Abstract

MgO-C and Al2O3-MgO-C bricks are widely used as working lining in the steelmaking ladles. Due to their carbon content they are particularly susceptible to high temperature oxidation in contact with ambient oxygen. These refractories are exposed to such conditions after casting end and during its pre-heating previous to the next heat.

At the end of each heat, LF slag remains partly adhered to ladle walls, generating a coating that exerts a barrier effect, protecting the refractory to subsequent decarburization. This slag suffers different transformations according to environmental thermal conditions, including degradation processes caused by hydration and/or spalling, which can affect its protective capacity to the refractory bricks.

For this reason, physico-chemical characterization of a steelmaking ladle slag and the evolution of its integrity over time under different conditions are carried out in this work. The degradation of the slag by weathering is evaluated through its granulometric evolution at different times for several months. In each case, samples were also characterized by different techniques: X-ray fluorescence (XRF), X-ray diffraction (XRD), differential thermal (DTA) and thermogravimetric analyses (TGA).

The obtained results show the hydration of different phases present in the slag. At short time, degradative processes of CaO are observed, and in lesser degree, the degradation of MgO. At longer time, changes in the calcium aluminate present in the system are also detected. These transformations involve volumetric expansions and then, the slag disintegration. This strongly affects the characteristics of the slag protective capacity to prevent decarburation of ladle working lining refractories in empty ladle conditions during its campaign