JP3405855B2 - Manufacturing equipment for hot-dip coated steel sheets - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for producing a hot-dip galvanized steel sheet, and more particularly, to a molten metal holding container having a relatively small volume for penetrating a hot-dip metal bath and running a steel strip vertically upward. The present invention relates to a technique for supplying components to a molten metal bath when plating molten metal using a so-called air pot.

[0002]

2. Description of the Related Art Molten metals (eg Zn, Al, Mn, P)
(b and its alloy) A general method for producing a plated steel sheet is as follows. That is, after the surface of the cold rolled steel sheet is cleaned in a pretreatment step, the steel sheet is heated and annealed in a non-oxidizing or reducing atmosphere, and then cooled to a temperature suitable for plating without being oxidized, and then the plating is performed. Immerse continuously in the bath. Excess molten metal adhering to the surface of the steel sheet in the bath is removed by an adhering amount adjusting device such as gas wiping to adjust the adhering amount and then cooled. The production of the plated steel sheet is usually carried out by adding unavoidable impurities to the molten metal as the main component, and typical products include hot-dip galvanized steel sheets (including alloyed hot-dip galvanized steel sheets) and hot-dip galvanized steel sheets. There are aluminized steel sheets. Specifically, in a hot-dip galvanized steel sheet, a slight amount of Al in the hot-dip zinc, which is the main component,
In hot-dip aluminized steel sheet, the main component is hot-melt A
A trace amount of Si is generally added to 1 l. The reason for adding them is to suppress the growth of a hard and brittle alloy layer at the interface between the molten metal and the base steel sheet, and improve the plating adhesion. However, in order to appropriately suppress the growth of the alloy layer, the addition amount must be controlled within an appropriate range.

In the case of a hot-dip galvanized steel sheet, the added Al reacts with the steel sheet preferentially over Zn in the hot-dip zinc bath, and an Al-rich layer (F) is formed at the interface between the plating layer and the base steel sheet.
e-Al intermetallic compound) to produce Fe-Zn.
The galvannealed steel sheet having excellent adhesiveness, and further the galvannealed steel sheet having good powdering resistance are manufactured by suppressing the alloying reaction of.

By the way, the amount of Al added to the hot dip galvanizing bath is (1) the formation of a preferential Al-rich layer,
(2) The dross is reduced by generation and removal of the dross from the plating bath. Therefore, it is necessary to supply the reduced amount to the plating bath. As a replenishment method thereof, conventionally, a Zn ingot and a pure Zn ingot containing a target or a higher concentration of Al are put into the plating bath. However, in the method of replenishing Al with the ingot, the ingot put in the plating bath dissolves and diffuses in the plating bath, and it takes time to form a uniform plating bath, or the ingot is completely dissolved and diffused. Since the Al concentration in the bath continues to decrease from the beginning until the next ingot is fed, there is a problem that the Al concentration in the plating bath greatly changes corresponding to the pitch at which the ingot is fed. That is, if the Al concentration in the plating bath fluctuates as described above, the above-described formation of the Al-enriched layer becomes non-uniform, and stable plating quality cannot be obtained.

Therefore, in order to solve such a problem, Japanese Patent Laid-Open No. 165753/1989 discloses that a supplementary component is melted in advance,
Using a plurality of held premelt pots (corresponding to the melting bath of the present application), the components are replenished from the premelt pot to the plating bath so as to correspond to the required concentration of the replenishment component and the reduction amount of the plating bath. Or using at least one premelt pot in which the replenishment component has been melted and held in advance and at least one hopper containing a metal lump or metal powder grain of the replenishment component, and the required concentration of the replenishment component and the reduction amount of the plating bath. In order to deal with the above, a method for supplying components to the plating bath is disclosed, in which the components are supplied from the premelt pot and the hopper to the plating bath. In addition, JP-A-2-
Japanese Laid-Open Patent Publication No. 104649 uses a plurality of premelt pots or at least one hopper in which a replenishment component is melted and held in advance, and is provided in a plating bath so as to correspond to a required concentration of the replenishment component and a reduction amount of the plating bath. The components are supplied from the premelt pot or the premelt pot and the hopper to a mixing tank (corresponding to the mixing tank of the present application), and the components are replenished by injecting from the mixing tank into a plating bath using an injection nozzle. Disclosed is a method of supplying components to a plating bath, which is characterized by the above.

