CN111618297B - Preparation method of rapid sintering forming silver-based contact - Google Patents
Preparation method of rapid sintering forming silver-based contact Download PDFInfo
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- CN111618297B CN111618297B CN202010316707.9A CN202010316707A CN111618297B CN 111618297 B CN111618297 B CN 111618297B CN 202010316707 A CN202010316707 A CN 202010316707A CN 111618297 B CN111618297 B CN 111618297B
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- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 title claims abstract description 72
- 229910052709 silver Inorganic materials 0.000 title claims abstract description 59
- 239000004332 silver Substances 0.000 title claims abstract description 59
- 238000005245 sintering Methods 0.000 title claims abstract description 56
- 238000002360 preparation method Methods 0.000 title description 10
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 74
- 238000000034 method Methods 0.000 claims abstract description 73
- 239000010439 graphite Substances 0.000 claims abstract description 64
- 229910002804 graphite Inorganic materials 0.000 claims abstract description 64
- UYKQQBUWKSHMIM-UHFFFAOYSA-N silver tungsten Chemical compound [Ag][W][W] UYKQQBUWKSHMIM-UHFFFAOYSA-N 0.000 claims abstract description 54
- 239000000843 powder Substances 0.000 claims abstract description 35
- UONOETXJSWQNOL-UHFFFAOYSA-N tungsten carbide Chemical compound [W+]#[C-] UONOETXJSWQNOL-UHFFFAOYSA-N 0.000 claims abstract description 34
- 238000002156 mixing Methods 0.000 claims abstract description 24
- 238000010438 heat treatment Methods 0.000 claims abstract description 22
- 238000000498 ball milling Methods 0.000 claims abstract description 17
- 239000000203 mixture Substances 0.000 claims abstract description 12
- 239000011812 mixed powder Substances 0.000 claims abstract description 7
- 238000005303 weighing Methods 0.000 claims abstract description 5
- 238000012545 processing Methods 0.000 claims abstract description 4
- 238000004381 surface treatment Methods 0.000 claims description 16
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 15
- 229920002545 silicone oil Polymers 0.000 claims description 14
- 239000008367 deionised water Substances 0.000 claims description 12
- 229910021641 deionized water Inorganic materials 0.000 claims description 12
- 239000007788 liquid Substances 0.000 claims description 12
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 11
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 claims description 11
- 239000002245 particle Substances 0.000 claims description 10
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 claims description 10
- 239000003995 emulsifying agent Substances 0.000 claims description 9
- 238000005507 spraying Methods 0.000 claims description 9
- 238000010329 laser etching Methods 0.000 claims description 8
- 239000000463 material Substances 0.000 claims description 8
- 238000001291 vacuum drying Methods 0.000 claims description 8
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 7
- 238000000465 moulding Methods 0.000 claims description 7
- 229910017604 nitric acid Inorganic materials 0.000 claims description 7
- 238000002490 spark plasma sintering Methods 0.000 claims description 7
- 238000001816 cooling Methods 0.000 claims description 5
- 230000003628 erosive effect Effects 0.000 claims description 5
- 230000003647 oxidation Effects 0.000 claims description 5
- 238000007254 oxidation reaction Methods 0.000 claims description 5
- 238000005406 washing Methods 0.000 claims description 5
- 238000007664 blowing Methods 0.000 claims description 4
- 239000012530 fluid Substances 0.000 claims description 4
- 239000012300 argon atmosphere Substances 0.000 claims description 3
- 238000001514 detection method Methods 0.000 claims description 3
- 238000005530 etching Methods 0.000 claims description 3
- 238000003754 machining Methods 0.000 claims description 3
- 238000005498 polishing Methods 0.000 claims description 3
- 230000001681 protective effect Effects 0.000 claims description 3
- 239000000725 suspension Substances 0.000 claims description 3
- 239000012298 atmosphere Substances 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 abstract description 11
- 230000009286 beneficial effect Effects 0.000 abstract description 3
- 230000000694 effects Effects 0.000 description 15
- 230000008595 infiltration Effects 0.000 description 13
- 238000001764 infiltration Methods 0.000 description 13
- 238000012360 testing method Methods 0.000 description 11
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 9
- 238000002474 experimental method Methods 0.000 description 7
- 238000002844 melting Methods 0.000 description 6
- 230000008018 melting Effects 0.000 description 6
- 238000011056 performance test Methods 0.000 description 6
- 239000010937 tungsten Substances 0.000 description 5
- 229910052721 tungsten Inorganic materials 0.000 description 5
- 230000033228 biological regulation Effects 0.000 description 4
- 239000007769 metal material Substances 0.000 description 4
- 229910052759 nickel Inorganic materials 0.000 description 4
- 229910000510 noble metal Inorganic materials 0.000 description 4
- 239000011148 porous material Substances 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 3
- 230000000704 physical effect Effects 0.000 description 3
- 238000000137 annealing Methods 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 230000003631 expected effect Effects 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 238000010998 test method Methods 0.000 description 2
