Refractory cores, production thereof and use thereof in casting of ferrous alloys.

摘要

The refractory cores, which have a porosity of at least 25% by volume and a modulus of rupture of at least 60 kilograms per square centimetre, are formed from a particulate material predominantly comprising vitreous silica grains bonded together by crystalline silica formed in situ at the grain boundaries in an amount of not more than 30% by weight of the core. The cores are made from a mixture comprising an organic binder, a mineralizer and refractory particles (at least 40% of the latter having a particle size of at least 50 microns and at least 20% of the refractory particles being vitreous silica particles of size 1 to 30 microns) by shaping the mixture, firing at at least 1000 DEG C to form crystalline silica in the amount specified above, and cooling. The cores are used for casting ferrous alloys at at least 1500 DEG C.