However, the above-mentioned Japanese Patent Laid-Open No. 16575/1989.
In the method described in Japanese Patent Publication No. 3, the concentration of the component varies near the nozzle for supplying the supplemental component to the plating bath and in other places, resulting in non-uniform concentration distribution in the plating tank.
Another problem has arisen that the plating quality is uneven over the entire steel sheet. Moreover, it has a large capacity (usually 100 to 20) using conventional plating equipment, that is, rolls (sink rolls, support rolls, etc.) for transporting steel plates in the plating bath.
It is about 0 ton) and the segregation of components hardly occurs in the plating tank.

Further, the present invention is a case where a so-called aerial pot disclosed in JP-A-4-356 or JP-A-7-48660 is used in a plating tank, and the plating bath capacity is less than 1 ton. It will be a small capacity not to exist.
That is, since the supplied plating bath has a small capacity, the supplied plating bath immediately adheres to the steel plate and is plated.Therefore, it may become more important for the supply component and the supply method of the molten metal. . For example, as shown in FIG.
(Described in Japanese Patent Publication No. 09149), the molten metal 6 is supplied to the plating bath in the molten metal holding container 2 by one tubular body 13 that is perpendicular to the surface of the steel strip. ing. In this case, it is clear that the components become non-uniform in the width direction of the steel strip 1, which may not be suitable for actual use. It should be noted that there are many published patent publications relating to the aerial pot method, but most of them are related to a technique for preventing molten metal from leaking from the pot, and no related method or apparatus for supplying molten metal is found. Is the current situation.

[0008]

DISCLOSURE OF THE INVENTION In view of the above circumstances, the present invention is directed to a hot-dip galvanized steel sheet for obtaining a product having excellent plating quality without segregation of the molten metal component depending on the position in the molten metal holding container. It is intended to provide a manufacturing apparatus.

[0009]

In order to achieve the above-mentioned object, the present inventor has sharply revised the conventional molten metal holding container of the air pot system (hereinafter, simply called a holding container). As a result, I realized that the holding container had a relatively small capacity, which deteriorated the plating quality, and conceived that the molten metal was appropriately supplied to the holding container as a countermeasure. That is, the present invention is a manufacturing apparatus for a molten metal-plated steel sheet, which comprises a molten metal holding container in which a molten metal bath is filled, a steel strip running vertically upward through the molten metal bath, is provided in the holding container. Is prepared and stored in advance, and an auxiliary container with a bath surface height adjusting means is connected, and a connecting passage for supplying the molten metal from the auxiliary container to the holding container is formed by a cylindrical body, and the arrangement of the cylindrical body is arranged. The apparatus for producing a hot-dip galvanized steel sheet is characterized in that the installation interval is 1/2 or less of the width of the steel strip passing through the holding container. Further, the present invention is an apparatus for producing a hot-dip galvanized steel sheet, characterized in that a slit having a width larger than a steel strip width is used instead of the tubular body, and further, the tubular body or the slit is a steel strip. The apparatus for manufacturing a hot-dip galvanized steel sheet, characterized in that it is provided so as to face the front and back surfaces of.

[0010]

In the present invention, in the apparatus for producing a molten metal-plated steel sheet, which is provided with a molten metal holding container in which a molten metal bath is filled and a steel strip travels vertically upward through the molten metal bath, An auxiliary container with a bath surface height adjusting means for preliminarily preparing and storing metal is connected, and a connecting passage for supplying the molten metal from the auxiliary container to the holding container is formed by a cylindrical body. The arrangement interval is 1 of the width of the steel strip passing through the holding container.
Since it is set to / 2 or less, fluctuations in the components of the plating bath in the plate width direction are suppressed, and quality defects due to uneven plating are eliminated. Further, in the present invention, instead of the tubular body, a slit having a width larger than the steel strip width is used, and further, the tubular body or the slit is provided so as to face the front and back surfaces of the steel strip. Therefore, the above-mentioned effect becomes more remarkable and can be surely achieved.

