CN111063568A - Preparation method of silver tungsten carbide electrical contact material for circuit breaker - Google Patents
Preparation method of silver tungsten carbide electrical contact material for circuit breaker Download PDFInfo
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- CN111063568A CN111063568A CN201911287784.XA CN201911287784A CN111063568A CN 111063568 A CN111063568 A CN 111063568A CN 201911287784 A CN201911287784 A CN 201911287784A CN 111063568 A CN111063568 A CN 111063568A
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H11/00—Apparatus or processes specially adapted for the manufacture of electric switches
- H01H11/04—Apparatus or processes specially adapted for the manufacture of electric switches of switch contacts
- H01H11/048—Apparatus or processes specially adapted for the manufacture of electric switches of switch contacts by powder-metallurgical processes
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H1/00—Contacts
- H01H1/02—Contacts characterised by the material thereof
- H01H1/021—Composite material
Abstract
The invention relates to the technical field of materials, and aims to provide a preparation method of a silver tungsten carbide electrical contact material for a circuit breaker. The invention adopts a second-order powder mixing process, namely a powder mixing-pressing-crushing-powder mixing-pressing-crushing process, so that the powder particles are further crushed and dispersed, and the crushed mixed powder particles have a certain particle size and have fluidity in the green body pressing process, thereby being capable of achieving the required size and shape. The AgWC electric contact material is prepared by adopting a second-order infiltration sintering process, so that the wettability of WC particles in an AgWC green body and Ag solution is effectively improved, the density of the material is improved, the resistivity is reduced, and the AgWC electric contact material has good arc ablation resistance in later electrified use. Compared with the AgWC electric contact material prepared by the traditional method, the mechanical life of the AgWC electric contact material prepared by the method is prolonged by 5-20%, and the electric life is prolonged by 10-30%; the preparation method is simple to operate, high in yield and suitable for large-scale production.
Description
Technical Field
The invention relates to the technical field of materials, in particular to a preparation method of a silver tungsten carbide (AgWC) electric contact material for a low-voltage circuit breaker.
Background
Because of the combination of the good electric and heat conducting properties of Ag and the characteristics of tungsten carbide (WC) such as abrasion resistance, arc corrosion resistance, good fusion welding resistance and the like, the AgWC series electric contact material is widely applied to the field of low-voltage electric appliances such as small-sized circuit breakers, molded case circuit breakers and the like.
AgWC is used as an electric contact material, the requirement on the dispersibility of particles in the material is high, the traditional AgWC electric contact material often has a WC aggregation phenomenon, so that silver particles in the material cannot penetrate into the material to generate holes, and meanwhile, the WC material has high resistivity, and the two factors can cause the reduction of the hardness and the density of the electric contact material, the increase of the resistivity and the reduction of the use performance of the material.
For AgWC electric contact materials with the silver content of less than 60%, two main production processes exist at present, (1) powder mixing-pressing-infiltration process. For example: chinese patent No. CN201710953299.6, a preparation method of an ultrafine high-dispersion silver-tungsten electrical contact material; (2) chemical cladding-pressing-infiltration processes, such as: chinese patent No. CN201810328475.1 entitled Ag-W electrical contact material and preparation method thereof. The preparation method related to the patent directly presses and infiltrates the mixed powder or the powder coated chemically, and for the electric contact material with a slightly large size or a thicker size, the elimination of air holes and the melting and sucking of the foreign silver in the infiltration process have higher requirements, and the requirements on production, quality management control and production equipment are higher.
Disclosure of Invention
The invention aims to solve the technical problem of overcoming the defects and shortcomings of the prior art and provides a preparation method of a silver tungsten carbide electrical contact material for a circuit breaker.
