Gray irons are a group of cast irons that form flake graphite during solidification, in contrast to the spheroidal graphite morphology of ductile irons. This article describes surface hardening of gray irons by flame and induction heating. It provides information on the classification of the gray irons in ASTM specification. The article presents examples that illustrate the use of stress relieving to eliminate distortion and cracking. It describes the three annealing treatments of gray iron: ferritizing annealing, medium (or full) annealing, and graphitizing annealing. The article discusses the parameters of the tensile strength and hardness of a normalized gray iron casting. These include combined carbon content, pearlite spacing, and graphite morphology. The article concludes with a discussion on the induction hardening of gray iron castings.

Cast irons, like steels, are iron-carbon alloys but with higher carbon levels than steels to take advantage of eutectic solidification in the binary iron-carbon system. This article introduces the solid-state heat treatment of iron castings and describes the various processes of heat treatment of cast iron. It provides information on stress relieving, annealing, normalizing, through hardening, and surface hardening of these castings. The article discusses general considerations for the heat treatment of cast iron. Cast irons are occasionally nitrided for various applications with the aim of enhancing surface hardness and corrosion resistance of the products. The article describes molten salt bath cyaniding and ion nitriding of cast iron.

Ductile cast irons are heat treated primarily to create matrix microstructures and associated mechanical properties not readily obtained in the as-cast condition. This article discusses the most important heat treatments of ductile irons and their purposes. International standards of ductile iron provided by ASTM International, the International Organization for Standardization (ISO), and SAE International are presented in a table. The article explains basic structural differences between the ferritic, pearlitic, martensitic, and ausferritic classes. It presents recommended practices for annealing ductile iron castings for different alloy contents and for castings with and without eutectic carbides. The article discusses the induction surface hardening and remelt hardening of ductile iron. It concludes with information on the effect of heat treatment on fatigue strength of ductile iron.

Gray irons are a group of cast irons that form flake graphite during solidification, in contrast to the spheroidal graphite morphology of ductile irons. The heat treatment of gray irons can considerably alter the matrix microstructure with little or no effect on the size and shape of the graphite achieved during casting. This article provides a detailed account of classes of gray iron, and heat treating methods of gray irons with examples. These methods include stress relieving, annealing, normalizing, transformation hardening, austenitizing, quenching, austempering, martempering, flame hardening, induction hardening, and nitriding.

This article introduces the general principles and applications of heat treatment to iron castings. It provides a detailed discussion on the heat treatment processes, namely, stress relieving, annealing, normalizing, throughhardening, and surface hardening for various types of cast irons. These include gray iron, ductile iron, compacted graphite iron, white iron, malleable iron, and high-alloy iron. The article describes how to control temperature and atmosphere during the heat treatment of the iron castings.

Tool steels are an important class of steels due to their distinct applications and their specific heat treating issues. This article provides an overview of the classification and production of tool steels, and discusses the procedures and process control requirements for heat treating principal types of tool steels. It reviews the various heat treating processes, namely, normalizing, annealing, stress relieving, austenitizing, quenching, and tempering, and surface treatments and cold treating. The article also provides information on the applicability of these processes to various types of tool steels.

Ductile cast irons are heat treated to create matrix microstructures and associated mechanical properties not readily obtained in the as-cast condition. This article provides a detailed account of the general characteristics of ductile irons. It discusses the most important heat treatments of ductile irons, namely, stress relieving, austenitizing, annealing, normalizing, quenching, martempering, austempering, and surface hardening. The article elucidates the effects of these heat treatments on the mechanical properties of the ductile irons.

