Thermomechanical behaviour of Al2O3-MgO-C refractories under non-oxidizing atmosphere

Abstract

Al2O3-MgO-C (AMC) refractory bricks are used as linings for the sidewalls (metal line) and bottoms of steel-making ladles. As a structural component of this type of vessel, these bricks undergo mechanical and thermal loading in service. For this reason, knowledge about their thermo-mechanical behavior is needed for material selection and ladle design using structural calculus. Even when the mechanical response of AMC refractories is similar to that of MgO-C bricks, which have been studied a great deal, they have distinctive features that have to be studied specifically. The aim of this paper is to evaluate the mechanical performance of three commercial Al2O3-MgO-C bricks by stress-strain curves from RT to 1260 °C, using a non-oxidizing atmosphere (nitrogen). From these curves, the following mechanical parameters were determined: Apparent Young modulus (E), mechanical strength (σR), fracture strain (εR) and yield stress (σY). In order to infer what the main factors are in determining the mechanical response of each AMC refractory, the tested specimens were analyzed by bulk density and apparent porosity measurements and SEM/EDS. The increasing porosity (pores and microcracks), the loss of graphite and the new solids formed as products of the reactions between the refractory components control the behavior of the studied AMC materials. However, the contribution of each depends on the temperature and the refractories characteristics.