High-strength steel nail and preparation process thereof

Abstract

The invention relates to the field of alloy steel, and provides a high-strength steel nail and a preparation process thereof. The steel nail is prepared from the following components in percentage by mass: 0.25 percent to 0.32 percent of C, 0.25 percent to 0.35 percent of Si, 1.2 percent to 1.8 percent of Mn, 2.0 percent to 2.5 percent of Cr, 0.8 percent to 1.2 percent of Ni, 0.3 percent to 0.5 percent of Cu, 0.4 percent to 0.6 percent of Mo, 0.15 percent to 0.25 percent of V, 0.06 percent to 0.10 percent of Nb, 0.03 percent to 0.07 percent of Ti, 0.03 percent to 0.05 percent of Al, 0.003 percent to 0.008 percent of B, 0.010 percent to 0.020 percent of N, 0.08 percent to 0.15 percent of Ce / Y mixed rare earth and the balance of Fe and other inevitable impurities. The plastic deformation capacity of the material is improved, and the corrosion resistance of the high-strength steel nail is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of alloy steel, and specifically, to a high-strength steel nail and its preparation process. Background Art

[0002] As a basic connecting piece, high-strength steel nails play a crucial role in the modern industrial system, and their application fields widely cover key industries such as construction, mechanical manufacturing, medical devices, and transportation. In the construction field, high-strength steel nails are the core components for connecting steel structure frameworks, precast concrete components, and wood structures. Their mechanical properties directly determine the seismic resistance, load-bearing capacity, and service life of buildings. For example, in high-rise buildings or long-span bridges, steel nails need to bear huge static and dynamic loads, and any minor failure may trigger a chain reaction, endangering the safety of the overall structure. In the field of mechanical manufacturing, high-strength steel nails are used to fix precision components, transmission devices, and heavy equipment. Their fatigue resistance and dimensional stability are crucial for the accuracy and reliability of mechanical operation. In the field of medical devices, high-strength steel nails such as orthopedic external fixation brackets and implantable screws need to have biocompatibility, mechanical strength, and corrosion resistance to meet the long-term use requirements in the complex human body environment. In the transportation field, high-speed rail track connectors, aviation fasteners, and automotive chassis steel nails, etc., need to maintain stable performance under extreme working conditions such as high temperature, low temperature, vibration, and corrosion to ensure the safe operation of transportation vehicles.

[0003] Traditional high-strength steel nails are mostly based on cold-heading steel (such as SWRCH22A, ML08Al) or 45# steel, and are prepared through processes such as cold-heading forming, thread processing, and heat treatment (quenching + tempering). Although such materials and processes can meet the use requirements under general working conditions, they face severe challenges in extreme environments. One of the core problems is the contradiction between strength and ductility. To improve the tensile strength and yield strength of steel nails, traditional processes often achieve this by increasing the carbon content or adding alloying elements (such as Cr, Mo), but this approach significantly reduces the plastic deformation ability of the material. In addition, the insufficient corrosion resistance of traditional steel nails in humid or corrosive environments is also a key problem restricting their application. Taking 45# steel as an example, its carbon content is relatively high and no corrosion-resistant alloying elements are added, so it is extremely easy to undergo electrochemical corrosion in marine climates, acid rain areas, or chemical plants. Corrosion products (such as rust) not only reduce the cross-sectional area of the steel nail, resulting in a decrease in load-bearing capacity, but may also cause hydrogen embrittlement, further accelerating the fracture process. Based on this, the present invention proposes a high-strength steel nail and its preparation process. Summary of the Invention

[0004] The present invention provides a high-strength steel nail and its preparation process, which improves the balance between the strength and ductility of the high-strength steel nail, solves the problem that the traditional process significantly reduces the plastic deformation ability of the material in order to improve the strength, and at the same time improves the corrosion resistance of the high-strength steel nail in humid or corrosive environments.

