Linde BOC RAPTOR 250R MIG Operating Manual page 41

Butt Welding
Face Reinforcement
Root Face
Root Gap
For use on thick plate that is accessible for welding from both
sides. For a given thickness it is faster, needs less weld metal
and causes less distortion than a single 'U' preparation.
Horizontal Butt Weld
The lower member in this case is bevelled to approximately 15°
and the upper member 45°, making an included angle of 60°.
This preparation provides a ledge on
the lower member, which tends
to retain the molten metal.
Electrode
Weld Pool
Slag
Weld Metal
Direction Of Welding
70˚ - 85˚
Arc
Electrode Angle for 1st and 2nd Layers
Weld Face
Layers
Layers
70˚ - 85˚
Arc
BOC RAPTOR 200C & 250R MIG Operating manual
Layers
Electrode Angle for Subsequent Layers
Weld Beads Layers
General notes on Butt Welds
The first run in a prepared butt weld should be deposited with an
electrode not larger than 4.0 mm. The angle of the electrode for
Weld Beads
the various runs in a butt weld is shown.
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.
Weld Beads
Weld Beads
Electrode
Weld Pool
Slag
Weld Metal
Direction Of Welding
41
A