Volume 1 Mechanical Engineers’ Handbook Third Edition Materials and Mechanical Design pdf

Volume 1
Mechanical Engineers’ Handbook
Third Edition
Materials and
Mechanical Design
Edited by
Myer Kutz
JOHN WILEY & SONS, INC.
This book is printed on acid-free paper.
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Library of Congress Cataloging-in-Publication Data:
Mechanical engineers’ handbook / edited by Myer Kutz.—3rd ed.
p. cm.
Includes bibliographical references and index.
ISBN-13 978-0-471-44990-4
ISBN-10 0-471-44990-3 (cloth)
1. Mechanical engineering—Handbooks, manuals, etc. I. Kutz, Myer.
TJ151.M395 2005
621—dc22
2005008603
Printed in the United States of America.
10987654321
To Sol, Dorothy, and Jeanne, in Blessed Memory
vii
Contents
Preface ix
Vision Statement xi
Contributors xiii
PART 1 MATERIALS 1
1. Carbon and Alloy Steels 3
Bruce L. Bramfitt
2. Stainless Steels 39
James Kelly
3. Aluminum Alloys 59

J. G. Kaufman
4. Copper and Copper Alloys 117
Konrad J. A. Kundig and John G. Cowie
5. Selection of Titanium Alloys for Design 221
Matthew J. Donachie
6. Nickel and Its Alloys 256
Gaylord D. Smith and Brian A. Baker
7. Magnesium and Its Alloys 278
Robert E. Brown
8. Selection of Superalloys for Design 287
Matthew J. Donachie and Stephen J. Donachie
9. Plastics: Information and Properties of Polymeric Materials 335
Edward N. Peters
10. Composite Materials 380
Carl Zweben
11. Smart Materials 418
James A. Harvey
12. Overview of Ceramic Materials, Design, and Application 433
R. Nathan Katz
13. Sources of Materials Data 450
J. G. Kaufman
14. Quantitative Methods of Materials Selection 466
Mahmoud M. Farag
PART 2 MECHANICAL DESIGN 489
15. Stress Analysis 491
Franklin E. Fisher
viii Contents
16. An Introduction to the Finite-Element Method 557
Tarek I. Zohdi
17. Design for Six Sigma: A Mandate for Competitiveness 581

James E. McMunigal and H. Barry Bebb
18. TRIZ 612
James E. McMunigal, Steven Ungvari, Michael Slocum, and Ruth E. McMunigal
19. Computer-Aided Design 642
Emory W. Zimmers, Jr., and Technical Staff of Enterprise Systems Center
20. Data Exchange Using STEP 725
Martin Hardwick
21. Engineering Applications of Virtual Reality 732
Xiaobo Peng and Ming C. Leu
22. 762
Maury A. Nussbaum and Jaap H. van Diee¨n
23. Electronic Materials and Packaging 782
Warren C. Fackler
24. Design Optimization: An Overview 819
A. Ravi Ravindran and G. V. Reklaitis
25. Design for Manufacturing and Assembly with Plastics 847
James A. Harvey
26. Failure Modes: Performance and Service Requirements for Metals 860
J. A. Collins and S. R. Daniewicz
27. Failure Analysis of Plastics 925
Vishu H. Shah
28. Failure Modes: Performance and Service Requirements for Ceramics 942
Dietrich Munz
29. Mechanical Reliability and Life Prediction for Brittle Materials 962
G. S. White, E. R. Fuller, Jr., and S. W. Freiman
30. Total Quality Management in Mechanical Design 980
B. S. Dhillon
31. Reliability in the Mechanical Design Process 1000
B. S. Dhillon
32. Lubrication of Machine Elements 1024

Bernard J. Hamrock
33. Seal Technology 1161
Bruce M. Steinetz
34. Vibration and Shock 1204
Singiresu S. Rao
35. Noise Measurement and Control 1230
George M. Diehl
36. Nondestructive Inspection 1253
Robert L. Crane and Jeremy S. Knopp
Index 1307
Physical Ergonomics
ix
Preface
The first volume of the third edition of the Mechanical Engineers’ Handbook is comprised
of two major parts. The first part, Materials, which has 14 chapters, covers metals, plastics,
composites, ceramics, and smart materials. The metals covered are carbon, alloy, and stain-
less steels; aluminum and aluminum alloys; copper and copper alloys; titanium alloys; nickel
and its alloys; magnesium and its alloys; and superalloys. Chapters on some of these ma-
terials, such as ceramics, smart materials, and superalloys, are updated versions of chapters
that have appeared in the Handbook of Materials Selection (Wiley, 2002), and they are
entirely new to the Mechanical Engineers’ Handbook. The intent in all of the materials
chapters is to provide readers with expert advice on how particular materials are typically
used and what criteria make them suitable for specific purposes. This part of Volume I
concludes with a chapter on sources of materials data, the intent being to provide readers
with guidance on finding reliable information on materials properties, in addition to those
that can be found in this volume, and a chapter on analytical methods of materials selection,
which is intended to give readers techniques for specifying which materials might be suitable
for a particular application.
The second part of Volume I, Mechanical Design, which has 22 chapters, covers a broad
range of topics, including the fundamentals of stress analysis, the finite-element method,

