JP2001020086A - Horizontal pickling device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a horizontal pickling device capable of suppressing the degradation of pickling ability by decreasing the integral of a boundary layer thickness in the horizontal pickling device and securing the optimum acid concentration or the optimum pickling liquid temp. SOLUTION: An inlet side nozzle 6 and an outlet side nozzle 7 are mounted in a pickling vessel 1 of the horizontal pickling device to be >=100 mm in the interval between the inlet side nozzle 6 and the outlet side nozzle 7 and the surface of a steel strip 10, >=5 deg. in the angle θ1 between the surface of the steel strip and the pickling liquid jetted from the inlet side nozzle 6 and the outlet side nozzle 7, <=150 m3/hr in the pickling liquid feed rate Q1 from the inlet side nozzle 6 and the outlet side nozzle 7 and to satisfy the relation, Q1> A1+(1√[cos(θ1)]-1) (where, A1=10000).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel strip pickling apparatus for continuously pickling and removing an oxide scale film formed on the surface of a steel strip, and more particularly to a steel strip in a plurality of pickling tanks having a shallow tank depth. The present invention relates to a horizontal pickling apparatus that applies tension and sequentially passes in the horizontal direction.

[0002]

2. Description of the Related Art An iron oxide film, that is, an oxide scale film, is formed on the surface of a hot-rolled steel strip hot-rolled at a high temperature. As a pickling apparatus for removing an oxide scale film formed on the surface of a steel strip, a dip-type pickling apparatus has conventionally been generally used.

[0003] In the dip type pickling apparatus, as shown in FIG. 14, a pickling tank 141 is divided into a plurality of parts by a partition 142 formed with a skid for supporting a steel strip, an upper part is closed by a cover 143, and an acid solution is contained therein. 144
Is stored. As shown by the arrow, the steel strip 145 enters the first tank of the pickling tank 141 from the support roll 146 on the inlet side, forms a loop in the acid solution 144 stored in the tank, and proceeds to form a loop.
Go over the 42 and enter the second tank. In the second tank as well, a loop is formed in the acid solution 144 as in the first tank, and the oxidation proceeds on the surface of the steel strip 145 while passing through the third and fourth tanks. The scale film is removed. Squeezing roll 147
After the acid solution adhering to the surface of the steel strip 145 is removed by rinsing, it is washed with water in a washing tank 148 and transported to the next step.

In the dip type pickling apparatus, the acid concentration is controlled only in the most downstream pickling tank among the pickling tanks, and the acid solution is sequentially supplied to the upstream pickling tank by overflow. The temperature of the acid solution is controlled by installing a heating device such as a steam coil inside each pickling tank and controlling the amount of heating.

[0005] Recently, from the viewpoint of thermal energy, the above-mentioned dip type pickling apparatus has a shallow bath immersion type (low bath type, sharo type) with a shallow pickling tank depth, a shallow bath depth, and A jet stirring type (turbulence type, jet type) in which an acid solution in a tank is stirred to shorten the pickling treatment time is also used. Those having a shallow tank depth are collectively referred to as a horizontal pickling apparatus, and the steel strip is tensioned between a pair of ringer rolls provided before and after the pickling tank, and is immersed in an acid solution. Pass through sequentially.

[0006] A typical turbulence type pickling apparatus of a horizontal pickling apparatus, as shown in Figs.
The acid solution in the circulation tank 152 is pressurized by the pump 153, and the temperature is raised by the heating device 154, so that the pickling tank is
The water is sprayed into each pickling tank 151 from the inlet nozzle 155 and the outlet nozzle 156 of 151 and the side nozzle 157 installed on the side wall of the pickling tank 151. The acid solution injected into each pickling tank 151 returns to the circulation tank 152 via the conduit 158, and is again circulated and injected into each pickling tank 151.

[0007] A pair of upper and lower ringer rolls 160 is provided between the adjacent pickling tanks 151, 151 to apply tension to the steel strip 159 and to prevent the acid solution from moving between the tanks. . In addition, not only between the pickling tanks 151, 151, but also the most upstream pickling tank 151.
A similar ringer roll 160 is installed at the inlet of the tank and at the outlet of the most downstream pickling tank. At the bottom of each pickling tank 151, in order to prevent the steel strip 159 from directly contacting the bottom brick 161 of the tank and to enhance the stirring effect of the acid solution, the corrosion resistance and the resistance of natural stones, ceramic bricks, etc. A plurality of skids 162 made of a material having excellent wear properties are laid at predetermined intervals in the conveying direction of the steel strip 159.

[0008] Further, the supply of the acid solution to each of the circulation tanks 152 involves first charging a new acid or a recovered acid and an oxidation inhibitor into the lowermost circulation tank and containing the oxidation inhibitor stored in the lowermost circulation tank. The acid solution is sequentially cascaded to the upstream circulation tank. In general, the control of the acid concentration is performed in the most downstream circulation tank. Furthermore, the most upstream circulation tank 15
Also in 2, the waste acid discharged from the uppermost circulation tank 152
In order to efficiently obtain a recovered acid in an acid recovery facility not described in 163, the acid concentration may be controlled.

[0009] A jet stirring type horizontal pickling apparatus such as a turbulence type or a jet type is intended to shorten the pickling treatment time with the speeding up of the pickling line. As shown in FIG. 17 (b), the thickness of the boundary layer, which indicates the distance from the steel strip surface in the region where the acid solution flows following the movement of the steel strip, is shown in FIG. It becomes large in the longitudinal direction of the washing tank, and the heat transfer from the acid solution and the replenishment of the acid solution to the surface of the oxide scale film and the inside of the cracks are stagnated, causing a problem that the pickling ability is reduced.

