JPH0892715A - Gas wiping device - Google Patents

Abstract

PURPOSE: To provide a wiping device which prevents edge overcoating by a simple method without adding intricate devices and mechanisms to an edge overcoating problem in gas wiping of a hot dip plating process, etc. CONSTITUTION: This gas wiping device is arranged with opposite wiping nozzles 3-1, 3-2 which are the main cause for edge overcoating and exist on the side outer than the width of a band body by intersecting the lines obtd. by projecting the gas ejection slits of both wiping nozzles disposed to face each other or the extensions of these slits on the plane parallel with the band body 1 with each other in order to avoid the direct collision of the gases ejected out of the slits 6, 6' of the wiping nozzles. The wiping nozzles are otherwise arranged by paralleling the lines obtd. by projecting the gas ejection slits of both wiping nozzles disposed to face each other on the plane parallel with the band body with each other by having a spacing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas wiping device for uniformly controlling the coating amount of a coating liquid in the plate width direction by a gas throttle for ejecting a gas onto a strip in a hot dip plating process or the like. is there.

[0002]

2. Description of the Related Art For example, in a continuous hot dip plating process, as shown in FIG. 1, a strip (belt) is generally immersed in a plating bath filled with a molten metal, and then the strip is vertically moved. After the dipping step of pulling up, so that the molten metal coating film adhered to the strip surface has a predetermined film thickness evenly in the plate width direction and plate length direction, in a plane parallel to the strip (strip), There is provided a gas wiping device that squeezes excess molten metal by ejecting a gas onto the strip from a wiping nozzle that extends in the width direction of the strip and is opposed to the strip. This gas wiping device, as shown in FIG.
Wiping nozzles are provided in a plane parallel to the strip (strip) so as to face each other across the strip (strip), and have a predetermined gap with the strip, and the gas ejection slits of both wiping nozzles are Usually, it is arranged so as to be orthogonal to the direction of travel of the strip, that is, to extend in the width direction of the strip. Further, when projecting the gas ejection slits of the two wiping nozzles, that is, the positions of the slits provided in the nozzles on a plane parallel to the strip, the two projection lines should be aligned on one straight line. The opposed wiping nozzles are arranged symmetrically with respect to the front and back of the strip surface. In addition, since the wiping nozzle is compatible with various widths of the strips, and at the same time, it is possible to deal with a shift in the width direction when the strips are pulled up,
It extends longer than the width of the strip, that is, extends outside the width end of the strip.

In such a gas wiping apparatus, an edge overcoat is produced in which the coating thickness of the strip edge portion becomes thicker than that of the central portion, which not only deteriorates the strip surface quality but also causes a coil winding. There was a problem that it would lead to the collapse of the load. The main cause of this edge overcoat is, as shown in FIG. 2, a gas flow that occurs when the high-speed gas flow ejected from the slits of the two wiping nozzles facing each other in the region outside the strip width end directly collides with each other. The turbulence lowers the wiping pressure at the strip edge and increases the basis weight of the strip edge.

To prevent such problems, many preventive measures have been taken conventionally. For example, a method of providing an auxiliary nozzle at the edge portion (JP-A-62-40350 and JP-A-63-9242) and a method of providing a shielding plate at the edge portion (JP-A-63-105955, JP-A-63-95555). 4-7
Japanese Patent No. 4857) has been proposed. However, in any case, in order to deal with the variable plate width and the meandering of the plate, the device is complicated and the sufficient effect cannot be obtained.

As another means, a method of applying an electromagnetic force to the edge portion (Japanese Patent Application Laid-Open No. 2-217454) has been proposed, but in this case as well, the apparatus becomes complicated and the cost becomes high. However, it has not been able to obtain a sufficient effect.

[0006]

SUMMARY OF THE INVENTION The present invention prevents the edge overcoating problem in gas wiping as described above by a simple method without adding a complicated device / mechanism. An object of the present invention is to provide a gas wiping device.

[0007]

In the gas wiping device of the present invention, the gas ejected from the slit of the wiping nozzle directly collides in the region outside the band width end, which is the main factor of the edge overcoat, It is a device for avoiding a bad influence on the gas wiping action. That is, the gist of the present invention is as follows.

(1) After the dipping step of immersing the strip in a liquid bath and pulling it out, gas is jetted from the wiping nozzles provided opposite to each other with the strip sandwiched in a plane parallel to the strip. In a gas wiping device for removing excess liquid on the body surface, the wiping nozzle is a gas ejection slit of both of the wiping nozzles provided opposite to each other, or a line obtained by projecting an extension of the slit on a plane parallel to the strip. A gas wiping device, which is arranged so as to cross each other.

(2) The wiping nozzles are arranged such that lines obtained by projecting the gas ejection slits of the opposing wiping nozzles on a plane parallel to the strip intersect with each other within the width of the strip. The gas wiping device according to (1) above, which is characterized in that. (3) Lines obtained by projecting the wiping nozzles on the gas ejection slits of the opposing wiping nozzles or the extensions of the slits on a plane parallel to the strip are outside the width end of the strip. The gas wiping device according to item (1), wherein the gas wiping device is arranged so as to intersect with each other.

