Cold rolling method and cold rolling equipment

Abstract

The cold rolling method includes a measurement step, a gain setting step, and a control step. The measurement step measures the shape of the steel sheet exiting the cold rolling mill. The gain setting step sets a control gain based on the shape of the steel sheet measured in the measurement step. The control step controls the cold rolling mill according to the control gain. In the gain setting step, a first control gain GCx, set as the control gain when the diameter of the work roll is greater than 75 mm, and a second control gain GCy, set as the control gain when the diameter is less than 75 mm, satisfy the relationship GCy - GCx > 0.

Description

Technical Field

[0001] This invention relates to a cold rolling method and a cold rolling apparatus. Prior Technology

[0002] A typical multi-stage rolling mill includes work rolls for rolling steel sheets, intermediate rolls that support the work rolls, and actuators that control the movement of the intermediate rolls. The operating range of the actuators is determined according to a specified control gain.

[0003] As a cold rolling method using this type of rolling mill, Patent Document 1 discloses a method that measures the shape of the steel sheet at the exit side of the rolling mill and performs feedback control on the rolling mill based on the measurement result to reflect the control gain, thereby keeping the shape of the steel sheet within the allowable range of the target shape. This suppresses breakage of the steel sheet. [Existing Technical Documents] [Patent Literature]

[0004] [Patent Document 1] International Publication No. 2021 / 192713 Summary of the Invention

[0005] [The problem that the invention aims to solve] However, even when steel sheets are cold-rolled using the aforementioned cold rolling method, they sometimes still break. Therefore, the object of the present invention is to provide a cold rolling method and cold rolling apparatus that can suppress steel sheet breakage. [Methods for solving problems]

[0006] To achieve the stated objective, the cold rolling method includes: a measurement step, measuring the shape of a steel sheet on the exit side of a cold rolling mill including work rolls; a gain setting step, setting a control gain based on the shape of the steel sheet measured in the measurement step; and a control step, controlling the cold rolling mill according to the control gain, wherein in the gain setting step, a first control gain GCx set as the control gain when the diameter of the work roll is greater than 75 mm and a second control gain GCy set as the control gain when the diameter is less than 75 mm satisfy the following equation (1) (first structure). GCy-GCx>0····(1)

[0007] The cold rolling method of the first structure can be configured such that the gain setting step includes: a derivation step, which derives the conformity rate between the shape of the steel plate measured in the measurement step and the multiple shape deviation patterns respectively, corresponding to each shape deviation pattern; and a calculation step, which calculates the multiplication value obtained by multiplying the intermediate gain value set separately for each shape deviation pattern by the conformity rate of each shape deviation pattern, and sets the sum of the multiplication values ​​as the control gain (second structure).

[0008] The cold rolling method of the second structure can be configured such that, in the calculation step, when the diameter is greater than 75 mm, the absolute value of the negative intermediate gain value among the intermediate gain values ​​is less than that when the diameter is less than 75 mm (third structure).

[0009] The cold rolling method of the third structure can be configured such that, in the calculation step, when reducing the absolute value of the negative intermediate gain value, it is set to be more than 1 / 10 and less than 3 / 5 of the original absolute value of the intermediate gain value (fourth structure).

[0010] The cold rolling method for any of the second to fourth structures can be configured such that, in the calculation step, when the diameter is greater than 75 mm, the absolute value of the positive intermediate gain value among the intermediate gain values ​​is greater than that when the diameter is less than 75 mm (fifth structure).

[0011] The cold rolling method of any of the first to fifth structures can be configured to include a detection step for detecting the diameter (sixth structure).

[0012] The cold rolling apparatus disclosed in the specification includes: a rolling section having a pair of work rolls for cold rolling steel sheets by means of the work rolls against each other; a measuring section for measuring the shape of the steel sheet at the exit side of the rolling section; and a control section for setting a control gain based on the shape of the steel sheet measured in the measuring section, and controlling the rolling section according to the control gain. The control gain is configured such that a first control gain GCx set as the control gain when the diameter of the work rolls is greater than 75 mm and a second control gain GCy set as the control gain when the diameter is less than 75 mm satisfy the following equation (2) (seventh structure). GCy-GCx>0····(2) [The effects of the invention]

[0013] According to the present invention, a cold rolling method and cold rolling apparatus that can suppress the fracture of steel plates can be provided. Simple Explanation of the Diagram

[0014] Figure 1 is a chart showing the target shape and actual shape of the steel plate when the diameter of the work roll is less than 75 mm. Figure 2 is a chart showing the target shape and actual shape of the steel plate when the diameter of the work roll is greater than 75 mm. Figure 3 is a diagram showing the cold rolling unit 1. Figure 4 is a plan view of the working roll 6 and the intermediate roll 8 viewed from the front. Figure 5 is a block diagram showing the structure of the control unit 5. Figure 6 is a flowchart illustrating the steps of the cold rolling process. Figure 7 is a flowchart showing the measurement procedure St1 in detail. Figure 8 is a flowchart showing the gain setting steps St2 in detail. Figure 9 is a diagram showing the actual shape and target shape of the steel sheet 20 rolled by the cold rolling method of the comparative example. Figure 10 is a diagram showing the actual shape and target shape of the steel sheet 20 rolled by the cold rolling method of the present invention. Figure 11 is a graph showing the breakage rate for each correction value when rolling steel plate 20 by changing the magnitude of each correction value when implementing gain correction. Figure 12 is a modified example of the cold rolling apparatus 1 according to the structure of the present invention. Implementation

[0015] <Research on the Fracture of Steel Plates> First, the process by which the inventors achieved this invention will be explained. In conventional cold rolling methods, the shape of the steel sheet is measured at the exit side of the rolling mill, and the cold rolling mill is controlled to provide feedback on the measurement result. In this feedback control, when the deviation of the actual shape of the steel sheet from the target shape reaches or exceeds a predetermined value, the actuator (actuator 10 described later) is activated to bring the steel sheet closer to the target shape.

