High-performance additive manufacturing die steel and preparation method thereof

Abstract

The invention discloses high-performance additive manufacturing die steel and a preparation method thereof, and belongs to the field of laser additive manufacturing high-end dies. The additive manufacturing die steel comprises an H13 steel matrix and internally coated TiC + TiB2 nano particles. Compared with the prior art, the die steel and the preparation method solve the problems that in the field of existing additive manufacturing die steel, forming is difficult, and the mechanical property is poor. Specifically, the intermediate alloy method is adopted for preparing the H13 steel powder internally coated with the nanoparticles, then technological parameter optimization is carried out, after technological parameter optimization, the density of the die steel is remarkably improved, and in addition, the mechanical property of the die steel is comprehensively improved. And the die steel with high compactness and excellent mechanical property is prepared through an additive manufacturing technology. Compared with traditional additive manufacturing die steel, the additive manufacturing die steel has the advantages of being easy to form, high in compactness, high in strength and toughness and the like.

Description

Technical Field

[0001] This invention relates to the field of high-end molds in laser additive manufacturing, specifically to a high-performance additive manufacturing mold steel and its preparation method. Background Technology

[0002] With the increasing demand for high-performance mold materials in industry, traditional mold steels often face problems such as insufficient strength, toughness, and wear resistance. Especially in complex mold manufacturing processes, mold materials need to possess high tensile strength, high elongation, and good toughness to withstand high-intensity mechanical loads and harsh service environments. Furthermore, existing mold steel materials often require long manufacturing cycles and complex processing techniques during forming, resulting in high manufacturing costs. H13 steel, as a typical hot-work mold steel, has advantages such as high hardenability, resistance to hot cracking, and high hardness, and is widely used in hot forging dies, aluminum alloy die-casting dies, and other fields. However, traditional forged H13 steel suffers from defects such as compositional segregation and coarse carbides, which are difficult to completely eliminate even after heat treatment.

[0003] Existing technologies show that the H13 steel provided by CN103981445A, after electroslag remelting, has a room temperature tensile strength of 1783 MPa. However, the production process in this invention is extremely cumbersome, increasing production time. CN105274443A exhibits an impact toughness of only 60 J / cm² at 550 °C, and this toughness decreases by 30% after tempering. While CN108707838A achieves a hardness of HRC 66–70, its impact toughness is as low as 4–9 J / cm², making it unable to withstand high impact loads. The SLM-formed part of CN118222933A, after heat treatment, has a maximum room temperature tensile strength of 2020 MPa and an engineering strain of 4.5%, which is almost identical to the performance of the untreated part of this invention. Furthermore, the sample in CN118222933A exhibited cracking. However, CN118222933A still uses traditional gas atomized powder, which does not control the microcracks caused by the thermal expansion mismatch between the carbide and the matrix, nor does it achieve fine grain / thermal mismatch reinforcement through internal nanoparticle coating. Therefore, its effect of simultaneously improving density, high temperature strength and impact toughness is limited, and there is room for further improvement.

[0004] The article "Nanocrystalline TiC-reinforced H13 steel matrix nanocomposites fabricated by selective laser melting," published in the journal Materials & Design by AlMangour et al., clearly points out that while the addition of nanoparticles improves the performance of H13 steel, mechanical mixing of nanoparticles places high demands on the powder mixing process. It typically requires extensive experimental optimization of ball milling time and speed, and is subject to significant randomness, making it difficult to achieve uniform mixing of nanoparticles in the additive powder. Furthermore, the surface of added nanoparticles is prone to contamination and severe agglomeration, resulting in poor formability of the additive powder after mechanical mixing, hindering mass production and industrial applications. In addition, the article "Enhanced High-Temperature Wear Performance of H13 Steel through TiC Incorporation by Laser Metal Deposition" published in the journal Materials by LU C, CHEN Z, YAN Y, et al. also pointed out that the wear resistance of H13 steel can be improved by adding nanoparticles through ball milling. However, the article clearly stated that the content of nanoparticles added should be 10% and should be mixed at a speed of 350 r / min for 36 hours, which makes the production process very complicated and increases the production cost.

