JP6252500B2 - Thickness control method in thick plate rolling - Google Patents

Description

  The present invention relates to a plate thickness control method in thick plate rolling that can improve the plate thickness accuracy of a biting end portion and a biting end portion in thick plate rolling that performs absolute value AGC and plate crown control. Thick plate rolling is rolling from a steel slab to a thick steel plate, and the material to be rolled is a steel plate (abbreviated as a plate). The steel slab is heated to about 1000 to 1250 ° C. in a heating furnace, and the rolling is performed hot. The thick steel plate means a steel plate having a product plate thickness of 4.5 to 360 mm.

  In automatic sheet thickness control (AGC: Automatic Gauge Control) of thick plate rolling, the absolute value AGC is widely adopted, and hydraulic reduction is used as a reduction method in terms of responsiveness and high output. In thick plate rolling, a quadruple rolling mill is widely used, and the plate is finished into a desired product by reverse rolling of a plurality of passes.

In general, AGC in thick plate rolling is performed based on a basic relationship represented by the following formula (1) that is established among a rolling load P, a mill stiffness coefficient M, a roll opening degree S, and a delivery side plate thickness h.
S = h−P / M (1)
Equation (1) is an equation that always holds in the rolling state, but in the prediction calculation before the plate bites, the same equation (2) as equation (1) is used in order to obtain the target exit thickness h ^*. The roll opening S ^* is set based on the predicted rolling load P ^* .
S ^* = h ^* −P ^* / M (2)
The absolute value AGC sets and controls the roll opening degree S according to the following equation (3) in order to make the delivery side plate thickness h obtained by the equation (1) coincide with the target delivery side plate thickness h ^* obtained by the equation (2). Is.
S = S ^* -(PP ^* ) / M (3)
On the other hand, in thick plate rolling, a roll that receives a rolling load is elastically deformed to cause a plate thickness deviation in the width direction (= plate thickness at the center portion of the plate width−plate width end portion) on the plate on the delivery side of the rolling mill. (Thickness) occurs. Since the plate crown has a great influence on the rolling shape and the yield, the bending force (bender in the direction in which the vertical facing distance between the left and right end portions is widened to the left and right end portions of the upper and lower work rolls by a pressing means called a work roll bender. A plate crown control for controlling the plate crown to an appropriate range by applying a load) is also performed. In the plate crown control, a plate crown prediction model is used in which the relationship between the exit side plate crown, which is the plate crown on the exit side of the rolling mill, and the bending force is obtained in advance from theory or experiment.

  In Patent Document 1, when AGC and roll bending are used in combination, the influence of both rolling load and bending force is reflected in the mill stiffness coefficient M in order to improve the prediction accuracy of the equations (2) and (3). The method is described.

  Patent Document 2 describes a method for accurately estimating the wear and heat crown of a rolling roll and reflecting the result in the plate crown prediction model in order to improve the accuracy of the plate crown prediction model.

JP-A-60-030508 JP 2000-288615 A

  As described above, absolute value AGC and plate crown control have been used in thick plate rolling. When the absolute value AGC is used, the position at which the target delivery thickness is set in the sheet width direction varies depending on the mill (which is a thick plate rolling line). For example, there are mills that use the set position of the target outlet side plate thickness as the central portion in the plate width direction, and other mills that use the end portion in the plate width direction. This is because, in general, a thickness measuring means such as a γ-ray thickness meter is installed in the mill to monitor the actual delivery side thickness, and the installation position of this thickness measurement means is the set position of the target delivery side thickness. It is said. Since the installation position of the plate thickness measuring means is determined by restrictions such as the contact with other equipment that varies depending on the mill, the installation position of the target outlet thickness varies depending on the mill.

