High-impact micro-nano ceramic particle reinforced die steel and preparation method thereof

Abstract

The application provides a micro-nano ceramic particle reinforced die steel with high impact performance and a preparation method. The preparation method comprises the following steps: putting TiAl alloy powder, BN powder and C powder into a mixing machine to obtain a mixture 1, and using pure aluminum strip to coat the mixture 1 to obtain a wire A; the wire A is subjected to buffer segmented electric explosion 1 to obtain a mixture 2; putting NbAl alloy powder and B4C powder into a mixing machine to obtain a mixture 3, and using pure aluminum strip to coat the mixture 1 to obtain a wire B through coating forming 2; the wire B is subjected to buffer segmented electric explosion 2 to obtain a mixture 4; the mixture 2 and the mixture 4 are coated by using stainless steel strip through coating forming 3 to obtain a wire C; the die steel is melted into a molten steel, the wire C is added into the molten steel, and then vacuum degassing, electroslag remelting, high-temperature diffusion, multi-directional forging and heat treatment are carried out to obtain the micro-nano ceramic particle reinforced die steel with high impact toughness. The longitudinal unnotched impact energy of the die steel is 578.9-601.6 J, the transverse unnotched impact energy is 576.7-590.9 J, and the isotropy is 0.96-0.99.

Description

Technical Field

[0001] This invention relates to the field of hot work die steel technology, specifically to a high-impact-performance die steel reinforced with micro-nano ceramic particles and its preparation method. Background Technology

[0002] In many manufacturing industries, especially the automotive, aerospace, machinery manufacturing, and aviation industries, mold steel plays a core role in manufacturing parts. Its excellent mechanical properties make it the core framework of processing technology in various industries. Hot work mold steel is used under extremely harsh conditions. When subjected to huge impacts, it is prone to forming microcracks at defective sites. These microcracks can then propagate into failure cracks, causing mold damage. Therefore, mold steel must possess excellent impact resistance. In recent years, China's mold steel export share has been increasing year by year, but there is still much room for improvement in the market share of high-end mold steel. Existing technologies mainly improve the impact performance of mold steel by adding rare earth elements, surface carburizing and nitriding, and optimizing alloying elements. However, these methods generally suffer from problems such as high difficulty in process control, significantly increased production costs, and segregation of steel parts. With current technology, the longitudinal unnotched impact energy of strengthened mold steel is ≤500J, the transverse unnotched impact energy is ≤440J, and the isotropy is ≤0.9. In summary, improving the impact performance of mold steel while reducing costs, simplifying processing procedures, enhancing the performance of mold steel, improving isotropy, and making the microstructure of mold steel finer and more uniformly distributed are the technical challenges that urgently need to be addressed. Summary of the Invention

[0003] To address the above problems, this invention provides a high-impact-performance micro-nano ceramic particle-reinforced mold steel, the preparation method of which includes the following steps: (1) TiAl alloy powder, BN powder and C powder are mixed in a mass ratio of 50-76:18-28:18-28 in a mixer with a speed of 30-60 r / min for 16-18 h to obtain mixture 1; mixture 1 is mixed with pure aluminum strip in a mass ratio of 63-72:28-37 through a continuous coating and sizing forming process 1 to obtain wire A; wire A is subjected to a buffered segmented electro-explosion reaction 1 to obtain aluminum-coated TiC+TiB2 nano-ceramic particle mixture 2. The diameter of the TiAl alloy powder is 15-100μm, the diameter of the BN powder is 25-85μm, and the diameter of the C powder is 70-130μm. The continuous coating and sizing forming process 1 is as follows: the pneumatic compaction pressure is 0.1-0.5 MPa, the forming pressure is 50-150 MPa, the forming temperature is 35℃-200℃, and the forming speed is 1-5 m / min; The buffered segmented electric explosion reaction 1 is as follows: current density is 1.0 × 10⁻⁶. 5Up to 8.0×10 5 A / mm², voltage 800-1700V; after triggering discharge for 30-55 s in a low-pressure high-purity argon atmosphere of 0.01-0.04 MPa, discharge for 80-180 s under high-pressure high-purity argon protection of 0.1-0.3 MPa; (2) Mix NbAl alloy powder and B4C powder at a mass ratio of 50-70:30-50 in a mixer with a rotation speed of 35-65 r / min for 17-20 h to obtain mixture 3; mix mixture 3 with pure aluminum strip at a mass ratio of 68-77:23-32 through continuous coating and sizing forming process 2 to obtain wire B; perform buffered segmented electro-explosion reaction 2 on wire B to obtain aluminum-coated NbC+NbB2 nano-ceramic particle mixture 4; mix mixture 2 and mixture 4 obtained in step (1) at a mass ratio of 56-66:34-44, and then use stainless steel strip to continuously coat and sizing form process 3 to obtain wire C; the total mass of mixture 2 and mixture 4 is 76-86:14-24 of stainless steel strip. The NbAl alloy powder has a diameter of 15-80 μm, and the B4C powder has a diameter of 20-300 μm; The continuous coating and sizing forming process 2 is as follows: the pneumatic compaction pressure is 0.2-0.6MPa, the forming pressure is 65-160MPa, the forming temperature is 40℃-220℃, and the forming speed is 2-6m / min; The buffered segmented electric explosion reaction 2 is as follows: current density is 1.5 × 10⁻⁶. 5 Up to 8.5×10 5 A / mm², voltage 900-1800V; discharge triggered for 35-60 s in a low-pressure high-purity argon atmosphere of 0.02-0.05 MPa, followed by discharge for 90-200 s under high-pressure high-purity argon protection of 0.2-0.5 MPa; The continuous coating and sizing forming process 3 is as follows: the pneumatic compaction pressure is 0.3-0.7MPa, the forming pressure is 70-180MPa, the forming temperature is 50℃-250℃, and the forming speed is 3-7m / min; (3) After melting the mold steel at 1590-1650℃, it is kept at the temperature for 1.5-2.5h and then refined to obtain the mold steel melt. Then, wire C obtained in step (2) is added at a speed of 150-200m / s. Argon gas is then blown into the melt for 20-35 minutes. After vacuum degassing, electroslag remelting, high-temperature diffusion, multi-directional forging and heat treatment, mold steel with high impact performance is obtained. The mass ratio of wire C to mold steel is 0.02-0.032%:1. The nano-ceramic particles contained in the mold steel with high impact performance are (TiC)Nb+(TiB2)N, with an average particle diameter of 118-125nm. The mass ratio of nano-ceramic particles to mold steel is 0.01-0.015%:1. The main components of the mold steel, by weight percentage, include: Cr: 4.5-5.5 wt.%, C: 0.1-1.4 wt.%, Si: 0.15-1.50 wt.%, Mn: 0.35-1.4 wt.%, Mo: 1.6-2.1 wt.%, V: 0.2-0.9 wt.%, P: 0.035-0.050 wt.%, S: 0.015-0.025 wt.%, Fe: balance; The vacuum degassing process involves degassing for 12-28 minutes at a vacuum level of 0.1-1.0 MPa and a temperature of 1600-1640℃. The electroslag remelting is characterized by a current of 6000-12000A, a voltage of 30-48V, and a temperature of 1640℃-1790℃. The high-temperature diffusion is described as follows: maintaining a temperature of 1240℃-1300℃ for 5-13 hours; The multi-directional forging process is characterized by a forging temperature of 950℃-1200℃ and a forging ratio of 6-12:1. The heat treatment is as follows: under vacuum conditions, hold at 635℃-665℃ for 60 minutes, then raise the temperature to 1010℃-1030℃ and hold for 100 minutes; oil quench, then hold at 385℃-410℃ for 4 hours. The obtained high-impact mold steel reinforced with micro-nano ceramic particles has a longitudinal unnotched impact strength of 578.9-601.6 J and a transverse unnotched impact strength of 576.7-590.9 J, with an isotropic value of 0.96-0.99.

