Sunday, December 4, 2022

Mig Welding Gas (What Gas To Use For Mig Welding)


When you are into MIG welding, there are a few factors you need to get absolutely correct so that the welding is top-notch. Apart from the entire setup for MIG welding, the shielding gas plays a major role. Therefore, the choice of the shielding gas is critical, and there are different shielding gases available for MIG welding. The shielding gas is directly responsible for the quality of welding, productivity of the process as well as overall costing. We will discuss which gas is to be used for MIG welding.

What Is The Role Of Shielding Gas in MIG Welding?

The shielding gas in MIG welding prevents the electrodes as well as the molten weld pool from getting oxidized and impurities. Therefore, there is no need to replace the electrodes or no need to clean up the electrodes. Naturally, due to the absence of impurities, the welding is going to be efficient. Besides, there is no need to waste time in cleaning up the electrodes.

The shielding gas prevents oxygen, hydrogen, and several such reactive gases from coming in contact with molten weld pool. There will be no spatters and holes in the final product after welding. As a matter of fact, MIG stands for Metal Inert Gas where inert gas stands for shielding gas.

What Are The Shielding Gas Used In MIG Welding?

There are certain shielding gases that are commonly used in MIG welding. Generally, inert gases are used such as Argon and Helium. But there are reactive gases also used such as Oxygen and Carbon Dioxide. This is because different gases have different characteristics that make them useful for shielding. In fact, the blends of these gases are also used as shielding gases in MIG welding.

1. Argon

Since Argon has a higher density, it settles down and protects the molten pool. Argon can also sustain a long electric arc as it can get ionized easily. But when you are welding steel, it is not suitable to use Argon as the shielding gas. Instead, the welders use Argon and Carbon Dioxide as a blend as well as a blend of Argon and Oxygen. On the contrary, Argon is ideal for welding non-ferrous metals.

2. Helium

Helium is another inert gas, but it is lighter, and hence, it floats around too much. That is why welders prefer argon over helium. When using helium, you better supply more because they flow away from the pool. Hence, it is not economical, and there are many who prefer reactive gases over helium.

3. Carbon Dioxide

Even though CO2 is a reactive gas, it can be a shielding gas for MIG welding. This is because CO2 is readily available and economical. However, 100% of CO2 is not suitable as it makes the electric arc unstable. That is why it is not possible to weld non-ferrous metal with CO2. You can use it to weld steel only. In fact, pure CO2 is used for welding thick sections and joints.

4. Oxygen

Oxygen is generally blended with carbon dioxide and argon to use as a shielding gas. In such a blend, the oxygen percentage cannot exceed 10%. Otherwise, it can be the reactive gas instead of the shielding gas. A small percentage of oxygen actually stabilizes the arc. It is suitable for steel alloys, but it is not suitable for aluminum and copper.

5. Blend Of Shielding Gases

Rather than standalone shielding gas, in all practical cases, blends of shielding gases are used to derive their best properties. Here are the most popular blends of shielding gases used in the industry.

Argon and CO2 – Argon and CO2 are used in 3:1 ratio to balance arc stability, reduce spatter, and better weld penetration.

Argon and Oxygen – Only a few percentage of oxygen is used which is generally less than 5%. It stabilizes the arc, and it is widely used in welding carbon and low steel alloys. For welding stainless steel, less than 1% oxygen is used. In fact, argon, oxygen, and carbon dioxide are used as shielding gas blends.

Argon and Helium – When welding aluminum, copper, magnesium, and nickel, the best shielding gas blend has to be argon and helium. Argon and helium can be used in any ratio starting from 3:1 to 1:3.

The higher the percentage of helium, the thicker the weld will be and hence, as per requirements, the percentage is calculated. In fact, argon, helium, and CO2 are used as well for stainless steel welding. In that case, helium has the majority while CO2 percentage stays below 5.

How To Choose The Best MIG Shielding Gas?

The MIG shielding gas for welding is determined based on the metal type, the thickness of the workpiece as well as the overall cost.

1. Metal Type

Carbon Steel

You should not use pure argon gas for carbon steel. You should add a few percentage of CO2 or O2 to improve arc stability. A small amount of oxygen or carbon dioxide is better for arc stability. In fact, oxygen is better than carbon dioxide. If you want a deeper penetration, you should go for CO2 with argon. The ratio of argon to CO2 is 3:1. If you want less penetration, you should use 5% CO2 only. For thick steel workpiece, you can use pure carbon dioxide only.

Aluminum

For welding aluminum, you should use Argon gas or Argon + Helium gas. There should not be any reactive gas like CO2 and O2. Helium enhances the penetration and speed of welding. But helium should never overpower argon. However, pure argon gas should be perfect when you pre-heat up the aluminum workpiece.

Wire Feeding

If you are using a wire feeding method, you should use inert gas or a combination of inert gases. This means you can use pure argon as well as argon + helium.

Stainless Steel

The most complex material to weld is stainless steel. That is why you cannot use the usual shielding gas in stainless steel MIG welding. You have to use a blend of shielding gases to get the job done.

  • Two Gas Blend – You should use 75% of argon and 25% of carbon dioxide. This can get the job done but there can be less corrosion resistance. You can use argon with 2% of oxygen while some prefer 5% of carbon dioxide.
  • Three Gas Blend – You can use argon, helium, and carbon dioxide and they serve as the best shielding gas. The argon can be 10% while helium can be 85% and carbon dioxide can be 5%. The penetration will be great and so will the arc stability.

2. Metal Thickness

 

Selection Table For MIG Welding Shielding Gas:

Conclusion

We have stated everything you need to know about MIG welding shielding gas. We have explained the popular choices of shielding gas along with their properties. Similarly, we have stated the best shielding gas for different materials. There are also tables to choose the perfect shielding gas from the table based on metal thickness.



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