A method for reducing work hardening of stainless steel by on-line solution annealing and acid-free descaling

Abstract

The application discloses an online solid solution and acid-free descaling method for reducing work hardening of stainless steel, and the solid solution process is performed by utilizing the surface residual heat of a steel coil, and the acid-free descaling process is performed after the solid solution process, and the specific process comprises the following steps: (1) the stainless steel strip after the solid solution process is subjected to S roller treatment and scale breaking treatment, and the S rollers at both ends are used to apply tension to both sides of the steel strip; water spraying treatment is performed during the scale breaking treatment; (2) the stainless steel strip after the scale breaking treatment is subjected to EPS treatment for surface descaling; (3) the stainless steel strip after the EPS treatment is subjected to brushing treatment by adopting a roller brush; (4) the stainless steel strip after the brushing treatment is subjected to rinsing treatment; and (5) the stainless steel strip after the rinsing treatment is subjected to drying treatment, and then is wound into a finished steel coil by using a coiling machine.

Description

Technical Field

[0001] This invention belongs to the field of stainless steel heat treatment production technology, and specifically relates to an online solution-free acid-free descaling method for stainless steel to reduce work hardening. Background Technology

[0002] The main process for descaling traditional stainless steel is as follows: uncoiling → welding → straightening and descaling → shot blasting → sulfuric acid pre-pickling → brushing → nitric acid + hydrofluoric acid mixed acid pickling → multi-stage water spray rinsing → hot water rinsing → drying → oiling → coiling.

[0003] Among these methods, descaling, using traditional large-diameter rollers, applies high tension to both sides of the steel strip via S-rollers at both ends. This method involves large equipment investment, high energy consumption, and is generally dry descaling. Although blowing and dust extraction are used, dust pollution still occurs, resulting in mediocre descaling effectiveness. Severe bending deformation causes some plastic deformation in the stainless steel strip. While the primary purpose is descaling, this deformation inevitably introduces work hardening. However, due to the overall bending, the hardened layer is very thin and can be covered or altered by subsequent, more severe processes (such as shot blasting). Dry shot blasting uses high-speed shot to impact the surface, essentially a surface bombardment process. While dry shot blasting can remove the work hardened layer, the size, material, shape, speed, and amount of shot directly determine the removal effect on the stainless steel strip surface. Improper use may lead to over-removal while removing the work hardened layer, affecting the surface roughness and other properties of the stainless steel strip. Therefore, the traditional process of straightening and descaling → shot blasting → sulfuric acid pre-pickled is not conducive to controlling the surface hardening of the stainless steel strip. Summary of the Invention

[0004] This invention provides an online solution-based acid-free descaling method for stainless steel that reduces work hardening. By miniaturizing the roller diameter, it achieves high stress concentration and energy consumption optimization, significantly improving oxide scale removal efficiency and surface quality. It is particularly suitable for the production of thin-gauge strip steel with high surface finish requirements, providing an economical and environmentally friendly solution for production line upgrades.

[0005] To achieve the above objectives, in a first aspect, the present invention provides an online solution-free acid-free descaling method for stainless steel to reduce work hardening, comprising raw material preparation, steelmaking, continuous casting, hot rolling, and solution treatment processes. The solution treatment process utilizes the residual heat on the surface of the steel coil for online solution treatment. Following the solution treatment process, an acid-free descaling process is performed. The specific process includes the following steps:

[0006] (1) The stainless steel strip after solution treatment is processed by S-roller and descaling. When the steel plate thickness is 4~5mm, the relationship between the descaling roller diameter D and the steel plate thickness t is: D / t=11~13.75; when the steel plate thickness is 2~4mm, the relationship between the descaling roller diameter D and the steel plate thickness t is: D / t=11.25~22.5; when the steel plate thickness is less than 2mm, the relationship between the descaling roller diameter D and the steel plate thickness t is: D / t≥20.

[0007] The stainless steel strip forms a wrap angle α = 20~50° with the surface of the scalding roller. The relationship between the distance L1 between the top and bottom adjacent scalding rollers, the distance L between the top two adjacent scalding rollers, and the diameter D of the scalding roller is: L1 / D = 1~1.5, L / D = 2~3.5. The downward pressure range of the scalding roller is: h = 0~D×2 / 3.

[0008] When breaking scales, water should be sprayed, and the nozzle orifice diameter on the spray pipe should be no less than 0.5 mm, and the water pressure should be no less than 1 bar.

[0009] (2) The stainless steel strip after the descaling treatment is descaled by EPS treatment;

[0010] (3) The stainless steel strip after EPS treatment is washed by using a roller brush;

[0011] (4) Rinse the stainless steel strip after brushing.

[0012] (5) The stainless steel strip after rinsing is dried and then wound into finished steel coils by a coiler.

[0013] Preferably, the solution treatment process utilizes the residual heat temperature of the steel coil surface at 800~900℃, the solution temperature at 1050~1150℃, and the holding time at 1.1~1.5min / mm.

[0014] Preferably, the solution treatment process involves a staged heating process. In the first stage, when the temperature of the solution treatment process is less than 920°C, the heating rate is 22~30°C / min. In the second stage, when the temperature of the solution treatment process is greater than or equal to 920°C but 10~30°C lower than the solution temperature, the heating rate is 9~14°C / min. In the third stage, when the temperature is raised to the solution temperature, the heating rate is 2~3°C / min.

[0015] Preferably, the hot rolling process includes rough rolling and final rolling, the final rolling temperature is 890~950℃, and the steel is swayed for 13~57s after hot rolling.

[0016] Preferably, in the hot rolling process, the stainless steel strip thickness is <1mm, the final rolling temperature is 890~910℃, the steel is swayed for 13-33s after hot rolling, and the stainless steel strip speed is 110m / min~155m / min.

[0017] The stainless steel strip thickness is ≥1mm, the final rolling temperature is 910~950℃, the steel is swayed after hot rolling for 34~57s, and the steel speed of the stainless steel strip is 60m / min~90m / min.

[0018] Preferably, in step (3), the brushing is in the re-brushing mode, and the surface roughness of the stainless steel strip decreases by >1.1μm.

[0019] Preferably, the re-brushing mode uses silicon carbide abrasive, the proportion of silicon carbide abrasive in the bristles is 15~35%, the particle size of silicon carbide abrasive is 60 mesh~150 mesh, the bristle diameter is 0.8~1.0 mm, the motor speed of the re-brushing mode is 1100~1300 RPM, the brush roller pressing amount is >3 mm, the single bristle load power is 90~160 kW, the water pressure is 2~4 bar, and the single bristle spray water volume is 250~400 L / min.

[0020] Preferably, the deformation amount in the rough rolling process accounts for 71-79% of the total deformation amount, the deformation amount in the final rolling process accounts for 21-29% of the total deformation amount, and the steel is swayed for 62-78 seconds after rough rolling.

[0021] Preferably, after EPS treatment, the hardness of the upper surface is higher than that of the lower surface. In the re-brushing mode, the motor speed of the upper surface is 8-12% higher than that of the lower surface, the brush roller pressure of the upper surface is 5-11% higher than that of the lower surface, the single brush bristle load power of the upper surface is 9-15% higher than that of the lower surface, and the water spray volume of the single brush bristle of the upper surface with a water pressure of 2-4 bar is 12-16% higher than that of the single brush bristle of the lower surface.

[0022] Preferably, the EPS-treated steel grit has a particle size of 0.1~0.4mm and a slinging speed of 25~40m / s.

