CN111406125B

CN111406125B - Molten zinc bath equipment

Info

Publication number: CN111406125B
Application number: CN201980005952.3A
Authority: CN
Inventors: 入江祐辅; 川村三喜夫; 大野功太郎; 吉田晋平
Original assignee: Nippon Steel and Sumitomo Metal Corp
Current assignee: Nippon Steel Corp
Priority date: 2018-03-26
Filing date: 2019-03-18
Publication date: 2022-10-28
Anticipated expiration: 2039-03-18
Also published as: JP6624348B1; JPWO2019188503A1; WO2019188503A1; CN111406125A

Abstract

The invention provides a molten zinc bath facility having excellent bath replacement effects inside and outside a V-zone. The rectifying plate in the molten zinc bath has a plurality of plate-like rectifying fins (12) disposed between the snout (6) and the sink roll (3) and above the contact portion (Q) between the entry-side steel plate (5) which is the steel plate entering the molten zinc bath (2) and the sink roll (3). The plate-shaped flow straightener (12) is each configured to: an angle theta 2 of 45 DEG to 135 DEG is formed with respect to the surface of the entry-side steel plate (5), and a cross section parallel to the surface of the entry-side steel plate (5) forms an angle theta 1 of more than 0 DEG and less than 90 DEG with respect to the plate width direction of the entry-side steel plate (5).

Description

Molten zinc bath equipment

Technical Field

The present invention relates to a molten zinc bath facility used in a hot-dip galvanizing line for a steel sheet.

Background

The molten zinc bath facility used in the hot-dip galvanizing line of the steel sheet is the following facility: a sink roll and a backup roll are provided in a molten zinc bath, a steel sheet is caused to enter the molten zinc bath obliquely downward from a furnace nose, the advancing direction is changed to upward along the lower surface of the sink roll, the steel sheet is vertically pulled up from the molten zinc bath while being guided by the backup roll, and molten zinc is attached to the surface of the steel sheet during this time.

In order to stabilize the quality of a galvanized steel sheet, it is necessary to strictly control the Al concentration in the molten zinc bath. For example, if the Al concentration is too high, an alloying failure occurs, and if the Al concentration is too low, bottom dross (bottom dross) is generated and accumulated in the bath, and adheres to the steel sheet, thereby generating dross defects (dross defects).

Conventionally, the Al concentration in a molten zinc bath is adjusted by charging a small-sized ingot of a Zn — Al alloy from a specific portion. However, since the region, which is generally called "V-zone" surrounded by the steel sheet on the sink roll in the molten zinc bath is surrounded by the steel sheet, the substitution rate of the bath inside and outside the V-zone is poor, the bath is likely to stay, al is consumed by the passage of the steel sheet, and the Al concentration is likely to be relatively low. Therefore, it can be said that the region is a region in which bottom dross, which causes dross defects, is easily generated and accumulated.

Therefore, if the amount of the small-sized ingot of the Zn — Al alloy is increased so that the dross defect is not generated, the alloying defect is caused. Further, when a small ingot of Zn — Al alloy is charged into the V zone in order to eliminate the difference in Al concentration between the inside and outside of the V zone, alloying failure occurs due to local concentration of Al, or the work load of the operator increases due to an increase in the charged portion.

In view of the above, patent document 1 proposes a technique of arranging a rectifying plate in a V-zone above a sink roll to promote bath replacement inside and outside the V-zone. The rectifying plate of patent document 1 is a plate obtained by bending or curving a flat plate around its center line, and the center line is arranged along the direction of advancement of the steel sheet on the side of entering the molten zinc bath. An accompanying flow (accompanying flow) generated along the steel sheet entering obliquely downward on the inlet side of the sink roll collides with the sink roll to become an upward zinc flow, and the zinc flow is directed to the outside in the sheet width direction of the steel sheet by being in contact with the rectifying plate, and it is desired to promote bath replacement inside and outside the V region.

However, in this flow regulating plate, since the angle of the upward zinc flow with respect to the contact with the flow regulating plate is shallow, the rectifying effect of the upward flow toward the outside in the plate width direction is weak, and the decrease in the Al concentration in the V region cannot be sufficiently eliminated. Therefore, there is a problem that the effect of suppressing bottom ash is insufficient.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2016-156077

Disclosure of Invention

Problems to be solved by the invention

Accordingly, an object of the present invention is to solve the above-mentioned conventional problems and to provide a molten zinc bath facility excellent in bath replacement effect inside and outside a V-zone.

