JP4046042B2 - Wiping equipment for continuous hot dipping - Google Patents

Description

  The present invention relates to a gas wiping apparatus for hot dipping that prevents splash adhesion to a plated steel sheet.

  The principle of molten metal plating by a normal gas wiping method will be described with reference to FIG. The steel strip S that has been subjected to surface cleaning and annealing in an annealing furnace (not shown) passes through the snout 1 and is immersed in a plating bath (a molten metal bath, hereinafter the same) 3, The direction is changed, and the molten metal plating is performed by pulling up vertically from the plating bath 3. Next, a gas such as air (hereinafter referred to as wiping gas) is blown onto the steel strip S from a pair of wiping nozzles 5 disposed opposite to each other across the steel strip S above the plating bath 3, and the excess melt adhering to the steel strip S is sprayed. The metal is wiped and adjusted to a predetermined plating thickness. This is the principle of molten metal plating by the gas wiping method.

  After the collision with the steel strip S, the wiping gas is divided into a downward flow and an upward flow along the steel strip surface. The downward flow collides with the bath surface. At that time, the bath surface is disturbed and molten metal splash is generated. If the splash adheres to the plated surface after wiping, the surface appearance of the plated steel sheet is significantly impaired, and the plating thickness is locally uneven. In particular, in the case of zinc-iron alloy plating, it causes local unalloying. In FIG. 2, reference numeral 2 denotes a plating tank for holding the plating bath 3, and a header for supplying gas to the wiping nozzle 5 is not shown.

  As a solution to the above problem, Patent Document 1 discloses that a wiping nozzle is provided by providing a rectifying plate 22 projecting behind the wiping nozzle 21 and a weir 23 on the upper front portion of the wiping nozzle 21 as shown in FIG. 21. By lowering the airflow from the lower side to the upper side through the rear and weakening the airflow toward the front of the steel strip S, the splash carried on the airflow above the wiping nozzle 21 is reduced and the carried splash is stopped by the weir 23. It is described that the splash is prevented from adhering to the steel strip S.

The prior art document information will be described below.
JP 2000-328218 A (FIGS. 1 to 3).

  However, in Patent Document 1, the effect of preventing the splash from adhering to the plated steel strip S after wiping is insufficient, and the splash generated when the wiping gas is sprayed onto the steel strip S is the tip of the upper surface of the wiping nozzle. It becomes easy to adhere to a part, and this causes a problem that uniform wiping is not performed in the width direction of the steel strip S, and the plating thickness becomes non-uniform in the width direction of the steel strip.

  An object of the present invention is to solve the above-mentioned problems and to provide a hot-dip gas wiping apparatus capable of preventing the adhesion of splash to a plated steel sheet or further suppressing the adhesion of splash to the top end portion of the wiping nozzle.

  The gist of the present invention for solving the above problems is as follows.

  (1) In a continuous galvanizing gas wiping apparatus provided with a wiping nozzle arranged oppositely across a steel strip in order to remove excess molten metal adhering to the surface of the steel strip pulled up continuously from a molten metal plating bath A splash receiving plate is provided above the wiping nozzle from the front end portion to the rear end portion of the wiping nozzle and provided with a weir at the upper edge of the front end portion at an appropriate interval from the wiping nozzle. A gas wiping apparatus for continuous hot dipping, wherein a shielding plate for shielding the upper part of the rear portion of the wiping nozzle is provided.

  (2) The continuous wiping gas wiping apparatus according to (1), further comprising gas supply means for supplying gas from the rear of the wiping nozzle to the front at a gap portion between the upper surface of the wiping nozzle and the splash receiving plate.

  (3) The continuous galvanizing gas wiping apparatus according to (1) or (2), wherein the tip of the splash receiving plate is disposed within a horizontal distance of 20 mm from the tip of the wiping nozzle.

  In this specification, the wiping nozzle rear refers to the side of the wiping nozzle that is away from the steel strip with reference to the steel strip surface, and the wiping nozzle forward refers to the side that approaches the steel strip.

