Casting moulds for top casting steel ingots - provided with silicon carbide and graphite-contg. recess-fitted refractory inserts at centre of bed plate

摘要

Bed plate centre of casting mould for top-casting steel ingots is provided with a recess-fitted insert consisting of a refractory C-bonded SiC-graphite material (A) having a heat conductivity of 20-30 kcal/mhr degree C. (A) consists mainly of natural graphite, SiC and silicic acid bonded with one another by an organic binder, e.g. tar and pref. contains, by wt., 30-50% C and graphite, 30-50 % SiC and 5-20 % SiO2. Insert is pref. fixed in recess with a binder compsn. contg., by wt., 45-55 % SiC, 10-15 % FeSi, 5-9 % frit and 25-35 % colloidal SiO2 soln. (5-20 % solids), and frit consists of 20-25 % alkali metal oxide, 8-15 % B2O3, 45-55 % siO2 and 10-15 % CaO. Compressive strengths are 260-700 kg/cm2. Higher compressive strengths are achieved with a higher SiC content and higher heat-conductivities with a higher graphite content.