Brazing aluminium.

[OxxAndBert]

I don't think MAPP gas exists any more - it is mostly propane.
…….
Jack

I don’t think that’s correct.
There may be some slight technical differences to original MAPP, but the gas being referred to here is the stuff in the yellow disposable canisters.
Although it is shown online as being used as a sort of acetylene substitute in a MAPP/oxy combo I’ve only ever seen it used here by itself.
Otherwise known as Map and I see that Tradeflame have branded it “Ultra”.
SDS says it’s Propene - but whatever it is it’s NOT propane and burns a lot hotter.

Steve

[Jack Ryan]

I don’t think that’s correct.
There may be some slight technical differences to original MAPP, but the gas being referred to here is the stuff in the yellow disposable canisters.
Although it is shown online as being used as a sort of acetylene substitute in a MAPP/oxy combo I’ve only ever seen it used here by itself.
Otherwise known as Map and I see that Tradeflame have branded it “Ultra”.
SDS says it’s Propene - but whatever it is it’s NOT propane and burns a lot hotter.

Steve

Wikipedia:

MAPP gas was widely regarded as a safer and easier-to-use substitute for acetylene, but, early in 2008, its production was discontinued at the only remaining plant in North America that still manufactured it. However, there are many MAPP substitutes on the market, often labeled "MAPP" but containing mostly propylene with some propane and in some cases also dimethyl ether.

I think that, these days, it is just an expensive substitute for propane.


Also from Wikipedia:

A MAPP/oxygen flame is not entirely appropriate for welding steel, due to the high concentration of hydrogen in the flame – higher than acetylene, but lower than any of the other petroleum fuel gases. The hydrogen infuses into the molten steel and renders the welds brittle. For small-scale welding with MAPP this is not a serious problem, as the hydrogen escapes readily, and MAPP/oxygen can in practice be used for welding small steel parts.

Hydrogen is a problem but that's not why you can't weld steel with MAPP/Propane - it doesn't have a reducing zone like acetylene does.


Jack

[Iron triangle]

Years ago there used to be a torch gun that apparently can weld & braze all steels with good results i.e stainless , copper , aluminium ect , mild steel , was called a henrob torch. Might be worth checking out, if i recall you could use it without any filler rods just melt the 2 surfaces together, would be perfect for small jobs.

[droog]

Years ago there used to be a torch gun that apparently can weld & braze all steels with good results i.e stainless , copper , aluminium ect , mild steel , was called a henrob torch. Might be worth checking out, if i recall you could use it without any filler rods just melt the 2 surfaces together, would be perfect for small jobs.

Yes in the right hands it can do a lot. The common demonstration was welding soft drink cans although I was never able to replicate.
To widen the search look for Dillon, Henrob, Cobra or DHC https://detroittorch.com/pages/about...mgnHq5MC9regbx
that is the different names it was / is known as.
End of the day it is just an Oxy Acetylene torch and the same rules apply.

Still have it and have never returned to conventional O/A torches.

[disco stu]

Wikipedia:
I think that, these days, it is just an expensive substitute for propane.


Also from Wikipedia:

Hydrogen is a problem but that's not why you can't weld steel with MAPP/Propane - it doesn't have a reducing zone like acetylene does.


Jack

I've heard this said before as to why your can't weld with oxygen propane. But reducing zone of a flame has to do with oxygen content in various parts (chemistry of burning), not to do with type of fuel being used. Can you explain further why this is the case with oxygen propane?

[droog]

I've heard this said before as to why your can't weld with oxygen propane. But reducing zone of a flame has to do with oxygen content in various parts (chemistry of burning), not to do with type of fuel being used. Can you explain further why this is the case with oxygen propane?

Not a chemist so hopefully someone with experience will chime in but the way I read it has everything to do with the fuel used.
https://en.wikipedia.org/wiki/Oxidiz...educing_flames
To get a reducing flame it must be fuel rich, oxygen poor. The fuel gas used must be rich enough that it cannot mix with oxygen quick enough before combustion.

Happy for anyone to correct any terminology in the above.

[Jack Ryan]

I've heard this said before as to why your can't weld with oxygen propane. But reducing zone of a flame has to do with oxygen content in various parts (chemistry of burning), not to do with type of fuel being used. Can you explain further why this is the case with oxygen propane?

When acetylene burns in oxygen, it creates a reducing zone that cleans the steel surface. Propane does not have a reducing zone like acetylene and hence cannot be used for welding.

The reducing zone is created because the acetylene combustion is a two stage reaction.

The first reaction involves the acetylene disassociating in the presence of oxygen to produce heat, carbon monoxide, and hydrogen gas:

C2H2 +O2 → 2 CO + H2.

The second reaction follows where the carbon monoxide and hydrogen combine with atmospheric oxygen to produce carbon dioxide and water vapor.

2CO + O2 → 2 CO2 2H2 + O2→ 2 H2O

Complete combustion of one volume of acetylene requires two and half volumes of oxygen; one volume of which is supplied from the oxygen cylinder and the balance from the atmosphere.

Jack

[disco stu]

When acetylene burns in oxygen, it creates a reducing zone that cleans the steel surface. Propane does not have a reducing zone like acetylene and hence cannot be used for welding.

The reducing zone is created because the acetylene combustion is a two stage reaction.

The first reaction involves the acetylene disassociating in the presence of oxygen to produce heat, carbon monoxide, and hydrogen gas:

C2H2 +O2 → 2 CO + H2.

The second reaction follows where the carbon monoxide and hydrogen combine with atmospheric oxygen to produce carbon dioxide and water vapor.

2CO + O2 → 2 CO2 2H2 + O2→ 2 H2O

Complete combustion of one volume of acetylene requires two and half volumes of oxygen; one volume of which is supplied from the oxygen cylinder and the balance from the atmosphere.

Jack

Awesome, thank you. That does explain it. I pictured it being like what you say but wasn't certain. I have searched in the past, even asked in various places, and could never find the actual explanation,, just the statement that you can't use it because....

It does make me wonder, and I had this thought last night, if you could have secondary fuel injected further along the flame to create the conditions needed to weld with propane.

[Jack Ryan]

It does make me wonder, and I had this thought last night, if you could have secondary fuel injected further along the flame to create the conditions needed to weld with propane.

You could do that, but those who could afford the torch would discover that it is rather difficult to get into tight places and almost impossible to adjust to remote jet.

Acetylene just turned out to be a gift from heaven - like flammable manna.

By the way:

2CO + O₂ → 2 CO₂ 2H₂ + O₂→ 2 H₂O

was meant to be:

2CO + O₂ → 2 CO₂

and

2H₂ + O₂→ 2 H₂O

but I'm sure you figured that out.

Jack

[disco stu]

Hang your head in shame! I didn't even look at the equations closely, your explanation was clear enough

[bollie7]

Years ago there used to be a torch gun that apparently can weld & braze all steels with good results i.e stainless , copper , aluminium ect , mild steel , was called a henrob torch. Might be worth checking out, if i recall you could use it without any filler rods just melt the 2 surfaces together, would be perfect for small jobs.

We got one of these at work over 25 years ago. (can't remember the price, but it wasn't cheap)
I think from memory it ran at a lower pressure than std oxy.
We all tried it and the consensus was it was a bit more comfortable to hold due to the different angle on the handle. Apart from that it wasn't any better than a std Comet 3 with a small tip.
Having said that we were not trying to do any really thin stuff. Mainly brazing and silver soldering brass fittings etc
The feeling among us Techo's was just buy a couple of small tips for the Comet 3.
Peter