JP2010089121A - Four-high skin pass rolling mill and skin pass rolling method for galvanized steel sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a large-diameter quadplex skin pass rolling mill and skin pass rolling method by which the skin pass rolling of the metallic strip of a galvanized steel sheet is performed at low load without bringing about remarkable increase of equipment cost and without generating edge wrinkles. <P>SOLUTION: The quadplex skin pass rolling mill for a galvanized steel sheet is provided with: a pair of upper and lower back up rolls having a flat shape or the convex crown shape 21 of a parabola pattern: a pair of upper and lower work rolls having the convex crown shape 21 of the parabola pattern and a tapered crown shape 20 in which the roll diameter is enlarged toward the roll ends in the range from the inside of 150 mm from the sheet end to the outside of 150 mm from the sheet end; and a bender device with which bending force in the vertical direction to the work roll is applied to the work roll at the ends of a roll shaft. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention can produce a product having a good surface property that prevents wrinkles when a metal strip of a hot dip galvanized steel sheet is supplied with lubricating oil on the inlet side of the rolling mill or is subjected to skin pass rolling without lubrication. The present invention relates to a possible rolling mill and a rolling method.

Hot dip galvanized steel sheets are used in vending machines, automobiles, etc., and after heat treatment and plating treatment are performed in equipment called a CGL line, they are straightened and shipped by a skin pass rolling mill. The hot dip galvanized steel sheet has a thickness of about 1 mm and is relatively thick. Also, since the yield stress of the material is less than 300 MPa and is relatively soft, the rolling load is low and it is about 980 KN per 1 m of the sheet width. For this reason, when a metal strip having an edge drop is subjected to skin pass rolling after plating, an appearance defect called an ear wrinkle may occur due to insufficient reduction of the edge of the plate.

FIG. 1 is a photograph of an appearance defect called an ear wrinkle generated at the end of the plate. In this case, the ear wrinkles are generated about 50 mm inside from the edge of the plate. Since the wrinkled part does not become a product, this part is discarded. In this example, it is necessary to cut off the entire width by 100 mm, which causes a large yield reduction.

The cause of this is due to insufficient reduction of the edge of the plate during skin pass rolling. This is because of this. Therefore, it is sufficient to take measures to eliminate the insufficient rolling at the end of the plate during skin pass rolling. As countermeasures, (1) Increase the rolling reduction (elongation rate) or increase the friction coefficient to increase the rolling load. (2) Install a decrease bender on the work roll. (3) Special for the work roll. A good roll profile. (4) Remodeling into a small diameter work roll mill. And so on.
Regarding the method of increasing the rolling load, when the rolling reduction is increased, if the rolling reduction is increased, the secondary workability deteriorates, so that the rolling reduction cannot be substantially increased. Further, when the friction coefficient is increased, if the friction coefficient is increased, seizure or unevenness occurs on the surface, which is not practical. Although installing a decrease bender on a large-diameter work roll is effective in preventing ear wrinkles, the plate shape has a large end elongation as a whole, and the flatness deteriorates. Installing a decrease bender on a small-diameter work roll is very effective in preventing ear wrinkles, and although flatness can be secured even as a plate shape, a large facility modification is required, resulting in an increase in manufacturing costs (for example, patent documents) 1).
Giving the work roll a special crown so that the roll diameter increases as it goes to the body end is effective when the rolling load is high (see, for example, Patent Document 2 and Patent Document 3). In such a quadruple skin pass rolling mill, when the rolling load is low, there is a portion where the work roll and the backup roll do not contact with each other in the crown application part, and the flatness may be satisfied as the plate shape. A streak mark is newly generated in the rolling direction.
Japanese Patent Laid-Open No. 2005-81429 Japanese Patent Laid-Open No. 2002-66608 JP-A-2006-130546

  The present invention solves the above-described problem, and does not cause a significant increase in equipment cost, and is a large-scale skin pass rolling that can prevent wrinkling of a metal strip of a hot dip galvanized steel sheet that is skin pass rolled at a low load. It is an object of the present invention to provide a quadruple skin pass rolling mill and a skin pass rolling method.

