Abstract:

To develop alumina bubble castables with low density,high strength,easy molding and good thermal insulation,MgCO₃ 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 MgCO₃ micro-powder.The effects of the MgCO₃ 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 1 500 ℃ for 3 h,the tabular crystal morphology of calcium hexaaluminate (CA₆) in the matrix is changed,a microcrystalline structure of smaller granular magnesium aluminate spinel (MA) coexisting with CA₆ microcrystalliteis formed,and the formed MA-CA₆ 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 1 500 ℃ 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%.

Key words: alumina bubble castables, magnesium carbonate micro-powder, calcium hexaaluminate-magnesium aluminate microcrystallite

摘要：

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MgCO₃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MgCO₃微粉制备了氧化铝空心球浇注料试样,研究了MgCO₃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1 500 ℃保温3 h热处理后,改变了基质中六铝酸钙(CA₆)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CA₆微晶共存的微晶结构,形成的MA-CA₆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;1 500 ℃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%。

关键词: 氧化铝空心球浇注料, MgCO₃微粉, CA₆-MA微晶