[0023] The beneficial effects of this invention are as follows:

[0024] In this invention, the solution treatment process utilizes the residual heat on the surface of the steel coil for online solution treatment. Following the solution treatment, an acid-free descaling process is performed. The stainless steel strip after the solution treatment is then processed by S-rollers and descaling. Descaling is achieved using a novel small-diameter roller method, applying tension to both sides of the steel strip via S-rollers at both ends. This tension is only 1 / 4 of that of traditional descaling, significantly reducing investment and energy consumption in S-roller operation. Simultaneously, the use of small-diameter descaling rollers, with different diameters tailored to different stainless steel strip thicknesses, increases the deformation and extrusion between the inner and outer sides of the steel coil. Due to the brittleness of the oxide scale, descaling is more efficient. The lower pressure of the descaling roller, combined with lower tension, significantly reduces the stress on the descaling roller, correspondingly reducing the load on the support rollers. Furthermore, the water spraying during operation not only washes away the oxide scale left on the surface and gaps of the work rollers and support rollers during descaling but also cleans the oxide scale accumulated inside the roller box. The working fluid also has a heat dissipation effect on the rollers, quickly removing the heat generated during operation and preventing the accumulation of high temperatures that could affect surface hardness and lifespan. It also prevents contamination caused by oxide scale dust. The working fluid contains rust inhibitors, lubricants, and cleaners, providing rust prevention, surface lubrication, and cleaning during roller rotation. Simultaneously, water spraying during the stainless steel strip descaling stage, with controlled water volume, reduces the temperature difference between the surface and core of the stainless steel strip, improving the uniformity of the internal and surface microstructure. This avoids uneven microstructure and potential work hardening caused by temperature differences during descaling. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram showing the relationship between the scale-breaking roller and the steel plate thickness, provided in an embodiment of the present invention.

[0027] Figure 2 This is a schematic diagram showing the relationship between the scale-breaking roller and the wrap angle provided in an embodiment of the present invention.

[0028] Explanation of reference numerals in the attached figures:

[0029] 1. Feeding direction; 2. Upper crushing roller; 3. Lower crushing roller; 4. Steel coil; 5. Wrap angle α1; 6. Wrap angle α2; 7. Wrap angle α3; 8. Wrap angle α4; 9. Downward pressure; 10. Steel plate thickness. Detailed Implementation

[0030] In this invention, unless otherwise stated, directional terms such as "up," "down," "left," and "right" are generally understood in conjunction with the accompanying drawings and the directions shown in actual applications.

[0031] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0032] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0033] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. The terms "optional" and "discretionary" mean that they may or may not be included (or may or may not be present).

[0034] The applicant of this invention discovered that existing stainless steel surface descaling methods use sulfuric acid pre-pickling, mainly involving preheating and preliminary pickling of the steel strip to remove most of the oxide scale, especially FeO and Fe3O4. Stainless steel surface descaling now utilizes a mixed acid pickling process of nitric acid and hydrofluoric acid, which is the core step in stainless steel pickling. 304 stainless steel oxide scale contains difficult-to-remove chromium oxides (such as Cr2O3), necessitating the use of a mixed acid with strong oxidizing and complexing abilities. Nitric acid (HNO3) is used in stainless steel surface descaling to oxidize and promote stainless steel passivation, forming a dense passivation film on the stainless steel surface, ensuring gloss and preventing excessive corrosion.

[0035] The traditional large-diameter roll method for descaling stainless steel strips presents several problems: When the S-rolls at both ends apply significant tension to the strip, especially in the contact area between the rolls and the strip, it easily leads to high localized stress concentration. This stress concentration may exceed the yield strength of the strip material, increasing the risk of plastic deformation, microcracks, and even macroscopic fracture. Edge cracking of the strip is a common phenomenon during rolling; parameters such as tension, reduction rate, roll diameter, and coefficient of friction all affect the initiation and propagation of edge cracks. Stainless steel is inherently difficult to form, making it prone to cracking and springback. For thinner strip surfaces, an excessively large roll diameter may not provide a sufficiently fine contact pressure distribution, resulting in uneven descaling or failure to achieve the desired effect. Diameter deviations of the work rolls, even localized ones, can be transmitted to the stainless steel strip, leading to flatness defects. Excessive tension can cause overstretching of the strip, affecting its internal structure and mechanical properties. For example, slippage between the strip and the rolls can cause fluctuations in rolling force, elongation, and strip tension, all of which can damage the strip surface quality and affect the stable operation of the production line. Although the goal of descaling is to remove iron oxide scale, improper tension control may alter the crystal structure of the steel strip at the macroscopic or microscopic level, leading to adverse changes such as surface hardening of the material.

[0036] To address the aforementioned problems, this invention provides an online solution-based acid-free descaling method for stainless steel to reduce work hardening. The solution-based process utilizes the residual heat on the surface of the steel coil for online solution treatment, followed by an acid-free descaling process. The specific process includes the following steps:

[0037] (1) The stainless steel strip after the solution treatment process is processed by S roller and descaling. When the steel plate thickness 10 is 4~5mm, the diameter D of the descaling roller is 55mm. The relationship between the diameter D of the descaling roller and the thickness t of the steel plate is: D / t=11~13.75; when the steel plate thickness 10 is 2~4mm, the diameter of the descaling roller is 45mm. The relationship between the diameter D of the descaling roller and the thickness t of the steel plate is: D / t=11.25~22.5; when the steel plate thickness 10 is less than 2mm, the diameter of the descaling roller is 40mm. The relationship between the diameter D of the descaling roller and the thickness t of the steel plate is: D / t≥20. Different descaling roller diameters are used according to different stainless steel strip thicknesses, which is conducive to stable and accurate control of tension and reduces the difficulty of work hardening control.

[0038] Tension is applied to both sides of the steel strip by S-rollers at both ends, and the tension is less than 10% of the material's yield strength.

[0039] The stainless steel strip forms a wrap angle α of 20~50° with the surface of the scale-breaking roller. See [reference needed] Figure 2The wrap angles α1 (5), α2 (6), α3 (7), and α4 (8) are: the distance L1 between the top and bottom adjacent breaking rollers, i.e. the distance between the adjacent upper breaking roller 2 and lower breaking roller 3; the distance L between the two adjacent breaking rollers at the top, i.e. the distance between the two adjacent upper breaking rollers 2; and the relationship between the breaking roller diameter D is: L1 / D = 1~1.5, L / D = 2~3.5. The downward pressure range (i.e., the downward pressure amount 9) of the breaking roller is: h = 0~D×2 / 3.

[0040] By controlling the wrap angle α, the distance L1 between the top and bottom adjacent descaling rollers, the distance L between the top two adjacent descaling rollers, the relationship with the descaling roller diameter D, and the downward pressure range of the descaling roller, it is beneficial to accurately control the contact area, contact gap, and tension between the descaling roller and the steel strip under small roller diameter, which is beneficial to stabilize and accurately control the tension and reduce the possibility of work hardening.

[0041] When breaking scales, water should be sprayed, and the nozzle orifice diameter on the spray pipe should be no less than 0.5 mm, and the water pressure should be no less than 1 bar.

[0042] (2) The stainless steel strip after the descaling treatment is descaled by EPS treatment;

[0043] (3) The stainless steel strip after EPS treatment is washed by using a roller brush;

[0044] (4) Rinse the stainless steel strip after brushing.

[0045] (5) The stainless steel strip after rinsing is dried and then wound into finished steel coils by a coiler.

[0046] Understandably, in one embodiment, the stainless steel strip after descaling can be re-brushed or otherwise treated as needed before surface descaling by EPS treatment. That is, the stainless steel strip after descaling can be a stainless steel strip after descaling treatment, or a stainless steel strip after descaling and re-brushing treatment.

[0047] In this embodiment of the invention, the solution treatment process utilizes the residual heat on the surface of the steel coil for online solution treatment. Following the solution treatment, an acid-free descaling process is performed. The stainless steel strip after the solution treatment is then processed by S-rollers and descaling. Descaling is achieved using a novel small-diameter roller method, applying tension to both sides of the steel strip via S-rollers at both ends. This tension is only 1 / 4 of that of traditional descaling, significantly reducing the investment and energy consumption of the S-rollers. Simultaneously, the small-diameter descaling rollers increase the deformation and compression between the inner and outer sides of the steel coil, making descaling more efficient due to the brittleness of the oxide scale. The lower pressure of the descaling rollers, combined with the lower tension, significantly reduces the stress on the descaling rollers, correspondingly reducing the load on the support rollers. Furthermore, the water spraying during operation not only washes away the oxide scale left on the surface and gaps of the work rollers and support rollers during descaling but also cleans the oxide scale accumulated inside the roller box. The working fluid also has a heat dissipation effect on the rollers, quickly removing the heat generated during operation and preventing the accumulation of high temperatures that could affect surface hardness and lifespan. It also prevents contamination caused by oxide scale dust. The working fluid contains rust inhibitors, lubricants, and cleaners, providing rust prevention, surface lubrication, and cleaning during roller rotation. Simultaneously, water spraying during the stainless steel strip descaling stage, with controlled water volume, reduces the temperature difference between the surface and core of the stainless steel strip, improving the uniformity of the internal and surface microstructure. This avoids uneven microstructure and potential work hardening caused by temperature differences during descaling.

