A method for preparing graphene-enhanced copper-chromium electrical contacts

Abstract

The present invention discloses a method for preparing a graphene-enhanced copper-chromium electrical contact, comprising the following steps: S1, ball milling; S2, cold isostatic pressing; S3, vacuum sintering; and S4, vacuum consumable arc melting. The method for preparing the graphene-enhanced copper-chromium electrical contact adopts a direct powder mixing method. Inert gas is introduced during the mixing process to prevent oxidation of the copper powder. By controlling the ball milling speed and ball size and ratio, good graphene dispersion is achieved. A vacuum consumable arc melting process is used for melting, resulting in good electrode rod degassing during the melting process and low gas content in the ingot after melting. Furthermore, the elements within the material are evenly distributed, with minimal macrosegregation, no macroscopic or microscopic defects such as element enrichment, and good structural uniformity.

Description

Technical Field

[0001] The present invention relates to the technical field of electric contacts, and in particular to a method for preparing a graphene-enhanced copper-chromium electric contact. Background Art

[0002] The conductivity of copper-chromium contact materials directly affects their electrical conductivity and breaking performance. Improving the conductivity of contact materials without compromising their mechanical properties is crucial. Graphene, with its extremely high elastic modulus and mechanical strength, as well as its excellent electrical and thermal conductivity, has become an important new material for structural engineering and functional device applications. It is considered the most effective reinforcing filler for composite materials.

[0003] Patent CN113897505A discloses a method for preparing graphene-enhanced copper-chromium electrical contact materials. The method includes uniformly mixing copper powder and chromium powder in a protective atmosphere to form a first mixed powder. The first mixed powder is subjected to chemical vapor deposition to form a graphene layer on the surface of the copper powder, thereby forming a second mixed powder of copper-based graphene and chromium powder. The second mixed powder is cold-pressed and then sintered to obtain a preform. The preform is re-pressed and re-fired to obtain an electrical contact material. This method uses chemical vapor deposition to deposit a layer of graphene on the surface of the copper powder. During this process, the copper powder is easily oxidized. In addition, the electrical contacts formed by press molding have high requirements on mold precision, low product density, and are prone to falling off during subsequent finished product processing.

[0004] Patent CN110172632A discloses a graphene oxide-enhanced dispersed copper-tungsten-chromium electrical contact material and its preparation method. Copper-aluminum alloy powder, tungsten powder, chromium powder, and cuprous oxide powder are uniformly mixed and set aside. Graphene oxide is then ultrasonically dispersed and added to the premixed powder, which is then transferred to a ball mill for ball milling. The material is then freeze-dried and vacuum hot-pressed to prepare graphene oxide-enhanced dispersed copper-tungsten-chromium electrical contacts. This method produces contacts with low production efficiency, high cost, high gas content, easy introduction of impurities, and poor overall performance.

[0005] Therefore, the present invention designs a method for preparing graphene-enhanced copper-chromium electrical contacts to improve the above problems. Summary of the Invention

[0006] In order to solve the above technical problems, the present invention provides a method for preparing a graphene-enhanced copper-chromium electrical contact.

[0007] The technical solution of the present invention is: a method for preparing a graphene-enhanced copper-chromium electrical contact, comprising the following steps:

[0008] S1, ball milling mixing:

[0009] Adding zirconia balls of various specifications to the mixed powder of metallic chromium powder and graphene into a ball mill for ball milling, and filling with argon gas during ball milling. After the ball mill rotates 360 degrees for 2 to 3 hours, electrolytic copper powder is added and mixed for 2 to 3 hours;

[0010] The mass ratio of the metallic chromium powder to the electrolytic copper powder is 1:1-3, and the graphene accounts for 1-3% of the total mass of the metallic chromium powder and the electrolytic copper powder;

[0011] S2, cold isostatic pressing:

[0012] The mixed powder after ball milling is placed in a rubber sleeve, the rubber plug is tightly plugged, the rubber sleeve is fixed in a steel sleeve for protecting the rubber sleeve, and cold isostatic pressing is performed in a cold isostatic press to obtain an electrode rod;

[0013] S3, vacuum sintering:

