Hot work die steel powder material for additive manufacturing and method for preparing the same

Abstract

The application discloses a hot work die steel powder material for additive manufacturing and a preparation method thereof, and belongs to the technical field of metal powder, and comprises the following elements in percentage by mass: C is 0.2% to 0.35%, Cr is 2.5% to 5.5%, Mo is 2% to 4%, V is 0.1% to 0.6%, Si is 0.1% to 0.6%, and Mn is 0.1% to 0.6%. By introducing the micro-alloy synergy of Ta and Nb and the rare earth composite regulation of Ce and Mg and Y and La on the basis of the matrix alloy system of C, Cr, Mo, V, Si and Mn, the powder can ensure forming adaptability, and meanwhile, strength, toughness and heat conduction performance are considered, and the demand of the hot work die on comprehensive performance under high-temperature and thermal shock working conditions can be met.

Description

Technical Field

[0001] This invention relates to the field of metal powder technology, and more specifically, to a hot work die steel powder material for additive manufacturing and its preparation method. Background Technology

[0002] In the manufacturing of mold parts with irregular flow channels, such as conformal cooling molds, cooling efficiency can be significantly improved and the surface quality of the product can be improved. However, traditional subtractive processing methods are difficult to process such complex flow channel structures. Therefore, the use of powder bed melting additive manufacturing technology such as selective laser melting for mold parts forming has gradually become an important development direction.

[0003] Hot work dies are typically subjected to high temperatures and cyclic thermal shock during service, and are also subjected to significant mechanical loads. In addition to meeting requirements for wear resistance, strength, hardness, and red hardness, materials also need to possess high toughness and resistance to thermal cracking. At the same time, high thermal conductivity helps reduce the thermal stress level of the die during service and improves heat dissipation efficiency. Among the metal powder materials commonly used in additive manufacturing, some martensitic aging steels have good formability, but they often cannot simultaneously achieve both toughness and thermal conductivity. Furthermore, due to the influence of alloying degree and phase transformation behavior, traditional hot work die steel systems are more prone to the superposition effect of large thermal stress and microstructure transformation stress during selective laser melting forming, thus exhibiting high crack sensitivity, resulting in a narrow process window and insufficient forming stability.

[0004] Furthermore, the quality of selective laser melting (SLM) forming is highly sensitive to the quality of the powder material. During melting, atomization, cooling, transport, and storage, oxygen may be introduced into the powder, forming oxide inclusions. These inclusions and porosity defects reduce the density of the formed part and weaken key properties such as impact toughness. Simultaneously, insufficient powder sphericity or fluctuations in particle size distribution can cause uneven powder spreading and decreased melt pool stability, easily inducing unfused porosity and uneven microstructure, thus increasing the dispersion of mechanical and thermal properties. For material systems like hot work die steel, which are inherently sensitive to cracking, the aforementioned powder quality fluctuations and defect amplification effects are more likely to make it difficult to achieve a consistently high forming density, and consequently, the overall performance after subsequent heat treatment may fail to meet actual service requirements. Summary of the Invention

[0005] To address the problems mentioned in the background section, the present invention provides the following technical solution:

[0006] A hot-work die steel powder material for additive manufacturing and its preparation method, comprising the following elements by mass percentage: C 0.2% to 0.35%, Cr 2.5% to 5.5%, Mo 2% to 4%, V 0.1% to 0.6%, Si 0.1% to 0.6%, Mn 0.1% to 0.6%, the sum of the mass percentages of Ta and Nb 0.005% to 0.2%, the sum of the mass percentages of Ce and Mg 0.005% to 0.2%, the sum of the mass percentages of Y and La 0.001% to 0.1%, Ni 0% to 0.2%, Cu 0% to 0.2%, P 0% to 0.05%, N 0% to 0.01%, O 0% to 0.05%, with the balance being Fe;

[0007] The powder material has a particle size of 15μm to 53μm, the yield of the powder in the particle size range is not less than 30%, and the sphericity of the powder is higher than 90%.

[0008] Furthermore, the density of the powder material reaches over 99% after selective laser melting and forming.

[0009] Furthermore, the sum of the mass percentages of Ce and Mg is 0.03% to 0.10%, the sum of the mass percentages of Y and La is 0.01% to 0.06%, the sum of the mass percentages of Ta and Nb is 0.02% to 0.15%, and the oxygen content of the powder material is not higher than 200 ppm and the sphericity is not lower than 94%.

[0010] Furthermore, the printed sample obtained by selective laser melting of the powder material satisfies the following:

[0011] The tensile strength is not less than 1800MPa, the yield strength is not less than 1300MPa, the elongation is not less than 15%, the room temperature impact energy KV2 is not less than 32J, the hardness HRC is not less than 48, and the room temperature thermal conductivity is not less than 25W / (m·K).

[0012] Furthermore, the printed sample, after quenching and two tempering treatments, satisfies the following:

[0013] The tensile strength is not less than 1500MPa, the yield strength is not less than 1300MPa, the elongation is not less than 15%, the room temperature impact energy KV2 is not less than 36J, the hardness HRC is not less than 44, and the room temperature thermal conductivity is not less than 28W / (m·K).

[0014] Furthermore, when the powder material is used in selective laser melting additive manufacturing, the density of the formed part reaches over 99% when the substrate preheating temperature is 100°C to 200°C, the laser power is 250W to 400W, the scanning speed is 600mm / s to 1000mm / s, the scanning spacing is 0.06mm to 0.14mm, and the layer thickness is 0.03mm to 0.06mm.

[0015] A method for preparing hot work die steel powder material for additive manufacturing includes the following steps:

[0016] S1. Under an inert atmosphere, iron-based binary alloy or pure metal raw materials are batched according to a defined element mass percentage and fed into the corundum crucible in the melting chamber, and a vacuum of 1×10⁻⁶ is applied. -2 After Pa is below, the temperature is raised and smelted to 1550°C to 1650°C and maintained to obtain a uniform alloy melt. Then the melt temperature is adjusted to 1500°C to 1600°C and refined for 8 to 14 minutes.

[0017] S2. Under the protection of an inert gas atomizing medium, the alloy melt is introduced into the atomizing area, and Ar or N2 is used as the atomizing medium and the alloy melt is atomized at an atomizing pressure of 2.0 MPa to 4.0 MPa, so that it is broken up and quickly solidified to form a pre-made powder.

