JPH0819512B2 - Hot metal plating equipment - Google Patents

Description

TECHNICAL FIELD The present invention relates to a hot dip metal plating apparatus. More specifically, the present invention relates to a hot-dip galvanizing apparatus capable of preventing bottom dross from depositing in a plating bath and / or capable of filtering hot-dip metal.

(Prior Art) As is well known, in North America and Canada, measures to prevent freezing of roads by rock salt spraying are currently taken to prevent automobile slip accidents in winter.

The car salt body is exposed to a severe corrosive environment due to such rock salt spraying, and a surface-treated steel sheet having high corrosion resistance is being used. Therefore, attention has been paid to alloyed steel sheets that have the same weldability and workability as those of cold rolled steel sheets for exterior steel sheets and have excellent corrosion resistance. Moreover,
As it is a steel plate for exteriors, high image clarity after painting is also required, and materials with increasingly strict specifications are being demanded.

By the way, in a hot-dip galvanizing line, for example, a hot-dip galvanizing line, a normal hot-dip galvanized steel sheet in the as-plated state and an alloying-treated steel sheet (galvanneale steel sheet) subjected to an alloying treatment after plating are generally manufactured. This 2
From the viewpoint of improving productivity, steel sheets of various types are continuously manufactured by appropriately switching in the same line.

However, in the hot-dip galvanizing tank where continuous strip galvanizing is performed, Fe in the strip elutes into the plating bath and a dross containing FeZn ₇ as the main component is generated. accumulate.

FIG. 7 is an explanatory view of the formation of bottom dross and winding in a plating bath during such hot dip galvanizing. In FIG. 7, the strip 3 sent to the plating tank 2 via the snout 1 is plated while circulating around the sink roll 4, and after the plating is completed, it is taken out from the plating tank 2 via the snap roll 5. At this time, the dross floating in the plating bath gradually accumulates at the bottom of the plating tank 2 to form a bottom dross 6. A part of the floating dross is combined with Al in the bath and floats as a top dross 7 on the top of the plating bath.

The bottom dross 6 thus deposited may be wound up in the plating bath by the accompanying flow of the strip 3 near the lower part of the sink roll 4 and attached to the upper surface of the strip 3.

As described above, under the current strict specifications for plated steel sheets, when such bottom dross 6 adheres to the surface of the strip 3, a surface non-uniform portion called a press bus is generated during pressing, which significantly impairs sharpness. Not only that, but surface defects that cause formation of local cells and lower corrosion resistance are caused, which causes quality defects in the plated steel sheet.

Conventionally, in order to prevent the dross from adhering to the surface of the strip 3, as a general method of suppressing the formation of the bottom dross 6, the Al content in the plating bath is enriched, and Fe ₂ Al ₅
There is a method of levitating and collecting as a top dross.

2FeZn ₇ ＋ 5Al → Fe ₂ Al ₅ ＋ 14Zn However, since Al has the effect of suppressing the alloying of the plating film, the amount of alloyed steel sheet is limited to the smallest possible amount. Yes, top dross 7
When Al is added to promote floating, a part of it remains in the plating bath, causing poor alloying and causing a problem of quality deterioration.

In particular, as described above, from the current situation that the surface texture capable of obtaining excellent image clarity is required even in the alloyed steel sheet, a means that can prevent the dross adhesion by means not by adding Al is strong. It has been demanded.

Further, as shown in FIG. 8, a method of filtering and separating a molten liquid containing dross floating in a plating tank by using a filtering material (eg, ceramic filter) provided in a subpot by a pump is proposed. However, this method was unavoidable because it often required replacement of the filter because the dross clogging the filter was likely to occur and this method was not effective. .

Further, Japanese Patent Publication No. 57-58434 discloses that a galvanizing bath is divided into two parts, a plating bath and a reaction bath, the upper part of which is openable and the lower part of which is open. There has been proposed a hot dip galvanizing bath which is characterized in that it is provided with such a partition wall.

