Abstract: In order to meet the heat treatment technical requirements of some parts with complex geometric shapes and high technical requirements, such as universal joint transmission shaft R, King Pin parts and transmission shaft (stub shaft) ears, etc, high-properties digital induction heating power supply and microcomputer programming automatic control medium frequency special-shaped inductor were used for induction hardening. For different parts, special-shaped inductor are different from circular inductor in terms of structural design, which is simple structure, and low production cost. The quenched parts can meet the technical requirements of the effective hardened layer depth, and also have a small range of deviations in microstructure and mechanical properties, stable quality. By using the special-shaped inductor during induction hardening, the problem of R hardened layer and coarse grain of thin-wall of the transmission shaft fork is solved, greatly improving the service life of the parts.

Key words: induction hardening, special-shaped inductor, universal joint transmission shaft, double layer spray ring