JP2002294425A - Wiping device with gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wiping device with gas, for suitably preventing an edge overcoating and a splash which occur at side edges in a widthwise direction of a steel strip, corresponding to a line speed or a plated coating weight. SOLUTION: The wiping device with gas 6 has a perpendicular distance L between a collision point 8 of the wiping gas spouted out from the wiping nozzle 7 and a shielding plate 9, in a range of the following formula (2); 1.0×D×(1+COSθ)>=L>=0.25×D×(1+COSθ)...(2), when a height H from the top surface of a hot-dip metal 2a to a wiping nozzle 7 is expressed in the following formula (1); H>-0.0375×D<2> +5.25×D-40...(1): and has the above distance L in a range of the following formula (4); L>=D×(0.25×(1+COSθ)+1.8×(1+ COSθ)<0.07> ×((P/PA)<0.2857> -1)<0.5> ×(H/D)<1.35> )...(4), when the above height H is expressed by the following formula (3); H<=-0.0375×D<2> +5.25×D-40...(3).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for performing hot metal plating on a steel strip, after removing the steel strip from the hot dipping bath, removing excess hot metal plating by gas wiping, and adjusting the amount of adhesion. To a gas wiping device.

[0002]

2. Description of the Related Art Generally, hot metal plating is performed on the surface of a steel strip in a continuous hot metal plating line 100 shown in FIG. This continuous hot metal plating line 1
At 00, after the steel strip S is drawn out of the plating bath via the upper and lower support rolls 103, 104 around the sink roll 102 provided in the hot-dip plating bath 101, the steel strip S is moved. A wiping gas is blown onto the front and back surfaces of the steel strip S from a pair of wiping nozzles 105 installed on the front and back surfaces, thereby removing excess molten metal and adjusting the amount of molten metal plating. I have.

In this method, gas from both wiping nozzles 105 facing each other, particularly at both side edges in the width direction of the steel strip S, collide with each other, causing turbulent gas flow and a thickness of 10 mm.
A so-called edge overcoat phenomenon in which an excess of molten gold of at least μm was adhered was observed. This is because the width of the wiping nozzle 105 of the gas wiping device is wider than the width of the steel strip S, so that the wiping gas flows outside the both side edges of the steel strip S in the width direction.

Conventionally, as a gas wiping device for preventing the edge overcoat phenomenon, for example, a gas wiping device shown in FIG.
No. 8441). This gas wiping device 201
Is a gas wiping device that adjusts the amount of molten metal plating to be applied to the continuously running steel strip S, and is a wiping nozzle that ejects a wiping gas toward the front and back surfaces of the steel strip S (see FIG. 1). (Not shown), and a collision point 2 of the wiping gas ejected from the wiping nozzle, which is located on the extension surface in the width direction of the steel strip near both side edges of the steel strip S in the width direction.
And a pair of shielding plates 203 installed at a height including a height 02.

According to the gas wiping device 201,
By the action of the pair of shielding plates 203, mutual interference of wiping gas ejected from the wiping nozzle is prevented, and edge overcoat is prevented. The gap ΔL between the side edges in the width direction of the steel strip S and the respective shield plates 203 varies depending on operating conditions such as the amount of plating and the line speed.
It is 10 mm.

On the other hand, a gas wiping device 2 shown in FIG.
In FIG. 01, in order to effectively exert the effect of preventing the edge overcoat, when the shielding plate 203 is brought closer to the widthwise side edge of the steel strip S by several mm or less, the shielding plate 20
In addition, small molten metal called splash generated at the time of wiping adheres and accumulates on 3 to make operation difficult. In addition, the molten metal frequently forms a bridge between the shielding plate 203 and the widthwise side edge of the steel strip S. The inconvenience of growing and having to take care to remove the molten metal frequently has arisen. In order to solve this inconvenience, the gas wiping device 201 includes a pair of edge wiping nozzles 2 that eject gas toward the upstream side in the running direction of the steel strip S in the steel strip width direction extending surface.
04 is installed between the inner end of the shielding plate 203 and both side edges in the width direction of the steel strip S, and reduces the splash scattered to the outside in the width direction of the steel strip S by the gas injected from the edge wiping nozzle 204. Like that.

The gas wiping device 2 shown in FIG.
In 01, the distance L between the collision point 202 of the wiping gas ejected from the wiping nozzle and the lower end of the shielding plate 203 should be about 5 to 20 mm, since if the distance L is long, splash tends to adhere. Is preferred.

