CaO含量对刚玉质浇注料性能与显微结构的影响

Effect of CaO content on properties and microstructure of corundum based castables

通过控制铝酸钙水泥加入量,研究了CaO含量分别为0、0.5%、1.3%、1.7%、2.5%、3%、3.5%、4.9%、5.6%和7.5%时对刚玉质浇注料烧结性能、抗热震性和显微结构的影响,同时借助XRD、SEM、EDS和高温热膨胀仪等手段对浇注料的物相变化、热膨胀系数和显微结构进行了分析和观察。结果表明:刚玉质浇注料中CaO含量显著影响着浇注料的烧结性能、抗热震性及其显微结构,当CaO含量低于2.5%时,随着CaO含量的增加,浇注料中片状CA6逐渐增多,并伴随着大量的体积膨胀,导致浇注料体积密度下降,显气孔率上升;当CaO含量超过2.5%时,随着CaO含量增加,浇注料中CA2相含量增加,CA6相含量逐渐减少,浇注料体积密度开始增加,显气孔率下降,线膨胀率减小,CaO含量高于5.6%的浇注料出现了收缩;刚玉质浇注料的抗热震性与显微结构密切相关,CaO含量为4.9%～7.5%的刚玉质浇注料具有很好的抗热震性,这是由于浇注料基质中粒状CA2与片状CA6相互穿插,刚玉骨料边缘片状CA6向基质中生长,强化了基质与骨料的结合,同时CA2相具有低膨胀性,导致浇注料具有较高的强度保持率和抗热震性。

The effects of CaO contents （0,0.5% ,1.3% ,1. 7% ,2.5% ,3% ,3.5% ,4.9% ,5.6% and 7. 5% respectively）on sintering properties,thermal shock resistance and microstructure of corundum based castables were investigated by conditioning the additions of pure calcium aluminate cement. The phase changes,thermal expansion coefficients and microstructures of the castables were determined and observed by means of XRD, SEM,EDS and thermal dilatometer,etc. The results show that. （1） The content of CaO affects the sintering properties,thermal shock resistance and microstructure of the castable remarkably. When CaO content is less than 2.5% ,the amount of platelet CA6 phase increases gradually with the increase of the CaO content in castables leading to the volume expansion,the decrease of bulk density and increase of apparent porosity. However,when CaO content is more than 2.5% ,the bulk density of the castable increases,the apparent, porosity and the linear expansion rate begin to decrease, accompanying the increment of CA2 phase and the decrease of the CA6 phase with the increase of CaO content in castables. When CaO content is more than 5.6%, the shrinkage phenomena occurrs in castables. .（2） The thermal shock resistance of the corundum based castable is directly related to its microstructure. When CaO content is in the range of 4.9% to 7. 5%, the castables have good thermal shock resistance in associate with the microstructure of overlapping each other of the granular CA2 phase and the platelet CA6 in the matrix. In addition ,the platelet CA6 grows from the edge of corundum grain into the matrix,which can strengthen the matrix and bond aggregate together.