JP4714800B2 - Steel plate pickling method and pickling device - Google Patents

Description

  The present invention relates to a steel plate pickling treatment method and a pickling treatment apparatus for removing oxidized scale on the surface of a steel plate.

  In the manufacturing process of a steel plate, the surface of the steel plate is cleaned for various purposes. For example, washing of a steel plate before plating or painting, pickling for removing oxide scale (descaling) of a hot-rolled steel plate, and the like can be mentioned. Usually, the steel sheet is oxidized and a scale is formed on the surface of the steel sheet in the process of being heat-treated and rolled, and this oxide scale is often involved in the rolling roll during the subsequent cold rolling process, which causes damage to the steel sheet surface. The removal of oxide scale has become an indispensable process.

  In relation to conventional oxide scale removal, the steel plate is often immersed in a plurality of acidic solutions and continuously passed through the plate to remove it by pickling. For example, as described in Non-Patent Document 1, there is a system in which a weir is provided in a pickling tank of a box, and a jet nozzle is installed therein to remove oxide scale by spraying acid onto a steel plate. .

As a method for removing the oxide scale mechanically, there are a rolling method, a polishing method, a shot blast method, a repeated bending method and the like as described in Non-Patent Document 2. In practice, these are often used in combination. These techniques are methods for mechanically removing the oxide scale, mechanically forming cracks in the oxide scale, and infiltrating the pickling solution to efficiently dissolve the oxide scale.
There is also a method (Patent Documents 1, 2, and 3) that uses a pickling solution to which hydrochloric acid or iron chloride has been added to apply a voltage to the steel sheet in the solution to cause a current to flow, thereby improving the dissolution rate of oxide scale.

There is also a method in which an induction heating apparatus is used in combination, and an oxide scale crack is advanced to the surface of the base metal by heating, and an apparatus for blowing the pickling solution therein is also used (Patent Document 4).
Contributing to the securing of the pickling solution and the reaction during pickling treatment by providing a nozzle for injecting the acid solution at the entrance and exit sides of the pickling tank and by providing a side nozzle for injecting the acid solution from the side There is also a method (Patent Document 5) in which the flow of pickling solution is changed from a laminar flow state to a turbulent flow state, and the boundary layer is destroyed to increase the pickling efficiency.

There is also a method (Patent Document 6) in which, after removing the oxide scale by electrolytic treatment, the steel strip is bent with a roll, and the removal of the oxide scale is promoted by injecting high-pressure water onto the bent convex surface. .
As a stainless steel strip descaling pretreatment device, after passing the stainless steel strip through a salt bath, the front and back surfaces of the steel strip are cooled with air from an air header, and then the cooled steel strip is washed into a washing tank. Patent Document 7 discloses a technique of washing through water.

Regarding the production of grain-oriented electrical steel sheets, as a method for mechanically removing melted deposits after forming grooves with laser light, a method using compressed air is exemplified along with brushes, grindstones, wipers, and high-pressure water (Patent Literature). 8).
In addition, regarding the continuous pickling method and apparatus for steel strips, air is blown from above the pickling tank and partition strips are used to remove (break or reduce) the acid solution layer (boundary film layer) that moves with the steel strip. A contact method and apparatus are disclosed. By removing the film layer by the above-described method, not only the acid solution in the preceding tank is prevented from being brought into the latter tank, but also in the latter tank, a new acid solution is formed between the steel plate and the steel sheet. It prevents the contact from being cut off. (Patent Document 9)

Japanese Patent Laid-Open No. 10-8298 Japanese Patent Laid-Open No. 55-48421 JP 58-64400 A Japanese Patent Laid-Open No. 9-78273 Japanese Patent Laid-Open No. 2001-20086 JP 2001-191108 A JP-A-9-87871 JP-A-10-183251 Japanese Patent Laid-Open No. Sho 62-243788

