High-compressibility water atomization steel powder and preparation method thereof

Abstract

The invention relates to the technical field of powder metallurgy, and provides high-compressibility water-atomized steel powder and a preparation method thereof.The preparation method of the high-compressibility water-atomized steel powder comprises the following steps of molten steel smelting, water atomization, rough powder screening, reduction, crushing, screening and mixing; the molten steel is prepared from the following target components in percentage by weight: 0.03 percent to 0.12 percent of C, 0.005 percent to 0.015 percent of S, 0.001 percent to 0.008 percent of P, 0.003 percent to 0.007 percent of Si, 0.010 percent to 0.03 percent of Cr, 0.010 percent to 0.022 percent of Ni, 0.009 percent to 0.022 percent of Cu, 0.05 percent to 0.10 percent of Mn, 0.005 percent to 0.01 percent of Mo, 0.01 percent to 0.015 percent of V, Ti and La and the balance of iron and inevitable impurities. According to the technical scheme, the problem of low compressibility of water atomized steel powder in related technologies is solved.

Description

Technical Field

[0001] This invention relates to the field of powder metallurgy technology, specifically to a highly compressible water-atomized steel powder and its preparation method. Background Technology

[0002] Water-atomized steel powder is a metal powder prepared by water atomization and is an important category of steel powder. Its preparation principle is as follows: molten steel flows out from a nozzle, forming a continuous flow of liquid metal; then, high-pressure water jets impact the liquid flow at high speed through a nozzle, breaking it into fine droplets; the droplets rapidly cool and solidify in the water, ultimately forming irregularly shaped steel powder particles, which is water-atomized steel powder.

[0003] Compressibility refers to the density (ratio of compact density to theoretical density) or formability that water-atomized steel powder can achieve when pressed into a compact under certain pressure. It is one of the core performance indicators of water-atomized steel powder. The better the compressibility, the easier it is to obtain a high-density compact during pressing, achieving the target density at lower pressures. This reduces mold wear and lowers equipment energy consumption. It can also meet the needs of high-end manufacturing products with high density requirements, expanding the application range of water-atomized steel powder.

[0004] Therefore, it is necessary to develop a highly compressible water-atomized steel powder to improve its quality and expand its application range. Summary of the Invention

[0005] This invention proposes a high compressibility water-atomized steel powder and its preparation method, which solves the problem of low compressibility in water-atomized steel powder in related technologies.

[0006] The technical solution of the present invention is as follows: This invention proposes a method for preparing highly compressible water-atomized steel powder, comprising the following steps: steel smelting, water atomization, raw powder screening, reduction, crushing, sieving, and mixing; the target component content of the molten steel, by weight percentage, consists of the following components: C: 0.03%~0.12%, S: 0.005%~0.015%, P: 0.001%~0.008%, Si: 0.003%~0.007%, Cr: 0.010%~0.03%, Ni: 0.010%~0.022%, Cu: 0.009%~0.022%, Mn: 0.05%~0.10%, Mo: 0.005%~0.01%, V+Ti+La: 0.01%~0.015%, with the remainder being iron and unavoidable impurities.

[0007] As a further technical solution, the mass relationship of V, Ti, and La in V+Ti+La is V:Ti:La=5:0.5:0.5~1.

[0008] As a further technical solution, the mass relationship of V, Ti, and La is V:Ti:La = 5:0.5:0.6~0.8.

[0009] As a further technical solution, the reduction temperature is 660~950℃.

[0010] As a further technical solution, the reduction zone consists of 9 zones, with the temperatures of zones 1 to 9 being 660℃, 860℃, 920℃, 950℃, 950℃, 950℃, 920℃, 890℃, and 880℃ respectively.

[0011] As a further technical solution, after reduction, the temperature is lowered to 500°C at a first cooling rate and then lowered to 200°C at a second cooling rate, wherein the first cooling rate is greater than the second cooling rate.

[0012] As a further technical solution, the first cooling rate is 15~25℃ / min, and the second cooling rate is 5~10℃ / min.