[0016] This feedback control employs a so-called neural-fuzzy control method. Furthermore, this feedback control utilizes control gain, which represents the actuator's operating input. The control gain value can be set, for example, from +1000 to -1000. The larger the absolute value of the control gain, the more agile the actuator's operation. Moreover, the positive or negative value of the control gain indicates the actuator's operating direction. When the control gain is positive, the actuator operates in an elongated shape, like a steel plate. Conversely, when the control gain is negative, the actuator operates in a widened shape, like a steel plate.

[0017] However, even with this type of feedback control using the control gain, the steel sheet can still sometimes break depending on the condition of the work rolls mounted on the rolling mill. Therefore, the inventors conducted a thorough investigation into the causes of steel sheet breakage.

[0018] The investigation confirmed that in cases where steel plate fracture occurred, the worn work rolls (work rolls that had been used for a specified period) were replaced with new work rolls (work rolls that were not yet worn). In particular, steel plate fractures occurred relatively frequently after work rolls with a diameter worn to less than 75 mm were replaced with new work rolls with a diameter exceeding 75 mm. Furthermore, the outer circumference of the work rolls is ground after rolling in preparation for the next rolling operation. The diameter of the work rolls (hereinafter referred to as "work roll diameter") is measured by the operator or an automatic measuring device during this grinding operation.

[0019] Based on the above, the inventors further investigated the differences in the shape of the steel plate when the working roll diameter is greater than 75 mm versus less than 75 mm. Figures 1 and 2 are used to illustrate the findings.

[0020] Figure 1 is a graph showing the target and actual shapes of the steel plate when the diameter of the work roll is less than 75 mm. Figure 2 is a graph showing the target and actual shapes of the steel plate when the diameter of the work roll is greater than 75 mm. In Figures 1 and 2, the vertical axis uses I-UNIT units to represent the target and actual shapes. Furthermore, in Figures 1 and 2, the operator's side is further to the left of the center of the horizontal axis, and the drive side is further to the right of the center of the horizontal axis.

[0021] I-Unit is a numerical value used to represent the elongation of a steel plate with a positive value and the widening of the steel plate with a negative value. I-Unit is calculated by multiplying the expansion rate Δε by a specified coefficient (=105).

[0022] The expansion rate Δε is defined by the following formula (1). In formula (1), l refers to the reference length of the interval when the steel plate is divided by a specified length. Moreover, Δl refers to the expansion difference within the interval (= the difference relative to the reference length l).

[0023] [Number 1]

[0024] As shown in Figures 1 and 2, the target shape of the steel plate is set such that the edge portion in the width direction is widened, and the middle portion between the edge portion and the center portion is elongated. With this shape distribution, the shape deviation in the width direction is small, and the steel plate is difficult to break. Furthermore, the middle portion between the edge portion and the center portion will be referred to as the "quarter portion" below.

[0025] Here, as shown in Figure 1, when the diameter of the work roll is 75 mm or less, the actual shape of the steel plate follows the target shape. That is, at this time, the actual shape of the steel plate is that the edge is widened and the quarter is elongated. Therefore, when the diameter of the work roll is 75 mm or less, the steel plate is relatively difficult to break.

[0026] On the other hand, as shown in Figure 2, when the diameter of the work roll is greater than 75 mm, the actual shape of the steel plate tends to differ from the target shape in a relatively wide area (shape deviation). In particular, the quarter section on the operator's side has a relatively large elongated shape, which differs greatly from the target shape.

[0027] If this shape distribution occurs, the cold rolling mill executes the feedback control after setting the control gain to eliminate the shape deviation. However, for portions other than those with shape deviation, the actuator operation becomes excessive, leading to shape collapse of the steel sheet. In the case shown in Figure 2, the actuator operates to set the steel sheet 20 into a widened shape. This promotes the elongation of the quarter section, causing shape collapse of the steel sheet. As a result, the steel sheet becomes prone to breakage. Based on the investigation results described above, the inventors have concluded that when the work roll diameter is greater than 75 mm, excessive control of the actuator (hereinafter referred to as "over-control") causes steel sheet breakage.

[0028] Therefore, the inventors set the diameter of the work roll, which is prone to shape collapse of the steel sheet, to 75 mm. Furthermore, in this invention, when the diameter of the work roll during rolling is greater than 75 mm, the control gain is made less than when the diameter of the work roll is less than 75 mm. This suppresses over-control of the actuator as described above without requiring equipment maintenance. Therefore, the cold rolling method according to this invention suppresses both increased costs and steel sheet breakage caused by shape collapse, thereby enabling stable steel sheet rolling.

[0029] <About the embodiments of the present invention> Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, the structure of the cold rolling apparatus 1 used in the cold rolling method of the present invention will be described. Then, the cold rolling method of the present invention will be described.

