Preparation method of high-density low-oxygen low-inclusion copper-chromium alloy contact material

Abstract

The application discloses a preparation method of high-density low-oxygen low-inclusion copper-chromium alloy contact material, which uses copper-tellurium alloy rods and high-purity degassed chromium blanks as raw materials, adopts high-purity rare earth lanthanum with a purity of 99.99%, and adopts a vacuum induction melting process to improve the uniformity and grain refinement degree of the copper-chromium-tellurium alloy, wherein the tellurium element is added in the form of copper-tellurium alloy rods, so that the volatilization of tellurium can be reduced, the uniformity of tellurium in the alloy ingot is ensured, and the copper-tellurium phase particle size is refined; the high-purity degassed chromium blank is used as the raw material to reduce the gas content and impurity content of the alloy ingot; the addition of the rare earth material La reduces the gas content of the alloy ingot and the metallographic impurity elements, and is beneficial to improving the comprehensive use performance of the copper-chromium-tellurium contact material; and the copper-chromium alloy prepared by the method has low gas content, dense structure, uniform composition, high purity, and is a high-quality and high-performance vacuum switch contact material.

Description

Technical Field

[0001] This invention relates to the field of contact technology, specifically to a method for preparing a high-density, low-oxygen, low-inclusion copper-chromium alloy contact material. Background Technology

[0002] Copper-chromium alloys possess excellent comprehensive mechanical properties, exhibiting high strength, good ductility and toughness, as well as good electrical and thermal conductivity. Their superior current-cutting capacity, resistance to arc erosion, resistance to welding, and pressure resistance compared to conventional contact materials make them the preferred contact material for high-power vacuum switches.

[0003] The gas and impurity content of copper-chromium alloys is crucial in determining their performance. High levels of gases such as oxygen and nitrogen, or a large number of inclusions, will significantly impair contact performance and may even render the material unusable. Therefore, continuously reducing the gas content and minimizing inclusion contamination are key to developing high-performance CuCr contact materials.

[0004] However, in the process of smelting and heating copper-chromium alloys prepared by existing technology, excessively high heating temperatures can cause crucible venting and crucible detachment, increasing the gas content and inclusion quantity of the ingot. CuCr alloy is a pseudo-alloy, which is prone to Cu and Cr liquid phase separation, forming segregation and resulting in copper-rich and chromium-rich defects. Inappropriate addition of tellurium element can lead to excessive distribution of metallographic inclusions in the alloy, reducing the service life and performance of the contacts.

[0005] Therefore, this invention designs a method for preparing a high-density, low-oxygen, low-inclusion copper-chromium alloy contact material to solve the above problems. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a method for preparing a high-density, low-oxygen, low-inclusion copper-chromium alloy contact material.

[0007] The technical solution of this invention is: a method for preparing a high-density, low-oxygen, low-inclusion copper-chromium alloy contact material, comprising the following steps:

[0008] S1. Preparation of raw materials:

[0009] The raw material was prepared using rare earth lanthanum, high-purity degassed chromium billet, and copper-tellurium alloy rod. The mass fraction of each component in the raw material was as follows:

[0010] Rare earth lanthanum: 0.45–0.65%,

[0011] Cr: 24-32%,

[0012] Tellurium: 0.45–0.65%,

[0013] Copper: Balance;

[0014] S2, Vacuum Induction Melting:

[0015] S2-1. Place the rare earth lanthanum, high-purity degassed chromium billet and copper tellurium alloy rod prepared in step S1 in the upper middle part of the crucible.

[0016] S2-2. Turn on the mechanical pump, Roots pump, and high vacuum pump to evacuate the equipment to a vacuum level of 10. -2 Pa, according to the gradient heating method, the power is increased to 10KW, 20KW, 30KW and 40KW respectively. The heating time of each gradient stage is 2 to 4 minutes. After each gradient heating is completed, the temperature is held for 2 to 4 minutes. After the heating and holding is completed, it is held for 3 to 5 minutes to obtain the alloy liquid.

[0017] S2-3. High-purity argon gas is introduced into the furnace until the pressure inside the furnace is -0.05 to -0.07 Pa. After the alloy liquid in the crucible is completely melted, the alloy liquid is poured to the crucible mouth for scalding. Then, the power is reduced to 30 to 35 KW within 2 to 4 minutes and maintained for 20 to 50 seconds after the power is reduced. Then, the casting is carried out in a slow-fast-slow manner to obtain copper-chromium-tellurium ingots.

