Surface treatment process of high Cr-Ni-Ti austenitic stainless steel sheet

Abstract

The invention discloses a surface treatment process of a high Cr-Ni-Ti austenitic stainless steel sheet, and belongs to the technical field of special steel material production. The technology sequentially comprises the steps of alkali washing, first cold water rinsing, acid pickling, second cold water rinsing, hot water rinsing and drying. The alkali washing adopts a melting reaction system formed by NaNO3 and NaOH at the temperature of 400-450 DEG C for treatment so as to deeply strip oxide skin; the acid pickling is carried out by adopting a mixed solution of HF and HNO3 at the temperature of 30-35 DEG C so as to realize surface passivation; in each rinsing step, the reaction termination and cleaning effects are ensured by strictly controlling the temperature. The method can effectively solve the problems that the oxide skin on the surface of the ultra-thin high-alloy stainless steel is difficult to remove, and the substrate is easy to over-corrode, the surface roughness Ra of the treated plate is less than or equal to 0.15 mu m, the brightness meets the 2D standard, and the method is suitable for the fields of aviation and the like.

Description

Technical Field

[0001] This invention belongs to the field of special steel material production technology, specifically relating to a surface treatment process for high Cr-Ni-Ti austenitic stainless steel thin plates. Background Technology

[0002] Austenitic stainless steel, due to its excellent corrosion resistance, good plasticity, and weldability, is widely used in key fields such as medical devices, aerospace, and marine engineering. In recent years, with the rapid development of my country's aerospace industry, the requirements for lightweighting and surface quality of special metal materials have become increasingly stringent, leading to the development of ultra-thin austenitic stainless steel plates. The surface quality of these plates directly determines their reliability and lifespan in harsh service environments. Especially for high-Cr-Ni-Ti austenitic stainless steel thin plates, as an important base material for precision aerospace components, their surfaces must meet extremely high cleanliness and uniformity requirements, and the presence of micro-pits, scratches, or oxide spots is not permitted to avoid stress concentration, media leakage, or corrosion failure caused by surface defects.

[0003] Therefore, in the production chain of austenitic stainless steel sheets (especially ultra-thin sheets), pickling has evolved from ordinary surface cleaning into a core process that precisely controls the surface condition through chemical action, repairs defects from previous processing, and builds a stable passivation film. Its treatment effect directly determines the surface performance in terms of precision, corrosion resistance, and consistency, becoming a crucial link between rolling, annealing, and subsequent deep processing, and is the most critical surface treatment step.

[0004] Currently, there are several studies on pickling processes for stainless steel in the industry. For example, CN119615178A discloses a hydrochloric acid-based step-by-step pickling method for austenitic stainless steel. This method uses a hydrochloric acid system to replace the traditional nitric acid-hydrofluoric acid mixed acid system. Through the synergy of pre-pickling and graded final pickling, it achieves surface polishing and passivation while removing the oxide layer, and has the advantages of waste liquid regeneration and recycling and low cost. CN115287419A provides an annealing and pickling process for cold-rolled strip of high-temperature resistant austenitic stainless steel. This process optimizes the annealing regime and controls the electrolytic pickling parameters to make the surface of high-silicon content austenitic stainless steel uniform in color, low in roughness, and with good oxidation and corrosion resistance.

[0005] However, these existing processes are mostly developed based on stainless steel of conventional thickness or steel grades with specific compositions (such as high-silicon high-temperature resistant steel). Aerospace-grade high-Cr-Ni-Ti austenitic stainless steel sheets are extremely thin and have sensitive, easily damaged surfaces. Their unique high-chromium, nickel, and titanium alloy system results in a denser and more complex oxide layer structure, placing more stringent demands on the kinetics and selectivity of the pickling medium. Directly using conventional pickling processes can easily lead to over-etching, microscopic inhomogeneity, or unstable passivation film quality due to insufficient reaction control precision, making it difficult to meet aerospace application standards. Therefore, existing technologies generally suffer from poor process applicability and difficulty in quality control in the application of such high-end thin sheets, necessitating the development of a dedicated pickling process that can balance efficiency, precision, and surface integrity. Summary of the Invention

[0006] The technical problem to be solved by this invention is that traditional surface treatment processes have poor process applicability and are difficult to control when applied to thin sheets of high Cr-Ni-Ti austenitic stainless steel for aerospace applications.

