Microstructure and Mechanical Properties of Welding Joints of S275 Low Alloy Steel

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.