Method for producing low-aluminum low-oxygen high-purity chromium metal through two-step method

Abstract

A two-step method for producing low-aluminum low-oxygen high-purity chromium metal comprises the following steps: uniformly mixing chromium oxide, aluminum particles, calcined coke and sodium chlorate to obtain a mixed raw material; putting the mixed raw material into a smelting furnace, covering the surface of the mixed raw material in the smelting furnace with magnesium chips, and igniting to finish smelting; after the furnace burden in the smelting furnace is naturally cooled to the room temperature, starting the furnace, finishing furnace slag on the surface of the metal chromium to obtain coarse chromium, crushing and grinding, and performing magnetic separation to remove iron to obtain metal chromium powder; uniformly mixing metal chromium powder with metal chromium sheet powder obtained by an electrolytic method or metal chromium powder obtained by an aluminothermy method to obtain a metal chromium mixture, and pressing the metal chromium mixture into a metal chromium ingot; and the metal chromium ingot is put into a horizontal vacuum furnace, the temperature is increased, vacuum deoxidation is conducted, and the low-aluminum low-oxygen high-purity metal chromium is obtained. The method has the advantages that other carbon sources do not need to be added, the process steps are simplified, and the degassing efficiency is improved; the carbon element in the metal chromium powder is effectively utilized in the degassing process, the content of the carbon element and the content of the oxygen element are reduced, and the purity of the high-purity metal chromium is improved.

Description

Technical Field

[0001] The present invention belongs to the field of powder metallurgy, and particularly relates to a method for producing low-aluminum and low-oxygen high-purity metallic chromium by a two-step process. Background Art

[0002] High-purity metallic chromium has become an important raw material for non-ferrous-based precision alloys, especially chromium-based alloys, due to its excellent toughness, high-temperature resistance, and corrosion resistance. In high-tech fields such as the aerospace industry, jet aircraft manufacturing, and gas turbine manufacturing, the application of high-purity metallic chromium is crucial. Currently, the main method for preparing high-purity metallic chromium is the metal chromium carbon reduction and degassing method. During the carbon reduction process, due to the large difference in the particle sizes of metallic chromium and carbon powder used, the mixing process is complex and time-consuming. Moreover, during the mixing process, dust is easily generated due to the difference in particle sizes between metallic chromium powder and carbon powder, polluting the environment. In addition, the quality of the raw material metallic chromium has a direct impact on the high purity of the final product. For example, if the ordinary metallic chromium raw material obtained by the aluminothermic method contains impurities or has too high an aluminum content, it will be difficult to completely remove them through subsequent degassing processes, thus affecting the quality of high-purity metallic chromium.

[0003] Currently, the smelting of ordinary metallic chromium is mainly carried out by two reduction methods: the aluminothermic reduction method and the carbon reduction method. The production principle of the aluminothermic reduction method is to rely on the heat generated by the aluminothermic reaction to maintain the reaction. However, the excessive input of aluminum source will lead to an increase in the aluminum content in metallic chromium, and these aluminum elements will remain in the high-purity metallic chromium after degassing, affecting the purity of the product. The production principle of the carbon reduction method is to use a carbon source as a reducing agent to reduce chromium oxide. The reaction is usually carried out under a vacuum or inert gas atmosphere, with harsh conditions and a slow reaction rate. Although the carbon reduction method can theoretically reduce the aluminum content in metallic chromium, due to its harsh reaction conditions and slow reaction rate, it is difficult to completely replace the aluminothermic reduction method in normal production.

[0004] CN119242958A discloses "a method for preparing low-gas high-purity chromium", which involves mixing an appropriate amount of carbon powder into the ordinary metallic chromium prepared by the aluminothermic method after crushing and the ordinary metallic chromium prepared by the electrolytic method, and acting as a reducing agent to remove oxygen elements during the high-temperature sintering process. In this method, the aluminum content in the ordinary metallic chromium prepared by the aluminothermic method is relatively high and cannot be removed, and only by adding an appropriate amount of the ordinary metallic chromium prepared by the electrolytic method can the aluminum content be adjusted downwards. The method has great limitations, and during the mixing process of ordinary metallic chromium and carbon powder, dust is easily generated due to the difference in particle sizes between metallic chromium powder and carbon powder, polluting the environment. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for producing low-aluminum and low-oxygen high-purity metallic chromium by a two-step process that does not require carbon powder mixing, has a simple mixing process, and reduces environmental pollution.

