Wide-temperature-range high-strength plastic stainless steel and manufacturing method thereof

Abstract

The present application relates to the field of metal material manufacturing, and provides a wide temperature range high strength and plasticity stainless steel and a manufacturing method thereof, wherein the wide temperature range high strength and plasticity stainless steel has the following element component ranges (mass fraction, %): C: 0.08-0.30, Si: 0.75-2.5, Cr: 13.0-18.0, Ni: 3.0-8.0, Mn: 1.0-3.0, Mo: 0.5-2.5, N: 0.10-0.35, W: 0-1.5, Cu: 0.05-1.5, Co: 0.05-2.0, V: 0.05-0.5, Nb: 0.01-0.1, and the rest is iron and inevitable impurities. The present application inhibits carbide precipitation in the aging process by Si, promotes the distribution of C and N elements in the aging process to stabilize austenite and strengthen austenite, and is combined with cold rolling and low-temperature distribution aging process treatment, so that the stainless steel has the following properties: room temperature tensile strength ≥ 1600 MPa, elongation ≥ 25%; low-temperature tensile strength ≥ 2000 MPa, elongation ≥ 20%; 100 ℃ temperature tensile strength ≥ 1400 MPa, elongation ≥ 10%.

Description

Technical Field

[0001] This invention belongs to the field of metal material manufacturing and aerospace high-performance structural component processing technology, specifically relating to a wide-temperature-range high-strength and ductile stainless steel and its manufacturing and application methods in key structural components of aerospace rockets. Background Technology

[0002] With the rapid development of my country's aerospace industry, the new generation of launch vehicles has placed extremely stringent requirements on structural materials. During service, rockets must withstand extreme temperature ranges and severe mechanical loads: Cryogenic environments: The rocket's liquid oxygen (-183℃) and liquid methane (-161℃) cryogenic propellant tanks require materials that not only possess extremely high tensile strength to reduce the rocket's weight but also excellent ductility and toughness to prevent catastrophic low-stress brittle fracture. Instantaneous high-temperature environments: Aerodynamically heated areas during atmospheric reentry (such as tank shells, rocket skin, instrument compartments), as well as the engine's surrounding structures, face temperature rises of 100℃ and above. Materials must maintain high strength at these temperatures, without creep or severe softening.

[0003] Traditional duplex stainless steel or austenitic stainless steel (such as 304 and 316), while possessing certain toughness and strength at low temperatures, typically struggles to exceed 1600 MPa in room temperature tensile strength while maintaining sufficient ductility. This results in excessively thick structural components, severely limiting the rocket's payload capacity. While martensitic ultra-high-strength steel meets strength requirements, it exhibits severe "low-temperature brittleness" at liquid oxygen / liquid methane temperatures, leading to a precipitous drop in elongation.

[0004] In existing technical literature, patent CN121951405B discloses a high-strength medium-manganese high-nitrogen austenitic stainless steel. Through refining austenite grains and strengthening via carbonitride precipitation, it ensures a grain size grade of 9 or higher, thus improving strength and low-temperature toughness. However, the room temperature tensile strength of this stainless steel still does not reach 1000 MPa.

[0005] The patent with publication number CN122256619A provides a method for preparing stainless steel sheet. The method involves sequentially performing austenitizing heat treatment, room temperature reciprocating torsion deformation, and low temperature tempering on the stainless steel sheet. This method can make the low temperature tensile strength of 304 stainless steel sheet reach 1800MPa, but its room temperature tensile strength is still lower than 1200MPa.

[0006] The patent with publication number WO2023 / 023083A1 provides a high-strength cold-rolled stainless steel. Through the composition design of low carbon, high nitrogen and the introduction of manganese / molybdenum, the austenite is maintained in the annealed state, and then the steel is strengthened and toughened by cold rolling with large deformation to induce deformation martensitic phase transformation. Although the room temperature tensile strength of this stainless steel can be close to 1600MPa, its corresponding elongation is less than 10%.

