Deep TIG (Deep Gas Tungsten Arc) development for thick-section horizontal welding

Gurevich's semi-submerged arc / deep-TIG technique: half-millimeter painted flux layer on top surface enables deep penetration via surface-tension-driven convection (Marangoni). Ken Mills at National Physical Lab hypothesized mechanism for stainless. Tom and Szekely modeled it in 1983, award-winning paper.

Then they had some other welds made by a process that Gurevich had also published on, back in the early '70s. We called it deep TIG — in Russian it was "shielded inert gas heating," and when translated into English it was always called semi-submerged arc weld. It wasn't really submerged arc like the one I showed you, which is one of the things that confused the Soviet papers — they never give you all the details. Semi-submerged arc — Gurevich had found that if you put just a little painted layer, half a millimeter thick, on the top surface of a piece of titanium, and you use a gas tungsten arc torch, with the flux, you can get a deep weld. Whereas if you have no flux there, you get a very shallow weld. [Tom passes a sample.] This was made in our lab with flux shielding on this one. This is 30-year-old technology.

The Soviets' "semi-submerged arc" was what the US now calls deep TIG. With a thin fluoride flux (calcium / strontium / sodium fluoride), gas tungsten arc at 1,000–2,000 amps with a quarter-inch tungsten electrode can weld 1.5–2 inch titanium in horizontal position in four passes. Navy funded EWI / Ohio State; sort-of works in aluminum and steel; really works in titanium.

The next thing — you couldn't weld everything in the vertical position, sometimes you've got to turn it sideways. It turns out another thing that Gurevich had been working on in the 1960s was electroslag welding. So that definitely was one of the processes. Submerged arc welding, who knows — it was kind of expensive on the flux, but his book goes through a hundred pages on how to make flux, so it's possible they were using submerged arc. But you can get almost the same qualities with gas tungsten arc.