摘要
DDC裂纹即高温失延裂纹,也称高温失塑裂纹,是高温下存在于厚截面、多道焊的奥氏体不锈钢和镍基合金焊缝中的一种固态晶间裂纹。它发生在低于固相线的一定温度区间内,尺寸较小,表面上可能看不出来,但是它往往会成为其它裂纹,如疲劳、腐蚀疲劳等的起裂源,潜在危害很大。文中通过对核电设备用690合金焊接材料发展过程的跟踪,介绍了适合于DDC敏感性研究的STF试验方法,并从微观角度阐述了DDC产生的机制和降低DDC敏感性的方法。分析表明,提高抗DDC能力的主要途径是改变晶界形貌,在焊缝凝固结束阶段的枝晶区域形成骨架分布的MC类碳化物,有效钉扎晶界,阻碍晶界的迁移,使晶界呈扭曲状。凝固结束后在迁移晶界上析出的M_(23)C_6碳化物从微观上可以起到一定的钉扎晶界的作用和阻碍晶界滑移的作用,但对DDC抗力的提高有限。
Ductility dip cracking(DDC) is a solid state intergranular crack occurred in highly restrained nickel alloys and austenitic stainless steels large welded structures.The development of Ni based alloy 690 and the filler metal applied to nuclear power plant was reviewed.To evaluate the sensitivity of the DDC,the strain to fracture Gleeble test technique was proposed.Several cracking mechanisms and the influencing factors were introduced from the aspect of metallurgy and process.Grain boundary is important to improve the DDC sensitivity.It means that MC type carbides at the end of solidification results in the effective pinning of the migrated grain boundaries that make these boundaries'tortuous'and improve the DDC sensitivity.
出处
《焊接》
北大核心
2012年第4期7-13,69,共7页
Welding & Joining
关键词
高温失延裂纹
镍基合金焊缝
机制
ductility dip cracking
Ni alloy weld metals
mechanism