[0018] S3, Hot forging and annealing:

[0019] After post-processing the copper-chromium-tellurium ingots obtained in step S2-3, the copper-chromium-tellurium ingots are hot-forged. The heating temperature of the hot forging is 700-900℃, and the deformation is 50-60%. After obtaining the forged ingots, they are annealed at a temperature of 500-900℃ and held at that temperature for 2-5 hours before being cooled in the furnace.

[0020] Furthermore, in step S1, the purity of the rare earth lanthanum is 99.99%, and the total purity of Cu and Ag in the copper tellurium alloy rod is ≥99.99%.

[0021] Explanation: The addition of rare earth element La refines the grain size, enhances the fine grain strengthening effect of the alloy, increases the hardness of the alloy, and can improve the arc erosion resistance of copper-chromium alloy materials, improve the uniformity of microstructure and the fineness of grains.

[0022] Furthermore, in step S2-3, the slow-fast-slow method is as follows: first, cast at a casting rate of 1-1.5 cm / s for 3-4 seconds, then at a casting rate of 4-6 cm / s for 75-85 seconds, and finally at a casting rate of 2-4 cm / s for 4-6 seconds.

[0023] Instructions: First, pour slowly to prevent the copper mold from being punctured and ensure the stability of the smelting process; then pour quickly to ensure the uniformity of the ingot material; finally, pour at a medium speed to reduce the depth of the shrinkage riser and improve material utilization.

[0024] Further, in step S1, the method for preparing the copper-tellurium alloy rod is as follows: the cathode copper and tellurium block are melted at a melting rate of 1150 kg / h to obtain a molten liquid, and then the molten liquid is used to prepare a copper-tellurium alloy rod with a tellurium content of 0.5-0.7% by the upward continuous casting method; wherein, the pitch of the upward continuous casting is 2.0-2.5 mm, the traction speed of the upward continuous casting is 250-300 mm / min, the water temperature of the cooling water is 28-30℃, and the water supply pressure to the crystallizer is 0.28-0.32 MPa.

[0025] Note: This method ensures the uniformity and stability of tellurium content in the alloy. Adding tellurium in the form of copper-tellurium alloy rods reduces tellurium volatilization, ensures the uniformity of tellurium in the alloy ingot, and refines the particle size of the copper-tellurium phase.

[0026] Furthermore, in step S2, the crucible is selected as a magnesium oxide crucible with an MgO content ≥ 95%.

[0027] Note: Magnesium oxide crucibles have better high-temperature stability than calcium oxide crucibles, and can effectively reduce the gas content and inclusions in alloy ingots.

[0028] Furthermore, in steps S2-3, the purity of the high-purity argon gas is ≥99.99%.

[0029] Note: High-purity argon gas is used to maintain the vacuum level and prevent the introduction of gaseous impurities.

[0030] Furthermore, in step S2-2, the alloy liquid is purified:

[0031] While setting the vacuum level, apply the initial ultrasonic wave T0 at a frequency of 15–20 kHz.

[0032] During the process of increasing the power to 10KW, a purifying agent of 0.05 to 0.08 parts by weight of the total alloy liquid is applied; during the process of increasing the power to 20KW, the first stage of ultrasonic waves T1 is applied; during the process of increasing the power to 30KW, a purifying agent of 0.08 to 0.10 parts by weight of the total alloy liquid is applied; during the process of increasing the power to 40KW, the second stage of ultrasonic waves T2 is applied.

[0033] The formulas for calculating T1 and T2 are as follows:

[0034] T1=(T0-10)*[(P t -P t-1 ) / t+P t-1 *w],T0∈[15,20] (1)

[0035] T2 = 0.5 * T1 * [(P t -P t-1 ) / t+P t-1 *w] (2)

[0036] Where T0 is the initial ultrasound, in kHz; T1 is the first-stage ultrasound, in kHz; T2 is the second-stage ultrasound, in kHz; P t This refers to the current heating power, measured in KW; P t-1 t represents the heating power of the previous stage, in KW; t represents the heating time of the stage, in min; w represents the mass percentage of the purifying agent in the total mass of the alloy liquid in the previous stage, in parts.

[0037] Explanation: By adding a purifying agent during smelting, inclusions and other impurities in the molten alloy can be further removed. Applying ultrasound can help to make the smelting more uniform and improve the contact effect between the purifying agent and the molten alloy, thereby improving the purification efficiency.