FIG. 9 is a schematic explanatory view of the apparatus according to this proposal, in which the plating tank 2 is provided with a barrier 30 for blocking the space where the sink roll 4 is installed and the space where the bottom dross 6 is deposited. There is. It is proposed that the bottom dross be levitated and collected as the top dross 7 by operating an agitator provided in the space where the bottom dross 6 is accumulated.

(Problems to be Solved by the Invention) However, even with the device proposed by this Japanese Patent Publication No. 57-58434, the lower part of the partition wall 30 remains open and convection occurs between the plating tank and the reaction tank. Since it is circulated, the dross rolled up in the plating tank by the operation of the stirrer mixes into the area where the sink roll 4 is installed from the lower and upper openings of the partition wall 30 to prevent the adhesion to the surface of the strip 3. The effect of doing was insufficient.

Thus, an object of the present invention is to provide a hot-dip galvanizing apparatus capable of suppressing bottom dross from adhering to a strip when producing a hot-dip galvanized metal sheet having excellent plating appearance and corrosion resistance.

A more specific object of the present invention is to produce a galvanized galvanized steel sheet under a plating bath condition of low Al concentration, in particular, to produce a galvannealed galvanized steel sheet having excellent image clarity, a plating tank, By partitioning into a pool and a space other than the pool, and blocking the two from each other, a structure in which dross does not accumulate inside the region where plating is performed is prevented, and bottom dross winding from the bottom of the plating tank is prevented, and /
Or it reduces clogging of the filter and enables continuous filtration,
Another object of the present invention is to provide a hot-dip galvanizing apparatus capable of performing continuous hot-dip galvanizing without bottom dross.

(Means for Solving the Problems) The inventors of the present invention have conducted various studies based on the results of hydrodynamic examinations in the plating tank to obtain bottom dross, and have obtained the following findings. That is, (a) the adhesion of bottom dross is based on the accompanying flow generated when the strip travels in the plating bath, and (b) the amount of bottom dross that settles and accumulates at the bottom of the plating tank is the sink roll. Under the influence of the rotating body in the bath of the party and the accompanying flow, there is the largest amount near the side wall on the snout side, and it tends to decrease as it approaches the sink roll, and further, near the side wall on the snap roll side, and (c) plating tank When a side wall is provided inside the plating tank so as to form a double structure, and a hole is made in the lower part of the side wall provided inside this, bottom dross accumulated in the plating tank causes the bottom part of the plating tank between the inner wall and the outer wall to be formed. Is to move and deposit.

Based on such findings, the present inventors have completed the present invention as a result of repeating many experiments and their analysis.

Here, the gist of the present invention is a molten metal plating apparatus having a sink roll that is axially supported in a plating tank to convey strips, and (i) a dross pool provided at the bottom of the plating tank. (Ii) Openable and freely openable dross for discharging the area where the dross reservoir is provided and the area other than the area that constitutes the plating bath main body, that is, the area where the sink roll is pivotally supported and the strip is plated. And a blocking member having an opening of 1.

In addition, the present invention is a molten metal plating apparatus having a sink roll that is axially supported from the other side and conveys strip in a plating tank, and (i) pumps out the molten liquid from the site where bottom dross has accumulated. (Ii) The lower end of the pump is located outside the plating tank and constitutes the dross discharge part. The pump is installed above the plating bath at an angle with respect to the liquid level of the plating bath. A filter material that forms a circulating flow of the plating bath and also serves as a dross discharge path,
And (iii) a hot-dip metal plating apparatus having a continuous filtering device including a pipe for sending the molten liquid pumped up by the pump to the filtering material.

Furthermore, it is preferable that the continuous filtration device is included in a molten metal plating device having the dross reservoir and the blocking member.

(Operation) In the molten metal plating apparatus according to the present invention, a dross reservoir is provided in a part of the bottom of the plating tank, and a space provided with the dross reservoir and a space provided with a sink roll are provided. A blocking member having a freely opening / closing opening for blocking is provided.

The action of the blocking member prevents the bottom dross accumulated in the dross pool from floating in the plating bath and adhering to the strip surface.

