JP2007319879A - Apparatus to be provided in reverse rolling mill to prevent downward warping, and method for preventing downward warping - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus and a method for preventing the downward warping and the buckling of a metallic plate in reverse rolling. <P>SOLUTION: The apparatus for preventing the downward warping comprises stripper guides having flat plane portions on their upper surfaces, and moving members for reciprocating the stripper guides between their operating positions and their receded positions, wherein the flat plane portions are arranged between the horizontal plane passing the upper edge of a lower work roll and the horizontal plane passing the upper edge of carrier rolls in the operating position. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an apparatus and a method for preventing a metal plate from warping when rolling a metal plate such as a thick steel plate.

  Generally, when rolling a metal plate having a large thickness (for example, a thick steel plate), a technique called reverse rolling is employed. Reverse rolling uses a rolling mill having a pair of upper and lower work rolls (hereinafter referred to as a reverse rolling mill) to produce a metal plate having a predetermined thickness by reducing a hot metal block (hereinafter referred to as a slab). The following (1) to (6) are listed as a series of procedures in order.

That is, reverse rolling
(1) Insert the slab from the front of the reverse rolling mill,
(2) The work roll is slab pressed down and discharged to the rear surface.
(3) Narrow the interval between work rolls and reversely rotate the work roll and the transport roll.
(4) Insert the slab from the rear of the reverse rolling mill,
(5) Roll down the slab with a work roll and discharge it to the front.
(6) By repeating the procedure of narrowing the interval between the work rolls and rotating the work rolls and the transport rolls in reverse, the slab is reciprocated between the front and rear faces of the reverse rolling mill to finish to a predetermined thickness. It is rolling technology.

However, since the reverse rolling machine is pressed down by a pair of upper and lower work rolls, the straightening effect during rolling cannot be expected, and the metal plate is likely to warp. The warpage is caused by various factors such as the difference between the upper surface temperature and the lower surface temperature of the metal plate, the peripheral speed of the upper work roll and the lower work roll, and the difference in surface properties.
(a) Upward warping: The end of the metal plate curves upward
(b) Downward warping: The end of the metal plate is roughly divided into a downward curve. Of these, downward warping causes troubles such as the end of the downwardly curved metal plate being caught under the transport roll and hindering transport. Thus, various techniques for preventing the metal sheet from warping in reverse rolling have been studied.

  For example, Patent Document 1 discloses a technique for preventing warpage of a metal plate by actually measuring warpage and adjusting a position of a pass line or a peripheral speed difference between upper and lower work rolls according to the measured value. . However, in reverse rolling performed in a high temperature environment, the sensor for measuring warpage is exposed to high heat and is affected by steam generated in the vicinity, so that the measurement accuracy is inevitably lowered. In addition, the downward warping is caused by various factors such as the difference between the upper surface temperature and the lower surface temperature of the metal plate, the peripheral speed of the upper work roll and the lower work roll, and the difference in surface properties. The effect of preventing downward warping cannot be obtained sufficiently only by adjusting the position and the peripheral speed difference between the upper and lower work rolls.

Further, in Patent Document 2 by the present applicant, a mechanism capable of raising a stripper guide installed between the lower work roll of the reverse rolling mill and the nearest transport roll along the outer periphery of the lower work roll is provided. Thus, a technique for raising the stripper guide located on the exit side of rolling and preventing the metal sheet from warping downward is disclosed. However, since the shape of the stripper guide remains the same, a curved portion remains at the tip of the metal plate. That is, the technique disclosed in Patent Document 2 has room for further improvement.
Japanese Patent No. 3298465 Japanese Patent Application No. 2005-277251

  An object of the present invention is to provide a downward warpage prevention device that solves the above-described problems and prevents the downward bending and hip folding of a metal plate in reverse rolling.

  The present invention is a downward warpage prevention device installed between a lower work roll of a reverse rolling mill for rolling a metal plate and a nearest transport roll, and operates a stripper guide having a flat portion on the upper surface and a stripper guide. A lower warp which has a moving member which can reciprocate between a position and a retracted position, and which places a plane portion between a horizontal plane passing through the upper end of the lower work roll and a horizontal plane passing through the upper end of the transport roll at the operating position. Prevention device.

  The present invention also provides a stripper guide having a flat surface on the upper surface between the lower work roll of the reverse rolling mill for rolling a metal plate and the nearest transport roll, and the stripper guide is located between the operating position and the retracted position. The warp that supports the metal plate by operating the stripper guide so that the plane part is located between the horizontal plane passing through the upper end of the lower work roll and the horizontal plane passing through the upper end of the transport roll at the operating position. It is a prevention method.

  In the downward warpage prevention method of the present invention, the stripper guide is operated to support the metal plate so that the plane portion is horizontal between the horizontal plane passing through the upper end of the lower work roll and the horizontal plane passing through the upper end of the transport roll. Is preferred.

