JP2021058895A - Method for production of hot rolled steel sheet and rolling machine - Google Patents

Abstract

To provide a production method for hot rolled steel sheets capable of avoiding high calculation load required for working out the heat expansion variation of a work roll and capable of performing further highly responsive gauge control.SOLUTION: A production method for hot rolled steel sheet in this invention includes processes of: acquiring the time change of difference between the calculated sheet thickness beneath a work roll and the sheet thickness at the outlet side of a rolling mill when controlling the rolling mill without considering a heat expansion variation of the work roll in at least one rolling mill; approximating the time change of difference by primary expression regarding a rolling time; and adding the primary expression to a calculation formula of the calculated sheet thickness as a term representing the heat expansion variation of the work roll, and controlling the rolling mill using the sheet thickness calculated by the primary expression-added calculation formula.SELECTED DRAWING: Figure 3

Description

The present invention relates to a method for producing a hot-rolled steel sheet and a rolling mill for producing a hot-rolled steel sheet by hot-rolling the steel sheet with a plurality of rolling mills.

Generally, roll force (RF) automatic gauge control (AGC) and monitor (MON) AGC are known as methods for controlling the thickness of hot-rolled steel sheets. RFAGC calculates the plate thickness of the steel plate at the position of the rolling mill using the measured values such as the rolling load of the rolling mill, and the roll gap of the rolling mill so as to keep the calculated plate thickness of the steel plate constant after the plate is engaged. It is a control to correct. MONAGC is a control for correcting the roll gap of the rolling mill so that the measured plate thickness of the steel plate measured by the thickness gauge arranged on the outlet side of the rolling mill is close to the target plate thickness. These RFAGC and MONAGC are used in combination, and hot rolling is performed so that the hot-rolled steel sheet has a target plate thickness.

In such hot rolling, the work roll of the rolling mill expands due to the heat received from the steel sheet. If hot rolling is performed without considering the thermal expansion of the work roll, an error occurs in the control of the roll gap, so that an error occurs in the plate thickness of the hot rolled steel sheet. It is not preferable that an error occurs in the thickness of the hot-rolled steel sheet even if it is several tens of μm.

For example, in Patent Document 1 and the like below, the thermal expansion amount of a work roll is calculated from the temperature distribution of the work roll using a heat conduction model, and hot rolling is performed based on the thermal expansion amount of the work roll. Proposed.

Japanese Unexamined Patent Publication No. 8-238515

If a heat conduction model is used as proposed in Patent Document 1 and the like, it may be possible to calculate the thermal expansion amount of the work roll with high accuracy. However, since the calculation of the thermal expansion amount of the work roll based on the heat conduction model has a high calculation load, it is difficult to shorten the calculation cycle and realize highly responsive plate thickness control.

The present invention has been made to solve the above problems, and an object of the present invention is to avoid requiring a high calculation load for calculating the amount of change in thermal expansion of a work roll, and to have higher responsiveness. It is an object of the present invention to provide a method for manufacturing a hot-rolled steel sheet and a rolling mill capable of controlling the plate thickness.

As a result of various studies conducted by the present inventor, the following findings were newly obtained. That is, the rolling mill was controlled so that the calculated plate thickness of the steel plate directly under the work roll of the rolling mill approaches the target plate thickness without considering the change in the thermal expansion amount of the work roll in the rolling material passing plate of the rolling mill. However, it was found that the difference between the calculated plate thickness of the steel plate directly under the work roll and the plate thickness of the steel plate on the exit side of the rolling mill increases linearly with the rolling time. It was found that the increase in this difference corresponds to the change in thermal expansion of the work roll, and by incorporating this increase in the calculation plate thickness into the calculation formula, the error in the plate thickness of the hot-rolled steel sheet can be suppressed.

The method for producing a hot-rolled steel sheet according to the present invention is a method for producing a hot-rolled steel sheet by hot-rolling a steel sheet with a plurality of rolling mills, and is a method for producing a hot-rolled steel sheet for a work roll of a rolling mill. Including controlling the rolling mill so that the calculated plate thickness of the steel plate directly underneath approaches the target plate thickness, the rolling mill in at least one rolling mill without considering the change in the amount of thermal expansion of the work roll of the rolling mill. The step of acquiring the time change of the difference between the calculated plate thickness of the steel plate directly under the work roll and the plate thickness of the steel plate on the exit side of the rolling mill, and the time change of the difference are related to the rolling time. The process of approximating with the linear formula and the calculation plate thickness calculated by the calculation formula with the linear formula added by adding the linear formula to the calculation plate thickness calculation formula as a term expressing the amount of change in thermal expansion of the work roll are used. Includes a step of controlling the rolling mill.

