EP4631636A1

EP4631636A1 - Method for changing running sheet thickness

Info

Publication number: EP4631636A1
Application number: EP24738636.0A
Authority: EP
Inventors: Sho Yoshida; Mayu Mori; Akihiro Nagahiro; Yutaro TAKENAKA
Original assignee: JFE Steel Corp
Current assignee: JFE Steel Corp
Priority date: 2023-01-06
Filing date: 2024-01-04
Publication date: 2025-10-15
Also published as: CN120456987A; WO2024147346A1; KR20250119616A; JPWO2024147346A1; JP7597279B2; EP4631636A4; TWI883766B; TW202435986A; MX2025007858A

Abstract

Provided is a flying thickness change method that can shorten a thickness off-gauge length and reduce tension fluctuation. The flying thickness change method is a method for performing flying thickness change during continuous rolling of a to-be-rolled material (6) by a tandem rolling mill (2), the to-be-rolled material (6) including a preceding material (61) and a succeeding material (62) that are metal sheets and joined to each other. The flying thickness change method includes: continuously measuring a thickness or a sheet speed of the to-be-rolled material (6) in a target inter-stand section between a target stand (for example, a second stand (2B)) as a rolling mill stand at which thickness change is performed and a preceding stand (for example, a first stand (2A)) as a rolling mill stand preceding to the target stand; detecting a thickness change position near a joined portion between the preceding material (61) and the succeeding material (62) based on measurement results of the thickness or tracking the thickness change position based on measurement results of the sheet speed; and changing a roll gap of a target stand in a timing when the thickness change position reaches the target stand.

Description

Technical Field

The present invention relates to a flying thickness change method.

Background Art

A technology called flying thickness change is used in cold rolling of a steel sheet to continue rolling without stopping a rolling mill as long as possible for the purpose of improvement of efficiency or yield. The flying thickness change is a technology to continuously perform rolling without stopping a rolling mill, by continuously changing the setting of an actuator for a preceding coil to the setting of the actuator for a succeeding coil at the time of rolling a welded potion between coils having different specifications. At the time when the setting of the actuator is changed in the flying thickness change, it takes time to change the setting particularly in a case where a change amount of a roll position or the like is large. Accordingly, a steady state temporarily breaks, so that tension becomes unstable, thereby resulting in sheet fracture or the like.
Conventionally, a method using an intermediate thickness is used as a method for restraining tension fluctuation in the flying thickness change. For example, as a method for determining an intermediate thickness to restrain tension fluctuation, PTL 1 discloses a method for determining an intermediate thickness in such a manner that an evaluation function with a fluctuation amount of a thickness being taken as a variable is formed, and the intermediate thickness is determined to fall within thresholds including the evaluation function. PTL 2 discloses a technique to restrain tension fluctuation by determining a value of the tension fluctuation and resetting a flying thickness change time to change setting values of a roll gap and a roll peripheral speed from a pass schedule A to a pass schedule B. In PTL 2, the value of the tension fluctuation is determined based on a tension fluctuation value predicted by a tension fluctuation learning unit by a neural network learning a tension fluctuation in actual flying thickness change as teacher data.

Citation List

Patent Literatures

PTL 1: JP 2022-12423 A
PTL 2: JP H10-249423 A

Summary of Invention

Technical Problem

Due to recent technological innovation and expansion of application of steel sheets, rolling is performed on various steel sheets (particularly, high deformation resistance materials represented by electromagnetic materials or high tensile strength steel), and flying thickness change is performed on a connection between coils largely different in specification (thickness, deformation resistance, or the like). As a result, a large tension fluctuation occurs in the flying thickness change, so that the aforementioned conventional technology is used to solve such a problem.
However, the method as disclosed in PTL 1 has such a problem that, due to an intermediate thickness, a thickness off-gauge length becomes long. In addition, tension fluctuation at the time when a joined portion passes depends on a change in a rolling condition before and after the joined portion, such as a thickness difference or a difference in deformation resistance between a preceding material and a succeeding material, but a prediction model in the method as disclosed in PTL 2 does not necessarily consider those effects. Accordingly, in the case of the method as disclosed in PTL 2, predictability of the tension fluctuation is low, and a large tension fluctuation might occur, for example.
The present invention is accomplished in view of the above problems, and an object of the present invention is to provide a flying thickness change method that can reduce tension fluctuation.