[0030] <Regarding the cold rolling apparatus 1 of the first embodiment> First, the cold rolling apparatus 1 of the first embodiment will be described. Figure 3 is a diagram showing the cold rolling apparatus 1. As shown in Figure 3, the cold rolling apparatus 1 is configured to perform reversible cold rolling on the steel sheet 20. The steel sheet 20 is wound on the reel 21 and the reel 22.

[0031] Reels 21 and 22 are rotatably supported. Steel plate 20 is fed from one reel 21 to the other along the direction of rotation of reels 21 and 22. For example, referring to Figure 1, when reels 21 and 22 rotate clockwise, steel plate 20 is fed from reel 21 to reel 22. Conversely, when reels 21 and 22 rotate counterclockwise, steel plate 20 is wound back from reel 22 to reel 21.

[0032] Hereinafter, the direction in which the steel plate 20 is fed from the reel 21 to the reel 22 (along the direction of arrow X shown in Figure 3) will be referred to as "forward".

[0033] The cold rolling unit 1 includes a rolling section 3, a measuring section 4, a control section 5, and a roll diameter input device 18. The rolling section 3 is a multi-stage rolling mill with a single rolling table. The detailed structure of the rolling section 3 is as follows.

[0034] <Regarding Rolling Section 3> As shown in Figure 3, the rolling section 3 includes a pair of work rolls 6, a pair of intermediate rolls 8, a pair of support rolls 9, and a pair of actuators 10. The rolling section 3 is a rolling mill of the so-called roll displacement method, in which the intermediate rolls 8 slide axially to control the shape of the steel plate 20 while performing cold rolling.

[0035] A pair of work rolls 6 sandwich the steel plate 20 in the middle and roll the steel plate 20. Work rolls 6 are generally used with a diameter R (hereinafter also simply referred to as "work roll diameter R") of 65 mm or more and 85 mm or less. The work rolls 6 are supported by an intermediate roll 8 and a support roll 9. Specifically, the outer peripheral surface of the work roll 6 contacts the outer peripheral surface of the intermediate roll 8. Furthermore, the outer peripheral surface of the intermediate roll 8 also contacts the outer peripheral surface of the support roll 9.

[0036] Figure 4 is a plan view of the work roll 6 and the intermediate roll 8 viewed from a forward direction. As shown in Figure 4, the intermediate roll 8 has a flat portion 12 and a tapered portion 13. The flat portion 12 is rod-shaped with a fixed outer diameter. The tapered portion 13 is connected to one axial end of the flat portion 12. The tapered portion 13 is tapered at its front end, with its outer diameter decreasing as it moves away from the flat portion 12.

[0037] The intermediate roll 8 is supported in a manner that allows it to move axially. The rolling section 3 controls the shape of the steel plate 20 by moving the intermediate roll 8 axially.

[0038] The actuator 10 is mechanically connected to the intermediate roller 8 in a manner that allows the intermediate roller 8 to move axially. Furthermore, the actuator 10 is electrically connected to the control unit 5, which will be described later, via a wired or wireless communication path.

[0039] The actuator 10 receives control command S1 (details will be described later) from the control unit 5 and moves the intermediate roller 8 axially according to the control command S1. The control command S1 is an electrical signal transmitted via the communication path between the actuator 10 and the control unit 5. The operation of the actuator 10 becomes more agile as the value of the control gain GC contained in the control command S1 increases. The specific structure of the actuator 10 is as follows.

[0040] As shown in Figure 4, the actuator 10 includes a drive unit 14 and a lever unit 15. The drive unit 14 is a power source such as a motor. The drive unit 14 generates power corresponding to the control command S1. The drive unit 14 transmits the power to the lever unit 15. The lever unit 15 is connected to the intermediate roller 8. Based on the power transmitted from the drive unit 14, the lever unit 15 causes the intermediate roller 8 to move parallel to the axial direction of the work roller 6.

[0041] As the control gain GC increases, the actuator 10 operates more nimbly. Specifically, as the control gain GC increases, the intermediate roll 8 moves more nimbly. The more nimbly the intermediate roll 8 moves, the stronger the shape control of the steel sheet 20 during rolling becomes. Details regarding the control gain GC will be described later.

[0042] <Regarding Measurement Section 4> Referring back to Figure 3, the measuring unit 4 is positioned on the exit side of the rolling section 3 in the forward direction (more specifically, on the downstream side relative to the work roll 6). The measuring unit 4 is configured to measure the shape of the steel plate 20 that has passed through the rolling section 3. Specifically, as follows.

[0043] The measuring unit 4 measures the shape of the steel plate 20 along the width direction after it has passed through the rolling unit 3. The measuring unit 4 may be, for example, a contact-type shape measuring device that measures the shape by bringing the dividing roller into contact with the steel plate 20.

[0044] The measuring unit 4 is electrically connected to the control unit 5 via a wired or wireless communication path. The measuring unit 4 receives control command S2 from the control unit 5 via this communication path to measure the shape of the steel plate 20. The control command S2 is an electrical signal transmitted via the communication path between the measuring unit 4 and the control unit 5. The measuring unit 4 sends the actual shape data S3 obtained from measuring the shape of the steel plate 20 to the control unit 5.

[0045] <About Control Department 5> The control unit 5 is a computer or other computing processing device. The control unit 5 receives input of actual shape data S3 and generates control commands S1. The control commands S1 include a control gain GC corresponding to the actual shape data S3. The detailed structure of the control unit 5 is as follows.

