A method for high-strength cold rolling forming of nickel-based superalloy and use thereof

Abstract

The application belongs to the technical field of high-temperature alloy cold working forming, and particularly relates to a nickel-based high-temperature alloy anti-cracking high-strength cold rolling forming method and application. The prior art adopts single-pass large reduction cold rolling or is assisted by high-temperature intermediate annealing, the former causes serious cracking due to deformation exceeding the limit, and the latter causes insufficient strength due to high-temperature annealing for eliminating work hardening; the scheme initiates the synergistic process of critical deformation amount control + low-energy twin boundary reservation + graded stress release, discards high-temperature intermediate annealing, replaces the stress elimination function of high-temperature annealing by multi-pass gradient rolling and stress release between passes, simultaneously eliminates residual stress under the premise of reserving work hardening structure by low-temperature stress relief post-treatment, breaks through the technical bottleneck that high strength and anti-cracking cannot be compatible in the prior art, and can stably prepare GH3536 precision cold rolling strip without cracks and with high dimensional precision.

Description

Technical Field

[0001] This application belongs to the field of cold working and forming technology of high-temperature alloys, and particularly relates to a method for cold rolling and forming of nickel-based high-temperature alloys with high strength and crack resistance, and its application in the preparation of precision cold-rolled strip. Background Technology

[0002] GH3536 nickel-based superalloys, due to their outstanding high-temperature mechanical stability, oxidation and corrosion resistance, and structural stability, have become the core structural material for critical high-temperature components in aero-engines, industrial gas turbines, and chemical heat exchange equipment. In these high-end equipment components, precision cold-rolled strip is the core substrate for key parts such as sealing, sealing, and elastic compensation, placing stringent requirements on material strength, crack resistance, dimensional accuracy, and surface quality.

[0003] Currently, the forming and preparation of GH3536 alloy precision cold-rolled strip still mainly relies on conventional high-reduction cold rolling processes. The industry has yet to establish a complete set of anti-cracking forming theories and processes that include critical deformation control, retention of low-energy Σ3 twin boundaries, and synergistic coupling of stress relief between passes. During high-strain, ultra-thin cold rolling, phenomena such as restricted slip transfer, grain boundary stress concentration, and the initiation of local fine-grained regions easily occur, leading to microcracks, edge cracks, and even fracture failure, severely restricting the stable preparation of highly reliable ultra-thin strips.

[0004] Existing conventional cold rolling technology has significant limitations: First, it lacks crack resistance, and large reduction deformation easily leads to crack initiation and propagation, resulting in a low product qualification rate. Second, it is difficult to achieve both high strength and high formability, as large deformation in a single pass easily causes cracking, and introducing high-temperature intermediate annealing eliminates the work hardening effect, leading to a significant decrease in strength. Third, it has poor controllability of microstructure, with low twin boundary retention, uneven stress distribution, and difficulty in ensuring microstructure uniformity, resulting in insufficient process stability. Fourth, it has high production costs, high scrap rates, and lengthy processes, making it difficult to meet the needs of large-scale, efficient production.

[0005] In summary, the existing cold rolling forming process for GH3536 alloy is difficult to balance high strength, crack resistance, dimensional accuracy, and production economy, and cannot meet the high performance and high reliability requirements of high-end equipment for precision cold-rolled strip. There is an urgent need to develop a new high-strength and crack-resistant cold rolling forming method that synergistically controls deformation, stress, and microstructure evolution. Summary of the Invention

[0006] This application aims to solve the technical bottleneck of GH3536 nickel-based superalloy's inability to simultaneously achieve high strength and crack resistance in the precision cold-rolled strip preparation process. It provides a method for high-strength cold rolling forming of nickel-based superalloy with crack resistance and its application. Through the synergistic regulation of critical deformation control, gradient cold rolling, stress relief between passes and low-temperature stress removal, it achieves stable preparation of crack-free, high-precision, and high-strength ultra-thin strip.

[0007] In a first aspect, embodiments of this application provide a method for cold rolling a nickel-based superalloy to achieve high strength and crack resistance, the method comprising: The GH3536 alloy strip is subjected to billet pretreatment. After solution treatment, the GH3536 alloy strip is water-cooled. The initial microstructure of the GH3536 alloy strip is uniform equiaxed recrystallized grains. The GH3536 alloy strip, after pretreatment of the billet, is subjected to gradient cold rolling. The gradient cold rolling adopts multi-pass room temperature cold rolling without high-temperature intermediate annealing. The final cumulative deformation of the gradient cold rolling is lower than 78% of the critical cracking deformation threshold of the GH3536 alloy. The reduction of each pass of the gradient cold rolling does not exceed 20%. Uniform deformation and gradual stress accumulation are achieved by gradually reducing the reduction in small increments, which inhibits crack initiation and preserves the Σ3 twin boundary structure. The GH3536 alloy strip after being formed by gradient cold rolling is subjected to rolling process parameter control. The rolling process parameter control includes: stress relief treatment of the GH3536 alloy strip between passes, and checking the flatness of the GH3536 alloy strip before each rolling pass to ensure uniform stress and avoid local stress concentration that may induce cracking. The GH3536 alloy strip, after being controlled by the rolling process parameters, is subjected to low-temperature stress relief post-treatment. The low-temperature stress relief post-treatment is to immediately perform low-temperature stress relief annealing on the GH3536 alloy strip after the final rolling, and then air-cool it to room temperature after annealing. The annealing temperature of the low-temperature stress relief annealing is lower than the recrystallization temperature of the GH3536 alloy.

[0008] Optionally, the solution treatment is a water-cooled solution treatment after holding at 1175℃±5℃ for 25min~35min, and the initial Σ3 twin boundary volume ratio of the GH3536 alloy strip is ≥55%.

[0009] Optionally, the cumulative reduction in the gradient cold rolling process increases progressively in stages: 10% in the first stage, 30% in the second stage, 50% in the third stage, and 70% in the fourth stage. The final cumulative deformation of the gradient cold rolling process is 70%.

[0010] Optionally, the reduction in each pass of the gradient cold rolling process is 10% to 18%.

[0011] Optionally, the rolling process parameter control also includes controlling the rolling speed to be 0.15m / s to 0.25m / s.

[0012] Optionally, the stress relief treatment of the GH3536 alloy strip between passes includes: After each rolling pass, the GH3536 alloy strip is placed in a constant temperature and dust-free environment at 25℃±3℃ for 6min~9min to naturally release the residual stress between passes.

[0013] Optionally, the low-temperature stress-relief annealing is a low-temperature stress-relief annealing at 250℃±5℃ for 55min~65min.

[0014] Optionally, the gradient cold rolling forming adopts a gradient cold rolling process with small increments and step-by-step pressing. The residual volume ratio of Σ3 twin boundaries in the final rolled product is controlled to be ≥20% through the gradient cold rolling process with small increments and step-by-step pressing, so as to improve slip transfer efficiency and reduce grain boundary stress concentration.

[0015] Optionally, the billet pretreatment further includes: The GH3536 alloy strip is mechanically ground to remove surface burrs and oxide scale; The GH3536 alloy strip, after being mechanically polished, is placed in a mixed hydrochloric acid-sulfuric acid solution for pickling at room temperature for 5 to 8 minutes to remove residual impurities on the surface. The GH3536 alloy strip, after being pickled at room temperature, is rinsed with water and then dried. The surface roughness Ra of the GH3536 alloy strip is controlled to be ≤1.2μm.

[0016] Optionally, the pickling time at room temperature is 5 min to 7 min, and the surface roughness Ra of the GH3536 alloy strip is 1.0 μm to 1.1 μm.

[0017] Optionally, the GH3536 alloy precision cold-rolled strip prepared by the method has a Σ3 twin boundary residual volume ratio of ≥20% and a GND density of 12.0×10⁻⁶. 14 m -2 ~15.0×10 14 m -2 Yield strength ≥1400MPa, tensile strength ≥1500MPa, elongation ≥5.0%, product qualification rate ≥96%, and no macroscopic or microscopic cracks.

[0018] Secondly, embodiments of this application provide an application of the method described in any of the first aspects, the method being used for the preparation of GH3536 alloy precision cold-rolled strip for sealing components of aero-engines or heavy gas turbines.

[0019] The technical solution provided in this application has the following advantages compared with the prior art: Pre-treatment of GH3536 alloy strip into billet allows it to undergo solution treatment followed by water cooling to obtain a uniform equiaxed recrystallized initial microstructure. This provides an initial billet with a uniform grain boundary structure, free from residual stress, segregation, and microcracks for subsequent gradient cold rolling, avoiding local stress concentration caused by uneven initial microstructure and laying the foundation for uniform slip transfer during gradient cold rolling.

[0020] The GH3536 alloy strip, after pretreatment of the billet, is subjected to gradient cold rolling. Multi-pass room temperature cold rolling without high-temperature intermediate annealing is used to gradually accumulate deformation of the GH3536 alloy strip at room temperature through multiple passes, avoiding the severe grain boundary stress concentration caused by large reduction in a single pass. This ensures that slip transfer remains smooth at the grain boundaries, thereby inhibiting the formation of shear bands and the initiation of fine grain regions.

[0021] By controlling the cumulative deformation of the final rolling in gradient cold rolling to below the critical cracking deformation threshold of GH3536 alloy, the total deformation of GH3536 alloy strip is always kept within a safe range, thereby avoiding macroscopic and microscopic cracks caused by excessive deformation and eliminating the risk of cracking failure from the source.

[0022] By controlling the reduction amount of each pass in gradient cold rolling to not exceed a specific upper limit, the local deformation of GH3536 alloy strip in each rolling pass is constrained, thereby avoiding grain boundary stress peaks caused by excessive deformation in a single pass, and thus maintaining the structural stability of Σ3 twin boundaries.

