High-toughness corrosion-resistant 0Cr22Ni60Mo9Nb4 alloy and preparation method thereof

Abstract

The application discloses a high-strength and high-toughness corrosion-resistant 0Cr22Ni60Mo9Nb4 alloy and a preparation method thereof, and belongs to the technical field of nickel-based high-temperature alloys.The alloy components comprise the following components in mass fraction: C: 0.0050.025%, Si: ≤0.10%, Mn: ≤0.50%, P: ≤0.015%, S: ≤0.010%, Cr: 20.022.5%, Mo: 8.09.5%, Nb: 3.63.9%, Ti: 0.150.25%, Al: 0.150.25%, N: ≤0.01%, B: ≤0.002%, Fe: ≤5.0%, and the balance is Ni and impurities.The alloy has the following properties at room temperature: tensile strength Rm≥870 MPa, yield strength Rp0.2≥400 MPa, elongation A≥58%, and reduction of area Z≥70%, and the corrosion resistance is outstanding, and the alloy is particularly suitable for manufacturing high-performance small-caliber precision pipes for petrochemical industry, nuclear power and marine engineering.

Description

Technical Field

[0001] This invention relates to the field of nickel-based corrosion-resistant alloy materials technology, specifically to a high-strength, high-toughness, and corrosion-resistant 0Cr22Ni60Mo9Nb4 alloy and its preparation method. Background Technology

[0002] In extreme service environments such as petrochemicals, marine engineering, and nuclear power, equipment components often face the combined effects of highly corrosive media, high temperature and pressure, and complex mechanical loads. While traditional stainless steel materials are relatively inexpensive, their corrosion resistance and high-temperature strength are insufficient, making them prone to pitting corrosion, crevice corrosion, and stress corrosion cracking, leading to shortened equipment lifespan and increased safety risks. The 0Cr22Ni60Mo9Nb4 alloy is a typical Ni-Cr-Mo-Nb system solid solution-strengthened corrosion-resistant alloy. Due to its excellent resistance to uniform corrosion, pitting corrosion, crevice corrosion, and stress corrosion cracking in both oxidizing and reducing environments, as well as its good high-temperature strength, it is widely used in extreme corrosive and high-temperature environments such as oil and gas extraction, offshore platforms, nuclear power plant evaporators, and flue gas desulfurization.

[0003] However, as equipment develops towards higher efficiency, lighter weight, and longer service life, more stringent requirements are placed on this alloy, especially for small-diameter, thin-walled tubes: it must maintain ultra-high corrosion resistance, possess higher strength and good plasticity to withstand complex stresses, and ensure excellent hot workability to cope with demanding tube manufacturing processes. Currently, this alloy faces three major technical bottlenecks in practical production applications: (1) The high Nb content in the alloy makes it easy for large deformation processes such as hot extrusion to crack, resulting in a low yield.

[0004] (2) It is difficult to meet the requirements of high strength and high toughness for high-end applications at the same time.

[0005] (3) Severe dendritic segregation (Mo and Nb segregation) in large-size ingots can be inherited by the final product, resulting in local deterioration of the alloy's corrosion resistance and making it difficult to meet the long-term service requirements of extreme corrosion environments. Therefore, it is urgent to develop a 0Cr22Ni60Mo9Nb4 alloy and its preparation method that have ultra-high strength, excellent toughness and excellent corrosion resistance to fill the existing technological gap. Summary of the Invention

[0006] Based on the above analysis, the present invention aims to provide a high-strength, high-toughness, and corrosion-resistant 0Cr22Ni60Mo9Nb4 alloy and its preparation method, which solves one of the problems of easy cracking in the large deformation process of the alloy, low yield, imbalance between strength and plasticity, local deterioration of corrosion resistance, and difficulty in meeting the long-term service requirements of extreme corrosion environments.

[0007] On one hand, the present invention provides a high-strength, tough, and corrosion-resistant 0Cr22Ni60Mo9Nb4 alloy, whose chemical composition, by mass fraction, includes: C: 0.005 0.025%, Si≤0.10%, Mn≤0.50%, P≤0.015%, S≤0.010%, Cr: 20.0 22.5%, Mo: 8.0 9.5%, Nb: 3.6 3.9%, Ti: 0.15 0.25%, Al: 0.15 0.25%, N≤0.01%, B≤0.002%, Fe≤5.0%, balance is Ni and unavoidable impurities.

[0008] Furthermore, its chemical composition, by mass fraction, includes: C: 0.020 0.025%, Si≤0.10%, Mn≤0.50%, P≤0.015%, S≤0.010%, Cr: 20.0 22.5%, Mo: 8.0 9.5%, Nb: 3.7-3.8%, Ti: 0.18-0.22%, Al: 0.18-0.22%, N≤0.01%, B≤0.002%, Fe≤5.0%, with the balance being Ni and unavoidable impurities.

[0009] Furthermore, the ratio of Ti to Al is 1:1.

[0010] Furthermore, the room temperature mechanical properties of the alloy satisfy the following: tensile strength Rm≥870 MPa, yield strength Rp0.2≥400 MPa, elongation A≥58%, and reduction of area Z≥70%.

[0011] On the other hand, the present invention provides a method for preparing a high-strength, high-toughness, and corrosion-resistant 0Cr22Ni60Mo9Nb4 alloy, used to prepare the high-strength, high-toughness, and corrosion-resistant 0Cr22Ni60Mo9Nb4 alloy described in any of the above-mentioned methods. The preparation method includes the following steps: (1) Smelting and casting: Vacuum induction melting or vacuum induction melting plus electroslag remelting is used to cast ingots; (2) Homogenization treatment: The ingot is subjected to two-stage high-temperature diffusion annealing; (3) Hot deformation blanking: The homogenized ingot is forged or hot extruded to produce hot deformation blanking; (4) Solution treatment: The hot-deformed blank is subjected to solution treatment and then cooled.

[0012] Furthermore, the two-stage high-temperature diffusion annealing described in step (2) is as follows: the first stage is at 1170°C. 1180℃ heat preservation for 20 28 hours; the second phase of temperature rises to 1195. Insulate at 1205℃ for 24 hours 28 hours; the diameter of the ingot is not less than 500 mm.

[0013] Furthermore, the deformation temperature of the hot deformation blank in step (3) is 1125℃. 1175℃, strain rate 0.01 1s - ¹.

[0014] Furthermore, the solution treatment temperature in step (4) is 1075°C. 1125℃, heat preservation time is 0.5 seconds. 2 hours; the cooling method is water cooling.

[0015] Furthermore, after the solution treatment in step (4), the corrosion performance of the alloy meets the following requirements: the corrosion rate is less than 0.075 mm / month according to ASTM A262 C method; and the ratio of the corrosion rate of the sensitized state to that of the solution-treated state is not greater than 1.5 according to ASTM G28 A method.

[0016] Thirdly, the present invention provides an application of the high-strength, tough, and corrosion-resistant 0Cr22Ni60Mo9Nb4 alloy described in any of the above claims in the preparation of high-strength, corrosion-resistant materials for use in the petrochemical, marine engineering, or nuclear power fields.

