CN117696903A - Cryogenic pulverizing and impurity controlling method for metallic chromium - Google Patents
Cryogenic pulverizing and impurity controlling method for metallic chromium Download PDFInfo
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- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 title claims abstract description 147
- 239000011651 chromium Substances 0.000 title claims abstract description 120
- 229910052804 chromium Inorganic materials 0.000 title claims abstract description 113
- 239000012535 impurity Substances 0.000 title claims abstract description 24
- 238000000034 method Methods 0.000 title claims abstract description 19
- 238000010298 pulverizing process Methods 0.000 title claims abstract description 4
- 229910052751 metal Inorganic materials 0.000 claims abstract description 127
- 239000002184 metal Substances 0.000 claims abstract description 127
- 239000002245 particle Substances 0.000 claims abstract description 65
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 56
- 238000010438 heat treatment Methods 0.000 claims abstract description 44
- 239000000843 powder Substances 0.000 claims abstract description 41
- 239000007789 gas Substances 0.000 claims abstract description 40
- 239000007788 liquid Substances 0.000 claims abstract description 37
- 238000000227 grinding Methods 0.000 claims abstract description 31
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 31
- 230000008014 freezing Effects 0.000 claims abstract description 22
- 238000007710 freezing Methods 0.000 claims abstract description 22
- 238000001816 cooling Methods 0.000 claims abstract description 18
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims abstract description 12
- 239000001257 hydrogen Substances 0.000 claims abstract description 12
- 229910052739 hydrogen Inorganic materials 0.000 claims abstract description 12
- 230000001681 protective effect Effects 0.000 claims abstract description 9
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 24
- 238000005507 spraying Methods 0.000 claims description 16
- 229910052786 argon Inorganic materials 0.000 claims description 12
- 230000008018 melting Effects 0.000 claims description 7
- 238000002844 melting Methods 0.000 claims description 7
- 230000006698 induction Effects 0.000 claims description 6
- 238000005469 granulation Methods 0.000 claims description 5
- 230000003179 granulation Effects 0.000 claims description 5
- 229910052760 oxygen Inorganic materials 0.000 claims description 5
- 238000003723 Smelting Methods 0.000 claims description 4
- 238000011049 filling Methods 0.000 claims description 4
- 238000009689 gas atomisation Methods 0.000 claims description 4
- 229910052799 carbon Inorganic materials 0.000 claims description 3
- 229910052717 sulfur Inorganic materials 0.000 claims description 3
- 230000009286 beneficial effect Effects 0.000 abstract description 3
- 229910001018 Cast iron Inorganic materials 0.000 description 7
- 230000000052 comparative effect Effects 0.000 description 7
- 238000005516 engineering process Methods 0.000 description 7
- 238000005272 metallurgy Methods 0.000 description 7
- 239000000126 substance Substances 0.000 description 7
- 238000004458 analytical method Methods 0.000 description 5
- 238000002360 preparation method Methods 0.000 description 5
- 238000005070 sampling Methods 0.000 description 5
- 238000004519 manufacturing process Methods 0.000 description 4
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- 229910045601 alloy Inorganic materials 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 235000011089 carbon dioxide Nutrition 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
- 238000000889 atomisation Methods 0.000 description 1
- 229910010293 ceramic material Inorganic materials 0.000 description 1
- 238000004134 energy conservation Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000005240 physical vapour deposition Methods 0.000 description 1
Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F9/00—Making metallic powder or suspensions thereof
- B22F9/02—Making metallic powder or suspensions thereof using physical processes
- B22F9/04—Making metallic powder or suspensions thereof using physical processes starting from solid material, e.g. by crushing, grinding or milling
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
- B22F1/06—Metallic powder characterised by the shape of the particles
- B22F1/065—Spherical particles
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
- B22F1/14—Treatment of metallic powder
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
- B22F1/14—Treatment of metallic powder
- B22F1/142—Thermal or thermo-mechanical treatment
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
- B22F1/14—Treatment of metallic powder
- B22F1/145—Chemical treatment, e.g. passivation or decarburisation
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F9/00—Making metallic powder or suspensions thereof