  By using the apparatus of the present invention, it is possible to prevent splash adhesion to the plated steel sheet after wiping, and it is possible to suppress the splash adhesion on the top end portion of the wiping nozzle, so that the molten metal is excellent in appearance quality and uniformity in the width direction adhesion amount. A plated steel sheet can be manufactured.

  The inventors of the present invention provide a method for preventing the splash from adhering to the plated steel strip after wiping, and the splash generated when wiping gas is sprayed onto the steel strip is prevented from adhering to the tip of the upper surface of the wiping nozzle. The method was studied earnestly. As a result, the following was found.

  In the above-described apparatus, the reason why the splash adheres to the plated steel strip after wiping is considered as follows.

  In the apparatus of FIG. 2, the wiping gas is divided into a downward flow and an upward flow along the steel strip surface after colliding with the steel strip S. By forming an upward flow along the steel strip surface, a strong flow from the rear of the nozzle to the front (hereinafter referred to as a wiping gas accompanying flow) is generated on the upper surface of the wiping nozzle 5. The upward flow along the steel strip surface diffuses away from the steel strip surface as it rises.

  The downward flow along the steel strip surface of the wiping gas flows to the rear of the wiping nozzle 5 after colliding with the bath surface, and further flows to the upper portion of the wiping nozzle 5 by the occurrence of the wiping gas accompanying flow described above. In accordance with this flow, the splash generated on the bath surface is carried to the upper portion of the wiping nozzle 5, and some drops onto the upper surface of the wiping nozzle 5.

  Further, when the wiping gas is sprayed onto the steel strip S, a fine splash of molten metal is generated. This fine splash is once transported upward by the upward flow along the above-mentioned steel strip surface, but if there is the above-mentioned wiping gas accompanying flow, it becomes easy to be transported above the wiping nozzle 5 and merges in the middle. Or a larger splash, or falls onto the upper surface of the wiping nozzle 5 and merges there to become a larger splash.

  If there is a lot of splash carried over the wiping nozzle 5 (including the one in which fine splashes are combined), it adheres directly to the plated steel strip after wiping, or falls on the upper surface of the wiping nozzle 5 and then flows along with the wiping gas accompanying flow. It is wound up and adheres to the plated steel strip after wiping.

  In the apparatus shown in FIG. 3, a strong wiping gas accompanying flow exists on the upper surface of the wiping nozzle 21 as in the apparatus of FIG. 2. Even though the rectifying plate 22 is provided in the upper part of the wiping nozzle 21 behind the wiping nozzle 21, the strong wiping gas accompanying flow is generated on the upper surface of the wiping nozzle 21, so that the wiping gas flows downward along the steel strip surface. Cannot be reliably prevented from flowing after the wiping nozzle 21 after colliding with the bath surface and further flowing over the rectifying plate 22 and above the wiping nozzle 21. Therefore, the splash generated from the bath surface is carried over the wiping nozzle 21. Further, a fine splash of molten metal generated when the wiping gas is sprayed onto the steel strip S is also easily carried upward of the wiping nozzle 5.

  Also in the apparatus of FIG. 3, as in the apparatus of FIG. 2, the fine splash generated when the wiping gas is blown onto the steel strip S is carried above the wiping nozzle 21. Therefore, in the apparatus of FIG. 3, since the effect which reduces the splash conveyed above the wiping nozzle 21 is not enough, there is little effect which improves the problem of the splash adhesion to the plated steel strip after wiping.

  Furthermore, in the apparatus shown in FIG. 3, by providing the weir 23, the accompanying flow of the wiping gas does not flow smoothly on the top surface of the tip portion of the wiping nozzle 21, and the flow is disturbed, as shown in FIG. A fine splash 25 generated when wiping gas is sprayed onto the steel strip on the top surface of the tip of the wiping nozzle 21 is deposited and deposited, thereby making the amount of plating adhered in the width direction of the steel strip non-uniform.