[0013] In this invention, after reducing water-atomized steel powder, a phased cooling process is performed. First, a first-stage cooling is carried out at 15~25℃ / min. After the reduction, the steel powder is in a high-temperature state, at which point the chemical activity of metallic iron is high. If the cooling is too fast or too slow, the oxygen content will increase. The first cooling rate of this invention can reduce the oxygen content of the water-atomized steel powder. Then, a second-stage cooling is carried out at 5~10℃ / min. In the second stage, the chemical activity of metallic iron decreases. At this cooling rate, water vapor can be fully released, further reducing the oxygen content in the water-atomized iron powder.

[0014] As a further technical solution, the first cooling rate is 20℃ / min, and the second cooling rate is 6℃ / min.

[0015] As a further technical solution, during the reduction process, the flow rate of the reducing gas is 80~100m³. 3 The material layer thickness is 25~30mm, the belt speed is 150~180mm / min, and the reducing gas is composed of hydrogen and nitrogen.

[0016] As a further technical solution, the volume ratio of hydrogen to nitrogen is 5.5:1.

[0017] As a further technical solution, during water atomization, the water pressure is 8~10MPa and the water flow rate is 68~80m³. 3 / h.

[0018] The present invention also proposes a highly compressible water-atomized steel powder, which is prepared by the aforementioned method for preparing highly compressible water-atomized steel powder.

[0019] The working principle and beneficial effects of this invention are as follows: In this invention, the high compressibility of water-atomized steel powder is achieved by optimizing the composition of the target molten steel during preparation. This is achieved by adjusting the composition of C, S, P, Si, Cr, Ni, Cu, and Mn, and limiting the mass percentage of V, Ti, and La to 0.1%~0.25%. The addition of V, Ti, and La refines the grain size and removes inclusions. A finer grain structure improves the plasticity of the iron matrix, making the steel powder less prone to brittle fracture during pressing, thus synergistically enhancing the compressibility of the water-atomized steel powder. Removing inclusions prevents large-sized inclusions from hindering deformation, further improving the compressibility of the water-atomized steel powder. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] Example 1 A method for preparing highly compressible water-atomized steel powder includes the following steps: S1. Steel smelting: Scrap steel is added to an electric arc furnace for smelting, the composition of the initial molten steel is determined, and corresponding elements are added and melted to obtain molten steel, so that the composition of the molten steel is consistent with the composition of the target molten steel. The target molten steel, by mass percentage, consists of the following components: C: 0.08%, S: 0.015%, P: 0.006%, Si: 0.007%, Cr: 0.03%, Ni: 0.022%, Cu: 0.020%, Mn: 0.05%, Mo: 0.01%, V + Ti + La: 0.010%, with the remainder being iron and unavoidable impurities; the mass ratio of V, Ti, and La is V:Ti:La = 5:0.5:0.5. S2. Water Atomization: Molten steel is added to an atomizer and atomized using high-pressure water. A 16mm zirconium core is used, the water ring angle of the atomizer is 11°, the ring gap width is 0.8mm, the nozzle is 16mm, the high-pressure water pressure is 11.0MPa, and the water flow rate is 68m³ / h. 3 / min, to obtain steel powder after water atomization; S3. Raw powder sieving: The steel powder after water atomization is sieved through a 60-mesh sieve to obtain sieved steel powder; S4. Reduction: The sieved steel powder is added to the reduction furnace, and a 9-segment reduction method is adopted. The temperatures of the 1st to 9th segments are: 660℃, 860℃, 920℃, 950℃, 950℃, 950℃, 920℃, 890℃, and 880℃ respectively. During the reduction stage, the flow rate of the reducing gas is 80 m³ / s. 3 / h, the material layer thickness is 30mm, and the belt speed is 150mm / min; after the reduction is completed, the temperature is reduced to 500℃ at a cooling rate of 15℃ / min, and then reduced to 200℃ at a cooling rate of 5℃ / min to obtain reduced steel powder, wherein the reducing gas is composed of hydrogen and nitrogen in a volume ratio of 5.5:1. S5. Crushing, screening, and mixing: The reduced steel powder is crushed using a crusher, screened using a 100-mesh sieve, and then mixed in a mixer for 10 minutes to obtain water-atomized pre-alloyed steel powder.

