Invention Journal of Research Technology in Engineering & Management (IJRTEM) www.ijrtem.com Ç Volume 1 Ç Issue 7 Ç
ISSN: 2455-3689
An investigation of Effect of Mould Vibrations on Mechanical and Metallurgical properties of Aluminum 356 Casting Nagaraju Tenali1, Dr. B. Karuna Kumar2, K.Ch. Kishor Kumar3 1
Assistant Professor, Mechanical Engineering Department, Gudlavalleru Engineering College, Sheshadri Rao Knowledge Village, Gudlavalleru- 521356, Andhra Pradesh, INDIA 2 Professor, Mechanical Engineering Department, Gudlavalleru Engineering College, Sheshadri Rao Knowledge Village, Gudlavalleru- 521356, Andhra Pradesh, INDIA 3 Associate Professor, Mechanical Engineering Department, Gudlavalleru Engineering College, Sheshadri Rao Knowledge Village, Gudlavalleru- 521356, Andhra Pradesh, INDIA
Abstract: Casting is one of the oldest and mostly used production processes in industry. The traditional casting has certain disadvantages like poor strength due to hot tears, shrinkage and poor surface finish. The property of casting process mostly depends on the microstructure after solidification. Providing Mould vibration during casting is one of the latest techniques employed in order to get better structure in the solidified casting. Mould vibration during casting gives reduced amount of shrinkage, better morphology, surface finish, and less chances of hot tear. In this research work, the effect of mould vibration during solidification of Aluminum 356alloys for different values of wavelengths at a fixed pouring temperature investigated to understand the modification in microstructure and mechanical properties of casting. The Al356 casting has been prepared in a graphite mould with and without vibrations. The frequencies are varied from 0 Hz to 20 Hz during the casting process. A casting has been made without vibration as well to compare the results of castings with vibration. The experimental results showed significant grain refinement and remarkably improvement in compression strength and hardness of castings with mechanical mould vibration during solidification. Key words: Mould Vibrations, Stir casting, Vibrating table, Ultimate tensile strength, hardness and microstructure.
Introduction Metal casting is one of the best manufacturing process in which heated liquid metal is poured into the mold cavity and allowed to solidify in that mould cavity. Out of all the manufacturing process, casting process is cheaper due to its simplified procedure. The quality of casting depends on the flow behavior of molten metal and other process parameters. In these days more than 85% of products are produced by casting processes. The totality of metals and alloys begin to work by a very important operation, that of solidification. Solidification is the operation that gives shape and structure. Currently the solidification technique has experienced a rapid development. Because of progresses made as yet the castings are used in high security parts in the aero-spatial industry, the automotive, chemical and metallurgical equipment [1]. Recent techniques suggest that, mold vibration during pouring and till solidification is one of the important methods to produce casting for better morphology, surface finish and reduced amount of shrinkage [2]. Mold conditions, pouring temperature, frequency of vibration and other process variables are factors that would have a definite effect on the microstructure and properties of the cast [3]. It must be noted that above mentioned factors are chosen bearing in the mind the requirement that the material solidify in a manner that would maximize the properties desired while simultaneously preventing potential defects such as shrinkage, porosity, voids and trapped inclusions. The most effective method of early fault detection in a metal cast is high frequency vibration analysis as its parameter changes quickly in the early stages of defect development. There are mainly three types of vibration such as ultrasonic vibration, electromagnetic vibration and mechanical vibration [4]. Out of above three methods Mechanical vibration is simple one due to its easier control over its parameters. A number of researchers have employed ultrasonic and electromagnetic vibration and studied their effect on casting product [5-8].Experimentation with mold vibration in order to alter the as-cast microstructure of cast components date back to 1868. In one of the earlier investigations, Chernov [9] found that application of mechanical vibration during solidification of steel caused refinement of austenite. Sokoloff [10] reported on the use of mechanical vibration for grain refinement. Cambell [11] investigated the mechanical vibration causes improvement in mechanical and corrosion properties of alloys. Dommaschk [12] studied the effect of vibration on pure aluminum, Alwt%SiMg alloys along with other non-ferrous alloy. His research focused on the grain refinement and reported that the dependence of the casting wall thickness on casting characteristics could be minimized with the use of mechanical vibration. S.S. Mishra [1] the mechanical mold vibration on liquid metallic materials and their crystallization has a significant effect on the grain structure casting, grain size reduced by vibration and grain became more compact, spheroidal in shape. Pillai [8] used very low frequency vibration to the study the effect on A356 and Al12Si alloy. He concluded that mechanical vibrations improve the density and elongation of cast component. Dheir [13] used electromagnetic shaker to induce mechanical vibration in a permanent mold and concluded that vibration homogenizes the temperature distribution in the mold and promotes more uniform dendrite structure and less porosity in the castings.
