WO2010077183A1 - Separable electrical contact connection and method for processing same - Google Patents

Abstract

The invention relates to the field of electronic engineering and can be used in electrical equipment. The separable electrical contact connection comprises contact elements, the current-conducting surfaces of which are coated with a gallium-based alloy having the following composition in weight percent: 64-99.9999 gallium, 0.001-35 indium, 0.001-28 tin, 0.001-7.5 silver, 0.001-5 cadmium, 0.001-25 zinc, 0.0001-10 copper and 0.0001-12 aluminium. A method for processing contact surfaces involves etching said contact surfaces to remove an oxide film using a first etchant, subsequently neutralizing said etchant and cleaning the surfaces to remove the etching products, mechanically cleaning the surfaces by polishing, heating the contact surfaces within a range of 10-70ºC and applying the gallium alloy in the medium of a second solution, the remainder of which is neutralized once processing is complete. The invention makes it possible to improve the quality of preparation of a contact surface in order to produce a reliable separable electrical contact connection while increasing the load-carrying capacity thereof and providing for stable electrical transition resistance characteristics during use.

Description

 Dismountable ELECTRIC CONTACT CONNECTION AND METHOD OF ITS PROCESSING

Technical field

The invention relates to the field of electrical engineering and can be used in the manufacture of electrical equipment used in all existing industrial facilities, one of the main elements of which are collapsible electrical contact connections (REKS), including contact details.

This group of inventions can be used in the processing of current-carrying contact surfaces of contact parts used in the manufacture of a collapsible electrical contact connection (REKS) containing two or more of these contact parts.

Existing developments in this area are aimed at increasing the reliability of collapsible electrical contact connections, which in turn increases the reliability of the entire electrical installation as a whole. This improves the quality of consumption and transmission of electricity. These tasks are solved by reducing and stabilizing the transient electrical resistance, as well as by increasing the effective contact area of the existing REKS.

In practice, various methods are used to reduce the transient electrical resistance of collapsible electrical contact joints, one of which is the use of special coatings on the current-transmitting surfaces of contact parts.

According to GOST 1431-79, when two contact parts are connected, a conditional contact area is formed, which is determined by the part of the working surface on which contact occurs contact parts and the effective contact area over which electric current passes from one contact part to another. Moreover, the effective contact area is only part of the conditional contact area. The discrepancy between the effective contact area and the conditional contact area in the REKS is the result of incomplete contact of the contact surfaces of the contact parts.

BACKGROUND OF THE INVENTION Collapsible electrical contact joints are known in which the conductive surfaces of the contact parts are coated with an alloy based on tin or silver or nickel, etc., but the deposition technology is expensive and is applicable only in a stationary production environment.

Known collapsible electrical contact joints [RU JCH22301847, op.27.06.2007], the contact surfaces of which are made of an alloy based on gallium with a coating thickness of not more than 0.1 mm

Application of the alloy to the contact surface with a coating thickness of not more than 0.1 mm does not allow to form a layer capable of improving and increasing the effective contact area, since practically the coating layer with a thickness of less than 0.1 mm completely diffuses into the contact surface to a depth of 15 μm and does not allow forming on the contact surface saturated layer of alloy, which does not allow to obtain an increase in the effective contact area during the assembly of the contact compound. Rigid machining of the contact surfaces with the formation of chips violates the contact surface. Deep scratches and irregularities appear on it, which reduces the accuracy of the connection of the contact surfaces, and, consequently, the effective contact area. The effective contact area operates in high load mode during current transmission, as it is less than the conventional contact area. The increase in transient electrical resistance as a result of oxidation processes on the contact surface and the increased load during current transmission lead to instability of the modes of electrical consumers, exceeding the temperature conditions of the electrical installation as a whole and loss of electricity.

In addition, the alloy with the specified composition of the components limits the ability to control the properties of the alloy, such as mechanical hardness, corrosion resistance, electrical conductivity.

