JP6102382B2 - Gas wiping device - Google Patents

Description

  The present invention assumes, for example, a steel strip as a strip material and a plating bath such as hot dip zinc as a liquid bath, and when performing hot-dip plating on the steel strip, after the steel strip has been pulled out of the hot-dip bath, The present invention relates to a gas wiping apparatus capable of reducing the occurrence of splash during gas wiping in a continuous hot dip plating process in which hot dip metal is wiped by gas wiping.

  Normally, in the continuous hot dip plating process of steel strip, gas (inert gas, air, etc.) is sprayed from a pair of slit-shaped wiping nozzles immediately after pulling on both sides of the steel strip that has been immersed in a plating bath and pulled up vertically. Then, the unsolidified hot dip plating metal adhering to the steel strip is removed, and the plating adhesion amount on the steel strip surface is adjusted.

  At this time, the unsolidified hot-dipped metal adhering to the end of the steel strip scatters from the end of the steel strip as splash (hereinafter referred to as splash) and adheres to the wiping nozzle or the plated surface of the steel strip. . If the splash adheres to the wiping nozzle, the nozzle is closed, and the plating metal is not sufficiently removed, so that the appearance of the plated surface is significantly impaired. Moreover, even if the splash itself adheres to the plated surface of the steel strip and solidifies as it is, the appearance of the plated surface is impaired.

  Also, in the above continuous hot dipping process, to increase the production rate, the steel strip threading speed should be increased. However, by increasing the steel strip threading speed, the amount of hot dip plated metal lifted by the steel strip is increased. , And the wiping gas pressure must be set to a higher pressure in order to control the plating adhesion amount within a certain range. As a result, the turbulent flow component of the wiping gas jet increases, so that the splash increases significantly and a good plated surface appearance cannot be maintained. That is, the occurrence of splash is an upper limit on the productivity of the hot dip galvanizing process.

  Therefore, until now, in order to prevent or suppress splash splash and adhesion, in addition to the wiping nozzle, a method of providing an additional gas nozzle near the steel strip ends, or on the extension surfaces of the steel strip ends. Various methods, such as providing a baffle plate, are disclosed, and in Patent Document 1, some representative examples are presented as prior art examples.

  However, as pointed out in Patent Document 1, these prior art examples have insufficient points such as that splash that is considered to be generated due to turbulence of gas blown from the wiping nozzle cannot always be stably suppressed. There were many.

  Therefore, Patent Document 1 discloses a method of suppressing the occurrence of splash by reducing gas turbulence with a more improved baffle plate. That is, in Patent Document 1, as shown in FIG. 4, a baffle plate 3 that blocks the collision between gases injected from the gas wiping nozzle 1 is provided on an extended surface in the vicinity of both ends of the steel strip S in the width direction. The baffle plate 3 is formed so that the thickness of the baffle plate 3 decreases in the plating bath direction, and the baffle plate 3 is positioned above the position where the gas jetted from the gas wiping nozzle 1 collides with the baffle plate 3. A method for manufacturing a hot-dip metal-plated steel strip is disclosed in which a baffle plate 4 having a width wider than the thickness of the plate 3 is attached.

Patent No. 4816105

  Regarding the method disclosed in Patent Document 1, when the inventors of the present invention confirmed the splash suppression effect by experiments, depending on the positional relationship between the baffle plate 4 and the gas wiping nozzle 1, a sufficient splash suppression effect cannot be obtained. It turned out to be inconvenient.

  Here, in order to elucidate the cause of such inconvenience, the inventors of the present application installed the gas wiping device disclosed in Patent Document 1 shown in FIG. When the positional relationship with the wiping nozzle 1 was systematically changed and the splash suppression effect was experimentally confirmed and investigated, the following knowledge was obtained.

  First, an outline of the effect confirmation experiment method performed by the present inventors will be described.

  FIG. 5 shows the positional relationship between the baffle plate 4 and the gas wiping nozzle 1 changed in the experiment. FIG. 5 is a view of the gas wiping nozzle 1, the baffle plate 3, and the baffle plate 4 of the method disclosed in Patent Document 1 as viewed from the side cross-sectional direction of the steel strip S, and the gas wiping nozzle 1, the baffle plate 3, The arrangement of the baffle plate 4 and the steel strip S is schematically shown. In the effect confirmation experiment conducted by the present inventors, the width B (mm) of the baffle plate 4, the height direction distance H (mm) from the lower surface of the baffle plate 4 to the upper end of the gas outlet of the gas wiping nozzle 1, the wiping nozzle Various distances D (mm) from 1 to the steel strip S were changed.

  It should be noted that the gap distance C (mm) between the end of the baffle plate 4 and the upper surface of the gas wiping nozzle 1 is changed by changing the width B, the distance D, and the height direction distance H. It is. As will be described later, a confirmation experiment conducted by the inventors of the present application revealed that the gap C greatly affects the splash suppression effect. As a result of earnestly elucidating the mechanism, the present invention is achieved. It has come.

