Rare earth dispersion strengthened electrothermal alloy ribbon and preparation method thereof

Abstract

The invention provides a rare earth dispersion strengthened electrothermal alloy ribbon and a preparation method thereof. The rare earth dispersion strengthened electrothermal alloy ribbon comprises the following raw materials: chromium Cr, silicon Si, titanium Ti, aluminum Al, carbon C, yttrium Y, cerium Ce, Yb ytterbium, niobium Nb, vanadium V and iron Fe. The preparation method comprises the steps that the raw materials are subjected to smelting, forming, heat treatment and oxidation film treatment, a dispersed phase of rare earth oxides Y2O3, CeO2 and Yb2O3 and carbides NbC and VC is formed, an electrothermal alloy thin strip is subjected to triple dispersion strengthening, an Al2O3 + Cr2O3 + Nb2O5 + V2O5 + Yb2O3 composite oxidation film is formed on the surface of the thin strip, and finally the electrothermal alloy thin strip with thermal shock resistance and oxidation film stability is prepared.

Description

Technical Field

[0001] This invention relates to the field of electrothermal alloy material preparation technology, and in particular to a rare earth dispersion-strengthened electrothermal alloy thin strip and its preparation method. Background Technology

[0002] Electrothermal alloys, as functional materials for converting electrical energy into heat energy, are widely used in industrial heating furnaces, electronic component packaging, and high-end home appliances due to their excellent high-temperature stability, resistivity characteristics, and mechanical properties. Thin-strip electrothermal alloys, with their advantages of high heat transfer efficiency, compact structure, and suitability for precision heating applications, have become a research hotspot and application focus in recent years.

[0003] Iron-chromium-aluminum alloys have gradually become the mainstream electrothermal alloys due to their lack of precious metals, low cost, and outstanding oxidation resistance. However, they have obvious technical drawbacks: the alloy oxide film is mainly composed of Al2O3 and Cr2O3. Although it has strong oxidation resistance, under alternating hot and cold thermal shock conditions, it is prone to internal stress due to the difference in thermal expansion coefficients between the film and the substrate, which can cause the oxide film to crack and peel off, shortening its service life. Traditional iron-chromium-aluminum alloys mostly use a single strengthening mechanism, which makes it difficult to balance high-temperature strength and oxidation resistance stability, thus limiting their application in higher temperatures and more complex working conditions.

[0004] Developing rare earth dispersion-reinforced electrothermal alloy thin strips with excellent oxidation resistance and thermal shock resistance has become an important development direction for breaking through existing technological bottlenecks and meeting the needs of high-end heating scenarios. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A rare earth dispersion-strengthened electrothermal alloy strip comprises the following raw materials: chromium (Cr), silicon (Si), titanium (Ti), aluminum (Al), carbon (C), yttrium (Y), cerium (Ce), ytterbium (Yb), niobium (Nb), vanadium (V), and iron (Fe).

[0007] Furthermore, the raw material ratio of the electrothermal alloy strip is as follows: Cr: 16%-18%, Si: 0.3%-0.6%, Ti: 0.1%-0.2%, Al: 5%-7%, C≤0.03%, Y: 0.05%-0.12%, Ce: 0.02%-0.05%, Yb: 0.03%-0.08%, Nb: 0.05%-0.20%, V: 0.05%–0.15%, Fe: balance.

[0008] This invention uses chromium (Cr), iron (Fe), and aluminum (Al) to form a Fe-Cr-Al alloy iron matrix material. Fe, as the core component of the Fe-Cr-Al matrix, provides basic mechanical support, ensuring the formability and structural stability of the thin strip. It also forms a solid solution with Cr and Al elements, providing an attachment carrier for the dispersion strengthening phase.

[0009] This invention uses Cr element to form a dense Cr2O3 oxide film on the surface of the electrothermal alloy strip, which hinders the diffusion of oxygen into the substrate, delays oxidation failure, and improves the thermal shock resistance of the substrate. At the same time, the synergistic effect of Cr and Al also optimizes the structural density of the composite oxide film and enhances the bonding force between the oxide film and the substrate.

[0010] This invention uses Al element, which is the core antioxidant element of the electrothermal alloy strip. It is used to form an Al2O3 oxide film at high temperatures, thereby increasing the maximum safe operating temperature of the electrothermal alloy strip. At the same time, Al element works synergistically with rare earth elements to refine the matrix grains and dispersed phases, thereby improving the toughness of the electrothermal alloy strip and reducing the risk of low-temperature brittleness.

[0011] This invention uses Si element, which helps to improve oxidation resistance and, together with Cr and Al, optimizes the composition of the oxide film and reduces the growth rate of the oxide film. At the same time, Si element enhances the structural stability of the electrothermal alloy strip at high temperatures and extends its high-temperature service life.

[0012] This invention utilizes Ti, which, by forming TiC carbide, hinders grain growth and improves the room temperature and high temperature toughness of the electrothermal alloy strip. Furthermore, Ti can fix the carbon element in the matrix, reducing the formation of Cr by the combination of carbon and Cr. 23 C6-induced grain boundary embrittlement improves the thermal shock resistance of the electrothermal alloy strip.

[0013] This invention uses element C, which assists in the formation of trace carbides TiC and YC at a low content (≤0.03%), participating in dispersion strengthening and improving the high-temperature strength of the electrothermal alloy strip.

[0014] This invention uses element Y as the core dispersion strengthening element, which combines with O and C to form nanoscale dispersed phases such as Y2O3 and YC, hindering metal dislocation movement and grain growth, and improving the stability of oxide films Cr2O3 and Al2O3; it also improves the toughness and thermal shock resistance of the electrothermal alloy strip, alleviates the low-temperature brittleness of Fe-Cr-Al alloy, and reduces the risk of electrothermal alloy strip fracture.

[0015] This invention utilizes Ce element, which works synergistically with Y to refine oxide film grains, improve oxide film density and adhesion, enhance dispersion strengthening effect, and improve the high-temperature strength and plasticity of electrothermal alloy strips. Ce reacts with impurities to purify the matrix, reduce grain boundary segregation, and improve the processing performance and service life of electrothermal alloy strips.

[0016] This invention uses Yb element, which synergistically forms a Y-Yb-O composite dispersed phase with Y, which is more effective than Y alone in inhibiting grain growth. At the same time, it also optimizes the self-healing property of the oxide film. When the oxide film is locally damaged, Yb can quickly form a new oxide film Yb2O3 at the damaged site. In addition, the price of Yb is lower than that of Y and Ce, which reduces the cost of electrothermal alloy strip.

[0017] This invention utilizes Nb, which forms a stable NbC carbide phase with C, refining the grains, hindering grain boundary migration, and improving the creep resistance of the electrothermal alloy strip. Nb also synergistically forms Nb3Al intermetallic compounds with Al, enhancing the high-temperature strength of the electrothermal alloy strip. Nb also optimizes the oxide film structure, reducing the tendency of Cr2O3 / Al2O3 oxide film to peel off.

[0018] This invention uses element V, which forms a VC carbide phase with C, refining the grains and enhancing the high-temperature hardness of the electrothermal alloy strip. Element V promotes the uniform growth of the Al2O3 oxide film and improves the adhesion between the oxide film and the substrate. Element V also reduces the coefficient of thermal expansion of the electrothermal alloy strip, reducing the risk of thermal shock cracking.

[0019] This invention relates to a rare-earth dispersion-strengthened electrothermal alloy strip, which utilizes element V. V and C form a VC carbide phase, refining the grain size. On one hand, this enhances the high-temperature hardness of the electrothermal alloy strip; on the other hand, element V reduces the coefficient of thermal expansion of the electrothermal alloy strip, thereby reducing internal stress caused by the difference in the coefficient of thermal expansion under alternating hot and cold thermal shock conditions, reducing the risk of thermal shock cracking of the electrothermal alloy strip, avoiding the cracking and peeling of the oxide film, and improving service life. This invention uses Y and Yb elements. Y combines with O and C to form Y2O3 and YC, which hinder metal dislocation movement and grain growth, and improve the stability of oxide films Cr2O3 and Al2O3. When the oxide film is locally damaged, Yb quickly forms a new oxide film Yb2O3 at the damaged site, thereby enhancing the oxidation resistance of the electrothermal alloy strip. This invention utilizes Ce, Nb, and V elements. Ce and Y work synergistically to refine the oxide film grains, improve the oxide film density and adhesion, and enhance the high-temperature strength of the electrothermal alloy strip. Nb and Al synergistically form Nb3Al intermetallic compounds, further enhancing the high-temperature strength of the electrothermal alloy strip. V and C form VC carbide phase, enhancing the high-temperature hardness of the electrothermal alloy strip. Simultaneously, the three rare earth elements Y, Yb, and Ce work synergistically, combined with NbC and VC composite carbide dispersed phases, thereby forming a triple dispersion strengthening mechanism of rare earth oxides Y2O3, CeO2, Yb2O3 and NbC, VC, which enhances the high-temperature strength of the electrothermal alloy strip.

[0020] This invention also proposes a method for preparing rare earth dispersion-strengthened electrothermal alloy thin strips, comprising the following steps: S1, the smelting steps: S11, Fe, Cr, Si, Ti, C, Nb, and V are added to a vacuum induction melting furnace, the temperature is raised to 1520℃–1550℃, and the temperature is held for 30–40 minutes to completely melt Fe, Cr, Si, Ti, Nb, and V and achieve uniform mixing.

[0021] Furthermore, the proportions of Fe, Cr, Si, and Ti are as follows: Cr: 16%-18%, Si: 0.3%-0.6%, Ti: 0.1%-0.2%, C: ≤0.03%; Nb: 0.05%-0.20%, V: 0.05%–0.15%.

[0022] Furthermore, the complete melting and homogeneous mixing of Fe, Cr, Si, Ti, Nb, and V includes the following steps: S111, Raw material selection and purification: Use industrial pure iron, metallic chromium blocks, ferrosilicon alloy (Si content ≥75%), sponge titanium, ferroniobium alloy (Nb content ≥60%), ferrovanadium alloy (V content ≥50%) and high-purity graphite (C content ≥99.9%) with a purity ≥99.5%; all raw materials must be baked at 200-400℃ for 2-4 hours to thoroughly remove surface moisture, oil and adsorbed gases, and avoid the generation of bubbles and oxide inclusions during smelting.

[0023] S112, precise proportion design: with Fe as the balance, the target proportion of each element is strictly controlled: Cr 16%-18%, Si 0.3%-0.6%, Ti 0.1%-0.2%, C≤0.03%, Nb 0.05%-0.20%, V 0.05%-0.15%, with the proportioning error controlled within ±0.02% to ensure that the alloy composition meets the standards.

[0024] S113, Equipment selection and loading process; Core equipment parameters: It adopts a 1-5t vacuum induction furnace, equipped with an electromagnetic stirring system, high-precision temperature measurement (error ±5℃) and vacuum monitoring device. The furnace lining is made of high-purity corundum material to avoid the reaction and contamination between refractory materials and molten steel.

[0025] Charging sequence: Following the principle of "low melting point at the bottom, refractory elements in the middle, and easily oxidized elements added later," charge in layers: Place small pieces of Fe at the bottom (20% of the total); in the middle layer, place Cr blocks, Fe and NbFe (5-30mm), and VFe (5-30mm) in sequence, ensuring full contact between refractory elements and the Fe matrix; leave a charging port at the top for subsequent addition of Si, Ti, and C. Avoid direct contact between C and Cr during charging to prevent premature carbide formation.

[0026] S114, Vacuum control: After loading, start the vacuum pump and gradually pump the vacuum in the furnace to ≤10Pa before power is supplied. Maintain the vacuum at ≤5Pa throughout the melting process to avoid the reaction of O and N in the atmosphere with alloying elements.

[0027] S115, stepped heating regime: Initial stage (room temperature - 1200℃): slow heating with low power, with the heating rate controlled at 5-8℃ / min, using the skin effect of electromagnetic induction to melt layer by layer and promote gas discharge; Mid-term (1200℃-1500℃): Medium power heating, with the rate increased to 10-12℃ / min to ensure rapid melting and clearing of the furnace charge; Final stage (1500℃-1550℃): Fine-tune the power to stabilize the temperature at 1520℃-1550℃, hold for 30-40 minutes to provide thermodynamic conditions for element dissolution and diffusion.

