JPH07185625A - Control method to guarantee minimum plate thickness of hoop steel sheet - Google Patents

Abstract

PURPOSE:To satisfy the required minimum plate thickness and to control rolling without taking a margin over a required level by correcting a plate thickness target value from the crown value of a stock sheet. CONSTITUTION:A crown meter 2 and a plate thickness meter 3 are provided at the output side of a tandem rolling mill 1, and an original plate information table 5 is a table provided with the crown value of the stock sheet of a steel sheet S, and a facility restriction table 6 is the one which determines the range of an operable manipulated variable. Moreover, target plate thickness preset correction logic 4, target plate thickness FB control logic 7, and a plate thickness control computer 8 are arranged. The crown value of a product is predicted from the crown value of the stock sheet by a model equation within the operable manipulated variable, and the minimum plate thickness extending over a width direction is found from a plate thickness target and a predicted crown value, and when deviation exists between found minimum plate thickness and the target value, the plate thickness target value is corrected based on relation between a crown improvement degree found in advance and an overall draft.

Description

Detailed Description of the Invention

[0001]

The present invention relates to the rolling of steel sheets,
The present invention relates to a control method for ensuring the minimum plate thickness in the plate width direction.

[0002]

2. Description of the Related Art In cold rolling, plate thickness control is performed to obtain a predetermined plate thickness. By the way, the material to be rolled that is subjected to cold rolling usually has different sheet thicknesses in the center portion in the width direction and the edge portion in the width direction due to edge drops and plate crowns generated in the hot rolling.

Conventionally, the crown control and the plate thickness control are performed by using different target values, and it has been impossible to control the minimum plate thickness including the crown. Therefore, for a material that should satisfy the minimum thickness, the target thickness is set in advance with a margin margin that is considered to satisfy the minimum thickness on the assumption of variations in crown control. It was constant over the entire length of the coil.

For the above reasons, if the crown of the original plate is large, the variation of the crown is larger than expected, and if it exceeds the expected margin, the minimum plate thickness cannot be satisfied and the plate becomes unfit, and conversely the crown of the original plate is Often, when the variation of the crown was smaller than expected, the minimum plate thickness had an extra margin, resulting in yield loss.

In order to deal with such a problem, Japanese Unexamined Patent Publication No.
JP-A-59114 discloses a plate thickness control method for a rolling mill, which uses a plate thickness measurement value to control the plate thickness of a material to be rolled, and a width direction edge portion and a width direction of the material to be rolled by two plate thickness gauges. A plate thickness control method is disclosed in which the plate thickness of the central portion is measured, and in the case of a strict material, both of these measured values are used to control the plate thickness of the material to be rolled.

[0006]

However, in the method disclosed in Japanese Unexamined Patent Publication No. 4-59114, the target plate thickness is given as the arithmetic average value of the plate thickness at the central portion and the plate thickness at the edge portion. However, there is a problem that it does not necessarily guarantee the minimum thickness.

The problem to be solved by the present invention is to provide a method capable of always obtaining a product satisfying the required minimum plate thickness.

[0008]

A first means for solving the above-mentioned problems is to set a target minimum width direction plate thickness when rolling a strip steel plate by a rolling mill having a crown controller and a plate thickness controller. If it is determined, the crown value of the original plate is used to predict the product crown value in the range of manipulatable amount by the model formula, the minimum plate thickness in the width direction is calculated from the target plate thickness and the predicted crown value, and the calculated minimum If there is a deviation between the plate thickness and the target value, the plate thickness target value is corrected on the basis of the relationship between the degree of crown improvement and the total rolling reduction which is obtained in advance.

A second means is to set a target minimum width direction plate thickness when rolling a strip steel plate by a rolling machine having a crown control device and a plate thickness control device, and a crown measuring device and a plate thickness measuring device. If it is, subtract the actual crown value obtained from the crown measuring device and plate thickness measuring device on the rolling mill exit side from the actual plate thickness to obtain the minimum width direction plate thickness, and the plate thickness is the target width direction minimum plate thickness. The total rolling reduction is corrected by the crown control device and the plate thickness control device so as not to fall below.

[0010]

The present invention provides a rolling mill having a crown control device and a strip thickness control device, and a crown measuring device and a strip thickness measuring device, which are obtained from the crown measuring device and the strip thickness measuring device on the delivery side of the rolling mill. The obtained actual crown value is subtracted from the actual plate thickness to obtain the minimum plate thickness in the width direction, and the total rolling reduction is changed so that the plate thickness does not fall below a predetermined target minimum plate thickness h _min .

