Inspection of metals : understanding the basics

496 Pages·2013·4.989 MB·English

by  Campbell, F. C

Inspection of Metals—Understanding the Basics Copyright © 2013 ASM International®
F.C. Campbell, editor All rights reserved
www.asminternational.org
INSPECTION
OF METALS
UNDERSTANDING
THE
BASICS
Edited
by
F.C. Campbell
ASM International®
Materials Park, Ohio 44073-0002
www.asminternational.org
Copyright © 2013
by
ASM International®
All rights reserved
No part of this book may be reproduced, stored in a retrieval system, or transmitted, in any
form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without
the written permission of the copyright owner.
First printing, April 2013
Great care is taken in the compilation and production of this book, but it should be made clear
that NO WARRANTIES, EXPRESS OR IMPLIED, INCLUDING, WITHOUT LIMITATION,
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR
PURPOSE, ARE GIVEN IN CONNECTION WITH THIS PUBLICATION. Although this
information is believed to be accurate by ASM, ASM cannot guarantee that favorable results
will be obtained from the use of this publication alone. This publication is intended for use
by persons having technical skill, at their sole discretion and risk. Since the conditions of
product or material use are outside of ASM’s control, ASM assumes no liability or obligation
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Comments, criticisms, and suggestions are invited, and should be forwarded to ASM
International.
Prepared under the direction of the ASM International Technical Book Committee (2012–
2013), Bradley J. Diak, Chair.
ASM International staff who worked on this project include Scott Henry, Senior Manager,
Content Development and Publishing; Karen Marken, Senior Managing Editor; Victoria
Burt, Content Developer; Steve Lampman, Content Developer; Sue Sellers, Editorial
Assistant; Bonnie Sanders, Manager of Production; Madrid Tramble, Senior Production
Coordinator; and Diane Whitelaw, Production Coordinator.
Library of Congress Control Number: 2012955193
ISBN-13: 978-1-62708-000-2
ISBN-10: 0-62708-000-7
SAN: 204-7586
ASM International®
Materials Park, OH 44073-0002
www.asminternational.org
Printed in the United States of America
Inspection of Metals—Understanding the Basics Copyright © 2013 ASM International®
F.C. Campbell, editor All rights reserved
www.asminternational.org
Contents
Preface � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � �vii
CHAPTER 1
Inspection Methods—Overview and Comparison� � � � � � � � � � � � � 1
Visual Inspection ......................................... 1
Coordinate Measuring Machines............................. 2
Machine Vision .......................................... 3
Hardness Testing ......................................... 5
Tensile Testing........................................... 7
Chemical Analysis........................................ 9
Metallography ........................................... 9
Nondestructive Testing ....................................11
CHAPTER 2
Visual Inspection� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 21
Visual Inspection Procedure ............................... 21
Visual Inspection Tools ................................... 27
CHAPTER 3
Coordinate Measuring Machines� � � � � � � � � � � � � � � � � � � � � � � � � 49
CMM Operating Principles ................................ 50
Types of CMMs......................................... 54
CHAPTER 4
Machine Vision � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 63
Machine Vision Process................................... 66
Machine Vision Applications............................... 82
iv / Contents
CHAPTER 5
Hardness Testing� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 85
Brinell Hardness Testing .................................. 85
Rockwell Hardness Testing ................................ 91
Vickers Hardness Testing (ASTM E384)..................... 100
Scleroscope Hardness Testing ............................. 102
Microhardness Testing................................... 106
CHAPTER 6
Tensile Testing� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 117
Stress-Strain Behavior....................................117
Properties from Test Results ...............................118
Testing Machines....................................... 124
General Procedures ..................................... 129
CHAPTER 7
Chemical Composition � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 139
X-Ray Fluorescence Spectroscopy (XRF).................... 139
Optical Emission Spectroscopy (OES) ...................... 146
Combustion and Inert Gas Fusion Analysis................... 150
Surface Analysis........................................ 152
Scanning Auger Microprobe (SAM) ........................ 152
Related Surface Analysis Techniques ....................... 158
CHAPTER 8
Metallography� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 161
Sectioning ............................................ 162
Mounting of Specimens.................................. 162
Grinding.............................................. 164
Polishing ............................................. 166
Etching............................................... 170
Microscopic Examination ................................ 171
