The main factors affecting the mechanical properties of compacted graphite irons both at room temperatures and at elevated temperatures are composition, structure (nodularity and matrix), and section size. This article presents a comparison between some properties of flake graphite (FG), compacted graphite (CG), and spheroidal graphite (SG) irons in a table. It discusses the effects of composition, structure, and section size on the mechanical properties of compacted graphite irons. The compressive and shear properties, modulus of elasticity, impact properties, fatigue strength, and elevated-temperature properties of compacted graphite irons are also reviewed.

This article discusses the chemical composition, castability, mechanical properties at room temperature and elevated temperature, and physical properties of compacted graphite (CG) cast iron. The change in graphite morphology from the flake graphite (FG) in the base iron to the CG in the final iron is achieved by liquid treatment with different minor elements. CG irons have strength properties close to those of spheroidal graphite (SG) irons, at considerably higher elongations than those of FG iron, and with intermediate thermal conductivities. The main factors affecting the mechanical properties of CG irons both at room temperatures and at elevated temperatures are composition, structure (nodularity and matrix), and section size. The article also discusses the applications of CG irons that stem from their relative intermediate position between FG and SG irons. The tables in the article list the values for tensile properties, hardness, thermal conductivity, fatigue strengths, endurance ratios, and compressive properties of CG, FG, and SG irons.

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.

Unlike gray iron, which contains graphite flakes, ductile iron has an as-cast structure containing graphite particles in the form of small, rounded, spheroidal nodules in a ductile metallic matrix. This article discusses the raw materials that are used for ductile iron production and outlines the most common and important requirements for controlling the composition of ductile iron. Treatment to produce ductile iron involves the addition of magnesium to change the form of the graphite, followed by or combined with inoculation of a silicon-containing material to ensure a graphitic structure with freedom from carbides. The article describes the methods of magnesium treatment, control of magnesium content, and inoculation. It concludes with a discussion on the metallurgical controls of ductile iron production.

Malleable iron is a type of cast iron that has most of its carbon in the form of irregularly shaped graphite nodules instead of flakes, as in gray iron, or small graphite spherulites, as in ductile iron. This article discusses the production of malleable iron based on the metallurgical criteria: to produce solidified white iron throughout the section thickness; and to produce the desired graphite distribution (nodule count) upon annealing. It describes the induction heating and quenching or flame heating and quenching for surface hardening of fully pearlitic malleable iron. Laser and electron beam techniques also have been used for hardening selected areas on the surface of pearlitic and ferritic malleable iron castings that are free from decarburization.

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.

Cast iron exhibits a considerable amount of eutectic in the solid state. This article discusses the structure of liquid iron-carbon alloys to understand the mechanism of the solidification of cast iron. It illustrates the nucleation of the austenite-flake graphite eutectic, austenite-spheroidal graphite eutectic, and austenite-iron carbide eutectic. The article provides a discussion on primary austenite and primary graphite. It also describes the growth of eutectic in cast iron in terms of isothermal solidification, directional solidification, and multidirectional solidification.

This article describes the metallographic specimen preparation procedures for cast iron test samples, including mounting, grinding, polishing, and etching. It discusses the makeup and use of black-and-white and selective color etchants and where one might be preferred over the other. The article provides information on nearly 100 micrographs, discussing the microstructure of flake graphite in gray iron, nodular graphite in ductile iron, and temper graphite in malleable iron. It also examines the matrix microstructures of gray, ductile, compacted, and malleable cast iron samples.

From the point of view of economics and ecology, thin-wall ductile iron (TWDI) castings can compete in terms of mechanical properties with the light castings made of aluminum alloys. This article discusses the effect of technological factors on the cooling rate and physicochemical state of the liquid metal for preparing thin-wall castings with good mechanical properties and performance while avoiding casting defects. It describes a variety of defects that may appear during the production of TWDI castings, such as casting skin anomalies (e.g., flake graphite, graphite segregation), graphite clusters, exploded graphite, slag inclusions, shrinkage porosity, eutectic chill and secondary carbides, and cold shuts. The article reviews the tensile, fatigue, impact, and wear properties of TWDI castings. It provides information on the production and applications of TWDI castings.

