JPH07124619A - Method for controlling fixed length of variable thickness part for differential thickness steel plate - Google Patents

Abstract

PURPOSE:To provide a simple and highly precise method by which the length of a variable thickness part is kept constant without being influenced by the change of rolling conditions such as a rolling load. CONSTITUTION:In manufacturing a differential thickness plate 2 by a hot rolling process, the rolling speed at the time of pass for the differential thickness rolling is set based on an idle running distance from the arrival at a differential thickness point P to the actual change of a roll gap, on the releasing speed of the roll gap and on the releasing quantity of the roll gap; a differential thickness rolling is thereby performed; the roll gap is made larger simultaneously with the arrival at the differential thickness point P; and also the rotation of the rolling roll is stopped. As a result, the length of the differential thickness part is able to be kept constant.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a difference thickness steel sheet having both rolling surfaces having step portions by hot rolling, and more specifically, a variation in the step portions of the difference thickness steel sheet. The present invention relates to a variable thickness portion constant length control method for making the length of a thick portion constant.

[0002]

2. Description of the Related Art As a method for producing a difference thickness steel sheet having a step portion on the rolling surface by hot rolling, for example, there is a prior art in which a roll gap of a rolling mill is enlarged during rolling to release the rolling halfway. It is known from the publication.

[0003]

In the above-mentioned prior art, the stepped portion, that is, the starting point of the difference in thickness is very clear, and it is possible to provide a product that meets the severe order size of the customer side by visual observation. However, on the other hand, there is a problem in that the lengths of the varying thickness portions (portions where the thickness changes at the boundary between the thick portion and the thin portion) are uneven. This is because the rolling load naturally changes due to differences in rolling conditions such as sheet thickness, thickness difference, rolling width, rolling temperature, and rolling roll diameter, and the roll gap setting for obtaining the required sheet thickness accordingly. This is because it is inevitable that the length of the variable thickness portion changes variously because the value changes.

The present invention has been made in order to solve such a problem, and an object of the present invention is to eliminate the influence of fluctuations in rolling conditions such as rolling load and the like in the changed thickness portion. An object of the present invention is to provide a simple and highly accurate variable thickness portion constant length control method capable of keeping the length constant.

[0005]

The present invention has the following constitution in order to achieve the above object. That is, the present invention, when producing a steel sheet with a different thickness by hot rolling, the rolling speed during the different thickness rolling pass is a running distance from when the difference thickness point is reached to when the roll gap is actually changed, and the roll gap. By setting the opening speed and the roll gap opening amount, differential thickness rolling is performed, and at the same time when the differential thickness point is reached, the roll gap is increased and the rotation of the rolling roll is stopped to make the length of the variable thickness part constant. This is a method for controlling the constant length of the varying thickness portion of the steel sheet with different thickness.

[0006]

According to the present invention, the rolling speed during the differential thickness rolling pass is set based on the idling distance, the roll gap opening speed, and the roll gap opening amount. It is possible to match the timing up to the opening time, that is, the variable thickness portion length to a predetermined value regardless of the rolling speed, and by stopping the rotation of the rolling roll at the same time, the influence of the rotation Can be eliminated and the length of the variable thickness portion can be constantly controlled with high accuracy.

[0007]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a flow chart showing a procedure for determining a differential thickness rolling speed according to an embodiment of the present invention, FIG. 2 is a simplified schematic diagram for explaining the method of the present invention, and FIG. It is an outline view of the different thickness steel plate obtained by operation of the invention, (A) is a perspective view and (B) is a front view. Further, FIG. 4 is a graph showing the actual results of the varying thickness portion length of the steel sheets of different thickness obtained by carrying out the present invention. Large diameter rolling roll R ₁ ,
And R _2, to the rolling roll R _3, hot finish rolling mill 1 of 4 stage consisting of R ₄ Metropolitan of smaller diameter, the rolling rolls R ₁ a hot rolled steel sheet in the middle and rolling in hot, By widening and opening the space between R ₂ and the rolling rolls R ₃ and R ₄ , the difference-thickness steel plate 2 having both the rolling surfaces having the step portions is manufactured. As shown in FIG. 3, the obtained difference-thickness steel plate 2 has a difference thickness amount: ΔT = T ₁ −T ₂ , and the variable thickness portion 3 having a length l ₃ is provided at the boundary portion between the thick steel plate and the thin steel plate. Have.

