JPH05179471A - Pickling device for strip steel - Google Patents

Abstract

PURPOSE:To provide the pickling device having a high descaling capacity. CONSTITUTION:One or >=2 fresh pickling liquid supplying devices 14 are disposed between the inlet side and outlet side of the pickling cell 1 in addition to the fresh pickling liquid supplying device 13 on the inlet side or outlet side of the pickling cell. A plurality of the above-mentioned pickling cells 1 are disposed in the traveling direction of the strip steel. Pickling liquids of the concn. successively higher toward the downstream side in the traveling direction of the strip steel are stored into the respective pickling cells 1 mentioned above. Sub-tanks 8 respectively disposed in the plural pickling cells 1, waste pickling liquid return pipings 12 respectively connected between the respective sub-tanks 8 and the respective pickling cells 1, cascase pipings 17 connected between the respective sub-tanks 8, fresh pickling liquid supplying pipings 15 respectively connected between the respective sub-tanks 8 and the respective fresh pickling liquid supplying devices 13, 14 and fresh pickling liquid supplying pumps 16 respectively interposed in the respective fresh pickling liquid supplying pipings are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pickling device for strip steel. The strip steel strip rolled by the hot strip mill has various oxide films (scales) formed on the surface of the strip during the cooling process, but these are completely removed before being rolled by the cold rolling mill in the next process. You need to do it. The present invention relates to a pickling apparatus of a type in which such a strip-shaped long thin steel sheet is continuously passed from a front tank to a rear tank while being immersed in a plurality of pickling tanks arranged in a line direction.

[0002]

2. Description of the Related Art As a conventional pickling apparatus, JP-A-63-30728
There are those disclosed in Japanese Patent Publication No. 7 and Japanese Patent Application Laid-Open No. 2-133589. As shown in FIG. 4, the pickling apparatus disclosed in Japanese Patent Laid-Open No. 63-307287 has large-sized seal rolls on the inlet and outlet sides of the pickling tank 50.
51 is arranged so that the liquid surface of the acid solution A is higher than the lower side of the seal roll 51, and the strip steel plate S is immersed in the acid solution A and run in the direction of arrow F to dissolve the acid solution. To remove the scale. The acid solution A in the pickling tank 50 is
While collecting the buffed amount in the tank 52, it is sent again to the acid liquid supply port 54 by the pump 53 and circulated. The acid solution supply port
54 is provided near the outlet side of the pickling tank 50. JP 2-13
As shown in FIG. 5, the pickling apparatus described in Japanese Patent No. 3589 has the same basic configuration as that of the apparatus shown in FIG.
Are provided on both the inlet side and the outlet side of the pickling tank 50.

In the pickling apparatus having the above basic structure, there is a problem that the descaling efficiency is lowered on the downstream side in the running direction of the strip steel due to a decrease in the acid concentration consumed by the descaling reaction. Therefore, in order to accelerate the pickling reaction rate, a stirrer for stirring the acid solution in order to replace the acid that has reacted in the pickling tank 50 with the surrounding unreacted acid may be provided, or it may adhere to the surface of the strip steel plate. There was an obstacle to remove the boundary layer.

[0004]

However, in the above-mentioned prior art, since the descaling is performed only by the acid solution stored in the pickling tank, the decrease in the acid concentration consumed by the descaling reaction is avoided. There was a problem that I could not.

In view of the above circumstances, it is an object of the present invention to provide a pickling apparatus which has a low descaling ability and a high descaling ability.

[0006]

The pickling apparatus of the first invention is
A new acid solution supply device is installed on the inlet side or outlet side of the pickling tank,
A pickling device for moving a strip steel plate by immersing it in an acid solution in the pickling tank, further comprising one or more new acid solution supplying devices between the inlet side and the outlet side of the pickling tank. It is characterized in that it is provided. In the pickling apparatus of the second invention, a plurality of the pickling tanks of the first invention are arranged in the running direction of the strip steel plate, and the pickling tanks in the pickling tanks each having a sequential concentration toward a downstream side in the running direction of the strip steel plate are provided. A pickling device that stores a high acid solution, a sub-tank disposed in each of the plurality of pickling tanks, a waste acid solution return pipe connected between each sub-tank and each pickling tank, Cascade pipes connected between the sub-tanks, the sub-tanks, a new acid liquid supply pipe connected between the new acid liquid supply device, and the new acid liquid supply pipe, respectively A new acid liquid supply pump is provided.
The new acid solution supply device in the present invention is a concept that includes all device devices for supplying the new acid solution such as nozzles, sprays, and openings of pipes.