Solution to Problem

(1) One aspect of the present invention provides a flying thickness change method for performing flying thickness change during continuous rolling of a to-be-rolled material by a tandem rolling mill, the to-be-rolled material including a preceding material and a succeeding material that are metal sheets and joined to each other. The flying thickness change method includes: continuously measuring a thickness or a sheet speed of the to-be-rolled material in a target inter-stand section between a target stand as a rolling mill stand at which thickness change is performed and a preceding stand as a rolling mill stand preceding to the target stand; detecting a thickness change position near a joined portion between the preceding material and the succeeding material based on measurement results of the thickness or tracking the thickness change position based on measurement results of the sheet speed; and changing a roll gap of the target stand in a timing when the thickness change position reaches the target stand.
(2) In the above configuration (1), the flying thickness change method further includes: calculating, by use of the sheet speed measured in the target inter-stand section, a length of a tapered thickness portion of the to-be-rolled material which tapered thickness portion is formed by rolling at the preceding stand; calculating a change speed to change a roll position at the target stand, by dividing the length of the tapered thickness portion by a change amount of the roll position at the target stand; and changing the roll gap of the target stand based on the change speed thus calculated.
(3) In the above configuration (1) or (2), the to-be-rolled material is a high deformation resistance steel sheet.

Advantageous Effects of Invention

One aspect of the present invention can provide a flying thickness change method that can reduce tension fluctuation.

Brief Description of Drawings

FIG. 1 is a schematic view illustrating a cold rolling facility according to a first embodiment of the present invention.
FIGS. 2A to 2F are explanatory drawings illustrating a conventional flying thickness change method. FIG. 2A illustrates a state where a thickness change position S₁ is on an upstream side from a first stand, FIG. 2B illustrates a state where the thickness change position S₁ reaches the first stand, FIG. 2C illustrates a state where a joined portion reaches the first stand, FIG. 2D illustrates a state where the thickness change position S₁ reaches a second stand, FIG. 2E illustrates a state where a thickness change position S₂ reaches the second stand, and FIG. 2F illustrates a state where the joined portion reaches the second stand.
FIG. 3 is a graph illustrating changes in tension between the first stand and the second stand in the conventional flying thickness change method.
FIGS. 4A to 4E are explanatory drawings illustrating a flying thickness change method according to the first embodiment. FIG. 4A illustrates a state where a thickness change position is on an upstream side from a first stand, FIG. 4B illustrates a state where the thickness change position reaches the first stand, FIG. 4C illustrates a state where a joined portion reaches the first stand, FIG. 4D illustrates a state where the thickness change position reaches a second stand, and FIG. 4E illustrates a state where the joined portion reaches the second stand.
FIG. 5 is a graph illustrating changes in tension between the first stand and the second stand in the flying thickness change method according to the first embodiment.
FIG. 6 is a schematic view illustrating a cold rolling facility according to a second embodiment of the present invention.
FIGS. 7A to 7F are explanatory drawings illustrating a flying thickness change method according to the second embodiment. FIG. 7A illustrates a state where a thickness change position is on an upstream side from a first stand, FIG. 7B illustrates a state where the thickness change position reaches the first stand, FIG. 7C illustrates a state where a joined portion reaches the first stand, FIG. 7D illustrates a state where the joined portion passes through the first stand and the thickness change position is on the upstream side from a second stand, FIG. 7E illustrates a state where the thickness change position reaches the second stand, and FIG. 7F illustrates a state where the joined portion reaches the second stand.
FIG. 8 is a flowchart illustrating the flying thickness change method according to the second embodiment of the present invention.
FIG. 9 is a graph illustrating changes in tension between the first stand and the second stand in a case where flying thickness change is ended early.

Description of Embodiments

With reference to the drawings, the following detailed description deals with embodiments of the present invention. In the following description, identical or similar constituents have identical or similar reference signs, and redundant descriptions are omitted. Each drawing is schematic and includes a case different from actual ones. Each embodiment described below describes a device or a method to embody the technical idea of the present invention, and the technical idea of the present invention does not specify a material, a structure, an arrangement, or the like of a component part to those described below. Various changes can be added to the technical idea of the present invention within a technical scope defined by claims described in Claims.

