Tail-end extrusion suppression device

Abstract

The present disclosure relates to a tail-end extrusion suppression device for a tandem rolling mill that rolls a rolled material by a series of N (N≥2) rolling stands. The i-th rolling stand (1≤i≤N) of the tandem rolling mill has an i-th roll bending device that presses the rolled material with a predetermined roll bending pressure. The tail-end extrusion suppression device continuously reduces the roll bending pressure of the (j+1)-th to N-th roll bending devices that are downstream of the j-th rolling stand from when the j-th rolling stand (1≤j≤N−1) is separated from the tail end of the rolled material until the N-th rolling stand is separated.

Description

Technical Field

[0001] This disclosure relates to a tail-end extrusion suppression device for a tandem rolling mill having multiple rolling stands. Background Technology

[0002] As a type of defect that occurs during the rolling of rolled material in a hot finishing mill, a crushing accident of the rolled material is known. A crushing accident occurs when the very end of the rolled material, under tension, is released as it passes through the mill stand, resulting in a serpentine state and folding upon contact with the side guides of the mill stand. When a crushing accident occurs, the very end of the rolled material is damaged, resulting in poor quality. Furthermore, as a result of this crushing portion being rolled, the surface of the work rolls is damaged, and this damage is transferred to subsequent rolled materials, resulting in poor quality.

[0003] The following patent documents are known as techniques for preventing serpentine movement that could cause crushing accidents.

[0004] Patent Document 1 discloses that, in order to prevent snake-like movement, an image of the tail end of the rolled material is displayed on a monitor for operator monitoring. Patent Document 2 discloses that, in order to prevent snake-like movement, considering the amount of snake-like movement with respect to the plate, the left-right asymmetry of the plate thickness (wedge shape), and the effect of this asymmetry on snake-like movement (parallel rigidity), which decreases as the rolling force is reduced, the amount of roll spacing is controlled by adjusting the amount calculated when the tail end separates. Patent Document 3 discloses that, in order to prevent snake-like movement, the amount of snake-like movement is calculated based on the torque difference detected from multiple segmented rolls arranged between stands, and the reduction level is adjusted accordingly.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2013-180322

[0008] Patent Document 2: Japanese Patent Application Publication No. 2002-096109

[0009] Patent Document 3: International Publication No. 2012 / 086043 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] Thus, methods for preventing serpentine movement are disclosed. However, control methods based on complex calculations are not necessarily optimal. It is preferable to prevent crushing accidents caused by serpentine movement of the rolled material through simpler control. The inventors of this application, through repeated and in-depth research, discovered a method for preventing crushing accidents caused by serpentine movement of the rolled material by using simple control of a roll bending device.

[0012] This disclosure was made to solve the aforementioned problems, and its purpose is to provide a tail-end extrusion suppression device that uses a roll bending device to control the rolled material to pass through the center of the rolling line, thereby preventing the rolled material from snaking and tail-end extrusion.

[0013] Methods for solving problems

[0014] The first viewpoint relates to a tail-end extrusion suppression device for a tandem rolling mill that rolls a workpiece using N (N≥2) rolling stands arranged in series.

[0015] The i-th rolling stand (1≤i≤N) of the aforementioned tandem rolling mill each has an i-th roll bending device that presses down the material to be rolled with a pre-set roll bending pressure.

[0016] The aforementioned tail-end extrusion suppression device continuously reduces the roll bending pressure of each roll bending device downstream of the aforementioned j+1 to Nth rolling mill stands from the time the roll is removed from a designated j-th rolling mill stand (1≤j≤N-1) until it is removed from the Nth rolling mill stand.

[0017] The second viewpoint, based on the first viewpoint, further possesses the following characteristics.

[0018] The aforementioned tail-end extrusion suppression device stores designated stand information, which determines the combination of steel grade and target plate thickness on the exit side of the Nth rolling stand, and multiple relationships between designated stands related to tail-end extrusion suppression.

[0019] The j-th rolling mill stand mentioned above is the designated mill stand selected from the designated mill stand information by taking the combination of steel grade and the target plate thickness on the exit side of the N-th rolling mill stand as input.

[0020] The third viewpoint, based on the first or second viewpoint, further possesses the following characteristics.

[0021] The bending devices for each of the above-mentioned j+1 to N rolls are configured to maintain the bending pressure at the above-mentioned equilibrium pressure when the bending pressure of the rolls reaches the equilibrium pressure.

[0022] Invention Effects

[0023] According to this disclosure, the tail-end extrusion suppression device reduces the bending pressure of the rolls on the subsequent stand when the rolled material leaves the designated stand, thereby causing the rolled material to develop a crown. Thus, the rolled material is controlled to pass through the center of the rolling line, and the serpentine movement and tail-end extrusion of the rolled material are suppressed. Attached Figure Description

[0024] Figure 1 This is a diagram illustrating an example of the configuration of a finishing mill for explaining the implementation method.

