GB1482088A - Casting steel ingots - Google Patents

Abstract

1482088 Casting steel ingots BRITISH STEEL CORP 14 March 1975 [15 March 1974] 11643/74 Heading B3F Steel ingots are cast with a low content of non-metallic inclusions by introducing a gas into the runner system together with the molten steel when the runner supplies steel to the mould from an upwardly facing exit into the bottom of the mould. The gas may be inert, i.e. Ar, N or reactive to form a flux with the steel constituents. The steel may be fluxed during or after casting, the flux containing at least one of Ca tetraborate, Ca borate, Na carbonate, Ca fluoride, hydroboracite, lime or magnesia. An ingot mould 10 rests on a recessed upper plate 11 on a base plate 12. A refractory lined -runner 14, 15, 16 is machined in plates 11 and 12. A gas conduit 17 enters vertical runner 14 just below the top of the vertical portion of runner 14 before it enters recess 13. In use, molten steel 20 is poured into runner 16, passing through cross runner 15 into runner 14 and into the recess 13 thence into mould 10. During the pouring or as soon as the pouring ceases, a gas is passed from supply 18 into conduit 17, so that bubbles of gas enter the runner and then ascend into molten ingot. The gas bubbles tend to follow the pattern indicated by the arrows, and then exert a scrubbing effect on the solidifying metal. The gas flow rate and pressure are adjusted to give visible signs of agitation in the ingot, and the input tube is of such a size to give generally coarse bubbles. Since runner 14 is centrally located in the mould, the action of the gas is relatively uniform over the whole ingot area. The process, apart from scavenging the ingot, also produces a reduction in oxygen content when an inert gas is used. In a modification, the gas-flow may be started prior to casting to flush the runner of oxidizing gases, and in a further modification, recess B may be omitted, and cross runner 15 may be recessed into the upper surface of the base plate 12.