Utilization of Egyptian quartz and quartzite raw materials for processing chemically-bonded ramming mixes

Abstract

Chemically-bonded refractory ramming mixes from Egyptian quartz and quartzite raw materials were processed for application in lining induction furnaces for ductile iron production.Two Egyptian quartz samples and one quartzite sample as well as an imported quartz mix were used. Chemical and mineralogical composition as well as crystallite size of quartz mineral and grain-size distribution of the latter mix were determined, using wet-chemical, XRD and sieve analysis methods. The obtained data were applied to process similar mixes from the Egyptian quartz and quartzite samples. Densification and thermo-mechanical properties of all mixes were determined along with the rate of transformation of quartz to cristobalite after firing up to 1400°C.The results led to recommend the Egyptian Rod EL-Lekah quartz raw material for processing chemically-bonded ramming silica mixes similar to the imported types in lining induction furnaces for ductile iron production after adding 1.2% boric acid. This is based on its relatively higher purity, larger crystallite size and hence lower rate of quartz-cristobalite transformation as compared with the other Egyptian quartz and quartzite mixes. Hence, the recommended mix shows relatively lower percentage of thermal expansion at 100-300°C and higher rate of subsidence under load up to 1500°C with higher degree of densification after firing up to 1400°C.The increase of boric acid content up to 3.2% leads to excessive development of liquid phase on firing up to 1400°C at the expense of quartz and cristobalite. Accordingly, higher rate of vitrification occurs which deteriorates the thermo-mechanical properties of the fired mixes.