Welding with propane

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I've done some searches and came up with very little on the subject. Most references here say "you can't weld with propane". Anyone have anything definitive on the subject? I did see a reference designation in European standards relating to propane/oxy welding, so it does exist as a process. I've seen all the comments saying it doesn't shield like acetylene, or there is hydrogen embrittlement, but nobody references a reliable source for the info. I figure if anyone knows, someone here will.
Reply:What quality of "weld" are you looking for" Are you code welding or just yard art welding?Lincoln SA200's... at least 15 - 20. They come and go. Growing partial to the "Short Hoods" in my old age. Last count on Short Hoods was 13 in possession.
Reply:The reason that acetylene is the only acceptable fuel for gas welding is that all other gasses cause hydrogen embrittlement. Can you make something stick together using propane? Maybe. Maybe even probably. But will the weld fail? That's why people are asking you if you're building yard art.If it weren't for this one property of acetylene it would have been off the market years ago. Propane or its derivatives (chemtane, MAPP) are enormously cheaper and work fine for heating, brazing or cutting. But you still have to have acetylene for welding.metalmagpie
Reply:And again, no references, just lore. Is there any document that outlines this hydrogen embrittlement problem? I'm not talking about yard art. You can do that with JB weld.
Reply:The reason propane is 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. Propane in combustion creates H2O. This lack of shield with propane and it's creation of H2O causes hydrogen infusion in the weld making it brittle.I'm sure there is a process and an environment/material where propane welding may be allowable. Propane is generally suitable for soldering and brazing. Have you read European the process?
Reply:Moparfever, The reference is basic chemistry, which is probably why nobody has taken the time to make a specifric point of it and put it in print. Hydrogen is not the issue, oxygen is. In a neutral O/A flame the secondary envelope has enough HC to unite with most of the atmospheric oxygen being drawn in, due to the tripple bond being released in the primary combustion zone. Other fuel gasses not having this bond use most of the HC in the primary combustion zone of the flame, and so the envelope is oxygen containing. If the material has a flux for oxidation sheilding, then these fuel gasses work fine ( i.e. aluminum, magnesium, brazing etc ), however if the welding relies on the oxygen free shielding envelope ( i.e. steel welding ), then alternative fuel gasses are unacceptable. -AaronP.S. This is covered in the ASM handbooks as well as most welding engineering handbooks, mostly just as a casual note since the mechanics behind the issue are so basic they shouldnt need explination to most professionals in the field. Unfortunately since the price increase of acetylene, more and more hobbyists are switching to alternative fuels, and there is an information gap apparently.
Reply:The primary acetylene flame (inner cone) produces CO and H2.  Then it further burns to produce CO2 and water vapor.  At the point of the inner cone, you have a hotter flame and, to my understanding,  an atmosphere that is more conducive to shielding from external oxygen.  Good explanation here:  http://www.solidmetals.net/2011/02/2...ylene-welding/"USMCPOP" First-born son: KIA  Iraq 1/26/05Syncrowave 250 w/ Coolmate 3Dialarc 250, Idealarc 250SP-175 +Firepower TIG 160S (gave the TA 161 STL to the son)Lincwelder AC180C (1952)Victor & Smith O/A torchesMiller spot welder
Reply:The CO visible in an O/A flame is in the "feather".  There is NO combustion within the inner cone.  The shape of the inner cone is determined by the flame front velocity, and the gas velocity, not the combustion byproducts, as there aren't any byproducts produced in that space.Oh, and H2 is NOT produced by an O/A flame.  That's just nuts.  H2 is far more combustible than C2H2.H2O is a product though.  Maybe that's what you meant.Back to the OP.  You've done some research, and found that the answer is no.Don't say you haven't found anything definitive on the subject.  There's plenty said on the subject, but the answer is always no.  Either you haven't looked, or you just want someone to say yes.Say the truth.  That you were not happy with the answers you found.  This is how new inventions come about.  Perhaps you will invent an oxy/propane welding process that uses a flux.  There's no harm in trying . . .  Experiment, and report back to us.I for one however don't have the time to devote to what I consider to be a fruitless enterprise.
Reply:Originally Posted by rlitmanThe CO visible in an O/A flame is in the "feather".  There is NO combustion within the inner cone.  The shape of the inner cone is determined by the flame front velocity, and the gas velocity, not the combustion byproducts, as there aren't any byproducts produced in that space.Oh, and H2 is NOT produced by an O/A flame.  That's just nuts.  H2 is far more combustible than C2H2.H2O is a product though.  Maybe that's what you meant.
