可水合氧化铝添加量对中温处理后刚玉浇注料强度和显微结构的影响

Effect of hydratable alumina additions on strength and microstructure of corundum castables after medium temperature treatment

为弄清可水合氧化铝(HA)结合浇注料中温强度低的原因,以板状刚玉、活性氧化铝粉、HA为原料制备刚玉浇注料。研究了HA添加量(w,1%、3%、6%、9%)和热处理温度(110℃保温24 h,400、600、800、1000、1100和1250℃保温5 h)对浇注料强度和显微结构的影响。结果表明:1)养护和干燥过程中,HA通过水化反应生成蜂窝状产物勃姆石和拜耳石,起到结构骨架的作用,为浇注料提供强度。2)HA结合浇注料在1000℃热处理后强度最低;在低于1000℃时,热处理温度的升高会逐渐破坏水化产物的结构,降低浇注料的强度;高于1000℃时,浇注料基质中发生了局部烧结,使得强度有所回升。3)提高HA的加入量无法提升浇注料的中温强度,说明中温热处理使得HA的水化产物结构完全坍塌,无法起到结构支撑的作用。

In order to find out the reason for the low strength of HA-bonded castables at intermediate temperatures,corundum castables were prepared using tabular corundum,active alumina powder,and hydratable alumina(HA)as raw materials.The effects of different HA additions(1%,3%,6%,and 9%,by mass)and the heat treatment temperature(drying at 110℃ for 24 h,heat treatment at 400,600,800,1000,1100 or 1250℃ for 5 h)on the strength and the microstructure of the castables were studied.The results show that:(1)during the curing and drying process,HA generates honeycomb products boehmite and bayerite through hydration,which act as the structural skeleton and provide strength for castables;(2)HA-bonded castables have the lowest strength after the heat treatment at 1000℃;with the increase of the heat treatment temperature below 1000℃,the structure of hydrates is damaged gradually,thus reducing the strength of the castables;when the heat treatment temperature is higher than 1000℃,partial sintering occurs in the castable matrix,enhancing the strength a little bit;(3)the strength of castables at intermediate temperatures cannot be improved by increasing the addition of HA,indicating that the hydration product structure of HA collapses completely due to the thermal treatment at intermediate temperatures,which could not play the role of structural support.