JP2508360B2 - Continuous hot dip coating equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a continuous hot dip plating apparatus provided with a wiping nozzle on the surface of a plating bath, and more specifically, the runout of the strip after hot dipping is small and the wiping nozzle is stripped. The present invention relates to a continuous hot-dip galvanizing apparatus that can be brought close to a substrate and can perform effective wiping.

(Prior Art) When a steel strip is continuously supplied to a plating bath and a surface of the steel strip is plated with a molten metal, for example, molten zinc, a continuous hot dipping apparatus as shown in FIG. 1 is used. In this apparatus, the strip 1 after the pretreatment is continuously immersed in the hot dip galvanizing bath 3 in the plating tank 2, the traveling direction is changed upward by the bottom roll 4 in the bath, and guided by the support roll 5. While being pulled vertically onto the bath surface.
The thickness of the strip 1 after plating is adjusted vertically by a gas such as air sprayed from a wiping nozzle 6 disposed oppositely on the bath surface with the strip 1 interposed therebetween, and the plating layer rises vertically until the plating layer almost solidifies. Be transferred. After that, the traveling direction is horizontally changed by the top roll 7 and sent to the next step.

In the above continuous hot-dip galvanizing apparatus, the strip must be pulled up vertically until the plating metal attached to the strip surface is solidified, so the distance between the vertical threading portions becomes long. Therefore, the strip is vibrated in the lateral direction (left-right direction) as shown in FIG. The width (amplitude) of the vibration increases as the strip passing speed increases. When the strip passing speed is increased, the solidified position of the deposited plating metal is increased, and thus the vertical strip passing portion requires a longer distance. For example, in high-speed threading of 150 m / min or more, the vertical threading portion may exceed 30 m. When the vertical threading section becomes long,
Since the vibration is amplified to that extent, the amplitude becomes larger.

When the vibration of the strip occurs, the distance between the tip of the wiping nozzle and the strip surface constantly fluctuates, so a uniform plating thickness cannot be obtained in the strip longitudinal direction, width direction, and front and back surfaces, resulting in uneven plating layers. ,
Product quality is significantly impaired. Further, since the magnitude of the amplitude for preventing the wiping nozzle and the strip from coming into contact with each other is predicted and the wiping nozzle must be arranged outside this range, the distance between the wiping nozzle and the strip surface becomes long, The wiping ability, that is, the control range of the coating weight is narrowed. If the control range of the coating weight is narrowed, it becomes difficult to carry out high-speed rolling. Since the amount of plating metal that adheres to the strip surface increases in proportion to the plate passing speed, it becomes impossible to adjust the coating weight to a predetermined value when the control range of the coating weight is narrowed.

However, in the conventional continuous hot-dip galvanizing apparatus, since the adhered metal on the surface is not solidified in the vertical threading portion, it is impossible to prevent vibration by contact-supporting the strip with a roll or the like.

Therefore, various devices for supporting the strip in a non-contact manner via a magnetic force or a fluid layer have been proposed. For example,
Japanese Patent Laid-Open No. 56-5821 proposes a device including a magnet 8 between a wiping nozzle 6 and a top roll 7 and a pad 10 having a gas supply nozzle 9 sandwiching the magnet 8 as shown in FIG. There is. Further, Japanese Patent Application Laid-Open No. 57-101657 proposes a device in which the static pressure pad 11 is arranged within 1000 mm above the installation position of the wiping nozzle 6 as shown in FIG.

However, in the case of the device described in Japanese Examined Patent Publication No. 56-5821, since the device is large, it is difficult to install it near the wiping nozzle, and the vibration preventing effect is diminished accordingly. In the case of the device described in JP-A-57-101657, when the pressure of the wiping gas is weak, the gas flow rising to the strip surface becomes weak, and this gas flow and the lower end of the static pressure pad flow. The synergistic effect of pressure due to the confinement phenomenon that occurs with the gas flow becomes small, and as a result, the static pressure of the static pressure pad decreases, so that vibration cannot be sufficiently prevented.

(Problem to be Solved by the Invention) An object of the present invention is to reliably prevent vibration of a strip after hot dipping. That is, an object of the present invention is to provide a continuous hot dip galvanizing apparatus capable of producing a plated product having a small vibration of the strip, allowing the wiping nozzle to be as close to the strip as possible, and having excellent quality without uneven plating. To do.