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An investigation of Effect of Mould Vibrations on Mechanical and Metallurgical properties of Aluminum 356 Casting Material selection Material examined in this project is Aluminium 356. The basic composition and mechanical properties were tabulated in table-1 and table 2 respectively. Table 1 Chemical Composition. Component %Wt
Tensile Strength (N/mm2) 230
Si 6.5 -7.5
Cu 0.2
Mg 0.25 -0.45
Ti 0.2
Fe 0.2
Mn 0.2
Table-2 Mechanical Properties: Hardness (RBH) Modulus of elasticity (N/mm2) 75 71
Zn 0.1
Elongation(%) 5
Methodology In this work, methodology consists of two steps. Step one specimen preparation by casting process, Step two testing the specimen as per standard A. SPECIMEN PREPARATION The work was performed in two phases. In first Phase casting the alloys without mould vibration, prepared the baseline for microstructure and mechanical properties, and. This baseline was used for comparison with corresponding information obtained in second Phase. In second phase the castings were prepared with mechanical mould vibrations, they were tested as similar of the first phase. The mechanical mould vibrations were created with pre-determined vibrating table (figure-1). A set up of vibration mold casting was designed to carry out the casting. The metallic mould (EN8), diameter of the mould was 20mm and depth of mould cavity was 180mm. The mould was robust to with stand the vibration. The schematic sketch of experimental set up is shown in the Figure 1. Heating of material (Al-356) carried out in the Muffle Furnace (figure-2) to suitable temperature. The molten alloy al-356 was cast in a metallic mould coated with zircon paint. From each casting the ingots of Al-356 were cut into smaller pieces and these pieces were used in the experiments for vibration mould casting. A required amount of Al-356 alloy was melted in the muffle furnace. The pouring temperature of molten metal kept constant at 720°C. To this molten Al 356 added degassing agent C2Cl6 then molten metal stirred with a motor operated stirrer. The molten metal was poured into the mould which is on the vibrating table ready to vibrate. The vibration was applied till the solidification of molten metal. Five numbers of test samples (two for tensile test, 3 for hardness test and microstructure) were cast for each frequency of vibration. Five numbers of test samples were also cast without vibration named as casting with 0Hz. Castings were made for different vibration frequencies as from no vibration or 0 Hz, 10Hz, 20 Hz. After casting, all the samples ware processed heat treatment. Some of the (two for each frequency) heat treated sample were converted into required tensile teat test specimen as per standard. Here used standard is E8. The samples were showed in figure 3. Reaming heat treated samples were prepared for hardness test and microstructure check up. These hardness and microstructure samples, each casted one made in to a four equivalent parts along its length. Hardness sample just grinded the surface by belt grander and followed polishing, the samples are shown in figure 4. The microstructure Samples were prepared by conducting different metallography steps like polishing on different silicon graded paper, fine polishing on double disc polishing machine and finally etching. The metallography samples are shown in figure 5.
