Cold-rolled mirror surface stainless steel band and preparation process

Abstract

The invention relates to the technical field of stainless steel material processing, and particularly discloses a cold-rolled mirror surface stainless steel band and a preparation process, the cold-rolled mirror surface stainless steel band comprises a base layer, a surface treatment layer and a double-layer protective film, the specific component design of the base layer ensures the comprehensive performance, the surface treatment layer reduces the roughness and improves the hardness, and the double-layer protective film enhances the protective effect. The preparation process comprises the steps of steel manufacturing, hot rolling, thermal annealing, cold rolling, surface treatment, film coating and rolling and the like, and through the technologies of deep pre-desulfurization before AOD, novel high-speed steel roller hot rolling, thermal annealing multi-procedure cooperation, cold rolling multi-stage accurate control, ultrasonic degreasing, electrolytic polishing surface treatment and the like, inclusions are effectively reduced; and the surface roughness Ra is reduced to be smaller than or equal to 0.08 microns (the surface treatment layer Ra is smaller than or equal to 0.05 microns), the yield is improved to be 90% or above, and the mechanical property is optimized. Compared with the prior art, the product quality is better, the performance is more excellent, the process is more stable and efficient, and the requirements of the high-end field are met.

Description

Technical Field

[0001] The present invention relates to the technical field of stainless steel material processing, and specifically to a cold-rolled mirror stainless steel strip and a preparation process thereof. Background Art

[0002] In the field of stainless steel strip production and manufacturing, cold-rolled mirror stainless steel strips occupy an important position in many high-end application scenarios due to their unique surface characteristics and good mechanical properties. With the rapid development of related industries, the quality requirements for cold-rolled mirror stainless steel strips are becoming increasingly stringent. It is not only expected that their surfaces are smoother and flatter to meet the high-precision requirements of fields such as optics and electronics, but also required to have a high production yield while ensuring high strength and good corrosion resistance, and reduce production costs.

[0003] Many efforts have been made in the prior art for the preparation of cold-rolled mirror stainless steel strips. For example, CN115948702B discloses a preparation process of cold-rolled mirror stainless steel strips. By controlling the steel-making process to reduce inclusions and optimizing the hot-rolling and cold-rolling process parameters to improve pitting and surface roughness, the surface quality of the stainless steel strip has been improved to a certain extent, and the surface roughness Ra reaches 0.1 - 0.2μm. However, there are still some problems that cannot be ignored in this technology: The surface roughness is difficult to meet high-end requirements. In the fields of high-end optical instrument manufacturing, semiconductor chip production, etc., extremely high requirements are placed on the surface roughness of materials, and it is usually expected to reach Ra ≤ 0.05μm or even lower. However, the surface roughness of the stainless steel strip prepared by CN115948702B cannot reach such high-precision standards, which limits its application in these high-end fields.

[0004] The problems of inclusions and pitting still exist. Although this technology takes measures to reduce inclusions, in actual production, improper control of the side guide pressure during hot-rolling coiling and inaccurate pickling parameters result in the appearance of pitting and residual inclusions on the surface of the stainless steel strip, affecting the appearance quality and performance stability of the product, and further making it difficult to further improve the production yield, which can only reach about 85%.

[0005] The optimization of mechanical properties is insufficient. In terms of mechanical properties, there are deficiencies in the prior art in controlling carbide precipitation to balance hardness and toughness. The annealing process does not control carbides precisely enough, so that while the stainless steel strip obtains a certain hardness (HV250 - 300), its toughness is affected, and defects such as cracks are likely to appear during deep processing, which limits its application in complex forming processes.

[0006] In addition, in the production process of cold-rolled mirror stainless steel strips, other related technologies also generally have problems such as complex processes and high costs, making it difficult to achieve large-scale and efficient production. Therefore, it is urgent to develop a cold-rolled mirror stainless steel strip and its preparation process that can produce a strip with low surface roughness, high yield, excellent comprehensive performance, and reasonable production costs. Summary of the Invention

[0007] To solve the above problems, the present invention adopts the following technical solutions.

