JP5444730B2 - Molten metal plating steel strip production equipment - Google Patents

Description

  The present invention relates to an apparatus for manufacturing a molten metal-plated steel strip that can reduce molten metal splash scattering in a hot-dip plating process.

  In a continuous hot dipping process or the like, as shown in FIG. 7, the steel strip S is generally immersed in a hot metal plating bath 8 in the hot metal bath 9 and the direction is changed by the sink roll 7. After the step of pulling the steel strip vertically upward, the steel provided facing the steel strip S 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, usually, a support roll 5 in the bath is disposed below the bath surface above the sink roll 7, and when alloying 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 steel strip width, that is, extends beyond the width end of the steel strip S, 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. 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 collides with the steel strip S, 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 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 significantly increasing the splash and not being able to maintain good surface quality.

  In order to solve the above problem, a method of reducing the amount of initial adhesion immediately after passing through the plating bath by reducing the amount of excess molten metal accompanying the steel strip to some extent until it reaches the wiping nozzle from the molten metal plating tank 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.

  Patent Document 2 discloses an apparatus for adjusting a plating thickness by gas wiping after removing surplus plating by providing a blade scraping device that is inclined with respect to the steel strip on both surfaces of the steel strip at the place where it comes out of the plating solution surface. Thus, there is disclosed a molten metal plating apparatus characterized in that the portion of the blade closest to the steel strip has a roundness with a diameter of 30 mm or less.

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 belt 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. There is a problem that the solidified and solidified metal adheres to the steel strip and causes surface defects. On the other hand, even when the molten metal squeezing member is disposed in the plating tank, the flow path gradually narrows by making the distance from the steel strip wider at the lower end of the molten metal squeezing member. The flow velocity increases locally and the throttle 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 small.

  Therefore, in the methods of Patent Documents 1 and 2, the effect of reducing the initial adhesion amount immediately after passing through the plating bath is not sufficiently exhibited, so that the effect of reducing the occurrence of molten metal splash in the gas wiping portion is insufficient.

  In consideration of the above problems, the present invention reduces the amount of initial adhesion immediately after passing through the plating bath, reduces the occurrence of splash even at normal plate feeding speed and at high plate feeding speed, and has excellent surface appearance. It is an object of the present invention to provide a molten metal plated steel strip manufacturing facility capable of stably manufacturing a metal plated steel strip.

  When installing the molten metal throttle member for removing excess molten metal between the sink roll and the gas wiping, 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 is 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 plating accompanying the steel strip coming out of the plating tank, detailed flow analysis is performed using a water model device that simulates the flow of molten metal around the molten metal throttle member. went. 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. The molten metal squeezing member is provided with a portion covering a bath surface side of 1/4 or more of the outer peripheral surface of the outer peripheral surface and a portion facing the steel strip, and further, the flow of the molten metal is applied to the steel strip facing portion of the molten metal squeezing member. The invention has been devised to provide a control mechanism, and the invention having the following features has been completed.

(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 a wiping nozzle that is disposed opposite to both sides of the steel strip above the molten metal plating tank. In the manufacturing equipment for hot metal plating steel strip,
Under the bath surface, on both sides of the steel strip above the support roll in the bath, a roll coating portion formed so as to cover at least 1/4 of the outer peripheral surface of the support roll in bath on the bath surface side, and the steel strip disposed above the roll coating portion A steel strip facing portion formed so as to face the steel strip, the steel strip facing portion and the roll covering portion have a width equal to or greater than a steel strip width, and the steel strip facing portion is a steel strip of the roll covering portion. The molten metal squeezing member connected to the side end portion is disposed in non-contact with the steel strip and the support roll in the bath, and at least part of the steel strip facing surface of the steel strip facing portion, the steel strip end portion An apparatus for producing a molten metal-plated steel strip, characterized by having a flow straightening structure that changes the flow of molten metal in the direction opposite to the steel strip travel and from the outside of the steel strip toward the center of the steel strip.

