Influence of Different Weld Heat Input on Microstructure and Properties of New Martensitic Heat-resistant Steel Joints by Automatic Welding

Abstract In this article, the influence of different automatic weld heat input about the microstructure and properties of the joint of new martensitic heat resistant steel of P92 is studied. Based on this, the key factors to obtain excellent quality of P92 joint are proposed. The results show that the weld is tempered martensite microstructure, the grain of Heat-affected zone (HAZ) is finer with the weld heat input lower. The width of the slats and the crystalline size of the coarse-grained zone (CGHAZ) in the weld metal microstructure is gradually larger with the heat input higher. Meanwhile, as the welding heat input increase, the hardness of weld bead in the welded joint of P92 steel has a gradual downward trend, the impact toughness has a significant decrease, and the impact fracture morphology changes from ductile fracture to brittle fracture. Therefore, when the automatic welding technology is used to repair P92, so as to obtain better performance of welded joints, appropriate gas protection flow and welding parameters should be ensured according to welding thickness, and heat input should be strictly controlled.