- 239000002699 waste material Substances 0.000 description 2
- 238000007546 Brinell hardness test Methods 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000007795 chemical reaction product Substances 0.000 description 1
- 238000013329 compounding Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 230000004927 fusion Effects 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000000462 isostatic pressing Methods 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 238000005086 pumping Methods 0.000 description 1
- 238000007493 shaping process Methods 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
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- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/10—Sintering only
- B22F3/105—Sintering only by using electric current other than for infrared radiant energy, laser radiation or plasma ; by ultrasonic bonding
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D3/00—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials
- B05D3/002—Pretreatement
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- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
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- B05D3/00—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials
- B05D3/10—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials by other chemical means
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- B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
- B05D7/22—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials to internal surfaces, e.g. of tubes
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C1/00—Making non-ferrous alloys
- C22C1/04—Making non-ferrous alloys by powder metallurgy
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- C22C29/02—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides
- C22C29/06—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides based on carbides, but not containing other metal compounds
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Abstract
The invention discloses a method for preparing a rapid sintering formed silver-based contact, which mainly comprises the following steps: s1: weighing tungsten carbide powder and silver powder according to the weight of the contact type prepared according to the required requirements to obtain a mixture ratio, wherein the content of tungsten carbide is 20-80 wt%, and the balance is silver; s2: putting the weighed powder into a mixer for ball milling, and putting the mixed powder into a graphite die after ball milling and mixing; s3: placing the graphite mold into a discharge plasma sintering device, pre-vacuumizing to below 10pa, and heating and pressure sintering; s4: and (4) performing small amount of fine processing on the blank prepared by sintering to obtain the silver tungsten carbide contact. The invention has simple process, high production efficiency and low cost, and is beneficial to the popularization and the application of the silver-based contact.
Description
Technical Field
The invention relates to the technical field of noble metal material manufacturing, in particular to a method for preparing a rapid sintering formed silver-based contact.
Background
The silver has stable chemical property, low activity, good heat conductivity and good electric conductivity. Tungsten carbide and tungsten have excellent fusion welding resistance, low contact resistance and high electric wear resistance. Therefore, silver tungsten carbide and silver tungsten contacts are widely used in electrical contact materials. Particularly, in vacuum contactors and load switches, electrical life is required several tens of thousands times, and thus, high tungsten carbide or tungsten content is required to maintain electrical wear, and in medium and low voltage vacuum contactors and loads, silver tungsten carbide and silver tungsten contacts are applied to high-end products because of excellent electrical conductivity and a lower cutoff value (below 0.8A), but are not widely applied because of the high price of the noble metal Ag.
The melting point of silver is different from the melting points of tungsten carbide and tungsten greatly, so that the silver tungsten carbide or the silver tungsten contact can only be prepared by adopting an infiltration method; in the infiltration process, excessive silver content is needed to ensure the infiltration sufficiency, and the high-temperature infiltration method has more silver volatilization, so that the cost of silver tungsten carbide and silver tungsten contacts is further increased, and the infiltration process cannot be popularized and used in a large range; the melting point of tungsten carbide is 2870 ℃, the melting point of tungsten is 3410 ℃, the melting point of silver is 961 ℃, and the melting points of silver tungsten and silver tungsten carbide are greatly different. The process has the characteristics that the silver tungsten carbide or silver tungsten contact with high tungsten carbide or tungsten content can be prepared, but the product prepared by the infiltration method has low dimensional precision, and in order to ensure sufficient infiltration, silver with 1-2 times of the actual silver content is needed for infiltration, so that the infiltration sufficiency is ensured; therefore, the waste of the noble metal silver is large, the process time is long, and the production efficiency is low.