[0008]

However, the conventional gas wiping apparatus 201 has the following problems. That is, the distance L between the collision point 202 of the wiping gas ejected from the wiping nozzle and the lower end of the shielding plate 203 is set to 5 to 20 mm.
Are determined only for a limited number of operating conditions, and have been found to be optimal for a wide range of line speeds and a wide range of coating weight to be deposited on the steel strip S. Not. Specifically, when the line speed is low (for example, 30 m / min) or when the coating weight is large (for example, 450 g / m ² ), the distance between the wiping nozzle and the steel strip is increased. It is necessary to reduce the amount of molten metal to be removed. In this case, it has been found that when the distance L is less than 10 mm, the effect of preventing the edge overcoat by the shielding plate 203 is small. On the other hand, when the line speed is high (for example, 80
m / min) or when the coating weight is small (for example, 45 g
/ m ² ), it is necessary to reduce the distance between the wiping nozzle and the steel strip to increase the amount of molten metal to be removed. In this case, when the distance L is 20 mm or more,
It has been found that the splash adheres and accumulates on the edge of the shielding plate 203, causing difficulty in operation, and also causes quality defects such as re-adhering to the lateral edge of the steel strip S.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to reduce the occurrence of edge overcoat and splash generated at the side edge of a steel strip in the width direction by controlling the line speed and the amount of adhered plating. It is an object of the present invention to provide a gas wiping device capable of optimally preventing gas wiping according to the following conditions.

[0010]

In order to solve the above-mentioned problems, a gas wiping apparatus according to claim 1 of the present invention is directed to a front side and a back side of a running steel strip which is drawn from a plating bath holding a molten metal and runs. A wiping nozzle for ejecting a wiping gas, and a wiping gas that is located on a steel strip width direction extending surface near both side edges of the steel strip in a width direction and is installed at a height including a collision point of the wiping gas ejected from the wiping nozzle. Shield plate, installed between the steel strip side end of the shield plate and both side edges in the width direction of the steel strip, toward the upstream side in the running direction of the steel strip in the steel strip width direction extension plane And an edge wiping nozzle for ejecting gas from the wiping nozzle when the height from the upper surface of the molten metal to the wiping nozzle is expressed by the following formula (1). When the vertical distance between the collision point of the gas and the lower end of the shielding plate is in the range of the following formula (2), and the height from the upper surface of the molten metal to the wiping nozzle is the following formula (3), the wiping nozzle The vertical distance between the collision point of the wiping gas ejected and the lower end of the shielding plate is set in the range of the following equation (4).

H> −0.0375 × D ² + 5.25 × D−40 (1) 1.0 × D × (1 + COS θ) ≧ L ≧ 0.25 × D × (1 + COS θ) (2) H ≦ ^{-0.0375 × D 2 + 5.25 × D} -40 ... (3) L ≧ D × (0.25 × (1 + COSθ) + 1.8 × (1 + COSθ) 0.07 × ((P / P A) 0.2857 -1) ^0.5 × (H / D) ^1.35 ) (4) where, L: vertical distance (mm) between the collision point of the wiping gas ejected from the wiping nozzle and the lower end of the shielding plate D: the surface of the steel strip and the wiping nozzle Distance (m
m) H: height from the upper surface of the molten metal to the wiping nozzle θ: jetting angle of the wiping gas to the shielding plate (°) P: wiping gas pressure (Pa) P _A : atmospheric pressure (Pa) If the height H from the upper surface of the molten metal to the wiping nozzle is not affected by the vortex between the wiping nozzle and the molten metal, H> −0.037
In the case of 5 × D ² + 5.25 × D-40, the vertical distance L between the collision point of the wiping gas ejected from the wiping nozzle and the lower end of the shielding plate is 1.0 × D × (1 + COS).
θ) ≧ L ≧ 0.25 × D × (1 + COSθ). The distance L is L ≧ 0.25 × D × (1 + COS
θ), the occurrence of the edge overcoat that occurs at the widthwise side edge of the steel strip is determined by the distance D between the surface of the steel strip and the wiping nozzle determined according to the line speed and the amount of adhered plating. Can be optimally prevented.
Further, since the distance L is L ≦ 1.0 × D × (1 + COSθ), the generation of the splash is determined by the line speed or the amount of deposited plating, and the distance D between the surface of the steel strip and the wiping nozzle is determined. Can be optimally prevented. On the other hand, the height H from the top surface of the molten metal to the wiping nozzle is affected by the vortex between the wiping nozzle and the molten metal. H ≦ −0.0375 × D ² + 5.25 × D−
In the case of 40, the vertical distance L between the collision point of the wiping gas ejected from the wiping nozzle and the lower end of the shielding plate is:
L ≧ D × (0.25 × (1 + COSθ) + 1.8 × (1
^{+ COSθ) 0.07 × ((P} / P A) 0.2857 -1) 0.5 ×
(H / D) ^1.35 ). Thereby, the occurrence of edge overcoat occurring at the widthwise side edge of the steel strip is determined by the distance D between the surface of the steel strip and the wiping nozzle determined according to the line speed and the amount of adhered plating, and the wiping gas pressure. It can be optimally prevented according to P.
In this case, since H is small, the line speed is low, and the amount of adhered plating is large, no splash occurs.

