JPH10183324A - Method and device for splash prevention at hot dip plating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively prevent splashing without generating a surface flaw to a hit dip plated product and without making noise larger. SOLUTION: When a jet stream 9 injected from a gas wiping nozzle 8 is blown on both faces of a steel strip 1 pulled out from a hot dip plating bath and a hot dip plating quantity is adjusted, a suction pump 12, which causes a hit dip plating metal to flow in the opposite direction to a running direction of the steel strip 1 at a position near the pulling up steel strip 1, is arranged in a hot dip bath, the hot dip plating metal near the steel strip 1 is caused to flow in the direction opposite to a running direction of the steel strip. By a descending flow 13 of the hot dip plating metal generated near the steel strip 1, the impact caused at the time when a descending flow 10 of wiping gas is collided on the surface of the hot dip plating bath, is alleviated, thus, generation of splash is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for preventing splash generated during production of a hot-dip coated steel sheet.

[0002]

2. Description of the Related Art In a hot-dip galvanizing line, as shown in FIG. 1, a steel strip 1, which is a raw plate for plating, is conveyed to a reduction annealing furnace 2 maintained in a reducing atmosphere to activate the surface of the steel strip 1. , From the reduction annealing furnace to the hot-dip plating bath 4 via the snout 3. The steel strip 1 goes around the sink roll 5 immersed in the hot-dip plating bath 4, and its traveling direction is changed upward. Next, the steel strip 1 is sent out from the hot-dip plating bath 4 via the support roll 6, and the amount of adhesion is adjusted by the gas wiping device 7. Hot-dip coated steel strip 1
Is subjected to an alloying heat treatment as required and transported to the next step. The gas wiping device 7 for adjusting the amount of plating is
As shown in FIG. 2, they are arranged on the front side and the back side of the steel strip 1. Excess hot-dip galvanized metal adhering to the steel strip 1 is removed from the air, N ₂ injected from the gas wiping nozzle 8.
A jet 9 of gas, exhaust gas, combustion gas or the like is squeezed from the steel strip 1 by spraying the jet 9 on the steel strip 1. After the jet 9 collides with the steel strip 1, the flow direction is changed to an upward direction and a downward direction.

[0003] Of these, the downward flow 10 collides with the surface of the hot-dip plating bath 4 and causes a splash 11 to be generated. When the generated splash 11 adheres to the surface of the steel strip 1, the appearance of the plated product deteriorates. If the nozzle holes are clogged by adhering to the gas wiping nozzle 8, the distribution of the jet 9 in the width direction of the steel strip 1 cannot be controlled, and the plating adhesion amount becomes uneven. In recent years, it has been desired to increase the line speed to improve the productivity of hot-dip plating. When the line speed is increased, the amount of hot-dip metal to be lifted from the hot-dip bath 4 when the steel strip 1 is lifted increases. In order to adjust the excess amount of hot-dip metal deposited on the steel strip 1, the flow rate of the jet 9 jetted from the gas wiping nozzle 8 is increased,
Therefore, measures such as the close arrangement of the gas wiping nozzle 8 are required. However, in any of the measures, the pressure of the downflow 10 colliding with the surface of the hot-dip bath 4 after colliding with the surface of the steel strip 1 increases, and a large amount of splash 11 is likely to be generated.

Therefore, a shielding plate provided with a heating mechanism is disposed between the hot-dip plating bath 4 and the gas wiping nozzle 8 (Japanese Patent Laid-Open No. 62-205259), and the vicinity of the gas wiping nozzle 8 is enclosed by a closed chamber. The gas flow 10 toward the hot-dip plating bath 4 is guided in a direction parallel to the hot-dip plating bath 4 by a guide vane, a cross-flow fan or the like (Japanese Patent Laid-Open No. 5-140).
No. 721), providing a suction nozzle and a gas injection nozzle in the immediate vicinity of the gas wiping nozzle 8 (Japanese Patent Laid-Open No. 6-4).
1710, JP-A-7-150327) and applying a magnetic field to the surface of the hot-dip bath 4 (JP-A-2-150327).
No. 80545) proposes to prevent splash.

[0005]

However, in the method of preventing splash by using a shield plate, guide vanes, a cross flow fan, etc., since the shield plate and the closed chamber are arranged above the hot-dip plating bath, the steel strip vibrates. As a result, it comes into contact with the shielding plate or the closed chamber, and the surface flaw is easily generated in the product. In the method of preventing splash with the suction nozzle, frequent maintenance is required because the sucked splash solidifies in the nozzle hole. The method of preventing splash by the gas injection nozzle has a disadvantage that noise is increased by injection of the splash prevention gas. In the method of preventing splash with a magnetic field, it is necessary to apply a refractory coating to protect the magnetic pole from solidification and adhesion of high temperature and Zn vapor, so that a very expensive device is required. The present invention was devised to solve such a problem, and focused on the fact that splash occurs due to collision of gas on the surface of a hot-dip plating bath,
It is an object of the present invention to effectively prevent a splash by reducing the impact due to the collision without causing surface flaws of the hot-dip coated product and increasing the volume of noise.

