9%Ni Steel Welding & Metallurgy

9%Ni

Cryogenic Tanks

Welding & Fabrications: an Introduction

Charlie/Jack/Xueliang/Fion

Prepared by 编辑: 2013 年上海/海盐浙江

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总结: 在次对 9%Ni 钢, 文章收集学习工作中,网上杰出学者论文, 产品资料等, 收集, 肤浅消化了中英 语资料. 以下为文章理解与结论: 

9%Ni 是用于-196°C 原材料与制作,焊接的一种成熟方案.

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不同于奥氏体不锈钢方案它的韧性下线温度极限为 -196°C 高于奥氏体材料 适用于 LNG/LPG.

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不同于奥氏体不锈钢 9%Ni 钢和一般合金钢表面腐蚀; 不适于用在需要高纯净储存内容如医药,食物, 电子用料等等.

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在 ASME 规范要求, 不同于奥氏体不锈钢材料, 对 WPS/PQR 参数与焊接复验等有不同的要求.

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9%Ni 和其他要求高的原材料等同,对原厂材料出厂资料必须严格把关.

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原材料机械性能, 化学成分复验与 PMI 对后续的质量工作有帮助.

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焊接焊材由于 Ni 合金的运用, 前期焊接施工面对的冷,热裂问题,此高 Ni 合金焊材对的运用, 配合焊 材焊前除氢, 焊弧保护, 母材/焊材除油等适当文明措施下上述焊接开裂缺陷不应当发生.

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为保证低温热影响区, 焊肉韧性, 焊接热输入为 0.6~2.0KJ/mm. 严格控制现场焊接 电流,电压, 速 度, 热输入 KJ/mm (等同熔敷速度, 等同焊肉成型大小),相应的焊丝,焊条直径大小等等约束. 进行多 层多焊道, 避免单焊道焊接.

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回火堆焊技术 Temper Bead Welding Techniques: 单道焊接热循环对 9%N 钢,母材粗晶热影响区(base metal-CGHAZ)热影响导致显著冲击功降低. 在多道焊接峰值温度大于 Ac3 的二次热循环后(对前一 道 CGHAZ 起热处理作用), 低温冲击功明显提高. 最后一道焊肉应当完全坐落在前焊肉上以避免新 的母材 CGHAZ.

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作为有效焊接热输入计算的重要因素, 除了清理表面水分,预热不必要. 一般情况之下不能大于 50°C, 层间温度保持在 100°C ~150°C.

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材料优越性综合比, 经双正火(NNT)热处理的 9Ni 钢,其低温韧度较差,调质热处理(QT)的次,QLT 与 IHT (α + γ) 双相区处理的低温韧度最好.然而这不影响现场施工方案.

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因 9%Ni 为高感磁性, 原材料到货残余磁量最大不能 >50 gauss, 焊接电流方案以 SMAW 运用交流电, SAW 运用直流波形控制方案, 工件运输与搬动不用磁性工具.

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焊接弧偏是存在的施工问题, 适当的措施包括:焊弧保持在 1~2mm, 焊接电流方案以 SMAW 运用交 流电, SAW 运用直流波形控制方案.

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高 Ni 合金焊条熔化温度比母材相对低 100 ~ 150°C . 这可能导致未溶合缺陷, 焊弧保持在 1~2mm 减 少弧偏与溶合.

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1.0

9%Ni 介绍：

The International Nickel Company laboratories found that low-carbon 9% (tempered martensite with appreciable amount of retained stable austenite) Nickel alloy steel, when appropriately heat treated, retained notch ductility at temperatures to -196oC and below.

Reverse austenite on tempering of quenched 9%Ni contributed to the excellent low temperature toughness.

The excellent low temperature notch impact properties of 9% nickel steels arise from the fine grained structure of tough nickel-ferrite free from embrittling carbide networks. These unique properties of the 9% Ni steel plates have resulted from the microstructure where consist mainly from fine martensite and from 5-15% retained austenite. This microstructure exists due to quenching and tempering NNT/Q&T.

Microstructure of 9Ni

The SA 553 type 1 (9% Ni) steel is the used material for the liquefied natural gas (LNG) tank application . Its microstructure content from martensite and retained austenite about (5 to 15% of structure size) as shown in (Fig 1) ,so this posses tensile strength range from 620 to 850 MPa , impact energy at -196 °C reach to 100J and more.

9%Ni 钢是 1944 年开发的 W(Ni) 9% 的中合金钢，由美国国际镍公司的产品研究实验室研制成功，它 是一种低碳调质钢，组织为马氏体加贝氏体。这种钢材在极低温度下具有良好的韧性和高强度，而且 与奥氏体不锈钢和铝合金相比具有热胀系数小，经济性好，使用温度最低可达 -196℃，自 1960 年通 过研究证明不进行焊后消除应力热处理亦可安全使用以来，9% Ni 钢就成为用于制造大型 LNG 储罐的 主要材料之一。钢的主要特点是高镍含量、高纯净度、较高强度、高的低温冲击韧性、良好焊接性能。 通过研发，钢材可以达到以下性能指标：

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2.0

9%Ni 标准：

9Ni 钢板标准 GB 24510-2009 9Ni490

EN 10028-4-2003 X8Ni9+NT640

JIS G3127-2005 SL9N520

9Ni590A 9Ni590B

X8Ni9+QT680 X7Ni9+QT680

SL9N590

ASTM

DIN

A-522

DIN 17280 X8Ni9 (1.5662) Plate

CCS-2007 9Ni

ASME SA-353 Double Normalized SA-553 Type 1 Quenched & Tempe red

UNS S21800

BS EN 10028-4:2003 Part 4: Nickel alloy steels with specified low temperature properties X8Ni9+QT680: ReH ≥ 585MPa，Rm = 680~820 MPa, A ≥ 18%, -196 oC, AKv (T) 50J, AKv(L) 70J

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3.0

9%Ni 用途：

目前超低温度用材料主要有以下几种：奥氏体不锈钢、镍基合金、铝合金和 9Ni 钢。相对与奥氏体不 锈钢和奥氏体铁-镍合金，9Ni 钢成本更低，相对于铝合金，9Ni 钢具有更好的力学性能，因此 LNG 储存和运输设备的结构材料国际上普遍使用 9Ni 钢。其中, 9Ni 钢是惟一可以在- 196°C 使用的铁素体 低温用钢,其-196°C 的夏比冲击功达到 200~230J ,是深冷环境下使用的韧度最好的材料。 Cryogenic storage for Methane (LNG), Oxygen. 气体 丁烷 丙烷（LPG） 丙烯 二氧化碳 乙烷 乙烯（LEG） 甲烷（LNG） 氧气 氮气 氢气 氦气