(Means for Solving the Problems) As shown in FIG. 6, the inventors of the present invention have shown in FIG. 6 that the flat plate above and below the vertical passage plate portion, which sandwiches the strip, is close to the installation position of the jet nozzle of the fluid, that is, the gas. Is parallel to the strip width direction of the nozzle and is inclined so that the distance increases toward the strip surface, and is arranged symmetrically with respect to the strip surface, and the fluid is placed in the narrow space between the strip and the flat plate. It has been found that when directed, the pressure of the fluid is increased and the vibration of the strip is suppressed.

The gist of the present invention based on the above findings is (1) to (3) below.

(1) In a continuous hot dip galvanizing apparatus equipped with opposing wiping nozzles across a hot dip bath with a strip sandwiched between them, a flat plate is placed close to and above the installation position of the wiping nozzle, and a flat plate is parallel to the strip width direction of the nozzle. A continuous hot dip galvanizing apparatus, which is inclined so that the distance increases toward the strip surface, and is arranged symmetrically with respect to the strip surface.

(2) In a continuous hot dip galvanizing apparatus having a wiping nozzle that faces a hot dip bath with a strip interposed therebetween, a gas that opposes the strip between the wiping nozzle and a top roll provided above the nozzle. A jet nozzle is provided, and a flat plate is tilted so that the flat plate is parallel to the strip width direction of the nozzle and widens toward the strip surface in proximity to the installation position of the gas jet nozzle, and with respect to the strip surface. Is a continuous hot-dip galvanizing system, which is arranged symmetrically about the plane.

(3) In a continuous hot-dip galvanizing apparatus provided with a wiping nozzle that faces a hot dip bath with a strip interposed therebetween, a gas that opposes the strip between the wiping nozzle and a top roll provided above the nozzle. A jet nozzle is provided, and the flat plate is parallel to the strip width direction of the nozzle and is widened toward the strip surface above and below the installation position of the gas jet nozzle and close to and above the installation position of the wiping nozzle. A continuous hot-dip galvanizing device, which is inclined and arranged symmetrically with respect to the strip surface.

In the above devices (1) to (3), it is desirable that the inclination angle of the flat plate with respect to the strip surface can be adjusted according to the pressure to be applied to the flat plate.

(Operation) The present invention will be described in detail below based on the embodiments shown in the drawings.

FIG. 5 to FIG. 7 are views showing an embodiment of the continuous hot-dip galvanizing apparatus of the present invention.

In the figure, 1 is a strip, 2 is a plating tank, 3 is a hot dip plating bath, 4 is a bottom roll, 6 is a wiping nozzle, and 7 is a top roll.

In the continuous hot-dip galvanizing apparatus of the first invention of the present application, as shown in FIG. 5, a pair of flat plates 12a and 12b are arranged above and below the installation position of the wiping nozzle 6, respectively.

As shown in FIG. 6, the continuous hot-dip galvanizing apparatus of the second invention is provided with a fluid ejection nozzle 13 which is opposed to the strip 1 between the wiping nozzle 6 and the top roll 7 with the strip 1 interposed therebetween. A pair of flat plates 12c and 12d are arranged above and below the installation position of.

In the continuous hot-dip galvanizing apparatus of the third invention, as shown in FIG. 7, a fluid jet nozzle 13 is provided between the wiping nozzle 6 and the top roll 7 so as to sandwich the strip 1, and the fluid jet nozzle 13 is provided. And wiping nozzle 6
A pair of flat plates 12a, 12b, 12 above and below the respective installation positions of
c and 12d are arranged. Specifically, the flat plate 12a on the upper side of the wiping nozzle 6 and the flat plate 12c on the upper side of the fluid ejection nozzle 13 are arranged so as to be plane-symmetrical with respect to the strip 1 so as to face each other in a V shape when viewed from the width direction of the strip. To be done. The flat plate 12b on the lower side of the wiping nozzle 6 and the flat plate 12d on the lower side of the fluid ejection nozzle 13 are arranged so as to be plane-symmetrical with the strip 1 sandwiched therebetween so as to face each other in an inverted V shape when viewed in the width direction of the strip. .

The flat plates arranged above and below the wiping nozzle or the fluid ejection nozzle do not necessarily have to be symmetrical with respect to these nozzles.

As shown in FIG. 8, the fluid ejection nozzle 13 has a slit 14 formed at the tip thereof, and ejects the fluid from the slit 14 toward the strip surface. As the fluid, for example, air or an inert gas such as nitrogen gas can be used. The fluid jet nozzle 13 and the upper and lower flat plates 12c and 12d are provided between the wiping nozzle 6 and the top roll 7, but it is preferable to place the fluid jet nozzle 13 substantially in the middle between the support roll and the top roll.