(Configuration of Cold Tandem Rolling Mill)

First described is a flying thickness change method according to a first embodiment of the present invention. FIG. 1 is a schematic configuration diagram illustrating an example of a cold continuous rolling facility 1 according to the first embodiment of the present invention. Note that, in FIG. 1, other devices (for example, devices such as an uncoiler, a welding machine, and a looper on an inlet side, and a cutter and a coiler on an outlet side) accompanying the facility are not illustrated.
As illustrated in FIG. 1, the cold continuous rolling facility 1 includes a tandem rolling mill 2, a plurality of thickness measuring devices 3, a rolling controller (PLC) 4 configured to control the tandem rolling mill 2, and a control computing machine (process computer) 5 configured to manage the cold continuous rolling facility including the rolling controller 4.
The tandem rolling mill 2 is a continuous cold tandem rolling mill including a first stand 2A to a fifth stand 2E sequentially from the inlet side in a feeding direction.
Each of the first stand 2A to the fifth stand 2E includes workrolls 21, a roll speed control device 22 as an electric machine configured to change the roll speeds of the workrolls 21, and a rolling-reduction control device 23 configured to change a roll gap between the upper and lower workrolls 21.
Each of the plurality of thickness measuring devices 3 is provided in a section (an inter-stand section) between corresponding stands adjacent to each other from among the first stand 2A to the fifth stand 2E and continuously measures the thickness of a to-be-rolled material 6 as a metal sheet passing through the inter-stand section. A thickness measurement method performed by the thickness measuring device 3 is not particularly limited, but a measuring device configured to emit γ-rays (X-rays), measure an attenuation of the γ-rays (X-rays) transmitting through a measured object, and convert the attenuation into a thickness is usable, for example. The measurement result of the thickness from the thickness measuring device 3 is sent to the control computing machine 5.
The control computing machine 5 sets a roll gap value, a roll gap change amount, a roll speed, a roll speed change amount, and so on of each stand. The rolling controller 4 performs, on-line, computing and processing to control the roll speed control device 22 of each of the first stand 2A to the fifth stand 2E and the rolling-reduction control device 23 of each of the first stand 2A to the fifth stand 2E based on each value acquired from the control computing machine 5.
In the cold rolling facility 1 configured as such, a tail end of a preceding material 61 and a top end of a succeeding material 62 in the to-be-rolled material 6 are joined to each other at a joined portion W by welding or the like by a welder (not illustrated) disposed on the inlet side of the tandem rolling mill 2. Then, the to-be-rolled material 6 is subjected to rolling sequentially performed by respective stands from the first stand 2A to the fifth stand 2E as a final stand in the cold rolling mill such that the to-be-rolled material 6 is rolled into a predetermined finishing thickness. After that, the to-be-rolled material 6 is cut by a flying shear machine at the joined portion W between the preceding material 61 and the succeeding material 62 or its vicinity, and a succeeding material 52 after the cutting is wound on a tension reel different from a tension real for a preceding material 51.
Here, in a case where the preceding material 61 and the succeeding material 62 have different rolling conditions (e.g., a motherboard thickness, a finishing thickness, a deformation resistance, and so on), when the preceding material 61 and the succeeding material 62 are continuously rolled by the cold rolling mill, the rolling conditions are changed on the fly (that is, with the to-be-rolled material 6 being conveyed inside the tandem rolling mill 2), that is, flying thickness change is performed.
In a general conventional method, based on tracking of the joined portion W (on the basis of the joined portion W), a roll gap setting value is changed in a timing when a thickness change position set on the preceding material 61 side to be apart from the joined potion just by a predetermined distance reaches a stand. More specifically, the flying thickness change is performed by a method illustrated in FIG. 2A to FIG. 2F. Tension fluctuation in an inter-stand section between the first stand 2A and the second stand 2B at this time is illustrated in FIG. 3. Note that respective timings (a) to (f) in FIG. 3 correspond to respective timings of the states of FIGS. 2A to F.
First, as illustrated in FIG. 2A, rolling is performed with a roll gap value of each stand being set to a value set for the preceding material 61. Note that, in FIG. 2A, a position indicated by S₁ on the tail end side of the preceding material 61 is a position where the roll gap setting value is changed at the first stand 2A.
When rolling further advances, the thickness change position S₁ of the preceding material 61 reaches the first stand 2A as illustrated in FIG. 2B, and changing of the roll gap setting value at the first stand 2A is started so that the roll gap setting value at the first stand 2A is changed to a value for the succeeding material 62. The thickness change position S₁ is set on the tail end side of the preceding material 61, at a position distanced from the joined portion W only by a predetermined distance. The thickness change position S₁ is set based on a time required to change the roll gap, a feeding speed, or the like to be described below.
When rolling further advances, the changing of the roll gap setting value at the first stand 2A is finished, and rolling of the succeeding material 62 is started at the first stand 2A, as illustrated in FIG. 2C. Generally, the thickness change position S₁ is set such that the changing of the roll gap setting value is finished before the joined portion W reaches the first stand 2A. When the roll gap setting value is changed as illustrated in FIGS. 2B and 2C, the thickness of the preceding material 61 from the tail end to the joined portion W changes into a tapered shape.
When rolling further advances, the thickness change position S₁ at the first stand 2A reaches the second stand 2B as illustrated in FIG. 2D. As will be described later, changing of the roll gap setting value at the second stand 2B is started when a thickness change position S₂ reaches the second stand 2B. Similarly to the thickness change position S₁, the thickness change position S₂ is set on the tail end side of the preceding material 61, at a position distanced from the joined portion W only by a predetermined distance. Note that, as illustrated in FIG. 2D, the preceding material 61 that has passed through the first stand 2A is rolled such that its length in the longitudinal direction is elongated, so that the thickness change position S₁ for the first stand 2A and the thickness change position S₂ for the second stand 2B are at different positions.
In the state illustrated in FIG. 2D, a thickness portion of the to-be-rolled material 6 which thickness portion is changed into a tapered shape reaches the second stand 2B before the roll gap at the second stand 2B is changed. At this time, the roll gap setting value at the second stand 2B is a value for the preceding material 61, and therefore, tension between the first stand 2A and the second stand 2B decreases as illustrated in FIG. 3. Accordingly, a large tension fluctuation occurs, so that a risk of breakage increases.
When rolling further advances, the thickness change position S₂ reaches the second stand 2B as illustrated in FIG. 2E, and changing of the roll gap setting value at the second stand 2B is started so that the roll gap setting value at the second stand 2B is changed to a value for the succeeding material 62.
Further, the changing of the roll gap setting value at the second stand 2B is finished as illustrated in FIG. 2F, and rolling of the succeeding material 62 is started at the second stand 2B. In the third stand 2C and its subsequent stands, the roll gap setting value is changed in a similar manner to the second stand 2B, and thus, the flying thickness change is performed. That is, at the third stand 2C and its subsequent stands, the roll gap setting value is also changed when each setting thickness change position S passes through its corresponding stand. Note that, in any of the stands, the setting of a roll circumferential speed is changed in sync with the roll gap setting change.

