2022 年 108 巻 12 号 p. 1002-1010
In this study, linear friction welding (LFW) is used to join high carbon steel such as S55C (JIS G 4051) because it controls the maximum temperature during the joining process. The effect of LFW conditions on Charpy absorbed energy is studied. The thickness of a rectangular parallelepiped shape is 14 mm, the width is 20 mm, and the length is 64 mm. The applied pressure (P) controls the maximum temperature. Under high-temperature conditions, P is 100 MPa. Under middle-temperatures conditions, P is between 250 and 350 MPa. Under low-temperature conditions, P is between 400 and 450 MPa. Under all condi-tions, joints are cooled to room temperature.
The microstructure and hardness of LFW joints are examined. The toughness is determined using a 300 J instrumented Charpy tester. The absorbed energy is estimated using two methods. The first method uses the potential energy difference, and the second involves calculating the area surrounded by the stroke–load relationship. With an increase in P, the microstructure changes from martensite to ferrite and microcementite. In addition, the maximum hardness at the interface decreases from 500 HV–700 HV to 400 HV. The maximum absorbed energy is confirmed at 400 MPa using the potential energy method and at P of 450 MPa using the area method. Energies absorbed before and after the maximum load are assumed to be crack initiation and propagation (Ep) energies, respectively. The maximum ener-gy is due to an increase in Ep, which is enhanced when the microstructure changes from martensite to ferrite and microcementite.