Patent CN201410711779 discloses a preparation method of a silver tungsten carbide contact material, which comprises the steps of boiling silver powder and tungsten carbide powder, then carrying out ball milling on the mixture with nickel balls and water, drying the obtained powder, annealing, carrying out press forming, and carrying out infiltration treatment to obtain a blank. Compared with the patent, the method has great difference in process flow, and the profiling method and the infiltration method are different from the patent;
Patent CN201410714850 patent has announced a silver tungsten carbide nickel contact material and preparation method thereof, and similar to above-mentioned patent, this patent need not add third element nickel, is favorable to improving the material conductivity to it is simpler and more easy to mix the powder process, need not add water and mixes, processes such as follow-up drying, annealing, shaping. The silver tungsten carbide contact blank with the density of more than 97 percent can be directly prepared, and the material utilization rate is high.
The traditional infiltration method is adopted to prepare the silver tungsten carbide, in order to improve the wettability of silver and tungsten carbide, a small amount of nickel powder needs to be added in the powder mixing process, and the mixed powder is dried, annealed, destressed and pressed to form.
Disclosure of Invention
In order to solve the technical problem, the invention provides a method for preparing a silver-based contact through rapid sintering molding.
The technical scheme of the invention is as follows: a method for preparing a silver-based contact formed by rapid sintering mainly comprises the following steps:
S1, batching: weighing tungsten carbide powder and silver powder according to the weight of the contact type prepared according to the required requirements to obtain a mixture ratio, wherein the content of tungsten carbide is 20-80 wt%, and the balance is silver;
s2 powder mixing: putting the weighed powder into a mixer for ball milling, and putting the mixed powder into a graphite die after ball milling and mixing;
s3 sintering: placing the graphite mold into a discharge plasma sintering device, pre-vacuumizing to below 10pa, and heating and pressure sintering;
s4 machining: and (4) performing small amount of fine processing on the blank prepared by sintering to obtain the silver tungsten carbide contact.
Further, in the step S1, the particle size of the tungsten carbide powder is 0.1-10 μm, the particle size of the silver powder is 1-50 μm, and the purity is more than 99.5%. The granularity of the tungsten carbide powder and the silver powder is limited in the granularity interval, so that the prepared silver tungsten carbide contact can meet the basic performance of the silver-based contact.
Further, in the step S1, the tungsten carbide powder may be replaced by tungsten powder to prepare a silver-tungsten contact, wherein the particle size of the tungsten powder is 0.1-10 μm. The process can replace tungsten carbide powder with tungsten powder to prepare the silver-tungsten contact, and the silver-tungsten carbide contact or the silver-tungsten contact can be prepared by the process, so that the production efficiency is high, the use and waste of silver are reduced, and the popularization and the use of the silver-based contact are facilitated.
Further, in the step S2, in the ball milling and mixing, the ball milling tank is protected by vacuum or atmosphere, the ball material ratio is 1 (1-5), and the powder mixing time is 3-10 h. The conventional ball milling and powder mixing are adopted, the process is simple, the production efficiency is high, and compared with the existing silver-based contact production technology, the process is simpler and the cost is low.
Further, the graphite mold used in step S2 is made of high-purity, isostatic-pressing graphite, and the inner layer of the graphite mold is subjected to a surface treatment.
