Abstract: The effect of heat input by submerged arc welding on microstructure and tensile deformation behavior of weld joint in Q460 steel was studied and its mechanism was also discussed. The results showed that with the increase of the heat input， the width of the heat affected zone (HAZ) of the welding joint and the proportion of columnar zone in the fusion zone (FZ) increase， meanwhile the microstructure becomes finer near the weld zone and the welding softening in the FZ is improved. It is also found that the heat input has little effect on the tensile strength of the welding joint， while the fracture elongation of the joint increases with increasing heat input. When the heat input is 19.0kJ/cm， the fracture of the joint occurs very easily due to the mismatch of plastic deformation at the joint interface between the FZ and HAZ. With increasing heat input， the microstructure in the FZ becomes finer and the hardness difference at the interface between the FZ and HAZ can be reduced. Therefore， the plasticity of the overall joint can be improved and the fracture of the joints is located from the FZ to BM.

Key words: Q460 steel, welding, heat input, microstructure, deformation behavior