[0014] The electrode rod is placed in a graphite card slot and then in a vacuum sintering furnace. After vacuuming, the temperature is gradually increased: first, the temperature is increased to 240-260° C. within 1-2 hours, and the temperature is kept for 1-2 hours. Then, the temperature is increased to 340-360° C. within 0.5-1.5 hours, and the temperature is kept for 0.5-1.5 hours. Then, the temperature is increased to 690-710° C. within 2.5-3.5 hours, and the temperature is kept for 0.5-1.5 hours. Then, the temperature is increased to 890-910° C. within 2-3 hours, and the temperature is kept for 0.5-1.5 hours. Finally, the temperature is increased to 1040-1060° C. within 0.5-1.5 hours, and the temperature is kept for 1.5-2.5 hours. After the temperature is reduced to 700-800° C., argon gas is added to 85-95 kPa, and the temperature is reduced to below 80° C. before being taken out of the furnace.

[0015] S4, Vacuum consumable melting:

[0016] The electrode rod obtained in step S3 is placed in a vacuum consumable furnace for vacuum consumable smelting to obtain a graphene-enhanced copper-chromium electrical contact;

[0017] First, turn on the refrigerator, set the cooling water pressure to 3-5 bar, the compressed air to 6-8 bar, the helium pressure to 2-5 bar, and the inlet water temperature to 16-24 °C; close the vacuum consumable furnace door and evacuate to 0-5×10 -3 mbar, when the pressure rise rate is less than 0.05mbar / min, fill with helium to make the vacuum degree 80~150mbar;

[0018] During smelting, the smelting current is 3-5KA, the smelting voltage is 20-30V, the droplet rate is 0.5-1.5 drops / s, the cooling water flow is 200-300L / min, and the smelting is performed after cooling for 10-20 minutes before being taken out of the furnace.

[0019] Furthermore, in step S1, the ball-to-material ratio during ball milling is 3:1, and the ball milling speed is 300-500 r / min.

[0020] Note: If the ball-to-material ratio is too large and the ball mill speed is too high, the self-wear between the zirconia grinding balls will be aggravated, resulting in uneven grinding, more large particles, and an increase in impurities in the material; if the ball-to-material ratio is too small and the ball mill speed is too low, the particle crushing efficiency will be low.

[0021] Furthermore, in step S1, the zirconia balls include three specifications: Φ3mm, Φ8mm, and Φ10mm, and the mass ratio of the three specifications of zirconia balls is 1:1:1.

[0022] Note: Using balls of various specifications can make the mixing of powder in ball mill more uniform.

[0023] Furthermore, in step S2, the pressure of the cold isostatic pressing is 200-330 MPa, and the pressure is maintained for 5-15 minutes; the length of the pressed electrode is 600-900 mm, and the diameter is 65-80 mm.

[0024] Note: The above parameter range can improve the consolidation degree of the product, increase the mechanical properties of the product, relatively centralize the data of the production process, and can control the production more safely. It has very low corrosion, high efficiency and low cost.

[0025] Furthermore, in step S2, the specification of the rubber sleeve is Φ90~Φ95×1100mm.

[0026] Note: The above specifications can obtain electrode rods of required length and diameter.

[0027] Furthermore, in step S3, the vacuuming is carried out for 1.5 to 3 hours until the vacuum degree of the vacuum sintering furnace reaches 5×10 -3 pa.

[0028] Note: The above vacuum degree can reduce impurities in the vacuum sintering furnace, thereby increasing the impurity content of the product.

[0029] Furthermore, before ball milling, the electrolytic copper powder is subjected to an antioxidant treatment:

[0030] First, tap water, an inert organic solvent, and electrolytic copper powder in a mass ratio of 1.1 to 1.3:1:1 are washed in a powder washing tank for 20 to 30 minutes, and ultrasonic waves are applied for 60 to 70% of the washing time. Helium is introduced into the powder washing tank at a ventilation rate of 0.02 to 0.03 mL / min during the remaining time. After the washing is completed, the powder is dried to obtain an anti-oxidation electrolytic copper powder.

[0031] The inert organic solvent is a mixture of tetraethylene glycol dimethyl ether and propylene glycol ether in a mass ratio of 1:0.01-0.03, and the power of the ultrasonic wave is 220-230W.

[0032] Description: By mixing the electrolytic copper powder with an inert organic solvent and tap water for cleaning, impurities on the electrolytic copper powder can be washed away, and the inert organic solvent is assisted by applying ultrasonic waves to form an antioxidant film on the surface of the electrolytic copper powder; and by introducing inert gas helium, residual solvents and impurities on the electrolytic copper powder can be washed away.

