Fusion-Welding Processes

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CHAPTER 27

• Fusion-Welding Processes

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General Characteristics of Fusion Welding
Processes
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Oxyacetylene Flames Used in Welding
Figure 27.1 Three basic types of oxyacetylene
flames used in oxyfuel-gas welding and cutting
operations (a) neutral flame (b) oxidizing
flame (c) carburizing, or reducing, flame. The
gas mixture in (a) is basically equal volumes of
oxygen and acetylene.
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Torch Used in Oxyacetylene Welding
Figure 27.2 (a) General view of and (b)
cross-section of a torch used in oxyacetylene
welding. The acetylene valve is opened first
the gas is lit with a spark lighter or a pilot
light then the oxygen valve is opened and the
flame adjusted. (c) Basic equipment used in
oxyfuel-gas welding. To ensure correct
connections, all threads on acetylene fittings
are left-handed, whereas those for oxygen are
right-handed. Oxygen regulators are usually
painted green, acetylene regulators red.
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Pressure-Gas Welding
Figure 27.3 Schematic illustration of the
pressure-gas welding process.
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Shielded Metal-Arc Welding
Figure 27.4 Schematic illustration of the
shielded metal-arc welding process. About 50 of
all large-scale industrial welding operations use
this process.
Figure 27.5 Schematic illustration of the
shielded metal-arc welding operations (also known
as stick welding, because the electrode is in the
shape of a stick).
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Multiple Pass Deep Weld
Figure 27.6 A deep weld showing the buildup
sequence of individual weld beads.
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Submerged-Arc Welding
Figure 27.7 Schematic illustration of the
submerged-arc welding process and equipment. The
unfused flux is recovered and reused. Source
American Welding Society.
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Gas Metal-Arc Welding
Figure 27.8 Schematic illustration of the gas
metal-arc welding process, formerly known as MIG
(for metal inert gas) welding.
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Equipment Used in Gas Metal-Arc Welding
Figure 27.9 Basic equipment used in gas
metal-arc welding operations. Source American
Welding Society.
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Flux-Cored Arc-Welding
Figure 27.10 Schematic illustration of the
flux-cored arc-welding process. This operation
is similar to gas metal-arc welding, showing in
Fig. 27.8.
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Electrogas Welding
Figure 27.11 Schematic illustration of the
electrogas welding process. Source American
Welding Society.
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Equipment for Electroslag Welding
Figure 27.12 Equipment used for electroslag
welding operations. Source American Welding
Society.
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Designations for Mild Steel Coated Electrodes
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Gas Tungsten-Arc Welding
Figure 27.13 The gas tungsten-arc welding
process, formerly known as TIG (for tungsten
inert gas) welding.
Figure 27.14 Equipment for gas tungsten-arc
welding operations. Source American Welding
Society.
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Plasma-Arc Welding
Figure 27.15 Two types of plasma-arc welding
processes (a) transferred, (b) nontransferred.
Deep and narrow welds can be made by this process
at high welding speeds.
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Comparison of Laser-Beam and Tungsten-Arc Welding
Figure 27.16 Comparison of the size of weld
beads in (a) electron-beam or laser-beam welding
to that in (b) conventional (tungsten-arc)
welding. Source American Welding Society,
Welding Handbook (8th ed.), 1991.
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Example of Laser Welding
Figure 27.17 Laser welding of razor blades.
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Flame Cutting and Drag Lines
Figure 27.18 (a) Flame cutting of steel plate
with an oxyacetylene torch, and a cross-section
of the torch nozzle. (b) Cross-section of a
flame-cut plate showing drag lines.