[0007] Therefore, developing a stainless steel material that can maintain both ultra-high strength and high elongation (high strength-ductility product) at room temperature, cryogenic (low temperature) and high temperature (1000°C) is of great strategic significance for achieving "ultimate lightweighting" of rocket structures and improving launch reliability. Summary of the Invention

[0008] The purpose of this invention is to provide a wide-temperature-range high-strength and ductile stainless steel, primarily used in critical load-bearing and propellant tank structures of aerospace rockets, and its manufacturing method. Through precise chemical composition ratios, combined with cold rolling and specific low-temperature aging treatments, the material achieves a perfect balance of strength and ductility across the entire temperature range during rocket service.

[0009] The solution provided by this invention is as follows: A wide-temperature-range high-strength and ductile stainless steel is provided, wherein the elemental composition and their mass percentage content (wt.%) of the stainless steel are as follows: C: 0.08~0.30, Si: 0.75~2.5, Cr: 13.0~18.0, Ni: 3.0~8.0, Mn: 1.0~3.0, Mo: 0.5~2.5, N: 0.10~0.35, W: 0~1.5, Cu: 0.05~1.5, Co: 0.05~2.0, V: 0.05~0.5, Nb: 0.01~0.1, with the remainder being iron and unavoidable impurities.

[0010] Preferably, the elemental composition and their mass percentage (wt.%) of the stainless steel are as follows: C: 0.10~0.25, Si: 1.0~2.0, Cr: 14.0~17.0, Ni: 4.0~7.0, Mn: 1.0~3.0, Mo: 0.5~2.5, N: 0.10~0.25, W: 0.01~1.0, Cu: 0.05~1.0, Co: 0.05~1.5, V: 0.05~0.3, Nb: 0.01~0.06, with the remainder being iron and unavoidable impurities.

[0011] Furthermore, the mass percentages of Si and Mn added to the stainless steel satisfy the condition: 0.25≤Si / Mn≤2. By controlling the ratio of Si to Mn, the precipitation of carbides during the production process is synergistically suppressed, and the distribution of C and N elements is promoted, thereby improving the stability of austenite and strengthening austenite.

[0012] Furthermore, the microstructure of the stainless steel is martensite and metastable retained austenite; wherein the volume fraction of the metastable retained austenite is 30% to 80%, and the metastable retained austenite is enriched with C and N elements, and the total mass fraction of C+N in the retained austenite is ≥0.3%.

[0013] A method for manufacturing a wide-temperature-range, high-strength, and ductile stainless steel is provided, comprising the following steps: 1) Smelting and casting: Smelting is carried out according to the stated composition ratio, and casting is carried out into steel ingots; 2) Forging: Heat the steel ingot to 1100℃~1200℃, hold for 1~5 hours, and then forge. The initial forging temperature is ≥1100℃ and the final forging temperature is ≥950℃. 3) Hot rolling: The steel ingot is heated to 1050℃~1200℃, held for 1~5h, and then hot rolled in multiple passes to produce hot rolled slab. The initial hot rolling temperature is ≥1100℃, the final rolling temperature is ≥900℃, the total reduction during the hot rolling process is controlled to be ≥50%, and the slab is water-cooled after hot rolling. 4) Cold rolling: The slab is subjected to multiple cold rolling passes, and the total deformation of the cold rolling is controlled at 10%~30% to produce aerospace thin plates with a thickness of 0.5mm~4.0mm; 5) Grading treatment: Heat the cold-rolled sheet to the grading temperature (T). P The carbon and nitrogen atoms are subjected to low-temperature partitioning and aging treatment, and then rapidly cooled to room temperature after partitioning.

[0014] Furthermore, the specific process parameters in step 5) are as follows: The heat treatment temperature T P (°C) satisfies: 200 ≤ T P ≤ 350 - 20×(C + N) + 15×Si 2 + 12×Cr -10×Ni - 10×Mn + 15×Mo + 10×W + 10×Cu + 15×Co + 15×(V + Nb); The heat preservation time t (s) satisfies: t ≥ 5 + 5×H, where H (mm) is the plate thickness.

[0015] Furthermore, during the low-temperature partitioning aging process in step 5), C and N atoms are partitioned from the martensite phase into the retained austenite phase. At the same time, a dispersed carbonitride composite phase of V and Nb with a size of less than 15 nm is precipitated in the martensite matrix to generate precipitation strengthening and pin the grain boundaries.