[0007] To achieve the above-mentioned objectives, the technical solution adopted in this application is as follows.

[0008] This invention provides a surface treatment process for high Cr-Ni-Ti austenitic stainless steel sheets, specifically including the following steps: S1. Alkali washing: The stainless steel sheet that has undergone annealing or solution treatment is placed in an alkaline washing medium for treatment at a temperature of 400~450℃; the alkaline washing medium is a high-temperature molten state and is composed of a system formed by the reaction of NaNO3 and NaOH at the treatment temperature. S2. First cold water rinse: Place the alkaline-washed stainless steel sheet in cold water at 0~5℃ for rinsing; S3. Pickling: The stainless steel sheet after the first cold water rinse is placed in a pickling solution for treatment. The pickling temperature is 30~35℃. The pickling solution is a mixed solution of HF, HNO3 and water. S4. Second cold water rinse: Rinse the pickled stainless steel sheet in cold water at 0~5℃. S5. Hot water rinsing: After rinsing with cold water, the stainless steel sheet is placed in hot water at 60~70℃ for rinsing. S6. Drying: Dry the stainless steel sheet after rinsing with hot water to obtain a high Cr-Ni-Ti austenitic stainless steel sheet with a surface roughness Ra≤0.15μm and a surface brightness that meets the 2D standard.

[0009] In step S1 above, when preparing the alkaline washing medium, the dosage of NaNO3 is 40~60g / L and the dosage of NaOH is 80~120g / L, based on the unit volume of the reaction vessel.

[0010] In step S1 above, the alkaline washing time is 20-30 minutes.

[0011] In step S3 above, based on the total mass of the pickling solution, the mass fraction of HF is 3-5% and the mass fraction of HNO3 is 20-30%.

[0012] In step S3 above, the pickling time is 20-30 minutes.

[0013] In step S2 and / or step S4 above, the first cold water rinsing time is 15-20 minutes.

[0014] In step S5 above, the hot water rinsing time is 5-10 minutes.

[0015] In step S6 above, the drying temperature is 50~60℃ and the time is 10~15min.

[0016] The chemical composition of the above-mentioned high Cr-Ni-Ti austenitic stainless steel sheet, by mass percentage, is as follows: C≤0.12%, Mn≤2.50%, Si≤1.20%, Ni 8.00~11.00%, Cr 17.00~20.00%, Ti 0.60~1.00%, Al 0.10~0.16%, S≤0.025%, P≤0.035%, with the balance being Fe and unavoidable impurities.

[0017] The thickness of the above-mentioned high Cr-Ni-Ti austenitic stainless steel sheet is 0.5~2mm.

[0018] The beneficial effects of this invention are as follows: This invention provides a surface treatment process for ultra-thin high-Cr-Ni-Ti austenitic stainless steel. Through a process of "alkali washing → cold water washing → mixed acid washing → cold water washing → hot water washing → drying," it effectively removes oxide scale and defects from the surface of the heat-treated sheet, meeting the stringent surface quality requirements of aerospace materials. Compared to traditional processes, this method lowers the mixed acid washing temperature to 30-35℃ and shortens the time to 20-30 minutes. While ensuring thorough removal of oxide scale, it significantly reduces the risk of over-corrosion of the ultra-thin substrate and avoids surface damage and deformation that may result from high-temperature, long-term processing. This process balances the passivation requirements of high-alloy stainless steel with the process sensitivity of ultra-thin sheets, achieving integrated treatment from surface cleaning and passivation to drying. Attached Figure Description