- B22F9/02—Making metallic powder or suspensions thereof using physical processes
- B22F9/06—Making metallic powder or suspensions thereof using physical processes starting from liquid material
- B22F9/08—Making metallic powder or suspensions thereof using physical processes starting from liquid material by casting, e.g. through sieves or in water, by atomising or spraying
- B22F9/082—Making metallic powder or suspensions thereof using physical processes starting from liquid material by casting, e.g. through sieves or in water, by atomising or spraying atomising using a fluid
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F9/00—Making metallic powder or suspensions thereof
- B22F9/02—Making metallic powder or suspensions thereof using physical processes
- B22F9/04—Making metallic powder or suspensions thereof using physical processes starting from solid material, e.g. by crushing, grinding or milling
- B22F2009/041—Making metallic powder or suspensions thereof using physical processes starting from solid material, e.g. by crushing, grinding or milling by mechanical alloying, e.g. blending, milling
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F9/00—Making metallic powder or suspensions thereof
- B22F9/02—Making metallic powder or suspensions thereof using physical processes
- B22F9/04—Making metallic powder or suspensions thereof using physical processes starting from solid material, e.g. by crushing, grinding or milling
- B22F2009/044—Making metallic powder or suspensions thereof using physical processes starting from solid material, e.g. by crushing, grinding or milling by jet milling
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F9/00—Making metallic powder or suspensions thereof
- B22F9/02—Making metallic powder or suspensions thereof using physical processes
- B22F9/06—Making metallic powder or suspensions thereof using physical processes starting from liquid material
- B22F9/08—Making metallic powder or suspensions thereof using physical processes starting from liquid material by casting, e.g. through sieves or in water, by atomising or spraying
- B22F9/082—Making metallic powder or suspensions thereof using physical processes starting from liquid material by casting, e.g. through sieves or in water, by atomising or spraying atomising using a fluid
- B22F2009/0824—Making metallic powder or suspensions thereof using physical processes starting from liquid material by casting, e.g. through sieves or in water, by atomising or spraying atomising using a fluid with a specific atomising fluid
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F9/00—Making metallic powder or suspensions thereof
- B22F9/02—Making metallic powder or suspensions thereof using physical processes
- B22F9/06—Making metallic powder or suspensions thereof using physical processes starting from liquid material
- B22F9/08—Making metallic powder or suspensions thereof using physical processes starting from liquid material by casting, e.g. through sieves or in water, by atomising or spraying
- B22F9/082—Making metallic powder or suspensions thereof using physical processes starting from liquid material by casting, e.g. through sieves or in water, by atomising or spraying atomising using a fluid
- B22F2009/0848—Melting process before atomisation
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- Thermal Sciences (AREA)
- Manufacture Of Metal Powder And Suspensions Thereof (AREA)
Abstract
The invention discloses a cryogenic pulverizing and impurity controlling method of metallic chromium, which comprises the following steps: 1. freezing the metal chromium blocks in liquid nitrogen and then crushing to obtain small-particle metal chromium; 2. carrying out vacuum heating treatment on small-particle metal chromium in a heating furnace, cooling, then introducing high-purity hydrogen into the heating furnace, and carrying out heating reaction; 3. taking out the small-particle metal chromium cooled to room temperature from the heating furnace, performing secondary freezing in liquid nitrogen, and coarsely grinding by using a grinder to obtain metal chromium coarse powder; 4. grinding the coarse metal chromium powder in a fluidized bed jet mill, and taking nitrogen as a protective gas to obtain nano-scale metal chromium powder. The beneficial effects are that: adopting vacuum heating to remove impurities and reducing with high-purity hydrogen to improve the purity of the metal chromium; the nano-scale metal chromium powder is prepared by utilizing the characteristics of easy embrittlement, easy crushing and the like of metal chromium at low temperature and using the metal chromium frozen by liquid nitrogen in a fluidized bed jet mill.
Description
Technical Field
The invention belongs to the technical field of metal powder preparation, and particularly relates to a cryogenic powder preparation and impurity control method for metal chromium.
