Method of manufacturing cold-rolled steel strip using temperature control strategy

Abstract

A method for manufacturing a cold-rolled steel strip using a temperature control strategy. The temperature control strategy includes an automatic temperature control mode and a constant power control mode. The automatic temperature control mode includes the steps of calculating a heating target temperature at a heating device, and obtaining an output power based on a power conversion table and heating the steel strip. The constant power control mode includes the steps of taking a maximum value from an output power of a front steel strip and an output power of a rear steel strip as P max; increasing the output power of the front steel strip to the P maxand heating a section between a safety length of the front steel strip and a safety length of the rear steel strip with the P max; and then reducing the output power from the P maxto the output power of the rear steel strip to obtain the cold-rolled steel strip. The method can ensure the stability production of steel strip and avoid the problem of excessive heating of the steel strip which leads to increased production costs.

Description

Technical Field

[0001] This invention relates to a method for preparing cold-rolled steel strip, and more particularly to a method for producing cold-rolled steel strip using a temperature control strategy. Prior Technology

[0002] Because brittle steel strips are sensitive to temperature, during the production of steel strips through the cold rolling process, before the steel strips enter the cold rolling mill for rolling, an induction heating device is used to heat the steel strips, raising their temperature to above the ductile-brittle transition temperature (Tg). This causes the material properties of the steel strips to change from brittle to tough, and also enables them to reduce thickness, thereby stabilizing the steel strip production process.

[0003] However, existing technology cannot calculate the optimal target heating temperature of the steel strip in the induction heating device and the temperature at which the steel strip moves to the cold rolling mill for rolling. This makes it impossible to ensure that the temperature of the steel strip during the rolling process is higher than the temperature required for stable production, or it may lead to overheating of the steel strip, resulting in increased production costs.

[0004] Based on the shortcomings of the existing technology, a method for preparing cold-rolled steel strip has been developed that can calculate the target heating temperature of the steel strip in the induction heating device. This method ensures that the temperature of the steel strip during the rolling process is higher than the temperature required for stable production of the steel strip and avoids overheating of the steel strip, which would increase the production cost. These are problems that urgently need to be solved in this field. Summary of the Invention

[0005] To address the problems of the prior art, the present invention aims to provide a method for producing cold-rolled steel strip using a temperature control strategy. Through the temperature control strategy, the most suitable target heating temperature of the steel strip in the induction heating device and the temperature at which the steel strip moves to the cold rolling mill for rolling can be calculated. This ensures that the temperature of the steel strip during the rolling process is higher than the temperature required for stable production, thereby achieving the effect of stable steel strip production and avoiding the problem of increased production costs due to overheating of the steel strip.

[0006] To achieve the above objectives, the present invention provides a method for producing cold-rolled steel strip using a temperature control strategy, wherein the temperature control strategy includes an automatic temperature control mode and a constant power control mode, and the method for producing the cold-rolled steel strip through the automatic temperature control mode includes: Step 1: Based on the steel grade and size of the strip, and the minimum rolling speed, set the initial strip speed and the target temperature at the mill inlet. Then, calculate the maximum cooling time from the heating device to the first cold rolling mill and the target heating temperature at the heating device based on the initial strip speed, the minimum rolling speed, and the target temperature at the mill inlet. The initial strip speed is the speed at which the heating point of the strip passes through the heating device, and the minimum rolling speed is the minimum speed at which the strip undergoes cold rolling. Step 2: Obtain the required output power according to the power conversion table provided by the supplier of the heating device, and use the heating device to heat the steel strip; The method for producing the cold-rolled steel strip through this constant power control mode includes: Step 10: Calculate the target heating temperatures required by the heating device for the front and rear steel strips based on the target heating temperature of the weld bead, and obtain the required first output power for the front steel strip and the required second output power for the rear steel strip according to the power conversion table. Take the maximum value between the required first output power for the front steel strip and the required second output power for the rear steel strip as Pmax. Step 20: When the front steel strip passes the heating device at a safe distance from the weld bead, the temperature control strategy is switched from the automatic temperature control mode to the constant power control mode. That is, in the automatic temperature control mode, the output power of the heating device is increased from the first output power to Pmax, and the section between the safe length of the front steel strip and the safe length of the rear steel strip is heated at a constant power of Pmax; and Step 30: After the steel strip passes the heating device at a safe distance from the weld bead, the temperature control strategy is switched from the constant power control mode to the automatic temperature control mode, that is, the output power of the heating device is reduced from Pmax to the second output power to obtain the cold-rolled steel strip.

