Die steel with high strength, high wear resistance and excellent high temperature tensile properties and preparation thereof

Abstract

The present application relates to high-strength, high-wear-resistance and excellent high-temperature tensile performance die steel and its preparation. The die steel is obtained by inserting electroslag remelting after vacuum treatment in the preliminary heat treatment stage of traditional H13 steel preparation process: initial smelting + refining + vacuum treatment, and by inserting deep cryogenic treatment after higher temperature quenching in the final heat treatment stage: quenching + tempering; the specific components and mass percentages are C: 0.35%-0.45%, Cr: 4.75%-5.50%, Mo: 1.10%-1.75%, V: 0.80%-1.20%, Si: 0.80-1.20%, Mn: 0.20%-0.50%, and the impurities and gas contents are strictly controlled as P≤0.03%, S≤0.005%, O≤20ppm, H≤1.5ppm, N≤80ppm, etc. The present application can effectively remove inclusions, ensure grain refinement and optimize the uniformity of the structure by the electroslag remelting process and by using higher temperature quenching and regulating deep cryogenic treatment time in the final heat treatment stage.

Description

Technical Field

[0001] This invention relates to the field of mold steel materials technology. Specifically, it relates to high-strength, high-wear-resistant mold steel with excellent high-temperature tensile properties and its preparation. Background Technology

[0003] Hot work die steel is one of the most widely used die steels, with AISI H13 steel being particularly favored for its excellent hardenability, toughness, and thermal fatigue properties. It is widely used in hot forging, die casting, and hot extrusion. During use, dies are prone to thermal stress concentration due to repeated heating and cooling, leading to the initiation and propagation of thermal fatigue cracks. They may also be affected by impact loads. The propagation of thermal fatigue cracks on the die surface and insufficient toughness can cause cracking, thus reducing the die's service life. Furthermore, dies exhibit various failure modes. Improper heat treatment is one of the main causes of die failure, accounting for as much as 42%. Therefore, when processing different types of dies, appropriate heat treatment processes must be selected to ensure their performance and service life.

[0004] In the pursuit of high-efficiency production and environmental sustainability, improving the performance of H13 steel as a mold material and extending mold life have become key challenges for the mold industry. Currently, research on improving the performance of H13 steel and mold life mainly focuses on optimizing alloying elements and improving heat treatment processes. However, these traditional methods often involve long development cycles and high costs associated with new material development. As an innovative alternative, by employing advanced heat treatment technologies and slight changes in composition to control the microstructure of H13 steel, material properties can be effectively improved at a lower cost. This method not only enhances the thermal fatigue resistance of molds but also extends their overall service life, thus playing a significant role in resource conservation and carbon emission reduction.

[0005] However, while there are considerable studies on the tensile and fatigue properties of H13 die steel, research on its wear resistance and high-temperature tensile properties is relatively limited. Its typical operating environments include high temperature, high pressure, and cyclic thermal shock conditions, such as in the manufacture of die-casting molds, hot forging molds, extrusion molds, and plastic molding molds. In these scenarios, H13 steel must withstand instantaneous high temperatures of 600-1000°C, intense mechanical impact, and repeated heating-cooling cycles. For example, in aluminum alloy die casting, H13 steel molds are in direct contact with molten metal and must withstand high-temperature corrosion and thermal fatigue; in hot forging processes, the steel must maintain high hardness and resistance to softening to cope with continuous mechanical stress and the risk of high-temperature softening. Furthermore, H13 steel is also commonly used in the manufacture of molding dies for aerospace components, glass molds, and high-temperature shearing tools, because it can maintain stable microstructure and mechanical properties under extreme conditions, ensuring long mold life and high-precision machining.

[0006] The study by Lu et al. points out that traditional H13 steel exhibits significant wear failure at high temperatures when molds operate in high-temperature, high-friction environments (such as high-temperature thermal friction at 500-600℃). This is particularly pronounced under specific mold operating conditions (thermal shock, high-temperature wear, high-speed friction), indicating that existing H13 steel still has insufficient high-temperature wear resistance and requires improvement in its service performance through material modification or surface strengthening processes (Lu, C.; Chen, Z.; Yan, Y.; Zhuo, Y.; Wang, C.; Jia, Q.). Enhanced High-Temperature Wear Performance of H13 Steel through TiC Incorporation by Laser Metal Deposition . Materials16(1), 99(2023).).

[0007] Therefore, improving the wear resistance and high-temperature tensile properties of H13 mold steel is of great significance for enhancing its overall performance. Summary of the Invention

[0008] Based on the above problems, it is necessary to provide an H13 mold steel with high strength, high wear resistance and excellent high temperature performance, as well as a heat treatment process and a method for improving the performance of this steel.

[0009] This invention proposes a technical solution for producing mold steel through optimized thermal processes and cryogenic treatment. In traditional heating processes, inaccurate temperature control (too high or too low) can lead to grain growth or excessive heterogeneous structures, affecting the material's performance. Optimizing the quenching temperature allows for precise attainment of the phase transformation temperature, resulting in a fine martensitic structure after quenching, optimizing the material's microstructure, and reducing the amount of retained austenite. Following heat treatment, a suitable period of cryogenic treatment further promotes grain refinement and the transformation of retained austenite, thereby improving wear resistance and high-temperature performance.

[0010] The technical solution of the present invention is as follows:

[0011] This invention provides a high-strength, high-wear-resistant mold steel with excellent high-temperature tensile properties. Based on the preliminary heat treatment stages of the traditional H13 steel preparation process (primary refining + refining + vacuum treatment), electroslag remelting is inserted after vacuum treatment, and the final heat treatment stage (quenching + tempering) is performed using high-temperature quenching followed by deep cryogenic treatment. Its specific composition and mass percentages are as follows: C: 0.35%-0.45%, Cr: 4.75%-5.50%, Mo: 1.10%-1.75%, V: 0.80%-1.20%, Si: 0.80%-1.20%, Mn: 0.20%-0.50%, with the remainder being iron and unavoidable impurities, wherein P≤0.03%, S≤0.005%, O≤20ppm, H≤1.5ppm, and N≤80ppm.

[0012] Furthermore, the chemical composition and mass percentage of H13 steel are as follows: C: 0.32%-0.45%, Cr: 4.75%-5.50%, Mo: 1.10%-1.75%, V: 0.80%-1.20%, Si: 0.80%-1.20%, Mn: 0.20%-0.50%, with the balance being Fe and unavoidable impurities. The mass percentage of impurities is controlled as follows: P≤0.03%, S≤0.03%, O≤20ppm, H≤1.5ppm, N≤80ppm.

[0013] Furthermore, the elements and their functions are as follows: (1) C: Carbon is the most common strengthening element in steel. 1. It forms a solid solution structure, which increases the strength of steel. 2. It forms a carbide structure, which can increase the hardness and wear resistance of steel.

[0014] (2) Influence of Cr: In hot work die steel, Cr is mainly used to form different types of carbides, the most common of which are M3C, M7C3, and M23C6 carbides. M7C3 carbides reduce the thermal stability and thermal fatigue life of the material because, with the extension of the holding time, the carbides tend to precipitate and aggregate at the martensite bundle boundaries and grain boundaries. Therefore, for some dies that need to be used in high-temperature environments, it is necessary to control the Cr content to avoid excessive precipitation and aggregation of M7C3 carbides. In addition, M3C carbides are also a common type of carbide. Due to their fine and uniform morphology and their reluctance to aggregate and grow at high temperatures, they greatly improve the thermal stability of the material. Therefore, for some dies that need to be used in high-temperature environments, a low-Cr, high-V alloy design can be adopted to improve thermal stability and thermal fatigue life.

[0015] (3) Effect of V: ​​V is a commonly used strengthening element in die steel. It can improve the strength and plasticity of hot work die steel, as well as improve its thermal fatigue performance. The addition of V can promote grain boundary recombination in hot work die steel and improve the strength of grain boundaries, thereby reducing the initiation and propagation of thermal fatigue cracks at grain boundaries. In addition, V is a carbide-forming element in hot work die steel, which can affect the precipitation and distribution of carbides, thereby improving the thermal stability and thermal fatigue resistance of the material.

[0016] (4) Influence of Mo: Mo is a strengthening element that can form hard carbides in hot work die steel, such as M2C type carbides, which can produce a secondary hardening effect. In addition, it forms strong compounds with iron, which can improve the hardness and strength of hot work die steel, making it more suitable for high-temperature and high-pressure working environments. Mo can exist stably at high temperatures, giving hot work die steel good heat resistance. At high temperatures, Mo can form a stable oxide film, protecting hot work die steel from oxidation and corrosion. In addition to forming strong carbides, Mo also produces fine MoC and MoN particles during rolling and heat treatment, which can refine the grain size of the test steel.

[0017] (5) Effect of Si: Si is a ferrite-forming element with a significant solid solution strengthening effect, which can improve the hardness and wear resistance of the material, but it will also reduce the plasticity and toughness of the material. In addition, Si can effectively inhibit the diffusion rate of carbon, thereby hindering the growth of carbides, resulting in an increase in small-sized carbides in the matrix, which can refine the grains and greatly improve the tempering stability and hardenability of the material.

[0018] (6) Influence of Mn: Mn is an element that does not easily form carbides. Mn generally forms a solid solution with Fe, which improves strength and hardness, and is beneficial to improving wear resistance and thermal fatigue resistance. At the same time, it can also be used as an effective desulfurizing agent, which can remove the hot brittleness caused by residual sulfur, and is beneficial to improving the hot working performance of materials.

[0019] (7) Influence of impurity elements. Among them, sulfur (S) has a significant impact. During hot rolling, it is distributed in a fibrous manner along the rolling direction, which not only generates greater stress on the die surface but also provides a path for subsequent crack propagation, thereby reducing its thermal fatigue performance. In addition, the micropore aggregation of sulfides formed by sulfur during fracture reduces fracture toughness and thermal fatigue performance. Some studies also suggest that manganese sulfide formed by sulfur tends to form voids in the matrix, which provides conditions for the in-depth development of oxidation, accelerates the propagation of thermal fatigue cracks, and thus reduces the thermal fatigue performance of die steel.

[0020] This invention also provides a method for preparing the above-mentioned high-strength, high-wear-resistant, and excellent high-temperature tensile steel, comprising the following steps: (1) Primary smelting: The primary smelting is carried out using an ultra-high power electric arc furnace (EAF). After melting, preliminary dephosphorization and composition control are completed, the molten steel is tapped into the ladle to obtain primary smelted steel. (2) Refining: The primary steel is transferred to the ladle refining furnace LF, and lime, fluorite and other slag-forming agents are added to form white slag. Desulfurization, deoxidation and fine-tuning of alloy composition are carried out, and electromagnetic stirring is used to promote the reaction between the steel liquid and the slag system and the floating of inclusions to obtain refined steel. (3) Vacuum treatment: The refined molten steel and the ladle are placed in a vacuum degassing device (VD) for vacuum treatment. While removing gases such as hydrogen and nitrogen from the molten steel, trace alloying elements are added by wire feeding. (4) Protective casting: The molten steel after vacuum treatment is cast into square or round billets through an intermediate ladle using a protective casting process. Electromagnetic stirring is applied during the casting process to refine the solidification structure and obtain high-quality billets. (5) Annealing: After cooling, the high-quality billet is placed in an annealing furnace for spheroidizing annealing to obtain annealed billet; (6) Electroslag remelting: The annealed billet is used as a consumable electrode and placed in an electroslag remelting furnace. Electroslag remelting is carried out using a CaF2-based slag system. The billet is then directionally solidified in a water-cooled crystallizer to obtain a remelted ingot. (7) Multi-directional forging: The remelted ingot is subjected to multi-directional forging and normalizing treatment to obtain normalized billet; (8) Annealing: The normalized billet is spheroidized annealed through a segmented heat preservation and slow cooling process; (9) Quenching: After spheroidizing annealing, the billet is heated and kept at a certain temperature, and then quenched by water cooling to obtain quenched billet; (10) Cryogenic treatment: The quenched billet is placed in liquid nitrogen for cryogenic treatment to obtain the cryogenically treated billet; (11) Tempering: Tempering the deep cryogenically treated billet to obtain high-strength, high-wear-resistant mold steel with excellent high-temperature tensile properties.

[0021] Furthermore, in step (1), the composition control is achieved by precisely controlling the content of impurities such as carbon and phosphorus through oxygen blowing with an oxygen lance, ensuring that the alloying elements are evenly distributed.

[0022] Furthermore, in step (3), the vacuum degree of the vacuum degassing device is strictly controlled at ≤67Pa, which is used to effectively reduce the hydrogen and nitrogen content and the amount of non-metallic inclusions in the molten steel.

