Mechanical Properties and Microstructure of Conical Joints for Dissimilar Steels Continuous Drive Friction Welding

The dissimilar conical joints between Q235 and 1045 steel were prepared by continuous drive friction welding. The conical design was carried out for 1045 steel, and the geometry of the conical was determined by the ratio of the diameter of the upper surface to the diameter of the lower surface. The effect of conical joints on microstructure and mechanical properties was investigated, and the results showed that the joints were clearly divided in weld zone (WZ). On the 1045 steel side, the microstructure is very heterogeneous, with less ferrite precipitation in thermo-mechanically affected zone and more ferrite formation in heat-affected zone (HAZ). On the Q235 steel side, a large number of fine equiaxed grains are formed in WZ. Due to element diffusion, C and Cr elements are enriched at the weld interface, producing carbides. The bonding mechanism of Q235 and 1045 steels is mechanically mixed and metallurgically bonded. Conical joints can change the width of mechanical mixing, resulting in a corresponding change in the microhardness of the WZ. The conical joint fails in HAZ on the Q235 steel side, indicating the higher strength of the welded joint. In addition, the fracture model is ductile fracture.