A method for preparing high-purity iron powder

Abstract

The present invention relates to a method for preparing high-purity iron powder, comprising the following steps: 1) adding blast furnace molten iron subjected to three-decarburization treatment to a converter, wherein the tapping temperature of the molten steel at the end of blowing is higher than 1750°C and the active oxygen content is ≥0.085%. 2) performing RH vacuum oxygen blowing decarburization treatment on the molten steel in the ladle, wherein the composition of the molten steel after treatment is [O] ≥0.010%. 3) moving the ladle to a VD, performing vacuum treatment, and allowing the molten steel to stand for ≥20 minutes. 4) forming an ingot from the molten steel using a vacuum casting method to obtain "oxygen-enriched high-purity iron" having an ingot composition of [Fe] + [O] ≥99.99%. 6) casting the "oxygen-enriched high-purity iron" ingot into "oxygen-enriched high-purity iron powder". 7) passing the "oxygen-enriched high-purity iron powder" through a hydrogen reduction furnace to remove oxygen and obtain "hydrogen-containing high-purity iron powder". 8) placing the "hydrogen-containing high-purity iron powder" in a vacuum heating furnace for vacuum heating dehydrogenation treatment, cooling the mixture after treatment, and packaging the mixture to ultimately obtain high-purity iron powder. The present invention can obtain high-purity iron powder with a purity greater than 99.99% and significantly reduce the production cost of the high-purity iron powder.

Description

Technical Field

[0001] The invention belongs to the field of production of high-purity iron powder, and in particular relates to a method for preparing high-purity iron powder. Background Art

[0002] High-purity iron refers to pure iron with an iron content of 99.99% to 99.999%, an order of magnitude higher in purity than industrial pure iron. High-purity iron powder is a key building block for the preparation of high-performance functional materials such as magnetic materials and amorphous materials. It is also an excellent electromagnetic shielding material, ensuring data security and the operation of precision equipment. It is also a key building block for the preparation of high-quality alloys, including high-end specialty steels, high-temperature alloys, corrosion-resistant alloys, aerospace alloys, nuclear industry materials, and military steels. It is widely used in energy, rail transportation, marine engineering, petrochemicals, and other fields, as well as in the manufacturing of high-end equipment such as machinery, weapons, aircraft, spacecraft, gas turbines, and semiconductor chip manufacturing equipment. However, due to technical limitations, the production of high-purity iron powder requires high-purity iron as a raw material, which is costly. Therefore, reducing the production cost of high-purity iron powder has always been a pressing challenge.

[0003] Patent document No. 202011018014.8 discloses a method for preparing ultra-high cleanliness, low oxygen, high-performance water-atomized pure iron powder, comprising the following steps: batching, EBT electric furnace smelting, tapping, LF refining furnace purification, atomization, and reduction furnace reduction. The method for preparing water-atomized pure iron powder of the present invention can effectively reduce the total oxygen content in the iron powder. The oxygen content in molten steel is 0.002%-0.003%, and the total oxygen content in the finished pure iron powder is 0.06-0.10%; the acid-insoluble matter content is 0.05-0.07%; and the compressibility is increased to 7.20-7.25g / cm 3 The power consumption per ton of steel in the production process is reduced from 680KW / t to 610KW / t, a reduction of about 10-12%. LAP100.29H water-atomized pure iron powder can be mass-produced.

[0004] The patent document with application number 202110830826.0 discloses a method for preparing activated carbon-loaded nano zero-valent pure iron powder and its application. The preparation method includes high-energy grinding of activated carbon micron powder and micro-nano iron red powder and re-mixing and grinding to obtain a precursor powder. The precursor powder is then reduced at medium temperature under a reducing atmosphere, and after the reduction is completed, activated carbon-loaded nano zero-valent pure iron powder is obtained. The prepared activated carbon-loaded nano zero-valent pure iron powder can be used to degrade heavy metals or organic pollutants in soil or water. Activated carbon and iron oxides are widely available and low in cost. The gas phase reduction method avoids the large-scale use of pure water and the pollution caused by chemical reducing agents in the production process. The process method of the present invention is more suitable for mass production. The particle size of the activated carbon-loaded nano zero-valent pure iron powder prepared by the present invention reaches the nanometer level and has good dispersibility, which improves the removal efficiency of Cr(VI) in water.

