A nano-precipitation phase reinforced ultra-fine grain high-strength steel and a preparation method thereof

Abstract

The application discloses a kind of nano precipitated phase reinforced ultrafine-grained high-strength steel, and the chemical composition of the high-strength steel includes, in atomic percentage: Ni: 24~28%, Al: 4~7%, Ti is 1~5%, C: 0~2%, Cr: 0~2%, Mo: 0~2%, W: 0~2%, Cr+Mo+W:<5%, the rest is iron and unavoidable impurities.The high-strength steel of the application is treated after heat treatment, and the nano precipitated strengthening phase Ni3(Al,Ti) of L12 structure is uniformly dispersed in the high-strength steel, the volume fraction is more than 30%, the size is 10-100 nm, and the high-strength steel with high strength and high toughness in low temperature to 500 o C range is obtained.The high-strength steel of the application does not contain precious elements and can contain a small amount of carbon elements, and does not need to use high-purity iron raw materials, and the cost is lower.

Description

Technical Field

[0001] This invention belongs to the field of metal material preparation, and in particular relates to an ultrafine-grained high-strength steel reinforced by nanoprecipitated phase and its preparation method. Background Technology

[0002] High-strength steel is widely used in major equipment manufacturing fields such as engineering machinery, marine engineering, energy and chemical industry, and transportation. It is not only an important structural material for national infrastructure construction and national defense, but also a key structural material for future lightweight design and energy conservation and emission reduction.

[0003] Currently, many high-strength steels have been developed, mainly divided into three categories: medium-carbon low-alloy steel, secondary hardening steel, and martensitic aging steel. The first two types of steel often have high carbon content, achieving high strength through the formation of carbides and martensite. However, to prevent decarburization, the heat treatment processes for medium-carbon low-alloy steel and secondary hardening steel are demanding, and the welding processes are relatively complex. Martensitic aging steel has low carbon content and generally contains higher amounts of elements such as Ni, Co, and Mo, forming lath martensite and precipitating small amounts of intermetallic compounds to achieve high strength, such as the traditional 18Ni series martensitic aging steel. However, due to the high content and expensive Co elements, the 18Ni series steel has a high cost, limiting its large-scale application. Subsequently, Co-free martensitic aging steels were developed. These aging steels improve alloy strength by forming intermetallic compounds such as η-Ni3Ti or B2-NiAl. However, these intermetallic compounds are unstable or have low strength at high temperatures, making it difficult to provide effective strengthening. Furthermore, martensite undergoes a phase transformation at high temperatures, and the strength of most martensitic aging steels will be severely reduced above 400℃. For example, the yield and tensile strength of M250 martensitic aging steel at room temperature are 1757 and 1810 MPa, respectively, under the same tensile rate, but drop to 543 and 620 MPa at 500℃.

[0004] There is an urgent need to develop low-carbon, high-strength steels with high strength and toughness over a wide temperature range. Since grain boundaries and nanoprecipitates can effectively hinder the movement of defects such as dislocations and improve alloy strength, refining grains and introducing relatively stable nanoprecipitates at high temperatures may be a method to design high-strength steels with both strength and toughness at low to high temperatures. However, the production process of ultrafine-grained steel is very complex, requiring large plastic deformation, cyclic phase transformation, and thermomechanical processing, including high-pressure torsion, equal-channel angle extrusion, heavy cold drawing, cyclic phase transformation between austenite and martensite, and tempering followed by cold rolling and recovery. This results in high production costs and is not suitable for large components, hindering large-scale application. Furthermore, the L12 structure Ni3(Al,Ti) precipitate is the most commonly used precipitate in nickel-based superalloys. Its strength increases with temperature and it is relatively stable at high temperatures, making it very suitable for high-temperature service. However, high-strength steels containing a large amount of Ni3Al nanoprecipitates have not yet been developed.

[0005] In summary, by designing a reasonable composition and heat treatment, a large amount of high-temperature stable L12 structure Ni3(Al,Ti) precipitates are formed in the steel, while the grain size is refined. This results in the development of a high-strength steel that combines strength and toughness at both low and high temperatures, which has extremely high engineering application and scientific value. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, this invention provides a high-strength, high-toughness, and widely applicable nano-precipitated phase-reinforced ultrafine-grained high-strength steel and its preparation method.

