阅读说明：本技术 一种采用湿法混合金属粉末制备高纯度金属铬块的方法 (Method for preparing high-purity metal chromium block by adopting wet-process mixed metal powder ) 是由 杨莉 聂红锋 闫利平 贺猛 翟荣荣 孙刚刚 于 2021-04-06 设计创作，主要内容包括：本发明公开了一种采用湿法混合金属粉末制备高纯度金属铬块的方法,涉及金属粉末制品制造技术领域,包括S1、制粉：机械制备一种粒度小于300μm的金属铬粉；S2、湿法混料：将制得的金属铬粉与有机还原剂前驱体湿法混合；S3、搅拌烘干：将混合后的粉末在真空干燥室中搅拌烘干；S4、压制成型：对烘干后的粉末进行压制成型；S5、真空烧结：对铬坯进行真空烧结,在一定温度及压力下实现提纯。本发明可制备纯度高、气体含量低、杂质含量低、化学成分均匀一致、外观精美的高纯金属铬,可满足高温合金、高纯靶材等行业对高纯金属原材料的需求。(The invention discloses a method for preparing a high-purity metal chromium block by mixing metal powder by a wet method, which relates to the technical field of metal powder product manufacture and comprises the following steps of S1: mechanically preparing metal chromium powder with the particle size of less than 300 mu m; s2, wet mixing: mixing the prepared metal chromium powder with an organic reducing agent precursor by a wet method; s3, stirring and drying: stirring and drying the mixed powder in a vacuum drying chamber; s4, press forming: pressing and forming the dried powder; s5, vacuum sintering: and (4) carrying out vacuum sintering on the chromium blank, and purifying at a certain temperature and under a certain pressure. The method can prepare high-purity metal chromium with high purity, low gas content, low impurity content, uniform and consistent chemical components and exquisite appearance, and can meet the requirements of industries such as high-temperature alloy, high-purity target materials and the like on high-purity metal raw materials.)

1. A method for preparing high-purity metal chromium blocks by adopting wet mixed metal powder is characterized by comprising the following steps:

s1: powder making

Selecting a chromium block prepared by an aluminothermic method as a raw material, placing the chromium block in a crusher for pre-crushing to obtain chromium particles with the particle size of less than 10mm, and then placing the obtained chromium particles in a grinder for milling to obtain metal chromium powder with the particle size of less than 300 mu m;

s2: wet mixing

Putting the prepared metal chromium powder and the organic reducing agent precursor into a mixer for wet mixing, and continuously stirring by using distilled water as a dispersing agent until the metal chromium powder, the organic reducing agent precursor and the distilled water are uniformly mixed;

s3: stirring and drying

Stirring and drying the mixed powder in a vacuum drying chamber at the temperature of 110-120 ℃, and drying until the powder is not bonded;

s4: press forming

Putting the dried powder into a die, and pressing under the pressure of 6-7Mpa to obtain a blocky chromium blank;

s5: vacuum sintering

And putting the chromium blank into a vacuum sintering furnace to carry out vacuum sintering on the chromium blank, carrying out heat preservation and carbonization at 300 ℃, and then heating to 1400 ℃ for reduction reaction.

2. The method for preparing high-purity metallic chromium blocks by using wet mixed metal powder as claimed in claim 1, wherein the organic reducing agent precursor in step S2 is sucrose or glucose.

3. The method for preparing high purity metallic chromium blocks using wet mixed metal powder as claimed in claim 1, wherein the dispersant is added in a volume ratio of 1:1 to the metallic chromium powder in step S2, and the stirring speed is 100-120 r/min.

4. The method for preparing high purity metallic chromium blocks using wet mixed metal powder as claimed in claim 1, wherein the vacuum degree of the vacuum drying chamber in step S3 is less than 1000Pa, the stirring speed is 20-30r/min, and the drying time is 1-1.5 h.