  (2) The flow straightening structure that changes the flow direction of the molten metal at the end of the steel strip in the direction opposite to the progress of the steel strip and from the outside of the end of the steel strip toward the center of the steel strip, The apparatus for producing a molten metal-plated steel strip according to (1), comprising at least one continuous groove or protrusion formed so as to have a large distance from the center line in the width direction.

  (3) The groove or protrusion has at least one end of the steel strip in any width of the steel strip within the range from the maximum width of the through plate when viewed from the direction perpendicular to the steel strip surface. The apparatus for producing a molten metal-plated steel strip according to (2), wherein the apparatus is formed so as to run on a groove or a projection of the metal strip.

  (4) The molten metal squeezing member further has a rectifying structure that changes the flow of the molten metal from the roll end toward the center in the roll width direction on at least a part of the roll facing surface of the roll coating portion. The apparatus for producing a molten metal-plated steel strip according to any one of (1) to (3), wherein:

  (5) The flow straightening structure that changes the flow of the molten metal from the center in the roll width direction to the roll end side is at least one line formed so that the distance from the center in the roll width direction decreases toward the roll rotation direction. (4) The molten metal plated steel strip manufacturing apparatus as described in (4) above.

  According to the present invention, even if the steel strip width is changed by the molten metal squeezing member provided under the plating bath surface, after the excess molten metal amount accompanying the steel strip is reduced over the entire steel strip width, the plating thickness is reduced by the gas wiping nozzle. Can be adjusted, so the amount of splash can be greatly reduced. In addition, according to the present invention, the amount of splashing can be greatly reduced even when the plate passing speed is significantly increased, so that it is possible to manufacture a molten metal plated steel strip without surface defects while maintaining high productivity. It becomes possible.

It is sectional drawing which shows one Embodiment of the hot-dip metal plating steel strip manufacturing apparatus of this invention. It is sectional drawing which shows one Embodiment of the molten metal throttle member used for the molten metal plating steel strip manufacturing apparatus of this invention. An embodiment of a groove formed on a steel strip facing surface of a steel strip facing portion and a roll facing surface of a roll coating portion of a molten metal drawing member used in the apparatus for manufacturing a molten metal plated steel strip of the present invention, and a stream line of the molten metal Indicates. The molten metal stream | line drawing member when a molten-metal drawing | shrink member provided with a steel strip opposing part and a roll coating | coated part does not have a groove | channel on the steel strip opposing surface of a steel strip opposing part and the roll opposing surface of a roll coating | coated part is shown. It is a figure explaining another embodiment of the cross-sectional shape of the molten metal restricting member used for the molten metal plating steel strip manufacturing apparatus of this invention. It is a figure explaining the groove | channel provided in the steel strip opposing surface of the steel strip opposing part of the molten metal restricting member used in the Example, and the roll opposing surface of a roll coating | coated part. It is sectional drawing which shows a general molten metal plating steel strip manufacturing apparatus.

  Hereinafter, embodiments of the present invention will be described 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 the apparatus for producing a molten metal plated steel strip of the present invention. In FIG. 1, 1a and 1b are molten metal drawing members installed in the plating bath, having a length equal to or greater than the steel strip width in the steel strip width direction, and sandwiching the steel strip S above the support roll 5 in the bath. In both sides, it is installed at a position away from the surface of the steel strip by a predetermined distance.

  FIG. 2 is a longitudinal sectional view showing an embodiment of a molten metal squeezing member used in the apparatus for manufacturing a molten metal plated steel strip according to the present invention. In FIG. 2, the arrow in the bath is the streamline of the molten metal. In FIG. 2, molten metal squeezing members 1 a and 1 b are opposite to a steel strip formed so as to face a roll coating portion formed to cover the bath surface side of the outer peripheral surface of the support roll 5 in the bath. A part. The steel strip side end of the roll coating portion is connected to the lower portion of the steel strip facing portion. The support rolls 5 in the bath are arranged on both sides of the steel strip so as to be in contact with the steel strip so that their vertical positions are different from each other. In the present embodiment, the lengths of the steel strip facing portions of the molten metal squeezing members 1a and 1b arranged on both sides of the steel strip S are different from each other. The steel strip opposing portions of the molten metal squeezing members 1a and 1b are provided so as to be parallel to the steel strip surface.