A gas wiping device according to a second aspect of the present invention is a wiping nozzle for jetting a wiping gas toward the front and back surfaces of a running steel strip drawn from a plating bath holding a molten metal, and a wiping nozzle for the steel strip. A shielding plate which is located on a steel strip width direction extending surface near both widthwise side edges and is installed at a height including a collision point of a wiping gas ejected from the wiping nozzle, and a steel strip side end of the shielding plate And an edge wiping nozzle which is installed between the portion and the side edges of the steel strip in the width direction, and ejects gas toward an upstream side in a running direction of the steel strip in a plane extending in the width direction of the steel strip. In the wiping device, at least a surface of the shielding plate located downstream of the discharge point of the edge wiping nozzle in the steel strip traveling direction has poor wettability to the molten metal. Further, the shielding plate itself may be a metal or a non-metal having poor wettability, or a metal or non-metal coating layer having a poor wettability to the molten metal is applied to the surface of the shielding plate. You may.

According to this gas wiping device, splash generated at the time of wiping is prevented from adhering to the surface of the shielding plate. In the gas wiping device of the present invention, in order to effectively prevent edge overcoat by the shielding plate, it is preferable that a distance between the both side edges in the width direction of the steel strip and the shielding plate is 4 to 7 mm. .

[0014]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a schematic side view of a continuous molten metal plating line to which a gas wiping device according to the present invention is applied, and FIG. 2 is a schematic partial plan view of the gas wiping device according to the present invention. As shown in FIG. 1, when performing the hot-dip metal plating on the surface of the steel strip S, the continuous hot-dip metal plating line 1 similar to FIG. 9 is used.

In the continuous hot-dip metal plating line 1, the steel strip S circulates around the sink roll 3 provided in the hot-dip plating bath 2 and passes from the plating bath via upper and lower support rolls 4 and 5 in the bath. After being drawn out, by the gas wiping device 6 arranged above the hot-dip plating bath 2,
The wiping gas is sprayed on the front and back of the steel strip S,
In this way, excess molten metal is removed, and the amount of molten metal plating is adjusted.

As shown in FIGS. 1 and 2, the gas wiping device 6 blows the wiping gas toward the front and back surfaces of the steel strip S drawn from the hot-dip plating bath 2 holding the molten metal 2a. The pair of wiping nozzles 7 and the wiping gas ejected from the wiping nozzles 7 are located at a height including the collision point 8 of the wiping gas ejected from the wiping nozzles 7 and located on the steel strip width direction extending surface near both side edges of the steel strip S in the width direction. A pair of shielding plates 9 on both sides in the width direction of the steel strip, and a steel plate installed between the steel strip side end of the shielding plate 9 and both side edges in the width direction of the steel strip S, A pair of edge wiping nozzles 10 on both sides in the width direction of the steel strip for jetting gas toward the upstream side in the running direction of the strip S
Is provided. Here, the gap between both side edges in the width direction of the steel strip S and the pair of shielding plates 9 is 4 to 7 m in consideration of operating conditions.
m is preferable. Further, the discharge point of the edge wiping nozzle 10 is preferably located on the downstream side in the running direction of the steel strip from the gas collision point injected from the wiping nozzle 7.

The present inventors have proposed a gas wiping device 6
In regard to the vertical distance L between the collision point 8 of the wiping gas ejected from the wiping nozzle 7 and the lower end of the shielding plate 9, it is called an edge overcoat generated on both side edges in the width direction of the steel strip S and prevention of generation of splash. We continued our research from a viewpoint and succeeded in finding an optimal design and an optimal operation method to prevent both.

