Study on microstructure and mechanical properties of Q235B/Q345qE dissimilar steel welded joints

Abstract In the process of welding and manufacturing of steel structure bridges, the steel beam structure is usually manufactured by the same kind of bridge steel. However, the stress requirements of different parts are not the same. This study proposes to use low-grade steel instead of low-stress areas to reduce costs. Due to the significant differences in chemical composition, metallographic structure, physical properties, and mechanical properties between the two steels, it is difficult to weld. The butt joint welding test of Q235B and Q345qE steel was carried out, and the influence of welding speed on weld formation, microstructure, and mechanical properties was studied. The results show that when the welding current is 250 A and the welding speed is 5.83 mm/s, the comprehensive mechanical properties of the welded joint are the best. The butt joint fractured in the heat affected zone of Q235 B side, and the fracture mode was ductile fracture. The research provides theoretical support for the application of dissimilar steel welding in bridge construction.