  In the molten metal squeezing members 1a, 1b, a flow 11 accompanying the in-bath support roll 5 is generated between the in-bath support roll 5 and the molten metal squeezing members 1a, 1b. When the flow 11 is generated, even if the accompanying flow 12 is generated along with the progress of the steel strip S, the steel strip S is provided near the molten metal throttle members 1a and 1b between the steel strip S and the molten metal throttle members 1a and 1b. A compulsory flow 13 is generated in a direction opposite to the traveling direction of, and the accompanying flow 12 is greatly suppressed. Thereby, the excessive molten metal amount accompanying the steel strip S pulled up from a plating bath is reduced significantly.

  In order to enhance the effect, the roll coating portion is preferably formed so as to cover at least ¼ of the bath surface side of the outer peripheral surface of the support roll 5 in the bath. Here, the length in which the roll coating portion covers the support roll 5 in the bath is a cross section perpendicular to the support roll center line in the bath, and the molten metal squeezing members 1a and 1b are projected toward the center of the support roll 5 in the bath. Sometimes it is the projected arc length of the molten metal squeezing member on the outer peripheral surface of the support roll 5 in the bath. The present inventors have applied for a patent for the invention of a molten metal plated steel strip manufacturing apparatus including the molten metal squeezing members 1a and 1b configured as described above (Japanese Patent Application No. 2007-229781).

  Furthermore, in the molten metal squeezing members 1a and 1b of the present embodiment, grooves are formed on the steel strip facing surface of the steel strip facing portion and the roll facing surface of the roll covering portion. FIG. 3 shows that the arc-shaped roll covering portion of the molten metal squeezing member 1a is developed flat on the lower portion of the steel strip facing portion, and the grooves formed on the steel strip facing surface and the roll facing surface are perpendicular to the steel strip surface. 1 shows an embodiment and a streamline of molten metal when viewed. In FIG. 3, 2 is a groove. The dotted line arrows in FIG. 3 indicate streamlines of the molten metal between the steel strip and the molten metal squeezing member and between the support roll and the molten metal squeezing member in the bath. The same groove is formed in the molten metal squeezing member 1b, and the flow is the same.

  The groove 2 is continuously formed on both sides of the steel strip width direction center line 10 of the steel strip facing surface of the molten metal squeezing members 1a and 1b from the end portion on the side opposite to the steel strip of the roll coating portion to the upper end of the steel strip facing surface. Then, one or a plurality of strips are formed symmetrically so that the distance from the center line 10 in the width direction of the steel strip increases toward the traveling direction of the steel strip.

  The operation of the grooves of the molten metal squeezing members 1a and 1b will be described.

  FIG. 4 shows the steel strip facing surface and the roll facing surface when the arc-shaped roll coating portion of the molten metal squeezing member 1a is developed flat on the lower portion of the steel strip facing portion and viewed from the direction perpendicular to the steel strip surface. The flow lines of the molten metal near the molten metal squeezing member 1a between the steel strip and the molten metal squeezing member 1a and between the support roll in the bath and the molten metal squeezing member 1a when there are no grooves are shown. The same flow occurs in the molten metal squeezing member 1b. If there are no grooves on the steel strip facing surface and the roll facing surface of the molten metal squeezing members 1a and 1b, as shown in FIG. 4, in the portion where the steel strip is located, between the steel strip S and the molten metal squeezing members 1a and 1b. A forced flow 13 in the direction opposite to the traveling direction of the steel strip S is generated in the vicinity of the molten metal restricting members 1a and 1b, and the accompanying flow 12 can be greatly suppressed. When the upward flow 14 is generated and flows into the end portion of the steel strip, the squeezing effect at the end portion of the steel strip is reduced.

