GB1302306A - - Google Patents

Abstract

1302306 Controlling pig iron refining CENTRE NATIONAL DE RECHERCHES METALLURGIQUES 19 April 1971 [13 March 1970 14 July 1970] 24023/71 Heading C7D The refining of haematite pig iron in a converter, in which oxygen is blown on to the charge through a lance, is controlled under adjustable refining conditions including lance height, oxygen flow-rate and lime and fluorspar additions by determining the composition and quantity of converter charge and the course to be followed by the decarburization rate during refining; continuously measuring the oxygen flow-rate and the temperature, flow-rate and analysis of the exhaust gases; continuously calculating the decarburization rate from the continuous measurements, and the quantity of Si (as SiO 2 ) and oxygen passing into the slag, the distribution of oxygen in the slag between SiO 2 and metal oxides, the FeO content of the slag and the quantity of CaO dissolved in the slag; and regulating the decarburization rate so that it follows the predetermined course and the FeO content of the slag to between 20 and 30 per cent by weight at least when the slag composition is saturated in 2CaO.SiO 2 by adjusting the refining conditions, preferably the oxygen flow-rate and lance height respectively. Preferably the noise level in the converter is continuously measured, and the predetermined course for the decarburization rate has 3 phases: a first phase wherein the rate is maintained between 10 and 60% of a given maximum value for the refining by adjusting the conditions until the noise level drops by a given amount e.g. between 50 and 80% of the maximum initial noise level; a second phase wherein the rate increases progressively to the maximum value by adjusting the conditions to progressively decrease the noise level; and a third phase wherein the rate remains at the maximum value.