阅读说明：本技术 银碳化钨金刚石复合触头材料及其制备方法 (Silver tungsten carbide diamond composite contact material and preparation method thereof ) 是由 兰岚 宋振阳 孔欣 赵阿强 崔永刚 王达武 陈松扬 于 2020-03-03 设计创作，主要内容包括：本发明公开了一种银碳化钨金刚石复合触头材料及其制备方法,包括以下组分：碳化钨粉的平均粒度为0.5-5μm,质量比为55～80wt％；金刚石粉末的平均粒度为0.1-10μm,质量比为0.01-2wt％；钴粉的平均粒度为1-5μm质量比为：1～4wt％,银为余量。本发明的银碳化钨金刚石触头材料添加了高熔点、高硬度的金刚石成分,提高了触头材料的抗熔焊性及耐电弧烧损的能力,降低了触头工作时由于熔焊粘连导致分断失败的风险。其制备方法为：将碳化钨粉与金刚石粉以及适量钴粉进行机械研磨；在高温、还原性气氛下将混合粉末进行还原扩散处理；然后将粉末破碎后加入成型剂；再采用常规压制、脱蜡、预烧、熔渗工艺获得致密的银碳化钨金刚石复合材料。(The invention discloses a silver tungsten carbide diamond composite contact material and a preparation method thereof, wherein the silver tungsten carbide diamond composite contact material comprises the following components: the average particle size of the tungsten carbide powder is 0.5-5 mu m, and the mass ratio is 55-80 wt%; the average particle size of the diamond powder is 0.1-10 μm, and the mass ratio is 0.01-2 wt%; the average particle size of the cobalt powder is 1-5 μm according to the mass ratio: 1-4 wt%, and the balance being silver. According to the silver tungsten carbide diamond contact material, the diamond component with high melting point and high hardness is added, so that the fusion welding resistance and the electric arc burning resistance of the contact material are improved, and the risk of breaking failure caused by fusion welding adhesion during the operation of the contact is reduced. The preparation method comprises the following steps: mechanically grinding tungsten carbide powder, diamond powder and proper amount of cobalt powder; carrying out reduction diffusion treatment on the mixed powder at high temperature in a reducing atmosphere; then crushing the powder and adding a forming agent; and then the compact silver tungsten carbide diamond composite material is obtained by adopting the conventional pressing, dewaxing, presintering and infiltration processes.)

1. The silver tungsten carbide diamond composite contact material is characterized by comprising the following components:

the average particle size of the tungsten carbide powder is 0.5-5 mu m, and the mass ratio is 55-80 wt%;

the average particle size of the diamond powder is 0.1-10 μm, and the mass ratio is 0.01-2 wt%;

the average particle size of the cobalt powder is 1-5 μm according to the mass ratio: 1 to 4 wt% of a catalyst,

the balance being silver.

2. A method of making a silver tungsten carbide diamond composite contact material according to claim 1, comprising the steps of:

(1) mixing the powder, namely uniformly mixing the tungsten carbide powder, the diamond powder and the cobalt powder to obtain mixed powder;

(2) mechanical grinding: mechanically grinding the mixed powder to ensure that cobalt dispersed and distributed in the mixed powder is diffused on the surfaces of the tungsten carbide and the diamond;

(3) reduction annealing: in a reducing atmosphere, sintering the mixed powder treated in the step (2) at the temperature of 700-900 ℃ for 2-5 hours in a heat preservation manner, reducing an oxide film on the surface of the mixed powder to diffuse cobalt on the surfaces of tungsten carbide and diamond, improving the bonding property of the powder, and then crushing and sieving the reduced mixed powder;

(4) and (3) granulating powder: adding the mixed powder treated in the step (3) into a granulator, and adding a forming agent for granulation;

(5) molding and pre-sintering: carrying out compression molding on the powder treated in the step (4), preparing a skeleton pressed blank with the skeleton porosity of 25-49%, removing a forming agent through sectional heating of the skeleton pressed blank in a reducing atmosphere, and carrying out skeleton pre-sintering, wherein the diamond particles coated with cobalt on the surface and tungsten carbide particles are sintered into an integral skeleton under the bonding action of cobalt in the pre-sintering;

(6) and (3) skeleton infiltration: and (3) stacking the presintered skeleton pressed blank and the silver sheet in a reducing atmosphere, putting the stacked skeleton pressed blank and the silver sheet into an infiltration furnace, carrying out infiltration at 1050-1100 ℃, and cooling and discharging to obtain the silver tungsten carbide diamond composite contact material.

3. The method for preparing the silver tungsten carbide diamond composite contact material according to claim 1, wherein the method comprises the following steps: and (2) mixing the powder in the step (1) by filling the powder into a mixer for mixing for 1-4 hours.

4. The method for preparing the silver tungsten carbide diamond composite contact material according to claim 1, wherein the method comprises the following steps: and (3) the mechanical grinding in the step (2) is to put the mixed powder treated in the step (1) into a ball-milling tank, add alloy balls in a ball-to-material ratio of 4:1, and carry out mechanical grinding treatment for 10-24 hours.

