Cold rolling method and cold rolling equipment

Abstract

To provide a cold rolling method enabling fracture of a steel plate to be suppressed.SOLUTION: A cold rolling method comprises: a measurement step; a gain setting step; and a control step. The measurement step measures a shape of a steel plate at an outlet side of a cold rolling mill. The gain setting step sets a control gain based on the shape of the steel plate measured by the measurement step. The control step controls the cold rolling mill according to the control gain. When a first control gain set as a control gain when a diameter of a work roll is more than 75 mm is GCx and a second control gain set as a control gain when a diameter of a work roll is 75 mm or less is GCy in the gain setting step, the following relation is satisfied: GCy-GCx>0.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a cold rolling method and a cold rolling apparatus. [Background technology]

[0002] A typical multi-stage rolling mill is equipped with work rolls for rolling steel plates, intermediate rolls for supporting the work rolls, and actuators for controlling the operation of the intermediate rolls. The amount of operation of the actuators is determined according to a predetermined control gain.

[0003] A cold rolling method using such a rolling mill is disclosed in Patent Document 1. The cold rolling method of Patent Document 1 measures the shape of a steel sheet at the delivery side of the rolling mill, and feedback controls the rolling mill so that the measurement results are reflected in a control gain, thereby keeping the shape of the steel sheet within an allowable range for a target shape. This suppresses breakage of the steel sheet. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2021 / 192713 Summary of the Invention [Problem to be solved by the invention]

[0005] However, even when a steel sheet is cold-rolled by the above-mentioned cold rolling method, the steel sheet may break. Therefore, an object of the present invention is to provide a cold rolling method and a cold rolling apparatus that can prevent the steel sheet from breaking. [Means for solving the problem]

[0006] In order to achieve the above object, a cold rolling method includes a measurement step of measuring the shape of a steel sheet at the delivery side of a cold rolling mill equipped with work rolls, a gain setting step of setting a control gain based on the shape of the steel sheet measured in the measurement step, and a control step of controlling the cold rolling mill in accordance with the control gain, wherein in the gain setting step, a first control gain GCx that is set as the control gain when the diameter of the work roll is larger than 75 mm and a second control gain GCy that is set as the control gain when the diameter is 75 mm or less satisfy the following formula (1) (first configuration). GCy-GCx>0 (1)

[0007] In the cold rolling method according to the first configuration, the gain setting step may be configured to include a derivation step of deriving, for each shape deviation pattern, a conformance rate between the shape of the steel sheet measured in the measurement step and each of a plurality of shape deviation patterns, and a calculation step of calculating, for each shape deviation pattern, a multiplication value obtained by multiplying an intermediate gain value set for each shape deviation pattern by the conformance rate for each shape deviation pattern, and setting the sum of the multiplication values ​​as the control gain (second configuration).

[0008] In the cold rolling method according to the second configuration, the calculation step may be configured so that when the diameter is greater than 75 mm, the absolute value of the negative intermediate gain value among the intermediate gain values ​​is smaller than when the diameter is 75 mm or less (third configuration).

[0009] In the cold rolling method according to the third configuration, the calculation step may be configured such that when reducing the absolute value of the negative intermediate gain value, the absolute value is set to be 1 / 10 or more and 3 / 5 or less times the absolute value of the original intermediate gain value (fourth configuration).

[0010] In the cold rolling method according to any one of the second to fourth configurations, the calculation step may be configured so that when the diameter is greater than 75 mm, the absolute value of the positive intermediate gain value among the intermediate gain values ​​is larger than when the diameter is 75 mm or less (fifth configuration).

[0011] The cold rolling method according to any one of the first to fifth configurations may be configured to include a detection step of detecting the diameter (sixth configuration).

