JP2010215929A - Equipment for manufacturing hot-dip metal coated steel strip and method for manufacturing hot-dip metal coated steel strip - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide equipment for manufacturing a hot-dip metal coated steel strip and a method for manufacturing a hot-dip metal coated steel strip, in which a hot-dip metal coated steel strip having an excellent surface appearance can be stably manufactured while reducing generation of splashes both at a normal passing speed and at a fast passing speed. <P>SOLUTION: The equipment for manufacturing a hot-dip metal coated steel strip controls the plating deposition amount on the surface of a steel strip by blowing air through a wiping nozzle 1 onto the surface of a steel strip 3 continuously pulled up from a hot-dip metal coating bath, wherein an auxiliary nozzle 2 is disposed below the wiping nozzle 1 and inside the steel strip edge, forming predetermined angles with respect to the advancing direction of the steel strip and to the steel strip surface in such a manner that the direction of gas injection is downward from the center in the width direction of the steel strip to the edge of the strip as well as approaching the strip surface, and a gas is injected from the auxiliary nozzle 2 to the steel strip surface. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention reduces the occurrence of molten metal splash in the hot dipping process at both normal plate passing speed and high speed plate passing, and can stably produce a hot dipped steel strip with excellent surface appearance. The present invention relates to a metal-plated steel strip manufacturing facility and a method for manufacturing a molten metal-plated steel strip.

  In a continuous hot dipping process or the like, as shown in FIG. 4, the steel strip 3 is generally immersed in a plating bath 8 filled with molten metal and changed in direction by a sink roll 7. After the step of pulling upward, the steel strip width provided facing this steel strip 3 so that the molten metal adhering to the steel strip surface has a predetermined plating thickness uniformly in the plate width direction and the plate longitudinal direction. There is provided a gas wiping device that jets pressurized gas from the wiping nozzle 1 extending in the direction onto the steel strip, squeezes excess molten metal, and controls the amount of adhesion of the molten metal (plating amount). .

  In order to stabilize the steel strip traveling position in the gas wiping section, the support roll 6 is usually disposed in the plating bath below the bath surface above the sink roll 7 and is necessary when alloying treatment is performed. Accordingly, the support roll 5 is installed above the wiping nozzle 1.

  The wiping nozzle 1 is usually longer than the steel strip width, that is, extending to the outside of the width end of the steel strip 3 in order to cope with various steel strip widths and at the same time to shift 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 below the steel strip is scattered by disturbance of the jet that has collided with the steel strip 3, and the surface quality of the steel strip is degraded.

  Moreover, in order to increase the production amount in the continuous process, the steel plate passing speed may be increased. However, in the case of controlling the coating amount by the gas wiping method in the continuous hot dipping process, due to the viscosity of the molten metal, Since the initial adhesion amount (lifting amount) immediately after passing through the plating bath of the steel strip increases as the steel strip passage speed increases, the wiping gas pressure must be increased to control the plating coverage within a certain range. It must be set, which greatly increases splash and makes it impossible to maintain good surface quality.

  In order to solve the above-mentioned problem, a method for reducing excess molten metal to some extent by injecting gas into a steel strip before reaching the gas wiping portion from the molten metal plating tank is disclosed as follows.

  In Patent Document 1, as shown in FIG. 5, a gas is jetted from an auxiliary nozzle 12 provided in parallel with the wiping nozzle 11 directly below the wiping nozzle 11 to the steel strip 13 to remove excess metal adhering to the steel strip 13. In addition, a method for attenuating the flow of the wiping gas 14 flowing down along the surface of the steel strip is disclosed.

  In Patent Document 2, as shown in FIG. 6, a gas is injected from the auxiliary nozzle 16 disposed above the edge of the steel strip above the wiping nozzle 11 at an angle in the center direction of the steel strip. A method of removing surplus metal adhering to 13 is disclosed.

  In Patent Document 3, as shown in FIG. 7, gas is injected from the side nozzle (auxiliary nozzle) 17 provided on the extension line in the width direction of the steel strip 13 toward the edge of the steel strip 13 to adhere to the steel strip 13. A method for removing the excess metal and reducing the edge overcoat is disclosed.

JP-A-7-150327 JP-A-6-256923 JP-A-6-158261

  However, in the method disclosed in Patent Document 1, the molten metal that is squeezed by the wiping nozzle 11 and flows down on the steel strip surface is dammed by the gas from the lower auxiliary nozzle 12, and the splash increases excessively. Moreover, the adhesion of the molten metal to the wiping nozzle 11 body was severe, and it could not withstand the operation.

