JPH01178307A - Method for controlling sheet width in rolling mill - Google Patents

Abstract

PURPOSE:To improve the sheet width accuracy and yield of a strip by setting a minimum value of variations in sheet width as a control target value and to control a tension between stands so that a measured sheet width value agrees with the target value. CONSTITUTION:A sheet width gage 3 is installed between stands of a rear stage rolling mill 2 of a hot continuous rolling mill and a sheet width minimum value detector 4 and a tension arithmetic unit 5 are also installed immediately after the gage 3. When the top end of a strip 1 reaches the gage 3, a measured sheet width value is inputted to the detector 4 and the detector 4 sets a sheet width minimum value at a moment where an output changing percentage changes from a minus value to a plus value as a target value of sheet width control and inputs the minimum value into the arithmetic unit 5. Then, the unit 5 finds a deviation between the measured sheet width value and the target value and inputs the deviation into a tension controller 6 to perform tension control. The sheet width accuracy and yield are improved because the sheet width control is performed by setting the target value restraining sheet width variation.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a method for controlling the width of a steel plate in continuous hot rolling. (Prior art) In continuous hot rolling of steel sheets, there is a problem that sheet width fluctuations occur due to skid marks, etc., resulting in a decrease in the yield of hot strips. Conventional methods to eliminate this sheet width fluctuation have been proposed. Various methods have been used, one of which is strip width control by tension adjustment.This strip width control by tension adjustment adjusts the tension according to changes in strip width to keep the strip width constant. This is a control method, and the following methods are conventionally known: ■ Based on the value measured with a strip width gauge installed on the entry or exit side of the strip in the downstream stand of the continuous hot rolling mill. , a method of controlling the strip width by varying the tension of the strip using a looper device installed between each stand (Japanese Patent Laid-Open No. 52-1
43953). ■ Strip width control device (Special Publication No. 5B-51
Publication No. 769).

