Induction heating

In the previous chapter, induction heating was discussed as a method for heating large metal sections. The purpose of that type of heating is to obtain a completely uniform temperature throughout the workpiece. In that application, the high power intensity of induction heating is limited by the rate at which heat conducts from the surface toward the center.

Surface hardening, however, makes direct use of this so-called “disadvantage.” Induction heating is highly important in this field. Although the basic principles of different induction heating applications are the same, their practical uses can vary greatly. The parts shown here are examples of components suitable for induction hardening, where only the areas requiring hardening are treated.

By using high frequency, a high power density can be obtained, allowing heat to concentrate rapidly in a localized area. Without affecting the rest of the material, only the metallurgical properties of this specific area are changed. As a result, the component obtains a thin hardened surface layer supported by a low-brittleness core. This structure allows the core to maintain adequate strength while the surface gains high wear resistance. In practice, the part undergoes little to no deformation during the hardening process.

For example, the torsional strength of a shaft after surface hardening may be three times that of a through-hardened shaft of the same diameter.

Another method that can replace induction hardening is carburizing, in which the workpiece is heated in a furnace. However, carburizing is a batch production process that requires a long processing time and skilled operation.