JP2602757B2 - Continuous hot-dip galvanizing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous hot-dip galvanizing method for a steel strip, in which the hot-dip metal deposited on a steel strip rising through a hot-dip metal bath is thinned and controlled. It is.

[0002]

2. Description of the Related Art Generally, a method for controlling hot-dip metal deposited on a steel strip by hot-dip plating is mainly performed by a gas wiping method. In this method, a gas such as air or nitrogen is blown at a high speed to a molten plating metal adhered to a steel strip rising while passing through a molten plating metal bath by passing the excess molten plating metal. This is to produce a plated steel sheet which is wiped and controlled to a predetermined plating weight. However, with such a manufacturing method, it has been difficult to manufacture an ultrathin plated steel sheet having a small plating weight. In addition, since high pressure gas is blown from the gas wiping nozzle to the steel strip on which the hot-dip metal is welded, there is a problem that the noise is intense and the working environment is deteriorated.

As a plating method for solving such a problem, for example, Japanese Patent Publication No. 58-23464,
As described in Japanese Unexamined Patent Publication No. 266560 and Japanese Unexamined Patent Publication No. Hei 1-7261, excessive plating metal adhering to a steel strip rising through a hot-dip plating metal bath is thinned by using both an electromagnetic force and a gas wiping nozzle. A hot-dip plating method for controlling the coating weight has been developed. These hot-dip plating methods are:
By using a magnetic field generator, the pressure of the gas ejected from the gas wiping nozzle is reduced and the noise problem is somewhat improved, but a lot of splashes of hot-dip galvanized metal appear due to the blowing of a considerably high pressure gas. In addition, there is a problem that the appearance of the manufactured plated product is remarkably deteriorated.

[0004]

SUMMARY OF THE INVENTION The present invention has been subjected to many experiments and studies for the purpose of producing a hot-dip coated steel sheet having a beautiful appearance in order to prevent splash generated by the continuous hot-dip plating method. One example of the result is shown in FIG. FIG.
Is 45 mm longer than the edge of the 1200 mm wide steel strip.
4 shows the distribution of electromagnetic force acting on the end of a steel strip when a 0 m moving magnetic field generator is arranged parallel to the steel strip and at a separation angle of 20 °. When the steel strip running on the magnetic field generator is installed in the width direction of the steel strip and at equal intervals (parallel) on the strip, as shown by the dotted line, the electromagnetic force is sharply reduced toward the center of the steel strip width, so that excess molten plating is performed. Many splashes occur because the metal is not pushed down to the hot-dip bath side and a large amount of excess hot-dip metal is wiped only by the gas wiping nozzle. However, when the magnetic field generator is installed gradually from the edge of the steel strip to the center in the width direction of the steel strip, as shown by the solid line, a sudden decrease in the electromagnetic force can be avoided, so that the occurrence of splash can be significantly suppressed. I learned.

[0005]

SUMMARY OF THE INVENTION The present invention has been made based on this finding. The gist of the present invention is to provide a hot-dip plating metal welded to a steel strip rising through a hot-dip metal bath on the bath surface side. A moving magnetic field generator that generates an electromagnetic force to be pushed down is gradually spaced from the edge of the steel strip to the center in the width direction, and a surplus hot-dip metal is blown by blowing gas onto the hot-dip metal in the range of electromagnetic force. This is a thinning continuous hot-dip plating method to wipe off.

Hereinafter, the method of the present invention will be described in detail with reference to the drawings. 1 and 2 schematically show an embodiment of the method of the present invention. FIG. 1 is a side sectional view of a continuous hot-dip plating apparatus, and FIG.
FIG. 3 shows a cross-sectional view taken along the line A. In FIG. 1, reference numeral 1 denotes a hot-dip plating metal bath in which a corrosion-resistant plating metal such as zinc, tin, and aluminum is dissolved. Reference numeral 2 denotes a pot roll, which is provided by dipping in a hot-dip metal bath 1. Reference numeral 3 denotes an exit roll, which is arranged below the surface of a hot-dip metal bath. 4 is a running steel strip, which is a material to be plated. That is, the traveling steel strip 4 is configured to rotate the pot roll 2, pass through the exit roll 3, weld the hot-dip plated metal 5, and rise. Reference numeral 6 denotes a moving magnetic field generator, which is constituted by arranging a plurality of magnetic field generating coils 7 in the running direction of the steel strip 4. Further, as shown in FIG. 2, the magnetic field generator 6 is installed at a wide angle gradually from the edge of the steel strip 4 to the center in the width direction. 8 is a gas wiping nozzle. The gas wiping nozzle 8 is installed at a position within the range of action of the electromagnetic force of the moving magnetic field generator 6 and blows gas onto the ascending molten metal adhering to the running steel strip 4 to wipe off excess molten metal. Is what you do.

