This article summarizes some of the effects of the major alloying elements in low-alloy steels and the heat treating for some common types of low-alloy steels. Coverage includes common alloys of the following low-alloy steel types: low-alloy manganese steels, low-alloy molybdenum steels, low-alloy chromium-molybdenum steels, low-alloy nickel-chromium-molybdenum steels, low-alloy nickel-molybdenum steels, low-alloy chromium steels, low-alloy chromium-vanadium steels, and low-alloy silicon-manganese steels. The article reviews heat treating parameters and processing considerations for each category of steel, including spherodizing, normalizing, annealing, hardening, and tempering.

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.

Tool steels are carbon, alloy, and high-speed steels that can be hardened and tempered to high hardness and strength values. This article discusses the classifications of commonly used tool steels: water-hardening tool steels, shock-resisting tool steels, cold-work tool steels, and hot-work tool steels. It describes four basic mechanisms of tool steel wear: abrasion, adhesion, corrosion, and contact fatigue wear. The article describes the factors to be considered in the selection of lubrication systems for tool steel applications. It also discusses the surface treatments for tool steels: carburizing, nitriding, ion or plasma nitriding, oxidation, boriding, plating, chemical vapor deposition, and physical vapor deposition. The article describes the properties of high-speed tool steels. It summarizes the important attributes required of dies and the properties of the various materials that make them suitable for particular applications. The article concludes by providing information on abrasive wear and grindability of powder metallurgy steels.

Steel springs are made in many types, shapes, and sizes, ranging from delicate hairsprings for instrument meters to massive buffer springs for railroad equipment. The primary focus of this article is small steel springs that are cold wound from wire. Wire springs are of four types: compression springs (including die springs), extension springs, torsion springs, and wire forms. Chemical composition, mechanical properties, surface quality, availability, and cost are the principal factors to be considered in selecting steel for springs. Both carbon and alloy steels are used extensively. The three types of wire used in the greatest number of applications of cold formed springs are hard-drawn spring wire, oil tempered wire and music wire. Residual stresses can increase or decrease the strength of a spring material, depending on their direction. Steel springs are often electroplated with zinc or cadmium to protect them from corrosion and abrasion. Although some hot-wound springs are made of steels that are also used for cold-wound springs, hot-wound springs are usually much larger, which results in significant metallurgical differences. All spring design is based on Hooke’s law; charts and formulas are available to aid in the design of springs.

This article provides useful information on the selection of steels for heat treatment in order to achieve the required hardness. It discusses the effects of alloying elements on hardenability using the Grossmann's concept, and presents a discussion on the effects of alloying elements in hot-worked and cold-drawn steels. The article focuses on the selection of carbon and alloy steels based on the function of the alloying elements, and discusses the specific effects of alloying elements in steel in a tabulated form. The depth and degree of hardening (percentage of martensite) are dictated by the engineering stress analysis. Mechanical properties of quenched and tempered steels develop similar tensile properties for all practical purposes for all compositions with the same hardness. The article also provides information on the selection of steels to meet the required hardness, and elucidates the concept of hardenability for wear resistance with the help of graphs.

This article describes die wear and failure mechanisms, including thermal fatigue, abrasive wear, and plastic deformation. It summarizes the important attributes required for dies and the properties of the various die materials that make them suitable for particular applications. Recommendations on the selection of the materials for hot forging, hot extrusion, cold heading, and cold extrusion are presented. The article discusses the methods of characterizing abrasive wear and factors affecting abrasive wear. It discusses various die coatings and surface treatments used to extend the lives of dies: alloying surface treatments, micropeening, and electroplating.

Austenitization refers to heating into the austenite phase field, during which the austenite structure is formed. This article highlights the purpose of austenitization, and reviews the mechanism and importance of thermodynamics and kinetics of austenite structure using an iron-carbon binary phase diagram. It also describes the effects of austenite grain size, and provides useful information on controlling the austenite grain size using the thermomechanical process.

This article provides an overview of the different classification and designation systems of wrought carbon steel and alloy steel product forms with total alloying element contents not exceeding 5″. It lists the quality descriptors, chemical compositions, cast or heat composition ranges, and product analysis tolerances of carbon and alloy steels. The major designation systems discussed include the Society of Automotive Engineers (SAE)-American Iron and Steel Institute (AISI) designations, Unified Numbering System (UNS) designations, American Society for Testing and Materials (ASTM) designations, Aerospace Material Specification (AMS), and other international designations and specifications.

This article addresses classifications and designations for carbon steels and low-alloy steels, particularly high-strength low-alloy (HSLA) steels, based on chemical composition, manufacturing methods, finishing method, product form, deoxidation practice, microstructure, required strength level, heat treatment and quality descriptors. It describes the effects of alloying elements on the properties and characteristics of steels. The article provides extensive tabular data pertaining to domestic and international designations of steels.

