Stock material or miscellaneous articles – All metal or with adjacent metals – Composite; i.e. – plural – adjacent – spatially distinct metal...
Reexamination Certificate
1999-08-13
2001-04-24
Jones, Deborah (Department: 1775)
Stock material or miscellaneous articles
All metal or with adjacent metals
Composite; i.e., plural, adjacent, spatially distinct metal...
C029S898120, C029S898140, C148S415000, C148S437000, C148S902000, C148S531000, C148S523000, C148S535000, C148S551000, C148S552000, C148S691000, C148S692000, C148S693000, C148S694000, C148S698000, C148S699000, C428S652000, C428S654000, C428S636000, C428S637000
Reexamination Certificate
active
06221515
ABSTRACT:
FIELD OF THE INVENTION
The present invention refers to a bimetallic strip, which is used in the formation of sliding bearings for internal combustion engines and which comprises a strip, which is made of an anti-friction or sliding material in aluminum base alloy usually containing silicon, tin and copper and which is adhered to a steel supporting strip. The present invention is also related to a process for producing said bimetallic strip.
BACKGROUND OF THE INVENTION
The internal combustion engines have been designed to work with increasingly higher speeds and loads, thereby requiring sliding bearings, which are able to support these increasingly severer operational conditions, through improved fatigue resistance and anti-sticking characteristics, and which can operate with forged steel or cast iron crankshafts, without the need to protect the bimetallic strip with a lead/tin electrodeposited overlayer.
It is known that the high fatigue resistance characteristics of these aluminum base alloys result from a finer and more uniform distribution of the silicon particles in the aluminum phase.
Nevertheless, the known alloys of these type, such as that described in U.S. Pat. No. 4,696,867, still present a silicon particle distribution which, in spite of a possible addition of small amounts of strontium or sodium to said alloys, does not reach a desirable refining to obtain a load capacity compatible with the operational requirements of the modern internal combustion engines.
The grain size of the known alloys of this type is from about 20 to 50 &mgr;m, avoiding the achievement of substantial increases of fatigue resistance in the produced bimetallic strips (see
FIG. 3
in the drawings). Besides de inconveniences cited above, it should be observed that the tin percentages of about 8% or more in the alloy composition do not allow said alloy, after its usual casting, to be hot rolled to the desired thickness for the sliding strip, because hot rolling these alloys presents the risk of the tin being squeezed out.
Another deficient aspect of the known solutions refers to the lack of treatment steps of the bimetallic strip, so as to obtain, in the sliding strip, a compound that is capable of hardening the aluminum alloy, increasing even more its fatigue resistance through a more accentuated silicon refining.
These prior art aluminum alloys are cast into billets with a shape which is very different from that to be attained by the sliding strip, thus making difficult and costly the manufacturing process of the bimetallic strip and the achievement of the minimum silicon refining in the alloy structure.
DISCLOSURE OF THE INVENTION
It is an objective of the present invention to provide a bimetallic strip for sliding bearings, which comprises an aluminum base alloy containing silicon and tin and which presents a structure with a high degree of silicon-tin refining, improved properties of fatigue resistance, anti-sticking and adherence to a supporting strip, without requiring the presence of strontium or sodium in the composition of the aluminum alloy and without leading to risks of the tin being squeezed out during the hot rolling steps of the sliding strip material.
Another objective of the invention is to provide a process which allows to obtain the above cited bimetallic strip in a economically feasible way.
REFERENCES:
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New Type Fatigue Phenomenon of Aluminum-Based Engine Bearings, SAE Technical Paper Series, International Congress and Exposition (Feb. 27-Mar. 3, 1989); Authors: Yukio Ogita, Kosaburo Niwa & Yoshitaka Kondo.
International Search Report.
Flores Denys da Cuhna
Ramos Júnior Joaquim de Oliveira
Santos Carlos Henrique Gaspar dos
Darby & Darby
Jones Deborah
Koehler Robert R.
Metal Leve S/A Industria E Comercio
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