Rolling mill for plate rolling, method for controlling roll reduction position of rolling mill, and method for manufacturing rolled plate

Abstract

To provide a plate rolling technique with reduced wedging and bending of a rolled material.SOLUTION: A rolling machine for plate rolling comprises: a pair of work rolls 1 which come into contact with each other directly or via a rolled material; and a pair of back-up rolls 2 which come into contact with respective work rolls via or not via an intermediate roll, in which both ends of each roll are assembled between housing windows via roll chocks on an operation side and on a driving side. The rolling machine for plate rolling has, on the roll chock of one of the back-up rolls, detection means for axial displacement of the back-up roll. A method for detecting a roll reduction position of the rolling machine for rolling the plate material measures an axial displacement magnitude of the back-up roll changed by a rolling load or a work roll shift for plate crown control, and estimates a difference between roll gap values of the work rolls on the operation side and the driving side by using the obtained displacement magnitude.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a rolling mill for rolling plate material, to a method for detecting and controlling the roll reduction position of the rolling mill, and further to a method for manufacturing a rolled plate using the control method. [Background technology]

[0002] In recent years, crown-controlled mills, such as pair cross mills and shift mills, have been put into practical use in fields such as continuous hot rolling. As a result, it has become possible to reliably produce flat steel strips without a crown. In rolling mills with high crown control capabilities, the roll gap between the work rolls is easily affected by the shift amount and cross angle, making accurate roll gap control difficult. In rolling mills with high crown control capabilities, where the roll position changes due to work roll shift and cross angle, the mill rigidity of the rolling mill is easily affected by changes in roll position. As a result, the mill rigidity on the operating and driving sides changes, resulting in differences in the roll gap opening depending on the rolling load, causing meandering of the rolled material. Furthermore, rolled materials with small crowns are particularly prone to meandering, causing problems such as side guide jamming due to bending of the leading edge and squeezing of the rolled material when the tail edge slips through the side guide. Improving the threadability of the finishing mill in hot strip mills is a crucial issue for improving both the operating rate and roll consumption.

[0003] For example, Patent Document 1 discloses a control device and method for a rolling mill that reliably suppresses meandering of the tail end of a steel plate during rolling. This technology reliably controls tail end meandering by predicting the rolling load at the tail end based on the tension distribution in the width direction of the steady portion, the rolling load in the steady portion, and the steel plate temperature at the tail end, and then varying the amount of leveling according to the predicted rolling load.

[0004] For example, Patent Document 2 discloses a rolling control method for correcting meandering and camber of a metal plate during rolling of the metal plate. In this technology, the rolling load difference between the operating side and the driving side used for controlling the meandering of the rolled material is first separated into a difference caused by a thrust load and a difference caused by the meandering of the material being rolled. Then, based on these separated rolling load differences, the leveling control is performed to operate the reduction positions of the driving side and the operating side.

[0005] For example, Patent Document 3 discloses a roll gap measuring device for the work rolls of a rolling mill, and a rolling mill and a method for manufacturing a hot-rolled steel strip that utilize this device. In this technology, to measure the roll gap of the work rolls, a pair of upper and lower work roll chocks are provided with a rope member and a take-up reel mechanism for holding the rope member so that it can be wound. This applies tension to the rope member, and the roll gap is measured according to the wound length of the rope member that corresponds to the roll gap.

[0006] For example, Patent Document 4 discloses a method for detecting and controlling the roll reduction position of a rolling mill. In this technology, the roll reduction position is detected to estimate the roll gap of the work rolls by measuring the displacement of the backup rolls in the reduction direction on both the operating and driving sides using distance sensors attached to the back surfaces of the upper and lower backup rolls on the operating and driving sides. These roll gap values ​​are used to appropriately correct and control the roll reduction position, thereby obtaining a rolled product without wedges or bends. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 2018-130732 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-178754 [Patent Document 3] Japanese Patent Application Laid-Open No. 2010-234407 [Patent Document 4] Japanese Patent Application Publication No. 08-024928 Summary of the Invention [Problem to be solved by the invention]

[0008] However, the above-mentioned conventional techniques have the following problems. To improve sheet threading, it is important to set a roll gap that prevents the material being rolled from meandering through the rolling mill. The roll gap varies depending on the machine position, such as the roll shift position and cross angle, and the difference in mill stiffness between the operating side and the driving side relative to the rolling load. There is no established method for accurately measuring this mill stiffness difference, and methods such as estimating it from the difference in rolling load between the operating side and the driving side are used.

