FusionWelding Processes

1
Fusion-Welding Processes

• CHAPTER 7-1

2
General Characteristics of Fusion Welding
Processes
3
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.
4
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.
5
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).
6
Multiple Pass Deep Weld
Figure 27.6 A deep weld showing the buildup
sequence of individual weld beads.
7
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.
8
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.
9
Equipment Used in Gas Metal-Arc Welding
Figure 27.9 Basic equipment used in gas
metal-arc welding operations. Source American
Welding Society.
10
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.
11
Equipment for Electroslag Welding
Figure 27.12 Equipment used for electroslag
welding operations. Source American Welding
Society.
12
Designations for Mild Steel Coated Electrodes
13
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.
14
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.
15
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.
16
Example of Laser Welding
Figure 27.17 Laser welding of razor blades.
17
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.
18
Summary
Submerged arc welding
Shielded metal-arc welding
metal-arc welding
TIG
TIG
19
(b)
(a)
(a) Welding joints
(b) Welding applications.
20
Where, K constant less than 1 related to heat
losses. I Current. R Resistance of ionized
air gap. t Welding time.