  When grooves as shown in FIG. 3 are provided in the steel strip facing surfaces and roll facing surfaces of the molten metal squeezing members 1a and 1b, the flow of molten metal near the molten metal squeezing member 1a between the steel strip and the molten metal squeezing member. As shown by a dotted arrow in FIG. 3, the flow 13 is directed from the outer side of the steel strip end toward the center of the molten metal drawing member in the direction opposite to the traveling direction of the steel strip. By forming such a flow, even in the vicinity of the end portion of the steel strip, the direction from the outer side of the end portion of the steel strip is directed to the center of the molten metal drawing member in the direction opposite to the traveling direction of the steel strip.

  By this flow 13, it is possible to suppress the upward flow 14 generated by the roll rotation in the bath in the portion where there is no steel strip from flowing from the outside to the inside at the end of the steel strip. The effect can be maintained up to the end of the steel strip. As a result, a sufficient squeezing effect is obtained over the entire width of the steel strip, and the plating thickness can be adjusted with the gas wiping nozzle after reducing the amount of excess molten metal over the entire width of the steel strip, greatly reducing the amount of splash generated. it can. Further, even if the plate passing speed is significantly increased, the amount of splash can be greatly reduced, and a hot-dip plated steel strip having no surface defects can be produced while maintaining high productivity.

  If the groove width is too narrow, the grooves formed on the steel strip facing surface and roll facing surface of the molten metal squeeze member will be blocked over time due to molten metal dross that adheres to and accumulates on the molten metal squeeze member. The groove width is desirably 10 mm or more and 200 mm or less, and the groove depth is desirably 10 mm or more and 100 mm or less. The groove width is more preferably 10 mm or more and 100 mm or less, and the groove depth is more preferably 10 mm or more and 50 mm or less. The pitch of the grooves is preferably 80 mm or more and 300 mm or less, and the angle of the grooves (in FIG. 3, the angle θ that the line indicating the grooves forms a vertical line) is preferably 20 to 85 degrees. The groove may not be a straight line, and may be a curve as long as the grooves do not intersect each other.

  The groove of the molten metal squeezing member is preferably formed continuously from the end of the roll facing surface of the roll coating portion on the side opposite to the steel strip to the upper end of the steel strip facing portion. It does not have to be continuous in parts. You may form only in the steel strip opposing part. Moreover, you may form in a part of steel strip opposing part.

  Steel strips of various widths are passed through the molten metal plated steel strip manufacturing apparatus. When viewed from a direction perpendicular to the steel strip surface, the groove has at least the steel strip end portion on the steel strip-facing surface in any width of the steel strip within the range from the maximum width of the through plate to the minimum width. If it is formed so as to run on a single groove, it is possible to obtain a drawing effect at the end of the steel strip in any width of the steel strip, and to reduce the amount of excess molten metal accompanying the steel strip over the entire width of the steel strip. it can.

  In the apparatus described above, a continuous groove is formed on the surface of the molten metal squeezing member facing the steel strip, but the same effect can be obtained by forming a continuous "projection" instead of the continuous groove. As for the size of the protrusion, the height is preferably 5 mm or more and 50 mm or less, but it should not contact the steel strip or the roll in the bath. Dimensions and shapes other than the height may be the same as the groove.

  The dimensions and shape of the molten metal squeezing member need to be determined as appropriate in consideration of the equipment to be applied and the sheet feeding speed of the steel strip.

  For example, in the shape as shown in FIG. 3, a steel strip traveling direction dimension of 10 to 300 mm (however, it should not protrude above the bath surface) can be used.