Structural steels with very high strength levels are often referred to as ultrahigh-strength steels. This article describes the commercial structural steels capable of a minimum yield strength of 1380 MPa (200 ksi). The ultrahigh-strength class of constructional steels includes several distinctly different families of steels. The article focuses on medium-carbon low-alloy steels, medium-alloy air-hardening steels, and high fracture toughness steels. The medium-carbon low-alloy family of ultrahigh-strength steels includes AISI/SAE 4130, the higher-strength 4140, and the deeper hardening, higher-strength 4340. Also from this family are descriptions for the 300M, D-6a and D-6ac, 6150, and 8640 steels. The medium-alloy air-hardening family of ultrahigh-strength steels includes H11 modified and H13 steels. The high fracture toughness family of ultrahigh-strength steels includes HP-9-4-30 steel and AF1410 steel. The article explains the mechanical properties and the heat treatments of the medium-carbon low-alloy steels, medium-alloy air-hardening steels, and high fracture toughness steels.

Ultrahigh-strength steels are designed to be used in structural applications where very high loads are applied and often high strength-to-weight ratios are required. This article discusses the composition, mechanical properties, processing, product forms, and applications of commercial structural steels capable of a minimum yield strength of 1380 MPa (200 ksi). These include medium-carbon low-alloy steels, such as 4340, 300M, D-6a and D-6ac steels; medium-alloy air-hardening steels, such as HI1 modified steel and H13 steel; high fracture toughness steels, such as HP-9-4-30, AF1410, and AerMet 100 steels; and maraging steels.

This article focuses on the forging behavior and practices of carbon and alloy steels. It presents general guidelines for forging in terms of practices, steel selection, forgeability and mechanical properties, heat treatments of steel forgings, die design features, and machining. The article discusses the effect of forging on final component properties and presents special considerations for the design of hot upset forgings.

Tempering of steel is a process in which hardened or normalized steel is heated to a temperature below the lower critical temperature and cooled at a suitable rate, primarily to increase ductility, toughness, and grain size of the matrix. This article provides an overview of the variables that affect the microstructure and mechanical properties of tempered steel, namely, the tempering temperature, tempering time, carbon content, alloy content, and residual elements. Tempering after hardening is performed to relieve quenching stresses and ensure dimensional stability of steel. The article discusses the embrittlement problems associated with tempering. Four types of equipment are used for tempering, namely, convection furnaces, salt bath furnaces, oil bath equipment and molten metal baths. Special procedures for tempering are briefly reviewed.

This article discusses factors involved in selecting welding processes and consumables and establishing procedures and practices for the arc welding of low-alloy steels. It provides information on welding consumables in terms of filler metals and fluxes and shielding gases. The article describes the various categories of low-alloy steels, such as high-strength low-alloy (HSLA) structural steels, high-strength low-alloy quenched and tempered(HSLA Q&T) structural steels, low-alloy steels for pressure vessels and piping, medium-carbon heat-treatable (quenched and tempered) low-alloy (HTLA) steels, ultrahigh-strength low-alloy steels, and low-alloy tool and die steels. It concludes with a discussion on repair practices for tools and dies.

Hot-rolled steel bars and other hot-rolled steel shapes are produced from ingots, blooms, or billets converted from ingots or from strand cast blooms or billets and comprise a variety of sizes and cross sections. Most carbon steel and alloy steel hot-rolled bars and shapes contain surface imperfections with varying degrees of severity. Seams, laps, and slivers are probably the most common defects in hot-rolled bars and shapes. Another condition that could be considered a surface defect is decarburization. Hot-rolled steel bars and shapes can be produced to chemical composition ranges or limits, mechanical property requirements, or both. Hot-rolled carbon steel bars are produced to two primary quality levels: merchant quality and special quality. Merchant quality is the least restrictive descriptor for hot-rolled carbon steel bars. Special quality bars are employed when end use, method of fabrication, or subsequent processing treatment requires characteristics not available in merchant quality bars.

Hardenability refers to the ability of steel to obtain satisfactory hardening to some desired depth when cooled under prescribed conditions. It is governed almost entirely by the chemical composition (carbon and alloy content) at the austenitizing temperature and the austenite grain size at the moment of quenching. This article describes the Jominy end-quench test, the Grossman method, and the air hardenability test to evaluate hardenability. It also reviews the factors that influence steel hardenability and selection.

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.

Shearing is a process of cutting flat product with blades, rotary cutters, or with the aid of a blanking or punching die. This article commences with a description of some wear and material factors for tools used to shear flat product, principally sheet. Methods of wear control are reviewed in terms of tool materials, coatings and surface treatments, and lubrication. The article discusses tool steels that are used for cold and hot shearing, and rotary slitting. It provides information on the materials used for two main categories of machine knives: circular knives and straight knife cutters. The article also discusses the selection of materials for blanking and piercing dies and provides examples that illustrate the various types of tooling changes for blanking high-carbon steel.

Hot-rolled steel bars and other hot rolled steel shapes are produced from ingots, blooms, or billets converted from ingots, or from strand cast blooms and billets, and comprise a variety of sizes and cross sections. This article provides a brief discussion on mechanical properties, quality descriptors and chemical compositions of hot-rolled steel bars, cold-finished steel bars, steel wire rod and steel wire. It contains tables that provide size tolerances for cold-finished carbon steel bar and cold-finished alloy steel bar.

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.