[0005] With the development of additive manufacturing technologies such as SLM (Surface Mount Technology), new approaches have been provided for the preparation of high-performance mold steels. These technologies can significantly refine the microstructure of H13 steel, eliminate macroscopic segregation, and thus improve the uniformity of the internal structure. However, due to the high carbon content of H13 steel, residual stress and cracks are easily generated during SLM forming, which seriously affects the forming quality and mechanical properties. Furthermore, existing SLM forming materials still suffer from insufficient strengthening effect, difficulty in forming, and susceptibility to cracking. Therefore, seeking new ways to solve the problems of difficulty in forming and susceptibility to cracking during SLM forming, thereby improving the overall performance of the material, is of great significance to the mold industry. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention proposes a high-performance additive manufacturing die steel and its preparation method.

[0007] The objective of this invention can be achieved through the following technical solutions: A first aspect of the present invention relates to an additive manufacturing die steel comprising: an H13 steel matrix and inner-coated TiC+TiB2 nanoparticles.

[0008] Optionally, TiC+TiB2 nanoparticles are introduced and uniformly distributed in the H13 steel matrix via an intermediate alloying method.

[0009] Optionally, the intermediate alloying method includes the following steps: Al powder, Ti powder and B4C are uniformly mixed and heated in a vacuum sintering furnace to undergo a combustion synthesis reaction, resulting in a TiC+TiB2 / Al master alloy.

[0010] Optionally, the chemical composition, by mass percentage, includes: C: 0.3-0.4 wt.%; Cr: 5.2-5.5 wt.%; TiC+TiB2: 0.02-0.05 wt.%; Si: 0.8-1.0 wt.%; and Mo: 1.1-1.3 wt.%.

[0011] Optionally, it also includes the following chemical composition by mass percentage: V: 0.95-1.1 wt.%; S: 0.007 wt.%; Mn: 0.35-0.40 wt.%; P: 0.012 wt.%.

[0012] A second aspect of the present invention relates to a method for preparing additive manufacturing die steel, comprising the following steps: Preparation of TiC+TiB2 nanoparticles with internal coating; H13 mold steel is heated and remelted, and TiC+TiB2 nanoparticles are added inside. Then, the H13 mold steel liquid is cast to obtain H13 steel with nanoparticles inside. The obtained H13 steel with inner nanoparticle coating was placed in the furnace chamber of a medium-frequency induction furnace and reheated and remelted to obtain molten metal. A protective gas was passed through to atomize the molten metal. After falling and cooling, H13 steel powder with inner nanoparticle coating was obtained. The additive manufacturing die steel is prepared by selective laser melting using H13 steel powder with internally coated nanoparticles as raw material.

[0013] Optionally, TiC+TiB2 nanoparticles are introduced and uniformly distributed in the H13 steel matrix by an intermediate alloying method, which includes the following steps: uniformly mixing Al powder, Ti powder and B4C, heating in a vacuum sintering furnace to carry out a combustion synthesis reaction, and obtaining TiC+TiB2 / Al intermediate alloy.

[0014] Optionally, the preparation method of the H13 steel powder with internally coated nanoparticles includes the following steps; The obtained H13 steel with inner nanoparticle coating was placed in the furnace chamber of a medium-frequency induction furnace for remelting. The inner nanoparticle coating was heated to a liquid state and held at 1600℃ for 2 minutes to obtain a solution of H13 steel with inner nanoparticle coating. In an argon atmosphere, the obtained molten liquid is transferred to an intermediate ladle. The solution flows freely downward from the opening at the bottom of the intermediate ladle. Then, argon gas at a pressure of about 3 MPa is introduced into the sealed channel to achieve the argon atomization process. After free fall, the atomized molten liquid cools at the bottom to form H13 steel powder with inner nanoparticle coating.

[0015] Optionally, before selective laser melting, the H13 steel powder with internally coated nanoparticles is sieved in two steps, with sieve sizes of 15-53 micrometers and 53-150 micrometers, respectively.

[0016] Optionally, the mass ratio of Al powder, Ti powder and B4C is 27:8:65.