[0028] S116, staged charging and deoxidation: After the furnace charge is fully melted (about 1500℃), Si is first added for pre-deoxidation (Si has a strong affinity for O, which reduces the oxygen content of the molten steel), and stirred for 5-10 minutes; then Ti and the remaining C are added, and the molten steel is further purified by vacuum carbon deoxidation reaction (C+O→CO↑), which improves the recovery rate of Ti, Nb and V.

[0029] S117, Mixing: During the heat preservation period, turn on the electromagnetic stirrer with a stirring power of 30%-40% of the melting power. Stir for 5 minutes every 10 minutes to promote the dissolution and diffusion of refractory elements (Nb, V). Take a sample at the end of the heat preservation period to test the composition. If segregation is present, add the corresponding alloying elements and extend the stirring for 10 minutes.

[0030] S118, control the final temperature of smelting: when the temperature of the molten steel is stable at 1520℃-1550℃, the holding time meets the standard, and the composition test shows that all elements are within the target range and there are no undissolved particles, the smelting ends; a molten and uniformly mixed Fe, Cr, Si, Ti, Nb, V metal melt is obtained.

[0031] This invention addresses several key aspects: First, by employing stepped heating, appropriate distribution of refractory elements, and electromagnetic stirring, it solves the problem of the difficulty in dissolving Nb and V (which have high melting points), achieving 100% melting of all elements and avoiding residual inclusions. Second, by using a vacuum environment, electromagnetic stirring, and staged feeding, it reduces the macroscopic segregation of Fe, Cr, Si, Ti, Nb, and V, and improves their microscopic uniformity, laying the foundation for the subsequent formation of uniform carbides and oxide films in the alloy. Third, by combining vacuum carbon deoxidation and pre-deoxidation processes, it reduces the oxygen and nitrogen content of the molten steel, effectively reducing oxide and nitride impurities and improving the purity of the alloy matrix. Fourth, by precisely controlling the C content and the uniform distribution of each strengthening element, it ensures that Cr and Si fully form an anti-oxidation film, and that Ti, Nb, and V uniformly precipitate fine carbides, significantly improving the mechanical properties and high-temperature stability of the alloy.

[0032] S12, cool down to 1480℃-1500℃, add Al blocks, keep warm, preferably for 20 minutes; cooling down and adding Al blocks prevents Al from volatilizing at high temperatures.

[0033] Furthermore, the Al content is 5%-7%.

[0034] S13, add Y, Ce, Yb rare earth alloy ingots (yttrium iron alloy, cerium iron alloy, ytterbium iron alloy), and hold for 15-20 minutes; pure Y, Ce, Yb are extremely chemically reactive and easily react with O2 and N2 in the furnace gas to form oxide / nitride inclusions, leading to uncontrolled composition and performance degradation. However, when they exist in the form of rare earth alloy ingots, they are easy to dissolve in the matrix, reducing oxidation loss and ensuring the precipitation of dispersed phases.

[0035] Furthermore, the proportions of Y, Ce, and Yb are as follows: Y: 0.05%-0.12%, Ce: 0.02%-0.05%, Yb: 0.03%-0.08%.

[0036] Furthermore, the Y rare earth alloy ingot is a yttrium-iron alloy, which contains yttrium and iron; the Ce rare earth alloy ingot is a cerium-iron alloy, which contains cerium and iron; and the Yb rare earth alloy ingot is a ytterbium-iron alloy, which contains ytterbium and iron.

[0037] S14, argon gas (purity ≥99.99%) is introduced and stirred at a flow rate of 0.3–0.5 m³ / h for 10 min to obtain molten steel; argon gas stirring removes hydrogen, oxygen, and nitrogen gases from the molten steel, reducing the interference of gases on the formation of Yb₂O₃, NbC, and VC.

[0038] Furthermore, reducing the interference of gases on the formation of Yb₂O₃, NbC, and VC includes the following steps: S141, Preliminary Preparations: Argon purification treatment: High-purity argon gas with a purity of ≥99.999% is selected and purified twice by a low-temperature adsorption dryer and a deoxygenation filter to prevent argon gas from carrying moisture and oxygen and contaminating the molten steel. Stirring device compatibility: The vacuum induction melting furnace is equipped with a bottom-blowing + top-blowing composite argon stirring system: the bottom uses permeable bricks and the top uses a liftable spray gun; Predicting the state of molten steel: After completing step S13 (adding rare earth alloy ingots and finishing the heat preservation), check the temperature and surface state of the molten steel. If the temperature of the molten steel is stable at 1480℃-1500℃ and there is no obvious slag or solidified layer on the surface of the molten steel, conditions are created for stirring and degassing. If there is obvious slag or solidified layer on the surface of the molten steel, clean it in time with a corundum slag skimmer to avoid slag being drawn into the molten steel and forming inclusions, which would interfere with the precipitation of dispersed phases.

[0039] S142, precise control of argon gas stirring parameters: Vacuum control: Before stirring, maintain the vacuum level in the furnace at ≤5Pa. During stirring, gradually increase it to 50-100Pa to avoid the vacuum being too high, which would cause the argon bubbles to break too quickly, or too low, which would affect the gas discharge.

[0040] Set the flow gradient: Start-up phase (0-3 min): Bottom-blown argon flow rate 0.1-0.2 m³ / min 3 / h, top blowing flow rate 0.05-0.1m³ / h 3 / h, slowly inflate to avoid splashing of molten steel, and initially form tiny bubbles; Main stirring stage (3-8 min): Bottom blowing flow rate increased to 0.3-0.5 m³ / min. 3 / h, top-blown flow rate 0.1-0.2m³ / h 3 / h, the bubble density increases and convective circulation is formed, which enhances gas adsorption and diffusion; Final stage (8-10 min): Bottom blowing flow rate reduced to 0.1-0.15 m³ / min. 3 / h, top blow flow rate 0.05m³ / h 3 / h, to achieve a smooth finish and avoid secondary air intake caused by drastic fluctuations in molten steel; Optimize stirring time: The total stirring time is 12-15 minutes to ensure that the average residence time of bubbles in molten steel is ≥3 minutes, so as to fully adsorb dissolved gases; control the stirring time to 10-12 minutes so that argon can adsorb H, O and N in molten steel and carry them out, and the temperature of molten steel will not drop excessively (≤1450℃).

[0041] S143, Post-stirring flow stabilization treatment: Argon gas is gradually shut off: After stirring, first shut off the top blowing lance, and then gradually reduce the bottom blowing argon gas flow rate to 0 at a rate of 0.05 m³ / h to avoid sudden gas stoppage causing the molten steel to draw back air.

[0042] Static holding: After shutting off the argon gas, maintain the vacuum degree in the furnace at 50-100 Pa and let it stand for 5-8 minutes to allow the tiny bubbles remaining in the molten steel to continue to rise, while allowing elements such as Y, Nb, and V to diffuse evenly, creating conditions for the nucleation of dispersed phases.

[0043] Temperature calibration: After standing, check the temperature of the molten steel. The temperature of the molten steel should be maintained at 1450℃-1470℃. If the temperature is insufficient, perform short-term heating to make up for the temperature.

[0044] This invention introduces purified argon gas to remove H, O, and N from the molten steel, preventing the gas from reacting with Y, Yb, Nb, and V to form harmful inclusions, thus ensuring the purity of the dispersed phase. Stirring promotes uniform element distribution, eliminating localized enrichment or deficiency and improving the uniformity of the dispersed phase. Degassing reduces the viscosity of the molten steel, improving the filling capacity during subsequent twin-roll casting and preventing cracks and porosity defects in the cast strip billet caused by inclusions.

[0045] S2, Molding: S21, Twin-roll thin strip casting and rolling: The temperature of molten steel is controlled at 1450℃–1470℃ and poured into the roll gap of the twin-roll thin strip casting and rolling mill to obtain the cast strip billet; the molten steel is poured into the roll gap of the twin-roll thin strip casting and rolling mill at a high temperature to avoid the segregation of Yb, Nb, and V elements and their local enrichment at the grain boundaries. The resulting cast strip billet has a thickness of 0.8-1.2mm, and the microstructure of the cast strip is fine-grained austenite, rare earth oxides (Y2O3, CeO2, Yb2O3) and primary carbides NbC and VC.

[0046] S22, gradient hot rolling: The cast strip billet is heated to 970℃-1030℃, held at that temperature for 15 minutes (preferably), and then hot rolled in a single pass. After hot rolling, it is immediately air-cooled to obtain a hot-rolled strip with a thickness of 0.5-0.8mm. Heating the cast strip billet promotes the diffusion of Yb elements and promotes the partial dissolution and re-precipitation of NbC and VC dispersed phases. Gradient hot rolling reduces the thickness of the cast strip billet, refines the grains, and inhibits grain growth and dispersion of the dispersed phases.

[0047] Furthermore, water cooling is performed immediately after hot rolling, with the cooling water temperature maintained at 25℃-35℃. Rapid water cooling can prevent the aggregation of dispersed phases such as Yb2O3, NbC, and VC at the grain boundaries. The cooling water temperature is maintained between 25℃ and 35℃ to avoid stress cracks on the strip surface caused by excessively low water temperature (<20℃) or excessively high water temperature (>40℃), which would reduce cooling efficiency.

[0048] Furthermore, gradient hot rolling includes the following steps: S221, Pretreatment of cast strip billet: Use a neutral cleaning agent to clean the cast strip billet and remove oxide scale and oil stains from the surface of the cast strip billet.

[0049] S222, Equipment Commissioning and Adaptation: A two-roll reversible hot rolling mill is selected, with a roll diameter of Φ500-600mm, a surface hardness of HRC≥60, and a roughness of Ra=0.8-1.2μm. The rolls are preheated to 150-200℃ to reduce plastic fluctuations caused by the temperature difference between the billet and the rolls. The heating furnace temperature control system (error ±5℃) and the hot rolling mill pressure sensor (accuracy ±1%) are calibrated to ensure precise and controllable heating temperature and pressing force; Process parameter presets: Based on the initial thickness of the cast strip billet, the target hot rolling thickness is set to 0.5-0.8mm, with 0.6mm being the best. The air cooling wind speed is preset to 8-10m / s.

[0050] S223, Heating and heat preservation: Tiered heating system: First stage (room temperature → 600℃): heating rate 10℃ / min, slow heating to avoid thermal shock cracking of billet, while removing trace amounts of moisture and gas adsorbed on the surface of billet. Second stage (600℃→970℃-1030℃): heating rate 15℃ / min, rapidly rising to the target temperature, preferably 1000℃; Once the temperature reaches the set value, the heat preservation stage begins, ideally lasting for 15 minutes.

[0051] Furthermore, the heating and heat preservation process also includes the following steps: during the heat preservation period, argon gas is introduced with a purity of ≥99.99% and a flow rate of 0.2 m³ / h.

[0052] Argon gas is introduced to protect the billet, preventing the formation of Cr2O3 and FeO composite oxide scale on the billet surface, which would affect subsequent cold rolling processes.

[0053] S224, implemented with single-pass gradient hot rolling: A gradient reduction strategy of "small at the beginning and large at the end" is adopted. The initial reduction force on the inlet side is 500-600kN, which is gradually increased to 800-900kN on the outlet side. The rolling speed is controlled at 1.5-2.0m / s. The gradual increase of pressure parameters ensures that the stress of the billet is gradually released from the time it contacts the rolls to the time it is rolled. This avoids the tearing of the structure caused by a single large reduction. Controlling the rolling speed ensures that the billet has sufficient contact with the rolls and avoids thickness fluctuations caused by excessive speed.

[0054] S225, air-cooled immediately after hot rolling: The forced air cooling system is activated immediately upon the billet leaving the rolls to prevent grain growth and dispersion of the billet from being cooled naturally in the air. Air cooling parameter control: air cooling wind speed 8-10m / s, wind direction at a 45° angle to billet movement direction, to ensure uniform cooling of the upper and lower surfaces of the billet, cooling rate controlled at 30-40℃ / s, so that the billet temperature drops from 1000℃ to below 600℃ within 30s; The final temperature of air cooling should be controlled at 300-400℃ to avoid excessively rapid cooling (wind speed > 12m / s) which could cause stress cracks on the surface of the billet, or excessively slow cooling (wind speed < 6m / s) which could cause the NbC and VC dispersed phases to re-aggregate.

