Method for improving mechanical property of additive manufacturing H13 steel

Abstract

The invention relates to the technical field of additive manufacturing die steel, in particular to a method for improving the mechanical property of additive manufacturing H13 steel. The method specifically comprises the following steps that H13 steel powder is used for additive manufacturing, and an H13 steel mold part is obtained; and the H13 steel mold part is sequentially subjected to stress relief annealing, hot isostatic pressing treatment, solid solution quenching treatment and secondary aging treatment, and the H13 tough mold steel is prepared. According to the invention, the hot isostatic pressing and the heat treatment system are combined to solve the problems of anisotropy of structure and performance, low impact toughness, low cost and the like of an existing additive manufacturing mold component; and segregation and internal stress caused by non-uniform cooling in an existing manufacturing method also can cause the problem that the H13 die steel is easy to crack.

Description

Technical Field

[0001] The invention relates to the technical field of additive manufacturing die steel, and in particular to a method for improving the mechanical properties of additive manufacturing H13 steel. Background Art

[0002] In the development of mold steel, due to the obvious deficiencies in toughness and thermal fatigue resistance of traditional 3Gr2W8V mold steel, it frequently fails in practical applications and cannot meet the needs of high-precision, high-quality molds. In order to overcome the above defects, researchers developed chromium-based mold steel, and on this basis, through the optimization of alloy elements, designed H13 steel, also known as 4Cr5MoSiV1 steel. H13 steel has quickly 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 due to its excellent resistance to thermal cracking, thermal fatigue resistance, high resistance to thermal softening, and high-temperature wear.

[0003] However, with the development of manufacturing industry, the working environment of molds is becoming increasingly complex, and the performance requirements for mold materials are becoming higher and higher. Hot working molds not only need to withstand multiple loads such as impact, vibration, friction, stretching, 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, as a material-structure-performance integrated preparation technology, provides a good design idea for conformal cooling molds. Unlike traditional metallurgical processes, the advantage of additive manufacturing molds is that they can directly form complex structures, refine grains, and reduce the size of precipitates, thereby significantly improving the performance of the mold. However, additive manufacturing technology still has some problems, such as anisotropy of organization and performance, low impact toughness, internal stress, microscopic defects such as micropores, etc. These microscopic defects will reduce the fatigue performance of the mold and affect its service life.

[0005] Related studies have shown that the intrinsic tempering caused by repeated heat flow parallel to the construction direction leads to the local precipitation of secondary carbides and the decomposition of highly saturated tempered martensite, which causes performance differences parallel to and perpendicular to the construction direction, resulting in the tensile properties parallel to the loading direction being better than those perpendicular to the construction direction. For example, the tensile properties parallel to the loading direction are tensile strength 1600MPa and elongation 2.25%; the tensile properties perpendicular to the construction direction are tensile strength 1200MPa and elongation 1.5%. In order to improve the organization and performance of additive manufacturing molds, researchers have tried a variety of methods. Among them, hot isostatic pressing has a unique hot-pressing coupling effect, which enables it to improve the organizational structure while eliminating the internal hole defects of the parts. Therefore, it has gradually been applied to the organization and performance regulation of additive manufacturing parts. However, segregation and internal stress caused by uneven cooling can also cause H13 mold steel to easily crack. Summary of the invention

[0006] In order to solve the shortcomings of additive manufacturing technology, the purpose of the present invention is to provide a method for improving the mechanical properties of H13 steel for additive manufacturing. The present invention mainly combines hot isostatic pressing and heat treatment systems to solve the problems of anisotropy of organization and performance, low impact toughness, internal stress and surface micro defects in existing additive manufacturing mold components, and segregation and internal stress caused by uneven cooling in existing manufacturing methods, which also cause H13 mold steel to easily crack.

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

[0008] The present invention provides a method for improving the mechanical properties of H13 steel manufactured by additive manufacturing, comprising the following steps:

[0009] H13 steel powder is used for additive manufacturing to obtain H13 steel mold parts;

[0010] The H13 steel mold parts were subjected to stress relief annealing, hot isostatic pressing, solution quenching and secondary aging treatment in sequence to prepare H13 strong and tough mold steel.

