UsING of CALCIUM MAGNESIUM ALUMINATE FLUX WITH HIGH MGO CONTENT TO IMPROVE secondary STEEL LADLE LIFE TIME

Abstract

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 TM RG (FLUX B) and OPTIMET TM HM (FLUX C), novel synthetic Calcium Magnesium Aluminate Fluxes (CMA) with high MgO-content, has been studied. Thermodynamic simulations with the FactSage © software and laboratory experiments have been conducted. A traditional slag fluxing practice with fluorspar (CaF 2 ) has been compared with Calcium Aluminate (CA), LDSF ® RG (FLUX A), and with these novel synthetic fluxes with different MgO-contents. Calcium Magnesium Aluminate Fluxes (CMA) allow 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 Calcium Aluminate (CA). Calcium Magnesium Aluminate Fluxes (CMA) bring the MgO-content in the slag, right after tapping, close to the saturation concentration and minimise the dissolution of Magnesia-Carbon or Doloma-Carbon bricks in the slag. Life time increase of the slag zone can be expected. Calcium Magnesium Aluminate Fluxes (CMA) help 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 CO 2 -emissions per ton of produced steel.