[0004] Further, in step (1), the TiAl alloy powder, BN powder and C powder are in a mass ratio of 53-74:19-26:19-26; the mass ratio of mixture 1 to pure aluminum strip is 64-71:29-36; the diameter of TiAl alloy powder is 30-90μm, the diameter of BN powder is 40-75μm, and the diameter of C powder is 80-100μm; the continuous coating and sizing forming process 1 is as follows: the pneumatic compaction pressure is 0.2-0.4MPa, the forming pressure is 60-130MPa, the forming temperature is 40℃-180℃, and the forming speed is 2-4m / min.

[0005] Further, the buffered segmented electric explosion reaction 1 described in step (1) is: a current density of 2.0 × 10⁻⁶. 5 Up to 7.0×10 5 A / mm², voltage 950-1500V; triggered discharge for 40-50s in a low-pressure high-purity argon atmosphere of 0.02-0.03 MPa, followed by discharge for 95-160s under high-pressure high-purity argon protection of 0.15-0.25 MPa.

[0006] Further, in step (2), the NbAl alloy powder and B4C powder are in a mass ratio of 53-69:31-47; the mass ratio of mixture 3 to pure aluminum strip is 69-76:24-31; the mass ratio of mixture 2 and mixture 4 is 57-64:36-43; the total mass of mixture 2 and mixture 4 is in a mass ratio of 77-85:15-23 to the stainless steel strip; the diameter of NbAl alloy powder is 25-75μm, and the diameter of B4C powder is 30-200μm. The continuous coating and sizing forming process 2 is as follows: the pneumatic compaction pressure is 0.35-0.5MPa, the forming pressure is 75-150MPa, the forming temperature is 55℃-200℃, and the forming speed is 4-5m / min.

[0007] Furthermore, the buffered segmented electric explosion reaction 2 described in step (2) is: a current density of 2.5 × 10⁻⁶. 5 Up to 7.5×10 5 A / mm², voltage 1000-1600V; discharge triggered for 45-55s in a low-pressure high-purity argon atmosphere of 0.03-0.04 MPa, followed by 100-180s discharge under high-pressure high-purity argon protection of 0.3-0.4 MPa. The continuous coating and sizing forming process 3 is as follows: the pneumatic compaction pressure is 0.4-0.6MPa, the forming pressure is 80-150MPa, the forming temperature is 70℃-220℃, and the forming speed is 5-6m / min.

[0008] Further, in step (3), the mass ratio of wire C to mold steel is 0.022-0.030%:1; the nano-ceramic particles are (TiC)Nb+(TiB2)N, with an average grain diameter of 119-124nm, and the mass ratio of nano-ceramic particles to mold steel is 0.012-0.014%:1; the main components of the mold steel include: Cr: 4.8-5.3 wt.%, C: 0.5-1.2wt.%, Si: 0.3-1.2wt.%, Mn: 0.5-1.0wt.%, Mo: 1.8-2.0 wt.%, V: 0.4-0.7wt.%, P: 0.040-0.045 wt.%, S: 0.018-0.020 wt.%, Fe: balance.