Nobuhiro Shibatomi et al., Mitsubishi Heavy Industries Technique, vol. 129 No. 1, 24-29 (1992) Sawa Kazunobu et al., Hitachi review, Vol. 6 No. 4, 41-46 (1985)

In the case of a steel sheet containing Si typified by high-strength steel, it is empirically known that the dissolution rate becomes slow when treated by a normal pickling method. In the case of a steel plate containing Si, Si in the steel may be concentrated as an oxide on the ground iron side of the oxide scale layer, and the Si oxide layer formed between the oxide scale layer and the ground iron is dissolved. It will be necessary to remove the entire oxide scale.
In addition, since the solubility of the Si oxide once dissolved simultaneously with the oxide scale is small in the pickling solution, Fe ions from the oxide scale may be present in the solution, but only the Si oxide is seen to reattach. . Depending on the concentration of Si ions in the pickling solution, the solution may change into a gel state in the solution, and it has been observed that the gel adheres to the surface of the steel sheet.

So far, the conventional pickling method has been used for dissolution and removal, but the sufficient dissolution rate has not been improved. Therefore, the pickling line speed cannot be increased, and efficient pickling has not necessarily been performed.
In addition, even with steel sheets that do not contain Si, there is no measure to deal with redeposition of oxide scale and some specific components of oxide scale, so the problem of achieving efficient oxide scale removal can be completely solved. Not.

  An object of this invention is to provide the continuous pickling treatment method of a steel plate and the continuous pickling processing apparatus of a steel plate which can remove the oxidation scale of a steel plate efficiently in order to solve the said problem. In particular, for steel sheets containing Si, a steel plate pickling method and a steel plate pickling apparatus capable of efficiently removing Si oxides contained in oxide scale and greatly improving the dissolution rate of the oxide scale are provided. The purpose is to do.

  As a result of earnestly examining the means for solving the above problems, the present inventors have taken out the steel plate temporarily from the pickling solution in the process of dissolving the oxide scale of the steel plate by the pickling treatment, and at least a part of the steel plate in the air. It was found that by injecting a gas onto the surface of the steel plate, the moisture of the acid solution adhering to the steel plate surface was evaporated, and the acid concentration could be locally increased. As a result, it was confirmed that the robust Si oxide contained in the oxide scale can be efficiently removed. And it discovered that the rate of melt | dissolution of the said oxide scale improved remarkably by pickling again after that.

  Furthermore, it has been found that the above-described effect becomes more remarkable in the direction in which the gas injection opposes the moving direction of the steel sheet. Furthermore, it has been found that the above-described effect becomes even more remarkable when the gas injection is performed in a direction opposite to the moving direction of the steel sheet and from an oblique direction with respect to the steel sheet surface. The present invention has been made based on these findings, and the gist thereof is as follows.

(1) A pickling treatment method for removing the oxide scale of a steel sheet containing 0.1 to 3.5% by mass of Si, the process A for pickling the steel sheet, and the process A in the air after the process A a step B of injecting a gas toward at least part of the surface of the steel sheet, after said step B, have a step C of pickling the steel sheet, acid of step a and pickling solution of step C In the step B, the Fe ²⁺ ion concentration of the pickling solution is 30 to 150 g / L, and the temperature of the pickling solution is from room temperature to 97 ° C. The gas is jetted in opposition to the moving direction of the steel plate, and an angle θ (°) between the gas jetting direction and at least a part of the surface of the steel plate is 15 ° ≦ θ ≦ 45 °, and the gas Part of the pickling solution sprayed at 0.5 to 1.0 MPa and adhered to the surface of the steel plate Pickling method of the steel sheet, characterized in Rukoto was concentrated.