  In the shape as shown in FIG. 3, the distance between the roll coating portion of the molten metal squeezing member and the support roll 5 in the bath is preferably 100 mm or less, and more preferably 50 mm or less. If it is larger than 100 mm, the flow of the accompanying flow 11 becomes weak, so the flow 13 is not generated, and the effect of reducing the amount of excess molten metal accompanying the steel strip is reduced. Moreover, since the flow itself which reduces the excess molten metal amount accompanying a steel plate can be suppressed when it becomes 50 mm or less, the effect of reducing the excessive molten metal amount accompanying a steel strip becomes still larger. The distance between the roll coating portion of the molten metal squeezing member and the support roll 5 in the bath may be reduced as long as the roll coating portion does not contact the support roll 5 in the bath.

  Further, the distance between the steel strip facing portion of the molten metal drawing member and the steel strip is preferably 100 mm or less, and more preferably 50 mm or less. When it becomes larger than 100 mm, the flow 13 in the direction opposite to the traveling direction of the steel strip does not affect the accompanying flow 12 accompanying the progress of the steel strip, and the effect of reducing the amount of excess molten metal accompanying the steel strip is reduced. Moreover, since the flow itself accompanying a steel strip can be suppressed when it becomes 50 mm or less, the effect of reducing the excessive molten metal amount accompanying a steel strip becomes still larger. The distance between the steel strip facing portion of the molten metal drawing member and the steel strip may be small as long as the steel strip facing portion does not contact the steel strip.

  It is preferable to install the upper end of the steel strip facing portion so as to be positioned within 100 mm from the surface of the metal plating bath. When the distance from the bath surface is larger than 100 mm, the accompanying flow 12 is developed with the progress of the steel strip above the steel strip facing portion, and the effect of reducing the amount of excess molten metal accompanying the steel strip is reduced. When the upper end of the steel strip facing portion is on the metal plating bath surface, there is a problem that excess molten metal that has been wiped adheres to the upper end of the steel strip facing portion and damages the steel plate.

  The molten metal squeezing member is not limited to that shown in FIG. For example, as shown in FIG. 5, the steel strip facing portion of the molten metal drawing member may have a shape inclined with respect to the steel strip surface in the steel strip traveling direction. Further, the distance between the roll coating portion and the support roll 5 in the bath may not be constant.

  The hot-dip galvanized steel strip production apparatus shown in FIG. 1 was installed in the continuous hot-dip galvanizing line, and a hot-dip galvanized steel strip production experiment was conducted. The vertical offset between the support rolls in the bath arranged on both sides of the steel strip S is 100 mm, and the distance between the bath surface and the upper end of the support roll in the bath on the side close to the bath surface is 180 mm. The diameter of the support roll in the bath is φ300 mm.

  In Example 1, Example 2, Comparative Example 2, and Comparative Example 4, the molten metal squeezing member provided with the steel strip facing portion and the roll coating portion shown in FIG. 2 was used. The molten metal squeezing member has a length of 2000 mm in the steel strip width direction, and the bath surface of the outer peripheral surface of the in-bath support roll 5 formed such that the distance between the support roll 5 in the bath and the molten metal squeeze members 1a and 1b is 30 mm. It is formed so that the distance between the arc-shaped roll covering portion covering the side and the steel strip and the steel strip facing portion of the molten metal squeezing member 1a, 1b is constant 20 mm, and the distance between the upper end and the bath surface is 30 mm. did. The length of the arc-shaped roll coating part was the length covering exactly half a circle of the support roll in the bath.

