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

The method for zero-adjusting a deviation angle of a hydraulic pair cross mill according to this invention is a method for zero-adjusting a deviation angle of a hydraulic pair cross mill for adjusting a zero point of a deviation angle θ2 between work rolls 11W, 12W and backup rolls 11B, 12B in an upper pair 11P and / or a lower pair 12P, wherein the method includes acquiring a correlation between a cross angle θ1 and a measured value of a thrust force F acting on the work rolls 11W, 12W and / or the backup rolls 11B, 12B for each deviation angle θ2 while changing the deviation angle θ2 in a state where a pressing pressure of a pressing cylinder 132 is set to a pressure for zero adjustment lower than a pressure during steady operation, and setting a value of the deviation angle θ2 at which the correlation showing the thrust force of zero when the cross angle θ1 is a zero degree is acquired, to a zero point.

Description

[Technical Field]

[0001] This invention relates to a method for zero-adjusting a 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.[Background Art]

[0002] A conventionally used hydraulic pair cross mill of this type can include for example, the structure disclosed in the following Patent Literature 1. Patent Literature 1 describes a hydraulic pair cross mill including: a pair of upper and lower work rolls; and a hydraulic actuator that horizontally moves a pair of upper and lower backup rolls that support the pair of upper and lower work rolls, respectively, wherein a cross angle between an upper pair consisting of the upper work roll and the upper backup roll and a lower pair consisting of the lower work roll and the lower backup roll is changed in a state where the upper pair and the lower pair is made parallel. The hydraulic actuator includes an adjusting cylinder (a hydraulic cylinder of a position control device for each roll) and a pressing cylinder (a hydraulic cylinder of a pressing device for each roll) that clamp each roll chock of the work roll and the backup roll. The adjusting cylinder includes a position detector for detecting an oil column position and is controlled based on the oil column position detected by the position detector. The pressing cylinder is controlled to constantly pressing the roll chocks against the adjusting cylinder.[Citation List][Patent Literature]

[0003] [PTL 1] WO 2021 / 220366 A1[Summary of Invention][Technical Problem]

[0004] Because of installation errors in the hydraulic pair cross mill or elastic deformation due to stress during threading, an unintended deviation angle may occur between the work rolls and backup rolls in the upper pair and / or the lower pair. The deviation angle may be otherwise referred to as a micro cross angle, skew angle or the like. If the deviation angle occurs, an unintended thrust force is generated on each roll. The unintentional thrust force can cause threading troubles such as meandering and bending of a metal strip (such as a steel strip) when the metal strip is rolled using the hydraulic pair cross mill. Therefore, it is required to adjust the zero point of the deviation angle between the work roll and the backup roll, taking into consideration installation errors, elastic deformation, and the like. Adjusting the zero point of the deviation angle may be referred to as zero-adjusting of the deviation angle.

[0005] It is known that there is a correlation between the deviation angle between the work roll and backup roll and the measured thrust force acting on the work roll and / or backup roll. The inventor thought that if such a correlation was obtained during steady operation and zero-adjusting of the deviation angle was performed based on the correlation, factors such as installation errors and elastic deformation could be taken into account, thereby reducing threading troubles. However, when the zero-adjusting of the deviation angle was performed based on the correlation acquired during steady operation, it was not sufficient to suppress the threading troubles.

[0006] As a result of intensive studies for its cause of the troubles, the inventors have found a new problem that even if the thrust force is measured to be lower than the actual value due to the clamping of the roll chocks by the adjusting cylinder and the pressing cylinder and the zero-adjusting of the deviation angle is performed based on the lower measured thrust force, the threading troubles cannot be sufficiently suppressed.

[0007] This invention has been made to solve the above problems, and one of objects of this invention is to provide a method for zero-adjusting a 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 troubles such as meandering and bending of a metal strip.[Solution to Problem]

[0008] In an embodiment, the method for zero-adjusting a deviation angle of a hydraulic pair cross mill is a method for zero-adjusting a deviation angle of a hydraulic pair cross mill comprising a hydraulic actuator for moving each of a pair of upper and lower work rolls and a pair of upper and lower backup rolls in a horizontal direction, the hydraulic pair cross mill being configured to change a cross angle between an upper pair comprised of an upper work roll and a lower backup roll and a lower pair of a lower work roll and a lower backup roll in a state where the upper pair is made parallel and the lower pair is made parallel, and method being for adjusting a zero point of a deviation angle between the work rolls and the backup rolls in the upper pair and / or the lower pair in the hydraulic pair cross mill, wherein the hydraulic actuator comprises an adjusting cylinder and a pressing cylinder that clamp each of roll chocks of the work rolls and the backup rolls; the adjusting cylinder comprises a position detector for detecting a position of an oil column and is controlled based on the position of the oil column detected by the position detector; and the pressing cylinder is controlled to constantly press the roll chocks against the adjusting cylinder; and wherein the method comprises acquiring a correlation between the cross angle and a measured value of a thrust force acting on the work rolls and / or the backup rolls for each deviation angle while changing the deviation angle in a state where a pressing pressure of the pressing cylinder is set to a pressure for zero adjustment lower than a pressure during steady operation, and setting a value of the deviation angle at which the correlation showing the thrust force of zero when the cross angle is a zero degree is acquired, to a zero point.

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

[0010] In an embodiment, the method for manufacturing a hot-rolled steel sheet according to this invention comprises manufacturing the hot-rolled steel sheet while performing the method for operating the hydraulic pair cross mill as described above.[Advantageous Effects of Invention]

[0011] According to an embodiment of the method for zero-adjusting a deviation angle of a hydraulic pair cross mill of this invention, the threading troubles can be suppressed because the correlation between the cross angle and the measured value of the thrust force acting on the work rolls and / or the backup rolls is acquired for each deviation angle while changing the deviation angle in the state where the pressing pressure of the pressing cylinder is set to a pressure for zero adjustment lower than a pressure during steady operation, and the value of the deviation angle at which the correlation showing the thrust force of zero when the cross angle is zero degree is acquired is set to the zero point.

[0012] According to an embodiment of the method for operating the hydraulic pair cross mill and a method for manufacturing a hot-rolled steel sheet, the threading troubles can be suppressed because the correlation between the cross angle and the measured value of the thrust force acting on the work rolls and / or backup rolls is acquired during the steady operation, and whether the deviation angle is deviated from the zero point is determined by comparing the correlation during the steady operation with the reference correlation.[Brief Description of Drawings]

[0013] [Fig. 1] Figure 1 is a side view showing a hydraulic pair cross mill in which a method for zero-adjusting a deviation angle of a hydraulic pair cross mill is carried out, according to an embodiment of this invention. [Fig. 2] Figure 2 is a plane view showing the lower work roll, adjusting cylinder, and pressing cylinder in Figure 1. [Fig. 3] Figure 3 is an explanatory view showing a first embodiment of a cross between the upper pair and the lower pair in Figure 1. [Fig. 4] Figure 4 is an explanatory view showing a second embodiment of a cross between the upper pair and the lower pair in Figure 1. [Fig. 5] Figure 5 is a plane view showing a first embodiment of deviation between the work roll and the backup roll in the lower pair in Figure 1. [Fig. 6] Figure 6 is a plane view showing a second embodiment of deviation between the work roll and the backup roll in the lower pair in Figure 1. [Fig. 7] Figure 7 is a plane view showing a third embodiment of deviation between the work roll and the backup roll in the lower pair in Figure 1. [Fig. 8] Figure 8 is a graph showing a correlation between a cross angle and a thrust rate estimated to be acquired in the first to third embodiments for the deviation shown in Figures 5 to 7. [Fig. 9] Figure 9 is an explanatory view showing a reaction force generated by clamping roll chocks by the adjusting cylinder and the pressing cylinder in Figure 1. [Fig. 10] Figure 10 is a graph showing a correlation between a cross angle and a thrust rate acquired in the method for zero-adjusting a deviation angle of a hydraulic pair cross mill according to an embodiment of this invention. [Fig. 11] Figure 11 is a graph showing a correlation between a cross angle and a thrust rate acquired in the method for zero-adjusting a deviation angle of a hydraulic pair cross mill according to an embodiment of this invention. [Fig. 12] Figure 12 is a graph showing a correlation between a cross angle and a thrust rate acquired in the method for zero-adjusting a deviation angle of a hydraulic pair cross mill according to an embodiment of this invention. [Fig. 13] Figure 13 is a graph showing a correlation between a cross angle and a thrust rate acquired in the method for zero-adjusting a deviation angle of a hydraulic pair cross mill according to an embodiment of this invention. [Fig. 14] Figure 14 is a graph showing a reference correlation acquired in a method for operating a hydraulic pair cross mill according to an embodiment of this invention. [Description of Embodiments]

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

[0015] Figure 1 is a side view showing a hydraulic pair cross mill 1 in which a method for zero-adjusting a deviation angle of the hydraulic pair cross mill 1 is carried out, according to an embodiment of this invention, Figure 2 is a plane view showing a lower work roll 12W, an adjusting cylinder 131, and a pressing cylinder 132 in Figure 1, Figure 3 is an explanatory view showing a first embodiment of a cross between an upper pair 11P and a lower pair 12P in Figure 1, and Figure 4 is an explanatory view showing a second embodiment of a cross between the upper pair 11P and the lower pair 12P in Figure 1.

