JP5556286B2 - Gas wiping equipment for molten metal plated steel strip - Google Patents

Description

  The present invention relates to a gas wiping apparatus for a molten metal plated steel strip that can stably produce a molten metal plated steel strip having reduced surface appearance and excellent surface appearance in a hot dip plating process.

  In a continuous hot dipping process or the like, as shown in FIG. 1, the steel strip 1 is generally immersed in a plating bath 2 made of a molten metal, the direction is changed by a sink roll 3, and then the steel strip 1 is pulled up vertically. After that, the molten metal adhering to the surface of the steel strip extends in the width direction of the steel strip provided facing the steel strip 1 so that the predetermined plating thickness is uniformly obtained in the width direction and the longitudinal direction of the plate. There is provided a gas wiping device for jetting pressurized gas from the gas wiping nozzle 5 to the surface of the steel strip, squeezing excess molten metal, and controlling the amount of molten metal deposited (plating amount).

  In order to stabilize the running position of the steel strip in the gas wiping part, the support roll 4 in the plating bath is usually disposed under the bath surface above the sink roll 3, and when alloying treatment or the like is performed, as necessary. A support roll 6 is installed above the gas wiping nozzle 5.

  The gas wiping nozzle 5 is usually longer than the steel strip width, that is, extending to the outside of the width end of the steel strip, in order to cope with various steel strip widths and at the same time, the deviation in the width direction when the steel strip is pulled up. Yes. In such a gas wiping apparatus, a so-called splash is generated in which molten metal falling downward is scattered by disturbance of a jet that has collided with the steel strip, and the surface quality of the steel strip is degraded.

  In order to increase the production rate in the continuous process, the steel strip passing speed may be increased. However, in the continuous hot dipping process, when the amount of coating is controlled by the gas wiping method, the steel strip is affected by the viscosity of the molten metal. Since the initial adhesion amount immediately after passing through the plating bath of the steel strip increases as the plate passing speed increases, the wiping gas pressure must be set to a higher pressure in order to control the plating adhesion amount within a certain range. , Thereby increasing splash and further reducing the surface quality of the steel strip.

  The following techniques for preventing the occurrence of splash are disclosed.

  In Patent Document 1, a baffle plate is provided outside both ends of the steel strip, and an inclined guide that changes the flow of the injected gas in the vicinity of the steel strip end inward is provided below the steel strip side corner of the baffle plate. It is disclosed.

  In Patent Document 2, an auxiliary nozzle (sub nozzle) is arranged around a wiping nozzle (main nozzle) that mainly controls the amount of molten metal adhering to the steel strip, and the partition plates of the main nozzle and the sub nozzle are arranged. Nozzle and steel that makes the tip of the jet outlet an acute angle, tilts the sub nozzle 5-20 ° with respect to the main nozzle, and lengthens the potential core, thereby improving the squeezability of the amount of deposit and making splash more likely to occur. A technique is disclosed in which the necessary wiping force is maintained without causing the band to approach and the splash is suppressed.

JP 2003-321756 A JP-A-10-204599

  However, in the techniques disclosed in Patent Documents 1 and 2, since the optimum conditions in which splash is unlikely to occur vary depending on the operation conditions such as the line speed, the amount of plating adhesion, and the amount of warp of the steel strip, Even if the occurrence could be reduced, the occurrence of splash could not be reduced stably.

  This invention makes it a subject to provide the gas wiping apparatus of the hot-dip metal plating steel strip which can reduce generation | occurrence | production of a splash stably.

  Splashes are likely to occur at the end of the steel strip where the gas jets jetted from the gas wiping nozzles arranged on both sides of the steel strip collide with each other, and the direction of the jet vibrates up and down. The main cause is a vibration phenomenon. The present invention prevents the occurrence of this vibration phenomenon by arranging a rectifier near the end of the steel strip at or near the collision position of the gas jet from the gas wiping nozzles arranged on both sides of the steel strip. Thus, the occurrence of splash at the end of the steel strip (hereinafter referred to as edge splash) is reduced.

  Means of the present invention for solving the above-described problems are as follows.

  [1] In a gas wiping apparatus for a molten metal-plated steel strip that controls the amount of coating on the surface of the steel strip by blowing gas from a gas wiping nozzle onto the surface of the steel strip that is continuously pulled up from the molten metal plating bath. A gas wiping device for a molten metal-plated steel strip, characterized in that a rectifying body is installed close to the end of the steel strip at or near the collision position of the gas jet injected from the gas wiping nozzles arranged on both sides of the steel plate It is.