Still further, the surface treatment step of the graphite mold includes:
1) coarsening the inner surface of the graphite mold through laser etching, and then carrying out oxidation erosion on the inner surface of the graphite mold for 1-3 min by using nitric acid with the concentration of 90%; the treatment liquid can be easily attached to the inner surface of the graphite mold through laser etching and nitric acid oxidation erosion, so that the surface treatment effect of the graphite mold is improved;
2) repeatedly washing with deionized water for many times, and then placing in a vacuum drying oven for vacuum drying; repeatedly washing by deionized water to remove residual nitric acid, carrying out vacuum drying to remove residual water so as to avoid influencing the dosage concentration of the treatment solution, and avoiding influencing the subsequent surface treatment effect of the graphite mold by the treatment;
3) Placing the dried graphite mold in an argon atmosphere protective environment, heating the graphite mold through contact resistance, and spraying the treatment liquid under the spraying pressure of 0.6-0.8 MPa and the spraying dose of 12-15 g/cm2Blowing to the inner surface thereof; the treatment liquid can be made to be internal by heating the inner surface of the graphite mold with contact resistance and blowing the treatment liquid on the inner surfaceThe graphite particles are quickly and uniformly attached to the inner surface of the graphite mold, so that the expected effect of surface treatment of the graphite mold is achieved;
4) carrying out surface flatness detection on the inner surface of the graphite mold, repeating the steps 2) to 3) if the surface still has etching traces until the surface is flat, and then polishing the inner surface of the graphite mold to obtain the graphite mold after surface treatment;
the treating fluid is prepared from silicon carbide powder, graphite powder, silicon dioxide powder, deionized water, silicone oil and an emulsifier according to a weight ratio of 4: 2: 1: (12-18): (3-7): 1 to form a suspension, wherein the particle sizes of the silicon carbide powder, the graphite powder and the silicon dioxide powder are 0.5-2 mu m; the emulsifier is added to emulsify the silicone oil and mix with the deionized water, and the heat conduction effect and the wear resistance of the inner surface of the graphite mold can be further enhanced by adding the silicon carbide powder, the silicon dioxide powder, the silicone oil and the like, so that the physical properties of the silver tungsten carbide contact and the silver tungsten contact after the discharge plasma sintering preparation are further improved.
The preparation method of the treatment fluid comprises the following steps: firstly, mixing silicone oil and an emulsifier to obtain emulsified silicone oil, then mixing the emulsified silicone oil with deionized water, finally, uniformly mixing silicon carbide powder, graphite powder and silicon dioxide powder, then adding the mixture into the mixture, uniformly stirring the mixture to form turbid liquid, and using the treating liquid as required.
Furthermore, the laser etching parameters are as follows: selecting pulse laser capable of exciting 60-90 ns, wherein the repetition frequency is 5-8 kHz, and the output power of the laser is 40-50W.
Further, the spark plasma sintering process in step S3 is specifically as follows: 1) pre-vacuumizing to below 10pa, raising the temperature to 400-480 ℃ at a temperature raising rate of 65-80 ℃/min under an initial pressure of 150-170 MPa; 2) boosting the pressure to 160-180 MPa, and raising the temperature to 570-650 ℃ at the speed of 40-55 ℃/min; 3) heating to 800-950 ℃ at the speed of 90-120 ℃/min, reducing the pressure to 50-80 MPa at the speed of 10MPa/min during the heating, keeping the temperature and the pressure for 15-25 seconds, carrying out air cooling to room temperature at the wind speed of 6-9 m/s, and then releasing the pressure to take out the blank. The sintering effect of the silver-based contact is controlled by the pressure change adjustment and the temperature regulation rate in the discharge plasma sintering process, internal pores are eliminated by the sintering processes of rapid temperature rise and pressure rise, slow temperature rise and pressure rise, rapid temperature rise and pressure drop and the like, the sintering density of the silver-based contact is improved, and therefore the relevant performance parameters of the silver-based contact are further improved.
Furthermore, the sintering temperature of the discharge plasma is 800-950 ℃, the pulse frequency is 0-50 Hz, and the pressure is 50-180 Mpa. The effect of sintering the discharge plasma under the parameters enables the discharge plasma to be effectively matched with a graphite mould to prepare the silver-based contact, and the silver-based contact meets the requirement of achieving the service performance.
The invention has the beneficial effects that:
(1) the process powder mixing method is simple, and impurity elements such as nickel and the like are not added to improve infiltration wettability; the powder is directly sintered and molded, the process is simple, and the production efficiency is high; can be precisely formed, reduces the use of silver and saves noble metal silver.
(2) The process method of the invention does not need to add a third element in the powder mixing process, adopts the conventional ball milling powder mixing, then fills the mixed powder in the graphite die after surface treatment, adopts discharge plasma to rapidly sinter, directly forms the mixed powder into a size close to the forming size, has simple process, high production efficiency and low cost, and is beneficial to the popularization and the application of the silver-based contact.