Microphotography ...................................... 180
Grain Size............................................. 181
CHAPTER 9
Liquid Penetrant, Magnetic Particle, and Eddy-Current
Inspection � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 183
Liquid Penetrant Inspection............................... 183
Magnetic Particle Inspection .............................. 197
Eddy Current Inspection ................................. 215
Contents / v
CHAPTER 10
Radiographic Inspection� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 233
Uses of Radiography .................................... 234
Principles of Radiography ................................ 236
Sources of Radiation .................................... 237
X-Ray Tubes .......................................... 239
Attenuation of Electromagnetic Radiation.................... 243
Principles of Shadow Formation ........................... 246
Image Conversion ...................................... 248
Characteristics of X-Ray Film............................. 254
Exposure Factors ....................................... 257
Neutron Radiography.................................... 262
CHAPTER 11
Ultrasonic Inspection � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 267
Ultrasonic Flaw Detectors ................................ 268
Ultrasonic Transducers and Search Units .................... 269
Couplants............................................. 271
Basic Inspection Methods ................................ 272
Pulse Echo Method ..................................... 273
Transmission Methods................................... 280
General Characteristics of Ultrasonic Waves.................. 282
Factors Influencing Ultrasonic Inspection.................... 285
Advantages, Disadvantages, and Applications ................ 291
CHAPTER 12
Inspection of Castings� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 293
Inspection Categories.................................... 293
Casting Defects ........................................ 294
Common Inspection Procedures ........................... 299
Computer-Aided Dimensional Inspection.................... 302
Liquid Penetrant Inspection............................... 308
Magnetic Particle Inspection .............................. 309
Eddy Current Inspection ................................. 310
Radiographic Inspection ................................. 310
Ultrasonic Inspection.................................... 314
Leak Testing........................................... 318
CHAPTER 13
Inspection of Steel Bar and Wire� � � � � � � � � � � � � � � � � � � � � � � � 321
Types of Flaws Encountered .............................. 321
Methods Used for Inspection of Steel Bars................... 324
vi / Contents
CHAPTER 14
Inspection of Tubular Products � � � � � � � � � � � � � � � � � � � � � � � � � 345
Selection of Inspection Method............................ 346
Inspection of Resistance Welded Steel Tubing ................ 347
Seamless Steel Tubular Products........................... 356
Nonferrous Tubing...................................... 362
CHAPTER 15
Inspection of Forgings� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 365
Flaws Originating in the Ingot............................. 365
Flaws Caused by the Forging Operation ..................... 370
Selection of Inspection Method............................ 371
Visual Inspection ....................................... 383
Magnetic Particle Inspection .............................. 383
Liquid Penetrant Inspection............................... 387
Ultrasonic Inspection.................................... 389
Radiographic Inspection ................................. 391
CHAPTER 16
Inspection of Powder Metallurgy Parts � � � � � � � � � � � � � � � � � � � 393
Dimensional Evaluation.................................. 393
Density Measurement ................................... 394
Apparent Hardness and Microhardness...................... 396
Mechanical Testing/Tensile Testing......................... 397
Powder Metallurgy Part Defects ........................... 398
Flaw Detection......................................... 400
CHAPTER 17
Inspection of Weldments and Brazed Assemblies � � � � � � � � � � � 411
Weldments .............................................411
Methods of Nondestructive Inspection ...................... 421
Brazed Assemblies...................................... 437
Methods of Inspection ................................... 442
Index� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 447
Inspection of Metals—Understanding the Basics Copyright © 2013 ASM International®
F.C. Campbell, editor All rights reserved
www.asminternational.org
Preface
Inspection of metals is used to ensure that the quality of the part or prod-
uct meets minimum quality and safety requirements. There are hundreds
of methods used to inspect metals during its fabrication (in-process in-
spection), when the part is completed and ready for delivery (final inspec-
tion), and during its service life (in-service inspection). While the three
stages of inspection are addressed to some extent in this book, the empha-
sis is on final part inspection. Because it is not possible to address all the
different inspection methods used in the industry, only the most widely
used inspection methods are covered.