vibration and shock, and noise measurement and control and then moving into modern
methodologies that engineers use to predict failures, eliminate defects, enhance quality and
reliability of designs, and optimize designs. There are chapters on failure analysis and design
with all classes of materials, including metals, plastics and ceramics, and composites. I should
point out that, to a large extent, the two parts of Volume I go hand in hand. After all, it is
useful to know about the properties, behavior, and failure mechanisms of all classes of
materials when faced with a product design problem. Coverage in the second part of Volume
I extends to lubrication of machine elements and seals technology. Chapters in this part of
Volume I provide practitioners with techniques to solve real, practical everyday problems,
ranging from nondestructive testing to CAD (computer-aided design) to TRIZ (the acronym
in Russian for Theory of Inventive Problem Solving), STEP [the Standard for the Exchange
of Product Model Data is a comprehensive International Organization for Standardization
standard (ISO 10303) that describes how to represent and exchange digital product infor-
mation], and virtual reality. Topics of special interest include physical ergonomics and elec-
tronic packaging.
While many of the chapters in Volume I are updates or entirely new versions of chapters
from the second edition of the Mechanical Engineers’ Handbook and the Handbook of
Materials Selection, a number of chapters—on Six Sigma, TRIZ, and STEP—are new ad-
ditions to this family of handbooks. Contributors of the chapters in Volume I include pro-
fessors, engineers working in industry and government installations, and consultants, mainly
from North America, but also from Egypt, the Netherlands, and Germany.
xi
Vision for the Third Edition
Basic engineering disciplines are not static, no matter how old and well established they are.
The field of mechanical engineering is no exception. Movement within this broadly based
discipline is multidimensional. Even the classic subjects on which the discipline was founded,
such as mechanics of materials and heat transfer, continue to evolve. Mechanical engineers
continue to be heavily involved with disciplines allied to mechanical engineering, such as
industrial and manufacturing engineering, which are also constantly evolving. Advances in
other major disciplines, such as electrical and electronics engineering, have significant impact

on the work of mechanical engineers. New subject areas, such as neural networks, suddenly
become all the rage.
In response to this exciting, dynamic atmosphere, the Mechanical Engineers’Handbook
is expanding dramatically, from one volume to four volumes. The third edition not only is
incorporating updates and revisions to chapters in the second edition, which was published
in 1998, but also is adding 24 chapters on entirely new subjects as well, incorporating updates
and revisions to chapters in the Handbook of Materials Selection, which was published in
2002, as well as to chapters in Instrumentation and Control, edited by Chester Nachtigal
and published in 1990.
The four volumes of the third edition are arranged as follows:
Volume I: Materials and Mechanical Design—36 chapters
Part 1. Materials—14 chapters
Part 2. Mechanical Design—22 chapters
Volume II: Instrumentation, Systems, Controls, and MEMS—21 chapters
Part 1. Instrumentation—8 chapters
Part 2. Systems, Controls, and MEMS—13 chapters
Volume III: Manufacturing and Management—24 chapters
Part 1. Manufacturing—12 chapters
Part 2. Management, Finance, Quality, Law, and Research—12 chapters
Volume IV: Energy and Power—31 chapters
Part 1: Energy—15 chapters
Part 2: Power—16 chapters
The mechanical engineering literature is extensive and has been so for a considerable
period of time. Many textbooks, reference works, and manuals as well as a substantial
number of journals exist. Numerous commercial publishers and professional societies, par-
ticularly in the United States and Europe, distribute these materials. The literature grows
continuously, as applied mechanical engineering research finds new ways of designing, con-
trolling, measuring, making and maintaining things, and monitoring and evaluating technol-
ogies, infrastructures, and systems.
Most professional-level mechanical engineering publications tend to be specialized, di-

