JPH1046310A - Hot dip coating method without using sinkroll and coating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To execute hot dip coating by perpendicularly passing a steel strip upward in a hot dip-coating bath while holding the steel strip at a reference position. SOLUTION: When the steel strip 1 is hot-dip coated by perpendicularly pulling up the steel strip 1 which is sent in the hot dip-coating bath 4 from a steel strip carrying-in part 8 provided at a lower part of the hot dip-coating bath 4, a pair of moving magnetic field generating coils 10a, 10b are disposed to face each other at an outside of the steel strip carrying-in part 8. A reference position is set up at an intermediate position between the magnetic field generating coils 10a, 10b. When the measurement position of the steel strip 1 detected by a position sensor 13 deviates from the reference position, currents supplied to the respective moving magnetic field generating coils 10a, 10b are adjusted so that magnetic field intensity is made smaller by the moving magnetic field generating coil 10a or 10b at a side to which the steel strip 1 approaches and magnetic field intensity is made larger by the moving magnetic field generating coil 10a or 10b at a side from which the steel strip 1 parts. Thus, electromagnetic sealing having smaller interval between the moving magnetic field generating coils 10a, 10b are attained and excellent hot-dip coated steel can be manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for hot-dip coating a steel strip by using a hot-dip bath in which a sink roll is not immersed, while preventing leakage of the plated metal with an electromagnetic seal. Related to the device.

[0002]

2. Description of the Related Art In a continuous hot-dip galvanizing line, as shown in FIG. 1, a steel strip 1, which is a raw plate for plating, is transferred to a reduction annealing furnace 2 maintained in a reducing atmosphere to activate the surface of the steel strip 1. After that, it is sent from the reduction annealing furnace 2 to the plating bath 4 via the snout 3. The steel strip 1 goes around the sink roll 5 immersed in the plating bath 4 and changes its traveling direction upward. Next, the steel strip 1 is sent out of the plating bath 4 via the support roll 6, and the amount of plating applied is adjusted by the gas wiping device 7 or the like. Then, the hot-dip plated steel strip 1 is transported to a post-process.

In this continuous hot-dip plating line, since the traveling direction of the steel strip 1 is changed by the sink roll 5 immersed in the plating bath 4, the sink roll 5 is eroded by the hot-dip metal. The erosion is particularly severe in the bearing portion, and the smooth rotation of the sink roll 5 is impaired, and the sink roll 5 must be replaced in a complicated manner. To avoid troubles caused by sink rolls,
No. 34 discloses a plating bath that does not use a sink roll. In this method, as shown in FIG. 2, a plating bath 4 provided with a steel strip carry-in section 8 at a lower portion is used. Then, the traveling direction of the steel strip 1 is changed upward by the deflor 9 disposed on the outlet side of the reduction annealing furnace 2, and the steel strip 1 is fed into the plating bath 4 above the steel strip 1. Leakage of the hot-dip metal from the steel strip carry-in portion 8 opened downward is prevented by applying an upward electromagnetic force to the plating bath 4. That is, a moving magnetic field generating coil 10 arranged opposite to the steel strip carry-in portion 8 generates a magnetic field in a direction penetrating the steel strip from front to back, and the electromagnetic field is directed upward together with the eddy current generated in the steel strip 1 and the hot-dip metal. Force acts on the hot-dip metal in the steel strip carry-in section 8.

[0004]

In the method of holding a hot-dip metal by an electromagnetic force, a moving magnetic field generating coil
When the distance between 0 and 10 is large, the force acting on the hot-dip coated metal decreases, despite the increase in the weight of the hot-dip coated metal held. Therefore, a large electromagnetic force for canceling the separation distance is generated, and a large amount of current supplied to the moving magnetic field generating coils 10, 10 is required to hold a large weight of the hot-dip plated metal. .

