Method for stopping and starting a thin strip steel continuously without shutdown, the thickness of the thin strip steel being not more than 0.5 mm

Abstract

This invention discloses a method for stopping and starting thin strip steel with a thickness of no more than 0.5 mm without breaking the strip, comprising the following steps: S1, adjusting the coiling tension of each section in the furnace; S2, increasing the coiling tension, reducing the production line speed, and lowering the annealing temperature; S3, adjusting the speed of the cooling fan; S4, closing the burner and reducing the opening degree of the cooling fan; S5, stopping the machine. By using the method for stopping and starting thin strip steel with a thickness of no more than 0.5 mm without breaking the strip, the risk of strip warping and deviation can be reduced, strip breakage can be avoided, and cost losses can be reduced.

Description

Technical Field

[0001] This invention belongs to the field of cold-rolled strip steel technology. Specifically, this invention relates to a method for stopping and starting thin strip steel with a thickness of no more than 0.5 mm without breaking the strip. Background Technology

[0002] Currently, in the annealing process of cold-rolled strip steel, if a production line malfunctions or other problems cause a shutdown and restart, the strip steel will experience severe warping. During the restart process, strip breakage may occur inside the furnace, resulting in a production line shutdown and restart. After the strip breaks, the product is scrapped, and the production line needs to be shut down and the furnace opened for manual strip reconnection. Therefore, the cost of each strip breakage restart is extremely high, which not only causes huge production cost losses but also makes it difficult to deliver products on time.

[0003] Patent CN104438320B, published on August 22, 2017, discloses a method for rolling ultra-thin strip steel using a Sendkimir mill. This method includes the following steps: raw material specification design, specifying the raw material thickness, width, and width allowance; cold rolling load distribution, determining the mill passes and their load distribution; roll shape design, setting the roll shape curves for the first and second intermediate rolls; coiling tension distribution, determining the unit coiling tension value for each pass; and strip shape control, designing the target strip shape control curve for each pass. This method cannot prevent strip breakage in thin strip steel and cannot reduce cost losses. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for starting up thin strip steel with a thickness of no more than 0.5 mm without interruption of strip steel during shutdown, which can reduce the risk of strip warping and deviation, avoid strip breakage, and reduce cost losses.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] The method for stopping and starting thin strip steel with a thickness of no more than 0.5 mm without interruption includes the following steps: S1, adjusting the coiling tension of each section in the furnace; S2, increasing the coiling tension, reducing the production line speed and the annealing temperature; S3, adjusting the speed of the cooling fan; S4, closing the burner and reducing the opening degree of the cooling fan; S5, stopping the machine.

[0007] In step S1, the winding tension of the compensating roller at the annealing furnace inlet is adjusted to 1.8-2.5 KN, the winding tension of the heating section is adjusted to 2.5-3.0 KN, the winding tension of the soaking section is adjusted to 2.0-2.5 KN, the winding tension of the slow cooling section and the fast cooling section is adjusted to 3.0-3.5 KN, the winding tension of the aging section is adjusted to 3.0-3.5 KN, the winding tension of the final cooling section is adjusted to 4.0-4.2 KN, and the winding tension of the compensating roller at the annealing furnace outlet is adjusted to 3.8-4.2 KN.

[0008] Step S2 includes the following steps: increasing the winding tension of each segment by 15-20%; reducing the production line speed from 200-250m / min to 120-150m / min; and reducing the annealing temperature to 600-650℃.

[0009] In step S2, the speed is gradually reduced by 20 m / min every ten seconds.

[0010] In step S3, the air volume of each cooling fan is adjusted by 15%-20%.

[0011] In step S4, the opening degree of the fans in the rapid cooling section and the slow cooling section is reduced by 5%-10%.

[0012] Step S5 includes the following steps: stopping the machine and reducing the winding tension to 1.5-2.2KN, restarting the production line; waiting for the production line speed to stabilize; and restoring the winding tension after observing that the strip does not warp.

[0013] Step S5 includes the following steps: stopping the machine and reducing the temperature; cooling with combustion air from the annealing furnace; and slowly pulling the strip steel out of the furnace.

[0014] In step S5, when the strip thickness is no more than 0.4 mm, the machine is stopped and the temperature is lowered to 400°C.

