A method for producing copper-chromium alloy by recycling copper-chromium alloy scrap

Abstract

This invention relates to the field of alloy materials and discloses a method for preparing copper-chromium alloys by recycling copper-chromium alloy waste, comprising: 1) degreasing: immersing the copper-chromium alloy waste in an organic solvent to remove oil, cleaning, and drying; 2) embrittlement: placing the copper-chromium alloy waste in a hydrogen atmosphere, heating to above 500°C for at least 1 hour to embrittle, and then cooling; 3) cryogenic crushing: ball milling the copper-chromium alloy waste in liquid nitrogen medium to obtain copper-chromium alloy powder; 4) molding and pre-sintering: molding and pre-sintering the copper-chromium alloy powder to obtain a sintered blank; 5) densification: densifying and sintering the sintered blank to obtain a copper-chromium alloy. This invention sequentially processes copper-chromium alloy waste through degreasing, embrittlement, cryogenic crushing, molding and pre-sintering, and densification to obtain a copper-chromium alloy with high purity, high electrical conductivity, and high strength, achieving efficient recycling and reuse of copper-chromium alloy waste.

Description

Technical Field

[0001] This invention relates to the field of alloy materials, and in particular to a method for preparing copper-chromium alloys by recycling copper-chromium alloy waste. Background Technology

[0002] Copper-chromium alloys are widely used in power equipment such as high-voltage circuit breakers and contactors due to their high electrical conductivity, resistance to arc erosion, and resistance to welding. However, waste materials such as shavings and scraps generated during the processing of copper-chromium alloys account for as much as 30%-40%, and traditional recycling methods have the following problems: physical crushing is inefficient because the copper matrix in copper-chromium alloys has excellent plasticity, making traditional mechanical crushing difficult and inefficient (e.g., patent CN202010991666.3); smelting methods suffer from high losses and severe segregation due to the extremely low solid solubility of copper and chromium (the maximum solubility of chromium in copper at 800℃ is only about 0.16 at%) and the significant difference in their melting points (copper melting point is 1084℃, chromium melting point is 1863℃). In addition, the recycled copper-chromium alloy materials are usually severely oxidized and have a high impurity content, resulting in significant performance degradation.

[0003] Therefore, there is an urgent need to develop a method that can efficiently recycle copper-chromium alloy waste and prepare high-purity, high-performance copper-chromium alloys. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for preparing copper-chromium alloys from recycled copper-chromium alloy waste. This invention sequentially processes the copper-chromium alloy waste through degreasing, embrittlement, cryogenic crushing, pre-sintering molding, and densification to obtain a high-purity, high-conductivity, and high-strength copper-chromium alloy, achieving efficient recycling and reuse of copper-chromium alloy waste.

[0005] The specific technical solution of the present invention includes: a method for preparing copper-chromium alloy by recycling copper-chromium alloy waste, which includes the following steps: 1) Degreasing: Soak the copper-chromium alloy waste in an organic solvent to remove oil, clean, and dry.

[0006] In step 1), the immersion treatment with organic solvents can effectively remove the oil stains adhering to the surface of the copper-chromium alloy waste, thereby reducing the impurity content.

[0007] 2) Embrittlement: Place the copper-chromium alloy scrap in a hydrogen atmosphere with a slight positive pressure of 10-50 Pa (i.e., 10-50 Pa higher than atmospheric pressure), heat it to above 500℃ for more than 1 hour, and then cool it.

[0008] In step 2), the cleaned copper-chromium alloy scrap is subjected to high-temperature heat treatment in a hydrogen atmosphere. This process allows hydrogen atoms to diffuse to the grain boundaries of the copper matrix and the copper-chromium interface at high temperatures, significantly increasing the material's brittleness. It also reduces oxides and lowers the oxygen content of the material. It is important to emphasize that the pressure of the hydrogen atmosphere has a significant impact on the embrittlement effect. Ultimately, this invention found that the optimal effect is achieved under the aforementioned micro-positive pressure of 10-50 Pa.

[0009] 3) Cryogenic crushing: The copper-chromium alloy waste is ball-milled in liquid nitrogen medium to obtain copper-chromium alloy powder.

