JP2009030142A - Apparatus for manufacturing hot-dip metal plated steel strip and method for manufacturing hot-dip metal plated steel strip - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for manufacturing a hot-dip metal plated steel strip and a method for manufacturing a hot-dip metal plated steel strip by which a hot-dip metal plated steel strip with excellent surface appearance can be stably manufactured while decreasing generation of splash. <P>SOLUTION: The apparatus for manufacturing a hot-dip metal plated steel strip controls a thickness of deposited metal by spraying a gas to a steel strip 2 which is continuously pulled up from a hot-dip metal plating tank 8, the gas blown through gas wiping nozzles 3 disposed as interposing the steel strip 2 above the hot-dip metal plating tank 8 and facing to both of the strip surfaces. The apparatus is equipped with: rolls 1 disposed in both sides of the steel strip 2 in a noncontact state with the strip 2, below the plating bath surface and above a support roll 5 in the bath, wherein the roll 1 disposed in a non-contact state with the strip 2 is driven to rotate in an opposite direction on the face opposing to the strip to the advance direction of the strip. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a manufacturing apparatus for a molten metal plated steel strip and a method for manufacturing a molten metal plated steel strip capable of reducing molten metal splash scattering in a molten metal plating process.

  In a continuous hot dipping process or the like, generally, as shown in FIG. 5, the steel strip 2 is immersed in a molten metal plating bath 7 filled in the plating tank 8, and the direction is changed by the sink roll 6. After the step of pulling the steel strip vertically upward, the steel provided oppositely across the steel strip 2 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. A gas wiping device is provided to control the amount of molten metal deposition (plating deposition amount) by jetting pressurized gas from the gas wiping nozzle 3 extending in the band width direction onto the steel strip to squeeze excess molten metal. It has been.

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

  The gas wiping nozzle 3 is usually longer than the width of the steel strip, that is, extends beyond the width end of the steel strip 2 in order to cope with various widths of the steel strip and at the same time shift in the width direction when the steel strip is pulled up. ing. In such a gas wiping apparatus, a so-called splash is generated in which molten metal falling below the steel strip is scattered due to the turbulence of the jet impinging on the steel strip 2, 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, As the line speed increases, the initial adhesion amount immediately after passing through the plating bath of the steel strip increases, so to control the plating adhesion amount within a certain range, the wiping gas pressure must be set to a higher pressure, As a result, the splash is greatly increased and good surface quality cannot be maintained.

  In order to solve the above problems, the amount of excess molten metal accompanying the steel strip is reduced to some extent until it reaches the gas wiping nozzle from the molten metal plating tank, and the initial adhesion amount immediately after passing through the plating bath is reduced. The method is disclosed as follows.

  In Patent Document 1, a molten metal squeeze member is provided between the support roll in the plating solution and the gas wiping nozzle in a non-contact manner on both surfaces of the steel strip, and after removing excess plating, the plating thickness is increased by gas wiping. In the adjusting device, the shape of the molten metal squeezing member is preferably a rectangular shape or a cylindrical body having an introduction portion whose distance from the front and back surfaces of the steel strip becomes wider at the lower end. A molten metal plating apparatus is disclosed in which the position over the liquid level is most desirable.

In Patent Document 2, a blade scraping device inclined with respect to the steel strip is provided on both surfaces of the steel strip on the surface of the plating solution to remove excess plating, and then the plating thickness is adjusted with a gas wiping nozzle. In the apparatus, a molten metal plating apparatus characterized in that a portion of the blade closest to the steel strip has a roundness with a diameter of 30 mm or less is disclosed.
JP 2004-76082 A JP 2005-15837 A

  However, in the method disclosed in Patent Document 1, when the molten metal drawing member extends above the plating bath surface or above and below the plating solution surface, the molten metal finally removed by gas wiping flows down, A liquid pool is formed in the gap between the steel strip and the molten metal squeezing member, and the distance from the height of the liquid reservoir to the gas wiping is short, resulting in a small squeezing effect. Also, the molten metal squeezing member There is a problem that the metal solidified by adhering to the surface adheres to the steel strip and causes surface defects. On the other hand, even when the molten metal squeezing member is arranged in the plating tank, the steel strip 2 and the molten metal squeezing member as shown in FIG. Since the flow path gradually narrows between 21, the molten metal concentrates and flows, the flow velocity increases locally, and the plating throttling effect is reduced.

