Preparation method of foamed steel powder, foamed steel and preparation method of foamed steel

Abstract

The invention relates to the technical field of foamed steel production, in particular to a preparation method of foamed steel powder, foamed steel and a preparation method of the foamed steel, the foamed steel adopts the foamed steel powder as a raw material, and the foamed steel comprises the following chemical components in percentage by weight: 0.006%-0.010% of C, 0.01%-0.02% of Si, 0.02%-0.04% of Mn, less than or equal to 0.008% of P, less than or equal to 0.005% of S and the balance of Fe and impurities; the density of the foam steel is 2.1-2.4 g / cm < 3 >, the compressive yield strength is greater than or equal to 110 MPa, and the energy absorption value under 50% strain is 65-85 MJ / m < 3 >. Firstly, hollow metal iron powder, namely foam steel powder, is prepared, then the foam steel is prepared through briquetting and sintering, the sintered foam steel is made of a single material and has no residues, the powder granularity and internal pore distribution are uniform, and therefore the uniformity of the performance of the foam steel is guaranteed.

Description

Technical Field

[0001] This invention relates to the field of foamed steel production technology, and in particular to a method for preparing foamed steel powder, foamed steel, and a method for preparing foamed steel. Background Technology

[0002] Foamed steel is a structural-functional integrated material with a steel matrix containing a large number of interconnected or disconnected pores. As a functional material, it possesses various properties such as sound absorption, heat insulation, flame retardancy, and electromagnetic shielding. As a structural material, by altering the porosity and pore structure, the density, elastic modulus, and yield strength of the steel can be changed. With the same amount of steel used, reasonable design can effectively improve the overall and local stability of structural components, thereby increasing load-bearing capacity and achieving steel conservation. Under strong earthquakes or impact loads, the plastic compression of the pores can absorb a large amount of energy, preventing brittle failure of the structure. Therefore, foamed steel has broad application prospects in lightweight steel structures, energy dissipation and vibration reduction structures, earthquake-resistant structures, and impact-resistant and blast-proof structures.

[0003] Currently, the main methods for preparing foamed steel include melt metal foaming, metal deposition, hollow sphere sintering, infiltration, and powder sintering. Among these, melt metal foaming struggles to uniformly disperse the foaming agent in the melt, making it difficult to control the size and uniformity of bubble distribution, resulting in poor mechanical properties of the obtained material. Hollow sphere sintering suffers from drawbacks such as difficulty in hollow sphere preparation and high requirements for process equipment. Infiltration methods have issues such as long process flows and difficulty in completely removing precursors. In contrast, powder sintering is a simple and low-cost preparation method, and its porosity, pore size, and pore size distribution can be effectively controlled.

[0004] Chinese patent application No. 201610257103.5 discloses "A method for preparing foamed steel using a pore-forming agent." The method uses pure iron powder and a pore-forming agent as raw materials, mixes them, presses them, and sintersulates them under a hydrogen protective atmosphere to obtain open-cell foamed steel. Based on the powder sintering method, it uses dextrin powder of different particle sizes and shapes, as well as various starch powders, as pore-forming agents. These agents are readily available and inexpensive, and leave no residue after thermal decomposition. The final product is blocky foamed steel with different pore structures and porosities, controllable pore parameters, and stable mechanical properties, enabling industrial production. However, because the pore-forming agents used are dextrin powder and various starch powders, whose main component is carbon, carbon can permeate into the iron during the sintering process, causing uneven carbon content distribution in the foamed steel and thus affecting its performance.

[0005] Chinese patent application No. 201110382548.3 discloses "a method for preparing open-cell foamed steel". The method uses sodium aluminate particles of different diameters with melting points higher than steel as a precursor. Steel is used as the percolating fluid, and the steel is percolated into the precursor via pressure percolation. After cooling, a composite is obtained. The sodium aluminate precursor is dissolved in water from the composite to obtain open-cell foamed steel. The diameter of the sodium aluminate precursor particles is 0.1–10 mm. The sodium aluminate particles are dried at 1000–1100℃ for 5–6 hours. The sodium aluminate is preheated at 400–600℃ for 2–30 minutes before percolation. The melting temperature of the steel matrix is ​​50–100℃ higher than the melting point of the steel matrix. During pressure percolation, the percolation pressure is controlled at 10–100 MPa, the percolation temperature is 10–50℃ lower than the melting temperature of the sodium aluminate particles, and the percolation velocity is 1–20 mm / s. The composite obtained after percolation is washed with water. This method uses sodium aluminate particles as a precursor for percolation and washes the composite after percolation with water to remove sodium aluminate. However, in actual production, sodium aluminate cannot be completely removed, and the sodium aluminate remaining in the metal will have an adverse effect on its performance, seriously affecting the use effect of foam metal.

