JPH0610331B2 - Molten metal plating device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a hot-dip galvanizing apparatus, and particularly to an attempt to obtain a hot-dip galvanized steel strip having a beautiful and smooth surface with high productivity. .

(Prior art) Zinc, a zinc-aluminum alloy, aluminum and lead, and a metal containing one or more of magnesium, silicon, ammothine, cobalt, chromium, and a rare earth element mainly for the purpose of anticorrosion and decoration. Various types of hot-dip galvanized steel strips are widely used for applications such as building materials, automobiles and home appliances.

These various hot-dip galvanized steel strips are generally cleaned and annealed on the steel strip surface, then the steel strip temperature is adjusted to a temperature suitable for plating, and a molten metal bath is introduced while the surface is clean. After the plating is applied, the amount of the applied coating is adjusted by the gas wiping method, and then various post-treatments are performed according to the purpose to obtain a product.

However, the conventional method as described above is a mechanism in which the steel strip is introduced and then introduced into the molten metal bath whose upper part is opened, so that dross that is almost inevitably generated and remains in the bath,
It was often observed that harmful foreign substances such as ash and bricks adhered to the surface of the steel strip and significantly impaired the appearance. Such foreign matter adhered to the surface of the steel strip causes troubles called star eyes or print-through defects when the steel strip is subjected to press working for automobile bodies, for example.

In addition to the harmful foreign substances, in the conventional method, for example, when a gas wiping method is used for adjusting the amount of adhesion, unevenness of the adhesion thickness called wrinkle occurs on the plated surface, which causes the above-mentioned surface appearance. Alternatively, it may be a problem from the viewpoint of press working. Although the mechanism of generation of such wrinkles has not been completely clarified, it is considered to be caused by rattling of the sink roll in the molten metal bath and oxidation at the time of adjusting the adhesion amount.

Furthermore, the conventional method also has a problem in that the improvement in productivity cannot be expected so much. That is, in order to improve the productivity of the hot-dip galvanized steel strip, it is essential that high-speed plating is possible. However, for example, when adjusting the basis weight by the gas wiping method, the amount of molten metal that adheres to the steel strip and is taken out of the molten metal bath increases as the line speed increases. It is necessary to increase the wiping gas pressure, increase the wiping gas pressure, increase the gas amount, or reduce the distance between the steel strip and the wiping gas nozzle. Due to this, splash (molten metal splash) is generated and troubles such as adhesion to the plating surface cannot be avoided. Therefore, in this case, high-speed production is virtually impossible.

Recently, several kinds of hot-dip galvanized steel strips are often produced in one production facility, but this causes a problem of time loss and reduction of productivity. For example, considering the case where a hot dip galvanized steel strip and a hot dip galvanized-aluminum plated steel strip are produced by one production facility, the molten metal bath is completely replaced or the molten metal bath is replaced in accordance with the switching of the operation. Although the contents, that is, the zinc plating solution and the zinc-aluminum plating solution are replaced, the former requires a long time for replacement due to structural problems of the device, while the latter requires a device for replacement, for example, a pumping speed of a pump. Since it is relatively slow and it takes time to adjust the components in the molten metal, in any case, it took a long time to change the plating metal species.

(Problems to be Solved by the Invention) The present invention is: i) Almost no harmful foreign substances such as drawers, ash, and bricks are attached to the surface of the plated steel strip. Ii) Water wrinkles and other uneven patterns, and No roll flaws occur, iii) high-speed production is possible without splashing, and iv) even when the plating metal type is changed variously in the same production facility, It is an object of the present invention to propose a hot-dip galvanizing apparatus having a new structure in which the metal type can be changed in a short time.

(Means for Solving Problems) That is, the present invention is a molten metal plating apparatus for plating a steel strip by immersing the steel strip in a molten metal plating bath for plating. It becomes a closed vertical tank that vertically passes from the lower part to the upper part of the tank, and the vertical tank has at least one pair of seal rolls on the inlet side and the outlet side of the steel strip, and A hot-dip galvanizing apparatus comprising a supply port and a discharge port for supplying and discharging.

