GB760561A - Ladle and method for the treatment of molten metals - Google Patents

Abstract

Treatment of molten metals by gases, e.g. for stirring or refining the metal, is effected in a ladle having a refractory lining, the bottom of the ladle comprising a porous portion substantially flush with the rest of the bottom lining, the ratio between the ladle depth at its normal filling level and the ladle's inner diameter at the said levels being between 1 and 1.8 and the relation between the porous area s and the area S of the ladle inner section at its normal filling level being such that 0.32 log S + 0.39 < log s < 0.67 log S-0.14 the base of the logarithms being decimal and S and s being expressed in square centrimetres. The porous portion is preferably a removable silicon carbide plug which may be sealed to the ladle lining by a chromium oxide base cement containing a small amount of bentonite and sodium silicate. The plug preferably has a porosity such that 50-200 litres of air pass, at room temperature and normal pressure, per minute per square decimetre of exposed porous area per kilogram per square centimetre of upstream pressure. Molten ferrous metals may be desulphurized by first charging a desulphurizing slag, e.g. blast furnace slag, in the solid state, then charging molten metal while blowing gas through the porous plug. Molten steel may be deoxidized by adding a small amount of carbon to the molten steel and blowing in an inert gas to disperse the carbon and lower the partial pressure of carbon monoxide as it is formed. Silicon may also be removed by blowing in an inert gas. Reference is also made to the incorporation in molten metals of highly reactive agents such as magnesium and/or boron, dispersion of the agents being rapidly effected by blowing in argon or helium. Reference has been directed by the Comptroller to Specification 671,678.