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.

The heat treatment of steel is based on the physical metallurgical principles that relate to its processing, properties, and structure. The microstructures that result from the heat treatment of steel are composed of one or more phases in which the atoms of iron, carbon, and other elements in steel are associated. This article describes the phases of heat treated steel, and provides information on effect of temperature change and the size of carbon atoms relative to that of iron atoms during the heat treatment.

This article discusses the five basic matrix structures in cast irons: ferrite, pearlite, bainite, martensite, and austenite. The alloying elements, used to enhance the corrosion resistance of cast irons, including silicon, nickel, chromium, copper, molybdenum, vanadium, and titanium, are reviewed. The article provides information on classes of the cast irons based on corrosion resistance. It describes the various forms of corrosion in cast irons, including graphitic corrosion, fretting corrosion, pitting and crevice corrosion, intergranular attack, erosion-corrosion, microbiologically induced corrosion, and stress-corrosion cracking. The cast irons suitable for the common corrosive environments are also discussed. The article reviews the coatings used on cast irons to enhance corrosion resistance, such as metallic, organic, conversion, and enamel coatings. It explains the basic parameters to be considered before selecting the cast irons for corrosion services.

Solid-state transformations from invariant reactions are of three types: eutectoid, peritectoid, and monotectoid transformations. This article focuses on structures from eutectoid transformations with an emphasis on the classic iron-carbon system of steel. It illustrates the morphology of a pearlite nodule and the effect of various substitutional alloy elements on the eutectoid transformation temperature and effective carbon content, respectively. Peritectic and peritectoid phase equilibria are very common in several binary systems. The article reviews structures from peritectoid reactions and details the formation of peritectic structures that can occur by at least three mechanisms: peritectic reaction, peritectic transformation, and direct precipitation of beta from the melt.

This article describes the microstructure and metallographic practices used for medium- to high-carbon steels as well as for low-alloy steels. It explains the microstructural constituents of plain carbon and low-alloy steels, including ferrite, pearlite, and cementite. The article provides information on how to reveal the various constituents using proven metallographic procedures for both macrostructural and microstructural examination. Emphasis is placed on the specimen preparation procedures such as sectioning, mounting, grinding, and polishing. The article illustrates the use of proven etching techniques for plain carbon and low-alloy steels.

The properties of irons and steels are linked to the chemical composition, processing path, and resulting microstructure of the material. Processing is a means to develop and control microstructure by hot rolling, quenching, and so forth. This article describes the role of these factors in both theoretical and practical terms, with particular focus on the role of microstructure in various irons. These include bainite, pearlite, ferfite, martensite, austenite, ferrite-pearlite, ferrite-cementite, ferrite-martensite, graphite, and cementite. The article discusses the evolution of microstructural change in rail steels, cast iron, and steel sheet. It contains tables that list the mechanical properties and compositions of selected steels. The article also discusses the basis of material selection of irons and steels.

This article reviews general trends in the cyclic response for representative commercial alloys to establish the spectrum of cyclic properties attainable through microstructural alteration. Individual alloy classes are examined in detail to assess the understanding of relationships between microstructure and fatigue resistance. These alloys classes include ferritic-pearlitic alloys, martensitic alloys, maraging steels, and metastable austenitic alloys. The article also discusses the role of internal defects and selective surface processing in influencing fatigue performance.

This article describes microstructures and microstructure-property relationships in steels. It emphasizes the correlation of microstructure and properties as a function of carbon content and processing in low-alloy steels. The article discusses the iron-carbon phase diagram and the phase transformations that change the structure and properties at varying levels of carbon content. Microstructures described include pearlite, bainite, proeutectoid ferrite and cementite, ferrite-pearlite, and martensite. The article depicts some of the primary processing steps that result in ferrite-pearlite microstructures. It shows the range of hardness levels which may be obtained by tempering at various temperatures as a function of the carbon content of the steel. To reduce the number of processing steps associated with producing quenched and tempered microstructures, new alloying approaches have been developed to produce high-strength microstructures directly during cooling after forging.