MIG Welding Gas Guide: Best Options for Stainless Steel & Aluminum

MIG welding (inert gas welding) is a very popular welding method that produces strong and clean welds in a very short time. It is very easy to learn. The quality of the welding matters a lot.

It not only depends on the quality of the weld but also on the type of shielding gas being used. Shielding gas protects the melted metal from contamination. It prevents the molten metal from reacting with the oxygen and other gases in the air as they can weaken the weld.

The type of shielding gas depends on the metal you are using. The two common metal materials are stainless steel and aluminum. Stainless steel is very strong. It does not rust easily. Aluminum is extremely lightweight and catches heat very quickly.

If you are dealing with stainless steel metal, then a mixture of CO2 and argon is best. Sometimes helium is also added to it to produce better performance results. For aluminum metal, the best option is pure argon.

Adding helium to it can help in deeper penetration especially when you are dealing with thicker metals. In this article, we will talk about the best shielding gases for MIG welding for aluminum and stainless Steel.

Basics of shielding gas in MIG welding

There are many gases present in the surroundings. Shielding gas protects the molten metal from coming in contact with oxygen, nitrogen and other gases in the surroundings.

If you don’t use shielding gas then weak welds can produce. The shielding gas forms a protective layer around the welding pool when it is supplied through the welding gun. By using this, it can help in maintaining a stable arc. It also improves penetration and reduces spatter.

There are different types of shielding gases but the right shielding gas should be chosen according to the metal being used. Common shielding gases are CO2, argon and helium.

MIG welding gas for stainless steel

1- Challenges of welding stainless steel:

Stainless steel has unique properties. One major issue when you are using stainless steel is oxidation. It reacts with oxygen present in the air quickly. This can cause discoloration and weaker welds.

Another major issue with stainless steel is that it stores heat more quickly than other metals. It increases the risk of wrapping and changing the metal’s shape. Excessive spatter can also result. This will make the cleanup very difficult.

2- Best shielding gas options for stainless steel:

Argon and carbon dioxide mix:

Argon and carbon dioxide mix shielding gases are the most common choice. The common ratio that is used is 98% argon and 2% carbon dioxide or 90% argon and 10% carbon dioxide.

By using argon you can get smooth and clean welds with minimum spatter. You can improve penetration by using CO2 but excessive use of it can cause oxidation.

Tri mix gas:

For producing smooth, strong and high-quality welds, tri-mixed gas like 7.5% argon, 90% helium and 2.5 % CO2 is used. Helium is ideal for welding thin stainless metal sheets by increasing the heat input. It gives you better arc quality and deeper penetration.

3- Choosing the right gas based on application:

The best choice of shielding gas depends on the thickness of the metal and the welding position.

If you are working on thin stainless steel sheets, then use 90% helium, 7.5% argon and 2.5% of CO2.

If the working is on general stainless steel metal, then the preferred gas is 98% argon and 2 % CO2 mix. If you need stronger penetration use 90% argon and 10 % CO2.

MIG welding gas for aluminum

1- Challenges of welding aluminum:

Aluminium has very high thermal conductivity. This makes it very difficult to maintain a stable arc and causes the heat to spread very quickly. One other issue is porosity.

It happens when the gas gets trapped in the weld and creates small holes.

Aluminium also has another problem. It forms an oxide layer on its surface and this layer must be removed because it can lead to defects.

2- Best shielding gas options for aluminum:

100% Argon:

Pure argon is the most common and safe choice for welding aluminum metal. The reason for this is it provides a stable arc, smooth weld bead and minimal splatter.

It prevents the problem of oxidation which is very common in aluminium metal. It works best for thin to medium-sized sheets.This results in good penetration without the problem of overheating the metal.

Argon and helium mix:

If you are working on thicker aluminium sections 75% argon and 25% helium is recommended. This is commonly used in industrial words because it produces stronger welds. Helium is more expensive than argon.

3- Choosing the right gas based on application:

If you are working on thin aluminium sheets then 100% argon is the best choice.

For working on thick aluminum, argon and helium mix is ideal because they help in deeper fusion.

Factors to consider when choosing MIG shielding gas:

Material type and Thickness:

Different materials require different shielding gases. Choosing the wrong shielding gas can result in ineffective results. For example, stainless steel works best with an argon CO2 mix.

Welding position:

Welding Position also varies according to the shielding gas. For example, some gas mixtures are ideal for vertical or overhead welding.

Cost and availability:

Some gases are cheap and some are expensive. Choose the gas according to the material type and your budget.

Common mistakes to avoid in MIg shielding gas selection

Choosing the wrong shielding gas for the metal:

For each metal, there is a specific type of shielding gas. It is very important for you to match the gas with the material. For example, using CO2 alone can cause weaker penetration in stainless steel.

Incorrect gas mixture ratio:

Choosing the incorrect gas mixture ratio can produce weak welds. For example, if you choose too much helium while welding aluminum, it can overheat the weld.

Low or high gas flow rate:

If you use too little gas it can result in porosity. On the other hand, if you use too much it can result in wasting resources.

Ignoring gas purity:

Always make sure that the gas is pure without any contamination because it can produce weak welds.

Conclusion

Choosing the right shielding gas is a very significant step in the welding process. You should consider the factors like material type and gas flow rate while welding. Avoiding mistakes and using the correct gas will surely help you get the desired results.