Which statement describes that cap steel is associated with slower cooling leading to the outer shell property?

• A. Killed steels
• B. Capped steels
• C. Semi-killed steels
• D. Rimmed steels

Answer: (B)

Cap steel illustrates how slowing the cooling of the outside of the ingot changes the surface layer while the interior continues to solidify differently. By pouring a cap of molten metal on top during solidification, the temperature drop at the outer shell is reduced. This allows the outer layers to form with a distinct microstructure—often with a higher carbon content or different carbide distribution—compared to the core, giving the outer shell its characteristic property. Other steel types achieve their surface differences through different solidification or deoxidation practices, not through a capped outer layer, so they don’t describe this deliberate slowing of cooling to create a shell with a particular property.