Abrasive tool making process – material – or composition – With carbohydrate or reaction product thereof
Patent
1989-10-06
1991-12-10
Rachuba, Martha
Abrasive tool making process, material, or composition
With carbohydrate or reaction product thereof
511631, 511641, B24B 100
Patent
active
050706586
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for the production of ceramic components which have at least one planar or curved sliding and sealing face.
Ceramic objects having a planar or curved sliding and sealing face are usually produced by shaping a green ceramic article, sintering, grinding and subsequent lapping or polishing the ground face. Sliding rings for gaskets or sealing and regulating washers for sanitary fittings are examples of objects produced in this way. During polishing, the moldings are treated for a relatively long period with a paste or emulsion of a polishing agent, for example diamond grit, and at the same time pressed against rotating surfaces, for example grooved planar steel disks, in special-purpose automatic polishers. Rough areas are leveled in this way. Machines for lapping and polishing require high investment; their operation is labor-intensive and therefore associated with high labor costs per unit.
For aluminum oxide sliding rings, a maximum permissible unevenness of 0.6 .mu.m is required for adequate sealing. The mean roughness (Ra) should not exceed 0.15 .mu.m (VDI Reports (sic) No. 194, 1973, p. 124). Such roughnesses can only be achieved by polishing or lapping.
European Offenlegungsschrift 043,456 discloses valve washers for mixing valves, in particular sanitary mixing faucets, which contain zirconium oxide or hafnium oxide and have a mean roughness of less than 0.3 .mu.m. Treatment by lapping or polishing is necessary for the production of these washers.
In the visual control of customary ceramic articles having a sliding and sealing face, those skilled in the art require that this face reflects.
The object was therefore to specify a process for the production of ceramic moldings which have planar or curved sliding and sealing surfaces, and with the aid of which it is possible to produce in a simple and inexpensive manner, surfaces of identical sliding and sealing behavior.
The present process achieves this object. This is a process for the production of ceramic sealing components for a machine, the components being in frictional contact and having at least one planar or curved sliding and sealing face, by shaping a green ceramic article, sintering, grinding and subsequently smoothing the sliding and sealing face formed and, if necessary, subsequently washing. This process comprises abrasive-polishing the articles in the presence of an aqueous phase, without using scouring elements, until a mean roughness of greater than 0.1 and not more than 0.8 .mu.m is reached, the articles used being shaped in such a way that they can develop their abrasive-polishing effect on the sliding and sealing face being formed.
In abrasive polishing, small parts, which are usually present in large numbers, are agitated in a container, together with an aqueous phase, for a relatively long period. This process is used for deburring or polishing metallic parts in electroplating.
This process is described in greater detail in the reference book "Trommeln" by A. Linek, Deutscher Fachzeit-schriften- und Fachbuchverlag GmbH, Stuttgart, 1953. It is stated that the metallic parts are agitated in the presence of added abrasive elements, for example sand or "Trowal" (synthetically prepared aluminum oxide). The treatment of ceramic surfaces is not mentioned in this literature citation.
The process according to the invention can be applied, in particular, to the smoothing of the surfaces of articles made from silicon carbide, steatite and aluminum oxide.
After grinding, the mean roughness Ra is 0.8 to more than 1 .mu.m, depending on the abrasive disk used. It is possible, but in most cases not necessary, to wash and thus to free of grinding dust, the ground ceramic articles before abrasive polishing. Washing or degreasing is appropriate, in particular, if the ceramic articles are contaminated by grinding oil. In this refinement of the process according to the invention, finely divided abrasive substances, such as sand, are not present. In the case of planar sliding faces, the grinding takes place by face grin
REFERENCES:
patent: 3745722 (1973-07-01), Balz
patent: 3965620 (1976-06-01), Dreher
patent: 4420142 (1983-12-01), Dworak et al.
A. Linek, "Trommeln", Deutscher Fachzeitschriften- und Fachbuchverlag GmbH, VDI-Berichte Nr. 194, 1973, pp. 124-125.
M. Dreher, "Die Gleitschlifftechnik in Trommeln und Fliehkraftgeraeten", Metalloberflaeche, vol. 41, No. 3, Mar. 1987, pp. 105-108.
Rajner Walter
Russner Klaus
Hoechst Ceramtec Aktiengesellschaft
Rachuba Martha
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