WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
oxidized or burned before reaching the molten metal.
The
direction of the molten filler metal, as it passes through the
arc, will be difficult to control and a considerable portion of
this metal will be lost as spatter. The long arc will melt the
electrode quickly, and the metal is not always deposited at the
point desired.
In general, the long arc results in poor weld
penetration, excessive overlap, and burned and porous metal in
the weld as shown in figure 13, views B through D, on the
previous page.
(3) Short Arc.
(a) The short arc (figure 13, view E) is the correct and
desired procedure for welding.
With the short arc, the molten
metal leaving the end of the electrode passes from the atmosphere
by way of an enveloping arc flame. The short arc permits better
control of the weld metal deposited resulting in a welded bead of
better quality.
Generally, a short arc provides maximum
penetration and better physical properties in the weld and
deposits the maximum amount of metal at the point of welding.
Porosity, overlap, and weld metal spatter are kept to a minimum.
(b) A very short arc, however, is undesirable. It will produce
much spatter, will go out frequently, and make continuous welding
difficult; the results being similar to those shown in figure 13,
view B.
e.
Bead Welding (figure 14 on the following page).
(1) When the arc is struck, metal particles melt off the end of
the electrode and are deposited in the molten puddle on the
surface of the work. As the electrode melts it becomes shorter
and causes the arc to increase in length unless the electrode is
fed down to the work as fast as the end is melted off and
deposited.
Before moving the electrode forward, the arc should
be held at the starting point for a short time to ensure good
fusion and to allow the bead to build up slightly.
When the
welding machine is adjusted for proper current and polarity, good
bead welds can be made by maintaining a short arc and welding in
a straight line at a constant speed.
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