[0017] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects: 1. This invention precisely controls the content ratio of Nb (3.6-3.9%), Ti (0.15-0.25%), and Al (0.15-0.25%) to form stable NbC carbides with C, which hinders grain growth, strengthens grain boundaries, and improves high-temperature strength. It significantly improves segregation elimination efficiency, providing a basis for synergistic optimization of mechanical properties and corrosion resistance of the finished product, avoiding the trade-off between the two. It achieves an excellent match between strength (Rm≥870MPa, yield strength Rp0.2≥400 MPa) and plasticity (A≥58%, Z≥70%), solving the core problem of strength-plasticity imbalance in traditional high-alloy 0Cr22Ni60Mo9Nb4 alloy.

[0018] 2. This invention limits the Nb content in the alloy to 3.6-3.9%, which provides the necessary high-temperature plasticity within this range without causing excessive aggregation and becoming a crack source. This makes it less prone to cracking in large deformation processes such as hot extrusion, thereby improving the yield.

[0019] 3. This invention effectively fixes the N element in the alloy by synergistic addition of Ti and Al in a 1:1 ratio, inhibits the precipitation of harmful nitrides such as NbN, avoids the increase in corrosion sensitivity caused by nitrides, and improves the corrosion resistance of the alloy.

[0020] 4. The two-stage high-temperature diffusion annealing process of this invention (holding at 1170-1180℃ for 20-28h + holding at 1195-1205℃ for 24-28h) can effectively eliminate the segregation of high-content, low-diffusion-rate elements such as Mo and Nb in large-diameter ingots, laying the foundation for obtaining uniform deformation capacity and uniform mechanical and corrosion-resistant properties of the final product during subsequent hot working; combined with 1100-1150℃ and 0.01-1 s - The stable hot deformation parameters¹ and the fine, uniform dynamic recrystallization structure obtained by deformation within the “stable processing zone” ensure the corrosion resistance and high strength and toughness of the alloy.

[0021] 5. The solution treatment temperature range of the present invention is (1075°C). 1125℃) is used to obtain a uniform supersaturated solid solution: strengthening elements such as Cr, Mo, and Nb are fully dissolved in the austenitic matrix, providing the alloy with basic solid solution strengthening and extremely high corrosion resistance potential. This is achieved through solution treatment (at a temperature of 1075℃). 1125℃, heat preservation time is 0.5 seconds. After 2 hours, its corrosion performance meets the following requirements: the corrosion rate is less than 0.075 mm / month according to ASTM A262C; and the ratio of the sensitized state to the solution-treated state corrosion rate is no greater than 1.5 according to ASTM G28 A, thus improving corrosion resistance and meeting the long-term service requirements in extreme corrosive environments. Solution treatment can be rapidly cooled by water, requiring no complex equipment and facilitating industrial application.

[0022] 6. The alloy of this invention has been tested by ASTM A262 C and ASTM G28 A methods, and its corrosion rate and corrosion rate ratio are superior to those of existing technologies. It exhibits excellent corrosion resistance in corrosive media containing chloride ions, sulfuric acid, and phosphoric acid, and can meet the service requirements of extreme corrosive environments. The alloy exhibits excellent corrosion resistance and mechanical stability in high temperature, high pressure, and highly corrosive media (such as those containing chloride ions, sulfuric acid, and phosphoric acid), and has been successfully applied to key parts such as hydrogenation reactor pipelines, deep-sea cooling systems, and nuclear power plant cooling water pipelines. Attached Figure Description

[0023] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0024] Figure 1 shows the effect of alloying element Nb on the microstructure of 0Cr22Ni60Mo9Nb4 alloy in Example 2 and Comparative Examples 1 and 2; Figure 2 shows the effect of alloying element Ti on the microstructure of 0Cr22Ni60Mo9Nb4 alloy in Examples 2 and Comparative Examples 3 and 5; Figure 3. Effect of Al content on the microstructure of 0Cr22Ni60Mo9Nb4 alloy corresponding to Example 2 and Comparative Examples 4 and 5; Figure 4 shows the alloy thermoplasticity curves of Example 2 and Comparative Examples 1-5 0Cr22Ni60Mo9Nb4; Figure 5 shows the effect of heat treatment temperature on the mechanical properties of 0Cr22Ni60Mo9Nb4 alloy in Example 2. Detailed Implementation

[0025] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0026] In extreme service environments such as petrochemicals, marine engineering, and nuclear power, equipment components often face the combined effects of highly corrosive media, high temperature and pressure, and complex mechanical loads. While traditional stainless steel materials are relatively inexpensive, their corrosion resistance and high-temperature strength are insufficient, making them prone to pitting corrosion, crevice corrosion, and stress corrosion cracking, leading to shortened equipment lifespan and increased safety risks. The 0Cr22Ni60Mo9Nb4 alloy is a typical Ni-Cr-Mo-Nb system solid solution-strengthened corrosion-resistant alloy. Due to its excellent resistance to uniform corrosion, pitting corrosion, crevice corrosion, and stress corrosion cracking in both oxidizing and reducing environments, as well as its good high-temperature strength, it is widely used in extreme corrosive and high-temperature environments such as oil and gas extraction, offshore platforms, nuclear power plant evaporators, and flue gas desulfurization.

[0027] However, as equipment develops towards higher efficiency, lighter weight, and longer service life, more stringent requirements are placed on this alloy, especially for small-diameter, thin-walled tubes: it must maintain ultra-high corrosion resistance, possess higher strength and good plasticity to withstand complex stresses, and ensure excellent hot workability to cope with demanding tube manufacturing processes. Currently, this alloy faces three major technical bottlenecks in practical production applications: (1) The high Nb content in the alloy makes it easy for large deformation processes such as hot extrusion to crack, resulting in a low yield.

[0028] (2) It is difficult to meet the requirements of high strength and high toughness for high-end applications at the same time.

[0029] (3) Severe dendritic segregation (Mo and Nb segregation) in large-size ingots can be inherited by the final product, resulting in local deterioration of the alloy's corrosion resistance and making it difficult to meet the long-term service requirements of extreme corrosion environments. Therefore, it is urgent to develop a 0Cr22Ni60Mo9Nb4 alloy and its preparation method that have ultra-high strength, excellent toughness and excellent corrosion resistance to fill the existing technological gap.

[0030] Therefore, on the one hand, the present invention provides a high-strength, tough, and corrosion-resistant 0Cr22Ni60Mo9Nb4 alloy, the chemical composition of which, by mass fraction, includes: C: 0.005-0.025%, Si≤0.10%, Mn≤0.50%, P≤0.015%, S≤0.010%, Cr: 20.0-22.5%, Mo: 8.0-9.5%, Nb: 3.6-3.9%, Ti: 0.15-0.25%, Al: 0.15-0.25%, N≤0.01%, B≤0.002%, Fe≤5.0%, with the balance being Ni and unavoidable impurities.

[0031] Furthermore, its chemical composition, by mass fraction, includes: C: 0.020 0.025%, Si≤0.10%, Mn≤0.50%, P≤0.015%, S≤0.010%, Cr: 20.0 22.5%, Mo: 8.0 9.5%, Nb: 3.7-3.8%, Ti: 0.18-0.22%, Al: 0.18-0.22%, N≤0.01%, B≤0.002%, Fe≤5.0%, with the balance being Ni and unavoidable impurities.

