EP2656933B1

EP2656933B1 - Rolling mill equipped with work roll shift function

Info

Publication number: EP2656933B1
Application number: EP13002093.6A
Authority: EP
Inventors: Takashi Norikura
Original assignee: Primetals Technologies Japan Ltd
Current assignee: Primetals Technologies Japan Ltd
Priority date: 2012-04-25
Filing date: 2013-04-22
Publication date: 2016-02-10
Anticipated expiration: 2033-04-22
Also published as: JP2013226573A; JP5905322B2; CN103372566A; IN2013MU01488A; CN103372566B; EP2656933A1

Description

{Technical Field}

The present invention relates to a rolling mill for performing rolling of a electrical steel strip, a high-tensile steel strip, a mild steel strip, or the like, the rolling mill equipped with a work roll shift function to shift work rolls tapered at one ends in roll axial directions, thereby controlling edge drop of a material to be rolled, or controlling a strip shape.

{Background Art}

Generally, when rolling is performed with straight (not tapered at one end) work rolls, in strip widthwise distribution of strip thickness in a material to be rolled, the strip thickness becomes extremely thin in the vicinity of strip widthwise ends compared to a strip central portion, because of Hertzian flattening of the work rolls. A so-called edge drop phenomenon occurs. If the amount of this edge drop is large, the amount of edge trimming in the following process increases, and the yield decreases accordingly. Therefore, a technique to reduce this edge drop has been demanded strongly.
Further, since a strip shape varies depending on a speed-load correlation during rolling speed acceleration or deceleration, smooth acceleration or deceleration cannot be performed, which also results in such a problem that production efficiency is not improved. Therefore, a technique to make it possible to reduce the strip shape variation during the acceleration or deceleration has also been demanded strongly.
Therefore, conventionally, in a six-high rolling mill or a four-high rolling mill, if taper shoulder positions of work rolls having tapered portions at one ends can be shifted in the vicinity of the inside of the strip widthwise ends as shown in Patent Literature 1, a reduction in the strip thicknesses of the strip widthwise ends after rolling (edge drop) can be suppressed by clearances of these tapered portions, the amount of edge trimming in the following process is reduced, and the yield is improved accordingly.
Further, it can be understood that by causing the taper shoulder positions of the tapered portions, which are arranged in positions in point symmetry, of upper and lower work rolls to coincide with the vicinities of the outsides of the strip widthwise ends, harmful contact linear pressure from the outside of the strip width to the work rolls from intermediate rolls or back-up rolls that are support rolls is reduced, and therefore shape stability (small shape variation relative to load variation) is significantly improved, stable rolling becomes possible, and production efficiency is improved.

{Citation List}

{Patent Literature}

{Patent Literature 1} Japanese Examined Patent Application Publication No. H07-16694
{Patent Literature 2} Japanese Patent Application Laid-Open No. S59-61511

{Summary of Invention}

{Technical Problem}

However, when an attempt is made to cause the taper shoulder positions of the tapered portions to coincide with the vicinities of the insides of the strip widthwise ends or the vicinities of the outsides of the strip widthwise ends, as shown in Patent Literature 1, it is inevitable to cause the taper shoulder positions of the tapered portions to coincide with presumptive strip widthwise end positions on the assumption that the strip is located in the center of the mill, because meandering of the strip during rolling makes it impossible to locate precise positions of the strip widthwise ends.
As a result, the taper shoulder positions of the tapered portions of the work rolls cannot be caused to coincide with the vicinities of the insides of correct strip widthwise ends or the vicinities of the outsides of correct strip widthwise ends,. Thus the work rolls are set with a deviation corresponding to the amount of strip meandering, leading to a problem that such improvement of yield due to reduction in edge drop or improvement of production efficiency due to realization of stable rolling as described above cannot sufficiently be achieved.
Further, Patent Literature 2 discloses a technique to obtain a positional difference between an actual position of the material to be rolled and a proper position thereof relative to the rolling mill on the basis of detection results of a strip end detector and a shift amount detector for a roll shift device, and adjust the respective sizes of right and left gaps of the work rolls according to the positional difference, thereby correcting a widthwise position of the material to be rolled, that is, correcting meandering of the strip.
This can also reduce edge drop, but there is the problem that control operation becomes complicated, which causes an increase in cost, together with an increase in the number of devices such as a control device.
In view of the above-described circumstances, an object of the present invention is to provide a rolling mill equipped with a work roll shift function that can improve yield and realize stable rolling with a simple means, and that can roll even a meandering metal strip into an operation side-drive side symmetrical shape.

