GB2271307A

GB2271307A - Sliding material

Info

Publication number: GB2271307A
Application number: GB9319767A
Authority: GB
Inventors: Yukimaro Tsukamoto; Yasuo Ido; Takashi Inaba; Susumu Thuzi
Original assignee: Daido Metal Co Ltd
Current assignee: Daido Metal Co Ltd
Priority date: 1992-09-25
Filing date: 1993-09-24
Publication date: 1994-04-13
Anticipated expiration: 2013-09-24
Also published as: JP2708139B2; GB9319767D0; DE4331887A1; DE4331887C2; JPH06106365A; GB2271307B

Abstract

A method of producing a sliding material having an alloy layer and a support layer involves forming a Pb alloy or Sn alloy sheet and roll-bonding the alloy sheet to the support material. The sliding material may then be heat-treated. With this method sliding materials of large width can be produced without the need for cutting. The mechanical properties can be changed by heat treatment at different temperatures depending on the intended use of the material. <IMAGE>

Description

1 2271307 SLIDING MATERIAL This invention relates to a sliding material

(e.g. a sliding contact material) that may be used extensively in automobiles, ships and industrial machines, and also to a method of producing such a sliding material.

In conventional methods of producing a sliding material of Pb alloy or Sn alloy, the alloy in a molten state is poured onto a support material. The molten alloy is then cooled either with water or other coolant material applied to a back surface of the support material, or by rotating the support material carrying the molten alloy.

is This conventional method has the following problems.

(1) When the support material is thin, strain develops during pouring of the molten alloy and cooling and it is therefore difficult to produce sliding materials of large width. In addition, at least part of the surf ace of alloy needs to be mechanically removed to obtain the required dimensions.

(2) When the support material is thick, it is necessary to cool the molten alloy while rotating it together with the support material, in order to prevent segregation of the alloy and also to secure efficient bonding. This method is time consuming and costly.

(3) Since the alloy is in the molten state, the types of support materials that can be used are limited. In addition since chloride is used to remove oxides on the support material, additional equipment for this purpose is also needed.

2 In view of these problems it is an objective of the present invention to provide a sliding material which overcomes or at least mitigates the disadvantages of the prior art.

According to a first aspect of the present invention, there is provided a method of producing a sliding material comprising a Pb alloy or a Sn alloy, the method comprising:

(a) providing (e.g. f orming) a Pb alloy or a Sn alloy in a sheet; and (b) roll-bonding the alloy sheet onto a support is material to provide a sliding material comprising an alloy layer and a support layer which are, respectively, the alloy sheet and the support material.

The present invention also extends to a method comprising:

(a) forming a Pb alloy or a Sn alloy into a sheet; (b) roll-bonding the alloy sheet onto a support material to provide a sliding material comprising an alloy layer and a support layer defined respectively by the alloy sheet and the support material; and (c) subsequently heat-treating the sliding material.

In the present invention the use of a roll-bonding method obviates:

3 (1) the need for an intentional cooling operation; and (2) the need f or a mechanical treatment to remove any surface of the support material.

This can therefore prevent a thermal strain from developing. Moreover, to satisfy desired applications or uses, a suitable sliding material can be manufactured using various types of support materials and multi-layer (e.g. two- to five-layer) structures can also be produced.

Furthermore, the thickness of the alloy layer can be suitably adjusted in accordance with the support material is used. Therefore the amount of alloy mechanically removed can be reduced to a minimum and sliding materials of desired dimensions can be obtained.

if a tin alloy is to be employed, this may preferably comprise copper and/or antimony. The copper may be present at from 2 to 6%, such as from 3 to 5% by weight.

The antimony (Sb) may be present at f rom 4 to 11-0. by weight, such as from 6 to 9?k.

if a lead alloy is employed, then this alloy may have zinc and/or tin and/or antimony as alloying metals. if present, zinc may be at from 2 to 4%, such as from 2.5 to 3.5% by weight. If tin is provided, this may be from 6 to 10%, such as from 7 to 9% by weight. Antimony, i f provided, may be at from 3 to 7%, such as from 4 to 6% by weight.

Thus, preferred alloys are Sn-Cu-Sb and/or Pb-Zn-Zn-Sb.

As will be appreciated, the major component is likely to 4 be tin or lead, depending upon the alloy employed, and will therefore usually be the balance after alloying metals have been considered, which may include any incidental impurities.

