CN112605390B - Preparation method of vacuum-grade low-nitrogen metal chromium for preparing high-temperature alloy by using chromium powder - Google Patents
Preparation method of vacuum-grade low-nitrogen metal chromium for preparing high-temperature alloy by using chromium powder Download PDFInfo
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- CN112605390B CN112605390B CN202011118691.7A CN202011118691A CN112605390B CN 112605390 B CN112605390 B CN 112605390B CN 202011118691 A CN202011118691 A CN 202011118691A CN 112605390 B CN112605390 B CN 112605390B
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- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 title claims abstract description 231
- 239000011651 chromium Substances 0.000 title claims abstract description 175
- 229910052804 chromium Inorganic materials 0.000 title claims abstract description 173
- IJGRMHOSHXDMSA-UHFFFAOYSA-N nitrogen Substances N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 title claims abstract description 67
- 229910052757 nitrogen Inorganic materials 0.000 title claims abstract description 47
- 229910052751 metal Inorganic materials 0.000 title claims abstract description 27
- 239000002184 metal Substances 0.000 title claims abstract description 27
- 239000000956 alloy Substances 0.000 title claims abstract description 21
- 229910045601 alloy Inorganic materials 0.000 title claims abstract description 20
- 238000002360 preparation method Methods 0.000 title claims abstract description 18
- 238000003825 pressing Methods 0.000 claims abstract description 80
- 238000005245 sintering Methods 0.000 claims abstract description 58
- 238000000227 grinding Methods 0.000 claims abstract description 43
- 238000005507 spraying Methods 0.000 claims abstract description 43
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 25
- 230000001070 adhesive effect Effects 0.000 claims abstract description 19
- 239000000853 adhesive Substances 0.000 claims abstract description 18
- 239000007789 gas Substances 0.000 claims abstract description 18
- 230000001681 protective effect Effects 0.000 claims abstract description 15
- 239000004484 Briquette Substances 0.000 claims abstract description 14
- 238000001816 cooling Methods 0.000 claims abstract description 14
- 239000012298 atmosphere Substances 0.000 claims abstract description 13
- 238000007789 sealing Methods 0.000 claims abstract description 13
- 238000011068 loading method Methods 0.000 claims abstract description 7
- 238000005470 impregnation Methods 0.000 claims abstract description 5
- 238000000034 method Methods 0.000 claims description 42
- 229910000831 Steel Inorganic materials 0.000 claims description 18
- 239000010959 steel Substances 0.000 claims description 18
- 239000000203 mixture Substances 0.000 claims description 16
- 239000000843 powder Substances 0.000 claims description 16
- 239000011324 bead Substances 0.000 claims description 15
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 12
- 238000007664 blowing Methods 0.000 claims description 12
- 239000002245 particle Substances 0.000 claims description 12
- 238000002156 mixing Methods 0.000 claims description 11
- 239000007849 furan resin Substances 0.000 claims description 10
- 239000007788 liquid Substances 0.000 claims description 10
- 229910002076 stabilized zirconia Inorganic materials 0.000 claims description 10
- 239000002994 raw material Substances 0.000 claims description 8
- 229910052786 argon Inorganic materials 0.000 claims description 6
- 238000007598 dipping method Methods 0.000 claims description 6
- 238000001125 extrusion Methods 0.000 claims description 6
- 230000003116 impacting effect Effects 0.000 claims description 6
- 239000011229 interlayer Substances 0.000 claims description 6
- 238000005488 sandblasting Methods 0.000 claims description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 6
- MCMNRKCIXSYSNV-UHFFFAOYSA-N ZrO2 Inorganic materials O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 claims description 5
- 238000004140 cleaning Methods 0.000 claims description 5
- 150000002240 furans Chemical class 0.000 claims description 5
- 239000011812 mixed powder Substances 0.000 claims description 5
- -1 phenolic modified furan Chemical class 0.000 claims description 5
- 238000005303 weighing Methods 0.000 claims description 5
- 238000002791 soaking Methods 0.000 claims description 4
- 238000007796 conventional method Methods 0.000 abstract description 2
- 238000010438 heat treatment Methods 0.000 description 15
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 10
- 239000012300 argon atmosphere Substances 0.000 description 10
- 229910000601 superalloy Inorganic materials 0.000 description 9
- 239000007767 bonding agent Substances 0.000 description 5
- 229910052759 nickel Inorganic materials 0.000 description 5
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 238000007254 oxidation reaction Methods 0.000 description 3
- 238000004321 preservation Methods 0.000 description 3
- 238000011160 research Methods 0.000 description 3
- 229910052782 aluminium Inorganic materials 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 238000001513 hot isostatic pressing Methods 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 239000011159 matrix material Substances 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000005204 segregation Methods 0.000 description 2