Figure 1: Vibrating Table
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Figure 2: Muffle Furnace
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An investigation of Effect of Mould Vibrations on Mechanical and Metallurgical properties of Aluminum 356 Casting
Figure- 3(a). Tensile test specimen 0 Hz mould vibrations
Parameter
Range
Temperature range
30 to1000C
Measuring controlling device
3½ digit
Chamber size
30 x15 cm
led
Figure- 3(b). Tensile test specimen with 10 Hz mould vibrations Figure 4: Hardness test specimens
Figure- 3(c). Tensile test specimen with 20 Hz mould vibrations Figure 5: Microstructure test specimens
Testing In this work the specimens are examined by conducting tensile test by computerized universal testing machine. The testing conducted on all frequency (0Hz, 10Hz, and 20Hz) samples the values is tabulated in table 4, 5, 6 and 7. Sample after testing shown in figure 6, 7 and 8. Hardness of the samples examined with rock well harness testing machine. The hardness tested different location of the samples, the values are tabulated. Metallography examined by Metallurgical microscope with image analysis software the images are shown in figures 9, 10 and 11.
Results and discussions A.
Tensile test Results 1. Without Mould vibrations Table 4: Tensile Test Results without Vibration Trail Ultimate Tensile Strength( N/mm2) 1
225
2
258
Avg
241
2. With 10Hz Mould vibrations Table 5: Tensile test results at 10 Hz Trail Ultimate tensile strength (N/mm2) 1
221
2
229
Avg
225
3. With 20Hz Mould vibrations Table 6: Tensile test results at 20 Hz Trail
Ultimate tensile strength (N/mm2)
1 2 Avg
222 202 212
Table 7: Tensile Test Average Results of Mould Vibration FREQUENCY(Hz) 0 5 10
ULTIMATE TENSILE STRENGTH(N/mm2) 241 225 212
Graphs are plotted with test results we observed that the tensile strength decreases by increases the mould vibration frequency. As we know that if tensile strength and compressive strength are reciprocal at tensile strength decreasing the compressive strength increased.
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An investigation of Effect of Mould Vibrations on Mechanical and Metallurgical properties of Aluminum 356 Casting So based on that we can say that if mould vibration increases the compressive strength of the component increases. Tensile results of vibrated and non-vibrated test samples are shown in table 7 and graph 1. 3. HARDNESS TEST Hardness results of the cast samples are shown in table 8 & 9. It is clear that hardness of casting increases with the increase in vibration frequency because vibration causes refinement of grains. The highest hardness is obtained at the bottom of each and every sample, because highest cooling rate and highest intensity of mould vibration at the bottom of sample, it is evident from the microstructure. More cooling action promotes creation of fine grain and at the same the vibration procedure fine grains. That means more grain boundary more hardness. So we may be concluded that due to combined effect of cooling rate and intensity of vibration, there are remarkable changes of hardness in the cast product. The variation of hardness with mould vibrations are shown in the graph 2 and table 9. GRAPH 1: Frequency Vs Ultimate Tensile Strength (N/mm2)
Graph 2: Frequency (Hz) Vs Hardness (RHB)
A. Microstructure of Different Casted samples Based on figure 9, it is clearly showing that by increasing the frequency of vibrations the grain refinement increases.
