Shielding Gas for MIG Welding with Metals Complete Guide

Shielding Gas for MIG Welding with Metals Complete Guide,shielding gas for mig welding mild steel

Shielding gases make the welding process safe and highly productive by preventing atmospheric gases like Nitrogen and Oxygen (which make up 99% of the atmosphere) to interact with the molten weld pool, reducing the chances of spatter and porosity at the operation point.

Learning about the gas for MIG welding is highly important because MIG is the starting point for any beginner and from that, you begin your journey to other kinds of weldings. My Welding Yard presents you with a complete guide about gases like argon, oxygen, carbon dioxide so let’s begin!

Advantages of MIG welding with Shielding Gases

  • MIG welding with shielding appropriate shielding gases produce clean welds.
  • It prevents spattering on the arc.
  • There is no need to replace electrodes frequently.
  • If suitable gas is chosen according to the nature of the specimen, disposition efficiency can be increased.

Shielding Gas Selection Criteria

It would help if you considered these things while choosing suitable shielding gas for MIG welding.

  • The cost of gas
  • Preparation entails and arc stability
  • Nature of base material
  • Post-weld cleanup requirements and weld properties

Mostly Used Shielding Gases

This section will discuss widely used shielding gases for MIG welding, their costs, benefits, drawbacks, and on which metals they should be used.

Carbon dioxide (CO2)

CO2 is noncombustible, cost-efficient, and the only gas used in its pure form as shielding gas. It is denser than atmospheric gases and provides deep penetration making it a perfect choice for welding thick metallic pieces. Also, It reacts with the welding arc to produce an aura hotter than flame produced by a mixture of CO2 and Argon gas.

It connects metals strongly through bigger beads, and this feature makes it preferable for short circuit welding. Due to high-temperature flame, fast welding, and deep penetration, you will see the droplets of molten metal around the welded area and the arc causing more spattering and less stable arc. As a result of this messy process, there may be a need for post-cleaning.

During MIG welding, arc heat causes Carbon dioxide to disassociate into Oxygen and carbon monoxide, released into the air. The latter may be hazardous to the welder. When CO2 is used as shielding gas, it produces fumes and smokes during its working. You must not use this gas in welding thin metal strips with low Amps as it can form holes in the frame. See Also: Best MIG Welder 2021

CO2 can be a suitable choice when you have a low budget, and you are not concerned about aesthetic finishing or welding area is not on the face structure or machine surface. For instance, you can use it in welding your car’s body where the welded part is not prominent or is underlying.

CO2 is the best choice in shielding welding arc for mild steel.

Argon (Ar)

It is referred to as ‘the big A’ argon gas in the industrial gas business. It was the first inert gas used at the beginning of the evolution period of shielding gases. This gas is an optimal choice for welding gas when narrow penetration is required.

It is a highly inert gas and sustains its non-reactive nature even at high welding arc temperature like 4000 Fahrenheit. This feature makes it non-oxidizable therefore, it does not affect the chemical composition of the metal.

It is commonly used when welders are concerned with the aesthetic aspect of materials, better filler wire transfer, seamless and durable welds, and reduced post-weld cleanup requirements. Moreover, it is also a base gas for other mixtures used for shielding the arc in welding. Being non-toxic and non-flammable, it is not poisonous, and it won’t burn.

Argon comes in compressed tanks, and you need to be careful when dealing with Argon in a confined area. Since it is 38% denser than air, there must be proper ventilation for safety purposes if it leaks out. Mostly, Argon 4.6 is used for welding purposes.

Sometimes welders use their mixtures with other gases as per condition requirements. Ultra-high pure or medical grade argon might not be needed for MIG welding. Argon is commonly used in TIG welding.

Showing you the other side of the picture, Argon is highly expensive, and you must not go for it if you have a short budget. Most of the welders don’t use Argon as shielding gas because its higher concentration decreases the arc’s penetration rate, and you have to maintain low pressure of the gas at the welding spot, so more time is required. Well, you can keep the pressure of a gas by using a regulator.

Pure Argon is used in the welding of non-ferrous materials like aluminum, magnesium, titanium. It is not acceptable to use 100% Argon when the metal being welded is mild or stainless steel. It often produces an unattractive weld with a tall and narrow bead with a weld-weakening undercut. Mild steel MIG welding with Argon makes the metal lose its ductility as welds are weak and brittle. The best shielding gas mild steel is carbon dioxide.

Helium (He)

Helium can also be used as a shielding gas in MIG welding for fast process. It is also an inert gas with high ionization potential; hence, the high voltage must start the arc. It is used in both TIG and MIG welding.

Owing to its high thermal conductivity, it produces a hotter flame and has a faster metal transfer rate than Argon. It has a density of 0.00018 grams per mL, so being lighter than air requires a high flow rate.

Helium prevents oxidation in MIG welding of non-ferrous metals like stainless steel or copper alloys. It forms an energy-rich flame but makes the arc less stable than Argon. Though it makes a broad and deep penetration profile, it is not recommended on a bigger scale when dealing with high volume production because of its high costs and expensive proceeding.

Like Argon, pure Helium is also not suitable for shielding the arc for steel as it makes an erratic arc and increases spatter.

Oxygen (O2)

Oxygen proves to be a reactive shielding gas. It is not used in pure form. Instead, it is used in small quantities as an additive in shielding gas mixes up to 9 percent. It is an oxidizing agent, and it is better not to use it while working on aluminum, magnesium, and other exotic metals Chances of slag formation increase in its presence.

