JP2008280584A - Method for controlling shape of steel strip in continuous hot dip plating line, and control device therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for controlling a shape where the C warpage/deformation of a steel strip in continuous hot dip plating can be corrected at high precision, and to provide a device therefor. <P>SOLUTION: In two supporting rolls sandwiching a steel strip passing through a sink roll and running upward, the supporting roll (3<SB>A</SB>) located at the side opposite to the sink roll is arranged at the upper part and the supporting roll (3<SB>B</SB>) located at the side same as that of the sink roll is arranged at the lower part, respectively, and intermesh (IM<SB>1</SB>) quantity between the supporting roll (3<SB>A</SB>) and the supporting roll (3<SB>B</SB>), and the distance (L<SB>2</SB>) between roll axes in the supporting roll (3<SB>A</SB>) and the supporting roll (3<SB>B</SB>) in the vertical direction are regulated, so as to be increased/decreased in accordance with the material kind and sheet thickness of the steel strip. As the effect of the regulation of the distance (L<SB>2</SB>) between the roll axes, the sensitivity of the supporting rolls (the dimensions of the change of C warpage quantity to the change of the IM<SB>1</SB>quantity) is relaxed with a sufficient degree, and reverse bending stress is regulated at high precision, so as to secure the satisfactory flatness of the steel strip. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a steel strip width warpage deformation control method and a control device for ensuring good flatness of a steel strip that passes through a hot dipping bath and is led out onto the bath in a continuous hot dipping line.

In the continuous hot dip plating line, as shown in FIG. 6, the hot dip plating of the steel strip is performed by using the sink roll (2) in the hot dip bath (1) and the supporting roll (3) above it. It is performed by running in the bath while supporting and guiding. Immediately above the plating bath (1), wiping nozzles (4) are arranged opposite to both sides of the steel strip (S) as means for adjusting the amount of plating adhesion (also referred to as the basis weight) on the surface of the steel strip. When the steel strip (S) pulled up from the plating bath passes therethrough, the plating adhesion amount is controlled by the wiping action of the gas flow injected from the wiping nozzle (4).
In order to control the coating amount of the steel strip so that it reaches a predetermined amount over the entire surface of the steel strip, the jet gas flow of the wiping nozzle (4) is applied to both the front and back surfaces of the steel strip (S). Therefore, the steel strip needs to be flat without deformation.

  However, warpage deformation in the plate width direction called “C warpage” occurs in the steel strip whose direction has been changed by the sink roll (2). This is because plastic deformation occurs due to winding around the roll peripheral surface when passing through the sink roll (2), and the amount of plastic deformation differs between the front side and the back side by the thickness of the steel strip (S). When the steel strip (S) is separated from the sink roll (2), the bending moment of the stress in the width direction is released and C warpage deformation occurs. This C warpage deformation exhibits a concave curved shape on the sink roll (2) side. When the steel strip (S) led out onto the plating bath is deformed in this way, the jet pressure and jet flow of the gas flow jetted from the wiping nozzle (4) to the steel strip are not uniform in the plate width direction. As a result, unevenness in the amount of plating is generated, and the plating quality is impaired.

As a method of correcting the C warpage deformation of the steel strip, a pair of supporting rolls (3 _A ) (3 _B ) sandwiching the steel strip (S) is provided above the sink roll (2) as shown in FIGS. A straightening method of placing and applying roll bending stress (reverse bending stress against C warpage deformation) to the steel strip (S), or installing an electromagnet (6) directly above the wiping nozzle (4) as shown in FIG. Devices such as a method of correcting C warp by reverse bending strain due to force have been proposed.