[0016] The hydraulic pair cross mill 1 shown in Figure 1 is a device for rolling a metal strip 2. The metal strip 2 may be a steel strip (steel sheet), although not limited thereto. Figure 1 shows one hydraulic pair cross mill 1 (one stand), but multiple hydraulic pair cross mills 1 may be arranged in series in a 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 longitudinal members extending in the direction perpendicular to the paper surface of Figure 1, respectively. One end side of each roll 11W, 12W, 11B, 12B (the side connected to a drive device such as a motor (drive side)) may be called a drive side (DS) and the other end side may be called a work side (WS). Figure 1 shows the hydraulic pair cross mill 1 as viewed from the work side.

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

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

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

[0021] The hydraulic actuator 13 includes an adjusting cylinder 131 and a pressing cylinder 132 that clamp each of 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 Figure 2) for detecting an oil column position 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 adjusting cylinder 131 and the pressing cylinder 132 are located on both the work side and the drive side of each of the rolls 11W, 12W, 11B, 12B, respectively (Figure 2 shows the lower work roll 12W, but the same is true for the other rolls 11W, 11B, 12B). By setting the oil column positions of the adjusting cylinder 131 on both sides to predetermined values, each of the rolls 11W, 12W, 11B, 12B can be rotated so that an axial direction A of each roll 11W, 12W, 11B, 12B is inclined at any angle to a perpendicular direction PD to the conveying direction 2A of the metal strip 2. The rattling between the roll chock 14 and the adjusting cylinder 131 is suppressed by the pressing cylinder 132, which constantly presses the roll chocks 14 against the adjusting cylinder 131.

[0023] Figure 2 shows the work side of the lower work roll 12W being displaced forward with respect to the conveying direction 2a of the metal strip 2 and the drive side being displaced backward with respect to the conveying direction 2a of the metal strip 2. Conversely, the work side may be displaced backward, while the drive side may be displaced forward. The adjusting cylinder 131 and the pressing cylinder 132 may be optionally positioned on each side. For example, in Figure 2, on the work side of the lower work roll 12W, the adjusting cylinder 131 is disposed forward with respect to the conveying direction 2a of the metal strip 2 and the pressing cylinder 132 is disposed backward with respect to the conveying direction 2a of the metal strip 2, but on the work side, the pressing cylinder 132 may be disposed forward with respect to the conveying direction 2a of the metal strip 2, and the adjusting cylinder 131 may be disposed backward with respect to the conveying direction 2a of the metal strip 2. The positions of the adjusting cylinder 131 and the pressing cylinder 132 disposed (forward or backward with respect to the conveying direction 2a of the metal strip 2) are reversed on the work side and the drive side, but the positions of the adjusting cylinder 131 and the pressing cylinder 132 disposed 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, a cross angle θ 1 between an upper pair 11P and a lower pair 12P is changed in a state where the upper pair 11P consisting of the upper work roll 11W and the upper backup roll 11B is made parallel and the lower pair 12P consisting of the lower work roll 12W and the lower backup roll 12B is made parallel.

[0025] In Figures 3 and 4, the upper pair 11P and the lower pair 12P are represented by planes, the lower work roll 12W is represented by relatively light shading, and the backup rolls 11B, 12B are represented by relatively dark shading. The upper work roll 11W is hidden under the upper backup roll 11B.

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

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

[0028] The hydraulic pair cross mill 1 is further provided with a thrust meter 15 for measuring the thrust force F acting on at least one of the upper work roll 11W, lower work roll 12W, upper backup roll 11B and lower backup roll 12B. The thrust meter 15 may be located on any side of any roll 11W, 12W, 11B, 12B, but it may be located on the side of the upper or lower work roll 11W, 12W that is displaced forward with respect to the conveying direction 2a of the metal strip 2. The thrust meter 15 may also be located at the work side where there is a relatively sufficient space for installation. In other words, in the hydraulic pair cross mill 1 set in the positive cross shown in Figure 3, the thrust meter 15 may be located 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 set in the reverse cross shown in Figure 4, the thrust meter 15 may be located 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, with reference to Figures 5 to 13, the method for zero-adjusting the deviation angle of the hydraulic pair cross mill 1 according to this invention is described.

[0030] Figures 5 to 7 are plane views showing first to third embodiments of deviation between the work roll 12W and the backup roll 12B in the lower pair 12P in Figure 1, and Figure 8 is a graph showing a correlation between a cross angle θ 1 and a thrust rate estimated to be acquired in the first to third embodiments for the deviation shown in Figures 5 to 7.

[0031] Figure 9 illustrates a reaction force C generated by clamping the roll chocks 14 using the adjusting cylinder 131 and the pressing cylinder 132 in Figure 1.

[0032] Figures 10 to 13 graphs each showing a correlation between the cross angle θ 1 and the thrust rate acquired in the method for zero-adjusting the deviation angle of the hydraulic pair cross mill 1 according to an embodiment of this invention.

[0033] The method for zero-adjusting the deviation angle of the hydraulic pair cross mill 1 according to an embodiment of this invention is a method for adjusting a zero point of a deviation angle θ 2 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 as described above. Adjusting the zero point of the deviation angle θ 2 may be referred to as zero-adjusting the deviation angle θ 2 .

[0034] It is known that there is a correlation between the deviation angle θ 2 between the work rolls 11W, 12W and the backup rolls 11B, 12B and the measured thrust force F acting on the work roll 11W, 12W and / or the backup roll 11B, 12B.

[0035] The correlation between the deviation angle θ 2 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.

[0036] The deviation between the work roll 12W and the backup roll 12B in the lower pair 12P can take the first to third embodiments shown in Figures 5 to 7.

[0037] The first embodiment shown in Figure 5 is an embodiment in which the work roll 12W and the backup roll 12B in the lower pair 12P are made parallel (no deviation is generated). In this case, it can be said that the deviation angle θ 2 between the work roll 12W and the backup roll 12B is a zero degree.

[0038] The second embodiment shown in Figure 6 is an embodiment in which 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 with respect to the conveying direction 2a of the metal strip 2. The deviation angle θ 2 between the work roll 12W and the backup roll 12B at this time is referred to as a positive deviation angle θ 2 .

[0039] The third embodiment shown in Figure 7 is an embodiment in which 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 backward of the drive side of the backup roll 12B with respect to the conveying direction 2a of the metal strip 2. The deviation angle θ 2 between the work roll 12W and the backup roll 12B at this time is referred to as a negative deviation angle θ 2 .

[0040] The correlation between the cross angle θ 1 and the thrust rate acquired in the first to third embodiments of deviation shown in Figures 5 to 7 is estimated to be the relationship shown by the respective straight lines in Figure 8.

[0041] When rolling the metal strip 2 between the work rolls 11W, 12W in the state where the deviation angle θ 2 between the work roll 12W and the backup roll 12B in the lower pair 12P is the zero degree (the work roll 12W and the backup roll 12B are made parallel), as in the first embodiment in Figure 5, the correlation between the cross angle θ 1 between the work rolls 11W, 12W and the thrust rate calculated from the measured thrust force F acting on the work roll 12W should be as shown in the solid line in Figure 8. In other words, in the state where the deviation angle θ 2 is the zero degree, when a regression line (solid line) is obtained on a coordinate plane with the thrust rate being a first coordinate axis (vertical axis) and the cross angle θ 1 being a second coordinate axis (horizontal axis), the regression line should pass through the origin (cross angle θ 1 = 0, thrust rate = 0). This is because, in the state where the deviation angle θ 2 is the zero degree, a second thrust force F2 from the backup roll 12B, which will be described below, is not substantially generated. The thrust rate is a dimensionless value obtained by dividing the measured value of the thrust force F by the rolling load.

[0042] As shown in Figure 6, when the metal strip 2 is rolled between the work rolls 11W, 12W in a state where the positive deviation angle θ 2 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 of the drive side of the backup roll 12B with respect to the conveying direction 2a of the metal strip 2), the correlation between the cross angle θ 1 between the upper and lower work rolls 11W, 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 dashed dotted line in Figure 8. In other words, in the state where the positive deviation angle θ 2 occurs, when a regression line (dashed dotted line) is obtained on a coordinate plane with the thrust rate being a first coordinate axis (vertical axis) and the cross angle θ 1 being a second coordinate axis (horizontal axis), the regression line should not pass through the origin (cross angle θ 1 = 0, thrust rate = 0), and the intercept of the regression line should take a positive value (when the cross angle θ 1 is the zero degree on the regression line, the thrust rate should take the positive value). This is because, in the state where the positive deviation angle θ 2 occurs, the second thrust force F2 (see Figure 6) in the same direction as 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.

[0043] As shown in Figure 7, when the metal strip 2 is rolled between the work rolls 11W, 12W in a state where the negative deviation angle θ 2 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 backward of the drive side of the backup roll 12B with respect to the conveying direction 2a of the metal strip 2), the correlation between the cross angle θ 1 between the upper and lower work rolls 11W, 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 two-dot chain line in Figure 8. In other words, in the state where the negative deviation angle θ 2 occurs, when a regression line (dashed dotted line) is obtained on a coordinate plane with the thrust rate being a first coordinate axis (vertical axis) and the cross angle θ 1 being a second coordinate axis (horizontal axis), the regression line should not pass through the origin (cross angle θ 1 = 0, thrust rate = 0), and the intercept of the regression line should take a negative value (when the cross angle θ 1 is the zero degree on the regression line, the thrust rate should take the negative value). This is because, in the state where the negative deviation angle θ 2 occurs, the second thrust force F2 (see Figure 7) 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.

