JPH10258306A - Plate shift prevention method of cross rolling and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably produce a high quality steel plate by arranging a mechanism, which controls an entry angle change device corresponding to a plate shift quantity detected with a plate shift detector and controlling a plate shift direction with changing an entry angle in the vertical direction when a metal strip enters into a rolling mill. SOLUTION: A plate shift detector 6 is arranged at a rolling mill outlet side, a plate shift quantity of the detector 6 is inputted in a controller 8. An operated output of the controller 8 gives a signal to operate an entry angle change device. The entry angle change device consists of a hydraulic cylinder 9, and two entry angle change rolls 31, 32. The rolls 31, 32 pinch a strip, are directly connected to the hydraulic cylinders and can change an entry angle by elevating the strip 2 at a rolling mill inlet side. By this method, a plate shape control function and a surface gloss improvement function of the rolling mill are not impaired, a plate shift can be prevented by a simple device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of rolling a metal strip using a rolling mill of a type in which work rolls are crossed, and more particularly to a method of preventing a metal strip from leaning and stably rolling the metal strip during cold rolling. The present invention relates to a method and an apparatus for performing an operation.

[0002]

2. Description of the Related Art In order to obtain a uniform thickness distribution in the width direction in rolling a metal strip, a rolling mill of a type in which upper and lower work rolls are crossed is used. Hereinafter, this type of rolling is referred to as roll cross type rolling or simply cross rolling, and a rolling mill of this type is referred to as a cross rolling mill.

FIG. 1 (a) is an explanatory diagram of the state of intersection of upper and lower work rolls in cross rolling. Work rolls 11, 1
2 has a certain angle with respect to the pass line, and by changing this angle, the thickness distribution of the metal strip in the width direction can be changed. The angle formed by the work rolls 11 and 12 with respect to the pass line is referred to as a deviation angle.
Has a bias angle of θ ₁ clockwise with respect to the rolling direction, and the lower roll 12 has a bias angle of θ ₂ counterclockwise. The deviation angle is represented with a sign, and clockwise as viewed from above is defined as a positive deviation angle. If the deflection angle θ ₁ of the upper roll 11 is positive, the deflection angle θ ₂ of the lower roll 12 is negative. In normal cross rolling |
θ ₁ | = | θ ₂ |, and the maximum value θ _max is about 1.2 °. Also, the crossing angle η of the upper and lower rolls is signed and η = θ
It can be represented by ₁ - [theta] _2.

In the state of | θ ₁ | = | θ ₂ |, the center line of the metal strip usually coincides with the pass line. When the signed deviation angles θ ₁ and θ _{2 of the} upper and lower rolls simultaneously increase (turn) in the same direction (for example, clockwise), assuming that the sign rotation angle is ζ, ζ = (θ ₁ + θ ₂ ) / 2. Since it can be expressed, ζ is called an average angle.

[0005] In a normal rolling mill without cross rolling, the work roll and the metal strip slide relative to each other only at the contact surface in the forward or backward direction in the rolling direction. In cross rolling, relative slip occurs between the work roll and the metal strip also in the width direction, and a frictional component in the width direction acts. The friction component in the width direction acts in opposite directions on the upper surface and the lower surface of the steel sheet, and is generally almost balanced.

In cross-rolling, when the roll or metal band has different surface roughness between the upper and lower sides, or when the amount of rolling lubricating oil drawn between the roll and the metal band is different between the upper and lower sides,
The friction component in the width direction of the upper and lower surfaces is different, and a phenomenon in which the steel strip is deviated from the center to one of the left and right sides (hereinafter, referred to as a plate shift) is likely to occur. When the sheet leaning occurs, the winding shape of the metal band deteriorates, and not only does the workability in the next step deteriorate, but if the sheet leaning amount is large, the rolling operation cannot be continued.

[0007] As a method for preventing the board shift, conventionally, the left and right pressing positions of the work roll have been adjusted. But,
In this method, the cross-sectional shape of the metal band becomes asymmetrical,
Gentle bending in the longitudinal direction (this is called camber)
There is a drawback that occurs.

[0008] Further, by utilizing the cross mechanism, the deviation angle of the upper and lower rolls is increased or decreased in the same direction (increase or decrease the average angle ζ) while keeping the crossing angle between the upper and lower work rolls constant, thereby reducing the leaning of the board. A correction method is disclosed in JP-A-57-4315.