[0016] Furthermore, the stainless steel exhibits the following excellent wide-temperature-range mechanical properties: at room temperature, tensile strength ≥1600MPa, elongation after fracture ≥25%; at low temperature (-196℃), tensile strength ≥2000MPa, elongation after fracture ≥20%; at high temperature (100℃), tensile strength ≥1400MPa, elongation after fracture ≥10%.

[0017] A wide-temperature-range, high-strength, and high-ductility stainless steel is provided, which is used in the manufacture of key structural components for aerospace launch vehicles.

[0018] A wide-temperature-range high-strength ductile stainless steel is provided. The key structural components of the aerospace launch vehicle specifically include: liquid oxygen tank and liquid methane tank of the launch vehicle; outer skin section of the rocket body that is heated by aerodynamic friction during high-speed flight; stiffening stringers and main load-bearing frames of the interstage section and instrument compartment of the rocket; and high-pressure cryogenic pipelines and load-bearing supports around the liquid rocket engine of the rocket.

[0019] The beneficial effects of this invention are as follows: By precisely controlling the mass fraction range of multiple elements such as C, N, Si, Cr, Ni, Mn, and Mo, and combining this with specific cold rolling deformation and low-temperature aging treatment processes, significant technological advancements have been achieved in the microstructure and wide-temperature-range mechanical properties of stainless steel materials. The beneficial effects are specifically reflected in the following aspects: This invention achieves a synergistic effect of ultra-high strength and ultra-high plasticity at room temperature (strength-plasticity product ≥ 40000 MPa·%): Traditional stainless steel or ultra-high-strength steel typically experiences elongation below 15% when tensile strength exceeds 1500 MPa, making it highly susceptible to early localized necking. This invention utilizes high Si (0.75~2.5%) to effectively suppress carbide precipitation during low-temperature partitioning aging treatment, enriching C and N elements in austenite, stabilizing and strengthening the austenite. This results in a tensile strength ≥ 1600 MPa and an elongation ≥ 25% when the material is stretched at room temperature. The ultra-high room-temperature plasticity allows large and complex components such as thin-walled sections of launch vehicle bodies and ellipsoidal box-shaped bottom segments to be directly cold-spun or deep-drawn on the ground with large deformation, completely eliminating the cumbersome intermediate annealing process of traditional methods and significantly reducing manufacturing residual stress and time costs.

[0020] It possesses excellent resistance to brittle fracture in cryogenic / deep cryogenic environments and a TRIP / TWIP phase transformation strengthening mechanism: In the extreme cryogenic environment of rocket propellant liquid oxygen (-183℃) and liquid methane (-161℃), traditional materials are prone to low-stress brittle fracture. The material of this invention exhibits a further increase in tensile strength to over 2000MPa across the entire cryogenic temperature range, while maintaining an elongation at break of ≥20%. The mechanism lies in the highly stable metastable residual austenite (15%~70%) exhibiting continuous, progressive deformation-induced martensitic transformation and deformation twinning reinforcement under extremely low-temperature loading, providing sustained work hardening. This effectively passivates microcrack tips, ensuring the safety of rocket cryogenic tanks under ignition vibration and overload service conditions.

[0021] It exhibits excellent mild high-temperature thermal stability and resistance to structural instability: During the stage of a rocket's high-speed passage through the atmosphere and the intense aerodynamic friction heating, the instantaneous temperature rise of components can reach 100°C. Traditional aluminum alloys or conventional stainless steel will undergo significant thermal softening and creep at this temperature. The material of this invention can still maintain a tensile strength of ≥1400MPa and an elongation after fracture of ≥10% at 100°C, effectively preventing unstable bending caused by local thermal softening of thin-walled skin and stringer structures, and ensuring precise control of the rocket's flight attitude. Attached Figure Description

[0022] Figure 1 This is a scanning electron microscope (EBSD) image of wide-temperature-range high-strength and ductile stainless steel from Example 1.

