JPH0372063A - Film thickness controller for hot dip metal coating - Google Patents

Abstract

PURPOSE:To allow the control of a film thickness without generating noises with a hot dip metal coating device for approximately vertically pulling up a sheet material to be coated by specifically providing 1st to 3rd high-frequency coils to the sheet material to be coated. CONSTITUTION:The sheet material 1 to be coated is pulled up with the sheet surface positioned vertically from the inside of a molten metal 3 and is cooled to solidify the molten metal, by which the material is coated. The 1st coil 4 which horizontally encloses the plate material 1 above the liquid level of the molten metal 3 and the 2nd and 3rd coils 5a, 5b which are disposed approximately symmetrically on both sides of the sheet surface of the sheet material 1 and the coil 4 and have the axis approximately perpendicular to the sheet surface mentioned above are provided in this device. The high-frequency current of the same phase is supplied to the 1st to 3rd coils to generate eddy currents in the liquid films sticking to the surface of the sheet material. Magnetic fluxes are passed in the eddy currents to generate downward force and to reduce the thickness of the liquid film. Since the magnitude of the above-mentioned force is determined by the high-frequency current flowing in the coils, the film thickness is controllable by adjusting the high-frequency current.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a plating film thickness control device applied to hot-dip metal plating equipment.

[Conventional technology]

FIG. 9 is a schematic diagram showing an example of conventional hot-dip metal plating equipment, and FIG. 10 is a detailed diagram of the vicinity of the gas jet nozzle.

The plate (1), which is the material to be plated, is passed from the reduction furnace (12) into the molten metal (3) in the molten metal pot (melting furnace) (2), and then approximately reduced by the deflation crawl (13). After being turned vertically and being pulled up above the pot,
It is cooled by a cooling device (14) and becomes a plated plate.

At this time, the plate material to be plated ( ) comes out from the free surface of the molten metal (3) and is passed in a direction opposite to gravity, so that a liquid film (11) will adhere to the surface. In order to adjust the thickness of the metal liquid film (11), a gas jet nozzle (10) is used to eject gas in a jet shape.
is provided. The gas ejected from the gas jet nozzle (10) collides with the plated plate (1) at high speed and generates pressure. The liquid film (11) attached to the surface of the plate (1) is adjusted to a predetermined thickness by the pressure.

[Problems to be Solved by the Invention] Conventional film thickness control devices for molten metal plating eject gas in the form of a jet, which has the disadvantage of producing large noise.

[Means for Solving the Problems] In order to solve the above-mentioned conventional problems, the present invention provides a method in which a plate material to be plated is pulled upward from a molten metal with its surface substantially vertical, and then cooled to solidify the molten metal. In the molten metal plating, a first coil horizontally surrounding the wave-plated plate material above the liquid surface of the molten metal, and a substantially symmetrical coil sandwiching the plate surface of the wave-plated plate material and the first coil. arranged,
A molten metal comprising second and third coils whose axes are substantially perpendicular to the plate surface, and means for supplying high-frequency currents of the same phase to the first, second, and third coils. Plating film thickness control device; In molten metal plating, in which the plate to be plated is pulled upward from the molten metal with the plate surface almost vertical, and then cooled to solidify the molten metal, it is used to form a truncated pyramid shape with a widened bottom. a coil that is wound and horizontally surrounds the wave-plated plate material above the liquid level of the molten metal;
The present invention proposes a film thickness control device for molten metal plating, characterized by comprising means for supplying a high-frequency current to the coil.

[Effect]

The present invention is constructed as described above, and uses the principle of induction heating to generate an eddy current in a liquid film attached to a plate surface, and causes a magnetic flux to pass through this current to generate a downward force. In this way, the force generated within the liquid film becomes thrust,
The thickness of the liquid film can be reduced. Since the magnitude of this force is determined by the high frequency current flowing through the coil, the film thickness can be controlled by adjusting the high frequency current.

(Embodiment) FIG. 1 is a longitudinal sectional side view showing a first embodiment of the present invention, FIG. 2 is a front view, FIG. 3 is a plan view, and FIG. 4 is an electrical wiring diagram.

In these figures, the plate material to be plated (e.g. steel plate) (1
) is a molten metal (e.g. molten zinc) (3
) is pulled upwards. (4) is a first coil for generating an eddy current, and surrounds the steel plate (1) horizontally above the liquid level of the molten metal (3).

(5a) and (5b) are the second and third
, the plate surface of the steel plate (1) and the first coil (
4), and their axes are perpendicular to the surface of the steel plate (1). As shown in Figure 4, the three coils (4), (5a), and (5b) are supplied with high-frequency currents of the same phase from the high-frequency power supply (7) via the cable (8). be done.

When a high frequency current flows through the first coil (4) surrounding the steel plate (1), an eddy current (2) is generated on the surface of the steel plate (1). The penetration depth δ of the eddy current I is expressed by the formula where ρ: specific resistance (Ω・m) μ: relative permeability (-) r: frequency (Hz). The frequency of the high-frequency power source is selected so that the film thickness is thinner than or equal to the film thickness of (11), and the eddy current is caused to flow only within the metal liquid film (11).

