JPH08253850A - Control method for uniform coating amount on hot-dip steel sheet - Google Patents

Abstract

(57) [Abstract] [Purpose] Performs highly precise flattening control of hot dip plated steel sheets or highly accurate control of simple C warpage. [Structure] Each surface of the front and back surfaces in the width direction of the steel plate is detected by detecting the intensity of fluorescent X-rays that are received by irradiating γ-rays or X-rays in the width direction of the plated steel plate 1 traveling from the hot dip bath through the gas wiping area. The plate shape is obtained by the shape calculator 8 from the amount of plating on the front and back sides in each width direction measured by the plate width direction scanning plating amount measuring device 7 for measuring the amount of adhesion,
The obtained steel plate shape is approximated by a quartic function, and by using the maximum value and the minimum value of this function, in the width direction of the steel plate 1 of the auxiliary dies 5 arranged in plural on at least one of above and below the wiping nozzle 4. The installation position and the pressure of the auxiliary die 5 are obtained by the computing device 8, the auxiliary die 5 is moved to the obtained set position by the driving device 11, and the pressure of the auxiliary die 5 is controlled by the pressure control device 10. A method for uniforming the amount.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the shape of a hot-dip steel sheet, in which a steel sheet and a steel sheet coated with a plating metal such as Ni run through a hot-dip galvanizing bath of a corrosion-resistant metal such as zinc, lead-tin or aluminum. The present invention relates to a method for controlling the amount of plating and controlling the coating amount.

[0002]

2. Description of the Related Art Hot-dip galvanized steel sheets are of many types, such as zinc, tin, and aluminum, which have relatively low melting points. Among them, galvanized steel sheets or their alloyed hot-dip galvanized steel sheets are characterized by excellent corrosion resistance and weldability. Therefore, it is widely used as a material for automobiles and home appliances. Such a hot-dip galvanized steel sheet is generally a hot-rolled or cold-rolled steel sheet that passes through a preliminary oxidation furnace, a reduction annealing furnace, and then a cooling furnace, and passes through a hot-dip galvanizing bath to deposit molten metal on the surface. Is controlled to a predetermined basis weight while being wiped by gas wiping, and if necessary, it is further manufactured by passing through an alloying heating furnace. However, the amount of the hot-dip galvanized steel sheet produced as described above varies greatly in the sheet width direction, and there is a problem that pressability, weldability, coating adhesion, etc. are affected. The problem that such adhesion amount varies in the width direction depends on the distance between the steel plate and the gas wiping nozzle,
The solution can be achieved by keeping the distance uniform, but the solution has not been solved because the steel sheet changes into various shapes and travels.

Techniques for flattening the shape of a steel sheet include a method of moving a sink roll in a plating bath, a support roll, a touch roll on gas wiping, or the like by the operator's visual judgment, or a sheet width using electromagnetic force. Some force the shape of the direction. However, in order to perform highly accurate shape automatic control, it is necessary to perform automatic control of the operating end based on the actual steel plate shape. In response to such a request for automatic control, as in Japanese Patent Laid-Open No. 265854/1990, the plating thickness at the end portion and the central portion in the steel sheet width direction is detected immediately above the gas wiping nozzle, and the detected value is minimized. As described above, a method of correcting the shape by automatically controlling the sync roll position has been developed.

However, such a straightening method is effective for a simple symmetrical warp, but the actual steel plate shape includes not only a symmetrical warp but also an asymmetrical warp. Therefore, the bilaterally asymmetric warp is disclosed in Japanese Patent Laid-Open No. 2-265.
The steel plate does not always become flat even if the method described in Japanese Patent No. 854 is adopted. Further, in the method of adjusting the pressing of the support roll as in Japanese Patent Laid-Open No. 3-17249, the shape can be corrected only in the case of a simple C warp of the steel plate, and the steel plate shape having two or more extreme values is flattened. Is difficult to do. That is, in a steel plate shape having two or more extreme values, an operation of flattening the extreme values is required, and continuous shape detection of the steel sheet is necessary. On the other hand, the applicant of the present invention discloses Japanese Patent Laid-Open Nos. 6-128710 and 6-1010.
It is proposed that the wrapping angle between the pot roll and the sink roll be controlled by a model formula to realize flattening of the steel plate shape as in Japanese Patent Publication No. 08-08. However, since the steel sheet ends are weakly constrained by the rolls, it has not been possible to completely flatten the steel plate shape that minimizes the variation in the adhered amount including the steel plate ends.

