This article commences with a description of the principles of induction heating followed by a discussion on the high temperature electrical, magnetic, and thermal properties of steel, which influence the performance of induction heaters. The importance of eddy current distribution in a workpiece is explained, with emphasis on the skin effect. The article discusses typical procedures for induction hardening of steel, namely, austenitizing and quenching to form martensite either on the surface (case hardening) or through the entire section (through hardening). It briefly describes induction heating parameters for surface hardening, through hardening, tempering, and some general heating operations in metalworking.

The handling of billets or bars is an essential part of an induction heating system. This article describes two types of handling systems available for bar heating lines: inclined ramps with escapement, and sling feeder with inclined ramp and escapement. It focuses on the various infeed billet handling systems such as bin tippers, elevator feeders, rotary feeders, vibratory bowl feeders, magazine loaders, and rod feeders. The article provides information on the main categories of billet feeding systems, namely, dual pinch roll drive assemblies, tractor drive assemblies, billet pusher systems, walking beam assemblies, and index/continuous conveyor systems. It also discussed the hot billet handling systems used to deliver heated billets to the forging cell. These methods include billet extractor conveyors, accept/reject systems with pyrometer measurements, extractor rolls, discharge chutes, pinch roll extractors, pick-n-place systems, and robots.

This article provides a rough estimate of the basic parameters, including coil efficiency, power, and frequency in induction heating of billets, rods, and bars. It focuses on the frequency selection for heating solid cylinders made of nonmagnetic metals, frequency selection when heating solid cylinders made from nonmagnetic alloys, and frequency selection when heating solid cylinders made from magnetic alloys. The article describes several design concepts that can be used for induction billet heating, namely, static heating and progressive/continuous heating. It presents the four major factors associated with the location and magnitude of subsurface overheating: frequency, refractory, final temperature, and power distribution along the heating line. The article summarizes the pros and cons of using a single power supply. It also reviews the design features of modular systems, and concludes with information on the temperature profile modeling software.