GB475345A - Improvements in and relating to the manufacture of iron - Google Patents

Abstract

In the production of pig iron in a blast furnace, especially from ores of low alumina content, the ores and fluxing media are mixed in such proportions as to form slags of relatively low melting points and in which the ratio of lime to silica is decreased progressively below the usual limits of 1,65 to 1,25 as the alumina content of the slag formed decreases downwardly from 15 per cent. For example with a slag containing 15 per cent of alumina the ratio of lime to silica is from 1,15 to 0,90 and for as lag containing 10 per cent of alumina the ratio is 1,10 to 0,875. The molten iron tapped from the furnace is desulphurized either by the addition of alkali or by allowing the liquid iron to stand in a heated receptacle under oxidizing conditions to enable manganese sulphide to be formed, sufficient manganese ores being added to the burden of the furnace, if required, to produce a pig iron having at least 0,7 per cent of manganese. In the latter case, the iron is maintained in the hot metal mixer long enough for the manganese sulphide producer to be oxidized and the sulphur eliminated in the form of sulphur dioxide. Specification 460,138 is referred to.