In the present invention, the arrangement interval of the cylindrical members is set to 1/2 or less of the width of the steel strip passing through the holding container, because if it is less than that, the components cannot be made uniform in the width direction of the steel strip. Is. Further, the width of the steel strip is usually about 800 mm to 2000 mm, and the holding container is designed corresponding to the width of the steel strip to be plated. The contents of the present invention will be specifically described below with reference to FIGS.

[0012]

【Example】

(Example 1) Using the plating apparatus according to the present invention shown in FIGS. 1 and 2 (connection passage of pipes), an aluminum-killed steel strip after cold rolling was subjected to hot dip galvanizing under the following conditions. Also,
In FIG. 1, the auxiliary container 3 is arranged only on one side of the steel strip 1, but the present invention also includes the case where it is arranged on both sides.

Molten metal composition: 0.25 wt% Al-0.
002wt% Pb-Zn Target plating composition: Al concentration in plating layer: 0.55 ± 0.10wt% Pb concentration in plating layer: 0.002 ± 0.001wt% Other plating conditions Bath temperature: 470 ° C Intrusion plate temperature: 475 ° C. Immersion time of steel strip in plating bath: 0.01 seconds Steel strip thickness: 0.7 mm Steel strip width: 1500 mm Steel strip traveling speed: 120 m / min Molten metal adhesion: 45 g / m ² ( One side) Inner diameter of pipe of connecting passage: 35 mm Disposing interval of pipe of connecting passage: 400 mm Hot dip galvanizing is continuously performed under the above conditions. At that time, the molten metal 6 is not supplied to the molten metal holding container 2. The bath surface height adjusting means 5 provided in the auxiliary container 3 adjusts the bath surface height to be constant. Further, the supply of the molten metal 6 to the auxiliary container 3 is performed from a separately provided molten metal melting tank 8.

The implementation results of the present invention were obtained by sampling the plated steel sheet at an arbitrary position in the width direction of the steel strip and analyzing the plated layer. The results are shown in FIG. 6, where A in the plating layer
From the result of the 1-concentration analysis, there was no variation in the plate width direction, and uniform plating quality was obtained. Further, the plating adhesion of the plated steel sheet was determined by using a known "0-T bending test method", and the result was no peeling or cracking.

Here, the "0-T bending test method" means that a sample of a predetermined size is extracted from a plated steel sheet and
After performing an 80 ° bending test (determined by peeling with cellophane tape), the bent portion is visually observed to determine the state of peeling and cracking. In addition, in Table 1, the plating adhesion is evaluated by the following symbols.

[0016]

[Table 1]

×: Poor adhesion ○: Good adhesion ◎: Excellent adhesion (Example 2) The same plating conditions as in Example 1 except that the slit-shaped connecting passage 4 shown in FIG. 3 was used. Hot-dip galvanizing was performed.

Slit gap: 20 mm Slit width: 1600 mm The same hot-dip galvanizing as described above was continuously performed under the above conditions, the plated steel sheet at any position was sampled, and the plating layer was analyzed. The execution result is shown in FIG. 7. Although the Al concentration increases at the position corresponding to the connecting passage 4 in the plate width direction, it is within the target range, and the object of the present invention is achieved. In addition, the result of the plating adhesion according to the "0-T bending test method" was also good (see Table 1).

(Embodiment 3) Hot dip galvanizing was performed in the case where the slit-shaped connecting passages shown in FIG. 3 were provided so as to face the front and back surfaces of the steel strip. Sampling was performed at an arbitrary position on the surface of the obtained galvanized steel sheet, and the plating layer was investigated. The results are shown by the curve A in FIG. 11, and the Al concentration did not vary in the plate width direction, and uniform plating quality was obtained. The plating adhesion was also very good and the results are shown in Table 1.

