JPH07113157A - Method for preventing attraction of steel strip to electromagnet in plating adhesion control by electromagnetic force - Google Patents

Abstract

PURPOSE:To prevent the attraction of a steel strip to electromagnets at the time of starting operation by measuring the vibration amplitude of the steel strip at the time of starting the continuous hot dip metal coating line operation in the stop state of moving magnetic field generating coils, then suppressing this vibration amplitude by these coils. CONSTITUTION:The plating adhesion of the steel strip 2 rising perpendicularly from a plating bath 1 is controlled by the electromagnetic forces of the moving magnetic field generating coils 3 disposed to face each other on both sides of the steel strip. The plating operation is started by stopping the coils 3 in this method and the vibration amplitude of the steel strip 2 is previously measure by a distance sensor 4 while the steel strip 2 is passed along this sensor. The coils 3 are then operated to apply vibrations of an anti-phase to the steel strip 2 by the varying intensities of the magnetic fields generated from the coils to decrease the vibration amplitude. The distance sensor 4 and the coils 3 are thereafter switched like heretofore and the respective coils 3 are so controlled that the moving magnetic fields of the coils 3 on the steel strip 2 follow up the vibrations of the steel strip 2 to equal the electromagnetic forces on both sides of the steel strip.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for controlling the amount of plating adhered when a steel strip is plated in a continuous hot-dip metal plating line by an electromagnetic force, which can be applied to a large front and back direction of the steel strip generated at the start of operation of the plating line. The present invention relates to a method of preventing a steel strip from being attracted to an electromagnet by vibration.

[0002]

2. Description of the Related Art As a method for controlling the coating amount of steel strip in a continuous hot-dip galvanizing line, moving magnetic field generating coils are installed facing each other like gas wiping nozzles on both sides of a steel strip rising vertically from a plating bath. A method has been proposed in which an electromagnetic force is applied to a steel strip in the direction of a plating bath by a moving magnetic field of a coil to wipe off excess plating metal attached to the steel strip (Japanese Patent Publication No. 42-762). Since the wiping force in this method becomes larger as the distance between the moving magnetic field generating coil and the steel strip becomes smaller, the distance may be shortened when it is desired to reduce the coating adhesion amount.

However, when the moving magnetic field generating coil is brought too close to the steel strip, the steel strip rising from the plating bath is constantly vibrating in the front and back directions, so that it is attracted by the magnetic force of the coil and the vibration of the steel strip becomes large. However, the amount of plating applied in the longitudinal direction becomes uneven. Therefore, the present inventors have previously proposed a method of making the amount of plating adhered in the longitudinal direction of the steel strip uniform by changing the output of the moving magnetic field generating coils on both sides in accordance with the vibration amplitude of the steel strip (special feature: Wishhei 4-2837
No. 15). In this method, a distance sensor capable of measuring the distance between the steel strip surface and the moving magnetic field generating coil is arranged in the vicinity of the steel strip, and when the measured distance of the sensor varies from a set value, the steel strip approaches the moving magnetic field generating coil. The moving magnetic field on one side is weakened, and the moving magnetic field on the other side is strengthened simultaneously, so that the electromagnetic force acting on both sides of the steel strip becomes equal to the electromagnetic force on the steel strip at the set value of the distance sensor. It controls the generator coil.

[0004]

However, when the plating operation is restarted after the line is stopped due to an accident or periodic repair, the vibration of the steel strip in the front and back directions is large, and in that state, the steel strip is moved to the steel strip by the moving magnetic field generating coil. When the application of the moving magnetic field is started, the steel strip may be attracted to the moving magnetic field generating coil. Once the steel strip has been attracted to the moving magnetic field generating coil, the magnetic force is large, so that the steel strip does not separate from the moving magnetic field generating coil, and there is a problem that the plating operation cannot be performed.

[0005]

In view of the above points, the present invention provides a method for preventing a steel strip from being attracted to an electromagnet due to a large vibration in the front and back directions of the steel strip that occurs at the start of operation of a plating line. It is a thing. That is, in the present invention, the vibration amplitude of the steel strip at the start of the plating line operation is measured in advance by the distance sensor in a state where the moving magnetic field generating coil is stopped, and then the moving magnetic field generating coil is actuated, so that the steel is moved by the coil. A magnetic field for suppressing the vibration amplitude is added to the band to reduce the vibration amplitude.

[0006]

According to the present invention, the distance set value of the distance sensor is set to a vertically stretched position with the steel strip stopped as in the conventional case, and the power sources of the moving magnetic field generating coils on both sides are individually adjusted. Since it is possible to use alternating current as a power source, the phases should be matched.