[0022] Example 2 A method for preparing highly compressible water-atomized steel powder includes the following steps: S1. Steel smelting: Scrap steel is added to an electric arc furnace for smelting, the composition of the initial molten steel is determined, and corresponding elements are added and melted to obtain molten steel, so that the composition of the molten steel is consistent with the composition of the target molten steel. The target molten steel, by mass percentage, consists of the following components: C: 0.09%, S: 0.011%, P: 0.006%, Si: 0.005%, Cr: 0.02%, Ni: 0.015%, Cu: 0.017%, Mn: 0.10%, Mo: 0.01%, V + Ti + La: 0.015%, with the remainder being iron and unavoidable impurities; the mass ratio of V, Ti, and La is V:Ti:La = 5:0.5:0.5. S2. Water Atomization: Molten steel is added to an atomizer and atomized using high-pressure water. A 16mm zirconium core is used, the water ring angle of the atomizer is 11°, the ring gap width is 0.8mm, the nozzle is 16mm, the high-pressure water pressure is 11.0MPa, and the water flow rate is 68m³ / h. 3 / min, to obtain steel powder after water atomization; S3. Raw powder sieving: The steel powder after water atomization is sieved through a 60-mesh sieve to obtain sieved steel powder; S4. Reduction: The sieved steel powder is added to the reduction furnace, and a 9-segment reduction method is adopted. The temperatures of the 1st to 9th segments are: 660℃, 860℃, 920℃, 950℃, 950℃, 950℃, 920℃, 890℃, and 880℃ respectively. During the reduction stage, the flow rate of the reducing gas is 100 m³ / s. 3 / h, the material layer thickness is 30mm, and the belt speed is 150mm / min; after the reduction is completed, the temperature is reduced to 500℃ at a cooling rate of 25℃ / min, and then reduced to 200℃ at a cooling rate of 10℃ / min to obtain reduced steel powder, wherein the reducing gas is composed of hydrogen and nitrogen in a volume ratio of 5.5:1. S5. Crushing, screening, and mixing: The reduced steel powder is crushed using a crusher, screened using a 100-mesh sieve, and then mixed in a mixer for 10 minutes to obtain water-atomized pre-alloyed steel powder.

[0023] Example 3 Compared with Example 1, the only difference in this example is that the mass ratio of V, Ti and La in the target molten steel is V:Ti:La = 5:0.5:1.

[0024] Example 4 Compared with Example 1, the only difference in this example is that the mass ratio of V, Ti, and La in the target molten steel is V:Ti:La = 5:0.5:0.6.

[0025] Example 5 Compared with Example 1, the only difference in this example is that the mass ratio of V, Ti, and La in the target molten steel is V:Ti:La = 5:0.5:0.8.

[0026] Example 6 Compared with Example 1, the only difference in this example is that after the reduction is completed, the temperature is lowered to 500°C at a cooling rate of 20°C / min, and then lowered to 200°C at a cooling rate of 6°C / min.

[0027] Example 7 Compared with Example 1, the only difference in this example is that after the reduction is completed, the temperature is lowered to 500°C at a cooling rate of 15°C / min, and then lowered to 200°C at a cooling rate of 6°C / min.

[0028] Example 8 Compared with Example 1, the only difference in this example is that after the reduction is completed, the temperature is lowered to 500°C at a cooling rate of 25°C / min, and then lowered to 200°C at a cooling rate of 6°C / min.

[0029] Example 9 Compared with Example 1, the only difference in this example is that after the reduction is completed, the temperature is lowered to 500°C at a cooling rate of 20°C / min, and then lowered to 200°C at a cooling rate of 5°C / min.

[0030] Example 10 Compared with Example 1, the only difference in this example is that after the reduction is completed, the temperature is lowered to 500°C at a cooling rate of 20°C / min, and then lowered to 200°C at a cooling rate of 10°C / min.

[0031] Example 11 Compared with Example 1, the only difference in this example is that after the reduction is completed, the temperature is reduced to 200°C at a rate of 20°C / min.

[0032] Example 12 Compared with Example 1, the only difference in this example is that after the reduction is completed, the temperature is reduced to 200°C at a rate of 6°C / min.

[0033] Comparative Example 1 Compared with Example 1, the only difference in this comparative example is that Ti is replaced with an equal amount of La in the molten steel.