The C-warp correction method of FIG. 7 is the supporting roll (3 _A ) located on the opposite side of the sink roll (2) across the steel strip (S), and the supporting roll located on the same side as the sink roll (2). while arranged rolls (3 _B) to the upper, connecting the horizontal position controller (5) to the supporting rolls (3 _a), bending stress applied to the strip by adjusting the pressing amount of supporting rolls (3 _a) To correct the C warpage deformation (Patent Documents 1 and 2).
The C warpage deformation correction method of FIG. 8 is opposite to that of FIG. 7 above, the supporting roll (3 _B ) on the same side as the sink roll (2) is placed on the lower side, and the supporting roll (3 _A ) on the opposite side is placed on the upper side. Each is disposed, and one (or both) of them is provided with a horizontal position control device (5) to correct the C warpage deformation of the steel strip (S) (Patent Documents 3 and 4).

On the other hand, as shown in FIG. 9, the correction method for C warpage deformation using electromagnetic force is usually performed in combination with roll bending (reverse bending) by a supporting roll, and is directly above the wiping nozzle (4). The electromagnet (6) is placed opposite to the left and right sides of the steel strip, the shape of the steel strip (S) pulled up from the plating bath is detected by the shape detection sensor (7), and depending on the amount of C warp detected The electromagnetic force is applied to the steel strip to correct the C warpage deformation (Patent Document 5).
JP 09-025552 A JP-A-10-130800 JP-A-62-030865 JP 2000-273610 A JP 2003-113460 A

In the method of correcting the C warpage deformation of the steel strip by pressing the supporting roll (3) (3 _A , 3 _B ), the change of the C warpage amount of the steel strip by controlling the roll push amount (intermesh amount) is not simple Absent. FIG. 10 shows an example of a change in the amount of C warpage deformation (warpage amount mm = mm / m per 1 m of plate width) by the control of intermesh.
This C warp deformation correcting operation is performed by fixing the lower supporting roll (3 _B ) in a predetermined position and moving the upper supporting roll (3 _A ) (located on the opposite side of the sink roll 2) in FIG. This is done by moving horizontally toward (S). The amount of intermesh (IM ₁ ) on the horizontal axis indicates the pushing amount (mm) of the supporting roll (3 _A ) with respect to the supporting roll (3 _B ). Further, + (positive sign) on the vertical axis indicates positive C warpage deformation (concave concave deformation toward the sink roll 2), and-(negative sign) indicates negative C warpage deformation (curve convex toward the sink roll 2). (Deformation). Positive C warpage deformation means insufficient reverse bending effect (remaining C warpage deformation), and negative C warpage deformation means that reverse bending stress is excessively applied (occurrence of reverse C warpage deformation). ing. The thickness (t) of each steel strip in the graphs (a), (b), and (c) in the figure is 6.0 mm, 3.0 mm, and 1.4 mm, respectively (all steel types are low carbon steels with the same chemical composition) ).

  As shown in the figure, the C warpage deformation of the steel strip changes sensitively by a slight change in the roll push-in amount (intermesh amount). Moreover, the state of the change varies greatly depending on the plate thickness. For this reason, in order to correct the C warp deformation of the steel strip without excess or deficiency and obtain a good flat shape, it is necessary to strictly adjust the amount of intermesh. For example, when the plate thickness is 3.0 mm (graph b), The amount of intermesh must be adjusted to within 25 ± 2mm in order to obtain flatness that satisfies warpage: 0 ± 2mm / m. However, when automatically controlling the indentation of the roll, it is not easy to finely adjust the amount of intermesh, and it is accompanied by variations due to plate thickness and material characteristics (hardness, etc.), so plating quality (uniformity of plating adhesion, etc.) On the other hand, deformation that cannot be ignored (C warpage or reverse C warpage deformation) remains.

  On the other hand, the method using the shape correction apparatus including the electromagnet (6) as shown in FIG. 9 is extremely expensive and requires a lot of equipment cost even if precise reverse bending control is possible by controlling the excitation current. When a steel strip with a large plate thickness is targeted, it becomes a remarkably large facility. In addition, since it is necessary to install in the vicinity of the wiping nozzle (4), it is often difficult to apply to existing plating lines due to layout restrictions.