[0008] A cold-rolled mirror stainless steel strip, comprising: Base layer: By mass percentage, its components include: C: 0.02 - 0.04; Si: 0.3 - 0.5; Mn: 1.2 - 1.4; P ≤ 0.03; S ≤ 0.008; Cr: 18.2 - 18.8; Ni: 8.2 - 8.4; Cu: 0.2 - 0.4; N ≤ 0.04; Mo ≤ 0.4; the balance is Fe and other inevitable impurities. The thickness of the cold-rolled mirror stainless steel strip is 0.3 - 3.0 mm, and the roughness Ra ≤ 0.08 μm. This composition design can ensure that the steel strip has good strength, toughness, and corrosion resistance.

[0009] Surface treatment layer: A nano-scale passivation film with a thickness of 50 - 100 nm, containing Cr2O3 and SiO2 in its composition, surface roughness Ra ≤ 0.05 μm, and hardness HV ≥ 300. This passivation film can further improve the corrosion resistance and surface hardness of the steel strip, while reducing the surface roughness, making the steel strip have a better mirror effect.

[0010] Double-layer protective film: The inner layer is a PVC electrostatic film, which has the functions of anti-static and scratch prevention; the outer layer is a PE film with rubber spacer strips, and the spacer strips are arranged at intervals of 5 - 10 mm along the width direction of the steel strip. The double-layer protective film can effectively protect the steel strip from damage during transportation and storage.

[0011] A preparation process for a cold-rolled mirror stainless steel strip, comprising the following steps: Steel making: Adopt the AOD pre-depth desulfurization technology, use high-purity Fe-Si and Ca-Si composite deoxidizers for deoxidation, and carry out VOD low-alkalinity operation, with the alkalinity controlled at 1.5 - 1.8 and the treatment time of 20 - 30 min. Through the depth pre-desulfurization technology and low-alkalinity operation, the sulfur content and impurity content in the steel can be effectively reduced, and the purity of the steel can be improved.

[0012] Hot rolling: Use a new type of high-speed steel roll for the finishing work roll, with the roll unit sequence ≤ 10, and the surface roughness Ra of the material ≤ 2.0 μm. The new type of high-speed steel roll has higher hardness and wear resistance, which can improve the rolling accuracy and surface quality during hot rolling.

[0013] Hot annealing: Solution annealing: At a temperature of 1150 - 1180 °C, the protective gas is 25% N2 + 75% H2 by volume, and the strip speed is 20 - 25 m / min. Solution annealing can eliminate the internal stress generated during hot rolling, make the alloying elements in the steel evenly distributed, and improve the toughness and workability of the strip.

[0014] Ageing treatment: Hold at a temperature of 800 - 850 °C for 10 - 15 min, and then cool in the furnace. Ageing treatment can precipitate carbides in the steel and improve the hardness and wear resistance of the strip.

[0015] Shot peening and cleaning: Use a new type of shot peening machine, with a projection speed of 1800 - 2000 r / min and a projection amount of 900 - 1000 kg / min. After shot peening, an ultrasonic cleaning process is added to make the surface roughness Ra of the material reach 0.2 - 0.4 μm. Shot peening and cleaning can remove the scale and impurities on the strip surface and improve the surface quality.

[0016] Cold rolling: Primary rolling: The reduction ratio is 60% - 70%, the roughness of the work roll Ra is 0.6 - 0.8 μm, and it is rolled to a thickness of 0.3 - 0.5 mm. Primary rolling can initially reduce the thickness of the strip, and at the same time break up the coarse grains, preparing for subsequent finish rolling and final rolling.

[0017] Finish rolling: The reduction ratio is 40% - 50%, the roughness of the work roll Ra is 0.2 - 0.4 μm, and it is rolled to a thickness of 0.1 - 0.3 mm. In the finish rolling process, a double - cone intermediate roll is used to control the edge wave height of the strip shape ≤ 2 mm and the sharpness ≤ 2%. The double - cone intermediate roll can effectively control the strip shape and improve the flatness and accuracy of the strip.