[0006] The technical solution of the present invention is as follows: A method for preparing high-purity metallic chromium, comprising the following steps: (1) Mixing materials Mix chromium oxide, aluminum particles, calcined coke, and sodium chlorate evenly according to the mass ratios of chromium oxide to reducing agent aluminum particles, calcined coke, and heat-generating agent sodium chlorate being 1:(0.31 - 0.35), 1:(0.01 - 0.021), and 1:(0.05 - 0.076) respectively to obtain a mixed raw material; (2) Smelting Put the mixed raw material into a smelting furnace, cover the surface of the mixed raw material in the smelting furnace with magnesium chips and ignite to complete the smelting; (3) Finishing and crushing After the charge in the smelting furnace cools naturally to room temperature, remove the furnace. Finish the slag on the surface of metallic chromium to obtain crude chromium, crush and grind it, and perform magnetic separation to remove iron to obtain metallic chromium powder with a carbon element mass content of 1 - 3 wt.%. (4) Pressing into shape Mix the metallic chromium powder produced in step (3) with oxygen-containing metallic chromium powder evenly. The oxygen-containing metallic chromium powder is metallic chromium flake powder obtained by electrolysis or metallic chromium powder obtained by aluminothermic process to obtain a metallic chromium mixture; press it into a metallic chromium ingot with a diameter of 28 - 30 mm; (5) Vacuum deoxidation Put the metallic chromium ingot into a horizontal vacuum furnace, heat it to 1400 - 1500 °C for vacuum deoxidation for 72 - 96 h to obtain low-aluminum and low-oxygen high-purity metallic chromium.

[0007] Further, in step (1), the reducing agent aluminum particles and calcined coke together reduce 91.5 wt.% of chromium oxide, that is, the total coefficient of the reducing agent added is 91.5%; among them, 83 - 87 wt.% of chromium oxide is reduced by aluminum particles, that is, the coefficient of aluminum added is 83 - 87 wt.%; the remaining 4.5 - 8.5 wt.% of chromium oxide is reduced by calcined coke, that is, the coefficient of carbon added is 4.5 - 8.5 wt.%.

[0008] Further, in step (1), the reaction heat per unit charge of the mixed raw material in the smelting furnace is 700 - 730 kcal / kg, where the reaction heat of calcined coke reducing chromium oxide is calculated based on the generation of carbon monoxide.

[0009] Further, the particle size of the metallic chromium flake powder obtained by electrolysis is -45 mesh, and the particle size of the metallic chromium powder obtained by aluminothermic process is -45 mesh.

[0010] Further, the molar ratio of O element to C element in the metallic chromium mixture is 1:1.

[0011] Further, the oxygen content of the oxygen-containing metallic chromium powder is 0.1 - 0.5 wt.%.

[0012] Further, the oxygen content of the metal chromium flake powder obtained by the electrolysis method is 0.4-0.5 wt.%, and the oxygen content of the metal chromium powder obtained by the aluminothermic method is 0.1-0.2 wt.%.

[0013] Further, when pressing the metal chromium ingot, the weight of each metal chromium ingot is 50-53 g.

[0014] Further, when crushing and grinding the crude chromium, the crude chromium is crushed and ground to pass through a 70-mesh sieve.