FIG. 2 shows the relationship between the degree of crown improvement α and the total rolling reduction r in the present invention, where α = C _s / H _s −C _f / h _f (1). Here, C _{s is an} original plate crown, H _{s is an} original plate thickness, C _{f is a} product crown, and h _{f is a} product plate thickness.
The first term on the right side of the equation (1) represents the original plate crown plate thickness ratio,
The second term represents the product crown plate thickness ratio.

Since the curve shown in FIG. 2 has different characteristics depending on the steel type and the plate width, it is measured in advance according to the type of the original plate.

The curve in FIG. 2 shows that when the target plate thickness is changed (that is, the total reduction ratio is changed), the amount of crown of the plate before and after the change changes. When controlling the width-direction minimum plate thickness of the steel plate including the plate crown as in the present invention, the minimum plate thickness cannot be guaranteed simply by changing the target plate thickness. For example, even if the calculation is performed using the crown value at the rolling reduction at the point C in FIG. 2 and the target plate thickness is changed from the point C to the point C ′, at the point C ′ rather than the crown value at the point C, Since the crown deteriorates, the minimum plate thickness cannot be satisfied. Therefore, the relation of FIG. 2, that is, the total rolling reduction is r
_The target control is performed by considering the improvement and deterioration of the crown by changing from _a to r '.

Specifically, the change amount of the total rolling reduction r is Δr,
Assuming that the actual crown value is C ^* , the predicted crown value C _est when only Δr is changed is represented by C ^* −kΔr × h _f = C _est (2). Here, k is a differential coefficient ∂α / ∂r obtained from the relationship between the degree of crown improvement α and the total rolling reduction r. Therefore, the amount of change in the total reduction ratio r can be obtained by letting Δh _f be the amount of change in plate thickness after changing the reduction ratio, and obtaining Δr closest to h _min that satisfies h _f + Δh _{f −Cest} ≧ h _min (3) Similarly, the target thickness value from the original plate crown is also changed.

[0015]

EXAMPLES Cold rolling of a steel sheet by a six-roll rolling mill will be described below as an example. FIG. 1 shows a system for carrying out the present invention. 1-No. The case where the present invention is applied to a tandem mill type rolling mill 1 including a 5-stage stand of No. 5 is shown. Reference numeral 2 is a crown gauge provided on the exit side of the rolling mill 1, and 3 is a plate thickness gauge. The original plate information table 5 is a table having the crown value of the original plate of the steel plate S, and the equipment constraint table 6 is an equipment constraint table that defines a range of operable amount of operation from the equipment constraints of the crown control device.

The FB (feedback) control logic 7 of FIG. 1 will be described as an example. First, the minimum thickness in the width direction obtained from the crown value of the crown gauge 2 and the thickness measurement value of the thickness gauge 3 provided on the exit side of the rolling mill 1 is the width β of the control accuracy of the crown control as a safety margin. When the minimum plate thickness control target value is set to h _ref = h _min + β, the following condition h _aL <h _ref (1) (where h _aL is the actual minimum plate thickness, h _ref Becomes a minimum plate thickness target value), the control may be started according to the present invention because the minimum plate thickness target value h _min may be exceeded depending on the variation in plate thickness. Here, the actual minimum plate thickness h _aL is _calculated from the actual crown C ^* by h _ac −C ^* .

First, the actual total rolling reduction r _a is calculated by the following equation: r _a = (H _S −h _ac ) / H _S (2) (where, h _ac is the plate center actual plate thickness, H _S is calculated from the original plate thickness).

Next, when the center thickness is shifted by an amount by which the actual minimum thickness h _aL deviates from the minimum target thickness h _ref , h _c = h _ac + (h _min + β−h _aL ).・ ・ ・ ・ (3) In this case, the total rolling reduction ratio r'is obtained. Where h
_c is the central plate thickness when the actual minimum plate thickness h _aL is simply changed to h _min + β without taking the crown improvement rate into consideration. The total reduction ratio of r 'is r' obtained in _{= (H S -h C) /} H S ····· (4).

A table showing the relationship between the total rolling reduction and the crown improvement rate shown in FIG. 2 is prepared. The table is categorized by steel type and size, and the table value is set as a mesh with an appropriate total reduction ratio, and when data between meshes is required, it is calculated by interpolation.

