JPH06277727A - Method for controlling plate crown - Google Patents

Abstract

PURPOSE:To provide a method for controlling a plate crown capable of obtaining nearly the same plate crown control ability irrespective of the moving positions in the axial directions of upper and lower work rolls. CONSTITUTION:An early profile of nearly the same shape is given to each of the upper and lower work rolls so that they are point symmetry, the upper and lower work rolls are moved in the reverse direction to each other along the axial direction and a bending force is actuated to the work rolls to control the plate crown. In this case, when the early profiles given to the upper and lower work rolls are given by a quartic expression, change of an equivalent roll crown quantity B defined by a difference between a value in the central position in the directions of the roll axes of a gap between the upper and lower work rolls and a value in the evaluation position of an arbitrary roll gap is shown by a quadratic expression to the movements in the axial directions of the work rolls.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a sheet crown of a metal sheet, and more particularly to a method for controlling a sheet crown by a rolling mill incorporating a work roll movable in the axial direction.

[0002]

2. Description of the Related Art Various methods have been proposed as a method for controlling a strip crown in strip rolling. Particularly, as a plate crown control method by a rolling mill incorporating a work roll movable in the axial direction, for example, Japanese Patent Publication No. 63-62283 discloses a work roll provided with a point-symmetric initial profile. A method of changing the roll axial distribution of the roll gap when the roll is moved is known. As the initial profile to be applied to the work roll, a method of using a cubic formula whose roll shape is schematically shown in FIG. 7 is generally practiced, and the principle thereof will be described below.

The profile given to the side of the upper work roll that contacts the reinforcing roll is expressed by the following cubic equation. R (x) = ax ³ + bx ² + cx x = X / (L / 2) where X: distance from the axial center position of the work roll,
L: work roll cylinder length, a, b, c: coefficient The profile of the upper work roll 11 on the side in contact with the rolled material 13 is given by the following equation.

R _u (x) = − ax ³ −bx ² −cx Further, the profile of the side of the lower work roll 12 in contact with the rolled material 13 is given by the following equation. R _L (x) = − ax ³ + bx ² −cx Therefore, when the upper and lower work rolls 11 and 12 are moved in the opposite directions by S, the distribution of the upper and lower work roll gaps in the roll axial direction is as follows. Become.

[0005] _{G (x) = R u (} x-s) -R L (x + s) = As can be seen from ^{(6as-2b) x 2 +} ( constant term) s = S / (L / 2) the above equation, The roll gap becomes a quadratic expression along the roll axial direction. If the plate crown control capability is represented by an equivalent roll crown defined by a difference between a value at an axial center position of the roll gap and a value at an arbitrary roll gap evaluation position, the amount thereof is a coefficient a representing an initial profile, b and the work roll movement amount S.

[0006]

SUMMARY OF THE INVENTION In the above prior art,
Since G (x) is expressed by a linear expression with respect to s, as shown in FIG. 8, the equivalent roll crown, that is, the plate crown control capability, changes linearly with respect to the axial movement position of the work roll. Therefore, in the case of continuous rolling of a material that requires a large plate crown control capability, in order to secure the plate crown of all the materials, the moving positions of the rolls have to be almost the same,
The other purpose of the axial movement of the work roll, the function of wear of the work roll and smoothing of the thermal crown, cannot be fulfilled. On the contrary, if the work roll moving position is changed so that the wear and the thermal crown are smoothed, there are cases in which sufficient plate crown control capability cannot be obtained.

An object of the present invention is to provide a plate crown control method capable of obtaining substantially the same plate crown control ability regardless of the axial movement positions of the upper and lower work rolls.

[0008]

In order to achieve the above object, the present invention provides the upper and lower work rolls of a rolling mill with initial profiles of substantially the same shape so as to be point-symmetric with respect to each other. In the method of controlling the plate crown by moving the upper and lower work rolls in opposite directions along the axial direction and applying a bending force to the work roll, an initial profile given to the upper and lower work rolls is expressed by a quaternary equation. As a result, the equivalent roll crown amount defined by the difference between the value at the roll axial center position of the gap between the upper and lower work rolls and the value at any roll gap evaluation position is the axial movement position of the work roll. In contrast, the quadratic equation is changed.

[0009]

The function of the present invention will be described below. When the roll profile is expressed by the following quartic equation, R (x) = ax ⁴ + bx ² + cx ² + dx ────────────────── (1) The gap distribution between the work rolls is given by the following equation.

G (x) =-2ax ⁴ + (6bs-2c-12as ² ) x ² + (constant value)-(2) In the above equation, the quadratic term of the work roll movement amount s is a coefficient of x ^2. Is included, the equivalent roll crown changes quadratically with respect to the axial movement position of the work roll. Therefore, for example, as shown in FIG. 1, the equivalent roll crown B is small in the work roll moving region m where the plate crown control capability A due to the work roll bending force is large, and the equivalent roll crown B is equivalent in the region n where the control capability A due to the bending force is small. By selecting the coefficients a, b, and c so that the roll crown B becomes large, the equivalent roll crown change due to the movement of the work roll and the plate crown control ability C due to the combination of the bending force become substantially the same regardless of the roll movement position. You can For the wear of the work rolls and the smoothing of the thermal crown, it is preferable that the moving range of the upper and lower work rolls is large, preferably 300 mm or more.

Further, as the initial profile given to the work roll has a higher degree of polynomial, it becomes more difficult to grind the roll more accurately. Therefore, according to the present invention, the equivalent roll crown is moved with respect to the axial movement position of the work roll. A quartic equation, which is the minimum order that can be changed in a curve, was used.