In order to solve the technical problem, the solution of the invention is as follows:
the preparation method of the silver tungsten carbide electrical contact material for the circuit breaker comprises the following steps:
(1) placing Ag powder, WC powder and additive powder in a stirring device, and uniformly stirring to obtain a premix; the mass percentage of each component in the premix is as follows: 10-40% of Ag powder, 1.5-3% of additive powder and the balance of WC powder; the additive powder is formed by mixing and matching Fe powder, Ni powder and Co powder;
(2) pressing the obtained premix into blocks, crushing and sieving;
(3) mixing the sieved premix powder with Ag powder according to the mass ratio of 3.6-17: 1 to obtain AgWC mixed powder;
(4) sieving the mixed powder, and then pressing into blocks; crushing again and sieving;
(5) carrying out infiltration sintering on the sieved powder;
(Ag powder is coated on the surfaces of AgWC premixed crushed particles in the previous powder mixing process, the Ag powder is slightly melted or melted into liquid at high temperature during infiltration sintering, and the liquid is immersed into the AgWC premixed crushed particles under the action of capillary force to obtain AgWC powder particles with certain hardness and density.)
(6) Crushing and sieving the powder after infiltration and sintering;
(7) pressing the sieved powder to obtain an AgWC green body;
(8) placing an Ag block or an Ag sheet at the bottom of the AgWC green body, and carrying out infiltration sintering to obtain an AgWC electric contact material; the weight ratio of the Ag block or Ag sheet to the AgWC green body is 0.133-0.375: 1;
(Ag melts to liquid at high temperature and is immersed into AgWC green body under the action of capillary force to obtain AgWC electric contact material with uniformly dispersed particles)
(9) And cleaning the AgWC electric contact material after infiltration and sintering.
In the invention, in the step (1), the rotation speed is controlled to be 40-100 r/min during stirring, and the time is 6-16 hours.
In the invention, in the step (2), the pressing pressure is controlled to be 10-25 MPa, and the pressed block is a cylindrical or square block; if the square block is cylindrical, the diameter is 5-15 cm, and if the square block is square, the side length is 4-10 cm; the mesh number of the screen used for sieving is between 100 and 200 meshes.
In the step (3), the rotating speed of the stirring equipment is controlled to be 60-150 rpm during mixing, and the time is 6-16 hours.
In the invention, in the step (4), the pressing pressure is controlled to be 10-25 MPa, and the pressed block is a cylindrical or square block; if the square block is cylindrical, the diameter is 5-15 cm, and if the square block is square, the side length is 4-10 cm; the mesh number of the screen used for sieving is 50-150 meshes.
In the invention, in the step (5), the infiltration sintering is carried out in a reducing atmosphere (such as hydrogen gas and the like), the temperature is controlled to be 900-980 ℃ and the time is 1-4 hours.
In the invention, in the step (6), the mesh number of the screen used for sieving is 60-100 meshes.
In the invention, in the step (7), the pressing pressure is controlled to be between 5 and 15 MPa.
In the invention, in the step (8), the infiltration sintering is carried out in a reducing atmosphere (such as hydrogen gas and the like), the temperature is 1000-1150 ℃, and the time is 2-5 hours.
Description of the inventive principles:
the invention adopts a second-order powder mixing process, namely a powder mixing-pressing-crushing-powder mixing-pressing-crushing process, and adopts a twice powder mixing-pressing-crushing process, so that on one hand, Ag powder, WC powder and additive powder are primarily dispersed by powder mixing, and the powder particles are prevented from being greatly aggregated; on the other hand, the powder particles are repeatedly crushed, so that the powder particles are further crushed and dispersed, the silver particles and the WC particles are further dispersed and distributed in a dispersed manner, and the crushed mixed powder particles have a certain particle size and have fluidity in the process of pressing green bodies, so that the green bodies can reach the required size and morphology.
Dispersing AgWC powder by adopting a second-order powder mixing process, namely a powder mixing-pressing-crushing-powder mixing-pressing-crushing process, wherein finally crushed powder particles are in a dispersed state and have a certain particle size; and the silver dots are prepared by combining a second-order infiltration sintering process, namely a powder infiltration sintering-press molding-infiltration sintering process, so that the prepared silver dots have good wear resistance, and the fusion welding resistance and arc ablation resistance of the silver dots are greatly improved.
