GB2144061A

GB2144061A - Process for producing aluminium-clad composite materials by roll cladding

Info

Publication number: GB2144061A
Application number: GB08418872A
Authority: GB
Inventors: Dr Martin Creydt; Rolf Pfoh
Original assignee: Kolbenschmidt AG
Current assignee: Kolbenschmidt AG
Priority date: 1983-07-30
Filing date: 1984-07-24
Publication date: 1985-02-27
Also published as: FR2549758A1; GB8418872D0; DE3327657A1; GB2144061B

Abstract

In the process an aluminium layer is bonded to a steel layer by cladding at a temperature of preferably 200 to 400 DEG C. In order to increase the strength of the aluminium alloy, the latter is homogenized at a temperature of 450 to 550 DEG C between 0.5 and 3 hours and is subsequently quenched and then bonded to the steel layer by roll-cladding, the resulting composite material being quenched as soon as it leaves the roll nip.

Description

SPECIFICATION Process for producing aluminium-clad com- posite materials This invention relates to a process for producing aluminium-clad composite materials by roll-cladding an aluminium layer to a steel layer.

It has been known for many years that composite materials can be produced by a roll-cladding process, in which sheet bars of a substrate metal and of a facing metal are jointly rolled so that they are bonded by welding under the rolling pressure. The substrate metal consists usually of plain carbon mild steel, which can easily be welded, or of high-temperature steel. The cladding may consist of copper and various kinds of copper alloys, nickel and nickel alloys, aluminium and aluminium alloys, silver and silver alloys, or of alloy steel. It is known to clad sheet metal elements, strip, tubing, rods, wires and sections whenever it is too expensive to produce these from the cladding metal alone and/or the cladding metal does not have the required mechanical properties. Examples of such products are coin banks, temperature-responsive bimetals or the like.Composite materials consisting of steel which is clad with aluminium alloys have been used for many years mainly in bearings. In such bearings, the aluminium alloy provides the sliding surface and the steel provides a backing (c.f. German Patent Specification No. 706,655). Owing to their high strength, such composite materials can be used in the manufacture of comparatively thin-walled bearing bushings, e.g. for connecing rod bearings, although they are inferior to steel-bronze composite materials made by sintering or casting when relatively high abrading and compressive stresses are to be expected, e.g. owing to the considerably increased power outputs of internal combustion engines per unit of displacement.This less satisfactory behaviour is due to the fact that, after the cladding operation, the aluminium alloy has a relatively low hardness corresponding to a Brinell Hardness Number of 45 to 55. The hardness cannot be increased by a specific heat treatment because the homogenization which has to be effected at a temperature of about 500 C and the succeeding quenching and artificial aging would destroy the frictionwelded joint formed between the aluminium alloy and the steel.

According to the present invention there is provided a process for producing an aluminium-clad composite material, wherein a precipitation-hardenable aluminium alloy strip is homegenized at a temperature of 450 to 550 C for 0.5 hour to 3 hours and is subsequently quenched, wherein the aluminium alloy strip is then bonded to a steel strip by rollcladding and the resulting composite material is quenched as soon as it leaves the roll nip.

With the present process it is possible to provide a process in which the aluminium alloy can be precipitation-hardened after the cladding operation to have properties which are substantially equivalent to the corresponding properties of steel-bronze composite materials whereas this should not adversely affect the strength of the friction-welded joint formed between the aluminium alloy and the steel.

The aluminium alloy strip preferably has a thickness of 0.5 to 5 mm. while the steel strip has a thickness of 0.5 to 10 mm. The rollcladding is conveniently effected at a cladding speed of 1.5 to 5 metres per minute.

It is desirable to use aluminium alloys which are capable of exhibiting high and/or low friction and are preferably of the type AlSill 2CuNiMg, AlZn5PbCuMg, AlSn6Cu, AlSi18NiMg or AlSi21CuNiMg.

