KR20150134917A

KR20150134917A - METHOD FOR MANUFACTURING Cu-Cr ELECTRIC CONTACT MATERIAL

Info

Publication number: KR20150134917A
Application number: KR1020140062358A
Authority: KR
Inventors: 손정룡; 조성현; 홍순형; 이성준; 장문경
Original assignee: 승림전기주식회사
Priority date: 2014-05-23
Filing date: 2014-05-23
Publication date: 2015-12-02

Abstract

Disclosed is a Cu-Cr electrical contact manufacturing method. According to an embodiment of the present invention, the Cu-Cr electrical contact manufacturing method comprises: a first step of mixing Cu powder and Cr powder such that an average particle-size distribution of the Cu powder, and an average particle size distribution of the Cr powder are 1:0.8 to 1:1.2; a second step of manufacturing a formed body by filling a mold with the mixed powder mixed in the first step, and pressing the mold; a third step of solid state-sintering the formed body at a temperature of a melting point or less; a fourth step of reducing a blow hole on a surface of a contact point by pressing a sintered body; and a fifth step of reducing an illumination intensity on the surface of a contact point of the sintered body.

Description

METHOD FOR MANUFACTURING Cu-Cr ELECTRIC CONTACT MATERIAL

The present invention relates to a method for manufacturing a Cu-Cr electrical contact, and more particularly, to a method for manufacturing a Cu-Cr electrical contact for a vacuum circuit breaker.

Vacuum circuit breakers (VCBs) are widely used because they have excellent blocking performance and insulation characteristics, are low in maintenance cost, and are free from external influences. The vacuum circuit breaker is equipped with a vacuum interrupter (VI) for opening and closing an electrode in vacuum. The performance of the vacuum interrupter is determined by an arc characteristic generated on the surface of a contact during current interruption, As shown in FIG. That's why electrical contact material is important.

Specifically, when the electrode of the vacuum switch is disconnected by the operating mechanism of the circuit breaker during energization, arc discharge occurs between the electrodes. The arc is caused by the ionization of the electrodes when the contact point on the contact part of the electrode is evaporated and transformed into the metal vapor. If the arc is continued in any part of the contact, the blocking performance is lowered due to melting of the contact and vapor evaporation. Loss of function. In order to solve the above problem, a slit-shaped contact point capable of improving the blocking performance while minimizing the damage of the contact point has been developed.

1 is a view schematically showing a slit-like contact material.

Referring to FIG. 1, the contact material 10 has a disk shape as a whole, a center hole 11 is formed at its center, and a spiral-shaped slit groove 12 having a curved shape for moving an arc generated is provided at the rim do. The edge has a wing-like shape separated by the slit groove 12 (the contact material shown in Fig. 1 corresponds to the (+) pole).

The contact material 10 having such a shape can be obtained by filling a raw material powder constituting the electrical contact into a mold capable of being formed into the shape described above and then pressing the material. .

The characteristics required for the contact material 10 are as follows. The breaking capacity is large, the withstanding voltage is high, the gas content is low, the contact resistance is small, the welding force is small, the consumed amount is small, the cutting current is small, the moldability is good, that. However, since the properties listed above may be inconsistent with each other, it is important to derive the optimum conditions for the characteristics and the process of the raw material powder forming the contact material.

Currently, the most widely used contact material for vacuum interrupters is Cu-Cr contact material. Cu-Cr alloys have excellent thermal and electrical properties. In particular, Cr components can easily be bonded (oxidized) to oxygen released during arc generation, thereby maintaining a high vacuum state. However, it is not easy to improve the properties of Cu-Cr contact materials due to the high oxygen affinity of Cr and the high vapor pressure of Cu near the melting point. This is why many studies have been conducted to improve the properties of Cu-Cr-based contact materials.

Patent Document 1: Korean Patent Laid-Open No. 10-2000-0045682 (Published on July 25, 2000)

Embodiments of the present invention seek to provide a manufacturing method capable of manufacturing a Cu-Cr electrical contact having high characteristics at a low cost.

