welding theory & application

741 Pages·2006·19.62 MB·English

WELDING THEORY & APPLICATION

WELDING THEORY & APPLICATION

Table of Contents
CHAPTER 1 - INTRODUCTION
Section I - General
Section II - Theory
CHAPTER 2 - SAFETY PRECAUTIONS IN WELDING OPERATIONS
Section I - General Safety Precautions
Section II - Safety Precautions in Oxyfuel Welding
Section III - Safety in Arc Welding and Cutting
Section IV - Safety Precautions for Gas Shielded Arc Welding
Section V - Safety Precautions for Welding and Cutting Containers That Have Held
Combustibles
Section VI - Safety Precautions for Welding and Cutting Polyurethane Foam Filled
Assemblies
CHAPTER 3 - PRINT READING AND WELDING SYMBOLS
Section I - Print Reading
Section II - Weld and Welding Symbols
CHAPTER 4 - JOINT DESIGN AND PREPARATION OF METALS
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WELDING THEORY & APPLICATION
CHAPTER 5 - WELDING AND CUTTING EQUIPMENT
Section I - Oxyacetylene Welding Equipment
Section II - Oxyacetylene Cutting Equipment
Section III - Arc Welding Equipment and Accessories
Section IV - Resistance Welding Equipment
Section V - Thermit Welding Equipment
Section VI - Forge Welding Tools and Equipment
CHAPTER 6 - WELDING TECHNIQUES
Section I - Description
Section II - Nomenclature of the Weld
Section III - Types of Welds and Welded Joints
Section IV - Welding Positions
Section V - Expansion and Contraction in Welding Operations
Section VI - Welding Problems and Solutions
CHAPTER 7 - METALS IDENTIFICATION
Section I - Characteristics
Section II - Standard Metal Designations
Section III - General Description and Weldability of Ferrous Metals
Section IV - General Description and Weldability of Nonferrous Metals
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WELDING THEORY & APPLICATION
CHAPTER 8 - ELECTRODES AND FILLER METALS
Section I - Types of Electrodes
Section II - Other Filler Metals
CHAPTER 9 - MAINTENANCE WELDING OPERATIONS FOR MILITARY
EQUIPMENT
CHAPTER 10 - ARC WELDING AND CUTTING PROCESSES
Section I - General
Section II - Arc Processes
Section III - Related Processes
CHAPTER 11 - OXYGEN FUEL GAS WELDING PROCEDURES
Section I - Welding Processes and Techniques
Section II - Welding and Brazing Ferrous Metals
Section III - Related Processes
Section IV - Welding, Brazing, and Soldering Nonferrous Metals
CHAPTER 12 - SPECIAL APPLICATIONS
Section I - Underwater Cutting and Welding with the Electric Arc
Section II - Underwater Cutting with Oxyfuel
Section III - Metallizing
Section IV - Flame Cutting Steel and Cast Iron
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WELDING THEORY & APPLICATION
Section V - Flame Treating Metal
Section VI - Cutting and Hard Surfacing with the Electric Arc
Section VII - Armor Plate Welding and Cutting
Section VIII - Pipe Welding
Section IX - Welding Cast Iron, Cast Steel, Carbon Steel, and Forgings
Section X - Forge Welding
Section XI - Heat Treatment of Steel
Section XII - Other Welding Processes
CHAPTER 13 - DESTRUCTIVE AND NONDESTRUCTIVE TESTING
Section I - Performance Testing
Section II - Visual Inspection and Corrections
Section III - Physical Testing
APPENDIX A - REFERENCES
APPENDIX B - PROCEDURE GUIDES FOR WELDING
APPENDIX C - TROUBLESHOOTING PROCEDURES
APPENDIX D - MATERIALS USED FOR BRAZING, WELDING, SOLDERING,
CUTTING, AND METALLIZING
APPENDIX E - MISCELLANEOUS DATA
GLOSSARY
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WELDING THEORY & APPLICATION
LIST OF ILLUSTRATIONS
LIST OF TABLES
WARNINGS
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Chptr 1 Introduction
CHAPTER 1
INTRODUCTION
Section I. GENERAL
1-1. SCOPE
This training circular is published for use by personnel concerned with welding and other metal joining
operations in the manufacture and maintenance of materiel.
1-2. DESCRIPTION
a. This circular contains information as outlined below:
(1) Introduction
(2) Safety precautions in welding operations
(3) Print reading and welding symbols
(4) Joint design and preparation of metals
(5) Welding and cutting equipment
(6) Welding techniques
(7) Metals identification
(8) Electrodes and filler metals
(9) Maintenance welding operations for military equipment
(10) Arc welding and cutting processes
(11) Oxygen fuel gas welding processes
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Chptr 1 Introduction
(12) Special applications
(13) Destructive and nondestructive testing
b. Appendix A contains a list of current references, including supply and technical manuals and other
available publications relating to welding and cutting operations.
c. Appendix B contains procedure guides for welding.
d. Appendix C contains a troubleshooting chart.
e. Appendix D contains tables listing materials used for brazing. welding, soldering, arc cutting, and
metallizing.
f. Appendix E contains miscellaneous data as to temperature ranges, melting points, and other
information not contained in the narrative portion of this manual.
Section II. THEORY
1-3. GENERAL
Welding is any metal joining process wherein coalescence is produced by heating the metal to suitable
temperatures, with or without the application of pressure and with or without the use of filler metals.
Basic welding processes are described and illustrated in this manual. Brazing and soldering, procedures
similar to welding, are also covered.
1-4. METALS
a. Metals are divided into two classes, ferrous and nonferrous. Ferrous metals are those in the iron class
and are magnetic in nature. These metals consist of iron, steel, and alloys related to them. Nonferrous