  [2] In the above [1], the length of the rectifying body projected in the vertical direction perpendicular to the steel strip surface is 1.3 times or less of the slit gap of the gas wiping nozzle. This is a gas wiping device for a hot-dip metal-plated steel strip.

  [3] In the above [1] or [2], the rectifier has a steel strip width direction projected length of 0.1 mm or more when projected onto a plane parallel to the steel strip surface. This is a gas wiping device for a metal-plated steel strip.

  [4] The gas wiping device for a hot-dip metal-plated steel strip according to any one of [1] to [3], wherein a distance between the rectifying body and the end portion of the steel strip is 20 mm or less.

  [5] In any one of the above [1] to [4], the height position of the rectifying body is set such that the collision position of the gas injected from the gas wiping nozzles arranged on both sides of the steel strip is 0 mm in height. A gas wiping device for a hot-dip metal-plated steel strip, characterized in that the height is in the range of +2 mm to -4 mm.

  According to the present invention, it is possible to suppress the vibration phenomenon caused by the collision of the gas jet injected from the gas wiping that becomes the splash generation source, thereby stably reducing the generation amount of the splash and stably producing the plated steel strip having no surface defect. It becomes possible to do.

It is a longitudinal cross-sectional view which shows the manufacturing apparatus of a general continuous molten metal plating steel strip. It is a figure explaining the generation | occurrence | production mechanism of edge splash. It is a figure explaining the size shape and arrangement position of a rectifier, (a) is a top view when a gas wiping nozzle part is seen from the gas wiping nozzle upper part, (b) is an XX arrow section expansion of (a). FIG. 4C is an enlarged view of the YY cross section of FIG. The result of investigating the relationship between the steel strip longitudinal projection length (L), the slit gap (B) and the splash amount of the rectifier is shown. The relationship between the space | interval (D) of a rectifier and a steel strip edge part, and a splash amount is shown. The relationship of the thickness (T) of the steel strip width direction of a rectifier and the amount of splashes is shown. The relationship between the height position (H) of a rectifier and the amount of splash is shown. It is a figure explaining the effect | action of a rectifier. It is a figure which shows the shape of the rectification | straightening body used for the Example, (a) is a projection figure to the surface parallel to a steel strip surface, (b) is a projection figure to the perpendicular plane at right angles to a steel strip surface.

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

  Most of the splash of molten metal that occurs when the amount of plating applied is controlled by blowing gas from the gas wiping nozzle onto the surface of the steel strip that is continuously pulled up from the molten metal plating bath. Edge splash. The reason why edge splash is likely to occur is considered as follows.

  The gas jet discharged from the gas wiping nozzles arranged opposite to both sides of the steel strip becomes a wall jet as a single jet after colliding with the steel strip at the center of the steel strip. In the section, gas jets from the gas wiping nozzles on both sides collide. On the outside of the steel strip end, as shown in FIGS. 2A to 2D, the gas jets injected from both gas wiping nozzles collide with each other ((a), (c)) and Then, the separation in the opposite direction ((b), (d)) in the up and down direction is repeated, and it vibrates up and down. Due to this vibration phenomenon, gas velocity fluctuations (disturbances) increase at the end of the steel strip, and splash is likely to occur.

  The inventor arranges a rectifier at or near the collision position of the gas jets from both gas wiping nozzles outside the steel strip end, and the gas jet injected from both gas wiping nozzles is the steel strip end. The idea was to prevent it from vibrating up and down outside.

  Therefore, using a hot dip galvanizing wiping simulator that can reproduce the hot dip galvanizing process, a rectifier was placed at the collision part of the gas jets from both gas wiping nozzles outside the steel strip end, and the effect was investigated. The rectifier has a circular cross-sectional shape perpendicular to the steel strip surface and a sphere whose cross-sectional shape parallel to the steel strip surface is an ellipse, and is divided into two equal parts in a cross-section perpendicular to the long axis. This was attached to the steel strip side end of the baffle plate.

  3A and 3B are diagrams for explaining the dimensional shape and arrangement position of the rectifying body. FIG. 3A is a plan view when the gas wiping nozzle portion is viewed from above the gas wiping nozzle, and FIG. 3B is an XX of FIG. An arrow cross-sectional enlarged view, (c) is a YY cross-sectional enlarged view of (a). In (c), the gas wiping nozzle on one side of the steel strip 11 is not described. In FIG. 3, 11 is a steel strip, 12 is a gas wiping nozzle, 13 is a baffle plate, 14 is a rectifier, and 15 is a slit gap. Reference numerals 12a and 12b denote nozzle members, and an alternate long and short dash line 16 denotes a jet collision position.