5. The method for preparing high purity metallic chromium blocks using wet mixing of metal powders as claimed in claim 1, wherein the grinding beads in the grinding mill of step S1 are made of stainless steel with a diameter of 25-30mm, ethanol is added as a protecting agent during grinding, the protecting agent and the chromium blocks are added in a mass ratio of 1:2, after grinding, chromium particles with a particle size of less than 10mm are sieved out through a screen, the grinding of chromium particles with a particle size of more than 10mm is continued, and the chromium particles with a particle size of less than 10mm are put into the grinding mill for milling.

6. The method for preparing high-purity metallic chromium blocks by using wet-mixing metal powder as claimed in claim 1, wherein the wet mixing is performed by injecting distilled water into the mixer at a constant speed, the injection speed of the distilled water is 50ml/s, and the temperature in the mixer is 25-50 ℃.

7. The method for preparing a high-purity metallic chromium block by using a wet-process mixed metal powder as claimed in claim 1, wherein the vacuum sintering is carried out at 300 ℃ for 1-1.5h, the heating rate is 10-15 ℃/min during the heating to 1400 ℃, and the sintering time is 3-5h at 1400 ℃.

8. The method for preparing high-purity metallic chromium blocks by using wet mixed metal powder according to claim 1, wherein the vacuum sintering furnace is a vacuum induction sintering furnace heated by medium frequency induction, and the degree of vacuum in the vacuum sintering furnace is 0.5 to 10 Pa.

9. The method for preparing high-purity metallic chromium blocks by using wet-process mixed metal powder as claimed in claim 1, wherein the temperature of the vacuum sintering furnace is reduced by cold air at a rate of 10-20 ℃/min until the surface temperature of the chromium blank is below 70 ℃, and the chromium blank is taken out and naturally cooled at room temperature.

Technical Field

The invention relates to the technical field of metal powder product manufacturing, in particular to a method for preparing a high-purity metal chromium block by mixing metal powder by a wet method.

Background

The current process development has extremely high requirements on high-purity metal and metal alloy, and can be used for manufacturing precise metal parts and surface coatings in the industries of aerospace, transportation, power transmission and transformation and the like. Among them, high-purity metal chromium is widely used in high-temperature alloys at present, accounts for a large proportion in the high-temperature alloys, and chromium is combined with carbon in a matrix to form a skeleton carbide structure, so that precipitation strengthening and grain boundary strengthening effects are achieved to a certain extent, and meanwhile, the high-temperature oxidation resistance and corrosion resistance of the alloy can be improved.

The metallic raw material prepared by purification from raw ore usually has a large amount of metallic oxide inclusions, and the oxygen content has a great influence on the chemical and mechanical properties of the metallic material. The low oxygen content is a basic factor for preventing oxidation and corrosion of the material, and if the oxygen content is increased, the impact resistance value of the high-temperature alloy is greatly reduced, the fatigue resistance is deteriorated, and the service life of the material is greatly reduced.

Therefore, it is important to reduce the oxygen content of the material by a method that uniformly reduces the non-metallic inclusions in the metallic starting material.

At present, the method for purifying metals at home and abroad mainly comprises dry mixing and vacuum reduction of graphite powder, granulation and vacuum reduction of graphite powder added with adhesive and reduction in hydrogen atmosphere.

The method for vacuum reduction of the graphite powder by dry mixing comprises the following steps: chromium powder and graphite powder are mixed according to the proportion of 0.1 to 1 percent and then are pressed and sintered. The graphite powder and the chromium powder have large specific gravity difference, so that the material mixing is possibly uneven, the sintering quality is greatly fluctuated, and the consistency of the purification effect is low; when graphite powder is added with a binder for granulation and vacuum reduction, the vacuum degree and the temperature are high, metal particles are easy to be bonded into irregular blocks, the porosity of the whole sintered body is reduced, the degassing efficiency is reduced, secondary processing is needed after reduction is finished, and the production cost is increased; the hydrogen atmosphere has high reduction cost, hydrogen is not easy to store, the cost is high, and the production efficiency is low.

Disclosure of Invention

In order to solve the technical problems, the invention provides a method for preparing a high-purity metal chromium block by mixing metal powder by a wet method.

