials can very easily lead to the undesired redissolving of oxides in the melt and cause casting defects.

Aluminium Casting Alloys 25

Figure 7

Conducting the melting operation

Hydrogen content of various casting alloy melts after different types of treatment

As long as the melt is in a liquid condi-

Hydrogen [ml/100g]

tion, it has a tendency to oxidise and

0.50

absorb hydrogen. Critical points during subsequent processing include decantation, the condition or maintenance of the transfer vessel, possible reactions with

0.40

refractory materials as well as transport or metal tapping. The addition of grain refiners and modifying agents above the

0.30

required amount can lead to an increase in non-metallic impurities and greater hydrogen absorption.

0.20

To minimise an enrichment of iron in the melt, direct contact between ferrous materials and the melt is to be avoided.

0.10

For this reason, steel tools and containers (casting ladles) must be carefully 0.00

flow channel, oxide skins can once again form which in turn can lead to casting defects. Casting technology is thus required to find ways of preventing the excessive oxidation of the melt, e.g. by means of intelligent runners and gating systems (please refer to the section on “Selecting the casting process”).

26 Aluminium Casting Alloys

Al Si8Cu3

Pantal 7

Al Mg5

20 24h

0.5

Type of melt treatment

Even during the casting process itself and especially due to turbulence in the

Rotary degassing [min]

feed tubes.

Gassing

now – should be replaced by ceramic

10 After melting

die casting – made from cast iron up to

Holding in [h]

grounds, the feed tubes for low-pressure

Rotary degassing [min]

dressed. Similarly, but also on economic

Cleaning and degassing the melt Our casting alloys consist of effectively

Dross can be removed from the surface

Apart from this, attention should also be

of the bath, possibly with the aid of ox-

paid to the quality and care of tools and

ide-binding salts.

auxiliary materials used for cleaning so

cleaned metal. Since reoxidation always

that the cleaning effect is not impaired.

takes place during smelting, and in

Inert-gas flushing by means of an im-

practice revert material is always used,

peller is a widely-used, economical and

If practically feasible, it is also possible

a thorough cleaning of the melt is nec-

environmentally-sound cleaning process.

to filter the melt using a ceramic foam

essary prior to casting.

The gas stream is dispersed in the form

filter. In the precision casting of high-

of very small bubbles by the rapid turn-

grade castings, especially in the sand

Holding the aluminium melt at the cor-

ing of a rotor and, in conjunction with the

casting process, the use of ceramic

rect temperature for a long time is an ef-

good intermixing of the melt, this leads

filters in the runner to the sand mould

fective cleaning method. It is, however,

to very efficient degassing. To achieve

has proved to be a success. Above all,

very time-intensive and not carried out

an optimum degassing effect, the vari-

such a filter leads to an even flow and

that often as a result. Foundrymen are

ous parameters such as rotor diameter

can retain coarse impurities and oxides.

thus left with only intensive methods, i.e.

and revolutions per minute, gas flow

using technical equipment or the usual

rate, treatment time, geometry and size

In the gravity die casting of sensitive

commercially available mixture of salts.

of the crucible used as well as the alloy,

hydraulic parts, or when casting sub-

have to be co-ordinated. The course of

sequently anodised decorative fittings

In principle, melt cleaning is a physical

degassing and reabsorption of hydrogen

in Al Mg3, ladling out of a device which

process: the gas bubbles rising through

is depicted for various casting alloys

is fitted with in-line filter elements and

the liquid metal attach oxide films to their

in Figure 7.

separated from the remaining melt bath

outer surfaces and allow hydrogen to dif-

is very common.

fuse into the bubbles from the melt. Both

When using commercially available salt

are transported to the bath surface by the

preparations, the manufacturerâ&#x20AC;&#x2DC;s instruc-

bubbles. It is therefore clear that in order

tions concerning use, proportioning,

for cleaning of the melt to be effective, it

storage and safety should be followed.

is desirable to have as many small gas bubbles as possible distributed across the entire cross-section of the bath.

Aluminium Casting Alloys 27

Melt testing and inspection procedure

The Density Index allows a certain infer-

Determination of the hydrogen

ence to be drawn about the hydrogen

content in the melt

To assess the effectiveness of the clean-

content of the melt. It is, however, strongly

ing process or the quality of the melt, the

influenced by the alloying elements and,

Reliable instruments have been in opera-

following test and inspection methods

above all, by varying content of impurities

tion for years for measuring the hydrogen

can be used to monitor the melt:

so that the hydrogen content must not

content in aluminium melts. They work

on any account be stated as a Density

according to the principle of establish-

Index value (Figure 8).

ing equilibration between the melt and a

Reduced pressure test

measuring probe so that the actual gas This method serves to determine the

The assessment of melt quality by means

content in the melt is determined and not

tendency to pore formation in the melt

of an underpressure density sample there-

in the solid sample. In this way, the effec-

during solidification. A sample, which

fore demands the specific determination

tiveness of the degassing treatment can

can contain a varying number of gas

of a critical Density Index value for each

be assessed quickly. The procurement of

bubbles depending on the gas content,

casting alloy and for each application.

such an instrument for continuous quality

is allowed to solidify at an underpressure

The underpressure density method is,

monitoring is only worthwhile when it is

of 80 mbar. The apparent density is then

however, a swift and inexpensive meth-

used frequently; in small foundries, the

compared with that of a sample which

od with the result that it is already used

hiring of an instrument to solve problems

is solidified at atmospheric pressure.

in many foundries for quality control.

is sufficient.

The so-called â&#x20AC;&#x153;Density Indexâ&#x20AC;? is then

To keep results comparable, sampling

calculated using the following equation:

should always be carried out according to set parameters.

= (dA - d80)/dA x 100 %

= Density Index

dA = density of the sample solidified at atmospheric pressure d80 = density of the sample solidified at under 80 mbar

28 Aluminium Casting Alloys

Figure 8

Determination of insoluble non-metallic impurities

Correlation between the hydrogen content and density index in unmodified Al Si9Mg alloy Density index [%]

For determining the number and type

Measurement acc. to Chapel at vacum 30 mbar

of insoluble non-metallic impurities in aluminium melts, the Porous Disc Filtra-

tion Apparatus (PoDFA) method, among others, can be used. In this particular method, a precise amount of the melt

25 20

is squeezed through a fine filter and the trapped impurities are investigated

metallographically with respect to their type and number. The PoDFA method is one of the determination procedures

10 5

which facilitates the acquisition, both qualitatively and quantitatively, of the impurity content. It is used primarily for evaluating the filtration and other cleaning treatments employed and, in casting

0 0

0.1

0.2

0.3

0.4

0.5

0.6

Hydrogen content [ml/100g]

alloys production, is utilised at regular intervals for the purpose of quality control. This method is not suitable for making constant routine checks since it is very time-consuming and entails high costs.

Aluminium Casting Alloys 29

Figure 9

Thermal analysis

Thermal analysis for monitoring the grain refinement of Al casting alloys

To evaluate the effectiveness of melt

Temperature [T]

treatment measures, e.g. modification, grain refinement and primary silicon reTL

fining, thermal analysis has proved itself TL

to be a fast and relatively inexpensive method in many foundries. The test method is based on the comparison of two cooling curves of the investigated melts (Figures 9 and 10). The undercooling effect (recalescence)

Time [t]

occurring during primary solidification allows conclusions to be made about the effectiveness of a grain refinement

With grain refinement

Without grain refinement

Liquidus temperature [TL]

treatment, whereby the recalescence values do not however allow conclusions to be drawn as regards the later grain size in the microstructure. Modification is

Figure 10

Thermal analysis for monitoring the modification of Al casting alloys

shown in thermal analysis by a decrease

Temperature [째C]

in the eutectic temperature (depression)

585

in comparison to the unmodified state. Here too, the level of the depression

580

values depend strongly on the content

577 575

of accompanying and alloying elements (e.g. Mg) and, consequently, the de-

570

pression values required for sufficient modification must be established case by case, by means of parallel microstruc-

565 560

tural investigations. 0

Time [sec] Modified

30 Aluminium Casting Alloys

Undermodified

Eutectic temperature

Selecting the casting process

As mentioned in the introduction, the

nesses can be favourably influenced

Squeeze-casting is another casting pro-

entire “casting” process is the shortest

with the help of risers. Cylinder heads

cess to be mentioned; here, solidification

route from molten metal to a part which

for water-cooled engines represent a

takes place at high pressure. In this way,

is almost ready for use. All sections of

typical application.

an almost defect-free microstructure

this catalogue contain advice on how the entire experience should be carried out.

can be produced even where there are In the low-pressure gravity die process

large transitions in the cross-section

with its upward and controllable cavity

and insufficient feeding.

The casting process is selected ac-

filling, the formation of air pockets is re-

cording to various criteria such as batch

duced to a minimum and, consequently,

Other special casting processes include:

size, degree of complexity or requisite

high casting quality can be achieved. In

•

Precision casting

mechanical properties of the casting.

addition to uphill filling, the overpressure

•

Evaporative pattern casting

Some examples:

of approx. 0.5 bar has a positive effect

•

Plaster mould casting

on balancing out defects caused by

•

Vacuum sand casting

The sand casting process is used

shrinkage. The low-pressure die casting

•

Centrifugal casting.

predominantly in two fields of appli-

process is particularly advantageous in

cation: for prototypes and small-scale

the casting of rotationally symmetrical

The considerations above concern cast-

production on the one hand and for the

parts, e.g. in the manufacture of pas-

ing as an overall process.

volume production of castings with a

senger vehicle wheels. In the following notes on casting prac-

very complex geometry on the other. For the casting of prototypes, the main

Pressure die casting is the most widely

tice, the actual pouring of the molten

arguments in favour of the sand casting

used casting process for aluminium

metal into prepared moulds and the

process are its high degree of flexibility

casting alloys. Pressure die casting is

subsequent solidification control are

in the case of design changes and the

of particular advantage in the volume

looked at in more detail.

comparably low cost of the model. In vol-

production of parts where the require-

ume production, the level of complexity

ment is on high surface quality and the

From the numerous casting processes,

and precision achieved in the castings

least possible machining. Special ap-

which differ from one another in the type

are its main advantages.

plications (e.g. vacuum) during casting

of mould material (sand casting, per-

enable castings to be welded followed

manent dies etc.) or by pressurisation

When higher mechanical properties are

by heat treatment which fully exploits

(pressure die casting, low-pressure die

required in the cast piece, such as higher

the property potential displayed by the

casting etc.), a few notes are provided

elongation or strength, gravity die cast-

casting alloy.

here on the most important processes.

ing, and to a limited extent pressure die casting, are used. In gravity die casting,

In addition to conventional pressure die

there is the possibility of using sand

casting, thixocasting is worthy of men-

cores. Large differences in wall thick-

tion since heat-treatable parts can also be manufactured using this process. The special properties are achieved by shaping the metal during the solidliquid phase.

Aluminium Casting Alloys 31

Pressure die casting process

Parts generated using the horizontal

Gravity die casting process

pressure die casting process are lightThis process takes up the largest share.

weight as low wall thicknesses can be

The gravity die casting which includes

The hydraulically-controlled pressure

achieved. They have a good surface

the well-known low-pressure die casting

die casting machine and the in-built

finish, high dimensional accuracy and

process is applied. The main fields of

die make up the central element of the

only require a low machining allowance

application are medium- or high-volume

process. The performance, the precise

in their design. Many bore holes can be

production using high-grade alloys, and

control of the hydraulic machine, the

pre-cast.

also low to medium component weight

quality of the relatively expensive tools

using heat-treatable alloys. Compared

made from hot work steel are the deci-

The melting and casting temperatures

with sand casting, the aluminium cast-

sive factors in this process. In contrast,

should not be too low and should be

ings display very good microstructural

the flow properties and solidification

checked constantly. Pre-melting alu-

properties as well as good to very good

of the aluminium casting alloys play a

minium casting alloys is useful. The melt

mechanical properties which result from

rather subordinate role in this “forced”

can thus be given a good clean in order

the rapid cooling times and the other

casting process.

to keep the melt homogeneous and to

easily-controlled operating parameters.

avoid undesirable gravity segregation The pouring operation in horizontal pres-

(see Figure 6). From a statistical point

The castings have high dimensional ac-

sure die casting begins with the casting

of view, more casting defects arise from

curacy and stability as well as a good

chamber being filled with metal. The

cold metal than from hot. It is particu-

surface finish, are heat-treatable and

first movement, i.e. the slow advance of

larly important to keep a sufficiently high

can also be anodised.

the plunger and the consequent pile-up

melting temperature, even with hypere-

of metal until the sleeve is completely

utectic alloys. These comments are also

The basis for good quality castings is,

filled, is the most important operation.

valid for other casting processes.

not least, the right melt treatment and

In doing this, no flashover of the metal

the appropriate casting temperature (see

or other turbulence may occur until all of

section on “Melt quality and melt clean-

the air in the sleeve has been squeezed

ing”). For castings with high surface or

out. Immediately afterwards, the actual

microstructural quality requirements,

casting operation begins with the rapid

such as in decorative or subsequently

casting phase. High injection pressure is

anodised components or in pressure-

essential to achieve high flow velocities

tight hydraulic parts, it is useful to filter

in the metal. In this way, the die can be

the melt before casting.

filled in a few hundredths of a second. Throughout the casting operation, the liquid metal streams are subject to the laws of hydrodynamics. Sharp turns and collisions with the die walls lead to a clear division of the metal stream.

32 Aluminium Casting Alloys

Demands on the casting system

The castings are usually arranged “up-

In low-pressure die casting, directing

right” in the die. The greatest mass can

the solidification by means of the gat-

To keep disadvantages and defects –

thus be placed in the bottom of the die.

ing system is not possible. Nor is there

which constantly arise from an oxide

Quality requirements can be, for example,

any great possibility of classic feeding.

skin forming on the melt – within limits,

high strength, high-pressure tightness or

Directional solidification is only possible

the gating system must guarantee low

decorative anodising quality.

by controlling the thermal balance of the die during casting. This mostly requires

turbulence in the metal stream and also a smooth, controlled filling of the die

One example of an “ideal” gating system

the installation of an expensive cooling-

cavity. With the transition from a liquid

which meets the highest casting require-

heating system.

to a solid condition, volume contraction

ments is the so-called “slit gate system”.

occurs; this can amount to up to 7 %

Here, the metal is conducted upwards

Simulation calculations for die filling and

of the volume. This shrinkage is con-

continuously or discontinuously to the

solidification can be useful when laying

trollable when the solid-liquid interface

casting via a main runner. During mould

out and designing the die and possibly

runs – controlled or directed – through

filling, the melt is thus superimposed layer

the cooling. In actual production, the

the casting, mostly from the bottom to

upon layer with the hotter metal always

cooling and cycle time can be optimised

the top. This task, namely to effect a

flowing over the already solidifying metal.

by means of thermography (see section

directed solidification, can be achieved

The standpipe ends in the top riser and

on “Solidification simulation and ther-

with a good pouring system.

supplies it with hot metal. This way, the

mography”).

solidification can be directed from below, possibly supported by cooling, towards the top running through the casting and safeguarding the continuous supply of hot metal. When there is a wide flare in the casting, the gating system has to be laid out on both sides. This symmetry ensures a division of the metal and also an even distribution of the heat in the die.

Aluminium Casting Alloys 33

Sand casting process

Another generally valid casting rule for

This facilitates keeping the run-in laun-

correct solidification is to arrange risers

der full and leads to a smoother flow

This process is used especially for in-

above the thick-walled parts, cooling (e.g.

of the metal. This way, the formation of

dividual castings, prototypes and small

by means of chills) at opposite ends. This

oxides due to turbulence can be kept

batch production. It is, however, also

way, the risers can perform their main

within limits. The main runner must lie

used for the volume production of cast-

task longer, namely to conduct the sup-

in the drag, the gates in the cope. In the

ings with a very complex geometry (e.g.

ply of molten metal into the contracted

production of high-grade castings, it is

inlet manifolds, cylinder heads or crank-

end. Insulated dies are often helpful.

normal to install ceramic filters or sieves

cases for passenger vehicle engines). During shaping and casting, most large

made from glass fibre. The selection of The cross-section ratio in the sprue system

the casting process and the layout of

should be something like the following:

the casting system should be carried

sand castings display in-plane expan-

out in close co-operation between the

sion. With this flat casting method, gating

Sprue :

customer, designer and foundryman (see

systems like those which are normal in

Sum of the runner cross-section :

section on â&#x20AC;&#x153;Casting-compliant designâ&#x20AC;?).

gravity die casting for directing solidifica-

Sum of the gates:

tion are often not applicable. If possible,

like 1 : 4 : 4.

a superimposed filling of the die cavity should be attempted here.

34 Aluminium Casting Alloys

Casting-compliant design

The following notes on the design of

In the valid European standard, DIN EN

Only through good cast quality can the

aluminium castings are provided to help

1706 for aluminium castings, there are

technical requirements be met and the

exploit in full the advantages and design

strength values only for separately-cast

full potential of the casting alloy be ex-

possibilities of near net shape casting.

bars using sand and gravity die casting.

ploited. Every effort and consideration

They also align practical requirements

For samples cut from the cast piece,

must be made therefore to design a light,

with material suitability.

a reduction in the 0.2 % proof stress

functionally efficient part whose manu-

and ultimate tensile strength values of

facture and machining can be carried out

Aluminium casting alloys can be pro-

up to 70 % and a decrease in elonga-

as efficiently as possible. For this and

cessed in practically all conventional

tion of up to 50 % from the test bar can

subsequent considerations, the use of

casting processes, whereby pressure die

be anticipated. When the alloy and the

solidification simulation is available (see

casting accounts for the largest volume,

casting process are specified, so too is

section on “Solidification simulation and

followed by gravity die casting and sand

the next point within the framework of

thermography”).

casting. The most useful casting process

the design, i.e. determination of the die

is not only dependent on the number and

parting line. Die parting on one level is

Casting alloys shrink during solidifica-

weight of pieces but also on other tech-

not only the cheapest for patterns and

tion, i.e. their volume is reduced. This

nical and economic conditions (see sec-

dies but also for subsequent working and

increases the risk of defects in the cast

tion on “Selecting the casting process”).

machining. Likewise, every effort should

structure, such as cavities, pores or

be made to produce a casting without

shrinkage holes, tears or similar. The

To find the optimum solution and produce

undercuts. This is followed by designing

most important requirement is thus to

a light part as cheaply and rationally as

and determining the actual dimensions

avoid material accumulations by hav-

possible, co-operation between the de-

of the part. The constant guideline must

ing as even a wall thickness as possible.

signer, caster and materials engineer is

be to achieve a defect-free cast structure

always necessary. Knowledge concern-

wherever possible.

