Deviation angle zero adjustment method for hydraulic pair cross mill, method for operating hydraulic pair cross mill, and method for manufacturing hot-rolled steel sheet

Abstract

A deviation angle zero adjustment method for a hydraulic pair cross mill according to the present invention is a method for adjusting the zero point of a deviation angle θ2 between work rolls 11W, 12W and back-up rolls 11B, 12B in an upper pair 11P and / or a lower pair 12P, the method including: setting the pressing pressure of a pressing cylinder 132 to a zero adjustment pressure lower than the pressure during steady state operation, and in this state, while changing the deviation angle θ2, acquiring, for each deviation angle θ2, a correlation between a cross angle θ1 and a thrust force F acting on the work rolls 11W, 12W and / or the back-up rolls 11B, 12B; and setting as the zero point the value of the deviation angle θ2 with which a correlation indicating that the thrust force F is zero when the cross angle θ1 is zero is acquired.

Description

Method for zero-adjusting deviation angle of hydraulic pair cross mill, method for operating hydraulic pair cross mill, and method for manufacturing hot-rolled steel sheet

[0001] The present invention relates to a method for zero-adjusting the misalignment angle of a hydraulic pair cross mill for adjusting the zero point of the misalignment angle between a work roll and a backup roll, a method for operating a hydraulic pair cross mill, and a method for manufacturing a hot-rolled steel sheet.

[0002] An example of a conventional hydraulic pair cross mill of this type is the configuration shown in Patent Document 1 below. Patent Document 1 describes a hydraulic pair cross mill equipped with hydraulic actuators that horizontally move a pair of upper and lower work rolls and a pair of upper and lower backup rolls that support the pair of upper and lower work rolls. The hydraulic actuators change the cross angle between the upper pair and the lower pair while keeping the upper pair consisting of the upper work roll and the upper backup roll parallel and the lower pair consisting of the lower work roll and the lower backup roll parallel. The hydraulic actuators include adjustment cylinders (hydraulic cylinders for controlling the position of each roll) and pressing cylinders (hydraulic cylinders for the pressing devices of each roll) that clamp the roll chocks of the work rolls and the backup rolls. The adjustment cylinders include position detectors for detecting the position of the oil column and are controlled based on the position of the oil column detected by the position detector. The pressing cylinders are controlled to constantly press the roll chocks against the adjustment cylinders.

[0003] International Publication No. 2021 / 220366

[0004] Due to installation errors in a hydraulic pair cross mill or elastic deformation due to stress during strip threading, an unintended misalignment angle may occur between the work rolls and backup rolls in the upper pair and / or lower pair. The misalignment angle is also known by other names, such as a small cross angle or a skew angle. When a misalignment angle occurs, an unintended thrust force is generated in each roll. When rolling a metal strip (such as a steel strip) using a hydraulic pair cross mill, the unintended thrust force can cause strip threading problems, such as meandering or bending of the metal strip. Therefore, it is necessary to adjust the zero point of the misalignment angle between the work rolls and backup rolls, taking into account installation errors, elastic deformation, and other factors. Adjusting the zero point of the misalignment angle is sometimes called zero adjustment of the misalignment angle.

[0005] It is known that there is a correlation between the slippage angle between the work roll and the backup roll and the measured value of the thrust force acting on the work roll and / or the backup roll. The inventors thought that if such a correlation could be obtained during steady operation and zero-adjustment of the slippage angle could be performed based on that correlation, factors such as installation error and elastic deformation could be taken into consideration, and strip threading problems could be suppressed. However, when zero-adjustment of the slippage angle was performed based on the correlation obtained during steady operation, strip threading problems were not sufficiently suppressed.

[0006] The present inventors have conducted various studies to find the cause of this problem, and have found a new problem in that the thrust force is measured lower than the actual value due to the clamping of the roll chocks by the adjustment cylinder and the pressing cylinder, and even if zero adjustment of the deviation angle is performed based on this lower measured thrust force, strip threading troubles cannot be sufficiently suppressed.

[0007] The present invention has been made to solve the above-mentioned problems, and one of its objects is to provide a method for zero adjustment of the deviation angle of a hydraulic pair cross mill, a method for operating a hydraulic pair cross mill, and a method for manufacturing a hot-rolled steel sheet, which are capable of suppressing threading problems such as meandering and bending of the metal strip.

[0008] In one embodiment, the method for zero-adjusting a slip angle of a hydraulic pair cross mill according to the present invention is a hydraulic pair cross mill that includes a hydraulic actuator for horizontally moving a pair of upper and lower work rolls and a pair of upper and lower backup rolls, and that changes the cross angle between the upper pair and the lower pair while keeping the upper pair consisting of the upper work roll and the upper backup roll parallel and the lower pair consisting of the lower work roll and the lower backup roll parallel.The method for zero-adjusting a slip angle of a hydraulic pair cross mill is for adjusting the zero point of the slip angle between the work roll and the backup roll in the upper pair and / or the lower pair, and the hydraulic actuator is The method includes an adjustment cylinder and a pressing cylinder that clamp the roll chocks of the work roll and backup roll, the adjustment cylinder including a position detector for detecting the position of the oil column and being controlled based on the position of the oil column detected by the position detector, the pressing cylinder being controlled to constantly press the roll chocks against the adjustment cylinder, and while the pressing pressure of the pressing cylinder is set to a zero adjustment pressure that is lower than the pressure during steady operation, the correlation between the cross angle and the measured value of the thrust force acting on the work roll and / or backup roll is obtained for each deviation angle while changing the deviation angle, and the value of the deviation angle at which the correlation that shows that the thrust force is zero when the cross angle is zero degrees is obtained is set as the zero point.

