Method for improving mechanical properties of additively manufactured h13 steel

Abstract

The present application relates to the technical field of additive manufacturing die steel, and particularly relates to a method for improving mechanical properties of additive manufacturing H13 steel. The specific method comprises the following steps: using H13 steel powder for additive manufacturing to obtain an H13 steel die part; sequentially performing stress relief annealing, hot isostatic pressing treatment, solid solution quenching treatment and secondary aging treatment on the H13 steel die part to obtain an H13 strong and tough die steel. The present application mainly combines hot isostatic pressing and heat treatment system to solve the problems of anisotropy of structure and performance, low impact toughness, internal stress and surface micro defects of the existing additive manufacturing die component, and segregation and internal stress caused by uneven cooling in the existing manufacturing method, which can also cause the problem of easy crack of H13 die steel.

Description

Technical Field

[0001] This invention relates to the field of additive manufacturing die steel technology, and specifically to a method for improving the mechanical properties of additive manufacturing H13 steel. Background Technology

[0002] In the development of mold steel, traditional 3Gr2W8V mold steel has significant deficiencies in toughness and thermal fatigue resistance, leading to frequent failures in practical applications and failing to meet the demands of high-precision, high-quality molds. To overcome these shortcomings, researchers developed chromium-based mold steels and, based on this, optimized alloy elements to design H13 steel, also known as 4Cr5MoSiV1 steel. H13 steel, with its excellent resistance to thermal cracking, thermal fatigue resistance, high resistance to thermal softening, and high-temperature wear resistance, has rapidly become the preferred material for high-precision, high-quality molds such as die-casting molds, extrusion molds, injection molds, forging molds, and hot extrusion molds.

[0003] However, with the development of the manufacturing industry, the working environment of molds is becoming increasingly complex, and the performance requirements for mold materials are also becoming higher. Hot work molds not only need to withstand various loads such as impact, vibration, friction, tension, bending and torsion, but also require materials to have good wear resistance, high red hardness, high temperature thermal stability, and toughness. These requirements pose challenges to traditional mold steel preparation technology.

[0004] Additive manufacturing, or 3D printing, is a material-structure-performance integrated fabrication technology that provides excellent design ideas for conformal cooling molds. Unlike traditional metallurgical processes, additive manufacturing molds have the advantage of directly forming complex structures, refining grains, and reducing precipitate size, thereby significantly improving mold performance. However, additive manufacturing technology still has some challenges, such as anisotropy of microstructure and properties, low impact toughness, internal stress, and microscopic defects like micropores. These microscopic defects can lead to reduced mold fatigue performance and affect service life.

[0005] Related studies have shown that intrinsic tempering caused by repeated heat flow parallel to the construction direction leads to localized precipitation of secondary carbides and decomposition of highly supersaturated tempered martensite, causing performance differences between parallel and perpendicular directions. This results in better tensile properties parallel to the loading direction compared to the direction perpendicular to the construction direction. For example, the tensile properties parallel to the loading direction are a tensile strength of 1600 MPa and an elongation of 2.25%, while those perpendicular to the construction direction are a tensile strength of 1200 MPa and an elongation of 1.5%. To improve the microstructure and properties of additive manufacturing dies, researchers have explored various methods. Among them, hot isostatic pressing (HIP) has a unique thermo-compression coupling effect, enabling it to improve the microstructure while eliminating internal hole defects in parts. Therefore, it has been increasingly applied to the microstructure and property control of additive manufacturing parts. However, segregation and internal stress caused by uneven cooling can also lead to cracking in H13 die steel. Summary of the Invention

[0006] To address the shortcomings of additive manufacturing technology, the present invention aims to provide a method for improving the mechanical properties of additively manufactured H13 steel. This invention primarily utilizes a combination of hot isostatic pressing and heat treatment to solve the problems of anisotropy in microstructure and properties, low impact toughness, internal stress, and surface micro-defects in existing additive manufacturing die components. Furthermore, the segregation and internal stress caused by uneven cooling in existing manufacturing methods can also lead to cracking in H13 die steel.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows.

