How to MIG Weld with Argon

Argon is one of the most commonly used shielding gases in MIG welding. Argon is most commonly used in combination with oxygen and carbon dioxide, although pure argon is used for non-ferrous metals. Setting your MIG welder up for argon requires you to be fitted with the appropriate contact tip, ventilation equipment, and gauges.

Be forewarned: using the incorrect shielding gas in a given scenario can lead to frustrating weld defects time and time again, even if you do everything else right. You can prevent many headaches by selecting the preferred blend, which may or may not include mostly argon. In this article, we’ll cover those details and more so you can correctly MIG weld with argon. 

How to Set Up Argon for a MIG Welder

Shielding gas cylinders come in all kinds of sizes, from 20 CF to 300 CF. If you are doing a lot of welding with pure argon, you will certainly want to have a cylinder on the larger side. You can always get smaller cylinders for lesser-used gases. A welding gas supplier should be able to provide recommendations on the best set-up for your circumstances.

What Equipment Do You Need to Weld with Argon?

To kick off the set-up process, you will need to take an inventory of the equipment you have on hand. The set-up for welding with argon is the same as the set-up for MIG welding with any other type of shielding gas, but it is still important to briefly review a few things:

  • A chain to secure the gas cylinder: For your safety, the gas cylinder should be secured by a chain.
  • Gauges: Must be fitted securely to the cylinder; if you have any issues with your gauges or would like some that are easier to read, you can find a good one here
  • Contact tip: A properly sized contact tip is necessary for the shielding gas to carry out its function.

Choosing the Right Contact Tip

With everything else going on, it’s easy to overlook the importance of selecting the right contact tip for argon. Size selection is essential because argon is denser than oxygen and helium and slightly less dense than carbon dioxide. 

Of significance is the recess of the contact tip. “Recess” refers to the positioning of the contact tip within the nozzle of the welding gun. Electrode extension (wire recess) is directly impacted, with higher recess numbers corresponding to a longer wire stick out. If the wire is sticking out too far because of the contact tip, then the voltage will be greater, and the arc will be less stable. 

Here are the contact tips sizes that you should be using if you are using mostly argon as your shielding gas:

  • ¼” recess
  • ⅛” recess

Be sure to purchase contact tips that are listed as being able to fit your specific machine. This is information that should be presented in the operator’s manual for your welder, as is seen in the manual for this Lincoln welder. Alternatively, you can note your specific model number and search for its listing in a contact tip’s product description.

Set the Gas Flow Rate

There is definitely an upper limit to the argon gas flow rate in your MIG set-up. It is commonly believed that higher flow rates of argon will provide greater shielding of the weld pool. However, if the gas flow rate is allowed to become too high, then turbulence will occur. What essentially happens is that air bubbles contaminate the weld.

In most shops, a flow rate of 15 CFM (cubic feet per minute) is a good start, but in an especially drafty shop, the gas flow rate may need to be cranked up to 50 CFM. Many welding machines will come with a chart of recommended settings on the side of the machine and/or in the user manual. This would be an excellent resource to consult for these purposes.

In fact, the manufacturer’s recommended settings should take precedence over any other flow rates found online or in literature. The potential for turbulence (air contamination in the weld) is directly related to the nozzle diameter. Welding gun design also has a measured effect on gas flow rate recommendations.

There are some general recommendations as far as gas flow range for specific materials:

Protect Yourself from Fumes

Welding fumes should always be a concern, regardless of whether you are using a shielding gas. 

That being said, shielding gases themselves are generally not toxic or particularly dangerous. Inert gases like argon are not reactive and therefore do not pose a significant flammability hazard. However, they can cause the operator to suffocate due to their tendency to collect in confined spaces. Argon is of particular concern since it is denser than the surrounding air.

This is not to mention the inherent risks associated with fumes from the metals. It is recommended that you work in a well-ventilated area. If there is any doubt about a work area’s natural ventilation, then you should look into getting a utility fan or some other piece of equipment that assists in the ventilation process.

Storing Argon

Since argon is an inert gas, it doesn’t come with quite the stringent storage requirements you can see with more hazardous chemicals. However, this is not to downplay the importance of safely storing gas cylinders that can quickly become projectiles if they are not handled properly.