[0010] Further, the control of the acid concentration in the horizontal pickling apparatus is as follows.
Since only the upstream or downstream circulation tank is used, and the intermediate circulation tank does not control the acid concentration, there is a problem that the acid concentration varies greatly and the pickling ability is reduced. .

[0011] Further, the temperature control of the acid solution in the horizontal pickling apparatus is an important factor for controlling the acid concentration and also for removing the oxide scale film on the steel strip, and when the acid solution is supplied from the circulation tank to the pickling tank. However, in the pickling tank on the most upstream side where the steel strip first enters, the heat removal by the steel strip is large, the temperature of the acid solution is lowered, and the pickling ability is reduced. Has occurred.

[0012] As a measure for preventing a decrease in the pickling capacity due to an increase in the speed of the pickling line, a steel strip supporting roller for supporting the steel strip from the lower surface between the ringer roll pairs is disposed on the bottom of the pickling tank. Horizontal pickling device (Japanese Patent Laid-Open No. 4-247889), a lower surface crest filled with an acid solution and supporting a steel strip on a lower surface, and an upper surface crest for suppressing a liquid flow on an upper surface are arranged at different positions in the running direction of the steel strip. An acid pickling device capable of tilting the upper surface crest in the running direction of the steel strip in order to make the gap between the upper surface crest and the lower surface crest variable.
(Japanese Unexamined Patent Publication No. 6-2179), based on the measurement result of the acid concentration in the circulation tank, throwing waste liquid from the most downstream circulation tank into the circulation tanks other than the most upstream circulation tank among the circulation tanks A method of pickling by adjusting the acid concentration by introducing one or more of the recovered acid and the new acid into the circulation tank or each circulation tank on the uppermost stream side (Japanese Patent Laid-Open No. 9-268390) and the like has been proposed. ing.

[0013]

The horizontal pickling apparatus disclosed in Japanese Patent Application Laid-Open No. 4-247889 discloses a steel sheet supporting roller for supporting a steel strip from a lower surface between a pair of ringer rolls. Is cut off, and the integral value of the boundary layer thickness decreases, but the upper surface of the steel strip has no support roller, so the boundary layer thickness increases, and the acid solution from the acid solution to the surface of the oxide scale film of the steel strip and into the cracks There is a disadvantage that heat transfer and replenishment of the acid solution are stagnated, and the pickling ability is reduced.

Further, the pickling apparatus disclosed in Japanese Patent Application Laid-Open No. 6-2179 discloses a pickling apparatus in which the upper crest of a steel strip is displaced in the running direction of the steel strip from the lower crest, and the gap between the upper crest and the lower crest is made variable. Thereby, the boundary layer is divided on both the upper and lower surfaces, and the integral value of the boundary layer thickness decreases. However, in a horizontal pickling apparatus with a shallow tank depth, when a steel strip having a shape that is distorted beyond the gap secured between the upper surface crest and the lower surface crest passes through the steel strip, scratches occur on the upper and lower surfaces of the steel strip. Has disadvantages.

[0015] Furthermore, the pickling method disclosed in Japanese Patent Application Laid-Open No. 9-268390 discloses a pickling method that improves the pickling ability by reducing the variation in the acid concentration of each circulation tank and reduces the adhesion of black substances to the steel strip surface. Can be prevented. However, in this pickling method, since the antioxidant or the pickling accelerator containing the antioxidant is not replenished together with at least one of waste acid, recovered acid, and new acid, the surface of the steel strip is roughened by peracid cleaning. Disadvantageously tends to occur. In addition, it is difficult to supply an acid solution having an optimum acid concentration for removing an oxide scale film that progresses every moment in an acid washing tank only by controlling the acid concentration of the circulation tank alone.

In the pickling tank on the most upstream side where the steel strip first passes,
As a method to solve the problem that the heat removal by the steel strip is large, the acid solution temperature is low, and the pickling capacity is reduced, if a heating tank is installed on the upstream side of the pickling equipment to raise the temperature of the steel strip Although it is possible to prevent the temperature of the acid solution from decreasing in the pickling tank on the most upstream side, a large capital investment is required.

An object of the present invention is to solve the above-mentioned drawbacks of the prior art, to reduce the integral value of the boundary layer thickness of the horizontal pickling apparatus,
An object of the present invention is to provide a horizontal pickling apparatus capable of securing an optimum acid concentration or an optimum acid solution temperature and suppressing a decrease in pickling ability.

[0018]

The horizontal pickling apparatus according to the present invention applies an acid solution to the surface of a steel strip which is conveyed in contact with an acid solution by applying tension to the surface of a steel strip at an inlet and an outlet of a pickling tank. An inlet nozzle and an outlet nozzle for injecting, and a side nozzle for injecting the acid solution from the side, a shallow pickling tank provided with a skid at the bottom of the tank, and an acid solution for the pickling tank. The horizontal pickling apparatus includes a circulation tank for supplying, and a piping system for supplying an acid solution from the circulation tank to the inlet nozzle, the outlet nozzle, and the side nozzle. The distance between the inlet nozzle and the outlet nozzle and the steel strip surface is 100 mm or more, the angle (θ1) between the acid solution injected from the inlet nozzle and the outlet nozzle and the steel strip surface is 5 ° or more, The acid solution flow rate (Q1) from the nozzle and outlet nozzle
An inlet nozzle and an outlet nozzle are provided so as to be 150 m ³ / hr or less and satisfy the following expression (1).

