JP2006007307A - Method for manufacturing steel plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrain the warp of a plate fully in manufacturing the plate by reverse rolling with a plurality of passes. <P>SOLUTION: In this invented method, the steel plate is manufactured by the reverse rolling of a material 5 to be rolled with the plurality of passes using upper and lower work rolls 2a and 2b. In manufacturing the steel plate, a warp controlling device 10 sets the surface speed of each of the upper and lower work rolls 2a and 2b at the time when the material 5 to be rolled is bitten by the upper and lower work rolls 2a and 2b in rolling at no. (i) pass out of the plurality of passes, on the basis of a deviation between a warp amount measured when rolling at no. (i-2) pass has been finished and a target warp amount. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a steel sheet, and relates to a method for manufacturing a steel sheet by performing a plurality of passes of reverse rolling on a material to be rolled, such as rolling of a thick plate or rough rolling of a hot strip.

  For example, when producing a steel sheet by performing reverse rolling of a plurality of passes on the material to be rolled, such as rolling a thick plate or rough rolling a hot strip, upward or downward at the tip of the rolling direction of the material to be rolled. May be warped.

  When this sheet warpage occurs, for example, the rolled material collides in the subsequent pass and breaks the strip guide, or when the downward warping occurs, the rolled material, which is the product, is bent back. This leads to major operational problems such as surface flaws and, furthermore, when the product is a controlled rolled material, cooling irregularities occur and desired characteristics cannot be obtained.

  As described above, the warpage of the plate causes a serious problem in operation, and its occurrence should be completely prevented. However, sheet warpage is affected by a large number of operational factors such as the temperature difference between the upper and lower surfaces of the steel sheet being rolled, the friction coefficient difference, the peripheral speed difference between the upper and lower work rolls, and the pickup amount. Generated by matching. For this reason, it is not easy to completely eliminate the occurrence of the warp.

  Therefore, in order to suppress the occurrence of such plate warpage to such an extent that there is no operational problem, for example, Patent Documents 1 and 2 terminate a path by a warp sensor installed on at least one side before and after the reverse rolling mill. The amount of warpage (warpage curvature) of the rolled material was measured, and based on the relationship between the warpage curvature and the peripheral speed difference between the upper and lower work rolls obtained in advance, the next pass was set so that this warpage curvature would be zero. An invention for setting the different speed ratio of the upper and lower work rolls when performing is disclosed.

Further, according to Patent Document 3, the present inventors, based on the average differential rate of the upper and lower work rolls in the period immediately after the biting in which occurrence of sheet warpage is expected in the material to be rolled, An invention is disclosed in which the peripheral speed is set so that the occurrence of plate warpage is suppressed or eliminated.
Japanese Patent Laid-Open No. 63-60012 Japanese Patent Laid-Open No. 11-47812 JP 2003-2111213 A

However, according to any of the conventional inventions, the amount of warpage of the material to be rolled cannot be reliably suppressed to such an extent that a large operational problem does not occur.
That is, as disclosed in Patent Document 3 by the present inventors, in order to reliably suppress or eliminate the amount of warpage of the tip of the material to be rolled, the peripheral speed of the upper and lower work rolls is set to the bite of the material to be rolled. It is necessary to set based on the peripheral speed after the insertion. For this reason, the degree of suppression of sheet warpage obtained by the inventions disclosed in Patent Documents 1 and 2 that do not set the peripheral speed of the upper and lower work rolls based on the peripheral speed after biting of the material to be rolled is obtained recently. Since it is not as good as it is, it needs to be improved.

  On the other hand, in the invention disclosed in Patent Document 3, the peripheral speed of the upper and lower work rolls is set based on the average differential speed rate in the period immediately after the biting where the occurrence of the plate warpage is expected. Can be considerably improved from the inventions disclosed in Patent Documents 1 and 2.

  Here, in the invention disclosed by this patent document 3, the setting of the peripheral speed of each of the upper and lower work rolls capable of canceling the amount of warpage occurring after the pass immediately before the pass for performing the warpage control (one pass before). The value is reflected in the path immediately after that.

  However, in general, the amount of sheet warpage at each of the leading end and the trailing end of the material to be rolled in rolling of a thick plate or rough rolling of a hot strip depends on the temperature and surface properties of the material to be rolled (between the material surface and the roll). (Friction coefficient) and the like are different, so they are not the same value but different. Therefore, in the invention disclosed in Patent Document 3, for example, the peripheral speed of each of the upper and lower work rolls capable of canceling the amount of warp at the front end is set to the rear end of the amount of warp different from the amount of warp at the front end. This is reflected in the control of the plate warpage of the part. For this reason, in the invention disclosed in Patent Document 3, an amount of cancellation that is larger or smaller than the amount of cancellation of the originally required sheet warpage is set, and the sheet warpage of the material to be rolled is sufficiently suppressed. Difficult to do.