Further, in the molten metal plating apparatus of another aspect according to the present invention, since the molten liquid pumped up by the pump is blown to the filter material supplemented with dross, the filter material is continuously cleared while clogging the filter material. The melt is filtered.

Note that these devices may also have respective functions.

Hereinafter, the present invention will be described with reference to the embodiments illustrated in the accompanying drawings.

1 and 2 are a schematic vertical sectional view and a schematic plan view, respectively, showing one embodiment of a molten metal plating apparatus according to the present invention.

In FIG. 1, a sink roll 4 for transporting a strip 3 supplied through a snout 1 is axially supported in a plating tank 2. Then, the strip 3 circulates around the sink roll 4 and, after passing through the snap roll 5, is subjected to molten metal plating, and then pulled up again above the plating tank 2.

Further, below the sink roll 4 and at the bottom of the plating tank 2, a block 8 having a rectangular vertical cross-sectional shape in this embodiment is arranged. The block 8 is provided to prevent the accumulation of dross below the sink roll 4. That is, the block 8 reduces the space between the sink roll 4 and the bottom of the plating tank 2,
It is provided to prevent the dross from depositing in the space by making the plating bath flow in the space higher than the flow velocity in the other space. Therefore, the bottom dross 6 will be deposited on the bottom portion of the plating tank 2 other than the portion where the block 8 is provided. That is, the bottom portion of the plating tank not provided with the block 8 forms a dross pool.

The block 8 may have any shape or size as long as it has such an effect, and no limitation is required. In FIGS. 1 and 2, a rectangular parallelepiped block is used as the block 8 and dross pools are provided on the four sides around the block (the block 8 does not contact any of the four side walls of the plating tank 2). ), But is not particularly limited to this aspect. For example, the block 8 may be installed at a position where it comes into contact with one or more of the four side walls of the plating tank.

The block 8 is, of course, fixedly installed so that the installation position is not displaced and the block 8 does not float in the plating bath during the operation of the plating tank.

Further, as a material of such a block 8, stainless steel, for example, may be used in consideration of use in the molten metal plating bath.

In addition, except when the block 8 is installed so as not to contact the four side walls of the plating tank 2, the height of the block becomes lower as the block 8 gets closer to the side wall that does not contact, Providing a slope on the upper surface of the block 8 is desirable from the viewpoint of preventing dross from depositing on the block 8.

In the accompanying drawings, a mode in which the block 8 independent of the plating tank is installed at the bottom of the plating tank 2 to form a dross pool has been described as an example, but the present invention is limited to this mode. is not. That is,
The shape of the bottom portion of the plating tank may be changed, the center portion (the portion where the block 8 is to be installed) may be formed in a convex shape, and a dross pool may be formed around it. That is, a recess, that is, a groove-shaped portion may be provided on the inner peripheral edge of the bottom of the plating tank.

In the present invention, the shape of such dross pool is collectively referred to as "deep bottom".

Further, in the molten metal plating apparatus according to the present invention, the strip 3 is provided above the block 8.
Further, a dross floats in the space where the sink roll 4 is provided, and a blocking member 9 for preventing the dross from adhering to the surface of the strip 3 is provided.

The blocking member 9 is located directly above each side of the block 8 (four sides in the embodiment shown in FIG. 2), and is installed so as to be movable in the vertical direction of the plating tank 2.

Therefore, by raising the blocking member 9,
An openable and closable opening is formed between the blocking member 9 and the block 8, and as described above, the dross 6 flown by the plating flow between the sink roll 4 and the block 8 is blocked by the block 8.
It can be moved and deposited on the bottom of the plating tank (in the embodiment shown in FIGS. 1 and 2), other than the bottom provided with.