[0044] The inventors thought that if such a correlation was obtained during steady operation and zero adjustment of the deviation angle θ 2 was performed based on the correlation, factors such as installation errors of the hydraulic pair cross mill 1 and elastic deformation could be taken into account, thereby reducing threading troubles such as meandering and bending of the metal strip 2. However, when the zero adjustment of the deviation angle θ 2 was performed based on the correlation obtained during steady operation, it was not sufficient to suppress the threading troubles. As a result of intensive studies for its causes of the troubles, the inventors have concluded that even if the thrust force F is measured to be lower than the actual value due to the clamping of the roll chocks 14 by the adjusting cylinder 131 and the pressing cylinder 132 and the zero adjustment of the deviation angle θ 2 is performed based on the lower measured thrust force F, the threading troubles cannot be sufficiently suppressed. The reason why the thrust force F is measured to be lower than the actual value due to the clamping of the roll chocks 14 by the adjusting cylinder 131 and the pressing cylinder 132 is because the reaction force C (friction force, etc.) in the opposite direction of the thrust force F acts on the roll chocks 14 when they are clamped by the adjusting cylinder 131 and the pressing cylinder 132 as shown in Figure 9.

[0045] The method for zero-adjusting the deviation angle of the hydraulic pair cross mill 1 according to an embodiment of this invention includes: acquiring the correlation between the cross angle θ 1 and the measured value of the thrust force F acting on the work roll 11W, 12W and / or the backup roll 11B, 12B for each deviation angle θ 2 while changing the deviation angle θ 2 in the state where the pressing pressure of the pressing cylinder 132 is set to a pressure for zero adjustment lower than a pressure during steady operation, and setting the value of the deviation angle θ 2 at which the correlation showing the thrust force F of zero when the cross angle θ 1 is zero is acquired, to the zero point. By setting the pressing pressure of the pressing cylinder 132 to a pressure for zero adjustment that is lower than the pressure for steady operation, the influence of the reaction force C generated by clamping the roll chocks 14 by the adjusting cylinder 131 and the pressing cylinder 132 on the correlation can be reduced. Then, by performing zero adjustment of the deviation angle θ 2 based on the correlation obtained under the condition where the influence of the reaction force C is reduced, the threading troubles can be suppressed. The measured thrust force F or thrust rate being zero includes not only the measured thrust force F or thrust rate being strictly zero, but also the measured thrust force F or thrust rate being zero, taking into account the error allowed in the technical field of this invention. For example, if the thrust rate is in the range of 0 ± 0.02, the thrust rate may be considered to be zero. For the purpose of accuracy, a thrust rate in the range of 0 ± 0.01 may be considered to be zero. Setting the pressing pressure of the pressing cylinder 132 to the pressure for zero adjustment may be performed on all rolls 11W, 12W, 11B, 12B, or only on any one of the rolls 11W, 12W, 11B, 12B or the upper pair 11P or lower pair 12P where the thrust force F is measured.

[0046] Acquiring the correlation may include repeatedly measuring the thrust force F when the metal strip 2 is passed between the pair of upper and lower work rolls 11W, 12W and rolled while changing the cross angle θ 1 with the deviation angle θ 2 set to the predetermined value. In other words, while the deviation angle θ 2 is fixed at a predetermined value, the cross angle θ 1 is changed and data on combinations of the measured value of the thrust force F and the value of the cross angle θ 1 at that time is accumulated. This can provide the data plotted in the graphs of Figures 10 to 13. Although not limited, the measured thrust force F can be used as the measured value of the thrust force F at the steady state of the threading, i.e., at a timing excluding the moment when the metal strip 2 bites into the work rolls 11W, 12W and the moment when the metal strip 2 exits the work rolls 11W, 12W. Measured values at any timing during the steady state of the threading may be used, but the measured values at the initial steady state of the threading may be used. The data may be accumulated using test materials or during actual operations (when rolling a product material). One plot in Figures 10 to 13 may correspond to one material (one coil).

[0047] The measured value of the thrust force F may be used as is for zero adjustment of the deviation angle θ 2 , but acquiring the correlation may include acquiring a dimensionless thrust rate 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 to be rolled and the size of the hydraulic pair cross mill 1 itself. For example, the rolling load varies 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 varies. The thrust rate obtained by dividing the measured thrust force F by the rolling load can be used to remove the influences of the characteristics and the like of the metal strip 2. If the characteristics and the like of the metal strip 2 are under constant conditions, the measured thrust force F may be used as it is.

[0048] Acquiring the correlation may include acquiring a regression line on a coordinate plane with the thrust rate being a first coordinate axis and the cross angle θ 1 (deg) being a second coordinate axis. The regression line is also shown in the graphs in Figures 10 to 13. The value of the deviation angle θ 2 at which a regression line showing a thrust force F of zero when the cross angle θ 1 is the zero degree can be the zero point of the deviation angle θ 2 . The regression line can be obtained by the least squares method from the data of the combination of the measured value of the thrust force F and the value of the cross angle θ 1 at that time. The regression line may be drawn sensibly by a person while viewing the plot. Alternatively, without obtaining the regression line, a person may determine based on the tendency of the plot whether the thrust force F is zero when the cross angle θ 1 is the zero degree.

[0049] When the correlations shown in Figures 10 to 13 are acquired, the value of the angle deviation θ 2 when the correlation of Figure 13 is acquired can be the zero point of the angle deviation θ 2 . When the correlation shown in Figure 10 is acquired, it is estimated that a positive deviation angle θ 2 has occurred between the work roll 12W and the backup roll 12B as shown in Figure 6. When the correlations shown in Figures 11 and 12 are acquired, it is estimated that a negative deviation angle θ 2 has 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 θ 2 is adjusted so that the positive or negative deviation angle θ 2 approaches zero, thereby acquiring the correlation shown in Figure 13. In Figure 11, the reason why the thrust rate does not increase until the cross angle θ 1 of the work roll 12W reaches the predetermined value is that in this embodiment, a load cell disposed on the work side is used as the thrust meter 15, and therefore 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 the plot is as shown in Figure 11, it can be estimated that the thrust force F takes a negative value when the cross angle θ 1 is the zero degree, as indicated by the dotted line in Figure 11. If the negative thrust force F is also measured, it can be estimated that the regression line will be extended even if the thrust ratio is below 0, as shown in Figure 12.

[0050] The pressure for zero adjustment may be more than or equal to 30% and less than or equal to 50% of the pressure during steady state operation. If it is less than or equal to 50%, the influence of the reaction force C generated by clamping the roll chocks 14 by the adjusting cylinder 131 and the pressing cylinder 132 on the correlation can be sufficiently reduced, and if it is more than or equal to 30%, rattle, vibration, and / or displacement of each roll 11W, 12W, 11B, 12B can be suppressed when rolling the metal strip 2 through the upper and lower work rolls 11W, 12W, and the thrust force F can be stably measured. The pressure for zero adjustment is more preferably more than or equal to 35% and less than or equal to 45% of the pressure during steady operation. In short, a lower pressure for zero adjustment is preferable from the viewpoint of minimizing the influence of the reaction force C shown in Figure 9 as much as possible. However, if is is too low, it is concern that the thrust force F cannot be stably measured because the load acting on the upper and lower work rolls 11W, 12W may cause rattle, vibration, and / or deviation in the upper and lower work rolls 11W, 12W and the upper and lower backup rolls 11B, 12B when the metal strip 2 is passed between the upper and lower work rolls 11W, 12W, particularly when the metal strip 2 is caught between the upper and lower work rolls 11W, 12W. Therefore, a pressure sufficient to allow stable threading is required as the pressure for zero adjustment.

[0051] The pressure for zero adjustment may be more than or equal to 35 kgf / cm 2< and less than or equal to 45 kgf / cm 2< or less (about 3.5 MPa to about 4.5 MPa).

[0052] Next, the method for operating the hydraulic pair cross mill 1 according to this invention is described. Figure 14 is a graph showing a reference correlation acquired in the method for operating the hydraulic pair cross mill 1 according to an embodiment of this invention. The method for operating the hydraulic pair cross mills 1 according to an embodiment of this invention includes the steps of: adjusting a zero point of a deviation angle θ 2 by the method for zero-adjusting the deviation angle of the hydraulic pair cross mill 1 as described above; setting the deviation angle θ 2 to a zero point, and passing a metal strip 2 between a pair of upper and lower work rolls 11W, 12W with a pressing pressure of a pressing cylinder 132 set to a pressure during steady operation, and acquiring a reference correlation between a cross angle θ 1 and a measured value of a thrust force F acting on the work rolls 11W, 12W and / or the backup rolls 11B, 12B at the pressure during steady operation; and acquiring a correlation between the cross angle θ 1 and the measured value of the thrust force F acting on the work rolls and / or backup rolls during steady operation, and comparing the correlation during steady operation with the reference correlation to determine whether the deviation angle θ 2 is deviated from the zero point.

[0053] The reference correlation for the pressure during steady operation is a correlation in a state where, after adjusting the zero point of the deviation angle θ 2 by the method for zero-adjusting the deviation angle of the hydraulic pair cross mill 1 as described above, the pressing pressure of the pressing cylinder 132 is set as the pressure during steady operation, and the influence of the reaction force C generated by clamping the roll chocks 14 by the adjusting cylinder 131 and the pressing cylinder 132 is taken into consideration. In Figure 14, the two-dot chain line indicates the correlation at the pressure for zero adjustment, and the solid line indicates the reference correlation at the pressure during steady operation. Due to the influence of the reaction force C, the reference correlation exhibits an overall lower thrust rate compared to the correlation during the pressure for the zero adjustment. The reference correlation indicated by the solid line in Figure 14 indicates that the thrust rate is 0 when the cross angle θ 1 is between 0 deg and about 0.3 deg. This is because, as described with reference to Figure 11, in this embodiment, a load cell arranged on the work side is used as the thrust meter 15. As shown by the dotted line in Figure 14, it can be estimated that the reference correlation also causes the thrust force F to take a negative value when the cross angle θ 1 is zero degree. Furthermore, if the negative thrust force F is also measured, it can be assumed that a reference correlation including the dotted line part can be acquired.