[0032] Furthermore, the ratio of Ti to Al is 1:1.

[0033] The function and content of each element are explained below: Ni, the matrix element, serves as the balance element, forming the austenitic matrix of the alloy. This ensures the alloy's good toughness, machinability, and corrosion resistance, while also providing a solid solution carrier for other alloying elements.

[0034] Corrosion-strengthening elements Cr and Mo: Cr content is controlled at 20.0-22.5% to form a dense Cr2O3 oxide film, improving the alloy's resistance to oxidation and corrosion in oxidizing media; Mo content is 8.0-9.5%, working synergistically with Cr to significantly enhance the alloy's resistance to pitting corrosion, crevice corrosion, and corrosion in reducing media (such as sulfuric acid and hydrochloric acid). For example, Cr content is 20.0%, 20.5%, 21.0%, 21.5%, 22.0%, 22.5%, and Mo content is 8.0%, 8.1%, 8.2%, 8.3%, 8.4%, 8.5%, 8.6%, 8.7%, 8.8%, 8.9%, 9.0%, 9.1%, 9.2%, 9.3%, 9.4%, 9.5%.

[0035] Strengthening elements Nb, Ti, and Al: The Nb content is limited to 3.6-3.9%, preferably 3.7-3.8%, which can achieve: (1) forming stable NbC carbides with C, hindering grain growth, strengthening grain boundaries and improving high-temperature strength; Ti and Al are each controlled at 0.15-0.25% (the preferred contents of Ti and Al are both 0.18-0.22%), and the ratio of Ti to Al is 1:1. Through solid solution strengthening and grain refinement, the strength of the alloy is further improved, and the toughness is improved at the same time. The three work together to achieve a balance between strength and toughness. (2) By controlling the contents of Nb (3.6-3.9%), Ti (0.15-0.25%), and Al (0.15-0.25%), the elements work together to provide an efficient diffusion basis for the subsequent two-stage homogenization heat treatment, greatly improve the segregation elimination efficiency, and provide a basis for the synergistic optimization of mechanical properties and corrosion resistance of the alloy, avoiding the loss of one aspect for the other. (3) By synergistically adding Ti and Al, the grain size of the alloy can be refined, the N element in the alloy can be effectively fixed, the precipitation of harmful nitrides such as NbN can be inhibited, the corrosion sensitivity caused by nitrides can be avoided, and the corrosion resistance of the alloy can be improved. (4) The Nb content in the alloy is limited to 3.6-3.9%. Within this range, the alloy can precipitate an appropriate amount of fine and dispersed NbC phase. These fine carbides can effectively pin the grain boundaries, refine the grains, and provide the necessary high-temperature plasticity. They will not become crack sources due to excessive aggregation, thus making it less prone to cracking in large deformation processes such as hot extrusion and improving the yield. If the content is too low, there is insufficient NbC to pin the grain boundaries, the grains are easy to coarsen, the coordination deformation ability of the coarse grain structure is poor, which will also lead to a decrease in thermoplasticity and easy cracking. If the content is too high, it promotes the large precipitation of brittle phases such as coarse MC phase and aggregates at the grain boundaries. These coarse second phases serve as preferential nucleation sites and propagation channels for cracks, leading to a sharp decrease in the high-temperature reduction of area, making them highly susceptible to cracking during hot extrusion. For example, the Nb content is 3.6%, 3.65%, 3.7%, 3.75%, 3.8%, 3.85%, and 3.9%; the Ti content is 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.20%, 0.21%, 0.22%, 0.23%, 0.24%, and 0.25%; and the Al content is 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.20%, 0.21%, 0.22%, 0.23%, 0.24%, and 0.25%.

[0036] Impurity and harmful element control: C content is controlled between 0.005-0.025%, with an optimal content of 0.020%. 0.025% ensures sufficient carbide reinforcement with Nb while avoiding excessive C leading to increased corrosion susceptibility; Si≤0.10% and Mn≤0.50% reduce the formation of non-metallic inclusions; P≤0.015% and S≤0.010% reduce hot working brittleness and corrosion risk; N≤0.01% and B≤0.002% avoid the formation of harmful nitrides and borides, ensuring alloy purity.

[0037] Fe element: An Fe content of ≤5.0% can reduce the cost of the alloy without affecting the strengthening effect and corrosion resistance of other elements.

[0038] Furthermore, the room temperature mechanical properties of the alloy satisfy the following: tensile strength Rm≥870 MPa, yield strength Rp0.2≥400 MPa, elongation A≥58%, and reduction of area Z≥70%.

[0039] On the other hand, the present invention provides a method for preparing the above-mentioned high-strength, high-toughness, and corrosion-resistant 0Cr22Ni60Mo9Nb4 alloy, comprising the following steps: (1) Smelting and casting: Vacuum induction melting or vacuum induction melting plus electroslag remelting is used to cast alloy ingots with a diameter of not less than 500 mm; (2) Homogenization treatment: The ingot is subjected to two-stage high-temperature diffusion annealing; (3) Hot deformation blanking: The homogenized ingot is forged or hot extruded to produce hot deformation blanking; (4) Solution treatment: The hot-deformed blank is subjected to solution treatment and then cooled.

[0040] Furthermore, the core task of step (1), smelting and casting, is to obtain large-sized ingots that are pure, dense, uniform in composition, and have good machinability. Vacuum induction melting: can remove gases (O, H, N) to the maximum extent and reduce non-metallic inclusions, which is the first step in ensuring the purity of the alloy. Vacuum induction melting plus electroslag remelting: using slag to wash the molten steel can further remove sulfur and non-metallic inclusions, making the inclusions in the ingot finer and more uniformly distributed. Alloy ingots of not less than 500 mm can obtain a relatively uniform as-cast structure from the surface to the core, laying the foundation for obtaining consistent performance in subsequent hot working. If the ingot diameter is small (e.g., 300 mm), its dendrite spacing is small, the degree of segregation is light, and the required diffusion time is short. If the two-stage high-temperature diffusion annealing of the present invention is still used, it will lead to a weakening of the fine grain strengthening effect and a reduction in room temperature strength and plasticity.

[0041] Furthermore, the two-stage high-temperature diffusion annealing described in step (2) is as follows: the first stage is at 1170°C. 1180℃ heat preservation for 20 28 hours; the second phase of temperature rises to 1195. Insulate at 1205℃ for 24 hours 28 hours; the diameter of the ingot is not less than 500 mm.

[0042] The core objective of this step is to completely eliminate severe dendritic segregation in large-sized ingots (≥500mm), especially the segregation of high-content, low-diffusion-rate elements such as Mo and Nb. The first stage is at 1170... 1180℃ heat preservation for 20 The first 28 hours primarily eliminate macroscopic segregation of Mo. This temperature range is sufficient to initiate short-range diffusion of Mo atoms, initially leveling the Mo concentration difference between dendrite trunks and dendrites, thus laying the foundation for greater homogenization in the second stage. If the temperature is directly increased to higher levels, these undissolved brittle phases may aggregate or react adversely with the matrix, worsening the microstructure. The second stage involves heating to 1195°C. Insulate at 1205℃ for 24 hours The 28-hour process mainly addresses the macroscopic segregation of Nb, laying the foundation for uniform deformation capacity and uniform mechanical and corrosion resistance of the final product during subsequent hot processing. The two-stage process is not simply a superposition of time. (1) It avoids the risk of overheating: If only a single-stage high temperature is used, before the harmful phase is fully dissolved, the local Nb and Mo rich areas may overheat (local melting) due to the decrease in melting point, resulting in defects; (2) The structure is genetically optimized: a highly uniform ingot structure is obtained, so that the difference between the longitudinal and transverse properties is minimal.

