Plastic and nonmetallic article shaping or treating: processes – Outside of mold sintering or vitrifying of shaped inorganic... – Simultaneously burning – vaporizing – or melting of embedded...
Patent
1997-07-23
2000-07-11
Derrington, James
Plastic and nonmetallic article shaping or treating: processes
Outside of mold sintering or vitrifying of shaped inorganic...
Simultaneously burning, vaporizing, or melting of embedded...
264 291, 264317, C04B 35573
Patent
active
060868147
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a method for the manufacture of a friction unit for frictional engagement with a counter-body, especially for the manufacture of a brake or clutch body, in which a porous carbon body is prepared which corresponds approximately to the final contour of the friction unit wherein the pores of this carbon body are infiltrated with fluid silicon, and the body is ceramicized by introducing a chemical reaction with the formation of silicon carbide.
A method for the manufacture of a friction unit was presented by a work group of the DLR (Deutsche Forschungsanstalt fuir Luft- und Raumfahrt e.V.), of Stuttgart, Institut fur Bauweisen- und Konstruktionsforschung, at the VDI Materials Convention in Duisburg on Mar. 9-10, 1994, the theme of which was lightweight structures and lightweight components, in the framework of the lecture entitled "Development of integral lightweight structures of ceramic fiber." In this lecture, a technology for manufacturing carbon fiber-reinforced carbons was presented. The carbon fiber-reinforced carbons are infiltrated with fluid silicon by a so-called "fluid silicification method" and subjected to a heat treatment, wherein the silicon is converted with carbon to SiC. One possible application of these C/C-SiC materials is, among others, brake disks.
Increasingly severe requirements are being made of brakes, especially in motor vehicle and aircraft construction. The speeds which are attained nowadays by such vehicles are constantly increasing. When brakes are applied, the kinetic energy is converted by friction to heat, which is absorbed by the brake disk and the brake linings. A brake system of this kind is accordingly limited by the friction characteristics of the brake material and its ability to store and remove heat. In general, brake materials must have very good thermomechanical properties, high and constant friction characteristics and good resistance to abrasion. Ordinary brake disks of cast iron or steel, which are today used in ordinary automobile construction, permit temperatures of approximately 650.degree. C. Brakes of carbon fiber-reinforced carbon materials (C/C) developed in recent years, such as those described for example in DE-A1 3 24 200, allow temperatures up to 1000.degree. C.
At the above-described VDI presentation, a C/C-SiC material was exhibited, as stated above, which shows decided advantages over a C/C material, especially in regard to thermal shock resistance, oxidation resistance, moisture absorption and frictional performance.
Setting out from the above-described state of the art, the present invention is addressed to the problem of improving a method for the manufacture of such a friction unit of the kind described above such that it will withstand an elevated thermal stress and furthermore will be able to be manufactured in a simple manner.
SUMMARY OF THE INVENTION
The above stated object is obtained by the method of the invention in that, before the silicon infiltration, the porous carbon body is so structured that cavities and/or recesses are formed in defined inner and/or outer areas for cooling and/or stiffening, which are substantially retained in their shape and size after the ceramicization. As it is generally known, ceramic material or ceramicized material is extremely difficult to work, so that structuring could be performed in such heretofore known friction units only at great expense. Consequently such structuring has been performed only on the outer circumference, for example in the form of radial bores in such components for the purpose of giving the friction units, for example, the necessary outside contour. By the method of the invention it is possible to create even complex structures in the form of recesses, since such recesses are formed in a state of the carbon body in which no ceramicization, which is performed by infiltration of silicon followed by heat treatment, is present. Furthermore, with the method of the invention not only are recesses formed in outside surfaces of
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Entwicklung Integraler Leichtbaustrukturen Aus Faserkeramik, by Walter Krenkel, Volkmar Dollhopf und Frank Kocian, DLR-Stuttgart, published at the VDI Werkstofftag '94, Leichtbau-Strukturen und Leichtebauteile, in Duisburg, 9./10. 3.1994.
Kochendorfer Richard
Krenkel Walter
Derrington James
Deutsche Forschungsanstallt fur Luft-und Raumfahrt, E.V.
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