JP2001303224A - Hot dip metal coating method and hot dip metal coating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hot dip metal coating method with which dross defect or ripple defect of a steel sheet obtained in a continuous hot dip metal coating for steel sheet can effectively be prevented, and a hot dip metal coating apparatus. SOLUTION: In the hot dip metal coating method, the steel sheet is continuously dipped into coating bath of molten metal through a snout for shutting off the atmosphere, and after turning around a sink roll disposed in the coating bath to change this running direction, the steel sheet is drawn upward from the coating bath surface to continuously apply the hot dip coating. Further, in the hot dip metal coating method, the waving of the bath surface in the snout is measured, and based on the obtained measured result, the vibration for eliminating the waving, is given to a vibrating plate dipped into the snout and the coating bath in the snout. This hot dip metal coating apparatus is the one suitably used for this hot dip metal coating method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot metal plating method and a hot metal plating capable of preventing dross defects or ripples in a steel strip (including a steel sheet) obtained in continuous hot metal plating of a steel strip. Related to the device.

[0002]

2. Description of the Related Art FIG. 5 is a longitudinal sectional view showing a conventional hot-dip metal plating apparatus. In FIG. 5, 1 is the plating bath is molten metal, 2 plating pot, the sink roll 3, 4 strip (: Strip), 5 snout, f ₁ is the transport direction of the steel strip (strip passing direction), f ₂ represents the rotation direction of the sink roll.

That is, in the continuous hot-dip metal plating of a steel strip, the steel strip is continuously penetrated into a plating bath 1 which is a molten metal through a snout 5 for shielding the atmosphere, and is disposed in the plating bath 1. After turning around the sink roll 3 thus turned, the direction is changed, and it is pulled up from the bath surface of the plating bath 1 to continuously perform plating. Hereinafter, the conventional technology in hot-dip metal plating,
A description will be given by taking hot-dip galvanizing, which is a typical example of hot-dip metal plating, as an example.

Heretofore, in hot-dip galvanizing, quality defects called dross defects and ripple defects on the surface of the hot-dip galvanized steel strip have been a major problem. The above-mentioned defects are caused by the dross and molten zinc oxide mainly composed of Fe ₂ Al ₅ formed and grown on the molten zinc bath surface in the snout 5 floating by waves generated on the bath surface and adhering to the steel strip surface. It occurs.

Conventionally, in order to prevent the above-mentioned defects from occurring, quality control of the molten zinc in the plating bath has been performed. That is, in order to prevent the formation of oxides of molten zinc, dew point management of atmospheric gas in snout, regulation of oxygen concentration, and the like are performed. Further, as a method of suppressing dross, for example, as disclosed in Japanese Patent Application Laid-Open No. 8-176770, a dout inside a snout is separated from a thread passing position of a steel strip by using a flow of a hot dip galvanizing bath. The snout was retained inside and removed, and as shown in Japanese Patent Application Laid-Open No. 10-158796, the steel strip was conveyed at a high speed without being vibrated, and the adhesion of foreign substances due to the waving of the bath surface was suppressed. A snout is disclosed.

Although the above-mentioned method of collecting generated dross and a method of suppressing vibration of the steel strip are effective means for preventing the dross from adhering, it is difficult to greatly reduce floating dross in the snout. In addition, it is difficult to significantly suppress the vibration of the steel strip conveyed at high speed. Therefore, there has been a demand for a hot-dip metal plating method and a hot-dip metal plating apparatus capable of effectively preventing the occurrence of dross defects and ripple defects on the surface of the hot-dip galvanized steel strip.

[0007]

An object of the present invention is to solve the above-mentioned problems of the prior art and to effectively prevent dross defects or ripple defects in the obtained steel strip in continuous hot-dip metal plating of the steel strip. It is an object of the present invention to provide a hot-dip metal plating method and a hot-dip metal plating apparatus capable of performing the above-described processes.

