GB2251661A - A lead containing copper alloy bearing - Google Patents

Abstract

A sliding member has a backing metal 1 and a sliding layer 2 consisting of a lead-containing copper alloy being bonded to the backing metal, the alloy comprising 5 to 40% by weight of lead, the lead being present as particles, 80% or more of which have a diameter of 50 microns or less. Preferably, there is a uniform and fine distribution of the lead particles in the copper alloy matrix. A method to produce the sliding members comprises using an atomised powder in which lead particles are finely and uniformly distributed in the alloy matrix Fig 7 and forming the sliding layer as a cladding layer using a plasma arc welding apparatus. Fig 6. <IMAGE>

Description

22-51661 1 BEARINGS The present invention relates to a composite sliding

member that can be used in many kinds of industries, and more particularly to a composite sliding member comprising a steel backing and a (suitably high quality) lining of copper-lead alloy or lead-bronze alloy which can be formed readily and economically on the steel backing by a plasma arc build up welding method and to a process for producing such composite sliding members.

Conventional composite sliding members having a copper-lead alloy or leadbronze alloy layer are usually produced by melting and casting those alloys. This method requires a number of steps, including casting, and is thus costly.

Alternatively, according to another method, a copper alloy layer is formed on a steel backing by cladding using a metal spraying method or one of the various kinds of build up welding methods (e.g. TIG welding, arc welding, gas welding, etc.). These methods have been used only for producing alloys containing no lead, such as aluminium-bronze, phosphorous bronze and brass except in the case of lead-containing alloys which exhibit improved friction properties. One reason why the metal spraying and build up methods are not employed for lead-containing alloys is that harmful lead evaporation results during the metal spraying or welding process. Also, the yield of lead is low and can result in extreme lead segregation in the alloy. Thus, the cladding methods of metal spraying or build up welding are used for 2 copper alloys with no lead, such as aluminium-bronze, phosphorous bronze and brass.

The method of producing composite sliding members by the casting process requires dangerous and hard work at high temperatures. Since the melting temperature of copper-lead alloys and lead-bronze alloys, in particular, is above 10000C, harmful lead fumes are generated so polluting the working environment. The control of casting conditions is difficult and requires the experience of skilled workers.

Excluding products that have a lining on an inner surface of a backing metal formed by a centrifugal casting process, one requires a stopper (or a weir) for molten metal when gravity casting on a thrust face or for lining an outer surface of the backing metal in order to prevent molten metal flowing out from the backing metal. Thus preparations for casting can be expensive.

In order to produce normal castings without blow holes by casting, a riser with a height several times as large as a thickness of - a product lining is required, which means a reduction in the yield and an increase in production costs.

In cases where one is casting onto a surface of a housing with a complicated shape, a non-uniform structure and segregation of the cast alloy, or poor bending to the housing, are apt to form due to unevenness in the cooling.

In many casting processes, even in the cases when a lining is required on a small part of a product, that part of the backing metal must be provided with a lining and the other (less necessary) parts thereof must be isolated, resulting in low yield which makes it 3 uneconomical.

on the other hand, methods of producing composite sliding members by metal spraying or welding can be free from the high-temperatures involved in casting, and may be a relatively easy method of cladding by build up welding of high melting point metals. However, metal spraying or welding of lead-containing alloys exhibiting good friction properties can be very harmful because of the evaporation of the lead during the metal spraying or welding process. Furthermore, in these processes, the yield of lead can be so low that the desired compositions cannot be obtained, and a uniform and fine structure cannot be produced due to considerable lead segregation. Using these techniques the properties of composite sliding members, which are required to withstand high speeds and greater loads, may not be improved.

A primary object of the present invention is to solve, or at least mitigate, some or all of the problems previously described and to provide a composite sliding member having a sliding layer comprising a leadcontaining copper alloy as well as a method of manufacturing it.

According to a first aspect of the present invention there is provided a sliding member comprising backing metal or support and a sliding layer which is copper alloy comprising from 5 to 40% by weight of lead, the lead being present as particles, 80% or more of which have a diameter of 50 microns (pm) or less.

Such sliding members are often called composite sliding members. Suitably the sliding layer will be in contact with, and therefore bonded to, the backing metal, although this is not essential since one or more 4 intermediate layers interposed between the backing metal and sliding layer may be provided. Thus, the backing metal can be thought of.as a supporting layer which is provided with one or more intermediate layers.