[0033] Furthermore, the copper-chromium electrical contact obtained in step S4 is subjected to corrosion resistance treatment, comprising the following steps:

[0034] Immerse the copper-chromium electrical contact in an anti-corrosion solution at 70-80°C for 8-10 minutes, and apply a uniform magnetic field with a magnetic field strength of 0.4-0.6T during the immersion process;

[0035] After one immersion is completed, a protective agent is sprayed on the surface of the copper-chromium electrical contact at a spraying rate of 0.1-0.3 mL / min and a spraying time of 3-4 minutes. After spraying, the contact is allowed to stand for 50-60 seconds. After standing, the contact is immersed in the anti-corrosion liquid again for 5-6 minutes, and the magnetic field strength is adjusted to 0.7-0.8 T.

[0036] Description: Immerse the copper-chromium electrical contact in the anti-corrosion liquid, so that the anti-corrosion liquid penetrates into the pores on the surface of the copper-chromium electrical contact, thereby improving the corrosion resistance of the copper-chromium electrical contact surface. Through auxiliary heating by the magnetic field, the active flow of the anti-corrosion liquid is increased, thereby enhancing the impregnation effect on the copper-chromium electrical contact.

[0037] By spraying a protective agent during the dipping process, on the one hand, the contact resistance of the electric contact is reduced under the action of the protective agent, and on the other hand, the surface of the electric contact is protected from oxidation during the dipping process.

[0038] Furthermore, the protective agent comprises, by mass, 0.7 to 1 parts of trichloroethyl phosphite, 30 to 35 parts of tetraethoxysilane, 0.2 to 0.4 parts of boron oxide, and 12 to 15 parts of anilinomethyltrimethoxysilane.

[0039] Description: The above protective agent can produce good adhesion to the surface of the electrical contact and can improve the surface oxidation resistance of the electrical contact.

[0040] Furthermore, the antiseptic solution comprises, by mass percentage, 0.5-1% of siloxane phosphate, 4-6% of 2-hydroxyphosphonoacetic acid, 0.03-0.06% of ethylenetrichlorosilane, and the balance of water.

[0041] Note: The above-mentioned anti-corrosion liquid can effectively remove residual impurities on the surface of the electrical contact, prevent dielectric corrosion of the entire and local electrical contacts, and thus improve the surface quality of the electrical contacts.

[0042] The beneficial effects of the present invention are:

[0043] (1) The preparation method of the graphene-enhanced copper-chromium electrical contact of the present invention adopts a direct powder mixing method to fully and evenly mix graphene, chromium powder and copper powder. Inert gas is introduced during the mixing process to prevent oxidation of the copper powder. By controlling the ball milling speed and ball stone specifications and ratio, the graphene has good dispersion.

[0044] (2) The preparation method of the graphene-enhanced copper-chromium electrical contact of the present invention adopts a vacuum consumable arc melting process for melting. During the melting process, the electrode rod has a good degassing effect, and the gas content of the ingot after melting is low. In addition, the elements inside the material are evenly distributed, with little macro-segregation, no macro- and micro-defects such as element enrichment, and good organizational uniformity. DETAILED DESCRIPTION

[0045] The present invention will be further described in detail below in conjunction with specific implementation methods to better demonstrate the advantages of the present invention.

[0046] Example 1

[0047] A method for preparing a graphene-enhanced copper-chromium electrical contact comprises the following steps:

[0048] S1, ball milling mixing:

[0049] Three sizes of zirconia balls are added to the mixed powder of metallic chromium powder and graphene and put into a ball mill for ball milling. The zirconia balls include three sizes of Φ3mm, Φ8mm, and Φ10mm, and the mass ratio of the three sizes of zirconia balls is 1:1:1. The ball-to-material ratio during ball milling is 3:1, the ball mill speed is 400 r / min, and argon is filled during ball milling. After the ball mill rotates 360 degrees and mixes for 2.5 hours, electrolytic copper powder is added and mixed for 2.5 hours;

[0050] The mass ratio of the metallic chromium powder to the electrolytic copper powder is 1:2, and the graphene accounts for 2% of the total mass of the metallic chromium powder and the electrolytic copper powder;

[0051] S2, cold isostatic pressing:

[0052] The mixed powder after ball milling was placed into a Φ92×1100mm rubber sleeve, the rubber plug was tightly plugged, and the rubber sleeve was fixed in a steel sleeve for protecting the rubber sleeve. The cold isostatic pressing was performed in a cold isostatic press at a pressure of 265 MPa for 10 minutes to obtain an electrode rod with a length of 750 mm and a diameter of 70 mm.

