Method for improving control of strip tension during hot strip coil unwinding

Abstract

The present application relates to a kind of control method for improving hot-rolled strip take-up draw narrow, belong to width size control technical field specially applicable to metal rolling mill.The method is by the historical process parameters of the occurrence take-up draw narrow of hot-rolled production line, utilize the width curve of the width model automatic tracking of existing L2 control system to obtain take-up draw narrow curve, and to take-up draw narrow curve with its mirror image orientation fitting curve, again using the position point coordinate required when fitting of the fitting curve to calculate the narrow amount S, narrow length L and the starting position P1 of take-up draw narrow form history parameter, then compare the current strip reading parameter of real-time production line with history parameter to trigger and calculate the starting position Pc of rough rolling E2 vertical roll required to compensate take-up draw narrow and compensation rolling length Lc, to finally compensate the width fluctuation of strip due to take-up draw narrow generated by previous rolling.

Description

Technical Field

[0001] This invention relates to a method for controlling the narrowing of hot-rolled strip due to coiling, thereby improving the control of strip narrowing. It belongs to the field of width dimension control technology specifically applicable to metal rolling mills. Background Technology

[0002] Hot-rolled strip steel uses continuously cast slabs as raw materials. After being heated in a heating furnace and having its surface iron oxide scale removed in a descaling box, it enters a roughing mill for reversible rolling. After the head and tail of the intermediate slab in the roughing mill are removed, it enters a finishing mill for continuous rolling. After laminar flow cooling, it enters a coiler for coiling and is finally delivered to the next user in the form of a plate coil.

[0003] The width of hot-rolled strip steel is controlled during the rolling process, specifically by the roughing mill, vertical rolling mill, and finishing mill. Under normal circumstances, the finished strip dimensions do not change after finishing rolling. However, for some softer steel grades and those using high-tension coiling, during coiling, a sudden longitudinal tension is generated between the finishing mill's last stand and the coiler, causing the strip head to narrow during coiling. This phenomenon is called "coiling necking," and it affects the width quality of the finished steel coil. Furthermore, during cold rolling, the necked section of the strip is prone to being cut off by the disc shear, further impacting the yield of cold-rolled strip steel.

[0004] The existing narrowing defect is mainly discovered by operators by monitoring the winding width curve displayed on the control system of the production line. Due to the fast production pace of the rolling line, the measures taken are often somewhat delayed.

[0005] Chinese patent application CN103464470A discloses a method for controlling necking compensation in hot strip rolling. This method corrects a preset necking amount for the strip based on its actual narrowing, and uses the corrected narrowing amount as the preset necking amount for the next coil. However, in actual production, due to significant differences in the necking position and amount for different steel grades and specifications, and frequent changes in steel grades and specifications in the rolling schedule, the corrected necking amount has a large error, resulting in poor necking compensation. Summary of the Invention

[0006] The technical problem to be solved by this invention is: how to eliminate the effect of coiling narrowing on the strip after rolling by adjusting the roughing roll gap width compensation method to improve the coiling narrowing of the strip in subsequent rolling.

[0007] The technical solution proposed by this invention to solve the above-mentioned technical problems is: a control method for improving the narrowing of hot-rolled strip during coiling, applicable to the roughing mill, finishing mill, coiler, and L2 control system involved in the hot-rolled strip production line. The L2 control system is equipped with a width model, which can automatically track and generate the width curve during strip coiling; including the following steps:

[0008] Step 1: Collect the tapping marks, rolling thickness grade, rolling width grade, finishing rolling temperature grade, and coiling temperature grade of the hot-rolled strip steel production line where coiling narrowing occurred historically. Simultaneously, read the coiling narrowing curve formed by coiling narrowing on the width curve from the width model, and fit a symmetrical curve to the coiling narrowing curve using its mirror image. Calculate the narrowing amount S, narrowing length L, and the starting position P1 of the coiling narrowing based on the coordinates of the required points on the fitted curve, as follows:

[0009] Let n be the number of positions required for fitting the curve, let the coordinates of the starting position Z1 of the fitting curve be (X1, Y1), let the coordinates of the ending position Zn of the fitting curve be (Xn, Yn), and let the maximum ordinate of all positions of the fitting curve be Ymax. Then P1 = X1, the narrowing amount S = Ymax - Y1, and the narrowing length L = Xn - X1.