The sliding layer suitably has a thickness of from 1 to 10 nm, such as from 2 to 5 mm. However, in preferred embodiments the thickness ranges from 0.2 to 4 mm, such as from 2 to 3 mm.

Preferably the lead particles will be uniformly distributed in the copper alloy matrix. This may be achieved by using copper or copper alloy particles (e.g. as a powder) into which the lead has been dispersed, such as by atomisation with an appropriate atomiser or by employing a water jet technique.

The copper alloy may suitably be a copper lead alloy. However, a leadbronze alloy may also be employed, for example one that comprises copper, lead and tin. The lead is preferably present at from 10 to 25% by weight. If tin is provided, then this is preferably present at from 1 to 15, such as from 3 to 10, % by weight. However, other alloying metals may be used in addition.

The sliding member may be a washer (such as a thrust washer) or a portion of an internal combustion engine (such as a cylinder block) or a bearing (such as of a turbocharger, supercharger or planetary gear).

The sliding layer will suitably have a hardness of at least Hv 50, such as of at least Hv 90.

Suitably the bond strength between the sliding layer and backing metal (or intermediate layer) will be at least 15, such as at least 22, kgf/mm. 2. The sliding members of the present invention will suitably have a seizure resistance of at least 600, such as at least 650, kgf/cm2.

A second aspect of the present invention relates to a method of manufacturing a sliding member, the method comprising providing A backing metal (or support) and forming a sliding layer which is a copper alloy comprising from 5 to 40% by weight of lead, the lead being present as particles, 80% or more of which have a diameter of 50 microns or less.

Suitably the sliding layer will have a thickness of from 0.2 to 4 mm. It will be advantageously bonded (e.g. directly) to the backing metal. Preferably the lead particles will be uniformly distributed in the copper alloy matrix.

The sliding layer may be formed by using a plasma arc, such as by plasma arc welding. This may involve the formation of a cladding layer. Thus, in a preferred process one employs a plasma arc cladding by build up welding process.

The formation of the sliding layer may be conducted in a non-oxidative atmosphere. This is suitably provided by using an atmosphere of gas that is inert, for example by employing an atmosphere of a noble gas (such as argon).

If one uses a plasma arc method then suitably, as the raw material, an atomised powder of the copper alloy will be employed. Thus, the process may additionally involve atomising a powder prior to use in plasma arc technique.

A third aspect of the present invention relates to method of manufacturing a sliding member comprising a backing metal and a sliding layer, the method comprising preparing a copper or copper alloy powder comprising from 5 to 40% by weight of lead and bonding the powder directly or indirectly onto the backing 6 metal in a non-pxidative atmosphere using a plasma arc to thereby produce a sliding lAyer. This method may be used to prepare a sliding member of the first aspect. Suitably the lead will be uniformly and finely distributed in the copper alloy matrix or powder.

For the third and fourth aspects indirect bonding contemplates the situation where one or more intermediate layers, interposed between the sliding layer and backing metal, is provided.

A fourth aspect relates to a sliding member comprising a backing metal and a sliding layer, wherein the sliding layer has been formed by bonding a copper or copper alloy powder comprising from 5 to 40% by weight of lead directly or indirectly onto the backing metal in a non-oxidative atmosphere using a plasma arc.

A fifth aspect of the present invention relates to a method of manufacturing a sliding member, the method comprising providing a support, such as a backing metal, and forming a copper alloy layer directly or indirectly onto the support by using a metal spraying process or a plasma arc in a non-oxidative atmosphere with a copper or copper alloy powder in which lead, such as in the form of Particles, is dispersed in the copper or copper alloy particles.

Suitably the copper or copper alloy powder will comprise 5 to 40% by weight lead. By dispersing lead inside copper or copper alloy particles one may be able to overcome the problems associated with the evaporation of lead. Thus, the copper alloy layer will suitably have the same composition as the copper or copper alloy powder employed, and will therefore also suitably have from 5 to 40% by weight lead. If the lead is dispersed within the copper or copper alloy particles in the form of particles itself, then 7 preferably 80% or more of lead particles will have a diameter of 50 microns or less.

The copper or copper alloy employed in the plasma arc process will suitably be made by using an atomisation process, for example with an atomiser, or by employing a water jet technique.

Suitably the copper or copper alloy will thus be substantially free of lead particles that exist independently of the copper or copper alloy particles.