Here are some basic safety tips:

  • Make sure that your shop is well-ventilated.
  • Keep the cylinder upright.
  • The storage area temperature should never exceed 125 degrees Fahrenheit.
  • If you ever need to move the cylinder for any reason, use a hand truck.

How Long Does Argon Gas Last?

Given that a standard bottle of argon is 250 CF, you can expect to go through one cylinder of argon after ten or so continuous hours of MIG welding with a flow rate average of 15-20 CFM. So you will most certainly go through at least one bottle per week if you are welding every day. For refills, you can contact a local welding gas supplier.

Additionally, since it is chemically inert, argon gas comes with a recommended shelf life of 48 months. In other words, it is unlikely to go “stale” before you use it up.

When Should You Weld with Argon Gas?

Of course, before welding with argon gas, you should figure out when you can even use it. Since it has a relatively low thermal conductivity, 100% pure argon will not be effective for every base metal. 

When added to carbon dioxide and/or oxygen, argon does increase the functionality of these shielding gases in ways that are described in further detail below.

Aluminum and Other Non-Ferrous Metals

Whenever you are welding non-ferrous metals like aluminum, titanium, and magnesium, you will definitely need to use either pure argon or an argon/helium combination as your shielding gas. This is because argon and helium are both chemically-inert noble gases. If you use carbon dioxide, it will react with the non-ferrous base metal.

Using Argon in Combination with Helium

Although 100% argon is the most common choice for aluminum, there are instances in which having a little bit of helium blended in will help; this comes in handy when aluminum is thicker than ½ of an inch.

Using an argon/helium combination rather than pure argon for your shielding gas will increase the arc’s heat. There are several benefits of this: 

  • The arc voltage will increase by 2-3 volts.
  • There is generally less porosity.
  • The weld can be completed in a shorter amount of time. 

The drawback is that argon/helium welds require more post-welding cleanup than pure argon welds.

Argon/helium combo shielding gases can contain anywhere from 25-75% helium in content. Like argon, helium is another one of the noble gases; this means that helium will also undergo very few chemical reactions. 

Argon is the primary inert gas of choice because it is easier to start an arc.

Performing Butt and Fillet Welds

Fillet welds and butt welds are both types of weld joints that require a weld bead with a narrow profile. This is where using 100% argon as a shielding gas could certainly be advantageous since argon is known for having less penetrating power at the site of the weld compared to alternatives such as Carbon Dioxide.

Welding in Spray Transfer Mode or Globular Transfer

Using argon also has advantages for those planning to use Spray Transfer as their mode of transfer in MIG welding. Argon improves arc stability and reduced spatter, which is definitely a plus when looking to use a well-regulated transfer mode. 

In fact, neither CO2 nor helium alone can produce an axially-propelled spray arc that is controlled and spatter-free. If you try to use purely carbon dioxide or helium, you will notice a non-directed globular transfer.

For these purposes, argon is often combined with carbon dioxide (unless you’re welding a non-ferrous material, of course). Combinations vary widely, as anywhere from 75-95% of the shielding gas may be composed of argon. The higher the CO2 level, the greater the amount of spatter.

Argon and CO2 Mixtures for Carbon and Stainless Steels

Mixtures of argon and carbon dioxide are commonly used as the shielding gas for carbon steels. These welds can be completed with carbon gas alone, but this produces quite a bit of smoke and a rough weld. Argon is added to the mix to bring the welding process under control.

The most popular combination of shielding gases for carbon steel is commonly called C25, a mixture composed of 25% carbon dioxide and 75% argon gas. There is a wide diversity of other similar shielding gas combos available at welding gas supply stores. It is not uncommon for some amount of oxygen to be added to the argon-carbon dioxide blend.

The story is similar with stainless steel, with the biggest difference being that helium is used in a tri-mix rather than oxygen. The popular tri-mix in this case is 90% helium, 7.5% argon and 2.5% carbon dioxide. The shielding gas most frequently used for stainless steel is C2, which is 98% argon, with the rest being carbon dioxide.

Note: If you are wondering why MIG (metal inert gas) welding is often referred to as GMAW welding, this is why. GMAW (gas metal arc welding) is a more appropriate term for MIG welding since shielding gases like carbon dioxide are not actually chemically-inert.

