Stock material or miscellaneous articles – All metal or with adjacent metals – Composite; i.e. – plural – adjacent – spatially distinct metal...
Reexamination Certificate
2001-10-16
2002-07-02
Koehler, Robert R. (Department: 1775)
Stock material or miscellaneous articles
All metal or with adjacent metals
Composite; i.e., plural, adjacent, spatially distinct metal...
C148S516000, C148S531000, C148S535000, C148S698000, C384S912000, C428S654000, C428S940000
Reexamination Certificate
active
06413654
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a multi-layered plain bearing which comprises a steel back and an aluminum-base bearing alloy layer which is bonded to the steel back via an intermediate layer made of an aluminum alloy, and to a producing method thereof.
2. Brief Description of the Art
Aluminum alloy plain bearings have excellent properties of conformability and wear resistance, and have been broadly used for high power engines of motor vehicles and general industrial machines. In general, the aluminum alloy plain bearings have a three-layer structure in which an aluminum bearing alloy layer is bonded to a steel back via an intermediate layer.
The intermediate layer has been conventionally made of a comparatively soft material of pure aluminum or an aluminum alloy. However, coping with the recent trend of high power engines, aluminum bearing alloys tend to be required to have further improved fatigue and wear resistance. A solution of such a requirement has been to strengthen the aluminum bearing alloys by adding alloying elements of Cu, Zn, Mg, Si and so on. With such strengthening of the aluminum bearing alloys, the intermediate layer has been also tried to have improved fatigue resistance by adding strengthening elements including Mn.
The aluminum bearing alloy with strengthening additive elements of Cu, Zn, Mg, Si and so on is so produced that an aluminum bearing alloy layer is bonded to a steel back via an intermediate aluminum alloy layer by rolling and subsequently the layered structure is subjected to a solid solution-treatment of heating to a temperature of not lower than 400° C. followed by rapid cooling. However, when it is heated to the solid solution treatment temperature of not lower than 400° C., an inter-metallic compound of Al—Fe is generated at the interface between the steel back and the intermediate aluminum alloy layer. Since the inter-metallic compound of Al—Fe is quite brittle, there is a risk that the intermediate aluminum alloy layer might be delaminated from the steel back under operating conditions in which engine bearings are subjected to a varying load.
According to JP-A-61-272358, in order to avoid occurrence of brittle inter-metallic compounds at an interface between a steel back and an intermediate layer, heating to a solid solution treatment temperature is performed at a higher heating rate and the aimed temperature is kept for fully short time so as not to rise therefrom once after attaining the temperature. However, such a process is not practical because it requires a strict temperature control.
On the other hand, it is necessary to perform the solid solution treatment at a temperature as high as possible in order to improve the strength of the aluminum bearing alloys. For this, an intermediate aluminum alloy layer is desired.
BRIEF SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to prevent occurrence of brittle inter-metallic compounds at the interface between the steel back and the intermediate aluminum alloy layer whereby realizing a high temperature in a solid solution treatment and to improve aluminum bearing alloy in strength so that a multi-layered plain bearing having excellent fatigue resistance and a producing method thereof are provided.
According to one aspect of the present invention, there is provided a multi-layered plain bearing which comprises a steel back, an intermediate layer made of an aluminum alloy and an aluminum-base bearing alloy layer comprising one or more elements selected from the group consisting of Cu, Zn, Mg and Si, the aluminum-base bearing alloy layer being bonded to the steel back via the intermediate layer and subsequently subjected to a solid solution treatment at a temperature of not lower than 400° C., wherein the adjacent region of the intermediate layer to the steel back consists of, by mass, 2% to 8% of Si, and the balance of Al and incidental impurities.
When producing the multi-layered plain bearing, the layered material is heated to a temperature of not lower than 400° C. in the solid solution treatment, the element(s) of Cu, Zn, Mg and/or Si dissolves in the aluminum matrix so that the aluminum-base bearing alloy is hardened and strengthened by rapid cooling after the above heating whereby improving the multi-layered plain bearing in fatigue resistance. During the solid solution treatment, while an Al—Fe—Si inter-metallic compound precipitates preferentially rather than the Al—Fe inter-metallic compound at the adjacent side of the aluminum alloy intermediate layer to the steel back, the Al—Fe—Si inter-metallic compound does not precipitate at a temperature only above 400° C. until above 550° C. Thus, it is possible to effectively prevent occurrence of the brittle Al—Fe inter-metallic compound to perform the solid solution treatment.
According to another aspect of the present invention, there is provided a multi-layered plain bearing which comprises a steel back, an intermediate layer made of an aluminum alloy and an aluminum-base bearing alloy layer comprising one or more elements selected from the group consisting of Cu, Zn, Mg and Si, the aluminum-base bearing alloy layer being bonded to the steel back via the intermediate layer and subsequently subjected to a solid solution treatment at a temperature of not lower than 400° C. The intermediate layer comprises a sub-layer adjacent to the steel back, and at least one sub-layer other than the sub-layer adjacent to the steel back, wherein the sub-layer adjacent to the steel back consists of, by mass, 2% to 8% of Si, and the balance of Al and incidental impurities, and the at least one sub-layer other than the sub-layer adjacent to the steel back consists of, by mass, at least one element selected from the group consisting of from more than 0% to not more than 2% of Mn, from more than 0% to not more than 2% of Cu, from more than 0% to not more than 2% of Mg, from more than 0% to not more than 2% of Fe, and the balance of Al and incidental impurities.
Also in this case, as described in the first case under the first aspect, when the multi-layered plain bearing is heated to a temperature of not lower than 400° C. during a solid solution treatment, it is possible to effectively prevent occurrence of the brittle Al—Fe inter-metallic compound to increase the bonding strength between the intermediate layer and the steel back. During the solid solution treatment, in the at least one sub-layer other than the sub-layer adjacent to the steel back (i.e. at least one sub-layer of the intermediate layer existing at the side of aluminum-base bearing alloy layer), the element(s) of Cu, Zn, Mg and/or Si dissolves in the aluminum matrix so that the aluminum-base bearing alloy is hardened and strengthened by rapid cooling after the above heating whereby improving the multi-layered plain bearing in fatigue resistance.
The intermediate layer can have two functions or advantages which are an effect of preventing occurrence of the Al—Fe inter-metallic compound during the solid solution treatment and a strengthening effect by composing it with the plurality of sub-layers while strengthening the aluminum-base bearing alloy layer by the solid solution treatment, whereby it is possible to provide the multi-layered plain bearing with excellent fatigue resistance.
Here, grounds of the criticality will be described with regard to the additive alloying elements in the intermediate aluminum alloy layer.
(1) Si (2 to 8 mass %)
Si dissolves in the aluminum matrix and crystallizes as highly hard Si particles to increase the alloy hardness. When the multi-layered material is heated to a temperature of not lower than 400° C. in the solid solution treatment, the Al—Fe inter-metallic compound is not precipitated in the intermediate layer due to presence of Si. If the Si amount is less than 2 mass %, the above effects can not be attained. If the Si amount exceeds 8 mass %, plastic workability such as ductility is markedly deteriorated. Preferably the Si amount is 6 to 8 mass %.
(2) Mn or Mg (from More tha
Fujita Masahito
Kagohara Yukihiko
Shibayama Takayuki
Yamamoto Koichi
Browdy and Neimark
Daido Metal Company Ltd.
Koehler Robert R.
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