Preparation method of ultrathin stainless steel band for electronic device

Abstract

The invention relates to a preparation method of an ultrathin stainless steel band for an electronic device, which relates to the technical field of stainless steel bands, and comprises the following steps: carrying out hot rolling cogging on an austenitic stainless steel casting blank to obtain a hot rolled plate coil; the hot-rolled plate coil is subjected to cold rolling, before rolling, a roller is subjected to grinding and surface treatment, the rolling force and temperature are controlled, and a cold-rolled stainless steel band is obtained; the cold-rolled stainless steel band is subjected to annealing treatment under the protective atmosphere, internal stress is removed, and the annealed stainless steel band is obtained; and the annealed stainless steel band is subjected to surface polishing and finishing treatment, and the ultrathin stainless steel band for the electronic device is obtained. Electrolytic polishing treatment is adopted for surface polishing, an electrolyte comprises 60-70 parts of phosphoric acid, 20-30 parts of sulfuric acid and 4-8 parts of a composite additive, and the composite additive comprises sodium dodecyl sulfate, sodium citrate and glycerin. The method has the effect of improving the thickness uniformity of the ultra-thin stainless steel band, and the stainless steel band has low roughness and oxidation degree.

Description

Technical Field

[0001] This application relates to the field of stainless steel strip technology, and in particular to a method for preparing ultrathin stainless steel strips for electronic devices. Background Technology

[0002] In the field of electronic devices, stainless steel strip is a crucial basic material, and its performance has a vital impact on the quality and stability of electronic devices. As electronic devices continue to evolve towards miniaturization and precision, higher demands are being placed on the thickness and quality of stainless steel strip. Due to its unique physical and chemical properties, ultra-thin stainless steel strip plays an increasingly important role in the manufacture of electronic devices, such as in the packaging, shielding, and circuit connections of electronic components. Its quality directly affects the overall performance and lifespan of electronic devices.

[0003] A common method for preparing ultra-thin stainless steel strip involves placing a stainless steel strip of a certain thickness in a 20-roll mill. First, it undergoes a cold rolling process with the aid of rolling agent A to reduce its thickness. This is followed by a first annealing, a second annealing, and pickling. Then, a second cold rolling process with the aid of rolling agent B further reduces the thickness. Subsequent complex steps include surface nitriding, electropolishing, quenching, and a third annealing. Finally, the strip is leveled to obtain the ultra-thin stainless steel strip. These steps are quite complex, requiring multiple processing stages to gradually achieve the thinning and performance improvement of the stainless steel strip. Furthermore, some traditional methods may focus on adjusting the properties of the stainless steel strip through a single rolling or annealing process, but these often fail to fully meet the high precision and high quality requirements of electronic devices for ultra-thin stainless steel strips.

[0004] However, these conventional methods in the existing technology have significant drawbacks. Traditional manufacturing methods struggle to precisely control the thickness of stainless steel strips, and uneven thickness easily occurs during multiple rolling and processing steps, failing to meet the high-precision requirements of ultra-thin stainless steel strips for electronic devices. Furthermore, existing processes are inadequate in ensuring the surface quality of stainless steel strips. Due to the lack of effective anti-oxidation and surface treatment measures, the stainless steel strip surface is prone to oxidation and high roughness, which in turn affects the performance and reliability of electronic devices, thus requiring improvement. Summary of the Invention

[0005] To improve the performance of ultra-thin stainless steel strips, this application provides a method for preparing ultra-thin stainless steel strips for electronic devices.

[0006] The method for preparing an ultra-thin stainless steel strip for electronic devices provided in this application adopts the following technical solution: A method for preparing an ultrathin stainless steel strip for electronic devices includes the following steps: S1. Hot rolling is performed on the austenitic stainless steel billet to obtain hot-rolled coils; S2. The hot-rolled coil is cold-rolled. Before rolling, the rolls are ground and surface-treated. The rolling force and temperature are controlled to uniformly reduce the thickness of the hot-rolled coil to the required size, so as to obtain the cold-rolled stainless steel strip. S3. Anneal the cold-rolled stainless steel strip under a protective atmosphere to remove internal stress and obtain annealed stainless steel strip. S4. The annealed stainless steel strip is polished and finished to obtain ultra-thin stainless steel strip for electronic devices. In step S4, surface polishing is performed using electrolytic polishing. The electrolyte includes 60-70 parts of phosphoric acid, 20-30 parts of sulfuric acid, and 4-8 parts of composite additives, which include sodium dodecyl sulfonate, sodium citrate, and glycerol.

