MIG (or GMAW) is a welding method that requires the use of shielding gas. Shielding gas (or welding gas) protects the molten weld pool from the air contamination and ensures the solidity and quality of the weld seam. The most common welding gasses used in MIG welding are argon, helium, oxygen and carbon dioxide. Out of all four, two are inert (argon Ar and Helium He) and the other two are reactive (oxygen O₂ and carbon dioxide CO₂). Sometimes, welders use welding gas blends to weld certain metals or for reasons such as cost. Let’s have a closer look at the use of each gas in MIG welding.

 

Choosing the right shielding gas for MIG welding

 

MIG welding with argon (Ar)

Pure argon is great for welding non-ferrous metals such as aluminum, titanium, copper, magnesium and nickel. An argon/helium blend is also great for welding aluminum with a MIG welding machine.

 

However, pure argon is not the best choice to weld steel or stainless steel as it has a low penetration rate. When MIG welding with pure argon, filler metal remains on top of the steel, resulting in a weld bead being “elevated” above the base metal. That’s why it is recommended to use a blend of argon and carbon dioxide or argon and oxygen to weld steel and stainless steel. 

 

MIG welding with helium (He)

Unlike argon, helium provides better weld penetration thanks to the hotter arc it produces, making it a great shielding gas for welding thick aluminum. 

 

However, helium is much lighter than argon and can easily float away from the weld pool, so you need to double the welding gas flow rate in order to ensure enough shielding. 

 

Helium is sometimes mixed with argon to make it more affordable. 

 

MIG welding with oxygen (O₂)

Oxygen is often mixed with argon and carbon dioxide to weld low alloys, mild steel and stainless steel as it provides good penetration and arc stability. It’s important to remember that the maximum content of oxygen in a gas mix is up to 9%. However, oxygen is not intended for use with aluminum, copper and magnesium as it causes these metals to oxidize. 

 

MIG welding with carbon dioxide (CO₂)

Carbon dioxide is the most commonly used welding gas among hobbyists thanks to its affordability. However, the use of CO₂is only limited to steel. It is not suitable for welding metals like aluminum, titanium, copper, magnesium and nickel. 

 

Pure carbon dioxide is great for welding thinker metals thanks to its good penetration level. However, CO₂can only be used in the short circuit metal transfer method. To learn more about short circuit filler metal transfer methods, read our blog on how to adjust a MIG welder’s settings.

 

Gas blends are also commonly used in welding. Below is the chart with the most commonly used gas blends.

 

If you need a reliable shielding gas supplier, Lock 8 is the go-to place. We carry a selection of different welding gasses and are capable of supplying large construction sites, small industrial shops or small home-based projects. Visit our website to browse the entire selection of welding equipment we offer or contact us to inquire about a product of your interest today.