Effect of ZrB₂-SiC Composite Powder Addition Amount on Performance of Low Carbon Magnesium Carbon Refractory

By the replacement of flake graphite with ZrB₂-SiC composite powder, ZrB₂-SiC/MgO-C refractories were prepared after curing at 473 K for 12 h, and then heat treated at 1 373 K and 1 673 K, respectively. The effects of addition amount (0-4.0 wt%) of the composite powder on the physical properties, mechanical properties and thermal shock resistance of the refractories were studied. The results show that with the increase of addition amount of the composite powder, the modulus of rupture and compressive strength at ambient temperature of the refractories after curing and after heat-treatment increased and then decreased. The heat-treatment temperature had little effect on the physical and mechanical properties at ambient temperature. The modulus of rupture at elevated temperature of the refractories after heat-treatment at 1 673 K increased and then decreased with the increase of addition amount of the composite powder. The refractory after heat-treatment at 1 673 K mainly deformed in elasticity at testing temperatures below 673 K and in plasticity at testing temperatures no lower than 673 K. The replacement of graphite with ZrB₂-SiC composite powder greatly improved the thermal shock resistance in the oxidization atmosphere of the refractory.