[0006] In summary, existing pore-forming agents and other precursors cannot be completely removed during the preparation of foamed steel, thus adversely affecting its performance, resulting in uneven properties and preventing it from realizing its advantages. Therefore, there is an urgent need to develop a method for preparing foamed steel that leaves no residue during sintering, fully guarantees the performance of the foamed steel, and is simple, safe, reliable, and even improves product quality. Summary of the Invention

[0007] This invention provides a method for preparing foamed steel powder, foamed steel, and a method for preparing foamed steel. First, hollow metal iron powder, i.e., foamed steel powder, is prepared. Then, foamed steel is prepared by pressing and sintering. The sintered foamed steel is a single material without any residue. The powder particle size and internal pore distribution are uniform, thereby ensuring the uniformity of the foamed steel's performance.

[0008] To achieve the above objectives, the present invention employs the following technical solution: A method for preparing foamed steel powder includes the following steps: 1) Pressure Melting: Industrial pure iron is used as raw material, and the raw material is melted in a pressure melting furnace using induction heating. Specifically: after the raw material is added to the pressure melting furnace, a vacuum is drawn, and after the vacuum degree reaches below 10 Pa, electric melting is performed, with the melting power controlled at 130-170 kW; nitrogen is introduced into the pressure melting furnace for pressurization, and the pressure inside the pressure melting furnace is controlled at 4-5 MPa, with a holding time of 25-35 min, and the nitrogen mass content in the molten steel is 0.060%-0.070%. 2) Gas atomization powder making: After the industrial pure iron raw material is melted, a carburizing agent, ferrosilicon and metallic manganese are added for alloying. The superheat of the molten steel is controlled at 150-200℃. After smelting, hollow metallic iron powder is prepared by gas atomization. The gas pressure of the gas atomization nozzle is 3.0-3.3MPa. The molten steel in the pressurized smelting furnace flows out through the guide pipe and enters the atomization chamber. Under the impact of the airflow formed by the gas sprayed from the gas atomization nozzle, the molten steel is broken into small particles. Due to the pressure drop in the atomization chamber, the nitrogen originally dissolved in the molten steel precipitates and forms fine nitrogen bubbles. The molten steel flowing out changes from liquid to solid instantly under the rapid cooling effect of the sprayed gas, thus obtaining hollow metallic iron powder. 3) Powder Collection: The iron powder in the atomized powder collector is collected, sieved, and then obtained as hollow metallic iron powder (i.e., foamed steel powder) with a particle size of 50–300 μm. The loose packing density of the foamed steel powder is 1.8–2.0 g / cm³. 3 .

[0009] In step 1), the chemical composition of industrial pure iron by weight percentage is: C≤0.003%, Si≤0.010%, Mn≤0.02%, P≤0.006%, S≤0.003%, with the balance being iron and unavoidable impurities.

[0010] In step 1), the purity of nitrogen is ≥99.9%.

[0011] In step 2), the diameter of the guide tube is ø4~ø8mm; the atomization chamber is equipped with a pressure reducing valve, and the setting value of the pressure reducing valve is 1~1.1atm.

[0012] A type of foamed steel, using foamed steel powder as raw material; the chemical composition of the foamed steel, by weight percentage, is: C: 0.006%–0.010%, Si: 0.01%–0.02%, Mn: 0.02%–0.04%, P≤0.008%, S≤0.005%, with the balance being Fe and unavoidable impurities; the density of the foamed steel is 2.1–2.4 g / cm³. 3 Compressive yield strength ≥110MPa, energy absorption value at 50% strain 65~85MJ / m 3 .