[0023] Furthermore, in step (3), the vacuum degassing temperature is 1500-1550℃ and the vacuum degassing time is 20-40 minutes.

[0024] Furthermore, in step (4), argon gas is used to protect the casting from secondary oxidation, the casting speed is 0.5-1.2 m / min, and the superheat is 20-40℃.

[0025] Furthermore, in step (6), the electroslag remelting uses a CaF2-based slag system with a mass ratio of CaF2:Al2O3:CaO = 70:20:10.

[0026] Furthermore, in step (6), the electroslag remelting conditions are: remelting current 8000-15000A, voltage 35-45V, and remelting speed 3-6kg / min.

[0027] Furthermore, in step (6), directional solidification controls the size of inclusions to ≤10μm.

[0028] Furthermore, in step (9), the quenching temperature is 1030-1090℃.

[0029] Furthermore, in step (10), the cryogenic treatment time is 0-10h.

[0030] The present invention also provides the above-mentioned high-strength, high-wear-resistant mold steel with excellent high-temperature tensile properties, and its application in the fields of machinery manufacturing, precision machining, and high-end equipment.

[0031] Compared with the prior art, the present invention has the following advantages and beneficial effects: (1) Compared with conventional high-quality mold steel production processes, this invention inserts an ESR electroslag remelting process into the traditional preliminary heat treatment stage: primary refining + refining + vacuum treatment, and adopts higher temperature quenching and deep cryogenic treatment in the final heat treatment stage, which significantly improves the purity and uniformity of the steel structure. Electroslag remelting, through directional solidification and efficient impurity removal, thoroughly removes non-metallic inclusions and harmful elements that are difficult to completely eliminate by conventional processes, making the carbide distribution finer and more dispersed, basically eliminating banded and network segregation, and resulting in a uniform and dense structure after forging, providing an extremely ideal initial state for the subsequent final heat treatment stage.

[0032] (2) In the final heat treatment stage, the alloying elements are fully dissolved and austenite is homogenized through quenching at a precise phase transformation temperature. The subsequent deep cryogenic treatment effectively promotes the transformation of residual austenite to martensite, significantly reduces the content of residual austenite, and further improves hardness, dimensional stability, and thermal fatigue resistance. The overall effect is that the initiation and propagation of hot cracks in the mold under high-temperature cyclic loading are significantly delayed, the impact toughness and wear resistance are synergistically improved, and the service life is greatly extended. It is especially suitable for harsh working conditions such as aluminum alloy die casting and hot forging, and achieves an excellent balance between the comprehensive performance and production cost of high-end mold steel.

[0033] (3) The mold steel finally obtained by the present invention has high purity, excellent wear resistance and stable mechanical properties (average friction coefficient 0.42, room temperature yield strength 1851MPa, tensile strength 2130MPa, total elongation 7.7%, high temperature yield strength 1076MPa, high temperature tensile strength 1127MPa, total elongation 19.5%).

[0034] (4) This invention can adapt to different usage needs by adjusting the cryogenic treatment time, and provides high-performance material support for high-end machinery manufacturing, precision machining, high-end equipment and other fields. It has significant industrial application value and promotion prospects. Attached Figure Description

[0035] Figure 1 This is a production flow chart of the preliminary heat treatment stage of the high-strength, high-wear-resistant mold steel with excellent high-temperature tensile properties of the present invention.

[0036] Figure 2 This is a process diagram of the final heat treatment stage of the high-strength, high-wear-resistant mold steel with excellent high-temperature tensile properties of the present invention.

[0037] Figure 3 The results are the engineering stress-strain curves of the high-strength, high-wear-resistant, and high-temperature tensile properties of the die steel prepared in Examples 6 to 11 under room temperature tension (C0: Example 6; C2: Example 7; C4: Example 8; C6: Example 9; C8: Example 10; C10: Example 11).

[0038] Figure 4 The results are the EBSD results of the high-strength, high-wear-resistant, and high-temperature tensile properties of the die steels prepared in Examples 6-11 (a: Example 6; b: Example 7; c: Example 8; d: Example 9; e: Example 10; f: Example 11).

[0039] Figure 5 This is a comparison chart of Rockwell hardness of high-strength, high-wear-resistant mold steels with excellent high-temperature tensile properties prepared by different cryogenic treatment times in Examples 6-11.

[0040] Figure 6 The diagram shows the engineering stress-strain curves of the high-strength, high-wear-resistant, and excellent high-temperature tensile properties of the mold steel prepared in Examples 6-11 at 650℃ (C0: Example 6; C2: Example 7; C4: Example 8; C6: Example 9; C8: Example 10; C10: Example 11).

[0041] Figure 7The friction and wear curves and average friction coefficient diagrams of the high-strength, high-wear-resistant, and high-temperature tensile properties of the mold steels prepared in Examples 6-11 are shown (a: friction and wear curve diagram; b: average friction coefficient diagram; C0: Example 6; C2: Example 7; C4: Example 8; C6: Example 9; C8: Example 10; C10: Example 11).

[0042] Figure 8 The impact toughness comparison diagrams of the high-strength, high-wear-resistant and excellent high-temperature tensile properties of the mold steels prepared in Examples 6 to 11 are shown (C0: Example 6; C2: Example 7; C4: Example 8; C6: Example 9; C8: Example 10; C10: Example 11).

[0043] Figure 9 These are transmission electron microscopy (TEM) images of the high-strength, high-wear-resistant, and high-temperature tensile properties of the mold steels prepared in Examples 6 and 10 (a: TEM view of Example 6; b: diffraction spots of precipitates in Example 6; c: TEM view of Example 10; d: diffraction spots of precipitates in Example 10). Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of this invention clearer, a detailed description will be provided below in conjunction with various embodiments and accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the invention; however, the embodiments of the invention are not limited thereto. Those skilled in the art can make similar modifications without departing from the spirit of the invention; therefore, the invention is not limited to the specific embodiments described below.

[0045] Unless otherwise defined, the technical terms used below have the same meaning as commonly understood by those skilled in the art, and all raw materials, reagents, instruments and equipment used in this invention can be purchased on the market or prepared by existing methods.

[0046] The present invention relates to a high-strength, high-wear-resistant mold steel with excellent high-temperature tensile properties, comprising the following elements: C: 0.35%-0.45%, Cr: 4.75%-5.50%, Mo: 1.10%-1.75%, V: 0.80%-1.20%, Si: 0.80%-1.20%, Mn: 0.20%-0.50%, with the balance being Fe and unavoidable impurities. The mass percentage of impurity chemical composition is controlled as follows: P≤0.03%, S≤0.005%, O≤20ppm, H≤1.5ppm, N≤80ppm.

[0047] Figure 1The diagram illustrates the production flow chart of the preliminary heat treatment stage for the high-strength, high-wear-resistance, and excellent high-temperature tensile properties of the mold steel of the present invention. The preliminary heat treatment stage of the present invention involves electroslag remelting (ESR) following primary refining in an electric arc furnace (EAF), refining in a ladle refining furnace (LF), and vacuum treatment in a vacuum degassing unit (VD).

[0048] Figure 2 The diagram illustrates the final heat treatment process of the high-strength, high-wear-resistance, and excellent high-temperature tensile properties of the mold steel of the present invention. The final heat treatment stage of the present invention includes quenching, cryogenic treatment, and tempering.

[0049] This invention proposes a technical solution for producing mold steel by optimizing the thermal process and performing deep cryogenic treatment. In traditional heating processes, inaccurate temperature control (too high or too low) can lead to grain growth or excessive non-uniform structure, thus affecting the material's performance. However, by optimizing the quenching temperature, the material can be precisely brought to the phase transformation temperature. This not only results in a fine martensitic structure after quenching, optimizing the material's microstructure, but also reduces the amount of retained austenite. After heat treatment, a deep cryogenic treatment for an appropriate time can further promote grain refinement and the transformation of retained austenite, thereby improving wear resistance and high-temperature performance. The specific operation steps are as follows: Step 1: Primary refining is carried out using an ultra-high power electric arc furnace (EAF). High-quality scrap steel and alloy materials such as Cr, Mo, and V are added to the furnace in proportion, and the melting temperature is controlled at 1550-1600℃. Oxygen lance is used to remove impurities such as carbon and phosphorus. After primary refining, the steel is tapped into a ladle to obtain primary molten steel. The chemical composition of the primary molten steel is controlled as follows: C: 0.35%-0.45%, Cr: 4.75%-5.50%, Mo: 1.10%-1.75%, V: 0.80%-1.20%, with the remainder being Fe and unavoidable impurities, ensuring uniform distribution of alloying elements and significantly reducing gas content. Step 2: The primary molten steel is transferred to the ladle refining furnace LF, heated by electricity and maintained at 1520-1580℃. Lime, fluorite and other slag-forming agents are added to form white slag, and deep desulfurization, deoxidation and fine-tuning of alloy composition are carried out. The refining time is 30-60 minutes, and electromagnetic stirring is used to promote the flotation of inclusions to obtain refined molten steel. The sulfur content of the refined molten steel is controlled to be ≤0.005% and the oxygen content is ≤20ppm, which greatly improves the purity of the molten steel. Step 3: Place the refined molten steel and ladle into a vacuum degassing device (VD) with a vacuum degree ≤67Pa and a temperature of 1500-1550℃ for 20-40 minutes to further remove hydrogen (≤1.5ppm), nitrogen (≤80ppm) and residual non-metallic inclusions. At the same time, trace alloying elements are added by wire feeding to ensure highly uniform composition and achieve extremely low gas content. Step four: The vacuum-treated molten steel is cast into Φ300-600mm square or round billets through an intermediate ladle using a full-process protective casting process. Argon gas is used to prevent secondary oxidation. The casting speed is controlled at 0.5-1.2m / min and the superheat is 20-40℃. Electromagnetic stirring is applied during the casting process to refine the solidification structure, and finally a high-quality billet with no macro segregation and no surface defects is obtained. Step 5: After cooling the high-quality billet, place it in an annealing furnace for spheroidizing annealing treatment. Heat it to 780-850℃ and hold it for 4-8 hours. Then, slowly cool it to below 500℃ at a rate of ≤20℃ / h and remove it from the furnace to obtain an annealed billet. This process eliminates as-cast segregation, softens the structure, and reduces hardness, creating favorable conditions for subsequent processing. Step 6: Using the annealed billet as a consumable electrode, place it in an electroslag remelting furnace, using a CaF2-based slag system (CaF2:Al2O3:CaO=70:20:10 (w / w / w)), a remelting current of 8000-15000A, a voltage of 35-45V, and a remelting speed of 3-6kg / min. A directional solidification is achieved in a water-cooled crystallizer to further remove inclusions (inclusion size ≤10μm), significantly refine the grains, improve the uniformity of the microstructure, and obtain a remelted ingot with extremely high purity. Step 7: Perform multi-directional forging on the remelted ingot. The initial forging temperature is 1100-1200℃, the final forging temperature is ≥900℃, and the total forging ratio is not less than 3. Normalize immediately after forging: heat to 950-1050℃ and hold for 1-2 hours (hold for 1 hour for every 25mm thickness), then air cool to room temperature at a cooling rate of 50-100℃ / h to homogenize the microstructure, eliminate forging stress, and increase the hardness to HB280-320, thus obtaining a normalized billet, which is ready for subsequent spheroidizing annealing. Step 8: Perform spheroidizing annealing on the normalized billet, heat to 780-820℃ and hold for 3-6 hours, then slowly cool to 650-700℃ at 10-20℃ / h and hold for 2-4 hours, and finally furnace cool to 500℃ to obtain a uniform spheroidized pearlite structure with a hardness controlled at HB179-229, which significantly improves machinability and optimizes the microstructure before quenching. Step 9: Heat the spheroidized annealed billet to 1060℃ for quenching, hold for 10 minutes, and then water cool to room temperature to obtain the quenched billet. Step 10: Place the quenched billet in liquid nitrogen for cryogenic treatment and hold for 0-10 hours to obtain the cryogenically treated billet. Step 11: After cryogenic treatment, the billet is heated to 550℃ and tempered twice. The tempering holding time is 2 hours. Between the two temperings, it is air-cooled to room temperature to obtain high-strength, high-wear-resistant mold steel with excellent high-temperature tensile properties. The following describes in detail, with reference to specific embodiments, the preparation method and application of the high-strength, high-wear-resistant, and high-temperature tensile steel of the present invention.

