What happens if the GMAW process is used with AC current?

Using the Gas Metal Arc Welding (GMAW) process with alternating current (AC) can indeed lead to instability in the arc. GMAW is primarily designed to operate with direct current (DC), which provides a more stable and consistent arc. When AC is applied, the alternating nature of the current can cause fluctuations in the arc, leading to difficulties in maintaining a uniform weld pool. This instability can result in issues such as erratic wire feeding, variations in weld penetration, and an uneven weld bead.

While there are specific applications where AC can be beneficial, notably in aluminum welding, the general consensus is that for most GMAW operations, especially with metals such as steel, DC is preferred for optimal performance and stable arc characteristics. Therefore, the reasoning behind the assertion that GMAW with AC creates an unstable arc is valid and recognizes the inherent limitations of the process in this configuration.