[0043] If the temperature or time in the first stage is too low or too short, or if the temperature or time in the second stage is too low or too short, insufficient Mo dissolution and elemental segregation may occur, leading to hot extrusion cracking and a significant decrease in yield. If the temperature or time in the first stage is too high or too long, or if the temperature or time in the second stage is too high or too long, some Nb-rich regions may prematurely enter the dangerous temperature range, posing a risk of localized overheating, or causing abnormal grain growth, weakening the potential for subsequent fine-grain strengthening and reducing the alloy's strength.

[0044] For example, the first stage temperature is 1170℃, 1171℃, 1172℃, 1173℃, 1174℃, 1175℃, 1176℃, 1177℃, 1178℃, 1179℃, and 1180℃, and the temperature is maintained for 20 hours, 21 hours, 22 hours, 23 hours, 24 hours, 25 hours, 26 hours, 27 hours, and 28 hours, respectively; the second stage temperature is 1195℃, 1196℃, 1197℃, 1198℃, 1199℃, 1120℃, 1121℃, 1122℃, 1123℃, 1124℃, and 1205℃, and the temperature is maintained for 24 hours, 25 hours, 26 hours, 27 hours, and 28 hours, respectively.

[0045] Furthermore, the deformation temperature of the hot deformation blank in step (3) is 1125℃. 1175℃, strain rate 0.01 1s - ¹.

[0046] Deformation temperature 1125 1175℃, strain rate 0.01 1 s - ¹ The fine, uniform dynamic recrystallized structure obtained by deformation within the "stable processing zone" possesses advantages such as high strength and toughness, uniform structure, and excellent corrosion resistance. If the hot deformation starting temperature is too low or the strain rate is too small, the temperature may fall into the precipitation range of certain harmful phases (such as Mo-rich and Nb-rich phases), resulting in insufficient dynamic recrystallization and making deformation or cracking very likely during hot deformation. If the hot deformation starting temperature is too high or the strain rate is too large, it leads to a significant decrease in room temperature strength and plasticity, a sharp decrease in the reduction of area, or the risk of overheating. For example, deformation temperatures of 1125℃, 1130℃, 1135℃, 1140℃, 1145℃, 1150℃, 1155℃, 1160℃, 1170℃, and 1175℃, and a strain rate of 0.01 s⁻¹ - ¹、0.1 s - ¹、0.2 s - ¹、0.3 s - ¹、0.4 s - ¹、0.5 s - ¹、0.6 s - ¹、0.7 s - ¹、0.8 s - ¹、0.9 s - ¹、1 s - ¹.

[0047] Furthermore, the solution treatment temperature in step (4) is 1075°C. 1125℃, heat preservation time is 0.5 seconds. 2 hours; the cooling method is water cooling.

[0048] This solution treatment temperature range is crucial for achieving a homogeneous supersaturated solid solution. This allows strengthening elements such as Cr, Mo, and Nb to fully dissolve in the austenitic matrix, providing fundamental solid solution strengthening and an extremely high corrosion potential, thus improving corrosion resistance and meeting the requirements for long-term service in extreme corrosive environments. For fine MC-type carbides (such as (Nb,Ti)C), some may re-dissolve at this temperature, but their primary function is to pin grain boundaries and inhibit excessive grain growth, contributing strength through precipitation strengthening. Holding time of 0.5-2 hours ensures complete dissolution and homogenization. Solution treatment is the core of achieving "high strength, toughness, and corrosion resistance," resulting in a microstructure with uniform composition, moderate grain size, clean grain boundaries, and full dissolution of strengthening elements. Water cooling is used to minimize the re-precipitation of any carbides or harmful phases at grain boundaries, ensuring the purest supersaturated solid solution. If the solution temperature is too low or the holding time is too short, insufficient solid solution strengthening will significantly reduce the material's plasticity and toughness, making it difficult to meet the required reduction of area and elongation. If the solution temperature is too high or the holding time is too long, the grains will coarsen rapidly, increasing the risk of overheating. Aggregation and coarsening will occur, transforming the strengthening phase into a crack source, making the alloy prone to cracking.

[0049] For example, the solution treatment temperatures are 1075℃, 1100℃, and 1125℃, and the holding times are 0.5 hours, 1 hour, 1.5 hours, and 2 hours, respectively.

[0050] Furthermore, after solution treatment, the corrosion performance of the alloy meets the following requirements: the corrosion rate is less than 0.075 mm / month according to ASTM A262 C method; and the ratio of the corrosion rate of the sensitized state to that of the solution-treated state is not greater than 1.5 according to ASTM G28 A method.

[0051] Thirdly, the present invention provides an application of the above-mentioned high-strength, high-toughness, and corrosion-resistant 0Cr22Ni60Mo9Nb4 alloy in the preparation of high-strength, corrosion-resistant materials for use in the fields of petrochemicals, marine engineering, or nuclear power.

[0052] In summary, this invention provides a high-strength, tough, and corrosion-resistant 0Cr22Ni60Mo9Nb4 alloy and its preparation method. By precisely controlling the chemical composition and ratio, the strength, toughness, and corrosion resistance are synergistically optimized. Simultaneously, the invention provides a preparation method for this alloy, ensuring product performance stability through a two-stage high-temperature diffusion annealing process, precise hot deformation, and solution treatment. Ultimately, this invention expands the application scenarios of this alloy under extreme working conditions, thereby solving problems such as easy cracking, low yield, imbalance between strength and plasticity, localized deterioration of corrosion resistance, and difficulty in meeting the long-term service requirements of extreme corrosive environments. Furthermore, it has been successfully applied in the petrochemical, marine engineering, and nuclear power fields, meeting the requirements for high strength and corrosion resistance, and satisfying the service requirements of extreme corrosive environments.

[0053] The following specific embodiments further illustrate the present invention: Example 1 This embodiment describes a high-strength, tough, and corrosion-resistant 0Cr22Ni60Mo9Nb4 alloy. Its chemical composition, by mass fraction, is as follows: C 0.022%, Si 0.03%, Mn 0.32%, P 0.004%, S 0.003%, Cr 21.51%, Mo 9.01%, Nb 3.62%, Ti 0.17%, Al 0.17%, Fe 3.48%, with the balance being Ni. See Table 1.

[0054] The preparation method of the high-strength, high-toughness, and corrosion-resistant 0Cr22Ni60Mo9Nb4 alloy in this embodiment includes the following steps: (1) Smelting and casting: Vacuum induction melting or vacuum induction melting plus electroslag remelting is used to cast alloy ingots with a diameter of not less than 500 mm; (2) Homogenization treatment: The ingot is subjected to two-stage high-temperature diffusion annealing. The first stage is held at 1175℃ for 24 hours, and the second stage is heated to 1200℃ and held for 26 hours. (3) Hot deformation blanking: Deformation temperature 1150℃, strain rate 0.01 s - ¹, The homogenized ingot is hot-extruded to produce a hot-deformed billet; (4) Solution treatment: The hot-deformed blank after hot deformation is solution treated and then water-cooled; the solution treatment is carried out by holding at 1100℃ for 1 hour.