[0012] The cold rolling apparatus disclosed in the specification comprises a rolling section having a pair of work rolls that cold rolls a steel sheet between the work rolls, a measuring section that measures the shape of the steel sheet at the delivery side of the rolling section, and a control section that sets a control gain based on the shape of the steel sheet measured in the measuring section and controls the rolling section in accordance with the control gain, and the control gains are configured so that a first control gain GCx that is set as the control gain when the diameter of the work roll is larger than 75 mm and a second control gain GCy that is set as the control gain when the diameter is 75 mm or less satisfy the following equation (1) (seventh configuration). GCy-GCx>0 (1) [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a cold rolling method and a cold rolling apparatus that can suppress breakage of a steel sheet. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a graph showing the target shape and actual shape of a steel sheet when the work roll diameter is 75 mm or less. [Figure 2] 1 is a graph showing the target shape and actual shape of a steel plate when the work roll diameter is greater than 75 mm. [Figure 3] FIG. 1 is a diagram showing a cold rolling apparatus 1. [Figure 4] FIG. 2 is a plan view of the work rolls 6 and the intermediate rolls 8 as viewed in the forward direction. [Figure 5] FIG. 2 is a block diagram showing the configuration of a control unit 5. [Figure 6] 2 is a flowchart showing steps of a cold rolling method. [Figure 7] 10 is a flowchart showing the measurement step St1 in detail. [Figure 8]10 is a flowchart showing the gain setting step St2 in detail. [Figure 9] 1 is a diagram showing the actual shape and the target shape of a steel sheet 20 rolled by a cold rolling method of a comparative example. [Figure 10] 1 is a diagram showing the actual shape and the target shape of a steel sheet 20 rolled by the cold rolling method of the present invention. FIG. [Figure 11] 10 is a graph showing the fracture rate for each correction value when the magnitude of each correction value is changed when performing gain correction and the steel sheet 20 is rolled. [Figure 12] FIG. 1 is a diagram showing a modified example of the cold rolling apparatus 1 according to the configuration of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] <Considerations on steel plate fracture> First, the circumstances that led the inventors to arrive at the present invention will be explained. In conventional cold rolling methods, the shape of a steel sheet is measured at the delivery side of the rolling section, and the cold rolling mill is controlled so as to feed back the measurement results. In the above feedback control, when the deviation of the actual shape of the steel sheet from the target shape exceeds a predetermined value, an actuator (actuator 10, which will be described later) is operated to bring the steel sheet closer to the target shape.

[0016] This feedback control employs the so-called neuro-fuzzy control method. Control gain is used in this feedback control. Control gain indicates the amount of actuator movement. The control gain value can be set to a value between +1000 and -1000, for example. The larger the absolute value of the control gain, the more agile the actuator movement. Furthermore, whether the control gain value is positive or negative indicates the direction of actuator movement. When the control gain is positive, the actuator operates so that the steel plate takes an elongated shape. Conversely, when the control gain is negative, the actuator operates so that the steel plate takes a tensile shape.

[0017] However, even when feedback control using such control gains is performed, the steel plate may break depending on the usage conditions of the work rolls mounted on the rolling mill. Therefore, the inventors conducted extensive research into the causes of steel plate breakage.

[0018] As a result of the investigation, it was confirmed that in cases where steel plate fractures occurred, work rolls that had been used for a certain period of time and had become worn were replaced with new (unworn) ones. In particular, steel plate fractures occurred relatively frequently after work rolls that had worn down to a diameter of 75 mm or less were replaced with new work rolls with a diameter of more than 75 mm. After rolling, the outer surfaces of the work rolls are ground in preparation for the next rolling run. The diameter of the work roll (hereinafter simply referred to as the "work roll diameter") is measured by an operator or an automatic measuring device during this grinding operation.

[0019] Based on the above, the inventors further investigated what differences occur in the shape of the steel sheet when the work roll diameter is greater than 75 mm and when it is 75 mm or less. The results of this investigation will be explained using Figures 1 and 2.

[0020] Figure 1 is a graph showing the target and actual shapes of a steel plate when the work roll diameter is 75 mm or less. Figure 2 is a graph showing the target and actual shapes of a steel plate when the work roll diameter is greater than 75 mm. In Figures 1 and 2, the vertical axis shows the target and actual shapes in units of I-UNIT. In Figures 1 and 2, the left side of the center of the horizontal axis is the operator side (=worker side), and the right side of the center of the horizontal axis is the drive side.

[0021] I-Unit is a numerical value that indicates the elongation of the steel sheet as a positive value and the tension of the steel sheet as a negative value. I-UNIT is calculated by multiplying the elongation difference rate Δε by a predetermined coefficient (=10 5 ) can be calculated by multiplying

[0022] The differential elongation rate Δε is defined by the following formula (1): In formula (1), l represents the reference length of a section when a steel sheet is divided into sections of a predetermined length, and Δl represents the differential elongation within this section (= the difference from the reference length l).

[0023]

number

[0024] As shown in Figures 1 and 2, the target shape of the steel sheet is set so that the edge portions in the width direction are tensile and the intermediate portion between the edge portions and the center portion is elongated. With such a shape distribution, the shape unevenness in the width direction is reduced, and the steel sheet is less likely to break. Hereinafter, the intermediate portion between the edge portions and the center portion will be simply referred to as the "quarter portion."

[0025] As shown in Figure 1, when the work roll diameter is 75 mm or less, the actual shape of the steel sheet conforms to the target shape. In other words, in this case, the actual shape of the steel sheet is tensile at the edge and elongated at the quarter. Therefore, when the work roll diameter is 75 mm or less, the steel sheet is relatively resistant to fracture.

