JP3015184B2 - Snout for hot dip plating 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 snout for a hot-dip plating apparatus capable of efficiently removing internal dross, since a hot-dip layer having no defects caused by dross biting is formed.

[0002]

2. Description of the Related Art In order to improve the corrosion resistance of a metal strip such as a steel strip, a method of plating Zn, Al or an alloy thereof on a strip surface by hot dip plating, electroplating, vapor deposition plating or the like has been adopted. Among them, the hot-dip plating has an advantage that a relatively thick plating layer can be formed in a short time on a metal strip continuously transported.

In the hot-dip plating method, for example, equipment schematically shown in FIG. 1 is used. The metal strip 10 to be plated
After the oxide film or the like on the surface is removed in the reduction furnace 20, the plating bath 5 contained in the plating tank 40 is passed through the snout 30.
0 is introduced. After the metal strip 10 goes around the sink roll 60 immersed in the plating bath 50, it is pulled up from the plating bath 50.

The snout 30 has a function of preventing contact between the metal strip 10 sent from the reduction furnace 20 and the atmosphere, and is provided between the reduction furnace 20 and the plating bath 50 in a cylindrical shape surrounding the metal strip 10. Have been. And Snout 30
Is slightly immersed in the plating bath 50. The snout 30 is filled with a reducing gas.

While the metal strip 10 passes through the plating bath 50, the plating metal such as Zn or Al in the plating bath is
No. 0 reacts with the surface and is pulled up from the plating bath 50 as a plating strip 11 to which a predetermined plating metal has adhered. A part of the plating metal in the molten state attached to the surface of the plating strip 11 drops by its own weight and is returned to the plating bath 50. After adjusting the amount of plating metal adhered to the surface by wiping, the plated strip 11 is sent to an alloying furnace as needed.

The plating metal reacts with the metal strip 10 to form a plating layer.
In some cases, it reacts with Fe that precipitates at 0 to become an intermetallic compound and is suspended in the plating bath 50. Further, since the liquid surface of the plating bath 50 is exposed to the atmosphere, an oxidation reaction occurs. As a result, dross is generated and deposited in the plating bath 50.

The dross in the steel strip region 51 surrounded by the entry-side metal strip 10 and the exit-side metal strip 10 easily enters the inside of the snout 30 or between the metal strip 10 and the sink roll 60. Even inside the snout 30, the plating metal reacts with oxygen, moisture, and the like contained in the atmosphere, Fe and the like deposited from the metal strip 10, and dross 52 is generated. Further, the reducing gas itself may react with the plating metal to become a component of dross. Since the dross 52 generated or flowed into the snout 30 is partitioned by the snout 30 and hardly flows out, the dross concentration inside the snout 30 increases as the plating operation continues.

Dross 52 suspended in plating bath 50
Adversely affects the surface properties of the plated strip 11. For example, at the early stage of the plating reaction, dross 52 is
When it adheres to the surface of No. 0, the adhesion of the plating layer formed thereon is reduced. Further, if the dross 52 adheres to the formed plating layer, the surface quality is significantly impaired. In addition, since the dross 52 is bitten by the plating layer, it is not possible to impart a given corrosion resistance to the plating strip 11. In particular, the metal strip 10 is a plating bath 50
Dross 5 inside snout 30 where it enters
2 has a great influence on the surface properties of the product.

The occurrence of defects due to the dross biting is greatly reduced by scraping out the dross 52 inside the snout 30. The scraping of the dross 52 needs to be performed without interrupting the plating operation that lowers productivity.

[0010] As means for removing dross in the snout, a cylindrical member provided with a spiral rotating groove is disposed inside the snout so as to be in contact with the plating bath surface in the snout. 188766. Further, dross in the snout is pumped up together with the plating metal (Japanese Patent Laid-Open No. 3-150338), and a dross collecting trough is movably provided in the snout (Japanese Patent Laid-Open No. 2-30).
No. 5948), a dross collection box interlocked with the snout is provided (JP-A-3-140448), and the outer wall of the double-structured snout is raised (JP-A-2-12935).
No. 3) removes dross inside the snout.

[0011]

When a dross pump, a dross collecting trough and a dross collection box are arranged in a snout, the dross separated from the inside of the snout passes through a dross discharge pipe immersed in a plating bath. And taken out. Since this dross discharge pipe is in contact with the plated metal in a molten state, the erosion is severe, and frequent replacement is required. The snout itself has a complicated structure,
Inspection becomes troublesome. On the other hand, in the method of removing dross by raising the outer wall of the double snout, it takes time and effort to replace the reducing atmosphere with the air atmosphere between the inner and outer walls of the snout.

