Linde BOC RAPTOR Operating Manual page 47

Defects caused by welding technique
Slag Inclusions
SLAG INCLUSIONS
Slag inclusions occur when slag particles are
trapped inside the weld metal which produces a
weaker weld. These can be caused by:
erratic travel speed
•
too wide a weaving motion
•
slag left on the previous weld pass
•
too large an electrode being used
•
letting slag run ahead of the arc.
•
This defect can be prevented by:
a uniform travel speed
•
a tighter weaving motion
•
complete slag removal before welding
•
using a smaller electrode
•
keeping the slag behind the arc which is done by
•
shortening the arc, increasing the travel speed,
or changing the electrode angle.
Undercutting
UNDERCUTTING
Undercutting is a groove melted in the base metal
next to the toe or root of a weld that is not filled by
the weld metal. Undercutting causes a weaker joint
and it can cause cracking.
This defect is caused by:
excessive welding current
•
too long an arc length
•
excessive weaving speed
•
excessive travel speed.
•
On vertical and horizontal welds, it can also be
caused by too large an electrode size and incorrect
electrode angles. This defect can be prevented by:
choosing the proper welding current for the type
•
and size of electrode and the welding position
holding the arc as short as possible
•
pausing at each side of the weld bead when a
•
weaving technique is used
using a travel speed slow enough so that the
•
weld metal can completely fill all of the melted
out areas of the base metal.
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