Influence of Repair Welding Time on Microstructure and MechanicalProperties of 30CrMnSiA Steel Joint

Multiple repair welding (for three and four times) tests were carried out on 30CrMnSiA welded joint by shielded metal arc welding. The effect of the repair welding time on the microstructure and mechanical properties of the joint was studied. The results show that increasing repair welding time had little effect on the microstructure type of the joint weld zone. The microstructures of the original weld and the repairing weld both consisted of austenite columnar crystals. Increasing repair welding time could lead to grain coarsening in the original weld zone, and reduce the distribution density of high angle grain boundaries and martensitic quantities in the heat-affected zone, resulting in negative effects on the strength of the joint. The tensile strength of the four-time repair welding joint was reduced by 7.8% and the percentage elongation after fracture was reduced by 25.3% comparing with those of the three-time repair welding joint, but the fracture mechanism was still ductile fracture. The bending resistance and hardness of the four-time repair welding joint were also lower than those of the three-time repair welding joint.