[0038] Experiments showed that intermittent addition of purifying agent and adjustment of ultrasonic frequency according to the heating rate of smelting and the proportion of purifying agent added can better remove impurities and gases, thereby improving the purity and uniformity of copper-chromium alloy. Ultrasonic treatment can further promote the dispersion of purifying agent, making the purifying agent more evenly distributed in the alloy, and can also promote the removal of gases in the alloy, thereby further improving the purity and uniformity of copper-chromium alloy and effectively enhancing the combined effect of purifying agent and ultrasonic treatment.

[0039] Furthermore, the purifying agent, by weight, comprises: 26-28 parts calcium hexaboride, 12-14 parts sodium fluorosilicate, 12-14 parts calcium fluoride, 8-10 parts antimony trioxide, and 3-4 parts barium chloride.

[0040] Explanation: Calcium hexaboride, as an excellent deoxidizer, has good deoxidation ability and purifies copper alloy liquid, enhances the mechanical properties of the copper matrix, and does not pollute the copper alloy liquid. Sodium fluorosilicate, when used in combination, forms a complex salt with inclusions in the melt, which has a strong adsorption and purification effect on the melt. Antimony trioxide can act as a strong oxidizing agent. During the melting process of copper-chromium alloy, antimony trioxide will react with impurities and oxides in the molten alloy, oxidizing and purifying them. Barium chloride is further used in combination to remove slag.

[0041] Furthermore, in step S2-2, a constant voltage of 5.5 to 7.5V is applied to the alloy liquid during the heat preservation period and the power is continuously supplied until the heat preservation ends.

[0042] Explanation: Applying a constant voltage during the heat preservation period can introduce electrical stress during the heat preservation process, which can cause grain boundaries to move rapidly, promote grain recrystallization, reduce grain boundary energy, and prevent recrystallized particles from adhering and growing. In addition, electrical stress can reduce the deformation space stress and residual stress of the alloy by controlling and eliminating hot spots, and reduce the generation of hot cracks.

[0043] The beneficial effects of this invention are:

[0044] (1) This invention selects copper tellurium alloy rods, high-purity degassed chromium billets, and rare earth (La) with a purity of 99.99% as raw materials. It uses the upward casting method to continuously cast copper tellurium alloy rods as raw materials. This method can ensure the uniformity and stability of tellurium content in the alloy. A magnesium oxide crucible is used as the melting carrier to perform vacuum induction melting to obtain copper-chromium alloy. Subsequently, hot forging and annealing are used to fully precipitate the supersaturated Cr in the Cu matrix, improve the material strength and conductivity, and achieve the purpose of refining the grains, thereby improving the overall performance of the material. Finally, a CuCrTeLa product with low gas content, low impurities, and uniform composition is obtained.

[0045] (2) In this invention, 0.45 to 0.65% rare earth (La) is added to copper-chromium alloy, which refines the grain size, enhances the fine grain strengthening effect of the alloy, increases the hardness of the alloy, and can enhance the arc erosion resistance of copper-chromium alloy materials, improve the uniformity of microstructure and the fineness of grains. Attached Figure Description

[0046] Figure 1 This is a metallographic image of the copper-chromium alloy contact of the present invention. Detailed Implementation

[0047] The present invention will now be described in more detail with reference to specific embodiments, so as to better demonstrate the advantages of the present invention.

[0048] Example 1

[0049] A method for preparing a high-density, low-oxygen, low-inclusion copper-chromium alloy contact material includes the following steps:

[0050] S1. Preparation of raw materials:

[0051] The raw material was prepared using rare earth lanthanum, high-purity degassed chromium billet, and copper-tellurium alloy rod. The mass fraction of each component in the raw material was as follows:

[0052] Rare earth lanthanum: 0.63%,

[0053] Cr: 26.18%,

[0054] Tellurium: 0.55%,

[0055] Copper: Balance;

[0056] The purity of the rare earth lanthanum is 99.99%, and the total purity of Cu and Ag in the copper tellurium alloy rod is 99.99%.