[0046] Figure 5 is a block diagram showing the structure of the control unit 5. As shown in Figure 5, the control unit 5 includes multiple interfaces I / F, a pattern storage unit 16, and a control unit 17.

[0047] The pattern storage unit 16 is a memory area that stores prescribed data. The pattern storage unit 16 stores pre-defined shape deviation patterns P1 to Pn (n is any natural number). The shape deviation patterns P1 to Pn are patterns that classify the deviations of the actual shape of the steel plate 20 from the target shape.

[0048] Each of the shape deviation patterns P1 to Pn has a separate intermediate gain value GV1 to GVn. The intermediate gain values ​​GV1 to GVn (where n is an arbitrary natural number) are stored in the pattern storage unit 16 according to their respective states related to the shape deviation patterns P1 to Pn. Some intermediate gain values ​​GV1 to GVn are set to positive values, while others are set to negative values.

[0049] The control unit 17 is the central processing unit (CPU) of the control unit 5. The control unit 17 comprehensively controls the actuator 10 and the measuring unit 4. The control unit 17 is connected to the measuring unit 4, the actuator 10, and the roller diameter input device 18 via separate interfaces I / F. Furthermore, the control unit 17 is configured to access the pattern storage unit 16.

[0050] The control unit 17 sends a control command S2 to the measurement unit 4 at any time.

[0051] The control unit 17 derives the conformity rates FV1 to FVn based on the actual shape data S3 transmitted by the self-measurement unit 4. The conformity rates FV1 to FVn are ratios representing the degree of conformity of the actual shape data S3 with respect to each of the shape deviation patterns P1 to Pn. The control unit 17 accesses the pattern storage unit 16 and individually compares the shape deviation patterns P1 to Pn with the actual shape data S3 to derive the conformity rates FV1 to FVn.

[0052] The control gain GC is calculated by formula (2) based on the intermediate gain value GV1 ~ intermediate gain value GVn and the compliance rate FV1 ~ compliance rate FVn.

[0053] [Number 2]

[0054] The control unit 17 generates a control command S1 that includes a control gain GC and inputs it to the actuator 10. In other words, the control unit 17 controls the operation of the actuator 10 by means of the control command S1. When the control gain GC is positive, the actuator 10 is controlled to make the steel plate 20 elongated. Conversely, when the control gain GC is negative, the actuator 10 operates to make the steel plate 20 approach a widened shape.

[0055] The roller diameter input device 18 is a device that inputs the work roller diameter R to the control unit 5 (more specifically, the control unit 17). The work roller diameter R is input from the roller diameter input device 18 to the control unit 17 via the interface I / F. Furthermore, the input work roller diameter R is either a measured value determined during the grinding operation of the work roller or an estimated value derived by calculation.

[0056] <Correction of intermediate gain values ​​GV1 to GVn> The control unit 17 is configured to perform gain correction at any time. Gain correction refers to the control of adjusting the intermediate gain values ​​GV1 to GVn using the configuration described later. When gain correction is performed, the control gain GC is calculated using the corrected intermediate gain values ​​GV1 to GVn according to equation (2). The control unit 17 performs gain correction when the input value of the working roll diameter R is greater than 75 mm.

[0057] When performing gain correction, the control unit 17 corrects the negative values ​​among the intermediate gain values ​​GV1 to GVn. More specifically, the absolute values ​​of the negative intermediate gain values ​​GV1 to GVn are corrected to be smaller than before the correction. Preferably, the absolute values ​​of the intermediate gain values ​​GV1 to GVn are corrected to be more than 1 / 10 and less than 3 / 5 (more preferably more than 1 / 5 and less than 1 / 2) compared to before the correction.

[0058] The correction is to add a specified correction value to the negative intermediate gain values ​​GV1 to GVn, which are the objects of the correction. Specifically, it is as follows.

[0059] For example, the intermediate gain value GV12 is preset to -500. In this case, when gain correction is performed, the intermediate gain value GV12 is increased by the correction value (+400) to become -100. Furthermore, when calculating the control gain GC using the aforementioned equation (2), the intermediate gain value GV12 is set to -100 for processing.

[0060] Therefore, when gain correction is performed, the control gain GC tends to become positive compared to the normal state. That is, when gain correction is performed, the operation of actuator 10 tends to be an action that sets the steel plate 20 into an elongated shape.

[0061] Furthermore, when gain correction is performed, even if the control gain GC is negative, the absolute value of the control gain GC is small. That is, when gain correction is performed, even if the control gain GC is negative, the operation of actuator 10 can be prevented from becoming abrupt.

[0062] As described above, the control unit 17 performs gain correction when the work roll diameter R is greater than 75 mm. Therefore, when the work roll diameter R is greater than 75 mm, the actuator 10 operates to elongate the steel plate 20, or operates slowly to widen the steel plate 20. This suppresses the tendency for the steel plate 20 to elongate from its quarter section to its edge. Consequently, when the work roll diameter R is greater than 75 mm, breakage of the steel plate 20 is suppressed.

[0063] Furthermore, as described above, each correction value is preferably set to a value where the absolute value of the negative intermediate gain values ​​GV1 to GVn, which are the targets of correction, is more than 1 / 10 and less than 3 / 5 compared to before correction. This better suppresses over-control of the actuator 10. More preferably, each correction value is set to a value where the absolute value of the negative intermediate gain values ​​GV1 to GVn, which are the targets of correction, is more than 1 / 5 and less than 1 / 2 compared to before correction. This further better suppresses over-control of the actuator 10.

