A 1900mpa-grade corrosion-resistant ultrahigh-strength stainless steel and a method for preparing the same

Abstract

The application relates to the technical field of stainless steel, and particularly discloses a 1900MPa-grade corrosion-resistant ultrahigh-strength stainless steel and a preparation method thereof.The stainless steel disclosed by the application is composed of the following elements in percentage by weight: C: 0.1-0.16%, Cr: 9.0-11.0%, Ni: 3.5-4.5%, Mo: 4.0-5.5%, Co: 8.0-10.0%, W: 0.5-0.8%, Cu: 0.5-1.0%, Nb<=0.05%, N<=0.0025%, O<=0.01%, and the balance of Fe and inevitable impurities.The alloy design idea of multiphase intermetallic compound composite strengthening is adopted, so that the stainless steel not only has ultrahigh strength, but also has good plasticity and toughness matching, and meanwhile, the salt mist corrosion resistance is excellent.

Description

Technical Field

[0001] This application relates to the technical field of stainless steel, specifically to a 1900MPa grade corrosion-resistant ultra-high strength stainless steel and its preparation method. Background Technology

[0002] Ultra-high strength stainless steel combines high strength, good toughness, excellent fatigue resistance, and corrosion resistance, making it one of the preferred materials for main load-bearing components in high-tech fields such as marine, aviation, aerospace, and energy. To meet the demands of lightweight structures, further improvements in its strength and toughness are needed.

[0003] High-strength stainless steels such as PH13-8Mo, 15-5PH, and 17-4PH, while possessing good corrosion resistance, have relatively low strength due to their single-phase intermetallic compound strengthening process. Currently, typical ultra-high-strength stainless steels with strengths exceeding 1850 MPa include Ferrium S53 from the United States and MLX19 from France. Ferrium S53 steel has a strength rating of 1900 MPa and a fracture toughness of 55 MPa·m. 1 / 2 This steel is carbide-strengthened with a Co content exceeding 12.0 wt.%. While Co can promote the precipitation of Mo-, Ti-, and Ni-rich second phases during aging, stabilize the dislocation structure in the martensitic matrix, and achieve a high dislocation density, providing more nucleation sites for the second phase precipitation, increasing its dispersion and strengthening effect, and giving the steel ultra-high strength, the high Co design increases the raw material cost of the steel itself. Furthermore, the carbon content exceeding 0.2 wt.% leads to a decrease in its corrosion resistance. MLX19 steel, on the other hand, employs a Co-free, ultra-low C alloying design, using Ni3Ti and NiAl phase composite strengthening. Although this reduces raw material costs, its strength level is 1850 MPa, and its fracture toughness (KIC) is only 45 MPa·m. 1 / 2 .

[0004] Therefore, there is a need for a new type of ultra-high strength stainless steel that balances strength and toughness while reducing raw material costs. Summary of the Invention

[0005] To address the aforementioned technical problems, this application provides a 1900MPa grade corrosion-resistant ultra-high strength stainless steel and its preparation method.

[0006] This application provides a 1900MPa grade corrosion-resistant ultra-high strength stainless steel. The elemental composition of the corrosion-resistant ultra-high strength stainless steel, by weight percentage, is: C: 0.1–0.16%, Cr: 9.0–11.0%, Ni: 3.5–4.5%, Mo: 4.0–5.5%, Co: 8.0–10.0%, W: 0.5–0.8%, Cu: 0.5–1.0%, Nb≤0.05%, N≤0.0025%, O≤0.01%, with the balance being Fe and unavoidable impurities.

[0007] The basis for using the above-mentioned components in this application is as follows:

[0008] Carbon: C can produce age hardening and solid solution hardening to improve the strength of steel, but the content of C should not be too high. Too high C content will reduce the toughness and corrosion resistance of steel. At the same time, the increase of carbon content will also promote the formation of twinned martensite. Therefore, the present invention controls the carbon content to 0.1 to 0.16 wt% to ensure that the steel has a high level of strength and toughness.

[0009] Chromium (Cr): Cr can form a passivation film, playing a decisive role in the corrosion resistance of materials. However, excessive Cr content can lead to the formation of ferrite in the matrix, resulting in reduced pitting corrosion resistance and strength. Furthermore, Cr can work with other elements to affect the microstructure and properties of steel. The ratio of Cr to Ni content determines the microstructure and type of stainless steel at room temperature. The Cr and Ni contents must be maintained within an appropriate range to achieve the best balance of strength and toughness; therefore, the Cr content is controlled between 9.0 and 11.0 wt%.