[0018] Final rolling: The reduction ratio is 20% - 30%, the roughness of the work roll Ra ≤ 0.1 μm and ultrasonic vibration (frequency 20 - 40 kHz) is applied, and it is rolled to the target thickness of 0.05 - 1.0 mm. Ultrasonic vibration can improve the metal flow during rolling and further reduce the surface roughness of the strip.

[0019] Surface treatment: Ultrasonic degreasing: Use an alkaline solution (pH 10 - 12, temperature 50 - 60 °C) combined with 40 kHz ultrasound and treat for 5 - 10 min. Ultrasonic degreasing can remove the oil and impurities on the strip surface and prepare for subsequent electrolytic polishing.

[0020] Electrolytic polishing: The electrolyte is 60 - 70% H3PO4 + 20 - 30% H2SO4, the voltage is 10 - 15 V, and the time is 30 - 60 s. Electrolytic polishing can further reduce the surface roughness of the strip and make the strip surface reach a mirror effect.

[0021] Film covering and winding: The PVC static film and the PE film are laminated with a rubber spacer strip, and the winding tension is 10 - 20 kN. Film covering and winding can protect the surface of the steel strip from damage and facilitate transportation and storage.

[0022] Preferably, mixed steel shots with different particle sizes are used, among which the steel shots with a particle size of 0.8 - 1.2 mm account for 60% - 70%, and the steel shots with a particle size of 0.3 - 0.6 mm account for 30% - 40%, so as to improve the shot blasting efficiency and surface cleaning effect.

[0023] Preferably, in the solution annealing stage, a protective gas is introduced into the annealing furnace. The protective gas is a mixed gas of nitrogen and hydrogen, where the volume fraction of nitrogen is 90% - 95% and the volume fraction of hydrogen is 5% - 10%, so as to prevent the surface of the steel strip from oxidation and ensure the surface quality.

[0024] Preferably, the surface-treated steel strip is dried by hot air drying. The hot air temperature is 80 - 100 °C and the drying time is 3 - 5 minutes, so as to remove the surface moisture and prevent rusting.

[0025] Preferably, in the aging treatment stage of hot annealing, a stepped heating process is adopted: heating at a rate of 5 - 8 °C / min to 500 - 550 °C and holding for 10 - 15 minutes, then heating at a rate of 3 - 5 °C / min to the target temperature, to promote the uniform and dispersed precipitation of carbides and improve the hardness uniformity.

[0026] Preferably, an ultrasonic deionized water cleaning step is added after the electrolytic polishing process. The ultrasonic frequency is switched to 80 - 100 kHz and the cleaning time is 2 - 3 minutes to remove the residual electrolyte, so that the detected value of the surface chloride ion content is lower than 5 ppm and the corrosion resistance is improved.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows: By optimizing the composition and adopting advanced preparation processes, the surface roughness Ra of the cold-rolled mirror stainless steel strip prepared by the present invention is ≤0.08 μm, and the surface roughness Ra of the surface treatment layer is ≤0.05 μm. It has a good mirror effect, the surface roughness is significantly reduced, and the competitiveness of the product in the high-end market is effectively improved.

[0028] In the steel-making process of the present invention, a deep pre-desulfurization technology and a low-alkalinity operation are adopted, effectively reducing the impurity content in the steel; in the hot rolling and cold rolling processes, by reasonably controlling the process parameters and adopting new rolls, the rolling accuracy and surface quality are improved, so that the yield rate of the steel strip is significantly increased, the production cost is reduced, and the production efficiency is improved.

[0029] The cold-rolled mirror stainless steel strip of the present invention has good strength, toughness, corrosion resistance and wear resistance. Through solution annealing and aging treatment, the structure of the steel strip is made uniform and the performance is stable; the nano-scale passivation film of the surface treatment layer further improves the corrosion resistance and hardness of the steel strip. While ensuring the hardness, the toughness is taken into account, solving the problem of difficult balance of mechanical properties in the prior art and meeting the requirements of complex deep processing technology.

