High temperature mechanical behavior of Al2O3–MgO–C refractories for steelmaking use

The advantages of Al2O3-MgO-C (AMC) refractories are achieved mainly by the incorporation of graphite and the formation of spinel by solid reaction between alumina and magnesia. Regarding other members of oxide-C refractories (such as MgO-C bricks) and others properties (such as the slag corrosion resistance or the PLC), the information about the mechanical behavior of this type of refractories is scarce. In this work, the mechanical behavior of commercial AMC brick used in steelmaking ladles was studied by stress-strain curves in compression at RT and 1000ADGC (nitrogen atmosphere). Before the mechanical testing, a comprehensive characterization of AMC materials was performed by several techniques: XRD, DTA/TGA, SEM/EDS, aggregate size distribution analysis and densities, porosities and thermal expansion measurements. Mechanical parameters such as fracture strength and strain, yield stress and Young modulus were determined together with the main characteristics of the fracture. In order to study the transformations occurred during the stay at high temperature, the specimens tested at 1000ADGC were analyzed by the same techniques used for the as-received bricks characterization (with the exception of the thermal expansion analysis). The AMC refractories displayed differences in the mechanical behavior and its dependence on the testing temperature. These results were explained considering the differences in the composition and microstructure of both refractories and in their thermal transformations.