[0053] S3, vacuum sintering:

[0054] The electrode rod was placed into the graphite card slot and then placed into the vacuum sintering furnace. The vacuum was pumped for 2 hours until the vacuum degree of the vacuum sintering furnace reached 5×10 -3 After pa, the temperature is increased in a gradient manner: first, the temperature is increased to 250℃ within 1.5h, and the temperature is kept for 1.5h. Then, the temperature is increased to 350℃ within 1.0h, and the temperature is kept for 1.0h. Then, the temperature is increased to 700℃ within 3.0h, and the temperature is kept for 1.0h. Then, the temperature is increased to 900℃ within 2.5h, and the temperature is kept for 1.0h. Finally, the temperature is increased to 1050℃ within 1.0h, and the temperature is kept for 2.0h. After the temperature is lowered to 750℃, argon gas is filled to 90kPa, and the temperature is lowered to 80℃ before being taken out of the furnace.

[0055] S4, Vacuum consumable melting:

[0056] The electrode rod obtained in step S3 is placed in a vacuum consumable furnace for vacuum consumable smelting to obtain a graphene-enhanced copper-chromium electrical contact;

[0057] First, turn on the refrigerator, set the cooling water pressure to 4 bar, the compressed air to 7 bar, the helium pressure to 3 bar, and the inlet water temperature to 20 °C; close the vacuum consumable furnace door and evacuate to 2.5×10 -3 mbar, when the pressure rise rate is less than 0.05mbar / min, helium is filled to make the vacuum degree 110mbar;

[0058] During smelting, the smelting current is 4KA, the smelting voltage is 25V, the drop rate is 1.0 drop / s, the cooling water flow is 250L / min, and the furnace is opened after cooling for 15 minutes.

[0059] Example 2

[0060] The difference between this embodiment and embodiment 1 is that in step S1, the zirconia balls only include those of Φ3 mm, and the ball milling speed is 300 r / min; after the ball mill rotates 360° and mixes for 2 hours, electrolytic copper powder is added and mixed for 2 hours.

[0061] Example 3

[0062] The difference between this embodiment and embodiment 1 is that in step S1, the zirconia balls include two specifications of Φ3mm and Φ8mm, and the mass ratio of the two specifications is 1:1; the ball mill speed is 500r / min; after the ball mill rotates 360° and mixes for 3h, electrolytic copper powder is added and mixed for 3h.

[0063] Example 4

[0064] The difference between this embodiment and embodiment 1 is that, in step S1, the mass ratio of the metallic chromium powder to the electrolytic copper powder is 1:1, and the graphene accounts for 1% of the total mass of the metallic chromium powder and the electrolytic copper powder.

[0065] Example 5

[0066] The difference between this embodiment and embodiment 1 is that, in step S1, the mass ratio of the metallic chromium powder to the electrolytic copper powder is 1:3, and the graphene accounts for 3% of the total mass of the metallic chromium powder and the electrolytic copper powder.

[0067] Example 6

[0068] The difference between this embodiment and embodiment 1 is that, in step S2, the specification of the rubber sleeve is Φ90×1100 mm, the cold isostatic pressing pressure is 200 MPa, and the pressure is maintained for 5 minutes; the length of the pressed electrode is 600 mm and the diameter is 65 mm.

[0069] Example 7

[0070] The difference between this embodiment and embodiment 1 is that, in step S2, the specification of the rubber sleeve is Φ95×1100 mm, the cold isostatic pressing pressure is 330 MPa, and the pressure is maintained for 15 minutes; the length of the pressed electrode is 900 mm and the diameter is 80 mm.

[0071] Example 8

[0072] The difference between this embodiment and embodiment 1 is that in step S3, the vacuum is evacuated for 1.5 hours until the vacuum degree of the vacuum sintering furnace reaches 5×10 -3 pa, gradient heating: first heat to 240℃ within 1h, keep warm for 1h, then heat to 340℃ within 0.5h, keep warm for 0.5h, then heat to 690℃ within 2.5h, keep warm for 0.5h, then heat to 890℃ within 2h, keep warm for 0.5h, finally heat to 1040℃ within 0.5h, keep warm for 1.5h, after the end of the heat preservation, cool to 700℃, fill with argon to 85kPa, cool to below 80℃ again and take out of the furnace.