Means for solving the problems

The molten zinc bath facility according to the present invention, which has been completed to solve the above problems, includes: a molten zinc bath; and a molten zinc bath rectifying plate having a plurality of plate-like rectifying pieces disposed between the snout and the sink roll and above a contact portion between an entry-side steel plate and the sink roll, which is a steel plate on the side entering the molten zinc bath, in the molten zinc bath; the fairings are each configured to: an angle theta 2 of 45 DEG to 135 DEG is formed with respect to the surface of the entry-side steel plate, and a cross section parallel to the surface of the entry-side steel plate forms an angle theta 1 exceeding 0 DEG and lower than 90 DEG with respect to the plate width direction of the entry-side steel plate.

The angle θ 2 is preferably 60 ° to 120 °, and the angle θ 1 is preferably 20 ° to 60 °. The plurality of flow-straightening vanes are preferably symmetrical with respect to the center of the sink roll in the longitudinal direction.

Effects of the invention

According to the present invention, the upward zinc flow generated by the collision of the accompanying flow of the entry-side steel sheet with the sink roll and the accompanying flow of the sink roll can be efficiently rectified and converted into a fluid in the outer direction in the steel sheet width direction, and therefore, the bath replacement in the region surrounded by the steel sheet on the sink roll called V zone can be promoted, and the reduction in Al concentration in this region can be prevented. As a result, the amount of the slag in the molten zinc bath can be reduced, and defects in the hot-dip galvanized steel sheet caused by the slag can be suppressed.

Drawings

FIG. 1 is a schematic sectional view showing a molten zinc bath facility according to embodiment 1.

FIG. 2 is a plan view showing a main part of a molten zinc bath facility according to embodiment 1.

Fig. 3 is a view from III-III of fig. 1.

FIG. 4 is a view of a part of a rectifying plate and a steel sheet of a molten zinc bath seen from IV-IV of FIG. 3 in the direction of view.

Fig. 5 is a view from V-V of fig. 3.

FIG. 6 is a view illustrating the structure of a rectifying plate for a molten zinc bath according to embodiment 1.

FIG. 7 is a view illustrating the structure of a rectifying plate for a molten zinc bath according to embodiment 2.

FIG. 8 is a view illustrating the structure of a rectifying plate for a molten zinc bath according to embodiment 3.

FIG. 9 is a view illustrating the structure of a rectifying plate for a molten zinc bath according to embodiment 4.

FIG. 10 is a view illustrating the structure of a rectifying plate for a molten zinc bath according to embodiment 5.

FIG. 11 is a view illustrating the structure of a rectifying plate for a molten zinc bath according to embodiment 6.

Detailed Description

Embodiments of the present invention will be described below. FIG. 1 is a schematic cross-sectional view showing a molten zinc bath facility according to embodiment 1, FIG. 2 is a plan view showing a main part thereof and is a view taken along the direction II-II in FIG. 1, FIG. 3 is a view taken along the direction III-III in the main part, FIG. 4 is a view in which a part of a rectifying plate 8 and a steel plate 5 of the molten zinc bath are viewed from the direction IV-IV in FIG. 3, and FIG. 5 is a view taken along the direction V-V in FIG. 3. In FIG. 1, 1 is a molten zinc bath, 2 is a molten zinc bath in the molten zinc bath, 3 is a sink roll provided in the

molten zinc bath

2, and 4 is a backup roll. The steel sheet 5 is introduced into the molten zinc bath 2 obliquely downward from the snout 6, passes around the lower surface of the sink roll 3, and is pulled upward vertically while being guided by the backup rolls 4. Further above the sink roll 3, a region 7 surrounded by the steel plate 5, which is referred to as a V-zone, is formed.