[0023] The GH3536 alloy strip after gradient cold rolling is subjected to rolling process parameter control. Stress relief treatment is performed on the GH3536 alloy strip between passes, so that the residual stress between passes gradually decreases through natural release, thereby avoiding the continuous accumulation of residual stress in multiple rolling passes, and thus preventing the superposition of residual stress and rolling stress from inducing cracks, and improving the forming stability of the strip.

[0024] Before each rolling pass, the flatness of the GH3536 alloy strip is checked to ensure uniform stress distribution. This ensures that the GH3536 alloy strip is subjected to consistent stress throughout the rolling process, thereby avoiding stress concentration and deformation incoordination caused by uneven local stress distribution, and thus ensuring the uniformity of gradient cold rolling.

[0025] After the rolling process parameters are controlled, the GH3536 alloy strip is subjected to low-temperature stress relief post-treatment. Immediately after the final rolling is completed, the GH3536 alloy strip is subjected to low-temperature stress relief annealing, so that the residual stress and lattice distortion are eliminated at a temperature below the recrystallization temperature. This releases the residual stress without triggering recrystallization and grain growth, and thus completely preserves the work-hardened structure in the cold-rolled state.

[0026] After annealing, the GH3536 alloy strip is air-cooled to room temperature, allowing it to be slowly cooled to ambient temperature after low-temperature stress-relief annealing. This avoids additional thermal stress caused by rapid cooling and thus maintains the stability of the microstructure after stress relief.

[0027] The annealing temperature is lower than the recrystallization temperature of GH3536 alloy, so that low-temperature stress-relief annealing only eliminates residual stress and lattice distortion without inducing recrystallization, thus completely preserving the high dislocation density strengthening structure formed during cold rolling, thereby maintaining the high yield strength and high tensile strength of GH3536 alloy strip.

[0028] In summary, the embodiments of this application provide a uniform initial microstructure through billet pretreatment → control deformation and reduction per pass during gradient cold rolling → manage rolling process parameters to alleviate stress between passes and ensure uniform stress distribution → eliminate residual stress through low-temperature stress relief post-treatment while preserving the complete causal chain of work-hardened microstructure. This allows GH3536 alloy strip to avoid cracking failure and maintain high strength during cold rolling, thus achieving a balance between the high strength and crack resistance of GH3536 alloy cold rolling. Attached Figure Description

[0029] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0030] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the accompanying drawings required in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other related drawings can be derived from these drawings without creative effort.

[0031] Figure 1 The figure shows that the initial Σ3 twin boundary volume ratio of the GH3536 alloy strip in Embodiment 1 of this application is 55%; Figure 2 The figure shows that the residual volume of the Σ3 twin boundary in the GH3536 alloy strip in Example 2 of this application is 31%. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0033] The range descriptions used herein, such as numerical ranges and proportional ranges, include all possible sub-ranges and single numerical values ​​within the range. For example, a range description of 1 to 6 or 1~6 covers all sub-ranges (such as 1 to 3, 2 to 5, etc.) and single numbers (such as 1, 2, 3, 4, 5, 6) between 1 and 6. Unless otherwise specified, the terms used herein include, but are not limited to, terms such as "include"; relational terms such as "first" and "second" are used only to distinguish different entities or steps and do not imply an actual order or relationship; and / or indicate that multiple situations may exist individually or simultaneously; expressions such as "at least one," "multiple," and "at least one" refer to any combination of the corresponding objects, including combinations of single or multiple objects. Proportional relationships mentioned herein, such as mass ratio and molar ratio, should be understood as the correspondence between the first and second terms of a proportional expression, according to the order of description. The raw materials, reagents, instruments, and equipment used herein can all be obtained through commercial purchase or prepared by existing methods.

[0034] In a first aspect, embodiments of this application provide a method for cold rolling a nickel-based superalloy to achieve high strength and crack resistance, the method comprising: The GH3536 alloy strip is subjected to billet pretreatment. After solution treatment, the GH3536 alloy strip is water-cooled. The initial microstructure of the GH3536 alloy strip is uniform equiaxed recrystallized grains. The GH3536 alloy strip, after pretreatment of the billet, is subjected to gradient cold rolling. The gradient cold rolling adopts multi-pass room temperature cold rolling without high-temperature intermediate annealing. The final cumulative deformation of the gradient cold rolling is less than 78% of the critical cracking deformation threshold of the GH3536 alloy. The reduction of each pass of the gradient cold rolling does not exceed 20%. The GH3536 alloy strip after gradient cold rolling is subjected to rolling process parameter control, which includes: stress relief treatment of the GH3536 alloy strip between passes, and checking the flatness of the GH3536 alloy strip before each pass to ensure uniform stress distribution. The GH3536 alloy strip, after being controlled by the rolling process parameters, is subjected to low-temperature stress relief post-treatment. The low-temperature stress relief post-treatment is to immediately perform low-temperature stress relief annealing on the GH3536 alloy strip after the final rolling, and then air-cool it to room temperature after annealing. The annealing temperature of the low-temperature stress relief annealing is lower than the recrystallization temperature of the GH3536 alloy.

[0035] In this embodiment, the thickness of the GH3536 alloy strip can be 0.10mm~0.50mm; the composition of the GH3536 alloy by mass fraction can be C: 0.05%~0.10%, Cr: 20.0%~23.0%, Fe: 17.00%~19.00%, Co: 0.50%~1.00%, Mo: 6.0%~8.0%, W: 0.2%~0.5%, B: 0.002%~0.008%, with the balance being Ni.

[0036] In this embodiment, GH3536 alloy strip refers to nickel-based high-temperature alloy strip that has undergone solution treatment and water cooling, with an initial microstructure consisting of uniform equiaxed recrystallized grains. In this embodiment, gradient cold rolling refers to a cold rolling method employing multi-pass room-temperature cold rolling without high-temperature intermediate annealing, where the final cumulative deformation is below the critical cracking deformation threshold of GH3536 alloy, and the reduction in each pass does not exceed a specific upper limit. In this embodiment, multi-pass room-temperature cold rolling refers to performing multi-pass continuous cold rolling of GH3536 alloy strip at ambient temperature without using heating methods to increase the rolling temperature. In this embodiment, the critical cracking deformation threshold refers to the cumulative deformation limit at which macroscopic or microscopic cracks begin to form in GH3536 alloy during cold rolling. In this embodiment, the interval between passes refers to the time interval between two adjacent rolling passes in gradient cold rolling. In this embodiment, the recrystallization temperature refers to the temperature limit at which recrystallization begins in GH3536 alloy during annealing.

[0037] The inventive approach of this application compared to the prior art lies in the following: the prior art uses single-pass large-reduction cold rolling or supplemented by high-temperature intermediate annealing. The former leads to severe cracking due to excessive deformation, while the latter results in insufficient strength due to the elimination of work hardening by high-temperature annealing. This solution is the first to use a synergistic process of critical deformation control + low-energy twin boundary retention + graded stress relief. It abandons high-temperature intermediate annealing and replaces the stress elimination function of high-temperature annealing with multi-pass gradient rolling and inter-pass stress relief. At the same time, it eliminates residual stress by low-temperature stress relief post-treatment while retaining the work hardened structure, thus breaking through the technical bottleneck of the prior art where high strength and crack resistance cannot be achieved simultaneously.

[0038] The cumulative deformation of the final rolling in gradient cold rolling is lower than the critical cracking deformation threshold of GH3536 alloy, including but not limited to: 50%, 55%, 60%, 65%, 70%, 75%, etc. The reduction in each pass of gradient cold rolling does not exceed 20%, including but not limited to: 5%, 8%, 10%, 12%, 15%, 18%, 20%, etc.

[0039] In some embodiments, the solution treatment is a solution treatment performed by holding at 1175℃±5℃ for 25min~35min followed by water cooling, and the initial Σ3 twin boundary volume ratio of the GH3536 alloy strip is ≥55%.

[0040] In this embodiment, solution treatment refers to a heat treatment process involving holding the GH3536 alloy strip at a specific temperature followed by water cooling. In this embodiment, Σ3 twin boundaries refer to low-energy grain boundary structures in the GH3536 alloy strip that have a specific crystallographic orientation relationship.

[0041] Solution treatment is limited to holding at a specific temperature for a specific time followed by water cooling solution treatment, so that the alloying elements in GH3536 alloy strip are fully dissolved in the matrix, thereby obtaining a uniform and single austenitic structure, and thus providing an initial billet with uniform composition and stable structure for subsequent cold rolling forming.

[0042] Water-cooled solution treatment allows the GH3536 alloy strip to cool rapidly after solution treatment, thereby inhibiting the nucleation and growth of precipitated phases during the cooling process, and thus maintaining the supersaturated solution effect and microstructure uniformity of the solution state.

[0043] The initial Σ3 twin boundary volume ratio of GH3536 alloy strip reaches a specific lower limit, so that GH3536 alloy strip has sufficient low-energy grain boundary reserves in the initial microstructure. Thus, in the subsequent gradient cold rolling forming, even if some Σ3 twin boundaries are transformed due to deformation, there is still a sufficient proportion of Σ3 twin boundaries remaining to maintain slip transfer efficiency, thereby reducing grain boundary stress concentration.

[0044] Solution treatment involves holding at a specific temperature for a specific time followed by water cooling, including but not limited to: holding at 1170℃ for 25 min, 1172℃ for 28 min, 1175℃ for 30 min, 1178℃ for 33 min, and 1180℃ for 35 min. The initial Σ3 twin boundary volume ratio of the GH3536 alloy strip reaches a specific lower limit, including but not limited to: 55%, 56%, 57%, 58%, 60%, 62%, and 65%.

[0045] In some embodiments, the cumulative reduction of the gradient cold rolling is increased in stages, reaching 10% in the first stage, 30% in the second stage, 50% in the third stage, and 70% in the fourth stage, and the final cumulative deformation of the gradient cold rolling is 70%.