[0019]

(Equation 3)

By installing the inlet nozzle and the outlet nozzle in this manner, replenishment of the acid solution from the inlet nozzle and the outlet nozzle and the outflow of the acid solution outside the tank due to the movement of the steel strip in the tank. Can be suppressed, the jet stirring effect can be enhanced while the acid solution is held in the tank, and the pickling treatment can be performed with high efficiency.

Further, in the horizontal pickling apparatus according to the present invention, in the above horizontal pickling apparatus, the distance between the side nozzle for injecting the acid solution from the side and the steel strip surface is 100 mm or more, and the side nozzle and the steel strip surface are used. (Θ2) is 5 ° or more, acid solution flow rate from side nozzle
(Q2) is 150 m ³ / hr or less, and the side nozzle is installed so as to satisfy the following expression (2).

[0022]

(Equation 4)

By installing the side nozzles in this manner, the supply of the acid solution from the side nozzles and the acid solution sprayed from the side nozzles generate the acid solution following the movement of the steel strip in the tank. The flow of the liquid is dammed, the flow of the acid liquid is changed from a laminar flow state to a turbulent flow state, and the boundary layer is destroyed, so that the pickling efficiency can be increased.

[0024] In the horizontal pickling apparatus of the present invention, a pickling accelerator containing a new acid or a recovered acid and an oxidation inhibitor or an oxidation inhibitor is provided in the most downstream circulation tank of the horizontal pickling apparatus provided with a plurality of pickling tanks. In a continuous horizontal pickling apparatus, the acid solution containing the antioxidant stored in the most downstream circulation tank is supplied in cascade to the upstream circulation tank, and the most downstream circulation tank together with the most downstream circulation tank It is characterized in that a new acid or a recovered acid and an oxidation inhibitor or an acid pickling accelerator containing an oxidation inhibitor are added to the circulation tanks other than the above to control the acid concentration in each circulation tank, thereby pickling.

As described above, the acid concentration in the circulation tanks other than the most downstream circulation tank together with the most downstream circulation tank is controlled by adding the oxidation inhibitor or the pickling accelerator containing the oxidation inhibitor together with the new or recovered acid. By performing pickling, the variation in the acid concentration can be reduced in the other circulation tanks as well as the lowermost circulation tank, and the pickling efficiency can be increased.
In addition, the removal time of the oxide scale film is shortened by the improvement of the pickling efficiency, and the time for exposing the base iron to the steel strip surface is shortened. Since the washing accelerator is added, dissolution of the ground iron after the removal of the excess oxide scale film of the steel strip is prevented, and the steel strip surface roughness due to peracid cleaning can be prevented.

[0026] The horizontal pickling apparatus according to the present invention comprises an inlet nozzle and an outlet nozzle for injecting an acid solution onto the surface of the steel strip at the entrance and exit of each pickling tank, and a steel pipe from the side of each pickling tank. It is characterized in that an intermediate spray is installed between a side nozzle for spraying an acid solution on the belt surface.

[0027] The oxide scale film of the steel strip is removed every time by contact with an acid solution, but at the same time as the oxide scale film is removed, the acid concentration also decreases in proportion. The region where the acid solution is injected from the inlet nozzle, the outlet nozzle and the side nozzle can maintain a constant acid concentration, but the other regions are regions where the acid concentration is low. Therefore, by installing an intermediate spray in that area, that is, between the inlet nozzle and the outlet nozzle and the side nozzle, an almost constant acid concentration can be secured over the entire pickling tank, Efficiency can be increased.

[0028] The horizontal pickling apparatus of the present invention is characterized in that an acid solution heating system is provided in an acid solution supply system for supplying an acid solution to a pickling tank, and a heating device for the acid solution stored in a circulation tank is provided. Features. Thereby, the temperature of the acid solution to be supplied to the pickling tank can be increased, and the temperature of the acid solution before being supplied to the pickling tank can be increased by an amount corresponding to the heat removal of the acid solution in the pickling tank. The acid temperature can be prevented from lowering, and the pickling efficiency can be increased.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION As a horizontal pickling apparatus to which the present invention can be applied, a turbulence type and a jet type jet stirring type pickling apparatus can be exemplified.

[0030] The present inventors have set the inlet nozzle and the outlet nozzle so that the inlet and outlet nozzles of the pickling tank do not come into contact with the steel strip surface even when the steel strip having a distorted shape is moved. Ensuring a sufficient distance of 100 mm from the steel strip surface, the angle between the inlet and outlet nozzles and the steel strip surface (θ1), and the flow rate of the acid solution injected from the inlet or outlet nozzle (Q1) The study was repeated on the relationship with. As a result, if the inlet side nozzle and outlet side nozzle are installed so as to satisfy the following Equation 5, it is possible to replenish the acid solution sufficiently and move the steel strip outside the tank by moving the steel strip in the pickling tank. It was confirmed that it was possible to control the outflow to the public.

[0031]

(Equation 5)

If the distance between the inlet nozzle and the outlet nozzle and the surface of the steel strip is less than 100 mm, when the steel strip having a distorted shape is moved, the inlet nozzle and the outlet nozzle come into contact with the surface of the steel strip. Then, scratches occur on the surface of the steel strip. However, by ensuring the distance between the inlet nozzle and the outlet nozzle and the steel strip surface of 100 mm or more, the steel strip can be moved without causing scratches on the steel strip surface.

