ROLLING MILL AND METHOD OF CONTROLLING THE SAME

Abstract

A rolling mill includes a roll pair, having first and second rolls, for rolling a bar steel, and first and second hydraulic cylinders for moving the first roll relative to the second roll, the first and second hydraulic cylinders being respectively connected to first and second supporting portions rotatably supporting the first roll at both ends thereof. A rolling area for rolling the bar steel, which is set as a partial continuous area in the longitudinal direction of the roll pair, is positioned so that distances from the rolling area to the supporting portions differ from each other, and the rolling mill includes: a distance sensor to measure a roll deflection in the rolling area of at least one of the rolls; and a controller to control the amount of depression of the hydraulic cylinders based on a detection value of the distance sensor.

Description

TECHNICAL FIELD

The present invention relates to a rolling mill and a method of controlling the rolling mill.

BACKGROUND ART

A rolling mill that includes a roll pair, having a first roll and a second roll, for rolling a bar steel to be rolled, and a first hydraulic press cylinder and a second hydraulic press cylinder for moving the first roll relative to the second roll, the first hydraulic press cylinder and the second hydraulic press cylinder being respectively connected to a first supporting portion and a second supporting portion that rotatably support the first roll at both ends of the first roll, has already been widely available.

There have been a problem of low accuracy in shape of the cross section of the bar steel, a problem of occurrence of a curve in the longitudinal direction of the bar steel, etc. when a rolling mill is used to roll the bar steel, in which a rolling area for rolling the bar steel, set as a partial continuous area in a longitudinal direction of the roll pair of the rolling mill, is positioned so that a distance between the first supporting portion and the rolling area and a distance between the second supporting portion and the rolling area differ from each other (the rolling mill, in which rolling is performed in the rolling area set as described above, will be referred to as the “offset rolling mill” for the sake of simplicity).

For this reason, in a conventional offset rolling mill, the position of the rolling area is detected in advance of rolling and the vertical positions of both ends of the rolls are individually set based on the position information to perform control for improving the accuracy in shape of the cross section of the bar steel (see Patent Document 1, for example).

PRIOR ART DOCUMENT

Patent Document

[Patent Document 1] Japanese Examined Utility Model Publication No. H06-46567 (JP 06-46567 Y (1994))

SUMMARY OF INVENTION

Problems to be Solved by the Invention

However, there still has been a problem of low accuracy in shape of the cross section of the bar steel in the case of conventional shape control methods used for offset rolling mills.

The present invention has been made in consideration of such a problem and an object of the present invention is to achieve highly-accurate shape control in rolling a bar steel with the use of an offset rolling mill.

Means for Solving the Problem

In order to achieve the above object, a primary aspect of the present invention is

a rolling mill that includes a roll pair, having a first roll and a second roll, for rolling a bar steel to be rolled, and a first hydraulic press cylinder and a second hydraulic press cylinder for moving the first roll relative to the second roll, the first hydraulic press cylinder and the second hydraulic press cylinder being respectively connected to a first supporting portion and a second supporting portion that rotatably support the first roll at both ends of the first roll, the rolling mill being characterized in that

a rolling area for rolling the bar steel, which is set as a partial continuous area in a longitudinal direction of the roll pair, is positioned so that a distance between the first supporting portion and the rolling area and a distance between the second supporting portion and the rolling area differ from each other, and

the rolling mill further includes:

a distance sensor configured to measure a roll deflection in the rolling area of at least one of the first roll and the second roll; and

a controller configured to control an amount of depression of the first hydraulic press cylinder and an amount of depression of the second hydraulic press cylinder based on a detection value of the distance sensor.

Other features of the present invention will be clarified by this description and the attached drawings.

Effects of the Invention

According to the present invention, it is made possible to achieve highly-accurate shape control in rolling a bar steel with the use of an offset rolling mill.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic front view of a rolling mill 10 according to an embodiment;

FIG. 2 is a diagram showing relation between a controller 40 and other devices of the rolling mill 10;

FIG. 3 includes an upper drawing that is a diagram showing a state where rolling is performed with a roll pair sandwiching a bar steel 1 in a bent state, and a lower drawing that is an explanatory diagram for explaining roll deflections of a first roll 14a;

FIG. 4 is a schematic front view of a rolling mill 10 according to a second embodiment; and

FIG. 5 is a schematic front view of the rolling mill 10 according to a third embodiment.

EMBODIMENT FOR CARRYING OUT THE INVENTION

At least the followings are clarified by this description and the attached drawings.

A rolling mill that includes a roll pair, having a first roll and a second roll, for rolling a bar steel to be rolled, and a first hydraulic press cylinder and a second hydraulic press cylinder for moving the first roll relative to the second roll, the first hydraulic press cylinder and the second hydraulic press cylinder being respectively connected to a first supporting portion and a second supporting portion that rotatably support the first roll at both ends of the first roll, is characterized in that

a rolling area for rolling the bar steel, which is set as a partial continuous area in a longitudinal direction of the roll pair, is positioned so that a distance between the first supporting portion and the rolling area and a distance between the second supporting portion and the rolling area differ from each other, and

the rolling mill further includes:

a distance sensor configured to measure a roll deflection in the rolling area of at least one of the first roll and the second roll; and

a controller configured to control an amount of depression of the first hydraulic press cylinder and an amount of depression of the second hydraulic press cylinder based on a detection value of the distance sensor.

According to the above-described rolling mill, it is made possible to achieve highly-accurate shape control in rolling a bar steel with the use of an offset rolling mill.

