SUS410L cold-rolled strip steel specification transition annealing method

Abstract

The invention belongs to the field of cold box stainless steel, and relates to a specification transition annealing method for SUS410L cold-rolled strip steel, which adopts the steps of welding, scale breaking, shot blasting, sulfuric acid pickling and mixed acid pickling to ensure that the performance of the SUS410L strip steel is stable, the process rate of a continuous rolling support switching single stand is reduced, and in addition, the production efficiency is improved and the delivery cycle is shortened on the premise of ensuring the performance.

Description

Technical Field

[0001] This invention belongs to the field of stainless steel for cold boxes, and relates to a method for transition annealing of SUS410L cold-rolled strip steel. The cold box industry is an important part of the modern stainless steel market. Stainless steel has become an important material for making cold box panels due to its advantages such as high strength, wear resistance, corrosion resistance, easy cleaning, and environmental friendliness, and is widely used in the container industry. Background Technology

[0002] SUS410L stainless steel is primarily used in container panels, requiring high performance, shape, and thickness. To ensure product quality, a production process of "bell furnace annealing + hot-line pickling + rolling + cold-line annealing and pickling" has been consistently employed. However, bell furnace annealing not only has a long production cycle but also high production costs, and edge annealing marks also affect the finished product pass rate and delivery cycle. To save production costs, shorten the manufacturing cycle, and reduce annealing mark defects, bell furnace annealing has been eliminated, and the process has become "hot-line annealing and pickling + rolling + cold-line annealing and pickling." For some coils with fluctuating plate temperatures, the continuous rolling process needs to be switched to a single-stand process. The surface and properties of SUS410L produced on a single stand differ from those produced in continuous rolling, affecting surface continuity and property uniformity. Therefore, improving the continuous rolling success rate of SUS410L is particularly important.

[0003] Analysis revealed that the main issue is that SUS410L strip properties are more sensitive to annealing temperature fluctuations than other steel grades during continuous hot-rolling annealing. Even slight temperature changes during specification transitions can cause significant fluctuations in strip elongation, impacting the safety of continuous rolling production. Consequently, the coil is switched to single-stand production. Because the surface finish and properties of single-stand production differ from continuous rolling, significant differences exist, affecting product quality consistency and continuity. Therefore, a method for transitional annealing of SUS410L cold-rolled strip specifications needs to be found.

[0004] The purpose of this invention is to provide a method for transition annealing of SUS410L cold-rolled strip steel, which reduces temperature fluctuations in SUS410L strip steel, ensures stable performance, improves the continuous rolling success rate of SUS410L, and further improves production efficiency, shortens delivery cycle, and enhances product quality uniformity and continuity while ensuring performance. Summary of the Invention

[0005] The purpose of this invention is to address the above-mentioned problems by providing a method for transition annealing of SUS410L cold-rolled strip steel.

[0006] The purpose of this invention is achieved as follows: A method for transitional annealing of SUS410L cold-rolled strip steel, comprising the following aspects: (1) SUS410L stainless steel is annealed online with furnace temperature control, using 12 zones, with a furnace temperature of 825-865℃. The furnace temperature in the first 3 zones is rapidly increased to the annealing temperature of 835-850℃, with a heating rate of 24-32℃ / s. The furnace temperature in the last 9 zones remains constant, and the annealing time is increased to 102-140s; (2) 0Cr13R is used for transitional annealing. The temperature is increased or decreased on 0Cr13R and adjusted to a suitable temperature of 835-855℃ to ensure stable plate temperature control after SUS410L enters the furnace, with the plate temperature being 835-855℃; 3) After annealing, the scale is broken. The scale breaking machine is controlled according to the tension mode, and the tension is set to 220-600KN. After the scale breaking, shot blasting is performed. 4-6 shot blasting machines are used, with a speed of 1700-1750rpm and a current of 90-105A. (4) Sulfuric acid pickling is performed. The sulfuric acid concentration is 220-280g / l, the temperature is 75-85℃, and the iron ion concentration is controlled within 45g / l. Mixed acid pickling is performed. A mixture of nitric acid and hydrofluoric acid is used. Two stages of mixed acid are used. The nitric acid concentration is 60-100g / l, the hydrofluoric acid concentration is 0-5g / l, the temperature is controlled at 40-50℃, and the iron ion concentration is controlled within 40g / l. Pickling speed: 25-50m / min.

[0007] The chemical composition of SUS410L cold-rolled strip steel, by weight percentage, consists of the following elements: C≤0.03%, Mn<0.25%, Cr: 11.00~12.40%, Ni<0.06%, Cu<0.01%, P<0.03%, Si<0.40%, N<0.02%, with the balance being Fe and other unavoidable impurity elements.

