JPH10140315A - Method of controlling the basis weight of hot-dip coated steel sheet - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To detect the continuous shape of a steel sheet at a nozzle position, and to detect the width of a steel sheet even in an asymmetric steel sheet shape or when the shape and properties of the steel sheet do not conform to the theory. An object of the present invention is to provide a control method for minimizing variation in the basis weight in the direction and reducing the dead time in the hot-dip coated steel sheet to uniform variation in the basis weight in the width direction. SOLUTION: In a steel sheet, the shape warping amount of the steel sheet in the vicinity of a wiping nozzle is measured by a shape width detecting device and a shape calculating device for obtaining a continuous shape, and a shape control calculating device for calculating an optimum roll position in the bath, and a bath control device based on the result. It is composed of a drive device for driving the middle roll, which minimizes the coating weight variation in the width direction of the steel sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a steel sheet,
Control method for uniforming the width-wise variation in the basis weight of hot-dip coated steel sheets, in which a steel sheet coated with a base plating metal such as zinc, lead-tin, and aluminum runs through a hot-dip bath of a corrosion-resistant metal such as aluminum It is about.

[0002]

2. Description of the Related Art In general, a hot-dip coated steel sheet is formed by passing a hot-rolled or cold-rolled steel sheet through a pre-oxidizing furnace, then a reduction annealing furnace and a cooling furnace, and passing through a hot-dip coating bath.
The molten metal plated on the surface is wiped by a gas wiping nozzle to control the weight per unit area, and if necessary, further manufactured through an alloying heating furnace. However, the weight per unit area of the plated metal of the manufactured hot-dip coated steel sheet has a large variation in the width direction, and there is a problem that the weldability or the adhesion paintability is hindered. These problems depend on the distance between the steel plate and the gas wiping nozzle,
The problem can be solved by always keeping the interval constant, but the problem has not been solved because the steel sheet travels in various shapes.

As means for flattening the shape of a steel sheet, a method of judging the shape of a steel sheet visually by an operator and moving a sink roll or a support roll in a plating bath or a touch roll above gas wiping is disclosed in Japanese Patent Application Laid-Open No. 2-54746. Japanese Patent Laid-Open Publication No. Hei 3-166354, Japanese Patent Application Laid-Open No. 3-166354 discloses a method of adjusting a roll position in a snout such that a warpage amount at a nozzle position becomes zero according to a steel plate size, a tension, and a material of a steel plate to be plated, A method in which a shape detector is installed before and after the position, and the position of the roll in the snout is adjusted so that the amount of warpage at the nozzle position becomes zero, or a steel plate above the gas wiping nozzle as disclosed in JP-A-2-26585. The thickness of the plating layer at the end and the center in the width direction is detected, and the position of the sink roll is automatically controlled so that the difference between the detected values becomes the minimum value. There is a positive method.

[0004] However, with respect to the technique of presetting the position of the sink roll or the support row based on the experience as described above, it is difficult to always flatten the shape of the steel sheet with large hits and misses. In addition, regarding the method of adjusting the roll position in the snout according to the steel sheet to be plated as described above, there are a huge number of combinations of steel sheet sizes and materials. Analysis is required. In automatic control using a shape detector, a highly accurate shape detector is required.However, since unsolidified molten zinc adheres to the steel sheet near the gas wiping nozzle, the contact type Because of the problem that the detector cannot be used, an electromagnetic non-contact type shape detector is mainly used.

Japanese Patent Publication No. Sho 57-60 discloses an electromagnetic shape detector.
As disclosed in Japanese Patent No. 54, there is a method of detecting the shape by applying an electromagnetic force from the outside of the steel sheet and measuring the tension distribution of the steel sheet, but in order to detect even the latent steel sheet shape,
High-precision detection of the steel sheet shape at the gas wiping position cannot be expected at present. In addition, there is a method of estimating the shape of the steel sheet from the measurement result of the coating weight in the width direction using a coating weight meter. In this method, the plating weight meter is physically installed because the temperature near the gas wiping nozzle is high. Since it is difficult to do so, there is a problem in that the dead time when performing the control is actually increased because the coating weight meter is actually installed at a distance from the wiping nozzle.

Further, the shape correction as described above is effective only in the case of a steel plate shape having a symmetrical simple warp.
Actual steel sheet shapes include not only simple left-right symmetric warpage but also left-right asymmetric steel plate shapes. In the case of an asymmetric steel shape, even if the difference between the thicknesses of the plating layers at the ends and the center in the width direction of the steel sheet is calculated and the position of the sink roll or the like is controlled, the steel sheet is not necessarily flat. That is, it is necessary to detect and control the continuous shape of the steel plate in the case of the asymmetric steel plate shape.

