Air hardening steel is a type of steel that has deep hardenability and can be hardened in large sections by air cooling. This article discusses the principles of heat treatment of air-hardening steel, and describes the recommended heat treating practices for air-hardening high-strength structural steels, namely, H11 Mod, H13 steel, 300M steel, D-6A and D-6AC, and AF1410 steel. It also provides information on recommended heat treating practices for air-hardening martensitic stainless steels.

This article is a compilation of tables that provide information on preheat and interpass temperatures and the postweld heat treatment for selected carbon steels, as well as steel pressure vessels and pipe welds. Information is also provided for preheat and interpass temperatures of heat treatable steels, namely, low-alloy steels and ultra high-strength steels.

Sheet forming comprises deformation processes in which a metal blank is shaped by tools or dies, primarily under the action of tensile stresses. This article discusses the classification of sheet-forming processes for obtaining desired dimensional features. It describes different process-related developments, namely, superplastic forming of aluminum, forming of tailor-welded blanks, rubber-pad forming, and high-velocity metal forming. The article explains cost-effective approaches of evaluating tooling designs prior to the manufacture of expensive steel dies and dieless forming techniques such as thermal forming and peen forming. It provides information on the application of advanced high-strength steels, magnesium alloys, and various ultrafine-grain materials for superplastic sheet forming. The article concludes with information on the development and application of simulation, design, and control of sheet-forming processes.

This article provides information on the classification of high-strength steels (HSS) and advanced high-strength steels (AHSS) and tabulates designation of HSS and AHSS as recommended by the American Iron and Steel Institute. It reviews the major grades of HSS and AHSS that are used or will potentially be used in industrial applications. The article discusses different stamping issues such as edge cracking and springback, encountered during forming of AHSS, and lists guidelines for reducing springback in stamped components. It concludes with a discussion on the major advantages and disadvantages of using HSS and AHSS in automotive applications.

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 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.

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.

Dual-phase steels are a new class of high-strength low alloy (HSLA) steels characterized by a microstructure consisting of about 20% hard martensite particles dispersed in a soft ductile ferrite matrix. In addition to high tensile strength, in the range of 550 MPa (80 ksi), dual-phase steels exhibit continuous yielding behavior, a low 0.2% offset yield strength, and a higher total elongation than other HSLA steels of similar strength. The article discusses some of the more pertinent aspects of dual-phase steels, such as heat treatment, microstructure, mechanical properties, chemical composition, and manufacturability. In general, these steels have a carbon content of less than 0.1%, which ensures that they can be spot welded. However, newer high-carbon dual-phase steels in development are generating interest due to their unique combination of total elongation and tensile strength.