[0055] This invention has three main advantages: First, it employs a stepped heating process to promote the diffusion of Yb and the partial dissolution and re-precipitation of NbC and VC dispersed phases, thus avoiding uneven distribution of dispersed phases due to component segregation during subsequent heat treatment. Second, it utilizes the synergistic effect of plastic deformation from single-pass hot rolling and rapid air cooling to refine the grain size, laying the foundation for further grain refinement during subsequent cold rolling. Third, the hot-rolled strip thickness is stable at 0.5-0.8 mm, making it suitable for subsequent multi-pass cold rolling operations and avoiding the risk of cold rolling cracking due to initial thickness deviations.

[0056] S23, Low-temperature annealing: The hot-rolled strip is held at 680℃–720℃ for 2 hours, and then naturally cooled to room temperature in the furnace to obtain the hot-rolled strip after low-temperature annealing. Low-temperature annealing eliminates hot rolling stress, promotes the uniform distribution of Yb2O3, NbC, and VC dispersed phases, improves elongation after annealing, and improves processing plasticity.

[0057] Furthermore, low-temperature annealing also includes the following steps: S231, Preliminary Preparations: Hot-rolled strip pretreatment: After the hot-rolled strip is forced to air-cool to room temperature, the surface is immediately cleaned: high-pressure air is used to blow away the surface oxide dust, and then anhydrous ethanol is used to wipe away the residual oil stains to avoid the oil stains carbonizing and forming impurity points during annealing, which would affect the distribution of the dispersed phase.

[0058] Equipment debugging and adaptation: Box-type vacuum annealing furnace (vacuum degree ≤10) is selected. -3 The furnace is equipped with a programmable temperature control system (error ±5℃) and an argon protection device. A graphite support is placed inside the furnace, and the hot-rolled strip is loaded into the furnace in a vertical suspension manner with a spacing of ≥8mm to avoid uneven local temperature caused by overlapping.

[0059] Pre-calibrate furnace temperature uniformity: Place 3 thermocouples in different areas of the furnace to ensure that the annealing temperature fluctuation is ≤±3℃, and avoid local high temperature causing coarsening of the dispersed phase.

[0060] S232, controls the low-temperature annealing temperature: Tiered heating system: First stage (room temperature → 400℃): heating rate 50℃ / h, slow heating to reduce the temperature difference between the inside and outside of the strip, avoid generating new thermal stress, and gradually remove trace amounts of moisture and gas adsorbed on the surface of the strip.

[0061] Second stage (400℃→680℃-720℃): Heating rate 80℃ / h, rapidly rising to the target annealing temperature, with the optimal target annealing temperature being 700℃.

[0062] Once the temperature reaches the set value, maintain the temperature for 2 hours, while simultaneously introducing argon gas with a purity of ≥99.99%. Introducing argon gas maintains a slight positive pressure inside the furnace to prevent air infiltration that could lead to oxidation of the strip surface, and also to inhibit the oxidation and failure of the dispersed phase.

[0063] S233, natural cooling: After the heat preservation is completed, turn off the heating system and keep argon gas continuously flowing in, allowing the strip to cool naturally to room temperature with the furnace. The cooling rate should be controlled at 20-30℃ / h to avoid rapid cooling that could cause stress to re-accumulate.

[0064] This invention employs a process of "hot-rolled strip pretreatment → low-temperature annealing temperature control → natural cooling," which reduces residual stress in the hot-rolled strip, prevents subsequent cold rolling cracking and warping, and promotes the diffusion and distribution of Yb₂O₃, NbC, and VC dispersed phases, laying the foundation for triple dispersion strengthening. Simultaneously, it can also improve the strip's elongation and enhance the processing plasticity of the hot-rolled strip.

[0065] S24, Precision Cold Rolling: The hot-rolled strip after low-temperature annealing is cold-rolled in multiple passes, with a reduction of 15%-20% per pass, and finally cold-rolled to a cold-rolled thin strip blank of 0.05-0.3mm. Precision cold rolling uses multiple passes to avoid strip structure cracking caused by a single large reduction, and to avoid structural cracking of composite dispersed phases due to stress concentration.

[0066] Furthermore, the use of multi-pass cold rolling in precision cold rolling also includes the following steps: S241, Pre-treatment before cold rolling: Optimization of billet condition: Select cast-rolled billets with a thickness of 2-3mm, and perform recrystallization annealing at 730℃ / 2h with a cooling rate of 80-100℃ / h. Remove the billets from the furnace at 160℃ and air cool them to eliminate defects and internal stress in the as-cast structure, make the grain size uniform, improve plasticity reserves, and reduce the risk of initial cracking.

[0067] Surface cleaning and lubrication: Alkaline degreasing (5% NaOH solution, 60℃ / 10min) + pickling (10% hydrochloric acid + 2% hydrofluoric acid, room temperature / 5min) + passivation treatment are used to remove surface oxide scale and oil stains; special cold rolling grease is applied to reduce the frictional stress between the roll and the strip.

[0068] Equipment calibration and debugging: A four-roll precision cold rolling mill is selected, with a roll diameter of Φ300-400mm and a surface roughness Ra≤0.02μm; the roll parallelism and pressure control system are calibrated in advance to ensure uniform distribution of rolling force and avoid local stress concentration.

[0069] S242, Intermediate Annealing and Stress Relief: Annealing timing selection: Precision cold rolling is performed 7-9 times, with intermediate annealing performed after the 3rd and 6th cold rolling passes to eliminate work hardening and internal stress generated in the previous rolling processes.

[0070] Annealing process parameters: A vacuum annealing furnace (vacuum degree ≤10⁻³Pa) is used, with a heating rate of 50℃ / h, an annealing temperature of 700-720℃, and a holding time of 2h; after cooling to 400℃ at a rate of 5℃ / min, argon gas is introduced to cool to room temperature to ensure complete recrystallization of the grains and reduce the dislocation density.

[0071] Post-annealing treatment: After annealing, the strip is straightened, the surface oxide color is removed, and grease is reapplied before entering the next rolling pass.

[0072] Furthermore, the dynamic control of the precision cold rolling process also includes the following steps: Tension gradient adaptation: The first three passes of the roll pressure control system adopt "front tension > rear tension" (difference 20MPa) to avoid deviation by utilizing the rigidity of the thick strip; subsequent passes adopt "rear tension > front tension" (difference 15MPa) to prevent the thin strip from breaking and reduce stress concentration at the dispersed phase interface.

[0073] Coordinating temperature and speed: Controlling the strip temperature during rolling at 90-120℃, and adjusting the rolling speed (increasing by 10-20m / min per pass) and the amount of cooling water for the rolls (5-8L / min) to avoid excessive temperature leading to lubrication failure, or excessive temperature leading to decreased plasticity.

[0074] S243, post-cold rolling treatment of the final pass: Stress relaxation annealing: After final rolling, low-temperature stress relaxation annealing is performed at a temperature of 320℃-380℃, held at the temperature, with the optimal temperature being 350℃, held for 1.5 hours, and then cooled to room temperature at a rate of 30℃ / h to eliminate residual stress from final rolling.

[0075] Surface cleaning: Select a neutral and environmentally friendly cleaning agent containing nonionic surfactants, heat it (preferably to 40°C), and spray the surface of the hot-rolled strip through a high-pressure electrostatic spraying device. Utilize the electrostatic adsorption effect to remove residual lubricating grease and fine oxidized dust. Then rinse with pure water under high pressure (preferably 60°C pure water under high pressure for 5 minutes), and finally dry with hot air at 75°C-80°C.

[0076] This invention utilizes a combination of multi-pass gradient reduction and intermediate annealing. Firstly, it avoids the microstructure tearing caused by a single large reduction, thus reducing the cracking rate of the thin strip. Secondly, it refines the grains after rolling, improving fracture toughness, and the multi-pass gradual approach to the target thickness enhances the uniformity of the thin strip thickness. Thirdly, the intermediate annealing process eliminates work hardening, preventing strip breakage caused by decreased plasticity in subsequent cold rolling passes.

[0077] S3, heat treatment: S31, Solution treatment: Cold-rolled thin strip billets are kept at 1200℃-1250℃ in an argon protective atmosphere for 1 hour, followed by water cooling (cooling rate ≥50℃ / min) to obtain solution-treated thin strip billets; high-temperature holding ensures that Yb, Nb and V are fully dissolved, creating conditions for the precipitation of triple dispersed phases.

[0078] S32, Aging Dispersion Treatment: The solution-treated strip billet is held at 850℃-900℃ for 4-6 hours and then cooled in the furnace to obtain rare earth dispersed strip billet; holding at 850℃-900℃ promotes the synergistic precipitation of rare earth oxides Y2O3, CeO2, Yb2O3 and carbides NbC, VC, forming a triple dispersion strengthening effect.

[0079] S33, Stress Relief Treatment: Rare earth dispersed thin strip billets are held at 450℃-500℃ for 1.5 hours, followed by natural cooling to obtain rare earth dispersed thin strips; this eliminates residual stress in precision cold-rolled and solution-treated billets, improving the toughness and thermal shock resistance of the thin strips.

[0080] Furthermore, eliminating residual stress in precision cold-rolled and solution-treated billets includes the following steps: S331, Billet Cleaning and Drying: A neutral, environmentally friendly cleaning agent containing nonionic surfactants is selected. The billet is heated, preferably to 40°C, and sprayed with a high-pressure electrostatic spray device to remove oil stains and fine oxide dust. The electrostatic adsorption effect is used to remove oil stains and fine oxide dust. Then, it is rinsed with pure water under high pressure and finally dried with hot air at 200°C-230°C. The billet cleaning and drying process avoids carbonization and contamination of oil stains and fine oxide dust during annealing, ensuring uniform stress release.

[0081] S332, billet condition inspection: X-ray stress meter is used to detect the residual stress on the surface of rare earth dispersed thin strip (target initial value ≤300MPa). The degree of grain distortion is observed by metallographic microscope. If the thickness of the deformed layer is >50μm, pre-stress relief treatment (300℃ / 1h, air cooling) is required.

[0082] S333, Equipment Preparation: Select a vacuum annealing furnace (vacuum degree ≤10). -3The furnace is equipped with a high-precision temperature control system (error ±5℃), an inert gas (argon, purity ≥99.99%) introduction device, and a gradient cooling module; graphite clamps are placed inside the furnace to prevent the billet from deforming due to heat.

[0083] S334, vacuum gradient annealing process: Stepwise heating phase: First stage (room temperature → 500℃): heating rate 50℃ / h, slow heating to avoid thermal shock and new stress. In this stage, the micro-stress generated by cold rolling is initially released through dislocation climb. Second stage (500℃→850℃): Heating rate 80℃ / h, heating to recrystallization temperature range, holding at the temperature, preferably 2h, to promote grain recrystallization and eliminate macroscopic residual stress. The third stage (850℃→1050℃): The heating rate is 100℃ / h, and the temperature is raised to 850℃-1050℃. The temperature is held for 1 hour, which allows the thermal stress generated by the solution treatment to fully relax, while suppressing the intergranular precipitation of elements such as Ti and Nb, and ensuring the purity of the matrix.

[0084] Gradient cooling stage: First gradient (1050℃→600℃): cooling rate 5℃ / min, slowly releasing thermal stress during the cooling process and avoiding stress re-accumulation.

[0085] Second gradient (600℃→400℃): cooling rate 10℃ / min, maintaining the stability of the billet structure and reducing phase transformation stress.

[0086] The third gradient (400℃ → room temperature): Argon gas is introduced for cooling at a rate of 20℃ / min to quickly pass through the brittle temperature range, while inert gas is used to protect the surface from oxidation.

[0087] S335, low-temperature stabilization treatment: After annealing, the billet is put back into the vacuum furnace, heated to 350-400℃, and held for 3 hours to allow the residual austenite to fully transform and the stress to be further evenly distributed.

[0088] The process employs a "heat preservation-small cooling-heat preservation" cycle: each 50℃ temperature drop is followed by a 30min heat preservation cycle, for a total of 3 cycles. This eliminates secondary stress generated during the cooling process, improves dimensional stability, and finally cools to room temperature at a rate of 30℃ / h to ensure that the internal stress gradient of the strip is ≤10MPa / mm.

[0089] S336, surface reinforcement auxiliary treatment: High-energy shot peening is performed on the surface of the thin strip: stainless steel shot with a diameter of 0.1~0.3mm is selected, the peening pressure is 0.3~0.5MPa, and the peening time is 30s. A nano-layer is formed on the surface, which introduces residual compressive stress to offset the internal residual tensile stress. At the same time, the surface grains are refined. After shot peening, low-temperature tempering is performed. Preferably, it is held at 200℃ for 30min to eliminate the local stress concentration caused by shot peening and improve the stability of the surface structure.

