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Brazing and Cutting with Propane
black85vette:
I first saw propane used with a cutting torch back in the sixties. Worked fine just was not as hot. Currently I use propane and oxygen for cutting but the welding tips I just use for body work, brazing, and heat treating. Using standard tips without any mods (is that allowed here?) Read somewhere that propane has something in it that weakens the steel at the weld. So I don't use it for welding. Mostly use the MIG anyway. Also; I just use the regular hoses that came with it. Since I don't use it often and don't leave the hose connected to the propane I figure it won't be a problem.
Another thing I do with propane is that I got a hose that adapts a 5gal / 20 lb tank to replace the little bottles used for lanterns and cook stoves. I use it with the torch that comes with the tall cylinders of propane or mapp fuel. It pulls air in to add with the propane and I find that it works for brazing if you don't have too much metal to heat up.
http://www.academy.com/webapp/wcs/stores/servlet/Product_10151_10051_751405_-1?kwid=ps_pla&mkid=PLA|023756711|Char-Broil%204%27%20Low-Pressure%20Propane%20Hose%20and%20Adapter
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I bought the conversion generator for my old Coleman stove and now run it off a 5 gal tank also. Much higher BTU and cook time!
vtsteam:
Great info black85vette.
I think the reason propane doesn't work for welding (weakens the joint) is that it is difficult to get the proper mix ratio with propane in the flame, so you're either oxidizing or laying down carbon in the joint. The reason for that, I think, is that propane has a much more restricted mixing range for complete combustion than acetylene does. Therefore the flame isn't as uniform inside, and when it's playing on something. That's a guess on my part.
But it leaves me wondering if I could actually weld with it on something that isn't critical for strength like sheet metal contraptions I sometimes build out of really high quality metal like electrical conduit, stovepipe metal, and chain link fence rails. :D
On the other hand brazing works well with thin stuff and with its very high strength compared to flame welding, and all it's other advantages re. heat distortion, cast iron cracking, etc. I gotta wonder why I would even bother trying to flame weld thin sheet. Maybe just for butt joints, where braze isn't so good.
I still think I might play around with making an atmospheric burner for brazing today. If I have time.
black85vette:
I don't think there is any problem welding with propane if there is no life or safety issue. I have welded with propane with good results.
I think it would be worth the effort to run some compressed air rather than oxygen and see how that works on a torch set using propane. Just need to make up the adapter and try it out. After all I am not trying to cut half inch plate or weld it back together.
vtsteam:
Well that's good news B85V! I had a feeling it was possible to weld with propane. Just hadn't been able to try it yet.
Blacksmiths weld with some propane fired forges. Depends on the burner. I would only want to flame weld thin stuff anyway. Looking forward to doing some experiments this week.
black85vette:
Thought it was worth a quick try. I made a quick and dirty adapter to hook up the oxygen hose to a air pressure regulator connected to the compressor. Tried several pressure settings but the air just blows the flame out.
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