KR20000071951A - Connection method of contact plate for a electric appliance making cu-w - Google Patents

Abstract

PURPOSE: A bonding method is provided to bond contact points for an electric apparatus made of copper-tungsten by a simple process while minimizing physical and chemical denaturation of a material. CONSTITUTION: After holding one of two materials by a rotary chuck(1) and the other by a fixed chuck(2), a spindle is rotated and the fixed chuck is shifted forwardly. A pressure is applied on the materials at a preliminary friction step to let the two faces of the materials in contact with each other. A friction force is increased and converted to a torsional moment. The friction force causes a shear strain while leveling the rough surface at most points of the contacting faces.

Description

CONNECTION METHOD OF CONTACT PLATE FOR A ELECTRIC APPLIANCE MAKING CU-W}

The present invention provides a method of bonding contacts for electrical devices made of copper-tungsten material, and more particularly, to improve the bonding properties of electrical contacts such as switchgear or circuit breaker that are installed in an electrical facility to open or close a circuit or are in mechanical contact. The present invention relates to a method for joining a contact for an electrical device made of copper-tungsten material, which simplifies the process and ensures safety of quality.

In general, electrical contacts of switches, relays, and high-voltage transmission and distribution facilities are becoming high-performance and large-capacity in accordance with the promotion of high pressure or ultra-high pressure in order to increase the power transmission efficiency. There is a demand for high functionality that can cope with characteristics such as thermal conductivity.

Among the materials used as conventional electrical contacts, materials such as copper-tungsten (Cu-W) have excellent electrical conductivity, arc resistance, and welding resistance, but are expensive, so when used as electrical contact parts, The material, ie, Cu (copper) or Cu alloy, is bonded by brazing.

However, the conventional brazing method is easy to change the physical and chemical properties of the material due to the nature of the bonding, and the performance of the joint is less than 60% of the tensile strength of the Cu base material, many improvements are required.

In addition, the melting point (680 ~ 750 ℃) of silver lead used as filler metal is lower than Cu or contact point during brazing operation, so that the junction part dissolves and separates due to arc heat caused by short-circuit current. This occurred.

Therefore, in the ultra-high voltage and the electrical contacts for chargers, there is an urgent need for a bonding method capable of obtaining a more stable quality by producing a uniform product having a higher adhesive strength than the bonding method by brazing.

The present invention has been made in view of the problems caused by the conventional method of joining electrical contacts as described above, the object of which is an electrical device made of copper-tungsten material that can be joined in a simple process while minimizing changes in physical and chemical properties of the material It is to provide a joining method for the contact.

In order to achieve the above object, the present invention is to produce a friction heat locally on the surface of a metal material, and to bring the metal into a plastic state, so as to produce a pressurized contact between rotating or moving workpieces to bond the metals (Solid By using state welding method, it is possible to improve the work efficiency, joining performance, and reproducibility of welding conditions, and to improve the reliability of quality. It is possible to join by friction welding even if the material used for the contact is made of different materials. It is characterized by the ability to reduce and improve quality.

1A to 1F are cross-sectional views showing one example of the friction welding method of the present invention for each process.

<Description of Codes by Major Parts of Drawings>

1: rotating shaft 2: fixed shaft

In the present invention, the material used as the electrical contact material is a copper-tungsten alloy, the content of which is preferably copper: tungsten in a ratio of 35: 65, but copper: tungsten in a ratio of 20: 80 depending on the intended use. It is possible to adjust the range up to 45:55.

1A to 1F are cross-sectional configuration diagrams showing an example of the friction welding method of the present invention for each process, and the friction welding method of the present invention generates friction heat locally on the surface of the metal material, thereby forming two surfaces with plastic flow. It is a solid state welding method that joins metals by causing pressure contact between rotating or moving workpieces to exchange metals.

In other words, when one material moves relative to another material and a force is applied between the two materials, it is a process of producing a product in metallography.

As shown in FIGS. 1A, 1B and 1C, one of the two materials is bitten by the rotary chuck 1 and the other by the fixed chuck 2 and then the fixed side 2 is advanced while rotating the spindle.

The friction process is divided into a preliminary friction stage and a friction stage. When pressure is applied in the preliminary friction stage and the two surfaces of the material come into contact with each other, the frictional force rises and is converted into a torsional moment. Shear deformations are blunted to blunt surfaces (see FIG. 1D).

At the beginning of the friction, the friction between the two surfaces is maximal, and the contaminated surface is separated and the surface of the substrate is exposed, forming a bond under the higher axial pressure of the friction phase, and causing plastic deformation with continuous rotation.

In addition, the frictional energy is generated and converted into heat as a result of local bonding and shearing forces, so the temperature of the friction surface rises rapidly. As a result of the axial pressure and the relative movement between the two materials, the material is plastically deformed and discharged into the spiral flash. This phenomenon consists of strong mixing of the sheared solid particles with some molten liquid.

On the other hand, intermetalic compounds may be employed as a result of mechanical forces at high temperatures, and interdispersion between elements occurs.

This depends locally on the alloy composition and the instantaneous temperature and is locally possible to exceed the solidus temperature of the formed alloy, thus forming crystals of intermetallic mixing and solid solution.

Hot forging of the material due to the high upset pressure when the spindle is stopped, as in FIG. 1E, is the completion of this process, and also in this step recrystallization takes place.

