This chapter discusses the processes involved in the heat treatment of steel, namely austenitizing, hardening, quenching, and tempering. It begins with an overview of austenitizing of steels by induction heating, followed by a discussion on the processes involved in transformation of the soft austenite into martensite or lower bainite in the hardening operation. The chapter provides information on various quenching systems and a description of quenching techniques, namely austempering, martempering, and patenting. Difficulties associated with hardening of steel are discussed. Further, the chapter describes the equipment used for and principal variables of tempering. It discusses the causes for various forms of embrittlement due to tempering. Information on multiple tempering, protective-atmosphere tempering, and selective tempering are also provided, along with processes involved in selection of tempering temperature. The chapter ends with a section discussing various effects, advantages, and disadvantages of precipitation hardening.

This chapter describes the causes of cracking, embrittlement, and low toughness in carbon and low-alloy steels and their differentiating fracture surface characteristics. It discusses the interrelated effects of composition, processing, and microstructure and contributing factors such as hot shortness associated with copper and overheating and burning as occur during forging. It addresses various types of embrittlement, including quench embrittlement, tempered-martensite embrittlement, liquid-metal-induced embrittlement, and hydrogen embrittlement, and concludes with a discussion on high-temperature hydrogen attack and its effect on strength and ductility.

This chapter discusses the processes used in manufacturing to thermally alter the properties of metals and alloys. It begins with a review of the iron-carbon system, the factors that affect hardenability, and the use of continuous cooling transformation diagrams. It then explains how various steels respond to heat treatments, such as annealing, normalizing, spheroidizing, tempering, and direct and interrupted quenching, and surface-hardening processes, such as flame and induction hardening, carburizing, nitriding, and carbonitriding. It also addresses the issue of temper embrittlement and discusses the effect of precipitation hardening on aluminum and other alloys.

This chapter reviews the causes and cases associated with the problems originated by tempering of steels. To provide background on this phenomenon, a brief description of the martensite reactions and the steel heat treatment of tempering is given to review the different stages of microstructural transformation. A section describing the types of embrittlement from tempering, along with mechanical tests for the determination of temper embrittlement (TE), is presented. Various factors involved in the interaction of the TE phenomenon with hydrogen embrittlement and liquid-metal embrittlement are also provided. The cases covered are grinding cracks on steel cam shaft and transgranular and intergranular crack path in commercial steels.

One of the primary advantages of steels is their ability to attain high strengths through heat treatment while still retaining some degree of ductility. Heat treatments can be used to not only harden steels but also to provide other useful combinations of properties, such as ductility, formability, and machinability. This chapter discusses various heat treatment processes, namely annealing, stress relieving, normalizing, spheroidizing, and hardening by austenitizing, quenching and tempering. It also discusses two types of interrupted quenching processes: martempering and austempering. The chapter concludes with a brief section on temper embrittlement.

This article discusses the role of alloying in the production and use of carbon and low-alloy steels. It explains how steels are defined and selected based on alloy content and provides composition and property data for a wide range of designations and grades. It describes the effect of alloying on structure and composition and explains how alloy content can be controlled to optimize properties and behaviors such as ductility, strength, toughness, fatigue and fracture resistance, and resistance to corrosion, wear, and high-temperature creep. It also examines the effect of alloying on processing characteristics such as hardenability, formability, weldability, machinability, and temper embrittlement. In addition, the article provides an extensive amount of engineering data with relevance in materials selection.

This chapter first examines the tempering behavior of plain carbon steels and then that of alloy steels. Next, some correlations are examined which allow estimations of the tempered hardness from the chemical compositions, tempering temperature and tempering time. The chapter then describes the effect of tempering on the mechanical properties of plain carbon steels and the microstructure of plain carbon steels. It shows examples of the structure of plain carbon steels. Additionally, the chapter explains the stages and kinetics of tempering in alloy steels and plain carbon steels. It also describes some methods of estimating the hardness. Finally, the chapter discusses the important problem of temper embrittlement.

The toughness of a material is its ability to absorb energy in the form of plastic deformation without fracturing. It is thus a measure of both strength and ductility. This chapter describes the fracture and toughness characteristics of metals and their effect on component lifetime and failure. It begins with a review of the ductile-to-brittle transition behavior of steel and the different ways to measure transition temperature. It then explains how to predict fracture loads using linear-elastic fracture mechanics and how toughness is affected by temperature and strain rate as well as grain size, inclusion content, and impurities. It also presents the theory and use of elastic-plastic fracture mechanics and discusses the causes, effects, and control of temper embrittlement in various types of steel.