Background
Chromium is an important alloy element, and because chromium has excellent characteristics of hardness, brittleness, corrosion resistance and the like, high-purity metal chromium has the characteristics of high melting point, high hardness, high temperature resistance, corrosion resistance, good toughness, and is widely applied to the fields of metallurgy, chemical industry, cast iron, fire resistance, electronics, aviation, aerospace, high-precision end science and technology and the like, and is mainly used for producing high-temperature alloys and targets, and the metal chromium applied to the fields not only needs extremely high purity, but also needs extremely small granularity, so that products required by the fields can be better manufactured and produced. However, the preparation method of the superfine chromium powder in the prior art often cannot reach the nanometer level, and the prepared metal chromium powder has higher impurity content and does not meet the production and use requirements of part of fields.
The preparation method of the superfine chromium powder disclosed in the invention patent with the publication number of CN102825257A adopts physical vapor deposition, and the metal chromium blocks are heated, melted and sublimated and then settled to obtain the superfine chromium powder, but the production cost of the method is higher, and the diameter of the finally obtained superfine chromium powder is larger; the invention patent with publication number CN104070171A discloses a preparation method of superfine chromium powder, which adopts nanometer Al 2 O 3 With ZrO 2 The vibrating grinding cylinder liner and the grinding body made of the high-toughness ceramic material are ground, the oxygen content of the finally prepared metal chromium powder product is less than 0.35 percent, the oxygen content is still higher, and the production and use requirements of part of fields are not met.
Disclosure of Invention
It is an object of the present invention to address at least the above problems and/or disadvantages and to provide at least the advantages described below.
To achieve these objects and other advantages and in accordance with the purpose of the invention, there is provided a method for preparing powder and controlling impurities by cryogenic cooling of metallic chromium, comprising the steps of:
step one, putting a metal chromium block into liquid nitrogen for freezing, and putting the frozen metal chromium block into a crusher for crushing to obtain small-particle metal chromium;
step two, putting the small-particle metal chromium obtained in the step one into a heating furnace, vacuumizing the heating furnace, performing vacuum heating treatment on the small-particle metal chromium for a period of time, cooling, introducing high-purity hydrogen into the heating furnace, and heating for a period of time;
step three, taking out the small-particle metal chromium naturally cooled to room temperature in the step two from a heating furnace, putting the small-particle metal chromium into liquid nitrogen for secondary freezing, and then carrying out coarse grinding by a grinding machine to obtain metal chromium coarse powder;
and step four, putting the metal chromium coarse powder obtained in the step three into a fluidized bed jet mill, taking nitrogen as a protective gas, and grinding in the fluidized bed jet mill to finally obtain the nano-scale metal chromium powder.
Preferably, the freezing time in the step one is 2-4 hours, and the particle size of the small-particle metal chromium is 20-25 mm.
Preferably, in the second step, the heating furnace is vacuumized to 0-15 Pa, heated to 1300-1500 ℃ and treated for 3-9 hours.
Preferably, in the second step, the purity of the introduced hydrogen is 99.99%, the heating reaction temperature of the hydrogen is 1400-1700 ℃, and the reaction is carried out for 4-12 hours.
Preferably, in the third step, the secondary freezing time is 4-6 hours, the rotating speed of the grinder is 1200-1600 rpm, the grinding time is 2-5 hours, and the grain size of the metal chromium coarse powder is 100-300 um.
Preferably, in the fourth step, the gas flow rate of the fluidized bed jet mill is 300-500 m/s, and the gas pressure is 0.7-0.85 MPa.
Preferably, the impurity content of the metallic chromium blocks in the first step is less than or equal to 0.5wt% of C, less than or equal to 0.02wt% of S, less than or equal to 0.1wt% of O and less than or equal to 0.01wt% of N.
Preferably, in the nano-scale metal chromium powder in the fourth step, cr is more than or equal to 99.9wt%, C is less than or equal to 0.02wt%, S is less than or equal to 0.002wt%, O is less than or equal to 0.03wt%, N is less than or equal to 0.002wt%, and the particle size of the nano-scale metal chromium powder is 60-100 nm.