[0005] The technical solution of the present invention is as follows: In a first aspect, the present invention provides a high-strength steel nail, which is composed of the following components by mass percentage: C 0.25% - 0.32%, Si 0.25% - 0.35%, Mn 1.2% - 1.8%, Cr 2.0% - 2.5%, Ni 0.8% - 1.2%, Cu 0.3% - 0.5%, Mo 0.4% - 0.6%, V 0.15% - 0.25%, Nb 0.06% - 0.10%, Ti 0.03% - 0.07%, Al 0.03% - 0.05%, B 0.003% - 0.008%, N 0.010% - 0.020%, Ce / Y mixed rare earth 0.08% - 0.15%, and the balance is Fe and other inevitable impurities.

[0006] As a further technical solution, the steel nail is composed of the following components by mass percentage: C 0.25% - 0.32%, Si 0.25% - 0.35%, Mn 1.2% - 1.8%, Cr 2.0% - 2.5%, Ni 0.8% - 1.2%, Cu 0.3% - 0.5%, Mo 0.4% - 0.6%, V 0.15% - 0.25%, Nb 0.06% - 0.10%, Ti 0.03% - 0.07%, Al 0.03% - 0.05%, B 0.003% - 0.008%, N 0.010% - 0.020%, Ce / Y mixed rare earth 0.08% - 0.15%, and the balance is Fe and other inevitable impurities, and the weight ratio of (Mn + Ni) / (Cr + Mo) is 0.85 - 0.95.

[0007] As a further technical solution, the steel nail is composed of the following components by mass percentage: C 0.25% - 0.32%, Si 0.25% - 0.35%, Mn 1.2% - 1.8%, Cr 2.0% - 2.5%, Ni 0.8% - 1.2%, Cu 0.3% - 0.5%, Mo 0.4% - 0.6%, V 0.15% - 0.25%, Nb 0.06% - 0.10%, Ti 0.03% - 0.07%, Al 0.03% - 0.05%, B 0.003% - 0.008%, N 0.010% - 0.020%, Ce / Y mixed rare earth 0.08% - 0.15%, and the balance is Fe and other inevitable impurities, and the weight ratio of Si / Al is 7 - 8.

[0008] As a further technical solution, the steel nail is composed of components with the following mass percentages: C 0.25%-0.32%, Si 0.25%-0.35%, Mn 1.2%-1.8%, Cr 2.0%-2.5%, Ni 0.8%-1.2%, Cu 0.3%-0.5%, Mo 0.4%-0.6%, V 0.15%-0.25%, Nb 0.06%-0.10%, Ti 0.03%-0.07%, Al 0.03%-0.05%, B 0.003%-0.008%, N 0.010%-0.020%, Ce / Y mixed rare earth 0.08%-0.15%, and the balance is Fe and other inevitable impurities, and the weight ratio of (V + Nb) / C is 0.95-1.05.

[0009] In the steel nail of the present invention, the mass percentage ratio of carbon element is carefully designed. C, as an important strengthening element in steel, forms carbides with alloying elements, which can significantly improve the strength and hardness of steel; Si and Mn play a role in deoxidation and solid solution strengthening, enhancing the strength and toughness of steel; Cr and Ni can improve the hardenability and corrosion resistance of steel; Cu can improve the atmospheric corrosion resistance of steel; Mo can refine the grain size and improve the high-temperature strength and tempering stability of steel; micro-alloying elements such as V, Nb, and Ti play a role in precipitation strengthening and grain refinement by forming fine precipitation phases such as carbides and nitrides; Al is a good deoxidizer, which can reduce oxide inclusions in steel; B can significantly improve the hardenability of steel; N combines with alloying elements to form nitrides, further enhancing the strength of steel; Ce / Y mixed rare earth has the effects of purifying molten steel, refining grain size, and improving the morphology of inclusions. By reasonably controlling the mass percentages of these elements, the comprehensive improvement of the properties such as strength, toughness, and corrosion resistance of the steel nail is achieved.