[0007] In the hot rolling initial stage, by rationally controlling the heating rate and rolling passes, the billet is heated evenly and deformed gradually, providing a uniformly structured and thickness-stable sheet for subsequent cold rolling, laying the foundation for thickness accuracy. During cold rolling, grinding of the rolls reduces surface roughness and minimizes scratches on the strip surface. Simultaneously, precise control of rolling force and temperature, through multiple rolling passes, ensures uniform strip thickness reduction, keeping thickness tolerances within a small range to meet the high-precision requirements of electronic devices. Annealing is performed under a protective atmosphere to effectively prevent oxidation of the stainless steel strip, fully eliminate internal stress, improve the internal structure of the material, and enhance the overall performance of the product. Surface polishing utilizes a specific ratio of phosphoric acid and sulfuric acid electrolysis. The electrolyte is prepared by adding a composite additive consisting of sodium dodecyl sulfonate, sodium citrate, and glycerol. Sodium dodecyl sulfonate enhances the dispersibility of the electrolyte, sodium citrate promotes the complexation of metal ions, and glycerol regulates the viscosity of the electrolyte. The three work synergistically, and combined with optimized electropolishing parameters, effectively remove surface oxide scale and micro-protrusions, reducing surface roughness. Subsequent tension finishing further eliminates micro-undulations, significantly improving surface smoothness and enhancing plate flatness. The ultra-thin stainless steel strip prepared by the above process has uniform thickness, low roughness and oxidation degree, and excellent corrosion resistance, meeting the stringent requirements of electronic devices for high precision, high surface quality, and high reliability of ultra-thin stainless steel strips.

[0008] Preferably, in step S1, the hot rolling billet is heated by gradient heating, with the temperature increased to 550-650℃ at a rate of 5-10℃ / min, held for 0.5-1h, and then increased to 1000-1100℃ at a rate of 10-15℃ / min.

[0009] The hot rolling billet preparation process is optimized by using a gradient heating method. First, the billet is heated at a low rate to an intermediate temperature range and held at that temperature. This allows for uniform temperature diffusion within the austenitic stainless steel billet, reducing thermal stress caused by excessive internal and external temperature differences and preventing billet cracking. Then, the billet is heated at a relatively high rate to the target hot rolling temperature, ensuring sufficient dissolution of alloying elements and the formation of a uniform austenitic structure, thus improving the material's plasticity and rollability. This gradient heating method, through staged control of the heating process, ensures both thermal stress release at low temperatures and microstructure optimization at high temperatures. This provides hot-rolled coils with uniform grains and good plasticity for subsequent rolling, improving the thickness uniformity and processing stability of ultra-thin stainless steel strips and laying the foundation for high-precision control in the cold rolling process.

[0010] Preferably, in step S1, the number of rolling passes is 6-8, the rolling speed is 1-3 m / s, and the single reduction rate decreases gradually, with the first pass ≤35% and the last pass 8-10%.

[0011] By employing multi-pass rolling with a gradually decreasing single-pass reduction rate, the slab can gradually refine its grains and homogenize its stress structure during multi-stage deformation. The first pass uses a large reduction rate to break down the original coarse grain structure of the slab and stimulate dynamic recrystallization. Subsequent passes gradually reduce the reduction rate to avoid excessive work hardening or surface defects caused by excessive single-pass deformation. At the same time, continuous multi-pass rolling ensures uniform deformation throughout the full thickness of the strip. Combined with appropriate rolling rate control of the temperature drop gradient, this ensures uniform thickness reduction and internal microstructure optimization of the strip during the hot rolling stage. This process, by controlling the deformation amount and rolling rhythm in stages, ensures hot rolling efficiency while avoiding thickness fluctuations or microstructure defects caused by unreasonable single-pass reduction rates. It provides a slab foundation with uniform microstructure and excellent surface quality for obtaining high-precision ultra-thin strips through cold rolling.

[0012] Preferably, in step S2, the first rolling force in the cold rolling process is 1600-2000 kN, and isothermal rolling is performed at 70-85℃. Thereafter, the rolling force is reduced by 5-10% for each subsequent pass, with a unit tension of 80-140 N / mm. 2 The rolling process involves 6-8 passes.