Closing the opening by lowering the blocking member 9 to make contact with the upper surface of the block 8;
That is, the space where the strip 3 and the sink roll 4 exist and the space where the bottom dross 6 accumulates, that is, the dross pool, can be physically blocked. Therefore, even when the bottom dross 6 accumulated in the dross reservoir is carried out of the plating tank, the bottom dross 6 is floated and mixed in the space where the strip 3 and the sink roll 4 exist, that is, the bottom dross 6 accumulated in the dross reservoir is removed. Even when stirring or gas bubbling is carried out when it is carried out to the outside of the plating tank, and even if it is absorbed, it is possible to prevent it from passing over the blocking member 9 and adhering to the surface of the strip 3. Therefore, it is possible to discharge the bottom dross or filter the plating bath while manufacturing a hot-dip galvanized metal plate of excellent quality during operation of the plating tank.

As described above, depending on how many faces the block 8 is in contact with the side wall of the plating tank 2, the above-mentioned cutoff required to separate the strip 3 and the sink roll 4 from the deposited bottom dross 6. It goes without saying that it is sufficient to determine the number of members 9 to be installed.

Further, according to another aspect of the present invention, in order to carry out the accumulated bottom dross to the outside of the plating tank, a pump is provided for pumping the melt from the site where the bottom dross are accumulated.

FIG. 3 is a schematic explanatory view showing an example of an installation mode of the pump 22, the pipe 21, and the valve 23 when the pump 22 is thus provided. The melt containing the bottom dross 6 is absorbed from the pipe 21 provided so that its tip is located in the vicinity of the bottom dross 6 accumulated in the dross pool, and the bottom dross 6 is separated from the melt by the filtration means described later, The plating bath thus cleaned is arranged so that it can be returned to the plating tank again.

Further, a filter medium is provided in the outer space of the plating tank 2, and the molten liquid is supplied from one side of the filter medium so as to clean the surface of the filter medium, and dross adhesion and deposition on the filter medium are suppressed. Therefore, filtration may be performed at the same time as washing.

FIG. 4 is another schematic aspect of the molten metal plating apparatus according to the present invention, and is a schematic perspective view showing an example of an apparatus in which a pump, piping, and a filter medium are provided outside the plating tank. For convenience, a part thereof is shown transparent or cut.

In FIG. 4, 18 is a part of the strip to be transported and plated, 19 is a plating tank, 20 is a bottom dross accumulated in the dross pool at the bottom of the plating tank, and 21 is a portion near the bottom dross 20 accumulation part. A pipe installed so that its tip is positioned, 22 is a pump connected to the pipe 21 to pump the bottom dross 20, 23 is a valve, and 24 is on the plating bath and has an angle with respect to the plating bath surface. In addition, the lower end of the dross discharged from the filtering material 24 is the filtering material directed to the outside of the plating tank in order to discharge the filtered dross out of the plating tank. The dross receiver installed outside the plating tank 19 to accommodate the
Reference numeral 26 denotes a plating solution from which dross has been removed by filtration, 27 denotes a filtration plating solution, 28 denotes a plating bath, and 29 denotes an opening between the upper surface of the block 8 and the blocking member 9.

In the molten metal plating apparatus shown in FIG. 4, filtration of the plating bath is performed as follows.

First, while the plating bath is in operation, as described above, the blocking member 9 that is movable in the vertical direction is pulled up to collect dross at the bottom of the plating tank 19 (hatched portion in FIG. 4).
Then, the bottom dross 3 is deposited.

When the plating bath is filtered, the blocking member 9
To lower the space where the strip 1 and the sink roll are provided and the space where the bottom dross is accumulated, and then the pump 22 is operated to pump up the molten liquid containing the bottom dross, and to raise the surface of the filter medium 24. The molten liquid is flowed through the filter medium 24 so as to be washed.

By doing this, the bottom dross is
Since the filter material 24 is inclined and arranged to be filtered by the melted liquid 24 at this time, the filter material 24 is discharged from the upstream side to the downstream side of the dross captured by the filter material 24. The dross also serves as a passage, and the dross thus sequentially extruded on the filter material 24 is discharged from the dross discharging portion at the lower end thereof to the outside of the plating tank.

In addition, by constantly flowing the melt during filtration,
The clogging of the filter provided on the horizontal plane as in the conventional case is extremely reduced, the molten liquid can be continuously filtered, and the plating quality can be improved.

