A method for controlling color difference at the edge of nickel-saving austenitic stainless steel coils

Abstract

This invention relates to the field of stainless steel production technology, and in particular to a method for controlling the color difference at the edge of nickel-saving austenitic stainless steel coils. This method, through steps such as material composition design, control of steelmaking elements, adjustment of continuous casting parameters and descaling treatment, and special treatment for stacking after coiling, effectively solves the color difference defect at the edge of nickel-saving austenitic stainless steel strips, ensures uniform color in the width direction of the strip, excellent performance, improves the quality of steel coils, and reduces acid consumption and environmental pressure.

Description

Technical Field

[0001] This invention relates to the field of stainless steel production technology, specifically to a method for controlling color difference in the edge of nickel-saving austenitic stainless steel coils. Background Technology

[0002] Austenitic stainless steel possesses excellent corrosion resistance, toughness, ductility, and non-magnetic properties, making it widely used in machinery manufacturing, household goods, aerospace, energy, and chemical industries. However, to reduce production costs and address the shortage of nickel resources, nickel-saving austenitic stainless steel has been developed by adding elements such as Mn and N to replace Ni, based on Cr and Ni-based austenitic stainless steel. Surface defects in stainless steel are a significant factor affecting product quality and yield. The edge color difference problem in nickel-saving austenitic stainless steel has long plagued the normal production and operation of enterprises. While pursuing output, enterprises often suffer from a decline in quality, which increases the cost per ton of steel by at least 200 yuan. Nickel-saving austenitic stainless steel is an incomplete austenitic steel. Due to the addition of Mn and N, it easily forms low-melting-point oxides or sulfides, which can easily cause changes in the hot plasticity and cold working properties of the steel during production, resulting in defects such as peeling, edge scaling, and edge cracking. Furthermore, due to the high-speed rolling process in large-scale industrial production, the unique high-temperature coiling process of austenitic stainless steel causes irregular river-like color difference bands within a 200mm range on the edge of the steel coil. As competition in the stainless steel industry intensifies and downstream customers place increasingly higher demands on upstream products, color difference defects in steel coils have become a limiting factor hindering nickel-saving austenitic stainless steel from reaching the high-end market.

[0003] A study published in the CNKI journal *Rolling Steel* in June 2019 investigated the color difference of iron oxide scale between the edges and center of hot-rolled strip steel. The article identified the fundamental reason for this difference: variations in the size of the interlayer gap and the cooling rate between the edges and center of the hot-rolled strip, leading to different iron oxide scale structures. To address this, measures were proposed, including reducing strip crown, preventing sudden drops in strip thickness at the edges, appropriately increasing coiling tension, and ensuring uniform cooling of the strip. These measures effectively improved the color difference of the iron oxide scale on the strip surface. However, the paper mainly focuses on plain carbon steel. Due to the sensitization of austenitic stainless steel, chromium carbide precipitates at the grain boundaries, resulting in intergranular corrosion. After pickling, corrosion color difference is prone to occur, and the equipment is prone to premature failure. It cannot solve the edge color difference problem of austenitic nickel-saving stainless steel. Furthermore, plain carbon steel has a low yield strength and generally a low delamination temperature, so there is no commonality for the hot rolling coiling process of stainless steel. Chinese patent CN202111620231.9 discloses a production process of non-annealing stainless steel sheet. The pickling process mentioned in the paper uses conventional pickling processes of shot blasting, sulfuric acid, and mixed acid. The pickling efficiency is low, the acid consumption is high, and the rewashing rate is high due to poor pickling.

[0004] To address this issue, a method for controlling edge color difference in nickel-saving austenitic stainless steel coils was designed. This method effectively improves edge color difference by adjusting the composition, hot rolling process, and post-rolling logistics, ensuring that the nickel-saving austenitic stainless steel has uniform mechanical properties and a smooth, glossy surface, while also reducing acid consumption and environmental impact. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for controlling color difference at the edge of nickel-saving austenitic stainless steel coils, thereby solving the problems of color difference at the edge and low pickling efficiency of nickel-saving austenitic stainless steel mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for controlling color difference in the edge of nickel-saving austenitic stainless steel, the method comprising the following steps;

[0007] S1: Steel is smelted according to the following chemical composition: C: ≤0.07%; Mn: 10.0%; P: ≤0.045%; S: ≤0.003%; Si: ≤0.45%; Cr: 12.8~13.1%; Ni: 1.2~1.3%; N: ≤0.16%; with the balance being Fe and other unavoidable impurity elements. The steel is then smelted in an EAF furnace, an AOD furnace, and an LF furnace to obtain steel with the target composition.