The gist of the present invention is as follows.
(1) A hot-dip galvanized steel quadruple skin pass rolling mill, comprising a pair of upper and lower backup rolls having a flat shape or a convex crown shape of a parabola pattern, a convex crown shape of a parabola pattern, A pair of upper and lower work rolls having a tapered crown shape whose roll diameter increases toward the roll end within a certain range, and a bending force perpendicular to the work roll is applied to the roll shaft end of the work roll. A quadruple skin pass rolling machine for hot-dip galvanized steel sheets.
(2) The tapered crown shape may be provided within the range of 150 mm inside from the plate end to 150 mm outside from the plate end, and may be provided at both plate ends in either the upper or lower work roll.
(3) The tapered crown shape is within a range of 150 mm inside from the plate end to 150 mm outside from the plate end within the range of shift capability of the work roll, and is provided one by one at the plate end of the upper and lower work rolls. ,
The upper and lower work rolls are arranged so that the tapered crown shape is point-symmetric with respect to the steel sheet,
You may provide the work roll shift apparatus which shifts the said work roll to a work roll trunk | drum length direction.
(4) A skin-pass rolling method for hot-dip galvanized steel sheet, based on the width of the metal strip of the hot-dip galvanized steel sheet and the rolling load at the desired light reduction, and a pair of upper and lower backup rolls and / or upper and lower A crown amount is imparted to a pair of work rolls, and a taper crown shape in which the roll diameter increases toward the roll end within a certain range before and after the plate end in the upper and lower work rolls, and the metal strip being rolled A skin pass rolling method for a hot-dip galvanized steel sheet, characterized in that the work roll bender force of the rolling mill is controlled such that the rolling mill delivery side plate shape becomes a desired plate shape.
(5) The tapered crown shape may be within a range 150 mm inside from the plate end to 150 mm outside from the plate end, and may be provided at both plate ends of the upper or lower work roll.
(6) The tapered crown shape is within a range of 150 mm inside from the plate end to 150 mm outside from the plate end within the shift capability range of the work roll, and is provided one by one at the plate end in the upper and lower work rolls. The upper and lower work rolls are arranged so that the tapered crown is in a point-symmetrical position with respect to the steel sheet, and the rolling mill work piece is shaped so that the rolling strip outlet side plate shape of the metal strip being rolled becomes a desired plate shape. The roll shift amount may be controlled.

In the present invention, a work roll having a tapered crown shape in which the roll diameter increases toward the roll end within the range of 150 mm inside from the plate end to 150 mm outside from the plate end, and perpendicular to the roll shaft end of the work roll Since the apparatus for applying the bending force in the direction is used, there is an advantage that it is only necessary to grind the work roll of the existing rolling mill. When carrying out the present invention with one upper or lower work roll when grinding the work roll portion that hits the plate edge, both ends of the work roll are used when the present invention is carried out with two upper and lower work rolls. It is preferable to grind one side of the work roll. When the present invention is carried out with one work roll, the work roll needs to be built up or down, and when the present invention is carried out with two work rolls, the work roll needs to be built up and down. However, in the method of grinding both ends of the work roll, the plate width that can be handled is about ± 30 mm with respect to the reference value, so it is necessary to have a work roll ground for each plate width. Accordingly, if the number of types of sheet widths to be manufactured is large, the number of work rolls is increased, but a rolling mill that manufactures a large amount of metal strips having the same width has a great effect. Further, depending on the steel type, the shape control ability may be insufficient even if a work roll bender is used, so it is necessary to attach a convex crown to the backup roll.
Also, in the present invention, work rolls having a tapered crown shape in which the roll diameter increases toward the roll end within a range of 150 mm inside from the plate end on one side to 150 mm outside from the plate end are arranged point-symmetrically in the vertical direction. In addition, since the shift device that shifts the upper and lower work rolls in the work roll body length direction is provided, the plate width restriction described above is eliminated and the number of work rolls held can be reduced. However, even if a work roll bender is used depending on the type of steel, the shape control ability may be insufficient, so it is necessary to attach a convex crown to the backup roll. Therefore, the rolling mill for producing metal strips having various plate widths has a great effect.
Furthermore, the present invention determines the amount of convex crown and work roll crown of the backup roll in the rolling mill described above, and the rolling of the metal strip during rolling so that the rolling strip outlet side plate shape becomes a desired plate shape. This represents a shape control method for controlling the work roll bender force or the work roll shift amount of the mill. This method enables preferable shape control of each rolling mill.
From the above, the present invention has a large diameter for skin pass rolling that does not cause a wrinkle in the metal strip of the hot dip galvanized steel sheet with a low load without causing a significant increase in equipment cost and can obtain a good plate shape. It is possible to provide a quadruple skin pass rolling machine and a skin pass rolling method.