In the following, a rectangular coordinate system is set in the drawing for the sake of explanation. The x-axis is set in the horizontal direction orthogonal to the axis 30 of the sink roll 3, and the y-axis is set in the vertical direction. The vertical direction upper side is set as the y-axis positive direction. The z-axis is set in the horizontal direction along the axis 30 of the sink roll 3. Further, an X axis is provided along the surface of the steel sheet 5 on the side of entering the molten zinc bath 2 (hereinafter also referred to as an entering-side steel sheet 5) in parallel with the direction of advance of the entering-side steel sheet 5, and the opposite side to the direction of advance of the entering-side steel sheet 5 is set as the positive X axis direction. A Y axis orthogonal to the surface of the entry side steel plate 5 is provided, and in a region 7 called a V-zone surrounded by the steel plate 5, the side away from the surface of the entry side steel plate 5 is set as the positive Y axis direction. The Z-axis is set along the axis 30 of the sink roll 3.

The molten zinc bath 2 is a bath containing Al in addition to zinc. As described above, the Al concentration in the molten zinc bath 2 is adjusted by charging small ingots of Zn — Al alloy from specific portions, but since the region 7 called the V region surrounded by the steel sheet 5 on the sink roll 3 is surrounded by the steel sheet 5 on both sides, the substitution rate of the bath 2 is poor, the Al concentration is lowered, and bottom dross is generated. In the present embodiment, the molten zinc bath rectifying plate 8 is disposed between the snout 6 and the sink roll 3 and above the contact portion Q between the intake-side steel sheet 5 and the sink roll 3. The molten zinc bath rectifying plate 8 may be supported inside the molten zinc bath 1 by a member connected to a holder for supporting the sink roll 3, for example.

As shown in fig. 1, in a region 7 called a V zone, an upward zinc flow 11 is generated by collision of an accompanying flow 9 entering the side steel plate 5 with an accompanying flow 10 accompanying rotation of the sink roll 3. The molten zinc bath rectifying plate 8 of the present embodiment is a rectifying plate including a plurality of plate-like rectifying pieces 12, and has a function of rectifying the upward zinc flow 11 so as to be directed outward in the steel sheet width direction, thereby increasing the replacement ratio of the bath 2.

In embodiment 1 shown in fig. 1 to 6, each plate-like flow straightener 12 is made of a rectangular flat plate having a width W and a length L, and is arranged so as to open upward (i.e., toward the positive X-axis direction) with the upper side (i.e., toward the positive X-axis direction) facing outward in the steel plate width direction. Here, the width W is a width of the plate-shaped rectifying piece 12 in a direction (Y-axis direction) perpendicular to the surface of the inlet-side steel plate 5. The length L is a length of the plate-like flow straightener 12 in the advancing direction (the direction of the through plate, i.e., the X-axis direction) of the inlet side steel plate 5.

Fig. 6 is a diagram illustrating the structure of the molten zinc bath rectifying plate 8 according to embodiment 1, and shows a cross section obtained by cutting each plate-like rectifying piece 12 with a plane parallel to the surface of the inlet-side steel plate 5, that is, a cross section of each plate-like rectifying piece 12 parallel to the surface of the inlet-side steel plate 5. Each plate-like flow straightener 12 is arranged symmetrically (i.e., symmetrically in the Z-axis direction) with respect to the center of the sink roll 3 in the body length direction (i.e., the Z-axis direction) which is denoted by CL. The plate-like flow straightener 12 is disposed at an angle θ 1 and an interval P1 at equal intervals with respect to the axis 30 (see fig. 1 and 3) of the sink roll 3. The angle θ 1 corresponds to an angle formed by a cross section of each plate-like flow straightener 12 parallel to the surface of the inlet side steel plate 5 with respect to the plate width direction (Z-axis direction) of the inlet side steel plate 5. The interval P1 between the plate-shaped flow-adjusting pieces 12 is a distance in the direction of the axis 30 (Z-axis direction) of the sink roll 3 between 2 adjacent and opposing plate-shaped flow-adjusting pieces 12. When the number N of the plate-shaped segments 12 is counted, the number of the plate-shaped segments 12A connected to two portions having an angle θ 1 exceeding 0 ° is counted as 2 segments. Therefore, the number N of plate-shaped flow straightener 12 is 6.