  Moreover, in the invention disclosed by patent documents 1-3, all perform rolling, providing the height difference in the circumferential speed of an up-and-down work roll. For this reason, the motor load of either the upper work roll drive motor or the lower work roll drive motor that rotates at a high speed is excessive with respect to the motor load of the other that rotates at a low speed. Therefore, if the setup schedule is set in the same way as when the upper and lower work rolls rotate at the same peripheral speed, the motor that rotates at high speed trips and rolling is interrupted, or a plate shape defect occurs due to mill slip or the like. . In order to avoid these problems, it is sufficient to set up a setup schedule based on the motor load of a motor that rotates at a high speed. However, in this case, it is necessary to increase the number of passes in order to obtain a desired reduction amount, and productivity is increased. Decreases.

  The object of the present invention is to provide a large operational problem with the amount of warpage of the material to be rolled when a steel plate is manufactured by performing reverse rolling of multiple passes, such as rolling of a thick plate or rough rolling of a hot strip. It is to provide a method of manufacturing a steel sheet that can be sufficiently suppressed to such an extent that it does not occur and that the thickness accuracy is not deteriorated. It is possible to suppress various operational problems such as quality degradation due to uneven cooling of the material due to the warpage of the material being rolled. Especially, the amount of warpage of the product after the final pass is accurately within the target range. It is possible to provide a steel sheet manufacturing method capable of improving the quality of the final product because it can be controlled so as to be accommodated.

As a result of intensive studies in order to solve the above-described problems, the present inventors have obtained the findings (1) to (4) listed below and completed the present invention.
(1) As described above, the amount of warpage at the leading end or the trailing end of the material to be rolled is different. Therefore, the feed-forward control of the set amount of the peripheral speed of each of the upper and lower work rolls is performed separately for each front end portion or rear end portion of the material to be rolled, so that the occurrence of plate warpage does not cause a large operational problem. It can be suppressed or eliminated sufficiently.

  (2) Since the plate warpage occurs only in a short period immediately after the material to be rolled is caught, it is not necessary to continuously provide the difference in the peripheral speed between the upper and lower work rolls over the entire length of the material to be rolled.

  (3) When rolling is performed on the entire length of the material to be rolled with a difference between the peripheral speeds of the upper and lower work rolls, the motor load of the work roll drive motor rotating at high speed becomes the motor load of the work roll drive motor rotating at low speed. On the other hand, problems such as rolling interruption due to trip of the work roll drive motor rotating at high speed and plate shape defects due to mill slip occur. If the rolling load of the work roll drive motor is reduced in order to avoid such a problem, the number of passes must be increased and productivity is lowered.

  (4) The setting of the peripheral speed of each of the upper and lower work rolls is the average value of the different speed ratios for a certain period after biting in which the occurrence of sheet warpage is expected in the material to be rolled (referred to as “average different speed ratio” in this specification). ) To suppress the occurrence of plate warpage.

  The present invention is a method of manufacturing a steel sheet by performing reverse rolling of a plurality of passes by a pair of upper work rolls and lower work rolls on a material to be rolled, and the material to be rolled is rolled in the i-th rolling of the plurality of passes. The peripheral speed of each of the upper work roll and the lower work roll at the time of biting into the upper work roll and the lower work roll, (i-2) between the measured plate warpage amount and the target plate warpage amount when the rolling of the pass is finished. A method of manufacturing a steel sheet, comprising a step of setting based on the deviation such that occurrence of sheet warpage of the material to be rolled at the time of finishing rolling of the i-th pass is suppressed or eliminated. In this case, it is desirable to perform the above steps in two or more passes including the final pass.

  In the steel sheet manufacturing method according to the present invention, the load difference between the upper work roll drive motor that drives the upper work roll and the lower work roll drive motor that drives the lower work roll in at least the i-th rolling is measured. It is desirable that the warp occurrence region existing at the tip of the rolled material passes through the upper work roll and the lower work roll, and is smaller than when the tip of the material to be rolled bites into the upper work roll and the lower work roll. .

  Furthermore, also in these steel sheet manufacturing methods according to the present invention, as disclosed in Patent Document 3 described above, the circumferential speed of each of the upper work roll and the lower work roll is set to generate sheet warpage in the material to be rolled. It is desirable to set based on the average differential speed ratio of the upper work roll and the lower work roll after the expected biting.

  As explained in detail above, according to the method for producing a steel sheet according to the present invention, when producing a steel sheet by reverse rolling of a plurality of passes, a sufficient amount of sheet warpage of the material to be rolled is provided for each front end and rear end. Can be suppressed.