[0009] In one embodiment, the method for operating a hydraulic pair cross mill according to the present invention includes the steps of: adjusting the zero point of the deviation angle using the above-described method for zero-adjusting the deviation angle for a hydraulic pair cross mill; setting the deviation angle to the zero point, and with the pressing pressure of the pressing cylinder set to the pressure during steady operation, passing a metal strip between a pair of upper and lower work rolls to obtain a reference correlation between the cross angle and the measured value of the thrust force acting on the work rolls and / or backup rolls at the pressure during steady operation; and obtaining a correlation between the cross angle and the measured value of the thrust force acting on the work rolls and / or backup rolls during steady operation, and determining whether the deviation angle has deviated from the zero point by comparing the correlation during steady operation with the reference correlation.

[0010] In one embodiment of the method for producing a hot-rolled steel sheet according to the present invention, a hot-rolled steel sheet is produced while carrying out the above-described method for operating a hydraulic pair cross mill.

[0011] According to one embodiment of the method for zero-adjusting the deviation angle of a hydraulic pair cross mill of the present invention, the pressing pressure of the pressing cylinder is set to a zero-adjustment pressure that is lower than the pressure during steady-state operation, and while the deviation angle is changed, the correlation between the cross angle and the measured value of the thrust force acting on the work roll and / or backup roll is obtained for each deviation angle, and the deviation angle value at which a correlation is obtained that shows that the thrust force is zero when the cross angle is zero degrees is set as the zero point, thereby suppressing strip threading problems.

[0012] According to one embodiment of the method for operating a hydraulic pair cross mill and the method for manufacturing a hot-rolled steel sheet of the present invention, a correlation between the cross angle and the measured value of the thrust force acting on the work rolls and / or backup rolls is obtained during steady operation, and by comparing the correlation during steady operation with a reference correlation, it is determined whether the deviation angle has deviated from the zero point, thereby suppressing sheet threading problems.

[0013] 1 is a side view showing a hydraulic pair cross mill in which a method for zero-adjusting a slip angle of a hydraulic pair cross mill according to an embodiment of the present invention is implemented. It is a plan view showing the lower work roll, adjustment cylinder, and press cylinder of FIG. 1. It is an explanatory view showing a first mode of cross between the upper pair and the lower pair of FIG. 1. It is an explanatory view showing a second mode of cross between the upper pair and the lower pair of FIG. 1. It is a plan view showing a first mode of misalignment between the work roll and the backup roll in the lower pair of FIG. 1. It is a plan view showing a second mode of misalignment between the work roll and the backup roll in the lower pair of FIG. 1. It is a plan view showing a third mode of misalignment between the work roll and the backup roll in the lower pair of FIG. 1. It is a graph showing the correlation between the cross angle and the thrust rate estimated to be obtained in the first to third modes of misalignment shown in FIGS. 5 to 7. It is an explanatory view showing the reaction force generated by clamping the roll chocks by the adjustment cylinder and press cylinder of FIG. 1. It is a graph showing the correlation between the cross angle and the thrust rate obtained in the method for zero-adjusting a slip angle of a hydraulic pair cross mill according to an embodiment of the present invention. 1 is a graph showing the correlation between the cross angle and thrust rate obtained in the method for zero-adjusting the deviation angle of a hydraulic pair cross mill according to an embodiment of the present invention; 2 is a graph showing the correlation between the cross angle and thrust rate obtained in the method for zero-adjusting the deviation angle of a hydraulic pair cross mill according to an embodiment of the present invention; 3 is a graph showing the correlation between the cross angle and thrust rate obtained in the method for zero-adjusting the deviation angle of a hydraulic pair cross mill according to an embodiment of the present invention; 4 is a graph showing the reference correlation obtained in the method for operating a hydraulic pair cross mill according to an embodiment of the present invention;

[0014] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to each embodiment, and the components can be modified and embodied without departing from the spirit of the present invention. Furthermore, various inventions can be formed by appropriately combining multiple components disclosed in each embodiment. For example, some components may be omitted from all the components shown in the embodiments. Furthermore, components of different embodiments may be appropriately combined.

[0015] FIG. 1 is a side view showing a hydraulic pair cross mill 1 in which a method for zero adjustment of the deviation angle of a hydraulic pair cross mill 1 according to an embodiment of the present invention is implemented; FIG. 2 is a plan view showing the lower work roll 12W, adjustment cylinder 131, and pressing cylinder 132 of FIG. 1; FIG. 3 is an explanatory diagram showing a first mode of the cross between the upper pair 11P and the lower pair 12P of FIG. 1; and FIG. 4 is an explanatory diagram showing a second mode of the cross between the upper pair 11P and the lower pair 12P of FIG. 1.

[0016] The hydraulic pair cross mill 1 shown in Figure 1 is an apparatus for rolling a metal strip 2. Although not limited thereto, the metal strip 2 may be a steel strip (steel plate). Although Figure 1 shows one hydraulic pair cross mill 1 (one stand), a plurality of hydraulic pair cross mills 1 may be arranged in series in the conveying direction 2a of the metal strip 2. As shown in Figure 1, the hydraulic pair cross mill 1 includes a pair of upper and lower work rolls 11W, 12W, a pair of upper and lower backup rolls 11B, 12B, and a hydraulic actuator 13.

[0017] The pair of upper and lower work rolls 11W, 12W and the pair of upper and lower backup rolls 11B, 12B are each longitudinal members extending in a direction perpendicular to the plane of the paper in Figure 1. One end of each roll 11W, 12W, 11B, 12B (the side connected to a drive device such as a motor (drive side)) is sometimes called the drive side (DS), and the other end is sometimes called the work side (WS). Figure 1 shows a hydraulic pair cross mill 1 as viewed from the work side.