In the above-described rolling mill, a plurality of the rolling areas may be set at different positions in the longitudinal direction of the roll pair.

According to the above-described rolling mill, it is made possible to achieve highly-accurate shape control regardless of in which of the rolling areas the bar steel is rolled.

In the above-described rolling mill, at least one distance sensor may be provided for each of the plurality of rolling areas set at the different positions.

According to the above-described rolling mill, it is possible to omit mechanism for moving the distance sensors and therefore, it is possible to simplify the structure related to the distance sensors.

The above-described rolling mill may further include a movably-supporting device that supports the distance sensor movably in the longitudinal direction.

According to the above-described rolling mill, it is possible to reduce the number of distance sensors as compared to the case where the distance sensors are provided for every one of the plurality of rolling areas.

In the above-described rolling mill, the movably-supporting device may include: a mounting portion, to which the distance sensor is fixed; a rail portion, with which the mounting portion slidably engages; and a driving device for moving the mounting portion along the rail portion.

According to the above-described rolling mill, it is possible to realize a reliable movable support with the use of simple components.

The above-described rolling mill may be configured to be able to measure the roll deflections in both end portions of the rolling area in the longitudinal direction.

According to the above-described rolling mill, it is made possible to determine the thicknesses of both edge portions of the bar steel in the longitudinal direction based on the roll deflections in both end portions of the rolling area in the longitudinal direction, so that it is made possible to make these thicknesses of both edge portions of the bar steel in the longitudinal direction more even.

In the above-described rolling mill, the controller may be configured to control the amount of depression of the first hydraulic press cylinder and the amount of depression of the second hydraulic press cylinder in real time while the bar steel is rolled.

According to the above-described rolling mill, it is made possible to achieve more accurate shape control in rolling a bar steel with the use of an offset rolling mill.

In the above-described rolling mill, each of the first roll and the second roll may be provided with a caliber in the rolling area.

According to the above-described rolling mill, the present invention is more effective because, when rolling is performed with the use of a roll pair provided with the calibers, the rolling is usually, or often, performed with the use of an offset rolling mill.

A method of controlling a rolling mill that includes a roll pair, having a first roll and a second roll, for rolling a bar steel to be rolled, and a first hydraulic press cylinder and a second hydraulic press cylinder for moving the first roll relative to the second roll, the first hydraulic press cylinder and the second hydraulic press cylinder being respectively connected to a first supporting portion and a second supporting portion that rotatably support the first roll at both ends of the first roll, is characterized by including:

setting a rolling area for rolling the bar steel, which is set as a partial continuous area in a longitudinal direction of the roll pair, is positioned so that a distance between the first supporting portion and the rolling area and a distance between the second supporting portion and the rolling area differ from each other;

measuring a roll deflection in the rolling area of at least one of the first roll and the second roll; and

controlling an amount of depression of the first hydraulic press cylinder and an amount of depression of the second hydraulic press cylinder based on the roll deflection.

The above-described method of controlling the rolling mill brings about the same operations and effects as those in the case of the above rolling mill.

===Rolling Mill 10 According to Embodiment===

A rolling mill 10 according to this embodiment is an apparatus for rolling a bar steel 1 to be rolled and is used as an offset rolling mill. This offset rolling mill means the rolling mill 10 characterized by the position of the bar steel 1 during rolling, which will be described in detail later. Examples of the bar steel 1 include flat steel, section steel, steel rods, wires, rails, and the like, meaning steel material with a shape having a very large length as compared to the size of the cross-sectional area. In this embodiment, flat steel is rolled as the bar steel 1.

FIG. 1 is a schematic front view of the rolling mill 10 according to this embodiment. In the drawings of this embodiment, lateral direction (horizontal direction) on the sheet is defined as “longitudinal direction,” and the left (right) side on the sheet is referred to as “WS (DS)” or “left (right),” while vertical direction on the sheet is defined as “vertical direction,” and the upper (lower) side on the sheet is referred to as “upper (lower) side.” FIG. 2 is a diagram showing relation between a controller 40 and other devices of the rolling mill 10.

A housing 11 of the rolling mill 10 is shown in FIG. 1. Disposed in the housing 11 (inside the housing 11) are a pair of rolls (a first roll 14a and a second roll 14b), supporting portions (a first supporting portion 13a, a second supporting portion 13b, and supporting portions for the second roll 14b), hydraulic press cylinders (a first hydraulic press cylinder 12a and a second hydraulic press cylinder 12b), load cells (a first load cell 15a and a second load cell 15b), distance sensors 20, a movably-supporting device 30, and a balance cylinder mechanism 50, which are included in the rolling mill 10.

The roll pair is a pair of upper and lower flat rolls, the first roll 14a and the second roll 14b. The first roll 14a and the second roll 14b are the same in shape and each has a rolling portion with a larger diameter and shaft portions with a smaller diameter, the shaft portions being provided at both ends of the rolling portion in the longitudinal direction. The roll pair catches the bar steel 1 in the gap between the first roll 14a provided on the upper side and the second roll 14b provided on the lower side as shown in FIG. 1, and is rotated for rolling by the rotation driven by a driving portion 32 shown in FIG. 2. In other words, the rolling mill 10 includes the roll pair of the first roll 14a and the second roll 14b for rolling the bar steel 1 to be rolled.