In specialist literature, the following lower

ing the loads applied, the distribution of

limits for wall thickness are given:

stress, the range of chemical loading and

•

operation temperatures is important.

•

Gravity die castings: 2-3 mm

•

Pressure die castings: 1-1.5 mm.

Sand castings: 3-4 mm

Aluminium Casting Alloys 35

The minimum values are also dependent

Another possible way of avoiding material

Fettling the casting, i.e. removing the

on the casting alloy and the elongation of

accumulations is to loosen the nodes.

riser and feeders, must be carried out as

the casting. In pressure die casting, the

At points where fins cross, a mass ac-

efficiently as possible. Grinding should

minimum wall thickness also depends

cumulation can be prevented by stag-

be avoided where possible. Reworking

on the position of and distance to the

gering the wall layout.

and machining should also be easy to

gate system.

carry out. Machining allowances are to The corners where walls or fins meet

be kept as small as possible.

Generally speaking, the wall thickness

should be provided with as large transi-

should be as thin as possible and only

tions as possible. Where walls of different

Essential inspections or quality tests

as thick as necessary. With increasing

thickness meet, the transitions should

should be facilitated by constructive

wall thickness, the specific strength of

be casting-compliant.

measures.

the cast structure deteriorates. Where the casting size and process Determining casting-compliant wall

permit, bores should be pre-cast. This

thicknesses also means, especially with

improves the cross-section ratio and

sand and gravity die casting, that the die

structural quality.

must first of all be filled perfectly. During subsequent solidification, a dense cast

Apart from the points referred to above,

structure can only occur if the shrinkage

a good design also takes account of

is offset by feeding from liquid melt. Here,

practical points and decorative appear-

a wall thickness extending upwards as a

ance as well as the work procedures

connection to the riser may be necessary.

and machining which follow the actual casting operation.

36 Aluminium Casting Alloys

Solidification simulation and thermography

Solidification simulation

Possible positive effects of simulation

Thermography

calculations include: A basic aim in the manufacture of cast-

•

ings is to avoid casting defects while minimising the amount of material in the

•

recycling circuit.

•

Optimisation of the manufacture of castings with regard to casting geometry,

•

gating and feeding system and casting parameters can be achieved via

•

numerical simulation of die filling and

•

the mechanisms of solidification on the

Optimisation of the casting before

Even after a casting goes into volume

casting actually takes place

production, it is often desirable and nec-

Avoiding casting defects

essary to optimise the casting process

Optimisation of the feeding system

and increase process stability. Besides

(reducing material in the recycling

the aforementioned solidification simula-

circuit)

tion, periodic thermal monitoring of the

Optimisation of the casting

dies by means of thermography is used

process (reducing cycle times)

in particular.

Increasing process stability Visualisation of the die-filling and

In this process, a thermogramme of the

solidification process.

die or casting to be investigated is made with the aid of an infrared camera. This

computer. Casting defects can thus be detected in good time and the casting

A simulation programme does not opti-

way, the effectiveness of cooling, e.g. in

design and casting system optimised

mise on its own and can not, and should

pressure or gravity die casting, can be

before the first casting operation takes

not, replace the experienced foundry-

checked or optimised and the optimum

place. In principle, flow and thermal con-

man. To exploit the potential of die-filling

time for lifting determined.

duction phenomena which occur during

and solidification simulation to the full,

casting can be calculated numerically

it should be applied as early as possi-

using simulation programmes.

ble, i.e. already at the design stage of the casting.

In calculation models, the casting and die geometry – which first of all must be available in a CAD volume model – is thus divided into small volume elements (Finite Difference Method). The flow velocities and temperatures in the individual volume elements are then calculated using a numerical method.

Aluminium Casting Alloys 37

Avoiding casting defects

As shown in Table 4, there are two

quality and melt cleaning” as well as

The type of solidification is also impor-

phenomena which – individually or in

“Methods for melt monitoring” and “Se-

tant when considering suitable casting/

combination – can lead to defects in

lecting the casting process”. Here are a

technical measures. In AlSi casting al-

emergent castings:

few key points:

loys with approx. 13 % Si, a frozen shell

1. The continuous (new) formation of

•

Use good quality ingots

forms during solidification while, in hy-

•

Quality-oriented melting technology

poeutectic AlSi casting alloys as well

and equipment

as in AlMg and AlCu casting alloys, a

Correct charging of the ingots

predominantly dendritic or globular so-

(dry, rapid melting)

lidification occurs.

oxides in the liquid state and 2. volume contraction during the transition from liquid to solid state. During transition from liquid to solid

• •

state, the dissolved hydrogen in the melt

Temperature control during melting and casting

In gravity die casting processes, the

precipitates and, on interacting with ox-

•

Melt cleaning and melt control

feeders are laid out in particularly critical

ides, causes the well-known problem of

•

Safety measures during treatment,

or thick areas of the casting. The feed-

transport and casting

ers require hot metal in appropriately

microporosity or gas porosity.

large volumes to execute their task. The The task of melt management and

Volume contraction during the transition

combination of feeding and cooling is

treatment is to keep oxide formation

from liquid to solid state can - depend-

useful. Heat removal to accelerate and

and, consequently, the dangers to cast

ing on the casting alloy - be up to 7 %

control solidification at the lower end

quality within limits. Information about

volume. Under unfavourable conditions,

of the casting or in solid areas can be

this is provided in the sections on “Melt

part of this volume difference can be the

effected by means of metal plates or

cause of defects in castings, e.g. shrink

surface chills (cooling elements).

marks, shrink holes, pores or tears. To produce a good casting, the possibility of feeding additional molten metal into the contracting microstructure during solidification must exist. In pressure casting processes, this occurs by means of pressurisation; in gravity die casting, this is done primarily by feeding.

38 Aluminium Casting Alloys

As already shown in the section on cast-

Two methods can be used to reduce

ing processes, an uncontrolled or tur-

the number of defective parts due to

bulent filling of the die cavity can have a

porosity: In hot isostatic pressing (HIP),

negative influence on the quality of the

porous castings are subjected to high

casting. A gating system which allows

pressure at elevated temperatures so

the solidification front to be controlled

that shrinkage and pores inside the cast-

upwards through the casting from the

ings are reduced; they do not, however,

bottom up to the feeder is helpful. A

completely disappear. A second and

good casting system, e.g. side stand

less costly possibility is the sealing of

pipe-slit gate, begins the filling in the

castings by immersing them in plastic

lower part of the die and always layers

solutions. The shrinkage and pores,

the new hot metal on the lower, already

which extend to the surface, are filled

solidified part and also supplies the

with plastic and therefore sealed.

feeder with hot metal. A casting system of this type can partially cushion the negative effect caused by volume contraction while conducting the molten metal in such a way that fresh oxidation of the melt due to turbulence is avoided.

Table 4

Classification of casting defects Source of defect

Consequences for the casting

Optimisation possibilities

•

• • • • • • •

Pores Aeration Inclusions Leakiness Surface defects Machining Loss of strength and elongation

•

Melt treatment and degassing Melting and casting temperature Filter

• • • • •

Cavity Shrinkage Aeration Leakiness Loss of strength and elongation

• • • • •

Gating system Solidification control Feeding Grain refinement Modification

•

Oxidation and hydrogenabsoption

Volume contraction

•

Aluminium Casting Alloys 39

Heat treatment of aluminium castings

Heat treatment gives users of castings

Metallurgy – fundamental principles

In ageing, mostly artificial ageing, precipitation of the forcibly dissolved com-

the possibility of specifically improving the mechanical properties or even

For age-hardening to take place, there

ponents takes place in the form of small

chemical resistance. Depending on the

must be a decreasing solubility of a par-

sub-microscopically phases which cause

casting type, the following common and

ticular alloy constituent in the α-solid so-

an increase in hardness and strength.

applied methods for aluminium castings

lution with falling temperature. As a rule,

These tiny phases, which are techni-

can be used:

age-hardening comprises three steps:

cally referred to as “coherent or semicoherent phases”, represent obstacles

•

Stress relieving

•

Stabilising

In solution annealing, sufficient amounts

to the movement of dislocations in the

•

Homogenising

of the important constituents for age-

metal, thereby strengthening the previ-

•

Soft annealing

hardening are dissolved in the α-solid

ously easily-formable metal.

•

Age-hardening.

solution. The following casting alloy types are

The most important form of heat treat-

With rapid quenching, these constituents

age-hardenable:

ment for aluminium castings is artificial

remain in solution. Afterwards, the parts

•

Al Cu

ageing. Further information is provided

are relatively soft.

•

Al CuMg

•

Al SiMg

•

Al MgSi

•

Al ZnMg.

below.

Figure 11.1

Figure 11.2

Yield strength of gravity die cast test bars (Diez die) in Al Si10Mg alloy

Elongation of gravity die cast test bars (Diez die) in Al Si10Mg alloy

Yield strength Rp0,2 [MPa]

Elongation A5 [%]

280

240

200

160

120

0 0

Ageing time [h] 160 °C

180 °C

40 Aluminium Casting Alloys

200 °C

Ageing time [h] As-cast state

160 °C

180 °C

200 °C

As-cast state

Solution annealing

suffices. The normally longer solution

Quenching

annealing times of up to 12 hours, as To bring the hardened constituents into

for example in Al SiMg alloys, produce

Hot castings must be cooled in water as

solution as quickly as possible and in a

a good spheroidising or rounding of the

rapidly as possible (5-20 seconds de-

sufficient amount, the solution anneal-

eutectic silicon and, therefore, a marked

pending on wall thickness) to suppress

ing temperature should be as high as

improvement in elongation.

any unwanted, premature precipitation of

possible with, however, a safety margin

the dissolved constituents. After quench-

of approx. 15 K to the softening point

The respective values for age-hardening

ing, the castings display high ductility.

of the casting alloy in order to avoid in-

temperatures and times for the individual

This abrupt quenching and the ensuing

cipient fusion. For this reason, it is often

casting alloys can be indicated on the

increase in internal stresses can lead

suggested that casting alloys containing

respective data sheets.

to distortion of the casting. Parts are

Cu should undergo step-by-step solution annealing (at first 480 °C, then 520 °C).

often distorted by vapour bubble presDuring the annealing phase, the strength

sure shocks incurred during the rapid

of the castings is still very low. They must

immersion of hollow castings. If this is

The annealing time depends on the wall

also be protected against bending and

a problem, techniques such as spraying

thickness and the casting process. Com-

distortion. With large and sensitive cast-

under a water shower or quenching in

pared with sand castings, gravity die cast-

ings, it may be necessary to place them

hot water or oil have proved their value

ings require a shorter annealing time to

in special jigs.

as a first cooling phase.

dissolve the constituents sufficiently due to their finer microstructure. In principle,

Nevertheless, any straightening work

an annealing time of around one hour

necessary at this stage should be carried out after quenching and before ageing.

Figure 11.3

Tensile strength of gravity die cast test bars (Diez die) in Al Si10Mg alloy Tensile strength Rm [MPa] 360 320 280 240 200 160 0

Ageing time [h] 160 °C

180 °C

200 °C

As-cast state

Aluminium Casting Alloys 41

Ageing

way, for example, the mechanical prop-

In Al SiMg casting alloys, a further pos-

erties can be adjusted specifically to at-

sibility of specifically adjusting strength

The procedure of ageing brings about

tain high hardness or strength although,

and elongation arises from varying the

the decisive increase in hardness and

in doing this, relatively lower elongation

Mg content in combination with different

strength of the cast structure through

must be reckoned with. Conversely, high

heat treatment parameters (Figure 12).

the precipitation of the very small hard-

elongation can be also achieved while

ening phases. Only after this does the

lower strength and hardness values will

part have its definitive service properties

be the result. When selecting the age-

and its external shape and dimensions.

ing temperatures and times, it is best to refer to the ageing curves which have

Common alloys mostly undergo artificial

been worked out for many casting al-

ageing. The ageing temperatures and

loys (Figures 11.1-11.4).

times can be varied as required. In this

Figure 11.4

Figure 12

Brinell hardness of gravity die cast test bars (Diez die) in Al Si10Mg alloy

Influence of Magnesium on the tensile strength (Diez bars)

Brinell hardness [HB]

Tensile strength Rm [MPa]

Alloy Al Si7 auf 99.9 base + 200 ppm Sr + 1 kg/mt Al Ti3B1 n=5

160 300 140 250 120 200 100 150 80 100 60 50 0

Ageing time [h] 160 °C

180 °C

200 °C

As-cast state

16 0 0

0.1

0.2

0.3

Magnesium [%] 8 h to 525 °C, H2O +6 h to 160 °C 8 h to 525 °C, H2O

42 Aluminium Casting Alloys

As-cast state

0.4

0.5

0.6

If the heat treatment does not work first

Regular maintenance, especially of the

of water. Artificial ageing in a furnace at

time, it can be repeated beginning with

measuring and control equipment, is

approx. 170 °C brings about the desired

solution annealing. By doubling the so-

therefore absolutely essential.

increase in hardness and strength.

silicon can arise in the grain structure.

For slightly higher hardness or strength

The procedure used in artificial ageing as

Since the solution treatment is performed

requirements, there is the non-standard

well as typical temperatures and times

close to the alloy‘s melting temperature

possibility of “simplified age-hardening”.

are shown in Table 5.

and the precipitation rate is highly sen-

This can be used in gravity die casting

sitive to variations in ageing tempera-

and pressure die casting when age-

ture, it is essential that a high degree

hardenable alloys are being poured.

of consistency and control is assured.

Decisive here is a further rapid cooling

lution time, a coarsening of the eutectic

after ejection from the die, e.g. by immediately immersing the part in a bath

Table 5

Procedures used in artificial ageing 1) Casting type

Example

Solution heat treatment Temperature Time [°C] [h]

Age-hardening Temperature Time [°C] [h]

Al SiMg

Al Si10Mg

530

4 - 10

160 - 170

6 - 8

Al SiCu

Al Si9Cu3

480

6 - 10

155 - 165

6 - 2

Al MgSi

Al Mg3Si

550

4 - 10

155 - 175

8 - 0

530*

8 - 18

140 - 170

6 - 8

Al CuMg

1) Typical temperature and time values * Poss. gradual annealing at approx. 480 °C / approx. 6 h

Aluminium Casting Alloys 43

Mechanical machining of aluminium castings

In general, parts made from aluminium

With softer materials and also with most

High-speed steel and hard metal or

casting alloys are easy-machinable.

hypoeutectic AlSi casting alloys, narrow

ceramic plates are used as cutting tool

This also applies for all metal-cutting

tools, i.e. with a large rake angle, cause

materials; for microfinishing, diamonds

processes. Low cutting force allows a

the least possible surface roughness.

are often utilised.

high volume of metal to be removed. The

These casting alloys produce narrow-

surface finish of the cast piece depends

spiral or short-breaking turnings. When

The following machining allowances are

on the machining conditions, such as

machining aluminium, suitable emul-

given for the main casting processes:

cutting speed, cutting geometry, lubri-

sions with water are used as cooling

•

sand castings: 1.5-3 mm

cation and cooling.

agents and lubricants. Friable and chips

•

gravity die castings: 0.7-1.5 mm

and fine to powdery Si dust arise when

•

pressure die castings: 0.3-0.5 mm.

The high cutting speeds required in alu-

machining hypereutectic casting alloys.

minium to achieve minimum roughness

In combination with the lubricant, this

In order to minimise value losses, turnings

necessitate, with regard to processing

powder produces an abradant which is

and chips should be sorted out according

machines and tools, stable, vibration-

often processed when dry. In some re-

to casting alloy type and stored possi-

free construction and good cutting tools.

spects, the machining of these casting

bly in briquettes. In addition, dampness,

alloy types is similar to grey cast iron.

grease and free iron reduce the value of

Besides the microstructure – including

chips and turnings. Aluminium chips and

defects, pores or inclusions – the silicon

With workpieces made from Al Si12

turnings are not hazardous materials and

content of the casting has a strong ef-

casting alloys with their very soft matrix,

there is no risk of fire during storage.

fect on tool wear. Modified, hypoeutectic

a large volume of long curly spirals are

AlSi casting alloys have, e.g. the highest

produced. In addition, the plastic mate-

When grinding aluminium parts, explosion-

tool time, while hypereutectic aluminium-

rial tends to build up edges on the tool.

proof separation of the dust is stipulated.

silicon piston casting alloys can cause

This leads to lubrication and, as a result,

very considerable tool wear.

a poor surface appearance. When this occurs, it often gives the machinist the subjective impression of bad machinability although tool wear is not the cause in this case.

44 Aluminium Casting Alloys

Welding and joining aluminium castings

Suitability and behaviour

The production welding sector should

using argon. The process is suitable

not be underestimated, e.g. for repair-

for both manual welding and for fully-

Similar to most wrought aluminium alloys,

ing defects in castings. Besides casting

mechanised and automatic welding. In

castings made from aluminium casting

defects, there is also the possibility of

fully-mechanised and automatic welding,

alloys can, in principle, also be joined by

correcting dimensional discrepancies,

both the power source and burner are

means of fusion welding. Near-eutectic

removing wear by build-up welding and

water-cooled. With the wire electrode

and hypoeutectic aluminium-silicon cast-

repairing broken components.

acting as the positive pole, the energy

ing alloys are the best to weld. Poor to

density is so high that it is able to break

unweldable are parts made from Al Cu4Ti

open the tenacious and high-melting

alloys types since the Cu-content can

Welding processes

cause the casting alloy to crack during

oxide layer by means of local, explosive metal vaporisation underneath the ox-

welding. In AlMg casting alloys, the ten-

The most frequently used fusion weld-

ide. With appropriate heat conduction,

dency to tearing must be counteracted

ing processes for joining castings are

it is possible to achieve a relatively nar-

by selecting a suitable weld filler.

metallic-insert-gas welding (MIG weld-

row heat-affected zone with satisfactory

ing) and Tungsten-inert-gas welding

strength and elongation values.

