硅溶胶型壳经高温作用后的形态和强度变化  

High Temperature Behavior of Silica Sol Shell and Its Influencing Factors

作　　者：郭馨[1] 李晓阳[1] 吕志刚[1] 崔旭龙[1] 王长明[1] 

机构地区：[1]清华大学机械工程系,先进成形制造教育部重点实验室,北京100084

出　　处：《特种铸造及有色合金》2011年第7期636-639,共4页Special Casting & Nonferrous Alloys

基　　金：国家自然科学基金资助项目(50875144)

摘　　要：研究对比了经900-1600℃高温焙烧后,硅溶胶型壳表面形态及残留强度的变化情况,分析认为耐火材料中氧化物杂质的存在对型壳表面形态的变化起重要作用。元素Fe、Mg、Ca、Na、K等在高温焙烧中与Al2O3、SiO2反应生成低熔点物质,导致型壳表面形态的变化,并可能引起型壳高温软化。为保证型壳具有高的表面质量和良好的脱壳性,减少浇注过程中高温软化发生的可能性,应严格控制型壳中有害杂质元素的含量。经900-1200℃焙烧后硅溶胶型壳残留强度基本稳定;经1200-1500℃焙烧由于二次莫来石化反应和碱性氧化物杂质的作用,型壳残留强度增高,可能发生高温软化;经1500℃以上焙烧时型壳已处于再结晶阶段,残留强度显著增加,脱壳性变差。With the development of investment casting industry, the performance, especially the high performance of the silica sol shell was been highly required, so it was necessary to improve the quality of the shell. It was important to improve the quality of shells and castings by investigating the high temperature performance of the shell. Surface change and residual strength of the shell baked at 900-1 600 ℃ were analyzed comparatively. The results show that existence of impurities in the refractory materials is closely related to the change of surface morphology of the shell. Fe, Mg, Ca, Na, and K in the refractory material can react with Al2O3 and SiO2 during baking process at high temperature to generate the low point phase, leading to the change of shell surface morphology and possible soft behavior of shell at high temperature. To ensure high surface quality and desirable de-shell ability and to reduce the possibility of high temperature softness of shell during pouring process, impurities in the shell should be strictly controlled. Residual strength of the shell exhibits basically stable at 900-1 200 ℃,and residual strength of the shell is increased at 1 200-1 500 ℃ as a result of mullite secondary reaction and effects of impurities, existing in the possibility of high temperature softness. Residual strength is greatly increased due to recrystallization of shell at above 1 500 ℃, resulting in the deterioration of de-shell performance.

关 键 词：硅溶胶型壳 高温 强度 形态变化 

分 类 号：TG249.5[机械工程—精密仪器及机械]