JP7226402B2 - Metal strip rolling control method, rolling control device, and manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a metal strip rolling control method, a rolling control apparatus, and a manufacturing method.

In a general metal strip rolling process, in order to produce a flat metal strip, the flatness of the metal strip during rolling is measured in real time, and a shape control actuator is used to ensure that the measured flatness matches the target value. is being manipulated. However, if the flatness of the metal strip before rolling is extremely poor, even if the shape of the metal strip after rolling is controlled to be flat, linear flaws called constrictions may occur in the metal strip. When the drawn portion of the metal strip is rolled, the rolling rolls may be damaged, and loss of time due to replacement of the rolling rolls may occur, resulting in a decrease in production efficiency.

In general, the flatness of a metal strip is represented by steepness, differential elongation, and I-Unit. Specifically, the steepness λ′ is represented by the ratio between the wave height δ of the metal band S shown in FIG. 5 and the wave pitch L, as shown in the following formula (1). The differential expansion rate Δε is represented by the ratio of the differential expansion ΔL of the metal band S shown in FIG. Further, when the shape of the metal strip S is approximated by a sine curve, the steepness λ' and the differential expansion rate Δε have the relationship shown in the following formula (3). Further, I-Unit is a value obtained by multiplying the differential elongation rate Δε by 10 to the 5th power as shown in the following formula (4).

As a method for measuring the flatness of the metal strip during rolling, for example, a flatness meter with a disk structure in which the rolling roll is divided in the width direction and a load detection sensor is embedded in each is used to measure the distance between the metal strip and the rolling roll. There is a method of calculating the shape of the metal strip by measuring the contact load of the metal strip. In addition, as a shape control actuator, in order to control the shape of the metal strip by changing the axial deflection of the work roll, there is a roll bender mechanism that applies a bending force to both ends of the work roll, and a single tapered intermediate roll that moves in the width direction. There is an intermediate roll shift mechanism that shifts to There is also a VC (Variable Crown) roll mechanism that operates the roll crown by hydraulic pressure.

On the other hand, in Patent Document 1, especially in the skin pass rolling process after hot rolling, the change in the shape (flatness) of the metal strip in the hot rolling process, the cooling process, and the winding process is predicted, and the skin pass rolling process is performed. Rolling control methods have been proposed to determine set values so as to optimize the shape of the metal strip after the process.

JP 2016-49553 A

However, the rolling control method described in Patent Document 1 performs rolling control only from the viewpoint of controlling the flatness of the metal strip, and does not perform rolling control from the viewpoint of preventing rolling (restriction) of the narrowed portion.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a metal strip rolling control method, a rolling control apparatus, and a manufacturing method capable of suppressing the occurrence of narrowing.

A metal strip rolling control method according to the present invention includes a calculation step of calculating the twist, C-warp, and edge elongation of the metal strip on the entry side of the rolling mill; , and when at least one of the edge elongation is equal to or greater than a predetermined threshold, a rolling control step of relatively increasing the reduction amount of the width direction center portion with respect to the reduction amount of the width direction end portions of the metal strip. and

A metal strip rolling control apparatus according to the present invention comprises measuring means for measuring the height distribution in the width direction of the metal strip at the entry side of the rolling mill, and the height distribution in the width direction of the metal strip measured by the measuring means. Calculate the twist, C warp, and edge elongation of the metal strip on the entry side of the rolling mill from, and if at least one of the calculated twist, C warp, and edge elongation is a predetermined threshold or more, the metal strip and a control means for relatively increasing the amount of reduction in the center portion in the width direction with respect to the amount of reduction in the end portions in the width direction.

A method for manufacturing a metal strip according to the present invention is characterized by including the step of manufacturing a metal strip using the rolling control method for a metal strip according to the present invention.

According to the metal strip rolling control method, rolling control apparatus, and manufacturing method according to the present invention, it is possible to suppress the occurrence of drawing.

FIG. 1 is a schematic diagram showing a configuration example of a rolling mill to which a metal strip rolling control method according to an embodiment of the present invention is applied. FIG. 2 is a flow chart showing the flow of rolling control processing, which is one embodiment of the present invention. FIG. 3 is a diagram for explaining the twist and C-warp of the metal band. FIG. 4 is a diagram for explaining the twist and C warp of the metal band. FIG. 5 is a diagram for explaining the steepness and the differential expansion rate of the metal band.

BEST MODE FOR CARRYING OUT THE INVENTION A metal strip rolling control method according to an embodiment of the present invention will be described below with reference to the drawings.