(TIG welding). A further development of MIG welding is

Applications in the aluminium sector

represented by MIG pulse welding. Here, Although near net shape casting gives

Metal inert-gas welding (MIG welding)

the welding current alternates between a so-called pulsed current and background

the designer the greatest possible freedom in the design of castings, welding is

In MIG welding, an inert-gas arc weld-

current. Using this process, it is possible

becoming increasingly important for the

ing process, a continuous arc burns

to carry out difficult tasks, i.e. thin wall

joining of aluminium cast components,

between a melting wire electrode and

thicknesses (1 mm) and out-of-position

either for welding two or more easy-to-

the workpiece. The process works with

work (overhead).

cast parts (e.g. half shells) â&#x20AC;&#x201C; whereas

direct current, the wire electrode acting

they would be difficult to cast as one â&#x20AC;&#x201C;

as the positive pole. The process is car-

Today, MIG welding is the most frequently

to form hollow bodies on the one hand

ried out under an inert gas in order to

used aluminium welding process be-

or for joining extruded sections or sheet

protect the melt area from the hazard-

cause, in addition to its easy manipula-

to castings to give a subassembly on

ous influences of the oxygen contained

tion, the investment and running costs

the other, such as the case in vehicle

in air and moisture. Argon and/or helium,

are favourable.

construction, lamp posts, lamp fittings

both inert gases, are used as shielding

and heat exchangers.

gases. Normally, it is cheaper to weld

Aluminium Casting Alloys 45

Tungsten-insert-gas welding

In one process variant, which has an

(TIG welding)

electrode with negative polarity as in the

Other thermal joining processes

welding of steel, welding is carried out

The group of so-called â&#x20AC;&#x153;pressure welding

In TIG welding, an inert-gas shielded

using direct current under a helium shield.

processesâ&#x20AC;? also includes friction stear

arc welding process, an arc burns con-

Compared with argon, helium displays

welding (FSW) which is frequently used

tinuously between a non-consumable

better thermal conductivity so that less

for welding aluminium castings. Since this

electrode made of a tungsten alloy and

current is required to break open the ox-

welding process works without any filler

the casting. Alternating current is nor-

ide layer. Consequently, the electrode is

material, it is possible to join materials

mally used when welding aluminium. The

not overloaded. In TIG welding, there are

together which are not fusion-weldable

welding filler is fed in separately from

also process variants which work with

since they would form brittle inter-metallic

outside either by hand or mechanically.

the pulsed-current technique.

phases. By means of friction welding, aluminium and steel, for example, can

The process is carried out under an inert gas in order to protect the melt area

With regard to freedom from porosity,

from the hazardous influences of the

the cleanest seams can be achieved

oxygen contained in air and moisture.

using TIG welding. One disadvantage

The principle behind the process is to heat

Argon and/or helium, both inert gases,

of the TIG welding process, however, is

the workpieces up to a pasty condition

are used as shielding gases. Welding is

the high local energy input. This leads

followed by subjecting them to strong

usually carried out with alternating cur-

to considerable softening of the zone

compression. A weld upset is thus de-

rent and argon which is cheaper. This is

adjacent to the weld which is also the

veloped and, if necessary, subsequently

primarily a manual welding process but

case with MIG welding. TIG welding, for

machined. The heating is done by rotat-

there is a possibility to work with a full

example, is an excellent process for the

ing one or both parts and finally press-

degree of mechanisation. In TIG weld-

repair of small casting defects. Com-

ing them against each other until they

ing, the power source and the burner are

pared with the MIG process, however,

stop moving. It even allows workpieces

both water-cooled. By using alternating

TIG welding operates at lower speeds.

of circular and square cross-sections to

current, the tenacious and high-melting

be joined together.

oxide layer is broken open during welding, similar to the MIG process. Weld-

As a result of the rotary movement and

ing normal diameter material with direct

in order to keep the compression load

current and a reverse-polarity tungsten

from increasing too much, a certain cross-

electrode would lead to destruction due

sectional area may not be exceeded.

to electric overload. The electrode diameter, however, can not be increased since

Another welding process is represented

the current density required for welding

by electron beam welding. Particular in-

is no longer sufficient.

terest is being shown in this process at the moment for the welding of aluminium pressure die castings.

46 Aluminium Casting Alloys

The process operates mostly under high

Weld preparation

vacuum. There are also process variants

A great danger in welding is the tendency of many materials to form cracks during

which work under partial vacuum and

To produce a sound weld, it is necessary

the transition from liquid to solid state.

atmosphere although in these the advan-

to observe certain “rules”. Weld prepa-

The cause of these cracks is weld shrink-

tages of this welding process, namely the

ration must match the welding process

age stresses which occur during cooling.

production of narrower seams even with

being used and the wall thicknesses to

Often the low melting point phases of

thick workpieces, are extensively lost.

be joined. Excessive oxide formation is

the weld filler materials are insufficient

worked off by metal-cutting. When grind-

to “heal” the cracks arising. Through the

The welding of workpieces takes place

ing, resin-bonded grinding discs may

selection of a softer weld filler material

without filler material. The welding en-

not be used (danger of pore formation).

with a larger share of low melting point phases, this danger is reduced. In do-

ergy is imparted by means of a bundled electron beam which is directed at the

Another possible way of removing ox-

ing this, however, the optimum strength

welding point. The electron beams are

ides is to etch the component. Grease

properties in the weld seam must be

generated like those of a cathode ray

and dirt in the welding area have to be

frequently foregone.

tube (television) in a high vacuum. Using

removed using suitable means (danger

electron-optical focussing, different dis-

of pore formation). Components with

The decorative anodisation of a welded

tances to the workpiece can be had with

greater wall thicknesses to be joined

joint with the aforementioned filler ma-

this equipment, even when the workpiece

should be pre-heated before welding.

terials is not possible because the weld

has undulating contours. Welding inside

seam would appear dark. Technical an-

closed containers is possible.

odic oxidation for protective and adhesive Weld filler materials

purposes is, however, always possible.

In addition to difficult-to-weld pressure die castings, e.g. inlet manifolds, this

Weld filler materials are standardised.

process has been successfully used with

The selection of weld filler materials is

cast semi-finished products in heat ex-

guided by the materials of the parts to

changers and in the welding of pistons

be joined. For the most commonly used

for internal combustion engines.

aluminium materials, such as near- and hypoeutectic AlSi casting alloys as well as age-hardenable Al Si10Mg and Al Si5Mg variants, S-Al Si12 and S-Al Si5 weld filler materials are recommended.

Aluminium Casting Alloys 47

Surface treatment: corrosion and corrosion protection

Aluminium casting alloys â&#x20AC;&#x201C; like wrought

slightly alkaline media (e.g. ammonia

remove the oxide film completely and,

aluminium alloys â&#x20AC;&#x201C; owe their corrosion

solutions) since magnesium oxide in

as a rule, act as a preparation to further

resistance to a thin, tenacious coating

contrast to aluminium oxide is insoluble

surface treatment. Possible sources of

layer of oxides and hydroxides. In the pH

in alkaline solutions.

defects leading to subsequent faults

range from 4.5 to 8.5, this oxide layer is

comprise the use of brushes made of

practically insoluble in aqueous media

Copper as an alloying element causes

brass or non-stainless steel as well as

and aluminium casting materials suffer

a deterioration in corrosion properties.

sand or steel shot.

only negligible mass disappearance.

This increases slightly with a rising Cucontent in the range below 0.2 % cop-

When grinding, the use of ceramic

This passivity can, however, be annulled

per, above 0.2 to 0.4 % more strongly.

grinding elements without further pre-

locally at weak points in the oxide layer

Already with a Cu-content of 0.2 %,

treatment frequently leads to good paint

due to the action of water containing

permanent action from aqueous solu-

adhesion. One precondition is that no

chloride. Since the aqueous medium,

tions containing chlorine can have a very

fines from the grinding elements are

e.g. weather, only acts periodically, a

negative effect on corrosion behaviour.

pressed into the surface of the cast-

protective oxide layer forms again at

The negative influence of iron on cor-

ing. Chemical degreasing agents with

small, local corrosion sites, e.g. repas-

rosion behaviour is not as distinctive

a pickling or etching effect remove the

sivation occurs. Deep pitting corrosion

as that of copper. With an Fe-content

oxide layer and, as a consequence, all

can only arise when there is a long-term

of up to 0.6 %, there is no significant

impurities. It is also worth mentioning

effect from aggressive water contain-

deterioration in the corrosion behaviour

that there is also matt or bright pickling

ing chloride (e.g. sea water). Beside the

of casting alloys.

before anodic oxidation to produce a

chloride content, the amount of oxygen

special surface finish.

in the water also plays a role; corrosion

The surface treatment of aluminium cast

reaction can only occur in neutral me-

products is carried out to improve their

Following the alkaline pickling of AlMg

dia (pH = 4.5-8.5) in the presence of

corrosion resistance, for decorative

or AlSi casting alloys, the pickling film

oxygen. The remedy for this can come

purposes or to increase the strength

must be removed by means of an acid

in the form of passive protection by

of the components.

after-treatment with nitric acid, nitric/

coating or by means of active cathodic

hydrofluoric acid or sulphuric/hydro-

corrosion protection using a sacrificial

A homogeneous, non-porous cast struc-

fluoric acid. Instead of alkaline pickling

anode, for example.

ture free from shrink holes and cracks

with final dipping, it is more beneficial

makes coating easier. The quality of the

to use an acidic fluoride-containing

Magnesium as an alloying element

coating is influenced decisively by the

pickling solution immediately.

causes the formation of a thicker oxide

pre-treatment.

layer containing MgO and, consequently, provides greater corrosion protection

Wiping, immersion and steam degreas-

against water containing chlorides and

ing (in that order) produce increasingly grease-free surfaces without removing the surface oxide film. Grinding, brushing, abrasive blasting or polishing do not

48 Aluminium Casting Alloys

Despite careful acid cleaning, a lac-

Of the unlimited number of application

The possibility of producing coloured

quered aluminium surface can still dis-

techniques used for volume lacquering,

oxide layers also exists by means of dip

play adhesive failure after a certain time

electrostatic powder coating, whirl sin-

painting, electrolytic colouring and in-

due to environmental effects. Firstly,

tering and electrophoretic dip coating

tegral colouring in special electrolytes

a conversion layer, which forms as a

are to be stressed in particular because

(integral process).

result of the reaction between chemi-

of their environmental soundness, in

cals containing chrome and the metal,

addition to the dip coating and spray-

For surfaces which have to meet particular

passivates the aluminium surface and

ing (air, airless and electrostatic) of wet

requirements with regard to hardness,

protects it from the water diffused by

paint containing solvents.

resistance to abrasion and wear, sliding capacity and electric strength, the

each layer of lacquer. With respect to the promotion of adhesion and corro-

With the aid of anodic oxidation, the

special possibility of using hard anodis-

sion inhibition, the almost equivalent

finish achieved using mechanical or

ing should be taken into consideration.

green and yellow chromate coatings

chemical surface treatment can be con-

have proved their worth over many

served permanently. These anodically

years. A clear chromate coating, pref-

produced oxide layers are connected

erably used under clear lacquer, offers

solidly to the aluminium and, in contrast

slightly less corrosion protection due

to lacquering, the surface structure of

to the layer being thinner. Cr-VI-free

the original metal is unchanged. This

chromate-phosphate coatings meet the

can prove disadvantageous, especial-

requirements of food processing and

ly in pressure die casting. In todayâ&#x20AC;&#x2DC;s

distribution laws and are permitted for

widely-used sulphuric acid anodising

the pre-treatment of aluminium which

process, the anodically-formed oxide

is used in food production, processing

layers become resistant to touch (e.g.

and packaging.

finger marking) and abrasion resistant after sealing in hot water and possess

A chrome-free epoxy primer should

good electric strength. The appearance

be mentioned as a possible but also

of anodically-oxidised aluminium cast-

qualitatively less favourable alternative.

ings is considerably influenced by the

A precondition for the effectiveness of

alloy composition and the microstruc-

this alternate process, however, is also

tural condition. For decorative purposes,

the removal of the aluminium oxide layer

Al Mg3H, Al Mg3, Al Mg3Si, Al Mg5,

by chemical or mechanical means.

Al Mg5Si and Al 99.5 and/or Al 99.7 casting alloys have proved their worth. A decorative anodic oxidation of alloys with an Si-content > 1 % is not possible (with the exception of Al Si2MgTi).

Aluminium Casting Alloys 49

Information on physical data, strength properties and strength calculations

The SI unit for force is the Newton (N).

The actual values reached in the casting

Strength at varying temperatures

Strength, or proof stress, is expressed in

depend on the casting/technical meas-

“MPa” (Mega Pascal). The Brinell hard-

ures taken, the solidification speed and

At low temperatures, the strength and

ness of aluminium parts is excluded from

also, where applicable, the heat treat-

elongation values of aluminium parts

this regulation.

ment. When the end product has to meet

scarcely change. Due to the crystal

special requirements, an appropriate

structure of aluminium alloys, no sharp

For the tensile strength, 0.2 proof stress,

casting alloy is required which, corre-

decrease in impact ductility can occur

elongation and Brinell hardness of cast-

spondingly, also incurs higher casting/

at low temperatures – as can happen

ings, DIN EN 1706 contains only binding

technical expenses. A few details for

with some ferrous metals.

minimum values at room temperature

calculating the strength of constructions

for separately-cast test bars using sand

which are subjected to static stress are

At higher temperatures, the strength and

casting, gravity die casting and invest-

given below. With dynamic stress, lower

hardness values decrease while elonga-

ment casting. The mechanical values

values are estimated.

tion increases. Up to approx. +150 °C, these changes are relatively small. With

for pressure die cast samples are not binding and are included only for infor-

•

mation. The values for fatigue strength or endurance are valid for the best avail-

•

able casting process and again are only for information. For samples taken from

•

Surface pressure:

further increases in temperature, strength

p = approx. 0.8 Rp0,2 [MPa]

and hardness decrease even more and

Shear strength:

elongation rises. Table 6 depicts the 0.2

B = approx. 0.5 Rp0,2 [MPa]

proof stress values for gravity die cast

Modulus of elasticity in shear:

samples at various test temperatures.

the casting, DIN EN 1706 sets out the

G = approx. 0.4 modulus of

following: with respect to the 0.2 proof

elasticity [GPa]

stress and tensile strength, the values reached in castings can be above the

•

Modulus of elasticity: E = approx. 70 GPa

set values in the tables (for separatelycast test pieces) but not below 70 % of Table 6

these set values. With regard to elongation, the values determined for the castings can be above the set values

Yield strength of gravity die cast samples Alloy / Temper

Yield strength Rp0,2 [MPa]

in the tables (for separately-cast test

-100 °C

+20 °C

+200 °C

+250 °C

140

100

110

100

150

100

170

100

200

170

210

180

220

210

200

220

210

200

pieces) or at certain critical points up

Al Mg3Si

160

150

to 50 % below these values. Individual

Silumin

120

details about the mechanical, physical

Al Si12Cu

110

and other properties as well as the ap-

Al Si8Cu3

120

proximate working figures can be taken

Silumin-Kappa

from the casting alloy sheets.

Al Mg5Si

130

120

Al Si18CuNiMg

180

170

Al Si12CuNiMg

200

190

Al Si10MgCu

220

Pantal 7

215

Silumin-Beta

Pantal 5

50 Aluminium Casting Alloys

+100 °C

Notes on the casting alloy tables

The following tables contain all standard-

The following designation

Chemical composition

ised casting alloys in accordance with

abbreviations are used in DIN EN 1676:

(all data in wt.-%)

DIN EN 1676 as well as other common

Aluminium

non-standardised alloys with details of

Ingots (solid or liquid metal)

their chemical composition. Provided that

Casting characteristics and other properties

deviations are envisaged for castings,

In DIN EN 1706, the following

the corresponding details (in conformity

abbreviations refer to product

with DIN EN 1706) are shown in brackets.

designations:

Where available, the well-known and very

Aluminium casting alloy

Mechanical properties at room

commonly used VDS numbers (e.g. 231,

Casting

temperature +20 째C

Physical properties

226 etc.) are given in these lists. The following abbreviations are used

Heat treatment of aluminium

The aluminium casting alloys are arranged

for the various casting processes:

castings

into seven families according to their typi-

Sand casting

cal casting and alloying similarities. The

Gravity die casting

Mechanical properties of gravity

data, properties, rankings and standard

Pressure die casting

die cast samples

values of the casting alloys, or the castings

Precision casting Processing guidelines

subsequently made from them, have been taken from DIN EN 1676 and 1706 or are

In DIN EN 1706, the following symbols

based on these standards in the case of

apply for material conditions:

non-standardised alloys. The details are

as cast

included for information only and do not

annealed

represent any guarantees.

controlled cooling from casting

Thermal and electrical conductivity are

solution heat-treated and natu-

and naturally aged dependent on the chemical composition within the given specification, solidifica-

rally aged where applicable T5

tion conditions and temper. In order to produce a casting with high conductivity,

and artificially aged or over-aged T6

it is necessary to keep the content of alloying and accompanying elements low

controlled cooling from casting solution heat-treated and fully artificially aged

T64 solution heat-treated and artificially

within the specification.

under-aged T7

solution heat-treated and artificially over-aged (stabilised)

Aluminium Casting Alloys 51

Overview: Aluminium casting alloys by alloy group

Eutectic aluminium-silicon casting alloys Chemical composition (all data in wt.-%) Alloy Numerical denomination 1) / VDS-No. Silumin Al Si12(a)

0.15

0.02

0.05

0.40 (0.55)

0.03 (0.05)

0.35

0.55

0.10 (0.65)

0.55 (0.15)

Other indiv. total Others

0.07

0.15

0.03

0.10

0.15

0.05

0.15

0.15 (0.20)

0.05

0.15

0.05

0.25

0.30

0.15

0.05

0.25

min max

12.5 13.5

min max

10.5 13.5

min max

10.5 13.5

min max

10.5 13.5

0.45 0.9 (1.0)

0.08 (0.10)

0.55

min max

10.0 13.5

0.45 0.9 (1.0)

0.18 (0.20)

0.55

0.40

min max

10.5 13.5

0.7 (0.8)

0.9 (1.0)

0.05 0.55

0.35

0.10

0.30

0.55

0.20

0.10

0.15 (0.20)

0.05

0.25

min max

10.5 13.5

0.6 1.1 (1.3)

0.7 1.2

0.55

0.35

0.10

0.30

0.55

0.20

0.10

0.15 (0.20)

0.05

0.25

44200 / 230 Al Si12(b)

0.10

0.15

0.10

44100 Al Si12(Fe)(a)

44300 / 230D Al Si12(Fe)(b)

44500 Al Si12(Cu)

47000 / 231 Al Si12Cu1(Fe)

47100 / 231D Values in brackets are valid for castings according to DIN EN 1706: 2010 1) According to DIN EN 1676: 2010

Near-eutectic wheel casting alloys Chemical composition (all data in wt.-%) Alloy Numerical denomination 1) Silumin-Kappa Sr Silumin-Beta Sr Al Si11

Other indiv. total Others

min max

10.5 11.0

0.15

0.02

0.10

0.05 0.25

0.07

0.15

0.03

0.10

min max

9.0 10.5

0.15

0.02

0.10

0.20 0.45

0.07

0.15

0.03

0.10

min max

10.0 11.8

0.15 (0.19)

0.03 (0.05)

0.10

0.45

0.07

0.15

0.03

0.10

44000 Values in brackets are valid for castings according to DIN EN 1706: 2010 1) According to DIN EN 1676: 2010

52 Aluminium Casting Alloys

The 10 per cent aluminium-silicon casting alloys Chemical composition (all data in wt.-%) Alloy Numerical denomination 1) / VDS-No.

