G115钢焊接热影响区组织特征

Microstructural characterization in the experimentally simulated weld heat-affected zone of G115 steels

通过热模拟法得到了G115钢在不同焊接峰值温度下的热影响区,分析了热影响区相转变规律,利用光学显微镜、扫描电镜观察了热影响区组织形貌,结果表明:G115钢粗晶区和细晶区的组织为板条马氏体,临界相变区为细小板条马氏体和高温回火马氏体,亚临界相变区为回火马氏体,高温回火组织的形成会降低临界相变区的综合性能.由于临界相变区形成的奥氏体内化学成分、均匀性及稳定性与母材存在较大的差异,导致在冷却过程中马氏体转变点有所提高,Ms由380℃提高到441℃.粗晶区和细晶区产生了强化效果,临界相变区和亚临界相变区产生了软化效果,软化效果与高温回火效应有密切联系.

The Heat Affected Zone(HAZ)of G115 steel at different welding peak temperatures was obtained by thermal simulation method.The phase transformation of the HAZ was analyzed.The microstructure of HAZ was characterized by using optical microscope(OM)and scanning electron microscopy(SEM).The results show that the microstructure of both CGHAZ and FGHAZ of G115 steel is lath martensite,with fine lath martensite and over-tempered martensite appearing in ICHAZ and tempered martensite in SCHAZ.The formation of the over-tempered structure reduced the comprehensive properties of ICHAZ.Because the chemical composition,homogeneity and stability of the austenite formed in ICHAZ were different from those of the base metal,the martensite transformation point Ms in the cooling process was increased from 380℃to 441℃.The strengthening effect was produced in CGHAZ and FGHAZ;and the softening effect was produced in ICHAZ and SCHAZ,which was closely related to the over-tempering effect.