[0010] As a further technical solution, a NiW alloy layer with a thickness of 1.0-1.2 μm is deposited on the surface of the steel nail.

[0011] As a further technical solution, the weight ratio of the target materials in the NiW alloy layer is Ni:W = 75:25.

[0012] In the second aspect, the present invention proposes a preparation process for high-strength steel nails, and the steps include: S1. Melting and casting: Weigh the raw materials according to the ratio, add them into a vacuum induction furnace for melting, and pour them into a billet after refining; S2. Solution treatment: Under the protection of Ar gas, heat it up to 1250 - 1300 °C at a rate of 135 - 140 °C / h and hold for 50 - 60 min, then quickly cool it to 1000 - 1100 °C. After that, introduce a mixed gas of N2 - 5%H2 with a flow rate of 14 - 16 L / min, keep it warm for 30 - 40 min, and process it into shape to obtain steel nails. S3. Surface treatment: Deposit a NiW alloy layer using a magnetron sputtering system. S4. Cryogenic treatment: Immerse it in liquid nitrogen at -190 ~ -200 °C for 15 - 25 min, then warm it up to 200 - 220 °C at a rate of 10 - 12 °C / min, and simultaneously apply ultrasonic waves at 20 kHz and keep it warm for 5 - 10 min; thus obtaining the high-strength steel nails.

[0013] As a further technical solution, the melting temperature in the vacuum induction furnace is 1600 - 1650 °C and the time is 30 - 60 min; the refining temperature is 1550 - 1600 °C and the time is 20 - 30 min.

[0014] As a further technical solution, the deposition parameters include: substrate bias voltage -150 V, pulse frequency 340 - 360 Hz, and deposition rate 0.8 - 1 μm / h.

[0015] As a further technical solution, the cryogenic treatment step is repeated 5 - 10 times.

[0016] The working principle and beneficial effects of the present invention are as follows: In the present invention, the weight ratio of (Mn + Ni) / (Cr + Mo) is 0.85 - 0.95. Among them, Mn and Ni mainly play a role in improving the hardenability and toughness of steel, while Cr and Mo contribute to improving the strength, hardness and corrosion resistance of steel, and will form strengthening phases such as carbides. When this ratio is within a suitable range, various strengthening mechanisms and toughness mechanisms in the steel can reach a better balance. If the ratio is too high, the contents of Cr and Mo may be relatively insufficient, the number of carbides formed is reduced, affecting the strength and corrosion resistance of the steel; if the ratio is too low, the effects of Mn and Ni may be overly inhibited, and the improvement effects of the toughness and hardenability of the steel are not obvious. Therefore, by controlling this ratio, the comprehensive performance of the steel nails can be optimized.

[0017] In the present invention, the weight ratio of Si / Al is controlled to be 7 - 8 because both Si and Al have deoxidizing effects in steel, but their effects on the properties of steel are different. Si mainly exists in solid solution form in steel, playing a role of solid solution strengthening, but excessive Si may lead to a decrease in the toughness of steel; Al is a stronger deoxidizer, which can effectively reduce oxide inclusions in steel. At the same time, precipitation phases such as AlN can refine the grains. By controlling the Si / Al ratio, the advantages of both can be fully utilized. While ensuring the deoxidation effect of steel, the decrease in toughness caused by excessive Si content can be avoided, and the strength and toughness of steel can be improved through the grain refinement effect of Al.

[0018] In the present invention, the weight ratio of (V + Nb) / C is controlled to be 0.95 - 1.05. V and Nb are strong carbide - forming elements. The fine precipitation phases such as carbides and nitrides formed by them and C play a role of precipitation strengthening in steel, which can significantly improve the strength of steel. At the same time, these precipitation phases can also pin the grain boundaries and hinder grain growth, playing a role in refining the grains. When the (V + Nb) / C ratio is within a suitable range, it can ensure that there are sufficient amounts of V and Nb combined with C to form precipitation phases, and the precipitation strengthening and grain refinement effects can be fully exerted. If the ratio is too low, the number of precipitation phases is insufficient and the strengthening effect is not obvious; if the ratio is too high, it may lead to a relatively insufficient C content, affecting the matrix strength and other properties of steel.

