RU2751355C1 - Method for applying galvanic coating on precision metal threads and installation for its implementation - Google Patents

Abstract

FIELD: electroplating.

SUBSTANCE: invention relates to the field of electroplating and can be used to apply a metal coating on precision metal threads. The method includes feeding a filament, cleaned of grease and oxides, into an electrolyte, applying a coating on the filament by an electroplating method, fixing the coating and winding the finished product, while cleaning the filament from grease and oxides is carried out immediately before it is fed into the electrolyte, while simultaneously bringing it to a given diameter by the method electrochemical etching by sequentially passing through alkaline fountain-type baths, acid bath and thread washing bath, and the coating is applied by repeatedly passing the filament through the electrolyte, before winding the finished product, the filament is washed and the coating is fixed, all operations being combined in a single process on one installation. The installation includes a winding unit, a galvanic bath with electrolyte, a coating fixing unit, a winding unit, while it additionally contains an electrochemical etching bath after the winding unit, as well as a bath for washing in front of the coating fixing unit, while the electrochemical etching bath contains successively installed alkaline fountain baths. type, an acid bath and a bath for washing the thread, slots for the thread are made in the walls of the baths, and electrodes are installed in the baths connected to the first adjustable current source, the galvanic bath contains two drums, located one above the other, providing the possibility of multiple immersion of the metal thread in the electrolyte, while the lower drum is immersed in the electrolyte, and the upper drum is connected to the negative output of the second current source, which is connected with a positive output to the anode in the galvanic bath.

EFFECT: invention increases the speed of the deposition process up to 40 m/min while ensures the uniformity of the diameter of the precision metal thread ±3% and uniformity of the coating thickness.

7 cl, 3 dwg

Description

The group of inventions relates to the field of electroplating and can be used to apply a metal coating (for example, gold, copper) on precision metal threads in motion, in particular to the process of coating threads from refractory materials.

Known device and method of electroplating on an electrically conductive substrate or on a structured or solid electrically conductive surface on a substrate that does not have electrical conductivity (see patent RU 2420616, IPC C25D 17/00, publ. 10.06.2011). The device contains one bath, one anode and one cathode, and the bath contains an electrolyte solution, from which metal ions are deposited on the electrically conductive surfaces of the substrate, while the cathode is in contact with the surface of the substrate to be coated, and the substrate is moved through the bath, and the cathode includes at least one belt with one electrically conductive section, which runs around at least two rotating shafts, and wherein several belts are arranged offset one after the other. The method is carried out in a device according to the invention, wherein a tape is applied to the substrate, which circulates at the same speed as that with which the substrate passes through the bath.

The disadvantage is that the invention does not allow thin layers of metals to be applied to long structures such as wire.

A number of inventions are known for applying a continuous galvanic coating with a thickness of 0.1 to 0.3 microns on an ultra-thin metal wire with a diameter of 10 to 100 microns (see patents CN 110004474, IPC C25D 7/06; CN 209974932, IPC C25D 7/06) ... To implement the coating method, a line is proposed that is located in a straight line and includes an unwinding unit located at the beginning of the production line, an electroplating unit located in the middle of the production line and a winding unit located at the tail end of the production line. The winding unit and unwinding unit are used to adjust the winding speed to prevent the metal wire from breaking, the unwinding end speed is adjusted in real time by the angle sensor and torque sensor in the unwinding control module, the winding speed is controlled by the winding control device.

Closest to the proposed method is a method for applying gold plating (see CN104451804). The process of wire processing includes the following stages: removing the wire from the winding unit and feeding it into the electrolyte, drying and winding the wire onto the wheel for removing the wire. The coating solution flows through a graphite tube above the electrolyte bath. The circulation of the solution is formed so that it passes in a circle through the coating bath. After passing through the graphite tube, the wire is dried in a heating oven and then wound on a wire winding wheel. A graphite tube is connected to a positive electrode of a power supply to form an anode, and an insoluble metal wire to be coated is connected to a negative electrode of a power supply to form a cathode. The wire is passed through the electroplating solution at a certain speed The processing process disclosed in the invention ensures that the gold plating layer of the insoluble metal wire is uniform and compact in thickness by applying the continuous gold plating method, so that the gold plating layer is obtained with high smoothness.

