Influence of granulated graphite on fracture behavior of MgO-C refractories based on Brazilian splitting test with digital image correlation method and acoustic emission technique

Flake graphite is prone to preferential orientation distribution owing to its flat geometric structure, resulting in significant anisotropy of the physical properties of MgO-C refractories, thus affecting their service performance. The preferential orientation of flake graphite within the material can be suppressed by granulation. In this study, the influence of granulated graphite on fracture behavior of MgO-C refractories was investigated based on the Brazilian splitting test combined with digital image correlation method and acoustic emission technique. The thermal shock resistance of the MgO-C refractories was compared using oil quenching method. The results showed that in the Brazilian splitting test, MgO-C refractories exhibited peak values for tensile strength, fracture energy, and maximum horizontal strain at fracture when 0 = 0o (0: angle between loading and shaping direction), followed by a subsequent decrease with increasing 0. Moreover, the introduction of granulated graphite effectively mitigated the anisotropy of mechanical and deformation characteristics of MgO-C refractories. Additionally, the addition of granulated graphite reduced the maximum thermal expansion coefficient and its anisotropy in MgO-C refractories, and promoted the generation of a higher proportion of shear or mixed crack modes, thereby contributing to enhancing the thermal shock resistance of MgO-C refractories.