Effect of welding speed on microstructure and mechanical properties of DP780 high‐strength steel

This study examined how welding speed affected the mechanical characteristics and microstructure of carbon dioxide gas‐shielded welding joints made of 2 mm thick DP780 high‐strength steel. The findings indicate that acicular ferrite makes up the majority of the weld zone, while slate bainite and slate martensite are found in the coarse and fine grain zones. The degree of recrystallization in the weld zone has a trend of rising and then falling with increasing welding speed. The welded joint's elongation was 13.4 % and its tensile strength was 713.32 MPa at the ideal welding speed of 430 mm·min −1 . The welded connection had a maximum microhardness of 352.2 HV 1. Tensile fracture surfaces show second‐phase precipitated particles that affect mechanical properties.