[0008] This invention provides a method for improving the mechanical properties of additively manufactured H13 steel, comprising the following steps:

[0009] H13 steel mold parts were obtained by additive manufacturing using H13 steel powder.

[0010] H13 strong and tough mold steel was prepared by sequentially performing stress-relieving annealing, hot isostatic pressing, solution quenching and secondary aging on H13 steel mold parts.

[0011] The hot isostatic pressing method is as follows: heat to 1120℃~1130℃, control the pressure at 140MPa~160MPa, and hold for 2.5h~3h.

[0012] The solution quenching process is as follows: heat to 1020℃~1040℃, hold for 50min~60min, and then use oil quenching to cool down to 360℃~380℃.

[0013] The method for secondary aging treatment is as follows: adjust the temperature to 580℃~600℃, maintain it for 180min~200min, cool it down to below 200℃, and allow it to cool naturally after opening the furnace; after tempering under the same conditions, cool it to room temperature.

[0014] Preferably, the particle size of H13 steel powder is 5μm to 120μm.

[0015] Preferably, the particle size of H13 steel powder meets the following conditions:

[0016] The mass percentage of H13 steel powder with a particle size of less than 50 μm is ~30%, and the mass percentage of H13 steel powder with a particle size of greater than 50 μm and less than 120 μm is ~70%.

[0017] Preferably, the particle size of H13 steel powder meets the following conditions:

[0018] The mass percentage of H13 steel powder with a particle size of less than 50 μm is ~30%, the mass percentage of H13 steel powder with a particle size of 50 μm to 90 μm is ~60%, and the mass percentage of H13 steel powder with a particle size of 90 μm to 120 μm is ~10%.

[0019] Preferably, the H13 steel powder is composed of the following elements by mass percentage:

[0020] 0.38%–0.40% C, 0.8%–1.0% Si, 0.30%–0.35% Mn, 4.85%–5.20% Cr, 1.3%–1.4% Mo, 0.8%–0.85% V, 0%–0.010% P, 0%–0.010% S, 0%–0.60% residual elements, balance Fe, total 100%.

[0021] The preferred method for preparing H13 steel mold parts is as follows:

[0022] The H13 steel powder is dried, and then filled and spread.

[0023] Set the parameters as follows: melting parameters: power current 14.0mA~17.0mA, scanning speed 4.500m / s~5.500m / s, defocusing amount 0V~0.500V, and beam size 0.100mm; preheating parameters: maximum current for powder bed preheating 40mA, average current for powder bed preheating 12mA~15mA, minimum setting time for powder bed preheating 10s~14s, and maximum setting time for powder bed preheating not exceeding 20s.

[0024] The temperature is preheated to 750℃~800℃ before printing to obtain H13 steel mold parts.

[0025] The preferred method for stress-relief annealing is as follows: heat to 640℃~650℃, hold for 3.5h~4h, cool with the furnace to 200℃ after holding, and air-cool to room temperature after removal from the furnace.

[0026] Preferably, the H13 steel powder is prepared from H13 steel by plasma rotary atomization.

[0027] Preferably, the H13 steel powder is a spherical alloy powder.

[0028] The beneficial effects of this invention are:

[0029] 1. This invention mainly combines hot isostatic pressing and heat treatment to solve the problems of anisotropy in microstructure and properties, low impact toughness, internal stress and surface micro-defects in existing additive manufacturing mold components, as well as segregation and internal stress caused by uneven cooling in existing manufacturing methods, which can also lead to cracking of H13 mold steel.

[0030] 2. The hot isostatic pressing of the present invention can significantly reduce the micro-defects and residual stress introduced by printing. The subsequent high-temperature solution treatment can homogenize the structure and dissolve the carbides. The smaller the spherical carbide particles and the more uniform the distribution, the easier it is to obtain a good spherical structure. The subsequent aging treatment further balances the strength and toughness, so that the quality of the mold is well guaranteed.