[Problem to be Solved by the Invention 1] The conventional board width control means described in ■■ above are all methods of adjusting the tension between stands based on the board width detection value, but in all of them, the board width target value is the control target. Board @! is not set. Even if IJ control is started, it is unclear how much width change should be controlled, and in some cases the board width may become too narrow, so it cannot necessarily be said that this is a method that can appropriately control the board width. There was a lot of stuff. This invention was made in view of the above problems,
This paper attempts to propose a method that enables appropriate sheet width control by setting control target values. (Means for Solving the Problems) A method for controlling the width of a steel plate according to the present invention is to control the width of a steel plate by adjusting the tension based on the measurement value of a width meter installed between the rear stands of a continuous hot rolling mill. When performing this, the minimum value of the board width at the time when the measured value of the board tip reaches the minimum value, or the minimum board width within a predetermined time or within a predetermined length from the time the board tip passes the board width meter, is set as a control target value. The present invention is characterized in that the tension between each stand is controlled so that the measured value of the plate width becomes the control target value. (Function) In this invention, the measured value of the plate tip becomes the minimum value The reason why we decided to set the minimum value of the plate width within a predetermined time or within a predetermined length from the time when the plate tip passes the plate width meter as the control target value is due to the following reasons. In other words, with the method of controlling the board width by adjusting the tension between stands, it is possible to increase the tension and narrow the board width, but it is not possible to reduce the tension and increase the board width. When controlling the strip width by setting a high tension in advance, setting the tension too high will lead to unstable rolling, which is undesirable.Therefore, in this invention, the minimum value of the strip width is set as the control target value, and the width is reduced. In addition, when setting the minimum value within a predetermined time or within a predetermined length after the tip of the board passes the board width gauge as the target value, the length When adopting, set it by considering the plate thickness at that time.In other words,
If the board is thin, use a long value, and if the board is thick, use a small value. Next, the method of this invention will be explained based on the drawings. FIG. 1 is a schematic diagram showing an example of an apparatus configuration for carrying out the method of the present invention, in which (1) is a strip, (2) is a rear rolling mill stand of a continuous hot rolling mill, and (3) is a strip width gauge. , (4
) is the plate width minimum value detector, (5) is the tension calculation device, (6)
indicate the inter-stand tension control device, respectively. In Figure 1, the tip of the strip (1) is the width gauge (3).
), measurement of the plate width is started, and the measured value is input to the plate width minimum value detector (4). The resolution of the plate width meter (3) is 0.1 mm, and the detection interval is every 300 mm/Sec. The minimum value detector (4) sets the sheet width at the time when the output change rate of the sheet width meter (3) changes from negative to positive, that is, the minimum value, as the sheet width control target value Waim, and the tension calculation device (5) Output to. The tension calculation device (5) calculates the deviation Δ- between the plate width control target value Wain set by the minimum value detector (4) and the measured value W input from the plate width meter (3), and calculates the deviation in proportion to this excess. The tension change rate Δt/T (T: tension) is obtained by multiplying by the gain K and output to the inter-stand tension calculation device (6). The inter-stand tension control device (6) changes the tension and controls the board width by multiplying the input tension change rate Δt/t by the previous tension setting value. That is, the tension between the stands is controlled so as to reach the board width control target value Waim. FIG. 2 (A> is a diagram showing an example of a change in sheet width in the case of no control. In the case of hot rolling, high temperature areas and low temperature areas (skid marks) are formed in the longitudinal direction of the slab due to the skid of the heating furnace. In the low-temperature section, the material is hard and wider than the high-temperature section.Also, the leading edge of the material is controlled to be wide before the finish rolling mill.This is to prevent insufficient width during pickling welding in the next process. This is because consideration has been taken to prevent this from occurring. Fig. 2 (B) is an example of the change in plate width when the plate width control of the present invention is applied in the same figure (A>), and the plate width control target By controlling the inter-stand tension to the value Waim, fluctuations in board width can be greatly suppressed. Figure 2 (C) shows an example of the control situation of the inter-stand tension in Figure 2 (B). [Example] This invention method was applied between the N15 stand and the positive 6 stand of a continuous hot rolling mill, and the positive 5 stand: plate thickness 2.7 mm;
NtL6 stand: board thickness 2.3mm, board width 1000m
When rolling m, the tension between the stands is 065 to 4.0 kg, 1
Tension was controlled within a range of 5/5. The control target value Waim (TM5 stand) at that time was set to 1002 mm. As a result, the strip width variation at the exit side of the positive 5 stand is ±
It was 4.1 mm, but it decreased to ±2.1 mm. In addition, the plate width at the exit side of the positive 6 stand was only 1001 mm wide, 1.3 mm wide, and there was only a slight variation.

【Effect of the invention】

As explained above, according to the method of the present invention, by clarifying the tension control target for suppressing fluctuations in the sheet width, it is possible to appropriately control the sheet width, and the Width fluctuations can be suppressed to a minimum, and this has a great effect on improving sheet width accuracy and strip yield.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of an apparatus configuration for carrying out the method of the present invention. FIG. 2 (A> is a diagram showing an example of a change in strip width in the case of no control in a hot continuous rolling mill, and FIG. 2 (B) is an example of a change in strip width when the strip width control method of the present invention is applied. The figure (C) is a figure showing an example of the control situation of the inter-stand tension in the same as above (B). 1... Strip 2... Rolling mill stand 3.
...Plate width meter 4...Plate width minimum value detector 5...
・Tension calculation device 6...Tension control device Applicant Sumitomo Metal Industries Co., Ltd. Agent Patent attorney Yoshihisa Oshida Suijin (A) End End (B
) Tip End
Edge (C)

Claims (1)

[Claims] 1 In a method of controlling the strip width based on the measurement value of a strip width meter installed between the rear stands of a continuous hot rolling mill, the strip width at the time when the measurement value at the strip tip reaches the minimum value, or the strip width at the tip of the strip The minimum value of the board width within a predetermined time or within a predetermined length from the time when the board passes the board width meter is set as a control target value,
A method for controlling strip width of a rolling mill, comprising controlling inter-stand tension so that a value measured by a strip width meter becomes the target value.