[0055] Example 2 This embodiment describes a high-strength, tough, and corrosion-resistant 0Cr22Ni60Mo9Nb4 alloy. Its chemical composition, by mass fraction, is as follows: C 0.024%, Si 0.03%, Mn 0.32%, P 0.005%, S 0.003%, Cr 21.53%, Mo 9.02%, Nb 3.71%, Ti 0.20%, Al 0.20%, Fe 4.48%, with the balance being Ni. See Table 1.

[0056] The preparation method of the alloy in this embodiment is the same as that in Example 1.

[0057] Example 3 This embodiment describes a high-strength, tough, and corrosion-resistant 0Cr22Ni60Mo9Nb4 alloy. Its chemical composition, by mass fraction, is as follows: C 0.022%, Si 0.03%, Mn 0.32%, P 0.004%, S 0.003%, Cr 21.50%, Mo 9.01%, Nb 3.86%, Ti 0.24%, Al 0.24%, Fe 3.50%, with the balance being Ni. See Table 1.

[0058] The preparation method of the high-strength, high-toughness, and corrosion-resistant 0Cr22Ni60Mo9Nb4 alloy in this embodiment includes the following steps: (1) Smelting and casting: Vacuum induction melting or vacuum induction melting plus electroslag remelting is used to cast alloy ingots with a diameter of not less than 500 mm; (2) Homogenization treatment: The ingot is subjected to two-stage high-temperature diffusion annealing. The first stage is held at 1175℃ for 24 hours, and the second stage is heated to 1200℃ and held for 26 hours. (3) Hot deformation blanking: deformation temperature 1140℃, strain rate 0.05s - ¹Inside, the homogenized ingot is hot-extruded to produce a hot-deformed billet; (4) Solution treatment: The hot-deformed blank after hot deformation is solution treated and then water-cooled; the solution treatment is carried out by holding at 1080℃ for 1.2 hours.

[0059] Comparative Example 1 This comparative example presents a high-strength, tough, and corrosion-resistant 0Cr22Ni60Mo9Nb4 alloy with an Nb content of 3.2%, and other elements are the same as in Example 2. See Table 1 for details.

[0060] The preparation method of the alloy in this embodiment is the same as that in Example 2.

[0061] Comparative Example 2 This comparative example presents a high-strength, tough, and corrosion-resistant 0Cr22Ni60Mo9Nb4 alloy with an Nb content of 4.2%, and other elements are the same as in Example 2. See Table 1 for details.

[0062] The preparation method of the alloy in this embodiment is the same as that in Example 2.

[0063] Comparative Example 3 This comparative example presents a high-strength, tough, and corrosion-resistant 0Cr22Ni60Mo9Nb4 alloy with a Ti content of 0.4%, and other elements are the same as in Example 2. See Table 1 for details.

[0064] The alloy in this comparative example was prepared using the same method as in Example 2.

[0065] Comparative Example 4 This comparative example presents a high-strength, tough, and corrosion-resistant 0Cr22Ni60Mo9Nb4 alloy with an Al content of 0.4%, and other elements are the same as in Example 2. See Table 1 for details.

[0066] The alloy in this comparative example was prepared using the same method as in Example 2.

[0067] Comparative Example 5 This comparative example presents a high-strength, high-toughness, and corrosion-resistant 0Cr22Ni60Mo9Nb4 alloy, without the addition of Ti and Al, while other elements are the same as in Example 2. See Table 1 for details.

[0068] The alloy in this comparative example was prepared using the same method as in Example 2.

[0069] Table 1. Chemical composition (mass fraction %) of alloys from Examples 1-3 and Comparative Examples 1-5

[0070] Performance testing The mechanical and corrosion properties of Examples 1-3 and Comparative Examples 1-5 were tested at room temperature, and are shown in Table 2. Mechanical properties were determined according to ASTM E8 / E8M standards, and corrosion properties were determined according to ASTM A262 C method and ASTM G28 A standards.

[0071] Table 2. Room temperature mechanical properties and corrosion properties of the alloys prepared in Examples 1-3 and Comparative Examples 1-3.

[0072] 1. Mechanical property analysis The above alloys were subjected to room temperature tensile tests, and the results are shown in Table 2.

[0073] Effect of Nb content: The alloy in Example 2 (3.7Nb) exhibited the highest tensile strength (879.0 MPa), superior to Comparative Example 1 (3.2Nb, 854.5 MPa) and Comparative Example 2 (4.2Nb, 862.0 MPa). This indicates that there is an optimal Nb content (around 3.7%), within which necessary high-temperature plasticity is provided without excessive aggregation that could become a crack initiation point, making large deformation processes such as hot extrusion less prone to cracking and improving yield. Too low an Nb content (e.g., Comparative Example 1) leads to grain coarsening and decreased thermoplasticity; too high an Nb content (e.g., Comparative Example 2) promotes the precipitation of large amounts of brittle phases such as coarse MC phase, which aggregate at grain boundaries. These coarse second phases are preferential nucleation sites and propagation channels for cracks, resulting in a sharp decrease in high-temperature reduction of area, making cracking highly likely during hot extrusion.

[0074] The effect of Ti and Al synergy: The strength of the alloy in Example 2 (0.2Ti-0.2Al) is significantly higher than that in Comparative Examples 3, 4, and 5. This demonstrates that the strengthening effect of adding Ti and Al in combination is better than adding them alone, and that excessive addition of either Ti or Al is not conducive to performance optimization. The alloy in Example 2 achieves high strength while maintaining an elongation of 58.75%, realizing an excellent balance between strength and ductility.

[0075] 2. High-Temperature Thermoplasticity Analysis The high-temperature reduction of area was tested on the Gleeble thermal simulation testing machine, and the results are as follows: Figure 4 As shown.

[0076] Within the 1060-1180℃ range, the reduction of area of ​​all alloys is >60%, which meets the requirements for hot working.

[0077] In the high-temperature range of 1200-1250℃, the thermoplasticity of alloys is extremely sensitive to composition. For example... Figure 4 As shown, at 1220°C, the reduction of area of ​​Comparative Example 2 (4.2Nb) dropped sharply to near 0%, while that of Example 2 (3.7Nb) remained at approximately 6.2%, and that of Comparative Example 1 (3.2Nb) was 7.6%. This indicates that controlling the Nb content below 3.9%, especially approximately 3.7%, can significantly improve the alloy's resistance to ductile instability at high temperatures and broaden the safe hot working window.

[0078] Comparing the effects of Ti and Al, Comparative Example 5 (0Ti0Al) showed the worst thermoplasticity, while Example 2 (0.2Ti0.2Al) showed the best, further demonstrating that the combined addition of Ti and Al is beneficial to improving thermoplasticity.

[0079] 3. Microstructural Analysis Figure 1-3 The metallographic structures of alloys with different compositions after solution treatment at different temperatures are shown.