[0010] As described in the background section, the excellent plasticity of the copper matrix in copper-chromium alloys makes traditional mechanical crushing difficult and inefficient. Therefore, this invention, based on the embrittlement treatment in step 2), further involves ball milling the embrittled copper-chromium alloy waste in liquid nitrogen in step 3), which efficiently crushes the material and yields copper-chromium alloy powder. This is because copper and chromium have extremely low solubility at room temperature (almost immiscible), resulting in a two-phase structure of "copper phase + a large amount of chromium phase," with the chromium phase being extremely predominant and potentially even forming a "continuous matrix phase." Chromium itself is a body-centered cubic metal, exhibiting a significant ductile-brittle transition under cryogenic conditions (liquid nitrogen medium), greatly increasing its brittleness and becoming a fracture initiation point. The copper phase, after treatment in step 2), shows significant embrittlement. Furthermore, the significant differences in the thermal expansion coefficients and elastic moduli between the copper and chromium phases lead to different shrinkage rates during cryogenic treatment, generating substantial internal stress at the interface, further increasing the material's brittleness and thus achieving efficient crushing.

[0011] 4) Molding and pre-sintering: Copper-chromium alloy powder is molded and pre-sintered to obtain a sintered blank.

[0012] In conventional processes, copper-chromium alloy powder is molded and then directly densified and sintered. The reason for setting step 4) of molding and pre-sintering in this invention is that: this invention found that if a high-density blank is molded in one step, on the one hand, it requires ultra-high pressure molding equipment, which has extremely high requirements for mold material and precision, resulting in large equipment investment and rapid mold wear; on the other hand, and more importantly, if a high-density blank is molded in one step, the pressure gradient and temperature gradient of the blank will exist simultaneously, which can easily lead to insufficient densification in some areas and inconsistent grain growth; and excessive pressure can easily lead to the formation of closed pores in the alloy, eventually producing bulges, thus affecting the electrical conductivity, hardness, density and other properties of the final product, resulting in significant anisotropy.

[0013] 5) Densification: Densification sintering of the sintered billet to obtain copper-chromium alloy.

[0014] To address the problems of high losses and severe segregation caused by the extremely low solid solubility of copper and chromium and the large difference in their melting points in existing smelting methods, this invention uses a ball milling crushing + pressing sintering forming process to make the chromium element more evenly distributed in the copper matrix, avoiding the compositional segregation caused by the high melting point of chromium in traditional smelting, and improving the consistency and stability of the material.

[0015] In summary, this invention sequentially processes copper-chromium alloy waste through degreasing, embrittlement, cryogenic crushing, molding pre-sintering, and densification to obtain a copper-chromium alloy with high purity, high electrical conductivity, and high strength, thus achieving efficient recycling and reuse of electrical waste (copper-chromium alloy waste).

[0016] Preferably, in step 1), the chromium content in the copper-chromium alloy scrap is 25-35 wt%.

[0017] Preferably, in step 1), the organic solvent is acetone.

[0018] Preferably, in step 1), ultrasonic treatment is performed during the soaking process.

[0019] Preferably, in step 2), the endpoint temperature of embrittlement is 800-900℃.

[0020] Within the aforementioned embrittlement temperature range, the reaction rate can be increased, thereby significantly improving the embrittlement effect.

[0021] Preferably, in step 2), the cooling is cooling to room temperature.

[0022] Preferably, in step 3), the ball mill rotation speed is 200-500 r / min and the time is 12-48 h.

[0023] Preferably, in step 2), the embrittlement process includes: first, heating to 140-160℃ at 1-5℃ / min and holding for 10-20min to gradually remove residual air from the furnace and prevent alloy oxidation; then heating to 280-320℃ at 5-10℃ / min and holding for 15-25min to remove moisture and air adsorbed on the alloy surface; then heating to 380-420℃ at 5-10℃ / min and holding for 25-35min, partly because hydrogen can reduce the residual small amount of oxides on the alloy surface at this temperature and remove gas at the alloy grain boundaries, and partly to uniform furnace temperature and eliminate internal stress in the alloy; finally, heating to above 500℃ at 1-5℃ / min and holding for more than 1 hour to fully utilize the embrittlement effect of hydrogen, while slow heating avoids thermal stress between copper and chromium.

[0024] This invention reveals that the multi-stage heating embrittlement process described above achieves a better embrittlement effect compared to one-step heating embrittlement.

[0025] Preferably, step 4) includes: loading copper-chromium alloy powder into a mold, pressing it with a pressure of 50-200 MPa, holding the pressure for 1-10 minutes, and sintering it at 800-900℃ for 1-3 hours in a vacuum atmosphere.

