High-strength corrosion-resistant austenitic stainless steel plate and deterministic preparation method and intelligent cooperative system thereof

Abstract

The invention discloses a high-strength corrosion-resistant austenitic stainless steel plate as well as a deterministic preparation method and an intelligent collaborative system thereof, and belongs to the field of metal materials and advanced manufacturing. The problem that strength and corrosion resistance of traditional austenitic stainless steel are difficult to synergistically improve is solved. The technical scheme forms a three-in-one deterministic manufacturing system: the first aspect is a high-performance austenitic stainless steel plate which is characterized in that the surface of the high-performance austenitic stainless steel plate is provided with a metallurgically bonded gradient alloy layer, the yield strength is greater than or equal to 550MPa, the first red rust time of a neutral salt spray test is greater than or equal to 4500 hours, and the second red rust time is greater than or equal to 4500 hours; and the matrix components are limited in a precise window meeting a specific relational expression. The second aspect is a deterministic collaborative method for preparing the plate, and the method sequentially comprises the multi-physical-field collaborative process steps of plasma catalytic nitrogen alloying, ultrasonic-electromagnetic anti-correlation regulation and control continuous casting, online plasma surface alloying, microwave solid solution, ultrasonic cooling and the like. The third aspect is an intelligent cooperative system for executing the method, and the whole process is dynamically and cooperatively regulated through a distributed sensor network and a central controller with a built-in multi-physics field digital model. Through deep coupling of components, processes and control, the strength and corrosion resistance of the stainless steel are synchronously and remarkably improved, and the method is mainly used for producing austenitic stainless steel plates with extreme requirements on mechanical and corrosion properties.

Description

Technical Field

[0001] This invention belongs to the field of metallic materials and advanced manufacturing, specifically relating to an austenitic stainless steel plate with excellent comprehensive mechanical and corrosion resistance properties, a deterministic preparation method to achieve these properties, and an intelligent collaborative system to ensure the stable execution of the method. Background Technology

[0002] Optimizing the performance of traditional austenitic stainless steel faces bottlenecks. Alloying to increase strength often leads to a decrease in ductility, toughness, and corrosion resistance; while post-treatment techniques such as coatings to improve the surface suffer from inherent problems such as weak interfacial bonding, lengthy processes, and environmental pollution. Existing improvement solutions mostly focus on adjusting single factors, such as fine-tuning the composition or applying a single physical field (e.g., electromagnetic stirring or plasma spraying alone), which have limited and unstable effects and cannot achieve a significant synergistic improvement in both the material's bulk and surface properties. Therefore, the industry has long lacked a technical solution that can fundamentally unify the requirements of high strength, high corrosion resistance, low cost, and continuous production. Summary of the Invention

[0003] This invention aims to overcome the shortcomings of existing technologies. Its core concept lies in the fact that the superior comprehensive performance of stainless steel originates from an inseparable deterministic manufacturing system formed by the deep coupling of three elements: a "precise composition window," a "multi-physics field collaborative sequence," and "intelligent collaborative logic." Only when this system is fully operational will the material undergo a predetermined physicochemical path during manufacturing, simultaneously achieving grain refinement, elemental micro-region gradient redistribution, and atomic-level interfacial bonding, thereby generating a "system effect" that individual elements do not possess.

[0004] To transform the above concepts into an implementable and protectable technical solution, this invention constructs the following three-in-one, logically closed-loop protection system: First aspect: A high-performance austenitic stainless steel sheet produced by a deterministic manufacturing system. This board is the inevitable product and final carrier of its unique manufacturing process, and its characteristics can be objectively verified and repeatedly validated: 1. Stable endogenous structure: The surface of this layer has a modified layer that is fully metallurgically bonded to the substrate. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) line scans confirm that the atomic percentage concentrations of chromium and molybdenum in this layer show a continuous and monotonous gradient decrease from the outer surface to the interior of the substrate, and there are no defects such as pores or cracks at the interface.

[0005] 2. Repeatably verifiable superior performance: The yield strength (Rp0.2) of the sheet metal is not less than 550 MPa, and the time to first appearance of matrix corrosion red rust on the surface is not less than 4500 hours according to the neutral salt spray test (NSS) performed according to ASTM B117. Unless otherwise specified, the mechanical properties described in this document are determined on gauge length specimens in the rolling direction of the sheet metal according to ISO 6892-1; all corrosion performance data are derived from tests strictly following ASTM B117.

