CN115488335A - Manufacturing method of copper-chromium contact material for high voltage grade - Google Patents
Manufacturing method of copper-chromium contact material for high voltage grade Download PDFInfo
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- 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
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- 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
- B22F3/02—Compacting only
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- 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
- B22F3/1003—Use of special medium during sintering, e.g. sintering aid
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- B22F9/00—Making metallic powder or suspensions thereof
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- H—ELECTRICITY
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Abstract
The invention discloses a method for manufacturing a copper-chromium contact material for high voltage grade, which comprises the following steps: s1, preparing high-purity low-gas Cr powder, S2, mixing, S3, carrying out cold isostatic pressing, S4, carrying out vacuum sintering and degassing, S5, carrying out repressing, and S6, carrying out vacuum consumable arc melting. The invention adopts fine-grained high-purity low-gas chromium powder to improve the stability of the electrode bar in the smelting process, and the electrical contact material with the copper and chromium content of 25-55 percent is manufactured, and simultaneously, the inclusion content and the gas content in the contact material tissue are reduced, thereby being beneficial to improving the stability of a vacuum switch in the switching-on and switching-off process.
Description
Technical Field
The invention belongs to the field of electrical contact materials, and particularly relates to a process method for preparing CuCr series alloy by adopting a vacuum consumable arc melting method.
Background
With the continuous global attention to carbon emission indexes and the continuous progress of vacuum switch manufacturing technology, vacuum switches have been gradually adopted to replace SF at high voltage levels above 72.5KV 6 The vacuum switch has larger dependence on a contact material when the vacuum switch is switched on and off at high voltage and high current levels, and the performance of the contact material is a key factor for determining successful switching-on and switching-off;
according to a phase diagram of the copper-chromium binary alloy, when the chromium content is between 40% and 94.5%, a liquid phase immiscible region exists, which can cause segregation problem even in the process of rapid cooling of copper-chromium melt, so that the smelting of the copper-chromium alloy with the chromium content of between 25% and 50% can only be realized through a smelting process, meanwhile, a certain non-metallic inclusion can be participated in a gold phase of a copper-chromium alloy contact material made of chromium powder by an aluminothermic reduction method, the existence of oxides can influence the voltage and current stability in the smelting process, and the existence of the inclusion can influence the electrical performance of vacuum breaking and can not meet the use at a high voltage level;
on the high voltage level, the manufacturing technology of the high chromium content copper-chromium contact material is mainly based on vacuum infiltration and vacuum consumable arc melting manufacturing technologies, wherein the chromium particles of the copper-chromium contact material manufactured by the vacuum infiltration process are relatively large, which is not beneficial to improving the comprehensive electrical property of the contact, the uniform distribution of the chromium content can be realized by the arc melting process, the pressure resistance and the fusion welding resistance of the contact material can be further improved by the increase of the chromium content, and the manufacturing of the copper-chromium contact with the chromium content of 25-50% can be realized by the conventional manufacturing process at present;
in order to further improve the use voltage and current grade of the copper-chromium contact, the invention manufactures the electrical contact material with the copper-chromium content of 25-55%, uniform distribution and high stability.
Disclosure of Invention
In order to solve the technical problem, the invention provides a manufacturing method of a copper-chromium contact material for high voltage grade.