A sixth aspect of the present invention relates to a sliding member prepared by the method of the fifth aspect.

Although various aspects of the present invention will now be described in further detail, it should be borne in mind that preferred features and characteristics of one aspect of the present invention are applicable to another aspect mutatis nutandis.

Thus the composite sliding member of the present invention preferably comprises a backing metal and a sliding layer bonded to the backing metal, characterised in that the sliding layer comprises a copper alloy suitably having a thickness of from 0.2 to 4 mm and comprising from 5 to 40 wtA lead, the lead being present in the form of fine (or minute) particles, advantageously uniformly distributed in the copper alloy matrix, 80% or more of the total number of lead particles being particles which have a diameter of 50 microns or less.

one method of producing the composite sliding member of the present invention comprises providing a copper alloy powder containing from 5 to 40 wt.% of lead which is fine and uniformly distributed (such as in the copper alloy matrix) and a backing metal, and thermally bonding the copper alloy powder to the 8 backing metal, suitably in a non-oxidative atmosphere. This can be done by plasma arc cladding, such as by build up welding, to produce a sliding layer in which the lead is finely and uniformly distributed throughout the copper alloy matrix.

It has been found that plasma arc cladding such as by build up welding, may solve the problems associated with a casting process or metal spraying process. That is to say, a voltage is applied between a torch and a badking metal, followed by flowing of argon gas to generate a plasma arc at a high temperature, into which a bearing alloy powder or wire is fed and melted on the surface of the backing metal so that a bearing alloy layer is formed on the backing metal.

In a similar cladding by build up welding method, there can be mentioned TIG welding, arc welding, gas welding and the like. In these welding methods, however, iron in the backing metal can dissolve into the bearing alloy to adversely affect the bearing alloy. In the case of cladding by build up welding of low-melting point metals such as bearing alloys, the dissolution of iron into the bearing alloy can be prevented by utilising a soft plasma such as in a plasma arc cladding by build up welding method. According to this method, the oxidation of the molten metal-can be prevented by using a shield gas, such as argon, whereby normal cladding by build up welding can be effected.

However, when using the plasma arc cladding by build up welding method, lead may readily evaporate when a mixture of a copper alloy powder and lead alloy powder is utilised as a raw material. In recognition of this, it was found that this lead evaporation could 9 be suppressed by using a powder comprising particles of lead, suitably uniformly and finely distributed in a copper alloy, which may thereby produce a sliding layer with lead uniformly distributed.

In the plasma arc cladding by build up welding process used in the present invention, an automatic or a remote controlled operation can be put into effect so that workers can be released from hard work at high temperatures in an unpleasant environment, such as takes place with casting work. Once the conditions of cladding by build up welding have been predetermined, cladding by the build up welding can be automatically carried out to produce a high-quality product in a stable manner, without requiring the experience of skilled workers.

In plasma arc welding, there is no need to place a weir onto a backing metal nor is there a need to effect sealing in order to prevent flowing out of molten metal, as is the case in the casting. For products with a thrust surface to be formed by gravity casting or with an outer surface lining, the number of steps can be reduced to make the process economical. Even in the case of forming a lining on a small portion of the backing metal, cladding by build up welding on a desired portion is possible and economical because it does not require one to isolate unnecessary parts after lining of its entire surface as is in the process of casting. In the case of casting, a riser with a height of several times as large as a thickness of a product lining is required. However, in the present invention one may only have to remove a slag layer of about 1 mm, which can avoid wasting expensive bearing alloy and may thus be economical.

In cases where a lining is formed onto a backing metal with a complicated shape by means of casting process, uniform and rapid cooling of the cast lining is difficult to achieve and delays solidification, resulting in the generation of shrinkage blow holes, a non-uniform structure and segregation (by non-uniform solidification) so that non-uniform shrinking forces act on the interface of the lining with the backing metal, causing an imperfect bond between the materials. In'the present invention, however, specific cooling is not required, so that a product with a stable quality may be obtained.

Furthermore, according to the present invention, because one can use atomised powder in which minute lead particles are suitably uniformly distributed, lead may not evaporate during the build up welding, thus differing from various kinds of welding methods that may use a blend of lead powder and a copper alloy powder, or from metal spraying methods. In the invention, because lead-containing copper alloys such as a copperlead alloy or a lead-bronze alloy can be used, the properties of seizure resistance, load resistance and the like can be remarkably improved when compared with composite sliding members produced by metal spraying or usual welding methods in which only brass or bronze is used.