Reply:Originally Posted by rlitmanThe CO visible in an O/A flame is in the "feather".  There is NO combustion within the inner cone.  The shape of the inner cone is determined by the flame front velocity, and the gas velocity, not the combustion byproducts, as there aren't any byproducts produced in that space.Oh, and H2 is NOT produced by an O/A flame.  That's just nuts.  H2 is far more combustible than C2H2.H2O is a product though.  Maybe that's what you meant.Back to the OP.  You've done some research, and found that the answer is no.Don't say you haven't found anything definitive on the subject.  There's plenty said on the subject, but the answer is always no.  Either you haven't looked, or you just want someone to say yes.Say the truth.  That you were not happy with the answers you found.  This is how new inventions come about.  Perhaps you will invent an oxy/propane welding process that uses a flux.  There's no harm in trying . . .  Experiment, and report back to us.I for one however don't have the time to devote to what I consider to be a fruitless enterprise.
Reply:Let me cut to the chase. There's a discussion on this subject on another board (machining), and someone finally mentioned the acetylene flame shielding against oxidation. I agreed, as this is something that had been discussed here. Then some people who have a good handle on chemistry chimed in on why that theory may not hold water. I came here since this is were the experts are. I was hoping for more of something like "that was tried and bridges fell down", or "that process is not certified by this organization because". You know, info from some authority as to why it is not an accepted process. Again, I have no skin in the game. I use whatever is best for the job and accept the cost.
Reply:Originally Posted by OldendumIf there is no combustion in the inner cone, then try sticking your finger in there.  It should be cool to the touch.
Reply:Originally Posted by rlitmanThe CO visible in an O/A flame is in the "feather".  There is NO combustion within the inner cone.  The shape of the inner cone is determined by the flame front velocity, and the gas velocity, not the combustion byproducts, as there aren't any byproducts produced in that space.Oh, and H2 is NOT produced by an O/A flame.  That's just nuts.  H2 is far more combustible than C2H2.H2O is a product though.  Maybe that's what you meant.Back to the OP.  You've done some research, and found that the answer is no.Don't say you haven't found anything definitive on the subject.  There's plenty said on the subject, but the answer is always no.  Either you haven't looked, or you just want someone to say yes.Say the truth.  That you were not happy with the answers you found.  This is how new inventions come about.  Perhaps you will invent an oxy/propane welding process that uses a flux.  There's no harm in trying . . .  Experiment, and report back to us.I for one however don't have the time to devote to what I consider to be a fruitless enterprise.
Reply:Originally Posted by rlitmanYou post a question, and disagree when you don't like the answer.  Ok.  Sucks to be a malcontent like you.  What more can I say.
Reply:At very least, acetylene has a much higher temperature inner cone and more BTU's released at that point than Propane.  Propane has a higher BTU output but you have to go to the outer flame to take advantage of the BTUs and temp.  My old Linde gas welding book warns of whipping the acet torch too much off to the side to avoid oxidation and bad welds.RLITMAN, if you are talking about the very tip of the nozzle where you have a bit of standoff so the velocity of the gas exceeds the burning speed of the gas mix, then yeah.  There is no flame cone.  Turn the gas pressure down enough and you'll have a flame inside the torch. Last edited by Oldendum; 08-28-2012 at 04:13 PM."USMCPOP" First-born son: KIA  Iraq 1/26/05Syncrowave 250 w/ Coolmate 3Dialarc 250, Idealarc 250SP-175 +Firepower TIG 160S (gave the TA 161 STL to the son)Lincwelder AC180C (1952)Victor & Smith O/A torchesMiller spot welder
Reply:Originally Posted by makoman1860Rlitman, I think you are mistaken. Remember that in a neutral flame, the oxygen to acetylene ratio delivered by the torch is not stoich, but instead fuel rich and so utilizing atmospheric oxygen for the secondary combustion or outer envelope. In fact the welding zone is Hydrogen rich with a neutral OA flame, but since there is atmospheric oxygen to complete the combustion process, it is not absorbed into the steel.
Reply:I was thinking that even if you could weld with propane you wouldn't have the nice pinpoint heat control you do with acetylene. I'm not that good so I need all the control I can get.
Reply:Originally Posted by OldendumRLITMAN, if you are talking about the very tip of the nozzle where you have a bit of standoff so the velocity of the gas exceeds the burning speed of the gas mix, then yeah.  There is no flame cone.  Turn the gas pressure down enough and you'll have a flame inside the torch.
Reply:Originally Posted by rlitmanMistaken about what?  I made a few statements.I cannot be more clear, that there is no combustion within the inner cone.  That's pretty cut and dry.Are you commenting about what I said about H2?  This is more of a grey area.The feather IS CO burning.  At the flame temperatures, H2 may exist, but only in really small percentages.  Monoatomic hydrogen is the dominant species of hydrogen in the oxygen starved feather, but CO is by far the biggest product.My understanding about a neutral flame, is that is is indeed stoichiometrically balanced, which is why it will stay neutral if you dunk the torch under water.  You can in fact collect the gases released by combustion in this way, to see (minus the water content, and what is water soluble) what is created.