[0013] A method for preparing foamed steel specifically includes the following steps: 1) Compression molding: The foamed steel powder is placed in a compression mold and vibrated to compact it, resulting in foamed steel powder blocks; the pressure during compression is 30-45 MPa, and the compression time is 9-15 min; 2) Vacuum sintering: The pressed foam steel powder briquettes, together with the pressing mold, are placed in a vacuum sintering furnace for pre-firing. During pre-firing, the temperature is increased at a rate of 60-90℃ / min, and after heating to 610-635℃, it is held for 1.2-1.8h. Then, the temperature is increased to 1060-1140℃ and held for 2.1-2.4h. The vacuum degree during sintering is ≤2Pa. After sintering, the foam steel is cooled to room temperature with the vacuum sintering furnace and demolded to obtain foam steel of a single material.

[0014] The pressing mold is an alloy steel mold, and the inner surface of the pressing mold is coated with a release agent.

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1) First, hollow metal iron powder, i.e. foamed steel powder, is prepared. Then, the foamed steel powder is bonded and molded by sintering to prepare foamed steel. The special preparation process can fully guarantee the performance of foamed steel. 2) The present invention prepares foam steel of a single material. Since no pore-forming agent or other precursors are used, there are no residues after sintering, which ensures that the particle size and internal pore distribution of the powder are uniform. After sintering, the foam steel can still maintain good performance with uniformity in all parts. 3) Foamed steel powder and the preparation process of foamed steel are simple, safe and reliable. Detailed Implementation

[0016] The method for preparing foamed steel powder according to the present invention includes the following steps: 1) Pressure Melting: Industrial pure iron is used as raw material. The chemical composition of industrial pure iron by weight percentage is: C≤0.003%, Si≤0.010%, Mn≤0.02%, P≤0.006%, S≤0.003%, with the balance being iron and unavoidable impurities. The raw material is melted in a pressure melting furnace using induction heating. Specifically: after adding the raw material to the pressure melting furnace, a vacuum is drawn. Once the vacuum level reaches below 10 Pa, electric melting is initiated, with the melting power controlled at 130–170 kW. Nitrogen gas (purity ≥99.9%) is introduced into the pressure melting furnace for pressurization. The pressure inside the furnace is controlled at 4–5 MPa, and the holding time is 25–35 min. The nitrogen content in the molten steel is 0.060%–0.070% by mass. 2) Gas atomization powder production: After the industrial pure iron raw material is melted, a carburizing agent, ferrosilicon, and metallic manganese are added for alloying. The superheat of the molten steel is controlled at 150-200℃. After smelting, hollow metallic iron powder is prepared by gas atomization. The gas pressure of the gas atomization nozzle is 3.0-3.3MPa. The molten steel in the pressurized smelting furnace flows out through the guide pipe (the diameter of the guide pipe is ø4-ø8mm) and enters the atomization chamber. Under the impact of the airflow formed by the gas sprayed from the gas atomization nozzle, the molten steel is broken into small particles. The atomization chamber is equipped with a pressure reducing valve with a set value of 1-1.1atm. Due to the pressure drop in the atomization chamber, the nitrogen originally dissolved in the molten steel precipitates and forms fine nitrogen bubbles. The molten steel flowing out instantly changes from liquid to solid under the action of the sprayed gas, thus obtaining hollow metallic iron powder. 3) Powder Collection: The iron powder in the atomized powder collector is collected, sieved, and then obtained as hollow metallic iron powder (i.e., foamed steel powder) with a particle size of 50–300 μm. The loose packing density of the foamed steel powder is 1.8–2.0 g / cm³. 3 .

[0017] The present invention discloses a foamed steel, which uses foamed steel powder as raw material; the chemical composition of the foamed steel, by weight percentage, is C: 0.006%–0.010%, Si: 0.01%–0.02%, Mn: 0.02%–0.04%, P≤0.008%, S≤0.005%, with the balance being Fe and unavoidable impurities; the density of the foamed steel is 2.1–2.4 g / cm³. 3 Compressive yield strength ≥110MPa, energy absorption value at 50% strain 65~85MJ / m 3 .

[0018] The reasons for selecting the chemical composition and setting the content range of the foamed steel are as follows: Carbon: Carbon is dissolved in the matrix and is a reinforcing element in steel. The higher its content, the higher the strength of the foamed steel. However, excessive carbon content will affect the plasticity of the foamed steel. Therefore, this invention controls the carbon content to 0.006% to 0.010%.

