Influence Of Andalusite Particle Size, Composition And Addition On Properties Of Bauxite-silicon Carbide Brick

In recent years, the application of andalusite for the domestic cement rotary kilngets fast development due to the bauxite-silicon carbide brick has good thermal shockresistance. The mullite interlaced structure formed during mullitization of andalusiteplays a key role in improving high-temperature properties and toughness of materials,which makes andalusite widely used in many fields. Considering the requirement ofrefractory used in transition zone of cement rotary kiln is harsh, the high-temperatureperformances, particularly thermal shock resistance and refractoriness under load, ofbauxite-silicon carbide brick should be improved after adding andalusite. Currently,the domestic refractories enterprises mostly use andalusite in powder to manufacturebauxite-silicon carbide brick. The literature of andalusite used in bauxite-siliconcarbide brick both at home and abroad is less, and few systematic reports aboutinfluence of andalusite particle size, composition and addition on properties ofbauxite-silicon carbide brick. The experiment is to systematically study the influenceof andalusite particle size, composition and addition on properties of bauxite-siliconcarbide brick, with emphasis on investigating influence on the thermal shockresistance and refractoriness under load and making clear the relationship amongandalusite, material properties and microstructure. The influence mechanism onperformances of bauxite-silicon carbide brick is characterized by observing themicrostructure. It is expected to develop the refractory with better performance andlower cost used in transition zone of cement kiln.The influence of andalusite on properties of bauxite-silicon carbide brick isstudied. Bauxite, andalusite, silicon carbide powder and clay are used as main rawmaterials to prepare samples of bauxite-silicon carbide brick in the experiment. Thesamples are fired at1480°C for3h and the general properties, thermal shockresistance, refractoriness under load and microstructure of samples after firing aredetected. The results show that, for the samples adding different particle size ofandalusite, the bulk density of samples after firing increases and the apparent porositydecreases with the increased size of andalusite because the smaller the particle size ofandalusite, the faster the speed of mullitization. The cold crushing strength of samplesdecreases with the increase of andalusite. As for the samples with different composition of andalusite, the bulk density decreases and the apparent porosityincreases with the increase of andalusite grade. The cold crushing strength of samplesincreases with the increase of andalusite grade. The addition of andalusite canimprove thermal shock resistance of bauxite-silicon carbide bricks. The reason for thisresult may be that andalusite is converted into quantities of mullite with capillarynetworks, which are distributed in the bricks disorderly, and connected capillarymullite grains can resist spread of cracks caused by thermal shock. And the greater theparticle size of andalusite, the larger mullite grains transformed form andalusite, andthe more micro cracks formed, leading to increase in the thermal shock resistance ofsamples after firing. The thermal shock resistance of samples improves gradually ingeneral with the rise of the andalusite grade. The connected capillary mullite formedafter mullitization of andalusite or the volume expansion of mullitization of theresidual andalusite in high temperature can increase the refractoriness under load, andthe refractoriness under load increases with the increase of andalusite addition. Therefractoriness under load of samples after firing increases with the increase ofandalusite grade.The study shows that the thermal shock resistance and refractoriness under loadare improved after adding andalusite compared with the samples without andalusite.The relationship between andalusite addition and performances of refractory productscan be understood preferably through the study of the influence of andalusite particlesize, composition and addition on bauxite-silicon carbide brick, providing guidancefor finding the right method to improve the properties, such as thermal shockresistance and refractoriness under load, of bauxite-silicon carbide brick.