CN113817922A - Method for recycling and utilizing copper-chromium contact waste - Google Patents
Method for recycling and utilizing copper-chromium contact waste Download PDFInfo
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Abstract
The invention relates to the field of metal materials, and discloses a method for recycling and utilizing copper-chromium contact waste, which comprises the following steps: (1) separating copper and chromium in the copper-chromium contact waste by using nitric acid as a dissolving solution, and filtering to obtain a copper nitrate solution and porous chromium; (2) washing the porous chromium with water, and drying; then placing the mixture in a reduction device for reduction: introducing dry hydrogen, heating to 350-450 ℃, keeping the temperature, heating to 900-1400 ℃ after the titanium alloy bar adsorbs hydrogen to be saturated, and reducing the titanium alloy bar to release hydrogen so as to remove the surface passivation film of porous chromium; and cooling, taking out the product, performing ball milling crushing in an inert atmosphere, and sieving to obtain the low-oxygen high-purity chromium powder. Firstly, the recovery method can effectively separate copper and chromium in the copper-chromium contact waste, and has low energy consumption and high product purity. Secondly, the copper-chromium iron material prepared by the method has good uniformity of all metal elements and good performance when being used as a copper-chromium contact and the like.
Description
Technical Field
The invention relates to the field of metal materials, in particular to a method for recycling and utilizing copper-chromium contact waste.
Background
The CuCr contact is used as a heart component of a medium-high voltage vacuum switch, and Cu and Cr components of the CuCr contact are not mutually soluble and have no reaction, so that the CuCr contact not only retains the excellent electric and heat conducting property of Cu, but also has the characteristics of strong affinity and refractory property of Cr to oxygen, so that the CuCr contact has the characteristics of high breaking capacity, high voltage resistance, good comprehensive performance and the like, and the CuCr contact basically replaces CuW, CuWC, CuMo, CuBi, CuBiAg and other contact materials originally used for the medium-high voltage vacuum switch.
In order to further improve the performance of the copper-chromium contact material, the addition of the third and fourth component is a hot spot of the current research, for example, the addition of tungsten and molybdenum can improve the voltage resistance of the contact; the addition of tellurium can improve the fusion welding resistance; the addition of bismuth or lead can reduce the cutoff value; the addition of iron can improve the voltage resistance strength and reduce the shutoff value, and the method for adding the third and fourth components is mainly carried out in a direct batching and mixing manner, so that the problem of poor uniformity exists.
The CuCr series contact material is produced by consumable electrode arc melting method, vacuum fusion casting method, infiltration method and powder mixing and pressure sintering method. The methods are all to produce blanks and then to prepare the blanks into various required shapes through turning, and the waste materials obtained through turning have the problem of difficult recovery, thereby causing great pressure on environment and resources.
Chinese patent CN201911225947.1 discloses a method for recovering copper-chromium contact waste, which comprises the following steps: (1) preparing the copper-chromium contact waste into a consumable electrode; (2) carrying out vacuum induction melting on the consumable electrode obtained in the step (1) to obtain an alloy melt; (3) atomizing the alloy melt obtained in the step (2) to obtain the alloy powder with copper and chromium. Because copper and chromium are immiscible, copper with a low melting point is melted first in the consumable electrode induction melting process, and chromium with a high melting point is not melted, so that the copper-chromium alloy powder can generate 'inclusion' powder only containing chromium or copper; furthermore, the chromium requires 1900 ℃ for complete melting, so high temperatures lead to severe evaporation of copper or chromium and the energy consumption is extremely high.
Disclosure of Invention
In order to solve the problems that the copper-chromium contact waste is difficult to recycle and high in energy consumption in the prior art and the mixing uniformity of the third element (iron) in the copper-chromium iron composite material prepared by the powder mixing method, the invention provides a method for recycling and utilizing the copper-chromium contact waste. Firstly, the recovery method can effectively separate copper and chromium in the copper-chromium contact waste, and has low energy consumption and high product purity. Secondly, the copper-chromium iron material prepared by the method has good uniformity of all metal elements and good performance when being used as a copper-chromium contact and the like.