{Solution to Problem}

A rolling mill equipped with a work roll shift function according to a first aspect of the present invention for solving the above problems is a rolling mill equipped with a work roll shift function, being a six-high rolling mill including a pair of upper and lower work rolls for rolling a metal strip, a pair of upper and lower intermediate rolls supporting the work rolls, and a pair of upper and lower back-up rolls supporting the intermediate rolls, or being a four-high rolling mill including a pair of upper and lower work rolls for rolling a metal strip and a pair of upper and lower back-up rolls supporting the work rolls, wherein:

the pair of upper and lower work rolls are provided with tapered portions in upper and lower positions in point symmetry;
work roll shift devices are provided for shifting the pair of upper and lower work rolls in roll axial directions, and a strip widthwise end position detector is provided for detecting operation-side and drive side strip widthwise ends of the metal strip; and
a control means is further provided for performing shift control of the work roll shift devices so as to cause taper start positions of the tapered portions of the pair of upper and lower work rolls to coincide with the vicinities of the insides of the operation-side and drive side strip widthwise ends or the vicinities of the outsides of the operation-side and drive side strip widthwise ends detected by the strip widthwise end position detector respectively for the upper side and the lower side.

In addition,
the rolling mill equipped with a work roll shift function according to a second aspect of the present invention is characterized in that the pair of upper and lower intermediate rolls of the six-high rolling mill are provided with tapered portions in upper and lower positions in point symmetry, and intermediate roll shift devices are also provided for shifting the pair of upper and lower intermediate rolls in roll axial directions; and
the control means performs shift control of the intermediate roll shift devices respectively for the upper side and the lower side so as to cause taper start positions of the tapered portions of the pair of upper and lower intermediate rolls to coincide with the vicinities of the outsides of the operation-side and drive side strip widthwise ends detected by the strip widthwise end position detector.
In addition,
the rolling mill equipped with a work roll shift function according to a third aspect of the present invention is characterized in that the pair of upper and lower intermediate rolls of the six-high rolling mill are also provided with tapered portions in upper and lower positions in point symmetry, and intermediate roll shift devices are provided for shifting the pair of upper and lower intermediate rolls in roll axial directions, and shift control of the intermediate roll shift devices is performed so as to perform operation side-drive side asymmetrical shift control of the pair of upper and lower intermediate rolls to correct asymmetry of a strip shape.
In addition,
a rolling mill equipped with a work roll shift function according to a fourth aspect of the present invention is a rolling mill including a pair of upper and lower work rolls for rolling a metal strip, a pair of upper and lower intermediate rolls supporting the work rolls, and a pair of upper and lower back-up rolls supporting the intermediate rolls, wherein:

the pair of upper and lower work rolls are provided with tapered portions in upper and lower positions in point symmetry, and work roll shift devices are provided for shifting the pair of upper and lower work rolls in roll axial directions;
the pair of upper and lower intermediate rolls are provided with tapered portions in upper and lower positions in point symmetry, and intermediate roll shift devices are provided for shifting the pair of upper and lower intermediate rolls in roll axial directions;
a strip widthwise end position detector for detecting strip widthwise ends of the metal strip is provided on an entry side or on a delivery side of the rolling mill, and a strip widthwise end thickness meter for measuring the thicknesses of the strip widthwise ends of the metal strip is provided on the delivery side of the rolling mill; and
a control means is provided for performing shift control of the intermediate roll shift devices so as to cause taper start positions of the tapered portions of the pair of upper and lower intermediate rolls to coincide with the vicinities of the outsides of the strip widthwise ends detected by the strip widthwise end position detector, and performing shift control of the work roll shift devices so as to cause taper start positions of the tapered portions of the pair of upper and lower work rolls to coincide with the vicinities of the insides of the strip widthwise ends respectively for the upper side and the lower side, such that the thicknesses of the strip widthwise ends on an operation side and on a drive side measured by the strip widthwise end thickness meter become predetermined thicknesses.