  In the method disclosed in Patent Document 2, the injection gas pressure from the auxiliary nozzle 16 has to be increased to the extent that it penetrates the gas jet from the wiping nozzle 11, and the excess metal at the edge of the steel strip was removable. However, since the gas flow velocity reaching the plating bath surface increased instead, a large amount of bath surface splash was generated, and as a result, splash defects could not be suppressed. Moreover, the apparatus which moves an auxiliary nozzle to the width direction according to a steel strip width is required.

  In the method disclosed in Patent Document 3, gas is injected from the side nozzle 17 that moves in accordance with the plate width, but the gas from both side nozzles 17 interferes at the steel strip center portion and is very strong. It was found that a disturbance was generated, resulting in a large amount of splash.

  In view of the above-mentioned problems, the present invention is a molten metal that can stably produce a molten metal-plated steel strip that reduces the occurrence of splash and is excellent in surface appearance at both normal plate speed and high-speed plate passing. It is an object of the present invention to provide a plating steel strip manufacturing facility and a method for manufacturing a molten metal plated steel strip.

  The present inventors made extensive studies. In particular, edge splash that occurs at the edge of the steel strip is a problem in operation, and it is a very effective means to remove excess zinc before reaching the wiping nozzle, but the molten metal that flows down As a result, the mechanism that opposes the flow of the gas and the wiping gas increases the splash at another point, and it is understood that a sufficient effect cannot be obtained. It was found that the state of occurrence of splash of molten metal changes greatly depending on the orientation. And the invention which has the following characteristics was completed.

[1] In a manufacturing apparatus for a molten metal plated steel strip that controls the amount of plating on the surface of the steel strip by blowing a gas from a wiping nozzle onto the surface of the steel strip that is continuously pulled up from the molten metal plating bath.
Inside the steel strip edge below the wiping nozzle, the steel strip traveling direction and the steel strip surface are predetermined so that the gas injection direction is downward from the steel strip width direction center toward the steel strip edge and approaches the steel strip surface. An apparatus for producing a molten metal-plated steel strip, characterized in that an auxiliary nozzle formed with an angle is provided and gas is injected from the auxiliary nozzle onto the steel strip surface.

  [2] An apparatus for manufacturing a molten metal-plated steel strip according to [1], wherein the auxiliary nozzle is a slit nozzle having a rectangular exit cross section.

  [3] In [1] or [2], the predetermined angle is 5 to 30 degrees between the gas injection direction and the steel strip surface when the auxiliary nozzle is viewed from above the auxiliary nozzle, An apparatus for producing a molten metal-plated steel strip, wherein an angle between a gas injection direction and a steel strip traveling direction when viewed from the vertical direction is 20 to 70 °.

  [4] A method for producing a molten metal-plated steel strip, comprising using the apparatus for producing a molten metal-plated steel strip according to any one of [1] to [3].

  According to the present invention, the surplus plating metal is caused to flow down onto the plating bath over the steel strip by the auxiliary nozzle, so that the flow of the molten metal or the flow of the wiping gas that is wiped down by the wiping nozzle flows down. Since the plating thickness can be adjusted by gas wiping after reducing excess plating metal without generating a flow, the amount of splash generated is greatly reduced at both normal plate feed speed and increased plate feed speed. In addition, it is possible to stably manufacture a plated steel strip having no surface defects while maintaining high productivity.

It is a front view which shows one Embodiment of the molten metal plating steel strip manufacturing apparatus of this invention. It is a side view which shows one Embodiment of the hot-dip metal plating steel strip manufacturing apparatus of this invention. It is a figure explaining the gas injection direction of an auxiliary nozzle, (a) shows the angle of the gas injection direction when it sees from a perpendicular direction on a steel strip surface, and a steel strip advance direction, (b) shows an auxiliary nozzle from the upper part. The angle between the gas injection direction and the steel strip surface when viewed is shown. It is a figure which shows a general molten metal plating apparatus. It is a figure which shows the auxiliary nozzle of patent document 1. FIG. It is a figure which shows the auxiliary nozzle of patent document 2. FIG. It is a figure which shows the auxiliary nozzle of patent document 3. FIG.

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

  One Embodiment of the hot-dip metal plating steel strip manufacturing apparatus of this invention is shown in FIG.1 and FIG.2. 1 is a schematic front view, and FIG. 2 is a side view. 1 and 2, 1 is a wiping nozzle, 2 is an auxiliary nozzle, and 3 is a steel strip.

  The auxiliary nozzle 2 is disposed below the wiping nozzle 1, sandwiches the steel strip 3, and is disposed on the inner side of both steel strip edges and at a predetermined distance from the steel strip surface.