The AgWC electric contact material is prepared by adopting a second-order infiltration sintering process, the first-stage AgWC mixed powder and the second-stage AgWC electric contact material are infiltrated and sintered to discharge part of air holes in the sieved powder particles and the pressed green bodies respectively, the density of the single powder particles and the electric contact material is improved, and meanwhile, Ag is melted in the infiltration sintering process and filled into the AgWC powder particles and the AgWC green bodies through the capillary action. In addition, the infiltration sintering of the powder in the first stage effectively improves the infiltration of WC particles in the AgWC green body with Ag melt in the second stage infiltration process, the material density is improved, the AgWC green body is infiltrated and sintered at high temperature in the second stage of infiltration sintering, the external Ag and the green body are fused into a whole, the AgWC electric contact material becomes high-density, ablation-resistant and wear-resistant AgWC electric contact material, the infiltration sintering in the second stage can further improve the density of the AgWC electric contact material, the resistivity is reduced, and the AgWC electric contact material has good arc ablation resistance in later electrification use.
Compared with the prior art, the invention has the beneficial effects that:
1. compared with the AgWC electric contact material prepared by the traditional method, the mechanical life of the AgWC electric contact material prepared by the method is prolonged by 5-20%, and the electric life is prolonged by 10-30%;
2. the preparation method disclosed by the invention is simple to operate, high in yield and suitable for large-scale production.
Drawings
Fig. 1 is a metallographic structure diagram of an AgWC50 material prepared according to an embodiment of the present invention.
Detailed Description
The invention is described in detail below with reference to examples, which are intended to be illustrative only and not to be construed as limiting the scope of the invention, and many insubstantial modifications and variations of the invention can be made by an engineer skilled in the art based on the teachings of the invention.
The preparation method of the AgWC electric contact material for the circuit breaker, provided by the invention, can be implemented according to the following steps:
firstly, premixing Ag powder, WC powder and additive powder;
in the embodiment of the present invention, the parameters in this step may preferably adopt: the content of Ag powder is 10-40%; the total content of the additive powder is 1.5-3%, the additive elements are three elements of Fe, Ni and Co which are mixed and matched, and the balance is WC powder. Further, in some embodiments, the powder mixing speed is between 40 rpm and 100 rpm; the powder mixing time is 6-16 hours.
Secondly, pressing the AgWC premixed powder into blocks, crushing and sieving;
in the embodiment of the present invention, the parameters in this step may preferably adopt: the pressing pressure is 10-25 MPa, the pressed block is a cylindrical or square block, if the pressed block is cylindrical, the diameter is 5-15 cm, if the pressed block is square, the side length is 4-10 cm, and the mesh number of the screen is 100-200 meshes;
thirdly, mixing the sieved powder with a small amount of Ag powder to obtain AgWC mixed powder;
in the embodiment of the present invention, the parameters in this step may preferably adopt: the weight ratio of the sieved powder to the Ag powder is (3.6-17): 1. Further, in some embodiments, the powder mixing speed is between 60 rpm and 150 rpm; the powder mixing time is 6-16 hours.