[0054] Since 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 θ 2 is deviated from the zero point by comparing them. In other words, acquiring the correlation at the pressure during steady operation can allow for determining whether the deviation angle θ 2 is deviated from the zero point without changing the pressing pressure of the pressing cylinder 132 to the pressure for zero adjustment. By performing the operation while checking that the deviation angle θ 2 is not deviated from the zero point, the threading troubles can be reduced. If it is determined that the deviation angle θ 2 is deviated from the zero point, the deviation angle θ 2 may be adjusted so that the correlation during steady operation matches or approaches the reference correlation.

[0055] The step of acquiring the reference correlation is performed after adjusting the zero point of the deviation angle θ 2 . The step of acquiring the reference correlation may include repeatedly measuring the thrust force F when the metal strip 2 is passed between the pair of upper and lower work rolls 11W, 12W in the state where the deviation angle θ 2 is set to the zero point and the pressing pressure of the pressing cylinder 132 is the pressure during steady operation, while changing the cross angle θ 1 . In other words, data on combinations of the measured values of the thrust force F and the value of the cross angle θ 1 at that time may be accumulated in the state where the deviation angle θ 2 is fixed at the zero point, while changing the cross angle θ 1 . Furthermore, in acquiring the reference correlation, the measured value of the thrust force F may be used as is, but a thrust rate that has been made dimensionless by dividing the measured value of the thrust force F by the rolling load may also be used. Furthermore, acquiring the correlation may also include acquiring the regression line on the coordinate plane with the thrust rate being a first coordinate axis and the cross angle θ 1 (deg) being a second coordinate axis.

[0056] The correlation during steady operation is obtained after the reference correlation is obtained. The method for acquiring the correlation during steady operation may be the same as that for the reference correlation. In other words, the step of acquiring the correlation during steady operation may include repeatedly measuring the thrust force F when the metal strip 2 is passed between the pair of upper and lower work rolls 11W, 12W with the deviation angle θ 2 set to the zero point. However, the cross angle θ 1 is set to a value according to the rolling conditions during operation. In this case, data on combinations of the measured value of the thrust force F and the value of the cross angle θ 1 at that time may be accumulated. Further, in acquiring the correlation during steady operation, the measured value of the thrust force F may be used as is, but a thrust rate that has been made dimensionless by dividing the measured value of the thrust force F by the rolling load may also be used. Furthermore, acquiring the correlation during steady operation may also include acquiring the regression line on the coordinate plane with the thrust rate being a first coordinate axis and the cross angle θ 1 (deg) being a second coordinate axis.

[0057] When acquiring the reference correlation and acquiring the correlation during steady operation includes acquiring the regression line, it can be determined that the deviation angle θ 2 is deviated from the zero point if there is deviation between the reference regression line of the reference correlation and the regression line during steady operation (which may, hereinafter, be referred to as "linear deviation"). 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 the predetermined value, it may be determined that the deviation angle θ 2 is deviated from the zero point. The determination of whether or not linear deviation has occurred may be performed periodically, for example, on each scheduled maintenance date.

[0058] The method for manufacturing a hot-rolled steel sheet according to an embodiment of this invention includes manufacturing a hot-rolled steel sheet while carrying out the method for operating the hydraulic pair cross mill 1 described above.

[0059] While the preferred embodiments of the invention have been described above in detail with reference to the drawings, the present invention is not limited to such embodiments. It is obvious that a person skilled in the art to which this invention belongs can arrive at various variations or modifications in the scope of the technical idea recited in the claims, and it is understood that they also belong to the technical scope of this invention.

[0060] The inventions disclosed in this specification can also be described as follows. [1] A method for zero-adjusting a deviation angle of a hydraulic pair cross mill comprising a hydraulic actuator for moving each of a pair of upper and lower work rolls and a pair of upper and lower backup rolls in a horizontal direction, the hydraulic pair cross mill being configured to change a cross angle between an upper pair comprised of an upper work roll and a lower backup roll and a lower pair of a lower work roll and a lower backup roll in a state where the upper pair is made parallel and the lower pair is made parallel, and method being for adjusting a zero point of a deviation angle between the work rolls and the backup rolls in the upper pair and / or the lower pair in the hydraulic pair cross mill, wherein the hydraulic actuator comprises an adjusting cylinder and a pressing cylinder that clamp each of roll chocks of the work rolls and the backup rolls; the adjusting cylinder comprises a position detector for detecting a position of an oil column and is controlled based on the position of the oil column detected by the position detector; and the pressing cylinder is controlled to constantly press the roll chocks against the adjusting cylinder; and wherein the method comprises acquiring a correlation between the cross angle and a measured value of a thrust force acting on the work rolls and / or the backup rolls for each deviation angle while changing the deviation angle in a state where a pressing pressure of the pressing cylinder is set to a pressure for zero adjustment lower than a pressure during steady operation, and setting a value of the deviation angle at which the correlation showing the thrust force of zero when the cross angle is a zero degree is acquired, to a zero point. [2] The method for zero-adjusting a deviation angle of a hydraulic pair cross mill according to [1], wherein acquiring the correlation comprises 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-adjusting a deviation angle of a hydraulic pair cross mill according to [1] or [2], wherein acquiring the correlation comprises acquiring a thrust rate made dimensionless by dividing the measured value of the thrust force by a rolling load. [4] The method for zero-adjusting a deviation angle of a hydraulic pair cross mill according to [3], wherein acquiring the correlation comprises acquiring a regression line on a coordinate plane with the thrust rate being a first coordinate axis and the cross angle being a second coordinate axis. [5] The method for zero-adjusting a deviation angle of a hydraulic pair cross mill according to any one of [1] to [4], wherein the pressure for zero adjustment is more than or equal to 30% and less than or equal to 50% of the pressure during steady operation. [6] The method for zero-adjusting a deviation angle of a hydraulic pair cross mill according to any one of [1] to [5], wherein the pressure for zero adjustment is more than or equal to 35 kgf / cm 2< and less than or equal to 45 kgf / cm 2< or less. [7] A method for operating a hydraulic pair cross mill, the method comprising the steps of: adjusting the zero point of the deviation angle by the method for zero-adjusting the deviation angle of the hydraulic pair cross mill according to any one of [1] to [6]; setting the deviation angle to a zero point, and passing a metal strip between the pair of upper and lower work rolls with a pressing pressure of the pressing cylinder set to a pressure during steady operation, and acquiring a reference correlation between the cross angle and a measured value of the thrust force acting on the work rolls and / or the backup rolls at the pressure during steady operation; and acquiring 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 comparing the correlation during steady operation with the reference correlation to determine whether the deviation angle is deviated from the zero point. [8] A method for manufacturing a hot-rolled steel sheet, the method comprising manufacturing the hot-rolled steel sheet while performing the method for operating the hydraulic pair cross mill according to [7]. [Description of Reference Numerals]

[0061] 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: pressing cylinder F: thrust force

Examples

first embodiment

[0037]The first embodiment shown in Figure 5 is an embodiment in which the work roll 12W and the backup roll 12B in the lower pair 12P are made parallel (no deviation is generated). In this case, it can be said that the deviation angle θ 2 between the work roll 12W and the backup roll 12B is a zero degree.

second embodiment

[0038]The second embodiment shown in Figure 6 is an embodiment in which 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 with respect to the conveying direction 2a of the metal strip 2. The deviation angle θ 2 between the work roll 12W and the backup roll 12B at this time is referred to as a positive deviation angle θ 2 .

third embodiment

[0039]The third embodiment shown in Figure 7 is an embodiment in which 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 backward of the drive side of the backup roll 12B with respect to the conveying direction 2a of the metal strip 2. The deviation angle θ 2 between the work roll 12W and the backup roll 12B at this time is referred to as a negative deviation angle θ 2 .

[0040]The correlation between the cross angle θ 1 and the thrust rate acquired in the first to third embodiments of deviation shown in Figures 5 to 7 is estimated to be the relationship shown by the respective straight lines in Figure 8.

[0041]When rolling the metal strip 2 between the work rolls 11W, 12W in the state where the deviation angle θ 2 between the work roll 12W and the backup roll 12B in the lower pair 12P is the zero degree (the work roll 12W and the backup roll 12B are made parallel), as in the first embodiment in F...

[Technical Field]

[0001] This invention relates to a method for zero-adjusting a 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.[Background Art]

[0002] A conventionally used hydraulic pair cross mill of this type can include for example, the structure disclosed in the following Patent Literature 1. Patent Literature 1 describes a hydraulic pair cross mill including: a pair of upper and lower work rolls; and a hydraulic actuator that horizontally moves a pair of upper and lower backup rolls that support the pair of upper and lower work rolls, respectively, wherein a cross angle between an upper pair consisting of the upper work roll and the upper backup roll and a lower pair consisting of the lower work roll and the lower backup roll is changed in a state where the upper pair and the lower pair is made parallel. The hydraulic actuator includes an adjusting cylinder (a hydraulic cylinder of a position control device for each roll) and a pressing cylinder (a hydraulic cylinder of a pressing device for each roll) that clamp each roll chock of the work roll and the backup roll. The adjusting cylinder includes a position detector for detecting an oil column position and is controlled based on the oil column position detected by the position detector. The pressing cylinder is controlled to constantly pressing the roll chocks against the adjusting cylinder.[Citation List][Patent Literature]

[0003] [PTL 1] WO 2021 / 220366 A1[Summary of Invention][Technical Problem]

[0004] Because of installation errors in the hydraulic pair cross mill or elastic deformation due to stress during threading, an unintended deviation angle may occur between the work rolls and backup rolls in the upper pair and / or the lower pair. The deviation angle may be otherwise referred to as a micro cross angle, skew angle or the like. If the deviation angle occurs, an unintended thrust force is generated on each roll. The unintentional thrust force can cause threading troubles such as meandering and bending of a metal strip (such as a steel strip) when the metal strip is rolled using the hydraulic pair cross mill. Therefore, it is required to adjust the zero point of the deviation angle between the work roll and the backup roll, taking into consideration installation errors, elastic deformation, and the like. Adjusting the zero point of the deviation angle may be referred to as zero-adjusting of the deviation angle.