[0018] The pair of upper and lower work rolls 11W, 12W are arranged apart in the vertical direction, and the metal strip 2 is passed between the upper and lower work rolls 11W, 12W.

[0019] The upper backup roll 11B is disposed above the upper work roll 11W, and the lower backup roll 12B is disposed below the lower work roll 12W. Each backup roll 11B, 12B is disposed so that its outer circumferential surface is in contact with the outer circumferential surface of each work roll 11W, 12W.

[0020] The hydraulic actuator 13 is a device for horizontally moving each of the pair of upper and lower work rolls 11W, 12W and the pair of backup rolls 11B, 12B.

[0021] The hydraulic actuator 13 includes an adjusting cylinder 131 and a pressing cylinder 132 that clamp the roll chocks 14 of the work rolls 11W, 12W and the backup rolls 11B, 12B. The adjusting cylinder 131 includes a position detector 131a (see FIG. 2) for detecting the position of the oil column, and is controlled based on the oil column position detected by the position detector 131a. The pressing cylinder 132 is controlled to constantly press the roll chocks 14 against the adjusting cylinder 131.

[0022] As shown in Figure 2, the adjustment cylinder 131 and the press cylinder 132 are respectively arranged on both the work side and the drive side of each of the rolls 11W, 12W, 11B, and 12B (although Figure 2 shows only the lower work roll 12W, the same applies to the other rolls 11W, 11B, and 12B). By setting the oil column positions of the adjustment cylinders 131 on both sides to predetermined values, each of the rolls 11W, 12W, 11B, and 12B can be rotated so that the axial direction A of each of the rolls 11W, 12W, 11B, and 12B is inclined at any angle with respect to the direction PD perpendicular to the conveying direction 2a of the metal strip 2. In addition, the press cylinder 132 constantly presses the roll chocks 14 against the adjustment cylinder 131, thereby suppressing play between the roll chocks 14 and the adjustment cylinder 131.

[0023] 2 shows a state in which the work side of the lower work roll 12W is displaced forward in the conveying direction 2a of the metal strip 2, and the drive side is displaced backward in the conveying direction 2a of the metal strip 2. Conversely, the work side may be displaced backward and the drive side may be displaced forward. The arrangement of the adjustment cylinder 131 and the press cylinder 132 on each side is optional. For example, in FIG. 2, on the work side of the lower work roll 12W, the adjustment cylinder 131 is arranged forward in the conveying direction 2a of the metal strip 2, and the press cylinder 132 is arranged backward in the conveying direction 2a of the metal strip 2. However, on the work side, the press cylinder 132 may be arranged forward in the conveying direction 2a of the metal strip 2, and the adjustment cylinder 131 may be arranged backward in the conveying direction 2a of the metal strip 2. In addition, the positions (front or rear with respect to the conveying direction 2a of the metal strip 2) of the adjustment cylinder 131 and the pressing cylinder 132 are reversed on the work side and the drive side, but the positions of the adjustment cylinder 131 and the pressing cylinder 132 may be the same on the work side and the drive side.

[0024] As shown in Figures 3 and 4, in the hydraulic pair cross mill 1 of this embodiment, the upper pair 11P consisting of the upper work roll 11W and the upper backup roll 11B is parallel, and the lower pair 12P consisting of the lower work roll 12W and the lower backup roll 12B is parallel, and the cross angle θ1 between the upper pair 11P and the lower pair 12P is changed.

[0025] 3 and 4, the upper pair 11P and the lower pair 12P are shown in plan view, the lower work roll 12W is shown with relatively light shading, and the backup rolls 11B, 12B are shown with relatively dark shading. The upper work roll 11W is hidden under the upper backup roll 11B.

[0026] As shown in Figure 3, a configuration in which the work side of the upper pair 11P is displaced forward relative to the work side of the lower pair 12P with respect to the conveying direction 2a of the metal strip 2 may be referred to as a forward cross configuration. As shown in Figure 4, a configuration in which the work side of the lower pair 12P is displaced forward relative to the work side of the upper pair 11P with respect to the conveying direction 2a of the metal strip 2 may be referred to as a reverse cross configuration. When multiple hydraulic pair cross mills 1 are arranged in series with respect to the conveying direction 2a of the metal strip 2, some hydraulic pair cross mills 1 may be arranged in a forward cross configuration, and other hydraulic pair cross mills 1 may be arranged in a reverse cross configuration. Furthermore, forward cross hydraulic pair cross mills 1 and reverse cross hydraulic pair cross mills 1 may be arranged alternately with respect to the conveying direction 2a of the metal strip 2.

[0027] When the axial direction A of each of the rolls 11W, 12W, 11B, and 12B is inclined with respect to the direction PD perpendicular to the conveying direction 2a of the metal strip 2, a thrust force F acts on each of the rolls 11W, 12W, 11B, and 12B as the metal strip 2 passes. The thrust force F is a force acting in the axial direction of each roll. For example, in the forward cross shown in FIG. 3, a thrust force F toward the work side acts on the upper pair 11P, and a thrust force F toward the drive side acts on the lower pair 12P. In the reverse cross shown in FIG. 4, a thrust force F toward the drive side acts on the upper pair 11P, and a thrust force F toward the work side acts on the lower pair 12P.

[0028] The hydraulic pair cross mill 1 of this embodiment further includes a thrust gauge 15 for measuring the thrust force F acting on at least one of the upper work roll 11W, the lower work roll 12W, the upper backup roll 11B, and the lower backup roll 12B. The thrust gauge 15 may be disposed on any side of any of the rolls 11W, 12W, 11B, and 12B, or on the side of the upper or lower work roll 11W or 12W that is displaced forward in the conveying direction 2a of the metal strip 2. The thrust gauge 15 may also be disposed on the work side where there is relatively ample installation space. That is, in the hydraulic pair cross mill 1 configured as a forward cross shown in FIG. 3, the thrust gauge 15 may be disposed on the work side of the upper work roll 11W to measure the thrust force F acting on the upper work roll 11W. Similarly, in the hydraulic pair cross mill 1 configured in the reverse cross configuration shown in FIG. 4, the thrust gauge 15 may be placed on the work side of the lower work roll 12W to measure the thrust force F acting on the lower work roll 12W.

