A method for producing a cold-drawn material of a precipitation-hardened stainless steel for high-strength fasteners

Abstract

The application discloses a preparation method of a high-strength fastener precipitated hardening stainless steel cold-drawing material, which comprises the steps of alloy ingredient mixing, vacuum smelting, electroslag remelting, hot working treatment, cold deformation strengthening, solid solution treatment and grading aging treatment. The stainless steel material prepared by the application has a tensile strength of no less than 1420 MPa, a yield strength of no less than 1280 MPa, an elongation after fracture of no less than 12.5%, and a Brinell hardness of no less than 430 HB, and simultaneously has excellent atmospheric corrosion resistance and medium corrosion resistance, and is suitable for the severe requirements of high-strength fasteners in the fields of aerospace, high-end equipment, ocean engineering and the like. The process has the advantages of high stability, high repeatability and convenience for industrialized batch production.

Description

Technical Field

[0001] This invention relates to the field of stainless steel processing technology, and more specifically to a method for preparing precipitation-hardening stainless steel cold-drawn material for high-strength fasteners. Background Technology

[0002] Precipitation hardening stainless steel (PH steel) is a type of high-strength stainless steel that is strengthened by precipitating phases through aging treatment. This type of material is made by adding strengthening elements such as copper, aluminum, titanium, and niobium to the basic stainless steel chemical composition. Through the precipitation hardening process, carbides, nitrides, carbonitrides, and intermetallic compounds are precipitated, which improves strength while maintaining sufficient toughness and machinability. It is widely used in the manufacture of various high-end fasteners.

[0003] With the rapid development of aerospace, marine engineering, and high-end equipment, higher requirements have been placed on the strength, toughness, and corrosion resistance of fasteners.

[0004] Existing precipitation-hardening stainless steel manufacturing processes often suffer from the following problems: First, unreasonable alloy composition design leads to insufficient precipitation or uneven distribution of strengthening phases, making it difficult to meet the high strength requirements of over 1400 MPa; second, poor synergy between hot working and heat treatment processes results in internal structural defects in the material (such as coarse grains, segregation, and stress concentration), leading to an imbalance between strength and toughness and insufficient fracture toughness; third, corrosion resistance, especially resistance to marine environment corrosion, needs to be improved, limiting its application in harsh environments such as marine engineering.

[0005] Therefore, there is an urgent need for a method for preparing precipitation-hardening stainless steel cold-drawn material for high-strength fasteners. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a method for preparing precipitation-hardening stainless steel cold-drawn material for high-strength fasteners, so as to solve the problems in the background art.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows.

[0008] A method for preparing precipitation-hardening stainless steel cold-drawn material for high-strength fasteners specifically includes the following steps: S1. Alloy Batching: The raw materials selected are industrial pure iron, ferrochrome, nickel plate, ferromolybdenum, electrolytic copper, ferrotitanium, ferroniobium, and aluminum ingots with a purity ≥99.9%, precisely batched according to the mass percentage composition of the stainless steel cold-drawn material; the alloy composition of the stainless steel cold-drawn material is: Cr 15.0~17.5%, Ni 4.5~6.5%, Mo 2.0~3.0%, Cu 1.5~2.5%, Ti 0.15~0.35%, Nb 0.05~0.15%, Al 0.05~0.15%, C ≤0.05%, Si ≤0.8%, Mn ≤1.0%, P ≤0.03%, S ≤0.02%, with the remainder being Fe and unavoidable impurities; S2, Vacuum melting: The ingredients from step S1 are put into a vacuum induction furnace and melted at 1520~1580℃ for 30~60 minutes. Then, the mixture is cast at 1480~1520℃ to obtain the electrode. S3. Electroslag remelting: The electrode obtained in step S2 is electroslag remelted at a melting rate of 3.5 to 4.1 kg / min and then cast to obtain an electroslag ingot. S4. Hot working treatment: The electroslag ingot obtained in step S3 is heated to 1100~1150℃ and held for 2~3 hours, and then hot forging is performed. The forging deformation is 60~75%. After forging, it is immediately air-cooled to room temperature. Then the forging is heated to 1050~1100℃ and held for 1~2 hours, and then hot-rolled. The rolling deformation is 50%~65%. After rolling, it is air-cooled to room temperature to obtain a bar. S5. Cold deformation strengthening: The bar after hot rolling in step S4 is cold drawn with a cold deformation of 30% to 45% to obtain the bar; graphite lubrication is used during the drawing process and the drawing speed is controlled at 5 to 10 m / min. S6. Solution treatment: Place the bar obtained in step S5 in a heat treatment furnace and keep it at 1020~1060℃ for 1.5~2.5h, then water cool it to room temperature at a cooling rate ≥80℃ / min. S7. Graded aging treatment: After cold deformation, the bar is subjected to first-stage aging and second-stage aging, straightened and machined to obtain stainless steel cold-drawn material.

