Effects of joint heat distribution on material flow and microstructure in continuous drive friction welding of 45 # steel

Continuous drive friction welding (CDFW) is an economical and productive method for joining similar metals. In this study, 45 # steel was joined via CDFW, and the material heat distribution, flow behaviour, flash formation and fracture mode were investigated via experiments and simulations. The bar was divided into three zones in the direction of radius (R), the R zone near the axis, the edge zone at the edge of the R and the 0.5 R zone between the R zone and edge zone. The maximum flow velocity and temperature of the joint first appeared in the 0.5 R zone, and as the friction continued, the maximum temperature moved to the edge zone, followed by flash. When the friction time was 9 s, the maximum tensile strength was 674 MPa, the fracture mode was the coexistence of ductile and brittle and the fracture location had an obvious boundary. Ductile fracture occurred in the R zone, and the flash took a lot of heat, brittle fracture occurred in the 0.5 R and edge zones. The maximum microhardness of the joint is 295 HV in the weld zone, and the microhardness decreased in the partially deformed zone. When the friction time was appropriate, the heat distribution was uniform and sufficient, and the grains exhibited a significant degree of dynamic recrystallisation refinement.