[0029] Next, a method for zero-adjusting the deviation angle of a hydraulic pair cross mill 1 according to an embodiment of the present invention will be described with reference to FIGS. 5 to 13. FIGS. 5 to 7 are plan views showing first to third modes of deviation between the work roll 12W and backup roll 12B in the lower pair 12P of FIG. 1 , and FIG. 8 is a graph showing the correlation between the cross angle θ1 estimated to be obtained for the first to third modes of deviation shown in FIGS. 5 to 7 and the thrust rate. FIG. 9 is an explanatory diagram showing the reaction force C generated by clamping the roll chocks 14 between the adjustment cylinder 131 and the pressing cylinder 132 of FIG. 1. FIGS. 10 to 13 are graphs showing the correlation between the cross angle θ1 and the thrust rate obtained in the method for zero-adjusting the deviation angle of a hydraulic pair cross mill 1 according to an embodiment of the present invention.

[0030] The method for zero adjustment of the deviation angle of a hydraulic pair cross mill 1 according to an embodiment of the present invention is a method for adjusting the zero point of the deviation angle θ between the work rolls 11W, 12W and the backup rolls 11B, 12B in the upper pair 11P and / or the lower pair 12P in the hydraulic pair cross mill 1 described above. Adjusting the zero point of the deviation angle θ is sometimes called zero adjustment of the deviation angle θ.

[0031] It is known that there is a correlation between the deviation angle θ between the work rolls 11W, 12W and the backup rolls 11B, 12B and the measured value of the thrust force F acting on the work rolls 11W, 12W and / or the backup rolls 11B, 12B.

[0032] The correlation between the offset angle θ between the work roll 12W and the backup roll 12B in the lower pair 12P and the measured value of the thrust force F acting on the work roll 12W will now be described as an example.

[0033] The misalignment between the work roll 12W and the backup roll 12B in the lower pair 12P can take the first to third modes shown in Figures 5 to 7. In the first mode shown in Figure 5, the work roll 12W and the backup roll 12B in the lower pair 12P are parallel (no misalignment occurs). In this mode, the misalignment angle θ2 between the work roll 12W and the backup roll 12B can be said to be zero degrees. In the second mode shown in Figure 6, the work roll 12W and / or the backup roll 12B are rotated so that the drive side of the work roll 12W in the lower pair 12P is positioned forward of the drive side of the backup roll 12B in the conveying direction 2a of the metal strip 2. The misalignment angle θ2 between the work roll 12W and the backup roll 12B in this mode is called a positive misalignment angle θ2. 7 is a third mode in which the work rolls 12W and / or the backup rolls 12B are rotated so that the drive side of the work roll 12W in the lower pair 12P is located further rearward than the drive side of the backup roll 12B in the conveying direction 2a of the metal strip 2. The offset angle θ between the work roll 12W and the backup roll 12B in this case is called a negative offset angle θ.

[0034] The correlation between the cross angle θ1 and the thrust ratio obtained in the first to third modes of deviation shown in FIGS. 5 to 7 is estimated to be the relationship shown by the respective straight lines in FIG.

[0035] As shown in the first embodiment of Figure 5, when the slip angle θ between the work roll 12W and backup roll 12B in the lower pair 12P is zero degrees (the work roll 12W and backup roll 12B are parallel), and a metal strip 2 is passed through and rolled between the work rolls 11W and 12W, the correlation between the cross angle θ between the upper and lower work rolls 11W and 12W and the thrust rate calculated from the measured value of the thrust force F acting on the work roll 12W should be as shown by the solid line in Figure 8. That is, when the slip angle θ is zero degrees, if a regression line (solid line) is obtained on a coordinate plane with the thrust rate as the first coordinate axis (vertical axis) and the cross angle θ as the second coordinate axis (horizontal axis), the regression line should pass through the origin (cross angle θ = 0, thrust rate = 0). This is because, when the slip angle θ is zero degrees, the second thrust force F from the backup roll 12B, described below, is not substantially generated. The thrust ratio is a dimensionless value obtained by dividing the measured value of the thrust force F by the rolling load.

[0036] As shown in FIG. 6, when a positive offset angle θ occurs between the work roll 12W and the backup roll 12B in the lower pair 12P (the work roll 12W and / or the backup roll 12B are rotated so that the drive side of the work roll 12W is located further forward in the conveying direction 2a of the metal strip 2 than the drive side of the backup roll 12B), when the metal strip 2 is rolled through the work rolls 11W, 12W, the correlation between the cross angle θ between the upper and lower work rolls 11W, 12W and the thrust ratio calculated from the measured value of the thrust force F acting on the work roll 12W should be as shown by the dashed dotted line in FIG. 8. That is, when a positive deviation angle θ2 is occurring, if a regression line (dashed line) is obtained on a coordinate plane with the thrust rate as the first coordinate axis (vertical axis) and the cross angle θ1 as the second coordinate axis (horizontal axis), the regression line will not pass through the origin (cross angle θ1 = 0, thrust rate = 0), and the intercept of the regression line will be positive (when the cross angle θ1 is zero degrees on the regression line, the thrust rate will be positive). This is because, when a positive deviation angle θ2 is occurring, a second thrust force F2 (see FIG. 6) acting in the same direction as the thrust force F acts on the work roll 12W from the backup roll 12B, and the resultant force of the thrust force F and the second thrust force F2 is measured by the thrust meter 15 as the measured value of the thrust force F.

