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.

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.

Quenching is a critical step in the production of hardened steel. This chapter untangles some of the complexities of the quenching process and its effect on the microstructure and properties of various steels. Making extensive use of cooling curves, it sheds light on the transformations that occur at different cooling rates and the extent to which they can be changed by adjusting quench parameters. It discusses the role of quenching in martempering and austempering along with related problems such as cracking and distortion and the challenges posed by low-hardenability steels. It also discusses the use of various quenchants, including oil, polymer, and molten salt, and explains how to measure and compare their performance using a standard (ISO 9950) test.

This chapter is a detailed account of heat treating techniques for cast irons (gray and ductile), providing the reader with a basic understanding of the differences among various types of cast irons and the concept of carbon equivalent. The types of heat treatments discussed are stress relieving, annealing, normalizing, surface hardening, quenching, martempering, austempering, and flame and induction hardening.

This chapter provides information on the selection of steel and the design of its heat treatment. It also discusses the purpose of this book.

This chapter describes the two types of Time-Temperature-Transformation (TTT) diagrams used and outlines the methods of determining them. As a precursor to the examination of the decomposition of austenite, it first reviews the phases and microconstituents found in steels. This includes a presentation of the iron-carbon phase diagram and the equilibrium phases. The chapter also covers the common microconstituents that form in steels, including the nomenclature used to describe them. The chapter provides a comparison of isothermal and continuous cooling TTT diagrams. These diagrams are affected by the carbon and alloy content and by the prior austenite grain size, and the way in which these factors affect them is examined.

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.

This chapter contains problems that illustrate the calculation or determination of such items as ideal critical diameter, the Jominy curve, and the severity of quench by methods. It presents solutions for the calculation of the effect of prior austenite grain size, carbon content, chromium content, and molybdenum content on ideal critical diameter. The chapter also contains solutions for calculation of Jominy curves and determination of minimum hardness of quenched steels, tempered hardness, ideal critical diameter, severity of quench, heat treatment, and effect of tempering during heat-up to tempering temperature.

This chapter discusses the method for calculating hardenability from composition. It contains tables listing multiplying factors, carbon content, initial hardness, and 50% martensite hardness. The tables also list Jominy distance for 50% martensite vs. DI (in. and mm), boron factors vs. % carbon and alloy factor, and distance hardness dividing factors for non-boron and boron steels (in. and mm).

This appendix contains a table listing the factors for calculating the ideal critical diameter for steels as given in the ASTM standard A255-67.

This data sheet includes a select list of factors for converting customary English units to metric (SI) units.

This appendix contains metric energy conversions for J and ft-lb.

This appendix contains the metric stress or pressure readings (MPa or ksi) to be converted.

This appendix contains a temperature conversion table listing temperatures to be converted, along with degree Centigrade or Fahrenheit equivalent.

This appendix lists AISI-SAE system of designations for steels.

This appendix contains tables listing the compositions of standard nonresulfurized carbon (1.0 manganese maximum and over 1.0 manganese) and the compositions of standard resulfurized and rephosphorized carbon steels.

This appendix contains tables listing the chemical compositions of standard carbon H-steels and standard carbon boron H-steels and the hardenability characteristics of alloys.

This appendix contains tables listing the chemical compositions of standard alloy steels.

This appendix lists the chemical compositions of standard alloy H-steels and standard boron (alloy) H-steels.

This appendix contains a cross-reference to steels, which was developed to help the Heat Treater cross-index chemically similar specifications. The specifications are listed alpha-numerically by country of origin.