Class 5 Boiler Practice Exam

Which of the following gases is commonly used as a shielding gas for GMAW?

1. Argon

2. Oxygen

3. Helium

4. Carbon dioxide

The correct answer is: Carbon dioxide

Carbon dioxide is commonly used as a shielding gas for Gas Metal Arc Welding (GMAW), primarily due to its ability to enhance the welding process. It serves several key purposes: it helps stabilize the arc, provides good penetration, and allows for a more fluid weld pool. Carbon dioxide is particularly effective in welding ferrous metals and, due to its relatively low cost compared to other gases, is a popular choice among welders. Additionally, the use of carbon dioxide often results in a deeper penetration than some other shielding gases, which can be advantageous for certain welding applications. While argon and helium are also utilized in GMAW for different purposes and metal types, carbon dioxide's role in providing sufficient shielding and overall weld characteristics makes it a frequent choice in this welding method. Argon is often employed for non-ferrous metals and certain specialized applications, while helium is typically used for higher heat and increased fluidity in the weld pool. Therefore, carbon dioxide stands out as a practical and effective shielding gas in many GMAW scenarios.