As shown in fig. 4, each plate-like flow straightener 12 is disposed at an angle θ 2 of 45 ° to 135 ° with respect to the surface of the inlet side steel plate 5. The value of θ 2 is preferably 90 °, but may be inclined with respect to the surface of the entry-side steel plate 5 in a range of ± 45 ° centering on 90 °. When the plate-like rectifying fins 12 are arranged so as to be inclined (in other words, opened) outward in the plate width direction of the entry-side steel plate 5 as going from the side of the entry-side steel plate 5 toward the bath surface 20 (the y-axis positive direction), the angle θ 2 becomes smaller than 90 °. For example, the angle θ 2 of the plate-like flow straightener 12 inclined 30 ° outward in the plate width direction with respect to the normal line of the entry side steel plate 5 is 60 °. On the other hand, when the plate-shaped rectifying pieces 12 are arranged so as to be inclined inward (in other words, closed) in the plate width direction of the entry-side steel plate 5 as going from the side of the entry-side steel plate 5 toward the bath surface 20, the angle θ 2 becomes larger than 90 °. For example, the angle θ 2 of the plate-shaped flow straightener 12 inclined inward by 30 ° in the plate width direction with respect to the normal of the entry side steel plate 5 is 120 °.

The following describes the structure of the rectifying plate 8 for molten zinc bath according to embodiments 2 to 6. When the molten zinc bath straightening plates 8 according to embodiments 2 to 6 are viewed from the direction of the axis 30 of the sink roll 3 (Z-axis direction), the same as embodiment 1 is shown in fig. 5. As shown in fig. 7 of embodiment 2, each plate-shaped flow straightener 12 may be a curved plate having a curvature radius R that is curved so as to bulge toward the opposite side (X-axis positive direction side) to the advancing direction of the inlet side steel plate 5, and may be arranged symmetrically and at equal intervals. As in embodiment 3 shown in fig. 8, each plate-like flow straightener 12 may be a curved plate that is curved in the direction opposite to that of fig. 7 (i.e., so as to bulge toward the negative X-axis side). In either case, the spacing between the upper portions (X-axis positive direction ends) and the spacing between the lower portions (X-axis negative direction ends) of the plate-shaped flow straightener 12 are equal. As shown in fig. 7 and 8, the angle θ 1 can be calculated as an angle formed by a virtual straight line connecting both ends in the longitudinal direction of the cross section of each plate-shaped flow straightener 12 with respect to the plate width direction (Z-axis direction) of the inlet steel plate 5.

In addition, in embodiment 4 shown in fig. 9, the plate-shaped flow straightener 12 is made of a rectangular flat plate, and is equally spaced from each other, but is arranged asymmetrically left and right. In other words, the center of the plurality of plate-shaped flow-regulating pieces 12 (specifically, the apexes 120 of the plate-shaped flow-regulating pieces 12A) is offset from the center CL of the sink roll 3 in the body length direction by the distance D in the direction of the axis 30 of the sink roll 3 (Z-axis direction). In addition, in embodiment 5 shown in fig. 10, each plate-shaped rectifying piece 12 is made of a rectangular flat plate, is inclined in the same direction as each other, and is arranged at equal intervals from each other. Further, in embodiment 6 shown in fig. 11, each plate-like flow straightener 12 is made of a rectangular flat plate, is symmetrical left and right, and is arranged at unequal intervals P1, P2. In the case where the plurality of plate-shaped flow segments 12 are arranged differently (for example, in the case where the plurality of plate-shaped flow segments 12 are arranged symmetrically with respect to the position) with respect to any position in the direction of the axis 30 of the sink roll 3 (the Z-axis direction), the interval between the plate-shaped flow segments 12 (for example, two flat plates constituting the plate-shaped flow segment 12A) facing each other across the position is not considered as the intervals P1 and P2.

As shown in these embodiments, the arrangement of each plate-shaped flow straightener 12 may be variously modified in addition to embodiment 1. In these embodiments, the angle θ 1 or the angle θ 2 may not have the same value between the plate-shaped flow straightener 12. In other words, the adjacent plate-shaped flow rectification pieces 12 may not be parallel to each other. The plate-shaped flow straightener 12A, which connects the two side portions with each other with the apex 120 interposed therebetween, may be configured such that the two side portions are disconnected from each other. The number N of the plate-shaped flow straightener 12 is not limited to 6, and may be 4, 5, 7, 8, or the like, as long as the number N is a plurality (2 or more).