ASTM specification A 48 classifies gray irons in terms of tensile strength. The usual microstructure of gray iron is a matrix of pearlite with graphite flakes dispersed throughout. Section sensitivity effects are used in the form of a wedge test in production control to judge the suitability of an iron for pouring a particular casting. Mechanical property values obtained from test bars are sometimes the only available guides to the mechanical properties of the metal in production castings. Gray iron castings are used widely in pressure applications such as cylinder blocks, manifolds, pipe and pipe fittings, compressors, and pumps. Where high impact resistance is needed, gray iron is not recommended. The machinability of most gray cast iron is superior to that of most other cast irons of equivalent hardness, as well as to that of virtually all steel. Gray iron is used widely for machine components that must resist wear.

The properties of irons and steels are linked to the chemical composition, processing path, and resulting microstructure of the material. For a particular iron and steel composition, most properties depend on microstructure. Processing is a means to develop and control microstructure, for example, 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. It lists the mechanical properties of selected steels in various heat-treated or cold-worked conditions. In steels and cast irons, the microstructural constituents have the names ferrite, pearlite, bainite, martensite, cementite, and austenite. The article presents four examples that have very different microstructures: the structural steel has a ferrite plus pearlite microstructure; the rail steel has a fully pearlitic microstructure; the machine housing has a ferrite plus pearlite matrix with graphite flakes; and the jaw crusher microstructure contains martensite and cementite.

This article reviews the graphite morphology, chemical composition requirements, castability, mechanical properties, and corrosion resistance of compacted graphite (CG) irons. It describes the factors affecting the mechanical properties of CG irons. The article also presents the advantages of CG irons.

The ferrous metals are the most significant class of commercial alloys. This article describes the solidification structures of plain carbon steel, low-alloy steel, high-alloy steel, and cast iron, with illustrations. The formation of nonmetallic inclusions in the liquid before and during solidification is also discussed.

The transformation of austenite of cast irons represents a more complex and less studied subject. This article discusses the general features of the decomposition of austenite into bainite. It describes the heat treatment cycles of austempered cast iron microstructure. The article reviews several factors, such as presence of graphite and austenite grain size, which affect the transformation rate of austenite during austempering of free-graphite cast irons.

This article discusses the fatigue and fracture behavior of various types of cast iron, such as gray iron, ductile iron, malleable iron, compacted graphite iron, and white iron, as a function of chemical composition, matrix microstructure, and graphite morphology.

A wide range of mechanical properties can be obtained with a given composition of cast iron, depending on the microstructural constituents that form during solidification and subsequent solid-state processing. This article discusses the mechanical properties of gray iron and provides some general property comparisons with malleable, ductile (nodular), and compacted graphite irons. The mechanical properties of gray iron are determined by the combined effects of its chemical composition, processing technique in the foundry, and cooling rates during solidification. The article provides information on the classification of gray irons based on ASTM International specification A48/A48M. It discusses the loading effect, surface effect, notch sensitivity, and environmental effect on the mechanical properties of gray iron. The chemical composition ranges of some of the more widely used heat-resistant gray irons suitable for elevated-temperature service are presented in a table.

Thin-wall gray cast iron (TWGCI) can be seen as a potential material for the preparation of lightweight castings in automotive engineering applications. This article discusses the most important challenges for TWGCI: cooling rate, solidification, macrostructure, microstructure, and chilling tendency. It reviews the tensile properties and thermophysical properties of gray cast iron. The article describes the variables that influence molten iron preparation: charge materials, melting furnace thermal regime, chemical composition, modification and inoculation treatment, holding time/pouring procedure, mold properties (mold temperature, thermophysical properties of mold and mold coating), and casting design.

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.

Gray irons are commonly classified by their minimum tensile strength. This article describes properties used in the selection of gray irons and the factors that affect properties, particularly the effect of solidification. It discusses the three steps that its processing undergoes in the foundry: liquid metal preparation, solidification, and solid-state transformation. The article discusses the tensile properties of gray cast iron: tensile strength, yield strength, ductility, and modulus of elasticity. It describes hardness tests that are performed for determining the approximate strength characteristics and machinability of a gray iron casting. The article also presents typical mechanical properties of heat-resistant gray irons in a table. It concludes with information on the automotive application of alloy cast irons.

This article provides a brief review of the classification and characteristics of cast irons. It describes the processes used to clean iron castings, including mechanical cleaning and finishing and nonmechanical cleaning. The article discusses surface treatments used to extend casting life when resistance to corrosion, wear, and erosion is required. The common methods include electroplating, electroless plating, hardfacing, weld cladding, surface hardening, porcelain enameling, and organic coatings.