[0010] The collected and calculated parameters are statistically classified to construct an interpolation table for width compensation process parameters;

[0011] Step 2: Real-time reading of the current strip's tapping mark, rolling thickness grade, rolling width grade, finishing temperature grade, and coiling temperature grade on the production line, and comparison with the corresponding process parameters in the width compensation process parameter interpolation table. When the two are completely consistent, width compensation is triggered as follows:

[0012] Step 2.1: Read the starting position P1 and narrowing length L of the coiling start for the same layer as the current strip to be rolled from the width compensation process parameter interpolation table. Calculate the starting position Pc and width compensation rolling length Lc of the current strip to be rolled on the E2 vertical roll of the roughing mill according to the following formulas (1) and (2).

[0013] Pc=P1×h1 / h2+ L1×h3 / h2 (1),

[0014] Lc=L×h1 / h2 (2)

[0015] In equations (1) and (2),

[0016] L1 is the length of the flying shear head for the intermediate billet, which is the strip steel after rough rolling.

[0017] h1 represents the thickness of the strip at the finish rolling exit.

[0018] h2 is the entry thickness of the last pass of the strip roughing process;

[0019] h3 is the thickness of the intermediate billet;

[0020] Step 2.2: Send Pc and Lc obtained in Step 2.1 to the L2 control system of the production line. When the current strip is rolled to the starting position Pc of the roll gap adjustment, the roll gap of the E2 vertical roll is increased according to the narrowing amount S corresponding to the current strip to be rolled in the interpolation table. Then, the current strip is rolled for a width compensation rolling length Lc and then the roll gap of the E2 vertical roll is restored to its original state.

[0021] The beneficial effects of this invention are as follows: By statistically analyzing the historical process parameters of coiling narrowing in the hot rolling production line, the width curve of the existing L2 control system is automatically tracked to obtain the coiling narrowing curve. The coiling narrowing curve is then fitted (or backfitted) with its mirror orientation to produce a fitting curve corresponding to the coiling narrowing curve. Then, based on the coordinates of the required position points of the fitting curve, the narrowing amount S (historical narrowing amount), narrowing length L (historical narrowing length), and starting position P1 (historical starting position) of the coiling narrowing are calculated and saved as historical process parameters in the width compensation process parameter interpolation table. After the process parameters of the strip to be rolled on the production line are read in real time and compared with the interpolation table, the width compensation function is triggered. The starting position Pc of the roll gap adjustment of the current strip to be rolled on the E2 vertical roll of the roughing mill and the width compensation rolling length Lc are calculated. The L2 system is then sent to control the E2 vertical roll to start adjusting the roll gap of the E2 vertical roll by increasing the narrowing amount when the current strip is rolled to position Pc. After rolling Lc, the roll gap of the E2 vertical roll is restored to its original state. The method provided by this invention fits the shape of the historical coiling and narrowing curve according to its mirror orientation to obtain a fitting curve. Using the coordinates of the position points required during fitting of the fitting curve, the narrowing amount S, the narrowing length L, and the starting position P1 of coiling and narrowing are calculated to form historical parameters. Then, the current strip reading parameters of the real-time production line are compared with the historical parameters to trigger and calculate the starting position Pc and the compensation rolling length Lc of the roughing E2 vertical roll that need to compensate for the coiling and narrowing. In this way, the width fluctuation of the strip caused by the coiling and narrowing in the previous rolling is finally compensated. Attached Figure Description

[0022] The method for improving the control of narrowing during hot-rolled strip winding according to the present invention will be further described below with reference to the accompanying drawings.

[0023] Figure 1 This embodiment describes an improved control method for the narrowing of hot-rolled strip during coiling, applicable to the equipment layout diagram of a hot-rolled strip production line.

[0024] Figure 2 This is a schematic diagram of the take-up width curve and its take-up narrowing curve.

[0025] Figure 3 This is a schematic diagram of the fitted curve. Implementation Example

[0026] This embodiment provides a control method for improving the narrowing of hot-rolled strip during coiling. It is applicable to the roughing mill, finishing mill, coiler, and L2 control system involved in a hot-rolled strip production line. Figure 1 As shown. The L2 control system has a built-in width model. A width measuring instrument is installed between the F7 mill and the coiler in the finishing mill unit. The width measuring instrument is used to detect the width of the strip during coiling, and the width model can automatically track and generate the width curve of the strip during coiling. The steps include:

[0027] Step 1: Collect the historical data of hot-rolled strip steel production lines showing strip narrowing during coiling, including the tapping mark, rolling thickness grade, rolling width grade, coiling temperature grade, finishing temperature grade, and coiling temperature grade. Simultaneously, read the coiling narrowing curve caused by coiling narrowing on the width curve from the width model (e.g., ...). Figure 2 (As shown in the circled portion of the take-up width curve), and then fit the take-up narrowing curve with its mirror image to obtain a fitting curve symmetrical to the take-up narrowing curve (such as...). Figure 3 As shown, although the fitted curve is fitted in the mirror position of the winding and narrowing curve, the fitted curve and the winding and narrowing curve are not completely mirror symmetrical due to the small number of fitted points. It only indicates that the overall shape of the two curves is symmetrical to each other in reverse, which can also be called reverse fitting. The narrowing amount S and the narrowing length L, and the starting position P1 of winding and narrowing (the length of the strip before winding and narrowing begins) are calculated based on the coordinates of the required position points of the fitted curve (i.e. the connecting points used to form the fitted curve).