rected to the specific needs of particular groups of practitioners. Overall, however, the me-
chanical engineering audience is broad and multidisciplinary. Practitioners work in a variety
of organizations, including institutions of higher learning, design, manufacturing, and con-
xii Vision for the Third Edition
sulting firms as well as federal, state, and local government agencies. A rationale for an
expanded general mechanical engineering handbook is that every practitioner, researcher,
and bureaucrat cannot be an expert on every topic, especially in so broad and multidiscipli-
nary a field, and may need an authoritative professional summary of a subject with which
he or she is not intimately familiar.
Starting with the first edition, which was published in 1986, our intention has always
been that the Mechanical Engineers’ Handbook stand at the intersection of textbooks, re-
search papers, and design manuals. For example, we want the handbook to help young
engineers move from the college classroom to the professional office and laboratory where
they may have to deal with issues and problems in areas they have not studied extensively
in school.
With this expanded third edition, we have produced a practical reference for the me-
chanical engineer who is seeking to answer a question, solve a problem, reduce a cost, or
improve a system or facility. The handbook is not a research monograph. The chapters offer
design techniques, illustrate successful applications, or provide guidelines to improving the
performance, the life expectancy, the effectiveness, or the usefulness of parts, assemblies,
and systems. The purpose is to show readers what options are available in a particular
situation and which option they might choose to solve problems at hand.
The aim of this expanded handbook is to serve as a source of practical advice to readers.
We hope that the handbook will be the first information resource a practicing engineer
consults when faced with a new problem or opportunity—even before turning to other print
sources, even officially sanctioned ones, or to sites on the Internet. (The second edition has
been available online on knovel.com.) In each chapter, the reader should feel that he or she
is in the hands of an experienced consultant who is providing sensible advice that can lead
to beneficial action and results.
Can a single handbook, even spread out over four volumes, cover this broad, interdis-

ciplinary field? We have designed the third edition of the Mechanical Engineers’Handbook
as if it were serving as a core for an Internet-based information source. Many chapters in
the handbook point readers to information sources on the Web dealing with the subjects
addressed. Furthermore, where appropriate, enough analytical techniques and data are pro-
vided to allow the reader to employ a preliminary approach to solving problems.
The contributors have written, to the extent their backgrounds and capabilities make
possible, in a style that reflects practical discussion informed by real-world experience. We
would like readers to feel that they are in the presence of experienced teachers and con-
sultants who know about the multiplicity of technical issues that impinge on any topic within
mechanical engineering. At the same time, the level is such that students and recent graduates
can find the handbook as accessible as experienced engineers.
xiii
Contributors
Brian A. Baker
Special Metals Corporation
Huntington, West Virginia
H. Barry Bebb
ASI
San Diego, California
Bruce L. Bramfitt
Research Laboratories
International Steel Group, Inc.
Bethlehem, Pennsylvania
Robert E. Brown
Magnesium Monthly Review
Prattville, Alabama
J. A. Collins
The Ohio State University
Columbus, Ohio
John G. Cowie

Copper Development Association
New York, New York
Robert L. Crane
Wright Patterson Air Force Base
Dayton, Ohio
S. R. Daniewicz
Mississippi State University
Starkville, Mississippi
B. S. Dhillon
University of Ottawa
Ottawa, Ontario, Canada
Jaap H. van Diee¨n
Vrije Universiteit
Amsterdam, The Netherlands
George M. Diehl
Machinery Acoustics
Phillipsburg, New Jersey
Matthew J. Donachie
Rennselaer at Hartford
Hartford, Connecticut
Stephen J. Donachie
Special Metals Corporation
Huntington, West Virginia
Warren C. Fackler
Telesis Systems
Cedar Rapids, Iowa
Mahmoud M. Farag
The American University in Cairo
Cairo, Egypt
Franklin E. Fisher

Loyola Marymount University
Los Angeles, Calaifornia
and
Raytheon Company
El Segundo, California
S. W. Freiman
National Institute of Standards and
Technology
Gaithersburg, Maryland
E. R. Fuller, Jr.
National Institute of Standards and
Technology
Gaithersburg, Maryland
Bernard J. Hamrock
The Ohio State University
Columbus, Ohio
xiv Contributors
Martin Hardwick
STEP Tools, Inc.
Troy, New York
James A. Harvey
Under the Bridge Consulting, Inc.
Corvallis, Oregon
R. Nathan Katz
Worcester Polytechnic Institute
Worcester, Massachusetts
J. G. Kaufman
Kaufman Associates
Columbus, Ohio
James Kelly

Rochester, Michigan
Jeremy S. Knopp
Wright Patterson Air Force Base
Dayton, Ohio
Konrad J. A. Kundig
Metallurgical Consultant
Tucson, Arizona
Ming C. Leu
University of Missouri-Rolla
Rolla, Missouri
James E. McMunigal
MCM Associates
Long Beach, California
Ruth E. McMunigal
MCM Associates
Long Beach, California
Dietrich Munz
University of Karlsruhe
Karlsruhe, Germany
Maury A. Nussbaum
Virginia Polytechnic Institute and State
University
Blacksburg, Virginia
Xiaobo Peng
University of Missouri-Rolla
Rolla, Missouri
Edward N. Peters
General Electric Company
Selkirk, New York
Singiresu S. Rao