When the molten zinc bath rectifying plate 8 configured as described above is disposed in the region 7 called the V-zone, the upward zinc flow 11 generated by collision of the accompanying flow 9 entering the side steel sheet 5 with the accompanying flow 10 of the sink roll 3 and the sink roll 3 can be efficiently rectified outside in the steel sheet width direction by the plate-shaped rectifying pieces 12. The range of arrangement of the molten zinc bath flow straightening plates 8 in the region 7 may be any range as long as the upward zinc flow 11 comes into contact with at least a part of each plate-like flow straightening piece 12. As shown by the alternate long and short dash line in fig. 1, at least a part of each plate-like flow straightener 12 may be disposed within a predetermined range (for example, within 1000 mm) upward (y-axis positive direction) from the contact portion Q of the entry side steel plate 5 and the sink roll 3, within a predetermined range (for example, within 500 mm) in the horizontal direction (x-axis positive direction) from the contact portion Q to the side of the snout 6, and within a predetermined range (for example, within ± 1000 mm) in the plate width direction (z-axis direction) from the center in the plate width direction of the steel plate 5 (or the center CL in the body length direction of the sink roll 3).

In particular, by disposing the plate-shaped flow straightening vanes 12 at an angle θ 2 of 45 ° to 135 ° with respect to the surface of the inlet-side steel plate 5 and disposing the cross sections of the plate-shaped flow straightening vanes 12 parallel to the surface of the inlet-side steel plate 5 at an angle θ 1 exceeding 0 ° and less than 90 ° with respect to the plate width direction of the inlet-side steel plate 5, the upward zinc flow 11 can be made to contact with the plate-shaped flow straightening vanes 12 at a larger angle than in the conventional flow straightening vanes in which the center lines of the bends or curves of the flow straightening vanes are disposed along the advancing direction of the inlet-side steel plate, and the replacement ratio of the bath 2 can be improved as compared with the conventional flow straightening vanes. As a result, the Al concentration in the region 7 called V zone can be prevented from decreasing, and defects in the hot-dip galvanized steel sheet due to the bottom dross can be suppressed. According to the results of the applicant company, the generation amount of the bottom ash can be reduced to less than half of the conventional amount. Examples of the above embodiments are explained below.

Examples

Dimensions W, L, an angle θ 1, a curvature radius R, the number of segments N, intervals P1, P2, a center offset D, and an angle θ 2 of the plate-shaped rectifying segment 12 were varied in various ways, and a substitution rate η of the bath 2 was calculated numerically using FLUENT (CFD simulation software). Wherein the substitution rate η is a ratio of the volume of the bath 2 newly flowed in 2 minutes after passing the steel sheet 5 through the steel sheet in the region 7 called V zone to the volume of the bath 2 before passing the steel sheet 5 through the steel sheet. The pass speed of the steel sheet 5 was set to 120m/min, and the sheet width was set to 1600mm. The results are shown in table 1.

TABLE 1

As shown in table 1, in comparative example 1 without the rectifying plate 8 for molten zinc bath, the substitution rate η of the bath 2 was 31%, but according to each example, the substitution rate η could be greatly increased to 41 to 88%. In addition, the substitution rate η can be improved to 95% in a simulation.

In comparative example 2, similarly to the flow regulating plate described in fig. 2 of japanese patent application laid-open No. 2016-156077, the flat plate is bent around its center line, and the center line is arranged along the advancing direction of the inlet-side steel plate 5, and the angle θ 2 is 20 ° (i.e., less than 45 °), and the angle θ 1 is 90 °. In comparative example 2, the substitution rate η was as small as 36%. This is believed to be due to: since the angle at which the upward zinc flow 11 and the plate-shaped rectifying piece 12 meet is shallow, the rectifying effect of the upward zinc flow 11 toward the outside in the plate width direction of the steel plate 5 is weak, and the decrease in the Al concentration in the region 7 called the V region cannot be sufficiently eliminated.