The technical scheme of the invention is as follows: the manufacturing method of the copper-chromium contact material for the high-voltage grade is characterized by comprising the following steps of:
s1, preparing high-purity low-gas Cr powder
Respectively mixing the components in a mass ratio of 1:2-5, weighing corresponding Cr2O3 powder and Al powder, placing the Cr2O3 powder and the Al powder into a crucible, adding a combustion-supporting material accounting for 15-30% of the total mass of the Cr2O3 powder and the Al powder into the crucible, reacting at 800-1000 ℃ to obtain mixed powder, loading the mixed powder into a stainless steel mold, compacting under the pressure of 30-50MPa, placing the stainless steel mold into a sintering furnace, filling inert protective gas into the sintering furnace, and degassing the mixed powder by adopting a gradient heating process to prepare high-purity low-gas Cr powder;
s2, mixing materials
Treating the high-purity low-gas Cr powder and the electrolytic Cu powder according to the weight ratio of 6-11:9-14, fully mixing the materials in a mixer for 4.5h-9.5h to obtain a mixed raw material, wherein the granularity of the high-purity low-gas chromium powder is 30-50 mu m, the oxygen content is less than or equal to 100ppm, and the nitrogen content is less than or equal to 10ppm;
s3, cold isostatic pressing
Placing the mixed raw material prepared in the step S2 into a custom mold, and pressing by using a cold isostatic press to obtain an alloy bar;
s4, vacuum sintering degassing
Primarily drying the alloy bar obtained in the step S3 for 0.5-3h under the vacuum condition of 80-120 ℃, then placing the alloy bar into a vacuum sintering furnace, heating to 700-1020 ℃, and sintering for 10-35h under the protective atmosphere of hydrogen; wherein, the sintering temperature is lower than 700 ℃ which can cause unmelted chromium particles in the smelting metallographic phase, and the smelting temperature higher than 1020 ℃ can cause copper segregation in the smelted product; when the sintering time is less than 10 hours, the gas content of the product is high, and the degassing treatment is not facilitated; higher power cost is caused by more than 35h;
s5, repressing
Putting the alloy bar sintered in the step S4 into a re-pressing die for re-pressing;
s6, vacuum consumable arc melting
And (5) placing the alloy bar material subjected to the repressing in the step (S5) into a vacuum consumable electrode furnace, closing a furnace door, vacuumizing the vacuum consumable electrode furnace until the pressure in the furnace is 0.003-0.005Pa, filling argon gas of 0.05-0.07Mpa into the furnace, smelting, and obtaining the required copper-chromium contact after smelting.
Further, in the step S1, the combustion-supporting material is potassium chlorate, the inert protective gas is any one of argon, nitrogen and helium, and the vacuum degree of the sintering furnace is kept higher than 1 × 10 during degassing -2 Pa；
Description of the invention: the potassium chlorate is adopted as a combustion-supporting material, so that the content of chromium in the product can be effectively improved, the inert protective gas is introduced to ensure that the product is not oxidized at a higher temperature, the boiling point of the liquid product is improved, the liquid product is solidified more compactly under the action of high-pressure argon, the vacuum degree is maintained, the service life of a graphite material in the vacuum sintering furnace can be prolonged, and the cost is saved.
Further, in the step S1, the gradient heating process includes: heating from room temperature, firstly heating for 0.8-1.2h to 150-170 ℃, then preserving heat for 0.8-1.2h, heating again for 1.3-1.7h to 300-320 ℃, then preserving heat for 2.9-3.1h, continuously heating for 2.8-3.2h to 400-420 ℃, then preserving heat for 1.8-2.2h, then filling hydrogen, continuously heating for 1.8-2.2h to 700-720 ℃, preserving heat for 0.8-1.2h, heating again to 1500-1520 ℃, preserving heat for 1.8-2.2h, then stopping heating, naturally cooling to 600-620 ℃, filling nitrogen, rapidly cooling to 60-70 ℃, and then taking out;
description of the drawings: the gradient heating process can be adopted to fully and effectively dehydrate the mixed powder under the vacuum condition, the gas can fully overflow under the condition of different temperatures, and the content of the gas in the mixed powder is further reduced, so that the chromium powder with high purity and low gas content is prepared.
Further, in the step S2, the mixing process is as follows: respectively and simultaneously adding 50 percent of Cr powder and 50 percent of electrolytic Cu powder into a mixer, preliminarily mixing for 2-6h, then adding the rest Cr powder and the electrolytic Cu powder into the mixer, and continuously mixing for 2.5-3.5h until the mixture is uniform;
description of the drawings: the mixing process is divided into two steps, so that the Cr powder and the electrolytic Cu powder can be effectively and fully mixed, and the powder is uniformly distributed in a customized die, so that the alloy is formed more compactly.
Further, in the step S3, the pressure of cold isostatic pressing is 150-300Mpa, and the pressure maintaining time is 1-10min;
description of the invention: by controlling the parameters of the cold isostatic pressing, the pressed alloy bar has the characteristics of more uniformity and higher density.
Further, in the step S5, the pressure restoring method is: performing single-time re-pressing at 150-300Mpa in the direction opposite to the cold isostatic pressing direction for 1-10min;
description of the drawings: the secondary repression and the cold isostatic pressing are opposite in direction, so that the internal components of the bar can be ensured to be more uniform.