[0018] S3. After the pre-made powder cools down, it is sieved in multiple stages using an ultrasonic vibrating screen with screens of 100 mesh, 230 mesh and 500 mesh in sequence. Powder with a particle size of 15μm to 53μm is collected as hot work die steel powder material for additive manufacturing.

[0019] The powder with a particle size of 15μm to 53μm has a yield of not less than 30%, a sphericity of more than 90%, and an oxygen content of not more than 200ppm.

[0020] Furthermore, before the melting and refining in step S1, the melting chamber is first purged with an inert gas, namely Ar or N2, for 2 to 3 times, followed by evacuation to a vacuum of 1×10⁻⁶. -2 After the temperature drops below Pa, the powder is heated and smelted to reduce the oxygen introduction during the smelting and atomization process and ensure that the oxygen content of the resulting powder with a particle size of 15 μm to 53 μm does not exceed 200 ppm.

[0021] Further, in step S1, the furnace exit temperature of the melt is 1550°C to 1650°C, the refining temperature is 1500°C to 1600°C, the refining time is 8 min to 14 min, and the furnace exit temperature is 50°C to 150°C higher than the refining temperature.

[0022] The atomization pressure in step S2 is 2.0 MPa to 4.0 MPa, the atomization medium is Ar or N2, and the flow rate of the atomization medium is 1 to 3 times the local speed of sound in the atomization region.

[0023] In step S3, the first sieve for multi-stage sieving is 50 to 100 mesh, the second sieve is 200 to 250 mesh, and the third sieve is 500 to 550 mesh, in order to obtain powder with a particle size of 15 μm to 53 μm.

[0024] In summary, the present invention has the following beneficial effects:

[0025] By introducing microalloying synergy of Ta and Nb and rare earth composite regulation of Ce and Mg, Y and La on the basis of the C, Cr, Mo, V, Si and Mn matrix alloy system, the powder can ensure the formability while taking into account the strength, toughness and thermal conductivity, which can meet the comprehensive performance requirements of hot work dies under high temperature and thermal shock conditions.

[0026] By limiting the powder particle size range to 15μm to 53μm and controlling the yield of this particle size range to no less than 30%, while increasing the powder sphericity to above 90% and, in preferred cases, no less than 94%, the powder spreading process is stabilized, the molten pool morphology is more consistent, and the probability of incomplete fusion and porosity defects is reduced, thereby improving the density of the formed parts and enhancing the performance consistency.

[0027] High performance in the printed state can be obtained by selective laser melting and forming. After quenching and two tempering treatments, it can still maintain high strength, toughness and thermal conductivity. This can achieve synergistic performance improvement between the printed state and the heat-treated state, thereby improving the service reliability and service life of hot work die parts. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a schematic diagram of the overall technical solution of the present invention;

[0030] Figure 2 Metallographic microscope image of the polished cross-section of the printed sample of the present invention; scale bar 200 μm;

[0031] Figure 3 Metallographic microscope image of the polished cross-section of the heat-treated sample of this invention; scale bar 200 μm;

[0032] Figure 4 The image shown is a scanning electron microscope (SE) image of the raw material powder at 100× magnification (scale bar 200μm), used to show the overall particle distribution and representative field of view.

[0033] Figure 5 This is a scanning electron microscope (SE) image of the raw material powder of the present invention at 200× magnification (scale bar 100μm), used to show the particle outline details and morphological features that affect sphericity, such as satellite powder adhesion and agglomerated particles. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] Example 1:

[0036] The following is in conjunction with the appendix Figure 1-5 The present invention will be described in further detail below.

[0037] Please see Figure 1-5 This invention provides a technical solution: a hot work die steel powder material for additive manufacturing, such as... Figure 1-5 As shown, the elements include the following mass percentages: C 0.2% to 0.35%, Cr 2.5% to 5.5%, Mo 2% to 4%, V 0.1% to 0.6%, Si 0.1% to 0.6%, Mn 0.1% to 0.6%, the sum of the mass percentages of Ta and Nb 0.005% to 0.2%, the sum of the mass percentages of Ce and Mg 0.005% to 0.2%, the sum of the mass percentages of Y and La 0.001% to 0.1%, Ni 0% to 0.2%, Cu 0% to 0.2%, P 0% to 0.05%, N 0% to 0.01%, O 0% to 0.05%, with the remainder being Fe;

[0038] The powder material has a particle size of 15μm to 53μm, the yield of the powder in the particle size range is not less than 30%, and the sphericity of the powder is higher than 90%.

[0039] Furthermore, the density of the powder material reaches over 99% after selective laser melting and forming.

[0040] Preferably, the hot work die steel powder material for additive manufacturing may further include the following elements by mass percentage: C 0.2%, Cr 2.5%, Mo 2%, V 0.1%, Si 0.1%, Mn 0.1%, the sum of the mass percentages of Ta and Nb is 0.005%, the sum of the mass percentages of Ce and Mg is 0.005%, the sum of the mass percentages of Y and La is 0.001%, Ni is 0%, Cu is 0%, P is 0%, N is 0%, O is 0%, and the remainder is Fe;

[0041] The powder material has a particle size of 15μm to 53μm, the yield of the powder in the particle size range is not less than 30%, and the sphericity of the powder is higher than 90%.

[0042] Preferably, the hot work die steel powder material for additive manufacturing may further include the following elements by mass percentage: C 0.35%, Cr 5.5%, Mo 4%, V 0.6%, Si 0.6%, Mn 0.6%, the sum of the mass percentages of Ta and Nb is 0.2%, the sum of the mass percentages of Ce and Mg is 0.2%, the sum of the mass percentages of Y and La is 0.1%, Ni 0.2%, Cu 0.2%, P 0.05%, N 0.01%, O 0.05%, and the remainder is Fe;

[0043] The powder material has a particle size of 53 μm, the yield of the powder within this particle size range is not less than 30%, and the sphericity of the powder is higher than 90%.