[0008] The beneficial effects of this invention are: this invention ensures that the temperature fluctuation range of SUS410L annealed plates is controlled within ±8℃, the elongation at room temperature is 22-30%, the yield strength is 310-320Mpa, and the tensile strength is 460-490Mpa, which are excellent and meet the requirements.

[0009] By interspersing other steel grades during specification transitions to adjust the plate temperature in advance, the hot-line online annealing production of SUS410L continuous rolling has increased the success rate by 10%. Detailed Implementation

[0010] SUS410L stainless steel is primarily used in container panels, requiring high performance, shape, and thickness. To ensure product quality, a production process of "bell-type furnace annealing + hot-line pickling + rolling + cold-line annealing and pickling" has been consistently employed. However, bell-type furnace annealing not only has a long production cycle but also high production costs, and edge annealing defects affect the finished product pass rate and delivery cycle. To save production costs, shorten the manufacturing cycle, and reduce annealing defects, the process was changed to "hot-line annealing and pickling + rolling + cold-line annealing and pickling." However, after a period of production, it was found that the production efficiency on other hot lines was slow and could not meet the needs of large-scale continuous rolling production. A new production method needs to be researched. Furthermore, some coils with fluctuating plate temperatures need to be switched from continuous rolling to single-stand processing, affecting surface continuity and performance uniformity. Therefore, a method for annealing and pickling SUS410L cold-rolled strip steel needs to be found. The purpose of this invention is to provide a method for annealing and pickling SUS410L cold-rolled strip steel, which ensures stable performance of SUS410L strip steel, reduces the single-stand process rate during continuous rolling support switching, and improves production efficiency and shortens delivery cycle while ensuring performance.

[0011] The chemical composition (by weight percentage) of a SUS410L cold-rolled strip steel consists of the following elements: C ≤0.03%, Mn <0.25%, Cr 11.00~12.40%, Ni <0.06%, Cu <0.01%, P <0.03%, Si <0.40%, N <0.02%, with the balance being Fe and other unavoidable impurity elements.

[0012] This invention utilizes a process for SUS410L stainless steel, primarily consisting of "welding-scale breaking-shot blasting-sulfuric acid pickling-mixed acid pickling." Specific process control points and objectives include: online annealing furnace temperature control for SUS410L stainless steel, employing 12 zones with a furnace temperature of 825-865℃. The first three zones are designed to rapidly raise the furnace temperature to the annealing temperature, while the latter nine zones maintain a constant furnace temperature to extend the annealing time. During specification transitions, 0Cr13R of the target thickness is interspersed to adjust the plate temperature.

[0013] During specification transitions, 0Cr13R is used for the transition. Heating or cooling is performed on 0Cr13R to adjust to the appropriate temperature, ensuring stable plate temperature control after SUS410L enters the furnace. By using reasonable material layout and uniform thickness production in batch production, plate temperature fluctuations caused by specification transitions are reduced, minimizing the impact of plate temperature fluctuations on the surface and performance consistency of the continuous rolling mill support and single stand cutting.

[0014] After annealing, the scale is broken. The scale breaking machine is controlled in tension mode, with the tension set to 220-600KN.

[0015] After phosphorus removal, shot blasting is performed. Six shot blasting machines are used, with a speed of 1700-1750 rpm and a current of 90-105A.

[0016] Sulfuric acid pickling is performed using sulfuric acid with a concentration of 220-280 g / L, a temperature of 75-85℃, and an iron ion concentration controlled below 45 g / L.

[0017] Mixed acid pickling uses a mixture of nitric acid and hydrofluoric acid, employing a two-stage mixed acid process. The nitric acid concentration is 60-100 g / L, the hydrofluoric acid concentration is 0-5 g / L, the temperature is controlled at 40-50℃, and the iron ion concentration is controlled below 40 g / L.

[0018] Speed: 25-50 m / min (based on the principle of cleaning the surface). Example 1

[0019] It has already been implemented on the No. 3 hot line of the stainless steel cold rolling mill of Taiyuan Iron & Steel Stainless Steel Co., Ltd. SUS410L cold-rolled strip with a thickness of 4.0mm is produced on the No. 3 hot line. The annealing and pickling process for the cold-rolled raw material involves annealing + descaling + shot blasting + sulfuric acid pickling + mixed acid pickling.

[0020] 1. SUS410L stainless steel uses online annealing furnace temperature control, operating in zones 7-18, with a furnace temperature of 825-865℃. The first three zones are designed to rapidly raise the furnace temperature to the annealing temperature, while the latter nine zones maintain a constant furnace temperature to extend the annealing time. When transitioning from 4mm to 3mm thickness in SUS410L specifications, a 3mm thick 0Cr13R plate is inserted in between. After the 4mm thick SUS410L is removed from the furnace, the plate temperature is adjusted on the 0Cr13R plate to ensure stable plate temperature after the 3mm thick SUS410L enters the furnace, reducing temperature fluctuations.