液化温度 °C 0 -42.1~ -45.5 -47.7 -78.5 -88.4 -103.8 -163 -182.9 -195.8 -252.8 -268.9

使用材料 C 钢、 细晶钢、 2.25%Ni 钢 3.5Ni 钢 5-9Ni 钢 奥氏体不锈钢 36%Ni-Fe 合金 Al 合金

中低温材料一览：

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4.0 4.1 

9%Ni 热处理方法 热处理方案： Double Normalized: NNT (SA-353)

双正火+回火(NNT)： 899°C (第一次正火-空冷) +788°C (第二次正火-空冷) +566~607°C (回火) 

Quenched & Tempered: Q&T (SA-553)

淬火+回火(QT)： 

866°C (淬火)+566~607°C (回火)

QLT (GB24510) (SA-844)

淬火+两相区淬火(IHT)+回火： 800°C (水淬)+670°C (水淬)+550~580°C (回火-水冷) 

Others: Inter-critical Heat Treatment IHT

两相区淬火(IHT)： 

800°C (空冷)+670°C (水淬)+550~580°C (回火)

(Inter-critical Heat Treatment)

Others: Direct Quenched & Tempered DQ-T

直接淬火(DQ-T)：

Ar3+580°C (回火)

9Ni 钢是在深冷条件下使用的铁素体型低温钢, 经适当的热处理后, 在 77K 下冲击韧度有大幅度的提高。 现有 9Ni 钢的热处理有三种基本规范, 即正火+正火+回火(NNT),淬火+回火(QT), 淬火+亚温淬火+回火 (IHT).

正火+正火+回火(NNT) 9Ni 钢的第一次正火为 900℃空冷, 保温时间根据板厚决定, 大约是 2.4min/mm,但必须保证保温时间 大于 15min, 第二次正火在 790℃左右空冷, 保温时间和第一次要求一样, 回火是在 550～580℃空冷或 水冷, 保温时间和正火处理要求的一样。正火处理的目的是细化奥氏体晶粒, 奥氏体晶粒越细小, 9Ni 钢热处理后的强度越高, 塑性越好,冲击韧度也越高。但如果正火温度过高, 或在高温下保持时间过长, 会使钢的奥氏体晶粒长大, 将显著降低钢的冲击韧度与裂纹扩展功和提高脆性转变温度。因而, 第一次 正火温度要高于 Ac3 或 Acm,其目的是细化晶粒。第二次正火温度稍低, 是为了使其发生相转变, 获得板 条状马氏体组织, 回火是为了是获得α相和少量的富碳、镍奥氏体。 NTT 主要适用于后加工,对淬火工序带来变形敏感的工件如:容器封头(在冷成型外纤维伸长大于 5% (ASME 要求)或冷加工导致未回火马氏体)

调质处理(Q&T/QLT/IHT) 淬火热处理方法,与双相区处理(IHT)调质处理时, 9Ni 钢的淬火温度一般为 800～900℃, 同时保温足 够的时间以使其完全奥氏体化后, 在 565～635℃回火, 回火时间按 1.2min/mm 计算，但至少大于 15min。 9Ni 钢的双相区处理是在调质的基础上, 在回火前进行(α+γ)双相区处理, 目的是使组织分布更加弥 散、均匀。9Ni 钢淬火后的组织为低碳板条状马氏体, 回火后得到的基体组织是回火马氏体以及部分回 转奥氏体。9Ni 钢经过(α+γ)双相区处理后, 其-196℃冲击韧度比调质热处理的提高 0.5～1 倍,甚至优 于 1Cr18Ni8Ti 不锈钢, 强度也是 1Cr18Ni8Ti 不锈钢的 2 倍,抗回火脆化能力也大大提高。在现有三种 热处理工艺中, 经双正火(NNT)热处理的 9Ni 钢其低温韧度较差, 调质热处理的次之, (α+γ)双相区处 理的低温韧度最好.

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4.2 规范要求： GB 24510-2009

BS EN 10028-4:2003 Part 4: Nickel alloy steels with specified low temperature properties

4.3

热处理对 9%Ni 钢低温的影响：

Heat Treatments for 9% Nickel Steel NNT

Double normalized and tempered (A353)

899oC + 788oC + (566oC - 607oC)

Q&T

Quenched and tempered (A553 Type 1)

802oC + (566oC - 607oC)

Nickel steel is heat treated either by double normalizing and tempering (NNT) or quenching and tempering (Q&T). The tempering is conducted within a restricted range, which results in the formation of a small amount (5-15%) of metallurgically stable reverse austenite (transform from tempered martensite), which is very important in developing the superior cryogenic toughness of the steels.

It is indicated that the quenching process led to a typical lamellar mixture of highly-dislocated fresh martensite and well-recovered original martensite. This “dual phase” lamellar structure caused reverse martensitic α→ γ transformation to take place in two stages during tempering. The final morphology of reversed austenite formed was either granular or thin film in shape surrounded by martensitic laths. The volume fraction of reversed austenite increased with the quenching temperature, and arrived at a peak value around 660 °C, then decreased subsequently. The enhancement of cryogenic toughness in the final structure was suggested as a result of formation of the reversed austenite with high thermodynamic stability. 合格的钢板金相中含有 5~15%的稳定逆转奥氏体. 

9%Ni 钢, 主要金相为回火马氏体, 第二相为回转奥氏体, 它不同于残留奥氏体, 是在回火过程中 由马氏体逆转变而来的, 特别之处这是当这稳定的回转奥氏体, 均匀,弥散分布时, 逆转奥氏体的 体积分数的亚温淬火温度上升,到达一个峰值在 660°C 然后随后下降.此外.在最终的结构中的增 强的低温韧性基体, 阻碍低温裂纹扩展的作用.

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

逆转或回转奥氏体不同于一般奥氏体，它是在低于 Ac1 温度时由马氏体逆转变而来的，其含有 较高的 Ni 及杂质元素，在低温有相对较还的机械与热稳定性。如果其弥散均匀的分布，具有割 裂基体，有利提高低温。

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以上原材料热处理工艺中, 以首三项为常规方法. 在这 3 种热处理工艺中, 经双正火(NNT )热处 理的 9Ni 钢, 其低温韧度较差, 调质热处理(QT )的次之, IHT (α + γ) 双相区处理的低温韧度最好.

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IHT (α + γ) 双相区, 回火温度较低. 在亚温下双相回火状态, 铁素体阻碍了奥氏体晶粒的长大, 这进而减弱了(α + γ) 晶粒大小, 对回转奥氏体分布均匀,弥散地分布有很大的关系. 在这亚温在 淬火下, 逆转奥氏体是在板条界与晶界上形成, 而 QT 处理后逆转奥氏体主要在晶界析出.