(2) having at least one pickling tank and means for injecting a gas toward at least a part of the surface of the steel sheet in the air; The step B for injecting gas toward at least a part of the surface of the steel sheet and the step C for pickling the steel sheet after the step B, and the means for injecting the gas include the step B. And an angle θ (°) between the gas injection direction and at least a part of the surface of the steel plate is 15 ° ≦ θ ≦ 45. A pickling treatment apparatus for steel sheets, characterized in that the pressure at the nozzle nozzle is 0.5 to 1.0 MPa.

(3) The pickling apparatus for steel sheets according to (2), wherein the pickling tank is two or more pickling tanks.

(4) In (2), in the step B, it has means for horizontally passing the steel sheet, and the means for injecting the gas injects gas to the steel sheet to be horizontally passed. The steel plate pickling apparatus of description.

(5) In the air between the pickling tank in step A and the pickling tank in step C,
The steel plate pickling apparatus according to (3), characterized in that it has means for horizontally passing the steel plate, and the means for injecting the gas injects gas to the horizontally passed steel plate. .

(6) The steel plate pickling apparatus according to any one of (2) to (5), wherein the nozzle includes an angle varying means.

(7) The pickling apparatus for steel sheets according to any one of (2) to (6), wherein two or more nozzles are arranged in the moving direction of the steel sheet.

  According to the present invention, the oxide scale of the steel sheet can be efficiently removed. In particular, the removal rate (pickling rate) of the oxide scale of the steel plate containing Si can be remarkably improved. Moreover, the steel plate after pickling obtained by this invention can obtain the clean surface without a descaling trace.

It is an example in the case of injecting gas on the steel plate surface in the middle of pickling in one pickling tank and performing the subsequent pickling in the same pickling tank as described above. It is an example in the case of injecting gas on the steel plate surface after pickling in the first pickling tank and performing the subsequent pickling in the second pickling tank. It is a schematic diagram which injects gas on the steel plate surface from the nozzle of this invention. It is an example of the pickling equipment provided with the pickling processing apparatus of this invention. This is an example in which nozzles are arranged in multiple stages. It is the figure which looked at arrangement | positioning of the nozzle by this invention from the top, and is the example at the time of turning the nozzle in the case of the slit-shaped nozzle of a steel plate width direction.

The present invention is described in detail below.
When removing the oxide scale formed on the surface of the steel sheet, in the process of dissolving the oxide scale with the pickling solution, when the gas is temporarily sprayed on at least a part of the surface of the steel sheet in the air, the acid It was found that the washing efficiency (oxidation scale removal efficiency) was improved.

  In other words, once the steel plate is taken out of the pickling tank and the gas is sprayed onto at least a part of the surface of the steel plate, the water of the pickling solution adhering to the surface of the steel plate in the sprayed portion is partially evaporated and concentrated. , The acid concentration increases (pH decreases). Since the acid concentration of the adhering pickling solution is locally increased in the recesses at the interface between the oxide scale layer and the steel plate surface that are about to peel off, the adhesion portion between the oxide scale layer and the steel plate is selectively dissolved, and again This is because the oxide scale is easily removed when immersed in the pickling solution. With respect to the gas injection, the effect can be obtained more remarkably when the gas is injected obliquely with respect to the surface of the steel sheet.

Patent Document 9 also discloses a method of blowing air to a steel strip. However, this method is originally intended to remove the acid solution layer (boundary film layer) adhering to the steel strip. For this purpose, the acid solution is wiped off with air and the end of the elastic partition plate is removed. It is essential to wipe the acid solution in contact with the steel strip. There is no description or suggestion that the pickling solution is concentrated on the surface of the steel sheet as described above. Therefore, even if it has the method and apparatus of patent document 9, since it will remove adhering pickling liquid, an adhering pickling liquid cannot be concentrated and the acid concentration cannot be made high as mentioned above, but it is the present invention. Such an effect cannot be obtained. Rather, since the pickling solution is removed, there is a concern that a new spot pattern (a pattern generated on the surface of the steel sheet due to unevenness of the acid solution) may occur.
Here, at least a part of the surface of the steel plate (hereinafter referred to as “steel plate surface”) may be one side surface of the steel plate, both sides (front and back) surfaces, side surfaces, or all surfaces. If so, the surface is not particularly limited.