5. The method for preparing the silver tungsten carbide diamond composite contact material according to claim 1, wherein the method comprises the following steps: the forming agent in the step (3) is paraffin or stearic acid, and the addition amount of the forming agent is 1-5% of the mass ratio of the forming agent to the mixed powder of tungsten carbide powder, diamond powder and cobalt powder.

6. The method for preparing the silver tungsten carbide diamond composite contact material according to claim 1, wherein the method comprises the following steps: the reducing atmosphere in the steps (4) and (5) is a hydrogen atmosphere or an ammonia decomposition atmosphere.

Technical Field

The invention relates to the field of electric contact material manufacturing processes, in particular to a silver tungsten carbide diamond composite contact material and a preparation method thereof.

Background

The silver tungsten carbide material has excellent electric wear resistance, better fusion welding resistance and lower contact resistance, and is mainly applied to various switching devices such as circuit breakers, contactors and the like with larger current. Under large and medium currents, the contact resistance of the silver tungsten carbide material is gradually increased along with the increase of the on-off times, the temperature rise is gradually increased, and the fusion welding risk and the arc corrosion speed of the contact are also continuously increased. The welding resistance and the electric wear resistance of the contact can be further improved by adding the diamond component particles with high melting point and high hardness into the silver tungsten carbide material, so that the service life and the safety of an electric appliance are improved.

In the silver tungsten carbide material, when the content of tungsten carbide is less than 30 wt%, the material has low hardness and good processability, and can obtain higher density by a solid-phase sintering and repressing or extrusion rolling mode, and the two processes can be used for conveniently adding various additives in the powder mixing stage to improve the material performance. With the increase of the content of tungsten carbide, the hardness of the material is continuously improved. When the content of tungsten carbide is more than 50 wt%, the material has high hardness and poor processability, and cannot be processed in an extrusion mode, the material is difficult to densify in a solid-phase sintering and repressing mode, and the high-density material can be obtained only in a liquid-phase sintering (infiltration) mode.

The process of silver tungsten carbide material liquid phase sintering is essentially the process of filling a tungsten carbide framework with silver solution. The whole process requires that the tungsten carbide framework and the silver melt have good wettability, and the tungsten carbide framework must be internally provided with mutually communicated and smooth infiltration channels. Therefore, liquid phase sintering has high requirements on the pressed compact skeleton and additives, and the additives cannot influence the wettability and permeability of the skeleton. The atomic structure of diamond causes the interface energy between the diamond and the general metal liquid to be relatively higher than the surface energy of the diamond, so that the diamond is not infiltrated by the general metal and alloy melt. The wetting angle of diamond and silver is 120 degrees at 1000 ℃, the wettability of the diamond and the silver is very poor, after the diamond is added into a tungsten carbide framework, due to the poor wettability, the silver solution cannot infiltrate the diamond, holes are formed at the edges of diamond particles, and the framework cannot be infiltrated by silver melt. And because diamond proportion is less, after adding the tungsten carbide skeleton, diamond granule can float in the silver melt in the infiltration process, along with the silver melt flows in the tungsten carbide skeleton, forms the gathering in the skeleton and blocks up the infiltration passageway, leads to the infiltration to go on smoothly, and the burning blank inside can consequently remain a large amount of holes that are not filled up by the silver melt. Therefore, the addition of diamond in liquid phase sintering products is difficult, and the further improvement of the material performance is limited.

Through search, chinese patent publication No. CN100365747C discloses an electrical contact material for low-voltage electrical appliances, which is a diamond-containing silver tungsten carbide material produced by extrusion rolling, and the specific processing method is powder mixing, isostatic pressing, sintering, extrusion and rolling.

Chinese patent publication No. CN104384512B discloses a method for preparing a silver tungsten carbide contact material, which mainly comprises the steps of mixing silver powder and tungsten carbide powder, carrying out ball milling treatment, drying, annealing, molding and infiltrating the powder after ball milling to obtain the silver tungsten carbide contact material. The material comprises silver, tungsten carbide and nickel, and the material does not contain diamond.

Chinese patent publication No. CN110064762A discloses a method for preparing a silver-tungsten carbide contact material, which is a process for obtaining silver-coated tungsten carbide composite powder by a coating process, then mixing the composite powder with silver powder and pressing the mixture into a framework, and finally infiltrating the framework and silver sheets together to obtain the silver-tungsten carbide contact material. The specific processing mode is coating, powder mixing, sintering and infiltration, the mass ratio of tungsten carbide of the material is 40-90%, and diamond components are not contained in the material composition.

None of the above-mentioned prior art addresses the problems of poor wetting between materials and free floating of additives in the molten metal that are addressed by the present application. There is therefore a need for improvement.