[0090] This invention has three main advantages: First, by using gradient annealing and stabilization treatment, residual stress in rare earth dispersed strips is eliminated, reducing warping deformation during subsequent processing. Second, recrystallization forms uniform and fine grains, reducing the dislocation density of the metal and improving the toughness of the strip during fracture. Third, a vacuum environment combined with inert gas protection optimizes the surface quality of the strip, reducing its surface roughness.

[0091] S4, Oxide film treatment: Rare earth dispersed thin strips are kept at 600℃-650℃ in air atmosphere for 3 hours to promote the full bonding of Yb oxide and multi-element oxide film, forming a dense Al2O on the surface of the strip. 3+ A composite oxide film of Cr2O3+Nb2O5+V2O5+Yb2O3 was formed, which ultimately yielded a rare earth dispersion-strengthened electrothermal alloy strip.

[0092] Furthermore, a dense Al2O layer forms on the surface of the thin strip. 3+ The Cr2O3+Nb2O5+V2O5+Yb2O3 composite oxide film includes the following steps: S41: Preprocessing: Surface deep cleaning: A three-step method of "alkaline degreasing + pickling + activation" is adopted: First, alkaline washing with 5% NaOH solution at 50℃-60℃ is used to remove residual rolling oil and carbides on the surface after cold rolling and heat treatment; then pickling with a mixture of 10% hydrochloric acid and 2% hydrofluoric acid at room temperature is used to remove the surface oxide scale and the surface enrichment layer of elements such as Ti and Nb; finally, activation is carried out with 5% sulfuric acid solution at room temperature to enhance the surface active sites; immediately after cleaning, it is rinsed three times with deionized water and then dried with hot air at 300℃ for 20 minutes to avoid moisture residue leading to increased porosity of the oxide film.

[0093] Pre-oxidation activation: Place the purified ribbon into a vacuum furnace (vacuum degree ≤10). -3 Pa) heat preservation, preferably 450℃ for 1 hour, to remove adsorbed gases such as H2O and CO2 on the surface; then argon gas with a purity of ≥99.99% is introduced to cool to room temperature, activate the activity of surface metal atoms, and create conditions for subsequent oxide film nucleation.

[0094] S42, gradient temperature controlled oxidation: Equipment and loading: A box-type atmosphere furnace is selected, equipped with an oxygen partial pressure control system (accuracy ±0.1%), a programmable temperature control module (error ±3℃) and an exhaust gas treatment device; the thin strip adopts vertical suspension loading with a spacing ≥5mm to avoid uneven local oxidation caused by overlapping.

[0095] Stepwise temperature increase oxidation: First stage (room temperature → 400℃): Heating rate 10℃ / min, air + argon mixed atmosphere introduced, oxygen partial pressure 5%, hold at this temperature, preferably for 1 hour. In this stage, an initial Cr2O3 film is preferentially formed, providing an adhesion substrate for subsequent multi-element oxide films, while inhibiting FeO formation.

[0096] The second stage (400℃→550℃): heating rate 8℃ / min, oxygen partial pressure increased to 10%, and held at this temperature for 2 hours. This promotes the nucleation of Al2O3 on the Cr2O3 film surface, while Nb and V elements begin to oxidize to form Nb2O5 and V2O5, forming a transition layer.

[0097] The third stage (550℃→650℃): heating rate 5℃ / min, oxygen partial pressure adjusted to 15%, hold at this temperature for 3 hours (ideally). Yb diffuses from the matrix to the surface, combining with oxygen to form Yb₂O₃, which then diffuses into the Al₂O₃ / Cr₂O₃ lattice (Yb₂O₃). 3+ With Al 3+ (The difference in ionic radius is ≤5%, and the lattice matching degree is high). At the same time, Yb2O3 forms a composite spinel phase with Nb2O5 and V2O5 (such as YbNbO4 and YbVO4) to achieve chemical bonding.

[0098] Fourth stage (650℃→700℃): Heating rate 3℃ / min, oxygen partial pressure maintained at 15%, hold at this temperature, preferably for 1 hour. This further promotes the growth and densification of oxide grains, reducing porosity and stress within the film.

[0099] Furthermore, the oxygen partial pressure sensor monitors the entire step-heating oxidation process in real time and adjusts the temperature according to a "low → medium → high" gradient: in the initial stage, the low oxygen partial pressure avoids excessive oxidation that could lead to a loose film layer; in the middle stage, the medium oxygen partial pressure promotes the synergistic nucleation of multi-element oxides; and in the later stage, the high oxygen partial pressure ensures the full oxidation of Yb2O3.

[0100] Furthermore, the third and fourth stages also include steps to suppress volatilization with the help of inert gas: In the third and fourth stages, high-purity argon gas (purity ≥99.99%) with a flow rate of 0.2 m³ / h is introduced to form an "oxygen-argon" mixed gas flow, which suppresses the volatilization loss of Yb2O3 at high temperature (the volatilization rate of Yb2O3 decreases at 650℃) and at the same time removes trace impurity gases generated by oxidation.

[0101] S43, Post-treatment for oxide film densification: Stable under low temperature tempering: After oxidation, the temperature was lowered to 300℃ at a rate of 5℃ / min, held at that temperature for 2 hours, and then allowed to cool naturally to room temperature. Tempering was used to eliminate thermal stress within the membrane and promote Yb production. 3+ It homogenizes the diffusion of other metal ions and improves the stability of the film structure.

[0102] Hole sealing treatment: The sol-gel method was used for pore sealing: the thin strip was immersed in an ethanol solution containing 5% tetraethyl orthosilicate + 2% Yb(NO3)3 (room temperature, 10 min), then dried at 150℃ for 10 min, and then calcined at 400℃ for 30 min. The resulting SiO2-Yb2O3 sealing layer can fill the micropores in the film, further improving the density.

[0103] This invention improves the density of the composite oxide film and reduces the micropore size through pretreatment, gradient temperature oxidation, and post-treatment to densify the oxide film. This effectively prevents oxygen diffusion into the substrate and enhances the antioxidant lifespan of the thin film. Gradient temperature control and oxygen partial pressure regulation ensure uniform distribution of each oxide, without local enrichment or deficiency, resulting in a uniform film thickness. Furthermore, the chemical bonding and lattice matching between Yb₂O₃ and the multi-element oxides enhance the film-substrate adhesion, solving the problem of easy thermal shock peeling of traditional oxide films.

[0104] Compared with the prior art, the beneficial effects of the present invention are as follows: By employing a triple rare earth synergy of Y-Yb-Ce, combined with a Nb-V composite carbide dispersed phase, a synergistic dispersed phase of rare earth oxides Y2O3, CeO2, and Yb2O3 and carbides NbC and VC is formed. A triple dispersion strengthening mechanism is formed with a size gradient of medium-fine (rare earth oxides) - fine (NbC) - ultrafine (VC), which not only solves the problem of insufficient high-temperature strength of electrothermal alloy strips, but also makes up for the lack of toughness.

[0105] Al₂O is formed through the synergistic effect of Al and rare earth elements. 3+ A composite oxide film of Cr2O3+Nb2O5+V2O5+Yb2O3 improves the thermal shock resistance and oxide film stability of the alloy. Detailed Implementation

[0106] To provide a further understanding of the purpose, structure, features, and functions of the present invention, detailed descriptions are provided below with reference to specific embodiments. Example

[0107] A rare earth dispersion-strengthened electrothermal alloy strip comprises the following raw materials: chromium (Cr), silicon (Si), titanium (Ti), aluminum (Al), carbon (C), yttrium (Y), cerium (Ce), ytterbium (Yb), niobium (Nb), vanadium (V), and iron (Fe).

[0108] Furthermore, the raw material ratio of the electrothermal alloy strip is as follows: Cr: 16%–18%, Si: 0.3%–0.6%, Ti: 0.1%–0.2%, Al: 5%–7%, C≤0.03%, Y: 0.05%–0.12%, Ce: 0.02%–0.05%, Yb: 0.03%–0.08%, Nb: 0.05%–0.20%, V: 0.05%–0.15%, Fe: balance; The Fe-Cr-Al alloy, composed of chromium (Cr), iron (Fe), and aluminum (Al), provides basic mechanical support and ensures the formability and structural stability of the strip. Fe, Cr, and Al have similar atomic radii and synergistically form a solid solution, providing an attachment carrier for the dispersion strengthening phase. Cr has a strong thermodynamic tendency to oxidize. At high temperatures, it forms a dense Cr2O3 oxide film on the surface, which hinders the diffusion of oxygen into the substrate, delays oxidation failure, and improves the thermal shock resistance of the substrate. At the same time, Cr2O3 and Al2O3 have a high lattice matching degree and synergistically form a continuous composite film, which optimizes the structural density of the composite oxide film and enhances the bonding force between the oxide film and the substrate. Al is the core antioxidant element. At high temperatures, it forms an Al2O3 oxide film. Al2O3 has a high melting point, which can improve the upper limit of the alloy's high temperature resistance. At the same time, it works synergistically with rare earth elements to refine the matrix grains and dispersed phases, improve the alloy's toughness, and reduce the risk of low-temperature brittleness. The silicon (Si) is used to enhance the antioxidant properties. Si readily combines with O to form SiO2. SiO2 fills the micropores of the Cr2O3 / Al2O3 film, optimizing the oxide film composition. At the same time, Si is dissolved in the Fe matrix, hindering atomic diffusion and reducing the oxide film growth rate; thus enhancing the structural stability of the thin strip at high temperatures. The titanium (Ti) forms carbides (TiC), which are nanoscale particles that pin grain boundaries and hinder grain growth, thus improving the alloy's room temperature and high temperature toughness. Ti preferentially fixes carbon in the matrix, reducing the formation of Cr by carbon combining with Cr. 23 C6-induced grain boundary embrittlement improves the thermal shock resistance of the thin strip; The carbon C at a low content (≤0.03%) helps to form trace carbides TiC and YC. These carbides have high hardness, can hinder the movement of metal dislocations, achieve dispersion strengthening, and improve high-temperature strength. The yttrium (Y) is the core dispersion strengthening element, which combines with O and C to form nanoscale dispersed phases such as Y2O3 and YC. These phases can pin dislocations and hinder grain growth. Y2O3 can fill defects in the Cr2O3 / Al2O3 film, improving the stability of the oxide film Cr2O3 and Al2O3. It also improves the toughness and thermal shock resistance of the alloy, alleviates the low-temperature brittleness of the Fe-Cr-Al alloy, and reduces the risk of thin strip fracture.

[0109] The synergistic effect of cerium (Ce) and y on the oxide film refines the grain size, increases the density and adhesion of the oxide film, enhances the dispersion strengthening effect, and improves the high-temperature strength and plasticity of the alloy. Ce reacts with impurities such as O and S to generate CeO2 and CeS, which purify the matrix, reduce grain boundary segregation, and improve the processing performance of the alloy.

[0110] The ytterbium (Yb) synergistically forms a Y-Yb-O composite dispersed phase with Y, which is more effective than Y alone in hindering grain growth. Yb has a fast diffusion rate, and when the oxide film is locally damaged, Yb can quickly migrate to the damaged area to form a new oxide film Yb2O3, thus optimizing the self-healing property of the oxide film. Yb is cheaper than Y and Ce, reducing the cost of the alloy.

[0111] The niobium (Nb) forms a stable NbC carbide phase with C. NbC has a high melting point, refines grains, hinders grain boundary migration, and improves creep resistance. Nb and Al synergistically form Nb3Al intermetallic compounds, enhancing high-temperature strength. Nb is oxidized to form Nb2O5, which forms a composite film with Cr2O3 / Al2O3, optimizing the oxide film structure and reducing the tendency of Cr2O3 / Al2O3 oxide film to peel off.

[0112] The vanadium (V) forms a VC carbide phase with C. VC has high hardness, refines grains, and enhances high-temperature hardness. V can reduce the nucleation energy of Al2O3, promote the growth of Al2O3 oxide film, and improve the bonding force between the oxide film and the matrix. V is dissolved in the matrix, which reduces the thermal expansion coefficient of the alloy and reduces the risk of thermal shock cracking.