[0007] In one specific embodiment, the maximum cooling time (T) from the heating device to the cold rolling mill of the first station is determined using formula (1): The calculations are as follows: t1 is the time (s) required for the initial strip speed (V0) to decrease to the minimum rolling speed; t2 is the rolling time at the minimum rolling speed (s); V0 is the initial strip speed (mpm); Vmin is the minimum rolling speed (mpm); L is the distance (m) between the heating device and the cold rolling mill of the first station; and a is the decreasing rate (m / s²). The target heating temperature at the heating device is determined using formula (2): TIH(n) is obtained by performing n iterations of calculations, where TIH(n) is the target heating temperature (°C) at the heating device, TIH(0) is the target temperature at the mill inlet (°C), Ta is the ambient temperature (°C), h is the heat transfer coefficient of the steel strip (W / m2C), L is the distance between the heating device and the cold rolling mill of the first station (m), n is the number of iterations, ρ is the density of the steel strip (kg / m3), C is the specific heat of the steel strip (J / kg°C), H is the thickness of the steel strip (mm), V is the rolling speed of the steel strip (mpm), and T is the maximum cooling time (s).

[0008] In one specific embodiment, the automatic temperature control mode is used during the production stage of the cold rolling process of the steel strip.

[0009] In one specific embodiment, the constant power control mode is used for the weld bead at the overlap between the front strip and the rear strip during the continuous cold rolling process.

[0010] In one specific embodiment, the temperature control strategy further includes a constant temperature control mode, which is used when the cold rolling mill is restarted after it has stopped operating, during the initial rolling stage. When the rolling speed during the initial rolling stage exceeds the minimum production speed limit, the temperature control strategy is switched from the constant temperature control mode to the automatic temperature control mode.

[0011] In one specific embodiment, the constant temperature control mode uses the upper limit of the temperature that the production line equipment for producing the cold-rolled steel strip can withstand as the heating target temperature of the constant temperature control mode.

[0012] In one specific embodiment, in step 20, the output power of the heating device is gradually increased to Pmax by setting a first rate of change, and in step 30, the output power of the heating device is gradually decreased to the second output power of the heating device by setting a second rate of change.

[0013] In one specific embodiment, the heating device includes an induction heating device, a hot air heater, or a tunnel furnace.

[0014] In one specific embodiment, the method is used in a continuous rolling mill or a reciprocating single rolling mill.

[0015] In one specific embodiment, the steel strip is a brittle steel strip.

[0016] The method for producing cold-rolled steel strip using temperature control strategies of the present invention can calculate the most suitable target heating temperature of the steel strip in the induction heating device and the temperature at which the steel strip moves to the cold rolling mill for rolling through temperature control strategies of automatic temperature control mode, constant power control mode and constant temperature control mode. This ensures that the temperature of the steel strip during the rolling process is higher than the temperature required for stable production of the steel strip, ensuring the stability of steel strip production and avoiding the problem of increased production costs due to overheating of the steel strip. Simple Explanation of the Diagram

[0017] Figure 1 is a schematic diagram of the production line hardware configuration of the method for producing cold-rolled steel strip using temperature control strategies according to the present invention. Figure 2 is a timing diagram of temperature mode switching in the method for producing cold-rolled steel strip using temperature control strategy of the present invention. Figure 3 is a schematic diagram of the method of producing cold-rolled steel strip using temperature control strategy of the present invention, which calculates the target heating temperature at the induction heating device through an automatic temperature control mode. Figure 4 is a flowchart of the steps of the method of producing cold-rolled steel strip using temperature control strategy according to the present invention, which obtains cold-rolled steel strip through automatic temperature control mode. Figure 5 is a schematic diagram of the method of producing cold-rolled steel strip using a temperature control strategy according to the present invention, which heats the weld bead, the safe length of the front steel strip and the safe length of the rear steel strip to the target heating temperature through a power control mode. Figure 6 is a flowchart illustrating the steps of the method for producing cold-rolled steel strip using a temperature control strategy according to the present invention, which involves obtaining cold-rolled steel strip through a constant power control mode. Figure 7 is a temperature control response diagram of a method for producing cold-rolled steel strip using a temperature control strategy according to an embodiment of the present invention. Implementation

[0018] The following describes the implementation of the present invention through specific embodiments. Those skilled in the art can understand other advantages and effects of the present invention from the content disclosed in this specification. However, the illustrative embodiments disclosed in this invention are for illustrative purposes only and should not be considered as limiting the scope of the invention. In other words, the present invention can also be implemented or applied through other different embodiments, and the details in this specification can also be modified and changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0019] Unless otherwise stated herein, the singular forms “a” and “the” used in the specification and the appended claims include the plural individuals. Unless otherwise stated herein, the term “or” used in the specification and the appended claims includes the meaning of “and / or”.