  Moreover, in the steel plate containing Si, a further remarkable effect is acquired. When examining in detail the process in which the oxide scale in the steel plate containing Si dissolves in the pickling solution, the oxide scale on the steel plate surface gradually dissolves and reaches the vicinity of the interface between the oxide scale and the steel plate. It was found that there was a layer enriched with Si oxide. It was found that the remaining oxide scale hardly separated from the steel plate surface in the concentrated layer portion. The concentrated layer of the Si oxide may be gelled after being dissolved by the pickling solution. Although such a gel-like Si oxide was liberated from the surface of the steel plate during the dissolution process of the oxide scale, it was observed that the gel Si oxide was present without being peeled (removed) at the interface between the oxide scale and the ground iron.

  In the present invention, the dissolved and free gel-like Si oxide and the oxide scale having a layer in which Si oxide is concentrated can be removed by gas injection. The removal of Si oxide and oxide scale has the effect of removing by mechanical action by gas injection, but moreover, as mentioned above, the chemical effect by the concentration of the pickling solution adhering to the surface is It is considered that they are efficiently removed by superimposing. And it is thought that the concentrated pickling solution concentrates at the interface between the steel plate and the oxide scale due to surface tension as the water evaporates, and selectively dissolves. Since there is a concentrated layer of Si oxide at the interface between the steel plate and the oxide scale, the removal of the Si oxide is promoted, which is considered to further improve the removal efficiency of the oxide scale.

  That is, the gel-like Si oxide or the interface between the oxide scale and the steel sheet surface is selectively dissolved, and the removal of the Si oxide is promoted. Since the Si oxide that hinders the removal of the oxide scale is efficiently removed as described above, the oxide scale is also efficiently removed when the steel sheet is immersed again in the pickling solution. That is, the dissolution rate of the oxide scale is improved. This is very effective when the Si oxide is in a gel form.

  The effect of improving the pickling efficiency is more remarkable with a steel sheet having a Si content of 0.1 to 3.5% by mass. When the content of Si contained in the steel sheet is 0.1% by mass or more, a layer in which Si oxides are concentrated is likely to be generated, so that a remarkable effect of improving pickling efficiency is obtained. As the Si content increases, the effect of improving the pickling efficiency increases. However, if the Si content in the steel sheet exceeds 3.5% by mass, further improvement in the pickling efficiency is observed. It disappears and becomes constant.

  In the case of injecting gas to the steel sheet surface, it is more effective to inject from an oblique direction with respect to the steel sheet surface. When the gas is injected obliquely, as shown in FIG. 1 or FIG. 2, it is more preferable that the gas is injected opposite to the moving direction of the steel plate. More preferably, the angle θ (°) between the jetting direction and the steel sheet surface is in the range of 1 ° ≦ θ ≦ 75 °. In FIG. 3, the enlarged view (only one side is shown) which injects gas on the steel plate surface is shown typically. FIG. 3 schematically shows a case where the oxide scale layer 6 is present on the surface of the steel plate, and the layer 7 in which Si oxide is concentrated is present between the oxide scale layer 6 and the steel plate 2.

  Since the Si oxide has once passed through the pickling tank, it is being dissolved. At this time, as shown in FIG. 3, if the gas is injected while being inclined with respect to the surface of the steel sheet, the gas directly hits the interface between the oxide scale layer and the steel sheet, so that a sufficient effect can be obtained. If the angle θ is less than 1 °, even if the gas injection pressure is increased, the gas that strikes the steel plate surface is dispersed, so the gas may not strike the steel plate surface at a sufficiently high pressure. When the angle θ exceeds 75 °, the injected gas often does not directly hit the interface between the oxide scale layer and the steel plate, and the above-described effect may not be sufficiently obtained.