[0019] Figure 1 The microscopic view of the surface quality of the stainless steel sheet after surface treatment in Example 1; Figure 2 The image shows the macroscopic surface quality of the stainless steel sheet after surface treatment in Example 1. Figure 3 The microscopic view of the surface quality of the stainless steel sheet after surface treatment in Example 2; Figure 4 The microscopic view of the surface quality of the stainless steel sheet after surface treatment in Example 3; Figure 5 The microscopic surface quality of the stainless steel sheet after surface treatment in Comparative Example 1 is shown. Figure 6 This is a macroscopic view of the surface quality of the stainless steel sheet after surface treatment in Comparative Example 1. Figure 7 The microscopic surface quality of the stainless steel sheet after surface treatment in Comparative Example 2; Figure 8 The microscopic surface quality of the stainless steel sheet after surface treatment is shown in Comparative Example 3. Detailed Implementation

[0020] To make the technical problems, solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with the embodiments. Unless otherwise defined, all technical terms used herein have the same meaning as understood by one of ordinary skill in the art.

[0021] This invention provides a surface treatment process for ultra-thin high-Cr-Ni-Ti austenitic stainless steel sheets for aerospace applications. The aim is to thoroughly remove the dense oxide scale generated after heat treatment, repair micro-defects, and form a uniform, stable, and highly glossy passivation film on the sheet surface by combining chemical treatment with physical cleaning. The process includes the following steps.

[0022] S1. Alkali washing: The stainless steel sheet that has been annealed or solution heat treated is immersed in a pre-prepared alkaline washing medium for treatment at a temperature of 400℃~450℃ for 20min~30min.

[0023] In one embodiment of the present invention, the alkaline washing medium is not a traditional aqueous solution, but a high-temperature molten reaction system that utilizes a strongly alkaline and oxidizing environment for degreasing, breaking the bond between the oxide scale and the substrate. The specific preparation method is as follows: 40g~60g of solid NaNO3 and 80g~120g of solid NaOH are added to a high-temperature resistant reaction vessel (such as a salt bath furnace), calculated per unit volume (liters) of the reaction vessel. The vessel is then heated to 400℃~450℃, causing the solid raw materials to melt and react, forming a molten composite medium with high ionic activity and strong oxidizing properties. Compared with traditional aqueous alkaline washing media, the high-temperature molten medium has higher ionic activity and stronger penetrating power, effectively cleaning the oxide scale stubbornly adhering to the surface of materials.

[0024] S2. First cold water rinse: Immerse the stainless steel sheet after the high-temperature alkaline wash in S1 into a low-temperature cold water bath at 0℃~5℃ for rinsing. The rinsing time is 15 min~20 min to ensure that the molten alkaline washing medium is completely removed.

[0025] S3. Pickling: The stainless steel sheet, after thorough cleaning in S2, is immersed in the pickling solution for treatment. The pickling temperature is 30℃~35℃, and the pickling time is 20min~30min. Strict temperature control is required during pickling; if the temperature exceeds 35℃, it must be cooled down promptly. The pickling temperature of this invention is much lower than that of traditional processes, greatly reducing the corrosion rate of the acid solution on the extremely thin substrate and the tendency for intergranular corrosion. This effectively avoids increased surface roughness, hydrogen embrittlement risk, and microscopic deformation of the sheet material caused by vigorous reactions.

[0026] In one embodiment of the present invention, the pickling solution is a mixed solution of HF, HNO3, and water. Based on the total mass of the pickling solution, the mass fraction of HF is 3%~5%, the mass fraction of HNO3 is 20%~30%, and the balance is water. HNO3 is a strong oxidizing agent that can promote the formation of an extremely dense and uniform passivation film on the stainless steel surface. The addition of HF not only regulates the corrosion rate and prevents over-corrosion of extremely thin plates, but also reacts with elements such as Ti to improve the uniformity and adhesion of the passivation film.

[0027] S4. Second cold water rinse: The stainless steel sheet after S3 pickling is quickly transferred to another low-temperature cold water tank of 0℃~5℃ for rinsing. The rinsing time is 15min~20min to ensure that the pickling solution is completely removed.