[0046] The cumulative reduction in gradient cold rolling is gradually increased in stages, with the first stage reaching a specific proportion, the second stage reaching a specific proportion, the third stage reaching a specific proportion, and the fourth stage reaching a specific proportion. This allows the deformation of the GH3536 alloy strip to gradually increase in each stage, thereby avoiding excessive deformation in the initial stage that could lead to premature destruction of the grain boundary structure. This, in turn, provides space for the gradual adaptation and control of the Σ3 twin boundaries.

[0047] The first stage, a low-strain plastic deformation stage with a specific ratio, allows the GH3536 alloy strip to undergo plastic deformation primarily through uniform slip during the initial deformation, thereby establishing a stable dislocation configuration and substructure, which in turn lays the microstructure foundation for subsequent stages of deformation.

[0048] The second stage is a uniform refinement stage that reaches a specific ratio, which gradually refines the grains of GH3536 alloy strip as the cumulative deformation increases, thereby improving the uniformity of the structure and avoiding local deformation concentration.

[0049] The third stage is the substructure regulation stage with a specific ratio, which enables the GH3536 alloy strip to form a stable subcrystalline structure under greater deformation, thereby optimizing the dislocation distribution and grain boundary configuration, and thus maintaining the continuity of slip transmission.

[0050] The fourth stage is the final rolling and shaping stage, which reaches a specific ratio, so that the GH3536 alloy strip completes the target deformation in the final stage, thereby obtaining the required thickness and mechanical properties, and thus realizing the precision forming of the strip and foil.

[0051] By limiting the cumulative deformation of the final rolling in gradient cold rolling to a specific ratio, the total deformation of GH3536 alloy strip is precisely controlled below the safety threshold, thereby ensuring that the final rolled product avoids the critical cracking deformation threshold and thus completely avoids the generation of macro and micro cracks.

[0052] The cumulative reduction in gradient cold rolling increases progressively in stages, reaching specific percentages in the first, second, third, and fourth stages, including but not limited to: 10% in the first stage, 30% in the second stage, 50% in the third stage, and 70% in the fourth stage. The final cumulative deformation in gradient cold rolling is a specific percentage, including but not limited to: 65%, 68%, 70%, 72%, and 75%.

[0053] In some embodiments, the reduction per pass of the gradient cold rolling process is 10% to 18%.

[0054] By limiting the reduction amount in each pass of gradient cold rolling to a specific range, the local deformation of GH3536 alloy strip in each rolling pass is more strictly constrained, thereby further reducing the peak grain boundary stress caused by single-pass deformation and thus more effectively maintaining the structural stability of Σ3 twin boundaries.

[0055] The reduction amount in each pass is controlled above the lower limit of a specific range, so that the GH3536 alloy strip can obtain sufficient plastic deformation in each pass to promote the cumulative deformation process, thereby avoiding too many rolling passes and low production efficiency due to too small a reduction amount, and thus ensuring the economic efficiency of the process.

[0056] The reduction amount in each pass is controlled below the upper limit within a specific range, so that the deformation of the GH3536 alloy strip in each pass is insufficient to trigger grain boundary cracking, thereby suppressing shear band initiation and maintaining the continuity of slip transmission.

[0057] The reduction amount in each pass of gradient cold rolling is a specific percentage, including but not limited to: 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, etc.

[0058] In some embodiments, the control of rolling process parameters further includes controlling the rolling speed to be 0.15 m / s to 0.25 m / s.

[0059] The control of rolling process parameters is extended to include controlling the rolling speed within a specific range, so that the GH3536 alloy strip passes through the rolls at a moderate speed during the rolling process, thereby avoiding the accumulation of deformation heat and local temperature rise caused by excessive rolling speed, and thus preventing the uneven structure and thermal stress caused by temperature rise.

[0060] The rolling speed is controlled above the lower limit of a specific range to ensure sufficient production efficiency of GH3536 alloy strip during the rolling process, thereby avoiding the extension of the production cycle due to excessively slow speed and thus ensuring the economic efficiency of the process.

[0061] The rolling speed is controlled below the upper limit of a specific range, so that the GH3536 alloy strip has sufficient time for plastic deformation and stress relaxation in each rolling pass, thereby avoiding dislocation pile-up and grain boundary stress concentration caused by excessive deformation rate, and thus maintaining smooth slip transfer.

[0062] The rolling speed is a specific value, including but not limited to: 0.15m / s, 0.16m / s, 0.18m / s, 0.20m / s, 0.22m / s, 0.24m / s, 0.25m / s, etc.

[0063] In some embodiments, the stress relief treatment of the GH3536 alloy strip between passes includes: After each rolling pass, the GH3536 alloy strip is placed in a constant temperature and dust-free environment at 25℃±3℃ for 6min~9min to naturally release the residual stress between passes.

[0064] In this embodiment, natural stress release refers to the process by which residual stress gradually decreases due to the stress relaxation of the GH3536 alloy strip itself, without the aid of external heating or mechanical means. In this embodiment, inter-pass residual stress refers to the stress remaining inside the GH3536 alloy strip after each rolling pass.

[0065] After each rolling pass, the GH3536 alloy strip is placed in a constant temperature and dust-free environment for a specific time to allow the GH3536 alloy strip to relax under stable ambient temperature and clean conditions. This avoids thermal stress interference caused by temperature fluctuations and surface defects caused by dust particles, thereby ensuring the purity and stability of the stress relief treatment.

[0066] The constant temperature environment keeps the GH3536 alloy strip at a constant temperature field between passes, thereby avoiding additional thermal stress and microstructure instability caused by temperature changes, and ensuring that residual stress is generated only by rolling deformation.

[0067] The dust-free environment prevents the surface of GH3536 alloy strip from being contaminated by foreign particles during the resting process, thereby avoiding microscopic defects on the surface from becoming sources of crack initiation in subsequent rolling passes and maintaining surface integrity.

[0068] Allowing the GH3536 alloy strip to stand for a specific period of time gives the dislocations enough time to rearrange and annihilate, thereby gradually reducing the residual stress between passes through natural release and thus reducing the stress superposition effect during the next rolling pass.

[0069] The natural release of residual stress between passes significantly reduces the internal stress level of GH3536 alloy strip at the start of the next rolling pass, thereby preventing the cumulative residual stress and the newly added rolling stress from exceeding the material's yield limit and thus inhibiting crack initiation.

[0070] The temperature of the constant temperature and dust-free environment is a specific value, including but not limited to: 22℃, 23℃, 24℃, 25℃, 26℃, 27℃, 28℃, etc. The settling time is a specific value, including but not limited to: 6min, 7min, 8min, 9min, etc.

[0071] In some embodiments, the low-temperature stress-relief annealing is a low-temperature stress-relief annealing performed at 250℃±5℃ for 55min~65min.

[0072] Low-temperature stress-relief annealing is defined as low-temperature stress-relief annealing with a specific temperature and holding time, so that the GH3536 alloy strip can be stress-relieved under precisely controlled low-temperature conditions, thereby ensuring that the annealing temperature is always lower than the recrystallization temperature of the GH3536 alloy, and thus strictly avoiding the occurrence of recrystallization.

[0073] The annealing temperature at a specific temperature allows the residual stress in the GH3536 alloy strip to obtain sufficient thermal activation energy for relaxation, thereby promoting dislocation rearrangement and annihilation, and effectively eliminating residual stress and lattice distortion.

[0074] The annealing temperature at a specific temperature is lower than the recrystallization temperature of GH3536 alloy, which results in insufficient driving force for recrystallization nucleation in GH3536 alloy strip, thereby inhibiting the nucleation and growth of new grains and thus preserving the work-hardened structure of the cold-rolled state.

[0075] Holding the material for a specific time ensures that the stress in the GH3536 alloy strip is fully eliminated during the low-temperature stress-relief annealing process, thereby avoiding incomplete elimination of residual stress due to insufficient holding time and thus ensuring the stress relief effect.

[0076] Low-temperature stress-relief annealing refers to low-temperature stress-relief annealing that involves holding at a specific temperature for a specific time, including but not limited to: holding at 245℃ for 55 min, holding at 248℃ for 58 min, holding at 250℃ for 60 min, holding at 252℃ for 62 min, holding at 255℃ for 65 min, etc.

[0077] In some embodiments, the gradient cold rolling forming adopts a gradient cold rolling process with small incremental step-down. The residual volume ratio of Σ3 twin boundaries in the final rolled product is controlled to be ≥20% through the gradient cold rolling process with small incremental step-down, so as to improve slip transfer efficiency and reduce grain boundary stress concentration.

[0078] In the embodiments of this application, "small incremental step-by-step reduction" refers to a reduction method in which the reduction amount in each pass of gradient cold rolling is gradually increased by a small increment. In the embodiments of this application, "slip transfer efficiency" refers to the smoothness of dislocation slip transfer from one grain to the other at the grain boundary. In the embodiments of this application, "grain boundary stress concentration" refers to the phenomenon of stress accumulating locally at the grain boundary to form a stress peak.

[0079] Gradient cold rolling forming adopts a gradient cold rolling process with small incremental reduction in each stage, so that the reduction increment of GH3536 alloy strip in each pass is small, thereby avoiding the severe damage to the grain boundary structure caused by abrupt deformation in a single pass, and thus creating conditions for the gradual adaptation and preservation of Σ3 twin boundaries.

[0080] By controlling the residual volume ratio of Σ3 twin boundaries in the final rolled product to a specific lower limit through a gradient cold rolling process with small increments, sufficient low-energy grain boundaries are retained in the final rolled product. This allows the low-energy characteristics of Σ3 twin boundaries to be utilized to improve slip transfer efficiency, thereby enabling dislocation slip to be smoothly transferred at the grain boundaries without pile-up.

[0081] The improved slip transfer efficiency makes the stress distribution of GH3536 alloy strip more uniform during cold rolling deformation, thereby reducing the stress peak at the grain boundaries and inhibiting grain boundary cracking and crack initiation.

[0082] The reduction of grain boundary stress concentration ensures that the local stress at the grain boundary of GH3536 alloy strip remains below the critical value for cracking during cold rolling, thereby preventing crack nucleation and propagation at the grain boundary and ensuring defect-free forming of GH3536 alloy strip.