[0057] The method for preparing the copper-tellurium alloy rod is as follows: Cathode copper and tellurium blocks are melted at a melting rate of 1150 kg / h to obtain a molten liquid. The molten liquid is then used to prepare a copper-tellurium alloy rod with a tellurium content of 0.55% using an upward continuous casting method. The upward continuous casting pitch is 2.3 mm, the upward continuous casting traction speed is 280 mm / min, the cooling water temperature is 29℃, and the water supply pressure to the crystallizer is 0.30 MPa. During the upward continuous casting process, the casting temperature is 1200℃, the molten liquid level in the crystallizer is level with the crystallizer, the pouring pipe is embedded 2 cm below the liquid surface, and the charcoal powder covering thickness is 150 mm.

[0058] S2, Vacuum Induction Melting:

[0059] S2-1. Place the rare earth lanthanum, high-purity degassed chromium billet and copper tellurium alloy rod prepared in step S1 in the upper middle part of a magnesium oxide crucible with 95% MgO content.

[0060] S2-2. Turn on the mechanical pump, Roots pump, and high vacuum pump to evacuate the equipment to a vacuum level of 10. -2 Pa, the power was increased to 10KW, 20KW, 30KW and 40KW respectively according to the gradient heating method. The heating time of each gradient stage was 3min. After each gradient heating was completed, the temperature was held for 3min. After the heating and holding were completed, the temperature was held for another 4min to obtain the alloy liquid.

[0061] S2-3. High-purity argon gas is introduced into the furnace until the pressure inside the furnace is -0.06Pa. The purity of the high-purity argon gas is 99.99%. After the alloy liquid in the crucible is completely melted, the alloy liquid is poured to the crucible mouth for scalding. Then, the power is reduced to 33KW within 3 minutes and held for 35 seconds after the power is reduced. Then, the casting is carried out in a slow-fast-slow manner to obtain copper-chromium-tellurium ingots.

[0062] The slow-fast-slow method is as follows: first, pour at a pouring rate of 1.3 cm / s for 3 seconds, then pour at a pouring rate of 5 cm / s for 80 seconds, and finally pour at a pouring rate of 3 cm / s for 5 seconds.

[0063] S3, Hot forging and annealing:

[0064] After turning the outer diameter of the copper-chromium-tellurium ingot obtained in step S2-3 to a size of 4mm, the copper-chromium-tellurium ingot is hot-forged at a heating temperature of 800℃ and a deformation of 55%. After obtaining the forged ingot, it is annealed at a temperature of 700℃ and held at that temperature for 3.5h before being cooled in the furnace.

[0065] Example 2

[0066] The difference between this embodiment and Embodiment 1 is that the mass fraction of each component in the raw materials is as follows: rare earth lanthanum: 0.45%, Cr: 31.98%, tellurium: 0.45%, copper: balance.

[0067] Example 3

[0068] The difference between this embodiment and Embodiment 1 is that the mass fraction of each component in the raw materials is as follows: rare earth lanthanum: 0.52%, Cr: 25.90%, tellurium: 0.62%, copper: balance.

[0069] Example 4

[0070] The difference between this embodiment and embodiment 1 is that in step S2-2, the heating time for each gradient stage is 2 minutes, the holding time is 2 minutes after each gradient heating is completed, and the holding time is 3 minutes after the heating and holding time are completed.

[0071] Example 5

[0072] The difference between this embodiment and embodiment 1 is that in step S2-2, the heating time for each gradient stage is 4 minutes, the holding time is 4 minutes after each gradient heating is completed, and the holding time is maintained for another 5 minutes after the heating and holding time are completed.

[0073] Example 6

[0074] The difference between this embodiment and embodiment 1 is that in steps S2-3, high-purity argon gas is introduced into the furnace until the pressure inside the furnace is -0.05Pa. After the alloy liquid in the crucible is completely melted, the alloy liquid is flowed to the crucible opening for scalding. Then, the power is reduced to 30KW within 4 minutes and maintained for 20 seconds after the power reduction.

[0075] Example 7

[0076] The difference between this embodiment and embodiment 1 is that in steps S2-3, high-purity argon gas is introduced into the furnace until the pressure inside the furnace is -0.07 Pa. After the alloy liquid in the crucible is completely melted, the alloy liquid is flowed to the crucible mouth for scalding. Then, the power is reduced to 35 KW within 2 minutes and maintained for 50 seconds after the power is reduced.

[0077] Example 8

[0078] The difference between this embodiment and embodiment 1 is that in steps S2-3, the slow-fast-slow method is as follows: first, cast at a casting rate of 1 cm / s for 3 seconds, then at a casting rate of 4 cm / s for 75 seconds, and finally at a casting rate of 2 cm / s for 4 seconds.