When the distance between the opposing moving magnetic field generating coils 10, 10 is reduced, the electromagnetic force can be effectively applied to the holding of the hot-dip metal. However, when the distance between the coils is reduced, when the steel strip 1 approaches the moving magnetic field generating coil 10 on one side at least, the steel strip 1 is attracted to the moving magnetic field generating coil 10 which is closer. As a result, the steel strip 1 comes into contact with the inner wall surface of the steel strip carry-in section 8, and the surface of the steel strip is likely to have a flaw. In an extreme case, vibration may be generated by the restoring force of the steel strip 1 and the balance of the electromagnetic force may be lost, and the hot-dip plated metal may spill out from a portion where the magnetic force is weak. The present invention has been devised to solve such a problem. By controlling the supply current according to the distance between the steel strip and the moving magnetic field generating coil, the distance between the moving magnetic field generating coils is reduced. It is another object of the present invention to suppress the adhesion of the steel strip to the moving magnetic field generating coil and to suppress the vibration of the steel strip, and to efficiently hold the hot-dip coated metal with a small input power.

[0006]

In order to attain the object, a hot-dip galvanizing method according to the present invention vertically moves a steel strip fed into a hot-dip plating bath from a steel strip carrying-in portion provided at a lower portion of the hot-dip plating bath. When pulling up and hot-dip coating the steel strip, a pair of moving magnetic field generating coils are arranged opposite to the outside of the steel strip carry-in section,
When the reference position is set in the middle of the magnetic field generating coil, and the measured position of the steel strip detected by the position sensor deviates from the reference position, the magnetic field strength is small in the moving magnetic field generating coil on the side closer to the steel strip, and the steel strip is The present invention is characterized in that the current supplied to each moving magnetic field generating coil is adjusted so that the magnetic field strength increases in the moving magnetic field generating coils on the distant side. The hot-dip plating apparatus for carrying out this method is a hot-dip plating tank provided with a steel strip carry-in section with a lower end opened at a lower portion, and a pair of moving magnetic field generating coils arranged to face the outside of the steel strip carry-in section,
A drive circuit that supplies a current to each moving magnetic field generating coil, a control circuit that adjusts a current supplied from each drive circuit to each moving magnetic field generating coil, and a position sensor that detects the position of the steel strip are provided. . The control circuit compares the measured position of the steel strip detected by the position sensor with the reference position, and outputs a control signal for supplying a current corresponding to the deviation of the measured position from the reference position to each drive circuit.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In a plating apparatus according to the present invention, as shown in FIG.
And a pair of moving magnetic field generating coils 10a and 10b are arranged to face each other. Moving magnetic field generating coils 10a, 10b
Are connected to a control circuit 12 via respective drive circuits (power supplies) 11a and 11b so that currents are individually adjusted. When using an AC power supply, the driving circuits 11a and 11b match the phases of the currents flowing through the moving magnetic field generating coils 10a and 10b. A signal representing the reference position of the steel strip 1 and a signal representing the measurement position of the steel strip detected by the position sensor 13 are input to the control circuit 12, and an electromagnetic force for canceling a deviation of the measurement position from the reference position is calculated. You. The set distance of the position sensor 13 is usually the moving magnetic field generating coil 1.
It is set between 0a and 10b.

[0008] The steel strip 1 is transferred from the reduction annealing furnace 2 to the hot-dip plating bath 4.
When passing through the steel strip 1, the steel strip 1 may approach the moving magnetic field generating coil 10a on one side due to the vibration in the front and back directions, may be separated from the other moving magnetic field generating coil 10b, and may deviate from the reference position. The deviation from the reference position is detected by the position sensor 13. According to the detection result, the moving magnetic field is generated such that the magnetic field generated by the moving magnetic field generating coil 10a closer to the steel strip 1 is weak and the magnetic field generated by the moving magnetic field generating coil 10b farther from the steel strip 1 is stronger. The control circuit 12 calculates a current to be supplied to each of the coils 10a and 10b, and outputs a predetermined current from the driving circuits 11a and 11b to the moving magnetic field generating coil 1.
0a and 10b. Thereby, the steel strip 1 is maintained at the reference position, and one of the moving magnetic field generating coils 10a or 1
Ob is prevented from coming into contact with the inner wall of the steel strip carry-in section 8 by being sucked into the inner strip 0b. As a result, no flaw is generated on the surface of the steel strip. Further, since the vibration of the steel strip 1 is suppressed, the balance of the electromagnetic force is not lost, and the leakage of the hot-dip plated metal from the lower end opening of the steel strip carry-in portion 8 is also prevented.

