Effect of zirconia addition on the properties of dolomite magnesia refractories used in steel industries

In this study, the influence of the zirconia addition on the properties and microstructure of alkali magnesia refractories without chrome band spinels was investigated. For this purpose, a primary formula based on magnesia and alumina to form spinel was considered, and different amounts of zirconia were added to achieve various samples. After thermal treatment at 1500 ̊C and 1600 ̊C, the physical and mechanical properties of fabricated samples such as density, apparent porosity, cold compressive and bending strength, refractoriness under load, and warm modulus of rupture according to ASTM were evaluated. The physical and mechanical properties of zirconia contained samples revealed that the addition of zirconia led to the formation of zirconate-based phases like magnesium zirconate, and calcium zirconate. This phase can be expanded by the thermal stresses due to its thermal mismatch with the phases of the field and improved the mechanical properties by creating microcracks in the structure. Addition of 2% by weight of zirconia increased the density from 2.8 g/cm3 to 2.95 g/cm3 at 1600 °C. Compressive strength also increased from 315 kg/cm2 to 550 kg/cm2 and flexural strength from 35 kg/cm2 to 65 kg/cm2.