[0073] Example 9

[0074] The difference between this embodiment and embodiment 1 is that in step S3, the vacuum is evacuated for 3 hours until the vacuum degree of the vacuum sintering furnace reaches 5×10 -3 pa, gradient heating: first heat to 260℃ within 2h, keep warm for 2h, then heat to 360℃ within 1.5h, keep warm for 1.5h, then heat to 710℃ within 3.5h, keep warm for 1.5h, then heat to 910℃ within 3h, keep warm for 1.5h, finally heat to 1060℃ within 1.5h, keep warm for 2.5h, after the end of the heat preservation, cool to 800℃, fill with argon to 95kPa, cool to below 80℃ again and take out of the furnace.

[0075] Example 10

[0076] The difference between this embodiment and embodiment 1 is that in step S4, the refrigerator is turned on, the cooling water pressure is set to 3 bar, the compressed air is set to 6 bar, the helium pressure is set to 2 bar, and the inlet water temperature is set to 16°C; the vacuum consumable furnace door is closed and the vacuum is evacuated to 0 mbar, and when the pressure rise rate is less than 0.05 mbar / min, helium is filled to a vacuum degree of 80 mbar.

[0077] Example 11

[0078] The difference between this embodiment and embodiment 1 is that in step S4, the refrigerator is turned on, the cooling water pressure is set to 5 bar, the compressed air pressure is set to 8 bar, the helium pressure is set to 5 bar, and the inlet water temperature is set to 24°C; the vacuum consumable furnace door is closed and the vacuum is drawn to 5×10 -3 mbar, when the pressure rise rate is less than 0.05mbar / min, helium is filled in to make the vacuum degree 150mbar.

[0079] Example 12

[0080] The difference between this embodiment and embodiment 1 is that in step S4, during smelting, the smelting current is 3KA, the smelting voltage is 20V, the droplet rate is 0.5 drops / s, the cooling water flow rate is 200L / min, and the furnace is cooled for 10 minutes.

[0081] Example 13

[0082] The difference between this embodiment and embodiment 1 is that, in step S4, during smelting, the smelting current is 5KA, the smelting voltage is 30V, the droplet rate is 1.5 drops / s, the cooling water flow rate is 300L / min, and the furnace is cooled for 20 minutes.

[0083] Example 14

[0084] The difference between this embodiment and embodiment 1 is that the electrolytic copper powder is subjected to an antioxidant treatment before the ball milling.

[0085] First, tap water, an inert organic solvent, and electrolytic copper powder in a mass ratio of 1.2:1:1 are washed in a powder washing tank for 25 minutes. Ultrasonic waves are applied for 65% of the washing time, and helium is introduced into the powder washing tank at a ventilation rate of 0.025 mL / min for the remaining time. After the washing is completed, the powder is dried to obtain an anti-oxidation electrolytic copper powder.

[0086] The inert organic solvent is a mixture of tetraethylene glycol dimethyl ether and propylene glycol ether in a mass ratio of 1:0.02, and the power of the ultrasonic wave is 225W.

[0087] Example 15

[0088] The difference between this embodiment and embodiment 14 is that the mass ratio of tap water, inert organic solvent and electrolytic copper powder is 1.1:1:1, and the inert organic solvent is a mixture of tetraethylene glycol dimethyl ether and propylene glycol ether in a mass ratio of 1:0.01.

[0089] Example 16

[0090] The difference between this embodiment and embodiment 14 is that the mass ratio of tap water, inert organic solvent and electrolytic copper powder is 1.3:1:1, and the inert organic solvent is a mixture of tetraethylene glycol dimethyl ether and propylene glycol ether in a mass ratio of 1:0.03.

[0091] Example 17

[0092] The difference between this embodiment and embodiment 14 is that the cleaning is carried out in the powder washing tank for 20 minutes, and 220W ultrasonic waves are applied for 60% of the time during the cleaning process, and helium is introduced into the powder washing tank at a ventilation rate of 0.02mL / min for the remaining time.

[0093] Example 18

[0094] The difference between this embodiment and embodiment 14 is that the cleaning is carried out in the powder washing tank for 30 minutes, and 230W ultrasonic waves are applied for 70% of the time during the cleaning process, and helium is introduced into the powder washing tank at a ventilation rate of 0.03mL / min for the remaining time.