[0008] S2: Continuously cast steel billet. Molten steel is transported to the continuous casting platform for continuous casting operations and injected into the crystallizer. The opening degree of the stopper rod of the tundish, the insertion depth of the nozzle, and the casting speed are adjusted to control the stability of the liquid level in the crystallizer. During the casting process, the superheat is maintained at 25-35℃, the water temperature difference between the wide and narrow faces of the crystallizer is controlled at 3-6℃, the casting speed is maintained at 0.6-1.2m / min, the secondary cooling water ratio is controlled at 0.5-0.8L / kg, and three sets of electromagnetic stirrers are set up to improve the segregation of the cast billet, thereby obtaining the continuously cast steel billet.

[0009] S3: Steel billet heat treatment. After the continuous casting steel billet passes online surface inspection and is free of defects, it is transported to a heating furnace for preheating treatment, where the billet temperature is preheated to 700-800℃. Then, it undergoes heat treatment and soaking treatment for 100-120 minutes to obtain the heat-treated steel billet.

[0010] S4: Rough rolling of steel billet. The heat-treated steel billet is sent to the rough rolling mill for five passes of rough rolling. There is a 30-second interval between each pass. During the rough rolling, the billet temperature is controlled at 1200-1250℃ to obtain an intermediate billet with a thickness of 30-50mm.

[0011] S5: Finished steel billet. The intermediate billet is transported to the finishing rolling mill for eight passes of finishing rolling. During the finishing rolling process, the billet temperature is controlled at 1180-1230℃, and the unevenness difference of the steel plate is controlled at 35-45μm, thus obtaining a thin steel plate with a thickness of 2.0-5.0mm.

[0012] S6: Coiling and cooling. Thin steel sheets are rolled into steel coils using a coiler. During the coiling process, the temperature of the thin steel sheets is controlled at 720℃±30℃. The steel coils are then transferred to the strong wind cooling zone of the hot-rolled finished product warehouse for cooling treatment.

[0013] S7: Grinding and pickling. After the cooled steel coil is descaled, shot blasted and straightened, it enters the grinding roller to remove the oxide scale on the surface of the steel coil. The surface-treated steel coil is sent to the pickling line for pickling treatment, and then washed and dried to form a coil, thus obtaining nickel-saving austenitic stainless steel coil.

[0014] Furthermore, the chemical composition of the ingredients in step S1 is as follows: C: 0.03-0.04%; Mn: 10.0%; P: ≤0.045%; S: ≤0.003%; Si: ≤0.45%; Cr: 12.8-13.1%; Ni: 1.2-1.3%; N: 0.10-0.13%; with the addition of Re element; the balance being Fe and other unavoidable impurity elements.

[0015] Furthermore, the three sets of electromagnetic stirrers in step S2 are as follows: the first set is for electromagnetic stirring of the crystallizer, which uses a linear electromagnetic stirrer with a stirring roller current of 400A and a power supply frequency of 1-5Hz; the second set is for electromagnetic stirring of the secondary cooling zone, with a stirring roller current of 400A and a power supply frequency of 2-10Hz; and the third set is for electromagnetic stirring of the solidification end, with a stirring roller current of 400A and a power supply frequency of 3-15Hz.

[0016] Furthermore, the heating furnace in step S3 includes a preheating section, a heating section, and a soaking section. The temperature of the preheating section is 1000℃, the temperature of the heating section is 1200℃, and the temperature of the soaking section is 1280~1290℃. The residual oxygen content in the heating section of the heating furnace is controlled to be less than 2%, and the residual oxygen content in the soaking section is controlled to be less than 1%. Burners are provided at both ends of the heating furnace, and the flame length of the burners is controlled to be 1 / 4 of the length of the billet, with the flame distance from the billet being 10~20cm.

