Search Results for austenitic ductile cast iron

The mechanical properties of ductile cast irons are determined largely by the microstructure of the steel matrix in combination with the shape, size, and distribution of the graphite nodules. This article describes the designation of ductile cast irons according to the ASTM International designation system and reviews standard-grade ductile cast irons. An overview of the most commonly used standards related to designation and specification of ductile cast iron is presented in a table. This article discusses the use of low-alloy ductile cast irons at elevated temperatures and the chemical compositions and some mechanical properties of austenitic ductile cast irons. The article concludes with a discussion on heat treatment of austempered ductile 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.

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.

The high-alloy irons can be categorized into two main groups: the high-alloy graphitic irons (covering both gray and ductile grades) and the high-alloy white irons. High-alloy irons are used in applications with demanding requirements, such as high resistance to wear, heat, and corrosion, or for combined properties. This article discusses the specification and selection of high-alloy irons. The common alloying elements and their effect on the stable and metastable eutectic temperatures are listed in a table. The article provides information on the compositions, properties and applications of high-alloy graphitic irons and high-alloy white irons.

High-alloy graphitic cast irons are used primarily in applications requiring corrosion resistance or strength and oxidation resistance in high-temperature service. This article describes the properties, applications and heat treatment processes of high-alloy graphitic cast irons, including austenitic gray irons and austenitic ductile irons. It also provides a discussion on the heat treatment of high-silicon irons for heat resisting and corrosion resisting applications.

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.

The metallographic specimen preparation process for microstructural investigations of cast iron specimens usually consists of five stages: sampling, cold or hot mounting, grinding, polishing, and etching with a suitable etchant to reveal the microstructure. This article describes the general preparation of metallographic specimens and the methods of macroscopic and microscopic examination. Usually, gray-scale (black-and-white) metallography is sufficient for microstructural analysis of cast irons. The article discusses the use of color metallography of gray irons and ductile irons. It also presents application examples of color metallography.

This article describes two contemporary approaches for preparing cast iron specimens with a wide range of phases and constituents as well as different graphite morphologies. It introduces concepts and preparation materials that enable metallographers to shorten the process while producing better, more consistent results. Recommended procedures to prepare cast irons and examples of high-alloy cast iron microstructures revealed using a variety of etchants are presented. Several etchants are used to reveal the matrix microstructure, depending on the alloy content. The article discusses the use of black and white etchants and lists the compositions of abrasion-resistant cast irons according to ASTM A532/A532M in a table.

This article discusses the melting and pouring practices, heat treatment, and applications of different types of high-alloy graphitic iron, namely, high-silicon gray irons, high-silicon ductile irons, nickel-alloyed austenitic irons, austenitic gray irons, austenitic ductile irons, and aluminum-alloyed irons.

Austempered ductile iron (ADI) results from a specialty heat treatment of ductile cast iron. This article discusses the production of austempered ductile iron by heat treatment. The austempered ductile iron grades, according to ISO 17804 and EN 1564, are presented in a table. For economic reasons, or to avoid metallurgical problems, combinations of alloys are often used to achieve the desired hardenability in austempered ductile iron. The article provides information on the alloy combinations for austempered ductile iron. The mechanical properties, fracture toughness, fatigue, and abrasion resistance of the austempered ductile iron are discussed. The article concludes with information on the applications for austempered ductile iron.

The cast iron family includes several different groups, including gray iron, ductile iron, compacted graphite iron, malleable iron, white iron, and many different grades within each of these alloy groups. This article addresses issues specific to gray iron, but in many instances the discussion can be related to the other cast iron groups and the various grades within those groups. It discusses the usage of techniques and procedures in cast iron fractography. The article presents a list of common defects that can initiate failure.

Cast irons may be compared with steels in their reactions to hardening. However, because cast irons (except white iron) contain graphite and substantially higher percentages of silicon, they require higher austenitizing temperatures. This article describes the effect of heat treatment processes such as annealing, normalizing, surface hardening, tempering, stress relieving, quenching, and austempering, on hardness and tensile properties of cast irons, namely gray irons, ductile irons, malleable irons, and austenitic irons.

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.

Alloy cast irons are considered to be those casting alloys based on the iron-carbon-silicon system that contain one or more alloying elements intentionally added to enhance one or more useful properties. Alloy cast irons can be classified as white cast irons, corrosion-resistant cast irons, and heat-resistant cast irons. This article discusses abrasion-resistant chilled and white irons, high-alloy corrosion-resistant irons, and medium-alloy and high-alloy heat-resistant gray and ductile irons. The article outlines in a list the approximate ranges of alloy content for various types of alloy cast irons. The article explains the effects of alloying elements and the effects of inoculants. In most cast irons, it is the interaction among alloying elements that has the greatest effect on properties. Inoculants other than appropriate graphitizing or nodularizing agents are used rarely, if ever, in high-alloy corrosion-resistant or heat-resistant irons.

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.

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.

Cast irons primarily are iron alloys that contain more than 2% carbon and from 1 to 3% silicon. This article provides a description of iron-iron carbide-silicon system; and discusses the classification, composition, and characteristics of cast irons, such as gray, ductile, malleable, compacted graphite, and white cast iron. A table shows the correspondence between commercial and microstructural classification, as well as final processing stage in obtaining common cast irons.