What is slag inclusion and how can it be prevented?

• A. Slag voids inside the metal; prevent by increasing current and speeding up travel.
• B. Slag crust forms on weld surface; prevent by cooling rapidly.
• C. Slag trapped in the weld metal; prevent by proper slag removal, correct travel speed, and keeping the weld area clean.
• D. Slag penetration increases root strength; prevent by using larger electrodes.

Answer: (C)

Slag inclusion happens when flux slag from the welding process gets trapped inside the weld metal or between layers instead of being carried to the surface. This creates nonmetallic pockets that weaken the weld and can lead to failure under load. To prevent it, remove slag after each pass so the next weld fuses with clean metal, maintain the correct travel speed so the slag is pushed to the surface rather than entombed, and keep the weld area clean and free of debris. Proper joint preparation and technique are also important so the molten weld can properly fuse without dragging slag into the weld pool.