Tweco 186 DC Inverter - Manual (Page 63)

BASIC WELDING 186 AC/DC INVERTER
Manual 0-5237 4-9 BASIC WELDING GUIDE
E. Preheating
Suitable preheating of parts of the structure other
than the area to be welded can be sometimes used
to reduce distortion. Figure 4-22 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 4-21: Principle of Presetting
Art # A-07708
B
Preheat Preheat
Dotted lines show effect if no preheat is used
Weld
C
Figure 4-22: Reduction of Distortion by Preheating
Art # A-07709
Figure 4-23: 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 4-24: Welding Sequence
Art # A-07711_AB
4
3
2
1
Figure 4-25: Step back Sequence
Art # A-07428_AB
Figure 4-26: Chain Intermittent Welding
Art # A-07713_AB
Figure 4-27: Staggered Intermittent Welding