[0019] In the present invention, a NiW alloy layer with a thickness of 1.0 - 1.2 μm is deposited on the surface of the steel nail. The NiW alloy has good corrosion resistance and wear resistance. Ni itself has good corrosion resistance and can form a stable oxide film in many corrosion environments to prevent further erosion by corrosive media; the addition of W can improve the hardness and wear resistance of the alloy, and at the same time further enhance the corrosion resistance of the alloy, making the alloy layer more dense and reducing the penetration channels of corrosive media. By depositing the NiW alloy layer through a magnetron sputtering system, a uniform and dense coating can be formed on the surface of the steel nail, effectively improving the surface properties of the steel nail and extending its service life. The weight ratio of the targets in the NiW alloy layer is controlled as Ni:W = 75:25, based on the physical and chemical properties of Ni and W and their roles in the alloy. Ni, as a matrix element, has good toughness and corrosion resistance, providing the basic mechanical properties and protective properties for the alloy layer; W has high hardness, high melting point and good wear resistance, but too high a content may lead to an increase in the brittleness of the alloy layer. By controlling the Ni:W ratio to be 75:25, while ensuring that the alloy layer has sufficient corrosion resistance and toughness, the alloy layer can maintain good performance in various harsh environments.

[0020] Specific embodiments Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present invention.

[0021] Example 1 In this embodiment, a high-strength steel nail is provided. The steel nail is composed of the following components by mass percentage: C 0.28%, Si 0.30%, Mn 1.5%, Cr 2.3%, Ni 1.0%, Cu 0.4%, Mo 0.5%, V 0.20%, Nb 0.08%, Ti 0.05%, Al 0.04%, B 0.005%, N 0.015%, Ce / Y = 0.12% (the mass ratio of the two is 3:1), and the balance is Fe and other inevitable impurities; Among them, (Mn + Ni) / (Cr + Mo) = 0.89; Si / Al = 7.5; (V + Nb) / C = 1.0; The preparation process of this steel nail includes the following steps: S1. Melting and casting: Weigh the raw materials according to the ratio, add them into a vacuum induction furnace for melting. The melting temperature is 1620 °C and the time is 45 min. After refining, pour them into a billet. The refining temperature is 1580 °C and the time is 25 min; S2. Solution treatment: Under the protection of Ar gas, heat up to 1270 °C at a rate of 138 °C / h and hold for 55 min, then quickly cool to 1050 °C. Then, introduce a mixed gas of N2 - 5%H2 with a flow rate of 15 L / min, keep warm for 35 min, and process and form to obtain the steel nail; S3. Surface treatment: Deposit a NiW alloy layer with a thickness of 1.1 μm by a magnetron sputtering system. During deposition, the weight ratio of the target materials Ni:W = 75:25, the substrate bias voltage is -150 V, the pulse frequency is 350 Hz, and the deposition rate is 0.9 μm / h; S4. Cryogenic treatment: Immerse in liquid nitrogen at -195 °C for 20 min, then warm up to 210 °C at a rate of 11 °C / min, and simultaneously apply ultrasonic waves of 20 kHz and keep warm for 8 min. Repeat the above steps 10 times; thus, the high-strength steel nail is obtained.

