Nine-month delayed hydrogen crack (High Sierra mountains)

Forward-reference — Tom flags a story of hydrogen crack appearing nine months post-weld, attributable to winter freezing trapping the hydrogen. Story itself not delivered in this section.

For nuclear submarines you have to wait a week from the time you complete the weld to the time you do your non-destructive testing, because with higher restraint on the submarine you might get hydrogen cracks days later. Usually the hydrogen cracks are only a problem in the first week or a couple of days. I'll tell you a story one of these days of where it lasted for nine months. But it was frozen in the High Sierra mountains in the winter — so you can trap it if you freeze it. We'll talk about that too.

The exception to the "hydrogen diffuses out within a few days" rule — a weld frozen all winter in the High Sierras retained its hydrogen and cracked the next spring.

No, not unless it's been reintroduced. It will cure itself if you keep it up. I know one case where it lasted a year, and that was in the High Sierras, where the weld was frozen all winter. If you want to keep hydrogen in steel: I had a student do his thesis 30 years ago on hydrogen cracking in armor steels. He was working for the Army over here at Watertown Arsenal. He would make his welds and within five seconds put them in liquid nitrogen, so he held the hydrogen in there long enough to do his hydrogen analysis. You all saw how fast it comes out. To get the actual hydrogen at the time of the weld, you can only extrapolate back, because you can't weld and do a diffusion analysis at the same time. Although Morris Cohen suggested that. That's where I learned about the impracticality of great academics.