  By the way, in the mill having the set position of the target outlet side plate thickness in the end portion in the plate width direction, even when the target outlet side plate thickness is obtained at the end portion in the plate width direction by the absolute value AGC, it is particularly referred to as a wide material. In a material to be rolled having a sheet width exceeding 4800 mm, a minus crown, which is a phenomenon in which the exit side sheet crown has a negative value, may occur. If this minus crown becomes excessive (the absolute value of the negative value is excessive), the exit side plate thickness at the center of the plate width deviates from the tolerance of the target exit side plate thickness, that is, the allowable range. In order to prevent this, the target exit side plate thickness of the final finishing pass needs to be obtained by adding an appropriate addition amount that minimizes yield loss and thickness failure to the initial set plate thickness in advance. In order to achieve this, there is a method for determining the appropriate addition amount based on the plate crown amount measured on the exit side of the forward rotation pass before the final finishing pass in the plate thickness learning performed before the final finishing pass. I took it.

  However, in the above countermeasure, due to the influence of skid marks generated in the heating furnace, material furnace time, etc., both ends in the longitudinal direction are hotter than the central part and the deformation resistance is smaller. In the material, the minus crown immediately after biting and immediately before biting may be larger than the steady portion, which is a problem. In addition, a stationary part means the remaining board length part remove | excluding the board length part of about 1000 mm from the board full length from the board longitudinal direction both ends.

  The present invention solves the above-described problem, and even when both ends in the longitudinal direction of the slab are heated to a higher temperature than the central portion, the minus crowns at the biting end and the biting end are larger than the steady portion. It was made into the subject to provide the plate | board thickness control method in thick plate rolling which can prevent.

The present inventors diligently studied to solve the above problems, and as a result, obtained the following knowledge.
(I) The influence of roll deformation, transfer, inheritance, etc. on the plate crown is incorporated in the plate crown prediction model used for setting up the rolling load and the bender load during the pass schedule. If the plate crown amount can be calculated for each AGC cycle by this plate crown prediction model, the calculation result is reflected in the AGC, and the minus crown at the biting end and the biting end is excessively larger than the steady portion. It is possible to prevent.
(Ii) However, in the control that requires high responsiveness such as the absolute value AGC, it is necessary to make the AGC cycle as short as, for example, 50 ms or less, and the plate crown prediction model is used for each short AGC cycle. It is difficult to calculate the plate crown amount in real time and reflect it in the absolute value AGC from the viewpoint of calculation time.
(Iii) Therefore, a plate thickness control method capable of being applied in real time with sufficient time for calculation was studied, and the following method was found. That is, before rolling, the predicted rolling load and the set bending force in the rolling pass schedule are fitted to the plate crown prediction model to calculate the plate crown amount. In this method, the influence coefficient of the bending force change is obtained in advance, and during actual rolling, the plate crown amount is calculated from the measured rolling load and the measured bending force using the previously determined influence coefficient.
(Iv) During the actual rolling, the sheet crown amount obtained by the calculation during the actual rolling is compared with a predetermined threshold, and the AGC is reduced by an amount corresponding to the lower amount in response to the sheet crown amount being lower than the predetermined threshold. It is possible to prevent the minus crown from becoming excessive by increasing the target outlet side plate thickness.

This invention is made | formed based on the said knowledge, The summary is as follows.
[1] In a plate thickness control method for plate rolling in which longitudinal thickness control by absolute value AGC and plate crown control by work roll bender are performed,
Apply the predicted rolling load and the set bending force of the rolling to the plate crown prediction model before rolling to calculate the plate crown amount, and obtain the influence factors of the rolling load change and bending force change on the obtained plate crown amount in advance. And the process to keep
While the rolling is being performed, the plate crown amount is calculated from the actual rolling load and the actual bending force using the previously determined influence coefficient, and when the obtained plate crown amount falls below a predetermined threshold, the lower value is exceeded. Then, the AGC target delivery side plate thickness is increased by that amount, and the process proceeds to the next step (230). On the other hand, if the obtained plate crown amount is equal to or greater than the predetermined threshold, the next step (230) is immediately performed. thickness control method in thick plate rolling, characterized in that a step proceeding.
[2] The plate thickness control method in plate rolling according to [1], wherein the set position of the target delivery side plate thickness is an end portion in the plate width direction.