Since it is effective for the auxiliary nozzle 2 to remove surplus metal at the edge portion of the steel strip with a surface, it is desirable that the auxiliary nozzle 2 is a slit nozzle having a rectangular exit cross section. From the viewpoint of suppressing the injection gas amount as much as possible, the slit gap of the slit nozzle is preferably 1 to 3 mm, the length is 50 to 200 mm, and the injection gas pressure is preferably 0.02 to 0.4 kgf / cm ² .

  The auxiliary nozzle 2 has a predetermined angle with the steel strip traveling direction and the steel strip surface so that the gas injection direction is downward from the steel strip width direction center toward the steel strip edge and approaches the steel strip surface.

  The predetermined angle is such that the angle between the gas injection direction and the steel strip traveling direction (angle α in FIG. 3A) when viewed from the vertical direction on the steel strip surface is 20 to 70 °, and the auxiliary nozzle 2 is opened from above. The angle between the gas injection direction and the steel strip surface when viewed (angle β in FIG. 3B) is preferably 5 to 30 °. With such an arrangement, surplus plating metal flows down on the steel strip in the direction of the plating bath or is scattered in a small amount outside the plate path, so that the surplus before wiping nozzle injection is performed without degrading the quality of the steel strip. Plating metal can be reduced.

  The angles α and β are the angles between the gas injection direction center (in the slit nozzle, the gas injection direction at the injection port longitudinal direction center and the slit gap center) and the steel strip traveling direction, and the auxiliary nozzle is viewed from above. The angle between the gas injection direction and the steel strip surface.

  If the predetermined angles α and β are out of the above range, the molten metal flowing down will be blocked, the gas velocity toward the bath surface will be too high, or the splash of molten metal will be blown out of the line. It is not preferable.

  The slit nozzle is basically arranged with the longitudinal direction of the injection port parallel to the steel strip surface for ease of installation, etc., but the longitudinal direction of the injection port is inclined about 5 ° with respect to the steel strip surface. May be.

  The height direction position of the auxiliary nozzle is preferably 50 to 300 mm below the wiping nozzle 1 and 100 mm or more above the bath surface. This is due to the following reason. When the position of the auxiliary nozzle 2 is less than 50 mm from the wiping nozzle, interference between the gas jet from the wiping nozzle and the gas jet from the auxiliary nozzle 2 becomes intense, and splash is likely to occur, and the generated splash adheres to the auxiliary nozzle 2. It becomes easy to do. When the position of the auxiliary nozzle is less than 100 mm from the bath surface, the gas sprayed from the auxiliary nozzle 2 tends to generate splash from the bath surface. In the slit nozzle, it is preferable that all of the longitudinal direction of the injection port is within the above range.

  Steel strips of various sizes are passed through the molten metal plated steel strip manufacturing apparatus. The gas sprayed from the auxiliary nozzle 2 needs to be sprayed onto the steel strip surface. The installation position of the auxiliary nozzle 2 in the width direction of the steel strip is set such that when the auxiliary nozzle 2 is installed at the above angle, the extension line of the auxiliary nozzle center line intersects the edge position of the minimum width of the steel strip to be passed through. That's fine. Even if the plate steel strip width changes, the gas injected from the auxiliary nozzle 2 can be sprayed onto the steel strip surface. If the auxiliary nozzle 2 is too close to the steel strip, splash from the wiping nozzle tends to adhere, and if it is too far away, the gas jet from the auxiliary nozzle 2 weakens and the effect of removing excess plating metal is reduced. It is preferable to install it 20 to 100 mm away from the surface. The distance between the auxiliary nozzle 2 and the steel strip surface is a vertical distance between the steel strip side end of the auxiliary nozzle 2 and the steel strip surface. The slit nozzle is preferably arranged so that the overall length in the jet port longitudinal direction satisfies the above.

  Since the auxiliary nozzle of the present invention injects gas from the steel strip center toward the edge, if the gas hits the steel strip edge at the minimum width, even a steel strip having a wider width will face outward. Excess plating metal can be poured and removed onto the molten metal bath. Excess plating metal can be reduced without generating a flow that opposes the flow of the molten metal that is wiped down by the wiping nozzle or the flow of the wiping gas. Even if the steel strip width changes, there is no need to change the position in the width direction of the auxiliary nozzle, so there is no need to install a device for adjusting the position in the width direction of the auxiliary nozzle.

