USING FLY ASH-BASED FOUNDRY COMPOSITION FOR MOLDS AND CORES (FASAND) TO POUR IRON CASTINGS

摘要

The study discusses the results of experiments and trials concerning application of fly ash as a base material of foundry sands (FASAND mixture) to produce iron castings for automotive industry. Two types of fly ash were examined; the fly ash from Eastlake Plant (USA) and, for comparison, the fly ash from Skawina Power Plant (Poland). For these two types of fly ash detailed investigation was made as regards chemical composition, phase constitution, density distribution of individual fractions, toxicity, and thermal characteristics. Sandmixes were prepared with the participation of the fly ash and mixtures of the fly ash, quartz sand and molochite. As chemically binding systems were used" soluble sodium silicate + diacctate ethylene glycol", "Portland cement + water", "hydrolyzed ethyl silicate + NH_4OH". In the case of thermal curing, soluble sodium silicate was used as binder. To the sandmixes were introduced also pore-forming additives (Genifor GK-B and the acid sodium carbonate NaHCO_3) whose thermal decomposition causes the emanation of gases - mostly CO_2. After initial selection of the sandmixes compositions, the technological properties of the FASAND type mixtures were tested. Using the three selected chemical compositions and fabrication methods, under the local conditions of Energy Industries of Ohio and Foundry Research Institute - Krakow, some trials were conducted on casting the gray and ductile irons, using cores assigned for the production of castings for automotive industry and the conventional sand casting technology. The ready castings were subjected to macroscopic examinations to check the suface condition and gas content. It has been stated that further work on practical application of FASAND mixtures in pouring iron castings should focus on searching for other types offly ash, characterized by higher thermal properties, and on search for other means to improve the permeability of the ready mixtures by raising their open porosity.