Last Updated on September 19, 2020 by Gary Hargrave
MIG welding professionals are more or less familiar with Argon (Ar)–Carbon Dioxide (CO2) blends. Those engaged in TIG welding usually rely on argon, helium, and the blends. You may want to switch the gas, hoping that it would save you the troubles of choosing gases for different projects. There comes the question if it is okay to use Argon CO2 mix for TIG welding.
You shouldn’t use Argon and CO2 mix because it usually results in poor weld puddle, and your tungsten electrode burns out almost instantly. There are risks of porosity with excessive spatters. Welding defects like brittleness and cracks may occur too.
I know you are looking for further explanations. This article presents everything on the topic and a few more insights into shielding gases for different welding processes.
Topics Covered in This Article
Shielding Gases for TIG Welding and Usability of Carbon Dioxide
A TIG welder lets you weld a wide variety of metals and alloys including aluminum, brass, bronze, copper, stainless steel, etc. All these metals are corrosion-resistant and extremely sensitive to air, hydrogen, nitrogen, oxygen, and water.
Presence of these elements is considered environmental contamination in a TIG welding setup. Any interaction of these contaminants with the weld puddle results in brittleness, carbide precipitation, ugly cracks, and weakened corrosion resistance.
This way, you can’t benefit from the shielding gases because the gas you use for TIG welding has to shield the electrode and molten weld pool from environmental impurities while contributing to a stable arc.
You might be wondering how CO2 fits in this situation. Well, it contains oxygen, and I already have discussed the outcome. Carbon dioxide, as an active gas, accelerates the arc voltage and causes excessive spatters, not to mention the porosity your weld bead will have.
Besides, you won’t like the fast speed at which your tungsten electrode may burn because it catches oxidation in the process. That is all the more reason you don’t want to use CO2 on a TIG welding job.
Now, let’s talk about argon.
As long as the weld puddle needs to be protected, argon is best suited for the purpose. It helps you keep the environment inert. It also helps to maintain a controllable and stable arc. However, mixing CO2 with argon critically affects the ability of the latter, and you’ll lose the benefits of using an inert noble gas.
So, you see argon is alright, and carbon dioxide is NOT. At this point, I can think of another question you might have.
Is There Any Argon Based Blend for Use in TIG Welding?
Of course, there are, and I can suggest you a few. Apart from argon as the only shielding gas, you can use helium (He) that helps with improved penetration and better fluidity of your weld pool by making it hotter. This blend makes it easy for you to weld virtually any grade.
Unlike carbon dioxide, hydrogen (H2) or nitrogen (N2) can be blended with argon because hydrogen can bring effects as strong as helium. But it doesn’t come without compromises. Follow this table to understand what you can expect from argon blends on stainless steels.
|Argon + Helium||Argon + Hydrogen (2-5%)||Argon + Nitrogen (1-2%) / Argon + Helium (30%) + Nitrogen (1-2%)|
|Austenitic||Fairly Well||Acceptable with high speed but risk of porosity||Not Recommended|
|High-Alloy Austenitic||Fairly Well||Acceptable with high speed but risk of porosity||Not Recommended|
|Duplex||Fairly Well||Not Recommended||Satisfactory|
|Super-Duplex||Fairly Well||Not Recommended||Satisfactory|
|Ferritic||Fairly Well||Not Recommended||Not Recommended|
With an argon and helium mixture, you can achieve good flow rate on nickel alloys. Adding hydrogen by 2-5% to argon, you can get an even higher flow rate, but there will be risks for porosity. For your information, flow rates for TIG welding can be at least 10 cubic feet per hour (CfH) and up to 35 cfh.
And that brings us to one decisive and perhaps the final question!
Is Argon – Carbon Dioxide Mixture Worth It?
It is a “yes” if you can think beyond TIG welding. You’ll receive what is more like an opposite result with a MIG welder. MIG welding with argon yields poor and wide penetration. CO2 helps you with a weld puddle that is hot enough to flow deep and quick.
Different proportions of these gases make excellent blends for structural steel works, machinery, and some variations of stainless steel, low-alloy, and carbon. The use of CO2 is good for weld penetration and improved weld bead properties.
These blends are useful in situations where you have to join metals with varying thickness using different metal transfer modes. Use lower than 20% CO2 for spray and pulse arc welding. A higher level is required for shielding flux-cored wires or short arc welding.
Low-alloy and carbon steels are the most suitable metals, and some stainless steels are good too, in case you choose to use these blends. You’ll have a lot of weld spatter if you maintain a high current level, which is a must for stabilizing spray transfer.
However, the amount of carbon dioxide, if any more than 20% in the blend, can cause the spray transfer mode to get unstable. Other consequences may include globular transfer and events of short-circuits.
Varying amounts of carbon dioxide being blended with argon to help you achieve different results while welding different metals. Now, I’m offering you a detailed overview.
Argon + CO2 (5%)
It is a very good, if not perfect, blend that facilitates short-circuit and pulsed spray transfer as you weld metals. This proportion provides arc forces which allow it to be more tolerant toward the mill scale. Besides, the weld puddle you’ll get is more controllable than the one you would have with an argon/oxygen mixture.
Argon + CO2 (10%)
Whether you undertake a spray or short-circuit transfer, you can expect higher heat input and a more fluid and wider puddle than the one with a 5% mix.
Argon + CO2 (15%)
If your welding project involves low-alloy or carbon steel, you’ll like this proportion, particularly in short-circuit mode. A gas blend with higher CO2 is likely to melt through thin-gauge materials. But this percentage helps minimize the issue with increased travel speeds and deposition rates. Consequently, you’ll get outstanding productivity.
Argon + CO2 (20%)
This percentage is meant for carbon steel, and the method can be either short-circuit transfer or spray. Be ready to see more spatter that what you would with a 15% blend.
Argon + CO2 (25%)
You’ll get the right gas blend for using short-circuit mode (not essentially spray transfer) on low-carbon steel when CO2 makes one-fourth of the mixture. Also, you can weld metals with a heavy base at high current levels. Stability of the arc, control over the weld pool, and characteristics of the bead usually remain good.
Argon + CO2 (40%)
While welding flux-cored wires, you want great arc stability and improved penetration, and the spatter needs to be reduced. Well, you got the right gas here.
Argon + CO2 (50%)
If you already have welded pipes, you know the short-arc method works well. It is a nearly perfect blend for the job, and you can stop worrying about other contaminants.
Now that I have described the possibilities of Argon CO2 mixtures, you might have noticed that two-gas blends are not without limitations. Some tri-mix blends containing higher amounts of helium and lower amounts of CO2 can help you minimize them considerably.
High helium with low argon and carbon content helps keep the corrosion resistance of the workpiece, increase heat input significantly, and reduce porosity. High argon and medium helium with low carbon yield better quality of weld and control over the puddle.
Alongside argon, helium can be the game changer when gas mixtures are in question. I hope you’ve found this article helpful. Ask any question regarding this topic and beyond. Happy welding!