Dependence of Mechanical Properties of MgO-C Bricks on Graphite Content

Abstract

MgO-C bricks containing 0 to 30 vol% flake graphite and expanded graphite were prepared and heat-treated at 800 and 1400°C. The dependence of mechanical properties of the MgO-C bricks on the graphite content was studied. The maximum values of bending strength, elastic modulus and fracture toughness were obtained at 2 to 3 vol% expanded graphite and at around 5 vol% flake graphite. The effective fracture energy increased with an increase in graphite content up to 30 vol% for expanded graphite. However, no slight increase in effective fracture energy was observed above 20 vol% flake graphite. Thermal shock resistance parameters R″″ and Rst were calculated based on the data obtained. R″″ was not correlated with graphite content. On the other hand, Rst remarkably increased above 7 vol% graphite and larger Rst was obtained with expanded graphite. Consequently, improvement of the spalling resistance of MgO-C brick was expected with expanded graphite.