Roll cladding is suitably effected at elevated temperatures above 200 C, preferably 200 to 400 C, and more preferably 250 C. Rollcladding may alternatively be effected at ambient temperatures if the fatigue limit of the bonding zone is of minor significance.

In order to facilitate the running-in of bearings made from a composite material which has been made in accordance with the present process, a layer of PbSnCu, AlSn, AlPb or iron phosphate in a thickness of a few microns is applied to the aluminium layer.

By the present process, the hardness of the aluminium alloy which has been clad onto steel can be increased from a Brinell Hardness Number 45 to 55 to a Brinell Hardness Number 65 to 85. This means that the hardness of bronze layers clad onto steel is reached or partly exceeded.

The invention will now be explained in greater detail in the following Example.

Strip steel having a width of 200 mm, and a thickness of 3 mm. is roughened on one side and is heated to about 500 C in an induction coil under a protective gas atmosphere. Thereafter the strip is fed to a roll nip for deforming the strip by roll cladding. An aluminium alloy of Type AlZn5PbCuMg or AlSi12CuNiMg in the form of strip having a thickness of 1.2 mm. and a width of 195 mm. is separately surface-activated and then homogenized at a temperature of 510 C for 2 hours. Thereafter the strip aluminium is quenched and is fed to the roll nip at the same time as the strip steel for deformation by roll cladding. The resulting composite material is quenched as soon as it leaves the roll nip and is subsequently artificially aged at a temperature of 1 85 > C for 10 hours. The aluminium alloy facing had the Brinell Hardness Number 81.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Process for producing aluminium-clad com- posite materials This invention relates to a process for producing aluminium-clad composite materials by roll-cladding an aluminium layer to a steel layer. It has been known for many years that composite materials can be produced by a roll-cladding process, in which sheet bars of a substrate metal and of a facing metal are jointly rolled so that they are bonded by welding under the rolling pressure. The substrate metal consists usually of plain carbon mild steel, which can easily be welded, or of high-temperature steel. The cladding may consist of copper and various kinds of copper alloys, nickel and nickel alloys, aluminium and aluminium alloys, silver and silver alloys, or of alloy steel. It is known to clad sheet metal elements, strip, tubing, rods, wires and sections whenever it is too expensive to produce these from the cladding metal alone and/or the cladding metal does not have the required mechanical properties. Examples of such products are coin banks, temperature-responsive bimetals or the like.Composite materials consisting of steel which is clad with aluminium alloys have been used for many years mainly in bearings. In such bearings, the aluminium alloy provides the sliding surface and the steel provides a backing (c.f. German Patent Specification No. 706,655). Owing to their high strength, such composite materials can be used in the manufacture of comparatively thin-walled bearing bushings, e.g. for connecing rod bearings, although they are inferior to steel-bronze composite materials made by sintering or casting when relatively high abrading and compressive stresses are to be expected, e.g. owing to the considerably increased power outputs of internal combustion engines per unit of displacement.This less satisfactory behaviour is due to the fact that, after the cladding operation, the aluminium alloy has a relatively low hardness corresponding to a Brinell Hardness Number of 45 to 55. The hardness cannot be increased by a specific heat treatment because the homogenization which has to be effected at a temperature of about 500 C and the succeeding quenching and artificial aging would destroy the frictionwelded joint formed between the aluminium alloy and the steel. According to the present invention there is provided a process for producing an aluminium-clad composite material, wherein a precipitation-hardenable aluminium alloy strip is homegenized at a temperature of 450 to 550 C for 0.5 hour to 3 hours and is subsequently quenched, wherein the aluminium alloy strip is then bonded to a steel strip by rollcladding and the resulting composite material is quenched as soon as it leaves the roll nip. With the present process it is possible to provide a process in which the aluminium alloy can be precipitation-hardened after the cladding operation to have properties which are substantially equivalent to the corresponding properties of steel-bronze composite materials whereas this should not adversely affect the strength of the friction-welded joint formed between the aluminium alloy and the steel. The aluminium alloy strip preferably has a thickness of 0.5 to 5 mm. while the steel strip has a thickness of 0.5 to 10 mm. The rollcladding is conveniently effected at a cladding speed of 1.5 to 5 metres per minute. It is desirable to use aluminium alloys which are capable of exhibiting high and/or low friction and are preferably of the type AlSill 2CuNiMg, AlZn5PbCuMg, AlSn6Cu, AlSi18NiMg or AlSi21CuNiMg. Roll cladding is suitably effected at elevated temperatures above 200 C, preferably 200 to 400 C, and more preferably 250 C. Rollcladding may alternatively be effected at ambient temperatures if the fatigue limit of the bonding zone is of minor significance. In order to facilitate the running-in of bearings made from a composite material which has been made in accordance with the present process, a layer of PbSnCu, AlSn, AlPb or iron phosphate in a thickness of a few microns is applied to the aluminium layer. By the present process, the hardness of the aluminium alloy which has been clad onto steel can be increased from a Brinell Hardness Number 45 to 55 to a Brinell Hardness Number 65 to 85. This means that the hardness of bronze layers clad onto steel is reached or partly exceeded. The invention will now be explained in greater detail in the following Example. Strip steel having a width of 200 mm, and a thickness of 3 mm. is roughened on one side and is heated to about 500 C in an induction coil under a protective gas atmosphere. Thereafter the strip is fed to a roll nip for deforming the strip by roll cladding. An aluminium alloy of Type AlZn5PbCuMg or AlSi12CuNiMg in the form of strip having a thickness of 1.2 mm. and a width of 195 mm. is separately surface-activated and then homogenized at a temperature of 510 C for 2 hours. Thereafter the strip aluminium is quenched and is fed to the roll nip at the same time as the strip steel for deformation by roll cladding. The resulting composite material is quenched as soon as it leaves the roll nip and is subsequently artificially aged at a temperature of 1 85 > C for 10 hours.The aluminium alloy facing had the Brinell Hardness Number 81. CLAIMS

