In steel works, where steel is made, castings are poured from open-hearth, Bessemer, or crucible steel, as may be required. The making of steel castings in large steel works is usually an incidential operation, as steel is made principally for rolling into various shapes, as described in Chapter Y.

In steel foundries, where steel is made only for castings, a small converter is used to make steel by "blowing" pig iron melted in the foundry cupolas. This is essentially the Bessemer process. The steel-making equipment of the usual steel foundry consists of (1) two or more cupolas for melting cast iron, (2) one or more small converters (usually in America the Tropenas type of about two tons capacity), and (3) a small cupola for melting the ferro-man-ganese or other recarburizer which is mixed with the converter contents after blowing.

In quality, steel for castings must be low in phosphorus and sulphur, although these ingredients are not so objectionable in cast as in rolled steel. Silicon and manganese should be kept within limits, and particularly should iron oxide and dissolved gas be reduced to the lowest limits possible. The hardness of the casting, and directly its tensile strength and brittleness, depend upon the per cent of carbon contained. Hard castings contain up to .9% of carbon, medium castings contain around .5%, and soft castings contain around .3%. Most castings contain between .35% and .50%. Soft castings are hardest to obtain because of the higher melting point of low-carbon steel. This grade of castings often looks very rough. The very best steel castings contain about 3 1/2% of nickel.