[0064] Furthermore, regarding the control gain GC, the control gain GC set when the working roll diameter R is greater than 75 mm (= control gain GC with gain correction performed) is set as the first control gain GCx. Moreover, the control gain GC set when the working roll diameter is less than 75 mm (= control gain GC without gain correction performed) is set as the second control gain GCy. Thus, the following relationship holds for the first control gain GCx and the second control gain GCy:

[0065] [Number 3] GCy-GCx>0

[0066] <Regarding the cold rolling apparatus 1 of the second embodiment> Next, the cold rolling apparatus 1 of the second embodiment will be described. Furthermore, the cold rolling apparatus 1 of this embodiment is basically the same in structure as that of the first embodiment. Therefore, only the structure different from that of the first embodiment will be described here.

[0067] In this embodiment, the generalizing unit 17 corrects the positive values ​​among the intermediate gain values ​​GV1 to GVn when performing gain correction. More specifically, the absolute values ​​of the positive intermediate gain values ​​GV1 to GVn that are subject to correction are corrected to be larger than before the correction. Similar to the first embodiment, this correction is performed by adding a positive correction value to the intermediate gain values ​​GV1 to GVn that are subject to correction.

[0068] For example, the intermediate gain value GV6 is preset to +200. In this case, when gain correction is performed, the intermediate gain value GV6 is increased by the correction value (+300) to become +500. Furthermore, when calculating the control gain GC using the aforementioned formula (2), the intermediate gain value GV6 is set to +500 for processing. Therefore, in the cold rolling apparatus 1 of this embodiment, when gain correction is performed, the control gain GC is more likely to become a positive value. Moreover, in the cold rolling apparatus 1 of this embodiment, even if the control gain GC is negative when gain correction is performed, the absolute value of the control gain GC will become smaller.

[0069] Furthermore, when performing gain correction, the generalizing part 17 of this embodiment can also correct the negative values ​​among the intermediate gain values ​​GV1 to GVn in the same way as in the first embodiment, or it can choose not to correct the negative values. Moreover, the relationship of the above equation (3) holds true in both cases.

[0070] <About Cold Rolling Methods> The cold rolling method of the present invention will now be described. Figure 6 is a flowchart showing the steps of the cold rolling method. Figure 7 is a flowchart showing the measurement step St1 in detail. Figure 8 is a flowchart showing the gain setting step St2 in detail. First, the overall cold rolling method of the present invention will be described along the steps in Figure 6. Next, the details of the measurement step St1 will be explained using Figure 7. Subsequently, the details of the gain setting step will be explained using Figure 8.

[0071] As shown in Figure 6, the cold rolling method using the cold rolling apparatus 1 includes a measurement step St1, a gain setting step St2, and a control step St3. When the series of cold rolling operations begins, the shape of the cold-rolled steel sheet 20 is first measured using the measurement step St1. Then, using the gain setting step St2, a control gain GC is set based on the actual shape data S3 of the steel sheet 20 obtained in the measurement step St1. Next, using the control step St3, the actuator is controlled based on the control gain GC set in the gain setting step St2, while the steel sheet 20 is cold-rolled. The cold rolling of the steel sheet 20 is then terminated at any time. Furthermore, a grinding operation is subsequently performed on the work roll 6 in preparation for the next rolling. This grinding operation includes a detection step that measures or calculates a predicted value of the work roll diameter R.

[0072] As shown in Figure 7, in measurement step St1, the control unit 5 first sends a control command S2 to the measurement unit 4 (step St11). Next, the measurement unit 4 receives the input of the control command S2 and measures the shape of the steel plate 20 on the exit side of the rolling section 3 (step St12). Then, the measurement unit 4 sends its measurement result, i.e., the actual shape data S3, to the control unit 5 (step St13). Subsequently, the process moves to the gain setting step St2.

[0073] In the gain setting step St2, as shown in Figure 8, firstly, the control unit 5 derives the compliance rates FV1 to FVn based on the input actual shape data S3 (deriving step St21). Next, the control unit 5 determines whether the work roll diameter R is 75 mm or less (step St22).

[0074] When the working roll diameter R is 75 mm or less (yes in step St22), the control unit 5 calculates the multiplicative values ​​MV1 to MVn without performing the gain correction (step St23). When the working roll diameter R is greater than 75 mm (no in step St22), the control unit 5 performs the gain correction (step St24), calculating the multiplicative values ​​MV1 to MVn using the corrected intermediate gain values ​​GV1 to GVn (step St23). Subsequently, the control unit 5 calculates the sum of the multiplicative values ​​MV1 to MVn and sets this calculation result as the control gain GC (step St25).

[0075] Furthermore, steps St23 and St25 can also be considered as a single "operation step". Moreover, the gain correction performed in step St24 can be either the gain correction of the first embodiment or the gain correction of the second embodiment.

[0076] As described above, in the gain setting step St2, gain correction is performed when the work roll diameter R is greater than 75 mm. Therefore, according to the cold rolling method of the present invention, when the work roll diameter R is greater than 75 mm, the actuator 10 can be prevented from falling into over-control, thereby preventing the steel sheet 20 from breaking.

[0077] The cold rolling method of the present invention will be specifically illustrated using examples below. [Example]

[0078] The difference in control gain GC between the conventional cold rolling method without gain correction (comparative example) and the cold rolling method of the present invention with gain correction was evaluated. Furthermore, the actual shape of the steel sheet 20 rolled by the cold rolling method of the comparative example was compared and evaluated with the actual shape of the steel sheet 20 rolled by the cold rolling method of the present invention. Furthermore, the correction value when gain correction was performed was changed to verify a better correction value.