[0031] 3. This invention proposes an integrated manufacturing method for the entire process from raw materials to mature components; the resulting components have a density of ≥99.9%, are basically free of internal defects, and achieve simultaneous improvement in strength and toughness after heat treatment, with tensile strength ≥1600MPa, yield strength ≥1050MPa, and elongation after fracture ≥10%.

[0032] 4. This invention utilizes electron beam powder bed additive manufacturing technology, which effectively prevents oxidation caused by excessively high temperatures. The composition is uniform and the microstructure is refined. By using additive manufacturing parts and their heat treatment processes, large-size, complex-structure H13 steel mold parts can be integrally formed with a density ≥99.9% and excellent comprehensive mechanical properties. Subsequent heat treatment can control its microstructure, resulting in fewer pore defects. By controlling the size, morphology, quantity, precipitation location, and microstructure of carbide precipitates, the strength and toughness of the material are simultaneously improved. Attached Figure Description

[0033] Figure 1 This is a SEM image of the surface morphology of the H13 strong and tough mold steel powder prepared in Example 1 of this invention.

[0034] Figure 2 These are macroscopic morphology images of SEBM-state H13 steel prepared in Examples 1 to 4 of this invention.

[0035] Figure 3 This is a schematic diagram of hot isostatic pressing and heat treatment in Embodiment 1 of the present invention.

[0036] Figure 4 These are SEM surface morphology images of SEBM-state H13 steel and hot isostatically pressed H13 steel prepared in Example 1 of this invention. Among them, (a) is SEBM-state H13 steel; (b) is hot isostatically pressed H13 steel. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0038] 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.

[0039] Spherical H13 steel powder is mainly prepared from H13 steel by plasma rotary atomization. The particle size of the spherical alloy powder is 5-120 micrometers, and the purity is ≥99.99%.

[0040] The method for preparing the spherical alloy powder includes the following steps:

[0041] Step 1: Prepare the H13 steel bar in its factory condition (rolled and annealed) into a standard part for the plasma rotating electrode atomization process, with L = 160 ± 10 mm and φ = 29 ± 0.5 mm.

[0042] Step 2: Clamp the H13 steel bar from Step 1 onto the motor spindle. The motor spindle drives the finished alloy bar to rotate at high speed. When the speed reaches 10000 r / min to 15000 r / min, the plasma tungsten electrode gun applies a current of 1200 A to 1500 A to ignite the arc, melting the end face of the finished alloy bar and forming a molten pool. Under the centrifugal force of high-speed rotation, the molten liquid metal is thrown out at high speed, further forming fine droplets. At the same time, the droplets spheroidize due to surface tension. Throughout the entire process, the vacuum degree of the atomization chamber is maintained at no less than 4.0 × 10⁻⁶. -2 Pa, and argon gas is continuously introduced for protection.

[0043] Step 3: Natural cooling, sieving, to obtain spherical alloy powder with a particle size of 5 micrometers to 120 micrometers.

[0044] The H13 steel powder is composed of the following elements by mass percentage:

[0045] 0.38%–0.40% C, 0.8%–1.0% Si, 0.30%–0.35% Mn, 4.85%–5.20% Cr, 1.3%–1.4% Mo, 0.8%–0.85% V, 0%–0.010% P, 0%–0.010% S, 0%–0.60% residual elements, balance Fe, total 100%.

[0046] The H13 steel powder is screened and batched, and by mass ratio, H13 steel powder with a particle size of less than 120 μm is screened as raw material, of which H13 steel powder with a particle size of less than 50 μm accounts for ~30%, and H13 steel powder with a particle size of greater than 50 μm and less than 120 μm accounts for ~70%.

[0047] The preparation method of H13 mold steel includes the following steps:

[0048] S1. Place the above-prepared ingredients in a vacuum drying oven and dry them at 100℃~110℃ for 2h~3h.

[0049] S2. Load the dried ingredients from S1 into the EBM equipment and perform substrate loading and leveling.

