JP5194612B2 - Manufacturing apparatus for molten metal plated steel strip and method for manufacturing molten metal plated steel strip - Google Patents

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 hot dipping process.

  In a continuous hot dipping process or the like, generally, as shown in FIG. 5, the steel strip 3 is immersed in a molten metal plating bath 8 filled in the plating tank 9 and the direction is changed by the sink roll 7. After the step of pulling the steel strip vertically upward, the steel provided opposite to the 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. A gas wiping device that controls the amount of molten metal deposited (plating deposited amount) by jetting pressurized gas onto the steel strip from the gas wiping nozzle 4 extending in the band width direction is provided. It has been.

  In order to stabilize the running position of the steel strip in the gas wiping unit, the in-bath support roll 6 is usually arranged below the bath surface above the sink roll 7, and when alloying or the like is performed, gas is used as necessary. A bath support roll 5 is installed above the wiping nozzle 4.

  The gas wiping nozzle 4 is usually longer than the width of the steel strip, that is, extending beyond the width end of the steel strip 3 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 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, 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 problem, the amount of excess molten metal that accompanies the steel strip is reduced to some extent by the time it reaches the gas wiping nozzle from the molten metal plating tank, and the initial adhesion amount immediately after passing the plating bath is reduced. The method of placing 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 with the gas wiping nozzle. The shape of the molten metal squeezing member is preferably a rectangular shape or a cylindrical body having an introduction portion with a wider distance from the front and back surfaces of the steel strip toward the lower end, and the installation position of the molten metal squeezing member is There has been disclosed a molten metal plating apparatus in which a position extending over and under the plating solution surface is most desirable.

In Patent Document 2, a blade scraping device that is inclined with respect to the steel strip is provided on both surfaces of the steel strip on the surface of the plating solution, and after removing excess plating, 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 the gas wiping nozzle 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 pool to the gas wiping nozzle is short, resulting in a small squeezing effect. There was a problem that the metal fixed to the member and solidified 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 3 and the molten metal squeezing member as shown in FIG. 6 are formed by increasing the distance from the steel strip toward the lower end of the molten metal squeezing member. 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 throttle 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 surplus plating amount cannot be reduced. Therefore, 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 traveling direction of the steel strip in the vicinity of the surface of the steel strip that affects the amount of molten metal lifted along with the steel strip, and is effective as the flow is reduced. 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. It was conceived that a roll (hereinafter referred to as a molten metal squeezing roll) that rotates in the direction opposite to the direction of travel of the steel strip by contact and the installation of a current plate so as to cover this roll, and completed the invention having the following characteristics. It was.

  [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 squeezing 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, and the molten metal squeezed A baffle plate is installed to cover 1/2 or more of the outer peripheral surface on the bath surface side of the roll and on the steel strip side, and the molten metal squeeze roll has a rotation direction at a position closest to the steel strip as a steel strip traveling direction. An apparatus for producing a molten metal-plated steel strip, which is driven so as to be in the reverse direction.

  [2] In the apparatus for manufacturing a molten metal-plated steel strip according to [1], the steel strip passing speed Vp [m / sec], the diameter D [m] of the molten metal squeeze roll, and the rotational speed Vr of the molten metal squeeze roll [Rad / sec], the closest distance S [mm] between the steel strip and the molten metal squeezing roll, the closest distance Sr [mm] between the molten metal squeezing roll and the rectifying plate, and the molten metal squeezing roll circumferential length L [ mm] satisfies the following formulas (1) and (2) and satisfies the following formulas (1) and (2).

[3] A method for producing a molten metal-plated steel strip, comprising performing the molten metal plating on the steel strip using the apparatus for producing a molten metal-plated steel strip according to [1] or [2].

  According to the present invention, a molten metal squeeze roll that rotates in a direction opposite to the direction of travel of the steel strip in a non-contact manner with the steel strip, and a surplus plating metal that accompanies the steel strip is reduced by providing a current plate to cover the roll. Since the plating thickness can be adjusted after gas wiping, 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. FIG. 1 is a diagram showing an embodiment of a manufacturing apparatus for a hot-dip metal-plated steel strip according to the present invention. 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. In FIG. 1, 1 is a molten metal squeeze roll, and 2 is a current plate. The effect | action which removes the excess molten metal accompanying a steel strip is show | played by the molten metal squeezing roll 1 and the baffle plate 2. FIG.

  The molten metal squeeze roll 1 is disposed with a steel strip in between, and is installed at a position away from the surface of the steel strip by a predetermined distance. The rectifying plate 2 is installed under the bath surface above the molten metal squeezing roll 1 so as to cover the roll with a gap from the molten metal squeezing roll 1. 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 squeeze roll in FIG. 1 and in the vicinity of the steel strip passing through the molten metal squeeze roll.

