通过拉伸、冲击、硬度测试和金相检验等方法对S275低合金钢熔化极活性气体保护焊(MAG)焊接接头的力学性能与显微组织进行了研究。结果表明: 采用JM-56焊丝对S275低合金钢进行焊接时, 接头具有较好的抗剪强度; 开45°坡口, 拉伸后均断在离焊缝位置较远的母材上, 焊接接头抗拉强度满足技术要求。焊缝组织晶内为细小密集的针状铁素体, 有极少量珠光体, 焊缝局部有魏氏组织; 熔合区、过热区为沿晶界析出的块状先共析铁素体和向晶内生长的条状铁素体以及少量的珠光体; 正火区组织为细小的铁素体和珠光体; 母材组织为铁素体和珠光体, 晶粒也比较细小。最后得出S275低合金钢用于转向架焊接构架是可行的。

By means of tensile and impact test, hardness testing and metallographic examination, microstructure and mechanical properties of MAG welding joints of S275 low alloy steel were studied. The results showed that, using JM-56 to S275 low alloy steel wire welding, the welded joints had good shearing strength; open 45° bevel, stretching away from the weld location was far off the base material, the tensile strength of welded joints met with the technical requirements. Intragranular microstructure of weld was tiny intensive acicular ferrite and few pearlite and local widmanstatten structure. Microstructure of fusion area and overheated zone was massive pro-eutectoid ferrite precipitated along grain boundary and ferrite banding growed to intragranular and small amounts of pearlite. Microstructure of normalized zone and base metal was tiny ferrite and pearlite.Finally, the conclusion was obtained that S275 low alloy steel was feasible for the bogie welding framework.