[0030] The preparation process parameters of the present invention are clear, the operation is simple, and it has high process stability, and can realize large-scale industrial production. Compared with some existing complex and unstable processes, it has better market application prospects. Brief Description of the Drawings

[0031] Figure 1 is the process flow chart of the present invention; Figure 2 is the hot annealing process flow chart of the present invention; Figure 3 is the cold rolling process flow chart of the present invention; Figure 4 is the surface treatment process flow chart of the present invention. Detailed Embodiments

[0032] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention; obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0033] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "upper", "lower", "inner", "outer", "top / bottom end", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0034] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "installed", "provided with", "sheathed / connected", "connected", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal communication of two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations. Example 1

[0035] A cold-rolled mirror stainless steel strip, comprising: Base layer: By mass percentage, the composition is as follows, C: 0.02; Si: 0.3; Mn: 1.2; P: 0.02; S: 0.005; Cr: 18.2; Ni: 8.2; Cu: 0.2; N: 0.03; Mo: 0.3; the balance is Fe and other inevitable impurities; Surface treatment layer: A nano-scale passivation film with a thickness of 50 - 100 nm, the composition contains Cr2O3 and SiO2, the surface roughness Ra ≤ 0.05 μm, and the hardness HV ≥ 300; Double-layer protective film: The inner layer is a PVC static film, and the outer layer is a PE film with a rubber spacer strip. The spacer strips are arranged at intervals of 5 - 10 mm along the width direction of the steel strip.

[0036] Preparation process of cold-rolled mirror stainless steel strip: Steel making: Adopt the deep pre-desulfurization technology before AOD, use high-purity Fe-Si and Ca-Si composite deoxidizers for deoxidation, and carry out VOD low-alkalinity operation with the alkalinity controlled at 1.5 and the treatment time of 20 min; Hot rolling: The finishing work roll uses a new type of high-speed steel roll, the roll unit sequence is 8, and the surface roughness Ra of the material is 1.8 μm; Hot annealing: Solution annealing: At a temperature of 1150 °C, the protective gas is 25% N2 + 75% H2 by volume ratio, and the steel strip speed is 20 m / min; Aging treatment: Keep warm at a temperature of 800 °C for 10 min, and then cool with the furnace; Shot peening and cleaning: Adopt a new type of shot peening machine with a projection speed of 1800 r / min and a projection amount of 900 kg / min. After shot peening, ultrasonic cleaning is carried out, and the surface roughness Ra of the material reaches 0.2 μm; Cold rolling: Initial rolling: The reduction rate is 60%, the roughness Ra of the work roll is 0.6 μm, and it is rolled to a thickness of 0.3 mm; Finishing rolling: The reduction rate is 40%, the roughness Ra of the work roll is 0.2 μm, a double-cone intermediate roll is adopted, the edge wave height of the flatness is controlled at 1.5 mm, and the steepness is 1.5%, and it is rolled to a thickness of 0.18 mm; Final rolling: The reduction rate is 20%, the roughness Ra of the work roll is 0.08 μm and ultrasonic vibration (frequency 20 kHz) is applied, and it is rolled to the target thickness of 0.144 mm; Surface treatment: Ultrasonic degreasing: Adopt an alkaline solution (pH 10, temperature 50 °C) combined with 40 kHz ultrasound and treat for 5 min.

[0037] Electropolishing: The electrolyte is 60% H3PO4 + 30% H2SO4, the voltage is 10V, and the time is 30s.

[0038] Film laminating and winding: Bond the PVC static film and the PE film with a rubber spacer strip, and the winding tension is 10kN.

[0039] The stainless steel strip is prepared by the above process. After testing, the thickness of the cold-rolled mirror stainless steel strip is 0.144mm, the surface roughness Ra is 0.06μm, the surface roughness Ra of the surface treatment layer is 0.03μm, the hardness HV is 320, the yield rate reaches 92%, and it has good strength, toughness and corrosion resistance. Example 2

[0040] A cold-rolled mirror stainless steel strip, including, Base layer: The composition of the base layer is as follows: C: 0.04; Si: 0.5; Mn: 1.4; P: 0.03; S: 0.008; Cr: 18.8; Ni: 8.4; Cu: 0.4; N: 0.04; Mo: 0.4; the balance is Fe and other inevitable impurities; Surface treatment layer: Nano-scale passivation film, with a thickness of 50 - 100nm, the composition contains Cr2O3 and SiO2, the surface roughness Ra ≤ 0.05μm, and the hardness HV ≥ 300; Double-layer protective film: The inner layer is a PVC static film, and the outer layer is a PE film with a rubber spacer strip. The spacer strips are arranged at intervals of 5 - 10mm along the width direction of the steel strip.

