Effect Of AlON Ceramic Bonding On Al₂O₃-C Refractories High Temperature Properties

Al2O3-C refractories are widely used in continuous casting process as submergednozzle, stopper and slide plate. Their main function is to keep steady flow, preventimpurity and avoid oxidant of molten steel. Currently the main problem of Al2O3-Crefractories is the short service life and the potential carbon increasing for steel. Inorder to solve above problem, this thesis study the evolution and microstructure ofAlON ceramic bonding phases Al2O3-C refractories. At the same time, the effect ofthis new bonding phase on the high temperature properties has been also researched.At first, the thermodynamic study of Al-Si-O-C-N the system has beenconducted. In reducing atmosphere, SiC and AlN are generated at1473K while AlONis generated at1846K. The study on matrix of Al2O3-C refractories shows thatmetallic Si is transformed into SiC and Al/AlN are transformed into Al2O3at1773K.There is no Al-O-N bonding but Si-C bonding in infrared spectroscopy. At1873K,the phase of Al2O3can react with AlN to form AlON phase. The corresponding FTIRis Al-O-N bonding at782cm-1. The microstructure shows that SiC phase have theshape of whisker and there is liquid drop at the top. The phase of AlON take onparticle shape. The generation of AlON phase can increase the strength from70.4MPato99.8MPa. The residual cold compress strength(CCSre) after thermal shock canincrease from62.1MPa to80.9MPa.The effect of composition and microstructure on the mechanic properties ofAl2O3-C refractories has been investigated. At1473K℃, SiC whiskers have generatedin samples and metallic Al react to form plate AlN. At1673K℃, the peaks of SiCand AlN increases obviously. When temperature increase to1873K℃, phases of AlNdisappear and AlON phases is formed because of the reaction of AlN and Al2O3. theresult agree with thermodynamic analysis. The generation of AlON in refractoties, thecold compress strength(CCS) can be increased from104.3MPa to120.54MPa. Thehot modulus of rupture(HMOR) can be enhanced from15.07MPa to22.64MPa. TheCCSre can be increased from78.48MPa to93.36MPa. The effect of AlON content on phase composition, microstructure and hightemperature properties of Al2O3-C refractory has been researched. A minor of AlONphases can be formed at the samples calcined at1600℃without AlN. When AlNaddition increases, the quantities of AlON increases correspondingly. AlON phasetakes on particle shape. The existence of AlON can increase CCS from79.53MPa to102.93MPa. The CMOR can be increased from14.56MPa to20.54MPa. The CCSreafter thermal shock is enhanced from63.58MPa to94.27MPa. The HMOR can beincreased from14.67MPa to22.71MPa.