[0079] Example 9

[0080] The difference between this embodiment and embodiment 1 is that in steps S2-3, the slow-fast-slow method is as follows: first, pour at a pouring rate of 1.5 cm / s for 4 seconds, then pour at a pouring rate of 6 cm / s for 85 seconds, and finally pour at a pouring rate of 4 cm / s for 6 seconds.

[0081] Example 10

[0082] The difference between this embodiment and Embodiment 1 is that, in step S1, the pitch of the upward continuous casting is 2.0 mm, the traction speed of the upward continuous casting is 250 mm / min, the water temperature of the cooling water is 28°C, and the water supply pressure to the crystallizer is 0.28 MPa.

[0083] Example 11

[0084] The difference between this embodiment and Embodiment 1 is that, in step S1, the pitch of the upward continuous casting is 2.5 mm, the traction speed of the upward continuous casting is 300 mm / min, the water temperature of the cooling water is 30°C, and the water supply pressure to the crystallizer is 0.32 MPa.

[0085] Example 12

[0086] The difference between this embodiment and embodiment 1 is that in step S3, the heating temperature of the hot forging is 700°C and the deformation amount is 50%.

[0087] Example 13

[0088] The difference between this embodiment and embodiment 1 is that in step S3, the heating temperature of the hot forging is 900°C and the deformation amount is 60%.

[0089] Example 14

[0090] The difference between this embodiment and Embodiment 1 is that in step S3, the annealing temperature is 500℃ and the holding time is 2h.

[0091] Example 15

[0092] The difference between this embodiment and Embodiment 1 is that in step S3, the annealing temperature is 900℃ and the holding time is 5h.

[0093] Example 16

[0094] The difference between this embodiment and Embodiment 1 is that, in step S2-2, the alloy liquid is purified:

[0095] While setting the vacuum level, an initial ultrasonic wave T0 with a frequency of 18kHz is applied.

[0096] During the process of increasing the power to 10KW, a purifying agent accounting for 0.065 parts of the total mass of the alloy liquid is applied; during the process of increasing the power to 20KW, the first stage of ultrasonic wave T1 is applied; during the process of increasing the power to 30KW, a purifying agent accounting for 0.09 parts of the total mass of the alloy liquid is applied; during the process of increasing the power to 40KW, the second stage of ultrasonic wave T2 is applied; during the heat preservation period, a constant voltage of 6.0V is applied to the alloy liquid and the power is continuously supplied until the heat preservation ends.

[0097] The purifying agent, by weight, comprises: 27 parts calcium hexaboride, 13 parts sodium fluorosilicate, 13 parts calcium fluoride, 9 parts antimony trioxide, and 3.5 parts barium chloride.

[0098] The formulas for calculating T1 and T2 are as follows:

[0099] T1=(T0-10)*[(P t -P t-1 ) / t+P t-1 *w],T0∈[15,20] (1)

[0100] T2=(T1-15)*[(P t -P t-1 ) / t+P t-1 *w] (2)

[0101] Where T0 is the initial ultrasound, in kHz; T1 is the first-stage ultrasound, in kHz; T2 is the second-stage ultrasound, in kHz; P t This refers to the current heating power, measured in KW; P t-1 t represents the heating power of the previous stage, in KW; t represents the heating time of the stage, in min; w represents the mass percentage of the purifying agent in the total mass of the alloy liquid in the previous stage, in parts.

[0102] With T0 = 18kHz, P t =20KW, P t-1 =10KW, t=3min, w=0.065 Substituting into formula (1), we get T1=31.86kHz;

[0103] With T1 = 31.86 kHz, P t =40KW, P t-1 =30KW, t=3min, w=0.09 Substituting into formula (2), we get T2=96.06kHz.

[0104] Example 17

[0105] The difference between this embodiment and embodiment 16 is that, during the period when the power is increased to 10KW, a purifying agent accounting for 0.05 parts of the total mass of the alloy liquid is applied; and during the period when the power is increased to 30KW, a purifying agent accounting for 0.08 parts of the total mass of the alloy liquid is applied.

[0106] T1 = 27.16 kHz was calculated using formula (1), and T2 = 77.85 kHz was calculated using formula (2).

[0107] Example 18

[0108] The difference between this embodiment and embodiment 16 is that, during the period when the power is increased to 10KW, a purifying agent accounting for 0.08 parts of the total mass of the alloy liquid is applied; and during the period when the power is increased to 30KW, a purifying agent accounting for 0.10 parts of the total mass of the alloy liquid is applied.