[0026] In step 4) of the molding pre-sintering process, the present invention controls the density of the resulting sintered blank by controlling the pressing conditions. The density after pressing should not be too high because a lower density ensures that closed pores will not form inside the blank, which is conducive to the smooth removal of residual hydrogen in the copper-chromium alloy under vacuum and high temperature.

[0027] Preferably, step 5) includes: loading the sintered billet into a densification mold, pressing it with a pressure of 500-1000MPa, holding the pressure for 1-10 minutes, and sintering it at 900-1000℃ for 1-12 hours in a vacuum atmosphere.

[0028] Compared with the prior art, the beneficial effects of the present invention are: (1) High-efficiency crushing and reduced energy consumption: This invention significantly improves the brittleness of copper-chromium alloy through hydrogen embrittlement and deep cryogenic treatment, solving the problem of low crushing efficiency caused by the high plasticity of the material and significantly reducing energy consumption.

[0029] (2) Improved composition uniformity: The present invention uses ball milling and pressing sintering process to make the chromium element more uniformly distributed in the copper matrix, avoiding composition segregation caused by the high melting point of chromium in traditional smelting, and improving the consistency and stability of the material.

[0030] (3) Excellent performance: The present invention effectively removes oxidation and impurities by acetone degreasing and high-temperature hydrogen reduction, improves the purity of the material, maintains the high electrical conductivity of the material, and at the same time adopts vacuum annealing to remove hydrogen and repressing and reheating process to effectively eliminate the effect of hydrogen embrittlement and avoid the reduction of the mechanical properties of the material. The overall performance is significantly better than traditional recycling methods.

[0031] (4) Environmental protection and energy saving, and improved resource utilization: The waste recycling rate of the entire recycling process of this invention can reach more than 98%, which reduces the waste of metal resources and conforms to the concept of green manufacturing. Attached Figure Description

[0032] Figure 1 The image shows the metallographic structure of the copper-chromium alloy prepared in Example 1 of this invention.

[0033] Figure 2 This is a metallographic diagram of the copper-chromium alloy prepared in Comparative Example 4 of the present invention. Detailed Implementation

[0034] The present invention will be further described below with reference to embodiments.

[0035] General Implementation Examples In a first aspect, the present invention provides a method for preparing copper-chromium alloys by recycling copper-chromium alloy waste, comprising the following steps: 1) Degreasing: Soak the copper-chromium alloy waste in an organic solvent to remove oil, clean, and dry.

[0036] In some preferred embodiments, in step 1), the chromium content in the copper-chromium alloy scrap is 25-35 wt%.

[0037] In some preferred embodiments, in step 1), the organic solvent is acetone.

[0038] In some preferred embodiments, in step 1), ultrasonic treatment is performed during the soaking process.

[0039] 2) Embrittlement: Place the copper-chromium alloy scrap in a slightly positive pressure hydrogen atmosphere, heat it to above 500℃ for more than 1 hour to embrittle it, and then cool it.

[0040] In some preferred embodiments, in step 2), the micro-positive pressure is 10-50 Pa.

[0041] In some preferred embodiments, in step 2), the endpoint temperature of embrittlement is 800-900°C.

[0042] In some preferred embodiments, in step 2), the cooling is cooling to room temperature.

[0043] 3) Cryogenic crushing: The copper-chromium alloy waste is ball-milled in liquid nitrogen medium to obtain copper-chromium alloy powder.

[0044] In some preferred embodiments, in step 3), the ball mill rotates at a speed of 200-500 r / min for 12-48 h.

[0045] 4) Molding and pre-sintering: Copper-chromium alloy powder is molded and pre-sintered to obtain a sintered blank.

[0046] In some preferred embodiments, step 4) includes: loading copper-chromium alloy powder into a mold, pressing it with a pressure of 50-200 MPa, holding the pressure for 1-10 minutes, and sintering it at 800-900°C for 1-3 hours in a vacuum atmosphere.

[0047] 5) Densification: Densification sintering of the sintered billet to obtain copper-chromium alloy.

[0048] In some preferred embodiments, step 5) includes: loading the sintered billet into a densification mold, pressing it with a pressure of 500-1000 MPa, holding the pressure for 1-10 min, and sintering it at 900-1000°C for 1-12 h in a vacuum atmosphere.

