Aluminum-based bearing alloy

Abstract

The present invention has been made by the fact that the wettability with lubricant increases when tin grains are broken within a certain range. In an aluminum-based bearing alloy containing from 2 to 20 mass % of tin, the tin grains in a sliding surface have a size not less than 20 μm2 but not more than 50 μm2 expressed in region partitioned areas of the tin grains measured in accordance with a region partitioning method.

Description

FIELD OF THE INVENTION[0001]The present invention relates to an aluminum-based bearing alloy suitable for a sliding member.BACKGROUND OF THE INVENTION[0002]A sliding bearing lined with an aluminum-based bearing alloy with excellent fatigue resistance has been well accepted as a bearing for an automobile engine. An Al—Sn-based bearing alloy and an Al—Sn—Si-based bearing alloy are widely used as aluminum-based bearing alloys. The aluminum-based bearing alloy thus contains tin (Sn) which is a soft and has a low melting point. The role of tin is summarized as follows: The element, tin, is interspersed in the bearing alloy, and melts when the temperature of the sliding surface becomes high, which prevents the aluminum from adhering to a counterpart shaft. When tin melts, the heat of fusion lowers the temperature of the sliding surface and prevents seizure.[0003]Such a sliding bearing lined with the aluminum-based bearing alloy (hereinafter simply referred to as a bearing) is manufactured...

AI Technical Summary

Benefits of technology

The present invention provides an aluminum-based bearing alloy that improves seizure resistance while maintaining good fatigue resistance. The alloy has increased hardness and wettability with lubricant, which prevents oil film shortage and metal contact. The size of tin grains in the alloy is made fine within a certain range to increase the interface area between the matrix and each grain, resulting in increased surface energy at the sliding surface. The alloy contains not less than 2 mass% but not more than 20 mass% of tin, with the size of tin grains in the sliding surface not less than 20 μm2 but not more than 50 μm2. The region partitioned areas of tin grains range not less than 20 μm2 but not more than 50 μm2. The amount of tin ranging not less than 2 mass% but not more than 20 mass% allows for excellent conformability, adherence prevention, and reduction in temperature at the sliding surface. The invention provides a method for reducing the region partitioned areas of tin grains by accumulating processing strain during the processes from casting to heat treatment.

Problems solved by technology

When a bearing deforms due to misalignment when the bearing is assembled to a housing or insufficient rigidity of the housing in association with reduction in weight and size of an engine, an uneven contact phenomenon likely occurs, in which the counterpart shaft comes into uneven and hard contact with the bearing, especially in an early stage of the operation.

In this case, a conventional aluminum-based bearing alloy has relatively low hardness, and uneven contact simply results in elastic deformation and unlikely ends up with oil film shortage.

Therefore, uneven contact simply results in weak metal contact, and the aluminum-based bearing alloy quickly conforms to the counterpart shaft.

In an aluminum-based bearing alloy having improved fatigue resistance in accordance with any of the methods described above, however, the aluminum-based bearing alloy has increased not only strength but also hardness, which makes it difficult to deform against uneven contact, and likely resulting in oil film shortage and metal contact.

The metal contact causes the portions under uneven contact to be heated and adhere to the counterpart shaft, resulting in seizure.

In particular, a bearing having a reduced amount of tin likely suffers from seizure.

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