  Further, in the method disclosed in Patent Document 2, even if the blade is inclined and the steel strip tip is rounded, a liquid pool is formed at the upper end as in Patent Document 1, and from there to gas wiping. As a result, the aperture effect is reduced.

  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 to provide a plating steel strip manufacturing facility.

  In addition, the present invention provides a method for producing a steel strip that can stably produce a molten metal-plated steel strip that reduces the occurrence of splash and has an excellent surface appearance, both at normal plate speed and during high-speed plate feeding. The task is to do.

  When installing the molten metal restricting member for removing excess molten metal between the sink roll and the gas wiping nozzle, the present inventors have a short distance between the liquid pool position and the gas wiping position as described above. As a result, there arises a problem that the amount of surplus plating cannot be reduced, so that it was concluded that it is best to install the molten metal drawing member below the plating solution surface. However, if the cross-sectional shape of the molten metal squeezing member is the same as the prior art, the plating squeezing effect is small. Therefore, in order to effectively reduce the amount of molten metal accompanying the steel strip coming out of the plating tank, a detailed flow analysis is performed using a water model device that simulates the flow of molten metal around the molten metal throttle member. It was. As a result, it is the so-called accompanying flow that flows in the direction of the steel strip in the vicinity of the surface of the steel strip that affects the amount of molten metal that is lifted accompanying the steel strip. I understood it.

  Based on the above knowledge, the present inventors have made extensive studies on the shape of a molten metal drawing member for removing excess molten metal associated with the steel strip. The invention having the following characteristics has been completed with the idea of arranging a roll that rotates in a direction opposite to the traveling direction of the steel strip by contact.

  [1] For the steel strip that is continuously pulled up from the molten metal plating tank, the thickness of the deposited metal is controlled by blowing gas from the gas wiping nozzle that is placed on both sides of the steel strip above the molten metal plating tank. In a manufacturing apparatus for a molten metal-plated steel strip, a molten metal squeeze roll disposed below the plating bath surface and above the support roll in the bath on both sides of the steel strip in a non-contact manner with the steel strip, An apparatus for producing a molten metal-plated steel strip, characterized in that the roll is driven so that the direction of rotation at the closest position to the steel strip is opposite to the direction of travel of the steel strip.

  [2] In the apparatus for manufacturing a molten metal-plated steel strip according to [1], a steel strip passing speed Vp [m / sec], a molten metal squeeze roll diameter D [m], a molten metal squeeze roll rotational speed Vr [rad] / Sec], and the closest distance S [mm] between the steel strip and the molten metal squeeze roll satisfies the following formula (1).

  [3] The molten metal squeeze roll arranged in non-contact with the steel strip is characterized in that the roll diameter at both ends in the steel strip width direction is larger than the roll diameter in the central portion in the steel strip width direction [1] Or the manufacturing apparatus of the molten metal plating steel strip as described in [2].

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

  According to the present invention, since the plating thickness can be adjusted by gas wiping after the excess plating metal attached to the steel strip is reduced by the molten metal squeezing roll provided in the plating bath, the amount of splash can be greatly reduced. In addition, in the prior art, when the plate passing speed is increased, the amount of splash is greatly increased. However, according to the present invention, even if the plate passing speed is significantly increased, the occurrence of splash can be suppressed, and there is no surface defect. It is possible to manufacture the belt while maintaining high productivity.

  Embodiments of the present invention will be described below with reference to the drawings. In the following drawings, the same reference numerals are given to parts having the same functions as the parts shown in the already described drawings, and the description thereof is omitted. FIG. 1 is a cross-sectional view showing an embodiment of an apparatus for producing a molten metal plated steel strip of the present invention. In FIG. 1, 1 is a molten metal squeeze roll for removing excess molten metal accompanying the steel strip. The molten metal squeeze roll 1 is disposed on both sides of the steel strip 2 below the bath surface and above the in-bath support roll 5, and is installed at a position away from the steel strip surface by a predetermined distance. The molten metal squeezing roll 1 is driven so as to rotate in the direction opposite to the traveling direction of the steel strip at a position closest to the steel strip. FIG. 2 is a view for explaining the flow of molten metal in the vicinity of the molten metal squeezing roll of FIG. 1 and in the vicinity of the steel strip passing through the molten metal squeezing roll.