[0079] Furthermore, in both the comparative example and the present invention, work rolls with a diameter R greater than 75 mm are used for cold rolling. Also, in both the comparative example and the present invention, the intermediate gain values ​​GV6, GV7, and GV8 are set to +200, GV12 and GV14 are set to -500. Moreover, the gain correction of the second embodiment is performed here.

[0080] Table 1 shows the shape deviation pattern Pn, detection shape, intermediate gain value GVn, compliance rate FVn, and multiplication value of the comparative examples. Table 1 prioritizes those with compliance rates greater than 0%.

[0081] [Table 1] Shape deviation pattern shape Intermediate gain value Compliance rate [%] Multiplication value P1 (omitted) (omitted) 0 0 P2 (omitted) (omitted) 0 0 P3 (omitted) (omitted) 0 0 … … … … … P6 OP side quarter elongation shape +200 60 +120 P7 DR side quarter elongation shape +200 40 +80 P8 The elongated shape of the OP side and DR side quarter section +200 80 +160 … … … … … P12 OP side edge elongation shape -500 100 -500 … … … … … P14 Elongated shape of the OP side and DR side edges -500 20 -100 … … … … … Pn (omitted) (omitted) 0 0

[0082] As shown in Table 1, the compliance rate FV12 (= compliance rate relative to shape deviation pattern P12) is 100%. Shape deviation pattern P12 is a pattern in which the operator-side edge of the steel plate 20 is elongated. Furthermore, the compliance rate FV14 (= compliance rate relative to shape deviation pattern P14) is 20%. Shape deviation pattern P14 is a pattern in which both the operator-side edge and the drive-side edge of the steel plate 20 are elongated.

[0083] Thus, it can be seen that when the diameter R of the work roll is greater than 75 mm, the edge of the steel plate 20 exhibits an elongated shape. The reason for this is as follows: When the diameter R of the work roll is relatively large, the load on the work roll 6 increases, and the tendency for the shape to widen is strong from the center of the steel plate 20 to its quarter-thickness. Due to this effect, it can be considered that the tendency for the shape to elongate is strong from the quarter-thickness of the steel plate 20 to its edge.

[0084] Because the tendency for the shape to elongate from the center to the edge is strong, the compliance rate of the intermediate gain values ​​GV1 to GVn that are set to negative values ​​is relatively high. Therefore, the control gain GC (the sum of multiplicative values ​​MV1 to MVn) of the comparative example is negative (-240). As a result, the actuator 10 operates to set the steel plate 20 into an extended shape. Thus, the actuator 10 will fall into the over-control state described above. Specifically, the actuator 10 operates such that the tendency for the shape to elongate from the center to the center of the steel plate 20 is strong. Therefore, through the operation of this actuator 10, the tendency for the shape to elongate from the center to the edge is even stronger.

[0085] The present invention will now be described. Table 2 is a table showing the shape deviation pattern Pn, detection shape, intermediate gain value GVn, compliance rate FVn, and multiplication value of the present invention. As described above, gain correction is performed in the cold rolling method of the present invention. In Table 2, regarding the corrected intermediate gain value, the root side of the arrow indicates the intermediate gain value before correction, and the tip side of the arrow indicates the intermediate gain value after correction.

[0086] [Table 2] Shape deviation pattern shape Intermediate gain value Compliance rate [%] Multiplication value P1 (omitted) (omitted) 0 0 P2 (omitted) (omitted) 0 0 P3 (omitted) (omitted) 0 0 … … … … … P6 OP side quarter elongation shape +200→+500 60 +300 P7 DR side quarter elongation shape +200→+500 40 +200 P8 The elongated shape of the OP side and DR side quarter section +200→+500 80 +400 … … … … … P12 OP side edge elongation shape -500→-100 100 -100 … … … … … P14 Elongated shape of the OP side and DR side edges -500→-100 20 -20 … … … … … Pn (omitted) (omitted) 0 0

[0087] The compliance rates FV1 to FVn are the same as in the comparative example. As shown in Table 2, positive correction values ​​were assigned to the intermediate gain values ​​GV1 to GVn. Therefore, the control gain GC of the present invention is +780. Thus, in the case of the present invention, the actuator 10 is controlled to set the steel plate into an elongated shape. Consequently, the tendency to widen the shape is weak from the center portion to the quarter portion of the steel plate 20, and the tendency to elongate the shape is difficult to promote from the quarter portion to the edge portion. That is, the over-controlling operation of the actuator 10 is suppressed.

[0088] Figure 9 is a diagram showing the actual shape and target shape of the steel sheet 20 rolled by the cold rolling method of the comparative example. In Figure 9, as in Figures 1 and 2, the operator's side is further to the left of the center in the horizontal axis direction, and the drive side is further to the right of the center.

[0089] As shown in Figure 9, when the steel sheet 20 is cold-rolled using the comparative example's cold rolling method, the actual shape of the steel sheet 20 deviates significantly from the target shape. Specifically, the actual shape of the steel sheet 20 from the quarter section to the edge (the inner portion enclosed by a dotted chain circle in Figure 9) on the drive side tends to elongate more than the target shape. With this shape distribution, as mentioned above, the steel sheet 20 is prone to breakage. The reason for this shape distribution is believed to be that the actuator 10 falls into over-control as described above.