[0037] As shown in FIG. 7, when a negative deviation angle θ occurs between the work roll 12W and the backup roll 12B in the lower pair 12P (the work roll 12W and / or the backup roll 12B are rotated so that the drive side of the work roll 12W is located further rearward in the conveying direction 2a of the metal strip 2 than the drive side of the backup roll 12B), when the metal strip 2 is rolled through the work rolls 11W, 12W, the correlation between the cross angle θ between the upper and lower work rolls 11W, 12W and the thrust ratio calculated from the measured value of the thrust force F acting on the work roll 12W should be as shown by the two-dot chain line in FIG. That is, when a negative deviation angle θ2 occurs, if a regression line (dashed line) is obtained on a coordinate plane with the thrust rate as the first coordinate axis (vertical axis) and the cross angle θ1 as the second coordinate axis (horizontal axis), the regression line will not pass through the origin (cross angle θ1 = 0, thrust rate = 0), and the intercept of the regression line will be negative (the thrust rate will be negative when the cross angle θ1 is zero degrees on the regression line). This is because, when a negative deviation angle θ2 occurs, a second thrust force F2 (see FIG. 7) acting in the opposite direction to the thrust force F acts from the backup roll 12B to the work roll 12W, and the resultant force of the thrust force F and the second thrust force F2 is measured by the thrust meter 15 as the measured value of the thrust force F.

[0038] The present inventors thought that if such a correlation were obtained during steady operation and the zero adjustment of the deviation angle θ2 were performed based on that correlation, factors such as installation error and elastic deformation of the hydraulic pair cross mill 1 could be taken into consideration, and strip threading problems such as meandering and bending of the metal strip 2 could be suppressed. However, when the zero adjustment of the deviation angle θ2 was performed based on the correlation obtained during steady operation, the strip threading problems were not sufficiently suppressed. After various studies on the cause of this, the present inventors came to the conclusion that the thrust force F was measured to be lower than the actual value due to the clamping of the roll chocks 14 by the adjustment cylinder 131 and the pressing cylinder 132, and that even if the zero adjustment of the deviation angle θ2 was performed based on the lower measured thrust force F, the strip threading problems could not be sufficiently suppressed. The reason why the thrust force F is measured lower than the actual value due to the clamping of the roll chock 14 by the adjustment cylinder 131 and the pressing cylinder 132 is that when the roll chock 14 is clamped by the adjustment cylinder 131 and the pressing cylinder 132 as shown in FIG. 9, a reaction force C (friction force or the like) in the opposite direction to the thrust force F acts on the roll chock 14.

[0039] A method for zero-adjusting the slip angle of a hydraulic pair cross mill 1 according to an embodiment of the present invention includes: setting the pressing pressure of the pressing cylinder 132 to a zero-adjustment pressure lower than the pressure during steady operation; changing the slip angle θ; and obtaining a correlation between the cross angle θ and the measured value of the thrust force F acting on the work rolls 11W, 12W and / or the backup rolls 11B, 12B for each slip angle θ; and setting the value of the slip angle θ at which the correlation is obtained, showing that the thrust force F is zero when the cross angle θ is zero, as the zero point of the slip angle θ. Setting the pressing pressure of the pressing cylinder 132 to a zero-adjustment pressure lower than the pressure during steady operation reduces the influence of the reaction force C generated by clamping the roll chocks 14 between the adjustment cylinder 131 and the pressing cylinder 132 on the correlation. Then, performing zero-adjustment of the slip angle θ based on the correlation obtained under conditions in which the influence of the reaction force C is reduced can suppress strip threading problems. Note that the measurement value of the thrust force F or the thrust rate being zero does not only mean that the measurement value of the thrust force F or the thrust rate is strictly zero, but also means that the measurement value or the thrust rate is zero taking into account the tolerance for error in the technical field of the present invention. For example, if the thrust rate is within a range of 0±0.02, the thrust rate may be considered to be zero. To improve accuracy, a thrust rate within a range of 0±0.01 may also be considered to be zero. Furthermore, the pressing pressure of the pressing cylinder 132 may be set to the zero adjustment pressure for all of the rolls 11W, 12W, 11B, and 12B, or may be set only for any of the rolls 11W, 12W, 11B, and 12B, or the upper pair 11P or the lower pair 12P, for which the thrust force F is measured.

[0040] Obtaining the correlation may involve repeatedly measuring the thrust force F when the metal strip 2 is passed through a pair of upper and lower work rolls 11W, 12W and rolled while the deviation angle θ2 is set to a predetermined value and the cross angle θ1 is changed. That is, while the deviation angle θ2 is fixed to a predetermined value and the cross angle θ1 is changed, data is accumulated for combinations of the measured thrust force F and the value of the cross angle θ1 at that time. This makes it possible to obtain the data plotted in the graphs of Figures 10 to 13. Although not limited to this, the measured thrust force F may be measured during steady-state strip threading, i.e., measured at a time other than the moment when the metal strip 2 engages the work rolls 11W, 12W and the moment when the metal strip 2 leaves the work rolls 11W, 12W. Measurements taken at any time during steady-state strip threading may be used, but initial measurements during steady-state strip threading may also be used. Data accumulation may be performed using test material or during actual operation (rolling product material). One plot in Figures 10 to 13 may correspond to one material (one coil).

