WO2019072240A1 - Preparation method for superfine high dispersion silver-tungsten electrical contact material - Google Patents

Abstract

A preparation method for a superfine high dispersion silver-tungsten electrical contact material: premixing spherical foam tungsten powder and an activated element, mixing with a part of silver powder to prepare a framework powder, forming a framework of a certain porosity by means of initial pressure, performing vacuum sintering, and performing silver infiltration to obtain a compact superfine high dispersion silver-tungsten alloy. In the high evenness silver-tungsten electrical contact material prepared by means of the method, the two-phase grains of base silver and high melting point tungsten are fine and are distributed interactively and dispersively, while the components and morphology within each micro-area range of a contact surface change slightly during an arc erosion process, thus representing high and reliable arc burning performance. The process for the method is simple and is suitable for mass production, and the prepared product may be widely used in circuit breakers and contactors.

Description

Preparation method of ultrafine high dispersion silver tungsten electrical contact material Technical field

The invention belongs to the field of electrical contact materials, and specifically relates to a preparation method of ultra-fine high-dispersion silver-tungsten electrical contact materials.

Background technique

Arc burnout is essentially the heat-force effect of arc energy on the contact material, and physical metallurgical processes such as heating, melting, gasification, flow, solidification, etc. occur on the contact surface, resulting in softening, splashing, and flow on the contact surface. , cracks and other phenomena. Improving the electrical performance of the contacts requires materials to be optimally designed and prepared through the components and tissues to delay or mitigate the occurrence of the above physical metallurgical processes.

The traditional silver-tungsten electrical contact material has a phenomenon of tungsten agglomeration in the structure, and the silver cannot completely penetrate into the hole. The aggregation and pores inside the material structure are often crack propagation channels due to the poor bonding strength. During the working of the contacts, the material is accelerated under the action of the heat of the arc. Therefore, it is necessary to prepare a silver-tungsten electrical contact material with uniform dispersion of tissue.

Patent CN104209520 discloses a method for manufacturing an electrical contact, which adopts a liquid pore-forming agent to improve the infiltration property of the skeleton, and improves the closed pore caused by the solid powder being unable to isolate the skeleton powder from each other, but is still uniform between the solid tungsten powder particles. The process cannot further refine the structure, and a single tungsten powder particle can still be regarded as a local "tungsten aggregation" phenomenon.

Patent CN105779804 A foam skeleton structure reinforced metal matrix composite material and a preparation method thereof, the surface of the foam skeleton is strengthened with a layer of high thermal conductive material, and the foam skeleton is composited with the metal matrix by pressure infiltration technology. In the patent, the high-heat-conducting particles, super-hard wear-resistant particles and conductive particles composed of different orientations are formed in the foam skeleton through various complicated processes to achieve the purpose of maximizing the heat conduction effect of the composite material. The foam metal skeleton structure in the patent mainly serves as a structural member of the support layer of the reinforcing layer, and its function is equivalent to the foam ceramic skeleton; the internal pore diameter is coarse, and the functional effect of the ultrafine dispersion structure cannot be obtained.

None of the above inventions relates to a method for preparing an ultrafine high-dispersion silver-tungsten electrical contact material having high and stable arc burning resistance.

Summary of the invention

The technical problem to be solved by the embodiments of the present invention is to provide a method for preparing an ultrafine high-dispersion silver-tungsten electrical contact material having high and stable arc-burning resistance.

To achieve the above object, the technical solution of the present invention includes the following steps:

S01: pre-mixing the spherical foamed tungsten powder with the activating element in a mass ratio of (99-99.5):(0.5-1) for 1-3 hours to obtain a pre-mixed powder; adding activated element to the tungsten foam in the step to promote tungsten Dissolving in silver and forming a high-diffusing interfacial mesophase of activating element and tungsten, which facilitates the penetration of silver into the pores of the skeleton to form a dense electrical contact material;

S02: mixing the premixed powder and the silver powder in a mass ratio of (60-75):(25-40) for 5-9 hours to obtain a mixed powder;

S03: pressing the mixed powder into a skeleton having a porosity of 30-45%;

S04: The skeleton is subjected to skeleton exhaust in a vacuum sintering furnace under an atmosphere of 50-120 Pa at 600-800 ° C for 2-4 hours; the skeleton prepared by the foamed tungsten powder in this step is pre-burned and exhausted in a vacuum atmosphere, which is favorable for reducing Capillary resistance during infiltration, forming a dense electrical contact material;

S05: The infiltrated silver piece is placed on the skeleton, and infiltrated in a hydrogen atmosphere at 1000-1300 ° C for 0.5-2 hours, so that the infiltration is filled with silver in the silver piece into the pores of the skeleton.

Further, the foamed tungsten powder is 0.5-6 um spherical porous tungsten powder, and the pore form thereof is a network-like structure, the pore diameter is 0.01-5 um, and the porosity is 50%-99.9%.

Further, the activation element is one or a combination of Be, Al, Ti, Ta, Nb, Ni-P, Li.

The innovative mechanism of the invention is:

The technical scheme of the invention adopts spherical foamed tungsten powder with a large amount of interconnected pores inside the particle as a skeleton powder raw material, and pre-burns and exhausts the skeleton in a vacuum atmosphere to reduce capillary capillary resistance during infiltration; and simultaneously added in the system The activating element promotes the dissolution of tungsten in the silver and forms a high-diffusing interfacial mesophase of the activating element and tungsten, which facilitates the penetration of silver into the pores of the framework powder and the formation of a dense electrical contact material.

