700 MPa级低合金高强钢低匹配焊接接头组织和性能研究

摘要

700 MPa grade high strength low alloy steel was welded by gas metal arc welding ( GMAW) process on the principle of a undermatching design .The microstructure and properties of the welded joint were investigated by OM, SEM and mechanical property tests .The results show that the microstructure of the weld zone consists mainly of acicular ferrite and a small amount of proeutectoid ferrite , the microstructure of coarse grain heat affected zone is upper bainite , and that the microhardness of the weld zone is significantly lower than that of the base metal , the impact toughness ( AKV ) of the weld zone is 58 J at -40 ℃, and the tensile strength of welded joint is as high as 92.4%of that of the base metal , the welded joint providing good comprehensive mechanical properties .%按照低匹配设计原则，采用熔化极气体保护焊对屈服强度为700 MPa级的低合金高强钢进行了焊接。采用光学显微镜、扫描电镜和力学性能试验研究了焊接接头的组织和性能。结果表明，焊缝区组织主要为针状铁素体和少量先共析铁素体，粗晶热影响区组织为上贝氏体；焊缝区显微硬度明显低于母材，焊缝区-40℃时的冲击韧度（AKV）为58 J，抗拉强度达到了母材抗拉强度的92．4％，焊接接头的综合力学性能良好。