PURPOSE: To carry out the effective surface hardening of a spring with a simple apparatus even when the spring has a complex shape by connecting a high frequency power source to the spring before or after forming and, directly supplying high frequency current to carry out hardening.
CONSTITUTION: For example, in the hardening of a spring before forming, roll electrodes 2, 3 are rolled while in electrical contact with a spring material 1a. The electrodes 2, 3 are connected to a high frequency power source 4, and high frequency current is supplied to the electrodes. The material 1a, chiefly the surface part generates heat quickly and attains to a high temp. The material 1a is then coiled to obtain a coil spring 1, and the surface is quenched by spraying cooling water on the surface or by other method. The surface part of the spring 1 can be heated up to a uniform depth, so hardening up to the uniform depth is carried out.
KOYAMA HIROSHI
TOUNO TOYOYUKI
AYADA TOMOHIKO
TANGE AKIRA
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