[0083] The residual volume percentage of Σ3 twin boundaries in the final rolled product reaches a specific lower limit, including but not limited to: 20%, 22%, 24%, 26%, 28%, 30%, etc.

[0084] In some embodiments, the billet pretreatment further includes: The GH3536 alloy strip is mechanically ground to remove surface burrs and oxide scale; The GH3536 alloy strip, after being mechanically polished, is placed in a mixed hydrochloric acid-sulfuric acid solution for pickling at room temperature for 5 to 8 minutes to remove residual impurities on the surface. The GH3536 alloy strip, after being pickled at room temperature, is rinsed with water and then dried. The surface roughness Ra of the GH3536 alloy strip is controlled to be ≤1.2μm.

[0085] The pretreatment of the billet also includes mechanical grinding of the GH3536 alloy strip to remove surface burrs and oxide scale, so that the macroscopic defects and oxide layer on the surface of the GH3536 alloy strip are removed, thereby avoiding surface burrs from scratching the surface of the GH3536 alloy strip or becoming a source of crack initiation during the rolling process, thus ensuring the surface quality of subsequent cold rolling.

[0086] After mechanical grinding, the GH3536 alloy strip is placed in a hydrochloric acid-sulfuric acid mixed solution for pickling at room temperature for a specific time to remove residual impurities on the surface. This chemically dissolves the micro-oxides, oil stains, and residual impurities on the surface of the GH3536 alloy strip, thereby obtaining a clean metal surface and eliminating the adverse effects of micro-surface defects on subsequent rolling.

[0087] Ambient temperature pickling cleans the surface of GH3536 alloy strip at ambient temperature, thus avoiding the risk of matrix structure changes or hydrogen embrittlement caused by heated pickling, thereby ensuring that the matrix properties of GH3536 alloy strip are not damaged.

[0088] After being acid-washed at room temperature, the GH3536 alloy strip is rinsed with clean water and then dried. This process thoroughly removes and dries the acid residue and reaction products from the surface of the GH3536 alloy strip, thereby preventing the acid residue from continuing to corrode the surface of the GH3536 alloy strip and maintaining the surface treatment effect.

[0089] By controlling the surface roughness of GH3536 alloy strip to a specific upper limit, the micro-unevenness of the GH3536 alloy strip surface is constrained, thereby avoiding excessive surface roughness that leads to local stress concentration during rolling, and thus ensuring uniform stress distribution on the GH3536 alloy strip during rolling.

[0090] The pickling time at room temperature is a specific value, including but not limited to: 5 min, 6 min, 7 min, 8 min, etc. The surface roughness Ra of GH3536 alloy strip reaches a specific upper limit, including but not limited to: 0.5 μm, 0.8 μm, 1.0 μm, 1.1 μm, 1.2 μm, etc.

[0091] In some embodiments, the pickling time at room temperature is 5 min to 7 min, and the surface roughness Ra of the GH3536 alloy strip is 1.0 μm to 1.1 μm.

[0092] By limiting the pickling time at room temperature to a specific range, the immersion time of GH3536 alloy strip in the mixed acid solution can be more precisely controlled. This ensures that surface impurities are fully removed while avoiding substrate damage caused by excessive pickling, thereby optimizing the surface treatment effect and substrate integrity.

[0093] The surface roughness Ra of GH3536 alloy strip is limited to a specific range, which controls the micro-unevenness of the surface of GH3536 alloy strip within a narrower range, thereby further reducing the risk of local stress concentration during the rolling process and thus more effectively ensuring the uniformity of stress distribution.

[0094] The surface roughness Ra is controlled above the lower limit within a specific range, so that the surface of GH3536 alloy strip retains a moderate micro-roughness to enhance frictional engagement during rolling, thereby avoiding rolling slippage caused by an overly smooth surface and ensuring rolling stability.

[0095] By controlling the surface roughness Ra below the upper limit within a specific range, the height of the microscopic peaks and valleys on the surface of the GH3536 alloy strip is limited, thereby avoiding the local compressive stress concentration caused by excessively high surface roughness during rolling, and thus inhibiting the initiation of surface cracks.

[0096] The pickling time at room temperature is a specific value, including but not limited to: 5 min, 6 min, 7 min, etc. The surface roughness Ra of GH3536 alloy strip is a specific value, including but not limited to: 1.0 μm, 1.05 μm, 1.1 μm, etc.

[0097] In some embodiments, the GH3536 alloy strip / foil prepared by the method has a Σ3 twin boundary residual volume ratio of ≥20% and a GND density of 12.0 × 10⁻⁶. 14 m -2~15.0×10 14 m -2 Yield strength ≥1400MPa, tensile strength ≥1500MPa, elongation ≥5.0%, product qualification rate ≥96%, and no macroscopic or microscopic cracks.

[0098] In this embodiment, GND density refers to geometrically necessary dislocation density, characterizing the dislocation density present in GH3536 alloy strip and foil due to deformation compatibility requirements. In this embodiment, macroscopic cracks refer to crack defects visible to the naked eye. In this embodiment, microscopic cracks refer to crack defects that require microscopic observation.

[0099] The method prepares GH3536 alloy strips and foils with a Σ3 twin boundary residual volume ratio that reaches a specific lower limit, thus retaining sufficient low-energy grain boundaries in the GH3536 alloy strips and foils, thereby improving slip transfer efficiency and reducing grain boundary stress concentration, and thus inhibiting crack initiation.

[0100] The GND density of GH3536 alloy strip and foil reaches a specific range, so that the GH3536 alloy strip and foil has a moderate geometrically necessary dislocation density, thereby improving the strength of GH3536 alloy strip and foil through the dislocation strengthening mechanism, while avoiding the aggravation of grain boundary stress concentration caused by excessive dislocation density, thus achieving a balance between strength and crack resistance.

[0101] The yield strength of GH3536 alloy strip and foil reaches a specific lower limit, enabling it to withstand high working loads without plastic deformation during service. This meets the high load-bearing requirements of sealing components for aero engines and heavy gas turbines, thereby ensuring service safety.

[0102] The tensile strength of GH3536 alloy strip and foil reaches a specific lower limit, giving it excellent ultimate load-bearing capacity under tensile loads, thereby avoiding fracture failure during service and extending the service life of components.

[0103] The elongation of GH3536 alloy strip and foil reaches a specific lower limit, which allows GH3536 alloy strip and foil to retain a certain plastic deformation capacity while possessing high strength. This enables it to alleviate stress concentration through local plastic deformation during service, thereby avoiding brittle fracture.

[0104] The product qualification rate of GH3536 alloy strip and foil reaches a certain lower limit, which significantly improves the quality stability of GH3536 alloy strip and foil products, thereby greatly reducing material loss and production costs, and thus adapting to the needs of large-scale production.

[0105] GH3536 alloy strip and foil are free of macroscopic and microscopic cracks, which completely avoids cracking defects during the forming process, thereby ensuring the integrity and reliability of the components and meeting the defect-free precision forming requirements of sealing components for aero-engines and heavy gas turbines.

[0106] The residual volume percentage of Σ3 twin boundaries in GH3536 alloy strips and foils reaches a specific lower limit, including but not limited to: 20%, 21%, 22%, 23%, 25%, etc. The GND density of GH3536 alloy strips and foils is a specific value, including but not limited to: 12.0 × 10⁻⁶. 14 m -2 12.5×10 14 m -2 13×10 14 m -2 13.5×10 14 m -2 14×10 14 m -2 14.5×10 14 m -2 15.0×10 14 m -2 The yield strength of GH3536 alloy strip and foil reaches a specific lower limit, including but not limited to: 1400MPa, 1450MPa, 1500MPa, etc. The tensile strength of GH3536 alloy strip and foil reaches a specific lower limit, including but not limited to: 1525MPa, 1528MPa, 1530MPa, 1535MPa, 1540MPa, etc. The elongation of GH3536 alloy strip and foil reaches a specific lower limit, including but not limited to: 5.2%, 5.3%, 5.5%, 5.8%, 6.0%, etc. The product qualification rate of GH3536 alloy strip and foil reaches a specific lower limit, including but not limited to: 96%, 96.5%, 97%, 98%, 99%, etc.

[0107] Secondly, embodiments of this application provide an application of the method described in any of the first aspects, the method being used for the preparation of GH3536 alloy strip and foil for sealing components of aero-engines or heavy-duty gas turbines.

[0108] In this embodiment of the application, "strip or foil material" refers to a thin strip or foil-shaped metal material.

[0109] The method is used to prepare GH3536 alloy strip and foil for sealing components of aero-engines or heavy gas turbines, which clearly points the application field of GH3536 alloy strip and foil to the harsh service environment of high temperature, high pressure and high stress. Therefore, GH3536 alloy strip and foil must have high strength to withstand extreme loads, and at the same time must have crack resistance to ensure long-term service reliability. This puts forward a rigid requirement for the preparation method to take into account both high strength and crack resistance.

[0110] GH3536 alloy strip and foil used in aero-engine sealing components are subjected to high-temperature gas erosion and mechanical vibration during service. Therefore, GH3536 alloy strip and foil must have excellent high-temperature mechanical stability and resistance to fatigue crack propagation. This requires that the work-hardened structure be completely preserved and residual stress be eliminated during the manufacturing process to ensure service safety.

[0111] The GH3536 alloy strip and foil used in the sealing components of heavy-duty gas turbines are subjected to high pressure differential and thermal cycling stress during service. This requires the GH3536 alloy strip and foil to have high yield strength to resist deformation and crack resistance to prevent sealing failure. Therefore, it is necessary to strictly control the amount of deformation and retain low-energy grain boundaries during the manufacturing process to ensure the reliability of the seal.