According to an aspect of the present invention, there is provided a method of mixing copper powder and chromium (Cr) powder so that the average particle size distribution of the copper powder and the average particle size distribution of the chrome powder are 1: 0.8 to 1: 1.2 Stage 1; Filling the mixed powder mixed in the step 1 into a mold die and pressurizing the mixture to produce a molded body; Solid-phase sintering the formed body at a temperature not higher than the melting point of copper (Cu); Removing the pores of the contact surface by re-pressing the sintered body; And a step of reducing the roughness of the contact surface of the sintered body.

In this case, the composition of the Cu-Cr electrical contact is 45 to 80 wt% of Cu and 20 to 55 wt% of Cr, and the third step is performed at a temperature of 900 to 1075 DEG C, Atmosphere or a vacuum atmosphere, and the degassing process may be performed together in the above three steps.

In the Cu-Cr electrical contact manufacturing method according to the embodiments of the present invention, mixing is performed such that the average particle size distribution of the Cu powder and the average particle size distribution of the Cr powder are 1: 0.8 to 1: 1.2, The occurrence of Cr segregation can be minimized.

Further, the durability of the electrical contact material can be improved by repressurizing the Cu-Cr sintered body to remove pores on the surface of the contact.

1 is a view schematically showing a slit-like contact material.
Fig. 2 is an optical microscope photograph showing a sintered structure of the Cu-Cr electrical contact material according to Example 1. Fig.
3 is an optical microscope photograph showing a sintered structure of Cu-Cr electrical contact material according to Example 2. Fig.
4 is an optical microscope photograph showing a sintered structure of a Cu-Cr electrical contact material according to Example 3. Fig.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

The method for manufacturing a Cu-Cr electrical contact according to an embodiment of the present invention includes a first step of mixing a copper (Cu) powder and a chromium (Cr) powder, a step of filling the mixed powder into a mold die, A step of sintering the solid body at a temperature not higher than the melting point of copper, and a step of removing the pores of the contact surface by re-pressing the sintered body. Each step will be described in detail below.

(1) Step 1

Step 1 is a powder mixing step of mixing copper (hereinafter referred to as Cu) powder and chromium (hereinafter referred to as Cr) powder. In the powder mixing process, Cu powder and Cr powder are uniformly mixed using a V-shaped mixer or a low-speed ball mill. At this time, the Cu powder and the Cr powder are weighed so that the composition of the Cu-Cr electrical contact material is 45 to 80 wt% of Cu and 20 to 55 wt% of Cr. When the Cu content is less than 45% by weight based on the Cu content, the electrical conductivity of the electrical contact material is lowered and the contact resistance is increased, and the electrification performance is lowered. When the Cu content exceeds 80% by weight, There is a problem that wear of the contact is severe and durability is reduced.

The Cu powder may be electrolytically the same, and the Cr powder may be a reducing powder (thermite). At this time, the Cr powder is spherical, and when the Cu powder is mixed, segregation of Cr particles may occur due to the difference in fluidity between the Cu powder and the Cr powder. Specifically, when Cr segregation occurs, the internal pores are localized according to the deviation of the molding density due to the non-homogeneity of the Cr particle dispersion. Since the densification is not progressed due to the sintering temperature deviation depending on the Cr content during sintering, As a result, the gas is released by the arc generated when the current is cut off, and the consumption of the contact is increased.

As described above, the segregation deteriorates the performance of the Cu-Cr electrical contact. In the method for manufacturing a Cu-Cr electrical contact according to an embodiment of the present invention, occurrence of Cr segregation is minimized and homogeneous Cu and Cr mixed The powder is mixed such that the average particle size distribution of the Cu powder and the average particle size distribution of the Cr powder are 1: 0.8 to 1: 1.2 in order to make the powder. For example, when the average particle size distribution of the Cu powder is 40 to 50 μm, the average particle size distribution of the Cr powder is 32 to 60 μm.

The inventors of the present invention have confirmed that a more homogeneous structure is formed when the average particle size distribution of both powders is controlled and then mixed, and it is possible to prevent the segregation of Cr powder and formation of micropores due to the segregation Respectively. This is because the particle size distribution of the Cu powder has little effect on the current interruption performance, but the Cr segregation due to the fluidity of the powder can be prevented and the Cu-Cr mixed powder can be homogeneously filled in the mold die.