Regarding the gas injection, any means may be used, and examples thereof include a method using a blower or a nozzle. In particular, it is preferable to inject gas with a nozzle.
Considering the size of the nozzle, the distance at which the gas is injected from the nozzle to the steel plate surface, etc., the angle θ is preferably 10 ° to 60 °, and more preferably the gas injection is concentrated at the interface between the oxide scale layer and the steel plate. Therefore, it is desirable that the angle θ is 15 ° to 45 °.

  The width of the injection nozzle port shown in FIG. 3 is preferably longer than the width of the steel plate surface. The nozzle port may have a slit shape in the width direction, or independent nozzle ports may be arranged side by side in the width direction. Further, as shown in FIG. 6, the nozzle port may be swung in a plane parallel to the steel plate surface.

  1 and 2, one gas injection nozzle 1 is described on each surface of the steel plate, but it is not necessary to limit the gas injection nozzle to one on one side of the steel plate. As shown, two or more gas injection nozzles may be installed in the moving direction of the steel sheet and gas injection may be performed in multiple stages. By using the multi-stage gas injection nozzle, it becomes possible to remove oxide scale more efficiently.

The gas injection nozzle is preferably installed on both surface sides of the steel plate, but may be installed only on one side. Of course, there is no necessity to perform gas injection on both sides simultaneously, and gas injection may be performed alternately on each side.
It is preferable that the angle θ formed between the gas injection direction by the nozzle and the steel sheet surface can be varied. For example, when the moving speed of the steel plate is large, a sufficient gas injection effect can be obtained even if the angle θ is increased, but when the moving speed of the steel plate is low, the angle θ is decreased to obtain a sufficient gas injection effect. In order to obtain it, it is made variable according to the moving speed of a steel plate.

  As described above, in order to inject gas onto the steel sheet surface in the middle of dissolution of oxide scale by pickling, for example, as shown in FIG. 1, the steel sheet was pickled and pickled in one pickling tank. It is conceivable that the steel plate is once taken out of the pickling tank, gas is injected, and the pickling is performed again in the pickling tank. Alternatively, pickling equipment in which a plurality of pickling tanks are arranged in series (FIG. 2 shows two examples of pickling tanks), and a steel plate pickled between the tanks is once taken out of the pickling tank and gas The structure which injects may be sufficient. FIG. 4 schematically shows the pickling equipment according to the present invention.

  Although the gas used by this invention is not specifically limited, For example, gas, such as air, nitrogen, argon, is mentioned. Moreover, those mixed gas may be sufficient. The effect of the present invention can be exhibited by setting the pressure of the gas to be injected to 0.5 to 1.0 MPa or more at the injection port. If it is less than 0.5 MPa, the pickling speed may not be improved. Further, the reason why the upper limit is defined as 1.0 MPa is that, when a gas exceeding 1.0 MPa is injected, the equipment relating to the pressurizing apparatus becomes large, and an economic effect may not be exhibited.

  Moreover, it is desirable that the gas injection nozzle port has a distance of 2 to 80 cm in terms of the gas injection path from the steel plate surface. Therefore, when the gas injection nozzle port is inclined, the distance is a value obtained by multiplying the shortest linear distance between the gas injection nozzle port and the steel plate surface by 1 / sin θ. If it is less than 2 cm, the gas injection nozzle port may come into contact with the vibration of the traveling steel plate. When it exceeds 80 cm, the gas injected toward the steel sheet surface may not reach the steel sheet surface sufficiently. Depending on the situation of peripheral equipment, etc., a high effect can be obtained if the distance is 5 cm to 30 cm.

