WO1993020264A1

WO1993020264A1 - Method of producing lamellar material or lamellar parts for plain bearings

Info

Publication number: WO1993020264A1
Application number: PCT/DE1993/000229
Authority: WO
Inventors: Helmut Tegebauer; Volker Falkowski
Original assignee: Braunschweiger Hüttenwerk Gmbh
Priority date: 1992-04-07
Filing date: 1993-03-10
Publication date: 1993-10-14
Also published as: DE4211642C1; EP0635073A1; DE4211642C2

Abstract

In order, in lamellar material or lamellar parts for plain bearings, to form a bonding layer of pure silver between a single-layer or multi-layer substrate material or part and an electrolytically deposited sliding-layer alloy, the invention calls for the bonding layer to be built up electrolytically in two stages, viz: a pre-silvering stage for the formation of a preliminary layer about 0.1 $g(m)m to about 0.5 $g(m)m thick and a main silvering stage for the formation of a main layer about 2 $g(m)m to about 10 $g(m)m thick. The galvanic silver-plating baths used in both stages contain substantially the same substances, but the concentrations of the substances differ significantly. In particular, the silver concentration is significantly lower in the pre-silvering bath than in the main silvering bath. In order to build up the bonding layer of pure silver on substrate layers of aluminium, a very thin metal coating is applied containing at least one of the metals zinc, nickel, copper and iron. This is preferably carried out using an appropriate aluminium immersion liquid.

Description

Process for producing plain bearing layer material or plain bearing

Layered workpieces

The invention relates to a method for producing plain bearing layer material or plain bearing layer workpieces, in which a binding layer made of silver and a sliding layer made of a lead-tin-copper or tin on a single-layer or multilayer carrier material or carrier workpiece -Antimony- plain bearing alloy (preferably lead-tin-copper alloy), galvanically attached.

From DE-AS 1 048 757 it is known to provide a thin zinc layer and a bonding layer made of silver between the carrier layer made of aluminum material and a galvanically applied sliding layer made of lead-based bearing metal in the case of plain bearings which consist entirely or mainly of aluminum. The binding layer made of silver offers the advantage that it is considerably softer and less susceptible to seizure than the binding and diffusion barrier layer made of nickel or similar hard metallic materials, which has been widely used in the case of multilayer plain bearings. However, the binding layer made of silver known from DE-AS 1 048 757 has the defect that it can only have a maximum thickness of 2.5 μm in order to retain sufficient binding to the thin zinc layer arranged underneath and the carrier layer made of aluminum material . In addition, the galvanic application of the known binding layer made of silver is associated with critical working conditions, so that the binding layer made of silver known from DE-AS 1 048 757 could not prevail in practice.

In contrast, the object of the invention is to create a method with which a galvanically applied bonding layer made of silver is thicker and more effective than before, in particular with regard to increased bonding strength on backing layers with emergency running properties, both on backing layers made of aluminum material as well as on carrier layers made of other materials, in particular bronze materials.

This object is achieved according to the invention in that the bonding layer made of pure silver is galvanically applied in two successive stages of silver dissolved in cyanide, namely in a pre-silvering stage as a thin pre-silvering layer with a thickness of approximately 0.1 μm to approximately 0.5 μm and a main - Silvering stage as the actual silver layer with a thickness of approximately 2 μm to approximately 10 μm, whereby in the pre-silvering stage a much lower silver concentration is used than in the main silvering stage, but current density of approximately the same order of magnitude is set up in both stages.

The structure of the bonding layer according to the invention as a thin pre-silvering layer and the actual silver layer ensures that the pre-silvering layer ensures a secure bond on the carrier layer, while the actual silver layer forms a secure bonding basis for the sliding layer applied galvanically over it. This is achieved even though both partial layers have the same material structure made of pure silver. Due to the galvanic structure of a pre-silvering layer, the silver bonding layer can be adapted to support layers of various material structures. The adaptation between the pre-silvering layer and the actual silver layer is not critical due to the material of the two layers being the same, as is the binding property of the actual silver layer with the sliding layer electroplated thereon.

The galvanic silver plating baths used to build up the two sub-layers of the silver bonding layer preferably differ in their material composition only with regard to the silver concentration and the concentration of the free alkali cyanide used in addition to the cyanide-dissolved silver. The concentration of the free alkali cyanide can thus lie between 50 g 1 and 200 g 1, it being possible to use a higher, preferably about 50% higher to twice the concentration of the free alkali cyanide in the main silvering stage. Silver concentrations of between approximately 1 g / l and approximately 60 g / l can be provided in the silver plating baths, an approximately 10-fold to 20-fold silver concentration being used in the main silver-plating stage compared to that in the pre-silver-plating stage.