(Flying Thickness Change Method)

FIGS. 4A to 4E are explanatory drawings illustrating the flying thickness change method according to the first embodiment. FIGS. 4A to 4E illustrate changing of the roll gap setting value at the first stand 2A, and the roll gap setting value is changed in a method similar to the method illustrated in FIGS. 2A to 2C. Tension fluctuation in an inter-stand section between the first stand 2A and the second stand 2B at this time is illustrated in FIG. 5. Note that respective timings (a) to (e) in FIG. 5 correspond to respective timings of the states of FIGS. 4A to E.
In the first embodiment, the thickness measuring device 3 is provided between the first stand 2A and the second stand 2B and continuously measures the thickness of the to-be-rolled material 6 to pass through the inter-stand section. The control computing machine 5 detects the thickness change position S at which the thickness of the to-be-rolled material 6 changes, from the measurement result from the thickness measuring device 3. The detected thickness change position S is a thickness change position S set at the first stand 2A and a position at which the thickness is changed into a tapered shape.
Then, when the thickness change position S is detected between the first stand 2A and the second stand 2B, the control computing machine 5 changes the roll gap setting value at the second stand 2B in a timing when the thickness change position S reaches the second stand 2B, as illustrated in FIG. 4D. At this time, the roll gap setting value at the second stand 2B is changed from a setting value for the preceding material 61 to a setting value for the succeeding material 62. Since the roll gap setting value at the second stand 2B is changed in the thickness change position S, even when a tapered-thickness portion reaches the second stand 2B, a decrease in tension is compensated as illustrated in FIG. 5, thereby making it possible to reduce a risk of breakage due to the decrease in tension.
When rolling advances, the changing of the roll gap setting value at the second stand 2B is finished as illustrated in FIG. 4E, and rolling of the succeeding material 62 is started at the second stand 2B. In the third stand 2C and its subsequent stands, the roll gap setting value is changed in a similar manner to the second stand 2B, and thus, the flying thickness change is performed. That is, in each of the third stand 2C and its subsequent stands, the thickness change position S is detected from a measurement result from the thickness measuring device 3 provided in its corresponding inter-stand section, and the roll gap setting value is changed when the setting thickness change position S reaches each stand. Note that, in any of the stands, the setting of a roll circumferential speed is also changed in sync with the roll gap setting change.
In the first embodiment, the to-be-rolled material 6 is a metal sheet, and it is preferable that the to-be-rolled material 6 be a steel sheet, particularly, a high deformation resistance steel sheet. The high deformation resistance steel sheet is a steel sheet such as an electromagnetic material or a high tensile material, for example. Such a high deformation resistance steel sheet increases in a rolling-reduction change amount at the flying thickness change, and the thickness of a portion forward of the welded portion which thickness is obtained by the flying thickness change in a preceding stand largely separates from a setting thickness, so that tension fluctuation is large. On this account, when the flying thickness change method according to the first embodiment is applied, it is possible to prevent troubles such as breakage and to perform manufacturing stably.
The flying thickness change method according to the first embodiment is a method for performing flying thickness change during continuous rolling of the to-be-rolled material 6 by the tandem rolling mill 2, the to-be-rolled material 6 including the preceding material 61 and the succeeding material 62 that are metal sheets and joined to each other. The flying thickness change method includes: continuously measuring the thickness of the to-be-rolled material in a target inter-stand section; detecting the thickness change position S near the joined portion W; and changing a roll gap of a target stand in the timing when the thickness change position reaches the target stand. Note that the target stand is a rolling mill stand at which the thickness is changed, and the preceding stand is a rolling mill stand provided on the upstream side from the target stand in a rolling direction so as to be adjacent to the target stand. For example, in FIG. 4, in a case where the roll gap of the second stand 2B is changed, the second stand 2B is the target stand, and the first stand 2A is the preceding stand.
In the flying thickness change method according to the first embodiment, it is not necessary to set an intermediate thickness, and therefore, it is possible to shorten a thickness off-gauge length in comparison with a method like PTL 1. Besides, in the flying thickness change method according to the first embodiment, the roll gap is changed with a thickness change point in the preceding stand being taken as a thickness change point in a subsequent stand. As a result, it is possible to restrain tension fluctuation without depending on a material or a specification of the to-be-rolled material 6.