[0010] Nickel: Ni is an important toughening element in the stainless steel of this application. It can improve the resistance of the martensitic matrix to cleavage fracture, lower the plastic-brittle transition temperature, and ensure that the steel has sufficient toughness. In addition, it can also improve the passivation tendency of stainless steel and improve the atmospheric corrosion resistance of martensitic stainless steel. However, its content in the steel cannot be too high. If the nickel content is too high, it will lead to excessive retained austenite in the room temperature microstructure and a decrease in yield strength. Therefore, its content is controlled at 3.5-4.5 wt%.

[0011] Molybdenum (Mo) primarily enhances the secondary hardening effect, thereby increasing the strength of the steel without reducing its toughness. The addition of Mo forms fine, topologically close-packed hexagonal Fe₂Mo type Laves phases, further enhancing the secondary hardening effect. The addition of Mo can improve the crack propagation resistance of the steel, even under seawater conditions, in components with large cross-sectional areas, and at weld joints that have not undergone sufficient heat treatment, exhibiting high crack propagation resistance. In this invention, the Mo content is controlled at 4.0–5.5 wt%.

[0012] Cobalt: Co can induce solid solution strengthening in steel and promote secondary hardening reactions. Adding cobalt can inhibit and delay the recovery of martensitic dislocation substructures, maintaining a high dislocation density in martensite laths, thus providing more nucleation sites for subsequent precipitation of precipitated phases. The combined addition of Mo and Co promotes the precipitation of the Laves phase, enhancing age hardening. The amount of cobalt added to steel should not be too high, otherwise it will increase the cost of steel; however, it should not be too low either, otherwise ferrite will form, leading to a decrease in the strength of the steel. When the cobalt content is in the range of 8.0-10.0 wt%, the mechanical properties of the steel are better.

[0013] Tungsten: W is a ferrite-forming element and a strong carbide-forming element. In steel, tungsten partially forms a solid solution and mostly forms special carbides. Tungsten plays a similar role to molybdenum, primarily increasing the tempering stability and red hardness of steel. Another important function is to purify grain boundaries, thereby improving grain boundary bonding and enhancing the stress corrosion resistance of the steel. The tungsten content should not be too high, otherwise it will lead to an increase in the full solid solution temperature of high-temperature carbides. An increased solid solution temperature leads to accelerated grain growth and reduced toughness. Therefore, in this invention, the tungsten content is 0.5–0.8 wt%.

[0014] Copper: Cu is the main strengthening element in steel. During aging, Cu-rich phases can be formed to improve the strength of steel. At the same time, Cu can promote the formation of reverse austenite, improving the toughness and plasticity of steel. In this application, the Cu content is controlled at 0.5 to 1.0 wt%.

[0015] The purpose and advantages of the above-mentioned technical solution provided in this application are, firstly, to ensure good corrosion resistance, the C content in the steel is controlled at 0.1–0.16 wt.%, the Cr content is controlled at 9.0–11.0 wt.%, and at the same time, to avoid the decrease in strength due to excessive Ni content leading to excessive reverse austenite content, the Ni content is controlled at 3.5–4.5 wt.%; secondly, to ensure that the steel maintains ultra-high strength while reducing raw material costs, Mo: 4.0–5.5%, Co: 8.0–10.0%, and Cu: 0.5–1.0% are added. To achieve the goal of composite strengthening of the Laves phase, α phase, and Cu-rich phase, the addition of too few of these elements will result in insufficient strength, while the addition of too many will cause a significant decrease in toughness. Third, to ensure the high toughness of the steel, appropriate amounts of Ni and Cu should be added. Too many Ni and Cu will cause a decrease in yield strength, while too few will affect the toughness of the steel. Fourth, good toughness and corrosion resistance require strict control of the content of impurities in the steel, such as Si≤0.05%, Mn≤0.05%, S≤0.003%, P≤0.005%, N≤0.0025%, O≤0.01%, and the five harmful elements.

[0016] Preferably, in the 1900MPa grade corrosion-resistant ultra-high strength stainless steel, the Cr to Ni content ratio is 2.4 to 2.8:1.

