Novel Fluxing Agent for Slags in Secondary Steel Ladles to Improve Refractory Life Time and Steel Quality

One of the most corroded zones in the secondary steel ladle is the contact area between the metallurgical slag and the refractory lining. The slag zone, even with specially designed Magnesia-Carbon and Doloma-Carbon bricks, is in many cases the life time limiting factor for the whole steel ladle. This makes repairs by gunning or intermediate slag zone replacements necessary. During the slag zone replacement the ladle has to be cooled down with further negative effect on the other parts of the ladle due to thermally induced stresses and consequently crack formation . In order to improve the life time of the slag zone the impact of OPTIMET RG and OPTIMET HM, novel synthetic Calcium Magnesium Aluminate Fluxes (CMA) with high MgO-content, have been studied. Thermodynamic simulations with the FactSage software and laboratory experiments have been conducted. A traditional slag fluxing practice with fluorspar (CaF2) has been compared with Calcium Aluminate LDSF RG (CA) and with these novel synthetic OPTIMET fluxes with different MgO-contents. OPTIMET allows a quick formation of a homogeneous and liquid slag with a high capacity to absorb sulphur and oxide inclusions from the steel bath, very similar to LDSF RG. OPTIMET™ brings the MgO-content in the slag right after tapping close to the saturation concentration and minimises the dissolution of Magnesia-Carbon or DolomaCarbon bricks in the slag. Life time increase of the slag zone can be expected. OPTIMET™ helps to reduce the specific ladle costs per tonne of steel. The efficiency of high quality steel production can be increased which supports the efforts to reduce the C02-emissions per ton of produced steel.