Method of application of metal coat on current-transmitting surfaces of detachable contact connectors

FIELD: method of application of metal coats on detachable contact connectors.

SUBSTANCE: proposed method is used for stabilization of contact resistance of connectors at level of initial assembly during entire period of operation in parts made from copper, aluminum and their alloys during assembly, operation and repair of electrical plants and plants manufacturing electrical equipment. Proposed method includes cleaning and degreasing the contact surfaces, applying liquid flux on these surfaces, preheating the surfaces and applying the metal coat; preheating is continued to temperature of 40-45C; metal coat is applied by means of local contact fusion and gallium alloy having melting point not above 30C is applied as metal coat at thickness not exceeding 0.1 mm.

EFFECT: reduction of contact resistance.

6 cl, 1 dwg

 

The invention relates to the field of electrical engineering and can be used in the installation, repair and maintenance of electrical equipment, power lines, electric power stations, substations, contact networks electrified transport, switchgear industrial enterprises and factories producing electrical equipment.

Operation of electrical networks and electrical equipment depends largely on the quality and reliability of many demountable contact devices connecting separate sections of an electrical circuit. Transient electrical resistance in these devices is a cause of significant electricity losses, invalid overheating or even burning of the contact parts, and its tendency to increase during operation causes instability of the parameters of the electric circuit and having frequent disconnections, bulkheads, inspection and repair contact connections, i.e. to increase the complexity and cost of operating expenses.

The greatest influence on the magnitude of transient electrical resistance has a high specific resistance of the oxide and sulfide films on temperedly surfaces of the contact parts of the folding contact devices. Therefore, in practice, all methods that reduce the TB and stabilize this resistance, aimed at the destruction of the integrity of these films and applied to the contact surface protective coatings, oxide film which has a higher electrical conductivity.

Widely used at the present time, rovaniementie and silvering temperedly surface of the contact devices, and the use of conductive grease. However, the ways of applying tin and silver plating (electroplating, plating, electrical discharge and plasma spraying) associated with either the use of special equipment, or with significant heating of the contact details that in many cases, especially in operating conditions on existing electrical equipment, eliminates the possibility of their use. As for the conductive greases, despite the simplicity and accessibility of their application, they can only improve the transient stability of electric resistance, without reducing its value. In addition, the lubricant having the composition of the liquid fraction, which can dry out or vymorazhivanija are covering short-lived. It should also be noted that the use of conductive grease does not address this pressing issue, as a direct connection between the aluminum contact details with copper, which is invalid due to electrochemical corrosion that occurs is between them when the current flows in the contact device.

Therefore, at present on power lines, contact network of electrified transport, substations and switchgear operated tens of thousands collapsible pin connections without any protective coatings on temperedly surfaces. In this situation, the development of new ways of applying a protective metal coating on temperedly surface contact devices available for use in any operating conditions and production of electrical equipment, is a very important task, one of the most effective ways to reduce energy losses, as well as the complexity and operating costs.

Applying a thin layer of metal coatings on various metal surface is called tinning. Tinning can be hot or electroplating. How galvanic deposition of metal coatings are not considered here because they represent a process, which by its physical nature and used equipment differs sharply from that of the proposed method.

A method of obtaining coatings to improve the reliability of electrical contact, based on ion-plasma spraying on a substrate double copper alloy with chromium by repeated changes in the process of applying a voltage to the substrate from the reference (90-120)to (100-2000)and back [USSR Author's certificate No. 1628564].

However, this method can only be used in a stationary plant production of electrical equipment.

A method of obtaining coverage for the reduction and stabilization of the transition resistance and, consequently, energy losses in the contact connections by applying the intermediate liquid metal environment [Izmailov CENTURIES, maturew A.A. Tribological aspects of the use of liquid metals in electrical contact // Materials of International conference "Electrical contacts". - S.-Pb., 1996. - P.52-53].

Among liquid metals - candidates for the role of positive opening operation of a conducting medium is the most promising gallium and its alloys. The most promising direction in electrical contact materials science is the development of composite materials based on solid skeleton is impregnated with liquid metal. As the material of the frame used metals, practically do not interact with gallium: tungsten or molybdenum.

The application of this method in electric vehicles reduces the loss of electricity in contact, saves precious and scarce non-ferrous metals that are used as coatings in conventional electrical contacts.

Fusible alloys of gallium used in composite liquid metal contacts, non-toxic (ha is Lee even used in dentistry) and are not scarce.

However, the use of this method is, in essence, making a pad of porous material impregnated with liquid metal, the components of which have a high specific resistance. The introduction of this liner complicates the configuration of the collapsible pin connections and, therefore, entails a change in the basic design of these compounds requires the production of matrix and, in addition, such vkladyshi are short-lived due to oxidation in air of liquid gallium.