1. A process for producing an aluminiumclad composite material, wherein a precipitation-hardenable aluminium alloy strip is homogenized at a temperature of 450 to 550 C for 0.5 hour for 3 hours and is subsequently quenched, and wherein the aluminium alloy strip is then bonded to a steel strip by rollcladding and the resulting composite material is quenched as soon as it leaves the roll nip.

2. A process as claimed in Claim 1, wherein the aluminium alloy strip has a thickness of 0.5 to 5 mm. and the steel strip has a thickness of 0.5 to 10 mm.

3. A process as claimed in Claim 1 or 2, wherein the roll-cladding is effected at a cladding speed of 1.5 to 5 metres per minute.

4. A process as claimed in any one of Claims 1 to 3, wherein the roll-cladding is effected at a temperature of 200 to 400 C.

5. A process as claimed in any one of Claims 1 to 4, wherein the roll-cladding is effected at a temperarture of 250 C.

6. A process as claimed in any one of Claims 1 to 3, wherein the roll-cladding is effected at ambient temperatures.

7. A process as claimed in any one of Claims 1 to 6, wherein the composite material is artificially aged at a temperature of 150 to 250 C for 2 hours to 10 hours.

8. A process as claimed in any one of Claims 1 to 7, wherein the aluminium alloy is one which is suitable for use as a low friction or bearing alloy.

9. A process as claimed in Claim 9, wherein the aluminium alloy is of the Type AlSil 2CuNiMg, AlZn5PbCuMg, AlSn6Cu, AlSil8NiMg or AlSi21CuNiMg.

10. A process as claimed in any one of Claims 1 to 9, wherein a layer consisting of PbSnCu, AlSn, AlPb or iron phosphate is applied in a thickness of a few micrometers to the aluminium layer.

11. A process for producing an aluminium-clad composite substantially as hereinbefore described in the foregoing Example.

12. An aluminium-clad composite produced by the process claimed in any preceding claim.