[0015] The technical advantages of this invention are as follows: By adopting the method of preventing strip breakage during shutdown and restart of thin strip steel with a thickness of no more than 0.5 mm, this invention effectively reduces the risk of strip warping and deviation during furnace operation by adjusting the coiling tension of each section in the furnace, controlling the production line speed and annealing temperature, and adjusting the air volume and opening degree of the cooling fan. This avoids the phenomenon of strip breakage in the furnace during the restart of thin strip steel, eliminating the need to restart the furnace, ensuring continuous production, and reducing the cost losses caused by strip breakage. Attached Figure Description

[0016] This manual includes the following figures, which illustrate the following:

[0017] Figure 1 This is a schematic diagram of the operation process of the method for stopping and starting thin strip steel with a thickness of no more than 0.5 mm without breaking the strip during operation according to the present invention;

[0018] Figure 2 This is a schematic diagram of the strip steel operation process. Detailed Implementation

[0019] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings, in order to help those skilled in the art to have a more complete, accurate and in-depth understanding of the inventive concept and technical solution of the present invention, and to facilitate its implementation.

[0020] like Figure 1 and Figure 2 As shown, the method for stopping and starting thin strip steel with a thickness of no more than 0.5 mm without interruption includes the following steps: S1, adjusting the coiling tension of each section in the furnace; S2, increasing the coiling tension, reducing the production line speed and reducing the annealing temperature; S3, adjusting the speed of the cooling fan; S4, closing the burner and reducing the opening degree of the cooling fan; S5, stopping the machine.

[0021] In step S1, the winding tension of the compensating roller at the annealing furnace inlet is adjusted to 1.8-2.5KN, the winding tension of the heating section is adjusted to 2.5-3.0KN, the winding tension of the soaking section is adjusted to 2.0-2.5KN, the winding tension of the slow cooling section and the fast cooling section is adjusted to 3.0-3.5KN, the winding tension of the aging section is adjusted to 3.0-3.5KN, the winding tension of the final cooling section is adjusted to 4.0-4.2KN, and the winding tension of the compensating roller at the annealing furnace outlet is adjusted to 3.8-4.2KN.

[0022] The annealing furnace is equipped with an annealing furnace inlet, a heating section, a soaking section, a slow cooling section, a rapid cooling section, an aging section, a final cooling section, and an annealing furnace outlet in sequence. The annealing furnace inlet section is the entrance for strip steel annealing. The heating section heats the strip steel through radiant tubes using heat generated by burners. The soaking section maintains the strip steel's temperature after heating. The slow cooling section cools the strip steel slowly using fans. The rapid cooling section cools the strip steel rapidly using fans to achieve a certain cooling rate. The aging section decarburizes the strip steel. The final cooling section provides the final cooling. The annealing furnace outlet is the exit point for the complete annealing process. Based on the detection and observation of the strip steel's movement within the furnace, the coiling tension in each section is adjusted using tension gauges. After adjusting the coiling tension in each section to the aforementioned values, the tension is within a reasonable and safe range, preventing thermal expansion and contraction during subsequent cooling that could increase the strip steel tension. The adjusted coiling tension improves the flatness of the strip steel by the furnace rolls and also prevents the strip steel from becoming loose upon arrival, thus reducing the risk of warping.

[0023] Step S2 includes the following steps: increasing the coiling tension of each section by 15-20%; reducing the production line speed to 120-150 m / min; and lowering the annealing temperature to 600-650℃. Increasing the coiling tension based on the secondary coiling tension results in a higher leveling force from the rolls on the strip, making it less prone to deviation. Before the speed reduction, the production line speed is at the normal process speed of 200-250 m / min. Operators use encoders to slowly reduce the speed of the continuous annealing furnace to control the production line speed. After the speed reduction, there will be no misalignment between strip layers, and no scratches or abrasions will appear on the strip surface, ensuring product quality. The annealing temperature is controlled according to the target value of the current strip steel grade. Based on the annealing temperature of each steel grade, the annealing temperature is reduced to within 600-650℃ to effectively control strip warping and deviation in the furnace. Lowering the annealing temperature reduces the expansion rate of the rolls, ensuring that the strip surface is in contact with and parallel to the rolls during operation. This results in uniform stress distribution across all parts of the strip, preventing deviation and improving strip flatness, thus reducing the risk of warping. The simultaneous operation of these three modes ensures that the strip does not deviate and guarantees its normal operation in the furnace.