For detecting the shape of the steel sheet, a contact type load detecting method, a laser type non-contact type shape detector, an electromagnetic type non-contact type shape detector and the like have been devised. However, the contact-type load detection method cannot be measured before and after gas wiping because the plated metal is not solidified on the steel plate surface. In the case of a laser non-contact type shape detector, there are a light cutting method and a method of processing an image projected on a screen of reflected light,
In the former case, since the steel plate immediately above the gas wiping does not have a mirror surface, diffuse reflection is unlikely to occur, resulting in sensitivity deterioration and measurement difficulty. In the latter case, there is a problem in that the accuracy of measurement is lacking due to the deviation of the reflected image due to the vibration of the steel sheet. As disclosed in Japanese Patent Publication No. 57-6054, the electromagnetic non-contact shape detector is a method of measuring the tension distribution of the steel sheet by applying an electromagnetic force to the steel sheet from the outside to detect the shape. It is difficult to install the detector in a high temperature atmosphere around the gas wiping, resulting in measurement at a position distant from the gas wiping position. However, the shape at the measurement position and the shape at the gas wiping position change in the sheet passing direction due to the subsequent roll restraint and tension deviation,
It does not mean that the shape at the gas wiping position is measured. On the other hand, the applicant of the present invention filed Japanese Patent Laid-Open No. 6-128
As disclosed in Japanese Patent No. 710, a method for calculating the shape from the amount of adhesion on the surface of the steel sheet has been proposed, and the results have been obtained.

However, even if the shape at the gas wiping position is calculated and the angle of wrapping the steel plate around the pot roll or sink roll is controlled as described above, a complicated shape may remain in the steel plate, and the width direction of the steel plate may be different. However, there is a problem that the plating adhesion amount cannot be controlled uniformly and stably.

[0007]

SUMMARY OF THE INVENTION The present invention overcomes the above-mentioned drawbacks of the prior art and is capable of detecting the continuous shape of a steel sheet, and has a steel sheet shape having two or more extreme values, for example, an M-shaped steel sheet. Even in such a steel plate shape, the purpose is to control the flattening control of the steel plate with high precision or the simple C warpage with high precision by operating the position and pressure of the auxiliary die attached around the wiping nozzle. .

[0008]

Means for Solving the Problems The gist of the present invention is to determine the fluorescent X-ray intensity received by irradiating γ-rays or X-rays in the width direction of a plated steel sheet traveling from a hot dip bath passing through a gas wiping zone. Detect and measure the amount of plating on each side of the steel plate in the width direction of the steel plate. The obtained steel plate shape is approximated by a quartic function, and using the maximum and minimum values of this function,
The position of the auxiliary dies arranged on the front and back of the wiping nozzle on at least one of the front and back sides and the pressure of the auxiliary dies are calculated by a computing device, and the auxiliary dies are moved to a set position by a driving device to assist. A method for controlling the uniform coating amount of a hot-dipped steel sheet, which comprises controlling the pressure of the die with a pressure control device.

[0009]

[Function] Conventional auxiliary die (auxiliary gas wiping nozzle)
Is to accelerate the wiping of the plating by applying an auxiliary die pressure for the purpose of preventing excessive adhesion of the steel plate end portion where a pressure drop occurs due to the impingement pressure of the wiping nozzle at the time of manufacturing the thick weight plated material. This time, in order to control the flattening of the steel plate with high precision or the simple C warpage with high precision, the drive for moving the auxiliary die and the auxiliary die placed directly above and below the wiping nozzle placed on the hot dip bath A device for controlling the amount of coated steel sheet, which is a pressure controller for controlling the pressure of the auxiliary die, is used.

Further, the intensity of fluorescent X-rays received by irradiating γ-rays or X-rays in the width direction of the plated steel sheet running from the hot dip bath passing through the gas wiping region is detected to detect the front and back surfaces of the steel sheet in the width direction. The amount of displacement when the center of the distance between the front and back gas wiping nozzles is set to 0 based on the plate width scanning scanning deposition amount measuring device for measuring the coating amount and each measured plating amount on the front and back surfaces in each width direction of the steel sheet. By using the shape calculation device for calculating the steel plate shape and the steel plate shape obtained from this can be approximated by a quartic function, the steel plate width direction of the auxiliary die arranged near the front and back steel plate edges around the wiping nozzle A shape calculation device that determines the installation position and the pressure of the auxiliary die, a drive device for moving the auxiliary die to the set position obtained from this, and a pressure control device that controls the pressure of the auxiliary die. It is possible to use a coating weight controller of the plated steel sheet.