The alloy sheet may be directly roll-bonded to the support materiald. which will usually be steel. However, it may be indirectly roll-bonded to the support layer, in which case there may be one or more intervening layers (in between the alloy layer and the support material layer). Preferably there is only one intervening (or intermediate) layer. In preferred embodiments this is either copper and/or aluminium.

is The alloy may f irst be cast before it is rolled into a sheet. It may then be cut, optionally degreased, and preferably subjected to brush treatment. Af ter this process, the sheet may be ready to be rollbonded to the support material.

If heat treatment is employed, this may be at from 75 to 2250C. Preferred temperatures are given in Figures 1, 2 and 6.

Suitable sliding materials of the invention include bearings. Suitably the hardness (Hv) of the alloy layer is from 10 to 30 Hv. The tensile strength of the alloy 2 layer may vary from 4 to 10 kgf /mm. Pref erably the bonding strength of the alloy layer to the support 2 material is from 2.5 to 6 kgf/mm Preferred embodiments and examples of the invention, which are not to be construed as limiting, will now be described. In the following description, reference is made to a number of drawings, in which:

Figure 1 is a graph of alloy hardness against temperature for a prior art sliding material and four sliding materials of the invention; Figure 2 is a graph of tensile strength against temperature for a prior art sliding material and four sliding materials of the invention;

Figure 3 is a photograph showing the microstructure of the conventional (prior art) product of Comparative Example 1;

Figure 4 is a photograph showing the microstructure of the product of Example 4 of the present invention; Figure 5 is a photograph showing the microstructure of Example 5 of the present invention which has an 20 intermediate layer; and Figure 6 is a graph of bonding strength against temperature for a prior art sliding material and four sliding materials of the invention. 25 The present invention will now be described by way of example with reference to the accompanying Examples which are provided for the purposes of illustration and are not to be construed as being limiting on the present 30 invention.

COMPARATIVE EXAMPLE 1 First, a comparative product was prepared by a method 6 known in the art. In detail, a steel strip (having a thickness of 1.10 mm and a width of 110 mm) to serve as a support layer was degreased, and a bonding surface thereof was treated with a sand belt, pickled and treated with a flux of zinc or ammonium chloride. The steel strip was then subjected to immersion-plating in a bath of molten Sn. An Sn alloy (the composition is shown in Table 1) in a molten state was poured onto the immersion plated steel strip, and the molten alloy cooled with water applied to a back surface of the strip.

The excess of the cast Sn alloy was removed by cutting to give Example 1 (a conventional product) for comparative purposes. The overall thickness of the product was 1.65 is mm, while the thickness of the support layer was 1.30 mm.

EXAMPLE 2

A sliding-contact material was prepared by a method according to the present invention. An alloy (the composition is shown in Table 1) having a thickness of 18 mm was cast by use of gravity casting. The cast alloy was rolled through rollers into a thickness of 1.10 mm, and was then cut into a width of 110 mm, degreased, and subjected to a brushing operation, to thereby provide an alloy strip or sheet.

Then, a surface of a support material (Fe-0.OSC) (to be roll-bonded) having a thickness of 1.14 mm and a width of 110 mm was degreased and treated with a sand belt. The alloy strip and the support material were roll-bonded together by making them pass rollers to provide a sliding material according to the present invention. The overall thickness of the sliding material was 1.65 mm, and the 7 thickness of a support layer was 1.30 mm.

EXAMPLE 3

A sliding material was prepared according to the same procedure as Example 2, and these sliding materials were heat-treated at various temperatures to provide sliding materials (Example 3) of the present invention. Note that the temperatures of heat treatment for Examples 3 to 10 5 are shown in Figures 1, 2 and 6.

EXAMPLE 4

An alloy (whose composition is shown in Table 1) having is a thickness of 18 mm was case by use of gravity casting. The cast alloy was rolled through rollers to a thickness of 1. 10 mm, and was then cut into a width of 110 mm, degreased, and subjected to a brushing operation, to thereby provide an alloy or strip or sheet. 20 A copper film having a thickness of 6 8 gm was formed by plating on a support material (Fe-0.1OC) having a thickness of 2.24 mm and a width of 110 mm. The sliding material (Example 4) of the present invention was then 25 produced following the procedure of Example 2. The sliding material of this Example had the same thickness as that of Example 2. The sliding materials thus produced were then heat30 treated at various respective temperatures.

