A method for preparing high-purity iron carbide micropowder with controllable particle size

Abstract

The invention relates to a method for preparing high-purity iron carbide micropowder with controllable particle size. The method comprises the following steps: using a billet of eutectoid steel as a raw material, obtaining iron carbide of a desired size and shape inside the steel through a heat treatment process, processing the heat-treated billet into iron chips, dissolving the iron matrix with dilute hydrochloric acid, and separating, rinsing, and drying the undissolved matter to obtain high-purity iron carbide micropowder with a particle size of 20 nm to 3 μm. The particle size of the high-purity iron carbide micropowder is uniform and controllable, the preparation process is simple and easy to operate, and the preparation cost is low. The hydrogen and ferrous chloride products generated by the reaction can be recycled and reused, and will not cause pollution to the environment.

Description

Technical Field

[0001] The invention relates to the technical field of iron carbide micropowder preparation, and in particular to a method for preparing high-purity iron carbide micropowder with controllable particle size. Background Art

[0002] As energy conservation and emission reduction efforts deepen, the automotive industry is further developing towards lightweight, low-pollution, and renewable energy. Consequently, automotive exhaust treatment, energy synthesis, and utilization are gaining increasing attention. Nano-iron carbide, as a catalyst for exhaust treatment and energy production, is widely used in automotive manufacturing and renewable energy synthesis. Furthermore, iron carbide has enormous potential for application in chemical energy conversion and storage, as well as high-density magnetic recording.

[0003] Ordinary iron carbide has the characteristics of high magnetic saturation strength and high stability, and has been used in production and life. Nano-scale iron carbide also has the characteristics of superparamagnetism and ultra-high catalytic activity, but the manufacturing process of existing nano-iron carbide is complicated, the particle size control is difficult, and the price is high. At present, the production of high-purity iron carbide powder is mainly through making a precursor, and then the precursor is subjected to hydrogen-carbon monoxide treatment at a certain temperature to obtain. It adopts flammable and toxic gas to process, and the process is complicated. In addition, the particle size and uniformity of nano-iron carbide are difficult to control, so the manufacturing cost is high. In addition, the non-iron carbide type iron impurities are difficult to eliminate in the manufacturing process, which is also a problem that needs to be solved.

[0004] Chinese patent application number CN202011064076.2 discloses a "composition containing precipitated ε iron carbide and θ iron carbide and preparation method." The iron carbide preparation process is as follows: an aqueous solution of an iron salt is mixed with an alkaline precipitant for co-precipitation, the precipitate is separated, washed, and calcined to obtain a precursor, the precursor is reduced with hydrogen at 470-620°C, treated with hydrogen and carbon monoxide in a molar ratio of 2:1 at 90-185°C, and finally treated with hydrogen and carbon monoxide in a molar ratio of 100:1 at 280-420°C for 20-120 hours. The entire production process requires the use of combustible gas at high temperatures, making it difficult to produce, complex, and costly.

[0005] Chinese invention patent application number CN201210580895.1 discloses a "method for preparing iron carbide." The process includes the following steps: mixing a carbonization inducer and a solvent at a molar ratio of 1:100-600 to obtain a mixed solution, wherein the carbonization inducer is a halide ammonium salt and the solvent is a long-chain amine solvent with a boiling point greater than 250°C; adding an organic compound containing zero-valent iron to the mixed solution heated to 180-200°C in a protective atmosphere; controlling the reaction system temperature to 250-380°C for 10-120 minutes; and, after cooling the reaction system, performing solid-liquid separation to collect the iron carbide particles. The preparation process is complex, and the product particle size is uncontrollable.

[0006] Chinese patent application number CN201810283708.0 discloses a "pure phase ε / ε' iron carbide catalyst for Fischer-Tropsch synthesis reaction and its preparation method", the preparation method of which includes the following steps: (1) surface purification treatment of nano iron powder or nano powder iron compound that can be obtained by in situ reduction with H2 at a temperature of 250-510 ° C; (2) pre-treatment of the material obtained in step (1) with H2 and CO at a temperature of 80-180 ° C, with a molar ratio of H2 to CO of 1.2-2.8:1; (3) preparation of carbide by the material obtained in step (2) with H2 and CO at a temperature of 180-280 ° C, with a molar ratio of H2 to CO of 1.0-3.0:1. The preparation process is complex, uses flammable and toxic gases, the product particle size is difficult to control, and the cost is high. Summary of the Invention