(3) The process method of the invention carries out surface treatment on the graphite mould so as to improve the service life and sintering preparation effect of the graphite mould, so that the graphite mould is heated uniformly and the thermal conductivity of the graphite mould is enhanced, and the physical properties of the silver tungsten carbide and the silver tungsten contact after the discharge plasma sintering preparation are improved.
Drawings
FIG. 1 is a process flow diagram of the process of the present invention.
Figure 2 is a metallographic X100X photograph of a silver tungsten carbide contact made by the process of the present invention.
Detailed Description
Example 1
A method for preparing a silver-based contact formed by rapid sintering mainly comprises the following steps:
s1, batching: weighing tungsten carbide powder and silver powder according to the weight of the contact type prepared according to the required requirements to obtain a mixture ratio, wherein the content of tungsten carbide is 50.2 wt%, and the balance is silver; the granularity of the tungsten carbide powder is 0.1-10 mu m, the granularity of the silver powder is 1-50 mu m, the purity is more than 99.5 percent, and the granularity of the tungsten carbide powder and the silver powder is limited in the granularity interval so as to ensure that the prepared silver tungsten carbide contact can meet the basic performance of the silver-based contact;
s2 powder mixing: the weighed powder is put into a mixer for ball milling, the ball milling tank adopts internal vacuum pumping protection, the ball-material ratio is 1:3, the powder mixing time is 6h, the mixed powder is put into a graphite die after ball milling and mixing, the conventional ball milling and powder mixing are adopted, the process is simple, the production efficiency is high, and compared with the existing silver-based contact production technology, the process is simpler and the cost is low;
s3 sintering: placing the graphite mold into a discharge plasma sintering device, pre-vacuumizing to below 10pa, and heating and pressure sintering; the sintering temperature is 870 ℃, the pulse frequency is 35Hz, the pressure is 175Mpa, and the effect of sintering the discharge plasma is carried out under the parameters, so that the silver-based contact is effectively prepared by matching with a graphite mold, and the silver-based contact meets the use performance;
S4 machining: and (4) performing small amount of fine processing on the blank prepared by sintering to obtain the silver tungsten carbide contact.
Example 2
This example is substantially the same as example 2, except that the spark plasma sintering process in step S3 is as follows: 1) pre-vacuumizing to below 10pa, raising the temperature to 400 ℃ at a temperature rise rate of 65 ℃/min under the initial pressure of 150 MPa; 2) boosting the pressure to 175MPa, and raising the temperature to 570 ℃ at the speed of 40 ℃/min; 3) heating to 870 ℃ at the speed of 90 ℃/min, reducing the pressure to 50MPa at the speed of 10MPa/min during the heating, keeping the temperature and the pressure for 15 seconds, carrying out air cooling to room temperature at the wind speed of 6m/s, and then releasing the pressure to take out the blank. The sintering effect of the silver-based contact is controlled by the pressure change adjustment and the temperature regulation rate in the discharge plasma sintering process, internal pores are eliminated by the sintering processes of rapid temperature rise and pressure rise, slow temperature rise and pressure rise, rapid temperature rise and pressure drop and the like, the sintering density of the silver-based contact is improved, and therefore the relevant performance parameters of the silver-based contact are further improved.
Example 3
This example is substantially the same as example 2, except that the spark plasma sintering process in step S3 is as follows: 1) pre-vacuumizing to below 10pa, starting pressure is 165MPa, and heating to 455 ℃ at a heating rate of 75 ℃/min; 2) boosting the pressure to 175MPa, and raising the temperature to 630 ℃ at the speed of 50 ℃/min; 3) heating to 870 ℃ at the speed of 110 ℃/min, reducing the pressure to 75MPa at the speed of 10MPa/min during the heating, keeping the temperature and the pressure for 23 seconds, carrying out air cooling to room temperature at the wind speed of 7m/s, and then releasing the pressure to take out the blank. The sintering effect of the silver-based contact is controlled by the pressure change adjustment and the temperature regulation rate in the discharge plasma sintering process, internal pores are eliminated by the sintering processes of rapid temperature rise and pressure rise, slow temperature rise and pressure rise, rapid temperature rise and pressure drop and the like, the sintering density of the silver-based contact is improved, and therefore the relevant performance parameters of the silver-based contact are further improved.