  The present invention has been made in view of the above, and in the C warpage deformation correction operation of the steel strip by roll indentation (roll bending) in the plating bath, the magnitude of the change of the C warpage deformation amount with respect to the increase / decrease change of the intermesh amount. By moderately mitigating (hereinafter also referred to as “roll sensitivity”), it is easy to adjust the amount of intermesh and automatically control it. Disclosed is a method and an apparatus for correcting the shape of a steel strip in continuous hot dipping, which can reduce deformation and secure a desired flat shape.

The method for correcting the shape of a steel strip in continuous hot dipping of the present invention (Claim 1)
Continuous hot-dip plating in which the steel strip is introduced into the hot dipping bath, supported and guided by the sink roll and supporting roll, run in the bath, led out onto the bath, and then the amount of plating on the surface of the steel strip is adjusted with the wiping nozzle in one of the two supporting rolls sandwiching the steel strip travels upward through the sink roll, the supporting rolls (3 _a) at an upper level on the opposite side of the sink roll, supporting rolls located on the same side as the sink roll (3 _B ) is placed below each,
Depending on the grade and the thickness of the steel strip, intermeshing (IM ₁₎ with the upper supporting rolls (3 _A) and the lower supporting rolls (3 _B) weight, and supporting rolls (3 _A) and the lower-level It is characterized by adjusting the distance (L ₂ ) between roll axes in the vertical direction with the supporting roll (3 _B ).
The vertical roll axis distance (L ₂ ) is preferably adjusted in the range of 100 to 260 mm.

The steel strip shape straightening apparatus (Claim 2) in the continuous hot dipping of the present invention comprises:
Continuous hot dip plating in which sink rolls and supporting rolls for supporting and guiding the steel strip introduced into the hot dipping bath are arranged in the bath, and wiping nozzles for adjusting the amount of plating on the surface of the steel strip are arranged on the plating bath In the device
The supporting roll is composed of an upper supporting roll (3 _A ) located on the opposite side of the sink roll and a lower supporting roll located on the same side as the sink roll with a steel strip passing upward through the sink roll. (3 _B )
Top supporting rolls (3 _A) and the lower supporting rolls (3 _B) and intermesh (IM ₁₎ the horizontal position controller for adjusting the amount, and the upper supporting rolls (3 _A) and the lower supporting rolls of A vertical position control device is provided for adjusting the vertical roll axis distance (L ₂ ) to (3 _B ).

In FIG. 3, when the steel strip (S) turned upward by the sink roll (2) passes through the upper supporting roll (3 _A ) (located on the opposite side of the sink roll 2), the C warp deformation occurs. A bending stress in the opposite direction to that (plastic deformation generated through the sink roll 2) is applied.
The effect of correcting the C warp deformation due to the reverse bending stress varies depending on the size of the contact angle (winding angle) (θ) of the steel strip with respect to the upper supporting roll (3 _A ), and the contact angle (θ) is lower It increases or decreases depending on the size of the intermesh (IM ₁ ) with the supporting roll 3 _B. Further, the contact angle (θ) can be increased or decreased by adjusting the distance (L ₂ ) between the upper support roll (3 _A ) and the lower support roll (3 _B ) (= the distance between the roll axes in the vertical direction). it can.
That is, as the distance (L ₂ ) between the roll axes is increased, the contact angle (θ) increases or decreases with the change in the pushing amount (intermesh amount) of the upper supporting roll (3 _A ), and the reverse due to it. The amount of change in bending stress increases and decreases. This means that the “roll sensitivity” becomes gentle, and it means that an appropriate intermesh control range for bringing the C warpage deformation amount close to 0 becomes wide. The present invention has the greatest feature in that the roll sensitivity can be adjusted by controlling the vertical position of the supporting roll in this way.
As a result, precise control of the reverse bending stress by the horizontal position control operation of the supporting roll is facilitated, and C warpage of the steel strip can be reduced and eliminated with high accuracy. In addition, automation of the horizontal movement control becomes easy.

