低入熱摩擦圧接法による中・高炭素鋼継手の引張強度に及ぼす摩擦時間，摩擦圧力の影響

This report describes the effect of friction time and friction pressure on tensile strength of carbon steel welded joint by a low heat input friction welding method (LHI method) that was developed by authors. Medium (0.35%) and high (0.55%) carbon steel joints were made by friction speed of 27.5s-1 through a continuous drive friction welding machine with an electromagnetic clutch in order to prevent braking deformation during rotation stop.The experiments produced the following summarized results.(1) Medium carbon steel joint did not obtain the same tensile strength as that of the base metal, and the fracture occurred at the welded interface when it was made at friction time up to the initial torque by friction pressure of 30MPa. However, the joint obtained the same tensile strength as that of the base metal, and the fracture occurred at the base metal when it was made at friction time up to the initial torque by 90MPa.(2) Medium carbon steel joint by 30MPa fractured at the welded interface due to the unjoined region, which was produced at the peripheral region of the welded interface during friction process. The unjoined region had not produced with increasing friction pressure.(3) High carbon steel joint did not obtain the same tensile strength as that of the base metal, and the fracture occurred at the welded interface when it was made at friction time up to the initial torque by 30 and 90MPa.(4) High carbon steel joint fractured at the welded interface due to the quench crack, which was produced during cooling stage after welding. The quench crack reduced with increasing friction pressure. However, the joint by high friction pressure (300MPa) did not obtain the same tensile strength as that of the base metal, and it fractured at the base metal, because the center portion at the welded interface hardly joined after the initial torque.