  If the rotating direction of the molten metal squeezing roll 1 is controlled as described above, the forced flow 12 in the opposite direction is generated even if the accompanying flow 11 accompanying the progress of the steel strip 2 is generated. The accompanying flow 11 of the steel strip 2 passing between the rolls 1 and 1 can be greatly suppressed, and the amount of excess molten metal accompanying the steel strip pulled up from the plating bath can be reduced. The molten metal squeezing roll 1 is parallel to the in-bath support roll 5.

  Next, a specific control method of the molten metal squeeze roll 1 for obtaining an actual effect was examined. As shown in FIG. 3, the steel plate 2 has a sheet passing speed of Vp [m / sec], a molten metal squeeze roll 1 has a diameter of D [m], a rotational speed of Vr [rad / sec], and the steel strip 2 and the molten steel. When the closest distance of the metal squeeze roll 1 is S [mm], the effective influence range of the flow generated by the rotation of the molten metal squeeze roll 1 can be estimated to be about 10 mm from the outer peripheral surface of the roll by a water model experiment. It has been found that the following formula (1) should be satisfied in order to reduce the excess molten metal accompanying the steel strip pulled up on the bath.

  The larger the right side of Equation (1), the more the effect of reducing the amount of excess molten metal associated with the steel strip can be improved.

  The molten metal squeezing roll 1 may be brought close to the steel strip 3 to such an extent that it does not generate scuffing (usually about 3 mm).

  FIG. 4 is a view showing the shape of the molten metal squeezing roll 1 in the steel strip width direction. (A) is the same diameter in the steel strip width direction full length. Splash which becomes a problem when performing gas wiping is usually generated at the edge of the steel strip. Therefore, if the excess molten metal at the edge of the steel strip can be reduced more, the splash reduction effect becomes higher. From Formula (1), since the right side of Formula (1) becomes large, so that the distance S of the steel strip side end part of a steel strip and a roll becomes small, a molten metal squeeze roll like (a) is steel strip width direction full length. Even if the steel strip cannot be brought close to the steel strip, it is possible to make the distance between the roll and the steel strip closer by increasing the roll diameter only at the edge portion in the steel strip width direction. At that time, as shown in (b), a certain range of the central portion of the roll may be a constant diameter, and the outer side may be a tapered crown roll in which the roll diameter is increased in a tapered shape. Thus, a radial crown roll in which the roll diameter is increased with a certain curvature from the center of the roll, or a combination thereof may be used. Alternatively, other forms than the above may be used.

  In the apparatus of FIG. 1, the in-bath support roll 5 is disposed on both sides of the steel strip 2, but the in-bath support roll 5 may be disposed on one side of the steel strip 2. In this case, the position of the molten metal squeeze roll 1 arranged on the side where the in-bath support roll 5 is not arranged is higher than the in-bath support roll 5 in which the vertical position is arranged on one side of the steel strip 2. Should also be above.

  The apparatus for producing a hot-dip galvanized steel strip shown in FIG. 1 was installed in a continuous hot-dip galvanizing line, and a hot-dip galvanized steel strip production experiment was conducted. The molten metal squeeze rolls are opposed to both sides of the steel strip, and a servo motor that rotates each roll is installed on the end of the frame extended from the position control device by the servo motor provided on the machine side, and directly connected to this servo motor. did. With such a structure, the distance from the steel strip can be easily controlled, and the rotational speed of the molten metal squeeze roll can be arbitrarily set.

  In the continuous hot dip galvanizing line, the distance between the bath surface and the upper end of the in-bath support roll on the side close to the bath surface was 80 mm. The diameter of the central part was fixed at 50 mm, and the distance between the bath surface and the roll center was fixed at 35 mm. The length of the molten metal squeeze roll in the width direction of the steel strip was set to 2000 mm corresponding to the gas wiping nozzle.

The galvanized steel strip production conditions are as follows: the slit gap of the gas wiping nozzle is 0.8 mm, the distance between the gas wiping nozzle and the steel strip is 7 mm, the nozzle height from the molten zinc bath is 400 mm, and the molten zinc bath temperature is 460 ° C. The size was 0.8 mm thickness × 1.2 m width, and the amount of plating was 45 g / m ^{2 on} one side. Table 1 shows the other manufacturing conditions, molten metal squeeze roll conditions, and the results of investigation of the amount of splash generated that is a product quality index. 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.

