N2对不锈钢GTAW焊缝铁素体含量和组织演变过程的影响  

Effect of N2 in Shielding Gas on the FN and Microstructural Evolution for the Stainless Steel GTAW Joint

作　　者：程尚华 张一琪[1] 邵珠晶 孔康骞 程方杰 Cheng Shanghua;Zhang Yiqi;Shao Zhujing;Kong Kangqian;Cheng Fangjie(School of Materials Science and Engineering,Tianjin University,Tianjin 300350,China;Penglai Jutal Offshore Engineering Heavy Industries Co.,Ltd.,Penglai 265607,China;Tianjin Key Laboratory of Advanced Joining Technology,Tianjin 300350,China)

机构地区：[1]天津大学材料科学与工程学院,天津300350 [2]蓬莱巨涛海洋工程重工有限公司,蓬莱265607 [3]天津市现代连接技术重点实验室,天津300350

出　　处：《天津大学学报（自然科学与工程技术版）》2020年第8期809-813,共5页Journal of Tianjin University：Science and Technology

基　　金：国家自然科学基金资助项目(51775372).

摘　　要：在不锈钢的焊接中,控制焊缝金属中的铁素体含量对于防止出现热裂纹、保证焊缝耐蚀性能和力学性能都有着重要的作用.在不锈钢中氮是强烈的奥氏体化元素,通过在保护气体中加入N2的方法向焊缝过渡氮元素从而调控焊缝中的铁素体含量是一种简单可行的技术思路.本研究采用实时调整气体配比技术配制不同配比的Ar-N2混合气作为保护气体,对304L奥氏体不锈钢和2205双相不锈钢进行了GTAW多层多道焊接试验.分析研究了保护气体中的N2添加量对奥氏体不锈钢焊缝金属中铁素体含量的影响以及对双相不锈钢焊缝金属中的相比例和微观组织的演变规律.结果表明,对304L不锈钢,保护气中加入0.5%~1.0%的N2能够将焊缝中平均铁素体数FN有效控制在3~7范围内.对2205双相不锈钢,打底焊时保护气中加入3.0%的N2能够有效促进一次奥氏体的形成并抑制二次奥氏体的析出;填充和盖面焊则应减少保护气中的N2含量或用纯Ar作为保护气才能保证焊缝的整体相比例在合理范围内.该研究工作对推广动态气体配比技术在不锈钢焊接生产中的应用提供了前期的理论基础.In the welding process of stainless steels,the control of ferrite content in the weldment is crucial in preventing the generation of hot cracks and ensuring good mechanical and anti-corrosion performance of the joint.Nitrogen is a strong austenite stabilizer.Adding N2 to the shielding gas during the welding process is a feasible way to control the ferrite content in the weldment.In this research,different mixtures of Ar-N2 gas with varying proportions were prepared using a dynamic mixing technique and were used as the shielding gas of 304 L stainless steel and 2205 stainless steel multi-pass gas tungsten arc weld(GTAW)joint.The influence of N2 content in shielding gas on the ferrite number(FN)of austenitic stainless steel and its effect on the phase ratio and microstructural evolution of duplex stainless steel were investigated.The results indicated that in the joint of the 304 L stainless steel,adding 0.5%-1.0%N2 in the shielding gas could control the FN range in the joint to be approximately 3-7.In the root of the 2205 stainless steel,adding 3.0%N2 in the shielding gas suppressed the formation of secondary austenite in the multi-pass welding process.The N2 content in the shielding gas of the filler and cover passes should be reduced or pure Ar should be used to achieve a phase balance.The results of this research provide a theoretical basis for the application of dynamic gas mixing technique in the industry.

关 键 词：不锈钢 铁素体数 相比例 Ar-N2混合保护气 组织演变 

分 类 号：TG441.2[金属学及工艺—焊接]