LIME-GYPSUM BINDERS IN THE TECHNOLOGY OF HEAT INSULATING MATERIALS SYSTEMS CaO - Al2O3 - SiO2

Abstract

In Ukraine, at present, insulating materials whose phase composition is represented by pseudo-wollastonite (CaO·SiO2) and anorthite (CaO·Al2O3·2SiO2) are not industrially produced. At the same time, such materials are more effective in heat-insulating ability compared to chamotte lightweight with comparable characteristics of porosity and apparent density. Moreover, these materials do not wet and do not react with aluminum melts and its alloys with other non-ferrous metals, which in recent years has led to the large-scale import of such products for lining electrolytic cells, induction furnaces and the manufacture of injection equipment. An additional motivation in the development of such materials is the modern and progressively growing tendency to obtain, on the basis of synthetic wollastonite, anhydrous and specially granulated in the form of microspheres powder mixtures of a new generation – slag-forming and heat-insulating steels for casting steel and molds of continuous casting machines. The above circumstances stimulated the development of such materials for reasons of availability of raw materials in Ukraine, the possibility of using a simple method of forming products – casting self-hardening masses into calcareous forms on lime-gypsum binders, as well as relatively low firing temperatures. The report discusses the issues of technology of heat-insulating materials based on pseudo-wollastonite and anorthite using examples of a number of experimental compositions of injection molding materials with varying amounts of binder, lime / gypsum ratio, and the addition of alumina. The technological parameters are analyzed: the moisture content of the casting mass, the setting end time and the firing temperature of the samples, as well as the physical and mechanical properties achieved by the samples of the materials: apparent density, compressive strength and general shrinkage. The results of x-ray phase analysis of samples of materials and the features of the formation of microporosity according to the results of petrographic analysis of powder samples in immersion preparations are presented. Variants of technology modification are proposed to expand the functional applicability of research materials and increase their physical and mechanical properties.