The vibration of the strip is generated by the support roll 5 as shown in FIG.
Between the supporting roll 5 and the top roll 7, a large amplitude δ ₁ is generated at approximately the center between the supporting roll 5 and the top roll 7,
Due to this effect, vibration of the amplitude δ ₂ also occurs at the position of the wiping nozzle 6. Therefore, if the fluid ejection nozzle 13 and the flat plates 12c and 12d are arranged substantially in the middle between the support roll 5 and the top roll 7, it is possible to suppress the vibration of large amplitude δ ₁ . As a result, the amplitude δ at the wiping nozzle 6 position
₂ can be reduced.

In the figure, 15a and 15b show wiping nozzles 6 and 15c and 15d show how gas ejected from the fluid ejection nozzle 13 flows. Of the gas ejected from the wiping nozzle 6 and colliding with the strip surface, the gas flow 15a directed upward along the strip surface is the strip 1
Flows toward the narrower gap between the flat plate 12a and
The downward gas flow 15b flows toward the narrower gap between the strip 1 and the flat plate 12b. As for the gas ejected from the fluid ejection nozzle 13 and colliding with the strip surface, the upward gas flow 15c flows toward the narrower gap between the strip 1 and the flat plate 12c, and the downward gas flow 15d. Flows into the narrower space between the strip 1 and the flat plate 12d.

Thus, when the gas flows from the wide side to the narrow side of the gap between the strip and the flat plate, the pressure of the gas increases, and the pressure acts on each of the flat plates 12a to 12d.

 FIG. 9 is an explanatory diagram showing this situation.

In the figure, the strip 1 moving in the direction of the arrow
When the fluid 16 flows into the space between the flat plate 12 and the flat plate 12 which is inclined at the angle θ, the fluid 16 is pushed in a wedge shape when flowing toward the narrower space at the velocity Va. When the fluid 16 is pushed into a wedge shape, the pressure of the fluid 16 increases, and upward pressure acts on the flat plate 12 and downward pressure acts on the strip 1 (hereinafter, referred to as wedge action). As shown in the figure, the pressure acting on the flat plate is low on the inlet side (fluid inflow side) and the outflow side (fluid outflow side) of the flat plate 12, and has the highest pressure distribution at a position closer to the narrower gap. Show.

When upward pressure is applied to the flat plate 12 and downward pressure is applied to the strip 1, this wedge action serves as a supporting force for the strip and suppresses vibration of the strip. Therefore, if a pair of flat plates are arranged with the strip sandwiched either above or below the installation position of the wiping nozzle 6 or above or below the installation position of the fluid ejection nozzle 13 as in the device of the present invention, the strip will be cut from both sides. Since the strip is pulled up while being subjected to the wedge action, the vibration of the strip is reduced.

It is preferable that the flat plates disposed above and below the respective installation positions of the wiping nozzle and / or the fluid ejection nozzle have a tilt angle with respect to the strip surface changed. Vibration of the strip can be suppressed even if the flat plate is fixedly arranged by inclining it at a certain angle, but if the inclination angle can be changed, the supporting force and the supporting position of the strip can be changed, so the vibration is suppressed more reliably. To be done.

FIG. 10 shows a qualitative tendency of the dimensionless pressure distribution acting on the flat plate, where m is a parameter representing the inclination of the flat plate defined as follows.

m = (h ₁ −h ₀ ) / h ₀ where h ₀ is the minimum air gap between the flat plate and the strip, h ₁ is the maximum air gap between the flat plate and the strip (see FIG. 9) At 5.0 and 10.0 (when the maximum air gap h ₁ between the flat plate and the strip is large), the pressure is slightly small, the highest point of the pressure is closer to the minimum air gap side, and when m is 0.1 and 0.2 (the maximum air gap h ₁ It can be seen that the pressure is small when the difference between the minimum gap h ₀ and the minimum gap h ₀ ) is small, the highest point of the pressure is almost in the center of the flat plate, and when m is 1.2 and 2.0, the highest pressure is high and the strip supporting force is large.

If the inclination angle of the flat plate with respect to the strip surface changes in this way, the magnitude of the generated pressure and the position of the maximum pressure change.
Therefore, in the case of a flat plate whose inclination angle can be changed, the supporting force and the supporting position of the strip can be changed, so that optimal support can be achieved with minimal vibration of the strip.

FIG. 11 is a schematic view showing an example of a flat plate whose tilt angle can be changed.

In the figure, 17 is a motor, 18 and 19 are gears, 12 is a flat plate attached to a support rod 20 whose one end is pivotally supported.
Is rotated by driving a motor 17 via gears 18 and 19, and the inclination angle with respect to the strip surface is changed.