  In the experiment, as described above, the width B, the distance D, and the height direction distance H were variously changed (that is, the gap interval C was also changed), and the amount of splash generated when the steel strip S was passed was evaluated. Although not shown in the figure, the amount of generated splash was evaluated by sampling for a certain period of time with a splash collecting device installed in the vicinity of the end of the steel strip S in the width direction and measuring the weight. In addition, it has been found from prior examination that there is a positive correlation between the weight per unit time of the splash collected by the splash collecting apparatus and the appearance defect occurrence frequency due to the splash. That is, it can be said that the smaller the weight per unit time collected by the splash collecting device, the smaller the amount of splash generated, and the greater the effect of suppressing the splash, that is, the effect of improving the surface quality of the steel strip.

  Hereinafter, the splash weight per unit time collected by the splash collection device is referred to as a splash generation amount.

  Experimental conditions other than the positional relationship between the baffle plate 4 and the gas wiping nozzle 1 are substantially the same as those of the preferred embodiments 11 to 14 disclosed in Patent Document 1. That is, the wiping nozzle slit gap was 0.8 mm, the nozzle height from the molten zinc bath was 420 mm, the molten zinc bath temperature was 460 ° C., and the size of the steel strip S was 1.0 mm thickness × 1.8 m width. The dimensions of the baffle plate 3 are 50 mm in length and 200 mm in width. The shape of the baffle plate 3 is such that the plating bath side becomes thinner toward the plating bath, and the end side of the steel strip S is at the end of the steel strip S. The shape becomes thinner toward the surface. The collision position of the wiping gas was 20 mm from the top of the baffle plate 3. The distance between the baffle plate 3 and the steel strip S was 10 mm. Similarly to Patent Document 1, the width B of the baffle plate 4 was changed to 10 mm and 20 mm, and the thickness was also 5 mm.

  In addition, as a point to be noted regarding the experimental conditions, in Patent Document 1, although the width B (mm) and the distance D (mm) are described, the height direction distance H (mm) and the tip angle θ of the wiping nozzle 1 ( Since there is no description of (°), there is an unknown point of clearance C (mm), which is geometrically determined from the width B, distance D, height direction distance H, and tip angle θ. Qualitatively, also in Patent Document 1, as compared in Example 12 and Example 13, when viewed from above the gas wiping device, the end portion of the baffle plate 4 becomes the wiping nozzle 1 injection port. Although it is suggested that it is preferable to provide the gap interval, the value of the gap interval C is not specifically mentioned. For example, even if the width B and the tip angle θ are constant, if the distance D or the height direction distance H is increased, the gap interval C is also increased. As will be described later, the technique disclosed in Patent Document 1 is an experiment that the present inventors have discovered that a stable splash prevention effect cannot be obtained unless the gap C is kept constant. It is a fact.

  The measurement results of the amount of splash generated by the above experiment are shown in FIG. 8 together with the experimental conditions. As shown in FIG. 8, in this verification experiment, the distance D is changed to 8 mm, 6 mm, and 4 mm (in Patent Document 1, the case where the distance D is only 8 mm is disclosed), and the width B is changed to 20 mm and 10 mm. Further, the gap distance C is changed between 0 mm and about 6 mm by changing the height direction distance H several times between 1 and 10 mm.

  FIG. 6 is a graph showing the results of the splash suppression effect confirmation experiment conducted by the inventors of the present application using the gas wiping apparatus disclosed in Patent Document 1, and the amount of splash generation shown in FIG. Is plotted for. In FIG. 6, the horizontal axis is shown organized with a width B (mm). From FIG. 6, as disclosed in Patent Document 1, when viewed from above the gas wiping device, the width B = 20 mm provided so that the end of the baffle plate 4 reaches the wiping nozzle 1 injection port. On the other hand, the amount of splash generation seems to be less than the width B = 10 mm which is not so. However, the variation is large, and it is difficult to say that the amount of splash generation is stably suppressed.

  On the other hand, FIG. 7 shows the result of the splash suppression effect confirmation experiment conducted by the present inventors using the gas wiping device disclosed in Patent Document 1, and the amount of splash generation is organized by the gap interval C. FIG. It can be seen that, unlike 6, it is roughly organized into a single curve. That is, the experiment was performed by changing the width B, the distance D, and the height direction distance H in various ways, but it can be understood that the amount of splash generation is mainly governed by the value of the gap interval C. Moreover, as can be seen from FIG. 7, it has been found that the effect of suppressing the splash is the greatest in the extremely narrow range of the gap interval C of about 2 mm, more specifically, the gap interval C = 1.5 mm to 2.5 mm.