The closest analogue adopted for the prototype in relation to the device is a collapsible contact connecting device, in which the reduction of the transient electrical resistance is achieved by coating the current-carrying surfaces of the contact parts, namely a coating based on a gallium alloy with a thickness of at least 15 μm, which prevents the formation of surfaces of contact parts of oxide and sulfide films having high electrical resistivity (RU patent for utility model JVb 8530, op. 16.11.1998). This technical solution is aimed at reducing and stabilizing the transient electrical resistance, but does not solve the problem of increasing the effective contact area.

In addition, the low percentage of gallium in the alloy gives an increase in the electrical resistivity of the layer formed by this alloy, which increases the transient electrical resistance of the joint as a whole and reduces the reliability of the contact joint and worsens its operational parameters.

Known methods for increasing the effective contact area include the following measures: More accurate surface treatment;

- An increase in the tightening force of bolted joints;

- An increase in the number of bolted joints;

- The use of gaskets made of soft easily deformable conductive materials.

The main method of assembling REKS is a bolted connection. (“The choice of stabilization of contact pressing in collapsible connections of low-voltage complete devices to Lesnykh V.V., Tsapenko A.V. journal“ Safety of labor in industry)) .N ° 7 2007.). For a bolted connection, the effective contact area is the contact surface in the area of the bolt head (area of the thrust washer). The remaining contact surface as a result of the relative surface roughness, low rigidity of the connecting structure has an incomplete fit of the contact surfaces and, as a result, has an increased transient electrical resistance already at the time of assembly, which increases during the period of operation as a result of access of the oxidizing medium.

The effective contact area operates in high load mode during current transmission, as it is less than the conventional contact area. The increase in transient electrical resistance as a result of oxidation processes on the contact surface of the compound and the increased load during current transmission lead to instability of the modes of electrical consumers, exceeding the temperature conditions of the electrical installation as a whole and loss of electricity.

During the operation of such electrical installations, the overhaul periods are reduced, the costs of maintenance and repairs of electrical installations are increased, the downtime is increased, and the technological regimes of production of industrial enterprises are violated. From the description of the RU patents for utility model N ° 8530, 8529, op.

11/16/1998 A method of treating contact surfaces of a collapsible electrical contact connector is known, in which a reduction in transient electric resistance is achieved by applying a special coating to the current-carrying surfaces of contact parts, namely, applying a gallium alloy with a coating thickness of at least 15 microns, which prevents the formation of contact parts oxide and sulfide films having a high electrical resistivity. This technical solution is aimed at reducing and stabilizing the transient electrical resistance, but does not solve the problem of increasing the effective contact area.

The closest analogue adopted for the prototype in relation to the method is a method of treating contact surfaces of a collapsible electrical contact connection, including cleaning the contact surfaces from an oxide film using flux, heating the contact surface, mechanically cleaning and applying a metal coating on it, while heating is carried out to temperature 40-45 ° C, the deposition of a metal coating is carried out using local contact melting, and a layer of g is applied as a metal coating llievogo alloy having a melting temperature not above 30 ^° C, not more than 0.1 mm thick (patent RU N ° 2,301,847, op. 27.06.2007).

The disadvantages of the method include the following: 1. When preparing the surface for processing and during processing, the flux solution is applied once, and then heating and mechanical cleaning take place. During heating and mechanical cleaning at the time of application of the alloy, the amount of flux on the contact surface is minimal, since the flux is removed during mechanical cleaning and partially evaporates when the surface is heated. To treat the contact surface, especially if we take into account the duration of the entire time period of the deposition of the alloy, to obtain maximum wettability of the contact surface, a constant presence on the surface of the flux during the entire time of deposition of the alloy is necessary. The flux removes the oxide film from the contact surface and prevents it from forming over the entire period of treatment of the contact surface. In the prototype, this condition is not satisfied.

2. After processing, the contact surface is not neutralized from the remainder of the flux and even with a very small amount on the contact surface, the etching process continues, which destroys the contact surface.

3. During mechanical cleaning of the surface with a metal brush installed on the drill as a result of processing, chips are formed, the appearance of which indicates a violation of the contact surface (the appearance of deep scratches and irregularities), which reduces the accuracy of the contact surfaces and, therefore, the effective contact area .

4. The application of the alloy on the contact surface with a thickness of not more than 0.1 mm does not allow to form a layer capable of improving and increasing the effective contact area, since in practice the layer of the specified thickness completely diffuses into the contact surface and does not allow to increase the effective contact area.

