A preparation method of a high-purity fine-grained copper-chromium contact material

Abstract

The present invention discloses a preparation method of a high-purity fine-grained copper-chromium contact material, belonging to the technical field of contact material preparation. S1: Prepare electrolytic chromium powder: Put electrolytic chromium sheets into a crusher for mechanical crushing, and then use a vibration mill and a jet mill to obtain chromium powder; S2: Mix raw materials: Mix the electrolytic chromium powder and electrolytic copper powder evenly in a double-screw mixer; S3: Prepare a consumable electrode rod: Press the mixed powder into shape through a cold isostatic press; S4: Sinter the electrode rod: Sinter the electrode rod into shape in a vacuum sintering furnace; S5: Vacuum consumable melting: Put the sintered electrode rod into a vacuum consumable melting furnace for vacuum consumable melting. The present invention uses fine-grained electrolytic chromium powder as a raw material to prepare a copper-chromium contact material with a purified matrix by vacuum consumable arc melting. The prepared copper-chromium series contacts have few inclusions, excellent electrical properties and wear resistance, and meet the requirements for breaking performance under high voltage or vacuum.

Description

Technical Field

[0001] The present invention relates to the technical field of contact material preparation, and particularly to a method for preparing a high-purity fine-grained copper-chromium contact material. Background Art

[0002] The contact is one of the key components of a switching device. The main performance and service life of the switching device largely depend on the quality of the contact material. The contact material is usually required to have good electrical conductivity, low contact resistance, high anti-welding performance, high arc erosion resistance and material transfer resistance. For vacuum contact materials, it is also required to have a small cut-off value, high breakdown voltage and high breaking capacity. The microstructure of the contact material has an important influence on its macroscopic properties. The electrical properties of the contact material, such as anti-welding property, arc erosion resistance and breakdown voltage, are not only related to the composition of the contact material, but also related to the grain size of the constituent materials.

[0003] The CuCr alloy belongs to the category of immiscible alloys. The solid solubility of the two components Cu and Cr is extremely low. There is a two-phase immiscible region above the peritectic line. The phase separation during cooling will cause the segregation of Cr. It is somewhat difficult to prepare a CuCr contact material with fine and non-segregated Cr phase. Moreover, due to the limitations of its own process, the traditional method cannot prepare a CuCr contact material with uniform structure and excellent comprehensive properties. In addition, for the copper-chromium alloy contact material, the gas components, mainly the oxygen content and nitrogen content, are very important performance indicators. When the oxygen content is too high, it is released from the material at high temperature, greatly reducing the vacuum degree of the vacuum interrupter, which is fatal to vacuum devices. Also, the size, uniform distribution, inclusions, porosity, etc. of each phase in the metallographic structure are also important technical indicators of the copper-chromium contact material.

[0004] Electric breakdown first occurs in the phase with relatively lower breakdown voltage strength. For copper-chromium contact materials, electric breakdown first occurs in the chromium phase. Refinement of the microstructure and homogenization of the composition on the contact surface can improve the breakdown voltage strength. The electrical and thermal conductivity coefficients of chromium are less than those of copper. When chromium and copper carry and interrupt large currents, their abilities to generate and subsequently dissipate heat are different. Non-uniform copper-chromium structures such as large chromium particles and chromium-rich regions will cause uneven local heating on the surface of the copper-chromium structure, exacerbating local thermionic emission and outgassing, leading to breakdown, reducing the breaking performance. Moreover, a copper-chromium contact surface with fine, dispersed, and uniform distribution of chromium in copper is beneficial to improving the anti-welding property of the contact. The morphology of Cr particles has a certain influence on the electrical properties of the contact. Cr powder with a near-spherical shape and fine Cr powder are beneficial to the breakdown voltage of the contact. Compared with near-spherical particles or fine Cr powder particles, irregularly shaped Cr powder or coarse Cr powder particles have a greater degree of surface protrusion. After machining or closing operation, edges of Cr particles are formed, which are prone to tip discharge and reignition or breakdown in the electric field. With the refinement and spheroidization of Cr particles, the degree of protrusion of the sharp parts is much smaller, so the breakdown voltage performance can be improved.

