Ok- sure this ain't new, but I have not seen it covered here yet. I just repaired an oil filled heat exchanger with 2 cracks in one of the connecting tubes, by using my TIG torch (Miller Diversion 180) and a bit of solder. I had the machine set up for stainless running straight argon gas at about 13...

Me? From Northeast Southwest Lower Upper Overshoe (a sister city to Bumfuqt Egypt)