Last updated on June 21st, 2023
MIG welding is a popular choice because of its versatility and ease of use. It is one of the most widely used welding methods in the world.
But what most people don’t realize is that gas plays a crucial role in achieving high-quality welding results in MIG welding.
Shielding gas is not only responsible for protection against contamination but also serves other functions. Also, there is no universal gas, and you have to select a specific gas for a specific purpose.
In this article, I will be discussing the importance of gas in MIG welding and exploring commonly used gasses along with their applications in this process.
Let’s dive into the valuable details that can help you make informed decisions.
The Significance of Shielding Gas in MIG Welding
MIG welding uses an electric arc to create a fusion between the welding wire and base metal. However, the weld pool, during the process, is susceptible to atmospheric contamination.
That’s where the shielding gas comes in. It protects the weld pool from contaminants like oxygen, nitrogen, and moisture, which can negatively impact the quality of the weld.
The shielding gas acts as a protective barrier against the contaminants. Hence, it creates a controlled environment around the weld. It ensures a clean and stable environment for the welding process.
The shielding gas is also responsible for reducing the oxides to some extent and blocking the oxygen from reaching the weld pool. It works in conjunction with the electric arc and welding wire to enhance the quality of the welds.
Hence, it ensures proper fusion and penetration of the weld which in turn ensures high-quality welding results.
Commonly Used Gasses in MIG Welding
MIG welding commonly uses a mixture of argon and CO2, but it is not a universal gas for all applications of MIG welding.
Let’s take a deep dive into the most commonly used gasses in MIG welding.
It is the most versatile shielding gas that is known for its effectiveness in a wide range of applications. Being an inert gas, Argon doesn’t interact with other elements.
It provides excellent coverage and stability to the weld pool, which means it is suitable for use with both thin and thick materials. The gas is easy to ionize, which means it can handle long arcs at low voltages easily.
Argon is well-suited for welding non-ferrous metals such as aluminum, copper, and stainless steel. The inert properties of the gas will prevent the formation of oxides on these metals, resulting in clean and high-quality welds.
Adding to this, argon is also used in applications where a narrow and precise weld bead is required especially in industries like automotive, aerospace, and electronics industries.
Using 100% argon is suitable for welding aluminum, magnesium, titanium, copper, and nickel.
One thing you must know is that the cathodic cleaning action of this gas removes the surface oxides on the base metal which makes it perfect for welding aluminum.
The following parameters are recommended for argon gas in MIG welding:
- Adjust the flow rate according to the welding project and the diameter of the nozzle. Flow Rate of 20-25 cubic feet per hour (CFH) is commonly recommended.
- Use appropriate nozzle size to maintain adequate shielding gas coverage. The smaller nozzle size provides better gas control while the larger size provides more coverage.
- The distance between the nozzle and the weld pool should be kept to a minimum. A distance of 3/8 inch is recommended for maintaining ideal gas flow.
On the downside, you should not use argon for welding steel or stainless steel. If you use pure argon, the penetration and fusion are low. The arc will be cold which means you will form tall beads.
That is why a blend of argon with other gasses is required for welding such materials.
Carbon Dioxide (CO2) is another widely used gas in MIG welding. CO2 is an active gas, not an inert gas, because of this the process is often named Metal Active Gas (MAG) Welding. But there is no difference, so it is considered in MIG welding.
Also, CO2 is the only active gas that can be used in pure form in MIG welding.
Unlike Argon, CO2 readily reacts with the weld pool which enhances the welding process and provides deeper penetration.
The gas is responsible for generating a hotter arc, which makes it perfectly suitable for welding thicker materials and achieving better penetration.
CO2 has tons of industrial applications and is also used in construction and fabrication projects. The gas is well-suited for welding carbon and low-alloy steel. The gas promotes better fusion and also ensures better-quality welds.
CO2 is the most affordable gas in MIG welding and is a popular choice because of its cost-effectiveness.
Here are some things you should keep in mind to use CO2 effectively in MIG welding:
- When you are using CO2 as a shielding gas, you need to make some alterations to voltage and wire speed to get the best performance. High voltage and wire feed speeds are required to maintain a stable arc.
- CO2 performs optimally well in both flat and horizontal welding positions. However, when you are welding in the vertical or overhead position, you cannot simply use just CO2. You will need to use a blend of this gas with another.
On the downside, CO2 creates a less stable arc and causes much more spatter as compared to the other gasses. Also, it is impossible to weld non-ferrous metals with CO2 or mixtures of CO2.
Additionally, working with CO2 is limited to short-circuit, metal transfer welding mode.
This is a perfect blend that combines the best characteristics of both gasses to improve arc stability, reduce spatter and enhance the welded beads’ appearance.