[0049] In some preferred embodiments, step 2) includes the following steps: First, the temperature is increased to 140-160℃ at a rate of 1-5℃ / min and held for 10-20 minutes to gradually remove residual air from the furnace and prevent alloy oxidation; then, the temperature is increased to 280-320℃ at a rate of 5-10℃ / min and held for 15-25 minutes to remove moisture and air adsorbed on the alloy surface; then, the temperature is increased to 380-420℃ at a rate of 5-10℃ / min and held for 25-35 minutes, partly because hydrogen can reduce the residual small amount of oxides on the alloy surface at this temperature and remove gas at the alloy grain boundaries, and partly to uniformize the furnace temperature and eliminate internal stress in the alloy; finally, the temperature is increased to above 500℃ at a rate of 1-5℃ / min and held for more than 1 hour to fully utilize the embrittlement effect of hydrogen, while slow heating avoids thermal stress between copper and chromium.

[0050] Specific embodiments and comparative examples Example 1

[0051] A method for recycling copper-chromium alloy waste, the specific steps of which are as follows: 1) Degreasing and drying: Soak the copper-chromium alloy scrap (chromium content of 30wt%) in acetone solution and ultrasonically treat for 30 minutes to remove the oil stains attached to the surface. After cleaning, rinse with clean water and dry for later use.

[0052] 2) Embrittlement: The cleaned copper-chromium alloy scrap is placed in a hydrogen atmosphere furnace and heated to 800℃ at a heating rate of 10℃ / min under a hydrogen pressure atmosphere (20 Pa higher than atmospheric pressure) and held for 3 hours, and then cooled to room temperature.

[0053] 3) Cryogenic crushing: The embrittled copper-chromium alloy waste is ball-milled into alloy powder in a liquid nitrogen environment. The ball milling speed is 500 r / min and the time is 24 h to obtain copper-chromium alloy powder.

[0054] 4) Molding and pre-sintering: The above copper-chromium alloy powder is loaded into a mold, pressed with a pressure of 100MPa, held for 5 minutes, and sintered at 850℃ for 2 hours in a vacuum atmosphere to obtain a sintered blank.

[0055] 5) Densification: The above sintered billet is placed into a densification mold, pressed with a pressure of 700 MPa, held for 5 minutes, and sintered at 950°C for 2 hours under vacuum to obtain a copper-chromium alloy.

[0056] Figure 1 This is a metallographic image of the copper-chromium alloy prepared in Example 1 of the present invention. Through observation... Figure 1 It can be seen that the metallographic structure of copper-chromium alloy is uniform and dense, and chromium is evenly distributed.

[0057] Comparative Example 1 The difference between this comparative example and Example 1 is that the copper-chromium alloy scrap was not subjected to acetone soaking for degreasing. The specific steps are as follows: 1) Embrittlement: Copper-chromium alloy scrap (chromium content 30wt%) is placed in a hydrogen atmosphere furnace and heated to 800℃ at a heating rate of 10℃ / min under hydrogen pressure (20 Pa higher than atmospheric pressure) and held for 3 hours, then cooled to room temperature.

[0058] 2) Cryogenic crushing: The embrittled copper-chromium alloy waste is ball-milled into alloy powder in a liquid nitrogen environment. The ball milling speed is 500 r / min and the time is 24 h to obtain copper-chromium alloy powder.

[0059] 3) Molding and pre-sintering: The above copper-chromium alloy powder is loaded into a mold, pressed with a pressure of 100MPa, held for 5 minutes, and sintered at 850℃ for 2 hours in a vacuum atmosphere to obtain a sintered blank.

[0060] 4) Densification: The above sintered billet is placed into a densification mold, pressed with a pressure of 700 MPa, held for 5 minutes, and sintered at 950°C for 2 hours under vacuum to obtain a copper-chromium alloy.

[0061] Comparative Example 2 The difference between this comparative example and Example 1 is that the copper-chromium alloy waste was ball-milled and crushed in an atmospheric environment. The specific steps are as follows: 1) Degreasing and drying: Soak the copper-chromium alloy scrap (chromium content of 30wt%) in acetone solution and ultrasonically treat for 30 minutes to remove the oil stains attached to the surface. After cleaning, rinse with clean water and dry for later use.

[0062] 2) Embrittlement: The cleaned copper-chromium alloy scrap is placed in a hydrogen atmosphere furnace and heated to 800℃ at a heating rate of 10℃ / min under a hydrogen pressure atmosphere (20 Pa higher than atmospheric pressure) and held for 3 hours, and then cooled to room temperature.