Further, the slit-shaped connecting passage 4 shown in FIG.
Hot dip galvanizing was also performed in which was provided only on the back side of the steel strip.
Similar to the above, the plating layer was investigated by sampling from the front and back sides at arbitrary positions. As a result, as is clear from the B curve in FIG. 11, the Al concentration does not vary in the plate width direction,
I was able to adjust within management objectives. However, the plating adhesion was slightly lower than in the case of the A curve, but it was in a good range without causing a big problem.

(Embodiment 4) The following hot dip galvanizing was carried out using the apparatus having the tubular connecting passage shown in FIG. Base material Steel type: Aluminum-killed cold-rolled steel strip Plating conditions: Tube inner diameter of connecting passage 40 mm Tube disposing interval of connecting passage 350 mm Sampled hot dip galvanized steel strip obtained at any position to obtain plating adhesion 0-T The bending test evaluated the results, and the results are shown in Table 1. The results were good.

(Comparative Example 1) Hot dip galvanizing was performed under the same plating conditions as in Example 1 except that the slit-shaped connecting passages having a plate width equal to or smaller than that of the steel sheet to be plated shown in FIG. 4 were used. Plating conditions Slit gap: 35 mm Slit width: 500 mm Hot dip galvanizing was continuously performed under the above conditions, the plated steel sheet at any position was sampled, and the plating layer was analyzed. The results are shown in FIG. 8. Although the plating layer having the target Al concentration was obtained at the position corresponding to the slit installation position in the plate width direction, the Al concentration was decreased at the edge of the plated steel sheet, and "0- According to the "T bending test", peeling of the plating layer was observed (see Table 1).

(Comparative Example 2) Hot dip galvanizing under the same plating conditions as in Example 1 except that the connecting passages of the pipes arranged at intervals similar to the plate width of the steel sheet to be plated shown in FIG. 5 were used. I went. Plating conditions Inner diameter of pipe body of connecting passage: 35 mm Disposing interval of pipe body of connecting passage: 1600 mm Hot dip galvanizing was continuously performed under the above conditions, and a plated steel sheet was sampled at an arbitrary position to analyze a plated layer. The results are shown in FIG. 9. A plating layer having a target Al concentration was obtained at a position corresponding to the connection passage disposition place in the plate thickness direction, but a decrease in Al concentration was observed in the central portion of the plated steel sheet. Moreover, the result of "0-T bending test method" was peeling of the plating layer (see Table 1).

In the embodiment, the pipe body 1 is used as the connecting passage 4.
However, in the present invention, the cross section may have any shape as long as it is cylindrical. (Comparative Example 3) In the same manner as above, hot dip galvanizing was performed under the following conditions using the apparatus shown in FIG. Base material Steel type: Aluminum-killed cold-rolled steel strip plating conditions Inner diameter of connecting passage tube: 40 mm Disposed interval of connecting passage tubes: 1350 mm The obtained hot-dip galvanized steel sheet was sampled in the same manner as above, and the result of 0-T bending test Is shown in Table 1, and it is clear that the plating adhesion is not good.

Although the electromagnetic coil for preventing the leakage of the molten metal is not provided at the bottom of the molten metal holding container in this embodiment and the comparative example, the present invention does not take any measures for preventing the leakage of the molten metal. It can also be applied to the existing air pot type molten metal plating apparatus.

[0026]

As described above, according to the present invention, the means for supplying the molten metal into the so-called aerial pot, which has a significantly smaller plating bath capacity than the conventional one, is improved, and the plate width of the obtained plated steel strip is improved. It has become possible to suppress variations in the plating composition in different directions. As a result, it has become possible to continuously and stably produce a hot-dip plated metal product having good plating adhesion.