If the angle (θ1) between the acid solution injected from the inlet nozzle and the outlet nozzle and the surface of the steel strip is less than 5 °, the acid solution to be injected and the acid solution flow in the tank become parallel. Therefore, the flow of the acid solution in the tank cannot be blocked, and the flow of the acid solution in the pickling tank due to the movement of the steel strip cannot be prevented from flowing out of the pickling tank. Therefore, by setting the angle (θ1) between the acid solution sprayed from the inlet nozzle and the outlet nozzle and the steel strip surface to be 5 ° or more, the acid solution in the tank is caused by the sprayed acid solution. And the outflow of the acid solution to the outside of the tank due to the movement of the steel strip in the pickling tank can be suppressed.

[0034] If the flow rate of the acid solution (Q1) injected from the inlet nozzle or the outlet nozzle is 150 m ³ / hr or less, the pickling tank is maintained without the meandering of the steel strip and maintaining the jet stirring state. The steel strip can be moved stably inside. On the other hand, 150m ³ /
If it exceeds hr, the jet stirring effect becomes excessive and the meandering of the steel strip becomes remarkable, so that the steel strip cannot be moved stably in the pickling tank.

Further, the relationship between the angle (θ1) formed between the acid solution sprayed from the inlet nozzle and the outlet nozzle and the steel strip surface and the flow rate of the acid solution (Q1) sprayed from the inlet nozzle or the outlet nozzle is as follows. When the formula (1) is satisfied, it is possible to prevent the acid solution flow in the pickling tank from flowing out of the pickling tank due to the movement of the steel strip. Therefore, the relationship between the angle (θ1) between the acid solution sprayed from the inlet nozzle and the outlet nozzle and the steel strip surface and the acid solution flow rate (Q1) sprayed from the inlet nozzle or the outlet nozzle is as described above ( By satisfying the expression (1), it is possible to replenish the acid solution sufficiently, and it is possible to prevent the acid solution from flowing out of the tank by moving the steel strip in the tank.

That is, the relationship between the angle (θ1) formed between the acid solution sprayed from the inlet nozzle and the outlet nozzle and the steel strip surface and the flow rate of the acid solution (Q1) sprayed from the inlet nozzle or the outlet nozzle is as follows. By ensuring the state of the hatched portion in the graph shown in FIG. 10, the acid solution can be held in the pickling tank, the jet stirring effect can be enhanced, and the pickling treatment can be performed with high efficiency.

When the side nozzles are installed on the side walls of the pickling tank, the present inventors set a line in which the flow of the acid solution can be visually confirmed at the center of the pickling tank farthest from the inlet nozzle and the outlet nozzle. At the speed, the flow of the acid solution in the pickling situation was visually observed in each of the case where there was no side nozzle, the case where the installation angle of the side nozzle was bad, and the case where the installation angle of the side nozzle was optimal. The results are shown in FIGS. 11, 12, and 13. Figure
11 is without the side nozzle 8, FIG. 12 is with the side nozzle 8, but the installation angle is poor, FIG. 13 is with the side nozzle 8, and the installation angle satisfies the condition of Equation 4 above Is schematically shown.

[0038] As shown in FIG. 11, the skid provided for supporting the lower surface of the steel strip 10 in a state where the side nozzle 8 is not provided.
13 forms a circulating flow on the lower surface of the steel strip. On the other hand, on the upper surface of the steel strip, only a laminar flow due to the movement of the steel strip 10 in the tank was observed. That is, in the central part of the pickling tank 1, the lower surface of the steel strip is in a jet stirring state by the skid 13,
The integral value of the boundary layer thickness becomes small, and the heat transfer from the acid solution to the surface of the oxide scale film on the surface of the steel strip and cracks and the replenishment of the acid solution are sufficient. On the other hand, the upper surface of the steel strip is not in the jet stirring state, and the heat transfer from the acid solution to the surface of the oxide scale film and the cracks and the replenishment of the acid solution are insufficient compared to the lower surface of the steel strip. Confirmed that there is.

As shown in FIG. 12, there is a side nozzle 8, but when the installation angle is poor, a circulating flow is formed on the lower surface of the steel strip by the skid 13 and the acid solution injected from the side nozzle 8. . On the other hand, on the upper surface of the steel strip, only a laminar flow due to the movement of the steel strip 10 in the tank was observed. That is, as in the case where the side nozzle 8 is not provided, the heat transfer from the acid solution and the replenishment of the acid solution to the surface of the oxide scale film on the steel band surface and the cracks are still insufficient on the upper surface of the steel band. It was confirmed.

As shown in FIG. 13, when the side nozzle 8 is installed at the optimum installation angle, a circulating flow is also formed on the upper surface of the steel strip. In other words, by installing the side nozzle 8 at the optimum installation angle, the acid solution injected from the side nozzle 8 in the same manner as the lower surface of the steel strip causes the upper surface of the steel strip to be in a jet stirring state, and the outer surface of the steel strip is bounded on both sides. It was confirmed that the layer was broken and the acid solution efficiency could be increased.

[0041] The distance between the side nozzle and the steel strip surface is 100 mm so that the steel strip does not come into contact with the meandering while moving through the pickling tank. Experiments were repeated on the relationship between the angle (θ2) formed by the above and the acid solution flow rate (Q2) injected from the side nozzle. As a result, if the side nozzle is installed so as to satisfy the following equation 6, heat transfer from the acid solution to the surface of the oxide scale film on the steel strip surface and into the cracks and sufficient replenishment of the acid solution is possible It was confirmed that.

