Nautilus submarine austenitic filler metal foundations

Brief reference. Early Nautilus foundations welded with austenitic filler (half the strength of HY80) as a deliberate under-matching strategy to absorb hydrogen and limit residual stress, until higher-strength procedures were qualified.

The problem could be relieved if you could use an under-matching filler metal. If you could use a 7018 electrode, you can't build up residual stress greater than the strength of the weld metal — the weld metal is going to yield, and your maximal residual stresses won't be 110 KSI, they'd be 70 KSI, the strength of the under-matching filler. That's what they did in the early days of fabricating some of the foundations for the Nautilus. They had to go to an austenitic filler metal which had half the strength of the HY80 and would absorb a lot of the hydrogen. They were able to do it until they developed procedures that wouldn't crack with the hydrogen and the higher residual stresses they were encountering.