[Configuration of rolling mill]
First, with reference to FIG. 1, the configuration of a rolling mill to which a metal strip rolling control method according to an embodiment of the present invention is applied will be described.

FIG. 1 is a schematic diagram showing a configuration example of a rolling mill to which a rolling control method according to an embodiment of the present invention is applied. As shown in FIG. 1, a rolling mill 1 to which a method for controlling rolling of a metal strip according to an embodiment of the present invention is applied, rolls a metal strip S while paying out and winding a metal strip S using reels 2a and 2b. It is a four-high rolling mill that corrects the shape of the metal strip S by rolling the strip S, and includes a pair of work rolls 3a and 3b, a pair of backup rolls 4a and 4b, a laser scanner 5, a flatness meter 6, and a controller. A device 7 is provided.

The pair of work rolls 3a and 3b are arranged to face each other in the thickness direction of the metal strip S across a transport path for transporting the metal strip S in the direction of the arrow. The work rolls 3a and 3b continuously roll the metal strip S by rotating (rotating) while sandwiching the metal strip S successively transported along the transport path in the plate thickness direction.

A pair of backup rolls 4a and 4b are arranged to face each other with a pair of work rolls 3a and 3b interposed therebetween. The upper backup roll 4a contacts the outer peripheral surface of the upper work roll 3a from above and presses the upper work roll 3a downward. Thereby, the upper backup roll 4a applies the load required for rolling the metal strip S to the upper work roll 3a. Further, the lower backup roll 4b contacts the outer peripheral surface of the lower work roll 3b from below and presses the lower work roll 3b upward. As a result, the lower backup roll 4b applies the load required for rolling the metal strip S to the lower work roll 3b.

Although not shown, a roll bender mechanism is connected to the pair of backup rolls 4a and 4b as a shape control actuator. The roll bender mechanism functions as a shape control section that controls the shape of the metal strip S after being rolled by the rolling mill 1 . Specifically, the roll bender mechanism bends or tilts the pair of work rolls 3a and 3b via the pair of backup rolls 4a and 4b, thereby changing the shape of the metal strip S after rolling by the rolling mill 1. Control. Operation of the roll bender mechanism is controlled by the controller 7 .

The laser scanner 5 is composed of a two-dimensional or three-dimensional laser scanner and is installed on the entry side of the rolling mill 1 . The laser scanner 5 measures the height distribution in the width direction of the metal strip S at the entry side of the rolling mill 1 and inputs an electrical signal indicating the measured height distribution in the width direction to the control device 7 . It is desirable that the height distribution of the metal strip S is measured at a position as close as possible to the work rolls 3a and 3b on the entrance side of the rolling mill 1 so that signs of drawing can be detected at an early stage. Also, in order to prevent detection errors due to accumulation of dust on the detection section of the laser scanner 5, it is desirable to install the laser scanner 5 so that the detection section faces downward as much as possible. An imaging device may be installed instead of the laser scanner 5, and the height distribution of the metal pairs S may be measured by image analysis.

The flatness meter 6 is configured by a roll-type flatness meter and installed on the delivery side of the rolling mill 1 . The flatness meter 6 measures the shape of the metal strip S on the delivery side of the rolling mill 1 and inputs an electrical signal indicating the measured shape to the control device 7 .

The control device 7 is composed of an information processing device such as a computer, and controls the operation of the entire rolling mill 1 using electrical signals input from the laser scanner 5 and the flatness meter 6 . Further, in the present embodiment, the control device 7 suppresses the occurrence of reduction by executing the rolling control process described below.

[Rolling control processing]
Next, with reference to FIG. 2, the operation of the control device 7 when executing the rolling control process will be described.

FIG. 2 is a flow chart showing the flow of rolling control processing, which is one embodiment of the present invention. In FIG. 2, the rolling control process starts at the timing when a command to execute the rolling control process is input to the control device 7, and the rolling control process proceeds to the process of step S1. This rolling control process is repeatedly executed at predetermined control cycles until the rolling process of the metal strip S is completed or stopped.

In the process of step S<b>1 , the control device 7 calculates the twist of the metal strip S based on the height distribution in the width direction of the metal strip S at the entry side of the rolling mill 1 measured by the laser scanner 5 . Specifically, as shown in FIG. 3, the control device 7 calculates the inclination θ of the straight line L1 connecting both ends in the width direction of the metal band S with respect to the horizontal direction (straight line L2) as the twist. However, the torsion may be an index that expresses the inclination of the metal band S with respect to the horizontal direction. For example, as shown in FIG. The coefficient b of the term may be defined as the twist, and the sum e+g of the coefficient e of the third term and the coefficient g of the first term when the height distribution L3 of the metal band S is approximated by a quartic curve is It may be defined as torsion. Thereby, the process of step S1 is completed, and the rolling control process proceeds to the process of step S2.