In addition,
the rolling mill equipped with a work roll shift function according to a fifth aspect of the present invention is characterized in that the work rolls of the four-high rolling mill are provided with independent roll bending devices on the operation side and on the drive side, and roll bending forces on the operation side and on the drive side are changed so as to correct asymmetry of a strip shape.
In addition,
the rolling mill equipped with a work roll shift function according to a sixth aspect of the present invention is characterized in that the work rolls and/or the intermediate rolls of the six-high rolling mill are provided with independent roll bending devices on the operation side and on the drive side, and roll bending forces on the operation side and on the drive side are changed so as to correct asymmetry of a strip shape.

{Advantageous Effect of Invention}

According to the configuration of the present invention, in case of meandering of the metal strip during rolling, the strip widthwise end position detector is provided for detecting actual strip widthwise end positions, and the taper start positions of the pair of upper and lower work rolls are caused to coincide with the vicinities of the insides of the actual strip widthwise ends detected by the strip widthwise end position detector independently for the upper side and the lower side. Therefore, the amount of edge drop, which is a reduction in the strip thicknesses of the strip widthwise ends, can be more effectively reduced. As a result, the amount of edge trimming in the following process is reduced, and the yield is improved.
In addition, the taper start positions of the pair of upper and lower work rolls are caused to coincide with the vicinities of the outsides of the actual strip widthwise ends detected by the strip widthwise end position detector. Therefore, harmful contact line pressure from the outside of the strip width to the work rolls from the support rolls is reduced, so that shape stability (small shape variation relative to load variation) is significantly improved, and stable rolling becomes possible.
In addition, since the taper start positions of the pair of upper and lower intermediate rolls of the six-high rolling mill are caused to coincide with the vicinities of the outsides of the strip widthwise ends detected by the strip widthwise end position detector, a roll mark is prevented from being transferred to the metal strip.
In addition, this meandering of the metal strip causes the shape of the metal strip to be asymmetrical on the operation side and on the drive side. Against this asymmetrization, the taper start positions of the pair of upper and lower intermediate rolls are caused to coincide with the vicinities of the outsides of the strip widthwise ends, and the taper start positions of the pair of upper and lower work rolls are caused to coincide with the vicinities of the insides of the strip widthwise ends respectively for the upper side and the lower side, such that the thicknesses of the strip widthwise ends on an operation side and on a drive side measured by the strip widthwise end thickness meter become predetermined thicknesses. Therefore, the metal strip can be rolled to have an operation side-drive side symmetrical shape, so that stable rolling can be realized.

{Brief Description of Drawings}

{Fig. 1} Fig. 1 is a front view of a six-high rolling mill according to a first example of the present invention.
{Fig. 2} Fig. 2 is an arrow sectional view taken along the line II-II of Fig. 1.
{Fig. 3} Fig. 3 is an arrow sectional view taken along the line III-III of Fig. 2.
{Fig. 4} Fig. 4 is a descriptive view of taper start positions of tapered portions of work rolls and intermediate rolls.
{Figs. 5A and 5B} Figs. 5A and 5B are graphs of results of comparison of strip shape variation relative to load variation, Fig. 5A being a graph showing a result of calculation of strip shape variation with load variation in a conventional technique, and Fig. 5B being a graph showing a result of calculation of strip shape variation with load variation in the present invention.
{Fig. 6} Fig. 6 is a descriptive view of strip meandering according to a second example of the present invention.
{Figs. 7A and 7B} Figs. 7A and 7B are descriptive views showing the necessity of an asymmetrical shape control means in case of strip meandering according to the second example, Fig. 7A being a descriptive view of a material linear pressure distribution and Fig. 7B being a descriptive view of a strip shape.
{Fig. 8} Fig. 8 is a descriptive view showing an example of application of the second example to a tandem rolling mill.
{Fig. 9} Fig. 9 is a front view of a six-high rolling mill according to a third example of the present invention.
{Fig. 10} Fig. 10 is a descriptive view showing an example of application of the third example to a tandem rolling mill.
{Fig. 11} Fig. 11 is a front view of a four-high rolling mill according to a fourth example of the present invention.
{Fig. 12} Fig. 12 is an arrow sectional view taken along the XII-XII of Fig. 11.