  According to the present invention, even when both end portions in the longitudinal direction of the slab are heated to a temperature higher than that of the central portion, it is possible to prevent the negative crowns of the biting end portion and the biting end portion from being excessively larger than the steady portion.

It is a flowchart which shows an example of embodiment of this invention. It is a block diagram which shows the example of this invention.

FIG. 1 is a flowchart showing an example of an embodiment of the present invention. In the present invention, step 100 and step 110 are first performed before rolling. In step 100, the predicted crown load and the set bending force are applied to the predicted crown model to calculate the amount of crown. The predicted rolling load and the set bending force are obtained by pass schedule calculation. The plate crown prediction model is expressed by the following equations (4) and (5).
C _r = a · C _m + b · C _rin (4)
C _m = f (P, P _b ) (5)
Here, _Cr is an exit side plate crown (hereinafter referred to as plate crown amount), C _rin is an entrance side plate crown, C _m is a mechanical crown, a is a transfer rate, b is a genetic coefficient, P is a rolling load, and P _b is Bender load (bending force). f is a function of P and P _b, an operational form by the model formula for determining the mechanical crown amount C _m. Further, a and b are constants obtained from the crown amount in the past rolling. During the fitting, the predicted rolling load to P, the set bending force is P _b, the values are. Since the calculation time in the calculation format f exceeds 50 ms, as described above, calculation for each AGC cycle during rolling is difficult. However, if it is before rolling, it usually takes at least 10 seconds from the completion of rolling of one material to be rolled to the start of the subsequent one rolling, so that the calculation can be completed with a sufficient margin during that time. it can.

In step 110, the influence coefficient of the rolling load change and the bending force change on the plate crown amount is derived from the calculation result and calculation conditions in step 100, respectively. This derivation method is as follows. That is, the influence coefficient of the rolling load change and bending force change on the plate crown amount is equivalent to partial differential coefficient when obtained by partially differentiating each C _r of equation (4) P, in P _b, in the following respectively (6 ) And (7).
∂C _r / ∂P = a · ∂C _m / ∂P (6)
∂C _r / ∂P _b = a · ∂C _m / ∂P _b (7)
(6) ∂C _m / ∂P _b of ∂C _m / ∂P and (7) wherein in the formula, from (5) to the difference form, the following respective (8), equation (9) Become.
∂C _m / ∂P = {f (P ₀ + ΔP, P _b0 ) −f (P ₀ , P _b0 )} / ΔP (8)
∂C _m / ∂P _b = {f (P ₀ , P _b0 + ΔP _b ) −f (P ₀ , P _b0 )} / ΔP _b (9)
(8), (9) from the right-hand side of the equation, by substituting predicted rolling load P _0, the set bending force P _b0, respectively, can be derived the value of the left side. Since P ₀ and P _b0 are generally different for each rolling pass, the left sides of equations (8) and (9) are described in a table format, for example, as functions of rolling load and bending force. Further, [Delta] P, [Delta] P _b respectively rolling load standard deviation is a vendor load standard deviation, these are appropriately set. For example [Delta] P, [Delta] P _b is 100 tons, respectively, 30 tons as an initial value, set to be fixed in a reference table.

Further, the reference mechanical crown C _m0 is calculated by the following equation (10).
C _m0 = f (P ₀ , P _b0 ) (10)
Next, during the rolling, steps 200 to 230 are repeated at an AGC cycle.

In step 200, using the influence coefficients 実 測 C _m / さ れ る P and ∂C _m / ∂P _b derived in step 110, the actual rolling load and the actual bending force sampled at an AGC cycle (for example, 2 ms). From this, the plate crown amount _Cr is calculated.