[0050] S2. Based on the shape and size of the metal part to be processed, a 3D model of a 55*10*55mm³ cuboid is constructed using 3D modeling software, and 3D slicing is performed with a slice thickness of 50μm. The print format file is exported, and the data information of the STL file is sent to the additive manufacturing molding equipment.

[0051] S3. Set the parameters of the solid model imported in step S2: power current 14.0mA~17.0mA, scanning speed 4.500m / s~5.500m / s, defocusing amount 0V~0.500V, beam size 0.100mm, melt pool spacing between 0.08mm and 0.15mm, and substrate preheating temperature between 700-800℃.

[0052] S4. Continuous vacuuming is introduced to ensure a high vacuum level in the forming chamber. High-purity helium is continuously introduced to reduce the charge accumulation effect. Data is loaded and the final mold part is printed layer by layer.

[0053] The technical solution of the present invention will be further described below through specific embodiments.

[0054] In the following embodiments, unless otherwise specified, the methods described are conventional methods; and unless otherwise specified, the reagents and materials described are commercially available.

[0055] Example 1

[0056] A method for improving the mechanical properties of additively manufactured H13 steel includes the following steps:

[0057] S1. Preparation of H13 mold steel samples by electron beam powder bed melting:

[0058] S1.1 Pre-printing preparation: Operators should take personal protective measures and perform pre-printing preparations, including checking the filament lifespan. If the required printing time exceeds the existing filament lifespan, the filament should be replaced. Clean the forming chamber and electron gun to ensure cleanliness. Install the substrate by adjusting the support screws under the substrate to ensure that the substrate is on the same horizontal plane and the height difference with the surrounding platforms.

[0059] S1.2 Powder pretreatment and filling: The prepared spherical H13 steel powder is dried at 110℃ for 3 hours, then cooled to room temperature and air-dried for 1 hour to obtain dried metal powder; the required metal powder is then added to the powder chamber, especially the bottom and sides of the substrate, which need to be filled tightly with metal powder.

[0060] S1.3 Powder spreading and vacuuming: After the preparation work is completed, a single layer of powder is spread to ensure that the H13 powder is evenly spread on the substrate and the thickness does not exceed 0.05mm. Clean the sealing ring of the heat insulation cover, the molding chamber door and the safety glass with a lint-free wiping paper dipped in anhydrous ethanol. Close the chamber door and vacuum.

[0061] S1.4 Process parameter adjustment: Based on the shape and dimensions of the metal part to be processed, a 55×10×55mm model is constructed using 3D modeling software. 3 A 3D model of a cuboid is created and sliced ​​into 3D slices with a thickness of 50μm. The resulting printable file is exported, and the data from the STL file is transmitted to the additive manufacturing equipment.

[0062] The imported solid model was configured with the following parameters: melting parameters: power current 15.0mA, scanning speed 5.000m / s, defocusing amount 0.500V, and spot size 0.100mm; preheating parameters: maximum powder bed preheating current 40.00mA, average powder bed preheating current 15.00mA, and powder bed preheating time 14.000s. Substrate preheating was performed using a stepped preheating method, holding at 300℃ and 600℃ for 10 minutes each to ensure sufficient preheating. Printing was then initiated after preheating to 750℃.

[0063] S1.5 Printing: Turn off the preheating, then introduce helium gas with a purity of ≥99.99%, load the data, and print layer by layer to obtain the printed mold part of the H13 mold steel sample.

[0064] S2, Stress-relieving annealing:

[0065] Clean the surface of oil, grease, or other contaminants using industrial alcohol or industrial acetone. Place the printed mold part manufactured in the previous stage into the vacuum heating furnace, ensuring the thermocouple is as close to the part as possible, and evacuate to 10°C. -1 Pa. The temperature was increased to 650℃ at a heating rate of 10℃ / min, and held at this temperature for 4 hours. After the holding period, the temperature was cooled to 200℃ in the furnace, and then air-cooled to room temperature after being removed from the furnace, thus completing the vacuum stress relief treatment of the printed mold part.