In the metal spraying method, the bonding force between a lining and a backing metal can be weak because the bonding depends upon an anchoring effect at spraying, and the mutual connecting of alloy particles is insufficient because the particles are bonded via oxide films that are produced by oxidation of the molten particles during spraying in air.

In contrast, because the powder is melted in an, e.g. argon, atmosphere, such as by a plasma arc in the present invention, the bonding of a backing metal with molten alloy particles, e.g. drops, and the mutual connecting of the molten alloy drops to each other can be complete.

In the present invention, frictional properties may be inferior at a level of less than 5% of lead in the copper alloy, while the alloy strength and the corrosion resistance may deteriorate at a level of 40% or more of lead in the copper alloy.

The invention will now be described by way of example with reference to the accompanying examples and drawings, which are provided by way of illustration and are not to be construed as being limiting. In the drawings:- Fig. 1 is a perspective view from above of a first composite sliding member according to the present invention made by the process of Example 1; Fig. 2 is a perspective view f rom above of a second composite sliding member according to the present invention made by the process of Example 3; Fig. 3 is a perspective view to one side of a third composite sliding member according to the present invention made by the process of Example 6; Fig. 4 is a perspective view f rom above of a fourth composite sliding member according to the present invention made by the process of Example 7; Fig. 5 is a f ront view with a partial section along line A-A of the composite sliding member in Fig. 4; Fig. 6 is a partial cut-away section of a plasma arc welding apparatus used in the present invention in 12 a state of operation; Fig. 7 is a section of a particle of atomised powder used in the present invention; and Fig. 8 is a microscopic photograph of a structure of a sliding layer of a composite sliding member according to the present invention at a magnification of 100.

EXAMPLE A some experiments were carried out using a plasma are welding apparatus as shown in Fig. 6. In this apparatus a powder of lead-containing copper alloy which was produced by an atomising process, having a particle size range of from 80 to 200 mesh (75 to 177,gm), is fed from a powder supply port 10 into the plasma arc welding apparatus by means of a carrier gas, and argon gas is simultaneously fed therein from a shield gas supply port 11. A voltage is applied between a backing metal 1 and a tungsten electrode 12 to generate a plasma arc so that molten lead-containing copper alloy is deposited on the backing metal so as to form a cladding layer (or build up layer) 13. Each particle 3 (see Fig. 7) of lead- containing copper alloy powder has a nearly spherical form, and has a structure where minute lead particles 5 are uniformly distributed in the copper-alloy matrix 4 of a particle of the powder as shown in Fig. 7 (which illustrates a schematic section of such a particle).

EXAMPLE 1

As is shown in Fig. 1, a lead-bronze alloy (Cu:10% Pb:10-% Sn) layer 2 of a thickness of 3 mm was subjected to the cladding by build up welding on the end face of a columnar backing metal 1 (JIS S45C) of 200 mm diameter and 150 mm height by means of the plasma arc 13 welding apparatus shown in Fig. 6. Thus, while the backing metal 1 was placed on a rotating rotary table, a torch was moved radially from the centre of the table to the peripheral edge so that a lining operation was effected in a spiral fashion. A powder of a lead-bronze alloy (Cu: 10% Pb: 10% Sn) which was produced by atomising was fed into the plasma arc generated between the torch and the backing metal 1, and was melted under an argon gas atmosphere to form thd layer 2 on the backing metal 1. The atomisation process produced an alloy powder where lead particles were dispersed within the bronze alloy particles.

After the cladding by build up welding, a top surface portion of the layer 2 was cut of f at 1 mm depth to remove slag for a penetration test. Consequently, no defects (including blow holes) were not found in the layer 2. The test of inspecting the bonding effectiveness was carried out by forcibly inserting a chisel between the layer 2 and the backing metal 1 in order to confirm whether or not the build up layer 2 could be separated from the backing metal. No separation was found and the bonding was excellent. Hardness and bonding strength were subsequently examined. Consequently, the hardness and the bonding strength were found to be excellent, that is HV 90 and 22 kgf/mm2, respectively, with no difference compared with a cast alloy. As a result of an analysis of the alloy layer 2, the composition was about the same as the supplied raw powder. As to the structure of the lead-containing copper alloy of the layer 2, lead was uniformly and finely distributed in the copper-alloy matrix (see Fig. 8).

