I've been using MAPP gas to weld, but it's not readily available any more.
(I only do occasional small scale work, and buy it in disposable canisters - sure it's not as good as acetylene, but I can make it weld okay, and acetylene cylinders cost a whole bunch of ££'s here in the UK, mainly for rental)
There is a replacement, MAP//PRO from Rothenberger, which is stabilised propylene - any good?
I've heard the flame temp with oxy is about 100-200 degrees less than MAPP, which would make it at best even more marginal for welding than MAPP.
Any fuel gas other than acetylene will inject way too much hydrogen into the weld pool, leading to hydrogen embrittlement. This is the reason they still have acetylene around - you have to have it to weld steels.
As they say in the western US, cowboy up! Buy acetylene.
"Grant Erwin wrote: As they say in the western US, cowboy up! Buy acetylene. ^^^^^^^^^^^^^^^^^^^^^^ For the occasional small jobs you do, your best bet is one of those small Prestolite cylinders--the kind plumbers use. If you already have oxy to use with Mapp gas, or planned to buy it to use with Mapp gas, you are most of the way there already. And you'll never regret it. Having the hotter, more concentrated flame doesn't just get you by--it gets you BETTER.
Not a problem for me - I stress-relieve everything anyway as soon as it's welded, which gets the hydrogen out as well (mostly nickel alloys, which are supposed to be particularly bad for hydrogen cracking, but some steel too - however the parts are small and I've never had a problem with it using MAPP gas even without stress relieving).
What I really want to know is whether it's *possible* to weld with propylene. Is the inner flame hot enough? Is the outer flame too hot?
That would cost me maybe $400 upfront then $250 per year in rental etc - and I as I only use one or two of the small disposable cylinders per year, maybe $30 worth, it would be highly uneconomic!
(yes, I'd love to have acetylene available, but it isn't practical)
Sorry I didn't make it clear - yes, I have oxygen in abundance (from a concentrator).
I have been using oxy/MAPP gas for years (for welding steel and nickel alloys), but I just ordered some more MAPP gas and they sent propylene instead today - should I send it back?
Oxy/propylene is no use to me if it won't weld, as oxy/propane is fine for the brazing I do, and a lot cheaper.
You can't do that in the UK, you have to rent acetylene tanks. I don't think you can buy and refill tanks anywhere in the EU either.
(though you can buy oxygen tanks, and maybe get them refilled, if you're lucky enough to live in the right place or know someone)
- but (I think) it's illegal in the UK to fill acetylene tanks unless you have a licence and the documentation for the tanks - which, inter alia, includes certificates for the materials which they were made from!.
BTW, BOC charges for a size H (about 7 cu m, 250 cu ft) acetylene cylinder are:
£118.62 cylinder rental, per year £77.44 contents £38.19 delivery - note, this is for delivery to the local stockist, not to your door £12.63 collection - this is what the local stockist charges you for collecting the bottles from them - if they deliver to your door it costs more.
So the initial outlay would be £247.88 + £43.37 VAT, or £291.25; which is $514.69, not $400.
!
There are some slightly cheaper options, but none much cheaper.
Which is why I used to use MAPP gas, and would like to use propylene if possible.
I own my Tig gas tank. It is a sale bottle. It has a thick ring on top of the bottle top. I walk it in - they put it aside (in the back for all of this) and they take from their filled rack a tank and put it in my truck.
I go in and pay for the gas. I own the tank. I swap it out. I do that before I have to test the tank. They do that themselves due to their volume and safety.
So tank is owned. We can buy them lots of places. Home Depot is one. Welding supplies others and best.
Martin
Mart> Bob F wrote:
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"Peter Fairbrother" wrote: I'm not familiar with Prestolite - what is it? (clip) ^^^^^^^^^^^^^^^^^ Prestolite is a name carried over from the old acetylene headlamp days. Early automobiles often had a tank of acetylene mounted horizontally on the running board. Since you could open a valve and have "instant headlights," the brand name "Prestolite" was adopted, and survives to this day. The commonest use today is with a small regulator and a single hose leading to a Prestolite torch, for soldering copper pipe. You buy the tank, full, initially, and then just hand it over the counter in exchange for a full one as necessary. Check plumbing or welding suppliers. May be available in the UK, possibly under a different name. Check also on what jewelers use.
A *small* equal pressure torch, yes - can just weld up to 1/8" with oxy/MAPP, (probably more, or perhaps better, with acetylene).
Brazes well up to 3/16" with oxy/propane, plus brazes a good bit thicker (3/8"+) with a bit of help from a propane/air torch, which is all I need.
Won't cut though, the pressure and flow are too low.
5 litres per minute, DeVilbiss. £200 on eBay, used for 400 hours, but they work for 50,000 (I think?) hours before needing servicing.
I don't know the exact time, but it's something like 5 years continuous use, and I use it less than 1/24 of the time - I should live 120 years to see it need it's first service!