[0019] Silicon: Silicon usually exists in steel in the form of a solid solution. If its content is too high, it will reduce the toughness and ductility of the steel and affect the performance of foamed steel. If its content is too low, it will be difficult to control the oxygen content in the steel. Therefore, the present invention controls the silicon content at 0.01% to 0.02%.

[0020] Manganese: Manganese exists in steel in the form of solid solution. If its content is too high, it will reduce the plasticity of steel. Manganese can combine with sulfur to form stable manganese sulfide, thereby eliminating the brittleness caused by sulfur. At the same time, manganese can work with silicon in steel to play a deoxidizing role. Therefore, the manganese content is controlled at 0.02% to 0.04% in this invention.

[0021] Phosphorus: Phosphorus tends to segregate at grain boundaries, increasing the brittleness of steel. In addition, phosphorus can improve the strength of steel plates through solid solution strengthening, but it will affect the plasticity of the steel plates. Therefore, the phosphorus content is controlled below 0.008% in this invention.

[0022] Sulfur: Sulfur increases the hot brittleness of steel. Considering production cost factors, the sulfur content in this invention is controlled below 0.005%.

[0023] The method for preparing foamed steel according to the present invention specifically includes the following steps: 1) Compression molding: The foamed steel powder is placed in a compression mold and vibrated to compact it, resulting in a foamed steel powder block; the compression mold is an alloy steel mold, and the inner surface of the compression mold is coated with a release agent to facilitate demolding of the compressed and sintered foamed steel. The pressure during compression is 30-45 MPa, and the compression time is 9-15 min; 2) Vacuum sintering: The pressed foam steel powder briquettes, together with the pressing mold, are placed in a vacuum sintering furnace for pre-firing. During pre-firing, the temperature is increased at a rate of 60-90℃ / min, and after heating to 610-635℃, it is held for 1.2-1.8h. Then, the temperature is increased to 1060-1140℃ and held for 2.1-2.4h. The vacuum degree during sintering is ≤2Pa. After sintering, the foam steel is cooled to room temperature with the vacuum sintering furnace and demolded to obtain foam steel of a single material.

[0024] To more intuitively illustrate the present invention, the embodiments of the present invention will be further described in conjunction with the examples. The following examples are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any technical solutions that can be obviously obtained by those skilled in the art within the scope of the technology disclosed in the present invention, including simple variations or equivalent substitutions, are all within the scope of protection of the present invention.

[0025]

Example 1

[0026] The preparation process of foamed steel includes pressure melting, gas atomization powdering, powder collection, pressing and molding, and vacuum sintering, specifically including the following steps: 1) Pressure Melting: Industrial pure iron is used as the smelting raw material. The chemical composition of industrial pure iron, by weight percentage, is: C: 0.002%, Si: 0.008%, Mn: 0.02%, P: 0.006%, S: 0.003%, with the balance being iron and unavoidable impurities. The smelting raw material is placed in a pressure melting furnace and smelted using induction heating. After adding the smelting raw material, a vacuum is drawn into the furnace. When the vacuum reaches 10 Pa, electric melting is initiated, with an electric power of 130 kW. Nitrogen gas is introduced into the pressure melting furnace from nitrogen cylinders to pressurize it. The pressure inside the pressure melting furnace is controlled at 4 MPa, and the holding time is 35 min. The nitrogen content in the molten steel is 0.065% by mass; the nitrogen purity is 99.92%.

[0027] 2) Gas Atomization Powder Production: After industrial pure iron is melted, a carburizing agent, ferrosilicon, and metallic manganese are added for alloying. The superheat of the molten steel is controlled at 150°C. After smelting, the guide pipe is opened, and hollow metallic iron powder is prepared by gas atomization. The gas pressure ejected from the gas atomizing nozzle is 3.0 MPa. The molten steel in the pressurized smelting furnace flows out through a guide pipe with a diameter of ø8 mm and enters the atomization chamber. Under the impact of the airflow formed by the gas ejected from the gas atomizing nozzle, the molten steel is broken into small particles. At the same time, as the molten steel in the pressurized smelting furnace flows out of the guide pipe into the atomization chamber, due to the pressure drop in the atomization chamber, the nitrogen originally dissolved in the molten steel will precipitate and form fine nitrogen bubbles. The outflowing molten steel changes from a liquid state to a solid state in a short time under the rapid cooling effect of the injected gas, thus obtaining hollow metallic iron powder. In this embodiment, a pressure reducing valve is installed in the atomization chamber, and the setting value of the pressure reducing valve is 1.05 atm.