  As described above, in the baffle plate 3 disclosed in Patent Document 1, it is clear from the confirmation experiment conducted by the present inventors that the gap interval C greatly affects the splash suppression effect. It has been found that there is an inconvenience that a sufficient splash suppression effect cannot be stably exhibited unless the value of the gap interval C is appropriately controlled. Furthermore, it has been found that the most effective value of the gap distance C is as narrow as about 1.5 mm to 2.5 mm, and the baffle plate 3 must be installed very carefully.

  On the other hand, the baffle plate is generally attached to the end of the frame extending from the width direction position control device by servo motors provided at the upper ends of both ends of the wiping nozzle. The baffle plate 3 disclosed in Patent Document 1 is also the same. At this time, the baffle plate 3 attached to the frame receives a strong pressure due to the gas jet from the wiping nozzle 1, so that a strong bending force acts on the frame, and the frame and the baffle plate 3 itself have a high temperature. Since it receives the radiant heat from the plating bath and the steel strip S, thermal distortion occurs, and it is difficult to accurately position the baffle plate 3. That is, in order to perform accurate positioning, a thick frame that does not bend even when subjected to strong pressure from a gas jet, a cooling mechanism for relaxing thermal strain, and a gap interval C are accurately measured and the size is measured. A control device that keeps the accuracy constant is required, which increases the equipment cost. In the first place, the wiping nozzle 1 is generally extremely narrow, and there is almost no extra space for installing a large frame, cooling mechanism, measuring device for the gap interval C, etc. Is significantly worse. That is, there is an inconvenience that maintaining an appropriate gap interval C with high accuracy is costly and the workability is deteriorated.

  The present invention has been made based on such knowledge, and an object of the present invention is to provide a gas wiping device that eliminates the increase in equipment cost and workability due to device installation and stably suppresses splash. And

In order to solve the above-mentioned problem, a belt-like material that is continuously pulled up from the liquid bath is sandwiched, and is disposed at the same height as the liquid bath surface and along the width direction of the belt-like material. the towards by ejecting the gas, to adjust the adhesion amount of liquid adhering to the surface of the strip material, and the gas wiping nozzle of at least one pair of opposed, both sides of the strip material on the extended surface in the width direction of the strip material And a pair of baffle plates disposed at a height including the gas collision point where the gas ejected from the wiping nozzle collides with the surface of the belt-like material, and the gas ejected from the gas wiping nozzle collides with the baffle plate A gas wiping device comprising a fluid resistance element having air permeability between the gas wiping nozzle and the baffle plate. It is.

  A baffle plate is arrange | positioned so that the gas jets injected from the gas wiping nozzle which opposes may collide in the position which remove | deviated from the strip | belt-shaped material. In addition, the fluid resistance element is provided to attenuate the turbulence caused by the collision of the gas jet against the baffle plate with a strong vortex by the damping effect, so that it is not affected by the gap distance between the gas wiping nozzle and the baffle plate. It is possible to stably suppress the occurrence of splash.

  The fluid resistance element may be a porous body having air permeability. By using a porous body as a fluid resistance element, a splash suppression effect due to a damping effect can be obtained without being affected by the gap spacing, and even better splash suppression is achieved particularly when the average pore diameter is in the range of 0.2 mm to 1.3 mm. An effect can be obtained.

  The fluid resistance element may be a fibrous body having air permeability. The fluid resistance element includes a large number of flow paths and various sizes of flow paths. Therefore, the epidemic resistance element is not limited to the porous body, and the same effect can be obtained even with a fibrous body, for example.

  According to the present invention, turbulence of gas flow generated when a gas jet with a strong vortex collides with a baffle plate due to a damping effect by a fluid resistance element arranged in a space sandwiched between a gas wiping nozzle and a baffle plate. The occurrence of splash can be stably suppressed by attenuating.

  In addition, according to the present invention, the occurrence of splash can be stably suppressed only by arranging the fluid resistance element in the space sandwiched between the gas wiping nozzle and the baffle plate. Cost can be reduced and workability around the device can be secured.

It is explanatory drawing which looked at the gas wiping apparatus which concerns on 1st Embodiment of this invention from the side cross-sectional direction of the steel strip. It is explanatory drawing which looked at the gas wiping apparatus which concerns on 2nd Embodiment of this invention from the side cross-sectional direction of the steel strip. It is a graph which shows the relationship between the clearance gap between the edge part of a baffle plate and the upper surface of a gas wiping nozzle, and the amount of splash generation about 2nd Embodiment of this invention, and the past. It is a schematic perspective view which shows the steel strip edge part vicinity part of the gas wiping apparatus disclosed by patent document 1. FIG. It is the figure which looked at the gas wiping apparatus disclosed by patent document 1 from the side cross-sectional direction. It is a graph which shows the result of the splash suppression effect confirmation experiment which the present inventors performed using the gas wiping apparatus indicated by patent documents 1. It is a graph which shows the result of the splash suppression effect confirmation experiment which the present inventors performed using the gas wiping apparatus indicated by patent documents 1. It is a table | surface which shows the experimental result of the effect confirmation test of the cited reference 1. It is a table | surface which shows the experimental result of the splash suppression effect test of 2nd Embodiment. It is a table | surface which shows the comparative example of the effect confirmation test result of the cited reference 1 with respect to an Example of this application. It is a table | surface which shows the experimental result of the splash suppression effect test of 1st Embodiment.