The specific technical scheme of the invention is as follows:
in a first aspect, the invention provides a method for recovering copper-chromium contact waste, which comprises the following steps:
(1) and (3) separating copper and chromium in the copper-chromium contact waste by using nitric acid as a dissolving solution, and filtering to obtain a copper nitrate solution and porous chromium. The reaction formula is as follows:
Cu+4HNO3＝Cu(NO3)2+2NO2↑+2H2O
in step (1), the invention dissolves copper in the copper-chromium contact waste by nitric acid, the copper reacts with the nitric acid to form copper nitrate, and the chromium is passivated by the nitric acid surface and is not dissolved. In the process of dissolving copper ions, a large number of pores are generated in the residual chromium, porous chromium is obtained after filtering, and the specific surface area of the porous structure is large, so that convenience is brought to the subsequent reduction treatment.
(2) Washing the porous chromium obtained in the step (1) with water, and drying to evaporate water; then placing the mixture in a reduction device; the reduction device comprises a shell and a titanium alloy bar material layer arranged in the shell, wherein a screen is laid on the upper surface of the titanium alloy bar material layer, and the porous chromium is laid on the screen; the reduction process is as follows: introducing dry hydrogen, heating to 350-450 ℃, keeping the temperature, heating to 900-1400 ℃ after the titanium alloy bar adsorbs hydrogen to be saturated, and reducing the titanium alloy bar to release hydrogen so as to remove the surface passivation film of porous chromium; and cooling, taking out the product, performing ball milling crushing in an inert atmosphere, and sieving to obtain the low-oxygen high-purity chromium powder.
In the step (2), the invention adopts a high-temperature hydrogen reduction method to remove the surface passivation film of the porous chromium so as to improve the purity of the chromium. Specifically, in the process of first heating to 350-450 ℃, enough hydrogen is absorbed by the titanium alloy bar, and then the temperature is quickly raised to 900-1400 ℃ for reduction. At the moment, the titanium alloy bar releases ultrahigh pure hydrogen to reduce chromium powder, and the low-oxygen high-purity chromium powder can be obtained after ball milling, crushing and screening. The special reduction process has the advantages that: the hydrogen molecules are firstly adsorbed by the surface of the titanium alloy bar when the temperature is raised for the first time, at the moment, the hydrogen molecules are dissociated to form hydrogen atoms, the hydrogen atoms are diffused into the interior of the alloy and stored in gaps among the titanium atoms, when the diffusion is saturated, the temperature is continuously raised to a high-temperature stage, the atomic hydrogen in the alloy is released to the surface of the titanium alloy bar, and accordingly ultrahigh-purity hydrogen is released, the ultrahigh-purity hydrogen reduction capability is stronger than that of common hydrogen, meanwhile, the affinity of titanium to oxygen is higher, the oxygen partial pressure in the environment is reduced, and the continuous proceeding of the hydrogen reduction chromium oxide reaction is facilitated. The screen is a gas diffusion channel used for separating the titanium alloy bar and the porous chromium, and simultaneously, the gas diffusion channel is a gas diffusion channel for releasing ultrahigh-purity hydrogen to reduce the porous chromium from the titanium alloy bar and capturing gaseous products by titanium after reaction.
Preferably, the step (1) specifically comprises: processing the copper-chromium contact waste into copper-chromium scraps, adding the copper-chromium scraps into a nitric acid aqueous solution, stirring and mixing, reacting copper with nitric acid to form copper nitrate, and passivating chromium by nitric acid without dissolving; filtering to obtain porous chromium.
Preferably, in the step (1), the mass concentration of the nitric acid aqueous solution is 1 to 50%.
Preferably, in the step (1), the thickness of the copper chromium filings is less than 1 mm.
Preferably, in the step (2), the drying condition is 50-120 ℃ for 30-90 min.
Preferably, in the step (2),
the thickness of the titanium alloy bar material layer is 10-50 mm; the titanium alloy is Ti-6A 1-4V; the diameter of the titanium alloy bar is 1-10 mm; the mesh number of the screen is-300 to +800 meshes; the paving thickness of the porous chromium is 1-5 cm.