[0017] The beneficial effects of this invention are: SLM (Sequencing Method for Molding) allows for precise control of the forming of each layer of mold steel, ensuring consistency in the microstructure of the material and thus improving its performance. The addition of nanoparticles refines the grain size; finer grains have more grain boundaries, which absorb dislocations and hinder their movement, resulting in grain refinement strengthening. However, due to the difference in thermal expansion coefficients between carbides and nanoparticles and H13 steel, significant stress is generated around the carbides during SLM forming, leading to a large number of geometric dislocations and resulting in thermal mismatch strengthening. The mold steel of this invention possesses high strength and toughness, high wear resistance, and high oxidation resistance. Specifically, the maximum room temperature tensile strength of the H13 mold steel of this invention is 1844.9±25.9 MPa, and the maximum engineering strain is 2.7±0.2; the maximum room temperature tensile strength of the H13 steel with internal nanoparticle coating is 1962.8±72.7 MPa, and the maximum engineering strain is 5.1±0.6%. The tensile strength was increased by 6.4%, and the engineering strain increased by 88.9%. The maximum tensile strength of H13 die steel at high temperature was 1057.1±12.1 MPa, and the maximum engineering strain was 9.5±0.6%. The maximum tensile strength of H13 steel with internal nanoparticle coating at high temperature was 1373.9±23.8 MPa, and the maximum engineering strain was 20.1±3.1%. The tensile strength was increased by 26.3%, and the engineering strain increased by 76.3%. This invention uses an intermediate alloying method to prepare H13 steel powder with internal nanoparticle coating, which not only avoids the problems of easy contamination and severe agglomeration of nanoparticles in the matrix, but also significantly reduces production costs by using only 0.02% nanoparticles. Attached Figure Description

[0018] The invention will now be further described with reference to the accompanying drawings.

[0019] Figure 1 Metallographic photographs of the mold steels in various embodiments.

[0020] Figure 2The laser absorption rate of the mold steel powder used in this example is shown.

[0021] Figure 3 The room temperature stretching curves for each embodiment are shown.

[0022] Figure 4 The high-temperature tensile curves for each embodiment are shown.

[0023] Figure 5 The diagram shows a comparison of room temperature shock effects across various embodiments. Detailed Implementation

[0024] 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.

[0025] Example 1: Design of H13 steel powder with internally coated nanoparticles: An intermediate alloy was prepared by uniformly mixing Al powder, Ti powder, and B4C in a mass ratio of 27:8:65. The mixed powder was then placed in a high-energy ball mill for ball milling at 40 r / min for 48 hours. The resulting powder was then coated with aluminum foil.

[0026] Pre-pressing is performed on a pre-pressing machine to obtain a cold-pressed block. The cold-pressed block is then placed in a graphite mold and heated in a vacuum sintering furnace to undergo a combustion synthesis reaction, ultimately yielding a TiC+TiB2 / Al master alloy.

[0027] The combustion synthesis reaction includes the following steps: The furnace was evacuated until the pressure inside was below 10 Pa. Heating then began at a rate of 30°C / min. The furnace temperature was initially raised to 500°C and held for 10 minutes to ensure the mold and the internal preform temperature were synchronized. The temperature was then increased to 920°C–980°C. At this point, a sudden and significant change in pressure and internal temperature of the compact was observed, indicating a combustion synthesis reaction had occurred within the system. Heating was then stopped after holding at this temperature for another 10 minutes. When the temperature dropped to 800°C, an axial pressure of 25–55 MPa was applied to the cylindrical compact, and the pressure was held for 60 seconds to densify it. Finally, the sample was allowed to cool to room temperature with the furnace.

[0028] A high-performance additive manufacturing die steel comprises the following chemical composition by weight percentage: C: 0.3 wt.%; Cr: 5.2 wt.%; Si: 0.8 wt.%; Mo: 1.1 wt.%; V: 0.95 wt.%; S: 0.007 wt.%; Mn: 0.35 wt.%; P: 0.012 wt.% and the balance being Fe.

[0029] High-performance mold steel is cut into 2kg blocks and remelted in a medium-frequency induction furnace. Pre-cut TiC+TiB2 / Al master alloy is added to the furnace to obtain molten steel. At approximately 1600℃, the molten steel is poured into a ladle at a uniform rate of approximately 1500℃. Nano-TiC+TiB2 particles disperse in the molten steel as it boils. Al acts as a deoxidizer, generating aluminum oxide that floats on top of the molten steel. The molten steel is then poured into a sand mold to obtain H13 steel with a TiC+TiB2 content of 0.02wt.% coated with nanoparticles, where the mass ratio of TiC to TiB2 is 3:1.

