GB2298871A

GB2298871A - Electroplating elongated substrate and drawing

Info

Publication number: GB2298871A
Application number: GB9526021A
Authority: GB
Inventors: Andrew Hughes
Original assignee: United Wire Ltd
Current assignee: Schlumberger UK Holdings Ltd
Priority date: 1993-05-08
Filing date: 1993-09-13
Publication date: 1996-09-18
Anticipated expiration: 2013-09-13
Also published as: GB2298871B; GB9526021D0

Abstract

In a method of continuously coating a conductive substrate such as brass wire 10 to produce a desired cross-sectional size of coated material, the wire is drawn through a first die to produce an oversize wire, electroplated in a bath 32, and then drawn through a final die 44 to reduce its area to the desired size and produce a controlled surface finish. The wire may be cleaned in an acid bath 20 and rinsed in a rinsing bath 30 prior to the electroplating bath. A further rinsing bath 36 and dryer 38 may be interposed upstream of the final die 44.

Description

TITLE: PRODUCtION OF SURFACE TREATED METAL ALLOY PINS Field of Invention This invention concems a method and apparatus for the production of surface treated, metal alloy pins. The invention is of particular application to the continuous coating or electroplating of such pins to achieve a coated material having a predetermined overall cross-sectional size.

Background to the Invention For many applications a metal alloy substrate, eg wire, must be plated on its external surface such as for protection or insulation. Where the overall cross-sectional size of the coated or plated material does not have to be held to a high tolerance, known processes may be employed.

Difficulties arise where continuous plating has to achieve a particular overall cross-sectional size for the end product and the invention is of particular importance in such processes.

It is therefore a primary object of the present invention to provide a method and apparatus for plating in a continuous manner a conductive metal alloy substrate, typically in the form of wire, so as to enable a final predictable and accurately controlled cross-sectioned size of the plated material to be obtained.

It is a subsidiary object of the invention to provide apparatus and method by which such continuously produced plated wire has not only a controlled cross-sectional size, but also a controlled surface finish.

Summarv of the Invention According to one aspect of the present invention there is provided a method for the production of surface treated, metal alloy pins of a predetermined overall cross-sectional size, which comprises continuously coating a conductive metal alloy substrate by the steps of: (a) drawing the metal alloy substrate through at least one die so as to produce a crosssectional size which is greater than that desired for the pins; (b) electroplating the drawn, metal alloy substrate to a thickness not exceeding approximately 1 micron in a continuous manner as it passes through an electroplating bath; and (c) drawing the plated, metal alloy substrate through a final die to reduce the crosssectional area to the predetermined pin size; and (d) forming the pins.I Preferably the surface of the metal alloy substrate is cleaned prior to the electroplating step using acid or alkaline washes as appropriate.

The first mentioned drawing step may be followed by a stress relieving step.

Preferably the plated substrate material is heated and dried after rinsing and prior to passing through the final die.

The reduction in size effected by the final die may also be arranged to introduce the desired temper into the metal substrate as a result of the drawing through the die.

It will be found that in general the drawing of the plated material through the final die will result in a more uniform thickness of plated material over the substrate and an improvement in the surface finish or smoothness of the plated surface. This is particularly so where high current density has to be employed in order to achieve rapid plating as the substrate passes through the electroplating bath.

Where two or more materials are to be plated on the original substrate one above the other, the substrate may be passed through second and subsequent electroplating baths with appropriate rinsing and washing stations between each bath, in manner known per se.

Additionally the invention envisages the use of two or more electroplating baths arranged in series, each plating the same metal alloy substrate onto material passing therethrough.

The invention also lies in apparatus for performing the aforementioned method comprising at least one die drawing means through which an elongate, metal alloy substrate in a continuous length can be drawn to achieve a first overall cross-sectional size, electroplating means through which the drawn substrate passes for electroplating on the surface thereof, a final die drawing means through which the coated substrate material is drawn to achieve the predetermined cross-sectional area for the pins, and means for forming the pins, when operated to produce pins electroplated to a thickness not exceeding approximately 1 micron before the final drawing means.

Stress relieving means may be located after the first mentioned die drawing means.

The apparatus may also include a cleaning bath situated between the incoming elongate material and the electroplating means, for surface cleaning of the substrate.

The apparatus may further comprise rinsing and washing baths situated between the electroplating means and the final die means.

Heating and drying means is advantageously located between the rinsing and washing baths and the final die means.

The invention further extends to a coated, elongate metal alloy material for use in the production of surface treated pins, when produced by steps a) to c) of the method as stated above.

Other aspects of the present invention are defined in the appended claims.

The invention is of particular application in the coating of alloys such as brass and the process has been used to coat a brass wire with Indium. Thus in one example brass wire of 1.46mm diameter was coated with Indium to a depth of 0.5 to 1.0 microns by passing it through an electroplating bath containing Indium Sulphamate 60% solution and Indium ingots with a direct current of 85 amps. Coating to the depth indicated was achieved at speeds of the order of 60 meters per minute.

The final die not only reduced the diameter to 1.39mm but improved the surface finish of the plated brass and also improved the temper of the brass enabling the latter to be formed into pins.

The surface finish achieved by the final die also enabled the plated brass to be shaped by metal forming processes so as to provide an enlarged diameter head at one end of a section housing a slightly smaller diameter than the head but still greater than the diameter of the remainder of the pin.