[0048] In step (1), when the steel plate thickness is 4~5mm, the diameter of the descaling roller used is 55mm. The relationship between the diameter D of the descaling roller and the plate thickness t is D / t = 11~13.75, which can be one of 11, 11.25, 11.5, 11.75, 12, 12.25, 12.5, 12.75, 13, 13.25, 13.75 or any two of these values. When the steel plate thickness is 2~4mm, the diameter of the descaling roller used is 45mm. The relationship between the diameter D of the descaling roller and the plate thickness t is... The relationship between thickness t and thickness D / t is given by a formula ranging from 11.25 to 22.5, which can be 11.25, 11.5, 11.75, 12, 12.25, 12.5, 12.75, 13, 13.25, 13.75, 14, 14.25, 14.5, 14.75, 15, 15.25, 15.5, 15.75, 16, 16.25, 16.5, 16.75, 17, 17.25, 17.5, 17.75, 18, 18.25, 18.5. The values ​​are within the range of one or any two of the following: 18.75, 19, 19.25, 19.5, 19.75, 20, 20.25, 20.5, 20.75, 21, 21.25, 21.5, 21.75, 22, 22.25, 22.5; when the steel plate thickness is less than 2mm, a diameter of 40mm for the descaling roller is recommended; the relationship between the descaling roller diameter D and the plate thickness t is D / t≥20, which can be 20, 20.25, 20.5, 20.75, 2... 1. A value within the range of one or any two of the following: 21.25, 21.5, 21.75, 22, 22.25, 22.5, 22.75, 23, 23.25, 23.5, 23.75, 24; In addition, a push-pull processing line can also be used to apply tension to both sides of the steel strip by applying tension to both ends of the S-rollers; If it is a push-pull processing line, the tension can also be established by the tension roller and winding machine at the exit of the scaler, as well as the unwinding machine and straightening machine at the entrance of the scaler, to achieve the stretching and scale breaking of the steel strip.

[0049] In one embodiment of the present invention, the tension of the steel strip descaling varies depending on the thickness, width and yield strength of the steel strip. Due to the use of a small roller diameter design, the greater the curvature (the smaller the roller diameter), the greater the surface elongation, which is more conducive to the removal of oxide scale. As a result, the tension requirement is relatively low, only 10% or even lower than the yield strength of the material, which is lower than the 20-30% range required by traditional descaling. Therefore, it is significantly more energy-efficient and reduces the wear and tear on the equipment caused by high tension.

[0050] In one embodiment of the invention, the downward pressure of the descaling roller is smaller. The downward pressure is related to the wrap angle formed between the steel strip and the surface of the descaling roller, as well as the distance between the descaling rollers. Generally, the recommended relationship between the distance L1 between the top and bottom adjacent descaling rollers and the diameter D of the descaling roller is L1 / D = 1~1.5; the recommended relationship between the distance L between the top two descaling rollers and the diameter D of the descaling roller is L / D = 2~3.5, which can be one of 2, 2.5, 3, 3.5 or any value between two of them. The downward pressure range of the descaling roller is h = 0~D. 2 / 3; at the same time, it is necessary to take into account the wrap angle range α=20~50°, which can be one of 20°, 30°, 40°, 50° or any value between two of them. Ensure that the descaling rate of the steel plate surface is ≥30% (the proportion of oxide scale falling off the surface of the steel coil), or the descaling speed is increased by ≥30%, while also helping to reduce the possibility of work hardening.

[0051] In one embodiment of the present invention, the descaling water spray (working fluid) serves two main purposes. First, the descaling roller generates heat during operation; spraying water reduces the surface temperature of the descaling roller, extending its service life. Second, during descaling, a large amount of oxide scale of varying sizes falls from the steel plate surface; spraying water cleans this oxide scale, preventing it from adhering to the descaling roller, support roller, or roller box, thus avoiding roller wear, failure, or oxide scale being pressed into the steel strip surface. Regarding the water spray volume, it is generally recommended that the nozzle orifice diameter on the spray pipe be no less than 0.5 mm to reduce the risk of nozzle blockage. Simultaneously, it is necessary to ensure that the rinsing water completely covers the steel plate surface or is sprayed onto the steel plate and the descaling roller surface. A water pressure of no less than 1 bar is recommended. To ensure the effectiveness of roller box rinsing and steel plate surface rinsing, at least one spray pipe is typically installed inside the roller box for each descaling working roller. Additionally, at least one spray pipe is installed on the upper and lower surfaces of the steel strip. A squeezing roller is installed on the equipment outlet side to reduce the amount of rinsing working fluid carried backward along the steel strip. The working fluid contains additives, which have at least the functions of rust prevention and lubrication. It can not only ensure that the equipment and roller box will not rust, but also play a lubricating role when the scale-breaking roller is working, reducing friction and rolling resistance.

[0052] In one embodiment of the present invention, the surface and microscopic layers of the steel strip are affected to a certain extent, which is not conducive to reducing work hardening. If a large roller diameter and a large reduction amount are used when the steel strip is descaled, the reduction amount of the descaled roller is relatively significant. The inner and outer surfaces of the steel strip are subjected to bending and compression, which may lead to the formation of a hardened layer on the surface, which is not conducive to reducing work hardening. If the work hardened layer remains, it is not conducive to improving the surface quality of the stainless steel strip. EPS, compared with traditional shot blasting and other processes, can reduce the impact on the hardened layer. Because EPS uses relatively finer steel grit and a lower blasting speed (40~60m / s), and it is a slurry impact on the steel surface, most of which is working fluid, it can buffer and soften the impact, avoid the formation or aggravation of the hardened layer on the steel surface, and avoid the residue of the hardened layer on the steel surface in the later stage. After passing through, for example, a heavy roller brush, the surface is thinned, so the hardened layer that may be generated can be ground off, thereby facilitating the removal of the hardened layer and thus helping to reduce the work hardening of the stainless steel strip.

[0053] In step (2), the stainless steel strip after the descaling treatment is descaled by EPS treatment.

[0054] In one embodiment of the present invention, EPS surface descaling differs from traditional dry shot blasting. It uses smaller particle sizes, achieving significant results compared to dry shot blasting which uses 1-3mm particles. The shape of the steel grit can be round or angular, with angular grit generally recommended for more efficient descaling. The blasting primarily involves a slurry containing particles and a working fluid (containing rust inhibitors). The water content acts as a buffer and softener upon impact with the steel plate surface, reducing the impact force of individual particles. The lower rotational speed of EPS blasting also results in a significantly smaller maximum impact force. However, due to the larger volume of slurry blasted per EPS turbine, the coverage width and length of a single blast head are greater than in traditional shot blasting. This is one reason why EPS, with fewer turbines, achieves a working efficiency 5 to 10 times that of traditional dry shot blasting. Regarding the hardening of the treated steel surface, since the steel shot used in EPS is relatively finer and the sling speed is lower, and the impact on the steel surface is a slurry, most of which is working fluid, it can buffer and soften the impact, thus avoiding the formation or aggravation of a hardened layer on the steel surface.

[0055] In one embodiment of the present invention, surface descaling of steel strips after descaling via EPS treatment has significant advantages, mainly in terms of environmental friendliness, efficiency, safety, quality stability, and economy. The abrasive waterjet descaling process, by adjusting the abrasive impact kinetic energy and matrix stress state, can alter the abrasive impact mode and the plastic deformation mechanism of the matrix, thereby determining surface quality and improving surface roughness, plastic deformation, material erosion, and microhardness.

[0056] In step (3), the stainless steel strip after EPS treatment is brushed with a roller brush.

[0057] In one embodiment of the invention, brushing primarily removes loose oxide scale that may remain on the surface and cleans fine particles adhering to the surface after rinsing with the working fluid. Simultaneously, if a rapid and significant adjustment (reduction) of the hardened layer formed on the surface of the EPS-treated steel is required, a roller brush device made of a harder material (e.g., silicon carbide) can be used for re-brushing. If a roller brush device made of ordinary nylon is used, it generally only has a cleaning function, further reducing any particles that may remain on the surface. If a roller brush device containing wear-resistant materials such as silicon carbide is used, it not only cleans but also grinds the outermost layer of the steel; the specific thinning amount can be set according to user requirements. Setting it to re-brushing provides the most thorough grinding and cleaning of the steel surface, removing work hardening, with iron loss >2‰.