Example 4
This example is substantially the same as example 2, except that the spark plasma sintering process in step S3 is as follows: 1) pre-vacuumizing to below 10pa, starting pressure is 170MPa, and heating to 480 ℃ at a heating rate of 80 ℃/min; 2) boosting the pressure to 175MPa, and raising the temperature to 650 ℃ at the speed of 55 ℃/min; 3) heating to 870 ℃ at the speed of 120 ℃/min, reducing the pressure to 80MPa at the speed of 10MPa/min during the heating period, keeping the temperature and the pressure for 25 seconds, carrying out air cooling to room temperature at the wind speed of 9m/s, and then releasing the pressure to take out the blank. The sintering effect of the silver-based contact is controlled by the pressure change adjustment and the temperature regulation rate in the discharge plasma sintering process, internal pores are eliminated by the sintering processes of rapid temperature rise and pressure rise, slow temperature rise and pressure rise, rapid temperature rise and pressure drop and the like, the sintering density of the silver-based contact is improved, and therefore the relevant performance parameters of the silver-based contact are further improved.
Example 5
This embodiment is substantially the same as embodiment 1, except that the compounding in step S1: weighing tungsten carbide powder and silver powder according to the weight of the contact type prepared according to the required requirements to obtain a mixture ratio, wherein the content of tungsten carbide is 59.8 wt%, and the balance is silver; the granularity of the tungsten carbide powder is 0.1-10 mu m, the granularity of the silver powder is 1-50 mu m, the purity is more than 99.5%, and the granularity of the tungsten carbide powder and the silver powder is limited in the granularity interval, so that the prepared silver tungsten carbide contact can meet the basic performance of the silver-based contact.
Example 6
This example is substantially the same as example 1, except that the graphite mold used in step S2 has its inner layer surface-treated.
The surface treatment step of the graphite mold comprises the following steps:
1) coarsening the inner surface of the graphite mold through laser etching, and then carrying out oxidation erosion on the inner surface of the graphite mold for 2min by adopting nitric acid with the concentration of 90%, wherein the laser etching parameters are as follows: selecting pulse laser capable of exciting 80ns, wherein the repetition frequency is 6kHz, and the output power of the laser is 45W; the treatment liquid can be easily attached to the inner surface of the graphite mold through laser etching and nitric acid oxidation erosion, so that the surface treatment effect of the graphite mold is improved;
2) repeatedly washing with deionized water for many times, then placing in a vacuum drying oven for vacuum drying, repeatedly washing with deionized water to remove residual nitric acid, performing vacuum drying to remove residual moisture so as to avoid influencing the dosage concentration of the treatment solution, and avoiding influencing the subsequent surface treatment effect of the graphite mold through the treatment;
3) placing the dried graphite mold in an argon atmosphere protective environment, heating the inner surface of the graphite mold by using contact resistance between a carbon rod and the graphite mold, and spraying the treatment solution at a spraying pressure of 0.7MPa and a spraying dose of 14g/cm 2Blowing to the inner surface; the inner surface of the graphite mould is heated through the contact resistance, and the treatment liquid is sprayed and blown on the inner surface of the graphite mould, so that the components in the treatment liquid can be quickly and uniformly attached to the inner surface of the graphite mould, and the expected effect of surface treatment of the graphite mould is achieved;
4) carrying out surface flatness detection on the inner surface of the graphite mold, repeating the steps 2) to 3) if the surface still has etching traces until the surface is flat, and then polishing the inner surface of the graphite mold to obtain the graphite mold after surface treatment;
wherein the treating fluid is prepared from silicon carbide powder, graphite powder, silicon dioxide powder, deionized water, silicone oil and an emulsifier according to the weight ratio of 4: 2: 1: 15: 5: 1 to form a suspension, wherein the particle sizes of the silicon carbide powder, the graphite powder and the silicon dioxide powder are 0.5-2 mu m; the emulsifier is 601 emulsifier produced by the process of the Huangze chemical industry, the emulsifier is added to emulsify the silicone oil and mix with the deionized water, and the heat conduction effect and the wear resistance of the inner surface of the graphite mold can be further enhanced by adding the silicon carbide powder, the silicon dioxide powder, the silicone oil and the like, so that the physical properties of the silver tungsten carbide and the silver tungsten contact after the discharge plasma sintering preparation are further improved;
The preparation method of the treatment liquid comprises the following steps: firstly, mixing silicone oil and an emulsifier to obtain emulsified silicone oil, then mixing the emulsified silicone oil with deionized water, finally, uniformly mixing silicon carbide powder, graphite powder and silicon dioxide powder, adding the silicon carbide powder, the graphite powder and the silicon dioxide powder into the emulsified silicone oil, uniformly stirring the mixture to form turbid liquid, and using a treatment solution as required
Wherein, fig. 2 is an X100-time metallographic photograph of the prepared silver tungsten carbide contact, and it can be seen that the surface is flat and compact, and the use requirement of the silver-based contact is met.
