Firepower MST 180i Operating Manual page 66

Firepower MST 180i
20°-30°
Tack Weld
Figure 4-21: Butt Weld
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 4-22. 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-section made by depositing metal in the corner of two faces meeting
at right angles. Refer to Figure 4-14.
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 Stick electrode at 100 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 electrode
to a position perpendicular to the line of the fillet and about 45º from the vertical. Some electrodes require to be sloped
about 20º away from the perpendicular position to prevent slag from running ahead of the weld. Refer to Figure 4-23.
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 4-24.
Weaving in HV fillet welds is undesirable.
45° from
vertical
Figure 4-23: Electrode Position for HV Fillet Weld
C. Vertical Welds
1. Vertical Up
Tack weld a three feet length of angle iron to your work bench in an upright position. Use a 1/8"(3.2mm) E7014 Stick
electrode and set the current at 100 amps. Make yourself comfortable on a seat in front of the job and strike the
arc in the corner of the fillet. The electrode needs to be about 10º from the horizontal to enable a good bead to be
deposited. Refer Figure 4-25. Use a short arc, and do not attempt to weave on the first run. When the first run has
been completed de-slag the weld deposit and begin the second run at the bottom. This time a slight weaving motion
is necessary to cover the first run and obtain good fusion at the edges. At the completion of each side motion, pause
for a moment to allow weld metal to build up at the edges, otherwise undercut will form and too much metal will
accumulate in the centre of the weld. Figure 4-26 illustrates multi-run technique and Figure 4-27 shows the effects
of pausing at the edge of weave and of weaving too rapidly.
BASIC WELDING GUIDE
Electrode
Tack Weld
Art # A-07697_AB
60° - 70° from line
of weld
Art # A-07699_AB
Figure 4-22: Weld Build up Sequence
6
Figure 4-24: Multi-runs in HV Fillet Weld
4-12
Art # A-07698
Art # A-07700_AB
3
5
2 4
1
Manual 0-5339