[0044] In this embodiment, iron-based binary alloys and pure metals are selected as raw materials for formulation. The target mass percentages of the alloy are as follows: C 0.30%, Cr 4.20%, Mo 3.00%, V 0.35%, Si 0.35%, Mn 0.25%, Ta 0.05%, Nb 0.03%, Ce 0.04%, Mg 0.02%, Y 0.015%, La 0.005%, Ni 0.10%, Cu 0.05%, P 0.01%, N 0.008%, O 0.018%, and the remainder is Fe. The sum of the mass percentages of Ta and Nb is 0.08%, the sum of the mass percentages of Ce and Mg is 0.06%, and the sum of the mass percentages of Y and La is 0.02%.

[0045] The above raw materials are proportioned according to the target mass percentage and then fed into the corundum crucible in the melting chamber. Under an inert atmosphere, a vacuum of 1×10⁻⁶ is drawn. -2After the temperature drops below Pa, the temperature is raised to 1600℃ and held for 20 minutes to promote composition homogenization. Then, the temperature is adjusted to 1550℃ and refined for 10 minutes to obtain an alloy melt. The alloy melt is then introduced into an atomization zone, using N2 as the atomization medium and setting the atomization pressure to 3.0 MPa to perform gas atomization, causing the melt to break up and solidify rapidly to form a pre-formed powder. After atomization, the pre-formed powder is cooled and collected under an inert atmosphere and then transported in a sealed manner to reduce powder moisture absorption and oxygenation.

[0046] The pre-prepared powder was fed into an ultrasonic vibrating screen for multi-stage sieving, with screens of 100 mesh, 230 mesh, and 500 mesh in sequence. The particle size of the sieved powder was verified using a laser particle size analyzer, and powder with a particle size of 15 μm to 53 μm was collected as the target powder material. The yield of the target particle size range relative to the total amount of pre-prepared powder was found to be 33% by weighing and statistical analysis.

[0047] The powder morphology images were obtained using a scanning electron microscope, and the sphericity of at least 300 randomly selected particles was calculated using image analysis software. The statistical average sphericity was 94.0%, which meets the requirement that the sphericity is higher than 90%.

[0048] The oxygen content of the powder was detected using an inert gas melting method oxygen-nitrogen analyzer, and the oxygen content was 180 ppm, corresponding to a mass percentage of approximately 0.018%.

[0049] The powder material with a particle size of 15 μm to 53 μm was used for selective laser melting forming. The substrate preheating temperature was set to 150 °C, the laser power to 320 W, the scanning speed to 800 mm / s, the scanning spacing to 0.10 mm, and the layer thickness to 0.04 mm. A cubic density sample was formed using a scanning strategy of rotating adjacent layers by 67°. After forming, the density of the formed part was determined by the Archimedes method, and the density was found to be 99.96%.

[0050] As can be seen from the above embodiments, by using the component ratio and atomization sieving process given in this embodiment, hot work die steel powder material with a particle size of 15μm to 53μm, a yield of not less than 30%, and a sphericity of more than 90% can be stably obtained, and the density of the powder material after selective laser melting and forming can reach more than 99%.

[0051] Example 2

[0052] like Figure 1-5 As shown, the sum of the mass percentages of Ce and Mg is 0.03% to 0.10%, the sum of the mass percentages of Y and La is 0.01% to 0.06%, the sum of the mass percentages of Ta and Nb is 0.02% to 0.15%, and the oxygen content of the powder material is not higher than 200 ppm and the sphericity is not lower than 94%.

[0053] In this embodiment, iron-based binary alloys and pure metal raw materials are selected for formulation. The target element mass percentages are as follows: C 0.30%, Cr 4.20%, Mo 3.00%, V 0.35%, Si 0.35%, Mn 0.25%, Ta 0.08%, Nb 0.04%, Ce 0.06%, Mg 0.02%, Y 0.03%, La 0.01%, Ni 0.10%, Cu 0.05%, P 0.01%, N 0.008%, and the remainder is Fe.

[0054] The sum of the mass percentages of Ta and Nb is 0.12%, the sum of the mass percentages of Ce and Mg is 0.08%, and the sum of the mass percentages of Y and La is 0.04%.

[0055] The above ingredients are fed into the corundum crucible in the melting chamber, and a vacuum of 1×10⁻⁻¹ is drawn under an inert atmosphere. 2 After the Pa is below, the temperature is raised and smelted to reach 1600℃ and held for 20 minutes to promote composition homogenization. Then the melt temperature is adjusted to 1550℃ and refined for 10 minutes to obtain the alloy melt.

[0056] The alloy melt is introduced into the atomization zone, Ar is selected as the atomization medium and the atomization pressure is set to 3.0 MPa to atomize the alloy melt, causing it to break up and solidify rapidly to form a pre-made powder.

[0057] After the pre-made powder cools, it is sieved in multiple stages using an ultrasonic vibrating screen with screens of 100 mesh, 230 mesh and 500 mesh in sequence, and the powder with a particle size of 15μm to 53μm is collected as the target powder material.

[0058] The target particle size range was weighed and statistically analyzed, and the yield was 35%.

[0059] To determine the oxygen content, a sample of the target powder was taken and tested using an inert gas melting oxygen and nitrogen analyzer. Each sample had a mass of not less than 1g, and the test was repeated 3 times. The arithmetic mean was taken as the oxygen content result.

[0060] To detect sphericity, a scanning electron microscope was used to obtain powder morphology images. No less than 300 particles were randomly selected, and the sphericity was calculated according to the equivalent circle area method. The average value was taken as the sphericity result.

[0061] The target powder was tested and found to have an oxygen content of 170 ppm and an average sphericity of 94.5%, which meets the above requirements that the oxygen content should not exceed 200 ppm and the sphericity should not be less than 94%.

[0062] Example 3

[0063] Using the same raw materials and process route as in Example 2, only the total content of Ce and Mg, Y and La, and Ta and Nb was adjusted to be close to the lower limit window. The target element mass percentages are as follows: C 0.28%, Cr 4.00%, Mo 2.80%, V 0.30%, Si 0.30%, Mn 0.25%, Ta 0.015%, Nb 0.008%, Ce 0.020%, Mg 0.015%, Y 0.008%, La 0.004%, Ni 0.10%, Cu 0.05%, P 0.01%, N 0.008%, and the remainder being Fe.

[0064] The sum of the mass percentages of Ta and Nb is 0.023%, the sum of the mass percentages of Ce and Mg is 0.035%, and the sum of the mass percentages of Y and La is 0.012%.