[0008]

According to a first aspect of the present invention, a steel strip is provided.
Continuously penetrate into the plating bath, which is a molten metal, through a snout for shielding the atmosphere, turn around the sink roll provided in the plating bath, change direction, and pull it up above the bath surface to continuously A method of plating a molten metal, wherein the vibration of the bath surface in the snout is measured, and the vibration for eliminating the wave is immersed in the plating bath in the snout and / or the snout based on the measurement result obtained. A hot-dip metal plating method characterized by applying the method to a vibrating plate.

It is preferable that the vibration for canceling the wave is given by horizontally reciprocating a diaphragm immersed in a snout and / or a plating bath in the snout. In the second invention, a snout 5 for blocking a steel strip from the atmosphere and continuously intruding into a plating bath which is a molten metal, a plating pot 2 for accommodating the plating bath, and an intrusion into the plating bath are provided. A molten metal plating apparatus having a sink roll 3 disposed in a plating bath to change the direction of the steel strip and raise the steel strip above the plating bath surface, and measures the wave motion of the bath surface in the snout 5. A wave measuring device 10 and a vibrating device 12 for applying vibration having an opposite phase to the wave obtained by the wave measuring device 10 to the snout 5 and / or the vibration plate 11 immersed in the plating bath in the snout 5 are provided. A hot-dip metal plating apparatus characterized in that:

It is preferable that the above-mentioned vibration of the opposite phase is one that horizontally reciprocates a diaphragm immersed in a snout and / or a plating bath in the snout.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The present inventor has conducted intensive studies in order to solve the above-described problems, and as a result, has obtained the following findings, leading to the present invention. (1) Adhesion mechanism of dross and molten zinc oxide on steel strip surface: In the process of dross and molten zinc oxide generated in snout (hereinafter referred to as molten zinc oxide) adhere to the steel strip surface The above-mentioned dross or molten zinc oxide floats due to waves generated on the bath surface and not only adheres to the steel strip surface, but also adheres to the inner wall surface of the snout, and the coagulated dross and molten zinc oxide grow. , Wave of the bath surface (swaying)
Was found to adhere to the steel strip surface while floating on the bath surface.

(2) Suppression of ripples on the bath surface of the plating bath in the snout: Based on the elucidation of the above-mentioned adhesion mechanism, generation of dross defects and ripple defects is prevented by suppressing the ripples on the bath surface. It was found that it is possible. FIG. 1 shows an example of a hot-dip metal plating apparatus of the present invention in a side sectional view (a) and a partial sectional view in section A (b).

In FIG. 1, reference numeral 1 denotes a plating bath made of a molten metal, 2 denotes a plating pot, 3 denotes a sink roll,
Is a steel strip (: strip), 5 is a snout, 10 is a wave measuring device for measuring the wave of the bath surface in the snout 5, 12 is a vibration device for applying vibration to the snout 5, 13 is an amplifier, and 14 is a calculator. , 15 is a vibration control device, 16 is a snout support plate, 17 is a wave valley of the snout 5 inner bath surface, 18 is a wave valley of the snout 5 inner bath surface, 19 is a wave peak of the snout 5 inner bath surface, f ₁ is steel the conveying direction of the strip (sheet passing direction), f ₂ is the rotational direction of the sink roll, f ₃ is the vibration direction, h is the snout 5 within the plating bath bath vibration direction, f ₄ is the snout 5 of snout supporting plate 16 and snout 5 The height (wave) of the surface 17 is shown.

In the hot-dip metal plating apparatus shown in FIG. 1, a wave measuring device 10 for measuring a wave (ripening) of a plating bath surface in the snout 5 is provided in the snout 5, and the wave measuring device 10 Is amplified by the amplifier 13 and the arithmetic unit 14
To calculate the height (amplitude) h and the cycle (time) W of the wave (ripening) of the bath surface. In addition, the above-mentioned measurement of the wave (ripening) of the plating bath surface is performed by measuring the fluctuation of the height of the bath surface at a specific point.