As a result of the study, as shown in FIG. 3, the wiping nozzle 7 was placed on the upper surface of the molten metal 2a in the plating bath 2.
When the height H is equal to the following formula (1), the collision point 8 of the wiping gas ejected from the wiping nozzle 7 and the shielding plate 9
The vertical distance L from the lower end of the molten metal 2 is set in the range of the following expression (2), and the height H from the upper surface of the molten metal 2a to the wiping nozzle 7 is set.
Is the following formula (3), it is preferable that the vertical distance L between the collision point 8 of the wiping gas ejected from the wiping nozzle 7 and the lower end of the shielding plate 9 is in the range of the following formula (4). I understood.

H> −0.0375 × D ² + 5.25 × D−40 (1) 1.0 × D × (1 + COSθ) ≧ L ≧ 0.25 × D × (1 + COSθ) (2) H ≦ ^{-0.0375 × D 2 + 5.25 × D} -40 ... (3) L ≧ D × (0.25 × (1 + COSθ) + 1.8 × (1 + COSθ) 0.07 × ((P / P A) 0.2857 -1) ^0.5 × (H / D) ^1.35 ) (4) where, L: vertical distance (mm) between the collision point of the wiping gas ejected from the wiping nozzle and the lower end of the shielding plate D: the surface of the steel strip and the wiping nozzle Distance (m
m) H: Height from the top surface of molten metal to wiping nozzle θ: Spout angle of wiping gas to shielding plate (°) P: Wiping gas pressure (Pa) P _A : Atmospheric pressure (Pa) From these equations (1) Consider the significance of equation (4).

First, as shown in the equations (1) and (3), the height H from the upper surface of the molten metal 2a to the wiping nozzle 7 is calculated.
The reason why the appropriate range of the distance L is divided according to the magnitude of the distance L will be described. As shown in FIG. 3A, when the wiping nozzle 7 is installed far away from the upper surface of the molten metal 2a and the height H to the wiping nozzle 7 is increased, the wiping nozzle 7 is located between the wiping nozzle 7 and the molten metal 2a. As shown in FIG. 3A, no vortex is generated, the wiping gas jet is not attracted to the molten metal 2a, and affects the wiping gas jet distribution 12 formed on the steel strip S and the shielding plate 9. There is no.

On the other hand, in an operation in which the plating amount of the steel strip S is increased or the line speed is low, the wiping nozzle 7 is generally moved closer to the upper surface of the molten metal 2a as shown in FIG. It is installed and the height H up to the wiping nozzle 7 is reduced. In this case, a strong vortex 11 is provided between the wiping nozzle 7 and the molten metal 2a as shown in FIG.
Is generated, and the jet of the wiping gas is attracted to the molten metal 2a by the generation of the vortex 11, thereby affecting the jet distribution 12 of the wiping gas formed on the steel strip S and the shielding plate 9.

Here, the size of the wiping nozzle height H is crucial to the generation of the vortex 11, but the wiping nozzle height H at which the jet of the wiping gas is attracted to the molten metal is determined by the wiping nozzle height H. Is affected by the distance D between the steel strip 7 and the steel strip S, as shown in the equation (3),
Experiments have revealed that vortices 11 are generated when ≦ −0.0375 × D ² + 5.25 × D−40 is satisfied.

Since the jet flow distribution 12 of the wiping gas has a strong influence on the vertical distance L between the collision point of the wiping gas jetted from a suitable wiping nozzle and the lower end of the shielding plate, the equations (1) and (3) are used. As described above, the appropriate range of the distance L is divided according to the magnitude of the height H from the upper surface of the molten metal 2a to the wiping nozzle 7. next,
When the height H from the upper surface of the molten metal 2a to the wiping nozzle 7 satisfies the range of the expression (1) and the case of the height H, the collision point of the wiping gas ejected from the wiping nozzle 7 is satisfied. An appropriate range of the vertical distance L between the lower end 8 and the lower end of the shielding plate 9 will be considered.

When the wiping nozzle height H satisfies the range of the equation (1): In this case, the distance L is not affected by the vortex 11. First, according to the two-dimensional free jet theory, as shown in FIG. 5, the gas jet from the wiping nozzle 7 has a development region including a potential core having no attenuation of the central velocity of the gas jet and a mixed region on both sides of the potential core, and It has been found that the gas jet consists of two regions: a fully developed region in which the central velocity of the gas jet is high and the velocity is gradually reduced on both sides, which is a fully developed turbulent flow. Then, the jet distribution 12 of the wiping gas formed on the shielding plate 9 indicates the distance D between the wiping nozzle 7 and the steel strip S, the wiping gas pressure P, and the jetting angle θ of the wiping gas with respect to the shielding plate 9 in FIG. 5 and the thickness B of the tip opening of the wiping nozzle 7 in FIG.