[0022] Example 2 In this embodiment, a high-strength steel nail is provided. The steel nail is composed of the following components by mass percentage: C 0.28%, Si 0.30%, Mn 1.8%, Cr 2.0%, Ni 1.2%, Cu 0.4%, Mo 0.6%, V 0.20%, Nb 0.08%, Ti 0.05%, Al 0.04%, B 0.005%, N 0.015%, Ce / Y = 0.12% (the mass ratio of the two is 3:1), and the balance is Fe and other inevitable impurities; Among them, (Mn + Ni) / (Cr + Mo) = 1.15; Si / Al = 7.5; (V + Nb) / C = 1.0; The preparation process of this steel nail includes the following steps: S1. Melting and casting: Weigh the raw materials according to the ratio, add them into a vacuum induction furnace for melting. The melting temperature is 1620 °C and the time is 45 min. After refining, it is cast into a billet. The refining temperature is 1580 °C and the time is 25 min; S2. Solution treatment: Under the protection of Ar gas, heat it to 1270 °C at a rate of 138 °C / h and hold for 55 min. After quickly cooling to 1050 °C, introduce a N2-5%H2 mixed gas with a flow rate of 15 L / min, keep it warm for 35 min, and process it into shape to obtain the steel nail; S3. Surface treatment: Deposit a NiW alloy layer with a thickness of 1.1 μm by using a magnetron sputtering system. During deposition, the weight ratio of the target material is Ni:W = 75:25, the substrate bias voltage is -150 V, the pulse frequency is 350 Hz, and the deposition rate is 0.9 μm / h; S4. Cryogenic treatment: Immerse it in liquid nitrogen at -195 °C for 20 min, then warm it up to 210 °C at a rate of 11 °C / min, and simultaneously apply ultrasonic waves at 20 kHz and keep it warm for 8 min. Repeat the above steps 10 times; thus, the high-strength steel nail is obtained.

[0023] Example 3 In this embodiment, a high-strength steel nail is provided. The steel nail is composed of the following components by mass percentage: C 0.28%, Si 0.30%, Mn 1.5%, Cr 2.3%, Ni 1.0%, Cu 0.4%, Mo 0.5%, V 0.15%, Nb 0.06%, Ti 0.05%, Al 0.04%, B 0.005%, N 0.015%, Ce / Y = 0.12% (the mass ratio of the two is 3:1), and the balance is Fe and other inevitable impurities; Among them, (Mn + Ni) / (Cr + Mo) = 0.89; Si / Al = 7.5; (V + Nb) / C = 0.75; The preparation process of this steel nail includes the following steps: S1. Melting and casting: Weigh the raw materials according to the ratio, add them into a vacuum induction furnace for melting. The melting temperature is 1620 °C and the time is 45 min. After refining, pour them into a billet. The refining temperature is 1580 °C and the time is 25 min. S2. Solution treatment: Under the protection of Ar gas, heat it up to 1270 °C at a rate of 138 °C / h and hold for 55 min. Then quickly cool it to 1050 °C, and introduce a N2-5%H2 mixed gas with a flow rate of 15 L / min, keep it warm for 35 min, and process it into shape to obtain steel nails. S3. Surface treatment: Deposit a NiW alloy layer with a thickness of 1.1 μm by using a magnetron sputtering system. During deposition, the weight ratio of the target materials Ni:W = 75:25, the substrate bias voltage is -150 V, the pulse frequency is 350 Hz, and the deposition rate is 0.9 μm / h. S4. Cryogenic treatment: Immerse it in liquid nitrogen at -195 °C for 20 min, then warm it up to 210 °C at a rate of 11 °C / min, and simultaneously apply ultrasonic waves at 20 kHz and keep it warm for 8 min. Repeat the above steps 10 times; thus obtaining the high-strength steel nails.

[0024] Comparative Example 1 In Comparative Example 1, Cu = 0%, and the rest is the same as in Comparative Example 1. The preparation steps are the same as in Comparative Example 1.

[0025] Comparative Example 2 In Comparative Example 2, Ce = 0, Y = 0, and the rest is the same as in Comparative Example 1. The preparation steps are the same as in Comparative Example 1.

[0026] Comparative Example 3 In Comparative Example 3, Si / Al = 15 (Al = 0.02%), and the rest is the same as in Comparative Example 1. The preparation steps are the same as in Comparative Example 1.

[0027] Comparative Example 4 In Comparative Example 4, the coating is only Ni layer (without W), and the rest is the same as in Comparative Example 1. The preparation steps are the same as in Comparative Example 1.