Therefore, Japanese Patent Application Laid-Open No. 3-111544 discloses that the contact angle of the snout with the plating bath, the immersion depth,
It is introduced that by defining the inner width of the snout, dross inside the snout is put on the flow of the plating metal accompanying the steel sheet and flows out to the outside. The snout used at this time does not require ancillary equipment such as a pump, a dross collecting trough, and a dross collection box, and has an advantage of a simplified structure basically similar to a conventional snout.

[0013] However, the accompanying flow of the plating metal accompanying the running of the steel sheet changes according to various conditions such as the passing speed, the surface condition of the steel sheet, and the fluidity of the plating bath. Therefore, it is necessary to prepare a plurality of snouts corresponding to the operating conditions and replace the snouts each time the operating conditions change. As a result, a long snout replacement operation is required to change the operating conditions.

In addition, since the interval between the inner surface of the snout and the surface of the steel sheet is set relatively short, when the plating operation is interrupted for a long time, a bridge is easily generated between the inner surface of the snout and the steel plate surface. Therefore, when the plating operation is restarted, it takes time to reach a stable steady state, and a defective and non-uniform plating layer is formed on the metal strip fed during that time. As a result, the yield of the plating material as a product is reduced.

The present invention has been devised in order to solve such a problem. By making the distance between the metal strip to be plated and the inner surface of the snout variable, the dross inside the snout can be reduced. To the outside efficiently,
An object of the present invention is to provide a snout that has high flexibility in changing operating conditions and quickly returns to a steady state even when resuming a plating operation.

[0016]

According to the present invention, there is provided a snout for a hot-dip plating apparatus, wherein a metal strip is guided from a reduction furnace to a plating tank in a reducing atmosphere in order to achieve the object. A front wall portion and a rear wall portion divided so as to be able to approach and separate along a direction perpendicular to the surface of the front wall portion, and the front wall portion is configured such that a degree of fitting between the front wall portion and the rear wall portion can be adjusted. And the rear wall portion is supported on the outlet side of the reduction furnace.

The front wall portion and the rear wall portion are formed, for example, on the U-shaped side, and both ends are fitted to each other. Further, the front wall portion and the rear wall portion can also be constituted by divided walls that slide in the width direction of the metal strip.

[0018]

[Operation] The present inventors conducted a simulation test using a water model device in order to grasp the flow behavior of the plated metal inside the snout. As shown in FIG.
A transparent snout 35 is immersed in a container filled with test water 55 in which colored acrylic beads 54 are suspended, and
Was run continuously. Thereby, the flow of the test water 55 is
It was visualized by the flow state of the acrylic beads 54.

Most of the acrylic beads 54 inside the snout 35 were sent out of the snout 35 on the accompanying flow of the test water 55 generated by the running of the strip 15 (54a). However, the acrylic beads 54 not discharged from the snout 35 stayed near the inner surfaces of the front wall 35a and the rear wall 35b of the snout 35 (54b). In addition, there was a case in which the wrapped material wrapped around the inner surfaces of the front wall 35a and the rear wall 35b and the inner surface of the side wall 35c (54c).

Therefore, the test water 5 generated by running the strip 15
The dross discharge action range exerted by the associated flow of No. 5 is Snout 35
It is supposed that increasing the proportion of the inside of the space is effective in removing dross. Based on this assumption, the width and depth of the snout 35 are adjusted, and the snout 35 is adjusted.
A simulation test was performed in which the proportion of the dross discharge action area occupying the internal space was changed.

The width and depth of the snout 35 are reduced, and the band 1 is removed from the front wall 35a, the rear wall 35b, and the side wall 35c.
It was observed that as the distance to 5 became shorter, most of the acrylic beads 54 in the snout 35 were sent out of the snout 35. Then, only a very small amount of the acrylic beads 54 stayed inside the snout 35. This indicates that the ratio of the dross discharge action area occupying the inner space of the snout 35 has been increased by reducing the width and the depth of the snout 35.

However, if the front wall 35a, the rear wall 35b, and the side wall 35c are too close to the strip 15, the strip 15 that travels in the snout 35 and enters the test water 55 has flapping. It was observed that the band material 15 was in contact with the inner surface of.

From a simulation test using such a water model, it has been found that when the distance between the inner surface of the snout and the metal strip is kept within a certain distance range, a hot-dip coating layer free of dross formation is formed. I understand. That is, the dross inside the snout is efficiently discharged to the outside of the snout by riding on the accompanying flow of the plated metal generated by running of the metal strip. Also, the contact of the metal strip with the inner surface of the snout is prevented by keeping the distance between the inner surface of the snout and the metal strip at a predetermined value or more.

