Induction Hardening

1. Induction hardening is a type of heat treatment in which metal parts are heated by electromagnetic induction and then quenched.

2. It is also a type of case hardening and can be used for many steel and steel alloys to improve surface layer properties such as fatigue resistance and hardness.

3. Materials such as steel are typically placed inside a water cooled copper coil where they are subject to an alternating magnetic field.

4. They undergo electromagnetic induction by means of an electromagnet and an electronic oscillator.

5. This oscillator sends alternating currents through the electromagnet, causing alternating magnetic fields that penetrate the material.

6. The results are eddy currents which heat the object within the coil. Induction hardening is a form of surface hardening in which the depth can be up to 8mm.

7. The deeper the currents penetrate, the higher the frequency of the alternating magnetic fields have to be.

8. Directly after the induction heating process, the object has to be quenched; it has to be cooled down extremely quickly.

9. Quenching ensures that only the surface is hardened and that heat doesn’t spread into the core of the material, avoiding phase transformations from arising.

10. Furthermore, the rapid cooling down creates a martensitic or ferritic-martensitic structure on the surface layer.

11. These structure display higher tensile strength and low initial yielding stress than a purely ferritic structure.

12. Quenching also reduced grain size which is a key factor to increasing hardness of materials.

13. A benefit of induction hardening is that if the depth of surface is more; the grain size can be considerably decreases and object gets resistance to wear and tear.