Inert Gas Purging is one of the welding techniques that were developed to remove harmful gases and air from behind the weldment. A pneumatic purge system contains an inert gas such as argon or nitrogen. The purge gas is then forced through the weld puddle and into the surrounding area to push out any oxygen, which is a reactive gas, and create a clean environment for welding. This is necessary because welding creates a lot of slag and oxidation which impurities that lead to cracking.

Inert gas purging can be used on all three types of weld joints: fillet, butt and T joints. This process uses arcing or plasma blowing to get rid of the oxidization around the weld area. When one layer of inert gas is applied over another, it forces out any oxygen in the second layer which is why this process works so well. The hollow cathode arc forms a quick path for the back purge gas to move through without reacting with it under low pressure.

Plasma Arcing Inert Gas Purging Procedure – Video from Weld-Aid on Vimeo.

Inerting itself has been a common technique to create a clean environment for welding for a while. However, high voltage plasma arc is the best way to remove oxygen from the weld puddle. Using an inert gas purging system speeds up this process and ensures that the cleaned area around the joint has low pressure in it. Most of the welder is done by using an inert gas supply line, which provides pure gases or mixtures of gases with pre-determined ratios through low pressure (LP) regulators (orifice meters).

An RKI Instruments Low-Pressure Regulator. Image courtesy of Welding Tips & Tricks magazine .

By removing the oxygen surrounding the joint, you increase your chances of leaving behind quality welds that don’t crack over time. A clean atmosphere also enables you to see the puddle better and work more precisely.

On another note, inert gas purging is necessary for metal inert gas (MIG) welding. However, if you are using flux cored wire or an electrode-less machine, it’s not needed unless your metal requires a shielding gas. If so, use argon with 5 – 10% CO2 instead of 100% argon because this ratio of gases gives off less spatter than pure argon.

If you’d like to learn more about how to weld aluminum correctly, be sure to check out this article: https://en.wikipedia.org/wiki/Purging_(gas)