[0009] To further optimize the technical solution, the alloy composition of the cold-drawn stainless steel in step S1 is as follows: Cr 16.0~17.5%, Ni 5.0~6.5%, Mo 2.4~2.7%, Cu 1.9~2.3%, Ti 0.16~0.32%, Nb 0.08~0.12%, Al 0.05~0.10%, C ≤0.02%, Si ≤0.65%, Mn ≤0.8%, P ≤0.02%, S ≤0.01%, with the remainder being Fe and unavoidable impurities.

[0010] To further optimize the technical solution, the vacuum degree of vacuum melting in step S2 is 5×10⁻⁶. 0 ~5×10 -2 Pa, during casting, the ingot cooling rate is 15~25℃ / s.

[0011] To further optimize the technical solution, electromagnetic stirring is performed during the smelting process in step S2, with a stirring rate of 30~50 r / min.

[0012] To further optimize the technical solution, the remelting process in step S3 is entirely purged with argon, with an argon flow rate of 3-6 m³ / h. 3 / min.

[0013] To further optimize the technical solution, the remelting process in step S3 adopts a ternary slag system. The mass percentage of each component in the ternary slag system is: CaF2 60±5%, Al2O3 20±5%, CaO 20±5%, and the amount of ternary slag system added is 3wt% of the electrode.

[0014] To further optimize the technical solution, in step S5, the cold drawing process adopts multi-pass drawing, with a deformation amount of 8~12% per pass, and stress-relief annealing at 300~350℃ for 30~60 minutes is performed between passes.

[0015] Further optimize the technical solution. In step S7, the first stage of aging is as follows: heat the cold-deformed bar to 420~450℃, hold it for 2~3 hours, and then cool it in the furnace to 280~320℃; the second stage of aging is as follows: hold it at 280~320℃ for 4~6 hours, and then air cool it to room temperature.

[0016] Due to the adoption of the above technical solutions, the technical progress achieved by this invention is as follows.

[0017] This invention provides a method for preparing precipitation-hardening stainless steel cold-drawn material for high-strength fasteners. The method involves controlling the alloy composition ratio, particularly the precise control of the Cr and Mo element ratios, to ensure the material exhibits excellent corrosion resistance in atmospheric, freshwater, and marine environments. By combining vacuum melting, electroslag remelting, hot working, cold deformation strengthening, solution treatment, and graded aging treatment, the method ensures sufficient and uniform precipitation of the Ni-Cu strengthening phase. Hot working breaks up coarse grains in the as-cast microstructure, overcomes porosity defects, and further refines the grains. This method solves the technical problems of existing precipitation-hardening stainless steels used in fasteners, where high strength and high toughness are difficult to achieve simultaneously, and corrosion resistance is insufficient.

[0018] The stainless steel material prepared by this invention has a tensile strength ≥1420MPa, yield strength ≥1280MPa, elongation after fracture ≥12.5%, and Brinell hardness ≥430HB. It also possesses excellent resistance to atmospheric and media corrosion, making it suitable for the stringent requirements of high-strength fasteners in aerospace, high-end equipment, and marine engineering fields. The process of this invention has the advantages of high stability, high repeatability, and ease of industrial-scale mass production. Attached Figure Description

[0019] Figure 1 This is a process flow diagram of the present invention; Figure 2 This is a metallographic diagram of Example 1 in this invention; Figure 3 This is a metallographic diagram of Example 2 in this invention; Figure 4 This is a metallographic diagram of Example 3 in this invention. Detailed Implementation

[0020] A method for preparing precipitation-hardening stainless steel cold-drawn material for high-strength fasteners, combined with Figures 1 to 4 As shown, the specific steps include: S1. Alloy Batching: The raw materials are selected from industrial pure iron, ferrochrome, nickel plates, ferromolybdenum, electrolytic copper, ferrotitanium, ferroniobium and aluminum ingots with a purity of ≥99.9%. The content of harmful impurities such as P and S is strictly controlled to ensure that the batching accuracy error is ≤±0.05%. The raw materials are accurately batched according to the following composition of stainless steel cold-drawn material by mass percentage.