[0015] Further, after vacuum deoxidation in step (4), the horizontal vacuum furnace is cooled to 400-500 °C to take out the metal chromium ingot, and it is naturally cooled to room temperature.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) Improve the metal chromium smelting process. By introducing the carbon reduction method to replace part of the aluminothermic reduction method, adding a reasonable amount of sodium chlorate to ensure the smooth progress of the aluminothermic reaction, and adding an appropriate amount of calcined coke, the violent reaction of sodium chlorate can be slowed down, effectively avoiding splashing, and achieving the purpose of reducing the aluminum element content in the target metal chromium; the cost of the carbon source (calcined coke) is much lower than that of the aluminum source (aluminum pellets). The introduction of an appropriate amount of calcined coke not only reduces the cost of raw materials in smelting production, but also the addition of an excessive amount of calcined coke is beneficial to improving the subsequent mixed degassing effect of the target metal chromium. (2) By adding an appropriate amount of carbon source and using the combined method of carbon reduction and aluminothermic reduction to obtain metal chromium powder with a carbon content of 1-3 wt.%, and mixing and degassing it with the oxygen-containing metal chromium powder obtained by the aluminothermic method or the electrolysis method, there is no need to add other carbon sources, such as carbon powder, for degassing. This not only simplifies the process steps but also improves the degassing efficiency. The carbon element in the metal chromium powder is effectively utilized during the degassing process, further reducing the carbon element and oxygen element content in the product and improving the purity of high-purity chromium. At the same time, this method of using metal chromium powder instead of carbon powder to reduce and prepare high-purity metal chromium reduces the particle flying phenomenon during the mixing process due to the relatively small difference in particle size between metal chromium powders, thus improving the operating environment and reducing the mixing difficulty. Specific Embodiments

[0017] In the examples and comparative examples of the present invention, the reducing agents aluminum pellets and calcined coke together reduce 91.5 wt.% of chromium oxide.

[0018] Example 1 (heat 725 kcal / kg, aluminum distribution coefficient 85%, electrolysis method metal chromium flake powder) (1) Mixing 7 kg of chromium oxide is mixed with 2.34 kg of aluminum pellets, 0.47 kg of sodium chlorate, and 0.11 kg of calcined coke and mixed evenly to obtain a mixed raw material; (2) Smelting Put the mixed raw materials into the smelting furnace, cover the surface of the mixed raw materials in the smelting furnace with magnesium chips and ignite them to complete the smelting; (3) Finishing and pulverizing After the charge in the smelting furnace cools naturally to room temperature, lift the furnace, finish the slag on the surface of metallic chromium to obtain crude chromium, crush and grind it to -70 mesh (pass through a 70-mesh sieve), and remove iron by magnetic separation to obtain metallic chromium powder; the elemental analysis of this metallic chromium powder is shown in Table 1: Among them, the aluminum element content is 0.07 wt.%, compared with the conventional aluminum element content of 0.05 - 0.35 wt.% in production, it is at a relatively low level; the elemental analysis shows that the carbon element content is 1.99 wt.%, exceeding the conventional carbon element content in production and being at an extremely high level; Table 1 Elemental analysis table of metallic chromium powder with carbon element mass content of 1 - 3 wt.% in Example 1 of the present invention (4) Take 300 g of the metallic chromium powder prepared in step (1) and mix it evenly with 1538 g of electrolytic metallic chromium flake powder (the composition is shown in Table 2 and the particle size is -45 mesh), and press it into metallic chromium ingots with a diameter of 28 - 30 mm. A total of 36 ingots are pressed, and the weight of each metallic chromium ingot is 50 - 53 g; Table 2 Elemental analysis table of electrolytic metallic chromium flake powder used in Example 1 of the present invention (5) Vacuum deoxidation Take 30 of the chromium ingots pressed in step (4), divide them into 5 batches and put them into the furnace, carry out vacuum degassing at 1450 °C for 75 h, conduct elemental analysis on the obtained high-purity metallic chromium ingots, and the obtained analysis results are shown in Table 3. Since the aluminum element content of the metallic chromium powder obtained by smelting is at a relatively low level as shown in Table 1, using this metallic chromium powder as the raw material and carrying out vacuum deoxidation, the elemental analysis of the obtained high-purity metallic chromium is shown in Table 3. The aluminum element content of the high-purity metallic chromium is low, only 0.012 wt.%; since the carbon element content of the metallic chromium powder obtained by smelting is at an extremely high level as shown in Table 1, the elemental analysis of the high-purity metallic chromium obtained after vacuum deoxidation is shown in Table 3. The residual oxygen element content of the high-purity metallic chromium is 0.023 wt.%, meeting the industrial level of high-purity metallic chromium of 500 ppm. The high-purity metallic chromium obtained in this example is low-aluminum and low-oxygen high-purity metallic chromium.

