This article describes some of the underlying factors of tool steel and bearing steel fractures and appearances. It also briefly introduces the general types of cold work and hot work tool steels and their typical performance requirements. This includes the importance of microstructural conditions achieved with powder metallurgy (PM) tool steels and the need for steel “cleanliness,” especially in preventing contact fatigue in bearings or bending fatigue in gears.

Tool steels are carbon, alloy, and high-speed steels that can be hardened and tempered to high hardness and strength values. This article discusses the classifications of commonly used tool steels: water-hardening tool steels, shock-resisting tool steels, cold-work tool steels, and hot-work tool steels. It describes four basic mechanisms of tool steel wear: abrasion, adhesion, corrosion, and contact fatigue wear. The article describes the factors to be considered in the selection of lubrication systems for tool steel applications. It also discusses the surface treatments for tool steels: carburizing, nitriding, ion or plasma nitriding, oxidation, boriding, plating, chemical vapor deposition, and physical vapor deposition. The article describes the properties of high-speed tool steels. It summarizes the important attributes required of dies and the properties of the various materials that make them suitable for particular applications. The article concludes by providing information on abrasive wear and grindability of powder metallurgy steels.

This article focuses on heat treating of the most important H-series and low-alloy hot-work tool steels, namely, normalizing, annealing, stress relieving, preheating, austenitizing, quenching, tempering, and surface hardening. It describes the heat-treating procedure for hot-work tools using examples. The article provides information on the North American Die-Casting Association's requirements for steel grades and heat treatment of dies made of hot-work tool steels. It also describes the chemical compositions and mechanical and metallurgical properties of hot-work tool steels.

Air hardening steel is a type of steel that has deep hardenability and can be hardened in large sections by air cooling. This article discusses the principles of heat treatment of air-hardening steel, and describes the recommended heat treating practices for air-hardening high-strength structural steels, namely, H11 Mod, H13 steel, 300M steel, D-6A and D-6AC, and AF1410 steel. It also provides information on recommended heat treating practices for air-hardening martensitic stainless steels.

This article addresses dies and die materials used for hot forging in vertical presses, hammers, and horizontal forging machines (upsetters). It reviews the properties of die materials for hot forging, including good hardenability, resistance to wear, plastic deformation, thermal fatigue, and mechanical fatigue. The article describes heat treating practices commonly employed for chromium- and tungsten-base AISI hot-work tool steels. It discusses the fabrication of impression dies, and the advantages and disadvantages of cast dies. The article concludes with a discussion on the factors that affect die life and safety precautions to be considered during die construction.

All tool steels are heat treated to develop specific combinations of wear resistance, resistance to deformation or breaking under loads, and resistance to softening at elevated temperature. This article describes recommended heat treating practices, such as normalizing, annealing, austenitizing, quenching, preheating, and tempering commonly employed in certain steels. These are water-hardening tool steels, shock-resisting tool steels, oil-hardening cold-work tool steels, medium-alloy air-hardening cold-work tool steels, high-carbon high-chromium cold-work tool steels, hot-work tool steels, high-speed tool steels, low-alloy special-purpose tool steels, and mold steels. The article presents tables that list the temperature ranges, holding time, and hardness values for all of these heat treating processes.

The powder metallurgy (P/M) process has been used primarily for the production of advanced high-speed tool steels. However, the P/M process is also being applied to the manufacture of improved cold-work and hot-work tool steels. The basic heat treatments for P/M high-speed tool steels include preheating, austenitizing, quenching, and tempering. This article describes manufacturing properties, cutting tool properties, and applications of P/M high-speed tool steels. It discusses the development of P/M high-speed alloy steels that cannot be made by conventional methods because of their high carbon, nitrogen, or alloy contents. For high-speed tool steels, a number of important end-user properties have been improved by powder processing; machinability, grindability, dimensional control during heat treatment, and cutting performance under difficult conditions where high edge toughness is essential. Several of these advantages also apply to P/M cold- and hot-work tool steels, which, compared to conventional tool steels, offer better toughness and ductility for cold-work tooling, better thermal fatigue life, and greater toughness for hot-work tooling.

Tool steels are any steel used to make tools for cutting, forming, or shaping manufactured parts. Most tool steels are wrought products alloyed with relatively large amounts of tungsten, molybdenum, vanadium, manganese, and/or chromium. The article describes a wide variety of tool steels, including high-speed steels, hot and cold-work steels, shock-resisting steels, and special-purpose steels. Hot-work steels are designed to withstand excessive amounts of heat, pressure, and abrasion, suiting them for punching, shearing, and high-temperature forming applications. Cold-work tool steels have exceptional dimensional stability and wear resistance, but lack the alloy content necessary to resist softening at temperatures above 205 to 260 deg C. The article examines standard designations for all tool steel types and provides corresponding composition and property ranges. It also discusses surface treatments, fabrication issues, and in-service measures of performance.