[0013] The first pass employs high rolling force combined with constant temperature rolling, which can effectively reduce the material when it has good plasticity, while avoiding uneven deformation caused by temperature fluctuations. Subsequent passes reduce the rolling force proportionally to match the material's work hardening characteristics, ensuring uniform and controllable deformation in each pass. With appropriate unit tension, the tension on the strip counteracts thickness fluctuations caused by rolling force, suppressing plate shape defects such as waviness and warping. Multi-pass rolling gradually thins the strip, precisely controlling the thickness of the hot-rolled coil to ultra-thin specifications. The surface treatment of the rolls and the parameter adjustment are linked in each pass to further ensure the uniformity of strip thickness and surface finish.

[0014] Preferably, the speed ratio of the upper and lower rolls in the cold rolling process is 1:(1.05-1.15).

[0015] By optimizing the cold rolling deformation mechanism through the speed difference between the upper and lower rolls, controllable additional shear deformation is generated in the strip during the rolling process. The fast roll side applies a forward frictional force to the strip, while the slow roll side applies a backward frictional force, forming a micro-shear force field. This force field can effectively eliminate the transverse thickness difference of the strip caused by uneven rolling pressure, and at the same time, break up coarse grains through shearing action, promoting the refinement of surface grains. In addition, the additional stress generated by the speed difference helps to suppress strip deviation, so that the strip extends uniformly in the width direction. Combined with the synergistic effect of rolling force and tension, it further improves the flatness and thickness uniformity of the strip.

[0016] Preferably, the protective atmosphere in the annealing process of step S3 is nitrogen and hydrogen.

[0017] By employing a mixed protective atmosphere of nitrogen and hydrogen to optimize the annealing environment, nitrogen, as an inert gas, can isolate oxygen in the annealing furnace, forming a physical protective barrier and inhibiting the oxidation of the stainless steel strip surface. Hydrogen, as a reducing gas, can react with trace oxides that may be generated during the annealing process, further eliminating the tendency for surface oxidation. At the same time, hydrogen atoms can penetrate to the grain boundaries, reducing the interfacial energy and inhibiting abnormal grain growth. The synergistic effect of the two forms a strong reducing atmosphere, ensuring that the stainless steel strip does not undergo oxidation and decarburization during the annealing process, and that diffusion annealing can eliminate lattice distortion and residual stress generated by cold rolling, refine the grains and homogenize the structure, providing a clean and stress-balanced substrate for subsequent polishing processes.

[0018] Preferably, in step S3, the annealing process involves heating to 600-700°C at a rate of 10-20°C / min, holding at that temperature for 8-10 minutes, and then quenching in an air at a rate of 50-80°C / s.

[0019] Heating to a specific temperature range at a moderate heating rate avoids excessive thermal stress caused by large temperature differences between the inside and outside of the stainless steel strip due to rapid heating, while ensuring sufficient diffusion of alloying elements. The holding stage allows the internal structure of the material to fully recover and recrystallize, effectively eliminating work hardening and residual stress generated by cold rolling, refining grains and uniformizing the microstructure. The gas quenching cooling stage uses a specific cooling rate to quickly suppress grain growth, retain the fine grain structure formed by recrystallization, and rapidly cool the material to room temperature, preventing uneven microstructure transformation caused by slow cooling.

[0020] Preferably, in step S4, the mass ratio of sodium dodecyl sulfonate, sodium citrate, and glycerol in the composite additive is (1-1.5):10:3.

[0021] Sodium dodecyl sulfonate, sodium citrate, and glycerol can form a stable micelle structure in the electrolytic polishing solution, enhancing the wettability and dispersibility of the electrolyte on the stainless steel strip surface, thus ensuring uniform polishing reaction. Sodium citrate, as a complexing agent, forms stable complexes with metal ions dissolved on the stainless steel surface, inhibiting excessive anodic polarization and preventing localized corrosion or over-polishing. Glycerol, as a viscosity modifier, optimizes the ion diffusion path by adjusting the electrolyte viscosity, preventing uneven polishing due to insufficient viscosity or affecting reaction efficiency due to excessive viscosity. By controlling the ratio of the three components, a dynamic balance of uniform wetting, controllable dissolution, and stable diffusion is achieved synergistically during electrolysis, enabling the uniform removal of oxide scale and micro-protrusions on the stainless steel strip surface, while inhibiting the formation of defects such as pitting corrosion and grooves, ultimately resulting in a high-quality surface with low roughness and uniform gloss.

[0022] Preferably, the current density for electropolishing in step S4 is 15-25 A / dm³. 2 Temperature 60-70℃, processing time 2-3 minutes.