The substitution rate η in comparative example 4 in which the angle θ 2 was 150 ° (i.e., more than 135 °) and the substitution rate η in comparative example 5 in which the angle θ 2 was 30 ° (i.e., less than 45 °) were all 39%, and were small. In contrast, the substitution rate η of example 24 with the angle θ 2 of 135 ° and the substitution rate η of example 26 with the angle θ 2 of 45 ° were both 50%, which were large. It is understood that by setting the angle θ 2 to 45 ° to 135 ° in this manner, the replacement of the bath 2 in the region 7 called V-zone can be promoted. This is believed to be due to: when the value of the angle θ 2 is outside the range of 45 ° to 135 °, the angle at which the upward zinc flow 11 contacts each plate-shaped rectifying piece 12 shown in fig. 1 and 2 is shallow, and therefore the rectifying action of the upward zinc flow 11 toward the outside in the plate width direction of the steel plate 5 is weak, whereas when the value of the angle θ 2 is within the range of 45 ° to 135 °, the upward zinc flow 11 can be efficiently rectified and converted into a fluid in the outside in the plate width direction.

The substitution rate η at an angle θ 2 of 60 ° (66% in example 25) is larger than the substitution rate η at an angle θ 2 of 45 ° (50% in example 26). The substitution rate η at an angle θ 2 of 120 ° (66% in example 23) is greater than the substitution rate η at an angle θ 2 of 135 ° (50% in example 24). The substitution rate η becomes the maximum (77% of example 21) when the angle θ 2 is 90 °. When the angle θ 2 is 60 ° to 90 °, the ratio of the increase in the substitution rate η to the increase in the angle θ 2 is small compared to when the angle θ 2 is 45 ° to 60 °. When the angle θ 2 is 90 ° to 120 °, the increase in the substitution rate η is smaller with respect to the decrease in the angle θ 2 than when the angle θ 2 is 120 ° to 135 °. It is understood that by setting the angle θ 2 to 60 ° to 120 ° in this manner, a large substitution rate η can be stably obtained.

The substitution rate η of comparative example 2 in which the angle θ 1 was 90 ° was as small as 36%. This is believed to be due to: the upward zinc flow 11 is less likely to contact the plate-like flow straightener 12 when viewed in the direction along the surface of the inlet side steel plate 5. In comparative example 3 in which the angle θ 1 was 0 °, the substitution rate η was as small as 32%. This is believed to be due to: when viewed in a direction along the surface of the inlet-side steel plate 5, the upward zinc flow 11 contacts the plate-shaped rectifying fins 12 in the perpendicular direction, whereby the rectifying action of the zinc flow 11 toward the outside of the steel plate 5 in the plate width direction is conversely weakened. In contrast, the substitution rate η in example 22 in which the angle θ 1 was 45 ° was as large as 53%. It is understood that by setting the angle θ 1 in the range exceeding 0 ° and lower than 90 ° in this manner, the replacement of the bath 2 in the region 7 called V-zone can be promoted. This is believed to be due to: when viewed in the direction along the surface of the entry-side steel sheet 5, the rectifying action for directing the upward zinc flow 11 toward the outside in the sheet width direction of the steel sheet 5 can be effectively generated.

The substitution rate η when the angle θ 1 is 20 ° (59% in example 9) is larger than the substitution rate η when the angle θ 1 is 10 ° (41% in example 8). The substitution rate η at an angle θ 1 of 60 ° (55% in example 13) is larger than the substitution rate η at an angle θ 1 of 70 ° (45% in example 14). The substitution rate η becomes maximum (75% of example 11) when the angle θ 1 is 30 °. When the angle θ 1 is 20 ° to 30 °, the ratio of the increase in the substitution rate η to the increase in the angle θ 1 is small compared to when the angle θ 1 is 10 ° to 20 °. When the angle θ 1 is 30 ° to 60 °, the rate of increase in the substitution rate η with respect to decrease in the angle θ 1 is small compared to when the angle θ 1 is 60 ° to 70 °.