A seizure test of the prepared sliding member was 14 carried out to examine seizure resistance. The maximum specific load without seizure was excellent at about 650 kgf/cm2. cladding by build up welding was also effected on a spherical surface of a cylindrical backing metal. The result was satisfactory.

After various machining processes, the product can be applied to a cylinder block of an oil pressure unit.

COMPARATIVE EXAMPLE 2 A blended powder composed of a copper powder, a ledd powder and a tin powder (so as to comprise separate particles of copper, lead and tin), of identical composition to that of the lead-bronze powder used in Example 1, was employed in plasma arc build up welding, but the desired composition could not be obtained due to evaporation of lead. In this case, a uniform structure could also not be obtained because lead segregated. Furthermore, regarding seizure resistance, the maximum specific load was about 350 kgf/cm2 which was inferior to that of the products of the present invention (see Table 1).

EXAMPLE 3

As is shown in Fig. 2, a lead-copper alloy layer 2 (Cu.: 23% Pb: 3% Sn) was formed on the top surface of a ring-like shaped backing metal 1 (JIS S15C) of 30 mm thickness, 400 mm outer diameter and 300 mm inner diameter by plasma arc build up welding. While the backing metal 1 placed on a rotary table as in Example 1 was in rotation, the torch of the plasma arc welding apparatus was moved from the centre of the table to the peripheral edge so that a lining operation was spirally carried out in order to f orm the layer 2 of 3 mm thickness on the backing metal 1. A powder of lead-bronze alloy (Cu: 23% Pb: 3% Sn) which was is produced by an atomising process was used which had lead dispersed within the bronze alloy particles. After cladding by build up we lding, a top surface portion of the layer 2 was cut of f at 1 mm depth to remove slag f or a penetration test. It was f ound consequently that the cladding by build up welding was successfully effected since no defects, such as blow holes, existed. An attempt at inserting a chisel between the layer 2 and the backing metal 1 to carry out a test of inspecting bonding was carried out. The test result was satisfactory like in Example 1. The hardness and a bonding strength were subsequently examined. The examined properties were good, since there was no difference between the properties and that of a cast alloy (a. casting). As to the structure of the lead- bronze alloy layer 2 bonded to the backing metal 1, the lead was uniformly and finely distributed in the alloy matrix. As a result of analysis of the alloy layer 2, the composition was about the same as that of the supplied raw powder. In a seizure test carried out in the same manner as in Example 1, the maximum specific load of about 700 kgf/CM2 was obtained (see Table 1).

After various machining processes, the product of the present invention could be applied to a thrust washer of a marine engine.

COMPARATIVE EXAMPLES 4. 5 AND 6 A blended powder composed of a lead powder and a bronze alloy powder (i.e. containing separate lead and bronze alloy particles), of identical composition to that of the lead-bronze powder in Example 3, was used in a casting process (Comparative Example 4) and a plasma are build up welding (Comparative Example 5), 16 the examined maximum specific loads were lower than that in Example 3 of the present invention (see Table l). A further casting process was conducted (Comparative Example 6) using the blended powder employed in Comparative Example 2.

EXAMPLE 7

As is shown in Fig. 3, a copper lead alloy layer 2 (JIS W3) was formed on the circumferential surface of a cylindrical solid backing metal 1 (JIS S1SC) with an outer diameter of 100 mm and 200 mm in length. In the welding process, the backing metal 1 was positioned on a rotation device and rotated in a horizontal position around the axis thereof, while a torch of a plasma arc welding apparatus was moved horizontally from one end to the other along the outer surface of the backing metal 1 so as to spirally form the alloy layer 2 of 3 mm thickness on the circumferential outer surf ace of the backing metal 1. Into plasma arc generated between the torch and the backing metal 1, an alloy powder of the copper-lead alloy, 30% lead with the balance copper (JIS W3), which was produced by an atomising process (to disperse the lead within the copper particles, was f ed and melted to ef f ect the cladding by build up welding under the protective atmosphere of argon gas.

