Mill Terms: Surface Defects

Lap—A surface defect appearing as a seam caused by folding over hot metal, fins, or sharp corners and then rolling or forging them into the surface but not welding them.

Mill-shearing—A defect which can be described as a feathering type light surface lap.

Rolled-in Scale—Rolled-in oxides of iron which form on the surface of hot steel.

Scabs—Elongated patches of loosened metal which have been rolled into the surface.

Seams—Open, broken surface running in straight longitudinal lines caused by the presence of oxides near the surface.

Silvers—Surface ruptures somewhat similar in appearance to skin laminations, but usually more prominent.