[0041] Preparation process of cold-rolled mirror stainless steel strip: Steel making: Adopt the AOD pre-depth desulfurization technology, use high-purity Fe-Si and Ca-Si composite deoxidizers for deoxidation, and carry out VOD low-alkalinity operation, with the alkalinity controlled at 1.8 and the treatment time of 30min; Hot rolling: The finishing work roll uses a new type of high-speed steel roll, the roll unit order is 10, and the surface roughness Ra of the material is 2.0μm; Hot annealing: Solution annealing: At a temperature of 1180°C, the protective gas is 25% N2 + 75% H2 by volume, and the steel strip speed is 25m / min; Aging treatment: Insulate at a temperature of 850°C for 15min, and then cool with the furnace; Shot peening and cleaning: Adopt a new type of shot peening machine, the projection speed is 2000r / min, the projection amount is 1000kg / min, and ultrasonic cleaning is carried out after shot peening, and the surface roughness Ra of the material reaches 0.4μm; Cold rolling: Primary rolling: The reduction ratio is 70%, the roughness Ra of the work roll is 0.8μm, and it is rolled to a thickness of 0.5mm; Finish rolling: The reduction ratio is 50%, the roughness of the work roll is Ra 0.4 μm, a double-cone intermediate roll is used, the height of the edge wave of the shape control is 2 mm, the steepness is 2%, and it is rolled to a thickness of 0.25 mm; Final rolling: The reduction ratio is 30%, the roughness of the work roll is Ra 0.1 μm and ultrasonic vibration (frequency 40 kHz) is applied, and it is rolled to the target thickness of 0.175 mm; Surface treatment: Ultrasonic degreasing: An alkaline solution (pH 12, temperature 60 °C) is used in combination with 40 kHz ultrasound and treated for 10 min; Electropolishing: The electrolyte is 70% H3PO4 + 20% H2SO4, the voltage is 15 V, and the time is 60 s; Film laminating and winding: A PVC electrostatic film and a PE film are laminated with a rubber spacer strip, and the winding tension is 20 kN.

[0042] The stainless steel strip is prepared by the above process. The cold-rolled mirror stainless steel strip has a thickness of 0.175 mm, a surface roughness Ra of 0.07 μm, a surface treatment layer roughness Ra of 0.04 μm, a hardness HV of 330, and a yield rate of 90%, and has good comprehensive performance.

[0043] Comparative example The cold-rolled mirror stainless steel strip is prepared by the process of CN115948702B, and its composition and process parameters are carried out according to the patent example: Composition: By mass percentage, C: 0.03 - 0.06; Si: 0.4 - 0.6; Mn: 1 - 1.5; P ≤ 0.04; S ≤ 0.01; Cr: 18.0 - 19.0; Ni: 8.0 - 8.5; Cu: 0.1 - 0.5; N ≤ 0.05; Mo ≤ 0.5; the balance is Fe and other inevitable impurities.

[0044] Preparation process Steelmaking: Pre-desulfurization is used before AOD, and high-purity Fe-Si is used for deoxidation; through VOD low-alkalinity operation, the alkalinity is 1.3 - 2.0, and the treatment time is 10 - 40 min. In actual operation, due to the large fluctuation range of the alkalinity and treatment time, it is difficult to accurately control the floating effect of inclusions. For example, in a certain production, the alkalinity was 1.3 and the treatment time was only 10 min, resulting in some inclusions in the steel not floating up sufficiently and remaining in the molten steel, affecting the quality of the subsequent steel strip.

[0045] Hot rolling: The finishing work roll uses an HSS roll, the roll unit sequence ≤ 12, and the surface roughness of the material Ra ≤ 2.5 μm. During the production process, it was found that when the roll unit sequence was close to 12, the surface roughness of the material increased significantly, approaching the upper limit of 2.5 μm. For example, in the production of a batch of steel strips, when the roll unit sequence reached 11, the surface roughness of some steel strips reached 2.4 μm, which increased the difficulty of the subsequent cold rolling process and affected the surface quality of the final product.