[0020] Unless otherwise stated herein, the term "rolling start stage" as used in the specification and the appended claims refers to the stage after the cold rolling mill has stopped operating and then restarted.

[0021] Unless otherwise stated herein, the term "weld bead heating" as used in the specification and the appended claims means that the target heating temperature of the weld bead is higher than the target temperature of the steel strip at the mill inlet.

[0022] Referring to Figure 1, when producing brittle steel strip 10 through a cold rolling process, the steel strip 10 must be heated by an induction heating device 30 before entering the tandem cold rolling mill 20, so that the temperature of the steel strip 10 at the moment the cold rolling mill 20 bites into it is higher than the ductile-brittle transition temperature. After being rolled by the tandem cold rolling mill 20, the steel strip 10 is coiled in the coiler 50.

[0023] Referring to Figures 1 and 2, this invention utilizes a temperature control strategy to produce cold-rolled steel strip 10. During the production process of the steel strip 10, the effects of factors such as the material properties and dimensions of the feed material, the steel strip's passage through the weld bead section, the rolling speed variation, and the cooling effect are simultaneously considered. The target heating temperature of the steel strip 10 at the induction heating device 30 is calculated, and then the heating outlet temperature is measured by the heating outlet thermometer 40. This ensures that after the steel strip 10 is heated at the induction heating device 30, when it moves to the cold rolling mill 20 for rolling, the temperature of the steel strip 10 remains above the ductile-brittle transition temperature during the production stage, the weld bead section, and the initial rolling stage. This temperature control strategy includes an automatic temperature control mode, a constant power control mode, and a constant temperature control mode.

[0024] Referring to Figure 3, the automatic temperature control mode is used during the production stage of the cold rolling process. As the steel strip 10 moves from the induction heating device 30 to the entrance of the cold rolling mill 20, its temperature decreases over time. Therefore, to prevent the temperature of the steel strip 10 from dropping below the ductile-brittle transition temperature during this process, the temperature drop before entering the cold rolling mill 20 must be considered. This means the target heating temperature at the induction heating device 30 = the target mill inlet temperature measured by the mill inlet thermometer 60 + the temperature drop. The temperature drop is affected by the time required for the steel strip 10 to move from the induction heating device 30 to the entrance of the cold rolling mill 20, i.e., the current rolling speed. For example, to avoid the production line of steel strip 10 being affected by other factors and having to reduce the rolling speed, the cooling time would increase, causing the temperature of steel strip 10 to be lower than the ductile-brittle transition temperature when it arrives at the entrance of the cold rolling mill 20, thus causing production abnormalities of steel strip 10. Therefore, the present invention uses an automatic temperature control mode to solve this production abnormality problem.

[0025] Referring to Figures 3 and 4, the method for producing cold-rolled steel strip using automatic temperature control includes the following steps: Step S1: Set the initial steel strip speed (V0), where the initial steel strip speed (V0) is the speed at which the heating point of the steel strip 10 passes through the induction heating device 30; Step S2: Calculate the maximum cooling time (T) using formula (1); …Formula (1), where t1 is the time (s) required for the initial strip speed (V0) to decrease to the minimum rolling speed; t2 is the rolling time at the minimum rolling speed (s); V0 is the initial strip speed (mpm); Vmin is the minimum rolling speed (mpm); L is the distance (m) between the induction heating device 30 and the cold rolling mill 20 of the first station; and a is the decreasing rate (m / s2). Step S3: Use formula (2) to perform n iterations to calculate the target heating temperature (TIH(n)) at point 30 of the induction heating device; …Formula (2), where TIH(n) is the target heating temperature (°C) at the induction heating device 30, TIH(0) is the target temperature at the mill inlet (°C); Ta is the ambient temperature (°C); h is the heat transfer coefficient of the steel strip 10 (W / m2C); L is the distance (m) between the induction heating device 30 and the cold rolling mill 20 of the first station; n is the number of iterations; ρ is the density of the steel strip 10 (kg / m3); C is the specific heat of the steel strip 10 (J / kg°C); H is the thickness of the steel strip 10 (mm); V is the rolling speed of the steel strip 10 (mpm), and T is the maximum cooling time (s); and Step S4: According to the power conversion table provided by the supplier of the induction heating device 30, obtain the required output power, and use the induction heating device 30 to heat the steel strip 10 to obtain cold-rolled steel strip.