[0006] To ensure the reproducibility of the sheet material, its matrix chemical composition is designed and limited to a precise window (mass percentage): C: ≤0.03%, Si: ≤0.7%, Mn: 10.0-11.0%, Cr: 18.5-19.5%, Ni: 4.0-5.0%, Mo: 0.8-1.2%, Cu: 1.0-1.5%, N: 0.90-1.00%, rare earth elements (RE): 0.03-0.05%, with the balance being Fe and unavoidable impurities. This composition system must simultaneously satisfy two constraints: (Cr) + 3.3 × (Mo) + 16 × (N) ≥ 38.0, and the value of (Mn) + (Ni) / (N) is between 15.0 and 16.5. This composition design is the chemical basis for the system's startup and effectiveness.

[0007] Second aspect: A deterministic collaborative method for preparing the aforementioned plate. This method defines the parameter-coupled dynamic process that must be followed to achieve the aforementioned "system effect": S1. Plasma-catalyzed nitrogen alloying: After preheating the raw materials in a microwave field (2.45 GHz), conventional smelting and AOD refining are performed. In the later stages of refining, an atmospheric plasma torch (100-150 kW power) is applied to the molten steel surface, simultaneously bottom-blowing nitrogen in a low-frequency pulse mode of 0.01-0.05 Hz. The high temperature and high activity of the plasma significantly reduce the kinetic barrier to nitrogen dissolution. Combined with pulse stirring, this ensures that the nitrogen content is precisely and uniformly controlled at 0.92% ± 0.02%.

[0008] S2. Dynamic Field Coordination and Control of Solidification Structure: During the slab continuous casting stage, a high-power ultrasonic transducer array with a working frequency of 20kHz is integrated into the crystallizer, and an electromagnetic stirrer is configured in the secondary cooling zone. Anti-correlation feedback control is implemented: The control system receives real-time temperature and ultrasonic vibration monitoring signals from multiple points in the slab shell; when an increase in local temperature gradient is detected (indicating columnar crystal growth), the electromagnetic stirring intensity is automatically increased while the ultrasonic amplitude is correspondingly slightly reduced to enhance melt convection and break dendrites, and vice versa. This control aims to stably maintain the equiaxed crystal ratio across the entire cross-section of the slab within a narrow range of 83%-87%.

[0009] S3. Online Thermo-Mechanical-Chemical Synergistic Surface Alloying: The billet is hot-rolled. At the exit of the final finishing pass, when the strip surface temperature is within the thermodynamic window of 940℃-960℃, an atmospheric pressure plasma jet is used to dynamically and synchronously clad a specific alloy powder (65%Cr-30%Mo-5%CeO2) onto the moving strip surface. This process follows the dynamic mass balance equation: Powder feed rate F (kg / min) = 0.5 × Strip speed v (m / s) + 0.1 × (Target layer thickness 10.0 μm - Real-time online thickness measurement Δ). The rolling pressure, residual heat, and plasma energy work together to achieve instantaneous melting, diffusion, and metallurgical bonding of the powder.

[0010] S4. Field-Assisted Solid-State Phase Transformation and Stress Synergistic Regulation: Microwave energy is applied to the strip for rapid and uniform bulk heating to 1080℃ ± 20℃, followed by short-term heat preservation to complete solution treatment. The strip is then passed through a high-efficiency atomizing cooling section integrated with a 40 kHz ultrasonic transducer. The ultrasonic cavitation effect breaks down the vapor film, ensuring uniform cooling, suppressing residual stress and deformation, and stabilizing the final microstructure.

[0011] Third aspect: An intelligent collaborative system that enables the method to be executed deterministically and stably. This system serves as the physical and computational hub for translating the aforementioned method from a "theoretical script" into "industrial reality." It comprises various physical field execution units (microwave, plasma, ultrasound, electromagnetic, and mechanical) distributed along the production line, and two core components endowing them with "collaborative intelligence": 1. Distributed high-precision sensor network: Real-time acquisition of multi-dimensional, full-process data, including steel composition (LIBS spectrum), temperature field distribution, billet solidification state, rolling parameters, and surface alloy layer thickness.

[0012] 2. Central Intelligent Controller and its Process Digital Model: The multiphysics process digital model built into the controller is the "decision brain" of this system. This model is constructed and operated through the following steps: First, a parameterized multiphysics coupled simulation model for heat transfer, mass transfer, fluid flow, and phase change is established based on the finite element method; second, key parameters of the simulation model (such as boundary conditions and material properties) are repeatedly calibrated and verified using historical production big data to ensure its predictive accuracy; finally, the calibrated high-fidelity model or a lightweight proxy model (such as a machine learning model) trained by it is deployed on the controller. Based on the real-time data stream from the sensor network, the controller drives the model to perform millisecond-level look-ahead simulation and optimization calculations, dynamically outputting adjustment commands to each physical field actuator, so that the entire manufacturing process automatically locks and stably operates within the preset "cooperative process window".

