JP2828596B2 - Hot-dip zinc bath in hot-dip galvanizing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot-dip galvanizing bath in a galvanizing facility for continuously hot-dip galvanizing a metal strip such as a steel strip, and particularly to quickly discharge impurities such as dross generated in a galvanizing bath out of the bath. And a removable zinc bath.

[0002]

2. Description of the Related Art An example of a hot-dip zinc bath in a plating facility for hot-dip galvanizing a metal strip such as a steel strip is shown in FIG.
Shown in This figure is a cross-sectional view of the plating bathtub viewed from the side.
1 is a steel strip, 2 is a plating bath (hot-dip zinc), 3 is a sink roll, 4a and 4b are support rolls in the bath, 5 is a plating tank, 11 is a bottom dross, 12 is a top dross, and the plating bath 2 is from the upper left direction. The steel strip 1 drawn into the tub is wound around the sink roll 3 and the running direction is changed, and the support roll 4
The shape correction and the rising position are controlled by a and 4b, and are lifted vertically upward.

In the plating tank 5, iron eluted from the steel strip 1, the sink roll 3, and the support rolls 4a and 4b in the bath (hereinafter collectively referred to as "roll in the bath") reacts with zinc to form dross. This produces a compound called, and contaminates the plating bath 2. The dross is roughly classified into a bottom dross 11, which has a higher specific gravity than molten zinc and settles and accumulates at the bottom of the plating tank 5, and a top dross 12, which has a lower specific gravity and floats on the plating bath surface.

[0004] Dross is generated almost in proportion to the amount of plating, and has the following problems. 1) The dross in the plating bath is pulled up as the steel strip travels, and adheres to the steel strip surface to deteriorate the quality. 2) When dross adheres to the surface of the roll in the bath,
Scratches, push marks, etc. occur in the steel strip, and the quality is reduced. 3) Adhesion of dross to the rotating part of the roll in the bath causes poor rotation and causes scratches on the steel strip. 4) The life of plating equipment caused by dross is shortened, and maintenance work such as maintenance of equipment and replacement of parts is increased, and productivity is reduced.

[0005] For this reason, the bottom dross needs to be pumped and discharged every operation for a certain period of time, and the top dross needs to be scraped and discharged at any time during the operation. It is a work and extremely dangerous. In order to reduce such dross removal work by human power, a molten zinc bath tub disclosed in Japanese Patent Application Laid-Open No. 4-54948 has been proposed. This will be described with reference to FIG.

FIG. 6 is a side sectional view of the molten zinc bath.
Is a bottom portion of the plating tank 5, 7 (7a, 7b) is an inclined portion, 8 is a shallow flow path connecting the plating tank 5 and the sedimentation tank 9, and 10 is a pump. This hot-dip zinc bath is composed of a plating bath 2 on the left side of FIG. 6 and a sedimentation bath 9 on the right side. The plating bath 2 part is along the steel strip 1 wound around the sink roll 3, The plating bath 2 has a shallow flow path 8 formed by a bottom 6 having a distance of 300 mm or less between itself and the body, and slopes 7a and 7b on both sides having an inclination of not less than the angle of repose reaching the bottom 6. A pump 10 is provided near the liquid level of the precipitation tank 9 for communicating with the precipitation tank 9 via the intermediation of the molten zinc and pumping the molten zinc back to the plating bath 2.

[0007] With this configuration, in the plating bath 2, dross sedimentation and deposition are prevented by the running of the steel strip 1 and the stirring action by the rotation of the sink roll 3, and the dross generated is shallow. Discharged into the sedimentation tank 9 via the channel 8 and settled, deposited or floated on this side, and clean molten zinc slightly dross below the liquid level was returned from the sedimentation tank 9 to the plating bath 2 side by the pump 10. As a result, dross does not adhere to the steel strip 1 and the sink roll 3, and a high-quality plating process is realized.

By the way, in this molten zinc bath,
The sedimentation tank 9 is the sink roll 3 viewed from the steel strip 1 pass route.
Because it is located on the exit side, that is, on the side to be pulled up, it is necessary to perform work such as replacing plating equipment such as rolls in the bath for regular maintenance of equipment, cutting and connecting steel strip 1 at that time. There is a problem that there is a sedimentation tank 9 at the foot, and it is necessary to provide a scaffold or the like on the sedimentation tank 9, which is extremely dangerous. Further, in the range of the body length of the sink roll 3, a flow from the plating tank 2 to the sedimentation tank 9 as described above is recognized, but a return flow in the opposite direction is generated outside the tank, that is, in the bearing portion, and it is desired to prevent this. When a weir or the like is provided, the structure of the plating bath 2 becomes complicated, and moreover, local stagnation occurs, and on the contrary, the amount of sediment increases.