[0026] Referring to Figures 1 and 5, the constant power control mode is used during continuous cold rolling at the weld bead 90 at the overlap between the front strip 70 and the rear strip 80. Since the material properties of the weld bead 90 are affected by weld line characteristics and welding parameters, its strength and properties are influenced by these factors. Therefore, to improve the rollability of the weld bead 90, the target heating temperature of the weld bead 90 often needs to be higher than the mill entry target temperature of the strip (i.e., weld bead heating) to improve the toughness of the weld bead 90 and increase production safety margin. Furthermore, the heating power required for the front strip 70 and the rear strip 80 at the weld bead 90 varies depending on the strip size, steel grade, and target temperature. Therefore, this invention uses a constant power control mode to produce cold-rolled steel strip to avoid sudden power fluctuations and ensure the rollability of the weld bead 90.

[0027] Referring to Figures 5 and 6, the method for producing cold-rolled steel strip using a constant power control mode includes the following steps: Step S10: Based on the target heating temperature of weld 90 (which is equal to the mill inlet target temperature of the front strip 70 and the rear strip 80 respectively + weld temperature increase), calculate the target heating temperatures required by the induction heating device 30 for the front strip 70 and the rear strip 80 respectively. According to the power conversion table provided by the supplier of the induction heating device 30, obtain the required output power of the front strip 70 and the rear strip 80, and take the maximum value of the two required output powers as Pmax. Step S20: When the safe length SL of the front steel strip 70 from the weld bead 90 passes the induction heating device 30, the temperature control strategy is switched from automatic temperature control mode to constant power control mode. That is, when the front steel strip 70 is in automatic temperature control mode, the output power P1 of the induction heating device 30 is increased to Pmax by a set rate of change a, and heating is performed at a constant power Pmax in the section between the safe length SL of the front steel strip 70 and the safe length SL of the rear steel strip 80; and Step S30: After the steel strip 80 passes through the induction heating device 30 at a safe length SL from the weld bead 90, the temperature control strategy is switched from constant power control mode to automatic temperature control mode. That is, the output power of the induction heating device 30 is gradually reduced from Pmax to the output power P2 of the induction heating device 30 through a set change rate b, so as to obtain cold-rolled steel strip.

[0028] The method of producing cold-rolled steel strip by means of constant power control mode can ensure that the safe lengths SL of weld 90, front steel strip 70 and rear steel strip 80 are heated by output power from Pmax, and when weld 90, front steel strip 70 and rear steel strip 80 enter the cold rolling mill 20, the temperature of weld 90, front steel strip 70 and rear steel strip 80 is higher than or equal to the mill inlet target temperature of weld 90.

[0029] Referring to Figure 2, the constant temperature control mode is used during the initial rolling stage when restarting the cold rolling process after the cold rolling mill has stopped operating. Since the temperature of the production line equipment, such as the drive rolls or rolling mill rolls, gradually decreases after shutdown, this invention uses a constant temperature control mode during the initial rolling stage to prevent excessive temperature drops in the steel strip during the threading and initial rolling processes, which could affect production stability. This constant temperature control mode uses the upper limit of the production line equipment's tolerable temperature as the target heating temperature. This method of producing cold-rolled steel strip using the constant temperature control mode not only increases the safety margin of the steel strip temperature, preventing it from falling below the brittle transition temperature, but also allows for mill warm-up operations, improving production stability and strip shape quality.

[0030] When the rolling speed in the initial rolling stage exceeds the minimum production speed limit (i.e., the low speed limit shown in Figure 2), the temperature control strategy is switched from constant temperature control mode to automatic temperature control mode, and heating is performed according to the heating target temperature at the induction heating device to avoid overheating and additional production costs.

[0031] The following examples are for producing cold-rolled steel strip on a continuous rolling production line.