According to the invention, the titanium alloy bar is used as a material for adsorbing hydrogen, and compared with pure titanium adopted by the team in the initial stage of research and development, the titanium alloy bar can resist high-temperature treatment for many times and has long service life. Pure titanium materials undergo severe pulverization after multiple high temperature treatments, contaminate reduced powders, require frequent replacement, and increase costs.
Preferably, the dry hydrogen has a dew point of less than-70 ℃; the heat preservation time is 10-60 min; the reduction time is 10-60 min; the ball milling and crushing time is 30-180 min.
In a second aspect, the present invention provides a process for preparing a copper-chromium-iron composite material from the product obtained by the above recovery process, comprising the steps of:
(A) performing a displacement reaction on the copper nitrate solution obtained in the step (1) by using iron powder under an acidic condition to obtain copper-coated iron composite powder, and reducing the copper-coated iron composite powder by using the reduction method in the step (2) with the difference that the reduction temperature is 550-650 ℃; and cooling, taking out the product, performing ball milling crushing in an inert atmosphere, and sieving to obtain the low-oxygen high-purity copper-coated iron composite powder. The reaction formula is as follows:
Fe+Cu(NO3)2＝Cu+Fe(NO3)2
(B) mixing the obtained low-oxygen high-purity chromium powder and the low-oxygen high-purity copper-clad iron composite powder, and then sequentially pressing, hydrogen reduction sintering and cooling to obtain the low-oxygen high-performance copper-chromium iron material.
Preferably, step (a) specifically comprises: heating the copper nitrate solution obtained in the step (1) to 60-100 ℃ until the concentration of copper ions in the solution is 60-150 g/L, adding sodium hydroxide to adjust the pH value to 3-5, then adding 100-200 meshes of iron powder, stirring for a displacement reaction, washing with water and drying to obtain copper-coated iron composite powder; then, carrying out reduction treatment on the copper-coated iron composite powder by adopting the reduction method in the step (2), wherein the difference is that the reduction temperature is 550-650 ℃; and cooling, taking out the product, performing ball milling crushing in an inert atmosphere, and sieving to obtain the low-oxygen high-purity copper-coated iron composite powder.
Preferably, in the step (A), the stirring time is 5-50 min, and the ball milling crushing time is 30-180 min.
Preferably, in step (B): the mass ratio of the low-oxygen high-purity chromium powder to the low-oxygen high-purity copper-coated iron composite powder is 1: 5-1: 1.
Preferably, the mixing time is 30-120 min; the pressing pressure is 300-700 MPa; the sintering temperature is 900-1100 ℃, and the heat preservation time is 60-180 min.
Compared with the prior art, the invention has the beneficial effects that:
(1) the recovery method can effectively separate copper and chromium in the copper-chromium contact waste, and has low energy consumption and high product purity.
(2) The copper-chromium iron material prepared by the method has good uniformity of all metal elements and good performance when being used as a copper-chromium contact and the like.
Drawings
FIG. 1 is a schematic diagram of a high temperature hydrogen reduction process of the present invention;
fig. 2 is a schematic diagram of a contact conductivity test position.
Detailed Description
The present invention will be further described with reference to the following examples.
General examples
A method for recycling copper-chromium contact waste comprises the following steps:
(1) processing the copper-chromium contact waste into copper-chromium scraps with the thickness less than 1mm, adding the copper-chromium scraps into 1-50 wt% of nitric acid aqueous solution, stirring and mixing, reacting copper with nitric acid to form copper nitrate, and passivating chromium by nitric acid without dissolving; filtering to obtain porous chromium. The reaction formula is as follows:
Cu+4HNO3＝Cu(NO3)2+2NO2↑+2H2O
(2) washing the porous chromium obtained in the step (1) with water, and drying at 50-120 ℃ for 30-90 min until the water is completely evaporated; then placing the mixture in a reduction device; as shown in fig. 1, the reduction device comprises a shell and a titanium alloy bar material layer (the thickness is 10-50 mm, the titanium alloy is Ti-6a1-4V, and the diameter of the titanium alloy bar material is 1-10 mm) arranged in the shell, wherein a sieve mesh of-300 to +800 meshes is laid on the upper surface of the titanium alloy bar material layer, and the porous chromium is laid on the sieve mesh with the laying thickness of 1-5 cm; the reduction process is as follows: introducing dry hydrogen with a dew point of less than-70 ℃, heating to 350-450 ℃, keeping the temperature for 10-60 min, and after the titanium alloy bar adsorbs hydrogen to be saturated, heating to 900-1400 ℃ to enable the titanium alloy bar to release hydrogen for reduction treatment for 10-60 min so as to remove the surface passivation film of porous chromium; and cooling, taking out the product, performing ball milling crushing in an inert atmosphere for 30-180 min, and sieving to obtain the low-oxygen high-purity chromium powder.