[0026] On the other hand, when the work roll diameter is larger than 75 mm, the actual shape of the steel plate tends to differ from the target shape over a relatively wide area (shape irregularities), as shown in Figure 2. In particular, the quarter area on the operator side shows a relatively large elongation, which is significantly different from the target shape.

[0027] When such a shape distribution occurs, the cold rolling mill performs the above-mentioned feedback control after setting a control gain to eliminate this shape unevenness. As a result, the actuator operates excessively in areas other than the area where the shape unevenness occurs, which actually leads to deformation of the steel sheet shape. In the case shown in Figure 2, the actuator operates to make the steel sheet 20 into a taut shape. This promotes the elongation of the quarter portion, causing deformation of the steel sheet shape. As a result, the steel sheet becomes more susceptible to breakage. Based on the above investigation results, the inventors have discovered that when the work roll diameter is greater than 75 mm, excessive control of the actuator (hereinafter simply referred to as "overcontrol") occurs, leading to breakage of the steel sheet.

[0028] Therefore, the inventors have determined that the work roll diameter at which deformation of the steel sheet is likely to occur is 75 mm. In the present invention, when the work roll diameter during rolling is greater than 75 mm, the control gain is set smaller than when the work roll diameter is 75 mm or less. This makes it possible to suppress overcontrol of the actuator as described above without requiring equipment modifications or the like. Therefore, according to the cold rolling method of the present invention, it is possible to suppress breakage of the steel sheet due to deformation of the steel sheet while suppressing an increase in costs, and to stably roll the steel sheet.

[0029] <Embodiments of the present invention> Hereinafter, each embodiment of the present invention will be described with reference to the drawings. First, the configuration of a cold rolling mill 1 used in the cold rolling method of the present invention will be described. After that, the cold rolling method of the present invention will be described.

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

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

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

[0033] The cold rolling apparatus 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 single-stand multi-stage rolling mill. The detailed configuration of the rolling section 3 is as follows.

[0034] <About Rolling Section 3> 3, the rolling unit 3 includes a pair of work rolls 6, a pair of intermediate rolls 8, a pair of backup rolls 9, and a pair of actuators 10. The rolling unit 3 is a so-called roll shift type rolling mill that performs cold rolling while controlling the shape of the steel sheet 20 by sliding the intermediate rolls 8 in the axial direction.

[0035] A pair of work rolls 6 sandwich a steel sheet 20 between them and roll the steel sheet 20. The work rolls 6 generally have a diameter R (hereinafter 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 intermediate rolls 8 and backup rolls 9. Specifically, the outer circumferential surfaces of the work rolls 6 are in contact with the outer circumferential surface of the intermediate rolls 8. The outer circumferential surface of the intermediate rolls 8 is also in contact with the outer circumferential surface of the backup rolls 9.

[0036] Figure 4 is a plan view of the work rolls 6 and the intermediate rolls 8 viewed in the forward direction. As shown in Figure 4, the intermediate rolls 8 have a flat portion 12 and a tapered portion 13. The flat portion 12 is rod-shaped with a constant outer diameter. The tapered portion 13 is connected to one end of the flat portion 12 in the axial direction. The tapered portion 13 has a tapered shape such that the outer diameter decreases with increasing distance from the flat portion 12.

[0037] The intermediate rolls 8 are supported so as to be movable in the axial direction. The rolling unit 3 controls the shape of the steel sheet 20 by moving the intermediate rolls 8 in the axial direction.

[0038] The actuator 10 is mechanically connected to the intermediate roll 8 so as to move the intermediate roll 8 in the axial direction. The actuator 10 is also electrically connected to a control unit 5 (described later) via a wired or wireless communication path.

[0039] The actuator 10 receives a control command S1 (details of which will be described later) from the control unit 5 and moves the intermediate roll 8 in the axial direction in accordance with the control command S1. The control command S1 is an electric signal transmitted via a 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 included in the control command S1 increases. The specific configuration of the actuator 10 is as follows.

[0040] As shown in FIG. 4, the actuator 10 includes a drive unit 14 and a rod unit 15. The drive unit 14 is a power source such as a motor. The drive unit 14 generates power according to a control command S1. The drive unit 14 transmits the power to the rod unit 15. The rod unit 15 is connected to the intermediate roll 8. The rod unit 15 moves the intermediate roll 8 parallel to the axial direction of the work roll 6 in accordance with the power transmitted from the drive unit 14.

[0041] As the value of the control gain GC increases, the operation of the actuator 10 becomes more agile. Specifically, as the value of the control gain GC increases, the intermediate rolls 8 move more agilely. The more agile the intermediate rolls 8 move, the stronger the shape control of the steel sheet 20 during rolling. Details of the control gain GC will be described later.

