Mechanical behavior and microstructural evolution of Al2O3-MgO-C refractories used in steelmaking ladles

V. MUÑOZ; C.A. CALAFIORE; A.L. CAVALIERI; A.G. TOMBA M.; P. GALLIANO

Conferencia; 17° Conferencia de Acería-Jornadas Instituto Argentino de Siderurgia.; 2009

Instituto Argentino de Siderurgia.

Among oxide-C refractories, the Al2O3-MgO-C bricks are mainly used on walls and floors of steelmaking ladles. The increasing demand for these materials in the steel industry is due to more severe operating conditions: mechanical loads at high temperatures, thermal gradients and aggressive chemically environments (slags, gases, solid particles). These conditions lead to the unavoidable material damage, being imperative their thermochemical and thermomechanical evaluation in order to improve their performance, increasing their lifetime and reducing both the costs and the environmental impact. In this work, stress-strain curves of two commercial Al2O3-MgO-C bricks used in the steel industry are determined to study their mechanical behavior in function of the temperature and the atmosphere. Their characterization includes: density and porosity measurements and mineralogical qualitative (XRD), thermal (DTA/TGA) and microstructural (microscopy) analysis. The stress-strain curves are obtained by uniaxial compression tests of cylindrical specimens at room temperature and 700, 1000 and 1260 °C in controlled atmosphere. An Instron 8501 servo-hydraulic machine for mechanical testing and an axial extensometer (± 0.6 μm) suitable for high temperature measurements are used. The tests are performed in displacement control (displacement 0.1 mm/min). From these curves, mechanical parameters: fracture strength and strain, and Young´s modulus are determined. The results are analyzed in terms of both the refractory composition and the material microstructural changes that depend on the temperature and the atmosphere.