FIG. 2 is a configuration diagram illustrating a large-diameter work roll quadruple skin pass rolling machine embodying the present invention. Usually, a thin metal strip rolled by a tandem cold rolling mill is subjected to skin pass rolling after heat treatment and plating treatment in a plating line called CGL.
The metal strip before being skin pass rolled is usually untrimmed and therefore there is an edge drop formed by cold tandem rolling on the metal strip before skin pass rolling.

Edge drop refers to a rapid decrease in the plate thickness at the end of the plate due to the flatness of the work roll when a metal strip is rolled by a rolling mill, such as roll diameter, roll Young's modulus, rolling load, etc. It is affected and usually occurs in the range of about 30-50 mm from the edge of the plate.
The contents of the present invention applied when the metal strip S in which such edge drop has occurred are plated with CGL and subjected to skin pass rolling with a large diameter rolling mill shown in FIG. 2 will be described below.

  FIG. 2 shows a quadruple skin pass rolling mill. Although not shown, a line for heat-treating and plating the metal strip rolled by the cold tandem rolling mill is installed upstream of the quadruple skin pass rolling mill. Continuously supplied. Although not shown, an apparatus for inspecting, chemical processing, shearing and winding the skin-pass-rolled metal strip S is installed downstream of the quadruple skin-pass rolling mill. In FIG. 2, the work roll of the rolling mill is composed of an upper work roll 1 and a lower work roll 1 ', and each work roll is supported by an upper work roll chock 7 and a lower work roll chock 7'. The roll profile of these work rolls can be changed. In addition, the surface of these work rolls has a surface roughness determined according to the needs of consumers, and what is called smooth bright is used.

As a shape control means, there is a bender device 12 capable of applying an increase and a decrease bender force for controlling the vertical deflection of the upper and lower work rolls 1 and 1 ′ with the upper and lower work roll chocks 7 and 7 ′ as fulcrums Has been placed. Moreover, although not shown in FIG. 2, a work roll shift device capable of shifting the upper and lower work rolls in the plate width direction is provided. The backup roll is composed of an upper backup roll 2 and a lower backup roll 2 ', and each backup roll 2, 2' is supported by an upper backup roll chock 8 and a lower backup roll chock 8 ', respectively. The profile of each backup roll 2, 2 ′ is basically flat, but a convex crown may be given to each backup roll 2, 2 ′ regarding the steel type when the shape control ability by the bender is insufficient. In some cases, a backup roll 2, 2 'whose roll profile is controllable by hydraulic pressure or the like may be used.

A load detection device 10 is disposed on the upper backup roll chock 8 to detect work side and drive side loads. In addition, an electric reduction device 11 is disposed above the load detection device 10, and a pass line adjustment when the metal strip S is rolled is performed. Here, this metal strip S is obtained by heat-treating and hot-dip galvanizing a metal strip after cold tandem rolling that has not been trimmed, and has an edge drop.

Furthermore, a hydraulic reduction device 9 for applying a rolling force is disposed below the lower backup roll chock 8 '. These devices, chock and the like are housed in a housing 13 of the rolling mill. Entry and exit deflector rolls 5 and 6 are arranged on the entry and exit sides of the rolling mill. Although not shown, pulse generators are installed on the entrance side and exit side deflector rolls 5 and 6 to detect the plate speed of the metal strips S on the entrance side and the exit side. The elongation at is detected. Although not shown, skin pass rolling lubricating oil is supplied toward the roll bite entrance on the rolling mill entrance side.