[0112] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to industry standards. If there is no corresponding industry standard, then generally accepted international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0113] I. Implementation Examples

[0114] Example 1 The GH3536 alloy strip is subjected to billet pretreatment. The GH3536 alloy strip is subjected to water-cooled solution treatment after being held at 1175℃ for 30 minutes. The initial microstructure of the GH3536 alloy strip is uniform equiaxed recrystallized grains, and the initial Σ3 twin boundary volume ratio of the GH3536 alloy strip is 55%.

[0115] The GH3536 alloy strip is mechanically ground to remove surface burrs and oxide scale.

[0116] The GH3536 alloy strip, after being mechanically polished, is placed in a hydrochloric acid-sulfuric acid mixed solution for pickling at room temperature for 6 minutes to remove residual impurities on the surface of the GH3536 alloy strip.

[0117] The GH3536 alloy strip, after being pickled at room temperature, is rinsed with water and then dried.

[0118] The surface roughness Ra of the GH3536 alloy strip is controlled to be 1.1 μm.

[0119] The GH3536 alloy strip, after pretreatment of the billet, is subjected to gradient cold rolling. The gradient cold rolling adopts multi-pass room temperature cold rolling without high-temperature intermediate annealing. The cumulative reduction of the gradient cold rolling increases progressively in the following stages: 10% in the first stage, 30% in the second stage, 50% in the third stage, and 70% in the fourth stage. The final cumulative deformation of the gradient cold rolling is 70%, and the reduction of each pass of the gradient cold rolling is 12% to 18%.

[0120] The GH3536 alloy strip, after being formed by gradient cold rolling, is subject to rolling process parameter control, which includes: controlling the rolling speed to 0.2 m / s; performing stress relief treatment on the GH3536 alloy strip between passes, wherein after each rolling pass, the GH3536 alloy strip is placed in a constant temperature and dust-free environment at 25°C and left to stand for 8 minutes to naturally relieve residual stress between passes; and checking the flatness of the GH3536 alloy strip before each rolling pass to ensure uniform stress distribution.

[0121] The GH3536 alloy strip, after being controlled by the rolling process parameters, is subjected to low-temperature stress relief post-treatment. The low-temperature stress relief post-treatment is to immediately after the final rolling is completed, the GH3536 alloy strip is held at 250°C for 60 minutes for low-temperature stress relief annealing, and then air-cooled to room temperature.

[0122] The GH3536 alloy strip and foil prepared by the method were tested and found to be free of macroscopic and microscopic cracks. The residual volume of Σ3 twin boundaries in the GH3536 alloy strip and foil was 32%, and the GND density of the GH3536 alloy strip and foil was 13.8 × 10⁻⁶. 14 m -2 The GH3536 alloy strip and foil has a yield strength of 1490 MPa, a tensile strength of 1530 MPa, an elongation of 5.2%, and a product qualification rate of 96.5%.

[0123] Example 2 The GH3536 alloy strip is subjected to billet pretreatment. The GH3536 alloy strip is subjected to water-cooled solution treatment after being held at 1180℃ for 30 minutes. The initial microstructure of the GH3536 alloy strip is uniform equiaxed recrystallized grains, and the initial Σ3 twin boundary volume ratio of the GH3536 alloy strip is 57%.

[0124] The GH3536 alloy strip is mechanically ground to remove surface burrs and oxide scale.

[0125] The GH3536 alloy strip, after being mechanically polished, is placed in a hydrochloric acid-sulfuric acid mixed solution for pickling at room temperature for 6 minutes to remove residual impurities on the surface of the GH3536 alloy strip.

[0126] The GH3536 alloy strip, after being pickled at room temperature, is rinsed with water and then dried.

[0127] The surface roughness Ra of the GH3536 alloy strip is controlled to be 1.0 μm.

[0128] The GH3536 alloy strip, after pretreatment of the billet, is subjected to gradient cold rolling. The gradient cold rolling adopts multi-pass room temperature cold rolling without high-temperature intermediate annealing. The cumulative reduction of the gradient cold rolling increases progressively in the following stages: 10% in the first stage, 30% in the second stage, 50% in the third stage, and 70% in the fourth stage. The final cumulative deformation of the gradient cold rolling is 70%, and the reduction of each pass of the gradient cold rolling is 10% to 15%.

[0129] The GH3536 alloy strip, after being formed by gradient cold rolling, undergoes rolling process parameter control, which includes: controlling the rolling speed to 0.2 m / s; performing stress relief treatment on the GH3536 alloy strip between passes, wherein after each rolling pass, the GH3536 alloy strip is placed in a constant temperature and dust-free environment at 25°C and left to stand for 7 minutes to naturally release residual stress between passes; and checking the flatness of the GH3536 alloy strip before each rolling pass to ensure uniform stress distribution.

[0130] The GH3536 alloy strip, after being controlled by the rolling process parameters, is subjected to low-temperature stress relief post-treatment. The low-temperature stress relief post-treatment is to immediately after the final rolling is completed, the GH3536 alloy strip is held at 245℃ for 60 minutes for low-temperature stress relief annealing, and then air-cooled to room temperature.

[0131] The GH3536 alloy strip and foil prepared by the method were tested and found to be free of macroscopic and microscopic cracks. The residual volume of the Σ3 twin boundaries in the GH3536 alloy strip and foil was 31%, and the GND density of the GH3536 alloy strip and foil was 13.6 × 10⁻⁶. 14 m -2The GH3536 alloy strip and foil has a yield strength of 1488 MPa, a tensile strength of 1528 MPa, an elongation of 5.5%, and a product qualification rate of 96%.

[0132] Example 3 The GH3536 alloy strip is subjected to billet pretreatment. The GH3536 alloy strip is subjected to water-cooled solution treatment after being held at 1175℃ for 30 minutes. The initial microstructure of the GH3536 alloy strip is uniform equiaxed recrystallized grains, and the initial Σ3 twin boundary volume ratio of the GH3536 alloy strip is 56%.

[0133] The GH3536 alloy strip is mechanically ground to remove surface burrs and oxide scale.

[0134] The GH3536 alloy strip, after being mechanically polished, is placed in a hydrochloric acid-sulfuric acid mixed solution for pickling at room temperature for 7 minutes to remove residual impurities on the surface of the GH3536 alloy strip.

[0135] The GH3536 alloy strip, after being pickled at room temperature, is rinsed with water and then dried.

[0136] The surface roughness Ra of the GH3536 alloy strip is controlled to be 1.0 μm.

[0137] The GH3536 alloy strip, after pretreatment of the billet, is subjected to gradient cold rolling. The gradient cold rolling adopts multi-pass room temperature cold rolling without high-temperature intermediate annealing. The cumulative reduction of the gradient cold rolling increases progressively in the following stages: 10% in the first stage, 30% in the second stage, 50% in the third stage, and 70% in the fourth stage. The final cumulative deformation of the gradient cold rolling is 70%, and the reduction of each pass of the gradient cold rolling is 15% to 18%.

[0138] The GH3536 alloy strip, after being formed by gradient cold rolling, is subject to rolling process parameter control, which includes: controlling the rolling speed to 0.18 m / s; performing stress relief treatment on the GH3536 alloy strip between passes, wherein after each rolling pass, the GH3536 alloy strip is placed in a constant temperature and dust-free environment at 23°C and left to stand for 9 minutes to naturally relieve residual stress between passes; and checking the flatness of the GH3536 alloy strip before each rolling pass to ensure uniform stress distribution.

[0139] The GH3536 alloy strip, after being controlled by the rolling process parameters, is subjected to low-temperature stress relief post-treatment. The low-temperature stress relief post-treatment is to immediately after the final rolling is completed, the GH3536 alloy strip is held at 248℃ for 58 minutes for low-temperature stress relief annealing, and then air-cooled to room temperature.

[0140] The GH3536 alloy strip and foil prepared by the method were tested and found to be free of macroscopic and microscopic cracks. The residual volume of the Σ3 twin boundaries in the GH3536 alloy strip and foil was 33%, and the GND density of the GH3536 alloy strip and foil was 12.5 × 10⁻⁶. 14 m -2 The GH3536 alloy strip and foil has a yield strength of 1492 MPa, a tensile strength of 1532 MPa, an elongation of 5.3%, and a product qualification rate of 97%.

[0141] Example 4 The GH3536 alloy strip is subjected to billet pretreatment. The GH3536 alloy strip is subjected to water-cooled solution treatment after being held at 1170℃ for 35 minutes. The initial microstructure of the GH3536 alloy strip is uniform equiaxed recrystallized grains, and the initial Σ3 twin boundary volume ratio of the GH3536 alloy strip is 58%.

[0142] The GH3536 alloy strip is mechanically ground to remove surface burrs and oxide scale.

[0143] The GH3536 alloy strip, after being mechanically polished, is placed in a hydrochloric acid-sulfuric acid mixed solution for pickling at room temperature for 5 minutes to remove residual impurities on the surface of the GH3536 alloy strip.

[0144] The GH3536 alloy strip, after being pickled at room temperature, is rinsed with water and then dried.

[0145] The surface roughness Ra of the GH3536 alloy strip is controlled to be 1.2 μm.

[0146] The GH3536 alloy strip, after pretreatment of the billet, is subjected to gradient cold rolling. The gradient cold rolling adopts multi-pass room temperature cold rolling without high-temperature intermediate annealing. The cumulative reduction of the gradient cold rolling increases progressively in the following stages: 10% in the first stage, 30% in the second stage, 50% in the third stage, and 70% in the fourth stage. The final cumulative deformation of the gradient cold rolling is 68%, and the reduction of each pass of the gradient cold rolling is 10%~12%.

[0147] The GH3536 alloy strip, after being formed by gradient cold rolling, is subject to rolling process parameter control, which includes: controlling the rolling speed to 0.25 m / s; performing stress relief treatment on the GH3536 alloy strip between passes, wherein after each rolling pass, the GH3536 alloy strip is placed in a constant temperature and dust-free environment at 27°C and left to stand for 6 minutes to naturally relieve residual stress between passes; and checking the flatness of the GH3536 alloy strip before each rolling pass to ensure uniform stress distribution.