[0007] The technical solution adopted by the present invention to solve its technical problem is: a nano-precipitated phase strengthened ultrafine grain high-strength steel, the chemical composition of the high-strength steel by atomic percentage includes: Ni: 24-28%, Al: 4-7%, Ti: 1-5%, C: 0-2%, Cr: 0-2%, Mo: 0-2%, W: 0-2%, Cr+Mo+W: <5%, the remainder being iron and unavoidable impurities.

[0008] Furthermore, in atomic percentage, the chemical composition of the high-strength steel includes: Ni: 25-28%, Al: 5-7%, Ti: 2-4%, C: 0-1%, Cr: 0-1%, Mo: 0-1%, W: 0-1%, with the remainder being iron and unavoidable impurities.

[0009] Furthermore, the high-strength steel matrix consists of two phases: ferrite and austenite, with the austenite content not exceeding 20% ​​and the average grain size of the alloy being less than 5 μm.

[0010] Furthermore, ordered L12-structured nano-γ′-Ni3(Al,Ti) intermetallic compounds are precipitated in the high-strength steel matrix, with a volume fraction greater than 30%.

[0011] Furthermore, the size of the precipitated strengthening phase γ′ with the L12 structure is in the range of 10-100 nm.

[0012] A method for preparing ultrafine-grained high-strength steel reinforced by nanoprecipitated phases includes the following steps:

[0013] Weigh the raw materials and mix them according to the required alloy composition ratio;

[0014] The prepared raw materials are placed in a smelting furnace for smelting, and after being mixed evenly, they are cast into ingots.

[0015] The ingot is heated to above 1000℃ for homogenization treatment for more than 1 hour, and then cooled to room temperature;

[0016] The ingot is subjected to cold / hot processing;

[0017] The steel obtained in the above steps is recrystallized at a temperature above 800°C for more than 5 minutes, and then quenched.

[0018] The steel obtained from the above steps is aged at 500-800℃ for more than 2 hours and then cooled to room temperature to obtain the high-strength steel finished product.

[0019] Furthermore, in the step of casting into ingots, a converter, electric furnace, induction furnace, magnetic levitation furnace, or electric arc furnace is used.

[0020] Furthermore, the cold / hot processing steps include rolling, forging, extrusion, and stamping.

[0021] The reasons for limiting the content range of each chemical component in the high-strength steel are explained below.

[0022] Ni is an important component of the intermetallic compound Ni3(Al,Ti), ensuring that the matrix phase is ferrite with good toughness. However, excessively high Ni content not only increases the cost of the alloy but also stabilizes austenite, inhibiting the austenite-ferrite phase transformation of the matrix and reducing the alloy's strength. Therefore, the Ni content should be controlled at 24-28%.

[0023] Al is a major component of the Ni3(Al,Ti) intermetallic compound phase and can also promote the austenite-ferrite phase transformation in the matrix. However, excessive Al content promotes the formation of intermetallic compounds such as NiAl and FeAl, which have low strength at high temperatures, thus impairing the mechanical properties of the alloy. Therefore, the Al content should be controlled at 5-7%.

[0024] Ti is an important element in the formation of the Ni3(Al,Ti) phase, stabilizing it and promoting the austenite-ferrite phase transformation in the matrix. However, Ti is also a strong MC-type carbide-forming element; excessive addition will lead to the formation of a large number of carbides and the precipitation of harmful phases, impairing the mechanical properties of the alloy. Therefore, the Ti content should be controlled at 2-4%.

[0025] Besides providing solid solution strengthening, carbon (C) can also form stable compounds with titanium (Ti), thus not only providing precipitation strengthening but also effectively controlling grain size. However, excessive C leads to excessive carbides and inhibits the austenite-ferrite phase transformation in the matrix, reducing the alloy's strength. Therefore, the C content should be controlled between 0% and 2%.

[0026] Cr, Mo, and W elements can effectively improve the strength of the matrix. High Cr content stabilizes austenite, inhibits the austenite-ferrite phase transformation in the matrix, and impairs the alloy's strength; high Mo and W contents impair the alloy's toughness. Therefore, the Cr+Mo+W content should be controlled between 0% and 5%.