[0009] Further, the vacuum degassing in step (3) is performed by degassing for 15-25 minutes at a vacuum of 0.2-0.8 MPa and a temperature of 1610℃-1630℃. The electroslag remelting is characterized by a current of 8000-10000A, a voltage of 35-42V, and a molten pool temperature of 1690℃-1760℃. The high-temperature diffusion is described as follows: maintaining a temperature of 1260℃-1290℃ for 7-10 hours; The multi-directional forging process is characterized by a forging temperature of 1000℃-1180℃ and a forging ratio of 7-10:1. The heat treatment is as follows: under vacuum conditions, hold at 645℃-655℃ for 60 minutes, then raise the temperature to 1015℃-1020℃ and hold for 100 minutes; oil quench, then hold at 390℃-400℃ for 4 hours. Compared with the prior art, the advantages of the present invention are: Currently, improving the impact performance of mold steel mainly involves traditional strengthening methods such as optimizing alloy composition or adding rare earth elements. While the former improves impact performance to some extent, it easily leads to defects such as banded segregation and uneven microstructure, and the processing is lengthy and inefficient. Adding rare earth elements can alleviate some segregation problems, but its complex process and cumbersome procedures make it difficult to achieve large-scale industrial application. This invention uses nano-ceramic particles to strengthen mold steel, with a mass fraction of only 0.01%-0.015%.

[0010] Advantages of this invention: Existing technologies typically add more than 0.02% rare earth elements to strengthen mold steel, while this invention adds ≤0.015% nanoparticles, significantly reducing material costs and making it suitable for mass production. Current technologies use electric arc furnaces to melt steel, refine the steel, vacuum process, continuously cast, and spheroidizing anneal to obtain mold steel. For continuous casting, steel can be processed efficiently and with a high operating rate. However, it is difficult to control inclusions and carbides in mold steel, and cracks are prone to occur during continuous casting. This invention adds nanoparticles to the steel, electroslag remelts it, and then forges it. This process ensures the quality of mold steel while saving costs and working time, making it more suitable for large-scale commercial production. Current technologies for strengthening mold steel primarily consist of martensite, retained austenite, and carbides, with the martensite length typically between 3.90 and 4.16 μm. In contrast, the mold steel strengthened by this invention does not produce retained austenite, and its microstructure consists of martensite and trace amounts of carbides. Furthermore, the martensite in the mold steel strengthened by this invention is more uniform and finer than that of existing technologies, with the length dimension controllable between 1.70 and 1.79 μm. Compared to existing technologies, this invention achieves a more uniform microstructure and finer grains. The existing technology for strengthening mold steel results in a longitudinal unnotched impact energy ≤500J, a transverse unnotched impact energy ≤440J, and isotropic properties ≤0.9. In contrast, the mold steel obtained by the claims of this invention achieves a longitudinal unnotched impact energy of 578.9-601.6J, a transverse unnotched impact energy of 576.7-590.9J, and an isotropic property of 0.98-0.99. Comparative analysis shows that the longitudinal and transverse impact energy of the mold steel obtained by this invention are significantly higher than those of the existing technology. Simultaneously, the anisotropy of the longitudinal and transverse impact energy is also significantly lower than that of the existing technology. Therefore, the mold steel obtained by this invention exhibits superior mechanical properties.

[0011] In summary, this invention achieves precise control of the microstructure of mold steel by dynamically adding trace amounts of fine nano-ceramic particles and utilizing uniformly dispersed nanoparticles. Through the interaction between nanoparticles and elements, and the synergistic control of processes and process parameters, it simultaneously improves transverse and longitudinal impact energy and isotropy. That is, while significantly improving impact performance, it solves the pain points of existing technologies such as uneven microstructure, high cost, complex processes, and difficulty in simultaneously improving transverse and longitudinal impact energy and isotropy, and has good prospects for large-scale industrial application. Attached Figure Description

[0012] Figure 1 This is an impact dynamometer diagram of the high-impact performance micro-nano ceramic particle reinforced mold steel 1 obtained in Example 1 of the present invention.

[0013] Figure 2 This is an impact dynamometer diagram of the high-impact performance micro-nano ceramic particle reinforced mold steel 2 obtained in Example 2 of the present invention.

[0014] Figure 3 This is an impact dynamometer diagram of the high-impact performance micro-nano ceramic particle reinforced mold steel 3 obtained in Example 3 of the present invention. Detailed Implementation

[0015] The present invention will be further illustrated by specific embodiments below. These embodiments are for illustrative purposes only, and the scope of protection of the present invention is not limited to these embodiments. Example 1

[0016] The high-impact performance micro-nano ceramic particle reinforced mold steel 1 is prepared by the following steps: (1) TiAl alloy powder, BN powder and C powder are mixed in a mixer at a mass ratio of 55:26:19 for 16 hours to obtain mixture 1; mixture 1 is mixed with pure aluminum strip at a mass ratio of 66:34 and then subjected to continuous coating and sizing forming process 1 to obtain wire A; wire A is subjected to buffered segmented electro-explosion reaction 1 to obtain aluminum-coated TiC+TiB2 nano-ceramic particle mixture 2. The TiAl alloy powder has a diameter of 30 μm, the BN powder has a diameter of 40 μm, and the C powder has a diameter of 80 μm. The continuous coating and sizing forming process 1 is as follows: pneumatic compaction pressure is 0.2 MPa; forming pressure is 70 MPa; forming temperature is 50℃; forming speed is 2 m / min. The buffered segmented electric explosion reaction 1 is as follows: current density is 2.5 × 10⁻⁶. 5 A / mm², voltage 1000V, first triggered discharge for 40s in a low-pressure high-purity argon atmosphere of 0.02MPa, then discharged for 100s under high-pressure high-purity argon protection of 0.15MPa; (2) Mix NbAl alloy powder and B4C powder in a mixer with a speed of 40 r / min at a mass ratio of 56:44 for 17 h to obtain mixture 3. Mixture 3 and pure aluminum strip in a mass ratio of 71:29 are continuously coated and sized to obtain wire B. Wire B is subjected to a buffered segmented electro-explosion reaction 2 to obtain aluminum-coated NbC+NbB2 nano-ceramic particle mixture 4. Mix mixture 2 and mixture 4 obtained in step (1) in a mass ratio of 58:42. Mix mixture 2 and mixture 4 are then continuously coated and sized to obtain wire C using stainless steel strip. The total mass ratio of mixture 2 and mixture 4 to stainless steel strip is 78:22. The diameter of NbAl alloy powder is 25μm, and the diameter of B4C powder is 30μm; The continuous coating and sizing forming process 2 is as follows: the pneumatic compaction pressure is 0.35MPa, the forming pressure is 75MPa, the forming temperature is 55℃, and the forming speed is 4m / min.