[0046] Hot annealing: The projection speed of the shot blasting machine is 1500 r / min, the projection amount is 850 kg / min, and the surface roughness of the material Ra is 0.3 - 0.5 μm. During the shot blasting process, due to the limitation of equipment parameters, it was impossible to completely remove the tiny impurities and oxide scale residues on the surface of the steel strip, so there were still some fine defects on the surface.

[0047] Cold rolling: The total reduction ratio is 41% - 85%; among them, the roughness Ra of the work roll in the first pass of the rolling mill is 0.6 - 1.0 μm, the reduction ratio in the first pass is 15% - 23%, and the reduction ratios of the subsequent passes gradually decrease; the surface roughness of the work roll in the last pass ≤ 0.2 μm. During the cold rolling process, it was difficult to precisely control the gradual decrease of the reduction ratio in each pass, resulting in poor thickness uniformity of the steel strip. For example, in the production of a certain batch, the reduction ratio in the first pass was 15%, and the adjustment of the reduction ratios in the subsequent passes was not precise enough, so that after the final rolling of the steel strip, the thickness deviation reached ±0.05 mm, exceeding the ideal range.

[0048] Performance testing Surface roughness: After testing, the surface roughness Ra of the cold-rolled mirror stainless steel strip prepared in this comparative example was 0.15 μm, which was significantly higher than that of the example of the present invention. In the simulation application of optical instrument manufacturing, due to the insufficiently smooth surface, the light reflection was uneven, resulting in the influence on the imaging quality and unable to meet the use requirements of high-end optical products.

[0049] Hardness: The hardness HV was 280, which was lower than the hardness (HV 320 - 330) of the example of the present invention. During the simple stamping processing test, it was found that the steel strip was prone to deformation and cracking, indicating its insufficient strength and wear resistance and unable to meet the processing technology with higher requirements for the mechanical properties of the material.

[0050] Yield rate: During the batch production process, the yield rate of the process of this comparative example was only 80%. Through the analysis of unqualified products, it was found that the main reasons included surface pitting, defects caused by inclusions, and thickness non-uniformity, etc. These problems not only increased the production cost but also reduced the production efficiency.

[0051] Through the above detailed comparison between the comparative examples and the embodiments of the present invention, it can be clearly seen that the present invention has advantages in terms of component optimization and process improvement, can effectively solve the problems existing in the prior art, and prepare cold-rolled mirror stainless steel strips with better performance.

[0052] The above is only the preferred specific implementation manner of the present invention; however, the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution of the present invention and its improved concept, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention.

Claims

1. A cold-rolled mirror stainless steel strip and its manufacturing process, characterized in that: It includes a base layer, and by mass percentage, its components include: C: 0.02 - 0.04; Si: 0.3 - 0.5; Mn: 1.2 - 1.4; P ≤ 0.03; S ≤ 0.008; Cr: 18.2 - 18.8; Ni: 8.2 - 8.4; Cu: 0.2 - 0.4; N ≤ 0.04; Mo ≤ 0.4; the balance is Fe and other inevitable impurities; the thickness of the cold-rolled mirror stainless steel strip is 0.3 - 3.0 mm, and the surface roughness Ra ≤ 0.08 μm; Surface treatment layer: a nano-level passivation film with a thickness of 50 - 100 nm, the composition contains Cr2O3 and SiO2, the surface roughness Ra ≤ 0.05 μm, and the hardness HV ≥ 300; Double-layer protective film: the inner layer is a PVC electrostatic film, and the outer layer is a PE film with rubber spacer strips. The spacer strips are arranged at intervals of 5 - 10 mm along the width direction of the steel strip.

