It is REQUIRED in some circumstances. ABS and Lloyd's qualified procedures for hull plate are often 7018-1 root to cap.
Originally Posted by weldgault
The reason? 7018-1 makes the low temperature Charpy (kind of important in the north Atlantic) and the '10's don't as welded (the '10's are specd' at -20F, the '18-1 is at -50). I'v seen at least one job where '18 root was spec'd on refrigeration equipment, as well, due to the low temperature in service.
It's a wide, wide world out there. The shop I was in over the summer had more '18 root procedures than any other. The shop I spend most of my time in doesn't have any '18 root procedure, but everything is '18 or TIG cap. For pipeliners, '10 root to cap is quite common.
It is easier to trap slag using '18 for a root than '10, so it isn't something to do if not needed.
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