Next, as a result of an experiment on the jet distribution 12 of the wiping gas formed on the steel strip S and the shielding plate 9 and the effect of the occurrence of the edge overcoat, a strong correlation was found between the distribution of the edge overcoat and the effect of the occurrence of the edge overcoat. Is obtained with the width W of the jet distribution 12 of the wiping gas formed on the shielding plate 9, and the vertical distance L between the collision point 8 of the wiping gas ejected from the wiping nozzle 7 and the lower end of the shielding plate 9. Found that the occurrence of edge overcoat can be prevented by covering the width W by 90% or more.

Thus, the range of the vertical distance L between the collision point 8 of the wiping gas ejected from the wiping nozzle 7 and the lower end of the shielding plate 9 that can prevent the occurrence of edge overcoat is as follows: L ≧ 0.25 × D × It can be confirmed that (1 + COSθ).

On the other hand, in order to prevent the fine molten metal called splash generated at the time of wiping from adhering to the shielding plate 9, the range of the distance L is 1.0 × D × (1 + COSθ) ≧ L. Confirmed by experiment. Therefore, when the wiping nozzle height H satisfies the range of the expression (1), the range of the distance L that can optimally prevent the occurrence of the edge overcoat and the splash generated at the side edge in the width direction of the steel strip S is as follows. 1.0 × D × (1 + COSθ) ≧ L ≧ 0.25 × D × (1 + COSθ) (2)

Since the distance D between the wiping nozzle 7 and the steel strip S is determined according to the line speed and the amount of adhered plating, the edge overcoat generated on the side edge of the steel strip S in the width direction and the distance D are determined. Splash generation can be optimally prevented according to the line speed and the amount of adhered plating. When the wiping nozzle height H satisfies the range of the formula (3): In this case, a vortex 11 is generated, the jet of the wiping gas is attracted to the molten metal 2a, and the wiping is formed on the steel strip S and the shielding plate 9. It affects the gas jet distribution 12.

Therefore, the above L ≧ 0.25 × D × (1+
It is necessary to correct the range of the vertical distance L between the collision point 8 of the wiping gas ejected from the wiping nozzle 7 and the lower end of the shielding plate 9 which can prevent the occurrence of the edge overcoat COS θ). The vertical distance L between the collision point 8 of the wiping gas ejected from the wiping nozzle 7 and the lower end of the shielding plate 9 in consideration of the amount of the wiping gas jet generated by the generation of the vortex 11 attracted to the molten metal 2a is L ≧ that D × (0.25 × (1 + COSθ) + 1.8 × (1 + COSθ) 0.07 × ((P / P A) 0.2857 -1) 0.5 × (H / D) 1.35) ... (4) has been confirmed by experiment Was.

Here, the distance D between the front (back) surface of the steel strip and the wiping nozzle, the height H from the upper surface of the molten metal to the wiping nozzle, and the wiping gas pressure P depend on the line speed and the amount of adhered plating. Therefore, it is possible to optimally prevent the occurrence of edge overcoat occurring at the side edge in the width direction of the steel strip according to the line speed and the amount of adhered plating. In this case, no splash occurs because H is small, the line speed is low, and the amount of adhered plating is large.

Although the embodiment of the present invention has been described above, the present invention is not limited to this, and various modifications can be made. For example, it is preferable that at least the surface of the shielding plate 9 located downstream of the discharge point of the edge wiping nozzle 10 in the running direction of the steel strip has poor wettability to molten metal. For this purpose, a metal or nonmetal coating layer having poor wettability to the molten metal 2a may be applied to the surface of the shielding plate 9. Further, the shielding plate 9 itself may be a metal or a nonmetal having poor wettability.

By providing a surface having poor wettability to the molten metal 2a in this manner, even if a splash is generated during wiping, it can be prevented from adhering to the surface. The poor wettability means that the contact angle of the molten metal on the surface of the shielding plate is 90 ° or more. As the metal or non-metal having poor wettability, for example, chromium, silicon, nitrided ceramics, and the like are preferable.

