Surface hardening in which a water-cooled copper coil induces eddy currents that heat a shallow layer in seconds, followed at once by a spray or immersion quench, usually polymer. Frequency sets depth: high frequency (100 kHz and up) gives shallow cases on small parts, while 1 to 10 kHz heats deeper for shafts and large gears. Medium-carbon steels such as 1045, 1050 and 4140 are typical, reaching 50 to 60 HRC over a tough core.
Induction hardening on the axle shafts: scan at 10 kHz, single-shot the spline, polymer at 10 percent.
The coil is the tooling: change the part and you usually need a new coil and a new recipe.
Also heard as
- induction harden
- IH
- scan hardening
Related terms
Case
The hardened outer layer of a case-hardened part, as opposed to its softer, tougher core.
Flame hardening
Surface hardening with an oxy-fuel torch followed by a water quench, used on large or one-off parts.
Polymer quenchant
A water solution of polymer that quenches at a speed between water and oil, tuned by its concentration.
Effective case depth
Depth below the surface where hardness falls to a set value, usually 50 HRC, on a case-hardened part.