- 238000005728 strengthening Methods 0.000 description 2
- 239000010936 titanium Substances 0.000 description 2
- 229910052719 titanium Inorganic materials 0.000 description 2
- 238000003723 Smelting Methods 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 230000004913 activation Effects 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 239000010953 base metal Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000007123 defense Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 239000010410 layer Substances 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 150000004767 nitrides Chemical class 0.000 description 1
- 238000001556 precipitation 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
- B22F1/10—Metallic powder containing lubricating or binding agents; Metallic powder containing organic material
- B22F1/102—Metallic powder coated with organic material
-
- 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
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/10—Sintering only
- B22F3/1003—Use of special medium during sintering, e.g. sintering aid
- B22F3/1007—Atmosphere
-
- 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
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/12—Both compacting and sintering
- B22F3/14—Both compacting and sintering simultaneously
- B22F3/15—Hot isostatic pressing
-
- 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
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/25—Process efficiency
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- Manufacturing & Machinery (AREA)
- Mechanical Engineering (AREA)
- Powder Metallurgy (AREA)
Abstract
The invention provides a preparation method of vacuum-grade low-nitrogen metal chromium for preparing high-temperature alloy by using chromium powder, which comprises the following steps: s1: grinding the chromium blocks subjected to low-temperature impregnation at low temperature to obtain chromium powder; s2: spraying a layer of chromium powder and a layer of graphite powder in a pressing mould by taking an adhesive as a carrier to obtain a chromium powder-graphite powder mixed blank; s3: sealing a pressing die of the chromium powder-graphite powder mixed blank in a protective gas atmosphere, and pressing the pressing die to obtain a pressed chromium blank block; s4: and (3) performing microwave treatment on the chromium briquette, then loading the chromium briquette into a vacuum sintering furnace, sealing and vacuumizing, and after the gradient sintering is finished, air-cooling to room temperature in a protective gas atmosphere to obtain the vacuum-grade low-nitrogen metal chromium. In conclusion, the metallic chromium prepared by the invention has the advantages of low O content and low N content compared with the conventional method.
Description
Technical Field
The invention belongs to the technical field of material preparation, and particularly relates to a preparation method of vacuum-level low-nitrogen metal chromium for preparing high-temperature alloy by using chromium powder.
Background
The high-temperature alloy has good high-temperature strength, oxidation resistance and corrosion resistance, and is an irreplaceable key material for modern national defense construction and national economy. With the rapid development of high temperature alloy materials, the market thereof is in a state of gradually expanding and growing. The vacuum-level high-purity degassed chromium is an important component in the high-temperature alloy, and the rapid development of the high-temperature alloy greatly improves the market demand of the vacuum-level high-purity degassed chromium.
Except for the base metal, chromium metal accounts for a large proportion of the superalloy. Chromium combines with carbon in the matrix to form a skeleton carbide structure, and plays roles of precipitation strengthening and grain boundary strengthening to a certain extent. In addition, the addition of chromium is mainly used for improving the high-temperature oxidation resistance and corrosion resistance of the alloy. When the chromium content in the alloy reaches a certain degree, a layer of Cr is formed on the surface of the high-temperature alloy 2 O 3 The oxide film has high thermal stability and strong protection on a matrix.
Nitrogen in the superalloy is present as a trace impurity element. Nitrogen is present in dissolved state or as a nitride or carbonitride. When the nitrogen content in the nickel-based superalloy is higher than the saturation solubility of TiN at the solidus temperature, coarse primary TiN inclusions are formed, and the content of the primary TiN inclusions in the nickel-based superalloy is even one order of magnitude higher than that of oxide inclusions, so that the mechanical behavior of the nickel-based superalloy is seriously influenced.
A great deal of research work at home and abroad shows that the high nitrogen content in the high-temperature alloy can greatly increase the micro-porosity of the casting. The nitrogen promotes segregation of aluminum and titanium at grain boundaries, resulting in grain boundary hardening. At a certain C content, increasing the N content also leads to an increase in brittle phases like carbonitrides, which reduces the plasticity of the superalloy.