3 and 4 are explanatory views at the time of rolling the metal strip S of the upper and lower work rolls 1, 1 '. FIG. 3 shows a case where tapered crown shapes 20 are provided at both plate ends in both the upper and lower work rolls 1, 1 ′, and FIG. 4 shows in the upper and lower work rolls 1, 1 ′. When one tapered crown shape 20 is provided at one plate end of each work roll, and the upper and lower work rolls 1, 1 ′ are arranged so that the tapered crown shape 20 is point-symmetric with respect to the steel plate Is shown. The point symmetry means that the taper crown shape 20 provided on the upper work roll 1 and the taper crown shape 20 provided on the lower work roll 1 ′ are located symmetrically with respect to the center point in the longitudinal section of the steel sheet. That is. In FIGS. 3 and 4, a crown shape 21 is formed in the vicinity of the center of the upper and lower work rolls 1, 1 ′, and both ends of the upper and lower work rolls 1, 1 ′ are supported by bearings 22. Here, the upper and lower work rolls 1, 1 ′ can be shifted in the roll body length direction by a work roll shift device 23 provided at the end of the roll.

The present invention provides a large-diameter quadruple skin path for rolling a metal strip S of a hot-dip galvanized steel sheet with low load without causing wrinkles and obtaining a good sheet shape without causing a significant increase in equipment cost. As a rolling skin pass rolling method, for example, a convex crown shape having a parabolic pattern as shown in FIG. 3 a) and at least a roll end within a range 150 mm from the plate end on one side to 150 mm outside from the plate end. Work rolls 1, 1 'having a tapered crown shape in which the roll diameter increases toward the part are employed. Further, a convex crown roll is employed for the backup rolls 2, 2 'as required. In addition, the taper crown in this invention means the inclination part to the steel plate width direction outer side provided in the board edge part in the work rolls 1 and 1 '. As the inclination of the taper crown shape, the taper angle is preferably 0.01 degrees to 0.04 degrees. This is because when the taper angle is 0.01 degrees or less, the effect of reducing the plate end is lost. On the other hand, when the taper angle is 0.04 degrees or more, the non-contact portion (gap) is not provided between the backup roll and the work roll. This is because of this.

In addition, as described above, in the present invention, it is preferable to have a tapered crown shape in which the roll diameter increases toward the roll end within at least 150 mm inside from the plate end on one side and 150 mm outside from the plate end. . Thereby, it is possible to further reduce the plate end portion that is insufficiently reduced without disturbing the plate shape (flatness) of the metal strip S. When the taper crown shape is formed on the work roll in a large range of 150 mm or more from the plate edge, the entire work roll is bent and the plate shape deteriorates. Therefore, the taper crown shape is formed 150 mm from the plate edge. It is preferable that it is in the range of 150 mm outside from the end of the plate from the inside.

An example of the work roll crown of the present invention is shown in a), b) and c) of FIG. The shape of the work roll shown in FIG. 5a) has a convex crown with a parabolic pattern, and a taper in which the roll diameter increases toward the roll end within the range of 150 mm inside from the plate end to 150 mm outside from the plate end. It has a crown shape 20.
The crown in the shape of this work roll needs to be changed for each sheet width and rolling load level. When the roll crown is attached to both ends of the work roll, it is not always necessary to attach the crown of the work roll to the upper and lower work rolls 1 and 1 ′, and only one of the upper work roll 1 and the lower work roll 1 ′ may be used.

Further, in the shapes of the work rolls shown in FIG. 5 b) and c), a crown is provided only on one side, the upper and lower work rolls 1 and 1 ′ are arranged symmetrically with respect to the steel plate, and the upper and lower work rolls are further provided. By making 1, 1 ′ shiftable in the body length direction, the above-described plate width restriction is almost eliminated, and the number of crown-rolled rolls can be significantly reduced. Further, by using a roll whose roll crown can be controlled as the backup rolls 2 and 2 ′, the number of backup rolls provided with a crown can be significantly reduced.

