What is the purpose of slag in the welding process?

The purpose of slag in the welding process is to protect the cooling weld metal. During welding, the molten metal fuses together, and as it cools and solidifies, slag forms on the surface. This slag acts as a protective layer that shields the weld from atmospheric contaminants, such as oxygen and moisture, which could cause defects in the weld. By preventing oxidation and contamination, the slag helps to ensure a sound and high-quality weld joint.

This function is critical in maintaining the structural integrity of the weld, as impurities can lead to problems like porosity, cracking, and reduced strength. Once the welding process is complete and the weld has cooled, the slag can typically be removed easily to reveal a clean weld surface beneath.