[0109] T1 = 33.06 kHz was calculated using formula (1), and T2 = 104.68 kHz was calculated using formula (2).

[0110] Example 19

[0111] The difference between this embodiment and embodiment 16 is that the initial ultrasonic wave T0 has a frequency of 15kHz; T1 is calculated to be 19.91kHz by formula (1), and T2 is calculated to be 60.05kHz by formula (2).

[0112] Example 20

[0113] The difference between this embodiment and embodiment 16 is that the initial ultrasonic wave T0 has a frequency of 20kHz; T1 is calculated to be 39.83kHz by formula (1), and T2 is calculated to be 120.14kHz by formula (2).

[0114] Example 21

[0115] The difference between this embodiment and Embodiment 16 is that the purifying agent, by weight, includes: 26 parts calcium hexaboride, 14 parts sodium fluorosilicate, 14 parts calcium fluoride, 10 parts antimony trioxide, and 4 parts barium chloride.

[0116] Example 22

[0117] The difference between this embodiment and Embodiment 16 is that the purifying agent, by weight, includes: 28 parts calcium hexaboride, 12 parts sodium fluorosilicate, 12 parts calcium fluoride, 8 parts antimony trioxide, and 3 parts barium chloride.

[0118] Example 23

[0119] The difference between this embodiment and embodiment 16 is that a constant voltage of 5.5V is applied to the alloy liquid during the heat preservation period and the power is continuously supplied until the heat preservation ends.

[0120] Example 24

[0121] The difference between this embodiment and embodiment 16 is that a constant voltage of 7.5V is applied to the alloy liquid during the heat preservation period and the power is continuously supplied until the heat preservation ends.

[0122] Experimental Example

[0123] For the copper-chromium alloy contacts prepared in each embodiment, five samples from each embodiment were taken to test the performance of the copper-chromium alloy contacts. The average value of the test results of the five samples in each embodiment was taken as the test result of that embodiment. The specific investigation is as follows:

[0124] 1. The influence of raw materials and proportions on the gas content and performance of copper-chromium alloy contacts.

[0125] Table 1 shows the gas content of the copper-chromium alloy contacts in Examples 1-3 and Comparative Example 1.

[0126]

[0127]

[0128] The difference between Comparative Example 1 and Example 1 is that the raw materials do not contain lanthanum, and the raw materials are smelted using a copper-clad tellurium method.

[0129] As shown in Table 1, the addition of rare earth lanthanum in this invention significantly reduces the gas content compared to Comparative Example 1 (CuCr25Te0.6), a copper-chromium alloy with the same chromium content but without rare earth lanthanum. Furthermore, due to the different smelting methods of the raw materials, Comparative Example 1 exhibits higher tellurium volatilization and a lower tellurium content. Examples 1-3, with the addition of rare earth lanthanum, show higher as-cast hardness and conductivity than Comparative Example 1, while their as-cast density, although lower than Comparative Example 1, shows a smaller reduction. Additionally, the addition of rare earth lanthanum in Examples 1-3 results in higher as-cast hardness and conductivity than Comparative Example 1. Figure 1 Metallographic images show that the copper-chromium alloy of the present invention has few inclusions, fine grains, and excellent performance.

[0130] 2. The effect of the preparation process on the hardness of copper-chromium alloy contacts.

[0131] Table 2 shows the as-cast hardness (HB) of the copper-chromium alloy contacts in Examples 4-15.

[0132]

[0133] As shown in Table 2, excessively small or large parameters in gradient heating, melting, casting, continuous casting, hot forging, and annealing will all reduce the hardness of the copper-chromium alloy contacts. Therefore, in comparison, the parameters in Example 1 are relatively better.

[0134] 3. The effect of the purification process on the hardness of the copper-chromium alloy contacts in the as-cast state.

[0135] Table 3 shows the as-cast hardness (HB) of the copper-chromium alloy contacts in Examples 16-24 and Comparative Examples 2-3.

[0136]

[0137] The difference between Comparative Example 2 and Example 16 is that the purifying agent was added all at once;

[0138] The difference between Comparative Example 3 and Example 16 is that the frequency of the ultrasound remains unchanged;

[0139] As shown in Table 3, Examples 16-24 all improved the hardness of the copper-chromium alloy contacts compared to Examples 1-15. However, Comparative Example 2 lacked the intermittent addition of the purifying agent, and Comparative Example 3 lacked the intermittent frequency conversion of the ultrasonic wave, thus reducing the hardness of the copper-chromium alloy contacts compared to Examples 16-24. Therefore, the steps in Examples 16-24 were more effective.

