Carbon and Low-Alloy Steels
This article describes ironmaking and steelmaking practices (melt or liquid processing, including hot metal desulfurization) and discusses the evolution of these processes and their effects on steel properties. The physical chemistry of steelmaking may appear deceptively simple for integrated steel mill operations where ore from the ground is converted into steel. The various refining steps that occur in steelmaking are reviewed. The article also describes solid processing of steel, with emphasis on hot and cold rolling, thermomechanical processing, and annealing of flat steel products.
This article describes microstructures and microstructure-property relationships in steels. It emphasizes the correlation of microstructure and properties as a function of carbon content and processing in low-alloy steels. The article discusses the iron-carbon phase diagram and the phase transformations that change the structure and properties at varying levels of carbon content. Microstructures described include pearlite, bainite, proeutectoid ferrite and cementite, ferrite-pearlite, and martensite. The article depicts some of the primary processing steps that result in ferrite-pearlite microstructures. It shows the range of hardness levels which may be obtained by tempering at various temperatures as a function of the carbon content of the steel. To reduce the number of processing steps associated with producing quenched and tempered microstructures, new alloying approaches have been developed to produce high-strength microstructures directly during cooling after forging.