[0005] The methods mentioned in the above-mentioned public documents can all obtain pure iron powder, but the purity is lower than 99.5%, and the cost is high, which cannot solve the problem of reducing the production cost of high-purity iron powder. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for preparing high-purity iron powder, thereby obtaining high-purity iron powder with a purity greater than 99.99% and significantly reducing the production cost of the high-purity iron powder.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A method for preparing high-purity iron powder comprises the following steps:

[0009] 1) Blast furnace hot metal that has undergone pre-desiliconization, pre-dephosphorization, and pre-desulfurization (three desulfurization treatments) is fed into a converter (BOF). The converter utilizes a double-slag process, producing a low-basicity slag (basicity <1) during the secondary slag making process. This process effectively reduces the phosphorus content in the molten steel to [P] ≤ 0.0020%. The primary purpose of producing this low-basicity slag (basicity <1) during the secondary slag making process is to remove manganese, reducing [Mn] to ≤ 0.002%. The molten steel at the end of blowing is then kept at a high temperature and highly oxidizing state. (During converter tapping, the molten steel is not completely poured out, but a small portion is retained to prevent slag from flowing out.) This allows the amount of slag to approach zero. Lime powder is added to the molten steel surface in the ladle to maintain heat and absorb inclusions. The high temperature means that the steel temperature is higher than 1750°C, and the high oxidizability means that the active oxygen content in the molten steel is ≥0.085%. The end point molten steel composition range is: [C]≤0.02%, [Si]≤0.002%, [Mn]≤0.002%, [P]≤0.0020%, [S]≤0.0010%, and [O]≥0.085%.

[0010] 2) The ladle is transported to the refining station, where the molten steel undergoes RH vacuum oxygen decarburization. The composition of the molten steel after decarburization is as follows: [C] ≤ 0.0005%, [Si] ≤ 0.002%, [Mn] ≤ 0.002%, [P] ≤ 0.0020%, [S] ≤ 0.0010%, and [O] ≥ 0.0080%. The ladle is allowed to stand for ≥ 20 minutes to ensure that any inclusions in the molten steel float freely.

[0011] 3) The molten steel is formed into an ingot by a vacuum casting method, and the ingot composition is obtained as follows: [C]≤0.0005%, [Si]≤0.002%, [Mn]≤0.002%, [P]≤0.0020%, [S]≤0.0010%, [O]≥0.0080%, that is, "oxygen-enriched high-purity iron" with [Fe]+[O]≥99.99%.

[0012] 4) Cutting the "oxygen-enriched high-purity iron" ingot into small pieces as smelting raw materials for manufacturing iron powder; adopting iron powder manufacturing methods such as VIGA (gas atomization) or PREP (rotating electrode) method to make "oxygen-enriched high-purity iron" ingot into "oxygen-enriched high-purity iron powder".

[0013] 5) Passing the "oxygen-enriched high-purity iron powder" through a hydrogen reduction furnace to remove oxygen from the "oxygen-enriched high-purity iron powder" to obtain "hydrogen-containing high-purity iron powder."

[0014] 6) The "hydrogen-containing high-purity iron powder" is placed in a vacuum heating furnace for vacuum heating and dehydrogenation treatment. After treatment, the powder is cooled and packaged to obtain high-purity iron powder. The iron powder composition is: [C] ≤ 0.0005%, [Si] ≤ 0.002%, [Mn] ≤ 0.002%, [P] ≤ 0.0020%, [S] ≤ 0.0010%, [O] ≤ 0.0001%, and [H] ≤ 0.0001%. The purity of the high-purity iron powder is > 99.99%.

[0015] The key technology of the present invention is:

[0016] 1) The oxygen-rich state throughout the entire smelting and casting process oxidizes and removes most impurities in the molten steel. This also prevents the residual deoxidizing elements and deoxidation products such as Al2O3 in the molten steel caused by the deoxidation operation. This results in "oxygen-rich high-purity iron."

[0017] 2) Taking advantage of the extremely high specific surface area of ​​the powder state, H2 is used to remove oxygen from the oxygen-rich iron powder to obtain reduced high-purity iron powder.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. The present invention can significantly reduce the production cost of high-purity iron powder.