Further, the present invention is a molten metal plating apparatus for performing plating by dipping a steel strip in a molten metal plating bath,
The plating bath is a closed vertical tank in which the steel strip is vertically passed from the bottom of the bath to the top of the bath, and the vertical bath has at least one pair of seal rolls on the inlet side and the outlet side of the steel strip, respectively. Further, a deposition amount adjusting chamber in a non-oxidizing atmosphere, which has a supply port and a discharge port for supplying and discharging molten metal into and from the tank, and further has a means for adjusting the plating solution deposition amount in the upper part of the vertical tank. In some cases, the molten metal plating apparatus is further provided with a plurality of storage tanks for the molten metal plating solution and supply and recovery pipes for the plating solution that connect the storage tank and the vertical tank.

The present invention will be specifically described below.

Now, the first feature of the present invention is to make a vertical pass for passing a steel strip from the lower side to the upper side, and to pass the steel strip in a vertical plating bath, which is also called a large gap tightly packed. This is where you get a beautiful plated surface with no harmful foreign substances.

FIG. 1 schematically shows a preferred example of the molten metal plating apparatus according to the present invention. In the figure, numeral 1 is a steel strip, 2 is a turn-up roll, and the steel strip 1 fed from the continuous furnace 3 is a turn. The path is changed upward by the up roll 2 and is guided to the plating chamber 4.

Reference numeral 5 denotes a closed vertical plating bath, which is preferably constructed of a ceramic material that does not react even when it comes into contact with a plating solution, or at least an inner wall is coated with a ceramic coating.

Further, the size of the bathtub 5 is set to be slightly wider than the expected maximum steel strip width in the steel strip width direction. On the other hand, the gap width and the length of the bath vary depending on the line speed, the type of plating plate and the required supply amount (supply speed) per unit time, but the gap width is 20 to 500 mm and the bath length is 1000 mm. It is preferably about 4000 mm.

In any case, the point is sufficient for the steel strip surface and the molten metal plating solution to come into sufficient contact with each other in the plating bath, and for the so-called plating reaction to occur mainly between Fe and the molten metal on the steel strip surface due to intermetallic bonding. For a certain period of time, avoiding contact between the inner wall of the gap and the steel strip so that they do not get scratched, and also promptly eliminating harmful foreign substances generated or mixed in the bathtub. It is important to make the size appropriate.

Reference numerals 6 and 7 denote pairs of seal rolls provided on the inlet side and the outlet side of the steel strip with the vertical plating bath 5 interposed therebetween. These seal roll pairs 6 and 7 prevent the plating solution from leaking from the bath 5 by strongly sandwiching the steel strip 1,
Moreover, the vibration of the steel strip 1 is prevented. Such a seal roll is rotated in a cylindrical casing,
The clearance between the inner surface of the casing and the roll surface is 1 mm
It is preferable to make the front and back as small as possible. For the roll cylinder and casing, it is desirable to select a material that is excellent in wear resistance and does not form an alloy even when it comes into contact with molten metal. The effect of preventing the leakage of the plating solution by the pair of seal rolls can be further enhanced by providing a throat portion 8 with a clearance of 20 mm or less between the plating bath 5 and the seal roll pairs 6, 7. The leakage prevention effect can be further enhanced by arranging two or more pairs of seal rolls on the inlet side.

Further, a small groove is formed on the roll cylinder of the seal roll pair on the exit side, that is, the upper seal roll pair 7, as in the case of the conventional squeezing roll, and the depth of the groove and the pitch of the groove are appropriately selected. By controlling the force, the amount of plating solution attached can be adjusted.

In addition, it is desirable to keep the whole of the vertical tank 5 so as not to lower the temperature of the molten metal, and in order to do so, the difference in the proper plating temperature peculiar to the plating solution type occurring at the start of operation or when the plating solution type is changed is taken into consideration. It is also important to have the function of actively heating.

Next, 9 and 10 are the supply of the molten metal plating solution to the vertical tank 5,
It is a supply port and a discharge port that control discharge.