[0005] It is known that there is a correlation between the deviation angle between the work roll and backup roll and the measured thrust force acting on the work roll and / or backup roll. The inventor thought that if such a correlation was obtained during steady operation and zero-adjusting of the deviation angle was performed based on the correlation, factors such as installation errors and elastic deformation could be taken into account, thereby reducing threading troubles. However, when the zero-adjusting of the deviation angle was performed based on the correlation acquired during steady operation, it was not sufficient to suppress the threading troubles.

[0006] As a result of intensive studies for its cause of the troubles, the inventors have found a new problem that even if the thrust force is measured to be lower than the actual value due to the clamping of the roll chocks by the adjusting cylinder and the pressing cylinder and the zero-adjusting of the deviation angle is performed based on the lower measured thrust force, the threading troubles cannot be sufficiently suppressed.

[0007] This invention has been made to solve the above problems, and one of objects of this invention is to provide a method for zero-adjusting a 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 troubles such as meandering and bending of a metal strip.[Solution to Problem]

[0008] In an embodiment, the method for zero-adjusting a deviation angle of a hydraulic pair cross mill is a method for zero-adjusting a deviation angle of a hydraulic pair cross mill comprising a hydraulic actuator for moving each of a pair of upper and lower work rolls and a pair of upper and lower backup rolls in a horizontal direction, the hydraulic pair cross mill being configured to change a cross angle between an upper pair comprised of an upper work roll and a lower backup roll and a lower pair of a lower work roll and a lower backup roll in a state where the upper pair is made parallel and the lower pair is made parallel, and method being for adjusting a zero point of a deviation angle between the work rolls and the backup rolls in the upper pair and / or the lower pair in the hydraulic pair cross mill, wherein the hydraulic actuator comprises an adjusting cylinder and a pressing cylinder that clamp each of roll chocks of the work rolls and the backup rolls; the adjusting cylinder comprises a position detector for detecting a position of an oil column and is controlled based on the position of the oil column detected by the position detector; and the pressing cylinder is controlled to constantly press the roll chocks against the adjusting cylinder; and wherein the method comprises acquiring a correlation between the cross angle and a measured value of a thrust force acting on the work rolls and / or the backup rolls for each deviation angle while changing the deviation angle in a state where a pressing pressure of the pressing cylinder is set to a pressure for zero adjustment lower than a pressure during steady operation, and setting a value of the deviation angle at which the correlation showing the thrust force of zero when the cross angle is a zero degree is acquired, to a zero point.

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

[0010] In an embodiment, the method for manufacturing a hot-rolled steel sheet according to this invention comprises manufacturing the hot-rolled steel sheet while performing the method for operating the hydraulic pair cross mill as described above.[Advantageous Effects of Invention]

[0011] According to an embodiment of the method for zero-adjusting a deviation angle of a hydraulic pair cross mill of this invention, the threading troubles can be suppressed because the correlation between the cross angle and the measured value of the thrust force acting on the work rolls and / or the backup rolls is acquired for each deviation angle while changing the deviation angle in the state where the pressing pressure of the pressing cylinder is set to a pressure for zero adjustment lower than a pressure during steady operation, and the value of the deviation angle at which the correlation showing the thrust force of zero when the cross angle is zero degree is acquired is set to the zero point.

[0012] According to an embodiment of the method for operating the hydraulic pair cross mill and a method for manufacturing a hot-rolled steel sheet, the threading troubles can be suppressed because the correlation between the cross angle and the measured value of the thrust force acting on the work rolls and / or backup rolls is acquired during the steady operation, and whether the deviation angle is deviated from the zero point is determined by comparing the correlation during the steady operation with the reference correlation.[Brief Description of Drawings]

[0013] [Fig. 1] Figure 1 is a side view showing a hydraulic pair cross mill in which a method for zero-adjusting a deviation angle of a hydraulic pair cross mill is carried out, according to an embodiment of this invention. [Fig. 2] Figure 2 is a plane view showing the lower work roll, adjusting cylinder, and pressing cylinder in Figure 1. [Fig. 3] Figure 3 is an explanatory view showing a first embodiment of a cross between the upper pair and the lower pair in Figure 1. [Fig. 4] Figure 4 is an explanatory view showing a second embodiment of a cross between the upper pair and the lower pair in Figure 1. [Fig. 5] Figure 5 is a plane view showing a first embodiment of deviation between the work roll and the backup roll in the lower pair in Figure 1. [Fig. 6] Figure 6 is a plane view showing a second embodiment of deviation between the work roll and the backup roll in the lower pair in Figure 1. [Fig. 7] Figure 7 is a plane view showing a third embodiment of deviation between the work roll and the backup roll in the lower pair in Figure 1. [Fig. 8] Figure 8 is a graph showing a correlation between a cross angle and a thrust rate estimated to be acquired in the first to third embodiments for the deviation shown in Figures 5 to 7. [Fig. 9] Figure 9 is an explanatory view showing a reaction force generated by clamping roll chocks by the adjusting cylinder and the pressing cylinder in Figure 1. [Fig. 10] Figure 10 is a graph showing a correlation between a cross angle and a thrust rate acquired in the method for zero-adjusting a deviation angle of a hydraulic pair cross mill according to an embodiment of this invention. [Fig. 11] Figure 11 is a graph showing a correlation between a cross angle and a thrust rate acquired in the method for zero-adjusting a deviation angle of a hydraulic pair cross mill according to an embodiment of this invention. [Fig. 12] Figure 12 is a graph showing a correlation between a cross angle and a thrust rate acquired in the method for zero-adjusting a deviation angle of a hydraulic pair cross mill according to an embodiment of this invention. [Fig. 13] Figure 13 is a graph showing a correlation between a cross angle and a thrust rate acquired in the method for zero-adjusting a deviation angle of a hydraulic pair cross mill according to an embodiment of this invention. [Fig. 14] Figure 14 is a graph showing a reference correlation acquired in a method for operating a hydraulic pair cross mill according to an embodiment of this invention. [Description of Embodiments]

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

[0015] Figure 1 is a side view showing a hydraulic pair cross mill 1 in which a method for zero-adjusting a deviation angle of the hydraulic pair cross mill 1 is carried out, according to an embodiment of this invention, Figure 2 is a plane view showing a lower work roll 12W, an adjusting cylinder 131, and a pressing cylinder 132 in Figure 1, Figure 3 is an explanatory view showing a first embodiment of a cross between an upper pair 11P and a lower pair 12P in Figure 1, and Figure 4 is an explanatory view showing a second embodiment of a cross between the upper pair 11P and the lower pair 12P in Figure 1.

[0016] The hydraulic pair cross mill 1 shown in Figure 1 is a device for rolling a metal strip 2. The metal strip 2 may be a steel strip (steel sheet), although not limited thereto. Figure 1 shows one hydraulic pair cross mill 1 (one stand), but multiple hydraulic pair cross mills 1 may be arranged in series in a 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 longitudinal members extending in the direction perpendicular to the paper surface of Figure 1, respectively. One end side of each roll 11W, 12W, 11B, 12B (the side connected to a drive device such as a motor (drive side)) may be called a drive side (DS) and the other end side may be called a work side (WS). Figure 1 shows the hydraulic pair cross mill 1 as viewed from the work side.

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

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

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

[0021] The hydraulic actuator 13 includes an adjusting cylinder 131 and a pressing cylinder 132 that clamp each of 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 Figure 2) for detecting an oil column position 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 adjusting cylinder 131 and the pressing cylinder 132 are located on both the work side and the drive side of each of the rolls 11W, 12W, 11B, 12B, respectively (Figure 2 shows the lower work roll 12W, but the same is true for the other rolls 11W, 11B, 12B). By setting the oil column positions of the adjusting cylinder 131 on both sides to predetermined values, each of the rolls 11W, 12W, 11B, 12B can be rotated so that an axial direction A of each roll 11W, 12W, 11B, 12B is inclined at any angle to a perpendicular direction PD to the conveying direction 2A of the metal strip 2. The rattling between the roll chock 14 and the adjusting cylinder 131 is suppressed by the pressing cylinder 132, which constantly presses the roll chocks 14 against the adjusting cylinder 131.

[0023] Figure 2 shows the work side of the lower work roll 12W being displaced forward with respect to the conveying direction 2a of the metal strip 2 and the drive side being displaced backward with respect to the conveying direction 2a of the metal strip 2. Conversely, the work side may be displaced backward, while the drive side may be displaced forward. The adjusting cylinder 131 and the pressing cylinder 132 may be optionally positioned on each side. For example, in Figure 2, on the work side of the lower work roll 12W, the adjusting cylinder 131 is disposed forward with respect to the conveying direction 2a of the metal strip 2 and the pressing cylinder 132 is disposed backward with respect to the conveying direction 2a of the metal strip 2, but on the work side, the pressing cylinder 132 may be disposed forward with respect to the conveying direction 2a of the metal strip 2, and the adjusting cylinder 131 may be disposed backward with respect to the conveying direction 2a of the metal strip 2. The positions of the adjusting cylinder 131 and the pressing cylinder 132 disposed (forward or backward with respect to the conveying direction 2a of the metal strip 2) are reversed on the work side and the drive side, but the positions of the adjusting cylinder 131 and the pressing cylinder 132 disposed 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, a cross angle θ 1 between an upper pair 11P and a lower pair 12P is changed in a state where the upper pair 11P consisting of the upper work roll 11W and the upper backup roll 11B is made parallel and the lower pair 12P consisting of the lower work roll 12W and the lower backup roll 12B is made parallel.