(Configuration of Cold Tandem Rolling Mill)

Next will be described a flying thickness method according to a second embodiment of the present invention. FIG. 6 is a schematic configuration diagram illustrating an example of the cold continuous rolling facility 1 according to the second embodiment of the present invention. Note that, in FIG. 6, other devices accompanying the facility are not illustrated, similarly to FIG. 1.
As illustrated in FIG. 6, the cold continuous rolling facility 1 includes the tandem rolling mill 2, the rolling controller (PLC) 4 configured to control the tandem rolling mill 2, the control computing machine (process computer) 5 configured to manage the cold continuous rolling facility including the rolling controller 4, and a plurality of sheet speed meters 7.
The tandem rolling mill 2 is a continuous cold tandem rolling mill including the first stand 2A to the fifth stand 2E sequentially from the inlet side in the feeding direction.
Each of the first stand 2A to the fifth stand 2E includes the workrolls 21, the roll speed control device 22 as an electric machine configured to change the roll speeds of the workrolls 21, and the rolling-reduction control device 23 configured to change a roll gap between the upper and lower workrolls 21.
The control computing machine 5 sets a roll gap value, a roll gap change amount, a roll speed, a roll speed change amount, and so on of each stand. The rolling controller 4 performs, on-line, computing and processing to control the roll speed control device 22 of each of the first stand 2A to the fifth stand 2E and the rolling-reduction control device 23 of each of the first stand 2A to the fifth stand 2E based on each value acquired from the control computing machine 5.
Each of the plurality of sheet speed meters 7 is provided in a section (an inter-stand section) between corresponding stands adjacent to each other from among the first stand 2A to the fifth stand 2E and continuously measures a sheet speed as the speed of the to-be-rolled material 6 in its conveyance direction which to-be-rolled material 6 is a metal sheet passing through the inter-stand section. A sheet-speed measuring method performed by the sheet speed meter 7 is not limited particularly, but the sheet speed meter 7 can be a laser Doppler velocimeter or the like, for example. The measurement result of the sheet speed from the sheet speed meter 7 is sent to the control computing machine 5.
Similarly to the first embodiment, in the cold rolling facility 1, the tail end of the preceding material 61 and the top end of the succeeding material 62 in the to-be-rolled material 6 are joined to each other at the joined portion W by welding or the like by a welder (not illustrated) disposed on the inlet side of the tandem rolling mill 2. Subsequently, the to-be-rolled material 6 is subjected to rolling sequentially performed by respective stands of the cold rolling mill from the first stand 2A to the fifth stand 2E as a final stand such that the to-be-rolled material 6 is rolled into a predetermined finishing thickness. After that, the roller material 6 is cut by a flying shear machine at the joined portion W between the preceding material 61 and the succeeding material 62 or its vicinity, and a succeeding material 52 after the cutting is wound on a tension reel different from a tension real for a preceding material 51. Similarly to the first embodiment, in a case where the preceding material 61 and the succeeding material 62 have different rolling conditions (e.g., a motherboard thickness, a finishing thickness, a deformation resistance, and so on), flying thickness change is performed.

