Physical Metallurgy of Steel

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Steel
Class Notes and lecture material
For
MSE 651.01--
Physical Metallurgy of Steel
Notes compiled by: Glyn Meyrick, Professor Emeritus
Notes revised by: Robert H. Wagoner, Distinguished
Professor of Engineering
Web installation by: Wei Gan, Graduate Research Associate
Last revision date: 1/8/01


STEEL
Foreword
This document is intended to augment formal lectures on the general topic of the physical
metallurgy of steels, presented within the MSE Department during the Fall Quarter, 1998. It is
based on a variety of texts and published articles and also on personal experience. Specific
references to sources are made within the document. However, the material is often in the form of
knowledge that has been accumulated by the work of many people and is "well-known" by experts
in the field. A detailed acknowledgment of the work of each contributor to the field is not attempted
because that would be an awesome task. This document is not intended for publication and is
restricted for use in MSE 651.01.
Texts: Steels; Microstructures and Properties by R.W.K. Honeycombe (Edward Arnold)
Principles of the Heat Treatment of Steel by G. Krauss (ASM)
The Physical Metallurgy of Steel by W.C. Leslie (McGraw Hill)
The ASM Metal Handbooks.
Handbook of Stainless Steels, Peckner and Bernstein (eds.) McGraw Hill 1977
Tool Steels Roberts and Cary, Edition 4, ASM, 1980
Ferrous Physical Metallurgy A. K. Sinha, Butterworths 1989.
Introduction
Steel is a family of materials that is derived from ores that are rich in iron, abundant in the
Earth’s crust and which are easily reduced by hot carbon to yield iron. Steels are very versatile; they
can be formed into desired shapes by plastic deformation produced by processes such as rolling
and forging; they can be treated to give them a wide range of mechanical properties which enable
them to be used for an enormous number of applications. Indeed, steel is ubiquitous in applications
that directly affect the quality of our lives. Steel and cement constitute about 90% of the structural
materials that are manufactured
( Westwood, Met and Mat Trans, Vol. 27 A, June 1996, 1413).
What, then, is steel?
A precise and concise definition of steel is not an easy thing to present because of the very
large variety of alloys that bear the name. All of them, however, contain iron. We might reasonably
begin by describing a steel as an alloy which contains iron as the major component. This is only a
beginning because there are alloys in which iron is the major constituent, that are not called steels;
for example, cast irons and some superalloys. The major difference between a cast iron and a steel
is that their carbon contents lie in two different ranges. These ranges are determined by the
maximum amount of carbon that can be dissolved into solid iron. This is approximately 2% by
weight (in FCC iron at 1146 °C). Steels are alloys that contain less than 2% carbon. Cast irons
contain more than 2 % carbon. Many steels contain specified minimum amounts of carbon. This
does not mean that all steels must contain substantial quantities of carbon; in some steels the
carbon content is deliberately made very small and, also, the amount actually in solution is reduced
further by the addition of alloying elements that have a strong tendency to combine with the carbon
to form carbides.
Steels can be divided into two main groups; plain carbon steels and alloy steels. The latter
can then be subdivided into many groups according to chemistry ( e.g. standard low alloy steels),
applications (e.g. tool steels ) or particular properties (e.g. stainless steels) etc. Let us begin with
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plain carbon steels; this group is the simplest to understand and it comprises steels that are used in
the greatest tonnage.

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