As shown in the figure, the supply and discharge ports 9 and 10 are provided with a supply port at the inlet side and a discharge port at the outlet side of the steel strip 1, as well as a discharge port at the inlet side and a supply port at the outlet side. May be provided. In the former case, it is advantageous to discharge harmful foreign particles having a low specific gravity to the outside of the bath, while in the latter case, the so-called plating reaction progress rate can be increased, so that the bath length can be shortened or the same. The bath length has an advantage that defects such as non-plating are less likely to occur.

Specifically, when hot-dip galvanizing a silicon-containing high-strength steel sheet, by selecting the latter, it is possible to produce a hot-dip galvanized steel strip with no adhesion and good adhesion. By selecting it, it is possible to reduce the adhesion of harmful foreign particles to the plated surface.

By using the plating equipment that works as described above, a beautiful and smooth plated surface with no harmful foreign substances attached can be obtained, but the strip running speed of the steel strip is increased for the purpose of improving productivity. In such a case, a beautiful plating surface may not be obtained due to insufficient adjustment of the amount of plating solution deposited.

The second feature of the present invention is that even under such a high-speed threading plate,
It is in the place of finishing the plating surface beautifully.

In FIG. 1 mentioned above, 11 is a plating solution adhesion amount adjusting means which may be a gas wiper, and 12 is an adhesion amount adjusting means 11
A recovery guide 13 for the plating solution wiped and removed in step (13) is a receiving box, and these constitute a plating solution adhesion amount adjusting chamber (14). The adhesion amount adjusting chamber 14 is kept in a non-oxidizing atmosphere by being filled with an inert gas such as nitrogen, argon or helium.

In the coating amount adjusting chamber 14 of the plating solution held in such a non-oxidizing atmosphere, the final adjusting amount of the plating amount is adjusted on the plating surface of which the amount is preliminarily adjusted by the upper seal roll pair 7. By doing so, it became possible to carry out plating under high-speed stripping without causing defects such as splash.

Furthermore, a third feature of the present invention is to provide a storage tank for a plurality of molten metal plating solutions and a supply and recovery pipe for the plating solution that connects the storage tank and the vertical difficult tank separately, thereby making it possible to change the plating metal type. However, it can be changed instantly by simply opening and closing the valve attached to the pipe, and therefore the loss of operating time due to the change of plating type can be eliminated.

In FIG. 1, 15 is a supply pipe for the plating solution, 16 is a recovery pipe, 17, 18 and 19 are storage tanks for the plating solution, and 20 is a transfer pump for the plating solution.

In the above plating solution supply / discharge system, a clean plating solution is sent into the vertical tank 5 through the supply pipe 15 and the supply port 9, and excess plating solution discharged from the discharge port 10 is collected in the recovery pipe 16. Although it is recovered again in the storage tanks 17 to 19 via the recovery tank, since the recovered molten metal often contains a relatively large amount of harmful foreign matter, in the storage tanks 17 to 19, the recovery pipe 16 and the supply pipe 15 are combined. It is desirable to separate the positions, and in order to remove harmful foreign substances during this period, it is preferable to clean the plating solution by providing a filter device or a sedimentation separation device utilizing a difference in specific gravity.

Further, it is preferable that the supply pipe 15 and the recovery pipe 16 are kept warm or actively heated in order to suppress the temperature drop of the molten metal.

In addition, in order to prevent the generation of harmful foreign substances as much as possible, it is desirable that the inner wall that contacts the molten metal be made of ceramic and that the molten metal surface be kept in a non-oxidizing atmosphere so that the surface does not oxidize. It is desirable to use an induction heating method.

In addition, it is desirable that the storage tank has a structure in which an unmelted metal block can be charged from the outside in order to supplement the molten metal that is plated and consumed.

Thus, it is possible to stably perform the plating treatment with a clean plating solution containing no harmful foreign matter at an appropriate molten metal temperature, and it is possible to obtain a beautiful and smooth plated surface.

In addition, when changing the type of plating metal, it suffices to supply the plating solution and open / close the valve attached to the recovery pipe, so there is almost no loss of operating time due to the change of the plating solution type.