[0017] Preferably, the elemental composition of the corrosion-resistant ultra-high strength stainless steel, by weight percentage, is: C: 0.10-0.13%, Cr: 9.5-10.5%, Ni: 3.5-5.0%, Mo: 4.5-5.5%, Co: 8.5-10.5%, W: 0.5-0.6%, Cu: 0.6-1.0%, Nb≤0.05%, N≤0.0025%, O≤0.01%, with the balance being Fe and unavoidable impurities.

[0018] Furthermore, the elemental composition of the corrosion-resistant ultra-high strength stainless steel, by weight percentage, is as follows: C: 0.10–0.13%, Cr: 9.5–10.5%, Ni: 3.5–4.5%, Mo: 4.5–5.5%, Co: 9.0–10.0%, W: 0.5–0.6%, Cu: 0.6–0.8%, Nb≤0.05%, N≤0.0025%, O≤0.01%, with the balance being Fe and unavoidable impurities.

[0019] In one specific embodiment, the elemental composition of the corrosion-resistant ultra-high strength stainless steel, by weight percentage, is: C: 0.1%, Cr: 10.10%, Ni: 3.82%, Mo: 5.12%, Co: 9.52%, W: 0.55%, Cu: 0.75%, Nb: 0.01%, N: 0.0025%, O: 0.0025%, with the remainder being Fe and unavoidable impurity elements.

[0020] Experimental analysis shows that by controlling the composition of each element in stainless steel within the above-mentioned range, this application can further improve the tensile strength and corrosion resistance of stainless steel.

[0021] Preferably, the elemental composition of the corrosion-resistant ultra-high strength stainless steel, by weight percentage, is: C: 0.13-0.16%, Cr: 9.0-10.0%, Ni: 3.5-4.5%, Mo: 4.0-5.0%, Co: 8.0-10.0%, W: 0.5-0.8%, Cu: 0.8-1.0%, Nb≤0.05%, N≤0.0025%, O≤0.01%, with the balance being Fe and unavoidable impurities.

[0022] Furthermore, the elemental composition of the corrosion-resistant ultra-high strength stainless steel, by weight percentage, is as follows: C: 0.13–0.16%, Cr: 9.0–9.4%, Ni: 3.5–4.5%, Mo: 4.0–4.5%, Co: 9.0–10.0%, W: 0.5–0.8%, Cu: 0.9–1.0%, Nb≤0.05%, N≤0.0025%, O≤0.01%, with the balance being Fe and unavoidable impurities.

[0023] In one specific embodiment, the elemental composition of the corrosion-resistant ultra-high strength stainless steel, by weight percentage, is: C: 0.16%, Cr: 9.05%, Ni: 3.90%, Mo: 4.10%, Co: 9.51%, W: 0.55%, Cu: 0.95%, Nb: 0.01%, N: 0.0020%, O: 0.0025%, with the remainder being Fe and unavoidable impurity elements.

[0024] Experimental analysis shows that by controlling the composition of each element in stainless steel within the above-mentioned range, this application can further improve the elongation after fracture, reduction of area, and fracture toughness of stainless steel.

[0025] Secondly, this application provides a method for preparing the aforementioned 1900MPa grade corrosion-resistant ultra-high strength stainless steel, specifically including the following steps in sequence:

[0026] Vacuum induction melting, high-temperature homogenization treatment, forging, preheating treatment, and final heat treatment.

[0027] Preferably, the forging step is as follows: heating the steel ingot in the temperature range of 1050 to 1180°C, holding it for 2 to 5 hours, with an initial forging temperature of ≥950°C and a final forging temperature of ≥750°C.

[0028] Preferably, in the pre-heat treatment step: normalizing temperature 900~1000℃, holding time ≥2h, air cooling to room temperature, high-temperature tempering temperature 680~780℃, holding time ≥10h.

[0029] Preferably, the final heat treatment process consists of the following steps in sequence: solution treatment at 1050–1100°C for 80–100 min, followed by oil cooling to room temperature; cryogenic treatment at ≤-70°C for 2–6 h; aging treatment at 520–540°C for 4–6 h, followed by air cooling.