[0017] Furthermore, in step S4, the rough rolling process is equipped with an insulation cover to reduce heat loss.

[0018] Furthermore, a descaling process is provided between steps S3 and S4, and between steps S4 and S5. The descaling process uses hot air purging for descaling, and the descaling pressure is greater than 25 MPa.

[0019] Furthermore, in step S7, the grinding roller is made of 120-mesh silicon carbide material, the grinding power of the grinding roller is 100-140KW, and the grinding depth of the grinding roller is controlled at 0.01mm.

[0020] Furthermore, in step S7, the pickling line includes a pickling tank and an ultrasonic cleaning device. The pickling tank has three sections: the first section contains 60±10 g / L of nitric acid and 20±5 g / L of hydrofluoric acid solution, with the solution temperature controlled at 50±5℃; the ultrasonic cleaning device has a vibration frequency of 700~800kHz and a power density of 1.9~2.1V / ㎡; the second section contains 40±10 g / L of nitric acid and 10±5 g / L of hydrofluoric acid solution, with the solution temperature controlled at 50±5℃; the ultrasonic cleaning device has a vibration frequency of 600~700kHz and a power density of 1.5~1.7V / ㎡; the third section contains 20±5 g / L of nitric acid and 5±2 g / L of hydrofluoric acid solution, with the solution temperature controlled at 50±5℃; the ultrasonic cleaning device has a vibration frequency of 500~600kHz and a power density of 1.2~1.4V / ㎡.

[0021] Compared with the prior art, the technical solution of this application has the following beneficial effects:

[0022] 1. In this invention, by designing the material composition, controlling the steelmaking elements, adjusting the continuous casting parameters and descaling treatment, and special treatment for stacking after coiling, the edge color difference defect of nickel-saving austenitic stainless steel strip is effectively solved, ensuring uniform color and excellent performance in the width direction of the strip, and improving the quality of the steel coil.

[0023] 2. In this invention, by employing multi-segment pickling tanks and ultrasonic cleaning devices in the pickling line, and controlling the concentration and temperature of the solution, the pickling efficiency is improved, ensuring the cleanliness of the steel coil surface. Attached Figure Description

[0024] Figure 1 This is a process flow diagram of a method for controlling color difference in the rolled edge of nickel-saving austenitic stainless steel according to the present invention. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Please see Figure 1This embodiment provides a method for controlling color difference at the edge of nickel-saving austenitic stainless steel coils. The method includes the following steps:

[0027] S1: Steel is smelted according to the following chemical composition: C: ≤0.07%; Mn: 10.0%; P: ≤0.045%; S: ≤0.003%; Si: ≤0.45%; Cr: 12.8~13.1%; Ni: 1.2~1.3%; N: ≤0.16%; with the balance being Fe and other unavoidable impurity elements. The steel is then smelted in an EAF furnace, an AOD furnace, and an LF furnace to obtain steel with the target composition.

[0028] It should be noted that replacing Ni with Mn achieves cost reduction. Simultaneously, strict control of elements such as P and S improves the purity of the molten steel.

[0029] S2: Continuously cast steel billet. Molten steel is transported to the continuous casting platform for continuous casting operations and injected into the crystallizer. The opening degree of the stopper rod of the tundish, the insertion depth of the nozzle, and the casting speed are adjusted to control the stability of the liquid level in the crystallizer. During the casting process, the superheat is maintained at 25-35℃, the water temperature difference between the wide and narrow faces of the crystallizer is controlled at 3-6℃, the casting speed is maintained at 0.6-1.2m / min, the secondary cooling water ratio is controlled at 0.5-0.8L / kg, and three sets of electromagnetic stirrers are set up to improve the segregation of the cast billet, thereby obtaining the continuously cast steel billet.

[0030] It should be noted that by using three sets of electromagnetic stirrers to break up the dendrites from the surface inward, the growth direction of the dendrites is broken up, and the grain boundary energy between the crystals is increased. This can improve the grain growth rate in subsequent processes, and is also beneficial to the grain uniformity of the cast billet and the control of the edge grains.

