Tweco 201 ts Thermal Arc - Manual (Page 41)

OPERATION THERMAL ARC 161 STL, 201 TS
Manual 0-5203 4-11 Operation
4.19 Making Welded Joints
Having attained some skill in the handling of an electrode,
you will be ready to go on to make up welded joints.
A. Butt Welds
Set up two plates with their edges parallel, as shown in
Figure 4-15, allowing 1/16" (1.6mm) to 3/32" (2.4mm)
gap between them and tack weld at both ends. This is to
prevent contraction stresses from the cooling weld metal
pulling the plates out of alignment. Plates thicker than 1/4"
(6.4mm) should have their mating edges beveled to form
a 70° to 90° included angle. This allows full penetration of
the weld metal to the root. Using a 1/8" (3.2mm) E7014
electrode at 120 amps, deposit a run of weld metal on the
bottom of the joint.
Do not weave the electrode, but maintain a steady rate of
travel along the joint sufficient to produce a well-formed
bead. At first you may notice a tendency for undercut to
form, but keeping the arc length short, the angle of the
electrode at about 20° from vertical, and the rate of travel
not too fast, will help eliminate this. The electrode needs
to be moved along fast enough to prevent the slag pool
from getting ahead of the arc. To complete the joint in thin
plate, turn the job over, clean the slag out of the back and
deposit a similar weld.
Art # A-07697_AB
Tack Weld
20°-30°
Electrode Tack Weld
Figure 4-15: Butt weld
Art # A-07698
Figure 4-16: Weld build up sequence
Heavy plate will require several runs to complete the joint.
After completing the first run, chip the slag out and clean
the weld with a wire brush. It is important to do this to
prevent slag being trapped by the second run. Subsequent
runs are then deposited using either a weave technique or
single beads laid down in the sequence shown in Figure
4-16. The width of weave should not be more than three
times the core wire diameter of the electrode. When the
joint is completely filled, the back is either machined,
ground or gouged out to remove slag which may be
trapped in the root, and to prepare a suitable joint for
depositing the backing run. If a backing bar is used, it
is not usually necessary to remove this, since it serves
a similar purpose to the backing run in securing proper
fusion at the root of the weld.
B. Fillet Welds
These are welds of approximately triangular cross-sec-
tion made by depositing metal in the corner of two faces
meeting at right angles. Refer to Figure 4-8.
A piece of angle iron is a suitable specimen with which to
begin, or two lengths of strip steel may be tacked together
at right angles. Using a 1/8" (3.2mm) E7014 electrode at
120 amps, position angle iron with one leg horizontal and
the other vertical. This is known as a horizontal-vertical
(HV) fillet. Strike the arc and immediately bring the elec-
trode to a position perpendicular to the line of the fillet
and about 45° from the vertical. Some electrodes require
to be sloped about 20° away from the perpendicular posi-
tion to prevent slag from running ahead of the weld. Refer
to Figure 4-17. Do not attempt to build up much larger
than 1/4" (6.4mm) width with a 1/8" (3.2mm) electrode,
otherwise the weld metal tends to sag towards the base,
and undercut forms on the vertical leg. Multi-runs can be
made as shown in Figure 4-18. Weaving in HV fillet welds
is undesirable.
Art # A-07699_AB
45° from
vertical
60° - 70° from line
of weld
Figure 4-17: Electrode position for HV fillet weld
Art # A-07700_AB
1 2
3
4
5
6
Figure 4-18: Multi-runs in HV fillet weld