In order to confirm the prior art, skin pass rolling was performed using the flat work roll shown in FIG. The work roll bender at that time was adjusted to a flat shape.

As a result of investigating the surface and shape of the metal strip after skin pass rolling, when the work roll was a flat roll, the work roll bender was -30 KN / chock and the plate shape was flat, but the ear wrinkle was from the edge of the plate. It occurred in the area inside 40mm. In addition, the wrinkle disappeared when the work roll bender was -150 KN / chock, but the plate shape had an edge elongation of 3% steepness. The work roll bender at the end extension with a maximum steepness of 1% allowed as a product was −80 KN / chock. At that time, the ear wrinkle occurred in the range 30 mm inside from the end of the plate.
Therefore, in the flat work roll of the prior art, there is no condition that satisfies both the prevention of ear wrinkles and the flatness of the plate shape at the same time.

Next, when a roll of a crown whose diameter increases as it goes to the body end is used as a conventional work roll as shown in FIG. 5 d), the maximum steepness allowed as a product when the crown amount is appropriate. The work roll bender at the end of 1% is + 30KN / chock. At that time, the wrinkle was generated within 5mm from the edge of the plate, and the effect was recognized, but the work roll and the backup were at the edge of the plate. A part (gap) that does not come into contact with the roll is generated, and the roll roughness of the part corresponding to the work roll position of the gap becomes rougher than other parts, and a continuous streak defect (pattern) on the surface of the rolled metal strip. Was noticeably generated after two-coil rolling. This streak defect occurred at the edge of the plate or 30 mm inside, and this part was eventually trimmed.
Therefore, in the case of using a special crown roll so that the roll diameter increases as it goes to the body end of the prior art, it is possible to satisfy both the prevention of ear wrinkles and the flatness of the plate shape at the same time. However, a new streak defect was generated and the yield improvement effect was not obtained. This is because the rolling load is small and sufficient work roll deflection and roll flatness cannot be obtained.

The skin pass rolling mill of the present invention is the same as the conventional one except for the work roll crown.
As shown in FIG. 5a), the work roll has a convex crown with a parabolic pattern of 100 microns per diameter over the length of the body roll, and at least 30 mm inside from the plate end on one side and 50 mm outside from the plate end. It has a 50 micron tapered crown per diameter with the roll diameter increasing towards the roll end.

As an example of the present invention, the work rolls shown in FIG. 5 a) were incorporated as upper and lower work rolls and rolled under the skin pass rolling conditions shown in Table 1. As a result, the work roll bender at the end extension with a maximum steepness of 1% allowed as a product was −10 KN / chock, and at that time, no ear wrinkles or streak defects were generated. Accordingly, it was possible to eliminate defective portions (total of about 60 mm) that occurred in the range about 30 mm inside from the edge of the conventional plate, and the effect was recognized.

As described above, as described above, in the flat work roll, there is no condition that satisfies both the prevention of wrinkle prevention and the flatness of the plate shape at the same time. In the case of using a special roll of crown to increase the resistance, it was possible to satisfy both the prevention of wrinkle prevention and the flatness of the plate shape at the same time, but a new streak defect occurred and the yield increased. The improvement effect was not obtained.

As is clear from the above, the yield could not be improved by the prior art, but the present invention has a convex crown with a parabolic pattern and 150 mm from the plate end on one side to 150 mm from the plate end. By adopting a work roll with a tapered crown whose roll diameter increases toward the roll end within the outer area, it is possible to prevent ear wrinkles with good flatness and no streak defects. Skin pass rolling of hot-dip galvanized steel sheets became possible.

  The present invention can produce a product having a good surface property that prevents wrinkles when a metal strip of a hot dip galvanized steel sheet is supplied with lubricating oil on the inlet side of the rolling mill or is subjected to skin pass rolling without lubrication. Applicable to possible rolling mills and rolling methods.