[0030] Preparation of nanoparticle-reinforced powder: The obtained H13 steel with inner nanoparticle coating was placed in the furnace chamber of a medium-frequency induction furnace for remelting. The inner nanoparticle coating was heated to a liquid state and held at 1600℃ for 2 minutes to obtain a solution of H13 steel with inner nanoparticle coating.

[0031] In an argon atmosphere, the obtained solution is transferred to an intermediate bath. The solution flows freely downward from the bottom opening of the intermediate bath with a diameter of about 3 mm. Then, argon gas at a pressure of about 3 MPa is introduced into the sealed channel. The argon gas can blow away the downward flowing metal solution, realizing the argon atomization process. After free fall, the atomized solution cools at the bottom to form H13 steel powder with inner nanoparticle coating.

[0032] The obtained powder was then sieved into two parts, with sieving requirements of 15-53 micrometers and 53-150 micrometers, respectively.

[0033] The selected laser additive manufacturing powder had a size of 15 micrometers. The absorption rates at the 1064 nm laser band before and after adding nanoparticles were 63.93% and 65.08%, respectively. Figure 3 As shown, selective laser melting technology was used for fabrication. The laser power was 200W, the scanning speed was 700mm / s, the powder layer thickness was fixed at 30 micrometers, the laser scanning spacing was fixed at 100 micrometers, and the laser scanning strategy was interlayer rotation of 67° to achieve high-density molding.

[0034] The final properties of the mold steel are shown in Table 1. The Rockwell hardness of the samples was measured using a Rockwell hardness tester (300HRSS-150) from Laizhou Huayin Testing Instruments Co., Ltd. Before testing, the samples were polished smooth to ensure the upper and lower surfaces were parallel. During the test, the experimental force was 150 kgf, and the force was held for 5 seconds. Eight points were randomly selected on the sample to measure the hardness. The average value after removing the maximum and minimum values ​​was taken as the final hardness value of the sample. The room temperature hardness of the H13 steel with internal nanoparticle coating and the H13 mold steel measured by the Rockwell hardness tester were 52.2 HRC and 51.6 HRC, respectively. The samples were prepared into standard tensile test specimens, and the surfaces were polished smooth with sandpaper. Tensile tests were conducted using a servo-hydraulic material testing system at a tensile speed of 10... -4 s -1 The tensile strengths of H13 steel and H13 die steel coated with nanoparticles at room temperature (25℃) are 1846 MPa and 1672 MPa, respectively, and their yield strengths are 960 MPa and 1109 MPa, respectively. The tensile strengths of H13 steel and H13 die steel coated with nanoparticles at high temperature (550℃) are 1254 MPa and 977 MPa, respectively, and their yield strengths are 1066 MPa and [missing data - likely related to fracture before yielding].

[0035] Example 2: Design of H13 steel powder with internally coated nanoparticles: An intermediate alloy was prepared by uniformly mixing Al powder, Ti powder, and B4C in a mass ratio of 27:8:65. The mixed powder was then placed in a high-energy ball mill for ball milling at 40 r / min for 36 hours. The resulting powder was then coated with aluminum foil.

[0036] Pre-pressing is performed on a pre-pressing machine to obtain a cold-pressed block. The cold-pressed block is then placed in a graphite mold and heated in a vacuum sintering furnace to undergo a combustion synthesis reaction, ultimately yielding a TiC+TiB2 / Al master alloy.

[0037] The combustion synthesis reaction includes the following steps: The furnace was evacuated until the pressure inside was below 10 Pa. Heating then began at a rate of 30°C / min. The furnace temperature was initially raised to 500°C and held for 10 minutes to ensure the mold and the internal preform temperature were synchronized. The temperature was then increased to 920°C–980°C. At this point, a sudden and significant change in pressure and internal temperature of the compact was observed, indicating a combustion synthesis reaction had occurred within the system. Heating was then stopped after holding at this temperature for another 10 minutes. When the temperature dropped to 800°C, an axial pressure of 25–55 MPa was applied to the cylindrical compact, and the pressure was held for 60 seconds to densify it. Finally, the sample was allowed to cool to room temperature with the furnace.

[0038] A high-performance additive manufacturing die steel comprises the following chemical composition by weight percentage: C: 0.35 wt.%; Cr: 5.2 wt.%; Si: 0.9 wt.%; Mo: 1.2 wt.%; V: 1.05 wt.%; S: 0.007 wt.%; Mn: 0.38 wt.%; P: 0.012 wt.% and the balance being Fe.