[0017] The buffered segmented electric explosion reaction 2 is as follows: current density is 2.5 × 10⁻⁶. 5A / mm², voltage 1100V, first triggered discharge for 45s in a low-pressure high-purity argon atmosphere of 0.03 MPa, then discharged for 100s under high-pressure high-purity argon protection of 0.3MPa; The continuous coating and sizing forming process 3 is as follows: the pneumatic compaction pressure is 0.4 MPa, the forming pressure is 80 MPa, the forming temperature is 70℃, and the forming speed is 5 m / min.

[0018] (3) After melting the mold steel at 1590℃ and holding it at that temperature for 1.5h, the mold steel melt is obtained by refining. Then, wire C obtained in step (2) is added at a speed of 150m / s. Argon gas is then blown into the melt for 20 minutes. After vacuum degassing, electroslag remelting, high-temperature diffusion, multi-directional forging and heat treatment, mold steel with high impact performance is obtained by micro-nano ceramic particles reinforced mold steel. The mass ratio of wire C to mold steel is 0.022%:1. The nano-ceramic particles are (TiC)Nb+(TiB2)N with an average diameter of 119nm. The mass ratio of nano-ceramic particles to mold steel is 0.012%:1. The main components of the mold steel include: Cr: 5.0 wt.%, C: 0.6 wt.%, Si: 0.6 wt.%, Mn: 0.7 wt.%, Mo: 1.9 wt.%, V: 0.4 wt.%, P: 0.042 wt.%, S: 0.018 wt.%, Fe: balance; The vacuum degassing process involves degassing for 15 minutes at a vacuum level of 0.2 MPa and a temperature of 1610 °C. The electroslag remelting is performed at a current of 8000A, a voltage of 35V, and a temperature of 1690℃. The high-temperature diffusion is described as: holding at 1260℃ for 7 hours; The multi-directional forging process is as follows: forging temperature is 1000℃, and forging ratio is 7:1; The heat treatment is as follows: under vacuum conditions, hold at 645℃ for 60 min, then raise the temperature to 1015℃ and hold for 100 min; oil quench, then hold at 390℃ for 4 h; The unnotched impact dynamometer of the high-impact performance micro-nano ceramic particle-reinforced mold steel 1 prepared in this embodiment is shown in the figure below. Figure 1 As shown, its longitudinal unnotched impact energy is 601.6J, its transverse unnotched impact energy is 589.9J, its isotropic property is 0.94, and its average martensite length is 1.73μm. Example 2

[0019] The high-impact performance micro-nano ceramic particle reinforced mold steel 2 is prepared by the following steps: (1) TiAl alloy powder, BN powder and C powder were mixed in a mixer at a mass ratio of 57:23:20 for 17 hours to obtain mixture 1; mixture 1 was mixed with pure aluminum strip at a mass ratio of 67:33 and then subjected to continuous coating and sizing forming process 1 to obtain wire A; wire A was subjected to buffered segmented electro-explosion reaction to obtain aluminum-coated TiC+TiB2 nano-ceramic particle mixture 2. The TiAl alloy powder has a diameter of 40 μm, the BN powder has a diameter of 55 μm, and the C powder has a diameter of 90 μm. The continuous coating and sizing forming process 1 is as follows: pneumatic compaction pressure is 0.3 MPa; forming pressure is 90 MPa; forming temperature is 70℃; forming speed is 3 m / min; The buffered segmented electric explosion reaction 1 is as follows: the current density is 5 × 10⁻⁶. 5 A / mm², voltage 1200V, first triggered discharge for 45 s in a low-pressure high-purity argon atmosphere of 0.025MPa, then discharged for 120 s under the protection of high-pressure high-purity argon atmosphere of 0.2MPa; (2) Mix NbAl alloy powder and B4C powder in a mixer with a speed of 50 r / min at a mass ratio of 62:38 for 18 hours to obtain mixture 3. Mixture 3 and pure aluminum strip in a mass ratio of 73:27 are continuously coated and sized to obtain wire B. Wire B is subjected to a buffered segmented electro-explosion reaction 2 to obtain aluminum-coated NbC+NbB2 nano-ceramic particle mixture 4. Mix mixture 2 and mixture 4 obtained in step (1) in a mass ratio of 59:41. Mix mixture 2 and mixture 4 are then continuously coated and sized to obtain wire C using stainless steel strip. The total mass ratio of mixture 2 and mixture 4 to the stainless steel strip is 79:21. The diameter of NbAl alloy powder is 30μm, and the diameter of B4C powder is 35μm; The continuous coating and sizing forming process 2 is as follows: the pneumatic compaction pressure is 0.4 MPa, the forming pressure is 80 MPa, the forming temperature is 80℃, and the forming speed is 4.5 m / min.

[0020] The buffered segmented electric explosion reaction 2 is as follows: the current density is 5 × 10⁻⁶. 5 A / mm², voltage 1300V, first trigger discharge for 50s in a low-pressure high-purity argon atmosphere at 0.035 MPa, then discharge for 150s under high-pressure high-purity argon protection at 0.35 MPa; The continuous coating and sizing forming process 3 is as follows: the pneumatic compaction pressure is 0.5 MPa, the forming pressure is 100 MPa, the forming temperature is 120℃, and the forming speed is 5.5 m / min.

