It's been way too many years since I learned OA to remember many exact details. I do  know that Oxy propane does not work for welding. it works fine for brazing and soldering. You need Oxy acet to do welding. I have a feeling it has to do with how the gases break down in the flame. My guess is with propane you get only a partial breakdown and you get some water vapor forming within the  propane flame, but that's just a guess. I know moisture does cause hydrogen embrittlement with arc welding. That's why 7018 and other low hydrogen rods need to be kept in an oven and most weld specs where this can be a concern often call for preheating the material at least past the point where the material "sweats".

 

I'm not sure if you realize you can do basic scratch start tig with any DC stick welder just by adding a tig torch and the gas reg and cylinder. It works best with machines that are infinitely adjustable vs cheaper tapped transformer units. I know several guys who have picked up some of the inexpensive DC inverter stick machines and "converted" them over to basic tig rigs relatively inexpensively. This give you both a stick and tig capable machine at a relatively inexpensive price.

i gotta agree with DSW i do alot of tig for my job and about the only thing you wont be able to do is aluminum with DC. I enjoy tig more than any othere process especially stainless.

I sure cant afford one but check out millers dynasty machine. we bought one at work a few months ago and i love that thing. stick tig aluminum stainless steel whatever xxxxxx machine, and you dont have to change tungsten everything runs with the same tungsten. also if you decide on tig check out E3 tungsten.

ceriated, couldnt remember what it was lol