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CN-122007416-A - Copper-chromium contact material for vacuum circuit breaker and preparation method thereof

CN122007416ACN 122007416 ACN122007416 ACN 122007416ACN-122007416-A

Abstract

The invention belongs to the technical field of vacuum circuit breakers, and in particular relates to a copper-chromium contact material for a vacuum circuit breaker and a preparation method thereof, wherein the preparation method comprises the following steps: performing plasma spheroidization on low-oxygen pure chromium powder to obtain low-oxygen spherical chromium powder, performing vacuum sintering at 1200-1350 ℃ on the spherical chromium powder, performing high-temperature sintering at 1600-1700 ℃ in a high-purity argon environment to obtain a chromium skeleton formed by microscopically connected spherical chromium powder, melting oxygen-free copper, and performing in-situ infiltration on the skeleton to prepare copper-chromium alloy for processing into copper-chromium contacts for vacuum circuit breakers. The invention can control the field enhancement factor generated in the microstructure and reduce the particle formation probability by improving the spheroidized chromium phase and forming the spheroidized chromium phase into the mutually connected microspheres, thereby obviously improving the voltage resistance of the contact gap.

Inventors

  • WANG YAPING
  • CHEN PENGYU

Assignees

  • 西安交通大学

Dates

Publication Date
20260512
Application Date
20260313

Claims (10)

  1. 1. The preparation method of the copper-chromium contact material for the vacuum circuit breaker is characterized by comprising the following steps of: brushing carbon powder on the surface of the electrolytic chromium sheet obtained by the electrolytic method, and carrying out hot-pressing deoxidization treatment in a hydrogen environment; Placing the irregularly-shaped chromium powder into radio frequency plasma spheroidizing technical equipment, generating induction coupling plasma by radio frequency magnetic field excitation and forming a high-temperature induction plasma torch, absorbing heat by the chromium powder in the high-temperature induction plasma torch, melting the chromium powder into chromium liquid drops, forming spherical liquid drops under the action of surface tension, and solidifying the spherical chromium powder under the cooling condition; Sintering the spherical chromium powder subjected to compaction at high temperature in a vacuum sintering furnace to obtain a high-strength chromium skeleton with microscopic interconnection of spherical chromium particles; and (3) melting oxygen-free copper and then penetrating into the framework to prepare the copper-chromium alloy for processing into the copper-chromium contact for the vacuum circuit breaker.
  2. 2. The method according to claim 1, wherein the high-temperature sintering is performed by first sintering at a vacuum of < 1x10 - 2 Pa and 1200-1350 ℃, then charging high-purity argon gas into the vacuum chamber, and heating to 1600-1700 ℃ in the high-purity argon gas.
  3. 3. The method according to claim 2, wherein the sintering time is 2-4 hours at 1200-1350 ℃ and the holding time is 1-2 hours at 1600-1700 ℃.
  4. 4. The preparation method of the chromium powder feeder is characterized in that a plasma spheroidizing chamber is vacuumized, protective gas is introduced into the spheroidizing chamber, the flow rate of carrier gas is controlled to be 20-30L/min, the flow rate of sheath gas is controlled to be 60-100L/min, the power of a plasma power supply is regulated to be 15-35kW, the air inlet speed of the protective gas is controlled to be 20-30L/min, an arc is started, the plasma torch is started, chromium powder is fed through the powder feeder, and the powder feeding speed of the powder feeder is regulated to be 5-30g/min.
  5. 5. The method according to claim 4, wherein the cooling condition is that the spherical liquid drops leave the high temperature zone under the action of air flow and self gravity, and the spherical liquid drops are cooled by the protective gas to form spherical chromium powder.
  6. 6. The method according to claim 1, wherein the hot-press deoxidizing treatment is to heat to 800-1250 ℃ and pressurize to 20-30 MPa in a hydrogen atmosphere below the dew point of-50 ℃ to reduce the oxygen content in the electrolytic chromium sheet to < 50 ppm.
  7. 7. The preparation method according to claim 1, wherein the hot-pressed deoxidized electrolytic chromium flakes are washed and dried, and then crushed into flakes with a maximum size of less than 5mm, and then subjected to freeze ball milling in a liquid nitrogen environment to prepare the irregularly-shaped chromium powder with a granularity of <100 μm, a purity of > 99.9% and an oxygen content of < 200ppm and of 35-150 μm.
  8. 8. The preparation method of claim 1, wherein the spherical chromium powder is classified by screening, the spherical chromium powder classified by screening is selected and filled into a graphite mold, the graphite mold has a blind hole structure, the inside of the graphite mold is a cylindrical hole, the diameter of the cylindrical hole is increased by 2-10mm on the basis of the diameter of a contact, and the spherical chromium powder in the graphite mold is compacted on a vibrating machine.
  9. 9. The preparation method according to claim 1, wherein the oxygen-free copper is a commercial TU0 oxygen-free copper rod, and the mass of the oxygen-free copper rod is 115% -130% of the mass of the chromium powder.
  10. 10. Copper-chromium contact material for vacuum circuit breaker prepared by the preparation method according to any one of claims 1 to 9.