[0050] Example 1 A high-strength, high-wear-resistant mold steel with excellent high-temperature tensile properties is prepared by the following steps: (1) A high-power electric arc furnace (EAF) is used for primary refining. High-quality scrap steel and alloy materials (such as Cr, Mo, V, etc.) are added to the furnace in proportion (89 kg of FeCr (65 wt.% of Cr), 23 kg of FeMo (60 wt.% of Mo), and 14 kg of FeV80 (80 wt.% of V) per 1000 kg of molten steel). The melting temperature is controlled at 1550℃. Oxygen lance is used to remove impurities such as carbon and phosphorus. After primary refining, the steel is tapped to the ladle to obtain primary molten steel. The composition and mass percentage of the primary molten steel are controlled as follows: C: 0.38%, Si: 0.82%, Mn: 0.38%, Cr: 5.02%, Mo: 1.75%, V: 0.87%, P: 0.008%, S: 0.001%. (2) The primary molten steel obtained in step (1) is transferred to the ladle refining furnace (LF), heated by electricity, and the temperature of the molten steel is controlled at 1550℃. A slag-forming agent is added to the ladle to form a low-oxidizing white slag system, wherein the slag-forming agent, based on the mass of the molten steel, includes: 12.0 kg / t of active lime (CaO), 1.5 kg / t of fluorite (CaF2), 2.0 kg / t of calcium aluminate or alumina (Al2O3), and 0.8 kg / t of lightly calcined magnesia powder (MgO). After slag formation, a high-basicity, low-oxidizing white slag is formed, and its (FeO+MnO) content is controlled at ≤1.0%. Desulfurization, deoxidation, and fine-tuning of alloy composition are carried out under white slag conditions, using aluminum deoxidation, with an aluminum addition amount of 1.0 kg / t. The refining time is controlled at 45 minutes. At the same time, the electromagnetic stirring of the ladle is turned on with a stirring current of 300A and a frequency of 4Hz to promote the floating of inclusions and homogenization of molten steel, so as to obtain refined molten steel. The sulfur content in the refined molten steel is controlled at 0.003-0.004%, and the total oxygen content is controlled at 12-18ppm.

[0051] (3) The refined steel obtained in step (2) along with the ladle is placed in a vacuum degassing device (VD) for vacuum treatment, and the vacuum is evacuated to ≤67Pa, while the temperature of the molten steel is maintained at 1500℃. The vacuum degassing time is 30min to further remove gases and residual non-metallic inclusions from the molten steel. After degassing, the hydrogen content in the molten steel is controlled to ≤1.2ppm and the nitrogen content is controlled to ≤70ppm. Trace alloying elements are added under vacuum conditions by wire feeding, and the wire feeding speed is controlled at 0.8m / min to ensure uniform steel composition and low gas content.

[0052] (4) The molten steel after vacuum treatment in step (3) is continuously cast using a protective casting process, and poured into a round billet with a diameter of Φ400mm through an tundish. Argon gas is used for protection during the casting process, and the argon gas flow rate in the tundish is controlled at 8L / min to prevent secondary oxidation of the molten steel. The casting speed is controlled at 0.8m / min, and the superheat of the molten steel is controlled at 30℃. At the same time, electromagnetic stirring is applied in the crystallizer and the secondary cooling zone to refine the solidification structure and obtain a high-quality billet with dense internal structure, no macroscopic segregation, and no obvious surface defects.

[0053] (5) After cooling the high-quality billet obtained in step (4) to room temperature, it is placed in an annealing furnace for spheroidizing annealing treatment. The annealing heating temperature is 820℃, and the holding time is 6h. Then, it is slowly cooled to below 500℃ at a cooling rate of 15℃ / h before being taken out of the furnace to obtain the annealed billet. After annealing treatment, the as-cast segregation is significantly reduced, and the microstructure is fully softened to meet the requirements of subsequent processing.

[0054] (6) The annealed billet obtained in step (5) is processed into a consumable electrode and placed in an electroslag remelting furnace for electroslag remelting. A CaF2-based slag system with a mass ratio of CaF2:Al2O3:CaO = 70:20:10 is used. During the remelting process, the remelting current is controlled at 8000A, the voltage at 35V, and the remelting speed at 3kg / min. Directional solidification is achieved in a water-cooled crystallizer. After remelting, the size of inclusions is controlled to ≤8μm, the grains are significantly refined, the uniformity of the structure is significantly improved, and a high-purity remelted ingot is obtained.

[0055] (7) The remelted ingot obtained in step (6) is subjected to multi-directional forging. The initial forging temperature is controlled at 1150℃, the final forging temperature is 900℃, and the total forging ratio is 3.0. After forging, normalizing treatment is performed immediately. The normalizing heating temperature is 1000℃, and the holding time is 1 hour for every 25mm thickness, with a total holding time of 2 hours. Then, it is air-cooled to room temperature at a cooling rate of 50℃ / h to obtain the normalized billet. The microstructure tends to be uniform after normalizing, providing a good microstructure basis for subsequent spheroidizing annealing.

[0056] (8) The normalized billet obtained in step (7) is subjected to spheroidizing annealing. The spheroidizing annealing heating temperature is 800℃, held for 4h, then slowly cooled to 680℃ at a rate of 15℃ / h and held for 3h, and then cooled in the furnace to below 500℃ before being removed from the furnace. After spheroidizing annealing, a uniform spheroidal pearlite structure is obtained, which significantly improves the machinability of the material and the microstructure before quenching.

[0057] (9) Heat the billet after spheroidizing annealing in step (8) to 1060°C, hold for 10 minutes and then quench it by water cooling to obtain quenched billet.

[0058] (10) The quenched blank obtained in step (9) is subjected to two tempering treatments, both at a tempering temperature of 550℃, each held for 2 hours, and air-cooled to room temperature between the two tempering treatments. After tempering, a mold steel with high strength, high wear resistance and excellent high-temperature tensile properties is obtained, which is called Sample 1.

[0059] Example 2 A high-strength, high-wear-resistant mold steel with excellent high-temperature tensile properties is prepared by the following steps: (1) A high-power electric arc furnace (EAF) is used for primary refining. High-quality scrap steel and alloy materials (such as Cr, Mo, V, etc.) are added to the furnace in proportion (89 kg of FeCr (65 wt.% of Cr), 23 kg of FeMo (60 wt.% of Mo), and 14 kg of FeV80 (80 wt.% of V) per 1000 kg of molten steel). The melting temperature is controlled at 1550℃. Oxygen lance is used to remove impurities such as carbon and phosphorus. After primary refining, the steel is tapped to the ladle to obtain primary molten steel. The composition and mass percentage of the primary molten steel are controlled as follows: C: 0.38%, Si: 0.82%, Mn: 0.38%, Cr: 5.02%, Mo: 1.75%, V: 0.87%, P: 0.008%, S: 0.001%. (2) The primary molten steel obtained in step (1) is transferred to the ladle refining furnace (LF), heated by electricity, and the temperature of the molten steel is controlled at 1550℃. A slag-forming agent is added to the ladle to form a low-oxidizing white slag system, wherein the slag-forming agent, based on the mass of the molten steel, includes: 12.0 kg / t of active lime (CaO), 1.5 kg / t of fluorite (CaF2), 2.0 kg / t of calcium aluminate or alumina (Al2O3), and 0.8 kg / t of lightly calcined magnesia powder (MgO). After slag formation, a high-basicity, low-oxidizing white slag is formed, and its (FeO+MnO) content is controlled at ≤1.0%. Desulfurization, deoxidation, and fine-tuning of alloy composition are carried out under white slag conditions, using aluminum deoxidation, with an aluminum addition amount of 1.0 kg / t. The refining time is controlled at 45 minutes. At the same time, the electromagnetic stirring of the ladle is turned on with a stirring current of 300A and a frequency of 4Hz to promote the floating of inclusions and homogenization of molten steel, so as to obtain refined molten steel. The sulfur content in the refined molten steel is controlled at 0.003-0.004%, and the total oxygen content is controlled at 12-18ppm.

[0060] (3) The refined steel obtained in step (2) along with the ladle is placed in a vacuum degassing device (VD) for vacuum treatment, and the vacuum is evacuated to ≤67Pa, while the temperature of the molten steel is maintained at 1500℃. The vacuum degassing time is 30min to further remove gases and residual non-metallic inclusions from the molten steel. After degassing, the hydrogen content in the molten steel is controlled to ≤1.2ppm and the nitrogen content is controlled to ≤70ppm. Trace alloying elements are added under vacuum conditions by wire feeding, and the wire feeding speed is controlled at 0.8m / min to ensure uniform steel composition and low gas content.

[0061] (4) The molten steel after vacuum treatment in step (3) is continuously cast using a protective casting process, and poured into a round billet with a diameter of Φ400mm through an tundish. Argon gas is used for protection during the casting process, and the argon gas flow rate in the tundish is controlled at 8L / min to prevent secondary oxidation of the molten steel. The casting speed is controlled at 0.8m / min, and the superheat of the molten steel is controlled at 30℃. At the same time, electromagnetic stirring is applied in the crystallizer and the secondary cooling zone to refine the solidification structure and obtain a high-quality billet with dense internal structure, no macroscopic segregation, and no obvious surface defects.

[0062] (5) After cooling the high-quality billet obtained in step (4) to room temperature, it is placed in an annealing furnace for spheroidizing annealing treatment. The annealing heating temperature is 820℃, and the holding time is 6h. Then, it is slowly cooled to below 500℃ at a cooling rate of 15℃ / h before being taken out of the furnace to obtain the annealed billet. After annealing treatment, the as-cast segregation is significantly reduced, and the microstructure is fully softened to meet the requirements of subsequent processing.

[0063] (6) The annealed billet obtained in step (5) is processed into a consumable electrode and placed in an electroslag remelting furnace for electroslag remelting. A CaF2-based slag system with a mass ratio of CaF2:Al2O3:CaO = 70:20:10 is used. During the remelting process, the remelting current is controlled at 12000A, the voltage at 40V, and the remelting speed at 4.5kg / min. Directional solidification is achieved in a water-cooled crystallizer. After remelting, the size of inclusions is controlled to ≤8μm, the grains are significantly refined, the uniformity of the structure is significantly improved, and a high-purity remelted ingot is obtained.

[0064] (7) The remelted ingot obtained in step (6) is subjected to multi-directional forging. The initial forging temperature is controlled at 1150℃, the final forging temperature is 900℃, and the total forging ratio is 3.0. After forging, normalizing treatment is performed immediately. The normalizing heating temperature is 1000℃, and the holding time is 1 hour for every 25mm thickness, with a total holding time of 2 hours. Then, it is air-cooled to room temperature at a cooling rate of 50℃ / h to obtain the normalized billet. The microstructure tends to be uniform after normalizing, providing a good microstructure basis for subsequent spheroidizing annealing.

[0065] (8) The normalized billet obtained in step (7) is subjected to spheroidizing annealing. The spheroidizing annealing heating temperature is 800℃, held for 4h, then slowly cooled to 680℃ at a rate of 15℃ / h and held for 3h, and then cooled in the furnace to below 500℃ before being removed from the furnace. After spheroidizing annealing, a uniform spheroidal pearlite structure is obtained, which significantly improves the machinability of the material and the microstructure before quenching.

[0066] (9) Heat the billet after spheroidizing annealing in step (8) to 1060°C, hold for 10 minutes and then quench it by water cooling to obtain quenched billet.

[0067] (10) The quenched blank obtained in step (9) is subjected to two tempering treatments, both at a tempering temperature of 550℃, each held for 2 hours, and air-cooled to room temperature between the two tempering treatments. After tempering, a mold steel with high strength, high wear resistance and excellent high-temperature tensile properties is obtained, which is called sample 2.

[0068] Example 3 A high-strength, high-wear-resistant mold steel with excellent high-temperature tensile properties is prepared by the following steps: (1) A high-power electric arc furnace (EAF) is used for primary refining. High-quality scrap steel and alloy materials (such as Cr, Mo, V, etc.) are added to the furnace in proportion (89 kg of FeCr (65 wt.% of Cr), 23 kg of FeMo (60 wt.% of Mo), and 14 kg of FeV80 (80 wt.% of V) per 1000 kg of molten steel). The melting temperature is controlled at 1550℃. Oxygen lance is used to remove impurities such as carbon and phosphorus. After primary refining, the steel is tapped to the ladle to obtain primary molten steel. The composition and mass percentage of the primary molten steel are controlled as follows: C: 0.38%, Si: 0.82%, Mn: 0.38%, Cr: 5.02%, Mo: 1.75%, V: 0.87%, P: 0.008%, S: 0.001%. (2) The primary molten steel obtained in step (1) is transferred to the ladle refining furnace (LF), heated by electricity, and the temperature of the molten steel is controlled at 1550℃. A slag-forming agent is added to the ladle to form a low-oxidizing white slag system, wherein the slag-forming agent, based on the mass of the molten steel, includes: 12.0 kg / t of active lime (CaO), 1.5 kg / t of fluorite (CaF2), 2.0 kg / t of calcium aluminate or alumina (Al2O3), and 0.8 kg / t of lightly calcined magnesia powder (MgO). After slag formation, a high-basicity, low-oxidizing white slag is formed, and its (FeO+MnO) content is controlled at ≤1.0%. Desulfurization, deoxidation, and fine-tuning of alloy composition are carried out under white slag conditions, using aluminum deoxidation, with an aluminum addition amount of 1.0 kg / t. The refining time is controlled at 45 minutes. At the same time, the electromagnetic stirring of the ladle is turned on with a stirring current of 300A and a frequency of 4Hz to promote the floating of inclusions and homogenization of molten steel, so as to obtain refined molten steel. The sulfur content in the refined molten steel is controlled at 0.003-0.004%, and the total oxygen content is controlled at 12-18ppm.