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逆转奥氏体的回火形成是由于碳化物的溶入而导致含碳量增高,使 Ms 和 Mf 点向更低的温度方向 移动, 逆转奥氏体相应的析出, 表现为低温时极为稳定,且不容易发生相变.

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9%Ni 钢含 0.10%左右的钼, 可以消除从奥氏体温度缓慢冷却时的脆化.

焊接线能量和层间温度会改变焊接热循环的峰值,温度,从而影响热影响区的金相组织.如峰值温度过高,会 使逆转奥氏体减少并产生粗大的贝氏体,从而使低温韧性下降.其它因素包括奥氏体/ 马氏体的界面共格 性,奥氏体周围位错的结构类型以及碳化物析出的影响等.

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5.0

9%Ni 金相

热处理工艺对组织金相的影响

5.1

DQ+T, QT, QLT, LT

Post hot working, before quenched & tempering heat treatment.

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5.2

NNT

5.2 QT

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5.3 IHT/QLT

5.4 逆转奥氏体分布: 以下图 3 与图 4 是机械稳定性实验的资料-三点弯曲后不同应力状态下逆转变奥氏体的分布进行了分析, 这里是用来表达逆转奥氏体的分布状况常识.

利用电子背散射衍射技术对三点弯曲后不同应力状态下逆转变奥氏体的分布进行了分析，其示意图和测 试位置如图 3 所示．图 4 给出了经 QLT 处理后的试样不同测试位置的电子背散射衍射扫描结果，其中 奥氏体用红色表示，体心立方基体用白色表示，角度为 10°和 5°的亚晶界用红色细线和绿色细线表示．从 图 4 可以看出，在中心未变形的位置 3( 图 4( f) ) 有部分逆转变奥氏体分布在晶粒内部，大部分分布在 原奥氏体晶界上． 由图 3 可知，位置 1 和 5 所承受的应力最大，其中位置 1 承受拉应力而位置 5 承受 压应力． 相对于未变形的位置 3，位置 1 [ 图 4( b) ) 和 5 ( 图 4 ( k)) 中逆转变奥氏体含量明显减少; 同 时，对比位置 1 和 5 可以看出，位置 5 的小角度晶界明显多于位置 1．承受压应力的位置 4 的小角度 晶界的数量要多于承受拉应力的位置 2，位置 4 的逆转变奥氏体的总量也小于未变形的位置 3 的逆转变 奥氏体.

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Reverse austenite distribution 逆转奥氏体分布: (a) QT 处理 (b) 630℃IHT 处理 (c) 650℃IHT 处 理 (d) 670℃IHT 处理 (e) 700℃IHT 处理

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5.5

热处理金相

Quenching temperature 淬火温度 : (a) 750°C (b) 800°C (c) 850°C

Tempering temperature 回火温度 : (a) 540°C (b) 570°C (c) 600°C (d) 630°C

Tempering time 回火时间: 570°C

(a) 0.5hr (b) 1.0hr (c) 1.5hr

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Inter-critical treatment temperatures (IHT): (a) QT 处理 (b) 630°C 两相区处理 (c) 650°C 两相区处理 (d) 670°C 两相区处理 (e) 相区处理

Inter-critical treatment holding time (IHT): 两相区保温 0.5h

(b) 两相区保温 1.5h

QLT tempering time: 540°C (a) IHT 回火 0.5h (b) IHT 回火 1.5h

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700°C 两

QLT tempering temperature: (a) 540°C (b) 600°C

5.6 微观学习 以下图示是逆转变奥氏体对 9Ni 钢低温冲击韧度的影响实验的资料-这里是用来表达逆转奥氏 体的微观组织常识.

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6.0 C Mn Si Ni

各合金元素的影响 Influences of Chemistry： 碳化物析出会造成孔蚀，一般控制在 < 0.08%； 奥氏体相稳定化元素，提高耐磨性及氮的固容量； 有助于高温耐高温氧化及耐酸蚀性能； 稳定化元素，减轻脆性并改善机械性能，增强耐酸能力。

C- Carbon strong austenitic former is the principal hardening element in steel, with each additional increment of carbon increasing the hardness and tensile strength of steel in the as-rolled, normalized or quenched and tempered condition. For structural applications, the carbon level is generally less than 0.30%.

For improved ductility, weldability and toughness, carbon contents below 0.20% are preferred. A compromise must be maintained between higher carbon levels required for tensile properties and lower carbon levels associated with improved ductility, weldability and toughness. For 9Ni carbon content is keep low to improved weldability and avoid cracking.

S- Sulfur / P- Phosphorous are generally considered an undesirable element.

Mn- Manganese austenitic former is present in all commercial steels, and contributes significantly to steel’s strength and hardness in much the same manner but to a lesser extent than does carbon. Its effectiveness depends largely upon, and is directly proportional to, the carbon content of the steel. Another important characteristic of this element is its ability to decrease the critical cooling rate during hardening, thereby increasing the steel’s hardenability. Its effect in this respect is greater than that of any of the other commonly used alloying elements. Manganese is an active deoxidizer and shows fewer tendencies to segregate than most other elements. Its presence in a steel is also highly beneficial to surface quality in that it tends to combine with sulfur, thereby minimizing the formation of iron sulfide, the causative factor of hot-shortness, or susceptibility to cracking and tearing at rolling temperatures.

S- Silicon ferrite former is one of the principal deoxidizers used in the manufacture of carbon and alloy steels and, depending on the type of steel, can be present in varying amounts up to 0.40%. Silicon is also a ferrite strengthener and is sometimes added as an alloying element up to approximately 0.5% in plate steel.

Ni- Nickel austenitic former is one of the fundamental steel alloying elements. When present in appreciable amounts, it provides improved toughness, particularly at low temperatures. Nickel lowers the critical temperatures of steel, widens the temperature range for effective quenching and tempering, and retards the decomposition of austenite. In addition, nickel does not form carbides or other compounds which might be difficult to dissolve during heating for austenitizing. All these factors contribute to easier and more successful thermal treatment. Because of the tight adherent scale formed on reheating nickel containing steels, the surface quality of plates with nickel is somewhat poorer than those without nickel.

Others Elements:

Mo- Molybdenum ferrite former exhibits a greater effect on hardenability per unit added than any other commonly specified alloying element except manganese or boron. It is a non-oxidizing element, making it highly useful in the melting of steels where close hardenability control is desired. Molybdenum is unique in the degree to which it increases the high-temperature tensile and creep strengths of steel. Its use also reduces steel’s susceptibility to temper embitterment.