[0007] The present invention provides a method for preparing high-purity iron carbide micropowder with controllable particle size. Based on the heat treatment of high-carbon steel, iron carbide (Fe3C) particles with controllable size and shape are generated in the steel. After the iron matrix is ​​dissolved by dilute hydrochloric acid, the remaining solids are rinsed, separated and dried to obtain high-purity iron carbide micropowder with uniform and controllable particle size.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] A method for preparing high-purity iron carbide micropowder with controllable particle size uses a hypereutectoid steel billet as raw material, obtains iron carbide of a desired size and shape inside the steel through a heat treatment process, processes the heat-treated billet into iron chips, and then dissolves the iron matrix with dilute hydrochloric acid. After the undissolved matter is separated, rinsed, and dried, high-purity iron carbide micropowder with a particle size of 20 nm to 3 μm is obtained; the particle size standard deviation is less than 10%.

[0010] Furthermore, the chemical composition of the hypereutectoid steel is C: 1.0% to 2.0%, Si+Mn+P+S<0.1%, and the balance is Fe in percentage by weight.

[0011] Furthermore, a method for preparing high-purity iron carbide micropowder with controllable particle size is provided, wherein the specific process is as follows:

[0012] (1) Cut the steel ingot into steel plates with a thickness of ≤25 mm, heat to Acm+20℃ to achieve austenitization, and keep warm for 90-150 minutes;

[0013] (2) quenching the steel plate obtained in step (1) to room temperature;

[0014] (3) tempering the steel plate obtained in step (2) at a temperature of 300 to 650° C. for 3 to 30 minutes;

[0015] (4) crushing the steel plate obtained in step (3) and dissolving it in a 2-5 mol / L aqueous hydrochloric acid solution;

[0016] (5) After the dissolution process in step (4) is completed, the undissolved matter is washed with water, calcined at 200-300°C, and dried to obtain high-purity iron carbide powder.

[0017] Furthermore, the Fe3C content in the high-purity iron carbide powder is ≥99.9%.

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

[0019] 1) Based on the heat treatment of high carbon steel, iron carbide (Fe3C) particles with controllable size and shape are generated in the steel. After the iron matrix is ​​dissolved with dilute hydrochloric acid, the remaining solids are rinsed, separated and dried to obtain high-purity iron carbide powder with uniform and controllable particle size;

[0020] 2) The particle size of the prepared iron carbide powder can be controlled in the range of 20nm to 3μm;

[0021] 3) The preparation process is simple and easy to operate, and the preparation cost is low;

[0022] 4) The products of the reaction, hydrogen and ferrous chloride, can be recycled and will not cause pollution to the environment. DETAILED DESCRIPTION

[0023] The present invention discloses a method for preparing high-purity iron carbide micropowder with controllable particle size. The method uses a hypereutectoid steel billet as raw material, obtains iron carbide of a desired size and shape inside the steel through a heat treatment process, processes the heat-treated billet into iron chips, and then dissolves the iron matrix with dilute hydrochloric acid. After the undissolved matter is separated, rinsed, and dried, high-purity iron carbide micropowder with a particle size of 20 nm to 3 μm is obtained; the particle size standard deviation is less than 10%.

[0024] Furthermore, the chemical composition of the hypereutectoid steel is C: 1.0% to 2.0%, Si+Mn+P+S<0.1%, and the balance is Fe in percentage by weight.

[0025] Furthermore, the present invention provides a method for preparing high-purity iron carbide micropowder with controllable particle size, and the specific process is as follows:

[0026] (1) Cut the steel ingot into steel plates with a thickness of ≤25 mm, heat to Acm+20℃ to achieve austenitization, and keep warm for 90-150 minutes;

[0027] (2) quenching the steel plate obtained in step (1) to room temperature;

[0028] (3) tempering the steel plate obtained in step (2) at a temperature of 300 to 650° C. for 3 to 30 minutes;

[0029] (4) crushing the steel plate obtained in step (3) and dissolving it in a 2-5 mol / L aqueous hydrochloric acid solution;

[0030] (5) After the dissolution process in step (4) is completed, the undissolved matter is washed with water, calcined at 200-300°C, and dried to obtain high-purity iron carbide powder.

[0031] Furthermore, the Fe3C content in the high-purity iron carbide powder is ≥99.9%.