  The pickling liquid of the pickling tank according to the present invention is a normal pickling liquid for removing oxide scale. For example, a hydrochloric acid aqueous solution, a sulfuric acid aqueous solution, a hydrofluoric acid aqueous solution (hydrofluoric acid), or an aqueous solution containing nitric acid, acetic acid, formic acid or the like in these solutions can be used. The acid concentration of the pickling solution is not particularly limited, but is in the range of 2% by mass to 20% by mass. If it is less than 2% by mass, a sufficient rate of dissolving the oxide scale may not be obtained. If it exceeds 20% by mass, corrosion of the pickling tank may become significant, or it may be necessary to enlarge the rinse tank.

Further, Fe ²⁺ ions may be added to the pickling solution. The Fe ²⁺ ion concentration is more preferably 30 to 150 g / L. If it is less than 30 g / L, stable pickling may not be possible. If it exceeds 150 g / L, the pickling speed may be slow. Further, Fe ³⁺ ions may be added to the pickling solution.
The temperature of the pickling solution is not particularly limited, but is preferably between room temperature and 97 ° C. for reasons such as pickling efficiency and temperature control.

  Although the steel plate moving speed in the gas injection part of this invention is not specifically limited, 50 m / min-400 m / min are preferable. If it is less than 50 m / min, productivity (pickling efficiency) may be lowered. If it exceeds 400 m / min, the effect of pickling efficiency improvement by gas injection may not be obtained. The steel plate traveling speed is particularly preferably 100 m / min to 200 m / min.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.
An oxidation scale removal test was performed using steel. As the steel material, a hot-rolled steel plate was used, C: 0.002 mass%, Mn: 0.53 mass%, S: 0.01 mass%, Nb: 0.006 mass%, and Si shown in Table 1. It adjusted to the mass%, remainder Fe, and an unavoidable impurity. The steel plate shape is a test steel strip having a thickness of 4 mm and a width of 100 mm. Using the pickling tank combined with the gas injection shown in FIG. 1, it is run at a speed of 10 to 100 m / min, and the pressure of the gas to be injected and the supply angle θ are changed within the range shown in Table 1 for descaling. The effect was investigated. The gas pressure at the injection port was measured with a pressure gauge provided on the side wall of the gas injection nozzle.

An aqueous HCl solution was used as the pickling solution, and was adjusted and controlled to be within a range of 6 to 9% by mass of hydrochloric acid during operation. Further, FeCl ₂ was added so that Fe ²⁺ in the solution was 80 g / L. Similarly, with respect to ^{Fe 3+,} as ^{Fe 3+} in the solution is 1 g / L, FeCl ₃ was also added. The pickling solution was heated to 70 ° C. (± 5 ° C.).

  As an evaluation method, the pickling treatment time when the plate removal speed (moving speed) of the steel sheet was changed and the oxide scale removal area ratio was 90% or more was measured and evaluated. Here, based on 50 mm × 50 mm on the surface of the steel plate, the ratio of the area of the portion without the oxide scale was examined and averaged on both the front and back surfaces of the steel plate to obtain the oxide scale removal area ratio. When the pickling treatment time at which the oxide scale removal area ratio is 90% or more exceeds 35 seconds: ×, when 30 to 35 seconds: Δ, when it is 25 to 30 seconds: ○, within 25 seconds Case: ◎.

  Table 1 shows the evaluation results. Compared with the case of not injecting gas, the time of pickling treatment was able to be shortened by injecting gas on the steel plate surface during the pickling process. Regarding the gas injection angle, the pickling efficiency was excellent in the range of 1 ° to 75 °. Moreover, the pickling efficiency was higher when the pressure of the gas at the injection port was in the range of 0.5 to 1.0 MPa. A gas injection effect remarkably appeared in a steel plate containing 0.1 to 3.6% by mass of Si.