  For this reason, due to the method of manufacturing the steel sheet according to the present invention, for example, equipment troubles, surface defects of the steel sheet, and quality deterioration due to uneven cooling of the control rolled material, due to sheet warpage occurring at the front end and rear end of the material to be rolled. The occurrence of various operational problems can be reliably suppressed to the extent that there are no operational problems. In particular, it is possible to control the amount of warpage of the product after the final pass so as to be accurately within the target range. Thereby, quality improvement of products, such as a rough rolled material of a thick board or a hot strip, can be aimed at, for example.

  Hereinafter, the best mode for carrying out the method for producing a steel sheet according to the present invention will be described in detail with reference to the accompanying drawings. In the following description, a case where the “steel plate” in the present invention is a thick plate manufactured by hot rolling is taken as an example.

  FIG. 1 is an explanatory diagram schematically showing the configuration of a rolling device 1 used in the present embodiment. As shown in the figure, the rolling device 1 includes a reverse rolling mill 4 having a pair of upper and lower work rolls 2a and 2b and backup rolls 3a and 3b for supporting the work rolls 2a and 2b, respectively. By this reverse rolling machine 4, the material to be rolled 5 is reverse-rolled in a plurality of passes hot, and finally a thick plate as a product is manufactured.

  On the front side and the rear side of the reverse rolling mill 4, warp sensors 6a and 6b for measuring the amount of warpage occurring at the tip of the material 5 to be rolled in each pass are installed. The warp sensor 6a, 6b measures the amount of warpage occurring at the tip of the material to be rolled 5 when each pass is completed. The amount of warpage measured by the warpage sensors 6 a and 6 b is sent to the image processing device 7. The warp curvature is calculated by the image processing device 7 based on the input plate warp amount, and the calculated warp curvature is sent to the warp control device 10 described later.

  In addition, the data collection device 8 shown in FIG. 1 collects the measured values of each data such as rolling load, work roll peripheral speed (rolling speed), rolling torque, etc. in each pass of reverse rolling by the reverse rolling mill 4 in real time. Is done. Then, the measurement values of these data collected in real time by the data collection device 8 are sent from the data collection device 8 to the warpage control device 10 described later.

  Furthermore, the pass schedule calculation of each pass by the reverse rolling mill 4 is performed by the rolling mill control process computer 9, and the obtained pass schedule is sent to the warpage control device 10.

  In the warpage control device 10, the warpage curvature input from the image processing device 7, the rolling load input from the data collection device 8, the work roll peripheral speed (rolling speed), and the measured values of each data such as rolling torque, Based on the pass schedule of each pass input from the rolling mill control process computer 9, the different speed ratios of the upper and lower work rolls 2a, 2b for reducing the amount of warpage at the front end portion and the rear end portion of the material 5 to be rolled. Is calculated, and the peripheral speeds of the upper and lower work rolls 2a and 2b are calculated based on the calculated different speed ratios of the upper and lower work rolls 2a and 2b.

  The different speed ratio and the peripheral speed of the upper and lower work rolls 2a and 2b calculated by the warpage control device 10 are sent to the monitor 11 and displayed as an instruction value to the operator. The operator manually sets the peripheral speeds of the upper and lower work rolls 2a, 2b in accordance with the different speed ratio and peripheral speed indication values of the upper and lower work rolls 2a, 2b displayed on the monitor 11. Unlike the present example, the peripheral speeds of the upper and lower work rolls 2a, 2b may be set automatically based on instructions from the process computer 9.

Using the rolling device 1 configured as described above, a plurality of passes are reverse-rolled on the material to be rolled 5 hot to produce a thick plate.
In the present embodiment, for example, when setting the peripheral speeds of the upper and lower work rolls 2a and 2b for suppressing plate warpage in the i-th pass by the warp control device 10, (i-2) before the second pass. Based on the deviation between the plate warpage amount measured in the pass and the target plate warp amount, and (i-2) the differential speed rate ΔV _i-2 measured before the rolling biting in the pass, the plate warp in the i pass. A different speed ratio ΔV _i for suppressing the amount is set.

That is, the invention disclosed in Patent Document 3, that is, the deviation between the plate warpage amount actually measured in the (i-1) pass before one pass and the target plate warp amount, and the (i-1) pass before one pass. Unlike the invention in which the peripheral speeds of the upper and lower work rolls 2a and 2b in the i pass are set based on the different speed ratio ΔV _i−1 actually measured before the rolling biting, in the present embodiment, two passes before (I-2) based on the deviation between the plate warpage amount actually measured in the pass and the target plate warp amount, and (i-2) the differential speed rate ΔV _i-2 measured before the rolling biting in the pass. The peripheral speeds of the upper and lower work rolls 2a and 2b in the i pass are set.

