CN112589101A - Preparation method of copper-chromium shielding case for vacuum arc-extinguishing chamber - Google Patents
Preparation method of copper-chromium shielding case for vacuum arc-extinguishing chamber Download PDFInfo
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Abstract
The invention discloses a preparation method of a copper-chromium shielding case for a vacuum arc-extinguishing chamber, which comprises the following steps of (1) batching: copper powder and chromium powder are selected as raw materials, and the weight percentage of the chromium powder is 1-30%; (2) mixing powder: putting the proportioned copper powder and chromium powder into a ball mill for ball milling to obtain mixed powder; (3) cold isostatic pressing: filling the mixed powder into a rubber sleeve for cold isostatic pressing to obtain a CuCr bar; (4) and (3) sintering: placing the CuCr bar stock into a vacuum furnace for vacuum sintering; (5) extruding: cutting the sintered CuCr bar into the thickness before extrusion, and performing reverse cold extrusion by adopting a hydraulic machine to obtain a CuCr blank; (6) finish machining: and cutting the extruded CuCr blank into a plurality of final products according to the length, and performing finish machining to obtain the final copper-chromium shielding case. The density of the CuCr shield can reach more than 97%, the production process is short, and the production efficiency is 5-10 times of that of the original mixed powder in a pressing and sintering mode.
Description
Technical Field
The invention belongs to the technical field of powder metallurgy, and particularly relates to a preparation method of a copper-chromium shielding case for a vacuum arc-extinguishing chamber.
Background
The CuCr alloy has better arc erosion resistance and good on-off current capability, and is used as a contact material and a shielding case in a medium-high voltage vacuum arc extinguishing chamber. In the vacuum arc extinguishing chamber, the shielding cover has the indispensable functions of balancing magnetic field distribution, protecting the outer ceramic shell, insulating protection and the like. At present, the main materials of the shielding case at home and abroad are pure Cu, stainless steel and CuCr materials. The CuCr material has the functions of high temperature resistance, arc ablation resistance, easy oxygen absorption and the like, has the best use effect, and is high in production cost mainly used as a high-end product at abroad due to the reasons of low production efficiency, complex process, difficulty in improving density and the like of the existing shielding cover.
The existing CuCr shield cover preparation processes comprise two processes, one is vacuum casting CuCr cast ingot extrusion and machining molding, and the process has low raw material utilization rate and long production flow; the other is formed by molding after mixing Cu and Cr powder and adding by a sintering machine. Due to the thin wall and high height of the shielding cover, the pressing efficiency is low, and the compactness is difficult to improve (generally 93%). Therefore, a technical method which has high density, high material utilization rate and production efficiency and meets the requirements is needed based on the current preparation difficulty.
Disclosure of Invention
Aiming at the technical problems of low production efficiency, low product density and the like of the existing copper-chromium shielding cover, the invention provides a preparation method of the copper-chromium shielding cover for the vacuum arc-extinguishing chamber, which can improve the efficiency and the density.
The technical scheme of the invention is as follows: a preparation method of a copper-chromium shielding case for a vacuum arc-extinguishing chamber comprises the following steps:
(1) preparing materials: copper powder and chromium powder are selected as raw materials, and the content of the chromium powder is 1-30% by weight;
(2) mixing powder: putting the proportioned copper powder and chromium powder into a ball mill with the ball-material ratio of 1:1-1:3, and ball-milling the mixed powder for 3-5h to obtain mixed powder;
(3) cold isostatic pressing: filling the mixed powder into a rubber sleeve for isostatic cool pressing, wherein the isostatic cool pressing pressure is 150-350Mpa, and the pressure maintaining time is 3-10min, so as to obtain a CuCr bar;
(4) and (3) sintering: placing the CuCr bar into a vacuum furnace for vacuum sintering at 950-;
(5) extruding: cutting the sintered CuCr bar into the thickness before extrusion, and performing reverse cold extrusion by adopting a hydraulic machine to obtain a CuCr blank;
(6) finish machining: and cutting the extruded CuCr blank into a plurality of final products according to the length, and performing finish machining to obtain the final copper-chromium shielding case.