[0023] The current density within the aforementioned range allows for appropriate anodic dissolution on the stainless steel strip surface, avoiding both insufficient polishing efficiency and residual oxide scale due to excessively low current, and excessive corrosion caused by excessively high current. The aforementioned temperature setting optimizes the activity and diffusion rate of ions in the electrolyte, allowing the polishing reaction to proceed under suitable kinetic conditions, promoting preferential dissolution of microscopic protrusions on the metal surface, and accelerating the surface smoothing process. The appropriate processing time, current density, and temperature work synergistically to ensure sufficient polishing of the stainless steel strip surface, eliminating microscopic defects generated during cold rolling and annealing, while preventing excessive surface dissolution or new roughness problems caused by prolonged polishing. The synergistic effect of these three factors ensures that the electropolishing process operates in a highly efficient and stable state, effectively improving the surface smoothness and flatness of the ultra-thin stainless steel strip.

[0024] Preferably, the finishing process in step S4 is tension finishing, with a pressure of 120-140 MPa and a speed of 15-25 m / min.

[0025] The aforementioned pressure range allows the strip to undergo slight plastic deformation under the action of the rolls, effectively eliminating surface micro-undulations and residual stress. Combined with appropriate speed control, this ensures uniform deformation of the strip under pressure, avoiding poor finishing due to excessive speed or reduced production efficiency due to excessively slow speed. During tension finishing, tension and pressure work together to ensure uniform force on the strip in the width direction, further correcting shape defects, improving the straightness and surface finish of the strip, and ultimately obtaining high-precision, high-quality ultra-thin stainless steel strip.

[0026] In summary, this application includes at least one of the following beneficial technical effects: 1. In the hot rolling initial stage, by rationally controlling the heating rate and rolling passes, the billet is heated evenly and deformed gradually, providing a uniformly structured and thickness-stable sheet for subsequent cold rolling, laying the foundation for thickness accuracy. During cold rolling, grinding of the rolls reduces surface roughness and minimizes scratches on the strip surface. Simultaneously, precise control of rolling force and temperature, through multiple rolling passes, ensures uniform strip thickness reduction, keeping thickness tolerances within a small range to meet the high-precision requirements of electronic devices. Annealing is performed under a protective atmosphere to effectively prevent stainless steel strip oxidation, fully eliminate internal stress, improve the internal structure of the material, and enhance the overall performance of the product. Surface polishing uses a specific ratio of phosphoric acid and sulfuric acid... The electrolyte is prepared by adding a composite additive consisting of sodium dodecyl sulfonate, sodium citrate, and glycerol. Sodium dodecyl sulfonate enhances the dispersibility of the electrolyte, sodium citrate promotes the complexation of metal ions, and glycerol adjusts the viscosity of the electrolyte. The three work synergistically, and combined with optimized electropolishing parameters, effectively remove surface oxide scale and micro-protrusions, reducing surface roughness. Subsequent tension finishing further eliminates micro-undulations, significantly improving surface smoothness and enhancing plate flatness. The ultra-thin stainless steel strip prepared by the above process has uniform thickness, low roughness and oxidation degree, and excellent corrosion resistance, meeting the stringent requirements of electronic devices for high precision, high surface quality, and high reliability of ultra-thin stainless steel strips.

[0027] 2. By optimizing the cold rolling deformation mechanism through the speed difference between the upper and lower rolls, controllable additional shear deformation is generated in the strip during the rolling process. The fast roll side applies a forward frictional force to the strip, while the slow roll side applies a backward frictional force, forming a micro-shear force field. This force field can effectively eliminate the transverse thickness difference of the strip caused by uneven rolling pressure, and at the same time, break up coarse grains through shearing action to promote the refinement of surface grains. In addition, the additional stress generated by the speed difference helps to suppress strip deviation, so that the strip extends uniformly in the width direction. Combined with the synergistic effect of rolling force and tension, the flatness and thickness uniformity of the strip are further improved.