[0005] Copper-chromium contacts are a type of functional material. Their performance depends not only on the composition, microstructure, and preparation process of the copper-chromium alloy but also on the types and contents of impurities in the copper-chromium alloy. The sources of impurities in copper-chromium alloys mainly include two categories: impurities brought in by Cu and Cr raw materials and impurities introduced during the preparation process. Therefore, strictly controlling the purity of raw materials and possible impurity contamination during the preparation process is a key part in the production of high-performance CuCr alloys.

[0006] The raw material chromium powder used to make copper-chromium contact materials usually adopts the aluminothermic process, that is, chromium oxide is obtained from chromite, and then chromium oxide is reduced with an aluminum reducing agent to obtain metallic chromium. In the process flow of preparing metallic chromium by the aluminothermic process, it is inevitable to introduce impurities such as silicon, iron, and aluminum, and the impurity content in the prepared metallic chromium block is relatively high. The stability of voltage and current during the melting process, and the presence of inclusions will affect the electrical properties of vacuum interruption and cannot meet the requirements for use in high voltage levels.

[0007] Currently, the main preparation methods of copper-chromium alloys include powder metallurgy, vacuum casting, vacuum infiltration, and vacuum consumable arc melting. Vacuum casting is prone to microstructural segregation. Vacuum infiltration has the disadvantages of low material utilization rate and low production efficiency. Powder metallurgy CuCr contact materials have high gas content and poor toughness. Their breaking ability is lower than that of infiltrated materials, and it is difficult to ensure the density requirements. The CuCr contact materials prepared by vacuum consumable arc melting have relatively fine grains and a more uniform tissue distribution.

[0008] During the melting process of vacuum consumable arc melting, the metal oxides have a high melting point and a low specific gravity. After copper and chromium are melted, the metal oxides will float up, accumulate on the surface of the molten pool, move to the top of the ingot with the molten pool until the end of melting and are cut off, or are blown to the edge of the molten pool by the arc and removed by turning the outer circle of the ingot's outer surface. The cooling method of vacuum consumable arc melting is to use a water-cooled copper mold or copper crystallizer with a relatively fast cooling rate. The relatively fast cooling rate increases the supercooling degree of alloy solidification, greatly inhibits the precipitation and separation of Cr phase during solidification, thereby refining the Cr phase and improving the comprehensive performance of CuCr alloy. In addition, vacuum consumable melting has the purification effect of zone melting, and the vacuum atmosphere of vacuum arc melting is conducive to the removal of low-melting and high-vapor-pressure elements in copper and chromium.

[0009] Aiming at the deficiencies of the prior art: The present invention provides a preparation method of a high-purity fine-grained copper-chromium contact material, so as to obtain a copper-chromium contact material with high performance, low inclusion and gas content, and spherical grains. Summary of the Invention

[0010] To solve the above technical problems, the present invention provides a preparation method of a high-purity fine-grained copper-chromium contact material.

[0011] The technical solution of the present invention is: A preparation method of a high-purity fine-grained copper-chromium contact material, comprising the following steps:

[0012] S1. Prepare electrolytic chromium powder:

[0013] Put electrolytic chromium flakes into a crusher for mechanical crushing, the rotation speed of the crusher is 60-80 r / min, the crushing time is 1-2 h, after crushing, put it into a vibration mill for vibration grinding, after vibration grinding, filter through a 40-mesh sieve, take the undersize A, put the undersize A into a vacuum sintering furnace at 1500-1600 °C for deoxidation sintering, after sintering, put it into a jet mill for cryogenic air flow crushing with liquid nitrogen, after crushing, first filter through an 80-mesh sieve, take the undersize B, then filter the undersize B through a 325-mesh sieve, take the oversize, and obtain electrolytic chromium powder after crushing;

[0014] S2. Mix raw materials:

[0015] Take electrolytic copper powder and the electrolytic chromium powder obtained in step S1 and put them into a double-screw mixer for mixing according to a mass ratio of 3:1-3, the mixing temperature is 60-80 °C, the mixing time is 3-10 h, the mixing speed is 30-60 r / min, and obtain mixed metal powder after mixing;

[0016] S3. Prepare a consumable electrode rod:

[0017] Load the mixed metal powder obtained in step S2 into a rubber sleeve, and tamp the powder 10 - 50 times in both forward and reverse directions. After tamping, place the rubber sleeve into a cold isostatic press for pressing. The pressing pressure of the cold isostatic press is 150 - 300 Mpa, and the pressure holding time is 5 - 15 min. After pressing, a consumable electrode rod is obtained;

[0018] S4. Electrode rod sintering:

[0019] Place the consumable electrode rod into a V-shaped graphite slot, and then place the slot into a vacuum sintering furnace for high-temperature degassing sintering. The sintering temperature is 600 - 1050 °C, and the sintering time is 10 - 30 h. After completion, a sintered electrode rod is obtained;

[0020] S5. Vacuum consumable melting:

[0021] Place the sintered electrode rod into a vacuum consumable melting furnace for vacuum consumable melting. The melting speed is 10 - 20 kg / min. After melting, a fine-grained copper-chromium contact material is obtained.

[0022] Furthermore, screen the electrolytic copper powder described in step S2. The screening uses a 200-mesh sieve. After filtration, take the material under the sieve and mix it with electrolytic chromium powder. The purity of the electrolytic copper powder ≥ 99.90%. The high purity of the electrolytic copper powder results in a high surface strength of the prepared contact material.

[0023] Furthermore, the purity of the electrolytic chromium flakes described in step S1 ≥ 99.95%. The C content in the electrolytic chromium flakes ≤ 800 ppm, the S content ≤ 500 ppm, and the O content ≤ 1500 ppm. The above are the technical indicators of the chromium powder. The contact material prepared from chromium powder meeting the above indicators has high strength.

[0024] Furthermore, the diameter of the rubber sleeve described in step S3 is 80 - 100 mm, and the length is 1100 mm. A too large rubber sleeve is not convenient for tamping powder. The above rubber sleeve size is convenient for tamping powder.

[0025] Furthermore, after pressing by the cold isostatic press in step S3, the diameter of the electrode rod is 65 - 80 mm, and the length is 800 mm. After pressing by the cold isostatic press, the diameter and length of the electrode rod are reduced.

[0026] Furthermore, the vacuum degree of the vacuum sintering furnace for chromium powder deoxidation sintering in step S1 is 0.4 - 0.9 Pa. In step S4, the electrode rod is placed into the vacuum sintering furnace and the vacuum sintering furnace is evacuated. The vacuum degree inside the vacuum sintering furnace is 0.1 - 0.5 Pa. The vacuum furnace prevents copper-chromium from oxidizing at high temperatures.

[0027] Further, before melting in the vacuum consumable melting furnace, the vacuum is pumped down to below 0.005 mba, the pressure rise rate < 0.0300 mba / min, during the consumable melting process, the voltage fluctuation < 2 V, the melting current: 2 - 4 KA, the melting voltage 20 - 25 V. Under the above technical parameters, the melting efficiency is high.

[0028] Further, in step S1, the rotational speed of the vibration mill is 900 - 1100 r / min, and the vibration crushing duration is 10 - 15 min. Under the above technical parameters, the vibration mill has the best effect.

[0029] Further, in step S1, the gas consumption of the jet mill is 10 - 20 m 3 / h, the oxygen content in the jet mill ≤ 100 ppm, and the purity of the liquid nitrogen used ≥ 99.991%. Under the above technical parameters, the jet mill has the highest efficiency.

[0030] Further, in step S1, after the electrolysis is mechanically crushed by a crusher and before being put into the vibration mill, a grinding aid is mixed in. The addition amount of the grinding aid is 0.5 - 0.8% of the mass of the chromium flakes, and the grinding aid is made by mixing sodium stearate and sodium stearate in a mass ratio of 1:1, which helps the chromium powder particles to be uniform in size.

[0031] The beneficial effects of the present invention are:

[0032] The present invention uses fine-grained electrolytic chromium powder as a raw material to prepare a purified matrix of copper-chromium contact materials by vacuum consumable arc melting. The prepared copper-chromium series contact has few inclusions, the Cr particles tend to be spheroidized and have a low gas content, the structure is uniform and fine, and the area is spheroidized. The copper-chromium contact material of the present invention has a high density, the grains of the copper-chromium contact material are relatively fine, the tissue distribution is relatively uniform, has excellent electrical properties and wear resistance, and meets the requirements of high-voltage or vacuum breaking performance. Brief Description of the Drawings

[0033] Figure 1 is a schematic process flow diagram of the preparation of the copper-chromium contact material of the present invention.