Fourthly, pressing the sieved powder into blocks, crushing again and sieving;
in the embodiment of the present invention, the parameters in this step may preferably adopt: the pressing pressure is 10-25 MPa, the pressed block is a cylindrical or square block, if the pressed block is cylindrical, the diameter is 5-15 cm, if the pressed block is square, the side length is 4-10 cm, and the mesh number of the screen is 50-150 meshes;
fifthly, infiltration sintering is carried out on the sieved powder;
in the embodiment of the invention, in the infiltration sintering in the step, the Ag powder is coated on the surfaces of AgWC premixed and crushed particles in the powder mixing process, the Ag powder is micro-melted or melted into a liquid state at high temperature, and the liquid Ag powder is immersed into the AgWC premixed and crushed particles under the action of capillary force, so that AgWC powder particles with certain hardness and density are obtained. Specifically, infiltration sintering may be performed in a reducing gas, wherein the reducing gas may be hydrogen gas or the like; the temperature is 900-980 ℃, and the heat preservation time is 1-4 hours. In the step, on one hand, as the AgWC particles after sieving have a certain size, part of air holes in the particles are discharged in the infiltration sintering process, AgWC particles with certain hardness and density are formed, and a porous framework of AgWC small particles is formed; on the other hand, in the infiltration sintering process, the Ag powder is melted and absorbed into the AgWC small-particle porous framework, so that the dispersion uniformity of Ag and WC particles is further improved, and the smooth proceeding of the second-stage infiltration process is facilitated. The additive elements facilitate the sintering process.
Sixthly, crushing and sieving the powder after infiltration sintering;
in the embodiment of the present invention, the parameters in this step may preferably adopt: the mesh number of the screen is 60-100 meshes;
step seven, pressing the sieved powder to obtain an AgWC green body;
in the embodiment of the invention, the thickness of the AgWC green body is obtained according to the calculation required by the product, and the forming pressure is between 5 and 15 MPa.
And eighthly, carrying out infiltration sintering on the AgWC green body and Ag to obtain the AgWC electric contact material.
In the embodiment of the invention, the infiltration sintering in the step is to place Ag at the bottom of the AgWC green body, melt the Ag into liquid at high temperature, and immerse the Ag into the AgWC green body under the action of capillary force to obtain the AgWC electric contact material with uniformly dispersed particles. Specifically, infiltration sintering can be carried out in reducing gas, wherein the reducing gas can be hydrogen and the like, the infiltration temperature is 1000-1150 ℃, and the heat preservation time is 2-5 hours; the weight ratio of the Ag to the AgWC green body is 0.133-0.375: 1, and the Ag can be an Ag block or an Ag sheet.
And step nine, cleaning the AgWC electric contact material obtained after infiltration and sintering.
The detailed technical operation of the present invention is explained by the following examples of specific applications.
Example one
The embodiment provides a preparation method of an AgWC electric contact material for a circuit breaker, which comprises the following steps:
in the first step, 30 wt% of Ag powder, 1 wt% of Ni powder, 1.5 wt% of Fe powder, 0.5 wt% of Co powder and 67 wt% of WC powder are placed in a powder mixer for premixing, wherein the premixing rotating speed is 70 r/min, and the time is 10 hours.
Secondly, pressing the AgWC premixed powder obtained in the first step into blocks, wherein the pressing pressure is 15MPa, the pressed blocks are cylindrical and have the diameter of 10cm, crushing the blocks, and sieving the blocks by a 150-mesh sieve;
thirdly, mixing the sieved powder with a small amount of Ag powder, wherein the weight ratio of the sieved powder to the Ag powder is 3.6:1, and the powder mixing speed is 100 revolutions per minute; the mixing time was 10 hours.
Fourthly, pressing the sieved powder into blocks, wherein the pressing pressure is 10MPa, the pressed blocks are cylindrical and have the diameter of 10cm, and then crushing the blocks and sieving the blocks by a 100-mesh sieve;
and fifthly, carrying out infiltration sintering on the sieved powder, wherein the infiltration sintering is carried out in ammonia decomposition gas (mixed gas of hydrogen and nitrogen in a volume ratio of 3:1), the infiltration sintering temperature is 900 ℃, and the heat preservation time is 2 hours.
Sixthly, crushing the powder after infiltration and sintering, and sieving the powder by a 80-mesh sieve;
and seventhly, pressing the sieved powder to obtain an AgWC green body, wherein the forming pressure is 5 MPa.
And eighthly, carrying out infiltration sintering on the AgWC green blank and the Ag sheet to obtain the AgWC40 electric contact material, wherein the infiltration sintering is carried out in ammonia decomposition gas (mixed gas of hydrogen and nitrogen in a volume ratio of 3:1), the infiltration sintering temperature is 1000 ℃, the heat preservation time is 4 hours, and the weight ratio of the Ag sheet to the AgWC green blank is 0.375: 1.