EXAMPLE 5

An alloy (whose composition is shown in Table 1) having 8 a thickness of 18 mm was cast by use of gravity casting, and then a brushing operation was applied to a surf ace of the cast alloy. A brushing operation was also applied to a surface of an Al sheet of thickness 0.8 mm. The cast alloy and the Al sheet were roll-bonded by making them pass rollers to provide a bearing alloy of thickness 1.2 mm having an Al layer. The bearing alloy sheet was then cut into a width of 110 mm, degreased, and subjected to brushing to thereby provide an alloy strip.

The same procedure as in Example 2 was followed for a support material (Fe-0.08C) having a thickness of 2.24 mm and a width of 110 mm. It was treated and then roll bonded to the alloy strip to obtain a sliding material (Example 5) of the present invention. The sliding material of this Example had the same thickness as that in Example 2. The sliding materials thus produced were then heat-treated at various temperatures.

Test Results The mechanical properties of the materials of Examples 1 to 5 are shown in Figures 1 and 2 (the hardness of the alloys was measured at room temperature after the heat treatment) The bonding strengths of these materials are shown in Figure 6 and photographs of the micro-structure of the materials of Comparative Example 1 and Examples 4 and 5 are shown in Figures 3, 4 and 5 respectively. ' In the Examples of the present invention, although the method of casting used is gravity casting, any other suitable casting method such as continuous casting may be used.

9 The support materials used in the present invention preferably comprise steel but may also be made of any other suitable material such as an Al alloy and/or a Cu alloy.

The materials of the present invention can be machined if desired and may also be f ormed into circular shapes, semi-circular shapes or any other required shape according to desired application.

The sliding materials of the present invention can have the following advantageous properties.

(1) Since thermal strain does not develop in the is material, materials of various thicknesses can be produced. Additionally materials of large width can be made.

(2) Since the surf ace of the material is flat and smooth, cutting operations or the like may not be needed.

(3) As will be readily appreciated f rom the drawings, the mechanical properties can be changed by heat treatment, and therefore the temperature of the heat treatment can be varied depending on the intended use.

(4) Since the casting structure can be destroyed by rolling, a uniform structure can be provided. No uneven variation with respect to components of the material occurs which often occurs during cooling, as is the case with conventional methods in which molten alloy is poured directly into a support material.

(5) Since chloride is not used, equipment for this purpose is not required and the work environment can be improved. In general the sliding material can be produced at a lower cost than prior art methods.

Table 1

Example Alloy Intermediate Heat No. Layer Treatment 1 Sn-4Cu-6Sb --- No 2 Sn-4Cu-6Sb No 3 Sn-4Cu-6Sb Yes 4 Pb-3Zn-8Sn-SSb Cu-plated Yes Sn-4Cu-Mb A1 Yes N.B. Figures indicate percentage by weight of subsequent elemental component.

C.

11

Claims

1. A method of producing a sliding material comprising an alloy layer and a support layer, the method comprising roll-bonding a Pb and/or Sn alloy sheet to a support material.

2. A method of producing a sliding material comprising an alloy layer and a support layer, the method comprising roll-bonding a Pb and/or Sn alloy sheet to a support material and subsequently heat-treating the roll-bonded sliding material.

3. A method as claimed in claim 1 or 2, further is comprising, prior to roll-bonding, providing an intermediate layer of Cu, Ni or an alloy thereof between the alloy layer and the support layer.

4. A method according to claim 3 wherein the intermediate layer is formed by plating.

5. A method as claimed in claim 1 or 2, further comprising, prior to roll-bonding, providing an intermediate layer of aluminium or an alloy thereof between said alloy layer and said support layer.

6. A method according to claim 5 wherein the intermediate layer is provided by roll-bonding.

7. A sliding material comprising an alloy layer comprising a Pb or Sn alloy and a support layer roll bonded onto the alloy layer.

8. A sliding material comprising an alloy layer 12 comprising a Pb or Sn alloy, and a support layer rollbonded onto the alloy layer and heat-treated after the roll-bonding.

9. A sliding material as claimed in claim 7 or 8 further comprising an intermediate plating layer of Cu, Ni or an alloy thereof in between the alloy layer and the support layer. 10

10. A sliding material as claimed in claim 7 or 8 further comprising an intermediate layer of aluminium or an alloy thereof between the alloy layer and the support layer, the intermediate layer being roll-bonded onto both the alloy layer and the support layer. is

11. A sliding material, or method for the production thereof, substantially as herein described with reference to any of Examples 2 to 6.