GB2153257A

GB2153257A - Process for the production of an adherent primary layer for composite friction bearings

Info

Publication number: GB2153257A
Application number: GB08432148A
Authority: GB
Inventors: Wolfgang Barthel; Ralf Weller; Lothar Hubel; Reinhardt Kunz
Original assignee: Kombinat Textima VEB
Current assignee: Kombinat Textima VEB
Priority date: 1983-12-23
Filing date: 1984-12-20
Publication date: 1985-08-21
Also published as: JPS6250500B2; GB8432148D0; DE3444938A1; DE3444938C2; JPS60231733A; GB2153257B; CH664196A5

Abstract

The present invention provides a process for the production of an adhesive primary layer for composite friction bearings in which on to a pre-treated metallic substrate there is applied a self- adhering porous adherent primary layer consisting essentially of aluminium powder to which is applied a friction bearing material in the form of a mixture of polytetrafluoroethylene, lead and phenolic resin, wherein a) the pre-treated substrate is wetted with a phenol-formaldehyde condensation product with a dry weight of from 0.4 to 0.5 g./dm<2> on to which b) there is sprinkled an aluminium powder with a particle size of from 10 to 20 mu m. in a thickness of from 200 to 300 mu m., c) the aluminium powder layer is rolled under slight pressure against the wetted substrate and, subsequently, d) the phenol- formaldehyde condensation product is hardened at about 145 DEG C, for about 30 minutes.

Description

SPECIFICATION Process for the production of an adherent primary layer for composite friction bearings The present invention is concerned with a process for the production of an adherent primary layer for composite friction bearings in which there is applied to a pretreated metallic substrate a porous, self-adhering adherent primary layer consisting of substantially aluminium powder to which is applied a friction bearing material in the form of a mixture of polytetrafluoroethylene, lead and phenolic resin.

Adherent primar layers of aluminium or aluminium alloys applied to steel substrates have hitherto been used for a variety of maintenance-free composite friction bearings, these layers serving the object of achieving a secure connection between a carrier material and a bearing layer applied thereto.

Hitherto, the application of aluminium adherent primary layers to steel substrates has been achieved by means of various techniques. Thus, in the case of composite friction bearings, it is known to sinter on the adherent primary layer in the form of powder (see Federal Republic of Germany Patent Specification No. 1,286,827), to apply it in the form of a flat body by hot rolling (see Federal Republic of Germay Patent Specification No.

3,017,544) or also to spray it on (see Federal Republic of Germany Patent Specification No.

2,928,572). The adherent primary layer applied in this way generally ensures the desired secure connection between the substrate and the bearing layer but the apparatus required is very expensive and, in addition, these techniques require a large amount of energy.

From German Democractic Republic Patent Specification No. 61.393, it is known to combine a bearing layer with a metallic carrier plate by applying to the pre-treated metallic carrier plate a heat-resistant adhesive and especiallu one based upon synthetic resin and applying directly to this layer of adhesive a powdered or granular mixture of bearing layer mixture, whereafter the layers are consolidated by the use of alternating pressures and temperatures. Although with this technique.

without a metallic adhesive base, there can be achieved secure layer connections suitable for general use, the limits of use are, however.

fixed by the high edge pressing which occurs in some cases which, in the case of the application of thick running layers, can lead to localised detachments of the layer.

It is an object of the present invention to reduce the expense required for the production of an aluminium adherent layer on a metallic substrate for high-stressed composite friction bearings.

It is a further object of the present invention to provide an efficient process by means of which there is achieved an extremely secure and stable layer connection between a substrate and a bearing layer in the case of which frictional heat arising during use is efficiently and effectively conducted away.

Thus, according to the present invention, there is provided a process for the production of an adherent primary layer for composite friction bearings in which on to a pre-treated metallic substrate there is applied a self-adhering porous adherent primary layer consisting essentially of aluminium powder to which is applied a friction bearing material in the form of a mixture of polytetrafluoroethylene, lead and phenolic resin, wherein (a) the pre-treated substrate is wetted with a phenol-formaldehyde condensation product with a dry weight of from 0.4 to 0.5 g./dm2 on to which (b) there is sprinkled an aluminium powder with a particle size of from 10 to 20 ,um. in a thickness of from 200 to 300 liy., (c) the aluminium powder is rolled under slight pressure against the wetted substrate and, subsequently, (d) the phenol4ormal- dehyde condensation product is hardened at about 145"C. for about 30 minutes.