V- Vanadium ferrite former is widely used as a strengthening agent in HSLA steels. Vanadium additions are normally 0.10% or lower. Vanadium bearing steels are strengthened by both precipitation hardening and refining the ferrite grain size. Precipitation of vanadium carbide and nitride particles in ferrite can provide a marked increase in strength. Thermo-mechanical-controlled-processing (for example, control rolling) increases the effectiveness of vanadium. Vanadium is also effective in increasing the hardenability and resistance to loss of strength on tempering in the quenched and tempered steels.

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7.0

9%Ni 钢材使用注意相

原材料接收检验注意相:     

8.0

材料热处理状态与金相. 机械性能. 化学成分. 材料复验, PMI. 残留磁场检查.

9%Ni 机械性能 Mechanical Properties：

9%Ni 钢与奥氏体不锈钢, 屈服/抗拉强度的差别很大, 在大型低温储罐设计, 9%Ni 钢占很大 的优势.

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9.0

9%Ni 超规范加强机械性能 Enhanced Mechanical Properties：

Super-9%Ni Whereas the thickness of the 9%Ni steel plates used for the conventional LNG tanks was 30 mm or so, the thickness of the plates used for large tanks was often as large as 50 mm, and the lowering of fracture toughness due to increased thickness began to constitute a serous concern about the very thick 9%Ni steel plates. For this reason, it was necessary to establish a technology to stably produce steel plates having a better low-temperature toughness than conventional 9%Ni steel plates either in base metal or in welded joints.

Methods include: 

Inter-critical Heat treatment-proprietary IHT/QLT 临界区热处理



通过 Si 含量的减少, 改进的韧性 Improvement of toughness by reduction of Si content. http://www.nssmc.com/en/tech/report/nsc/pdf/n9006.pdf It has been known that reduction of Si content is effective in improving base metal toughness of 9%Ni steels5). This is because controlling Si content to about 0.05% significantly lowers sensitivity to temper brittleness and stabilizes the austenitic phase in steel. These improve toughness after tempering.



降低碳,硫磷含量,增加镍含量显著的提高材料在-196oC 的冲击性能.

The benefit of lower carbon, sulfur, phosphorus and higher nickel levels is shown with the improvement in toughness. 9% nickel steel can be ordered with 0.002% S and 0.005% P maximums when required will improved Charpy-V notch performance at -196oC.

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10.0

屈强比与冷却率 Cooling rate & yield to tensile ratio：

淬火+回火带给的高屈强比与冷却率增强冲击试块横向扩展. (如 A553 Type 1).

Other factors contribute to the improved toughness of 9% nickel steels. Traditionally, toughness improves with quenched and tempered material over that produced in the normalized condition. Cooling rate plays a major role in determining Charpy toughness for 9% nickel steels. Experimental work has shown that lateral expansion and the ratio of yield to tensile for A353 and A553 are directly correlated, and the higher the yield to tensile ratio, the more lateral expansion is expected. This is shown in the figures below. Consideration must be given then to choosing A353, a NNT product with generally lower Y/T, or A553, a Q&T product with higher Y/T and considerably higher Charpy and lateral expansion values. The cooling rate has a major affect on the resultant yield to tensile ratio, as illustrated below.

This information may be important when considering heat treatments other than as provided from the steel mill.

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11.0  



其他 Other Information

Inconel http://www.specialmetals.com/products/index.php Corrosion resistance in Nickel containing alloys in petrochemical environments; NASA Doc. http://www.specialmetals.com/documents/Corrosion%20Resistance%20of%20Nickel-Containing%20 Alloys%20in%20Petrochemical%20Environments.pdf http://exchange.dnv.com/Publishing/TAP/TAP1-401-1.pdf

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12.0

研讨/Discussion

12.1

Design Codes and Standards:

Rules for design, fabrication and testing of pressure vessels are given by the; ASME Code Section VIII, Divisions 1 and 2 (including applicable Code Cases 2214, 2335 and 2345), Section III Class 3 Components.





Except as provided by the fabrication requirements of ULT-79, the ASME Code requires no post weld heat treatment for 9% Nickel up to 2 in.(51 mm)inclusive in thickness. See AF630.1 (Division 2) and UHT56 (Division 1).

API Standard 620 “Design and construction of large, welded storage tanks”. Appendix Q.



12.2    

Material:

Project material specifications Is there any enhanced CVN requirements at -196oC What are the specified C (carbon), S (sulfur), P (phosphorus) and N (nickel) levels Base material residual magnetism requirement of 50 gauges maximum.

12.3

Forming:

当冷成型外纤维伸长大于 5% ASME 要求热处理工序 The ASME Code requires post heat treatment where outer fiber elongation in cold forming exceeds 5% by the formula:

%E T Rf Ro

Percent extreme fiber elongation Plate thickness Final radius Original radius (equals infinity for flat plate)

冷成型导致未回火的马氏体 Deleterious effect of untempered martensite; In addition, cold forming of 9% Nickel steel may cause the transformation of retained austenite into untempered martensite due to cold work. This may have a deleterious effect on toughness, but may be partially restored by an inter-critical post heat treatment. Fabricators are urged to determine the effect of forming practices on final material properties. The post heat treatment, where necessary, is conducted in accordance with the rules of Section VIII Division 1 UHT-56 within the range of 551-583oC, but not exceeding the tempering temperature, holding at temperature for one hour per inch of thickness, followed by cooling at a rate no less than 167oC per hour. Slower cooling rates may reduce the notch toughness of the steel.

Post heat treatment 热处理温 度 Cooling at a rate

551-583oC no less than 167oC per hour

热成型锻造 Hot forming operation: In some cases, it may be desirable to form hot. The formed part must be either completely reheat treated or in the case of the double normalized and tempered specification, A353, the forming operation may be conducted at 899-954oC and treated as the first normalizing operation. The ASME Code requires that tests be made by the fabricator to verify the heat treatment. It is suggested that hot forming be limited to non-welded plate, unless it is first demonstrated that the weld metal is capable of meeting required mechanical properties after being heat treated.

Forming 锻造温度 Post heat treatment

899-954oC NTT/Q&T + Testing

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12.4

Welding and Fabrications

9Ni钢焊接施工钢焊接过程中容易出现的焊接 (1) 裂纹, (2) 接头的低温韧性降低和(3) 电弧的磁 偏吹等 (4) 由于采用Ni基型焊接材料焊接,焊缝金属的熔点比9Ni钢低100-150oC左右,容易造成未 熔合等类缺陷问题，以及为避免这些问题所采取的措施 9Ni 钢焊接主要考虑 keys consideration: 

Cold and hot cracking 冷和热裂纹.

Solution: By proper selecting of welding consumables (Ni based alloy) and clean welding practices cold and hot cracking could be avoided. 通过适当的选择焊材(镍基合金)及清洁焊接方法,可避 免冷和热裂纹.



Deterioration of low temperature toughness property 低温韧性属性恶化.