[0030] As described in the above technical solution, the manufacturing process of the novel ultra-high strength stainless steel of this application is as follows: according to the chemical composition ratio of the steel of this application → vacuum induction melting → high temperature homogenization treatment → forging → pre-heat treatment → final heat treatment. The selection and control principles of the main processes are as follows:

[0031] (1) Forging: Heating is carried out in the temperature range of 1050~1180℃, and the holding time is 2~5h. The initial forging temperature is ≥950℃. Within this temperature range, the steel ingot has a single-phase austenitic structure. The austenitic structure is easy to deform, thus having good thermoplasticity and being easy to process. The final forging temperature is ≥750℃. If the temperature is too low, carbides will precipitate, the plasticity will decrease significantly, and it will easily lead to forging cracks or microcracks. The steel ingot must undergo upsetting and drawing processes to ensure that the transverse and longitudinal properties of the product are close and meet the standards, and to reduce the tendency of anisotropy.

[0032] (2) Preliminary heat treatment: Preliminary heat treatment includes normalizing + high-temperature tempering. Since the forging billet will undergo martensitic phase transformation when cooled to room temperature after forging, martensitic stainless steel is highly sensitive to cracks. In addition, a large amount of residual stress is distributed in the forging bar after forging, which will cause cracking or microcrack initiation. Furthermore, the irregular grains of the forging billet after forging need to be normalized to obtain all equiaxed grains. At the same time, high-temperature tempering can produce a large amount of austenite, thereby reducing the risk of forging billet cracking caused by residual stress. After experimental research, the preliminary heat treatment process is as follows: normalizing temperature 900~1000℃, holding time ≥2h, air cooling to room temperature, high-temperature tempering temperature 680~780℃, holding time ≥10h.

[0033] (3) Final heat treatment

[0034] The final heat treatment process for ultra-high strength stainless steel of the present invention is solution quenching, cryogenic treatment, and aging treatment. The optimal heat treatment regime can obtain the best comprehensive performance. The specific process is as follows: solution treatment temperature 1050~1100℃, holding time 80~100min, oil cooling to room temperature; cryogenic treatment temperature ≤-70℃, holding time 2~6h; aging treatment temperature 520~540℃, holding time 4~6h, air cooling.

[0035] In summary, the technical solution of this application has the following effects:

[0036] The stainless steel provided in this application has a tensile strength greater than 1900 MPa, a yield strength greater than 1650 MPa, and a fracture toughness greater than 60 MPa·m. 1 / 2 The acidic salt spray corrosion rate in a 50 g / L NaCl solution (pH = 7) is less than 0.03 g / m³. 2 Its raw material cost is lower than that of Ferrium S53 steel in the United States. Under the condition of comparable tensile strength, its yield strength and salt spray corrosion resistance are superior to Ferrium S53 steel.

[0037] The main features of the corrosion-resistant ultra-high strength stainless steel provided in this application are the reduction of carbon and cobalt content, which lowers the cost of raw materials, while employing an alloy design that combines Laves phase, α phase, and Cu-rich phase for reinforcement. During the aging process, a large number of dispersed fine second phases precipitate. Figure 1 This ensures the steel possesses an ultra-high strength and a good balance of strength and toughness. At this point, the steel exhibits ultra-high strength (Rm≥1900MPa, Rp...). 0.2 While maintaining a strength of ≥1650MPa, it also greatly ensures the fracture toughness of the steel (≥60MPa·m). 1 / 2 ).

[0038] The technical solution provided in this application reduces the content of carbon (C) and co (Co) elements in the steel. To ensure that the steel has a good strength-toughness ratio, it is reinforced with a three-phase composite of Laver phase, α phase and Cu-rich phase. While maintaining a high strength of 1900 MPa, it also has an excellent toughness ratio. This not only meets the lightweight design requirements of aircraft and reduces the cost of raw materials, but also improves the intrinsic corrosion resistance of the steel by reducing the carbon content. Attached Figure Description

[0039] Figure 1 This is a bright-field transmission electron microscope image of the composite precipitate phase of stainless steel in Example 1.

[0040] Figure 2 This is a dark-field transmission electron microscope image of the composite precipitate phase of stainless steel in Example 1.

[0041] Figure 3 This is a salt spray corrosion morphology image of Ferrium S53 stainless steel.

[0042] Figure 4 This is a salt spray corrosion morphology image of the stainless steel in Example 1. Detailed Implementation

[0043] The present application will be further described in detail below with reference to embodiments, comparative examples and performance test results. These embodiments should not be construed as limiting the scope of protection claimed in this application.

[0044] Example

[0045] Examples 1-3

[0046] Examples 1-3 respectively provide a 1900MPa grade corrosion-resistant ultra-high strength stainless steel and its preparation method.

[0047] The differences between the ultra-high strength stainless steels in Examples 1-3 are as follows: the elemental composition is different, as shown in Table 1.

