GB1475247A - Method of incorporating a highly reactive material into molten steel - Google Patents

Abstract

1475247 Alloying steel JONES & LAUGHLIN STEEL CORP 30 Oct 1975 [11 Nov 1974] 44790/75 Heading C7D [Also in Division B3] In a method of alloying molten steel with highly reactive materials, such as rare earths, Al, Ti, and/or Zr, all of which have a high oxygen affinity and act as sulphide shape control agents, the following steps, (steps b and c not necessarily in the sequence shown) are employed (a) The steel is deoxidised; (b) A mixture of alkaline earth - reactive metal is added below the surface of the molten steel, and (c) the alloyed steel is teemed through a gaseous reducing atmosphere such as propane, butane, natural or coke oven gas, into a mould 'wherein there is a gas generating material which vaporizes to purge the mould of air and create a reducing atmosphere. The alkaline earth with which the reactive material is mixed is selected from 2-8% Mg, 10-20% Ca or 10-20% Ba, with 10-20% Ca as the preferred material. The function of the alka- line earth is to tie-up any remaining oxygen present in the steel after deoxidation, usually with Si and/ or Al, and to vaporize and create a stirring of the steel bath to ensure uniform distribution of the reactive metal. The reactive material may be elemental or alloyed and is preferentially a rare earth or mixture of misch metal and rare earth silicide. The gas generating: material placed in the mould prior to teeming may be a hydrocarbon together with a fluxing agent which on casting provides a further cast to the molten steel. The hydrocarbon to flux ratio is 5-50% hydrocarbon 95-50% flux. A second embodiment of the process may con- sist of (1) deoxidation (2) teeming as before through a gaseous atmos- phere into a mould with the gas generating material therein, (3) allowing the mould to stand for 2-4 minutes to permit a shell to solidify and allow any inclusions to float out, and (4) adding the alkaline-earth-reactive material mixture, possibly in briquetted form, by plunging it below the surface of the molten steel in the mould. In this embodiment, the alkaline earth may be selected from 0À5-2% Mg, 5-10% Ca, 5-10% Ba, the reactive material being unchanged from the first embodiment. In a third embodiment, the alkaline earthreactive materials may be added to the steel in the mould where it is being teemed through the gas- eous reducing atmosphere. The materials may be added consecutively or simultaneously, and if added consecutively, the alkaline earth should be added first.