[0041] The measured value of the thrust force F may be used directly for zero adjustment of the deviation angle θ2, but obtaining the correlation may include calculating a dimensionless thrust ratio by dividing the measured value of the thrust force F by the rolling load. The value of the thrust force varies depending on the characteristics of the metal strip 2 being rolled and the size of the hydraulic pair cross mill 1 itself. For example, the rolling load differs when rolling a hard, thick metal strip 2 and when rolling a soft, thin metal strip 2, and therefore the absolute value of the thrust force also changes. By using the thrust ratio obtained by dividing the measured value of the thrust force F by the rolling load, it is possible to eliminate the influence of the characteristics of the metal strip 2, etc. Under constant conditions, the measured value of the thrust force F may be used directly.

[0042] Obtaining the correlation may include obtaining a regression line on a coordinate plane with the thrust rate as the first coordinate axis and the cross angle θ1 (deg) as the second coordinate axis. The regression line is also shown in the graphs of FIGS. 10 to 13. The value of the deviation angle θ2 at which the regression line indicates that the thrust force F is zero when the cross angle θ1 is zero degrees can be set as the zero point of the deviation angle θ2. The regression line can be obtained by the least squares method from data combining the measured values ​​of the thrust force F and the value of the cross angle θ1 at that time. The regression line may be drawn intuitively by a person while viewing the plot. Alternatively, without obtaining a regression line, a person may determine whether the thrust force F indicates zero when the cross angle θ1 is zero degrees based on the trend of the plot.

[0043] When the correlations shown in Figures 10 to 13 are obtained, the value of the deviation angle θ2 when the correlation in Figure 13 is obtained can be set as the zero point of the deviation angle θ2. When the correlation in Figure 10 is obtained, it is presumed that a positive deviation angle θ2 occurred between the work roll 12W and the backup roll 12B, as shown in Figure 6. When the correlations in Figures 11 and 12 are obtained, it is presumed that a negative deviation angle θ2 occurred between the work roll 12W and the backup roll 12B, as shown in Figure 7. When the correlations shown in Figures 10 to 12 are obtained, the deviation angle θ2 is adjusted so that the positive or negative deviation angle θ2 approaches zero, and the correlation in Figure 13 is obtained. In Figure 11, the thrust rate does not increase until the cross angle θ1 of the work roll 12W reaches a predetermined value. This is because, in this embodiment, a load cell disposed on the work side is used as the thrust meter 15, and only the pressing force toward the thrust meter 15 is measured, and no output from the thrust meter 15 is obtained until the thrust force F becomes larger than the second thrust force F2 (tensile force). When plotted as in Figure 11, it can be inferred that the thrust force F takes a negative value when the cross angle θ1 is zero degrees, as shown by the dotted line in Figure 11. If negative thrust forces F were also measured, it can be inferred that the regression line would be extended even when the thrust rate falls below zero, as shown in Figure 12.

[0044] The zero adjustment pressure may be 30% or more and 50% or less of the pressure during steady operation. By setting it to 50% or less, the influence on the correlation of the reaction force C generated by the clamping of the roll chocks 14 by the adjustment cylinder 131 and the pressing cylinder 132 can be sufficiently reduced, and by setting it to 30% or more, rattle, vibration, and / or displacement of the rolls 11W, 12W, 11B, and 12B can be suppressed when rolling the metal strip 2 between the upper and lower work rolls 11W and 12W, thereby enabling stable measurement of the thrust force F. It is more preferable that the zero adjustment pressure be 35% or more and 45% or less of the pressure during steady operation. In short, the zero adjustment pressure is preferably low from the viewpoint of minimizing the effect of the reaction force C shown in FIG. 9 as much as possible. However, if the zero adjustment pressure is too low, when the metal strip 2 passes between the upper and lower work rolls 11W, 12W, particularly when the metal strip 2 becomes caught between the upper and lower work rolls 11W, 12W, the load acting on the upper and lower work rolls 11W, 12W may cause rattle, vibration, and / or misalignment in the upper and lower work rolls 11W, 12W and the upper and lower backup rolls 11B, 12B, making it impossible to stably measure the thrust force F. Therefore, a pressure that allows stable sheet passage is required as the zero adjustment pressure.

[0045] Zero adjustment pressure: 35 kgf / cm 2 or more and 45 kgf / cm 2 or less (about 3.5 MPa to about 4.5 MPa).

[0046] Next, a method for operating the hydraulic pair cross mill 1 according to an embodiment of the present invention will be described. Fig. 14 is a graph showing the reference correlation obtained in the method for operating the hydraulic pair cross mill 1 according to an embodiment of the present invention. A method for operating a hydraulic pair cross mill 1 according to an embodiment of the present invention includes the steps of: adjusting the zero point of the deviation angle θ2 using the deviation angle zero adjustment method for the hydraulic pair cross mill 1 described above; setting the deviation angle θ2 to the zero point, and with the pressing pressure of the pressing cylinder 132 set to the pressure during steady operation, passing a metal strip 2 between the pair of upper and lower work rolls 11W, 12W, and obtaining a reference correlation between the cross angle θ1 and the measured value of the thrust force F acting on the work rolls 11W, 12W and / or backup rolls 11B, 12B under pressure during steady operation; and obtaining a correlation between the cross angle θ1 and the measured value of the thrust force F acting on the work rolls and / or backup rolls during steady operation, and determining whether the deviation angle θ2 has deviated from the zero point by comparing the correlation during steady operation with the reference correlation.

[0047] The reference correlation for pressure during steady operation is a correlation obtained by adjusting the zero point of the deviation angle θ using the deviation angle zero adjustment method for the hydraulic pair cross mill 1 described above, with the pressure of the pressure cylinder 132 set as the pressure during steady operation, taking into account the influence of the reaction force C generated by the clamping of the roll chock 14 between the adjustment cylinder 131 and the pressure cylinder 132. In Figure 14, the dashed two-dot line represents the correlation for the zero adjustment pressure, and the solid line represents the reference correlation for pressure during steady operation. Due to the influence of the reaction force C, the reference correlation exhibits an overall lower thrust rate than the correlation for the zero adjustment pressure. Note that the reference correlation shown by the solid line in Figure 14 indicates that the thrust rate is zero when the cross angle θ is between 0 degrees and approximately 0.3 degrees. This is because, as explained using Figure 11, this embodiment uses a load cell located on the workpiece side as the thrust gauge 15. 14, it can be inferred that the thrust force F has a negative value when the cross angle θ1 is zero degrees in the reference correlation. Furthermore, if the negative thrust force F is also measured, it can be inferred that the reference correlation including the dotted line portion can be obtained.

