GE turbine heavy-section preheat foundation welds

Half-inch weld layers required 3–4 hour preheat holds to allow hydrogen to diffuse out before the next pass. Used as a contemporary parallel to the WWII armor case.

When they were doing some of the foundation welds on GE turbines, they could put in half an inch of weld metal, then they had to stop and keep the preheat on for three or four hours just to allow the hydrogen out before you put more on top. If you're doing armor steel back in World War II — that's 17 inches thick — they had to go slow. They went slow anyway because of stick electrodes, but if you didn't allow time for the hydrogen to diffuse out, you had a problem.