[0140] Comparing Examples 16-24, it can be seen that excessive or insufficient single addition of purifying agent, excessive or insufficient frequency of initial ultrasound, excessive or insufficient proportion of Liu Penghua Gai component in purifying agent, and excessive or insufficient constant voltage during heat preservation will all reduce the hardness of copper-chromium alloy contacts. Therefore, in summary, the parameters of Example 16 are the most effective.

Claims

1. A method for preparing a high-density, low-oxygen, low-inclusion copper-chromium alloy contact material, characterized in that, Includes the following steps: S1. Preparation of raw materials: The raw material was prepared using rare earth lanthanum, high-purity degassed chromium billet, and copper-tellurium alloy rod. The mass fraction of each component in the raw material was as follows: Rare earth lanthanum: 0.45~0.65%, Cr：24~32%， Tellurium: 0.45~0.65%, Copper: Balance; In step S1, the copper-tellurium alloy rod is prepared by melting cathode copper and tellurium blocks at a melting rate of 1150 kg / h to obtain a molten liquid, and then preparing a copper-tellurium alloy rod with a tellurium content of 0.5-0.7% by using an upward continuous casting method; wherein, the pitch of the upward continuous casting is 2.0-2.5 mm, the traction speed of the upward continuous casting is 250-300 mm / min, the water temperature of the cooling water is 28-30℃, and the water supply pressure to the crystallizer is 0.28-0.32 MPa; S2, Vacuum Induction Melting: S2-1. Place the rare earth lanthanum, high-purity degassed chromium billet and copper tellurium alloy rod prepared in step S1 in the upper middle part of the crucible; the crucible is selected as a magnesium oxide crucible with MgO content ≥95%. S2-2. Turn on the mechanical pump, Roots pump, and high vacuum pump to evacuate the equipment to a vacuum level of 10. -2 Pa, according to the gradient heating method, the power is increased to 10KW, 20KW, 30KW and 40KW respectively. The heating time of each gradient stage is 2~4min. After each gradient heating is completed, the temperature is held for 2~4min. After the heating and holding is completed, it is held for 3~5min to obtain alloy liquid. S2-3. High-purity argon gas is introduced into the furnace until the pressure inside the furnace is -0.05~-0.07Pa. After the alloy liquid in the crucible is completely melted, the alloy liquid is poured to the crucible mouth for scalding. Then, the power is reduced to 30~35KW within 2~4 minutes and maintained for 20~50 seconds after the power is reduced. Then, the casting is carried out in a slow-fast-slow manner to obtain copper-chromium-tellurium ingots. S3, Hot forging and annealing: After the outer diameter of the copper-chromium-tellurium ingot obtained in step S2-3 is processed, the copper-chromium-tellurium ingot is hot-forged. The heating temperature of the hot forging is 700~900℃, the deformation is 50~60%, and the ingot is then annealed at a temperature of 500~900℃ for 2~5 hours and then cooled in the furnace.

2. The method for preparing a high-density, low-oxygen, low-inclusion copper-chromium alloy contact material according to claim 1, characterized in that, In step S1, the purity of the rare earth lanthanum is 99.99%, and the total purity of Cu and Te in the copper tellurium alloy rod is ≥99.99%.

3. The method for preparing a high-density, low-oxygen, low-inclusion copper-chromium alloy contact material according to claim 1, characterized in that, In step S2-3, the slow-fast-slow method is as follows: first, cast at a casting rate of 1~1.5cm / s for 3~4s, then at a casting rate of 4~6cm / s for 75~85s, and finally at a casting rate of 2~4cm / s for 4~6s.

4. The method for preparing a high-density, low-oxygen, low-inclusion copper-chromium alloy contact material according to claim 1, characterized in that, In steps S2-3, the purity of the high-purity argon gas is ≥99.99%.

5. The method for preparing a high-density, low-oxygen, low-inclusion copper-chromium alloy contact material according to claim 1, characterized in that, In step S2-2, a constant voltage of 5.5~7.5V is applied to the alloy liquid during the heat preservation period and the power is continuously supplied until the heat preservation ends.

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