In this embodiment, a plurality of partial continuous areas, corresponding to rolling areas AP, are set in the longitudinal direction of the rolling portions of the roll pair as positions in the longitudinal direction of the roll pair, between which the bar steel 1 is passed, and are stored in a memory unit 41 described later. In other words, in the rolling mill 10, a plurality of the rolling areas AP are set at different positions in the longitudinal direction of the roll pair.

The supporting portions support both ends of each of the rolls of the roll pair in a state where the roll pair are rotatable, so that the roll pair can be rotated by the rotation driven by the driving portion 32. In this description, “both ends of the roll” supported by the supporting portions mean the positions that are symmetric with respect to a roll center line RC (the center line in the longitudinal direction of the roll pair), in other words, the shaft portions (that is, not the rolling portion). The WS shaft portion of the first roll 14a is supported by the first supporting portion 13a and the DS shaft portion thereof is supported by the second supporting portion 13b. These supporting portions are connected to the hydraulic press cylinders with a balance beam 51 interposed therebetween, which will be described later. Both ends of the second roll 14b are supported by the supporting portions for the second roll 14b that are fixed to a lower surface of a housing 11 (lower surface of the inside of the housing 11).

The hydraulic press cylinders (the first hydraulic press cylinder 12a and the second hydraulic press cylinder 12b), which are devices for moving the first roll 14a relative to the second roll 14b, are fixed to an upper side surface of the housing 11 (upper side surface of the inside of the housing 11) with the load cells, described later, interposed therebetween. Specifically, the first hydraulic press cylinder 12a and the second hydraulic press cylinder 12b are respectively connected to the first supporting portion 13a and the second supporting portion 13b and cause the first roll 14a to move relative to the second roll 14b by moving the supporting portions, to which the first hydraulic press cylinder 12a and the second hydraulic press cylinder 12b are connected. In other words, the rolling mill 10 includes the first hydraulic press cylinder 12a and the second hydraulic press cylinder 12b for moving the first roll 14a relative to the second roll 14b, the first hydraulic press cylinder 12a and the second hydraulic press cylinder 12b being respectively connected to the first supporting portion 13a and the second supporting portion 13b that rotatably support the first roll 14a at both ends of the first roll 14a.

The load cells (the first load cell 15a and the second load cell 15b), which are sensors for detecting the pressure applied to the supporting portions by the hydraulic press cylinders connected thereto, are interposed between the housing 11 and the hydraulic press cylinders. Specifically, the first load cell 15a is provided between an upper side surface (installation surface) of the first hydraulic press cylinder 12a and the upper side surface of the housing 11, and the second load cell 15b is provided between an upper side surface (installation surface) of the second hydraulic press cylinder 12b and the upper side surface of the housing 11. The load cells continuously detect the pressure (reaction force to the pressure applied to the supporting portions by the hydraulic press cylinders connected thereto), at which the load cells are pressed between the housing 11 and the hydraulic press cylinders, as pressure values, at which the hydraulic press cylinders apply the pressure to the connected supporting portions. The load cells immediately transmit the detection results to the controller 40.

The controller 40 has an automatic gap control (AGC) function and can perform compensation, based on the pressure detected by the load cells, by the amount of vertical displacement of the first supporting portion 13a and the second supporting portion 13b, the displacement being caused by vertical elongation (vertical deformation) of the housing 11.

The controller 40 having received the pressure values detected by the load cells calculates the amount of vertical deformation of the housing 11 and the amount of vertical deformation of bearings of the supporting portions (members for rotatably supporting the first roll 14a), which are not shown, with the use of the detected pressure values. The controller 40 then corrects the amount of depression of the first hydraulic press cylinder 12a and the amount of depression of the second hydraulic press cylinder 12b with the use of the calculated amounts of vertical deformation. Note that the deformation of the bearing is calculated based on a graph between load and radial displacement of the bearing and the detected pressure values.

The distance sensors 20 are sensors for measuring the roll deflections, each detecting the distance between the distance sensor 20 and the roll. The “roll deflection” herein means the difference between the vertical position of the roll that is measured by a detection value of the distance sensor 20 in a state where the roll pair is not bent (hereinafter also referred to as the “zero-deflection state”) and the vertical position of the roll that is measured by the detection value of the distance sensor 20 in a state where the roll pair is bent.

In this embodiment, the distance sensors 20 are fixed to mounting portions 30a of the movably-supporting device 30, which will be described later, provided above the first roll 14a. Over one end portion and the other end portion, in the longitudinal direction, of the rolling area AP for the bar steel 1 to be rolled (both end portions of the rolling area AP), two distance sensors 20, one over each end portion, are provided. Accordingly, the distance sensors 20 detect the distances to the first roll 14a in both end portions of the rolling area AP and transmit the detected distances to the controller 40. For example, eddy-current displacement sensors, laser distance sensors, or the like, can be used as the distance sensors 20.

The movably-supporting device 30 is provided on the lower side surface of the balance beam 51, which is positioned above the first roll 14a and will be described later, so as to be extended between both end portions, one end portion and the other end portion, of the first roll 14a. The movably-supporting device 30 includes the mounting portions 30a, to which the distance sensors 20 are fixed, a rail portion 30b, with which the mounting portions 30a slidably engage, and driving devices (not shown) for moving the mounting portions 30a along the rail portion 30b. In other words, the movably-supporting device 30 is a device for moving the distance sensors 20 between both end portions, one end portion and the other end portion, of the first roll 14a above the first roll 14a. Note that “both end portions of the roll” mean both end portions of the rolling portion of the roll (that is, not the shaft portions). One mounting portion 30a and one driving device are provided for each distance sensor 20. A plurality of the mounting portions 30a can slidably engage one rail portion 30b. This means that the plurality of mounting portions 30a (distance sensors 20) engaging with the rail portion 30b are moved along the rail portion 30b by the driving devices between the one end portion and the other end portion of the rolling portion of the first roll 14a. In other words, the rolling mill 10 includes the movably-supporting device 30 supporting the distance sensors 20 movably along the longitudinal direction.