[0039] High-performance mold steel is cut into 2kg blocks and remelted in a medium-frequency induction furnace. Pre-cut TiC+TiB2 / Al master alloy is added to the furnace to obtain molten steel. At approximately 1600℃, the molten steel is poured into a ladle at a uniform rate of approximately 1500℃. Nano-TiC+TiB2 particles disperse in the molten steel as it boils. Al acts as a deoxidizer, generating aluminum oxide that floats on top of the molten steel. The molten steel is then poured into a sand mold to obtain H13 steel with a TiC+TiB2 content of 0.02wt.% coated with nanoparticles, where the mass ratio of TiC to TiB2 is 3:1.

[0040] Preparation of nanoparticle-reinforced powder: The obtained H13 steel with inner nanoparticle coating was placed in the furnace chamber of a medium-frequency induction furnace for remelting. The inner nanoparticle coating was heated to a liquid state and held at 1650℃ for 2 minutes to obtain a solution of H13 steel with inner nanoparticle coating.

[0041] In an argon atmosphere, the obtained solution is transferred to an intermediate bath. The solution flows freely downward from the bottom opening of the intermediate bath with a diameter of about 3 mm. Then, argon gas at a pressure of about 3 MPa is introduced into the sealed channel. The argon gas can blow away the downward flowing metal solution, realizing the argon atomization process. After free fall, the atomized solution cools at the bottom to form H13 steel powder with inner nanoparticle coating.

[0042] The obtained powder was then sieved into two parts, with sieving requirements of 15-53 micrometers and 53-150 micrometers, respectively.

[0043] The selected laser additive manufacturing powder had a size of 15 micrometers. The absorption rates at the 1064 nm laser band before and after adding nanoparticles were 63.93% and 65.08%, respectively. Figure 3 As shown, selective laser melting technology was used for fabrication. The laser power was 270W, the scanning speed was 800mm / s, the powder layer thickness was fixed at 30 micrometers, the laser scanning spacing was fixed at 100 micrometers, and the laser scanning strategy was interlayer rotation of 67° to achieve high-density molding.

[0044] The final properties of the mold steel are shown in Table 1. The Rockwell hardness of the samples was measured using a Rockwell hardness tester (300HRSS-150) from Laizhou Huayin Testing Instruments Co., Ltd. Before testing, the samples were polished smooth to ensure the upper and lower surfaces were parallel. During the test, the experimental force was 150 kgf, and the force was held for 5 seconds. Eight points were randomly selected on the sample to measure the hardness. The average value after removing the maximum and minimum values ​​was taken as the final hardness value of the sample. The room temperature hardness of the H13 steel with internal nanoparticle coating and the H13 mold steel measured by the Rockwell hardness tester were 53.1 HRC and 51.9 HRC, respectively. The samples were prepared into standard tensile test specimens, and the surfaces were polished smooth with sandpaper. Tensile tests were conducted using a servo-hydraulic material testing system at a tensile speed of 10... -4 s -1 The tensile strengths of H13 steel and H13 die steel with internal nanoparticle coating at room temperature (25℃) are 1950 MPa and 1844 MPa, respectively. Their yield strengths are 939 MPa and 1306 MPa, respectively. At high temperature (550℃), the tensile strengths of H13 steel and H13 die steel with internal nanoparticle coating are 1286 MPa and 1087 MPa, respectively, and their yield strengths are 1168 MPa and 783 MPa, respectively.

[0045] Example 3: Design of H13 steel powder with internally coated nanoparticles: An intermediate alloy was prepared by uniformly mixing Al powder, Ti powder, and B4C in a mass ratio of 27:8:65. The mixed powder was then placed in a high-energy ball mill for ball milling at 40 r / min for 48 hours. The resulting powder was then coated with aluminum foil.

[0046] Pre-pressing is performed on a pre-pressing machine to obtain a cold-pressed block. The cold-pressed block is then placed in a graphite mold and heated in a vacuum sintering furnace to undergo a combustion synthesis reaction, ultimately yielding a TiC+TiB2 / Al master alloy.