[0031] S3: Steel billet heat treatment. After the continuous casting steel billet passes online surface inspection and is free of defects, it is transported to a heating furnace for preheating treatment, where the billet temperature is preheated to 700-800℃. Then, it undergoes heat treatment and soaking treatment for 100-120 minutes to obtain the heat-treated steel billet.

[0032] It should be noted that preheating treatment effectively utilizes the residual heat of the slab, reduces fuel consumption, and also reduces the degree of oxidation on the slab surface, thus providing a good raw material foundation for subsequent descaling.

[0033] S4: Rough rolling of steel billet. The heat-treated steel billet is sent to the rough rolling mill for five passes of rough rolling. There is a 30-second interval between each pass. During the rough rolling, the billet temperature is controlled at 1200-1250℃ to obtain an intermediate billet with a thickness of 30-50mm.

[0034] It should be noted that there is a 30-second interval between each rolling pass to ensure the recrystallization of the billet and the growth of the grains; the thickness of the intermediate billet is determined by the final thickness of the finishing roll.

[0035] S5: Finished steel billet. The intermediate billet is transported to the finishing rolling mill for eight passes of finishing rolling. During the finishing rolling process, the billet temperature is controlled at 1180-1230℃, and the unevenness difference of the steel plate is controlled at 35-45μm, thus obtaining a thin steel plate with a thickness of 2.0-5.0mm.

[0036] It should be noted that the size of the gaps between the layers at the edge of the strip has a decisive influence on the properties of the oxide scale between the layers of the steel coil. The smaller the gap, the less air enters between the layers of the steel coil, effectively preventing further oxidation of the edge oxide scale and helping to reduce the area of ​​color difference at the edge.

[0037] S6: Coiling and cooling. Thin steel sheets are rolled into steel coils using a coiler. During the coiling process, the temperature of the thin steel sheets is controlled at 720℃±30℃. The steel coils are then transferred to the strong wind cooling zone of the hot-rolled finished product warehouse for cooling treatment.

[0038] It should be noted that after the steel coil is wound, it is bundled and numbered using an automatic bundling machine and an automatic marking machine; placing the steel coil in a strong air cooling zone effectively reduces the eutectoid reaction of oxide scale; the steel coil has less stress at a winding temperature of 720℃, making it easier to wind, and the subsequent rapid cooling mode can effectively avoid the eutectoid reaction zone of 350-650℃.

[0039] S7: Grinding and pickling. After the cooled steel coil is descaled, shot blasted and straightened, it enters the grinding roller to remove the oxide scale on the surface of the steel coil. The surface-treated steel coil is sent to the pickling line for pickling treatment, and then washed and dried to form a coil, thus obtaining nickel-saving austenitic stainless steel coil.

[0040] In this embodiment, the chemical composition of the ingredients in S1 is: C: 0.03-0.04%; Mn: 10.0%; P: ≤0.045%; S: ≤0.003%; Si: ≤0.45%; Cr: 12.8-13.1%; Ni: 1.2-1.3%; N: 0.10-0.13%; with added Re element; the balance is Fe and other unavoidable impurity elements.

[0041] It should be noted that controlling the C content can avoid carbide precipitation caused by sensitization; controlling C and N reduces the resistance to grain growth and increases the grain growth rate during recovery recrystallization; since Re has a good affinity with C, adding Re can further prevent carbide precipitation caused by sensitization.

[0042] In this embodiment, the three sets of electromagnetic stirrers in step S2 are as follows: the first set: electromagnetic stirring of the crystallizer, which adopts a linear electromagnetic stirrer with a stirring roller current of 400A and a power supply frequency of 1-5Hz; the second set: electromagnetic stirring of the secondary cooling zone, with a stirring roller current of 400A and a power supply frequency of 2-10Hz; and the third set: electromagnetic stirring of the solidification end, with a stirring roller current of 400A and a power supply frequency of 3-15Hz.