[0028] Comparative Example 5 In Comparative Example 5, the coating is only W layer (without Ni), and the rest is the same as in Comparative Example 1. The preparation steps are the same as in Comparative Example 1.

[0029] Comparative Example 6 In Comparative Example 6, there is no surface coating, and the rest is the same as in Comparative Example 1. The preparation steps are the same as in Comparative Example 1.

[0030] Comparative Example 7 In Comparative Example 7, the cryogenic treatment is only 1 cycle, and the rest is the same as in Comparative Example 1. The preparation steps are the same as in Comparative Example 1.

[0031] Comparative Example 8 In Comparative Example 8, Mn = 2.0%, Ni = 1.5%, Cr = 2.0%, Mo = 0.4%, (Mn + Ni) / (Cr + Mo) = 1.46, and the rest is the same as in Comparative Example 1. The preparation steps are the same as in Comparative Example 1.

[0032] Test Example 1: The steel nails prepared in the foregoing Examples 1-3 and Comparative Examples 1-8 were tested as follows: Mechanical properties: Referring to the ASTM E8 / E8M standard, cylindrical specimens with a diameter of 6 mm and a gauge length of 30 mm were prepared using the foregoing preparation method; the tensile rate was controlled at 2 mm / min, and the tensile strength and elongation of the steel nails at different temperatures were tested using an Instron 5985 universal testing machine at room temperature; Damp heat cycle test: At 40°C / 95% RH, with one cycle every 24 h for 30 days; Neutral salt spray resistance: The steel nails were continuously sprayed with a 5% (by mass) NaCl aqueous solution at a constant temperature of 35°C, and the initial rusting time of the steel nails was recorded; The results are shown in Table 1 below: Table 1

[0033] Combined with the foregoing content, it can be seen that the salt spray resistance time of Comparative Example 1 was only 800 hours, significantly lower than that of Example 1, indicating that Cu enhances corrosion resistance by improving the passivation ability. The impact energy of Comparative Example 2 decreased to 38 J, and the damp heat cycle oxidation was aggravated, indicating that rare earths refine the grain size and improve the corrosion resistance stability. In Comparative Example 3, due to the too low Al content, the inclusions increased, the elongation decreased to 6.5%, and the salt spray time decreased to 1200 hours, reflecting the necessity of Al for deoxidation and inclusion control. The salt spray resistance time of Comparative Examples 4-5 was lower than that of Example 1, and pitting corrosion occurred, proving that the addition of W improves the coating densification and wear resistance. The tensile strength of Comparative Example 7 decreased to 1550 MPa, indicating that multiple cryogenic treatments can fully eliminate the residual stress and increase the dislocation density. Although the tensile strength of Comparative Example 8 ((Mn + Ni) / (Cr + Mo) = 1.46) reached 1650 MPa, the elongation was only 6.0% and the corrosion resistance was poor, indicating that too high a ratio results in insufficient Cr / Mo carbides, sacrificing toughness and corrosion resistance.

[0034] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A high-strength steel nail, characterized in that, The steel nail consists of the following components by mass percentage: C 0.25% - 0.32%, Si 0.25% - 0.35%, Mn 1.2% - 1.8%, Cr 2.0% - 2.5%, Ni 0.8% - 1.2%, Cu 0.3% - 0.5%, Mo 0.4% - 0.6%, V 0.15% - 0.25%, Nb 0.06% - 0.10%, Ti 0.03% - 0.07%, Al 0.03% - 0.05%, B 0.003% - 0.008%, N 0.010% - 0.020%, Ce / Y mixed rare earth 0.08% - 0.15%, and the balance is Fe and other inevitable impurities.

