The current frequencies commonly used in high-frequency quenching equipment are:

1. High frequency heating: 100～500KHZ, commonly used 200～300KHZ, it is electronic tube type high frequency heating, the hardening layer depth is 0.5～2.5mm, suitable for small and medium-sized parts.

2. 2. Intermediate frequency heating: The current frequency is 500～10000HZ, usually 2500～8000HZ. The power supply equipment is a mechanical intermediate frequency heating device or a silicon controlled intermediate frequency generator. The depth of the hardened layer is 2-10 mm. Suitable for large diameter shafts, medium and large gears, etc. 3. Power frequency heating: The current frequency is 50HZ. Using mechanical power frequency heating power equipment, the depth of the hardened layer can reach 10-20mm, which is suitable for surface quenching of large-diameter workpieces.