(3) Heating the copper nitrate solution obtained in the step (1) to 60-100 ℃ until the concentration of copper ions in the solution is 60-150 g/L, adding sodium hydroxide to adjust the pH value to 3-5, then adding 100-200 meshes of iron powder, stirring for 5-50 min to perform a displacement reaction, washing with water and drying to obtain copper-coated iron composite powder; then, carrying out reduction treatment on the copper-coated iron composite powder by adopting the reduction method in the step (2), wherein the difference is that the reduction temperature is 550-650 ℃; and cooling, taking out the product, performing ball milling crushing in an inert atmosphere for 30-180 min, and sieving to obtain the low-oxygen high-purity copper-coated iron composite powder. The reaction formula is as follows:
Fe+Cu(NO3)2＝Cu+Fe(NO3)2
(4) mixing the obtained low-oxygen high-purity chromium powder and the low-oxygen high-purity copper-clad iron composite powder for 30-120min according to the mass ratio of 1: 5-1: 1, and then sequentially performing pressing (300-700 MPa), hydrogen reduction sintering (900-1100 ℃, heat preservation for 60-180 min) and cooling to obtain the low-oxygen high-performance copper-chromium iron material.
Example 1
Preparing a 10 mass percent nitric acid solution in a beaker, putting the beaker into cooling water, lathing copper-chromium waste materials until the thickness is 0.8mm to obtain copper-chromium scraps, pouring the copper-chromium scraps into the nitric acid solution, stirring for dissolving, and filtering to obtain a copper nitrate solution and porous chromium. Washing the porous chromium by using deionized water, drying in an oven at 70 ℃ for 60min, taking out for standby, placing a layer of titanium alloy bar (Ti-6A-4V) at the bottom of the stainless steel boat, wherein the diameter of the titanium alloy bar is 3mm, the thickness of the titanium alloy bar is 20mm, then laying a layer of 500-mesh screen mesh on the titanium alloy bar, and then laying a layer of the obtained porous chromium with the thickness of 3cm on the screen mesh. Reducing by using dry hydrogen, wherein the dew point of the dry hydrogen is-73 ℃, heating to 450 ℃, preserving heat for 15min, then quickly heating to 1150 ℃ for reduction, reducing for 30min, cooling, taking out the spongy porous chromium with low oxygen and high purity, carrying out ball milling and crushing for 60min under the protection of argon with the purity of 99.999 percent, and sieving by a-200-mesh sieve to obtain the chromium powder with low oxygen and high purity.
Heating the obtained copper nitrate solution to 80 ℃ until the concentration of copper ions in the solution is 100g/L, adding sodium hydroxide to adjust the pH value to 4, then adding 200-mesh iron powder into the solution, stirring the solution for 25min to obtain copper-coated iron composite powder, cleaning the copper-coated iron composite powder by using deionized water, drying the powder in an oven at 80 ℃ for 45min, taking out the powder for later use, placing a layer of titanium alloy bar (Ti-6Al-4V) at the bottom of a stainless steel boat, wherein the diameter of the titanium alloy bar is 5mm, the thickness of the titanium alloy bar is 20mm, then laying a layer of 600-mesh screen on the top of the titanium alloy bar, then laying a layer of the obtained copper-coated iron composite powder with the thickness of 4 cm on the screen, reducing the powder by dry hydrogen, raising the dry hydrogen dew point to-70 ℃, heating to 450 ℃, keeping the temperature for 40min, then rapidly raising the temperature to 650 ℃ for reduction, reducing the powder for 25min and then cooling, and cooling, taking out the low-oxygen high-purity spongy copper-coated iron composite powder, carrying out ball milling and crushing for 150min under the protection of argon with the purity of 99.999 percent, and sieving with a-250-mesh sieve to obtain the low-oxygen high-purity copper-coated iron composite powder.