[0048] Because both the reference correlation and the correlation during steady operation include the influence of the reaction force C, it is possible to determine whether the deviation angle θ2 deviates from the zero point by comparing them. In other words, by obtaining the correlation at the pressure during steady operation, it is possible to determine whether the deviation angle θ2 deviates from the zero point without changing the pressing pressure of the pressing cylinder 132 to the zero adjustment pressure. By performing operation while confirming that the deviation angle θ2 does not deviate from the zero point, strip threading problems can be suppressed. If it is determined that the deviation angle θ2 deviates from the zero point, the deviation angle θ2 may be adjusted so that the correlation during steady operation matches or approaches the reference correlation.

[0049] The step of acquiring the reference correlation is performed after adjusting the zero point of the deviation angle θ2. The step of acquiring the reference correlation may include repeatedly measuring the thrust force F when the metal strip 2 passes between the pair of upper and lower work rolls 11W, 12W while changing the cross angle θ1 and setting the pressure of the pressure cylinder 132 to the pressure during steady operation, with the deviation angle θ2 set to zero. That is, while the deviation angle θ2 is fixed at zero, the cross angle θ1 may be changed and data on combinations of the measured thrust force F and the value of the cross angle θ1 at that time may be accumulated. Furthermore, in acquiring the reference correlation, the measured value of the thrust force F may be used as is, or a thrust ratio that is dimensionless by dividing the measured value of the thrust force F by the rolling load may be used. Furthermore, in acquiring the reference correlation, the step of acquiring the reference correlation may also include obtaining a regression line in a coordinate plane with the thrust ratio as the first coordinate axis and the cross angle θ1 (deg) as the second coordinate axis.

[0050] The correlation during steady operation is acquired after the reference correlation is acquired. The method for acquiring the correlation during steady operation may be the same as that for the reference correlation. That is, the process for acquiring the correlation during steady operation may include repeatedly measuring the thrust force F when the metal strip 2 passes between the pair of upper and lower work rolls 11W, 12W with the deviation angle θ2 set to zero. However, the cross angle θ1 is set to a value corresponding to the rolling conditions during operation. At this time, data combining the measured value of the thrust force F and the value of the cross angle θ1 at that time may be accumulated. Furthermore, in acquiring the correlation during steady operation, the measured value of the thrust force F may be used as is, or a thrust ratio that is dimensionless by dividing the measured value of the thrust force F by the rolling load may be used. Furthermore, in acquiring the correlation during steady operation, the process may also include obtaining a regression line in a coordinate plane with the thrust ratio as the first coordinate axis and the cross angle θ1 (deg) as the second coordinate axis.

[0051] When obtaining the reference correlation and the correlation during steady operation includes obtaining a regression line, if there is a deviation between the reference regression line of the reference correlation and the regression line during steady operation (hereinafter sometimes referred to as "linear deviation"), it can be determined that the deviation angle θ2 deviates from zero. The linear deviation can be determined from the deviation of the slope and / or intercept of each regression line. When the deviation of the slope and / or intercept exceeds a predetermined value, it can be determined that the deviation angle θ2 deviates from zero. The determination of whether or not linear deviation has occurred can be performed periodically, for example, on each scheduled maintenance day.

[0052] The method for manufacturing a hot-rolled steel sheet according to an embodiment of the present invention includes manufacturing a hot-rolled steel sheet while carrying out the above-described method for operating the hydraulic pair cross mill 1.

[0053] Although the preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to these examples. It is clear that a person skilled in the art to which the present invention pertains can conceive of various modifications and alterations within the scope of the technical ideas set forth in the claims, and it is understood that these also naturally fall within the technical scope of the present invention.

