An incompletely deoxidized steel usually containing less than 0.25% carbon and having the following characteristics:

(1) During solidification, an evolution of gas occurs sufficient to maintain a liquid ingot top (“open” steel) until a side and bottom rim of substantial thickness has formed. If the rimming action is intentionally stopped shortly after the mold is.filled, the product is termed capped steel.

(2) After complete solidification, the ingot consists of two distinct zones: A rim somewhat more pure than when poured, and a core containing scattered blow-holes, with a minimum amount of pipe, and having an average metalloid somewhat higher than when poured, and markedly higher in the upper portion of the ingot.

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