The movably-supporting device 30 has a position detection function of detecting positions of the mounting portions 30a in the longitudinal direction and the position information obtained by the detection is transmitted to the controller 40. Thus, it is possible to move the mounting portions 30a carrying the distance sensors 20 along the rail portion 30b to the instructed positions in the longitudinal direction between the one end portion and the other end portion of the rolling portion by the driving devices as drivers according to instructions from the controller 40.

The controller 40 shown in FIG. 2 is included in the rolling mill 10 and receives information transmitted from various devices as described above. The controller 40 has the memory unit 41 that stores the information, and an arithmetic unit 42 that performs calculation with the use of the received information, the information stored in the memory unit 41, etc. The controller 40 sends instructions to the various devices based on the results of calculation by the arithmetic unit 42, etc. In other words, the controller 40 controls the various devices included in the rolling mill 10 based on the various kinds of information.

The balance cylinder mechanism 50 includes a first balance cylinder 50a, a second balance cylinder 50b, and the balance beam 51. The first balance cylinder 50a and the second balance cylinder 50b are fixed to the upper side surface of the housing 11 so as to be positioned symmetrically with respect to the roll center line RC, and the vertically-movable cylinder portions of the first balance cylinder 50a and the second balance cylinder 50b are connected to the balance beam 51. The balance beam 51 is provided so as to be extended from the first supporting portion 13a to the second supporting portion 13b in the longitudinal direction and is configured to, when rolling is not performed, raise the first supporting portion 13a and the second supporting portion 13b so as to maintain a gap between the first roll 14a and the second roll 14b. When the first hydraulic press cylinder 12a and the second hydraulic press cylinder 12b move the connected supporting portions, the balance beam 51 is also moved accordingly. The balance beam 51 is also connected to the first balance cylinder 50a and the second balance cylinder 50b so that the balance beam 51 can pivot about pivot axes extending along the direction perpendicular to the sheet of FIG. 1.

As described above, in the rolling mill 10, the plurality of rolling areas AP are set at different positions in the longitudinal direction of the roll pair. As shown in FIG. 1 as an example, each rolling area AP according to this embodiment is set so that the center of the rolling area AP in the longitudinal direction does not coincide with the roll center line RC. In other words, each rolling area AP is set so that both end portions of the rolling area AP are positioned asymmetrically with respect to the roll center line RC. This means that the rolling area AP for rolling the bar steel 1, which is set in a partial continuous area in the longitudinal direction of the roll pair, is positioned so that the distance between the first supporting portion 13a and the rolling area AP and the distance between the second supporting portion 13b and the rolling area AP differ from each other because the first supporting portion 13a and the second supporting portion 13b are provided symmetrically with respect to the roll center line RC.

A method of controlling the offset rolling mill (the rolling mill 10 shown in FIG. 1 that shows a state where the bar steel 1 is rolled at one of the set rolling areas AP) will be described below.

===Control of the Rolling Mill 10===

Control of the rolling mill 10 according to this embodiment will be described with reference to FIG. 1, and upper and lower drawings of FIG. 3.

The upper drawing of FIG. 3 is a diagram showing a state where rolling is performed with the roll pair sandwiching the bar steel 1 in a bent state. The lower drawing of FIG. 3 is an explanatory diagram for explaining the roll deflections of the first roll 14a. While the roll pair during ordinary rolling is not deflected so greatly as shown in the upper and lower drawings of FIG. 3, the deflections are exaggerated for ease of understanding.

As shown in the upper drawing of FIG. 3, in the roll pair during rolling according to this embodiment, the first roll 14a is bent so that the central portion (at the roll center line RC) of the first roll 14a is positioned upward and both ends thereof are positioned downward, and the second roll 14b is bent so that the central portion of the second roll 14b is positioned downward and both ends thereof are positioned upward. For this reason, when the bar steel 1 is rolled with the use of the rolling mill 10 as the offset rolling mill as show in FIG. 1, the bar steel 1 having a cross-sectional shape conforming to the bent shape of the roll pair is produced, which results in the difference between thicknesses of both edge portions of the bar steel 1 in the longitudinal direction.

In this Embodiment, in order to improve accuracy in shape of the cross section of the bar steel 1, control is performed so that the thickness of the bar steel 1 rolled by the offset rolling mill shown in FIG. 1 becomes a predetermined dimension and the thicknesses of both edge portions of the bar steel 1 in the longitudinal direction become equal to each other. Steps of the control will be described in order below.

A rolling area AP shown in FIG. 1 is selected as the rolling area AP to be used from among the plurality of rolling areas AP set in the rolling mill 10. The controller 40 of the rolling mill 10 then disposes, or moves, the distance sensors 20 to the positions corresponding to both end portions, one end portion and the other end portion, of the selected rolling area AP in the longitudinal direction. In other words, the rolling mill 10 is configured to be able to measure the roll deflections in both end portions of the rolling area AP in the longitudinal direction.

The selection of the rolling area AP to be used may be performed manually, or may be performed, for example, based on the results of detection by a sensor for detecting the rolling area AP of the bar steel 1, the sensor being provided on the upstream side of the roll pair in the travel direction of the bar steel 1 (direction perpendicular to the sheet in FIG. 1).