[0011] The method of hot isostatic pressing is: heating to 1120℃~1130℃, controlling the pressure to 140MPa~160MPa, and keeping the temperature for 2.5h~3h;

[0012] The method of solution quenching treatment is: heating to 1020℃~1040℃, keeping warm for 50min~60min, then quenching with oil, cooling to 360℃~380℃;

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

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

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

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

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

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

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

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

[0021] Preferably, the preparation method of the H13 steel mold part is as follows:

[0022] Dry, fill and spread the H13 steel powder;

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

[0024] The base is preheated to 750℃~800℃, and then printed to obtain H13 steel mold parts.

[0025] Preferably, the stress relief annealing method is: heating to 640°C to 650°C, keeping the temperature for 3.5h to 4h, cooling to 200°C with the furnace after the end of the heat preservation, and air cooling to room temperature after taking out of the furnace.

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

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

[0028] Beneficial effects of the present invention:

[0029] 1. The present invention mainly combines hot isostatic pressing and heat treatment systems to solve the problems of anisotropy of organization and performance, low impact toughness, internal stress and surface micro defects in existing additive manufacturing mold components, and segregation and internal stress caused by uneven cooling in existing manufacturing methods, which also cause H13 mold steel to easily crack.

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

[0031] 3. The present invention proposes an integrated preparation method for the entire process from raw materials to mature components; the density of the obtained components is ≥99.9%, and there are basically no internal defects. After heat treatment, the strength and toughness are simultaneously improved, and the tensile strength is ≥1600MPa, the yield strength is ≥1050MPa, and the elongation after fracture is ≥10%.

[0032] 4. The present invention uses electron beam powder bed additive manufacturing technology to effectively prevent oxidation caused by excessive temperature, with uniform composition and refined structure. The additively manufactured parts and their heat treatment process methods can realize the integrated molding of large-size and complex structure H13 steel mold parts, with a density of ≥99.9% and excellent comprehensive mechanical properties. Subsequent heat treatment can regulate its microstructure, with few pore defects, and the simultaneous improvement of material strength and toughness is achieved by controlling the size, morphology, quantity, precipitation position and microstructure of the carbide precipitation phase. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a SEM surface morphology image of the H13 tough die steel powder prepared in Example 1 of the present invention.

[0034] Figure 2 It is a macroscopic morphology picture of SEBM state H13 steel prepared in Example 1 to Example 4 of the present invention.

[0035] Figure 3 Schematic diagram of hot isostatic pressing and heat treatment in Example 1 of the present invention.

[0036] Figure 4 The SEM surface morphology images of the SEBM H13 steel and the hot isostatically pressed H13 steel prepared in Example 1 of the present invention are shown in FIG. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0038] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making any creative work shall fall within the scope of protection of the present invention.

[0039] The 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 microns and the purity is ≥99.99%.

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

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

[0042] Step 2: Clamp the H13 steel bar in step 1 on the motor spindle, and the motor spindle drives the finished alloy bar to start high-speed rotation. When the speed reaches 10000r / min~15000r / min, the plasma tungsten pole gun is loaded with a current of 1200A~1500A to start arcing, melt the end face of the finished alloy bar, and form a molten pool. Under the centrifugal force of high-speed rotation, the molten liquid metal is thrown out at high speed to further form fine molten droplets. At the same time, the molten droplets are spheroidized due to the effect of their surface tension. The vacuum degree of the atomization chamber is guaranteed to be not less than 4.0×10 -2 Pa, and continuously filled with argon gas for protection.

[0043] Step 3, naturally cooling and sieving to obtain spherical alloy powder with a particle size of 5 microns to 120 microns.

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

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

[0046] The H13 steel powder is screened and mixed. According to the mass ratio, H13 steel powder with a particle size less than 120 μm is selected as the raw material, wherein H13 steel powder with a powder particle size less than 50 μm accounts for ∼30%, and powder powder with a particle size greater than 50 μm and less than 120 μm accounts for ∼70%.

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

[0048] S1. Place the above-prepared ingredients in a spread manner in a vacuum drying oven and dry them at a temperature of 100° C. to 110° C. for 2 h to 3 h.

[0049] S2. Load the ingredients dried in S1 into the EBM equipment, and load and level the substrate.

[0050] S2. According to the shape and size of the metal parts 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 transmitted to the additive manufacturing molding equipment.