[0024] Changes in production line speed need to be matched with the amount of strip handled by the inlet and outlet loopers. As a device for storing strip steel, the inlet and outlet loopers ensure the normal operation of the continuous annealing furnace and prevent production line downtime when welding or other temporary malfunctions occur. When the production line speed changes, the looper's amount of strip steel is stored, thus allowing more time for furnace operation. When problems affecting the smooth operation of the production line occur, such as re-welding, equipment failure, quality issues, roll changes, or single-channel issues, the production line speed must be gradually reduced to 120 m / min. During production line operation, the amount of strip handled needs to be closely monitored, and the speed should be gradually increased or decreased depending on the actual situation of the problem.

[0025] In step S2, the speed is gradually reduced by 20 m / min every ten seconds. This gradual reduction in 20 m / min increments prevents excessive speed reduction from causing uneven strip surface temperature, which could lead to misalignment or warping. Simultaneously, the strip as a whole can better adapt to speed changes on the production line, reducing the impact of speed variations on its operation.

[0026] In step S3, adjust the airflow of each cooling fan section by 15%-20%. Monitor the rotational speed of each cooling fan section within the furnace. The fan speed and airflow must match the current production line speed. Adjusting the airflow prevents excessive strip vibration and scratches in the cooling section, effectively ensuring product quality. Simultaneously, observe the changes in strip scratch effects at the annealing furnace outlet to identify the location of scratches within the furnace, and then readjust the airflow of the cooling fan in that section to further reduce the probability of strip scratches.

[0027] In step S4, the opening degree of the fans in the rapid cooling section and the slow cooling section is reduced by 5%-10%. Timely shutdown of the burners to lower the temperature and reduction of the fan opening degree can prevent the strip from continuing to warp. If the strip has not yet deviated, the speed is rapidly increased to 60-80 m / min to ensure that production continues and reduce the risk of strip warping.

[0028] Step S5 includes the following steps: stopping the machine and reducing the coiling tension to 1.5-2.2 KN, restarting the production line; waiting for the production line speed to stabilize; and restoring the coiling tension after observing that the strip is no longer warped. These steps are used to ensure the strip continues to follow the production line.

[0029] Step S5 includes the following steps: stopping the machine and reducing the temperature; cooling with combustion air from the annealing furnace; and slowly pulling the strip out of the furnace. After stopping the furnace, the compensating rollers at the furnace inlet and outlet are loosened, and the coiling tension inside the furnace is reduced by feeding the strip into the furnace immediately, thereby reducing the risk of warping; the strip needs to be pulled out slowly to avoid damage caused by operational errors.

[0030] In step S5, when the strip thickness is no more than 0.4 mm, the machine is stopped and the temperature is lowered to 400°C. This temperature is the safest and most reliable temperature to prevent strip breakage. When the strip is at this temperature, it will not undergo plastic deformation, thus preventing breakage and warping. This is the optimal temperature control. Furthermore, it facilitates subsequent preparations for restarting production. This temperature differs from the 500°C required for hydrogen introduction in the continuous annealing furnace by 100°C, allowing for rapid heating and hydrogen introduction during the subsequent heating and restarting process. This saves energy and time for heating, shortens the restart time, and increases the unit's production capacity.

[0031] Example 1: A 0.4mm thick strip runs at 250m / min inside the furnace. When a production line malfunction or other unforeseen factors cause a speed reduction, the coiling tension of the annealing furnace inlet compensating roller is adjusted to 2KN; the coiling tension in the heating and soaking sections is adjusted to 2.5KN; the coiling tension in the slow and fast cooling sections is adjusted to 3KN; the coiling tension in the aging section is manually adjusted to 3.5KN; the coiling tension in the final cooling section is adjusted to 4KN; and the coiling tension of the annealing furnace outlet compensating roller is adjusted to 4KN. Subsequently, the coiling tension is increased by 15% and passed through… The production line speed is gradually reduced to 120 m / min to prevent deviation. Then, the annealing temperature is reduced to 650℃, the cooling fan airflow is reduced by 15%, and the opening degree is adjusted by 10% to prevent strip warping. The machine is then stopped, and the coiling tension in the furnace is reduced to 1.5 KN. The temperature is lowered to 400℃. The production line is restarted, and the production line speed is stabilized and the strip is free from warping. The coiling tension can then be restored. By following the above steps, the risk of strip warping and deviation can be avoided. Therefore, the strip will not break during the equipment shutdown and restart process.