[0069] (3) The refined steel obtained in step (2) along with the ladle is placed in a vacuum degassing device (VD) for vacuum treatment, and the vacuum is evacuated to ≤67Pa, while the temperature of the molten steel is maintained at 1500℃. The vacuum degassing time is 30min to further remove gases and residual non-metallic inclusions from the molten steel. After degassing, the hydrogen content in the molten steel is controlled to ≤1.2ppm and the nitrogen content is controlled to ≤70ppm. Trace alloying elements are added under vacuum conditions by wire feeding, and the wire feeding speed is controlled at 0.8m / min to ensure uniform steel composition and low gas content.

[0070] (4) The molten steel after vacuum treatment in step (3) is continuously cast using a protective casting process, and poured into a round billet with a diameter of Φ400mm through an tundish. Argon gas is used for protection during the casting process, and the argon gas flow rate in the tundish is controlled at 8L / min to prevent secondary oxidation of the molten steel. The casting speed is controlled at 0.8m / min, and the superheat of the molten steel is controlled at 30℃. At the same time, electromagnetic stirring is applied in the crystallizer and the secondary cooling zone to refine the solidification structure and obtain a high-quality billet with dense internal structure, no macroscopic segregation, and no obvious surface defects.

[0071] (5) After cooling the high-quality billet obtained in step (4) to room temperature, it is placed in an annealing furnace for spheroidizing annealing treatment. The annealing heating temperature is 820℃, and the holding time is 6h. Then, it is slowly cooled to below 500℃ at a cooling rate of 15℃ / h before being taken out of the furnace to obtain the annealed billet. After annealing treatment, the as-cast segregation is significantly reduced, and the microstructure is fully softened to meet the requirements of subsequent processing.

[0072] (6) The annealed billet obtained in step (5) is processed into a consumable electrode and placed in an electroslag remelting furnace for electroslag remelting. A CaF2-based slag system with a mass ratio of CaF2:Al2O3:CaO = 70:20:10 is used. During the remelting process, the remelting current is controlled at 15000A, the voltage at 45V, and the remelting speed at 6kg / min. Directional solidification is achieved in a water-cooled crystallizer. After remelting, the size of inclusions is controlled to ≤8μm, the grains are significantly refined, the uniformity of the structure is significantly improved, and a high-purity remelted ingot is obtained.

[0073] (7) The remelted ingot obtained in step (6) is subjected to multi-directional forging. The initial forging temperature is controlled at 1150℃, the final forging temperature is 900℃, and the total forging ratio is 3.0. After forging, normalizing treatment is performed immediately. The normalizing heating temperature is 1000℃, and the holding time is 1 hour for every 25mm thickness, with a total holding time of 2 hours. Then, it is air-cooled to room temperature at a cooling rate of 50℃ / h to obtain the normalized billet. The microstructure tends to be uniform after normalizing, providing a good microstructure basis for subsequent spheroidizing annealing.

[0074] (8) The normalized billet obtained in step (7) is subjected to spheroidizing annealing. The spheroidizing annealing heating temperature is 800℃, held for 4h, then slowly cooled to 680℃ at a rate of 15℃ / h and held for 3h, and then cooled in the furnace to below 500℃ before being removed from the furnace. After spheroidizing annealing, a uniform spheroidal pearlite structure is obtained, which significantly improves the machinability of the material and the microstructure before quenching.

[0075] (9) Heat the billet after spheroidizing annealing in step (8) to 1060°C, hold for 10 minutes and then quench it by water cooling to obtain quenched billet.

[0076] (10) The quenched blank obtained in step (9) is subjected to two tempering treatments, both at a tempering temperature of 550℃, each held for 2 hours, and air-cooled to room temperature between the two tempering treatments. After tempering, a mold steel with high strength, high wear resistance and excellent high-temperature tensile properties is obtained, which is called sample 3.

[0077] Example 4 A high-strength, high-wear-resistant mold steel with excellent high-temperature tensile properties is prepared by the following steps: (1) A high-power electric arc furnace (EAF) is used for primary refining. High-quality scrap steel and alloy materials (such as Cr, Mo, V, etc.) are added to the furnace in proportion (89 kg of FeCr (65 wt.% of Cr), 23 kg of FeMo (60 wt.% of Mo), and 14 kg of FeV80 (80 wt.% of V) per 1000 kg of molten steel). The melting temperature is controlled at 1550℃. Oxygen lance is used to remove impurities such as carbon and phosphorus. After primary refining, the steel is tapped to the ladle to obtain primary molten steel. The composition and mass percentage of the primary molten steel are controlled as follows: C: 0.38%, Si: 0.82%, Mn: 0.38%, Cr: 5.02%, Mo: 1.75%, V: 0.87%, P: 0.008%, S: 0.001%. (2) The primary molten steel obtained in step (1) is transferred to the ladle refining furnace (LF), heated by electricity, and the temperature of the molten steel is controlled at 1550℃. A slag-forming agent is added to the ladle to form a low-oxidizing white slag system, wherein the slag-forming agent, based on the mass of the molten steel, includes: 12.0 kg / t of active lime (CaO), 1.5 kg / t of fluorite (CaF2), 2.0 kg / t of calcium aluminate or alumina (Al2O3), and 0.8 kg / t of lightly calcined magnesia powder (MgO). After slag formation, a high-basicity, low-oxidizing white slag is formed, and its (FeO+MnO) content is controlled at ≤1.0%. Desulfurization, deoxidation, and fine-tuning of alloy composition are carried out under white slag conditions, using aluminum deoxidation, with an aluminum addition amount of 1.0 kg / t. The refining time is controlled at 45 minutes. At the same time, the electromagnetic stirring of the ladle is turned on with a stirring current of 300A and a frequency of 4Hz to promote the floating of inclusions and homogenization of molten steel, so as to obtain refined molten steel. The sulfur content in the refined molten steel is controlled at 0.003-0.004%, and the total oxygen content is controlled at 12-18ppm.

[0078] (3) The refined steel obtained in step (2) along with the ladle is placed in a vacuum degassing device (VD) for vacuum treatment, and the vacuum is evacuated to ≤6Pa, while the temperature of the molten steel is maintained at 1500℃. The vacuum degassing time is 30min to further remove gases and residual non-metallic inclusions from the molten steel. After degassing, the hydrogen content in the molten steel is controlled to ≤1.2ppm and the nitrogen content is controlled to ≤70ppm. Trace alloying elements are added under vacuum conditions by wire feeding, and the wire feeding speed is controlled at 0.8m / min to ensure uniform steel composition and low gas content.

[0079] (4) The molten steel after vacuum treatment in step (3) is continuously cast using a protective casting process, and poured into a round billet with a diameter of Φ400mm through an tundish. Argon gas is used for protection during the casting process, and the argon gas flow rate in the tundish is controlled at 8L / min to prevent secondary oxidation of the molten steel. The casting speed is controlled at 0.8m / min, and the superheat of the molten steel is controlled at 30℃. At the same time, electromagnetic stirring is applied in the crystallizer and the secondary cooling zone to refine the solidification structure and obtain a high-quality billet with dense internal structure, no macroscopic segregation, and no obvious surface defects.

[0080] (5) After cooling the high-quality billet obtained in step (4) to room temperature, it is placed in an annealing furnace for spheroidizing annealing treatment. The annealing heating temperature is 820℃, and the holding time is 6h. Then, it is slowly cooled to below 500℃ at a cooling rate of 15℃ / h before being taken out of the furnace to obtain the annealed billet. After annealing treatment, the as-cast segregation is significantly reduced, and the microstructure is fully softened to meet the requirements of subsequent processing.

[0081] (6) The annealed billet obtained in step (5) is processed into a consumable electrode and placed in an electroslag remelting furnace for electroslag remelting. A CaF2-based slag system with a mass ratio of CaF2:Al2O3:CaO = 70:20:10 is used. During the remelting process, the remelting current is controlled at 12000A, the voltage at 40V, and the remelting speed at 4.5kg / min. Directional solidification is achieved in a water-cooled crystallizer. After remelting, the size of inclusions is controlled to ≤8μm, the grains are significantly refined, the uniformity of the structure is significantly improved, and a high-purity remelted ingot is obtained.

[0082] (7) The remelted ingot obtained in step (6) is subjected to multi-directional forging. The initial forging temperature is controlled at 1150℃, the final forging temperature is 900℃, and the total forging ratio is 3.0. After forging, normalizing treatment is performed immediately. The normalizing heating temperature is 1000℃, and the holding time is 1 hour for every 25mm thickness, with a total holding time of 2 hours. Then, it is air-cooled to room temperature at a cooling rate of 50℃ / h to obtain the normalized billet. The microstructure tends to be uniform after normalizing, providing a good microstructure basis for subsequent spheroidizing annealing.

[0083] (8) The normalized billet obtained in step (7) is subjected to spheroidizing annealing. The spheroidizing annealing heating temperature is 800℃, held for 4h, then slowly cooled to 680℃ at a rate of 15℃ / h and held for 3h, and then cooled in the furnace to below 500℃ before being removed from the furnace. After spheroidizing annealing, a uniform spheroidal pearlite structure is obtained, which significantly improves the machinability of the material and the microstructure before quenching.

[0084] (9) Heat the billet after spheroidizing annealing in step (8) to 1030°C, hold for 10 minutes and then quench it by water cooling to obtain quenched billet.

[0085] (10) The quenched blank obtained in step (9) is subjected to two tempering treatments, both at a tempering temperature of 550℃, each held for 2 hours, and air-cooled to room temperature between the two tempering treatments. After tempering, a mold steel with high strength, high wear resistance and excellent high-temperature tensile properties is obtained, which is called sample 4.

[0086] Example 5 A high-strength, high-wear-resistant mold steel with excellent high-temperature tensile properties is prepared by the following steps: (1) A high-power electric arc furnace (EAF) is used for primary refining. High-quality scrap steel and alloy materials (such as Cr, Mo, V, etc.) are added to the furnace in proportion (89 kg of FeCr (65 wt.% of Cr), 23 kg of FeMo (60 wt.% of Mo), and 14 kg of FeV80 (80 wt.% of V) per 1000 kg of molten steel). The melting temperature is controlled at 1550℃. Oxygen lance is used to remove impurities such as carbon and phosphorus. After primary refining, the steel is tapped to the ladle to obtain primary molten steel. The composition and mass percentage of the primary molten steel are controlled as follows: C: 0.38%, Si: 0.82%, Mn: 0.38%, Cr: 5.02%, Mo: 1.75%, V: 0.87%, P: 0.008%, S: 0.001%. (2) The primary molten steel obtained in step (1) is transferred to the ladle refining furnace (LF), heated by electricity, and the temperature of the molten steel is controlled at 1550℃. A slag-forming agent is added to the ladle to form a low-oxidizing white slag system, wherein the slag-forming agent, based on the mass of the molten steel, includes: 12.0 kg / t of active lime (CaO), 1.5 kg / t of fluorite (CaF2), 2.0 kg / t of calcium aluminate or alumina (Al2O3), and 0.8 kg / t of lightly calcined magnesia powder (MgO). After slag formation, a high-basicity, low-oxidizing white slag is formed, and its (FeO+MnO) content is controlled at ≤1.0%. Desulfurization, deoxidation, and fine-tuning of alloy composition are carried out under white slag conditions, using aluminum deoxidation, with an aluminum addition amount of 1.0 kg / t. The refining time is controlled at 45 minutes. At the same time, the electromagnetic stirring of the ladle is turned on with a stirring current of 300A and a frequency of 4Hz to promote the floating of inclusions and homogenization of molten steel, so as to obtain refined molten steel. The sulfur content in the refined molten steel is controlled at 0.003-0.004%, and the total oxygen content is controlled at 12-18ppm.

[0087] (3) The refined steel obtained in step (2) along with the ladle is placed in a vacuum degassing device (VD) for vacuum treatment, and the vacuum is evacuated to ≤67Pa, while the temperature of the molten steel is maintained at 1500℃. The vacuum degassing time is 30min to further remove gases and residual non-metallic inclusions from the molten steel. After degassing, the hydrogen content in the molten steel is controlled to ≤1.2ppm and the nitrogen content is controlled to ≤70ppm. Trace alloying elements are added under vacuum conditions by wire feeding, and the wire feeding speed is controlled at 0.8m / min to ensure uniform steel composition and low gas content.