[0113] Example 2: A method for preparing a rare earth dispersion-strengthened electrothermal alloy thin strip, comprising the following steps: This invention also proposes a method for preparing rare earth dispersion-strengthened electrothermal alloy thin strips, comprising the following steps: S1, the smelting steps: S11, Fe, Cr, Si, Ti, C, Nb, and V are added to a vacuum induction melting furnace, the temperature is raised to 1550℃, and the temperature is held for 30 minutes to completely melt Fe, Cr, Si, Ti, Nb, and V and achieve uniform mixing.

[0114] Furthermore, the proportions of Fe, Cr, Si, and Ti are as follows: Cr: 17%, Si: 0.4%, Ti: 0.1%, C: 0.02%; Nb: 0.12%, V: 0.10%.

[0115] Furthermore, the complete melting and homogeneous mixing of Fe, Cr, Si, Ti, Nb, and V includes the following steps: S111, Raw material selection and purification: Industrial pure iron, metallic chromium blocks, ferrosilicon alloy (Si content ≥75%), sponge titanium, ferroniobium alloy (Nb content ≥60%), ferrovanadium alloy (V content ≥50%) and high-purity graphite (C content ≥99.9%) with a purity ≥99.5% are selected; all raw materials must be baked at 400℃ for 2 hours to thoroughly remove surface moisture, oil and adsorbed gases, and avoid the generation of bubbles and oxide inclusions during smelting.

[0116] S112, precise proportion design: with Fe as the balance, the target proportion of each element is strictly controlled: Cr: 17%, Si: 0.4%, Ti: 0.1%, C: 0.02%; Nb: 0.12%, V: 0.10%, and the material proportioning error is controlled within ±0.02% to ensure that the alloy composition meets the standards.

[0117] S113, Equipment selection and loading process; Core equipment parameters: It adopts a 1-5t vacuum induction furnace, equipped with an electromagnetic stirring system, high-precision temperature measurement (error ±5℃) and vacuum monitoring device. The furnace lining is made of high-purity corundum material to avoid the reaction and contamination between refractory materials and molten steel.

[0118] Charging sequence: Following the principle of "low melting point at the bottom, refractory elements in the middle, and easily oxidized elements added later," charge in layers: Place small pieces of Fe at the bottom (20% of the total); in the middle layer, place Cr blocks, Fe and NbFe (5-30mm), and VFe (5-30mm) in sequence, ensuring full contact between refractory elements and the Fe matrix; leave a charging port at the top for subsequent addition of Si, Ti, and C. Avoid direct contact between C and Cr during charging to prevent premature carbide formation.

[0119] S114, Vacuum control: After loading, start the vacuum pump and gradually pump the vacuum in the furnace to ≤10Pa before power is supplied. Maintain the vacuum at ≤5Pa throughout the melting process to avoid the reaction of O and N in the atmosphere with alloying elements.

[0120] S115, stepped heating regime: Initial stage (room temperature - 1200℃): slow heating with low power, heating rate controlled at 8℃ / min, using electromagnetic induction skin effect to melt layer by layer and promote gas discharge; Mid-term (1200℃-1500℃): Medium power heating, with the rate increased to 12℃ / min to ensure rapid melting and clearing of the furnace charge; Final stage (1500℃-1550℃): Fine-tune the power to stabilize the temperature at 1550℃ and hold for 30 minutes to provide thermodynamic conditions for element dissolution and diffusion.

[0121] S116, staged charging and deoxidation: After the furnace charge is fully melted (about 1500℃), Si is added first for pre-deoxidation and stirred for 10 minutes; then Ti and the remaining C are added, and the molten steel is further purified by vacuum carbon deoxidation reaction (C+O→CO↑) to improve the recovery rate of Ti, Nb and V.

[0122] S117, Mixing: During the heat preservation period, turn on the electromagnetic stirrer with a stirring power of 30%-40% of the melting power. Stir for 5 minutes every 10 minutes to promote the dissolution and diffusion of refractory elements (Nb, V). Take a sample at the end of the heat preservation period to test the composition. If segregation is present, add the corresponding alloying elements and extend the stirring for 10 minutes.

[0123] S118, control the final temperature of smelting: when the temperature of the molten steel stabilizes at 1550℃, the holding time meets the standard, and the composition test shows that all elements are within the target range and there are no undissolved particles, the smelting ends; a molten and uniformly mixed Fe, Cr, Si, Ti, Nb, V metal melt is obtained.

[0124] This invention addresses several key aspects: First, by employing stepped heating, appropriate distribution of refractory elements, and electromagnetic stirring, it solves the problem of the difficulty in dissolving Nb and V (which have high melting points), achieving 100% melting of all elements and avoiding residual inclusions. Second, by using a vacuum environment, electromagnetic stirring, and staged feeding, it reduces the macroscopic segregation of Fe, Cr, Si, Ti, Nb, and V, and improves their microscopic uniformity, laying the foundation for the subsequent formation of uniform carbides and oxide films in the alloy. Third, by combining vacuum carbon deoxidation and pre-deoxidation processes, it reduces the oxygen and nitrogen content of the molten steel, effectively reducing oxide and nitride impurities and improving the purity of the alloy matrix. Fourth, by precisely controlling the C content and the uniform distribution of each strengthening element, it ensures that Cr and Si fully form an anti-oxidation film, and that Ti, Nb, and V uniformly precipitate fine carbides, significantly improving the mechanical properties and high-temperature stability of the alloy.

[0125] S12, cool down to 1500℃, add Al block, keep warm for 20 minutes; cooling down and adding Al block prevents Al from volatilizing at high temperatures.

[0126] Furthermore, the Al content is 6%.

[0127] S13, add Y, Ce, Yb rare earth alloy ingots (yttrium iron alloy, cerium iron alloy, ytterbium iron alloy), and hold for 20 minutes; pure Y, Ce, Yb are extremely chemically reactive and easily react with O2 and N2 in the furnace gas to form oxide / nitride inclusions, leading to uncontrolled composition and performance degradation. However, when they exist in the form of rare earth alloy ingots, they are easy to dissolve in the matrix, reducing oxidation loss and ensuring the precipitation of dispersed phases.

[0128] Furthermore, the proportions of Y, Ce, and Yb are as follows: Y: 0.08%, Ce: 0.03%, Yb: 0.06%.

[0129] Furthermore, the Y rare earth alloy ingot is a yttrium-iron alloy, which contains yttrium and iron; the Ce rare earth alloy ingot is a cerium-iron alloy, which contains cerium and iron; and the Yb rare earth alloy ingot is a ytterbium-iron alloy, which contains ytterbium and iron.

[0130] S14, argon gas (purity ≥99.99%) is introduced and stirred at a flow rate of 0.5 m³ / h for 10 min to obtain molten steel; argon gas stirring removes hydrogen, oxygen, and nitrogen gases from the molten steel, reducing the interference of gases on the formation of Yb₂O₃, NbC, and VC.

[0131] Furthermore, reducing the interference of gases on the formation of Yb₂O₃, NbC, and VC includes the following steps: S141, Preliminary Preparations: Argon purification treatment: High-purity argon gas with a purity of ≥99.999% is selected and purified twice by a low-temperature adsorption dryer and a deoxygenation filter to prevent argon gas from carrying moisture and oxygen and contaminating the molten steel. Stirring device compatibility: The vacuum induction melting furnace is equipped with a bottom-blowing + top-blowing composite argon stirring system: the bottom uses permeable bricks and the top uses a liftable spray gun; Predicting the state of molten steel: After completing step S13 (adding rare earth alloy ingots and finishing the heat preservation), check the temperature and surface state of the molten steel. If the temperature of the molten steel is stable at 1500℃ and there is no obvious slag or solidified layer on the surface of the molten steel, conditions are created for stirring and degassing. If there is obvious slag or solidified layer on the surface of the molten steel, use a corundum slag skimmer to clean it in time to avoid the slag being drawn into the molten steel and forming inclusions, which would interfere with the precipitation of dispersed phases.

[0132] S142, precise control of argon gas stirring parameters: Vacuum control: Before stirring, maintain the vacuum level in the furnace at ≤5Pa. During stirring, gradually increase it to 50-100Pa to avoid the vacuum being too high, which would cause the argon bubbles to break too quickly, or too low, which would affect the gas discharge.

[0133] Set the flow gradient: Start-up phase (0-3 min): Bottom-blown argon flow rate 0.2 m³ / min 3 / h, top-blown flow rate 0.1m³ / h 3 / h, slowly inflate to avoid splashing of molten steel, and initially form tiny bubbles; Main stirring stage (3-8 min): Bottom blowing flow rate increased to 0.5 m³ / min. 3 / h, top-blown flow rate 0.2m³ / h 3 / h, the bubble density increases and convective circulation is formed, which enhances gas adsorption and diffusion; Final stage (8-10 min): Bottom blowing flow rate reduced to 0.15 m³ / min. 3 / h, top blow flow rate 0.05m³ / h3 / h, to achieve a smooth finish and avoid secondary air intake caused by drastic fluctuations in molten steel; Optimize stirring time: The total stirring time is 10 minutes to ensure that the average residence time of bubbles in molten steel is ≥3 minutes, so as to fully adsorb dissolved gases; control the stirring time to 10 minutes so that argon can adsorb H, O and N in molten steel and carry them out, and the temperature of molten steel will not drop excessively (≤1450℃).

[0134] S143, Post-stirring flow stabilization treatment: Argon gas is gradually shut off: After stirring, first shut off the top blowing lance, and then gradually reduce the bottom blowing argon gas flow rate to 0 at a rate of 0.05 m³ / h to avoid sudden gas stoppage causing the molten steel to draw back air.

[0135] Static holding: After shutting off the argon gas, maintain the vacuum degree in the furnace at 80 Pa and let it stand for 5 minutes to allow the tiny bubbles remaining in the molten steel to continue to rise, while allowing elements such as Y, Nb, and V to diffuse evenly, creating conditions for the nucleation of dispersed phases.

[0136] Temperature calibration: After standing, the temperature of the molten steel is checked and maintained at 1470℃. If the temperature is insufficient, short-term heating is performed to compensate for the temperature.

[0137] This invention introduces purified argon gas to remove H, O, and N from the molten steel, preventing the gas from reacting with Y, Yb, Nb, and V to form harmful inclusions, thus ensuring the purity of the dispersed phase. Stirring promotes uniform element distribution, eliminating localized enrichment or deficiency and improving the uniformity of the dispersed phase. Degassing reduces the viscosity of the molten steel, improving the filling capacity during subsequent twin-roll casting and preventing cracks and porosity defects in the cast strip billet caused by inclusions.

[0138] S2, Molding: S21, Twin-roll thin strip casting and rolling: The temperature of molten steel is controlled at 1470℃ and poured into the roll gap of the twin-roll thin strip casting and rolling mill to obtain the cast strip billet; the molten steel is poured into the roll gap of the twin-roll thin strip casting and rolling mill at a high temperature to avoid the segregation of Yb, Nb, and V elements and their local enrichment at the grain boundaries. The resulting cast strip billet has a thickness of 0.8-1.2mm, and the microstructure of the cast strip is fine-grained austenite, rare earth oxides (Y2O3, CeO2, Yb2O3) and primary carbides NbC and VC.

[0139] S22, gradient hot rolling: The cast strip billet is heated to 1030℃, held for 15min, and then hot rolled in a single pass. After hot rolling, it is immediately air-cooled to obtain a hot-rolled strip with a thickness of 0.8mm. Heating the cast strip billet promotes the diffusion of Yb elements and promotes the partial dissolution and re-precipitation of NbC and VC dispersed phases. Gradient hot rolling reduces the thickness of the cast strip billet, refines the grains, and inhibits grain growth and dispersion of the dispersed phases.

[0140] Furthermore, water cooling is performed immediately after hot rolling, with the cooling water temperature maintained at 25°C. Rapid water cooling can prevent the aggregation of dispersed phases such as Yb2O3, NbC, and VC at the grain boundaries. The cooling water temperature is kept between 25°C to avoid stress cracks on the strip surface caused by excessively low water temperature (<20°C) or excessively high water temperature (>40°C) which would reduce cooling efficiency.

[0141] Furthermore, gradient hot rolling includes the following steps: S221, Pretreatment of cast strip billet: Use a neutral cleaning agent to clean the cast strip billet and remove oxide scale and oil stains from the surface of the cast strip billet.