The first half of this book attempts to answer three questions for each of
these inspection methods:
• How is the inspection method performed?
• When is it used?
• How does it compare with other inspection methods?
The inspection methods covered are:
• Visual inspection
• Coordinate measuring machines
• Machine vision
• Hardness testing
• Tensile testing
• Chemical composition
• Metallography
• Liquid penetrant, magnetic particle, and eddy current inspection
• Radiographic inspection
• Ultrasonic inspection
The second half of the book covers how these inspection methods are
used in different metal fabrication industries:
vii
viii / Preface
• Castings
• Steel bar and wire
• Tubular products
• Forgings
• Powder metallurgy parts
• Weldments and brazed assemblies
The emphasis in the second half of the book shows why certain inspec-
tion methods are selected for different product forms.
Since the purpose of this book is to cover the basics of inspection of
metals, the reader is referred to more advanced texts for detailed informa-
tion. In particular, for nondestructive test methods, Nondestructive Evalu-
ation and Quality Control, Volume 17, ASM Handbook, for mechanical
property test methods, Mechanical Testing and Evaluation, Volume 8,
ASM Handbook, and for metallography, Metallography and Microstruc-
tures, Volume 9, ASM Handbook.
I would like to acknowledge the help and guidance of Karen Marken,
ASM International, and the staff at ASM for their valuable contributions.
F.C. Campbell
Inspection of Metals—Understanding the Basics Copyright © 2013 ASM International®
F.C. Campbell, editor All rights reserved
www.asminternational.org
1
CHAPTER
Inspection Methods—
Overview and
Comparison
INSPECTION is an organized examination or formal evaluation exer-
cise. In engineering, inspection involves the measurements, tests, and
gages applied to certain characteristics in regard to an object or activity.
The results are usually compared to specified requirements and standards
for determining whether the item or activity is in line with these targets.
Some inspection methods are destructive; however, inspections are usu-
ally nondestructive.
Nondestructive examination (NDE), or nondestructive testing (NDT),
are a number of technologies used to analyze materials for either inherent
flaws (such as fractures or cracks), or damage from use. Some common
methods are visual, microscopy, liquid or dye penetrant inspection, mag-
netic particle inspection, eddy current testing, x-ray or radiographic test-
ing, and ultrasonic testing. This chapter provides an overview of the in-
spection methods that will be covered in the remainder of this book.
Visual Inspection
Visual inspection provides a means of detecting and examining a vari-
ety of surface flaws, such as corrosion, contamination, surface finish, and
surface discontinuities on joints (for example, welds, seals, and solder
connections). Visual inspection is also the most widely used method for
detecting and examining surface cracks that are particularly important be-
cause of their relationship to structural failure mechanisms. Even when
other inspection techniques are used to detect surface cracks, visual in-
spection often provides a useful supplement. For example, when the eddy
2 / Inspection of Metals—Understanding the Basics
current examination of process tubing is performed, visual inspection is
often performed to verify and more closely examine the surface distur-
bance. In some instances, acid etching (macroetching) can be used to re-
veal structures that would not be visible to the naked eye, as shown in the
flow lines in Fig. 1.
Given the wide variety of surface flaws that may be detectable by visual
examination, the use of visual inspection can encompass different tech-
niques, depending on the product and the type of surface flaw being mon-
itored. The methods of visual inspection involve a wide variety of
equipment, ranging from examination with the naked eye to the use of
interference microscopes for measuring the depth of scratches in the finish
of finely polished or lapped surfaces.
Coordinate Measuring Machines
Coordinate measuring machines (CMMs) are used to inspect the di-
mensions of a finished product. CMMs consist of the machine itself and
its probes and moving arms for providing measurement input, a computer
for making rapid calculations and comparisons based on the measurement
input, and the computer software that controls the entire system. An ex-
ample of a CMM probe taking measurements on a machined stiffener is
illustrated in Fig. 2. Coordinate measuring machines are primarily charac-
Fig� 1 Flow lines in closed die forged UNS G41400 steering knuckle revealed
by cold deep acid etching with 10% aqueous HNO (0.5×) and en-
3
hanced with inking. Source: Ref 1