[0063] 3) Cryogenic crushing: The embrittled copper-chromium alloy waste is ball-milled into alloy powder in an atmospheric environment. The ball milling speed is 500 r / min and the time is 24 h to obtain copper-chromium alloy powder.

[0064] 4) Molding and pre-sintering: The above copper-chromium alloy powder is loaded into a mold, pressed with a pressure of 100MPa, held for 5 minutes, and sintered at 850℃ for 2 hours in a vacuum atmosphere to obtain a sintered blank.

[0065] 5) Densification: The above sintered billet is placed into a densification mold, pressed with a pressure of 700 MPa, held for 5 minutes, and sintered at 950°C for 2 hours under vacuum to obtain a copper-chromium alloy.

[0066] Comparative Example 3 The difference between this comparative example and Example 1 is that the molding preforming sintering pressure is 500 MPa, and the specific steps are as follows: 1) Degreasing and drying: Soak the copper-chromium alloy scrap (chromium content of 30wt%) in acetone solution and ultrasonically treat for 30 minutes to remove the oil stains attached to the surface. After cleaning, rinse with clean water and dry for later use.

[0067] 2) Embrittlement: The cleaned copper-chromium alloy scrap is placed in a hydrogen atmosphere furnace and heated to 800℃ at a heating rate of 10℃ / min under a hydrogen pressure atmosphere (20 Pa higher than atmospheric pressure) and held for 3 hours, and then cooled to room temperature.

[0068] 3) Cryogenic crushing: The embrittled copper-chromium alloy waste is ball-milled into alloy powder in a liquid nitrogen environment. The ball milling speed is 500 r / min and the time is 24 h to obtain copper-chromium alloy powder.

[0069] 4) Molding and pre-sintering: The above copper-chromium alloy powder is loaded into a mold, pressed with a pressure of 500MPa, held for 5 minutes, and sintered at 850℃ for 2 hours in a vacuum atmosphere to obtain a blank.

[0070] 5) Densification: The above sintered billet is placed into a densification mold, pressed with a pressure of 700 MPa, held for 5 minutes, and sintered at 950°C for 2 hours under vacuum to obtain a copper-chromium alloy.

[0071] Comparative Example 4 The difference between this comparative example and Example 1 is that it undergoes cryogenic crushing directly without embrittlement treatment. The specific steps are as follows: 1) Degreasing and drying: Soak the copper-chromium alloy scrap (chromium content of 30wt%) in acetone solution and ultrasonically treat for 30 minutes to remove the oil stains attached to the surface. After cleaning, rinse with clean water and dry for later use.

[0072] 2) Cryogenic crushing: The dried copper-chromium alloy waste is ball-milled into alloy powder in a liquid nitrogen environment. The ball milling speed is 500 r / min and the time is 24 h to obtain copper-chromium alloy powder.

[0073] 3) Molding and pre-sintering: The above copper-chromium alloy powder is loaded into a mold, pressed with a pressure of 100MPa, held for 5 minutes, and sintered at 850℃ for 2 hours in a vacuum atmosphere to obtain a sintered blank.

[0074] 4) Densification: The above sintered billet is placed into a densification mold, pressed with a pressure of 700 MPa, held for 5 minutes, and sintered at 950°C for 2 hours under vacuum to obtain a copper-chromium alloy. Figure 2 This is a metallographic image of the copper-chromium alloy prepared in Comparative Example 4 of this invention. Through observation... Figure 2 It can be seen that the metallographic structure of copper-chromium alloys is relatively loose.

[0075] Comparative Example 5 The difference between this comparative example and Example 1 is that the final temperature of the embrittlement treatment in step 2) is 400°C. The specific steps are as follows: 1) Degreasing and drying: Soak the copper-chromium alloy scrap (chromium content of 30wt%) in acetone solution and ultrasonically treat for 30 minutes to remove the oil stains attached to the surface. After cleaning, rinse with clean water and dry for later use.

[0076] 2) Embrittlement: The cleaned copper-chromium alloy scrap is placed in a hydrogen atmosphere furnace and heated to 400℃ at a heating rate of 10℃ / min under a hydrogen pressure atmosphere (20 Pa higher than atmospheric pressure) and held for 3 hours, and then cooled to room temperature.