[0019] Table 3 Elemental analysis table of low-aluminum and low-oxygen high-purity metallic chromium in Example 1 of the present invention The present invention generally realizes the purpose of reducing the aluminum element content in high-purity metallic chromium (as shown in Table 3) by replacing part of the aluminum particles with an appropriate amount of calcined coke, thereby reducing the production cost of metallic chromium. The particle size of the raw metallic chromium powder prepared by this method is under 70 mesh sieve, which reduces the mixing difficulty with the metallic chromium flake powder with a particle size under 45 mesh sieve, improves the mixing operation environment and reduces the operation cost at the same time.

[0020] Example 2 (heat 725 kcal / kg, aluminum distribution coefficient 85%, aluminothermic metallic chromium powder) (1) Mixing 7 kg of chromium oxide is mixed with 2.34 kg of aluminum particles, 0.47 kg of sodium chlorate and 0.11 kg of calcined coke to obtain a mixed raw material. (2) Smelting The mixed raw material is put into the smelting furnace, and magnesium chips are covered on the surface of the mixed raw material in the smelting furnace and ignited to complete the smelting. (3) Finishing and pulverizing After the furnace charge in the smelting furnace is naturally cooled to room temperature, the furnace is lifted. The slag on the surface of the metallic chromium is finished to obtain crude chromium, which is broken, ground and sieved through a 70-mesh sieve, and magnetically separated to remove iron to obtain metallic chromium powder. The elemental analysis of this metallic chromium powder is shown in Table 4: among them, the aluminum element content is 0.07 wt.%, which is at a relatively low level compared with the conventional aluminum element content of 0.05 - 0.35 wt.% in production; the elemental analysis shows that the carbon element content is 1.99 wt.%, which exceeds the conventional carbon element content in production and is at a super high level. Table 4 Elemental analysis table of metallic chromium powder with a carbon element mass content of 1 - 3 wt.% in Example 2 of the present invention (4) Take 130 g of the metallic chromium powder prepared in step (1) and mix it evenly with 1998.82 g of aluminothermic metallic chromium powder (the composition is shown in Table 5, particle size is -45 mesh), and press it into metallic chromium ingots with a diameter of 28 - 30 mm. A total of 40 ingots are pressed, and the weight of each metallic chromium ingot is 50 - 53 g. Table 5 Elemental analysis table of aluminothermic metallic chromium powder used in Example 2 of the present invention (5) Vacuum deoxidation Take 30 chromium ingots pressed in step (4), evenly divide them into 5 batches and put them into the furnace. Carry out vacuum degassing at 1450 °C for 75 h. Conduct elemental analysis on the obtained high-purity metal chromium ingots. The analysis results are shown in Table 6. Since the aluminum element content of the metal chromium powder obtained by smelting is at a relatively low level as shown in Table 4, using this metal chromium powder as the raw material, carry out vacuum deoxidation. The elemental analysis of the obtained high-purity metal chromium is shown in Table 6. The aluminum element content of the high-purity metal chromium is low, only 0.035 wt.%. Since the carbon element content of the metal chromium powder obtained by smelting is at an extremely high level as shown in Table 4, the elemental analysis of the high-purity metal chromium obtained after vacuum deoxidation is shown in Table 6. The residual oxygen element content of the high-purity metal chromium is 0.028 wt.%, meeting the industrial level of high-purity metal chromium of 500 ppm. The high-purity metal chromium obtained in this example is low-aluminum and low-oxygen high-purity metal chromium.