The obtained low-oxygen high-purity metal chromium powder and copper-coated iron composite powder are respectively mixed according to the proportion of 30 percent, 40 percent and 50 percent of chromium content, poured into a mixer for mixing, taken out after being mixed for 70min, pressed on an oil press under the pressing pressure of 500MPa, then sintered in a hydrogen sintering furnace at the sintering temperature of 950 ℃, kept warm for 120min and cooled along with the furnace to obtain the low-oxygen high-performance copper-chromium iron contact material.
Example 2
Preparing a nitric acid solution with the mass concentration of 25% in a beaker, putting the beaker into cooling water, lathing copper-chromium waste materials until the thickness is 1mm to obtain copper-chromium scraps, pouring the copper-chromium scraps into the nitric acid solution, stirring, dissolving, and filtering to obtain the copper nitrate solution and porous chromium. And cleaning the porous chromium by using deionized water, drying the porous chromium in an oven for 90min at 50 ℃, taking out the porous chromium for standby, placing a layer of titanium alloy bar (Ti-6Al-4V) at the bottom of the stainless steel boat, wherein the diameter of the titanium alloy bar is 2mm, the thickness of the titanium alloy bar is 12mm, then paving a layer of 300-mesh screen mesh on the titanium alloy bar, and then paving a layer of the obtained porous chromium on the screen mesh, wherein the thickness of the porous chromium is 5 cm. Reducing by using dry hydrogen, wherein the dew point of the dry hydrogen is-72 ℃, heating to 350 ℃, keeping the temperature for 60min, then quickly heating to 950 ℃ for reduction, reducing the temperature for 60min, cooling, taking out the spongy porous chromium with low oxygen and high purity, carrying out ball milling and crushing for 30min under the protection of argon with the purity of 99.999 percent, and sieving by a-200-mesh sieve to obtain the chromium powder with low oxygen and high purity.
Heating the obtained copper nitrate solution to 65 ℃ until the concentration of copper ions in the solution is 60g/L, adding sodium hydroxide to adjust the pH value to 4, then adding 150-mesh iron powder into the solution, stirring the solution for 45min to obtain copper-coated iron composite powder, cleaning the copper-coated iron composite powder by using deionized water, drying the powder in an oven for 50min at 60 ℃, taking out the powder for standby application, placing a layer of titanium alloy bar (Ti-6Al-4V) at the bottom of a stainless steel boat, wherein the diameter of the titanium alloy bar is 2mm, the thickness of the titanium alloy bar is 12mm, then laying a layer of 800-mesh screen on the top of the titanium alloy bar, then laying a layer of the obtained copper-coated iron composite powder with the thickness of 1.5cm on the screen, reducing by dry hydrogen, raising the dry hydrogen dew point to-72 ℃, heating to 350 ℃, keeping the temperature for 60min, then rapidly raising the temperature to 550 ℃ for reduction, reducing the temperature after 60min, and cooling, taking out the low-oxygen high-purity spongy copper-coated iron composite powder, carrying out ball milling and crushing for 40min under the protection of argon with the purity of 99.999 percent, and sieving with a-250-mesh sieve to obtain the low-oxygen high-purity copper-coated iron composite powder.
The obtained low-oxygen high-purity metal chromium powder and copper-coated iron composite powder are respectively mixed according to the chromium content of 30%, 40% and 50%, poured into a mixer for mixing, taken out after 30min of mixing, pressed on an oil press at the pressing pressure of 700MPa, then sintered in a hydrogen sintering furnace at the sintering temperature of 1020 ℃, and cooled along with the furnace after 60min of heat preservation to obtain the low-oxygen high-performance copper-chromium iron contact material.
