| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a high frequency induction hardening method and its apparatus, with which the high hardness can be obtained on the surface and the inner part can be kept comparatively soft and excellent toughness is given, and the residual stress due to a heat treatment is relaxed to prevent the deformation and the hardened crack, and which are applied for e.g. a bearing raceway ring etc. <P>SOLUTION: This high frequency induction hardening method uses a high frequency electric source 2 which can be supplied to a heating coil 1 by changing over high frequency current having two kinds of high and low frequencies. After raising the temperature of the whole body of a work to setting change-over temperature T2 near the austenitizing temperature with the high frequency current at the low frequency side, the heating of only the surface is performed by changing over to the high frequency current at the high frequency side. This high frequency hardening apparatus is provided with a temperature measuring means 28 for measuring the temperature of the work during heating and an electric source control unit 21 for controlling the high frequency electric source 2. The electric source control unit 21 has a frequency change-over control means 26 for changing over the output of the high frequency electric source 2 into the high frequency current at the high frequency side when the temperature measured with the temperature measuring means 28 reaches the setting change-over temperature T2. <P>COPYRIGHT: (C)2006,JPO&NCIPI</p> |
