This chapter introduces the metallographer to the various types of steels and cast irons and explains how they are classified and defined. Classification and designation details are provided for plain carbon steels, alloy steels, and gray, white, ductile, and malleable cast irons.

This chapter introduces the basic ferrous physical metallurgy principles that need to be understood by the metallographer. The discussion focuses on the variations in microstructures that are generated as a result of the phase transformations that occur during both heat treatment (as in steels) and solidification (as in cast irons). The chapter describes how the development of the iron-carbon phase diagram, coupled with the understanding of the kinetics of phase transformations through the use of isothermal transformation diagram, were breakthroughs in the advancement of ferrous physical metallurgy. Several examples of the morphological features of microstructural constituents in steels are also presented.

Microstructures can be altered intentionally or unintentionally. In some cases, metallographers must diagnose what may have happened to the steel or cast iron based on the microstructural details. This chapter discusses how microstructure in steels and cast irons can be intentionally altered during heat treatment, solidification, and deformation (hot and cold working). Some specific examples are then shown to illustrate what can go wrong through unintentional changes in microstructure, for example, the loss of carbon from the surface of the steel by the process known as decarburization or the buildup of brittle carbides on the grain boundaries of an austenitic stainless steel by the process known as sensitization.

This chapter discusses the important role of metallography and the metallographer in predicting and understanding the properties of metals and alloys. Examples are presented of a metallographer working as part of a team in a research laboratory of a large steel company and a metallographer working alone at a small iron foundry. The three basic areas in all metallography laboratories are discussed: the specimen preparation area, the polishing/etching area, and the observation/micrography area. Important safety issues in a metallographic laboratory are also considered.

This chapter describes the various features of the metallurgical microscope. Key concepts are defined such as resolving power, the virtual image, bright- and dark-field illumination, numerical aperture, focal length, image contrast, depth of field, and spherical and chromatic aberration. Metallurgical microscope features such as apochromatic objectives, hyperplane oculars, vertical illuminators, counting reticles, widefield oculars, polarization filters, field diaphragms, interferometers, and tungsten-halogen lamps are explained. The optical system, nosepiece, types of objectives (the lens assembly close to the specimen) and eyepieces, and components of the illumination system are all explained. The last part of this chapter describes special procedures involved in using and calibrating the metallurgical microscope.

Several specialized instruments are available for the metallographer to use as tools to gather key information on the characteristics of the microstructure being analyzed. These include microscopes that use electrons as a source of illumination instead of light and x-ray diffraction equipment. This chapter describes how these instruments can be used to gather important information about a microstructure. The instruments covered include image analyzers, transmission electron microscopes, scanning electron microscopes, electron probe microanalyzers, scanning transmission electron microscopes, x-ray diffractometers, microhardness testers, and hot microhardness testers. A list of other instruments that are usually located in a research laboratory or specialized testing laboratory is also provided.

This chapter instructs the metallographer on the basic skills required to prepare a polished metallographic specimen. It is organized in a chronological sequence starting with the information-gathering process on the material being investigated, then moving on to sectioning, mounting, grinding, and polishing processes, and ending with methods used to properly store metallographic specimens. The discussion covers the preparation procedures, the materials being investigated, and equipment used to perform these procedures.

This chapter discusses the important aspects that a metallographer should understand in order to effectively reveal a microstructure. It begins by exploring etching response and how it can be a tool for revealing various microstructural features. The next part of the chapter discusses methods for revealing microstructure in the as-polished (unetched) specimen, then guidelines for selecting and using etchants when needed. The chapter discusses different types of etchants in terms of their ingredients, etching procedure, and major uses. The etchants discussed include basic etchants (nital and picral and their variations) and tint etchants for carbon and low-alloy steels and cast irons, and basic etchants for stainless steels. Finally, information is provided on different illumination methods (differential interference contrast and dark-field illumination) that can be used to highlight certain features in microstructures.

This chapter presents definitions of terms related to the metallurgy and metallographic study of irons and steels.

This appendix is a compilation of tables helpful to metallographers in characterizing irons and steels. The tables include AISI/SAE designations and specific composition ranges for various steels and irons, listings of companies that sell metallographic equipment and supplies, and compositions and usage guidance for etchants, chemical polishing solutions, and coatings.