  As described above, in the conventional technique described in Patent Document 1, the amount of splash generation is affected by the gap interval C from the baffle plate 4 to the upper surface of the gas wiping nozzle 1, and attempts to suppress the splash stably. In order to achieve this, it is necessary to accurately control the gap interval C within a narrow range. Therefore, the inventors of the present application conducted further research based on the above findings. As a result, the amount of splash generation is not essentially affected by the gap interval C, but the baffle plate 3 and the baffle plate 4 and the gas. It has been found that the space sandwiched between the wiping nozzle 1 is essentially influenced by the magnitude of fluid resistance. That is, after the gas ejected from the wiping nozzle 1 collides with the buffer plate, a part of the gas flows through the space sandwiched between the baffle plate 4 and the gas wiping nozzle 1, but this flow acts. It was found that the magnitude of fluid resistance affects the amount of splash generated. For example, this may change the roughness of the surface of the baffle plate 4 or the upper surface of the gas wiping nozzle 1 or, as shown in FIG. It shows that the amount of splash generation changes by arranging a member that changes ventilation resistance such as a porous body or a fibrous body. In the first place, in the first place, increasing or decreasing the gap interval C is exactly the same as changing the flow path cross-sectional area of the space sandwiched between the baffle plate 4 and the gas wiping nozzle 1 to increase the magnitude of the fluid resistance. This corresponds to one means for changing. That is, in order to suppress the splash, it is not essential to increase or decrease the gap interval C, but it is essential to provide fluid resistance to the space sandwiched between the baffle plate 4 and the gas wiping nozzle 1. I understand.

  Furthermore, as shown in FIG. 2, the inventors of the present application arrange a fluid resistance element such as a porous body or a fibrous body having air permeability in a space sandwiched between the gas wiping nozzle 1 and the baffle plate 4. It has been found that even if the interval C changes slightly, the splash suppression effect is not significantly affected, and stable operation is possible.

With regard to the above findings, the inventors of the present application considered the mechanism as follows.
In general, splash is likely to occur at the end of the steel strip S. In the portion where the steel strip S is not present, gas jets jetted from the gas wiping nozzle 1 collide with each other, and the gas flow is greatly disturbed. It is considered because. The anti-splash technique using the baffle plate 3 as disclosed in Patent Document 1 tries to suppress the splash by blocking the collision between the gas jets with the baffle plate 3 so that the gas flow is not easily disturbed. Is.

  Certainly, the baffle plate 3 reduces the turbulence caused by the collision between the gas jets, and it is considered that the splash suppressing effect is exhibited. However, since the gas flow ejected from the gas wiping nozzle 1 is very high in the first place, the surrounding gas is entrained immediately after it is ejected from the gas wiping nozzle 1 and a strong vortex is formed at the outer edge of the gas jet. Accompanying. This strong vortex collides with the baffle plate 3 together with the gas jet to cause a strong turbulence around it, which is considered to be a major cause of splash.

  That is, in order to suppress the occurrence of splash, it is necessary not only to reduce the turbulence caused by the collision between the gas jets caused by the baffle plate 3, but also to reduce the turbulence caused by the gas jet that collides with the baffle plate 3 with a strong vortex. I think there is.

  As shown in FIG. 2, the inventors of the present application arrange a fluid resistance element such as a porous body or a fibrous body having air permeability in a space sandwiched between the gas wiping nozzle 1 and the baffle plate 4. It was thought that the turbulence caused by the gas jet impinging on the baffle plate 3 ′ with a strong vortex could be reduced. In other words, the fluid resistance element acts as a damper against the turbulence of the gas jet caused by the collision of the gas jet with a strong vortex against the baffle plate 3 ′, and converts the kinetic energy of the turbulence of the gas jet into thermal energy. As a result, it was assumed that the disturbance was attenuated.

  As disclosed in Patent Document 1, attaching the baffle plate 4 to the upper part of the baffle plate 3 results in increasing the fluid resistance by reducing the gap interval C, and causing the above-described damping effect. However, as shown in the experiment conducted by the inventors of the present application, the fluid resistance is controlled by the gap interval C. It is considered that the fluid resistance greatly changes due to a slight difference in the gap interval C. That is, as seen in the result of the splash suppression effect confirmation experiment conducted by the inventors of the present application using the gas wiping device disclosed in Patent Document 1 described above with reference to FIG. Is about 2 mm, the splash suppression effect becomes the largest, and the splash suppression effect becomes smaller even if the gap interval C is wider or narrower.