[0034] Comparative Example 2 Compared with Example 1, the only difference in this comparative example is that La is replaced with an equal amount of Ti in the molten steel.

[0035] Comparative Example 3 Compared with Example 1, the only difference in this comparative example is that La and Ti are replaced with equal amounts of V in the molten steel.

[0036] Comparative Example 4 Compared with Example 1, the only difference in this comparative example is that V in the molten steel is replaced by La and Ti in a mass ratio of 1:1.

[0037] Experimental Example 1 The compressibility of water-atomized steel powder in Examples 1-12 and Comparative Examples 1-4 was determined using the following methods: The compressibility of metal powders (excluding cemented carbide powders) was tested in accordance with GB / T 1481-2022 "Determination of compressibility of metal powders (excluding cemented carbide powders) in uniaxial pressing". The pressing pressure was 600 MPa. The test results are shown in Table 1.

[0038] Table 1. Results of compressibility testing of water-atomized steel powder in Examples 1-5 and Comparative Examples 1-4

[0039] As shown in Table 1, the compressibility of water-atomized steel powder in Examples 1-5 is higher than that in Comparative Examples 1-4, indicating that the optimization and limitation of the steel composition in this invention can improve the compressibility of water-atomized steel powder.

[0040] Experimental Example 2 The oxygen content in the reduced steel powder of Examples 1, 6-12 was determined, and the results are shown in Table 2.

[0041] Table 2. Results of oxygen content determination in the reduced steel powder in Examples 1, 6-12

[0042] As shown in Table 2, the oxygen content in the reduced steel powder in Examples 1 and 6-10 is lower than that in Examples 11 and 12, indicating that the oxygen content in the reduced steel powder can be reduced by cooling at two different rates after reduction in this invention.

[0043] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for producing a high compressibility water atomized steel powder, characterized by, The method comprises the following steps: molten steel smelting, water atomization, coarse powder screening, reduction, crushing, screening, and mixing; The target component content of the molten steel consists of, by weight percentage, C: 0.03%-0.12%, S: 0.005%-0.015%, P: 0.001%-0.008%, Si: 0.003%-0.007%, Cr: 0.010%-0.03%, Ni: 0.010%-0.022%, Cu: 0.009%-0.022%, Mn: 0.05%-0.10%, Mo: 0.005%-0.01%, V+Ti+La: 0.01%-0.015%, and the rest is iron and unavoidable impurities.

2. The method of claim 1, wherein the water-atomized steel powder has a compressibility of 20% or more. The mass ratio of V, Ti, and La in the V+Ti+La is V:Ti:La=5:0.5:0.5-1.

3. The method of claim 2, wherein the high compressibility water atomized steel powder is produced by the steps of: The mass ratio of V, Ti, and La is V:Ti:La=5:0.5:0.6-0.

8. ​ 4. The method of claim 1, wherein the water-atomized steel powder has a high compressibility. The temperature of the reduction is 660-950°C.

5. The method of claim 4, wherein the high compressibility water atomized steel powder is produced by the steps of: The reduction section is 9 sections, and the temperature from section 1 to section 9 is, in sequence, 660°C, 860°C, 920°C, 950°C, 950°C, 950°C, 920°C, 890°C, and 880°C.

6. The method of claim 4, wherein the water-atomized steel powder has a compressibility of 20% or more. After the reduction, the temperature is reduced to 500°C at a first cooling rate and then reduced to 200°C at a second cooling rate, wherein the first cooling rate is greater than the second cooling rate.

7. The method of claim 1, wherein the water-atomized steel powder has a compressibility of at least 25%. The first cooling rate is 15-25°C / min, and the second cooling rate is 5-10°C / min.

8. The method of claim 1, wherein the water-atomized steel powder has a high compressibility. The flow rate of the reducing gas is 80 to 100 m 3 / h, the layer thickness is 25 to 30 mm, and the belt speed is 150 to 180 mm / min, and the reducing gas is composed of hydrogen and nitrogen.

9. The method of claim 1, wherein the water-atomized steel powder has a high compressibility. The water pressure is 8-10 MPa and the water flow is 68-80 m 3 / h.

10. A high-compressibility water atomized steel powder prepared by the method of any one of claims 1-9.

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