[0042] <About measurement unit 4> Returning to Fig. 3, the measurement unit 4 is disposed at a position on the delivery side of the rolling unit 3 in the forward direction (more specifically, a position downstream of the work rolls 6 in the forward direction). The measurement unit 4 is configured to be able to measure the shape of the steel sheet 20 threaded through the rolling unit 3. Specifically, it is as follows.

[0043] The measuring unit 4 measures the shape along the width direction of the steel sheet 20 passed through the rolling unit 3. The measuring unit 4 can employ, for example, a contact-type shape measuring device that brings divided rolls into contact with the steel sheet 20 to measure the shape.

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

[0045] <Regarding the control unit 5> The control unit 5 is an arithmetic processing device such as a computer. The control unit 5 receives actual shape data S3 and generates a control command S1. The control command S1 includes a control gain GC according to the actual shape data S3. The detailed configuration of the control unit 5 is as follows.

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

[0047] The pattern storage unit 16 is a storage area in which predetermined data is stored. Pre-set shape deviation patterns P1 to Pn (n is an arbitrary natural number) are stored in the pattern storage unit 16. The shape deviation patterns P1 to Pn are patterns obtained by classifying deviations of the actual shape of the steel sheet 20 from the target shape.

[0048] Individual intermediate gain values ​​GV1 to GVn are set for each of the shape deviation patterns P1 to Pn. The intermediate gain values ​​GV1 to GVn (n is an arbitrary natural number) are associated with each of the shape deviation patterns P1 to Pn and stored in the pattern storage unit 16. Some of the intermediate gain values ​​GV1 to GVn are set to positive values, and some are set to negative values.

[0049] The control unit 17 is a central processing unit (CPU) of the control unit 5. The control unit 17 controls the actuator 10 and the measurement unit 4 in an integrated manner. The control unit 17 is electrically connected to each of the measurement unit 4, the actuator 10, and the roll diameter input device 18 via individual interfaces I / F. The control unit 17 is also configured to be able to access the pattern storage unit 16.

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

[0051] The control unit 17 derives conformance rates FV1 to FVn based on the actual shape data S3 transmitted from the measurement unit 4. The conformance rates FV1 to FVn indicate the degree of conformance of the actual shape data S3 with each of the shape deviation patterns P1 to Pn, expressed as a ratio. The control unit 17 accesses the pattern storage unit 16 and compares the shape deviation patterns P1 to Pn with the actual shape data S3 individually to derive the conformance rates FV1 to FVn.

[0052] The control unit 17 calculates the control gain GC based on the intermediate gain values ​​GV1 to GVn and the conformance rates FV1 to FVn using the following equation (2).

[0053]

number

[0054] The supervision unit 17 generates a control command S1 that includes the control gain GC and inputs it to the actuator 10. In other words, the supervision unit 17 controls the operation of the actuator 10 using the control command S1. When the control gain GC has a positive value, the actuator 10 is controlled so that the steel sheet 20 assumes an elongated shape. Conversely, when the control gain GC has a negative value, the actuator 10 operates so that the steel sheet 20 approaches a tensile shape.

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

[0056] <Correction of intermediate gain values ​​GV1 to GVn> The control unit 17 is configured to be able to perform gain correction at any timing. Gain correction is a control that corrects the intermediate gain values ​​GV1 to GVn in a manner described below. When gain correction is performed, the control gain GC is calculated from equation (2) using the corrected intermediate gain values ​​GV1 to GVn. The control unit 17 performs gain correction when the value of the work roll diameter R input to itself is greater than 75 mm.

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

[0058] The above-mentioned correction is performed by adding a predetermined correction value to the negative intermediate gain values ​​GV1 to GVn to be corrected.

[0059] For example, suppose the intermediate gain value GV12 is set to -500 in advance. When gain correction is performed in this case, a correction value (+400) is added to the intermediate gain value GV12, making it -100. When the control gain GC is calculated using the above formula (2), the intermediate gain value GV12 is treated as -100.

[0060] Therefore, when gain correction is performed, the control gain GC is more likely to have a positive value than under normal circumstances. In other words, when gain correction is performed, the actuator 10 is more likely to operate in a manner that causes the steel sheet 20 to assume an elongated shape.

[0061] Furthermore, when gain correction is performed, even if control gain GC becomes a negative value, the absolute value of control gain GC becomes smaller. That is, when gain correction is performed, even if control gain GC becomes a negative value, it is possible to prevent the operation of actuator 10 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. When the work roll diameter R is greater than 75 mm, the actuator 10 operates to make the steel sheet 20 elongated, or operates slowly to make the steel sheet 20 taut. This prevents the tendency of the steel sheet 20 to elongate from the quarter portion to the edge portion from becoming more pronounced. Therefore, when the work roll diameter R is greater than 75 mm, breakage of the steel sheet 20 is suppressed.