[0028] 3) Powder Collection: After gas atomization powder production, the iron powder in the powder collector is collected and sieved to obtain hollow metallic iron powder with a particle size of 50-300 μm, i.e., foamed steel powder. The loose packing density of the foamed steel powder is 1.8 g / cm³. 3 .

[0029] 4.) Press molding: Place the foamed steel powder into the pressing mold and vibrate to compact it. The pressing mold is made of alloy steel and the inner surface of the mold is coated with a release agent so that it can be easily demolded after being fired into foamed steel. The pressing pressure is 30MPa and the pressing time is 15min.

[0030] 5) Vacuum sintering: The pressed foam steel powder briquettes are placed in a vacuum sintering furnace along with the pressing mold for pre-sintering. During pre-sintering, the temperature is increased at a rate of 60℃ / min, and after reaching 610℃, it is held for 1.8 hours. Then, the temperature is increased to 1060℃ and held for 2.4 hours. The vacuum degree during sintering is 1 Pa. After sintering, the mixture is cooled to room temperature in the vacuum sintering furnace and then demolded to obtain foam steel of a single material.

[0031] The foamed steel produced in this embodiment has a density of 2.1 g / cm³. 3 The product performance meets the following requirements: compressive yield strength of 110 MPa, and energy absorption value of 65 MJ / m at 50% strain. 3 .

[0032]

Example 2

[0033] The preparation process of foamed steel includes pressure melting, gas atomization powdering, powder collection, pressing and molding, and vacuum sintering, specifically including the following steps: 1) Pressure Melting: Industrial pure iron is used as the smelting raw material. The chemical composition of industrial pure iron, by weight percentage, is: C: 0.003%, Si: 0.007%, Mn: 0.018%, P: 0.005%, S: 0.003%, with the balance being iron and unavoidable impurities. The smelting raw material is placed in a pressure melting furnace and smelted using induction heating. After adding the smelting raw material, a vacuum is drawn into the furnace. When the vacuum reaches 10 Pa, electric melting is initiated, with an electric power of 150 kW. Nitrogen gas is introduced into the pressure melting furnace from nitrogen cylinders to pressurize it. The pressure inside the pressure melting furnace is controlled at 4 MPa, and the holding time is 30 min. The nitrogen content in the molten steel is 0.061% by mass; the nitrogen purity is 99.94%.

[0034] 2) Gas Atomization Powder Production: After industrial pure iron is melted, a carburizing agent, ferrosilicon, and metallic manganese are added for alloying. The superheat of the molten steel is controlled at 180°C. After smelting, the guide pipe is opened, and hollow metallic iron powder is prepared by gas atomization. The gas pressure ejected from the gas atomizing nozzle is 3.1 MPa. The molten steel in the pressurized smelting furnace flows out through a guide pipe with a diameter of ø6 mm and enters the atomization chamber. Under the impact of the airflow formed by the gas ejected from the gas atomizing nozzle, the molten steel is broken into small particles. At the same time, as the molten steel in the pressurized smelting furnace flows out of the guide pipe into the atomization chamber, due to the pressure drop in the atomization chamber, the nitrogen originally dissolved in the molten steel will precipitate and form fine nitrogen bubbles. The outflowing molten steel changes from a liquid state to a solid state in a short time under the rapid cooling effect of the injected gas, thus obtaining hollow metallic iron powder. In this embodiment, a pressure reducing valve is installed in the atomization chamber, and the setting value of the pressure reducing valve is 1.05 atm.

[0035] 3) Powder Collection: After gas atomization powder production, the iron powder in the powder collector is collected and sieved to obtain hollow metallic iron powder with a particle size of 50-300 μm, i.e., foamed steel powder. The loose packing density of the foamed steel powder is 1.9 g / cm³. 3 .