Argon-Oxygen for Pulsed-Arc Transfer

A blend of 99% argon and 1% oxygen is used in pulsed-arc transfer. This is because this transfer mode requires a brief high current pulse of the appropriate magnitude and duration. At least 1% of the shielding gas mixture does need to be oxygen to stabilize the arc. If only argon is used, then a sufficient transfer of electrons will not occur during the process.

Welding Out-of-Position

If you are welding against the flow of gravity, then you may have a lot of trouble laying down a good weld bead; this is because oxygen shielding gas alone doesn’t really do the trick for out-of-position welding. Argon can make it a lot simpler for operators who are doing out-of-position welding.

The oxygen-argon blends are helpful for this type of welding since oxygen alone increases the puddle fluidity. The greater the fluidity, the higher the risk that the weld pool will start to get away from you when welding out of position.

Challenges with MIG Welding with Argon

Argon is not perfect. There are some challenges posed by using 100% argon. In fact, most of the time, you will be using argon in combination with one of the other shielding gases, particularly oxygen and carbon dioxide. 

Can You MIG Weld Steel With 100% Argon?

Say that you’ve found yourself in a situation where argon is the only shielding gas that you have. Can you go ahead and weld steel anyway? 

You may be able to complete the weld, but it won’t be easy. Also, the result will be a brittle weld. If you need a strong, competent weld, you are encouraged to hold off until you can get your hands on some oxygen or carbon dioxide.

The reason that 100% argon does not work well with steel is the lack of arc stability. During the GMAW welding of steel, the weld pool is the cathode (part of the arc that produces electrons), while the filler wire is the anode (part of the arc that attracts electrons). The presence of oxygen makes it easier for electrons to be delivered from the weld pool to the filler metal. This oxygen can come from either an oxygen shielding gas or as a by-product of carbon dioxide gas.

If you are going to try using 100% argon to weld either steel or stainless steel, you will notice the arc wandering a lot more. As long as it’s not a major project or a critical piece, then you may be fine.

Pure Argon is Ineffective on Thick Metals

Weld defects can be an issue for those using 100% argon. This is why pure argon is rarely used on base metals other than thin aluminum. Pure argon has a low thermal conductivity and is thus less effective when welding thick metals.

Go with an argon-helium mixture when aluminum is ½ of an inch or thicker. The purpose of the helium is to create a hotter arc capable of penetrating the aluminum; this doesn’t mean that it will be impossible to weld heavy plate aluminum with pure argon, but it will undoubtedly be a challenge.

A Non-Uniform Penetration of the Weld

One of the challenges or drawbacks to using argon as a shielding gas is that it will produce what has been described as a “finger-like penetration of the base weld.” What does this mean? The weld bead may be strong at its center but not along the sidewalls.

This likelihood of this unfortunate defect can be reduced if the operator adds a small amount of another gas to the shielding gas mixture. You may add 2-5% oxygen to the mix or 5-25% carbon dioxide.

Conclusion

Make sure that you have the right equipment for using argon BBC as a shielding gas. If you have already used other shield gases in the past, you will be fine using the set-up you already have. The big difference is that you will need to use a ¼” recess or ⅛” recess contact tip for welding with argon.

In summary, here are some of the most popular shielding gas blends with argon that you can choose from, depending on your project:

  • Pure Argon: When welding non-ferrous materials like aluminum that are less than ½” thick, you may use pure argon for welding butt and fillet welds as well.
  • Argon-Helium Blends: 25-75% helium may be included for welding thicker, non-ferrous materials.
  • 99% Argon-1% Oxygen: This is commonly used in pulsed-arc welding.
  • 25% Carbon Dioxide-75% Argon: C25 is a popular choice for welding stainless steel and carbon steel. Pure argon does not work on stainless or carbon steel.

If you liked this article, have a look at my other articles I wrote about the topic!

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Alexander Berk

A bit about myself: I am a certified international welding engineer (IWE) who worked in different welding projects for TIG, MIG, MAG, and Resistance Spot welding. Most recently as a Process Engineer for Laser and TIG welding processes. To address some of the questions I frequently got asked or was wondering myself during my job, I started this blog. It has become a bit of a pet project, as I want to learn more about the details about welding. I sincerely hope it will help you to improve your welding results as much as it did improve mine.

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