[0090] Figure 10 is a diagram showing the actual shape and target shape of the steel sheet 20 rolled by the cold rolling method of the present invention. In Figure 10, similar to Figures 1 and 2, the operator side is further to the left of the center in the horizontal axis direction, and the drive side is further to the right of the center.

[0091] As shown in Figure 10, when the steel sheet 20 is cold-rolled using the cold rolling method of the present invention, the actual shape of the steel sheet 20 tends to be the same as the target shape. For example, the actual shape of the driving side of the steel sheet 20 from the quarter portion to the edge portion (the inner portion enclosed by the dotted chain circle in Figure 10) is similar to the target shape, tending to be approximately between an elongated shape and a widened shape. With this shape distribution, shape deviations are suppressed, and the steel sheet 20 is less likely to break. Thus, it has been confirmed that when the cold rolling method of the present invention is used, the breakage of the steel sheet 20 is suppressed.

[0092] Next, the correction values ​​for the gain correction were varied, and the breakage rate during continuous cold rolling was verified for each correction value. The verification results are shown in Figure 11. Figure 11 is a graph showing the breakage rate for each correction value when rolling steel sheet 20 by varying the magnitude of the correction values ​​when performing the gain correction. In Figure 11, the number of passes of steel sheet 20 is represented by a bar chart, and the breakage rate of steel sheet 20 is represented by a line graph.

[0093] Furthermore, the steel plate 20 in the comparative examples and present inventions 1 to 4 uses a steel plate with a thickness of 0.1 mm or more and 3.5 mm or less, and a width of 600 mm or more and 1300 mm or less. Moreover, in the comparative examples and present inventions 1 to 4, the rolling speed (rotation speed of the rolls 21 and 22) is set to 30 rpm or more and 2000 rpm or less for cold rolling. Furthermore, in the comparative examples and present inventions 1 to 4, cold rolling begins with a work roll diameter R greater than 75 mm.

[0094] Furthermore, in Invention 1, the correction value for gain correction is set to a value such that the absolute value of the negative intermediate gain values ​​GV1 to GVn, which are the targets of correction, is 3 / 5 times that before correction. In Invention 2, the correction value is set to a value such that the absolute value of the negative intermediate gain values ​​GV1 to GVn, which are the targets of correction, is 1 / 2 times that before correction. In Invention 3, the correction value is set to a value such that the absolute value of the negative intermediate gain values ​​GV1 to GVn, which are the targets of correction, is 1 / 5 times that before correction. In Invention 4, the correction value is set to a value such that the absolute value of the negative intermediate gain values ​​GV1 to GVn, which are the targets of correction, is 1 / 10 times that before correction.

[0095] As shown in Figure 11, the fracture rate of the comparative example is approximately 4.5%. In contrast, the fracture rate is lower than that of the comparative example in all of the present inventions 1 to 4. In particular, the fracture rate of the present inventions 2 and 3 is 0%, which is a significant decrease compared to the comparative example. On the other hand, the fracture rate of the present invention 1 is approximately 3.9%, and the fracture rate of the present invention 4 is 3.1%, which is a result of suppressed decrease in the fracture rate compared to the present inventions 2 and 3. The reasons for this are as follows.

[0096] In this invention, the correction value is relatively small. Therefore, the rate of change of the control gain GC is small when the working roll diameter R is greater than 75 mm and when the working roll diameter R is less than 75 mm. Thus, it can be considered that the gain correction effect of this invention is relatively weaker compared to this invention and this invention. Therefore, although this invention suppresses the fracture of the steel plate 20, the fracture rate is higher compared to this invention and this invention.

[0097] On the other hand, regarding invention 4, the correction value is relatively large. Therefore, when the working roll diameter R is greater than 75 mm, the control gain GC becomes a relatively small value. Consequently, the operating amount of actuator 10 decreases, and the operation of actuator 10 becomes slow. Thus, it can be considered that the effect of feedback control based on the shape of steel plate 20 is inherently weak.

[0098] Based on the above, it has been confirmed that the correction value for gain correction is preferably set to the following value: the negative intermediate gain values ​​GV1 to GVn to be corrected are more than 1 / 10 and less than 3 / 5 compared to before correction. Furthermore, it has been confirmed that the correction value is even more preferably set to the following value: the negative intermediate gain values ​​GV1 to GVn to be corrected are more than 1 / 5 and less than 1 / 2 compared to before correction.

[0099] <Variation Example> Furthermore, the present invention is not limited to the described embodiments, and various modifications can be made without departing from the spirit of the invention. For example, when performing gain correction, a predetermined correction value is added to the intermediate gain values ​​GV1 to GVn, which are the objects of correction, but the invention is not limited to this. For example, correction can also be performed by multiplying by a predetermined number.

[0100] Furthermore, the cold rolling apparatus 1 has been described for example as including a rolling section 3 with a single rolling table, but it is not limited to this structure. Specifically, as shown in FIG12, the cold rolling apparatus 1 can be configured as a tandem cold rolling apparatus in which multiple (five if described in conjunction with this figure) rolling sections 3 are arranged in a forward direction.

[0101] At this time, the measuring unit 4 is positioned on the exit side of the last stage (the rightmost side in Figure 12) of the rolling section 3 in the forward direction. This measuring unit 4 is common to all rolling sections 3. At this time, the control unit 5 controls the actuator 10 of each rolling section 3 individually while changing the control gain of each rolling section 3 as described. The control unit 5 changes the control gain of the actuator 10 of the corresponding rolling section 3 individually based on whether the diameter R of the work roll 6 of each rolling section 3 is greater than 75 mm. Regarding gain correction, the control gain GC of each rolling section 3 is also performed individually.