[0042]

(Equation 6)

The distance between the side nozzle and the surface of the steel strip should be 100 mm or more so that the steel strip does not come into contact with the meandering while moving in the pickling tank. If the angle (θ2) between the acid solution injected from the side nozzle and the steel strip surface is less than 5 °, the acid solution injected cannot destroy the boundary layer, and the surface of the oxide scale film on the steel strip surface and cracks Heat transfer from the acid solution into the inside and replenishment of the acid solution are insufficient.

Further, the flow rate of the acid solution injected from the side nozzle (Q2)
If it is 150 m ³ / hr or less, it is possible to stably move the steel strip in the pickling tank while maintaining the jet agitation state without meandering the steel strip. On the other hand, when it exceeds 150 m ³ / hr, the jet stirring effect becomes excessive, and the meandering of the steel strip becomes remarkable, and the steel strip cannot be moved stably in the pickling tank.

Further, the relationship between the angle (θ2) between the acid solution injected from the side nozzle and the steel strip surface and the flow rate of the acid solution (Q2) injected from the side nozzle satisfies the above equation (2). As a result, the boundary layer on the top surface of the steel strip is destroyed, and the
Heat transfer from the acid solution and replenishment of the acid solution to the surface and cracks of the oxide scale film on the steel strip surface are sufficiently performed,
It was confirmed that the acid solution efficiency could be increased.

In a normal horizontal pickling apparatus, the acid solution in each circulation tank is pressurized by a pump to each of a plurality of connected pickling tanks, and the temperature is raised by each heating device to each pickling tank. Inject into each pickling tank from the installed nozzle. The acid solution injected into each pickling tank returns to each circulation tank via each pipe, is pressurized again by each pump, is heated by each heating device, and is circulated and injected into each pickling tank.

In general, when supplying the acid solution to the pickling tank, first, a new acid or a recovered acid and an oxidation inhibitor are supplied to the most downstream circulation tank. The supply control of the acid solution is performed by measuring the acid concentration with an acid concentration meter installed in the circulation tank and supplying the required amount of the acid solution. There is a circulation tank level control method to supply.

Using the above-described acid solution supply control method, an acid solution containing an oxidation inhibitor is supplied to the most downstream circulation tank. Next, in the supply of the acid solution to the circulation tank, the acid solution in the circulation tank is supplied by the circulation tank level control. The supply of the acid solution to the circulation tank is carried out by controlling the circulation tank level. Finally, the waste acid discharged from the uppermost circulation tank is discharged by the circulation tank level control. In order to efficiently obtain the recovered acid from the waste acid with the acid recovery equipment, the acid concentration is measured by an acid concentration meter and the acid concentration is controlled to discharge a necessary amount of the waste acid, together with the circulation tank level control in the circulation tank. In some cases.

In the present invention, the acid concentration is measured by an acid concentration measuring device in the circulation tanks other than the most downstream one in the same manner as in the most downstream circulation tank, and the required amount of the new or recovered acid and the oxidation inhibitor or the oxidation inhibitor are measured. Supply the pickling accelerator containing the agent. As described above, similarly to the most downstream circulation tank, by controlling the acid concentration of the acid solution in the circulation tanks other than the most downstream, the variation in the acid concentration in each circulation tank is reduced, and the pickling efficiency can be increased. it can.

In the present invention, as an acid solution supplied by controlling the acid concentration, a required amount of an oxidation inhibitor or an acid washing accelerator containing an oxidation inhibitor is supplied together with a new acid or a recovered acid. In this way, by supplying the oxidation inhibitor or the pickling accelerator containing the oxidation inhibitor together with the new acid or the recovered acid, the time required for removing the base iron exposed on the steel strip surface by shortening the scale removal time due to the efficiency of the pickling is improved. Of the steel strip can be prevented, and the surface of the steel strip can be prevented from being roughened due to peracid cleaning.

Further, in the present invention, the time delay for securing the required acid concentration in the circulation tank other than the most downstream circulation tank is reduced, and the acid concentration in the most downstream circulation tank can be reduced. The basic unit can be improved. Further, the target value of the acid concentration in each circulation tank is set so that the acid concentration increases in order from the most upstream in order to supply the acid solution from the most downstream to the most upstream. As a result, it is possible to use both the circulating tank level control and the acid concentration control without reducing the acid solution basic unit.

The present inventors have developed an intermediate spray between an inlet nozzle and an outlet nozzle for spraying an acid solution from an inlet and an outlet of a pickling tank, and a side nozzle for spraying an acid solution from a side. Prior to the installation, the change over time in the acid concentration inside the pickling tank in the horizontal pickling apparatus was investigated. FIG. 7 shows the results. In addition,
During the study period, the recycle tank was not replenished with acid solution from other recycle tanks and was not replenished with fresh or recovered acid and an acid inhibitor or an acid scavenger with an antioxidant.

As shown in FIG. 7A, in a region (2) where the acid solution is not supplied from the circulation tank via the nozzle at any time, a region (1) where the acid solution is supplied from the circulation tank via the nozzle at any time The decrease in the acid concentration is remarkable as compared with In other words, the region where the acid solution is supplied as needed can prevent a decrease in the acid concentration due to the removal of the oxide scale film of the steel strip, and a constant pickling efficiency can be obtained regardless of the elapsed time, but the acid solution is not supplied as needed. In the region, the pickling efficiency decreases with the lapse of time as the acid concentration decreases as the oxide scale film on the steel strip is removed.