{Description of Embodiments}

Hereinafter, examples of a rolling mill equipped with a work roll shift function according to the present invention will be described in detail by using the drawings.

{First Example}

Fig. 1 is a front view of a six-high rolling mill according to a first example of the present invention, Fig. 2 is an arrow sectional view taken along the line II-II of Fig. 1, Fig. 3 is an arrow sectional view taken along the line III-III of Fig. 2, Fig. 4 is a descriptive view of taper start positions of tapered portions of work rolls and intermediate rolls, and Figs. 5A and 5B are graphs of results of comparison of strip shape variation relative to load variation, Fig. 5A being a graph showing a result of calculation of strip shape variation relative to load variation in a conventional technique and Fig. 5B being a graph showing a result of calculation of strip shape variation relative to load variation in the present invention.
The rolling mill of the first example is a six-high rolling mill as shown in Figs. 1 to 4, and a metal strip (hereinafter simply called strip) 1, which is a material to be rolled, is rolled by a pair of upper and lower work rolls 2. This pair of upper and lower work rolls 2 are supported in contact with a pair of upper and lower intermediate rolls 3, respectively, and this pair of upper and lower intermediate rolls 3 are supported in contact with a pair of upper and lower back-up rolls 4, respectively.
The upper back-up roll 4 is supported by bearing boxes 10a and 10c via unillustrated bearings. These bearing boxes 10a and 10c are supported by housings 7a and 7b via pass line adjusters 5a and 5b, such as a worm jack or a taper wedge and a stepped rocker plate. Here, the pass line adjusters 5a and 5b may incorporate load cells to measure rolling loads. In addition, the lower back-up roll 4 is supported by bearing boxes 10b and 10d via unillustrated bearings. These bearing boxes 10b and 10d are supported by the housings 7a and 7b via hydraulic cylinders 6a and 6b.
The pair of upper and lower work rolls 2 have tapered portions (portions reduced in diameter) 2b in upper and lower positions in point symmetry about the strip widthwise center of the strip 1, respectively, and Reference Sign 2a in the drawings denotes a taper start position of the tapered portion. In addition, bearing boxes 8a to 8d are attached to roll neck portions of the pair of upper and lower work rolls 2 via unillustrated bearings.
Moreover, the pair of upper and lower work rolls 2 can be moved (shifted) in roll axial directions by a pair of right and left shift cylinders (work roll shift devices) 13 via the drive side bearing boxes 8c and 8d, detachable hooks 12, and shift frames 11. Further, these bearing boxes 8a to 8d are provided with bending cylinders (roll bending devices) 31a to 31d for applying roll bending. Rolling bending is thus applied to the work rolls 2 by the bending cylinders 31a to 31 d.
Here, rolling loads are applied by the hydraulic cylinders 6a and 6b described above, and rolling torques are transmitted to the pair of upper and lower work rolls 2 directly by unillustrated spindles, or transmitted to the work rolls 2 indirectly via the intermediate rolls 3 by the spindles.
The pair of upper and lower intermediate rolls 3 have tapered portions (portions reduced in diameter) 3b in upper and lower positions in point symmetry about the center of strip width of the strip 1, respectively, and Reference Sign 3a in the drawings denotes a taper start position of the tapered portion. In addition, bearing boxes 9a to 9d are attached to roll neck portions of the pair of upper and lower intermediate rolls 3 via unillustrated bearings.
In addition, the pair of upper and lower intermediate rolls 3 can be moved (shifted) in roll axial directions by a pair of right and left shift cylinders (intermediate roll shift devices) 34 via the drive side bearing boxes 9c and 9d, unillustrated attachable and detachable hooks, and unillustrated shift frames. Further, these bearing boxes 9a to 9d are provided with bending cylinders (roll bending devices) 30a to 30d applying roll bending. Rolling bending is thus applied to the intermediate rolls 3.