[0043] In this embodiment, the heating furnace in step S3 includes a preheating section, a heating section, and a soaking section. The temperature of the preheating section is 1000℃, the temperature of the heating section is 1200℃, and the temperature of the soaking section is 1280~1290℃. The residual oxygen content in the heating section of the heating furnace is controlled to be less than 2%, and the residual oxygen content in the soaking section is controlled to be less than 1%. Burners are provided at both ends of the heating furnace. The flame length of the burners is controlled to be 1 / 4 of the length of the billet, and the distance between the flame and the billet is 10~20cm.

[0044] It should be noted that increasing the hot rolling temperature is beneficial to the hot rolling process. On the other hand, it creates greater thermal stress on the surface during rolling, which is conducive to the cracking and effective removal of the surface oxide scale. By controlling the residual oxygen content, the heating atmosphere is strictly controlled, thereby effectively controlling the thickness and properties of the oxide scale layer. Controlling the combustion gas, residual oxygen, and flame morphology controls the oxide scale on the billet, achieving the production of a thinner oxide layer and providing favorable conditions for hot rolling without descaling.

[0045] In this embodiment, a descaling process is provided between steps S3 and S4, and between steps S4 and S5. The descaling process uses hot air purging for descaling, and the descaling pressure is greater than 25 MPa.

[0046] It should be noted that descaling can remove foreign objects from the surface of the billet, preventing them from being pressed into the billet surface and affecting the quality of the steel coil.

[0047] In this embodiment, the grinding roller in step S7 is made of 120-mesh silicon carbide material, the grinding power of the grinding roller is 100-140KW, and the grinding depth of the grinding roller is controlled at 0.01mm; the pickling line in S7 includes a pickling tank and an ultrasonic cleaning device. The pickling tank has three sections. The first section of the pickling tank contains 60±10g / L of nitric acid and 20±5g / L of hydrofluoric acid solution, and the solution temperature is controlled at 50±5℃. The vibration frequency of the ultrasonic cleaning device is 700-800kHz, and the power density is 1.9-2 The first pickling tank contains 40±10 g / L nitric acid and 10±5 g / L hydrofluoric acid, with the solution temperature controlled at 50±5℃. The ultrasonic cleaning device has a vibration frequency of 600~700kHz and a power density of 1.5~1.7V / ㎡. The second pickling tank contains 20±5 g / L nitric acid and 5±2 g / L hydrofluoric acid, with the solution temperature controlled at 50±5℃. The ultrasonic cleaning device has a vibration frequency of 500~600kHz and a power density of 1.2~1.4V / ㎡.

[0048] The nickel-saving austenitic stainless steel coils produced by the above method have a tensile strength >515 MPa, a yield strength >205 MPa, an elongation of 40% to 60%, and a hardness of 85 to 89 HRB. They also have uniform gloss, good roughness, and the surface is free of watermarks, corrosive color differences, sensitization, and intergranular corrosion.