[0027] This invention employs a design concept that combines composition and microstructure control. Through rational composition and heat treatment design, it refines grains and controls the matrix crystal structure while precipitating nanophases. It successfully introduces L12 structure γ′-Ni3(Al,Ti) intermetallic compounds with a volume fraction greater than 30% and a size of 10-100nm. Simultaneously, the matrix undergoes an austenite-ferrite phase transformation, refining the grains to below 5μm. This results in the alloy exhibiting high strength in the low-temperature range up to 500℃ (for example, in Example 1, the alloy steel has a yield strength greater than 1.4GPa, a tensile strength greater than 2GPa, and a fracture elongation of about 7% at -70℃; a yield strength of 1.1GPa, a tensile strength of 1.9GPa, and a fracture elongation greater than 10% at room temperature; and yield and tensile strengths greater than 900MPa and 1GPa, respectively, and an elongation greater than 10% at 500℃).

[0028] The innovation of this invention lies in the successful introduction of a high volume fraction of L12-structured γ′-Ni3(Al,Ti) intermetallic compound, and the induction of matrix phase transformation during aging heat treatment to achieve grain refinement. Multiple strengthening methods (precipitation strengthening, grain refinement strengthening, and phase transformation strengthening) are applied to the design of high-strength steel, resulting in high-strength steel with high strength and high toughness in a temperature range from low temperature to 500℃. The production process of this invention is relatively simple, the alloy does not contain expensive elements such as Co, the cost is controllable, and it is suitable for manufacturing larger components, meeting the needs of structural parts in fields such as petrochemicals, energy and power, and high-end equipment manufacturing.

[0029] The advantages and beneficial effects of this invention are:

[0030] (1) After heat treatment, the high-strength steel of the present invention precipitates the nano-precipitated strengthening phase Ni3(Al,Ti) with L12 structure, which is uniformly and diffusely distributed in the high-strength steel with a volume fraction of more than 30% and a size of 10-100nm.

[0031] (2) The present invention can induce phase transformation and grain refinement of the matrix by simple aging heat treatment, while precipitating the strengthening phase, thereby obtaining high-strength steel with both high strength and high toughness in the range of low temperature to 500℃.

[0032] (4) The preparation and heat treatment process of the high-strength steel of the present invention is simple and suitable for large-scale production;

[0033] (5) Since the high-strength steel of the present invention does not contain precious elements and may contain a small amount of carbon, it does not require the use of high-purity iron raw materials, thus the cost is low. Attached Figure Description

[0034] Figure 1The microstructure of the high-strength steel after heat treatment in Example 1 of this invention is shown in the following images: a) Size and distribution of nano-precipitated phases in the high-strength steel under dark field transmission electron microscopy; b) Distribution of ferrite and austenite phases in the high-strength steel under backscatter diffraction of scanning electron microscopy; c) Submicron-sized grains of the high-strength steel under bright field transmission electron microscopy.

[0035] Figure 2 The stress-strain tensile curves of the high-strength steel product in Example 1 of this invention at -70, 25, 400 and 500°C are shown.

[0036] Figure 3 The stress-strain tensile curves of the high-strength steel product in Example 2 of this invention at -70, 25, 400 and 500°C are shown.

[0037] Figure 4 The stress-strain tensile curves of the high-strength steel product in Example 3 of the present invention at -70, 25, 400 and 500°C are shown. Detailed Implementation

[0038] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0039] Prepare metal raw materials according to the following alloy composition (atomic percentage).

[0040] Ni: 24-28%, Al: 4-7%, Ti: 1-5%, C: 0-2%, Cr: 0-2%, Mo: 0-2%, W: 0-2%, Cr+Mo+W: <5%, the remainder being iron and unavoidable impurities.

[0041] In this embodiment, raw materials of each element are weighed according to the raw material ratio and smelted and cast into cast steel ingots using a smelting furnace. First, the ingots are homogenized at a temperature above 1000°C for at least 1 hour and then air-cooled or water-cooled to room temperature. Then, the homogenized steel ingots are subjected to cold / hot processing. Subsequently, the processed plates are recrystallized at a temperature above 800°C, held at that temperature for at least 5 minutes, and then cooled to room temperature. Afterward, the recrystallized plates are aged at a temperature of 500-800°C for at least 2 hours and then cooled to room temperature to obtain the high-strength steel finished product.

[0042] Example 1

[0043] Metal raw materials are prepared using metal materials with a purity ≥ 99.5% according to the following alloy composition (atomic percentage): Ni: 26%, Al: 6.0%, Ti: 3.0%, C: 0.2%, Cr: 0%, Mo: 0%, W: 0%, with the remainder being iron and unavoidable impurities.