The nature of the material must be kept in mind before using Oxygen because increased Oxygen flow can cause the oxidation of electrodes and lead to porosity and brittleness in the affected area.

The mixture of Gases

To customize the shielding gas properties like flow rate, metal transfer, penetration, reduce spatter, and post-weld cleanup, welders use the inert gases in a specific ratio.

Argon and Carbon dioxide Mixing

Argon and CO2 mixture is a widely used gas mixture for shielding in MIG welding. C-25 mixture comprises 75% Argon and 25% carbon dioxide. It provides improved arc stability, puddle control, and much reduced spatter compared to pure carbon dioxide, and moreover, it has a moderate cost. Experts recommend using this shielding mix at a pressure of 20 psi at the welding arc.

You can change this ratio depending on your need for better finishing or in-depth penetration requirements. Shielding mix with more Argon percentage will help neat welding with better quality. For smoother beads, welders also use 85%-25% mix.

Keep in mind that a higher concentration of Argon means a more expensive combination. It is also called the ‘C15’ mix and is useful for carbon and low alloy steels with maximum productivity in short circuit mode and suitably high deposition rates. Mixed gases are also used in the spray transfer process. Also during welding, keep yourself protected with an auto darkening welding helmet.

Trimix gas for MIG Welding

A unique mixture of Helium, Argon, and carbon dioxide is used in an approximate ratio of 85:10:5. This combination is mainly used in MIG welding for stainless steel because of its low thermal conductivity and cool short circuit transfer.

MIG Welding Gas Containers

Welders might find it challenging to estimate their need for MIG welding gas requirements because they don’t want to run out of gas during work and gigantic tanks are hard to manage and store. Hers is a short guide for them.

If welding is your hobby or you need a backup as a housekeeper, you can keep a 40 or maximum 80 cubic feet tanks of Argon or MIG gas mix. The 40 cubic feet tank is easily portable. Keep them filled. There is a tip: the larger tank will cost less in refilling.

Because of its excessive use, Carbon dioxide is sold in weights, and there are no particular tank specifications.

For professional and high-volume production, you should go for a 125 cubic feet tank. The gas suppliers usually use these tanks.

Duration of Tanks

These tanks can last for different periods. Their duration depends on the flow rate at which the gas or shielding mix is being used.

Gas welding time (hours) = tank volume in cubic feet/flow rate in cubic feet per hour

This equation can estimate because the flow rate may vary due to temperature or leakage in the tank.

Furthermore, you can know whether you are running out of your shielding gas or not by using a pressure gauge on regulators.

MIG Welding Gas Prices

MIG welding gas costs depend on their availability and processing before they can be used. Buying a Q tank filled with pure Argon (100% Argon) can cost you up to $230. A 150 cubic feet tank of Argon can cost around $350. You can avail of 80 cubic feet Argon tank (with air gases) for an estimated $185.

A tank refill can cost you from $40 to $50. An 80 cubic feet C-25 tank’s worth is about $315, with a refill costing up to $75. Crude helium costs around $4.29 per cubic meter, which means 80 cubic feet of Helium will be worth $344. It is expensive because it occurs underground as a mixture with other natural gases and requires proper processing to get its pure form.

These gases are available online. Also, you can find carbon dioxide in any gas station near you. You can use carbon dioxide or gas mix for portable MIG welders.

Gas Flow Rate for MIG Welders

Usually, you can keep the flow rate of shielding gas from 12 to 14 lpm (liters per minute) or 20 to 25 cubic feet per hour. This flow rate is set on the tank’s gas regulator to control the gas availability at the welding arc during the process.

Gas settings for MIG Welders

For a smooth flow of shielding gas, there are some steps to ensure before you start welding:

  1. Set the gas bottle in the holder to secure it.
  2. Check the gas regulator’s hoses and replace them if you find any damage to stop gas leakage.
  3. To remove the dirt on the valve, open it quickly and close it immediately.
  4. Fix the gas regulator to the gas tank/bottle’s threaded valve area and tighten the locking nut.
  5. Set the regulator to the desired value and turn on the MIG welder.
  6. For activation of the gas valve, press the trigger of the MIG gun. The reading on the left gas regulator should read between 25 to 30 cubic feet- hours. If not, you can rotate the knob below it to set the reading.
  7. Trim the excess wire that extended from the nozzle while you were setting the gas regulator reading.
  8. Adjust the gas pressure according to the requirements.

Frequently Asked Questions

How much is a bottle of gas for a MIG welder?

A bottle of MIG welder shielding gas varies in costs. It depends on the amount and type of gas. Argon and Helium bottles are expensive and can cost up to $350 per cylinder.

How do I calculate gas for a MIG welder?

You can approximate your gas needs by keeping in mind that the gas flow rate is 25 to 30 cubic foot-pounds per hour on average.


Summarizing this article, you need to select the appropriate shielding gas for MIG welding depending on many factors like the thickness of base material, the amount of material on which you are working, the penetration requirements, and what kind of finished weld do you want. We hope this article helped you find answers to your queries if anything you want to add just use the comment section.

Hello Everyone, I am James from Kentucky and been into this welding fiasco for 13 years in that time I have worked as a private welder and did most of the auto restoration work. In this recent, COVID-19 outbreak I decided to start a welding blog and share welding tips along with product reviews.

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