  The reason why the splash suppression effect becomes smaller as the gap interval C becomes wider than 2 mm is that the fluid resistance decreases as the gap interval C increases. On the other hand, as the gap C becomes narrower than 2 mm, the splash suppression effect becomes smaller because the fluid resistance becomes too large and the fluid that flows through the gap between the end of the baffle plate 4 and the upper surface of the gas wiping nozzle 1. This is because the ratio of converting the kinetic energy of the turbulence of the gas jet into heat energy has decreased. That is, the rate of converting the turbulent kinetic energy of the gas jet into thermal energy is affected by both the magnitude of the fluid resistance and the flow rate of the fluid flowing through the gap between the end of the baffle plate 4 and the upper surface of the gas wiping nozzle 1. It is. Therefore, as a result, the splash suppression effect is maximized when the gap interval C is around 2 mm, and even if it is wider or narrower, the splash suppression effect is small, and the splash cannot be stably suppressed. it is conceivable that.

  On the other hand, when a fluid resistance element such as a porous body or a fibrous body having air permeability is arranged in a space sandwiched between the gas wiping nozzle 1 and the baffle plate 4, a large number of fine flow paths are provided in the gap between the fluid resistance elements. It is considered that a larger damping effect is exhibited than when the baffle plate 4 is simply placed.

  Furthermore, the flow path diameters of a large number of flow paths formed in the gaps between porous bodies and fibrous bodies are generally distributed and have various sizes. Accordingly, the fluid resistance of the space sandwiched between the gas wiping nozzle 1 and the baffle plate 4 is also the sum of the fluid resistances according to the respective flow paths. For example, even if the arrangement or shape of the fluid resistance elements changes slightly. The total fluid resistance itself is not significantly changed, and is considered to exhibit a stable splash suppressing effect.

  That is, when the baffle plate 4 is simply attached to the upper part of the baffle plate 3 and no fluid resistance element is arranged, there is only a single fluid resistance control factor, the gap interval C, and the gap interval C A slight difference is thought to have led to a large fluctuation in the splash suppression effect.

  On the other hand, when a fluid resistance element such as a porous body or a fibrous body having air permeability is arranged in a space sandwiched between the gas wiping nozzle 1 and the baffle plate 4, a large number of fluid resistance elements are present in the gaps in the first place. The flow path diameter of the fine flow path is considerably smaller than the gap interval C, and it is considered that a larger damping effect is exhibited than simply placing the baffle plate 4. Further, since the flow path diameter has a distribution, it is considered that the fluctuation of the fluid resistance value of the entire fluid resistance element due to the difference in the gap interval C is alleviated, and as a result, a stable splash preventing effect is obtained.

  Furthermore, as a result of intensive studies in view of the mechanism of the splash preventing effect by the fluid resistance element, the inventors of the present application have found that the baffle plate 4 is unnecessary in the first place. That is, as shown in FIG. 1, the same splash suppression effect can be obtained simply by disposing a fluid resistance element such as a porous body or a fibrous body having air permeability in the space between the gas wiping nozzle 1 and the baffle plate 3. It was found that can be demonstrated. This is presumably because the damping effect on the turbulence of the gas jet is mainly due to the fluid resistance element.

  Embodiments of the present invention will be described below with reference to the drawings.

<First Embodiment>
FIG. 1 is a view of the gas wiping device according to the first embodiment of the present invention as viewed from the side sectional direction of the steel strip S. FIG. FIG. 1 shows a gas wiping apparatus, particularly in a hot-dip plating process of a steel strip. In FIG. 1, 1 is a gas wiping nozzle, 3 ′ is a baffle plate, 2 is a gas wiping nozzle 1 and a baffle plate 3 ′. The fluid resistance element S, which is disposed in the space, is a steel strip. Further, a curve 5 with an arrow divided into two in FIG. 1 schematically shows an average flow of the gas injected from the gas wiping nozzle 1, and the direction of the arrow indicates the flow direction. The curve represents the trajectory of gas flow. Further, the fact that the curve is divided into two branches indicates that the gas flow collides with the baffle plate 3 ′ in the vicinity thereof, and the flow is divided up and down.

  The gas wiping nozzle 1 is disposed so as to face the steel strip S that is continuously pulled up from the hot dipping bath, and is located at the same height from the plating bath surface and along the width direction of the steel strip S. Then, the amount of hot-dip plated metal adhering to the surface of the steel strip S is adjusted by jetting gas toward the surface of the steel strip S.

Further, the baffle plate 3 ′ is on an extended surface near both sides in the width direction of the steel strip S and at a height including a gas collision point where the gas ejected from the wiping nozzle 1 collides with the surface of the steel strip S. Has been placed. The material and thickness of the baffle plate 3 ′ are materials that can withstand the plating bath temperature of molten plating metal (in the case of molten zinc, about 420 ° C. to 480 ° C.), and the gas collision pressure (0.1 × 10 ⁵ Pa~0.9 × may be any thickness having a strength to withstand ¹⁰ about 5 Pa). For example, the material of the baffle plate 3 ′ may be stainless steel and the thickness thereof may be about 4 to 10 mm.

