Tweco 175 SE Arc Master - Manuel (Page 36)

ARC MASTER 175 SE OpERATION
OPERATION 4-10 Manual 0-5054
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-07707
Figure 4-22: Principle of presetting
Art # A-07708
B
Preheat Preheat
Dotted lines show effect if no preheat is used
Weld
C
Figure 4-23: Reduction of distortion by preheating
Art # A-07709
Figure 4-24: Examples of distortion
Art # A-07710_AB
1
Block Sequence.
The spaces between the welds are
filled in when the welds are cool.
2
3
Figure 4-25: Welding sequence
Art # A-07711_AB
4
3
2
1
Figure 4-26: Step back sequence
Art # A-07712
Figure 4-27: Chain intermittent welding
Art # A-07713_AB
Figure 4-28: Staggered intermittent welding