Hardenable steels with high-alloy content includes a family of nickel-cobalt steels with high strength and high toughness. This article describes various heat treatments, namely, normalizing, annealing, hardening, tempering, stress relieving, overaging, quenching, refrigeration, and straightening treatment, applied to HP9-4-20, HP9-4-25, HP9-4-30, and HP9-4-45 steels. These steels have high fracture toughness when heat treated to very high strength levels. The article also describes heat treatments applied to other alloys such as AF 1410, AerMet 100, AerMet 310, and AerMet 340, which provide a good combination of high strength and toughness that make them attractive for aerospace application. It also presents tables that provide information on the effect of aging temperatures and heat treatment on mechanical properties and impact energy of these steels.

This article provides a discussion on heat treating practices, namely, carburizing, normalizing, annealing, stress relieving, preheating, austenitizing, quenching, tempering, and nitriding for various grades of mold and corrosion-resistant tool steels. It details the characteristics of various grades of mold and corrosion-resistant tool steels, including type P20, type P20Mod, AISI type 420, and AISI type 440B.

This article describes the metallurgy and process specifics of subcritical annealing, which involves heating below the lower critical temperature such that austenite does not form during subcritical annealing. It provides information on the nominal subcritical annealing temperatures of plain carbon, low-alloy and high-alloy steels and temperature-time relations of subcritical annealing. Practical implications for induction annealing and induction normalizing are included. The article concludes by describing induction softening, which softens the threaded area on carburized components such as hypoid pinion gears, to prevent the occurrence of delayed fractures from occurring.

Normalizing of steel is a heat treating process that is often considered from both thermal processing and microstructural standpoints. In terms of thermal processing, normalizing is defined as heating of a ferrous alloy to a suitable temperature above the transformation range and then cooling it in air to a temperature substantially below the transformation range. This article provides information on the normalizing of carbon and alloy steels, and discusses the processes involved and the furnaces used in normalizing of steel forgings, bar and tubular products, and castings. It contains tables that list the typical normalizing temperatures for standard carbon and alloy steels and typical mechanical properties of selected carbon and alloy steels in hot-rolled, normalized, and annealed conditions.

This article describes the applications of induction heat treatment of metals, including normalizing, annealing, hardening, and tempering and stress relieving. It discusses the simulation techniques of the electromagnetic and thermal processes that occur during induction heat treating. The article explains the finite-difference method, finite-element method, mutual impedance method, and boundary-element method for the numerical computation of the induction heat treating processes. It also discusses the direct and indirect coupling approaches for coupling the electromagnetic and heat-transfer problems. Modern computer simulation techniques are capable of effectively simulating electromagnetic and thermal phenomena for many processes that involve electromagnetic induction. The article considers the challenges faced by developers of modern simulation software.

The term cast iron designates a group of materials that contain more than one constituent in their microstructure due to excess carbon that result in unique characteristics such as the fracture appearance and graphite morphology. This article discusses the classification of cast iron and the various metallurgical aspects, such as the composition, alloying element, solidification, and graphite morphologies, of different types of cast iron. It describes the physical properties for various cast irons and the influence of microstructure and chemical composition on each property. The article provides a detailed account on thermal properties, conductive properties, magnetic properties, and acoustic properties of cast iron. It also examines heat treatment, namely, stress relieving, annealing, normalizing, through hardening, and surface hardening. The article presents a discussion on the welding, machining and grinding, and coating of the types of cast iron.

This article describes the heat treating (stress relieving, normalizing, annealing, quenching, tempering, martempering, austempering, and age hardening) of different types of steels, including ultrahigh-strength steels, maraging steels, and powder metallurgy steels. Tabulating the recommended temperatures for normalizing and austenitizing, it provides information on mechanism, cooling media, principal variables, process procedures, and applications of heat treating. In addition, the article gives a short note on the cold and cryogenic treatment of steel.

The properties of carbon and alloy steels are dependent on the relationships between chemical composition, processing, and microstructure. This article discusses the effects of alloying and residual elements on the mechanical properties of carbon and alloy steels. Tables listing values for the mechanical properties of selected carbon and alloy steels in the hot-rolled, normalized, annealed, and quenched-and tempered condition are provided.