Preferably, before the fourth step, the molten gas atomization granulation is carried out on the metal chromium coarse powder obtained in the third step, and the specific steps are as follows:
s1, placing metal chromium coarse powder into an induction smelting furnace of a metal powder atomizing device, melting to metal chromium melt, and filling argon into the induction smelting furnace as protective gas;
s2, leaking the molten liquid obtained in the step S1 into an atomizer through a metal liquid flow outlet with the aperture of 5-10 mm at the flow rate of 10-15 kg/min, spraying gas to atomize the metal liquid by a gas spraying component around the metal liquid flow outlet, wherein the gas is argon, the gas spraying pressure is 10-30 MPa, and the spraying speed of the gas is 240-400 m/S;
and S3, collecting the granulated metal chromium particles, and filling argon into a collecting device to obtain the metal chromium particles with the particle size of 30-50 um.
The invention at least comprises the following beneficial effects: adopting vacuum heating to remove impurities and reducing with high-purity hydrogen to improve the purity of the metal chromium; the nano-scale metal chromium powder is prepared by utilizing the characteristics of easy embrittlement, easy crushing and the like of metal chromium at low temperature and using the metal chromium frozen by liquid nitrogen in a fluidized bed jet mill; the nitrogen is used as grinding protective gas, so that the production cost is reduced, and the energy conservation and consumption reduction are realized; the molten gas is utilized for atomization and granulation, so that the particle size of the metal chromium coarse powder before the fluidized bed jet mill grinding is further reduced, the sphericity is high, the subsequent grinding in the fluidized bed jet mill is facilitated, and the quality of the final metal chromium nano powder is improved.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention.
The specific embodiment is as follows:
the present invention is described in further detail below to enable those skilled in the art to practice the invention by reference to the specification.
It will be understood that terms, such as "having," "including," and "comprising," as used herein, do not preclude the presence or addition of one or more other elements or groups thereof.
Example 1
A method for preparing powder and controlling impurities by deep cooling of metallic chromium comprises the following steps:
step one, putting 10kg of metal chromium blocks into liquid nitrogen for freezing for 4 hours, and putting the frozen metal chromium blocks into a crusher for crushing to obtain small-particle metal chromium with the particle size of about 22 mm;
step two, putting the small-particle metal chromium obtained in the step one into a heating furnace, vacuumizing the heating furnace to 10Pa, heating to 1350 ℃, heating for 4 hours, cooling, then introducing high-purity hydrogen with the purity of 99.99% into the heating furnace, heating to 1500 ℃, and reacting for 6 hours;
step three, taking out the small-particle metal chromium naturally cooled to room temperature in the step two from a heating furnace, putting the small-particle metal chromium into liquid nitrogen for secondary freezing, and then carrying out coarse grinding by a grinding machine at 1400rpm for 3 hours to obtain metal chromium coarse powder with the particle size of about 200 um;
and step four, putting the metal chromium coarse powder obtained in the step three into a fluidized bed jet mill, grinding in the fluidized bed jet mill by taking nitrogen as a protective gas, wherein the gas flow rate is 400m/s, and the gas pressure is 0.7MPa, so as to finally obtain the nanoscale metal chromium powder.
Through sampling analysis, 99.94wt% of Cr, 0.012wt% of C, 0.001wt% of S, 0.018wt% of O and 0.001wt% of N in the nano metal chromium powder, and the particle size of D97 is 77nm, thereby meeting the use requirements in the fields of metallurgy, chemical industry, cast iron, fire resistance, electronics, aviation, aerospace, high-precision end science and technology and the like.