[0066] S3, Hot Isostatic Pressing:

[0067] Clean the surface of the printed mold part with industrial alcohol or industrial acetone to remove oil, grease or other contaminants. Place the vacuum-stress-relieved printed mold part into a hot isostatic press (HIP). Evacuate the HIP to 50 MPa and simultaneously start heating at a rate of 10°C / min to 15°C / min until the HIP reaches 1125°C. During this process, simultaneously increase the pressure to 150 MPa. Maintain the temperature at 1125°C and 150 MPa for 3.0 hours. After the heat and pressure holding is completed, cool the mold part to 500°C, reduce the pressure to atmospheric pressure, and finally cool it to 300°C. Then, introduce air to rapidly cool it to room temperature, thus completing the HIP treatment of the printed mold part.

[0068] S4. Solution quenching treatment:

[0069] Clean the surface of oil, grease, or other contaminants using industrial alcohol or industrial acetone. Place the hot isostatically pressed mold part into a vacuum furnace, ensuring the thermocouple is as close to the part as possible, and evacuate to 10°C. -1 Pa. Increase the temperature to 650℃ at 6℃ / min and hold for 10min. Continue increasing the temperature to 1020℃ at 10℃ / min and hold at this temperature for 50min. After holding, immediately transfer the printed mold part to a quenching oil medium for quenching.

[0070] S5. Secondary aging process:

[0071] Use industrial alcohol or industrial acetone to clean oil, grease or other dirt from surfaces.

[0072] First aging treatment: Place the solution-hardened printed mold part into a vacuum heating furnace, ensuring the thermocouple is as close as possible to the part, and evacuate to 10°C. -1 Pa. Adjust the temperature to 580℃ at a rate of 10℃ / min to 15℃ / min and maintain for 3 hours. Cool down to room temperature using air cooling.

[0073] Second aging treatment: Adjust the temperature to 580℃ at a rate of 10℃ / min to 15℃ / min and maintain for 3 hours. Open the furnace and allow it to cool naturally to room temperature to obtain strong and tough mold steel.

[0074] Example 2

[0075] A method for improving the mechanical properties of additively manufactured H13 steel is basically the same as the method in Example 1, except that the printing process parameters used in step S1.4 are as follows:

[0076] The substrate preheating temperature was 750℃, the power current was 15.00mA, the scanning speed was 4.500m / s, the defocusing amount was 0.500V, the beam spot size was 0.100mm, and the volume energy density was 40J / mm². 3 .

[0077] Example 3

[0078] A method for improving the mechanical properties of additively manufactured H13 steel is basically the same as the method in Example 1, except that the printing process parameters used in step S1.4 are as follows:

[0079] The substrate preheating temperature was 750℃, the power current was 15.00mA, the scanning speed was 5.500m / s, the defocusing amount was 0.500V, the beam spot size was 0.100mm, and the volume energy density was 32.73J / mm². 3 .

[0080] Example 4

[0081] A method for improving the mechanical properties of additively manufactured H13 steel is basically the same as that in Example 1, except that water is used as the quenching medium in step S4. In step S5, both the first and second aging treatments are performed at 580°C for 4 hours.

[0082] Example 5

[0083] A method for improving the mechanical properties of additively manufactured H13 steel is basically the same as the method in Example 1, except that in step S4, the temperature is further increased to 1050℃ at a rate of 10℃ / min. In step S5, both the first aging treatment and the second aging treatment are held at 600℃ for 3 hours.

[0084] Example 6

[0085] A method for improving the mechanical properties of additively manufactured H13 steel is basically the same as the method in Example 1, except that in step S4, the temperature is increased to 1020°C at a rate of 10°C / min and held at this temperature for 1 hour. In step S5, both the first and second aging treatments involve heating to 600°C, holding at this temperature for 3 hours, and then furnace cooling directly without removing the steel from the furnace.