The rolling mill according to the present invention is a rolling mill for producing a hot-rolled steel plate by hot-rolling a steel plate, and is a rolling mill for a plurality of rolling mills and a calculated plate thickness of the steel plate directly under the work roll of the rolling mill. The rolling mill is provided with a control device for controlling the rolling mill so that the thickness approaches the target plate thickness, and the control mode of the control device is set in at least one rolling mill without considering the change in the amount of thermal expansion of the work roll of the rolling mill. The rolling mill is controlled, the time change of the difference between the calculated plate thickness of the steel plate directly under the work roll and the plate thickness of the steel plate on the exit side of the rolling mill is acquired, and the time change of the difference is the primary with respect to the rolling time. The first mode for approximation by the formula and the calculation plate calculated by the calculation formula to which the linear formula is added by adding the linear formula to the calculation plate thickness calculation formula as a term expressing the amount of change in thermal expansion of the work roll. It includes a second mode in which the rolling mill is controlled using the thickness.

According to the method for manufacturing a hot-rolled steel sheet and the rolling mill of the present invention, a linear equation is used as a term representing the amount of change in thermal expansion of the work roll, so that a high calculation load is required for calculating the amount of change in thermal expansion of the work roll. This can be avoided, and more responsive plate thickness control can be performed.

It is a block diagram which shows the rolling mill for carrying out the manufacturing method of the hot-rolled steel sheet by embodiment of this invention. Time change of the difference between the calculated plate thickness of the steel plate directly under the work roll of the rolling mill and the plate thickness of the steel plate on the exit side of the rolling mill when the control device of FIG. 1 controls the rolling mill in the first mode. It is a graph which shows. It is a flowchart which shows the manufacturing method of the hot-rolled steel sheet of this embodiment. It is a graph which shows the plate thickness change of the hot-rolled steel sheet in the comparative example. It is a graph which shows the plate thickness change of the hot-rolled steel sheet in an Example. It is a graph which shows the relationship between the plate thickness deviation of the tail end portion of the hot-rolled steel sheet in the comparative example, and the plate thickness deviation of the tail end portion of the hot-rolled steel sheet in the example.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. The present invention is not limited to each embodiment, and the components can be modified and embodied without departing from the gist thereof. In addition, various inventions can be formed by appropriately combining the plurality of components disclosed in each embodiment. For example, some components may be removed from all the components shown in the embodiments. Furthermore, the components of different embodiments may be combined as appropriate.

FIG. 1 is a block diagram showing a rolling mill 1 for carrying out a method for manufacturing a hot-rolled steel sheet according to an embodiment of the present invention. The rolling mill 1 shown in FIG. 1 is an apparatus for manufacturing a hot-rolled steel sheet 3 by hot-rolling a steel sheet 2. The rolling mill 1 shown in FIG. 1 is sometimes called a finishing rolling mill. Although not shown, on the upstream side of the rolling mill 1 related to the transport direction 2a of the steel plate 2, a heating furnace for heating the steel plate 2 to a predetermined temperature and a rough rolling mill for rough rolling the heated steel plate 2 are provided. May have been rolled. Further, a winder for winding the hot-rolled steel sheet 3 in a coil shape may be provided downstream of the rolling mill 1 related to the transport direction 2a of the steel sheet 2. The steel plate 2 is sometimes called a hot bar that has been roughly rolled by a rough rolling machine.

As shown in FIG. 1, the rolling mill 1 includes a plurality of rolling mills 4, a plurality of thickness gauges 5, and a control device 6.

The rolling mills 4 are arranged side by side along the transport direction 2a of the steel sheet 2. When the rolling mills 4 are described separately, the rolling mills 4 are referred to as the first to seventh rolling mills 4-1 to 4-7 from the upstream side related to the transport direction 2a.

