The possible classification for tool steels is their division into four groups according to their final application: hot-worked, cold-worked, plastic mold, and high-speed tool steels. This chapter mainly follows such division by application, but the grade nomenclatures used here are primarily from AISI. It presents the classification of tool steels and discusses the principles and processes of tool steel heat treating, namely normalizing, annealing, hardening, and tempering. Various factors associated with distortion in several tool steels are also covered. The chapter discusses the composition, classification, and properties of unalloyed and low-alloy cold-worked tool steels; medium and high-alloy cold-worked tool steels; and 18% nickel maraging steels.

There is a fairly wide variety of different tool steels for different applications. The American Iron and Steel Institute (AISI) classification of tool steels includes seven major categories: water-hardening tool steels, shock-resisting tool steels, cold work tool steels, hot work tool steels, low-alloy special-purpose tool steels, mold tool steels, high-speed tool steels, and powder metallurgy tool steels. This chapter provides discusses the manufacturing process, composition, properties, types, and applications of these tool steels and other cutting tool materials, such as cemented carbides. It also describes the methods of applying coatings to cutting tools to improve tool life.

Mold steels are used for plastic molding and certain die-casting applications and are designated as group P steels in the AISI classification system. The fabrication and performance requirements that differentiate them from other types of tool steels are described in this chapter. It provides information on hubbing and machined cavity grades of mold steels and describes the performance of the corrosion-resistant mold steels. The chapter discusses the processes involved in forging, annealing, stress relieving, carburizing, hardening, and tempering of mold steels. It presents the selection criteria and applications of mold steels.