JPH05200418A - Method for rolling thick plate - Google Patents

Abstract

PURPOSE:To keep good flatness on the outlet side of rolling pass by constituting this method of a method for deciding the target mechanical crown, method for deciding manipulated variable of an actuating element for crown control and method for deciding the target sheet crown on the inlet side. CONSTITUTION:Taking the target thickness on the outlet side, target sheet crown on the outlet side, target flatness and target rolling load as given conditions, the target mechanical crown is decided in the range of the max. value and min. value of mechanical crown and in the range of mechanical crown that is determined by the restriction of equipment of a rolling mill and the actuating element for crown control and the manipulated variable for crown control is determined based on the structural formula of mechanical crown that is shown by a formula. On the other hand, draft and thickness on the inlet side are determined from the target rolling load based on a load estimating model and the target sheet crown on the inlet side is decided based on the constituent formula of flatness that is shown by formula. Such operations are started from the target thickness of product at the final pass and repeated till the thickness on the inlet side exceeds the thickness of slab or at the time of completion of edge rolling, and the target crown of product can be attained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention, in a reverse rolling mill having a plate crown and a flatness control operation end, achieves a product target crown and maintains good outgoing flatness of each rolling pass. The present invention relates to a plate rolling method for determining a rolling schedule and a crown control operation amount.

[0002]

2. Description of the Related Art Generally, a rolling schedule in plate rolling is determined so that the number of rolling passes is the minimum under the following constraint conditions. ． The rolling load, rolling power (torque), and rolling reduction per pass must not exceed the maximum allowable value determined by the equipment specifications of the rolling mill. ． Good finish flatness and plate crown appropriate for the yield of the claimed material (slab).

In the conventional rolling mill having neither the plate crown nor the flatness control means, the crown ratio between the passes (plate crown / plate thickness) for the purpose of realizing a rolling schedule in which the flatness is good and the plate crown is appropriate. ) Is strictly constant, or the amount of deflection of the rolling mill that changes depending on the rolling load can be changed by several passes downstream so that rolling can be performed within the allowable range of the limited crown ratio that does not impair the flatness. In general, the method of reducing the bending amount of the rolling mill is to limit the rolling amount of several passes downstream to keep the rolling load or rolling torque below the allowable maximum capacity. (Recent Progress in Plate Manufacturing Technology (The Iron and Steel Institute), p. 264). Hereinafter, a path for reducing the rolling load or the rolling torque for the purpose of ensuring a good flatness and an appropriate plate crown is referred to as a shape adjusting path.

[0004]

According to the above-mentioned conventional method, from the viewpoint of ensuring the flatness, it is necessary to reduce the rolling load or rolling torque in the several downstream passes to the maximum allowable capacity or less, and in the several downstream passes. In addition, the amount of reduction per pass is limited, the number of passes is increased more than necessary, and the rolling efficiency is reduced.

The present invention has been made by paying attention to such problems of the conventional method. A reverse rolling mill having a plate crown and a flatness control means is used to secure a good flatness and achieve a target product thickness. In addition, the rolling schedule and crown control operation aiming at achieving the product target plate crown and reducing the number of passes by eliminating the shape adjustment pass in the downstream few passes of the conventional method and improving the rolling efficiency. It is intended to provide a thick plate rolling method in which the amount is simply and automatically determined.

[0006]

DISCLOSURE OF THE INVENTION The present invention is directed to a delivery side target sheet thickness, a delivery side target sheet crown, a target flatness and a target rolling in a sheet rolling by a reverse rolling machine having a sheet crown and flatness control means. With the load as a condition, the target mechanical crown is determined within the range of the maximum and minimum values of the mechanical crown determined by the flatness allowable limit, and within the range of the mechanical crown determined by the equipment restrictions of the rolling mill and crown control operation end. The crown control operation amount is obtained based on the constitutive equation of the mechanical crown shown in the equation (2) described below, while the rolling reduction and the entry side plate thickness are obtained from the target rolling load based on the load prediction model, and shown in the equation (3) described below. The target plate crown on the entry side is determined based on the constitutive equation of flatness, and such an operation is started from the product target plate thickness of the final n-pass, and the entry side plate thickness is the slab thickness or the width drawing pressure. Achieving the finished products target crown by repeating to over completion thickness, and a reverse rolling method for determining the crown control operation amount of reduction schedule and the path to be flatness good.