[0011]

1 shows an embodiment of the shaping apparatus of the present invention. In the figure, reference numeral 1 denotes a steel plate which is plated with a corrosion resistant metal such as zinc and which runs. The steel sheet 1 is plated by turning around a sink roll 2 in a hot dip bath, is raised while its shape is corrected by one or two support rolls 3, gas wiping, and an electromagnetic wiping nozzle 4 installed as necessary. Then, the coating weight is controlled to a predetermined value and then it rises. Reference numeral 5 denotes an auxiliary die for flattening the shape of the plated steel sheet 1 or making it simple C-warp by the output of the displacement meter 6, and has a plurality of movable driving devices 11 installed in the width direction. Reference numeral 7 is a scanning plating adhesion amount measuring device in the plate width direction of the plated steel plate, which detects the fluorescent X-ray intensity received by irradiating γ rays or X-rays in the plate width direction to measure the plating adhesion amount of the steel plate. Reference numeral 8 denotes a shape calculation device, which calculates the distance between the steel plate 1 and the gas wiping 4 according to the following equation based on the adhesion amount value in the width direction transmitted from the plate width direction scanning type plating adhesion measuring device 7 to obtain the steel plate shape. .

Factors that determine the adhesion amount are the steel sheet passing speed V (m / min), the distance between the steel plate 1 and the gas wiping nozzle D (mm), and the gas wiping nozzle pressure P (Kg / mm).
² ), steel plate components, steel plate surface properties, plating bath components, plating bath temperatures, etc., but the effects can be ignored if the conditions are constant except P, V, and D. Can be expressed as

W = F (P, V, D) (5) This function F is an expression that also depends on the wiping nozzle shape, the plating component, and the steel component. Therefore, by limiting the equipment or bath component, I can decide. In particular, when the coating weight per one surface is 30 to 200 g / m ² , it is possible to obtain the coating weight regression model equation such as the equation (6).

W = exp (K0 + K1 × P + K2 × V + K3 × D) Expression (6) Incidentally, K0 to K3 are constants and take different values depending on the steel plate.
Here, if the steel plate shape value is calculated by using the adhesion amount values on the front and back and P and V are constant, it becomes possible to express it in the form of equation (7).

ΔD = (D1-D2) / 2 = (lnW1-lnW2) / 2K3 (7) where ΔD is the displacement when the center of the distance between the front and back gas wiping nozzles 4 is 0, and D1 is the steel plate The distance between the front wiping nozzles, D2 is the distance between the steel plate and the front wiping nozzle,
W1 represents the amount of plating applied on the front side, and W2 represents the amount of plating applied on the back side.

The shape calculator 8 using the above equation (7) can obtain the shape of the steel sheet in the width direction. Reference numeral 5 denotes an auxiliary die, which sets the auxiliary die pressure by using the following formula (9) by setting the distance between the steel plate and the wiping nozzle at an arbitrary location from the steel plate shape obtained by the shape calculation device 8. Is possible.

The adhered amount in the vicinity of the auxiliary die 5 can be expressed by the equation (8) obtained by modifying the equation (5).

W = exp {K0 + K1 × (P + ΔP) + K2 × V + K3 × D} Equation (8) where ΔP is the auxiliary nozzle pressure (Kg / mm ² ). Note that K0 to K3 are constants, take different values depending on the steel plate, and V is constant using the front and back adhesion amount, and if the set wiping nozzle to steel plate distance is D1 (mm) and D2 (mm), the auxiliary die pressure ΔP is given by the following equation (9).

ΔP = {-P + (lnW1-lnW2)} / 2K1 (9) Formula The installation position of the set of the displacement gauge 6 and the auxiliary die is determined and controlled by the formula described below.

The steel plate shape obtained by the shape calculator 8 is (1
It can be approximated by a quartic function such as equation (0).

G (X) = C0 + C1 × X + C2 × X ² + C3 × X ³ + C4 × X ⁴ (10) Equation (10) Here, C0 to C4 are constants, and X represents a position in the width direction of the steel plate shape. Using ΔD calculated using the adhesion amount output by the adhesion amount detector and X at that time, C0 to C4
By determining the constant of, the function approximation of the steel plate shape becomes possible. Equation (11) is obtained by taking the first derivative of Equation (10) with respect to X.

G ′ (X) = C1 + 2 × C2 × X + 3 × C3 × X ² + 4 × C4 × X ³ (11) Equation (1) The real solution of G ′ (X) = 0 is α1, α2, α3, and the most edge part. Let X1, β2 be the X-coordinates of α1, α2, α3, β
By substituting 1 and β2 into the equation (11), G (α1), G
(Α2), G (α3), G (β1), and G (β2) are obtained.

In this way, the installation position of the set of the displacement gauge 6 and the auxiliary die 5 is set by the auxiliary die and the displacement gauge plate width direction driving device 11 at the points G (α1) to G (β2).

As a substitute for the displacement meter 6 and the auxiliary die driving device 11, a set of an extremely short displacement meter and an auxiliary die is installed,
There is also a method of using a set of displacement gauges and auxiliary dies close to the positions of α1 to β2, a method of driving only the outermost displacement gauge and auxiliary die, or a method of combining both.