[0023] Figure 2 This is the room temperature tensile curve of wide-temperature-range high-strength ductile stainless steel in Example 1. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of protection of this invention.

[0025] This invention provides a wide-temperature-range high-strength and ductile stainless steel, its manufacturing method, and its applications. Unless otherwise stated, the content of each element involved in this invention is expressed as a mass percentage (wt%).

[0026] The wide-temperature-range high-strength and ductile stainless steel provided in this embodiment of the invention comprises the following chemical composition by mass percentage (wt.%): C: 0.08~0.30, Si: 0.75~2.5, Cr: 13.0~18.0, Ni: 3.0~8.0, Mn: 1.0~3.0, Mo: 0.5~2.5, N: 0.10~0.35, W: 0~1.5, Cu: 0.05~1.5, Co: 0.05~2.0, V: 0.05~0.5, Nb: 0.01~0.1, with the remainder being iron and unavoidable impurities.

[0027] As a preferred embodiment, the chemical composition of the stainless steel comprises, by mass percentage (wt.%): C: 0.10~0.25, Si: 1.0~2.0, Cr: 14.0~17.0, Ni: 4.0~7.0, Mn: 1.0~3.0, Mo: 0.5~2.5, N: 0.10~0.25, W: 0.01~1.0, Cu: 0.05~1.0, Co: 0.05~1.5, V: 0.05~0.3, Nb: 0.01~0.06, with the remainder being iron and unavoidable impurities.

[0028] In this embodiment of the invention, the design principles of each chemical component and the mechanism of action of each element in a wide temperature range (covering -196°C to 100°C) are as follows: Carbon (C): An interstitial solid solution strengthening element and a strong austenite stabilizer. In this invention, C not only significantly improves the yield strength and tensile strength of the matrix at room temperature and low temperature, but also enriches itself in the retained austenite during subsequent low-temperature partitioning aging treatment through its partitioning behavior from martensite to retained austenite. This provides crucial stability for the TRIP (deformation-induced martensitic transformation) effect under external forces, thereby ensuring that the material exhibits a room temperature tensile strength exceeding 1600 MPa and a room temperature elongation of over 25%.

[0029] Si (silicon): A non-carbide-forming element. Besides its strong solid solution strengthening effect, Si's core role in this invention lies in effectively suppressing the precipitation of coarse carbides (such as cementite) in the martensitic matrix and grain boundaries during low-temperature partitioning aging. Through this suppression, Si drives C atoms to partition more efficiently into the retained austenite, improving the stability and strength of austenite and preventing intergranular fracture caused by brittle carbides.

[0030] Cr (chromium): a basic ferrite / martensite forming element, and a core element that ensures the high corrosion resistance and oxidation resistance of the stainless steel of this invention in various service environments (especially aerospace multi-medium environments). At the same time, Cr, together with elements such as Ni and Mn, adjusts the martensite transformation temperature (Ms) to a suitable range, laying the microstructure foundation for obtaining the target proportion of metastable residual austenite after controlled rolling and controlled cooling.

[0031] Ni (Ni): A typical austenitic stabilizing element. Ni can significantly enhance the toughness of the matrix in cryogenic environments down to -196°C, lower the brittle transition temperature of materials, and effectively inhibit the initiation and propagation of low-temperature shear cracks. In addition, Ni, when combined with elements such as Cr, can precisely control the work hardening rate and prevent premature local necking of materials under stress.

[0032] Manganese (Mn): An austenite stabilizing element that can partially replace Ni to regulate phase transformation kinetics and reduce material costs. In this invention, the key role of Mn is to form a composite regulation with Si. Si / Mn ratio: The mass percentages of Si and Mn added to the stainless steel must meet a constraint relationship. By strictly controlling the Si / Mn ratio within a specific range of 0.25 to 2, the microscopic thermodynamic interaction between the two can be utilized to synergistically suppress the precipitation of coarse cementite while optimizing the diffusion paths of N and C atoms, thereby maximizing the enrichment of interstitial elements in austenite.