(4) After the dipping step of immersing the strip in a liquid bath and pulling it out, gas is ejected from the wiping nozzles provided in the plane parallel to the strip to face each other with the strip sandwiched therebetween. In a gas wiping device for removing excess liquid on the body surface, the wiping nozzles have a line in which the gas ejection slits of the opposing wiping nozzles are projected on a plane parallel to the strip. A gas wiping device characterized by being arranged in parallel.

Here, the line projected onto the plane parallel to the band of the slit includes the slit itself and a line obtained by extending the slit in the extending direction of the nozzle, and the line parallel to the band. The surface includes the surface of the strip itself and the surface obtained by expanding the strip.

[0012]

The gas wiping device of the present invention will be described in detail with reference to FIGS. 3 to 8 which are examples of the present invention. In FIG. 3, the strip 1 is just pulled up from the liquid bath 2, and the strip 1 is sandwiched in a plane parallel to the strip 1 with a predetermined gap 10 in the front in the traveling direction of the strip 1. As described above, the wiping nozzles 3-1 and 3-2 are provided so as to face each other.

The wiping nozzles 3-1 and 3-2 are
The gas ejection slits 6 and 6'of the wiping nozzle are attached to the strip 1
When projected onto a plane, the two projection lines 6p and 6p 'are installed so as to intersect each other at an angle 5 (Fig. 4). The intersecting angle 5 in this case is determined by operating conditions such as the moving speed of the strip 1, the predetermined coating film thickness, the gas ejection pressure, the viscosity of the liquid, etc., but 5 to 90 degrees is suitable. Further, even if the intersection angle 5 is fixed to a certain predetermined value, the effect of preventing the edge overcoat is obtained, but if the operating condition or the edge overcoat condition is measured and the intersection value 5 is controlled by feeding back the measured value. , A greater effect can be obtained.

The length 7 of the wiping nozzles 3-1 and 3-2
Is the maximum width of the strip 1 and outside the both ends of the strip 8 as a margin allowance for accommodating variations in the width of the strip 1 and fluctuations in the width direction at the passage position. It is necessary to have a length longer than the length of ′ ′ and is also affected by the intersection angle 5 of the slit projection lines 6p and 6p ′. The wiping nozzle shown in FIG. 4 is an example in which the slits 6 and 6'are projected on the surface of the strip, that is, the slit projection lines 6p and 6p 'are arranged so as to be antisymmetric on the front and back of the strip 1. As another form, as shown in FIG. 5, it is possible to incline only one of the nozzles and arrange it so that the slit projection lines intersect. 4 and 5, the line in which the slits 6 and 6'are projected onto the band surface, that is, the slit projection lines 6p and 6p 'intersect on the band center line 4 in both cases. Although these forms are optimal in consideration of the vibration and deformation behavior of the strip 1, the projection lines 6p and 6p 'of the slit do not necessarily have to intersect on the strip center line 4, and as shown in FIG. As shown, it is preferable that they intersect within the width of the strip 1.

Further, as shown in the example of FIG. 7, the nozzles may be arranged so that the slit projection line, in this case, a line obtained by projecting the extension of the slit, intersects outside the width end of the strip. That is, in FIG. 7, lines obtained by projecting a line extending from the slit of the nozzle onto a plane parallel to the strip, that is, slit projection lines 6p and 6p 'intersect in a region outside the width end of the strip. Even with such an arrangement, the direct gas collision does not occur in the lines facing each other as in the conventional case, but becomes a point, so that the edge overcoat is reduced. In this case, the slit projection lines 6p, 6 differ depending on the operating conditions such as the moving speed of the strip, the predetermined coating film thickness, the gas ejection pressure, and the viscosity of the liquid.
The position intersecting with the area outside the width end of the strip of p ′ is
It is preferable to arrange the slits so as to be sufficiently separated from the width end of the strip, and in general, if the nozzles are arranged so as to be separated by 30 to 50 mm or more, the direct collision of the gas ejected from the wiping nozzle slits can be further improved. You can often avoid it.

Further, in another apparatus of the present invention, as shown in FIG. 8, in a plane parallel to the strip 1, one of the wiping nozzles is connected to the other by a predetermined gap distance 9
When the gas ejection slits 6 and 6'of the opposing wiping nozzles are projected on a plane parallel to the strip, these two projection lines 6p and 6p
The wiping nozzle is installed so that p'is parallel to each other with a gap. That is, the projection lines 6p and 6p 'obtained by projecting the slits 6 and 6'on the strip surface are
The parallel lines are separated by a predetermined gap distance 9.
In this case, the gap distance 9 is the operating speed such as the moving speed of the strip 1, the predetermined coating film thickness, the gas ejection pressure, the viscosity of the liquid, and the strip 1.
It depends on the vibration situation of. If the gap distance 9 is too short, the effect of preventing edge overcoat is weakened,
On the contrary, if it is too long, it induces the vibration of the strip 1, so that when it is used for wiping in the hot dip plating process, it is 20 to 1
00 mm is optimal.