The control of the inclination angle is preferably performed by mounting a pressure sensor 21 on the back surface of the flat plate 12 as shown in the figure and measuring the pressure acting on the flat plate with this. For example, when manufacturing different thickness plated steel sheets with different amounts of adhesion on the front and back surfaces, it is necessary to change the pressure of the gas ejected from the wiping nozzle on the front and back surfaces of the strip. When the pressure of the ejected gas on the front and back of the strip changes, the strip deviates to the lower side of the ejected gas, but the pressure generated by the flat plate on the lower side of the ejected gas is measured with a pressure sensor. If the inclination angle of the flat plate is controlled so as to be larger than the pressure generated in the flat plate having the higher ejection gas pressure, the deviation of the strip can be prevented. In this case, if a position detector such as a displacement gauge is attached to the flat plate, more accurate control can be performed.

In the present invention, a plurality of pairs of flat plates may be arranged above and below the respective installation positions of the wiping nozzle and / or the fluid ejection nozzle with a strip interposed therebetween.

In FIG. 12, a pair of flat plates 12a and 12b are arranged above and below the installation position of the wiping nozzle 6, and a pair of flat plates 12c and 12d and another pair of flat plates 12 are arranged above and below the installation position of the fluid ejection nozzle 13.
It shows another embodiment of the present invention in which a total of two sets of flat plates of e and 12f are arranged.

If a plurality of sets of flat plates are arranged above and below the respective installation positions of the wiping nozzle and / or the fluid ejection nozzle,
Vibration can be suppressed more effectively because the strip can be supported over longer distances.

When the flat plates are arranged above and below the installation position of the wiping nozzle 6, the lower end of the lower flat plate 12b may be immersed in the plating bath 3 as shown in FIG. This prevents the gas flow 15b descending along the strip surface from passing through the gap between the strip 1 and the flat plate 12b, so that a larger pressure is generated on the flat plate 12b and the magnitude strip supporting force is increased. can get.

Further, each flat plate may be a flat plate having a stopper as shown in FIG. Note that (a) is a side view, (b) is a front view taken along the line AA, and (c) is a front view taken along the line BB.

Even in the case of the flat plate 12 with the stoppers 22 attached to both ends and the end on the narrow side of the gap, the gas is prevented from passing through the gap or escaping from both sides, resulting in a higher gas pressure and a larger strip. Supportive power is obtained.

 Next, specific examples will be described.

(Example) A pair of fluid ejection nozzles facing each other with a strip sandwiched between a wiping nozzle and a top roll are provided in proximity to the installation position of the fluid ejection nozzles, and a flat plate in the strip width direction of the nozzle. Are inclined parallel to each other so that the distance increases toward the strip surface, and one set is arranged so as to be plane-symmetric with respect to the strip surface to obtain a continuous hot dip coating apparatus having the structure shown in FIG.

The size of the flat plates 12c and 12d above and below the installation position of the fluid jet nozzle 13 is 400 mm × 1000 mm, the minimum gap h ₀ between the strip 1 and these flat plates 12c and 12d is 20 mm, and the maximum gap h ₁
Was 50 mm, m was 1.5, the air pressure blown out from the fluid jet nozzle 13 was 0.8 kg / cm ² , and a strip having a plate thickness of 0.8 mm and a plate width of 900 mm was hot-dip galvanized at a sheet passing speed of 150 m / min. When the vibration at this time was examined, it was found that the amplitude of one side contact at the wiping nozzle position in the conventional device without a flat plate.
Although it was about 10 mm, in the device of the present invention
The amplitude was about 1 mm.

Next, the flat plate 12a, 12b having a size of 200 mm × 1000 mm is arranged above and below the installation position of the wiping nozzle 6 of this apparatus in the same manner as in the case of the above fluid ejection nozzle, and the continuous hot-dip plating apparatus having the structure shown in FIG. And

The minimum gap h ₀ between the strip 1 and these flat plates 12a, 12b is 20 mm, the maximum gap h ₁ is 50 mm, and m is 1.5. The gas pressure blown out from the wiping nozzle 6 is set to 0.3 kg / cm ^2, and the sizes of the flat plates 12c and 12d above and below the installation position of the fluid jet nozzle 13, the maximum gap, the minimum gap, m and the gas pressure of the fluid jet nozzle are the same as above. When strips of the same size were hot dip galvanized at the same speed under the conditions, the amplitude at the position of the wiping nozzle 6 was as small as 0.5 mm or less per side.