[0009] Further, when the amount of reflux by the pump 10 is increased to suppress the above-mentioned return flow, the bath flow in the sedimentation tank 9 becomes faster, and sedimentation and separation of zinc and dross, which originally do not have a large difference in specific gravity, are performed. There is also a problem that the sedimentation tank 9 needs to be increased in size.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to realize a plating bath which efficiently discharges dross without impairing workability such as maintenance.

[0011]

Means for Solving the Problems The present inventors have studied the bath flow in the bath tub in detail using a two-bath type hot-dip zinc bath as shown in FIG. The molten zinc was agitated by the running of the steel strip and the flow in the direction of travel of the metal strip was remarkable, but it was recognized that a return flow in the opposite direction occurred in the portion outside the body length of the sink roll. Was done.

Therefore, the return flow is effectively used by disposing the settling tank on the inlet side of the plating bath, contrary to the case of FIG.
Purification of the plating bath was realized, and the present invention was completed. That is, the present invention provides a plating tank having a bottom portion and a sloped portion on both sides thereof along a traveling path of a metal strip wound around a sink roll in the plating tank, and a settling tank connected to the plating tank through a shallow flow path. And, in a molten zinc bath provided with a pump for refluxing the molten zinc pumped from immediately below the bath surface of the sedimentation tank into the plating tank, wherein the sedimentation tank is arranged on the entry side of the metal strip into the plating tank. A hot-dip galvanizing bath in the hot-dip galvanizing equipment, preferably, the bath surface of the sedimentation tank is partitioned by a partition plate, and a pump is provided on a side of the precipitation tank that is not directly connected to the plating tank in an area partitioned by the partition plate. 2 is a hot-dip galvanizing bath in the hot-dip galvanizing equipment provided with a suction port of (1).

[0013]

[Operation] According to the present invention, the sedimentation tank is connected to the entrance side of the plating tank,
That is, by arranging it on the back side of the snout, the return flow generated outside the body of the sink roll and the bath flow accompanying the rotation of the sink roll are merged to form a flow toward the sedimentation tank through both sides of the snout. The dross was discharged to the settling tank side by this flow. Furthermore, the snout functions as a wall for preventing backflow of the dross once discharged to the settling tank side, and the plating bath is efficiently cleaned.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described in detail with reference to FIGS. 1 is a side sectional view of a molten zinc bathtub of this embodiment, FIG. 2 is a partial sectional view showing a part of FIG. 1, FIG. 3 is a plan view, and FIG. 4 is a partial plan view showing a part of FIG. 5 and 6
The same reference numerals are used for the parts common to. 14
Is a plating tank front wall, 15 is a plating tank side wall, 18 is a wiping nozzle, 19 is a snout, and 21 and 22 are partition plates.

The steel strip 1 enters a plating bath 2 through a snout 19 from a reduction annealing furnace, which is a plating pretreatment facility (not shown), turns around with a sink roll 3, and is pulled up in the upper right direction. A support roll 4 is provided in the zinc bath near the exit of the plating bath 2, and a pair of wiping nozzles 18 are provided above the zinc bath. The bottom part 6 of the plating tank 5 and the inclined parts 7 on both sides thereof are formed substantially along the traveling path of the steel strip 1 and have an inclination greater than the angle of repose so as not to deposit dross. The distance between them is less than 300mm to prevent dross settling. The sedimentation tank 9 communicating via the shallow flow path 8 is arranged on the steel strip entry side with respect to the plating tank 5.

Looking at the flow of the plating bath, a flow indicated by an arrow A is formed along the bottom 6 of the plating tank along with the running of the steel strip 1 and the rotation of the sink roll 3, and the flow near the bath surface is accompanied by the steel strip 1. To rise. It turns on the plating tank front wall 14 as shown by the arrow B, flows along the plating tank side wall 15 as indicated by the arrow C, and proceeds leftward on the outside of the body of the sink roll 3 and passes on both sides of the snout 19. , And flows into the precipitation tank 9 via the flow path 8.