[0007] We have addressed the above-mentioned problems in Japanese Patent Application No. 8-881.
No. 89, based on the relationship between the amount of warpage of the sink roll and the amount of warpage that is theoretically determined in advance so as to minimize the amount of warpage of the steel plate calculated from the shape detection by the laser and based on this. By the method of moving the sink roll in the horizontal direction, even in the case of an asymmetrical steel plate shape, it was possible to uniformly control the basis weight variation in the steel plate width direction.
However, in reality, the shape and properties of the steel sheet do not always match the theory. If the theory does not match, an error occurs between the theoretical formula and the relationship obtained from the actual data. However, there is a problem that the control response until the delay becomes longer.

[0008]

SUMMARY OF THE INVENTION The present invention overcomes such disadvantages of the prior art and enables detection of the continuous shape of a steel sheet at a nozzle position. Even if the shape or properties do not conform to the theory, operate the sink roll to minimize the total amount of warpage, minimize the variation in the basis weight in the width direction of the steel sheet, and reduce the dead time. The purpose is to enable.

[0009]

[MEANS FOR SOLVING THE PROBLEMS] A steel plate to be plated is caused to run in a hot-dip plating bath through a hot bridle roll, a sink roll and a support roll in the hot-dip coating bath, and gas wiping is performed on the plating metal in a molten state adhering to the surface. In a hot dip coating method for a steel sheet which is controlled to a predetermined basis weight while wiping with a nozzle, the shape of the steel sheet to be plated is detected using a laser immediately above the wiping nozzle, and the warpage amount of the steel sheet is obtained from the detected value. , And
The relationship between the horizontal movement amount and the warpage amount of the sink roll is measured in advance, the measured data is modeled by fuzzy modeling, the model and the warpage amount actually measured by the method, the position of the sink roll at that time. And compare
Based on the model, the sink roll movement amount is calculated so as to minimize the amount of warpage of the steel sheet, and the sink roll is moved in the horizontal direction so as to minimize the amount of warpage of the steel sheet, thereby minimizing variation in the basis weight in the width direction of the steel sheet. This is a method of controlling the basis weight in the width direction of a hot-dip coated steel sheet.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of a method of controlling a basis weight in a width direction according to the present invention. Reference numeral 15 denotes a traveling steel plate plated with a corrosion-resistant metal such as zinc or lead-tin. The steel sheet 15 passes through the hot bridle rolls 1 to 4 and is plated around the sink roll 5 in the hot-dip plating bath, rises while the shape is corrected by the lower support roll 6 and the upper support roll 7, and is further raised by the gas wiping nozzle 8. Is controlled by a wiping nozzle installed as necessary at a predetermined plating weight, and then rises to reach the top roll 9. Reference numeral 20 denotes an apparatus for detecting the shape of the plated steel sheet 15 in the sheet width direction, which is installed immediately above the gas wiping nozzle 8. The sheet width direction shape detecting device 20 irradiates a laser beam in the sheet width direction of the traveling plated steel sheet 15, detects reflected light thereof, and detects each laser spot in the sheet steel sheet width direction. Reference numeral 13 denotes a shape calculation device, and reference numeral 14 denotes a warpage amount calculation device, which obtains the width of the steel sheet transmitted from the width direction shape detection device 20 in each width direction by a method described below.

First, the equipment used in the method for detecting the shape of a steel sheet will be described. FIG. 2 is a perspective view showing a method for measuring the warpage of the steel sheet. FIG. 2 shows a glass flat plate 17 which is an example of a light-transmitting flat plate arranged substantially parallel to a plated steel plate 15 and a plurality of glass flat plates 17 arranged on the near side of the glass flat plate 17. A semiconductor laser 18 that is an example of a laser light source that emits laser light as parallel spot light, a CCD camera 19 that captures reflected light of the spot laser light, and a shape calculation device 13 that is connected to the CCD camera 19. have.

The glass flat plate 17 is a glass flat plate having a uniform thickness, is provided with an appropriate frame around the glass flat plate so as not to bend due to weight or the like, and is supported at a predetermined position by a support member (not shown). On the front and back of the glass flat plate 17, a translucent process is performed in which part of the irradiated spot laser light is diffusely reflected (for example, a process of applying fine irregularities to the front and back such as frosted glass, and the front and back are coated with a slightly opaque resin or the like). Or a half mirror process in which a part of a spot laser beam passes and a part of the spot laser beam is reflected), so that the laser beam passing through the front and back of the glass plate 17 can be imaged. In addition, when the half mirror process having an appropriate light transmission efficiency is performed, the irradiation spot light to the steel plate 15 to be further irradiated does not become the diffusion laser light, so that accurate measurement can be performed.