Compared with the prior art, the beneficial effects of the invention are: in the prepared silver-tungsten electrical contact material, silver can not only form a network of connections between the tungsten particles, but also penetrate into the inner pores of the tungsten particles to form an integral network with the outside, and maintain The continuity of each phase. Due to the high energy density, short-term and random characteristics of the arc, the phase change of the contact material in the arc erosion process is complicated. In an ultra-fine and high-dispersion distribution system, tungsten distribution is uniform and effectively resists arc heat-force action, reducing silver melting, gasification and splashing; uniformity of silver distribution effectively improves contact conductivity, reduces body resistance, and conducts electricity quickly. Thermal conductivity. During the two-phase interaction, the composition and morphology of the micro-areas on the contact surface of the arc erosion process are small, which shows high and reliable arc burning performance.

DRAWINGS

1 is a SEM comparison diagram of the first embodiment of the present invention, and the left diagram of FIG. 1 is a conventional process, and the right drawing process of the present application;

2 is a SEM comparison diagram of the second embodiment of the present invention, and the left diagram of FIG. 1 is a conventional process, and the right drawing process of the present application;

3 is a SEM comparison diagram of the third embodiment of the present invention, and the left diagram of FIG. 1 is a conventional process, and the right drawing process of the present application.

Detailed ways

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described in detail below.

Embodiment 1:

Taking AgW50 material preparation as an example

1) The spherical foamed tungsten powder and the activating element (Be, Ti, Nb) are premixed for 2 hours at a ratio of 99.3:0.2:0.3:0.2; the spherical foamed tungsten powder has a particle size of 2 um, a pore diameter of 0.1-0.5 um, and a porosity of 90. %;

2) mixing the premixed powder and the silver powder in a ratio of 65:35 for 6 hours to obtain a mixed powder;

3) pressing the mixed powder into a skeleton having a porosity of 35%;

4) The skeleton is subjected to skeleton exhaust in a vacuum sintering furnace under a vacuum atmosphere of 100 Pa at 800 ° C for 2 hours;

5) The remaining weight of the silver piece was placed on the skeleton, and infiltration was carried out in a hydrogen atmosphere at 1300 ° C for 0.5 hour.

	Resistivity μΩ·cm	Hardness HV
Conventional process	2.57	142
Test process	2.01	183

Embodiment 2:

Taking AgW55 material preparation as an example

1) pre-mixing spherical foamed tungsten powder with activating element (Ta, Ti, Ni-P) at a ratio of 99.1:0.3:0.5:0.1 for 1 hour; spherical foamed tungsten powder having a particle size of 5 um, a pore diameter of 0.3-0.8 um, pores Rate of 85%;

2) mixing the premixed powder and the silver powder in a ratio of 70:30 for 7 hours to obtain a mixed powder;

3) pressing the mixed powder into a skeleton having a porosity of 38%;

4) The skeleton is subjected to skeleton exhaust in a vacuum sintering furnace under a vacuum atmosphere of 80 Pa at 750 ° C for 1.5 hours;

5) The remaining weight of the silver piece was placed on the skeleton, and infiltration was carried out at 1,200 ° C for 1 hour in a hydrogen atmosphere.

	Resistivity μΩ·cm	Hardness HV
Conventional process	2.72	151
Test process	2.27	197

Embodiment 3:

Taking AgW60 material preparation as an example

1) pre-mixing spherical foamed tungsten powder with activating elements (Al, Li, Nb) at a ratio of 99.5:0.1:0.3:0.1; spherical foamed tungsten powder having a particle size of 3 umn, a pore diameter of 0.2-0.6 um, and a porosity of 95 %;

2) mixing the premixed powder and the silver powder in a ratio of 75:25 for 6 hours to obtain a mixed powder;

3) pressing the mixed powder into a skeleton having a 42% porosity;

4) The skeleton is subjected to skeleton exhaust in a vacuum sintering furnace under a vacuum atmosphere of 50 Pa at 700 ° C for 4 hours;

5) The remaining weight of the silver piece was placed on the skeleton, and infiltration was carried out at 1000 ° C for 2 hours in a hydrogen atmosphere.

	Resistivity μΩ·cm	Hardness HV
Conventional process	2.94	166
Test process	2.41	211

The above is only the preferred embodiment of the present invention, and the scope of the present invention is not limited thereto, and thus equivalent changes made in the claims of the present invention are still within the scope of the present invention.

Claims (3)

1. A method for preparing an ultrafine high-dispersion silver-tungsten electrical contact material, comprising the steps of:

   S01: pre-mixing the spherical foamed tungsten powder with the activating element in a mass ratio of (99-99.5):(0.5-1) for 1-3 hours to obtain a pre-mixed powder;

   S02: mixing the premixed powder and the silver powder in a mass ratio of (60-75):(25-40) for 5-9 hours to obtain a mixed powder;

   S03: pressing the mixed powder into a skeleton having a porosity of 30-45%;

   S04: The skeleton is subjected to skeleton exhaust in a vacuum sintering furnace under an atmosphere of 50-120 Pa at 600-800 ° C for 2-4 hours;

   S05: The infiltrated silver sheet is placed on the skeleton, and infiltrated in a hydrogen atmosphere at 1000-1300 ° C for 0.5-2 hours, thereby infiltrating the infiltrated silver in the silver sheet into the pores of the skeleton.
2. The method for preparing an ultrafine high-dispersion silver-tungsten electrical contact material according to claim 1, wherein the foamed tungsten powder is a 0.5-6 um spherical porous tungsten powder, and the pore form is a network-like structure. The pore diameter is 0.01-5 um, and the porosity is 50%-99.9%.
3. The method for preparing an ultrafine high-dispersion silver-tungsten electrical contact material according to claim 1, wherein the activating element is one or more of Be, Al, Ti, Ta, Nb, Ni-P, and Li. Combination.

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