[0033] Nitrogen (N): An extremely strong interstitial solid solution strengthening element. Its solid solution strengthening efficiency is far higher than that of carbon (C), and it does not cause chromium-depleted corrosion in materials. During low-temperature distribution, N also enriches in retained austenite, producing a synergistic effect with carbon (C), significantly improving the hardening ability of metastable austenite during deformation. It is an important factor in maintaining high room temperature strength above 1600 MPa and low-temperature tensile strength above 2000 MPa.

[0034] Mo (molybdenum) and W (tungsten): Both are large atomic radius elements, producing significant solid solution strengthening effects. The introduction of Mo and W can greatly improve the steel's resistance to pitting and crevice corrosion. More importantly, in high-temperature service environments of 100°C, Mo and W can increase lattice distortion energy and slow down dislocation recovery in the matrix, thereby maintaining the material's high-temperature load-bearing capacity under aerodynamic friction heating.

[0035] Cu (copper): A weak austenitic stabilizing element that can improve the work hardening behavior of high-strength steel and enhance the impact toughness of the material. Simultaneously, Cu may form fine clusters during low-temperature partitioning aging, synergistically strengthening the matrix.

[0036] Cobalt (Co) is a solid solution strengthening element. Unlike other austenite-stabilizing elements, Co does not significantly lower the Ms point, providing a large processing window for precise control of the retained austenite volume fraction. Co can also improve the toughness of martensite and enhance the low-temperature toughness of materials.

[0037] Vanadium (V) and niobium (Nb) are strong carbonitride forming elements. In this invention, they are added in trace amounts in a composite manner. During the low-temperature partitioning aging process after cold rolling, V and Nb precipitate in situ a dispersed composite phase with a size of less than 15 nm. This nanoscale second phase produces extremely significant precipitation strengthening, compensating for the matrix strength loss caused by the detachment of C and N from martensite. On the other hand, it strongly pins the martensite lath boundaries and the original austenite grain boundaries, preventing grain growth and achieving fine-grained toughening of the microstructure.

[0038] After the above-mentioned chemical composition optimization and subsequent heat treatment, the microstructure of the stainless steel is martensite and metastable retained austenite. The volume fraction of the metastable retained austenite is stable at 30%~80%; the metastable retained austenite is significantly enriched in C and N elements, and the total mass fraction of C+N in the retained austenite is ≥0.3%.

[0039] This invention also provides a method for manufacturing the above-mentioned wide-temperature-range high-strength and ductile stainless steel, specifically including the following process steps: Step 1) Smelting and casting: Smelt according to the above-designed component ratio and cast into steel ingots.

[0040] Step 2) Forging: Heat the steel ingot to 1100℃~1200℃ and hold for 1~5h to fully homogenize its dendritic structure and alloying elements, and then carry out the forging process to break up the coarse cast grains; wherein, the initial forging temperature is controlled at ≥1100℃ and the final forging temperature is controlled at ≥950℃.

[0041] Step 3) Hot rolling: The forged steel ingot is reheated to 1050℃~1200℃ and held for 1~5 hours. It is then hot rolled in multiple passes to produce a hot-rolled slab. The initial hot rolling temperature is ≥1100℃ and the final hot rolling temperature is ≥900℃. The total reduction during hot rolling is controlled to be ≥50%. The microstructure is reorganized through large deformation. After hot rolling, water cooling is performed immediately to suppress the precipitation of brittle phases.

[0042] Step 4) Cold rolling: The hot-rolled slab is subjected to multiple cold rolling processes. The total deformation of the cold rolling is controlled at 10%~30%. By introducing high-density dislocations of deformation, the microstructure is strengthened and diffusion channels are provided for the next step of distribution aging, resulting in a thin aerospace plate with a final thickness of 0.5mm~4.0mm.

[0043] Step 5) Aging treatment: The cold-rolled sheet is heated to a specific aging temperature (T).P The carbon and nitrogen atoms are subjected to low-temperature partitioning and aging treatment, and then rapidly cooled to room temperature after the partitioning reaction is completed.