We don't *have* Home Depot in the UK. Or anywhere in the EU, afaik.
You can buy argon or argon mix bottles in the UK, and swap them out (if you are near the only place that does it properly, in Kent, which I'm not - carriage fees usually make it uneconomic otherwise, but if you only use a little bit it might be okay - or are lucky enough to have a supplier who caters for small orders, which is unusual but not unheard of. But try getting industrial helium!).
But TIG gas isn't acetylene, and you *can't* do that with acetylene in the UK, it's seriously against the law (for all practical purposes).
Oxygen isn't quite as bad, but it's still not easy.
A local gas supplier also does a free weekend or weekdays-in-a-week loaner of TIG gas, and even oxygen bottles - but this is unusual in the UK, to put it mildly! Won't do it for acetylene though.
There's a whole bunch of newish EU law about gas bottles (actually it's oldish EU law, but the exemptions people have been working under have ended), which the UK takes seriously, and especially about oxy and acetylene bottles.
Been bad for a few years now, especially for small scale suppliers who have almost all gone out of business - the big boys just charge more for the paperwork, and even more than ever for smaller orders (which they never really wanted in the first place).
There are probably some safety benefits involved, but they are swamped by the cost of paperwork ..
.. and also because the Fire Brigades close off the roads next to a fire where there is an acetylene cylinder for 24 hours, which costs Megabux. Even if it's not needed for safety reasons, that's the regulations. More than my job's worth not to comply.
:(
And can anyone answer my original question please!!: can you weld steel with oxy/propylene? Is the inner flame hot enough, is the outer flame too hot? For my purposes, you can just about weld with oxy/MAPP.
Just got a case of propylene (bought as MAPP, but supplier is cool), don't know whether to open it or send it back - and it's burning a hole in my imagination (or something) ...
Base gasses, such as Methane, Propane, Propylene, Propadiene, methyl-Acetylene, and butane are all LP gasses, as in Liquified Petroleum gasses. They are all derived from Petroleum Production.
These gasses can be made into mixes such as MAPP, Flamal, or Chemtane to name a few. MAPP stands for Methyl-Acetylene Poly Propadiene, and is a gas mix.
Here is a decent comparison of some fuel gasses.
MAPP is going away in the US because Propadiene is becoming more valuable to the plastics industry than the welding industry. Flamal and Chemtane are newer mix gasses that are replacing MAPP.
Here in Seattle, it is nearly impossible to get a large MAPP cylinder filled.
Propylene is a little hotter than Propane, but not as hot as any of the gas mixes.
None of these gasses are appropriate for gas welding of steel because of he high Hydrogen content of the flame, which gets infused into the weld puddle, rendering the weld very brittle.
Soldering, Brazing, Cutting, heating, bending are all excellent uses for LP fuel gasses.
No - it stands for Methyl-Acetylene, Propadiene, Propane.
MAPP gas is, or was, a mixture of these chemicals*, made almost exclusively by Dow Corning, who have now ceased selling MAPP gas - though there is also a similar mix available in Australia, can't remember the name, which afaik is not made by Dow.
these are proper-ish chemical names btw, all identifying exact substances; unlike "propylene", which is often used to mean many different things unless it's marked UN 1077 - in which case it is then an alternative name for propene, CH3-CH=CH2.
It doesn't include propylene (or propene) though.
:(
That's what I thought - but am not still sure of.
Is oxy/propylene hot enough to weld with? Is the inner flame hot enough, or the outer flame too hot?
As I explained in an earlier post, that isn't significant to me.
But the point was to buy your bottle. Not rent it. Then it is a trade in and buy gas only.
Leasing a bottle normally requires a deposit and a yearly fee. It might be that acetylene is only for business customers only or those with accounts. It might have been removed as being more dangerous and only top tier companies can get them.
I'd talk to your dealer and find out what are the facts. And to provide specs on the gas. And is it equal or better.
Comparison to Acetylene would be important. Temperature and heat.
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Search your vendor gas company web pages. Get hasmat as it might contain more than you think.
Martin
Mart> Mart>> Peter you missed something.
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If I were you, I would look into a small inverter TIG welder. Since you have been using gas welding, I think you would find TIG easy. It is very much like gas welding, but the " flame " is hotter.
Ernie is the US expert on welding. If he says you are out of luck on the gas, you probably are.
I have the greatest respect for Ernie's knowledge of welding - but he's not a chemist.
I agree that it's going to be almost impossible to get MAPP gas - but will oxy/propylene weld?
No-one has answered that question. So I did a bit of chemistry math, and it seems unlikely :( - but not impossible, and any reports from practical experience would be good.
Oxy/MAPP gas will weld, it was designed for welding - but oxy/propylene wasn't.
An alternative might be acetylene from carbide. I can get carbide cheaply enough, but only very small low-pressure (~ 1 psi) generators and I'm not dumb enough to try and make my own - acetylene is extremely dangerous!
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