Preparation method of ultrafine-grained copper-chromium contact
Technical Field
The invention relates to the technical field of medium voltage, in particular to a preparation method of an ultrafine grain copper-chromium contact.
Background
The copper-chromium alloy contact is a core component of a vacuum switch in the medium-voltage field, researches show that along with the reduction of the size of a chromium phase in a metallographic structure, the electrical property and the mechanical property of a material can be greatly optimized, and the preparation process of the copper-chromium alloy contact at present mainly comprises two types, namely smelting and powder metallurgy.
The conventional copper-chromium alloy contact prepared by vacuum induction melting has low cooling speed, the chromium phase size is generally larger, and the chromium phase size of the central area and the edge area of the contact has larger difference, even if a more advanced electric arc melting process is adopted, the cooling speed is further improved, but the size of the chromium phase is still kept between 20 and 50um, and is still larger than the size of an electric arc spot in a working condition environment, the copper-chromium contact prepared by adopting the powder metallurgy process is limited by the original size of chromium powder, the size of a chromium phase is thicker than that of a smelting process, the gas atomization powder preparation is carried out by relying on the vacuum induction melting process, and the chromium phase with fine structure can be obtained by the powder mixing and sintering process, but is limited by the vacuum induction melting, the chromium content of the contact prepared by the method is less than or equal to 40 percent, and because a ceramic crucible is required to be used as a carrier in the vacuum induction melting process, impurities are inevitably introduced.
Therefore, a new method for preparing an ultra-fine grain copper-chromium contact is needed to solve these problems, so as to reduce the size of the chromium phase, ensure the purity of the raw material, and obtain an ultra-fine grain copper-chromium contact with better performance.
Disclosure of Invention
In order to solve the technical problem, the invention provides a preparation method of an ultrafine grain copper-chromium contact, which is used for obtaining the ultrafine grain copper-chromium contact with better performance.
The technical scheme of the invention is that the preparation method of the ultrafine grain copper-chromium contact comprises the following steps:
s1: mixing powder: selecting copper powder and chromium powder as raw materials, and mixing the copper powder: the weight ratio of chromium powder is 9: 1 to 5: 5, mixing to obtain mixed powder; and mixing the mixed powder: the weight ratio of the copper ball is 100: 100, performing ball milling and powder mixing for 3-10 h;
s2: preparing an electrode: pressing the mixed powder in a cold isostatic pressing mode, then performing vacuum sintering, and keeping the temperature at 950-1050 ℃ for 2 h;
s3: electrode induction gas atomization powder preparation: the vacuum degree reaches 3 multiplied by 10-1pa below, performing zone melting on the prepared copper-chromium alloy electrodeSmelting to obtain molten metal liquid; continuously and vertically enabling the molten metal to pass through a close coupling nozzle and flow downwards, atomizing and crushing the molten metal into a large number of fine liquid drops through the close coupling nozzle, solidifying the fine liquid drops into particles in flight, and selecting alloy powder with the powder granularity smaller than 100 meshes as a subsequent raw material through screening;
s4: pressing and sintering: pressing the copper-chromium alloy powder obtained in the step S3 in a mould pressing mode, then performing vacuum sintering, and preserving heat for 3-5h at the temperature of 950-;
s5: and (3) machining: and (5) machining according to the drawing requirements.
Furthermore, the copper powder is selected to be less than 200 meshes and the purity is more than or equal to 99.7 percent, and the chromium powder is selected to be 80-320 meshes and the purity is more than or equal to 99.0 percent. The copper powder and the chromium powder with the purity and the mesh number are selected, and the prepared superfine-grained copper-chromium contact has more excellent performance.