5. Alloy with the specified composition of the components limits the possibility of: regulating the melting temperature of the alloy, and, therefore, limits the possibility of regulating the temperature of the technological process of processing the contact surface; - regulation of the properties of the alloy, such as mechanical hardness, corrosion resistance, electrical conductivity.

Disclosure of invention

The problem to which this invention is directed, is to create a reliable, efficient in operation collapsible electrical connection, improve the quality of preparation of the contact surface and increase the load capacity of a collapsible electrical contact connection by increasing its effective contact surface, while ensuring the stability of the characteristics of the transient electrical resistance in the process operation.

The problem is solved in that in a collapsible electrical contact connection, including contact - parts whose current-carrying contact surfaces contain a metal coating made of gallium-based alloy, according to a utility model, the metal coating is made of an alloy of the following composition: gallium - 64 ÷ 99, 9999, indium - 0.001 + 35, tin - 0.001 ÷ 28, silver - 0.001 ÷ 7.5, cadmium - 0.001 ÷ 5, zinc - 0.001 + 5, copper -0.0001 ÷ S, aluminum - 0.000 l ÷ l 2 this metal coating is made with a thickness of 0.1-0.5 mm.

Contact details can be made of copper and its alloys, steel and its alloys, cobalt, silver, tin, lead, aluminum, grades AO ÷ ADZ IT and its alloys.

The task in terms of the method is solved by the fact that in the method of processing current-carrying contact surfaces of contact parts of a collapsible electrical contact connection, including processing current-carrying contact surfaces of contact parts in order to remove an oxide film by applying a liquid flux to these surfaces, heating the current-carrying contact surfaces of contact details their mechanical cleaning, applying a metal coating, which is used as a gallium-based alloy, according to the invention, initially carry out chemical treatment - etching of the contact surfaces with a first flux solution, followed by its neutralization and cleaning of the contact surfaces from the results of chemical treatment - etching, then carry out mechanical cleaning of the indicated contact surfaces by grinding, after which they are heated and metal coated gallium-based alloy in the environment of the second flux solution, after the deposition of the metal coating, the flux residues are neutralized to stop the etching process.

The composition of the metal coating alloy is as follows, May,%: gallium -64 ÷ 99.9999, indium - 0.001 ÷ 35, tin - 0.001 ÷ 28, silver - 0.001 ÷ 7.5, cadmium - 0.001 ÷ 5, zinc - 0.001 ÷ 25, copper - 0.0001 ÷ 10, aluminum - 0.0001 ÷ 12

The metal coating is applied with a layer thickness of 0.1-0.5 mm.

The contact surface is heated between 10-70 ° C.

The first flux solution is prepared on the basis of hydrochloric acid with a concentration of 5-35% or on the basis of alkali with a concentration of 5-18%. As the second flux, a solution similar to the first flux solution with a concentration of 1.5-2.5 times lower than the concentration of the first flux solution is used.

The melting temperature of the metal coating of the gallium alloy is 9.0-30.8 ° C. The drawing shows a collapsible contact electrical connection containing contact parts 1, 2, the current-transmitting surfaces of which contain a coating containing a saturated layer of alloy 3 and layers 4, 5, diffused , respectively, in the contact parts 1 and 2. The coating is made of an alloy based on gallium of the following composition: gallium - 64 ÷ 99.9999, indium - 0.001 ÷ 35, tin - 0.001 ÷ 28, silver - 0.001 ÷ 7.5, cadmium - 0.001 ÷ 5, zinc - 0.001 ÷ 25, copper -0.0001 ÷ S, aluminum - 0,000 l ÷ l 2.

The coating is made with a thickness of 0.1-0.5 mm. Due to the deposition of a layer with a thickness of more than 0.1 mm in the claimed technical solution, a layer diffused into the contact surface up to 20 μm and a saturated alloy layer on the contact surface itself are obtained, with which the effective contact area is increased during assembly of the contact joint. Contact - parts can be made of copper and its alloys, steel and its alloys, cobalt, silver, tin, lead, aluminum, preferably AO ÷ ADZ IT grades and its alloys and can be interconnected by a fastening element 6, for example, bolted connection.