The distance between the inner surface of the snout and the metal strip is determined by the size and surface condition of the metal strip to be plated.
It changes depending on the passing speed of the metal strip, the fluidity of the plated metal, and the like. That is, the front wall and the rear wall are relatively movable so that the distance can be changed because the distance changes with the change in the plating condition. Also,
The side walls can also be moved relative to each other as needed so that it can handle plating of metal strips of different widths. This allows
It is possible to provide a snout internal space in which the proportion of the dross discharge action range suitable for various plating conditions is high.

[0025]

EXAMPLE Based on the results of the above simulation test, a hot-dip plating apparatus having a snout 31 with a variable distance was assembled as shown in FIG. Front wall 31 of snout 31
a and the rear wall 31b were connected to the outlet 22 of the reduction furnace 20 via bellows 21a and 21b, respectively. The front wall 31a and the rear wall 31b are both formed in a U-shape, and as shown in FIG.
It defines a cylindrical internal space 32 through which 0 passes.

The internal space 32 can change its internal cross section by moving the front wall 31a and the rear wall 31b, including the bellows 21a and 21b, close to or away from each other. FIG.
(A) shows a state where the front wall 31a and the rear wall 31b are brought close to each other with the pressing force F, and the metal strip 10 is hot-dip plated. On the other hand, FIG. 3B shows the front wall 31a and the rear wall 31.
b shows a state where they are separated from each other.

A plating bath 50 was prepared by injecting 170 tons of Zn into the plating tank 40 and maintaining the temperature at 460 ° C.
Then, a 1 mm-thick ordinary steel sheet as the metal strip 10 is subjected to a heat reduction treatment at 485 ° C. in the reduction furnace 20, and then sent to the plating tank 40 via the snout 31 at a sheet passing speed of 90 m / min. After that, it was pulled up from the plating bath 50. At this time, the metal strip 1 running in the snout 31
The distance from 0 to the inner surface of the front wall 31a and the rear wall 31b is
Both were set to 42 mm.

Under these conditions, hot-dip plating on the metal strip 10 was continued for 6 hours. During the plating period, a probe was inserted into the snout 31 and the liquid level of the plating bath 50 was observed. As a result, the stays 54b, 5 explained in FIG.
4c was not observed inside snout 31. In addition, a plating layer having excellent surface properties without defects due to dross biting was formed on the obtained plated strip 11.

Next, the front wall 31a and the rear wall 31b are
As shown in (b), the distance between the front wall 31a, the rear wall 31b, and the metal strip 10 was set to 100 mm, which is equivalent to the conventional technology, while being separated from each other. Then, the metal strip 10 was subjected to hot-dip plating under the same conditions. At this time, in the internal space 32 of the snout 31 observed by the probe, FIG.
The stagnation 54b, 54c described in (1) was observed. In addition, the obtained plated strip 11 also had a plated layer in which defects caused by dross biting were scattered.

FIG. 5 shows an embodiment of the present invention in which the distance between the front wall 31a, the rear wall 31b and the metal band 10 is set to 42 mm, and the distance between the front wall 31a, the rear wall 31b and the metal band 10. For the comparative example in which the distance was set to 100 mm, the snout 31 was used.
The dross inside the snout is observed with a probe, and the distribution state is expressed as the distribution ratio of the ratio of the area where the dross exists to the opening area of the snout. As is clear from FIG. 5, in the embodiment of the present invention, the dross existing in the snout 31 is reduced by about 15% as compared with the comparative example. Moreover, it was confirmed by observation with a probe that the dross in the snout 31 was constantly discharged to the outside. It is presumed that this difference in the dross distribution rate affects the quality of the plating layer formed on the plating strip 11 described above.

The running of the metal strip 10 was stopped, and the plating operation was interrupted. At this time, the distance between the front wall 31a, the rear wall 31b, and the metal strip 10 was increased to 100 mm. Then, after the interruption for 3 hours, the distance between the front wall 31a, the rear wall 31b and the metal strip 10 was returned to 42 mm, and the plating operation was restarted. Thirty seconds after the restart, the plating conditions returned to a steady state. On the other hand, the front wall 31a, the rear wall 31b and the metal strip 1
When the plating operation was restarted after the interruption of 3 hours while maintaining the distance between the distance to 0 and 100 mm, it took 60 seconds until the plating conditions returned to the steady state.

From this, it is apparent that the snout of the present invention is suitable for forming a high-quality plating material having no defects caused by dross biting, and of course, the front wall 31a and the rear wall 31a can be changed according to the change of plating conditions. By changing the distance between the wall 31b and the metal strip 10, a high-quality plating material can be manufactured. In addition, even when the plating operation is continued, interrupted, or resumed, the start-up time required to return to the steady state is reduced, and a hot-dip plating apparatus with high flexibility can be obtained.

The width of the metal strip 10 to be plated is substantially constant. Therefore, as shown in FIG.
Most of the metal strip can be hot-dip plated with the snout 31 that can change the distance between the rear wall 31b and the metal strip 10.

