2
These techniques are based on the same
principles as continuous mig welding except that there is no travel
speed involved; instead, there is a
welding time interval. The weld is made by placing the welding torch
directly on the top plate and holding
it motionless as shown in Figure 11-2. When the torch trigger is
depressed, the electrode wire and shielding
gas will be continuously fed. The arc will be maintained for a
predetermined period of time and it
will continue to penetrate the material in only one place. Eventually, the
weld will penetrate into the bottom
sheet. The amount of penetration attained for a particular material is
determined primarily by the welding
current and the arc duration. This relationship is illustrated in Figure 11-
3 for 1/16 (1.6mm), 1/8 (3.2mm), 3/16
(4.8mm) and 1/4 (6.4mm) in. mild steel plate. Note that the weld
current has by far the greatest influence
on penetration. Figure
11-2 - Technique of Making a Spot Weld Continued
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