[0044] In step 5), the specific process parameters for the allocation of aging treatment must strictly satisfy the following mathematical boundaries: The heat treatment temperature T P (°C) satisfies: 200 ≤ T P ≤ 350 - 20×(C + N) + 15×Si 2 + 12×Cr -10×Ni - 10×Mn + 15×Mo + 10×W + 10×Cu + 15×Co + 15×(V + Nb); where the symbols of each element represent their actual mass percentage content in the steel. This temperature boundary equation comprehensively considers the dynamic thermodynamic balance of elements that stabilize austenite, elements that inhibit carbide formation, and elements that strengthen phase precipitation, ensuring that the effective distribution of C and N and the dispersed precipitation of nanocomposite phases are maximized without destroying the supersaturated martensite matrix.

[0045] The holding time t(s) for the aging process satisfies: t ≥ 5 + 5×H, where H is the actual thickness of the cold-rolled sheet in mm. This formula ensures that a uniform diffusion response can occur inside and on the surface of steel sheets of different thicknesses.

[0046] During this low-temperature partitioning aging process, the matrix undergoes a microstructural evolution: carbon and nitrogen atoms are fully distributed from the martensite phase into the retained austenite phase, enhancing the chemical stability and strength of the retained austenite. Simultaneously, a dispersed carbonitride composite phase of V and Nb with a size less than 15 nm precipitates within the martensite matrix. This nanoscale composite phase exhibits a significant precipitation strengthening effect and effectively pins grain boundaries, preventing grain growth.

[0047] Example To further verify the effectiveness of the technical solution of the present invention, several embodiments with brand names were manufactured.

[0048] Table 1 shows the specific alloy composition (wt.%) of the embodiments and comparative examples of the present invention, with the remainder being iron and unavoidable impurities. Table 2 shows the manufacturing process of the embodiments and comparative examples, where H is the plate thickness (mm). Table 3 shows the mechanical properties of the embodiments and comparative examples. Figure 1 This is a scanning electron microscope (EBSD) image of wide-temperature-range high-strength and ductile stainless steel from Example 1. Figure 2 This is the room temperature tensile curve of wide-temperature-range high-strength ductile stainless steel in Example 1.

[0049] The results show that Examples 1-5 of this invention achieve an excellent match between elongation after fracture still exceeding 25% at ultra-high strength levels (tensile strength greater than 1600 MPa at room temperature). This allows the steel plate to complete the deep cold working of complex aerospace propellant tank segments without any intermediate annealing. Simultaneously, its cryogenic tensile elongation remains stable above 20%, and its strength at 100°C is still above 1400 MPa, covering the entire service temperature range of the launch vehicle's launch and recovery lifecycle. In contrast, Comparative Example 1, due to the reduction of C and Si content, disrupted the low-temperature distribution mechanism, failing to obtain a high volume fraction of stable residual austenite, resulting in severe strength-ductility fracture. Comparative Example 2, by increasing Mn and decreasing Ni, caused the austenite to lose thermodynamic stability at extremely low temperatures, resulting in a precipitous drop in tensile elongation to 5.2% at low temperatures, making it unusable on rockets. Although Comparative Example 3 has the same composition as Example 1, it only uses traditional cold rolling and lacks the primary martensite quenching and low-temperature reverse distribution process. As a result, the matrix cannot retain the metastable residual austenite rich in C and N, and its room temperature elongation is only 15.1%.

[0050] Table 1 Table 2 Table 3 The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A wide-temperature-range, high-strength, and ductile stainless steel, characterized in that, The elemental composition and their mass percentage (wt.%) of the stainless steel are as follows: C: 0.08~0.30, Si: 0.75~2.5, Cr: 13.0~18.0, Ni: 3.0~8.0, Mn: 1.0~3.0, Mo: 0.5~2.5, N: 0.10~0.35, W: 0~1.5, Cu: 0.05~1.5, Co: 0.05~2.0, V: 0.05~0.5, Nb: 0.01~0.1, with the remainder being iron and unavoidable impurities.