(Operation) According to the present invention, by vertically passing the steel strip in a vertical tank filled with a clean plating solution, it is possible not only to advantageously avoid the adhesion of harmful foreign matter to the plating surface, but Since it is possible to prevent the occurrence of surface defects such as wrinkles and roll defects due to rattling of the sink roll installed in the bathtub, a beautiful and smooth plated surface can be obtained.

In addition, by providing a plating solution adhesion amount adjusting chamber at the upper part of the vertical tank, after performing a preliminary adhesion amount adjustment with the upper seal roll pair, a so-called final adjustment amount is adjusted in the adjustment chamber. Since the two-step attachment adjustment can be performed, the burden of the second step in the adjustment chamber is lightened, and therefore, it is possible to adjust the appropriate basis weight without the occurrence of splash even under high-speed threading.

Furthermore, by arranging multiple plating solution storage tanks and connecting each to a vertical tank individually, the plating metal type can be changed quickly, and the loss of operating time due to such changes can be avoided. Can be resolved.

(Example) The plating apparatus shown in FIG. 1 was used as a continuous furnace capable of continuously annealing a steel strip in a (H ₂ + N ₂ ) mixed gas atmosphere and controlling the temperature of the steel strip suitable for hot metal plating. Attached. This plating apparatus comprises a continuous furnace 3, a roll-up chamber 22 in which a turn-up roll 2 and a leaked molten metal recovery device 21 are housed, and a plating chamber 4 mainly composed of a molten metal plating bath 5 according to the present invention. And the deposition amount adjusting chamber 14 for final adjustment of the deposition amount in a non-oxidizing atmosphere are arranged in series, and three storage tanks (17, 18, 19) for the molten metal to be supplied to the plating bath 5 are provided. . The molten metal is supplied from the storage tank to the plating bath through the pipe 15, and is pumped to the supply port 9 by the power of the transfer pump 20. The molten metal discharged from the bath 5 is recovered again in the storage tank through the discharge port 10 and the recovery pipe 16. Further, the excess molten metal generated in the adhesion amount adjusting chamber 14 is connected to the recovery pipe 16 through the recovery guide 12, the receptacle 13, and the pipe 23. The adhesion amount was adjusted with a gas wiper 11 that is normally used, and the gas species was nitrogen gas. Further, the upper (outgoing) seal roll pair 7 is a grooved roll and has a function of freely changing the pressing force. On the other hand, the lower (entrance side) seal roll pair 6 was a flat roll, and the steel strip was strongly sandwiched by both seal rolls. Plating bath 5 has a clearance of 100 m
The length in the width direction of the steel strip was 250 mm, and the distance from the lower seal roll pair 6 to the upper seal roll pair 7 was 1000 mm (the bath length excluding the throat portion 8 was about 750 mm).

Molten zinc (Al: 0.18
%), Molten zinc-aluminum alloy (Zn: Al = 95:
5) and molten zinc (Al: 0.13%) were filled, and the storage tank was covered with a N ₂ gas atmosphere.

In the above-mentioned hot-dip galvanizing line, two kinds of hot-dip galvanized steel strips and one kind of hot-dip galvanized aluminum strip were manufactured under the plating conditions shown in Table 1 below.

Further, as a comparative example, a conventional galvanizing apparatus as shown in FIG. 2 was attached to a continuous furnace, and hot-dip galvanized steel strip was manufactured under the same plating conditions as shown in Table 1. However, in this case, the molten zinc temperature in the plating bath was 470 ℃, and the bath composition (0.18% A
l). The number 24 in the figure is a sync roll.

For each solution metal-plated steel strip obtained as described above,
Table 2 shows the results of an examination of the degree of adherence of harmful foreign substances, the presence or absence of wrinkles, and the amount achieved.

As is clear from Table 2, in the conventional product (comparative example), many harmful foreign substances were recognized and wrinkles were also generated, whereas three plated steels obtained using the device of the present invention Almost no harmful foreign matter adhered to the belt, and no wrinkles were observed. From this, the effect that the present invention makes the plated surface beautiful and smooth is clear. Regarding the achieved adhesion amount, when comparing the hot-dip galvanized steel strip (1) of the invention example and the conventional product (comparative example) produced under substantially the same plating conditions, the former is 22 g / m ² less than the latter, The effect of reducing the adhered amount in this invention is clear, and it is clear that this invention brings about high productivity.