Assuming that the crown improvement rate α when the total rolling reduction is r _a is α _a and the crown improvement rate when r ′ is α ′ is α ′, there are the following three types depending on the relationship between α _a and α ′. Break up in the case.

1) When α '> α _a (case like A in FIG. 2) The crown is improved by changing the total rolling reduction, so that the plate thickness can be reduced accordingly. Therefore, the change amount Δr of the total rolling reduction
It is possible to secure a sufficient minimum plate thickness with a change amount smaller than (= r _a −r ′), that is, a thinner central plate thickness. Therefore, the amount of change in the total rolling reduction is decreased by an appropriate, sufficiently small increment width Δr ′, and the crown improvement rate α at that time is obtained from the above table. At this time, assuming that the difference in the degree of crown improvement from the point A is Δα, the predicted crown amount C _{ect there} is C ^* −Δα × h _ac = C _est ··· using the actual crown C ^* at the point A.・ ・ ・ (5) Therefore, the minimum thickness after changing Δr 'is Δ
If the center plate thickness after changing r ′ is h _ac ′, then h _ac ′ −C _est
Given in. It is checked whether or not this value satisfies the following condition, that is, h _ac '−C _est ≧ h _min + β (6), and if the value satisfies the following condition, the total rolling reduction amount is further decreased by the increment width described above, Perform the same calculation. By repeating such calculation,
The minimum plate thickness that satisfies the above condition (6) is obtained. The value of h _ac 'at this time is output to the plate thickness control computer 8 as the changed target plate thickness.

2) When α '> α _a (in the case of C in FIG. 2) On the contrary, since the crown is deteriorated by changing the total rolling reduction, the plate thickness must be increased accordingly. Therefore, it is necessary to control with a change amount larger than the change amount Δr of the total reduction rate, that is, with a thicker central plate thickness.
The plate thickness h _ac ′ after the change is obtained in the same manner as in 1) by increasing it by r ′.

3) When α '= α _a (case B in FIG. 2) Since the crown improvement rate does not change, the changed plate thickness is given by the expression (3). With the above logic, the minimum thickness F
B Correct.

Similarly, with respect to the preset correction logic 4, the original plate information table 5 having the original plate crown value of the steel plate S and the equipment constraint table 6 which defines the operable amount range from the equipment constraints of the crown controller. From each table information, the crown value on the rolling mill exit side is predicted by the crown prediction model formula, the minimum plate thickness in the width direction obtained by subtracting the crown value from the plate thickness target value is obtained, and the same logic as the feedback correction logic 7 is used. Set the target plate thickness setting value.

[0025]

As described above, the present invention takes into consideration the crown improving effect due to the change in the total rolling reduction so that the minimum thickness in the width direction of the material to be rolled does not fall below the minimum thickness target value. This is a method of controlling so as not to take the above margin allowance, and it is possible to reduce the mismatch of the minimum plate thickness and reduce the yield loss due to the margin margin more than necessary.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a system that implements the present invention.

FIG. 2 is a graph showing the relationship between the total rolling reduction and the degree of crown improvement.

[Explanation of symbols]

1 Tandem rolling mill, 2 Crown gauge, 3 Plate gauge, 4
Target thickness preset correction logic, 5 original plate information table, 6 equipment constraint table, 7 target thickness feedback correction logic, 8 thickness control calculator

Claims (2)

[Claims] 1. When rolling a strip-shaped steel sheet by a rolling mill having a crown control device and a plate thickness control device, when a target minimum width direction plate thickness is set, an operation that can be operated from a crown value of an original plate by a model formula. Predict the product crown value in the range of quantity, find the minimum thickness in the width direction from the target thickness value and the predicted crown value, and if there is a deviation between the obtained minimum thickness and the target value, obtain it in advance. A control method for ensuring the minimum thickness of a strip steel sheet, which is characterized by correcting a target thickness value based on the relationship between the degree of crown improvement and the total rolling reduction. 2. When rolling a strip steel sheet by a rolling mill having a crown control device and a plate thickness control device, and a crown measuring device and a plate thickness measuring device, when a target width direction minimum plate thickness is set, a rolling mill The minimum crown thickness in the width direction is calculated by subtracting the actual crown value obtained from the crown measuring device and the thickness measuring device on the exit side from the actual thickness, and the crown is controlled so that the thickness does not fall below the target minimum width thickness. A control method for ensuring the minimum plate thickness, which is characterized in that the strip-shaped steel plate is modified by a device and a plate thickness control device.