[0095] Example 19

[0096] This embodiment differs from embodiment 14 in that the copper-chromium electrical contact obtained in step S4 is subjected to corrosion resistance treatment, comprising the following steps:

[0097] The copper-chromium electrical contact was immersed in a 75°C anti-corrosion solution for 9 minutes, and a uniform magnetic field with a magnetic field strength of 0.5 T was applied during the immersion process;

[0098] After the first immersion, the protective agent was sprayed on the surface of the copper-chromium electrical contact at a spraying rate of 0.2 mL / min and a spraying time of 3.5 min. After the spraying was completed, the contact was allowed to stand for 55 s. After the standing time, the contact was immersed in the anti-corrosion liquid again for 5.5 min. The magnetic field strength was adjusted to 0.75 T.

[0099] The protective agent comprises, by weight, 0.8 parts of trichloroethyl phosphite, 32 parts of tetraethoxysilane, 0.3 parts of boron oxide, and 14 parts of anilinomethyltrimethoxysilane;

[0100] The antiseptic solution comprises, by mass percentage, 0.8% of siloxane phosphate, 5% of 2-hydroxyphosphonoacetic acid, 0.04% of ethylene trichlorosilane and the balance of water.

[0101] Example 20

[0102] The difference between this embodiment and embodiment 19 is that the copper-chromium electrical contact is immersed in a 70° C. anti-corrosion liquid for 8 minutes, and a uniform magnetic field with a magnetic field strength of 0.4 T is applied during the immersion process.

[0103] Example 21

[0104] The difference between this embodiment and embodiment 19 is that the copper-chromium electrical contact is immersed in an anti-corrosion liquid at 80° C. for 10 minutes, and a uniform magnetic field with a magnetic field strength of 0.6 T is applied during the immersion process.

[0105] Example 22

[0106] The difference between this embodiment and embodiment 19 is that the spraying rate of the protective agent is 0.1 mL / min, the spraying time is 3 min, and the protective agent is allowed to stand for 50 s after spraying.

[0107] Example 23

[0108] The difference between this embodiment and embodiment 19 is that the spraying rate of the protective agent is 0.3 mL / min, the spraying time is 4 min, and the protective agent is allowed to stand for 60 s after spraying.

[0109] Example 24

[0110] The difference between this embodiment and embodiment 19 is that after standing still, the sample is immersed in the antiseptic solution again for 5 minutes, and the magnetic field strength is adjusted to 0.7T.

[0111] Example 25

[0112] The difference between this embodiment and embodiment 19 is that after standing still, the sample is immersed in the antiseptic solution again for 6 minutes, and the magnetic field strength is adjusted to 0.8T.

[0113] Example 26

[0114] The difference between this embodiment and embodiment 19 is that the protective agent includes, by mass, 0.7 parts of trichloroethyl phosphite, 30 parts of tetraethoxysilane, 0.2 parts of boron oxide, and 12 parts of phenylaminomethyltrimethoxysilane.

[0115] Example 27

[0116] The difference between this embodiment and embodiment 19 is that the protective agent comprises, by mass, 1 part of trichloroethyl phosphite, 35 parts of tetraethoxysilane, 0.4 parts of boron oxide, and 15 parts of phenylaminomethyltrimethoxysilane.

[0117] Example 28

[0118] The difference between this embodiment and embodiment 19 is that the antiseptic solution includes, by mass percentage, 0.5% of siloxane phosphate, 4% of 2-hydroxyphosphonoacetic acid, 0.03% of ethylenetrichlorosilane, and the balance of water.

[0119] Example 29

[0120] The difference between this embodiment and embodiment 19 is that the antiseptic solution includes, by mass percentage, 1% of siloxane phosphate, 6% of 2-hydroxyphosphonoacetic acid, 0.06% of ethylenetrichlorosilane, and the balance of water.

[0121] Experimental example

[0122] For the graphene-enhanced copper-chromium electrical contacts prepared in each embodiment, 5 samples of each embodiment were taken to test the performance of the graphene-enhanced copper-chromium electrical contacts. The performance measurement results of the 5 samples of each embodiment were averaged as the performance measurement results of the embodiment. The specific exploration is as follows:

[0123] 1. Investigate the influence of parameters in each step of the preparation process on the conductivity of copper-chromium electrical contacts.