The following equation (11) is used for this calculation.
C _r = a · {(∂C _m / ∂P) · (P−P ₀ ) + (∂C _m / ∂P _b ) · (P _b −P _b0 ) + C _m0 } + b · C _rin = a · ( ∂C _r / ∂P) · (P−P ₀ ) + a · (∂C _r / ∂P _b ) · (P _b −P _b0 ) + a · C _m0 + b · C _rin (11)
The expression (11) is obtained by replacing the expression for calculating the mechanical crown C _{m with} the expression (5) in the expression (4) and the following expression (12).
C _m = (∂C _m / ∂P) · (P−P ₀ ) + (∂C _m / ∂P _b ) · (P _b −P _b0 ) + C _m0 (12)
In (11), P, the variables other than P _b Substituting known numbers had been determined before the rolling. P, the P _b, performance rolling load detected during rolling, immediately assigns each actual bending force. Equation (11) is a simple linear function, and the influence coefficients (∂C _r / ∂P) and (∂C _r / ∂P _b ) corresponding to the actual rolling load and the actual bending force to be substituted are For example, the calculation time is less than 1 ms because it can be determined by a simple conversion process such as table reference. Therefore, the plate crown amount _Cr can be calculated in real time from the equation (11).

The calculated _Cr is used in step 210 to determine whether or not C _r <threshold α. In the case of a minus crown, _Cr has a negative value. α is set in advance to a value that is about the actual result of the conventional shortage of the plate thickness (= plate thickness below the target delivery side plate thickness lower limit−target delivery side plate thickness lower limit). In addition, the track record for the insufficient plate thickness is a negative value.

If C _r <α, the target outlet side thickness of the AGC is increased by (α−C _r ) in step 220, and then the process proceeds to step 230. Note that (α−C _r ) is a positive value. Here, the target outlet side thickness of the AGC is h ^* in the equation (2). On the other hand, if (α−C _r ) ≧ α, the process immediately proceeds to step 230.

  In step 230, it is determined whether or not the AGC is finished. If the AGC is finished, the operation of this flow is finished. If the AGC is not completed, the process returns to step 200 and is repeated below.

As described above, in the present invention, the influence coefficients ∂C _r / ∂P and ∂C _r / ∂P _b of the rolling load change and bending force change to the plate crown amount C _r previously obtained before rolling are used. The amount of crown of the sheet is calculated in real time in the AGC cycle from the actual rolling load and the actual bending force during the rolling, and the AGC target outlet thickness is increased by an amount corresponding to the calculation result falling below the threshold. Even when both ends in the longitudinal direction of the slab are heated to a higher temperature than the central portion, there is an effect that it is possible to prevent the minus crown of the biting end portion and the biting end portion from being excessively larger than the steady portion. .

  In the present invention, when the setting position of the target outlet side plate thickness is set to the end portion in the plate width direction, the above effect is obtained as compared with the case where the setting position of the target outlet side plate thickness is set to the center portion other than the end portion in the plate width direction. Is more prominently expressed. Therefore, in the present invention, it is preferable that the set position of the target outlet side plate thickness is an end portion in the plate width direction.

  A steel slab having a slab thickness of 80 to 403 mm, a slab width of 1100 to 2345 mm, and a slab length of 1620 to 5310 mm is heated in a heating furnace, hot reverse-rolled by a quadruple rolling mill, and a rolling thickness of 5.08 to Automatic plate in a thick plate rolling line to finish a product (thick steel plate) of 228.11 mm (but less than slab thickness), rolling width = 1120 to 5331 mm (exceeding slab width) and rolling length = 3.1 to 54.2 m The present invention was carried out for thickness control, and an example of the present invention was obtained.

  In the thick plate rolling line, the setting position of the target delivery side plate thickness is set at the end in the plate width direction. Further, in the above-described thick plate rolling line, in order to prevent the exit side plate thickness at the center portion of the plate width from deviating below the tolerance of the target exit side plate thickness, the target exit side plate thickness of the final finishing pass is conventionally set to the initial set plate thickness. In addition, it is necessary to add in advance an appropriate addition amount that minimizes yield loss and thickness failure. In order to achieve this, there is a method for determining the appropriate addition amount based on the plate crown amount measured on the exit side of the forward rotation pass before the final finishing pass in the plate thickness learning performed before the final finishing pass. I took it. This is a conventional example.

  FIG. 2 is a block diagram showing an example of the present invention.

