Induction heat treating is used in a wide range of applications. Typical uses, as described in this chapter, include the surface hardening of many types of shafts as well as gears and sprockets and the through-hardening of gripping teeth, cutting edges, and impact zones incorporated into various types of tools and track pins manufactured for off-highway equipment.

This appendix illustrates the effect of various operating parameters on the case depth or thickness of scan hardened components.

This chapter describes important requirements for ferrous and nonferrous alloys used for gears. Wrought surface-hardening and through-hardening carbon and alloy steels are the most widely used of all gear materials and are emphasized in this chapter. The processing characteristics of gear steels and the bending fatigue strength and properties of carburized steels are reviewed. In addition to wrought steels, the chapter provides information on the other iron-base alloys that are used for gears, namely cast carbon and alloy steels, gray and ductile cast irons, powder metallurgy irons and steels, stainless steels, and tool steels. In terms of nonferrous alloys, the chapter addresses copper-base alloys, die cast aluminum alloys, zinc alloys, and magnesium alloys.

The through-hardening process is generally used for gears that do not require high surface hardness. Four different methods of heat treatment are primarily used for through-hardened gears. In ascending order of achievable hardness, these methods are annealing, normalizing and annealing, normalizing and tempering, and quenching and tempering. This chapter discusses the processes involved in the through-hardening of gears. It provides information on designing procedures, hardness, distortion, and applications of the through-hardened gears. The chapter presents a case history on the design and manufacture of a through-hardened gear rack.

Through-hardening heat treatment is generally used for gears that do not require high surface hardness. In through hardening, gears are first heated to a required temperature and then cooled either in the furnace or quenched in air, gas, or liquid. Four heat treatment methods are primarily used for through-hardened gears: annealing, normalizing and annealing, normalizing and tempering, and quenching and tempering. This chapter begins with a discussion of these through-hardening processes. This is followed by sections providing some factors affecting the design and hardness levels of through-hardened gears. Next, the chapter reviews the considerations related to distortion of through-hardened gears. It then discusses the applications of through-hardened gears. Finally, the chapter presents a case history of the design and manufacture of a through-hardened gear rack.