[0142] S222, Equipment Commissioning and Adaptation: A two-roll reversible hot rolling mill is selected, with a roll diameter of Φ500mm, a surface hardness of HRC≥60, and a roughness of Ra=0.8μm. The rolls are preheated to 200℃ to reduce plastic fluctuations caused by the temperature difference between the billet and the rolls. The heating furnace temperature control system (error ±5℃) and the hot rolling mill pressure sensor (accuracy ±1%) are calibrated to ensure precise and controllable heating temperature and pressing force; Process parameter presets: Based on the initial thickness of the cast strip billet, the target hot rolling thickness is set to 0.6 mm, and the air cooling speed is preset to 10 m / s.

[0143] S223, Heating and heat preservation: Tiered heating system: First stage (room temperature → 600℃): heating rate 10℃ / min, slow heating to avoid thermal shock cracking of billet, while removing trace amounts of moisture and gas adsorbed on the surface of billet. Second stage (600℃→1000℃): Heating rate 15℃ / min, rapidly rising to the target temperature of 1000℃; Once the temperature reaches the set value, the heat preservation stage begins, lasting for 15 minutes.

[0144] Furthermore, the heating and heat preservation process also includes the following steps: during the heat preservation period, argon gas is introduced with a purity of ≥99.99% and a flow rate of 0.2 m³ / h.

[0145] Argon gas is introduced to protect the billet, preventing the formation of Cr2O3 and FeO composite oxide scale on the billet surface, which would affect subsequent cold rolling processes.

[0146] S224, implemented with single-pass gradient hot rolling: A gradient reduction strategy of "small at the beginning and large at the end" is adopted. The initial reduction force on the inlet side is 600kN, which is gradually increased to 900kN on the outlet side, and the rolling speed is controlled at 2.0m / s. The gradual increase of pressure parameters ensures that the stress of the billet is gradually released from the time it contacts the rolls to the time it is rolled, avoiding the microstructure tearing caused by a single large reduction. Controlling the rolling speed ensures sufficient contact between the billet and the rolls, while avoiding thickness fluctuations caused by excessive speed.

[0147] S225, air-cooled immediately after hot rolling: The forced air cooling system is activated immediately upon the billet leaving the rolls to prevent grain growth and dispersion of the billet from being cooled naturally in the air. Air cooling parameter control: air cooling wind speed 10m / s, wind direction at a 45° angle to billet movement direction, to ensure uniform cooling of the upper and lower surfaces of the billet, cooling rate controlled at 40℃ / s, so that the billet temperature drops from 1000℃ to below 600℃ within 30s; The final temperature of air cooling is controlled at 400℃ to avoid stress cracks on the surface of the billet caused by excessively rapid cooling (wind speed > 12m / s) or excessively slow cooling (wind speed < 6m / s) causing the NbC and VC dispersed phases to re-aggregate.

[0148] This invention has three main advantages: First, it employs a stepped heating process to promote the diffusion of Yb and the partial dissolution and re-precipitation of NbC and VC dispersed phases, thus avoiding uneven distribution of dispersed phases due to component segregation during subsequent heat treatment. Second, it utilizes the synergistic effect of plastic deformation from single-pass hot rolling and rapid air cooling to refine the grain size, laying the foundation for further grain refinement during subsequent cold rolling. Third, the hot-rolled strip thickness is consistently maintained at 0.8 mm, making it suitable for subsequent multi-pass cold rolling operations and avoiding the risk of cold rolling cracks caused by initial thickness deviations.

[0149] S23, Low-temperature annealing: The hot-rolled strip is held at 720℃ for 2 hours and then naturally cooled to room temperature in the furnace to obtain the hot-rolled strip after low-temperature annealing. Low-temperature annealing eliminates hot rolling stress, promotes the uniform distribution of Yb2O3, NbC, and VC dispersed phases, improves elongation after annealing, and improves processing plasticity.

[0150] Furthermore, low-temperature annealing also includes the following steps: S231, Preliminary Preparations: Hot-rolled strip pretreatment: After the hot-rolled strip is forced to air-cool to room temperature, the surface is immediately cleaned: high-pressure air is used to blow away the surface oxide dust, and then anhydrous ethanol is used to wipe away the residual oil stains to avoid the oil stains carbonizing and forming impurity points during annealing, which would affect the distribution of the dispersed phase.

[0151] Equipment debugging and adaptation: Box-type vacuum annealing furnace (vacuum degree ≤10) is selected. -3The furnace is equipped with a programmable temperature control system (error ±5℃) and an argon protection device. A graphite support is placed inside the furnace, and the hot-rolled strip is loaded into the furnace in a vertical suspension manner with a spacing of ≥8mm to avoid uneven local temperature caused by overlapping.

[0152] Pre-calibrate furnace temperature uniformity: Place 3 thermocouples in different areas of the furnace to ensure that the annealing temperature fluctuation is ≤±3℃, and avoid local high temperature causing coarsening of the dispersed phase.

[0153] S232, controls the low-temperature annealing temperature: Tiered heating system: First stage (room temperature → 400℃): heating rate 50℃ / h, slow heating to reduce the temperature difference between the inside and outside of the strip, avoid generating new thermal stress, and gradually remove trace amounts of moisture and gas adsorbed on the surface of the strip.

[0154] Second stage (400℃→700℃): Heating rate 80℃ / h, rapidly rising to the target annealing temperature of 700℃.

[0155] After the temperature reaches the set value, it is kept at that temperature for 2 hours, while argon gas with a purity of ≥99.99% is introduced. Argon gas is introduced to maintain a slight positive pressure inside the furnace to prevent air from seeping in and causing oxidation of the strip surface, while also inhibiting the oxidation failure of the dispersed phase.

[0156] S233, natural cooling: After the heat preservation is completed, turn off the heating system and keep argon gas continuously flowing in, allowing the strip to cool naturally to room temperature with the furnace. The cooling rate is controlled at 30℃ / h to avoid rapid cooling that could cause stress to re-accumulate.

[0157] This invention employs a process of "hot-rolled strip pretreatment → low-temperature annealing temperature control → natural cooling," which reduces residual stress in the hot-rolled strip, prevents subsequent cold rolling cracking and warping, and promotes the diffusion and distribution of Yb₂O₃, NbC, and VC dispersed phases, laying the foundation for triple dispersion strengthening. Simultaneously, it can also improve the strip's elongation and enhance the processing plasticity of the hot-rolled strip.

[0158] S24, Precision Cold Rolling: The hot-rolled strip after low-temperature annealing is cold-rolled in multiple passes, with a reduction of 20% in each pass, and finally cold-rolled to a cold-rolled thin strip blank of 0.3mm. Precision cold rolling uses multiple passes to avoid strip structure cracking caused by a single large reduction, and to avoid structural cracking of composite dispersed phases due to stress concentration.

[0159] Furthermore, the use of multi-pass cold rolling in precision cold rolling also includes the following steps: S241, Pre-treatment before cold rolling: Optimization of billet condition: Select 3mm thick cast-rolled billet, and anneal it at 730℃ for 2h for recrystallization. The annealing cooling rate is 100℃ / h. After reaching 160℃, the billet is removed from the furnace and air-cooled to eliminate defects and internal stress in the as-cast structure, so that the grain size is uniform, the plasticity reserve is improved, and the risk of initial cracking is reduced.

[0160] Surface cleaning and lubrication: Alkaline degreasing (5% NaOH solution, 60℃ / 10min) + pickling (10% hydrochloric acid + 2% hydrofluoric acid, room temperature / 5min) + passivation treatment are used to remove surface oxide scale and oil stains; special cold rolling grease is applied to reduce the frictional stress between the roll and the strip.

[0161] Equipment calibration and debugging: A four-roll precision cold rolling mill is selected, with a roll diameter of Φ300-400mm and a surface roughness Ra≤0.02μm; the roll parallelism and pressure control system are calibrated in advance to ensure uniform distribution of rolling force and avoid local stress concentration.

[0162] S242, Intermediate Annealing and Stress Relief: Annealing timing selection: The precision cold rolling is performed 9 times, with intermediate annealing performed after the 3rd and 6th cold rolling passes to eliminate work hardening and internal stress generated by the previous rolling.

[0163] Annealing process parameters: Vacuum annealing furnace (vacuum degree ≤10) is used. -3 (Pa), heating rate 50℃ / h, annealing temperature 720℃, hold for 2h; then cool to 400℃ at 5℃ / min, and then purge with argon to cool to room temperature to ensure complete recrystallization of the grains and reduce dislocation density.

[0164] Post-annealing treatment: After annealing, the strip is straightened, the surface oxide color is removed, and grease is reapplied before entering the next rolling pass.

[0165] Furthermore, the dynamic control of the precision cold rolling process also includes the following steps: Tension gradient adaptation: The first three passes of the roll pressure control system adopt "front tension > rear tension" (difference 20MPa) to avoid deviation by utilizing the rigidity of the thick strip; subsequent passes adopt "rear tension > front tension" (difference 15MPa) to prevent the thin strip from breaking and reduce stress concentration at the dispersed phase interface.

[0166] Coordinated temperature and speed: Control the strip temperature at 100℃ during rolling. By adjusting the rolling speed (increase by 20m / min per pass) and the amount of cooling water for the rolls (5L / min), we can prevent excessive temperature from causing lubrication failure or excessive temperature from causing a decrease in plasticity.

[0167] S243, post-cold rolling treatment of the final pass: Stress relaxation annealing: After final rolling, low-temperature stress relaxation annealing is performed at 350℃ for 1.5h, followed by cooling to room temperature at a rate of 30℃ / h to eliminate residual stress from final rolling.

[0168] Surface cleaning: A neutral and environmentally friendly cleaning agent containing nonionic surfactants is selected, heated to 40°C, and sprayed onto the surface of the hot-rolled strip through a high-pressure electrostatic spraying device. The electrostatic adsorption effect is used to remove residual lubricating grease and fine oxidized dust. Then, it is rinsed with 60°C pure water under high pressure for 5 minutes, and finally dried with 80°C hot air.

[0169] This invention utilizes a combination of multi-pass gradient reduction and intermediate annealing. Firstly, it avoids the microstructure tearing caused by a single large reduction, thus reducing the cracking rate of the thin strip. Secondly, it refines the grains after rolling, improving fracture toughness, and the multi-pass gradual approach to the target thickness enhances the uniformity of the thin strip thickness. Thirdly, the intermediate annealing process eliminates work hardening, preventing strip breakage caused by decreased plasticity in subsequent cold rolling passes.

[0170] S3, heat treatment: S31, Solution treatment: Cold-rolled thin strip billet is kept at 1250℃ under an argon protective atmosphere for 1 hour, and then water-cooled (cooling rate ≥50℃ / min) to obtain solution-treated thin strip billet; high temperature holding ensures that Yb, Nb and V are fully dissolved, creating conditions for the precipitation of triple dispersed phases.

[0171] S32, Aging Dispersion Treatment: The solution-treated strip billet is held at 900℃ for 6 hours and then cooled in the furnace to obtain rare earth dispersed strip billet; the holding at 900℃ promotes the synergistic precipitation of rare earth oxides Y2O3, CeO2, Yb2O3 and carbides NbC, VC, forming a triple dispersion strengthening effect.

[0172] S33, Stress Relief Treatment: Rare earth dispersed thin strip billets are held at 500℃ for 1.5h and then naturally cooled to obtain rare earth dispersed thin strips; this eliminates residual stress in precision cold-rolled and solution-treated billets, and improves the toughness and thermal shock resistance of the thin strips.

[0173] Furthermore, eliminating residual stress in precision cold-rolled and solution-treated billets includes the following steps: S331, Billet Cleaning and Drying: A neutral, environmentally friendly cleaning agent containing nonionic surfactants is selected, heated to 40°C, and sprayed onto the surface of precision cold-rolled and solution-treated billets through a high-pressure electrostatic spraying device. The electrostatic adsorption effect is used to remove oil stains and fine oxide dust. Then, it is rinsed with pure water under high pressure and finally dried with hot air at 200°C. The billet cleaning and drying process avoids carbonization and contamination of oil stains and fine oxide dust during annealing, ensuring uniform stress release.

[0174] S332, billet condition inspection: X-ray stress meter is used to detect the residual stress on the surface of rare earth dispersed thin strip (target initial value ≤300MPa). The degree of grain distortion is observed by metallographic microscope. If the thickness of the deformed layer is >50μm, pre-stress relief treatment (300℃ / 1h, air cooling) is required.

[0175] S333, Equipment Preparation: Select a vacuum annealing furnace (vacuum degree ≤10). -3 The furnace is equipped with a high-precision temperature control system (error ±5℃), an inert gas (argon, purity ≥99.99%) introduction device, and a gradient cooling module; graphite clamps are placed inside the furnace to prevent the billet from deforming due to heat.