  The fluid resistance element 2 that most characterizes the present invention is above the position where the gas jetted from the gas wiping nozzle 1 collides with the baffle plate 3 ′, and in the width direction of the baffle plate 3 ′ (in FIG. It is installed so as to be in close contact with the baffle plate 3 ′ by an appropriate method over the entire width in the direction). Here, FIG. 1 shows a case where the fluid resistance element 2 is in close contact with the upper surface of the gas wiping nozzle 1, but is not necessarily in close contact with the upper surface of the gas wiping nozzle 1. . Further, the fluid resistance element 2 is disposed above the position where the gas jetted from the gas wiping nozzle 1 collides with the baffle plate 3 ′, but may be disposed below or both above and below, Although a splash prevention effect can be obtained, if it is disposed below, a slight amount of splash may adhere to and accumulate on the fluid resistance element 2, and during long-term operation, the amount of adhesion increases and the tip of the deposit passes. Since there is a possibility of contact with the steel strip S to be plated, it is not desirable.

  The material of the fluid resistance element 2 is capable of withstanding the plating bath temperature of molten plating metal (about 420 ° C. to 480 ° C. in the case of molten zinc), and has a strength that is not blown off by the gas jet from the wiping nozzle 1. Therefore, it is only necessary to have appropriate air permeability. For example, the fluid resistance element 2 may be any material that can withstand high temperatures such as a porous body such as a porous metal body or a sintered ceramic body, a fibrous metal or glass fiber, and has air permeability. In the present invention, a metal porous body (for example, Celmet (registered trademark)) is exclusively used. As for the flow path diameter of this metal porous body (in this case, it is regarded as the pore diameter), those having various sizes are commercially available, but the average pore diameter is 0.2 mm to the most effective for suppressing the splash. It was 1.3 mm.

<Second Embodiment>
FIG. 2 is a view of the gas wiping device according to the second embodiment of the present invention as viewed from the side sectional direction of the steel strip S. In FIG. 2, 1 is a gas wiping nozzle, 3 'is a baffle plate, 4 is a baffle plate, 2 is a fluid resistance element, and S is a steel strip. The gas wiping apparatus according to the present embodiment is different from the first embodiment in that the baffle plate 3 ′ is also provided with a baffle plate 4. Moreover, the average flow of the gas injected from the gas wiping nozzle 1 is shown like FIG. The baffle plate 3 ′ according to this embodiment may have a uniform thickness as shown in FIG. In Patent Document 1, as shown in FIGS. 4 and 5, the thickness of the baffle plate 3 is reduced toward the plating bath direction, so that gas disturbance can be suppressed. In the present invention, it is not always necessary to do so because of the effect of suppressing gas turbulence by the fluid resistance element 2 that characterizes the present invention.

  The two embodiments have been described above. As described above, the baffle plate 4 as shown in the second embodiment of FIG. 2 is essentially unnecessary, and the essential features of the present invention are as follows. As shown in FIG. 1, the fluid resistance element 2 is disposed in a space sandwiched between the gas wiping nozzle 1 and the baffle plate 3 ′. Hereinafter, in order to clarify that the baffle plate 4 is not an essential element but a fluid resistance element 2 is essential for preventing splash, the result of verifying the effect of suppressing the splash according to the embodiment of the present invention is described below. Will be described in the order of the embodiments of FIGS.

  The gas wiping apparatus according to the first and second embodiments is installed in the hot dip galvanizing line, and the splash suppression effect is tested in the same manner as the effect confirmation experiment of the gas wiping nozzle of Patent Document 1 previously conducted by the present inventors. Surveyed.

  In the first embodiment described below, as shown in FIG. 2, the baffle plate 4 that is also a constituent element of the patent document 1 is provided so that the effect of the fluid resistance element 2 of the present invention becomes clear. The fluid resistance element 2 is arranged in the gas wiping device, and the effect on the amount of splash is investigated by changing the gap interval C as in the previous experiment, and the result is compared with the case without the fluid resistance element 2 And the difference of the splash inhibitory effect by the presence or absence of the fluid resistance element 2 was confirmed.

  In the following second embodiment, the gas wiping apparatus according to the present invention as shown in FIG. 1 is installed in a hot dip galvanizing line, and the effect confirmation experiment of the gas wiping nozzle of Patent Document 1 previously conducted by the present inventors. In the same manner as above, the splash suppression effect was experimentally investigated. That is, the fluid resistance element 2 made of a metal porous body was disposed in a space sandwiched between the gas wiping nozzle 1 and the baffle plate 3 ′, and the amount of splash generated was investigated and confirmed.