Example 2
A method for preparing powder and controlling impurities by deep cooling of metallic chromium comprises the following steps:
step one, putting 10kg of metal chromium blocks into liquid nitrogen for freezing for 4 hours, and putting the frozen metal chromium blocks into a crusher for crushing to obtain small-particle metal chromium with the particle size of about 22 mm;
step two, putting the small-particle metal chromium obtained in the step one into a heating furnace, vacuumizing the heating furnace to 10Pa, heating to 1400 ℃, heating for 4 hours, cooling, then introducing high-purity hydrogen with the purity of 99.99% into the heating furnace, heating to 1600 ℃, and reacting for 6 hours;
step three, taking out the small-particle metal chromium naturally cooled to room temperature in the step two from a heating furnace, putting the small-particle metal chromium into liquid nitrogen for secondary freezing, and then carrying out coarse grinding by a grinding machine at 1400rpm for 3 hours to obtain metal chromium coarse powder with the particle size of about 200 um;
and step four, putting the metal chromium coarse powder obtained in the step three into a fluidized bed jet mill, grinding in the fluidized bed jet mill by taking nitrogen as a protective gas, wherein the gas flow rate is 450m/s, and the gas pressure is 0.8MPa, so as to finally obtain the nanoscale metal chromium powder.
Through sampling analysis, 99.95wt% of Cr, 0.011wt% of C, 0.001wt% of S, 0.014wt% of O and 0.001wt% of N in the nano metal chromium powder, and the particle size of D97 is 75nm, so that the use requirements of the fields of metallurgy, chemical industry, cast iron, fire resistance, electronics, aviation, aerospace, high-precision end science and technology and the like are met.
Example 3
A method for preparing powder and controlling impurities by deep cooling of metallic chromium comprises the following steps:
step one, putting 10kg of metal chromium blocks into liquid nitrogen for freezing for 4 hours, and putting the frozen metal chromium blocks into a crusher for crushing to obtain small-particle metal chromium with the particle size of about 22 mm;
step two, putting the small-particle metal chromium obtained in the step one into a heating furnace, vacuumizing the heating furnace to 10Pa, heating to 1500 ℃, heating for 4 hours, cooling, then introducing high-purity hydrogen with the purity of 99.99% into the heating furnace, heating to 1700 ℃, and reacting for 6 hours;
step three, taking out the small-particle metal chromium naturally cooled to room temperature in the step two from a heating furnace, putting the small-particle metal chromium into liquid nitrogen for secondary freezing, and then carrying out coarse grinding by a grinding machine at 1400rpm for 3 hours to obtain metal chromium coarse powder with the particle size of about 200 um;
and step four, putting the metal chromium coarse powder obtained in the step three into a fluidized bed jet mill, grinding in the fluidized bed jet mill by taking nitrogen as a protective gas, wherein the gas flow rate is 500m/s, and the gas pressure is 0.85MPa, so as to finally obtain the nanoscale metal chromium powder.
Through sampling analysis, 99.96wt% of Cr, 0.009wt% of C, 0.001wt% of S and 0.012wt% of O in the nano metal chromium powder, and 0.001wt% of N, wherein the particle size of D97 is 74nm, thereby meeting the use requirements in the fields of metallurgy, chemical industry, cast iron, fire resistance, electronics, aviation, aerospace, high-precision end science and technology and the like.
Example 4
The difference between this example and example 1 is that, before the fourth step, the molten gas atomization granulation is performed on the coarse chromium powder obtained in the third step, and the specific steps are as follows:
s1, placing metal chromium coarse powder with the particle size of about 200um into an induction melting furnace of a metal powder atomizing device filled with argon, and melting to metal chromium melt;
s2, leaking the molten liquid obtained in the step S1 into an atomizer through a metal liquid flow outlet with the aperture of 8mm at a flow rate of 13kg/min, spraying gas to atomize the metal liquid by a gas spraying component around the metal liquid flow outlet, wherein the gas is argon, the gas spraying pressure is 20MPa, and the gas spraying speed is 250m/S;
s3, collecting the granulated metal chromium particles by using a collecting device filled with argon to obtain metal chromium particles with the particle size of about 40um, and then performing the step four to finally obtain the nanoscale metal chromium powder.
Through sampling analysis, 99.97wt% of Cr, 0.008wt% of C, 0.001wt% of S, 0.011wt% of O and 0.001wt% of N in the nano metal chromium powder, and the particle size of D97 is 65nm, thereby meeting the use requirements in the fields of metallurgy, chemical industry, cast iron, fire resistance, electronics, aviation, aerospace, high-precision end science and technology and the like.
