The primary advantage of Induction Heating is that heating of only selected areas of the parts can be achieved. This provides for selective heat treatments including hardening, surface hardening, and annealing.

In Induction Heating, a high frequency current is passed through a coil surrounding the part to be treated – resulting in heating by electro-magnetic induction. The heat-affected zone can be controlled by the configuration of the induction coil, the orientation of the part in the coil, the frequency and amount of power used, and by rotating or scanning the length of the part. The time required to heat the part to obtain a complete austenitic transformation is brief, typically only a few seconds for a surface hardening application. Once the part has been heated, it can be quenched or slow cooled as required by the particular heat treatment.

It is frequently desirable to harden only the surface of steels by simply changing their microstructure without altering the chemical composition of the surface layers. If steel contains sufficient carbon to respond to hardening, it is possible to harden the surface layers only by very rapid heating for a short period of time, thus conditioning the surface for hardening by quenching.

Induction Hardening allows the selective hardening of a part to achieve desired hardness over a specific area and depth. Because the part is selectively heated, the heat-affected zone can be adjusted to minimize distortion and other problems.

Surface hardening with induction creates parts that have excellent resistance to fatigue. A hard outer case is created over a ductile core, with high compressive forces at the surface. These compressive forces at the surface improve fatigue properties by delaying crack initiation and propagation during service.