In the process of step S<b>2 , the controller 7 calculates the C warp of the metal strip S based on the height distribution in the width direction of the metal strip S at the entry side of the rolling mill 1 measured by the laser scanner 5 . Specifically, as shown in FIG. 3, the control device 7 calculates the distance H between a straight line L1 connecting both ends of the metal band S in the width direction and the central portion of the metal band S in the width direction as C warp. do. However, the C warp may be an index that expresses the difference between the height of the widthwise end portion and the height of the widthwise center portion of the metal band S. For example, as shown in FIG. 4, the height distribution of the metal band S The coefficient a of the secondary term when L3 is approximated by a quadratic curve may be defined as the C warp, or the coefficient a of the quartic term when the height distribution L3 of the metal band S is approximated by a quartic curve. The sum d+f of the coefficient d and the coefficient f of the second-order term may be defined as the C warp. Thereby, the process of step S2 is completed, and the rolling control process proceeds to the process of step S3.

In the process of step S<b>3 , the control device 7 calculates the edge elongation of the metal strip S based on the height distribution in the width direction of the metal strip S at the entry side of the rolling mill 1 measured by the laser scanner 5 . Here, the edge elongation is not particularly limited as long as it is an index that expresses a state in which the edge portions in the width direction are more elongated than the elongation in the center portion in the width direction of the metal band S. For example, indices such as steepness λ′, differential expansion rate Δε, I-Unit, wave height δ, and the like can be used. Thereby, the process of step S3 is completed, and the rolling control process proceeds to the process of step S4.

In the process of step S4, the control device 7 controls the torsion of the metal band S calculated in the process of step S1, the C warp of the metal band S calculated in the process of step S2, and the metal band S calculated in the process of step S3. It is determined whether or not at least one of the edge extensions of the band S is equal to or greater than a threshold. As a result of determination, when at least one is equal to or greater than the threshold (step S4: Yes), the control device 7 advances the rolling control process to the process of step S5. On the other hand, if none of them is equal to or greater than the threshold (step S4: No), the control device 7 terminates the series of rolling control processes. It should be noted that the above threshold value is a value that varies according to the rolling conditions of the rolling mill 1, and is determined in advance based on the actual rolling performance.

In the process of step S5, the control device 7 controls the shape control actuator to relatively increase the amount of reduction in the widthwise central portion with respect to the amount of reduction in the widthwise end portions. Here, the shape control actuator may be any device capable of pressing down the central portion in the width direction of the metal strip S, and examples thereof include a roll bender mechanism, an intermediate roll shift mechanism, an As-U mechanism, and a VC roll. When a metal strip S having a large edge elongation is rolled, the width direction end portions of the metal strip S are stretched more than the width direction center portion, and out-of-plane deformation occurs at the width direction end portions. Directly under the roll, this out-of-plane deformation is forcibly flattened, and in order to make the elongation of the ends in the width direction uniform, compressive stress is applied to the ends in the width direction where elongation is large, and tensile stress is applied to the central portion in the width direction where elongation is small. Occur. As a result, the stress difference between the widthwise end portions and the widthwise central portion causes shear buckling and constriction. Therefore, in the rolling control process of the present embodiment, the shape control actuator is controlled so as to relatively increase the amount of rolling reduction at the center portion in the width direction with respect to the amount of rolling reduction at the end portions in the width direction. This reduces the elongation of the widthwise end portions on the delivery side of the rolling mill, and alleviates the large elongation of the widthwise end portions on the entry side of the rolling mill, thereby suppressing the occurrence of drawing. As a result, the processing of step S5 is completed, and the series of rolling control processing ends.

As is clear from the above description, in the rolling control process, which is one embodiment of the present invention, the control device 7 calculates the twist, C warp, and edge elongation of the metal strip S on the entry side of the rolling mill 1, When at least one of the calculated twist, C warp, and edge elongation of the metal band S is equal to or greater than a predetermined threshold value, the amount of reduction in the widthwise central portion of the metal band S relative to the amount of reduction in the widthwise end portions is calculated. Since it is made large, it is possible to suppress the occurrence of diaphragm.