[0028] The narrowing amount S, narrowing length L, and starting position P1 of the winding narrowing are calculated and determined according to the coordinates of the required position points of the fitted curve as follows:

[0029] In this embodiment, the fitting curve (also called the width compensation curve) for the winding and narrowing curve is obtained by fitting the curve according to its mirror image orientation. This fitting is performed using a minimum of four points, i.e., the number of position points n=4. For example... Figure 3As shown, the four points required for fitting the curve include the starting position Z1, two intermediate points (first intermediate point Z2, second intermediate point Z3), and the ending position Z4. The coordinates of these four points are Z1 (X1, Y1), Z2 (X2, Y2), Z3 (X3, Y3), and Z4 (X4, Y4), respectively. The width compensation model can obtain the simplest fitting curve for the winding and narrowing curve based on these four coordinate values. Then, in the interpolation table, the starting position for winding and narrowing (the length the strip has traveled since winding and narrowing began) is P1 = X1, and the narrowing length is L = X4 - X1; the maximum ordinate of all points on the fitted curve is Ymax = Y2, and the narrowing amount is S = Y2 - Y1.

[0030] For example, for the strip steel with the tapping mark IT8210B1, the coordinates of four positions are selected as follows: Z1 coordinate (110m, 0mm), Z2 coordinate (125m, 8mm), Z3 coordinate (195m, 8mm) and Z4 coordinate P3 (210m, 0mm); then P1=110m, L=210-110=100m, S=8-0=8mm.

[0031] Obviously, besides fitting the narrowed curve to its mirror image using the minimum four position points required for fitting the curve in this embodiment, it is also possible to fit using five, six, or more position points. Let n be the number of position points required for fitting the curve, let the coordinates of the starting position point Z1 of the fitting curve be (X1, Y1), let the coordinates of the ending position point Zn of the fitting curve be (Xn, Yn), and let the maximum ordinate of all position points of the fitting curve be Ymax. Then P1 = X1, the narrowing amount S = Ymax - Y1, and the narrowing length L = Xn - X1.

[0032] The collected and calculated parameters are statistically classified to construct a width compensation process parameter interpolation table, as shown in Table 1 below as an example of a width compensation process parameter interpolation table.

[0033] Table 1 Width Compensation Indicators

[0034] Steel tapping mark Thickness grade Width levels Finishing rolling temperature grade Winding temperature rating P1 S L L1 IT8210B1 10 4 7 11 110m 8mm 100m 0.1m IT9010B1 10 4 6 7 120m 6mm 70m 0.1m AP1361C1 8 2 9 8 60m 6mm 120m 0.1m AP0941D1 8 4 6 7 110m 5mm 60m 0.1m IT9010B1 10 4 6 7 120m 6mm 45m 0.1m AP1360C1 9 10 9 8 115m 6mm 50m 0.1m

[0035] Step 2: Read in real time the information of the current strip steel to be rolled, including the tap mark, rolling thickness grade, rolling width grade, finishing temperature grade, and coiling temperature grade, and compare it with the corresponding process parameters in the width compensation process parameter interpolation table. When the two are completely consistent, trigger width compensation.

[0036] For example, if the current strip to be rolled has the exit mark IT8210B1, a rolling width of 1250mm, a rolling thickness of 2.75mm, and a coiling temperature of 680℃, then the strip's width grade is 4, thickness grade is 10, and coiling temperature grade is 11. This information matches the width compensation process parameter interpolation table, therefore triggering the width compensation function as follows:

[0037] Step 2.1: Read the starting position P1 and narrowing length L of the coiling start for the same layer as the current strip to be rolled from the width compensation process parameter interpolation table. Calculate the starting position Pc (i.e., the length of the strip already rolled before the roll gap adjustment in the E2 vertical roll roughing mill) and the width compensation rolling length Lc of the current strip to be rolled according to the following formulas (1) and (2).

[0038] Pc=P1×h1 / h2+ L1×h3 / h2 (1),

[0039] Lc=L×h1 / h2 (2)

[0040] In equations (1) and (2),

[0041] L1 is the length of the flying shear head for the intermediate billet, which is the strip steel after rough rolling.

