What is the role of slag in the welding process?

The role of slag in the welding process is primarily to protect the weld from contaminants. When welding occurs, especially in processes such as shielded metal arc welding (SMAW), the flux coating on the electrode melts and forms a layer of slag over the molten weld pool. This layer acts as a barrier against atmospheric gases, dirt, and other environmental factors that could compromise the integrity of the weld joint. By preventing oxidation and contamination, slag helps in ensuring a strong bond once the weld cools and solidifies.

While some other functions are associated with the welding process, they do not encompass the primary function of slag as effectively as this answer. For instance, enhancing conductivity, acting as a filler material, or improving weld appearance are not the main objectives of slag formation. The core purpose remains its protective role during and after the welding to maintain the quality of the weld.