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AssigneeElektroschmelzwerk Kempten GmbH
InventorsPeter Sindlhauser, Klaus Hunold, Alfred Lipp
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Pressure-sintered polycrystalline mixed materials, with a base of boron nitride, oxides and carbides, are provided in which the hexagonal boron nitride fraction is about 30 to about 85% by weight, the oxide fraction (ZrO.sub.2, MgO) is about 10 to about 50% by weight, and the carbide fraction (SiC, TiC, ZrC) is about 5 to about 20% by weight. These mixed materials have a density of at least 94% of the theoretical density and can be produced by hot-pressing powder mixtures composed of hexagonal boron nitride, the selected oxides and carbides at temperatures in the range of from 1500.degree. C. to 1800.degree. C. under a die pressure of 7 to 20 MPa or by isostatically hot-pressing, in a vacuum tight closed case, at temperatures in the range from about 1400.degree. C. to about 1700.degree. C. under a pressure of about 100 to about 300 MPa in a high-pressure autoclave using an inert gas as the pressure transfer medium. These mixed materials are resistant to liquid metals, wear resistant and thermal shock resistant and, owing to these properties, are suitable for use as detachment or break rings in the horizontal continuous casting of steel and non-ferrous metals.
A pressure-sintered polycrystalline mixed material with a base of powders of boron nitride, an oxide and a carbide, in which the boron nitride fraction is hexagonal and is present in an amount of from about 30 to about 85% by weight, the oxide is selected from the group consisting of zirconium oxide and magnesium oxide and is from about 10 to about 50% by weight, and the carbide is selected from the group consisting of silicon carbide, titanium carbide and zirconium carbide and is from about 5 to about 20% by weight, and which have a density of at least about 94% of the theoretically possible density, the weight being based on the total weight of said mixed material.
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