When the distance sensors 20 have been moved to the positions corresponding to both end portions of the rolling area AP, the controller 40 detects the values from the distance sensors 20 in “the state where the roll pair is not bent (zero-deflection state)” described above, and stores the values to the memory unit 41 in advance of rolling.

The controller 40 then starts rolling the bar steel 1 in the rolling mill 10. During the rolling, two distance sensors 20 positioned over a first detection point P1 and a second detection point P2 shown in the upper and lower drawings of FIG. 3 (positioned over both end portions of the rolling area AP) detect the distances to the first roll 14a and transmit the detected values to the controller 40.

The controller 40 having received the detected values of the first detection point P1 and the second detection point P2 measures, or calculates, a first roll deflection X1 from the detected value of the first detection point P1 and a second roll deflection X2 from the detected value of the second detection point P2. The dashed straight line extending in the longitudinal direction shown in the lower drawing of FIG. 3 is a straight line (hereinafter also referred to as the “reference line BL”) expressing the position of the first roll 14a in a zero-deflection state. Specifically, the first roll deflection X1 and the second roll deflection X2 are values by which the detection values of the distance sensors 20 received by the controller 40 during rolling differ from the detection values of the distance sensors 20 obtained in the zero-deflection state.

The controller 40 having measured the first roll deflection X1 and the second roll deflection X2 calculates the amount of depression (compensation amount) of the first hydraulic press cylinder 12a and the second hydraulic press cylinder 12b so that the thicknesses of both edge portions of the bar steel 1 in the longitudinal direction are equalized.

Specifically, the arithmetic unit 42 calculates the inclination (corresponding to the inclination S1 between both end portions) between the first detection point P1 and the second detection point P2 in the longitudinal direction with respect to the reference line BL from the first roll deflection X1 and the second roll deflection X2 with the use of the following equation.

Inclination S1 between both end portions=(First roll deflection X1−Second roll deflection X2)/(Second distance L2−First distance L1)

As shown in the lower drawing of FIG. 3, the first distance L1 is the distance between the first detection point P1 and the roll center line RC in the longitudinal direction, and the second distance L2 is the distance between the second detection point P2 and the roll center line RC. A supporting-portion distance L, which is used in an equation described later, is the distance between the first supporting portion 13a and the roll center line RC in the longitudinal direction. These values are determined from the positions of the actually-used rolling areas in the longitudinal direction, the configuration of the rolling mill 10, etc., and are therefore stored in the memory unit 41 in advance.

The arithmetic unit 42 having calculated the inclination S1 between both end portions calculates compensation values in the vertical direction for the first supporting portion 13a and the second supporting portion 13b with the use of the following equations.

Compensation value for First hydraulic press cylinder 12a (First supporting portion 13a)=((First roll deflection X1+Second roll deflection X2)/2)−(Inclination S1 between both end portions×Supporting-portion distance L)

Compensation value for Second hydraulic press cylinder 12b (Second supporting portion 13b)=((First roll deflection X1+Second roll deflection X2)/2)+(Inclination S1 between both end portions×Supporting-portion distance L)

In these equations, the part, “(First roll deflection X1+Second roll deflection X2)/2,” is the average of the first roll deflection X1 and the second roll deflection X2 (hereinafter also referred to as the “average roll deflection”), and the part, “(Inclination S1 between both end portions×Supporting-portion distance L),” is the compensation value for the supporting portions that is used to make the inclination S1 between both end portions parallel to the reference line BL.

The controller 40 then causes the supporting portions connected to the respective hydraulic press cylinders to move in the vertical direction based on the calculated compensation values. Specifically, the amount of depression is increased by the average roll deflection and the first supporting portion 13a and the second supporting portion 13b are moved in the vertical direction so as to make the inclination S1 between both end portions parallel to the reference line BL.

Specifically, the compensation amount for the first hydraulic press cylinder 12a is the sum of the increase of the amount of depression (positive value) corresponding to the average roll deflection, which compensates for shortage of the amount of depression caused by deflection of the rolls, and the increase of the amount of depression (negative value) to make the inclination S1 between both end portions parallel to the reference line BL. When this sum is positive, the amount of depression of the first hydraulic press cylinder 12a is increased, so that the first supporting portion 13a is additionally moved downward by the compensation amount. When this sum is negative, the amount of depression of the first hydraulic press cylinder 12a is reduced, so that the first supporting portion 13a is moved upward by the compensation amount.

The compensation amount for the second hydraulic press cylinder 12b is the sum of the increase of the amount of depression (positive value) corresponding to the average roll deflection, which compensates for shortage of the amount of depression caused by deflection of the rolls, and the increase of the amount of depression (positive value) to make the inclination S1 between both end portions parallel to the reference line BL. This means that the amount of depression of the second hydraulic press cylinder 12b is increased, and therefore, the second supporting portion 13b is additionally moved downward by the compensation amount.

In this way, control of the amount of depression of the first hydraulic press cylinder 12a and the amount of depression of the second hydraulic press cylinder 12b, focusing on the first roll 14a, is performed.

As shown in the upper drawing of FIG. 3, the second roll 14b is also bent as in the case of the first roll 14a, and therefore, it is also necessary to perform correction (control) of the hydraulic press cylinders, focusing on the second roll 14b. For this reason, in this embodiment, it is assumed that the second roll 14b is also bent similarly to the first roll 14a. Specifically, it is assumed that the rolls are bent symmetrically in the vertical direction with respect to the center line of the bar steel 1 in the thickness direction (vertical direction).