Solution: By proper control of welding heat inputs and interpass temperature, low temperature toughness could be ensured: Heat input < 2.0KJ/mm, interpass temperature 100-150oC, low ferrite, 2 FN, C< 0.03%, N< 0.05%. 通过适当的控制焊接热输入和层间温度，可确保低温韧性。



Arc stray due strong magnetic property of 9Ni. 电弧偏离与残磁 Solution: Used AC source for SMAW and GMAW and AC Square curve for SAW could avoid induced magnetism. 用交流电源 (SMAW/GMAW) 或交流弧形控制-交流方波 (SAW).



Lack of side wall and interpass fusion due to low heat input.

Solution: Used short arc length for SMAW and AC Square curve for SAW. 采用短弧(SMAW) 或交流弧形控制 –方波(SAW)



Low impact toughness of Base metal-CGHAZ 母材-CGHAZ 粗晶热影响区低冲击工 Solution: Temper Bead Welding Techniques 回火堆焊技术: 单道焊接热循环对 9%N 钢,母材粗 晶热影响区( Base metal-CGHAZ)热影响导致显著冲击功降低. 在多道焊接峰值温度大于 Ac3 的二次热循环后(对前一道 CGHAZ 起热处理作用), 低温冲击功明显提高. 最后一道应当完全 坐落在焊肉上以避免新的母材 CGHAZ.

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描写与讨论 Cold and hot cracking 冷和热裂纹 9％Ni 钢具有良好的焊接性能，对冷裂纹的敏感性很低. 要保证焊缝高强度及低温韧性, 焊接时严 格控制焊接参数, 特别是预热, 层间温度及热输入. 通常厚度小于 50 mm 的焊缝无需预热，焊前 温度高于 10℃即可, 层问温度控制在 100oC~150oC 以下, 以避免焊缝热影响区韧性的下降.

BS EN 10028-4:2003 Part 4:

热裂纹 钢材的焊接冷裂纹敏感性一般与母材和焊缝金属的化学成分有关，焊接规范等。采用 Ni 基合金 材料焊接，使熔合区基本上不出现高硬度马氏体带.有利于避免冷裂纹的产生. 母材热影响区的冷 裂倾向；为了说明冷裂纹敏感性与钢材化学成分的关系，通常用碳当量来表示:

By using high Nickel alloy (Inconel) as welding consumable, the susceptibility of weld metal and fusion zone to cold and hot cracking is very low. On the base metal the susceptibility could be numerically represented by:

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Pcm X8Ni9 =0.10 + (0.35)/30 + (0.8+0+0)/20 + 10/60 + .1/15 + 0.01/10 +0 = 0.431

The 9%Ni calculated Pcm at maximum contents is 0.431; the weldability index is graded “Good”

或

1 1 1 1 1 CEN  w(C)  A(C){ w(Si)  w(Mn)  w(Cu)  w(Ni)  w(Cr  Mo V  Nb)  5w(B)} 24 16 15 20 5

(1)

式中A(C) -碳的适用系数 A(C)=0.75+0.25tanh[20（W(C)-0.12）]式中tanh双曲线正切函数。 A(C)=0.75+0.25*tanh(20*(0.05-0.12)=0.56 CEN=0.05+0.56*(0.27/24+0.48/16+0.02/15+8.86/20+0.1/5) CEN=0.333 根据JGJ81-2002规定：钢材碳当量小于0.38，焊接难度一般；在0.38～0.45范围内，焊接程度较难。 9Ni钢的碳当量0.333，可焊接性比较好。 冷裂纹产生的原因有三方面： 

 

熔合区出现硬化层。9Ni 钢本身含碳量不变(≤ 0.10)，焊接时本不会产生硬化组织，但如果选 用含碳量较高的焊材也会因熔合、扩散使熔合区含碳量增高而产生硬化层。这里我们的假设 是用高镍基焊材，熔合区不会产生硬化组织. 氢含量过高。氢在硬化层中积聚是由于焊缝坡口附近不洁(有水,油及有机物),及焊条扩散氢含 量高所致.焊前烘干除氢工作必须到位, 焊接接头应力包括组织应力,热应力和拘束应力-合理的安排焊接工序, 工件组对等.

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热裂纹 热裂纹的产生与焊缝金属结晶过程中的低熔点杂质偏析的数量及分布有关。液体金属结晶过程越 长偏折越严重，偏析产生的低熔点杂质分布在晶界上，尤其在纯奥氏体组织中，杂质在晶界上的 分布是连续的. 焊接热裂纹具有高温沿晶断裂性质，发生高温沿晶断裂的条件是，在高温阶段晶 间延性或塑性变形能力 δ min 不足以承受凝固过程或高温时冷却过程积累的应变量 ε，即 ε ≥ δ min。宏观可见的焊接热裂纹，其断口均有较明显的氧化色彩，这可作为初步判断是否属于热裂 纹的依据。 对于低温钢的热裂敏感系 HCS 公式：

HCS 

1 1 w( Si )  w( Ni )] 25 100 *103 3w( Mn)  w(Cr )  w( Mo)  w(V )

w(C ) *[ w( S )  w( P) 

当 HCS < 4时可以防止热裂纹。 焊材选用 ENiCrMo-6:

用一般值(一例) 计算: HCS Index = [%C x (%S + %P + 0.04Si + 0.01Ni ) ] / [ 3x%Mn + %Cr +%Mo + %V ] x 103 HCS Index = [0.030/33.53]x 1000 = 0.89 < 4 可以防止热裂纹.

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CGHAZ 粗晶热影响区低冲击工

HAZ 由不同区域的组织构成. 每一区域的组织都受加热速度、峰值温度和冷却速度的影响。如图 2 所示, 对 于单道焊，根据峰值温度, HAZ 可划分为粗晶区(GCHAZ), 细晶区(GRHAZ),中间临界区(ICHAZ)和亚临界 区(SCHAZ):对于双道焊或多层焊，第二道焊道的 HAZ 与第一道重叠，在第一道的 HAZ 中形成被部分或完 全再热区，其中最引人注目的是亚临界再热粗晶区(SCGCHAZ)和中间临界再热粗晶区(ICGCHAZ).

处于 CGHAZ 临界温度(1100oC)上,下的组织出 现十分明显的差异。分析表明，在焊接热过程 高温阶段形成的粗晶区中，由于晶粒粗大，使 得奥氏体转变的稳定性增加和非平衡的低温 转变产物增多,因而在 CGHAZ 中可以观察到 少量上贝氏体。由于上贝氏体条间的碳化物易 于萌生裂纹或成为裂纹扩展的通道,致使材料 的韧性降低.