According to a preferred embodiment of the present invention, a favourable relationship between obtaining adhesion and conducting away of heat is achieved when the porous aluminium powder application application takes place in an amount of from 2.5 to 3.0 g./dm2.

For the avoidance of faulty places in the layer structure, according to another preferred feature of the present invention, all non-bound aluminium particles are removed, which takes place after sprinkling on to the adhesive layer by tilting and after the hardening process by brushing off.

The advantage of the present invention is the fact that, with comparatively small expenditure, there are achieved extremely strong and stable layer connections between a metallic substrate and a bearing layer made up of polytetrafluoroethylene, lead and phenolic resin.

The porous aluminium layer, which, according to the described process. has about 35 to 40% of hollow spaces. provides very good anchoring possibilities for the bearing layer and can effectively and efficiently conduct away frictional heat arising during operation to the substrate because, as a result of the gentle rolling on of the aluminium particles, many of them penetrate into the adhesive layer and have a direct contact with the substrate. At the same time, aluminium powder has proved to be especially well suited for providing the adhesion since, in contradistinction to other metallic layers, it is substantially more coalescent.

The following Example is given for the purpose of illustrating the present invention: Example.

A 1.5 mm. thick steel sheet is degreased by pickling and thereafter one surface thereof is roughened by chemical treatment. This pretreated substrate is then wetted with an adhesive binding agent in the form of a phenolformaldehyde condensation product with a dry weight of from 0.4 to 0.5 g./dm2. Such a binding agent is commercially available under the designation "Plastatherm 2355".

Thereafter, aluminium powder with a particle size of from 10 to 20 lim. is sprinkled on, with the use of an appropriate device, in a thickness of from 200 to 300,um. and rolled on under slight pressure. Insofar as the aluminium powder applied does not bind with the adhesive binding agent, the particles which are only loosely lying on the substrate are removed therefrom by tilting.

For the hardening of the phenol-formaldehyde condensation product, there then follows a heat treatment at 145"C. for 30 minutes. Particles which hereafter are still loose or not securely bound are then brushed off.

On to this layer serving for adhesive purposes is then applied a bearing layer which is, for example, a homogeneous sliding material mixture comprising, by weight, 37% of crystalline polytetrafluoroethylene, 50% of lead powder and 13% of phenolic resin. This coating can also take place by dry sprinkling on or also by application in the form of a paste and, depending upon the intended use of the friction bearing, can have a thickness of from 1.5 to 2.5 mm.

Subsequent to this application, for the precondensation of the phenolic resin there first follows a heat treatment at about 85"C. for 60 minutes. A compression subsequently takes place at a pressure of from 20 to 40 MPa for 25 seconds, then a pressureless heat treatment at 145"C. and finally a post-compression at 20 to 40 MPa for 25 seconds.

Friction bearing surfaces produced in this manner can be milled to an appropriate thickness and, if desired, can be rounded to give journal bearing bushings. They are characterised by an especially advantageous running property in maintenance-free operation and are very well suited for highly specific surface loadings.

Claims

1. Process for the production of an adherent primary layer for composite friction bearings in which on to a pre-treated metallic substrate there is applied a self-adhering porous adherent primary layer consisting essentially of aluminium powder to which is applied a friction bearing material in the form of a mixture of polytetrafluoroethylene, lead and phenolic resin, wherein (a) the pre-treated substrate is wetted with a phenol-formaldehyde condensation product with a dry weight of from 0.4 to 0.5 g./dm2 on to which (b) there is sprinkled an aluminium powder with a particle size of from 10 to 20 ,um. in a thickness of from 200 to 300 lim., (c) the aluminium powder layer is rolled under slight pressure against the wetted substrate and, subsequently, (d) the phenol-formaldehyde condensation product is hardened at about 145"C. for about 30 minutes.

2. Process according to claim 1, wherein the aluminium powder is applied in step (b) in an amount of from 2.5 to 3.0 g./dm7.

3. Process according to claim 1 or 2, wherein the aluminium powder particles which are not bound after step (b), as well as after hardening of the phenolformaldehyde condensation product after step (c). are removed in appropriate manner.

4. Process according to claim 3, wherein non-bound aluminium particles are removed after step (b) by tilting and after step (d) by brushing off.

5. Process according to claim 1 for the production of an adherent primary layer for composite friction bearings, substantially as hereinbefore described and exemplified.

6. Adherent primary layers for composite friction bearings, whenever produced by the process according to any of claims 1 to 5.