Anybody out there using an acetylene alternative to braze/weld?

Am told that Propane is OK for brazing, but not welding.

No real viable alternative for welding the advantage is it gives a very concentrated intense point heat, although MAPP gas gives a hotter flame than butane or propane it really isn't up to the job.

[Edited on 22/3/16 by britishtrident]

I remember using MAPP gas years ago, seemed to work well.

We use propane for cutting as its a hot gas

SGS do an alternative:

Link

SGS sounds good, and just up the road from me now I'm in UK

I think this is Propylene a gas used in the refrigeration industry. I have a cylinder of it as I use it for brazing and heating up steel that is corroded. It burns about 280 deg C less than acetylene = 3480deg C. I assure you it is virtually impossible to do any decent welding with it as it will not concentrate the heat properly.

MAPP has changed a bit in recent years, what is labelled as 'MAPP' in B+Q et. al. (those useful little yellow cylinders), isn't what it used to be. When I bought the kit (torches, hoses, reg., etc.) some time a ago, MAPP was a mix of methylacetylene and propadiene. It welded, beautifully. Now, as 'theprisioner' has said, it's now a mix of (mainly) propylene and propyne. This will weld, but not beautifully and not quickly either.

Recent MAPP is still great for brazing/silver soldering/whatever, just not really for welding. My use for it is now non-existent as I've gone over to TIG and Plasma Cutter.

I have a fully functional MAPP assembly (Regulator, hoses, cutting torch and welding torch with an assortment of related usefuls - tips etc.), all in good order, with MAPP gas bottles..... open to offers if you wish to acquire it.

The alternative to acetylene is……….



electricity

Hobby weld do acetylene in rental free bottles. If you search on line you will find a stockists but there is one in Avonmouth Bristol if you struggle. They do oxygen as well

I've stolen this from a welding forum:

"Lots of conjecture out there on why you can't weld with propane. Some say Propane is not hot enough. Actually that has nothing to do with it. Take a #7 Oxygen / Propane tip and compare it to a tiny #1 welding tip. Even though the Propane tip has a far higher BTU output you still will not get a good weld. The reason Propane ( and other alternative fuels ) are not suitable is that when Acetylene is burning with Oxygen it creates a cone of CO2 forming a shielding gas over the weld puddle. Propane does not produce this shielding CO2"

Also

"MAPP like all of the Liquified Petroleum gasses is not appropriate for welding of steel, due to the high concentration of hydrogen in the flame. The hydrogen infuses into the molten steel and renders the welds brittle."

Regards
Hugh

Hugh - yes, exactly so. Originally, MAPP was lovely to use, giving the protective CO2 cone.
Now that MAPP is an LPG mixture (not MAPP i.e methylacetylene-propadiene), the welds are contaminated, often porous and somewhat brittle.

Last time I used the rig in anger was the removal of a car 'dragon' clamp, utilised by an over zealous University car park 'officer'. This before the advent of the Li-ion angle grinder.

I always enjoyed chemistry so 'scuse me butting in.


The inner cone =

acetylene + oxy becomes two molecules of carbon monoxide + hydrogen
C2 H2 + O2 becomes 2CO + H2



Carbon Dioxide forms in the edges of the outer envelope.

( I'll take off my anorak now )

Paul G


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