JPH0635649B2 - Electromagnetic wiping method for molten metal plated steel pipe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a molten metal (Zn, Sn, Al, etc.) plating equipment for steel pipes, in which the amount of molten metal adhered to the inner and outer surfaces of the steel pipe is adjusted by electromagnetic force. The present invention relates to a so-called wiping method for suppressing the amount.

(Prior Art) Conventionally, for example, the amount of zinc adhering to the inner and outer surfaces of a molten zinc plated steel pipe is usually considerably larger than the appropriate amount when the steel pipe is just immersed in a molten molten plating tank and pulled up. Further, in the case of steel pipe mates pulled up from the tank one by one, the amount of adhered mates is different at the upper end and the lower end. (Lower end amount> Upper end amount). Therefore, it is important for the zinc thickness unit to iron the adhered zinc on the inner and outer surfaces of the steel pipe by some method (hereinafter referred to as wiping) and obtain a uniform and appropriate amount of plating thickness in the length direction. For this reason, for example, as shown in FIG. 5, while the steel pipe 3 pulled up from the plating tank 4 is being sent by the magnet roll 5, N ₂ sent from the pressurized fluid source 21 from the ring-shaped nozzle 22 to the outer surface. , A method of spraying a pressurized fluid such as air (JP-A-56-38460)
No.), or a method of blowing pressurized fluid from one end of the steel pipe 3 to the inner surface of the steel pipe 3 through a nozzle 6 and recovering the wiped lead from the other end. Further, a method of inserting a spherical metal-ironing device into the inner surface of the steel pipe, as described in Japanese Patent Application Laid-Open No. 49-131917 (not shown), is known and used.

In these methods, the wiping device for the outer surface is installed in the vicinity of the outlet side of the plating tank, and the wiping of the inner surface is performed in the next step.

[1] Since the wiping methods for the inner surface and outer surface of the steel pipe are different, it is necessary to separate the process into two steps.

[2] The following problems exist in the wiping method for the inner surface of the steel pipe. For example, (1) In the method of injecting pressurized fluid from one end of the steel pipe, 1) Since the pressurized fluid nozzle applied to one side of the moving pipe needs to run synchronously with the pipe, it becomes a large-scale device and is located near the metal tank. It is difficult to install; 2) In the next step, if the nozzle is applied to the stationary steel pipe and the inner surface is wiped, the recovered zinc will be powdered zinc with a low value mixed with oxides. The loss is larger than that in the case of returning to 3). 3) Since the fluid is blown from one end of the pipe, the wiping ability is different on the blowing end side and the other end side, which leads to uneven thickness. . In addition, (2) In the method of inserting the spherical ironing and ironing device into the inner surface of the steel pipe, 1) There is a possibility that linear flaws are generated on the inner surface of the pipe by the ironing and ironing device; 2) The recovered zinc is zinc powder. Therefore, the value is low and the loss is large;

(Object of the invention) The present invention has been made in order to eliminate the above-mentioned drawbacks. Simultaneous wiping of the inner surface and the outer surface of the steel pipe can be performed in the immediate vicinity of the plating tank in one step, and zinc can be efficiently recovered in the plating tank, and An object of the present invention is to provide a wiping method capable of obtaining a high quality product.

(Means for Solving the Problems) The gist of the method of the present invention for achieving the above object is, in a method for wiping a steel pipe subjected to molten metal plating, pulling up a steel pipe immersed in a plating tank with a magnetol, The moving direction of the steel pipe is moved by moving the magnetic field in the direction opposite to the moving direction of the steel pipe by a moving magnetic field generator installed on the steel pipe transfer line above the tank in the vicinity of the magnet roll and moving the inside of the coil or between the coils. Is a method for electromagnetically wiping a molten metal plated steel pipe, wherein the molten metal attached to the steel pipe is wiped at the same time on the inner and outer surfaces by an electromagnetic force in the opposite direction.

(Embodiment) Next, the method of the present invention will be described in detail with reference to the drawings with reference to several examples of apparatus configurations for performing the method of the present invention.

FIG. 1 is a simplified explanatory diagram showing an example of a device configuration for carrying out the method of the present invention.