University of Miami
Coral Gables, Florida
A. Ravi Ravindran
Pennsylvania State University
University Park, Pennsylvania
G. V. Reklaitis
Purdue University
West Lafayette, Indiana
Michael Slocum
Breakthrough Management Group
Longmont, Colorado
Vishu H. Shah
Consultek
Brea, California
Gaylord D. Smith
Special Metals Corporation
Huntington, West Virginia
Bruce M. Steinetz
NASA Glenn Research Center at Lewis
Field
Cleveland, Ohio
Steven Ungvari
Strategic Product Innovations, Inc.
Columbus, Ohio
G. S. White
National Institute of Standards and
Technology
Gaithersburg, Maryland
Emory W. Zimmers, Jr
Lehigh University

Bethlehem, Pennsylvania
Tarek I. Zohdi
University of California
Berkeley, California
Carl Zweben
Devon, Pennsylvania
Mechanical Engineers’ Handbook
PART 1
MATERIALS
3
CHAPTER 1
CARBON AND ALLOY STEELS
Bruce L. Bramfitt
International Steel Group, Inc.
Research Laboratories
Bethlehem, Pennsylvania
1 INTRODUCTION 3
2 STEEL MANUFACTURE 4
3 DEVELOPMENT OF STEEL
PROPERTIES 5
4 ROLE OF ALLOYING
ELEMENTS IN STEEL 18
5 HEAT TREATMENT OF STEEL 25
6 CLASSIFICATION AND
SPECIFICATIONS OF STEELS 26
6.1 Carbon Steels 27
6.2 Alloy Steels 29
7 SUMMARY 37
BIBLIOGRAPHY 37
1 INTRODUCTION

Steel is the most common and widely used metallic material in today’s society. It can be
cast or wrought into numerous forms and can be produced with tensile strengths exceeding
5 GPa. A prime example of the versatility of steel is in the automobile where it is the
material of choice and accounts for over 60% of the weight of the vehicle. Steel is highly
formable as seen in the contours of the automobile outerbody. Steel is strong and is used in
the body frame, motor brackets, driveshaft, and door impact beams of the vehicle. Steel is
corrosion resistant when coated with the various zinc-based coatings available today. Steel
is dent resistant when compared with other materials and provides exceptional energy ab-
sorption in a vehicle collision. Steel is recycled and easily separated from other materials
by a magnet. Steel is inexpensive compared with other competing materials such as alumi-
num and various polymeric materials.
In the past, steel has been described as an alloy of iron and carbon. Today, this descrip-
tion is no longer applicable since in some very important steels, e.g., interstitial-free (IF)
steels and type 409 ferritic stainless steels, carbon is considered an impurity and is present
in quantities of only a few parts per million. By definition, steel must be at least 50% iron
and must contain one or more alloying elements. These elements generally include carbon,
manganese, silicon, nickel, chromium, molybdenum, vanadium, titanium, niobium, and alu-
minum. Each chemical element has a specific role to play in the steelmaking process or in
achieving particular properties or characteristics, e.g., strength, hardness, corrosion resistance,
magnetic permeability, and machinability.
Reprinted from Handbook of Materials Selection, Wiley, New York, 2002, by permission of the publisher.
Mechanical Engineers’ Handbook: Materials and Mechanical Design, Volume 1, Third Edition.
Edited by Myer Kutz
Copyright
 2006 by John Wiley & Sons, Inc.
4 Carbon and Alloy Steels
2 STEEL MANUFACTURE
In most of the world, steel is manufactured by integrated steel facilities that produce steel
from basic raw materials, i.e., iron ore, coke, and limestone. However, the fastest growing
segment of the steel industry is the ‘‘minimill’’ that melts steel scrap as the raw material.

Both types of facilities produce a wide variety of steel forms, including sheet, plate, struc-
tural, railroad rail, and bar products.
Ironmaking. When making steel from iron ore, a blast furnace chemically reduces the ore
(iron oxide) with carbon in the form of coke. Coke is a spongelike carbon mass that is
produced from coal by heating the coal to expel the organic matter and gasses. Limestone
(calcium carbonate) is added as a flux for easier melting and slag formation. The slag, which
floats atop the molten iron, absorbs many of the unwanted impurities. The blast furnace is
essentially a tall hollow cylindrical structure with a steel outer shell lined on the inside with
special refractory and graphite brick. The crushed or pelletized ore, coke, and limestone are
added as layers through an opening at the top of the furnace, and chemical reduction takes
place with the aid of a blast of preheated air entering near the bottom of the furnace (an
area called the bosh). The air is blown into the furnace through a number of water-cooled
copper nozzles called tuyeres. The reduced liquid iron fills the bottom of the furnace and is
tapped from the furnace at specified intervals of time. The product of the furnace is called
pig iron because in the early days the molten iron was drawn from the furnace and cast
directly into branched mold configurations on the cast house floor. The central branch of
iron leading from the furnace was called the ‘‘sow’’ and the side branches were called ‘‘pigs.’’
Today the vast majority of pig iron is poured directly from the furnace into a refractory-
lined vessel (submarine car) and transported in liquid form to a basic oxygen furnace (BOF)
for refinement into steel.
Steelmaking. In the BOF, liquid pig iron comprises the main charge. Steel scrap is added to
dilute the carbon and other impurities in the pig iron. Oxygen gas is blown into the vessel
by means of a top lance submerged below the liquid surface. The oxygen interacts with the
molten pig iron to oxidize undesirable elements. These elements include excess carbon (be-
cause of the coke used in the blast furnace, pig iron contains over 2% carbon), manganese,
and silicon from the ore and limestone and other impurities like sulfur and phosphorus.
While in the BOF, the liquid metal is chemically analyzed to determine the level of carbon
and impurity removal. When ready, the BOF is tilted and the liquid steel is poured into a
refractory-lined ladle. While in the ladle, certain alloying elements can be added to the steel
to produce the desired chemical composition. This process takes place in a ladle treatment