[0088] (4) The molten steel after vacuum treatment in step (3) is continuously cast using a protective casting process, and poured into a round billet with a diameter of Φ400mm through an tundish. Argon gas is used for protection during the casting process, and the argon gas flow rate in the tundish is controlled at 8L / min to prevent secondary oxidation of the molten steel. The casting speed is controlled at 0.8m / min, and the superheat of the molten steel is controlled at 30℃. At the same time, electromagnetic stirring is applied in the crystallizer and the secondary cooling zone to refine the solidification structure and obtain a high-quality billet with dense internal structure, no macroscopic segregation, and no obvious surface defects.

[0089] (5) After cooling the high-quality billet obtained in step (4) to room temperature, it is placed in an annealing furnace for spheroidizing annealing treatment. The annealing heating temperature is 820℃, and the holding time is 6h. Then, it is slowly cooled to below 500℃ at a cooling rate of 15℃ / h before being taken out of the furnace to obtain the annealed billet. After annealing treatment, the as-cast segregation is significantly reduced, and the microstructure is fully softened to meet the requirements of subsequent processing.

[0090] (6) The annealed billet obtained in step (5) is processed into a consumable electrode and placed in an electroslag remelting furnace for electroslag remelting. A CaF2-based slag system with a mass ratio of CaF2:Al2O3:CaO = 70:20:10 is used. During the remelting process, the remelting current is controlled at 12000A, the voltage at 40V, and the remelting speed at 4.5kg / min. Directional solidification is achieved in a water-cooled crystallizer. After remelting, the size of inclusions is controlled to ≤8μm, the grains are significantly refined, the uniformity of the structure is significantly improved, and a high-purity remelted ingot is obtained.

[0091] (7) The remelted ingot obtained in step (6) is subjected to multi-directional forging. The initial forging temperature is controlled at 1150℃, the final forging temperature is 900℃, and the total forging ratio is 3.0. After forging, normalizing treatment is performed immediately. The normalizing heating temperature is 1000℃, and the holding time is 1 hour for every 25mm thickness, with a total holding time of 2 hours. Then, it is air-cooled to room temperature at a cooling rate of 50℃ / h to obtain the normalized billet. The microstructure tends to be uniform after normalizing, providing a good microstructure basis for subsequent spheroidizing annealing.

[0092] (8) The normalized billet obtained in step (7) is subjected to spheroidizing annealing. The spheroidizing annealing heating temperature is 800℃, held for 4h, then slowly cooled to 680℃ at a rate of 15℃ / h and held for 3h, and then cooled in the furnace to below 500℃ before being removed from the furnace. After spheroidizing annealing, a uniform spheroidal pearlite structure is obtained, which significantly improves the machinability of the material and the microstructure before quenching.

[0093] (9) Heat the billet after spheroidizing annealing in step (8) to 1090°C, hold for 10 minutes and then quench it by water cooling to obtain quenched billet.

[0094] (10) The quenched blank obtained in step (9) is subjected to two tempering treatments, both at a tempering temperature of 550℃, each held for 2 hours, and air-cooled to room temperature between the two tempering treatments. After tempering, a mold steel with high strength, high wear resistance and excellent high-temperature tensile properties is obtained, which is called sample 5.

[0095] Example 6 A high-strength, high-wear-resistant mold steel with excellent high-temperature tensile properties is prepared by the following steps: (1) A high-power electric arc furnace (EAF) is used for primary refining. High-quality scrap steel and alloy materials (such as Cr, Mo, V, etc.) are added to the furnace in proportion (89 kg of FeCr (65 wt.% of Cr), 23 kg of FeMo (60 wt.% of Mo), and 14 kg of FeV80 (80 wt.% of V) per 1000 kg of molten steel). The melting temperature is controlled at 1550℃. Oxygen lance is used to remove impurities such as carbon and phosphorus. After primary refining, the steel is tapped to the ladle to obtain primary molten steel. The composition and mass percentage of the primary molten steel are controlled as follows: C: 0.38%, Si: 0.82%, Mn: 0.38%, Cr: 5.02%, Mo: 1.75%, V: 0.87%, P: 0.008%, S: 0.001%. (2) The primary molten steel obtained in step (1) is transferred to the ladle refining furnace (LF), heated by electricity, and the temperature of the molten steel is controlled at 1550℃. A slag-forming agent is added to the ladle to form a low-oxidizing white slag system, wherein the slag-forming agent, based on the mass of the molten steel, includes: 12.0 kg / t of active lime (CaO), 1.5 kg / t of fluorite (CaF2), 2.0 kg / t of calcium aluminate or alumina (Al2O3), and 0.8 kg / t of lightly calcined magnesia powder (MgO). After slag formation, a high-basicity, low-oxidizing white slag is formed, and its (FeO+MnO) content is controlled at ≤1.0%. Desulfurization, deoxidation, and fine-tuning of alloy composition are carried out under white slag conditions, using aluminum deoxidation, with an aluminum addition amount of 1.0 kg / t. The refining time is controlled at 45 minutes. At the same time, the electromagnetic stirring of the ladle is turned on with a stirring current of 300A and a frequency of 4Hz to promote the floating of inclusions and homogenization of molten steel, so as to obtain refined molten steel. The sulfur content in the refined molten steel is controlled at 0.003-0.004%, and the total oxygen content is controlled at 12-18ppm.

[0096] (3) The refined steel obtained in step (2) along with the ladle is placed in a vacuum degassing device (VD) for vacuum treatment, and the vacuum is evacuated to ≤67Pa, while the temperature of the molten steel is maintained at 1500℃. The vacuum degassing time is 30min to further remove gases and residual non-metallic inclusions from the molten steel. After degassing, the hydrogen content in the molten steel is controlled to ≤1.2ppm and the nitrogen content is controlled to ≤70ppm. Trace alloying elements are added under vacuum conditions by wire feeding, and the wire feeding speed is controlled at 0.8m / min to ensure uniform steel composition and low gas content.

[0097] (4) The molten steel after vacuum treatment in step (3) is continuously cast using a protective casting process, and poured into a round billet with a diameter of Φ400mm through an tundish. Argon gas is used for protection during the casting process, and the argon gas flow rate in the tundish is controlled at 8L / min to prevent secondary oxidation of the molten steel. The casting speed is controlled at 0.8m / min, and the superheat of the molten steel is controlled at 30℃. At the same time, electromagnetic stirring is applied in the crystallizer and the secondary cooling zone to refine the solidification structure and obtain a high-quality billet with dense internal structure, no macroscopic segregation, and no obvious surface defects.

[0098] (5) After cooling the high-quality billet obtained in step (4) to room temperature, it is placed in an annealing furnace for spheroidizing annealing treatment. The annealing heating temperature is 820℃, and the holding time is 6h. Then, it is slowly cooled to below 500℃ at a cooling rate of 15℃ / h before being taken out of the furnace to obtain the annealed billet. After annealing treatment, the as-cast segregation is significantly reduced, and the microstructure is fully softened to meet the requirements of subsequent processing.

[0099] (6) The annealed billet obtained in step (5) is processed into a consumable electrode and placed in an electroslag remelting furnace for electroslag remelting. A CaF2-based slag system with a mass ratio of CaF2:Al2O3:CaO = 70:20:10 is used. During the remelting process, the remelting current is controlled at 12000A, the voltage at 40V, and the remelting speed at 4.5kg / min. Directional solidification is achieved in a water-cooled crystallizer. After remelting, the size of inclusions is controlled to ≤8μm, the grains are significantly refined, the uniformity of the structure is significantly improved, and a high-purity remelted ingot is obtained.

[0100] (7) The remelted ingot obtained in step (6) is subjected to multi-directional forging. The initial forging temperature is controlled at 1150℃, the final forging temperature is 900℃, and the total forging ratio is 3.0. After forging, normalizing treatment is performed immediately. The normalizing heating temperature is 1000℃, and the holding time is 1 hour for every 25mm thickness, with a total holding time of 2 hours. Then, it is air-cooled to room temperature at a cooling rate of 50℃ / h to obtain the normalized billet. The microstructure tends to be uniform after normalizing, providing a good microstructure basis for subsequent spheroidizing annealing.

[0101] (8) The normalized billet obtained in step (7) is subjected to spheroidizing annealing. The spheroidizing annealing heating temperature is 800℃, held for 4h, then slowly cooled to 680℃ at a rate of 15℃ / h and held for 3h, and then cooled in the furnace to below 500℃ before being removed from the furnace. After spheroidizing annealing, a uniform spheroidal pearlite structure is obtained, which significantly improves the machinability of the material and the microstructure before quenching.

[0102] (9) Heat the billet after spheroidizing annealing in step (8) to 1060°C, hold for 10 minutes and then quench it by water cooling to obtain quenched billet.

[0103] (10) The quenched blank obtained in step (9) is subjected to two tempering treatments, both at a tempering temperature of 550℃, each held for 2 hours, and air-cooled to room temperature between the two tempering treatments. After tempering, a mold steel with high strength, high wear resistance and excellent high-temperature tensile properties is obtained, which is called sample 6.

[0104] Example 7 A high-strength, high-wear-resistant mold steel with excellent high-temperature tensile properties is prepared by the following steps: (1) A high-power electric arc furnace (EAF) is used for primary refining. High-quality scrap steel and alloy materials (such as Cr, Mo, V, etc.) are added to the furnace in proportion (89 kg of FeCr (65 wt.% of Cr), 23 kg of FeMo (60 wt.% of Mo), and 14 kg of FeV80 (80 wt.% of V) per 1000 kg of molten steel). The melting temperature is controlled at 1550℃. Oxygen lance is used to remove impurities such as carbon and phosphorus. After primary refining, the steel is tapped to the ladle to obtain primary molten steel. The composition and mass percentage of the primary molten steel are controlled as follows: C: 0.38%, Si: 0.82%, Mn: 0.38%, Cr: 5.02%, Mo: 1.75%, V: 0.87%, P: 0.008%, S: 0.001%. (2) The primary molten steel obtained in step (1) is transferred to the ladle refining furnace (LF), heated by electricity, and the temperature of the molten steel is controlled at 1550℃. A slag-forming agent is added to the ladle to form a low-oxidizing white slag system, wherein the slag-forming agent, based on the mass of the molten steel, includes: 12.0 kg / t of active lime (CaO), 1.5 kg / t of fluorite (CaF2), 2.0 kg / t of calcium aluminate or alumina (Al2O3), and 0.8 kg / t of lightly calcined magnesia powder (MgO). After slag formation, a high-basicity, low-oxidizing white slag is formed, and its (FeO+MnO) content is controlled at ≤1.0%. Desulfurization, deoxidation, and fine-tuning of alloy composition are carried out under white slag conditions, using aluminum deoxidation, with an aluminum addition amount of 1.0 kg / t. The refining time is controlled at 45 minutes. At the same time, the electromagnetic stirring of the ladle is turned on with a stirring current of 300A and a frequency of 4Hz to promote the floating of inclusions and homogenization of molten steel, so as to obtain refined molten steel. The sulfur content in the refined molten steel is controlled at 0.003-0.004%, and the total oxygen content is controlled at 12-18ppm.

[0105] (3) The refined steel obtained in step (2) along with the ladle is placed in a vacuum degassing device (VD) for vacuum treatment, and the vacuum is evacuated to ≤67Pa, while the temperature of the molten steel is maintained at 1500℃. The vacuum degassing time is 30min to further remove gases and residual non-metallic inclusions from the molten steel. After degassing, the hydrogen content in the molten steel is controlled to ≤1.2ppm and the nitrogen content is controlled to ≤70ppm. Trace alloying elements are added under vacuum conditions by wire feeding, and the wire feeding speed is controlled at 0.8m / min to ensure uniform steel composition and low gas content.

[0106] (4) The molten steel after vacuum treatment in step (3) is continuously cast using a protective casting process, and poured into a round billet with a diameter of Φ400mm through an tundish. Argon gas is used for protection during the casting process, and the argon gas flow rate in the tundish is controlled at 8L / min to prevent secondary oxidation of the molten steel. The casting speed is controlled at 0.8m / min, and the superheat of the molten steel is controlled at 30℃. At the same time, electromagnetic stirring is applied in the crystallizer and the secondary cooling zone to refine the solidification structure and obtain a high-quality billet with dense internal structure, no macroscopic segregation, and no obvious surface defects.