[0028] 3. Sodium dodecyl sulfonate, sodium citrate, and glycerol can form a stable micelle structure in the electrolytic polishing solution, enhancing the wettability and dispersibility of the electrolyte on the stainless steel strip surface, thus ensuring uniform polishing reaction. Sodium citrate, as a complexing agent, forms stable complexes with metal ions dissolved on the stainless steel surface, inhibiting excessive anodic polarization and preventing localized corrosion or over-polishing. Glycerol, as a viscosity modifier, optimizes the ion diffusion path by adjusting the electrolyte viscosity, preventing uneven polishing due to insufficient viscosity or affecting reaction efficiency due to excessive viscosity. By controlling the ratio of the three components, a dynamic balance of uniform wetting, controllable dissolution, and stable diffusion is achieved synergistically during electrolysis, enabling the uniform removal of oxide scale and micro-protrusions on the stainless steel strip surface, while inhibiting the formation of defects such as pitting corrosion and grooves, ultimately obtaining a high-quality surface with low roughness and uniform gloss. Detailed Implementation

[0029] This application discloses a method for preparing ultra-thin stainless steel strips for electronic devices. Unless otherwise specified, all raw materials used in this application are commercially available. The following detailed description, in conjunction with embodiments, further illustrates this application: Raw material specifications: Sodium dodecyl sulfonate (CAS No.: 2386-53-0), sodium citrate (CAS No.: 68-04-2), glycerin (CAS No.: 56-81-5), cold rolling was performed using a 20-roll Sendzimir mill.

[0030] Example 1 Ultra-thin stainless steel strip for manufacturing electronic devices S1. The austenitic stainless steel billet is hot rolled and opened. The temperature is raised to 550℃ at a rate of 5℃ / min, held for 1 hour, and then raised to 1000℃ at a rate of 10℃ / min. The rolling passes are 8, the rolling speed is 3m / s, and the single reduction rate decreases gradually, with the first pass ≤35% and the last pass 8-10%, to obtain hot-rolled coil. S2. The hot-rolled coil is cold-rolled. Before rolling, the rolls are ground and surface-treated. The rolling force and temperature are controlled. The speed ratio of the upper and lower rolls is 1:1.05. The first rolling force is 1600kN, and constant temperature rolling is carried out at 85℃. Thereafter, the rolling force is reduced by 5% for each pass, and the unit tension is 140N / mm. 2 The hot-rolled sheet is rolled in 8 passes to uniformly reduce its thickness to the required size, thus obtaining the cold-rolled stainless steel strip. S3. The cold-rolled stainless steel strip is annealed under nitrogen and hydrogen in a volume ratio of 4:1. The temperature is raised to 600℃ at a rate of 10℃ / min, held for 10min, and then cooled by gas quenching at a rate of 50℃ / s to remove internal stress and obtain the annealed stainless steel strip. S4. Surface polishing and finishing of the annealed stainless steel strip. The electrolyte consists of 60 parts phosphoric acid, 20 parts sulfuric acid, and 4 parts composite additives. The composite additives are composed of sodium dodecyl sulfate, sodium citrate, and glycerol in a mass ratio of 1:10:3. The current density for electropolishing is 15 A / dm³. 2 The temperature is 70℃ and the processing time is 3min; the finishing process adopts tension finishing, pressure 120MPa, speed 15m / min, to obtain ultra-thin stainless steel strip for electronic devices.

[0031] Example 2 Ultra-thin stainless steel strip for manufacturing electronic devices S1. The austenitic stainless steel billet is hot rolled and opened. The temperature is raised to 650℃ at a rate of 10℃ / min, held for 0.5h, and then raised to 1100℃ at a rate of 15℃ / min. There are 6 rolling passes and the rolling speed is 1m / s. The single reduction rate decreases gradually, with the first pass ≤35% and the last pass 8-10%, to obtain hot-rolled coil. S2. The hot-rolled coil is cold-rolled. Before rolling, the rolls are ground and surface-treated. The rolling force and temperature are controlled. The speed ratio of the upper and lower rolls is 1:1.15. The first rolling force is 2000kN, and constant temperature rolling is carried out at 70℃. Thereafter, the rolling force is reduced by 10% for each pass, and the unit tension is 80N / mm. 2 The hot-rolled sheet is rolled in 8 passes to uniformly reduce its thickness to the required size, thus obtaining the cold-rolled stainless steel strip. S3. The cold-rolled stainless steel strip is annealed under nitrogen and hydrogen in a volume ratio of 4:1. The temperature is raised to 700℃ at a rate of 20℃ / min, held for 8min, and then quenched by gas at a rate of 80℃ / s to remove internal stress and obtain the annealed stainless steel strip. S4. The annealed stainless steel strip undergoes surface polishing and finishing. The electrolyte consists of 70 parts phosphoric acid, 30 parts sulfuric acid, and 8 parts composite additives. The composite additives are composed of sodium dodecyl sulfate, sodium citrate, and glycerol in a mass ratio of 1.5:10:3. The current density for electropolishing is 25 A / dm³. 2 The temperature is 60℃ and the processing time is 2min; the finishing process adopts tension finishing, pressure 140MPa, speed 25m / min, to obtain ultra-thin stainless steel strip for electronic devices.