[Brief description of drawings]

FIG. 1 is a diagram showing a cross-sectional view of a hot-dip galvanizing facility showing an embodiment of the present invention.

FIG. 2 is an embodiment of the present invention showing a sectional view taken along the line AA ′ of FIG. 1, in which the connecting passage is an example of a tubular body.

3 is an embodiment of the present invention showing a sectional view taken along the line AA ′ of FIG. 1, in which the connecting passage is an example of a slit.

FIG. 4 is a diagram showing a comparative example in which the connecting passage is a slit but does not satisfy the claims of the present invention.

FIG. 5 is a view showing a comparative example in which the connecting passage is a tubular body but does not satisfy the claims of the present invention.

FIG. 6 is a diagram showing the results of implementation of the present invention, which is the result of measuring the Al concentration in the plating layer of a hot-dip galvanized steel sheet in the width direction (the connecting passage is a tubular body).

FIG. 7 is a diagram showing the results of implementation of the present invention, and is a result of measuring the Al concentration in a plating layer of a hot-dip galvanized steel sheet in the plate width direction (the connecting passage is a slit).

FIG. 8 is a view showing the performance results of Comparative Example 1, and is a result of measuring the Al concentration in the plating layer of the hot-dip galvanized steel sheet in the plate width direction (the connecting passage is a slit).

FIG. 9 is a view showing the performance results of Comparative Example 2, and is a result of measuring the Al concentration in the plating layer of the hot-dip galvanized steel sheet in the plate width direction (the connecting passage is a tubular body).

FIG. 10 is an explanatory view of supplying molten metal that is a plating bath to a molten metal holding container (using an electromagnetic pump), (a) is a vertical sectional view, and (b) is a horizontal sectional view.

FIG. 11 is a diagram showing the results of Example 3 of the present invention.

[Explanation of symbols]

1 Steel strip (steel plate) 2 Molten metal holding container (air pot) 3 auxiliary containers 4 connecting passages 5 Bath height adjusting device 6 Molten metal (plating bath) 7 Guide roll 8 melting tank 9 Molten metal supply pump 10, 11, Plate width of steel strip to be plated 12 slit gap 13 slits 14 Cylindrical body (tubular body) 15 gas wiper 16 electromagnetic coil

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuya Miyakawa 1 Kawasaki-cho, Chuo-ku, Chiba City Kawasaki Steel Co., Ltd. Inside Chiba Works (72) Inventor Takashi Nito 1 Kawasaki-cho, Chuo-ku, Chiba City Kawasaki Steel Co., Ltd. Company Chiba Steel Works (56) Reference JP 4-36446 (JP, A) JP 1-180954 (JP, A) JP 62-112767 (JP, A) JP 64-28354 (JP , A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C23C 2/00-2/40

Claims (3)

(57) [Claims] 1. An apparatus for producing a molten metal-plated steel sheet, comprising: a molten metal holding container filled with a molten metal bath; and a steel strip running vertically upward through the molten metal bath, wherein the holding container is filled with molten metal. An auxiliary container with a bath surface height adjusting means to be prepared and stored in advance is connected, and a connecting passage for supplying the molten metal from the auxiliary container to the holding container is formed in a tubular body, and the tubular body is disposed. An apparatus for producing a hot-dip galvanized steel sheet, characterized in that the interval is 1/2 or less of the width of the steel strip passing through the holding container. 2. A molten metal-plated steel sheet manufacturing apparatus provided with a molten metal holding container in which a molten metal bath is filled, a steel strip runs vertically upward through the molten metal bath, and the molten metal is put in the holding container. An auxiliary container with a bath surface height adjusting means to be prepared and stored in advance is connected, and a connecting passage for supplying the molten metal from the auxiliary container to the holding container is formed by a slit having a width larger than the width of the steel strip. An apparatus for producing a hot dip plated steel sheet. 3. The apparatus for producing a hot-dip galvanized steel sheet according to claim 1, wherein the connecting passages are provided so as to face the front and back surfaces of the steel strip.