[0044] Raw materials of each element were weighed according to the raw material ratio, melted and mixed uniformly in an electric arc melting furnace under a protective atmosphere, and cast into alloy ingots. First, the ingots were homogenized at 1225℃ for 8 hours and then water-cooled. Then, the homogenized steel ingots were cold-rolled with a reduction rate of about 86%. Subsequently, the cold-rolled steel ingots were recrystallized at 1050℃ for 1 hour and then water-cooled. After that, they were aged at 680℃ for 24 hours and then air-cooled to obtain high-strength steel.

[0045] Figure 1 The image shows the microstructure of the high-strength steel product in Example 1. As can be seen from the image, a large number of dispersed γ′ strengthening phases are precipitated in the high-strength steel, with an average diameter of about 10-50 nm and a volume fraction of 39%. The high-strength steel matrix is ​​a dual-phase structure of austenite and ferrite, with an austenite volume fraction of about 4% and dispersed carbides. The average grain size of the high-strength steel is about 1 μm.

[0046] Figure 2 The stress-strain tensile curves of the high-strength steel in Example 1 at -70, 25, 400, and 500°C are shown. Clearly, the high-strength steel exhibits high strength from low to high temperatures. At -70°C, the yield strength is greater than 1.4 GPa, and the tensile strength exceeds 2 GPa; at room temperature, the yield strength reaches 1.1 GPa, and the tensile strength reaches 1.9 GPa; at 400°C, the yield and tensile strengths exceed 1.1 and 1.3 GPa, respectively; and at 500°C, the yield and tensile strengths exceed 900 MPa and 1 GPa, respectively. Simultaneously, the alloy exhibits good toughness, with a fracture elongation of approximately 7% at -70°C, and fracture elongation greater than 10% from room temperature to 500°C.

[0047] Example 2

[0048] Metal raw materials are prepared using metal materials with a purity ≥ 99.5% according to the following alloy composition (atomic percentage): Ni: 26%, Al: 6.0%, Ti: 3.0%, C: 0.2%, Mo: 0.6%, Cr: 0%, W: 0%, with the remainder being iron and unavoidable impurities.

[0049] Raw materials of each element were weighed according to the raw material ratio, melted and mixed uniformly in an electric arc melting furnace under a protective atmosphere, and cast into alloy ingots. First, the ingots were homogenized at 1225℃ for 8 hours and then water-cooled. The homogenized ingots were then cold-rolled with a reduction rate of approximately 86%. The cold-rolled ingots were then recrystallized at 1050℃ for 1 hour and water-cooled. After aging at 720℃ for 24 hours, they were air-cooled to obtain the high-strength steel product. The high-strength steel product was then processed into tensile test specimens and subjected to tensile property testing.

[0050] In Example 2, a large amount of γ′ strengthening phase was also precipitated in the high-strength steel, with an average diameter of about 10-50 nm and a volume fraction of 42%. The high-strength steel matrix was composed of austenite (volume fraction less than 1%) and ferrite dual phases, with an average grain size of about 3 μm. Figure 3 The stress-strain tensile curves of the high-strength steel in Example 2 at -70, 25, 400, and 500°C show that at -70°C, the yield strength is higher than 1.6 GPa and the tensile strength exceeds 2.0 GPa; at room temperature, the yield strength is higher than 1.4 GPa and the tensile strength reaches 1.9 GPa; at 400°C, the yield strength is higher than 1.3 GPa and the tensile strength exceeds 1.5 GPa; and at 500°C, the yield strength is greater than 1 GPa and the tensile strength exceeds 1.1 GPa. The tensile elongation at break exceeds 5% within the temperature range of -70 to 500°C.

[0051] Example 3

[0052] Metal raw materials are prepared using metal materials with a purity ≥ 99.5% according to the following alloy composition (atomic percentage): Ni: 26%, Al: 6.0%, Ti: 3.0%, C: 0.2%, Mo: 0%, Cr: 0%, W: 0.3%, with the remainder being iron and unavoidable impurities.