Closest to the proposed device is a device for electrolytic gilding of refractory metal wire (CN 204417623 IPC C25D 5/50). The device includes a wire winding unit, a galvanic bath with electrolyte, a drying unit, and a winding unit. According to the device, the base is a graphite tube located above the reservoir for the galvanic liquid, through the holes of which the wire passes. Liquid for electroplating the wire circulates through the graphite tube. The graphite tube is the anode. Before and after the graphite tube, there are contact rollers that transmit a negative potential to the wire, forming a cathode.

In the industrial production of wires of various diameters, a lubricant is used, both for the implementation of the drawing process in part, and for protecting the surface of the finished wire from oxidation. Mainly in the refractory industry, graphite grease is used. The disadvantage of the known solutions, including prototypes, is that the wire supplied to them must be pre-cleaned of graphite grease and traces of oxides. For this, there must be special installations that require additional space and time, as well as working personnel. In addition, the disadvantage of the prototypes should be attributed to the low coating speed of 5-10 m / min.

The technical problem to be solved by the group of inventions is to solve the problem of using a metal filament in a graphite lubricant or with an oxidized surface as a blank (starting material) with the simultaneous possibility of applying coatings of various thicknesses to it by the galvanic method.

The technical result consists in increasing the speed of the application process up to 40 m / min. while ensuring the uniformity of the diameter of the precision metal thread ± 3% and uniformity of the coating thickness.

To achieve the technical result in the method of coating a refractory metal thread, including feeding the thread, cleaned of grease and oxides, into the electrolyte, coating the thread with a galvanic method, fixing the coating and winding the finished product, according to the decision, cleaning the thread from grease and oxides is carried out immediately before it is fed into the electrolyte by the method of electrochemical etching, while simultaneously bringing it to a given diameter, the coating is applied by repeatedly passing the filament through the electrolyte, before winding the finished product, the filament is washed and the coating is fixed, while all operations are combined in a single process on one installation.

To achieve the technical result, the installation for applying a coating on a refractory metal thread, including a winding unit, an electroplating bath with electrolyte, a coating fixing unit, a winding unit, according to the solution, additionally contains an electrochemical etching bath after the winding unit, as well as a washing bath in front of the coating fixing unit. In this case, the electrochemical etching bath contains sequentially installed alkaline fountain-type baths, an acid bath and a thread washing bath. In the walls of the trays, slots for the thread are made, and in the trays, electrodes are installed, connected to the first adjustable current source. The galvanic bath contains two drums, located one above the other, providing the possibility of multiple immersion of the metal thread in the electrolyte, while the lower drum is immersed in the electrolyte, and the upper drum is connected to the negative output of the second current source, which is connected with a positive output to the anode in the galvanic bath ...

The invention is illustrated by illustrations.

FIG. 1 schematically shows an installation for implementing the method.

FIG. 2 is a schematic view of an etching bath.

FIG. 3 is a schematic view of a gilding bath.

Positions in the drawings indicate:

1.winding device;

2. regulator of thread tension;

3. sensor of speed and length of the thread;

4. bath of electrochemical etching;

5. fountain type alkaline baths;

6. acid bath;

7. bath for washing the thread;

8. ultrasonic bath;

9.Slot;

10. inlet for supplying the etching electrolyte;

11. electrodes;

12. the first source of current;

13. precision metal thread;

14. electroplating baths;

15. electrolyte;

16. top drum;

17. lower drum;

18. heater;

19. anode;

20. second current source;

21. bath for washing;

22. block for fixing the cover (oven);

23. winding unit.