[0020] 2. The present invention does not require equipment modification, has low equipment investment, and is quickly put into production.

[0021] 3. The present invention can obtain high-purity iron powder with a purity greater than 99.99%. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the specific implementation methods of the present invention are further described below in conjunction with examples. The following examples are used to specifically illustrate the contents of the present invention. These examples are only general descriptions of the contents of the present invention and do not limit the contents of the present invention.

[0023] Example 1:

[0024] High-purity iron powder was prepared by VIGA (gas atomization).

[0025] 1. Blast furnace hot metal, pre-desiliconized, pre-dephosphorized, and pre-desulfurized (three desulfurization treatments), is fed into the converter. The converter utilizes a double-slag process, with a low-basicity slag (<1) produced during the secondary slag formation process. This maintains the molten steel at a high temperature and high oxidation state at the end of the blowing process. The steel is then tapped, reducing the amount of slag to near zero. Lime powder is added to the molten steel surface in the ladle to maintain heat and absorb inclusions.

[0026] The steel temperature is 1755°C, the active oxygen content in the molten steel is 0.087%, and the final molten steel composition is: [C] 0.018%, [Si] 0.0016%, [Mn] 0.0015%, [P] 0.0015%, [S] 0.0008%, and [O] 0.087%.

[0027] 2. The ladle is transported to the refining station, where the molten steel undergoes RH vacuum oxygen decarburization. The composition of the molten steel after treatment is: [C] 0.0003%, [Si] 0.0014%, [Mn] 0.0015%, [P] 0.0014%, [S] 0.0008%, and [O] 0.0087%. The ladle is allowed to stand for 20 minutes.

[0028] 3. The molten steel is made into an ingot by vacuum casting. The composition of the ingot is: [C] 0.0003%, [Si] 0.0014%, [Mn] 0.0015%, [P] 0.0014%, [S] 0.0008%, [O] 0.0081%, that is, "oxygen-rich pure iron" with [Fe] + [O] = 99.9946%.

[0029] 4. Cut the "oxygen-enriched pure iron" ingot into small pieces as smelting raw materials for the VIGA (gas atomization) method.

[0030] 5. Use VIGA (gas atomization) method to convert "oxygen-enriched pure iron" ingot into "oxygen-enriched iron powder".

[0031] 6. Pass the "oxygen-rich iron powder" through a hydrogen reduction furnace to remove oxygen from the "oxygen-rich iron powder" and obtain "hydrogen-containing high-purity iron powder".

[0032] 7. The "hydrogen-containing high-purity iron powder" is placed in a vacuum heating furnace for vacuum heating and dehydrogenation treatment. After treatment, the powder is cooled and packaged to obtain high-purity iron powder. The iron powder composition is: [C] 0.0003%, [Si] 0.0014%, [Mn] 0.0015%, [P] 0.0014%, [S] 0.0008%, [O] ≤ 0.0001%, [H] ≤ 0.0001%. This is high-purity iron powder with [Fe] > 99.99%.

[0033] Example 2:

[0034] High-purity iron powder was prepared by PREP (rotating electrode) method.

[0035] 1. Blast furnace hot metal, pre-desiliconized, pre-dephosphorized, and pre-desulfurized (three desulfurization treatments), is fed into the converter. The converter utilizes a double-slag process, with a low-basicity slag (<1) produced during the secondary slag formation process. This maintains the molten steel at a high temperature and high oxidation state at the end of the blowing process. The steel is then tapped, reducing the amount of slag to near zero. Lime powder is added to the molten steel surface in the ladle to maintain heat and absorb inclusions.

[0036] The steel temperature is 1758°C, the active oxygen content in the molten steel is 0.089%, and the final molten steel composition is: [C] 0.019%, [Si] 0.0017%, [Mn] 0.0015%, [P] 0.0013%, [S] 0.0008%, and [O] 0.089%.

[0037] 2. The ladle is transported to the refining station, where the molten steel undergoes RH vacuum oxygen decarburization. The composition of the molten steel after treatment is: [C] 0.0003%, [Si] 0.0015%, [Mn] 0.0014%, [P] 0.0013%, [S] 0.0008%, and [O] 0.0087%. The ladle is then allowed to stand for 20 minutes.

