Refining of steel to remove nitrogen using fluxes with high nitride capacities

摘要

Nitrogen solubility and nitride capacities in Al_2O_3-CaO-TiO_2 and CaF_2-TiO_2 fluxes were measured by application of an experimental technique with regulation and precise control of oxygen partial pressure P_(O_2) at 1873 K. On the basis of experimental findings the values of nitrogen distribution ratio between slags and liquid iron and degree of denitrogenation of metal were estimated as functions of P_(O_2)- The removal of nitrogen from pure iron and chromium alloyed steels by fluxes containing TiO_2 was investigated using the technique of preliminary mixing of slag and metal powders with subsequent heating and melting in a crucible at 1873 K and also in a ladle after tapping molten metal from a 10 kg induction furnace. The oxygen potential in the system was regulated by the content of aluminium or titanium in refining slag mixtures. Experimental results indicated that it is possible to remove nitrogen from low alloyed steel using Al_2O_3-CaO-TiO_2 slags with a denitrogenation degree of over 60 percent. The technological parameters for effective nitrogen removal from high alloyed steel under ladle treatment by slag mixtures, including CaF_2-TiO_2 fluxes in an industrial process, are discussed.