[0063] As described above, it is preferable that each correction value be set so that the absolute value of the negative intermediate gain values ​​GV1 to GVn to be corrected is 1 / 10 or more and 3 / 5 or less than the value before correction. In this way, overcontrol of the actuator 10 can be suitably suppressed. Furthermore, it is more preferable that each correction value be set so that the absolute value of the negative intermediate gain values ​​GV1 to GVn to be corrected is 1 / 5 or more and 1 / 2 or less than the value before correction. In this way, it is possible to more suitably suppress overcontrol of the actuator 10.

[0064] Regarding the above-mentioned control gain GC, the control gain GC (= control gain GC after gain correction) that is set when the work roll diameter R is greater than 75 mm is defined as the first control gain GCx. Also, the control gain GC (= control gain GC without gain correction) that is set when the work roll diameter is 75 mm or less is defined as the second control gain GCy. Then, the relationship between the first control gain GCx and the second control gain GCy is expressed by the following equation (3).

[0065]

number

[0066] <Regarding the cold rolling apparatus 1 according to the second embodiment> Next, a cold rolling apparatus 1 according to a second embodiment will be described. The cold rolling apparatus 1 of this embodiment basically has the same configuration as that of the first embodiment. Therefore, only the configuration that differs from that of the first embodiment will be described here.

[0067] When the control unit 17 according to this embodiment executes gain correction, it corrects the positive intermediate gain values ​​GV1 to GVn. More specifically, it corrects the absolute values ​​of the positive intermediate gain values ​​GV1 to GVn to be corrected so that they are larger than before correction. As in the first embodiment, this correction adds a positive correction value to the intermediate gain values ​​GV1 to GVn to be corrected.

[0068] For example, suppose that the intermediate gain value GV6 is set to +200 in advance. When gain correction is performed in this case, a correction value (+300) is added to the intermediate gain value GV6, resulting in +500. When the control gain GC is calculated using the above formula (2), the intermediate gain value GV6 is treated as +500. Therefore, in the cold rolling mill 1 according to this embodiment, when gain correction is performed, the control gain GC is more likely to become a positive value. Furthermore, in the cold rolling mill 1 according to this embodiment, when gain correction is performed, the absolute value of the control gain GC becomes smaller even if the control gain GC becomes a negative value.

[0069] Note that when performing gain correction, the control unit 17 according to this embodiment may or may not correct negative values ​​among the intermediate gain values ​​GV1 to GVn, as in the first embodiment. In either case, the relationship of the above formula (3) is established.

[0070] <About the cold rolling method> Next, the cold rolling method of the present invention will be described. Fig. 6 is a flowchart showing each step of the cold rolling method. Fig. 7 is a flowchart showing the measurement step St1 in detail. Fig. 8 is a flowchart showing the gain setting step St2 in detail. First, the entire cold rolling method of the present invention will be described along each step of Fig. 6. Next, the measurement step St1 will be described in detail using Fig. 7. After that, the gain setting step will be described in detail using Fig. 8.

[0071] As shown in FIG. 6 , the cold rolling method using the cold rolling mill 1 includes a measurement step St1, a gain setting step St2, and a control step St3. When a series of cold rolling operations is started, first, in the measurement step St1, the shape of the steel sheet 20 after cold rolling is measured. Next, in the gain setting step St2, a control gain GC is set based on actual shape data S3 of the steel sheet 20 obtained in the measurement step St1. Next, in the control step St3, the steel sheet 20 is cold rolled while controlling the actuator based on the control gain GC set in the gain setting step St2. Then, the cold rolling of the steel sheet 20 is terminated at an arbitrary timing. After this, the work rolls 6 are polished in preparation for the next rolling. This polishing operation includes a detection step of measuring the actual value of the work roll diameter R or calculating an estimated value.

[0072] 7, in the measurement step St1, first, a control command S2 is sent from the control unit 5 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 sheet 20 at the delivery side of the rolling unit 3 (step St12). Then, the measurement unit 4 sends actual shape data S3, which is the measurement result, to the control unit 5 (step St13). Thereafter, the process proceeds to the gain setting step St2.

[0073] In the gain setting step St2, as shown in Fig. 8, the control unit 5 first derives the conformance rates FV1 to FVn in accordance with 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] If the work roll diameter R is 75 mm or less (Yes in step St22), the control unit 5 calculates the multiplication values ​​MV1 to MVn without performing the gain correction described above (step St23). If the work roll diameter R is greater than 75 mm (No in step St22), the control unit 5 performs the gain correction described above (step St24) and calculates the multiplication values ​​MV1 to MVn using the corrected intermediate gain values ​​GV1 to GVn (step St23). Thereafter, the control unit 5 calculates the sum of the multiplication values ​​MV1 to MVn and sets this calculation result as the control gain GC (step St25).

