USS Seawolf HY-100 hydrogen cracking

The Nautilus was the first ship that had HY-80 in it, sometime in the '50s. They had all kinds of hydrogen cracking problems, such that some of the first subs they actually welded with austenitic stainless steel, because they couldn't solve the hydrogen cracking problem. It took them about 10 years to really get their arms around that, and then they had the Thresher problem and they had Subsafe. They didn't actually start putting HY-100 into ships until the late '80s. There were two ships before the Seawolf that they put modules — cylinders in the center of the ship — with HY-100. I'm familiar with that because my first student ever still works at Electric Boat as a welding engineer. He was in charge of welding up those HY-100 cylinders. When the Seawolf had all its cracking problems, the two captains who were in charge of the ships came to me and said, well, what about our two ships with the HY-100 that are out there? I said, don't worry about it, just inspect them when they come back in. They're not going to fall apart tomorrow — but they could fall apart if you didn't inspect them properly.

Cited to make two points: (1) the redone Sea Wolf used high preheat plus the "blue jelly suits" humidity control to prevent recurrence; (2) the Sea Wolf cracking was unusual in that it occurred in the weld metal rather than the heat-affected zone, because of overmatching weld metal strength. Tom notes Electric Boat shut down production for about a year and salaried workers still had to be paid.

The highest temperature I've ever seen in steel preheat is about 600, and that's for a very thick highly restrained steel. Most steels are not above about 400. But even though I told you about the Sea Wolf and the blue jelly suits, when they redid the Sea Wolf they didn't want to have it crack a second time, so that's why they went to the blue jelly suits. They actually, I think, shut down production at Electric Boat for about a year. Even that cost a few dollars, because you might be able to lay off the hourly workers but you can't lay off the salaried workers — they still got to come and eat their lunch in the cafeteria. Actually they had a lot to do trying to figure out how to solve the problem.

Two prior 688-class attack submarines had 20–40 ft HY-100 test sections built into them as a precursor to Seawolf. After the Seawolf cracks were found, the Navy asked Tom whether those existing ships had to be derated. His answer: no — increase inspection budget, the sixteenth-inch cracks won't grow fast enough to threaten ship life.

Sea Wolf submarine MIG (gas metal arc) welding hydrogen problem — no flux to suppress hydrogen pickup.

It shows up with all processes. The Sea Wolf submarine, the problem was with MIG welding, gas metal arc welding, where you had no flux. I'll show you a plot of how much hydrogen you get with different welding processes. So we're going to spend a fair amount of time on steel. We will get to aluminum, but that'll be probably next week. Let's take a break until about 8:39.