Example 3
Preparing a 45 mass percent nitric acid solution in a beaker, putting the beaker into cooling water, lathing copper-chromium waste materials until the thickness is 0.7mm to obtain copper-chromium scraps, pouring the copper-chromium scraps into the nitric acid solution, stirring for dissolving, and filtering to obtain a copper nitrate solution and porous chromium. Washing the porous chromium by using deionized water, drying in an oven at 100 ℃ for 30min, taking out for standby, placing a layer of titanium alloy bar (Ti-6Al-4V) at the bottom of the stainless steel boat, wherein the diameter of the titanium alloy bar is 8mm, the thickness of the titanium alloy bar is 40mm, laying a layer of 800-mesh screen mesh on the titanium alloy bar, and laying a layer of the obtained porous chromium with the thickness of 1cm on the screen mesh. Reducing by using dry hydrogen, wherein the dew point of the dry hydrogen is-73 ℃, heating to 400 ℃, keeping the temperature for 45min, then quickly heating to 1300 ℃ for reduction, reducing for 15min, cooling, taking out the spongy porous chromium with low oxygen and high purity, carrying out ball milling and crushing for 150min under the protection of argon with the purity of 99.999 percent, and sieving by a-200-mesh sieve to obtain the chromium powder with low oxygen and high purity.
Heating the obtained copper nitrate solution to 95 ℃, until the concentration of copper ions in the solution is 130g/L, adding sodium hydroxide to adjust the pH value to 5, then adding 100-mesh iron powder into the solution, stirring the solution for 15min to obtain copper-coated iron composite powder, cleaning the copper-coated iron composite powder by using deionized water, drying the powder in an oven for 15min at 100 ℃, taking out the powder for standby application, placing a layer of titanium alloy bar (Ti-6Al-4V) at the bottom of a stainless steel boat, wherein the diameter of the titanium alloy bar is 8mm, the thickness of the titanium alloy bar is 40mm, then laying a layer of 800-mesh screen on the top of the titanium alloy bar, then laying a layer of the obtained copper-coated iron composite powder with the thickness of 1.5cm on the screen, reducing by dry hydrogen, raising the dry hydrogen dew point to-73 ℃, heating to 400 ℃, keeping the temperature for 45min, then rapidly raising the temperature to 600 ℃ for reduction, reducing the temperature after 45min, and (3) cooling, taking out the low-oxygen high-purity spongy copper-coated iron composite powder, carrying out ball milling and crushing for 80min under the protection of argon with the purity of 99.999%, and sieving with a-250-mesh sieve to obtain the low-oxygen high-purity copper-coated iron composite powder.
The obtained low-oxygen high-purity metal chromium powder and copper-coated iron composite powder are respectively mixed according to the proportion of 30 percent, 40 percent and 50 percent of chromium content, poured into a mixer for mixing, taken out after being mixed for 120min, pressed on an oil press at the pressing pressure of 400MPa, then sintered in a hydrogen sintering furnace at the sintering temperature of 1090 ℃, and cooled along with the furnace after heat preservation for 180min, so as to obtain the low-oxygen high-performance copper-chromium iron contact material.
Comparative example 1
Respectively mixing commercially available metal chromium powder, electrolytic copper powder and iron powder according to the proportion of 30 percent, 40 percent and 50 percent of chromium content, pouring the mixture into a mixer for mixing, taking out the mixed powder after mixing for 90min, pressing the mixed powder on an oil press at the pressing pressure of 600MPa, then sintering the pressed powder in a hydrogen sintering furnace at the sintering temperature of 1000 ℃, preserving heat for 180min, and then cooling the pressed powder along with the furnace to obtain the copper-chromium iron composite contact material.
Comparative example 2
The porous chromium and copper-coated iron composite powder obtained in example 1 and not subjected to high-temperature hydrogen reduction is directly subjected to ball milling and screening treatment, ball milling is carried out under the protection of a high-purity argon atmosphere of 99.999%, the ball milling time is 45min and 30min respectively, then the porous chromium and copper-coated iron composite powder is poured into a mixer according to the proportion of 30%, 40% and 50% of chromium respectively to mix, the mixture is taken out after 70min of mixing, the mixed powder is pressed on an oil press, the pressing pressure is 500MPa, then the porous chromium and copper-coated iron composite powder is sintered in a hydrogen sintering furnace, the sintering temperature is 950 ℃, the temperature is kept for 120min, and then the temperature is reduced along with the furnace, so that the copper-chromium-iron composite contact material is obtained.