[0065] The powder was prepared using the same vacuuming, melting, refining, gas atomization, and multi-stage sieving steps as in Example 2. Powder with a particle size of 15 μm to 53 μm was collected as the target powder material, and the yield of the target particle size range was 33%.

[0066] The oxygen content of the target powder was measured to be 195 ppm and the average sphericity was 94.0% using the same detection aperture as in Example 2, which also met the above-mentioned requirements.

[0067] Comparative Example 1

[0068] The same preparation process as in Example 2 was used, except that the total content of Ce and Mg, Y and La, and Ta and Nb was set outside the window of Example 2. The mass percentage of the target elements was as follows: Ta 0.006%, Nb 0.004%, Ce 0.006%, Mg 0.004%, Y 0.003%, La 0.002%, and the remaining elements were kept within the range of Example 1 as in Example 2.

[0069] The total content of Ta and Nb is 0.010%, the total content of Ce and Mg is 0.010%, and the total content of Y and La is 0.005%.

[0070] Powder with a particle size of 15 μm to 53 μm was prepared and sieved according to the same process as in Example 2; the oxygen content was measured to be 240 ppm and the average sphericity was 92.0% according to the same detection aperture, which did not meet the requirement that the oxygen content should not be higher than 200 ppm and the sphericity should not be lower than 94%.

[0071] Comparison table of key powder indicators between the examples and comparative examples (#Table 1)

[0072] Sample number The sum of the mass percentages of Ta and Nb The sum of the mass percentages of Ce and Mg The sum of the mass percentages of Y and La Oxygen content ppm sphericity% Harvest rate % Particle size range μm Example 2 0.12 0.08 0.04 170 94.5 35 15 to 53 Example 3 0.023 0.035 0.012 195 94.0 33 15 to 53 Comparative Example 1 0.010 0.010 0.005 240 92.0 32 15 to 53

[0073] As can be seen from Examples 2 and 3, when the total content of Ce and Mg, Y and La, and Ta and Nb falls within the limited window of Example 2, and when inert atmosphere vacuum melting and refining and inert gas atomization and sieving classification processes are used, powder materials with a particle size of 15μm to 53μm can be stably obtained, and the oxygen content is not higher than 200ppm and the sphericity is not lower than 94%.

[0074] As can be seen from Comparative Example 1, when the total content deviates from the limit window in Example 2, even if the same atomization and sieving process is used, the resulting powder may still have an increased oxygen content and a decreased sphericity, thus failing to meet the quality index limit in Example 2.

[0075] Example 4:

[0076] like Figure 1-5 As shown, the printed sample obtained by selective laser melting of the powder material satisfies the following:

[0077] The tensile strength is not less than 1800MPa, the yield strength is not less than 1300MPa, the elongation is not less than 15%, the room temperature impact energy KV2 is not less than 32J, the hardness HRC is not less than 48, and the room temperature thermal conductivity is not less than 25W / (m·K).

[0078] In this embodiment, hot work die steel powder material is prepared using the process route described in the text, and powder with a particle size of 15μm to 53μm is collected by multi-stage sieving; the oxygen content and sphericity of the obtained powder are tested, and the powder oxygen content is 170ppm, the average sphericity of the powder is 94.5%, and the powder yield is 35%. The powder material meets the limiting conditions of Examples 1 and 2 and is used for subsequent selective laser melting forming.

[0079] The above-mentioned powder material was used for selective laser melting and forming. The forming equipment was protected by an inert atmosphere. Before forming, the forming cavity was purged with inert gas to ensure that the oxygen content in the cavity was below 100 ppm. The substrate preheating temperature was set to 150°C; the laser power was set to 320W; the scanning speed was set to 800 mm per second; the scanning spacing was set to 0.10 mm; the layer thickness was set to 0.04 mm; the scanning strategy adopted was to rotate adjacent layers by 67°; and a printed sample blank was obtained by forming according to the above parameters.

[0080] The printed samples are not subjected to quenching and tempering treatment, but only support removal and surface cleaning. After wire cutting sampling, necessary machining is performed to obtain standard samples that meet the requirements of mechanical and thermal conductivity testing.

[0081] The tensile property test specifically involved the following steps: sampling location and specimen preparation were conducted according to GB / T 2975 2018, and the tensile test was conducted according to GB / T 228.1 2021. Samples were taken from the printed specimen along the forming direction and machined into proportional tensile specimens. The gauge length of the specimens was precision machined and the surface was free of visible defects. The test temperature was 23℃. An electronic universal testing machine was used for loading and continuous recording of the force-displacement curves to obtain the yield strength, tensile strength, and elongation after fracture. Each group of specimens consisted of no less than 3 pieces, and the arithmetic mean was taken as the tensile result of this embodiment.

[0082] The impact toughness test was conducted as follows: sampling and specimen preparation were carried out in accordance with GB / T 2975 2018, and the Charpy pendulum impact test was carried out in accordance with GB / T 229 2020; V-notch impact specimens were used, with the notch direction consistent with the sampling direction, and the test temperature was 23℃; the impact absorbed energy was expressed as KV2; each group of specimens consisted of no less than 3 pieces, and the arithmetic mean was taken as the impact result of this embodiment;

[0083] The hardness test is specifically as follows: sampling and sample preparation are carried out in accordance with GB / T 2975 2018, and Rockwell hardness test is carried out in accordance with GB / T 230.1 2018; after grinding and polishing the cross section of the printed sample, HRC scale is used for testing, and the measuring points avoid the edge and defect areas. The number of measuring points is not less than 5 points and the average value is taken as the hardness result.

[0084] The thermal conductivity test specifically involves obtaining a circular sample from the printed sample, measuring the thermal diffusivity α using the laser flash method, and measuring the sample density ρ and specific heat capacity Cp. The test method for sample density ρ is: referring to the density determination method of ISO 3369-2006 or GB / T 1423-1996, using the Archimedes hydrostatic weighing method.

[0085] After the samples are degreased and dried, their mass m1 in air and apparent mass m2 when fully immersed in deionized water at a temperature of 20℃ to 25℃ are weighed using an analytical balance. During weighing, surface air and air bubbles are removed, and a small amount of wetting agent may be added. The density ρw of water is obtained from a table based on the water temperature. The sample density ρ is calculated using ρ = m1 ÷ (m1 - m2) × ρw. If the sample has open pores that absorb water, liquid paraffin can be used to seal the pores before weighing to correct the density calculation. The room temperature thermal conductivity λ is calculated using the formula λ = α × ρ × Cp. Each group should contain at least three samples, and the arithmetic mean is taken as the thermal conductivity result.