[0021] The alloy composition of cold-drawn stainless steel is as follows: Cr 15.0~17.5%, Ni 4.5~6.5%, Mo 2.0~3.0%, Cu 1.5~2.5%, Ti 0.15~0.35%, Nb 0.05~0.15%, Al 0.05~0.15%, C ≤0.05%, Si ≤0.8%, Mn ≤1.0%, P ≤0.03%, S ≤0.02%, with the remainder being Fe and unavoidable impurities.

[0022] S2, Vacuum Melting: Add the ingredients from step S1 into the vacuum induction furnace, close the furnace door, and evacuate the furnace to a vacuum level of 5×10⁻⁶. 0 ~5×10 -2 Pa is used to prevent the oxidation and burn-off of alloying elements during the smelting process; the temperature is raised to 1520~1580℃ to completely melt the raw materials, and held for 30~60 minutes. During the smelting, electromagnetic stirring is performed at a stirring rate of 30~50 r / min to eliminate component segregation; then the melt is poured into a mold at 1480~1520℃ to form the electrode. During casting, the cooling rate of the ingot is controlled at 15~25℃ / s to obtain the electrode.

[0023] S3. Electroslag Remelting: The electrode obtained in step S2 is electroslag remelted at a melting rate of 3.5–4.1 kg / min. The entire remelting process is purged with argon at a flow rate of 3–6 m³ / min. 3 / min; The remelting process uses a ternary slag system, and the mass percentage of each component in the ternary slag system is: CaF2 60±5%, Al2O3 20±5%, CaO 20±5%. The amount of ternary slag system added is 3wt% of the electrode; after casting, an electroslag ingot is obtained.

[0024] S4. Hot working treatment: Heat the electroslag ingot obtained in step S3 to 1100~1150℃ and hold for 2~3 hours to ensure uniform internal temperature of the ingot. Then, perform hot forging with a forging deformation of 60~75% to break up coarse grains and loose defects in the as-cast structure. After forging, immediately air cool to room temperature to avoid carbide precipitation. Then, heat the forging to 1050~1100℃ and hold for 1~2 hours before hot rolling with a rolling deformation of 50%~65% to further refine the grains and make the structure dense. After rolling, air cool to room temperature to obtain bar stock.

[0025] S5. Cold Deformation Strengthening: The hot-rolled bar from step S4 undergoes multi-pass cold drawing, with a deformation of 8-12% per pass and a drawing speed controlled at 5-10 m / min. Stress-relief annealing at 300-350℃ for 30-60 minutes is performed between passes to eliminate processing stress and prevent material cracking. Cold deformation generates numerous dislocations in the austenite matrix, providing more nucleation sites for the precipitation of strengthening phases during subsequent aging treatment. The total cold deformation is 30%-45%, yielding the bar. Graphite lubrication is used during the drawing process to reduce frictional damage.

[0026] S6. Solution treatment: Place the bar obtained in step S5 in a heat treatment furnace and hold it at 1020~1060℃ for 1.5~2.5h to allow the alloying elements to fully dissolve into the austenite matrix; then rapidly cool it to room temperature with water at a cooling rate ≥80℃ / min to suppress the precipitation of carbides and other precipitates during the cooling process and obtain a supersaturated austenite structure.

[0027] S7. Graded aging treatment: After cold deformation, the bar is subjected to first-stage aging and second-stage aging, straightened and machined to obtain stainless steel cold-drawn material.

[0028] The first stage of aging involves heating the cold-deformed bar to 420-450℃ and holding it for 2-3 hours to promote the rapid diffusion of elements such as Ni and Cu and the formation of fine pre-precipitated phases. Then, the bar is cooled in the furnace to 280-320℃ to prevent the pre-precipitated phases from growing. The second stage of aging involves holding the bar at 280-320℃ for 4-6 hours to allow the pre-precipitated phases to grow fully and distribute evenly, forming stable Ni-Cu strengthening phases. At the same time, the dislocations interact with the strengthening phases, significantly improving the material strength. Finally, the bar is air-cooled to room temperature to avoid stress residue caused by excessively rapid cooling.