Closest to the claimed purpose and essential features is the method of applying a metallic coating on temperedly surface demountable contact connections by tinning the contact surfaces tin-lead solder with a soldering iron [Maximian B.A. processes soldering of electrical connections. Leningrad, "Energy", 1980. page 42-46].

The method is as follows. Clean the contact surface from dirt and clean it with acetone, then apply it with a brush liquid flux to remove the oxide film. When tinning steel, copper and its alloys using alcohol-rosin fluxes type EC, CS, LTI-120, LTI-115. The contact surface is heated by a soldering iron or a gas burner to a temperature of 280-320°C. heated to 280-320°and covered fluco the surface carry a soldering iron, a small amount of metal coating, and then, moving the soldering iron in different directions, level of the applied layer evenly over the entire surface. As a metallic coating for steel, copper and its alloys put tin-lead solder type POS-61, POS 40 POS 18, POSS-6.

Specific contact processes of interaction of solid metal with a liquid at a temperature below the temperature of the Autonomous melting of solid metal are contact solid-liquid melting [Lasko NF, Lasko SV Contact metallurgical processes for soldering. M, metallurgy, 1977, p.52-77]. Applying a layer of liquid metal on the surface of the solid at the local contact melting after solidification metallurgy is called brazing. The implementation of this method of applying the metal coating is the formation of temperedly surfaces of the contact parts soldering tin-lead solder with a thickness of 0.5 mm.

The necessity of heating the contact details to the temperature 280-320°does not allow me to use this method in real conditions of service applicable or are in the process of installation and repair of electrical equipment due to the high thermal conductivity of copper and its alloys and proximity to the contact surfaces of the sections of conductors covered with insulation, for which this temperature is Nedap stimey.

In addition, the application using this method of metal coating on an aluminum surface requires heating of these surfaces to a temperature of 400°C and above, and the application of solder is performed by rubbing the last in the contact surface that is technologically complicated and difficult.

This method is used mainly in a stationary plant production and practically cannot be used in the conditions of operation of the existing electrical equipment

The basis of the invention is to provide a method of applying metal coating on temperedly surface of the collapsible pin connections that reduce transient electrical resistivity of these compounds, stabilizing its value at the level of the initial Assembly during the whole period of its operation and the possibility of direct connection of the contact parts made of copper, aluminium and their alloys in the implementation of this method both in terms of installation, repair and maintenance on existing power plants and for use in stationary conditions at the enterprises producing electrical equipment

The problem is solved in that in the method of applying a metallic coating on temperedly surface and collapsible pin connections, including cleaning and degreasing of the contact surface, causing the surface of the liquid flux, preheating it and the metal coating according to the invention are heated to a temperature of 40-45°C, the metal coating is carried out using local surface melting, and as the metal coating is applied a layer of gallium alloy having a melting temperature not above 30°With thickness not more. 0.1 mm

When you do this:

- contact surface of the steel, copper and its alloys as a liquid flux take a saturated aqueous solution of ZnCl2;

- contact surfaces of aluminum and its alloys as a liquid flux take 10% aqueous solution of NaOH;

- contact details of steel cause the eutectic alloy composition, wt.%:

Gallium - 82

Tin - 12

Zinc - 6

- contact parts made of copper and its alloys put eutectic alloy in the composition, wt.%:

Gallium is 98.2

Zinc - 1,79

Copper - 0,01

- contact parts made of aluminium and its alloys cause the alloy composition, wt.%:

Gallium - 92

Aluminum - 8

- for contact details, one of which is made of copper and the other of aluminum, is applied to the alloy composition, wt.%:

Gallium - 95

Zinc - 4

Cadmium - 1

after heating the contact surface before the application of a gallium alloy carried the t mechanical Stripping from the oxide film.

When applied to temperedly surface of the collapsible pin connections, a layer of low-melting gallium alloy having a melting temperature not above 30°at last after curing, the formed film solid solution with a thickness of 5-10 microns of material contact parts (substrate) and a deposited gallium alloy, which is formed as a result of local contact of solid-melting, during which there is the mutual diffusion of the transition of the atoms of the solid metal in the liquid, and Vice versa (diffusion-hardening a metallic coating), and not surfacing applied liquid metal, as in the known solution, taken as a prototype.

Obtained in this way, the metallic coating is a new substance with different physical and chemical properties as the material of the contact details, and put on her temperedly the surface of the low-melting gallium alloy, ensuring the reduction of transient electrical resistivity of these compounds, stabilizing its value at the level of the initial Assembly during the whole period of its operation and the possibility of direct connection of the contact parts made of copper, aluminium and their alloys.

Use as a coating material gallium alloy has also made it possible to reduce the temperature p of the heating-up to 40-45° With that provided an opportunity for the implementation of this method both in terms of installation, repair and maintenance on existing electric power facilities and use in stationary conditions at the enterprises producing electrical equipment.