[0058] In addition, the EPS-treated stainless steel strip is brushed with a roller brush containing silicon carbide abrasive. The brushing can be adjusted to three levels: light brush mode, medium brush mode, and heavy brush mode.

[0059] When set to light brush mode, it only cleans the fine particles remaining on the surface, with minimal impact on the roughness of the substrate, resulting in a roughness decrease of only 0.1~0.5μm (iron loss less than 1‰). If set to medium brush mode, it can clean the particles remaining on the surface and the outermost layer, resulting in a roughness decrease of 0.5~1μm (with iron loss increasing by 1~2‰). If set to heavy brush mode, it provides the most thorough grinding and cleaning of the steel surface, resulting in a roughness decrease of more than 1μm and an iron loss greater than 2‰.

[0060] The silicon carbide used in the light brush mode has a particle size of 500-1500 mesh, which can be one or any two of 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, and 1500 mesh. The bristle diameter is 0.3-0.5 mm, which can be one or any two of 0.3 mm, 0.4 mm, and 0.5 mm. Alternatively, ultrafine bristles can be used, with a diameter of 0.02-0.2 mm, which can be one or any two of 0.02 mm, 0.05 mm, 0.1 mm, 0.15 mm, and 0.2 mm. By weaving together multi-dimensional filaments, a larger diameter bristle is formed, thus taking into account durability and polishing effect. Using large-grained abrasive and coarse-diameter bristles improves the brushing effect during the rebrushing stage and significantly improves the surface roughness of the strip steel; using fine-grained and fine-filament bristles allows for smaller adjustments and improvements to the surface roughness of the strip steel, thereby enhancing the improvement effect.

[0061] The silicon carbide particle size of the medium brush mode is 180 mesh to 320 mesh, which can be one or any two of 180 mesh, 200 mesh, 220 mesh, 240 mesh, 260 mesh, 280 mesh, 300 mesh, and 320 mesh. The bristle diameter is 0.5 to 0.7 mm, which can be one or any two of 0.5 mm, 0.55 mm, 0.6 mm, 0.65 mm, and 0.7 mm. The nylon material of the bristles is also very important. Ultra-high molecular weight nylon is used as the raw material (such as UHMW-PA6, which greatly enhances its wear resistance, toughness and mechanical strength). At the same time, during the processing and manufacturing process, the voids and impurities in the nylon bristles are minimized, which can significantly increase the durability and mechanical properties of the bristles.

[0062] The silicon carbide particle size in the heavy brushing mode is 60-150 mesh, which can be any one or any two of 60, 70, 80, 90, 100, 110, 120, 130, 140, and 150 mesh. The bristle diameter is 0.8-1.0 mm, which can be any one or any two of 0.8 mm, 0.85 mm, 0.9 mm, 0.95 mm, and 1.0 mm. Using a roller brush with low abrasive content is beneficial for achieving light brushing, medium brushing, and heavy brushing modes; if the abrasive content is too high, it will have a significant impact on the surface of the stainless steel strip, affecting the surface roughness.

[0063] Optionally, in some embodiments, the motor speed in the light brush mode is 500~800 RPM, which can be one or any value between 500 RPM, 550 RPM, 600 RPM, 650 RPM, 700 RPM, 750 RPM, and 800 RPM. By using a lower brush roller speed, it is beneficial to reduce the impact of abrasive on the surface of the stainless steel strip. Excessive brush roller speed will introduce too much cutting amount, further increasing the impact on the surface roughness of the stainless steel strip, which is not conducive to roughness control. The brush roller reduction is 0~2. The thickness can be 0.2mm, 0.4mm, 0.6mm, 0.8mm, 1mm, 1.2mm, 1.4mm, 1.6mm, 1.8mm, 2mm, or any combination thereof. The single brush bristle load power is 20~50kW, or 20kW, 25kW, 30kW, 35kW, 40kW, 45kW, 50kW, or any combination thereof. The water pressure is 2~4bar, and the water spray rate per brush bristle is 80~120L / min, or 80L / min, 90L / min, 100L / min, 110L / min, 120L / min, or any combination thereof. By reducing the single brush bristle load power and the single brush bristle water spray rate, water consumption is saved, and the excessive impact on the roughness of the stainless steel strip is reduced. For light brushing, two sets of brush rollers (four brushes) are used in conjunction to achieve both surface cleaning and roughness adjustment functions.

[0064] The motor speed in the medium brush mode is 800~1100 RPM, which can be one or any two of 800 RPM, 850 RPM, 900 RPM, 950 RPM, 1000 RPM, 1050 RPM, and 1100 RPM. By using a higher brush roller speed, it is more conducive to improving the cutting effect of the abrasive on the stainless steel surface and to improving the adjustment and precise control of the rough surface of EPS. The brush roller deflection is 2~3 mm, which can be one or any two of 2 mm, 2.2 mm, 2.4 mm, 2.6 mm, 2.8 mm, and 3 mm. By significantly bending the bristles, stable pressure is applied to the strip surface, thereby improving the cutting ability of the strip surface. The load power of a single brush bristle is 50~90kW, which can be one or any two of the following values: 50kW, 55kW, 60kW, 65kW, 70kW, 75kW, 80kW, 85kW, 90kW. The water spray volume of a single brush bristle is 120~250L / min, which can be one or any two of the following values: 120L / min, 130L / min, 140L / min, 150L / min, 160L / min, 170L / min, 180L / min, 190L / min, 200L / min, 210L / min, 220L / min, 230L / min, 240L / min, 250L / min. By increasing the load power and water spray volume of a single brush bristle, the kinetic energy of the abrasive acting on the surface of the stainless steel strip is increased, the influence of heat generation during brushing is suppressed, and the roughness of the stainless steel strip is further improved.

[0065] The motor speed in the re-brushing mode is 1100~1300RPM, which can be one of 1100RPM, 1150RPM, 1200RPM, 1250RPM, 1300RPM or any two of these values. By using a higher brush roller speed, it is beneficial to improve the cutting effect of the abrasive on the stainless steel surface and to improve the adjustment and precise control of the EPS on the increased roughness surface. The brush roller pressure is >3mm, which can be one of 3mm, 3.2mm, 3.4mm, 3.6mm, 3.8mm, 4mm or any two of these values. Through the obvious large bending of the brush bristles, stable pressure is applied to the strip steel surface to improve the cutting ability of the strip steel surface. The load power of a single brush bristle is 90~160kW, which can be one or any two of the following values: 90kW, 95kW, 100kW, 105kW, 110kW, 115kW, 120kW, 125kW, 130kW, 135kW, 140kW, 145kW, and 150kW. The water spray volume of a single brush bristle is 250~400L / min, which can be one or any two of the following values: 250L / min, 260L / min, 270L / min, 280L / min, 290L / min, 300L / min, 310L / min, 320L / min, 330L / min, 340L / min, 350L / min, 360L / min, 370L / min, 380L / min, 390L / min, and 400L / min. By increasing the load power and water spray volume of a single brush bristle, the kinetic energy of the abrasive acting on the surface of the stainless steel strip is increased, suppressing the heat generated during brushing and improving the surface roughness of the stainless steel strip. The heavy brushing mode can grind the surface of the stainless steel strip at high speed, which generates heat and a lot of abrasive debris, causing heat damage to the brush bristles, affecting the life of the equipment and also hindering the control of surface roughness. By increasing the pressure and flow rate of cooling water, it is ensured that the coolant can strongly penetrate the brush bristle barrier at high brush roller linear speed. At the same time, the large flow rate of cooling water reduces the surface temperature of the steel strip, thereby facilitating precise control of surface roughness.

[0066] In step (4), the stainless steel strip after brushing is rinsed.

[0067] In one embodiment of the invention, if the preceding stage is a nylon roller brush wash, this rinsing step can be omitted. If the preceding stage uses a roller brush device with significant abrasion, this stage is generally necessary, primarily to remove any uncleaned fine particles and any remaining residues on the surface to achieve the user's desired surface cleanliness. The rinsing water is deionized water or demineralized water, and the temperature is generally controlled between 20°C and 80°C.

