Abstract
Friction welding of spheroidal graphite cast iron (FCD) and mild steel (S20C) were carried out under various rotation conditions. The friction pressure, the forge pressure and friction time were constant. The dimensions of the test pieces were 15mm in diameter and 70mm in length respectively. Micro and macroscopic observation, and scanning electron microscopic (SEM) observation were employed in order to clarify the characterization at the welding interface. The tensile strength of the joint was also investigated. In the FCD adjacent to the center of the welding interface, the deformation layer of spheroidal graphite (DLSG) was observed and the shape of the graphite in this DLSG was similar to the one of A or D-type flaky graphite. It is considered that DLSG was formed by the plastic deformation of the spheroidal graphite during friction welding. The tensile strength of the joint with DLSG was very low. There was a close relationship between the percentages of the area of the DLSG and tensile strengths of the joints. The appropriate welding condition reduced the amount of DLSG in the joints of FCD and S20C.