  The height of the rectifying body is the length projected in the longitudinal direction of the steel strip when the rectifying body is projected onto a vertical plane perpendicular to the steel strip surface, and is “L” in FIG.

  The thickness of the rectifier is the projected length of the rectifier in the width direction of the steel strip when the rectifier is projected onto a plane parallel to the steel strip surface, and is “T” in FIG.

  The height position of the rectifying body is such that the projected length of the rectifying body in the width direction of the steel strip is T when the collision position of the gas jet injected from the gas wiping nozzles on both sides of the steel strip is taken as the reference position (height 0 mm). This is the height from the reference position of the portion (steel strip end closest part of the rectifier), which is “H” in FIG. The gas jet collision position is a geometric collision position of the jet center of the gas wiping nozzle on both sides of the steel strip. H = 0 mm indicates that the steel strip end closest portion of the rectifier is at the gas jet collision position, and H> 0 mm indicates that the steel strip end closest portion of the rectifier is above the gas jet collision position. <0 mm means that the steel strip end closest portion of the rectifier is below the collision position of the gas jet. When the steel strip end closest part of the rectifier has a length in the longitudinal direction of the steel strip, the intermediate position is set as the height position of the rectifier.

  The slit gap is “B” in FIG. 3B, and the distance between the rectifier and the steel strip end is “D” in FIG. 3B.

A gas wiping nozzle with a length of 300 mm in the width direction of the steel strip is used, the gas pressure is fixed at 0.8 kgf / cm ² , the nozzle-steel strip distance is fixed at 10 mm, the hot dip galvanizing bath temperature is 460 ° C., A steel strip with a thickness of 0.4 mm and a plate width of 150 mm is passed through at 2.5 m / s, the dimensions of the rectifier, the arrangement conditions, and the slit gap are variously changed, and the splash scattered under the gas wiping nozzle is collected. The amount of splash collected was investigated. The investigation results and the reasons for limitation of the present invention will be described below.
Standard conditions are as follows.
Slit gap (B): 1.0 mm, projected length of rectifier (L): 0.2 mm, thickness of rectifier (T): 2 mm, height of rectifier (H): 0 mm, steel strip edge of rectifier Interval (D): 8 mm
In the following figures, conditions other than the horizontal axis are fixed to the standard conditions. The splash amount was evaluated based on the ratio of the splash amount when the distance between the steel strip and the baffle plate was 20 mm, the slit gap was 1.0 mm, and there was no rectifier, and the ratio relative to the splash amount.

  FIG. 4 shows the results of investigating the relationship between the projection length (L), slit gap (B) and splash amount of the steel strip in the longitudinal direction. There is a good correlation between the ratio (projection distance ratio) L / B to the slit gap (B) of the length of the steel strip in the longitudinal direction of the rectifier (L) and the splash amount. L / B is about 0.3, and the splash amount takes the minimum value. The splash amount slightly increases when L / B is less than about 0.3, but is sufficiently low when L / B is 0.1 or more. If L / B is greater than about 0.3, the amount of splash generation increases as L / B increases. From the point of preventing the occurrence of a splash amount, the projected length (L) in the longitudinal direction of the steel strip when projected onto a vertical plane perpendicular to the steel strip surface is 1.3 times or less the slit gap (B) of the gas wiping nozzle. Preferably there is.

  In order to reduce the splash, the height of the rectifying body is set to a height corresponding to the width of the gas jet at the collision position of the gas jet from the gas wiping nozzles arranged on both sides of the steel strip (the jet width in the direction of travel of the steel strip). It is important to make it easy. The width of the gas jet at the collision position of the gas jet affects the nozzle-rectifier distance in addition to the slit gap (B) of the gas wiping nozzle, but the nozzle-rectifier distance is in the range of about 10 mm ± 5, In such a range, since the influence of the nozzle-rectifier distance on the width of the gas jet flow is small, it is considered that the amount of splash generation can be arranged by L / B as shown in FIG.

  In addition, since the slit gap of a gas wiping nozzle is 0.5-2.0 mm normally, and most is 0.8-1.2 mm, the steel strip longitudinal direction projection length (L) of a rectifier is usually 0.00. It is 15 to 3.3 mm, and many are 0.24 to 2.0 mm. From this, it is understood that a member having a small length may be used.

