A process for the pretreatment of a for the continuous casting certain unkilled or part of calmed steel

摘要

In a continuous casting process rimming steel is over-deoxidized prior to pouring so that the product of the carbon and oxygen contents is brought to less than the optimum value which has been predetermined for the particular conditions of operation, to yield suitable subcutaneous blow-holes and the steel is then re-oxidized to the optimum value. Deoxidation may be achieved with aluminium, or preferably with silicon, as in the form of ferrosilicon, and re-oxidation by the addition of iron oxide, e.g. as a powder in a stream of carrier gas or by surface blowing the metal with jets of oxidizing gas either as it enters the mould or preferably as it leaves the ladle. As illustrated in Fig. 6, over-deoxidized metal flows from ladle 1 into launder 4 and thence to tundishes 6 and nozzles 7 leading to moulds 9. Oxygen is blown against stream 3 by means of pipes N controlled by valves 13, or may be blown against streams 5 and 8. The flow of oxygen may be additionally monitored by gamma-ray equipment 16, 17, Fig. 7, which assesses whether the blowholes in the ingot are PICT:0952929/C3/1 PICT:0952929/C3/2 adequately buried and operates valve 13 accordingly. According to the Provisional Specification control can also be effected by means of photo-cells which monitor the height to which molten metal is thrown above the pool in the mould.