Further, in step S5, the repressing method is: carrying out secondary pressing for 2-5 times, wherein the primary secondary pressing pressure is 150-200Mpa, and the pressure maintaining time is 3-5min; when the number of times of repressing is increased once, the repressing pressure is increased by 50-70Mpa, and sodium tungstate solution with the mass concentration of 20-30% is sprayed on the surface of the alloy bar material before each repressing; when the re-pressing pressure is increased by 30-50Mpa, the pressure maintaining time is reduced by 0.5-1min;
description of the invention: the combination of the copper-chromium layer and the copper layer can be further enhanced through the matching control of the repressing times, the repressing pressure and the pressure maintaining time, the uniformity of powder inside the bar is guaranteed, the compressive strength of contact gaps is further improved by adding sodium tungstate solution, and therefore the mechanical strength of the bar is effectively enhanced.
Further, in the step S6, the smelting current is 3KA to 5KA, the smelting voltage is 25V to 30V, and the gas pressure is 90mbar to 200mbar;
description of the invention: the electrode rod with uniformity and high density can be effectively prepared by the parameters of the electric arc melting.
Further, in the step S3, the customized mold is a long tubular mold with one closed end, and is composed of a plastic mold, a rigid mold arranged on the periphery of the plastic film, a support sleeve arranged between the plastic mold and the rigid film, and a seal ring arranged at the end of the mold, wherein the mold has a length of 750-850mm and an outer diameter of 60-80mm;
description of the invention: the plastic die can play a role of a forming die and also can play a role of transmitting pressure to enable powder to be molded compactly, the support sleeve arranged between the plastic die and the rigid film can reduce friction between the powder and the die wall in the filling process, and meanwhile, the rigid film and the plastic film can be ensured to be stable and not to deform, so that the filling density of the powder is improved; the specification of the customized die is convenient for mass production.
The beneficial effects of the invention are:
(1) The invention adopts fine-grained high-purity low-gas chromium powder as a raw material to manufacture the CuCr series products by electric arc melting, improves the stability of the electrode bar in the melting process, and manufactures the electric contact material with the copper and chromium content of 25-55 percent.
(2) The preparation method of the contact material can reduce the content of impurities and the content of gas in the contact material structure, so that the prepared CuCr series contact material has the characteristics of less impurities and low gas content, meets the application of a vacuum arc-extinguishing chamber with the high voltage of more than 40.5KV grade, and has the advantages of low cost, batch production and high production efficiency.
Drawings
FIG. 1 is a metallographic picture of a CuCr40% product prepared in example 1 of the present invention;
FIG. 2 is the metallographic picture of a CuCr55% product prepared in example 2 of the present invention.
Detailed Description
The present invention will be described in further detail with reference to specific embodiments thereof for better understanding the advantages of the invention.
Example 1
A method for manufacturing a copper-chromium contact material for high voltage class comprises the following steps:
s1, preparing high-purity low-gas Cr powder
Respectively mixing the components in a mass ratio of 1:2 weighing corresponding Cr 2 O 3 Putting the powder and Al powder into a crucible, and then adding Cr into the crucible 2 O 3 Reacting combustion-supporting materials with the total mass percentage of 15% of powder and Al powder at 800 ℃ to obtain mixed powder, loading the mixed powder into a stainless steel die, compacting the stainless steel die under the pressure of 30MPa, placing the stainless steel die into a sintering furnace, filling inert protective gas into the sintering furnace, and degassing the mixed powder by adopting a gradient heating process to prepare high-purity low-gas Cr powder; wherein the combustion-supporting material is potassium chlorate, the inert protective gas is any one of argon, nitrogen and helium, and the vacuum degree of the sintering furnace is kept to be 1.1 multiplied by 10 in the degassing process -2 Pa；
The gradient heating process comprises the following steps: heating from room temperature, firstly heating for 0.8h to 150 ℃, then preserving heat for 0.8h, heating again for 1.3h to 300 ℃, then preserving heat for 2.9h, continuing heating for 2.8h to 400 ℃, then preserving heat for 1.8h, then filling hydrogen, continuing heating for 1.8h to 700 ℃, preserving heat for 0.8h, heating again to 1500 ℃, then preserving heat for 1.8h, stopping heating, and filling nitrogen to rapidly cool to 60 ℃ after the temperature naturally drops to 600 ℃, and then taking out;