[0032] Example: A method for producing cold-rolled steel strip using a temperature control strategy includes: Step 1: Under normal rolling conditions, cold rolling of the steel strip is performed using an automatic temperature control mode. In this step, based on the steel grade and size of the steel strip used, the target temperature at the mill inlet is set to 145℃ and the steel strip moving speed is set to 50 mpm. The maximum cooling time (T) is calculated using formula (1) to be 23.98 s. …Formula (1), where: t1 is the time (s) required for the initial strip speed (V0) to decrease to the minimum rolling speed; t2 is the rolling time (s) at the minimum rolling speed; V0 is the initial speed of the steel belt (m), V0 = 50 mpm; Vmin is the minimum rolling speed (mpm), Vmin = 45 mpm; L is the distance (m) between the induction heating device and the cold rolling mill at the first station, L = 18 m, and a is the rate of descent (m / s²), a = 15 m / s²; Step 2: Calculate the target heating temperature (TIH(n)) at the induction heating device using formula (2) = 154℃. …Formula (2), where: TIH(0) is the target temperature at the mill inlet (°C), TIH(0) = 145°C; Ta represents the ambient temperature (°C), where Ta = 50°C; h is the heat transfer coefficient of the steel strip (W / m2C), h=28 W / m2C; L is the distance (m) between the induction heating device and the cold rolling mill at the first station, L = 18 m; n represents the number of iterations, n=10; ρ is the density of the steel strip (kg / m3), ρ = 7650 kg / m3; C is the specific heat of the steel strip (J / kg℃), C = 500 J / kg℃; and H is the thickness of the steel strip (mm), H = 3.8 mm; Step 3: According to the power conversion table provided by the supplier of the induction heating device, the required output power is 24%. The steel strip is heated according to this required output power of 24%. Referring to section A in Figure 7, the results show that after the steel strip passes through the induction heating device, the heating outlet temperature measured by the heating outlet thermometer is approximately 152°C, and the steel strip temperature at the mill inlet can be maintained at approximately 147°C. Step 4: When the steel strip 6 meters before and after the weld bead (i.e., the safe distances between the front and rear steel strips and the weld bead are each 6 meters) enter the induction heating device, switch the temperature control strategy from automatic temperature control mode to constant power control mode, and the heating range of the weld bead is 10℃, that is, the target temperature at the mill inlet is increased from 145℃ to 155℃. Based on this, according to the power conversion table provided by the supplier of the induction heating device, obtain the required output power of the front and rear steel strips, and take the maximum value of the two required output powers, Pmax = 27%, as shown in section B of Figure 7. Increase the output power of the induction heating device from 24% to 27%, and the temperature of the steel strip at the outlet of the induction heating device can be increased from 152℃ to 170℃ (see section D of Figure 7), so that the temperature of this weld bead section when it moves to the mill inlet can reach 155℃ (see section E of Figure 7); and Step 5: Referring to section C in Figure 7, as the speed of the steel strip entering the mill entrance increases, the production line system will automatically recalculate the target heating temperature and power required to ensure that the temperature of the steel strip at the mill entrance remains stable and meets the requirement of the mill entrance target temperature of 145°C under the condition of speed change.

[0033] As can be seen from the above, the method of producing cold-rolled steel strip using temperature control strategy of the present invention, through temperature control strategies of automatic temperature control mode, constant power control mode and constant temperature control mode, can calculate the most suitable heating target temperature of steel strip in induction heating device and the temperature at which steel strip moves to cold rolling mill for rolling, thereby ensuring that the temperature of steel strip during rolling process is higher than the temperature required for stable production of steel strip, ensuring the stability of steel strip production, and avoiding the problem of increased production cost due to overheating of steel strip.

[0034] The above embodiments are merely illustrative of the method for producing cold-rolled steel strip using temperature control strategies according to the present invention, and are not intended to limit the invention. Anyone skilled in the art can make modifications and alterations to the above embodiments without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be as set forth in the following claims.