  From the above, in order to prevent the splash from adhering to the plated steel strip after wiping, it is necessary to reduce the splash carried above the wiping nozzle. For that purpose, the wiping generated on the upper surface of the wiping nozzle 21 is required. It is considered effective to weaken the gas wake. Further, in order to prevent splash from adhering to the upper surface of the tip of the wiping nozzle 21 and resulting in non-uniform plating adhesion in the width direction of the steel strip, the accompanying flow of wiping gas flows smoothly at the upper surface of the tip of the wiping nozzle 21. It was considered necessary.

  The present invention has been made by further studying the aforementioned findings. Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view of an essential part of a continuous hot dipping plating apparatus in which a gas wiping apparatus according to an embodiment of the present invention is installed. In FIG. 1, the same reference numerals are given to parts having the same functions as those in FIG. In FIG. 1, 8 is a common gas header, 11 is a shielding plate, 12 is a splash receiving plate, 13 is a weir, and the snout 1 and the sink roll 4 are not shown. The wiping gas is supplied to the common gas header 8 and further supplied to the wiping nozzle 5 through the flexible tube 7.

  The shielding plate 11 is disposed above the wiping nozzle 5 rear part and in front of the common gas header 8 and the flexible pipe 7 (on the steel strip S side) with the upper side inclined obliquely rearward. The lower end of the shielding plate 11 is disposed so as to substantially contact the gas header 6 of the wiping nozzle 5, and the upper end is disposed so as to extend to the common gas header 8 portion, and the width thereof is substantially the same as the width of the wiping nozzle 5.

  The splash receiving plate 12 is installed above the wiping nozzle 5 so as to cover the upper surface of the wiping nozzle 5 so as to cover from the rear end portion to the front end portion of the wiping nozzle 5. A weir 13 for storing the splash dropped on the splash receiving plate 12 on the splash receiving plate 12 is installed at the edge of the plate.

  Further, a gas header 14 for blowing gas such as air into the gap between the splash receiving plate 12 and the upper surface of the wiping nozzle 5 and a nozzle 15 having a slit-like opening in the width direction of the wiping nozzle 5 are installed at the rear end of the splash receiving plate 12. Has been.

  By providing the shielding plate as described above, the airflow directed from the lower side of the wiping nozzle 5 to the front side of the steel strip S passing rearward is weakened, and the splash carried on the airflow can be reduced.

  Since the splash receiving plate 12 is disposed at a distance from the upper surface of the wiping nozzle 5, the wiping gas accompanying flow flows through the gap portion between the two. As a result, the generation of the wiping gas accompanying flow above the splash receiving plate 12 is suppressed, and the flow from the rear of the wiping nozzle 5 over the shielding plate 11 to the upper portion of the splash receiving plate 12 is weakened and is carried above the splash receiving plate 12. Splash is reduced. The fine splash generated when the wiping gas is blown onto the steel strip S is also reduced from being carried to the wiping nozzle 21.

  Further, the splash carried by the upper portion of the splash receiving plate 12 is weakened, so that the splash is easily dropped on the splash receiving plate 12, and the dropped splash is prevented from being rolled up. Therefore, splash adhesion to the plated steel strip after wiping is reduced.

  Further, the wiping gas accompanying flow flows through the splash receiving plate 12, the upper surface of the wiping nozzle 5 and the gap portion, so that the wiping gas is prevented from being disturbed at the upper surface portion of the wiping nozzle 5, and when the wiping gas is sprayed on the steel strip. Is prevented from adhering to the upper surface of the tip of the wiping nozzle 5.