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

[0052] S4. Continuously evacuate the chamber to ensure a high vacuum degree, continuously introduce high-purity helium to reduce the charge accumulation effect, load the data, and print the final mold layer by layer.

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

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

[0055] Example 1

[0056] A method for improving the mechanical properties of H13 steel produced by additive manufacturing, comprising the following steps:

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

[0058] S1.1. Preparation before printing: The operator should take personal protection measures and make preparations before going online, including checking the service life of the filament. If the required printing time exceeds the existing filament life, the filament should be replaced; clean the molding 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 level and has the same height difference with the surrounding platforms.

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

[0060] S1.3, Powder spreading and vacuuming: After the preparation work is completed, spread the powder in a single layer to ensure that the H13 powder is evenly spread on the substrate and the thickness does not exceed 0.05mm. Use dust-free wipes dipped in anhydrous ethanol to clean the insulation cover, the sealing ring of the forming chamber door and the safety glass, close the door and vacuumize.

[0061] S1.4, process parameter adjustment: according to the shape and size of the metal parts to be processed, use 3D modeling software to build a 55×10×55mm 3 The three-dimensional model of the cuboid is sliced ​​three-dimensionally with a slice thickness of 50 μm. The print format file is exported and the data information of the STL file is transmitted to the additive manufacturing molding equipment.

[0062] The imported solid model is parameterized, and the melting parameters are as follows: power current 15.0mA, scanning speed 5.000m / s, defocus 0.500V, beam spot size 0.100mm; preheating parameters are as follows: the maximum current of powder bed preheating is 40.00mA, the average current of powder bed preheating is 15.00mA, and the time of powder bed preheating is 14.000s. For substrate preheating, step-by-step preheating is used, and the temperature is kept at 300℃ and 600℃ for 10 minutes respectively to ensure that the substrate is fully preheated, and then preheated to 750℃, and then printing begins.

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

[0064] S2, stress relief annealing:

[0065] Use industrial alcohol or industrial acetone to clean the oil, grease or other dirt on the surface. Place the printed mold part manufactured in the previous stage into the vacuum heating furnace, making sure the thermocouple is as close to the part as possible, and evacuate to 10 -1 Pa. The temperature was raised to 650°C at a heating rate of 10°C / min, and kept at this temperature for 4 hours. After the end of the heat preservation, the mold was cooled to 200°C with the furnace, and then air-cooled to room temperature after being taken out of the furnace to complete the vacuum stress relief treatment of the printed mold parts.

[0066] S3, hot isostatic pressing treatment:

[0067] Use industrial alcohol or industrial acetone to clean the oil, grease or other dirt on the surface, put the printed mold parts that have been subjected to vacuum stress relief treatment into a hot isostatic press, and then evacuate the hot isostatic press to 50MPa, and start heating at the same time to raise the temperature of the hot isostatic press to 1125℃ at a heating rate of 10℃ / min~15℃ / min. During this process, the pressure is simultaneously increased to 150MPa, and maintained at 1125℃ and 150MPa for 3.0h; after the heat and pressure holding is completed, cool to 500℃ with the furnace, reduce the pressure to normal pressure, and finally cool to 300℃, and then let air in to quickly cool to room temperature to complete the hot isostatic pressing treatment of the printed mold parts.

[0068] S4, solution quenching treatment:

[0069] Use industrial alcohol or industrial acetone to clean the oil, grease or other dirt on the surface. Place the hot isostatically pressed printed mold part into a vacuum heating furnace, making sure the thermocouple is as close to the part as possible, and evacuate to 10 -1 Pa. Raise the temperature to 650℃ at 6℃ / min and keep it at this temperature for 10min. Continue to raise the temperature to 1020℃ at 10℃ / min and keep it at this temperature for 50min. After the insulation is completed, the printed mold parts are quickly transferred to the quenching oil medium for quenching.

[0070] S5. Secondary aging treatment:

[0071] Use denatured alcohol or industrial acetone to clean oil, grease or other contaminants from the surface.

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

[0073] Second aging treatment: adjust the temperature to 580℃ at 10℃ / min~15℃ / min, maintain for 3h. Open the furnace and cool naturally to room temperature to obtain strong and tough die steel.