[0025] In Figures 3 and 4, the upper pair 11P and the lower pair 12P are represented by planes, the lower work roll 12W is represented by relatively light shading, and the backup rolls 11B, 12B are represented by relatively dark shading. The upper work roll 11W is hidden under the upper backup roll 11B.

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

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

[0028] The hydraulic pair cross mill 1 is further provided with a thrust meter 15 for measuring the thrust force F acting on at least one of the upper work roll 11W, lower work roll 12W, upper backup roll 11B and lower backup roll 12B. The thrust meter 15 may be located on any side of any roll 11W, 12W, 11B, 12B, but it may be located on the side of the upper or lower work roll 11W, 12W that is displaced forward with respect to the conveying direction 2a of the metal strip 2. The thrust meter 15 may also be located at the work side where there is a relatively sufficient space for installation. In other words, in the hydraulic pair cross mill 1 set in the positive cross shown in Figure 3, the thrust meter 15 may be located 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 set in the reverse cross shown in Figure 4, the thrust meter 15 may be located 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, with reference to Figures 5 to 13, the method for zero-adjusting the deviation angle of the hydraulic pair cross mill 1 according to this invention is described.

[0030] Figures 5 to 7 are plane views showing first to third embodiments of deviation between the work roll 12W and the backup roll 12B in the lower pair 12P in Figure 1, and Figure 8 is a graph showing a correlation between a cross angle θ 1 and a thrust rate estimated to be acquired in the first to third embodiments for the deviation shown in Figures 5 to 7.

[0031] Figure 9 illustrates a reaction force C generated by clamping the roll chocks 14 using the adjusting cylinder 131 and the pressing cylinder 132 in Figure 1.

[0032] Figures 10 to 13 graphs each showing a correlation between the cross angle θ 1 and the thrust rate acquired in the method for zero-adjusting the deviation angle of the hydraulic pair cross mill 1 according to an embodiment of this invention.

[0033] The method for zero-adjusting the deviation angle of the hydraulic pair cross mill 1 according to an embodiment of this invention is a method for adjusting a zero point of a deviation angle θ 2 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 as described above. Adjusting the zero point of the deviation angle θ 2 may be referred to as zero-adjusting the deviation angle θ 2 .

[0034] It is known that there is a correlation between the deviation angle θ 2 between the work rolls 11W, 12W and the backup rolls 11B, 12B and the measured thrust force F acting on the work roll 11W, 12W and / or the backup roll 11B, 12B.

[0035] The correlation between the deviation angle θ 2 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.

[0036] The deviation between the work roll 12W and the backup roll 12B in the lower pair 12P can take the first to third embodiments shown in Figures 5 to 7.

[0037] The first embodiment shown in Figure 5 is an embodiment in which the work roll 12W and the backup roll 12B in the lower pair 12P are made parallel (no deviation is generated). In this case, it can be said that the deviation angle θ 2 between the work roll 12W and the backup roll 12B is a zero degree.

[0038] The second embodiment shown in Figure 6 is an embodiment in which 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 with respect to the conveying direction 2a of the metal strip 2. The deviation angle θ 2 between the work roll 12W and the backup roll 12B at this time is referred to as a positive deviation angle θ 2 .

[0039] The third embodiment shown in Figure 7 is an embodiment in which 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 backward of the drive side of the backup roll 12B with respect to the conveying direction 2a of the metal strip 2. The deviation angle θ 2 between the work roll 12W and the backup roll 12B at this time is referred to as a negative deviation angle θ 2 .

[0040] The correlation between the cross angle θ 1 and the thrust rate acquired in the first to third embodiments of deviation shown in Figures 5 to 7 is estimated to be the relationship shown by the respective straight lines in Figure 8.

[0041] When rolling the metal strip 2 between the work rolls 11W, 12W in the state where the deviation angle θ 2 between the work roll 12W and the backup roll 12B in the lower pair 12P is the zero degree (the work roll 12W and the backup roll 12B are made parallel), as in the first embodiment in Figure 5, the correlation between the cross angle θ 1 between the work rolls 11W, 12W and the thrust rate calculated from the measured thrust force F acting on the work roll 12W should be as shown in the solid line in Figure 8. In other words, in the state where the deviation angle θ 2 is the zero degree, when a regression line (solid line) is obtained on a coordinate plane with the thrust rate being a first coordinate axis (vertical axis) and the cross angle θ 1 being a second coordinate axis (horizontal axis), the regression line should pass through the origin (cross angle θ 1 = 0, thrust rate = 0). This is because, in the state where the deviation angle θ 2 is the zero degree, a second thrust force F2 from the backup roll 12B, which will be described below, is not substantially generated. The thrust rate is a dimensionless value obtained by dividing the measured value of the thrust force F by the rolling load.

[0042] As shown in Figure 6, when the metal strip 2 is rolled between the work rolls 11W, 12W in a state where the positive deviation angle θ 2 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 of the drive side of the backup roll 12B with respect to the conveying direction 2a of the metal strip 2), the correlation between the cross angle θ 1 between the upper and lower work rolls 11W, 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 dashed dotted line in Figure 8. In other words, in the state where the positive deviation angle θ 2 occurs, when a regression line (dashed dotted line) is obtained on a coordinate plane with the thrust rate being a first coordinate axis (vertical axis) and the cross angle θ 1 being a second coordinate axis (horizontal axis), the regression line should not pass through the origin (cross angle θ 1 = 0, thrust rate = 0), and the intercept of the regression line should take a positive value (when the cross angle θ 1 is the zero degree on the regression line, the thrust rate should take the positive value). This is because, in the state where the positive deviation angle θ 2 occurs, the second thrust force F2 (see Figure 6) in the same direction as 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.

[0043] As shown in Figure 7, when the metal strip 2 is rolled between the work rolls 11W, 12W in a state where the negative deviation angle θ 2 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 backward of the drive side of the backup roll 12B with respect to the conveying direction 2a of the metal strip 2), the correlation between the cross angle θ 1 between the upper and lower work rolls 11W, 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 two-dot chain line in Figure 8. In other words, in the state where the negative deviation angle θ 2 occurs, when a regression line (dashed dotted line) is obtained on a coordinate plane with the thrust rate being a first coordinate axis (vertical axis) and the cross angle θ 1 being a second coordinate axis (horizontal axis), the regression line should not pass through the origin (cross angle θ 1 = 0, thrust rate = 0), and the intercept of the regression line should take a negative value (when the cross angle θ 1 is the zero degree on the regression line, the thrust rate should take the negative value). This is because, in the state where the negative deviation angle θ 2 occurs, the second thrust force F2 (see Figure 7) 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.

[0044] The inventors thought that if such a correlation was obtained during steady operation and zero adjustment of the deviation angle θ 2 was performed based on the correlation, factors such as installation errors of the hydraulic pair cross mill 1 and elastic deformation could be taken into account, thereby reducing threading troubles such as meandering and bending of the metal strip 2. However, when the zero adjustment of the deviation angle θ 2 was performed based on the correlation obtained during steady operation, it was not sufficient to suppress the threading troubles. As a result of intensive studies for its causes of the troubles, the inventors have concluded that even if the thrust force F is measured to be lower than the actual value due to the clamping of the roll chocks 14 by the adjusting cylinder 131 and the pressing cylinder 132 and the zero adjustment of the deviation angle θ 2 is performed based on the lower measured thrust force F, the threading troubles cannot be sufficiently suppressed. The reason why the thrust force F is measured to be lower than the actual value due to the clamping of the roll chocks 14 by the adjusting cylinder 131 and the pressing cylinder 132 is because the reaction force C (friction force, etc.) in the opposite direction of the thrust force F acts on the roll chocks 14 when they are clamped by the adjusting cylinder 131 and the pressing cylinder 132 as shown in Figure 9.

[0045] The method for zero-adjusting the deviation angle of the hydraulic pair cross mill 1 according to an embodiment of this invention includes: acquiring the correlation between the cross angle θ 1 and the measured value of the thrust force F acting on the work roll 11W, 12W and / or the backup roll 11B, 12B for each deviation angle θ 2 while changing the deviation angle θ 2 in the state where the pressing pressure of the pressing cylinder 132 is set to a pressure for zero adjustment lower than a pressure during steady operation, and setting the value of the deviation angle θ 2 at which the correlation showing the thrust force F of zero when the cross angle θ 1 is zero is acquired, to the zero point. By setting the pressing pressure of the pressing cylinder 132 to a pressure for zero adjustment that is lower than the pressure for steady operation, the influence of the reaction force C generated by clamping the roll chocks 14 by the adjusting cylinder 131 and the pressing cylinder 132 on the correlation can be reduced. Then, by performing zero adjustment of the deviation angle θ 2 based on the correlation obtained under the condition where the influence of the reaction force C is reduced, the threading troubles can be suppressed. The measured thrust force F or thrust rate being zero includes not only the measured thrust force F or thrust rate being strictly zero, but also the measured thrust force F or thrust rate being zero, taking into account the error allowed in the technical field of this invention. For example, if the thrust rate is in the range of 0 ± 0.02, the thrust rate may be considered to be zero. For the purpose of accuracy, a thrust rate in the range of 0 ± 0.01 may be considered to be zero. Setting the pressing pressure of the pressing cylinder 132 to the pressure for zero adjustment may be performed on all rolls 11W, 12W, 11B, 12B, or only on any one of the rolls 11W, 12W, 11B, 12B or the upper pair 11P or lower pair 12P where the thrust force F is measured.