[0077] 3) Cryogenic crushing: The embrittled copper-chromium alloy waste is ball-milled into alloy powder in a liquid nitrogen environment. The ball milling speed is 500 r / min and the time is 24 h to obtain copper-chromium alloy powder.

[0078] 4) Molding and pre-sintering: The above copper-chromium alloy powder is loaded into a mold, pressed with a pressure of 100MPa, held for 5 minutes, and sintered at 850℃ for 2 hours in a vacuum atmosphere to obtain a sintered blank.

[0079] 5) Densification: The above sintered billet is placed into a densification mold, pressed with a pressure of 700 MPa, held for 5 minutes, and sintered at 950°C for 2 hours under vacuum to obtain a copper-chromium alloy.

[0080] Comparative Example 6 The difference between this comparative example and Example 1 is that the hydrogen pressure for the embrittlement treatment in step 2) is too low. The specific steps are as follows: 1) Degreasing and drying: Soak the copper-chromium alloy scrap (chromium content of 30wt%) in acetone solution and ultrasonically treat for 30 minutes to remove the oil stains attached to the surface. After cleaning, rinse with clean water and dry for later use.

[0081] 2) Embrittlement: The cleaned copper-chromium alloy scrap is placed in a hydrogen atmosphere furnace and heated to 800℃ at a heating rate of 10℃ / min under a hydrogen pressure (20 Pa lower than atmospheric pressure) atmosphere, and held for 3 hours, and then cooled to room temperature.

[0082] 3) Cryogenic crushing: The embrittled copper-chromium alloy waste is ball-milled into alloy powder in a liquid nitrogen environment. The ball milling speed is 500 r / min and the time is 24 h to obtain copper-chromium alloy powder.

[0083] 4) Molding and pre-sintering: The above copper-chromium alloy powder is loaded into a mold, pressed with a pressure of 100MPa, held for 5 minutes, and sintered at 850℃ for 2 hours in a vacuum atmosphere to obtain a sintered blank.

[0084] 5) Densification: The above sintered billet is placed into a densification mold, pressed with a pressure of 700 MPa, held for 5 minutes, and sintered at 950°C for 2 hours under vacuum to obtain a copper-chromium alloy. Example 2

[0085] A method for recycling copper-chromium alloy waste, the specific steps of which are as follows: 1) Degreasing and drying: Soak the copper-chromium alloy scrap (chromium content of 30wt%) in acetone solution and ultrasonically treat for 30 minutes to remove the oil stains attached to the surface. After cleaning, rinse with clean water and dry for later use.

[0086] 2) Embrittlement: The cleaned copper-chromium alloy scrap is placed in a hydrogen atmosphere furnace and heated to 750°C at a heating rate of 10°C / min under a hydrogen pressure atmosphere (20 Pa higher than atmospheric pressure) for 3 hours, and then cooled to room temperature.

[0087] 3) Cryogenic crushing: The embrittled copper-chromium alloy waste is ball-milled into alloy powder in a liquid nitrogen environment. The ball milling speed is 500 r / min and the time is 24 h to obtain copper-chromium alloy powder.

[0088] 4) Molding and pre-sintering: The above copper-chromium alloy powder is loaded into a mold, pressed with a pressure of 100MPa, held for 5 minutes, and sintered at 850℃ for 2 hours in a vacuum atmosphere to obtain a sintered blank.

[0089] 5) Densification: The above sintered billet is placed into a densification mold, pressed with a pressure of 700 MPa, held for 5 minutes, and sintered at 950°C for 2 hours under vacuum to obtain a copper-chromium alloy. Example 3

[0090] A method for recycling copper-chromium alloy waste, the specific steps of which are as follows: 1) Degreasing and drying: Soak the copper-chromium alloy scrap (chromium content of 30wt%) in acetone solution and ultrasonically treat for 30 minutes to remove the oil stains attached to the surface. After cleaning, rinse with clean water and dry for later use.

[0091] 2) Embrittlement: The cleaned copper-chromium alloy scrap is placed in a hydrogen atmosphere furnace and heated to 800℃ at a heating rate of 10℃ / min under a hydrogen pressure atmosphere (20 Pa higher than atmospheric pressure) and held for 3 hours, and then cooled to room temperature.

[0092] 3) Cryogenic crushing: The embrittled copper-chromium alloy waste is ball-milled into alloy powder in a liquid nitrogen environment. The ball milling speed is 500 r / min and the time is 24 h to obtain copper-chromium alloy powder.

