Alternating current throughout induction coil adjacent the part to be treated induces eddy current via the part that is so heated. The benefit of such heating is as; no gas or liquid source for heating is utilized and coil can be shaped to surround the part geometrically. Figure of Coils for Induction Heating illustrates example of induction coils that usually are made in copper or copper based alloy such are water cooled. The coil is implicated also for quenching the part after heating. For surface hardening needing local heating induction heating is proper.
Figure: Coils for Induction Heating
If the heating is not through salt bath, after that the job to be treated is subject to varying atmosphere that could be atmospheric air or any one of various gases. Surface oxidation, tarnishing and decarburization are the problems which the metals face. Oxygen can reason oxidation, scaling and rusting. Carbon dioxide may reason decarburization depending on its concentration in furnace atmosphere. Thin blue film, is appearances on the surface in the presence of water vapour. Bluing of surface is completed for enhancing surface appearance. Nitrogen offers a neutral atmosphere. Vacuum furnaces often utilized for small and exactly finished parts offer whole safety from effects of atmosphere.