[0053] Raw materials of each element were weighed according to the raw material ratio, melted and mixed uniformly in an electric arc melting furnace under a protective atmosphere, and cast into alloy ingots. First, the ingots were homogenized at 1225℃ for 8 hours and then water-cooled. The homogenized ingots were then cold-rolled with a reduction rate of approximately 86%. The cold-rolled ingots were then recrystallized at 1050℃ for 1 hour and water-cooled. After aging at 720℃ for 24 hours, they were air-cooled to obtain the high-strength steel product. The high-strength steel product was then processed into tensile test specimens and subjected to tensile property testing.

[0054] In Example 3, the high-strength steel also precipitated a large amount of γ′ strengthening phase, with an average diameter of about 10-50 nm and a volume fraction of 44%. The high-strength steel matrix is ​​composed of austenite (volume fraction less than 3%) and ferrite dual phases, with an average grain size of about 3 μm. Figure 4The stress-strain tensile curves of the high-strength steel in Example 3 at -70, 25, 400, and 500°C show that at -70°C, its yield strength exceeds 1.5 GPa and its tensile strength is close to 2 GPa; at room temperature, its yield strength is higher than 1.4 GPa and its tensile strength exceeds 1.8 GPa; at 400°C, its yield strength is higher than 1.2 GPa and its tensile strength is close to 1.5 GPa; and at 500°C, its yield strength is close to 1 GPa and its tensile strength exceeds 1.1 GPa. The tensile elongation at break exceeds 4% within the temperature range of -70 to 500°C.

[0055] Comparative Example 1

[0056] Metal raw materials are prepared using metal materials with a purity ≥ 99.5% according to the following alloy composition (atomic percentage): Ni: 30%, Al: 6%, Ti: 3%, C: 0.2%, Cr: 0%, Mo: 0%, W: 0%, with the remainder being iron and unavoidable impurities.

[0057] Raw materials of each element were weighed according to the raw material ratio, melted and mixed uniformly in an electric arc melting furnace under a protective atmosphere, and cast into alloy ingots. First, the ingots were homogenized at 1225℃ for 8 hours and then water-cooled; then the homogenized ingots were cold-rolled with a rolling reduction of about 86%; the cold-rolled ingots were then recrystallized at 1050℃ for 1 hour and water-cooled; after that, they were aged at 680℃ for 24 hours and then air-cooled.

[0058] The room temperature tensile data of the steel in Comparative Example 1 are shown in Table 1. The yield strength is less than 700 MPa and the ultimate tensile strength is only 1200 MPa, which is much lower than that of Examples 1, 2 and 3.

[0059] Comparative Example 2

[0060] Metal raw materials are prepared using metal materials with a purity ≥ 99.5% according to the following alloy composition (atomic percentage): Ni: 20%, Al: 6%, Ti: 3%, C: 0.2%, Cr: 0%, Mo: 0%, W: 0%, with the remainder being iron and unavoidable impurities.

[0061] Raw materials of each element were weighed according to the raw material ratio, melted and mixed uniformly in an electric arc melting furnace under a protective atmosphere, and cast into alloy ingots. First, the ingots were homogenized at 1225℃ for 8 hours and then water-cooled; then the homogenized ingots were cold-rolled with a rolling reduction of about 86%; the cold-rolled ingots were then recrystallized at 1050℃ for 1 hour and water-cooled; after that, they were aged at 680℃ for 24 hours and then air-cooled.

[0062] The room temperature tensile data of the steel in Comparative Example 2 are shown in Table 1. The alloy yield strength is about 1130 MPa, but the ultimate tensile strength is only 1340 MPa, which is much lower than that of Examples 1, 2 and 3.

[0063] Comparative Example 3

[0064] Metal raw materials are prepared using metal materials with a purity ≥ 99.5% according to the following alloy composition (atomic percentage): Ni: 26%, Al: 6.0%, Ti: 3.0%, C: 0.2%, Cr: 5%, Mo: 0%, W: 0%, with the remainder being iron and unavoidable impurities.

[0065] Raw materials of each element were weighed according to the raw material ratio, melted and mixed uniformly in an electric arc melting furnace under a protective atmosphere, and cast into alloy ingots. First, the ingots were homogenized at 1225℃ for 8 hours and then water-cooled; then the homogenized ingots were cold-rolled with a rolling reduction of about 86%; the cold-rolled ingots were then recrystallized at 1050℃ for 1 hour and water-cooled; after that, they were aged at 680℃ for 24 hours and then air-cooled.

