The Basics of MIG Welding Shielding Gas

28 June 2022

As products become more complex, the general welding process has evolved into various types. One type of welding that fabricators utilise nowadays is metal inert gas (MIG) welding.

MIG welding is a welding process wherein an electric arc is formed between a consumable MIG wire electrode and the workpiece material. This electric arc then heats the workpiece and causes them to fuse, forming a weld pool. The wire electrode is utilised as a heat source and a filler metal for the welding joint.

The Significance of Shielding Gas

To ensure that the MIG welding can generate high-quality results, it should maximise the right shielding gas. Shielding gas, after all, prevents the molten weld pool from being exposed to elements in the atmosphere. Some of these elements are hydrogen, nitrogen, and oxygen. Without shielding gas, these elements can easily affect the porosity of the workpiece. They can also cause excessive spatter.

While all types of shielding gas can protect the weld pool from issues, their varying characteristics allow them to generate different effects on the workpiece. The variation of their qualities allows them to provide different weld penetration profiles, mechanical properties, arc stability, and many more.

Common Types of Shielding Gas

To date, there are four common types of shielding gas that can be used for MIG welding.

• Argon: Fabrication companies that want to achieve great weld quality, attain appeal, and reduce post-weld clean up can readily utilise the combination of argon (75-95%) and carbon dioxide (5-25%). The combination of these elements can ensure arc stability, reduced spatter, and puddle control. It also allows welders to carry out a spray transfer process, yielding higher productivity rates, more appealing welds, and a narrower penetration profile. Pure argon, however, should be used when processing non-ferrous metals like aluminium, magnesium, and titanium.
• Carbon Dioxide: Carbon dioxide is the most common reactive gas utilised in MIG welding. Even without adding an inert gas, welders can already maximise carbon dioxide as their shielding gas. One thing that makes this popular among welders is it is cheap. It can also provide a very deep weld penetration, making it suitable for welding thick material. Carbon dioxide, however, generates a less stable arc and more spatter. It is also restricted to short circuit transfer.
• Helium: Similar to argon, helium can also work with materials made from non-ferrous metals. However, it can also work with stainless steel. And when paired with argon, it can effectively yield a wide, deep penetration profile, making it capable of processing thick materials. Helium is also known for faster travel speeds and higher productivity rates as it can generate a hotter arc. One downside of helium is it is expensive. It also needs a higher flow rate as opposed to argon.
• Oxygen: Lastly, oxygen is a reactive gas that is maximised in ratios of 9% or less to enhance weld pool fluidity, arc stability, and penetration in mild carbon, stainless steel, and low alloy. One downside of oxygen is it can oxidise weld metal out of aluminium, magnesium, and copper.

To know more about MIG welding, you can call us at Kinetic Engineering.

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