[0034] Figure 2 is a metallographic structure diagram of the copper-chromium material prepared in Example 3 of the present invention. Detailed Description of the Embodiments

[0035] Example 1:

[0036] As Figure 1 shown, a method for preparing a high-purity fine-grained copper-chromium contact material includes the following steps:

[0037] S1. Prepare electrolytic chromium powder:

[0038] Put the electrolytic chromium sheet into a crusher for mechanical crushing. The rotational speed of the crusher is 60 r / min, and the crushing duration is 1 h. After crushing, put it into a vibration mill for vibration grinding. After vibration grinding, filter it through a 40-mesh sieve, and take the material A under the sieve. Put the material A into a vacuum sintering furnace at 1500 °C for deoxidation sintering. After sintering, put it into a jet mill for cryogenic air crushing with liquid nitrogen. After crushing, first filter it through an 80-mesh sieve, take the material B under the sieve, and then filter the material B through a 325-mesh sieve, take the material on the sieve. After crushing, electrolytic chromium powder is obtained;

[0039] S2. Raw material mixing:

[0040] Put the electrolytic copper powder and the electrolytic chromium powder obtained in step S1 into a double-screw mixer for mixing according to a mass ratio of 3:1. The mixing temperature is 60 °C, the mixing duration is 3 h, the mixing speed is 30 r / min, and after mixing, mixed metal powder is obtained;

[0041] S3. Preparation of consumable electrode rod:

[0042] Put the mixed metal powder obtained in step S2 into a rubber sleeve, and compact the powder 10 times in both forward and reverse directions. After powder compaction, put the rubber sleeve into a cold isostatic press for pressing. The pressing pressure of the cold isostatic press is 150 Mpa, and the pressure holding duration is 5 min. After pressing, a consumable electrode rod is obtained;

[0043] S4. Electrode rod sintering:

[0044] Put the consumable electrode rod into a V-shaped graphite slot, and put the slot into a vacuum sintering furnace for high-temperature degassing sintering. The sintering temperature is 600 °C, and the sintering duration is 10 h. After completion, a sintered electrode rod is obtained;

[0045] S5. Vacuum consumable melting:

[0046] Put the sintered electrode rod into a vacuum consumable melting furnace for vacuum consumable melting. The melting speed is 10 kg / min. After melting, a fine-grained copper-chromium contact material is obtained.

[0047] Sieve the electrolytic copper powder in step S2. The sieving uses a 200-mesh sieve. After filtration, take the material under the sieve and mix it with the electrolytic chromium powder. The purity of the electrolytic copper powder is 99.99%. The high purity of the electrolytic copper powder results in a high surface strength of the prepared contact material.

[0048] The purity of the electrolytic chromium sheet in step S1 is 99.99%. The C content in the electrolytic chromium sheet is 800 ppm, the S content is 500 ppm, and the O content is 1500 ppm. The above are the technical indicators of the chromium powder. The contact material prepared from the chromium powder reaching the above indicators has high strength.

[0049] In step S3, the diameter of the rubber sleeve is 80 mm and the length is 1100 mm. A too large rubber sleeve is not convenient for tamping powder, and the above-mentioned size of the rubber sleeve is convenient for tamping powder.

[0050] After being pressed by a cold isostatic press in step S3, the diameter of the electrode bar is 65 mm and the length is 800 mm. After being pressed by the cold isostatic press, the diameter and length of the electrode bar are reduced.

[0051] In step S1, the vacuum degree of the vacuum sintering furnace for deoxidizing and sintering chromium powder is 0.4 Pa. In step S4, the electrode bar is placed in the vacuum sintering furnace and the vacuum sintering furnace is evacuated. The vacuum degree in the vacuum sintering furnace is 0.1 Pa. The vacuum furnace prevents copper chromium from oxidizing at high temperatures.