  When the rotational direction of the molten metal squeeze roll 1 is controlled as described above, the molten metal squeeze roll 1 generates a forced flow 12 in the opposite direction to the accompanying flow 11 even when the accompanying flow 11 is generated as the steel strip advances. Therefore, the accompanying flow 11 can be suppressed. The rectifying plate 2 can develop the accompanying flow 12 generated by the rotational drive of the molten metal squeezing roll 1 by limiting it to the region between the molten metal squeezing roll 1 and the rectifying plate 2. Since the flow to be generated for suppressing the accompanying flow 11 is a flow in a direction opposite to the accompanying flow 11 as shown by the flow 12 in FIG. 2, it is possible to add the rectifying plate 2 in addition to rotating the roll alone. The effect is greater. Further, accompanying the flow 12 by the molten metal squeezing roll 1, a flow in the opposite direction to the accompanying flow 11 accompanying the progress of the steel strip is also generated above the rectifying plate 2. This flow also contributes to the suppression of the accompanying flow 11. As a result, the accompanying flow 11 is significantly 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, when the required length of the current plate 2 was examined, in order to sufficiently develop the flow 12, the current plate 2 was formed on the outer peripheral surface of the molten metal squeeze roll 1 on the bath surface side and on the steel strip side (FIG. 3). The arc AB of the quadrant OAB, where AO is perpendicular to the steel strip surface and BO is parallel to the steel strip surface), and the length of the rectifying plate 2 is As long as the molten metal squeeze roll is covered, the longer the effect is, the better the effect is. However, the outer peripheral surface of the molten metal squeeze roll 1 on the side opposite to the bath and the steel strip side (the arc AC of the quadrant OAC in FIG. 3). However, CO is parallel to the steel strip surface.) It was found that the portion should not be covered with the current plate 2.

  Next, a specific control method of the molten metal squeeze roll 1 and the current plate 2 for obtaining an actual effect was examined. In order to confirm the basic performance of the rectifying plate, the shape of the rectifying plate 2 is an arc having the same center as that of the molten metal squeeze roll 1, as shown in FIG. 3, and the plate passing speed of the steel strip is Vp [m / sec], the diameter of the molten metal squeezing roll 1 is D [m], the rotational speed is Vr [rad / sec], the closest distance between the steel strip 3 and the molten metal squeezing roll 1 is S [mm], and the molten metal squeezing roll 1 When the distance between the rectifying plate 2 is Sr [mm] and the peripheral length of the molten metal squeeze roll 1 covered by the rectifying plate 2 is L [mm], the bath surface side of the molten metal squeeze roll 1 and the steel strip 3 side In order to reduce the excess molten metal pulled up on the bath accompanying the steel strip 3 under the condition that the rectifying plate 2 is installed so as to cover more than half of the outer peripheral surface of the steel plate, the following formula (1) And it discovered that it should just satisfy | fill Formula (2).

  Here, the circumferential length L of the molten metal squeezing roll 1 covered by the rectifying plate 2 is obtained by projecting the rectifying plate 2 toward the center of the molten metal squeezing roll 1 in a cross section perpendicular to the molten metal squeezing roll center line. The projected arc length of the current plate on the outer peripheral surface of the molten metal squeeze roll 1.

  Further, the fact that the rectifying plate 2 covers the arc AB portion of the quadrant OAB in FIG. 3 means that the rectifying plate 2 is rectified on the outer peripheral surface of the molten metal squeezing roll 1 when the rectifying plate 2 is projected toward the center of the molten metal squeezing roll 1. This means that at least a part of the plate 2 is projected, and that the current plate 2 does not cover the arc AC of the quadrant OAC in FIG. 3, the current plate 2 is projected toward the center of the molten metal squeeze roll 1. This means that the rectifying plate 2 is not projected on the outer peripheral surface of the molten metal squeeze roll 1.

  Formula (2) means that the distance Sr between the molten metal squeezing roll 1 and the rectifying plate 2 is set to 5 times or less the closest distance S between the steel strip 3 and the molten metal squeezing roll. The larger the right side of the formula (1), the more the effect of reducing the amount of excess molten metal accompanying the steel strip can be improved.

  The molten metal squeezing roll 1 and the rectifying plate 2 may be brought close to the steel strip 3 to the extent that rubbing is not generated (usually about 3 mm).

  The rectifying plate 2 does not need to keep the distance from the molten metal squeezing roll 1 constant. Therefore, the shape of the current plate 2 is not limited to an arc shape. When the distance between the rectifying plate 2 and the molten metal squeezing roll 1 is not constant, the flow rate of the molten metal flowing between the rectifying plate 2 and the molten metal squeezing roll 1 is restricted by the portion where the distance is the narrowest. 2 and the closest distance Sr between the molten metal squeezing rolls 1 as a representative value, the effect of reducing the amount of excess molten metal can be evaluated.