[0048] The specific preparation methods of the ultra-high strength stainless steel in Examples 1-3 are as follows.

[0049] Vacuum induction melting: The raw materials are batched and then subjected to vacuum induction melting. The vacuum is drawn until the material is completely melted. The composition is measured, oxygen is drawn out, and the molten steel is stirred. The molten steel is then poured into the vacuum atmosphere.

[0050] High-temperature homogenization treatment: Heat the steel ingot to 1200℃ and hold for 20 hours.

[0051] Forging: Before forging, the steel ingot is heated to 1180℃ and held for 3 hours; forging begins at 1180℃ and the final forging temperature is 950℃. After forging, the steel is air-cooled to room temperature.

[0052] Preliminary heat treatment: First, normalize at 1000℃ for 2 hours, then air cool to room temperature. The high-temperature tempering temperature is 680℃, and the holding time is 12 hours.

[0053] Final heat treatment: solution temperature 1080℃, hold for 60 min, oil cool to room temperature, followed by cryogenic treatment at -73℃ for 6 h, aging temperature 520℃, hold for 4 h, and then air cool.

[0054] Figure 1 This is a bright-field transmission electron microscope image of the composite precipitate phase of stainless steel in Example 1. Figure 2 This is a dark-field transmission electron microscope (TEM) image of the composite precipitates in the stainless steel of Example 1. Analysis shows that the precipitates are diffusely distributed in the martensitic matrix, which can significantly improve the strength of the steel while maintaining good toughness.

[0055] Table 1. Amounts of each raw material component in Examples 1-3 and Comparative Examples 1-3

[0056] Comparative Example

[0057] Comparative Examples 1-3

[0058] Comparative Examples 1-3 each provide a stainless steel and a method for its preparation.

[0059] The difference between the above comparative example and Example 1 is that the elemental composition is different, as shown in Table 1.

[0060] All other process parameters in the above comparative examples are the same as those in Example 1.

[0061] Performance testing

[0062] Experimental Example 1

[0063] This experiment investigated the room temperature mechanical properties of stainless steel.

[0064] Tensile strength Rm, yield strength Rp0.2, elongation after fracture A and reduction of area Z: measured by the methods described in GB / T228.

[0065] Fracture toughness KIC: Measured by the method described in GB / T 4161.

[0066] Salt spray corrosion performance: The method described in GJ 150.11A was used for measurement.

[0067] Test results: Table 2 shows the room temperature mechanical properties of common stainless steel varieties in the prior art; Table 3 shows the room temperature mechanical properties of longitudinal parallel stainless steel samples in Examples 1-3 and Comparative Examples 1-3.

[0068] Table 2. Room temperature mechanical properties and strengthening systems of common stainless steel varieties in the prior art.

[0069]

[0070] Table 3. Room temperature mechanical properties of stainless steel in Examples 1-3 and Comparative Examples 1-3

[0071]

[0072]

[0073] By comparing the room temperature mechanical properties of common stainless steel varieties in the prior art, and the stainless steel in Examples 1-3 and Comparative Examples 1-3, it can be seen that the stainless steel obtained by using the technical solution provided in this application has excellent mechanical properties.

[0074] Experimental Example 2

[0075] This test case investigated the salt spray corrosion performance of stainless steel.

[0076] Stainless steel salt spray corrosion rate: The test standard adopted is GJB150.11A-2009; sodium chloride solution concentration: 50g / L, salt spray chamber temperature: 35℃±2℃, pH value is 7.0.

[0077] Figure 3 This image shows the salt spray corrosion morphology of Ferrium S53 stainless steel. It can be seen that Ferrium S53 stainless steel has poor corrosion resistance.

[0078] Figure 4 The image shows the salt spray corrosion morphology of the stainless steel in Example 1. It can be seen that the stainless steel obtained by the technical solution provided in this application has excellent corrosion resistance.

[0079] Test results are shown in Table 4.

[0080] Table 4. Salt spray corrosion rate performance results of stainless steel in Examples 1-3 and Comparative Examples 1-3.

[0081] Example 1 1900MPa 0.021 Example 2 1900MPa 0.025 Example 3 1900MPa 0.029 Comparative Example 1 1400MPa 0.026 Comparative Example 2 1800MPa 0.028 Comparative Example 3 1700MPa 0.038 MLX19 1700MPa 0.005 Ferrium S53 1900MPa 0.045

[0082] By comparing the salt spray corrosion rate performance of common stainless steel varieties in the prior art, and the stainless steel in Examples 1-3 and Comparative Examples 1-3 with those in Table 4, it can be seen that the 1900MPa stainless steel obtained by using the technical solution provided in this application has excellent corrosion resistance.

