Synthesis And Properties Of Nitrides Bonded MgAl₂O₄-C Material By High-temperature Nitriding

Carbon containing refractories have been widely used in steelmaking due to their excellent thermal shock and slag resistance.However,carbon containing refractories affect the production of clear steel due to its easier oxidation.High quality fused spinel,flake graphite and silicon powder were used as primary materials.In-situ nitriding to form ?-Sialon and AlON to improve the strength and properties of MgAl₂O₄-C materials.?1?Nitriding temperature and nitriding time have a important effect on the?-Sialon bonded MgAl₂O₄-C materials and AlON bonded MgAl₂O₄-C materials.The samples were sintered at 1400?,1450?,1500?,1550? and 1600? for 1h,2h,3h and 4h respectively.The results show that ?-Sialon was formed in the samples sintered at 1400?,1450? and 1500?,the compressive strength?64.75MPa?and bending strength?15.18MPa?are generated when the temperature is 1450?.AlON was formed in else samples sintered at 1550? and 1600?,the compressive strength?58.44MPa?and bending strength?14.27MPa?are generated when the temperature is1550?.Compared with traditional MgAl₂O₄-C materail,?-Sialon or AlON bonded MgAl₂O₄-C materails has better properties.Because of ?-Sialon,AlON can form direct chemical bonding with MgAl₂O₄ and C.The optimal nitriding temperature of SMAC material is 1450?.And,the optimal nitriding temperature of AMAC material is 1550?.?2?The experiment of slag corrosion resistance for SMAC and AMAC materials were carried out with static crucible method.In the process of slag corrosion,?-Sialon,Si₃N₄ and SiC happened to oxide and dissolved into slag,which increase the ciscosity of slag and prevent the further slag penetration.Apparent activations energy are202 k J/mol and 141 k J/mol respectively.And,the oxide of AlON can produce Al₂O?g?and N₂?g?to prevent the further penetration.The alumina rich spinel can absorbed FeO from the slag to form a solid solution and the reaction of Al₂O₃ and CaO produced Al₂O₃-CaO compounds with high melting point,prevent the further penetration also.?3?High temperature oxidation behavior of SMAC and AMAC materials wereinvestigated in 1100?,1200? and 1300?.The SMAC material oxidation behavior can be divided into three stages: interface chemical reaction,reaction and diffusion controlled,and diffusion controlled stage,apparent activation energies are 253 k J/mol,342 k J/mol and 355 k J/mol.The AMAC material have the same oxidation behavior with SMAC material,and apparent activation energies are 305 k J/mol,314 k J/mol and357 k J/mol.