And step nine, cleaning the AgWC40 electric contact material obtained after infiltration and sintering.
The AgWC40 electric contact material with good performance is finally obtained in the embodiment, wherein the silver point hardness HV5 is 135, the material tissue is dispersed uniformly, and the material is qualified after being subjected to 50 times of tests after being subjected to 6-time disjunction of 150A current.
Example two
The embodiment provides a preparation method of an AgWC electric contact material for a circuit breaker, which comprises the following steps:
in the first step, 20 wt% of Ag powder, 0.5 wt% of Ni powder, 1.0 wt% of Fe powder, 0.5 wt% of Co powder and 78 wt% of WC powder are placed in a powder mixer for premixing, wherein the premixing rotating speed is 40 r/min, and the time is 16 hours.
Secondly, pressing the AgWC premixed powder obtained in the first step into blocks, wherein the pressing pressure is 25MPa, the pressed blocks are cylindrical and have the diameter of 15cm, crushing the blocks, and sieving the blocks by a 100-mesh sieve;
thirdly, mixing the sieved powder with a small amount of Ag powder, wherein the weight ratio of the sieved powder to the Ag powder is 15:1, and the powder mixing speed is 60 revolutions per minute; the mixing time was 16 hours.
Fourthly, pressing the sieved powder into blocks, wherein the pressing pressure is 25MPa, the pressed blocks are cylindrical and have the diameter of 10cm, and then crushing the blocks and sieving the blocks by a 50-mesh sieve;
fifthly, carrying out infiltration sintering on the sieved powder in hydrogen at 980 ℃ for 4 hours.
Sixthly, crushing the powder after infiltration and sintering, and sieving the powder by a 60-mesh sieve;
and seventhly, pressing the sieved powder to obtain an AgWC green body, wherein the forming pressure is 15 MPa.
And eighthly, carrying out infiltration sintering on the AgWC green body and the Ag block to obtain the AgWC60 electric contact material, wherein the infiltration sintering is carried out in hydrogen, the infiltration sintering temperature is 1150 ℃, the heat preservation time is 5 hours, and the weight ratio of the Ag block to the AgWC green body is 0.25: 1.
And step nine, cleaning the AgWC60 electric contact material obtained after infiltration and sintering.
The AgWC60 electric contact material with good performance is finally obtained in the embodiment, wherein the silver point hardness HV5 is 265, the material tissue is dispersed uniformly, the current is 250A, and the electric life is qualified after 5000 tests.
EXAMPLE III
The embodiment provides a preparation method of an AgWC electric contact material for a circuit breaker, which comprises the following steps:
in the first step, 28 wt% of Ag powder, 0.3 wt% of Ni powder, 1.0 wt% of Fe powder, 0.2 wt% of Co powder and 70.5 wt% of WC powder are placed in a powder mixer for premixing, wherein the premixing rotating speed is 100 revolutions per minute, and the time is 6 hours.
Secondly, pressing the AgWC premixed powder obtained in the first step into blocks, wherein the pressing pressure is 10MPa, the pressed blocks are cylindrical and have the diameter of 5cm, crushing the blocks, and sieving the blocks by a 200-mesh sieve;
thirdly, mixing the sieved powder with a small amount of Ag powder, wherein the weight ratio of the sieved powder to the Ag powder is 9.3:1, the powder mixing speed is 150 r/min, and the powder mixing time is 6 hours;
fourthly, pressing the sieved powder into blocks, wherein the pressing pressure is 15MPa, the pressed blocks are square, the side length is 8cm, and then crushing the blocks and sieving the blocks by a 150-mesh sieve;
and fifthly, carrying out infiltration sintering on the sieved powder, wherein the infiltration sintering is carried out in methane gas, the infiltration sintering temperature is 950 ℃, and the heat preservation time is 1 hour.