[0021] (3) After melting the mold steel at 1620℃ and holding it at that temperature for 2 hours, the mold steel melt is obtained by refining. Then, wire C obtained in step (2) is added at a speed of 160 m / s. Argon gas is then blown into the melt for 20 minutes. After vacuum degassing, electroslag remelting, high-temperature diffusion, multi-directional forging and heat treatment, mold steel with high impact performance is obtained by micro-nano ceramic particles reinforced mold steel. The mass ratio of wire C to mold steel is 0.024%:1. The nano-ceramic particles are (TiC)Nb+(TiB2)N with an average diameter of 121 nm. The mass ratio of nano-ceramic particles to mold steel is 0.013%:1. The main components of the mold steel include: Cr: 5.1 wt.%, C: 0.8 wt.%, Si: 0.7 wt.%, Mn: 0.8 wt.%, Mo: 1.9 wt.%, V: 0.5 wt.%, P: 0.043 wt.%, S: 0.019 wt.%, Fe: balance; The vacuum degassing process is as follows: degassing for 20 minutes at a vacuum of 0.4 MPa and a temperature of 1620°C. The electroslag remelting is performed at a current of 9000A, a voltage of 37V, and a temperature of 1700℃. The high-temperature diffusion is described as: holding at 1270℃ for 8.5 hours; The multi-directional forging process is as follows: the forging temperature is 1100℃ and the forging ratio is 8:1; The heat treatment is as follows: under vacuum conditions, hold at 650℃ for 60 min, then raise the temperature to 1018℃ and hold for 100 min; oil quench, then hold at 395℃ for 4 h. The unnotched impact dynamometer of the high-impact performance micro-nano ceramic particle-reinforced mold steel 2 prepared in this embodiment is shown in the figure below. Figure 2 As shown, its longitudinal unnotched impact energy is 600.4 J, its transverse unnotched impact energy is 590.9 J, its isotropic property is 0.98, and its average martensite length is 1.72 μm. Example 3

[0022] A high-impact performance micro-nano ceramic particle-reinforced mold steel, characterized in that its preparation method includes the following steps: (1) TiAl alloy powder, BN powder and C powder are mixed in a mixer with a speed of 40 r / min for 19 h at a mass ratio of 59:22:19 to obtain mixture 1; mixture 1 and pure aluminum strip are mixed in a continuous coating and sizing forming process 1 at a mass ratio of 69:31 to obtain wire A; wire A is subjected to a buffered segmented electro-explosion reaction to obtain aluminum-coated TiC+TiB2 nano-ceramic particle mixture 2; The TiAl alloy powder has a diameter of 50 μm, the BN powder has a diameter of 65 μm, and the C powder has a diameter of 95 μm. The continuous coating and sizing forming process 1 is as follows: pneumatic compaction pressure is 0.4 MPa; forming pressure is 100 MPa; forming temperature is 80℃; forming speed is 4 m / min. The buffered segmented electric explosion reaction 1 is as follows: the current density is 6 × 10⁻⁶. 5 A / mm², voltage 1300V, first triggered discharge for 50 s in a low-pressure high-purity argon atmosphere of 0.03MPa, then discharged for 140 s under the protection of a high-pressure high-purity argon atmosphere of 0.25MPa; (2) Mix NbAl alloy powder and B4C powder in a mixer with a speed of 60 r / min at a mass ratio of 64:36 for 18 hours to obtain mixture 3. Mixture 3 and pure aluminum strip in a mass ratio of 74:26 are continuously coated and sized to obtain wire B. Wire B is subjected to a buffered segmented electro-explosion reaction 2 to obtain aluminum-coated NbC+NbB2 nano-ceramic particle mixture 4. Mix mixture 2 and mixture 4 obtained in step (1) in a mass ratio of 61:39. Mix mixture 2 and mixture 4 are then continuously coated and sized to obtain wire C using stainless steel strip. The total mass ratio of mixture 2 and mixture 4 to stainless steel strip is 81:19. The diameter of NbAl alloy powder is 35μm, and the diameter of B4C powder is 40μm; The continuous coating and sizing forming process 2 is as follows: the pneumatic compaction pressure is 0.5 MPa, the forming pressure is 90 MPa, the forming temperature is 90℃, and the forming speed is 5 m / min.

[0023] The buffered segmented electric explosion reaction 2 is as follows: the current density is 7×10 5 A / mm², voltage 1500V, first triggered discharge for 55s in a low-pressure high-purity argon atmosphere of 0.04 MPa, then discharged for 170s under the protection of high-pressure high-purity argon atmosphere of 0.4 MPa; The continuous coating and sizing forming process 3 is as follows: the pneumatic compaction pressure is 0.6 MPa, the forming pressure is 130 MPa, the forming temperature is 160℃, and the forming speed is 6 m / min.

[0024] (3) After melting the mold steel at 1630℃ and holding it at that temperature for 2.5h, the mold steel melt is obtained by refining. Then, wire C obtained in step (2) is added at a speed of 170m / s. Argon gas is then blown into the melt for 20 minutes. After vacuum degassing, electroslag remelting, high-temperature diffusion, multi-directional forging and heat treatment, mold steel with high impact performance is obtained by micro-nano ceramic particles reinforced mold steel. The mass ratio of wire C to mold steel is 0.03%:1. The nano-ceramic particles are (TiC)Nb+(TiB2)N, and the average diameter of the crystal particles is 124nm. The mass ratio of nano-ceramic particles to mold steel is 0.014%:1. The main components of the mold steel include: Cr: 5.2 wt.%, C: 0.9 wt.%, Si: 0.8 wt.%, Mn: 0.9 wt.%, Mo: 2.0 wt.%, V: 0.6 wt.%, P: 0.045 wt.%, S: 0.020 wt.%, Fe: balance; The vacuum degassing process is as follows: degassing for 25 minutes at a vacuum of 0.6 MPa and a temperature of 1630°C. The electroslag remelting is performed at a current of 10000A, a voltage of 40V, and a temperature of 1730℃. The high-temperature diffusion is described as follows: holding at 1290℃ for 9 hours; The multi-directional forging process is as follows: the forging temperature is 1160℃ and the forging ratio is 9:1; The heat treatment is as follows: under vacuum conditions, hold at 655℃ for 60 min, then raise the temperature to 1020℃ and hold for 100 min; oil quench, then hold at 400℃ for 4 h. The unnotched impact dynamometer of the high-impact performance micro-nano ceramic particle-reinforced mold steel 3 prepared in this embodiment is shown in the figure below. Figure 3 As shown, its longitudinal unnotched impact energy is 578.9 J, its transverse unnotched impact energy is 576.7 J, its isotropic property is 0.99, and its average martensite length is 1.75 μm. Comparative Example 1