Because the nickel-based superalloy contains more elements with strong affinity with nitrogen, such as Cr, Al, Ti and the like, particularly Cr remarkably increases the solubility of nitrogen in the nickel-based superalloy liquid, and the nitrogen removal by a vacuum smelting process is very difficult. The most effective way to reduce the nitrogen content in the superalloy at present is to reduce the nitrogen content in the raw materials. Therefore, the invention designs a preparation method of vacuum-grade low-nitrogen metal chromium for preparing high-temperature alloy by using chromium powder.
Disclosure of Invention
Aiming at the problems, the invention provides a preparation method of vacuum-level low-nitrogen metal chromium for preparing high-temperature alloy by using chromium powder.
The technical scheme of the invention is as follows: a method for preparing vacuum-level low-nitrogen metal chromium for high-temperature alloy by using chromium powder mainly comprises the following steps:
s1: preparation of chromium powder
Selecting chromium blocks with similar specifications as raw materials, removing oxide skins on the surfaces of the chromium blocks, dipping the chromium blocks in a cryogenic tank, crushing the chromium blocks subjected to cryogenic dipping into chromium particles by using an extrusion crusher, adding the chromium particles into a cryogenic grinder, adding a grinding medium into the cryogenic grinder, continuously introducing liquid nitrogen into an interlayer on the inner wall of the cryogenic grinder, keeping the temperature in the cryogenic grinder at-150 +/-10 ℃, and separating the grinding medium after grinding to obtain chromium powder;
s2: mixed powder
Weighing graphite powder which is 0.1-5% of the mass of the chromium powder prepared by S1 and serves as a deoxidizer, respectively uniformly mixing the chromium powder and the graphite powder, putting the mixture into a powder spraying machine, adding an adhesive which is the same as the total mass of the chromium powder and the graphite powder into the powder spraying machine, uniformly mixing, cleaning and precooling a pressing mold, spraying a mixed material of the chromium powder, the graphite powder and the adhesive into the pressing mold by taking the adhesive as a carrier, always keeping the temperature in the pressing mold at-30-0 ℃ in the spraying process, and obtaining a chromium powder-graphite powder mixed blank after spraying;
s3: pressing
Sealing the pressing mould filled with the chromium powder-graphite powder mixed blank obtained in the step S2 in the protective gas atmosphere, vacuumizing the inside of the pressing mould to 20-30Pa, performing pressing treatment on the pressing mould, and obtaining a pressed chromium blank block after the pressing treatment is finished;
s4: vacuum sintering
Firstly carrying out microwave treatment on the chromium briquette obtained in the step S3, then blowing the inside of a vacuum sintering furnace by using protective gas, blowing out air in the vacuum sintering furnace, loading the chromium briquette subjected to microwave treatment into the vacuum sintering furnace in the protective gas atmosphere, sealing and vacuumizing the vacuum sintering furnace to 0.5-1Pa, raising the temperature in the vacuum sintering furnace to 400 ℃ of plus 300 ℃ at the heating rate of 3 ℃/min, carrying out heat preservation for 10-20min, then raising the temperature in the vacuum sintering furnace to 1000 ℃ of plus 900 ℃ at the heating rate of 5 ℃/min, carrying out heat preservation for 1-2h, raising the temperature in the vacuum sintering furnace to 1500 ℃ of plus 900 ℃ at the heating rate of 10 ℃/min, carrying out heat preservation for 3-5h, and carrying out air cooling to room temperature in the protective gas atmosphere after sintering is finished to obtain the vacuum-grade low-nitrogen metal chromium.
Further, in S1, the specific process for removing the scale on the surface of the chromium block is as follows: the method comprises the steps of placing a chromium block in a high-speed sand blasting machine, spraying steel grit to the surface of the chromium block at a high speed, crushing oxide skin on the surface of the chromium block by utilizing the high-speed sprayed steel grit, then using a high-pressure water pump to remove the crushed oxide skin on the surface of the chromium block and the embedded steel grit in an impacting manner to obtain a pure chromium block, wherein the oxide skin on the surface of the chromium block can influence the performance of preparing vacuum-grade low-nitrogen metal chromium.
Further, in S1, the specific process of low-temperature impregnation of the chrome block is as follows: putting the chromium blocks into a low-temperature tank, adding liquid nitrogen into the low-temperature tank, reducing the temperature in the low-temperature tank to-100 +/-10 ℃ at a cooling rate of 5 ℃/min, and soaking the chromium blocks in the low-temperature tank for 15-18h at a low temperature, wherein the brittleness of the chromium blocks can be changed by the low-temperature soaking of the chromium blocks, so that the chromium blocks are more easily crushed and crushed.