[0124] Table 1 Electrical conductivity (Ms / m) of copper-chromium electrical contacts in Examples 1-29 and Comparative Examples 1-2

[0125]

[0126] The difference between Control Example 1 and Example 14 is that helium is not introduced during the cleaning process;

[0127] The difference between Control Example 2 and Example 19 is that the magnetic field intensity remains unchanged before and after spraying the protective agent;

[0128] As shown in Table 1, when the control example 1 lacks helium and the control example 2 lacks the change in magnetic field strength, the electrical conductivity of the copper-chromium electrical contacts prepared in the control examples 1 and 2 is lower than that in the examples 14 and 19.

[0129] By comparing Examples 1 to 13, it can be seen that when the ball mill speed and the powder mixing time are too small or too large, the parameters of the cold isostatic pressing are too small or too large, the parameters of the step-by-step heating are too small or too large, the parameters of the refrigerant are too small or too large, and the parameters of the vacuum consumable melting are too small or too large, the conductivity of the copper-chromium electrical contact will be reduced. Example 5 has the highest conductivity, but the improvement is smaller than that of Example 1, and the mass of the graphene is consumed more. Therefore, from an economic point of view, the parameter effect of Example 1 is relatively better.

[0130] Comparing Examples 1 to 18, it can be seen that the electrical conductivity of the copper-chromium electrical contacts prepared after the antioxidant treatment of Examples 14 to 18 is significantly improved compared with Examples 1 to 13. Comparing Examples 14 to 18 again, it can be seen that too little or too much cleaning liquid, too much or too much propylene glycol ether in the inert organic solvent, too short or too long cleaning time, too little or too much ultrasonic parameters applied during the cleaning process, and too little or too much ventilation parameters will reduce the electrical conductivity of the copper-chromium electrical contacts. Therefore, the parameter effect of Example 14 is relatively better.

[0131] By comparing Examples 14 to 29, it can be seen that the electrical conductivity of the copper-chromium electrical contacts prepared after the corrosion-resistant treatment of Examples 19 to 29 is significantly improved compared with Examples 14 to 18. By comparing Examples 19 to 29, it can be seen that the electrical conductivity of the copper-chromium electrical contacts will be reduced if the immersion parameters before spraying the protective agent are too small or too large, the parameters for spraying the protective agent are too small or too large, the immersion parameters after spraying the protective agent are too small or too large, the proportion of trichloroethyl phosphite in the protective agent is too large, and the proportion of ethylenetrichlorosilane in the preservative liquid is too small or too large. Therefore, on the whole, the preparation parameters of Example 19 are relatively optimal.

Claims

1. A method for preparing a graphene-enhanced copper-chromium electrical contact, characterized in that: The following steps are involved: S1, ball milling mixing: Add zirconia balls of various specifications to the mixed powder of metallic chromium powder and graphene, put it into a ball mill for ball milling, and fill it with argon gas during ball milling. After the ball mill rotates 360 degrees for 2 to 3 hours, add electrolytic copper powder and mix for 2 to 3 hours; The mass ratio of the metallic chromium powder to the electrolytic copper powder is 1:1-3, and the graphene accounts for 1-3% of the total mass of the metallic chromium powder and the electrolytic copper powder; Before ball milling, the electrolytic copper powder is first treated with antioxidant treatment: First, tap water, an inert organic solvent, and electrolytic copper powder in a mass ratio of 1.1 to 1.3:1:1 are washed in a powder washing tank for 20 to 30 minutes. Ultrasonic waves are applied for 60 to 70% of the washing time, and helium is introduced into the powder washing tank at a ventilation rate of 0.02 to 0.03 mL / min for the remaining time. After the washing is completed, the powder is dried to obtain an anti-oxidation electrolytic copper powder. The inert organic solvent is a mixture of tetraethylene glycol dimethyl ether and propylene glycol ether in a mass ratio of 1:0.01-0.03, and the power of the ultrasonic wave is 220-230W; S2, cold isostatic pressing: The mixed powder after ball milling is placed in a rubber sleeve, the rubber plug is tightly plugged, the rubber sleeve is fixed in a steel sleeve for protecting the rubber sleeve, and cold isostatic pressing is performed in a cold isostatic press to obtain an electrode rod; S3, vacuum sintering: The electrode rod is placed in a graphite card slot and then in a vacuum sintering furnace. After vacuuming, the temperature is gradually increased: first, the temperature is increased to 240-260° C. within 1-2 hours, and the temperature is kept for 1-2 hours. Then, the temperature is increased to 340-360° C. within 0.5-1.5 hours, and the temperature is kept for 0.5-1.5 hours. Then, the temperature is increased to 690-710° C. within 2.5-3.5 hours, and the temperature is kept for 0.5-1.5 hours. Then, the temperature is increased to 890-910° C. within 2-3 hours, and the temperature is kept for 0.5-1.5 hours. Finally, the temperature is increased to 1040-1060° C. within 0.5-1.5 hours, and the temperature is kept for 1.5-2.5 hours. After the temperature is reduced to 700-800° C., argon gas is added to 85-95 kPa, and the temperature is reduced to below 80° C. before being taken out of the furnace. S4, Vacuum consumable melting: The electrode rod obtained in step S3 is placed in a vacuum consumable furnace for vacuum consumable smelting to obtain a graphene-enhanced copper-chromium electrical contact; First, turn on the refrigerator, set the cooling water pressure to 3~5 bar, the compressed air to 6~8 bar, the helium pressure to 2~5 bar, and the inlet water temperature to 16~24℃; close the vacuum consumable furnace door and evacuate to 0~5×10 -3 mbar, when the pressure rise rate is less than 0.05mbar / min, fill with helium to make the vacuum degree 80~150mbar; During smelting, the smelting current is 3~5KA, the smelting voltage is 20~30V, the droplet rate is 0.5~1.5 drops / s, the cooling water flow is 200~300L / min, and the smelting is carried out of the furnace after cooling for 10~20 minutes.

