View Full Version : MIG Sheilding Gases

02-11-2004, 04:41 PM
Well, I got my new MM 251 on the way, and now the endless debate over sheilding gases has begun. What do yall use?

I will primarily be running .035 solid wire, on thicker (3/16+) mild steels.

Is it possible to spray transfer on a 75 argon 25 CO2 mix, or do I need to go down to 84/16? My supplier doesnt carry the 84%, so that would need to be ordered in advance.

What kind of gas can I use to run an .045 hardfacing wire?

Also, what are the economics of it? Does the 19 dollar CO2 bottle not last as long as the 53 dollars for the argon mixes, or do they run the same time?

Mike W
02-11-2004, 06:10 PM
All I can say is that I have been using Co2 for......20 years and see no reason to change. :)

02-11-2004, 06:24 PM
Do you run spray transfer on CO2?

Mike W
02-11-2004, 06:40 PM
No, I haven't seen any reason to do spray transfer either. I am just a short circuit guy. :D

Actually most of my welding is done on 1/8 " or smaller steel. I didn't mean to sound flipant. :)

02-11-2004, 06:52 PM
No problem, just wondering.

I would like to take advantage of the spray mode, and just need to know what gasses I can get away with.

02-11-2004, 08:22 PM
I've run Co2 for steel for a good 30 years, and do it short circ. In order to get into spray transfer you need to run an argon mix, witch will pretty much makes spray a costl;ier process.
There is some dofference of opinion on exactly what gas mix is necessary for spray.
At 3/16, unless you are running long passes I don't see an advantage to spray. Co2 will give you better penetration on steel than mixed gas.
20# of Co2 will run at least 50# of wire, if not more. That figure will be somewhat dependant on how many CFH you run thru the gun.

Additionally, I should mention, the factory provided regulator that came with your machine is a mixed gas regulator, NOT a Co2 regulator. Straight Co2 will adversly effect that regulator. Also, if you run straight Co2 thru the regulator Miller will NOT honor the warranty, they can tell when they inspect it.

Planet X
02-11-2004, 09:40 PM
Originally posted by Franz
There is some dofference of opinion on exactly what gas mix is necessary for spray.

The following are 'old' opinions, I dont have anything current, but some may have an interest;
1981 Linde 'Mig Welding Handbook' " desirable spray.... not obtained...gas mix more than 15%co2"
1991 Miller "Gas Metal Arc Welding" "generally 8-10 % Co2 max...to obtain Spray transfer"
Liquid Air; "Spray transfer...not available... w/argon/co2...with over 10%CO2"
Air products "great Truths & facts" 1993, "when selecting CO2 as a shielding gas ...can not get spray... with more than 8% CO"

I do not have all of the above publications I am just quoting a quote " from one that I do :eek:

02-11-2004, 10:01 PM
Yeah I know about the regulator, but I've heardmost guys run an adapter, and it works. If they don't warentee it, I will be out the same as I would be buying another regulator, except I still wouldn't have 2 of them. I'm still unsure what I'm going to do.

What argon mixture does spray start at?

I will be doing a bunch of long passes on some thicker steel, like a loader bucket.

What gas will hardfacing need?

02-11-2004, 10:08 PM
Thanks X,

I had the reply window open a while before replying, so I didn't see yours before I replied.

02-11-2004, 11:04 PM
Bolt, trust me on this, you don't want to run straight Co2 thru a new Miller regulator, the diaphram just won't handle it.

As to MIG gasses, probably the best information is available on Ed Craig's site.

Planet X
02-11-2004, 11:09 PM
Originally posted by Bolt
Thanks X,

I had the reply window open a while before replying, so I didn't see yours before I replied.

Bolt, fwiw one of the two mixes I use will suit your needs.
I use each mix for specific reasons but from info you have given the following may be helpful as the mix will spray & short. Airgas brand 'Steelmix'
A 'full' sized cylinder 300(?) will have a ratio of Argon w/17% Co2- this mix or the Argon/16%C02 (155 cylinder size) should be the only mix you need;
1) if you are welding steel stuff
2) if its 1/8"or thicker, you spray
3) if its 1/8 or less , you short
It can be used for gas shielded flux wires too-however I have no personal knowledge of hardfacing wires so cannot help there.

The 'informational' quotes... are not exactly true, they are just to give you an idea what you can expect when searching 'sales' information for facts.
Thats my story and I'm stickin to it:D

02-12-2004, 12:11 AM
I was just talking today with a local welding supply and was told that outside the US a lot of people are going back to CO2 over mixed gases, where they could. He said the US was probably going to be slower, as they didn't want to lose the mixed gas sales.