[0021] 2. After annealing, scale breaking is performed. Scale breaking is controlled according to the tension mode, with the tension set to 340KN.

[0022] After the scales are broken, shot blasting is performed. Six shot blasting machines are used, with a speed of 1750 rpm and a current of 90A.

[0023] Sulfuric acid pickling is performed using sulfuric acid with a concentration of 280 g / L and a temperature of 80℃. The iron ion concentration is controlled to be below 45 g / L.

[0024] Mixed acid pickling uses a mixture of nitric acid and hydrofluoric acid, employing a two-stage mixed acid process. The nitric acid concentration is 60-100 g / L, the hydrofluoric acid concentration is 0-5 g / L, the temperature is controlled at 40-50℃, and the iron ion concentration is controlled below 40 g / L. Example 2

[0025] It has already been implemented on the No. 3 hot line of the stainless steel cold rolling mill of Taiyuan Iron & Steel Co., Ltd. SUS410L cold-rolled strip with a thickness of 3.0mm is produced on the No. 3 hot line. The annealing and pickling process for the cold-rolled raw material involves annealing + descaling + shot blasting + sulfuric acid pickling + mixed acid pickling.

[0026] 1. SUS410L stainless steel uses online annealing furnace temperature control, operating in zones 7-18, with a furnace temperature of 825-865℃. The first three zones are designed to rapidly raise the furnace temperature to the annealing temperature, while the latter nine zones maintain a constant furnace temperature to extend the annealing time. When transitioning from 3mm to 4mm thickness in SUS410L specifications, a 4mm thick 0Cr13R plate is inserted in between. After the 3mm thick SUS410L is removed from the furnace, the plate temperature is adjusted on the 0Cr13R plate to ensure stable plate temperature after the 4mm thick SUS410L enters the furnace, reducing temperature fluctuations.

[0027] 2. After annealing, scale breaking is performed. Scale breaking is controlled according to the tension mode, with the tension set to 300KN.

[0028] After the scales are broken, shot blasting is performed. Six shot blasting machines are used, with a speed of 1750 rpm and a current of 90A.

[0029] Sulfuric acid pickling is performed using sulfuric acid with a concentration of 280 g / L and a temperature of 80℃. The iron ion concentration is controlled to be below 45 g / L.

[0030] Mixed acid pickling uses a mixture of nitric acid and hydrofluoric acid, employing a two-stage mixed acid process. The nitric acid concentration is 60-100 g / L, the hydrofluoric acid concentration is 0-5 g / L, the temperature is controlled at 40-50℃, and the iron ion concentration is controlled below 40 g / L.

[0031] The above description is only a specific embodiment of the present invention, but the structural features protected by the present invention are not limited thereto. Any changes or modifications made by those skilled in the art within the scope of the present invention are covered by the patent scope of the present invention.

Claims

1. A method for transition annealing of SUS410L cold-rolled strip steel, characterized in that: Including the following aspects: (1) SUS410L stainless steel is used for online annealing furnace temperature control. There are 12 zones with a furnace temperature of 825-865℃. The furnace temperature in the first 3 zones is set to rise rapidly to the annealing temperature of 835-850℃, with a heating rate of 24-32℃ / s. The furnace temperature in the last 9 zones remains constant, and the annealing time is increased to 102-140s. (2) Use 0Cr13R for the transition when the specifications are changed. Heat up or cool down on 0Cr13R and adjust to a suitable temperature of 835-855℃. Ensure that the plate temperature is stable after the SUS410L enters the furnace. The plate temperature is 835-855℃. (3) After annealing, the scale is broken. The scale breaking machine is controlled in tension mode, and the tension is set to 220-600KN. After the scale breaking, shot blasting is performed. 4-6 shot blasting machines are used, with a speed of 1700-1750rpm and a current of 90-105A. (4) Sulfuric acid pickling: Sulfuric acid concentration is 220-280 g / l, temperature is 75-85℃, and iron ion concentration is controlled within 45 g / l; Mixed acid pickling: Nitric acid and hydrofluoric acid are mixed and pickled in two stages. Nitric acid concentration is 60-100 g / l, hydrofluoric acid concentration is 0-5 g / l, temperature is controlled at 40-50℃, and iron ion concentration is controlled within 40 g / l; Pickling speed: speed 25-50 m / min.

2. The method for transition annealing of SUS410L cold-rolled strip steel according to claim 1, characterized in that: The chemical composition of SUS410L cold-rolled strip steel, by weight percentage, consists of the following elements: C≤0.03%, Mn<0.25%, Cr: 11.00~12.40%, Ni<0.06%, Cu<0.01%, P<0.03%, Si<0.40%, N<0.02%, with the balance being Fe and other unavoidable impurity elements.