[0009]

EXAMPLE Using the apparatus shown in FIG.
The steel strip 1 having a width of 1200 mm and a width of 1200 mm is supplied from the reduction annealing furnace 2 to the hot-dip plating bath 4 through the deflow 9
It was fed at a speed of m / min to perform hot-dip plating. At this time, in the steel strip loading section 8, the height is 320 mm and the width is 1500 m.
The moving magnetic field generating coils 10a and 10b of m are arranged to face each other with an interval of about 30 mm across the steel strip 1. Further, a position sensor 13 is provided on one side of the steel strip 1 below the moving magnetic field generating coils 10a and 10b. Moving magnetic field generating coils 10a, 1
0b was supplied with a three-phase alternating current having an average current of 2500A.
The supply current was changed and controlled in the range of 1000 to 4000 A in accordance with the measured distance detected by the position sensor 13 so that the steel strip 1 was held at the center between the moving magnetic field generating coils 10a and 10b.

As a result, the steel strip 1 was maintained at the center of the moving magnetic field generating coils 10a and 10b without vibrating. Therefore, it did not contact the wall surface of the plating bath 4, and the obtained hot-dip galvanized steel strip had a sound plating layer and a good surface state. For comparison, moving magnetic field generating coils 10a,
Constant value 2500 without controlling the supply current to 10b
Except for keeping at A, hot-dip plating was performed under the same conditions. In this case, the steel strip 1 is connected to one of the moving magnetic field generating coils 10a or 10a.
b, and the steel strip 1 was passed while being in contact with the inner wall surface of the steel sheet carry-in portion 8, so that a flaw causing unplating occurred on the surface of the steel strip 1.

[0011]

As described above, in the present invention, while controlling the position of the steel strip, the electromagnetic force for preventing the hot-dip metal from leaking from the lower end opening of the steel strip carry-in portion is applied. Therefore, even if the distance between the moving magnetic field generating coils is set to be small, the steel strip does not contact the inner wall surface of the steel strip loading portion due to the attraction force of the moving magnetic field generating coil, which causes plating defects such as non-plating. Is prevented from occurring on the surface of the steel strip. Further, since the steel strip is maintained at the reference position without vibrating, the magnetic balance is not lost, and the hot-dip plated metal does not leak from the lower end opening of the steel strip carry-in portion. In addition, since the distance between the moving magnetic field generating coils is small, the electromagnetic force for holding the hot-dip metal can be reduced.

[Brief description of the drawings]

FIG. 1 A conventional hot-dip bath immersed in a sink roll

Fig. 2 Hot-dip plating bath with an electromagnetic sealing mechanism in place of the sink roll

FIG. 3 is a hot-dip plating bath capable of controlling the electromagnetic force 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: Steel strip loading section
9: Deflor 10, 10a, 10b: Moving magnetic field generating coils 11a, 11b: Drive circuit (power supply) 12: Control circuit 13: Position sensor

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazunari Nakamoto 1 Tsurumachi, Amagasaki-shi, Hyogo Prefecture Nisshin Steel Co., Ltd.

Claims (2)

[Claims] When a steel strip fed into a hot-dip bath is pulled vertically upward from a steel strip loading section provided at a lower portion of the hot-dip plating bath and hot-dip plating is performed on the steel strip, a pair of steel strips is provided outside the steel strip loading section. A moving magnetic field generating coil is placed on the side closer to the steel strip when the measuring position of the steel strip detected by the position sensor deviates from the reference position by setting the reference position in the middle of the magnetic field generating coil. Adjust the supply current to each moving magnetic field generating coil so that the magnetic field strength is small and the magnetic field strength is large at the moving magnetic field generating coil on the side away from the steel strip. Plating method. 2. A hot-dip galvanizing tank having a steel strip carry-in portion having an open lower end provided at a lower portion, a pair of moving magnetic field generating coils disposed opposite to the outside of the steel belt carry-in portion, and a current flowing through each of the moving magnetic field generating coils. And a control circuit that adjusts the current supplied from each drive circuit to each moving magnetic field generating coil, and a position sensor that detects the position of the steel strip, wherein the control circuit is a position sensor. Comparing the detected measurement position of the steel strip with the reference position and outputting a control signal for supplying a current corresponding to the deviation of the measurement position from the reference position to each drive circuit; Plating equipment.