[0021] Table 6 Elemental analysis table of low-aluminum and low-oxygen high-purity metal chromium in Example 2 of the present invention The present invention generally realizes the purpose of reducing the aluminum element content in high-purity metal chromium (as shown in Table 6) by using an appropriate amount of calcined coke to replace part of the aluminum particles, thereby reducing the production cost of metal chromium. The particle size of the raw material metal chromium powder prepared by this method is under a 70-mesh sieve, and the mixing difficulty with the metal chromium powder with a particle size under a 45-mesh sieve is reduced. While improving the mixing operation environment, the operation cost is also reduced.

[0022] Example 3 (heat 700 kcal / kg, aluminum distribution coefficient 83%, electrolytic metal chromium flake powder) (1) Mixing Charge 7 kg of chromium oxide, 2.24 kg of aluminum particles, 0.36 kg of sodium chlorate, and 0.14 kg of calcined coke into the mixture and mix evenly to obtain a mixed raw material; (2) Smelting Put the mixed raw material into the smelting furnace, cover the surface of the mixed raw material in the smelting furnace with magnesium chips and ignite to complete the smelting; (3) Finishing and pulverizing After the furnace charge in the smelting furnace cools naturally to room temperature, remove the furnace. Finish the slag on the surface of the metal chromium to obtain crude chromium. Crush and grind it to pass through a 70-mesh sieve, and carry out magnetic separation to remove iron to obtain metal chromium powder. The elemental analysis of this metal chromium powder is shown in Table 7: Among them, the aluminum element content is 0.02 wt.%, compared with the conventional aluminum element content of 0.05 - 0.35 wt.% in production, it is at an extremely low level; the elemental analysis shows that the carbon element content is 2.79 wt.%, exceeding the conventional carbon element content in production, and it is at an extremely high level; Table 7 Elemental analysis table of metal chromium powder with a carbon element mass content of 1 - 3 wt.% in Example 3 of the present invention (4) Take 250 g of the metallic chromium powder prepared in step (1) and mix it evenly with 1769 g of electrolytic metallic chromium flake powder (the composition is shown in Table 8, and the particle size is -45 mesh), and press it into metallic chromium ingots with a diameter of 28 - 30 mm. A total of 40 ingots are pressed, and the weight of each metallic chromium ingot is 50 - 53 g; Table 8 Elemental analysis table of the electrolytic metallic chromium flake powder used in Example 3 of the present invention (5) Vacuum deoxidation Take 30 of the chromium ingots pressed in step (4), evenly divide them into 5 batches and put them into the furnace, and carry out vacuum degassing at 1450 °C for 73 h. Elemental analysis is carried out on the obtained high-purity metallic chromium ingots, and the obtained analysis results are shown in Table 9. Since the aluminum element content of the metallic chromium powder obtained by smelting is at a relatively low level as shown in Table 7, using this metallic chromium powder as the raw material and carrying out vacuum deoxidation, the elemental analysis of the obtained high-purity metallic chromium is shown in Table 9. The aluminum element content of the high-purity metallic chromium is low, only 0.005 wt.%. Since the carbon element content of the metallic chromium powder obtained by smelting is at an extremely high level as shown in Table 7, the elemental analysis of the high-purity metallic chromium obtained after vacuum deoxidation is shown in Table 9. The residual oxygen element content of the high-purity metallic chromium is 0.01 wt.%, meeting the industrial level of high-purity metallic chromium of 500 ppm. The high-purity metallic chromium obtained in this example is low-aluminum and low-oxygen high-purity metallic chromium.

[0023] Table 9 Elemental analysis table of the low-aluminum and low-oxygen high-purity metallic chromium in Example 3 of the present invention The present invention generally realizes the purpose of reducing the aluminum element content in high-purity metallic chromium (as shown in Table 9) by replacing part of the aluminum particles with an appropriate amount of calcined coke and reducing the aluminum element content in metallic chromium, and reduces the production cost of metallic chromium. The particle size of the raw material metallic chromium powder prepared by this method is below 70 mesh, and the mixing difficulty with the metallic chromium flake powder with a particle size below 45 mesh is reduced, improving the mixing operation environment and reducing the operation cost at the same time.