[0086] The principles of "weighing in air and weighing in liquid" in Archimedes' hydrostatic weighing method, the requirements for wetting agent and air bubble removal, and the density calculation relationship can be found in the description of ISO 3369 2006.

[0087] GB / T 1423 1996 can be referenced as a standard for density determination;

[0088] The test results are shown in the table below:

[0089] Table 2: Comprehensive Performance Test Results of Printed Samples

[0090] Sample number Tensile strength (MPa) Yield strength MPa Elongation % Impact absorption energy KV2 J Hardness HRC Thermal conductivity W per mK T1 1860 1335 16.2 34 49 25.6 T2 1885 1328 15.6 33 50 25.1 T3 1840 1316 16.0 35 49 25.4 average value 1862 1326 15.9 34 49.3 25.4

[0091] Among them, the tensile strength of the printed sample shall not be less than 1800MPa; the yield strength shall not be less than 1300MPa; the elongation shall not be less than 15%; the room temperature impact energy KV2 shall not be less than 32J; the hardness HRC shall not be less than 48; and the room temperature thermal conductivity shall not be less than 25W / (m·K).

[0092] As can be seen from the above embodiments, when the composition range, oxygen content and sphericity of the powder material meet the limitations in Examples 1 and 2, and the printed sample is prepared using the above selective laser melting parameters, a printed sample with high strength, high toughness and high thermal conductivity can be stably obtained.

[0093] Example 5:

[0094] like Figure 1-5 As shown, the printed sample, after quenching and two tempering treatments, meets the following requirements:

[0095] The tensile strength is not less than 1500MPa, the yield strength is not less than 1300MPa, the elongation is not less than 15%, the room temperature impact energy KV2 is not less than 36J, the hardness HRC is not less than 44, and the room temperature thermal conductivity is not less than 28W / (m·K).

[0096] In this embodiment, hot work die steel powder material is prepared using the formulation and atomization sieving process described in Example 2. Powder with a particle size of 15μm to 53μm is collected as target powder. The target powder is tested and found to have an oxygen content of 170ppm, an average sphericity of 94.5%, and a target particle size range yield of 35%. The powder material is used for subsequent selective laser melting and forming.

[0097] The above-mentioned powder material was used for selective laser melting and forming. The forming cavity was protected by an inert atmosphere. Before forming, the inert gas was replaced and the oxygen content in the cavity was reduced to less than 100 ppm. The substrate preheating temperature was set to 150°C; the laser power was set to 320W; the scanning speed was set to 800 mm per second; the scanning spacing was set to 0.10 mm; the layer thickness was set to 0.04 mm; the scanning strategy adopted was to rotate adjacent layers by 67°; and a printed sample blank was obtained by forming according to the above parameters.

[0098] The printed samples only undergo support removal and surface cleaning, without any heat treatment or surface strengthening treatment. Then, wire cutting is used to sample and machine to prepare tensile test specimens, impact test specimens, hardness test specimens and thermal conductivity test specimens.

[0099] The printed sample is placed in a vacuum heat treatment furnace or an inert atmosphere protection furnace for quenching and two tempering processes, as follows:

[0100] Quenching: Heat the sample to 1030℃ and hold for 30 minutes, then transfer it to oil to cool to below 80℃;

[0101] First tempering: Heat the sample to 560℃ and hold for 2 hours, then air cool to room temperature;

[0102] Second tempering: The sample was heated to 610℃ and held for 2 hours, then air-cooled to room temperature;

[0103] The above treatment yielded a sample after quenching and two tempering processes;

[0104] Tensile property testing: Sampling location and specimen preparation shall be carried out in accordance with GB / T 2975 2018, and tensile testing shall be carried out in accordance with GB / T 228.1 2021; the test temperature shall be 23℃, and force-displacement data shall be recorded and yield strength, tensile strength and elongation after fracture shall be calculated using an electronic universal testing machine; the number of specimens in each group shall not be less than 3, and the arithmetic mean shall be taken as the result.

[0105] Impact toughness testing was conducted: sampling and specimen preparation were carried out in accordance with GB / T 2975 2018, and impact testing was carried out in accordance with GB / T 229 2020; V-notch Charpy impact specimens were used with the notch direction kept consistent, the test temperature was 23℃, and the impact absorbed energy was expressed as KV2; the number of specimens in each group was not less than 3, and the arithmetic mean was taken as the result.

[0106] Hardness testing: Sampling and surface preparation shall be carried out in accordance with GB / T 2975 2018, and Rockwell hardness testing shall be carried out in accordance with GB / T 230.1 2018; HRC testing shall be carried out after the cross section of the sample is polished, and the measuring points shall avoid the edges and defect areas. The number of measuring points shall not be less than 5 points and the average value shall be taken as the result.

[0107] Thermal conductivity was tested, and the room temperature thermal diffusivity α was measured using the laser flash method. The sample density ρ and specific heat capacity Cp were also measured. The sample density ρ was tested using the Archimedes hydrostatic weighing method, referring to the density determination method of ISO 3369 2006 or GB / T 1423 1996.

[0108] After the sample is degreased and dried, the mass m1 of the sample in air and the apparent mass m2 of the sample when it is completely immersed in deionized water at a temperature of 20℃ to 25℃ are weighed using an analytical balance. When weighing, the sample surface and air bubbles are removed and a small amount of wetting agent can be added.

[0109] The density ρw of water is obtained from the table based on the water temperature. The density ρ of the sample is calculated by ρ = m1 ÷ (m1 - m2) × ρw.

[0110] If the sample has open pores that absorb water, liquid paraffin can be used to seal the pores before weighing to correct the density calculation. The room temperature thermal conductivity λ can be calculated according to λ=α×ρ×Cp.

[0111] Each group of samples shall contain no fewer than 3 pieces, and the arithmetic mean shall be taken as the result.