That is, the present invention provides a hot-dip plating metal bath 1
While the excess plating metal welded to the steel strip ascending by passing through the steel plate is pushed down to the bath surface side by the electromagnetic force and the gas wiping nozzle 8, a thin melted steel sheet is continuously manufactured. However, in the present invention, since the moving magnetic field generator is installed so as to be gradually separated from the edge of the steel strip toward the center in the width direction, the electromagnetic force largely acts on the edge of the steel strip, and the central portion of the strip is moved. As a result, the electromagnetic force is prevented from suddenly decreasing, the rapid change in the thickness of the hot-dip metal deposited on the steel strip is prevented, and the effect of suppressing splash is exerted. According to the method of the present invention as described above, a plated product having an excellent appearance in which splash of a hot-dip plated metal is prevented is produced. Next, examples of the present invention will be described.

[0008]

[Example] A steel strike having a thickness of 0.8 mm and a width of 1200 mm.
Pass the lip at a speed of 150 m / min.
Steel strike pulled from hot-dip galvanized pot
The molten zinc attached to the lip was wiped off. At this time the device width 4
50mm, 350mm high moving magnetic field generator with steel
Inside the steel strip width direction across the edge of the strip
It was installed at an angle of 20 ° toward. In addition, the moving magnetic field generator
25mm from the steel strip at the edge of the steel strip
0 mm apart. The magnetic flux density at that position is B = 0.25 wb
/ M^Two To generate a moving magnetic field of frequency f = 1500 Hz
Was. At this time, gas wiping can be performed without splash
30g / m ^Two Of moving magnetic field generator
Power consumption was 900 KVA. On the other hand, the conventional steel
A moving magnetic field generator is placed over the entire width of the
The degree is B = 0.25 wb / m^Two At frequency f = 1500Hz
Generating a moving magnetic field of
28g / m^Two Moving magnet with one piece
The power consumption of the field generator was 1200 KVA. that's all
As described above, the thinning effect of the present invention is at the same level as
Power consumption and less than conventional methods.

[0009]

As described above, in order to suppress the splash due to gas wiping which hinders the thinning of the hot-dip metal or the high-speed plating of the steel strip,
A moving magnetic field generator (electromagnetic force generator) that suppresses hot-dip galvanized metal adhering to the steel strip pulled up from the plating pot is provided at both edges of the steel strip at the edge of the steel strip where splash is particularly likely to occur. By arranging it so as to increase the distance from the steel strip toward the inside in the width direction, it is possible to make the plating amount thinner at the same level as the conventional method with a more compact apparatus than the conventional method.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing one embodiment of the method of the present invention.

FIG. 2 is a cross-sectional view taken along the line AA of the hot-dip metal wiping area of FIG. 1;

FIG. 3 shows the distribution of electromagnetic force acting on the end of a steel strip when a moving magnetic field generator 450 m long from a 1200 mm wide edge of the steel strip is arranged parallel to the steel strip and at a separation angle of 20 °. FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hot-dip metal bath 2 Pot roll 3 Exit roll 4 Steel strip 5 Hot-dip metal 6 Moving magnetic field generator 7 Magnetic field generating coil 8 Gas wiping nozzle

Claims (1)

(57) [Claims] 1. A moving magnetic field generator for generating an electromagnetic force for pushing down a hot-dip metal deposited on a steel strip passing through a hot-dip metal bath to a bath surface side from a steel strip edge to a widthwise center thereof. A thinning continuous hot-dip plating method characterized in that the hot-dip hot-dip metal is wiped off by spraying a gas on the hot-dip metal in the range of the electromagnetic force, while gradually separating the hot-dip metal from the hot metal.