2. A preparation process of the cold-rolled mirror stainless steel strip as described in claim 1, characterized in that, It includes the following steps: Steel making: Adopt the AOD pre-depth desulfurization technology, use high-purity Fe-Si and Ca-Si composite deoxidizers for deoxidation, and carry out VOD low-alkalinity operation with the alkalinity controlled at 1.5 - 1.8 and the treatment time of 20 - 30 min; Hot rolling: Use a new type of high-speed steel roll for the finishing work roll, the roll unit sequence ≤ 10, and the surface roughness Ra of the material ≤ 2.0 μm; Hot annealing: Solution annealing: 1150 - 1180 °C, the protective gas is 25% N2 + 75% H2 by volume ratio, and the steel strip speed is 20 - 25 m / min; Aging treatment: Keep warm at 800 - 850 °C for 10 - 15 min and cool with the furnace; Use a new type of shot blasting machine with a projection speed of 1800 - 2000 r / min and a projection amount of 900 - 1000 kg / min. After shot blasting, an ultrasonic cleaning process is added, and the surface roughness Ra of the material reaches 0.2 - 0.4 μm; Cold rolling: Initial rolling: The reduction rate is 60% - 70%, the surface roughness Ra of the work roll is 0.6 - 0.8 μm, and it is rolled to a thickness of 0.3 - 0.5 mm; Finishing rolling: The reduction rate is 40% - 50%, the surface roughness Ra of the work roll is 0.2 - 0.4 μm, and it is rolled to a thickness of 0.1 - 0.3 mm; Final rolling: The reduction rate is 20% - 30%, the surface roughness Ra of the work roll ≤ 0.1 μm and ultrasonic vibration (frequency 20 - 40 kHz) is applied, and it is rolled to the target thickness of 0.05 - 1.0 mm; Surface treatment: Ultrasonic degreasing: An alkaline solution (pH 10 - 12, temperature 50 - 60 °C) is combined with 40 kHz ultrasound and treated for 5 - 10 min; Electrolytic polishing: The electrolyte is 60 - 70% H3PO4 + 20 - 30% H2SO4, the voltage is 10 - 15 V, and the time is 30 - 60 s; Film laminating and winding: Bond the PVC electrostatic film and the PE film with rubber spacer strips, and the winding tension is 10 - 20 kN.

3. The preparation process according to claim 2, characterized in that, In the finishing rolling process, a double-cone intermediate roll is used to control the edge wave height of the plate shape ≤ 2 mm and the sharpness ≤ 2%.

4. The preparation process according to claim 2, characterized in that, In the descaling process of the descaling machine, the elongation rate of the steel strip with a thickness of 2.5 - 3.0 mm is controlled at 2.0% - 2.5%, and it is combined with high-pressure water descaling of 35 - 40 MPa.

5. The preparation process according to claim 2, characterized in that, Use mixed steel shots with different particle sizes, where the steel shots with a particle size of 0.8 - 1.2 mm account for 60% - 70%, and the steel shots with a particle size of 0.3 - 0.6 mm account for 30% - 40% to improve the shot peening efficiency and surface cleaning effect.

6. The preparation process according to claim 2, characterized in that, During the solution annealing stage, introduce a protective gas into the annealing furnace. The protective gas is a mixed gas of nitrogen and hydrogen, where the volume fraction of nitrogen is 90% - 95% and the volume fraction of hydrogen is 5% - 10% to prevent oxidation of the steel strip surface and ensure surface quality.

7. The preparation process according to claim 2, characterized in that, The surface-treated steel strip is subjected to a drying process. The hot air drying method is adopted, with the hot air temperature being 80 - 100 °C and the drying time being 3 - 5 minutes to remove surface moisture and prevent rusting.

8. The preparation process according to claim 2, characterized in that, In the aging treatment stage of hot annealing, a stepped heating process is adopted: heat up at a rate of 5 - 8 °C / min to 500 - 550 °C and hold for 10 - 15 minutes, then heat up to the target temperature at a rate of 3 - 5 °C / min to promote the uniform and dispersed precipitation of carbides and improve the hardness uniformity.

9. The preparation process according to claim 2, characterized in that, After the electrolytic polishing process, add an ultrasonic deionized water cleaning step. The ultrasonic frequency is switched to 80 - 100 kHz, and the cleaning time is 2 - 3 minutes to remove the residual electrolyte, making the detected value of the surface chloride ion content lower than 5 ppm and improving the corrosion resistance.

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