[0009] The roll gap changes depending on the rolling load, causing the material to meander. During rolling in a finishing mill, thermal rundown, a phenomenon in which the entry temperature changes between head and tail rolling, occurs, causing the rolling load to change relative to the rolling length. In addition, the reduction position is AGC controlled to keep the delivery thickness of the rolling mill constant, and as the reduction position changes in a balanced manner, the rolling load of each stand changes. These changes in rolling load during rolling cause changes in the difference in the opening between the operating side and driving side of the roll gap, which contributes to the meandering of the material to be rolled.

[0010] The present invention has been made in consideration of the above circumstances, and aims to provide a rolling technology that detects the roll reduction position of a rolling mill that rolls plate material, thereby reducing wedging and bending of the rolled material. [Means for solving the problem]

[0011] The rolling mill for plate rolling according to the present invention, which advantageously solves the above-mentioned problems, is a rolling mill for plate rolling comprising a pair of work rolls which contact each other directly or via the material to be rolled, and a pair of backup rolls which roll-contact each work roll with or without an intermediate roll, and both ends of each roll being incorporated between housing windows via roll chocks on the operating side and the driving side, and is characterized in that one of the roll chocks of the backup rolls has means for detecting the axial displacement of the backup roll.

[0012] The plate rolling mill according to the present invention is (a) the backup roll has an oil film bearing; The detecting means is a non-contact displacement meter attached to the chock end cover on the side having the thrust bearing. (b) further comprising a control means for changing the roll pressure position based on the axial displacement of the backup roll detected by the detection means so that the difference in roll gap value between the work rolls on the operating side and the drive side approaches zero; This may be a more preferable solution.

[0013] The method for detecting the roll reduction position of a rolling mill according to the present invention, which advantageously solves the above-mentioned problems, is a method for detecting the roll reduction position of a rolling mill that rolls a plate material, and is characterized by measuring the amount of axial displacement of the backup roll that changes due to the rolling load or due to work roll shifting for plate crown control, and estimating the difference in roll gap values ​​between the work rolls on the operating side and the drive side using the obtained displacement amount.

[0014] The method for controlling the roll reduction position of a rolling mill according to the present invention, which advantageously solves the above-mentioned problem, is characterized in that, based on the difference in the roll gap values ​​of the work rolls estimated by the above-mentioned detection method, the roll reduction position is controlled so that the difference asymptotically approaches zero.

[0015] The method for producing a rolled plate according to the present invention, which advantageously solves the above-mentioned problems, is characterized in that rolling is performed while reducing wedging and bending of the rolled material by the above-mentioned control method. [Effects of the Invention]

[0016] The rolling mill for rolling gold plates, the method for detecting and controlling the roll reduction position of the rolling mill, and the method for manufacturing rolled plates according to the present invention prevent meandering of the rolled material and enable the production of rolled products without wedges or bends. Furthermore, the axial displacement of the backup rolls can be measured even during rolling, which can be used for online control of the roll reduction position. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a schematic side view of a four-high rolling mill according to one embodiment of the present invention. [Figure 2] FIG. 2 is a schematic front view of the four-high rolling mill. [Figure 3] FIG. 2 is a schematic front view illustrating an installation state of the displacement meter according to the embodiment. [Figure 4] FIG. 4 is a schematic side view of a six-high rolling mill according to another embodiment of the present invention. [Figure 5] FIG. 2 is a schematic front view of the six-high rolling mill. [Figure 6] Graph (a) shows the relationship between the shift change amount of the upper work roll and the axial displacement amount of the upper backup roll, and graph (b) shows the relationship between the shift change amount of the lower work roll and the axial displacement amount of the lower backup roll. [Figure 7] 1 is a graph showing the relationship between the amount of axial displacement of a backup roll and a change in rolling load within a bar in the first stand of a finishing mill. DETAILED DESCRIPTION OF THE INVENTION

[0018] The following describes in detail the embodiments of the present invention. The following embodiments are merely examples of equipment and methods for embodying the technical concept of the present invention, and are not intended to limit the configuration to those described below. In other words, the technical concept of the present invention can be modified in various ways within the technical scope described in the claims.