[0009]

However, the method disclosed in JP-A-57-4315 has the following problems.

The problem will be described below with reference to FIG. In general, the cross rolling mill limits the cross direction from the parallel arrangement of the rolls to one direction in each of the upper and lower directions due to structural restrictions. For example, as shown in FIG. 1 (b), the upper roll 11 has a bias angle θ ₁ of a maximum θ _max clockwise when viewed from above.
If it is possible, the lower limit of θ ₁ is 0 ° as shown in FIG. For the lower roll 12, the deviation angle is −
θ _max ≦ θ ₂ ≦ 0 ° are possible range. Therefore, if, for example, θ _max is 1.2 ° and the intersection angle η is 1.0 °, the control range of the average angle ζ is limited to ± 0.5 °. Conversely, when the intersection angle η is 1.0 °, the average angle ζ is 0.4 °
In this case, even if the crossing angle is reduced in accordance with the change in the rolling conditions, the crossing angle cannot be reduced to 0.8 ° or less, and the original purpose of the cross rolling may interfere with the sheet leaning control.

Further, when the cross rolling is performed cold, there is a phenomenon that the glossiness of the surface of the metal strip is improved, and the cross rolling may be performed for the purpose. In this case, if the average angle ζ is added, the cross angle of the roll differs between the upper and lower rolls with respect to the metal strip, and there is also a problem that a difference occurs in the glossiness of the upper and lower surfaces of the metal strip.

[0012] In view of the above-mentioned problems, an object of the present invention is to provide:
It is an object of the present invention to provide a method and an apparatus for controlling and preventing leaning of a metal strip while maintaining a shape control effect, a surface gloss control effect, and the like in cross rolling of a metal strip.

[0013]

SUMMARY OF THE INVENTION In a rolling mill using a rolling lubricating oil such as a cold rolling of a steel strip, when the vertical angle of entry of the metal strip into the rolling mill changes,
It has been found that the friction state between the metal strip and the work roll differs between the upper and lower rolls.

On the other hand, in the cross rolling, when the friction state of the upper and lower rolls is different, the thrust force acting in the body length direction of the roll is different in the upper and lower directions, and the friction force in the width direction acting on the metal band is also different in the upper and lower surfaces. I found to come. Therefore,
It has been found that if these relationships are used, the leaning of the metal strip during cross rolling can be controlled by controlling the angle of entry into the rolling mill.

[0015] The gist of the present invention is "a cross-rolling prevention method for a cross-rolling characterized by changing a vertical approach angle when a metal strip enters a rolling mill to control the direction of the sheet-rolling".
And `` an apparatus for detecting a leaning of a metal strip installed on the exit side of a cross rolling mill, and an approach angle for changing the vertical approach angle when the metal strip installed on the entry side of the cross rolling mill enters the rolling mill. A cross-rolling plate shift prevention device, comprising: a change device; and a mechanism for controlling the approach angle changing device in accordance with the amount of plate shift detected by the plate shift detection device.
It is in.

[0016]

FIG. 2 is a schematic view for explaining the relationship between the bite angle α and the approach angle β at the portion where the metal strip 2 is bitten between the rolls.

Usually, the metal strip 2 is composed of upper and lower work rolls 11, 1
In the gap of No. 2, the vehicle enters in a straight direction (in a direction perpendicular to a line connecting the centers of the upper and lower work rolls) represented by a thick solid line in FIG. At this time, the biting angle α is an angle formed between the tangential direction of the roll surface at the biting point (represented by a thin solid line in the figure) and the metal band. The entry angle β of the metal strip is, for example, an angle formed between the direction of the metal strip when the metal strip enters straight when the metal strip is pressed down on the entry side of the rolling mill (indicated by a thick dotted line in the drawing). .

[0018] During rolling, the approach angle of the metal strip 2 beta is changed in the vertical direction, (the upper roll 11 α → α _1, the lower roll 12 α → α ₂₎ different states bite angle alpha with the vertical becomes Therefore, a difference occurs in the amount of lubricating oil drawn in. As a result, the coefficient of friction between the roll and the metal strip contact surface changes. For example, when the metal band 2 is pushed down on the entrance side, the amount of lubricating oil drawn in on the lower surface of the metal band increases, the friction coefficient decreases, and the amount of lubricating oil drawn in on the upper surface decreases, increasing the friction coefficient.