[0080] Grain refinement: such as Figure 1 As shown, at 1150℃, as the Nb content increased from 3.2% to 4.2%, the grain size first decreased and then slightly increased. Example 2 (3.7Nb) exhibited the finest grains and tortuous grain boundaries. This is due to the NbC phase pinning the grain boundaries. However, when the Nb content exceeds 3.9% (as in Comparative Example 2), it promotes the precipitation of large amounts of coarse brittle phases such as the MC phase, which then accumulate at the grain boundaries. These coarse second phases are preferential nucleation sites and propagation channels for cracks, leading to a sharp decrease in the high-temperature reduction of area, making cracking highly likely during hot extrusion. This is consistent with the observation that "the strength of the 4.2Nb alloy is slightly lower than that of the 3.7Nb alloy" in mechanical properties.

[0081] The roles of Ti and Al: Comparison Figure 2 and Figure 3 It can be seen that the alloy with 0.2% Ti and 0.2% Al (Example 2) has the finest grain size. The grain refining effect of adding Comparative Example 3 (0.4% Ti) or Comparative Example 4 (0.4% Al) alone is not as good as that of the combined addition. In particular, the grain size of Comparative Example 5 (0Al) and Comparative Example 2 (0.4Al) alloys is not much different, indicating that Al has little direct influence on the formation of the high-temperature MC phase, and its effect is more reflected in its synergy with Ti.

[0082] 4. Optimization of heat treatment temperature Figure 5 The effect of solution treatment temperature on the mechanical properties of the alloy in Example 2 is demonstrated.

[0083] Strength decreases linearly with increasing temperature, while plasticity (elongation and reduction of area) increases in a stepwise manner and then tends to stabilize or decrease slightly in the high-temperature region.

[0084] When solution treated at 1100℃, the alloy exhibits a tensile strength of 879 MPa, an elongation of 58.75%, and a reduction of area of ​​70.5%, achieving an optimal balance between strength and plasticity. Therefore, 1080-1120℃ is the preferred solution treatment temperature range for this invention.

[0085] Based on comprehensive mechanical properties, thermoplasticity, and microstructure analysis, the 0Cr22Ni60Mo9Nb4 alloy with a composition of 3.7% Nb, 0.2% Ti, and 0.2% Al (i.e., Example 2), and solution treated at approximately 1100℃, exhibits the optimal combination of comprehensive properties, namely high strength, high plasticity, good hot working window, and corrosion resistance. This constitutes the core basis of the claims of this invention.

[0086] Example 4 This embodiment describes a high-strength, tough, and corrosion-resistant 0Cr22Ni60Mo9Nb4 alloy. Its chemical composition, by mass fraction, is as follows: C 0.015%, Si 0.03%, Mn 0.30%, P 0.005%, S 0.004%, Cr 20.05%, Mo 8.1%, Nb 3.62%, Ti 0.15%, Al 0.15%, Fe 3.2%, with the balance being Ni. See Table 2.

[0087] The preparation method of the high-strength, high-toughness, and corrosion-resistant 0Cr22Ni60Mo9Nb4 alloy in this embodiment includes the following steps: (1) Smelting and casting: Vacuum induction melting or vacuum induction melting plus electroslag remelting is used to cast alloy ingots with a diameter of not less than 500 mm; (2) Homogenization treatment: The ingot is subjected to two-stage high-temperature diffusion annealing. The first stage is held at 1175℃ for 24 hours, and the second stage is heated to 1200℃ and held for 26 hours. (3) Hot deformation blanking: Deformation temperature 1150℃, strain rate 0.1 s - ¹, The homogenized ingot is hot-extruded to produce a hot-deformed billet; (4) Solution treatment: The hot-deformed billet after hot deformation was solution treated and then water-cooled; the solution treatment was carried out by holding at 1090℃ for 1 hour and then water-cooled. The room temperature mechanical properties and corrosion properties were tested, and the results are shown in Table 3.

[0088] Example 5 This embodiment describes a high-strength, tough, and corrosion-resistant 0Cr22Ni60Mo9Nb4 alloy. Its chemical composition, by mass fraction, is as follows: C 0.026%, Si 0.06%, Mn 0.38%, P 0.004%, S 0.003%, Cr 21.1%, Mo 8.7%, Nb 3.69%, Ti 0.20%, Al 0.20%, Fe 3.9%, with the balance being Ni. See Table 3.

[0089] The preparation method parameters of the alloy in this embodiment are the same as those in Example 4.

[0090] Example 6 This embodiment describes a high-strength, tough, and corrosion-resistant 0Cr22Ni60Mo9Nb4 alloy. Its chemical composition, by mass fraction, is: C 0.01%, Si 0.08%, Mn 0.45%, P 0.005%, S 0.004%, Cr 22.4%, Mo 9.5%, Nb 3.89%, Ti 0.25%, Al 0.25%, Fe 4.9%, with the balance being Ni. See Table 3.

[0091] The preparation method parameters of the alloy in this embodiment are the same as those in Example 4.

[0092] Example 7 This embodiment describes a high-strength, tough, and corrosion-resistant 0Cr22Ni60Mo9Nb4 alloy. Its chemical composition, by mass fraction, is as follows: C 0.021%, Si 0.03%, Mn 0.32%, P 0.004%, S 0.003%, Cr 21.4%, Mo 8.9%, Nb 3.72%, Ti 0.18%, Al 0.18%, Fe 3.5%, with the balance being Ni. See Table 3.

[0093] The preparation method of the alloy in this embodiment is the same as that in Example 1.

[0094] Example 8 This embodiment describes a high-strength, tough, and corrosion-resistant 0Cr22Ni60Mo9Nb4 alloy. Its chemical composition, by mass fraction, is as follows: C 0.013%, Si 0.08%, Mn 0.48%, P 0.005%, S 0.005%, Cr 21.8%, Mo 9.1%, Nb 3.76%, Ti 0.20%, Al 0.20%, Fe 3.8%, with the balance being Ni. See Table 3.

[0095] The preparation method of the alloy in this embodiment is the same as that in Example 1.

[0096] Example 9 This embodiment describes a high-strength, tough, and corrosion-resistant 0Cr22Ni60Mo9Nb4 alloy. Its chemical composition, by mass fraction, is as follows: C 0.018%, Si 0.04%, Mn 0.32%, P 0.004%, S 0.004%, Cr 22.2%, Mo 9.3%, Nb 3.81%, Ti 0.21%, Al 0.21%, Fe 4.2%, with the balance being Ni. See Table 3.

[0097] The preparation method of the alloy in this embodiment is the same as that in Example 1.

[0098] Table 3 Chemical composition (mass fraction %) of alloys in Examples 4-9

[0099] Performance testing The mechanical and corrosion properties of Examples 4-9 were tested at room temperature, and are shown in Table 4. Mechanical properties were determined according to ASTM E8 / E8M standards, and corrosion properties were determined according to ASTM A262 C method and ASTM G28 A standard.

[0100] Table 4. Room temperature mechanical properties and corrosion properties of the alloys prepared in Examples 4-9

[0101] Example 10 The high-strength, tough, and corrosion-resistant 0Cr22Ni60Mo9Nb4 alloy of this embodiment has the same chemical composition as that of Example 8.