Description

Copper-chromium contact material for vacuum circuit breaker and preparation method thereof Technical Field The invention belongs to the technical field of vacuum circuit breakers, and particularly relates to a copper-chromium contact material for a vacuum circuit breaker and a preparation method thereof, in particular to a copper-chromium contact material for a high-voltage and ultrahigh-voltage vacuum circuit breaker and a preparation method thereof. Background The vacuum circuit breaker has the characteristics of long service life, no maintenance, green environmental protection and the like, and is the development direction of high-voltage and ultrahigh-voltage switching appliances in the future. At present, 126KV and 252KV vacuum circuit breakers are produced in small batches at home and abroad, and the development of vacuum circuit breakers with higher voltage levels of 750 KV, 1100KV and the like is an important development target of the power industry. An important factor in determining the operating voltage level of a vacuum circuit breaker is the withstand voltage capability of its contact gap. The electrical breakdown of the vacuum gap is caused by the pre-breakdown. When the voltage of the vacuum gap is continuously increased, tiny current flows between electrodes before an arc is generated, namely pre-breakdown current, and the pre-breakdown phenomenon influences the basic behaviors of electric breakdown of a plurality of vacuum gaps such as arc initiation, development, movement, reburning and the like, so that the performance and reliability of the high-voltage and ultra-high-voltage vacuum circuit breaker are determined. Increasing the voltage class of a vacuum circuit breaker must effectively control the pre-breakdown behavior of the vacuum gap. Numerous studies have shown that field electron emission and microdischarge are fundamental causes of vacuum pre-breakdown. In addition, when the contact gap is continuously enhanced, the substance on the electrode surface can generate substance migration of particles under the action of the electric field, and the pre-breakdown behavior can be enhanced and initiated. At present, people mainly adopt ways of improving the surface finish of the contact, adopting voltage or current aging and the like to improve the surface quality of the contact, reducing microscopic protrusions and the like to improve the voltage resistance of a contact gap. However, the method has encountered a technical bottleneck, the voltage withstand capability of the contact gap is difficult to be continuously improved, and the improvement of the voltage class of the vacuum circuit breaker is hindered. Disclosure of Invention In order to solve the technical problems, the invention provides a copper-chromium contact material for a vacuum circuit breaker and a preparation method thereof, and adopts different improvement ideas from the prior art, wherein the ideas of the invention are as follows: At present, the research of vacuum pre-breakdown behavior and ultra-high voltage contact materials only focuses on improving the surface finish of the contact and reducing microscopic protrusions on the surface of the contact, and the effect of the internal microstructure morphology of the contact materials is rarely noticed. In fact, for contact materials of the same composition, even though the basic physical performance parameters are the same, differences in the microstructure morphology of the materials can in theory severely affect the initiation and development of vacuum electrical breakdown. If the phase structure inside the microstructure of the contact material can be spheroidized, microscopic projections in the microstructure which possibly cause field emission enhancement can be removed, the method is an effective way for further improving the voltage resistance strength of the contact gap. The invention proposes (1) changing the irregular chromium phase in the copper-chromium contact material for the vacuum circuit breaker into a spherical morphology, reducing the field enhancement factor generated in the microstructure due to the protrusion of the tip of the chromium phase inside, adopting a spheroidizing method and an angle for the second phase of the microstructure for the first time to improve the voltage resistance strength of the contact, and (2) forming a uniform microsphere network with high strength and interconnection by vacuum high-temperature sintering, and reducing the probability of copper phase and chromium phase melting to form microscopic particles escaping to a vacuum gap during arc combustion by utilizing a uniform capillary phenomenon. The two methods can obviously improve the voltage resistance of the contact gap in theory of electric breakdown, and provide a novel tissue design method and a novel high-voltage-resistant contact material for the development of high-voltage and ultra-high-voltage vacuum circuit breakers. The technical scheme of the invention is