[0032] Example 3 Ultra-thin stainless steel strip for manufacturing electronic devices S1. The austenitic stainless steel billet is hot rolled and opened. The temperature is raised to 600℃ at a rate of 7.5℃ / min, held for 0.75h, and then raised to 1050℃ at a rate of 12.5℃ / min. There are 7 rolling passes and the rolling speed is 2m / s. The single reduction rate decreases gradually, with the first pass ≤35% and the last pass 8-10%, to obtain hot-rolled coil. S2. The hot-rolled coil is cold-rolled. Before rolling, the rolls are ground and surface-treated. The rolling force and temperature are controlled. The speed ratio of the upper and lower rolls is 1:1.1. The first rolling force is 1800kN, and constant temperature rolling is carried out at 77.5℃. Thereafter, the rolling force is reduced by 7.5% for each pass, and the unit tension is 110N / mm. 2 The hot-rolled sheet is rolled in 7 passes to uniformly reduce its thickness to the required size, thus obtaining the cold-rolled stainless steel strip. S3. The cold-rolled stainless steel strip is annealed under nitrogen and hydrogen in a volume ratio of 4:1. The temperature is raised to 650℃ at a rate of 15℃ / min, held for 9min, and then quenched by gas at a rate of 65℃ / s to remove internal stress and obtain the annealed stainless steel strip. S4. Surface polishing and finishing of the annealed stainless steel strip. The electrolyte consists of 65 parts phosphoric acid, 25 parts sulfuric acid, and 6 parts composite additives. The composite additives are composed of sodium dodecyl sulfate, sodium citrate, and glycerol in a mass ratio of 1.25:10:3. The current density for electropolishing is 20 A / dm³. 2 The temperature was 65℃ and the processing time was 2.5 min. The finishing process was performed using tension finishing at a pressure of 130 MPa and a speed of 20 m / min to obtain ultra-thin stainless steel strips for electronic devices.

[0033] Example 4 Example 4 is based on Example 3. The only difference between Example 4 and Example 3 is that in Example 4, in step S1, the temperature is increased to 500°C at a rate of 2.5°C / min, held for 2 hours, and then increased to 900°C at a rate of 5°C / min. The rolling passes are 5, and the rolling speed is 0.5 m / s.

[0034] Example 5 Example 5 is based on Example 3. The only difference between Example 5 and Example 3 is that in Example 5, in step S1, the temperature is increased to 700°C at a rate of 12.5°C / min, held for 0.25h, increased to 1200°C at a rate of 20°C / min, rolled 9 times, and rolled at a rate of 3.5m / s.

[0035] Example 6 Example 6 is based on Example 3. The only difference between Example 6 and Example 3 is that in Example 6, the first rolling force in the cold rolling process of step S2 is 1500kN, and isothermal rolling is performed at 90°C. Thereafter, the rolling force is reduced by 2.5% for each pass, and the unit tension is 160N / mm. 2 The rolling process involves 4 passes.

[0036] Example 7 Example 7 is based on Example 3. The only difference between Example 7 and Example 3 is that in Example 7, the first rolling force in the cold rolling process of step S2 is 2100 kN, and isothermal rolling is performed at 65°C. Thereafter, the rolling force is reduced by 12.5% ​​for each pass, and the unit tension is 60 N / mm. 2 The rolling process involves 10 passes.

[0037] Example 8 Example 8 is based on Example 3. The only difference between Example 8 and Example 3 is that the speed ratio of the upper and lower rolls in the cold rolling process in step S2 of Example 8 is 1:1.

[0038] Example 9 Example 9 is based on Example 3. The only difference between Example 9 and Example 3 is that the speed ratio of the upper and lower rolls in the cold rolling process in step S2 of Example 9 is 1:1.2.

[0039] Example 10 Example 10 is based on Example 3. The only difference between Example 10 and Example 3 is that in Example 10, the annealing process in step S3 is heated to 550°C at a rate of 5°C / min, held for 12min, and then cooled by gas quenching at a rate of 40°C / s.

[0040] Example 11 Example 11 is based on Example 3. The only difference between Example 11 and Example 3 is that in Example 11, the annealing process in step S3 is heated to 750°C at a rate of 25°C / min, held for 6min, and then cooled by gas quenching at a rate of 100°C / s.