  The reason for this is that, as described above, since the warp generation behavior differs between the front end portion and the rear end portion of the steel plate 5, in the invention disclosed in Patent Document 3, for example, upper and lower workpieces that can cancel the amount of warp at the front end portion. This prevents the peripheral speed of each roll from being reflected in the control of the plate warp at the rear end of the plate warp amount, which is different from the plate warp amount at the tip, and prevents the accuracy of control of the plate warp from deteriorating. It is to do.

Here, the different speed ratio ΔV is obtained by the equation (1), where Vu is the peripheral speed of the upper work roll 2a and Vl is the peripheral speed of the lower work roll 2b.
ΔV = (Vl−Vu) / Vl (1)
The i-th average speed change rate ΔVI is an average value of the different speed rates in the period immediately after the i-th bite biting. That is, in the present embodiment, in the i-th pass, the period immediately after biting of the material to be rolled 5 is a region where occurrence of sheet warpage is expected (for example, in this embodiment, rolling from the biting of the tip of the material to be rolled 5 is performed. (The tip portion having a length of 1000 mm in the direction) is defined as the time required for rolling (in this embodiment, 0.3 seconds), and the circumference of each of the upper and lower work rolls 2a, 2b in the period immediately after the biting The relationship between the speed and time is obtained, and the relationship between the circumferential speed and time of each of the obtained work rolls 2a and 2b is obtained from the equation (1), and the relationship between the speed ratio and the time in the period immediately after the biting is obtained, and this average value To obtain the average differential speed rate ΔVI in the i-th pass.

  Further, the warp curvature κ generated in the material to be rolled 5 is expressed as in equation (2) using a function f having an average variable speed rate ΔVI in the period immediately after biting in the i-th pass as a variable. Here, the coefficient a in the equation (2) is expressed using a parameter called a shape ratio.

κ = a × f (ΔVI) (2)
FIG. 3 is an example showing equation (2).
Since the function f varies depending on the characteristics of the rolling mill, it is desirable to determine the function f by collecting the rolling data of the actual machine in advance.

Shape ratio is the thickness at entrance side and h _1, when the thickness at delivery side of the h _2, further contact arc length is l _d, (contact arc length) / (thickness at entrance side and exit average of side thickness), i.e. 2l _It is obtained as _d / (h ₁ + h ₂ ).

Figure 2 is a graph showing the relationship between the coefficient a and the shape ratio in (2) _{2l d / (h 1 + h} 2). For this reason, since the shape ratio of the i-th pass is determined in advance by the rolling pass schedule, the shape ratio is determined before rolling. If this shape ratio is determined, the coefficient a is determined from the graph shown in FIG. For this reason, the average speed difference ΔVI in the period immediately after biting in the i-th pass is calculated from the equation (2).

In other words, in the present embodiment, the equation (2) and the relationship shown in the graph of FIG. Then, the warp control apparatus 10, when the schedule of the path of the immediately preceding calculated by the mill control process computer 9 is input, the warpage control device 10, the shape ratio _{2l d / (h 1 + h} 2) of the calculated value And the value of the coefficient a is obtained based on the relationship of the graph of FIG. 2 input in advance. Then, the warpage control device 10 reduces the warpage curvature κ so that the amount of warpage in the i-th pass is within an allowable range by substituting the obtained value of the coefficient a into the above-described equation (2). The average differential speed ratio ΔVI in the period immediately after biting in the i-th pass can be calculated.

  By the way, what is actually set for the i-th pass by manual operation of the operator or automatic setting by a computer is not the average speed difference ΔVI in the period immediately after the biting, but each of the upper and lower work rolls 2a, 2b at the time of no load. The differential speed ratio ΔV is defined by the peripheral speeds Vu and Vl. For this reason, in the present embodiment, the upper and lower work rolls 2a at the time of no load are set by an operator's operation or automatic setting by a computer so that the average speed difference ΔVI calculated by the warpage control device 10 as described above is obtained. In order to set the peripheral speeds Vu and Vl of 2b, the average differential speed rate ΔVI in the period immediately after the i-th biting is calculated using the relationship between the characteristics of the reverse rolling mill 4 and the rolling conditions in the period immediately after the biting. A prediction formula that can accurately calculate the different speed ratio ΔV at the time of no load, that is, the peripheral speeds Vu and Vl of the upper and lower work rolls 2a and 2b is used. Therefore, the prediction formulas (3) to (12) will be described below.