[0025] Figure 2 This is a diagram of a roll bending device for illustrating an embodiment of a rolling mill stand.

[0026] Figure 3 This is a diagram of a roll bending device for illustrating an embodiment of a rolling mill stand.

[0027] Figure 4 This is a diagram illustrating an example of specified rack information for an implementation method.

[0028] Figure 5 This is a timing diagram used to illustrate the timing of controlling the bending pressure of the rolls in the implementation method.

[0029] Figure 6 This is a block diagram illustrating an example of the hardware configuration of the control device in an implementation method. Detailed Implementation

[0030] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Furthermore, common elements are labeled with the same reference numerals in the various drawings, and repeated descriptions are omitted.

[0031] Implementation method.

[0032] 1. System Composition

[0033] Figure 1 This is a diagram illustrating an example of the configuration of the finishing mill 1 in a hot rolling line.

[0034] Upstream of finishing mill 1 are a heating furnace (not shown), a roughing mill, a descaling machine, etc. Downstream of finishing mill 1 are an output roller table (ROT, not shown) and a coiler, etc.

[0035] The finishing mill 1 is a series rolling mill with N (N≥2) rolling stands 2 connected in series. Figure 1The finishing mill 1 shown has 7 (N=7) rolling stands 2 (first rolling stand 21, second rolling stand 22, third rolling stand 23, fourth rolling stand 24, fifth rolling stand 25, sixth rolling stand 26, and seventh rolling stand 27). The finishing mill 1 continuously rolls the strip steel (rolled material 3) from upstream to downstream in one direction (arrow 4). The finishing rolling determines the final quality of the rolled material 3, including its thickness and width, and other dimensional factors.

[0036] Furthermore, the number of rolling mill stands 2 is not limited to this. Without specifically distinguishing each rolling mill stand, it is simply referred to as "rolling mill stand 2".

[0037] Each rolling mill stand 2 is equipped with a work roll (WR) 5 and a back roll (BUR) 6. The work roll 5 is a rolling roll that rotates while in contact with the workpiece 3 to roll the workpiece 3. An electric motor and its drive device are connected to the work roll 5 to drive its rotation axis. The back roll 6 supports the work roll 5 and corrects any deflection of the work roll 5 in the direction of its rotation axis. The back roll 6 rotates along with the work roll 5 through friction between it and the work roll 5.

[0038] In addition, the finishing mill 1 may further include an intermediate roll between the working roll 5 and the support roll 6.

[0039] Each rolling mill stand 2 is equipped with various actuators, including a roll bending device 7 for controlling the roll bending pressure, a drive device (not shown) for controlling the speed of the work rolls 5, and a pressing device (not shown) for controlling the roll gap. The control device 8 controls these actuators based on calculated operating parameters to meet target plate thickness and temperature at the final stand exit. Furthermore, the control device 8 controls the actuators by feeding back the difference between the measured values ​​from sensors (thickness gauges, speed gauges, thermometers, etc., not shown) and the target values.

[0040] Figure 2 as well as Figure 3 This is a diagram illustrating the roll bending device 7 of the rolling mill stand 2.

[0041] Each rolling mill stand 2 is equipped with a roll bending device 7. Figure 1 The i-th rolling mill stand shown (1≤i≤N) is equipped with an i-th roll bending device (first roll bending device 71, second roll bending device 72, third roll bending device 73, fourth roll bending device 74, fifth roll bending device 75, sixth roll bending device 76, and seventh roll bending device 77) that presses down the rolled material 3 with a preset roll bending pressure. Without specifically distinguishing each roll bending device, it is simply referred to as "roll bending device 7".

[0042] The roll bending device 7 is an actuator that bends the roll by deflecting the central axis of the work roll 5. The roll bending device 7 has hydraulic cylinders at both ends of the rotation axis of the upper and lower pair of work rolls 5 for applying roll bending pressure (bending force).

[0043] like Figure 3 As shown in (A), by increasing the bending pressure of the rolls, the rolling force at both ends of the work rolls decreases, while the rolling force at the center of the work rolls increases. Therefore, the sheet crown can be reduced. Sheet crown is the difference in sheet thickness between the center and the ends in the width direction of the product. Furthermore, as... Figure 3 As shown in (B), by reducing the bending pressure of the rolls, the rolling force at both ends of the work rolls increases, while the rolling force at the center of the work rolls decreases. Therefore, the convexity of the plate can be increased.

