Modification of steelmaking slag by additions of salts from aluminum production

Abstract

The most common slag fluidiser in steelmaking is fluorspar, a mineral primarily composed of CaF2. Because of increasing consumption and decreasing availability of inexpensive fluorspar, steelmakers are seeking alternative means of achieving slag fluidity. One possible alternative to fluorspar is salt cake from secondary aluminium production. This salt is obtained from the used flux in remelting aluminium scrap and dross. This material is widely available and considered toxic (meaning that use in steelmaking helps to reduce environmental impacts from disposal). This project is an investigation of salt cake as a replacement for fluorspar in slag-fluidising applications by viscosity measurements and mass loss measurements at high temperatures (to evaluate the amounts of gases formed). In addition, characterisation of raw materials and melted slags by XRD, chemical analysis, and EPMA have been undertaken. The salt cake addition has a positive effect on slag fluidity, and shows promise for use in steelmaking slags.