[0029] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. Example 1:

[0030] S1. Alloy Ingredients: The raw materials are selected from industrial pure iron, ferrochrome, nickel plates, ferromolybdenum, electrolytic copper, ferrotitanium, ferroniobium and aluminum ingots with a purity of ≥99.9%, and are precisely proportioned according to the following composition of stainless steel cold-drawn materials by mass percentage.

[0031] The alloy composition of cold-drawn stainless steel is as follows: Cr 15.5%, Ni 4.8%, Mo 2.2%, Cu 1.8%, Ti 0.20%, Nb 0.08%, Al 0.08%, C 0.04%, Si 0.5%, Mn 0.7%, P 0.025%, S 0.015%, with the remainder being Fe.

[0032] S2, Vacuum Melting: Add the ingredients from step S1 into the vacuum induction furnace, close the furnace door, and evacuate the furnace to a vacuum level of 3×10⁻⁶. -1 Pa; heat to 1550℃ to completely melt the raw material, and hold at that temperature for 45 min. During the melting process, electromagnetic stirring is performed at a stirring rate of 40 r / min to eliminate component segregation; then the melt is poured into a mold at 1500℃ to form the electrode. During casting, the ingot cooling rate is controlled at 20℃ / s to obtain the electrode.

[0033] S3. Electroslag Remelting: The electrode obtained in step S2 is electroslag remelted at a melting rate of 3.7 kg / min. The entire remelting process is purged with argon gas at a flow rate of 3.8 m³ / min. 3 / min; The remelting process uses a ternary slag system, and the mass percentage of each component in the ternary slag system is: CaF2 57%, Al2O3 23%, CaO 20%, and the amount of ternary slag system added is 3wt% of the electrode; after casting, an electroslag ingot is obtained.

[0034] S4. Hot working treatment: The electroslag ingot obtained in step S3 is heated to 1120℃ and held for 2.5h. Then it is hot forged and the forging deformation is 70%. After forging, it is immediately air-cooled to room temperature. Then the forging is heated to 1080℃ and held for 1.5h. Then it is hot-rolled and the rolling deformation is 60% to further refine the grains and make the structure dense. After rolling, it is air-cooled to room temperature to obtain the bar.

[0035] S5. Cold Deformation Strengthening: The bar stock after hot rolling in step S4 is subjected to multi-pass cold drawing, with a deformation amount of 10% per pass and a drawing speed controlled at 8 m / min; stress-relief annealing is performed at 320℃ for 45 min between passes. The total cold deformation amount is 40%, and the bar stock is obtained; graphite lubrication is used during the drawing process to reduce friction damage.

[0036] S6. Solution treatment: Place the bar obtained in step S5 in a heat treatment furnace and keep it at 1040℃ for 2 hours, then rapidly cool it to room temperature with water at a cooling rate of 90℃ / min.

[0037] S7. Graded Aging Treatment: The cold-deformed bars undergo first-stage aging and second-stage aging, followed by straightening and finishing to obtain cold-drawn stainless steel. The first-stage aging involves heating the cold-deformed bars to 430℃ and holding them at that temperature for 2.5 hours, then furnace cooling to 300℃. The second-stage aging involves holding the bars at 300℃ for 5 hours, followed by air cooling to room temperature. Example 2:

[0038] S1. Alloy Ingredients: The raw materials are selected from industrial pure iron, ferrochrome, nickel plates, ferromolybdenum, electrolytic copper, ferrotitanium, ferroniobium and aluminum ingots with a purity of ≥99.9%, and are precisely proportioned according to the following composition of stainless steel cold-drawn materials by mass percentage.

[0039] The alloy composition of cold-drawn stainless steel is as follows: Cr 15%, Ni 4.5%, Mo 3.0%, Cu 1.5%, Ti 0.15%, Nb 0.15%, Al 0.05%, C 0.05%, Si 0.1%, Mn 0.2%, P 0.005%, S 0.02%, with the remainder being Fe.