[0013] Unexpected technical effects The complete intelligent collaborative system provided by this invention effectively overcomes the inherent contradiction between "high strength" and "high corrosion resistance" in traditional stainless steel. The resulting sheet material exhibits superior synergistic performance with a yield strength exceeding 550 MPa (approximately three times that of conventional 304 stainless steel) and a neutral salt spray corrosion life exceeding 4500 hours (approximately nine times better). This "unexpected technical effect" is the inevitable result of the aforementioned component system, deterministic collaborative method, and intelligent collaborative system operating as an inseparable whole, and cannot be achieved by simple permutations or conventional parameter optimizations in existing technologies. Detailed Implementation

[0014] The following comparative experiments, using repeatable data, confirm the necessity, synergy, and transformative effect of the technical solution of this invention. All tests strictly followed the aforementioned international standards.

[0015] Example 1 (Execution of the complete system of this invention) Production is organized according to the preferred composition (C 0.02%, Si 0.5%, Mn 10.5%, Cr 19.0%, Ni 4.5%, Mo 1.0%, Cu 1.25%, N 0.95%, Ce 0.04%). The deterministic collaborative method is executed using a complete intelligent collaborative system.

[0016] Results: The yield strength of the plate was 612 MPa, and the time to first appearance of red rust in the salt spray test was 5150 hours. Microscopic characterization showed that the equiaxed crystal ratio was 85%, the surface gradient alloy layer thickness was 10.1 μm, the interface was clean, and the elemental gradient was smooth.

[0017] Examples 2 and 3 (System Robustness Verification) The composition was fine-tuned separately (N 0.90%, Cu 1.5%) and (N 1.00%, Mo 1.2%). The control system automatically adjusted the parameters of steps S1 and S3 based on the model.

[0018] Results: Both systems consistently meet the core performance indicators (strength > 550 MPa, salt spray > 4500 hours), demonstrating the system's adaptive robustness.

[0019] Comparative Example 1 (Pre-existing Technology Benchmark) Commercial 304 stainless steel (C 0.05%, Cr 18.2%, Ni 8.1%) is produced using traditional processes.

[0020] Results: Yield strength 205 MPa, salt spray time 510 hours. Performance benchmarks were established.

[0021] Comparative Example 2 (Isolated component elements are invalid) The material composition is exactly the same as that in Example 1, but a conventional step-by-step process is used: conventional smelting and continuous casting, hot rolling followed by offline plasma spraying of the same alloy powder, and box furnace solution treatment.

[0022] Results: Due to the lack of online thermo-mechanical coupling and overall synergy, the coating interface bonding was weak, and it failed after 850 hours of salt spray testing, with a strength of only 278 MPa. This proves that even with the correct components, without a synergistic manufacturing system and deterministic method, the performance of this invention cannot be obtained.

[0023] Comparative Example 3 (Missing Key Field Collaborative Logic) Same as Example 1, but in the S2 continuous casting step, only electromagnetic stirring is enabled, and ultrasonic waves and their inverse correlation control are disabled.

[0024] Results: Uncontrolled solidification occurred, with the equiaxed crystal ratio plummeting to 48% and severe macroscopic segregation. The final sheet exhibited uneven properties (strength fluctuation > 60 MPa), and the salt spray test time was drastically reduced to 2100 hours. This demonstrates that "ultrasonic-electromagnetic anti-correlation control" is a necessary and indispensable synergistic logic for ensuring microstructure uniformity.

[0025] Comparative Example 4 (Deviation from Critical Process Parameters) Same as Example 1, but in step S3, the alloy powder is replaced with pure chromium powder that does not contain Mo and CeO2.

[0026] Results: Due to the solid solution strengthening effect of missing Mo and the fine-grained pinning effect of CeO2, a network of microcracks was generated in the surface layer during cooling. Corrosive media penetrated rapidly, and the salt spray time decreased to 1950 hours. This demonstrates that the specific composition of the alloy powder is a necessary condition for the formation of a defect-free gradient layer.

[0027] Comparative Example 5 (Breaking through the core ingredient window) An attempt was made to use the process of this invention, but the nitrogen content at the S1 endpoint was set to 0.80%.

[0028] Results: Although the material properties (strength 498 MPa, salt spray resistance 3200 hours) are superior to those of traditional products, they show a significant decline compared to the example. This confirms that a nitrogen content of 0.90% is the chemical critical point that triggers the performance transition of this invention.