[0028] S5. Hot water rinse: Transfer the stainless steel sheet after the S4 cold water rinse to a hot water bath at 60℃~70℃ for 5min~10min. Hot water reduces the surface tension of the water and accelerates the evaporation of moisture from the surface of the sheet and any gaps, preventing mineral watermarks, spots or localized corrosion marks from being left on the high-gloss surface due to slow evaporation.

[0029] S6. Drying: The stainless steel sheet rinsed with hot water in S5 is then dried. A clean, forced-air drying system is preferred, and the sheet is dried at an ambient temperature of 50℃~60℃ for 10~15 minutes. After drying, the finished sheet with surface treatment is obtained.

[0030] In one embodiment of the present invention, the thickness of the ultra-thin high Cr-Ni-Ti austenitic stainless steel sheet for aerospace applications is 0.5~2mm; its chemical composition by mass percentage is: C≤0.12%, Mn≤2.50%, Si≤1.20%, Ni8.00~11.00%, Cr 17.00~20.00%, Ti 0.60~1.00%, Al 0.10~0.16%, S≤0.025%, P≤0.035%, with the balance being Fe and unavoidable impurities.

[0031] The following specific embodiments will be provided to explain the solution of the present invention. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0032] Example 1: Surface treatment of high Cr-Ni-Ti austenitic stainless steel sheet.

[0033] The chemical composition of the high Cr-Ni-Ti austenitic stainless steel sheet described in this embodiment, by mass percentage, is: C 0.10%, Mn 2.20%, Si 0.08%, Ni 9.10%, Cr 18.5%, Ti 1.00%, Al 0.13%, S 0.020%, P 0.028%, with the balance being Fe and unavoidable impurities; the surface treatment specifically includes the following steps.

[0034] S1. Alkaline Washing: Add 50g of solid NaNO3 and 100g of solid NaOH to the alkaline washing container by unit volume (liters). Then heat to 400℃ to melt and react the solid raw materials, obtaining a high-temperature molten alkaline washing medium. Then place the stainless steel sheet in the alkaline washing medium for treatment at 400℃ for 20 minutes.

[0035] S2. First cold water rinse: Quickly immerse the alkaline-washed stainless steel sheet in 5°C cold water for 20 minutes to ensure that the alkaline washing medium is completely removed.

[0036] S3. Pickling: Prepare a pickling solution by mixing HF, HNO3, and water at a mass ratio of 4% HF, 25% HNO3, and the balance being water. Place the stainless steel sheet after the initial cold water rinse into the pickling solution for treatment. The pickling temperature is 35℃, and the pickling time is 20 minutes. Strict temperature control is required during the mixed pickling process; if the temperature exceeds 35℃, it must be cooled down promptly.

[0037] S4. Second cold water rinse: Quickly immerse the pickled stainless steel sheet in 5°C cold water for 20 minutes to ensure that the pickling solution is completely removed.

[0038] S5. Hot water rinse: After the second cold water rinse, quickly immerse the stainless steel sheet in 70℃ hot water for 10 minutes to accelerate water evaporation and avoid surface watermarks.

[0039] S6. Drying: Use a blower to dry the stainless steel sheet after rinsing with hot water. The ambient temperature is controlled at 60℃ and the drying time is 15 minutes.

[0040] After drying, a high-Cr-Ni-Ti austenitic stainless steel sheet with a surface roughness of 0.08 μm and a surface gloss meeting the 2D standard was obtained. Its surface quality microstructure is as follows: Figure 1 As shown in the figure, the surface exhibits a uniform granular structure with tightly bonded particles and no obvious pores / defects, indicating that the surface treatment process of Example 1 can create a dense and regular microstructure on the board surface. The macroscopic surface quality is as follows: Figure 2 As shown in the figure, its surface is flat, the color is uniform, and there are no obvious defects, cracks or bumps, which meets the appearance standards of high-quality boards.

[0041] Example 2: Surface treatment of high Cr-Ni-Ti austenitic stainless steel sheet.

