Induction Heat Treatment

Definition - What does Induction Heat Treatment mean?

Induction heat treatment is a method of surface hardening where heating is achieved without any direct physical contact.

As there is limited or no physical contact, there are potential advantages in production. For example, there is less risk of contamination, a simpler heating arrangement and less insulation may be required.

Induction heat treatment can:

  • Increase wear resistance
  • Increase surface strength for load carrying (crush resistance)
  • Induce suitable residual and compressive stresses
  • Improve fatigue life
  • Improve impact resistance

Corrosionpedia explains Induction Heat Treatment

Induction heat treatment is used in almost every industry where metals are used, including:

  • Alloying
  • Metal forming
  • Tempering
  • Hot working
  • Shrink fitting

The induction heat treatment technique is capable of heating materials at rates of temperature rise not normally associated with other methods, such as electrical resistance or gas heating, with a high degree of efficiency. Induction heat treatment is most commonly applied in:

  • Induction hardening of steel parts
  • Induction soldering/brazing as a means of joining metal components
  • Induction annealing to selectively soften an area of a steel part

This process relies on induced electrical currents within the material to produce heat. The basic components of an induction heating system are:

  • AC power supply
  • Induction coil
  • Material to be heated

The power supply provides an alternating current through the coil, generating a magnetic field. When the work piece is placed in the coil, the magnetic field induces eddy currents in the work piece and thus generates localized heat without any physical contact between the coil and the work piece.

There is a relationship between the frequency of the alternating current and the depth to which there is penetration of the work piece. Low frequencies (up to 30kHz) are effective for thicker materials requiring deep heat penetration, while higher frequencies (100 to 400kHz) are effective for smaller parts or shallow penetration. In addition, the higher the frequency used, the higher the rate of heating.

Owing to the effect of hysteresis, magnetic materials are more readily heated compared to non-magnetic materials. Magnetic materials resist the rapidly changing magnetic fields within the induction coil. As a result, heat is produced by hysteresis in addition to eddy current heating.

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