  As experimental conditions, in both the first and second examples, the wiping nozzle slit gap was 0.8 mm, the nozzle height from the molten zinc bath was 420 mm, the molten zinc bath temperature was 460 ° C., and the size of the steel strip S was 1.0 mm thick. X 1.8 m width. The dimensions of the baffle plate 3 'are 50 mm in length and 200 mm in width, and the shape thereof is a flat plate having a uniform thickness of 5 mm. The distance between the baffle plate 3 ′ and the steel strip S was 10 mm. The average pore diameter α of the fluid resistance element 2 made of a metal porous body was changed in a range of 0.1 mm to 3.2 mm. In the first embodiment, the width B of the baffle plate 4 is changed to 10 mm and 20 mm, and the thickness is 5 mm.

  The measurement results of the amount of splash generated by the experiment of the above embodiment are shown in FIGS. FIG. 9 shows the experimental results of the first example for the gas wiping apparatus according to the second embodiment having the baffle plate 4 and the fluid resistance element 2, and FIG. 11 shows only the fluid resistance element 2 without the baffle plate 4. It is an experimental result of 2nd Example with respect to the gas wiping apparatus which concerns on 1st Embodiment. Moreover, FIG. 10 is a result of the effect confirmation test of the cited reference 1 which measured the splash generation amount with respect to the gas wiping apparatus which does not have the fluid resistance element 2 only by the baffle plate 4 as a comparative example with respect to the Example of this invention.

[First embodiment]
First, based on FIG. 9, the experimental result with respect to the gas wiping apparatus which concerns on the said 2nd Embodiment which has the baffle plate 4 and the fluid resistance element 2 is demonstrated. In FIG. 9, Examples 1 to 6 are examples when the average pore diameter α of the fluid resistance element 2 made of a metal porous body is 0.1 mm, and Examples 7 to 12 are examples when the pore diameter α is 0.2 mm. Nos. 13 to 18 have a hole diameter α = 0.5 mm, Examples 19 to 22 have a hole diameter α = 1.0 mm, and Examples 23 to 26 have a hole diameter α = 1.3 mm. 30 shows a case where the hole diameter α = 1.9 mm, and Examples 31 to 33 show a case where the hole diameter α = 3.2 mm. And the gap | interval space | interval C is also changed with respect to each condition of the hole diameter (alpha).

  Further, FIG. 3 shows a comparison of the amount of splash generated in the embodiment shown in FIG. 9 and the comparative example shown in FIG. As shown in FIG. 3, when the fluid resistance element 2 is installed (the data of FIG. 9 showing the results of the example, plotted in *, □, ◇, ○, Δ, ×, + in FIG. 3) In the range of the hole diameter α = 0.1 mm to 3.2 mm, regardless of the size, even if the gap interval C changes, the amount of splash generated is substantially constant corresponding to the value of each hole diameter α. It is suppressed. On the other hand, when there is no fluid resistance element 2 (the data in FIG. 10 showing the result of the comparative example and plotted with ● in FIG. 3), as described above, the amount of splash generation varies greatly depending on the value of the gap interval C. End up. That is, it can be seen that by installing the fluid resistance element 2, splash can be stably suppressed even if the value of the gap interval C is slightly different.

  Further, as shown in FIG. 3, when the fluid resistance element 2 is installed, the splash is suppressed particularly in the range of the hole diameter α = 0.2 mm to 1.3 mm (indicated by □, ◇, ○, and Δ in FIG. 3). It can be seen that the amount of splash generation is the lowest when the effect is large and there is no fluid resistance element 2 (plotted with ● in FIG. 3). However, if the hole diameter α is smaller than 0.2 mm (when the hole diameter α is 0.1 mm, plotted as * in FIG. 3), if the hole diameter α is too small, the airflow resistance becomes too large and eventually splash The amount of generation becomes the same as the case where the gap interval C of the baffle plate 4 alone is 0 mm, and a sufficient damping effect cannot be obtained. That is, it is considered that because the ventilation resistance is too large, the amount of fluid flowing through the fluid resistance element 2 is too small, and the rate of converting the turbulent kinetic energy of the gas jet into heat energy is reduced. However, even when the hole diameter α is 0.1 mm, the generated amount is suppressed to be smaller than the amount of splash generated (about 120 g / min) when the gap distance C is about 5 mm or more without the fluid resistance element 2. Yes.

  On the other hand, if α is too large, as shown in the case where the hole diameter α is larger than 1.3 mm (the case where the hole diameter α is 1.9 mm and 3.2 mm, respectively plotted with x and + in FIG. 3), the fluid resistance element Although there is a sufficient amount of fluid flowing through 2, the ventilation resistance becomes too small, so the rate of converting the turbulent kinetic energy of the gas jet into thermal energy decreases, which is also a sufficient damping effect I think that is no longer available. However, even in the case of the hole diameter α = 1.9 mm and 3.2 mm, it is still suppressed to a splash generation amount (about 120 g / min) when the gap interval C is about 5 mm or more.