s2, mixing materials
Treating the high-purity low-gas Cr powder and the electrolytic Cu powder according to the weight ratio of 3: and 7, fully mixing the materials in a mixer for 4.5 hours to obtain a mixed raw material, wherein the granularity of the high-purity low-gas chromium powder is 30 mu m, the oxygen content is 97ppm, the nitrogen content is 8ppm, and the mixing process comprises the following steps: firstly, respectively and simultaneously adding 50 percent of Cr powder and 50 percent of electrolytic Cu powder into a mixer, preliminarily mixing for 2 hours, then adding the rest Cr powder and the electrolytic Cu powder into the mixer, and continuously mixing for 2.5 hours until the mixture is uniform;
s3, cold isostatic pressing
Placing the mixed raw material prepared in the step S2 into a custom mold, and pressing by using a cold isostatic press to obtain an alloy bar; wherein the cold isostatic pressing pressure is 150Mpa, and the pressure maintaining time is 10min; the customized mould is a long tubular mould with one closed end and consists of a plastic mould, a rigid mould arranged at the periphery of the plastic film, a support sleeve arranged between the plastic mould and the rigid film and a sealing ring arranged at the end part of the mould, wherein the length of the mould is 750mm, and the outer diameter of the mould is 60mm;
s4, vacuum sintering degassing
Primarily drying the alloy bar obtained in the step S3 for 0.5h under the vacuum condition of 80 ℃, then placing the alloy bar into a vacuum sintering furnace, heating to 700 ℃, and sintering for 10h under the protective atmosphere of hydrogen;
s5, repressing
Putting the alloy bar material subjected to vacuum sintering in the step S4 into a re-pressing die for re-pressing; wherein, the repressing mode is as follows: and (3) carrying out single-time repressing, wherein the repressing pressure is 150Mpa, the repressing direction is opposite to the cold isostatic pressing direction, and the pressure maintaining time is 10min.
S6, vacuum consumable arc melting
Placing the alloy bar stock subjected to the repressing in the step S5 into a vacuum consumable electrode furnace, closing a furnace door, vacuumizing the vacuum consumable electrode furnace until the pressure in the furnace is 0.003Pa, filling argon of 0.05Mpa into the furnace for smelting, and obtaining the required copper-chromium contact after smelting; wherein the smelting current is 3KA, the smelting voltage is 25V, and the gas pressure is 90mbar.
Example 2
The present embodiment is different from embodiment 1 in that, in step S1, the ratio of the mass of the first component to the mass of the second component is 1:3 weighing corresponding Cr 2 O 3 Putting the powder and Al powder into a crucible, and then adding Cr into the crucible 2 O 3 Reacting combustion-supporting materials with the total mass percentage of the powder and the Al powder being 20% at 900 ℃ to obtain mixed powder, loading the mixed powder into a stainless steel die, compacting the stainless steel die under the pressure of 40MPa, placing the stainless steel die into a sintering furnace, filling inert protective gas into the sintering furnace, and degassing the mixed powder by adopting a gradient heating process to prepare the high-purity low-gas Cr powder.
Example 3
The present embodiment is different from embodiment 1 in that, in step S1, the ratio of the mass of the first component to the mass of the second component is 1:5 weighing corresponding Cr 2 O 3 Putting the powder and Al powder into a crucible, and then adding Cr into the crucible 2 O 3 Reacting combustion-supporting material with the total mass percentage of the powder and the Al powder being 30% at 1000 ℃ to obtain mixed powder, filling the mixed powder into a stainless steel die, compacting under the pressure of 50MPa, and placing the stainless steel die into a sintering furnaceAnd filling inert protective gas into the sintering furnace, and then performing degassing treatment on the mixed powder by adopting a gradient heating process to prepare high-purity low-gas Cr powder.
Example 4
The present embodiment is different from embodiment 1 in that, in step S1, the gradient heating process includes: heating from room temperature, heating for 1h to 160 ℃, then preserving heat for 1h, heating for 1.5h to 310 ℃, then preserving heat for 3h, heating for 3h to 410 ℃, then preserving heat for 2h, then filling hydrogen, heating for 2h to 710 ℃, preserving heat for 1h, heating for 1510 ℃, then stopping heating, naturally cooling to 610 ℃, filling nitrogen, and rapidly cooling to 65 ℃, and then taking out.