(a): Without vibration
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(b): With frequency at 5HZ Figure 9: Microstructure with and without Vibrations
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(c): With frequency at 10HZ
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An investigation of Effect of Mould Vibrations on Mechanical and Metallurgical properties of Aluminum 356 Casting Hardness Test Results at each vibration and each sample
TYPE
Table 8: Measurement of Hardness. NO OF SPECIMENS HARDNESS(RHB)
AVERAGE (RHB)
NO OF TRALIS 1 2
3
Without vibrations
1
62
60
58
60
With vibrations at 5 HZ
2 3 4 1
35 62 64 84
58 60 67 97
74 74 66 86
65 65 66 89
2 3 4 1 2 3 4
90 81 90 91 86 88 97
87 84 97 93 95 92 88
89 83 93 93 92 88 91
89 83 93 93 91 90 92
With vibrations at 10 HZ
Table 9: Average Hardness Test Results Frequency(Hz) 0 5 10
Hardness(RHB) 64.25 88.5 91.5
CONCLUSION The effect of mechanical mold vibration on mechanical properties casting characteristics of Al-356 alloy was evaluated. Based on the experimental results there are three main conclusions we can say, one tensile strength by increasing the mould vibration frequency of the casting the compressive strength increases while tensile strength decreases .The increasing of compressive strength is best sign of the casted product. Second conclusion by increasing the mould vibration frequency of the casting the hardness values increases. This is also very good sign. Third and last conclusion that the frequency of mould vibration increasing the grain refinement increases, which leads to good strength of the casting, Further study can be focused on the effect of poring temperature, effect of frequency more than 20 Hz. Apart from the above, effect of size variation of the casting and use of different materials can be studied as well.
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Crenguţa Manuela Pîrvulescu, Constantin Bratu, “Mechanic Vibrations Generation System And Effect On The Casting Alloys Solidification Process”, U.P.B. Sci. Bull., Series B, Vol. 72, Iss. 3, 2010 ISSN 1454-2331. Deshpande J., “The effect of mechanical mold vibration on the characteristics of Al-alloy”, 2006, Ph.D. thesis, Worcester polytechnic institute. Jackson K.A,” Mechanism of growth liquid metals and solidification”, 1958, American society of metal, overland, Ch. 187. S.S. Mishra, S.S Sahu, V. Ray, “Effect of Mold Vibration On Mechanical And Metallurgical Properties Of Al-Cu Alloys”, IJTRE Volume 3, Issue 1, September-2015 ISSN (Online): 2347 – 4718. Jian X., Refinement of eutectic silicon phase of Al A356 alloy using high ultrasonic vibration, 2006, Scripta Materialia, vol. 54, pp. 893-896. Jian X., XU H., Meek T.T, Han Q., effect of power ultrasound on solidification of Al A356 alloy, 2005, materials letters, vol.59, pp. 190-193. Abugh A., Kuncy I.K, Microstructure and mechanical properties of vibrated and weldments, 2013, University of agriculture, P.M.B 2373, Makurdi-Nigeria, pp.7-13. Pillai R.M., journal of material processing technology, 2004, vol.146, pp. 338-348. Sokoloff, Saito K., Male A., mater sci. Engg. A, 2005, vol. 393w, pp. 109-117. Cambell J., international metals reviews, 1981, vol. 26, no-2, pp. 71-108.
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An investigation of Effect of Mould Vibrations on Mechanical and Metallurgical properties of Aluminum 356 Casting 11. 12. 13. 14. 15. 16. 17.
Dommaschk C., Ph.D. d thesis, 2003, university of Freiberg, Germany. Abu Dheir N., solidification of Al-alloy, 2004, TMS, pp. 361-368. V. Sofroni, V.Brabie, C. Bratu, Theoretical Basis for Casting, Didactică si pedagogic publishing, house Bucharest, 1980 Ghe. Buzdugan, L. Fetcu, Vibraţii mecanice (Mechanical vibrations), E.D.P. Bucureşti 1982. Ghe. Buzdugan ş.a., (Vibration Measurement), Ed. Academiei R.S.R. 1979. Fl. Ştefănescu, Alloys solidification kinematic under the mechanic oscillations action (Cinematica solidificării aliajelor sub acţiunea oscilaţiilor mecanice), Metalurgica 42, 1990. C. Cernat, C. Bratu, Researches over the vibrations influence on the structure and mechanic characteristics of the cast steels (Cercetări privind influenţa vibraţiilor asupra structurii şi proprietăţilor mecanice ale o ţelurilor de turnătorie), Metalurgica 1978
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