  FIG. 5 shows the relationship between the distance (D) between the rectifier and the end of the steel strip and the splash amount. The effect of reducing the splash amount is noticeable when the distance between the rectifier and the end of the steel strip is 1 to 20 mm, and the more remarkable effect is recognized when the distance is 1 to 12 mm. If the distance (D) between the rectifier and the steel strip end is too small, the rectifier may come into contact with the steel strip. From this point, the distance (D) between the rectifier and the steel strip end is more preferably 3 mm or more. . Therefore, the distance (D) between the rectifier and the steel strip end is preferably 1 to 20 mm, more preferably 1 to 12 mm, and even more preferably 3 to 12 mm.

  FIG. 6 shows the relationship between the thickness (T) of the rectifier in the width direction of the steel strip and the splash amount. In FIG. 6, a region where the thickness T of the horizontal axis is 6 mm or less is shown with the horizontal axis enlarged compared to a region where the thickness T is 10 mm or more. The effect of reducing the amount of splash is noticeable when the thickness is 0.1 mm or more. If the thickness is less than 0.1 mm, there is a problem of strength. From this, it is preferable that the thickness of the rectifier in the steel strip width direction is 0.1 mm or more. If it is 1 mm or more, the effect of reducing the amount of splash can be obtained more stably, which is more preferable. If the steel strip width direction thickness (T) is too large, the amount of splash generation increases. Therefore, the steel strip width direction thickness (T) is preferably 33 mm or less, and more preferably 15 mm or less.

  It has been found that reducing splash with only the baffle plate requires the baffle plate to be close to the distance of about 5 mm from the end of the steel strip. However, if the baffle plate is too close to the end of the steel strip, the molten metal splash generated at the end of the steel strip due to the collision of the gas jet will adhere to the end of the steel strip below the gas wiping position of the baffle plate. , The effect of suppressing the occurrence of splash is impaired. In order to prevent this problem, it is necessary to set the distance between the baffle plate and the steel strip end to 10 mm or more.

  Splashing due to the collision of gas jets can be reduced by attaching the rectifier to the steel strip side end of the baffle plate, but the distance between the baffle plate and the steel strip end (thickness of the rectifier in the width direction of the steel strip (T ) And the sum of the distance (D) between the rectifier and the steel strip edge T + D) is less than 10 mm, the splash of molten metal generated by the collision of the gas jets is below the gas wiping position of the baffle plate. There exists a possibility that the effect which adheres to a part and suppresses generation | occurrence | production of a splash may be impaired. Therefore, it is preferable that the sum T + D of the thickness (T) in the steel strip width direction of the rectifier and the distance (D) between the rectifier and the end of the steel strip is 10 mm or more. If T + D is too large, the effect of reducing the occurrence of splash is reduced. Therefore, T + D is preferably 40 mm or less.

  FIG. 7 shows the relationship between the height position (H) of the rectifier and the splash amount. When the height position (H) of the rectifying body is about -1 mm, the splash amount takes a minimum value. When the height position (H) of the rectifying body is in the range of +2 mm to −4 mm, the effect of reducing the splash amount is significantly recognized, and when it is in the range of +1 mm to −3 mm, a more remarkable effect is recognized. From this, the height position (H) of the rectifier is preferably in the range of +2 mm to −4 mm, and more preferably in the range of +1 mm to −3 mm.

  If the gas jet direction projection length ("W" in Fig. 3 (c)) when the rectifying body is projected onto a vertical plane perpendicular to the steel strip surface is too long, the rectifying body is too close to the gas wiping nozzle. Since the gas in the part may not easily be emitted, it is preferably 1/2 or less of the nozzle-nozzle distance. If the projection length in the gas jet direction when the rectifying body is projected onto a vertical plane perpendicular to the steel strip surface is less than 0.1 mm, there is a problem of strength, so it is preferable to set it to 0.1 mm or more. Therefore, the projected length of the gas jet direction when the rectifying body is projected onto the vertical plane perpendicular to the steel strip surface is preferably 0.1 mm or more and 1/2 or less of the nozzle-nozzle distance. Usually, since the nozzle-nozzle distance is 10 to 30 mm, the projected length in the gas jet direction when the rectifying body is projected on a vertical plane perpendicular to the steel strip surface is usually 15 mm or less.

  As described above, the occurrence of splash can be reduced by arranging the rectifying body near the end of the steel strip under appropriate conditions. The reason is considered as follows.

