| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a heat treatment method for a spline shaft having a stepped part formed therein. <P>SOLUTION: When induction-hardening the spline shaft 200, this heat treatment method includes induction-heating a large-diameter part 250 only with a low-frequency wave and a spline part 210 with a combined wave of the low-frequency wave and a high-frequency wave, respectively. In this way, the method can appropriately heat each of a rising part 251, a tooth bottom 212 and a tooth top 211, and can form a hardened layer 270 having predetermined hardness down to sufficient depth on each of these parts. Here, the spline shaft is heated in a fixed position or while moving, with the low-frequency wave. Thereby, the large-diameter part 250 is not damaged by overheat, but is heated down to appropriate depth as well as a corner part 251R of the bottom of the rising part 251. In addition, in a step of supplying two waves of different frequencies to the spline part, which starts after an induction heating coil has passed through the rising part 251, the tooth bottom 212 is heated with the low-frequency wave and the tooth top 211 is heated with the high-frequency wave, so that the whole surface of the spline part 210 can be heated down to the appropriate depth. <P>COPYRIGHT: (C)2008,JPO&INPIT</p> |