[0176] S334, vacuum gradient annealing process: Stepwise heating phase: First stage (room temperature → 500℃): heating rate 50℃ / h, slow heating to avoid thermal shock and new stress. In this stage, the micro-stress generated by cold rolling is initially released through dislocation climb. Second stage (500℃→850℃): Heating rate 80℃ / h, heating to recrystallization temperature range, holding for 2h, promoting grain recrystallization, and eliminating macroscopic residual stress. The third stage (850℃→1050℃): The heating rate is 100℃ / h, the temperature is raised to 1050℃, and held for 1h to allow the thermal stress generated by the solution treatment to fully relax, while suppressing the intergranular precipitation of elements such as Ti and Nb, and ensuring the purity of the matrix.

[0177] Gradient cooling stage: First gradient (1050℃→600℃): cooling rate 5℃ / min, slowly releasing thermal stress during the cooling process and avoiding stress re-accumulation.

[0178] Second gradient (600℃→400℃): cooling rate 10℃ / min, maintaining the stability of the billet structure and reducing phase transformation stress.

[0179] The third gradient (400℃ → room temperature): Argon gas is introduced for cooling at a rate of 20℃ / min to quickly pass through the brittle temperature range, while inert gas is used to protect the surface from oxidation.

[0180] S335, low-temperature stabilization treatment: After annealing, the billet is put back into the vacuum furnace, heated to 350°C, and held for 3 hours to allow the residual austenite to fully transform and the stress to be further evenly distributed.

[0181] The process employs a "heat preservation-small cooling-heat preservation" cycle: each 50℃ temperature drop is followed by a 30min heat preservation cycle, for a total of 3 cycles. This eliminates secondary stress generated during the cooling process, improves dimensional stability, and finally cools to room temperature at a rate of 30℃ / h to ensure that the internal stress gradient of the strip is ≤10MPa / mm.

[0182] S336, surface reinforcement auxiliary treatment: High-energy shot peening treatment of the thin strip surface: φ0.2mm stainless steel shot is selected, the blasting pressure is 0.5MPa, and the blasting time is 30s. A nano layer is formed on the surface, which introduces residual compressive stress to offset the internal residual tensile stress. At the same time, the surface grains are refined. After shot peening, the surface is tempered at 200℃ for 30min to eliminate the local stress concentration caused by shot peening and improve the stability of the surface structure.

[0183] This invention has three main advantages: First, by using gradient annealing and stabilization treatment, residual stress in rare earth dispersed strips is eliminated, reducing warping deformation during subsequent processing. Second, recrystallization forms uniform and fine grains, reducing the dislocation density of the metal and improving the toughness of the strip during fracture. Third, a vacuum environment combined with inert gas protection optimizes the surface quality of the strip, reducing its surface roughness.

[0184] S4, Oxide film treatment: Rare earth dispersed thin strips were kept at 650℃ in air for 3 hours to promote the full bonding of Yb oxide and multi-element oxide film, forming a dense Al2O on the surface of the thin strips. 3+ A composite oxide film of Cr2O3+Nb2O5+V2O5+Yb2O3 was formed, which ultimately yielded a rare earth dispersion-strengthened electrothermal alloy strip.

[0185] Furthermore, a dense Al2O layer forms on the surface of the thin strip. 3+ The Cr2O3+Nb2O5+V2O5+Yb2O3 composite oxide film includes the following steps: S41: Preprocessing: Surface deep cleaning: A three-step method of "alkaline degreasing + pickling + activation" is adopted: First, alkaline washing with 5% NaOH solution at 60℃ is used to remove residual rolling oil and carbides on the surface after cold rolling and heat treatment; then pickling with a mixture of 10% hydrochloric acid and 2% hydrofluoric acid at room temperature is used to remove the surface oxide scale and the surface enrichment layer of elements such as Ti and Nb; finally, activation is carried out with 5% sulfuric acid solution at room temperature to enhance the surface active sites; immediately after cleaning, it is rinsed three times with deionized water and then dried with hot air at 300℃ for 20 minutes to avoid moisture residue leading to increased porosity of the oxide film.

[0186] Pre-oxidation activation: Place the purified ribbon into a vacuum furnace (vacuum degree ≤10). -3The surface is heated to 450℃ for 1 hour to remove adsorbed gases such as H2O and CO2. Then, argon gas with a purity of ≥99.99% is introduced to cool the surface to room temperature, which activates the activity of surface metal atoms and creates conditions for subsequent oxide film nucleation.

[0187] S42, gradient temperature controlled oxidation: Equipment and loading: A box-type atmosphere furnace is selected, equipped with an oxygen partial pressure control system (accuracy ±0.1%), a programmable temperature control module (error ±3℃) and an exhaust gas treatment device; the thin strip adopts vertical suspension loading with a spacing ≥5mm to avoid uneven local oxidation caused by overlapping.

[0188] Stepwise temperature increase oxidation: First stage (room temperature → 400℃): Heating rate 10℃ / min, air + argon mixed atmosphere introduced, oxygen partial pressure 5%, hold for 1 hour. In this stage, the initial Cr2O3 film is preferentially formed, providing an adhesion substrate for the subsequent multi-element oxide film, while inhibiting the formation of FeO.

[0189] Second stage (400℃→550℃): Heating rate 8℃ / min, oxygen partial pressure increased to 10%, held for 2h. Promotes Al2O3 nucleation on the Cr2O3 film surface, while Nb and V elements begin to oxidize to form Nb2O5 and V2O5, forming a transition layer.

[0190] Third stage (550℃→650℃): Heating rate 5℃ / min, oxygen partial pressure adjusted to 15%, holding for 3h. Yb diffuses from the matrix to the surface, combines with oxygen to form Yb₂O₃, and integrates into the Al₂O₃ / Cr₂O₃ lattice (Yb₂O₃) through lattice diffusion. 3+ With Al 3+ (The difference in ionic radius is ≤5%, and the lattice matching degree is high). At the same time, Yb2O3 forms a composite spinel phase with Nb2O5 and V2O5 (such as YbNbO4 and YbVO4) to achieve chemical bonding.

[0191] Fourth stage (650℃→700℃): Heating rate 3℃ / min, oxygen partial pressure maintained at 15%, hold for 1 hour. This further promotes the growth and densification of oxide grains, reducing porosity and stress within the film.

[0192] Furthermore, the oxygen partial pressure sensor monitors the entire step-heating oxidation process in real time and adjusts the temperature according to a "low → medium → high" gradient: in the initial stage, the low oxygen partial pressure avoids excessive oxidation that could lead to a loose film layer; in the middle stage, the medium oxygen partial pressure promotes the synergistic nucleation of multi-element oxides; and in the later stage, the high oxygen partial pressure ensures the full oxidation of Yb2O3.

[0193] Furthermore, the third and fourth stages also include steps to suppress volatilization with the help of inert gas: In the third and fourth stages, high-purity argon gas (purity ≥99.99%) with a flow rate of 0.2 m³ / h is introduced to form an "oxygen-argon" mixed gas flow, which suppresses the volatilization loss of Yb2O3 at high temperature (the volatilization rate of Yb2O3 decreases at 650℃) and at the same time removes trace impurity gases generated by oxidation.

[0194] S43, Post-treatment for oxide film densification: Stable under low temperature tempering: After oxidation, the temperature was lowered to 300℃ at a rate of 5℃ / min, held at that temperature for 2 hours, and then allowed to cool naturally to room temperature. Tempering was used to eliminate thermal stress within the membrane and promote Yb production. 3+ It homogenizes the diffusion of other metal ions and improves the stability of the film structure.

[0195] Hole sealing treatment: The sol-gel method was used for pore sealing: the thin strip was immersed in an ethanol solution containing 5% tetraethyl orthosilicate + 2% Yb(NO3)3 (room temperature, 10 min), then dried at 150℃ for 10 min, and then calcined at 400℃ for 30 min. The resulting SiO2-Yb2O3 sealing layer can fill the micropores in the film, further improving the density.

[0196] This invention improves the density of the composite oxide film and reduces the micropore size through pretreatment, gradient temperature oxidation, and post-treatment to densify the oxide film. This effectively prevents oxygen diffusion into the substrate and enhances the antioxidant lifespan of the thin film. Gradient temperature control and oxygen partial pressure regulation ensure uniform distribution of each oxide, without local enrichment or deficiency, resulting in a uniform film thickness. Furthermore, the chemical bonding and lattice matching between Yb₂O₃ and the multi-element oxides enhance the film-substrate adhesion, solving the problem of easy thermal shock peeling of traditional oxide films.

[0197] The present invention has been described in the above-described embodiments; however, these embodiments are merely examples for implementing the present invention. It must be noted that the disclosed embodiments do not limit the scope of the present invention. Conversely, any modifications and refinements made without departing from the spirit and scope of the present invention are within the scope of patent protection of the present invention.

Claims

1. A rare earth dispersion strengthened electrothermal alloy ribbon, characterized by: The raw materials include chromium Cr, silicon Si, titanium Ti, aluminum Al, carbon C, yttrium Y, cerium Ce, Yb ytterbium, niobium Nb, vanadium V, and iron Fe.

2. The rare earth dispersion strengthened electrocaloric alloy ribbon of claim 1, wherein: The raw material ratio is: Cr: 16%-18%, Si: 0.3%-0.6%, Ti: 0.1%-0.2%, Al: 5%-7%, C≤0.03%, Y: 0.05%-0.12%, Ce: 0.02%-0.05%, Yb: 0.03%-0.08%, Nb: 0.05%-0.20%, V: 0.05%-0.15%, and Fe: the balance.

3. A method for producing a rare earth dispersion strengthened electrothermal alloy thin strip, characterized by: The method comprises the following steps: S1, a melting step: S11, adding Fe, Cr, Si, Ti, Nb, V, and C into a vacuum induction melting furnace, heating to 1520-1550°C, and maintaining for 30-40 min; S12, after cooling to 1480-1500°C, adding Al blocks and maintaining; S13, adding Y, Ce, and Yb rare earth alloy ingots and maintaining for 15-20 min again; S14, passing in argon with a purity of ≥99.99% and a flow rate of 0.3-0.5 m³ / h, stirring in the argon atmosphere, and obtaining molten steel; S2, a forming step: S21, double-roller thin strip casting: controlling the temperature of the molten steel at 1450-1470°C, pouring into the roll gap of a double-roller thin strip casting machine, and obtaining a cast strip blank; S22, gradient hot rolling: heating the cast strip blank to 970-1030°C, maintaining, then performing single-pass hot rolling, immediately air cooling after hot rolling, and obtaining hot-rolled strips with a thickness of 0.5-0.8 mm; S23, low-temperature annealing: maintaining the hot-rolled strips at a temperature of 680-720°C, naturally cooling to room temperature in the furnace, and obtaining hot-rolled strips after low-temperature annealing; S24, precise cold rolling: adopting multi-pass cold rolling on the hot-rolled strips after low-temperature annealing, with a reduction of 15%-20% for each pass, and finally cold rolling to cold-rolled thin strip blanks with a thickness of 0.05-0.3 mm; S3, a heat treatment step: S31, solid solution treatment: maintaining the cold-rolled thin strip blanks at a temperature of 1200-1250°C in an argon protective atmosphere, then performing water cooling, with a water cooling rate of ≥50°C / min, and obtaining solid solution treated thin strip blanks; S32, aging dispersion treatment: maintaining the solid solution treated thin strip blanks at a temperature of 850-900°C for 4-6 h, and cooling in the furnace, and obtaining rare earth dispersed thin strips; S33, stress relief treatment: maintaining the rare earth dispersed thin strips at a temperature of 450-500°C, and naturally cooling, and obtaining rare earth dispersed thin strips; S4, a step of oxide film treatment: The rare earth dispersed thin strips are maintained at a temperature of 600-650°C in an air atmosphere, a dense Al2O3+Cr2O3+Nb2O5+V2O5+Yb2O3 composite oxide film is formed on the surface of the rare earth dispersed thin strips, and rare earth dispersed strengthened electric heating alloy thin strips are obtained.