[0052] Before melting in the vacuum consumable melting furnace, it is evacuated to below 0.003 mba, the pressure rise rate is 0.0200 mba / min, the voltage fluctuation during the consumable melting process is 0.5 V, the melting current: 2 KA, and the melting voltage is 20 V. Under the above technical parameters, the melting efficiency is high.

[0053] In step S1, the rotation speed of the vibration mill is 900 r / min and the vibration crushing duration is 10 min. Under the above technical parameters, the vibration mill has the best effect.

[0054] In step S1, the gas consumption of the jet mill is 10 m 3 / h, the oxygen content in the jet mill is 40 ppm, and the purity of the liquid nitrogen used is 99.995%. Under the above technical parameters, the jet mill has the highest efficiency.

[0055] Example 2:

[0056] As Figure 1 shown, a method for preparing a high-purity fine-grained copper-chromium contact material includes the following steps:

[0057] S1. Prepare electrolytic chromium powder:

[0058] Put the electrolytic chromium flakes into a crusher for mechanical crushing. The rotation speed of the crusher is 70 r / min and the crushing duration is 1.5 h. After crushing, put it into a vibration mill for vibration grinding. After vibration grinding, filter it through a 40-mesh sieve, take the undersize A, put the undersize A into a vacuum sintering furnace at 1550 °C for deoxidizing sintering. After sintering, put it into a jet mill for cryogenic gas crushing with liquid nitrogen. After crushing, first filter it through an 80-mesh sieve, take the undersize B, then filter the undersize B through a 325-mesh sieve, take the oversize. After crushing, electrolytic chromium powder is obtained;

[0059] S2. Mix raw materials:

[0060] Put the electrolytic copper powder and the electrolytic chromium powder obtained in step S1 into a double - helix mixer in a mass ratio of 3:2 for mixing. The mixing temperature is 70 °C, the mixing duration is 8 h, and the mixing speed is 50 r / min. After mixing, a mixed metal powder is obtained;

[0061] S3. Prepare a consumable electrode rod:

[0062] Put the mixed metal powder obtained in step S2 into a rubber sleeve, and ram the powder 30 times in both forward and reverse directions. After ramming the powder, put the rubber sleeve into a cold isostatic press for pressing. The pressing pressure of the cold isostatic press is 200 Mpa, and the pressure - holding duration is 10 min. After pressing, a consumable electrode rod is obtained;

[0063] S4. Sinter the electrode rod:

[0064] Put the consumable electrode rod into a V - type graphite slot, and put the slot into a vacuum sintering furnace for high - temperature degassing sintering. The sintering temperature is 900 °C, and the sintering duration is 20 h. After completion, a sintered electrode rod is obtained;

[0065] S5. Vacuum consumable melting:

[0066] Put the sintered electrode rod into a vacuum consumable melting furnace for vacuum consumable melting. The melting speed is 15 kg / min. After melting, a fine - grained copper - chromium contact material is obtained.

[0067] Sieve the electrolytic copper powder in step S2. The sieve mesh used is 200 - mesh. After filtration, take the undersize and mix it with the electrolytic chromium powder. The purity of the electrolytic copper powder is 99.96%. The high purity of the electrolytic copper powder results in a high surface strength of the prepared contact material.

[0068] The purity of the electrolytic chromium flakes in step S1 is 99.97%. The C content in the electrolytic chromium flakes is 700 ppm, the S content is 450 ppm, and the O content is 1400 ppm. The above are the technical indicators of the chromium powder. The contact material prepared from the chromium powder meeting the above indicators has high strength.

[0069] In step S3, the diameter of the rubber sleeve is 90 mm and the length is 1100 mm. A too - large rubber sleeve is not convenient for ramming the powder, and the above - mentioned rubber sleeve size is convenient for ramming the powder.

[0070] In step S3, the diameter of the electrode rod after pressing by the cold isostatic press is 75 mm and the length is 800 mm. After pressing by the cold isostatic press, the diameter and length of the electrode rod are reduced.

[0071] In step S1, the vacuum degree of the vacuum sintering furnace during the deoxidation sintering of the chromium powder is 0.8 Pa. In step S4, the electrode rod is put into the vacuum sintering furnace and the vacuum sintering furnace is evacuated. The vacuum degree in the vacuum sintering furnace is 0.4 Pa. The vacuum furnace prevents copper - chromium from oxidizing at high temperatures.