[0074] Example 2

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

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

[0077] Example 3

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

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

[0080] Example 4

[0081] A method for improving the mechanical properties of H13 steel for additive manufacturing is basically the same as the method in Example 1, except that in step S4, the quenching medium used is water. In step S5, the primary aging treatment and the secondary aging treatment are both carried out at a temperature of 580° C. for 4 hours.

[0082] Example 5

[0083] A method for improving the mechanical properties of H13 steel for additive manufacturing is basically the same as the method in Example 1, except that in step S4, the temperature is further increased to 1050°C at 10°C / min. In step S5, the first aging treatment and the second aging treatment are both kept at 600°C for 3h.

[0084] Example 6

[0085] A method for improving the mechanical properties of H13 steel for additive manufacturing is basically the same as the method in Example 1, except that in step S4, the temperature is further increased to 1020°C at 10°C / min and kept at this temperature for 1 hour. In step S5, the primary aging treatment and the secondary aging treatment are both heated to 600°C, kept for 3 hours, and then directly cooled in the furnace without leaving the furnace.

[0086] Example 7

[0087] A method for improving the mechanical properties of H13 steel for additive manufacturing is basically the same as the method in Example 1, except that in step S5, the first aging treatment is to adjust the temperature to 580°C at 10°C / min to 15°C / min, maintain for 3 hours, and cool to room temperature by air cooling. The second aging treatment is to adjust the temperature to 580°C at 10°C / min to 15°C / min, maintain for 3 hours, and cool to room temperature by air cooling. The third aging treatment is to adjust the temperature to 580°C at 10°C / min to 15°C / min, maintain for 3 hours, open the furnace and cool naturally to room temperature to obtain a strong and tough mold steel.

[0088] Comparative Example 1

[0089] A method for improving the mechanical properties of H13 steel in additive manufacturing is basically the same as the method in Example 1, except that the printed mold part subjected to vacuum stress relief treatment prepared in steps S1 and S2 in 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, and directly measures the mechanical properties of the prepared printed mold part after stress relief annealing, in order to explore the effect of combining hot isostatic pressing and heat treatment process methods in the embodiment of the present 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 H13 steel produced by additive manufacturing 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] The method of comparative example 2 does not perform the solution aging heat treatment in step S5, and directly measures the mechanical properties of the prepared printed mold part after the solution quenching treatment, in order to explore the effect of the embodiment of the present invention on improving the mechanical properties of H13 steel additive manufacturing parts through the solution oil quenching combined with the secondary aging heat treatment process method. The test results are shown in Table 1.

[0094] Test 1: Warm tensile mechanical properties test.

[0095] The 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 Room temperature tensile mechanical properties test

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

[0098] In Examples 1 to 3, the density of the prepared strong and tough die steel specimens gradually increased, which was mainly attributed to the low energy density leading to poor fusion; 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 as a medium for quenching, which can significantly improve the yield strength, tensile strength, elongation and maximum hardness of the prepared strong and tough die steel sample.

[0100] Compared with Example 1, Examples 5 and 6 may reduce the mechanical properties by changing the solid solution quenching treatment conditions and the secondary aging treatment conditions.

[0101] Compared with Example 1, Example 7 causes a decrease in mechanical properties by increasing the number of failure treatments.

[0102] Compared with comparative example 1, example 1 of the present invention can significantly improve the elongation of the strong and tough die steel sample by combining hot isostatic pressing and heat treatment process methods.

[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 combining solid solution oil quenching with secondary aging heat treatment process.

[0104] From the above analysis, it can be seen that the embodiment of the present invention reduces the influence of additive manufacturing defects on mechanical properties through a post-processing method combining hot isostatic pressing and heat treatment, which provides a reference for the large-scale application of additive manufacturing high-quality H13 molds.

[0105] Test 2: Macromorphology analysis and micromorphology analysis.

[0106] Figure 1 This is a SEM surface morphology of the H13 tough die steel powder prepared in Example 1 of the present invention. Scanning Electron Microscope, the full name in English is Scanning Electron Microscope, referred to as SEM.

[0107] Depend on Figure 1 It can be seen that the H13 tough mold steel powder prepared in Example 1 of the present invention presents typical PREP powder making characteristics, with high sphericity and solidified dendrites on the powder surface. The particle size of the H13 tough mold steel powder prepared in Example 1 is 5 microns to 120 microns; the purity is ≥99.99%.