FIG. 1 shows an example of the arrangement of a supporting roll (3) and a control mechanism for carrying out shape control of a steel strip according to the present invention.
Sink roll (2) in the upward direction change the steel strip (S) is derived on the two supporting rolls _{(3) (3 A, 3} B) and through to the plating bath (1). Steel strip opposite the arranged upper supporting rolls sink roll (2) across the (S) (3 _A) and the sink roll (2) and disposed on the same side lower supporting rolls (3 _B) A horizontal position control device (5) and a vertical position control device (8) are connected to each other. The amount of intermesh (IM ₁ ) between the upper supporting roll (3 _A ) and the lower supporting roll (3 _B ) is the horizontal position controller (5) of one or both of the two rolls (3 _A ) (3 _B ). ), And the vertical roll axis distance (L ₂ ) between the upper supporting roll (3 _A ) and the lower supporting roll (3 _B ) is either or both of the vertical position control devices ( 8) is adjusted.

In the steel strip shape control according to the present invention, the horizontal position control device (5) and the vertical position control device (8) are necessarily provided on both of the two supporting rolls (3 _A ) and (3 _B ). There is no need, one supporting roll adopts an embodiment in which the height position in the bath is fixed and only the horizontal position control is performed, and the other supporting roll is fixed in the horizontal direction and only the vertical position control is performed. You can also. An example is shown in FIG. In this example the horizontal position controller (5) is connected to the upper supporting rolls (3 _A), vertical position control system to the lower supporting rolls (3 _B) (8) is connected. The amount of intermesh (IM ₁ ) between the upper support roll (3 _A ) and the lower support roll (3 _B ) is adjusted by the horizontal position control of the upper support roll (3 _A ), and the upper support roll The vertical roll axis distance (L ₂ ) between (3 _A ) and the lower supporting roll (3 _B ) is adjusted by the vertical position control of the lower supporting roll (3 _B ).

An example of the analysis result will be described with respect to the C warpage deformation correction effect of the steel strip according to the present invention.
The supporting roll (3) in the hot dipping bath has the structure shown in FIG. 2, and the intermesh (IM ₁ ) with the lower supporting roll (3 _B ) is controlled by the horizontal position control of the upper supporting roll (3 _A ). ) Adjust the amount, and adjust the distance (L ₂ ) between the roll axes by controlling the vertical position of the lower supporting roll (3 _B ).
The analysis conditions are as shown in Table 1.

The analysis results are shown in FIG. The vertical axis (warp deformation amount mm / m) in the figure is the same as in FIG. 10, the positive sign (+) is positive C warpage (curved deformation concave toward the sink roll 2), and the negative sign (− ) Represents a negative C warp (curved deformation convex toward the sink roll 2), a positive C warp means that the reverse bending effect is insufficient, and a negative C warp means that the reverse bending stress is excessively applied. is doing. The correlation between intermesh (IM ₁ ) and C warpage deformation (mm / m) of each graph in the figure is expressed by the following equation.
Graph i [L ₂ = 130mm] y = -2.3309x + 28.372 (R ² = 0.9873)
Graph ii [L ₂ = 195mm] y = -1.2500x + 25.398 (R ² = 0.9865)
Graph iii [L ₂ = 260mm] y = -0.7907x + 22.870 (R ² = 0.9797)

As is clear from comparison between FIG. 4 and FIG. 10, the graph is shown as the height of the supporting roll (3 _B ) is lowered (the distance L ₂ between the roll axes with the supporting roll 3 _A is increased). The slope of is gentle. That is, the distance between the roll axes (L ₂ ) is increased, and the change in reverse bending stress with respect to the amount of pushing of the supporting roll (3 _A ) into the supporting roll (3 _B ) (intermesh (IM ₁ ) amount) is reduced. It has become.
Incidentally, in the graph (c) of FIG. 10 and the graph (iii) of FIG. 4, the roll sensitivity (intermesh (IM ₁ ) per ₁ mm in the vicinity where the C warpage deformation amount becomes 0 (C warpage amount = 0 ± 5 mm). (Change in C warpage amount mm / m) is as follows (the thickness of the graph c in FIG. 10 is 1.4 mm, the thickness of the graph iii in FIG. 4 is 1.5 mm, and the steel type is the same).
Roll sensitivity (mm / m / mm) shown in graph (c) of FIG. 10 = 9/10
Roll sensitivity (mm / m / mm) shown in graph (iii) of FIG. 4 = 6/10