As shown in FIG. 4, the front wall 31a and the rear wall 31b
Is fitted, the flow f of the plating metal flowing into the internal space 32 of the snout 31 is also seen from the gap between the fitting portions of the front wall 31a and the rear wall 31b. This flow f can also increase the proportion of dross accompanying the metal strip and sent out of the snout 31.

Alternatively, in order to promote the inflow of the plating metal into the snout 31, a plating bath 50 as shown in FIG.
The inflow hole 33 can be formed in the side wall of the snout 31 at a position slightly lower than the liquid level 50a. Inlet 33
The plated metal that has flowed into the snout 31 through the metal strip 10 is accompanied by the metal band material 10 and flows out from the lower end opening of the snout 10. Snout 3 with inflow and outflow of plating metal
The dross inside the snout 31 is constantly discharged, and the inside of the snout 31 is maintained at a dross concentration of almost the same cleanliness as the plating bath 50 outside the snout 31.

Depending on the demand, metal strips having different widths may be used as the material to be plated. In such a case, the distance between the metal strip 10 and the inner surface of the side wall of the snout 31 becomes large, and the stagnation 54c of the plating metal may occur near the inner surface of the side wall 35c described with reference to FIG.

Therefore, as shown in FIG.
_1, the front wall 31a at 31a _2, the dividing wall 31b _1, 31b
₂ , the rear wall 31b is made, and the divided walls 31a ₁ and 31a ₂ and the divided walls 31b ₁ and 31b ₂ are slid with each other to adjust the width of the front wall 31a and the rear wall 31b according to the width of the metal strip 10. I do. This makes it possible to use the same snout 31 for the metal strips 10 having different widths and to form a high-quality plating layer without dross biting.

The distance from the surface of the metal band plate 10 to the inner surfaces of the front wall 31a and the rear wall 31b and the distance from the edge of the metal band material 10 to the side wall surface of the snout 31 efficiently increase the dross 52 in the snout 31. This is important for discharging the powder on the accompanying flow of the plating metal.

For example, without restricting the present invention, the distance from the surface of the metal strip 10 to the inner surfaces of the front wall 31a and the rear wall 31b is set within a range of 30 to 100 mm under normal operating conditions. . Then, an appropriate value in a range of 30 to 100 mm is determined in consideration of plating conditions such as past results and a passing speed. Alternatively, even when the plating operation is continued, the distance can be changed while observing the surface state of the plating material 11 pulled up from the plating bath 50.

[0040]

As described above, the snout according to the present invention is provided so that the dross inside can be efficiently discharged by riding the flow of the plating metal generated by the movement of the metal strip as the material to be plated. The distance from the surface of the strip to the inner surface of the snout can be changed. Therefore, a high-quality plating layer free from defects due to dross bite is formed on the obtained plated product. Further, since the distance from the surface of the metal strip to the inner surface of the snout can be changed according to the plating conditions such as the passing speed and the size of the metal strip, an extremely flexible hot-dip plating apparatus can be obtained.

[Brief description of the drawings]

FIG. 1 Conventional hot-dip plating equipment

Fig. 2 Water model for investigating the flow of plating metal inside the snout

FIG. 3 is a hot-dip plating apparatus according to an embodiment of the present invention.

FIG. 4 is a cross section of the snout used in the embodiment.

FIG. 5 is a graph showing the dross discharging action of the snout together with a comparative example.

FIG. 6 shows an example of a snout having an inflow hole for plated metal.

FIG. 7 shows an example of a snout in which the length is also variable in the width direction of the metal strip.

[Explanation of symbols]

Reference Signs List 10 Metal strip 20 Reduction furnace 22 Exit side
31 snout 31a front wall 31a _1, 31a ₂ dividing walls
31b rear wall 31b _1, 31b ₂ dividing walls 40 plating tank 50 plating bath 52 dross

────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Nobuo Hatanaka 1 Nisshin Steel Co., Ltd. Ichikawa Works, ⁷ Takayashinmachi, Ichikawa City, Chiba Prefecture (58) Field surveyed (Int.Cl. ⁷ , DB name) / 00-2/40

Claims (2)

(57) [Claims] 1. A snout for guiding a metal strip from a reduction furnace to a plating tank under a reducing atmosphere, wherein the front wall is divided so as to be able to approach / separate along a direction orthogonal to the surface of the metal strip; It has a rear wall portion, and the front wall portion and the rear wall portion are supported on the outlet side of the reduction furnace so that the degree of fitting between the front wall portion and the rear wall portion can be adjusted. Snout for hot-dip plating equipment. 2. A snout for a hot-dip plating apparatus according to claim 1, wherein the front wall portion and the rear wall portion are formed of divided walls that slide in the width direction of the metal strip.