[0112] The comprehensive performance test results of the samples after quenching and two tempering treatments are shown in the table below:

[0113] Table 3: Comprehensive Performance Test Results of Samples After Heat Treatment

[0114] Sample number Tensile strength (MPa) Yield strength MPa Elongation % Impact absorption energy KV2 J Hardness HRC Thermal conductivity W per mK HT1 1565 1342 16.1 38 45 28.6 HT2 1540 1328 15.4 37 44 29.1 HT3 1580 1335 15.8 39 45 28.4 average value 1562 1335 15.8 38 44.7 28.7

[0115] Among them, the tensile strength is not less than 1500MPa; the yield strength is not less than 1300MPa; the elongation is not less than 15%; the room temperature impact energy KV2 is not less than 36J; the hardness HRC is not less than 44; and the room temperature thermal conductivity is not less than 28W / (m·K).

[0116] As can be seen from the above embodiments, under the premise that the composition range and powder quality index of the powder material meet the requirements of Embodiments 1 and 2, the printed sample can be obtained by selective laser melting forming, and after quenching and two tempering treatments, a heat-treated sample that simultaneously meets the requirements of high strength, high toughness, appropriate hardness and high thermal conductivity can be stably obtained.

[0117] Example 6:

[0118] like Figure 1-5 As shown, when the powder material is used in selective laser melting additive manufacturing, the density of the formed part reaches more than 99% when the substrate preheating temperature is 100°C to 200°C, the laser power is 250W to 400W, the scanning speed is 600mm / s to 1000mm / s, the scanning spacing is 0.06mm to 0.14mm, and the layer thickness is 0.03mm to 0.06mm.

[0119] In this embodiment, hot work die steel powder material for additive manufacturing was prepared using the formulation and powder preparation and sieving process described in Example 2. Powder with a particle size of 15μm to 53μm was collected as powder for forming. The quality indicators of the powder were confirmed, and the average sphericity of the powder was 94.5%, the oxygen content of the powder was 170ppm, and the yield of powder in the target particle size range was 35%.

[0120] The powder was dried in a drying oven at 60°C for 6 hours and then sealed for later use to reduce the impact of moisture absorption and oxygenation on the molding stability.

[0121] Selective laser melting equipment with inert atmosphere protection is used for forming;

[0122] Before forming, the forming cavity is purged with inert gas to ensure that the oxygen content in the cavity does not exceed 100 ppm; the substrate is made of stainless steel and is cleaned.

[0123] The substrate preheating temperature is set in the range of 100℃ to 200℃; a cubic density sample is formed under each set of parameters. The cubic sample has a side length of 10mm. After forming, only the support is removed and the surface is cleaned. No heat treatment is performed.

[0124] To verify that a density of over 99% can be achieved within the parameter window, this embodiment selects a representative combination covering the window boundary and the window value. This combination simultaneously covers the following situations:

[0125] A combination of low power and low scan speed;

[0126] High power combined with high scan speed;

[0127] Combination of small scanning spacing and thin layer thickness;

[0128] Large scanning spacing combined with thick layer thickness;

[0129] Median parameter combination;

[0130] Each set of parameters requires the independent forming of no fewer than three specimens, and the density of each specimen must be measured.

[0131] The Archimedes method was used to determine the density of the sample in deionized water. The Archimedes method density determination followed GB / T 3850-2015, the method for determining the density of dense sintered metal materials and cemented carbides, and was equivalent to the buoyancy method in ISO 3369. The deionized water was placed in a constant-temperature water bath, with the temperature controlled between 20°C and 23°C and the temperature fluctuation not exceeding 1°C. The water temperature was recorded to correct the liquid density ρ_water using a table. An analytical balance with a graduation value not exceeding 0.0001 g and a density measuring frame or suspension device was used to ensure stable sample immersion weighing. After ultrasonic cleaning, the sample was rinsed with anhydrous ethanol and dried at 60°C for 30-60 minutes, then cooled to room temperature before weighing its mass in air (m1). The sample was then completely immersed in deionized water using a thin wire or basket, avoiding contact with the container walls and bottom, and the immersion mass (m2) was weighed. The deionized water was deionized before immersion. Gas treatment is performed, and a neutral wetting agent with a volume fraction not exceeding 0.1% is added if necessary to reduce bubble adhesion; after immersion, the sample is gently shaken and visible bubbles on the surface are removed with a soft brush, and the reading is taken after standing for 30 seconds; the bulk density of the sample is calculated by dividing m1 by m1 minus m2 and then multiplying by ρwater; the compacted density is calculated by multiplying the ratio of bulk density ρ to theoretical density ρ0 by 100%; when the sample has open pores that need to be sealed by vacuum impregnation, low viscosity epoxy resin is selected as the impregnation medium and kept under vacuum conditions not exceeding 10 -20 Pa for 10 to 20 minutes, then restored to normal pressure and cured, and the density and compacted density are calculated according to the above weighing steps;

[0132] Before the test, the sample was ultrasonically cleaned to remove the powder adhering to the surface. If there were obvious openings on the sample surface, they were sealed by vacuum impregnation before the test. At least 3 samples were tested for each parameter group and the arithmetic mean was taken as the density result of the parameter group. At the same time, at least 1 sample was selected for metallographic preparation for each parameter group and the cross-sectional pore area fraction was statistically analyzed by image analysis to serve as an auxiliary verification of the Archimedes method results.

[0133] The compaction results for each parameter group are shown in the table below:

[0134] Selected area laser melting parameter window and density verification results table (#Table 4)

[0135] Group number Preheating temperature °C Laser power W Scanning speed mm per second Scan spacing (mm) Layer thickness (mm) Density 1% Density 2% Density 3% Average density % Cross-sectional pore area ratio % G1 100 250 600 0.06 0.03 99.62 99.58 99.65 99.62 0.35 G2 100 250 1000 0.14 0.06 99.10 99.06 99.12 99.09 0.85 G3 150 320 800 0.10 0.04 99.96 99.94 99.95 99.95 0.08 G4 150 400 600 0.14 0.03 99.41 99.38 99.45 99.41 0.52 G5 200 400 1000 0.06 0.06 99.28 99.22 99.31 99.27 0.62 G6 200 320 800 0.14 0.03 99.53 99.49 99.56 99.53 0.40

[0136] As shown in Table 4, within the parameter window of substrate preheating temperature of 100℃ to 200℃, laser power of 250W to 400W, scanning speed of 600mm / s to 1000mm / s, scanning spacing of 0.06mm to 0.14mm, and layer thickness of 0.03mm to 0.06mm, the density of the obtained molded parts reached over 99% by verifying representative combinations of window boundaries and values ​​within the window. At the same time, the porosity fraction of the metallographic cross-section was at a low level, which can provide auxiliary verification for the high density results measured by the Archimedes method.