Each rolling mill 4 has a pair of upper and lower work rolls 4a that come into contact with the steel plate 2 and a pair of upper and lower backup rolls 4b that support each work roll 4a. The 4th to 7th rolling mills 4-4 to 4-7 further have a pair of upper and lower intermediate rolls 4c interposed between the work roll 4a and the backup roll 4b. The roll configuration of each rolling mill 4 is not limited to the embodiment shown in FIG. 1, and all rolling mills 4 may or may not have an intermediate roll 4c.

The steel plate 2 is rolled as it passes between the work rolls 4a. Each rolling mill 4 is configured so that the rolling load applied to the work roll 4a via the backup roll 4b can be adjusted. Further, each rolling mill 4 is configured so that the roll gap between the work rolls 4a can be adjusted.

The thickness gauge 5 is arranged on the outlet side of the rolling mill 4 related to the transport direction 2a of the steel plate 2, and the plate thickness of the steel plate 2 on the outlet side of the rolling mill 4 can be measured. The thickness gauge 5 may be configured by a device such as an X-ray thickness gauge. The thickness gauge 5 can measure the plate thickness of the steel plate 2 at the center in the width direction and / or the plate thickness of the steel plate 2 at the end in the width direction according to the installation position. In the rolling mill 1 of the present embodiment, the film thickness meter 5 is arranged on the exit side of the 4th rolling mill 4-4, the 6th rolling mill 4-6, and the rolling mill 4-7. The film thickness meter 5 may be arranged on the outlet side of the other rolling mill 4.

For example, the plate thickness of the steel plate 2 on the outlet side of the rolling mill 4 in which the thickness gauge 5 is not arranged on the outlet side of the fifth rolling mill 4-5 or the like is the volume of the steel plate 2 per unit time passing through each rolling mill 4. Can also be calculated using the following equation (1) based on the fact that is constant.
H _a = (H _b · V _b ) / V _a ... Equation (1)
Here, a calculation target H _a is the thickness of the steel plate 2 (mm) in the delivery side of the particular rolling mill, V _a is circumference of the sheet passing speed (work roll 4a of the steel plate 2 in that particular rolling mill Speed) (mm / s). Further, H _b is the plate thickness (mm) of the steel plate 2 on the outlet side of the reference mill, and this is the plate thickness gauge measurement value of the mill in which the plate thickness gauge is installed in the downstream portion of the mill. V _b is the plate passing speed (mm / s) of the steel plate 2 in the reference rolling mill.

The control device 6 is a device for controlling each rolling mill 4. The control device 6 can be configured by, for example, a device such as a computer or a dedicated circuit that performs arithmetic processing based on a program. The control device 6 can set the roll gap and / or the rolling load of each rolling mill 4 based on the rolling conditions such as the steel type of the steel plate 2 and the target plate thickness. The control device 6 can execute automatic gauge control (AGC) for each rolling mill 4. The control device 6 of the present embodiment executes AGC on the first to seventh rolling mills 4-1 to 4-7.

The AGC mode of the control device 6 is provided with a first mode and a second mode. The first mode is a mode in which the rolling mills 4-1 to 4-7 are controlled without considering the change in the amount of thermal expansion of the work rolls 4a of the rolling mills 4-1 to 4-7. The second mode is a mode in which the rolling mills 4-1 to 4-7 are controlled in a state where the change in the amount of thermal expansion of the work rolls 4a of the rolling mills 4-1 to 4-7 is taken into consideration. The change in the amount of thermal expansion of the work roll 4a means that the work roll 4a of each rolling mill 4-1 to 4-7 expands due to the heat received from the steel plate 2 when the steel plate 2 is rolled from the front end to the rear end. The work roll 4a may expand into a barrel shape due to the heat received from the steel plate 2. That is, the axial central portion of the work roll 4a may expand more than the axial end portion.

In both the first and second modes, the control device 6 of the present embodiment targets the calculated plate thickness of the steel plate 2 directly under the work rolls 4a of the first to seventh rolling mills 4-1 to 4-7. The first to seventh rolling mills 4-1 to 4-7 are controlled so as to approach the plate thickness. The calculated plate thickness h of the steel plate 2 is obtained for each rolling mill 4-1 to 4-7, and is controlled for each rolling mill 4-1 to 4-7.

On the other hand, the first mode and the second mode are different from each other in the calculation method of the calculated plate thickness of the steel plate 2.