[0042] The chemical composition of the high Cr-Ni-Ti austenitic stainless steel sheet described in this embodiment, by mass percentage, is: C 0.8%, Mn 2.50%, Si 1.13%, Ni 10.98%, Cr 19.7%, Ti 0.76%, Al 0.10%, S 0.018%, P 0.022%, with the balance being Fe and unavoidable impurities; the surface treatment specifically includes the following steps.

[0043] S1. Alkaline Washing: Add 40g of solid NaNO3 and 120g of solid NaOH to the alkaline washing container by unit volume (liters). Then heat to 450℃ to melt and react the solid raw materials, obtaining a high-temperature molten alkaline washing medium. Then place the stainless steel sheet in the alkaline washing medium for treatment at 450℃ for 20 minutes.

[0044] S2. First cold water rinse: Quickly immerse the alkaline-washed stainless steel sheet in 0℃ cold water for 15 minutes to ensure that the alkaline washing medium is completely removed.

[0045] S3. Pickling: Prepare a pickling solution by mixing HF, HNO3, and water at a mass ratio of 3% HF, 30% HNO3, and the balance being water. Place the stainless steel sheet after the initial cold water rinse into the pickling solution for treatment. The pickling temperature is 30℃, and the pickling time is 30 minutes. Strict temperature control is required during the mixed pickling process; if the temperature exceeds 35℃, it must be cooled down promptly.

[0046] S4. Second cold water rinse: Quickly immerse the pickled stainless steel sheet in 0℃ cold water for 15 minutes to ensure that the pickling solution is completely removed.

[0047] S5. Hot water rinse: After the second cold water rinse, quickly immerse the stainless steel sheet in 70℃ hot water for 10 minutes to accelerate water evaporation and avoid surface watermarks.

[0048] S6. Drying: Use a blower to dry the stainless steel sheet after rinsing with hot water. The ambient temperature is controlled at 50℃ and the drying time is 15 minutes.

[0049] After drying, a high-Cr-Ni-Ti austenitic stainless steel sheet with a surface roughness of 0.15 μm and a surface gloss meeting the 2D standard was obtained. Its surface quality microstructure is as follows: Figure 3 As shown in the figure, its surface has a granular structure at the microscopic level, and the particles are more numerous than those in the figure. Figure 1 The surface is finer and more evenly distributed, resulting in improved surface smoothness. This demonstrates that the surface treatment process in Example 2 can create a finer microstructure on the surface of the board.

[0050] Example 3: Surface treatment of high Cr-Ni-Ti austenitic stainless steel sheet.

[0051] The chemical composition of the high Cr-Ni-Ti austenitic stainless steel sheet described in this embodiment, by mass percentage, is: C 0.12%, Mn 1.80%, Si 0.7%, Ni 11.00%, Cr 19.98%, Ti 0.88%, Al 0.15%, S 0.013%, P 0.034%, with the balance being Fe and unavoidable impurities; the surface treatment specifically includes the following steps.

[0052] S1. Alkaline Washing: Add 60g of solid NaNO3 and 80g of solid NaOH to the alkaline washing container by unit volume (liters). Then heat to 420℃ to melt and react the solid raw materials, obtaining a high-temperature molten alkaline washing medium. Then place the stainless steel sheet in the alkaline washing medium for treatment at 420℃ for 25 minutes.

[0053] S2. First cold water rinse: Quickly immerse the alkaline-washed stainless steel sheet in 2°C cold water for 18 minutes to ensure that the alkaline washing medium is completely removed.

[0054] S3. Pickling: Prepare a pickling solution by mixing HF, HNO3, and water in a mass ratio of 5% HF, 20% HNO3, and the balance being water. Place the stainless steel sheet after the initial cold water rinse into the pickling solution for treatment. The pickling temperature is 32℃, and the pickling time is 25 minutes. Strict temperature control is required during the mixed pickling process; if the temperature exceeds 35℃, it must be cooled down promptly.

[0055] S4. Second cold water rinse: Quickly immerse the pickled stainless steel sheet in 2°C cold water for 15 minutes to ensure that the pickling solution is completely removed.