Moreover, a strip widthwise end position detector 32 is provided on an entry side or on a delivery side (entry side in the example shown in the drawings) of the rolling mill to detect actual strip widthwise end positions of the strip 1. A detection signal of the strip widthwise end position detector 32 is inputted to a controller (control means) 35. Based on the detection signal, the controller 35 performs shift control of the pairs of right and left shift cylinders 13 and 34, thereby adjusting shift directions and shift amounts of the work rolls 2 and the intermediate rolls 3.
With such a configuration, in case of meandering of the strip 1 during rolling, the actual strip widthwise end positions are detected by the strip widthwise end position detector 32. Then, the taper start positions 2a, which are arranged in upper and lower positions in point symmetry, of the pair of upper and lower work rolls 2 are shifted independently for the upper side and the lower side so as to coincide with the vicinities of the insides of the actual strip widthwise ends detected by the strip widthwise end position detector 32.
This causes strip widthwise ends 1a to be thicker by clearances (see δW and δd in Fig. 4) of the taper start positions 2a than a strip central portion. Consequently, a reduction in the strip thicknesses of the strip widthwise ends 1a after rolling (edge drop) is also suppressed, the amount of edge trimming in the following process is reduced, and the yield is improved accordingly.
In addition, in the first example, an example of applying roll bending to the pair of upper and lower intermediate rolls 3 has been shown, and the first example provides excellent strip shape controllability in combination with the shift function of the pair of upper and lower intermediate rolls 3 described above. It should be noted that rolling bending may not necessarily be applied to the intermediate rolls 3. In this case, the shape controllability decreases but the structure becomes simple.
Here, by shifting the taper start positions 2a, which are arranged in upper and lower positions in point symmetry, of the pair of upper and lower work rolls 2 so as to coincide with the vicinities of the insides of actual strip widthwise ends and causing the taper start positions 3a, which are arranged in upper and lower positions in point symmetry, of the pair of upper and lower intermediate rolls 3 to always coincide with the vicinities of the actual strip widthwise ends detected by the strip widthwise end position detector 32 (see δiw and δid in Fig. 4), a roll mark is prevented from being transferred to the strip 1 (due to deviations of the taper start positions 3a to the insides of actual strip widthwise ends) or edge waves are prevented from occurring (due to deviations of the taper start positions 3a to the outsides of actual strip widthwise ends).
In addition, by shifting the taper start positions 2a of the work rolls 2 so as to coincide with the vicinities of the outsides of strip widthwise ends and further causing the taper start positions 3a of the intermediate rolls 3 to coincide with the vicinities of the outsides of the strip widthwise ends, shape stability (small shape variation relative to load variation) is improved.
This shape stability will be described by using Figs. 5A and 5B. Fig. 5A shows a case where conventional straight work rolls 200, which do not have taper shoulders, are used and taper start positions of intermediate rolls 300 are shifted so as to coincide with the vicinities of the outsides of strip widthwise ends. In this case, when a load changes by 1.2 times from 1041 tons to 1245 tons, the shape changes by 23 I-units (steel strip widthwise positions and a difference in elongation percentage when a steel strip is rolled). On the other hand, Fig. 5B shows a case where the taper start positions of the work rolls 2 are shifted so as to coincide with the vicinities of the outsides of strip widthwise ends, and further, the taper start positions of the intermediate rolls 3 are shifted so as to coincide with the vicinities of the outsides of strip widthwise ends. In this case, when a load changes by 1.2 times from 1041 tons to 1245 tons similarly, the shape changes by 15 I-units, and the amount of change is reduced to 65% (= 15/23). This means that shape variation is small relative to load variation during acceleration/deceleration of rolling speed, and indicates that the shape stability is significantly improved accordingly in the present invention.