[0137] Example 7:

[0138] A method for preparing hot work die steel powder material for additive manufacturing, such as Figure 1-5 As shown, it includes the following steps:

[0139] S1. Under an inert atmosphere, iron-based binary alloy or pure metal raw materials are batched according to the element mass percentages specified in Example 1 and fed into the corundum crucible in the melting chamber, and the vacuum is evacuated to 1×10⁻⁶. -2 After Pa is below, the temperature is raised and smelted to 1550°C to 1650°C and maintained to obtain a uniform alloy melt. Then the melt temperature is adjusted to 1500°C to 1600°C and refined for 8 to 14 minutes.

[0140] S2. Under the protection of an inert gas atomizing medium, the alloy melt is introduced into the atomizing area, and Ar or N2 is used as the atomizing medium and the alloy melt is atomized at an atomizing pressure of 2.0 MPa to 4.0 MPa, so that it is broken up and quickly solidified to form a pre-made powder.

[0141] S3. After the pre-made powder cools down, it is sieved in multiple stages using an ultrasonic vibrating screen with screens of 100 mesh, 230 mesh and 500 mesh in sequence. Powder with a particle size of 15μm to 53μm is collected as hot work die steel powder material for additive manufacturing.

[0142] Wherein, the yield of the powder with a particle size of 15μm to 53μm is not less than 30%, the sphericity of the powder is higher than 90%, and the oxygen content of the powder is not higher than 200ppm;

[0143] Before the melting and refining in step S1, the melting chamber is first purged with an inert gas, either Ar or N2, 2 to 3 times, followed by evacuation to a vacuum of 1×10⁻⁶. -2 After the Pa is below, the temperature is raised for melting to reduce the oxygen introduction during the melting and atomization process and to ensure that the oxygen content of the resulting powder with a particle size of 15μm to 53μm is not higher than 200ppm.

[0144] In step S1, the furnace exit temperature of the melt is 1550°C to 1650°C, the refining temperature is 1500°C to 1600°C, the refining time is 8 min to 14 min, and the furnace exit temperature is 50°C to 150°C higher than the refining temperature.

[0145] The atomization pressure in step S2 is 2.0 MPa to 4.0 MPa, the atomization medium is Ar or N2, and the flow rate of the atomization medium is 1 to 3 times the local speed of sound in the atomization region.

[0146] In step S3, the multi-stage sieving process uses a first sieve of 50 to 100 mesh, a second sieve of 200 to 250 mesh, and a third sieve of 500 to 550 mesh to obtain powder with a particle size of 15 μm to 53 μm.

[0147] In this embodiment, iron-based binary alloys and pure metals are selected as raw materials for batching. The mass percentage of each element meets the range specified in Example 1, and the sum of the mass percentages of Ce and Mg is between 0.03% and 0.10%, the sum of the mass percentages of Y and La is between 0.01% and 0.06%, and the sum of the mass percentages of Ta and Nb is between 0.02% and 0.15%. The batched raw materials are loaded into the corundum crucible in the melting chamber and the furnace is sealed.

[0148] Before heating and melting, the melting chamber is purged with an inert gas, specifically Ar. The purging process is repeated three times. Each purging involves introducing Ar into the melting chamber at a pressure of 0.05 MPa to 0.15 MPa and maintaining this pressure for 30 to 120 seconds before releasing it, followed by the next purging. After the purging is complete, the melting chamber is evacuated to a vacuum of 1 × 10⁻⁶ MPa. -2 Pa is kept below and maintained to reduce oxygen introduction during smelting and subsequent atomization processes;

[0149] Under an inert atmosphere, the melt is heated to 1650℃ and held for 15 minutes to promote homogenization of the melt composition and prepare for tapping. Then the melt temperature is adjusted to 1550℃ and refined for 12 minutes. The temperature difference between the tapping temperature of 1650℃ and the refining temperature of 1550℃ is 100℃, which is within the range of 50℃ to 150℃.

[0150] The alloy melt is introduced into the atomization zone. N2 is selected as the atomization medium, and the atomization pressure is set to 3.0 MPa, within the range of 2.0 MPa to 4.0 MPa. The flow rate of the atomization medium is calibrated according to the local speed of sound in the atomization zone and controlled at twice the local speed of sound. The local speed of sound, 'a', is calculated based on the real-time temperature T of the atomization zone. The temperature T is collected by a temperature sensing element located 50 mm to 150 mm downstream of the atomizing nozzle and refreshed every 1 to 5 seconds. The local speed of sound, 'a', is calculated using the formula a = √(κRT), where κ is the adiabatic index of the atomizing medium, R is the gas constant of the atomizing medium, and T is the real-time temperature in Kelvin. Closed-loop flow rate control is achieved by adjusting the total pressure of the atomizing medium supply and the nozzle opening, ensuring that the nozzle outlet flow rate, 'v', satisfies the ratio of 'v' to 'a' being within the range of 1 to 3. Under these conditions, the alloy melt is atomized, causing it to break down and rapidly solidify to form a pre-formed powder. The pre-formed powder is cooled, collected, and sealed for transport under an inert atmosphere.

[0151] After the pre-made powder cools, it is subjected to multi-stage sieving using an ultrasonic vibrating screen. The first screen is 100 mesh with particles ranging from 50 to 100 mesh; the second screen is 230 mesh with particles ranging from 200 to 250 mesh; and the third screen is 500 mesh with particles ranging from 500 to 550 mesh. After sieving, the powder within the target particle size range is collected, weighed, and the yield is calculated. At the same time, a laser particle size analyzer is used to verify the particle size of the target powder. If the verification results show that the lower limit of the particle size distribution is not less than 15 μm and the upper limit is not greater than 53 μm, the collected powder is determined to be within the particle size range of 15 μm to 53 μm.

[0152] The oxygen content of the target powder sample was determined using an inert gas melting oxygen-nitrogen analyzer. Each sample had a mass of not less than 1g, and the determination was repeated 3 times. The arithmetic mean was taken as the oxygen content result.

[0153] The powder morphology images were obtained by scanning electron microscopy. No less than 300 particles were randomly selected, and the sphericity was calculated by image analysis software using the equivalent circle area method. The average value was taken as the sphericity result.