[0102] Furthermore, in Figures 1 and 12, the rolling section 3 is simplified for ease of explanation, but the rolling section 3 can be configured as a multi-stage (e.g., 20-stage) Sendzimir rolling mill. In this case, the rolling section 3 includes the AS-U roll. Moreover, the actuator 10 controls not only the intermediate roll 8 but also the AS-U roll. Furthermore, by changing the control gain GC, the movement of both the intermediate roll 8 and the AS-U roll is controlled.

[0103] Furthermore, the control unit 17 controls the actuator 10 and the measuring unit 4 in a comprehensive manner, but is not limited thereto. For example, the following structure may be adopted, in which the actuator 10 and the measuring unit 4 each include a control unit for controlling their own actions (different from the control unit 5).

[0104] At this time, the actuator 10 and the control unit 5 can also be non-electrically connected. Furthermore, the control command S1 is text information that can be interpreted by the operator. The operator directly inputs the content of the control command S1 (e.g., the value of the control gain GC) they have read into the control unit of the actuator 10. Moreover, it can be understood that the interface I / F between the control unit 17 and the actuator 10 in Figure 5 includes the operator.

[0105] Furthermore, while the control unit 17 may be the central processing unit of the control unit 5, it is not limited to this. An operator may also function as the control unit 17. In this case, the designated processing unit of the control unit 5 calculates the compliance rates FV1 to FVn. The operator then calculates the control gain GC based on the calculated compliance rates FV1 to FVn and the intermediate gain values ​​GV1 to GVn. The intermediate gain values ​​GV1 to GVn are then adjusted by the operator. Finally, the operator directly inputs the calculated control gain GC value into the control unit of the actuator 10.

[0106] Furthermore, the measuring unit 4 is electrically connected to the control unit 5, but this is not the only connection. For example, the actual shape data S3 can also be input to the control unit 5 by an operator. In this case, the operator directly inputs the actual shape data S3 output by the measuring unit 4 to the control unit 5. It can be understood that the interface I / F between the control unit 17 and the measuring unit 4 in Figure 5 includes the operator.

[0107] 1: Cold rolling unit 3: Rolling Section 4: Measurement Section 5: Control Department 6: Work roll 8: Intermediate Roller 9: Support rollers 10: Actuator 12: Flat area 13: Conical part 14: Drive Unit 15: Pole section 16: Pattern Preservation Department 17: General Section 18: Roller Diameter Input Device 20: Steel plate 21, 22: Scrolls FV1~FVn: Compliance Rate GC: Control Gain GV1~GVn: Intermediate gain values I / F: Interface MV1~MVn: Multiplication values P1~Pn: Shape deviation pattern R: Diameter of the work roll S1: Control Command S2: Control Command S3: Actual Shape Data St1~St3, St11~St13, St21~St25: Steps X: Arrow

Claims

1. A cold rolling method, comprising: The measurement procedure involves measuring the shape of the steel sheet exiting the cold rolling mill, including the work rolls. The gain setting step sets a control gain based on the shape of the steel plate determined in the measurement step; and the control step controls the cold rolling mill according to the control gain. In the gain setting step, a first control gain GCx set as the control gain when the diameter of the work roll is greater than 75 mm and a second control gain GCy set as the control gain when the diameter is less than 75 mm satisfy the following equation (1): GCy-GCx>0····(1).

2. The cold rolling method as claimed in claim 1, wherein the gain setting step comprises: a derivation step, wherein for each shape deviation pattern, the conformity rate between the shape of the steel sheet determined in the measurement step and each of the plurality of shape deviation patterns is separately derived; and a calculation step, wherein for each shape deviation pattern, a multiplicative value is calculated by multiplying an intermediate gain value separately set for each shape deviation pattern by the conformity rate of each shape deviation pattern, and the sum of the multiplicative values ​​is set as the control gain.

3. The cold rolling method as claimed in claim 2, wherein in the calculation step, when the diameter is greater than 75 mm, the absolute value of the negative intermediate gain value among the intermediate gain values ​​is made smaller than the absolute value of the original intermediate gain value.

4. The cold rolling method as described in claim 3, wherein in the calculation step, when reducing the absolute value of the negative intermediate gain value, it is set to be more than 1 / 10 and less than 3 / 5 of the original absolute value of the intermediate gain value.

5. The cold rolling method according to any one of claims 2 to 4, wherein in the calculation step, when the diameter is greater than 75 mm, the absolute value of the positive intermediate gain value among the intermediate gain values ​​is made greater than the absolute value of the original intermediate gain value.

6. The cold rolling method as claimed in claim 1, including a detection step for detecting the diameter.

7. A cold rolling apparatus, comprising: The rolling section has a pair of work rolls, which are used to cold roll steel sheets against each other; The measuring unit measures the shape of the steel plate at the exit side of the rolling section; and the control unit sets a control gain based on the shape of the steel plate measured in the measuring unit, and controls the rolling section according to the control gain. Regarding the control gain, a first control gain GCx set as the control gain when the diameter of the work roll is greater than 75 mm and a second control gain GCy set as the control gain when the diameter is less than 75 mm satisfy the following equation (2): GCy-GCx>0····(2).

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