The addition of CO2 in argon helps in improving the penetration and speed while reducing the welding spatter which was a common issue when using just CO2.
Commonly used argon-CO2 blends include a mixture with ratios such as 75% argon and 25% CO2 or 80% argon and 20% CO2.
The first mixture is ideal for the best balance of arc stability, spatter reduction, and penetration for welding carbon and stainless steel.
However, these ratios are not absolute. You can adjust them based on specific welding requirements to achieve the desired results.
Keep the following factors in mind to achieve the best results when using this blend:
- When you are welding thicker material, you will need a higher concentration of CO2 in the mixture to ensure better penetration.
- When welding thinner material, you can increase the concentration of argon to reduce the spatter, improve arc stability and achieve better-looking welds.
- You must adjust the gas flow rate according to the specific requirements of the project. Since you are using a blend, it will be much different from the commonly used flow rate.
Specialized Gases for Specific MIG Welding Applications
Besides the above-mentioned commonly used gasses, there are also some other gasses that can be used in MIG welding to achieve specific results.
Oxygen is an active gas that can be added to the shielding gas mixture in MIG welding. You cannot use oxygen directly, but it can be used in a mixture to enhance welding penetration, especially when working with thicker materials.
This gas can be blended into CO2 or Argon. However, you can only mix it in small concentrations and the maximum limit for mixing is 9%.
Oxygen will promote hotter arc generation and provide you with improved control over the weld pool. Hence, you will be able to achieve deeper penetration during the welding process.
Not only deeper penetration but also high welding speeds are also achieved by using oxygen in the blend. This mixture is used in a variety of applications including shipbuilding, construction, and heavy fabrication industries.
I mentioned that pure argon cannot be used for steel but when a small concentration of oxygen is added, it significantly improves arc stability and enables you to use the bend for steel and stainless steel.
While it is a very advantageous gas, it is also a very dangerous one. It requires careful handling, and you must take certain precautions to ensure safe usage.
Here are some of the things you should keep in mind when using oxygen in the shielding gas mixture:
- Ensure that the workspace has plenty of ventilation which will significantly reduce the risk of fire hazards.
- You will have to carefully monitor and maintain a controlled and precise amount of oxygen in the mixture. Excessive concentration of oxygen can lead to oxidation or porosity in the weld.
- Never work without Personal Protective Equipment (PPE), especially when using this blend because of its highly flammable nature.
On the downside, oxygen causes metal oxidation. So, you must never use it for aluminum, copper, or magnesium.
When you need to amplify the heat and energy in the welding process then you can add Helium to the shielding gas mixture.
The gas is much lighter than argon but has a higher ionization potential. However, it has low weight which means it will float away from the weld pool easily.
So, you will have to use a double flow rate when using helium as a shielding gas.
Not only will it improve the arc stability but also provide deeper penetration and improve welding performance.
The better ionization property ensures that the gas produces a much hotter arc when used, which is beneficial for welding thicker material.
Helium is commonly used in the aerospace and automotive industry. It has the ability to control the welding process in a better fashion which makes welding materials like aluminum and stainless steel quite efficient.
So, you will be able to get high-quality and precise welds. Here are some of the tips that can help you achieve the best results when working with Helium:
- Helium requires a higher gas flow rate as compared to the other gasses that are used in MIG welding. Hence, you will have to adjust the gas flow rate according to the specific requirements of the project.
- As the heat input will be increased because of Helium, you will have to modify the voltage and wire feed speed, and travel speed as well. Fine-tuning these parameters is a must to achieve the desired results.
- When using helium, you must ensure that the base metal is properly cleaned up before you start the welding process. There should be proper joint preparation including cleaning and fit-up.
On the downside, helium is an expensive gas and since you are using the double flow rate it will cost you even more. That is why it is almost never used in pure form and is always blended with other gasses.
Tri-Mix Gases: Customizing for Unique Needs
Professionals and experienced welders also have a unique approach to getting specific welding requirements by mixing three gasses together known as Tri-mixing.
The tri-mix gasses consist of a combination of argon, CO2, and oxygen/helium. This mixture provides a wide range of possibilities for achieving precise and high-quality welds.
You can try different tri-mix combinations to achieve specific welding objectives.
For example, a mixture of argon, CO2, and oxygen will enhance penetration and control while a mixture of argon and CO2 with helium will provide a better balance between heat input and arc stability.
Here are some of the most common tri-mix gas mixtures that are used in MIG welding.
10% Ar + 85-90% He + 2-5% CO2: Ideal for stainless steel MIG welding.
Ar + CO2 + O2: Used for welding low-alloy steel and some stainless-steel alloys.
So, the former is more suitable for welds that require deeper penetration and better-quality weld while the latter is more suitable when high welding speed and quality are desired.