Silumin-Beta / Al Si9Mg min

9.0

max

10.0

0.15 (0.19)

0.03 (0.05)

0.10

0.30 (0.25) 0.45 (0.45)

0.07

Other indiv. total Others

0.15

0.03

0.10

43300 Al Si10Mg(a)

min

9.0

max

11.0

min

9.0

max

11.0

0.45 (0.55)

min

9.0

0.45

max

11.0

0.9 (1.0)

min

9.0

max

11.0

min max

8.0 11.0

min max

0.40 (0.55)

0.03 (0.05)

0.45

0.25 (0.20) 0.45 (0.45)

0.05

0.10

0.05

0.15

0.05

0.15

0.05

0.10

0.05

0.15

0.05

0.15

0.05

0.15 (0.20)

0.05

0.15

0.35

0.10

0.15 (0.20)

0.05

0.15

0.05

0.15

0.05

0.15

0.05

0.15

43000 / 239 Al Si10Mg(b)

0.08 (0.10)

0.45

0.25 (0.20) 0.45 (0.45)

43100 Al Si10Mg(Fe)

0.08 (0.10)

0.55

0.25 (0.20) 0.50 (0.50)

43400 / 239D Al Si10Mg(Cu)

0.25 (0.20) 0.45 (0.45)

0.55 (0.65)

0.30 (0.35)

0.55

0.55 (0.65)

0.08 (0.10)

0.50

0.10

9.0 10.5

0.3 0.4

0.02

0.3 0.4

0.03

0.07

0.15

0.03

0.10

min max

9.0 11.3

0.15

0.02

0.4 0.9

0.15 0.6

0.10

0.15

0.03

0.10

min

9.0

0.40

max

11.5

0.15 (0.10) 0.60 (0.60)

0.07

0.15 (0.20)

0.05

0.15

43200 / 233 Al Si9

0.05

44400 Silumin-Delta Silumin-Gamma Al Si10MnMg

0.20 (0.25)

0.03 (0.05)

0.80

43500 Values in brackets are valid for castings according to DIN EN 1706: 2010 1) According to DIN EN 1676: 2010

Aluminium Casting Alloys 53

Overview: Aluminium casting alloys by alloy group

The 7 und 5 per cent aluminium-silicon casting alloys Chemical composition (all data in wt.-%) Alloy Numerical denomination 1) / VDS-No. Pantal 7 / Al Si7Mg0.3

min

6.5

max

7.5

min

6.5

max

7.5

min

6.5

max

7.5

min max

0.15 (0.19)

0.03 (0.05)

0.10

0.30 (0.25) 0.45 (0.45)

Other indiv. total Others

0.07

0.18 (0.25)

0.03

0.10 Na / Sr

0.07

0.18 (0.25)

0.03

0.10

0.20 (0.25)

0.05

0.15

42100 Al Si7Mg0.6

0.15 (0.19)

0.03 (0.05)

0.10

0.50 (0.45) 0.70 (0.70)

42200 Al Si7Mg

0.25 (0.20) 0.65 (0.65)

0.45 (0.55)

0.15 (0.20)

0.35

0.15

0.05

5.0 6.0

0.15

0.02

0.10

0.40 0.80

0.07

0.05 0.20

0.03

0.10

min max

5.0 6.0

0.3

0.03

0.4

0.40 0.80

0.10

0.05 0.20

0.05

0.15

min

4.5

max

5.5

0.20 (0.25)

0.05

0.15

min

6.5

max

7.5

0.20

0.03

0.10

42000 Pantal 5 Al Si5Mg - / 235 Al Si5Cu1Mg

1.0 0.55 (0.65)

1.5

0.55

0.40 (0.35) 0.65 (0.65)

0.25

0.15

0.05

45300 Al Si7Cu0.5Mg

0.2 0.25

0.7

0.15

45500 Values in brackets are valid for castings according to DIN EN 1706: 2010 1) According to DIN EN 1676: 2010

54 Aluminium Casting Alloys

0.25 (0.20) 0.45 (0.45)

0.07

Al SiCu casting alloys Chemical composition (all data in wt.-%) Alloy Numerical denomination 1) / VDS-No. Al Si8Cu3

2.0

0.15 0.65

0.15 (0.05) 0.55 (0.55)

min

7.5

max

9.5

0.7 (0.8)

3.5

min

8.0

0.6

2.0

max

11.0

1.1 (1.3)

4.0

0.55

min max

10.0 12.0

0.45 1.0 (1.1)

1.5 2.5

0.55

0.30

min

6.5

3.0

0.20

max

8.0

4.0

0.65

0.35 (0.30) 0.60 (0.60)

min

8.3

0.8

0.15

max

9.7

0.7 (0.8)

1.3

0.55

min

8.0

0.6

2.0

max

11.0

1.2 (1.3)

4.0

0.55

min max

6.0 8.0

1.5 2.5

0.15 0.65

0.35

min max

5.0 7.0

3.0 5.0

0.20 0.65

0.55

min

4.5

max

6.0

min max

4.5 6.0

Other indiv. total Others

0.35

1.2

0.25

0.15

0.20 (0.25)

0.05

0.25

0.15

0.55

1.2

0.35

0.15

0.20 (0.25)

0.05

0.25

0.15

0.45

1.7

0.25

0.15

0.20 (0.25)

0.05

0.25

0.30

0.65

0.15

0.10

0.20 (0.25)

0.05

0.25

0.20

0.8

0.10

0.18 (0.20)

0.05

0.25

0.55

3.0

0.35

0.15

0.20 (0.25)

0.05

0.25

0.35

1.0

0.25

0.15

0.20 (0.25)

0.05

0.15

0.45

2.0

0.30

0.15

0.20 (0.25)

0.05

0.35

0.10

0.20

0.10

0.05

0.20 (0.25)

0.05

0.15

0.10

0.20

0.10

0.05

0.20 (0.25)

0.05

0.15

46200 / 226 Al Si9Cu3(Fe)

0.15 (0.05) 0.55 (0.55)

46000 / 226D Al Si11Cu2(Fe)

46100 Al Si7Cu3Mg

0.7 (0.8)

46300 Al Si9Cu1Mg

0.30 (0.25) 0.65 (0.65)

46400 Al Si9Cu3(Fe)(Zn)

0.15 (0.05) 0.55 (0.55)

0.15

46500 / 226/3 Al Si7Cu2

0.7 (0.8)

46600 Al Si6Cu4

0.9 (1.0)

0.15

45000 / 225 Al Si5Cu3Mg

2.6 0.50 (0.60)

3.6

0.55

2.6 3.6

0.55

0.20 (0.15) 0.45 (0.45)

45100 Al Si5Cu3

0.50 (0.60)

0.05

45400 Values in brackets are valid for castings according to DIN EN 1706: 2010 1) According to DIN EN 1676: 2010

Aluminium Casting Alloys 55

Overview: Aluminium casting alloys by alloy group

AlMg casting alloys Chemical composition (all data in wt.-%) Alloy Numerical denomination 1) / VDS-No. Al Mg3(H) Al Mg3

min max

0.45

0.15

0.02

0.40

2.7 3.2

min max

2.7 (2.5) 3.5 (3.5)

Other indiv. total Others

0.07

0.02

0.03

0.10 B/Be

0.10

0.15 (0.20)

0.05

0.15 B/Be

0.45 (0.55)

0.40 (0.55)

0.03 (0.05)

0.45

min max

0.60

0.55

0.15

0.45

2.5 3.2

0.30

0.20

0.05

0.15 B/Be

min max

0.9 1.3

0.15

0.02

0.40

2.7 3.2

0.07

0.15

0.03

0.10 B/Be

0.10

0.15 (0.20)

0.05

0.15 B/Be

0.10

0.15 (0.20)

0.05

0.15 B/Be

0.07

0.15

0.03

0.10 B/Be

0.15 (0.20)

0.05

0.15 B/Be

0.20 (0.25)

0.05

0.15

0.05

0.15

51100 / 242 Al Mg3(Cu) - / 241 Al Mg3Si(H) Al Mg5

min max

0.35 (0.55)

0.45 (0.55)

0.05 (0.10)

0.45

4.8 (4.5) 6.5 (6.5)

51300 / 244 Al Mg5(Si)

min max

1.3 (1.5)

0.45 (0.55)

0.03 (0.05)

min max

1.7 2.5

0.50

0.02

0.45

4.8 (4.5) 6.5 (6.5)

51400 / 245 Al Mg9(H) Al Mg9

min

0.2 0.5

0.45

max

2.5

min

1.8

max

2.6

min

1.6

max

2.4 (0.60)

0.9 (1.0)

0.08 (0.10)

0.55

8.5 10.5 8.5 (8.0) 10.5 (10.5)

0.10

0.25

0.10

51200 / 349 Al Mg5Si2Mn

0.4 0.20 (0.25)

0.03 (0.05)

0.8

5.0 (4.7) 6.0 (6.0)

0.07

51500 Al Si2MgTi

0.30 0.50 (0.10)

0.08

0.50 (0.65)

41000 Values in brackets are valid for castings according to DIN EN 1706: 2010 1) According to DIN EN 1676: 2010

56 Aluminium Casting Alloys

0.50 (0.45) 0.65

0.05

0.10

0.05

0.07 (0.05) 0.15 (0.20)

Casting alloys for special applications Chemical composition (all data in wt.-%) Alloy Numerical denomination 1) / VDS-No.

Other indiv. total Others

High-strength casting alloys Al Cu4Ti

min max

4.2 0.15 (0.18)

0.15 (0.19)

5.2

0.55

0.15 (0.15) 0.25 (0.30)

0.07

0.03

0.10

0.03

0.10

0.03

0.10

0.03

Ag 0.4 0.10 1.0

21100 Al Cu4MgTI

min max

4.2 0.15 (0.20)

0.30 (0.35)

0.20 (0.15) 0.35 (0.35)

5.0

0.10

4.0

0.20

5.0

0.50

4.0

0.01

0.15

5.2

0.50

0.35

4.5

0.1

5.2

0.3

0.05

0.10

0.05

0.03 (0.05)

0.05 (0.10)

0.03

0.15 (0.15) 0.25 (0.30)

21000 Al Cu4MnMg

min max

0.10

0.15 (0.20)

0.20 (0.15) 0.50 (0.50)

0.05 (0.10)

21200 Al Cu4MgTiAg

min max

Al Cu5NiCoSbZr

0.05

0.10

min max

0.20

0.30

0.5 0.05 1.3

0.10

1.7

0.9 (0.8) 1.5 (1.5)

0.7

0.35 0.15

****

0.10

0.30

0.05

0.15

1.3

0.35

0.20 (0.25)

0.05

0.15 P

0.8 1.3

0.10

0.15

0.05

0.15 P

Piston casting alloys Al Si12CuNiMg

min

10.5

max

13.5

min max

17.0 19.0

0.8 0.6 (0.7)

1.5

0.35

0.8 1.3

0.10

48000 / 260 Al Si18CuNiMg

0.3

0.8 1.3

****) Co 0.10-0.40 Sb 0.10-0.30 Zr 0.10-0.30 Values in brackets are valid for castings according to DIN EN 1706: 2010 1) According to DIN EN 1676: 2010

Continuation of the table on the next page.

Aluminium Casting Alloys 57

Overview: Aluminium casting alloys by alloy group

Casting alloys for special applications Chemical composition (all data in wt.-%) Alloy Numerical denomination 1)

4.0 5.0

0.15

0.5 0.65

0.10

0.3

1.5

Other indiv. total Others

Hyper eutectic casting alloys Al Si17Cu4Mg* Al Si17Cu4Mg**

min max

16.0 18.0

min

16.0

max

18.0

0.3

4.0

0.45 (0.25) 0.65 (0.65)

0.15

0.20

0.05

0.15 P

0.20 (0.25)

0.05

0.25

1.0 (1.3)

5.0

0.50

0.15

0.02

0.05

0.3 0.5

9.5 10.5

0.15

0.03

0.10

0.30

0.3 0.5

9.5 10.5

0.15

0.03

0.10

0.25 (0.20) 0.5 (0.5)

9.0 0.15

0.05

0.15

48100 Self-hardening casting alloys Autodur

min max

8.5 9.5

Autodur (Fe)*

min max

8.5 9.5

Autodur (Fe)**

min

7.5

max

9.5

0.27 (0.30)

0.08 (0.10)

0.15

min max

0.07

0.20

0.01

0.005

0.02

0.004

0.04

Mn+Cr+ 0.03 V+Ti= 0.02

B 0.04

min max

0.10

0.30

0.01

0.007

0.02

0.005

0.04

Mn+Cr+ 0.03 V+Ti= 0.030

B 0.04

0.40

0.02

10.5

71100 Rotor-Aluminium Al 99.7E***

Al 99.6E***

*) Non-standardised version **) According to DIN EN 1706: 2010 ***) According to DIN EN 576 Values in brackets are valid for castings according to DIN EN 1706: 2010 1) According to DIN EN 1676: 2010

58 Aluminium Casting Alloys

Eutectic aluminium-silicon casting alloys

Chemical composition (all data in wt.-%) Alloy Numerical denomination 1) / VDS-No.

0.15

0.02

0.05

0.40 (0.55)

0.03 (0.05)

0.35

0.55

0.10 (0.65)

0.55 (0.15)

Other indiv. total Others

0.07

0.15

0.03

0.10

0.15

0.05

0.15

0.15 (0.20)

0.05

0.15

0.05

0.25

0.30

0.15

0.05

0.25

Silumin

min max

12.5 13.5

Al Si12(a)

min max

10.5 13.5

min max

10.5 13.5

min max

10.5 13.5

0.45 0.9 (1.0)

0.08 (0.10)

0.55

min max

10.0 13.5

0.45 0.9 (1.0)

0.18 (0.20)

0.55

0.40

min max

10.5 13.5

0.7 (0.8)

0.9 (1.0)

0.05 0.55

0.35

0.10

0.30

0.55

0.20

0.10

0.15 (0.20)

0.05

0.25

min max

10.5 13.5

0.6 1.1 (1.3)

0.7 1.2

0.55

0.35

0.10

0.30

0.55

0.20

0.10

0.15 (0.20)

0.05

0.25

44200 / 230 Al Si12(b)

0.10

0.15

0.10

44100 Al Si12(Fe)(a)

44300 / 230D Al Si12(Fe)(b)

44500 Al Si12(Cu)

47000 / 231 Al Si12Cu1(Fe)

47100 / 231D Values in brackets are valid for castings according to DIN EN 1706: 2010 1) According to DIN EN 1676: 2010

Aluminium Casting Alloys 59

Eutectic aluminium-silicon casting alloys

Casting characteristics and other properties of castings Alloy

Fluidity

Thermal crack stability

Pressure tightness

As-cast state

Ageability

Corrosion resistance

Decorative anodisation

Weldability

Polishability

Density

E-Modulus

Thermal capacity at 100 째C

Solidification temperature

Coefficient of thermal expansion

Electrical conductivity

Thermal conductivity

g/cm3

MPa

J/gK

째C

10-6/K 293 K - 373 K

MS/m

W/(m . k)

Silumin Al Si12(a) Al Si12(b) Al Si12(Fe)(a) Al Si12(Fe)(b) Al Si12(Cu) Al Si12Cu1(Fe)

Physical properties Alloy

Silumin

2.68

75,000

0.91

~ 577

18 - 24

140 - 170

Al Si12(a)

2.68

75,000

0.90

~ 577

17 - 24

140 - 170

16 - 23

130 - 160

2.68

75,000

0.90

~ 577

16 - 22

130 - 160

16 - 22

130 - 160

Al Si12(Cu)

2.70

75,000

0.89

~ 577

16 - 22

130 - 150

Al Si12Cu1(Fe)

2.70

75,000

0.89

~ 577

15 - 20

120 - 150

Al Si12(b) Al Si12(Fe)(a) Al Si12(Fe)(b)

60 Aluminium Casting Alloys

Mechanical properties at room temperature +20 °C Alloy / Temper

Casting method

Tensile strength Rm Yield strength Rp0,2 Elongation A MPa

MPa

Brinell hardness HB

Fatigue resistance MPa

min

Silumin

Sand casting

150

60 - 90

Al Si12(a)

Sand casting

150

60 - 90

Al S12(b)

Sand casting

150

Al Si12(Cu)

Sand casting

150

60 - 90

Silium

Gravity die casting

170

60 - 90

Al Si12(a)

Gravity die casting

170

60 - 90

Al Si12(Cu)

Gravity die casting

170

60 - 90

Al Si12(Fe)(a)

Pressure die casting 240

130

60 - 90

Al Si 12(Fe)(b)

Pressure die casting 240

140

Al Si12Cu1(Fe)

Pressure die casting 240

140

60 - 90

The values apply for separately-cast sample bars in sand and gravity die casting. Mechanical properties of pressure die casting samples are not binding and merely serve as information. The values representing vibration testing and/or fatigue strength apply for the best available casting process and merely serve as information.