[0007]

According to the first aspect of the present invention, since the fresh acid solution is replenished from the fresh acid solution supply device even in the intermediate portion between the inlet side and the outlet side of the pickling tank, the strip steel sheet is placed on the entrance side of the pickling tank. While moving from the
It will move while touching the highly concentrated new acid solution for several times. Therefore, the effect of lowering the acid concentration is small, and the descaling time is shortened. According to the second invention, the reacted waste acid solution is collected in the sub-tank corresponding to each pickling tank. However, since the acid solution in the pickling tank has a higher concentration on the next tank side, the recovered acid solution Also has a higher concentration than the acid solution recovered in the previous tank side. Therefore, by sending the recovered acid solution on the next tank side to the sub tank on the front tank side by cascade piping,
The concentration of the acid solution in the sub tank on the front tank side is increased. The acid solution whose concentration has been increased is supplied to the new acid solution supply device provided on the inlet side and the middle part of the pickling tank by the new acid solution supply pipe and the new acid solution supply pump, so that the strip steel plate is made into one acid. While moving the washing tank, the descaling time is shortened because it is exposed to a new concentrated acid solution several times. Further, since the apparatus of the present invention can be constructed by simply adding a new acid solution supply pipe and a new acid solution supply apparatus to the existing pickling apparatus, the equipment cost is extremely low.

[0008]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a partial side sectional view of a pickling apparatus according to an embodiment of the present invention. In the pickling apparatus of this embodiment, 2 to 5 pickling tanks are arranged in the line direction of the strip steel plate, but FIG. 1 shows only an intermediate tank and connecting portions before and after it. The pickling tank 1 is provided with a brick lining on the inner surface, and protective skids 2 are attached to the upper side of the pickling tank 1 to protect the lining and prevent the strip steel plate S from being scratched. A skid 3 is provided at the front end and the rear end of each of the plurality of pickling tanks 1 and has a very small gap above the skid 3 at the rear end with respect to the skid 3. The large-diameter seal roll 4 is pivotally supported.

The acid solution A is supplied into the pickling tank 1 so that the liquid level As is higher than the lower surface of the seal roll 4, and is kept at this liquid level As by a pump system described later. The acid solution A is circulated and supplied. Ringer rolls 6 are arranged on the outlet side of each pickling tank 1. The strip steel sheet S as the material to be treated passes through between the skid 3 and the seal roll 4 of the pickling tank 1 while being guided by the ringer roll 5 on the exit side of the front layer and enters the tank, and also the skid on the exit side of the tank. 3, seal roll 4
Exit from the space and pass through Ringerol 6. The ringer roll 6 is a device that sandwiches the strip steel S from the pickling tank 1 and squeezes out the pickling solution adhering to the strip S. This prevents the acid solution from being transferred to the adjacent pickling tank on the strip steel plate S. In this way, the strip steel sheet S enters the next tank and sequentially moves to the succeeding tank.

A sub tank 8 is provided in each of the pickling tanks 1.
Are arranged. An acid liquid return port 7 is provided below the front and rear ends of the pickling tank 1, and the return port 7 and the sub tank 8 are provided.
A waste acid solution return pipe 9 is connected between and to collect the acid solution A overflowing the pickling tank 1. Further, an acid solution return port 11 is formed at a position adjacent to the protection skid 2 provided in the middle part of the pickling tank 1 and also on the upstream side in the traveling direction of the strip steel plate S. The return port 11 and the sub tank A waste acid solution return pipe 12 is also connected to the pipe 8. Therefore, the waste acid solution is also recovered from the acid solution return port 11 in the middle part of the tank.