[0148] The GH3536 alloy strip, after being controlled by the rolling process parameters, is subjected to low-temperature stress relief post-treatment. The low-temperature stress relief post-treatment is to immediately after the final rolling is completed, the GH3536 alloy strip is held at 252℃ for 62 minutes for low-temperature stress relief annealing, and then air-cooled to room temperature.

[0149] The GH3536 alloy strip and foil prepared by the method were tested and found to be free of macroscopic and microscopic cracks. The residual volume of the Σ3 twin boundaries in the GH3536 alloy strip and foil was 35%, and the GND density of the GH3536 alloy strip and foil was 12.2 × 10⁻⁶. 14 m -2 The GH3536 alloy strip and foil has a yield strength of 1485 MPa, a tensile strength of 1525 MPa, an elongation of 5.8%, and a product qualification rate of 96%.

[0150] Example 5 The GH3536 alloy strip is subjected to billet pretreatment. The GH3536 alloy strip is subjected to water-cooled solution treatment after being held at 1180℃ for 25 minutes. The initial microstructure of the GH3536 alloy strip is uniform equiaxed recrystallized grains, and the initial Σ3 twin boundary volume ratio of the GH3536 alloy strip is 60%.

[0151] The GH3536 alloy strip is mechanically ground to remove surface burrs and oxide scale.

[0152] The GH3536 alloy strip, after being mechanically polished, is placed in a hydrochloric acid-sulfuric acid mixed solution for pickling at room temperature for 8 minutes to remove residual impurities on the surface of the GH3536 alloy strip.

[0153] The GH3536 alloy strip, after being pickled at room temperature, is rinsed with water and then dried.

[0154] The surface roughness Ra of the GH3536 alloy strip is controlled to be 0.8 μm.

[0155] The GH3536 alloy strip, after pretreatment of the billet, is subjected to gradient cold rolling. The gradient cold rolling adopts multi-pass room temperature cold rolling without high-temperature intermediate annealing. The cumulative reduction of the gradient cold rolling increases progressively in the following stages: 10% in the first stage, 30% in the second stage, 50% in the third stage, and 70% in the fourth stage. The final cumulative deformation of the gradient cold rolling is 72%, and the reduction of each pass of the gradient cold rolling is 16% to 18%.

[0156] The GH3536 alloy strip, after being formed by gradient cold rolling, is subject to rolling process parameter control, which includes: controlling the rolling speed to 0.15 m / s; performing stress relief treatment on the GH3536 alloy strip between passes, wherein after each rolling pass, the GH3536 alloy strip is placed in a constant temperature and dust-free environment at 24°C and left to stand for 8 minutes to naturally relieve residual stress between passes; and checking the flatness of the GH3536 alloy strip before each rolling pass to ensure uniform stress distribution.

[0157] The GH3536 alloy strip, after being controlled by the rolling process parameters, is subjected to low-temperature stress relief post-treatment. The low-temperature stress relief post-treatment is to immediately after the final rolling is completed, the GH3536 alloy strip is held at 255℃ for 55 minutes for low-temperature stress relief annealing, and then air-cooled to room temperature.

[0158] The GH3536 alloy strip and foil prepared by the method were tested and found to be free of macroscopic and microscopic cracks. The residual volume of the Σ3 twin boundaries in the GH3536 alloy strip and foil was 30%, and the GND density of the GH3536 alloy strip and foil was 14.0 × 10⁻⁶. 14 m -2 The GH3536 alloy strip and foil has a yield strength of 1495 MPa, a tensile strength of 1535 MPa, an elongation of 5.0%, and a product qualification rate of 95%.

[0159] II. Comparative Example Comparative Example 1 (Traditional single-pass large reduction process) The GH3536 alloy strip is subjected to billet pretreatment. The GH3536 alloy strip is subjected to water-cooled solution treatment after being held at 1175℃ for 30 minutes. The initial microstructure of the GH3536 alloy strip is uniform equiaxed recrystallized grains, and the initial Σ3 twin boundary volume ratio of the GH3536 alloy strip is 55%.

[0160] The GH3536 alloy strip is mechanically ground to remove surface burrs and oxide scale.

[0161] The GH3536 alloy strip, after being mechanically polished, is placed in a hydrochloric acid-sulfuric acid mixed solution for pickling at room temperature for 6 minutes to remove residual impurities on the surface of the GH3536 alloy strip.

[0162] The GH3536 alloy strip, after being pickled at room temperature, is rinsed with water and then dried.

[0163] The surface roughness Ra of the GH3536 alloy strip is controlled to be 1.1 μm.

[0164] The GH3536 alloy strip, after pretreatment of the billet, is directly cold rolled to 78% deformation. The cold rolling is a single-pass large-reduction cold rolling, without inter-pass static resting process or low-temperature stress relief post-treatment process.

[0165] The GH3536 alloy strip and foil prepared by the method were tested and found to have: obvious macroscopic microcracks on the surface of the GH3536 alloy strip and foil; a large number of microcracks inside the GH3536 alloy strip and foil; a residual volume of Σ3 twin boundaries of the GH3536 alloy strip and foil; and a GND density of 15.8 × 10⁻⁶. 14 m -2 The GH3536 alloy strip and foil has a yield strength of 1550 MPa, a tensile strength of 1580 MPa, an elongation of 2%, and a product qualification rate of 72%.

[0166] Comparative Example 2 (High-Temperature Intermediate Annealing Process) The GH3536 alloy strip is subjected to billet pretreatment. The GH3536 alloy strip is subjected to water-cooled solution treatment after being held at 1175℃ for 30 minutes. The initial microstructure of the GH3536 alloy strip is uniform equiaxed recrystallized grains, and the initial Σ3 twin boundary volume ratio of the GH3536 alloy strip is 55%.

[0167] The GH3536 alloy strip is mechanically ground to remove surface burrs and oxide scale.

[0168] The GH3536 alloy strip, after being mechanically polished, is placed in a hydrochloric acid-sulfuric acid mixed solution for pickling at room temperature for 6 minutes to remove residual impurities on the surface of the GH3536 alloy strip.

[0169] The GH3536 alloy strip, after being pickled at room temperature, is rinsed with water and then dried.

[0170] The surface roughness Ra of the GH3536 alloy strip is controlled to be 1.1 μm.

[0171] The GH3536 alloy strip, after pretreatment of the billet, is cold-rolled to 50% deformation.

[0172] The GH3536 alloy strip, after being cold-rolled to 50% deformation, was annealed at 800°C for 30 minutes.

[0173] The GH3536 alloy strip, after being annealed at 800℃, is further cold-rolled to 70% deformation.

[0174] The GH3536 alloy strip and foil prepared by the method were tested and found to be free of macroscopic and microscopic cracks. The residual volume of Σ3 twin boundaries in the GH3536 alloy strip and foil was 36%, and the GND density of the GH3536 alloy strip and foil was 11.8 × 10⁻⁶. 14 m -2 The GH3536 alloy strip and foil has a yield strength of 1260 MPa, a tensile strength of 1382 MPa, an elongation of 7.6%, and a product qualification rate of 90%.

[0175] Comparative Example 3 (Inter-pass settling process) The GH3536 alloy strip is subjected to billet pretreatment. The GH3536 alloy strip is subjected to water-cooled solution treatment after being held at 1175℃ for 30 minutes. The initial microstructure of the GH3536 alloy strip is uniform equiaxed recrystallized grains, and the initial Σ3 twin boundary volume ratio of the GH3536 alloy strip is 55%.

[0176] The GH3536 alloy strip is mechanically ground to remove surface burrs and oxide scale.

[0177] The GH3536 alloy strip, after being mechanically polished, is placed in a hydrochloric acid-sulfuric acid mixed solution for pickling at room temperature for 6 minutes to remove residual impurities on the surface of the GH3536 alloy strip.

[0178] The GH3536 alloy strip, after being pickled at room temperature, is rinsed with water and then dried.

[0179] The surface roughness Ra of the GH3536 alloy strip is controlled to be 1.1 μm.

[0180] The GH3536 alloy strip, after pretreatment of the billet, is subjected to gradient cold rolling. The gradient cold rolling adopts multi-pass room temperature cold rolling without high-temperature intermediate annealing. The cumulative reduction of the gradient cold rolling increases progressively in the following stages: 10% in the first stage, 30% in the second stage, 50% in the third stage, and 70% in the fourth stage. The final cumulative deformation of the gradient cold rolling is 70%, and the reduction of each pass of the gradient cold rolling is 12% to 18%.

[0181] The GH3536 alloy strip, after being formed by gradient cold rolling, is subject to rolling process parameter control, which includes: controlling the rolling speed to 0.2 m / s; checking the flatness of the GH3536 alloy strip before each rolling pass to ensure uniform stress; and no resting process between passes.

[0182] The GH3536 alloy strip, after being controlled by the rolling process parameters, is subjected to low-temperature stress relief post-treatment. The low-temperature stress relief post-treatment is to immediately after the final rolling is completed, the GH3536 alloy strip is held at 250°C for 60 minutes for low-temperature stress relief annealing, and then air-cooled to room temperature.

[0183] The GH3536 alloy strip and foil prepared by the method were tested and found to have localized microcracks, significant grain boundary stress concentration, a Σ3 twin boundary residual volume ratio of 22%, and a GND density of 14.8 × 10⁻⁶. 14 m -2 The GH3536 alloy strip and foil has a yield strength of 1558 MPa, a tensile strength of 1462 MPa, an elongation of 5.0%, and a product qualification rate of 83%.

[0184] Comparative Example 4 (without low-temperature stress relief post-treatment process) The GH3536 alloy strip is subjected to billet pretreatment. The GH3536 alloy strip is subjected to water-cooled solution treatment after being held at 1175℃ for 30 minutes. The initial microstructure of the GH3536 alloy strip is uniform equiaxed recrystallized grains, and the initial Σ3 twin boundary volume ratio of the GH3536 alloy strip is 55%.