[0083] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A 1900MPa grade corrosion-resistant ultra-high strength stainless steel, characterized in that, The elemental composition of the corrosion-resistant ultra-high strength stainless steel, by weight percentage, is as follows: C: 0.1~0.16%, Cr: 9.0~11.0%, Ni: 3.5~4.5%, Mo: 4.0~5.5%, Co: 8.0~10.0%, W: 0.5~0.8%, Cu: 0.5~1.0%, Nb≤0.05%, N≤0.0025%, O≤0.01%, with the balance being Fe and unavoidable impurities; the Cr to Ni content ratio is 2.4~2.8:1; the stainless steel achieves three-phase composite strengthening through aging precipitation of Laves phase, α phase and Cu-rich phase; The preparation method of the 1900MPa grade corrosion-resistant ultra-high strength stainless steel includes the following steps: vacuum induction melting, high temperature homogenization treatment, forging, preheating treatment, and final heat treatment. The final heat treatment process consists of the following steps in sequence: solution treatment at 1050~1100℃ for 80~100 min, followed by oil cooling to room temperature; cryogenic treatment at ≤-70℃ for 2~6 h; and aging treatment at 520~540℃ for 4~6 h, followed by air cooling.

2. The 1900MPa grade corrosion-resistant ultra-high strength stainless steel according to claim 1, characterized in that, The elemental composition of the corrosion-resistant ultra-high strength stainless steel, by weight percentage, is as follows: C: 0.10~0.13%, Cr: 9.5~10.5%, Ni: 3.5~5.0%, Mo: 4.5~5.5%, Co: 8.5~10.5%, W: 0.5~0.6%, Cu: 0.6~1.0%, Nb≤0.05%, N≤0.0025%, O≤0.01%, with the balance being Fe and unavoidable impurities.

3. The 1900MPa grade corrosion-resistant ultra-high strength stainless steel according to claim 2, characterized in that, The elemental composition of the corrosion-resistant ultra-high strength stainless steel, by weight percentage, is as follows: C: 0.10~0.13%, Cr: 9.5~10.5%, Ni: 3.5~4.5%, Mo: 4.5~5.5%, Co: 9.0~10.0%, W: 0.5~0.6%, Cu: 0.6~0.8%, Nb≤0.05%, N≤0.0025%, O≤0.01%, with the balance being Fe and unavoidable impurities.

4. The 1900MPa grade corrosion-resistant ultra-high strength stainless steel according to claim 1, characterized in that, The elemental composition of the corrosion-resistant ultra-high strength stainless steel, by weight percentage, is as follows: C: 0.13~0.16%, Cr: 9.0~10.0%, Ni: 3.5~4.5%, Mo: 4.0~5.0%, Co: 8.0~10.0%, W: 0.5~0.8%, Cu: 0.8~1.0%, Nb≤0.05%, N≤0.0025%, O≤0.01%, with the balance being Fe and unavoidable impurities.

5. The 1900MPa grade corrosion-resistant ultra-high strength stainless steel according to claim 4, characterized in that, The elemental composition of the corrosion-resistant ultra-high strength stainless steel, by weight percentage, is as follows: C: 0.13~0.16%, Cr: 9.0~9.4%, Ni: 3.5~4.5%, Mo: 4.0~4.5%, Co: 9.0~10.0%, W: 0.5~0.8%, Cu: 0.9~1.0%, Nb≤0.05%, N≤0.0025%, O≤0.01%, with the balance being Fe and unavoidable impurities.

6. The method for preparing 1900MPa grade corrosion-resistant ultra-high strength stainless steel according to claim 1, characterized in that, The forging steps are as follows: heating the steel ingot in the temperature range of 1050 to 1180°C, holding it for 2 to 5 hours, with an initial forging temperature of ≥950°C and a final forging temperature of ≥750°C.

7. The method for preparing 1900MPa grade corrosion-resistant ultra-high strength stainless steel according to claim 1, characterized in that, In the pre-heat treatment step: normalizing temperature 900~1000℃, holding time ≥2h, air cooling to room temperature, high-temperature tempering temperature 680~780℃, holding time ≥10h.

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