Therefore, in the present invention, an intermediate spray is provided between the inlet nozzle, the outlet nozzle, and the side nozzle in order to maintain the acid concentration over the entire length of the pickling tank. As shown in Fig. 6, in the horizontal pickling device with an intermediate spray, the intermediate spray is provided between the side nozzle and the outlet nozzle, in an area where the acid solution is not supplied from the circulation tank, but is installed between the side nozzles. You can also. In addition, even if the intermediate spray sprays a certain amount of acid solution per hour, the flow rate can be controlled similarly to the inlet nozzle, the outlet nozzle, or the side nozzle.

Further, the intermediate spray is provided for the purpose of making the acid concentration uniform over the entire length of the pickling tank, as long as the acid concentration can be made uniform, and the shape of the nozzle and the angle of the nozzle are not limited. The installation of the intermediate spray in the horizontal pickling apparatus can make the acid concentration uniform over the entire length of the pickling tank, and can increase the pickling efficiency.

[0056] The inventors of the present invention, prior to providing the equipment for raising the temperature of the acid solution supplied to the pickling tank and the equipment for raising the temperature of the acid solution stored in the circulation tank, before installing the equipment inside the pickling tank of the horizontal pickling apparatus. The temperature distribution of the acid solution was investigated. Investigation of the acid solution temperature distribution was carried out in the central part and the outlet side of the most upstream pickling tank where the steel strip at room temperature enters first.
It is a comparison of the acid solution temperature of each circulation tank that supplies the acid solution to the central part of the downstream pickling tank and the pickling tank. Further, a steel strip having a cross-sectional area of 2300 mm ² was used as a narrow material, and a steel strip having a cross-sectional area of 7200 mm ² was used as a wide material. The heating capacity of each acid solution was constant. The results are shown in Table 1.

[0057]

【table 1】

As shown in Table 1, the temperature of the acid solution in the pickling tank is greatly affected by the amount of heat removed by the steel strip in the most upstream pickling tank for both narrow and wide materials. In addition, the larger the cross-sectional area of the steel strip, the greater the effect of the heat removal of the steel strip, and the lower the acid solution temperature. The temperature of the acid solution in the circulation tank is affected by the amount of heat removed by the steel strip, as in the acid temperature in the pickling tank. As the acid passes through the pickling tank, the temperature of the acid solution decreases.

In general, it is known that the acid solution temperature and the descaling ratio of the steel strip surface are in a proportional relationship, and the descaling ratio decreases as the acid solution temperature decreases. Therefore, in order to increase the pickling efficiency, it is necessary to prevent a decrease in the temperature of the acid solution in the most upstream pickling tank into which the steel strip at normal temperature enters first.

[0060] In the present invention, as shown in FIG. 8, the acid solution was added to the heating device 5 for raising the temperature in the middle of the pipe for supplying the acid solution from the circulation tank 2 to the pickling tank 1, and stored in the circulation tank 2. A heating device for raising the temperature of the acid solution 3 is installed. Examples of the heating device for raising the temperature of the acid solution 3 include a device for indirectly heating the acid solution stored in the circulation tank by a gas burner or an electric heater, an indirect heating device such as a heat exchanger, steam, an electric heater, and a gas burner. Any of the direct heating devices for directly heating the acid solution stored in the circulation tank can be used. FIG. 8 shows a configuration in which a heat exchanger 82 of an indirect heating device is provided as a heating device.

As a method of raising the temperature of the acid solution, although not shown in FIG. 8, a target temperature is set in advance in a computer, and the heating device is measured so as to reach the target temperature by measuring the acid solution temperature. Automatic control is also possible. The temperature of the acid solution stored in the circulation tank can be raised by using a heating device in the piping that supplies the acid solution from the circulation tank to the pickling tank, and the acid solution temperature can be further increased. Thus, it is possible to secure a temperature rise amount of the acid solution, to secure an acid solution temperature of about 90 ° C. at which the descaling rate of the steel strip is optimal, and to improve the pickling efficiency.

[0062]

Embodiment 1 An embodiment of the present invention will be described below with reference to the drawings. Figure
1 is a schematic explanatory view of a horizontal pickling apparatus of the invention according to claim 1 of the present invention, and FIG. 2 is a schematic explanatory view of the vicinity of an outlet nozzle and an inlet nozzle of the horizontal pickling apparatus. The horizontal pickling device is a pickling tank 1
Usually, 3 to 5 tanks are connected in series, and the acid solution 3 in the circulation tank 2 is pressurized by the pump 4, heated to a predetermined temperature by the heating device 5, and the inlet nozzle 6, the outlet nozzle 7 and the side. It is sprayed from each section nozzle 8 into each pickling tank 1. The acid solution injected into each pickling tank 1 returns to the circulation tank 2 via the conduit 9, and then returns to each pickling tank.
It is circulated in 1

[0063] The inlet nozzle 6 and the outlet nozzle 7 are
The relationship between the angle (θ1) between the acid solution sprayed from the nozzle 6 and the outlet nozzle 7 and the surface of the steel strip 10 and the flow rate of the acid solution (Q1) sprayed from the inlet nozzle 6 and the outlet nozzle 7 is expressed by Equation 5 above. It is installed to satisfy the conditions of In addition, the inlet nozzle 6 and the outlet nozzle 7 are provided with a distance of 100 mm or more from the surface of the steel strip 10.

A pair of upper and lower ringer rolls 11 are provided between the adjacent pickling tanks 1 and 1 to apply tension to the steel strip 10 and to prevent the acid solution from moving between the tanks. ing. Similar ringer rolls 11 are provided not only between the pickling tanks 1 and 1 but also at the inlet of the most upstream pickling tank 1 and at the outlet of the most downstream pickling tank 1. At the bottom of the pickling tank 1, the steel strip 10 is prevented from directly contacting the bottom brick 12, and the corrosion resistance and wear resistance of natural stone, porcelain brick, etc. Skids 13 made of a material having excellent properties are laid at predetermined intervals in the transport direction of the steel strip 10.