As in Example 1, using a test steel sheet containing C, Mn, S, Nb and containing Si shown in Table 2, gas injection was performed between the two pickling tanks shown in FIG. Went and pickled. The pickling solutions in the two pickling tanks are the same as in Example 1. The pickling solution was heated to 75 ° C. (± 5 ° C.).
The evaluation method is the same as in Example 1. Table 2 shows the evaluation results. Compared with the case of not injecting gas, the time of pickling treatment was able to be shortened by injecting gas on the steel plate surface during the pickling process. Regarding the gas injection angle, the pickling efficiency was excellent in the range of 1 ° to 75 °. Moreover, the pickling efficiency was higher when the pressure of the gas at the injection port was in the range of 0.5 to 1.0 MPa.

  The present invention can be used in the steel manufacturing industry. According to the present invention, it is possible to efficiently remove the oxide scale of the steel plate. In particular, the oxide scale removal rate (pickling rate) of a Si-containing steel plate represented by high-tensile steel can be remarkably improved. Moreover, the steel plate after pickling obtained by the present invention can obtain a clean surface having no descaling trace. As a result, the productivity of hot-rolled steel sheets, particularly high-tensile steel sheets such as automobile steel sheets, can be dramatically improved, and it is convinced that it can contribute to the supply of high-quality and low-cost steel sheets.

DESCRIPTION OF SYMBOLS 1, 1 'gas injection nozzle 2 Steel plate to run 3 Pickling tank 4 1st pickling tank 5 2nd pickling tank 6 Oxide scale layer 7 Si oxide layer 8 Gas injection nozzle port 9 Pickling part 9' Gas Injection unit 10 Rinse tank 11 Rewinding machine 12 Welding machine 13 Inlet looper 14 Tension leveler 15 Outlet looper 16 Lubricator 17 Winder

Claims (7)

A pickling treatment method for removing the oxidized scale of a steel sheet containing 0.1 to 3.5% by mass of Si, the process A for pickling the steel sheet, and after the process A, at least of the steel sheet in the air a step B of injecting a gas toward the portion of the surface, after the step B, have a step C of pickling said steel sheet,
The acid concentration of the pickling solution in Step A and Step C is 2 to 20% by mass, the Fe ²⁺ ion concentration in the pickling solution is 30 to 150 g / L, and the temperature of the pickling solution Is from room temperature to 97 ° C,
In the step B, the gas is injected in opposition to the moving direction of the steel plate, and an angle θ (°) formed by the gas injection direction and at least a part of the surface of the steel plate is 15 ° ≦ θ ≦ 45 °. there are, injection pressure of the gas injected in 0.5～1.0MPa, pickling method of the steel sheet, characterized in Rukoto concentrated pickling solution adhering to the surface of the steel sheet. It possesses at least one pickling tank, and means for injecting a gas toward at least part of the surface of the steel sheet in the air,
Step A for pickling the steel plate, Step B for injecting gas toward at least a part of the surface of the steel plate in the air after Step A, and Step for pickling the steel plate after Step B C and
The means for injecting the gas is in the step B, and is a nozzle that injects the gas so as to face the moving direction of the steel sheet, and an angle θ formed by the gas injection direction and at least a part of the surface of the steel sheet (°) is a 15 ° ≦ θ ≦ 45 °, pickling device steel sheet pressure is characterized 0.5~1.0MPa der Rukoto of the injection port of the nozzle. The pickling treatment apparatus for steel sheets according to claim 2 , wherein the pickling tank is two or more tanks. 3. The steel plate according to claim 2, wherein in the step B, the steel plate has means for horizontally passing the steel plate, and the means for injecting the gas injects gas to the steel plate to be horizontally passed. Pickling treatment equipment. In the air between the pickling tank in step A and the pickling tank in step C,
The steel plate pickling apparatus according to claim 3, further comprising means for horizontally passing the steel plate, wherein the means for injecting the gas injects gas to the horizontally passed steel plate. . The steel plate pickling apparatus according to any one of claims 2 to 5 , wherein the nozzle has an angle varying means. Two or more said nozzles are located in a line with the moving direction of the said steel plate, The pickling processing apparatus of the steel plate of any one of Claims 2-6 characterized by the above-mentioned.

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