[0032] Comparative Example: If producing strip steel with a thickness of 0.4mm, the measures and parameters used in steps 1 to 4 are the same as in Example 1. When restarting the machine, if the temperature is lowered to below or above 400℃, the strip steel will warp severely, which will lead to strip breakage and product scrap.

[0033] Example 2: When producing 0.45mm thick strip steel, the coiling tension of the annealing furnace inlet compensating roller is adjusted to 2.2KN, the coiling tension of the heating and soaking sections is adjusted to 2.5KN, the coiling tension of the slow cooling and fast cooling sections is adjusted to 3.5KN, the coiling tension of the aging section is manually adjusted to 3.5KN, the coiling tension of the final cooling section is adjusted to 4KN, and the coiling tension of the annealing furnace outlet compensating roller is adjusted to 4KN. Then, the coiling tension is increased by 20%, the production line speed is reduced to 120m / min by slow deceleration, the annealing temperature is reduced to 650℃, the cooling fan airflow is reduced by 20%, the opening degree is adjusted by 10%, the machine is stopped, and the coiling tension inside the furnace is reduced to 2KN, the temperature is reduced to 400℃, the production line is restarted, and the production line speed is stabilized and the strip steel is free from warping. The coiling tension can then be restored. The above steps can prevent strip steel breakage.

[0034] This method for preventing strip breakage during shutdown and restart of thin strip steel (with a thickness of no more than 0.5 mm) effectively reduces the risk of strip warping and deviation during furnace operation by adjusting the coiling tension of each section in the furnace, controlling the production line speed and annealing temperature, and regulating the airflow and opening degree of the cooling fan. It also avoids strip breakage during restart of thin strip steel, eliminating the need to restart the furnace, ensuring continuous production, and reducing the cost losses caused by strip breakage.

[0035] The present invention has been described above by way of example with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvements made using the inventive concept and technical solution; or the direct application of the inventive concept and technical solution to other situations without modification, are all within the protection scope of the present invention.

Claims

1. A method for starting a machine without interrupting the production of thin strip steel with a thickness not exceeding 0.5 mm, characterized in that, Includes the following steps: S1. Adjust the winding tension of each section in the furnace; S2. Increase the winding tension, reduce the production line speed, and reduce the annealing temperature; S3. Adjust the speed of the cooling fan; S4. Close the burner and reduce the opening degree of the cooling fan; S5. Shut down the machine; In step S1, the winding tension of the annealing furnace inlet compensating roller is adjusted to 1.8-2.5KN, the winding tension of the heating section is adjusted to 2.5-3.0KN, the winding tension of the soaking section is adjusted to 2.0-2.5KN, the winding tension of the slow cooling section and the fast cooling section is adjusted to 3.0-3.5KN, the winding tension of the aging section is adjusted to 3.0-3.5KN, the winding tension of the final cooling section is adjusted to 4.0-4.2KN, and the winding tension of the annealing furnace outlet compensating roller is adjusted to 3.8-4.2KN; Step S2 includes the following steps: increasing the coiling tension of each section by 15-20%; reducing the production line speed from 200-250 m / min to 120-150 m / min; reducing the annealing temperature to 600-650℃; in step S2, slowly reducing the speed by 20 m / min every ten seconds; in step S3, adjusting the airflow of the cooling fans in each section by 15%-20%; in step S4, reducing the opening degree of the fans in the fast cooling section and the slow cooling section by 5%-10%; step S5 includes the following steps: stopping the machine and reducing the coiling tension to 1.5-2.2 KN, restarting the production line; waiting for the production line speed to stabilize; and restoring the coiling tension after observing that the strip is free of warping.

2. The method for stopping and starting thin strip steel with a thickness of no more than 0.5 mm without breaking the strip, as described in claim 1, is characterized in that: Step S5 includes the following steps: stopping the machine and reducing the temperature; cooling with combustion air from the annealing furnace; and slowly pulling the strip steel out of the furnace.

3. The method for stopping and starting thin strip steel with a thickness of no more than 0.5 mm according to claim 1 or 2 without breaking the strip during operation, characterized in that: In step S5, when the strip thickness is no more than 0.4 mm, the machine is stopped and the temperature is lowered to 400°C.

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