Further, the filtered plating bath may be returned to the plating tank 19 through the return port, and the dross separated by filtration may be collected in the dross receiver 25 to be solidified and taken out.

Further, the dross attached to the surface of the filter medium can be continuously filtered while being washed by using a pumped-up bath flow (molten metal), and may be discharged to the dross receiver 25 as necessary.

Further, at this time, the filter material is provided so as to be inclined, so that the filter material also functions as a dross discharge path as described above. If the installation angle of the filter material is less than 10 ° with respect to the plating bath surface, it becomes difficult for dross to flow on the filter material. On the other hand, if it is 90 ° or more, the filterability deteriorates. Therefore, it is desirable that the installation angle of the filter medium with respect to the plating bath surface is 10 ° or more and less than 90 °.

Then, the plating bath thus obtained by filtration can be circulated into the plating tank for continuous plating.

As described above, according to the present invention, the number of dross attached to the plating surface can be suppressed by 90 to 95%.

Furthermore, the present invention will be described with reference to examples, but this is merely an example of the present invention, and the present invention is not limited thereto.

(Example) Example 1 An experiment of the present invention was conducted using the apparatus (water model) whose outline is shown in FIGS. 1 and 5 according to the following procedure.

As shown in FIG. 5, water is poured into a container 10 corresponding to a plating tank, and acrylic powder 11 (specific gravity 1.2, average diameter 250 μ) is attached to the bottom.
m) 80 Kg / 1.4 m ³ was placed, the strip 13 was inserted from the snout portion 12 provided on the upper part of the bath, the sink roll 14 was orbited, and then it was pulled out of the bath via the guide rolls 15 and 15. A suction sampling pipe 16 is arranged above the region where the strip 13 contacts the sink roll 14, and the plating bath is sucked from the periphery thereof, and the amount of acrylic powder wound up by the accompanying flow that accompanies the running of the strip is filtered outside. It was detected by measuring the concentration of the filtration treatment of the device 17.

As a concrete experimental procedure, the water model shown in FIG. 5 was used as a conventional type, and the operation was performed at a plate passing speed of 100 m / min, suction sampling was performed, and concentration was measured.

Next, the method of the present invention has the same shape as that shown in FIG.
A water model of 1/10 was produced and implemented. 1st and 2nd
A four-fold double structure shown in the figure with dross pools on all four rounds, and (a) part and / or (b) in the second
A test was also conducted on a pot shape in which a dross reservoir was formed only in a part.

Regarding the filtration, it was decided to perform the filtration using an actual zinc bath using the above-mentioned means.

A part of the experimental results is shown graphically in FIG. As is clear from FIG. 6, when the conventional apparatus is used, the dross winding amount reaches a certain value and becomes saturated after 40 minutes have passed from the start of strip running. This is a comparison of the data after 40 passages.

It can be seen from Table 1 that the device according to the present invention can reduce the winding amount of bottom dross to a maximum of 1/20 as compared with the conventional device.

Example 2 Based on the knowledge obtained in Example 1, a test was conducted using an actual plating bath to investigate the effect of the present invention. The test method of this example was carried out as follows.

For comparison, a conventional type (hot dip galvanizing bath shown in FIG. 7) was used. For the shape of the present invention, a stainless steel partition plate (blocking member) and a block shown in FIGS. 1, 2 and 3 are fixed in a conventional plating tank to form a water model. The shape was similar to the case of.

The operation form was limited to GA steel sheet manufacturing. (The actual concentration of Al in the plating bath was 0.09 to 0.11%.) The number of dross adhered on the surface (contact side of the sink roll) was examined with a sample collection area of plate width x 500 mm. The N number was 50, and simple average data comparison was performed.

 The results are summarized in Table 2.

According to these test results, as shown in Table 2,
In the case of the present invention, the number of dross adhered was reduced in all cases, and it was confirmed that the effect was remarkable as the findings in the water model test.