[Example 1]
A mild steel plate having an entry side thickness of 1.400 mm, an exit side thickness of 1.386 mm and a width of 1100 mm was rolled. The unit tension was set to 20 MPa on the entry side and 40 MPa on the exit side. The rolling mill shown in FIG. 1 was used. The rolling mill has a work roll diameter of Φ450 mm and a backup roll diameter of Φ1200 mm. The rolling mill is equipped with work roll benders as shape control actuators. A roll-type flatness meter is installed on the delivery side of the rolling mill, and the shape of the mild steel plate on the delivery side of the rolling mill can be measured. There is a two-dimensional laser scanner on the entrance side of the rolling mill, which can measure the height distribution in the width direction of the mild steel plate. The distance between the straight line connecting both ends in the width direction of the mild steel plate and the center in the width direction is defined as C warp, and the inclination of the straight line connecting both ends in the width direction of the mild steel plate with respect to the horizontal direction is defined as twist. Based on the results of coils that could be rolled without any problems, it was determined that a C warp of 20 mm or more and a twist of 0.05 rad or more were signs of the occurrence of drawing. Both the C warp and twist were measured, and when there was a sign of drawing, the work roll bender was operated to roll down the widthwise central portion of the mild steel plate. When there was no indication of drawing, the work roll bender was operated so that the shape of the mild steel sheet after rolling measured by the flatness meter on the delivery side was flattened as much as possible. As a result of the experiment, reduction occurred in 3 coils after rolling 500 coils in the conventional operation, but no reduction occurred after rolling 2500 coils by applying the present invention.

[Example 2]
A mild steel plate having an entry side thickness of 1.400 mm, an exit side thickness of 1.386 mm and a width of 1100 mm was rolled. The unit tension was set to 20 MPa on the entry side and 40 MPa on the exit side. The rolling mill shown in FIG. 1 was used. The rolling mill has a work roll diameter of Φ450 mm and a backup roll diameter of Φ1200 mm. The rolling mill is equipped with work roll benders as shape control actuators. There is a roll-type flatness meter on the delivery side of the rolling mill, and the shape of the mild steel plate on the delivery side of the rolling mill can be measured. There is a two-dimensional laser scanner on the entrance side of the rolling mill, which can measure the height distribution in the width direction of the mild steel plate. I-Unit was used as an index representing the degree of ear elongation. I-Unit is calculated as a relative value with the elongation at the center in the width direction as zero, and the I-Unit at the end in the width direction is 50 or more based on the results of coils that have been rolled without reduction in the past. was determined to be a sign of the occurrence of squeezing. When there was a sign of occurrence of drawing, the work roll bender was operated to roll down the widthwise central portion of the mild steel plate. In addition, when there was no indication of drawing, the work roll bender was operated so that the shape of the mild steel sheet after rolling measured by the flatness meter on the delivery side was as flat as possible. As a result of the experiment, reduction occurred in 3 coils after rolling 500 coils in the conventional operation, but no reduction occurred after rolling 1000 coils by applying the present invention.

Although the embodiments to which the inventions made by the present inventors are applied have been described above, the present invention is not limited by the descriptions and drawings forming part of the disclosure of the present invention according to the embodiments. That is, other embodiments, examples, operation techniques, etc. made by those skilled in the art based on this embodiment are all included in the scope of the present invention.

1 rolling mill 2a, 2b reel 3a, 3b work roll 4a, 4b backup roll 5 laser scanner 6 flatness meter 7 controller S metal strip

Claims (3)

a calculation step of calculating the torsion, C-warp, and edge elongation of the metal strip on the entry side of the rolling mill;
When at least one of the torsion, C warp, and edge elongation of the metal strip calculated in the calculation step is equal to or greater than a predetermined threshold value, the reduction amount of the widthwise central portion of the metal band with respect to the reduction amount of the widthwise end portions is relatively a rolling control step that increases exponentially;
A metal strip rolling control method comprising: measuring means for measuring the height distribution in the width direction of the metal strip at the entry side of the rolling mill;
From the height distribution in the width direction of the metal strip measured by the measuring means, the twist, C-warp, and edge extension of the metal strip on the entry side of the rolling mill are calculated, and the calculated twist, C-warp, and a control means for relatively increasing the amount of rolling reduction at the center portion in the width direction with respect to the amount of rolling reduction at the ends in the width direction of the metal strip when at least one of the edge stretches is equal to or greater than a predetermined threshold;
A metal strip rolling control device comprising: A method for manufacturing a metal strip, comprising the step of manufacturing a metal strip using the rolling control method for a metal strip according to claim 1 .

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