Further, in S1, the grinding medium is one or a mixture of two or more of yttrium-stabilized zirconia beads, cerium-stabilized zirconia beads, and 80-zirconia beads, and does not contaminate the raw material during the grinding process.
Further, in S2, in the spray coating process, the pressing mold and the powder blower are always in the protective gas atmosphere, so as to avoid that the air is mixed into the chromium powder-graphite powder mixed blank in the spray coating process, and the air and the chromium block generate oxidation reaction in the subsequent treatment process, thereby reducing the performance of the vacuum-level low-nitrogen metal chromium.
Furthermore, in S2, the adhesive is a mixture of phenolic modified furan resin and ketoaldehyde modified furan resin in a mass ratio of 3:1, the adhesive is good in adhesive effect and easy to remove, and the performance of the vacuum-level low-nitrogen metal chromium cannot be affected.
Further, in S3, the specific process of the pressing treatment is as follows: and applying 1-2MPa to the pressing mould for pre-pressing and forming, then applying 5-20MPa to the pressing mould, and pressing to obtain the pressed chromium compact.
Further, in S4, the specific microwave treatment process of the chromium block is as follows: placing the chromium block in a microwave generator, starting the frequency of the microwave generator to 0.3-0.5kW, raising the frequency of the microwave generator to 0.8-1.0kW after the temperature of the chromium block in the microwave generator is raised to 400 +/-10 ℃, preserving heat for 5-8min, naturally cooling after preserving heat for 20-30min, and performing microwave treatment to activate atoms in the chromium compact after hot isostatic pressing and improve the performance of the prepared vacuum-grade low-nitrogen metal chromium.
Further, in S3 and S4, the shielding gas is argon gas with a purity of 99.99%.
The invention has the beneficial effects that: the invention provides a preparation method of vacuum-level low-nitrogen metal chromium for preparing high-temperature alloy by using chromium powder, which comprises the steps of immersing chromium blocks at a low temperature, grinding and crushing the chromium blocks, adding no impurities into the chromium blocks in the grinding and crushing process, enabling the chromium powder ground and crushed at the low temperature to have low segregation degree, uniformly mixing graphite powder and the chromium powder in a powder spraying mode, bonding the chromium powder and the graphite powder by using an easily removable bonding agent, avoiding that the chromium powder and the graphite powder are not uniformly dispersed due to density weight in the subsequent treatment process, pressing the chromium powder into a high-density blank in a hot isostatic pressing mode, and performing vacuum gradient sintering on a chromium blank block after microwave activation to remove nitrogen elements in the metal chromium to the maximum extent. In conclusion, the metallic chromium prepared by the invention has the advantages of low O content and low N content compared with the conventional method.
Detailed Description
In order to facilitate understanding of the technical solutions of the present invention, the following embodiments are further described in detail, and the embodiments do not limit the scope of the present invention.
Example 1: a method for preparing vacuum-level low-nitrogen metal chromium for high-temperature alloy by using chromium powder mainly comprises the following steps:
s1: preparation of chromium powder
Selecting chromium blocks with similar specifications as raw materials, removing oxide skin on the surfaces of the chromium blocks, crushing the chromium blocks into chromium particles by using an extrusion crusher, adding the chromium particles into a low-temperature grinding machine, adding a grinding medium into the low-temperature grinding machine, continuously introducing liquid nitrogen into an interlayer on the inner wall of the low-temperature grinding machine to keep the temperature in the low-temperature grinding machine at-160 ℃, separating the grinding medium after grinding to obtain chromium powder,
the specific process for removing the oxide skin on the surface of the chromium block comprises the following steps: placing the chromium blocks in a high-speed sand blasting machine, spraying steel grit to the surfaces of the chromium blocks at a high speed, crushing oxide skins on the surfaces of the chromium blocks by using the steel grit sprayed at the high speed, and then removing the crushed oxide skins and the embedded steel grit on the surfaces of the chromium blocks by using a high-pressure water pump in an impacting manner to obtain pure chromium blocks;
s2: mixed powder
Weighing graphite powder with the mass of 0.1 percent of that of the chromium powder prepared by S1 as a deoxidizer, respectively uniformly mixing the chromium powder and the graphite powder, putting the mixture into a powder spraying machine, adding an adhesive with the same total mass as the chromium powder and the graphite powder into the powder spraying machine, uniformly mixing, wherein the adhesive is a mixture of phenolic modified furan resin and ketoaldehyde modified furan resin in a mass ratio of 3:1, cleaning and pre-cooling a pressing mold, spraying and coating the mixture of the chromium powder and the graphite powder and the adhesive in the pressing mold by taking the adhesive as a carrier, always keeping the temperature in the pressing mold at-30 ℃ in the spraying process, obtaining a chromium powder-graphite powder mixed blank after the spraying is finished, and always keeping the pressing mold and the powder spraying machine in an argon atmosphere with the purity of 99.99 percent in the spraying process;