After each step, a series of pressure welding cycles are completed by removing the specimen from the rotary chuck 1 and the fixed chuck 2 (see FIG. 1F).

<Example>

In the present invention, the WCu sintered alloy and copper used as the electrical contact material for the 25.8KV gas switch is manufactured by a friction welding process to evaluate the mechanical and physical properties thereof, and the contact by the conventional brazing and the contact by the friction welding are used for the 25.8KV gas. The following conclusions were obtained by applying the switch to the electrical test.

end. Mechanical and physical test results

(1) Cu-W hardly deformed at friction welding of Cu-W and Cu, and Cu formed a flash by plastic deformation.

(2) The tensile strength of the friction welding contact reached a frictional pressure of 45 MPa, a friction time of 0.6 seconds, and an upset pressure of 125 MPa to 298 MPa, which corresponds to 96% of the Cu base material tensile strength (310 MPa).

(3) Tensile fracture of frictional pressure weld shows soft fracture in which dimples exist, and the W ribs at the base of fracture surface dimple cause fracture in Cu adjacent to the junction.

(4) Under the same conditions as above, the shear strength of the friction welding portion was 180 MPa, reaching 92% of the Cu base material shear strength.

(5) Under the same conditions as above, the bending strength of the friction welding portion was 306 MPa, reaching 73% of the Cu base material bending strength.

(6) As a result of spraying liquid nitrogen on Cu during friction welding to increase the plastic deformation resistance of Cu, the tensile strength of the weld was improved to 98% of the Cu base metal tensile strength.

(7) As a result of measuring the hardness of each junction of the contact by conventional brazing and the contact by friction welding, the former was less than HS10 or impossible to measure. In the latter, HS14 maintained the same hardness as the base material. .

(8) As a result of measuring each conductivity for the same sample of item 7, there was a difference of about twice. This means that in brazing operation, silver lead of 231ACS% is used, but friction welding is the same as W-Cu contact of 451ACS% of conductivity. This is because it is directly bonded.

I. Electrical test result

For comparison and verification of contacts by brazing and contacts by friction welding, attach the contacts to Bosung Heavy Industries Co., Ltd's 25.8KV gas insulated load switch to measure the resistance of the main circuit, temperature rise test, commercial frequency withstand voltage test, and impact A comparative verification test was performed on the contact structure by carrying out the breakdown voltage test and the partial discharge test before and after the large power test. Also, in order to evaluate the performance of the contact point through the high power test, the input current test was performed under more severe conditions than the switch test (10.2KA 3). ), The overload opening and closing test (818a 25 times) was carried out as a result of more than equivalent to the conventional brazing contact.

(1) The resistance value (Rt) of the normal contact by brazing and the contact by friction welding was calculated from the main circuit resistance measurement test results. This was improved by 3.3% and the measured resistance was 3%.

(2) Examining the results of the temperature rise test, the comparison of the temperature rise difference after the overload opening and closing test for the normal contact by conventional brazing and the contact by friction welding is 6% higher than the normal contact by brazing. It was found to be low.

(3) Examining the results of the commercial frequency withstand voltage test, impact withstand voltage test and partial discharge test, the insulation performance of the general contact by the conventional brazing and the contact by the friction welding were almost the same and there was no change in the contact change. More than equivalent improvements were made without affecting performance.

The bonding method of the contact point for the electrical device made of copper-tungsten material of the present invention has the effect of improving the work efficiency, the bonding performance and the reproducibility of the pressure welding conditions, and the ease of monitoring to increase the reliability of the quality.

In addition, even if the material used for the contact is made of a heterogeneous material, it can be joined by friction welding, which has the advantage of reducing cost and improving quality.

Claims (4)

One of the two materials of the base material and the copper-tungsten bonded to it is bitten by the rotary chuck (1) and the other by the fixed chuck (2), and the fixed side (2) is advanced while rotating the spindle so that the two materials come into contact with each other. To do that, The pressure applied to the two materials in contact causes the frictional forces generated on both sides of the material to rise to the torsional moment, and the frictional force causes shear deformation at the most points of the contacting surface, causing blunt surfaces. Friction stage, A friction step in which the contaminated surface is separated by the preliminary friction step and the surface of the base material is exposed, thereby forming a joint under a higher axial pressure and causing plastic deformation by continuous rotation; As a result of the temperature rise of the friction surface due to the friction energy and the relative motion between the two materials subjected to the axial pressure, the material is plastically deformed and discharged into the helical flash. This phenomenon is caused by the strong effect of the sheared solid particles and some molten liquid. The intermetalic compound is dissolved in the mixing process, Copper-tungsten material, characterized in that the step of removing the test piece by completing the hot forging of the material due to the high upset pressure when the spindle of the rotating shaft (1) is stopped and recrystallization occurs to complete the pressing cycle To join contacts for electrical equipment. The method of joining an electrical device contact made of a copper-tungsten material according to claim 1, wherein the content ratio of copper-tungsten alloy used as the electrical contact material is 35:65. 2. The method of joining an electrical device contact made of copper-tungsten material according to claim 1, wherein the content ratio of copper-tungsten alloy used as the electrical contact material is 20:80. 2. The method of joining an electrical device contact made of copper-tungsten material according to claim 1, wherein the content ratio of copper-tungsten alloy used as the electrical contact material is 45:55.