{Second Example}

Fig. 6 is a descriptive view of strip meandering according to a second example of the present invention, Figs. 7A and 7B are descriptive views showing the necessity of an asymmetrical shape control means in case of strip meandering according to the second example, Fig. 7A being a descriptive view of a material linear pressure distribution and Fig. 7B being a descriptive view of a strip shape, and Fig. 8 is a descriptive view showing an example of application of the second example to a tandem rolling mill.
When the strip 1 meanders, and accordingly the taper start positions 2a, which are arranged in upper and lower positions in point symmetry, of the pair of upper and lower work rolls 2 are shifted so as to coincide with the vicinities of the outsides of strip widthwise ends or the vicinities of the insides of strip widthwise ends, the shape of the strip becomes asymmetrical on the operation side and on the drive side. This asymmetrization of the strip shape in case of meandering of the strip 1 will be described by using Fig. 6 and Figs. 7A and 7B.
First, when a strip center O1 has meandered by "e" from a mill center 02 toward the drive side, the taper start positions 2a are shifted by an amount corresponding to the meandering accordingly. This makes it possible to set the taper start positions 2a in the vicinities of the insides of the strip widthwise ends or the vicinities of the outsides of the strip widthwise ends of actual strip widthwise ends. However, since the strip center O1 has been offset by "e" from the mill center 02 toward the drive side, the linear pressure distribution in material of the work rolls 2 and the strip 1 is such that, as shown by the vertical straight arrows in Figure 7A, the linear pressure is low on the drive side and high on the operation side. As a result, the shape of the strip 1 takes a strip shape where edge waves T occur on the operation side, as shown in Figure 7B.
Therefore, as an operation side-drive side asymmetrical shape control means, shift control of the shift cylinders 34 is performed and upper-lower asymmetrical shifting of the pair of upper and lower intermediate rolls 3 is performed by the controller 35 described in the first example. Specifically, in this case, the taper start position 3a of the upper intermediate roll 3 is shifted toward the drive side, and the taper start position 3a of the lower intermediate roll 3 is also shifted toward the drive side (see the horizontal straight arrows in Fig. 7A).
This makes it possible to roll the strip 1 into a shape symmetrical on the operation side and the drive side, so that stable rolling can be realized. Note that at this time, as shown by the curved arrows in Fig. 7A, roll bender forces of roll bender devices of the work rolls 2 and/or the intermediate rolls 3 may be made larger on the operation side than on the drive side.
Further, as shown in Fig. 8, it is preferred that the rolling mill of the second example be installed in at least one stand of a tandem rolling mill including, for example, No. 1 to No. 5 stands (for example, in the No. 5 stand in the example shown in Fig. 8) and the strip widthwise end position detector 32 be installed on the entry side (or the delivery side) of this at least one stand (the No. 5 stand in the example shown in Fig. 8). According to this, also in a tandem rolling mill, the amount of edge drop can be reduced with the inexpensive strip widthwise end position detector 32.

{Third Example}

Fig. 9 is a front view of a six-high rolling mill according to a third example of the present invention, and Fig. 10 is a descriptive view showing an example of application of the third example to a tandem rolling mill.
The third example is such that in case of meandering of the strip 1 during rolling, actual strip widthwise end positions are detected by the strip widthwise end position detector 32 installed on the entry side (or the delivery side) of the rolling mill, the taper start positions 3a, which are arranged in upper and lower positions in point symmetry, of the pair of upper and lower intermediate rolls 3 are shifted independently for the upper side and the lower side so as to coincide with the vicinities of the outsides of the actual strip widthwise ends detected by the strip widthwise end position detector 32, and a strip widthwise end thickness meter 33 is installed on the delivery side of the rolling mill, and the taper start positions 2a, which are arranged in upper and lower positions in point symmetry, of the pair of upper and lower work rolls 2 are shifted respectively for the upper side and the lower side to the vicinities of the insides of the strip widthwise ends so that the thicknesses of the strip widthwise ends measured on the operation side and on the drive side become predetermined thicknesses (reduction in amount of edge drop).
Here, a method of reducing edge drop by shift of the work rolls 2 having the taper start positions 2a will be described below. First, the work rolls 2 are provided with the taper start positions 2a in upper and lower positions in point symmetry, and distances between the taper start positions 2a and the strip widthwise ends are represented as δw and δd (see Fig. 4). In addition, a strip widthwise end thickness meter 36 measures a strip thickness or strip thicknesses at a single point or a plurality of points in the vicinities of the strip widthwise ends, on the operation side and on the drive side, on the delivery side of the rolling mill.
If the strip thickness at the single point or the strip thicknesses at the plurality of points in the vicinity of the strip widthwise end measured on the operation side is or are thinner than a predetermined strip thickness, the upper work roll 2 is shifted in a roll axial narrowing direction. In other words, the upper work roll 2 is shifted in a direction in which the distance δw increases. On the other hand, if the strip thickness or the strip thicknesses in the vicinities of the strip widthwise end measured is or are thicker than the predetermined strip thickness, the upper work roll 2 is shifted in a roll axial widening direction. In other words, the upper work roll 2 is shifted in a direction in which the distance δw decreases. In addition, if the strip thickness at the single point or the strip thicknesses at the plurality of points in the vicinities of the strip widthwise end measured on the drive side is or are different from the predetermined strip thickness, the lower work roll 2 is similarly shifted so that the predetermined strip thickness can be obtained.
According to this, though an expensive strip widthwise end thickness meter 33 using X-ray is used, the amount of edge drop can be reduced with high accuracy in combination with the inexpensive strip widthwise end position detector 32. It should be noted that also in the third example, as an operation side-drive side asymmetrical shape control means, shift control of the shift cylinders 34 may be performed by the controller 35 described in the first example to perform upper-lower asymmetrical shifting of the pair of upper and lower intermediate rolls 3 so that improvement of shape stability can be achieved.
In addition, as shown in Fig. 10, it is preferred that the rolling mill of the third example be installed in at least one stand of a tandem rolling mill including, for example, No. 1 to No. 5 stands (for example, in the No. 5 stand in the example shown in Fig. 10) and the strip widthwise end position detector 32 be installed on the entry side (or the delivery side) of this at least one stand (the No. 5 stand in the example shown in Fig. 10), while the strip widthwise end thickness meter 33 be installed on the delivery side (or the entry side). According to this, also in a tandem rolling mill, the amount of edge drop can be reduced.