[0107] (5) After cooling the high-quality billet obtained in step (4) to room temperature, it is placed in an annealing furnace for spheroidizing annealing treatment. The annealing heating temperature is 820℃, and the holding time is 6h. Then, it is slowly cooled to below 500℃ at a cooling rate of 15℃ / h before being taken out of the furnace to obtain the annealed billet. After annealing treatment, the as-cast segregation is significantly reduced, and the microstructure is fully softened to meet the requirements of subsequent processing.

[0108] (6) The annealed billet obtained in step (5) is processed into a consumable electrode and placed in an electroslag remelting furnace for electroslag remelting. A CaF2-based slag system with a mass ratio of CaF2:Al2O3:CaO = 70:20:10 is used. During the remelting process, the remelting current is controlled at 12000A, the voltage at 40V, and the remelting speed at 4.5kg / min. Directional solidification is achieved in a water-cooled crystallizer. After remelting, the size of inclusions is controlled to ≤8μm, the grains are significantly refined, the uniformity of the structure is significantly improved, and a high-purity remelted ingot is obtained.

[0109] (7) The remelted ingot obtained in step (6) is subjected to multi-directional forging. The initial forging temperature is controlled at 1150℃, the final forging temperature is 900℃, and the total forging ratio is 3.0. After forging, normalizing treatment is performed immediately. The normalizing heating temperature is 1000℃, and the holding time is 1 hour for every 25mm thickness, with a total holding time of 2 hours. Then, it is air-cooled to room temperature at a cooling rate of 50℃ / h to obtain the normalized billet. The microstructure tends to be uniform after normalizing, providing a good microstructure basis for subsequent spheroidizing annealing.

[0110] (8) The normalized billet obtained in step (7) is subjected to spheroidizing annealing. The spheroidizing annealing heating temperature is 800℃, held for 4h, then slowly cooled to 680℃ at a rate of 15℃ / h and held for 3h, and then cooled in the furnace to below 500℃ before being removed from the furnace. After spheroidizing annealing, a uniform spheroidal pearlite structure is obtained, which significantly improves the machinability of the material and the microstructure before quenching.

[0111] (9) Heat the billet after spheroidizing annealing in step (8) to 1060°C, hold for 10 minutes and then quench it by water cooling to obtain quenched billet.

[0112] (10) Place the quenched blank obtained in step (9) into a liquid nitrogen tank for deep cryogenic treatment for 2 hours.

[0113] (11) The blank after the cryogenic treatment in step (10) is heated to 550°C and tempered twice, each time for 2 hours, and air-cooled to room temperature between the two temperings. After tempering, a mold steel with high strength, high wear resistance and excellent high temperature tensile properties is obtained, which is called sample 7.

[0114] Example 8 A high-strength, high-wear-resistant mold steel with excellent high-temperature tensile properties is prepared by the following steps: (1) A high-power electric arc furnace (EAF) is used for primary refining. High-quality scrap steel and alloy materials (such as Cr, Mo, V, etc.) are added to the furnace in proportion (89 kg of FeCr (65 wt.% of Cr), 23 kg of FeMo (60 wt.% of Mo), and 14 kg of FeV80 (80 wt.% of V) per 1000 kg of molten steel). The melting temperature is controlled at 1550℃. Oxygen lance is used to remove impurities such as carbon and phosphorus. After primary refining, the steel is tapped to the ladle to obtain primary molten steel. The composition and mass percentage of the primary molten steel are controlled as follows: C: 0.38%, Si: 0.82%, Mn: 0.38%, Cr: 5.02%, Mo: 1.75%, V: 0.87%, P: 0.008%, S: 0.001%. (2) The primary molten steel obtained in step (1) is transferred to the ladle refining furnace (LF), heated by electricity, and the temperature of the molten steel is controlled at 1550℃. A slag-forming agent is added to the ladle to form a low-oxidizing white slag system, wherein the slag-forming agent, based on the mass of the molten steel, includes: 12.0 kg / t of active lime (CaO), 1.5 kg / t of fluorite (CaF2), 2.0 kg / t of calcium aluminate or alumina (Al2O3), and 0.8 kg / t of lightly calcined magnesia powder (MgO). After slag formation, a high-basicity, low-oxidizing white slag is formed, and its (FeO+MnO) content is controlled at ≤1.0%. Desulfurization, deoxidation, and fine-tuning of alloy composition are carried out under white slag conditions, using aluminum deoxidation, with an aluminum addition amount of 1.0 kg / t. The refining time is controlled at 45 minutes. At the same time, the electromagnetic stirring of the ladle is turned on with a stirring current of 300A and a frequency of 4Hz to promote the floating of inclusions and homogenization of molten steel, so as to obtain refined molten steel. The sulfur content in the refined molten steel is controlled at 0.003-0.004%, and the total oxygen content is controlled at 12-18ppm.

[0115] (3) The refined steel obtained in step (2) along with the ladle is placed in a vacuum degassing device (VD) for vacuum treatment, and the vacuum is evacuated to ≤67Pa, while the temperature of the molten steel is maintained at 1500℃. The vacuum degassing time is 30min to further remove gases and residual non-metallic inclusions from the molten steel. After degassing, the hydrogen content in the molten steel is controlled to ≤1.2ppm and the nitrogen content is controlled to ≤70ppm. Trace alloying elements are added under vacuum conditions by wire feeding, and the wire feeding speed is controlled at 0.8m / min to ensure uniform steel composition and low gas content.

[0116] (4) The molten steel after vacuum treatment in step (3) is continuously cast using a protective casting process, and poured into a round billet with a diameter of Φ400mm through an tundish. Argon gas is used for protection during the casting process, and the argon gas flow rate in the tundish is controlled at 8L / min to prevent secondary oxidation of the molten steel. The casting speed is controlled at 0.8m / min, and the superheat of the molten steel is controlled at 30℃. At the same time, electromagnetic stirring is applied in the crystallizer and the secondary cooling zone to refine the solidification structure and obtain a high-quality billet with dense internal structure, no macroscopic segregation, and no obvious surface defects.

[0117] (5) After cooling the high-quality billet obtained in step (4) to room temperature, it is placed in an annealing furnace for spheroidizing annealing treatment. The annealing heating temperature is 820℃, and the holding time is 6h. Then, it is slowly cooled to below 500℃ at a cooling rate of 15℃ / h before being taken out of the furnace to obtain the annealed billet. After annealing treatment, the as-cast segregation is significantly reduced, and the microstructure is fully softened to meet the requirements of subsequent processing.

[0118] (6) The annealed billet obtained in step (5) is processed into a consumable electrode and placed in an electroslag remelting furnace for electroslag remelting. A CaF2-based slag system with a mass ratio of CaF2:Al2O3:CaO = 70:20:10 is used. During the remelting process, the remelting current is controlled at 12000A, the voltage at 40V, and the remelting speed at 4.5kg / min. Directional solidification is achieved in a water-cooled crystallizer. After remelting, the size of inclusions is controlled to ≤8μm, the grains are significantly refined, the uniformity of the structure is significantly improved, and a high-purity remelted ingot is obtained.

[0119] (7) The remelted ingot obtained in step (6) is subjected to multi-directional forging. The initial forging temperature is controlled at 1150℃, the final forging temperature is 900℃, and the total forging ratio is 3.0. After forging, normalizing treatment is performed immediately. The normalizing heating temperature is 1000℃, and the holding time is 1 hour for every 25mm thickness, with a total holding time of 2 hours. Then, it is air-cooled to room temperature at a cooling rate of 50℃ / h to obtain the normalized billet. The microstructure tends to be uniform after normalizing, providing a good microstructure basis for subsequent spheroidizing annealing.

[0120] (8) The normalized billet obtained in step (7) is subjected to spheroidizing annealing. The spheroidizing annealing heating temperature is 800℃, held for 4h, then slowly cooled to 680℃ at a rate of 15℃ / h and held for 3h, and then cooled in the furnace to below 500℃ before being removed from the furnace. After spheroidizing annealing, a uniform spheroidal pearlite structure is obtained, which significantly improves the machinability of the material and the microstructure before quenching.

[0121] (9) Heat the billet after spheroidizing annealing in step (8) to 1060°C, hold for 10 minutes and then quench it by water cooling to obtain quenched billet.

[0122] (10) Place the quenched blank obtained in step (9) into a liquid nitrogen tank for deep cryogenic treatment for 4 hours.

[0123] (11) The blank after the cryogenic treatment in step (10) is heated to 550°C and tempered twice, each time for 2 hours, and air-cooled to room temperature between the two temperings. After tempering, a mold steel with high strength, high wear resistance and excellent high-temperature tensile properties is obtained, which is called sample 8.

[0124] Example 9 A high-strength, high-wear-resistant mold steel with excellent high-temperature tensile properties is prepared by the following steps: (1) A high-power electric arc furnace (EAF) is used for primary refining. High-quality scrap steel and alloy materials (such as Cr, Mo, V, etc.) are added to the furnace in proportion (89 kg of FeCr (65 wt.% of Cr), 23 kg of FeMo (60 wt.% of Mo), and 14 kg of FeV80 (80 wt.% of V) per 1000 kg of molten steel). The melting temperature is controlled at 1550℃. Oxygen lance is used to remove impurities such as carbon and phosphorus. After primary refining, the steel is tapped to the ladle to obtain primary molten steel. The composition and mass percentage of the primary molten steel are controlled as follows: C: 0.38%, Si: 0.82%, Mn: 0.38%, Cr: 5.02%, Mo: 1.75%, V: 0.87%, P: 0.008%, S: 0.001%. (2) The primary molten steel obtained in step (1) is transferred to the ladle refining furnace (LF), heated by electricity, and the temperature of the molten steel is controlled at 1550℃. A slag-forming agent is added to the ladle to form a low-oxidizing white slag system, wherein the slag-forming agent, based on the mass of the molten steel, includes: 12.0 kg / t of active lime (CaO), 1.5 kg / t of fluorite (CaF2), 2.0 kg / t of calcium aluminate or alumina (Al2O3), and 0.8 kg / t of lightly calcined magnesia powder (MgO). After slag formation, a high-basicity, low-oxidizing white slag is formed, and its (FeO+MnO) content is controlled at ≤1.0%. Desulfurization, deoxidation, and fine-tuning of alloy composition are carried out under white slag conditions, using aluminum deoxidation, with an aluminum addition amount of 1.0 kg / t. The refining time is controlled at 45 minutes. At the same time, the electromagnetic stirring of the ladle is turned on with a stirring current of 300A and a frequency of 4Hz to promote the floating of inclusions and homogenization of molten steel, so as to obtain refined molten steel. The sulfur content in the refined molten steel is controlled at 0.003-0.004%, and the total oxygen content is controlled at 12-18ppm.

[0125] (3) The refined steel obtained in step (2) along with the ladle is placed in a vacuum degassing device (VD) for vacuum treatment, and the vacuum is evacuated to ≤67Pa, while the temperature of the molten steel is maintained at 1500℃. The vacuum degassing time is 30min to further remove gases and residual non-metallic inclusions from the molten steel. After degassing, the hydrogen content in the molten steel is controlled to ≤1.2ppm and the nitrogen content is controlled to ≤70ppm. Trace alloying elements are added under vacuum conditions by wire feeding, and the wire feeding speed is controlled at 0.8m / min to ensure uniform steel composition and low gas content.

[0126] (4) The molten steel after vacuum treatment in step (3) is continuously cast using a protective casting process, and poured into a round billet with a diameter of Φ400mm through an tundish. Argon gas is used for protection during the casting process, and the argon gas flow rate in the tundish is controlled at 8L / min to prevent secondary oxidation of the molten steel. The casting speed is controlled at 0.8m / min, and the superheat of the molten steel is controlled at 30℃. At the same time, electromagnetic stirring is applied in the crystallizer and the secondary cooling zone to refine the solidification structure and obtain a high-quality billet with dense internal structure, no macroscopic segregation, and no obvious surface defects.

[0127] (5) After cooling the high-quality billet obtained in step (4) to room temperature, it is placed in an annealing furnace for spheroidizing annealing treatment. The annealing heating temperature is 820℃, and the holding time is 6h. Then, it is slowly cooled to below 500℃ at a cooling rate of 15℃ / h before being taken out of the furnace to obtain the annealed billet. After annealing treatment, the as-cast segregation is significantly reduced, and the microstructure is fully softened to meet the requirements of subsequent processing.

[0128] (6) The annealed billet obtained in step (5) is processed into a consumable electrode and placed in an electroslag remelting furnace for electroslag remelting. A CaF2-based slag system with a mass ratio of CaF2:Al2O3:CaO = 70:20:10 is used. During the remelting process, the remelting current is controlled at 12000A, the voltage at 40V, and the remelting speed at 4.5kg / min. Directional solidification is achieved in a water-cooled crystallizer. After remelting, the size of inclusions is controlled to ≤8μm, the grains are significantly refined, the uniformity of the structure is significantly improved, and a high-purity remelted ingot is obtained.

