Which one among the following fuels is used in gas welding ?

Acetylene (C2H2) is the primary fuel gas used in gas welding, specifically in the oxy-acetylene welding process [1]. It is preferred because it produces the hottest flame temperature (approximately 5,720°F or 3,160°C) and has the highest flame propagation rate among common fuel gases. This high intensity is essential for melting metals like steel, copper, and aluminum efficiently. While other gases like propane, butane, or methane (natural gas) are used for heating and cutting, they are generally unsuitable for welding because they lack the reducing shield required to prevent oxidation in the weld puddle. Acetylene's low hydrogen content and high primary flame output make it the most effective choice for creating clean, fused joints in metalworking.

Sources

1. [1] https://www.sciencedirect.com/topics/engineering/acetylene-gas