s3: pressing
Sealing the pressing mould filled with the chromium powder-graphite powder mixed blank obtained in the step S2 in an argon atmosphere with the purity of 99.99 percent, vacuumizing the inside of the pressing mould to 20Pa, pressing the pressing mould to obtain a pressed chromium blank block after the pressing treatment is finished,
the specific process of the pressing treatment comprises the following steps: applying 1MPa pressure to a pressing mold for prepressing and molding, then applying 5MPa pressure to the pressing mold, and obtaining a pressed chromium compact after pressing;
s4: vacuum sintering
Blowing argon with the purity of 99.99% into the vacuum sintering furnace, blowing air out of the vacuum sintering furnace, loading the chromium briquette obtained in the step S3 into the vacuum sintering furnace in the argon atmosphere with the purity of 99.99%, sealing and vacuumizing the vacuum sintering furnace until the vacuum degree is 0.5Pa, raising the temperature in the vacuum sintering furnace to 300 ℃ at the heating rate of 3 ℃/min, preserving the heat for 10min, raising the temperature in the vacuum sintering furnace to 900 ℃ at the heating rate of 5 ℃/min, preserving the heat for 1h, raising the temperature in the vacuum sintering furnace to 1400 ℃ at the heating rate of 10 ℃/min, preserving the heat for 3h, and cooling the sintered chromium to room temperature in the protective gas atmosphere to obtain the vacuum-grade low-nitrogen metal chromium.
Example 2: a method for preparing vacuum-level low-nitrogen metal chromium for high-temperature alloy by using chromium powder mainly comprises the following steps:
s1: preparation of chromium powder
Selecting chromium blocks with similar specifications as raw materials, removing oxide skin on the surfaces of the chromium blocks, crushing the chromium blocks into chromium particles by using an extrusion crusher, adding the chromium particles into a low-temperature grinding machine, adding a grinding medium into the low-temperature grinding machine, wherein the grinding medium is any one of more than two mixed media of yttrium-stabilized zirconia beads, cerium-stabilized zirconia beads and 80-zirconia beads, continuously introducing liquid nitrogen into an interlayer on the inner wall of the low-temperature grinding machine, keeping the temperature in the low-temperature grinding machine at-150 ℃, separating the grinding medium after grinding to obtain chromium powder,
the specific process for removing the oxide skin on the surface of the chromium block comprises the following steps: placing the chromium blocks in a high-speed sand blasting machine, spraying steel grit to the surfaces of the chromium blocks at a high speed, crushing oxide skins on the surfaces of the chromium blocks by using the steel grit sprayed at the high speed, and then removing the crushed oxide skins and the embedded steel grit on the surfaces of the chromium blocks by using a high-pressure water pump in an impacting manner to obtain pure chromium blocks;
s2: mixed powder
Weighing graphite powder with the mass of 2% of that of the chromium powder prepared by S1 as a deoxidizer, respectively uniformly mixing the chromium powder and the graphite powder, putting the mixture into a powder spraying machine, adding an adhesive with the same total mass as the chromium powder and the graphite powder into the powder spraying machine, uniformly mixing, wherein the adhesive is a mixture of phenolic modified furan resin and ketoaldehyde modified furan resin in a mass ratio of 3:1, cleaning and pre-cooling a pressing mold, spraying the mixture of the chromium powder and the graphite powder and the adhesive in the pressing mold by taking the adhesive as a carrier, always keeping the temperature in the pressing mold at-15 ℃ in the spraying process, obtaining a chromium powder-graphite powder mixed blank after the spraying is finished, and always keeping the pressing mold and the powder spraying machine in an argon atmosphere with the purity of 99.99% in the spraying process;
s3: pressing
Sealing the pressing mould filled with the chromium powder-graphite powder mixed blank obtained in the step S2 in an argon atmosphere with the purity of 99.99 percent, vacuumizing the inside of the pressing mould to 25Pa, pressing the pressing mould to obtain a pressed chromium blank block after the pressing treatment is finished,
the specific process of the pressing treatment comprises the following steps: applying 1.5MPa pressure to a pressing mould for pre-pressing forming, then applying 17MPa pressure to the pressing mould, and pressing to obtain a pressed chromium compact;
s4: vacuum sintering
Blowing argon with the purity of 99.99% into the vacuum sintering furnace, blowing air out of the vacuum sintering furnace, loading the chromium briquette obtained in the step S3 into the vacuum sintering furnace in the argon atmosphere with the purity of 99.99%, sealing and vacuumizing the vacuum sintering furnace until the vacuum degree is 1Pa, raising the temperature in the vacuum sintering furnace to 350 ℃ at the heating rate of 3 ℃/min, preserving the heat for 15min, raising the temperature in the vacuum sintering furnace to 950 ℃ at the heating rate of 5 ℃/min, preserving the heat for 1.5h, raising the temperature in the vacuum sintering furnace to 1450 ℃ at the heating rate of 10 ℃/min, preserving the heat for 4h, and cooling the sintered chromium to room temperature in the protective gas atmosphere to obtain the vacuum-grade low-nitrogen metal chromium.