  Information that can be grasped before the i-th pass is started by the warpage control device 10 in FIG. 1 is the calculated rolling torque of each pass calculated by the rolling mill control process computer 9 and the reference rolling speed. Here, the reference rolling speed is the rolling speed of each pass when rolling at the same speed, and when performing different peripheral speed rolling, either the upper work roll 2a or the lower work roll 2b is rolled. Is speed.

Here, the relationship of the formula (3) is established between the calculated rolling torque Tqs and the average value Tqi of the upper and lower work rolls 2a and 2b of the maximum rolling torque in the period immediately after the i-th biting. Incidentally, a C ₁ is the coefficient in equation (3).

Tqi = C ₁ × Tqs (3)
Further, in the different peripheral speed rolling in which the peripheral speeds of the upper and lower work rolls 2a and 2b are different, the torque of the work roll 2a or 2b on the higher peripheral speed side is increased, whereas the work roll on the lower peripheral speed side is increased. The torque of 2a or 2b decreases. For this reason, the maximum rolling torque Tqiu in the period immediately after biting of the upper work roll 2a and the maximum rolling torque Tqil in the period immediately after biting of the lower work roll 2b are set as (4), where ΔV is the speed difference at no load of the i-th pass. ) To (6). Note that C ₂ and C ₃ in equation (6) are both coefficients.

Tqiu = (1−Tqa × ΔV) × Tqi (4)
Tqil = (1 + Tqa × ΔV) × Tqi (5)
Tqa = C ₂ × (Tqi−C ₃ ) ² (6)
Furthermore, when the time when the material 5 to be rolled is caught in the work rolls 2a and 2b in the i-pass is set to 0, the rolling torque Tqu (t) of the upper work roll 2a at the time when t seconds have elapsed from the time of biting, The rolling torque Tql (t) of the lower work roll 2b is calculated by the equations (7) and (8), respectively.

Tqu (t) = Tqiu × g (t) (7)
Tql (t) = Tqil × g (t) (8)
Here, g (t) is a function representing a trajectory in which the torque changes with the passage of time from the plate biting. This function is a function determined depending on the rolling mill, and is a function considering that the rolling torque changes due to impact drop, recovery, etc. immediately after the material to be rolled 5 is caught. In this case, it is possible to predict how the torque changes in time series by collecting actual machine data (data for a certain period immediately after biting).

  On the other hand, the speed Spu (t) of the upper work roll 2a and the speed Spl (t) of the lower work roll 2b at the time when t seconds have elapsed from the time of biting in the i-th pass, respectively, are represented by equations (9) to (12). It is calculated by the formula. Here, Vu in the equation (9) and Vl in the equation (11) are set speeds when there is no load in the i path of each of the upper work roll 2a and the lower work roll 2b.

Spu (t) = (1−αu) × Vu (9)
αu = h (Tqu (t)) (10)
Spl (t) = (1-αl) × Vl (11)
αl = h (Tql (t)) (12)
Here, h (Tqu (t)) and h (Tql (t)) are functions that link the time change of torque and the time change of speed.

By substituting the speed Spu (t) of the upper work roll 2a and the speed Spl (t) of the lower work roll 2b, which are obtained as described above, into (1), the time change of the different speed rate can be calculated.
ΔVI (t) = (Spl (t) −Spu (t)) / Spl (t) (13)
The average speed change rate is obtained by calculating the sum of the above equation (13), for example, n times every Δt seconds from 0 to 0.3 seconds, and dividing it by n.

  Thus, the speed Vu of the upper work roll 2a and the speed of the lower work roll 2b, which are information that can be grasped before the i-th pass by using the formulas (1) to (13) described above. Based on Vl and the calculated rolling torque Tqs, the relationship between the time and the roll peripheral speed in the period immediately after biting in the i-th pass can be obtained by calculation. The average differential rate ΔVI in the immediately following period can be obtained by calculation.

  On the other hand, in order to obtain the no-load differential speed ΔV in the i-th pass from the average differential speed ΔVI in the period immediately after biting in the i-th pass, for example, assuming the no-load differential speed ΔV in the i-th pass. Using the formulas (1) to (13), the average speed change rate ΔVI in the period immediately after biting in the i-th pass is obtained, and the obtained average speed change rate ΔVI becomes a predetermined value of the average speed change rate obtained from the plate warpage amount. By repeatedly performing the calculation, the set speeds Vu and Vl of the upper and lower work rolls 2a and 2b at the time of no load to be set in the i-th pass can be obtained.