[0056] S5. Hot water rinse: After the second cold water rinse, quickly immerse the stainless steel sheet in 65℃ hot water for 10 minutes to accelerate water evaporation and avoid surface watermarks.

[0057] S6. Drying: Use a blower to dry the stainless steel sheet after rinsing with hot water. The ambient temperature is controlled at 55℃ and the drying time is 15 minutes.

[0058] After drying, a high-Cr-Ni-Ti austenitic stainless steel sheet with a surface roughness of 0.11 μm and a surface gloss meeting the 2D standard was obtained. Its surface quality microstructure is as follows: Figure 4 As shown in the figure, its surface microstructure exhibits a granular structure, and the particles are relatively large compared to... Figure 1 , 3 It is the finest and most uniform, with almost no roughness on the surface, and has the best microscopic quality.

[0059] Comparative Example 1: A comparative experiment was conducted using a high-Cr-Ni-Ti austenitic stainless steel sheet with the same composition as in Example 1. The surface treatment specifically included the following steps.

[0060] S1. Pickling: Prepare an H2SO4 solution as the pickling solution by mixing 10% H2SO4 with the balance being water. Place the stainless steel sheet in the pickling solution for treatment at 80℃ for 120 minutes.

[0061] S2. Cold water rinsing: Quickly immerse the pickled stainless steel sheet in cold water at 5°C for 15 minutes to ensure that the pickling solution is completely removed.

[0062] S3. Drying: Use a blower to dry the stainless steel sheet after rinsing with cold water. The ambient temperature is controlled at 55℃ and the drying time is 15 minutes.

[0063] The high-Cr-Ni-Ti austenitic stainless steel sheet obtained after drying exhibits obvious micropores and defects, with a surface roughness of 0.85 μm and a surface gloss level that does not meet the 2D standard. Its surface quality microstructure is as follows: Figure 5 As shown in the figure, the surface exhibits obvious microscopic defects such as pores and cracks. The particles are loosely bonded and the structure is irregular, indicating that the surface treatment process in Comparative Example 1 resulted in a loose microstructure and poor surface quality. The macroscopic surface quality is as follows: Figure 6 As shown in the figure, its surface has uneven reflection, mottled / rough areas, obvious defects, cracks or bumps, and does not meet the appearance standards of high-quality boards.

[0064] Comparative Example 2: A comparative experiment was conducted using a high-Cr-Ni-Ti austenitic stainless steel sheet with the same composition as in Example 1. The surface treatment specifically included the following steps.

[0065] S1~S2: The operation is the same as in Example 1.

[0066] S3. Pickling: Prepare an H2SO4 solution as the pickling solution by mixing 10% H2SO4 with the remainder being water. Place the stainless steel sheet after the initial cold water rinse into the pickling solution for treatment. The pickling temperature is 35℃, and the pickling time is 20 minutes. Strict temperature control is required during the mixed pickling process; if the temperature exceeds 35℃, it must be cooled down promptly.

[0067] S4~S6: The operation is the same as in Example 1.

[0068] The high-Cr-Ni-Ti austenitic stainless steel sheet obtained after drying exhibits obvious micropores and defects, with a surface roughness of 0.65 μm and a surface gloss level that does not meet the 2D standard. Its surface quality microstructure is as follows: Figure 7 As shown in the figure, its surface micropore ratio is... Figure 5 It is finer but more numerous, and the overall structure is still not dense, with microscopic defects and poor surface quality.

[0069] Comparative Example 3: A comparative experiment was conducted using a high-Cr-Ni-Ti austenitic stainless steel sheet with the same composition as in Example 1. The surface treatment specifically included the following steps.

[0070] S1~S3: The operation is the same as in Example 1.

[0071] S4. Rinse with room temperature water: Quickly immerse the pickled stainless steel sheet in room temperature water at 25°C for 20 minutes to ensure that the pickling solution is completely removed.

[0072] S5. Rinse with room temperature water: After rinsing with cold water, quickly immerse the stainless steel sheet in room temperature water at 25°C for 10 minutes to accelerate water evaporation and avoid surface watermarks.