It is understood that by setting the angle θ 1 to 20 ° to 60 ° in this manner, a large substitution rate η can be stably obtained. This is believed to be due to: by setting the lower limit value of the angle θ 1 to 20 °, when viewed in the direction along the surface of the inlet-side steel sheet 5, it is possible to suppress the angle at which the upward zinc flow 11 and the plate-shaped flow straightener 12 contact each other from becoming excessively large, thereby securing the rectifying effect, and to suppress the plurality of plate-shaped flow straightener 12 from becoming excessively close to each other, thereby securing the flow path cross-sectional area between them to some extent. In addition, it is considered that: by setting the upper limit value of the angle θ 1 to 60 °, when viewed in a direction along the surface of the inlet-side steel plate 5, the amount of contact between the upward zinc flow 11 and the plate-like flow straightener 12 can be secured to some extent, and the upward zinc flow 11 is directed outward in the plate width direction of the steel plate 5. Further, it is found that by setting the angle θ 1 to 25 ° to 40 °, a substitution rate η of 70% or more (70% in example 10 and 72% in example 12) can be stably obtained. This is believed to be due to: the above-described effects can be obtained more effectively.

The substitution rate η in comparative example 3 in which the number N of the plate-like flow straightener 12 is 1 is as small as 32%. In contrast, the substitution rate η in example 22 in which the number N of the plate-like flow straightener 12 was 2 was as large as 53%. Therefore, it is understood that a large substitution rate η can be obtained by setting the number N of the plate-shaped flow straightener 12 to 2 or more.

The substitution rate η when the number N of the plate-like flow-regulating fins 12 is 2 is 66% (example 15), the substitution rate η when the number N of the plate-like flow-regulating fins is 4 is 75% (example 11), the substitution rate η when the number N of the plate-like flow-regulating fins is 6 is 85% (example 16), and the substitution rate η when the number N of the plate-like flow-regulating fins is 8 is 88% (example 17). Therefore, it is found that when the number of sheets N is 4 or more, a large substitution rate η of 75% or more can be obtained. It is also understood that the larger the number of sheets N, the larger the substitution rate η obtained. However, if the number N of the plate-like flow straightener 12 is too large, the plate-like flow straightener 12 may interfere with each other due to space limitation in the equipment. From this viewpoint, the upper limit value of N is preferably 6 to 8, for example.

The replacement ratio η when the width W of the plate-like flow straightener 12 is 150mm (59% of example 2) is larger than the replacement ratio η when the width W is 50mm (50% of example 1). The substitution rate η when the width W was 250mm (63% in example 3) was larger than the substitution rate η when the width W was 150mm (59% in example 2). The substitution rate η when the width W was 350mm (63% in example 4) was the same as the substitution rate η when the width W was 250mm (63% in example 3).

It is found that by setting the width W to 50mm or more in this manner, a large substitution rate η can be stably obtained. It is considered that if the width W is too small, the upward zinc flow 11 is less likely to contact the plate-shaped rectifying piece 12, and the rectifying action of the upward zinc flow 11 toward the outside of the steel plate 5 in the plate width direction is weakened. By setting the lower limit of the width W to 50mm, the amount of contact between the upward zinc flow 11 and the plate-like flow straightening vanes 12 can be secured to some extent so as to be directed outward in the plate width direction of the steel plate 5. On the other hand, if the width W is too large, the possibility of interference between the plate-shaped flow straightener 12 and the steel plate 5 is likely to occur because the plate-shaped flow straightener 12 and the steel plate 5 are close to each other in the region 7 called V-zone. By setting the upper limit of the width W to, for example, 250mm, it is possible to obtain a large replacement ratio η and suppress interference between the plate-shaped flow straightener 12 and the steel plate 5.

The replacement ratio η when the length L of the plate-shaped flow straightener 12 is 200mm (63% in example 3) is slightly larger than the replacement ratio η when the length L is 100mm (61% in example 5). The degree of substitution η at a length L of 300mm (63% in example 6) was slightly greater than the degree of substitution η at a length L of 400mm (60% in example 7). It is found that by setting the length L to 100mm or more in this manner, a large substitution rate η can be stably obtained. Further, it is found that a large substitution rate η can be obtained more stably by setting the length L to 200 to 300 mm.

