Induction Hardening

Definition - What does Induction Hardening mean?

Induction hardening is a heat treatment process carried out to enhance the mechanical properties in a localized area of a ferrous component. The resultant hardened area improves the wear and fatigue resistance along with strength.

Induction hardening is used to selectively harden areas of a part or assembly without affecting the properties of the part as a whole. It is favored for components that are subjected to heavy loading, torsional loading and impact forces.

Applications of induction hardening include:

  • Surface hardening of steel or steel alloys
  • Wheel hubs
  • Edge hardening of complex parts
  • Gears
  • Springs
  • Sprockets
  • Axle shafts
  • Pins
  • Steering components
  • Transmission components
  • Power tools
  • Drive shafts

Corrosionpedia explains Induction Hardening

Induction hardening is used for surface hardening of steel and other alloy components through heating and then quenching. By quenching this heated layer in water, oil or a polymer, the surface layer is altered to form a martensitic structure which is harder than the base metal.

The parts to be heat treated are placed inside a copper coil and then heated above their transformation temperature by applying an alternating current at a specific frequency and power level to the coil. The components are heated by means of an alternating magnetic field to a temperature at or above the transformation range followed by immediate quenching.

Properties of induction hardening include:

  • Very quick and efficient
  • Allows for localized hardening
  • Core of the material remains the same
  • Typically uses carbon and alloy steels with a carbon content between 0.30% and 1.00%
  • High control over quality
  • Less distortion than other heating methods like carburizing and flame hardening
  • Material costs are reduced as process is compatible with lower hardenability, lower-cost alloys
  • Increases durability and resistance to wear

Induction-surface-hardened low-alloyed medium-carbon steels are widely used for critical automotive and machine applications which require high wear resistance. Wear resistance behavior of induction-hardened parts depend on hardening depth and the magnitude and distribution of residual compressive stress in the surface layer.

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