station or ladle furnace where the steel is maintained at a particular temperature by external
heat from electrodes in the lid placed on the ladle. After the desired chemical composition
is achieved, the ladle can be placed in a vacuum chamber to remove undesirable gases such
as hydrogen and oxygen. This process is called degassing and is used for higher quality steel
products such as railroad rail, sheet, plate, bar, and forged products. Stainless steel grades
are usually produced in an induction or electric arc furnace, sometimes under vacuum. To
refine stainless steel, the argon–oxygen decarburization (AOD) process is used. In the AOD,
an argon–oxygen gas mixture is injected through the molten steel to remove carbon without
a substantial loss of chromium (the main element in stainless steel).
Continuous Casting. Today, most steel is cast into solid form in acontinuous-casting (also
called strand casting) machine. Here, the liquid begins solidification in a water-cooled copper
mold while the steel billet, slab, or bloom is withdrawn from the bottom of the mold. The
3 Development of Steel Properties 5
partially solidified shape is continuously withdrawn from the machine and cut to length for
further processing. The continuous-casting process can proceed for days or weeks as ladle
after ladle of molten steel feeds the casting machine. Some steels are not continuously cast
but are poured into individual cast-iron molds to form an ingot that is later reduced in size
by forging or a rolling process to some other shape. Since the continuous-casting process
offers substantial economic and quality advantages over ingot casting, most steel in the world
is produced by continuous casting.
Rolling/Forging. Once cast into billet, slab, or bloom form, the steel is hot rolled through
a series of rolling mills or squeezed / hammered by forging to produce the final shape. To
form hot-rolled sheet, a 50–300-mm-thick slab is reduced to final thickness, e.g., 2 mm, in
one or more roughing stands followed by a series of six or seven finishing stands. To obtain
thinner steel sheet, e.g., 0.5 mm, the hot-rolled sheet must be pickled in acid to remove the
iron oxide scale and further cold rolled in a series of rolling stands called a tandem mill.
Because the cold-rolling process produces a hard sheet with little ductility, it is annealed
either by batch annealing or continuous annealing. New casting technology is emerging
where thin sheet (under 1 mm) can be directly cast from the liquid through water-cooled,
rotating rolls that act as a mold as in continuous casting. This new process eliminates many

of the steps in conventional hot-rolled sheet processing. Plate steels are produced by hot
rolling a slab in a reversing roughing mill and a reversing finishing mill. Steel for railway
rails is hot rolled from a bloom in a blooming mill, a roughing mill, and one or more finishing
mills. Steel bars are produced from a heated billet that is hot rolled in a series of roughing
and finishing mills. Forged steels are produced from an ingot that is heated to forging tem-
perature and squeezed or hammered in a hydraulic press or drop forge. The processing
sequence in all these deformation processes can vary depending on the design, layout, and
age of the steel plant.
3 DEVELOPMENT OF STEEL PROPERTIES
In order to produce a steel product with the desired properties, basic metallurgical principles
are used to control three things:
Composition
Processing
Microstructure
Properties
6 Carbon and Alloy Steels
This means that the steel composition and processing route must be closely controlled in
order to produce the proper microstructure. The final microstructure is of utmost importance
in determining the properties of the steel product. This section will explore how various
microstructures are developed and the unique characteristics of each microstructural com-
ponent in steel. The next section will discuss how alloy composition also plays a major role.
Iron–Carbon Equilibrium Diagram. Since most steels contain carbon, the basic principles
of microstructural development can be explained by the iron–carbon equilibrium diagram.
This diagram, shown in Fig. 1, is essentially a map of the phases that exist in iron at various
carbon contents and temperatures under equilibrium conditions. Iron is an interesting chem-
ical element in that it undergoes three phase changes when heated from room temperature
to liquid. For example, from room temperature to 912
ЊC, pure iron exists as ferrite (also
called alpha iron), from 912 to 1394
ЊC, it exists as austenite (gamma iron), from 1394 to