In the present invention, by attaching the wiping nozzle as described above, it is possible to easily avoid the direct collision of the gas ejected from the slit of the opposing wiping nozzle outside the band width, which is the main factor of the edge overcoat. Therefore, it is possible to prevent the wiping pressure of the plate edge portion from decreasing, and as a result, it is possible to prevent thickening of the plate edge portion, that is, edge overcoat. Further, in the gas wiping device of the present invention, direct collision of the gas ejected from the slit of the opposing wiping nozzle located outside the band width is avoided, so that the wiping nozzle noise caused by the gas collision can be reduced at the same time. it can.

[0018]

EXAMPLES Next, examples in which the present invention is applied to a hot dip plating process will be shown. Line operating conditions include a plate width of 11
27 mm, plate thickness 1.6 mm, line speed 80 m / m
and the target areal thickness is 5 μm. As for the wiping nozzle specifications, the nozzle slit gap is 0.7 m.
m, nozzle length 1500 mm, nozzle-strip gap 30 mm. As shown in FIG. 4, the intersecting angle of the lines projected on the strip of the opposing wiping nozzle is 20 degrees,
The intersection was on the center line of the strip. Figure 9
In order to see the effect of the present invention, the distribution of the basis weight in the plate width direction before and after carrying out the present invention is shown.

[0019]

As can be seen from FIG. 9, by using the present invention, the edge overcoat can be prevented by a simple method. In addition, with respect to gas wiping noise, there was a noise reduction effect of about 50% compared to the current wiping method.

[Brief description of drawings]

FIG. 1 is a diagram showing a conventional gas wiping device.

FIG. 2 is a diagram showing an edge overcoat state.

FIG. 3 is a diagram showing one example of the present invention, (a)
Shows a bird's-eye view and (b) shows a side view.

FIG. 4 is a diagram showing one embodiment of the gas wiping device of the present invention viewed from a direction perpendicular to the plate surface, in which slit projection lines intersect in the plane of the strip.

FIG. 5 is a diagram showing another example of the gas wiping device of the present invention viewed from a direction perpendicular to the plate surface, in which slit projection lines intersect in the plane of the strip.

FIG. 6 is a diagram showing another example of the gas wiping device of the present invention viewed from a direction perpendicular to the plate surface, in which slit projection lines intersect in the plane of the strip.

FIG. 7 is a view showing another example of the gas wiping device of the present invention viewed from the direction perpendicular to the plate surface, in which slit projection lines intersect outside the width end of the strip.

FIG. 8 is a diagram showing another example of the gas wiping device of the present invention when viewed from the direction perpendicular to the plate surface.

FIG. 9 is a diagram showing a distribution of basis weight in the plate width direction when the present invention is used.

[Explanation of symbols]

 1 strip (steel strip) 2 liquid bath 3-1 3-2 wiping nozzle 4 steel strip center line 5 crossing angle of projection line of slit 6, 6'wiping nozzle slit 6p, 6p 'projection line of wiping nozzle slit 7 Wiping nozzle length 8, 8'Outside distance of wiping both ends plate path 9 Distance between opposing wiping 10 Gap between wiping nozzle and strip 11 Extension surface of strip

Claims (4)

[Claims] 1. After the dipping step of immersing the strip in a liquid bath and pulling it out, gas is jetted from a wiping nozzle provided in a plane parallel to the strip to face each other with the strip sandwiched therebetween. In a gas wiping device for removing surplus liquid on the surface, the wiping nozzles are arranged such that the gas ejection slits of the two wiping nozzles provided opposite to each other or the lines obtained by projecting the extensions of the slits on a plane parallel to the band are mutually formed. A gas wiping device characterized by being arranged so as to cross each other. 2. The wiping nozzle is arranged such that lines obtained by projecting the gas ejection slits of the opposing wiping nozzles on a plane parallel to the strip intersect with each other within the width of the strip. The gas wiping device according to claim 1, wherein: 3. A line obtained by projecting the gas jetting slits of the wiping nozzles facing each other or the extension of the slits on a plane parallel to the strip is outside the width end of the strip. 2. The gas wiping device according to claim 1, wherein the gas wiping devices are arranged so as to intersect with each other. 4. After the dipping step of immersing the strip in a liquid bath and pulling it out, gas is jetted from a wiping nozzle provided opposite to the strip in a plane parallel to the strip to strip the strip. In a gas wiping device for removing excess liquid on the surface, the wiping nozzles are arranged such that lines projecting the gas ejection slits of the opposing wiping nozzles on a plane parallel to the strip are spaced from each other. A gas wiping device characterized by being arranged in parallel.