| 摘要 |
PURPOSE:To improve fatigue resistant strength without change of design items by applying low-temperature sulphurizing treatment to a shaft to which a needle bearing is fitted in a universal joint for a vehicle. CONSTITUTION:A tripod shaft 2 is made by SCM420H or SCr420H. Standard cementation hardening treatment is applied to the tripod shaft, and after the shaft is subjected to polishing, the shaft is subjected to low-temperature sulphurizing dipping treatment. The low-temperature sulphurizing dipping treatment is conducted by adding sodium sulfide to an alkali metal salt bath, maintaining same at 180 deg.C, dipping the tripod shaft 2 therein, and applying an electric current for ten minutes with the tripod shaft 2 as an anode, and the treatment bath as a cathode. Thus, coating of iron sulfide is formed on the contact surface of the tripod shaft 2 and a needle roller bearing 3. When high load is applied to the coating, plastic flow is caused to increase the contact area, so that the fatigue resistant strength can be improved remarkably. |
