Abstract:

Al₂O₃-SiO₂ castables were prepared using three-grade bauxite (5-0.088 and ≤0.088 mm ),special-grade bauxite ( 1-0.088 and ≤0.088 mm ) and silicon carbide (≤0.074 mm ) as main raw materials,calcium aluminate cement as the binder,and adding an appropriate amount of α-Al₂O₃ micropowder,SiO₂ micropowder and water reducing agent.The linear change rate,the apparent porosity,the chemical composition,the phase composition and the microstructure of the samples fired at 1 400 ℃ for 24 h in air atmosphere were analyzed,and the influence of inert oxidation of SiC on the linear change rate of the samples was discussed when the SiC addition was 3%,6%,8% and 10%,by mass,respectively.The results show that:(1)the product SiO₂ of SiC inert oxidation can fill the pores and reduce the apparent porosity,but it does not react with Al₂O₃ to form mullite immediately after formation;(2)secondary mullitization is the main factor for the increase of the linear change rate of the samples;excessive SiC inhibits its own inert oxidation,leading to a relative reduction of the oxidation product SiO₂,which is not conducive to the sintering and the continuous secondary mullitization of the samples;(3)when the SiC addition is 6% in the full-component sample,the sample has the maximum linear change rate,while maintaining relatively uniform microstructures.

Key words: silicon carbide, inert oxidation, alumina-silica castable, linear change rate, expansion

摘要：

以三级矾土(5~0.088、≤0.088 mm)、特级矾土(1~0.088、≤0.088 mm)、碳化硅(≤0.074 mm)为主要原料,以铝酸钙水泥为结合剂,加入适量的α-Al₂O₃微粉、SiO₂微粉和减水剂制备了Al₂O₃-SiO₂浇注料。对经1 400 ℃空气气氛保温24 h烧后试样的线变化率、显气孔率、化学组成、物相组成和微观结构进行分析,探讨了SiC加入量(w)分别为3%、6%、8%、10%时SiC的惰性氧化对试样线变化率的影响。结果表明:1)SiC惰性氧化产物SiO₂可以填充气孔,降低显气孔率,但SiO₂生成后并不会立即与Al₂O₃发生反应形成莫来石;2)二次莫来石化是试样线变化率提高的主要因素,过量SiC抑制了自身的惰性氧化,氧化产物SiO₂相对减少,不利于试样的烧结以及二次莫来石化的持续进行;3)全组分试样中SiC加入量(w)为6%时,可以使试样在线变化率最大化的同时保持相对均匀的内、外部组织结构。

关键词: SiC, 惰性氧化, Al₂O₃-SiO₂浇注料, 线变化率, 膨胀