In the first mode, the calculated plate thickness h of the steel plate 2 directly under the work roll 4a is calculated by the following equation (2).
h = S + (P / M) + d ... Equation (2)
Here, S is the roll gap (mm) between the work rolls 4a, P is the rolling load (Ton), and M is the mill constant (Ton / mm). The mill constant indicates the rigidity of each rolling mill 4 in the vertical direction, and the flexure of the roll, the flatness of the roll, the elongation of the housing, and the like are incorporated into the calculation of the calculated plate thickness h according to the P / M term. d is a disturbance element that does not fluctuate during the plate passing, and is a term indicating the amount of wear of the work roll 4a, the amount of influence on the roll gap due to the backlash of the rolling mill, and the like.

In the second mode, the calculated plate thickness h of the steel plate 2 directly under the work roll 4a is calculated by the following equation (3).
h = S + (P / M) + d-F (t _RT ) ... Equation (3)
Here, F (t _RT ) is a term added to the equation (2), and is a correction term for the amount of change in thermal expansion of the work rolls 4a of the first to seventh rolling mills 4-1 to 4-7. And, as will be described in detail later, F (t _RT ) is a linear equation with respect to the rolling time t _RT. The rolling time t _RT is a time counted from the time when the steel plate 2 is engaged with the work rolls 4a of each rolling mill 4-1 to 4-7. _{F (t RT} ) increases with the lapse of rolling time t _RT. F (t _RT ) functions as a term for correcting the calculated plate thickness h to be smaller with the passage of the rolling time t _RT. An upper limit value may be set for F (t _RT). That is, even if the rolling time t elapses, the upper limit value may be maintained without increasing _{F (t RT).} This is because, for a material having an extremely long rolling time, the amount of heat received by the roll from the material to be rolled and the amount of heat lost due to external cooling are balanced, and the amount of thermal expansion of the roll does not change over time.

Controlling each rolling mill 4-1 to 4-7 without considering the change in the amount of thermal expansion of the work rolls 4a of each rolling mill 4-1 to 4-7 in the first mode is used in the second mode. It means that each rolling mill 4-1 to 4-7 is controlled based on the calculated plate thickness of the steel plate 2 calculated by the calculation formula lacking F (t _RT).

Next, FIG. 2 shows the calculated plate thickness of the steel plate 2 immediately below the work roll 4a of the rolling mill 4-7 when the control device 6 of FIG. 1 controls the rolling mill 4-7 in the first mode, and the calculated plate thickness thereof. It is a graph which shows the time change of the difference GME with the thickness of the steel plate 2 on the exit side of a rolling mill 4-7.

The horizontal axis of FIG. 2 is the rolling time (sec) of the rolling mill 4-7, and the vertical axis of FIG. 2 is the calculated plate thickness of the steel plate 2 immediately below the work roll 4a of the rolling mill 4-7 and the rolling mill 4-7. It is the difference GME from the thickness of the steel plate 2 on the exit side of. As the plate thickness of the steel plate 2 on the outlet side of the rolling mill 4-7, the plate thickness measured by the thickness gauge 5 or the plate thickness calculated based on the formula (1) can be used. The same arrangement is performed for the rolling mills 4-1 to 4-6.

When the control device 6 controls the rolling mills 4-1 to 4-7 in the first mode, that is, without considering the change in the amount of thermal expansion of the work rolls 4a of each rolling mill 4-1 to 4-7, each When the rolling mills 4-1 to 4-7 are controlled, it can be confirmed that the difference GME increases linearly with the rolling time as shown in FIG.

This difference GME can be approximated by a linear equation for rolling time. That is, the linear equation F (t _RT ) shown in the following equation (4) can be obtained.
F (t _RT ) = a · t _RT ... Equation (4)
In the formula (4), t _RT is the rolling time (sec), and a is the amount of change in the difference GME per unit time. This linear equation F (t _RT ) can be obtained by applying an approximation method such as the least squares method to the data of the difference GME. However, it is preferable to exclude the tip of the plate from the range of the approximate straight line because the load fluctuates due to the correction of the plate thickness and is affected by the mill elongation error and the like.

As shown in the above equation (3), in the second mode of the control device 6, the calculation plate is calculated by adding the _{linear equation F (t RT) as a term expressing the amount of change in thermal expansion of the work roll 4a.} The thickness is calculated, and the rolling mills 4-1 to 4-7 are controlled using the calculated plate thickness.

