氮含量对高氮钢PMIG焊接头组织和性能的影响
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摘要
文中采用H307Mo焊丝,开展了高氮钢PMIG焊接工艺试验,重点分析了焊缝中氮含量对接头组织和性能的影响,并通过调整工艺参数,控制焊缝中氮的含量.结果表明,当焊缝中氮含量低于0.24%时,焊缝以FA模式凝固,焊缝组织为骨架状铁素体枝晶和奥氏体基体组成,并且随着氮含量的提高,铁素体含量降低,显微硬度逐渐下降;当焊缝中氮含量高于0.30%时,焊缝以A模式凝固,组织为单相奥氏体枝晶组织,随着焊缝氮含量的提高,奥氏体枝晶不断增大,显微硬度逐渐提高.随着氮含量的提高,焊缝中气孔逐渐增多,冲击韧性呈现先增大后减小的趋势.
To meet high quality welding requirement of high nitrogen austenitic stainless steel components,the steel is welded by PMIG welding with 307Mo weld wire.By adjusting the shielding gas composition,the jointswith different N-content are obtained,and the influence of N-content on microstructure and mechanical properties of joints is investigated.The experimental results indicate thatif the N-content of the weldmetal is lower than0.24%,the solidification mode is FA and the microstructure is austenite and skeletal ferrite.The higher N-contentin the weldmetal,the less ferrite in it and a lower microhardness will be got.When the N-content of the weldmetal is higher than 0.30%,the solidification mode is A and the microstructure is single austenite.The austenite dendrites become progressive coarse and the microhardness become higher while there is a higher nitrogen level.No nitrides can be found in the weld joints.The nitrogen pore will increase when the N-content of the weld metal ishigher.The higher N-content in the weld also can benefit the toughness,but if the N-content is too high,nitrogen pores can damage the toughness of the weld.
To meet high quality welding requirement of high nitrogen austenitic stainless steel components,the steel is welded by PMIG welding with 307Mo weld wire.By adjusting the shielding gas composition,the jointswith different N-content are obtained,and the influence of N-content on microstructure and mechanical properties of joints is investigated.The experimental results indicate thatif the N-content of the weldmetal is lower than0.24%,the solidification mode is FA and the microstructure is austenite and skeletal ferrite.The higher N-contentin the weldmetal,the less ferrite in it and a lower microhardness will be got.When the N-content of the weldmetal is higher than 0.30%,the solidification mode is A and the microstructure is single austenite.The austenite dendrites become progressive coarse and the microhardness become higher while there is a higher nitrogen level.No nitrides can be found in the weld joints.The nitrogen pore will increase when the N-content of the weld metal ishigher.The higher N-content in the weld also can benefit the toughness,but if the N-content is too high,nitrogen pores can damage the toughness of the weld.
引文
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[2]Speidel M O,Speidel H J.Nitrogen containing austenitic stainless steels[C]//High Nitrogen Steels 2006,China:Sichuan,2006:21-29.
[3]Ikegami Y,Nemoto R.Effect of thermo-mechanical treatment on mechanical properties of high-nitrogen containing Cr-Mn-Ni Austenitic stainless steels[J].ISIJ International,1996,36(7):855-861.
[4]Ilola R J,Hanninen H E,Ullakko K M.Mechanical properties of austenitic high-nitrogen Cr-Ni and Cr-Mn steels at lowtemperatures[J].ISIJ International,1996,36(7):873-877.
[5]Woo I,Horinouchi T,Kikuchi Y.Effect of microstructure on the heat affected zone of high nitrogen containing Ni-free austenite stainless steel[J].Transaction of JWRI,2001,30(1):77-84.
[6]李冬杰,陆善平.高氮钢焊缝的组织和冲击性能研究[J].金属学报,2013,2(2):129-136.Li Dongjie,Lu Shanping.Investigation of the microstructure and impact properties of the high nitrogen stainless steel weld[J].Acta Metallurgica Sinica,2013,2(2):129-136.
[7]Harzenmoser M.Welding of high nitrogen steels[J].Materials and Manufacturing Processes,2004,19(1):75-86.
[8]Woo I,Kikuchi Y.Weldability of high nitrogen stainless steel[J].ISIJ International,2002,42(12):1334-1343.
[9]杜挽生,彭云,赵琳,等.高氮奥氏体不锈钢MIG焊接头的组织和性能[J].焊接,2008(10):25-29.Du Wansheng,Pen Yun,Zhao Lin,et al.Microsturcture and mechanical properties of MIG welded joint of high nitrogen austenite stainless steel[J].Welding&Joining,2008(10):25-29.
[10]Schaeffler A L,Constitution diagram for stainless steel weld metal[J].Metal Progress,1949,56(11):680-680.
[11]Hammar O,Svensson U.Soldification and Casting of Metals[M].London:The Metals Society,1979.
[12]Di Schino A,Mecozzi M G,Barteri M,et al.Solidification mode and residual ferrite in low-Ni austenitic stainless steels[J].Journal of Materials Science,2000,35(2):375-380.