Next, current flows from the same power source as the coil (4) for the vortex main flow into the second and third coils (5a) and (5b), which are arranged facing each other so as to sandwich the steel plate (1). As a result, a magnetic field having almost the same phase as the convex current I flowing through the metal diode Di (11) is generated. At this time, the coils are wound or connected to the power source so that the directions of the magnetic flux produced by the opposing magnetic field coils (5a) and (5b) are opposite to each other.

When a current flows in a magnetic field, a force P expressed by the following equation is generated.

P = B X I X n (N) However, 1i
ft Flux density (Wb/m") ■ = Strength of current (^) l: Length (width of plated plate) (m) In the above, the current is an eddy current flowing through the metal liquid film (11), and the magnetic field is If we consider that the A-method coils (5a) and (5b) are created, a force in the direction according to Fleming's left-hand rule is generated on the metal liquid film (II).As shown in Fig. 5, a vortex is generated. By adjusting the direction of the current and magnetic flux, the direction of the force can be directed downward.

Now, the force F required for film thickness control is F=T (L-hlriα) where, T: Density of liquid film (kgf/m3) L: Thickness of liquid film (m) h: Film thickness control Length (height) of the liquid film (m) g: Width of plated plate (m) α: Acceleration (m/s2) Here, the above force P due to the current and magnetic field is equal to F. Then, if we set δ−, then 1 ・B v”l−= r h a X 503
This is the condition for controlling the film thickness according to this embodiment. Taking the case of zinc plating as an example, r = 6900 kgf/m" h = 15 x 10-1 m α-7000 In/s" (estimated from the gas flow rate) p m = 38 x 10-" Ω-mμ = 1 (
Calculating as B = 0.071Wb/m2 (relative magnetic permeability of zinc), the film thickness can be controlled with frequency r =lOOkllz current ■main 100OOA.

Next, FIG. 6 is a longitudinal sectional side view showing a second embodiment of the present invention, and FIG. 7 is a front view of the same. In these figures, the same parts as in the first embodiment are given the same reference numerals,
Detailed explanation will be omitted.

In this embodiment, instead of the first, second, and third coils (4), (5a), and (5b) in the first embodiment, a coil (6
) above the liquid level of the molten metal (3).
) surrounding the steel plate (1).

Similar to the first embodiment, a high frequency current is supplied to this coil (6). Then, an eddy current I is generated on the surface of the steel plate (11). Also, since the coil (6) is wound in the shape of a truncated cone, the magnetic flux in the coil has a horizontal component BN. Therefore, as shown in FIG. As shown, the metal liquid film (11)
A downward force P is generated inside.

〔Effect of the invention〕

In the present invention, eddy currents and horizontal components of magnetic flux are generated in the liquid film by supplying a high-frequency current to the coil, and the film thickness is controlled using the downward force generated by this current and magnetic field as thrust. This allows for much quieter operation than conventional methods.

[Brief explanation of drawings]

Fig. 1 is a vertical side view showing the first embodiment of the present invention, Fig. 2 is a front view, Fig. 3 is a plan view, Fig. 4 is an electrical wiring diagram, and Fig. 5 is a functional diagram. It is a perspective view for explaining. FIG. 6 is a longitudinal sectional side view showing a second embodiment of the present invention, FIG. 7 is a front view thereof, and FIG. 8 is a diagram for explaining the operation. FIG. 9 is a schematic diagram showing an example of conventional hot-dip metal plating equipment, and FIG. 10 is a detailed diagram of the vicinity of the gas jet nozzle. (1) Plated plate material (steel plate), (2) Molten metal pot, (3) Molten metal, (4), (5a), (5b), (6)
--1 illumination, (7) --- power supply, (8) -- cable, (10) --- gas jet nozzle, (11)
...metal'/& film, (12)...reduction furnace, (
I3〉...Deflation crawl, (14)...Cooling device, ■...Eddy current, B, B,...Magnetic flux, P...Force.

Claims (2)

[Claims] (1) In molten metal plating, in which the plate material to be plated is pulled upward from the molten metal with the plate surface almost vertical, and then cooled to solidify the molten metal, the plate material to be plated is horizontally held above the liquid surface of the molten metal. and second and third coils that are arranged approximately symmetrically across the plate surface of the plate material to be plated and the first coil, and whose axes are substantially perpendicular to the plate surface. and means for supplying high frequency currents of the same phase to the first, second and third coils. (2) In molten metal plating, in which the plate material to be plated is pulled upward from the molten metal with the plate surface almost vertical, and then cooled to solidify the molten metal, the plate material is rolled into a truncated quadrangular pyramid shape with the bottom widened, and the molten metal is A film thickness control device for molten metal plating, comprising: a coil horizontally surrounding the plate material to be plated above the liquid surface of the metal; and means for supplying a high frequency current to the coil.