2. The method for preparing a graphene-enhanced copper-chromium electrical contact according to claim 1, characterized in that: In step S1, the ball-to-material ratio during ball milling is 3:1, and the ball milling speed is 300-500 r / min.

3. The method for preparing a graphene-enhanced copper-chromium electrical contact according to claim 1, characterized in that: In step S1, the zirconia balls include three specifications of Φ3mm, Φ8mm, and Φ10mm, and the mass ratio of the three specifications of zirconia balls is 1:1:1; the ball-to-material ratio during ball milling is 3:1, and the ball milling speed is 300~500r / min.

4. The method for preparing a graphene-enhanced copper-chromium electrical contact according to claim 1, wherein: In step S2, the pressure of cold isostatic pressing is 200-330 MPa, and the pressure is maintained for 5-15 minutes; the length of the pressed electrode is 600-900 mm, and the diameter is 65-80 mm.

5. The method for preparing a graphene-enhanced copper-chromium electrical contact according to claim 1, characterized in that: In step S2, the specification of the rubber sleeve is Φ90~Φ95×1100mm.

6. The method for preparing a graphene-enhanced copper-chromium electrical contact according to claim 1, characterized in that: In step S3, the vacuuming is carried out for 1.5 to 3 hours until the vacuum degree of the vacuum sintering furnace reaches 5×10 -3 pa.

7. The method for preparing a graphene-enhanced copper-chromium electrical contact according to claim 1, characterized in that: The copper-chromium electrical contact obtained in step S4 is subjected to corrosion resistance treatment, comprising the following steps: Immerse the copper-chromium electrical contact in an anti-corrosion solution at 70-80°C for 8-10 minutes, and apply a uniform magnetic field with a magnetic field strength of 0.4-0.6T during the immersion process; After one immersion is completed, a protective agent is sprayed on the surface of the copper-chromium electrical contact. The spraying rate is 0.1~0.3mL / min and the spraying time is 3~4min. After spraying, let it stand for 50~60s. After standing, immerse it in the anti-corrosion liquid again for 5~6min. The magnetic field strength is adjusted to 0.7~0.8T.

8. The method for preparing a graphene-enhanced copper-chromium electrical contact according to claim 7, characterized in that: The protective agent comprises, by weight, 0.7 to 1 parts of trichloroethyl phosphite, 30 to 35 parts of tetraethoxysilane, 0.2 to 0.4 parts of boron oxide, and 12 to 15 parts of anilinomethyltrimethoxysilane.

9. The method for preparing a graphene-enhanced copper-chromium electrical contact according to claim 7, characterized in that: The antiseptic solution comprises, by mass percentage, 0.5-1% of siloxane phosphate, 4-6% of 2-hydroxyphosphonoacetic acid, 0.03-0.06% of ethylene trichlorosilane, and the balance of water.

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