Besides oxygen, what is the most common gas used when welding?

The most common gas used when welding, aside from oxygen, is acetylene. This gas is particularly favored in oxyacetylene welding because it produces a high-temperature flame, reaching temperatures of around 3,500 degrees Celsius (6,332 degrees Fahrenheit). This significant heat output allows for effective fusion of metals, making it suitable for a variety of welding applications, including those that require strong joints or the ability to cut through thick materials.

Acetylene is widely used in welding processes due to its efficiency and versatility, particularly when combined with oxygen in welding torches. The flame characteristics can be adjusted for specific jobs by controlling the ratio of acetylene to oxygen, accommodating different welding needs and material types.

While other gases like propane and butane can also be used in welding applications, they do not achieve the same temperature levels as acetylene. Argon, on the other hand, is primarily used as a shielding gas in processes like TIG (Tungsten Inert Gas) welding and does not combine with oxygen to produce a flame in the same manner as acetylene. Therefore, acetylene stands out in the context of common welding gases, making it the correct answer.