  From the viewpoint of preventing the splash from falling on the upper surface of the wiping nozzle, the rear end of the splash receiving plate 12 is preferably arranged to extend to the rear end of the upper surface of the wiping nozzle 5, and the front end of the splash receiving plate 12 is arranged to receive the splash. The distance between the plate 12 and the steel strip S is within the range of the position where the distance is about +20 mm from the position where the distance between the tip of the wiping nozzle and the steel strip (the distance between the wiping nozzle and the steel strip) is the same. Preferably they are arranged. The width of the splash receiving plate 12 is almost the same as the width of the wiping nozzle 5. The distance between the splash receiving plate 12 and the wiping nozzle 5 is preferably about 5 to 50 mm, more preferably about 30 mm.

  From the viewpoint of preventing the splash from falling on the top surface of the wiping nozzle tip side and preventing the deposition of fine splash on the top surface of the wiping nozzle tip, the weir 13 is substantially parallel to the steel strip surface or upwards. The weir 13 is preferably 20 to 50 mm in height, and the weir 13 is preferably at a position within 10 mm from the edge of the splash receiving plate 12 on the tip side of the wiping nozzle 5. It is preferable to provide it.

  In the apparatus of FIG. 1, a nozzle 15 that supplies gas to a gap portion between the splash receiving plate 12 and the wiping nozzle 5 may be provided on the rear side of the wiping nozzle 5. By supplying the gas from the nozzle 15 to the gap portion between the splash receiving plate 12 and the wiping nozzle 5, the generation of the wiping gas accompanying flow generated above the splash receiving plate 12 is surely suppressed, and at the upper surface portion of the tip of the wiping nozzle 5. Wiping gas is less disturbed. As a result, the effect of improving the above-mentioned problem of splash adhesion to the plated steel strip after wiping and the problem of fine splash adhering to the top surface of the tip of the wiping nozzle 5 is more excellent, and the appearance quality and the amount of adhesion in the width direction are more uniform. A plated steel sheet can be manufactured. If the gas pressure supplied from the nozzle 15 is too high, the gas flow of the wiping nozzle 5 is disturbed and the effect of preventing splash adhesion is reduced. Therefore, the gas pressure supplied from the nozzle 15 is appropriately set to a pressure lower than the gas pressure supplied from the nozzle 15. That's fine.

  The apparatus of the present invention can be used as a gas wiping apparatus for molten metal plating for preventing splash adhesion to a plated steel sheet.

It is principal part sectional drawing of the continuous hot dipping equipment in which the gas wiping apparatus which concerns on embodiment of this invention was installed. It is a cross-sectional schematic diagram which shows the generation | occurrence | production mechanism of a splash defect. It is a figure which shows the principal part of the apparatus currently disclosed by patent document 1. FIG. It is a figure explaining the splash adhering to the wiping nozzle tip upper surface.

Explanation of symbols

S Steel strip 1 Snout 2 Plating tank 3 Plating bath (molten metal bath)
4 Sink roll 5, 21 Wiping nozzle 6 Gas header 7 Flexible pipe 8 Common gas header 11 Shielding plate 12 Splash receiving plate 13, 23 Weir 14 Gas piping 15 Nozzle 22 Current plate 24 Splash 25 Splash adhering to the upper surface of the nozzle tip

Claims (3)

In a continuous galvanizing gas wiping apparatus having a wiping nozzle disposed oppositely across a steel strip in order to remove excess molten metal adhering to the surface of the steel strip pulled up continuously from a molten metal plating bath, A splash receiving plate that covers from the front end to the rear end of the wiping nozzle and has a weir at the upper end of the wiping nozzle is provided at an appropriate interval from the wiping nozzle, and at the rear of the wiping nozzle A gas wiping apparatus for continuous hot dipping, wherein a shielding plate for shielding the upper part is provided. 2. The gas wiping apparatus for continuous hot dipping according to claim 1, further comprising gas supply means for supplying gas from the rear side of the wiping nozzle to the front side at a gap portion between the upper surface of the wiping nozzle and the splash receiving plate. The gas wiping apparatus for continuous hot dipping as claimed in claim 1 or 2, wherein the tip of the splash receiving plate is arranged within a horizontal distance of 20 mm from the tip of the wiping nozzle.

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