[0036] 4.) Pressing and molding: The foamed steel powder is placed in the pressing mold and vibrated to compact it. The pressing mold is made of alloy steel and the inner surface of the mold is coated with a release agent so that it can be easily demolded after being fired into foamed steel. The pressing pressure is 37MPa and the pressing time is 12min.

[0037] 5) Vacuum sintering: The pressed foam steel powder briquettes are placed in a vacuum sintering furnace along with the pressing mold for pre-sintering. During pre-sintering, the temperature is increased at a rate of 75℃ / min, reaching 623℃ and held for 1.5 hours. Then, the temperature is increased to 1100℃ and held for 2.3 hours. The vacuum degree during sintering is 1 Pa. After sintering, the mixture is cooled to room temperature in the vacuum sintering furnace and then demolded to obtain foam steel of a single material.

[0038] The foamed steel produced in this embodiment has a density of 2.3 g / cm³. 3 The product performance meets the following requirements: compressive yield strength of 120 MPa, and energy absorption value of 74 MJ / m at 50% strain. 3 .

[0039]

Example 3

[0040] The preparation process of foamed steel includes pressure melting, gas atomization powdering, powder collection, pressing and molding, and vacuum sintering, specifically including the following steps: 1) Pressure Melting: Industrial pure iron is used as the smelting raw material. The chemical composition of industrial pure iron, by weight percentage, is: C: 0.003%, Si: 0.01%, Mn: 0.02%, P: 0.004%, S: 0.002%, with the balance being iron and unavoidable impurities. The smelting raw material is placed in a pressure melting furnace and smelted using induction heating. After adding the smelting raw material, a vacuum is drawn into the furnace. When the vacuum reaches 8 Pa, electric melting is initiated, with an electric power of 170 kW. Nitrogen gas is introduced into the pressure melting furnace from nitrogen cylinders to pressurize it. The pressure inside the pressure melting furnace is controlled at 5 MPa, and the holding time is 25 min. The nitrogen content in the molten steel is 0.0070%, and the nitrogen purity is 99.92%.

[0041] 2) Gas Atomization Powder Production: After industrial pure iron is melted, a carburizing agent, ferrosilicon, and metallic manganese are added for alloying. The superheat of the molten steel is controlled at 200℃. After smelting, the guide pipe is opened, and hollow metallic iron powder is prepared by gas atomization. The gas pressure ejected from the gas atomizing nozzle is 3.3 MPa. The molten steel in the pressurized smelting furnace flows out through a guide pipe with a diameter of ø4 mm and enters the atomization chamber. Under the impact of the airflow formed by the gas ejected from the gas atomizing nozzle, the molten steel is broken into small particles. At the same time, as the molten steel in the pressurized smelting furnace flows out of the guide pipe into the atomization chamber, due to the pressure drop in the atomization chamber, the nitrogen originally dissolved in the molten steel will precipitate and form fine nitrogen bubbles. The outflowing molten steel changes from a liquid state to a solid state in a short time under the rapid cooling effect of the injected gas, thus obtaining hollow metallic iron powder. In this embodiment, a pressure reducing valve is installed in the atomization chamber, and the setting value of the pressure reducing valve is 1.05 atm.

[0042] 3) Powder Collection: After gas atomization powder production, the iron powder in the powder collector is collected and sieved to obtain hollow metallic iron powder, i.e., foamed steel powder, with a particle size of 50-300 μm. The loose packing density of the foamed steel powder is 2.0 g / cm³. 3 .

[0043] 4.) Press molding: The foamed steel powder is placed in the pressing mold and vibrated to compact it. The pressing mold is made of alloy steel and the inner surface of the mold is coated with a release agent so that it can be easily demolded after being fired into foamed steel. The pressing pressure is 45MPa and the pressing time is 9min.

[0044] 5) Vacuum sintering: The pressed foam steel powder briquettes are placed in a vacuum sintering furnace along with the pressing mold for pre-firing. During pre-firing, the temperature is increased at a rate of 90℃ / min, reaching 635℃ and held for 1.2 hours. Then, the temperature is increased to 1140℃ and held for 2.1 hours. The vacuum degree during sintering is 2Pa. After sintering, the mixture is cooled to room temperature in the vacuum sintering furnace and then demolded to obtain foam steel of a single material.