Example 3: a preparation method of vacuum-grade low-nitrogen metal chromium for preparing high-temperature alloy by using chromium powder mainly comprises the following steps:
s1: preparation of chromium powder
Selecting chromium blocks with similar specifications as raw materials, removing oxide skin on the surfaces of the chromium blocks, crushing the chromium blocks into chromium particles by using an extrusion crusher, adding the chromium particles into a low-temperature grinding machine, adding a grinding medium into the low-temperature grinding machine, wherein the grinding medium is any one of more than two mixed media of yttrium-stabilized zirconia beads, cerium-stabilized zirconia beads and 80-zirconia beads, continuously introducing liquid nitrogen into an interlayer on the inner wall of the low-temperature grinding machine, keeping the temperature in the low-temperature grinding machine at-140 ℃, separating the grinding medium after grinding to obtain chromium powder,
the specific process for removing the oxide skin on the surface of the chromium block comprises the following steps: placing the chromium blocks in a high-speed sand blasting machine, spraying steel grit to the surfaces of the chromium blocks at a high speed, crushing oxide skins on the surfaces of the chromium blocks by using the steel grit sprayed at the high speed, and then removing the crushed oxide skins and the embedded steel grit on the surfaces of the chromium blocks by using a high-pressure water pump in an impacting manner to obtain pure chromium blocks;
s2: mixed powder
Weighing graphite powder with the mass of 5% of that of chromium powder prepared by S1 as a deoxidizer, respectively uniformly mixing the chromium powder and the graphite powder, putting the mixture into a powder spraying machine, adding a bonding agent with the same total mass as the chromium powder and the graphite powder into the powder spraying machine, uniformly mixing, wherein the bonding agent is a mixture of phenolic aldehyde modified furan resin and ketoaldehyde modified furan resin in a mass ratio of 3:1, cleaning and pre-cooling a pressing mold, spraying and covering the mixture of the chromium powder and the graphite powder and the bonding agent in the pressing mold by taking the bonding agent as a carrier, always keeping the temperature in the pressing mold at 0 ℃ in the spraying process, obtaining a chromium powder-graphite powder mixed blank after the spraying and covering are finished, and in the spraying and covering process, the pressing mold and the powder spraying machine are always in an argon atmosphere with the purity of 99.99%;
s3: pressing
Sealing the pressing mould filled with the chromium powder-graphite powder mixed blank obtained in the step S2 in an argon atmosphere with the purity of 99.99 percent, vacuumizing the inside of the pressing mould to 30Pa, pressing the pressing mould to obtain a pressed chromium blank block after the pressing treatment is finished,
the specific process of the pressing treatment comprises the following steps: applying 2MPa pressure to a pressing mould for prepressing and forming, then applying 20MPa pressure to the pressing mould, and obtaining a pressed chromium briquette after pressing;
s4: vacuum sintering
Blowing argon with the purity of 99.99% into the vacuum sintering furnace, blowing air out of the vacuum sintering furnace, loading the chromium briquette obtained in the step S3 into the vacuum sintering furnace in the argon atmosphere with the purity of 99.99%, sealing and vacuumizing the vacuum sintering furnace until the vacuum degree is 1Pa, raising the temperature in the vacuum sintering furnace to 400 ℃ at the heating rate of 3 ℃/min, preserving the heat for 20min, raising the temperature in the vacuum sintering furnace to 1000 ℃ at the heating rate of 5 ℃/min, preserving the heat for 2h, raising the temperature in the vacuum sintering furnace to 1500 ℃ at the heating rate of 10 ℃/min, preserving the heat for 5h, and after sintering, air-cooling to room temperature in the protective gas atmosphere to obtain the vacuum-grade low-nitrogen metal chromium.