The installation for the implementation of the integrated technology includes a sequential winding unit consisting of a winding device 1, a thread tension regulator 2 and a thread speed and length sensor 3, an electrochemical etching bath 4, an ultrasonic bath 8, a galvanic bath 14 (for example, a gilding bath), a bath for washing with water 21, oven 22 for fixing the coating (drying) on a precision metal thread and a winding unit 23 containing a take-up commercial reel and a winding head for winding and laying out the finished yarn on a take-up commercial reel. An electric motor with a coil can be used as a winding device. The winding unit allows you to fully control the tension of the metal thread 13 and maintain it during operation. The yarn speed and length sensor 3 is required to continuously monitor the speed and length during the technological process. Etching bath 4 contains alkaline fountain-type baths 5, acid bath 6, wire washing bath 7 and allows cleaning the surface of the initial thread of a semi-finished product from graphite grease and oxides immediately before the moment of coating with simultaneous preparation of the surface of a precision metal thread for electroplating, in particular gold. Etching bath 4 makes it possible to reduce the diameter of the initial thread (semi-finished product) to the required diameter of the precision metal thread immediately before applying the electroplating coating, in particular gold, by etching off the surface layer containing lubricant and oxides. For etching, a potassium hydroxide solution with a specific gravity of 1.05 to 1.07 g / cm3 can be used. The etching bath units are equipped with alkaline fountain-type baths 5, acid bath 6 serving to neutralize alkali and water rinsing bath 7. Alkaline baths are made with end walls having a slot 9 0.3 mm wide. The etching electrolyte enters the baths from below under a slight pressure through inlet 10, quietly spreads over the bath, forming a slightly convex surface, and merges from the sides of the baths. The original thread (semi-finished product) passes through the slot of 9 trays. In the baths, electrodes 11 are installed, connected to the first adjustable current source 12, which provides setting modes from 1.5 A to 5.0 A. The baths for water and acid are similar to alkaline. Bath 14 contains electrolyte 15. As the electrolyte, traditional compositions based on cyanide electrolytes for gold and copper sulfate electrolytes for copper can be used. Other electrolyte compositions can also be used, depending on the metal of the coating. The electrolyte in the bath is heated by a heater 18 to 90 ° C. The galvanic bath contains two drums 16, 17 located one above the other, which provide the possibility of multiple immersion of the precision metal thread in the electrolyte, while the lower drum is immersed in the electrolyte, and the upper drum is connected to the negative output of the second current source 20 and transfers a negative potential to the thread 13, which is the cathode. The positive output of the second current source 20 is connected to the anode located in a bath with a heated heater 18 with electrolyte 15. Precision metal thread 13, repeatedly wrapping around the upper drum 16 and the lower drum 17, passes through the electrolyte in the gilding bath 14 and then through the bath with rinsing water 21 After rinsing, the coated precision metal filament passes through oven 22 where the coating is adhered to the filament surface.

As a starting material, a starting thread in a graphite lubricant can be used. The installation allows you to minimize the time spent on a precision metal filament of the required diameter, cleaned from grease, in air, which in turn reduces the likelihood of its contamination and oxidation. As a result, the quality of the coating and the strength of its adhesion to the precision metal filament are improved. The device makes it possible to increase the speed of coating up to 40 m / min due to the use of a gilding bath with repeated rounding of the drums by the thread, placed in the gilding electrolyte and, as a consequence, to increase the surface area of the filament in contact with the electrolyte. The use of the winding head 23 makes it possible to wind the finished precision metal thread, coated with metal, in particular gold, directly onto the sales reel, eliminating additional rewinding operations.

The implementation of the method is shown using the example of the proposed installation.

The initial thread is unwound from the winder 1. The electric motor with the tension regulator 2 maintains the tension of the metal thread constant throughout the entire production cycle. For continuous measurement of the speed and counting the length of the released precision metal thread, a speed and length sensor 3 is used. The original thread in the lubricant enters the etching bath 4, where, under the action of the current from the current source 12, its electrochemical etching takes place. As a result of electrochemical etching, the thread is cleaned of graphite grease and traces of oxides, while at the same time reaching the diameter of a precision metal thread required for the product with an accuracy of ± 3%. Next, the precision metal thread passes through the acid bath 6 in order to neutralize the etching electrolyte on it and the bath with rinsing water 7. After washing with water, the precision metal thread enters the ultrasonic bath 8 for additional cleaning of the surface, and then into the galvanic bath 14, where, repeatedly wrapping the upper drum 16 and the lower drum 17 pass through the electrolyte. Under the action of a current from the current source 20, the wire is electroplated, in particular gold. Refractory metals and their alloys can be used as the initial thread (wire) of the semi-finished product. Then a precision metal-coated metal thread passes through a bath of rinsing water, where it is cleaned of electrolyte residues.