  Comparative Example 2 and Comparative Example 4 do not form grooves on the steel strip facing surface and the roll facing surface, and Examples 1 and 2 are arc-shaped roll facing at the bottom of the steel strip facing surface of the molten metal drawing member. As shown in FIG. 6 in which the portion is developed in a plane, a continuous groove having a width of 530 mm, a width of 530 mm, a pitch of 150 mm, and a groove width of 20 mm and a depth of 10 mm from the steel strip facing surface of the molten metal drawing member 1a Were applied to both sides of the center line in the steel strip width direction of the molten metal drawing member. Furthermore, only one groove each having a gap of 500 mm between the grooves at the lower end of the steel strip facing surface was applied to only the steel strip facing surface at the same pitch inside. From the steel strip facing surface of the molten metal squeezing member 1b to the roll facing portion, a continuous groove having a width of 460 mm and a pitch of 80 mm and a groove width of 20 mm and a depth of 10 mm is provided. 7 pieces were given to both sides of each. Further, only one groove each having an interval of 720 mm between the grooves at the lower end of the steel strip facing surface was provided only on the steel strip facing surface at the same pitch. The angle (angle θ in FIG. 6) formed by the groove with the steel band width direction center line of the molten metal squeezing member is 34 degrees for both the molten metal squeezing members 1a and 1b. The dimensions 220 mm and 565 mm described in FIG. 6 are the length of the steel strip facing surface and the length of the roll facing surface of the molten metal drawing member 1a.

The production conditions of the hot dip galvanized steel strip 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 hot dip zinc bath is 400 mm, and the hot dip 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 results of the investigation of the amount of splash generation, which is another production condition and 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 addition, the continuous hot-dip galvanizing line in which the experiment was performed has a minimum width of the plate steel strip of 800 mm and a maximum width of 1600 mm. The groove formed in the steel strip facing surface of the molten metal drawing member used in Example 1 and Example 2 is a steel strip of any width within the above range when viewed from the direction perpendicular to the steel strip surface. The steel strip end portion is also formed so as to run on at least one groove formed on the steel strip facing surface. In the steel strip having a width of 1.2 m, the end portion of the steel strip passes over a single groove formed on the steel strip facing surface.

  Under the condition that the plate passing speed was 2.5 m / sec, in Comparative Example 1 (conventional example) having no molten metal drawing member, the splash occurrence rate was 1.40%. Comparative Example 2 using a molten metal drawing member having an arc-shaped roll covering portion and a steel strip facing portion parallel to the steel strip surface and having no grooves on the steel strip facing surface and the roll facing surface is compared with Comparative Example 1. The incidence of splash was reduced by approximately 84%. Example 1 using a molten metal drawing member having an arc-shaped roll covering portion and a steel strip facing portion parallel to the steel strip surface and having grooves in the steel strip facing surface and the roll facing surface is compared with Comparative Example 2. The incidence of splash was reduced by approximately 64%.

  Under the condition that the plate passing speed was 4.0 m / sec, in Comparative Example 3 without the molten metal drawing member, the splash occurrence rate was 25.32%. Comparative Example 4 using a molten metal drawing member having an arc-shaped roll covering portion and a steel strip facing portion parallel to the steel strip surface and having no grooves on the steel strip facing surface and the roll facing surface is compared to Comparative Example 2. The incidence of splash decreased by approximately 97%. Example 2 using a molten metal squeezing member provided with an arc-shaped roll covering portion and a steel strip facing portion parallel to the steel strip surface and having grooves in the steel strip facing surface and the roll facing surface is compared to Comparative Example 4. The splash generation rate was reduced by about 66%, and operation was possible at a lower splash generation rate than Comparative Example 1 in which the plate was passed at 2.5 m / s without using a molten metal drawing member.

  As described above, under the same condition of the plate passing speed, the roll-shaped roll covering portion and the steel strip facing portion parallel to the steel strip surface are provided, and the groove defined in the present invention is provided on the steel strip facing surface and the roll facing surface. When the molten metal squeezing member was used (Examples 1 and 2), when the molten metal squeezing member was not used (Comparative Example 1 and Comparative Example 3), the steel parallel to the arc-shaped roll coating portion and the steel strip surface Compared with the case where a molten metal squeezing member having a band facing portion and having no grooves on the steel band facing surface and the roll facing surface is used (Comparative Example 2 and Comparative Example 4), the splash occurrence rate is low.