[0047] The combustion synthesis reaction includes the following steps: The furnace was evacuated until the pressure inside was below 10 Pa. Heating then began at a rate of 30°C / min. The furnace temperature was initially raised to 500°C and held for 10 minutes to ensure the mold and the internal preform temperature were synchronized. The temperature was then increased to 920°C–980°C. At this point, a sudden and significant change in pressure and internal temperature of the compact was observed, indicating a combustion synthesis reaction had occurred within the system. Heating was then stopped after holding at this temperature for another 10 minutes. When the temperature dropped to 800°C, an axial pressure of 25–55 MPa was applied to the cylindrical compact, and the pressure was held for 60 seconds to densify it. Finally, the sample was allowed to cool to room temperature with the furnace.

[0048] A high-performance additive manufacturing die steel comprises the following chemical composition by weight percentage: C: 0.4 wt.%; Cr: 5.2 wt.%; Si: 1.0 wt.%; Mo: 1.3 wt.%; V: 1.1 wt.%; S: 0.007 wt.%; Mn: 0.40 wt.%; P: 0.012 wt.% and the balance being Fe.

[0049] High-performance mold steel is cut into 2kg blocks and remelted in a medium-frequency induction furnace. Pre-cut TiC+TiB2 / Al master alloy is added to the furnace to obtain molten steel. At approximately 1600℃, the molten steel is poured into a ladle at a uniform rate of approximately 1500℃. Nano-TiC+TiB2 particles disperse in the molten steel as it boils. Al acts as a deoxidizer, generating aluminum oxide that floats on top of the molten steel. The molten steel is then poured into a sand mold to obtain H13 steel with a TiC+TiB2 content of 0.02wt.% coated with nanoparticles, where the mass ratio of TiC to TiB2 is 3:1.

[0050] Preparation of nanoparticle-reinforced powder: The obtained H13 steel with inner nanoparticle coating was placed in the furnace chamber of a medium-frequency induction furnace for remelting. The inner nanoparticle coating was heated to a liquid state and held at 1600℃ for 2 minutes to obtain a solution of H13 steel with inner nanoparticle coating.

[0051] In an argon atmosphere, the obtained solution is transferred to an intermediate bath. The solution flows freely downward from the bottom opening of the intermediate bath with a diameter of about 3 mm. Then, argon gas at a pressure of about 3 MPa is introduced into the sealed channel. The argon gas can blow away the downward flowing metal solution, realizing the argon atomization process. After free fall, the atomized solution cools at the bottom to form H13 steel powder with inner nanoparticle coating.

[0052] The obtained powder was then sieved into two parts, with sieving requirements of 15-53 micrometers and 53-150 micrometers, respectively.

[0053] The selected laser additive manufacturing powder had a size of 15 micrometers. The absorption rates at the 1064 nm laser band before and after adding nanoparticles were 63.93% and 65.08%, respectively. Figure 3 As shown, selective laser melting technology was used for fabrication. The laser power was 230W, the scanning speed was 500mm / s, the powder layer thickness was fixed at 30 micrometers, the laser scanning spacing was fixed at 100 micrometers, and the laser scanning strategy was interlayer rotation of 67° to achieve high-density molding.

[0054] The final properties of the mold steel are shown in Table 1. The Rockwell hardness of the samples was measured using a Rockwell hardness tester (300HRSS-150) from Laizhou Huayin Testing Instrument Co., Ltd. Before testing, the samples were polished smooth to ensure the upper and lower surfaces were parallel. During the test, the experimental force was 150 kgf, and the force was held for 5 seconds. Eight points were randomly selected on the sample to measure the hardness. The average value after removing the maximum and minimum values ​​was taken as the final hardness value of the sample. The room temperature hardness of the H13 steel with internal nanoparticle coating and the H13 mold steel measured by the Rockwell hardness tester were 53.3 HRC and 52.2 HRC, respectively. The samples were prepared into standard tensile test specimens, and the surfaces were polished smooth with sandpaper. Tensile tests were conducted using a servo hydraulic material testing system at a tensile speed of 10... -4 s -1 The tensile strengths of H13 steel and H13 die steel coated with nanoparticles at room temperature (25℃) are 1962 MPa and 1521 MPa, respectively. Their yield strengths are 948 MPa and 953 MPa, respectively. The tensile strengths of H13 steel and H13 die steel coated with nanoparticles at high temperature (550℃) are 1373 MPa and 1057 MPa, respectively. Their yield strengths are 1270 MPa and 735 MPa, respectively.