Further, the copper powder in the step (1) is electrolytic copper powder with the particle size of 60-75 microns, the oxygen content of less than 500ppm and the nitrogen content of less than 60 ppm; the chromium powder is prepared from aluminothermic chromium powder with the particle size of 130-150 mu m, the oxygen content of less than 1000ppm and the nitrogen content of less than 80 ppm. The invention has low requirement on the grain diameter of the copper powder and chromium powder raw materials and has lower corresponding cost.
Further, the cold extrusion pressure of the reverse cold extrusion in the step (6) is 800-. The backward cold extrusion can greatly improve the utilization rate of the material compared with the forward cold extrusion.
Further, in order to improve the density of the final finished product of the copper-chromium shielding case, the mixed powder in the step (2) can also be: fully mixing the proportioned copper powder and chromium powder, and then dividing the mixture into large-component mixed powder and small-component mixed powder according to a certain weight ratio, wherein the large-component mixed powder is mixed by a ball mill to obtain copper-chromium mixed powder A with the particle size of 35-75 micrometers after ball milling, and the small-component mixed powder is atomized to prepare powder after laser remelting to obtain copper-chromium mixed powder B with the particle size of 10-15 micrometers; and then fully mixing the copper-chromium mixed powder A and the copper-chromium mixed powder B, filling the mixture into a rubber sleeve, and carrying out cold isostatic pressing to obtain a CuCr bar, wherein the cold isostatic pressing pressure is 150-350MPa, and the pressure maintaining time is 3-10 min. By mixing the large-grain-size and small-grain-size copper-chromium mixed powder and utilizing the characteristic that the liquid phase temperature of the small-grain-size powder is lower, the small-grain-size copper-chromium mixed powder B is subjected to liquid phase sintering to be in a liquid phase state, so that the small-grain-size copper-chromium mixed powder B can be conveniently filled into the pores between the large-grain-size powder in a flowing manner to improve the density of the material, the dead weight of the CuCr bar is offset by the buoyancy of ultrasonic standing wave suspension, the pores between the large-grain-size powder can be more uniformly filled in the liquid phase state of the copper-chromium mixed powder B in the flowing manner, and the bar collapse caused by the dead weight.
Further, the vacuum sintering of the CuCr bar stock comprises the following specific steps:
s1: placing the CuCr bar stock into a vacuum sintering furnace with an ultrasonic suspension device, and suspending the CuCr bar stock in the vacuum sintering furnace by adopting an ultrasonic standing wave suspension technology;
s2: firstly, raising the sintering temperature to 950 ℃, and preserving the heat for 30min to ensure that the copper-chromium mixed powder B with small particle size reaches a liquid phase state and flows into a gap formed by the copper-chromium mixed powder A with large particle size;
s3: and then raising the sintering temperature to 1080 ℃, carrying out solid-phase sintering on the copper-chromium mixed powder A with large particle size, keeping the temperature for 1-5 hours, and gradually cooling to room temperature to obtain a sintered CuCr rod blank.
Furthermore, the weight ratio of the large-component mixed powder to the small-component mixed powder is 5-10: 1. Too high proportion of the small-component mixed powder can cause too much liquid phase during sintering to cause bar collapse, and too low proportion can cause insufficient volume of the liquid phase formed during sintering to fill pores, so that the density of a finished product cannot be effectively improved.
Furthermore, the ultrasonic suspension device comprises an arc transmission plate, an arc reflection plate and at least two transducers, wherein the arc transmission plate is located below the CuCr bar and has an upward opening, the arc reflection plate is located above the CuCr bar and has a downward opening, the at least two transducers are used for providing ultrasonic vibration for the arc transmission plate, the transducers are connected with an ultrasonic power supply and are used for forming a standing wave sound field between the arc transmission plate and the arc reflection plate, and the CuCr bar is suspended at a sound pressure node.
Furthermore, the arc-shaped reflecting plate and the arc-shaped transmission plate are made of zirconia ceramics, the concave surface is processed by mirror surface processing, the frequency of an output signal of the ultrasonic power supply is 30-50KHz, and the voltage is 220V. The zirconia material ceramic has the characteristic of high temperature resistance, has high reflection efficiency after mirror surface processing and is not easy to oxidize, and is favorable for the CuCr bar to keep a suspension state by regulating and controlling proper ultrasonic power supply frequency.