Example 5
The difference between this example and example 2 is that, before the fourth step, the molten gas atomization granulation is performed on the coarse chromium powder obtained in the third step, and the specific steps are as follows:
s1, placing metal chromium coarse powder with the particle size of about 200um into an induction melting furnace of a metal powder atomizing device filled with argon, and melting to metal chromium melt;
s2, leaking the molten liquid obtained in the step S1 into an atomizer through a metal liquid flow outlet with the aperture of 8mm at a flow rate of 13kg/min, spraying gas to atomize the metal liquid by a gas spraying component around the metal liquid flow outlet, wherein the gas is argon, the gas spraying pressure is 25MPa, and the gas spraying speed is 300m/S;
s3, collecting the granulated metal chromium particles by using a collecting device filled with argon to obtain spherical metal chromium particles with the particle size of about 36um, and then performing the step four to finally obtain the nanoscale metal chromium powder.
Through sampling analysis, 99.98wt% of Cr, 0.004wt% of C, 0.001wt% of S, 0.006wt% of O and 0.001wt% of N in the nano metal chromium powder, and the D97 particle size is 63nm, thereby meeting the use requirements in the fields of metallurgy, chemical industry, cast iron, fire resistance, electronics, aviation, aerospace, high-precision end science and technology and the like.
Comparative example 1
This comparative example differs from example 1 in that the method used for freezing metallic chromium in step one and step three was freezing with dry ice, but not freezing with liquid nitrogen, and the other steps were identical to example 1.
Because the dry ice is used for freezing the metal chromium in the first step and the third step, the temperature is not as low as that of the liquid nitrogen, so that the metal chromium is subjected to certain influence in crushing, subsequent impurity removal, rough grinding and grinding in a fluidized bed air flow mill, and the finally obtained metal chromium powder comprises 99.64wt% of Cr, 0.062wt% of C, 0.008wt% of S, 0.044wt% of O, 0.006wt% of N and the particle size of D97 is 114nm.
Comparative example 2
The comparative example differs from example 1 in that in step three, the small-particle metallic chromium was not subjected to secondary freezing using liquid nitrogen, but was directly subjected to coarse grinding, and the obtained metallic chromium coarse powder had a particle diameter of about 400um, and the other steps were identical to example 1.
Because the small-particle metal chromium is not frozen by liquid nitrogen in the step three, the subsequent metal chromium coarse powder is directly coarsely ground, so that grinding in a fluidized bed jet mill is influenced to a certain extent, and the finally obtained metal chromium powder contains 98.71 weight percent of Cr, 0.13 weight percent of C, 0.014 weight percent of S, 0.12 weight percent of O, 0.008 weight percent of N and the particle size of D97 is 143nm.
Comparative example 3
The comparative example is different from example 1 in that the metallic chromium is not frozen by liquid nitrogen in the first and third steps, but is directly crushed, the particle size of the obtained metallic chromium particles reaches about 30mm, and other steps are identical to example 1.
Because the liquid nitrogen is not used for freezing the metal chromium in the first step and the third step, the metal chromium is directly crushed and coarsely ground, so that the grinding of the subsequent metal chromium coarse powder in a fluidized bed air flow mill is affected to a certain extent, and the finally obtained metal chromium powder contains 97.66wt% of Cr, 0.18wt% of C, 0.019wt% of S, 0.18wt% of O, 0.009wt% of N and the particle size of D97 is 178nm.
As can be seen from the results of examples 1 to 5 and comparative examples 1 to 3, the use of liquid nitrogen to freeze the metallic chromium before crushing and grinding the metallic chromium can make the metallic chromium more fragile and easy to crush, is beneficial to obtaining lower impurity content and smaller D97 particle size, and meets the use requirements in the fields of metallurgy, chemical industry, cast iron, fire resistance, electronics, aviation, aerospace, high-precision end science and technology and the like.
Although the embodiments of the present invention have been disclosed above, it is not limited to the use as set forth in the description and embodiments, it is well suited to various fields of use for the invention, and further modifications may be readily apparent to those skilled in the art, and accordingly, the invention is not limited to the particular details without departing from the general concepts defined in the claims and the equivalents thereof.