The difference GME may be a difference in the plate thickness of the steel plate 2 at the center in the width direction, or may be a difference in the plate thickness of the steel plate 2 at the end in the width direction. It is a known fact that the calculation plate thickness He of the plate end portion required for calculating the difference GME of the end portion in the width direction is simply expressed by the following formula. (3rd Edition Steel Handbook III (1) Rolling Foundation / Steel Sheet, P.54, etc.)
He = hc-Cr = hc-α _P P-α _C R _CW- (α _C- (B / L) ² ) R _CB- α _B J-F _e (t _RT ) + d
Here, hc is the thickness of the plate central portion, Cr crown amount (hc-He), P is the rolling load, R _CW the work roll crown, B product width, L is roll width, R _CB backup roll crown , J is bending force, F _e (t _RT) is the thermal expansion amount of change in the edge portion, d is a disturbance element which does not vary during Tsuban. α _P , α _{B, and} α _C are each influence coefficient. This impact factor is calculated by a cold offline test while changing the load, bending force, and roll crown conditions. When the difference GME is the difference in the plate thickness of the steel plate 2 in the center in the width direction, the rolling mills 4-1 to 4-7 are controlled so that the calculated plate thickness of the steel plate 2 in the center in the width direction approaches the target plate thickness. .. Similarly, when the difference GME is the difference in the plate thickness of the steel plate 2 at the width direction end, the rolling mills 4-1 to 4-7 so that the calculated plate thickness of the steel plate 2 at the width direction end approaches the target plate thickness. Is controlled. Both the control by the difference GME of the plate thickness of the steel plate 2 at the center in the width direction and the control by the difference GME of the plate thickness of the steel plate 2 at the end in the width direction may be performed at the same time.

Next, FIG. 3 is a flowchart showing a method for manufacturing a hot-rolled steel sheet according to the present embodiment. As shown in FIG. 3, the method for manufacturing a hot-rolled steel sheet of the present embodiment includes a time change acquisition step (step S1), an approximation step (step S2), and a primary formula addition step (step S3). There is.

In the time change acquisition step (step S1), when the rolling mill 4 is controlled in at least one rolling mill 4 without considering the change in the thermal expansion amount of the work roll 4a of the rolling mill 4, the work roll is controlled. This is a step of acquiring the time change of the difference GME between the calculated plate thickness of the steel plate 2 directly under 4a and the plate thickness of the steel plate 2 on the exit side of the rolling mill 4. In the present embodiment, when the first to seventh rolling mills 4-1 to 4-7 are controlled in the first mode, the time change of the difference GME for each rolling mill 4-1 to 4-7 is changed. get. As described above, controlling the rolling mill 4 without considering the change in the amount of thermal expansion of the work roll 4a of the rolling mill 4 means that the steel sheet 2 is calculated by a calculation formula lacking the _{primary formula F (t RT).} It means that each rolling mill 4-1 to 4-7 is controlled based on the calculation plate thickness of. The time change of the difference GME can be obtained for each rolling mill 4-1 to 4-7.

The approximation step (step S2) is a step of approximating the time change of the difference GME acquired in the time change acquisition step with a linear equation regarding the rolling time. The linear equation F (t _RT ) = a · t _RT is obtained. The linear equation F (t _RT ) can be obtained for each rolling mill 4-1 to 4-7.

In the primary formula addition step (step S3), the primary formula F (t _RT ) is added to the calculation formula for the calculation plate thickness _{as a term representing the amount of change in thermal expansion of the work roll 4a, and the primary formula F (t RT} ) is added. This is a step of controlling the rolling mills 4-1 to 4-7 using the calculated plate thickness calculated by the calculated formula. In the present embodiment, the rolling mills 4-1 to 4-7 are controlled by the second mode. The control by the second mode can be performed for each rolling mill 4-1 to 4-7.