Next, so-called feed-forward control (hereinafter referred to as “FF control”) in which information on the (i-4) th pass and the (i-2) th pass is reflected on the i-pass will be described.
In the present embodiment, the warpage control device 10 obtains the control error of the plate warpage amount from the measured value of the plate warpage amount of the (i-2) -th pass and the target value of the plate warpage amount, and the control error is determined as i. The control of the FF control is performed to set the different speed ratio in the pass, that is, the speed settings of the upper and lower work rolls 2a and 2b, that is, the learning control of the error of the plate warpage amount (warpage curvature) is performed. For this reason, even if the plate warpage amount changes for each pass, the peripheral speeds Vu and Vl of the upper and lower work rolls 2a and 2b can be set sufficiently following the changed plate warpage amount.

  The method of the present embodiment is greatly different from the invention described in Patent Document 3 in that the amount of warpage after the final pass is controlled in order to perform control by tracking the leading end and the trailing end of the rolled material. Compared with the invention described in Patent Document 3, the target value can be controlled with higher accuracy.

  In this embodiment, such FF control is performed for two paths (i-2) path and i path. However, the FF control is also applied to a plurality of paths before the (i-2) path. Accordingly, the FF control may be performed in a plurality of paths including two or more paths including the final path.

  Further, the above description relates to the case where the above-described FF control is performed on a plurality of paths including two or more paths including the final path. However, the FF control is performed on a plurality of paths including two or more paths not including the final path. You may do it. Also by this, the amount of sheet warpage occurring in the material to be rolled 5 after finishing the last pass subjected to the FF control can be remarkably reduced, thereby eliminating operational problems in the pass in the vicinity of this pass. be able to.

  Hereinafter, the case where this FF control is performed will be generalized and described. FIG. 4 is a flowchart showing an example of the FF control performed by the warpage control device 10 in the present embodiment. This example shows a case where FF control is applied to the (i-2) -th path and the i-th path.

In step (hereinafter abbreviated as “S”) 1 in FIG. 4, the amount of warpage (curvature curvature κ _i−) generated at the tip of the material to be rolled 5 after the rolling of the (i-4) th pass is completed. ₄ ) Measure. The (i-4) th path is a path that does not perform warpage control. And it moves to S2 after a measurement.

In S2, a control error Δκ _i-4 (Δκ _i−4 = κ _i−4 −κ _o ) of the warp amount is obtained from the warp curvature κ _i-4 and the target value κ _o of the warp curvature, and this control error Δκ _i Assuming that ₋₄ is inherited as it is in the (i−2) pass after 2 passes, the warp correction amount Δκ _i−2 = Δκ _i−4 to be corrected in the (i−2) pass is zero. From the relationship between the equation (2) and the coefficient a shown in FIG. 2 and the shape ratio of the (i-2) th pass, an average speed change rate ΔVI _i-2 in the period immediately after biting is obtained. A correction amount ΔVS _i-2 of the different speed rate before biting set in the (i-2) -th pass is obtained from the speed rate ΔVI _i-2 using the equations (1) to (12). Then, the process proceeds to S3.

In S3, the actual speed ratio ΔV _{i-4 of} the (i-4) th pass (usually zero because it is a path where warpage control is not performed), and the corrected differential speed ratio ΔVS _i-2 obtained in S2. the from the (i-2) a different speed ratio [Delta] V _i-2 which is set in the _{path, ΔV i-2 = ΔV i} -4 + calculated as .DELTA.VS _i-4, in the different gear ratio [Delta] V _i-2 the (i-2 ) Roll pass. Warpage control starts from the rolling of the (i-2) th pass. Then, the process proceeds to S4.

In S4, the amount of plate warp κ _i-2 generated at the tip of the material to be rolled 5 after the rolling of the (i-2) th pass is finished is measured. And it shifts to S5 after a measurement.
In S5, the control error Δκ _i-2 of the plate warp amount is obtained as Δκ _i−2 = κ _i−2 −κ from the plate warp amount κ _i−2 and the target value κ _o of the plate warp amount, and this control error Δκ _{i In the same} manner as described in S2 to S2, the correction amount ΔVS _i for the different speed ratio is obtained. Then, the process proceeds to S6.

In S6, from the actual speed ratio ΔV _{i−2 of} the (i−2) th pass and the corrected speed difference ΔVS _i obtained in S5, the speed ratio ΔV _i of the i th path is the same as the technique described in S3. Then, the rolling of the final pass, which is the i-th pass, is performed at this different speed ratio ΔV _i .

  Furthermore, in the present embodiment, the difference in load between the upper work roll drive motor that drives the upper work roll 2a and the lower work roll drive motor that drives the lower work roll 2b in rolling of each pass that performs warpage control, After the warp occurrence region existing at the tip of the material to be rolled 5 passes through the upper work roll 2a and the lower work roll 2b, the time when the tip of the material to be rolled 5 bites into the upper work roll 2a and the lower work roll 2b. It is desirable to make it smaller. In the present embodiment, the load difference between the upper work roll drive motor and the lower work roll drive motor is set to zero.

