The influence of MgO, K2O, Na2O and gas pressure on slag foaming behaviour under reducing conditions

Abstract

Using a photoelectric measuring technique to determine the foaming behaviour of iron oxide‐containing slag, investigations were carried out into the influences of magnesium oxide and the alkali oxides K2O and Na2O on melt foaming behaviour under reducing conditions. An MgO content of just a few percent intensifies the foaming action of acidic and self‐fluxing melts. This behaviour is also induced by a relatively low addition of alkali oxide. If the magnesium oxide and alkali oxide addition is further increased, slag volume growth during foaming declines. With basic compositions, both the magnesium oxide and the alkali oxides may reduce the volume increase of the foaming slag. Overall, melts undergo maximum foaming under conditions of medium basicity and in the medium temperature range. Alkali oxides promote the phenomenon of melt resolidification often observed in the tests. Tests with different furnace gas pressures up to max. 3 bar reveal that foaming volume of the melt increases with rising gas pressures.