[0045] The foamed steel produced in this embodiment has a density of 2.4 g / cm³. 3 The product performance meets the following requirements: compressive yield strength of 124 MPa, and energy absorption value of 85 MJ / m at 50% strain. 3 .

[0046] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing foamed steel powder, characterized in that, Includes the following steps: 1) Pressure Melting: Industrial pure iron is used as raw material, and the raw material is melted in a pressure melting furnace using induction heating. Specifically: after the raw material is added to the pressure melting furnace, a vacuum is drawn, and after the vacuum degree reaches below 10 Pa, electric melting is performed, with the melting power controlled at 130-170 kW; nitrogen is introduced into the pressure melting furnace for pressurization, and the pressure inside the pressure melting furnace is controlled at 4-5 MPa, with a holding time of 25-35 min, and the nitrogen mass content in the molten steel is 0.060%-0.070%. 2) Gas atomization powder making: After the industrial pure iron raw material is melted, a carburizing agent, ferrosilicon and metallic manganese are added for alloying. The superheat of the molten steel is controlled at 150-200℃. After smelting, hollow metallic iron powder is prepared by gas atomization. The gas pressure of the gas atomization nozzle is 3.0-3.3MPa. The molten steel in the pressurized smelting furnace flows out through the guide pipe and enters the atomization chamber. Under the impact of the airflow formed by the gas sprayed from the gas atomization nozzle, the molten steel is broken into small particles. Due to the pressure drop in the atomization chamber, the nitrogen originally dissolved in the molten steel precipitates and forms fine nitrogen bubbles. The molten steel flowing out changes from liquid to solid instantly under the rapid cooling effect of the sprayed gas, thus obtaining hollow metallic iron powder. 3) Powder Collection: The iron powder in the atomized powder collector is collected, sieved, and then obtained as hollow metallic iron powder (i.e., foamed steel powder) with a particle size of 50–300 μm. The loose packing density of the foamed steel powder is 1.8–2.0 g / cm³. 3 .

2. The method for preparing foamed steel powder according to claim 1, characterized in that, In step 1), the chemical composition of industrial pure iron by weight percentage is: C≤0.003%, Si≤0.010%, Mn≤0.02%, P≤0.006%, S≤0.003%, with the balance being iron and unavoidable impurities.

3. The method for preparing foamed steel powder according to claim 1, characterized in that, In step 1), the purity of nitrogen is ≥99.9%.

4. The method for preparing foamed steel powder according to claim 1, characterized in that, In step 2), the diameter of the guide tube is ø4~ø8mm; the atomization chamber is equipped with a pressure reducing valve, and the setting value of the pressure reducing valve is 1~1.1atm.

5. A type of foamed steel, characterized in that, The foamed steel powder prepared by the method described in any one of claims 1 to 4 is used as raw material; the chemical composition of the foamed steel, by weight percentage, is C: 0.006% to 0.010%, Si: 0.01% to 0.02%, Mn: 0.02% to 0.04%, P≤0.008%, S≤0.005%, with the balance being Fe and unavoidable impurities; the density of the foamed steel is 2.1 to 2.4 g / cm³. 3 Compressive yield strength ≥110MPa, energy absorption value at 50% strain 65~85MJ / m 3 .

6. The method for preparing foamed steel as described in claim 5, characterized in that, Specifically, the steps include the following: 1) Compression molding: The foamed steel powder is placed in a compression mold and vibrated to compact it, resulting in foamed steel powder blocks; the pressure during compression is 30-45 MPa, and the compression time is 9-15 min; 2) Vacuum sintering: The pressed foam steel powder briquettes, together with the pressing mold, are placed in a vacuum sintering furnace for pre-firing. During pre-firing, the temperature is increased at a rate of 60-90℃ / min, and after heating to 610-635℃, it is held for 1.2-1.8h. Then, the temperature is increased to 1060-1140℃ and held for 2.1-2.4h. The vacuum degree during sintering is ≤2Pa. After sintering, the foam steel is cooled to room temperature with the vacuum sintering furnace and demolded to obtain foam steel of a single material.

7. The method for preparing foamed steel according to claim 6, characterized in that, The pressing mold is an alloy steel mold, and the inner surface of the pressing mold is coated with a release agent.