Further, a precision metal thread coated with metal 13 enters the furnace 22 to fix the coating, in particular gold. The final operation is the winding and spreading of the metal-coated precision metal filament directly onto the product reel on the winding head 23.

As it accumulates, gold from the wash water is recovered and utilized.

The proposed complex installation for coating wire by electrolysis makes it possible to obtain a precision metal thread (accuracy of maintaining the diameter of ± 3%) with a coating depending on the customer's requirements (for example, gold with a coating thickness of 0.23 µm ± 0.02 µm). The technical result is achieved by combining in one production cycle the operations of winding the initial thread, cleaning from grease, preparing the surface of the wire, coating, fixing the coating and winding the finished product onto a commercial reel.

This eliminates the operation of preliminary preparation of the thread before applying the coating. The invention makes it possible to obtain precision metal filaments with a diameter of:

- for tungsten from 10 microns to 150 microns, gold-plated with a thickness of 0.1 to 0.3 microns.

- for molybdenum from 15 microns to 150 microns, gold-plated with a thickness of 0.1 to 0.3 microns.

- when selecting processing modes and electrolyte compositions, other options for the original wire and coating materials are also possible.

- Replacing the units of the installation with similar ones in design, but with different power characteristics, it is possible to expand the upper range of diameters up to 250-300 microns.

Claims (7)

1. A method of applying a coating on a refractory metal thread, including feeding a thread, cleaned of grease and oxides, into an electrolyte, applying a coating to the thread by electroplating, fixing the coating and winding the finished product, characterized in that the filament is cleaned of grease and oxides immediately before it is fed into the electrolyte, while simultaneously bringing it to a given diameter by electrochemical etching by sequentially passing through alkaline fountain-type baths, an acid bath and a bath for washing the thread, and the coating is applied by repeatedly passing the thread through the electrolyte, before winding the finished product, the thread is washed and the coating is fixed, while all operations are combined in a single process on one installation. 2. A method according to claim 1, characterized in that tungsten or molybdenum or alloys based on them are used as the refractory metal, and gold or copper is used as the coating material. 3. The method according to claim 1, characterized in that additionally after cleaning by the method of electrochemical etching, cleaning is carried out by the method of ultrasonic treatment. 4. Installation for applying a coating on a refractory metal thread for implementing the method according to claim 1, including a winding unit, a galvanic bath with electrolyte, a coating fixing unit, a winding unit, characterized in that it additionally contains an electrochemical etching bath after the winding unit, as well as a bath for washing in front of the coating fixing unit, while the electrochemical etching bath contains sequentially installed alkaline baths of the fountain type, an acid bath and a bath for washing the thread, slots for the thread are made in the walls of the baths, and electrodes are installed in the baths connected to the first adjustable current source, and The galvanic bath contains two drums, located one above the other, which provide the possibility of multiple immersion of the metal thread in the electrolyte, while the lower drum is immersed in the electrolyte, and the upper drum is connected to the negative output of the second current source, which is connected with the positive output to a a node in an electroplating bath. 5. Installation according to claim 4, characterized in that the winding unit contains an electric motor with a coil, a tension regulator for a metal thread, and a speed and length sensor. 6. Installation according to claim 4, characterized in that the winding unit contains a receiving commodity bobbin and a winding head for winding and laying out the finished yarn on the receiving commodity bobbin. 7. Installation according to claim 4, characterized in that it contains an ultrasonic bath for additional cleaning of the wire, located between the electrochemical etching bath and the galvanic bath.

Images