Class 5 Boiler Practice Exam

Which of the following gases can be used as shielding gas for GMAW?

1. Oxygen

2. Helium

3. Argon

4. Carbon dioxide

The correct answer is: Carbon dioxide

The use of carbon dioxide as a shielding gas for Gas Metal Arc Welding (GMAW), also known as MIG welding, is common due to its effectiveness in providing a stable arc and improving penetration when welding different types of materials, particularly ferrous metals. Carbon dioxide is relatively inexpensive compared to other shielding gases, making it a cost-effective choice for many applications. In the context of GMAW, the role of shielding gas is to protect the weld pool from atmospheric contamination, which can negatively affect the characteristics of the weld, such as its strength and corrosion resistance. Carbon dioxide, while typically used for its cost and effectiveness, can sometimes lead to higher spatter levels when compared to other inert gases like argon or helium. However, it still provides good penetration and is often used in conjunction with other gases for blended applications. The other gases mentioned, such as oxygen, while they can be involved in various welding processes, are generally not used as shielding gases in GMAW due to their oxidizing nature. Oxygen can cause weld defects and compromise the quality of the weld. Helium and argon are inert gases that are also used in GMAW, but are commonly chosen for specific applications based on their different properties and costs; they don't have