[0108] Figure 2 The macroscopic morphology of the SEBM-state H13 steel prepared in Examples 1 to 4 of the present invention is shown in Figure 1. The full name of the electron beam selective melting is Selective Electron Beam Melting, or SEBM for short.

[0109] Depend on Figure 2 It shows that the surface of the printed sample is smooth and there are no defects such as warping and cracks.

[0110] Figure 3 Schematic diagram of hot isostatic pressing and heat treatment in Example 1 of the present invention. Figure 4 The SEM surface morphology images of the SEBM H13 steel and the hot isostatically pressed H13 steel prepared in Example 1 of the present invention are shown in FIG.

[0111] By comparison, it was found that after hot isostatic pressing treatment, the hot isostatically pressed H13 steel sample had almost no pores and showed a high density.

[0112] The above are only 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 in the protection scope of the present invention.

Claims

1. A method for improving the mechanical properties of H13 steel produced by additive manufacturing, characterized in that: The following steps are involved: H13 steel powder is used for additive manufacturing to obtain H13 steel mold parts; The H13 steel mold parts were subjected to stress relief annealing, hot isostatic pressing, solution quenching and secondary aging treatment in sequence to prepare H13 strong and tough mold steel. The method of hot isostatic pressing is: heating to 1120℃~1130℃, controlling the pressure to 140MPa~160MPa, and keeping the temperature for 2.5h~3h; The method of solution quenching treatment is: heating to 1020℃~1040℃, keeping warm for 50min~60min, then quenching with oil, cooling to 360℃~380℃; The method of secondary aging treatment is: adjust the temperature to 580℃~600℃, maintain for 180min~200min, cool down to below 200℃, open the furnace and cool naturally; after tempering again under the same treatment conditions, cool to room temperature.

2. The method for improving the mechanical properties of H13 steel produced by additive manufacturing according to claim 1, characterized in that: The particle size of the H13 steel powder is 5 μm to 120 μm.

3. The method for improving the mechanical properties of H13 steel produced by additive manufacturing according to claim 2, characterized in that: The particle size of H13 steel powder meets the following conditions: The mass proportion of H13 steel powder with a particle size of less than 50 μm is ∼30%, and the mass proportion of H13 steel powder with a particle size of greater than 50 μm and less than 120 μm is ∼70%.

4. The method for improving the mechanical properties of H13 steel produced by additive manufacturing according to claim 1, characterized in that: H13 steel powder is composed of the following elements in mass percentage: 0.38% to 0.40% C, 0.8% to 1.0% Si, 0.30% to 0.35% Mn, 4.85% to 5.20% Cr, 1.3% to 1.4% Mo, 0.8% to 0.85% V, 0% to 0.010% P, 0% to 0.010% S, 0% to 0.60% residual elements, and the balance is Fe, totaling 100%.

5. The method for improving the mechanical properties of H13 steel produced by additive manufacturing according to claim 1, characterized in that: The preparation method of H13 steel mold parts is as follows: Dry, fill and spread the H13 steel powder; The parameters are set as follows: the melting parameters are: power current 14.0mA ~ 17.0mA, scanning speed 4.500m / s ~ 5.500m / s, defocusing amount 0V ~ 0.500V, and beam spot size 0.100mm; the preheating parameters are: the maximum current of powder bed preheating is 40mA, the average current of powder bed preheating is 12mA ~ 15mA, the minimum setting time of powder bed preheating is 10s ~ 14s, and the maximum setting time of powder bed preheating does not exceed 20s; The base is preheated to 750℃~800℃, and then printed to obtain H13 steel mold parts.

6. The method for improving the mechanical properties of H13 steel produced by additive manufacturing according to claim 1, characterized in that: The method of stress relief annealing is: heating to 640℃~650℃, keeping warm for 3.5h~4h, cooling to 200℃ with the furnace after the end of the insulation, and air cooling to room temperature after taking out of the furnace.

7. The method for improving the mechanical properties of H13 steel produced by additive manufacturing according to claim 1, characterized in that: The H13 steel powder is prepared from H13 steel by a plasma rotary atomization method.

8. The method for improving the mechanical properties of H13 steel produced by additive manufacturing according to claim 7, characterized in that: The H13 steel powder is spherical alloy powder.

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