Investigation of Ladle Castables that Contain a Novel Calcium Magnesium Aluminate Matrix: Fid-Bau Portal

Investigation of Ladle Castables that Contain a Novel Calcium Magnesium Aluminate Matrix

Wöhrmeyer, C. / Auvray, J.M. / Fryda, H. / Parr, C. / Iiyama, M. / Li, S.

Calcium magnesium aluminate (CMA) is a novel hydraulic binder for steel ladle castables that is beneficial to prevent ladle slag penetration and corrosion. The CMA grain contains microcrystalline magnesium aluminate spinel which is homogeneously distributed between hydraulic calcium aluminate phases. In the castable it develops a unique micro spinel matrix. This study investigates alumina-spinel castables with matrices built on fused spinel, sintered spinel and spinel from CMA. It has been found that at equal CaO contents in the castable the CMA creates the same strength after drying but higher strength after firing when compared with a matrix based on calcium aluminate cement (CAC) combined with added spinel. This is assumed to be the effect of the microspinel matrix and its higher sintering reactivity due to the small crystal size of spinel inside CMA. When used in alumina magnesia castables CMA enables a reduction of free magnesia leading to an improvement of rheological properties and reduction of cracking risk associated with Brucite formation during drying. Furthermore less permanent expansion due to less in-situ spinel formation has been observed. This enables a reduction of silica to improve the thermo-mechanical properties. It has also been found that with the reduction of silica the porosity at ladle service temperature decreases. This can further enhance the resistance against slag penetration and corrosion. But it has also been discovered that a very small amount of silica should be kept inside the castable matrix to minimise the magnesia hydration and crack formation during castable drying.