This chapter discusses steel’s compositions, metallurgical phases, microstructures, and heat treatments. It then presents the structure-property relationships of steel. The chapter describes the deformation and strengthening mechanisms of steel. It also presents an overview of deformation processing and annealing.

Carbon and low-alloy steels are the most frequently welded metallic materials, and much of the welding metallurgy research has focused on this class of materials. Key metallurgical factors of interest include an understanding of the solidification of welds, microstructure of the weld and heat-affected zone (HAZ), solid-state phase transformations during welding, control of toughness in the HAZ, the effects of preheating and postweld heat treatment, and weld discontinuities. This chapter provides information on the classification of steels and the welding characteristics of each class. It describes the issues related to corrosion of carbon steel weldments and remedial measures that have proven successful in specific cases. The major forms of environmentally assisted cracking affecting weldment corrosion are covered. The chapter concludes with a discussion of the effects of welding practice on weldment corrosion.

This chapter describes case depth and discusses flame hardening, laser heat treatment, electron beam hardening, induction heat treatment, and induction hardening.

Steel is broadly classified as plain-carbon steels, low-alloy steels, and high-alloy steels. This chapter begins by describing microconstituents of low- and medium-carbon steel, including bainite and martensite. This is followed by a section discussing the effect of alloying elements on steel. Then, it provides an overview of steel casting applications. Next, the chapter reviews engineering guidelines for steel castings and feeder design. The following section provides information on feeding aids. Further, the chapter describes the elements of gating systems for steel castings. It also describes the alloys, properties, applications, and engineering details of steel. Finally, the chapter explains defects in steel castings and presents guidelines for problem solving with examples.

Iron and steel have been the most useful materials to meet the needs of several industries for many decades. Each iron and steel alloy offers unique attributes that make them the best choice for an application. This chapter provides an overview of each ferrous alloy—gray iron, malleable iron, compacted graphite iron (CGI), ductile iron, austempered ductile iron (ADI), and carbon steel and low-alloy steel; its versatile attributes; and its individual applications. A large section of the chapter covers the impact of electric vehicles on the future of the iron and steel castings industry, including discussion on electric vehicle categories and weights; impact of center of gravity on stability and steering; lightweighting incentives; and engineering for improved suspension.

This chapter covers the tribological properties of stainless steel and other corrosion-resistant alloys. It describes the metallurgy and microstructure of the basic types of stainless steel and their suitability for friction and wear applications and in environments where they are subjected to liquid, droplet, and solid particle erosion. It also discusses the tribology of nickel- and cobalt-base alloys as well as titanium, zinc, tin, aluminum, magnesium, beryllium, graphite, and different types of wood.

The existence of austenite and ferrite, along with carbon alloying, is fundamental in the heat treatment of steel. In view of the importance of structure and its formation to heat treatment, this chapter describes the various microstructures that form in steels, the various factors that determine the formation of microstructures during heat treatment processing of steel, and some of the characteristic properties of each of the microstructures. The discussion also covers the constitution of iron during heat treatment and the phases of heat-treated steel with elaborated information on iron phase transformation, hysteresis in heating and cooling, ferrite and austenite as two crystal structures of solid iron, and the diffusion coefficient of carbon.

The decomposition of austenite, during controlled cooling or quenching, produces a wide variety of microstructures in response to such factors as steel composition, temperature of transformation, and cooling rate. This chapter provides a detailed discussion on the isothermal transformation and continuous cooling transformation diagrams that characterize the conditions that produce the various microstructures. It discusses the mechanism and process variables of quenching of steel, explaining the factors involved in the mechanism of quenching. In addition, the chapter provides information on the causes and characteristics of residual stresses, distortion, and quench cracking of steel.

This chapter discusses the processes involved in the heat treatment of steel, namely austenitizing, hardening, quenching, and tempering. It begins with an overview of austenitizing of steels by induction heating, followed by a discussion on the processes involved in transformation of the soft austenite into martensite or lower bainite in the hardening operation. The chapter provides information on various quenching systems and a description of quenching techniques, namely austempering, martempering, and patenting. Difficulties associated with hardening of steel are discussed. Further, the chapter describes the equipment used for and principal variables of tempering. It discusses the causes for various forms of embrittlement due to tempering. Information on multiple tempering, protective-atmosphere tempering, and selective tempering are also provided, along with processes involved in selection of tempering temperature. The chapter ends with a section discussing various effects, advantages, and disadvantages of precipitation hardening.