  As shown in FIG. 8, by arranging the rectifier at or near the collision position of the gas jet outside the steel strip edge, the gas jet from the gas wiping nozzles on both sides of the steel strip collides with the rectifier and moves up and down. Therefore, a stable flow is obtained, and the occurrence of the vibration phenomenon peculiar to the collision jet is suppressed. By suppressing the vibration phenomenon due to the collision jet, the occurrence of splash is suppressed.

  Although the shape of the rectifier is not particularly defined, it is better to avoid the one that becomes excessively resistant to the flow because it may disturb the flow and increase the occurrence of splash.

  The arrangement method is not limited as long as the rectifying body can be arranged close to the end portion of the steel strip, but it is easy to attach to the end portion of the known baffle plate facing the end portion of the steel strip. The thickness in the direction perpendicular to the steel strip surface when the rectifying body is projected onto the horizontal plane may be thicker or thinner than the thickness of the baffle plate.

An example of manufacturing a hot-dip galvanized steel strip in which a steel strip having a plate thickness of 1.0 mm and a plate width of 1000 mm is controlled at a sheet feeding speed of 2.5 m / s and a single-side plating adhesion amount of 45 to 50 g / m ² will be described.

  The gas wiping nozzle has a slit gap (B) of 1.0 mm and a nozzle-steel strip distance of 10 mm, and a baffle plate (width 100 mm × height 50 mm × height) at the gas jet collision position of the gas wiping nozzle outside both ends of the steel strip. When the rectifier was attached to the end of the baffle plate opposite to the steel strip end portion, the amount of splash defects generated when the baffle plate was not attached was investigated.

  A rectifying body is prepared by dividing a sphere whose vertical cross section perpendicular to the steel strip surface is circular and whose horizontal cross section is an ellipse into two equal parts on a plane perpendicular to the major axis. It stuck on the edge part opposite side of the steel strip end part of a baffle plate as shown in FIG. The rectifier has a steel strip width direction thickness (T) of 10 mm and a steel strip longitudinal direction projection length (L) of 0.2 mm (projection distance ratio L / B is 0.2). When the rectifying body was attached, the height position (H) of the rectifying body was 0 mm, and the distance (D) from the end of the steel strip was 3 mm. When the rectifier was not attached, the distance between the baffle plate and the steel strip end was 13 mm.

  As a result, in the conventional example using only the baffle plate, the amount of occurrence of splash defects was 1.13%, whereas in the example of the present invention in which a rectifier was attached to the baffle plate, the amount of occurrence of splash defects was 0. It decreased to 09%. The amount of splash generated is the ratio of the steel strip length determined to have a splash defect in the inspection process to the steel strip length passed under each manufacturing condition, and includes a slight splash defect that does not cause a problem in practice. Yes.

  The apparatus of the present invention can be used as a manufacturing facility for a hot-dip metal-plated steel strip that reduces the occurrence of splash and has an excellent surface appearance.

DESCRIPTION OF SYMBOLS 1,11 Steel strip 2 Plating bath 3 Sink roll 4 Support rolls 5 and 12 in plating bath Gas wiping nozzle 6 Support rolls 12a and 12b Nozzle member 13 Baffle plate 14 Rectifier 15 Slit gap 16 Jet collision position

Claims (4)

In the gas wiping equipment for the molten metal plating steel strip, which controls the amount of plating on the surface of the steel strip by blowing gas from the gas wiping nozzle onto the surface of the steel strip that is continuously pulled up from the molten metal plating bath, on both sides of the steel strip A rectifying body was installed close to the end of the steel strip at or near the collision position of the gas jet injected from the gas wiping nozzle arranged, and the rectifying body was projected on a vertical plane perpendicular to the steel strip surface. strip longitudinal projection length gas wiping apparatus for molten metal plated steel strip, characterized in der Rukoto 1.3 times or less of the slit gaps of the gas wiping nozzle of time. 2. The gas wiping of a hot-dip metal-plated steel strip according to claim 1, wherein the rectifier has a steel strip width direction projected length of 0.1 mm or more when projected onto a plane parallel to the steel strip surface. apparatus. The gas wiping device for a hot-dip metal-plated steel strip according to claim 1 or 2 , wherein a distance between the rectifier and the end of the steel strip is 20 mm or less. The height position of the rectifying body is within a range of height +2 mm to −4 mm when the collision position of the gas injected from the gas wiping nozzles arranged on both sides of the steel strip is 0 mm in height. The gas wiping device for a hot-dip metal-plated steel strip according to any one of claims 1 to 3 .

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