[0154] The yield is calculated as the ratio of the mass of the powder in the target particle size range after sieving to the total mass of the pre-made powder.

[0155] Table 5: Results of Process Conditions and Powder Quality Indicators

[0156] project numerical values unit Cleaning gas Ar Number of cleaning times 3 Second-rate vacuum degree 1×10⁻² Pa tapping temperature 1650 ℃ Refining temperature 1550 ℃ temperature difference 100 ℃ Refining time 12 min atomized gas <![CDATA[N2]]> atomization pressure 3.0 MPa Volume ratio V / A 2 ratio Screen 1 100 Head Screen 2 230 Head sieve 3 500 Head Target particle size range 15 to 53 μm Target particle size range yield 34 % Oxygen content 185 ppm Mean sphericity 94.2 %

[0157] As shown in Table 5, the method involved three replacements followed by vacuuming to 1×10⁻⁶. -2 After the pressure is below Pa, the powder is smelted and refined. Then, it is atomized at 3.0 MPa and the nozzle outlet flow rate is controlled to twice the local speed of sound. Combined with ultrasonic sieving of 100 mesh, 230 mesh and 500 mesh, the target particle size range of powder can be obtained. The yield of powder with a particle size of 15 μm to 53 μm is not less than 30%, the sphericity of the powder is not less than 94%, and the oxygen content of the powder is not higher than 200 ppm.

[0158] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0159] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the present invention. Various changes and modifications can be made to the present invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed.

Claims

1. A hot-work die steel powder material for additive manufacturing, characterized in that, It includes the following elements in the following mass percentages: C 0.2% to 0.35%, Cr 2.5% to 5.5%, Mo 2% to 4%, V 0.1% to 0.6%, Si 0.1% to 0.6%, Mn 0.1% to 0.6%, Ta and Nb totaling 0.02% to 0.15%, Ce and Mg totaling 0.03% to 0.10%, Y and La totaling 0.01% to 0.06%, Ni 0% to 0.2%, Cu 0% to 0.2%, P 0% to 0.05%, N 0% to 0.01%, O 0% to 0.05%, with the remainder being Fe; The powder material has a particle size of 15μm to 53μm, the yield of the powder in the particle size range is not less than 30%, and the sphericity of the powder is higher than 90%. Furthermore, the density of the powder material reaches over 99% after selective laser melting and forming.

2. The hot work die steel powder material for additive manufacturing according to claim 1, characterized in that, The printed sample obtained by selective laser melting of the powder material satisfies the following requirements: The tensile strength is not less than 1800MPa, the yield strength is not less than 1300MPa, the elongation is not less than 15%, the room temperature impact energy KV2 is not less than 32J, the hardness HRC is not less than 48, and the room temperature thermal conductivity is not less than 25W / (m·K).

3. The hot work die steel powder material for additive manufacturing according to claim 2, characterized in that, The printed sample, after quenching and two tempering processes, meets the following requirements: The tensile strength is not less than 1500MPa, the yield strength is not less than 1300MPa, the elongation is not less than 15%, the room temperature impact energy KV2 is not less than 36J, the hardness HRC is not less than 44, and the room temperature thermal conductivity is not less than 28W / (m·K).

4. The hot work die steel powder material for additive manufacturing according to claim 1, characterized in that, When the powder material is used in selective laser melting additive manufacturing, the density of the formed part reaches over 99% under the following conditions: substrate preheating temperature of 100°C to 200°C, laser power of 250W to 400W, scanning speed of 600mm / s to 1000mm / s, scanning spacing of 0.06mm to 0.14mm, and layer thickness of 0.03mm to 0.06mm.

5. A method for preparing hot work die steel powder material for additive manufacturing, based on the hot work die steel powder material for additive manufacturing according to any one of claims 1-4, characterized in that, Includes the following steps: S1. Under an inert atmosphere, iron-based binary alloy or pure metal raw materials are batched according to a defined element mass percentage and fed into the corundum crucible in the melting chamber, and a vacuum of 1×10⁻⁶ is applied. -2 After Pa is below, the temperature is raised and smelted to 1550°C to 1650°C and maintained to obtain a uniform alloy melt. Then the melt temperature is adjusted to 1500°C to 1600°C and refined for 8 to 14 minutes. S2. Under the protection of an inert gas atomizing medium, the alloy melt is introduced into the atomizing area, and Ar or N2 is used as the atomizing medium and the alloy melt is atomized at an atomizing pressure of 2.0 MPa to 4.0 MPa, so that it is broken up and quickly solidified to form a pre-made powder. S3. After the pre-made powder cools down, it is sieved in multiple stages using an ultrasonic vibrating screen with screens of 100 mesh, 230 mesh and 500 mesh in sequence. Powder with a particle size of 15μm to 53μm is collected as hot work die steel powder material for additive manufacturing. The powder with a particle size of 15μm to 53μm has a yield of not less than 30%, a sphericity of more than 90%, and an oxygen content of not more than 200ppm.

6. The method for preparing hot work die steel powder material for additive manufacturing according to claim 5, characterized in that, Before the melting and refining in step S1, the melting chamber is first purged with an inert gas, either Ar or N2, 2 to 3 times, followed by evacuation to a vacuum of 1×10⁻⁶. -2 After the temperature drops below Pa, the powder is heated and smelted to reduce the oxygen introduction during the smelting and atomization process and ensure that the oxygen content of the resulting powder with a particle size of 15 μm to 53 μm does not exceed 200 ppm.

7. The method for preparing hot work die steel powder material for additive manufacturing according to claim 6, characterized in that, In step S1, the furnace exit temperature of the melt is 1550°C to 1650°C, the refining temperature is 1500°C to 1600°C, the refining time is 8 min to 14 min, and the furnace exit temperature is 50°C to 150°C higher than the refining temperature. The atomization pressure in step S2 is 2.0 MPa to 4.0 MPa, the atomization medium is Ar or N2, and the flow rate of the atomization medium is 1 to 3 times the local speed of sound in the atomization region. In step S3, the first sieve for multi-stage sieving is 50 to 100 mesh, the second sieve is 200 to 250 mesh, and the third sieve is 500 to 550 mesh, in order to obtain powder with a particle size of 15 μm to 53 μm.

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