By manipulating the pressure of the auxiliary die installed in the width direction as described above, it becomes possible to flatten the steel plate between the wiping nozzles.

An example in which the shape of the hot-dip galvanized steel sheet is controlled by using the apparatus of the above embodiment will be described below. The position of the auxiliary die in this embodiment is attached to the end of the steel plate.

In a hot-dip galvanized steel sheet having a sheet thickness of 0.76 mm and a sheet width of 1835 mm, the coefficient of the equation (5) takes the following values.

K0 = 2.88, K1 = -0.7, K2 =
0.02, K3 = 0.04 Further, the pressure of the auxiliary die attached to the end of the steel plate takes the following values.

P1 = 0.31 Kg / mm ² , P2 = 0.
43 kg / mm ²

[0030]

EFFECTS OF THE INVENTION With respect to the steel plate shape as shown in FIG. 2 calculated using the plate width direction scanning plating amount measuring device and the shape calculating device, the auxiliary die position and the auxiliary die pressure are calculated from the steel sheet shape to correct the shape. As a result, the steel plate shape becomes as shown in FIG. 3, the steel plate becomes flat, and it is possible to control with high accuracy.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of the shaping apparatus of the present invention.

FIG. 2 is a graph showing a steel plate shape.

FIG. 3 is a graph showing a steel plate shape after shape correction according to the present invention.

[Explanation of symbols]

1 steel plate, 2 sink rolls, 3 support rolls, 4
Wiping nozzle, 5 auxiliary dies, 6 displacement gauge, 7
Plate width direction scanning coating amount measuring device, 8 shape calculation device, 9 shape control calculation device, 10 auxiliary die pressure control device, 11 auxiliary die and displacement gauge drive device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hisaku Miyakoshi 1-1 Tobata-cho, Tobata-ku, Kitakyushu City Nippon Steel Corporation Yawata Works Co., Ltd.

Claims (2)

[Claims] 1. The front and back surfaces in the width direction of the steel sheet are detected by detecting the intensity of fluorescent X-rays which are received by irradiating γ-rays or X-rays in the width direction of the plated steel sheet traveling from the hot dipping bath through the gas wiping region. Plate width direction scanning to measure the amount of plating applied From the amount of plating applied to the front and back sides in each width direction measured with a device for measuring the amount of applied plating, determine the shape of the steel plate using the shape calculator.
The obtained steel plate shape is approximated by a quartic function, and by using the maximum value and the minimum value of this function, the auxiliary dies arranged on the front and back surfaces of at least one of the wiping nozzle and the lower side, the installation position in the steel plate width direction and The pressure of the auxiliary die is calculated by a computing device, the auxiliary die is moved to the set position obtained by the drive device, and the pressure of the auxiliary die is controlled by the pressure controller. Method. 2. The front and back surfaces in the width direction of the steel sheet are detected by detecting the intensity of fluorescent X-rays that are received by irradiating γ-rays or X-rays in the width direction of the plated steel sheet running from the hot dip bath passing through the gas wiping zone. Plate width direction scanning plating amount measuring device for measuring the amount of plating applied. From the amount of applied plating on the front and back sides in each width direction measured by the device for measuring the amount of applied plating, the shape calculation device was used to obtain the steel plate shape based on the following equation (1). The shape of the steel plate is approximated by a quartic function, and by using the maximum and minimum values of this function, a plurality of auxiliary dies are arranged on at least one of the upper and lower sides of the wiping nozzle based on the following equations (2) to (3). of,
The hot-dip galvanizing method characterized in that the installation position in the width direction of the steel plate and the pressure of the auxiliary die are obtained by a computing device, the auxiliary die is moved to the obtained set position by a driving device, and the pressure of the auxiliary die is controlled by a pressure control device. Control method for uniform coating amount of steel sheet. W = exp (K0 + K1 × P + K2 × V + K3 × D) Formula (1) where W: coating amount of steel plate (g / m ² ) P: wiping pressure (kg / mm ² ) V: stripping speed (m / min) ) D: Distance between steel plate and wiping nozzle (mm) K0 to K3: constant Here, assuming that P and V are constant, the displacement amount ΔD when the center of the distance between the front and back gas wiping nozzles is 0 is It can be expressed by the formula 2). ΔD = (lnW1-lnW2) / K (2) where W1: coating amount on the front side of the steel plate (g / m ² ) W2: coating amount on the back side of the steel plate (g / m ² ) K: type of steel plate Constant determined by the above The steel plate shape can be calculated by the above equation (2).
Then, the auxiliary die pressure ΔP can be set by giving ΔD to be corrected by the auxiliary die from the steel plate shape calculation result. ΔP = {-P + (lnW1-lnW2)} / 2K1 (3) Formula