  When the hot-dip galvanized steel strip is manufactured using the hot-dip metal-plated steel strip manufacturing apparatus of the present invention, the amount of splash is greatly reduced at both the normal plate feed speed and the plate feed speed. It is possible to stably produce a defect-free plated steel strip while maintaining high productivity.

The manufacturing conditions of the hot dip galvanized steel strip were as follows: slit gap of wiping nozzle 0.9 mm, wiping nozzle-steel strip distance 8 mm, wiping nozzle height 450 mm from hot dip zinc bath, hot dip zinc bath temperature 460 ° C. The size was 0.8 mm thickness × 1.4 m width, and the amount of plating was 50 g / m ^{2 on} one side. The gas supplied to the auxiliary nozzle was provided with one conduit on one side of the steel strip, which was connected to the auxiliary nozzles at both edges. The injection gas pressure of the auxiliary nozzle can be adjusted with a pressure gauge and an adjustment valve located at a position outside the line just before bifurcating, 0.15 kgf / cm ² in Example 1, and 0.3 kgf / cm in Example 2. ² .

  The auxiliary nozzle of the present invention is a flat slit nozzle having a slit gap of 2 mm and a length of 100 mm, and is directed to the steel strip edge toward the steel strip edge with respect to the vertical downward direction (of FIG. 3 (a)). The angle α) is 60 °, the angle with the steel strip surface (angle β in FIG. 3 (b)) is 10 °, the slit longitudinal direction is parallel to the steel strip surface, and is 200 mm from the outermost edge of the production steel strip. Thus, it was installed at a position 30 mm from the steel strip, 200 mm below the wiping nozzle.

  In the side nozzle of the comparative example, the spray angle was set to 45 ° downward, and the spray pressure was set to the same pressure as that of the wiping nozzle.

  Table 1 shows the results of investigating the amount of splash generated, which is an index of other manufacturing conditions and product quality. The splash generation amount is a 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.

  Under the condition of a plate passing speed of 2.5 m / s, in Comparative Example 1 in which the auxiliary nozzle was not used, the splash occurrence rate was 1.20%. In Comparative Example 3 using the auxiliary nozzle described in Patent Document 3, the splash occurrence rate was only slightly reduced compared to Comparative Example 1. In contrast, in Example 1 using the auxiliary nozzle of the present invention, the splash occurrence rate decreased by 90% or more compared to Comparative Example 1 and 88% compared to Comparative Example 3.

  In the condition where the plate passing speed is increased to 4.0 m / s, in Comparative Example 2 in which the auxiliary nozzle is not used and in Comparative 4 in which the auxiliary nozzle described in Patent Document 3 is used, the splash occurrence rate is at a level where it cannot be operated. However, Example 2 using the auxiliary nozzle of the present invention was capable of operation at a splash rate of the same level as Comparative Example 1 where the auxiliary nozzle was not used at a plate passing speed of 2.5 m / s.

  According to the present invention, even at a normal plate speed and even when the plate speed is increased, the amount of splash is greatly reduced, and a plated steel strip without surface defects is stably manufactured while maintaining high productivity. It becomes possible to do.

1, 11 Wiping nozzle 2, 12, 16 Auxiliary nozzle 3, 13 Steel strip 5, 6 Support roll 7 Sink roll 8, 18 Molten metal plating bath 14 Wiping gas 17 Side nozzle (auxiliary nozzle)

Claims (4)

In the manufacturing apparatus of the molten metal plating steel strip, which controls the amount of plating on the surface of the steel strip by blowing gas from the wiping nozzle onto the surface of the steel strip that is continuously pulled up from the molten metal plating bath.
Inside the steel strip edge below the wiping nozzle, the steel strip traveling direction and the steel strip surface are predetermined so that the gas injection direction is downward from the steel strip width direction center toward the steel strip edge and approaches the steel strip surface. An apparatus for producing a molten metal-plated steel strip, characterized in that an auxiliary nozzle formed with an angle is provided and gas is injected from the auxiliary nozzle onto the steel strip surface. The molten metal plated steel strip manufacturing apparatus according to claim 1, wherein the auxiliary nozzle is a slit nozzle having a rectangular exit cross section. The predetermined angle is such that the angle between the gas injection direction and the steel strip surface when viewing the auxiliary nozzle from above the auxiliary nozzle is 5 to 30 °, and the gas injection direction and steel when viewed from the vertical direction on the steel strip surface. The apparatus for producing a hot-dip metal-plated steel strip according to claim 1 or 2, wherein an angle with the belt traveling direction is 20 to 70 °. The manufacturing method of the hot-dip metal plating steel strip characterized by using the hot-dip metal-plating steel strip manufacturing apparatus as described in any one of Claims 1-3.

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