In the invention according to claim 1 of the present invention, as described above, the distance between the inlet nozzle 6 and the outlet nozzle 7 and the surface of the steel strip 10 is 100 mm or more, and the inlet nozzle 6 and the outlet nozzle
The angle (θ1) between the acid solution injected from 7 and the surface of the steel strip 10 is
5 ° C. or higher, the acid solution flow rate (Q1) injected from the inlet nozzle 6 and the outlet nozzle 7 is 150 m ³ / hr or less, and by installing so as to satisfy the above formula (1), steel strip 10 Pickling tank for moving steel strip 10 without causing scratches on the surface
1 to prevent the acid solution flow from flowing out of the pickling tank and keep the steel strip 10
Can be moved stably.

Embodiment 2 FIG. 3 is a schematic explanatory view showing the vicinity of a side nozzle according to a second embodiment of the present invention. The supply of the acid solution to the pickling tank 1 is performed by the side nozzle 8 together with the inlet nozzle 6 and the outlet nozzle 7 as described above. The side nozzle 8 has an angle (θ2) formed between the acid solution sprayed from the side nozzle 8 and the surface of the steel strip 10 and the relationship between the acid solution flow rate (Q2) sprayed from the side nozzle 8 and Equation 6 above. It is installed to meet the conditions. Also, the side nozzle 8 is
The gap between the steel strip 10 and the surface is 100 mm or more.

In the invention according to claim 2 of the present invention, as described above, the distance between the side nozzle 8 and the surface of the steel strip 10 is 100 mm or more, and the acid solution injected from the side nozzle 8 and the steel strip 10 The angle (θ2) made with the surface is 5 ° or more, and the acid solution flow rate (Q2) injected from the side nozzle 8 is 150 m ³ / hr or less, and by being installed so as to satisfy the formula (2). In addition, the acid layer sprayed from the side nozzle 8 on the surface of the steel strip 10 destroys the boundary layer associated with the movement of the steel strip 10 in the tank, and enters a jet stirring state, so that the pickling efficiency can be improved.

Embodiment 3 FIG. 4 is a schematic explanatory view of a continuous horizontal pickling apparatus according to the third aspect of the present invention. The hydrochloric acid concentration of the acid solution in the circulation tanks 2a, 2b, and 2c is set at 3% by weight, 8% by weight, and 13% by weight from the most upstream side.
%, And set so that the acid concentration increases in order from the most upstream side. The acid concentration is set in each of the circulation tanks 2a, 2b, 2c with an acid concentration measuring device 41a, 41b, 41c, and each of the acid concentration measuring devices 41a, 41c.
b, 41c, each circulation tank 2a, 2b, 2c
A new acid or recovered acid and an oxidation inhibitor or an acid inhibitor containing an oxidation inhibitor via a conduit 42a, 42b, 42c to an acid supply tank
It is configured to supply from 43.

Then, the acid concentration in each of the circulation tanks 2a, 2b, 2c was controlled based on the measured values of the acid concentration measuring devices 41a, 41b, 41c.
The result is shown as A in FIG. Also, for comparison, a new acid or a recovered acid and an oxidation inhibitor or an acid inhibitor containing an oxidation inhibitor were added to the lowermost circulation tank 2c based on the measurement value of the acid concentration meter 41c installed in the lowermost circulation tank 2c. Control was performed by replenishing the acid from the acid replenishing tank 43 via the conduit 42c, and controlling the other circulation tanks 2a and 2b by cascading replenishment from the downstream circulation tanks 2c and 2b. The result is shown as B in FIG.

As shown in FIG. 5, based on the measurement results of the acid concentration measuring devices 41a, 41b, 41c of the respective circulation tanks 2a, 2b, 2c, each of the circulation tanks 2a, 2b, 2c is charged with a new acid or a recovered acid and oxidized. A of the present invention, in which the pickling accelerator containing an inhibitor or an oxidation inhibitor is replenished and controlled via conduits 42a, 42b, and 42c, the new acid or recovered acid and the oxidation inhibitor or the oxidation are supplied only to the most downstream circulation tank 2c. Each circulation tank was compared with B in the comparative example, in which the pickling accelerator containing the inhibitor was replenished via the conduit 42c and the other circulation tanks 2a, 2b were cascaded from the downstream circulation tanks 2c, 2b and controlled. The variation in the acid concentration of 2a, 2b, 2c is reduced. Further, since the variation in the acid concentration is reduced, the acid concentration in the most downstream circulation tank 2c can be reduced without lowering the pickling efficiency. In addition, by replenishing the oxidation inhibitor or the pickling accelerator containing the oxidation inhibitor together with the new acid or the recovered acid, the occurrence of surface roughness of the steel strip can be prevented.

Embodiment 4 FIG. 6 is a schematic explanatory view of a continuous horizontal pickling apparatus according to the fourth aspect of the present invention. In this embodiment, an intermediate spray 61 is provided between the side nozzle 8 and the outlet nozzle 7. The acid solution of the intermediate spray 61 was piped from the circulation tank 2 to the outlet nozzle 7 via the pump 4 and the heating device 5 via a pipe for replenishing the acid solution 3 so as to be replenished. Then, the acid solution is supplied from the intermediate spray 61 and the elapsed time from the start of the measurement and the acid concentration at the same position as in FIG. 7A, that is, near the position of the side nozzle 8 (1) and near the intermediate spray (2). Was measured. The result is shown in FIG. 7 (b). However, during the measurement, the circulation tank
The replenishment of the acid solution from the other circulation tank to 2 and the replenishment of the new acid or recovered acid and the oxidation inhibitor or the pickling accelerator containing the oxidation inhibitor were not performed.

