Mig welding gas choices... Need your real world input?

[CGCINC]

I found this information below and would like to get some input from you guys. What mix do you use? What is a good "general" mix for Carbon Steel and Stainless?
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Most of the times these gasses are used in a mixture form, typically consisting of carbon dioxide, and Argon or Oxygen. Oxygen is what causes most weld defects, however, in small percentages, mixed with other gasses, it improves the arc characteristics. Argon and Carbon Dioxide can be used by themselves. In some case there is tri-mix shielding gas containing Argon, Carbon dioxide, and Helium, or, Argon, Carbon dioxide, and Oxygen.

The more common mixtures and gasses are.

C2 or 2% Carbon Dioxide and 98% Argon
C25 or 25% Carbon Dioxide and 95% Argon
100% Carbon Dioxide
100% Argon


Some basic guidelines for choosing the proper gas are as follows:

Welding of carbon steel can be done with Carbon Dioxide alone and it produces the deepest penetration, the most smoke and the roughest weld. A mixture of gasses ranging from 2% to 25% Carbon Dioxide and the rest Argon can be used. However, a higher percent of Argon will result in a smoother, better looking weld, and improves the arc characteristics.

Welding of stainless steel is typically done with C2 or 2% Carbon Dioxide and 98% Argon. In some cases there is tri-mix shielding gas containing 90% Helium, 7.5% Argon, and 2.5%Carbon dioxide.

Welding of aluminum is typically done with Argon alone, with one exception. If the aluminum being welded is thicker then ½ of an inch there may be Helium added to the mix.

Argon gas by itself works well on most exotic metals like:

Copper
Copper Alloys
Magnesium
Nickel
Nickel Alloys
Titanium

[kenwhite]

For GMAW:

Argon is an inert gas and it provides greater cleaning action than other gases. Because it is heavier than air, argon blankets the weld from contamination. Argon reduces splatter by producing a smooth arc by creating a reduced arc voltage and that results in a lower arc power and thus lower penetration. The combination of lower penetration and reduced splatter makes argon desirable. Pure argon is seldom used for arc shielding except when welding such metals as aluminum, copper, nickel, and titanium. The use of pure argon to weld steel usually results in undercutting, poor bead contour, and the penetration is somewhat shallow.

Oxegen is normally added to argon in amounts of 1%, 2%, or 5%. When oxygen is added to argon, it improves the penetration pattern. It also improves the bead contour and eliminates the undercut at the edge of the weld. You use argon-oxygen mixtures in welding alloy steels, carbon steels, and stainless steel.

Helium, like argon, is an inert gas. But there are few similarities between the two gases. Argon is heavier than air and helium is lighter than air. Helium creates a high-voltage change as the arc length changes. When helium is used, more arc energy is lost in the arc itself which means the energy is not transmitted to the work, so it produces a broader weld bead, but shallower penetration. Because of its higher cost, helium is primarily used for special welding tasks and for welding nonferrous metals, such as aluminum, magnesium, and copper. It is mainly used in combination with other gases.

Carbon dioxide is essentially an inert gas. However, at high temperatures it decomposes into carbon monoxide (CO) and oxygen (O2). Because the excess oxygen atoms create an active gas that will combine with carbon or iron in the weld metal, wires used with this gas must contain deoxidizing elements. Since it is low cost, CO2 is often used in combination with other shielding gases for welding different types of metals. The current is about 25 percent higher with CO2 than with other shielding gases. Carbon dioxide produces a broad, deep penetration pattern. It also produces a good bead contour and there is no tendency toward undercutting. The only problem with CO2 gas is the tendency for the arc to be violent. This can lead to splatter problems, however, for most applications this is not a problem and the advantages of CO2 far outweigh the disadvantages.

EDIT: The different gasses when combined with higher currents produces different arc transfer types - globular (CO2), short circuit (Ar/CO2) which is what the I-MIG 200 is capable of, and spray (higher Ar % mix with other gasses) and higher currents.

[CGCINC]

[]

Did I miss where you say what mix You use and what You think is a good general mix for Carbon and Stainless?

[kenwhite]

Did I miss where you say what mix You use and what You think is a good general mix for Carbon and Stainless?

Doh... I must have deleted it when I added my edit... Sorry.

I use a 75-80% Ar with a 25-20% CO2 mix for steel and will use 100% Ar for aluminum with my Spool-Gun. I haven't welded any stainless yet with my I-MIG, sorry.

[performance]

When you are getting setup, you're probably going to have to stick with one or two gas selections, unless you have really deep pockets, and can afford the cost of having extra cylinders laying around. I have 2 basic gases I use: Ar/CO2 and Ar. My blend of Ar/CO2 is C18, or 82/18. It works fine for spray in my larger machine, and in short circuit, it yields good clean welds in my smaller Everlast unit. Still, you have plenty of penetration, excellent wet in, and good bead profile.

[DaveO]

This article...
http://en.wikipedia.org/wiki/Gas_metal_arc_welding
...has this to say about co2 content and spray transfer, which dovetails well with Ken's and Mark's posts:

"As the carbon dioxide content increases over 20%, spray transfer GMAW becomes increasingly problematic, especially with smaller electrode diameters."

The article doesn't specify what "increasingly problematic" means, though.

[SeanMurphy265]

75%/25% for mild steel,
I have used tri mix with mild steel, but that was given to me on accident. I believe it's more expensive per bottle.
100% argon for aluminum

[CGCINC]

75%/25% for mild steel,
I have used tri mix with mild steel, but that was given to me on accident. I believe it's more expensive per bottle.
100% argon for aluminum

Do you remember what the tri mix was? Did it weld smoother than the Argon/Co2?

[Brian Ski]

Thanks for the link to this post... Answers some more questions.

For the MIG I have have been using 75/25 Argon Co2 mix for steel. (That was what the LWS recommended) Been using it ever since. Pretty much all what I use it for (steel).

I did have to do some stainless welding and it worked as well as I could tell. Someone told me I could braze the stainless. Well that was a train wreck!!!! haha

[everlastsupport]

For MIG I use 75/25 Ar/Co2, my son likes Stargon (Prax air tri gas). The Stargon does seem to weld a bit better.

TIG is straight argon for me.