What is the purpose of the slag created during SMAW?

The purpose of the slag created during Shielded Metal Arc Welding (SMAW) is primarily to protect the weld bead while it cools and solidifies. As the electrode melts during the welding process, the flux coating generates a slag that forms on the surface of the molten weld pool. This slag serves as a protective layer that shields the weld from atmospheric contaminants such as oxygen and nitrogen, which can adversely affect the quality and integrity of the weld. By preventing these gases from interacting with the hot weld metal, the slag helps ensure a stronger and more durable weld.

While some might think that the slag enhances the aesthetic appearance of the weld or contributes to its strength directly, its main function is protective. Slag does not eliminate the need for cleaning before welding, as pre-welding surface preparation is still crucial for ensuring good adhesion and quality in the final weld. Therefore, the correct answer underscores the essential role of slag in safeguarding the weld during the critical cooling phase.