(Flying Thickness Change Method)

FIGS. 7A to 7E and FIG. 8 are explanatory drawings illustrating a flying thickness change method according to the second embodiment. FIGS. 7A to 7C illustrate a method (the flying thickness change method) for changing the roll gap setting value at the first stand 2A, and the roll gap setting value is changed in a similar manner to the method illustrated in FIGS. 2A to 2C.
The following describes the method for changing the roll gap setting value at the second stand 2B, that is, the flying thickness change method. The flying thickness change at the second stand 2B is performed according to a processing flow illustrated in FIG. 8. Note that, in rolling mill stands subsequent to the second stand 2B, the flying thickness change is also performed in a similar manner to the second stand 2B. Here, similarly to the first embodiment, a rolling mill stand targeted for the flying thickness change is referred to as a target stand, and a rolling mill stand preceding to the target stand is also referred to as a preceding stand. The processing flow illustrated in FIG. 8 is started in response to start of the flying thickness change at the preceding stand (the first stand 2A), that is, in response to the state of FIG. 7B being established.
When the flying thickness change at the first stand 2A starts, the sheet speed of the to-be-rolled material 6 passing through a target inter-stand section is first measured continuously by use of the sheet speed meter 7 provided in the target inter-stand section (S100). The target inter-stand section indicates a section between the target stand and its preceding stand, and in a case where the target stand is the second stand 2B, the target inter-stand section is between the second stand 2B and the first stand 2A. The measurement of the sheet speed is continuously performed at least until the flying thickness change is performed at the target stand. That is, in a case where the target stand is the second stand 2B, the measurement of the sheet speed is at least continuously performed after the thickness change position S illustrated in FIG. 7B reaches the first stand 2A but until the thickness change position S illustrated in FIG. 7E reaches the second stand 2B. Furthermore, the control computing machine 5 tracks the thickness change position S of the to-be-rolled material 6 from measurement results of the sheet speed measured by the sheet speed meter 7 in the target inter-stand section.
After step S100, the control computing machine 5 calculates a length L_N-1 of a tapered thickness portion after rolling at the preceding stand (S102). Note that N indicates a number (an N-th stand) of the target stand. That is, in a case where the target stand is the second stand 2B, a length L₁ of the tapered thickness portion after rolling at the first stand 2A is calculated. The tapered thickness portion is a portion of the to-be-rolled material 6 in which portion the thickness is changed into a tapered shape due to the flying thickness change at the preceding stand. In a case where the target stand is the second stand 2B, the tapered thickness portion is a portion from the thickness change position S to the joined portion W in FIG. 7D.
The length L_N-1 of the tapered thickness portion is calculated by multiplying the sheet speed at the preceding stand by time until the flying thickness change at the preceding stand is ended. More specifically, the length L_N-1 of the tapered thickness portion is calculated by use of Formula (1) as follows. In Formula (1), a measurement timing of the sheet speed is taken as a timestep, and the length L_N-1 is calculated from a sheet speed v_n-1(i) at each timestep and a time T_i. Note that a timestep number is such that a measurement timing at the start of the flying thickness change is 1, and a measurement timing at the end of the flying thickness change is m. The time T_i indicates an elapsed time from a predetermined timing as a starting point to each timestep.
[Math. 1] $L_{N - 1} = \sum_{i = 1}^{m} \frac{T_{i + 1} - T_{i}}{2} (v_{N - 1 (i)} + v_{N - 1 (i + 1)})$
Here, T_i is a time [s] in a timestep i, and v_N-1(i) is a sheet speed [m/s] in a target inter-stand section at the timestep i.
After step S102, the control computing machine 5 calculates a time t_N taken until the tapered thickness portion fully enters the target stand (S104). In step S104, the time t_N is calculated by use of the sheet speed in the target inter-stand section which sheet speed is measured by the sheet speed meter 7 just before the flying thickness change is performed at the target stand, that is, just before step S104, and the length L_N-1 calculated in step S102. In the second embodiment, the time t_N corresponds to a time after the thickness change position S of the to-be-rolled material 6 enters the target stand but before the joined portion W enters the target stand. The time t_N can be calculated by use of Formula (2) as follows.
[Math. 2] $t_{N} = \frac{L_{N - 1}}{v_{N - 1}}$
After step S104, the control computing machine 5 calculates a change speed R_N at a roll position from a change amount ΔS_N of the roll position at the target stand and the time t_N (S106). The change amount of the roll position at the target stand corresponds to an adjustment amount of a roll gap of the target stand and is a moving amount of each of the upper and lower workrolls 21 in the thickness direction of the to-be-rolled material 6 along with thickness change. The thickness change amount is a value set in advance. The change speed R_N of the roll position at the target stand is a moving speed of each workroll 21 at the time when the roll position is changed (that is, when the flying thickness change is performed). The change speed R_N can be calculated by use of Formula (3) as follows. Note that the processes up to step S104 are performed before the thickness change position S reaches the target stand. Further, it is preferable that the processes of step S102 and S104 be performed just before the tapered thickness portion reaches the target stand.