[0007]

First, in order to help understanding of the present invention, the above-mentioned plate crown (Ci), mechanical crown (CMi),
And a model formula representing the relationship between the flatness will be described.
That is, the constitutive formula of plate crown Ci Ci = (1-η) · CMi + η · (1-ri) · Ci-1 (1) η: Crown genetic coefficient CMi: Mechanical crown r: Reduction ratio Constitutive formula of mechanical crown CMi CMi = Cp * Pi + Cr + Cx * xi (2) Cp: Crown influence coefficient of rolling load Pi: Rolling load Cr: Crown influence term of roll profile Cx: Crown control amount influence coefficient of crown control operating means xi: Crown control operation amount Flatness fi Constitutive formula of fi = ξ (Ci / hi-Ci-1 / hi-1 + α) (3) h: Plate thickness ξ: Shape change coefficient (influence of crown ratio change on flatness) α: Width direction metal flow influence term Here, Cp, ξ, η, α are model parameters determined by the plate thickness, plate width, and roll dimension, and the suffix i is arbitrary. Indicates i-pass.

Based on the relational expressions shown in the above formulas (1) to (3) as basic formulas, the rolling schedule and the crown control operation amount of each pass, which are the objects of the present invention, are determined as follows. First, the outgoing target plate crown C in an arbitrary i-path
i ^* , outgoing target flatness fi ^* (flat when f = 0)
As a condition, the output side target mechanical crown Ci ^* is obtained from the equations (1) and (3) by the following equation (reference numeral 1 in FIG. 1).

CMi ^* = Ci ^* −η / (1−η) · (fi ^* / ξ−α) (4) Similarly, the flatness allowable limit values fi ^L and f shown in the following equation (5)
The allowable limit value of the mechanical crown in the rolling pass is obtained from i ^U (reference numeral 2 in FIG. 1). Flatness allowable limit fi ^L ≦ fi ^* ≦ fi ^U , fn ^L ≦ fn ^U ≦ fn ^* (5) L: Lower limit (medium wave limit) U: Upper limit (ear wave limit) n: Final rolling pass, that is, flatness When the maximum value of the mechanical crown that can be taken within the allowable limit is ^{CMi max1} and the minimum value is ^{CMi min1} , the formula (6) is obtained as the allowable range of the mechanical crown determined by the flatness.

^{CMi min1} ≤ ^{CMi *} ≤ CM ^max1 , CMn ^min1 = CMn ^max1 = CMn ^* (6) where ^{CMi min1} = Ci ^* -η / (1-η) · (fi ^L / ξ-α) (7) ) CMi ^max1 = Ci ^* -η / (1-η) · (fi ^U / ξ-α) (8) On the other hand, within the range of the maximum rolling load of the rolling mill, the target rolling load P
Given i ^*, the allowable limit value of the mechanical crown that can be taken within the range of the crown control manipulated variable shown in the following equation (9) is obtained (reference numeral 3 in FIG. 1). Crown control manipulated variable limit x ^L ≤ xi ≤ x ^U (9) That is, the maximum allowable mechanical crown value within the range of the crown control manipulated variable is CMi ^max2 , and the minimum value is C min.
If Mi ^min2 , the formula (10) is obtained as the allowable range of the mechanical crown determined by the crown control operation amount.

CMi ^min2 ≤ CMi ^* ≤ CMi ^max2 (10) where CMi ^min2 = Cp · Pi ^* + Cr + Cx · x ^L (11) CMi ^max2 = Cp · Pi ^* + Cr + Cx · x ^U (12) Therefore, the above ( From equations (6) and (10), the range of the mechanical crown that can be realized within the allowable limit of flatness and on the equipment of the crown control operating means is as follows (reference numeral 4 in FIG. 1).

In the present invention, the maximum value CMi ^max of this mechanical crown range is called an allowable maximum mechanical crown, and the minimum value CMi ^min is called an allowable minimum mechanical crown.
Allowable maximum mechanical crown range CMi ^min ≤CMi ^* ≤CMi ^max (13) where ^{CMi min} = max [ ^{CMi min1} , ^{CMi min2} ] (14) CMi ^max = min [CMi ^max1 , CMi ^max2 ] (15) At this time, Target mechanical crown C calculated by equation (4)
If i ^* is within the permissible limit shown in the equation (13), the target mechanical crown CMi is obtained by the means indicated by reference numeral 5 in FIG.
After replacing ^* with CMi ^max or CMi ^min ,
The crown control manipulated variable xi is obtained from the equation (2) as follows (reference numeral 6 in FIG. 1). That is, xi = {CMi ^* -(Cp · Pi ^* + Cr)} / Cx (16) Next, the rolling reduction ratio ri is calculated from the load prediction model based on the above-described target rolling load Pi ^*, and based on the definition equation of the rolling reduction ratio. The entrance side plate thickness hi-1 is obtained (reference numeral 7 in FIG. 1). Definition equation of rolling reduction ri = (hi-1-hi) / hi-1 (17) Finally, the output target plate thickness hi ^* , the target flatness fi ^* , and the output target plate crown Ci ^{* given as conditions.} , The target plate crown Ci-1 ^* on the input side is obtained from the formula (2) based on the input plate thickness hi-1 calculated by the formula (17) as follows (reference numeral 8 in FIG. 1).