Further, the mixing processing in step S1 specifically includes: and (3) mixing copper powder: the weight ratio of chromium powder is 9: 1 to 5: 5, mixing for 20-35min, rapidly cooling the primary mixed powder to-5 +/-3 ℃, uniformly spraying a strong effect liquid accounting for 5-8% of the total mass of the primary mixed powder, then carrying out infrared irradiation treatment for 5-10min, washing for 4-7 times by using deionized water accounting for 7-9 times of the total mass of the primary mixed powder, and naturally air-drying at room temperature to obtain mixed powder; wherein the power of the infrared radiation is 3-5kW, and the distance between the light source of the infrared radiation and the premixed powder is 30-45 cm. The copper powder and the chromium powder are treated, so that the metal properties of the copper powder and the chromium powder can be improved to be more excellent, and meanwhile, the high-efficiency liquid with the dosage is sprayed at a low temperature and is treated by being matched with infrared radiation, so that the chromium phase size of a subsequently prepared copper-chromium alloy contact can be reduced, and the more excellent superfine-grained copper-chromium contact can be obtained.
Further, the powerful liquid is prepared from graphene, vinyl naphthalene, polyethylene glycol and deionized water according to a mass ratio of 5: 1: 2: 38 are mixed and configured. The powerful liquid prepared by the ratio can obviously improve the treatment effect of infrared radiation combined with graphene on copper powder and chromium powder, the vinylnaphthalene can improve the stability of infrared radiation, and the polyethylene glycol can improve the stability and the action effect of the powerful liquid, so that the treatment effect of the method is improved.
Further, the cold isostatic pressing of step S2 is specifically: at a pressure of 150MPa and 300MPa, maintaining the pressure for 5-15min, and then performing vacuum sintering to obtain a vacuum degree of 5 × 10-2Below pa grade, 950-. The cold isostatic pressing is carried out under the condition, and the whole process does not need a crucible, so that the purity of the raw material is ensured.
Further, the vacuum degree of the vacuum sintering in the step S4 should be 5 × 10-2The temperature is kept below pa level and 1050 ℃ for 3-5h, so that the compactness and low gas content of the electrode are ensured.
Further, the parameters of the zone melting in step S3 are: the power is 20-50kw, and the frequency is 100-250 KHz.
Further, the atomization pressure in the step S3 is 2-6 MPa.
Further, in the step S3, post-processing is performed on the subsequent raw material, where the post-processing includes the following steps:
1) adding the subsequent raw materials into a stirring barrel, adding iron oxide powder accounting for 0.5 percent of the total mass of the raw materials, sealing, vacuumizing, injecting inert gas, and adjusting the pressure in the stirring barrel to 1.2 KPa;
2) then heating to 175 ℃, stirring at the speed of 35rpm for 2h, then reducing the temperature to 120 ℃, increasing the stirring speed to 105rpm, and stirring for 0.5 h;
3) then the temperature is reduced to the room temperature at the speed of 5 ℃/min, and the subsequent raw materials after treatment are obtained by magnetic separation. By adding the ferric oxide powder and carrying out post-treatment at variable temperature and variable speed in vacuum, the shape of the powder can be improved, the flatness of the surface of the powder can be improved, and further the excellent superfine-grained copper-chromium contact can be obtained.
The working principle of the invention is as follows: pressing the uniformly mixed copper-chromium mixed powder in a cold isostatic pressing manner, preparing a copper-chromium alloy electrode through vacuum sintering, then performing zone melting on the prepared copper-chromium alloy electrode by adopting electrode induction gas atomization powder making equipment, continuously and vertically enabling molten metal to pass through a nozzle and flow downwards, atomizing and crushing the metal liquid into a large number of fine liquid drops through a tight coupling nozzle by using high-pressure argon gas flow, solidifying the fine liquid drops into particles in flight, selecting alloy powder with the particle size of-100 meshes as a subsequent raw material through screening, finally performing pressing and vacuum sintering on the screened-100-mesh copper-chromium alloy powder in a mould pressing manner, and preparing an ultra-fine-grained copper-chromium contact through machining;
the invention has the beneficial effects that:
(1) the invention combines the technical advantages of electrode induction gas atomization and mixed powder sintering, and the size of the chromium phase reaches between 200nm and 5um by 'quenching' of the electrode induction gas atomization, which is far smaller than that of the conventional preparation process.