[0072] Before vacuum consumable melting, the vacuum is pumped to 0.004 mba, the pressure rise rate is 0.0250 mba / min, during the consumable melting process, the voltage fluctuation is 1 V, the melting current is 3 KA, and the melting voltage is 23 V. Under the above technical parameters, the melting efficiency is high.

[0073] In step S1, the rotation speed of the vibration mill is 1000 r / min, and the vibration crushing duration is 13 min. Under the above technical parameters, the effect of the vibration mill is the best.

[0074] In step S1, the gas consumption of the jet mill is 15 m 3 / h, the oxygen content in the jet mill is 60 ppm, and the purity of the liquid nitrogen used is 99.995%. Under the above technical parameters, the efficiency of the jet mill is the highest.

[0075] Example 3:

[0076] As Figure 1 shown, a method for preparing a high-purity fine-grained copper-chromium contact material includes the following steps:

[0077] S1. Prepare electrolytic chromium powder:

[0078] Put electrolytic chromium sheets into a crusher for mechanical crushing. The rotation speed of the crusher is 80 r / min, and the crushing duration is 2 h. After crushing, put them into a vibration mill for vibration grinding. After vibration grinding, filter through a 40-mesh sieve, and take the undersize A. Put the undersize A into a vacuum sintering furnace at 1600 °C for deoxidation sintering. After sintering, put it into a jet mill for cryogenic gas crushing with liquid nitrogen. After crushing, first filter through an 80-mesh sieve, take the undersize B, and then filter the undersize B through a 325-mesh sieve, take the oversize. After crushing, electrolytic chromium powder is obtained;

[0079] S2. Mix raw materials:

[0080] Put electrolytic copper powder and the electrolytic chromium powder obtained in step S1 into a double-screw mixer for mixing according to a mass ratio of 1:1. The mixing temperature is 80 °C, the mixing duration is 10 h, and the mixing speed is 60 r / min. After mixing, mixed metal powder is obtained;

[0081] S3. Prepare a consumable electrode rod:

[0082] Put the mixed metal powder obtained in step S2 into a rubber sleeve, and ram the powder 50 times in both forward and reverse directions. After ramming the powder, put the rubber sleeve into a cold isostatic press for pressing. The pressing pressure of the cold isostatic press is 300 Mpa, and the pressure holding duration is 15 min. After pressing, a consumable electrode rod is obtained;

[0083] S4. Sinter the electrode rod:

[0084] Place the consumable electrode rod into the V-shaped graphite card slot, and put the card slot into a vacuum sintering furnace for high-temperature degassing sintering. The sintering temperature is 1050 °C, and the sintering duration is 30 h. After completion, a sintered electrode rod is obtained.

[0085] S5. Vacuum consumable melting:

[0086] Place the sintered electrode rod into a vacuum consumable melting machine for vacuum consumable melting. The melting speed is 20 kg / min. After melting, a fine-grained copper-chromium contact material is obtained.

[0087] Sieve the electrolytic copper powder in step S2. The sieve used is a 200-mesh sieve. After filtration, take the material under the sieve and mix it with electrolytic chromium powder. The purity of the electrolytic copper powder is 99.90%. The high purity of the electrolytic copper powder results in a high surface strength of the prepared contact material.

[0088] In step S1, the purity of the electrolytic chromium flakes is 99.95%. The C content in the electrolytic chromium flakes is 600 ppm, the S content is 400 ppm, and the O content is 1300 ppm. The above are the technical indicators of the chromium powder. The contact material prepared from chromium powder meeting the above indicators has high strength.

[0089] In step S3, the diameter of the rubber sleeve is 100 mm and the length is 1100 mm. A too large rubber sleeve is not convenient for powder ramming, and the above rubber sleeve size is convenient for powder ramming.

[0090] In step S3, after being pressed by a cold isostatic press, the diameter of the electrode rod is 80 mm and the length is 800 mm. After being pressed by the cold isostatic press, the diameter and length of the electrode rod are reduced.