[Math. 3] $R_{N} = \frac{Δ s_{N}}{t_{N}}$
When the thickness change position S reaches the target stand after step S106, the control computing machine 5 performs the flying thickness change, that is, changes the roll gap setting value, with the use of the change speed R_N and the thickness change amount Δs_N calculated in step S106 (S108). As described above, the thickness change position S is tracked based on the measurement results of the sheet speed, and the control computing machine 5 performs the flying thickness change in response to detection of the thickness change position S reaching the target stand, based on the tracking result. In step S108, the flying thickness change is performed with the use of the change speed R_N and the thickness change amount Δs_N, and hereby, the flying thickness change is ended in the timing when the joined portion W reaches the target stand. In a case where the target stand is the second stand 2A, the roll gap setting value at the second stand 2B is changed in response to detection of the thickness change position S reaching the second stand 2A by tracking as illustrated in FIG. 7D. In step S108, the flying thickness change is performed with the use of the change speed R_N and the thickness change amount Δs_N, so that the flying thickness change is ended in the timing when the joined portion W reaches the second stand 2B, as illustrated in FIG. 7F.
Note that, in the third stand 2C to the fifth stand 2E, the flying thickness change is also performed in a similar manner to the second stand 2B as described above. In this case, the thickness change position S can be tracked in the line of the tandem rolling mill 2 by using measurement results of the sheet speed in a plurality of target inter-stand sections from the first stand 2A.
In the second embodiment, the to-be-rolled material 6 is a metal sheet, and it is preferable that the to-be-rolled material 6 be a steel sheet, particularly, a high deformation resistance steel sheet. The high deformation resistance steel sheet is a steel sheet such as an electromagnetic material or a high tensile material, for example. Such a high deformation resistance steel sheet increases in a rolling-reduction change amount at the flying thickness change, and the thickness of a portion forward of the welded portion which thickness is obtained by the flying thickness change in a preceding stand largely separates from a setting thickness, so that tension fluctuation is large. On this account, when the flying thickness change method according to the second embodiment is applied, it is possible to prevent troubles such as breakage and to perform manufacturing stably.
The flying thickness change method according to the second embodiment is a method for performing flying thickness change during continuous rolling of the to-be-rolled material 6 by the tandem rolling mill 2, the to-be-rolled material 6 including the preceding material 61 and the succeeding material 62 that are metal sheets and joined to each other. The flying thickness change method includes: continuously measuring the sheet speed of the to-be-rolled material in the target inter-stand section; tracking the thickness change position S near the joined portion W; and changing the roll gap of the target stand in the timing when the thickness change position reaches the target stand.
With such a method, it is not necessary to set the intermediate thickness, similarly to the first embodiment, so that the thickness off-gauge length can be shortened. Besides, in the flying thickness change method according to the second embodiment, the roll gap is changed with a thickness change point in the preceding stand being taken as a thickness change point in a subsequent stand. As a result, it is possible to restrain tension fluctuation without depending on a material or a specification of the to-be-rolled material 6.
In the flying thickness change method according to the second embodiment, the length L_N-1 of the tapered thickness portion after rolling at the preceding stand is calculated by use of the sheet speed measured in the target inter-stand section, the change speed R_N of the roll position is calculated by dividing the length L_N-1 of the tapered thickness portion by the change amount of the roll position at the target stand, and the roll gap of the target stand is changed based on the calculated change speed R_N.
Here, FIG. 9 illustrates tension fluctuation in the inter-stand section between the first stand 2A and the second stand 2B in a case where the flying thickness change is ended in the middle of the tapered thickness portion at the second stand 2B, that is, in a case where the end of the flying thickness change is earlier than the second embodiment. When the end of the flying thickness change is too early, the change of the roll gap is ended in the middle of the tapered thickness portion, as illustrated in vicinity of a timing (f) in FIG. 9, so that tension may become excessive in subsequent metal rolling performed on the tapered thickness portion. However, with the flying thickness change method according to the second embodiment, respective timings of passing of a start point (the thickness change position S in FIG. 7) and an end point (the joined portion W in FIG. 7) of the tapered thickness portion through the target stand can be the same timings of the start and the end of the change of the roll gap. Hereby, with the flying thickness change method according to the second embodiment, it is possible to restrain the tension from becoming excessive.
Note that the thickness in the first embodiment and the sheet speed in the second embodiment are collectively called operation data. That is, in the flying thickness change method according to the present invention, the flying thickness change is performed in the timing when the thickness change position S reaches a target stand, by detecting or tracing the thickness change position S from operation data of the to-be-rolled material 6 which operation data is measured in a target inter-stand section.