When the operation of the plating line which has been stopped in this state is started, the steel strip normally vibrates greatly in the front and back directions. However, in the present invention, the vibration amplitude is measured in advance by the distance sensor in a state where the moving magnetic field generating coil is stopped, and the moving magnetic field generating coil is operated to move the vibration of the opposite phase corresponding to the vibration amplitude. By adding to the steel strip by the strength of the magnetic field generated from the magnetic field generating coil to reduce the vibration, the distance sensor and the moving magnetic field generating coil are switched as before, and the moving magnetic field of each moving magnetic field generating coil steel strip is changed to steel. Each moving magnetic field generating coil is controlled so that the electromagnetic force on both sides of the steel strip is equalized by following the vibration of the strip.

[0008]

EXAMPLE As shown in FIG. 1, a moving magnetic field generating coil 3 is placed opposite to both sides of a steel strip 2 stretched so as to rise vertically from a plating bath 1 of a continuous molten metal plating line, and one side The distance sensor-4 was placed on the plate, and plating was performed on both sides of the plating amount. The steel strip 2 has a thickness of 0.5 mm,
Each of the moving magnetic field generating coils 3 having a width of 1000 mm and a height of 1000 mm and a width of 1500 mm is installed at a position of 200 mm from the bath surface of the plating bath 1 and at a position of 10 mm from the steel strip 2 at a distance. Sensor-4 is a laser
The system was used. In addition, 5 is a synchro immersed in the plating bath 1, 6 is a top roll arranged vertically above the synchro 5, and 7 is arranged inside the plating bath 1 vertically above the synchro 5. It is an auxiliary roll.

In this state, the moving magnetic field generating coil 3 is stopped, the plating operation is started, and the steel strip 2 is moved to 100 m / min.
The vibration of the steel strip 2 was measured by the distance sensor-4 while the steel strip was passed at the speed of. Next, the moving magnetic field generating coil 3 was actuated, and vibrations of opposite phases were applied to the steel strip due to the strength of the magnetic field generated from the moving magnetic field generation coil 3 to reduce the vibration amplitude of the steel strip 2. After that, the distance sensor and the moving magnetic field generating coil are switched, a current of 1500 A is passed through the moving magnetic field generating coil 3, the excess magnetic metal is wiped off by the moving magnetic field, and the current is increased to 1000 in response to the vibration of the steel strip 2. The electromagnetic force acting on the steel strip 2 was controlled so as to be equal to that when it was separated from the moving magnetic field generating coil 3 by 10 mm. Figure 2 shows the change in deviation from the set value of the steel strip from the start of plating operation.

[0010]

As described above, according to the present invention, it is possible to prevent the steel strip from being attracted to the moving magnetic field generating coil at the start of the plating operation.

[Brief description of drawings]

FIG. 1 is a diagram near a plating bath showing a method for carrying out the method of the present invention.

FIG. 2 shows the relationship between the elapsed time from the start of plating operation and the deviation from the set value due to the vibration of the steel strip.

[Explanation of symbols]

1 ... Plating bath, 2 ... Steel strip, 3 ... Moving magnetic field generating coil, 4
... distance sensor, 5 ... synchronous, 6 ... top roll
7 ... Auxiliary roll,

Claims (1)

[Claims] 1. A moving magnetic field generating coil is installed opposite to both sides of a steel strip rising vertically from a plating bath of a continuous molten metal plating line, and the moving magnetic field of the coil causes an electromagnetic force in the direction of the plating bath on the steel strip. Is applied to wipe away excess plating metal adhered to the steel strip, and a distance sensor capable of measuring the distance between the steel strip surface and the moving magnetic field generating coil is arranged in the vicinity of the steel strip. When the strip measurement distance fluctuates from the set value, the moving magnetic field on the approaching side of the steel strip to the moving magnetic field generating coil is weakened, and the moving magnetic field on the detached side is strengthened at the same time, and the electromagnetic force acting on both sides of the steel strip is reduced by the distance. When controlling the coating adhesion amount at the start of plating line operation by controlling each moving magnetic field generating coil so that it becomes equal to the electromagnetic force on the steel strip at the set value of the sensor, when starting the plating line operation before starting control Steel strip After measuring the vibration amplitude of the distance sensor in advance with the moving magnetic field generation coil stopped,
Adhesion of a steel strip to an electromagnet in electroplating amount control by electromagnetic force, characterized in that a moving magnetic field generating coil is operated to add a magnetic field for suppressing the vibration amplitude to the steel strip by the coil to reduce the vibration amplitude. Prevention method.