The technical scheme of the invention is as follows: a method for preparing high-purity metal chromium blocks by adopting wet mixed metal powder comprises the following steps:

s1: powder making

Selecting a chromium block prepared by an aluminothermic method as a raw material, placing the chromium block in a crusher for pre-crushing to obtain chromium particles with the particle size of less than 10mm, and then placing the obtained chromium particles in a grinder for milling to obtain metal chromium powder with the particle size of less than 300 mu m;

s2: wet mixing

Putting the prepared metal chromium powder and the organic reducing agent precursor into a mixer for wet mixing, and continuously stirring by using distilled water as a dispersing agent until the metal chromium powder, the organic reducing agent precursor and the distilled water are uniformly mixed;

s3: stirring and drying

Stirring and drying the mixed powder in a vacuum drying chamber at the temperature of 110-120 ℃, and drying until the powder is not bonded;

s4: press forming

Putting the dried powder into a die, and pressing under the pressure of 6-7Mpa to obtain a blocky chromium blank;

s5: vacuum sintering

And putting the chromium blank into a vacuum sintering furnace to carry out vacuum sintering on the chromium blank, carrying out heat preservation and carbonization at 300 ℃, and then heating to 1400 ℃ for reduction reaction.

Further, the organic reducing agent precursor in step S2 is sucrose or glucose, which is non-toxic and harmless, and is easily carbonized and has low raw material cost.

Furthermore, the adding amount of the dispersing agent in the step S2 is 1:1 of the volume ratio of the dispersing agent to the metal chromium powder, the stirring speed is 100-120r/min, and the stirring efficiency is high.

Further, in the step S3, the vacuum degree of the vacuum drying chamber is less than 1000Pa, the stirring speed is 20-30r/min, and the drying time is 1-1.5h, so that the bonding of the saccharides and the container during standing and drying is avoided, and the utilization rate of the raw materials is improved.

Further, the grinding beads in the grinding machine in the step S1 are made of stainless steel with a diameter of 25-30mm, ethanol is added as a protective agent during grinding, the protective agent and the chromium blocks are added according to a mass ratio of 1:2, after grinding is completed, chromium particles with a particle size of less than 10mm are sieved out through a screen, the chromium particles with a particle size of more than 10mm are continuously ground, the chromium particles with a particle size of less than 10mm are placed in the grinding machine to be pulverized, and the chromium blocks are coarsely ground through mechanical grinding to improve the overall grinding efficiency.

Furthermore, during wet mixing, distilled water is injected into the mixer at a constant speed, the injection speed of the distilled water is 50ml/s, the temperature in the mixer is 25-50 ℃, the mixing uniformity is improved, and the manual loss caused by the traditional dry graphite mixing is reduced.

Further, the organic precursor with high carbon content is carbonized for 1-1.5h at 300 ℃ during vacuum sintering, a degassing gap is created for the chromium blank by virtue of the residual carbon skeleton of the carbonization of the organic matter, the degassing purification of superfine powder generated during powder preparation can be completed by the gap, the material utilization rate is high, the cost is low, after the carbonization is completed, the temperature rise speed in the process of rising to 1400 ℃ is 10-15 ℃/min, the sintering time is 3-5h at 1400 ℃, the chromium oxide is subjected to redox reaction, and the purity of the chromium is improved.

Furthermore, the vacuum sintering furnace adopts a vacuum induction sintering furnace heated by medium-frequency induction, the vacuum degree in the furnace is 0.5-10Pa during vacuum sintering, and oxygen is reduced during vacuum sintering, so that chromium oxidation is prevented.

Further, after the vacuum sintering is finished, cooling the vacuum sintering furnace by cold air at the cooling speed of 10-20 ℃/min until the surface temperature of the chromium blank is below 70 ℃, and taking out the chromium blank to naturally cool at room temperature.

The invention has the beneficial effects that:

1. according to the invention, a wet mixing mode is adopted, sucrose is used as a reducing agent, most common water is used as a dispersing agent, soaking type mixing is adopted, and organic matters are coated in metal powder, so that the uniformity of mixing is improved, the manual loss caused by traditional graphite dry mixing is reduced, and the condition that the reducing agent is not uniformly dispersed due to the particle size difference of the mixing is avoided.

