What is the composition of slag in welding?

Slag in welding is primarily understood as a byproduct that forms during the welding process when the flux or coating on the electrode reacts with unwanted impurities. This process aids in eliminating contaminants such as oxides and other non-metallic materials from the molten metal as it solidifies. By creating this byproduct, slag plays a vital role in protecting the weld pool from atmospheric contamination and oxidation.

The formation of slag helps ensure a cleaner and stronger weld by encapsulating the impurities, preventing their inclusion in the final weld. It also provides a certain degree of thermal insulation, which can help control cooling rates in the weld and promote better mechanical properties of the weld metal.

The other options do not accurately reflect the role and composition of slag in welding. While pure metal composition is crucial, it doesn’t describe slag. Similarly, molten metal typically refers to the weld pool itself rather than slag, and compressed air does not relate to the welding process. Thus, recognizing slag as a byproduct that combines unwanted impurities is essential for understanding its function in welding.