Specialized metallurgical processes – compositions for use therei – Compositions – Consolidated metal powder compositions
Patent
1999-05-20
2000-11-07
Mai, Ngoclan
Specialized metallurgical processes, compositions for use therei
Compositions
Consolidated metal powder compositions
75230, 75246, 419 24, 419 38, B22F 300
Patent
active
06143051&
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a friction material and in particular a brake lining material comprising a sintered mass of iron in which graphite particles are dispersed.
A number of commercially available brake lining materials comprise particles, such as iron particles and graphite particles, bonded together by an organic binder, such as a phenol-formaldehyde resin.
If brake linings consisting of such a material are exposed to severe energy loads and consequently high temperatures, such as temperatures of the order of 700.degree. C., which e.g. arise when they are used in brakes for trucks, a decomposition of the organic binder occurs under formation of gaseous decomposition products. Hereby the useful life of the brake linings is reduced.
Metal bonded brake lining materials are also known, viz. materials comprising a sintered iron matrix containing comparatively small amounts of dispersed graphite particles. These known metal bonded lining materials suffer from the disadvantage that at severe energy loads melting may occur of parts of the iron matrix, whereby an incipient welding together of the brake pads and the. brake drum or the brake disc occurs.
It is known to use brake linings which essentially consist of graphite ill brakes for Formula I racers. Such brakes are very efficient, but they are worn down very rapidly and normally only last one race.
It has been attempted to prepare metal bonded brake lining materials having a large content of graphite particles, but these attempts have run up against the difficulty that increasing content of graphite particles in the iron matrix entails decreasing strength and consequently reduced wear resistance.
EP 0 093 673 discloses a friction material comprising a major amount (72-85 weight-%) of iron powder, graphite (3-14 weight-%), coke (2-12 weight-%), low melting material (3-10 weight-%), such as tin, and a friction modifying agent (up to 3 weight-%), some of the iron powder being optionally replaced with iron fibres.
It is the object of the present invention to provide a friction material having haigher wear resistance than the friction material according to EP 0 093 673.
The friction material according to the invention is characterized in that the sintered mass comprises from between 13 and 22 vol.-% of iron fibres, between 13 and 22 vol.-% of iron particles having a particle size of 10-400 .mu.m, between 40 and 70 vol.-% of graphite particles having a particle size of 25-3000 .mu.m, and between 10 and 15 vol.-%, of a metallic binder having a melting point of 800-1140.degree. C.
The invention is based on the discovery that by using comparatively large graphite particles, the graphite particles normally used in metallurgical processes typically have a particle size of 0.1-10 .mu.m, and a metallic binder having a melting point within the temperature range ill which the sinterinig takes place, a strong and stable iron framework is formed in which the graphite particles are embedded, and from where they can be released under the influence of friction and form a film between brake pad and brake drum or brake disc.
The iron fibres, the iron particles and the metallic binder are thus the sintering active and consequently strength imparting components, while the graphite particles are the friction controlling components of the sintering mass.
The iron fibres present in the friction material are preferably steel fibres, i.e. fibres of an iron alloy having a carbon content of up to 2%;. The iron fibres preferably have a length between 0.5 and 5 mm and a thickness within the range 10-100 .mu.m.
As mentioned, the iron particles have a particle size from 10 to 400 .mu.m, and preferably a particle size from 20 to 200 .mu.m.
As mentioned, the graphite particles have a particle size from 25 to 3000 .mu.m, and preferably a particle size from 90 to 1000 .mu.M.
As metallic binder, preferably a metallic material selected from Cu, Sn and Zn is used.
Bronze in powder form and of a type in which the content of copper is from 85 to 99%, and the content of tin is from 1 to 15%,
REFERENCES:
patent: 3835118 (1974-09-01), Rhee et al.
patent: 4415363 (1983-11-01), Sanftleben et al.
patent: 5096661 (1992-03-01), Lang
patent: 5266395 (1993-11-01), Yamashita et al.
patent: 5501728 (1996-03-01), Shepley et al.
EPODOC/EPO, CN1079973 A 19931229, "Drilling Rig Skate Brake-Block . . . Method" of Yimeng Braking Material Factory (CN).
EPODOC/EPO, CN1110286 A 19951018, "High Temp. Resistance Non-Asbestos Friction Material" of Liu Junya (CN).
Brams.o slashed. Niels
De Leon Noel
Kr.ae butted.mer Ole
Kuylenstierna Claes
Simonsen Erik
A/S Roulunds Fabriker
Mai Ngoclan
Volvo Truck Corporation
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