Further, the copper-chromium shielding case is applied to a third electrode of the vacuum arc-extinguishing chamber.
The invention has the beneficial effects that: 1) the density of the CuCr shielding case produced by the method can reach more than 97 percent; 2) the production process flow is short, and the production efficiency is 5-10 times of that of the original mixed powder in a pressing and sintering way; 3) the produced CuCr shielding case has good vacuum air tightness and no defects of air release and the like.
Drawings
FIG. 1 is a photograph of an extruded blank shield of the present invention;
figure 2 is a photograph of a finished shield made according to the present invention.
Detailed Description
Example 1
A preparation method of a copper-chromium shielding case for a vacuum arc-extinguishing chamber comprises the following steps:
(1) preparing materials: selecting copper powder and chromium powder as raw materials, wherein the copper powder is electrolytic copper powder with the particle size of 60-75 mu m, the oxygen content of less than 500ppm and the nitrogen content of less than 60 ppm; the chromium powder is prepared from aluminothermic chromium powder with the particle size of 130-150 mu m, the oxygen content of less than 1000ppm and the nitrogen content of less than 80 ppm. According to the weight percentage, the content of the chromium powder is 2 percent;
(2) mixing powder: putting the proportioned copper powder and chromium powder into a ball mill, wherein the ball-material ratio is 1:1, and ball-milling and mixing the powder for 3 hours to obtain mixed powder;
(3) cold isostatic pressing: filling the mixed powder into a rubber sleeve for cold isostatic pressing, wherein the cold isostatic pressing pressure is 150Mpa, and the pressure maintaining time is 3min, so as to obtain a CuCr bar;
(4) and (3) sintering: putting the CuCr bar into a vacuum furnace for vacuum sintering, wherein the sintering temperature is 950 ℃, and keeping the temperature for 1 hour;
(5) extruding: cutting the sintered CuCr bar into the thickness before extrusion, and performing reverse cold extrusion by using a hydraulic machine, wherein the cold extrusion pressure of the reverse cold extrusion is 800MPa, and the extrusion speed is 1cm/s, so as to obtain a CuCr blank;
(6) finish machining: and cutting the extruded CuCr blank into a plurality of final products according to the length, and performing finish machining to obtain the final copper-chromium shielding case.
Example 2
A preparation method of a copper-chromium shielding case for a vacuum arc-extinguishing chamber comprises the following steps:
(1) preparing materials: selecting copper powder and chromium powder as raw materials, wherein the copper powder is electrolytic copper powder with the particle size of 60-75 mu m, the oxygen content of less than 500ppm and the nitrogen content of less than 60 ppm; the chromium powder is prepared from aluminothermic chromium powder with the particle size of 130-150 mu m, the oxygen content of less than 1000ppm and the nitrogen content of less than 80 ppm. According to the weight percentage, the content of the chromium powder is 10 percent;
(2) mixing powder: putting the proportioned copper powder and chromium powder into a ball mill, wherein the ball-material ratio is 1:2, and ball-milling and mixing the powder for 4 hours to obtain mixed powder;
(3) cold isostatic pressing: filling the mixed powder into a rubber sleeve for cold isostatic pressing, wherein the cold isostatic pressing pressure is 250Mpa, and the pressure maintaining time is 7min, so as to obtain a CuCr bar;
(4) and (3) sintering: putting the CuCr bar into a vacuum furnace for vacuum sintering, wherein the sintering temperature is 1000 ℃, and keeping the temperature for 3 hours;
(5) extruding: cutting the sintered CuCr bar into the thickness before extrusion, and performing reverse cold extrusion by using a hydraulic machine, wherein the cold extrusion pressure of the reverse cold extrusion is 1650Mpa, and the extrusion speed is 3cm/s, so as to obtain a CuCr blank;
(6) finish machining: and cutting the extruded CuCr blank into a plurality of final products according to the length, and performing finish machining to obtain the final copper-chromium shielding case.