When working with tri-mix gasses, you must consider some important factors.
- Since you are mixing three different gasses, you will need to do some experimentation and fine-tuning before you find optimal gas ratios for specific welding applications.
- The gas mix will also require you to make adjustments to voltage, wire feed speed, and travel speed. You will need a lot of practice to get these parameters right.
- Once you get these parameters, you can instantly set them the next time and each time after that.
- Different tri-mix combinations will have different effects on various materials. Hence, you must be careful not to increase the concentration of one gas too much which could have a harmful impact on a certain material.
How to Select a Shielding Gas for MIG Welding
While selecting the ideal gas for your welding job, you will have to take a few important factors into account. Let’s take a look at them in detail.
Type of Metal
No gas is compatible with all metal types and similarly, no metal is compatible with all gasses.
So, the very first factor that impacts your choice of shielding gas is the type of metal you are welding.
Let’s discuss each metal one by one:
While welding steel, you can use a lot of combinations of gasses. But using each gas will have its own pros and cons.
It is best to use a blend of argon with carbon dioxide or oxygen for welding carbon steel. Using this mixture will improve arc stability.
Using this blend will produce an even iron oxide layer on the surface which is easier for the electric arc to follow. Hence, you will be able to weld with perfect control.
It is important to note that you will only have to use a small concentration of oxygen as compared to CO2 because oxygen is a much stronger oxidizer.
However, it also means that the welding wire with more deoxidizers has to be used to prevent porosity in the welded metal.
When welding thin sheets of steel, you should not use 100% CO2 because it will burn through the thin sheet and distort it.
On the other hand, when you are welding thick sheets of steel, you can totally go for 100% CO2 to get deeper penetration.
You cannot use Argon for welding steel because it causes iron oxide to attract the arc which causes irregularity in the arcs path and weld deposits.
Stainless steel is much more complex to weld in MIG welding because of the shielding gas choice. It’s mainly because you cannot use a single inert or active gas for the job.
So, you will have two options, either you can use a two-gas blend or a tri-mix blend to get the job done.
Usually, you can use an Argon-CO2 blend which works for most people, but it is not perfect. Why?
While this blend is perfectly suited for most other metals, it will deposit carbon in the joints of stainless steel which will cause the steel to lose its corrosion resistance.
So, if you are not working on a critical joint, then the combination might just be right for you. But when you are working on a sensitive joint, you cannot risk losing the corrosion resistance, then you will have to change the blend.
You can still use the Ar-CO2 blend, but you will have to reduce the concentration of CO2 below 5%.
However, if you don’t mind switching gas tanks then using oxygen blended with argon will give you much better results. You can only use a max of 2% blend, but it would be enough and provide you with a much better travel speed than the above mixture.
If you are looking for the best shielding gas for MIG welding Stainless Steel, then the ideal choice is a tri-mix blend of Helium-Argon and CO2.
Using a tri-mix blend will provide you with deep penetration, a clean bead appearance, a stable arc, and perfect control of the welding process.
The generally suggested concentration for the tri-mix blend is 10% argon, 85-90% helium, and 2-5% CO2.
Having said that, even this tri-mix blend might not be suitable for all alloys of stainless steel. Stainless Steel comes in many grades and numerous types. Each of them will require a different blend to get the desired welding results.
Experimentation and fine-tuning can get you the right mixture you need for the job.
Aluminum is a strictly inert gas welding metal. You cannot use any of the active gasses for welding aluminum because it would result in a disastrous weld.
So, in technical terms, you can MIG welds aluminum easily, but you cannot MAG (Metal Active Gas) weld aluminum.
Hence, carbon dioxide and oxygen are a big NO-NO.
Using 100% argon or a blend of argon and helium is the ideal choice. Most of the time, you won’t need anything other than argon for the job.
If the metal sheet or pipe is thick, then you can preheat it to avoid purchasing a helium gas cylinder to create the blend.
However, if you want to use the blend, it will provide you with certain benefits. You can maximize the penetration capability of your MIG welder with limited amperage.
You cannot use pure helium for MIG welding aluminum. It will have the same effect on aluminum as carbon dioxide has on carbon steel.
So, when welding thicker sheets of aluminum, you can use the blend of argon and helium to get higher heat input and better penetration. When welding thinner sheets, you can stick with just argon.
Thickness of Metal
From the above guide, you might have noticed one thing. Each time the thickness of metal changed from thick to thin or vice versa, you had to change the shielding gas or use a bend.
So, it must be clear to you that the thickness of the metal plays a significant role in the choice of shielding gas.