[0129] (7) The remelted ingot obtained in step (6) is subjected to multi-directional forging. The initial forging temperature is controlled at 1150℃, the final forging temperature is 900℃, and the total forging ratio is 3.0. After forging, normalizing treatment is performed immediately. The normalizing heating temperature is 1000℃, and the holding time is 1 hour for every 25mm thickness, with a total holding time of 2 hours. Then, it is air-cooled to room temperature at a cooling rate of 50℃ / h to obtain the normalized billet. The microstructure tends to be uniform after normalizing, providing a good microstructure basis for subsequent spheroidizing annealing.

[0130] (8) The normalized billet obtained in step (7) is subjected to spheroidizing annealing. The spheroidizing annealing heating temperature is 800℃, held for 4h, then slowly cooled to 680℃ at a rate of 15℃ / h and held for 3h, and then cooled in the furnace to below 500℃ before being removed from the furnace. After spheroidizing annealing, a uniform spheroidal pearlite structure is obtained, which significantly improves the machinability of the material and the microstructure before quenching.

[0131] (9) Heat the billet after spheroidizing annealing in step (8) to 1060°C, hold for 10 minutes and then quench it by water cooling to obtain quenched billet.

[0132] (10) Place the quenched blank obtained in step (9) into a liquid nitrogen tank for deep cryogenic treatment for 6 hours.

[0133] (11) The blank after the cryogenic treatment in step (10) is heated to 550°C and tempered twice, each time for 2 hours, and air-cooled to room temperature between the two temperings. After tempering, a mold steel with high strength, high wear resistance and excellent high-temperature tensile properties is obtained, which is called sample 9.

[0134] Example 10 A high-strength, high-wear-resistant mold steel with excellent high-temperature tensile properties is prepared by the following steps: (1) A high-power electric arc furnace (EAF) is used for primary refining. High-quality scrap steel and alloy materials (such as Cr, Mo, V, etc.) are added to the furnace in proportion (89 kg of FeCr (65 wt.% of Cr), 23 kg of FeMo (60 wt.% of Mo), and 14 kg of FeV80 (80 wt.% of V) per 1000 kg of molten steel). The melting temperature is controlled at 1550℃. Oxygen lance is used to remove impurities such as carbon and phosphorus. After primary refining, the steel is tapped to the ladle to obtain primary molten steel. The composition and mass percentage of the primary molten steel are controlled as follows: C: 0.38%, Si: 0.82%, Mn: 0.38%, Cr: 5.02%, Mo: 1.75%, V: 0.87%, P: 0.008%, S: 0.001%. (2) The primary molten steel obtained in step (1) is transferred to the ladle refining furnace (LF), heated by electricity, and the temperature of the molten steel is controlled at 1550℃. A slag-forming agent is added to the ladle to form a low-oxidizing white slag system, wherein the slag-forming agent, based on the mass of the molten steel, includes: 12.0 kg / t of active lime (CaO), 1.5 kg / t of fluorite (CaF2), 2.0 kg / t of calcium aluminate or alumina (Al2O3), and 0.8 kg / t of lightly calcined magnesia powder (MgO). After slag formation, a high-basicity, low-oxidizing white slag is formed, and its (FeO+MnO) content is controlled at ≤1.0%. Desulfurization, deoxidation, and fine-tuning of alloy composition are carried out under white slag conditions, using aluminum deoxidation, with an aluminum addition amount of 1.0 kg / t. The refining time is controlled at 45 minutes. At the same time, the electromagnetic stirring of the ladle is turned on with a stirring current of 300A and a frequency of 4Hz to promote the floating of inclusions and homogenization of molten steel, so as to obtain refined molten steel. The sulfur content in the refined molten steel is controlled at 0.003-0.004%, and the total oxygen content is controlled at 12-18ppm.

[0135] (3) The refined steel obtained in step (2) along with the ladle is placed in a vacuum degassing device (VD) for vacuum treatment, and the vacuum is evacuated to ≤67Pa, while the temperature of the molten steel is maintained at 1500℃. The vacuum degassing time is 30min to further remove gases and residual non-metallic inclusions from the molten steel. After degassing, the hydrogen content in the molten steel is controlled to ≤1.2ppm and the nitrogen content is controlled to ≤70ppm. Trace alloying elements are added under vacuum conditions by wire feeding, and the wire feeding speed is controlled at 0.8m / min to ensure uniform steel composition and low gas content.

[0136] (4) The molten steel after vacuum treatment in step (3) is continuously cast using a protective casting process, and poured into a round billet with a diameter of Φ400mm through an tundish. Argon gas is used for protection during the casting process, and the argon gas flow rate in the tundish is controlled at 8L / min to prevent secondary oxidation of the molten steel. The casting speed is controlled at 0.8m / min, and the superheat of the molten steel is controlled at 30℃. At the same time, electromagnetic stirring is applied in the crystallizer and the secondary cooling zone to refine the solidification structure and obtain a high-quality billet with dense internal structure, no macroscopic segregation, and no obvious surface defects.

[0137] (5) After cooling the high-quality billet obtained in step (4) to room temperature, it is placed in an annealing furnace for spheroidizing annealing treatment. The annealing heating temperature is 820℃, and the holding time is 6h. Then, it is slowly cooled to below 500℃ at a cooling rate of 15℃ / h before being taken out of the furnace to obtain the annealed billet. After annealing treatment, the as-cast segregation is significantly reduced, and the microstructure is fully softened to meet the requirements of subsequent processing.

[0138] (6) The annealed billet obtained in step (5) is processed into a consumable electrode and placed in an electroslag remelting furnace for electroslag remelting. A CaF2-based slag system with a mass ratio of CaF2:Al2O3:CaO = 70:20:10 is used. During the remelting process, the remelting current is controlled at 12000A, the voltage at 40V, and the remelting speed at 4.5kg / min. Directional solidification is achieved in a water-cooled crystallizer. After remelting, the size of inclusions is controlled to ≤8μm, the grains are significantly refined, the uniformity of the structure is significantly improved, and a high-purity remelted ingot is obtained.

[0139] (7) The remelted ingot obtained in step (6) is subjected to multi-directional forging. The initial forging temperature is controlled at 1150℃, the final forging temperature is 900℃, and the total forging ratio is 3.0. After forging, normalizing treatment is performed immediately. The normalizing heating temperature is 1000℃, and the holding time is 1 hour for every 25mm thickness, with a total holding time of 2 hours. Then, it is air-cooled to room temperature at a cooling rate of 50℃ / h to obtain the normalized billet. The microstructure tends to be uniform after normalizing, providing a good microstructure basis for subsequent spheroidizing annealing.

[0140] (8) The normalized billet obtained in step (7) is subjected to spheroidizing annealing. The spheroidizing annealing heating temperature is 800℃, held for 4h, then slowly cooled to 680℃ at a rate of 15℃ / h and held for 3h, and then cooled in the furnace to below 500℃ before being removed from the furnace. After spheroidizing annealing, a uniform spheroidal pearlite structure is obtained, which significantly improves the machinability of the material and the microstructure before quenching.

[0141] (9) Heat the billet after spheroidizing annealing in step (8) to 1060°C, hold for 10 minutes and then quench it by water cooling to obtain quenched billet.

[0142] (10) Place the quenched blank obtained in step (9) into a liquid nitrogen tank for deep cryogenic treatment for 8 hours.

[0143] (11) The blank after the cryogenic treatment in step (10) is heated to 550°C and tempered twice, each time for 2 hours, and air-cooled to room temperature between the two temperings. After tempering, a mold steel with high strength, high wear resistance and excellent high-temperature tensile properties is obtained, which is called sample 10.

[0144] Example 11 A high-strength, high-wear-resistant mold steel with excellent high-temperature tensile properties is prepared by the following steps: (1) A high-power electric arc furnace (EAF) is used for primary refining. High-quality scrap steel and alloy materials (such as Cr, Mo, V, etc.) are added to the furnace in proportion (89 kg of FeCr (65 wt.% of Cr), 23 kg of FeMo (60 wt.% of Mo), and 14 kg of FeV80 (80 wt.% of V) per 1000 kg of molten steel). The melting temperature is controlled at 1550℃. Oxygen lance is used to remove impurities such as carbon and phosphorus. After primary refining, the steel is tapped to the ladle to obtain primary molten steel. The composition and mass percentage of the primary molten steel are controlled as follows: C: 0.38%, Si: 0.82%, Mn: 0.38%, Cr: 5.02%, Mo: 1.75%, V: 0.87%, P: 0.008%, S: 0.001%. (2) The primary molten steel obtained in step (1) is transferred to the ladle refining furnace (LF), heated by electricity, and the temperature of the molten steel is controlled at 1550℃. A slag-forming agent is added to the ladle to form a low-oxidizing white slag system, wherein the slag-forming agent, based on the mass of the molten steel, includes: 12.0 kg / t of active lime (CaO), 1.5 kg / t of fluorite (CaF2), 2.0 kg / t of calcium aluminate or alumina (Al2O3), and 0.8 kg / t of lightly calcined magnesia powder (MgO). After slag formation, a high-basicity, low-oxidizing white slag is formed, and its (FeO+MnO) content is controlled at ≤1.0%. Desulfurization, deoxidation, and fine-tuning of alloy composition are carried out under white slag conditions, using aluminum deoxidation, with an aluminum addition amount of 1.0 kg / t. The refining time is controlled at 45 minutes. At the same time, the electromagnetic stirring of the ladle is turned on with a stirring current of 300A and a frequency of 4Hz to promote the floating of inclusions and homogenization of molten steel, so as to obtain refined molten steel. The sulfur content in the refined molten steel is controlled at 0.003-0.004%, and the total oxygen content is controlled at 12-18ppm.

[0145] (3) The refined steel obtained in step (2) along with the ladle is placed in a vacuum degassing device (VD) for vacuum treatment, and the vacuum is evacuated to ≤67Pa, while the temperature of the molten steel is maintained at 1500℃. The vacuum degassing time is 30min to further remove gases and residual non-metallic inclusions from the molten steel. After degassing, the hydrogen content in the molten steel is controlled to ≤1.2ppm and the nitrogen content is controlled to ≤70ppm. Trace alloying elements are added under vacuum conditions by wire feeding, and the wire feeding speed is controlled at 0.8m / min to ensure uniform steel composition and low gas content.

[0146] (4) The molten steel after vacuum treatment in step (3) is continuously cast using a protective casting process, and poured into a round billet with a diameter of Φ400mm through an tundish. Argon gas is used for protection during the casting process, and the argon gas flow rate in the tundish is controlled at 8L / min to prevent secondary oxidation of the molten steel. The casting speed is controlled at 0.8m / min, and the superheat of the molten steel is controlled at 30℃. At the same time, electromagnetic stirring is applied in the crystallizer and the secondary cooling zone to refine the solidification structure and obtain a high-quality billet with dense internal structure, no macroscopic segregation, and no obvious surface defects.

[0147] (5) After cooling the high-quality billet obtained in step (4) to room temperature, it is placed in an annealing furnace for spheroidizing annealing treatment. The annealing heating temperature is 820℃, and the holding time is 6h. Then, it is slowly cooled to below 500℃ at a cooling rate of 15℃ / h before being taken out of the furnace to obtain the annealed billet. After annealing treatment, the as-cast segregation is significantly reduced, and the microstructure is fully softened to meet the requirements of subsequent processing.

[0148] (6) The annealed billet obtained in step (5) is processed into a consumable electrode and placed in an electroslag remelting furnace for electroslag remelting. A CaF2-based slag system with a mass ratio of CaF2:Al2O3:CaO = 70:20:10 is used. During the remelting process, the remelting current is controlled at 12000A, the voltage at 40V, and the remelting speed at 4.5kg / min. Directional solidification is achieved in a water-cooled crystallizer. After remelting, the size of inclusions is controlled to ≤8μm, the grains are significantly refined, the uniformity of the structure is significantly improved, and a high-purity remelted ingot is obtained.

[0149] (7) The remelted ingot obtained in step (6) is subjected to multi-directional forging. The initial forging temperature is controlled at 1150℃, the final forging temperature is 900℃, and the total forging ratio is 3.0. After forging, normalizing treatment is performed immediately. The normalizing heating temperature is 1000℃, and the holding time is 1 hour for every 25mm thickness, with a total holding time of 2 hours. Then, it is air-cooled to room temperature at a cooling rate of 50℃ / h to obtain the normalized billet. The microstructure tends to be uniform after normalizing, providing a good microstructure basis for subsequent spheroidizing annealing.