The porous chromium and copper-coated iron composite powder which is obtained in the example 1 and is not subjected to high-temperature hydrogen reduction is subjected to conventional hydrogen reduction, namely, titanium alloy is not placed at the bottom of the boat, wherein the process for reducing the porous chromium is that the dew point of hydrogen is-70 ℃, the heat preservation temperature is 1150 ℃, and the heat preservation time is 30 min; the process for reducing the copper-coated iron composite powder comprises the steps of keeping a hydrogen dew point at-70 ℃, keeping a heat preservation temperature of 650 ℃, keeping a heat preservation time of 25min, carrying out ball milling and screening after reduction, carrying out ball milling under the protection of a high-purity argon atmosphere with the ball milling being 99.999%, wherein the ball milling time is 45min and 30min respectively, then pouring the ball milling into a mixer according to the proportion of 30%, 40% and 50% of chromium respectively, mixing the mixture for 70min, taking out the mixed powder, pressing the mixed powder on an oil press at a pressing pressure of 500MPa, sintering in a hydrogen sintering furnace at a sintering temperature of 950 ℃, keeping the temperature for 120min, and then cooling along with the furnace to obtain the copper-chromium iron composite contact material.
Performance testing
The impurity content test of chromium powder and copper-coated iron composite powder comprises the following steps: the chromium powder and the copper-coated iron composite powder obtained in each of the above examples and comparative examples were tested for their impurity contents, and the results are shown in table 1.
TABLE 1 impurity contents of the powders of the examples and comparative examples
As is clear from the data in Table 1, the chromium powder and the copper-coated iron composite powder obtained in examples 1 to 3 had extremely low oxygen content due to the special hydrogen reduction treatment. Comparative example 1 is commercially available metallic chromium powder and electrolytic copper powder and iron powder, which were not subjected to oxygen removal treatment before use, and therefore, the oxygen content was high; the chromium powder and the copper-coated iron composite powder in the comparative example 2 are not subjected to oxygen removal treatment, and the oxygen content is highest; the comparative example 3, in which a more conventional hydrogen reduction method was used, has a significant difference from the examples 1-3 although the oxygen content was lower than that of the comparative examples 1-2, which fully demonstrates the significant advantages of the specific hydrogen reduction oxygen removal processes of the examples 1-3 over the conventional processes.
And (II) testing the performance of the contact material: since the distribution uniformity of iron is closely related to the conductivity of each portion of the contact material, the conductivity of each portion of the examples and comparative examples was tested at the test position shown in fig. 2; the oxygen content of the contact material was tested using an oxygen-nitrogen-hydrogen tester. The test results are shown in Table 2.
TABLE 2 gas content and conductivity of the contact material
As can be seen from the data in table 2, the oxygen content of the resulting contact materials of examples 1-3 is significantly lower than that of comparative examples 1-3. Meanwhile, in the aspect of conductivity, since the comparative example 1 is a process of mixing commercially available chromium metal powder, electrolytic copper powder and iron powder and then pressing and sintering the mixture, it has a significant disadvantage in uniformity of conductivity as compared with other cases using a coating method. In conclusion, the copper-chromium iron contact prepared by the method has low oxygen content and uniform conductivity, and the method solves the problems that the copper-chromium waste is difficult to recover and the copper-chromium contact is difficult to distribute uniformly.
The raw materials and equipment used in the invention are common raw materials and equipment in the field if not specified; the methods used in the present invention are conventional in the art unless otherwise specified.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and all simple modifications, alterations and equivalents of the above embodiments according to the technical spirit of the present invention are still within the protection scope of the technical solution of the present invention.