[0075] Note that steps St23 and St25 can be considered as one “computation step.” In addition, the gain correction executed in step St24 may be that of the first embodiment or that of the second embodiment.

[0076] As described above, in the gain setting step St2, if the work roll diameter R is greater than 75 mm, gain correction is executed. Therefore, according to the cold rolling method of the present invention, when the work roll diameter R is greater than 75 mm, it is possible to prevent the actuator 10 from falling into overcontrol and to prevent the steel sheet 20 from breaking.

[0077] Next, the cold rolling method of the present invention will be specifically described using examples. [Example]

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

[0079] In both the comparative example and the present invention, cold rolling was performed using work rolls with a diameter R of greater than 75 mm. In both the comparative example and the present invention, the intermediate gain value GV6 was set to +200, the intermediate gain value GV7 was set to +200, the intermediate gain value GV8 was set to +200, the intermediate gain value GV12 was set to -500, and the intermediate gain value GV14 was set to -500. In addition, the gain correction according to the second embodiment was performed.

[0080] Table 1 shows the shape deviation pattern Pn, the detected shape, the intermediate gain value GVn, the matching rate FVn, and the multiplication value for the comparative example. In Table 1, matching rates greater than 0% are given priority.

[0081] [Table 1]

[0082] As shown in Table 1, the conformance rate FV12 (= conformance rate for the shape deviation pattern P12) was 100%. The shape deviation pattern P12 is a pattern in which the operator-side edge portion of the steel plate 20 has an elongated shape. Furthermore, the conformance rate FV14 (= conformance rate for the shape deviation pattern P14) was 20%. The shape deviation pattern P14 is a pattern in which both the operator-side edge portion and the drive-side edge of the steel plate 20 have an elongated shape.

[0083] As described above, it was found that when the work roll diameter R is greater than 75 mm, the steel sheet 20 becomes elongated near its edge. The following reason is thought to be the cause of this: When the work roll diameter R becomes relatively large, the load on the work roll 6 increases, and the tendency for the steel sheet 20 to become taut increases from the center to the quarter portions. It is thought that this influence strengthens the tendency for the steel sheet 20 to become elongated from the quarter portions to the edge portions.

[0084] Because the tendency toward an elongated shape is strengthened from the quarter portion to the edge portion, the conformance 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 the multiplication values ​​MV1 to MVn) in the comparative example is a negative value (-240). As a result, the actuator 10 operates to make the steel sheet 20 tensile. As a result, the actuator 10 falls into the over-control state described above. Specifically, the actuator 10 operates to strengthen the tendency toward a tensile shape from the center portion to the quarter portion of the steel sheet 20. As a result, this operation of the actuator 10 further strengthens the tendency toward an elongated shape from the quarter portion to the edge portion.

[0085] Next, the present invention will be described. Table 2 shows the shape deviation pattern Pn, detected shape, intermediate gain value GVn, conformance 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, for the corrected intermediate gain values, the base 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]

[0087] The conformance rates FV1 to FVn are the same as those in the comparative example. As shown in Table 2, positive correction values ​​are assigned to the intermediate gain values ​​GV1 to GVn. As a result, the control gain GC of the present invention is +780. Therefore, in the present invention, the actuator 10 is controlled to make the steel sheet elongated. As a result, the tendency of the steel sheet 20 to become tensile is weakened from the center to the quarter portions, and the tendency of the steel sheet 20 to become elongated is less likely to be promoted from the quarter portions to the edge portions. In other words, the operation of the actuator 10 is prevented from falling into overcontrol.

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

[0089] As shown in Figure 9, when steel sheet 20 is cold-rolled using the cold rolling method of the comparative example, the actual shape of steel sheet 20 deviates significantly from the target shape. Specifically, the actual shape from the quarter portion to the edge portion on the drive side of steel sheet 20 (the inner portion surrounded by the dashed-dotted circle in Figure 9) tends to be more elongated than the target shape. With such a shape distribution, as described above, steel sheet 20 is prone to fracture. It is believed that such a shape distribution is caused by the actuator 10 falling into overcontrol as described above.

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

[0091] As shown in Figure 10, when a 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 similar to the target shape. For example, the actual shape from the quarter portion to the edge portion on the drive side of the steel sheet 20 (the inner portion surrounded by the dashed-dotted circle in Figure 10) tends to be roughly halfway between the elongated shape and the tensile shape, similar to the target shape. With such a shape distribution, shape irregularities are suppressed, and the steel sheet 20 is less likely to break. In this way, it was confirmed that fracture of the steel sheet 20 is suppressed when the cold rolling method of the present invention is adopted.