The present invention is characterized by a control method for making the length l ₃ of the variable thickness portion 3 constant, and its outline is shown in FIG.
And it demonstrates based on FIG. The present invention uses the central processing unit (CPU, not shown) in the control device for operating the four-stage hot finishing mill 1 to set the rolling speed during the differential thickness rolling pass and then perform the differential thickness rolling. When the difference thickness point P is reached, the roll gap of the rolling roll is increased and the rotation is stopped. The differential thickness rolling pass speed in this case is determined as follows.

In the calculation processing by the CPU, in the first step m1, the rolling load of the differential thickness rolling pass is determined, and then, the process proceeds to steps m2 and m3, and the minimum rolling speed v _{m that} can be rolled.
And the set roll gap value G are determined. On the basis of the minimum rolling speed v _m capable of rolling, the idling distance from the thickness difference point P is calculated at step m4, while the roll gap opening time t ₂ is calculated at the next step m5 based on the set roll gap value G. calculate. When the free running distance and the roll gap opening time t ₂ are determined, step m
Moving to 6, the distance required to open the roll gap under the minimum rollable rolling speed v _m is calculated. Based on the distance of this calculation result, in the next step m7,
The length of the variable thickness portion is obtained, and this length is compared with the commanded variable thickness portion length to be obtained in the next step m8.

If the above comparison result shows that the variable thickness portion length ≧ the command variable thickness portion length, the process proceeds to the next step m9 to determine the differential thickness rolling pass speed v corresponding to the command variable thickness portion length. On the other hand, if the comparison result is that the variable thickness portion length <command variable thickness portion length,
Since the commanded variable thickness portion length cannot be obtained with the minimum rollable rolling speed v _m , the reference minimum rollable rolling speed v _m is +
Need to fix on the side. Therefore, after the calculation for adding the correction value A to the minimum rolling speed v _m that can be rolled is performed in step m10, steps m4, m6, m7, m are again performed.
The difference thickness rolling pass speed v corresponding to the command variable thickness portion length is finally determined by performing the arithmetic processing in the order of 8 and m9.

By the above calculation processing, the differential thickness rolling pass speed v
Is determined, the differential thickness rolling is performed as described above, the roll gap of the rolling roll is increased at the same time when the differential thickness point P is reached, and the rotation of the rolling gap is stopped. It is possible to manufacture the steel plate 2 having a different thickness and having a length l ₃ of the variable thickness portion 3. The difference thickness steel sheet obtained by the method of the present invention is as shown in FIG.
The error of the actual actual variable thickness portion length l ₃ with respect to the planned variable thickness portion length is extremely small, and it is clear that the variable thickness portion constant control is realized as expected.

[0012]

As described above, according to the present invention, the rolling speed during the differential thickness rolling pass is set based on the idling distance, the roll gap opening speed, and the roll gap opening amount. It is possible to match the timing from the arrival of the thickness point to the opening time of the rolling roll, that is, the variable thickness length to a predetermined value regardless of the rolling conditions, and to stop the rotation at the same time when the rolling roll is opened. Therefore, the length of the variable thickness portion can be controlled to be constant with high accuracy.

[Brief description of drawings]

FIG. 1 is a flow diagram showing a procedure for determining a differential thickness rolling speed according to an example of the present invention.

FIG. 2 is a simplified schematic diagram for explaining the method of the present invention.

FIG. 3 is an outline view of a steel sheet of different thickness obtained by carrying out the present invention, in which (A) is a perspective view and (B) is a front view.

FIG. 4 is a graph showing actual results of the length of the variable thickness portion of the steel sheets of different thickness obtained by carrying out the present invention.

[Explanation of symbols]

 1 ... Hot finish rolling mill 2 ... Differential thickness steel plate 3 ... Varied thickness part

Claims (1)

[Claims] 1. When manufacturing a steel sheet with a different thickness by hot rolling, the rolling speed during a different thickness rolling pass is set to a free running distance from when the difference thickness point is reached to when the roll gap is actually changed, and a roll gap is opened. Set the speed and roll gap opening amount to perform differential thickness rolling, increase the roll gap as soon as the differential thickness point is reached, and stop the rotation of the rolling rolls to make the length of the variable thickness part constant. A method for controlling a constant length of a variable thickness portion of a steel sheet of different thickness, which is characterized in that