[0091] In step S1, the vacuum degree of the vacuum sintering furnace during the chromium powder deoxidation sintering is 0.9 Pa. In step S4, the electrode rod is placed in the vacuum sintering furnace and the vacuum sintering furnace is evacuated. The vacuum degree inside the vacuum sintering furnace is 0.5 Pa. The vacuum furnace prevents copper-chromium from oxidizing at high temperatures.

[0092] Before melting in the vacuum consumable melting furnace, evacuate to 0.005 mba, the pressure rise rate is 0.0200 mba / min, the voltage fluctuation during the consumable melting process is 2 V, the melting current: 4 KA, and the melting voltage is 25 V. Under the above technical parameters, the melting efficiency is high.

[0093] In step S1, the rotation speed of the vibration mill is 1100 r / min, and the vibration crushing duration is 15 min. Under the above technical parameters, the vibration mill has the best effect.

[0094] In step S1, the gas consumption of the air jet mill is 20 m 3 / h, the oxygen content in the air jet mill is 100 ppm, and the purity of the liquid nitrogen used is 99.993%. Under the above technical parameters, the air jet mill has the highest efficiency.

[0095] Comparing Examples 1 - 3, the copper-chromium contact material prepared in Example 3 has the best wear resistance and the highest strength. As Figure 2 shown, Figure 2 This is the metallographic structure diagram of the copper-chromium contact material prepared in Example 3. Therefore, Example 3 is the best example.

[0096] Example 4:

[0097] Based on Example 3, the difference between Example 4 and Example 3 is that in step S1, after the electrolysis is mechanically crushed by a crusher and before being put into a vibration mill, a grinding aid is mixed in. The addition amount of the grinding aid is 0.5% of the mass of the chromium flakes. The grinding aid is made by mixing sodium stearate and sodium stearate in a mass ratio of 1:1, which helps to make the particle size of the chromium powder uniform.

[0098] Example 5:

[0099] Based on Example 3, the difference between Example 5 and Example 3 is that in step S1, after the electrolysis is mechanically crushed by a crusher and before being put into a vibration mill, a grinding aid is mixed in. The addition amount of the grinding aid is 0.6% of the mass of the chromium flakes. The grinding aid is made by mixing sodium stearate and sodium stearate in a mass ratio of 1:1, which helps to make the particle size of the chromium powder uniform.

[0100] Example 6:

[0101] Based on Example 3, the difference between Example 6 and Example 3 is that in step S1, after the electrolysis is mechanically crushed by a crusher and before being put into a vibration mill, a grinding aid is mixed in. The addition amount of the grinding aid is 0.8% of the mass of the chromium flakes. The grinding aid is made by mixing sodium stearate and sodium stearate in a mass ratio of 1:1, which helps to make the particle size of the chromium powder uniform.

[0102] Comparing Examples 4 - 6, the chromium powder in Example 6 has the best uniformity, and the prepared copper-chromium contact material has the best use effect. Therefore, Example 6 is the best example.

[0103] The physical and chemical properties of the copper-chromium contact materials prepared in Examples 1 - 6 are detected as shown in Table 1.

[0104] Table 1: Physical and Chemical Properties Table of Copper-Chromium Contact Materials in Examples 1 - 6

[0105]

[0106]

[0107] It can be seen from Table 1 that the copper-chromium contact material in Example 6 has the best performance.

[0108] The copper-chromium contact material prepared in Example 6 was further tested for trace elements, and the test results are shown in Table 2.

[0109] Table 2: Content Table of Trace Elements in the Copper-Chromium Contact Material Prepared in Example 6

[0110]

