调质态Q690D高强钢GMAW多道次焊接组织与性能

Microstructure and properties of GMAW multipass welding of Q-T high strength steel Q690D

在无预热和焊后热处理条件下,采用熔化极气体保护焊(GMAW)对10 mm厚的调质高强钢Q690D进行三道次焊接试验,通过组织观察和硬度测试分析了该钢焊接接头组织转变特征及硬度分布规律。结果表明,Q690D热影响区组织主要为粒状贝氏体和少量下贝氏体,热影响区产生软化现象,最大失强率达到23%,粗晶区受再热作用后发生组织遗传;采用实芯焊丝CHW-70C(ER69-G)使焊缝得到90%的针状铁素体组织,硬度值比母材低;为控制软化区宽度,焊接线能量以8 kJ/cm为宜。

Quenching-tempering high strength steel Q690D of 10 mm thick were welded by three passes gas metal arc welding ( GMAW) without pre-& post-welding treatment process, then the microstructural evolution characteristic and hardness distribution of the weldment were investigated by metallographic observation and hardness test.The results show that the constituents in heat affected zone ( HAZ) of the Q690D steel are mainly granular bainite and a small amount of lower bainite.A soften area exists in the HAZ, in which the lowest hardness is equivalent to 23% strengh loss of the base metal.The structure heredity phenomenon takes place in the coarse grain HAZ which is reheated by the latter weld pass.Acicular ferrite abtained in the weld is about 90%by use of CHW-70C(ER69-G) electrode.The srength of weld is lower than parent metal's.For controlling the width of soften zone, the welding heat input should be about 8 kJ/cm.