[0150] (8) The normalized billet obtained in step (7) is subjected to spheroidizing annealing. The spheroidizing annealing heating temperature is 800℃, held for 4h, then slowly cooled to 680℃ at a rate of 15℃ / h and held for 3h, and then cooled in the furnace to below 500℃ before being removed from the furnace. After spheroidizing annealing, a uniform spheroidal pearlite structure is obtained, which significantly improves the machinability of the material and the microstructure before quenching.

[0151] (9) Heat the billet after spheroidizing annealing in step (8) to 1060°C, hold for 10 minutes and then quench it by water cooling to obtain quenched billet.

[0152] (10) Place the quenched blank obtained in step (9) into a liquid nitrogen tank for cryogenic treatment for 10 hours.

[0153] (11) The blank after the cryogenic treatment in step (10) is heated to 550°C and tempered twice, each time for 2 hours, and air-cooled to room temperature between the two temperings. After tempering, a mold steel with high strength, high wear resistance and excellent high temperature tensile properties is obtained, which is called sample 11.

[0154] The samples prepared in the above-described embodiments 1-3 were subjected to component analysis, and the test results are shown in Table 1.

[0155] Table 1 lists the chemical compositions of samples obtained under different electroslag remelting process parameters (Examples 1-3). The results show that the composition fluctuations within the specified process parameter window are small and can meet the requirements of actual production. The parameters of Example 2 were used in this invention to prepare subsequent samples.

[0156] The die steels prepared in Examples 4-11 above, possessing high strength, high wear resistance, and excellent high-temperature tensile properties, were subjected to room temperature tensile property tests, high-temperature tensile property tests, and wear resistance tests. The test results are shown in Table 2.

[0157] Table 2 shows the mechanical properties of the high-strength, high-wear-resistant mold steels with excellent high-temperature tensile properties prepared in each example.

[0158] As shown in Table 2, samples 4 and 5, prepared at the extreme quenching temperatures (1030℃ and 1090℃) used in Examples 4 and 5, still achieved performance close to that of sample 6 prepared in Example 6 (1060℃), but were slightly inferior overall. Therefore, 1060℃ was selected as the optimal quenching temperature in this invention. The mold steel prepared using the method of this invention exhibits outstanding performance in terms of high strength, high wear resistance, and excellent high-temperature tensile properties. Specifically, the room temperature yield strength and tensile strength of these samples can be increased from 1452MPa to 1851Pa and from 1661MPa to 2130MPa respectively through appropriate cryogenic treatment time (8h), demonstrating excellent load-bearing capacity, and the elongation does not decrease significantly.

[0159] Figure 3 The results of room temperature tensile stress-strain curves for the high-strength, high-wear-resistant, and excellent high-temperature tensile properties of the die steels prepared in Examples 6-11 are shown. The stress-strain curves show a consistent trend: all samples exhibit an initial elastic stage, followed by a plastic deformation stage (the stress corresponding to the inflection point of the engineering stress-strain curve is the yield strength), and the peak stress (the peak stress is the tensile strength) gradually decreases until fracture. Sample 6, prepared in Example 6, serves as a control group and has the lowest yield strength (1452 MPa) and ultimate tensile strength (1661 MPa), but a relatively high elongation (9.2%), indicating good ductility and moderate strength. With increasing cryogenic treatment time, the curves shift upwards overall, reflecting the increase in strength. Samples 10 and 11, prepared in Examples 10 and 11, reach the highest ultimate tensile strength (2130 MPa and 2025 MPa, respectively), showing a significant strengthening effect, which is due to microstructural changes caused by prolonged cryogenic treatment.

[0160] Figure 4 The EBSD diagrams of the high-strength, high-wear-resistant, and high-temperature tensile steels prepared in Examples 6-11 show that cryogenic treatment significantly refined the grain size, effectively increasing the strength of the material. Furthermore, the transformation of fine precipitates and retained austenite also has a significant impact on the strength.

[0161] Figure 5 This is a comparison chart of the Rockwell hardness of the high-strength, high-wear-resistant mold steels with excellent high-temperature tensile properties prepared by different cryogenic treatment times in Examples 6-11. The chart shows that the mold steels prepared by cryogenic treatment times of 6 and 8 hours have better Rockwell hardness, indicating that cryogenic treatment can further improve the hardness of the mold steel.

[0162] Figure 9 Transmission electron microscopy (TEM) images of the high-strength, high-wear-resistant, and high-temperature tensile properties of the die steels prepared in Examples 6 and 10 are shown. Figure 9a is a TEM perspective view of Example 6; Figure 9 b represents the diffraction spot of the precipitate from Example 6; Figure 9 c is a TEM perspective view of Example 10; Figure 9 d represents the diffraction spot of the precipitate in Example 10; as shown in the figure, the sample 10 prepared by the cryogenic treatment (DCT) in Example 10 exhibits a higher dislocation density and precipitates finer and more uniformly distributed M6C type carbides.

[0163] The mold steel provided by this invention, which has high strength, high wear resistance and excellent high-temperature tensile properties, also has excellent tensile properties at high temperatures. Figure 6 The engineering stress-strain curves of the high-strength, high-wear-resistant, and excellent high-temperature tensile properties of the die steels prepared in Examples 6-11 are shown under tensile stress at 650°C. The peak stress of sample 6 prepared in Example 6 is 920±32 MPa, occurring at 5-10% of the engineering strain. The stress then rapidly decreases, indicating that conventional heat treatment is weak at high temperatures. This may be due to excessive tempering or recrystallization of its microstructure at 650°C, leading to a decrease in strength. In contrast, samples 7-11 prepared in Examples 7-11, which underwent cryogenic treatment, show higher peak stresses (peak stress is equivalent to tensile strength): sample 7 is 1042±13 MPa, sample 8 is 1022±37 MPa, sample 9 is 1105±11 MPa, sample 10 is 1125±30 MPa, and sample 11 is 1157±26 MPa. This indicates that cryogenic treatment significantly improves the material's load-bearing capacity, with sample 11 prepared in Example 11 (corresponding to C10) reaching the highest value of 1157±37 MPa. The initial elastic regions of all samples were similar, reflecting that the elastic modulus was unaffected by the treatment and that atomic bonds remained stable. These differences stem from the strengthening effect of cryogenic treatment on the material's microstructure and phase composition. The lower peak stress of sample 6 prepared in Example 6 indicates that conventional heat treatment failed to effectively resist thermal softening at 650°C, possibly due to insufficient phase stability of its underlying microstructure. Cryogenic treatment induces the transformation of retained austenite into martensite through low-temperature exposure and may form fine carbides, thus enhancing high-temperature performance.

[0164] Figure 7 Figure a shows the friction and wear curves. According to the curves, the curve of sample 6, which did not undergo cryogenic treatment, fluctuated significantly during the break-in period. This is because its surface hardness is low, its microstructure is uneven, and its micro-protrusions are prone to plastic deformation or adhesive tearing, resulting in a longer break-in time and a higher friction coefficient after stabilization. In contrast, the curves of samples 7-11, which underwent cryogenic treatment, fluctuated less, resulting in a more efficient break-in process and the lowest friction coefficient after stabilization. Figure 7b is the average friction coefficient diagram. This diagram shows that samples 7-11 prepared in Examples 7-11 have a smaller average friction coefficient than sample 6 prepared in Example 6. This further illustrates that cryogenic treatment can reduce the friction coefficient, and the prepared high-strength, high-wear-resistant mold steel with excellent high-temperature tensile properties has a more efficient running-in process.

[0165] Figure 8 The impact toughness comparison graph shows that the overall impact toughness of the samples under different treatment conditions exhibits a trend of first increasing and then slightly decreasing. Compared with sample 6 prepared in Example 6, the impact toughness gradually increases with increasing cryogenic time (Example 7 → Example 10), reaching its maximum value (approximately 20.68 J / cm²) under the conditions of sample 10 prepared in Example 10. 2 This indicates that the material's toughness was most significantly improved at this point; when the cryogenic time was further increased to 10 hours as in Example 11, the impact toughness of sample 11 decreased slightly (approximately 19.1 J / cm). 2 However, it is still significantly higher than the initial state. Overall, moderate treatment conditions are beneficial to improving impact toughness, while excessive cryogenic treatment may cause a decrease in toughness.

[0166] In summary, the cryogenic treatment method of this invention not only significantly improves the strength of steel, but also effectively enhances its wear resistance and high-temperature tensile properties, ensuring the long-term stability of steel in high-temperature environments. It has significant advantages in production efficiency, cost control, and application prospects, making it particularly suitable for large-scale industrial production and possessing broad application potential.

[0167] The embodiments described above merely illustrate concentrated implementations of the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still make various modifications and improvements to the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features, without departing from the concept of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims, and the specification and drawings can be used to interpret the content of the claims.

Claims

1. A high-strength, high-wear-resistant mold steel with excellent high-temperature tensile properties, characterized in that, Based on the preliminary heat treatment stage of the traditional H13 steel preparation process (primary refining + refining + vacuum treatment), electroslag remelting is inserted after vacuum treatment, and the final heat treatment stage (quenching + tempering) is performed using high-temperature quenching followed by deep cryogenic treatment. Its specific composition and mass percentage are as follows: C: 0.35%-0.45%, Cr: 4.75%-5.50%, Mo: 1.10%-1.75%, V: 0.80%-1.20%, Si: 0.80%-1.20%, Mn: 0.20%-0.50%, with the remainder being iron and unavoidable impurities, of which P≤0.03%, S≤0.005%, O≤20ppm, H≤1.5ppm, and N≤80ppm.

2. The method for preparing a high-strength, high-wear-resistant mold steel with excellent high-temperature tensile properties as described in claim 1, characterized in that, Includes the following steps: (1) Primary smelting: The primary smelting is carried out using an ultra-high power electric arc furnace (EAF). After melting, preliminary dephosphorization and composition control are completed, the molten steel is tapped into the ladle to obtain primary smelted steel. (2) Refining: The primary steel is transferred to the ladle refining furnace LF, and lime, fluorite and other slag-forming agents are added to form white slag. Desulfurization, deoxidation and alloy composition are fine-tuned, and electromagnetic stirring is performed to obtain refined steel. (3) Vacuum treatment: The refined molten steel and the ladle are placed in a vacuum degassing device (VD) for vacuum treatment, and trace alloying elements are added by wire feeding. (4) Protective casting: The molten steel after vacuum treatment is subjected to a protective casting process. Electromagnetic stirring is applied during the casting process to obtain high-quality billets. (5) Annealing: After cooling, the high-quality billet is placed in an annealing furnace for spheroidizing annealing to obtain annealed billet; (6) Electroslag remelting: The annealed billet is used as a consumable electrode and placed in an electroslag remelting furnace. Electroslag remelting is carried out using a CaF2-based slag system. The billet is then directionally solidified in a water-cooled crystallizer to obtain a remelted ingot. (7) Multi-directional forging: The remelted ingot is subjected to multi-directional forging and normalizing treatment to obtain normalized billet; (8) Annealing: The normalized billet is spheroidized annealed through a segmented heat preservation and slow cooling process; (9) Quenching: After spheroidizing annealing, the billet is heated and kept at a certain temperature, and then quenched by water cooling to obtain quenched billet; (10) Cryogenic treatment: The quenched billet is placed in liquid nitrogen for cryogenic treatment to obtain the cryogenically treated billet; (11) Tempering: Tempering the deep cryogenically treated billet to obtain high-strength, high-wear-resistant mold steel with excellent high-temperature tensile properties.

3. The preparation method according to claim 2, characterized in that, In step (1), the component control is achieved by precisely controlling the content of impurities such as carbon and phosphorus through oxygen blowing with an oxygen lance.

4. The preparation method according to claim 2, characterized in that, In step (3), the vacuum degree of the vacuum degassing device is strictly controlled at ≤67Pa, the vacuum degassing temperature is 1500-1550℃, and the vacuum degassing time is 20-40 minutes.

5. The preparation method according to claim 2, characterized in that, In step (4), the protective casting uses argon gas to prevent secondary oxidation, the casting speed is 0.5-1.2 m / min, and the superheat is 20-40℃.

6. The preparation method according to claim 2, characterized in that, In step (6), the electroslag remelting adopts a CaF2-based slag system with a mass ratio of CaF2:Al2O3:CaO = 70:20:

10.

7. The preparation method according to claim 2, characterized in that, In step (6), the electroslag remelting conditions are: remelting current 8000-15000A, voltage 35-45V, and remelting speed 3-6kg / min; the directional solidification controls the inclusion size to ≤10μm.

8. The preparation method according to claim 2, characterized in that, In step (9), the quenching temperature is 1030-1090℃.

9. The preparation method according to claim 2, characterized in that, In step (10), the cryogenic treatment time is 0-10h.

10. The application of the high-strength, high-wear-resistant mold steel with excellent high-temperature tensile properties as described in claim 1 in the fields of machinery manufacturing, precision machining, and high-end equipment.

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