“Skin Lamination” associated with entrapped mold powder in sheet steel
“Skin lamination” is a term often used to describe surface imperfections of various types including that associated with entrapped mold powder.
Mold powder is an inherent part of the casting process; a consumable used to lubricate the mold and to protect the molten steel from the atmosphere. Mold powder that is entrapped in the solidifying steel shell can be rolled out into a thin layer close beneath, or just at, the surface of the hot rolled sheet. It sometimes becomes obvious only during forming.
Steelmakers endeavor, through careful control of the casting process, to keep the mold conditions as “quiet” as possible to minimize mold powder entrapment. This includes maintaining precise control of the liquid steel level in the mold, and controlling steel flow in the mold. The process is monitored using an “automatic mold level control system” to eliminate the subjectivity associated with humans. Detection of events by mold level measurement enables a decision-making process on acceptance for an order, which may lead to slab conditioning.