[0068] In one embodiment of the invention, rinsing helps improve the cleanliness of the stainless steel surface, preventing subsequent corrosion or contamination. The structure of contaminants on the stainless steel surface affects its resistance to rinsing and cleaning; removing these deposits through rinsing significantly improves the surface condition. Rinsing stainless steel strips after brushing is not only a basic operation to remove surface residues and improve cleanliness, but also a crucial step in fundamentally ensuring the corrosion resistance of stainless steel, maintaining its excellent appearance, and meeting subsequent demanding application conditions.

[0069] In step (5), the rinsed stainless steel strip is dried and then fed into a coiler to form the finished steel coil. After drying, the rinsed stainless steel strip may or may not be oiled.

[0070] In one embodiment of the invention, drying the rinsed stainless steel strip aims to thoroughly remove residual moisture from the rinse process and prevent oil spots or rust during subsequent oiling. Before drying, the strip passes through an edge blowing or squeezing device to further reduce moisture content. After drying, the strip typically enters the exit looper to maintain tension and prevent curling. The purpose of oiling is to form a rust-preventive oil film on the metal surface, preventing oxidation caused by moisture in the air and providing lubrication for subsequent winding. Tension adjustment is performed before oiling to ensure uniform strip tension. After oiling, the strip typically undergoes another drying process to solidify the oil film. Between drying and oiling, the strip often passes through online leveling or tension rollers to adjust its straightness and tension, preventing curling or slack during subsequent winding.

[0071] Optionally, in some embodiments, the temperature of the residual heat on the surface of the steel coil after the hot rolling process is 800~900°C, for example, it can be one of 800°C, 820°C, 840°C, 860°C, 880°C, 900°C or any range between two of them. By recovering residual heat, the fuel demand of the heating furnace is reduced, carbon emissions are reduced, the rate of temperature drop of the steel coil is reduced, and the temperature is kept uniform. The uniform temperature distribution reduces rolling resistance, reduces the power demand of the finishing mill, and improves the stability of the mill. After being heated by residual heat, the steel strip is already in a suitable temperature range before entering the finishing mill, which can achieve higher plastic deformation, reduce cracks and surface oxide scale, and improve surface finish and thickness accuracy.

[0072] Optionally, in some embodiments, the solution treatment temperature is 1050~1150℃, which can be one of 1050℃, 1100℃, 1150℃, or any value between two of these. The holding time is 1.1~1.5 min / mm, which can be one of 1.1 min / mm, 1.2 min / mm, 1.3 min / mm, 1.4 min / mm, 1.5 min / mm, or any value between two of these. Solution treatment can eliminate carbide precipitation and lattice defects caused by cold working, restoring the corrosion resistance of stainless steel to its optimal state. Sufficient holding time ensures complete dissolution of carbides, avoiding the formation of chromium-depleted zones at grain boundaries, thereby preventing intergranular corrosion. Appropriate holding time can prevent uneven microstructure and unstable properties caused by insufficient holding time, reducing risks in subsequent processing and use.

[0073] Optionally, in some embodiments, the above-mentioned solution treatment process involves staged heating. The first stage occurs when the solution treatment temperature is below 920°C, with a heating rate of 22-30°C / min, which can be any one of 22°C / min, 24°C / min, 26°C / min, 28°C / min, or 30°C / min, or any combination thereof. The second stage occurs when the solution treatment temperature is greater than or equal to 920°C or 10-30°C below the solution temperature, with a heating rate of 9-14°C / min, which can be any one of 9°C / min, 11°C / min, 13°C / min, or 14°C / min, or any combination thereof. The third stage occurs when the temperature reaches the solution temperature, with a heating rate of 2-3°C / min, which can be any one of 2°C / min, 3°C / min, or any combination thereof. The advantages of staged heating in the solution treatment process are precise control of precipitate dissolution, suppression of grain growth, reduction of deformation risk, and optimization of energy efficiency.

[0074] In one embodiment of the present invention, the heating rate in the heating section below 920°C is controlled at 22-30°C / min. The high temperature of the hot-rolled steel strip results in less carbide precipitation. Therefore, a higher heating rate can be used at relatively low temperatures. This higher heating rate does not excessively affect heating uniformity, and it reduces the possibility of temperature drop when the hot-rolled steel strip enters the heating furnace, suppressing carbide precipitation. This further avoids the occurrence of uneven grain size during solid solution treatment caused by uneven carbide precipitation, which helps reduce mixed crystals and the possibility of work hardening. Simultaneously, since the ambient temperature decreases during the conveying process before the hot-rolled steel strip enters the heating furnace, the surface temperature of the steel strip decreases more than the core. A faster heating rate can heat the surface temperature of the steel plate more quickly, thereby rapidly reducing the internal and surface temperatures of the stainless steel strip. This is beneficial for improving the uniformity of the stainless steel strip's structure, especially avoiding problems such as uneven structure on the surface of the stainless steel strip, and further reducing work hardening.

[0075] In one embodiment of the present invention, the temperature is raised from above 920°C to 10-30°C below the solution temperature, which can be any value between 10°C, 15°C, 20°C, 25°C, and 30°C; the heating rate is controlled at 9-14°C / min, which can be any value between 9°C / min, 10°C / min, 11°C / min, 12°C / min, 13°C / min, and 14°C / min; then the temperature is raised to the solution temperature of 1050-1150°C, which can be any value between 1050°C, 1075°C, 1100°C, 1125°C, and 1150°C; the heating rate is reduced to 2-3°C / min, which can be any value between 2°C / min, 2.5°C / min, and 3°C / min; the holding time at the solution temperature is 1.1-1.5 min / mm, which can be 1.1 min / mm or 1.2 min / mm. The value is within the range of one or more of m, 1.3 min / mm, 1.4 min / mm, and 1.5 min / mm, or any two of them; the holding time is extended according to the thickness of the stainless steel strip at the solution temperature, and the strip is quenched to room temperature immediately after being taken out of the furnace; online solution treatment is achieved; by adopting a lower heating rate below the solution temperature, it is beneficial to improve the overall temperature uniformity of the steel strip. By reducing the heating rate, the crystal transformation process of the steel strip at high temperature can be controlled more precisely and for a longer time, which is conducive to the full and uniform dissolution of carbide precipitation, and further reduces the uneven distribution of precipitated carbides. By further heating to the solution temperature, heating for a longer time at a lower heating rate, the carbides in the previous step are more fully dissolved, reducing the impact of precipitated carbides on recrystallization, which is conducive to promoting uniform recrystallization of the steel strip throughout its thickness at high temperature, avoiding the possibility of mixed crystals. By controlling the holding time according to the thickness of the stainless steel strip, it is more conducive to the homogenization of composition and structure. By distributing the heating and controlling the heating rate as described above, mixed crystals are avoided, which helps to reduce the possibility of work hardening during online solution treatment.

[0076] Optionally, in some embodiments, the above-mentioned hot rolling process is divided into rough rolling and final rolling, which has the advantages of optimizing deformation efficiency, refining grain structure, improving dimensional accuracy, and reducing energy consumption. The above-mentioned final rolling temperature is 890~950℃, and can be a range of one or any two of 890℃, 900℃, 910℃, 920℃, 930℃, 940℃, and 950℃. The swaying time after hot rolling is 13~57s, and can be a range of one or any two of 13s, 18s, 23s, 28s, 33s, 38s, 43s, 48s, 53s, and 57s. The residual heat temperature of the steel strip surface after the hot rolling process is controlled at 800~900℃. In the existing technology, the temperature of the steel strip entering the finishing mill is generally controlled by swaying the steel after rough rolling. Due to the use of online solution treatment process in hot rolling, the stainless steel strip after hot rolling still has a large possibility of work hardening. In order to avoid the product being affected by work hardening, and to remove slight work hardening by EPS and re-brushing process, short-term swaying of the steel strip after hot rolling reduces work hardening before entering the online solution treatment stage. The grains are more uniform and the temperature is more uniform throughout the thickness. This is conducive to the uniform solidification of carbides under the rapid heating conditions in the later online solution treatment stage, as well as the uniformity of the recrystallized grains.