The substitution rate η (70%) of example 28 as an example of embodiment 3 shown in fig. 8 is larger than the substitution rate η (61%) of example 27 as an example of embodiment 2 shown in fig. 7. This is believed to be due to: in embodiment 2 (fig. 7), the flow path cross-sectional area between the adjacent plate-shaped flow straightener 12 is smaller on the outlet side (positive X-axis direction) than on the inlet side (negative X-axis direction) of the flow path, whereas in embodiment 3 (fig. 8), the flow path cross-sectional area is larger on the outlet side (positive X-axis direction) than on the inlet side (negative X-axis direction) of the flow path, and the upward zinc flow 11 flows more smoothly along the plate-shaped flow straightener 12.

The replacement ratio η when the distance P1 between the plate-shaped flow-rectifying pieces 12 is 300mm (75% in example 11) is slightly larger than the replacement ratio η when the distance P1 is 200mm (70% in example 18) and the replacement ratio η when the distance P1 is 400mm (72% in example 19). It is found that by setting the interval P1 to 200 to 400mm in this manner, a large substitution rate η can be stably obtained. Further, it is found that a large substitution rate η can be obtained more stably by setting the interval P1 to 300mm or thereabouts.

The replacement rate η when the intervals between the plate-shaped flow-straightening vanes 12 are equal to each other (75% in example 20 and 77% in example 21) is slightly larger than the replacement rate η when the intervals are different (72% in example 31). Therefore, it is considered that the intervals are preferably the same, but the influence on the substitution rate η is small even if the intervals are different to some extent.

The replacement ratio η when the plate-shaped flow straightener 12 is arranged symmetrically with respect to the center CL in the body longitudinal direction of the sink roll (77% in example 21) is larger than the replacement ratio η when the plate-shaped flow straightener 12 is arranged asymmetrically (63% in example 29). It is understood that a larger replacement ratio η can be obtained by arranging the plate-like flow-regulating pieces 12 symmetrically with respect to the center CL in the body length direction of the sink roll. Further, it is considered that, when the plate-shaped flow-straightening vanes 12 are arranged symmetrically, the upward zinc flow 11 can be suppressed from being biased to one side in the plate width direction of the steel plate 5, and therefore, the occurrence of a pattern defect in the steel plate 5 can be suppressed.

The replacement ratio η when the plate-shaped flow-rectifying pieces 12 are arranged while being inclined in different directions (77% in example 21) is larger than the replacement ratio η when the plate-shaped flow-rectifying pieces 12 are arranged while being inclined in the same direction (66% in example 30). It is understood that a larger replacement ratio η can be obtained by disposing the plate-like rectifying pieces 12 so as to be inclined in different directions. Further, it is considered that the upward zinc flow 11 is suppressed from being biased to one side in the plate width direction of the steel plate 5 by arranging the plate-like rectifying pieces 12 so as to be inclined in different directions, and therefore, the occurrence of the pattern defect in the steel plate 5 can be suppressed.

Description of the symbols:

1. molten zinc bath

2. Molten zinc bath

3. Sink roll

4. Supporting roll

5. Steel plate

6. Furnace nose

7. Region called V region

8. Rectifying plate for molten zinc bath

9. Accompanying flow of steel plate

10. Accompanying flow of sink roll

11. Upward flow of zinc

12. Plate-shaped commutator segment

Claims

1. A molten zinc bath facility comprising:

a molten zinc bath; and

a molten zinc bath rectifying plate having a plurality of plate-like rectifying pieces disposed between a snout and a sink roll and above a contact portion between an entry-side steel sheet and the sink roll, the entry-side steel sheet being a steel sheet entering the molten zinc bath;

the fairings are each configured to: an angle θ 2 of 45 ° to 135 ° is formed with respect to a surface of the entry side steel plate, and a cross section parallel to the surface of the entry side steel plate forms an angle θ 1 of more than 0 ° and less than 90 ° with respect to a plate width direction of the entry side steel plate.

2. The molten zinc bath apparatus according to claim 1, wherein the angle θ 2 is 60 ° to 120 °.

3. The molten zinc bath apparatus of claim 1, wherein the angle θ 1 is from 20 ° to 60 °.

4. The molten zinc bath apparatus according to claim 2, wherein the angle θ 1 is 20 ° to 60 °.

5. The molten zinc bath apparatus according to any one of claims 1 to 4, wherein the plurality of current plates are centrosymmetric with respect to a body length direction of the sink roll.