[0038] 3. The molten steel is made into an ingot by vacuum casting. The composition of the ingot is: [C] 0.0003%, [Si] 0.0015%, [Mn] 0.0014%, [P] 0.0013%, [S] 0.0008%, [O] 0.0083%, that is, "oxygen-rich pure iron" with [Fe] + [O] > 99.99%.

[0039] 4. Cutting "oxygen-enriched pure iron" ingots as smelting raw materials for the PREP (rotating electrode) method.

[0040] 5. Use PREP (rotating electrode) to convert "oxygen-enriched pure iron" ingot into "oxygen-enriched iron powder".

[0041] 6. Pass the "oxygen-rich iron powder" through a hydrogen reduction furnace to remove oxygen from the "oxygen-rich iron powder" and obtain "hydrogen-containing high-purity iron powder".

[0042] 7. The "hydrogen-containing high-purity iron powder" is placed in a vacuum heating furnace for vacuum heating and dehydrogenation treatment. After treatment, the powder is cooled and packaged to obtain high-purity iron powder. The iron powder composition is: [C] 0.0003%, [Si] 0.0015%, [Mn] 0.0014%, [P] 0.0013%, [S] 0.0008%, [O] ≤ 0.0001%, [H] ≤ 0.0001%. This is high-purity iron powder with [Fe] > 99.99%.

Claims

1. A method for preparing high-purity iron powder, characterized in that: The steps include: 1) blast furnace molten iron that has undergone pre-desiliconization, pre-dephosphorization, and pre-desulfurization treatments is added to a converter, which is smelted using a double slag process, with low-basicity slag (basicity < 1) being produced during secondary slagging, and the molten steel at the end of blowing being in a high-temperature and highly oxidizing state, wherein the high temperature refers to a steelmaking temperature exceeding 1750° C., and the high oxidizing state refers to an active oxygen content in the molten steel of ≥0.085%; 2) The ladle is transported to the refining station, and the molten steel in the ladle is subjected to RH vacuum oxygen blowing decarburization treatment. The composition of the molten steel after treatment is: [C] ≤ 0.0005%, [Si] ≤ 0.002%, [Mn] ≤ 0.002%, [P] ≤ 0.0020%, [S] ≤ 0.0010%, [O] ≥ 0.0080%; after treatment, the molten steel is allowed to stand for ≥ 20 minutes; 3) Using vacuum casting to form ingots from the molten steel, "oxygen-enriched high-purity iron" is obtained with an ingot composition of [Fe] + [O] ≥ 99.99%; 4) Using an atomized iron powder manufacturing method, the "oxygen-enriched high-purity iron" ingot is made into "oxygen-enriched high-purity iron powder"; 5) Passing the "oxygen-enriched high-purity iron powder" through a hydrogen reduction furnace to remove oxygen from the "oxygen-enriched high-purity iron powder" to obtain "hydrogen-containing high-purity iron powder"; 6) The "hydrogen-containing high-purity iron powder" is placed in a vacuum heating furnace for vacuum heating and dehydrogenation treatment. After treatment, the temperature is lowered and the powder is packaged to obtain high-purity iron powder with a purity of >99.99%.

2. The method for preparing high-purity iron powder according to claim 1, wherein: In the step 1), steel is retained and tapped to avoid slag.

3. The method for preparing high-purity iron powder according to claim 1, wherein: In the step 1), the endpoint molten steel composition range is: [C]≤0.02%, [Si]≤0.002%, [Mn]≤0.002%, [P]≤0.0020%, [S]≤0.0010%, and [O]≥0.085%.

4. The method for preparing high-purity iron powder according to claim 1, wherein: In the step 4), the ingot composition is: [C]≤0.0005%, [Si]≤0.002%, [Mn]≤0.002%, [P]≤0.0020%, [S]≤0.0010%, and [O]≥0.0080%.

5. The method for preparing high-purity iron powder according to claim 1, wherein: In step 7), the composition of the high-purity iron powder is: [C]≤0.0005%, [Si]≤0.002%, [Mn]≤0.002%, [P]≤0.0020%, [S]≤0.0010%, [O]≤0.0001%, [H]≤0.0001%, and the rest is iron.

6. The method for preparing high-purity iron powder according to claim 1, wherein: The atomized iron powder manufacturing method includes VIGA or PREP method.