Lincoln Electric Welder - Manual (Page 36)

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the joint are always recommended
when butt welding 14 gauge
(2.0mm) and thinner material. A
groove in the bar helps form the
bead shape. NOTE: Keep the arc
away from the copper. Copper
contamination of the weld causes
cracking.
Without fixtures, tack weld the joint
every couple of inches and peen the
tacks to remove shrinkage stresses.
Finish the joint with a welding
sequence designed to minimize
distortion.
A planned sequence of welding
always helps control distortion. The
techniques used in mild steel
welding can be used. Skip welding
and back-step welding are
recommended for light gauge steels.
Low current and stringer beads
reduce distortion by limiting the
amount of heat at the weld. Also, do
not deposit excessive weld metal. It
seldom adds to the strength of the
weld and does increase heat input
and promotes distortion.
If a structure of heavy steel is not
rigidly held during welding, many
small beads will cause more total
distortion than a few large beads.
Distortion Control in Ferritic and
Martensitic Stainless Steels
Since they have heat expansion
properties similar to mild steel, plate
structures of ferritic and martensitic
stainless steels are designed and
welded with about the same
distortion controls and allowances as
mild steel. However, because they
have lower thermal conductivity than
mild steel, the heat remains
concentrated in the area of the weld.
This causes distortion problems in
thin-gauge steel. This distortion can
be controlled with suitable jigs and
fixtures, proper joint design and a
correct welding sequence.