This chapter discusses the engineering significance of steel and briefly describes its chemical composition, crystal structure, Fe-C phases, and associated characterization techniques.

This chapter examines the microstructure of special bar quality (or engineering) steels and how it is influenced by carbon content, tempering temperature, and prior austenitic grain size. It explains how some of the changes are difficult to detect and require special etching and/or measurement techniques. It provides information on many types of engineering steel, including medium and high-carbon steels used in rail applications. It also examines the effect of nickel-phosphorus coatings on stainless steel and phosphate coatings used to reduce friction during thread rolling and other such procedures.

This chapter focuses on the evolution of steel production from 1870 to 1900. It begins with a review of the life of the inventor of the air-boiling process, William Kelly. This is followed by a discussion on how Bessemer's air-blowing process entered the steel production industry and the development of the Kelly-Bessemer process by Alexander Holley. The chapter then discusses how Andrew Carnegie lowered the cost to produce steel, how he entered the iron and steelmaking industry, and how Captain Billy Jones joined Carnegie to expand Carnegie steel. The chapter further provides information on the great strike of 1892 at Homestead and the rapid growth in steel markets. It ends with a discussion about the factors that led Carnegie to sell his steel empire.

This chapter discusses the development of stainless steel. It begins with some information on the discovery of stainless steel. This is followed by a discussion on the most important patents issued for stainless steel. Applications of stainless steel beyond their original use in cutlery and tableware are then presented. Information on the development of alloys for specific applications and on the argon oxygen decarburization process is also provided. The chapter ends with a discussion on the major use for stainless steel after WWII.

This chapter describes issues related to corrosion of carbon steel weldments and remedial measures that have proven successful in specific cases. The forms of corrosion covered includes preferential heat affected zone corrosion, preferential weld metal corrosion, and galvanic corrosion. Industrial case studies demonstrating the necessity for testing each galvanic couple in the environment for which it is intended are presented. The chapter also discusses various factors associated with stress-corrosion cracking in oil refineries.

This chapter discusses various factors that affect corrosion of stainless steel weldments. It begins by providing an overview of the metallurgical factors associated with welding. This is followed by a discussion on preferential attack associated with weld metal precipitates in austenitic stainless steels as well as several forms of corrosion associated with welding. The effects of gas-tungsten arc weld shielding gas composition and heat-tint oxides on corrosion resistance are then covered. Microbiological corrosion of butt welds in water tanks is also illustrated. In addition, the chapter provides information on corrosion of ferritic and duplex stainless steel weldments.

This chapter provides perspective on the physical dimensions associated with the microstructure of steel and the instruments that reveal grain size, morphology, phase distributions, crystal defects, and chemical composition, from which properties and behaviors derive. The chapter also reviews the definitions and classifications used to identify and differentiate commercial steels, including the AISI/SAE and UNS designation systems.

This chapter traces the history of steelmaking over three millennia, from the discovery of martensite in a mining tool dating from the twelfth century B.C. to the nineteenth century development of the Bessemer and Siemens processes. It also describes the work of early metallographers who discovered many phases and microstructures associated with steel and gave them their now familiar names. The chapter concludes with a brief discussion on the emergence of continuous casting and the subsequent development of strip casting production techniques.

This chapter discusses the compositions, metallurgical phases, microstructure, heat treatment, grades, and structure-property relationships of steels. In addition, it describes the mechanisms involved in deformation, strengthening, and annealing of steels.

This chapter focuses on key requirements for obtaining third-generation advanced high-strength steels (AHSS). The discussion covers the microstructure design for AHSS, novel AHSS processing routes, the development of nanostructured AHSS, and the development of third-generation AHSS by the Integrated Computational Materials Engineering approach.

This chapter focuses on the inspection of steel bars for the detection and evaluation of flaws. The principles involved also apply, for the most part, to the inspection of steel wire. The nondestructive inspection methods discussed include magnetic particle inspection, liquid penetrant inspection, ultrasonic inspection, and electromagnetic inspection. Eddy current and magnetic permeability are also covered.