Properties and corrosion behaviour of corundum-spinel castables with different spinel formation methods: Role of in-situ spinel

In order to investigate the effects of in-situ spinel on the mechanical properties and corrosion behaviors of corundum-spinel castables, tabular corundum, magnesia fine powders and pre-synthesized spinel fine powders were used as raw materials to prepare corundum-spinel castables. The results showed that corundum-spinel castables with 3 wt% of magnesia fine powders and pre-synthesized spinel exhibited the best physical properties, thermal shock stability and corrosion resistance. The cold modulus of rupture was 28.6 MPa and cold compressive strength was 141.7 MPa. The residual strength ratio after thermal shock was 55.87 %. For the corrosion behaviors, the corrosion index and penetration index were 8 % and 11.86 %, respectively. Due to the better ceramic bonding interface by the in-situ spinel and the weaker volume expansion effect by the presynthesized spinel, densification of the samples could be significantly improved, which could enhance the properties of the samples. Besides, according to the thermodynamic calculation, spinel and corundum underwent obvious phase transition during the corrosion process. The ability of the samples with 3 wt% magnesia fine powders and pre-synthesized spinel to maintain the primary crystalline phases was relatively stable when reacting with slag, which made the castables show preferable slag penetration resistance.