  Examples 1 to 4 are flat molten metal squeezed rolls whose diameter does not change in the roll width direction as shown in FIG. 4A, and the distance S to the steel strip and the rotational speed Vr are changed. In any of the examples, compared to the case of the comparative example 1 which is the current operation mode (conventional device), the splash occurrence rate is decreased, and the effect is more remarkable as the right side of the formula (1) is larger. there were.

  Example 5 is a case of a taper crown roll in which the roll center is flat and the roll diameter increases toward both ends as shown in FIG. 4B. In this example, even if the distance between the roll center portion (width direction center portion) and the steel strip is 9 mm, the steel strip end portion can be close to about 6 mm, and the right side of the formula (1) at the steel strip end portion is Between Example 3 and 4. Splash incidence was also a result.

  In Examples 6 and 7 and Comparative Example 2, the plate passing speed was increased to 4.0 m / s. In Comparative Example 2, splash occurred frequently and the operation was impossible. , 7, it became possible to operate at a quality level better than the current example of the plate passing speed of 2.5 m / s (Comparative Example 1).

  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. Since the apparatus of the present invention can suppress the occurrence of splash even at the time of high-speed plate feeding, it can be used as an apparatus for manufacturing a molten metal plated steel strip excellent in surface appearance while maintaining high productivity.

  Moreover, the manufacturing method of the steel strip of this invention can be utilized as a manufacturing method of the hot-dip metal plating steel strip which reduces generation | occurrence | production of a splash and is excellent in surface appearance.

It is sectional drawing which shows one Embodiment of the manufacturing apparatus of the molten metal plating steel strip of this invention. It is a figure which shows the flow of the molten metal of the steel strip vicinity which passes the molten metal squeeze roll periphery and the molten metal squeeze roll part of the manufacturing apparatus of the molten metal plating steel strip of this invention. It is the figure used for description of the control method of the molten metal squeeze roll of the manufacturing apparatus of the molten metal plating steel strip of this invention. It is a top view explaining the roll shape of the molten metal squeeze roll of the manufacturing apparatus of the molten metal plating steel strip of this invention. It is sectional drawing which shows the manufacturing apparatus of a general molten metal plating steel strip. FIG. 6 is a view of a molten metal squeezing member described in Patent Document 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Molten metal squeeze roll 2 Steel strip 3 Gas wiping nozzle 4 Bath support roll 5 In-bath support roll 6 Sink roll 7 Molten metal plating bath 8 Plating tank 11 Accompanied flow 12 along with steel strip progression Generated by rotation of molten metal squeeze roll To flow 21 Molten metal throttle member

Claims (4)

Molten metal that controls the thickness of the deposited metal by blowing gas from a gas wiping nozzle that is placed opposite to both sides of the steel strip above the molten metal plating bath against the steel strip that is continuously pulled up from the molten metal plating bath In the apparatus for producing a plated steel strip, a molten metal squeeze roll disposed below the plating bath surface and above the support roll in the bath on both sides of the steel strip without contact with the steel strip is provided. An apparatus for manufacturing a hot-dip metal-plated steel strip, wherein the rotating direction at the closest position to the strip is driven so as to be opposite to the traveling direction of the strip. The apparatus for producing a molten metal-plated steel strip according to claim 1, wherein the steel strip passing speed Vp [m / sec], the molten metal squeeze roll diameter D [m], and the molten metal squeeze roll rotational speed Vr [rad / sec]. An apparatus for producing a molten metal-plated steel strip, characterized in that the closest distance S [mm] between the steel strip and the molten metal squeeze roll satisfies the following formula (1).

The molten metal squeeze roll arranged in non-contact with the steel strip has roll diameters at both ends in the steel strip width direction larger than the roll diameter at the central portion in the steel strip width direction. The manufacturing apparatus of the molten metal plating steel strip of description. A method for producing a molten metal-plated steel strip, comprising performing molten metal plating on the steel strip using the apparatus for producing a molten metal-plated steel strip according to any one of claims 1 to 3.

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