The time change acquisition step (step S1) and the primary formula addition step (step S3) are rolling using the step of acquiring the time change of the difference GME and the calculation plate thickness calculated by the calculation formula to which the primary formula is added. The step of controlling the mill may be carried out in one steel plate 2, but it is preferably carried out in different steel plates 2. When these steps are performed on different steel sheets 2, in the time change acquisition step (step S1), the rear end of the steel sheet 2 is formed from the time when the steel sheet 2 is engaged with the work rolls 4a of the rolling mills 4-1 to 4-7. It is preferable to acquire the time change of the difference GME until the work roll 4a is exited. The different steel plate 2 means a physically separated steel plate. It is preferable that the steel type and the target plate thickness of the different steel plates 2 are the same. In other words, the primary formula addition step (step S3) is performed using the _{primary formula F (t RT) based on the difference GME before the front material.} If these steps are performed in one steel plate 2, it may not be possible to obtain _{an appropriate linear equation F (t RT) due to an error included in the difference GME.} By performing these steps on different steel plates 2, it is possible to avoid the occurrence of such a problem.

Next, an example will be given. As an example, the present inventors have manufactured the hot-rolled steel sheet 3 by applying the method for manufacturing the hot-rolled steel sheet of the present embodiment. That is, by adding the amount of thermal expansion above change as a term representing a linear equation F of the work rolls 4a (t _RT) to calculate thickness of the equation, calculated by the calculation equation linear equation F (t _RT) is added The hot-rolled steel sheet 3 was manufactured by controlling the rolling mill 4 using the calculated plate thickness. Further, the change in the thickness of the hot-rolled steel sheet 3 related to the rolling length at that time was investigated. Further, as a comparative example, the present inventors manufacture the hot-rolled steel sheet 3 without considering the change in the coefficient of thermal expansion of the work roll 4a of the rolling mill 4, and the hot-rolled steel sheet 3 related to the rolling length thereof. The change in plate thickness was investigated.

The results are shown in FIGS. 4 and 5. FIG. 4 is a graph showing a change in the thickness of the hot-rolled steel sheet 3 in the comparative example, and FIG. 5 is a graph showing the change in the thickness of the hot-rolled steel sheet 3 in the example. In FIGS. 4 and 5, the horizontal axis represents the rolling length of the hot-rolled steel sheet 3, and the vertical axis represents the thickness of the hot-rolled steel sheet 3. 4 and 5 show a change in plate thickness from the middle portion (intermediate portion between the front end and the tail end) of the hot-rolled steel sheet 3 to the tail end.

As shown in FIG. 4, when the hot-rolled steel sheet 3 is manufactured without considering the change in the coefficient of thermal expansion of the work roll 4a of the rolling mill 4, the thickness of the hot-rolled steel sheet 3 increases as the rolling length increases. I was away from the thick target. This is because the thickness of the hot-rolled steel sheet 3 becomes thinner than expected due to the change in the amount of thermal expansion of the work roll 4a. On the other hand, as shown in FIG. 5, when the hot-rolled steel sheet 3 is manufactured by applying the method for manufacturing the hot-rolled steel sheet 3 of the present embodiment, the hot-rolled steel sheet 3 is formed even if the rolling length is extended. The thickness can maintain the value near the plate thickness target.

Next, FIG. 6 is a graph showing the relationship between the plate thickness deviation of the tail end portion of the hot-rolled steel sheet 3 in the comparative example and the plate thickness deviation of the tail end portion of the hot-rolled steel sheet 3 in the example. The plate thickness deviation aggregated here uses the minimum value at the tail end, and is a diagram that evaluates the improvement effect of the phenomenon that the amount of thermal expansion of the roll increases, the actual roll gap becomes smaller, and the plate thickness becomes thinner. It becomes. FIG. 6 shows the evaluation of the plate thickness deviation of the tail end portion of the hot-rolled steel sheet 3 in the example, based on the plate thickness deviation of the tail end portion of the hot-rolled steel sheet 3 in the comparative example. As shown in FIG. 6, when the plate thickness deviation of the tail end portion of the hot-rolled steel sheet 3 in the comparative example is 1, the plate thickness deviation of the tail end portion of the hot-rolled steel sheet 3 in the example is about 0.74. Was low. That is, in the example, the plate thickness deviation of the tail end portion of the hot-rolled steel sheet 3 could be reduced by about 26% as compared with the comparative example.

From these results, it was confirmed that the plate thickness accuracy of the hot-rolled steel sheet 3 can be improved by applying the method for producing the hot-rolled steel sheet 3 of the present embodiment.

In such a method for manufacturing a hot-rolled steel sheet and a rolling mill, since the linear equation F (t _RT ) is used as a term representing the amount of change in thermal expansion of the work roll 4a, it is high in calculating the amount of change in thermal expansion of the work roll 4a. It is possible to avoid the demand for a calculation load, and it is possible to control the plate thickness with higher responsiveness.