[0077] Optionally, in some embodiments, during the hot rolling process, the stainless steel strip thickness is <1 mm, and the final rolling temperature is 890~910℃, which can be one or any two of 890℃, 900℃, and 910℃. The post-hot rolling swaying time is 13-33 seconds, which can be one or any two of 13s, 18s, 23s, 28s, and 33s. The stainless steel strip speed is 110m / min~155m / min, which can be one or any two of 110m / min, 115m / min, 120m / min, 125m / min, 130m / min, 135m / min, 140m / min, 145m / min, 150m / min, and 155m / min. Using a high strip speed is beneficial for improving production efficiency and matching with subsequent processes such as EPS. At a high strip speed, for thinner strips, the final rolling temperature can be reduced and the sloshing time can be shortened. Thin strips tend to have a more uniform microstructure and higher heating uniformity. Reducing the sloshing and final rolling temperatures helps to avoid the generation of new stresses in the strip caused by excessive sloshing, which would affect the reduction of work hardening.

[0078] Optionally, in some embodiments, during the hot rolling process, the stainless steel strip thickness is ≥1mm, and the final rolling temperature is 910~950℃, which can be one or any two of 910℃, 920℃, 930℃, 940℃, and 950℃. The swaying time after hot rolling is 34~57s, which can be one or any two of 34s, 38s, 43s, 48s, 53s, and 57s. The stainless steel strip speed is 60m / min~90m / min, which can be one or any two of 60m / min, 65m / min, 70m / min, 75m / min, 80m / min, 85m / min, and 90m / min. Using a reduced strip speed helps to achieve uniform heating and reduce residual work hardening. At a reduced strip speed, for thicker strips, increasing the final rolling temperature and extending the swaying time helps to achieve uniform microstructure and high heating uniformity. This helps to avoid the generation of new stress in the strip caused by excessive swaying, which would affect the work hardening reduction effect.

[0079] Optionally, in some embodiments, in step (2), the EPS treatment is a re-brushing mode, and the surface roughness of the stainless steel strip decreases by >1.1μm, which can be one of 1.1μm, 1.2μm, 1.3μm, 1.4μm, 1.5μm, 1.6μm or any value between two of them. By adjusting parameters such as steel grit size, spraying angle and speed, the surface of the stainless steel strip is treated more finely, further reducing the surface roughness. After the roughness is reduced, the surface micro-peaks and valleys are reduced, making it more difficult for corrosive media to adhere and penetrate, making pitting corrosion difficult to form, and eliminating work hardening residue.

[0080] Optionally, in some embodiments, the roller brush bristles using silicon carbide abrasive are made of ultra-high molecular weight nylon, the S-roller and EPS roller are rubber rollers, the slurry for EPS treatment includes solid particles and working fluid, and the stainless steel strip undergoes water spraying treatment during the descaling stage. The working fluid for water spraying treatment includes a rust inhibitor and a lubricating additive, wherein the rust inhibitor is benzotriazole, and the lubricating additive is polyethylene glycol or polypropylene glycol. The working fluid, containing both rust inhibitor and lubricating additives, not only prevents the roller box from rusting but also lubricates the descaling roller, reducing friction and rolling resistance. Lower friction means reducing additional plastic deformation and temperature rise caused by severe surface shearing, thus mitigating hardening at its source. Combined with a filtration system, the oxide scale can be filtered out, and the working fluid can be recycled.

[0081] In one embodiment of the present invention, EPS surface descaling results in a steel plate surface quality superior to traditional pickling, with a more uniform surface roughness, making it more suitable for subsequent painting processes. Unlike traditional dry shot blasting, it uses smaller particle sizes, achieving significant results with 1-3mm dry shot blasting. The shape of the steel grit can be round or angular, with angular grit generally recommended for more efficient descaling. The blasting primarily involves a slurry containing particles and a working fluid (containing rust inhibitor). The water content acts as a buffer and softener upon impact with the steel plate surface, reducing the impact force of individual particles. The lower rotational speed of EPS blasting also results in a significantly smaller maximum impact force. However, due to the larger volume of slurry blasted per EPS turbine, the coverage width and length of a single blast head are greater than in traditional shot blasting. This is one reason why EPS, with fewer turbines, achieves a working efficiency 5 to 10 times that of traditional dry shot blasting.

[0082] Optionally, in some embodiments, the above-described rebrushing mode uses silicon carbide abrasive, and the proportion of silicon carbide abrasive in the bristles is 15% to 35%, which can be one of 15%, 20%, 25%, 30%, 35% or any range between two of them. This can vary depending on the silicon carbide particle size and the operating conditions.

[0083] Optionally, in some embodiments, the deformation amount in the roughing rolling process accounts for 71-79% of the total deformation amount, and can be a value within the range of 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, or any two of these values. The deformation amount in the finishing rolling process accounts for 21-29% of the total deformation amount, and can be a value within the range of 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, or any two of these values. The 62-78s sizing after roughing rolling can be a value within the range of 62s, 64s, 66s, 68s, 70s, 72s, 74s, 76s, 78s, or any two of these values. By controlling the deformation amounts in roughing and finishing rolling, and by using a short sizing time after roughing rolling, work hardening during the rolling process is reduced, thereby reducing the work hardening residue in the final stainless steel strip, improving the uniformity of the stainless steel strip structure, and improving the surface quality of the steel strip.

[0084] Optionally, in some embodiments, the hardness of the upper surface after EPS treatment is higher than that of the lower surface, the motor speed of the upper surface in the re-brushing mode is increased by 0.1-20% relative to the motor speed of the lower surface, and / or, the brush roller pressure of the upper surface is increased by 0.1-20% relative to the brush roller pressure of the lower surface, and / or, the single brush bristle load power of the upper surface is increased by 0.1-50% relative to the single brush bristle load power of the lower surface, and / or, the single brush bristle water spray volume of the upper surface with a water pressure of 2-4 bar is increased by 0.1-50% relative to the single brush bristle water spray volume of the lower surface.

[0085] Optionally, in some embodiments, after the EPS treatment, the hardness of the upper surface is higher than that of the lower surface. In the re-brushing mode, the motor speed of the upper surface is increased by 8-12% relative to the motor speed of the lower surface, which can be a value within the range of 8%, 9%, 10%, 11%, 12%, or any two of these values. The brush roller pressure on the upper surface is increased by 5-11% relative to the brush roller pressure on the lower surface, which can be a value within the range of 8%, 9%, 10%, 11%, 12%, or any two of these values. The single brush bristle load power on the upper surface is increased by 9-15% relative to the single brush bristle load power on the lower surface, which can be a value within the range of 9%, 10%, 11%, 12%, 13%, 14%, 15%, or any two of these values. The water spray volume per brush bristle on the upper surface at a water pressure of 2-4 bar is increased by 12-16% relative to the single brush bristle spray volume on the lower surface, which can be a value within the range of 12%, 13%, 14%, 15%, 16%, or any two of these values. After EPS processing, the hardness of the upper surface is higher than that of the lower surface. Therefore, the upper surface can be re-brushed relative to the lower surface. The re-brushing parameters of the upper surface can be appropriately increased to improve the re-brushing effect of the upper surface. This avoids the surface quality improvement caused by the hardness deviation between the inner and outer surfaces of the stainless steel strip due to EPS processing.

[0086] Optionally, in some embodiments, the diameter of the steel grit treated with EPS is 0.1–0.4 mm, which can be one or any two of 0.1 mm, 0.15 mm, 0.2 mm, 0.25 mm, 0.3 mm, 0.35 mm, and 0.4 mm; the projectile velocity is 25–40 m / s, which can be one or any two of 25 m / s, 30 m / s, 55 m / s, and 40 m / s; preferably 25–34 m / s, to further achieve descaling and improve the descaling effect. Meanwhile, by using steel grit with the smallest particle size and reducing the blasting speed, it is possible to further smooth out any excessively sharp protrusions that may appear on the surface of the stainless steel strip. This makes the rough protrusions and pits on the surface of the stainless steel strip relatively smoother. The reduced speed and impact energy avoid excessive roughening of the stainless steel surface by multiple EPS passes. While further descaling, it reduces the risk of excessively increasing roughness. The fine steel grit can generate dense, shallow impacts, effectively removing any tiny burrs that may be left from the first two passes, further improving surface uniformity.