Sixthly, crushing the powder after infiltration and sintering, and sieving the powder by a 100-mesh sieve;
and seventhly, pressing the sieved powder to obtain an AgWC green body, wherein the forming pressure is 10 MPa.
And eighthly, carrying out infiltration sintering on the AgWC green body and the Ag block to obtain the AgWC50 electric contact material, wherein the infiltration sintering is carried out in propane gas, the infiltration sintering temperature is 1100 ℃, the heat preservation time is 2 hours, and the weight ratio of the Ag block to the AgWC green body is 0.3: 1.
And step nine, cleaning the AgWC50 electric contact material obtained after infiltration and sintering.
The AgWC50 electric contact material with good performance is finally obtained in the embodiment, wherein the silver point hardness HV5 is 195, the material tissue is dispersed uniformly, the current is 100A, and the electric contact material is qualified after a short circuit test is operated.
Example four
The embodiment provides a preparation method of an AgWC electric contact material for a circuit breaker, which comprises the following steps:
in the first step, 10 wt% of Ag powder, 1 wt% of Ni powder, 1.5 wt% of Fe powder, 0.5 wt% of Co powder and 87 wt% of WC powder are placed in a powder mixer for premixing, wherein the premixing rotating speed is 70 r/min, and the time is 10 hours.
Secondly, pressing the AgWC premixed powder obtained in the first step into blocks, wherein the pressing pressure is 10MPa, the pressed blocks are square, the side length is 4cm, and then crushing the blocks and sieving the blocks by a 150-mesh sieve;
thirdly, mixing the sieved powder with a small amount of Ag powder, wherein the weight ratio of the sieved powder to the Ag powder is 17:1, and the powder mixing speed is 80 r/min; the mixing time was 12 hours.
Fourthly, pressing the sieved powder into blocks, wherein the pressing pressure is 18MPa, the pressed blocks are cylindrical and have the diameter of 12cm, and then crushing the blocks and sieving the blocks by a 50-mesh sieve;
and fifthly, carrying out infiltration sintering on the sieved powder, wherein the infiltration sintering is carried out in ammonia decomposition gas (mixed gas of hydrogen and nitrogen in a volume ratio of 3:1), the infiltration sintering temperature is 980 ℃, and the heat preservation time is 3 hours.
Sixthly, crushing the powder after infiltration and sintering, and sieving the powder by a 60-mesh sieve;
and seventhly, pressing the sieved powder to obtain an AgWC green body, wherein the forming pressure is 6 MPa.
And eighthly, carrying out infiltration sintering on the AgWC green body and the Ag sheet to obtain the AgWC75 electric contact material, wherein the infiltration sintering is carried out in methane gas, the infiltration sintering temperature is 1150 ℃, the heat preservation time is 5 hours, and the weight ratio of the Ag sheet to the AgWC green body is 0.133: 1.
And step nine, cleaning the AgWC75 electric contact material obtained after infiltration and sintering.
The AgWC75 electric contact material with better performance is finally obtained in the embodiment, wherein the silver point hardness HV5 is 295, the material tissue is dispersed uniformly, and the material is qualified after being subjected to 50-time test by 6-time breaking of 200A current.
EXAMPLE five
The embodiment provides a preparation method of an AgWC electric contact material for a circuit breaker, which comprises the following steps:
in the first step, 40 wt% of Ag powder, 0.3 wt% of Ni powder, 1.0 wt% of Fe powder, 0.2 wt% of Co powder and 58.5 wt% of WC powder are placed in a powder mixer for premixing, wherein the premixing rotating speed is 100 revolutions per minute, and the time is 6 hours.
Secondly, pressing the AgWC premixed powder obtained in the first step into blocks, wherein the pressing pressure is 25MPa, the pressed blocks are square, the side length is 10cm, and then crushing the blocks and sieving the blocks by a 100-mesh sieve;
thirdly, mixing the sieved powder with a small amount of Ag powder, wherein the weight ratio of the sieved powder to the Ag powder is 11:1, and the powder mixing speed is 60 revolutions per minute; the mixing time was 16 hours.