Example 5
The present embodiment is different from embodiment 1 in that, in step S1, the gradient heating process includes: heating from room temperature, heating for 1.2h to 170 ℃, preserving heat for 1.2h, heating again for 1.7h to 320 ℃, preserving heat for 3.1h, continuing heating for 3.2h to 420 ℃, preserving heat for 2.2h, then filling hydrogen, continuing heating for 2.2h to 720 ℃, preserving heat for 1.2h, heating again to 1520 ℃, preserving heat for 2.2h, stopping heating, and filling nitrogen to rapidly cool to 70 ℃ after the temperature naturally decreases to 620 ℃.
Example 6
The present example is different from example 1 in that, in the step S2, the processed high-purity low-gas Cr powder and the electrolytic Cu powder are mixed in a weight ratio of 2:3, fully mixing materials in a mixer for 7 hours to obtain a mixed raw material, wherein the granularity of the high-purity low-gas Cr powder is 40 microns, the oxygen content is 97ppm, the nitrogen content is 8ppm, and the mixing process comprises the following steps: firstly, respectively and simultaneously adding 50 percent of Cr powder and 50 percent of electrolytic Cu powder into a mixer, preliminarily mixing for 4 hours, then adding the rest of Cr powder and electrolytic Cu powder into the mixer, and continuously mixing for 3 hours until the mixture is uniform.
Example 7
The present example is different from example 1 in that, in the step S2, the treated high-purity low-gas Cr powder and the electrolytic Cu powder are mixed in a weight ratio of 11:9, fully mixing materials in a mixer for 9.5 hours to obtain mixed raw materials, wherein the granularity of the high-purity low-gas Cr powder is 50 microns, the oxygen content is 94ppm, the nitrogen content is 8ppm, and the mixing process comprises the following steps: firstly, respectively and simultaneously adding 50 percent of Cr powder and 50 percent of electrolytic Cu powder into a mixer, preliminarily mixing for 6 hours, then adding the rest of Cr powder and electrolytic Cu powder into the mixer, and continuously mixing for 3.5 hours until the mixture is uniform.
Example 8
The difference between this example and example 1 is that in step S3, the pressure of the cold isostatic pressing is 220Mpa, and the dwell time is 5min; the customized die is a long tubular die with one closed end and consists of a plastic die, a rigid die arranged on the periphery of the plastic die, a support sleeve arranged between the plastic die and the rigid die and a seal ring arranged at the end part of the die, wherein the length of the die is 800mm, and the outer diameter of the die is 70mm.
Example 9
The difference between this example and example 1 is that in step S3, the pressure of the cold isostatic pressing is 300Mpa, and the dwell time is 1min; the customized die is a long tubular die with one closed end and consists of a plastic die, a rigid die arranged on the periphery of the plastic film, a support sleeve arranged between the plastic die and the rigid film and a sealing ring arranged at the end part of the die, wherein the length of the die is 850mm, and the outer diameter of the die is 80mm.
Example 10
The difference between this embodiment and embodiment 1 is that, in step S4, the alloy rod obtained in step S3 is primarily dried for 2 hours under a vacuum condition at 100 ℃, and then the alloy rod is placed into a vacuum sintering furnace, heated to 920 ℃, and sintered for 22 hours under a protective atmosphere of hydrogen.
Example 11
The difference between this embodiment and embodiment 1 is that, in step S4, the alloy rod obtained in step S3 is primarily dried for 3 hours under a vacuum condition at 120 ℃, and then the alloy rod is placed into a vacuum sintering furnace, heated to 1020 ℃, and sintered for 35 hours under a protective atmosphere of hydrogen.
Example 12
The present embodiment is different from embodiment 1 in that, in the step S5, the re-pressing manner is: and (3) carrying out single-time repressing, wherein the repressing pressure is 220Mpa, the direction is opposite to the direction of the cold isostatic pressing pressure, and the pressure maintaining time is 5min.
Example 13
The present embodiment is different from embodiment 1 in that, in step S5, the repressing method is: and (3) carrying out single-time repressing, wherein the repressing pressure is 300Mpa, the direction is opposite to the direction of the cold isostatic pressing pressure, and the pressure maintaining time is 1min.