[0029] Ultimate Summary of Invention Logic The examples and comparative examples constitute a rigorous "controlled variable" experimental group, irrefutably revealing that the superior performance achieved by this invention is the sole output of a deterministic manufacturing system that forms a closed loop between the precise composition window (A), the multiphysics collaborative process (B), and the intelligent collaborative system (C). Comparative examples 2-5, by disrupting A, B, C, or their internal relationships, respectively, all resulted in system failure and significant performance degradation. This ultimately proves that the technical solution of this invention is a non-obvious, systematic creation that must exist as a whole, producing unexpected technical effects and possessing outstanding substantive characteristics and significant progress.

Claims

1. A high-strength, corrosion-resistant austenitic stainless steel sheet, characterized in that, Its surface has an alloy layer that is metallurgically bonded to the substrate, wherein the content of chromium and molybdenum in the alloy layer decreases in a gradient from the surface to the interior; and the yield strength of the plate is not less than 550 MPa, and the time for the first appearance of red rust on the substrate in the neutral salt spray test according to ASTM B117 standard is not less than 4500 hours.

2. The austenitic stainless steel sheet according to claim 1, characterized in that, Its matrix chemical composition, by mass percentage, includes: C: ≤0.03%, Si: ≤0.7%, Mn: 10.0-11.0%, Cr: 18.5-19.5%, Ni: 4.0-5.0%, Mo: 0.8-1.2%, Cu: 1.0-1.5%, N: 0.90-1.00%, rare earth element RE: 0.03-0.05%, with the balance being Fe and unavoidable impurities.

3. The austenitic stainless steel sheet according to claim 2, characterized in that, Its chemical composition satisfies the following relationship: (Cr) + 3.3×(Mo) + 16×(N) ≥ 38.

0.

4. The austenitic stainless steel sheet according to claim 2 or 3, characterized in that, Its chemical composition satisfies the relationship: (Mn) + (Ni) / (N) with a value between 15.0 and 16.

5.

5. A deterministic synergistic method for preparing austenitic stainless steel sheet as described in any one of claims 1 to 4, characterized in that, Includes the following steps: S1. Plasma-catalyzed nitrogen alloying: The raw materials are preheated by microwave and then melted and refined. In the later stage of refining, an atmospheric plasma torch is applied to the surface of the molten steel and nitrogen is pulsed and blown from the bottom. S2. Synergistic control of solidification structure: During continuous casting, ultrasonic vibration and electromagnetic stirring are applied simultaneously in the crystallizer and the secondary cooling zone, and anti-correlation feedback control is performed. S3. Online surface gradient alloying: After hot rolling, the alloy powder is clad onto the surface of the strip online using plasma jet at the finish rolling exit; S4. Integrated solution treatment and cooling: The strip is subjected to microwave solution treatment followed by ultrasonic-assisted cooling.

6. The deterministic cooperative method according to claim 5, characterized in that, In step S1, the power of the atmospheric plasma torch is 100 to 150 kW, the pulsation frequency of the bottom-blown nitrogen is 0.01 to 0.05 Hz, and the final liquid steel nitrogen content is 0.92% ± 0.02%.

7. The deterministic cooperative method according to claim 5, characterized in that, In step S2, the ultrasonic vibration frequency is 20 kHz, and the anti-correlation feedback control is: dynamically adjusting the electromagnetic stirring intensity and ultrasonic amplitude according to the temperature gradient of the billet shell and the ultrasonic vibration monitoring signal, so that the equiaxed crystal ratio of the billet is 83% to 87%.

8. The deterministic cooperative method according to claim 5, characterized in that, In step S3, the surface temperature of the strip during cladding is 940°C to 960°C. The alloy powder composition is 65%Cr, 30%Mo, and 5%CeO2. The powder feeding rate F (kg / min) and the strip speed v (m / s) satisfy: F = 0.5v + 0.1Δ, where Δ is the difference (μm) between the measured alloy layer thickness and the target value of 10.0 μm.

9. The deterministic cooperative method according to claim 5, characterized in that, In step S4, the target temperature for microwave solidification is 1080℃ ± 20℃, and the temperature is maintained for 1 to 2 minutes; the cooling is atomized cooling under the action of 40 kHz ultrasound.

10. An intelligent collaborative system for implementing the deterministic collaborative method according to any one of claims 5 to 9, comprising a microwave preheating unit, a smelting and refining unit, a continuous casting unit, a hot rolling and online plasma alloying unit, and a microwave solution treatment and ultrasonic cooling unit arranged sequentially; characterized in that, It also includes a distributed sensor network and a central controller; the central controller has a built-in multi-physics process digital model, which is used to dynamically and collaboratively adjust the physical field parameters of each unit by calculating the model based on real-time sensor data.