FIG. 2A shows a calculation result of a signal from the wave measuring device 10. Next, based on the obtained calculation result, the frequency and amplitude of the vibration applied from the vibrating device 12 that cancels the wave (undulation) of the plating bath surface are calculated, and the obtained calculation result is used as a control output. The vibration is transmitted to the vibration device 12 and the vibration device 12 causes the snout 5 to generate a vibration having a phase opposite to that of the wave obtained by the wave measurement device 10 (reciprocal motion in the horizontal direction).

FIG. 2B shows an example of a waveform obtained by a control output from the vibration control device 15. In FIG. 2B, W ₀ indicates a period, and h ₀ indicates an amplitude. Also,
FIG. 2 (c) shows a state of undulation of the bath surface (result of calculation of a signal from the wave measuring device 10) controlled by the vibration device 12 via the control output.

The vibration device 12 of the present invention can apply a vibration having a frequency and an amplitude capable of canceling the waving of the plating bath in the snout 5 to the snout and / or a diaphragm described later. The type of the vibrating device 12 is not particularly limited. In FIG.
An example of the vibration device 12 is shown.

In FIG. 3, 5 is a snout, 11 is a diaphragm, 21 is a motor, 22 is an inverter, 23 is an eccentric cam,
24 is a slide plate, 25 is an eccentric cam rotation drive shaft, f ₆
Represents the rotation direction, the vibration direction of the horizontal f ₇ is a horizontal reciprocating direction of the slide plate (vibration direction), f ₈ is snout 5 or diaphragm 11 of the rotary drive shaft 25. The vibration device 12 shown in FIG.
And the motor 21 whose rotation speed is determined by the inverter 22
And a mechanism having an eccentric cam 23 for changing the rotation of the motor 21 into a reciprocating motion in the horizontal direction, and a slide plate 24 reciprocating in the horizontal direction, and by changing the amount of eccentricity of the eccentric cam 23, the snout 5 or The amplitude of the vibration of the diaphragm 11 (11A, 11B) shown in FIG. 4 in the horizontal direction can be changed.

FIG. 3 shows an example in which the plate surface of the snout 5 or the diaphragm 11 shown in FIG. 4, which will be described later, is arranged in a vertical direction, but the plate surface of the snout 5 is arranged in an oblique direction. The snout 5 or the diaphragm 11 shown in FIG.
A vibration device similar to the vibration device 12 shown in FIG. As described above, according to the hot-dip metal plating apparatus shown in FIG. 1, by giving the control output in the opposite phase of the undulation,
The vibration of the snout 5 acts as a control force on the bath surface, so that the ripple of the plating bath surface in the snout 5 can be largely suppressed.

As a result, dross and molten zinc oxide can be prevented from floating and adhering to the steel strip surface due to waves generated on the bath surface, and dross and molten zinc oxide adhered to and grown on the inner wall surface of the snout. The solidified material can be prevented from exfoliating due to the wave (sway) of the bath surface, preventing it from adhering to the steel strip surface while floating on the bath surface, and drastically reducing dross defects and ripple defects on the steel band surface It became.

Next, FIG. 4 shows another example of the vibration imparting device according to the present invention by a partial sectional view of a portion A in FIG.
FIG. 4 shows a method in which a diaphragm is immersed in a plating bath in the snout 5 to apply vibration to the diaphragm. FIG.
, 10A and 10B are wave measuring devices for measuring the wave of the bath surface in the snout, 11A and 11B are vibration plates immersed in the plating bath in the snout 5, and 12A and 12B apply vibration to the vibration plates 11A and 11B. Exciters, 13A, 13B are amplifiers, 14A,
14B is arithmetic unit, 15A, 15B is oscillated controller, 20 an opening for the wave measuring apparatus 10B of the plating bath bath surface, f ₅ the diaphragm
The vibration directions of 11A and 11B are shown, and the other symbols indicate the same contents as those in FIG.