The following types of contact surfaces can be used as contact pairs: copper-copper, copper-aluminum, aluminum-aluminum.

The coating represents a new intermetallic layer formed by gallium alloy and contact surface material. The use of a coating thickness of the contact surface of less than 0.1 mm reduces the quality of the coating and, accordingly, the reliability of the connection, by increasing the transient electrical resistivity.

The use of a contact surface coating thickness of more than 0.5 mm is technically and economically impractical, since this leads to a rise in the cost of the structure and does not improve technical characteristics.

In some cases, to improve the quality and reliability of REKS, it is enough to process the current-transmitting contact surface of at least one of the contact parts.

The processing method is as follows. Initially, chemical treatment is carried out - etching of the contact surfaces with the first flux solution to clean the contact surfaces from oxide films. Depending on the contacted surfaces, the first flux solution can be prepared on the basis of hydrochloric acid with a concentration of 5-35% with possible adjustment by zinc, iron in an aqueous medium, for example, a saturated solution of zinc chloride for contact surfaces based on copper and its alloys, steel and its alloys, cobalt, silver, tin, lead. Contact surfaces based on aluminum and its alloys are treated with the first alkali-based flux solution - NaOH in an aqueous solution with a concentration of 5-18%.

Then, the first flux solution is neutralized by wiping with a cotton swab moistened with a neutralization solution and the contact surfaces are cleaned of the results of etching with a dry cotton swab. The neutralization of the first flux residues is carried out depending on the type of flux: acid flux is neutralized, for example, with a solution of 5% bicarbonate of soda, alkaline flux is neutralized, for example, with a solution of 8% acetic acid.

Then carry out mechanical cleaning of the contact surfaces by grinding. Then, with a dry swab, wipe the contact surface from the results of grinding - metal dust. Then, the contact surface is heated at temperatures of 10-70 ° C, while the contact surfaces made of copper and its alloys, steel and its alloys, cobalt, silver, tin, and lead are heated at –10–7 ° C, and the contact is heated surfaces made of aluminum and its alloys - within 10-52 ° C.

After that, a solution of the second flux is applied with the simultaneous application of a metal coating with a gallium alloy with a thickness of 0.1-0.5 mm without leaving the temperature range of 10-70 ^° C. Application of the second flux immediately after heating the contact surface allows you to protect the contact surface from oxidative processes and increase the wettability of the applied alloy.

As the second flux, a solution similar to the first flux solution with a concentration of 1.5-2.5 times lower than the concentration of the first flux solution is used.

The deposition of the alloy is carried out by local contact melting of the contact surface, a gallium alloy having a melting point of 9.0 ÷ 30.8 ° C is used as the alloy. The composition of the applied metal coating - gallium-based alloy is as follows: Gallium - 64 ÷ 99.9999, Indium - 0.001 ÷ 35, Tin - 0.001 ÷ 28, Silver - 0.001 ÷ 7.5, Cadmium - 0.001 ÷ 5, Zinc - 0.001 ÷ 25 , Copper - 0.0001 ÷ S, Aluminum - 0.000 l ÷ l 2.

Then the electrical contact joint is assembled, for example, by means of a bolted joint, excess gallium alloy squeezed out of the contact surface after tightening the bolted joint is removed.

After the assembly of the compound, the flux residues are neutralized with a neutralization solution and, if necessary, washed with water. The mechanical and chemical treatment of the contact surface ensures good wettability of the contact surfaces; an equilibrium state of the surface tension forces of the gallium alloy liquid layer on the solid surface of the contact material is created. Moreover, the contact material within the treated surface is a new intermetallic layer formed by a gallium alloy and the material of the contact surface. The wetting angle of the liquid gallium alloy is 65-91.0 ° with a bond strength of 27-29 MPa with a contact surface with a thickness of the liquid gallium alloy of 0.1-0.5 mm. The given thickness of the liquid layer of gallium alloy provides alignment of the contact surface and increases the effective contact area of REKS, and taking into account the properties of gallium alloys, minimizes and stabilizes the electrical transient resistance in the contact connection. A wide range of liquid state of gallium alloy (about 9-

250 ^° C) allows you to create stability of the contact area under external mechanical and thermal influences on the design of REKS during operation.