[0086] Example 7

[0087] A method for improving the mechanical properties of additively manufactured H13 steel is basically the same as the method in Example 1, except that in step S5, the first aging treatment involves adjusting the temperature to 580°C at a rate of 10°C / min to 15°C / min, maintaining it for 3 hours, and then cooling it to room temperature using air cooling. The second aging treatment involves adjusting the temperature to 580°C at a rate of 10°C / min to 15°C / min, maintaining it for 3 hours, and then cooling it to room temperature using air cooling. The third aging treatment involves adjusting the temperature to 580°C at a rate of 10°C / min to 15°C / min, maintaining it for 3 hours, and then allowing it to cool naturally to room temperature after furnace opening, resulting in a strong and tough die steel.

[0088] Comparative Example 1

[0089] A method for improving the mechanical properties of additively manufactured H13 steel is basically the same as the method in Example 1, except that the vacuum stress-relief printed mold part prepared in Steps S1 and S2 of Example 1 is used as Comparative Example 1.

[0090] The method of Comparative Example 1 does not perform hot isostatic pressing, solution quenching and aging treatment in steps S3 to S5. After stress-relief annealing, the mechanical properties of the prepared printing mold parts are directly measured to explore the effect of the combination of hot isostatic pressing and heat treatment processes in this embodiment of the invention on improving the mechanical properties of H13 steel additive manufacturing parts. The test results are shown in Table 1.

[0091] Comparative Example 2

[0092] A method for improving the mechanical properties of additively manufactured H13 steel is basically the same as the method in Example 1, except that the printed mold part prepared by steps S1 to S4 in Example 1 is used as Comparative Example 2.

[0093] Comparative Example 2 does not perform the solution aging heat treatment in step S5. After solution quenching, the mechanical properties of the prepared printing mold parts are directly measured to explore the effect of the solution oil quenching combined with secondary aging heat treatment process of the present invention on improving the mechanical properties of H13 steel additive manufacturing parts. The test results are shown in Table 1.

[0094] Test 1: Temperature tensile mechanical property test.

[0095] Porosity, yield strength, tensile strength, elongation, maximum hardness and grain size of the samples prepared in Examples 1 to 7, and Comparative Examples 1 and 2 were analyzed respectively. The results are shown in Table 1.

[0096] Table 1. Tensile mechanical properties at room temperature

[0097] As can be seen from the test results in Table 1, the porosity and mechanical properties of the strong and tough die steel specimens are closely related. The heat treatment regime has little effect on the yield strength and tensile strength of the specimens, but has a significant effect on the elongation.

[0098] In Examples 1 to 3, the density of the prepared strong and tough mold steel samples gradually increased, which was mainly attributed to the poor fusion caused by low energy density; mechanical properties such as yield strength, tensile strength, elongation and maximum hardness showed a positive correlation with density.

[0099] Compared with Example 4, Example 1 uses quenching oil medium for quenching, which can significantly improve the yield strength, tensile strength, elongation and maximum hardness of the prepared strong and tough mold steel sample.

[0100] Compared with Example 1, Examples 5 and 6 show a decrease in mechanical properties due to changes in solution quenching and secondary aging treatment conditions.

[0101] Compared to Example 1, Example 7 reduces mechanical properties by increasing the number of failure treatments.

[0102] Compared with Comparative Example 1, Embodiment 1 of the present invention can significantly improve the elongation of strong and tough die steel specimens by combining hot isostatic pressing and heat treatment processes.

[0103] Compared with Comparative Example 2, Example 1 of the present invention can significantly improve the tensile strength, elongation and maximum hardness of the strong and tough die steel sample by using a solution oil quenching combined with a secondary aging heat treatment process.

[0104] In summary, the embodiments of the present invention reduce the impact of additive manufacturing defects on mechanical properties through a post-processing method combining hot isostatic pressing and heat treatment, providing a reference for the large-scale application of high-quality H13 molds in additive manufacturing.

[0105] Test 2: Macroscopic morphology analysis and microscopic morphology analysis.

[0106] Figure 1 This is a SEM image of the surface morphology of the H13 strong and tough mold steel powder prepared in Example 1 of this invention. Scanning electron microscopy (SEM) is a microscope used for this purpose.