That is, as shown in FIG. 4, in the present invention, instead of imparting vibration to the snout 5, the diaphragms 11A and 11B are immersed in a plating bath in the snout 5 to impart vibration to the diaphragm. May be. In the vibration applying method shown in FIG. 4, the wave measuring devices 10A and 10B are provided on both the front side and the back side of the steel strip, and based on the respective measurement results, each of them is independently shown in FIG. In the same manner as described above, the vibrations are obtained by the vibration measuring devices 10A and 10B on the diaphragms 11A and 11B via the amplifiers 13A and 13B, the arithmetic units 14A and 14B, the vibration control devices 15A and 15B, and the vibration devices 12A and 12B. Vibration of the opposite phase to the generated wave is applied to suppress the ripple of the plating bath surface in the snout 5.

In the method shown in FIG. 4 in which vibration is applied to the diaphragm immersed in the plating bath in the snout 5, the magnitude of the waving of the plating bath surface on the front side of the steel strip and the back surface of the steel strip are determined. Vibration may be applied to only one of the diaphragms 11A and 11B, or only one of the diaphragms may be provided, depending on the magnitude of the waving of the plating bath surface on the side. Further, in the present invention, a wave measuring device is provided on the front side and / or the back side of the steel strip, and based on the obtained measurement result, a vibration having a phase opposite to that of the wave obtained by the wave measuring device is provided to the snout. And vibration having a phase opposite to the wave obtained by the wave measuring device may be applied to the diaphragm immersed in the plating bath.

As described above, in the present invention, in order to suppress the undulation of the bath surface of the plating bath in the snout, the undulation of the bath surface is measured. The frequency that counteracts the wave of the bath surface,
By imparting the amplitude to the snout and / or the diaphragm immersed in the plating bath in the snout, the wave of the bath surface in the snout is eliminated.

As a result, according to the present invention, the bath surface in the snout is no longer wavy, and dross or molten zinc oxide floats on the bath surface and adheres to the steel plate. Ripple defects can be greatly reduced. Although the present invention has been described above, the molten metal in the continuous hot-dip metal plating of the steel strip in the present invention is not limited to molten zinc, but is a molten metal containing zinc as a main component (zinc-aluminum: Zn-Al). A molten metal other than molten zinc, such as molten aluminum (Al-Zn) containing aluminum as a main component, can also be used.

That is, the present invention is based on the above-mentioned functions and effects of the present invention, in which a steel strip formed by adhesion of a floating material on a plating bath surface in a snout in a steel strip hot metal plating apparatus using a molten metal other than molten zinc. It can also be suitably used as a hot-dip metal plating method and a hot-dip metal plating apparatus for the purpose of preventing surface defects.

[0027]

EXAMPLES The present invention will be described below more specifically based on examples. Continuous hot-dip galvanizing was performed on a steel strip using the hot-dip metal plating apparatus of the present invention, and the occurrence of dross defects and ripple defects on the steel strip surface was examined. (Example 1) Using the hot-dip galvanizing apparatus of the present invention shown in FIG. 1 described above, continuous hot-dip galvanizing of a steel strip was performed under the following conditions, and the quality of the obtained hot-dip galvanized steel strip was determined by the following test method. evaluated.

In the present embodiment, the quality of the hot-dip galvanized steel strip after the operation of the vibrating device 12 (Example 1 of the present invention) and the hot-dip galvanized steel strip before the operation of the vibrating device 12 (Comparative Example 1). Quality and contrast. (Conditions of hot-dip galvanizing :) Steel strip: Cold-rolled steel strip, sheet thickness 0.4 to 3.2 mm x sheet width 750 to 1850 mm Hot-dip galvanizing bath penetration plate temperature: 470 to 480 ° C Hot-dip galvanizing bath Al concentration: 0.13 to 0.15 % Passing speed: 30 to 150m / min (Method of preventing the plating bath surface in the snout from waving :) The wave measuring device 10 measures the wave (waving) of the plating bath surface in the snout 5, and the wave measuring device 10 Was amplified by an amplifier 13 and taken into a computing unit 14 to calculate a height h and a cycle W of a wave (undulation) on the bath surface.