一般热影响区的分区 Page 39 of 66

在 9%Ni 钢单道焊中（CGHAZ）是热影响区中韧 性最薄弱的环节。粗晶区的韧性随着焊接热输入 的加大而下降。引起这种局部脆化的主要原因是 晶粒粗化和组织恶化．工程上管线钢热影响区冲 击试验所获得的韧性值，实际上是母材、焊缝和 热影响区性能的平均值，并未反映热影响区的真 实情况。多层多道，最后一道焊采用回火堆焊能 有效地缓解上述问题．

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Residual and induce magnetism.  

Workshop practices: Strong magnetic properties of 9Ni necessitate handling methods not to introduce residual magnetism. (magnetic handling equipments shall be avoided) Residual magnetism measurement of 50 gauge maximum.

直流焊接时磁偏吹现象的预防。9％Ni 钢属强磁性材料，用直流电源焊接时会产生磁偏吹现象. 预防措施是：焊接母材从钢厂运到工地的过程中，要避免磁化，不允许用磁力起重机。焊接过程 中合理连接地线和焊接电缆，注意电缆的走向和布线方式，同时电缆线不要和工件表面接触，可 采用绝缘支架的形式架离表面；在焊完一层焊道后，测量焊缝的各点剩磁强度，若超标则应采取 去磁措施。 克服磁偏吹的途径: 

母材和焊接材料：母材运至现场时的剩磁要求,必要时进行消磁处理,同时选择能防止电弧磁 偏吹的焊接材料。



9Ni 钢属强磁材料，直流焊接时会产生磁偏吹现象,在焊接时应尽量使用交流焊接（焊接设备： 采用交流方波焊接电源）或用磁铁进行退磁。



打磨方式：由于碳弧气刨采用直流电焊机，气刨电流通常在 500A 以上，这样气刨、直流焊 机和罐壁之间构成直流外加强磁场，当碳刨结束,罐壁中容易产生较强的剩磁，从而导致焊接 电弧磁偏吹.因此尽量用砂轮打磨

Forming, cutting and shearing (fit-up)  

It should be noted that 9% Nickel steel has high yield strength and requires approximately three times the forming capacity of mild steel.

Preheat prior to forming and cutting may not be necessary except for removing moisture on surface.

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Preheating for welding and cutting   

Preheating for cutting generally is not necessary Plate over 25mm in thickness may be preheated to about 35oC and that lighter plate not be welded below the dew point.

Section VIII Code Case 2214 provides additional information on preheats requirements in special situations.

Scenario Preheat Plate >25mm Plate >50mm High humidity with plate surface temperature at/below Dew Point

Recommended Practices Generally not necessary 35oC recommended 50oC recommended Preheat to remove moisture.

Welding Parameters.   

Use low heat input as compare with general structural steel welding for offshore engineering, Heat input shall be limit to 1.4~1.6 KJ/mm and shall be less than 2.0 KJ/mm Caution is advised for plate under about 13mm both because light plate chills the weld less rapidly and because transverse plate Charpy values tend to be lower initially for thin plate. Data from laboratory tests suggest the following guide for preparing the qualification test plate.

Welding interpass temperature  

For thin plate 13mm used the heat input range from 1.4 to 2KJ/mm max and controlling interpass temperature within 80°C. For thick plate >13mm used the heat input range from 1.4 to 2KJ/mm max and control interpass temperatures at 100°C ~ 150°C or lower.

Welding Processes 

(1) Short arc length and (2) richer alloy welding chemistry (e.g. Inconel) to improve mechanical properties and dilution at weld interface.

For 9%Ni Steel For welding of 9%Ni steel, Ni-base alloys such as Ni-Cr alloy (e.g., Inconel) and Ni-Mo alloy (e.g., Hastelloy) welding consumables are commonly used to obtain sufficient notch toughness at cryogenic temperatures. 9%Ni steel is used for storage tanks for liquefied natural gas (LNG), liquefied oxygen and liquefied nitrogen, and LNG carriers. In the construction of such cryogenic temperature service equipment, automatic gas tungsten arc welding and submerged arc welding are often used to ensure consistent weld quality, as shown in Fig. 1

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█ Tips for better welding results for individual welding processes

SMAW (1) Use proper welding currents because the use of an excessive welding current causes electrode-burn and thereby usability and weld metal properties can be deteriorated.

(2) Use no preheating for welding matching Ni-base alloys. Control interpass temperatures at 150°C or lower.

(3) Use the back-step technique when an arc is struck in the welding groove, or strike an arc on a piece of metal outside the groove to prevent the occurrence of blowholes at the arc starting area of a bead.

(4) Keep the arc length as short as possible 1~2mm.

(5) Use flat-position welding as much as possible because vertical or overhead welding requires higher welding skill.

(6) Minimize welding currents and speeds to prevent hot cracking.

FCAW (1) Use Ar-CO2 mixtures with 20-25%CO2 for shielding gas. The gas flow rates should be 20-25 l/min.

(2) Refer to Pages 205 of the stainless steel article about power source, wire extension, protection against wind and welding fumes, and storage of welding wires.

GMAW (1) Pulsed arc welding with the spray droplet transfer mode using low currents is most appropriate, although conventional gas metal arc welding power sources can be used. DC-EP polarity is suitable.

(2) Argon gas shielding with gas flow rates in the 25-30 l/min range is suitable. Ar-He mixture gases are also suitable.

(3) Use no preheating and control interpass temperatures at 150°C or lower.

(4) Minimize welding currents and speeds to prevent hot cracking.

GTAW (1) Use DC-EN polarity.

(2) Argon gas shielding with gas flow rates in the 10-15 l/min range is suitable where welding currents are within 100-200A. In one-side welding, back shielding is needed to avoid oxidation of the back side bead.

(3) Control the arc length at approximately 2-3 mm because the use of an excessive arc length may cause lack of shielding, thereby causing blowholes.

(4) Use no preheating and control interpass temperatures at 150°C or lower.

(5) Minimize welding currents and speeds to prevent hot cracking.

SAW (1) Re-dry fluxes by 200-300°C for 1 hour before use.

(2) Use multi-pass welding because the use of single-pass welding may cause a decrease of weld metal strength affected by the dilution from the base metal.

(3) Heat input to control at <2.0 KJ/mm (4) Submerged-arc welds with Inconel are best made with 1.6mm wire.

ASME IX code welding variables.   

Welding code for WPS, WPQT and WQT are ASME IX Code.

For qualification purposes, the double normalized (A353) and quenched grades (A553) are: P-No. P11A, Group 1.

Additional tension tests at or below the vessel minimum allowable temperatures are required for Section VIII Page 43 of 66

Div 1 ULT applications. Section VIII, Divisions 1 and 2, Section III and API Standard 620 Appendix Q specify that the weld metal and heat affected zone of procedure qualification tests shall meet the Charpy V-Notch requirements for the plate.