[0044] 2. Tail-end squeezing suppression control

[0045] When rolling is performed through the aforementioned finishing mill 1, the very end of the rolled material becomes serpentine as it passes through the rolling mill stand 2, resulting in poor sheet permeability and potentially causing a "crushing accident" where it comes into contact with and folds against the side guide of the rolling mill stand 2. Therefore, the control device 8 of this embodiment includes a tail-end crushing suppression unit 9, which can prevent tail-end crushing accidents caused by the serpentine movement of the rolled material 3 by appropriately controlling the roll bending device 7.

[0046] The tail-end extrusion suppression section 9 continuously reduces the roll bending pressure of each roll bending device 7 downstream of the j+1 to Nth rolling stand during the period from when the rolls 3 leave a designated j-th rolling stand (1≤j≤N-1) until they leave the Nth rolling stand. The roll bending pressure is continuously reduced from a set value according to a ramp function.

[0047] Furthermore, the bending devices for each of the (j+1)th to (N)th rolls are configured to maintain the bending pressure at a balance pressure when the bending pressure reaches the balance pressure. The balance pressure is the reference pressure when the support roll 6 is in contact with the work roll 5 without any material being rolled 3.

[0048] (Specified rack information)

[0049] The specified stand mentioned above, i.e. the j-th rolling mill stand, is selected based on the specified stand information. Figure 4This diagram illustrates an example of the designated stand information in this embodiment. The designated stand information determines multiple relationships between the combination of the steel grade of the rolled material 3 and the target plate thickness at the exit side of the Nth rolling stand, and the designated stand (jth rolling stand) related to tail-end extrusion suppression. The designated stand information is pre-stored in the memory 82 of the control device 8. Figure 6 ).

[0050] Tail-end extrusion suppression control is applicable to thin-thick rolled products 3 that are prone to tail-end extrusion due to tail-end serpentine movement. For example, the target plate thickness at the exit side of the Nth mill for rolled products 3 prone to tail-end extrusion due to serpentine movement is 2.5 mm. On the other hand, when tail-end extrusion suppression control is applied to thicker rolled products 3, shape defects may occur. Therefore, depending on the combination of steel grade and the target plate thickness at the exit side of the Nth mill, a specific mill may not necessarily be designated to address the generation of tail-end extrusion due to serpentine movement.

[0051] The tail-end extrusion suppression unit 9 selects a specified stand (jth rolling stand) from the specified stand information by taking the combination of the steel grade of the rolled material 3 and the target plate thickness at the exit side of the Nth rolling stand as input. In addition, the steel grade related to the product specifications and the target plate thickness at the exit side of the Nth rolling stand can be obtained from an external device before rolling begins.

[0052] 3. Control Example

[0053] Reference Figure 5 An example of tail-end squeezing suppression control is illustrated. Figure 5 It is a timing diagram used to illustrate the timing of the control of the bending pressure of the rolls.

[0054] t1 is the timing when the leading edge of the rolled material 3 reaches the third rolling mill stand 23. t2 is the timing when the leading edge of the rolled material 3 reaches the fourth rolling mill stand 24. t3 is the timing when the leading edge of the rolled material 3 reaches the fifth rolling mill stand 25. t4 is the timing when the leading edge of the rolled material 3 reaches the sixth rolling mill stand 26. t5 is the timing when the leading edge of the rolled material 3 reaches the final stand, i.e., the seventh rolling mill stand 27.

[0055] t6 is the timing when the tail end of the rolled material 3 leaves the third rolling mill stand 23. t7 is the timing when the tail end of the rolled material 3 leaves the fourth rolling mill stand 24. t8 is the timing when the tail end of the rolled material 3 leaves the fifth rolling mill stand 25. t9 is the timing when the tail end of the rolled material 3 leaves the sixth rolling mill stand 26. t10 is the timing when the tail end of the rolled material 3 leaves the final stand, i.e., the seventh rolling mill stand 27.

[0056] exist Figure 5In the example shown, the third rolling mill stand 23 (j=3) was selected as the designated stand (j-th rolling mill stand). At time t6, the tail end of the rolled material 3 passes through the third rolling mill stand 23, which is the designated stand. As a result, the tail end of the rolled material 3 loses the restraining force of the work rolls 5 of the third rolling mill stand 23. From time t6, when the tail end of the rolled material 3 leaves the third rolling mill stand 23, the roll bending pressure of each roll bending device 7 after the designated stand begins to decrease.

[0057] During the period from the moment t6 when the tail end of the rolled material 3 leaves the third rolling mill stand 23 to the moment t7 when the tail end of the rolled material 3 leaves the fourth rolling mill stand 24, the fourth roll bending device 74 continuously reduces the roll bending pressure from the set value at moment t6.

