MULTIPLE PASS WELDING
Butt Weld Joints. When butt welding thicker
materials, you will need to prepare the edges
of the material to be joined by grinding a
bevel on the edge of one or both pieces of
the metal being joined. When this is done, a
V is created between the two pieces of
metal, that will have to be welded closed. In
most cases more than one pass or bead will
need to be laid into the joint to close the V.
Laying more than one bead into the same
weld joint is known as a multiple-pass weld.
The illustrations in Figure 15 show the
sequence for laying multiple pass beads into
a single V butt joint.
NOTE: WHEN USING SELF-SHIELDING
FLUX-CORE WIRE it is very important to
thoroughly chip and brush the slag off each
completed weld bead before making another
pass or the next pass will be of poor quality.
First or
Root Pass
Finished
Weld
Figure 15. Triple Pass V Butt Joint
Fillet Weld Joints. Most fillet weld joints, on
metals of moderate to heavy thickness, will
require multiple pass welds to produce a
strong joint. The illustrations in Figure 16
show the sequence of laying multiple pass
beads into a T fillet joint and a lap fillet joint.
Lap Joint Welded
In Three Passes
f
T Joint in
Three Passes
Figure 16. Triple Pass Lap and
T Weld Joint
SPECIAL WELDING METHODS
SPOT WELDING
The purpose of a spot weld is to join pieces
of metal together with a spot of weld instead
of a continuous weld bead. There are three
methods of spot welding: Bum-Through,
Punch and Fill, and Lap (see Figure 17).
Each has advantages and disadvantages
depending on the specific application as well
as personal preference.
PUNCH AND FILL _ LAP SPOT
BURN THROUGH
Figure 17. Spot Weld Methods
1. The BURN-THROUGH METHOD welds
two overlapped pieces of metal together
by burning through the top piece and into
the bottom piece.
With the burn-through method, larger wire
diameters tend to work better than smaller
diameters because they have greater
current carrying capabilities allowing the
arc to burn through very quickly while
leaving a minimal amount of filler metal
build up.
17
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