However, since there is no equipment provided for moving the second roll 14b in the vertical direction, the second roll 14b cannot be moved. For this reason, in this embodiment, the first roll 14a is moved in the vertical direction by the sum of the amount corresponding to the deflection of the first roll 14a and the amount corresponding to the deflection of the second roll 14b (that is, twice of the amount corresponding to the deflection of the first roll 14a). This makes it possible to perform control the amount of depression of the first hydraulic press cylinder 12a and the amount of depression of the second hydraulic press cylinder 12b, focusing on both of the first roll 14a and the second roll 14b.

By moving the first roll 14a in the vertical direction as described above, it is made possible to attain movement by the amount corresponding to the sum of the average roll deflection of the first roll 14a and that of the second roll 14b and to reduce the inclination in the rolling area (to make the inclinations of both rolls between both end portions parallel to the reference line BL). Specifically, the controller 40 controls the amount of depression of the first hydraulic press cylinder 12a and the amount of depression of the second hydraulic press cylinder 12b based on the detection values of the distance sensors 20 so as to reduce the dimensional error of the bar steel 1 by compensating for shortage of the amount of depression caused by deflection of the rolls and to improve accuracy in shape of the cross section by reducing the inclination of the first roll 14a between both end portions of the rolling area AP in the longitudinal direction set in the first roll 14a and reducing the inclination of the second roll 14b between both end portions of the rolling area AP in the longitudinal direction set in the second roll 14b.

When the controller 40 according to this embodiment receives the information on distance at the first detection point P1 and the second detection point P2 from the distance sensors 20, the controller 40 immediately calculates the compensation amount at the arithmetic unit 42. When compensation is needed, the controller 40 controls the amount of depression of the first hydraulic press cylinder 12a and the second hydraulic press cylinder 12b and waits for the next transmission from the distance sensors 20. The distance sensors 20 continuously detect the distance to the first detection point P1 and the distance to the second detection point P2 and immediately transmit the detection results to the controller 40. In other words, the controller 40 controls the amount of depression of the first hydraulic press cylinder 12a and the amount of depression of the second hydraulic press cylinder 12b in real time while the bar steel 1 is rolled.

===Effectiveness of the Rolling Mill 10 According to this Embodiment===

As described above, the rolling mill 10 according to this embodiment includes: the roll pair having the first roll 14a and the second roll 14b for rolling the bar steel 1 to be rolled; and the first hydraulic press cylinder 12a and the second hydraulic press cylinder 12b for moving the first roll 14a relative to the second roll 14b, the first hydraulic press cylinder 12a and the second hydraulic press cylinder 12b being respectively connected to the first supporting portion 13a and the second supporting portion 13b that rotatably support the first roll 14a at both ends of the first roll 14a. In the rolling mill 10, each of the rolling areas AP for rolling the bar steel 1, each of which is set as a partial continuous area in the longitudinal direction of the roll pair, is positioned so that the distance between the first supporting portion 13a and the rolling area AP and the distance between the second supporting portion 13b and the rolling area AP differ from each other. The rolling mill 10 further includes the distance sensors 20 configured to measure the roll deflections at the rolling areas AP of the first roll 14a, and the controller 40 configured to control the amount of depression of the first hydraulic press cylinder 12a and the amount of depression of the second hydraulic press cylinder 12b based on the detection values of the distance sensors 20. Accordingly, it is made possible to achieve highly-accurate shape control in rolling the bar steel 1 with the use of the offset rolling mill.

When an offset rolling mill is used to roll the bar steel 1, there have been a problem of low accuracy in shape of the cross section of the bar steel 1, a problem of occurrence of a curve in the longitudinal direction of the bar steel 1, etc. because shortage of the amount of depression and inclination in the rolling areas AP of the rolls occur due to deflection of the roll, which causes the occurrence of dimensional error of the bar steel 1 and unevenness in thickness between both edge portions of the rolled bar steel 1 in the longitudinal direction.

By contrast, the rolling mill 10 according to this embodiment includes the distance sensors 20 configured to measure the roll deflections at the rolling areas AP of the first roll 14a, and the controller 40 configured to control the amount of depression of the first hydraulic press cylinder 12a and the amount of depression of the second hydraulic press cylinder 12b based on the detection values of the distance sensors 20. By detecting deformation of the first roll 14a with the use of the distance sensors 20, it is possible to directly keep track of the deformation of the roll pair caused during rolling and measure the roll deflections in the rolling areas AP based on the deformation. Moreover, since the controller 40 controls the amount of depression of the first hydraulic press cylinder 12a and the amount of depression of the second hydraulic press cylinder 12b in accordance with the roll deflections, it is made possible to achieve highly-accurate shape control in rolling the bar steel 1 with the use of the offset rolling mill.

In this embodiment, the rolling mill 10 is configured to be able to measure the roll deflections in both end portions of the rolling area AP in the longitudinal direction. Accordingly, by correcting the amount of depression of the hydraulic press cylinders based on the roll deflections in both end portions of the rolling area AP in the longitudinal direction, it is made possible to reduce the dimensional error of the bar steel 1 by compensating for shortage of the amount of depression caused by deflection of the rolls and to reduce the inclination of the first roll 14a between both end portions of the rolling area AP in the longitudinal direction set in the first roll 14a and the inclination of the second roll 14b between both end portions of the rolling area AP in the longitudinal direction set in the second roll 14b, which makes it possible to achieve highly-accurate shape control.