(2) The invention prepares the copper-chromium alloy contact on the basis of electrode induction gas atomization, mixes the powder of copper and chromium according to a certain proportion, presses and sinters to prepare the prefabricated electrode, and then adopts the regional smelting gas atomization mode of the prefabricated electrode to prepare the powder, the powder preparation process is not limited by the requirement that the chromium content of the induction smelting copper-chromium alloy is less than or equal to 40 percent, the copper-chromium alloy powder with the chromium content of more than 40 percent can be prepared, and simultaneously, the whole preparation process of the alloy powder does not use a crucible, and the introduction of impurities is avoided, so the prepared copper-chromium contact is purer.
(3) The size of the chromium phase of the copper-chromium alloy contact prepared by the method is far smaller than that of the conventional contact, and the superfine-grained copper-chromium contact finally obtained by the method has better performance.
Detailed Description
Example 1
A preparation method of an ultrafine grain copper-chromium contact comprises the following steps:
s1: mixing powder: the raw material is copper powder with the granularity of-210 meshes and the purity of 99.7 percent, the chromium powder with the granularity of-310 meshes and the purity of 99.0 percent, and the copper powder: the weight ratio of chromium powder is 9: 1, mixing to obtain mixed powder; and mixing the mixed powder: the weight ratio of the copper ball is 100: 100, performing ball milling and powder mixing for 3 hours; the copper powder and the chromium powder with the purity and the mesh number are selected, so that the prepared superfine-crystal copper-chromium contact has more excellent performance;
the mixing treatment specifically comprises the following steps: and (3) mixing copper powder: the weight ratio of chromium powder is 9: 1, mixing for 20min, rapidly cooling the primary mixed powder to-8 ℃, uniformly spraying a strong effect liquid accounting for 5% of the total mass of the primary mixed powder, then carrying out infrared irradiation treatment for 5min, washing for 4 times by using deionized water accounting for 7 times of the total mass of the primary mixed powder, and naturally air-drying at room temperature to obtain mixed powder; wherein, the power of infrared irradiation is 3kW, and the distance between the light source of infrared irradiation and the premixed powder is 30 cm. The copper powder and the chromium powder are subjected to the treatment, so that the metal properties of the copper powder and the chromium powder can be improved and are more excellent, and meanwhile, the high-efficiency liquid with the dosage is sprayed at a low temperature and is assisted with infrared radiation for treatment, so that the chromium phase size of a subsequently prepared copper-chromium alloy contact can be reduced, and the more excellent superfine-grained copper-chromium contact can be obtained;
the high-efficiency liquid is prepared from graphene, vinyl naphthalene, polyethylene glycol and deionized water according to a mass ratio of 5: 1: 2: 38 are mixed and configured. The powerful liquid prepared by the ratio can obviously improve the treatment effect of infrared radiation combined with graphene on copper powder and chromium powder, the vinylnaphthalene can improve the stability of infrared radiation, and the polyethylene glycol can improve the stability and the action effect of the powerful liquid, so that the treatment effect of the method is improved;
s2: preparing an electrode: pressing the mixed powder by isostatic cool pressing under 150Mpa for 5min, and vacuum sintering to obtain a vacuum degree of 4.9 × 10-2pa, keeping the temperature at 950 ℃ for 2 h; the whole process does not need to use a crucible, so that the purity of the raw materials is ensured;
s3: electrode induction gas atomization powder preparation: the vacuum degree reaches 2.8 multiplied by 10-1pa, carrying out zone melting on the prepared copper-chromium alloy electrode, wherein the power is 20kw, and the frequency is 100KHz, so as to obtain molten metal liquid; continuously and vertically passing molten metal liquid through a tightly coupled nozzle to flow downwards, atomizing and crushing the molten metal liquid into a large amount of fine liquid drops by high-pressure argon through the tightly coupled nozzle, wherein the atomizing pressure is 2Mpa, and the fine liquid drops are solidified into particles in flight and pass throughScreening and selecting alloy powder with the powder granularity of-110 meshes as a subsequent raw material; post-processing the subsequent raw materials;
