9%Cr-2.25%Cr异种钢焊接接头碳迁移行为研究  

Investigation on the Carbon Migration of 9%Cr-2.25%Cr Dissimilar Welded Joint

作　　者：刘霞[1,2] 蔡志鹏 LIU Xia;CAI Zhipeng(Department of Mechanical Engineering,Tsinghua University,Beijing 100084,China;Shanghai Electric Power Generation Equipment Co.,Ltd.Turbine Plant,Shanghai 200240,China)

机构地区：[1]清华大学机械工程系,北京100084 [2]上海电气电站设备有限公司汽轮机厂,上海200240

出　　处：《热力透平》2018年第1期24-28,共5页Thermal Turbine

基　　金：上海市科学技术委员会资助项目(13DZ1101502)

摘　　要：采用钨极氩弧焊打底、埋弧焊填充及盖面的多层多道次焊接工艺,将9%Cr马氏体耐热钢和2.25%Cr贝氏体耐热钢进行连接,填充金属采用5%Cr的焊丝。热处理后,研究了异种钢焊接接头的碳迁移现象。研究表明,在整个焊接接头中,强碳化物形成元素Cr在熔合线两侧的浓度区别会造成碳的活度差,驱使焊接接头中的碳从低Cr侧向高Cr侧进行扩散,并在扩散过程中与基体中的合金元素结合形成碳化物。光学显微镜下,在紧邻熔合线的9%Cr钢的热影响区和紧邻2.25%Cr钢侧熔合线的焊缝金属中均存在贫碳区和富碳区。采用扫描电子显微镜(SEM)对贫碳区和富碳区进行观察,发现富碳区存在大量碳化物,而贫碳区中碳化物的数量较少。研究成果可为焊接接头长时间稳定运行方面的研究提供参考。The 9%Cr-2.25%Cr dissimilar welded joint was performed through narrow gap submerged arc welding(NG-SAW)accompanied with multi-layer and multi-pass technique after the root pass welding with gas tungsten arc welding(GTAW).In addition,the carbon migration and its mechanism was systematically investigated.The results showed that the carbon migrated from the side with low content of chromium(Cr)element to the side with high content of that,determined by the difference of chemical potential generated by the strong-carbide forming element Cr.As a result,the carbides were formed during the carbon migration process.According to the results obtained by optional microscope(OM),carbon migration zone(CMZ)accompanied with the carbon-depleted zone(CDZ)was observed in both sides of fusion line.Carbon migration zone with plenty of carbides and carbon-depleted zone with rare carbides were detected by scanning electron microscope(SEM).The results can provide reference for the study on long-term operation stability of welded joints.

关 键 词：异种焊接接头 碳迁移 化学势 碳化物 

分 类 号：TG407[金属学及工艺—焊接]