[0032] The method for preparing high-purity iron carbide fine powder with controllable particle size described in the present invention uses a hypereutectoid steel billet as raw material. The chemical composition range of the hypereutectoid steel is determined for the following reasons:

[0033] C: The carbon content determines the final iron carbide yield of the preparation method described herein, so a high carbon content should be selected as much as possible. However, if the carbon content exceeds 2.11%, coarse primary cementite will form, making it difficult to obtain fine iron carbide powder. Therefore, the carbon content in the hypereutectoid steel is controlled to 1.0% to 2.0%.

[0034] Si, Mn, P, S: All of them are impurity elements that will reduce the concentration of iron carbide powder, so the lower the content, the better. However, considering that controlling the content too low will greatly increase the smelting cost of steel, the present invention controls the total amount of these impurities to be less than 0.1%.

[0035] During the preparation of high-purity iron carbide powder, the steel plate is heated to 20°C above Acm in order to evenly distribute the carbon in the austenite. If the heating temperature is too high, a liquid phase will appear and the heat treatment cannot be completed.

[0036] The steel plate tempering temperature is controlled between 300 and 650°C. This is because iron carbide increases in size when tempering temperatures exceed 650°C, while iron carbide formation becomes difficult at temperatures below 300°C. Within this range, lower temperatures produce finer iron carbide particles, while higher temperatures result in coarser iron carbide particles. The shape and size of the iron carbide can be controlled by the tempering time. Longer tempering times lead to spheroidization and larger iron carbide particles. However, once equilibrium is reached, further tempering times have no effect on the shape and size of the iron carbide. Therefore, the present invention sets the tempering time to 3 to 30 minutes, based on the particle size of the prepared high-purity iron carbide powder and considering production costs.

[0037] The following examples are implemented on the premise of the technical solution of the present invention, and provide detailed implementation methods and specific operating processes, but the protection scope of the present invention is not limited to the following examples.

[0038] [Example]

[0039] In this embodiment, the preparation process of high-purity iron carbide powder is as follows:

[0040] 80 kg of hypereutectoid steel ingots with qualified composition were cut into 20 mm thick plates, heated to Acm + 20°C, held for 120 ± 30 minutes, and then water-quenched to room temperature. The plates were then tempered at 300-650°C for 3-30 minutes. The steel plates were then cut into chips and dissolved in a 2-5 mol / L aqueous hydrochloric acid solution. After dissolution, the undissolved material was collected, washed with water, calcined at 200-300°C, and dried to obtain high-purity iron carbide fine powder.

[0041] The chemical composition of the ingots in each embodiment is shown in Table 1, the preparation process parameters are shown in Table 2, and the size and purity of the high-purity iron carbide powder are shown in Table 2.

[0042] Table 1 Chemical composition of the ingots in each example (wt, %)

[0043]

[0044] Table 2 Process parameters and iron carbide size and purity

[0045]

[0046] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A method for preparing high-purity iron carbide micropowder with controllable particle size, characterized in that: Hypereutectoid steel billets are used as raw materials. Iron carbide of the required size and shape is obtained inside the steel through a heat treatment process. The heat-treated billets are processed into iron chips, and then the iron matrix is ​​dissolved by dilute hydrochloric acid. The undissolved matter is separated, rinsed, and dried to obtain high-purity iron carbide powder with a particle size of 20nm to 3μm; the particle size standard deviation is less than 10%.

2. The method for preparing high-purity iron carbide micropowder with controllable particle size according to claim 1, characterized in that: The chemical composition of the hypereutectoid steel is C: 1.0% to 2.0%, Si+Mn+P+S<0.1%, and the balance is Fe.

3. The method for preparing high-purity iron carbide micropowder with controllable particle size according to claim 1, characterized in that: The specific process is as follows: (1) Cut the steel ingot into steel plates with a thickness of ≤25 mm, heat to Acm+20°C to achieve austenitization, and keep warm for 90 to 150 minutes; (2) quenching the steel plate obtained in step (1) to room temperature; (3) tempering the steel plate obtained in step (2) at a temperature of 300 to 650° C. for 3 to 30 minutes; (4) crushing the steel plate obtained in step (3) and dissolving it in a 2-5 mol / L aqueous hydrochloric acid solution; (5) After the dissolution process in step (4) is completed, the undissolved matter is washed with water, calcined at a temperature of 200-300° C., and dried to obtain high-purity iron carbide powder.

4. The method for preparing high-purity iron carbide micropowder with controllable particle size according to claim 1, characterized in that: The Fe3C content in the high-purity iron carbide fine powder is ≥99.9%.

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