The present invention has been described with reference to a particular embodiment, but this is not intended to limit the invention by these descriptions. Other embodiments of the present invention including various modifications are also apparent to those skilled in the art as well as the embodiments disclosed herein by referring to the description of the present invention. In view of this, it should be understood that the embodiment of the invention described in claims also covers an embodiment including those modifications described herein solely or in combination.
For example, in the first and second embodiments, the tandem rolling mill 2 illustrated in FIG. 1 is a rolling mill including five stands, but the present invention is not limited to such an example. The number of stands of the tandem rolling mill 2 should be two or more or may be six or more. Note that, in a case of a general tandem rolling mill 2, the upper limit of the number of stands is six.
The first and second embodiments have described a case where the thickness of the succeeding material 62 is thinner than the thickness of the preceding material 61 in the to-be-rolled material 6, but the present invention is not limited to such an example. The to-be-rolled material 6 may be configured such that the thickness of the succeeding material 62 is thicker than the thickness of the preceding material 61. In this case, tension between the stands fluctuates to become large.
In the first and second embodiments, four thickness measuring devices 3 or sheet speed meters 7 are provided, and the roll gap setting values of the second stand 2B to the fifth stand 2E are changed based on respective measurement results from the four thickness measuring devices 3 or sheet speed meters 7, but the present invention is not limited to such an example. For example, only the roll gap setting value of an inter-stand section having a large tension fluctuation that causes a problem may be changed in a similar manner to the above embodiments, and the roll gap setting values of the other inter-stand sections may be changed in a control method similar to the conventional method. In this case, the thickness measuring device 3 or the sheet speed meter 7 may be provided only for a necessary inter-stand section. Alternatively, each inter-stand section may be provided with either the thickness measuring device 3 or the sheet speed meter 7, so that each target stand may perform flying thickness change corresponding to the first embodiment or the second embodiment based on the thickness measuring device 3 or the sheet speed meter 7 provided for a corresponding inter-stand section.
Further, in the second embodiment, the sheet speed meter 7 is used as a method for measuring the sheet speed, but the present invention is not limited to such an example. For example, the sheet speed may be calculated by calculating a motor rotation speed of each rolling mill stand which motor rotation speed is measured by PLG or ABSOCODER and a forward slip calculated from operation data. Note that it is preferable to measure the sheet speed by the sheet speed meter 7, in consideration of measurement accuracy.

Reference Signs List

1: cold rolling mill facility
2: tandem rolling mill
2A to 2E: first stand to fifth stand
21: workroll
22: roll speed control device
23: rolling-reduction control device
3: thickness measuring device
4: rolling controller
5: control computing machine
6: to-be-rolled material
61: preceding material
62: succeeding material
7: sheet speed meter

Claims

A flying thickness change method for performing flying thickness change during continuous rolling of a to-be-rolled material by a tandem rolling mill, the to-be-rolled material including a preceding material and a succeeding material that are metal sheets and joined to each other, the flying thickness change method comprising:
continuously measuring a thickness or a sheet speed of the to-be-rolled material in a target inter-stand section between a target stand as a rolling mill stand at which thickness change is performed and a preceding stand as a rolling mill stand preceding to the target stand;

detecting a thickness change position near a joined portion between the preceding material and the succeeding material based on measurement results of the thickness or tracking the thickness change position based on measurement results of the sheet speed; and

changing a roll gap of the target stand in a timing when the thickness change position reaches the target stand.
The flying thickness change method according to claim 1, further comprising:
calculating, by use of the sheet speed measured in the target inter-stand section, a length of a tapered thickness portion of the to-be-rolled material which tapered thickness portion is formed by rolling at the preceding stand;

calculating a change speed to change a roll position at the target stand, by dividing the length of the tapered thickness portion by a change amount of the roll position at the target stand; and

changing the roll gap of the target stand based on the change speed thus calculated.
The flying thickness change method according to claim 1 or 2, wherein the to-be-rolled material is a high deformation resistance steel sheet.