the post-treatment comprises the following steps:
1) adding the subsequent raw materials into a stirring barrel, adding iron oxide powder accounting for 0.5 percent of the total mass of the raw materials, sealing, vacuumizing, injecting inert gas, and adjusting the pressure in the stirring barrel to 1.2 KPa;
2) then heating to 175 ℃, stirring at the speed of 35rpm for 2h, then reducing the temperature to 120 ℃, increasing the stirring speed to 105rpm, and stirring for 0.5 h;
3) then the temperature is reduced to the room temperature at the speed of 5 ℃/min, and the subsequent raw materials after treatment are obtained by magnetic separation. By adding the ferric oxide powder and carrying out post-treatment at variable temperature and variable speed in vacuum, the shape of the powder can be improved, the flatness of the surface of the powder can be improved, and further the excellent superfine-grained copper-chromium contact can be obtained;
s4: pressing and sintering: pressing the copper-chromium alloy powder obtained in the step S3 in a mould pressing mode, wherein the required density is 96%, and then carrying out vacuum sintering, wherein the vacuum degree needs to reach 4.9 multiplied by 10-2pa, keeping the temperature at 950 ℃ for 3 h;
s5: and (3) machining: and (5) machining according to the drawing requirements.
Example 2
A preparation method of an ultrafine grain copper-chromium contact comprises the following steps:
s1: mixing powder: the raw material is copper powder with the granularity of-210 meshes and the purity of 99.7 percent, the chromium powder with the granularity of-310 meshes and the purity of 99.0 percent, and the copper powder: the weight ratio of chromium powder is 72: 13, mixing to obtain mixed powder; and mixing the mixed powder: the weight ratio of the copper ball is 100: 100, ball milling and mixing powder for 7 hours; the copper powder and the chromium powder with the purity and the mesh number are selected, so that the prepared superfine-crystal copper-chromium contact has more excellent performance;
the mixing treatment specifically comprises the following steps: and (3) mixing copper powder: the weight ratio of chromium powder is 72: 13, mixing for 30min, rapidly cooling the primary mixed powder to-5 ℃, uniformly spraying a strong effect liquid accounting for 7% of the total mass of the primary mixed powder, then carrying out infrared irradiation treatment for 8min, then washing for 6 times by using deionized water accounting for 8 times of the total mass of the primary mixed powder, and naturally air-drying at room temperature to obtain mixed powder; wherein, the power of the infrared radiation is 4kW, and the distance between the light source of the infrared radiation and the premixed powder is 38 cm. The copper powder and the chromium powder are subjected to the treatment, so that the metal properties of the copper powder and the chromium powder can be improved and are more excellent, and meanwhile, the high-efficiency liquid with the dosage is sprayed at a low temperature and is assisted with infrared radiation for treatment, so that the chromium phase size of a subsequently prepared copper-chromium alloy contact can be reduced, and the more excellent superfine-grained copper-chromium contact can be obtained;
the high-efficiency liquid is prepared from graphene, vinyl naphthalene, polyethylene glycol and deionized water according to a mass ratio of 5: 1: 2: 38 are mixed and configured. The powerful liquid prepared by the ratio can obviously improve the treatment effect of infrared radiation combined with graphene on copper powder and chromium powder, the vinylnaphthalene can improve the stability of infrared radiation, and the polyethylene glycol can improve the stability and the action effect of the powerful liquid, so that the treatment effect of the method is improved;
s2: preparing an electrode: pressing the mixed powder by cold isostatic pressing at 230Mpa for 10min, and vacuum sintering to obtain a vacuum degree of 4.9 × 10-2pa, keeping the temperature at 1020 ℃ for 2 h; the whole process does not need to use a crucible, so that the purity of the raw materials is ensured;