[0046] Acquiring the correlation may include repeatedly measuring the thrust force F when the metal strip 2 is passed between the pair of upper and lower work rolls 11W, 12W and rolled while changing the cross angle θ 1 with the deviation angle θ 2 set to the predetermined value. In other words, while the deviation angle θ 2 is fixed at a predetermined value, the cross angle θ 1 is changed and data on combinations of the measured value of the thrust force F and the value of the cross angle θ 1 at that time is accumulated. This can provide the data plotted in the graphs of Figures 10 to 13. Although not limited, the measured thrust force F can be used as the measured value of the thrust force F at the steady state of the threading, i.e., at a timing excluding the moment when the metal strip 2 bites into the work rolls 11W, 12W and the moment when the metal strip 2 exits the work rolls 11W, 12W. Measured values at any timing during the steady state of the threading may be used, but the measured values at the initial steady state of the threading may be used. The data may be accumulated using test materials or during actual operations (when rolling a product material). One plot in Figures 10 to 13 may correspond to one material (one coil).

[0047] The measured value of the thrust force F may be used as is for zero adjustment of the deviation angle θ 2 , but acquiring the correlation may include acquiring a dimensionless thrust rate 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 to be rolled and the size of the hydraulic pair cross mill 1 itself. For example, the rolling load varies 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 varies. The thrust rate obtained by dividing the measured thrust force F by the rolling load can be used to remove the influences of the characteristics and the like of the metal strip 2. If the characteristics and the like of the metal strip 2 are under constant conditions, the measured thrust force F may be used as it is.

[0048] Acquiring the correlation may include acquiring a regression line on a coordinate plane with the thrust rate being a first coordinate axis and the cross angle θ 1 (deg) being a second coordinate axis. The regression line is also shown in the graphs in Figures 10 to 13. The value of the deviation angle θ 2 at which a regression line showing a thrust force F of zero when the cross angle θ 1 is the zero degree can be the zero point of the deviation angle θ 2 . The regression line can be obtained by the least squares method from the data of the combination of the measured value of the thrust force F and the value of the cross angle θ 1 at that time. The regression line may be drawn sensibly by a person while viewing the plot. Alternatively, without obtaining the regression line, a person may determine based on the tendency of the plot whether the thrust force F is zero when the cross angle θ 1 is the zero degree.

[0049] When the correlations shown in Figures 10 to 13 are acquired, the value of the angle deviation θ 2 when the correlation of Figure 13 is acquired can be the zero point of the angle deviation θ 2 . When the correlation shown in Figure 10 is acquired, it is estimated that a positive deviation angle θ 2 has occurred between the work roll 12W and the backup roll 12B as shown in Figure 6. When the correlations shown in Figures 11 and 12 are acquired, it is estimated that a negative deviation angle θ 2 has 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 θ 2 is adjusted so that the positive or negative deviation angle θ 2 approaches zero, thereby acquiring the correlation shown in Figure 13. In Figure 11, the reason why the thrust rate does not increase until the cross angle θ 1 of the work roll 12W reaches the predetermined value is that in this embodiment, a load cell disposed on the work side is used as the thrust meter 15, and therefore 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 the plot is as shown in Figure 11, it can be estimated that the thrust force F takes a negative value when the cross angle θ 1 is the zero degree, as indicated by the dotted line in Figure 11. If the negative thrust force F is also measured, it can be estimated that the regression line will be extended even if the thrust ratio is below 0, as shown in Figure 12.

[0050] The pressure for zero adjustment may be more than or equal to 30% and less than or equal to 50% of the pressure during steady state operation. If it is less than or equal to 50%, the influence of the reaction force C generated by clamping the roll chocks 14 by the adjusting cylinder 131 and the pressing cylinder 132 on the correlation can be sufficiently reduced, and if it is more than or equal to 30%, rattle, vibration, and / or displacement of each roll 11W, 12W, 11B, 12B can be suppressed when rolling the metal strip 2 through the upper and lower work rolls 11W, 12W, and the thrust force F can be stably measured. The pressure for zero adjustment is more preferably more than or equal to 35% and less than or equal to 45% of the pressure during steady operation. In short, a lower pressure for zero adjustment is preferable from the viewpoint of minimizing the influence of the reaction force C shown in Figure 9 as much as possible. However, if is is too low, it is concern that the thrust force F cannot be stably measured because the load acting on the upper and lower work rolls 11W, 12W may cause rattle, vibration, and / or deviation in the upper and lower work rolls 11W, 12W and the upper and lower backup rolls 11B, 12B when the metal strip 2 is passed between the upper and lower work rolls 11W, 12W, particularly when the metal strip 2 is caught between the upper and lower work rolls 11W, 12W. Therefore, a pressure sufficient to allow stable threading is required as the pressure for zero adjustment.

[0051] The pressure for zero adjustment may be more than or equal to 35 kgf / cm 2< and less than or equal to 45 kgf / cm 2< or less (about 3.5 MPa to about 4.5 MPa).

[0052] Next, the method for operating the hydraulic pair cross mill 1 according to this invention is described. Figure 14 is a graph showing a reference correlation acquired in the method for operating the hydraulic pair cross mill 1 according to an embodiment of this invention. The method for operating the hydraulic pair cross mills 1 according to an embodiment of this invention includes the steps of: adjusting a zero point of a deviation angle θ 2 by the method for zero-adjusting the deviation angle of the hydraulic pair cross mill 1 as described above; setting the deviation angle θ 2 to a zero point, and passing a metal strip 2 between a pair of upper and lower work rolls 11W, 12W with a pressing pressure of a pressing cylinder 132 set to a pressure during steady operation, and acquiring a reference correlation between a cross angle θ 1 and a measured value of a thrust force F acting on the work rolls 11W, 12W and / or the backup rolls 11B, 12B at the pressure during steady operation; and acquiring a correlation between the cross angle θ 1 and the measured value of the thrust force F acting on the work rolls and / or backup rolls during steady operation, and comparing the correlation during steady operation with the reference correlation to determine whether the deviation angle θ 2 is deviated from the zero point.

[0053] The reference correlation for the pressure during steady operation is a correlation in a state where, after adjusting the zero point of the deviation angle θ 2 by the method for zero-adjusting the deviation angle of the hydraulic pair cross mill 1 as described above, the pressing pressure of the pressing cylinder 132 is set as the pressure during steady operation, and the influence of the reaction force C generated by clamping the roll chocks 14 by the adjusting cylinder 131 and the pressing cylinder 132 is taken into consideration. In Figure 14, the two-dot chain line indicates the correlation at the pressure for zero adjustment, and the solid line indicates the reference correlation at the pressure during steady operation. Due to the influence of the reaction force C, the reference correlation exhibits an overall lower thrust rate compared to the correlation during the pressure for the zero adjustment. The reference correlation indicated by the solid line in Figure 14 indicates that the thrust rate is 0 when the cross angle θ 1 is between 0 deg and about 0.3 deg. This is because, as described with reference to Figure 11, in this embodiment, a load cell arranged on the work side is used as the thrust meter 15. As shown by the dotted line in Figure 14, it can be estimated that the reference correlation also causes the thrust force F to take a negative value when the cross angle θ 1 is zero degree. Furthermore, if the negative thrust force F is also measured, it can be assumed that a reference correlation including the dotted line part can be acquired.

[0054] Since 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 θ 2 is deviated from the zero point by comparing them. In other words, acquiring the correlation at the pressure during steady operation can allow for determining whether the deviation angle θ 2 is deviated from the zero point without changing the pressing pressure of the pressing cylinder 132 to the pressure for zero adjustment. By performing the operation while checking that the deviation angle θ 2 is not deviated from the zero point, the threading troubles can be reduced. If it is determined that the deviation angle θ 2 is deviated from the zero point, the deviation angle θ 2 may be adjusted so that the correlation during steady operation matches or approaches the reference correlation.

[0055] The step of acquiring the reference correlation is performed after adjusting the zero point of the deviation angle θ 2 . The step of acquiring the reference correlation may include repeatedly measuring the thrust force F when the metal strip 2 is passed between the pair of upper and lower work rolls 11W, 12W in the state where the deviation angle θ 2 is set to the zero point and the pressing pressure of the pressing cylinder 132 is the pressure during steady operation, while changing the cross angle θ 1 . In other words, data on combinations of the measured values of the thrust force F and the value of the cross angle θ 1 at that time may be accumulated in the state where the deviation angle θ 2 is fixed at the zero point, while changing the cross angle θ 1 . Furthermore, in acquiring the reference correlation, the measured value of the thrust force F may be used as is, but a thrust rate that has been made dimensionless by dividing the measured value of the thrust force F by the rolling load may also be used. Furthermore, acquiring the correlation may also include acquiring the regression line on the coordinate plane with the thrust rate being a first coordinate axis and the cross angle θ 1 (deg) being a second coordinate axis.