Example 3
A preparation method of a copper-chromium shielding case for a vacuum arc-extinguishing chamber comprises the following steps:
(1) preparing materials: selecting copper powder and chromium powder as raw materials, wherein the copper powder is electrolytic copper powder with the particle size of 60-75 mu m, the oxygen content of less than 500ppm and the nitrogen content of less than 60 ppm; the chromium powder is prepared from aluminothermic chromium powder with the particle size of 130-150 mu m, the oxygen content of less than 1000ppm and the nitrogen content of less than 80 ppm. According to the weight percentage, the content of the chromium powder is 25 percent;
(2) mixing powder: putting the proportioned copper powder and chromium powder into a ball mill, wherein the ball-material ratio is 1:3, and ball-milling and mixing the powder for 5 hours to obtain mixed powder;
(3) cold isostatic pressing: filling the mixed powder into a rubber sleeve for cold isostatic pressing, wherein the cold isostatic pressing pressure is 350Mpa, and the pressure maintaining time is 10min, so as to obtain a CuCr bar;
(4) and (3) sintering: putting the CuCr bar into a vacuum furnace for vacuum sintering at 1080 ℃, and keeping the temperature for 5 hours;
(5) extruding: cutting the sintered CuCr bar into the thickness before extrusion, and performing reverse cold extrusion by using a hydraulic machine, wherein the cold extrusion pressure of the reverse cold extrusion is 2500Mpa, and the extrusion speed is 5cm/s, so as to obtain a CuCr blank;
(6) finish machining: and cutting the extruded CuCr blank into a plurality of final products according to the length, and performing finish machining to obtain the final copper-chromium shielding case.
Example 4
A preparation method of a copper-chromium shielding case for a vacuum arc-extinguishing chamber comprises the following steps:
(1) preparing materials: selecting copper powder and chromium powder as raw materials, wherein the copper powder is electrolytic copper powder with the particle size of 60-75 mu m, the oxygen content of less than 500ppm and the nitrogen content of less than 60 ppm; the chromium powder is prepared from aluminothermic chromium powder with the particle size of 130-150 mu m, the oxygen content of less than 1000ppm and the nitrogen content of less than 80 ppm. According to the weight percentage, the content of the chromium powder is 10 percent;
(2) mixing powder: fully mixing the proportioned copper powder and chromium powder, and then dividing the mixture into large-component mixed powder and small-component mixed powder according to the weight ratio of 7.5:1, wherein the large-component mixed powder is mixed by a ball mill to obtain copper-chromium mixed powder A with the particle size of 35-75 micrometers after ball milling, and the small-component mixed powder is atomized to prepare powder after laser remelting to obtain copper-chromium mixed powder B with the particle size of 10-15 micrometers;
(3) cold isostatic pressing: then fully mixing the copper-chromium mixed powder A and the copper-chromium mixed powder B, filling the mixture into a rubber sleeve, and carrying out cold isostatic pressing to obtain a CuCr bar, wherein the cold isostatic pressing pressure is 250Mpa, and the pressure maintaining time is 7min to obtain the CuCr bar;
(4) and (3) sintering: putting the CuCr bar into a vacuum furnace for vacuum sintering, wherein the sintering temperature is 1000 ℃, and keeping the temperature for 3 hours;
(5) extruding: cutting the sintered CuCr bar into the thickness before extrusion, and performing reverse cold extrusion by using a hydraulic machine, wherein the cold extrusion pressure of the reverse cold extrusion is 1650Mpa, and the extrusion speed is 3cm/s, so as to obtain a CuCr blank;
(6) finish machining: and cutting the extruded CuCr blank into a plurality of final products according to the length, and performing finish machining to obtain the final copper-chromium shielding case.
Example 5
This example is substantially the same as example 4 except that the sintering step is:
s1: placing a CuCr bar into a vacuum sintering furnace, firstly raising the sintering temperature to 950 ℃, and preserving the temperature for 30min to ensure that the copper-chromium mixed powder B with small particle size reaches a liquid phase state and flows into a gap formed by the copper-chromium mixed powder A with large particle size;
s3: and then raising the sintering temperature to 1080 ℃, carrying out solid-phase sintering on the copper-chromium mixed powder A with large particle size, keeping the temperature for 1-5 hours, and gradually cooling to room temperature to obtain a sintered CuCr rod blank.