[0087] Optionally, in some embodiments, when using the light brush mode, the steel coil weight is reduced by 1‰ (calculated based on a thickness of 3mm, the average thinning amount per side is 1.5 micrometers, and the total thinning amount for both sides is 3 micrometers), and the surface roughness decreases by approximately 0.5 to 1 micrometer (2.5 to 3.5 micrometers for pure EPS; 2.0 to 3.0 micrometers for EPS + light brush). When using the medium brush mode, the steel coil weight is reduced by 2‰ (calculated based on a thickness of 3mm, the average thinning amount per side is 3 micrometers, and the total thinning amount for both sides is 6 micrometers), and the surface roughness decreases by approximately 1 micrometer (2.5 to 3.5 micrometers for pure EPS; 1.5 to 2.5 micrometers for EPS + medium brush). When using the heavy brush mode, the steel coil weight is reduced by 3‰ (calculated based on a thickness of 3mm, the average thinning amount per side is 4.5 micrometers, and the total thinning amount for both sides is 9 micrometers), and the surface roughness decreases by approximately 1.5 micrometers or more (2.5 to 3.5 micrometers for pure EPS; 0.8 to 1.5 micrometers for EPS + heavy brush). Different bristle diameters, hardnesses, and silicon carbide particles can be used, along with multi-pass brush roller devices, to achieve more precise control.

[0088] The solution treatment method in this invention has the following advantages: Dividing the heating process into three holding stages—low temperature, medium temperature, and high temperature—allows for a longer holding time concentrated in the high-temperature zone, enabling alloying elements to diffuse fully as the diffusion coefficient increases with temperature, significantly improving the degree of solution treatment and reducing component segregation. In the low-temperature stage, the precipitated phases are uniformly dissolved, preventing sudden localized rapid dissolution at high temperatures that could lead to sudden grain coarsening. Subsequently, controlled, uniform, and prolonged solution treatment is performed in the high-temperature stage, allowing grains to grow uniformly under constrained conditions, avoiding the formation of mixed or coarse-grained structures. This combination of low-temperature, short-time, high-temperature, and long-time treatments allows for the full dissolution of low-melting-point eutectic phases without exceeding safe temperature limits, resulting in the highest possible supersaturation state and significantly improving key alloy properties such as strength and creep resistance. The multi-stage heating also functions as solution annealing, gradually eliminating residual processing stress throughout the heating-holding-cooling process, resulting in a more uniform stress distribution within the material and improving the reliability of subsequent processing and use. By controlling the heating rate and holding time in stages, the solution treatment effect can be guaranteed while avoiding prolonged high-temperature holding at one time, thereby reducing overall energy consumption and improving production efficiency.

[0089] The hot rolling process in this invention has the following advantages: the high-temperature plasticity of the rough rolling stage makes the metal easy to deform, enabling continuous and automated high-speed rolling, significantly increasing production capacity. Rough rolling, conducted above the recrystallization temperature, breaks down and refines the coarse grains and casting defects (such as porosity and cracks) of the original ingot, forming a dense deformed structure, providing a good material basis for subsequent finish rolling. Rough rolling focuses on large-scale and rapid initial deformation, which can significantly improve production capacity, reduce energy consumption, and lay the foundation for refining the material structure; finish rolling, through precise temperature and thickness control, optimizes the microstructure, improves mechanical properties, and reduces residual stress. The two complement each other and together constitute the core advantages of modern hot rolling production lines.

[0090] Example 1

[0091] An online solution-based acid-free descaling method for stainless steel to reduce work hardening includes raw material preparation, steelmaking, continuous casting, hot rolling, and solution treatment. The solution treatment process utilizes residual heat from the surface of the steel coil (813°C) and performs online solution treatment at a temperature of 1130°C. The coil is then connected to a heating furnace, heated and held at that temperature, followed by rapid cooling at a rate of 30°C / s to achieve online solution treatment. Following the solution treatment, an acid-free descaling process is performed, specifically including the following steps: The stainless steel grade is 304.

[0092] The solution treatment process involves staged heating. The first stage occurs when the solution temperature is 900℃, with a heating rate of 22℃ / min. The second stage occurs when the solution temperature is 28℃ lower than the solution temperature, with a heating rate of 9℃ / min. The third stage occurs when the temperature reaches the solution temperature, with a heating rate of 2℃ / min. The hot rolling process consists of roughing and finishing rolling. The stainless steel strip thickness is 0.8mm, the finishing rolling temperature is 890℃, the strip is swayed for 13 seconds after hot rolling, and the strip speed is 110m / min. The deformation during roughing accounts for 71% of the total deformation, and the deformation during finishing rolling accounts for 29%. The strip is swayed for 62 seconds after roughing.

[0093] (1) The stainless steel strip after the solution treatment process is processed by S-roller and descaling. When the steel plate thickness is less than 2mm, the diameter of the descaling roller is 40mm. The relationship between the diameter D of the descaling roller and the plate thickness t is: D / t=50.

[0094] Tension is applied to both sides of the steel strip by S-rollers at both ends, and the tension is less than 10% of the material's yield strength.

[0095] The stainless steel strip forms a wrap angle α = 20~50° with the surface of the scalding roller. The relationship between the distance L1 between the top and bottom adjacent scalding rollers, the distance L between the top two adjacent scalding rollers, and the diameter D of the scalding roller is: L1 = 60mm, L = 140mm.

[0096] When breaking up scales, water should be sprayed. The nozzle orifice diameter on the spray pipe should be no less than 2mm, and the water pressure should be no less than 2bar.

[0097] (2) The stainless steel strip after the descaling treatment is descaled by EPS treatment; the EPS treatment steel grit particle size is 0.4mm and the blasting speed is 40m / s.

[0098] (3) The EPS-treated stainless steel strip was brushed again using a roller brush; the EPS-treated stainless steel strip was brushed using a roller brush containing silicon carbide abrasive, and the brushing was carried out in a heavy brushing mode, which reduced the surface roughness of the stainless steel strip by 1.2 μm. The proportion of silicon carbide in the brush bristles was 35%; the particle size of silicon carbide in the heavy brushing mode was 150 mesh, and the bristle diameter was 1.0 mm. The rotation speed RPM of the heavy brushing mode was 1100, the roller pressure was 4 mm, the single bristle load power was 90 kW, and the water pressure was 2~4 bar with a single bristle spray volume of 250 L / min. The material of the roller brush containing silicon carbide abrasive was ultra-high molecular weight nylon, the S roller and EPS roller were rubber rollers, and the EPS-treated slurry included solid particles and working fluid, and the working fluid contained water and rust inhibitor.

[0099] (4) Rinse the stainless steel strip after brushing.

[0100] (5) The stainless steel strip after rinsing is dried and then wound into finished steel coils by a coiler.

[0101] The steel strip surface quality reaches the highest grade Sa3.0 (GB / T8923.1-2011). It has low surface roughness, with an average roughness Ra of less than 1.3 μm. The average Vickers hardness of the steel strip surface is 257 (tested by applying a 10 kg load and measuring the Vickers hardness HV10 value), and the average oxide residue thickness is 1.4 μm.

[0102] Example 2

[0103] The difference from Example 1 is that the above solution treatment process utilizes the residual heat of the steel coil surface, with a residual heat of 850°C. In the hot rolling process, the stainless steel strip thickness is 1.5 mm, the final rolling temperature is 930°C, the strip is swayed for 45 seconds after hot rolling, and the stainless steel strip speed is 80 m / min. The deformation during the rough rolling process accounts for 75% of the total deformation, and the deformation during the final rolling process accounts for 25% of the total deformation. The strip is swayed for 75 seconds after rough rolling.

[0104] (1) The stainless steel strip after the solution treatment process is processed by S-roll and descaling. The relationship between the descaling roll diameter D and the plate thickness t, as well as the roll distance, are adjusted according to the actual situation.

[0105] (2) The stainless steel strip after the descaling treatment is descaled by EPS treatment; the EPS treatment steel grit particle size is 0.1mm and the blasting speed is 25m / s.

[0106] (3) The stainless steel strip treated with EPS was re-brushed using a roller brush, which reduced the surface roughness of the stainless steel strip by 1.5 μm. The proportion of silicon carbide in the brush bristles was 25%; the particle size of silicon carbide in the re-brushing mode was 90 mesh, and the bristle diameter was 0.9 mm. The rotation speed of the re-brushing mode was 1200 RPM, the brush roller pressure was 5 mm, the load power of a single brush bristle was 110 kW, and the water spray volume of a single brush bristle was 300 L / min with a water pressure of 2~4 bar.