The semiconductor laser 18 is provided so that its optical axis is parallel to and perpendicular to the glass plate 17 to facilitate correction after measurement.
If the position is corrected after the measurement, the glass plate 17 may be slightly inclined. In this embodiment, the number of the semiconductor lasers 18 is six. However, in order to obtain a more precise profile of the steel sheet, a large number of semiconductor lasers 18 are provided, and if the coarseness is acceptable, the number is reduced.
Further, it is also possible to obtain a profile by moving the semiconductor laser 18 in parallel in the plate width direction according to the plate width of the steel plate.

The CCD camera 19 is disposed at an angle with respect to the optical axis of the semiconductor laser 18 and reflects the spot laser light emitted from the semiconductor laser 18 from the glass flat plate 17 and the steel plate 15 to a certain extent. Can be taken at intervals of. Therefore, C
It is preferable that the CD camera 19 is arranged at a slight angle at the front or rear part of the glass plate 17 in the traveling direction of the steel plate 15. The shape calculation device 13 receives a video signal from the CCD camera 19, converts the video signal into a digital signal when necessary, and stores the digital signal. Computer. The computer has 2
Means for calculating the position of the center of gravity of the digitized video signal and calculating a profile including the amount of warpage of the steel plate 15 from the obtained data is described as a program.

The present invention will now be described with reference to FIGS.
A detailed explanation of the steel sheet shape detection method in
Spot laser from the body laser 18 through the glass plate 17
Irradiates the CCD camera from an oblique direction.
Camera 19 (step a), and the imaging signal is
And binarize it with an appropriate threshold (step
b). And it is irradiated from one semiconductor laser 18
Shining spots on the front and back of the glass and on the surface of the steel plate
Creates an image and stores it in the image memory coordinate system for each captured spotlight.
When the position of the center of gravity is obtained, P (x,
y), P₁(X₁, Y ₁), P₀(X₀, Y₀)
Step c). This P₀, P₁, P are the front and back of the glass plate 17
, Ie, the thickness (t), and the surface position of the steel plate 15
The thickness t of the glass plate 17 is kept constant.
And the distance L between the steel plate 15 and the glass plate 17₁Is L₀Is L₁
If it is sufficiently larger, it is approximated by the following equation (1).
(Step d).

[0016]

(Equation 1)

Equation (1) is independent of the angle of the spot laser beam or the position of the CCD camera, so that even if these change, the position of the steel plate can be accurately measured. The above processing is performed for each semiconductor laser 18, and the position of the steel plate corresponding to each spot laser beam is plotted as shown in FIG. (Step e). Thereby, the steel plate shape is obtained by the shape calculation device 13 in FIG. According to this detection method, the gas wiping nozzle 8
Since the shape can be detected immediately above the time, the dead time in the shape control described below can be reduced. 1
Reference numeral 4 denotes a warp calculating device, and reference numeral 10 denotes a shape control calculating device, which determines an operation amount of the sink roll based on a steel sheet shape obtained by the shape calculating device 13 based on a formula described below. Reference numeral 14 denotes a warpage amount calculation device. The steel plate shape obtained by the shape calculation device 13 can be approximated by a function of a quartic equation such as the following equation (2).

G (x) = C ₀ + C ₁ x + C ₂ x ² + C ₃ x ³ + C ₄ x ⁴ (2) where C _{0 to} C ₄ are constants, and x is the width of the steel plate in the width direction. Indicates the position. ΔC calculated after detection by laser
By determining C _{0 to} C ₄ by using x at that time and x at that time, a function approximate value of the shape of the steel sheet can be obtained. Next, an extreme value is calculated in order to recognize the shape of the steel plate shape approximated by the fourth order function. In equation (2), which is the derivative of the quartic function,
X is calculated so that G ′ (x) = 0.

G ′ (x) = C ₁ + 2C ₂ x + 3C ₃ x ² + 4C ₄ x ³ (3) If the number of extrema calculated here is one, simple warping occurs.
If there are three, it is recognized as S warp, and if there are three, it is recognized as W warp. next,
The amount of warpage is calculated. In the case of the S warpage, as shown in FIG. 9, the warpage of ΔC _DS which is the amount of warpage on the left side with respect to the center and the warpage of ΔC _WS which is the amount of warpage on the right side are calculated. The absolute value of each warpage amount can be calculated by the following equation.