2. The method utilizes the residual carbon skeleton carbonized by the organic matters in the medium-temperature section to reduce, greatly improves the uniformity of reduction, simultaneously generates a large amount of gaps in the compact in the carbonization process, and improves the degassing rate in the reduction process.

3. The invention adopts a vacuum stirring type drying method, avoids the adhesion between saccharides and a container during standing and drying, and improves the utilization rate of raw materials.

4. The raw material adopted by the invention is metal powder with the granularity less than 300 mu m, and the degassing purification of superfine powder generated during powder preparation can be completed by virtue of the degassing gap created by the carbon skeleton, so that the material utilization rate is high, and the cost is low.

Drawings

FIG. 1 is a process flow diagram of the present invention.

Detailed Description

Example 1:

as shown in fig. 1, a method for preparing a high purity metallic chromium block using a wet mixed metal powder, comprises the steps of:

s1: powder making

Selecting a chromium block prepared by an aluminothermic method as a raw material, placing the chromium block in a crusher for pre-crushing, wherein grinding beads in a grinding machine are made of stainless steel with the diameter of 25mm, adding ethanol as a protective agent during grinding, adding the protective agent and the chromium block according to the mass ratio of 1:2, screening out chromium particles with the particle size of less than 10mm by using a screen after grinding is finished, continuously grinding the chromium particles with the particle size of more than 10mm, placing the chromium particles with the particle size of less than 10mm in the grinding machine for milling to obtain metal chromium powder with the particle size of less than 300 mu m, and crushing and then grinding to improve the overall milling efficiency;

s2: wet mixing

Putting the prepared metal chromium powder and an organic reducing agent precursor into a mixer for wet mixing, wherein the organic reducing agent precursor is sucrose, the sucrose is ground into powder with the granularity smaller than 325 mu m and is mixed with the metal chromium powder, and the sucrose has high carbon content, is easy to carbonize and has low raw material cost;

during mixing, distilled water is used as a dispersing agent, the adding amount of the dispersing agent is added according to the volume ratio of the dispersing agent to the metal chromium powder of 1:1, the stirring speed is 100r/min, the stirring efficiency is high, and the stirring is continuously carried out until the metal chromium powder, the organic reducing agent precursor and the distilled water are uniformly mixed;

during wet mixing, distilled water is injected into the mixer at a constant speed, the injection speed of the distilled water is 50ml/s, the temperature in the mixer is 25 ℃, the uniformity of mixing is improved, and the manual loss caused by the traditional graphite dry mixing is reduced;

s3: stirring and drying

Stirring and drying the mixed powder in a vacuum drying chamber at 110 ℃ until the powder is not bonded, wherein the vacuum degree of the vacuum drying chamber is 3Pa, the stirring speed is 20r/min, and the drying time is 1h, so that the bonding of the saccharides and the container during standing and drying is avoided, and the utilization rate of the raw materials is improved;

s4: press forming

Putting the dried powder into a die, and pressing the powder into a blocky chromium blank under the pressure of 6 Mpa;

s5: vacuum sintering

Putting the chromium blank into a vacuum sintering furnace to carry out vacuum sintering on the chromium blank, preserving heat and carbonizing for 1h at 300 ℃, then heating to 1400 ℃ to carry out reduction reaction, wherein the heating speed in the process of heating to 1400 ℃ is 10 ℃/min, the sintering time is 3h at 1400 ℃, organic matters with high carbon content are carbonized firstly, and then the chromium oxide is subjected to redox reaction to improve the purity of the chromium, the vacuum sintering furnace adopts a vacuum induction sintering furnace with medium-frequency induction heating, the vacuum degree in the vacuum sintering furnace is 0.5Pa, and oxygen is reduced during vacuum sintering to prevent chromium from being oxidized;

and after the vacuum sintering is finished, cooling the inside of the vacuum sintering furnace by cold air at the cooling speed of 10 ℃/min until the surface temperature of the chromium blank reaches 70 ℃, taking out the chromium blank, and naturally cooling at room temperature.