Example 6
This example is substantially the same as example 4 except that the sintering step is:
s1: placing the CuCr bar stock into a vacuum sintering furnace with an ultrasonic suspension device, and suspending the CuCr bar stock in the vacuum sintering furnace by adopting an ultrasonic standing wave suspension technology; the ultrasonic suspension device comprises an arc transmission plate with an upward opening and located below the CuCr bar, an arc reflection plate with a downward opening and located above the CuCr bar, and at least two transducers used for providing ultrasonic vibration for the arc transmission plate, wherein the transducers are connected with an ultrasonic power supply and used for forming a standing wave sound field between the arc transmission plate and the arc reflection plate and suspending the CuCr bar in a sound pressure node. The arc reflecting plate and the arc transmission plate are made of zirconia ceramics, the concave surface of the arc reflecting plate and the arc transmission plate is processed by mirror finishing, the frequency of an output signal of the ultrasonic power supply is 30-50KHz, and the voltage is 220V. The zirconia material ceramic has the characteristic of high temperature resistance, has high reflection efficiency after mirror surface processing and is not easy to oxidize, and is favorable for the CuCr bar to keep a suspension state by regulating and controlling proper ultrasonic power supply frequency.
S2: firstly, raising the sintering temperature to 950 ℃, and preserving the heat for 30min to ensure that the copper-chromium mixed powder B with small particle size reaches a liquid phase state and flows into a gap formed by the copper-chromium mixed powder A with large particle size;
s3: and then raising the sintering temperature to 1080 ℃, carrying out solid-phase sintering on the copper-chromium mixed powder A with large particle size, keeping the temperature for 3 hours, and gradually cooling to room temperature to obtain a sintered CuCr rod blank.
By mixing the large-grain-size and small-grain-size copper-chromium mixed powder and utilizing the characteristic that the liquid phase temperature of the small-grain-size powder is lower, the small-grain-size copper-chromium mixed powder B is subjected to liquid phase sintering to be in a liquid phase state, so that the small-grain-size copper-chromium mixed powder B can be conveniently filled into the pores between the large-grain-size powder in a flowing manner to improve the density of the material, the dead weight of the CuCr bar is offset by the buoyancy of ultrasonic standing wave suspension, the pores between the large-grain-size powder can be more uniformly filled in the liquid phase state of the copper-chromium mixed powder B in the flowing manner, and the bar collapse caused by the dead weight.
Examples of the experiments
The copper-chromium shields prepared in examples 1-6 were tested for performance and the results are shown in table 1:
table 1 results of performance tests on cu-cr shielding cans prepared in examples 1-6
As can be seen from Table 1, the copper-chromium shielding case prepared by the method has excellent performance, wherein the compactness can reach more than 97%, and the optimal compactness can reach more than 99%. And as can be seen from fig. 1 and fig. 2, the extruded blank shield and the finished blank shield both have good appearance forms, and can be used as a third electrode of a vacuum arc-extinguishing chamber.
Claims (9)
1. A preparation method of a copper-chromium shielding case for a vacuum arc-extinguishing chamber is characterized by comprising the following steps:
(1) preparing materials: copper powder and chromium powder are selected as raw materials, and the content of the chromium powder is 1-30% by weight;
(2) mixing powder: putting the proportioned copper powder and chromium powder into a ball mill with the ball-material ratio of 1:1-1:3, and ball-milling the mixed powder for 3-5h to obtain mixed powder;
(3) cold isostatic pressing: filling the mixed powder into a rubber sleeve for isostatic cool pressing, wherein the isostatic cool pressing pressure is 150-350Mpa, and the pressure maintaining time is 3-10min, so as to obtain a CuCr bar;
(4) and (3) sintering: placing the CuCr bar into a vacuum furnace for vacuum sintering at 950-;
(5) extruding: cutting the sintered CuCr bar into the thickness before extrusion, and performing reverse cold extrusion by adopting a hydraulic machine to obtain a CuCr blank;
(6) finish machining: and cutting the extruded CuCr blank into a plurality of final products according to the length, and performing finish machining to obtain the final copper-chromium shielding case.