FIG. 5 is a graph showing the relationship between each height position of the supporting roll (3 _B ) and its roll sensitivity (C warpage variation per 1 mm of intermesh IM) based on the data shown in FIG. As shown in the figure, the roll sensitivity decreases as the height position of the lower supporting roll (3 _B ) is lowered (the roll axis distance L ₂ is increased). The roll sensitivity changes from about 2.3 to 0.8 in the range of the distance between the roll axes (L ₂ ) of 100 to 260 mm.
In continuous hot dipping operation, the distance between axes (L ₂ ) should be adjusted within the range of 100 to 260 mm according to specific conditions such as steel strip grade, plate thickness, sink roll offset (IM ₀ ), etc. The roll sensitivity can be moderated moderately, and as a relaxation effect, automatic control of the horizontal position of the supporting roll for applying reverse bending stress to the steel strip is facilitated, and C warpage deformation correction is efficiently and accurately performed. Can be achieved.

The control operation of the steel strip shape of the present invention is performed in order to adjust the roll sensitivity (change amount of C warpage deformation per ₁ mm of IM ₁ ) of the supporting roll (3) that applies reverse bending stress to the steel strip. Performed in the same way as normal C-curvature deformation correction operation, except that the vertical roll axis distance (L ₂ ) between the roll (3 _A ) and the lower supporting roll (3 _B ) is adjusted. can do.
The horizontal position of the two supporting rolls (3 _A ) (3 _B ), the mutual mesh (IM ₁ ) amount and the distance between the roll axes (L ₂ ) in the vertical direction, etc. are the material properties depending on the steel strip type It is preset (initially set) based on (strength, Young's modulus, yield strength, etc.) and its thickness.
The shape quality of the steel strip passed through the plating bath and led out onto the bath (the presence or absence of C warpage deformation or reverse C warpage deformation and its degree) is determined by the shape installed near the wiping nozzle (4) on the bath. It is continuously detected by the detection sensor (7). In addition, when deformation remains in the steel strip, the plating adhesion amount after passing through the wiping nozzle is not uniform in the plate width direction, so the amount of deformation (C warpage or reverse C warpage) of the steel strip and the plate width direction in advance. By correlating with the distribution unevenness of the plating adhesion amount, the presence or absence of the steel strip and the magnitude of the deformation can be determined from the detected distribution in the plate width direction.

If the detected deformation of the steel strip is positive C warpage deformation (concave concave deformation toward the sink roll 2), the reverse bending stress due to the supporting rolls (3 _A ) (3 _B ) is insufficient. This means that negative C warpage deformation (curved deformation convex toward the sink roll 2) indicates that the reverse bending stress is excessive. If the amount of deformation is out of the predetermined tolerance range, either one or both of the two supporting rolls (3 _A ), (3 _B ) are controlled in the horizontal direction, and the intermesh (IM ₁ ) amount is set. By adjusting, the excess or deficiency of the reverse bending stress is corrected, and the distance (L ₂ ) between the roll axes of the supporting rolls (3 _A ) (3 _B ) is corrected as appropriate. Thereby, the flatness of the steel strip led out on the bath is ensured.
Incidentally, the supporting rolls (3 _A) horizontal position control device (5) of (3 _B), the driving method of the vertical position control device (8) is motorized, a hydraulic type or the like arbitrarily.