  In addition, as for the appearance of the plated surface of the steel strip, a sufficient quality level can be secured if the amount of splash generated is generally about 120 g / min or less, and the splash in the range of hole diameter α = 0.2 mm to 1.3 mm. If the generated amount (about 50 g / min or less), it can be said that the quality level can sufficiently meet the high appearance quality requirement.

[Second Embodiment]
Next, based on FIG. 11, an experimental result for the gas wiping apparatus according to the first embodiment in which only the fluid resistance element 2 is provided without the baffle plate 4 will be described. In FIG. 11, in Examples 34 to 40, the average pore diameter α of the fluid resistance element 2 made of a metal porous body is 0.1 mm, 0.2 mm, 0.5 mm, 1.0 mm, 1.3 mm, 1.9 mm. 3 shows a case of changing to 3.2 mm. In addition, a present Example is a thing with respect to the gas wiping apparatus which concerns on 1st Embodiment shown in FIG. 1, Since there is no baffle plate 4, the clearance gap C cannot be defined. For this reason, there is no data of the gap interval C in the item of the baffle plate condition in FIG.

  As can be seen from FIG. 11, even in the gas wiping apparatus having only the fluid resistance element 2 without the baffle plate 4, the splash suppression effect is generally good, and the splash diameter is in the range of 0.2 mm to 1.3 mm. It can be seen that the suppression effect is large. That is, even in the gas wiping device having only the fluid resistance element 2 without the baffle plate 4, as described above, a sufficient damping effect cannot be obtained if the ventilation resistance is too large or too small.

  The damping effect described above is the same for the result of the effect confirmation test of the cited document 1, and the amount of splash generated with respect to the gap interval C as shown in FIG. The decrease in the narrow range of 2.5 mm indicates that the damping effect is effectively obtained in this range. That is, in order to prevent the splash, the baffle plate 4 as disclosed in Patent Document 1 is not essential in the first place, and the fluid resistance is set in the space between the gas wiping nozzle 1 and the baffle plate 3. It is essentially necessary to arrange element 2. Furthermore, it was shown that by using the fluid resistance element 2 such as a porous body or a fibrous body having air permeability, the fluctuation of the gap interval C can be reduced and the splash suppressing effect can be stably exhibited.

  The embodiment of the gas wiping device according to the present invention has been described above. However, the conditions in the examples are one condition example adopted to confirm the feasibility and effects of the present invention, and the present invention is not limited to this one condition example. The present invention can adopt various conditions as long as the object of the present invention is achieved without departing from the gist of the present invention.

  The present invention assumes, for example, a steel strip as a strip material and a plating bath such as hot dip zinc as a liquid bath, and when performing hot-dip plating on the steel strip, after the steel strip has been pulled out of the hot-dip bath, In a continuous hot dipping process in which hot dip metal is wiped off by gas wiping, it can be used as a gas wiping device that can stably reduce the occurrence of splash during gas wiping.

DESCRIPTION OF SYMBOLS 1 Gas wiping nozzle 2 Fluid resistance element 3 Baffle plate disclosed by patent document 1 3 'Baffle plate 4 Baffle plate 5 Gas flow ejected from gas wiping nozzle 1 S Steel strip B Width of baffle plate 4 C Baffle plate 4 The gap distance between the end of the gas wiping nozzle 1 and the upper surface of the gas wiping nozzle 1 D Distance between the wiping nozzle 1 and the steel strip S in the perpendicular direction H Distance between the baffle plate 4 and the gas wiping nozzle 1 θ The angle between the upper surface of the fluid and the horizontal direction α The average pore diameter of the fluid resistance element 2 made of porous

Claims (4)

A belt-shaped material that is continuously pulled up from the liquid bath is sandwiched, and is disposed at the same height from the bath surface of the liquid bath and along the width direction of the belt-shaped material, toward the surface of the belt-shaped material. And at least a pair of opposing gas wiping nozzles for adjusting the amount of liquid attached to the surface of the belt-like material by jetting gas,
Provided on both sides of the belt-shaped member on the extended surface in the width direction of the belt-shaped member and disposed at a height including a gas collision point gas ejected from the gas wiping nozzle impinges on the surface of the strip material A pair of baffle plates,
An air-permeable fluid resistance element provided above the position where the gas jetted from the gas wiping nozzle collides with the baffle plate and between the gas wiping nozzle and the baffle plate;
A gas wiping apparatus comprising:   The gas wiping apparatus according to claim 1, wherein the fluid resistance element is a porous body having air permeability.   The gas wiping apparatus according to claim 2, wherein the porous body has an average pore diameter in a range of 0.2 mm to 1.3 mm. The gas wiping apparatus according to claim 1, wherein the fluid resistance element is a fibrous body having air permeability.

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