Example 14
The present embodiment is different from embodiment 1 in that, in step S5, the repressing method is: and (2) carrying out secondary pressing for 2 times, wherein the primary secondary pressing pressure is 200MPa, the secondary pressing pressure is increased by 50MPa when the secondary pressing frequency is increased once, and sodium tungstate solution with the mass concentration of 20% is sprayed on the surface of the alloy bar material before each secondary pressing.
Example 15
The present embodiment is different from embodiment 1 in that, in the step S5, the re-pressing manner is: and (3) carrying out 5 times of repressing, wherein the primary repressing pressure is 150Mpa, the repressing pressure is increased by 70Mpa once the repressing times are increased, and a sodium tungstate solution with the mass concentration of 30% is sprayed on the surface of the alloy bar material at the front edge of each repressing.
Example 16
The present embodiment is different from embodiment 15 in that, in step S5, the repressing mode is: when the re-pressing pressure is increased by 30MPa, the pressure maintaining time is reduced by 0.5min.
Example 17
The present embodiment is different from embodiment 15 in that, in step S5, the repressing mode is: when the re-pressing pressure is increased by 50Mpa, the pressure maintaining time is reduced by 1min.
Example 18
The difference between the embodiment and the embodiment 1 is that in the step S6, the smelting current is 4KA, the smelting voltage is between 27V, the gas pressure is 140mbar, and the smelting is completed to obtain the desired cu-cr contact.
Example 19
The difference between this embodiment and embodiment 1 is that in step S6, the smelting current is 5KA, the smelting voltage is 30V, the gas pressure is 200mbar, and the smelting is completed to obtain the desired cu-cr contact.
Examples of the experiments
Aiming at the copper-chromium contact material prepared in each embodiment, the copper-chromium contact material is divided into experimental samples with equal volume and size respectively, and the performance of the copper-chromium contact material is tested respectively, specifically:
1. exploring Cr with different mass ratios 2 O 3 Influence of the powder and the Al powder on the prepared copper-chromium contact material.
The results of experimental comparisons of examples 1, 2 and 3 are shown in tables 1 and 2:
table 1 test table for performance of chromium powder samples prepared in example 1, example 2 and example 3
Table 2 table for testing the properties of copper-chromium contact specimens prepared in examples 1, 2 and 3
As can be seen from the comparison of tables 1 and 2, cr in different proportions 2 O 3 The aluminothermic reduction reaction between the powder and the Al powder has certain influence on various properties of the prepared copper-chromium contact, the purity of the chromium powder prepared in the example 2 is higher than that of the chromium powder prepared in the examples 1 and 3, but the conductivity of the contact is reduced due to the reduction of the Cu content, and the through-flow capacity is poor, so the example 1 is the optimal scheme;
2. the influence of the chromium powder prepared by gradient heating on the prepared copper-chromium contact material is explored.
Examples 1, 4, 5 were compared as experiments and control 1 was set up and the results are shown in table 3:
the difference between the comparison group 1 and the example 1 is that after the inert protective gas is filled into the sintering furnace, the temperature in the furnace is raised to 1500-1520 ℃ from the room temperature at 150 ℃/h, and the mixed powder is degassed;
table 3 performance test tables for copper chromium contact samples prepared in examples 1, 4 and 5
As can be seen from table 3, the performance of the prepared copper-chromium contact is better because the chromium powder prepared by gradient heating is denser than that prepared by uniform heating;
3. the influence of Cr powder and electrolytic Cu powder with different mass ratios on the prepared copper-chromium contact material is explored.
The results of experimental comparisons of examples 1, 6 and 7 are shown in Table 4
Table 4 test table for performance of copper-chromium contact sample prepared in example 1, example 4 and example 5
As can be seen from table 4, the electrical conductivity and density of the cu-Cr contact both decreased gradually with the increase of Cr content, the hardness increased with the increase of Cr content, and the mechanical strength increased substantially linearly with the increase of Cr content, wherein the chromium content of example 7 was at most 55% but the electrical conductivity was the lowest, and thus example 6 was the most preferable;
wherein, fig. 1 and fig. 2 are the metallographic diagrams of the embodiment 6 and the embodiment 7 respectively, and it can be seen that the metallographic structure of the copper-chromium contact material prepared by the method of the invention is uniformly dispersed;
4. the influence of different cold isostatic pressing pressures on the prepared copper-chromium contact material is explored.
