What Is Gas Metal Arc Welding Process?

The emergence of gas shielded arc welding process can be traced back to the 1920s. However, due to limited research, these technologies did not become commercially viable until the 1940s and 50s. The initial driving force for research was World War II. Over the past 50 years, the industrial gas industry has made significant contributions to the welding industry through the production and purification of different gases and gas mixtures. Today, people are still conducting extensive research on new gas mixtures and their impact on welding.

The gas basic principles of gas metal arc welding process

The basic purpose of a protective gas is to keep nitrogen and oxygen in the atmosphere out of the molten pool when it cools. In the process of developing the GMAW welding gas process, CO2 was chosen as the protective gas. This choice was the result of an analysis of the gases produced by welding electrodes during the process of protecting the metal arc. Researchers found that during the shielded metal arc welding process, CO2 was the main gas in the protective layer surrounding the molten pool. In some cases, this gas is still the preferred gas for gas metal arc welding process and FCAW. The GTAW process has different demands than the gas metal arc welding process. This process requires a truly inert protective gas, and before the appearance of argon (Ar), helium gas was the only inert gas available at that time.

The influence of argon

Argon, known as "Big A" in the industrial gas industry, is an inert gas. This means that it does not oxidize and does not affect the chemical composition of the welded metal. Pure argon cannot be used for gas shielded metal arc welding of steel because the arc becomes too unstable. Therefore, an oxidizing gas component is used to stabilize the arc and ensure the smooth transition of the metal during the welding process. This oxidizing component can be CO2, oxygen (O), or a combination of these gases. The amount of added oxidizing component will depend on the type and application of the steel.

The arc in gas shielded metal arc welding can be divided into three parts: arc plasma, cathode area, and anode area. In gas metal arc welding process, when the electrode forms the positive pole (anode), the cathode area serves as one or more cathode points on the workpiece. The addition of an oxidizing agent is necessary to stabilize these cathode points; otherwise, the arc will flicker all over the workpiece surface, resulting in spatter and irregular welds. Using only CO2 and argon gas usually offers advantages. One advantage is that the geometry and appearance of the weld seam are slightly improved compared to Ar-O mixtures. Another advantage is improved joint penetration, especially on the backside.