It is a picture of an ear wrinkle. It is a lineblock diagram showing one embodiment of a skin pass rolling mill of the present invention. It is explanatory drawing at the time of the metal strip S rolling of the upper and lower work rolls 1 and 1 'in case the taper crown shape 20 is provided in both plate edge part. One upper and lower work rolls when one tapered crown shape 20 is provided at one plate end, and the upper and lower work rolls 1 and 1 'are arranged so that the tapered crown shape 20 is point-symmetric with respect to the steel plate. It is explanatory drawing at the time of 1, 1 'metal strip S rolling. a) It is a figure which shows the example of the work roll profile of this invention. b) It is a figure which shows the example of the work roll profile of this invention. c) It is a figure which shows the example of the work roll profile of this invention. d) It is a figure which shows the example of the work roll profile of a prior art. e) It is a figure which shows the example of the work roll profile (flat) of a prior art.

Explanation of symbols

1: Upper work roll 1 ': Lower work roll 2: Upper backup roll 2': Lower backup roll 5: Incoming deflector roll 6: Outgoing deflector roll 7: Upper work roll chock 7 ': Lower work roll chock 8: Upper backup roll chock 8 ': Lower backup roll chock 9: Hydraulic reduction device 10: Load detection device 11: Electric reduction device 12: Bender device 13: Housing 20: Tapered crown shape 21: Crown shape 22: Bearing 23: Work roll shift device S: Metal strip

Claims (6)

A galvanized steel sheet quadruple skin pass rolling machine,
A pair of upper and lower backup rolls having a flat shape or a convex crown shape of a parabolic pattern;
A convex crown shape of a parabolic pattern, and a pair of upper and lower work rolls having a tapered crown shape in which the roll diameter increases toward the roll end within a certain range before and after the plate end,
A quadruple skin pass rolling machine for hot-dip galvanized steel sheets, comprising: a bender device that applies a bending force in a direction perpendicular to the work roll to a roll shaft end of the work roll.   The tapered crown shape is within a range of 150 mm inside from the plate end to 150 mm outside from the plate end, and is provided at both plate ends in either one of the upper and lower work rolls. 4. A four-skin-pass rolling mill for hot-dip galvanized steel sheets according to 1. The tapered crown shape is within a range of 150 mm from the plate end to 150 mm outside from the plate end within the shift capability range of the work roll, and is provided one by one at the plate end in the upper and lower work rolls,
The upper and lower work rolls are arranged so that the tapered crown shape is point-symmetric with respect to the steel sheet,
The quadruple skin pass rolling machine for hot-dip galvanized steel sheets according to claim 1, further comprising a work roll shift device that shifts the work roll in the work roll body length direction. A skin pass rolling method for hot-dip galvanized steel sheet,
Based on the width of the metal strip of the hot dip galvanized steel sheet and the rolling load at the desired light reduction, a crown amount is given to the pair of upper and lower backup rolls and / or the pair of upper and lower work rolls,
In the upper and lower work rolls, giving a tapered crown shape in which the roll diameter increases toward the roll end within a certain range before and after the plate end,
A skin pass rolling method for a hot-dip galvanized steel sheet, characterized in that the work roll bender force of the rolling mill is controlled so that a rolling mill delivery side plate shape of the metal strip being rolled becomes a desired plate shape.   The taper crown shape is in a range of 150 mm inside from the plate end to 150 mm outside from the plate end, and is provided at both plate ends in the upper or lower one of the work rolls. A skin pass rolling method for the hot-dip galvanized steel sheet.   The tapered crown shape is provided within a range of 150 mm from the plate end to 150 mm outside from the plate end within the shift capability range of the work roll, and is provided one by one at the plate end of the upper and lower work rolls. The upper and lower work rolls are arranged so that the crown is point-symmetric with respect to the steel plate, and the work roll shift amount of the rolling mill is such that the rolling strip outlet side plate shape of the metal strip during rolling becomes a desired plate shape. The skin pass rolling method for hot-dip galvanized steel sheets according to claim 4, characterized in that control is performed.