The results of experimental comparisons of examples 1, 8, 9 are shown in Table 5:
table 5 test table for performance of copper-chromium contact sample prepared in example 1, example 8 and example 9
As can be seen from table 5, different cold isostatic pressing pressures have certain influences on the density and the conductivity of the copper-chromium contact, wherein example 8 is the optimal scheme;
5. the influence of different vacuum sintering temperatures on the prepared copper-chromium contact material is explored.
The results of experimental comparisons of examples 1, 10, 11 are shown in Table 6:
table 6 test table for performance of copper-chromium contact sample prepared in example 1, example 10 and example 11
As can be seen from Table 6, different vacuum sintering temperatures have certain influence on the performance of the prepared copper-chromium contact material, and the performance of the embodiment 11 is optimal;
6. the influence of different re-pressing pressures, re-pressing times and pressure maintaining time on the prepared copper-chromium contact material is explored.
The results of experimental comparisons of examples 1, 12, 13, 14, 15, 16, 17 and control 2 are shown in Table 7:
the difference between the comparison group 2 and the example 14 is that the step of spraying the sodium tungstate solution on the surface of the alloy bar before each re-pressing is eliminated;
TABLE 7 TEST TABLE FOR PERFORMANCE OF COPPER-CHROMIUM CONTACT SAMPLES PREPARED BY EXAMPLES 1, 12-17 AND COMPARATIVE GROUP 2
| Group of | Conductivity Ms/m | Mechanical strengthDegree MPa | Probability of re-breakdown% |
| Example 1 | 27.9 | 326 | 0.25 |
| Example 12 | 27.6 | 329 | 0.27 |
| Example 13 | 27.7 | 327 | 0.26 |
| Example 14 | 27.4 | 332 | 0.15 |
| Example 15 | 29.2 | 347 | 0.13 |
| Example 16 | 28.9 | 349 | 0.27 |
| Example 17 | 29.1 | 348 | 0.24 |
| Control group 2 | 27.4 | 327 | 0.31 |
As can be seen from table 7, the re-pressing pressure, the re-pressing frequency and the pressure holding time have certain effects on the performance of the cu-cr contact sample, wherein, as can be seen from examples 1, 12 and 13, and examples 15, 16 and 17, the performance difference of the prepared cu-cr contact is smaller because the re-pressing pressure and the pressure holding time are changed correspondingly under the condition of a certain re-pressing frequency; compared with the examples 1, 14 and 15, the number of times of re-pressing has certain influence on the performance of the copper-chromium contact, and the table shows that the example 15 is better; as is clear from example 14 and comparison with control 2, the addition of the sodium tungstate solution increases the alloy strength, and although there is a possibility of cracking of Cr powder, the probability of heavy punch-through is significantly reduced, and the dielectric breakdown characteristics of the copper-chromium contact can be further improved.
7. The influence of different arc melting parameters on the prepared copper-chromium contact material is explored.
The results of experimental comparisons of examples 1, 18, 19 are shown in Table 8:
table 8 test table for performance of copper chromium contact sample prepared in example 1, example 18 and example 19
As can be seen from Table 8, the different arc melting parameters have a certain effect on the performance of the Cu-Cr contact specimens, and example 19 is optimal.
Claims (10)
1. The manufacturing method of the copper-chromium contact material for the high-voltage grade is characterized by comprising the following steps of:
s1, preparing high-purity low-gas Cr powder
Respectively mixing the components in a mass ratio of 1:2-5 weighing corresponding Cr 2 O 3 Putting the powder and Al powder into a crucible, and then adding Cr into the crucible 2 O 3 Reacting combustion-supporting materials with the total mass percent of powder and Al powder being 15-30% at 800-1000 ℃ to obtain mixed powder, loading the mixed powder into a stainless steel mould, compacting under the pressure of 30-50MPa and placing in a sintering furnace, filling inert protective gas into the sintering furnace, and then degassing the mixed powder by adopting a gradient heating process to prepare high-purity low-gas Cr powder;
s2, mixing materials
Treating the high-purity low-gas Cr powder and the electrolytic Cu powder according to the weight ratio of 6-11:9-14, fully mixing for 4.5h-9.5h in a mixer to obtain a mixed raw material, wherein the granularity of the high-purity low-gas Cr powder is 30-50 mu m, the oxygen content is less than or equal to 100ppm, and the nitrogen content is less than or equal to 10ppm;
s3, cold isostatic pressing
Placing the mixed raw material prepared in the step S2 into a customized die, and pressing by using a cold isostatic press to obtain an alloy bar;
s4, vacuum sintering degassing
Primarily drying the alloy bar obtained in the step S3 for 0.5-3h under the vacuum condition of 80-120 ℃, then placing the alloy bar into a vacuum sintering furnace, heating to 700-1020 ℃, and sintering for 10-35h under the protective atmosphere of hydrogen;
s5, repressing
Putting the alloy bar material subjected to vacuum sintering in the step S4 into a re-pressing die for re-pressing;
s6, vacuum consumable arc melting
And (5) placing the alloy bar material subjected to the repressing in the step (S5) into a vacuum consumable electrode furnace, closing a furnace door, vacuumizing the vacuum consumable electrode furnace until the pressure in the furnace is 0.003-0.005Pa, filling argon gas of 0.05-0.07Mpa into the furnace, smelting, and obtaining the required copper-chromium contact after smelting.