  ADVANTAGE OF THE INVENTION According to this invention, the downward curvature of the metal plate in reverse rolling can be prevented more effectively.

FIG. 1 is a cross-sectional view schematically showing an example of a reverse rolling mill provided with the warpage prevention device of the present invention. An arrow A in FIG. 1 indicates the conveyance direction of the slab 1. P1 indicates a horizontal plane passing through the upper end of the lower work roll 2b, and P2 indicates a horizontal plane passing through the upper end of the transport roll 3.
The slab 1 is conveyed in the direction of arrow A on the conveying roll 3 from the right side of the reverse rolling mill having a pair of upper and lower work rolls (that is, the upper work roll 2a and the lower work roll 2b). It is rolled down by the upper work roll 2a and the lower work roll 2b, and discharged to the left side of the reverse rolling mill (for convenience, this is referred to as the rear face). Here, a material used for reverse rolling is referred to as a slab, and is distinguished from a metal plate finished to a predetermined thickness.

  Next, although not shown in the drawings, the intervals between the upper work roll 2a and the lower work roll 2b are narrowed, and the upper work roll 2a, the lower work roll 2b, and the transport roll 3 are reversely rotated to move the slab 1 from the rear surface to the front surface. While transporting, press down again. In this way, by reciprocating the slab 1 between the front surface and the rear surface of the reverse rolling mill, a metal plate having a predetermined thickness is manufactured by repeatedly reducing the slab.

Stripper guides 5a and 5b are installed between the conveying rolls 3a and 3b closest to the reverse rolling mill (hereinafter referred to as the nearest) and the lower work roll 2b. The stripper guides 5a and 5b reciprocate between an operating position and a retracted position by a moving member (not shown). The structure of the moving member is not particularly limited, and a conventionally known member such as a cylinder or an electric motor is used.
For example, as shown in FIG. 1, when the slab 1 is transported in the direction of arrow A (ie, from the front to the rear), the front stripper guide 5a is moved to the retracted position, and the rear stripper guide 5b is moved to the operating position. . Although not shown, when the slab 1 is transported from the rear surface to the front surface, the rear stripper guide 5b is moved to the retracted position, and the front stripper guide 5a is moved to the operating position. The retreat position refers to a position where the stripper guides 5a and 5b do not become an obstacle when the slab 1 is conveyed.

Hereinafter, the stripper guide 5b moved to the operating position will be described with reference to FIG. FIG. 2 shows an enlarged view of the stripper guide 5b moved to the operating position in FIG.
As shown in FIG. 2, the stripper guide 5b has a flat portion 6 on its upper surface. The upper surface of the stripper guide 5b is a part that is transported from the lower work roll 2b to the nearest transport roll 3b while the tip of the slab 1 slides. The prevention effect is improved. If this plane part 6 rises to a position higher than the horizontal plane P1, it will hinder the conveyance of the slab 1. On the other hand, if the plane portion 6 is lowered to a position lower than the horizontal plane P2, the metal plate cannot be effectively warped downward. Therefore, the plane portion 6 needs to be disposed between the horizontal plane P1 and the horizontal plane P2.

As shown in FIG. 2, the plane portion 6 is preferably disposed horizontally between the horizontal plane P1 and the horizontal plane P2. By arranging the plane portion 6 horizontally, the pair of upper and lower work rolls 2a, 2b and the stripper guide 5b exhibit a correction effect, and therefore the effect of preventing the metal plate from warping down is further improved.
However, the plane portion 6 is not necessarily horizontal and may be inclined. In that case, as shown in FIG. 3, it is preferable to lower the nearest conveyance roll 3b side. The reason is that if the height of the nearest transporting roll 3b is raised, the transport of the slab 1 may be hindered.

  When the upper surface of the stripper guide 5b is entirely formed of a flat surface, an end portion (hereinafter referred to as a front end portion) near the lower work roll 2b becomes thin. As a result, when the slab 1 comes into contact, the tip of the stripper guide 5b is easily damaged. Further, an end portion (hereinafter referred to as a rear end portion) far from the lower work roll 2b is also easily damaged by an impact when the slab 1 passes. Therefore, as shown in FIG. 4, it is preferable to chamfer the front end portion and the rear end portion of the stripper guide 5b to provide the front end chamfered portion 7 and the rear end chamfered portion 8. The chamfered shape of the front end chamfer 7 and the rear end chamfer 8 may be a flat surface or a curved surface.

As shown in FIG. 4, the upper surface of the stripper guide 5 b includes a flat portion 6, a front end chamfered portion 7, and a rear end chamfered portion 8. Assuming that the lengths of the flat portion 6, the front end chamfered portion 7 and the rear end chamfered portion 8 in the slab conveying direction are L ₆ , L ₇ and L ₈ respectively, the plane ratio (%) calculated by the following formula is If it is less than 70%, the metal plate cannot be warped downward. Therefore, the plane ratio is preferably 70% or more.