1538
ЊC it exists as ferrite again (delta iron), and above 1538ЊC it is liquid. In other words,
upon heating, iron undergoes allotropic phase transformations from ferrite to austenite at
912
ЊC, austenite to ferrite at 1394ЊC, and ferrite to liquid at 1538ЊC. Each transformation
undergoes a change in crystal structure or arrangement of the iron atoms in the crystal lattice.
It must be remembered that all chemical elements in their solid form have specific arrange-
ments of atoms that are essentially the basic building blocks in producing the element in the
form that we physically observe. These atomic arrangements form a latticework containing
billions of atoms all aligned in a systematic way. Some of these lattices have a cubic ar-
rangement, with an atom at each corner of the cube and another atom at the cube center.
This arrangement is called body-centered-cubic (bcc). Others have an atom at each corner
of the cube and atoms at the center of each face of the cube. This is called face-centered-
cubic (fcc). Other arrangements are hexagonal, some are tetragonal, etc. As an example, pure
iron as ferrite has a bcc arrangement. Austenite has a fcc arrangement. Upon heating, bcc
ferrite will transform to fcc austenite at 912
ЊC. These arrangements or crystal structures
impart different properties to steel. For example, a bcc ferritic stainless steel will have prop-
erties much different from a fcc austenitic stainless steel, as described later in this chapter.
Since pure iron is very soft and of low strength, it is of little interest commercially.
Therefore, carbon and other alloying elements are added to enhance properties. Adding
carbon to pure iron has a profound effect on ferrite and austenite, discussed above. One way
to understand the effect of carbon is to examine the iron–carbon diagram (Fig. 1). This is a
binary (two-element) diagram of temperature and composition (carbon content) constructed
under near-equilibrium conditions. In this diagram, as carbon is added to iron, the ferrite
and austenite phase fields expand and contract depending upon the carbon level and tem-
perature. Also, there are fields consisting of two phases, e.g., ferrite plus austenite.
Since carbon has a small atomic diameter when compared with iron, it is called an
interstitial element because it can fill the interstices between the iron atoms in the cubic
lattice. Nitrogen is another interstitial element. On the other hand, elements such as man-

ganese, silicon, nickel, chromium, and molybdenum have atomic diameters similar to iron
and are called substitutional alloying elements. These substitutional elements can thus replace
iron atoms at the cube corners, faces, or center positions. There are many binary phase
diagrams (Fe–Mn, Fe– Cr, Fe–Mo, etc.) and tertiary-phase diagrams (Fe–C–Mn, Fe–C–Cr,
etc.) showing the effect of interstitial and substitutional elements on the phase fields of ferrite
and austenite. These diagrams are found in the handbooks listed at the end of the chapter.
Being an interstitial or a substitutional element is important in the development of steel
properties. Interstitial elements such as carbon can move easily about the crystal lattice
whereas a substitutional element such as manganese is much more difficult to move. The
movement of elements in a crystal lattice is called diffusion. Diffusion is a controlling factor
3 Development of Steel Properties 7
Figure 1 Iron–carbon binary-phase diagram. (Source: Steels: Heat Treatment and Processing Princi-
ples, ASM International, Materials Park, OH 44073-0002, 1990, p. 2.)
in the development of microstructure. Another factor is solubility, which is a measure of
how much of a particular element can be accommodated by the crystal lattice before it is
rejected. In metals when two or more elements are soluble in the crystal lattice, a solid
solution is created (somewhat analogous to a liquid solution of sugar in hot coffee). For
example, when added to iron, carbon has very limited solubility in ferrite but is about 100
times more soluble in austenite, as seen in the iron–carbon diagram in Fig. 2 (a limited
version of the diagram in Fig. 1). The maximum solubility of carbon in ferrite is about
8
Figure 2 Expanded portion of the iron–carbon binary-phase diagram in Fig. 1. (Source: Steels: Heat Treatment and Processing Principles,
ASM International, Materials Park, OH 44073-0002, 1990, p. 18.)
3 Development of Steel Properties 9
0.022% C at 727ЊC while the maximum solubility of carbon in austenite is 100 times more,
2.11% C at 1148
ЊC. At room temperature the solubility of carbon in iron is only about
0.005%. Any amount of carbon in excess of the solubility limit is rejected from solid solution
and is usually combined with iron to form an iron carbide compound called cementite. This
hard and brittle compound has the chemical formula Fe