Mechanical properties of gravity die casting samples 1) Alloy / Temper

Tensile strength Rm MPa

Yield strength Rp0,2 MPa

Elongation A %

Brinell hardness HB

-100°C +20°C +100°C +200°C -100°C +20°C +100°C +200°C -100°C +20°C +100°C +200°C -100°C +20°C +100°C +200°C Silumin

220

180

150

110

120

Al Si12(a)

220

180

150

110

120

2,5

Al Si12(b)

220

180

150

110

120

2.5

190

170

110

100

Al Si12(Cu)

3.4

1) Mechanical properties in minimum values / values after long-term maintenance of the respective temperature.

Typical process parameters Alloy

Casting temperature Sand Gravity casting die casting

Pressure die casting

Contraction allowance Sand Gravity casting die casting

Pressure die casting

°C

620 - 660

1.0 - 1.2

0.5 - 0.8

1.0 - 1.2

0.5 - 0.8

1.0 - 1.2

0.5 - 0.8

Silumin

670 - 740

Al Si12(a)

670 - 740

Al Si12(Fe)(a) Al Si12(Cu) Al Si12Cu1(Fe)

620 - 660

0.4 - 0.6

Aluminium Casting Alloys 61

Eutectic aluminium-silicon casting alloys

Application notes

The shell thickness does not decrease.

Heat treatment

If the flow of liquid metal is interrupted Universal aluminium casting alloy with

in the middle wall region during feeding,

In the case of sand and gravity die cast-

medium strength; in part, very good elon-

a coarse cavity can evolve. (Additional

ings made from casting alloys low in

gation and very good flow properties.

notes also provided in the sections en-

Cu and Mg, a selective improvement

Suitable for thin-walled, complicated,

titled “Influencing the microstructural

in ductility can be achieved. This is ef-

pressure-tight, vibration- and impact-

formation of aluminium castings” and

fected by means of solution annealing at

resistant constructions.

“Avoiding casting defects”.)

520-530 °C with subsequent quenching in cold water.

Properties and processing

This type of aluminium casting alloy can only be modified with sodium. Sodium

Comments

From the range of AlSi casting alloys,

modification is indicated for sand cast-

this type of alloy containing 13 % silicon

ings and gravity die castings if particular

The DIN EN 1676 and DIN EN 1706

has the best fluidity. In some respects,

requirements are placed on elongation

standards allow a very wide range of

the behaviour of the casting alloys in this

of the microstructure (see Figure 2). As

major alloying elements – silicon from

range represents a special case. Some

a general rule, casting alloys for use in

10.5 to 13.5 %. The practical range for

advice is provided below.

sand and gravity die casting are offered

the silicon content is from 12.5 to 13.5

in a slightly modified version. Chemical

and, in a slightly hypoeutectic range of

In the case of free solidification, e.g. a

resistance as well as resistance to weath-

10.5 to 11.2 %. However, these two al-

dense, bevel-shaped surface, the so-

ering and a marine climate increase with

loys display entirely different solidification

called “hammer blow”, forms on the top

the purity of the casting alloy used. A pri-

behaviour. The intermediate range, with

of the ingot. This type of solidification is

mary silicon casting alloy thus meets the

approx. 11.5 to 12.5 % silicon, runs the

“shell-forming”, i.e. the crystallisation of

highest requirements in a variety of fields

risk of shrinkage cavities. Casting alloys

the subsequent casting begins with the

of application, e.g. in the food industry

in this critical range are not offered. Even

formation of a solid shell which then grows

or in shipbuilding. The elongation of the

a blend of these different yet similar-

towards the middle of the cast wall. In

cast structure is significantly determined

sounding alloys is not recommended.

this type of casting alloy, there are only

by the iron content and other impurities.

two states, i.e. “solid” and “liquid”. Full

The demand for high proof stress values

solidification of a casting takes place

in the casting often requires the use of

at the eutectic temperature of approx.

primary casting alloys with the lowest

577 °C). During the solidification process,

possible content of iron and impurities.

the volume can contract by up to 7 %.

62 Aluminium Casting Alloys

Near-eutectic wheel casting alloys

Chemical composition (all data in wt.-%) Alloy Numerical denomination 1) Silumin-Kappa Sr Silumin-Beta Sr Al Si11

Other indiv. total Others

min max

10.5 11.0

0.15

0.02

0.10

0.05 0.25

0.07

0.15

0.03

0.10

min max

9.0 10.5

0.15

0.02

0.10

0.20 0.45

0.07

0.15

0.03

0.10

min max

10.0 11.8

0.15 (0.19)

0.03 (0.05)

0.10

0.45

0.07

0.15

0.03

0.10

44000 Values in brackets are valid for castings according to DIN EN 1706: 2010 1) According to DIN EN 1676: 2010

Casting characteristics and other properties of castings Alloy

Fluidity

Thermal crack stability

Pressure tightness

As-cast state

Ageability

Corrosion resistance

Decorative anodisation

Weldability

Polishability

Density

E-Modulus

Thermal capacity at 100 째C

Solidification temperature

Coefficient of thermal expansion

Electrical conductivity

Thermal conductivity

g/cm3

MPa

J/gK

째C

10-6/K 293 K - 373 K

MS/m

W/(m . k)

Silumin-Kappa Sr

2.68

74,000

0.91

600 - 555

20 - 26

150 - 180

Silumin-Beta Sr

2.68

74,000

0.91

600 - 550

20 - 26

150 - 180

Al Si11

2.68

74,000

0.91

600 - 550

18 - 24

140 - 170

Silumin-Kappa Sr Silumin-Beta Sr Al Si11

Physical properties Alloy

Aluminium Casting Alloys 63

Near-eutectic wheel casting alloys

Mechanical properties at room temperature +20 °C Alloy / Temper

Casting method

Tensile strength Rm Yield strength Rp0,2 Elongation A MPa

MPa

Brinell hardness HB

Fatigue resistance MPa

min

Silumin-Kappa Sr

Gravity die casting

170

60 - 90

Silumin-Beta Sr

Gravity die casting

170

60 - 90

Al Si11

Gravity die casting

290

210

60 - 90

T64 Gravity die casting

250

180

60 - 90

170

60 - 90

Gravity die casting

Heat treatment of aluminium castings Alloy / Temper

Solution heat treatment temperature

Annealing time

Water temperature for quenching

Ageing tempetarure

Ageing time

°C

Silumin-Kappa Sr

520 - 535

4 - 10

160 - 170

- 8

Silumin-Beta Sr

520 - 535

4 - 10

150 - 160

- 3

Mechanical properties of gravity die casting samples 1) Alloy / Temper

Tensile strength Rm MPa

Yield strength Rp0,2 MPa

Elongation A %

Brinell hardness HB

-100°C +20°C +100°C +200°C -100°C +20°C +100°C +200°C -100°C +20°C +100°C +200°C -100°C +20°C +100°C +200°C Silumin-Kappa Sr

180

170

160

120

Silumin-Beta Sr

T64

260

250

210

120

200

180

170

4,5

Al Si11

230

170

160

130

1) Mechanical properties in minimum values / values after long-term maintenance of the respective temperature.

Typical process parameters Alloy

Casting temperature Sand Gravity casting die casting

Pressure die casting

Contraction allowance Sand Gravity casting die casting

Pressure die casting

°C

Silumin-Kappa Sr

670 - 740

1.0 - 1.2

0.5 - 0.8

Silumin-Beta Sr

670 - 740

1.0 - 1.2

0.5 - 0.8

Al Si11

670 - 740

1.0 - 1.2

0.5 - 0.8

64 Aluminium Casting Alloys

Application notes

ured by means of the elongation value,

In the course of subsequent solidifica-

for example, plays a vital role. The level

tion, aluminium dendrites grow into the

These casting alloy types have been

of the iron content and the level of the

liquid melt. They form an interconnect-

developed primarily for the casting of

other additions are particularly important

ing network whose intervening spaces

car wheels by means of low-pressure

quantities for the ductility or elongation

are then filled with the highly-fluid AlSi

die casting processes.

of the cast structure. On request, these

eutectic which then solidifies. If feeding

casting alloys can have a magnesium

is incomplete or the highly-fluid eutectic

content of between 0.05 and 0.45 %.

is drawn to another place, defects such

With an increasing Mg content, the al-

as sinks or microporosity occur. The so-

Properties and processing

loysâ&#x20AC;&#x2DC; strength can be improved slightly,

lidification range is approx. 30 to 45 K.

These casting alloys have good fluidity;

their elongation decreases a little with the

With this type of casting alloy, cleaning

the grain structure displays very high

level of the Mg content, their machinabil-

the melt can only be effected by means

ductility and good corrosion resistance.

ity â&#x20AC;&#x201C; with respect to chip formation, chip

of inert gas or using a vacuum. Cleaning

The casting alloy Silumin-Kappa has an

removal and surface appearance â&#x20AC;&#x201C; is

agents containing chlorine would remove

optimum silicon content of 10.5 to 11.0 %.

improved, the resistance of the casting

strontium from the melt. In practice, the

In Silumin-Beta, the silicon content ranges

to chemical attack increases, lacquer

use of purging lances or impeller equip-

from 9.0 and 10.5 % silicon. As a rule,

adherence, however, can be impaired

ment have proven their worth.

these casting alloys already undergo a

by the magnesium content. Only some

long-lasting strontium modification (HV)

of the Silumin-Beta casting alloys are

during production of the ingots. The

age-hardenable. The age hardening of

strontium addition is approx. 0.020 to

wheels made from alloys of the Silumin-

0.030 %. Normally, this smelter modifi-

Kappa type is not recommended. It could

cation does not need to be repeated at

cause partial embrittlement which would

the foundry. The modification of eutectic

reduce the fatigue strength of the material.

silicon, i.e. the formation of a modified microstructure, is a necessity since the

For wheels which have to be heat-treated,

ductility of the cast structure of the wheels

casting alloys of the Al Si7Mg (Pantal 7)

produced from these casting alloys meas-

type are recommended. The solidification characteristics of these casting alloys are hypoeutectic. During solidification, the transition is from pasty to mushy.

Aluminium Casting Alloys 65

The 10 per cent aluminium-silicon casting alloys

Chemical composition (all data in wt.-%) Alloy Numerical denomination 1) / VDS-No.

Silumin-Beta / Al Si9Mg min

9.0

max

10.0

0.15 (0.19)

0.03 (0.05)

0.10

0.30 (0.25) 0.45 (0.45)

0.07

Other indiv. total Others

0.15

0.03

0.10

43300 Al Si10Mg(a)

min

9.0

max

11.0

min

9.0

max

11.0

0.45 (0.55)

min

9.0

0.45

max

11.0

0.9 (1.0)

min

9.0

max

11.0

min max

8.0 11.0

min max

9.0 10.5

min max

9.0 11.3

min

9.0

max

11.5

0.40 (0.55)

0.03 (0.05)

0.45

0.25 (0.20) 0.45 (0.45)

0.05

0.10

0.05

0.15

0.05

0.15

0.05

0.10

0.05

0.15

0.05

0.15

0.05

0.15 (0.20)

0.05

0.15

0.35

0.10

0.15 (0.20)

0.05

0.15

0.05

0.15

0.05

0.15

0.05

0.15

43000 / 239 Al Si10Mg(b)

0.08 (0.10)

0.45

0.25 (0.20) 0.45 (0.45)

43100 Al Si10Mg(Fe)

0.08 (0.10)

0.55

0.25 (0.20) 0.50 (0.50)

43400 / 239D Al Si10Mg(Cu)

0.25 (0.20) 0.45 (0.45)

0.55 (0.65)

0.30 (0.35)

0.55

0.55 (0.65)

0.08 (0.10)

0.50

0.3 0.4

0.02

0.3 0.4

0.03

0.07

0.15

0.03

0.10

0.02

0.4 0.9

0.15 0.6

0.10

0.15

0.03

0.10

0.40

0.15 (0.10) 0.60 (0.60)

0.07

0.15 (0.20)

0.05

0.15

43200 / 233 Al Si9

0.10

0.05

44400 Silumin-Delta Silumin-Gamma Al Si10MnMg

0.15

0.20 (0.25)

0.03 (0.05)

0.80

43500 Values in brackets are valid for castings according to DIN EN 1706: 2010 1) According to DIN EN 1676: 2010

66 Aluminium Casting Alloys

Casting characteristics and other properties of castings Alloy

Fluidity

Thermal crack stability

Pressure tightness

As-cast state

Ageability

Corrosion resistance

Decorative anodisation

Weldability

Polishability

Density

E-Modulus

Thermal capacity at 100 째C

Solidification temperature

Coefficient of thermal expansion

Electrical conductivity

Thermal conductivity

g/cm3

MPa

J/gK

째C

10-6/K 293 K - 373 K

MS/m

W/(m . k)

Silumin-Beta / Al Si9Mg

2.68

74,000

0.91

600 - 555

20 - 26

150 - 180

Al Si10Mg(a)

2.68

74,000

0.91

600 - 550

19 - 25

150 - 170

Al Si10Mg(b)

2.68

74,000

0.91

600 - 550

18 - 25

140 - 170

Al Si10Mg(Fe)

2.68

74,000

0.91

600 - 550

16 - 21

130 - 150

Al Si10Mg(Cu)

2.68

74,000

0.91

600 - 550

16 - 24

130 - 170

Al Si9

2.69

74,000

0.91

605 - 570

16 - 22

130 - 150

Silumin-Delta

2.69

74,000

0.91

605 - 570

18 - 26

130 - 170

Silumin-Gamma

2.68

74,000

0.91

610 - 560

20 - 26

140 - 180

19 - 25

140 - 170

Silumin-Beta / Al Si9Mg Al Si10Mg(a) Al Si10Mg(b) Al Si10Mg(Fe) Al Si10Mg(Cu) Al Si9 Silumin-Delta Silumin-Gamma Al Si10MnMg

Physical properties Alloy

Al Si10MnMg

Aluminium Casting Alloys 67

The 10 per cent aluminium-silicon casting alloys

Mechanical properties at room temperature +20 째C Alloy / Temper

Silumin-Beta / Al Si9Mg

Al Si10Mg(a)

Al Si10Mg(b)

Al Si10Mg(Cu)

Silumin-Beta / Al Si9Mg

Al Si10Mg(a)

Al Si10Mg(b)

Casting method

Tensile strength Rm Yield strength Rp0,2 Elongation A MPa

MPa

% min

Brinell hardness HB

min

Sand casting

150

Sand casting

230

190

Sand casting

150

Sand casting

220

180

Sand casting

150

Sand casting

220

180

Sand casting

160

Sand casting

220

180

Fatigue resistance MPa

min

Gravity die casting

290

210

80 - 110

T64 Gravity die casting

250

180

80 - 110

Gravity die casting

180

2.5

80 - 110

Gravity die casting

260

220

80 - 110

T64 Gravity die casting

240

200

Gravity die casting

180

2.5

80 - 110 80 - 110

Gravity die casting

260

220

T64 Gravity die casting

240

200

Gravity die casting

180

80 - 110

Gravity die casting

240

200

80 - 110

Al Si10Mg(Fe)

Pressure die casting 240

140

60 -

Al Si9

Pressure die casting 220

120

60 -

Silumin-Delta

Pressure die casting 220

120

60 -

Silumin-Gamma

Pressure die casting 240

120

80 -

Pressure die casting 290

210

100

Al Si10Mg(Cu)

68 Aluminium Casting Alloys

Heat treatment of aluminium castings Alloy / Temper

Solution heat treatment temperature

Annealing time

Water temperature for quenching

Ageing tempetarure

Ageing time

°C

520 - 535

4 - 10

160 - 170

T64

520 - 535

4 - 10

150 - 160

520 - 535

4 - 10

160 - 170

T64

520 - 535

4 - 10

150 - 160

520 - 535

4 - 10

160 - 170

T64

520 - 535

4 - 10

150 - 160

520 - 535

4 - 10

160 - 170

500 - 530

4 -

150 - 170

T64

500 - 530

4 -

180 - 340

Silumin-Beta / Al Si9Mg T6

Al Si10Mg(a)

Al Si10Mg(b)

Al Si10Mg(Cu) Silumin-Gamma

Mechanical properties of gravity die casting samples 1) Alloy / Temper

Tensile strength Rm MPa

Yield strength Rp0,2 MPa

Elongation A %

Brinell hardness HB

-100°C +20°C +100°C +200°C -100°C +20°C +100°C +200°C -100°C +20°C +100°C +200°C -100°C +20°C +100°C +200°C Silumin-Beta / Al Si9Mg

290

260

120

220

210

200

3.5

Al Si10Mg(a)

280

260

230

120

220

170

Al Si10Mg(Cu)

280

240

210

120

220

200

180

1) Mechanical properties in minimum values / values after long-term maintenance of the respective temperature.