  Here, after the warp occurrence region of the material to be rolled 5 has elapsed from the time of biting, the load difference between the work roll drive motor and the lower work roll drive motor is zero, that is, the work roll drive that drives the upper and lower work rolls 2a and 2b. The reason for setting the same load for each motor will be described.

  The sheet warp does not occur over the entire length of the material 5 to be rolled, but occurs at a part of the biting tip during rolling. Therefore, the peripheral speeds of the upper and lower work rolls 2a, 2b only need to be able to eliminate only a part thereof. As described above, if rolling is performed with a difference between the peripheral speeds of the upper and lower work rolls 2a and 2b, the work roll drive motor load of the work roll 2a or 2b rotating at a high speed becomes excessive. In order to reduce the load difference between the upper work roll drive motor and the lower work roll drive motor as soon as possible after rolling within 1 second at the earliest at least as long as possible, for example, to reduce the load difference in the second step. It is desirable to set the load difference to be substantially zero.

The “warp occurrence region” differs depending on the rolling mill and the material 5 to be rolled, but in the case of a thick steel plate, it is a tip portion within about 2 m from the biting tip at the longest, and is set to about 1 m in the present invention.
For this reason, the board warpage control can be performed in these passes toward the time when these at least two passes are completed, and the amount of board warpage can be gradually reduced to approach the target value. For this reason, according to the present embodiment, even if the amount of warpage in each of these passes fluctuates irregularly, the occurrence of warpage is suppressed or eliminated at the time when at least these two passes are completed. Therefore, it is possible to control the target warp amount with high accuracy.

  As described above, according to the present embodiment, when a steel plate is manufactured by reverse rolling of a plurality of passes, the amount of warpage of the material to be rolled 5 is sufficiently suppressed to such an extent that a large operational problem does not occur, and the plate It can be rolled so that the thickness accuracy does not deteriorate. As a result, it is possible to reliably suppress the occurrence of various operational problems due to sheet warpage, such as equipment troubles, surface deterioration of the steel sheet, and quality deterioration due to uneven cooling of the control rolled material, especially products after the final pass. Therefore, the quality of products such as thick plates and hot strip rough rolled material can be improved.

Further, the present invention will be described in more detail with reference to examples.
The rolling apparatus 1 shown in FIG. 1 provided with front and rear warpage sensors 6a and 6b for measuring the amount of warpage (warpage curvature κ) at the tip of the material 5 to be rolled used in the embodiment allows the total number of finish passes. Reverse rolling consisting of 9 passes was performed, the steel plate manufacturing method according to the present invention was performed, and a thick steel plate was manufactured by hot rolling.

  That is, as an example of the present invention, the amount of warpage in the material to be rolled 5 after finishing the rolling of the fifth pass is measured, and the measured amount of warpage becomes the target value of the amount of warpage of the fifth pass. Using the average speed ratio in the period immediately after the biting, the correction amount of the top speed of the upper and lower work rolls 2a, 2b is calculated, and the correction speed of the calculated speed ratio and the speed ratio set in the fifth pass (empirically The set value of the different speed ratio of the seventh pass was obtained. Then, the seventh pass rolling was performed with the set value of the different speed ratio of the seventh pass.

  Then, the amount of sheet warpage in the material 5 to be rolled after finishing the rolling of the seventh pass is measured, and in the period immediately after biting of the seventh pass so that the measured amount of sheet warpage becomes the target value of the amount of sheet warpage. Using the average speed change rate, the amount of correction of the speed change rate of the upper and lower work rolls 2a, 2b is obtained, and by adding the obtained speed change rate correction amount and the speed change rate set in the seventh pass, The set value of the different speed rate was obtained. Then, rolling in the ninth pass was performed with the set value of the different speed ratio in the ninth pass.

  On the other hand, as a comparative example, using the rolling apparatus 1 shown in FIG. 1, the upper and lower work rolls were measured so that the plate warp amount after the seventh pass rolling was measured and the measured plate warp amount became the target value of the plate warp. By calculating the correction amount of the differential speed ratios 2a and 2b, and adding the correction amount and the differential speed ratio set in the seventh pass, the differential speed ratio in the eighth pass is determined, and the plate warp after rolling in the eighth pass. Measure the amount, find the correction amount of the different speed rate of the upper and lower work rolls 2a, 2b so that the measured plate warpage amount becomes the target value of the plate warpage, and this correction amount and the different speed rate set in the eighth pass Was added to obtain the different speed ratio of the ninth pass, which was the final pass, and the final pass was rolled with this different speed ratio set.