[0058] During the period from time t6 until time t8 when the tail end of the rolled material 3 leaves the fifth rolling mill stand 25, the fifth roll bending device 75 continuously reduces the roll bending pressure from the set value at time t6.

[0059] The sixth roll bending device 76 continuously reduces the roll bending pressure from the set value at time t6 during the period from time t6 to time t8. At time t8, when the roll bending pressure reaches the equilibrium pressure, the sixth roll bending device 76 stops controlling the reduction of the roll bending pressure. During the period from time t8 to time t9, the roll bending pressure is maintained at the equilibrium pressure.

[0060] The seventh roll bending device 77 continuously reduces the roll bending pressure from the set value at time t6 to time t8. At time t8, when the roll bending pressure reaches the equilibrium pressure, the seventh roll bending device 77 stops controlling the reduction of the roll bending pressure. From time t8 to time t10, the roll bending pressure is maintained at the equilibrium pressure.

[0061] 4. Effects

[0062] As explained above, according to the control device 8 of this embodiment, by reducing the bending pressure of the rolls on the rolling mill stand 2, which is located after the designated stand, the shape of the rolled material 3 is made into a shape with side extension (the end in the width direction of the plate extends further than the central portion). As a result, the rolled material 3 is controlled to pass through the center of the rolling line, and the serpentine movement and tail-end extrusion of the rolled material 3 are suppressed.

[0063] 5. Hardware Configuration Example

[0064] Figure 6This is a conceptual diagram illustrating an example of the hardware configuration of the processing circuitry of the control device 8, which functions as a tail-end squeezing suppression device in various embodiments. Each component within the device represents a part of a function, which is implemented by the processing circuitry. In one embodiment, the processing circuitry includes at least one processor 81 and at least one memory 82. In another embodiment, the processing circuitry includes at least one dedicated hardware 83.

[0065] When the processing circuit includes a processor 81 and a memory 82, each function is implemented by software, firmware, or a combination of software and firmware. At least one of the software and firmware is recorded as a program. At least one of the software and firmware is stored in the memory 82. The processor 81 reads the program stored in the memory 82 and executes it, thereby implementing the functions.

[0066] When the processing circuit has dedicated hardware 83, the processing circuit may be, for example, a single circuit, a composite circuit, a programmed processor, or a combination thereof. Each function is implemented through the processing circuit.

[0067] The embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention. When numerical values ​​for the number, quantity, amount, range, etc., of each element are mentioned in the above embodiments, the present invention is not limited to those mentioned values, unless specifically stated or clearly determined in principle. Furthermore, the structures, etc., described in the above embodiments are not necessarily essential to the present invention, unless specifically stated or clearly determined in principle.

[0068] Explanation of reference numerals in the attached figures

[0069] 1 Finishing mill

[0070] 2 Rolling Mill Stand

[0071] 3. Rolled material

[0072] 5 Working rolls

[0073] 6 Support rolls

[0074] 7. Roll bending device

[0075] 8. Control device

[0076] 9. Tail end compression suppression section

[0077] 21-27 First Rolling Stand - Seventh Rolling Stand

[0078] 71-77 First Roll Bending Device - Seventh Roll Bending Device

[0079] 81 processor

[0080] 82 Memory

[0081] 83 Hardware

Claims

1. A tail-end extrusion suppression device, used in a tandem rolling mill with N rolling stands arranged in series to roll a workpiece, characterized in that, The i-th rolling stand of the aforementioned tandem rolling mill is equipped with an i-th roll bending device that presses down the material to be rolled with a pre-set roll bending pressure. From the moment the rolled material exits a designated j-th rolling mill stand until it exits the N-th rolling mill stand, the bending pressure of each roll in the (j+1)-to-Nth roll bending devices downstream of the j-th rolling mill stand is continuously reduced from a pre-set bending pressure for each roll in the (j+1)-to-Nth roll bending devices. This continuous reduction in the bending pressure of each roll in the (j+1)-to-Nth roll bending devices begins when the rolled material exits the j-th rolling mill stand. Where N≥3, 1≤i≤N, 1≤j≤N-1.

2. The tail-end extrusion suppression device as described in claim 1, characterized in that, The system stores specified stand information that determines the combination of steel grade and target plate thickness at the exit side of the Nth rolling stand, as well as multiple relationships between specified stands related to tail-end extrusion suppression. The j-th rolling mill stand mentioned above is the designated mill stand selected from the designated mill stand information by taking the combination of steel grade and the target plate thickness on the exit side of the N-th rolling mill stand as input.

3. The tail-end extrusion suppression device as described in claim 1 or 2, characterized in that, The aforementioned roll bending devices j+1 to N are configured to maintain the roll bending pressure in their respective roll bending devices at the aforementioned balance pressure when the roll bending pressure in each roll bending device reaches the balance pressure.

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