[0035] 10: Steel strip 20: Cold rolling mill 30: Induction heating device 40: Heating outlet thermometer 50: Coil machine 60: Rolling mill inlet temperature gauge 70: Front steel belt 80: Rear steel belt 90: Weld bead a: Rate of change b: Rate of change A: Section B: Section C: Section Section D E: Section L: Distance P1: Power P2: Power Pmax: Power SL: Safety Length t1: Time t2: Time S1: Steps S2: Steps S3: Steps S4: Steps S10: Steps S20: Steps S30: Steps

Claims

1. A method for producing cold-rolled steel strip using a temperature control strategy, wherein the temperature control strategy includes an automatic temperature control mode and a constant power control mode, and the steps for producing the cold-rolled steel strip through the automatic temperature control mode include: Step 1: Based on the steel grade and size of the steel strip, set the initial steel strip speed, minimum rolling speed, and target temperature at the mill inlet. Calculate the maximum cooling time from the heating device to the first cold rolling mill and the target heating temperature at the heating device based on these parameters. The initial steel strip speed is the speed at which the heating point of the steel strip passes through the heating device, and the minimum rolling speed is the minimum speed at which the steel strip undergoes cold rolling. Step 2: Based on the power conversion table provided by the supplier of the heating device and the target heating temperature at the heating device, obtain the required output power and use the heating device to heat the steel strip. The steps for producing the cold-rolled steel strip through this constant power control mode include: Step 10: Calculate the target heating temperatures required by the heating device for the front and rear steel strips based on the target heating temperature of the weld bead, and obtain the required first output power of the front steel strip and the required second output power of the rear steel strip according to the power conversion table, and take the maximum value of the required first output power of the front steel strip and the required second output power of the rear steel strip as Pmax; Step 20: When the front steel strip passes the heating device at a safe distance from the weld bead, the temperature control strategy is switched from the automatic temperature control mode to the constant power control mode. That is, in the automatic temperature control mode, the output power of the heating device is increased from the first output power to Pmax, and the section between the safe length of the front steel strip and the safe length of the rear steel strip is heated at a constant power of Pmax. Step 30: After the rear steel strip passes the heating device at a safe distance from the weld bead, the temperature control strategy is switched from the constant power control mode to the automatic temperature control mode. That is, the output power of the heating device is reduced from Pmax to the second output power to obtain the cold-rolled steel strip.

2. The method as described in claim 1, wherein the maximum cooling time (T) from the heating device to the cold rolling mill of the first station is calculated using formula (1): where t1 is the time (s) required to reduce from the initial strip speed (V0) to the minimum rolling speed; t2 is the rolling time (s) at the minimum rolling speed; V0 is the initial strip speed (mpm); Vmin is the minimum rolling speed (mpm); L is the distance (m) between the heating device and the cold rolling mill of the first station, and a is the cooling rate (m / s2); and the target heating temperature at the heating device is calculated using formula (2). TIH(n) is obtained by performing n iterations of calculations, where TIH(n) is the target heating temperature (°C) at the heating device, TIH(0) is the target temperature at the mill inlet (°C), Ta is the ambient temperature (°C), h is the heat transfer coefficient of the steel strip (W / m2C), L is the distance (m) between the heating device and the cold rolling mill of the first station, n is the number of iterations, ρ is the density of the steel strip (kg / m3), C is the specific heat of the steel strip (J / kg°C), H is the thickness of the steel strip (mm), V is the rolling speed of the steel strip (mpm), and T is the maximum cooling time (s).

3. The method as described in claim 1, wherein the automatic temperature control mode is used during the production stage of the cold rolling process of the steel strip.

4. The method as described in claim 1, wherein the constant power control mode is used for the weld bead at the overlap between the front strip and the rear strip during continuous cold rolling.

5. The method as described in claim 1, wherein the temperature control strategy further includes a constant temperature control mode, which is used when the cold rolling mill is restarted after it has stopped operating, during the initial rolling stage; when the rolling speed during the initial rolling stage exceeds the minimum production speed limit, the temperature control strategy is switched from the constant temperature control mode to the automatic temperature control mode.

6. The method as described in claim 5, wherein the constant temperature control mode is based on the upper limit of the tolerable temperature of the production line equipment for producing the cold-rolled steel strip as the heating target temperature of the constant temperature control mode.

7. The method as claimed in claim 1, wherein in step 20, the output power of the heating device is gradually increased to Pmax by setting a first rate of change, and in step 30, the output power of the heating device is gradually decreased to the second output power of the heating device by setting a second rate of change, wherein Pmax is gradually decreased to the second output power of the heating device.

8. The method as described in claim 1, wherein the heating device includes an induction heating device, a hot air heater, or a tunnel furnace.

9. The method as described in claim 1, wherein the method is used for a continuous rolling mill or a reciprocating single rolling mill.

10. The method as described in claim 1, wherein the steel strip is a brittle steel strip.

Images