[0033]

EXAMPLES In order to verify the effects of the present invention, the following operation was performed. As the gas wiping device, a gas wiping device having a configuration similar to that of the gas wiping device shown in FIG. 2 is used, and as the operation examples 1 to 24 shown in Table 1, the collision point 8 of the wiping gas ejected from the wiping nozzle 7 and the shielding are performed. The vertical distance L from the lower end of the plate 9, the distance D between the wiping nozzle 7 and the steel strip S, the height H from the upper surface of the molten metal 2 a to the wiping nozzle 7, the wiping gas pressure P, the coating layer on the shielding plate 9 The operation was performed by changing the presence / absence, the passing speed of the steel strip S, and the amount of zinc plating adhered to the steel strip. In this case, the judgment was made based on the edge overcoat ratio and the state of the trouble of splash adhesion and deposition.

Here, in FIG. 6, the edge overcoat ratio is such that the thickness W1 of the hot-dip metal plating (zinc plating) at the center of the steel strip S and the thickness W2 of the hot-dip metal plating at both lateral edges of the steel strip S in FIG. Is calculated from the following equation, and the ratio is 5
% Or less, there is no practical problem, so the judgment result was "good". Edge overcoat ratio = (W2−W1) / W1 × 100 (%) The results are shown in Table 1. In Table 1, for each of the operation examples 1 to 24, the right-hand side value of the expressions (1) and (3) {−0.0375 × D ² + 5.25 × D−40},
Right side value of equation (2) ２0.25 × D × (1 + COS
θ)｝, the left side value of (2)） 1.0 × D × (1 + COS
θ)} and the right-hand side value of equation (4) {D × (0.25 × (1
+ COS θ) + 1.8 × (1 + COS θ) ^0.07 × ((P
_{^{/ P A) 0.2857 -1) 0.}} 5 × (H / D) 1.35)} are shown together, each distance L claims operation examples 1 to 24 1
It was determined whether or not the equation (2) or (4) specified in the above was satisfied.

[0035]

[Table 1]

First, the results in the case of the operation examples 1 to 6 will be described. In the operation examples 1 to 6, the vertical distance L between the collision point 8 of the wiping gas ejected from the wiping nozzle 7 and the lower end of the shielding plate 9 is 10 mm. Form an embodiment satisfying the range of the expression (2) defined in claim 1. On the other hand, in the operation example 3, the distance L was small and did not satisfy the range of the expression (2) defined in claim 1, constituting a comparative example. Further, with respect to the operation examples 4 to 6, the distance L is small and does not satisfy the range of the expression (4) defined in claim 1, and constitutes a comparative example.

Here, for the operation examples 1 and 2 in which the distance L satisfies the range of the expression (2) defined in claim 1,
Since the edge overcoat ratio was as small as 1% and 2% and there was no splash adhesion trouble, the judgment result was "good". On the other hand, the operation example 3 in which the distance L is small and does not satisfy the range of the expression (2) defined in claim 1 and the operation examples 4 to 6 which do not satisfy the range of the expression (4) specified in claim 1 are edge-acquired, respectively. The overcoat ratio is 7% and 9 to 15%, and the determination result is “No”.

Next, the operation examples 7 to 12 will be described. In the operation examples 7 to 12, the vertical distance L between the collision point 8 of the wiping gas ejected from the wiping nozzle 7 and the lower end of the shielding plate 9 is 20 mm, but in the operation example 7, the distance L is large. Since it does not satisfy the range of the expression (2) defined in claim 1, a comparative example is configured. On the other hand, in the operation examples 8 and 9, the distance L is defined as
Since the range of Expression (2) defined in (1) is satisfied, an embodiment is configured. Further, with respect to the operation examples 10 to 12, the distance L was small and did not satisfy the range of the expression (4) defined in claim 1, thus constituting a comparative example.

Here, in the operation example 7 in which the distance L is large and does not satisfy the range of the expression (2) defined in claim 1, the edge overcoat ratio is as small as 1%, but since the distance L is too large, There is a splash adhesion trouble, and the determination result is “No”. On the other hand, in the operation examples 8 and 9 in which the distance L satisfies the range of the expression (2) defined in claim 1, since the edge overcoat ratio is as small as 2% and there is no splash adhesion trouble, The judgment result is “good”.

For the operation examples 10 to 12 in which the distance L is small and does not satisfy the range of the expression (4) defined in claim 1, the edge overcoat ratio is 7% to 12%, and the judgment result is " No. " Next, operation example 1
Cases 3 to 18 will be described. Operating examples 13 to 1
8 is a case where the vertical distance L between the collision point 8 of the wiping gas ejected from the wiping nozzle 7 and the lower end of the shielding plate 9 is 40 mm, but the distance L is too large for the operation examples 13 and 14. Since the range of the expression (2) defined in the item 1 is not satisfied, a comparative example is configured. On the other hand, in the operation example 15, the distance L satisfies the range of the expression (2) defined in claim 1, and thus, the embodiment is configured. Further, for the operation examples 16 to 18, since the distance L satisfies the range of the expression (4) defined in claim 1,
An embodiment is configured.