In this embodiment, the controller 40 controls the amount of depression of the first hydraulic press cylinder 12a and the amount of depression of the second hydraulic press cylinder 12b in real time while the bar steel 1 is rolled. Since the controller 40 controls the amount of depression of the hydraulic press cylinders in real time, control is swiftly performed when it becomes necessary to control the amount of depression of the hydraulic press cylinders. This means that more accurate shape control is achieved in rolling the bar steel 1 with the use of the offset rolling mill.

In this embodiment, the rolling areas AP are set at different positions in the longitudinal direction of the roll pair and the present invention can be applied to all the rolling areas AP set at the different positions in the longitudinal direction of the roll pair. This means that it is possible to achieve highly-accurate shape control regardless in which of the rolling areas AP the bar steel 1 is rolled.

In this embodiment, the rolling mill 10 includes the movably-supporting device 30 that supports the distance sensors 20 movably in the longitudinal direction. When a switch from a rolling area AP to another rolling area AP is made, the movably-supporting device 30 can move the distance sensors 20 to the rolling area AP after the switch and the moved distance sensors 20 can detect the values at the rolling area AP after switch. Accordingly, it is possible to reduce the number of distance sensors 20 as compared to the case where the distance sensors 20 are provided for every one of the plurality of rolling areas AP.

In this embodiment, the movably-supporting device 30 includes the mounting portions 30a, to which the distance sensors 20 are fixed, the rail portion 30b, with which the mounting portions 30a slidably engage, and the driving devices for moving the mounting portions 30a along the rail portion 30b. This means that a reliable movably-supporting device 30 can be realized with the use of simple components including the mounting portions 30a, the rail portion 30b, and the driving devices.

Other Embodiments

While the rolling mill 10 according to the present invention has been described with reference to the embodiment, the above-described embodiment is for ease of understanding of the present invention and the present invention is not limited to the above-described embodiment. Needless to say, modification and improvement can be made without departing from the spirit of the present invention, and the equivalent thereof is included in the present invention.

While the roll pair is made up of the flat rolls in the above-described embodiment, the present invention is not limited to this configuration. For example, the roll pair may be provided with calibers (grooves provided in the roll pair and formed in the same cross-sectional shape as that of the bar steel 1, for forming the cross-sectional shape of the bar steel 1 by passing the bar steel 1 through the grooves; the grooves correspond to the rolling areas AP). Each of the first roll 14a and the second roll 14b may be provided with the caliber(s) in the rolling area(s) AP.

When rolling is performed with the use of a roll pair provided with the calibers, the rolling is usually, or often, performed with the use of an offset rolling mill and therefore, the present invention is more effective.

While the balance cylinder mechanism 50 is provided above the first roll 14a and the movably-supporting device 30 is provided on the lower surface of the balance beam 51 in the above-described embodiment, the present invention is not limited to this configuration. For example, as shown in FIG. 4, the position of the movably-supporting device 30 may be changed and a first supporting-portion balance cylinder 60a and a second supporting-portion balance cylinder 60b may be provided instead of the balance cylinder mechanism 50.

FIG. 4 is a schematic front view of a rolling mill 10 according to a second embodiment. As shown in FIG. 4, differences from the first embodiment are as follows: the movably-supporting device 30 is provided on the upper side surface of the housing 11; and instead of the balance cylinder mechanism 50, the first supporting-portion balance cylinder 60a is provided for the first supporting portion 13a and the second supporting-portion balance cylinder 60b is provided for the second supporting portion 13b.

A modification example of the second embodiment is a rolling mill, in which the installation position of the movably-supporting device 30 is changed from the housing 11 to a fixed beam 70 as shown in FIG. 5. FIG. 5 is a schematic front view of the rolling mill 10 according to a third embodiment.

As shown in FIG. 5, the third embodiment differs from the second embodiment in that the fixed beam 70 is provided separately from the housing 11 and the movably-supporting device 30 is provided on the lower side surface of the fixed beam 70 instead of the housing 11.

In the first embodiment, the inclination of the first roll 14a (difference in height between the first supporting portion 13a side and the second supporting portion 13b side) caused by the difference between the pressing loads on the first supporting portion 13a side and the second supporting portion 13b side (measurement values obtained from the first load cell 15a and the second load cell 15b) is compensated for owing to the AGC function. Accordingly, the balance beam 51 (rail portion 30b) provided with the distance sensors 20 is always kept horizontal and the controller 40 can therefore correctly measure the roll deflections based on the detection values of the distance sensors 20.

However, in the second and third embodiments, the rail portion 30b cannot be kept in a horizontal position with the use of the AGC function and therefore, the controller 40 cannot correctly measure the roll deflections based on the detection values of the distance sensors 20. For this reason, the controller 40 in the second embodiment and the third embodiment corrects the detection values of the distance sensors 20 by the amount of displacement caused by the vertical deformation of the housing 11 and controls the amount of depression of the hydraulic press cylinders 12a and 12b based on the corrected values.

While the distance sensors 20 are provided only above the first roll 14a in the above-described embodiments, the present invention is not limited to this configuration. For example, the distance sensors 20 may be provided only below the second roll 14b or may be provided both above the first roll 14a and below the second roll 14b. However, it is preferable that the distance sensors 20 be provided above the first roll 14a so that the cooling water used during rolling is not splashed onto the distance sensors 20.