Plane Ratio _{(%) = 100 × L 6} / (L 6 + L 7 + L 8)
However, if the plane ratio exceeds 90%, the leading end or the trailing end of the stripper guide 5b tends to be damaged. Therefore, the plane ratio is more preferably 70 to 90%.
In addition, the flat part 6 is worn by contacting with the tip part of the slab 1, and a concave part is generated. The allowable range of the depth and width of the recess is appropriately set according to the material of the metal plate.

  A slab 1 (thickness 250 mm) cast by continuous casting of molten steel was subjected to the reverse rolling mill shown in FIG. 1 to produce a thick steel plate (thickness 40 mm). When the slab 1 is loaded from the front side of the reverse rolling mill (that is, the right side of the reverse rolling mill shown in FIG. 1), the stripper guide 5a on the front side is moved to the retracted position, and the rear side (that is, the left side of the reverse rolling mill shown in FIG. 1). ) Stripper guide 5b was moved to the operating position. The rear stripper guide 5b was moved using a hydraulic lifting device.

Further, when the slab 1 was loaded from the rear surface of the reverse rolling mill, the rear surface stripper guide 5b was moved to the retracted position, and the front surface stripper guide 5a was moved to the operating position. The front stripper guide 5a was moved using a hydraulic elevator.
In this way, the slab 1 was subjected to 11 times of reduction (so-called 11 passes). The diameters of the upper work roll 2a and the lower work roll 2b are both 1200 mm. The stripper guides 5a and 5b are both 700 mm in height, and the upper surface thereof is arranged so that the plane portion 6 is between the horizontal plane P1 and the horizontal plane P2 at the operating position and is horizontal as shown in FIG. The width of the upper surface (= L ₆ + L ₇ + L ₈ ) is 470 mm. As shown in FIG. 4, the chamfered shape is such that the front end chamfered portion 7 is a flat surface and the rear end chamfered portion 8 is an arcuate curved surface. This is an invention example.

On the other hand, as a comparative example, a thick steel plate was manufactured using a stripper guide having a convex upper surface as shown in FIG. Since other conditions are the same as those of the invention example, the description is omitted.
About the invention example and the comparative example, as shown in FIG. 6, the amount of downward warp H of the obtained thick steel plate 9 was measured 20 sheets at a time. As a result, the average amount of warpage H of the inventive examples was 3 mm, while the comparative examples had an average of 10 mm.

  As described above, in the inventive examples, it was confirmed that the downward warping of the thick steel plate (that is, the metal plate) in reverse rolling can be prevented.

It is sectional drawing which shows typically the example of the reverse rolling mill which installed the curvature prevention apparatus of this invention. It is sectional drawing which shows typically the example which expanded the stripper guide of the rear surface in FIG. 1, and its periphery. It is sectional drawing which shows typically the other example which expanded the stripper guide of the rear surface in FIG. 1, and its periphery. It is sectional drawing which expands and typically shows the upper part of the stripper guide of the rear surface in FIG. It is sectional drawing which shows typically the example which expanded the stripper guide used for the comparison, and its periphery. It is sectional drawing which shows typically the measurement site | part of the amount of downward curvature of a thick steel plate.

Explanation of symbols

1 Slab
2a Top work roll
2b Lower work roll 3 Transport roll
3a The latest transport roll
3b The latest transport roll
4a Upper backup roll
4b Lower backup roll
5a Stripper guide
5b Stripper guide 6 Flat part 7 Front chamfer 8 Rear chamfer 9 Thick steel plate

Claims (3)

  A lower warpage prevention device installed between a lower work roll of a reverse rolling mill for rolling a metal plate and a nearest transport roll, a stripper guide having a flat surface on the upper surface, and retracting the stripper guide from its operating position. A movable member that is capable of reciprocating between positions, and disposing the planar portion between a horizontal plane passing through the upper end of the lower work roll and a horizontal plane passing through the upper end of the transport roll at the operating position. An anti-warping device characterized by.   A stripper guide having a flat portion on the upper surface is installed between the lower work roll of the reverse rolling mill that rolls the metal sheet and the nearest transport roll so that the stripper guide can reciprocate between the operating position and the retracted position. The stripper guide is operated to support the metal plate so that the plane portion is positioned between a horizontal plane passing through the upper end of the lower work roll and a horizontal plane passing through the upper end of the transport roll at the operating position. A method of preventing downward warping characterized by the above.   The stripper guide is operated to support the metal plate so that the plane portion is horizontal between a horizontal plane passing through the upper end of the lower work roll and a horizontal plane passing through the upper end of the transport roll. Item 3. The method for preventing warpage according to Item 2.

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