Production impact testing may be exempt for welding under certain conditions in Section VIII, and for API 620 Appendix Q after the initial tank construction.



12.5

POST Weld Heat Treatment-PWHT

Except as provided by the fabrication requirements of ULT-79, the ASME Code requires no post weld heat treatment for 9% Nickel up to 2 in.(51 mm)inclusive in thickness. See AF630.1 (Division 2) and UHT56 (Division 1). Where post weld heat treatment is performed, it is necessary to control the temperature within the range of 551-583oC but not over the tempering temperature and to cool at a rate not less than 167oC per hour to avoid possible reduction in notch toughness of the steel.

12.6

ASME Section VII/IX 要求-Welding Procedures and Qualifications

Some important Section VII requirements for welded construction of 9Ni steel vessels include; 

 

Welding procedure qualifications, performed in accordance with Section IX, require impact tests of weld metal and HAZ in addition to transverse tensile and bend tests. Impact tests are made at -196 or at lower of design or operating temperature.

Charpy V-notch tests (three specimens each test) are required to meet a minimum of 0.38mm lateral expansion rather than J energy criteria.

Impact test plates are required for each 400 ft of production welds. Tests are made of the weld and HAZ at -196 or at lower of design or operating temperature. Nickel-based filler metals exempted from production weld testing are the electrodes SFA5.11, ENiCrFe-2, ENiCrFe-3 and bare metals SFA.14 ERNiCrFe6 and ERniCr-3

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12.7

推荐的焊接材/ Recommended Welding Consumable

焊缝金属的低温韧性主要与采用的焊接材料的类型有关。用与 9Ni 钢成分相同的焊接材料焊接时 (TIG 焊除外)，因焊缝金属含氧量过高，焊缝金属的低温韧性很差，因此焊接材料常选择 Ni 基或。 焊缝金属的低温韧性主要与采用的焊接材料的类型有关。用与 9Ni 钢成分相同的焊接材料焊接时 (TIG 焊除外)，因焊缝金属含氧量过高，焊缝金属的低温韧性很差，因此焊接材料常选择 Ni 基或 Fe-Ni 基两种类型，且又多采用前者。另外，由于 9Ni 钢的膨胀系数较大，在选择焊接材料时，应 使焊缝与母材的膨胀系数相近，以免产生裂纹.

镍合金焊条(如ENiCrMo-6))具有如下特点： 

ENiCrMo-6焊条中的镍合金与9Ni钢在室温和高温下的线胀系数基本相近，从而避免因 不均匀的热胀冷缩造成的热应力。



ENiCrMo-6镍合金焊条中含Ni量高达55％～ 66％，含碳量与9Ni钢相同，均为低碳型， 考虑母材对焊缝金属的稀释作用，仍有足够高的奥氏体组织避免熔合线出现硬脆马氏 体带。



ENiCrMo-6镍合金焊条具有低碳性(含碳量保持在0.05％左右，在Fe-C状态图中处于很 小的“脆性温度区间”以及高纯度(含S≤0.03％ ，P≤0.02％)，低含氢量等特性。



采用Ni基、Fe-Ni基焊条焊接9Ni钢,所得的组织为奥氏体组织。强度略低,焊接时对热 裂纹敏感性高,熔深浅,控制不当易产生未焊透及熔合不良等缺陷。要消除以上裂纹， 最有效的方法是减少有害杂质、采用正确的收弧技术并配合打磨处理。



9Ni钢本身与同等强度水平的其它低合金钢相比有较好的抗裂纹的能力，在低氢情况下 一般不会产生冷裂纹。但采用低镍高锰型奥氏体焊条时，因母材的稀释作用，在熔合 区会出现高硬度的马氏体带，对氢脆敏感。防止冷裂纹的措施是在施焊中严格执行焊 接工艺规程，特别是焊条烘干、焊接环境温度、焊接规范等。采用Ni基合金材料焊接， 使熔合区基本上不出现高硬度马氏体带。有利于避免冷裂纹的产生。由此可见， ENiCrMo-6镍合金焊条的使用可提供降低9Ni钢焊缝冷、热裂纹倾向的基本条件。同时 说明，在严格控制扩散氢含量的条件下，选用ENiCrMo-6镍合金焊条可基本避免9Ni钢 的焊接冷、热裂纹倾向。

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Selecting ENiCrMo-6/3 and ERNiCrMo-3/4

国内供应商 LOCAL: http://qhxl.cn.gongchang.com

Material

9%Ni 钢 JIS G3127 SL9N590 ASTM A553 Type 1

Processes

Brand

ASME/AWS

Polarity

Flux (Mesh) Rod/Electrode Sizes （mm￠）

SAW (Flux/Wire)

PF-N4/ US-709S

SFA/A5.14 ERNiMo-8 (US-709S)

DCEP

Flux：12×65 2.4

NI-C70S

SFA/A5.11 ENiCrFe-9 AC

3.2 4.0，5.0

SMAW NI-C1S

SFA/A5.11 ENiMo-8

GTAW

TG-S709S

SFA/A5.14 ERNiMo-8

DCEN

1.2，1.6 2.0，2.4

FCAW

DW-N70S

--

DCEP

1.2

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国外供应商 : http://specialmetalswelding.com/ Base Materials Information

Welding Consumables Information

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SMAW WELDING ELECTRODES INCONEL® Welding Electrode 112 (ENiCrMo-3) A basic coated electrode with fully alloyed core wire and reduced coating thickness offers: 



 

 

  

Strength levels (0.2% proof stress and ultimate tensile stress) consistently exceeding the minimum requirement of 9% Nickel Steels Excellent Charpy impact toughness at -196°C All positional weldability Applicable on both DC and AC (square wave) power sources Non-hygroscopic coating Optimum alloy transfer Reduced power consumption

• Exceed the minimum strength requirement of 9% Nickel Steel • Offer excellent resistance to brittle fracture • Offer excellent Charpy impact toughness at -196°C INCONEL® Filler Metal 625 is generally restricted to a maximum diameter of 1.6 mm for use with the SAW process in order to minimise the incidence of hot cracking defects.

INCO-WELD® Welding Electrode C-276 (ENiCrMo-4) Offers all the features of INCONEL? Welding Electrode 112 with the added benefit of improved Charpy impact toughness at -196°C (70 joules minimum) to meet the latest European specifications. This improvement is attained by removing Niobium (Nb) and increasing Molybdenum (Mo) maintaining the balance of weld deposit strength and low temperature toughness.

GMAW/GTAW FILLER METAL Special Metals Welding Products Filler Metals for GMAW/GTAW are available in a wide variety of diameters and spool sizes to suit automated systems and in straight length format for manual operations. The filler metals are processed specifically to provide optimum delivery to the weld pool.