Typical process parameters Alloy

Casting temperature Sand Gravity casting die casting

Pressure die casting

Contraction allowance Sand Gravity casting die casting

Pressure die casting

°C

Silumin-Beta / Al Si9Mg

670 - 740

1.0 - 1.2

0.5 - 0.8

Al Si10Mg(a)

670 - 740

1.0 - 1.2

0.5 - 0.8

Al Si10Mg(b)

670 - 740

1.0 - 1.2

0.5 - 0.8

Al Si10Mg(Fe)

620 - 660

Al Si10Mg(Cu)

670 - 740

Al Si9

660 - 740

0.4 - 0.6 1.0 - 1.2

620 - 700

0.5 - 0.8 0.5 - 0.8

0.4 - 0.6

Silumin-Delta

620 - 700

0.4 - 0.6

Silumin-Gamma

620 - 730

0.4 - 0.6

Aluminium Casting Alloys 69

The 10 per cent aluminium-silicon casting alloys

Application notes

Properties and processing

This causes porous areas and also leads

This important group of casting alloys

The fluidities of these casting alloys are

section. During casting, therefore, atten-

is used for castings with medium wall

still good. Heat-treatable castings made

tion must be paid to ensure good feed-

thicknesses which require higher, to the

from alloys containing magnesium dis-

ing and, as far as possible, controlled

highest strength properties. The fields of

play particularly good machinability. With

solidification. The solidification range

application comprise mechanical and

increasing purity, the ductility of the cast

amounts to approx. 45 K.

electrical engineering, the food industry

structure also increases. Where the re-

Where requirements on elongation or

as well as in engine and motor vehicle

quirements on corrosion resistance are

ductility are higher, modification of the

construction. Silumin-Beta casting alloys

high, high-purity grades are selected.

melt is recommended. The casting alloys

are also used for car wheels. Silumin-

Sand and gravity die castings can be

for use in gravity die casting are modi-

Gamma is a heat-treatable high-pressure

artificially aged. In doing so, however,

fied with sodium or strontium. For sand

die casting alloy. However, successful

ductility decreases. The solidification

casting, modification with sodium only

treatment requires the use of an adequate

characteristics of this group of casting

is recommended. As a general rule, the

casting process (e.g. vacuum-assisted

alloys are hypoeutectic. During the so-

casting alloys for sand and gravity die

high-pressure die casting).

lidification process, aluminium dendrites

casting are offered in versions which can

grow into the melt first. The highly-fluid

be easily modified.

to a weakening of the structural cross-

AlSi eutectic then penetrates the intervening spaces of the network and clamps the microstructural framework together. If the feeding of the remaining eutectic melt is hindered in any way, defects such as sinks or micro/macrocavities occur.

70 Aluminium Casting Alloys

The 7 and 5 per cent aluminium-silicon casting alloys

Chemical composition (all data in wt.-%) Alloy Numerical denomination 1) / VDS-No. Pantal 7 / Al Si7Mg0.3

min

6.5

max

7.5

min

6.5

max

7.5

min

6.5

max

7.5

min max

5.0 6.0

min max

5.0 6.0

min

4.5

max

5.5

min

6.5

max

7.5

0.15 (0.19)

0.03 (0.05)

0.10

0.30 (0.25) 0.45 (0.45)

Other indiv. total Others

0.07

0.18 (0.25)

0.03

0.10 Na / Sr

0.07

0.18 (0.25)

0.03

0.10

0.20 (0.25)

0.05

0.15

42100 Al Si7Mg0.6

0.15 (0.19)

0.03 (0.05)

0.10

0.50 (0.45) 0.70 (0.70)

42200 Al Si7Mg

0.25 (0.20) 0.65 (0.65)

0.45 (0.55)

0.15 (0.20)

0.35

0.15

0.02

0.10

0.40 0.80

0.4

0.40 0.80

0.15

0.05

42000 Pantal 5 Al Si5Mg

0.3

0.03

0.07

0.05 0.20

0.03

0.10

0.05 0.20

0.05

0.15

0.20 (0.25)

0.05

0.15

0.20

0.03

0.10

- / 235 Al Si5Cu1Mg

1.0 0.55 (0.65)

1.5

0.55

0.40 (0.35) 0.65 (0.65)

0.25

0.15

0.05

45300 Al Si7Cu0.5Mg

0.2 0.25

0.7

0.15

0.25 (0.20) 0.45 (0.45)

0.07

45500 Values in brackets are valid for castings according to DIN EN 1706: 2010 1) According to DIN EN 1676: 2010

Aluminium Casting Alloys 71

The 7 and 5 per cent aluminium-silicon casting alloys

Casting characteristics and other properties of castings Alloy

Fluidity

Thermal crack stability

Pressure tightness

As-cast state

Ageability

Corrosion resistance

Decorative anodisation

Weldability

Polishability

Density

E-Modulus

Thermal capacity at 100 째C

Solidification temperature

Coefficient of thermal expansion

Electrical conductivity

Thermal conductivity

g/cm3

MPa

J/gK

째C

10-6/K 293 K - 373 K

MS/m

W/(m . k)

Pantal 7 / Al Si7Mg0.3

2.66

73,000

0.92

625 - 550

21 - 27

160 - 180

Al Si7Mg0.6

2.66

73,000

0.92

625 - 550

20 - 26

150 - 180

Al Si7Mg

2.66

73,000

0.92

625 - 550

19 - 25

150 - 170

Pantal 5

2.67

72,000

0.92

625 - 550

21 - 29

150 - 180

Al Si5Mg

2.67

72,000

0.92

625 - 550

21 - 26

150 - 180

Al Si5Cu1Mg

2.67

72,000

0.92

625 - 550

Pantal 7 / Al Si7Mg0.3 Al Si7Mg0.6 Al Si7Mg Pantal 5 Al Si5Mg Al Si5Cu1Mg Al Si7Cu0.5Mg

Physical properties Alloy

Al Si7Cu0.5Mg

72 Aluminium Casting Alloys

19 - 23

140 - 150

16 - 22

150 - 165

Mechanical properties at room temperature +20 째C Alloy / Temper

Casting method

Tensile strength Rm Yield strength Rp0,2 Elongation A MPa

MPa

Brinell hardness HB

min

Pantal 7 / Al Si7Mg0.3

Sand casting

230

190

Al Si7Mg0.6

Sand casting

250

210

Al Si7Mg

Sand casting

140

Sand casting

220

180

Sand casting

240

220

Sand casting

200

150

Sand casting

240

220

Sand casting

200

150

Sand casting

230

200

100

Sand casting

170

120

Pantal 5

Al Si5Mg

Al Si5Cu1Mg

Pantal 7 / Al Si7Mg0.3

Al Si7Mg0.6

min

Gravity die casting

290

210

T64 Gravity die casting

250

180

Gravity die casting

320

240

100

T64 Gravity die casting

290

210

Gravity die casting

170

2.5

Gravity die casting

260

220

Al Si7Mg

T64 Gravity die casting

240

200

Pantal 5

Gravity die casting

160

120

Gravity die casting

260

240

Gravity die casting

210

160

Gravity die casting

160

120

Gravity die casting

260

240

Gravity die casting

210

160

Gravity die casting

280

210

Gravity die casting

230

140

Gravity die casting

320

240

100

Al Si7Mg

Al Si5Mg

Al Si5Cu1Mg

Al Si7Cu0.5Mg

Fatigue resistance MPa

80 - 110

70 -

75 110

70 - 100

Aluminium Casting Alloys 73

The 7 and 5 per cent aluminium-silicon casting alloys

Heat treatment of aluminium castings Alloy / Temper

Pantal 5

Al Si5Mg

Al Si5Cu1Mg

Pantal 7 / Al Si7Mg0.3

Al Si7Mg0,6

Al Si7Mg

Solution heat treatment temperature

Annealing time

Water temperature for quenching

Ageing tempetarure °C

Ageing time

°C

520 - 535

4 - 10

520 - 535

4 - 10

520 - 535

4 - 10

520 - 535

4 - 10

520 - 535

4 - 10

520 - 535

4 - 10

155 - 165

6 - 10

520 - 545

4 - 10

155 - 165

6 - 10

T64

520 - 545

4 - 10

150 - 160

2 -

520 - 545

4 - 10

155 - 165

6 - 10

T64

520 - 545

4 - 10

520 - 545

4 - 10

T64

520 - 545

4 - 10

20 - 30

120

155 - 165 20

6 - 10

20 - 30

120

155 - 165 20

6 - 10

20 - 30

120

150 - 160

2 -

155 - 165

6 - 10

150 - 160

2 -

Mechanical properties of gravity die casting samples 1) Alloy / Temper

Tensile strength Rm MPa

Yield strength Rp0,2 MPa

Elongation A %

Brinell hardness HB

-100°C +20°C +100°C +200°C -100°C +20°C +100°C +200°C -100°C +20°C +100°C +200°C -100°C +20°C +100°C +200°C Pantal 7 / Al Si7Mg0.3

290

240

120

210

180

Pantal 5

280

260

200

120

250

240

170

Al Si5Mg

280

260

200

120

250

240

170

0.5

1) Mechanical properties in minimum values / values after long-term maintenance of the respective temperature.

Typical process parameters Alloy

Casting temperature Sand Gravity casting die casting

Pressure die casting

Contraction allowance Sand Gravity casting die casting

Pressure die casting

°C

Pantal 7 / Al Si7Mg0.3

680 - 750

1.0 - 1.2

0.7 - 1.1

Al Si7Mg0.6

680 - 750

1.0 - 1.2

0.7 - 1.1

Al Si7Mg

680 - 750

1.0 - 1.2

0.7 - 1.1

Pantal 5

690 - 760

1.1 - 1.2

0.8 - 1.1

Al Si5Mg

690 - 760

1.1 - 1.2

0.8 - 1.1

Al Si5Cu1Mg

690 - 760

1.0 - 1.2

0.8 - 1.1

74 Aluminium Casting Alloys

Application notes

Properties and processing

magnesium content which ranges from

These casting alloys are used in the

Owing to the low silicon content, fluid-

sibility of adjusting the elongation of the

motor vehicle industry (chassis compo-

ity is only moderate. Castings with very

castings to the particular requirements.

nents, motor car and lorry wheels), for

thin walls can not, therefore, be cast in

With a low magnesium content of around

components in the aerospace industry,

these alloys. This group of casting al-

0.25 %, relatively high elongation values

for parts in mechanical engineering, for

loys containing around 7 % silicon is in

can be achieved. Where greater hardness

hydraulic elements, in the food industry,

some respects an exception. Looking

is required, casting alloys with a mag-

in shipbuilding, for fittings and apparatus

at a micrograph, it can be seen that the

nesium content of 0.70 % can be used.

as well as for fire extinguisher compo-

proportion by area of light matrix (i.e.

nents. Their use makes particular sense

the aluminium-rich solid solution) and

The group of casting alloys with approx.

when the castings undergo age harden-

the proportion by area or eutectic silicon

5 % silicon displays many sequences

ing. As a result of age hardening, these

(i.e. the dotted grey areas) each amount

and properties which are similar to the

casting alloys are used in structures

to approx. 50 %. Like in all hypoeutectic

7 per cent group. The solidification range

requiring high strength. In addition, the

AlSi casting alloys, solidification takes

is slightly greater, fluidity is slightly less.

cast structure â&#x20AC;&#x201C; particularly of primary

place in phases. First of all, the dendritic

Due to the lower silicon content, the ef-

casting alloys â&#x20AC;&#x201C; still displays remarkable

network made up of aluminium-rich solid

fect of the aluminium-rich solid solution

toughness and ductility. Resistance to

solution grows into the still liquid melt.

dominates. The casting alloy variants

chemical attack increases with purity

The remaining highly-fluid eutectic melt

with low copper content display the best

and is very good in the case of primary

infiltrates this sponge and locks the struc-

possible corrosion-resistance behaviour

casting alloys.

ture together like in a two-component

of all aluminium-silicon casting alloys.

composite. By means of age-harden-

Castings made from these alloys find

ing, the aluminium-rich solid solution

application in such areas as the food

in particular is strengthened while the

industry, in domestic appliances or in

connecting eutectic remains ductile. In

parts for the food processing industry.

0.20 to 0.70 % gives the user the pos-

this way, the ideal microstructure occurs, giving the highest possible strength with still acceptable elongation. The variable

Aluminium Casting Alloys 75

Al SiCu casting alloys

Chemical composition (all data in wt.-%) Alloy Numerical denomination 1) / VDS-No. Al Si8Cu3

2.0

0.15 0.65

0.15 (0.05) 0.55 (0.55)

min

7.5

max

9.5

0.7 (0.8)

3.5

min

8.0

0.6

2.0

max

11.0

1.1 (1.3)

4.0

0.55

min max

10.0 12.0

0.45 1.0 (1.1)

1.5 2.5

0.55

0.30

min

6.5

3.0

0.20

max

8.0

4.0

0.65

0.35 (0.30) 0.60 (0.60)

min

8.3

0.8

0.15

max

9.7

0.7 (0.8)

1.3

0.55

min

8.0

0.6

2.0

max

11.0

1.2 (1.3)

4.0

0.55

min max

6.0 8.0

1.5 2.5

0.15 0.65

0.35

min max

5.0 7.0

3.0 5.0

0.20 0.65

0.55

min

4.5

max

6.0

min max

4.5 6.0

Other indiv. total Others

0.35

1.2

0.25

0.15

0.20 (0.25)

0.05

0.25

0.15

0.55

1.2

0.35

0.15

0.20 (0.25)

0.05

0.25

0.15

0.45

1.7

0.25

0.15

0.20 (0.25)

0.05

0.25

0.30

0.65

0.15

0.10

0.20 (0.25)

0.05

0.25

0.20

0.8

0.10

0.18 (0.20)

0.05

0.25

0.55

3.0

0.35

0.15

0.20 (0.25)

0.05

0.25

0.35

1.0

0.25

0.15

0.20 (0.25)

0.05

0.15

0.45

2.0

0.30

0.15

0.20 (0.25)

0.05

0.35

0.10

0.20

0.10

0.05

0.20 (0.25)

0.05

0.15

0.10

0.20

0.10

0.05

0.20 (0.25)

0.05

0.15

46200 / 226 Al Si9Cu3(Fe)

0.15 (0.05) 0.55 (0.55)

46000 / 226D Al Si11Cu2(Fe)

46100 Al Si7Cu3Mg

0.7 (0.8)

46300 Al Si9Cu1Mg

0.30 (0.25) 0.65 (0.65)

46400 Al Si9Cu3(Fe)(Zn)

0.15 (0.05) 0.55 (0.55)

0.15

46500 / 226/3 Al Si7Cu2

0.7 (0.8)

46600 Al Si6Cu4

0.9 (1.0)

0.15

45000 / 225 Al Si5Cu3Mg

2.6 0.50 (0.60)

3.6

0.55

2.6 3.6

0.55

0.20 (0.15) 0.45 (0.45)

45100 Al Si5Cu3

0.50 (0.60)

45400 Values in brackets are valid for castings according to DIN EN 1706: 2010 1) According to DIN EN 1676: 2010

76 Aluminium Casting Alloys

0.05

Casting characteristics and other properties of castings Alloy

Fluidity

Thermal crack stability

Pressure tightness

As-cast state

Ageability

Corrosion resistance

Decorative anodisation

Weldability

Polishability

Density

E-Modulus

Thermal capacity at 100 째C

Solidification temperature

Coefficient of thermal expansion

Electrical conductivity

Thermal conductivity

g/cm3

MPa

J/gK

째C

10-6/K 293 K - 373 K

MS/m

W/(m . k)

Al Si8Cu3

2.77

75,000

0.88

600 - 500

14 - 18

110 - 130

Al Si9Cu3(Fe)

2.76

75,000

0.88

600 - 500

13 - 17

110 - 120

Al Si11Cu2(Fe)

2.75

75,000

0.88

600 - 500

14 - 18

120 - 130

Al Si7Cu3Mg

2.77

75,000

0.88

600 - 500

14 - 17

110 - 120

Al Si9Cu1Mg

2.76

75,000

0.88

600 - 500

16 - 22

130 - 150

Al Si9Cu3(Fe)(Zn)

2.76

75,000

0.88

600 - 500

13 - 17

110 - 120

Al Si7Cu2

2.77

75,000

0.88

600 - 500

15 - 19

120 - 130

Al Si6Cu4

2.80

74,000

0.88

630 - 500

14 - 17

110 - 120

Al Si5Cu3Mg

2.79

74,000

0.88

630 - 500

16 - 19

130

Al Si5Cu3

2.79

74,000

0.88

630 - 500

16 - 19

120 - 130

Al Si8Cu3 Al Si9Cu3(Fe) Al Si11Cu2(Fe) Al Si7Cu3Mg Al Si9Cu1Mg Al Si9Cu3(Fe)(Zn) Al Si7Cu2 Al Si6Cu4 Al Si5Cu3Mg Al Si5Cu3

Physical properties Alloy

Aluminium Casting Alloys 77

Al SiCu casting alloys

Mechanical properties at room temperature +20 째C Alloy / Temper

Casting method

Tensile strength Rm Yield strength Rp0,2 Elongation A MPa

MPa

% min

Brinell hardness HB

Fatigue resistance MPa

min

Al Si8Cu3

Sand casting

150

Al Si7Cu3Mg

Sand casting

180

100

Al Si9Cu1Mg

Sand casting

135

Al Si7Cu2

Sand casting

150

Al Si6Cu4

Sand casting

150

Al Si5Cu3Mg

Sand casting

140

Sand casting

230

200

Al Si5Cu3

Gravity die casting

170

100

60 -

Al Si7Cu3Mg

Gravity die casting

180

100

60 -

Al Si7Cu2

Gravity die casting

170

100

50 -

Al Si9Cu1Mg

Gravity die casting

170

100

60 -

Gravity die casting

275

235

1.5

Gravity die casting

270

180

2.5

Gravity die casting

320

280

110

Gravity die casting

170

100

60 -

Gravity die casting

230

110

70 - 100

Al Si5Cu3Mg

Al Si6Cu4

min

105 80 - 110

Al Si8Cu3

Pressure die casting 240

140

60 -

Al Si11Cu2(Fe)

Pressure die casting 240

140

60 -

78 Aluminium Casting Alloys

Heat treatment of aluminium castings Alloy / Temper

Al Si5Cu3Mg

Solution heat treatment temperature

Annealing time

Water temperature for quenching

Ageing tempetarure °C

°C

480

6 - 10

480

6 - 10

Al Si5Cu3

480

6 - 10

Al Si9Cu1Mg

480

6 - 10

Ageing time

20 - 30

120

160

6 - 12

20 - 30

120

160

6 - 12

Mechanical properties of gravity die casting samples 1) Alloy / Temper

Yield strength Rp0,2 MPa

Tensile strength Rm MPa

Elongation A %

Brinell hardness HB

-100°C +20°C +100°C +200°C -100°C +20°C +100°C +200°C -100°C +20°C +100°C +200°C -100°C +20°C +100°C +200°C Al Si8Cu3

170

160

120

100

Al Si6Cu4

170

160

130

100

1.5

1) Mechanical properties in minimum values / values after long-term maintenance of the respective temperature.