Silver tungsten carbide contact related performance test experiment
The silver tungsten carbide contacts prepared in examples 1 to 5 were subjected to the relevant performance tests (hardness, conductivity and density of the silver tungsten carbide contacts) by the following specific test methods:
1. the method for testing the hardness of the silver tungsten carbide contact comprises the following steps: selecting CuCr contacts prepared in each embodiment as samples, and testing each test according to GB/T231.1-2018 Brinell hardness test of metal materials;
2. the method for testing the conductivity of the silver tungsten carbide contact comprises the following steps: selecting CuCr contacts prepared in each embodiment as samples, and carrying out conductivity test on each sample by using an FD series metal material conductivity tester;
3. the method for testing the density of the silver tungsten carbide contact comprises the following steps: selecting CuCr contacts prepared in each embodiment as samples, and carrying out metal density test on each sample by using a metal material wide-range density tester ET-1 KG;
The above examples were grouped as follows, and the test method described above was used to test the relevant performance tests of silver tungsten carbide contacts and to perform data comparison, with the following results:
experiment group I
Comparative examples 1-4, which used the same tungsten carbide content (wt%), different sintering process steps, the silver tungsten carbide contacts prepared with the relevant performance parameters as shown in table 1 below:
table 1 relevant performance testing parameters for prepared silver tungsten carbide contacts prepared in examples 1-4
Experiment group two
Comparative examples 1 and 5, which employ different tungsten carbide contents (wt%), the same process parameters, produced silver tungsten carbide contacts having the relevant performance parameters as shown in table 2 below:
table 2 relevant performance testing parameters for prepared silver tungsten carbide contacts from examples 1 and 5
Experiment group III
Comparative examples 1 and 6, which used the same tungsten carbide content (wt%), the same process parameters, except that example 1 did not surface treat the graphite mold, example 6 surface treated the graphite mold, and the silver tungsten carbide contacts were prepared with the relevant performance parameters as shown in table 3 below:
table 3 relevant performance testing parameters for prepared silver tungsten carbide contacts from examples 2 and 6
And (4) experimental conclusion:
1) experiment group one: comparing example 1 and examples 2-4, it can be seen from the data in table 1 that, comparing different sintering process steps at the same tungsten carbide content, the relevant performance parameters of examples 2-4 are greatly different from those of example 1, and are superior to those of example 1 in conductivity, hardness and density; next, comparing examples 2-4, it can be seen from the data in table 1 that the difference in parameters has a certain effect on the related performance parameters of the silver tungsten carbide contact under the same sintering process step, wherein the related performance parameters of the silver tungsten carbide contact in example 3 are the best.
2) Experiment group two: comparing experimental examples 1 and 5, it can be seen from the data in table 2 that, under the same process parameters, the silver tungsten carbide contacts prepared under different tungsten carbide contents are compared with the related performance test parameters, and it can be seen from table 2 that the differences among conductivity, hardness and density are large, especially the conductivity, and it can be seen that the decrease of conductivity, hardness and the like is caused due to the relative decrease of silver content, but the density is improved along with the increase of tungsten carbide content.
3) Experiment group three: comparing experimental examples 1 and 6, it can be seen from the data in table 3 that, under the same tungsten carbide content and process parameters, the related performance test parameters of the silver tungsten carbide contact prepared by using different graphite molds are improved in hardness, conductivity and density as can be seen from table 3, and under the same silver content, the silver tungsten carbide contact of example 6 has better performance, so that the consumption of silver can be reduced on the premise of keeping the same conductivity and other related performance test parameters by the process method of example 6, thereby further reducing the production cost.