metals are those that contain either no ferrous metals or very small amounts. These are generally divided
into the aluminum, copper, magnesium, lead, and similar groups.
b. Information contained in this circular covers theory and application of welding for all types of metals
including recently developed alloys.
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Chptr 2 Safety Precautions in Welding Operations
CHAPTER 2
SAFETY PRECAUTIONS IN WELDING OPERATIONS
Section I. GENERAL SAFETY PRECAUTIONS
2-1. GENERAL
a. To prevent injury to personnel, extreme caution should be exercised when using any types of welding
equipment. Injury can result from fire, explosions, electric shock, or harmful agents. Both the general
and specific safety precautions listed below must be strictly observed by workers who weld or cut
metals.
b. Do not permit unauthorized persons to use welding or cutting equipment.
c. Do not weld in a building with wooden floors, unless the floors are protected from hot metal by means
of fire resistant fabric, sand, or other fireproof material. Be sure that hot sparks or hot metal will not fall
on the operator or on any welding equipment components.
d. Remove all flammable material, such as cotton, oil, gasoline, etc., from the vicinity of welding.
e. Before welding or cutting, warm those in close proximity who are not protected to wear proper
clothing or goggles.
f. Remove any assembled parts from the component being welded that may become warped or otherwise
damaged by the welding process.
g. Do not leave hot rejected electrode stubs, steel scrap, or tools on the floor or around the welding
equipment. Accidents and/or fires may occur.
h. Keep a suitable fire extinguisher nearby at all times. Ensure the fire extinguisher is in operable
condition.
i. Mark all hot metal after welding operations are completed. Soapstone is commonly used for this
purpose.
2-2. PERSONAL PROTECTIVE EQUIPMENT
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Chptr 2 Safety Precautions in Welding Operations
a. General. The electric arc is a very powerful source of light, including visible, ultraviolet, and infrared.
Protective clothing and equipment must be worn during all welding operations. During all oxyacetylene
welding and cutting proccesses, operators must use safety goggles to protect the eyes from heat, glare,
and flying fragments of hot metals. During all electric welding processes, operators must use safety
goggles and a hand shield or helmet equipped with a suitable filter glass to protect against the intense
ultraviolet and infrared rays. When others are in the vicinity of the electric welding processes, the area
must be screened so the arc cannot be seen either directly or by reflection from glass or metal.
b. Helmets and Shields.
(1) Welding arcs are intensely brilliant lights. They contain a proportion of ultraviolet light which
may cause eye damage. For this reason, the arc should never be viewed with the naked eye within
a distance of 50.0 ft (15.2 m). The brilliance and exact spectrum, and therefore the danger of the
light, depends on the welding process, the metals in the arc, the arc atmosphere, the length of the
arc, and the welding current. Operators, fitters, and those working nearby need protection against
arc radiation. The intensity of the light from the arc increases with increasing current and arc
voltage. Arc radiation, like all light radiation, decreases with the square of the distance. Those
processes that produce smoke surrounding the arc have a less bright arc since the smoke acts as a
filter. The spectrum of the welding arc is similar to that of the sun. Exposure of the skin and eyes
to the arc is the same as exposure to the sun.
(2) Being closest, the welder needs a helmet to protect his eyes and face from harmful light and
particles of hot metal. The welding helmet (fig. 2-1) is generally constructed of a pressed fiber
insulating material. It has an adjustable headband that makes it usable by persons with different
head sizes. To minimize reflection and glare produced by the intense light, the helmet is dull
black in color. It fits over the head and can be swung upward when not welding. The chief
advantage of the helmet is that it leaves both hands free, making it possible to hold the work and
weld at the same time.
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Chptr 2 Safety Precautions in Welding Operations
(3) The hand-held shield (fig. 2-1) provides the same protection as the helmet, but is held in
position by the handle. This type of shield is frequently used by an observer or a person who
welds for a short period of time.
(4) The protective welding helmet has lens holders used to insert the cover glass and the filter
glass or plate. Standard size for the filter plate is 2 x 4-1/4 in. (50 x 108 mm). In some helmets
lens holders open or flip upwards. Lenses are designed to prevent flash burns and eye damage by
absorption of the infrared and ultraviolet rays produced by the arc. The filter glasses or plates
come in various optical densities to filter out various light intensities, depending on the welding
process, type of base metal, and the welding current. The color of the lens, usually green, blue, or
brown, is an added protection against the intensity of white light or glare. Colored lenses make it
possible to clearly see the metal and weld. Table 2-1 lists the proper filter shades to be used. A
magnifier lens placed behind the filter glass is sometimes used to provide clear vision.
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