I asked about CO2 causing problems with the regulator and having to invert my cylinder (beverage type). He said that all newer regulators had no problems with CO2 and that my cylinder was not equiped with a dip tube, so it should be OK. He did however say that I might not want to open the cylinder valve all the way.


Other than that, I don't use shielding gas that much, but when I do its CO2.


02-12-2004, 12:26 AM
Franz....Thanks for the Ed Craig site....Very interesting !

02-12-2004, 12:31 AM
Thanks guys,

I had previously explored Ed Craig's site, but I was just looking for a few more opinions.

Now I need to get my guy to get a steelmix, or find it somewhere else.

02-12-2004, 12:36 AM
BM, I'm a little confused by your comments regarding a dip tube liquid delivering cylinder, but then, I confuse easily.
It would be rare to find a liquid delivery Co2 bottle on anything smaller than a 330 size cylinder (6 feet tall and about a foot in diameter), and every liquid delivery cylinder I've ever seen was clearly labeled.
Among the things I know about Co2;
Co2 can be corrosive to certain metals, such as those containing zink.
Co2 also exhibits an interesting ability to generate static electricity when rapidly discharged from a cylinder, that's why the ground wire is across the horn of a fire extinguisher.
Co2 valves are not "back seated" as Oxygen or refridgerant valves are, so there in no need to fully open one.
Consider that Co2 becomes a refridgerant as it passes thru the regulator, very much as Freon does when it passes thru an expansion valve. Regulators are acting as expansion valves on a gas cylinder.
Over the years, I've seen people use beer regulators on MIG machines, and they were NOT happy campers when the regulator froze open and tank pressure hit the machine. Using a MIG gun as a fire extinguisher to deposit Dry Ice on the fillet is probably the textbook definition of FAST Freeze. Generally, it doesn't damage the machine, but it's real interesting watching somebody holding an ice crystal spewing gun try to figure out how the he!! to stop the action. OK, nothing is totally negative, and you can cool your beer reaL quick this way.
Also consider the previous statement on the corrosive nature of Co2, and that most regulators have brass bodys and diaphrams. Brass contains zink, eventually, Co2 will damage a brass regulator. Co2 regulators are generally NOT made from brass.
Lets cut to my favorite line, "the salesman said" need I detail the value of that statement? Salesmen are all lyars, and generally make money from your misfortune.

Planet X
02-12-2004, 01:32 AM
Originally posted by Bolt
Thanks guys,

I had previously explored Ed Craig's site, but I was just looking for a few more opinions.

Now I need to get my guy to get a steelmix, or find it somewhere else.

An Argon/Co2 mix with around 20-15% Co2 would work, 'steelmix' is just the one that is available in my area.

Expect your gas salesman to try to pawn off some 'special tri-mix'...
It is also a good idea to avoid any mixes containing Oxygen, unless you have a special reason to use it.

02-12-2004, 02:28 AM
Nope, not pushing the tri-mixes, just CO2 and Ar-CO2's. I just think that some places don't move with the times so much. "It's worked in the past, so why change," "my customers buy it...," that kind of idea.

That kind of attutude is not going to get me anywhere, its called progress.

02-12-2004, 03:07 AM
Originally posted by Bolt
Thanks guys,

I had previously explored Ed Craig's site, but I was just looking for a few more opinions.

Now I need to get my guy to get a steelmix, or find it somewhere else. Bolt, Ive got a MM251 and trying to learn spray. Have learned a ton from the likes of Planet X , Franz, Dan,Arron etc. One thing I found out quick, the M25 gun wont take the heat from spray, esp. 1/4" & up material. I went to a C4015 Roughtneck gun which runs cool. BTW Im using steelmix, and getting ( finnally ) in a 125:D I dont know how thick of material those buckets are, but long welds on 1/4 ( spray ) will quickly exceed your duty cycle . Im going to post some meter readings & pics in next week or two cause Planet X is on my case:eek: :D

02-13-2004, 02:02 AM
Your not confused, I was. I thought the dip tubes were available in the smaller cylinders too.

Thanks for the further info on the CO2.

Like I said I don't use gas too much and when I do it's probably for less than an hour total time, so maybe I won't have a snow blower mig gun. If I get to where I am using gas on a consistant basis I'll definitly switch regulators or go to a mixed gas.

Oh, I'm a salesman too and I'm a chronic liar, you can believe me.


10-10-2004, 05:25 AM
I've never really understood this problem. I use straight Argon for both my mig and tig welding. never had a problem. Now the thickest I typicaly weld is 1/4" material down to 18 gauge so maybe that's why.

just my 2 cents, and it keeps it simple