Here, the operating examples 13 and 14 in which the distance L is large and do not satisfy the range of the expression (2) defined in claim 1
For each, the edge overcoat ratio is 1
% And 2%, but because the distance L is too large, there is a splash adhesion trouble, and the determination result is “No”. On the other hand, in the operation example 15 in which the distance L satisfies the range of the expression (2) defined in claim 1, since the edge overcoat ratio is as small as 2% and there is no splash adhesion trouble, the judgment result is It is considered "good."

The distance L is defined in claim 1 (4).
For the operation examples 16 to 18 satisfying the range of the expression, the edge overcoat ratio was as small as 2% to 3%,
In addition, since there is no splash adhesion trouble, the judgment result is “good”. Lastly, operation examples 19 to 24 will be described. In the operation examples 19 to 24, the vertical distance L between the collision point 8 of the wiping gas ejected from the wiping nozzle 7 and the lower end of the shielding plate 9 is 40 mm, but the coating layer is formed on the surface of the shielding plate 9. That is, plating thickness 2
Since the hard chrome plating of μm is applied, in any case, the problem of splash adhesion is avoided. And about the edge overcoat ratio,
Each of the operation examples 19 to 24 was as small as 1% to 3%,
The judgment result is “good”.

In any of the above operation examples 1 to 24, zinc plating is adhered to the steel strip, but aluminum plating or aluminum-zinc alloy plating may be adhered to the steel strip. Investigations were conducted on the reduction in the amount of zinc plating consumption by reducing the edge overcoat ratio according to the present invention and the improvement in product yield by preventing splash adhesion trouble according to the present invention. 7 shows the result shown in FIG. 7, and the result shown in FIG. 8 shows the improvement of the product yield.

Referring to FIG. 7, the present invention (Operation Example 24)
As a result, the consumption of galvanizing is reduced by about 2.times. Compared to the conventional example (Operation Example 12).
It is understood that the reduction is 5%. Further, referring to FIG. 8, the product stop is prevented by the splash (accumulation example 20) according to the present invention (operation example 1).
It is understood that the improvement is about 0.5% compared to 4).

[0045]

As described above, according to the gas wiping device according to the first aspect of the present invention, the height H from the upper surface of the molten metal to the wiping nozzle is increased by the vortex between the wiping nozzle and the molten metal. H> -0.
In the case of 0375 × D ² + 5.25 × D-40, the vertical distance L between the collision point of the wiping gas ejected from the wiping nozzle and the lower end of the shielding plate is 0.80 × D × (1+
COS θ)> L ≧ 0.25 × D × (1 + COS θ). When the distance L is L ≧ 0.25 × D × (1 + C
OSθ), the occurrence of edge overcoat that occurs at the side edges of the steel strip in the width direction is determined by the difference between the front (back) surface of the steel strip and the wiping nozzle, which is determined according to the line speed and the amount of adhered plating. It can be optimally prevented according to the distance D between them. When the distance L is L <0.80 × D × (1 + C
OSθ), the occurrence of splash can be optimally prevented according to the distance D between the front (back) surface of the steel strip and the wiping nozzle, which is determined according to the line speed and the amount of adhered plating. . On the other hand, the height H from the upper surface of the molten metal to the wiping nozzle is affected by the vortex between the wiping nozzle and the molten metal, H ≦ −0.0375.
In the case of × D ² + 5.25 × D-40, the vertical distance L between the collision point of the wiping gas ejected from the wiping nozzle and the lower end of the shielding plate is L ≧ D × (0.25 × (1 + C
OSθ) + 1.8 × (1 + COSθ) ^0.07 × ((P / P
_A ) ^0.2857 -1) It is determined in the range of ^0.5 x (H / D) ^1.35 ). As a result, the occurrence of edge overcoat occurring at the widthwise side edge of the steel strip is determined by the distance D between the front (back) surface of the steel strip and the wiping nozzle, which is determined according to the line speed and the amount of deposited plating. In addition, it can be optimally prevented according to the wiping gas pressure P. In this case, since H is small, the line speed is low, and the amount of adhered plating is large, no splash occurs.

According to the gas wiping device of the second aspect of the present invention, at least the surface of the shielding plate located downstream of the discharge point of the edge wiping nozzle in the running direction of the steel strip has wettability with respect to the molten metal. Therefore, splash generated at the time of wiping can be prevented from adhering to the surface of the shielding plate.