[0019] Fig. 1 is a schematic side view of a four-high rolling mill according to one embodiment of the present invention, and Fig. 2 is a schematic front view thereof. Fig. 3 is a schematic front view illustrating the installation of displacement meters for measuring the axial displacement of backup rolls according to this embodiment.

[0020] For example, a four-high rolling mill such as that shown in Figures 1 and 2, which is installed in a hot rolling line, is installed in a roughing mill for hot rolling, and is equipped with upper and lower work rolls 1, 1 that sandwich the material S to be rolled, and backup rolls 2, 2 that roll and contact the work rolls 1, 1. Both ends of the work roll 1 are incorporated into the housing window via work roll chocks 3, 3. The backup roll 2 is incorporated into the housing window via backup roll chocks 4, 4. Furthermore, the backs (outsides) of the backup roll chocks 4, 4 have chock end covers 5, 5 that cover the roll shaft.

[0021] 1 and 2, the traveling direction FD of the rolled material S is the positive direction of the z-axis, the vertically upward direction is the positive direction of the y-axis, and the axial direction of the rolls perpendicular to these axes is the x-direction.

[0022] In this embodiment, as shown in FIG. 3, a chock end cover 5 provided on the back surface of one of the roll chocks 4 of the backup roll 2 has a means 6 for detecting the displacement of the backup roll 2 in the axial direction.

[0023] Roll bearings include plain bearings, rolling bearings, and oil film bearings. In particular, chocks with oil film bearings have a large gap between the roll and the chock, and tend to have large axial roll displacements. Therefore, this embodiment is preferably applied to backup rolls with oil film bearings. A non-contact displacement meter is preferable as the detection means, and an eddy-current type non-contact displacement meter is an example. In particular, in oil film bearings, the displacement measurement location is filled with oil, and it is necessary to detect the position of the metal roll end without being affected by this.

[0024] In the example shown in Figure 3, the non-contact displacement sensor 6 is installed on the keeper KP side of the chocks 4 at both ends of the backup roll 2. Generally, the chocks 4 of the backup roll 2 are equipped with thrust bearings on the keeper KP side. The rotating roll is significantly displaced from the keeper KP side to the opposite keeper AK side. This is because the thrust force acts in the direction of escape.

[0025] The displacement detection means 6 is preferably installed at the end of the chock end cover 5. The chock end cover 5 is tightly fixed to the chock 4 and is integrated with it, which prevents the displacement detection means from measuring the displacement of the chock 4 itself. This makes it possible to accurately measure the axial displacement of the roll relative to the chock. It is preferable that the chock keeper and the housing keeper are in an installation condition where there is no rattle due to wear. If mechanical rattle occurs on the keeper side, there is a risk that the axial displacement of the roll relative to the chock cannot be accurately measured.

[0026] In the example shown in Figure 3, the non-contact displacement sensor 6, acting as a displacement detector, outputs its signal via a cable 7 routed within the measuring jig 8. The end of the measuring jig 8 opposite the end where the non-contact displacement sensor 6 is installed is sealed with a seal 9 to prevent oil leakage. The cable 7 of the non-contact displacement sensor 6 is preferably routed to the top of the rolling mill housing and connected to an amplifier so that it can be viewed as a time series chart. Because the backup roll 2 moves up and down toward the roll reduction position during roll reassembly, it is preferable to provide slack in the cable 7 and route it so that it is not subjected to tension. The non-contact displacement sensor 6 is installed via the measuring jig 8 attached to the chock end cover 5, enabling measurements with minimal error without being affected by mill vibrations. In addition, in cases where the chock 4 of the backup roll 2 does not have a chock end cover 5, it is preferable to attach the displacement detector to a chock structural component that does not rotate with the roll.