Claims (9)
1. A cryogenic pulverizing and impurity controlling method for metallic chromium is characterized by comprising the following steps:
step one, putting a metal chromium block into liquid nitrogen for freezing, and putting the frozen metal chromium block into a crusher for crushing to obtain small-particle metal chromium;
step two, putting the small-particle metal chromium obtained in the step one into a heating furnace, vacuumizing the heating furnace, performing vacuum heating treatment on the small-particle metal chromium for a period of time, cooling, introducing high-purity hydrogen into the heating furnace, and heating for a period of time;
step three, taking out the small-particle metal chromium naturally cooled to room temperature in the step two from a heating furnace, putting the small-particle metal chromium into liquid nitrogen for secondary freezing, and then carrying out coarse grinding by a grinding machine to obtain metal chromium coarse powder;
and step four, putting the metal chromium coarse powder obtained in the step three into a fluidized bed jet mill, taking nitrogen as a protective gas, and grinding in the fluidized bed jet mill to finally obtain the nano-scale metal chromium powder.
2. The method for preparing powder and controlling impurities by deep cooling of metal chromium according to claim 1, wherein the freezing time in the first step is 2-4 h, and the particle size of the small-particle metal chromium is 20-25 mm.
3. The method for preparing powder and controlling impurities by deep cooling of chromium metal according to claim 1, wherein in the second step, the heating furnace is vacuumized to 0-15 Pa, heated to 1300-1500 ℃ and treated for 3-9 h.
4. The method for preparing powder and controlling impurities by deep cooling of metallic chromium according to claim 1, wherein in the second step, the purity of the introduced hydrogen is 99.99%, the heating reaction temperature of the hydrogen is 1400-1700 ℃, and the reaction is carried out for 4-12 h.
5. The method for preparing powder and controlling impurities by deep cooling of chromium metal according to claim 1, wherein in the third step, the secondary freezing time is 4-6 hours, the rotating speed of a grinding machine is 100-1600 rpm, the grinding time is 2-5 hours, and the grain size of the coarse powder of the chromium metal is 100-300 um.
6. The method for preparing powder and controlling impurities by cryogenic cooling of metallic chromium according to claim 1, wherein in the fourth step, the gas flow rate of the fluidized bed jet mill is 300-500 m/s, and the gas pressure is 0.7-0.85 MPa.
7. The method for preparing powder and controlling impurities by deep cooling of metallic chromium according to claim 1, wherein the impurity content of the metallic chromium block in the first step is less than or equal to 0.5wt% of C, less than or equal to 0.02wt% of S, less than or equal to 0.1wt% of O, and less than or equal to 0.01wt% of N.
8. The method for preparing powder and controlling impurities by cryogenic cooling of metallic chromium according to claim 1, wherein in the fourth step, cr is more than or equal to 99.9wt%, C is less than or equal to 0.02wt%, S is less than or equal to 0.002wt%, O is less than or equal to 0.03wt%, N is less than or equal to 0.002wt%, and the grain size of the metallic chromium powder is 60-100 nm.
9. The method for preparing powder and controlling impurities by cryogenic cooling of metallic chromium according to claim 1, wherein before the fourth step, the metallic chromium coarse powder obtained in the third step is subjected to melt gas atomization granulation, and the specific steps are as follows:
s1, placing metal chromium coarse powder into an induction smelting furnace of a metal powder atomizing device, melting to metal chromium melt, and filling argon into the induction smelting furnace as protective gas;
s2, leaking the molten liquid obtained in the step S1 into an atomizer through a metal liquid flow outlet with the aperture of 5-10 mm at the flow rate of 10-15 kg/min, spraying gas to atomize the metal liquid by a gas spraying component around the metal liquid flow outlet, wherein the gas is argon, the gas spraying pressure is 10-30 MPa, and the spraying speed of the gas is 240-400 m/S;
and S3, collecting the granulated metal chromium particles, and filling argon into a collecting device to obtain the metal chromium particles with the particle size of 30-50 um.
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