For welding Carbon Steel, you can use a mixture of 90-95% Argon and 5-10% CO2 for 3/32 inch to 5/8 inch of metal thickness. However, for thicker sheets. You will have to use a higher concentration of CO2 i.e., 75-80% Argon + 20-25% CO2.
The choice of shielding gas for stainless steel is quite tricky.
Generalizing it would be too difficult, but as a guide, you use 98% Argon + 2% Oxygen for 1/16 inch to ¼ inch metal thickness. You can also use a triple blend for the same or higher thickness i.e., 10% argon + 85-90% helium + 2-5% CO2.
For Aluminum, you can use 100% argon for thin sheets up to 3/8 inch. For thicknesses more than this, you can use a blend of Argon and Helium. The concentration of Helium will depend on how hot you want the arc to be. A 50-50 blend is considered ideal.
Shielding Gas Cylinder
Fortunately, you have a lot of cost-efficient choices when it comes to selecting a shielding gas cylinder for MIG welding.
You can buy or rent a gas bottle and you also have a choice between disposable and refillable bottles.
The disposable bottles are more suited for minor welding tasks and aren’t cost-effective in the long run. On the other hand, it is much more cost-effective to buy a refillable gas tank.
It is important to consider that purchasing a cylinder too small will require you to refill it again and again, which means frequent trips to the gas supply center.
So, in the long run, you will end up spending more money on a small cylinder than on refilling a big cylinder.
Cost of Gas
Shielding gas is not always cheap and of which budget becomes an important consideration when choosing shielding gas as a hobbyist or DIYer.
Inert gasses are more expensive than active gasses. So, getting argon would cost you much more than getting CO2.
We have already discussed the benefits and drawbacks of each gas, so I won’t get into that again.
The blends of Argon with other gasses also cost similar to the price of 100% argon.
Keep in mind that while using carbon dioxide might seem cost-effective, it will present you with certain other challenges which you won’t be able to get around if you are a beginner.
Always choose a gas that makes the welding process easier for you and gets you welds that are less distorted, stronger, and more reliable. Consider the money spent as an investment in the long run.
Safety Precautions and Gas Cylinder Handling
Proper handling and management of the gas cylinders are essential to ensure the safety as well as longevity of the gasses. You must store the cylinders properly in well-ventilated areas, and away from heat sources, direct sunlight, or flammable materials.
The best way to store the cylinders is in an upright position because it prevents them from tipping or falling.
You must always handle the cylinders with care and use proper lifting methods to avoid dropping or damaging them. Never roll the cylinders as it can cause damage to the valves.
Maintenance of the gas cylinders is also important. Always store them properly when not in use and make sure that there are no leaks.
If you are using bigger cylinders then you have to be extra careful, because any mistake and you might blow the whole area.
You might have to switch cylinders when using mixtures. To do that, you can create a proper setup at your workplace where you won’t have to go through much of a hassle to change the gas source to get the desired blend.
Frequently Asked Questions
Is MIG welding gas CO2 or argon?
MIG welding uses both CO2 and argon, as well as a mixture of both gasses. The choice will depend on the type of metal you are welding and specific welding requirements. Hence, no one gas can be called dedicated MIG welding gas.
Can I use CO2 for MIG welding?
Yes, CO2 is used commonly for MIG welding. It is a cost-effective choice and also results in deeper penetration during the welding of thicker materials. However, it results in more spatter compared to other gasses.
Do you need gas for a MIG welder?
Yes, gas is essential for MIG welding. It serves the function of a shield that protects the weld pool from atmospheric contamination while improving the quality of the weld itself. Hence, you cannot weld without gas in MIG welding.
What gas does a TIG or MIG welder use?
For MIG welding, commonly used gasses include Argon, CO2, or mixtures of the two. TIG welding typically uses Argon or Helium as shielding gas, and also their mixture with some of the other gasses.
Is CO2 cheaper than argon?
Yes, CO2 is generally cheaper than Argon. This cost-effectiveness is one of the reasons it’s often used in MIG welding, However, using CO2 in MIG welding also means you are opting for more spatter during the welding process.
Is Argon better than CO2?
One gas cannot be named better than the other as each comes with different properties and has its own applications. Argon ensures better weld quality and arc stability while CO2 has deeper penetration and is more cost-efficient.
To sum it all up, MIG welding commonly uses Argon or CO2 for welding purposes as well as a mixture of the two gasses.
There are also some other gasses that are used to achieve specific purposes in MIG welding. You can mix these gasses in argon or CO2 to achieve the desired results.
There is no one universal gas for MIG welding and each gas used comes with its own set of characteristics and results.
Hence, the choice of gas will ultimately depend on the type of material being welded and the specific requirements of the task.
If you have any questions, you can drop them in the comments section below and I will get back to you as soon as I can. Happy Welding!
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