replacing the normal inert shielding gas with a flammable gas to increase heat output

[HAWK]

BB Rider,

Miller does make some multi-process machines capable of MIG and TIG in the DC mode, but not in AC. Tigging .500" aluminum is going to require a Dynasty 300DX for regular use. A Syncrowave 250 will do it occasionally. The MM251X will handle all your MIG needs. The MM251X sells around $1700 and the Dynasty 300DX near the $5500 mark. Check out this link and explore the products by category:

www.millerwelds.com


Beveling and preheating are options, but it sounds like you have simply outgrown your equipment.

[Brad-Man]

What makes you think that the snall amount of heat available from a flammable gas would do you any good compared to the temperature of the arc?

Why would you even WANT to add oxygen to the mixture in enough quantity to support the combustion of the flammable gas?

Sounds like grounds for the Darwin Awards to me....

[dseman]

Originally posted by Brad-Man
What makes you think that the snall amount of heat available from a flammable gas would do you any good compared to the temperature of the arc?

Actually it's done all the time. GMAW uses Ar/CO2 blends (for one example). The CO2 disassociates into CO and O. When it recombines in the outer envelope of the arc plasma, tremendous additional heat is given off. Too much Oxygen, Nitrogen, or Hydrogen will cause porosity problems. But in the right ratio, they can be very helpful in providing additional heat for melting the base metal. Try migging steel with just Argon and you'll find that you have a convex bead with poor wetting at the toes. Oxygen also reduces the surface tension of molten iron. There is a lot of chemistry and physics in gas blending.

Yes, I know Oxygen is not a flammable gas, but it does serve as an oxidizer. Hydrogen however is quite flammable.

-dseman

[Brad-Man]

dseman:

Your short explanation of what CO2 does when subjected to high heat was very enlightening - THANKS! - I always enjoy learning a little more about whatever activity I am involved in, but it did not address the issue of adding a flammable gas to the mixture and the necessity of having to add oxygen to the mix in order to utilize the gas in order to produce a hopefully hotter weld.

The last time I heard, neither Argon or CO2 was considered flammable - either alone or together, so I don't see where your excellent observation of what happens with this non-flammable mixture when exposed to high heat enters into the discussion of adding a flammable gas to the gas mixture.

My point was that the idea of using a flammable gas, without supplying oxygen in order to use it, would be ridiculous, and also dangerous.

If there was NO oxygen added, the benefit of the breakdown of CO2 would certainly be diminished - the flammable gas would utilize the oxygen to the detriment of the weld. If too much oxygen was added, well - we know why we were using gas in the first place.

If the metal is too thick, then multi-pass is always preferred - even when it isn't too thick and you need ultimate levels of safety/quality.

I was also questioning the quality of the thinking involved in even broaching the subject - MIG welding has been around for years, and other than messing with the composition of wire, not much has changed with the processes - gases certainly haven't changed much.

While I have 'engineered' a lot of solutions mechanically and programatically when dealing with cars and writing software, I have never tried to second guess or take a shortcut when dealing with the fabrication of a structure, whether I was nailing, welding, gluing screwing or typing it together. I prefer to ensure the safety of everyone/data that will be using said structure and think in those terms.

While welding is only a hobby to me, utilized in a car restoration project, I am very interested in learning more - basically because I like learning in and of itself.

I am looking forward to something approaching an enlighted response refuting my actual first observations:

That the small amount of heat produced compared to the arc would
not help much.

That the idea of having to add what would probably be a surplus
of oxygen to the mix in order to guarantee combustion of the
flammable gas would be detrimental to the weld.

The fact that someone who even asked the question in the first
place knowing that MIG and TIG welding have been around for quite
a number of years with plenty of research continually being done,
is a likely candidate for the Darwin Awards.

[fun4now]

mm251

the mm251 sounds like what you need add a spool gun and youre a happy aluminum welder as well
good luck and happy welding

[thehat]

If there's no way this can work, please tell me. How does one preheat a weld? If I do need to bite the bullet and buy a larger machine, is there one which is capable of both processes?


I would pick up some 6010 and 7018 and stick weld it.Use the 6010 for the root and cover with the 7018.

[BCarlucci]

I just sat through a 5 hour class with my gas supplier on different shielding gases, and i do know that they mix an Argon 98% and hydrogen 2% mix for tig welding only, is what he told me, then he also told me about a new gas that Air Gas is coming up with that somehow includes nitrogen, which confused the **** out of me, because isn't that what shielding gas is for? pushing nitrogen and all the other gases out of the way so there's an intert gas around the weld? But what do i know, it could also be because i fell alseep till i heard the word nitrogen mixture for welding, then i woke up. Well if anyone can confirm this mix from airgas i would appreciate it, or maybe you can expand on it.

BC

[Glenn B]

KAAAAAABBBOOOOOOOOOOOOOOOOOOOOOOOOOOOOMMMMMM
Bye BYe BBrider
As posted above I'm glad you asked before trying something that could get you vaporized.
Beleive me if it could be done the weld engineers at Nasa, Lockheed, Boeing, Rocketdyne, MILLER, ESAB, Lincoln, PRAXAIR, Air Liquide, Airco, Etc...
Have already analyzed it, Probably tried it under controlled conditions. And decided it's not worth doing. If it could be done safely we would be doing it already. They have tried things we still haven't thought of too. Did you know you can take a steel rod shove it through a dried up corn cob & it will weld half *** decent? any way for my two cents the best you can do with what you have is just stick weld it or bite the bullet & pay someone who has the right equipment & knowlege to weld it for you. Sorry to say but it's good to recognize when we are over our heads on a project & call in the Experts.

[Andy249]

Usually you preheat a weld area to prevent underbead cracking from forming when the job cools down too quickly. You could try purchasing some heat crayons elevate the temperature by 100 degrees celcius or so (you can tell when you mark the steel on the opposite side to which you are heating and it changes colour). Use Oxy Acetylene or LPG to heat your steel. You can get more indepth if you want, but it sometimes has the effect of confusing the whole issue!

[dseman]

Originally posted by BCarlucci
I just sat through a 5 hour class with my gas supplier on different shielding gases, and i do know that they mix an Argon 98% and hydrogen 2% mix for tig welding only, is what he told me, then he also told me about a new gas that Air Gas is coming up with that somehow includes nitrogen, which confused the **** out of me, because isn't that what shielding gas is for? pushing nitrogen and all the other gases out of the way so there's an intert gas around the weld? But what do i know, it could also be because i fell alseep till i heard the word nitrogen mixture for welding, then i woke up. Well if anyone can confirm this mix from airgas i would appreciate it, or maybe you can expand on it.

BC

BCarlucci,
Good question. Both Linde and Praxair make blends involving Nitrogen. The Nitrogen increases the penetration profile in a similar way to Hydrogen blends, but when mixed with Hydrogen (and the balance Argon) the N seems to interact and reduce the porosity potential of the hydrogen. The blends I see from Linde are Croniwig N H: 97%Ar/2%N/1%H and Croniwig N He:
78%Ar/20%He/2%N. They are recommended for reducing the ferrite content in CrNi,Ni, and Duplex Steels. You've peaked my interest in the gas class. I'll have to see if any of my dealers will offer such a thing.

-dseman

[BCarlucci]

Dseman,

The class was great, see i'm also a distributor so i get the best of both worlds here. I'm sure your supplier would be able to set something like that up, if he can get enough people to attend and make it worth having a rep or tech come in to discuss the shielding gas/ new mixes. Thank you for the info on the nitrogen in the mixes, like i said i fell asleep and woke up once i heard the word.

Once again Thanks,
BC