High-temperature property enhancement of low carbon MgO-C refractory by introducing microporous magnesia

The development of low-carbon MgO-C refractories has become an urgent need for high-end transformation of the steel industry. However, the low carbonization of MgO-C refractories will lead to a sharp decline in its thermal shock resistance and slag permeability. To overcome the performance shortcomings, low-carbon MgO-C refractories were prepared by using the microporous magnesia as aggregates (MMC), and their effects on the structure and properties after annealing at various temperatures were studied. The results indicate that the high sintering activity of microporous magnesia ensured the highly dense structure and strong bonding between aggregates and matrix after firing. At 1000 degrees C, a substantial amount of MgO and Al4C3 whiskers were generated in-situ. Subsequently, at 1400 degrees C, these whiskers continued to grow. The reason for this is that the porous structure within MMC supplies the essential space and boosts the gas phase mass transfer rate, consequently leading to a significant enhancement in the high-temperature mechanical properties. The thermal stress was relieved by micro-pores and the crack propagation is suppressed by the in-situ whiskers. These two factors not only greatly enhance the thermal shock resistance but also reduce the thermal conductivities. MMC exhibited much better slag resistance than conventional fused magnesia-C refractory (FMC). The corrosion index and penetration index could be decreased by approximately 28 % and 55 % respectively. This was attributed to the lower dissolution rate of microporous magnesia and the significant blocking effect on slag penetration by the integrated corrosion interface. Based on these findings, a corrosion mechanism was summarized.