2. The high-strength steel nail according to claim 1, characterized in that, The steel nail consists of the following components by mass percentage: C 0.25% - 0.32%, Si 0.25% - 0.35%, Mn 1.2% - 1.8%, Cr 2.0% - 2.5%, Ni 0.8% - 1.2%, Cu 0.3% - 0.5%, Mo 0.4% - 0.6%, V 0.15% - 0.25%, Nb 0.06% - 0.10%, Ti 0.03% - 0.07%, Al 0.03% - 0.05%, B 0.003% - 0.008%, N 0.010% - 0.020%, Ce / Y mixed rare earth 0.08% - 0.15%, and the balance is Fe and other inevitable impurities, and the weight ratio of (Mn + Ni) / (Cr + Mo) is 0.85 - 0.

95.

3. The high-strength steel nail according to claim 2, wherein The steel nail consists of the following components by mass percentage: C 0.25% - 0.32%, Si 0.25% - 0.35%, Mn 1.2% - 1.8%, Cr 2.0% - 2.5%, Ni 0.8% - 1.2%, Cu 0.3% - 0.5%, Mo 0.4% - 0.6%, V 0.15% - 0.25%, Nb 0.06% - 0.10%, Ti 0.03% - 0.07%, Al 0.03% - 0.05%, B 0.003% - 0.008%, N 0.010% - 0.020%, Ce / Y mixed rare earth 0.08% - 0.15%, and the balance is Fe and other inevitable impurities, and the weight ratio of Si / Al is 7 - 8.

4. The high-strength steel nail according to claim 3, characterized in that, The steel nail is composed of the following components by mass percentage: C 0.25% - 0.32%, Si 0.25% - 0.35%, Mn 1.2% - 1.8%, Cr 2.0% - 2.5%, Ni 0.8% - 1.2%, Cu 0.3% - 0.5%, Mo 0.4% - 0.6%, V 0.15% - 0.25%, Nb 0.06% - 0.10%, Ti 0.03% - 0.07%, Al 0.03% - 0.05%, B 0.003% - 0.008%, N 0.010% - 0.020%, Ce / Y mixed rare earth 0.08% - 0.15%, the balance being Fe and other inevitable impurities, and the weight ratio of (V + Nb) / C is 0.95 - 1.

05.

5. A high-strength steel nail according to claim 1, characterized in that, A NiW alloy layer with a thickness of 1.0 - 1.2 μm is deposited on the surface of the steel nail.

6. The high-strength steel nail according to claim 5, wherein, In the NiW alloy layer, the weight ratio of the target materials Ni:W = 75:

25.

7. A preparation process for a high-strength steel nail as described in any one of claims 1-6, characterized in that the steps Including: S1. Melting and casting: Weigh the raw materials according to the ratio, add them into a vacuum induction furnace for melting, and pour them into a billet after refining. S2. Solution treatment: Under the protection of Ar gas, heat up to 1250 - 1300 °C at a rate of 135 - 140 °C / h and hold for 50 - 60 min, then quickly cool to 1000 - 1100 °C, and then introduce a N2 - 5%H2 mixed gas with a flow rate of 14 - 16 L / min, keep warm for 30 - 40 min, and process into shape to obtain the steel nail. S3. Surface treatment: Deposit the NiW alloy layer by using a magnetron sputtering system. S4. Cryogenic treatment: Immerse it in liquid nitrogen at -190 ~ -200 °C for 15 - 25 min, then warm it back to 200 - 220 °C at a rate of 10 - 12 °C / min, and simultaneously apply ultrasonic waves of 20 kHz, and keep warm for 5 - 10 min; thus obtaining the high-strength steel nail.

8. A high-strength steel nail according to claim 7, characterized in that The melting temperature in the vacuum induction furnace is 1600 - 1650 °C and the time is 30 - 60 min; the refining temperature is 1550 - 1600 °C and the time is 20 - 30 min.

9. The high-strength steel nail according to claim 7, characterized in that, The deposition parameters include: substrate bias voltage -150 V, pulse frequency 340 - 360 Hz, deposition rate 0.8 - 1 μm / h.

10. The preparation process of the high-strength steel nail according to claim 7, characterized in that, The cryogenic treatment step is repeated 5 - 10 times.

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