[0024] Example 4 (heat 730 kcal / kg, aluminum distribution coefficient 87%, aluminothermic metallic chromium powder) (1) Mixing Charge 7 kg of chromium oxide, 2.41 kg of aluminum particles, 0.51 kg of sodium chlorate and 0.08 kg of calcined coke into the mixture and mix evenly to obtain a mixed raw material; (2) Smelting Put the mixed raw material into the smelting furnace, cover the surface of the mixed raw material in the smelting furnace with magnesium chips and ignite it to complete the smelting; (3) Finishing and pulverizing After the furnace charge in the smelting furnace is naturally cooled to room temperature, start the furnace, refine the slag on the surface of metallic chromium, obtain crude chromium, crush and grind it to pass through a 70-mesh sieve, and remove iron by magnetic separation to obtain metallic chromium powder; the elemental analysis of this metallic chromium powder is shown in Table 10: Among them, the aluminum element content is 0.15 wt.%, compared with the conventional aluminum element content of 0.05 - 0.35 wt.% in production, it is at a normal level; the elemental analysis shows that the carbon element content is 1.07 wt.%, exceeding the conventional carbon element content in production and being at a super-high level. Table 10 Elemental analysis table of metallic chromium powder with carbon element mass content of 1 - 3 wt.% in Example 4 of the present invention (4) Take 200 g of the metallic chromium powder prepared in step (1) and mix it evenly with 1842.22 g of aluminothermic metallic chromium powder (the composition is shown in Table 11 and the particle size is -45 mesh), and press them into metallic chromium ingots with a diameter of 28 - 30 mm. A total of 40 ingots are pressed, and the weight of each metallic chromium ingot is 50 - 53 g; Table 11 Elemental analysis table of aluminothermic metallic chromium powder used in Example 4 of the present invention (5) Vacuum deoxidation Take 30 of the chromium ingots pressed in step (4), evenly divide them into 5 batches and put them into the furnace, and carry out vacuum degassing at 1450 °C for 73 h. Carry out elemental analysis on the obtained high-purity metallic chromium ingots, and the obtained analysis results are shown in Table 12. Since the aluminum element content of the metallic chromium powder obtained by smelting is at a normal level as shown in Table 10, using this metallic chromium powder as the raw material and carrying out vacuum deoxidation, the elemental analysis of the obtained high-purity metallic chromium is shown in Table 12. The aluminum element content of the high-purity metallic chromium is low, only 0.057 wt.%; since the carbon element content of the metallic chromium powder obtained by smelting is at a super-high level as shown in Table 10, and the elemental analysis of the high-purity metallic chromium obtained after vacuum deoxidation is shown in Table 12, the residual oxygen element content of the high-purity metallic chromium is 0.039 wt.%, meeting the industrial level of high-purity metallic chromium of 500 ppm. The high-purity metallic chromium obtained in this example is low-aluminum and low-oxygen high-purity metallic chromium.

[0025] Table 12 Elemental analysis table of low-aluminum and low-oxygen high-purity metallic chromium in Example 4 of the present invention The present invention generally realizes the purpose of reducing the aluminum element content in high-purity metallic chromium (as shown in Table 12) by using an appropriate amount of calcined coke to replace part of the aluminum particles and reducing the aluminum element content in metallic chromium, and reduces the production cost of metallic chromium. The particle size of the raw material metallic chromium powder prepared by this method is below 70 mesh, and the mixing difficulty with metallic chromium powder with a particle size below 45 mesh is reduced. While improving the mixing operation environment, the operation cost is reduced.