Three samples were prepared by this example, and the O content (%) and the C content (%) of the three samples were measured, wherein the results of the measurement of the O content (%) were: 0.0310%, 0.0280%, 0.0320%, and the mean value of O content (%) is 0.0303%; the results of the detection of the C content (%) were respectively: 0.0024%, 0.0012% and 0.0027%, and the mean value of C content (%) is 0.0021.

Example 2:

as shown in fig. 1, a method for preparing a high purity metallic chromium block using a wet mixed metal powder, comprises the steps of:

s1: powder making

Selecting a chromium block prepared by an aluminothermic method as a raw material, placing the chromium block in a crusher for pre-crushing, wherein grinding beads in a grinding machine are made of stainless steel with the diameter of 28mm, adding ethanol as a protective agent during grinding, adding the protective agent and the chromium block according to the mass ratio of 1:2, screening out chromium particles with the particle size of less than 10mm by using a screen after grinding is finished, continuously grinding the chromium particles with the particle size of more than 10mm, placing the chromium particles with the particle size of less than 10mm in the grinding machine for milling to obtain metal chromium powder with the particle size of less than 300 mu m, and crushing and then grinding to improve the overall milling efficiency;

s2: wet mixing

Putting the prepared metal chromium powder and an organic reducing agent precursor into a mixer for wet mixing, wherein the organic reducing agent precursor is glucose, the granularity of the glucose is less than 355 mu m, the glucose has high carbon content, is easy to carbonize and has low raw material cost;

during mixing, distilled water is used as a dispersing agent, the adding amount of the dispersing agent is added according to the volume ratio of the dispersing agent to the metal chromium powder of 1:1, the stirring speed is 110r/min, the stirring efficiency is high, and the stirring is continuously carried out until the metal chromium powder, the organic reducing agent precursor and the distilled water are uniformly mixed;

during wet mixing, distilled water is injected into the mixer at a constant speed, the injection speed of the distilled water is 50ml/s, the temperature in the mixer is 40 ℃, the uniformity of mixing is improved, and the manual loss caused by the traditional dry graphite mixing is reduced;

s3: stirring and drying

Stirring and drying the mixed powder in a vacuum drying chamber at 115 ℃ until the powder is not bonded, wherein the vacuum degree of the vacuum drying chamber is 500Pa, the stirring speed is 25r/min, and the drying time is 1.2h, so that the bonding of saccharides and a container is avoided when the powder is kept stand and dried, and the utilization rate of raw materials is improved;

s4: press forming

Putting the dried powder into a die, and pressing the powder into a blocky chromium blank under the pressing pressure of 6.5 Mpa;

s5: vacuum sintering

Putting the chromium blank into a vacuum sintering furnace to carry out vacuum sintering on the chromium blank, preserving heat and carbonizing for 1.2h at 300 ℃, then heating to 1400 ℃ to carry out reduction reaction, wherein the heating speed in the process of heating to 1400 ℃ is 13 ℃/min, the sintering time at 1400 ℃ is 4h, firstly carbonizing organic matters with high carbon content, and then carrying out redox reaction on chromium oxide to improve the purity of chromium, wherein the vacuum sintering furnace adopts a vacuum induction sintering furnace with medium-frequency induction heating, the vacuum degree in the vacuum sintering furnace is 5Pa, and the vacuum sintering reduces oxygen to enter so as to prevent chromium from being oxidized;

and after the vacuum sintering is finished, cooling the inside of the vacuum sintering furnace by cold air at the cooling speed of 15 ℃/min until the surface temperature of the chromium blank reaches 50 ℃, taking out the chromium blank, and naturally cooling at room temperature.

Three samples were prepared by this example, and the O content (%) and the C content (%) of the three samples were measured, wherein the results of the measurement of the O content (%) were: 0.0270%, 0.0320%, 0.0290%, and the mean value of O content (%) is 0.0293%; the results of the detection of the C content (%) were respectively: 0.0012%, 0.0014% and 0.0008%, and the mean value of C content (%) is 0.0011.

