43
It is necessary to maintain the root gap by tacking
at intervals or by other means, as it will tend to
close during welding.
All single ‘V’, single ‘U’ and square butt welds
should have a backing run deposited on the
underside of the joint; otherwise 50% may be
deducted from the permissible working stress of
the joint.
Before proceeding with a run on the underside of
a weld it is necessary to remove any surplus metal
or under penetration that is evident on that side of
the joint.
Butt welds should be overfilled to a certain extent
by building up the weld until it is above the surface
of the plate. Excessive build-up, however, should
be avoided.
In multi-run butt welds it is necessary to remove all
slag, and surplus weld metal before a start is made
on additional runs; this is particularly important
with the first run, which tends to form sharp
corners that cannot be penetrated with subsequent
runs. Electrodes larger than 4.0 mm are not
generally used for vertical or overhead butt welds.
The diagrams following indicate the correct
procedure for welding thick plate when using
multiple runs.
Electrode Angle for 1st and 2nd Layers
WELD BEADS
LAYERS
70˚ - 85˚
WELD BEADS
LAYERS
ELECTRODE
SLAG
WELD POOL
WELD METAL
ARC
DIRECTION OF WELDING
Electrode Angle for Subsequent Layers
WELD BEADS
LAYERS
70˚ - 85˚
WELD BEADS
LAYERS
ELECTRODE
SLAG
WELD POOL
WELD METAL
ARC
DIRECTION OF WELDING
11.6 Fillet Welds
A fillet weld is approximately triangular in section,
joining two surfaces not in the same plane and
forming a lap joint, tee joint or corner joint. Joints
made with fillet welds do not require extensive
edge preparation, as is the case with butt welded
joints, since the weld does not necessarily
penetrate the full thickness of either member. It
is important that the parts to be joined be clean,
close fitting, and that all the edges on which
welding is to be carried out are square. On sheared
plate it is advisable to entirely remove any ‘false
cut’ on the edges prior to welding. Fillet welds are
used in the following types of joints:
Convex Fillet Weld
ACTUAL THROAT
EFFECTIVE THROAT
CONVEXITY
LEG
LENGH
THEORETICAL THROAT
CONCAVITY
ACTUAL THROAT
AND EFFECTIVE
THROAT
LEG
SIZE
SIZE LEG
THEORETICAL THROAT
Concave Fillet Weld
ACTUAL THROAT
EFFECTIVE THROAT
CONVEXITY
LEG
LENGH
THEORETICAL THROAT
CONCAVITY
ACTUAL THROAT
AND EFFECTIVE
THROAT
LEG
SIZE
SIZE LEG
THEORETICAL THROAT
Summary of Contents for BOC RAPTOR
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