Method of producing low carbon, non-aging, deep drawing steel

1,169,874. Deoxidising steel. UNION CARBIDE CORP. Oct.21, 1966 [Oct.23, 1965], No.47136/66. Addition to 1,081,147. Heading C7D. Low-carbon non-ageing deep-drawing steel is produced by tapping into a degassing vessel a steel containing less than 0À04% each of sulphur and phosphorus and carbon at least 0À05% and above that desired in the final product, an inert atmosphere being maintained in the vessel and above the surface of the metal; an inert gas is then bubbled through the steel from below the surface thereof to reduce the carbon and oxygen contents to the desired level, at least the major part of the inert gas being introduced while the bath is substantially free from oxidizing slag, the latter being defined as one containing more than 10% of iron oxide. An amount of aluminium substantially corresponding to that desired in the product is then added and the steel cast while being shielded from contact with air. Manganese corresponding to the desired final amount is added either prior to the treatment with inert gas or together with the aluminium. The inert gas is generally one of the rare gases, although in some circumstances nitrogen may be employed. Preferably introduction of the inert gas is substantially complete before slag enters the treatment vessel, but alternatively the slag may be neutralised, either in the furnace or the treatment vessel, with a scavenging material such as aluminium shot, ferrosilicon, calcium-silicon or carbon. A formula is given from which the amount of inert gas necessary to achieve complete hulling of the steel may be determined. Extension of the process to the production of alloy steels is referred to, alloying additions being made only after the oxygen content has been reduced to a suitably low level.