Example 4: the same as example 1 except that:
s1: preparation of chromium powder
Selecting chromium blocks with similar specifications as raw materials, removing oxide skin on the surfaces of the chromium blocks, dipping the chromium blocks in a cryogenic tank, crushing the chromium blocks after low-temperature dipping into chromium particles by using an extrusion crusher, adding the chromium particles into a cryogenic grinder, adding a grinding medium into the cryogenic grinder, wherein the grinding medium is any one or more than two of yttrium-stabilized zirconia beads, cerium-stabilized zirconia beads and 80-zirconia beads, continuously introducing liquid nitrogen into an interlayer on the inner wall of the cryogenic grinder to keep the temperature in the cryogenic grinder at-160 ℃, separating the grinding medium after grinding to obtain chromium powder,
the specific process for removing the oxide skin on the surface of the chromium block comprises the following steps: putting the chromium blocks in a high-speed sand blasting machine, spraying steel grit to the surfaces of the chromium blocks at a high speed, crushing oxide skins on the surfaces of the chromium blocks by using the steel grit sprayed at the high speed, then removing the crushed oxide skins and the embedded steel grit on the surfaces of the chromium blocks by using a high-pressure water pump in an impacting manner to obtain pure chromium blocks,
the specific process of low-temperature impregnation of the chromium blocks comprises the following steps: putting the chromium blocks into a cryogenic tank, adding liquid nitrogen into the cryogenic tank, reducing the temperature in the cryogenic tank to-110 ℃ at a cooling rate of 5 ℃/min, and soaking the chromium blocks in the cryogenic tank at a low temperature for 15 h.
Example 5: the same as example 1 except that:
s4: vacuum sintering
Firstly, carrying out microwave treatment on the chromium briquette obtained in the step S3, then blowing the inside of a vacuum sintering furnace with argon with the purity of 99.99%, blowing out air in the inside of the vacuum sintering furnace, loading the chromium briquette subjected to microwave treatment into the vacuum sintering furnace in the argon atmosphere with the purity of 99.99%, sealing and vacuumizing the inside of the vacuum sintering furnace to 0.5Pa, raising the temperature in the vacuum sintering furnace to 300 ℃ at the heating rate of 3 ℃/min, preserving heat for 10min, raising the temperature in the vacuum sintering furnace to 900 ℃ at the heating rate of 5 ℃/min, preserving heat for 1h, raising the temperature in the vacuum sintering furnace to 1400 ℃ at the heating rate of 10 ℃/min, preserving heat for 3h, cooling the chromium briquette to room temperature under the atmosphere of protective gas after sintering is finished, and obtaining vacuum-grade low-nitrogen metal chromium,
the microwave treatment process of the chromium block comprises the following specific steps: and (3) placing the chromium block in a microwave generator, starting the microwave generator to enable the frequency of the microwave generator to be 0.3kW, raising the frequency of the microwave generator to be 0.8kW after the temperature of the chromium block in the microwave generator is raised to 390 ℃ and the temperature is kept for 5min, and naturally cooling after the temperature is kept for 20 min.
Experimental example 1: research on influence of low-temperature impregnation of chromium blocks on properties of prepared chromium powder
The chromium powder was prepared by the methods provided in examples 1 and 4, and the parameters of the prepared chromium powder were analyzed and determined, and the results are shown in table 1:
TABLE 1 comparison table of chromium powder parameters obtained by different preparation methods
And (4) conclusion: the chromium blocks are soaked at low temperature and then crushed and ground, so that the preparation time is saved, and the prepared chromium powder has smaller and more average granularity.