Reply:I'm sure there is a lot more temperature variation than we can see in what appears to be two (or three) distinct zones.  Point is acet is hotter closer than propane, and can deliver more BTUs at that point than propane.  As far as the matches go, you must have been using those D.D. Bean book matches.  Those things are the worst excuse for matches and never want to light.  "USMCPOP" First-born son: KIA  Iraq 1/26/05Syncrowave 250 w/ Coolmate 3Dialarc 250, Idealarc 250SP-175 +Firepower TIG 160S (gave the TA 161 STL to the son)Lincwelder AC180C (1952)Victor & Smith O/A torchesMiller spot welder
Reply:Nope.  Those equations are only valid for final products, and the temperature at the surface of the inner cone is almost sure to break up most of the diatomic hydrogen, and much of the diatomic oxygen (which is not completely consumed in this zone).Here's a reference I found online for what you would expect in that area:33.3% CO 12.5% O2 12.0% CO2 11.1% O 10.5% H2O 9.5% HO 7.4% H 3.7% H2 C2H2 is conspicuously absent btw.
Reply:I have tried it and you can't weld to any quality with propane, you can't hardly get a puddle there is a scale over the puddle that forms,  It is day and night different between propane and acetylene, on trying to weld with it, for all practical purpose you can not or will not weld with any quality with propane.
Reply:Originally Posted by OldendumI'm sure there is a lot more temperature variation than we can see in what appears to be two (or three) distinct zones.  Point is acet is hotter closer than propane, and can deliver more BTUs at that point than propane.  As far as the matches go, you must have been using those D.D. Bean book matches.  Those things are the worst excuse for matches and never want to light.
Reply:Hi.  I heard that it can be done, but you need to do it differently than with an OA torch.  It works a lot more like forge welding.  I hear that there is a video floating around somewhere of it being done at a blacksmithing conference, maybe on the umba site.  I tried it out, but did not succeed.  The metal scaled up and sparkled away, but never stuck.  I have used this technique to successfully weld steel with a regular propane turbo torch without oxygen.  Heat to red, dip in borax, play the torch against the joint backed up by a hollowed out firebrick.  When it gets to welding temperature, pinch the joint with tongs or lightly hammer it.  This did work.  I asked an old smith what I was doing wrong with the oxy-propane, and he said "use a bigger tip".  I've never seen it done, but I believe those who say they have done it, and since I could weld with a regular propane torch, probably due to the more diffuse flame, there is really no reason to doubt them.  But it isn't the typical OA welding.  You won't make a puddle.
Reply:Forge welding is a different beast.RLITMAN, the Ohio Blue Tips must be the ones my Grandpa was carrying loose in his pocket when he caught fire years ago.  Wish I could have seen him dancing around, he only had one leg.  He did live in Ohio.I suspect that folks decided that oxy/propane welding wasn't possible, or at least practical, because the results sucked.  Too many variables all stacked the wrong way."USMCPOP" First-born son: KIA  Iraq 1/26/05Syncrowave 250 w/ Coolmate 3Dialarc 250, Idealarc 250SP-175 +Firepower TIG 160S (gave the TA 161 STL to the son)Lincwelder AC180C (1952)Victor & Smith O/A torchesMiller spot welderOriginally Posted by rlitmanNope.  Those equations are only valid for final products, and the temperature at the surface of the inner cone is almost sure to break up most of the diatomic hydrogen, and much of the diatomic oxygen (which is not completely consumed in this zone).Here's a reference I found online for what you would expect in that area:33.3% CO 12.5% O2 12.0% CO2 11.1% O 10.5% H2O 9.5% HO 7.4% H 3.7% H2 C2H2 is conspicuously absent btw.
Reply:I too have tried oxy/propane welding with very mixed results.Now in theory propane has almost twice the heating value of acetylene, and a combustion temperature only very slightly lower.BUT...There is one huge difference, the speed of combustion.With acetylene you can get a nice tight inner cone that is much easier to see, control, and work with.Propane burns very slowly, and you will have a large dispersed flame that blows out if you try increasing the gas pressure.  Like trying to weld with a forest fire....Now you certainly can weld with oxy propane, you sure can melt metal, and get things to flow and stick together, but neat looking quality welding that is not !!So you hear some guys saying, welding with propane, no worries.Others say possible, but the welds are crap.And some say absolutely impossible to weld properly with propane.They are probably all correct from their own personal perspective and expectations, it depends on what you would accept as being a good looking strong weld.Cheers,  Tony._________________________________Transmig 310 + Argoshield LightOxy acetyleneOxy propanePrehistoric stick welder_________________________________