[0056] The correlation during steady operation is obtained after the reference correlation is obtained. The method for acquiring the correlation during steady operation may be the same as that for the reference correlation. In other words, the step of acquiring the correlation during steady operation may include repeatedly measuring the thrust force F when the metal strip 2 is passed between the pair of upper and lower work rolls 11W, 12W with the deviation angle θ 2 set to the zero point. However, the cross angle θ 1 is set to a value according to the rolling conditions during operation. In this case, data on combinations of the measured value of the thrust force F and the value of the cross angle θ 1 at that time may be accumulated. Further, in acquiring the correlation during steady operation, the measured value of the thrust force F may be used as is, but a thrust rate that has been made dimensionless by dividing the measured value of the thrust force F by the rolling load may also be used. Furthermore, acquiring the correlation during steady operation may also include acquiring the regression line on the coordinate plane with the thrust rate being a first coordinate axis and the cross angle θ 1 (deg) being a second coordinate axis.

[0057] When acquiring the reference correlation and acquiring the correlation during steady operation includes acquiring the regression line, it can be determined that the deviation angle θ 2 is deviated from the zero point if there is deviation between the reference regression line of the reference correlation and the regression line during steady operation (which may, hereinafter, be referred to as "linear deviation"). 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 the predetermined value, it may be determined that the deviation angle θ 2 is deviated from the zero point. The determination of whether or not linear deviation has occurred may be performed periodically, for example, on each scheduled maintenance date.

[0058] The method for manufacturing a hot-rolled steel sheet according to an embodiment of this invention includes manufacturing a hot-rolled steel sheet while carrying out the method for operating the hydraulic pair cross mill 1 described above.

[0059] While the preferred embodiments of the invention have been described above in detail with reference to the drawings, the present invention is not limited to such embodiments. It is obvious that a person skilled in the art to which this invention belongs can arrive at various variations or modifications in the scope of the technical idea recited in the claims, and it is understood that they also belong to the technical scope of this invention.

[0060] The inventions disclosed in this specification can also be described as follows. [1] A method for zero-adjusting a deviation angle of a hydraulic pair cross mill comprising a hydraulic actuator for moving each of a pair of upper and lower work rolls and a pair of upper and lower backup rolls in a horizontal direction, the hydraulic pair cross mill being configured to change a cross angle between an upper pair comprised of an upper work roll and a lower backup roll and a lower pair of a lower work roll and a lower backup roll in a state where the upper pair is made parallel and the lower pair is made parallel, and method being for adjusting a zero point of a deviation angle between the work rolls and the backup rolls in the upper pair and / or the lower pair in the hydraulic pair cross mill, wherein the hydraulic actuator comprises an adjusting cylinder and a pressing cylinder that clamp each of roll chocks of the work rolls and the backup rolls; the adjusting cylinder comprises a position detector for detecting a position of an oil column and is controlled based on the position of the oil column detected by the position detector; and the pressing cylinder is controlled to constantly press the roll chocks against the adjusting cylinder; and wherein the method comprises acquiring a correlation between the cross angle and a measured value of a thrust force acting on the work rolls and / or the backup rolls for each deviation angle while changing the deviation angle in a state where a pressing pressure of the pressing cylinder is set to a pressure for zero adjustment lower than a pressure during steady operation, and setting a value of the deviation angle at which the correlation showing the thrust force of zero when the cross angle is a zero degree is acquired, to a zero point. [2] The method for zero-adjusting a deviation angle of a hydraulic pair cross mill according to [1], wherein acquiring the correlation comprises 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-adjusting a deviation angle of a hydraulic pair cross mill according to [1] or [2], wherein acquiring the correlation comprises acquiring a thrust rate made dimensionless by dividing the measured value of the thrust force by a rolling load. [4] The method for zero-adjusting a deviation angle of a hydraulic pair cross mill according to [3], wherein acquiring the correlation comprises acquiring a regression line on a coordinate plane with the thrust rate being a first coordinate axis and the cross angle being a second coordinate axis. [5] The method for zero-adjusting a deviation angle of a hydraulic pair cross mill according to any one of [1] to [4], wherein the pressure for zero adjustment is more than or equal to 30% and less than or equal to 50% of the pressure during steady operation. [6] The method for zero-adjusting a deviation angle of a hydraulic pair cross mill according to any one of [1] to [5], wherein the pressure for zero adjustment is more than or equal to 35 kgf / cm 2< and less than or equal to 45 kgf / cm 2< or less. [7] A method for operating a hydraulic pair cross mill, the method comprising the steps of: adjusting the zero point of the deviation angle by the method for zero-adjusting the deviation angle of the hydraulic pair cross mill according to any one of [1] to [6]; setting the deviation angle to a zero point, and passing a metal strip between the pair of upper and lower work rolls with a pressing pressure of the pressing cylinder set to a pressure during steady operation, and acquiring a reference correlation between the cross angle and a measured value of the thrust force acting on the work rolls and / or the backup rolls at the pressure during steady operation; and acquiring 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 comparing the correlation during steady operation with the reference correlation to determine whether the deviation angle is deviated from the zero point. [8] A method for manufacturing a hot-rolled steel sheet, the method comprising manufacturing the hot-rolled steel sheet while performing the method for operating the hydraulic pair cross mill according to [7]. [Description of Reference Numerals]

[0061] 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: pressing cylinder F: thrust force

Examples

first embodiment

[0037]The first embodiment shown in Figure 5 is an embodiment in which the work roll 12W and the backup roll 12B in the lower pair 12P are made parallel (no deviation is generated). In this case, it can be said that the deviation angle θ 2 between the work roll 12W and the backup roll 12B is a zero degree.

second embodiment

[0038]The second embodiment shown in Figure 6 is an embodiment in which 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 with respect to the conveying direction 2a of the metal strip 2. The deviation angle θ 2 between the work roll 12W and the backup roll 12B at this time is referred to as a positive deviation angle θ 2 .

third embodiment

[0039]The third embodiment shown in Figure 7 is an embodiment in which 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 backward of the drive side of the backup roll 12B with respect to the conveying direction 2a of the metal strip 2. The deviation angle θ 2 between the work roll 12W and the backup roll 12B at this time is referred to as a negative deviation angle θ 2 .

[0040]The correlation between the cross angle θ 1 and the thrust rate acquired in the first to third embodiments of deviation shown in Figures 5 to 7 is estimated to be the relationship shown by the respective straight lines in Figure 8.

[0041]When rolling the metal strip 2 between the work rolls 11W, 12W in the state where the deviation angle θ 2 between the work roll 12W and the backup roll 12B in the lower pair 12P is the zero degree (the work roll 12W and the backup roll 12B are made parallel), as in the first embodiment in F...

Claims

1. A method for zero-adjusting a deviation angle of a hydraulic pair cross mill comprising a hydraulic actuator for moving each of a pair of upper and lower work rolls and a pair of upper and lower backup rolls in a horizontal direction, the hydraulic pair cross mill being configured to change a cross angle between an upper pair comprised of an upper work roll and a lower backup roll and a lower pair of a lower work roll and a lower backup roll in a state where the upper pair is made parallel and the lower pair is made parallel, and method being for adjusting a zero point of a deviation angle between the work rolls and the backup rolls in the upper pair and / or the lower pair in the hydraulic pair cross mill, wherein the hydraulic actuator comprises an adjusting cylinder and a pressing cylinder that clamp each of roll chocks of the work rolls and the backup rolls; the adjusting cylinder comprises a position detector for detecting a position of an oil column and is controlled based on the position of the oil column detected by the position detector; and the pressing cylinder is controlled to constantly press the roll chocks against the adjusting cylinder; and wherein the method comprises acquiring a correlation between the cross angle and a measured value of a thrust force acting on the work rolls and / or the backup rolls for each deviation angle while changing the deviation angle in a state where a pressing pressure of the pressing cylinder is set to a pressure for zero adjustment lower than a pressure during steady operation, and setting a value of the deviation angle at which the correlation showing the thrust force of zero when the cross angle is a zero degree is acquired, to a zero point.

2. The method for zero-adjusting a deviation angle of a hydraulic pair cross mill according to claim 1, wherein acquiring the correlation comprises 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-adjusting a deviation angle of a hydraulic pair cross mill according to claim 2, wherein acquiring the correlation comprises acquiring a thrust rate made dimensionless by dividing the measured value of the thrust force by a rolling load.

4. The method for zero-adjusting a deviation angle of a hydraulic pair cross mill according to claim 3, wherein acquiring the correlation comprises acquiring a regression line on a coordinate plane with the thrust rate being a first coordinate axis and the cross angle being a second coordinate axis.

5. The method for zero-adjusting a deviation angle of a hydraulic pair cross mill according to claim 1, wherein the pressure for zero adjustment is more than or equal to 30% and less than or equal to 50% of the pressure during steady operation.

6. The method for zero-adjusting a deviation angle of a hydraulic pair cross mill according to claim 1, wherein the pressure for zero adjustment is more than or equal to 35 kgf / cm2 and less than or equal to 45 kgf / cm2 or less.

7. A method for operating a hydraulic pair cross mill, the method comprising the steps of: adjusting the zero point of the deviation angle by the method for zero-adjusting the deviation angle of the hydraulic pair cross mill according to any one of claims 1 to 6; setting the deviation angle to a zero point, and passing a metal strip between the pair of upper and lower work rolls with a pressing pressure of the pressing cylinder set to a pressure during steady operation, and acquiring a reference correlation between the cross angle and a measured value of the thrust force acting on the work rolls and / or the backup rolls at the pressure during steady operation; and acquiring 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 comparing the correlation during steady operation with the reference correlation to determine whether the deviation angle is deviated from the zero point.

8. A method for manufacturing a hot-rolled steel sheet, the method comprising manufacturing the hot-rolled steel sheet while performing the method for operating the hydraulic pair cross mill according to claim 7.

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