2. The method for preparing the copper-chromium shielding case for the vacuum arc-extinguishing chamber as claimed in claim 1, wherein in the step (1), the copper powder is electrolytic copper powder with the particle size of 60-75 μm, the oxygen content of less than 500ppm and the nitrogen content of less than 60 ppm; the chromium powder is prepared from aluminothermic chromium powder with the particle size of 130-150 mu m, the oxygen content of less than 1000ppm and the nitrogen content of less than 80 ppm.
3. The method for preparing the copper-chromium shielding case for the vacuum arc-extinguishing chamber as claimed in claim 1, wherein the cold extrusion pressure of the reverse cold extrusion in step (6) is 800Mpa and 2500Mpa, and the extrusion speed is 1-5 cm/s.
4. The method for preparing the copper-chromium shielding case for the vacuum arc-extinguishing chamber according to claim 1, wherein the mixed powder in the step (2) is further: fully mixing the proportioned copper powder and chromium powder, and then dividing the mixture into large-component mixed powder and small-component mixed powder according to a certain weight ratio, wherein the large-component mixed powder is mixed by a ball mill to obtain copper-chromium mixed powder A with the particle size of 35-75 micrometers after ball milling, and the small-component mixed powder is atomized to prepare powder after laser remelting to obtain copper-chromium mixed powder B with the particle size of 10-15 micrometers; and then fully mixing the copper-chromium mixed powder A and the copper-chromium mixed powder B, filling the mixture into a rubber sleeve, and carrying out cold isostatic pressing to obtain a CuCr bar, wherein the cold isostatic pressing pressure is 150-350MPa, and the pressure maintaining time is 3-10 min.
5. The method for preparing the copper-chromium shielding case for the vacuum arc-extinguishing chamber as claimed in claim 1 or 4, wherein the step of vacuum sintering the CuCr bar stock comprises the following steps:
s1: placing the CuCr bar stock into a vacuum sintering furnace with an ultrasonic suspension device, and suspending the CuCr bar stock in the vacuum sintering furnace by adopting an ultrasonic standing wave suspension technology;
s2: firstly, raising the sintering temperature to 950 ℃, and preserving the heat for 30min to ensure that the copper-chromium mixed powder B with small particle size reaches a liquid phase state and flows into a gap formed by the copper-chromium mixed powder A with large particle size;
s3: and then raising the sintering temperature to 1080 ℃, carrying out solid-phase sintering on the copper-chromium mixed powder A with large particle size, keeping the temperature for 1-5 hours, and gradually cooling to room temperature to obtain a sintered CuCr rod blank.
6. The method for preparing the copper-chromium shielding case for the vacuum interrupter as claimed in claim 4, wherein the weight ratio of the major component mixed powder to the minor component mixed powder is 5-10: 1.
7. The method for manufacturing the copper-chromium shielding case for the vacuum interrupter as claimed in claim 5, wherein the ultrasonic suspension device comprises an arc transmission plate, an arc reflection plate, and a transducer, wherein the transducer is connected to an ultrasonic power source for forming a standing wave sound field between the arc transmission plate and the arc reflection plate.
8. The method for manufacturing the copper-chromium shielding case for the vacuum interrupter as claimed in claim 5, wherein the ultrasonic suspension device comprises an arc transmission plate with an upward opening and located below the CuCr bar, an arc reflection plate with a downward opening and located above the CuCr bar, and at least two transducers for providing ultrasonic vibration to the arc transmission plate, wherein the transducers are connected with an ultrasonic power supply for forming a standing wave sound field between the arc transmission plate and the arc reflection plate, so as to suspend the CuCr bar at a sound pressure node.
9. The method for manufacturing the copper-chromium shielding case for the vacuum interrupter as claimed in any one of claims 1 to 7, wherein the copper-chromium shielding case is applied to a third electrode of the vacuum interrupter.
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