[0006]

In order to achieve the object, the method for preventing splash according to the present invention adjusts the amount of hot-dip coating by spraying a jet from a gas wiping nozzle on both surfaces of a steel strip pulled up from a hot-dip coating bath. In doing so, the hot-dip metal in the vicinity of the steel strip being pulled is caused to flow in a direction opposite to the running direction of the steel strip. In a continuous hot-dip galvanizing line that sprays a jet from a gas wiping nozzle on both sides to adjust the amount of hot-dip coating, the hot-dip metal flows in a direction opposite to the running direction of the steel strip at a position near the steel strip being pulled up A suction pump is arranged in the hot-dip bath so as to face the front and back surfaces of the steel strip.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 3, a splash prevention device according to the present invention is a suction device for feeding hot-dip metal into hot-dip bath 4 at a position near steel strip 1 pulled up from hot-dip bath 4. The pump 12 is disposed on the front side and the back side of the steel strip 1. FIG. 3 shows the suction pump 12 arranged in parallel with the steel strip 1, but the arrangement of the suction pump 12 is not limited to this. For example, the downflow 13 of a hot-dip metal having a vertical component
It is also possible to incline upward or downward with respect to the steel strip 1 as long as When the suction pump 12 is operated, the steel strip 1 pulled up from the hot-dip plating bath 4 is removed.
Is flowing in the direction opposite to the running direction of the steel strip 1. The downflow 13 of the hot-dip metal absorbs the shock when the downflow 10 of the wiping gas collides with the hot-dip bath 4 and prevents the splash 10 from splashing the hot-dip metal.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Steel strip 1 having a thickness of 0.8 mm and a width of 1200 mm
Into the hot-dip plating bath 4 at a line speed of 100 m / min.
It was pulled vertically through the sink roll 5 and the amount of plating applied was controlled by the gas wiping device 7. The gas wiping nozzle 8 of the gas wiping device 7 has a height of 1 m.
m, having a spray hole of 2000 mm in width, was arranged on the front side and the back side of the steel strip 1 at a height of 200 mm from the hot-dip plating bath 4. The distance from the gas wiping nozzle 8 to the steel strip 1 was set to 20 mm. Also, depth 45
pump 1 with a suction port of 2,000 mm width and 2000 mm width
2 was placed in the hot-dip plating bath 4 on the front side and the back side of the steel strip 1 in parallel with the steel strip 1. The installation position of the suction pump 12 was set at a depth of 100 mm from the surface of the hot-dip plating bath 4 and a position 30 mm away from the steel strip 1. The pressure of the jet 9 injected from the gas wiping nozzle 8 is set to 0.25 kgf /
The suction amount of the hot-dip plated metal by the suction pump 12 was set to 1700 liters / minute to adjust the amount of plating applied to cm ² . For comparison, the amount of plating was adjusted under the same conditions except that the suction pump 12 was not operated.

The amount of plating applied could be reduced to 60 g / m ² irrespective of whether the suction pump 12 was operated or not.
However, when observing the splash attached to the surface of the hot-dip coated product, when the suction pump 12 is not operated, the length of the hot-dip coated product is 1000 mm and the width is 1200 mm.
Splash was attached to an area of about 40% with respect to the area of. On the other hand, when the suction pump 12 was operated, the area where the splash adhered could be suppressed to about 10%. In addition, the distribution of the coating amount in the plate width direction was ± 40 g / m ² when the suction pump 12 was not operated, but ± 20 g / m ² when the suction pump 12 was operated.
The variation was suppressed in the range of m ² . This is because, by operating the suction pump 12, the splash 10 is prevented from adhering to the gas wiping nozzle 8, and fluctuation due to nozzle blockage does not occur in the flow rate distribution of the wiping gas in the plate width direction. It means that the function was maintained.

[0010]

As described above, in the present invention, the suction pump is disposed in the hot-dip bath in the vicinity of the steel strip being lifted from the hot-dip plating bath, and is arranged in the direction opposite to the running direction of the hot-dip steel strip. Hot-dip metal near the steel strip is flowing. Due to the flow of the hot-dip metal, the impact when the wiping gas is blown down to the surface of the steel strip and collides with the surface of the hot-dip bath as a downward flow is reduced, thereby suppressing the generation of splash. As described above, according to the present invention, splash can be effectively prevented without causing surface flaws of the hot-dip product and increasing the volume of noise. In addition, since the splash adhesion to the gas wiping nozzle is also suppressed, high-precision control of the plating adhesion amount is maintained for a long time.

[Brief description of the drawings]

Fig. 1 Conventional hot-dip galvanizing system incorporating gas wiping system

Fig. 2 Splash generation situation

FIG. 3 is a hot-dip plating apparatus having a suction pump disposed in a hot-dip plating bath according to the present invention.

[Explanation of symbols]

1: Steel strip 2: Reduction annealing furnace 3: Snout 4:
Hot-dip plating bath 5: Sink roll 6: Support roll 7: Gas wiping device 8: Gas wiping nozzle 9: Jet flow 10: Downflow of wiping gas 11: Splash 12: Suction pump
13: Downflow of hot-dip metal

Claims (2)

[Claims] 1. A method for spraying a jet from a gas wiping nozzle onto both surfaces of a steel strip pulled up from a hot-dip plating bath to adjust the amount of hot-dip coating, the hot-dip plating metal in the vicinity of the steel strip being pulled up is stripped. A splash prevention method at the time of hot-dip plating, characterized by flowing in a direction opposite to the traveling direction of the steel sheet. 2. In a continuous hot-dip galvanizing line for spraying jets from gas wiping nozzles on both sides of a steel strip pulled up from a hot-dip plating bath to adjust the amount of hot-dip coating, at a position near the steel strip being pulled up, A splash prevention device in which a suction pump for flowing a hot-dip metal in a direction opposite to a running direction of a steel strip is opposed to a front surface and a rear surface of the steel strip in a hot-dip plating bath.