The induction heating furnace is divided into five series of ultra-high frequency, high frequency, super audio, intermediate frequency and power frequency according to the frequency. Quenching is taken as an example.

1 UHF induction heating current frequency 27 MHz, the heating layer is very thin, only about 0.15 mm, can be used for thin surface quenching of complex shapes such as circular saws.

2 high frequency induction heating current frequency is usually 200 ~ 300 kHz, heating layer depth of 0.5 ~ 2 mm, can be used for surface quenching of gears, cylinder liners, cams, shafts and other parts.

3 Super-audio induction heating current frequency is generally 20 ~ 30 kHz, using super-audio induction current to heat the small modulus gear, the heating layer is distributed along the tooth profile, and the performance is better after the fire.

4 medium frequency induction heating current frequency is generally 2.5 ~ 10 kHz, the heating layer depth is 2 ~ 8 mm, mostly used for surface quenching of large modulus gears, larger diameter shafts and cold rolls.

5 power frequency induction heating current frequency is 50 ~ 60 Hz, heating layer depth is 10 ~ 15 mm, can be used for surface quenching of large workpieces.