[0107] The steel strip surface quality reaches the highest grade Sa3.0 (GB / T8923.1-2011). It has low surface roughness, with an average roughness Ra of less than 1.1 μm. The average Vickers hardness of the steel strip surface is 235 (tested by applying a 10 kg load and measuring the Vickers hardness HV10 value), and the average oxide residue thickness is 0.8 μm.

[0108] Example 3

[0109] The difference from Example 1 is that the residual heat is 900℃, the hot rolling process is divided into rough rolling and final rolling, the stainless steel strip thickness is 2mm, the final rolling temperature is 950℃, the steel is swayed for 57s after hot rolling, and the stainless steel strip speed is 90m / min. The deformation in the rough rolling process accounts for 79% of the total deformation, the deformation in the final rolling process accounts for 21% of the total deformation, and the steel is swayed for 78s after rough rolling.

[0110] (1) The stainless steel strip after the solution treatment process is processed by S-roll and descaling. The relationship between the descaling roll diameter D and the plate thickness t, as well as the roll distance, are adjusted according to the actual situation.

[0111] (3) The brushing adopts the heavy brushing mode; the proportion of silicon carbide in the bristles is 15%; the particle size of silicon carbide in the heavy brushing mode is 60 mesh, and the bristle diameter is 0.8 mm. The rotation speed of the heavy brushing mode is 1200 RPM, the brush roller pressure is 6 mm, the single bristle load power is 120 kW, and the water pressure is 2~4 bar with a single bristle spray volume of 400 L / min.

[0112] The steel strip surface quality reaches the highest grade Sa3.0 (GB / T8923.1-2011). It has low surface roughness, with an average roughness Ra of less than 1.2 μm. The average Vickers hardness of the steel strip surface is 241 (tested by applying a 10 kg load and measuring the Vickers hardness HV10 value), and the average oxide residue thickness is 1.1 μm.

[0113] Example 4

[0114] The only difference from Example 1 is that there is no pendulum.

[0115] The steel strip surface quality reaches the highest grade Sa3.0 (GB / T8923.1-2011). It has low surface roughness, with an average roughness Ra of less than 1.4 μm. The average Vickers hardness of the steel strip surface is 314 (tested by applying a 10 kg load and measuring the Vickers hardness HV10 value), and the average oxide residue thickness is 1.6 μm.

[0116] Comparative Example 1

[0117] The only difference from Example 1 is that after the solution treatment, the sample is acid-washed and descaled, using 25% sulfuric acid.

[0118] The steel strip surface quality reaches the highest grade Sa3.0 (GB / T8923.1-2011). It has high surface roughness, with an average roughness Ra greater than 2.7 μm. The average Vickers hardness of the steel strip surface is 378 (tested by applying a 10 kg load and measuring the Vickers hardness HV10 value), and the average oxide residue thickness is 1.7 μm.

[0119] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for reducing work hardening of stainless steel through online solution treatment and acid-free descaling, comprising raw material preparation, steelmaking, continuous casting, hot rolling, and solution treatment processes, characterized in that, The solution treatment process utilizes the residual heat on the surface of the steel coil for online solution treatment. After the solution treatment, the coil undergoes an acid-free descaling process. The specific process includes the following steps: (1) The stainless steel strip after the solution treatment process is processed by S roller and descaling. When the steel plate thickness is 4~5mm, the relationship between the descaling roller diameter D and the steel plate thickness t is: D / t=11~13.75; when the steel plate thickness is 2~4mm, the relationship between the descaling roller diameter D and the steel plate thickness t is: D / t=11.25~22.5; when the steel plate thickness is less than 2mm, the relationship between the descaling roller diameter D and the steel plate thickness t is: D / t≥20; the stainless steel strip forms a wrap angle α=20~50° with the surface of the descaling roller, the distance L1 between the top and bottom adjacent descaling rollers, the distance L between the top two adjacent descaling rollers, and the relationship between the descaling roller diameter D are: L1 / D=1~1.5, L / D=2~3.5, and the downward pressure range of the descaling roller is: h=0~D×2 / 3; When breaking scales, water should be sprayed, and the nozzle orifice diameter on the spray pipe should be no less than 0.5 mm, and the water pressure should be no less than 1 bar. (2) The stainless steel strip after the descaling treatment is descaled by EPS treatment. The EPS treatment adopts abrasive slurry spraying technology. (3) The stainless steel strip after EPS treatment is washed by using a roller brush; (4) Rinse the stainless steel strip after brushing. (5) The stainless steel strip after rinsing is dried and then wound into finished steel coils by a coiler.

2. The online solution-based acid-free descaling method for reducing work hardening of stainless steel according to claim 1, characterized in that, The solution treatment process utilizes the residual heat temperature of the steel coil surface at 800~900℃, the solution temperature at 1050~1150℃, and the holding time at 1.1~1.5min / mm.

3. The online solution-based acid-free descaling method for reducing work hardening of stainless steel according to claim 2, characterized in that, The solution treatment process involves a phased heating process. In the first phase, when the solution temperature is below 920°C, the heating rate is 22-30°C / min. In the second phase, when the solution temperature is above or equal to 920°C but 10-30°C below the solution temperature, the heating rate is 9-14°C / min. In the third phase, when the temperature reaches the solution temperature, the heating rate is 2-3°C / min.

4. The online solution-based acid-free descaling method for reducing work hardening of stainless steel according to claim 1, characterized in that, The hot rolling process includes rough rolling and final rolling, with the final rolling temperature being 890~950℃ and the steel being swayed for 13~57s after hot rolling.

5. The online solution-based acid-free descaling method for reducing work hardening of stainless steel according to claim 1, characterized in that, In the hot rolling process, the stainless steel strip thickness is <1mm, the final rolling temperature is 890~910℃, the steel is swayed for 13-33s after hot rolling, and the stainless steel strip speed is 110m / min~155m / min. The stainless steel strip thickness is ≥1mm, the final rolling temperature is 910~950℃, the steel is swayed after hot rolling for 34~57s, and the stainless steel strip speed is 60m / min~90m / min.

6. The online solution-based acid-free descaling method for reducing work hardening of stainless steel according to claim 1, characterized in that, In step (3), the brushing is in re-brushing mode, and the surface roughness of the stainless steel strip decreases by >1.1μm.

7. The online solution-based acid-free descaling method for reducing work hardening of stainless steel according to claim 6, characterized in that, The re-brushing mode uses silicon carbide abrasive, which accounts for 15-35% of the bristles. The particle size of the silicon carbide abrasive is 60-150 mesh, and the bristle diameter is 0.8-1.0 mm. The motor speed in the re-brushing mode is 1100-1300 RPM, the brush roller pressing amount is >3 mm, the single bristle load power is 90-160 kW, and the water spray volume of a single bristle is 250-400 L / min with a water pressure of 2-4 bar.

8. The online solution-based acid-free descaling method for reducing work hardening of stainless steel according to claim 4, characterized in that, The deformation during the rough rolling process accounts for 71-79% of the total deformation, the deformation during the final rolling process accounts for 21-29% of the total deformation, and the steel is swayed for 62-78 seconds after rough rolling.

9. The online solution-based acid-free descaling method for reducing work hardening of stainless steel according to claim 7, characterized in that, After EPS treatment, the hardness of the upper surface is higher than that of the lower surface. In the re-brushing mode, the motor speed of the upper surface is increased by 0.1-20% compared to the motor speed of the lower surface, and / or, the brush roller pressure of the upper surface is increased by 0.1-20% compared to the brush roller pressure of the lower surface, and / or, the single brush bristle load power of the upper surface is increased by 0.1-50% compared to the single brush bristle load power of the lower surface, and / or, the single brush bristle water spray volume of the upper surface with a water pressure of 2-4 bar is increased by 0.1-50% compared to the single brush bristle water spray volume of the lower surface.

10. The online solution-based acid-free descaling method for reducing work hardening of stainless steel according to claim 1, characterized in that, The EPS-treated steel shot has a particle size of 0.1~0.4mm and a projectile speed of 25~40m / s.

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