3
C and a carbon content of 6.7%.
This is illustrated in the following two examples. The first example is a microstructure of a
very low carbon steel (0.002% C), shown in Fig. 3a. The microstructure consists of only
ferrite grains (crystals) and grain boundaries. The second example is a microstructure of a
low-carbon steel containing 0.02% C, in Fig. 3b. In this microstructure, cementite can be
seen as particles at the ferrite grain boundaries. The excess carbon rejected from the solid
solution of ferrite formed this cementite. As the carbon content in steel is increased, another
form of cementite appears as a constituent called pearlite, which can be found in most carbon
steels. Examples of pearlite in low-carbon (0.08% C) and medium-carbon (0.20% C) steels
are seen in Figs. 4a and 4b. Pearlite has a lamellar (parallel-plate) microstructure, as shown
at higher magnification in Fig. 5, and consists of layers of ferrite and cementite. Thus, in
these examples, in increasing the carbon level from 0.002 to 0.02 to 0.08 to 0.20%, the
excess carbon is manifested as a carbide phase in two different forms, cementite particles
and cementite in pearlite. Both forms increase the hardness and strength of iron. However,
there is a trade-off; cementite also decreases ductility and toughness.
Pearlite forms on cooling austenite through a eutectoid reaction as seen below:
Austenite
↔ Fe C ϩ ferrite
3
A eutectoid reaction occurs when a solid phase or constituent reacts to form two different
solid constituents on cooling (a eutectic reaction occurs when a liquid phase reacts to form
two solid phases). The eutectoid reaction is reversible on heating. In steel, the eutectoid
reaction (under equilibrium conditions) takes place at 727
ЊC and can be seen on the iron–
carbon diagram (Fig. 1) as the ‘‘V’’ at the bottom left side of the diagram. A fully pearlitic
microstructure forms at 0.77% C at the eutectoid temperature of 727
ЊC (the horizontal line
on the left side of the iron–carbon diagram). Steels with less than 0.77% C are called
hypoeutectoid steels and consist of mixtures of ferrite and pearlite with the amount of pearlite

increasing as the carbon content increases. The ferrite phase is called a proeutectoid phase
because it forms prior to the eutectoid transformation that occurs at 727
ЊC. A typical example
of proeutectoid ferrite is shown in Fig. 6. In this photomicrograph, the ferrite (the white-
appearing constituent) formed on the prior austenite grain boundaries of hypoeutectoid steel
with 0.60% C. The remaining constituent (dark appearing) is pearlite. Steels between
0.77% C and about 2% C are called hypereutectoid steels and consist of pearlite with proeu-
tectoid cementite. Cementite forms a continuous carbide network at the boundaries of the
prior austenite grains. Because there is a carbide network, hypereutectoid steels are charac-
terized as steels with little or no ductility and very poor toughness. This means that in the
commercial world the vast majority of carbon steels are hypoeutectoid steels.
Thus, according to the iron–carbon diagram, steels that are processed under equilibrium
or near-equilibrium conditions can form (a) pure ferrite at very low carbon levels generally
under 0.005% C, (b) ferrite plus cementite particles at slightly higher carbon levels between
0.005% C and 0.022% C, (c) ferrite plus pearlite mixtures between 0.022% C and 0.77% C,
(d) 100% pearlite at 0.77% C, and (e) mixtures of pearlite plus cementite networks between
0.77% C and 2% C. The higher the percentage of cementite, the higher the hardness and
strength and lower the ductility and toughness of the steel.
Departure from Equilibrium (Real World). Industrial processes do not occur at equilibrium,
and only those processes that take place at extremely slow heating and cooling rates can be
considered near equilibrium, and these processes are quite rare. Therefore, under real con-
10 Carbon and Alloy Steels
(a)
(b)
Figure 3 (a) Photomicrograph of a very low carbon steel showing ferrite grains and (b) photo-
micrograph of a low-carbon steel showing ferrite grains with some cementite on the ferrite grain bound-
aries. (a) 500X and (b) 200X. Marshalls etch.
3 Development of Steel Properties 11
(a)
(b)

