Nautilus submarine hydrogen cracking during construction

Centerpiece historical case of the lecture. Mid-1950s Nautilus mockup construction with HY-80; egg-crate stiffener welds made during the day; cracks audible as rifle-shot reports during the night shift — delayed hydrogen cracking, 8-hour diffusion timescale to crack tip. Workaround: switch to austenitic stainless steel electrodes (FCC structure, higher H solubility, lower cracking susceptibility) at the cost of undermatched strength.

But they did, when they went to build some of the mockup for the Nautilus submarine in the mid-1950s, which was the first nuclear sub. Before that they just used low-strength steel. The other night, Run Silent, Run Deep was on, and the Olympics hadn't come on, so I just put on this old Clark Gable, Burt Lancaster movie, and that submarine, when they dive deep, they go to 200 feet, because they just used regular old low-strength mild steel, whatever you want to call it, for submarines in World War II. For nuclear submarines, when they came with the Nautilus, they were using HY-80 — that's the piece I passed around — 80 ksi as opposed to 35 or 40 ksi. And so they could dive deeper. I won't tell you how much deeper, because it's classified, but it's a lot more than 200. It is more than double 200, because they did other things on the design and fracture mechanics and other stuff. They can go a lot deeper than 200 feet. But I can't tell you how deep.