Disclosure of Invention

In order to solve the problems and the defects in the prior art, the invention aims to provide a silver tungsten carbide diamond composite contact material and a preparation method thereof.

In order to achieve the purpose, the technical scheme of the invention is that the silver tungsten carbide diamond composite contact material is characterized by comprising the following components:

the average particle size of the tungsten carbide powder is 0.5-5 mu m, and the mass ratio is 55-80 wt%;

the average particle size of the diamond powder is 0.1-10 μm, and the mass ratio is 0.01-2 wt%;

the average particle size of the cobalt powder is 1-5 μm according to the mass ratio: 1 to 4 wt% of a catalyst,

the balance being silver.

The invention also provides a preparation method of the silver tungsten carbide diamond composite contact material as claimed in claim 1, which comprises the following steps:

(1) mixing the powder, namely uniformly mixing the tungsten carbide powder, the diamond powder and the cobalt powder to obtain mixed powder;

(2) mechanical grinding: mechanically grinding the mixed powder to ensure that cobalt dispersed and distributed in the mixed powder is diffused on the surfaces of the tungsten carbide and the diamond;

(3) reduction annealing: under the reducing atmosphere, the mixed powder treated in the step (2) is at the temperature of 700 ℃ to 900 DEG C

Sintering for 2-5 hours under heat preservation, reducing the oxide film on the surface of the mixed powder to diffuse cobalt on the surfaces of tungsten carbide and diamond, improving the powder bonding property, and then crushing and sieving the reduced mixed powder;

(4) and (3) granulating powder: adding the mixed powder treated in the step (3) into a granulator, and adding a forming agent for granulation;

(5) molding and pre-sintering: carrying out compression molding on the powder treated in the step (4), preparing a skeleton pressed blank with the skeleton porosity of 25-49%, removing a forming agent through sectional heating of the skeleton pressed blank in a reducing atmosphere, and carrying out skeleton pre-sintering, wherein the diamond particles coated with cobalt on the surface and tungsten carbide particles are sintered into an integral skeleton under the bonding action of cobalt in the pre-sintering;

(6) and (3) skeleton infiltration: and (3) stacking the presintered skeleton pressed blank and the silver sheet in a reducing atmosphere, putting the stacked skeleton pressed blank and the silver sheet into an infiltration furnace, carrying out infiltration at 1050-1100 ℃, and cooling and discharging to obtain the silver tungsten carbide diamond composite contact material.

And further setting that the powder mixing in the step (1) is carried out by filling the powder into a mixer for mixing for 1-4 hours.

And further setting that the mechanical grinding in the step (2) is to place the mixed powder treated in the step (1) into a ball-milling tank, add alloy balls in a ball-to-material ratio of 4:1, and perform mechanical grinding for 10-24 hours.

And (3) further setting that the forming agent in the step (3) is paraffin or stearic acid, and the adding amount of the forming agent is 1-5% of the mass ratio of the forming agent to the mixed powder of the tungsten carbide powder, the diamond powder and the cobalt powder.

It is further provided that the reducing atmosphere in the steps (4) and (5) is a hydrogen atmosphere or an ammonia decomposition atmosphere.

The invention has the advantages that:

the mixed powder is treated mainly in a mechanical grinding mode, and the tungsten carbide powder, the diamond powder and the cobalt powder are ground for a long time, so that the powder particles are repeatedly broken and deformed in the mechanical grinding process, and further refinement, homogenization of components and dispersion distribution of additives of the powder particles are promoted. The powder is subjected to high-temperature treatment in a reducing atmosphere, an oxide film on the surface of the powder is reduced, cobalt which is dispersed and distributed in the mixed powder is diffused on the surfaces of tungsten carbide and diamond, the bonding effect of the cobalt on the tungsten carbide is utilized, the bonding property of the powder in the later sintering is improved, and the processing stress generated in the powder grinding process is eliminated. The processed mixed powder is added with a forming agent to be pressed into a skeleton, and the skeleton is sintered into a solidified whole at high temperature, so that independent diamond particles are prevented from floating and moving in the silver melt in the subsequent infiltration process to block a channel. The surface of the diamond particles is coated with cobalt, so that the wettability of the diamond particles with silver is greatly improved, the silver solution can smoothly fill the whole framework, and finally the silver tungsten carbide diamond composite material with high density is obtained. The invention can realize the preparation of the high-density silver tungsten carbide diamond material by a liquid phase sintering process, solves the problem of high porosity inside the infiltration contact after adding the diamond component, and comprehensively improves the fusion welding resistance and the electric wear resistance of the contact material.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is within the scope of the present invention for those skilled in the art to obtain other drawings based on the drawings without inventive exercise.

FIG. 1 is a cross-sectional scanned view of a silver tungsten carbide diamond composite electrical contact material prepared in accordance with a first embodiment of the present invention;

FIG. 2 is a magnified (1000X) metallographic view of a silver tungsten carbide diamond composite electrical contact material prepared according to a first embodiment of the present invention.

Detailed Description

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