In the conventional hot-dip plating, correction of the C warp deformation of the steel strip is performed by adjusting the intermesh of the rolls in the plating bath to apply reverse bending stress to the steel strip. It is extremely difficult to obtain an effect that can sufficiently guarantee the quality of the steel sheet. Arranging the electromagnet outside the plating bath is unavoidable in terms of equipment. The present invention employs an unprecedented configuration in which the height position of the supporting roll is adjusted up and down, thereby making it possible to accurately control the increase and decrease of the reverse bending stress on the steel strip. This makes it possible to easily adjust the appropriate reverse bending stress according to the characteristics of each steel strip and ensure the desired flatness in actual operations with various steel strip thicknesses and grades. is doing. This ensures high stabilization of the plating quality of the product-plated steel sheet.
Moreover, expensive equipment such as a shape correction device using an electromagnet is unnecessary, and it is rich in practical value.

The typical explanatory view showing the example of the roll arrangement and control mechanism in the continuous hot dipping bath used for carrying out the present invention. The typical explanatory view showing other examples of the roll arrangement in the hot dipping bath used for carrying out the present invention, and a control mechanism. The typical explanatory view which adjusts the roll sensitivity of a supporting roll. Graph showing an example of roll sensitivity of supporting rolls differ by the distance between the roll axis (L _2). Graph showing an example of the relationship between the roll sensitivity and roll axis distance between the supporting rolls (L _2).

Explanatory drawing of the basic composition of the roll arrangement | positioning of a continuous hot dipping apparatus. Explanatory drawing which shows the example of roll arrangement | positioning and control structure for C curvature deformation correction of a steel strip. Explanatory drawing which shows the other example of the roll arrangement | positioning and control structure for C curvature deformation correction of a steel strip. Explanatory drawing which shows the other example of the roll arrangement | positioning and control structure for C curvature deformation correction of a steel strip. The graph which illustrates the relationship between the mesh of a supporting roll in conventional C curvature deformation correction, and the amount of C curvature deformation.

Explanation of symbols

1: Hot dipping bath 2: Sink roll 3: Supporting roll 3 _A : Supporting roll (roll on the opposite side of the sink roll)
3 _B : Supporting roll (roll on the same side as the sink roll)
4: Wiping nozzle 5: Horizontal position control device 6: Electromagnet 7: Steel strip shape detection sensor 8: Vertical position control device θ: Winding angle S: Steel strip

Claims (3)

Continuous hot-dip plating in which the steel strip is introduced into the hot dipping bath, supported and guided by the sink roll and supporting roll, run in the bath, led out onto the bath, and then the amount of plating on the surface of the steel strip is adjusted with the wiping nozzle Out of the two supporting rolls sandwiching the steel strip that runs upward through the sink roll, the supporting roll located on the opposite side of the sink roll is on the upper side and the supporting roll on the same side as the sink roll is on the lower side, respectively Place and
Adjust the amount of intermesh between the upper support roll and the lower support roll and the distance between the roll axes in the vertical direction between the upper support roll and the lower support roll according to the steel strip grade and thickness. A method for correcting the shape of a steel strip in continuous hot dipping. Continuous hot dip plating in which sink rolls and supporting rolls for supporting and guiding the steel strip introduced into the hot dipping bath are arranged in the bath, and wiping nozzles for adjusting the amount of plating on the surface of the steel strip are arranged on the plating bath In the device
The supporting roll is composed of an upper supporting roll located on the opposite side of the sink roll and a lower supporting roll located on the same side as the sink roll, with the steel strip traveling upward through the sink roll,
Horizontal position control device for adjusting the amount of intermesh between the upper support roll and the lower support roll, and the vertical position for adjusting the vertical roll axis distance between the upper support roll and the lower support roll A steel strip shape correcting device in continuous hot dipping, wherein a control device is provided. Strip straightening method in a continuous hot dipping of claim 1, wherein the adjusting the vertical roll axis distance L ₂ between the upper supporting rolls and the lower supporting rolls in the range of 100～260Mm.

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