Induction hardening is a process used for the surface hardening of steel alloys which require high wear resistance such as springs, shafts, gears and other alloy components. Heat is produced within the surface layer of an object using a non-contact heating process based on the principles of Electromagnetic Induction.
The parts to be heat treated are placed inside a water cooled copper coil and then heated above their transformation temperature by applying an alternating current to the coil. The alternating current in the coil induces an alternating magnetic field within the workpiece, which if made from steel, causes the outer surface of the part to heat to a temperature above the transformation range.
Parts are held at that temperature until the appropriate depth of hardening has been achieved, and then quenched in an oil, water or polymer base, depending upon the steel type and hardness desired. By quenching the heated layer, the surface layer is transformed to form a martensitic structure leaving the core component unaffected by the treatment.
This process is most widely used to improve the durability of the steel which extends the fatigue life and wear resistance.