On the other hand, a fresh acid solution supply nozzle 13 is arranged at the inlet side end of the pickling tank 1 as in the conventional device, and in the present embodiment, the intermediate portion of the pickling tank 1, for example, the protection skid 2 is provided. Two new acid solution supply nozzles 14 are additionally provided so as to divide the pickling tank 1 into approximately three equal parts at adjacent positions along the running direction of the strip steel S. In the illustrated embodiment, the additional new acid liquid supply nozzle 14 is provided with the same number of two units corresponding to the position of the protective skid 2, but the number may be smaller or larger than that, but the strip steel plate In order to bring the new acid solution into uniform contact with S, it is desirable to provide the strips at substantially equal intervals along the running direction of the strip S. Further, as the number of additional new acid solution supply nozzles 14 installed increases, the degree to which the new acid solution contacts the strip steel plate S increases, which is effective in shortening the descaling time. Further, it is preferable that the new acid solution supply nozzles 13 and 14 are arranged so that the new acid solution is sprayed from the upper surface and the lower surface of the strip steel plate S because the acid solution uniformly touches the surface of the strip steel plate. A new acid solution supply pipe 15 is connected between the new acid solution supply nozzles 13 and 14 and the sub tank 8, and a new acid solution supply pump 16 is interposed in the new acid solution supply pipe 15.

The sub-tank 8 has a sub-tank 8a of the next tank.
Cascade piping 17 to connect with and sub tank 8b of the previous tank
A cascade pump 18 is connected to each of the cascade pipes 18, 18, and a cascade pump 20 is provided in each of the cascade pipes 17, 18. It is a conventional technique in a continuous pickling apparatus in which a plurality of pickling tanks 1 are connected, but since the pickling tank having a higher concentration is used in the pickling tank on the downstream side in the traveling direction of the strip steel sheet S, the subtank 8a on the downstream side is used. The acid solution sent in has a higher concentration than the acid solution recovered from the pickling tank 1, and therefore, when mixed in the sub-tank 8, has a higher concentration than the waste acid solution in the pickling tank 1. The acid solution whose concentration has been recovered is supplied with the new acid solution supply pump 16
Through the new acid solution supply pipe 15, the new acid solution supply nozzles 13, 14
Is supplied to. The acid solution mixed in the sub tank 8 is sent to the previous tank sub tank 8b by the cascade pump 20. Since the concentration of the acid solution in the sub tank 8 is higher than that of the acid solution recovered from the pickling tank corresponding to the previous tank sub tank 8b, the concentration of the acid solution in the previous tank sub tank 8b is also recovered. The pickling apparatus of this embodiment basically collects the waste acid solution overflowing the pickling tank 1 into the sub tank 8 through the acid solution return ports 7 and 11 and the waste acid solution return pipes 9 and 12, and collects the recovered acid. The solution is supplied from the new acid solution supply pipe 15 and the new acid solution supply pump 16 into the pickling tank 1 by a pump system to be circulated and used.

In the present embodiment, the fresh acid solution is supplied also in the middle part of the pickling tank 1, so that the fresh acid solution is replaced with the acid having a low concentration by reaction, so that the reduction of the reaction rate can be suppressed. .. Hereinafter, this point will be described in detail. The reaction rate for dissolving the scale is expressed by the following equation (1). v = kα {aα (1-p) t + Xo ^1-p } ^b g / m ² · sec (1) where a, α and p are experimental constants Xo is the initial acid solution concentration v is at time t Reaction rate k is a conversion coefficient b is p / (1-p). The descaling amount, which indicates the amount of scale dissolved by the acid solution, is represented by the following formula (2). S = k / a · [{ aα (1-p) t + Xo 1-p} C -Xo] g / m 2 ...... (2) equation However, c is a 1 / (1-p). The above-mentioned reaction rate v and descaling amount S are shown in the graph as shown in FIG. 3. The reaction rate v is represented by the line L4, and the descaling amount S4 is represented by the area of the shaded portion. If only the new acid solution is supplied at the tank inlet like the conventional pickling apparatus, the acid solution may adhere to the strip steel and react with the scale to gradually decrease the concentration and slow the reaction rate v. It is shown.

