Figure 7-15.Work angle.
Figure 7-16.Travel angle.
The angle at which you hold the electrode greatly
affects the shape of the weld bead which is very impor-
tant in fillet and deep groove welding. The electrode
angle consists of two positions: work angle and travel
angle. Work angle is the angle from the horizontal
measured at right angles to the direction of welding (fig,
7-15). Travel angle is the angle in the direction of
welding and may vary from 5 to 30 degrees, depending
on the welders choice and conditions (fig. 7-16).
Work angle is especially important in multiple-pass
fillet welding. Normally, a small variance of the work
angle will not affect the appearance or quality of a weld;
however, when undercuts occur in the vertical section
of a fillet weld, the angle of the arc should be lowered
and the electrode directed more toward the vertical
Travel speed is the rate at which the electrode travels
along a weld seam. The maximum speed of welding
depends on the skill of the operator, the position of the
weld, the type of electrode, and the required joint pene-
Normally, when the travel speed is too fast, the
molten pool cools too quickly, locking in impurities and
causing the weld bead to be narrow with pointed ripples,
as shown in figure 7-12, view D. On the other hand, if
the travel speed is too slow, the metal deposit piles up
excessively and the weld is high and wide, as shown in
figure 7-12, view E. In most cases, the limiting factor is
the highest speed that produces a satisfactory surface
appearance of a normal weld, as shown in figure 7-12,
Breaking the Arc
The most commonly used method to break the arc
is to hold the electrode stationary until the crater is filled
and then slowly withdraw the electrode. This method
reduces the possibilities of crater cracks.
Reestablishing the Arc
When it becomes necessary to reestablish the arc (as
in a long weld that requires the use of more than one
electrode), the crater must first be cleaned before strik-
ing the arc. Strike the tip of the new electrode at the
forward (cold) end of the crater and establish an arc.
Move the arc backward over the crater, and then move
forward again and continue the weld. This procedure
fills the crater and prevents porosity and slag inclusions.
Peening is a procedure that involves lightly ham-
mering a weld as it cools. This process aids in relieving
built-up stresses and preventing surface cracking in the
joint area; however, peening should be done with care
because excess hammering can work harden and in-
crease stresses in the weld. This condition leads to weld
embrittlement and early failure. Some welds are cov-
ered by specific codes that prohibit peening so you
should check the weld specification before peening.
ARC WELDING POSITIONS
The types of welds, joints, and welding positions
used in manual-shielded metal arc welding are very
similar to those used in oxygas welding. Naturally, the
techniques are somewhat different because of the equip-
ment involved is different.