Mechanism study on the microstructure, mechanical properties, and low-temperature toughness of Q355E welded joints with different wire compositions: experimental and simulation research

This manuscript investigates the effects of different welding wires on the microstructure and mechanical properties of Q355E steel welded joints, and calculates the solidification process of the melt pool through simulation. The results indicate that there are differences in the microstructure of the weld zone between different welding joints. Due to the mechanisms of fine grain strengthening and dislocation strengthening, the mechanical tensile properties and hardness of different welded joints vary. The difference in the composition of welding wire has a significant impact on the low-temperature impact toughness of welded joints, and the impact fracture surface also presents different fracture forms. Through simulation of the solidification of the melt pool, it was found that different alloy elements have a significant impact on grain phase transformation during the solidification process, resulting in significant differences in grain size, large angle grain boundaries, and dislocation density. This further proves that Ti element is conducive to promoting the nucleation of acicular ferrite, while Ni element reduces the precipitation temperature of ferrite, thus affecting the low-temperature impact toughness of welded joints.