CALCIUM SILICATE-GRAPHITE-COMPOUND A NEW MATERIAL FOR THE FLOW CONTROL OF LIQUID ALUMINIUM ALLOYS

摘要

Introduction The combination of Calcium Silicate with carbon fibers is well known and such materials are used for many years in numerous applications, especially as transition plates in billet casters. The carbon fibers used are PAN based (polyacrylonitrile), also the use of pitch based fibers is known. The fibers are chopped; the orientation is mostly parallel to the plane of pressing, but randomly distributed. The weight fraction does in general not exceed 2% [1, 2, 3,4]. The carbonized fibers oxidize and burn off very fast during the use in liquid aluminium. Therefore after a short time of use at temperatures above 400°C a progressive fade away of the fibers following the heat gradient in the Calcium Silicate is observed. Compared to Calcium Silicate grades without carbon fibers there is obviously no significant difference in the mechanical and physical properties by adding carbon fibers of only around 2%. To combine the mechanical and physical properties of Calcium Silicate and Graphite and to utilize the Graphite properties it is obviously necessary to increase significantly the amount of Graphite and also to select the right type of the carbon material. Of particular interest are to tailor the thermo-physical properties, especially thermal conductivity and coefficient of thermal expansion and to minimize the oxidation of the Graphite component.