Effect of carbon sources on the properties of lightweight corundum‐spinel refractory with density gradient

Abstract Lightweight refractories are expected to have excellent performance in high and room temperature in addition to energy consumption reduction. Lightweight corundum‐spinel refractory was fabricated by carbothermal reduction of MgO, the oxygen diffusion rate controlled oxidation of Mg vapor, and subsequent reaction between MgO and Al ₂ O ₃ . The lightweight corundum‐spinel refractory was characterized by X‐ray diffraction and scanning electron microscopy. Effects of flaky graphite particle size and carbon black content on the properties of lightweight corundum‐spinel refractory were investigated. The results showed that flaky graphite particle size had great effect on the stacking density of green compacts and the properties of refractory. When flaky graphite particle size was 42.44 µm, the refractory possessed bulk density 2.68 g/cm ³ , compressive strength (CS) 63.5 MPa, and refractoriness under load 1641°C fired at 1550°C for 4 hours. With the decrease of carbon black content, the properties of refractory increased, but the CS was low due to the generation of structure defects including large pores and cracks when compared with the samples using graphite as carbon source. In order to obtain lightweight refractory with good performance, the carbon particle size and content should be chosen properly in addition to firing temperature and holding time.