The material 1 to be rolled is rolled by a pair of upper and lower work rolls 3 and 3 backed up by a pair of upper and lower backup rolls 2 and 2 in a quadruple rolling mill, and the amount of reduction is controlled by a hydraulic cylinder 4. At that time, the roll opening degree S of the work rolls 3 and 3 is detected by the magnescale 5, and the rolling load P is detected by the load cell 6. Further, bending force P _b is detected by a pressure sensor (not shown) that came with the roll bender servo valve 13. Detected rolling load P, is transmitted roll angle S, the bending force P _b each actual rolling load P, actual roll angle S, as actual bending force P _b to the AGC control panel 8.

  The controller 9 obtains the plate length direction position information from the roll rotation speed of the work roll 3 detected by the pulse generator 7 and transmits it to the AGC control panel 8, and the actual rolling load P and actual roll transmitted from the AGC control panel 8. The opening degree S is transferred to the process computer 10, and the plate width W detected by a width meter (not shown) is transmitted to the process computer 10 as the actual plate width W.

On the other hand, the process computer 10 executes the flow of the "pre-rolling" in FIG. 1, the rolling load change of the plate crown amount C _r, respectively bending force changes influence coefficient _{∂C r / ∂P, ∂C r /} ∂ _Pb is derived. The derived influence coefficients ∂C _r / ∂P and ∂C _r / ∂P _b are the transfer rate a, the genetic coefficient b, the predicted rolling load P ₀ , the set bending force P _b0 , and the standard in the above equation (11). Along with the mechanical crown C _m0 and the entry-side plate crown C _rin, it is transmitted to the AGC control panel 8 via the controller 9.

The AGC control panel 8 sets the transmitted set bending force _Pb0 to the work roll bender servo valve 13, and at the same time, executes the "rolling in progress" flow in FIG. That is, as described above, the plate crown amount C _r is obtained in real time in the AGC cycle according to the equation (11), and when C _r <α, the target delivery side plate thickness is increased by (α−C _r ). This increment ΔS = (α−C _r ) is used as a roll opening correction amount from the AGC control panel 8 through the servo amplifier 11 and the servo valve 12 is operated to operate the hydraulic cylinder 4 to open the upper and lower work rolls 3. The degree S is changed to the open side by ΔS.

  In the example of the present invention, the threshold value α is set to a value of about the actual result of the conventional sheet thickness deficiency (= thickness below the lower limit of the target delivery side thickness−lower limit of the target delivery side thickness) = − 500 μm.

  In the present invention example and the conventional example, the failure weight ratio caused by insufficient plate thickness at one or both of the biting end and the biting end was investigated and compared. As a result, in the example of the present invention, the unacceptable weight ratio was reduced by 0.02% compared to the conventional example (yield was improved by 0.02%), and the effect of the present invention was confirmed.

1 Material to be rolled (steel plate, plate for short)
2 Backup roll 3 Work roll 4 Hydraulic cylinder 5 Magnescale 6 Load cell 7 Pulse generator 8 AGC control panel 9 Controller 10 Process computer 11 Servo amplifier 12 Servo valve 13 Work roll bender servo valve 100, 110, 200, 210, 220, 230 Step

Claims (2)

In the plate thickness control method of the plate rolling that performs the plate thickness control by the absolute value AGC and the plate crown control by the work roll bender,
Apply the predicted rolling load and the set bending force of the rolling to the plate crown prediction model before rolling to calculate the plate crown amount, and obtain the influence factors of the rolling load change and bending force change on the obtained plate crown amount in advance. And the process to keep
While the rolling is being performed, the plate crown amount is calculated from the actual rolling load and the actual bending force using the previously determined influence coefficient, and when the obtained plate crown amount falls below a predetermined threshold, the lower value is exceeded. Then, the AGC target delivery side plate thickness is increased by that amount, and the process proceeds to the next step (230). On the other hand, if the obtained plate crown amount is equal to or greater than the predetermined threshold, the next step (230) is immediately performed. thickness control method in thick plate rolling, characterized in that a step proceeding.   The plate thickness control method in plate rolling according to claim 1, wherein the set position of the target delivery side plate thickness is an end portion in the plate width direction.

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