[0042] h1 represents the thickness of the strip at the finish rolling exit.

[0043] h2 is the entry thickness of the last pass of the strip roughing process;

[0044] h3 is the thickness of the intermediate billet.

[0045] For example, for the current steel marking IT8210B1 to be rolled out, P1=110m, the narrowing length L=100m, and according to production requirements, h1=2.75mm, the real-time measured h2=57.47mm, the real-time measured L1=0.1m, and the real-time measured h3=36mm, then...

[0046] Pc=110×2.75 / 57.47+ 0.1×36 / 57.47=5.33m

[0047] Lc = 100 × 2.75 / 57.47 = 4.78m

[0048] Step 2.2: Send Pc and Lc obtained in Step 2.1 to the L2 control system of the production line. When the current strip is rolled to the starting position Pc of the roll gap adjustment (i.e., when the current strip to be rolled is rolled to 5.33 meters on the E2 vertical roll, or when the strip has rolled 5.33 meters), the roll gap of the E2 vertical roll is increased according to the narrowing amount S corresponding to the current strip to be rolled in the interpolation table. The narrowing amount S corresponding to IT8210B1 in the width compensation process parameter interpolation table (Table 1) is 8mm. Therefore, the roll gap of the E2 vertical roll is increased by 8mm (that is, the opening of the roll gap of the E2 vertical roll is increased by 8mm). Then, the current strip is rolled for a width compensation rolling length of 4.78 meters, and then the roll gap of the E2 vertical roll is restored to its original state. The reduction in strip width caused by the previous coiling and narrowing is compensated by adjusting (increasing) the roll gap of the E2 vertical roll, thereby improving the reduction in strip width caused by the previous coiling and narrowing during subsequent rolling.

[0049] The above description is only a preferred embodiment of the present invention, but the present invention is not limited thereto. All equivalent substitutions or modifications made to the concepts and technical solutions of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for improving the control of the strip tension during coiling of hot rolled strip, suitable for use in a hot strip production line involving a roughing mill train, a finishing mill train, a coiler and an L2 control system, the L2 control system having a width model incorporated therein, the width model being capable of automatically tracking and generating a width profile for the strip as it is coiled; characterised in that Comprising the following steps: Step 1, collect the history of the hot strip production line of the steel grade, rolling thickness grade, rolling width grade, finishing temperature grade and coiling temperature grade, and the width model reads the coiling narrow curve on the width curve due to the coiling narrow of the strip, and the coiling narrow curve is fitted with its mirror position to obtain the fitting curve symmetrical to the coiling narrow curve, and the narrow amount S, the narrow length L and the starting position P1 of the coiling narrow are calculated according to the coordinates of the position points required by the fitting curve as follows, Let the number of position points required by the fitting curve be n, let the coordinates of the starting position point Z1 of the fitting curve be (X1, Y1), let the coordinates of the ending position point Zn of the fitting curve be (Xn, Yn), and let the maximum vertical coordinate of all position points of the fitting curve be Ymax, then P1 = X1, the narrow amount S = Ymax - Y1, and the narrow length L = Xn - X1; The collected and calculated parameters are statistically classified to construct a width compensation process parameter interpolation table; Step 2, real-time read the information of the steel grade, rolling thickness grade, rolling width grade, finishing temperature grade and coiling temperature grade of the current strip to be rolled on the production line, and compare with the corresponding process parameters in the width compensation process parameter interpolation table, when they are completely consistent, trigger the width compensation as follows, Step 2.1, read the starting position P1 and the narrow length L of the coiling start narrow of the same layer of the current strip to be rolled in the width compensation process parameter interpolation table, and calculate the starting position Pc of the roll gap adjustment of the current strip to be rolled in the rough rolling E2 vertical roll and the width compensation rolling length Lc according to the following formulas (1) and (2) respectively, Pc = P1 × h1 / h2 + L1 × h3 / h2 (1), Lc = L × h1 / h2 (2); In formulas (1) and (2), L1 is the length of the intermediate billet flying shear cut head, and the intermediate billet is the strip after rough rolling, h1 is the thickness of the strip at the outlet of the finishing rolling, h2 is the thickness of the strip at the entrance of the last pass of the rough rolling; h3 is the thickness of the intermediate billet; Step 2.2, send Pc and Lc obtained in step 2.1 to the production line L2 control system, control the roll gap of E2 vertical roll when the current strip is rolled to the starting position Pc of roll gap adjustment, and then continue to roll the current strip through the width compensation rolling length Lc, and then restore the roll gap of E2 vertical roll to the original state.

Images