[0066] The room temperature tensile data of the steel in Comparative Example 3 are shown in Table 1. The addition of 5% Cr element greatly weakened the strength of the steel, with yield strength and tensile strength of 730 and 1170 MPa, respectively, which are much lower than those in Examples 1, 2 and 3.

[0067] Comparative Example 4

[0068] Metal raw materials are prepared using metal materials with a purity ≥ 99.5% according to the following alloy composition (atomic percentage): Ni: 26%, Al: 6.0%, Ti: 3.0%, C: 0%, Cr: 0.1%, Mo: 1.2%, W: 1.2%, with the remainder being iron and unavoidable impurities.

[0069] Raw materials of each element were weighed according to the raw material ratio, melted and mixed uniformly in an electric arc melting furnace under a protective atmosphere, and cast into alloy ingots. First, the ingots were homogenized at 1225℃ for 8 hours and then water-cooled; then the homogenized ingots were cold-rolled with a rolling reduction of about 86%; the cold-rolled ingots were then recrystallized at 1050℃ for 1 hour and water-cooled; after that, they were aged at 720℃ for 24 hours and then air-cooled.

[0070] The room temperature tensile data of the steel in Comparative Example 3 are shown in Table 1. After adding 1.2% Mo and 1.2% W, the yield strength and tensile strength of the alloy are only 670 and 1180 MPa, respectively, which are much lower than those in Examples 1, 2 and 3.

[0071] Table 1. Room temperature tensile properties of high-strength steels prepared in Examples 1-3 and Comparative Examples 1-4

[0072] Example Yield strength (MPa) Ultimate tensile strength (MPa) Elongation at break (%) Example 1 1150 1940 11.5 Example 2 1480 1890 6.8 Example 3 1450 1860 5.9 Comparative Example 1 690 1200 36 Comparative Example 2 1130 1340 10 Comparative Example 3 730 1170 28 Comparative Example 4 670 1180 35

[0073] The above specific embodiments are used to explain and illustrate the present invention, but not to limit the present invention. Any modifications and changes made to the present invention within the spirit and scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A nano-precipitated phase-reinforced ultrafine-grained high-strength steel, characterized in that, The chemical composition of the high-strength steel, by atomic percentage, is as follows: Ni: 24-28%, Al: 4-7%, Ti: 1-5%, C: 0-2%, Cr: 0-2%, Mo: 0-2%, W: 0-2%, Cr+Mo+W: <5%, with the remainder being iron and unavoidable impurities; The high-strength steel matrix consists of two phases: ferrite and austenite. The volume fraction of austenite, based on the entire alloy, is no more than 20%, and the average grain size of the alloy is less than 5 μm. Ordered L12 structured nano-γ′-Ni3(Al,Ti) intermetallic compounds precipitate in the high-strength steel matrix. The size of the L12 structured strengthening phase γ′ is in the range of 10-100 nm. The preparation method of the above-mentioned nano-precipitated phase-reinforced ultrafine-grained high-strength steel includes the following steps: Weigh the raw materials and mix them according to the required alloy composition ratio; The prepared raw materials are placed in a smelting furnace for smelting, and after being mixed evenly, they are cast into ingots. The ingot is heated to above 1000℃ for homogenization treatment for more than 1 hour, and then cooled to room temperature; The ingot is subjected to cold or hot processing; The steel obtained by the above cold or hot working steps is recrystallized at a temperature above 800°C for more than 5 minutes, and then quenched. The steel obtained by the above quenching steps is aged at 500-800℃ for more than 2 hours and then cooled to room temperature to obtain the high-strength steel product.

2. The nano-precipitated phase-reinforced ultrafine-grained high-strength steel according to claim 1, characterized in that, The chemical composition of the high-strength steel, by atomic percentage, is as follows: Ni: 25-28%, Al: 5-7%, Ti: 2-4%, C: 0-1%, Cr: 0-1%, Mo: 0-1%, W: 0-1%, with the remainder being iron and unavoidable impurities.

3. The nano-precipitated phase-reinforced ultrafine-grained high-strength steel according to claim 1, characterized in that: The volume fraction of ordered L12-structured nano-γ′-Ni3(Al,Ti) intermetallic compounds precipitated in the high-strength steel matrix is ​​greater than 30% based on the entire alloy.

4. The nano-precipitated phase-reinforced ultrafine-grained high-strength steel according to claim 1, characterized in that: In the step of casting into ingots, a converter or electric furnace is used.

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