Experimental example 2: research on the influence of the microwave treatment on the chromium briquette before vacuum sintering on the performance of the prepared vacuum-grade low-nitrogen metal chromium
The vacuum sintering methods provided in example 1, example 2, example 3 and example 5 were respectively used to perform vacuum sintering on the chromium compacts prepared in the same batch, and the content of N in the prepared vacuum-grade low-nitrogen metallic chromium was respectively detected, and the detection results are shown in table 2:
TABLE 2 table for detecting N content in vacuum-grade low-nitrogen metal chromium prepared by different vacuum sintering methods
| Group of | Example 1 | Example 2 | Example 3 | Example 5 |
| Content of N/%) | 0.0013 | 0.0012 | 0.011 | 0.008 |
And (4) conclusion: the chromium compact is subjected to microwave treatment before vacuum sintering, so that the content of N in the vacuum-grade low-nitrogen metal chromium can be greatly reduced in the sintering process.
Claims (3)
1. A preparation method of vacuum-grade low-nitrogen metal chromium for preparing high-temperature alloy by using chromium powder is characterized by mainly comprising the following steps:
s1: preparation of chromium powder
Selecting chromium blocks with similar specifications as raw materials, removing oxide skin on the surfaces of the chromium blocks, dipping the chromium blocks in a cryogenic tank, crushing the chromium blocks after low-temperature dipping into chromium particles by using an extrusion crusher, adding the chromium particles into a cryogenic grinding machine, adding a grinding medium into the cryogenic grinding machine, continuously introducing liquid nitrogen into an interlayer of the inner wall of the cryogenic grinding machine, keeping the temperature in the cryogenic grinding machine at-150 +/-10 ℃, and separating the grinding medium after grinding to obtain chromium powder;
s2: mixed powder
Weighing graphite powder which is 0.5-5% of the mass of the chromium powder and is prepared by S1 as a deoxidizer, respectively uniformly mixing the chromium powder and the graphite powder, putting the mixture into a powder spraying machine, adding an adhesive which is the same as the total mass of the chromium powder and the graphite powder into the powder spraying machine, uniformly mixing, cleaning and precooling a pressing die, spraying a mixture of the chromium powder, the graphite powder and the adhesive into the pressing die by taking the adhesive as a carrier, always keeping the temperature in the pressing die at-30-0 ℃ in the spraying process, and obtaining a chromium powder-graphite powder mixed blank after the spraying is finished;
s3: pressing
Sealing the pressing mould filled with the chromium powder-graphite powder mixed blank obtained in the step S2 in the protective gas atmosphere, vacuumizing the inside of the pressing mould to 20-30Pa, pressing the pressing mould, and obtaining a pressed chromium blank block after pressing;
s4: vacuum sintering
Firstly carrying out microwave treatment on the chromium briquette obtained in the step S3, blowing the inside of a vacuum sintering furnace by using protective gas, blowing out the air in the vacuum sintering furnace, loading the chromium briquette subjected to microwave treatment into the vacuum sintering furnace in the protective gas atmosphere, sealing and vacuumizing the vacuum sintering furnace to 0.5-1Pa, raising the temperature in the vacuum sintering furnace to 400 ℃ of 300-;
in S1, the specific process for removing the scale on the surface of the chromium block comprises: placing the chromium blocks in a high-speed sand blasting machine, spraying steel grit to the surfaces of the chromium blocks at a high speed, crushing oxide skins on the surfaces of the chromium blocks by using the steel grit sprayed at the high speed, and then removing the crushed oxide skins and the embedded steel grit on the surfaces of the chromium blocks by using a high-pressure water pump in an impacting manner to obtain pure chromium blocks;
in S1, the grinding medium is one or a mixture of two or more of yttrium-stabilized zirconia beads, cerium-stabilized zirconia beads, and 80-zirconia beads;
in S1, the specific process for low-temperature impregnation of the chromium block comprises the following steps: putting the chromium blocks into a cryogenic tank, adding liquid nitrogen into the cryogenic tank, reducing the temperature in the cryogenic tank to-100 +/-10 ℃ at a cooling rate of 5 ℃/min, and soaking the chromium blocks in the cryogenic tank at a low temperature for 15-18 h;
s2, in the spraying process, the pressing die and the powder spraying machine are always in a protective gas atmosphere;
in S2, the adhesive is a mixture of phenolic modified furan resin and ketoaldehyde modified furan resin in a mass ratio of 3: 1.
2. The method for preparing vacuum-grade low-nitrogen metal chromium for preparing high-temperature alloy from chromium powder as claimed in claim 1, wherein in S3, the specific process of the pressing treatment is as follows: and applying pressure of 1-2MPa to the pressing mould for pre-pressing forming, then applying pressure of 5-20MPa to the pressing mould, and pressing to obtain a pressed chromium compact.
3. The method of claim 1, wherein the shielding gas used in S3 and S4 is argon with a purity of 99.99%.
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