[0027] In the example of FIG. 3, the displacement meter measurement distance 10 is the distance from the tip of the non-contact displacement meter 6 to the axial end of the backup roll 2.

[0028] This embodiment is preferably applied to a shift mill that rolls by moving the work rolls 1 in the axial direction. The backup rolls 2 also tend to be displaced more to the side opposite the keeper AK than to the side toward the keeper KP. In a shift mill, when the work rolls 1 shift, the backup rolls 2 are displaced significantly in the axial direction. Therefore, it is presumed that in a shift mill, the roll gap between the operating side and the driving side of the work rolls 1 increases due to the shift, leading to displacement of the backup rolls 2.

[0029] Generally, when calculating the roll gap change in response to the axial displacement of the backup roll, a method is used in which the roll gap change is calculated geometrically from the axial surface pressure distribution caused by the change in the contact position between the work roll and the backup roll. However, this method does not accurately match the actual roll gap change. Judging from the rolling load, leveling correction amount, and meandering amount during actual operation, it is thought that the roll gap change is larger. This is because, in the case of a backup roll with an oil film bearing, it is thought that the oil film thickness on the operating side and the driving side changes when the roll changes in the axial direction, and this oil film thickness change is not included in the geometric method.

[0030] Although the above description has been given using a four-high rolling mill as an example, this embodiment can also be suitably applied to a six-high rolling mill as shown in Figures 4 and 5. In a six-high rolling mill, intermediate rolls 11 are arranged between work rolls 1 and backup rolls 2, and are in rolling contact with each roll. Both axial ends of the intermediate rolls 11 are incorporated into housing windows via intermediate roll chocks 12. [Example]

[0031] The non-contact displacement meter shown in Figure 3 was installed using a measurement jig on the chock end cover 5 on the side having the thrust bearing of the backup roll 2 of a finishing mill in a hot rolling facility, which is a four-high rolling mill equivalent to that shown in Figures 1 and 2. The non-contact displacement meter shown in Figure 3 was installed using a measurement jig on the chock end cover 5 on the side having the thrust bearing of the backup roll 2 of a finishing mill in a hot rolling facility, which is a six-high rolling mill equivalent to that shown in Figures 4 and 5. An eddy-current type was used as the non-contact displacement meter.

[0032] An example of the axial displacement of the backup rolls 2 during the shifting operation of the work rolls 1 is shown in Figure 6. Figure 6(a) shows the relationship between the upper work roll and the upper backup roll, and Figure 6(b) shows the relationship between the lower work roll and the lower backup roll. Due to the shifting operation of the work rolls 1, the backup rolls 2 move in the axial direction within a range of -2 mm to +8 mm, with the direction opposite the keeper AK being considered positive. Here, the backup roll position before the shifting operation of the work rolls 1 is set to 0 mm. For both the upper and lower backup rolls 2, the displacement on the side opposite the keeper AK is greater than the displacement toward the keeper KP.

[0033] When the backup roll 2 moves axially due to the shifting of the work roll 1, the backup roll 2 moves back to its original position after the shifting operation is completed. In other words, if the rolled material S gets caught immediately after the shifting operation, the backup roll 2 remains displaced axially and a rolling load is generated. As a result, the roll flatness on the operating side and the drive side differ, and a maximum roll gap opening difference of 20 μm occurs in calculations. In reality, the film thickness of the oil film bearing also changes, so the actual roll gap change amount is thought to be greater than this value.