[0041] Example 12 Example 12 is based on Example 3. The only difference between Example 12 and Example 3 is that in step S4 of Example 12, the mass ratio of sodium dodecyl sulfonate, sodium citrate and glycerol in the composite additive is 0.5:10:3.

[0042] Example 13 Example 13 is based on Example 3. The only difference between Example 13 and Example 3 is that in step S4 of Example 13, the mass ratio of sodium dodecyl sulfonate, sodium citrate and glycerol in the composite additive is 2:10:3.

[0043] Example 14 Example 14 is based on Example 3. The only difference between Example 14 and Example 3 is that the current density for electropolishing in step S4 of Example 14 is 10 A / dm. 2 Temperature 80℃, processing time 4 min.

[0044] Example 15 Example 15 is based on Example 3. The only difference between Example 15 and Example 3 is that the current density for electropolishing in step S4 of Example 15 is 30 A / dm. 2 Temperature 50℃, processing time 1.5 min.

[0045] Example 16 Example 16 is based on Example 3. The only difference between Example 16 and Example 3 is that in step S4 of Example 16, the pressure of tension finishing is 100MPa and the speed is 10m / min.

[0046] Example 17 Example 17 is based on Example 3. The only difference between Example 17 and Example 3 is that in step S4 of Example 17, the pressure of tension finishing is 160 MPa and the speed is 30 m / min.

[0047] Comparative Example 1 Comparative Example 1 is based on Example 3. The only difference between Comparative Example 1 and Example 3 is that no composite additive is added to the electrolyte in Comparative Example 1. The electrolyte consists of 70 parts of phosphoric acid and 30 parts of sulfuric acid.

[0048] Performance testing (1) GB / T3280-2015 Stainless Steel Cold Rolled Steel Plate and Strip was selected as the standard. A high-precision laser thickness gauge (resolution 0.1μm) was used. Three measurement points were taken at the head, middle and tail of the sample, with an interval of ≥1m between each point. The sample was kept flat without tension during measurement. The ambient temperature was 23℃. The difference between the average value and the nominal thickness was the thickness tolerance. Each sample was tested three times. The average value was taken after measurement and the results were recorded in Table 1.

[0049] (2) The standard GB / T1031-2009 "Product Geometric Specification (GPS) Surface Structure Profile Method Surface Roughness Parameters and Their Values" was selected. A stylus-type surface roughness measuring instrument was used to select three different areas on the surface of the stainless steel strip. Each area was measured three times, and the average value was taken as the surface roughness Ra value of that area. The results are recorded in Table 1.

[0050] (3) Select GB / T10125-2021 Artificial Atmosphere Corrosion Test Salt Spray Test as the standard, cut a 100mm×150mm sample, inject 5% sodium chloride solution (pH 7) into the salt spray test chamber which has been preheated to 35℃ inside the chamber and 40℃ saturator temperature, install the sample at a 30° angle to the vertical direction, turn on the spray system, spray continuously for 200h, rinse with clean water and dry, observe whether there is red rust on the surface, and record the results in Table 1.

[0051] Table 1. Test results of thickness uniformity, roughness, and oxidation degree of ultra-thin stainless steel strips. As shown in Table 1, the thickness tolerance of Examples 1-3 is less than ±1.0 μm, the roughness Ra is less than 0.10 μm, and there is no red rust after 200 h. This shows that the ultra-thin stainless steel strip prepared in this application has good thickness uniformity, low roughness and low oxidation degree.

[0052] As shown in Table 1, the only difference between Examples 4 and 5 and Example 3 is that the optimal parameter range for hot rolling billet was disrupted in Examples 4 and 5. Too fast or too slow heating, or too high or too low temperature rise, will affect the grain size. Compared with Example 3, the performance of Examples 4 and 5 is significantly reduced.

[0053] As shown in Table 1, the difference between Examples 6-8 and Example 3 is only that: Examples 6 and 7 disrupted the optimal parameter range for cold rolling, affecting the performance of cold rolling; Examples 7 and 8 disrupted the speed ratio limit of the upper and lower rolls, affecting the shear deformation performance, and the transverse thickness difference and surface roughness of the strip were affected.

[0054] As shown in Table 1, the only difference between Examples 10 and 11 and Example 3 is that the optimal parameter range of the annealing process was disrupted in Examples 10 and 11, which affected the elimination of internal stress in the strip. The cooling temperature affected the degree of surface refinement. Compared with Example 3, the performance of Examples 10 and 11 has decreased.