Ci−1 ^* = {Ci ^* / hi ^* − (fi ^* / ξ−α)} · hi-1 (18) Here, the output side target plate crown Ci ^* is the target mechanical crown by the formula (13). When CMi ^* is replaced by CMi ^min or CMi ^max , it is assumed that the correction calculation is performed according to the equation (4).

By repeating the above-mentioned calculation from the last n passes until the entrance side plate thickness hi-1 exceeds the slab thickness or the tenter rolling completion thickness, the product target plate crown which is the object of the present invention is achieved. In addition, it is possible to obtain the rolling schedule and the amount of crown control operation for each pass that achieves good flatness.

Further, according to this method, when the crown control capability of the crown control means is sufficiently large, it is possible to adopt the maximum allowable load of the rolling mill as the target rolling load in all rolling passes, which is a conventional method. By eliminating the shape adjustment path in the above, the rolling efficiency is dramatically improved.

As shown in Table 1, as a result of applying the method of the present invention to an actual machine, the number of passes was reduced and the rolling efficiency was improved as compared with the conventional method.

[0017]

[Table 1]

[0018]

EXAMPLE An example in which the rolling schedule and crown control operation amount determining method according to the present invention are applied to a plate rolling mill having specifications shown in Table 2 will be described.

[Table 2]

FIG. 2 shows the rolling schedule when the present invention is applied to rolling of the rolling size and the slab size shown in Table 3 and after the completion of tenter rolling to the final pass. The solid line in the figure is the rolling schedule obtained by the method of the present invention, and the dotted line is that by the conventional method, but the number of passes is reduced by 2 compared to the conventional method, and the rolling time is shortened by about 30 seconds. There is.

[0020]

[Table 3]

Although the maximum allowable load of the thick plate rolling machine to which the present invention is applied is 8000 tons, in this embodiment, in order to prevent overload due to plate thickness error or temperature error occurring in the rolling process, The final pass target rolling load is intentionally kept at 6500 tons, but it is of course possible to create a rolling schedule with this as the allowable maximum load.

3 and 4 show the product target plate crown Cn.
³ is an example of calculation of a target plate crown and a crown control operation amount of each pass calculated at the same time as the rolling schedule of FIG. 2 by the method of the present invention, where ^* is 40 μm and target flatness fn ^* is 0%.

The crown control operation amount shown in FIG.
FIG. 6 shows the relative movement amount when the upper and lower work rolls provided with the initial crown having the shape shown in FIG. 5 are relatively moved in the axial direction to control the crown.
For example, in the case of pair cross rolling, the amount should be calculated as a cross angle, and any method that positively controls the crown does not depart from the essence of the present invention.

[0024]

According to the method of the present invention, in a reverse rolling machine having a plate crown and means for controlling the crown,
It is possible to determine a rolling schedule and a crown control operation amount that achieve the product target plate crown and well maintain the exit shape of each rolling pass. Further, according to this method, when the crown control capability of the crown control means is sufficiently large, it is also possible to adopt the maximum allowable load of the rolling mill as the target rolling load in all rolling passes, and in the conventional method. By eliminating the shape adjustment path, the rolling efficiency is dramatically improved.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating an operation of the present invention.

FIG. 2 is a chart of a calculation example of a rolling schedule to which the present invention is applied.

FIG. 3 is a chart of a calculation example of a target plate crown to which the present invention is applied.

FIG. 4 is a chart of an example of calculating a crown control operation amount to which the present invention is applied.

FIG. 5 is an explanatory diagram of crown control means used in the embodiment of the present invention.

Claims (1)

[Claims] 1. In plate rolling by means of a reverse rolling machine having means for controlling a plate crown and flatness, a flatness is obtained with a target output plate thickness, a target target plate crown, a target flatness and a target rolling load as conditions. Of the target mechanical crown within the range of the maximum and minimum values of the mechanical crown determined by the tolerance limit of the rolling mill, and within the allowable range of the mechanical crown determined by the equipment constraints of the rolling mill and the crown control operation means, and the target mechanical crown. A method of determining the operation amount of the crown control operation end from the output from the determination means,
The reduction rate is calculated from the target rolling load based on a load prediction model, the entry side sheet thickness is calculated from the reduction rate, and the entry side target sheet crown is determined from the exit side target sheet thickness, the exit side target sheet crown, and the target flatness. A rolling schedule and crown control operation that achieves the target crown of the product and achieves good flatness by repeating such an operation from the final n passes to the slab thickness or the tentering and rolling completion thickness, starting from the last n passes. A method for rolling a plate, characterized in that the amount is determined.