(2) Step 2

In step 2, the mixed powder (Cu-Cr mixed powder) mixed in step 1 is filled in a mold die and pressurized to manufacture a molded article. In order to prevent abrasion of the mold due to friction of Cr powder, the mold die is thermally stable and has a lubricating effect at the interface between the mold base material and the wear-resistant coating layer in order to increase the abrasion resistance or the abrasion resistance. It is desirable to use a product with The molded body manufactured in this step has a spiral-shaped slit groove having a curved shape as shown in Fig.

(3) Step 3

Step 3 is a step of solid-phase sintering the formed body produced in step 2 above at a temperature lower than the melting point of copper (Cu). Concretely, the formed body (Cu-Cr formed body) can be sintered for a long time (for example, 6 hours or more) in a temperature range of Cu melting point (1083 ° C) or less in a reducing atmosphere or a high vacuum atmosphere. Here, the temperature range below the Cu melting point may be, for example, 900 ° C to 1075 ° C. In this step, a degassing process may be performed together. The degassing treatment step means a step of discharging the gas existing inside the sintered body to the outside.

When the sintering is carried out at the Cu melting point or higher, the surface energy of the Cr particles is solidified in Cu from the activated part, and after the completion of sintering, the fine Cr particles precipitate again as Cr fine particles upon cooling. There is a problem in that the current interruption performance of the contact point is not kept constant since it is not constant depending on the heat treatment condition. In addition, in this case, the electric conductivity is lowered, and the current interruption performance is lowered.

On the other hand, when sintering is performed at a temperature lower than the Cu melting point (particularly, at 1075 ° C or less near the Cu melting point), sintering due to interdiffusion of Cu particles proceeds and the gas existing therein is discharged to the outside, 98% of dense tissue can be obtained.

(4) Step 4

Step 4 is a step of repressurizing the sintered body to remove pores on the surface of the contact. The sintered body produced in the above step 3 forms a dense structure close to the theoretical density (98%) without deformation as described above. However, the contact surface structurally acts as a large current supply through the contact with the relative object and the contact between the contact point It is necessary to remove the pores present on the contact surface as much as possible in order to ensure a more stable durability life of the electrical contact material.

Accordingly, in the method for manufacturing a Cu-Cr electrical contact according to an embodiment of the present invention, the sintered body is re-pressurized to remove pores existing on the surface of the contact, thereby providing a denser structure than the sintered density. By performing the above-described steps, it is possible to provide an electrical contact free of pores on the surface of the sintered body.

(5) Step 5

The method for manufacturing a Cu-Cr electrical contact according to an embodiment of the present invention may further include a step 5 for reducing the illuminance of the contact surface of the sintered body after the fourth step.

The roughness of the contact surface differs greatly depending on the dispersion form of Cr particles and the post-treatment process. Minimizing the roughness of the contact surface is effective in reducing the contact resistance and the cut current value, and a post-treatment process capable of lowering the roughness of the contact surface can be introduced.

As described above, in the method of manufacturing a Cu-Cr electrical contact according to the embodiments of the present invention, the Cu powder and the Cr powder are mixed so that the average particle size distribution of the Cu powder and the average particle size distribution of the Cr powder are 1: 0.8 to 1: It is possible to minimize occurrence of Cr segregation in the Cr powder mixing process. Further, the durability of the electrical contact material can be improved by repressurizing the Cu-Cr sintered body to remove pores on the surface of the contact.

Hereinafter, the present invention will be described in detail with reference to examples of the present invention. However, it is apparent that the present invention is not limited to the following examples.