On the other hand, in the apparatus of this embodiment, as shown in FIG. 2, the reaction rate v is restored each time by supplying the fresh acid solution in the middle portion of the tank. Next, this point will be described based on experimental examples. The pickling tank 1 shown in FIG. 1 is provided with two new acid solution supply nozzles 14 in the middle part of the tank, and the same pickling tank 1 is prepared except that the new acid solution supply nozzle in the middle part of the tank is not provided. Filling both pickling tanks 1 with a subtank concentration of 8% acid solution (HCl) and immersing the steel strip S, all scales (50.6 g / m
^The experiment was conducted under the condition that ² ) was dropped. In the pickling tank in which two new acid solution supply nozzles 14 of the present invention are additionally provided, as shown in FIG. 2, the reaction rate v of the acid solution supplied from the first new acid solution supply nozzle 13 is linear. The reaction rate by the acid solution that is represented by L1 and is supplied from the second and third fresh acid solution supply nozzles 14 is represented by lines L2 and L3. The descaling amount S1 of the portion indicated by the line L1 is 16.9 g / m ² , and the descaling amounts S2 and S3 are also 19.9 g / m ² , so all scale (50.6 g / m ² ) is removed. It took 17.46 seconds. On the other hand, in a pickling tank without a new acid solution supply nozzle in the middle of the tank, the descaling time is as shown in FIG.
It took 20 seconds. In the above example, only one tank is used for all scales (50.6
This is an example of an experiment in which g / m ² ) was dropped, but even in a continuous pickling apparatus with multiple pickling tanks having different acid concentrations, the same descaling time reduction effect was obtained for each pickling tank. Be done.

Next, another embodiment of the present invention will be described. Although the nozzles 13 and 14 are used as the new acid liquid supply device in the above-mentioned embodiment, they may be opened pipes for discharging the acid liquid from the lateral wall surface of the tank toward the inside of the tank. In the above embodiment, the acid solution return port 11 is formed on the lateral wall of the pickling tank 1 and the waste acid solution return pipe 12 collects the waste acid solution. However, the waste acid solution return pipe 12 has a large diameter pipe. However, the acid solution return port 11 and the waste acid solution return pipe 12 may not be provided if economic efficiency is important. In this case, although the effect is somewhat reduced, if the method of removing the acid solution thinned by the reaction and bringing the new acid solution into contact with the strip steel plate S (for example, spraying), the descaling efficiency is slightly reduced. OK. Although the above embodiment is an example applied to a shallow type bath main body, the present invention can also be applied to a deep immersion type pickling bath.

[0016]

According to the present invention, the descaling time can be shortened considerably. Further, the present invention can be constructed by simply adding a new acid solution supply nozzle and piping to the middle part of the existing pickling tank, so the equipment cost is low.

[Brief description of drawings]

FIG. 1 is a side sectional view of a pickling device according to an embodiment of the present invention.

FIG. 2 is a graph showing the descaling time of the pickling apparatus of the present invention.

FIG. 3 is a graph showing the descaling time of a conventional pickling apparatus.

FIG. 4 is a side sectional view showing an example of a conventional pickling apparatus.

FIG. 5 is a side sectional view showing another example of a conventional pickling apparatus.

[Explanation of symbols]

1 pickling tank 2 protection skid
7 Acid solution return port 8 Sub tank 9 Waste acid solution return pipe
11 Acid solution return port 12 Waste acid solution return pipe 13 New acid solution supply nozzle
14 New acid solution supply nozzle 16 New acid solution supply pump 17 Cascade piping
18 Cascade piping

Claims (2)

[Claims] 1. A pickling device comprising a new acid solution supply device disposed on the inlet side or the outlet side of a pickling tank, which is immersed in the acid solution of the pickling tank to run a strip steel sheet. A pickling device for strip steel, wherein one or more new pickling solution supply devices are further arranged between the inlet side and the outlet side of the pickling tank. 2. A plurality of the pickling tanks according to claim 1 are arranged in the running direction of the strip steel, and each of the pickling tanks collects an acid solution having a higher concentration toward the downstream side in the running direction of the strip steel. A sub-tank disposed in each of the plurality of pickling tanks, a waste acid solution return pipe connected between each sub-tank and each pickling tank, and a connection between each sub-tank Cascade pipes, the sub tanks, the new acid liquid supply pipes connected between the new acid liquid supply devices, and the new acid liquid supply pumps respectively interposed in the new acid liquid supply pipes And a pickling device.