[0107] Depend on Figure 1 It can be seen that the H13 strong and tough die steel powder prepared in Example 1 of this invention exhibits typical PREP powdering characteristics, with high sphericity and solidified dendrites on the powder surface. Furthermore, the particle size of the H13 strong and tough die steel powder prepared in Example 1 is 5 micrometers to 120 micrometers; its purity is ≥99.99%.

[0108] Figure 2 These are macroscopic morphology images of the SEBM-state H13 steel prepared in Examples 1 to 4 of this invention. Selective Electron Beam Melting (SEBM) is a technique where electron beam melting is used to selectively melt areas.

[0109] Depend on Figure 2 The printed sample showed a smooth surface and was free of defects such as warping and cracks.

[0110] Figure 3 This is a schematic diagram of hot isostatic pressing and heat treatment in Embodiment 1 of the present invention. Figure 4 These are SEM surface morphology images of SEBM-state H13 steel and hot isostatically pressed H13 steel prepared in Example 1 of this invention. Among them, (a) is SEBM-state H13 steel; (b) is hot isostatically pressed H13 steel.

[0111] Comparative analysis revealed that the H13 steel samples in the hot isostatic pressing state exhibited almost no porosity and high density after hot isostatic pressing treatment.

[0112] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements 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 improving the mechanical properties of additively manufactured H13 steel, characterized in that, Includes the following steps: H13 steel mold parts were obtained by additive manufacturing using H13 steel powder. H13 strong and tough mold steel was prepared by sequentially performing stress-relieving annealing, hot isostatic pressing, solution quenching and secondary aging on H13 steel mold parts. The hot isostatic pressing method is as follows: heat to 1120℃~1130℃, control the pressure at 140MPa~160MPa, and hold for 2.5h~3h. The solution quenching process is as follows: heat to 1020℃~1040℃, hold for 50min~60min, and then use oil quenching to cool down to 360℃~380℃. The method for secondary aging treatment is as follows: adjust the temperature to 580℃~600℃, maintain it for 180min~200min, cool it down to below 200℃, and allow it to cool naturally after opening the furnace; after tempering under the same conditions, cool it to room temperature. The particle size of H13 steel powder must meet the following conditions: The mass percentage of H13 steel powder with a particle size of less than 50 μm is ~30%, and the mass percentage of H13 steel powder with a particle size of greater than 50 μm and less than 120 μm is ~70%. H13 steel powder is composed of the following elements by mass percentage: 0.38%–0.40% C, 0.8%–1.0% Si, 0.30%–0.35% Mn, 4.85%–5.20% Cr, 1.3%–1.4% Mo, 0.8%–0.85% V, 0%–0.010% P, 0%–0.010% S, 0%–0.60% residual elements, balance Fe, total 100%; The preparation method of H13 steel mold parts is as follows: The H13 steel powder is dried, and then filled and spread. Set the parameters as follows: melting parameters: power current 14.0mA~17.0mA, scanning speed 4.500m / s~5.500m / s, defocusing amount 0V~0.500V, and beam size 0.100mm; preheating parameters: maximum current for powder bed preheating 40mA, average current for powder bed preheating 12mA~15mA, minimum setting time for powder bed preheating 10s~14s, and maximum setting time for powder bed preheating not exceeding 20s. The temperature is preheated to 750℃~800℃ before printing to obtain H13 steel mold parts.

2. The method for improving the mechanical properties of additively manufactured H13 steel according to claim 1, characterized in that, The particle size of H13 steel powder ranges from 5 μm to 120 μm.

3. The method for improving the mechanical properties of additively manufactured H13 steel according to claim 1, characterized in that, The method for stress-relief annealing is as follows: heat to 640℃~650℃, hold for 3.5h~4h, cool with the furnace to 200℃ after holding, and air-cool to room temperature after removing from the furnace.

4. The method for improving the mechanical properties of additively manufactured H13 steel according to claim 1, characterized in that, The H13 steel powder is prepared from H13 steel by plasma rotary atomization.

5. The method for improving the mechanical properties of additively manufactured H13 steel according to claim 4, characterized in that, The H13 steel powder is a spherical alloy powder.

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