[0093] 4) Molding and pre-sintering: The above copper-chromium alloy powder is loaded into a mold, pressed with a pressure of 100MPa, held for 5 minutes, and sintered at 850℃ for 2 hours in a vacuum atmosphere to obtain a sintered blank.

[0094] 5) Densification: The above sintered billet is placed into a densification mold, pressed with a pressure of 700MPa, held for 5 minutes, and sintered at 1000℃ for 2 hours in a vacuum atmosphere to obtain a copper-chromium alloy. Example 4

[0095] A method for recycling copper-chromium alloy waste, the specific steps of which are as follows: 1) Degreasing and drying: Soak the copper-chromium alloy scrap (chromium content of 30wt%) in acetone solution and ultrasonically treat for 30 minutes to remove the oil stains attached to the surface. After cleaning, rinse with clean water and dry for later use.

[0096] 2) Embrittlement: The cleaned copper-chromium alloy scrap is placed in a hydrogen atmosphere furnace and heated to 750°C at a heating rate of 10°C / min under a hydrogen pressure atmosphere (20 Pa higher than atmospheric pressure) for 3 hours, and then cooled to room temperature.

[0097] 3) Cryogenic crushing: The embrittled copper-chromium alloy waste is ball-milled into alloy powder in a liquid nitrogen environment. The ball milling speed is 300 r / min and the time is 24 h to obtain copper-chromium alloy powder.

[0098] 4) Molding and pre-sintering: The above copper-chromium alloy powder is loaded into a mold, pressed with a pressure of 100MPa, held for 5 minutes, and sintered at 850℃ for 2 hours in a vacuum atmosphere to obtain a sintered blank.

[0099] 5) Densification: The above sintered billet is placed into a densification mold, pressed with a pressure of 700 MPa, held for 5 minutes, and sintered at 900°C for 2 hours under vacuum to obtain a copper-chromium alloy.

[0100] Example 5 (using a multi-stage embrittlement process) 1) Degreasing and drying: Soak the copper-chromium alloy scrap (chromium content of 30wt%) in acetone solution and ultrasonically treat for 30 minutes to remove the oil stains attached to the surface. After cleaning, rinse with clean water and dry for later use.

[0101] 2) Embrittlement: The cleaned copper-chromium alloy scrap is placed in a hydrogen atmosphere furnace. Under hydrogen pressure (20 Pa higher than atmospheric pressure), the temperature is first increased to 150℃ at 3℃ / min and held for 15 min to gradually remove residual air from the furnace and prevent alloy oxidation. Then, the temperature is increased to 300℃ at 8℃ / min and held for 20 min to remove moisture and air adsorbed on the alloy surface. Next, the temperature is increased to 400℃ at 8℃ / min and held for 30 min. This is because hydrogen can reduce the residual oxides on the alloy surface and remove gas at the alloy grain boundaries at this temperature. It also helps to uniformize the furnace temperature and eliminate internal stress in the alloy. Finally, the temperature is increased to 800℃ at 3℃ / min and held for 2 h to fully utilize the embrittlement effect of hydrogen, while slow heating avoids thermal stress between copper and chromium.

[0102] 3) Cryogenic crushing: The embrittled copper-chromium alloy waste is ball-milled into alloy powder in a liquid nitrogen environment. The ball milling speed is 500 r / min and the time is 24 h to obtain copper-chromium alloy powder.

[0103] 4) Molding and pre-sintering: The above copper-chromium alloy powder is loaded into a mold, pressed with a pressure of 100MPa, held for 5 minutes, and sintered at 850℃ for 2 hours in a vacuum atmosphere to obtain a sintered blank.

[0104] 5) Densification: The above sintered billet is placed into a densification mold, pressed with a pressure of 700 MPa, held for 5 minutes, and sintered at 950°C for 2 hours under vacuum to obtain a copper-chromium alloy.

[0105] Figure 1 This is a metallographic image of the copper-chromium alloy prepared in Example 1 of the present invention. Through observation... Figure 1 It can be seen that the metallographic structure of copper-chromium alloy is uniform and dense, and chromium is evenly distributed.

[0106] Performance Comparison The copper-chromium alloys obtained in each embodiment and comparative example were tested, and the results are shown in Table 1.