[0102] The preparation method of the high-strength, high-toughness, and corrosion-resistant 0Cr22Ni60Mo9Nb4 alloy in this embodiment includes the following steps: (1) Smelting and casting: Vacuum induction melting and electroslag remelting are used to cast alloy ingots with a diameter of not less than 500 mm; (2) Homogenization treatment: The ingot is subjected to two-stage high-temperature diffusion annealing. The first stage is held at 1180℃ for 28 hours, and the second stage is heated to 1205℃ and held for 28 hours. (3) Hot deformation blanking temperature: 1150℃, strain rate: 0.1 s - ¹, The homogenized ingot is hot-extruded to produce a hot-deformed billet; (4) Solution treatment: The hot-deformed blank after hot deformation is solution treated and then water-cooled; the solution treatment is carried out by holding at 1100℃ for 1 hour.

[0103] Example 11 The high-strength, tough, and corrosion-resistant 0Cr22Ni60Mo9Nb4 alloy of this embodiment has the same chemical composition as that of Example 8.

[0104] The preparation method of the high-strength, high-toughness, and corrosion-resistant 0Cr22Ni60Mo9Nb4 alloy in this embodiment includes the following steps: (1) Smelting and casting: Vacuum induction melting and electroslag remelting are used to cast alloy ingots with a diameter of not less than 500 mm; (2) Homogenization treatment: The ingot is subjected to two-stage high-temperature diffusion annealing. The first stage is held at 1175℃ for 24 hours, and the second stage is heated to 1200℃ and held for 26 hours. (3) Hot deformation blanking: Deformation temperature 1125℃, strain rate 0.01 s - ¹, The homogenized ingot is hot-extruded to produce a hot-deformed billet; (4) Solution treatment: The hot-deformed blank after hot deformation is solution treated and then water-cooled; the solution treatment is carried out by holding at 1125℃ for 1 hour.

[0105] Example 12 The high-strength, tough, and corrosion-resistant 0Cr22Ni60Mo9Nb4 alloy of this embodiment has the same chemical composition as that of Example 8.

[0106] The preparation method of the high-strength, high-toughness, and corrosion-resistant 0Cr22Ni60Mo9Nb4 alloy in this embodiment includes the following steps: (1) Smelting and casting: Vacuum induction melting and electroslag remelting are used to cast alloy ingots with a diameter of not less than 500 mm; (2) Homogenization treatment: The ingot is subjected to two-stage high-temperature diffusion annealing. The first stage is held at 1170℃ for 24 hours, and the second stage is heated to 1195℃ and held for 24 hours. (3) Hot deformation blanking: Deformation temperature 1150℃, strain rate 0.5 s - ¹, The homogenized ingot is hot-extruded to produce a hot-deformed billet; (4) Solution treatment: The hot-deformed billet after hot deformation is solution treated and then water-cooled; the solution treatment is carried out by holding at 1075℃ for 1 hour.

[0107] Example 13 The high-strength, tough, and corrosion-resistant 0Cr22Ni60Mo9Nb4 alloy of this embodiment has the same chemical composition as that of Example 8.

[0108] The preparation method of the high-strength, high-toughness, and corrosion-resistant 0Cr22Ni60Mo9Nb4 alloy in this embodiment includes the following steps: (1) Smelting and casting: Vacuum induction melting and electroslag remelting are used to cast alloy ingots with a diameter of not less than 500 mm; (2) Homogenization treatment: The ingot is subjected to two-stage high-temperature diffusion annealing. The first stage is held at 1174℃ for 25 hours, and the second stage is heated to 1202℃ and held for 25 hours. (3) Hot deformation blanking: Deformation temperature 1155℃, strain rate 0.8 s - ¹, The homogenized ingot is hot-extruded to produce a hot-deformed billet; (4) Solution treatment: The hot-deformed blank after hot deformation is solution treated and then water-cooled; the solution treatment is carried out by holding at 1082℃ for 1.5 hours.

[0109] Example 14 The high-strength, tough, and corrosion-resistant 0Cr22Ni60Mo9Nb4 alloy of this embodiment has the same chemical composition as that of Example 8.

[0110] The preparation method of the high-strength, high-toughness, and corrosion-resistant 0Cr22Ni60Mo9Nb4 alloy in this embodiment includes the following steps: (1) Smelting and casting: Vacuum induction melting and electroslag remelting are used to cast alloy ingots with a diameter of not less than 500 mm; (2) Homogenization treatment: The ingot is subjected to two-stage high-temperature diffusion annealing. The first stage is held at 1173℃ for 23 hours, and the second stage is heated to 1201℃ and held for 26.5 hours. (3) Hot deformation blanking: Deformation temperature 1165℃, strain rate 0.6 s - ¹, The homogenized ingot is hot-extruded to produce a hot-deformed billet; (4) Solution treatment: The hot-deformed blank after hot deformation is solution treated and then water-cooled; the solution treatment is carried out by holding at 1122℃ for 0.8 hours.

[0111] Comparative Example 6 The components of this comparative example are the same as those of Example 8, and the preparation method is similar to that of Example 8. The difference is that in the preparation method, in step (2), conventional single-stage homogenization (1200℃×48h) is used.

[0112] Comparative Example 7 The composition of this comparative example is the same as that of Example 8, and its preparation method is similar to that of Example 8. The difference is that in the preparation method, the two-stage high-temperature diffusion annealing in step (2) is: the first stage is held at 1200℃ for 30 hours; the second stage is heated to 1210℃ and held for 30 hours; the diameter of the ingot is not less than 500mm.

[0113] Comparative Example 8 The composition of this comparative example is the same as that of Example 8, and its preparation method is similar to that of Example 8. The difference is that in the preparation method, the deformation temperature of the hot deformation blank in step (3) is 1120℃, and the strain rate is 1.5 s. - ¹.

[0114] Comparative Example 9 The composition of this comparative example is the same as that of Example 8, and its preparation method is similar to that of Example 8. The difference is that in the preparation method, the temperature of the solid solution treatment in step (4) is 1050°C and the holding time is 0.3 hours; the cooling method is water cooling.

[0115] Performance testing The mechanical and corrosion properties of Examples 10-14 and Comparative Examples 4-9 were tested at room temperature, and are shown in Table 5. Mechanical properties were determined according to ASTM E8 / E8M standards, and corrosion properties were determined according to ASTM A262 C method and ASTM G28 A standards.

[0116] Table 5. Room temperature mechanical properties and corrosion properties of the alloys prepared in Examples 10-14 and Comparative Examples 4-6.

[0117] The test results of Examples 4-9 show that the chemical composition range defined by the present invention can effectively guarantee the comprehensive performance of the alloy. The preferred formulations (Examples 7-9) have tensile strengths exceeding 870 MPa, elongation ≥ 58%, corrosion rates below 0.03 mm / month, and corrosion rate ratios ≤ 1.1, which are significantly better than comparative examples 1-5.

