Tweco 170 HF Weldskill - Manual (Page 34)

WELDSKILL 170 HF INVERTER
4-12 April 23, 2008
D. Presetting
It is possible in some cases to tell from past
experience or to find by trial and error (or less
frequently, to calculate) how much distortion will take
place in a given welded structure. By correct pre-
setting of the components to be welded,
constructional stresses can be made to pull the parts
into correct alignment. A simple example is shown in
Figure 4-22.
E. Preheating
Suitable preheating of parts of the structure other than
the area to be welded can be sometimes used to
reduce distortion. Figure 4-23 shows a simple
application. By removing the heating source from b
and c as soon as welding is completed, the sections
b and c will contract at a similar rate, thus reducing
distortion.
Art # A-07710
Figure 4-25: Welding sequence
Art # A-07711
Figure 4-26: Step back sequence
Art # A-07712
Figure 4-27: Chain intermittent welding
Art # A-07713
Figure 4-28: Staggered intermittent welding
Art # A-07707
Figure 4-22: Principle of presetting
Figure 4-23: Reduction of distortion by preheating
Art # A-07708
Art # A-07709
Figure 4-24: Examples of distortion