When machining, a soft stainless steel brush is used to grind metal surfaces. When processing, large scratches and chips should not be allowed.

Performing machining before heating the contact surfaces, and not after heating, as in the prototype, reduces the period of contact surface in the open air, i.e. slow down oxidative processes.

This method is applicable for connecting the following types of contact surfaces: copper-copper, copper-aluminum, aluminum-aluminum.

Example 1. A method of processing the contact surfaces of a collapsible electrical connection copper - copper.

A cotton swab dipped in the first flux solution (20% hydrochloric acid solution adjusted by zinc to a saturation state) is wiped on the contact surface to remove contamination and oxide film. After thorough cleaning of the surface, it is wiped with a swab moistened in a solution for neutralization (5% solution of bicarbonate of soda) and wiped dry. With a stainless steel soft brush to grind the metal surface, the contact surface is cleaned with a grinder, after cleaning, the metal dust residues are removed - the result of grinding. Hair dryer or the infrared heat source heats the contact surface to a temperature of 35 ^° C. Temperature control is carried out by any device with a measurement accuracy of ± 0.5 ° C. A tampon moistened with a flux solution of -8% hydrochloric acid solution, adjusted to a saturation state with zinc, moisten the contact surface and immediately apply a 0.4 mm thick gallium alloy layer. The alloy layer on the contact surface should have a saturated (moistened) appearance of a brilliant (mirror) color. The contact surfaces are connected, the bolts are tightened with force according to the technical conditions. The remaining gallium alloy extruded from the contact surface is removed with a swab. The collected contact compound is treated with a swab dipped in a solution to neutralize the flux of a 5% solution of bicarbonate of soda, if necessary, washed with water and wiped dry.

The alloy composition for the indicated temperature conditions: gallium - 67%, indium - 22%, tin - 5%, silver - 1.5%, cadmium - 0.5%, zinc - 4%, copper - 0, 0001%, aluminum - 0, 0001% The melting point of the alloy is 12.5 ° C.

Example 2. A method of processing contact surfaces of a collapsible electrical connection aluminum - aluminum. Cotton swab dipped in the first flux solution -

15% alkali solution, wipe the contact surface to remove contamination and oxide film. After thorough cleaning of the surface, it is wiped with a swab dipped in a solution for neutralization - an 8% solution of acetic acid, and wiped dry. With a stainless steel soft brush to grind the metal surface, the contact surface is cleaned with a grinder, after cleaning, the metal dust residues are removed - the result of grinding. Use a hairdryer or infrared heat source to heat the contact surface to a temperature of 25 ° C. Temperature control is carried out any instrument with a measurement accuracy of ± 0.5 ° C. A swab dipped in a flux solution - 6% alkali solution, moisten the contact surface and immediately apply a layer of gallium alloy with a thickness of 0.3 mm. The alloy layer on the contact surface should have a saturated (moistened) appearance of a brilliant (mirror) color. The contact surfaces are connected, the bolts are tightened with force according to the technical conditions. The remaining gallium alloy extruded from the contact surface is removed with a swab. The collected contact compound is treated with a swab dipped in a solution to neutralize the flux -6% solution of acetic acid, and wiped dry.

The alloy composition for the indicated temperature regimes: gallium - 80%, indium - 10%, tin - 5%, silver - 0.5%, cadmium - 1.5%, zinc - 3%, copper - 0, 0001%, aluminum - 0, 0001% The melting point of the alloy is 17.5 "C. Up to 0.05% of intermetallic compounds may be present in the alloy due to impurities contained in the components.

In a collapsible electrical contact connection can be processed by the claimed method, the conductive contact surface of at least one of the contact parts. The analysis of theoretical and experimental data on the use of one to eight component gallium alloys in the processing of REKS contact surfaces allowed us to create a universal method for processing REKS contact surfaces, taking into account the features of the treated contact surfaces and determining the method of pretreatment, the choice of alloy and the procedure for applying it.