[0185] The GH3536 alloy strip is mechanically ground to remove surface burrs and oxide scale.

[0186] The GH3536 alloy strip, after being mechanically polished, is placed in a hydrochloric acid-sulfuric acid mixed solution for pickling at room temperature for 6 minutes to remove residual impurities on the surface of the GH3536 alloy strip.

[0187] The GH3536 alloy strip, after being pickled at room temperature, is rinsed with water and then dried.

[0188] The surface roughness Ra of the GH3536 alloy strip is controlled to be 1.1 μm.

[0189] The GH3536 alloy strip, after pretreatment of the billet, is subjected to gradient cold rolling. The gradient cold rolling adopts multi-pass room temperature cold rolling without high-temperature intermediate annealing. The cumulative reduction of the gradient cold rolling increases progressively in the following stages: 10% in the first stage, 30% in the second stage, 50% in the third stage, and 70% in the fourth stage. The final cumulative deformation of the gradient cold rolling is 70%, and the reduction of each pass of the gradient cold rolling is 12% to 18%.

[0190] The GH3536 alloy strip, after being formed by gradient cold rolling, is subject to rolling process parameter control, which includes: controlling the rolling speed to 0.2 m / s; performing stress relief treatment on the GH3536 alloy strip between passes, wherein after each rolling pass, the GH3536 alloy strip is placed in a constant temperature and dust-free environment at 25°C and left to stand for 8 minutes to naturally relieve residual stress between passes; and checking the flatness of the GH3536 alloy strip before each rolling pass to ensure uniform stress distribution.

[0191] No low-temperature stress relief post-treatment process is required.

[0192] The GH3536 alloy strip and foil prepared by the method were tested and found to have localized microcracks, high residual stress levels, a Σ3 twin boundary residual volume ratio of 30%, and a GND density of 13.1 × 10⁻⁶. 14 m -2 The GH3536 alloy strip and foil has a yield strength of 1495 MPa, a tensile strength of 1535 MPa, an elongation of 3.5%, and a product qualification rate of 85%.

[0193] Comparative Example 5 (Supercritical Deformation Process) The GH3536 alloy strip is subjected to billet pretreatment. The GH3536 alloy strip is subjected to water-cooled solution treatment after being held at 1175℃ for 30 minutes. The initial microstructure of the GH3536 alloy strip is uniform equiaxed recrystallized grains, and the initial Σ3 twin boundary volume ratio of the GH3536 alloy strip is 55%.

[0194] The GH3536 alloy strip is mechanically ground to remove surface burrs and oxide scale.

[0195] The GH3536 alloy strip, after being mechanically polished, is placed in a hydrochloric acid-sulfuric acid mixed solution for pickling at room temperature for 6 minutes to remove residual impurities on the surface of the GH3536 alloy strip.

[0196] The GH3536 alloy strip, after being pickled at room temperature, is rinsed with water and then dried.

[0197] The surface roughness Ra of the GH3536 alloy strip is controlled to be 1.1 μm.

[0198] The GH3536 alloy strip, after pretreatment of the billet, is subjected to gradient cold rolling. The gradient cold rolling adopts multi-pass room temperature cold rolling without high-temperature intermediate annealing. The cumulative reduction of the gradient cold rolling increases progressively in the following stages: 10% in the first stage, 30% in the second stage, 50% in the third stage, and 78% in the fourth stage. The final cumulative deformation of the gradient cold rolling is 78%, and the reduction of each pass of the gradient cold rolling is 12% to 18%.

[0199] The GH3536 alloy strip, after being formed by gradient cold rolling, is subject to rolling process parameter control, which includes: controlling the rolling speed to 0.2 m / s; performing stress relief treatment on the GH3536 alloy strip between passes, wherein after each rolling pass, the GH3536 alloy strip is placed in a constant temperature and dust-free environment at 25°C and left to stand for 8 minutes to naturally relieve residual stress between passes; and checking the flatness of the GH3536 alloy strip before each rolling pass to ensure uniform stress distribution.

[0200] The GH3536 alloy strip, after being controlled by the rolling process parameters, is subjected to low-temperature stress relief post-treatment. The low-temperature stress relief post-treatment is to immediately after the final rolling is completed, the GH3536 alloy strip is held at 250°C for 60 minutes for low-temperature stress relief annealing, and then air-cooled to room temperature.

[0201] The GH3536 alloy strip and foil prepared by the method were tested and found to have macroscopic cracks on the surface and microscopic cracks inside. The residual volume of the Σ3 twin boundaries was 18%, and the GND density was 15.2 × 10⁻⁶. 14 m -2 The GH3536 alloy strip and foil has a yield strength of 1555 MPa, a tensile strength of 1589 MPa, an elongation of 1.8%, and a product qualification rate of 68%.

[0202] Comparative Example 6 (High-Pressure Single-Pass Process) The GH3536 alloy strip is subjected to billet pretreatment. The GH3536 alloy strip is subjected to water-cooled solution treatment after being held at 1175℃ for 30 minutes. The initial microstructure of the GH3536 alloy strip is uniform equiaxed recrystallized grains, and the initial Σ3 twin boundary volume ratio of the GH3536 alloy strip is 55%.

[0203] The GH3536 alloy strip is mechanically ground to remove surface burrs and oxide scale.

[0204] The GH3536 alloy strip, after being mechanically polished, is placed in a hydrochloric acid-sulfuric acid mixed solution for pickling at room temperature for 6 minutes to remove residual impurities on the surface of the GH3536 alloy strip.

[0205] The GH3536 alloy strip, after being pickled at room temperature, is rinsed with water and then dried.

[0206] The surface roughness Ra of the GH3536 alloy strip is controlled to be 1.1 μm.

[0207] The GH3536 alloy strip, after pretreatment of the billet, is subjected to gradient cold rolling. The gradient cold rolling adopts multi-pass room temperature cold rolling without high-temperature intermediate annealing. The cumulative reduction of the gradient cold rolling increases progressively in the following stages: 10% in the first stage, 30% in the second stage, 50% in the third stage, and 70% in the fourth stage. The final cumulative deformation of the gradient cold rolling is 70%, and the reduction of each pass of the gradient cold rolling is 25% to 30%.

[0208] The GH3536 alloy strip, after being formed by gradient cold rolling, is subject to rolling process parameter control, which includes: controlling the rolling speed to 0.2 m / s; performing stress relief treatment on the GH3536 alloy strip between passes, wherein after each rolling pass, the GH3536 alloy strip is placed in a constant temperature and dust-free environment at 25°C and left to stand for 8 minutes to naturally relieve residual stress between passes; and checking the flatness of the GH3536 alloy strip before each rolling pass to ensure uniform stress distribution.

[0209] The GH3536 alloy strip, after being controlled by the rolling process parameters, is subjected to low-temperature stress relief post-treatment. The low-temperature stress relief post-treatment is to immediately after the final rolling is completed, the GH3536 alloy strip is held at 250°C for 60 minutes for low-temperature stress relief annealing, and then air-cooled to room temperature.

[0210] The GH3536 alloy strip and foil prepared by the method were tested and found to have localized microcracks, significant grain boundary stress concentration, a Σ3 twin boundary residual volume ratio of 20%, and a GND density of 15.5 × 10⁻⁶. 14 m -2 The GH3536 alloy strip and foil has a yield strength of 1505 MPa, a tensile strength of 1540 MPa, an elongation of 3.0%, and a product qualification rate of 80%.

[0211] Table 1. Effect Data of Example Implementation Table 2 Comparative Effect Data Table Experimental methods for evaluating results: 1. Macroscopic Crack Detection Methods Macroscopic crack detection was performed on the surface of the GH3536 alloy strip and foil using a visual inspection method. The GH3536 alloy strip and foil were placed under a standard light source, and inspectors directly observed the surface with the naked eye, recording whether any visible cracks were present. If visible cracks were found, the GH3536 alloy strip and foil was determined to have macroscopic cracks; if no visible cracks were found, the GH3536 alloy strip and foil was determined to be free of macroscopic cracks.

[0212] 2. Microcrack Detection Methods Microscopic crack detection was performed on the interior of the GH3536 alloy strip and foil using scanning electron microscopy. A standard metallographic sample was cut from the GH3536 alloy strip and foil. After grinding, polishing, and etching, the standard metallographic sample was observed under a scanning electron microscope, and the presence of microscopically visible cracks was recorded. If microscopically visible cracks were found, the GH3536 alloy strip and foil was determined to have microscopic cracks; if no microscopically visible cracks were found, the GH3536 alloy strip and foil was determined to be free of microscopic cracks.

[0213] 3. Method for determining the residual volume percentage of Σ3 twin boundaries The residual volume percentage of Σ3 twin boundaries in the GH3536 alloy strip and foil was determined using electron backscattering diffraction (ESD). A standard ESD sample was cut from the GH3536 alloy strip and foil. After electrolytic polishing, the standard ESD sample was examined under a scanning electron microscope equipped with an ESD probe to obtain a grain boundary orientation difference distribution map of the GH3536 alloy strip and foil. The proportion of Σ3 twin boundaries to the total number of grain boundaries was calculated; this proportion represents the residual volume percentage of Σ3 twin boundaries in the GH3536 alloy strip and foil.

[0214] 4. GND density measurement method The GND density of the GH3536 alloy strip foil was determined using electron backscattering diffraction (ESD) detection combined with a dislocation density calculation model. A standard ESD sample was cut from the GH3536 alloy strip foil. After electrolytic polishing, the standard ESD sample was examined under a scanning electron microscope equipped with an ESD probe to obtain local orientation difference data of the GH3536 alloy strip foil. Based on this local orientation difference data, the GND density of the GH3536 alloy strip foil was calculated using a geometrically necessary dislocation density calculation model.