  As the plate passing speed increases, the splash occurrence rate increases in any case, but the increase rate of the splash occurrence rate = [splash occurrence rate when the plate passing speed is 4.0 m / sec] / [plate passing speed is 2]. Defined by the occurrence rate of splash at 5 m / sec], an arc-shaped roll covering portion and a steel strip facing portion parallel to the steel strip surface are provided, and the groove defined in the present invention on the steel strip facing surface and the roll facing surface When the molten metal squeezing member is used, when the molten metal squeezing member is not used, an arc-shaped roll covering portion and a steel strip facing portion parallel to the steel strip surface are provided. The rate of increase in the splash occurrence rate is lower than when a molten metal squeezing member having no groove on the opposing surface is used. From this, it can be seen that the use of a molten metal squeezing member provided with grooves defined in the present invention has an effect of suppressing the occurrence of splash when the plate passing speed is increased.

  The apparatus of the present invention can be used as a manufacturing apparatus for a hot-dip 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.

S Steel strip 1, 1a, 1b Molten metal squeezing member 2 Molten metal squeezing member 3 Gas wiping nozzle 4 On-bath support roll 5 In-bath support roll 7 Sink roll 8 Molten metal plating bath 9 Molten metal bath 10 Molten metal squeezing member steel Centerline 11 in the width direction of the steel strip on the opposite surface of the strip Flow 12 associated with the support roll in the bath 12 Concomitant flow 13 associated with the progress of the steel strip 14 Flow 14 generated between the steel strip and the molten metal throttle member in the direction opposite to the steel strip travel direction Flow generated in the part without the steel strip of the molten metal throttle member

Claims (5)

Molten metal plating that controls the thickness of the deposited metal by blowing gas from a 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 steel strip production equipment,
Under the bath surface, on both sides of the steel strip above the support roll in the bath, a roll coating portion formed so as to cover at least 1/4 of the outer peripheral surface of the support roll in bath on the bath surface side, and the steel strip disposed above the roll coating portion molten metal diaphragm member Ru comprises formed a strip facing portion so as to face provided on said roll cover portion and the steel strip facing portion has a width greater than the strip width, the steel strip facing portion Is connected to the steel strip side end of the roll coating portion, and the molten metal drawing member is disposed in non-contact with the steel strip and the support roll in the bath, and the steel strip facing surface of the steel strip facing portion at least a portion, having a rectifying structure for flow of molten metal in the steel strip width direction end portion in the opposite direction of the steel strip traveling, and to flow from the outer strip end portion in the width direction in the steel strip width direction center of the An apparatus for producing a hot-dip metal-plated steel strip. The rectifying structure that changes the flow direction of the molten metal at the end of the steel strip width direction in the direction opposite to the steel strip travel direction and from the outside of the steel strip width direction end portion toward the center of the steel strip width direction is the steel strip travel direction. The apparatus for producing a hot-dip metal-plated steel strip according to claim 1, comprising at least one continuous groove or protrusion formed so that the distance from the center line in the width direction of the steel strip increases.   In the steel strip having any width within the range from the maximum width of the sheet passing plate to the minimum width when viewed from the direction perpendicular to the steel strip surface, the groove or protrusion has an end portion of the steel strip on at least one groove or The molten metal plated steel strip manufacturing apparatus according to claim 2, wherein the apparatus is formed so as to run on the protrusion.   The molten metal squeezing member further has a rectifying structure that makes the flow of the molten metal flow from the roll end toward the center in the roll width direction on at least a part of the roll facing surface of the roll coating portion. The molten metal plated steel strip manufacturing apparatus according to any one of claims 1 to 3.   The flow straightening structure that makes the flow of the molten metal flow from the center in the roll width direction toward the roll end side is at least one continuous line formed so that the distance from the center in the roll width direction decreases toward the roll rotation direction. The apparatus for manufacturing a molten metal-plated steel strip according to claim 4, comprising a groove or a protrusion.

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