Strengthening And Toughening Of Mullite-silicon Carbide Materials For CDQ

Coke dry quenching(CDQ)is an advanced technology being popularized in china because of the advantages of saving energy and environmentally friendly,but the damage of CDQ furnace ramp pillar seriously affected the safe operation and production efficiency in the CDQ.Therefore,the development of a durable refractory for CDQ furnace ramp pillar is of great significance.In this paper,firstly the mechanism for the damage of mullite-SiC materials of CDQ furnace ramp pillar was analyzed by numerical simulation and experiment,then the performance of different binders on mullite-SiC materials were compared,and the toughening effect of steel fiber of different type and amounts,as well as the in-situ generated AlN whiskers on mullite-Si C materials were studied and examined.Finally,the mechanism for the toughening of mullite-SiC material by steel fiber and AlN whiskers was discussed.The results are as follows:(1)The CDQ furnace ramp pillar need withstand great bending stress and thermal stress,but the strength and thermal shock resistance of current mullite-silicon carbide material is poor.So the main reason for damage is that the bending stress after repeated temperature fluctuations is too great for the refractory to bear.(2)The castables with calcium aluminate cement as binding have the best mechanical properties,thermal shock resistance and wear resistance.(3)The mechanical properties,thermal shock resistance and wear resistance of mullite-SiC castables can be significantly increased by adding steel fibers,of which the steel fiber of melt pumping meniscu has better performance.The appropriate adding amount is 2vol%.(4)The metal aluminum powder was added to the mullite-SiC materials,which could promote the sintering and increase the strength and bulk density of materials obviously.The best results appears at the amount of 6wt%.The hexagonal Al N phase formed in materials added with metal aluminium after nitriding at 850?,and the in-situ generated AlN whiskers with a length2?m~10?m,a diameter 5nm~100nm after nitriding at 1000? improved the strength effectively,the flexural strength of the sample at 1000? was up to 39.6MPa.Reducing the particle size of metal aluminium powder and adding catalyst can promote the generating of AlN whiskers.The metal Al powder in the sample containing nano Fe powder as catalyst transfered into AlN films after nitriding at 600?,and the AlN whiskers formed at 850? after nitriding.(5)The fracture energies and tougheness of the mullite-SiC castables enhanced by steel fiber through the bond strength and mechanical anchoring force between steel fiber and castable interface;a network structure of AlN whiskers formed in the matrix material,improved the tougheness through whiskers pull out and whiskers federation.