[0034] Figure 7 shows an example of the change in rolling load and the resulting axial displacement of the backup roll 2 that occurred during the rolling of the rolled material S. Figure 7 shows the results for the first finishing mill in hot rolling. The axial displacement of the backup roll 2 changes linearly with the rolling load at a rate of 2.5 μm / tf (0.255 μm / kN). The change in rolling load from the head to the tail end of the first stand of the finishing mill (F1) can reach 500 tf (4900 kN) or more. In such cases, the axial displacement of the backup roll 2 during rolling is approximately 1 mm. When the change in oil film thickness due to the axial displacement of the backup roll 2 is also taken into account, the amount of roll gap change during rolling cannot be ignored.

[0035] When the axial displacement of the backup roll is measured as described above, a difference is made in the rolling loads applied to the operating side and the driving side so as to bring the displacement amount closer to zero, thereby controlling the roll gap difference to approach zero. Note that, when the axial displacement of the backup roll is measured, a difference is made in the rolling loads applied to the operating side and the driving side so as to bring the displacement amount closer to zero, thereby controlling the roll gap difference to approach zero. This means that the displacement of the steel sheet during rolling is confirmed, and if the steel sheet displaces to the operating side, the reduction amount on the operating side is made higher than the reduction amount on the driving side, thereby bringing the roll gap difference closer to zero. Also, if the steel sheet displaces to the driving side, the reduction amount on the driving side is made higher than the reduction amount on the operating side, thereby bringing the roll gap difference closer to zero. This makes it possible to roll while reducing wedging and bending of the rolled material. The control of the reduction amounts on the operating side and the driving side described above is performed automatically or manually using the measurement data of the axial displacement of the backup roll. The control range of the roll gap difference is preferably within ±0.10 mm, more preferably within ±0.03 mm. [Industrial Applicability]

[0036] According to the rolling mill for plate rolling, the method for detecting and controlling the roll reduction position of the rolling mill, and the method for manufacturing rolled plate of the present invention, it is possible to roll plate material with reduced wedge and bending of the rolled material, so that plate rolling can be performed without trouble and with a good yield. This contributes to improving productivity and is therefore industrially useful. [Explanation of symbols]

[0037] 1 Work roll 2 Backup Role 3 Work roll chocks 4 Backup Roll Chocks 5 Chock end cover 6. Non-contact displacement meter (displacement detection means) 7 Cable 8 Measuring Jig 9 Seals 10 Displacement meter measurement distance 11 Intermediate roll 12 Intermediate Roll Chock S Rolled material FD direction of travel KP Keeper (direction) AK Anti-keeper (direction)

Claims

1. A rolling mill for plate rolling, comprising a pair of work rolls that contact each other directly or via a material to be rolled, and a pair of backup rolls that roll-contact the work rolls with or without an intermediate roll, and both ends of each roll being incorporated between housing windows via roll chocks on the operating side and the driving side, a detection means for detecting axial displacement of the backup roll, attached to one of the roll chocks of the backup roll; a control means for changing the roll pressure reduction position based on the axial displacement of the backup roll detected by the detection means so that the difference in roll gap value between the operation side work roll and the drive side work roll gradually approaches zero; Have the control means is configured to make a difference in the rolling loads applied to the operating side and the driving side so as to make the axial displacement of the backup roll approach zero, thereby making the difference in the roll gap approach zero.

2. The backup roll has an oil film bearing, 2. The rolling mill for plate rolling according to claim 1, wherein said detecting means is a non-contact displacement meter attached to a chock end cover on the side having a thrust bearing.

3. A method for detecting a roll reduction position of a rolling mill that rolls a plate material, comprising: The amount of axial displacement of the backup roll, which changes depending on the rolling load or the work roll shift for plate crown control, is measured. The difference in roll gap value between the work rolls on the operating side and the work roll on the driving side is estimated using the obtained displacement amount, When controlling the roll pressure position based on the difference in the estimated roll gap value of the work rolls so that the difference asymptotically approaches 0, The rolling loads applied to the operating side and the driving side are made different so that the axial displacement of the backup roll approaches zero, and the difference in the roll gap is controlled so as to approach zero. A method for controlling the roll reduction position of a rolling mill.

4. A method for producing a rolled plate, wherein rolling is performed while reducing wedge and bending of the material to be rolled by the control method according to claim 3.

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