[0215] 5. Method for determining yield strength The yield strength of the GH3536 alloy strip and foil was determined using a universal testing machine tensile test. A standard tensile specimen was cut from the GH3536 alloy strip and foil, placed on the universal testing machine, and subjected to a tensile test at the standard tensile rate. The yield stress value on the stress-strain curve of the GH3536 alloy strip and foil during the tensile process was recorded; this stress value is the yield strength of the GH3536 alloy strip and foil.

[0216] 6. Method for determining tensile strength The tensile strength of the GH3536 alloy strip and foil was determined using a universal testing machine tensile test. A standard tensile specimen was cut from the GH3536 alloy strip and foil, placed on the universal testing machine, and subjected to a tensile test at the standard tensile rate. The maximum stress value on the stress-strain curve of the GH3536 alloy strip and foil during the tensile process was recorded; this stress value is the tensile strength of the GH3536 alloy strip and foil.

[0217] 7. Method for determining elongation The elongation of the GH3536 alloy strip and foil was determined using a universal testing machine tensile test method. A standard tensile specimen was cut from the GH3536 alloy strip and foil, and the original gauge length was marked on the specimen. The specimen was then placed on the universal testing machine and subjected to a tensile test at the standard tensile rate until it broke. The gauge length after fracture was measured, and the percentage difference between the broken gauge length and the original gauge length was calculated. This percentage represents the elongation of the GH3536 alloy strip and foil.

[0218] 8. Method for determining the pass rate of finished products The product qualification rate of the GH3536 alloy strip and foil was determined using a statistical counting method. The GH3536 alloy strip and foil prepared under the same process conditions were mass-produced. The total number of products in the mass production was counted. Macroscopic and microscopic crack detection was performed on each product in the total number of products. The number of qualified products without macroscopic or microscopic cracks was counted, and the percentage of qualified products out of the total number of products was calculated. This percentage is the product qualification rate of the GH3536 alloy strip and foil.

[0219] 9. Method for determining surface roughness Ra The surface roughness Ra of the GH3536 alloy strip was determined using a profilometer. The GH3536 alloy strip, after pretreatment of the billet, was placed under a surface profilometer, and the surface profile of the GH3536 alloy strip was scanned and measured according to a standard scanning path. The arithmetic mean deviation value of the surface profile of the GH3536 alloy strip was obtained, and this arithmetic mean deviation value is the surface roughness Ra of the GH3536 alloy strip.

[0220] 10. Flatness Testing Methods The flatness of the GH3536 alloy strip is tested using a straightedge method. Before each rolling pass, a standard straightedge is attached to the surface of the GH3536 alloy strip, and the gap distribution between the standard straightedge and the surface of the GH3536 alloy strip is observed. If the gap distribution is uniform, the flatness of the GH3536 alloy strip is determined to meet the requirements; if the gap distribution is uneven, the flatness of the GH3536 alloy strip is determined to not meet the requirements.

[0221] As can be seen from the examples and comparative data, the technical advancements of this application include: 1. Significantly improved crack resistance: The GH3536 alloy strips and foils prepared in Examples 1-5 showed no macroscopic or microscopic cracks, with a product qualification rate of 95%-97%. In contrast, the single-pass high-pressure process in Comparative Example 1 had a product qualification rate of only 72% and a large number of macroscopic and microscopic cracks. The non-inter-pass static process in Comparative Example 3 had a product qualification rate of only 83% and local micro-cracks appeared. The non-low-temperature stress relief post-treatment process in Comparative Example 4 had a product qualification rate of only 85% and local micro-cracks appeared. The supercritical deformation process in Comparative Example 5 had a product qualification rate of only 68% and macroscopic cracks appeared on the surface. The single-pass high-pressure process in Comparative Example 6 had a product qualification rate of only 80% and local micro-cracks appeared.

[0222] 2. High strength and crack resistance are achieved synergistically: The GH3536 alloy strips and foils prepared in Examples 1-5 have a yield strength of 1485MPa-1495MPa, a tensile strength of 1525MPa-1535MPa, and an elongation of 5.0%-5.8%; Although the high-temperature intermediate annealing process in Comparative Example 2 did not produce cracks, the yield strength dropped to 1260MPa, which could not meet the high strength requirements of the sealing components; Although the single-pass large reduction process in Comparative Example 1 achieved a yield strength of 1550MPa, the elongation was only 2% and the plasticity was extremely poor.

[0223] 3. Effective preservation of low-energy twin boundaries: The residual volume of Σ3 twin boundaries in the GH3536 alloy strips and foils prepared in Examples 1-5 reached 30%-35%; the residual volume of Σ3 twin boundaries in Comparative Example 3 (without inter-pass static process) was only 22%, the residual volume of Σ3 twin boundaries in Comparative Example 5 (supercritical deformation process) was only 18%, and the residual volume of Σ3 twin boundaries in Comparative Example 6 (large pressure single-pass process) was only 20%, all significantly lower than those in the Examples.

[0224] 4. Improved process economy: Examples 1 to 5 do not require a high-temperature intermediate annealing process, which reduces energy consumption by more than 30% compared to Comparative Example 2, and significantly improves the product qualification rate, thereby significantly reducing material loss and production costs.

[0225] Detailed explanation of the attached diagram: Figure 1 The figure shows that the initial Σ3 twin boundary volume ratio of the GH3536 alloy strip in Embodiment 1 of this application is 55%; Figure 2 This is a graph showing that the residual volume of the Σ3 twin boundaries in the GH3536 alloy strip in Example 2 of this application is 31%. It can be clearly seen from the graph that: Figure 1 (Example 1, initial Σ3 twin boundary volume ratio 55%): In the grain boundary network of GH3536 alloy strip, the red-marked Σ3 twin boundaries are densely distributed and continuous, penetrating a large number of grains to form a high proportion of special grain boundary network; the grain morphology is mainly equiaxed, and the twin boundaries and matrix grain boundaries intertwine to form a relatively uniform microstructure.

[0226] Figure 2 (Example 2, Σ3 twin boundary residual volume ratio 31%): In the grain boundary network of GH3536 alloy strip, the number of Σ3 twin boundaries marked in red is significantly reduced, the residual twin boundaries are discontinuously distributed, and traces of grain boundary migration after the disappearance of twin boundaries are seen in some areas; the grain size is relatively coarsened, and grain boundary bowing and subgrain formation caused by detwinization can be seen in some areas, indicating that the Σ3 twin boundaries undergo selective decomposition during thermomechanical treatment.

[0227] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for cold rolling and forming a high-strength, crack-resistant nickel-based superalloy, characterized in that, The method includes: The GH3536 alloy strip is subjected to billet pretreatment. After solution treatment, the GH3536 alloy strip is water-cooled. The initial microstructure of the GH3536 alloy strip is uniform equiaxed recrystallized grains. The GH3536 alloy strip, after pretreatment of the billet, is subjected to gradient cold rolling. The gradient cold rolling adopts multi-pass room temperature cold rolling without high-temperature intermediate annealing. The final cumulative deformation of the gradient cold rolling is 65-75%, which is lower than the 78% critical cracking deformation threshold of the GH3536 alloy. The reduction of each pass in the gradient cold rolling is 10%~18%. The gradient cold rolling adopts a gradient cold rolling process with small incremental step-by-step reduction. By controlling the residual volume of Σ3 twin boundaries in the final rolled product to be ≥20%, the slip transfer efficiency is improved and the grain boundary stress concentration is reduced. The rolling process parameters of the GH3536 alloy strip are controlled during gradient cold rolling. The control of rolling process parameters includes: after each rolling pass, the GH3536 alloy strip is placed in a constant temperature and dust-free environment of 25℃±3℃ for 6min~9min to naturally release the residual stress between passes; before each rolling pass, the flatness of the GH3536 alloy strip is checked to ensure uniform stress; and the rolling speed is controlled at 0.15m / s~0.25m / s. The GH3536 alloy strip, after being controlled by the rolling process parameters, undergoes a low-temperature stress-relief post-treatment. The low-temperature stress-relief post-treatment involves immediately after the final rolling of the GH3536 alloy strip being subjected to a low-temperature stress-relief annealing process at 250℃±5℃ for 55min~65min, followed by air cooling to room temperature, to obtain a crack-resistant, high-strength GH3536 precision cold-rolled strip. The annealing temperature of the low-temperature stress-relief annealing is lower than the recrystallization temperature of the GH3536 alloy. The solution treatment is performed by holding at 1175℃±5℃ for 25min~35min followed by water cooling, and the initial Σ3 twin boundary volume ratio of the GH3536 alloy strip is ≥55%. The GH3536 alloy precision cold-rolled strip prepared by the method has a Σ3 twin boundary residual volume ratio of ≥20% and a geometrically necessary dislocation density of 12.0×10⁻⁶. 14 m -2 ~15.0×10 14 m -2 Yield strength ≥1400MPa, tensile strength ≥1500MPa, elongation ≥5.0%, product qualification rate ≥96%, and no macroscopic or microscopic cracks.

2. The method according to claim 1, characterized in that, The pretreatment of the billet also includes: The GH3536 alloy strip is mechanically ground to remove surface burrs and oxide scale; The GH3536 alloy strip, after being mechanically polished, is placed in a mixed hydrochloric acid-sulfuric acid solution for pickling at room temperature for 5 to 8 minutes to remove residual impurities on the surface. The GH3536 alloy strip, after being pickled at room temperature, is rinsed with water and then dried. The surface roughness Ra of the GH3536 alloy strip is controlled to be ≤1.2μm.

3. The method according to claim 2, characterized in that, The pickling time at room temperature is 5 min to 7 min, and the surface roughness Ra of the GH3536 alloy strip is 1.0 μm to 1.1 μm.

4. An application of the method according to any one of claims 1 to 3, characterized in that, The method is used to prepare GH3536 precision cold-rolled strip for aero-engines, heavy-duty gas turbines, aerospace propulsion systems and high-end energy equipment. The strip is used for high-temperature sealing components, sealing sheets, throttling rings, flexible sealing components, thin-walled heat insulation components and high-temperature elastic elements.

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