Further, since the step of obtaining the time change of the difference GME and the step of controlling the rolling mills 4-1 to 4-7 using the calculated plate thickness calculated by the calculation formula including the linear formula are performed on the steel plates 2 which are different from each other. , It is possible to avoid the inability to obtain _{an appropriate linear equation F (t RT} ) due to the error included in the difference GME.

Further, since the upper limit is set in the term representing the amount of change in thermal expansion of the work roll 4a, that is, the linear equation F (t _RT ), the amount of change in thermal expansion of the roll can be appropriately estimated even for a material having a long rolling time. ..

Further, the difference GME is the difference in the plate thickness of the steel plate 2 in the center in the width direction, and the rolling mills 4-1 to 4-7 are controlled so that the calculated plate thickness of the steel plate 2 in the center in the width direction approaches the target plate thickness. Therefore, the plate thickness of the steel plate 2 at the center in the width direction can be more reliably set as the target plate thickness.

Further, the difference GME is the difference in the plate thickness of the steel plate 2 at the end in the width direction, and the rolling mills 4-1 to 4-7 are controlled so that the calculated plate thickness of the steel plate 2 at the end in the width direction approaches the target plate thickness. Therefore, the plate thickness of the steel plate 2 at the end in the width direction can be more reliably set as the target plate thickness.

2 Steel plate 3 Hot rolled steel plate 4 Rolling mill 4a Work roll

Claims (6)

A method for producing a hot-rolled steel sheet by hot-rolling a steel sheet with a plurality of rolling mills, in which the calculated sheet thickness of the steel sheet directly under the work roll of the rolling mill is the target sheet thickness. Including controlling the rolling mill to approach
In at least one of the rolling mills, when the rolling mill is controlled without considering the change in the amount of thermal expansion of the work roll of the rolling mill, the calculated plate thickness of the steel plate immediately below the work roll and the rolling are performed. The process of acquiring the time change of the difference from the thickness of the steel plate on the outlet side of the mill, and
A process of approximating the time change of the difference with a linear equation regarding the rolling time, and
The linear formula is added to the calculation formula of the calculation plate thickness as a term representing the amount of change in thermal expansion of the work roll, and the rolling is performed using the calculation plate thickness calculated by the calculation formula to which the primary formula is added. Including the process of controlling the mill,
A method for manufacturing a hot-rolled steel sheet. The step of acquiring the time change of the difference and the step of controlling the rolling mill using the calculated plate thickness calculated by the calculation formula to which the linear formula is added are performed on different steel plates.
The method for producing a hot-rolled steel sheet according to claim 1. An upper limit is set for the term representing the amount of change in thermal expansion of the work roll.
The method for producing a hot-rolled steel sheet according to claim 1 or 2. The difference is the difference in the thickness of the steel sheet at the center in the width direction.
The rolling mill is controlled so that the calculated plate thickness of the steel plate at the center in the width direction approaches the target plate thickness.
The method for manufacturing a hot-rolled steel sheet according to any one of claims 1 to 3. The difference is the difference in the thickness of the steel plate at the end in the width direction.
The rolling mill is controlled so that the calculated plate thickness of the steel plate at the end in the width direction approaches the target plate thickness.
The method for manufacturing a hot-rolled steel sheet according to any one of claims 1 to 4. A rolling mill for producing hot-rolled steel sheets by hot-rolling steel sheets.
With multiple rolling mills,
A control device for controlling the rolling mill so that the calculated plate thickness of the steel plate immediately below the work roll of the rolling mill approaches the target plate thickness is provided.
The control mode of the control device is set to
In at least one of the rolling mills, the rolling mill is controlled without considering the change in the amount of thermal expansion of the work roll of the rolling mill, and the calculated plate thickness of the steel plate and the output of the rolling mill directly under the work roll are controlled. The first mode for acquiring the time change of the difference from the thickness of the steel sheet on the side and approximating the time change of the difference with a linear equation regarding the rolling time.
The linear formula is added to the calculation formula of the calculation plate thickness as a term representing the amount of change in thermal expansion of the work roll, and the rolling is performed using the calculation plate thickness calculated by the calculation formula to which the primary formula is added. Includes a second mode to control the mill,
Rolling machine.

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