Example 1

A Cu powder having an average particle size of 60 탆 and a Cr powder having an average particle size of 70 탆 were weighed in a Cu-25% Cr composition ratio and mixed in a V-shaped mixer. The mixture was filled in a mold die and pressurized to 100 ton, (Three slit grooves were provided). Thereafter, the formed body was sintered at 1070 캜 for 6 hours (the oxygen content was 460 ppm or less and the nitrogen content was 10 ppm or less), which is lower than the Cu melting point. Then, the total density, hardness, and conductivity of the resulting sintered body were measured, and the density of the main portion was measured to determine the deviation from the total density. The density was measured by the Archimedes water method. As a result of measurement, the total density was 8.28 g / cm ³ , the hardness (HRF) was 55, the conductivity (IACS%) was 55, and the density deviation was ± 0.02. Thereafter, the sintered body was re-pressed to form a dense structure close to the theoretical density on the contact surface.

Fig. 2 is an optical microscope photograph showing a sintered structure of the Cu-Cr electrical contact material according to Example 1. Fig. Referring to FIG. 2, it is confirmed that the dispersion of particles is uniform.

Example 2

Cu powder having an average particle size of 50 탆 and Cr powder having an average particle size of 57 탆 were weighed in a Cu-25% Cr composition ratio and mixed in a V-shaped mixer. The mixture was filled in a mold die and pressurized to 135 ton, (Three slit grooves were provided). Thereafter, the formed body was sintered at 1070 캜 for 8 hours (the oxygen content was 460 ppm or less and the nitrogen content was 10 ppm or less), which is lower than the Cu melting point. Then, the total density, hardness, and conductivity of the resulting sintered body were measured, and the density of the main portion was measured to determine the deviation from the total density. The density was measured by the Archimedes water method. As a result of measurement, the total density was 8.27 g / cm ³ , the hardness (HRF) was 55, the conductivity (IACS%) was 55, and the density deviation was ± 0.03. Thereafter, the sintered body was re-pressed to form a dense structure close to the theoretical density on the contact surface.

3 is an optical microscope photograph showing a sintered structure of Cu-Cr electrical contact material according to Example 2. Fig. Referring to FIG. 3, it is confirmed that the dispersion of the particles is uniform.

Example 3

Cu powder having an average particle size of 60 탆 and Cr powder having an average particle size of 70 탆 were weighed in a Cu-40% Cr composition ratio and mixed in a V-shaped mixer. The mixture was filled in a mold die and pressurized to 50 tons, (Three slit grooves were provided). Thereafter, the formed body was sintered at 1075 DEG C for 8 hours (the oxygen content was 500 ppm or less and the nitrogen content was 30 ppm or less), which is lower than the Cu melting point. Then, the total density, hardness, and conductivity of the resulting sintered body were measured, and the density of the main portion was measured to determine the deviation from the total density. The density was measured by the Archimedes water method. As a result of the measurement, the total density was 8.05 g / cm ³ , the hardness (HRF) was 62, the conductivity (IACS%) was 45, and the density deviation was ± 0.02. Thereafter, the sintered body was re-pressed to form a dense structure close to the theoretical density on the contact surface.

4 is an optical microscope photograph showing a sintered structure of a Cu-Cr electrical contact material according to Example 3. Fig. Referring to FIG. 4, it is confirmed that the dispersion of the particles is uniform.

The embodiments of the present invention have been described above. It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventive concept as defined by the appended claims. It will be understood that various modifications may be made without departing from the scope of the present invention.

10: Contact material 11: Center hole
12: Slit groove

Claims

Mixing the copper powder and chromium (Cr) powder so that the average particle size distribution of the copper powder and the average particle size distribution of the chrome powder are 1: 0.8 to 1: 1.2;
Filling the mixed powder mixed in the step 1 into a mold die and pressurizing the mixture to produce a molded body;
Solid-phase sintering the formed body at a temperature not higher than the melting point of copper (Cu);
Removing the pores of the contact surface by re-pressing the sintered body; And
And reducing the roughness of the contact surface of the sintered body.

The method according to claim 1,
The Cu-Cr electrical contact has a composition of 45 to 80% by weight of Cu and 20 to 55% by weight of Cr, and the third step is performed at a temperature of 900 to 1075 캜. The sintering atmosphere of the third step is a reducing atmosphere or a vacuum Atmosphere, and the degassing process is performed together in the above-described three steps.