[0092] Next, the correction value of the gain correction was changed, and the fracture rate when continuous cold rolling was performed for each correction value was verified. The verification results are shown in Fig. 11. Fig. 11 is a graph showing the fracture rate for each correction value when rolling a steel sheet 20 while changing the magnitude of each correction value when performing gain correction. In Fig. 11, the number of times the steel sheet 20 was threaded is shown in a bar graph, and the fracture rate of the steel sheet 20 is shown in a line graph.

[0093] The steel sheets 20 used in the comparative example and present inventions 1 to 4 had 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. In the comparative example and present inventions 1 to 4, cold rolling was performed at a rolling speed (the rotation speed of the reels 21, 22) of 30 rpm or more and 2000 rpm or less. In the comparative example and present inventions 1 to 4, cold rolling was started with a work roll diameter R of greater than 75 mm.

[0094] Furthermore, in invention 1, the correction value when performing gain correction is set to a value such that the absolute values ​​of the negative intermediate gain values ​​GV1 to GVn to be corrected are 3 / 5 times larger than before correction. In invention 2, the correction value is set to a value such that the absolute values ​​of the negative intermediate gain values ​​GV1 to GVn to be corrected are 1 / 2 times larger than before correction. In invention 3, the correction value is set to a value such that the absolute values ​​of the negative intermediate gain values ​​GV1 to GVn to be corrected are 1 / 5 times larger than before correction. In invention 4, the correction value is set to a value such that the absolute values ​​of the negative intermediate gain values ​​GV1 to GVn to be corrected are 1 / 10 times larger than before correction.

[0095] As shown in Figure 11, the breaking rate of the comparative example was approximately 4.5%. In contrast, the breaking rate of all of inventions 1 to 4 was lower than that of the comparative example. In particular, the breaking rate of inventions 2 and 3 was 0%, which is a significant decrease compared to the comparative example. On the other hand, the breaking rate of invention 1 was approximately 3.9%, and the breaking rate of invention 4 was 3.1%, which resulted in a smaller decrease in breaking rate compared to inventions 2 and 3. The following reasons are thought to be the cause of this.

[0096] In Invention 1, the correction value is relatively small. Therefore, the rate of change in the control gain GC is small when the work roll diameter R is greater than 75 mm and when it is 75 mm or less. This is thought to be why Invention 1 has a relatively weaker effect of gain correction than Inventions 2 and 3. Therefore, although Invention 1 suppresses breakage of the steel sheet 20, the breakage rate is higher than Inventions 2 and 3.

[0097] On the other hand, in the present invention 4, the correction value is relatively large. Therefore, when the work roll diameter R is larger than 75 mm, the control gain GC becomes a relatively small value. As a result, the movement amount of the actuator 10 becomes small, and the movement of the actuator 10 becomes slow. This is thought to have weakened the effect of the feedback control based on the shape of the steel sheet 20.

[0098] From the above, it was confirmed that the correction value when performing gain correction is preferably set to a value that makes the negative intermediate gain values ​​GV1 to GVn to be corrected 1 / 10 or more and 3 / 5 or less compared to before correction. Furthermore, it was confirmed that the correction value is more preferably set to a value that makes the negative intermediate gain values ​​GV1 to GVn to be corrected 1 / 5 or more and 1 / 2 or less compared to before correction.

[0099] <Modification> The present invention is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit of the present invention. For example, when performing gain correction, a predetermined correction value is added to the intermediate gain values ​​GV1 to GVn to be corrected, but this is not limiting. For example, correction may be performed by multiplying by a predetermined number.

[0100] Furthermore, for example, the cold rolling mill 1 has been described as having a single stand rolling section 3, but is not limited to this configuration. Specifically, as shown in Fig. 12, the cold rolling mill 1 can be a tandem cold rolling mill in which a plurality of rolling sections 3 (five in this figure) are arranged in the forward direction.

[0101] In this case, the measurement unit 4 is disposed on the delivery side of the rolling unit 3 at the last stage in the forward direction (the rightmost one in FIG. 12). This measurement unit 4 is common to each rolling unit 3. In this case, the control unit 5 controls the actuator 10 of each rolling unit 3 individually while changing the control gain of each rolling unit 3 in the manner described above. The control unit 5 changes the control gain of the actuator 10 of the corresponding rolling unit 3 individually depending on whether the diameter R of the work roll 6 of each rolling unit 3 is larger than 75 mm. Gain correction is also performed individually on the control gain GC of each rolling unit 3.

[0102] 1 and 12, the rolling unit 3 is shown in a simplified form for ease of explanation, but the rolling unit 3 can be a multi-stage (e.g., 20-stage) Sendzimir rolling mill. In this case, the rolling unit 3 is equipped with AS-U rolls. The actuator 10 controls not only the intermediate rolls 8 but also the AS-U rolls. Furthermore, by changing the control gain GC, it is possible to control the movement of not only the intermediate rolls 8 but also the AS-U rolls.