  The shape of the rectifying plate 2 is not an arc as shown in FIG. 3, for example, an inverted L shape in which a horizontal portion and a vertical portion are connected as shown in FIG. 4A, a horizontal portion as shown in FIG. In the case of a shape in which the vertical portion and the inclined portion are connected, although the pressure drop is somewhat caused and the effect is reduced, the closest distance Sr between the molten metal squeezing roll 1 and the rectifying plate 2 and the rectifying plate 2 are used as the molten metal squeezing roll By applying the projected arc length L of the rectifying plate 1 on the outer peripheral surface of the molten metal squeeze roll 1 to the center (1) and the formula (2) when projected toward the center, the approximate effect can be calculated. Is possible.

  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 squeezing roll 1 is opposed directly 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 is directly connected to this servo motor. did. With such a structure, the distance to the steel strip can be easily controlled, and the rotational speed of the molten metal squeeze roll 1 can be arbitrarily set. The rectifying plate 2 is attached to a frame on which a servo motor is installed, and the distance between the steel strip side end of the rectifying plate 2 and the steel strip 3 is set to be the same as the distance between the molten metal squeeze roll 1 and the steel strip 3.

  In the above-mentioned 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, so that the diameter of the molten metal squeeze roll 1 ( D) was 50 mm, the distance between the bath surface and the molten metal squeeze roll center was fixed to 35 mm, and the closest distance (Sr) between the molten metal squeeze roll 1 and the current plate 2 was fixed to 2 mm. The shape of the rectifying plate 2 was an arc as shown in FIG. 3 (Examples 1 to 3) or an inverted L shape (horizontal direction 70 mm, vertical direction 50 mm; Example 4) shown in FIG. The length of the molten metal squeezing roll 1 and the current plate 2 in the steel strip width direction 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 squeezing 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.

  In Examples 1 and 2, the length (L) of the rectifying plate 2 covering the outer peripheral surface of the molten metal squeeze roll is different, but both are larger than Comparative Example 1 which is the current operation mode (conventional device). Splash reduction effect was obtained.

  In Example 3 and Comparative Example 2, the plate passing speed was increased to 4.0 m / s, and in Comparative Example 2 using the conventional apparatus, splash was frequently generated and operation was impossible. In Example 3, it was possible to operate at a quality level better than the current 2.5 m / s.

  Example 4 is the conditions which made the shape of the baffle plate 2 into an inverted L shape. Compared with Examples 1 and 2, the splash reduction effect was slightly inferior, but a significant splash reduction effect was obtained as compared with 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 vicinity of the molten metal squeeze roll and the baffle plate of the manufacturing apparatus of the molten metal plating steel strip of this invention, and the steel strip vicinity which passes a molten metal squeeze roll part. It is the figure used for description of the control method of the molten metal squeeze roll and the baffle plate of the manufacturing apparatus of the molten metal plating steel strip of this invention. It is sectional drawing which shows another embodiment of the baffle plate 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 Current plate 3 Steel strip 4 Gas wiping nozzle 5 On-bath support roll 6 In-bath support roll 7 Sink roll 8 Molten metal plating bath 9 Plating tank 11 Accompanied with progress of steel strip 12 By molten metal squeeze roll Generated flow 21 Molten metal throttle member

Claims (3)

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 in-bath support roll, on both sides of the steel strip in non-contact with the steel strip, and a bath of the molten metal squeeze roll A rectifying plate that covers at least half of the outer peripheral surface on the surface side and the steel strip side is installed, and the molten metal squeezing roll has a rotation direction at a position closest to the steel strip and a direction opposite to the steel strip traveling direction. An apparatus for producing a molten metal-plated steel strip, which is driven to be The apparatus for producing a molten metal-plated steel strip according to claim 1, wherein the steel strip passage speed Vp [m / sec], the diameter D [m] of the molten metal squeeze roll, and the rotational speed Vr [rad / rad] of the molten metal squeeze roll. sec], the closest distance S [mm] between the steel strip and the molten metal squeeze roll, the closest distance Sr [mm] between the molten metal squeeze roll and the rectifying plate, and the molten metal squeeze roll circumferential length L [mm] covered by the rectifying plate The manufacturing apparatus of the hot-dip metal plating steel strip characterized by satisfy | filling satisfying following formula (1) and Formula (2).

A method for producing a molten metal-plated steel strip, comprising performing the molten metal plating on the steel strip using the apparatus for producing a molten metal-plated steel strip according to claim 1 or 2.

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