When the distance sensors 20 are provided only below the second roll 14b, the controller 40 may perform the calculation, described in connection with the above embodiments, with regard to the rolling areas AP of the second roll 14b. When the distance sensors 20 are provided both above the first roll 14a and below the second roll 14b, the controller 40 may perform the calculation, described in connection with the above embodiments, with regard to both of the rolling areas AP of the first roll 14 and the rolling areas AP of the second roll 14b, and, based on the results of the calculation (without the assumption that one of the rolls is bent symmetrically in the vertical direction with respect to the center line of the bar steel 1 in the vertical direction), the controller 40 may calculate the amount of depression of the first hydraulic press cylinder 12a and the second hydraulic press cylinder 12b for control.

In summary, it suffices that the rolling mill 10 includes the distance sensors 20 configured to measure the roll deflections in the rolling areas AP of at least one of the first roll 14a and the second roll 14b.

While the rolling mill is provided with the movably-supporting device 30 to move the distance sensors 20 in the longitudinal direction in the above-described embodiments, the present invention is not limited to this configuration. For example, the distance sensors 20 may be provided for all the plurality of rolling areas AP in an immovable manner. In other words, a configuration may be adopted such that at least one distance sensor 20 is provided for each of the plurality of rolling areas AP set at different positions. When this configuration is adopted, it is possible to omit the mechanism for moving the distance sensors 20 and therefore, it is possible to simplify the structure related to the distance sensors 20.

While control performed in the rolling mill 10 using two distance sensors 20 has been described in connection with the above-described embodiments, the present invention is not limited to this configuration. For example, three or more distance sensors 20 may be used to control the rolling mill 10.

DESCRIPTION OF REFERENCE NUMERALS

• 1: bar steel
• 10: rolling mill
• 11: housing
• 12a: first hydraulic press cylinder
• 12b: second hydraulic press cylinder
• 13a: first supporting portion
• 13b: second supporting portion
• 14a: first roll
• 14b: second roll
• 15a: first load cell
• 15b: second load cell
• 20: distance sensor
• 30: movably-supporting device
• 30a: mounting portion
• 30b: rail portion
• 32: driving portion
• 40: controller
• 41: memory unit
• 42: arithmetic unit
• 50: balance cylinder mechanism
• 50a: first balance cylinder
• 50b: second balance cylinder
• 51: balance beam
• 60a: first supporting-portion balance cylinder
• 60b: second supporting-portion balance cylinder
• 70: fixed beam
• AP: rolling area
• P1: first detection portion
• P2: second detection portion
• S1: inclination between both end portions
• X1: first roll deflection
• X2: second roll deflection
• RC: roll center line
• BL: reference line
• L1: first distance
• L2: second distance
• L: supporting-portion distance

Claims

1. A rolling mill that includes a roll pair, having a first roll and a second roll, for rolling a bar steel to be rolled, and a first hydraulic press cylinder and a second hydraulic press cylinder for moving the first roll relative to the second roll, the first hydraulic press cylinder and the second hydraulic press cylinder being respectively connected to a first supporting portion and a second supporting portion that rotatably support the first roll at both ends of the first roll, wherein

a rolling area for rolling the bar steel, which is set as a partial continuous area in a longitudinal direction of the roll pair, is positioned so that a distance between the first supporting portion and the rolling area and a distance between the second supporting portion and the rolling area differ from each other, and

the rolling mill further comprises:

a distance sensor configured to measure a roll deflection in the rolling area of at least one of the first roll and the second roll; and

a controller configured to control an amount of depression of the first hydraulic press cylinder and an amount of depression of the second hydraulic press cylinder based on a detection value of the distance sensor.

2. The rolling mill according to claim 1, wherein

a plurality of the rolling areas are set at different positions in the longitudinal direction of the roll pair.

3. The rolling mill according to claim 2, wherein

at least one distance sensor is provided for each of the plurality of rolling areas set at the different positions.

4. The rolling mill according to claim 1, further comprising a movably-supporting device that supports the distance sensor movably in the longitudinal direction.

5. The rolling mill according to claim 4, wherein

the movably-supporting device includes: a mounting portion, to which the distance sensor is fixed; a rail portion, with which the mounting portion slidably engages; and a driving device for moving the mounting portion along the rail portion.

6. The rolling mill according to claim 1, wherein

the rolling mill is configured to be able to measure the roll deflections in both end portions of the rolling area in the longitudinal direction.

7. The rolling mill according to claim 1, wherein

the controller is configured to control the amount of depression of the first hydraulic press cylinder and the amount of depression of the second hydraulic press cylinder in real time while the bar steel is rolled.

8. The rolling mill according to claim 1, wherein

each of the first roll and the second roll is provided with a caliber in the rolling area.

9. A method of controlling a rolling mill that includes a roll pair, having a first roll and a second roll, for rolling a bar steel to be rolled, and a first hydraulic press cylinder and a second hydraulic press cylinder for moving the first roll relative to the second roll, the first hydraulic press cylinder and the second hydraulic press cylinder being respectively connected to a first supporting portion and a second supporting portion that rotatably support the first roll at both ends of the first roll, the method comprising:

positioning a rolling area for rolling the bar steel, which is set as a partial continuous area in a longitudinal direction of the roll pair, so that a distance between the first supporting portion and the rolling area and a distance between the second supporting portion and the rolling area differ from each other;

measuring a roll deflection in the rolling area of at least one of the first roll and the second roll; and

controlling an amount of depression of the first hydraulic press cylinder and an amount of depression of the second hydraulic press cylinder based on the roll deflection.