On the other hand, as shown in FIG. 2, the bath flow in a portion surrounded by the steel strip 1 and the sink roll 3 is the same as the bath flow by the steel strip 1 rising from the plating bath and the wiping nozzle 18 indicated by an arrow D. Then, there is a downward flow of the wiping gas that collides with the steel strip 1 and a bath flow accompanying the rotation of the sink roll 3 indicated by an arrow E. The wiping gas flow D blows the top dross floating on the bath surface to the snout side and joins the flow C along the plating tank side wall 15. The wiping gas flow on the back side of the steel strip 1 with respect to the arrow D also blows the top dross floating on the bath surface toward the plating tank front wall side and joins the flows B and C.
After colliding with the snout 19, the stream E becomes a stream F toward the side wall 15 of the plating tank, and merges with the above-mentioned stream C near both sides of the snout 19 and flows into the precipitation tank 9, so that the stream E is formed in the plating bath. The dross discharged is discharged to the sedimentation tank 9 by this flow. The snout 19 serves as a wall for preventing backflow of the dross once discharged to the sedimentation tank 9 side, and furthermore, a clean plating bath pumped up from the sedimentation tank 9 by the pump 10 is suitable for a position where the flow of the plating bath is further promoted. Make sure to supply in quantity. In this embodiment, the flow G is supplied near the rising position of the steel strip 1 so as to energize the flow B. A part of the flow F is drawn into the plating bath 2 by the rotation of the sink roll 3, but the plating bath 2 is gradually cleaned as time passes by repeating the above-described circulation.
Dross accumulates in the sedimentation tank 9.

The sedimentation tank 9 is provided with two partition plates 21 and 22. Partition plate 21 that partitions only near the bath surface
Is provided so that the pump 10 does not suck the floating top dross 12, and a partition plate 22 that has a whole cross section excluding the inflow port below the bath surface is a top dross.
Neither 12 nor bottom dross 11 is provided so as to be sucked into the pump 10. By these partition plates 21 and 22, accumulated dross can be easily removed,
The suction port of the pump is provided immediately below the bath surface further ahead of the partition plates 21 and 22 when viewed from the direction in which dross flows from the plating tank, and is configured to pump only a clean plating bath.

Further, since the precipitation tank 9 is disposed on the entrance side of the steel strip 1 with respect to the plating tank 5, equipment such as a roll in a bath in the plating tank 5 is pulled up or installed, and a steel strip for that purpose is installed. When performing operations such as disconnection and connection 1, there is no sedimentation tank 9 at the feet, and the safety of the operation is significantly improved.

[0020]

According to the present invention, 1) dross generated in a plating bath can be quickly discharged and removed from the plating tank, so that there is no generation of a pressing flaw or a flaw due to dross, and the quality of a plated product is reduced. improves. 2) No dross adheres to the equipment immersed in the plating bath, the life of the equipment is extended, and maintenance work is reduced. 3) By arranging the sedimentation tank on the entrance side of the steel strip, necessary maintenance work and accompanying steel strip cutting work can be performed safely at regular intervals, thereby reducing maintenance costs and productivity. Improvement can be achieved. It has excellent effects such as.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing an embodiment of the present invention.

FIG. 2 is a partial sectional view showing a part of FIG. 1;

FIG. 3 is a plan view showing an embodiment of the present invention.

FIG. 4 is a partial plan view showing a part of FIG. 3;

FIG. 5 is a side sectional view showing a conventional technique.

FIG. 6 is a side sectional view showing another conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal strip (steel strip) 2 Plating bath 3 Sink roll 4 Support roll in bath 5 Plating tank 6 Bottom 7 Inclined section 8 Flow path 9 Sedimentation tank 10 Pump 11 Bottom dross 12 Top dross 14 Front wall of plating tank 15 Side wall of plating tank 18 Wiping nozzle 19 Snout 21, 22 Partition plate

Continuation of the front page (56) References JP-A-5-171388 (JP, A) JP-A-5-9689 (JP, A) JP-A-4-154948 (JP, A) JP-A-4-52257 (JP) , A) Hira 4-649 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) C23C 2/00-2/40

Claims (2)

(57) [Claims] 1. A sink roll (3) in a plating tank (5).
A plating tank (5) having a bottom (6) and inclined portions (7) on both sides thereof along a traveling path of the metal strip (1) wound around the plating tank (5), and the plating tank (5) through a shallow flow path (8). ), And a molten zinc bath comprising a pump (10) for refluxing molten zinc pumped from immediately below the bath surface of the precipitation tank (9) into the plating tank (5). A hot-dip galvanizing bath in a hot-dip galvanizing facility, wherein a sedimentation tank (9) is arranged on an entry side of a metal strip into a plating tank (5). 2. The bath surface of the settling tank (9) is divided into partition plates (21, 2).
This partition plate (21,22) of the sedimentation tank (9)
The hot-dip galvanizing bath in the hot-dip galvanizing equipment according to claim 1, wherein a suction port of a pump (10) is provided on a side of the area partitioned by the step (3) that is not directly connected to the plating tank (5).