Fourthly, pressing the sieved powder into blocks, wherein the pressing pressure is 25MPa, the pressed blocks are square, the side length is 10cm, and then crushing the blocks and sieving the blocks by a 100-mesh sieve;
fifthly, carrying out infiltration sintering on the sieved powder in hydrogen at 900 ℃ for 2 hours.
Sixthly, crushing the powder after infiltration and sintering, and sieving the powder by a 60-mesh sieve;
and seventhly, pressing the sieved powder to obtain an AgWC green body, wherein the forming pressure is 12 MPa.
And eighthly, carrying out infiltration sintering on the AgWC green blank and the Ag sheet to obtain the AgWC45 electric contact material, wherein the infiltration sintering is carried out in ammonia decomposition gas (mixed gas of hydrogen and nitrogen in a volume ratio of 3:1), the infiltration sintering temperature is 1000 ℃, the heat preservation time is 4 hours, and the weight ratio of the Ag sheet to the AgWC green blank is 0.222: 1.
And step nine, cleaning the AgWC45 electric contact material obtained after infiltration and sintering.
The AgWC45 electric contact material with good performance is finally obtained in the embodiment, wherein the silver point hardness HV5 is 160, the material tissue is dispersed uniformly, and the 150A current electric life is up to 10000 times.
EXAMPLE six
The embodiment provides a preparation method of an AgWC electric contact material for a circuit breaker, which comprises the following steps:
in the first step, 40 wt% of Ag powder, 0.3 wt% of Ni powder, 1.0 wt% of Fe powder, 0.2 wt% of Co powder and 58.5 wt% of WC powder are placed in a powder mixer for premixing, wherein the premixing rotating speed is 100 revolutions per minute, and the time is 6 hours.
Secondly, pressing the AgWC premixed powder obtained in the first step into blocks, wherein the pressing pressure is 15MPa, the pressed blocks are square, the side length is 8cm, and then crushing the blocks and sieving the blocks by a 200-mesh sieve;
thirdly, mixing the sieved powder with a small amount of Ag powder, wherein the weight ratio of the sieved powder to the Ag powder is 11:1, and the powder mixing speed is 60 revolutions per minute; the mixing time was 16 hours.
Fourthly, pressing the sieved powder into blocks, wherein the pressing pressure is 10MPa, the pressed blocks are square, the side length is 4cm, and then crushing the blocks and sieving the blocks by a sieve of 80 meshes;
and fifthly, carrying out infiltration sintering on the sieved powder, wherein the infiltration sintering is carried out in propane gas, the infiltration sintering temperature is 900 ℃, and the heat preservation time is 2 hours.
Sixthly, crushing the powder after infiltration and sintering, and sieving the powder by a 100-mesh sieve;
and seventhly, pressing the sieved powder to obtain an AgWC green body, wherein the forming pressure is 12 MPa.
And eighthly, carrying out infiltration sintering on the AgWC green blank and the Ag sheet to obtain the AgWC45 electric contact material, wherein the infiltration sintering is carried out in ammonia decomposition gas (mixed gas of hydrogen and nitrogen in a volume ratio of 3:1), the infiltration sintering temperature is 1000 ℃, the heat preservation time is 4 hours, and the weight ratio of the Ag sheet to the AgWC green blank is 0.222: 1.
And step nine, cleaning the AgWC45 electric contact material obtained after infiltration and sintering.
The AgWC45 electric contact material with good performance is finally obtained in the embodiment, wherein the silver point hardness HV5 is 155, the material tissue is dispersed uniformly, the current is 100A, and the material is qualified after a limit short circuit test.
As shown in fig. 1, the metallographic structure of the AgWC50 material obtained in the above embodiment of the present invention is as follows: the silver particles and the WC particles are in dispersion distribution, the silver particles are in a slender strip shape, the WC particles are wrapped in the silver particles, and small-size silver particles are clamped in part of the WC particles.