Claims

1. A method for preparing a high-purity fine-grained copper-chromium contact material, characterized in that, it comprises the following steps: S1. Prepare electrolytic chromium powder: Put electrolytic chromium sheets into a crusher for mechanical crushing. The rotational speed of the crusher is 60 - 80 r / min, and the crushing duration is 1 - 2 h. After crushing, put it into a vibratory mill for vibratory grinding. After vibratory grinding, filter through a 40-mesh sieve, and take the material A under the sieve. Put the material A into a vacuum sintering furnace at 1500 - 1600 °C for deoxidation sintering. After sintering, put it into a jet mill for cryogenic gas crushing with liquid nitrogen. After crushing, first filter through an 80-mesh sieve, take the material B under the sieve, then filter the material B through a 325-mesh sieve, and take the material on the sieve. After crushing, electrolytic chromium powder is obtained; S2. Raw material mixing: Take electrolytic copper powder and the electrolytic chromium powder obtained in step S1 and put them into a double-screw mixer for mixing according to a mass ratio of 3:1 - 3. The mixing temperature is 60 - 80 °C, the mixing duration is 3 - 10 h, and the mixing speed is 30 - 60 r / min. After mixing, mixed metal powder is obtained; S3. Prepare a consumable electrode rod: Put the mixed metal powder obtained in step S2 into a rubber sleeve, and ram the powder 10 - 50 times in both forward and reverse directions. After ramming the powder, put the rubber sleeve into a cold isostatic press for pressing. The pressing pressure of the cold isostatic press is 150 - 300 Mpa, and the pressure holding duration is 5 - 15 min. After pressing, a consumable electrode rod is obtained; S4. Electrode rod sintering: Put the consumable electrode rod into a V-shaped graphite slot, and put the slot into a vacuum sintering furnace for high-temperature degassing sintering. The sintering temperature is 600 - 1050 °C, and the sintering duration is 10 - 30 h. After completion, a sintered electrode rod is obtained; S5. Vacuum consumable melting: Put the sintered electrode rod into a vacuum consumable melting furnace for vacuum consumable melting. The melting speed is 10 - 20 kg / min. After melting, a fine-grained copper-chromium contact material is obtained.

2. A method for preparing a high-purity fine-grained copper-chromium contact material as described in claim 1, characterized in that, the electrolytic copper powder described in step S2 is sieved. The sieving is carried out with a 200-mesh sieve, and the material under the sieve is taken after filtration and mixed with the electrolytic chromium powder. The purity of the electrolytic copper powder is ≥ 99.90%; 3. A method for preparing a high-purity fine-grained copper-chromium contact material as described in claim 1, characterized in that, the purity of the electrolytic chromium sheets described in step S1 is ≥ 99.95%, the C content in the electrolytic chromium sheets is ≤ 800 ppm, the S content is ≤ 500 ppm, and the O content is ≤ 1500 ppm; 4. A method for preparing a high-purity fine-grained copper-chromium contact material as described in claim 1, characterized in that, the diameter of the rubber sleeve described in step S3 is 80 - 100 mm, and the length is 1100 mm; 5. A method for preparing a high-purity fine-grained copper-chromium contact material as described in claim 1, characterized in that, the diameter of the electrode rod after pressing by the cold isostatic press in step S3 is 65 - 80 mm, and the length is 800 mm; 6. A method for preparing a high-purity fine-grained copper-chromium contact material as described in claim 1, characterized in that, In the chromium powder deoxidation sintering in step S1, the vacuum degree of the vacuum sintering furnace is 0.4 - 0.9 Pa. In step S4, the electrode rod is placed in the vacuum sintering furnace and the vacuum sintering furnace is evacuated, and the vacuum degree in the vacuum sintering furnace is 0.1 - 0.5 Pa.

7. A method for preparing a high-purity fine-grained copper-chromium contact material as claimed in claim 1, characterized in that, before melting in the vacuum consumable melting furnace, it is evacuated to below 0.005 mba, and the pressure rise rate < 0.0300 mba / min. During the consumable melting process, the voltage fluctuation < 2 V, the melting current: 2 - 4 KA, and the melting voltage 20 - 25 V.

8. A method for preparing a high-purity fine-grained copper-chromium contact material as claimed in claim 1, characterized in that, in step S1, the rotation speed of the vibration mill is 900 - 1100 r / min, and the vibration crushing duration is 10 - 15 min.

9. A method for preparing a high-purity fine-grained copper-chromium contact material as claimed in claim 1, characterized in that, The gas consumption of the jet mill described in step S1 is 10 - 20 m 3 / h, the oxygen content in the jet mill is ≤ 100 ppm, and the purity of the liquid nitrogen used is ≥ 99.991%.

10. A method for preparing a high-purity fine-grained copper-chromium contact material as claimed in claim 1, characterized in that, The air consumption of the jet mill described in step S1 is 10 - 20 m 3 / h, and the oxygen content in the jet mill is ≤ 100 ppm.

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