Next, the obtained calculation result is transmitted to the vibration control device 15.
To calculate the frequency and amplitude of the vibration applied from the vibration device 12 such as to cancel the wave (ripening) of the plating bath surface, and to use the obtained calculation result as a control output as the vibration device 12
The vibrator 12 caused the snout 5 to generate a vibration (a horizontal reciprocating motion) having a phase opposite to that of the wave obtained by the wave measuring device 10.

The vibration device 12 is the same as that shown in FIG.
The vibration device 12 shown in FIG. As a result, the waving state of the plating bath surface in the snout was wavy as shown in FIG. 2A before actuation of the vibrating device 12 (Comparative Example 1). After the operation of the shaking device 12 (Example 1 of the present invention), the wave was formed as shown in FIG. 2 (c), and the wave of the plating bath surface in the snout 5 could be largely canceled.

(Testing method for hot-dip galvanized steel strip :) The following test was performed on 100 coils of the obtained steel strip to evaluate the quality. Defect rate due to dross defects on the steel strip surface: Hot-dip galvanized steel strip was pressed, and products with an average dross adhesion number of 2 pieces / m ² or more after the press processing were regarded as defective.

Failure rate due to ripple defects on steel strip surface:
The surface of the hot-dip galvanized steel strip was visually observed, the presence or absence of generation of a wave pattern in each coil was investigated, and the weight ratio of the ripple-defect-generating site in all the coils was determined. Table 1 shows the test results obtained. As shown in Table 1, according to the present invention, the ripple of the plating bath surface in the snout of the hot dip galvanizing apparatus is effectively suppressed, and as a result, dross on the steel strip,
It has become possible to effectively prevent the occurrence of dross defects or ripple defects on the steel strip surface due to the adhesion of the molten zinc oxide.

(Example 2) In the hot-dip metal plating apparatus of the present invention shown in FIG. 1 described above, except for suppressing the ripple of the plating bath surface in the snout 5 based on the vibration imparting method shown in FIG. 4 and described below. Was subjected to continuous hot-dip galvanizing on a steel strip under the same conditions as in Example 1, and the quality of the obtained hot-dip galvanized steel strip was evaluated in the same manner as in Example 1 described above.

In this embodiment, the quality of the hot-dip galvanized steel strip after the operation of the vibration device 12 (Example 2 of the present invention) and before the operation of the vibration device 12 (comparative example) 2)
And the quality of hot-dip galvanized steel strip. (Method for preventing ripples on plating bath surface in snout :) Wave measurement device 10A installed on both front and back sides of steel strip
And 10B, based on the respective measurement results, independently of the amplifier 13B in the same manner as the method shown in FIG.
A, 13B, computing units 14A, 14B, vibration control devices 15A, 15B
To the diaphragms 11A and 11B via the vibration devices 12A and 12B,
Vibrations having a phase opposite to that of the waves obtained by the wave measuring devices 10A and 10B were applied to suppress the ripple of the plating bath surface in the snout 5.

As the vibration device 12 (12A, 12B), the above-described vibration device 12 shown in FIG. 3 was used. As a result, the state of the plating bath surface in the snout was wavy as shown in FIG. 2A before actuation of the vibration device 12 (Comparative Example 2). After the operation of the shaking device 12 (Example 2 of the present invention), the wave was formed as shown in FIG. 2 (c), and the wave of the plating bath surface in the snout 5 could be largely canceled.

Table 1 shows the test results obtained. As shown in Table 1, according to the present invention, undulation of the plating bath surface in the snout of the hot dip galvanizing apparatus is effectively suppressed, and as a result, dross and adhesion of the molten zinc oxide to the steel strip are caused. It has become possible to effectively prevent the occurrence of dross defects or ripple defects on the steel strip surface.

In the first and second embodiments described above, hot-dip galvanizing of a steel strip has been described. However, the present invention is based on the above-described functions and effects of the present invention. The present invention can also be suitably used as a molten metal plating method and a molten metal plating apparatus for the purpose of preventing a steel strip surface defect due to adhesion of a plating bath bath surface in a snout in a used steel strip molten metal plating apparatus.