s3: electrode induction gas atomization powder preparation: the vacuum degree reaches 2.8 multiplied by 10-1Below pa, carrying out zone melting on the prepared copper-chromium alloy electrode, wherein the power is 35kw, and the frequency is 210KHz, so as to obtain molten metal liquid; continuously and vertically enabling the molten metal to pass through a close coupling nozzle and flow downwards, atomizing and crushing the molten metal into a large number of fine liquid drops through the close coupling nozzle by high-pressure argon, wherein the atomizing pressure is 5Mpa, the fine liquid drops are solidified into particles in flight, and screening and selecting alloy powder with the powder granularity of-110 meshes as a subsequent raw material; post-processing the subsequent raw materials;
the post-treatment comprises the following steps:
1) adding the subsequent raw materials into a stirring barrel, adding iron oxide powder accounting for 0.5 percent of the total mass of the raw materials, sealing, vacuumizing, injecting inert gas, and adjusting the pressure in the stirring barrel to 1.2 KPa;
2) then heating to 175 ℃, stirring at the speed of 35rpm for 2h, then reducing the temperature to 120 ℃, increasing the stirring speed to 105rpm, and stirring for 0.5 h;
3) then the temperature is reduced to the room temperature at the speed of 5 ℃/min, and the subsequent raw materials after treatment are obtained by magnetic separation. By adding the ferric oxide powder and carrying out post-treatment at variable temperature and variable speed in vacuum, the shape of the powder can be improved, the flatness of the surface of the powder can be improved, and further the excellent superfine-grained copper-chromium contact can be obtained;
s4: pressing and sintering: pressing the copper-chromium alloy powder obtained in the step S3 in a mould pressing mode, wherein the required density is 96%, and then carrying out vacuum sintering, wherein the vacuum degree needs to reach 4.9 multiplied by 10-2pa, keeping the temperature at 1020 ℃ for 4 h;
s5: and (3) machining: and (5) machining according to the drawing requirements.
Example 3
A preparation method of an ultrafine grain copper-chromium contact comprises the following steps:
s1: mixing powder: the raw material is copper powder with the granularity of-210 meshes and the purity of 99.7 percent, the chromium powder with the granularity of-310 meshes and the purity of 99.0 percent, and the copper powder: the weight ratio of chromium powder is 5: 5, mixing to obtain mixed powder; and mixing the mixed powder: the weight ratio of the copper ball is 100: 100, ball milling and mixing powder for 10 hours; the copper powder and the chromium powder with the purity and the mesh number are selected, so that the prepared superfine-crystal copper-chromium contact has more excellent performance;
the mixing treatment specifically comprises the following steps: and (3) mixing copper powder: the weight ratio of chromium powder is 5: 5, mixing for 35min, rapidly cooling the primary mixed powder to-2 ℃, uniformly spraying a strong effect liquid accounting for 8% of the total mass of the primary mixed powder, then carrying out infrared irradiation treatment for 10min, then washing for 7 times by using deionized water accounting for 9 times of the total mass of the primary mixed powder, and naturally air-drying at room temperature to obtain mixed powder; wherein, the power of infrared irradiation is 5kW, and the distance between the light source of infrared irradiation and the premixed powder is 45 cm. The copper powder and the chromium powder are subjected to the treatment, so that the metal properties of the copper powder and the chromium powder can be improved and are more excellent, and meanwhile, the high-efficiency liquid with the dosage is sprayed at a low temperature and is assisted with infrared radiation for treatment, so that the chromium phase size of a subsequently prepared copper-chromium alloy contact can be reduced, and the more excellent superfine-grained copper-chromium contact can be obtained;
the high-efficiency liquid is prepared from graphene, vinyl naphthalene, polyethylene glycol and deionized water according to a mass ratio of 5: 1: 2: 38 are mixed and configured. The powerful liquid prepared by the ratio can obviously improve the treatment effect of infrared radiation combined with graphene on copper powder and chromium powder, the vinylnaphthalene can improve the stability of infrared radiation, and the polyethylene glycol can improve the stability and the action effect of the powerful liquid, so that the treatment effect of the method is improved;