Claims (10)
1. The method for recycling the copper-chromium contact waste is characterized by comprising the following steps of:
(1) separating copper and chromium in the copper-chromium contact waste by using nitric acid as a dissolving solution, and filtering to obtain a copper nitrate solution and porous chromium;
(2) washing the porous chromium obtained in the step (1) with water, and drying to evaporate water; then placing the mixture in a reduction device; the reduction device comprises a shell and a titanium alloy bar material layer arranged in the shell, wherein a screen is laid on the upper surface of the titanium alloy bar material layer, and the porous chromium is laid on the screen; the reduction process is as follows: introducing dry hydrogen, heating to 350-450 ℃, keeping the temperature, heating to 900-1400 ℃ after the titanium alloy bar adsorbs hydrogen to be saturated, and reducing the titanium alloy bar to release hydrogen so as to remove the surface passivation film of porous chromium; and cooling, taking out the product, performing ball milling crushing in an inert atmosphere, and sieving to obtain the low-oxygen high-purity chromium powder.
2. A recycling method according to claim 1, characterized in that: the step (1) specifically comprises the following steps: processing the copper-chromium contact waste into copper-chromium scraps, adding the copper-chromium scraps into a nitric acid aqueous solution, stirring and mixing, reacting copper with nitric acid to form copper nitrate, and passivating chromium by nitric acid without dissolving; filtering to obtain porous chromium.
3. A recycling method according to claim 2, characterized in that: in the step (1), the mass concentration of the nitric acid aqueous solution is 1-50%.
4. A recycling method according to claim 2, characterized in that: in the step (1), the thickness of the copper chromium scraps is less than 1 mm.
5. A recycling method according to claim 1, characterized in that: in the step (2), the drying condition is that the temperature is 50-120 ℃ and the time is 30-90 min.
6. A recycling method according to claim 1, characterized in that: in the step (2),
the titanium alloy material is Ti-6 Al-4V;
the thickness of the titanium alloy bar material layer is 10-50 mm;
the diameter of the titanium alloy bar is 1-10 mm;
the mesh number of the screen is-300 to +800 meshes;
the paving thickness of the porous chromium is 1-5 cm.
7. A recycling method according to claim 1, characterized in that:
the dew point of the dry hydrogen is less than-70 ℃;
the heat preservation time is 10-60 min;
the reduction time is 10-60 min;
the ball milling and crushing time is 30-180 min.
8. A process for the preparation of a copper-chromium-iron composite material from the product of the recovery process according to any one of claims 1 to 7, characterised in that it comprises the steps of:
(A) performing a displacement reaction on the copper nitrate solution obtained in the step (1) by using iron powder under an acidic condition to obtain copper-coated iron composite powder, and reducing the copper-coated iron composite powder by using the reduction method in the step (2) with the difference that the reduction temperature is 550-650 ℃; cooling, taking out the product, performing ball milling crushing in an inert atmosphere, and sieving to obtain low-oxygen high-purity copper-coated iron composite powder;
(B) mixing the obtained low-oxygen high-purity chromium powder and the low-oxygen high-purity copper-clad iron composite powder, and then sequentially pressing, hydrogen reduction sintering and cooling to obtain the low-oxygen high-performance copper-chromium iron material.
9. A recycling method according to claim 8, characterized in that: the step (A) specifically comprises: heating the copper nitrate solution obtained in the step (1) to 60-100 ℃ until the concentration of copper ions in the solution is 60-150 g/L, adding sodium hydroxide to adjust the pH value to 3-5, then adding 100-200 meshes of iron powder, stirring for a displacement reaction, washing with water and drying to obtain copper-coated iron composite powder; then, carrying out reduction treatment on the copper-coated iron composite powder by adopting the reduction method in the step (2), wherein the difference is that the reduction temperature is 550-650 ℃; and cooling, taking out the product, performing ball milling crushing in an inert atmosphere, and sieving to obtain the low-oxygen high-purity copper-coated iron composite powder.
10. A recycling method according to claim 8, characterized in that: in the step (B):
the mass ratio of the low-oxygen high-purity chromium powder to the low-oxygen high-purity copper-coated iron composite powder is 1: 5-1: 1;
mixing for 30-120 min;
the pressing pressure is 300-700 MPa;
the sintering temperature is 900-1100 ℃, and the heat preservation time is 60-180 min.
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| CN114914109A (en) * | 2022-04-26 | 2022-08-16 | 浙江省冶金研究院有限公司 | Preparation method of copper-chromium-tellurium-copper-chromium composite contact |
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