Japanese heavy-section electron beam welding project

Mid-80s Japanese national project, ~$200M, to weld 6-8 inch thick steel pressure vessels for coal gasification. Tom spent a year there. The problem-list catalog of §7 derives from this experience. Includes thermocouple/Seebeck effect on beam path (§1.p3) and oxide-induced porosity (§7.p3).

Heavy-section electron beam. I spent a year in Japan in the mid 80s because the Japanese had spent a couple hundred million dollars on a national project to try to build these coal gasifiers and weld heavy-section steels. Someone's going to come along when you're a captain in the Navy and say, oh, we're going to build an electron beam machine for you, it can weld 2-inch thick steel very rapidly. Well, what they found was long-term beam stability. If you're going to weld one of these 30-foot diameter pressure vessels 6 or 8 inches thick, it takes about an hour to go around, and typically you'll have some hiccup in the beam every 10 or 15 minutes, which means you're going to produce a defect every 10 or 15 minutes. When you produce a defect as you're welding continuously, you now have to worry about how you repair those defects in this narrow little weld.

Built a 600 kV / 60 kW machine for EB welds in 4–8 inch thick steel. Tom flags that "it didn't work all that well" but does not develop the case in this lecture.

There are plenty of electron beam melting furnaces out there that use three amps, but they have a spot size this big — you don't care about spot size if you're just trying to melt. But if you're trying to weld, you want a very sharp spot, and you can't focus very well above two- or three-tenths of an amp. Most machines are limited to about a tenth of an amp for good focusing. Which means if I want greater than 10 kilowatts, I go to 100 kilovolts so that at a tenth of an amp I can get 10 kilowatts. The Japanese built one at 600 kilovolts and got 60 kilowatts, and were doing electron beam welds in four, five, six, eight inch thick steel. We'll talk about why that didn't work all that well.