[0020]

(Equation 2)

Here, △ C _DS is the amount of warpage on the left side with respect to the center, △ C _WS is the amount of warpage on the right side with respect to the center, and △ D _DS is the value of the fourth-order function at the leftmost edge position in the width direction. , △ D _WS
Is the fourth-order function value at the rightmost edge position in the width direction,
ΔD _DS (extreme) is a quartic function value at the extreme value position on the left side in the width direction, and ΔD _WS (extreme) is a quartic function value at the extreme value position on the right side in the width direction.

Regarding the directionality of the warp, when the derivative of the quartic function value is observed near the extremum position, when it goes from negative to positive, it has a downward convex direction (+ warp) and goes from positive to negative. Is recognized as a shape (−warpage) having a direction of upward convexity. In W warp is the center warped as shown in FIG. 10 △ C _C
And △ C _E as edge warpage are calculated. First, ΔC _C and ΔC _E are calculated based on the following equations. The direction of the warpage is determined in the same manner as in the case of the S warp near the extreme values of the left extreme value, the center extreme value, and the right extreme value in the plate width direction.

The directionality is changed from negative to positive (+
Warp) and positive to negative (-warp) at the central extreme value,
And when the extreme value on the right side is from negative to positive (+ warpage) ΔD _DS (pole)> ΔD _WS (pole) ΔC _C = ΔD _CC (pole) −ΔD _WS (pole) (6) If ΔD _DS (pole) ≦ ΔD _WS (pole), ΔC _C = ΔD _CC (pole) −ΔD _DS pole) …… (7) ΔC _E is ΔC _DS and ΔC _DS and whichever is larger in the C _WS.

Here, the quartic function value at the extreme value position at the center of △ D _CC (pole), △ C _DS and △ C _WS , are respectively ΔC _DS = △ D _DS − △ D _DS (pole). (8) ΔC _WS = △ D _WS- △ D _WS (pole) ... (9)

The directionality is positive to negative (-warp) at the extreme value on the left side, negative to positive (+ warp) at the extreme value at the center, and positive to negative (-warp) at the extreme value on the right side. If △ D _DS (pole)> △ D _WS (pole) if △ _C C = △ D _DS (pole) - △ D _{CC (pole) ......... (10) △ D DS} ( pole) ≦ △ D _WS ( pole) if △ _C C = △ D _WS (pole) - △ D _CC pole) ......... (11) △ C _E is the larger one in the △ C _DS and △ C _WS.

Here, ΔC _DS and ΔC _WS can be calculated as follows. △ C _DS = △ D _{DS (pole) - △ D DS ......... (12} ) △ C WS = △ D WS ( pole) - △ D _WS (pole) ......... (13) or more arithmetic processing performed apparatus Is the warpage amount calculation device 14. Reference numeral 10 denotes a shape control arithmetic unit. Next, the relationship between the amount of sink roll movement and the amount of warpage is obtained from actual data by fuzzy modeling.

Data on the amount of warpage of the strip and the amount of movement of the sink roll near the wiping nozzle immediately above the pot are collected in advance. The warpage amount data may be obtained from the main shape detection unit and the amount of adhesion. FIG. 7 shows an example of the data.
For that data, the linear form is calculated from both ends of the amount of movement of the sink roll by the least squares method, etc., and the linear form that minimizes the linear form value and the standard deviation of the data is adopted as the model formula of the data range I do.

The non-linear part between the linear forms is expressed as a fuzzy area by a plurality of fuzzy rules using the amount of movement of the sink roll as a fuzzy variable as shown in equations (14) and (15). FIG. 8 shows a fuzzy region and a membership function in this case. if P _Shift = Small Then △ C = b ₁ + a ₁ × P _Shift (14) if P _Shift = Big Then △ C = b ₂ + a ₂ × P _Shift (15) where P _Shift is Sink roll movement amount, a ₁ , a ₂ , b ₁ ,
b ₂ is a constant, and Small and Big are labels of membership functions.

The relationship between the amount of movement of the sink roll and the amount of warpage in the non-linear portion is determined by weighted averaging using the degree of conformity to each rule obtained by the above fuzzy rule, as (1)
It can be obtained as in equation (6). ΔC = Σ ｛△ C × μ (P _Shift )｝ / Σμ (P _Shift ) (16) Here, μ (P _Shift ) is the degree of fitness of each membership function based on the amount of sink roll shift.