[0040] S2, Vacuum Melting: Add the ingredients from step S1 into the vacuum induction furnace, close the furnace door, and evacuate the furnace to a vacuum level of 5×10⁻⁶. 0 Pa; heat to 1520℃ to completely melt the raw material, and hold for 30 min. During the melting process, electromagnetic stirring is performed at a stirring rate of 30 r / min to eliminate component segregation; then the melt is poured into a mold at 1480℃ to form the electrode. During casting, the ingot cooling rate is controlled at 15℃ / s to obtain the electrode.

[0041] S3. Electroslag Remelting: The electrode obtained in step S2 is electroslag remelted at a melting rate of 4.1 kg / min. The entire remelting process is purged with argon at a flow rate of 3 m³ / min. 3 / min; The remelting process uses a ternary slag system, and the mass percentage of each component in the ternary slag system is: CaF2 60%, Al2O3 25%, CaO 15%, and the amount of ternary slag system added is 3wt% of the electrode; after casting, an electroslag ingot is obtained.

[0042] S4. Hot working treatment: The electroslag ingot obtained in step S3 is heated to 1100℃ and held for 2 hours. Then it is hot forged and the forging deformation is 60%. After forging, it is immediately air-cooled to room temperature. Then the forging is heated to 1050℃ and held for 1 hour before hot rolling. The rolling deformation is 50% to further refine the grains and make the structure dense. After rolling, it is air-cooled to room temperature to obtain the bar.

[0043] S5. Cold Deformation Strengthening: The bar stock after hot rolling in step S4 is subjected to multi-pass cold drawing, with a deformation amount of 8% per pass and a drawing speed of 5 m / min. Stress-relief annealing is performed at 300℃ for 30 min between passes. The total cold deformation amount is 30%, and the bar stock is obtained. Graphite lubrication is used during the drawing process to reduce friction damage.

[0044] S6. Solution treatment: Place the bar obtained in step S5 in a heat treatment furnace and hold it at 1020℃ for 1.5 minutes, then rapidly cool it to room temperature with water at a cooling rate of 80℃ / min.

[0045] S7. Graded Aging Treatment: The cold-deformed bars undergo first-stage aging and second-stage aging, followed by straightening and finishing to obtain cold-drawn stainless steel. The first-stage aging involves heating the cold-deformed bars to 420℃ and holding them at that temperature for 2 hours, then furnace cooling to 280℃. The second-stage aging involves holding the bars at 280℃ for 4 hours, followed by air cooling to room temperature. Example 3:

[0046] S1. Alloy Ingredients: The raw materials are selected from industrial pure iron, ferrochrome, nickel plates, ferromolybdenum, electrolytic copper, ferrotitanium, ferroniobium and aluminum ingots with a purity of ≥99.9%, and are precisely proportioned according to the following composition of stainless steel cold-drawn materials by mass percentage.

[0047] The alloy composition of cold-drawn stainless steel is as follows: Cr 17.5%, Ni 6.5%, Mo 2.0%, Cu 2.5%, Ti 0.35%, Nb 0.05%, Al 0.15%, C 0.01%, Si 0.8%, Mn 0.1%, P 0.03%, S 0.01%, with the remainder being Fe.

[0048] S2, Vacuum Melting: Add the ingredients from step S1 into the vacuum induction furnace, close the furnace door, and evacuate the furnace to a vacuum level of 5×10⁻⁶. -2 Pa; heat to 1580℃ to completely melt the raw material, and hold at that temperature for 60 min. During the melting process, electromagnetic stirring is performed at a stirring rate of 50 r / min to eliminate component segregation; then the melt is poured into a mold at 1520℃ to form the electrode. During casting, the ingot cooling rate is controlled at 25℃ / s to obtain the electrode.

[0049] S3. Electroslag Remelting: The electrode obtained in step S2 is electroslag remelted at a melting rate of 3.5 kg / min. The entire remelting process is purged with argon at a flow rate of 6 m³ / min. 3 / min; The remelting process uses a ternary slag system, and the mass percentage of each component in the ternary slag system is: CaF2 63%, Al2O3 15%, CaO 22%, and the amount of ternary slag system added is 3wt% of the electrode; after casting, an electroslag ingot is obtained.

[0050] S4. Hot working treatment: The electroslag ingot obtained in step S3 is heated to 1150℃ and held for 3 hours. Then it is hot forged and the forging deformation is 75%. After forging, it is immediately air-cooled to room temperature. Then the forging is heated to 1100℃ and held for 2 hours. Then it is hot-rolled and the rolling deformation is 65% to further refine the grains and make the structure dense. After rolling, it is air-cooled to room temperature to obtain the bar.