{Fourth Example}

Fig. 11 is a front view of a four-high rolling mill according to a fourth example of the present invention, and Fig. 12 is an arrow sectional view taken along the XII-XII of Fig. 11.
A rolling mill of the fourth example is a four-high rolling mill, and has a configuration obtained by removing the pair of upper and lower intermediate rolls 3 and the set of bearing boxes 9a to 9d from the six-high rolling mills of the first to third examples. In addition, the strip widthwise end position detector 32 is installed on the delivery side of the rolling mill. In this case, though the absence of the shift function of the intermediate rolls 3 causes a significant decrease in strip shape controllability, there is the advantage that the structure is simpler than those of the first to third examples.

{Industrial Applicability}

The present invention shifts work rolls having tapered shoulders to the vicinities of the insides of actual strip widthwise ends or the vicinities of the outsides of actual strip widthwise ends detected by a strip widthwise end position detector, and is applicable to a rolling mill having excellent edge drop reduction and shape stability.

{Reference Signs List}

1: METAL STRIP
1a: STRIP WIDTHWISE END
2: WORK ROLL
2a: TAPER START POSITION
2b: TAPERED PORTION
3: INTERMEDIATE ROLL
3a: TAPER START POSITION
3b: TAPERED PORTION
4: BACK-UP ROLL
5(5a, 5b): PASS LINE ADJUSTER
6(6a, 6b): HYDRAULIC CYLINDER
7(7a, 7b): HOUSING
8a to 8d: BEARING BOX OF WORK ROLL
9a to 9d: BEARING BOX OF INTERMEDIATE ROLL
10a to 10d: BEARING BOX OF BACK-UP ROLL
11: SHIFT FRAME
12: DETACHABLE HOOK
13: SHIFT CYLINDER (WORK ROLL SHIFT DEVICE)
30a to 30d: BENDING CYLINDER
31a to 31d: BENDING CYLINDER
32: STRIP WIDTHWISE END POSITION DETECTOR
33: STRIP WIDTHWISE END THICKNESS METER
34: SHIFT CYLINDER (INTERMEDIATE ROLL SHIFT DEVICE)
35: CONTROLLER (CONTROL MEANS)
e: OFFSET AMOUNT OF STRIP CENTER
O1: STRIP CENTER
02: MILL CENTER
T: EDGE WAVE

Claims

A rolling mill equipped with a work roll shift function, being a six-high rolling mill including a pair of upper and lower work rolls (2) for rolling a metal strip (1), a pair of upper and lower intermediate rolls (3) supporting the work rolls (2), and a pair of upper and lower back-up rolls (4) supporting the intermediate rolls (3), or being a four-high rolling mill including a pair of upper and lower work rolls (2) for rolling a metal strip and a pair of upper and lower back-up rolls (4) supporting the work rolls (2), wherein:
the pair of upper and lower work rolls (2) are provided with tapered portions (2b) in upper and lower positions in point symmetry;