[0055] As shown in Table 1, the differences between Examples 12-17 and Example 3 are only as follows: In Examples 12 and 13, the mass ratio of the composite additive was adjusted, which affected the dispersibility and complexing ability of the electrolytic polishing solution, resulting in uneven polishing and decreased corrosion resistance; In Examples 14 and 15, the electrolysis parameters were adjusted, which could lead to insufficient polishing or corrosion; In Examples 16 and 17, the parameters of tension finishing were adjusted, which could not effectively improve the surface performance. Compared with Example 3, the performance of Examples 12-17 has decreased.

[0056] As shown in Table 1, the only difference between Comparative Example 1 and Example 3 is that no composite additives are added to the electrolyte in the electropolishing step of Comparative Example 1. The electropolishing solution has poor dispersibility and metal ions cannot be effectively complexed, resulting in severe corrosion of the strip surface and the appearance of a large amount of red rust. Compared with Example 3, the performance of Comparative Example 1 is significantly reduced.

[0057] This specific embodiment is merely an explanation of this application and is not intended to limit it. Based on the above description, those skilled in the art can make various changes and modifications without departing from the technical concept of this application. The technical scope of this application is not limited to the contents of the specification but must be determined according to the scope of the claims.

Claims

1. A method for preparing ultrathin stainless steel strip for electronic devices, characterized in that: Includes the following steps: S1. Hot rolling is performed on the austenitic stainless steel billet to obtain hot-rolled coils; S2. The hot-rolled coil is cold-rolled. Before rolling, the rolls are ground and surface-treated. The rolling force and temperature are controlled to uniformly reduce the thickness of the hot-rolled coil to the required size, so as to obtain the cold-rolled stainless steel strip. S3. Anneal the cold-rolled stainless steel strip under a protective atmosphere to remove internal stress and obtain annealed stainless steel strip. S4. The annealed stainless steel strip is polished and finished to obtain ultra-thin stainless steel strip for electronic devices. In step S4, surface polishing is performed using electrolytic polishing. The electrolyte includes 60-70 parts of phosphoric acid, 20-30 parts of sulfuric acid, and 4-8 parts of composite additives, which include sodium dodecyl sulfonate, sodium citrate, and glycerol.

2. The method for preparing an ultra-thin stainless steel strip for electronic devices according to claim 1, characterized in that: In step S1, the hot rolling billet is heated in a gradient manner, with the temperature increased to 550-650℃ at a rate of 5-10℃ / min, held for 0.5-1h, and then increased to 1000-1100℃ at a rate of 10-15℃ / min.

3. The method for preparing an ultra-thin stainless steel strip for electronic devices according to claim 2, characterized in that: In step S1, the rolling passes are 6-8, the rolling speed is 1-3 m / s, and the single reduction rate decreases gradually, with the first pass ≤35% and the last pass 8-10%.

4. The method for preparing an ultra-thin stainless steel strip for electronic devices according to claim 1, characterized in that: In step S2, the first rolling force in the cold rolling process is 1600-2000 kN, and isothermal rolling is performed at 70-85℃. Thereafter, the rolling force is reduced by 5-10% for each subsequent pass, with a unit tension of 80-140 N / mm. 2 The rolling process involves 6-8 passes.

5. The method for preparing an ultra-thin stainless steel strip for electronic devices according to claim 4, characterized in that: The speed ratio of the upper and lower rolls in the cold rolling process is 1:(1.05-1.15).

6. The method for preparing an ultra-thin stainless steel strip for electronic devices according to claim 1, characterized in that: The protective atmosphere in step S3, annealing, is nitrogen and hydrogen.

7. The method for preparing an ultra-thin stainless steel strip for electronic devices according to claim 6, characterized in that: In step S3, the annealing process involves heating the temperature to 600-700℃ at a rate of 10-20℃ / min, holding it at that temperature for 8-10 minutes, and then quenching it in the air at a rate of 50-80℃ / s.

8. The method for preparing an ultra-thin stainless steel strip for electronic devices according to claim 1, characterized in that: In step S4, the mass ratio of sodium dodecyl sulfonate, sodium citrate, and glycerol in the composite additive is (1-1.5):10:

3.

9. The method for preparing an ultra-thin stainless steel strip for electronic devices according to claim 8, characterized in that: The current density for electropolishing in step S4 is 15-25 A / dm. 2 Temperature 60-70℃, processing time 2-3 minutes.

10. The method for preparing an ultrathin stainless steel strip for electronic devices according to claim 9, characterized in that: In step S4, the finishing process is performed using tension finishing at a pressure of 120-140 MPa and a speed of 15-25 m / min.

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