[0103] Furthermore, although the description has been given in which the control unit 17 controls the actuator 10 and the measurement unit 4 in an integrated manner, this is not limiting. For example, each of the actuator 10 and the measurement unit 4 may have a control unit (separate from the control unit 5) for controlling its own operation.

[0104] In this case, the actuator 10 and the control unit 5 do not need to be electrically connected. The control command S1 is character information that can be read by an operator. In this case, the operator directly inputs the content of the control command S1 that he or she has read (for example, the value of the control gain GC) into the control unit of the actuator 10. In this case, it is understood that the interface I / F between the control unit 17 and the actuator 10 in FIG. 5 includes the operator.

[0105] Furthermore, for example, although the supervision unit 17 is the central processing unit of the control unit 5, this is not limiting. An operator may function as the supervision unit 17. In this case, a predetermined calculation unit of the control unit 5 calculates the conformance rates FV1 to FVn. Then, the operator calculates the control gain GC based on the calculated conformance rates FV1 to FVn and the intermediate gain values ​​GV1 to GVn. In this case, the intermediate gain values ​​GV1 to GVn are gain-corrected by the operator. Furthermore, the operator directly inputs the calculated value of the control gain GC to the control unit of the actuator 10.

[0106] Furthermore, although the measurement unit 4 is described as being electrically connected to the control unit 5, this is not limiting. For example, the actual shape data S3 may be input to the control unit 5 via an operator. In this case, the operator directly inputs the actual shape data S3 output by the measurement unit 4 to the control unit 5. In this case, it is understood that the interface I / F between the control unit 17 and the measurement unit 4 in FIG. 5 includes the operator. [Explanation of symbols]

[0107] 1 Cold rolling equipment 3. Rolling section 4 Measuring part 5. Control section 6 Work Rolls 8 intermediate rolls 9 Backup Role 10 Actuator 12 Flat area 13 Tapered section 14 Drive unit 15 Rod section 16 Pattern storage section 17 General Affairs Department 18 Roll diameter input device 20 steel plate 21, 22 reels FV1~FVn precision rate GC Control Gain GV1~GVn Intermediate gain value I / F interface MV1~MVn multiplication value P1~Pn Shape deviation patterns R Work roll diameter S1 control command S2 control command S3 Actual shape data

Claims

1. a measuring step of measuring the shape of the steel sheet at the delivery side of a cold rolling mill equipped with work rolls; a gain setting step of setting a control gain based on the shape of the steel plate measured in the measuring step; a control step of controlling the cold rolling mill in accordance with the control gain; Equipped with a first control gain GCx that is set as the control gain when the diameter of the work roll is greater than 75 mm, and a second control gain GCy that is set as the control gain when the diameter is 75 mm or less, in the gain setting step, which satisfy the following formula (1): GCy-GCx>0...(1)

2. The gain setting step includes: a derivation step of deriving a conformance rate between the shape of the steel sheet measured in the measurement step and each of a plurality of shape deviation patterns individually for each of the shape deviation patterns; a calculation step of multiplying an intermediate gain value individually set for each of the shape deviation patterns by the adaptability for each of the shape deviation patterns to calculate a multiplication value for each of the shape deviation patterns, and setting a sum of the multiplication values ​​as the control gain; 2. The cold rolling method of claim 1, comprising:

3. 3. The cold rolling method according to claim 2, wherein the calculation step makes the absolute value of the negative intermediate gain value among the intermediate gain values ​​smaller when the diameter is greater than 75 mm than when the diameter is 75 mm or less.

4. 4. The cold rolling method according to claim 3, wherein the absolute value of the negative intermediate gain value is reduced to be 1 / 10 or more and 3 / 5 or less times the absolute value of the original intermediate gain value in the calculation step.

5. 5. The cold rolling method according to claim 2, wherein the calculation step makes the absolute value of the positive intermediate gain value among the intermediate gain values ​​larger when the diameter is greater than 75 mm than when the diameter is 75 mm or less.

6. The cold rolling method according to claim 1 , further comprising a detecting step of detecting the diameter.

7. a rolling section having a pair of work rolls that cold rolls the steel sheet between the work rolls; a measuring unit for measuring the shape of the steel sheet at the delivery side of the rolling unit; a control unit that sets a control gain based on the shape of the steel sheet measured by the measuring unit and controls the rolling unit in accordance with the control gain; Equipped with The cold rolling mill is configured such that a first control gain GCx, which is set as the control gain when the diameter of the work roll is greater than 75 mm, and a second control gain GCy, which is set as the control gain when the diameter is 75 mm or less, satisfy the following formula (1): GCy-GCx>0...(1)

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