After the build up welding, a top surf ace portion of the layer 2 was cut off at 1 mm depth to remove slag for a penetration test. ' Consequently, it was f ound that the build up welding was successfully done since no defects such as blow holes existed. An attempt at inserting a chisel between the alloy layer 2 and the backing metal 1 was made to carry out a test of inspecting the bonding. The test result was good. Hardness and bonding strength were subsequently examined. The examined properties were a lso good, since there was no difference between the properties 17 and that of a cast alloy (a casting) As to the structure of the alloy layer 2, lead was uniformly and finely distributed in the alloy matrix. The structure was essentially the same as the structure as shown in Fig. 8. As a result of an analysis of the alloy layer 2, the composition was about the same as that of the supplied raw powder.

After various machining processes, the product of the present invention can be applied to a bearing of a planetary gear in reduction gears.

EXAMPLE 8

As shown in Figs. 4 and 5, lead-bronze alloy layers 2 (Cu: 10% Pb: 10% Sn) were formed on both surfaces of a backing metal ring 1 (JIS S15C) of an outer diameter of 50 mm, an inner diameter of 10 mm and 5 mm thickness by plasma arc build up welding. Each of the formed alloy layers 2 had a ring-like shape of an outer diameter of 40 mm and an inner diameter of 30 mm. In the welding process, the backing metal ring 1 was positioned on a rotary table, while a torch of a plasma arc welding apparatus was fixed to effect the build up welding so as to form a ring like alloy layer 2 of 5 mm width and 3 mm thickness on the backing metal ring 1. A raw powder of an atomised lead-bronze alloy (Cu: 10% Pb: 10-0. Sn) was used in the build up welding. The backing metal ring 1 was subsequently turned over in order to effect a subsequent build up welding on an opposite side surface.

After the build up welding, a top surface portion of each of the alloy layers 2 was cut off at 1 mm depth to remove slag for a penetration test. It was found consequently that the build up welding was successfully done since no defence such as blow holes existed. An 18 attempt at inserting a chisel between the alloy layer 2 and the backing metal ring 1 was made to carry out a test of inspecting the bonding.. The test result was good. Hardness and bonding strength were subsequently examined. The examined properties were also good, since there was no difference between the properties and that of a cast alloy (a casting). As a result of an analysis of the alloy layer 2, the composition was about the same as thatof the supplied raw powder. The structure of the alloy layer 2 was essentially the same as that of the supplied raw powder. The structure of the alloy layer 2 was essentially the same as the structure of Fig. 8 in which lead was uniformly and finely distributed in the alloy matrix.

After various machining processes, the product of the present invention can be applied to a thrust washer of a turbo-charger, both of which surfaces are used as a bearing surface.

-In the Examples described previously, the build up alloy layers were 2 mm and 3 nm thick. It is, however, possible to form build up layers with greater thicknesses of cladding by the plasma are build up welding method. The thickness of the build up layer is preferably from 1 mm to 10 mm, more preferably from 2 mm to 5 mm.

Table 1

Seizure Test 1 Composition of sliding Method of 2 layer (wt.%) forming Maximum specific load (kgflcm sliding layer 300 400 500 600 700 800 Example Plasma arc Cu-10% Sn-10% Pb welding by Example of the using Invention Example a tomized 3 Cu-3% Sn-23% Pb powder 6 Cu-10% Sn-10% Pb Casting 4 Cu-3% Sn-23% Pb Casting 9 Compara- Plasma arc tive 2 Cu-10% Sn-10% Pb welding by Example using a blended powder Plasma arc Cu-3% Sn-23% Pb welding by using a blended powder 1 1 k_ I'D 1 It was decided that specimens developed seizure when the temperature of the back surface exceeded 200 0 C or when the current of motor excgeded 10A. Condition of the seizure test: Shaft diameter Speed of rotation Lubricant oil Flow rate of feed oil Shaft material Loading manner, 53 mm 2,000 rpm JIS SAE 20 20 cc/min. UIS S55C The load was increased by 50 kg/cm2 step by step, 20 minutes for each load.

In Comparative Examples 2 and 5, Cu: 10% Sn alloy powder and Pb powder were blended and used in the plasma arc welding.