In FIG. 1, the steel pipe 3 which is immersed in the molten metal 10 in the plating tank 4 and is plated is pulled up by the pull-up magnet rolls 5 and 5 ′ in an inclined posture, and the steel pipe 3 in the vicinity of the magnet roll 5 is pulled up. It penetrates through the coil of the moving magnetic field generator 9 provided on the upper transfer line and moves in the direction of arrow 8. An electromagnetic force in a direction opposite to the traveling direction of the steel pipe is generated in the steel pipe by the moving magnetic field generator 9, and the metal adhered to the steel pipe (still molten) is returned to the plating tank 4 by the electromagnetic force. The steel pipe 3 whose inner and outer surfaces are wiped is conveyed to the next step by the magnet roll 5 ', and the wiped metal is again collected in the plating tank 4. Reference numeral 7 is a power source of the moving magnetic field generator 9.

Next, the principle of the moving magnetic field generator 9 will be described with reference to an embodiment shown in FIGS. 2 and 4. The moving magnetic field generator 9 comprises a coil 9-1, an iron core 9-2 and a switch 9-3. A large number of coils 9-1 are arranged at regular intervals, a switch 9-3 is provided in each coil, and each coil 9-1 is connected to the power supply 7. The switches 9-3 are sequentially switched to generate a moving magnetic field so that the steel pipe penetrates through the coil. An example of the cross-sectional structure is shown in FIG. Switch 9-3 and power supply 7 in FIG.
Can also be realized by multi-phase alternating current.

The moving magnetic field generated by such a large number of coils is
According to the law of electromagnetic induction, a current in the direction of canceling the moving magnetic field is induced in the steel pipe wall thickness. Due to the effect of this current and magnetic flux, an electromagnetic force acts on the steel pipe in the same direction as the moving direction of the magnetic field. Since the metal on the surface is melted just after being pulled up from the plating tank, it is pushed back toward the plating tank by the above force if the magnetic field is moving in the direction of the plating tank. Since the magnitude of the force acting on the outer and inner surfaces follows the skin effect, it becomes maximum on the outer surface and minimum on the inner surface, but in the case of thin-walled steel pipe, the difference between the inner surface force and the outer surface force can be reduced by lowering the AC frequency. Can be reduced.

FIG. 3 shows a moving magnetic field generation mechanism according to another method, in which n coils wound in a spiral shape (n is shown in the figure).
= 3) 9-1 is switched by the switch (R, S, T) 9-3 to generate a moving magnetic field. In this case also, switch 9
-3 It is also possible to realize the power supply 7 by n-phase multi-phase alternating current.

Although not shown, it goes without saying that it can be realized by installing moving magnetic field generators on the upper and lower surfaces of the steel pipe.

(Effects of the Invention) As described above, according to the method of the present invention, as compared with the conventional wiping method using a pressurized fluid and the spherical mesh ironing device, (1) the inner surface that has been conventionally performed in a separate step Wiping can be done at the same time as the outer surface, so that the process can be omitted and the device can be made compact; (2) Wiping of the molten metal that has been wiped because the wiping of the inner surface is performed immediately after pulling the steel pipe from the plating tank. (3) High quality product can be obtained because it is non-contact; and it has excellent effects.

[Brief description of drawings]

FIG. 1 is a simplified explanatory view showing an example of a device configuration for carrying out the method of the present invention, and FIGS. 2 and 3 are simplified explanatory diagrams showing an embodiment of a coil for generating a moving magnetic field of the present invention, respectively. FIG. 4 is a simplified cross-sectional explanatory view of the coil shown in FIG. 2, FIG. 5 is a simplified explanatory view of a conventional technique in which a ring-shaped nozzle is used for external wiping, and FIG. 6 is a simplified explanatory diagram of a prior art example of internal wiping. Is. 1 ... 2 ... 3 ... Steel pipe, 4 ... Mesh tank, 5,
5 '... Magnetoroll, 6 ... Nozzle, 7 ... Power supply, 8 ... Steel tube moving direction, 9 ... Moving magnetic field generator, 9
-1 ... Coil, 9-2 ... Iron core, 9-3 ... Switch, 10 ... Molten metal, 21 ... Pressurized fluid source, 22 ...
Ring nozzle

Claims (1)

[Claims] 1. A method of wiping a steel pipe having a molten metal plating, wherein a steel pipe 3 immersed in a plating tank 4 is pulled up by a magnet roll 5, 5 ', and is placed on a steel pipe conveying line above the tank in the immediate vicinity of the magnet roll. The moving magnetic field generator 9 provided is used to move the above-mentioned pulled steel pipe in the coil 9-1 or between the coils 9-1 to which a moving magnetic field in the direction opposite to the steel pipe moving direction 8 is applied, and the electromagnetic force in the direction opposite to the moving direction of the steel pipe is moved. An electromagnetic wiping method for a molten metal plated steel pipe, wherein the molten metal attached to the steel pipe is wiped at the same time by the force.