[0051] S5. Cold Deformation Strengthening: The bar stock after hot rolling in step S4 is subjected to multi-pass cold drawing, with a deformation of 12% per pass and a drawing speed of 10 m / min. Stress-relief annealing is performed at 350℃ for 60 min between passes. The total cold deformation is 45%, resulting in the bar stock. Graphite lubrication is used during the drawing process to reduce friction damage.

[0052] S6. Solution treatment: Place the bar obtained in step S5 in a heat treatment furnace and keep it at 1060℃ for 2.5h, then rapidly cool it to room temperature with water at a cooling rate of 90℃ / min.

[0053] S7. Graded Aging Treatment: The cold-deformed bars undergo first-stage aging and second-stage aging, followed by straightening and finishing to obtain cold-drawn stainless steel. The first-stage aging involves heating the cold-deformed bars to 450℃ and holding them at that temperature for 3 hours, then furnace cooling to 320℃. The second-stage aging involves holding the bars at 320℃ for 6 hours, followed by air cooling to room temperature. Comparative Example 1:

[0054] Stainless steel with the following composition by mass percentage: C 0.05, Si 0.40, Mn 0.50, P 0.0043, S 0.0031, Cr 14.8, Mo 0.07, Ni 5.05, Cu 2.01, Ti 0.18 was heated to 1000℃ in a furnace, held at that temperature for 1.5h, and then air-cooled to room temperature. It was then subjected to an adjustment treatment at 580℃ for 1h, followed by air cooling to room temperature. Finally, after the adjustment treatment, it was subjected to an aging treatment at 550℃ for 0.5h, and then air-cooled to room temperature. Comparative Example 2:

[0055] Stainless steel with the following composition by mass percentage: C 0.05, Si 0.40, Mn 0.50, P 0.0043, S 0.0031, Cr 14.8, Mo 0.07, Ni 5.05, Cu 2.01, Ti 0.18 was heated to 1000℃ in a furnace, held at that temperature for 1.5h, and then air-cooled to room temperature. It was then subjected to an adjustment treatment at 580℃ for 1h, followed by air cooling to room temperature. Finally, after the adjustment treatment, it was subjected to an aging treatment at 600℃ for 0.5h, and then air-cooled to room temperature.

[0056] The stainless steel cold-drawn materials obtained in Examples 1-3 and Comparative Examples 1-2 were tested for tensile strength, yield strength, elongation after fracture, and Brinell hardness, respectively. The test results are shown in the table below: Example 1 1480 1320 14 445 Example 2 1420 1280 13 430 Example 3 1530 1350 12.5 455 Comparative Example 1 1035 989 10.5 420 Comparative Example 2 1032 980 11 425 In summary, this invention controls the alloy composition ratio, especially the precise control of the Cr and Mo element ratio, enabling cold-drawn stainless steel to exhibit excellent corrosion resistance in atmospheric, freshwater, and marine environments. By combining vacuum melting, electroslag remelting, hot working, cold deformation strengthening, solution treatment, and graded aging treatment in a synergistic process, the Ni-Cu strengthening phase is fully precipitated and evenly distributed. Furthermore, hot working breaks up coarse grains in the as-cast microstructure and overcomes porosity defects, further refining the grain size, as shown in the attached figure. Figure 2-4 As shown, stainless steel materials have a tensile strength ≥1420MPa, yield strength ≥1280MPa, elongation after fracture ≥12.5%, and Brinell hardness ≥430HB. They also have excellent resistance to atmospheric corrosion and media corrosion, which is significantly superior to existing technologies.