Further, for filtration, a continuous filtration device shown in FIG. 3 is used,
Pumping was performed, and continuous filtration (2 hours) was performed using the apparatus shown in FIG. The filtering material used was made of Ni, Al-based ceramics.

As a conventional example, filtration was performed by the method of FIG. 8 as compared with the method of the above invention.

As a result, in the conventional method, the filter was clogged in only about 20 minutes, and it became impossible to continue the filtration.

On the other hand, in the method according to the present invention, the filtration can be performed for 2 hours, the bottom dross can be reliably carried out of the plating tank, and the molten liquid can be cleaned.

(Effect of the invention) As described in detail above, according to the present invention, the reduction of dross adhesion, which has been the greatest quality problem of hot-dip galvanized alloy-treated steel sheets for exterior packaging, is a plating condition, For example, bottom dross deposition in the plating pot could be prevented by hydrodynamic means without changing the Al concentration during hot dip galvanizing.

Further, when the bottom dross is discharged, it is possible to continuously filter the melt while preventing the filter of the filter device from being clogged. Therefore, filtration can be continuously performed even during operation of the plating tank, and the cleanliness of the plating bath during plating can be controlled.

The practical significance of the present invention having such effects is extremely remarkable.

[Brief description of drawings]

1 is a schematic sectional view showing the configuration of a molten metal plating apparatus according to the present invention; FIG. 2 is a schematic horizontal sectional view showing the configuration of a molten metal plating apparatus according to the present invention; FIG. 4 is a schematic sectional view showing the hot dip galvanized steel sheet according to the present invention; FIG. 4 is a schematic perspective view showing the configuration of the apparatus according to the present invention; and FIG. 5 is a schematic view showing the configuration of the apparatus used in the embodiment of the present invention. Explanatory drawing; FIG. 6 is a graph showing the relationship between the winding amount and the elapsed time; FIGS. 7 and 8 are schematic sectional views showing a conventional technique;
And FIG. 9 is a schematic explanatory view showing an apparatus proposed by Japanese Patent Publication No. 57-58434. 1: Snout, 2: Plating bath 3: Strip, 4: Sink roll, 5: Snap roll, 6: Bottom dross, 7: Top dross, 8: Block 9: Blocking member, 10: Container 11: Acrylic powder, 12: Snout 13: Strip, 14: sink roll 15: guide roll, 16: suction sampling pipe 17: filtration device, 18: strip 19: plating tank, 20: bottom dross 21: pipe, 22: pump 23: valve, 24: filter 25: dross Receive, 26: Filtered plating solution 27: Filtration plating solution, 28: Plating bath 29: Opening between block upper surface and blocking member 30: Partition wall

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-3-47956 (JP, A) JP-A-3-68746 (JP, A) JP-A-3-31460 (JP, A) JP-A-3- 271353 (JP, A) JP 63-219559 (JP, A) JP 63-69956 (JP, A) Actually developed 57-147263 (JP, U)

Claims (3)

[Claims] 1. A molten metal plating apparatus having a sink roll that is axially supported in a plating tank to convey strips, comprising: (i) a dross reservoir provided at the bottom of the plating tank; and (ii) the dross. A molten metal plating apparatus, comprising: a blocking member having a freely openable / closable opening for discharging dross, which blocks a region where a pool is provided and a region other than the region that constitutes the plating bath main body. 2. A molten metal plating apparatus having a sink roll which is axially supported in a plating tank and conveys a strip, comprising: (i) a pump for pumping a molten liquid from a portion where bottom dross has accumulated, (ii) Its lower end is outside the plating tank and constitutes a dross discharge part, which is installed above the plating bath with an inclination with respect to the liquid level of the plating bath and forms a circulating flow of the plating bath in the plating tank. In addition, the molten metal plating apparatus is characterized by having a continuous filtering device including a filtering material that also serves as a dross discharge path, and (iii) a pipe that sends the molten liquid pumped up by the pump to the filtering material. 3. The molten metal plating apparatus according to claim 1, further comprising the continuous filtration apparatus according to claim 2.