[0012]

EXAMPLE Next, an example in which the present invention is applied to a post-stand of a hot finish rolling mill train will be described. FIG. 2 shows a hot rolling mill train embodying the present invention. The rolling mill train consists of seven stands, and the first to third stands are four-high rolling mills 1,2,3 with conventional upper and lower work rolls 8,8.
The fourth to seventh stands are rolling mills 4, which are provided with upper and lower work rolls 9 and 9 that can move in the axial direction.
5,6,7 with powerful work roll bending equipment. Axial movement of work roll is -300 to 300 mm
The bending force is 210 tons per chock, and the work roll body length is 2186mm. 10 indicates a rolled material.

The initial profile applied to the work roll is
It is expressed by equation (1). Of the coefficients a, b, c, d, three conditions are required to determine the coefficients a, b, c related to the plate crown control capability. Therefore, the roll gap evaluation position is set at a position 25 mm (plate crown evaluation point) from the plate width end of the material with a plate width of 1250 mm, and when the absolute value of the work roll movement amount is large, the plate crown control ability by the bending force is considered Then, 1) when S = 300 mm, equivalent roll crown = 45 μm 2) when S = 0 mm, equivalent roll crown = 90 μm 3) when S = −300 mm, the condition that equivalent roll crown = 45 μm was set. By substituting these conditions into Eq. (2) and solving the simultaneous equations, the coefficients a, b, and c are obtained as follows. Since the coefficient d is not related to the plate crown controllability, it can be arbitrarily selected.

A = 0.1652 b = 0 c = -0.1991 FIG. 3 shows the relationship between the roll gap distribution and the roll movement amount when this coefficient is used. However, since the upper and lower rolls move in opposite directions, only the area where the upper and lower rolls overlap is shown. The roll gap has a quartic distribution, but in the region where the plate is actually rolled (the roll gap region shown in the figure-100 mm), the distribution increases almost monotonically.

FIG. 4 shows the relationship between the equivalent roll crown and the amount of roll movement when the roll gap evaluation position is 1200 mm.
It can be seen that the equivalent roll crown changes quadratically with respect to the amount of roll movement. FIG. 5 schematically shows the shape of the work roll 9 to which d = 0 and the initial profile is given by using the coefficients a, b, and c determined as described above. However, the region of the body end portion not in contact with the rolled material 10 may be changed to have a flat shape or the like in order to avoid concentration of contact pressure with the reinforcing roll.

Next, as another embodiment, a case where the axial movement amount of the work roll is 0 to 600 mm will be described. The conditions for determining the coefficients a, b, and c were set as follows. 1) When S = 600mm, equivalent roll crown at 900mm position = 0μm 2) When S = 300mm, equivalent roll crown at 1200mm position = 60μm 3) When S = 0mm, equivalent roll crown at 1200mm position = 90 μm In this case, when S = 600 mm, the overlapping length of the upper and lower work rolls was 986 mm, so the evaluation position was 900 mm.

At this time, the coefficients a, b and c are as follows, and the roll shape when a = 0.0645 b = -0.0251 c = -0.1688 d = 0 is as shown in FIG.

Further, in the present embodiment, the case where the present invention is applied to the latter stage stand of the hot rolling mill train has been described.
It goes without saying that the present invention can be applied to a front stand of a hot rolling mill train and other rolling mills.

[0019]

As described above, according to the present invention, the initial profile given to the upper and lower work rolls is of the quaternary formula, so that the same plate can be obtained regardless of the axial movement positions of the upper and lower work rolls. Since the crown control ability can be obtained, it is possible to achieve both wear of the work roll and smoothing of the thermal crown and plate crown control at the same time, which in turn can greatly contribute to the improvement of yield by reducing the plate crown. .

[Brief description of drawings]

FIG. 1 is a conceptual diagram of plate crown control ability according to the present invention.

FIG. 2 is a schematic view of a hot rolling mill train according to the present invention.

FIG. 3 is a diagram showing a relationship between a roll gap distribution and a roll movement amount in the example.

FIG. 4 is a diagram illustrating a relationship between an equivalent roll crown and a roll movement amount according to the embodiment.

FIG. 5 is a schematic view of a work roll provided with an initial profile according to an embodiment.

FIG. 6 is a schematic view of a work roll provided with an initial profile according to another embodiment.

FIG. 7 is a schematic view of a conventional work roll provided with an initial profile.

FIG. 8 is a conceptual diagram of plate crown control ability by a conventional method.

[Explanation of symbols]

A Plate crown controllability by work roll bending force B Equivalent roll crown C Plate crown controllability by combination 4,5,6,7 Rolling machine equipped with work rolls that can move in 9 axial directions 9 Can move in axial directions Work roll

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location B21B 31/18 A 8727-4E

Claims (1)

[Claims] 1. An upper profile and a lower work roll of a rolling mill are provided with initial profiles having substantially the same shape so as to be point-symmetric with respect to each other, and the upper and lower work rolls are moved in opposite directions along an axial direction. In addition, in the method of controlling the plate crown by applying a bending force to the work rolls, the initial profile given to the upper and lower work rolls is
By using the following formula, the equivalent roll crown amount defined by the difference between the value at the central position in the roll axial direction of the gap between the upper and lower work rolls and the value at the arbitrary roll gap evaluation position is the axial direction of the work rolls. A plate crown control method characterized in that a quadratic expression is changed with respect to a moving position.