Example 3:

as shown in fig. 1, a method for preparing a high purity metallic chromium block using a wet mixed metal powder, comprises the steps of:

s1: powder making

Selecting a chromium block prepared by an aluminothermic method as a raw material, placing the chromium block in a crusher for pre-crushing, wherein grinding beads in a grinding machine are made of stainless steel with the diameter of 30mm, adding ethanol as a protective agent during grinding, adding the protective agent and the chromium block according to the mass ratio of 1:2, screening out chromium particles with the particle size of less than 10mm by using a screen after grinding is finished, continuously grinding the chromium particles with the particle size of more than 10mm, placing the chromium particles with the particle size of less than 10mm in the grinding machine for milling to obtain metal chromium powder with the particle size of less than 300 mu m, and crushing and then grinding to improve the overall milling efficiency;

s2: wet mixing

Putting the prepared metal chromium powder and an organic reducing agent precursor into a mixer for wet mixing, wherein the organic reducing agent precursor is glucose, the granularity of the glucose is less than 355 mu m, the glucose has high carbon content, is easy to carbonize and has low raw material cost;

during mixing, distilled water is used as a dispersing agent, the adding amount of the dispersing agent is added according to the volume ratio of the dispersing agent to the metal chromium powder of 1:1, the stirring speed is 120r/min, the stirring efficiency is high, and the stirring is continuously carried out until the metal chromium powder, the organic reducing agent precursor and the distilled water are uniformly mixed;

during wet mixing, distilled water is injected into the mixer at a constant speed, the injection speed of the distilled water is 50ml/s, and the temperature in the mixer is 50 ℃, so that the uniformity of mixing is improved, and the manual loss caused by the traditional graphite dry mixing is reduced;

s3: stirring and drying

Stirring and drying the mixed powder in a vacuum drying chamber at 120 ℃ until the powder is not bonded, wherein the vacuum degree of the vacuum drying chamber is 900Pa, the stirring speed is 30r/min, and the drying time is 1.5h, so that the bonding of saccharides and a container is avoided when the powder is kept stand and dried, and the utilization rate of raw materials is improved;

s4: press forming

Putting the dried powder into a die, and pressing to obtain a blocky chromium blank under the pressing pressure of 7 Mpa;

s5: vacuum sintering

Putting the chromium blank into a vacuum sintering furnace to carry out vacuum sintering on the chromium blank, preserving heat and carbonizing for 1.5h at 300 ℃, then heating to 1400 ℃ to carry out reduction reaction, wherein the heating speed in the process of heating to 1400 ℃ is 15 ℃/min, the sintering time at 1400 ℃ is 5h, firstly carbonizing organic matters with high carbon content, and then carrying out redox reaction on chromium oxide to improve the purity of chromium, wherein the vacuum sintering furnace adopts a vacuum induction sintering furnace with medium-frequency induction heating, the vacuum degree in the vacuum sintering furnace is 10Pa, and the vacuum sintering reduces oxygen entering to prevent chromium from being oxidized;

and after the vacuum sintering is finished, cooling the inside of the vacuum sintering furnace by cold air at the cooling speed of 20 ℃/min until the surface temperature of the chromium blank reaches 30 ℃, taking out the chromium blank, and naturally cooling at room temperature.

Three samples were prepared by this example, and the O content (%) and the C content (%) of the three samples were measured, wherein the results of the measurement of the O content (%) were: 0.0340%, 0.0320% and 0.0330%, wherein the mean value of O content (%) is 0.0330%; the results of the detection of the C content (%) were respectively: 0.0019%, 0.0029% and 0.0008%, and the mean value of C content (%) is 0.0019.

From the data of the O content (%) and C content (%) and the respective mean values of the three groups of samples of each example, it can be found that the method for preparing a high-purity metallic chromium block by wet mixing the metal powder according to the present invention produces a chromium block having a low O content (%) and C content (%) and the mean values of the O content (%) and C content (%) of the three groups of samples of comparative examples 1, 2 and 3 and example 2 are the lowest, so that example 2 is the most preferable example.