INCONEL® Filler Metal 625 (ERNiCrMo-3) This NiCrMo Filler Metal with NB is suited to applications on both GMAW/GTAW processes, in either manual or automated systems offering: 





SAW FILLER METALS AND FLUXES INCONEL® Filler Metal 625 – ERNiCrMo-3 INCO-WELD® Filler Metal C-276 – ERNiCrMo-4 Both of these NiCrMo Filler Metals are utilized extensively for the fabrication of 9% Nickel Steels by the SAW process and offer weld deposits which:

Strength levels consistently exceeding the minimum requirements of the 9% Nickel Steels Excellent Charpy impact toughness at -196°C Improved wire delivery to the weld pool resulting from controlled filler metal processing.

INCO-WELD® Filler Metal C-276 with increased Mo and reduced Nb is less sensitive to hot cracking and can generally be utilized in diameters up to and including 2.4 mm. This offers productivity benefits in addition to being commensurate with available on site SAW equipment generally designed to handle larger diameter filler metals.

FLUXES INCOFLUX® 9 This semi-basic fused flux is suitable for welding on either DC or AC in the down-hand and horizontal position with resultant smooth weld beads and self releasing slag. • Applicable on both AC/DC power source • Utilizes 10% less energy than agglomerated equivalents • Greater density supports weld pool in the HV position INCOFLUX® 7 This basic agglomerated flux is alloy compensated offering optimum alloy transfer on material thickness up to and including 50 mm.

The flux operates on Direct Current (DC) and offers excellent weldability in the down-hand and horizontal position, provides good melting, self releasing slag and prevents formation of secondary slag. Both the above products are applicable with either INCONEL® Filler Metal 625 or INCO-WELD® Filler Metal C-276.

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INCO-WELD® Filler Metal C-276 (ERNiCrMo-4) This NiCrMo Filler Metal with increased Mo, W, and reduced Nb is suited to both GMAW or GTAW processes either manually or fully automated and offers: 





Strength levels consistently exceeding the minimum requirements of the 9% Nickel Steels.

Excellent Charpy impact toughness at -196°C Improved wire delivery to the weld pool resulting from controlled filler metal processing

GSFCAW INCO-CORED® 625 AP/DH This NiCrMo gas shielded flux cored wire offers weldability and metallurgical integrity of covered electrodes and higher deposition rates associated with automated processes. The fully alloyed sheath allows for optimum alloy transfer to the weld pool and offers deposits which:  Consistently meet the minimum strength level requirement  of the 9% nickel steel  Exhibit excellent Charpy impact toughness at -196°C  Are free from defects  Offer resistance to brittle fracture

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国外供应商 : http://www.oerlikon-welding.com

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ESAB;

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Boehler Recommendations: www.boehler-welding.com Care must be taken to control the heat input when welding cryogenic and fine-grain constructional steels to keep the heat affected zone as narrow as possible and still prevent hardness peaks. Basic-coated non-alloy and low-alloy stick electrodes according to EN ISO 2560 and EN 757 is suitable. The hydrogen content in the welded joint should be as low as possible to prevent cold cracks, i.e. rebaking of the electrodes immediately prior to welding is recommended. This statement also applies to the flux powder in submerged-arc welding. The problem of excessively high hydrogen contents does not normally exist for gas-shielded arc welding. Particular attention should be paid to the low-temperature toughness and strength required when selecting wire and flux combinations or wire and shielding gas combinations.

9 % Ni-steel is mainly joined using completely austenitic filler metals with a high nickel content of the “NIBAS 625“type. This nickel-based type has advantages over conventional austenite due to a higher yield point and the possibility of heat treating welds. It may also be used for steels with low nickel content. Crack resistance and adequate cold toughness down to -200 °C are ensured if dilution with the parent metal is limited. Hereafter are listed the most important particulars: 

Cleanliness is a top priority. Weld edge and weld area must be free of any residues and in particular free of grease, oil and dust. Oxide skin must be removed approx. 10 mm on each side of the weld.



The opening angle has to be wider than on C-steel, in general 60 – 70°. Tag welding must be done in short intervals. The root opening has to be 2 – 3 mm wide and the root face should be approx. 2 mm high.

Electrodes have to be re-dried prior to any welding。

 

For most applications we recommend string bead technique. When weaving, the oscillation should be limited to 2.5 x the diameter of the electrode core wire. This does not apply to vertical up welding.



The electrode should be welded with an angle of approx. 10 – 20° and the arc should be as short as possible.



The end crater is to be filled, in the root to be grinded out. Ignition of a new electrode should be approx.

10 mm before the last end crater, and then the arc has to be taken back to the end crater where the actual welding starts. The ignition points are then over welded again.



The interpass temperature should not exceed 150 °C and heat input should be limited to approx. 2 KJ/cm maximum.



If multi layer welding has to be made, each layer has to be cleaned with a stainless wire brush to remove slag residues and oxide skins.



Weld surfaces can be cleaned by grinding, brushing with a stainless steel wire brush or by pickling.

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12.8

Sample PQR

Sample PQR: SMAW-01

3G / 16mm Electrode re-bake at 300~350째C for I hour.

2G/16mm

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Sample PQR: SAW-01

1G/18mm/ α= 60° / p = 2mm/ b= 2mm Heat input 0.7~3.5 KJ/mm Preheat 20°C Interpass <=100°C

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Sample PQR: 02

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Sample PQR: SMAW-02 PQR-9702/ Interpass <100째C/ ESAB OK 92.55

Sample PQR: SAW-02 PQR-9805/ Interpass <100째C/ ESAB wire OK 19.82/ flux OK 10.16

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Sample PQR: 03 SAW 背面采用焊剂保护，使背面的成形良好，可大幅度减少清根工作量，只用砂轮稍加修整，经 PT 检测合 格后，即可焊接。这样即可避免碳刨时对 9％Ni 钢的影响，又可节省劳动力和焊材。用交流方波电源，降低 焊接工序对母材 9％Ni 钢产生磁性。

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Sample PQR: 04

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13.0

Others

Standard for Certification - No. 2.9, March 2012 Type Approval Programme No. 1-401.1 Sec.11. Welding Consumables for Welding of Steel Grades NV 1, 5Ni; NV 3, 5Ni; NV 5Ni and NV 9Ni – Page 35

Rules for Ships, January 1996 Pt.2 Ch.3 Sec.3 – Page 37

11. Welding Consumables for Welding of Steel Grades NV 1, 5Ni; NV 3, 5Ni; NV 5Ni and NV 9Ni

Charpy Notch specimen breaks at -196 oC

---------------- 21 January 2013 镇江 ----------------

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