MgCO_(3)微粉加入量对氧化铝空心球浇注料结构和性能的影响

Effect of MgCO_(3) micro-powder addition on structure and properties of alumina bubble castables

为了开发出低密度、高强度、易成型、保温效果好的氧化铝空心球浇注料,将MgCO_(3)微粉引入到氧化铝空心球浇注料基质中。采用粒度分别为5~3、3~1和1~0.2 mm的氧化铝空心球,板状刚玉细粉、氧化铝微粉和MgCO_(3)微粉制备了氧化铝空心球浇注料试样,研究了MgCO_(3)微粉加入量(w,0、1%、2%、3%、4%)对试样显微结构和性能的影响。结果表明:1)经1500℃保温3 h热处理后,改变了基质中六铝酸钙(CA_(6))板片状的晶体形态,生成了粒度更加细小的镁铝尖晶石(MA)和CA_(6)微晶共存的微晶结构,形成的MA-CA_(6)微晶复合体均匀分布在基质空隙内部。2)110℃保温24 h处理后,浇注料体积密度从1.83 g·cm^(-3)降低到1.58 g·cm^(-3),常温抗折强度大于5 MPa;1500℃保温3 h处理后,加热永久线变化率保持在0~0.5%微膨胀,体积稳定性优异;400℃时的热导率下降近30%。

To develop alumina bubble castables with low density,high strength,easy molding and good thermal insulation,MgCO_(3)micro-powder was introduced into their matrix.The alumina bubble castable samples were prepared using alumina bubbles with particle sizes of 5-3,3-1 and 1-0.2 mm,tabular corundum fine powder,alumina micro-powder and MgCO_(3)micro-powder.The effects of the MgCO_(3)micro-powder addition(0,1%,2%,3%and 4%,by mass)on the microstructure and the properties of the samples were studied.The results show that:(1)after firing at 1500℃for 3 h,the tabular crystal morphology of calcium hexaaluminate(CA_(6))in the matrix is changed,a microcrystalline structure of smaller granular magnesium aluminate spinel(MA)coexisting with CA_(6)microcrystalliteis formed,and the formed MA-CA_(6)micro crystallite complex is uniformly distributed in the matrix pores;(2)after firing at 110℃for 24 h,the bulk density of the castables decreases from 1.83 g·cm^(-3) to 1.58 g·cm^(-3),and the cold modulus of ruptureis over 5 MPa;after firing at 1500℃for 3 h,the sample slightly expands(0-0.5% of the permanent linear change),showing excellent volume stability;and the thermal conductivity at 400℃decreases by nearly 30%.