Typical process parameters Alloy

Al Si8Cu3

Casting temperature Sand Gravity casting die casting

Pressure die casting

Contraction allowance Sand Gravity casting die casting

Pressure die casting

°C

680 - 750

630 - 680

1.0 - 1.2

0.6 - 1.0

0.4 - 0.6

Al Si9Cu3(Fe)

630 - 680

Al Si11Cu2(Fe)

0.4 - 0.7

630 - 680

Al Si7Cu3Mg

680 - 750

Al Si9Cu1Mg

680 - 750

Al Si9Cu3(Fe)(Zn)

0.4 - 0.8 1.0 - 1.2

0.6 - 1.0

1.0 - 1.2

0.6 - 1.0

630 - 680

Al Si7Cu2

680 - 750

Al Si6Cu4

690 - 750

Al Si5Cu3Mg

690 - 750

Al Si5Cu3

690 - 750

0.4 - 0.7 1.0 - 1.2

0.6 - 1.0

1.0 - 1.2

0.6 - 1.0

690 - 750

1.0 - 1.2

0.6 - 1.0

690 - 750

1.0 - 1.2

0.6 - 1.0

640 - 690

0.4 - 0.6

Aluminium Casting Alloys 79

Al SiCu casting alloys

Application notes

Properties and processing

Heat treatment

The alloys in this group are among the

Aluminium casting alloys with approx. 6

With castings made from these casting

most commonly used aluminium cast-

to 8 % silicon, 3 to 4 % copper as well

alloys, age hardening is possible when

ing alloys around. They are regarded

as 0.3 to 0.5 % magnesium have the

the Cu and Mg content is appropriate. It

as universal casting alloys for the most

optimum high-temperature strength.

is, however, seldom carried out. In these

important casting processes and are

The cast structure hardens on its own

castings, due to the Cu content in con-

widely used in pressure die casting in

within a week of casting. Afterwards, the

nection with the Mg and Zn content, an

particular. They are easily cast and are

mechanical machinability of the casting

independent structural hardening occurs.

suitable for parts which are subjected

is very good. Age hardening is some-

This process is complete within about a

to relatively high loads. They are heat

times possible. Treatment of the melt:

week. Only then should the castings be

resistant and, as such, are used for en-

In sand castings or thick-walled grav-

finished followed by checking the me-

gine components and cylinder heads.

ity die castings, sodium modification is

chanical properties. To achieve thermal

possible. Often, grain refinement is also

and dimensional stability in parts suit-

carried out. The casting and solidifica-

able for high-pressure applications, e.g.

tion behaviour usually poses no problem.

crankcases, cylinder heads or pistons,

The type of solidification is hypoeutec-

solution annealing with artificial ageing

tic. During the transition from liquid to

beyond the peak aged condition is sug-

solid state, there is a wide solidification

gested (T7). This process is also known

range of a pasty-mushy character. At-

as “stabilising” or “overageing”.

tention must be paid to controlling the solidification and feeding of the metal. There is no distinctive tendency to hot cracking or draws.

80 Aluminium Casting Alloys

AlMg casting alloys

Chemical composition (all data in wt.-%) Alloy Numerical denomination 1) / VDS-No. Al Mg3(H) Al Mg3

min max

0.45

0.15

0.02

0.40

2.7 3.2

min max

2.7 (2.5) 3.5 (3.5)

Other indiv. total Others

0.07

0.02

0.03

0.10 B/Be

0.10

0.15 (0.20)

0.05

0.15 B/Be

0.45 (0.55)

0.40 (0.55)

0.03 (0.05)

0.45

min max

0.60

0.55

0.15

0.45

2.5 3.2

0.30

0.20

0.05

0.15 B/Be

min max

0.9 1.3

0.15

0.02

0.40

2.7 3.2

0.07

0.15

0.03

0.10 B/Be

0.10

0.15 (0.20)

0.05

0.15 B/Be

0.10

0.15 (0.20)

0.05

0.15 B/Be

0.07

0.15

0.03

0.10 B/Be

0.15 (0.20)

0.05

0.15 B/Be

0.20 (0.25)

0.05

0.15

0.05

0.15

51100 / 242 Al Mg3(Cu) - / 241 Al Mg3Si(H) Al Mg5

min max

0.35 (0.55)

0.45 (0.55)

0.05 (0.10)

0.45

4.8 (4.5) 6.5 (6.5)

51300 / 244 Al Mg5(Si)

min max

1.3 (1.5)

0.45 (0.55)

0.03 (0.05)

min max

1.7 2.5

0.50

0.02

0.45

4.8 (4.5) 6.5 (6.5)

51400 / 245 Al Mg9(H) Al Mg9

min

0.2 0.5

0.45

max

2.5

min

1.8

max

2.6

min

1.6

max

2.4 (0.60)

0.9 (1.0)

0.08 (0.10)

0.55

8.5 10.5 8.5 (8.0) 10.5 (10.5)

0.10

0.25

0.10

51200 / 349 Al Mg5Si2Mn

0.4 0.20 (0.25)

0.03 (0.05)

0.8

5.0 (4.7) 6.0 (6.0)

0.07

51500 Al Si2MgTi

0.30 0.50 (0.10)

0.08

0.50 (0.65)

0.50 (0.45) 0.65

0.05

0.10

0.05

0.07 (0.05) 0.15 (0.20)

41000 Values in brackets are valid for castings according to DIN EN 1706: 2010 1) According to DIN EN 1676: 2010

Aluminium Casting Alloys 81

AlMg casting alloys

Casting characteristics and other properties of castings Alloy

Fluidity

Thermal crack stability

Pressure tightness

As-cast state

Ageability

Corrosion resistance

Decorative anodisation

Weldability

Polishability

Density

E-Modulus

Thermal capacity at 100 째C

Solidification temperature

Coefficient of thermal expansion

Electrical conductivity

Thermal conductivity

g/cm3

MPa

J/gK

째C

10-6/K 293 K - 373 K

MS/m

W/(m . k)

Al Mg3(H)

2.68

70,000

0.93

650 - 600

17 - 22

130 - 140

Al Mg3

2.68

70,000

0.93

650 - 600

17 - 22

130 - 140

Al Mg3(Cu)

2.68

70,000

0.93

650 - 600

17 - 22

130 - 140

Al Mg3(H) Al Mg3 Al Mg3(Cu) Al Mg3Si(H) Al Mg5 Al Mg5(Si) Al Mg9(H)/Fe Al Mg9 Al Mg3(Zr) Al Mg5Si2Mn Al Si2MgTi

Physical properties Alloy

Al Mg3Si(H)

2.68

70,000

0.93

650 - 600

17 - 22

130 - 140

Al Mg5

2.66

69,000

0.94

630 - 550

15 - 21

110 - 130

Al Mg5(Si)

2.66

69,000

0.94

630 - 550

15 - 21

110 - 140

Al Mg9(H)/Fe

2.63

68,000

0.94

620 - 520

11 - 14

Al Mg9

2.63

68,000

0.94

620 - 520

60 -

11 - 14

Al Mg5Si2Mn

14 - 16

110 - 130

Al Si2MgTi

19 - 25

140 - 160

82 Aluminium Casting Alloys

Mechanical properties at room temperature +20 째C Alloy / Temper

Casting method

Tensile strength Rm Yield strength Rp0,2 Elongation A MPa

MPa

% min

Brinell hardness HB

Fatigue resistance MPa

min

Al Mg3(H)

Sand casting

140

min 50

Al Mg3

Sand casting

140

Al Mg3(Cu)

Sand casting

140

Al Mg3Si(H)

Sand casting

140

Al Mg5

Sand casting

Al Si2MgTi

Sand casting

140

Sand casting

240

180

Al Mg5(Si)

Sand casting

160

100

Al Mg3(H)

Gravity die casting

150

Al Mg3

Gravity die casting

150

Al Mg3(Cu)

Gravity die casting

150

Al Mg3Si(H)

Gravity die casting

150

Gravity die casting

220

150

Al Mg5

Gravity die casting

180

100

Al Si2MgTi

Gravity die casting

140

Gravity die casting

240

180

Gravity die casting

180

110

Gravity die casting

210

120

Al Mg5(Si)

Al Mg3

140

Al Mg5

160

Al Mg5(Si)

180

110

Al Mg9(H)/Fe

Pressure die casting 200

140

Al Mg9

Pressure die casting 200

130

Al Si2MgTi

Gravity die casting

170

Al Si2MgTi

Gravity die casting

260

180

Heat treatment of aluminium castings Alloy / Temper

Al Mg3Si(H)

Solution heat treatment temperature

Annealing time

째C

545 - 555

4 - 10

Water temperature for quenching

Ageing tempetarure

Ageing time

째C

160 - 170

8 - 10

Al Mg5(Si)

540 - 550

4 - 10

160 - 170

8 - 10

Al Si2MgTi

520 - 535

4 - 10

155 - 165

7 - 10

Aluminium Casting Alloys 83

AlMg casting alloys

Mechanical properties of gravity die casting samples 1) Alloy / Temper

Tensile strength Rm MPa

Yield strength Rp0,2 MPa

Elongation A %

Brinell hardness HB

-100°C +20°C +100°C +200°C -100°C +20°C +100°C +200°C -100°C +20°C +100°C +200°C -100°C +20°C +100°C +200°C Al Mg3Si(H)

220

210

120

150

140

Al Mg5(Si)

210

200

170

140

120

110

100

1) Mechanical properties in minimum values / values after long-term maintenance of the respective temperature.

Typical process parameters Alloy

Casting temperature Sand Gravity casting die casting

Pressure die casting

Contraction allowance Sand Gravity casting die casting

Pressure die casting

°C

Al Mg3(H)

700 - 750

1.0 - 1.5

0.7 - 1.2

Al Mg3

700 - 750

1.0 - 1.5

0.7 - 1.2

Al Mg3(Cu)

700 - 750

1.0 - 1.5

0.7 - 1.2

Al Mg3Si(H)

700 - 750

1.0 - 1.5

0.7 - 1.2

Al Mg5

700 - 750

1.0 - 1.5

0.7 - 1.2

Al Mg5(Si)

700 - 750

1.0 - 1.5

0.7 - 1.2

Al Mg9(H)/Fe

680 - 640

0.5 - 0.7

Al Mg9

680 - 640

0.5 - 0.7

84 Aluminium Casting Alloys

Application notes

Properties and processing

Notes about surface treatment

We produce Al Mg3-type casting alloys

The highest requirements are placed on

As a pre-treatment, the surfaces of cast-

for handles, window handles or security

the quality of these casting alloys â&#x20AC;&#x201C; par-

ings made from Al Mg3, for example, are

covers in decorative anodised quality.

ticularly for decorative parts which are

mechanically machined as well as often

For structures in the chemical industry, in

anodised. The manufacture of these cast-

being chemically polished. In the anodis-

shipbuilding or the food industry, which

ing alloys represents a special challenge

ing process (electrolytically-oxidised alu-

demand the highest possible resistance

for smelters requiring much experience,

minium), a protective oxide layer, which

to chemical attack and the influences of

the best raw materials and quality-ori-

grows inwards and is essentially more

maritime climates, Al Mg5-type cast-

ented work.

impervious, thicker, more wear resistant

ing alloys are suitable. Heat-resistant

and more homogeneous than a natural

Al Mg5Si-type casting alloys are suit-

oxide skin, is produced on the surface

able for high-temperature applications

of a casting. On pure aluminium and on

such as engine construction. In France,

aluminium alloys which are low in pre-

the Al Si2MgTi alloy is used for handles.

cipitates, these layers are transparent.

For pressure die castings with good cor-

All defects such as precipitated inter-

rosion resistance, Al Mg9-type casting

metallic phases, inclusions, heteroge-

alloys are used.

neities, oxide films, wrinkles and other casting defects lead to disturbances in the growth of the layer formation and, consequently, impairment of the decorative appearance. As the electro-chemically formed oxide layer is also the possible carrier of discolouring substances, defects near the surface can lead to the parts having a blemished, non-decorative appearance. Hollow spaces such as wrinkles or pores which have been cut can be taken up by the aqueous solutions or electrolyte during treatment. Even later, due to a secondary reaction, the remainder of this medium can lead to local decomposition of the anodised or colour coating.

Aluminium Casting Alloys 85

AlMg casting alloys

The following alloying constituents can

Notes on casting techniques

have an influence on the quality and appearance of anodised layers:

Bale-out vessels with ceramic filter elements have also proven their worth. Dur-

To avoid the tendency to hot tearing

ing casting, only the filtrate is baled out;

during casting and particularly for deco-

the ladle remainder and subsequently

Silicon

rative reasons, the cast structure must

charged metal enter into the outside

With Si concentrations higher than

be fine-grained. This fine-grained struc-

areas of the melting or holding crucible.

0.6 %, the precipitated silicon or Mg2Si

ture can already be achieved during the

The casting operation requires particular

impairs transparency. The anodised layer

production of the ingots by means of

care in order to produce a sound cast-

loses its brilliance.

intensive grain refinement. As a general

ing despite the constant risk of forming

rule, this grain refinement does not have

oxides and shrinkage. In doing this, the

Iron, chromium and manganese

to be repeated during pouring. Should

configuration of the dies and the cast-

The sum total of these elements can

grain refinement decrease as a result

ing system play an important role. The

have a yellowing effect on the anodised

of prolonged holding, we recommend

type of solidification is globular-mushy.

layer. Limiting concentrations can not

that it be freshened up using TiB grain

A good feeding system is an essen-

be established. Their influence depends

refining wire. Melt cleaning or keeping

tial prerequisite for producing a dense

on the phase composition and chemi-

the melt clean is important in order to

structure.

cal back-dissolution during anodising.

produce a cast piece of good quality. We recommend that only those refin-

Copper

ing fluxes which are specifically suited

It has no negative influence when found

to AlMg casting alloys be used.

in normal concentrations. In the case of higher additions, the layer becomes softer and the composition rougher. Zinc This element has no influence on the anodising process or pigmentation. Titanium Concentrations of Ti above 0.02 % have a negative effect on the electrolytic colouration of aluminium castings.

86 Aluminium Casting Alloys

Casting alloys for special applications

Chemical composition (all data in wt.-%) Alloy Numerical denomination 1) / VDS-No.

Other indiv. total Others

High-strength casting alloys Al Cu4Ti

min max

4.2 0.15 (0.18)

0.15 (0.19)

5.2

0.55

0.15 (0.15) 0.25 (0.30)

0.07

0.03

0.10

0.03

0.10

0.03

0.10

0.03

Ag 0.4 0.10 1.0

21100 Al Cu4MgTI

min max

4.2 0.15 (0.20)

0.30 (0.35)

0.20 (0.15) 0.35 (0.35)

5.0

0.10

4.0

0.20

5.0

0.50

4.0

0.01

0.15

5.2

0.50

0.35

4.5

0.1

5.2

0.3

0.05

0.10

0.05

0.03 (0.05)

0.05 (0.10)

0.03

0.15 (0.15) 0.25 (0.30)

21000 Al Cu4MnMg

min max

0.10

0.15 (0.20)

0.20 (0.15) 0.50 (0.50)

0.05 (0.10)

21200 Al Cu4MgTiAg

min max

Al Cu5NiCoSbZr

0.05

0.10

min max

0.20

0.30

0.5 0.05 1.3

0.10

1.7

0.9 (0.8) 1.5 (1.5)

0.7

0.35 0.15

****

0.10

0.30

0.05

0.15

1.3

0.35

0.20 (0.25)

0.05

0.15 P

0.8 1.3

0.10

0.15

0.05

0.15 P

Piston casting alloys AlSi12CuNiMg

min

10.5

max

13.5

min max

17.0 19.0

0.8 0.6 (0.7)

1.5

0.35

0.8 1.3

0.10

48000 / 260 Al Si18CuNiMg

0.3

0.8 1.3

****) Co 0.10-0.40 Sb 0.10-0.30 Zr 0.10-0.30 Values in brackets are valid for castings according to DIN EN 1706: 2010 1) According to DIN EN 1676: 2010

Continuation of the table on the next page.

