Which statement about slag covering is true?

Which statement about slag covering is true?

• A. It accelerates cooling
• B. It protects from atmospheric contamination and slows cooling
• C. It has no effect on cooling
• D. It cures weld defects

Answer: (B)

Slag covering acts as both a protective shield and an insulator for the weld pool. As the weld forms, the slag crust blocks the molten metal from air, moisture, and other contaminants, reducing oxidation and hydrogen-related defects. At the same time, the slag layer slows the cooling by insulating the weld as it solidifies, helping to control cooling rates and minimize cracking. It does not accelerate cooling, and it doesn’t cure weld defects; rather, it provides protection and a controlled cooling environment, with the slag needing to be chipped away after welding to inspect the bead.

Slag covering acts as both a protective shield and an insulator for the weld pool. As the weld forms, the slag crust blocks the molten metal from air, moisture, and other contaminants, reducing oxidation and hydrogen-related defects. At the same time, the slag layer slows the cooling by insulating the weld as it solidifies, helping to control cooling rates and minimize cracking. It does not accelerate cooling, and it doesn’t cure weld defects; rather, it provides protection and a controlled cooling environment, with the slag needing to be chipped away after welding to inspect the bead.