As a result of applying a metal coating on temperedly surface of the collapsible pin connections of the inventive method transient electrical resistance in these compounds decreases:

- contact parts made of aluminum 10-20 times,

- contact parts made of copper and aluminum 3-7 times

- when performing the contact details of copper, 1.4-2 times,

as well as stabilization of a transient electrical resistance in the folding contact connections of all types at the level of initial Assembly during the entire lifetime of the connection and the possibility of direct connection of the contact parts made of copper, aluminium and their alloys.

All these characteristics are very well proven both in the laboratory and in the real environment on the individual power generation facilities.

The drawing shows the dependence of the transient electrical resistance in the folding contact connections from the working time for the contact details of the RA is personal materials under different types of coatings temperedly surfaces.

The method is as follows.

Clean from dirt and degrease the contact surface of the collapsible pin connections acetone or alcohol. To remove the oxide film applied by brush on temperedly surface contact parts made of steel, copper and its alloys saturated aqueous solution of chloride of zinc, for the contact details of aluminium and its alloys - a 10% solution of sodium hydroxide.

Next, heat up the dryer the contact surface to a temperature of 40-45°using flat or round wire brushes mounted on the drill, produce mechanical cleaning of the contact surface and a dry cloth to remove sawdust. Then with a swab of foam evenly applied on temperedly surface a thin layer of gallium alloy special composition having a melting temperature not above 30°With, of a thickness not exceeding 0.1 mm:

- contact parts made of copper and its alloys cause the alloy composition, wt.%:

Gallium is 98.2

Zinc - 1,79

Copper - 0,01

- contact parts made of aluminium and its alloys cause the alloy composition, wt.%:

Gallium - 92

Aluminum - 8

- contact details of steel cause the alloy composition, wt.%:

Gallium - 82

Tin - 12

Zinc - 6

- for contact details, one of which is made of copper and the other of aluminum, is applied to the alloy composition, wt.%:

Galli is - 95

Zinc - 4

Cadmium - 1

After performing the above operations, the contact part is ready for Assembly contact connection and its temperedly surface protective film is formed with a thickness of 5-10 microns, which is a solid solution of the metal contact details (substrate) and deposited gallium alloy.

The proposed method, a metallic coating may be deposited on temperedly surface contact parts made from any used for these purposes, metal: copper, aluminum, lead, steel and alloys based on them.

The method is carried out at a temperature of the heating surface not exceeding 40-45°and it does not require any special equipment.

Contact with the coating of the inventive method, can be used in harsh environments, indoors and outdoors at a temperature of from -50°C to +500°C.

Applied as a metal coating, the proposed method, the material is chemically inactive, does not contain toxic and precious metals, and the technology of its application is not dangerous for human health.

The application of the method allows to eliminate the phenomenon of electrochemical corrosion, directly connect copper and aluminum contacts without any copper cladding and inserts, which greatly panel is protected design of the contact device, reduces the complexity and cost of manufacture.

The flow of the coating material in the implementation of the proposed method is 100 g per 1 square meter of the surface.

The basis of the metallic coating - gallium - produced by the domestic industry. Wholesale price until recently is$ 220 per 1 kg

Contact device with the coating of the inventive method, successfully tested in a laboratory plant SAMS", a member of the Association of test centers high-voltage electrical equipment "Energiser" (test report No. 17/T4-02 from 27.06.02).

On gallium alloys are used as the metal coating in the proposed method, the obtained "Sanitary-epidemiological conclusion No. 66.01.10.176. T. from 13.07.2005" and "Technical conditions TU-001-71672579-2005"that allow the use of this material in almost all industrial sectors of energy, transport, utilities and equipment.

Thus, the use of the proposed method will improve the reliability of electrical networks and electrical equipment, greatly reduce energy losses, as well as the complexity and operating costs.

1. The method of applying a metallic coating on tocope edusa surface of the collapsible pin connections, including cleaning and degreasing of the contact surface, causing the surface of the liquid flux, it is heated and the metal coating, wherein the heating is carried out to 40-45°C, the metal coating is carried out using local surface melting, and as the metal coating is applied a layer of gallium alloy having a melting temperature not above 30°With thickness not more than 0.1 mm

2. The method according to claim 1, characterized in that the contact surface of steel put eutectic alloy composition, wt.%:

Gallium82
Tin12
Zinc6

3. The method according to claim 1, characterized in that the contact surfaces of copper and its alloys put eutectic alloy composition, wt.%:

Galliumof 98.2
Zinc1,79
Copper0,01

4. The method according to claim 1, characterized in that the contact surfaces of aluminum and its alloys cause the alloy composition, wt.%:

5. The method according to claim 1, characterized in that the contact surfaces, one of which is made of copper and the other of aluminum, is applied to the alloy composition, wt.%:

Gallium92
Aluminum8
Gallium95
Zinc4
Cadmium1

6. The method according to claim 1, characterized in that after heating the contact surface before the application of a gallium alloy is carried out by mechanical Stripping from the oxide film.



 

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