work roll shift devices (13) are provided for shifting the pair of upper and lower work rolls (2) in roll axial directions; and

a strip widthwise end position detector (32) is provided for detecting operation-side and drive side strip widthwise ends of the metal strip (1);

characterized by a control means (35) for performing shift control of the work roll shift devices so as to cause taper start positions (2a) of the tapered portions (2b) of the pair of upper and lower work rolls (2) to coincide with the vicinities of the insides of the operation-side and drive side strip widthwise ends or the vicinities of the outsides of the operation-side and drive side widthwise ends detected by the strip widthwise end position detector (32) respectively for the upper side and the lower side.
The rolling mill equipped with a work roll shift function according to claim 1, characterized in that the pair of upper and lower intermediate rolls (3) of the six-high rolling mill are provided with tapered portions (3b) in upper and lower positions in point symmetry, and intermediate roll shift devices (34) are also provided for shifting the pair of upper and lower intermediate rolls (3) in roll axial directions; and
the control means (35) performs shift control of the intermediate roll shift devices (34) respectively for the upper side and the lower side so as to cause taper start positions (3a) of the tapered portions (3b) of the pair of upper and lower intermediate rolls (3) to coincide with the vicinities of the outsides of the operation-side and drive side strip widthwise ends detected by the strip widthwise end position detector (32).
The rolling mill equipped with a work roll shift function according to claim 1 or 2, characterized in that the pair of upper and lower intermediate rolls (3) of the six-high rolling mill are also provided with tapered portions (3b) in upper and lower positions in point symmetry, and intermediate roll shift devices (34) are provided for shifting the pair of upper and lower intermediate rolls (3) in roll axial directions, and shift control of the intermediate roll shift devices (34) is performed so as to perform operation side-drive side asymmetrical shift control of the pair of upper and lower intermediate rolls (3) to correct asymmetry of a strip shape.
A rolling mill equipped with a work roll shift function including a pair of upper and lower work rolls (2) for rolling a metal strip (1), a pair of upper and lower intermediate rolls (3) supporting the work rolls (2), and a pair of upper and lower back-up rolls (4) supporting the intermediate rolls (3), wherein:
the pair of upper and lower work rolls (2) are provided with tapered portions (2b) in upper and lower positions in point symmetry, and work roll shift devices (13) are provided for shifting the pair of upper and lower work rolls (2) in roll axial directions;

the pair of upper and lower intermediate rolls (3) are provided with tapered portions (3b) in upper and lower positions in point symmetry, and intermediate roll shift devices (34) are provided for shifting the pair of upper and lower intermediate rolls (3) in roll axial directions;

a strip widthwise end position detector (32) for detecting strip widthwise ends of the metal strip (1) is provided on an entry side or on a delivery side of the rolling mill, and a strip widthwise end thickness meter (33) for measuring the thicknesses of the strip widthwise ends of the metal strip (1) is provided on the delivery side of the rolling mill; and

a control means (35) is provided for performing shift control of the intermediate roll shift devices (34) so as to cause taper start positions (3a) of the tapered portions (3b) of the pair of upper and lower intermediate rolls (3) to coincide with the vicinities of the outsides of the strip widthwise ends detected by the strip widthwise end position detector (32), and performing shift control of the work roll shift devices (13) so as to cause taper start positions (2a) of the tapered portions (2b) of the pair of upper and lower work rolls (2) to coincide with the vicinities of the insides of the strip widthwise ends respectively for the upper side and the lower side, such that the thicknesses of the strip widthwise ends measured on an operation side and on a drive side detected by the strip widthwise end thickness meter (33) become predetermined thicknesses.
The rolling mill equipped with a work roll shift function according to claim 1, characterize in that the work rolls (2) of the four-high rolling mill are provided with independent roll bending devices (31a to 31d) on the operation side and on the drive side, and roll bending forces on the operation side and on the drive side are changed so as to correct asymmetry of a strip shape.
The rolling mill equipped with a work roll shift function according to claim 1, 2 or 3, characterized in that the work rolls (2) and/or the intermediate rolls (3) of the six-high rolling mill are provided with independent roll bending devices (30a to 30d, 31a to 31d) on the operation side and on the drive side, and roll bending forces on the operation side and on the drive side are changed so as to correct asymmetry of a strip shape.