2. A wide-temperature-range high-strength and ductile stainless steel as described in claim 1, characterized in that, The preferred elemental composition and their mass percentage (wt.%) of the stainless steel are as follows: C: 0.10~0.25, Si: 1.0~2.0, Cr: 14.0~17.0, Ni: 4.0~7.0, Mn: 1.0~3.0, Mo: 0.5~2.5, N: 0.10~0.25, W: 0.01~1.0, Cu: 0.05~1.0, Co: 0.05~1.5, V: 0.05~0.3, Nb: 0.01~0.06, with the remainder being iron and unavoidable impurities.

3. A wide-temperature-range high-strength and ductile stainless steel as described in claim 1, characterized in that, The mass percentages of Si and Mn added to the stainless steel satisfy the following condition: 0.25 ≤ Si / Mn ≤ 2.

4. A wide-temperature-range high-strength and ductile stainless steel as described in claim 1, characterized in that, The microstructure of the stainless steel is martensite and metastable retained austenite; wherein the volume fraction of the metastable retained austenite is 30%~80%, and the metastable retained austenite is enriched with C and N elements, and the total mass fraction of C+N in the retained austenite is ≥0.3%.

5. A method for manufacturing a wide-temperature-range high-strength and ductile stainless steel as described in any one of claims 1 to 4, characterized in that, Includes the following steps: 1) Smelting and casting: Smelting is carried out according to the stated composition ratio, and casting is carried out into steel ingots; 2) Forging: Heat the steel ingot to 1100℃~1200℃, hold for 1~5 hours, and then forge. The initial forging temperature is ≥1100℃ and the final forging temperature is ≥950℃. 3) Hot rolling: The steel ingot is heated to 1050℃~1200℃, held for 1~5h, and then hot rolled in multiple passes to produce hot rolled slab. The initial hot rolling temperature is ≥1100℃, the final rolling temperature is ≥900℃, the total reduction during the hot rolling process is controlled to be ≥50%, and the slab is water-cooled after hot rolling. 4) Cold rolling: The slab is subjected to multiple cold rolling passes, and the total deformation of the cold rolling is controlled at 10%~30% to produce aerospace thin plates with a thickness of 0.5mm~4.0mm; 5) Grading treatment: Heat the cold-rolled sheet to the grading temperature (T). P The carbon and nitrogen atoms are subjected to low-temperature partitioning and aging treatment, and then rapidly cooled to room temperature after partitioning.

6. The manufacturing method according to claim 5, characterized in that, The specific process parameters in step 5) are as follows: The heat treatment temperature T P (°C) satisfies: 200 ≤ T P ≤ 350 - 20×(C + N) + 15×Si 2 + 12×Cr-10×Ni - 10×Mn + 15×Mo + 10×W + 10×Cu + 15×Co + 15×(V + Nb); The heat preservation time t (s) satisfies: t ≥ 5 + 5×H, where H (mm) is the plate thickness.

7. The manufacturing method according to claim 5, characterized in that, During the low-temperature partitioning aging process in step 5), C and N atoms are partitioned from the martensite phase into the retained austenite phase. At the same time, a dispersed carbonitride composite phase of V and Nb with a size of less than 15 nm is precipitated in the martensite matrix to generate precipitation strengthening and pin the grain boundaries.

8. The wide-temperature-range high-strength and ductile stainless steel according to any one of claims 1 to 4, characterized in that, The stainless steel exhibits the following excellent wide-temperature-range mechanical property matching: At room temperature, tensile strength ≥1600MPa, elongation after fracture ≥25%; At low temperatures (-196℃), the tensile strength is ≥2000 MPa, and the elongation after fracture is ≥20%. At high temperature (100℃), the tensile strength is ≥1400MPa and the elongation after fracture is ≥10%.

9. The wide-temperature-range high-strength and ductile stainless steel according to any one of claims 1 to 4, or the stainless steel prepared by the method according to any one of claims 5 to 7, is used in the manufacture of key structural components for aerospace launch vehicles.

10. The application according to claim 9, characterized in that, The key structural components of the space launch vehicle specifically include: the liquid oxygen tank and liquid methane tank of the launch vehicle; the outer skin section of the rocket body that is heated by aerodynamic friction during high-speed flight; the stiffening stringers and main load-bearing frames of the interstage section and instrument compartment; and the high-pressure cryogenic pipelines and load-bearing supports around the liquid rocket engine.

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