Further, the flat plates 12c, 1 above and below the installation position of the fluid ejection nozzle 13
The test was conducted by setting 2d to a size of 400 mm × 1000 mm, adjusting the maximum void and the minimum void, and changing the m value to 1.5, 5.0 and 0.2. Other conditions are the same as those of the apparatus shown in FIG. As a result, when the m value was 1.5, the amplitude was about 1.0 mm per side, and when the m values were 0.2 and 5.0, the amplitude was about 5 mm per side.

From this result, it can be said that supporting the strip with a high pressure over a wide range of the flat plate as when the m value is 1.5 is effective in reducing the vibration amplitude of the strip.

(Effects of the Invention) As described above, the vibration of the strip can be reduced by using the continuous hot-dip galvanizing apparatus of the present invention.
Therefore, in the continuous hot-dip galvanizing apparatus of the present invention, the wiping nozzle can be brought close to the strip surface, the control range of the basis weight is greatly expanded, and the wiping capability is greatly improved. Further, since the distance between the tip of the wiping nozzle and the strip surface hardly changes, the obtained plated steel sheet has a uniform plating thickness in the longitudinal direction, the width direction, and the front and back surfaces, and is of excellent quality.

[Brief description of drawings]

FIG. 1 is a schematic view showing a conventional continuous hot-dip galvanizing apparatus, FIG. 2 is an explanatory view showing vibration of a strip in a lateral direction (horizontal direction), and FIG. 3 is a conventional diagram equipped with a strip supporting device. FIG. 4 is a schematic view showing a continuous hot-dip galvanizing apparatus, FIG. 4 is a schematic view showing a conventional continuous hot-dip galvanizing apparatus similarly equipped with a strip supporting device, and FIG. 5 is a drawing of the continuous hot-dip galvanizing apparatus of the first invention of the present application. FIG. 6 is a view showing an embodiment, FIG. 6 is a view showing an embodiment of a continuous hot-dip plating apparatus according to the second invention of the present application, and FIG. 7 is a view showing an embodiment of a continuous hot-dip plating apparatus according to the third invention of the present application. Fig. 8 is a diagram showing the tip of the fluid ejection nozzle, Fig. 9 is a diagram explaining the pressure acting on the flat plate through the fluid layer, and Fig. 10 is a difference in the inclination angle of the flat plate with respect to the strip surface. Graph showing the distribution of the dimensionless pressure acting on the flat plate by FIG. 11 is a schematic view showing a flat plate in which the inclination angle with respect to the strip surface can be changed, FIG. 12 is a view showing a continuous hot dip plating apparatus of the present invention in which a plurality of sets of flat plates are arranged, and FIG. 13 is a wiping. FIG. 14 is a partial schematic view of a continuous hot dip galvanizing apparatus of the present invention in which a flat plate under a nozzle is arranged so that its lower end is immersed in a plating bath, and FIG. 14 is a view showing a flat plate having a stopper. 1: strip, 2: plating bath, 3: plating bath, 4: bottom roll, 5: support roll, 6: wiping nozzle, 7: top roll, 12, 12a, 12b, 12c, 12d, 12e and 12f: flat plate, 13: Fluid ejection nozzle, 15a, 15b, 15c and 15d: Gas flow.

Claims (4)

(57) [Claims] 1. A continuous hot-dip galvanizing apparatus having a wiping nozzle facing a hot dip bath with a strip interposed therebetween. Flat plates are provided above and below the wiping nozzle in the strip width direction of the nozzle. A continuous hot-dip galvanizing apparatus, which is inclined so as to be parallel and widens toward the strip surface, and symmetrically arranged with respect to the strip surface. 2. A continuous hot dip coating apparatus provided with a wiping nozzle facing a hot dipping bath with a strip interposed therebetween. A strip is sandwiched between the wiping nozzle and a top roll provided above the nozzle. A gas ejection nozzle is provided, and flat plates are provided close to the installation position of the gas ejection nozzle, parallel to the strip width direction of the nozzle, and inclined so that the distance increases toward the strip surface. Contrary to this, the continuous hot dip galvanizing device is characterized by being arranged symmetrically. 3. A continuous hot dip galvanizing apparatus provided with a wiping nozzle which faces a hot dip bath with a strip interposed therebetween. A strip is sandwiched between the wiping nozzle and a top roll provided above the nozzle. A gas ejection nozzle is provided, and a flat plate is provided above and below the installation position of the gas ejection nozzle and close to the installation position of the wiping nozzle, and the gaps are parallel to the strip width direction of the nozzle toward the strip surface. A continuous hot-dip galvanizing apparatus, which is inclined so as to spread and is symmetrically arranged with respect to the strip surface. 4. A continuous hot dip galvanizing apparatus according to claim 1, further comprising means for adjusting an inclination angle of the flat plate with respect to the strip surface.