4. The production method according to claim 3, characterized by: S11 comprises the following steps: S111, raw material selection and purification: select industrial pure iron with purity ≥ 99.5%, metal chromium block, ferrosilicon alloy, titanium sponge, niobium iron alloy, vanadium iron alloy and high-purity graphite; all raw materials are baked at 200-400℃ for 2-4h; The silicon content in the ferrosilicon alloy is ≥75%; the vanadium content in the vanadium iron alloy is ≥50%; the carbon content in the high-purity graphite is ≥99.9%; the niobium content in the niobium iron alloy is ≥60%; S112, precise proportioning design: Fe as the balance, the target proportion of each element: Cr: 16%-18%, Si: 0.3%-0.6%, Ti: 0.1%-0.2%, C≤0.03%, Nb: 0.05%-0.20%, V: 0.05%-0.15%, the proportioning error is controlled within ±0.02%; S113, equipment selection and charging process; Core equipment parameters: use 1-5t level vacuum induction furnace, equipped with electromagnetic stirring system, high-precision temperature measurement and vacuum monitoring device, furnace lining selects high-purity corundum material; Charging sequence: according to the principle of "low melting point bottom, difficult to melt in the middle, easy to oxidize later", layered charging: small Fe block at the bottom; Cr block, Fe and NbFe, VFe in turn in the middle layer; reserve the charging port at the top; S114, vacuum degree control: start the vacuum pump after charging, gradually draw the vacuum degree in the furnace to ≤10Pa, then start power supply, and keep the vacuum degree ≤5Pa during the whole melting process; S115, stepwise temperature rising system: Initial stage: from room temperature to 1200℃: low power slow heating, the heating rate is controlled at 5-8℃ / min; Middle stage: from 1200℃ to 1500℃: medium power heating, the rate is increased to 10-12℃ / min; Final stage: from 1500℃ to 1550℃: fine-tune the power to stabilize the temperature at 1520℃-1550℃, and keep for 30-40min; S116, stage-by-stage charging and deoxidization: after the furnace charge is fully melted, first add Si for pre-deoxidization, and stir for 5-10min; then add Ti and the remaining C; S117, mixing: turn on electromagnetic stirring during the holding period, the stirring power is 30%-40% of the melting power, stir for 5min every 10min; at the end of the holding period, take a sample for composition detection, if there is segregation, add corresponding alloy elements and extend the stirring for 10min; S118, control the end point temperature of melting: when the steel liquid temperature is stable at 1520℃-1550℃, the holding time is up to standard, and the composition detection shows that each element is within the target range and there is no undissolved particle, the melting is completed.

5. The production method according to claim 3, characterized by: S14 includes the following steps: pre-preparation: Argon purification treatment: select high-purity argon with purity ≥ 99.999%, purified by low-temperature adsorption dryer and deoxidizing filter twice; Stirring device adaptation: vacuum induction melting furnace is equipped with bottom blowing + top blowing composite argon stirring system: bottom uses gas brick, top uses liftable lance; Steel water state prediction: after completing S13 step, detect the steel water temperature and surface state, the steel water temperature is stable at 1480℃-1500℃, and there is no obvious scum and solidification layer on the surface of the steel water; if there is obvious scum and solidification layer on the surface of the steel water, use corundum skimmer to clean it in time; S142, precise control of argon stirring parameters: Control the vacuum degree: maintain the vacuum degree in the furnace ≤5 Pa before stirring, and gradually increase to 50-100 Pa during stirring; Set the flow gradient: Start-up phase time 0-3 min: bottom argon flow 0.1-0.2 m 3 / h, top flow 0.05-0.1 m 3 / h; Main agitation phase time 3-8 min: bottom blow flow rate increased to 0.3-0.5 m 3 / h, top blow flow rate 0.1-0.2 m 3 / h; End phase time 8-10 min: bottom blow rate reduced to 0.1-0.15 m 3 / h, top blow rate 0.05 m 3 / h; Optimize the stirring time: the total stirring time is 12-15 min, ensure that the average residence time of gas bubbles in the molten steel is ≥3 min, and fully adsorb the dissolved gas; S143, after stirring, stable flow treatment: Gradually stop argon: after stirring, first close the top blowing lance, and gradually reduce the bottom blowing argon flow to 0 at a rate of 0.05 m³ / h; Keep still and heat preservation: after stopping argon, maintain the vacuum degree in the furnace at 50-100 Pa, and keep still for 5-8 min; Temperature calibration: after keeping still, detect the temperature of the molten steel, and maintain the temperature of the molten steel at 1450-1470℃. If the temperature is insufficient, perform short-time heating to supplement the temperature.

6. The production method according to claim 3, characterized by: The S22 step also includes: S221, cast strip blank pretreatment: use a neutral cleaning agent to clean the cast strip blank; S222, equipment debugging and adaptation: Select a two-high reversible hot rolling mill, the roll diameter is Φ500-600mm, the surface hardness is HRC≥60, the roughness is Ra=0.8-1.2μm, and the roll is preheated to 150-200℃ in advance; Calibrate the heating furnace temperature control system error ±5℃, the hot rolling mill pressure sensor, the precision ±1%; Process parameter preset: according to the initial thickness of the cast strip blank, set the target hot rolling thickness to 0.5-0.8mm, and the air cooling wind speed is preset to 8-10m / s; S223, heating and heat preservation: Step-up heating system: The first stage is heated from room temperature to 600℃ at a rate of 10℃ / min; The second stage is heated from 600℃ to 970-1030℃ at a rate of 15℃ / min; After the temperature reaches the set value, heat preservation is performed; S224, implement single pass gradient hot rolling: Use the gradient reduction strategy of "small at the entrance and large at the exit", the initial reduction force at the entrance side is 500-600kN, gradually increases to 800-900kN at the exit side, and the rolling speed is controlled at 1.5-2.0m / s; S225, immediately air cooling after hot rolling: Immediately start the forced air cooling system as soon as the blank leaves the roller; Air cooling parameter control: air cooling wind speed 8-10m / s, wind direction and blank movement direction 45° angle, cooling rate control 30-40℃ / s, blank temperature drops below 600℃.

7. The production method according to claim 3, wherein: S23 includes the following steps: S231, front preparation: Hot strip pretreatment: After the hot strip is forced air cooled to room temperature, immediately clean the surface: use high-pressure air to blow off the surface oxidation dust, and then use anhydrous ethanol to wipe off the residual oil stains; Equipment debugging and adaptation: Select a box-type vacuum annealing furnace, equipped with a programmable temperature control system and an argon protection device, place graphite supports in the furnace, and use vertical suspension method to load the hot strip into the furnace with a spacing of ≥8mm; The vacuum degree of the box-type vacuum annealing furnace is ≤10 -3 Pa; Calibrate the furnace temperature uniformity in advance: place three thermocouples in different areas of the furnace; S232, control low-temperature annealing temperature: Step-up heating system: The first stage is heated from room temperature to 400℃ at a rate of 50℃ / h, The second stage is heated from 400℃ to 680-720℃ at a rate of 80℃ / h; After the temperature reaches the set value, keep the temperature constant while passing argon gas with purity ≥99.99% through; S233, natural cooling: After the temperature keeps constant, turn off the heating system and keep passing argon gas, and the strip is cooled to room temperature naturally.

8. The production method according to claim 3, characterized by: The S24 step further comprises: S241, pretreatment before cold rolling: Optimization of the state of the blank: choose cast-rolled blank with thickness of 2-3 mm, recrystallize annealing at 730℃ for 2h, annealing cooling rate of 80-100℃ / h, and take out the furnace and air cool at 160℃; Surface cleaning and lubrication: adopt alkaline degreasing + pickling + passivation treatment, and then smear special cold rolling lubricating grease; The alkaline degreasing adopts 5% NaOH solution, and the pickling adopts 10% hydrochloric acid + 2% hydrofluoric acid at room temperature for 5 min; Equipment calibration and debugging: choose four-roll precision cold rolling mill, roller diameter Φ300-400mm, surface roughness Ra≤0.02μm; S242, intermediate annealing and stress release: Annealing timing: the number of precision cold rolling is 7-9 times, and each of the third and sixth cold rolling is followed by intermediate annealing; Annealing process parameters: adopt vacuum annealing furnace, heating rate of 50℃ / h, reach annealing temperature of 700-720℃, and keep constant; Post-annealing treatment: straighten the strip after annealing, remove the surface oxidation color, re-smear lubricating grease, and then enter the next rolling; S243, post-treatment after final cold rolling: Stress relaxation annealing: low-temperature stress relaxation annealing after final rolling, temperature of 320℃-380℃, keep constant, and then cool to room temperature at a rate of 30℃ / h; Surface cleaning: choose neutral environment-friendly cleaning agent containing non-ionic surfactant, heat, spray the surface of the hot-rolled strip through high-voltage electrostatic spraying device, then high-pressure flush with pure water, and finally dry through 75℃-80℃ hot air.

9. The production method according to claim 3, characterized by: S33 comprises the following steps: S331, blank cleaning and drying: choose neutral environment-friendly cleaning agent containing non-ionic surfactant, heat, spray the surface of the precision cold rolling and solid solution treatment blank through high-voltage electrostatic spraying device, then high-pressure flush with pure water, and finally dry through 200℃-230℃ hot air; S332, blank state detection: detect the residual stress of the rare earth dispersed thin strip surface layer by X-ray stress meter, and observe the grain distortion degree by metallographic microscope, if the deformation layer thickness is >50μm, pre-stress relief treatment is needed; S333, equipment preparation: choose vacuum annealing furnace, equipped with high-precision temperature control system, inert gas introduction device and gradient cooling module, and place graphite clamp in the furnace; The inert gas is argon, and the purity of argon is ≥99.99%; S334, vacuum gradient annealing process: Stepwise heating stage: The first stage is to heat from room temperature to 500℃ at a rate of 50℃ / h; The second stage is to heat from 500℃ to 850℃ at a rate of 80℃ / h, and keep constant at 850℃; The third stage is to heat from 850℃ to 1050℃ at a rate of 100℃ / h, and keep constant at 1050℃; Gradient cooling stage: The first gradient is to cool from 1050℃ to 600℃ at a rate of 5℃ / min; The second gradient is from 600℃ to 400℃ at a rate of 10℃ / min; The third gradient is from 400℃ to room temperature at a rate of 20℃ / min with argon gas cooling; S335, low-temperature stabilization treatment: After annealing, the blank is reloaded into the vacuum furnace and heated to 350-400℃ for 3h; S336, surface strengthening auxiliary treatment: High-energy shot blasting is performed on the surface of the thin strip: stainless steel shots of φ0.1-0.3mm are selected, the blasting pressure is 0.3-0.5MPa, the blasting time is 30s, and low-temperature tempering is performed after shot blasting.

10. The use according to claim 3, characterized in that: S4 includes the following steps: S41: pre-treatment: Surface depth purification: three-step method of "alkali degreasing + pickling + activation": first, alkali washing with 5% NaOH solution at 50-60℃; then pickling with 10% hydrochloric acid + 2% hydrofluoric acid mixture at room temperature; finally, activation with 5% sulfuric acid solution at room temperature; after cleaning, immediately rinse with deionized water for 3 times, and then dry with hot air at 300℃ for 20min; Pre-oxidation activation: the purified thin strip is placed in a vacuum furnace for heat preservation; then pure argon gas with a purity of ≥99.99% is introduced to cool to room temperature; S42, gradient temperature control oxidation: Equipment and loading: box-type atmosphere furnace equipped with oxygen partial pressure control system, programmable temperature control module and tail gas treatment device; thin strip is vertically hung for loading with a spacing of ≥5mm; Stepwise temperature rising oxidation: The first stage is from room temperature to 400℃ at a rate of 10℃ / min, with air + argon mixed atmosphere, oxygen partial pressure 5%, and heat preservation; The second stage is from 400℃ to 550℃ at a rate of 8℃ / min, with oxygen partial pressure increased to 10%, and heat preservation; The third stage is from 550℃ to 650℃ at a rate of 5℃ / min, with oxygen partial pressure adjusted to 15%, and heat preservation; The fourth stage is from 650℃ to 700℃ at a rate of 3℃ / min, with oxygen partial pressure maintained at 15%, and heat preservation; S43, post-treatment for densification of oxidation film: Low-temperature tempering stabilization: After oxidation, the temperature is lowered to 300℃ at a rate of 5℃ / min, heat preservation for 2h, and then natural cooling to room temperature; Sealing treatment: Sol-gel sealing: the thin strip is immersed in an ethanol solution containing 5% tetraethyl orthosilicate + 2% Yb(NO3)3 at room temperature for 10min, then taken out and dried at 150℃ for 10min, and then calcined at 400℃ for 30min.