FIG. 3 (a) shows the result of a calculation simulation using a rolling model for the relationship between the difference in the frictional force in the width direction of the upper and lower rolls (the lower roll frictional force-the upper roll frictional force) with respect to the entry angle β of the metal band. Show. Normally, the approach angle β is zero, the engagement angles of the upper and lower rolls are equal, and the width direction frictional force against the metal band (the roll axial direction thrust force in the opposite directions to the roll) is balanced in a state where there is no board deviation. I have.

When the approach angle β is changed, a difference occurs in the frictional force between the upper and lower rolls in the width direction. The metal strip moves in the direction of the deviation angle of the roll having the larger frictional force, and the sheet shifts.
The change rate of the difference in the frictional force with respect to the change in the approach angle β increases as the intersection angle increases.

The present invention utilizes this characteristic to control the leaning by changing the approach angle of the metal strip in cross rolling. For example, in a cross rolling mill in which the upper work roll is deflected to the right (clockwise direction) and the lower work roll is deflected to the left (counterclockwise) as viewed from the rolling direction, the lower surface of the roll is crossed by some factor. When the force increases, the metal band shifts in the direction of the deviation angle (left side) of the lower roll. At this time, if the metal band is pushed downward on the entry side (this state is defined as a negative approach angle), the leftward frictional force on the lower surface decreases, and the rightward frictional force increases on the upper surface. Returned to the direction.

In cold rolling, the frictional force tends to increase because the lubricating oil is usually less adhered to the lower surface.
In some cases, the roughness of one side of the steel sheet is always slightly larger than that of the other side due to the rolling in the previous step. Since the difference between the frictional forces of the upper and lower rolls is constantly present as described above, the cross rolling often causes the sheet to always lean in one direction.

FIG. 3B is a graph showing the difference in the frictional force in the width direction when the frictional force of the lower surface of the metal band is larger than that of the upper surface. The upper and lower rolls have a state in which the average angle is zero, and a state in which a difference in frictional force is generated on the left side of the traveling direction (direction of the declination angle of the lower roll). In this state, the metal band leans toward the left in the traveling direction. In this state, if the approach angle β is set to the minus side (the side where the entry side of the metal strip is pushed down), the difference in the frictional force between the upper and lower rolls becomes smaller, and this indicates that the board lean can be eliminated.

[0024]

FIG. 4 is a block diagram showing an example of a single-stand steel strip rolling mill as an example of the apparatus of the present invention. In this example, the metal strip 2 is represented by a steel strip 2. FIG. 1 shows a four-high rolling mill as an example of the rolling mill 10 in which the rolls are arranged in a line in the vertical direction. In the example of FIG.
Reference numeral 72 designates a bias angle in conjunction with the work rolls 11 and 12, respectively. Regarding the operation of the present invention, 2
There is no difference between a high-speed rolling mill, a six-high rolling mill, and a rolling mill having a tandem arrangement of a plurality of stands.

A plate shift detector 6 is provided on the exit side of the rolling mill. As the board-side detector 6, for example, a non-contact type optical detector can be used. The board shift amount signal of the detector 6 is input to the control device 8. The arithmetic output of the control device 8 gives a signal for operating the approach angle changing device.

The approach angle changing device includes, for example, a hydraulic cylinder 9 and two approach angle changing rolls 31 as shown in FIG.
31. In FIG.
Reference numeral 2 denotes a pinch of a steel strip, which is directly connected to a hydraulic cylinder, and the approach angle β can be changed by moving the steel strip 2 up and down on the rolling mill entry side. The rolls 31 and 32 do not always need to pinch the steel strip 2, and the roll interval may be set to be larger than the maximum thickness of the metal strip 2.

The roll angle of the approach angle changing device may be such that a fixed roll on the upstream side of the rolling mill is previously shifted downward from the pass line, and is pushed up only from below the metal strip 2 by the elevating roll.

When the fixed roll 5 forms a part of the tension meter, the fixed roll 5 is fixed as shown in FIG. 4 so that the operation of the lifting rolls 31 and 32 does not change the contact angle of the steel strip with the roll 5 of the tension meter. It is necessary to consider the roll 4, etc.