Figure 4 (a) Photomicrograph of an SAE / AISI 1008 steel showing ferrite grains and pearlite (dark)
and (b) photomicrograph of an SAE / AISI 1020 steel showing ferrite grains with an increased amount
of pearlite. (a) and (b) both 200X. 4% picral
ϩ 2% nital etch.
12 Carbon and Alloy Steels
Figure 5 Scanning electron micrograph of pearlite showing the platelike morphology of the cementite.
5000X. 4% picral etch.
ditions, the iron–carbon diagram can only be used as a rough guideline since the equilibrium
transformation temperatures shift to lower temperatures on cooling and to higher tempera-
tures on heating. If steels are cooled at very fast rates, e.g., quenching in water, the iron–
carbon diagram can no longer be used since there is a major departure from equilibrium. In
fact, during the quenching of steel, new constituents form that are not associated with the
iron–carbon diagram. Therefore, at fast cooling rates the concept of time–temperature trans-
formation (TTT) diagrams must be considered. These diagrams are constructed under iso-
thermal (constant) temperature (called IT diagrams) or continuous-cooling conditions (called
CT diagrams). It is important to know how these diagrams are constructed so that we can
understand the development of nonequilibrium microstructures, which are so important in
carbon and alloy steels.
Isothermal Transformation Diagram. This diagram is formed by quenching very thin spec-
imens of steel in salt baths set at various temperatures. For example, thin specimens of
0.79% C steel can be quenched into seven different liquid salt baths set at 650, 600, 550,
500, 450, 400, and 200
ЊC. The specimens are held for various times at each temperature
then pulled from the bath and quickly quenched in cold water. The result will be a diagram
called an isothermal transformation (IT) diagram, as shown in Fig. 7. The diagram is essen-
tially a map showing where various constituents form. For example, at 650
ЊC, austenite (A)
begins to transform to pearlite if held in the bath for 10 s. The curve drawn through this
point is the pearlite transformation start temperature and is labeled beginning of transfor-
mation in Fig. 7. At about 100 s the pearlite transformation is finished. The second curve

represents the pearlite transformation finish temperature and is labeled the end of transfor-
3 Development of Steel Properties 13
Figure 6 Photomicrograph of a medium-carbon hypoeutectoid steel showing a pearlite matrix and
proeutectoid ferrite nucleating on the original (prior) austenite grain boundaries. 200X. 4% picral
ϩ 2%
nital etch.
mation in Fig. 7. In this steel, pearlite forms at all temperatures along the start of the
transformation curve from 727
ЊC (the equilibrium temperature of the iron –carbon diagram)
to 540
ЊC, the ‘‘nose’’ of the curve. At the higher transformation temperatures, the pearlite
interlamellar spacing (the spacing between cementite plates) is very coarse and decreases in
spacing as the temperature is decreased, i.e., nose of the IT diagram is approached. This is
an important concept since a steel with a coarse pearlite interlamellar spacing is softer and
of lower strength than a steel with a fine pearlite interlamellar spacing. Commercially, rail
steels are produced with a pearlitic microstructure, and it has been found that the finer the
interlamellar spacing, the harder the rail and the better the wear resistance. This means that
rails will last longer in track if produced with the finest spacing allowable. Most rail pro-
ducers employ an accelerated cooling process called head hardening to obtain the necessary
conditions to achieve the finest pearlite spacing in the rail head (the point of wheel contact).
If the specimens are quenched to 450
ЊC and held for various times, pearlite does not
form. In fact, pearlite does not isothermally transform at transformation temperatures (in this
case, salt pot temperatures) below the nose of the diagram in Fig. 7. The new constituent is
called bainite, which consists of ferrite laths with small cementite particles (also called
precipitates). An example of the microstructure of bainite is shown in Fig. 8. This form of
bainite is called upper bainite because it is formed in the upper portion below the nose of
the IT diagram (between about 540 and 400
ЊC). Lower bainite, a finer ferrite–carbide mi-
crostructure, forms at lower temperatures (between 400 and about 250

ЊC). Bainite is an
important constituent in tough, high-strength, low-alloy steel.
If specimens are quenched into a salt bath at 200
ЊC, a new constituent called martensite
will form. The start of the martensitic transformation is shown in Fig. 7 as M
s
(at 220ЊC).
14 Carbon and Alloy Steels
Figure 7 Isothermal transformation diagram of SAE / AISI 1080 steel showing the beginning and end
of transformation curves with temperature and time. (Source: ASM Handbook, Vol. 1, Properties and
Selection: Irons, Steels, and High-Performance Alloys, ASM International, Materials Park, OH 44073-
0002, 1990, p. 128.)
Martensite is a form of ferrite that is supersaturated with carbon. In other words, because of
the very fast cooling rate, the carbon atoms do not have time to diffuse from their interstitial
positions in the bcc lattice to form cementite particles. An example of martensite is shown
in Fig. 9. Steel products produced with an as-quenched martensitic microstructure are very
hard and brittle, e.g., a razor blade. Most martensitic products are tempered by heating to
temperatures between about 350 and 650
ЊC. The tempering process allows some of the
carbon to diffuse and form as a carbide phase from the supersaturated iron lattice. This
softens the steel and provides some ductility. The degree of softening is determined by the
tempering temperature and the time at the tempering temperature. The higher the temperature
and the longer the time, the softer the steel. Most steels with martensite are used in the
quenched and tempered condition.
Continuous-Cooling Transformation Diagram. The other more useful form of a time–
temperature transformation diagram is the continuous-cooling transformation (CT) diagram.
This differs from the IT diagram in that it is constructed by cooling small specimens at
various cooling rates and measuring the temperatures at which transformations start and finish
using a device called a dilatometer (a machine that measures dilation). Each phase transfor-