In the case of S-warp, the amount of warpage on the left side with respect to the center at a certain shape recognition timing is △ C _DS , and the amount of warpage on the right side is △.
When the P _shift of when is the C _WS is assumed to be P _A, △ C _DS
The following functional formula is established for P _shift and the amount of C warp that minimize both △ C _WS and △ C _WS . ΔC = Q ₁ (P _shift ) + (ΔC _DS + ΔC _WS ) −ΔC _A (17) Here, ΔC _A = Q ₁ (P _A ). From this, ΔC =
If you calculate P _shift to be 0, this will be △ C _DS and △ C _WS
The the P _Shift as both minimized. Similarly for W warp, may be calculated P _Shift as to both minimize certain △ C _C and is at the edge warp △ C _E at the center warpage.

According to the above method, even if the shape detected by the laser is an asymmetric steel plate shape such as S-warp or W-warp, or if the shape or properties of the steel plate do not conform to the theory, the fuzzy modeling can be used. Since the model is obtained in accordance with the actual data, it is possible to calculate the amount of movement of the sink roll 5 so as to minimize the total amount of warpage,
By moving the sink roll based on this, the weight variation in the width direction of the steel sheet can be minimized.

[0032]

An embodiment of the present invention will be described with reference to the data shown in FIG. The model in this case uses this method: When P _Shift ≦ 13.8, ΔC = 5.52−0.4
When 8 × P _Shift · P _Shift ≧ 16.5, ΔC-2.17-0.1
When 1 × P _Shift · 13.8 <P _Shift <16.5, it is calculated by equation (16). The fuzzy rules at that time are as follows. if P _Shift = Small Then △ C = 5.52-0.48 × P _Shift (18) if P _Shift = Big Then △ C = -2.17-0.11 × P _Shift (19)

As for the membership function, P ₁ and P ₂ in FIG. 8 are as follows. P ₁ = 13.8 P ₂ = 16.5 In the data of FIG. 7, when the data of the mark “x” is measured when the steel sheet is simply warped, the warpage amount is −5 m by one control operation.
m was changed to 0.3 mm, and the amount of warpage could be reduced to almost 0 mm in the second control operation.

[0034]

According to the basis weight control method of the present invention,
Even if the shape of the steel sheet has a simple warp or asymmetric steel sheet, or if the shape and properties of the steel sheet do not conform to the theory, simply operate the sink roll to minimize the variation in the weight per unit area in the width direction of the steel sheet. And a uniform plated steel sheet can be obtained regardless of the shape of the steel sheet. In addition, the present shape detection method can speed up steel sheet shape detection and improve control response, so that dead time in shape control can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a width direction basis weight control method according to the present invention.

FIG. 2 is a perspective view showing a method for measuring the amount of warpage of a steel sheet according to one embodiment of the present invention.

FIG. 3 is a partial cross-sectional view illustrating a measurement principle.

FIG. 4 is an explanatory diagram showing points on an image.

FIG. 5 is a flowchart.

FIG. 6 is a graph showing measurement results.

FIG. 7 is a diagram illustrating an example of collected data of a sink roll movement amount and a warpage amount.

FIG. 8 is a diagram illustrating an example of a membership function of a fuzzy area and a movement amount of a sink roll.

FIG. 9 is a diagram showing the relationship between the definition of the amount of warpage of S warpage and the directionality of warpage in the present invention.

FIG. 10 is a diagram showing the relationship between the definition of the amount of warpage of the W warp and the directionality of the warp in the present invention.

[Explanation of symbols]

 1-4 Hot bridle roll 5 Sink roll 6 Lower support roll 7 Upper support roll 8 Gas wiping nozzle 9 Top roll 10 Shape control calculator 11 Driving device for sink roll and support roll 13 Shape calculator 14 Warp amount calculator 15 Steel plate 16 C warp detector 17 glass flat plate (translucent flat plate) 18 semiconductor laser 19 CCD camera 20 board width direction shape detector (17, 18, 19)

Claims (1)

[Claims] 1. A steel plate to be plated is caused to run in a hot-dip bath while being passed through a hot bridle roll, a sink roll and a support roll in the hot-dip plating bath, and the molten plating metal adhered to the surface is wiped by a gas wiping nozzle. In the hot-dip coating method for a steel sheet while controlling to a predetermined basis weight, while detecting the shape of the steel sheet to be plated using a laser just above the wiping nozzle, and calculating the amount of warpage of the steel sheet from the detected value The relationship between the amount of horizontal movement of the sink roll and the amount of warpage is measured in advance, the measured data is modeled by fuzzy modeling, and the model and the amount of warpage actually measured by the above method, the position of the sink roll at that time The sink roll movement amount is calculated based on the model to minimize the amount of warpage of the steel sheet, and the warp of the steel sheet is calculated. A method for controlling the weight of a hot-dip coated steel sheet in the width direction, wherein the sink roll is moved in the horizontal direction so as to minimize the amount, and the weight variation in the width direction of the steel sheet is minimized.