The final die drawing stage did not disturb the plating and produced a surface finish and tempered product which was not only capable of being formed as aforesaid but constructed to a high tolerance.

The method and apparatus has also been employed to plate lead onto brass wire to a similar depth.

The invention will now be described by way of example, with reference to the accompanying drawing which illustrates diagrammatically apparatus for performing the method of the invention.

Detailed description of drawings In the drawing the brass wire (10) produced through a series of dies and wound onto a large reel (12) is then mounted on a let-off unit (14) and passed in to the plating equipment. Within the plating equipment, the wire is passed through a tensioning stage (18) after which it passes through a cleaning bath (20) containing an acid solution supplied with current from an adjustable DC source (28) and thereafter a rinsing bath (30). The wire then passes into the plating bath (32) supplied with current from an adjustable DC source (34). Both the cleaning and plating currents are indicated by ammeters, and controls are provided in manner known per se to adjust the currents to suit conditions.

After plating, the wire passes through a rinsing bath (36) after which is passes through a dryer (38) containing an electrically powered heater (40), after which it passes through a tensioning device (42), before passing into the final die drawing apparatus (44).

The final die is adjusted to reduce the cross-sectional area of the plated material to 1.39mm. After drawing through the final die the finished material is wound up on a take-up reel (46) driven by motor means (not shown).

The electro-plating bath (32) contains a salt of the metal which is to be coated on the brass wire, and in the case of Indium the material is preferably Indium Sulphamate.

Claims

1. A method for the production of surface treated, metal alloy pins of a predetermined overall cross-sectional size, which comprises continuously coating a conductive metal alloy substrate by the steps of: (a) drawing the metal alloy substrate through at least one die so as to produce a crosssectional size which is greater than that desired for the pins; (b) electroplating the drawn, metal alloy substrate to a thickness not exceeding 2 microns in a continuous manner as it passes through an electroplating bath; (c) drawing the plated, metal alloy substrate through a final die to reduce the crosssectional area to the predetermined pin size; and (d) forming the pins.

2. A method according to claim 1 in which the surface of the metal alloy sub'strate is cleaned prior to the electroplating step using acid or alkaline washes as appropriate.

3. A method according to claim 1 or claim 2 in which the plated, metal alloy substrate is rinsed and dried after it is passed through the electroplating bath and before it is drawn, so as to remove any plating bath materials from the surface of the plated substrate.

4. A method according to any one of claims 1 to 3 in which the first mentioned drawing step is followed by a stress relieving step.

5. A method according to claim 3 or claim 4 in which the plated substrate material is heated and dried after rinsing and prior to passing through the final die.

6. A method according to any one of claims 1 to 5 in which the metal alloy substrate is a brass substrate, and in which the reduction in size effected by the final die is also arranged to introduce the desired temper into the brass substrate as a result of the drawing through the die.

7. A method according to any one of claims 1 to 6 in which two or more materials are plated on the metal alloy substrate one above the other, the substrate being passed through second and subsequent electroplating baths with appropriate rinsing and washing stations between each bath, in manner known per se.

8. A method according to any one of claims 1 to 6 using two or more electroplating baths arranged in series, each plating the same material onto the metal alloy substrate passing therethrough.

9. A method according to any one of claims 1 to 8 in which the step of drawing the plated, metal alloy substrate through the final die also controls the surface finish required for the pins.

10. A method according to any of claims 1 to 9 in which the electroplating is carried out at a speed of approximately 60 metres per minute. I

11. Apparatus for producing surface treated, metal alloy pins by the method of claims 1 to 10 comprising at least one die drawing means through which an elongate, metal alloy substrate in a continuous length can be drawn to achieve a first overall cross-sectional size, electroplating means through which the drawn substrate passes for electroplating on the surface thereof, a final die drawing means through which the coated substrate material is drawn to achieve the predetermined cross-sectional area of the pins, and means for forming the pins, when operated to produce pins electroplated to a thickness not exceeding - 2 microns before the final die drawing means.

12. Apparatus according to claim 11 further comprising stress relieving means located after the first mentioned die drawing means.

13. Apparatus according to claim 11 or claim 12 further comprising a cleaning bath situated between the incoming elongate material and the electroplating means, for surface cleaning of the substrate.

14. Apparatus according to any one of claims 11 to 13 further comprising rinsing and washing baths situated between the electroplating means and the final die means.

15. Apparatus according to claim 14 further comprising heating and drying means located between the rinsing and washing baths and the final die means.

16. A coated elongate metal alloy material for use in the production of surface treated pins, when produced by steps a) to c) of the method according to claim 1.

17. A coated elongate material as claimed in claim 16 in which the substrate is a brass wire coated with indium to a thickness not exceeding 1 micron.

18. A coated elongate material as claimed in claim 16 or claim 17 in which two or more materials are plated on the substrate one above the other.

19. A method of producing surface treated pins by continuously coating a conductive metal alloy substrate, substantially as herein described with reference to, and as shown in, the accompanying drawings.

20. Apparatus for the production of surface treated pins by continuously coating a conductive metal alloy substrate, when operated to produce an electroplating thickness not exceeding 2 microns before the final die drawing means, substantially as herein described with reference to, and as shown in, the accompanying drawings.