The above description is only a partial example of the present invention and is not intended to limit the technical scope of the present invention, and any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A preparation method of a silver tungsten carbide electric contact material for a circuit breaker is characterized by comprising the following steps:
(1) placing Ag powder, tungsten carbide powder and additive powder in a stirring device, and uniformly stirring to obtain a premix; the mass percentage of each component in the premix is as follows: 10-40% of Ag powder, 1.5-3% of additive powder and the balance of WC powder; the additive powder is formed by mixing and matching Fe powder, Ni powder and Co powder;
(2) pressing the obtained premix into blocks, crushing and sieving;
(3) mixing the sieved premix powder with Ag powder according to the mass ratio of 3.6-17: 1 to obtain AgWC mixed powder;
(4) sieving the mixed powder, and then pressing into blocks; crushing again and sieving;
(5) carrying out infiltration sintering on the sieved powder;
(6) crushing and sieving the powder after infiltration and sintering;
(7) pressing the sieved powder to obtain an AgWC green body;
(8) placing an Ag block or an Ag sheet at the bottom of the AgWC green body, and carrying out infiltration sintering to obtain an AgWC electric contact material; the weight ratio of the Ag block or Ag sheet to the AgWC green body is 0.133-0.375: 1;
(9) and cleaning the AgWC electric contact material after infiltration and sintering.
2. The method according to claim 1, wherein in the step (1), the rotation speed is controlled to be between 40 and 100 revolutions per minute for 6 to 16 hours during stirring.
3. The method according to claim 1, wherein in the step (2), the pressing pressure is controlled to be 10-25 MPa, and the pressed block is a cylindrical or square block; if the square block is cylindrical, the diameter is 5-15 cm, and if the square block is square, the side length is 4-10 cm; the mesh number of the screen used for sieving is between 100 and 200 meshes.
4. The method according to claim 1, wherein in the step (3), the rotation speed of the stirring device is controlled to be 60-150 rpm for 6-16 hours during the mixing.
5. The method according to claim 1, wherein in the step (4), the pressing pressure is controlled to be 10-25 MPa, and the pressed block is a cylindrical or square block; if the square block is cylindrical, the diameter is 5-15 cm, and if the square block is square, the side length is 4-10 cm; the mesh number of the screen used for sieving is 50-150 meshes.
6. The method according to claim 1, wherein in the step (5), the infiltration sintering is performed in a reducing atmosphere, and the temperature is controlled to be 900-980 ℃ for 1-4 hours.
7. The method according to claim 1, wherein in the step (6), the mesh number of the screen used for screening is 60 to 100 meshes.
8. The method according to claim 1, wherein in the step (7), the pressing pressure is controlled to be between 5 and 15 MPa.
9. The method according to claim 1, wherein in the step (8), the infiltration sintering is performed in a reducing atmosphere at a temperature of 1000 to 1150 ℃ for 2 to 5 hours.
10. The method of claim 6 or 9, wherein the reducing atmosphere is hydrogen or ammonia decomposition gas.
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| CN113245548A (en) * | 2021-05-27 | 2021-08-13 | 攀时（上海）高性能材料有限公司 | Infiltration processing technology and silver-tungsten contact material prepared by same |
| CN114086023A (en) * | 2021-11-10 | 2022-02-25 | 浙江福达合金材料科技有限公司 | Method for preparing copper-based electric contact material based on foaming infiltration process and product thereof |
| CN114086022A (en) * | 2021-11-10 | 2022-02-25 | 浙江福达合金材料科技有限公司 | Method for preparing Ag-based tungsten-containing electric contact material based on foaming infiltration process and product thereof |
| CN116904787A (en) * | 2023-07-14 | 2023-10-20 | 苏州市希尔孚新材料股份有限公司 | Preparation method of silver-saving high-performance silver tungsten carbide nickel contact |
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