烧成温度对SiC-CA6复合材料性能的影响

Effect of firing temperature on properties of SiC-CA6 composites

为开发煤气化炉用无铬耐火材料,以SiC颗粒(2.5~1.43、1.43~0.5、≤0.5 mm)为骨料,CA 6细粉为基质,制备了SiC-CA 6复合材料坯体,在埋碳气氛下分别于1300、1400、1500、1550、1600、1650℃保温3 h。对烧后试样的加热永久线变化率、质量变化率、显气孔率、体积密度、常温抗折强度和常温耐压强度以及显微结构进行了检测和表征。结果表明:当烧成温度低于1500℃时,烧后试样略微膨胀,试样的致密度低,强度低,且随着温度的升高,抗折强度、耐压强度缓慢增加,显气孔率略有减小;当烧成温度在1500~1600℃时,烧后试样产生一定收缩,致密度、力学强度等显著提高,且随着烧成温度的增加,烧后试样的显气孔率减小,体积密度增大,抗折强度、耐压强度急剧增大;当烧成温度高于1600℃时,烧成试样的质量明显减少,致密度下降。综合认为,1600℃是该复合材料较为理想的烧成温度。

In order to develop chromium-free refractories for coal gasifiers,the SiC-CA 6 composites green bodies were prepared using SiC particles(2.5-1.43 mm,1.43-0.5 mm,≤0.5 mm)as aggregates and CA 6 powder as the matrix.These green bodies were thermal treated at 1300,1400,1500,1550,1600,and 1650℃in carbon embedded atmosphere for 3 h,respectively.The permanent linear change rate,the mass change rate,the apparent porosity,the bulk density,the cold modulus of rupture,the cold crushing strength and the microstructure of the fired specimens were measured and characterized.The results show that:when the firing temperature is lower than 1500℃,the fired specimens expand slightly,with low density and strength,and with the increase of the temperature,the cold modulus of rupture and the cold crushing strength increase slowly,the apparent porosity decreases slightly.When the firing temperature is 1500-1600℃,the specimens shrink in a certain degree,and the density and the mechanical strength increase obviously.In addition,with the increase of the firing temperature,the apparent porosity decreases while the bulk density of the fired specimens increases,the cold modulus of rupture and the cold crushing strength increase sharply.When the firing temperature is higher than 1600℃,the mass of the specimens loses greatly and the bulk density decreases.Comprehensive comparison shows that 1600℃is the ideal firing temperature of the composite.