[0054] The invention described in this specification can also be described as follows: [1] A hydraulic pair cross mill includes hydraulic actuators for horizontally moving a pair of upper and lower work rolls and a pair of upper and lower backup rolls, and changes the cross angle between the upper pair and the lower pair while an upper pair consisting of an upper work roll and an upper backup roll is parallel and a lower pair consisting of a lower work roll and a lower backup roll is parallel, the hydraulic pair cross mill comprising a method for zero adjustment of a misalignment angle for adjusting the zero point of the misalignment angle between the work roll and the backup roll in the upper pair and / or the lower pair, the hydraulic actuators including adjustment cylinders and pressing cylinders for clamping the roll chocks of the work roll and the backup roll, the adjustment cylinders including position detectors for detecting the position of an oil column and are controlled based on the position of the oil column detected by the position detector, and the pressing cylinders are controlled to constantly press the roll chocks against the adjustment cylinders, A method for zero-adjusting a slip angle of a hydraulic pair cross mill, comprising: acquiring, for each slip angle, a correlation between the cross angle and a measured value of the thrust force acting on the work roll and / or the backup roll while changing the slip angle in a state where the pressing pressure of the pressing cylinder is set to a zero-adjustment pressure that is lower than the pressure during steady operation; and setting the value of the slip angle at which the correlation is acquired, in which the thrust force shows zero when the cross angle is zero, as a zero point. [2] The method for zero-adjusting a slip angle of a hydraulic pair cross mill, as described in paragraph 1, wherein acquiring the correlation includes repeatedly measuring the thrust force when a metal strip is passed between the pair of upper and lower work rolls while changing the cross angle in a state where the slip angle is set to a predetermined value. [3] The method for zero-adjusting a slip angle of a hydraulic pair cross mill, as described in paragraph 1 or 2, wherein acquiring the correlation includes dividing the measured value of the thrust force by the rolling load to obtain a dimensionless thrust ratio. [4] The method for zero adjustment of the deviation angle of a hydraulic pair cross mill described in paragraph 3, wherein the acquisition of the correlation includes obtaining a regression line in a coordinate plane with the thrust ratio as a first coordinate axis and the cross angle as a second coordinate axis.[5] The method for zero-adjusting a deviation angle of a hydraulic pair cross mill according to any one of items 1 to 4, wherein the zero-adjustment pressure is 30% or more and 50% or less of the pressure during steady operation. [6] The zero-adjustment pressure is 35 kgf / cm. 2 or more and 45 kgf / cm 2 A method for zero-adjusting a deviation angle of a hydraulic pair cross mill according to any one of items 1 to 5. [7] A method for operating a hydraulic pair cross mill, comprising: adjusting the zero point of the deviation angle by the method for zero-adjusting a deviation angle of a hydraulic pair cross mill according to any one of items 1 to 6; setting the deviation angle to the zero point, and passing a metal strip between the pair of upper and lower work rolls with the pressing pressure of the pressing cylinder set to the pressure during steady operation, and obtaining a reference correlation between the cross angle and measured values ​​of thrust forces acting on the work rolls and / or backup rolls at the pressure during steady operation; and obtaining a correlation between the cross angle and measured values ​​of thrust forces acting on the work rolls and / or backup rolls during steady operation, and determining whether the deviation angle has deviated from the zero point by comparing the correlation during steady operation with the reference correlation. [8] A method for manufacturing a hot-rolled steel sheet while carrying out the method for operating a hydraulic pair cross mill according to item 7.

[0055] 1: Hydraulic pair cross mill 2: Metal strip 11P: Upper pair 11W: Upper work roll 11B: Upper backup roll 12P: Lower pair 12W: Lower work roll 12B: Lower backup roll 13: Hydraulic actuator 14: Roll chock 131: Adjusting cylinder 131a: Position detector 132: Press cylinder F: Thrust force

Claims

1. A hydraulic pair cross mill which is provided with hydraulic actuators for horizontally moving a pair of upper and lower work rolls and a pair of upper and lower backup rolls, and which changes the cross angle between the upper pair and the lower pair while an upper pair consisting of an upper work roll and an upper backup roll is parallel and a lower pair consisting of a lower work roll and a lower backup roll is parallel, comprising a method for zero adjustment of a misalignment angle between the work roll and the backup roll in the upper pair and / or the lower pair, the method comprising the steps of: adjusting a roll chock between the work roll and the backup roll in the upper pair and / or the lower pair; the hydraulic actuator including an adjustment cylinder and a pressing cylinder which sandwich the roll chocks of the work roll and the backup roll; the adjustment cylinder including a position detector for detecting the position of an oil column and being controlled based on the position of the oil column detected by the position detector; and controlling the pressing cylinder so as to constantly press the roll chock against the adjustment cylinder; A method for zero-adjusting a deviation angle of a hydraulic pair cross mill, comprising: while changing the deviation angle in a state where the pressing pressure of the pressing cylinder is set to a zero-adjustment pressure lower than the pressure during steady operation, obtaining a correlation between the cross angle and a measured value of the thrust force acting on the work roll and / or the backup roll for each deviation angle; and setting the value of the deviation angle at which the correlation indicating that the thrust force is zero when the cross angle is zero degrees as the zero point.

2. A method for zero adjustment of the deviation angle of a hydraulic pair cross mill as described in claim 1, wherein obtaining the correlation includes repeatedly measuring the thrust force when a metal strip is passed between the pair of upper and lower work rolls while changing the cross angle with the deviation angle set to a predetermined value.

3. The method for zero adjustment of deviation angle of a hydraulic pair cross mill according to claim 2, wherein obtaining the correlation includes determining a non-dimensional thrust ratio by dividing the measured value of the thrust force by the rolling load.

4. A method for zero adjustment of the deviation angle of a hydraulic pair cross mill as described in claim 3, wherein obtaining the correlation includes obtaining a regression line in a coordinate plane with the thrust ratio as the first coordinate axis and the cross angle as the second coordinate axis.

5. A method for zero-adjusting a deviation angle of a hydraulic pair cross mill as set forth in claim 1, wherein the zero-adjustment pressure is 30% or more and 50% or less of the pressure during steady operation.

6. The zero adjustment pressure is 35 kgf / cm 2 More than 45 kgf / cm 2 The method for zero adjustment of a deviation angle of a hydraulic pair cross mill according to claim 1, wherein the deviation angle is:

7. A method for operating a hydraulic pair cross mill comprising the steps of: adjusting the zero point of the deviation angle by a method for zero adjustment of the deviation angle of a hydraulic pair cross mill as defined in any one of claims 1 to 6; setting the deviation angle to the zero point and, with the pressing pressure of the pressing cylinder set to the pressure during steady operation, passing a metal strip between the pair of upper and lower work rolls and obtaining a reference correlation between the cross angle and the measured value of the thrust force acting on the work roll and / or the backup roll at the pressure during steady operation; and obtaining a correlation between the cross angle and the measured value of the thrust force acting on the work roll and / or the backup roll during steady operation and determining whether or not the deviation angle has deviated from the zero point by comparing the correlation during steady operation with the reference correlation.

8. A method for producing hot-rolled steel sheets, comprising carrying out the method for operating a hydraulic pair cross mill as set forth in claim 7.

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