2. The method for manufacturing the copper-chromium contact material for high voltage class according to claim 1, wherein in the step S1, the combustion-supporting material is potassium chlorate, the inert protective gas is any one of argon, nitrogen and helium, and the vacuum degree of the sintering furnace is kept to be higher than 1 x 10 during degassing -2 Pa。
3. The method for manufacturing the copper-chromium contact material for the high-voltage grade according to claim 1, wherein in the step S1, the gradient heating process comprises the following steps: heating from room temperature, heating for 0.8-1.2h to 150-170 ℃, preserving heat for 0.8-1.2h, heating again for 1.3-1.7h to 300-320 ℃, preserving heat for 2.9-3.1h, heating again for 2.8-3.2h to 400-420 ℃, preserving heat for 1.8-2.2h, then filling hydrogen, continuing heating for 1.8-2.2h to 700-720 ℃, preserving heat for 0.8-1.2h, heating again to 1500-1520 ℃, preserving heat for 1.8-2.2h, stopping heating, naturally cooling to 600-620 ℃, filling nitrogen, rapidly cooling to 60-70 ℃, and taking out.
4. The method for manufacturing the copper-chromium contact material for the high-voltage grade according to claim 1, wherein in the step S2, the material mixing process comprises the following steps: firstly, respectively and simultaneously adding 50 percent of Cr powder and 50 percent of electrolytic Cu powder into a mixer, primarily mixing for 2-6h, then adding the rest Cr powder and the rest electrolytic Cu powder into the mixer, and continuously mixing for 2.5-3.5h until the mixture is uniform.
5. The method of claim 1, wherein in step S3, the cold isostatic pressing is performed at a pressure of 150-300MPa for a dwell time of 1-10min.
6. The method for manufacturing a copper-chromium contact material for high voltage class according to claim 1, wherein in the step S5, the repressing mode is as follows: and (3) carrying out single-time repressing, wherein the repressing pressure is 150-300Mpa, the repressing direction is opposite to the cold isostatic pressing direction, and the pressure maintaining time is 1-10min.
7. The method for manufacturing a copper-chromium contact material for high voltage class according to claim 1, wherein in the step S5, the repressing mode is as follows: carrying out secondary pressing for 2-5 times, wherein the primary secondary pressing pressure is 150-200Mpa, and the pressure maintaining time is 3-5min; when the number of times of repressing is increased once, the repressing pressure is increased by 50-70Mpa, and sodium tungstate solution with the mass concentration of 20-30% is sprayed on the surface of the alloy bar material before each repressing; when the re-pressing pressure is increased by 30-50MPa, the pressure maintaining time is reduced by 0.5-1min.
8. The method of claim 1, wherein in step S6, the melting current is 3KA to 5KA, the melting voltage is 25V to 30V, and the gas pressure is 90mbar to 200mbar.
9. The method of claim 1, wherein in step S3, the cold isostatic pressing is performed at a pressure of 150-300MPa for a dwell time of 1-10min.
10. The method for manufacturing a copper-chromium contact material for high voltage class according to claim 1, wherein in step S3, the customized mold is a long tubular mold with one end closed, and is composed of a plastic mold, a rigid mold arranged at the periphery of the plastic mold, a support sleeve arranged between the plastic mold and the rigid mold, and a sealing ring arranged at the end of the mold, the mold has a length of 750-850mm and an outer diameter of 60-80mm.
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