In all of the invention examples, the attachment of splash was not observed, but in the comparative examples, it was slightly observed.

Furthermore, three galvanized steel strips of Inventive Example were used to form hot-dip galvanized steel strips.
(2), hot-dip zinc-aluminum alloy coated steel strip, and then hot-dip galvanized steel strip (1) were manufactured in this order. Switching of the molten metal plating species at the time of manufacturing can be performed only by opening and closing the electromagnetic shutoff valve, and the time required for each was extremely short, within 3 minutes. It should be noted that most of the time required was a period after the supply of the plating solution was stopped until the molten metal remaining in the flow paths such as the plating bath and the pipe was recovered.

(Effects of the Invention) The effects of the present invention are summarized as follows.

(1) It is possible to produce a hot-dip galvanized steel strip having a beautiful and smooth surface with almost no harmful foreign particles or splash attached to the surface and no wrinkling.

(2) The plated steel strip described above can be produced at high speed, and productivity can be improved.

(3) The time required for switching the molten metal plating species is extremely short, which contributes to improved productivity.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a preferred example of a hot dip galvanizing apparatus according to the present invention, and FIG. 2 is a schematic diagram of a conventional hot dip galvanizing apparatus. 1 ... Steel strip, 2 ... Turn-up roll 3 ... Continuous furnace, 4 ... Plating chamber 5 ... Vertical plating bath, 6 ... Inlet side seal roll pair 7 ... Outlet side seal roll pair 8 ... Throat part, 9 ... Supply port 10 … Discharge port 11… Adhesion amount adjustment means (gas wiper) 12… Recovery guide, 13… Reception box 14… Adhesion amount adjustment chamber, 15… Supply pipe 16… Recovery pipe, 17 to 19… Reservoir 20… Transfer pump 21… Leakage Molten metal recovery device 22… Roll hood chamber, 23… Piping 24… Sink roll

Claims (4)

[Claims] 1. A molten metal plating apparatus for plating a steel strip by dipping the steel strip in a molten metal plating bath, the plating bath being a closed type in which the steel strip is vertically passed from the lower part of the bath to the upper part of the bath. It becomes a vertical tank, and the vertical tank has at least a pair of seal rolls on the inlet side and the outlet side of the steel strip, and a supply port and a discharge port for supplying and discharging the molten metal into the tank. A hot-dip galvanizing apparatus, which is provided with: 2. The apparatus according to claim 1, wherein the pair of upper seal rolls also serves as a means for adjusting the amount of plating solution adhered. 3. A molten metal plating apparatus for plating a steel strip by dipping the steel strip in a molten metal plating bath, the plating bath being a closed type in which the steel strip is vertically passed from the lower part of the bath to the upper part of the bath. A vertical tank, which has at least one pair of sealing rolls on the inlet side and the outlet side of the steel strip, and a supply port and a discharge port for supplying and discharging the molten metal into the tank. A molten metal plating apparatus, further comprising: a deposition amount adjusting chamber in a non-oxidizing atmosphere, which has a means for adjusting a deposition amount of a plating solution, provided above the vertical tank. 4. A molten metal plating apparatus for plating a steel strip by dipping the steel strip in a molten metal plating bath, the plating bath being a closed type in which the steel strip is vertically passed from the lower part of the bath to the upper part of the bath. It becomes a vertical tank, and the vertical tank has at least a pair of seal rolls on the inlet side and the outlet side of the steel strip, and a supply port and a discharge port for supplying and discharging the molten metal into the tank. And a deposition amount adjustment chamber under a non-oxidizing atmosphere, further having a means for adjusting the deposition amount of the plating solution on the upper portion of the vertical tank,
A molten metal plating apparatus, further comprising: a storage tank for a plurality of molten metal plating solutions; and a supply and recovery pipe for the plating solution that connects the storage tank and the vertical tank, respectively.