[0073] S6: The operation is the same as in Example 1.

[0074] The high-Cr-Ni-Ti austenitic stainless steel sheet obtained after drying exhibits obvious micropores and defects, with a surface roughness of 0.44 μm and a surface gloss level that does not meet the 2D standard. Its surface quality microstructure is as follows: Figure 8 As shown in the figure, its surface exhibits a microscopic distribution of fine cracks, is rough with scattered defects, and has obvious defects, resulting in poor surface quality.

Claims

1. A surface treatment process for high-Cr-Ni-Ti austenitic stainless steel thin plates, characterized in that, Includes the following steps: S1. Alkali washing: The stainless steel sheet that has undergone annealing or solution treatment is placed in an alkaline washing medium for treatment at a temperature of 400~450℃; the alkaline washing medium is a high-temperature molten state and is composed of a system formed by the reaction of NaNO3 and NaOH at the treatment temperature. S2. First cold water rinse: Place the alkaline-washed stainless steel sheet in cold water at 0~5℃ for rinsing; S3. Pickling: The stainless steel sheet after the first cold water rinse is placed in a pickling solution for treatment. The pickling temperature is 30~35℃. The pickling solution is a mixed solution of HF, HNO3 and water. S4. Second cold water rinse: Rinse the pickled stainless steel sheet in cold water at 0~5℃. S5. Hot water rinsing: After rinsing with cold water, the stainless steel sheet is placed in hot water at 60~70℃ for rinsing. S6. Drying: Dry the stainless steel sheet after rinsing with hot water to obtain a high Cr-Ni-Ti austenitic stainless steel sheet with a surface roughness Ra≤0.15μm and a surface brightness that meets the 2D standard.

2. The surface treatment process for high Cr-Ni-Ti austenitic stainless steel thin plates according to claim 1, characterized in that: In step S1, when preparing the alkaline washing medium, the dosage of NaNO3 is 40~60g / L and the dosage of NaOH is 80~120g / L, based on the unit volume of the reaction vessel.

3. The surface treatment process for high Cr-Ni-Ti austenitic stainless steel thin plates according to claim 1, characterized in that: In step S1, the alkaline washing time is 20-30 minutes.

4. The surface treatment process for high Cr-Ni-Ti austenitic stainless steel thin plates according to claim 1, characterized in that: In step S3, based on the total mass of the pickling solution, the mass fraction of HF is 3-5% and the mass fraction of HNO3 is 20-30%.

5. The surface treatment process for high Cr-Ni-Ti austenitic stainless steel thin plates according to claim 1, characterized in that: In step S3, the pickling time is 20-30 minutes.

6. The surface treatment process for high Cr-Ni-Ti austenitic stainless steel thin plates according to claim 1, characterized in that: In step S2 and / or step S4, the first cold water rinsing time is 15-20 minutes.

7. The surface treatment process for high Cr-Ni-Ti austenitic stainless steel thin plates according to claim 1, characterized in that: In step S5, the hot water rinsing time is 5-10 minutes.

8. The surface treatment process for high Cr-Ni-Ti austenitic stainless steel thin plates according to claim 1, characterized in that: In step S6, the drying temperature is 50~60℃ and the time is 10~15min.

9. The surface treatment process for high Cr-Ni-Ti austenitic stainless steel thin plates according to claim 1, characterized in that, The chemical composition of the high Cr-Ni-Ti austenitic stainless steel sheet, by mass percentage, is as follows: C≤0.12%, Mn≤2.50%, Si≤1.20%, Ni 8.00~11.00%, Cr 17.00~20.00%, Ti 0.60~1.00%, Al 0.10~0.16%, S≤0.025%, P≤0.035%, with the balance being Fe and unavoidable impurities.

10. The surface treatment process for high Cr-Ni-Ti austenitic stainless steel thin plates according to claim 1, characterized in that: The thickness of the high Cr-Ni-Ti austenitic stainless steel sheet is 0.5~2mm.

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