[0038]

[Table 1]

[0039]

According to the present invention, ripples on the plating bath surface in the snout of the hot dip galvanizing apparatus are effectively suppressed,
As a result, it is possible to effectively prevent dross defects or ripple defects on the surface of the steel strip due to the attachment of dross and molten zinc oxide to the steel strip, which can greatly contribute to stable operation.

The present invention is based on the actions and effects of the present invention.
Also suitable as a hot metal plating method and a hot metal plating apparatus for the purpose of preventing steel strip surface defects due to adhesion of floating substances on the bath surface of a plating bath in a snout in a hot metal plating apparatus for steel strip using a molten metal other than molten zinc Can be used.

[Brief description of the drawings]

FIG. 1 is a side sectional view (a) and an A part partial side sectional view (b) showing an example of a hot-dip metal plating apparatus of the present invention.

FIG. 2 is a graph (a) showing a calculation result of a signal from a wave measurement device, and a graph (b) showing a control output from a vibration control device.
FIG. 7C is a graph (c) showing the state of undulation on the bath surface controlled by the vibrating device (the calculation result of the signal from the wave measuring device).

FIG. 3 is an explanatory view showing an example of a vibration device according to the present invention.

FIG. 4 is a partial sectional view of a part A in FIG. 1 showing another example of the vibration imparting device according to the present invention.

FIG. 5 is a side sectional view showing a conventional hot-dip metal plating apparatus.

[Explanation of symbols]

Reference Signs List 1 plating bath (molten metal) 2 plating pot 3 sink roll 4 steel strip (strip) 5 snout 10, 10A, 10B wave measuring device 11, 11A, 11B diaphragm 12, 12A, 12B vibrating device 13, 13A, 13B Amplifier 14, 14A, 14B Computing unit 15, 15A, 15B Vibration control unit 16 Snout support plate 17 Snout inner bath surface 18 Wave trough of snout inner bath surface 19 Wave peak of snout inner bath surface 20 Opening 21 Motor 22 Inverter 23 Eccentric cam 24 Slide plate 25 Rotary drive shaft of eccentric cam f ₁ Transport direction of steel strip (passing direction) f ₂ Rotation direction of sink roll f ₃ Vibration direction of snout support plate and snout f ₄ Vibration direction of snout f ₅ Vibration direction of diaphragm f ₆ Rotation direction of rotary drive shaft f ₇ Reciprocating direction of horizontal reciprocation of slide plate (vibration direction) f ₈ Horizontal vibration direction of snout or diaphragm h Plating bath surface in snout Wave of the wave Period of the wave of the plating bath bath surface in the amplitude W snout of the vibration (waving) that imparts from a height h ₀ vibrator (: Time) cycle of the vibration applied from the W ₀ vibrator

Claims (2)

[Claims] 1. A steel strip is continuously penetrated into a plating bath, which is a molten metal, through a snout for shielding air, and after turning around a sink roll provided in the plating bath, the steel strip is turned.
A hot-dip metal plating method in which a plating bath is raised above a bath surface to continuously perform plating, wherein a wave of the bath surface in the snout is measured, and vibration for eliminating the wave based on the obtained measurement result is measured. A hot-dip metal plating method, which is applied to a diaphragm immersed in a snout and / or a plating bath in the snout. 2. A snout (5) for shielding a steel strip from the atmosphere and continuously intruding into a plating bath which is a molten metal;
A plating pot (2) for storing the plating bath and a sink roll (3) disposed in the plating bath to change the direction of the steel strip penetrating into the plating bath and pull it upward from the plating bath surface. A molten metal plating apparatus having a wave measuring apparatus for measuring a wave of a bath surface in the snout (5).
And a vibration device (10) for applying vibration having an opposite phase to the wave obtained by the wave measurement device (10) to the snout (5) and / or the diaphragm (11) immersed in the plating bath in the snout (5). A hot-dip metal plating apparatus characterized by including 12).