Claims

1. A method for preparing precipitation-hardening stainless steel cold-drawn material for high-strength fasteners, characterized in that, Specifically, the following steps are included: S1. Alloy Batching: The raw materials are selected from industrial pure iron, ferrochrome, nickel plates, ferromolybdenum, electrolytic copper, ferrotitanium, ferroniobium, and aluminum ingots with a purity ≥99.9%, and are precisely batched according to the mass percentage of the stainless steel cold-drawn material composition; the alloy composition of the stainless steel cold-drawn material is as follows: Cr 15.0~17.5%, Ni 4.5~6.5%, Mo 2.0~3.0%, Cu 1.5~2.5%, Ti 0.15~0.35%, Nb 0.05~0.15%, Al 0.05~0.15%, C ≤0.05%, Si ≤0.8%, Mn ≤1.0%, P ≤0.03%, S ≤0.02%, with the remainder being Fe and unavoidable impurities; S2, Vacuum melting: The ingredients from step S1 are put into a vacuum induction furnace and melted at 1520~1580℃ for 30~60 minutes. Then, the mixture is cast at 1480~1520℃ to obtain the electrode. S3. Electroslag remelting: The electrode obtained in step S2 is electroslag remelted at a melting rate of 3.5 to 4.1 kg / min and then cast to obtain an electroslag ingot. S4. Hot working treatment: The electroslag ingot obtained in step S3 is heated to 1100~1150℃ and held for 2~3 hours, and then hot forging is performed. The forging deformation is 60~75%. After forging, it is immediately air-cooled to room temperature. Then the forging is heated to 1050~1100℃ and held for 1~2 hours, and then hot-rolled. The rolling deformation is 50%~65%. After rolling, it is air-cooled to room temperature to obtain a bar. S5. Cold deformation strengthening: The bar after hot rolling in step S4 is cold drawn with a cold deformation of 30% to 45% to obtain the bar; graphite lubrication is used during the drawing process and the drawing speed is controlled at 5 to 10 m / min. S6. Solution treatment: Place the bar obtained in step S5 in a heat treatment furnace and keep it at 1020~1060℃ for 1.5~2.5h, then water cool it to room temperature at a cooling rate ≥80℃ / min. S7. Graded aging treatment: After cold deformation, the bar is subjected to first-stage aging and second-stage aging, straightened and machined to obtain stainless steel cold-drawn material.

2. The method for preparing a precipitation-hardening stainless steel cold-drawn material for high-strength fasteners according to claim 1, characterized in that: The alloy composition of the cold-drawn stainless steel in step S1 is as follows: Cr 16.0~17.5%, Ni 5.0~6.5%, Mo 2.4~2.7%, Cu 1.9~2.3%, Ti 0.16~0.32%, Nb 0.08~0.12%, Al 0.05~0.10%, C ≤0.02%, Si≤0.65%, Mn ≤0.8%, P ≤0.02%, S ≤0.01%, with the remainder being Fe and unavoidable impurities.

3. The method for preparing a precipitation-hardening stainless steel cold-drawn material for high-strength fasteners according to claim 2, characterized in that: The vacuum degree of vacuum melting in step S2 is 5×10⁻⁶. 0 ~5×10 -2 Pa, during casting, the ingot cooling rate is 15~25℃ / s.

4. The method for preparing a precipitation-hardening stainless steel cold-drawn material for high-strength fasteners according to claim 3, characterized in that: In step S2, electromagnetic stirring is performed during the smelting process at a stirring rate of 30-50 r / min.

5. The method for preparing a precipitation-hardening stainless steel cold-drawn material for high-strength fasteners according to claim 1, characterized in that: In step S3, the remelting process is entirely purged with argon gas, with an argon flow rate of 3-6 m³ / h. 3 / min.

6. The method for preparing a precipitation-hardening stainless steel cold-drawn material for high-strength fasteners according to claim 1, characterized in that, The remelting process in step S3 uses a ternary slag system. The mass percentage of each component in the ternary slag system is: CaF2 60±5%, Al2O3 20±5%, CaO 20±5%. The amount of ternary slag system added is 3wt% of the electrode.

7. The method for preparing a precipitation-hardening stainless steel cold-drawn material for high-strength fasteners according to claim 1, characterized in that: In step S5, the cold drawing process adopts multi-pass drawing, with a deformation amount of 8~12% per pass, and stress-relieving annealing at 300~350℃ for 30~60 minutes between passes.

8. The method for preparing a precipitation-hardening stainless steel cold-drawn material for high-strength fasteners according to claim 1, characterized in that, The first stage of aging in step S7 is as follows: the cold-deformed bar is heated to 420~450℃, held for 2~3 hours, and then cooled in the furnace to 280~320℃; the second stage of aging is as follows: the bar is held at 280~320℃ for 4~6 hours, and then air-cooled to room temperature.

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