Microstructure and Mechanical Properties of G20Mn5 Cast Steel MAG Welded Joint

G20Mn5 cast steel plates with thickness of 8 mm were connected by metal active gas (MAG) arc butt welding with one-side two-pass welding method. The microstructure, hardness, tensile property and fatigue property of the joint were studied. The results show that the joint had the good surface and no obvious welding defects were found. The joint consisted of base metal, heat affected zone and weld zone, and the heat affected zone was subdivided into incomplete normalized zone, normalized zone and overheated zone. From the base metal to the weld center, the hardness of the joint increased first and then decreased. The fusion zone had the highest hardness of about 70 HRB, and the hardness of the weld was 55-60 HRB, which was a little higher than that of the base metal. The tensile strength of the joint was obviously higher than that of the base metal, while the percentage elongation after fracture was lower than that of the base metal. The high cycle fatigue strength of the joint was equivalent to that of the base metal, and both fractured at heat affected zone. The properties of the joint met the design requirements.