I wanted to weld some relatively thin steel tube to the furnace base. Normally I'd burn a hole right through the tube sooner or later even using 1/16" welding rod. Not to mention the furnace shell which is .020" stainless -- backed by insulating refractory. I wouldn't even have to look at that with a stick welder before there'd be a ragged hole in it. (For the stainless shell, I've decided it's fastenings and clamps all the way.)
But I thought about brazing the thin steel tube to the steel furnace base. Starting to run out of acetylene though I noticed this morning. But then I remembered I've also had the correct hoses and a spare gauge to switch over from oxy-acetylene to oxy-propane -- still in boxes. Just never actually set it up.
Well I have a full 20 lb tank of propane and this morning I thought I'd give it a try, so I hooked up the propane hoses to the torch, and switched over to a #2 (Victor style) welding tip to try some propane brazing.
Welding is not supposed to be possible w/oxy-prop, but cutting and brazing are. Propane is considerably cheaper than acetylene, and far more available. Brazing has always been a little difficult for me -- I like gas welding better, but perhaps I just didn't have the right tip for the job. Seemed to take forever to heat up to flowing, and by then I'd burn the braze.
Anyway, The #2 welding tip was a cheap one from Harbor Freight -- purchased just for trying out brazing w/propane, and so I tried it. First problem was that since it was really an acetylene tip, the flame blew out immediately when cranked even slightly -- plus it was a very windy day.
But from reading online, I knew this would happen, and heeded the suggestion I read somewhere to drill the tip slightly to form a recessed flame holder.So I used a 3/32" drill bit and went in maybe 1/16th". Well, that really made a difference and I was able to maintain a flame. Cranking the flame up still proceeded in a couple stages, but I got it to a very slight hissing flame easily.
So then I thought I'd try a really tough test, and grabbed a really crappy piece of bent cracked and rained-on coated brazing rod to try to get some braze on a piece of rusty reinforcing bar lying in the dirt. NO surface prep. Was this a planned torture test? Nah -- they were both handy to where I was standing with the torch lit! I had little expectation of braze doing anything but balling up and rolling off the rod.
Imagine my surprise when after seconds of heating, the stuff started to just flow over the end of the rebar. I could not believe it! Man that propane puts out some decent spot heat! The flame was pinpoint accurate. I don't think the rebar behind the end was even hot. You can see the rust isn't even turned black a half inch back.
I think I'm going to like brazing with propane!