The processing method includes a list of preparatory operations for mechanical and chemical treatments, temperature conditions, the composition of the gallium alloy. Depending on the technical requirements for collapsible electrical contact joints during the manufacture, operation and repair of electrical equipment, this method can be used to solve such problems as reducing and stabilizing the transient electrical resistance of a contact joint, as well as increasing the effective contact area. This method allows to increase by 5-15% the load capacity of REKS when transmitting electrical energy without changing the design of the contact connection, while the temperature regime does not exceed the permissible limits. This is confirmed by the results of experimental and experimental studies.

The technical result of the group of inventions is to create a reliable operation of a collapsible electrical contact connection, by ensuring the stability of the transitional electrical resistance for a period commensurate with the life of the electrical equipment as a whole.

The inventive combination of features can minimize the loss of electrical energy in contact electrical connections, as well as improve the quality and efficiency of its transmission. Industrial applicability

The claimed group of inventions can be used in the field of electrical engineering in the manufacture of electrical equipment used in all existing industrial facilities, one of the main elements of which are collapsible electrical contact joints (REKS), including contact parts, namely when processing current-carrying contact surfaces of these contact parts used in the manufacture of a collapsible electrical contact connection (REKS) containing two or more of these contacts t-parts. In some cases, To improve the quality and reliability of REKS, it is enough to process the current-transmitting contact surface of at least one of the contact parts in the claimed manner.

Claims

Claim 1. A collapsible electrical contact connection, including contact parts, the conductive contact surfaces of which contain a metal coating made of gallium-based alloy, characterized in that the metal coating is made of an alloy of the following composition: Gallium - 64 ÷ 99.9999, indium - 0.001 ÷ 35, tin - 0.001 ÷ 28, silver - 0.001 ÷ 7.5, cadmium - 0.001 ÷ 5, zinc - 0.001 ÷ 25, copper -0.0001 ÷ S, aluminum - 0.0001 ÷ 12 2. The collapsible electrical contact connection according to claim 1, characterized in that the metal coating is made with a thickness of 0.1-0.5 mm. 3. A collapsible electrical contact connection according to claim 1, characterized in that the contact parts can be made of copper and its alloys, steel and its alloys, cobalt, silver, tin, lead, aluminum of AO ÷ ADZIT brands and its alloys. 4. A method of processing current-carrying contact surfaces of contact parts of a collapsible electrical contact connection, including processing current-carrying contact surfaces of contact parts in order to remove an oxide film by applying a liquid flux to these surfaces, heating the current-carrying contact surfaces of contact parts, their mechanical cleaning, applying a metal coating , which is used as a gallium alloy, characterized in that initially carry out chemical treatment - etching specified x the contact surfaces of the first flux solution, followed by neutralization and purification of said contact surfaces by chemical treatment results - etching is then carried out mechanical cleaning of the contact surfaces of said grinding, which is performed after their heating and applying a metal coating of a gallium-based alloy in the environment of the second flux solution, after the completion of the metal coating application, the flux residues are neutralized to stop the etching process. 5. The method according to claim 1, characterized in that the composition of the metal coating alloy is as follows, May,%: Gallium - 64 ÷ 99.9999 Indium - 0.001 ÷ 35 Tin - 0.001 ÷ 28 Silver - 0.001 ÷ 7, 5 Cadmium - 0.001 ÷ 5 Zinc - 0.001 ÷ 25 Copper -0.0001 ÷ Yu Aluminum - 0,000 l ÷ l 2 6. The method according to claim 1, characterized in that the metal coating is applied with a layer thickness of 0.1-0.5 mm. 7. The method according to p. 1, characterized in that the heating of the contact surface is carried out in the range of 10-70 ° C. 8. The method according to claim 1, wherein the first flux solution is prepared on the basis of hydrochloric acid with a concentration of 5-35% 9. The method according to claim 1, characterized in that the solution of the first flux solution is prepared on the basis of alkali with a concentration of 5-18%. 10. The method according to claim 1, characterized in that the second flux is a solution similar to the first flux solution with a concentration of 1.5-2.5 times lower than the concentration of the first flux solution. 11. The method according to p. 1, characterized in that the melting temperature of the metal coating is 9.0-30.8 ° C.