[0118] Optimized preparation process: Two-stage homogenization treatment (Examples 8, 10) effectively eliminates component segregation in large-diameter ingots, improves microstructure uniformity, and compared with conventional single-stage homogenization (Comparative Example 6), tensile strength is increased and corrosion rate is reduced; hot deformation parameters are within the stable processing range (Examples 12-13), ensuring molding quality and performance stability. Figure 4 As shown, in the temperature range of 1060~1180℃, the reduction of area of ​​the alloy is >70%, indicating good thermoplasticity, which provides a basis for determining the heat distortion temperature range of this invention. Figure 5 As shown, the elongation reaches its maximum of 58.75% at 1100℃. At this temperature, the grain size is suitable, avoiding insufficient strength due to excessively coarse grains while ensuring sufficient deformation compatibility, consistent with the optimal solution treatment temperature range determined in this invention. Comparative Example 7 If the first stage temperature or time of hot deformation blanking described in step (3) is too high or the second stage temperature or time is too high or the time is too long, some Nb-rich regions may enter the dangerous temperature range prematurely, posing a risk of local overheating, or causing abnormal grain growth, weakening the potential for subsequent fine grain strengthening and reducing the strength of the alloy. In Comparative Example 8, the hot deformation blanking temperature was too low and the strain rate was too small, resulting in cracks. In Comparative Example 9, the solution temperature was too low and the holding time was too short, resulting in insufficient solution strengthening, significantly reducing the plasticity and toughness of the material, and making it difficult to meet the standards for reduction of area and elongation.

[0119] Microstructure analysis: As shown in Figure 1, at 1150℃, the grains of 3.2Nb, 3.7Nb, and 4.2Nb gradually become finer, and the grain boundary tortuosity increases. The grain-refining effect of Nb is achieved through "pinning grain boundaries." However, when the Nb content exceeds 3.7%, the excess second phase tends to aggregate, leading to a weakening of the grain growth inhibition effect. This is consistent with the phenomenon that the strength of the 4.2Nb alloy is slightly lower than that of the 3.7Nb alloy in terms of mechanical properties. As shown in Figures 2 and 3, the grain size of the 0.2Al0.2Ti experimental steel is finer than that of other Al and Ti composition experimental steels. The Al content has no significant effect on the formation of high-temperature MC. All alloys with different compositions exhibit recrystallization characteristics. Increasing the heating temperature can significantly promote the recrystallization process, providing theoretical support for the optimization of temperature parameters in the preparation process.

[0120] Corrosion resistance advantages: The alloy of this invention has been tested by ASTM A262 C method and ASTM G28 A method. The corrosion rate and corrosion rate ratio are superior to the existing technology. It exhibits excellent corrosion resistance in corrosive media containing chloride ions, sulfuric acid, phosphoric acid and other corrosive media, and can meet the service requirements of extreme corrosive environments.

[0121] Application Example 1 The alloy prepared in Example 8 of this invention was used in the feed pipeline of a hydrogenation reactor in a large petrochemical enterprise. This pipeline is in long-term contact with high-temperature and high-pressure hydrogen and sulfide corrosive media. After 18 months of use, the pipeline was tested and found to have no pitting corrosion or crevice corrosion. The mechanical properties were retained at a rate of over 95%, which is significantly better than that of traditional stainless steel pipelines (whose service life is usually 6-12 months).

[0122] Application Example 2 The alloy was prepared using the process described in Example 12 and used in the seawater cooling system of a deep-sea oil and gas extraction platform. The service environment was high-salt-spray, high-pressure seawater. After 24 months of use, the corrosion rate was only 0.048 mm / month, and the mechanical properties showed no significant decrease, meeting the requirements for long-term stable operation of deep-sea equipment.

[0123] Application Example 3 The alloy prepared in Example 14 was used in the cooling water piping of a nuclear power reactor, operating at a temperature of 300-350°C, in contact with boron-containing cooling water. Long-term monitoring showed low corrosion sensitivity, stable mechanical properties, no leakage risk, and compliance with the safety service standards for nuclear power equipment.

[0124] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A high-strength, high-toughness, and corrosion-resistant 0Cr22Ni60Mo9Nb4 alloy, characterized in that, Its chemical composition, by mass fraction, includes: C: 0.005 0.025%, Si≤0.10%, Mn≤0.50%, P≤0.015%, S≤0.010%, Cr: 20.0 22.5%, Mo: 8.0 9.5%, Nb: 3.6 3.9%, Ti: 0.15 0.25%, Al: 0.15 0.25%, N≤0.01%, B≤0.002%, Fe≤5.0%, balance is Ni and unavoidable impurities.

2. The alloy according to claim 1, characterized in that, Its chemical composition, by mass fraction, includes: C: 0.020 0.025%, Si≤0.10%, Mn≤0.50%, P≤0.015%, S≤0.010%, Cr: 20.0 22.5%, Mo: 8.0 9.5%, Nb: 3.7-3.8%, Ti: 0.18-0.22%, Al: 0.18-0.22%, N≤0.01%, B≤0.002%, Fe≤5.0%, with the balance being Ni and unavoidable impurities.

3. The alloy according to any one of claims 1-2, characterized in that, The ratio of Ti to Al is 1:

1.

4. The alloy according to claim 1, characterized in that, The room temperature mechanical properties of the alloy meet the following requirements: tensile strength Rm≥870 MPa, yield strength Rp0.2≥400 MPa, elongation A≥58%, and reduction of area Z≥70%.

5. A method for preparing a high-strength, tough, and corrosion-resistant 0Cr22Ni60Mo9Nb4 alloy, characterized in that, For use in the preparation of claim 1 The high-strength, high-toughness, and corrosion-resistant 0Cr22Ni60Mo9Nb4 alloy described in any one of the four claims, wherein the preparation method comprises the following steps: (1) Smelting and casting: Vacuum induction melting or vacuum induction melting plus electroslag remelting is used to cast ingots; (2) Homogenization treatment: The ingot is subjected to two-stage high-temperature diffusion annealing; (3) Hot deformation blanking: The homogenized ingot is forged or hot extruded to produce hot deformation blanking; (4) Solution treatment: The hot-deformed blank is subjected to solution treatment and then cooled.

6. The method according to claim 5, characterized in that, The two-stage high-temperature diffusion annealing described in step (2) is as follows: the first stage is at 1170°C. 1180℃ heat preservation for 20 28 hours; the second phase of temperature rises to 1195. Insulate at 1205℃ for 24 hours 28 hours; the diameter of the ingot is not less than 500 mm.

7. The method according to claim 5, characterized in that, The deformation temperature of the hot deformation blank in step (3) is 1125℃. 1175℃, strain rate 0.01 1 s - ¹.

8. The method according to claim 5, characterized in that, The solution treatment temperature in step (4) is 1075°C. 1125℃, heat preservation time is 0.5 seconds. 2 hours; the cooling method is water cooling.

9. The method according to claim 6, characterized in that, After the alloy undergoes solution treatment in step (4), its corrosion performance meets the following requirements: the corrosion rate is less than 0.075 mm / month according to ASTM A262 C method; and the ratio of the corrosion rate of the sensitized state to that of the solution-treated state is not greater than 1.5 according to ASTM G28 A method.

10. The application of an alloy according to any one of claims 1-4 or an alloy obtained by the preparation method according to any one of claims 5-9 in the preparation of high-strength corrosion-resistant materials for use in the petrochemical, marine engineering or nuclear power fields.

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