s2: preparing an electrode: pressing the mixed powder by cold isostatic pressing at 300Mpa for 5-15min, and vacuum sintering to obtain a vacuum degree of 4.9 × 10-2pa, keeping the temperature at 1050 ℃ for 2 h; the whole process does not need to use a crucible, so that the purity of the raw materials is ensured;
s3: electrode induction gas atomization powder preparation: the vacuum degree reaches 2.8 multiplied by 10-1pa, carrying out zone melting on the prepared copper-chromium alloy electrode, wherein the power is 50kw, and the frequency is 250KHz, so as to obtain molten metal liquid; continuously and vertically enabling the molten metal to pass through a close coupling nozzle and flow downwards, atomizing and crushing the molten metal into a large number of fine liquid drops through the close coupling nozzle by high-pressure argon, wherein the atomizing pressure is 6Mpa, the fine liquid drops are solidified into particles in flight, and screening and selecting alloy powder with the powder granularity of-110 meshes as a subsequent raw material; post-processing the subsequent raw materials;
the post-treatment comprises the following steps:
1) adding the subsequent raw materials into a stirring barrel, adding iron oxide powder accounting for 0.5 percent of the total mass of the raw materials, sealing, vacuumizing, injecting inert gas, and adjusting the pressure in the stirring barrel to 1.2 KPa;
2) then heating to 175 ℃, stirring at the speed of 35rpm for 2h, then reducing the temperature to 120 ℃, increasing the stirring speed to 105rpm, and stirring for 0.5 h;
3) then the temperature is reduced to the room temperature at the speed of 5 ℃/min, and the subsequent raw materials after treatment are obtained by magnetic separation. By adding the ferric oxide powder and carrying out post-treatment at variable temperature and variable speed in vacuum, the shape of the powder can be improved, the flatness of the surface of the powder can be improved, and further the excellent superfine-grained copper-chromium contact can be obtained;
s4: pressing and sintering: pressing the copper-chromium alloy powder obtained in the step S3 in a mould pressing mode, wherein the required density is 96%, and then carrying out vacuum sintering, wherein the vacuum degree needs to reach 4.9 multiplied by 10-2pa, keeping the temperature at 1050 ℃ for 5 h;
s5: and (3) machining: and (5) machining according to the drawing requirements.
Comparison of experiments
The raw materials are copper powder with the particle size of-210 meshes and the purity of 99.7 percent, the chromium powder with the particle size of-310 meshes and the purity of 99.0 percent, the copper-chromium alloy contacts prepared by the embodiments 1, 2, 3 and 4 are respectively prepared into experimental examples 1, 2, 3 and 4, and the copper-chromium alloy contacts prepared by the traditional smelting process are used as a comparative example;
comparative example: the size of the chromium phase exceeds 200nm-5um, and the surface hardness of the copper-chromium alloy contact is 110 Hv;
experimental example 1: the size of the chromium phase is between 200nm and 5um, the surface hardness of the copper-chromium alloy contact is 113Hv, and the conductivity of the copper-chromium alloy contact is improved by 6 percent compared with that of a control example;
experimental example 2: the size of the chromium phase is between 200nm and 5um, the surface hardness of the copper-chromium alloy contact is 121Hv, and the conductivity of the copper-chromium alloy contact is improved by 8 percent compared with that of a control example;
experimental example 3: the size of the chromium phase is between 200nm and 5um, the surface hardness of the copper-chromium alloy contact is 117Hv, and the conductivity of the copper-chromium alloy contact is improved by 5 percent compared with that of a control example;
experimental example 4: the size of the chromium phase is between 150nm and 3um, the surface hardness of the copper-chromium alloy contact is 125Hv, and the conductivity of the copper-chromium alloy contact is improved by 11 percent compared with that of a control example;
as can be seen from the above, the experimental examples 1-4 are all superior to the control group, and finally, the superfine grained copper-chromium contact with better performance is obtained.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.