[0026] Comparative Example 1 (heat 730 kcal / kg, aluminum distribution coefficient 90%, electrolytic chromium metal flake powder) (1) Mixing materials Mix 7 kg of chromium oxide with 2.5 kg of aluminum pellets, 0.54 kg of sodium chlorate, and 0.03 kg of calcined coke evenly to obtain mixed raw materials; (2) Smelting Put the mixed raw materials into the smelting furnace, cover the surface of the mixed raw materials in the smelting furnace with magnesium chips and ignite to complete the smelting; (3) Finishing and pulverizing After the charge in the smelting furnace is naturally cooled to room temperature, remove the furnace, finish the slag on the surface of the metallic chromium, obtain crude chromium, crush and grind it to pass through a 70-mesh sieve, and remove iron by magnetic separation; the elemental analysis of this metallic chromium powder is shown in Table 13: among them, the aluminum element content is 1.36 wt.%, compared with the conventional aluminum element content of 0.05 - 0.35 wt.% in production, it is at an extremely high level; the elemental analysis shows that the carbon element content is 0.262 wt.%, compared with the conventional carbon element content of 0 - 1 wt.% in production, it is at a normal level; Table 13 Elemental analysis table of metallic chromium powder with a carbon element mass content of 0.262 wt.% in Comparative Example 1 of the present invention (4) Take 1100 g of the metallic chromium powder prepared in step (1) and mix it evenly with 763.48 g of electrolytic chromium metal flake powder (the composition is shown in Table 14, particle size -45 mesh), press it into metallic chromium ingots with a diameter of 28 - 30 mm, a total of 32 ingots are pressed, and the weight of each metallic chromium ingot is 50 - 53 g; Table 14 Elemental analysis table of electrolytic chromium metal flake powder used in Comparative Example 1 of the present invention (5) Vacuum deoxidation Take 30 chromium ingots pressed in step (4), divide them into 5 batches and put them into the furnace, carry out vacuum degassing at 1450 °C for 73 h, conduct elemental analysis on the obtained high-purity metallic chromium ingots, and the obtained analysis results are shown in Table 15. Since the aluminum element content of the metallic chromium powder obtained by smelting is at an extremely high level as shown in Table 13, using this metallic chromium powder as the raw material, after vacuum deoxidation, the elemental analysis of the obtained high-purity metallic chromium is shown in Table 15, and the aluminum element content of the high-purity metallic chromium is high, being 0.54 wt.%; since the carbon element content of the metallic chromium powder obtained by smelting is at a relatively low level as shown in Table 13, after vacuum deoxidation, the elemental analysis of the obtained high-purity metallic chromium is shown in Table 15, and the residual oxygen element content of the high-purity metallic chromium is 0.472 wt.%, which cannot meet the industrial level of high-purity metallic chromium of 500 ppm.

[0027] Table 15 Element analysis table of low-aluminum and low-oxygen high-purity metallic chromium in Comparative Example 1 of the present invention A small amount of calcined coke was added. The raw material metallic chromium obtained by this method (as shown in Table 13) had a high aluminum element content and could not achieve the purpose of reducing the aluminum element content in high-purity metallic chromium (as shown in Table 15); the content of the effective component carbon chromium compound in the raw material metallic chromium (as shown in Table 13) was almost 0, resulting in the ineffective progress of the degassing reaction, and the carbon and oxygen element contents in high-purity metallic chromium (as shown in Table 15) remained high.

[0028] Comparative Example 2 (heat 730 kcal / kg, aluminum distribution coefficient 80%) (1) Mixing 7 kg of chromium oxide was mixed with 2.2 kg of aluminum particles, 0.43 kg of sodium chlorate and 0.19 kg of calcined coke and mixed evenly to obtain a mixed raw material; (2) Smelting The mixed raw material was put into the smelting furnace, and magnesium chips were covered on the surface of the mixed raw material in the smelting furnace and ignited to complete the smelting; (3) Finishing and pulverizing After the furnace charge in the smelting furnace was naturally cooled to room temperature, the furnace was removed. The slag on the surface of the metallic chromium was finished to obtain crude chromium, which was crushed, ground to pass through a 70-mesh sieve, and magnetically separated to remove iron; the element analysis of this metallic chromium powder is shown in Table 16: among them, the aluminum element content was 0.09 wt.%, compared with the conventional aluminum element content of 0.05 - 0.35 wt.% in production, it was at a relatively low level; the element analysis showed that the carbon element content was 3.17 wt.%, compared with the conventional carbon element content of 0 - 1 wt.% in production, it was at an extremely high level; Table 16 Element analysis table of metallic chromium powder with a carbon element mass content of 3.17 wt.% in Comparative Example 2 of the present invention Since the carbon reduction reaction rate was significantly slower than the aluminothermic reduction reaction rate, the large amount of calcined coke added led to insufficient smelting reduction reaction of the material chromium oxide, causing a large waste of raw materials such as chromium oxide, aluminum particles, and sodium chlorate.