[0025] A mold steel 4, the preparation method of which includes the following steps: (1) The mold steel is melted at 1630℃, then kept at the temperature for 2.5h, and then refined to obtain mold steel melt. After vacuum degassing, electroslag remelting, high temperature diffusion, multi-directional forging and heat treatment, mold steel 4 is obtained. The main components of the mold steel include: Cr: 5.2 wt.%, C: 0.9 wt.%, Si: 0.8 wt.%, Mn: 0.9 wt.%, Mo: 2.0 wt.%, V: 0.6 wt.%, P: 0.045 wt.%, S: 0.020 wt.%, Fe: balance; The vacuum degassing process is as follows: degassing for 25 minutes at a vacuum of 0.6 MPa and a temperature of 1630°C. The electroslag remelting is performed at a current of 10000A, a voltage of 40V, and a temperature of 1730℃. The high-temperature diffusion is described as follows: holding at 1290℃ for 9 hours; The multi-directional forging process is as follows: the forging temperature is 1160℃ and the forging ratio is 9:1; The heat treatment is as follows: under vacuum conditions, hold at 655℃ for 60 min, then raise the temperature to 1020℃ and hold for 100 min; oil quench, then hold at 400℃ for 4 h. The mold steel 4 obtained in this comparative example has a longitudinal unnotched impact energy of 532.5 J, a transverse unnotched impact energy of 486.1 J, an isotropic property of 0.91, and an average martensite length dimension of 3.92 μm.

[0026] In Example 3 of this invention, the types of raw materials and elemental contents are the same as in Comparative Example 1, and the process parameters are the same. The difference is that: The main difference lies in the addition of 0.014% nano-ceramic particles in Example 3, while Comparative Example 1 did not include any nano-particles. The high-impact performance micro-nano-ceramic particle-reinforced mold steel 3 prepared in Example 3 exhibits a longitudinal unnotched impact energy of 578.9 J, a transverse unnotched impact energy of 576.7 J, an isotropic property of 0.99, and an average martensite length of 1.75 μm. In contrast, the mold steel 4 prepared in Comparative Example 1 exhibits a longitudinal unnotched impact energy of 532.5 J, a transverse unnotched impact energy of 486.1 J, an isotropic property of 0.91, and an average martensite length of 3.92 μm. Compared to mold steel 4, Example 3 shows an 8.7% increase in longitudinal unnotched impact energy, an 18.6% increase in transverse unnotched impact energy, a 0.08 increase in isotropic property, and a 55.4% reduction in martensite length. Therefore, compared to Comparative Example 1, this invention demonstrates superior impact performance. Comparative Example 2

[0027] Patent CN104818424B, published by Lei et al. in 2017, discloses a rare earth mold steel and its preparation method, which involves adding 0.02% rare earth cerium and rare earth lanthanum to the mold steel for strengthening. The final rare earth-reinforced mold steel is obtained through a process of electric furnace smelting of molten steel followed by treatment with rare earth cerium and rare earth lanthanum, water-cooled die casting, heavy extrusion forming, and fine spheroidizing annealing. The main components of the mold steel include: C: 0.37-0.42%, Si: 0.8-1.2%, Mn: 0.2-0.5%, Cr: 5.0-5.5%, Mo: 1.2-1.75%, V: 0.8-1.2%, S≤0.005%, P≤0.025%, and the balance Fe. Its longitudinal unnotched impact energy is 348.8 J, its transverse unnotched impact energy is 300.1 J, and its isotropic property is 0.86.

[0028] Compared to Comparative Example 2, in all embodiments of the present invention, Example 3 has the highest content of added nanoparticles, at only 0.014%, while Comparative Example 2 added 0.02% rare earth cerium and rare earth lanthanum. Compared to Comparative Example 2, the present invention significantly reduces costs. Comparative Example 2 requires water cooling, while the present invention, after adding nanoparticles in the steel refining process, does not require water cooling and can directly proceed to the next step of electroslag remelting, saving production time. Comparative Example 2 has high equipment requirements for extrusion forming, and the fine spheroidizing annealing time is long and the steps are more complex. In contrast, the present invention saves production time, simplifies the production process, and saves production costs. Comparative Example 2 has a longitudinal unnotched impact energy of 348.8 J, a transverse unnotched impact energy of 300.1 J, and an isotropic property of 0.86, while Example 3 has a longitudinal unnotched impact energy of 578.9 J, a transverse unnotched impact energy of 576.7 J, and an isotropic property of 0.99. It is clear that the minimum impact performance and isotropic property of the embodiments of the present invention are far superior to the maximum performance of the mold steel strengthened by the technology used in Comparative Example 2.

[0029] Therefore, this invention only requires the addition of trace amounts of nanoparticles, reduces raw material costs, simplifies the process, and saves production time, while simultaneously improving the impact performance and isotropy of mold steel.