As will be apparent lead-containing copper bearing metal can easily be subjected to cladding by build up welding on a necessary portion of a backing metal in any form, which can release workers from hard work involved with casting in an unpleasant environment at high temperatures. No experience of skilled workers is required, as is the case in casting, and the setting up of the appropriate conditions may enable the production of stable-quality products. There is no need to weld a weir onto a backing metal in order to prevent flowing out of molten melt as is the case in casting, which enables the shortening of such a process; the avoidance of a riser may enable saving of alloy, which is more economical. Automatic setting and removing of a backing metal and an automatic welding by means of computer control may allow unmanned operation, which can decrease man power and the number of workers 21 involved, leading to a lowering in costs. Use of atomised powder where particles of lead are uniformly and f inely distributed may solVe the problem of lead evaporation which can make it impossible to obtain a lead component of a predetermined composition and to obtain unif orm structures due to the segregation of lead in the alloy, as are observed when a blended alloy powder consisting of a copper alloy powder and a lead powder is used.

Since a composite sliding member with a leadcontaining copper alloy layer(s) can be readily produced in any f orm, the seizure resistance and the load resistance properties can be improved remarkably, so higher speeds and greater power of general industrial machines and internal combustion engines can be achieved, with greatly improved performance.

22

Claims (27)

1. A sliding member comprising a backing metal and a sliding layer, the sliding layer being a copper alloy comprising from 5 to 40 wt.% of lead, the lead being present as particles 80% or more of which have a diameter of 50 microns or less.

2. A sliding member as claimed in Claim 1 wherein the sliding layer is bonded to the backing metal.

3. A sliding member as claimed in claim 1 or 2 wherein the sliding layer has a thickness of from 0.2 to 4 mm.

4. A sliding member as claimed in any preceding claim wherein the lead is uniformly distributed in the copper alloy matrix.

5. A sliding member as claimed in any preceding claim wherein the lead is present at from 10 to 25% by weight.

6. A sliding member as claimed in any preceding claim wherein the sliding layer comprises tin at from 3 to 10% by weight.

7. A sliding member as claimed in any preceding claim which is a washer or bearing.

8. A method of manufacturing a sliding member, 23 the method comprising providing a backing metal and forming a sliding layer, the sliding layer being a copper alloy comprising from to 40% by weight of lead, the lead being present as particles 80% or more of which have a diameter of 50 microns or less.

9. A method as claimed in Claim 8 wherein the lead particles are uniformly distributed in the copper alloy matrix.

10. A method as claimed in Claim 8 or 9 wherein the sliding layer is formed by using a plasma arc.

11. A method as claimed in any of claims 8 to 10 wherein the sliding layer is formed under a non-oxidative atmosphere.

12. A method as claimed in any of Claims 8 to 11 wherein an atomised copper or copper alloy powder is used to form the sliding layer.

13. A method of manufacturing a sliding member comprising a backing metal and a sliding layer, the method comprising preparing a copper or copper alloy powder comprising from 5 to 40% by weight of lead and bonding the powder directly or indirectly onto the backing metal in a non-oxidative atmosphere using a plasma arc to produce the sliding layer.

14. A method as claimed in Claim 13 wherein the sliding layer is bonded to the backing metal.

15. A method as claimed in Claim 13 or 14 wherein 24 the lead is uniformly and f inely distributed in the copper alloy matrix.

16. A method as claimed in any of claims 13 to 15 wherein the plasma arc is employed in a plasma arc welding process.

17. A method as claimed in any of Claims 13 to 16 wherein bonding of the copper alloy powder is effected by using plasma arc cladding by build up welding.

18. A method as claimed in any of Claims 13 to 17 wherein the copper or copper alloy powder has been atomised.

19. A method as claimed in any of Claims 13 to 18 wherein the lead is dispersed within the copper or copper alloy particles.

20. A method as claimed in Claim 19 wherein 80% or more of the lead particles have a diameter of 50 microns or less.

21. A method as claimed in any of Claims 13 to 20 for manufacturing a sliding member according to any of Claims 1 to 7.

22. A method of manufacturing a sliding member, the method comprising providing a backing metal and forming a copper alloy layer directly or indirectly on the support by using a metal spraying process or a plasma arc in a non-oxidative atmosphere with a copper or copper alloy powder comprising lead, where the lead is dispersed Vithin the copper or copper alloy particles.

23. A method as claimed in Claim 22 wherein the lead is present as particles within the copper or copper alloy particles.

24. A method as claimed in Claim 22 or 23 wherein the lead is dispersed within the copper or copper alloy particles by atomisation.

25. A sliding member produced according to a method according to any of Claims 22 to 24.

26. A sliding member substantially as herein described with reference to the examples, but not the comparative examples.

27. A method of manufacturing a sliding member substantially as herein described with reference to any of the examples, but not the comparative examples.