Claims (7)
1. A method for preparing a silver-based contact formed by rapid sintering is characterized by mainly comprising the following steps:
s1, batching: weighing tungsten carbide powder and silver powder according to the weight of the contact type prepared according to the required requirements to obtain a mixture ratio, wherein the content of tungsten carbide is 20-80 wt%, and the balance is silver;
S2 mixing powder: the method comprises the following steps of (1) putting weighed powder into a mixer for ball milling, putting mixed powder into a graphite die after ball milling and mixing, wherein the inner layer of the graphite die is subjected to surface treatment, and the surface treatment step of the graphite die comprises the following steps:
1) coarsening the inner surface of the graphite mold through laser etching, and then carrying out oxidation erosion on the inner surface of the graphite mold for 1-3 min by adopting nitric acid with the concentration of 90%;
2) repeatedly washing with deionized water for many times, and then placing in a vacuum drying oven for vacuum drying;
3) placing the dried graphite mold in an argon atmosphere protective environment, heating the graphite mold through contact resistance, and spraying the treatment liquid under the spraying pressure of 0.6-0.8 MPa and the spraying dose of 12-15 g/cm2Blowing to the inner surface thereof;
4) carrying out surface flatness detection on the inner surface of the graphite mold, repeating the steps 2) to 3) if the surface still has etching traces until the surface is flat, and then polishing the inner surface of the graphite mold to obtain the graphite mold after surface treatment;
the treating fluid is prepared from silicon carbide powder, graphite powder, silicon dioxide powder, deionized water, silicone oil and an emulsifier according to a weight ratio of 4: 2: 1: (12-18): (3-7): 1 to form a suspension, wherein the particle sizes of the silicon carbide powder, the graphite powder and the silicon dioxide powder are 0.5-2 mu m;
S3 sintering: placing the graphite mold into a discharge plasma sintering device, pre-vacuumizing to below 10pa, and heating and pressure sintering;
s4 machining: and (4) performing small amount of fine processing on the blank prepared by sintering to obtain the silver tungsten carbide contact.
2. The method for preparing a silver-based contact through rapid sintering molding according to claim 1, wherein the particle size of the tungsten carbide powder in the step S1 is 0.1-10 μm, the particle size of the silver powder is 1-50 μm, and the purity is more than 99.5%.
3. The method for preparing a silver-based contact through rapid sintering molding according to claim 1, wherein tungsten carbide powder in the step S1 can be replaced by tungsten powder to prepare the silver-tungsten contact, wherein the particle size of the tungsten powder is 0.1-10 μm.
4. The method for preparing a silver-based contact through rapid sintering molding according to claim 1, wherein in the step S2 ball milling and mixing, a ball milling tank is protected by vacuum or atmosphere, the ball-to-material ratio is 1 (1-5), and the powder mixing time is 3-10 hours.
5. The method for preparing a silver-based contact through rapid sintering molding according to claim 1, wherein the laser etching parameters are as follows: selecting pulse laser capable of exciting 60-90 ns, wherein the repetition frequency is 5-8 kHz, and the output power of the laser is 40-50W.
6. The method for preparing a silver-based contact through rapid sintering molding according to claim 1, wherein the spark plasma sintering process in the step S3 is specifically as follows: 1) pre-vacuumizing to below 10pa, raising the temperature to 400-480 ℃ at a temperature raising rate of 65-80 ℃/min under an initial pressure of 150-170 MPa; 2) boosting the pressure to 160-180 MPa, and raising the temperature to 570-650 ℃ at the speed of 40-55 ℃/min; 3) heating to 800-950 ℃ at the speed of 90-120 ℃/min, reducing the pressure to 50-80 MPa at the speed of 10MPa/min during the heating, keeping the temperature and the pressure for 15-25 seconds, carrying out air cooling to room temperature at the wind speed of 6-9 m/s, and then releasing the pressure to take out the blank.
7. The method for preparing a silver-based contact through rapid sintering molding according to claim 6, wherein the spark plasma sintering temperature is 800-950 ℃, the pulse frequency is 0-50 Hz, the pressure is 50-180 MPa, and the spark plasma sintering equipment is pre-vacuumized to below 10 Pa.
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