Aluminium Casting Alloys 87

Casting alloys for special applications

Chemical composition (all data in wt.-%) Alloy Numerical denomination 1)

4.0 5.0

0.15

0.5 0.65

0.10

0.3

1.5

Other indiv. total Others

Hyper eutectic casting alloys Al Si17Cu4Mg* Al Si17Cu4Mg**

min max

16.0 18.0

min

16.0

max

18.0

0.3

4.0 1.0 (1.3)

5.0

0.50

0.45 (0.25) 0.65 (0.65)

0.15

0.20

0.05

0.15 P

0.20 (0.25)

0.05

0.25

48100 Self-hardening casting alloys Autodur Autodur (Fe)* Autodur (Fe)**

min max

8.5 9.5

0.15

0.02

0.05

0.3 0.5

9.5 10.5

0.15

0.03

0.10

min max

8.5 9.5

0.40

0.02

0.30

0.3 0.5

9.5 10.5

0.15

0.03

0.10

min

7.5

9.0

max

9.5

0.27 (0.30)

0.08 (0.10)

0.15

0.25 (0.20) 0.5 (0.5)

0.15

0.05

0.15

min max

0.07

0.20

0.01

0.005

0.02

0.004

0.04

Mn+Cr+ 0.03 V+Ti= 0.02

B 0.04

min max

0.10

0.30

0.01

0.007

0.02

0.005

0.04

Mn+Cr+ 0.03 V+Ti= 0.030

B 0.04

10.5

71100 Rotor-Aluminium Al 99.7E***

Al 99.6E***

*) Non-standardised version **) According to DIN EN 1706: 2010 ***) According to DIN EN 576 Values in brackets are valid for castings according to DIN EN 1706: 2010 1) According to DIN EN 1676: 2010

88 Aluminium Casting Alloys

Casting characteristics and other properties of castings Alloy

Fluidity

Thermal crack stability

Pressure tightness

As-cast state

Ageability

Corrosion resistance

Decorative anodisation

Weldability

Polishability

High-strength casting alloys Al Cu4Ti Al Cu4TiMgTi Al Cu4TiMgAg Al Cu5NiCoSbZr Piston casting alloys Al Si12CuNiMg Al Si18CuNiMg Hyper eutectic casting alloys Al Si17Cu4Mg 1) Al Si17Cu4Mg 2) Self-hardening casting alloys Autodur Autodur(Fe) Al Zn10Si8Mg 1) Rotor-Aluminium Al 99.7E Al 99.6E 1) Non-standardised version 2) According to DIN EN 1706: 2010

Aluminium Casting Alloys 89

Casting alloys for special applications

Physical properties Alloy

Density

E-Modulus

Thermal capacity at 100 째C

Solidification temperature

Coefficient of thermal expansion

Electrical conductivity

Thermal conductivity

g/cm3

MPa

J/gK

째C

10-6/K 293 K - 373 K

MS/m

W/(m . k)

High-strength casting alloys Al Cu4Ti

2.79

72,000

0.91

640 - 550

16 - 23

120 - 150

Al Cu4MgTi

2.79

72,000

0.91

640 - 550

16 - 23

120 - 150

Al Cu4TiMgAg

2.79

72,000

0.91

640 - 550

16 - 23

120 - 150

Al Cu5NiCoSbZr

2.84

76,000

0.91

650 - 550

18 - 24

120 - 155

Al Si12CuNiMg

2.68

77,000

0.90

600 - 540

15 - 23

130 - 160

Al Si18CuNiMg

2.68

81,000

0.90

680 - 520

14 - 18

115 - 140

81,000

0.89

650 - 510

14 - 18

115 - 130

14 - 17

120 - 130

15 - 20

115 - 150

Piston casting alloys

Hyper eutectic casting alloys Al Si17Cu4Mg 1)

2.73

Al Si17Cu4Mg 2) Self-hardening casting alloys Autodur

2.85

75,000

0.86

640 - 550

Autodur(Fe)

2.85

75,000

0.86

640 - 550

Al Zn10Si8Mg 2)

15 - 20

115 - 150

17 - 20

120 - 130

Rotor-Aluminium Al 99.7E

2.70

70,000

0.94

660

34 - 36

180 - 210

Al 99.6E

2.70

70,000

0.94

660

32 - 34

180 - 210

1) Non-standardised version 2) According to DIN EN 1706: 2010

90 Aluminium Casting Alloys

Mechanical properties at room temperature +20 °C Alloy / Temper

Casting method

Tensile strength Rm Yield strength Rp0,2 Elongation A MPa

MPa

min

Brinell hardness HB

Fatigue resistance MPa

min

High-strength casting alloys Al Cu4Ti

Sand casting

300

200

T64 Sand casting

280

180

Al Cu4TiMg

Sand casting

300

200

Al Cu4TiMgAg

Sand casting

460 - 510

410 - 450

7 14 -

90 130 - 150

T64 Sand casting

370 - 430

200 - 270

Al Cu5NiCoSbZr

Sand casting

180 - 220

145 - 165

1 - 1.5

105 - 120 85 -

90 - 100

Sand casting

180 - 220

160 - 180

1 - 1.5

80 -

90 - 100

Al Cu4Ti(H)

Gravity die casting

330

220

T64 Gravity die casting

320

180

Al Cu4MgTi

Gravity die casting

320

200

Al Cu4TiMgAg

Gravity die casting

460 - 510

410 - 460

Sand casting

140

130

≤1

Sand casting

220

190

≤1

Sand casting

160

140

≤1

Sand casting

140

130

≤1

Sand casting

240

≤1

110

Sand casting

230

220

≤1

100

Sand casting

140

130

≤1

Sand casting

230

210

≤1

100

Gravity die casting

200

190

≤1

Gravity die casting

280

240

≤1

100

Gravity die casting

200

185

≤1

Gravity die casting

180

170

≤1

100

Gravity die casting

280

270

≤1

130

Gravity die casting

165

160

≤1

105

Gravity die casting

180

170

≤1

Gravity die casting

280

270

≤1

120

Gravity die casting

180

170

≤1

80 - 110

130 - 150

100 - 110

Piston casting alloys Al Si12CuNiMg

Hyper eutectic casting alloys Al Si17Cu4Mg

Al Si18CuNiMg

Piston casting alloys Al Si12CuNiMg

Al Si17Cu4Mg

Al Si18CuNiMg

80 - 110

Continuation of the table on the next page.

Aluminium Casting Alloys 91

Casting alloys for special applications

Mechanical properties at room temperature +20 °C Alloy / Temper

Casting method

Tensile strength Rm Yield strength Rp0,2 Elongation A MPa

MPa

min

Brinell hardness HB

Fatigue resistance MPa

min

Piston casting alloys Al Si12CuNiMg

Al Si17Cu4Mg

Al Si18CuNiMg

Pressure die casting 240

140

≤1

Pressure die casting 240

140

≤1

Pressure die casting 220

200

≤1

100

Pressure die casting 230

210

≤1

100

Pressure die casting 210

180

≤1

100

Self-hardening casting alloys Autodur

Sand casting

210

190

≤1

Al Zn10Si8Mg

Sand casting

210

190

Autodur

Gravity die casting

260

210

≤1

100

Autodur(Fe)

Pressure die casting 290

230

≤1

100

Al 99.7E

Gravity die casting

Al 99.6E

Gravity die casting

Al 99.7E

Pressure die casting

Al 99.6E

Pressure die casting

80 - 100

Rotor-Aluminium

1) Non-standardised version The values apply for separately-cast sample bars in sand and gravity die casting. Mechanical properties of pressure die casting samples are not binding and merely serve as information. The values representing vibration testing and/or fatigue strength apply for the best available casting process and merely serve as information.

92 Aluminium Casting Alloys

Heat treatment of aluminium castings Alloy / Temper

Solution heat treatment temperature

Annealing time

Water temperature for quenching

Ageing tempetarure

Ageing time

°C

520 - 530

8 - 16

20 - 80

High-strength casting alloys Al Cu4TiMg

Al Cu5NiCoSbZr

> 120

Air

345 - 355

535 - 545

Al Cu4Ti

515 - 535

Al Cu4TiMgAg

Al Cu4Ti(H)

T64

Air quenching

520 - 530

Air quenching

495 - 505

7 - 10

495 - 505

7 - 10

15 -

8 - 10

10 - 15

20 - 80

210 - 220

12 - 16

8 - 18

20 - 80

170 - 180

6 -

525 - 535

8 - 18

20 - 80

170 - 180

6 -

515 - 535

8 - 18

20 - 80

135 - 145

6 -

Piston casting alloys Al Si12CuNiMg

Al Si18CuNiMg

None 5 - 10

210 - 230

10 - 14

165 - 185

5 - 10

225 - 235

7 - 12

20 - 80

165 - 185

7 - 10

20 - 80

225 - 235

7 - 10

225 - 235

7 - 12

20 - 80

None

Hyper eutectic casting alloys Al Si17Cu4Mg 1)

Air quenching

None

495 - 505

7 - 10

20 - 80

165 - 185

7 - 10

495 - 505

7 - 10

20 - 80

225 - 235

7 - 10

1) Non-standardised version

Mechanical properties of gravity die casting samples 1) Alloy / Temper

Tensile strength Rm MPa

Yield strength Rp0,2 MPa

Elongation A %

Brinell hardness HB

-100°C +20°C +100°C +200°C -100°C +20°C +100°C +200°C -100°C +20°C +100°C +200°C -100°C +20°C +100°C +200°C Piston casting alloys Al Si12CuNiMg

200

160

100

190

170

100

≤1

1.5

2.5

Al Si18CuNiMg

180

160

120

170

150

100

≤1

180

160

120

170

150

100

≤1

100

Hyper eutectic casting alloys Al Si17Cu4Mg 2)

1) Mechanical properties in minimum values / values after long-term maintenance of the respective temperature. 2) Non-standardised version

Aluminium Casting Alloys 93

Casting alloys for special applications

Typical process parameters Alloy

Casting temperature Sand Gravity casting die casting

Pressure die casting

Contraction allowance Sand Gravity casting die casting

Pressure die casting

째C

High-strength casting alloys Al Cu4Ti

690 - 750

1.1 - 1.5

0.8 - 1.2

Al Cu4MgTi

690 - 750

1.1 - 1.5

0.8 - 1.2 0.8 - 1.2

Al Cu4TiMgAg

690 - 750

1.1 - 1.5

Al Cu5NiCoSbZr

690 - 750

1.1 - 1.5

Al Si12CuNiMg

670 - 740

620 - 660

1.0 - 1.2

0.5 - 1.0

0.4 - 0.6

Al Si18CuNiMg

730 - 760

0.6 - 1.0

0.4 - 0.8

0.3 - 0.6

720 - 760

0.6 - 1.0

0.4 - 0.8

0.3 - 0.6

1.0 - 1.2

0.8 - 1.0

Piston casting alloys

Hyper eutectic casting alloys Al Si17Cu4Mg 1)

720 - 760

Self-hardening casting alloys Autodur

740 - 690

Autodur(Fe)

700 - 650

0.5 - 0.8

Rotor-Aluminium Al 99.7E

700 - 730

690 - 730

1.5 - 1.9

1.2 - 1.6

1.0 - 1.4

Al 99.6E

700 - 730

690 - 730

1.5 - 1.9

1.2 - 1.6

1.0 - 1.4

1) Non-standardised version

94 Aluminium Casting Alloys

High-strength casting alloy

Application notes

being added to optimise their strength.

from all sprues. From practical experi-

Furthermore, there are also casting al-

ence, some users recommend having a

These casting alloys are used for parts

loy types which contain silver so as to

separate foundry department for these

which – compared to all other aluminium

meet the maximum strength require-

casting alloys. Melt cleaning and degas-

casting alloys – require maximum strength.

ments. The corrosion resistance of cast

sing can be carried out without any trou-

Where their reduced corrosion resistance

pieces is reduced, however, due to the

ble using normal means. Melt treatment

represents no obstacles, these casting

high copper content.

is restricted to grain refinement which,

alloys can be used to manufacture high-

among other things, slightly counteracts

strength components, for example, for

The casting technique for these alloys is

the susceptibility to hot cracking. Inten-

the defence industry, aerospace, auto-

demanding. Most defects in the castings

sive grain refinement is already performed

motive, rail vehicles, mechanical engi-

stem from “contamination” with silicon.

by us so it does not usually need to be

neering and the textile industry.

The silicon content should be kept as

repeated in the foundry. The fluidity of

low as possible and always lower than

these casting alloys is comparable with

the iron content. An excess of silicon

other hypoeutectic AlSi casting alloys.

produces a low melting phase and in-

The solidification characteristics are best

Properties and processing

creases the susceptibility to hot tearing

described as being globular-mushy. At

The use of these relatively demanding

during solidification. Even slight impedi-

approx. 90 K, the solidification range is

casting alloys only makes sense if the

ments to solidification shrinkage can

relatively high. Using a good filling system

component undergoes heat treatment.

lead to structural separation. The most

in conjunction with steered or controlled

Only then, can the potential of these

important requirement in the foundry is

solidification and suitable feeding, opti-

casting alloys be fully utilised. Following

therefore cleanliness to prevent the take-

mum structural qualities can be achieved

heat treatment, the castings still have ex-

up of silicon. Here are some recommen-

with the sand and gravity die casting

cellent elongation as well as displaying

dations: The melting crucible must not

processes. Thanks to their good struc-

the highest possible strength and hard-

contain any remainder of silicon alloys.

tural quality and optimum heat treatment,

ness. This combination of high strength

It also makes good sense to melt several

these high-strength casting alloys are

and good elongation values gives these

batches of an alloy which is low in sili-

suitable for the manufacture of castings

casting alloys the highest possible Qual-

con in a new crucible to free the crucible

whose unmatched mechanical proper-

ity Index “Q”.

material of silicon. There are users who,

ties comply with maximum demands.

for this reason, use melting crucibles By means of special heat treatment,

made of graphite or cast iron for these

hardness and elongation values can be

casting alloys. Return material should

adjusted within determined limits. There

also be checked very strictly and stored

are other variants of these aluminium

separately; residual sand and other return

casting alloys, e.g. with nickel and cobalt

material must be painstakingly removed

Aluminium Casting Alloys 95

High-strength casting alloy

Heat treatment

is recommended. First of all, the cast pieces undergo preliminary annealing

The heat treatment of castings is another

at 480 to 490 째C for between 4 and 8

important step in the production of quality

hours; they are then given a solution heat

cast parts. Exact temperature regulation

treatment at approx. 515 to 535 째C for a

of the annealing furnace, good tempera-

further 6 to 10 hours. To avoid distortion,

ture distribution by means of circulating

quenching of the casting after anneal-

air and the correct positioning of the

ing can be effected by means of a water

casting in the baskets, holders or racks

shower followed by immersion in warm

are essential prerequisites for success.

water at temperatures of up to 80 째C.

In solution annealing, the temperature

Fully-annealed Al Cu4TiMg castings have

increase should be moderate in order

a susceptibility to stress corrosion. This

to allow enough time for temperature

condition is therefore not standardised

equalisation to take place in the castings

for this casting alloy. Such parts are only

and to avoid incipient fusion. The relief

used in naturally-aged condition (T4).

of casting strain, the removal of microstructural inhomogeneity and the diffusion of hardening constituents require longer periods of time. In these casting alloys, especially in thick-walled, slowsolidifying castings, stepped annealing

96 Aluminium Casting Alloys

Piston alloys

Application notes

Properties and processing

These casting alloys are used for cast-

The wear resistance of these casting al-

ings with wear-resistant surfaces and for

loys is due to many hard, rectangular or

structures which have to possess good

polygonal primary silicon crystals which

strength properties at high temperatures.

are embedded in the ductile base mate-

The main applications comprise: pistons

rial and jut out of the surface of the track

for combustion engines, crankcases

with an edge (while the neighbouring

without additional cylinder liners, pump

troughs act as reservoirs for lubricant).

casings, valve casings, valve slides, gear

In addition, alloying elements such as

elements etc.

Cu, Mg or Ni give these casting alloys remarkable high-temperature strength. In order to produce as many small and evenly-distributed silicon crystals as possible in the cast structure, phosphorous is added. This treatment is already carried out during production of the ingots in our secondary smelters and, as a rule, does not need to be repeated by the foundry. The fluidity of these types of casting alloy is very good. In spite of this, silicon crystals forming in the melt at too low casting temperatures are to be avoided because of their abrasive effect. Additional information is provided in the section on â&#x20AC;&#x153;Selecting aluminium casting alloysâ&#x20AC;?.

Aluminium Casting Alloys 97

Self-hardening aluminium-silicon-zinc casting alloys

Application notes

Properties and processing

In cases where the exposure to corrosion

These casting alloys are used in the

The fluidity of Autodur in particular is very

dur are assembled with other castings or

manufacture of models, foamed shapes,

good. Solidification behaviour is similar

parts made from other aluminium alloys,

wearing parts or the bases of electric

to that of other casting alloys containing

or indeed fitted to steel parts, there is a

irons, for example. The use of these

approx. 9 % silicon. Alloys of this type

strong tendency to contact corrosion.

casting alloys is not recommended for

are self-hardening, i.e. after casting, the

Compared with all other aluminium cast-

machine parts which are subject to al-

castings are stored at room tempera-

ing alloys, castings made from these al-

ternating or impact stress, are obliged

ture and within approx. 10 days reach

loys display the lowest high-temperature

to absorb bending and shearing stress

their service properties. This hardening

strength. (Precipitation treatment carried

or requiring a specific ductility.

takes place as a result of precipitation

out at room temperature to increase hard-

of the complex Al ZnMg. The advantage

ness has no clearly definable effect.) Ex-

of these casting alloys lies exclusively

perience shows that castings, even after

in their saving of heat treatment costs.

many years, can fracture spontaneously

There are, however, disadvantages in

under the slightest impact or shock load.

using these casting alloys. The following

Over time, the microstructure appears to

information should serve as a warning:

be embrittled.

is great or where parts made from Auto-

Under unfavourable conditions whilst molten, the zinc content is reduced due to its high vapour pressure. The resistance of Autodur to corrosion is sharply reduced as a result of its high zinc content of around 10 %.

98 Aluminium Casting Alloys

Rotor aluminium

Application notes This pure aluminium is mostly used in pressure die casting and goes into the manufacture of rotors (short-circuit armatures) and stators for the electric motor sector. It can also be cast into other construction elements which require high electrical and thermal conductivity.

Properties and processing There is a particular hurdle in the near net shape casting of pure aluminium, i.e. sensitivity to hot tearing. The most important prerequisite for keeping this problem within limits is to maintain the correct ratio between iron and silicon. The silicon content must be as low as possible and the iron content must always be at least double the silicon content. Molten pure aluminium readily absorbs silicon from any standing material it comes into contact with. This can easily lead to an â&#x20AC;&#x153;imbalanced ratioâ&#x20AC;?. Cleanliness is therefore important during processing and it is also essential to check tools and the melting crucible. In extreme emergencies when silicon enrichment occurs, it helps to increase the iron content within the permitted tolerance range.

Aluminium Casting Alloys 99

Aluminium Casting Alloys

We have taken the relevant specialist literature into consideration while drawing up this Aluminium Casting Alloy Catalogue. Please do not hesitate to contact us if you require more detailed literary explanations.

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Aluminium Casting Alloys

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