[0107] Table 1 A comparison of the data in Table 1 shows that: The copper-chromium alloy prepared in Example 1 has basically the same properties as the normal copper-chromium alloy, and can realize the effective recycling of copper-chromium contact waste.

[0108] Comparison of Comparative Example 1 and Example 1: The copper-chromium alloy scrap in Comparative Example 1 was not treated with acetone soaking for degreasing, which resulted in increased inclusions, higher oxygen content, and lower electrical conductivity in the alloy.

[0109] Comparison of Comparative Example 2 and Example 1: The copper-chromium alloy waste of Comparative Example 2 was ball-milled in an atmospheric environment. The ball-milling effect was poor, resulting in a decrease in alloy density and hardness.

[0110] Comparison of Comparative Example 3 and Example 1: The molding preforming sintering pressure in Comparative Example 3 was 500 MPa. The results showed that excessive pressure would cause bulging and reduce the alloy density and hardness.

[0111] Comparison of Comparative Example 4 and Example 1: In Comparative Example 4, the deep cryogenic crushing treatment was carried out directly without embrittlement treatment, and the results showed that the crushing effect was poor, and the alloy density and hardness were reduced.

[0112] Comparison of Comparative Example 5 and Example 1: The endpoint temperature of the embrittlement treatment in step 2) of Comparative Example 5 is 400°C. The results show that if the embrittlement temperature is too low, the embrittlement effect will decrease, thereby reducing the alloy density and hardness.

[0113] Comparison of Comparative Example 6 with Example 1: In step 2) of Comparative Example 6, the hydrogen pressure for the embrittlement treatment was too low, at 0.99 atm, which resulted in the alloy being oxidized and the oxygen content being significantly increased.

[0114] The difference between Example 5 and Example 1 is that Example 5 uses a multi-stage heating embrittlement process in step 2), which further eliminates the internal stress in the final alloy and enhances the embrittlement effect, thus improving the various indicators.

[0115] Unless otherwise specified, the raw materials and equipment used in this invention are all commonly used in the field; unless otherwise specified, the methods used in this invention are all conventional methods in the field.

[0116] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, alterations, and equivalent transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for producing a copper-chromium alloy by recycling a copper-chromium alloy scrap, characterized by The method comprises the following steps: 1) oil removal: soaking the copper-chromium alloy waste in an organic solvent, cleaning, and drying; 2) embrittlement: placing the copper-chromium alloy waste in a hydrogen atmosphere with a micro-positive pressure of 10-50 Pa, heating to above 500 ℃ for more than 1 h, and cooling; 3) cryogenic crushing: ball-milling the copper-chromium alloy waste in a liquid nitrogen medium to obtain a copper-chromium alloy powder; 4) pre-sintering molding: pre-sintering molding the copper-chromium alloy powder to obtain a sintered blank; 5) densification: densifying sintering the sintered blank to obtain a copper-chromium alloy.

2. The method of claim 1, wherein: In step 1), the content of chromium in the copper-chromium alloy waste is 25-35 wt%.

3. The method according to claim 1 or 2, characterized in that: In step 1), the organic solvent is acetone.

4. The method of claim 1 or 2, wherein: In step 1), ultrasonic treatment is performed during the soaking process.

5. The method of claim 1, wherein: In step 2), the final temperature of the embrittlement is 800-900 ℃.

6. The method of claim 1 or 5, wherein: In step 2), the cooling is cooling to room temperature.

7. The method of claim 1, wherein: In step 2), the embrittlement process comprises: first, heating at 1-5 ℃ / min to 140-160 ℃ for 10-20 min; then, heating at 5-10 ℃ / min to 280-320 ℃ for 15-25 min; then, heating at 5-10 ℃ / min to 380-420 ℃ for 25-35 min; finally, heating at 1-5 ℃ / min to above 500 ℃ for more than 1 h.

8. The method of claim 1, wherein: In step 3), the rotation speed of the ball-milling is 200-500 r / min, and the time is 12-48 h.

9. The method of claim 1, wherein: Step 4) comprises: loading the copper-chromium alloy powder into a mold, pressing at a pressure of 50-200 MPa for 1-10 min, and sintering at 800-900 ℃ for 1-3 h in a vacuum atmosphere.

10. The method of claim 1, wherein: Step 5) comprises: loading the sintered blank into a densification mold, pressing at a pressure of 500-1000 MPa for 1-10 min, and sintering at 900-1000 ℃ for 1-12 h in a vacuum atmosphere.

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