There are various possibilities for adapting the pre-silvering to the material properties of the respective carrier layer, which are to be chosen by the expert from case to case. For example, the pretreatment prior to the silvering step can be provided for carrier layers made of bronze material by pickling or electrical etching and pickling. Pretreatment prior to pre-silvering can also be provided in the case of carrier layers made of aluminum material by pickling or electro-etching and pickling and then very thin pre-metallization. In the case of carrier layers made of aluminum material such as aluminum alloy or aluminum dispersion alloy, a pre-treatment by pickling and acid immersion and subsequent immersion in an aluminum immersion liquid are preferred before the pre-silvering step, in order to deposit a very thin layer of at least one, preferably several, of the metals zinc, nickel, Make copper, iron. However, it is also possible, in the case of carrier layers made of aluminum material such as aluminum alloy or aluminum dispersion alloy, to carry out a pretreatment prior to the pre-silvering step, which contains the removal of the oxide layer and the formation of a very thin metal layer by electrochemical metallization.

EXAMPLES

example 1

Pre-silvering bath:

1 to 5 g / 1 dissolved silver 50 to 200 gl potassium cyanide current density: 1 to 3 A / dm ²

Main silver plating bath:

20 to 50 g / 1 dissolved silver 120 to 200 g / 1 potassium cyanide current density: 2 to 5 A dm ²

The free alkali cyanide can also be sodium cyanide in one or the other or in both silver plating baths.

Example 2

Alumim ^'s immersion solution with the main components:

10 to 20 g / 1 zinc ions 5 to 10 g / 1 nickel ions 1 to 2 g / 1 copper ions small amount of iron ions. These constituents are provided in the form of salts, the acids of which can bind large amounts of aluminum.

Example 3

Preformed carrier workpieces for plain bearings with a steel backing and aluminum-tin dispersion alloy coating are degreased in organic solvent and then pickled in a solution of sulfuric acid, hydrofluoric acid and zinc oxide. The workpieces are then immersed in a mixed acid of sulfuric and chromic acid. This is followed by immersion in an aluminum immersion liquid according to Example 2 over a period of 1 to 3 minutes. This is followed by electrodeposition of a pre-silvering layer with a thickness of 0.1 to 0.5 μ and the electrodeposition of a pure silver layer of approx. 5 μm thickness in pre-silvering and main silvering baths according to example 1. The galvanic deposition of the pure silver layer is followed by the galvanic deposition of a ternary or binary sliding layer (PbSnCu or SnSb) in the desired thickness. After the ternary or binary sliding layer has been deposited, a heat test is carried out to check the bond strength.

The usual and known washing and rinsing processes take place between the individual treatment steps.

Example 4

Preformed plain bearing workpieces made of steel backing and an applied intermediate layer made of tin-lead-bronze are degreased in organic solvents and then subjected to electro-etching. Electroetching is followed by immersion in acid (pickling). After pickling, the electrodeposition of a pre-silvering layer of about 0.1-1.5 μm thickness is carried out and the electrodeposition of a pure silver layer of about 5 μm thickness in silvering baths according to Example 1. Electrodeposition of a ternary or binary is carried out on the deposited pure silver layer Sliding layer of the desired composition and thickness.

The usual and known washing and rinsing steps take place between the treatment steps. The finished plain bearings are subjected to a heat test to check the bond strength.

Claims

1. A process for the production of plain bearing layer material or plain bearing layer workpieces, in which a binding layer made of silver and a sliding layer made of plain bearing alloy, preferably lead-tin-copper or tin-antimony, on a single-layer or multi-layer support material or support workpiece -Alloy, electroplated,

characterized in that

the bonding layer of pure silver is applied galvanically in two successive stages of silver dissolved in cyanide, specifically in a pre-silvering stage as a thin pre-silvering layer with a thickness of about 0.1 to about 0.5 μm and in a main silvering stage as a silver layer with about 2 μm to about 10 μm in thickness, wherein a much lower silver concentration is used in the pre-silvering stage than in the main silvering stage, but a current density of approximately the same order of magnitude is established in both stages.

2. The method according to claim 1, characterized in that in the galvanic silver plating baths of both stages in addition to the cyanide-dissolved silver free alkali cyanide is used in concentrations between 50 g / 1 and 200 g / 1, with higher, preferably about 50% higher in the main silvering stage until double concentration of the free alkali cyanide is used.

3. The method according to claim 1 or 2, characterized in that Silberkonzen¬ trations in the silver plating baths between 1 g / 1 and 10 g / 1 are provided, wherein in the main silvering stage about 10 times to 20 times the silver concentration compared to that is applied in the pre-silvering stage.

4. The method according to one of claims 1 to 3, characterized by pickling or electro-etching and de-papering as pretreatment steps before the pre-silvering step for carrier layers made of bronze material or before a very thin pre-metallization as a further pretreatment before the pre-silvering step for carrier layers made of aluminum material.

5. The method according to any one of claims 1 to 3, characterized in that in the case of carrier layers made of aluminum material, such as aluminum alloy or Alu¬ minium dispersion alloy, a treatment by pickling and acid dipping and subsequent immersion in an aluminum immersion liquid for separating a very before the pre-silvering step thin layer of one, preferably several, of the metals zinc, nickel, copper, iron.

6. The method according to any one of claims 1 to 3, characterized in that in the case of carrier layers made of aluminum material, such as aluminum alloy or aluminum dispersion alloy, a pre-treatment is carried out before the pre-silvering step, which eliminates the oxide layer and forms a very thin layer Contains metal layer by electrochemical pre-metallization.