[0029] The above are only specific embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing high-purity metallic chromium, characterized in that: The specific steps are as follows: (1) Mixing Chromium oxide, aluminum particles, calcined coke and sodium chlorate are uniformly mixed according to the mass ratios of chromium oxide, reducing agent aluminum particles and calcined coke, and heating agent sodium chlorate of 1:(0.31-0.35), 1:(0.01-0.021), and 1:(0.05-0.076) to obtain a mixed raw material; (2) Smelting The mixed raw materials are put into a smelting furnace, and the surface of the mixed raw materials in the smelting furnace is covered with magnesium chips and ignited to complete the smelting; (3) Finishing and crushing After the charge in the smelting furnace is naturally cooled to room temperature, the furnace is started, the slag on the surface of the metal chromium is refined to obtain the rough chromium, which is crushed and ground, and the iron is removed by magnetic separation to obtain the metal chromium powder with a carbon content of 1 to 3 wt.%; (4) Pressing The metal chromium powder produced in step (3) is uniformly mixed with oxygen-containing metal chromium powder, wherein the oxygen-containing metal chromium powder is metal chromium flake powder obtained by electrolysis or metal chromium powder obtained by aluminothermic method, to obtain a metal chromium mixture; and pressed into a metal chromium ingot with a diameter of 28 to 30 mm; (5) Vacuum deoxidation The metal chromium ingot is placed in a horizontal vacuum furnace, heated to 1400-1500°C for vacuum deoxidation for 72-96 hours to obtain low-aluminum, low-oxygen and high-purity metal chromium.

2. The method for preparing high-purity metallic chromium according to claim 1, characterized in that: In step (1), the reducing agent aluminum particles and calcined coke reduce 91.5 wt.% of chromium oxide in total; among which, 83-87 wt.% of chromium oxide is reduced by the aluminum particles; and the remaining 4.5-8.5 wt.% of chromium oxide is reduced by the calcined coke.

3. The method for preparing high-purity metallic chromium according to claim 1, characterized in that: The unit charge reaction heat of the mixed raw materials in the smelting furnace in step (1) is 700-730 kcal / kg, wherein the reaction heat of the calcined coke reducing chromium oxide is calculated based on the generation of carbon monoxide.

4. The method for preparing high-purity metallic chromium according to claim 1, characterized in that: The particle size of the metal chromium flake powder obtained by the electrolytic method is -45 mesh, and the particle size of the metal chromium powder obtained by the aluminothermic method is -45 mesh.

5. The method for preparing high-purity metallic chromium according to claim 1, characterized in that: The molar ratio of the O element to the C element in the metal chromium mixture is 1:

1.

6. The method for preparing high-purity metallic chromium according to claim 1, characterized in that: The oxygen content of the oxygen-containing metal chromium powder is 0.1-0.5wt.%.

7. The method for preparing high-purity metallic chromium according to claim 6, characterized in that: The oxygen content of the metal chromium flake powder obtained by the electrolysis method is 0.4-0.5wt.%, and the oxygen content of the metal chromium powder obtained by the aluminothermic method is 0.1-0.2wt.%.

8. The method for preparing high-purity metallic chromium according to claim 1, characterized in that: When the metal chromium ingots are pressed, the weight of each metal chromium ingot is 50 to 53 g.

9. The method for preparing high-purity metallic chromium according to claim 1, characterized in that: When the coarse chromium is crushed and ground, the coarse chromium is crushed and ground to pass through a 70-mesh sieve.

10. The method for preparing high-purity metallic chromium according to claim 1, characterized in that: After vacuum deoxidation in step (4), the horizontal vacuum furnace is cooled to 400-500° C., the metal chromium ingot is taken out, and naturally cooled to room temperature.

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