[Brief description of the drawings]

FIG. 1 is a schematic side view of a continuous hot-dip metal plating line to which a gas wiping device according to the present invention is applied.

FIG. 2 is a schematic partial plan view of the gas wiping device according to the present invention.

FIG. 3 shows a state of a wiping gas jet according to a difference in wiping nozzle height, and FIG. 3A is a schematic explanatory diagram of a wiping gas jet state when the wiping nozzle height is high;
(B) is a schematic explanatory view of a wiping gas jet state when the wiping nozzle height is low.

FIG. 4 is a schematic side view showing a configuration of a wiping nozzle.

FIG. 5 is a schematic explanatory view showing a state of a gas jet injected from a wiping nozzle.

FIG. 6 is a partial sectional view of a steel strip showing an edge overcoat.

FIG. 7 is a graph showing a reduction in the amount of zinc plating consumed by reducing the edge overcoat ratio according to the present invention.

FIG. 8 is a graph showing an improvement in product yield by preventing splash adhesion trouble according to the present invention.

FIG. 9 is a schematic side view of a general continuous hot-dip metal plating line.

FIG. 10 is a partial plan view of a conventional gas wiping device.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 continuous molten metal plating line 2 molten plating bath 2a molten metal 3 sink roll 4 upper support roll in bath 5 lower support roll in bath 6 gas wiping device 7 wiping nozzle 8 collision point of wiping gas ejected from wiping nozzle 9 shielding Plate 10 Edge wiping nozzle 11 Vortex 12 Wiping gas jet distribution S Steel strip

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takefumi Kameya 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba F-term inside the Chiba Works, Kawasaki Steel Co., Ltd. 4K027 AA22 AC52 AD22

Claims (2)

[Claims] 1. A wiping nozzle for blowing a wiping gas toward the front and back surfaces of a traveling steel strip drawn from a plating bath holding a molten metal, and a widthwise extension of the steel strip in the vicinity of both side edges in the width direction of the steel strip. A shielding plate located on a surface and provided at a height including a collision point of the wiping gas ejected from the wiping nozzle, a steel strip side end of the shielding plate, and both side edges of the steel strip in the width direction; And an edge wiping nozzle for ejecting gas toward the upstream side in the running direction of the steel strip in the steel strip width direction extending surface, wherein the wiping is performed from the upper surface of the molten metal. When the height to the nozzle is the following formula (1), the vertical distance between the collision point of the wiping gas ejected from the wiping nozzle and the lower end of the shielding plate is defined by the following formula (2), and of When the height from the upper surface to the wiping nozzle is the following formula (3), the vertical distance between the collision point of the wiping gas ejected from the wiping nozzle and the lower end of the shielding plate is defined as the range of the following formula (4). A gas wiping device characterized by performing. H> −0.0375 × D ² + 5.25 × D−40 (1) 1.0 × D × (1 + COSθ) ≧ L ≧ 0.25 × D × (1 + COSθ) (2) H ≦ −0. ^{0375 × D 2 + 5.25 × D} -40 ... (3) L ≧ D × (0.25 × (1 + COSθ) + 1.8 × (1 + COSθ) 0.07 × ((P / P A) 0.2857 -1) 0.5 × ( H / D) ^1.35 ) (4) where, L: vertical distance (mm) between the collision point of the wiping gas ejected from the wiping nozzle and the lower end of the shielding plate D: between the surface of the steel strip and the wiping nozzle Distance (m
m) H: Height from the top surface of the molten metal to the wiping nozzle θ: Spout angle of the wiping gas to the shielding plate (°) P: Wiping gas pressure (Pa) P _A : Atmospheric pressure (Pa) 2. A wiping nozzle for ejecting a wiping gas toward the front and back surfaces of a traveling steel strip drawn from a plating bath holding a molten metal, and a steel strip width direction extension near both side edges in the width direction of the steel strip. A shielding plate located on a surface and provided at a height including a collision point of the wiping gas ejected from the wiping nozzle, a steel strip side end of the shielding plate, and both side edges of the steel strip in the width direction; And an edge wiping nozzle that ejects gas toward the upstream side in the running direction of the steel strip in the steel strip width direction extension plane, wherein the discharge point of at least the edge wiping nozzle A gas wiping device characterized in that the surface of the shielding plate located on the downstream side in the steel strip traveling direction has poor wettability to the molten metal.