[0030] Table 1. Impact performance values ​​of die steels in Examples 1-3 and Comparative Examples 1-2

[0031] In summary, compared with existing technologies, the impact performance of the mold steel prepared by this invention is significantly improved. Its core advantages are: existing technologies generally add more than 0.02% rare earth elements to strengthen mold steel, while this invention controls the addition content to below 0.015%, significantly reducing material costs and making it suitable for large-scale production; existing technologies use electric arc furnace melting of steel, refining, vacuum treatment, continuous casting, and spheroidizing annealing to obtain mold steel, while this invention, due to the addition of nanoparticles, results in a uniform microstructure distribution of the mold steel, which, combined with electroslag remelting, yields high-quality strengthened mold steel. This simplifies the process, effectively avoids cracking that may occur during continuous casting, and achieves stable and efficient control of the microstructure; the microstructure of the strengthened mold steel produced by existing technologies contains martensite, retained austenite, and some carbides (of which... The martensite length is generally between 3.90-4.16 μm, which is less effective in refining the microstructure compared to the present invention. The microstructure strengthened by the present invention consists of martensite and trace amounts of carbides, with no retained austenite and a lower carbide content. The martensite is more uniform and finer (the martensite length can be controlled between 1.70-1.79 μm), thus achieving microstructure homogenization and refinement. Existing technologies have difficulty improving the longitudinal and transverse impact energy of die steel while simultaneously improving isotropy. However, the present invention achieves a longitudinal unnotched impact energy ≥578.9 J, a transverse unnotched impact energy ≥576.7 J, and isotropy ≥0.98, thus improving the longitudinal and transverse impact energy of die steel while simultaneously improving isotropy.

[0032] The three embodiments of this invention employ different component ratios and process parameters, yet all exhibit significantly superior impact performance compared to existing reinforced die steels. The different ratios and process parameters in each embodiment result in varying performance levels, demonstrating that the optimal effect achieved by this invention is not determined by any single component, ratio, process, or process parameter, but rather by the synergistic regulation of component interactions, ratios, processes, and process parameters. Furthermore, only within the scope of the claims of this invention can such significantly improved technical effects be achieved.

Claims

1. A high-impact performance micro-nano ceramic particle reinforced die steel, characterized in that, Its preparation method includes the following steps: (1) TiAl alloy powder, BN powder and C powder are mixed in a mass ratio of 50-76:18-28:18-28 in a mixer with a speed of 30-60 r / min for 16-18 h to obtain mixture 1; mixture 1 is mixed with pure aluminum strip in a mass ratio of 63-72:28-37 through a continuous coating and sizing forming process 1 to obtain wire A; wire A is subjected to a buffered segmented electro-explosion reaction 1 to obtain aluminum-coated TiC+TiB2 nano-ceramic particle mixture 2. The diameter of the TiAl alloy powder is 15-100μm, the diameter of the BN powder is 25-85μm, and the diameter of the C powder is 70-130μm. The continuous coating and sizing forming process 1 is as follows: the pneumatic compaction pressure is 0.1-0.5 MPa, the forming pressure is 50-150 MPa, the forming temperature is 35℃-200℃, and the forming speed is 1-5 m / min; The buffered segmented electric explosion reaction 1 is as follows: current density is 1.0 × 10⁻⁶. 5 -8.0×10 5 A / mm², voltage 800-1700V; after triggering discharge for 30-55 s in a low-pressure high-purity argon atmosphere of 0.01-0.04 MPa, discharge for 80-180 s under high-pressure high-purity argon protection of 0.1-0.3 MPa; (2) Mix NbAl alloy powder and B4C powder at a mass ratio of 50-70:30-50 in a mixer with a rotation speed of 35-65r / min for 17-20h to obtain mixture 3; mix mixture 3 with pure aluminum strip at a mass ratio of 68-77:23-32 through continuous coating and sizing forming process 2 to obtain wire B; perform buffered segmented electro-explosion reaction 2 on wire B to obtain aluminum-coated NbC+NbB2 nano-ceramic particle mixture 4; mix mixture 2 and mixture 4 obtained in step (1) at a mass ratio of 56-66:34-44, and then use stainless steel strip to continuously coat and sizing form process 3 to obtain wire C; the total mass of mixture 2 and mixture 4 is 76-86:14-24 of stainless steel strip. The NbAl alloy powder has a diameter of 15-80 μm, and the B4C powder has a diameter of 20-300 μm; The continuous coating and sizing forming process 2 is as follows: the pneumatic compaction pressure is 0.2-0.6MPa, the forming pressure is 65-160MPa, the forming temperature is 40℃-220℃, and the forming speed is 2-6m / min; The buffered segmented electric explosion reaction 2 is as follows: current density is 1.5 × 10⁻⁶. 5 -8.5×10 5 A / mm², voltage 900-1800V; discharge triggered for 35-60 s in a low-pressure high-purity argon atmosphere of 0.02-0.05 MPa, followed by discharge for 90-200 s under high-pressure high-purity argon protection of 0.2-0.5 MPa; The continuous coating and sizing forming process 3 is as follows: the pneumatic compaction pressure is 0.3-0.7MPa, the forming pressure is 70-180MPa, the forming temperature is 50℃-250℃, and the forming speed is 3-7m / min; (3) After melting the mold steel at 1590-1650℃, it is kept at the temperature for 1.5-2.5h and then refined to obtain the mold steel melt. Then, wire C obtained in step (2) is added at a speed of 150-200m / s. Argon gas is then blown into the melt for 20-35 minutes. After vacuum degassing, electroslag remelting, high-temperature diffusion, multi-directional forging and heat treatment, mold steel with high impact performance is obtained. The mass ratio of wire C to mold steel is 0.02-0.032%:

1. The nano-ceramic particles contained in the mold steel with high impact performance are (TiC)Nb+(TiB2)N, with an average particle diameter of 118-125nm. The mass ratio of nano-ceramic particles to mold steel is 0.01-0.015%:

1. The main components of the mold steel, by weight percentage, include: Cr: 4.5-5.5 wt.%, C: 0.1-1.4 wt.%, Si: 0.15-1.50 wt.%, Mn: 0.35-1.4 wt.%, Mo: 1.6-2.1 wt.%, V: 0.2-0.9 wt.%, P: 0.035-0.050 wt.%, S: 0.015-0.025 wt.%, Fe: balance; The vacuum degassing process is as follows: degassing for 12-28 minutes at a vacuum of 0.1-1.0 MPa and a temperature of 1600-1640℃. The electroslag remelting process is as follows: current 6000-12000A, voltage 30-48V, and temperature 1640-1790℃; The high-temperature diffusion is described as follows: holding at 1240-1300℃ for 5-13 hours; The multi-directional forging process is characterized by a forging temperature of 950-1200℃ and a forging ratio of 6-12:

1. The heat treatment is as follows: under vacuum conditions, hold at 635℃-665℃ for 60 minutes, then raise the temperature to 1010℃-1030℃ and hold for 100 minutes; oil quench, then hold at 385℃-410℃ for 4 hours. The obtained high-impact mold steel reinforced with micro-nano ceramic particles has a longitudinal unnotched impact strength of 578.9-601.6 J and a transverse unnotched impact strength of 576.7-590.9 J, with an isotropic value of 0.96-0.

99.

2. The high-impact performance micro-nano ceramic particle reinforced die steel according to claim 1, characterized in that, In step (1), the TiAl alloy powder, BN powder and C powder are in a mass ratio of 53-74:19-26:19-26; the mass ratio of mixture 1 to pure aluminum strip is 64-71:29-36; the diameter of TiAl alloy powder is 30-90μm, the diameter of BN powder is 40-75μm, and the diameter of C powder is 80-100μm; the continuous coating and sizing forming process 1 is as follows: the pneumatic compaction pressure is 0.2-0.4MPa, the forming pressure is 60-130MPa, the forming temperature is 40℃-180℃, and the forming speed is 2-4m / min.

3. The high-impact performance micro-nano ceramic particle reinforced die steel according to claim 1, characterized in that, The buffered segmented electric explosion reaction 1 described in step (1) is as follows: the current density is 2.0 × 10⁻⁶. 5 -7.0×10 5 A / mm², voltage 950-1500V; discharge triggered for 40-50 s in a low-pressure high-purity argon atmosphere of 0.02-0.03 MPa, followed by discharge for 95-160 s under high-pressure high-purity argon protection of 0.15-0.25 MPa.

4. The high-impact performance micro-nano ceramic particle reinforced die steel according to claim 1, characterized in that, In step (2), the NbAl alloy powder and B4C powder are mixed in a mass ratio of 53-69:31-47; the mass ratio of mixture 3 to pure aluminum strip is 69-76:24-31; the mass ratio of mixture 2 and mixture 4 is 57-64:36-43; the total mass of mixture 2 and mixture 4 is 77-85:15-23 to the mass of stainless steel strip; the diameter of NbAl alloy powder is 25-75μm, and the diameter of B4C powder is 30-200μm. The continuous coating and sizing forming process 2 is as follows: the pneumatic compaction pressure is 0.35-0.5MPa, the forming pressure is 75-150MPa, the forming temperature is 55℃-200℃, and the forming speed is 4-5m / min.

5. A high-impact performance micro-nano ceramic particle reinforced die steel according to claim 1, characterized in that, The buffered segmented electric explosion reaction 2 mentioned in step (2) is: current density of 2.5 × 10 5 -7.5×10 5 A / mm², voltage 1000-1600V; discharge triggered for 45-55 s in a low-pressure high-purity argon atmosphere of 0.03-0.04 MPa, followed by discharge for 100-180 s under high-pressure high-purity argon protection of 0.3-0.4 MPa; The continuous coating and sizing forming process 3 is as follows: the pneumatic compaction pressure is 0.4-0.6MPa, the forming pressure is 80-150MPa, the forming temperature is 70℃-220℃, and the forming speed is 5-6m / min.

6. A high-impact performance micro-nano ceramic particle reinforced die steel according to claim 1, characterized in that, In step (3), the mass ratio of wire C to mold steel is 0.022-0.030%:1; the nano-ceramic particles are (TiC)Nb+(TiB2)N, with an average particle diameter of 119-124nm, and the mass ratio of nano-ceramic particles to mold steel is 0.012-0.014%:1; the chemical composition of the mold steel before reaction, by mass percentage, is: Cr: 4.8-5.3 wt.%, C: 0.5-1.2wt.%, Si: 0.3-1.2wt.%, Mn: 0.5-1.0wt.%, Mo: 1.8-2.0 wt.%, V: 0.4-0.7wt.%, P: 0.040-0.045 wt.%, S: 0.018-0.020 wt.%, Fe: balance.

7. The high-impact performance micro-nano ceramic particle reinforced die steel according to claim 1, characterized in that, The vacuum degassing in step (3) is performed for 15-25 minutes at a vacuum of 0.2-0.8 MPa and a temperature of 1610℃-1630℃. The electroslag remelting is characterized by a current of 8000-10000A, a voltage of 35-42V, and a molten pool temperature of 1690℃-1760℃. The high-temperature diffusion is described as follows: maintaining a temperature of 1260℃-1290℃ for 7-10 hours; The multi-directional forging process is characterized by a forging temperature of 1000℃-1180℃ and a forging ratio of 7-10:

1. The heat treatment is as follows: under vacuum conditions, hold at 645℃-655℃ for 60 minutes, then raise the temperature to 1015℃-1020℃ and hold for 100 minutes. Oil quenching followed by heat treatment at 390℃-400℃ for 4 hours.

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