Next, an embodiment of the method of the present invention will be described. The board shift amount signal of the detector 6 is input to the control device 8. The control operation of the control device 8 was proportional-integral control. However, the control gain of the control device 8 is not constant but depends on the intersection angle. The reason is as follows.

As shown in FIG. 3A, when the intersection angle η is small, the change in the difference in the frictional force is small with respect to the change in the approach angle β. In an extreme case, when the intersection angle η is zero, the approach angle β
No matter how much is changed, the difference in the frictional force in the width direction does not change. Therefore, the leaning control of the control device 8 is performed when the intersection angle η is 0.2.
° is valid only when it is more than
That is, the lifting rolls 31 and 32 are fixed at the current position. Further, the control gain of the lifting rolls 31 and 32 is set to be inversely proportional to the intersection angle η. For example, when the crossing angle is 1.0 °, the lifting speed of the lifting roll is 2.0
The control gain of the control device 8 was changed so that the speed was twice as high as that in the case of °.

Under the above preparation, test rolling was performed. The work roll diameter of the cross mill was 470 mm. As the steel strip 2, a low carbon steel strip having a thickness of 3.2 mm on the entry side and a width of 1000 mm was rolled at a rolling reduction of 20%. Roll peripheral speed is 94mpm,
The entrance tension was 1.8 kgf / mm ² and the exit tension was 9.6 kgf / mm ² . Crossing angles of upper and lower work rolls are 0.4 °, 0.8 °, 1.2
°, the control was performed from a state where the board lean was stable under each condition.

FIG. 5 shows the time variation of the crossing angle, the approach angle, and the board deviation amount in the rolling test. FIGS. 5 (a1), (b1), and (c1) show the approach angle β of the steel strip 2 when the intersection angle η is 0.4 °, 0.8 °, and 1.2 °, respectively, and FIGS. 5 (a2), (b2), (c2) represents a board-side situation. According to FIG. 5, the board leaning has a slight response delay to the change of the approach angle, but responds well, and in any case, the direction of the board lean is corrected by changing the approach angle within ± 3.0 °. We were able to. Also, comparing the change amount of the approach angle β with the change amount of the board side, the larger the intersection angle, the larger β
It was found that the amount of board shift greatly changed with the change of.

[0033]

According to the rolling method of the present invention, it is possible to prevent the leaning of the plate by a relatively simple device without impairing the plate shape control function and the surface gloss improving function of the roll cloth type rolling mill. It is possible to stably produce high-quality steel sheets.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic explanatory view showing the positional relationship of cross-rolling rolls. FIG. 1 (a) shows the relationship between the upper and lower roll angles, and FIG. 1 (b) shows the upper roll deflection angle θ ₁ having a maximum θ. changeable range of the average angle ζ when the _max, FIG (c) is lower roll bias angle theta ₂
Indicates the range in which the average angle ζ can be changed when is the maximum (−θ _max ).

FIG. 2 is a schematic explanatory view showing a relationship between an entry angle of a metal band and a bite angle.

3 is a graph showing a change in a difference in a frictional force in a width direction with respect to a change in an entering angle of a metal band. FIG. 3 (a) shows a case where there is no board leaning, and FIG. 3 (b) shows a case where there is a board leaning. .

FIG. 4 is a layout view of an apparatus for performing the rolling method of the present invention.

5 (a1), (b1), and (c1) are time-lapse graphs showing the results of the embodiment of the board leaning control according to the present invention, in which the crossing angles η are 0.4 °, 0.8 °, and 1.2 °, respectively. 5 (a2), 5 (b2) and 5 (c2) show the approaching state of the plate.

[Explanation of symbols]

11, 12: Work roll 2: Metal strip 31, 32: Elevating roll for changing the entry angle of the metal strip 5: Tensiometer sensor roll 6: Board-side sensor 71, 72: Backup roll 8: Control device 9: Elevating roll Hydraulic cylinder for

Claims (2)

[Claims] 1. A method for preventing cross-rolling in a cross-rolling method, comprising changing a vertical approach angle when a metal strip enters a rolling mill to control the direction of the sheet-rolling. 2. A device for detecting a deviation of a metal strip placed on the exit side of a cross rolling mill, and changing a vertical approach angle when the metal strip installed on the entry side of the cross rolling mill enters the rolling mill. And a mechanism for controlling the approach angle changing device according to the amount of the approach angle detected by the approach angle detection device.