  Table 1 summarizes the rolling conditions for each of the inventive examples and comparative examples.

  FIG. 5 is a graph showing the set value of the different speed ratio and the change in warp curvature for each pass as a result of carrying out the example of the present invention under the rolling conditions shown in Table 1. In addition, FIG. 6 is a graph showing changes in the different speed ratio setting values and warping curvatures for each pass as a result of carrying out a comparative example under the rolling conditions shown in Table 1.

Regarding the rolling of the present example, the warping tends to occur in the odd-numbered path, while the tendency to slightly warp in the even-numbered path.
As shown in FIG. 5, in the example of the present invention in which odd-numbered paths and even-numbered paths are controlled separately, the curvature of curvature can be gradually reduced after the seventh path when the warp control is started. I was able to get a warp.

  On the other hand, as shown in FIG. 6, in the comparative example in which the warpage control was performed in each path, the warpage control was performed in the 8th path having the upward warping tendency based on the actual warpage measurement in the 7th path having the downward warping tendency. However, a fairly large warpage has occurred. Based on the result of the 8th pass, the speed difference rate was lowered in the direction of reducing the upward warp. As a result, the final 9th pass resulted in a slight downward warp due to insufficient control capability.

(Deformation)
In the description of the embodiment, the case where the “steel plate” is a thick plate manufactured by hot rolling is taken as an example. However, the present invention is not limited to thick plates, and can be equally applied to steel plates manufactured by performing multiple passes of reverse rolling, such as hot strip rough rolled material.

  In the description of the embodiment, the correction amount for the different speed rate set in (i-4) pass is obtained, and (i-2) from the corrected amount and the different speed rate set in (i-4) pass. The case where the peripheral speed of the upper and lower work rolls is finally set by obtaining the different speed ratio set in the pass is taken as an example. However, the present invention is not limited to such a form. For example, (i-4) an actual speed rate of a path is measured, a correction amount for the actual value of the different speed rate is obtained, and this correction amount and (i-4) ) (I-2) The different speed ratio to be set for the path may be obtained from the actually measured value of the different speed ratio in the path.

  In the present embodiment, the warpage control for the 5, 7, and 9 paths has been described, but the warpage control was similarly performed for the 6 and 8 paths.

It is explanatory drawing which shows typically the structure of the rolling apparatus used by embodiment. (2) is a graph showing the relationship between the coefficient a and the shape ratio _{2l d / (h 1 + h} 2) in the equation. This is an example showing the equation (2). 4 is a flowchart illustrating an example of feedforward control performed by the warpage control device 10 in the embodiment. It is a graph which shows the setting value of the different speed rate and the change for every path | pass of the curvature rate as a result of implementing this invention example on the rolling conditions shown in Table 1. FIG. It is a graph which shows the setting value of the different speed rate as a result of implementing a comparative example on the rolling conditions shown in Table 1, and the change for every path | pass of curvature curvature.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rolling apparatus 2a, 2b A pair of upper and lower work rolls 3a, 3b Backup roll 4 Reverse rolling mill 5 Rolled material 6a, 6b Warpage sensor 7 Image processing apparatus 8 Data collection apparatus 9 Rolling mill control process computer 10 Warpage control apparatus 11 Monitor

Claims (4)

A method of manufacturing a steel plate by performing reverse rolling of a plurality of passes by a pair of upper work rolls and lower work rolls on a material to be rolled, wherein the material to be rolled is rolled in the i-th rolling of the plurality of passes. The circumferential speed of each of the upper work roll and the lower work roll at the time of biting into the work roll and the lower work roll, (i-2) between the measured plate warpage amount and the target plate warpage amount at the time when the rolling of the pass is finished. A method of manufacturing a steel sheet, comprising a step of setting based on the deviation so that occurrence of sheet warpage of the material to be rolled at the time of completion of rolling of the i-th pass is suppressed or eliminated. A method of manufacturing a steel sheet, wherein the step is performed in two or more passes including a final pass. At least the difference in load between the upper work roll drive motor that drives the upper work roll and the lower work roll drive motor that drives the lower work roll in the i-th rolling is a warp that exists at the tip of the material to be rolled. It is described in Claim 1 or Claim 2 made smaller than when the generation | occurrence | production area | region passes through this upper work roll and a lower work roll, and the front-end | tip of this to-be-rolled material bites into this upper work roll and a lower work roll. Steel plate manufacturing method. The peripheral speed of each of the upper work roll and the lower work roll is set based on the average differential speed ratio of the upper work roll and the lower work roll after the biting in which the occurrence of sheet warpage is expected in the material to be rolled. The manufacturing method of the steel plate described in any one of Claim 1- Claim 3.

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