[0049] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0050] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for controlling color difference at the edge of nickel-saving austenitic stainless steel coils, characterized in that: The method includes the following steps: S1: Steel is smelted according to the following chemical composition: C: 0.03-0.04%; Mn: 10.0%; P: ≤0.045%; S: ≤0.003%; Si: ≤0.45%; Cr: 12.8-13.1%; Ni: 1.2-1.3%; N: 0.10-0.13%; with the addition of Re element; the balance being Fe and other unavoidable impurity elements. The steel is then smelted in an EAF furnace, an AOD furnace, and an LF furnace to obtain steel with the target composition. S2: Continuously cast steel billet. Molten steel is transported to the continuous casting platform for continuous casting operations and injected into the crystallizer. The opening degree of the stopper rod of the tundish, the insertion depth of the nozzle, and the casting speed are adjusted to control the stability of the liquid level in the crystallizer. During the casting process, the superheat is maintained at 25-35℃, the water temperature difference between the wide and narrow faces of the crystallizer is controlled at 3-6℃, the casting speed is maintained at 0.6-1.2m / min, the secondary cooling water ratio is controlled at 0.5-0.8L / kg, and three sets of electromagnetic stirrers are set up to improve the segregation of the cast billet, thereby obtaining the continuously cast steel billet. S3: Steel billet heat treatment. After the continuous casting steel billet passes online surface inspection and is free of defects, it is transported to a heating furnace for preheating treatment, where the billet temperature is preheated to 700-800℃. Then, it undergoes heat treatment and soaking treatment for 100-120 minutes to obtain the heat-treated steel billet. S4: Rough rolling of steel billet. The heat-treated steel billet is sent to the rough rolling mill for five passes of rough rolling. There is a 30-second interval between each pass. During the rough rolling, the billet temperature is controlled at 1200-1250℃ to obtain an intermediate billet with a thickness of 30-50mm. S5: Finished steel billet. The intermediate billet is transported to the finishing rolling mill for eight passes of finishing rolling. During the finishing rolling process, the billet temperature is controlled at 1180-1230℃, and the unevenness difference of the steel plate is controlled at 35-45μm, thus obtaining a thin steel plate with a thickness of 2.0-5.0mm. S6: Coiling and cooling. Thin steel sheets are rolled into steel coils using a coiler. During the coiling process, the temperature of the thin steel sheets is controlled at 720℃±30℃. The steel coils are then transferred to the strong wind cooling zone of the hot-rolled finished product warehouse for cooling treatment. S7: Grinding and pickling. After the cooled steel coil is descaled, shot blasted and straightened, it enters the grinding roller to remove the oxide scale on the surface of the steel coil. The surface-treated steel coil is sent to the pickling line for pickling treatment, and then washed and dried into coils to obtain nickel-saving austenitic stainless steel coils. The three sets of electromagnetic stirrers in step S2 are as follows: the first set is for electromagnetic stirring of the crystallizer, which uses a linear electromagnetic stirrer with a stirring roller current of 400A and a power supply frequency of 1-5Hz; the second set is for electromagnetic stirring of the secondary cooling zone, with a stirring roller current of 400A and a power supply frequency of 2-10Hz; and the third set is for electromagnetic stirring of the solidification end, with a stirring roller current of 400A and a power supply frequency of 3-15Hz. The heating furnace in step S3 includes a preheating section, a heating section, and a soaking section. The temperature of the preheating section is 1000℃, the temperature of the heating section is 1200℃, and the temperature of the soaking section is 1280~1290℃. The residual oxygen content in the heating section is controlled to be less than 2%, and the residual oxygen content in the soaking section is controlled to be less than 1%. Burners are provided at both ends of the heating furnace. The flame length of the burners is controlled to be 1 / 4 of the length of the billet, and the distance between the flame and the billet is 10~20cm. In step S7, the grinding roller is made of 120-mesh silicon carbide material, the grinding power of the grinding roller is 100-140KW, and the grinding depth of the grinding roller is controlled at 0.01mm. The pickling line in step S7 includes a pickling tank and an ultrasonic cleaning device. The pickling tank has three sections: a first pickling tank, a second pickling tank, and a third pickling tank. The first pickling tank contains 60±10 g / L of nitric acid and 20±5 g / L of hydrofluoric acid solution, and the solution temperature is controlled at 50±5℃. The ultrasonic cleaning device has a vibration frequency of 700~800kHz and a power density of 1.9~2.1V / ㎡. The second pickling tank contains 40± The first section contains 10 g / L nitric acid and 10 ± 5 g / L hydrofluoric acid, with the solution temperature controlled at 50 ± 5℃. The ultrasonic cleaning device has a vibration frequency of 600–700 kHz and a power density of 1.5–1.7 V / ㎡. The second section contains 20 ± 5 g / L nitric acid and 5 ± 2 g / L hydrofluoric acid, with the solution temperature controlled at 50 ± 5℃. The ultrasonic cleaning device has a vibration frequency of 500–600 kHz and a power density of 1.2–1.4 V / ㎡.

2. The method for controlling color difference at the edge of nickel-saving austenitic stainless steel coils according to claim 1, characterized in that: In step S4, the rough rolling process is equipped with an insulation cover to reduce heat loss.

3. The method for controlling color difference at the edge of nickel-saving austenitic stainless steel coils according to claim 1, characterized in that: A descaling process is performed between steps S3 and S4, and between steps S4 and S5. The descaling process uses hot air purging to remove scale, and the descaling pressure is greater than 25 MPa.

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