[0055] Table 1 Performance indicators of mold steels obtained in Examples 1-3 In Table 1 above, H13 mold steel is a commercially available product, manufactured by AVIC MITEK.

[0056] According to the experimental data in Table 1, it can be seen that in each embodiment, the density of H13 steel with internal nanoparticle coating is around 99%, which is a significant improvement compared to the density of H13 mold steel (around 96%). This indicates that H13 steel with internal nanoparticle coating can be formed more densely at low energy density, and its mechanical properties are comprehensively improved compared to H13 mold steel.

[0057] 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.

[0058] 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 invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. An additive manufacturing die steel, characterized in that, include: H13 steel matrix with TiC+TiB2 nanoparticles inside.

2. The additive manufacturing die steel according to claim 1, characterized in that, TiC+TiB2 nanoparticles were introduced and uniformly distributed in the H13 steel matrix via an intermediate alloying method.

3. The additive manufacturing die steel according to claim 2, characterized in that, The intermediate alloy method includes the following steps: Al powder, Ti powder and B4C are uniformly mixed and heated in a vacuum sintering furnace to undergo a combustion synthesis reaction, resulting in a TiC+TiB2 / Al master alloy.

4. The additive manufacturing die steel according to claim 1, characterized in that, The chemical composition by mass percentage includes: C: 0.3-0.4 wt.%; Cr: 5.2-5.5 wt.%; TiC+TiB2: 0.02-0.05 wt.%; Si: 0.8-1.0 wt.%; and Mo: 1.1-1.3 wt.%, wherein the mass ratio of TiC to TiB2 is 3:

1.

5. The additive manufacturing die steel according to claim 1, characterized in that, It also includes the following chemical composition by mass percentage: V: 0.95-1.1 wt.%; S: 0.007wt.%; Mn: 0.35-0.40wt.%; P: 0.012 wt.%.

6. A method for preparing additive manufacturing die steel, comprising the following steps: Preparation of TiC+TiB2 nanoparticles with internal coating; H13 mold steel is heated and remelted, and TiC+TiB2 nanoparticles are added inside. Then, the H13 mold steel liquid is cast to obtain H13 steel with nanoparticles inside. The obtained H13 steel with inner nanoparticle coating was reheated and remelted to obtain molten metal. A protective gas was passed through to atomize the molten metal, and after free fall and cooling, H13 steel powder with inner nanoparticle coating was obtained. The additive manufacturing die steel is prepared by selective laser melting using H13 steel powder with internally coated nanoparticles as raw material.

7. The method for preparing additive manufacturing die steel according to claim 6, characterized in that, TiC+TiB2 nanoparticles are introduced and uniformly distributed in an H13 steel matrix by an intermediate alloying method. The intermediate alloying method includes the following steps: uniformly mixing Al powder, Ti powder and B4C, and heating in a vacuum sintering furnace to carry out a combustion synthesis reaction to obtain a TiC+TiB2 / Al intermediate alloy.

8. The method for preparing additive manufacturing die steel according to claim 6, characterized in that, The preparation method of the H13 steel powder with internally coated nanoparticles includes the following steps; The obtained H13 steel with inner nanoparticle coating was placed in the furnace chamber of a medium-frequency induction furnace for remelting. The inner nanoparticle coating was heated to a liquid state and held at 1600℃ for 2 minutes to obtain a solution of H13 steel with inner nanoparticle coating. In an argon atmosphere, the obtained molten liquid is transferred to an intermediate ladle. The solution flows freely downward from the opening at the bottom of the intermediate ladle. Then, argon gas at a pressure of about 3 MPa is introduced into the sealed channel to achieve the argon atomization process. After free fall, the atomized molten liquid cools at the bottom to form H13 steel powder with inner nanoparticle coating.

9. The method for preparing additive manufacturing die steel according to claim 6, characterized in that, Before selective laser melting, the H13 steel powder with internally coated nanoparticles is sieved in two steps, with sieve sizes of 15-53 micrometers and 53-150 micrometers, respectively.

10. The method for preparing additive manufacturing die steel according to claim 7, characterized in that, The mass ratio of Al powder, Ti powder and B4C is 27:8:65, and the mass ratio of TiC to TiB2 is 3:1.

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