As shown in FIG. 7 (b), by installing an intermediate spray 61 between the side nozzle 8 and the outlet nozzle 7,
A decrease in the acid concentration of the acid solution in the pickling tank 1 can be prevented. Accordingly, the acid concentration can be made uniform over the entire length in the pickling tank 1.

Embodiment 5 FIG. 8 is a schematic explanatory view of a continuous horizontal pickling apparatus according to the fifth aspect of the present invention. As shown in FIG. 8, a heat exchanger is adopted as a heating device for raising the temperature of the acid solution stored in the circulation tank 2, and a pump is supplied from the most upstream circulation tank 2 into which the steel strip 10 at normal temperature enters first. After the acid solution 3 was introduced into the heat exchanger 82 by 81 and the temperature was raised to 90 ° C., it was configured to be able to return to the circulation tank 2 again.

Then, the acid solution 3 is introduced into the heat exchanger 82 by the pump 81 from the uppermost circulation tank 2 into which the steel strip 10 at normal temperature first enters, and heat-exchanges with steam to raise the temperature to 90 ° C. While returning to the circulation tank 2 again, the temperature of the acid solution at a predetermined position in the pickling tank 1 was measured. The results are shown in Table 2. The acid solution temperature was measured at the same position as in Table 1 above. That is, the most upstream pickling tank 2 into which the steel strip 10 at normal temperature enters first.
The acid solution temperature at the center and outlet of the
And the acid solution temperatures of the uppermost circulation tank and the downstream circulation tank are measured and compared. Also, the cross-sectional area of the steel strip is 2300 mm
² compares the acid solution temperatures when a narrow material of No. ^{2 and} a wide material of 7200 mm ² in cross section move in the pickling tank.

[0075]

[Table 2]

As shown in Table 2, the acid temperature of the most upstream pickling tank 1 and the circulation tank 2 into which the steel strip 10 at normal temperature first enters is:
As with other downstream pickling tanks and circulation tanks, a steel strip descaling efficiency of around 90 ° C is optimal. Therefore, it is possible to optimize the temperature of the acid solution in the most upstream pickling tank and the circulation tank in which the steel strip at normal temperature first enters.

Example 6 As a test material, a test material A which is a low-acid pickling material having a low carbon content and a high winding temperature in hot rolling, a high carbon content, and a winding temperature in hot rolling Test material that is a high acid resistant cleaning material
B, a test material C which is a general carbon steel was prepared. Each test material A to C
Has a plate thickness of 1.0 to 7.0 mm, a plate width of 600 to 1800 mm, a winding temperature in hot rolling of 500 to 700 ° C, and a scale thickness of the test material surface of 5 to 2
0 μm. For each of the test materials A to C, using the horizontal pickling apparatus of the present invention including all of the above Examples 1 to 5 and a conventional horizontal pickling apparatus, descaling is performed, and scale remains on the test material surface. The moving speed of the steel strip which can be pickled without any heat was investigated. The results are shown in FIG. 9 as an example and a conventional example.
The upper limit of the moving speed of the steel strip is 300 m / m
in.

[0078] As shown in Fig. 9, the upper limit of the traveling speed of the steel strip was 300 m / min for the test material C, whether the horizontal pickling apparatus of the present invention was used or the conventional horizontal pickling apparatus. are doing. But,
Test materials A and B, which are difficult to pickle, could not be sufficiently descaled using a conventional horizontal pickling apparatus unless the traveling speed of the steel strip was reduced to 200 m / min and 150 m / min. In the example using the horizontal pickling apparatus of the present invention, the upper limit of the moving speed of the steel strip was 300 m / min for both test materials A and B. That is, when the horizontal pickling apparatus of the present invention was used, all of the test materials A to C were able to satisfy the upper limit of the moving speed of the entire steel strip without the surface scale of the steel strip remaining. In addition, a high-quality pickling material could be stably secured without causing surface roughness of the steel strip.

[0079]

According to the horizontal pickling apparatus of claim 1 of the present invention, the distance between the inlet nozzle and the outlet nozzle of the pickling tank and the surface of the steel strip is 100 mm or more, and the injection from the inlet nozzle and the outlet nozzle is performed. The angle between the acid solution to be formed and the surface of the steel strip (θ1) is 5 ° or more, the acid solution flow rate (Q1) of the inlet nozzle and the outlet nozzle is 150 m ³ / hr or less, and satisfies the above formula (1). So that the inlet nozzle and the outlet nozzle are installed. This suppresses the replenishment of the acid solution from the inlet nozzle and the outlet nozzle and the outflow of the acid solution out of the tank due to the movement of the steel strip in the tank, while maintaining the acid solution in the tank and improving the jet stirring effect. The pickling treatment can be performed with high efficiency and high efficiency.

[0080] In the horizontal pickling apparatus according to claim 2 of the present invention, the distance between the side nozzle for injecting the acid solution from the side of the pickling tank and the surface of the steel strip is 100 mm or more, and the acid jet from the side nozzle is provided. The angle between the liquid and the surface of the steel strip (θ2) is 5 ° or more, and the acid liquid flow rate (Q2) of the side nozzle is 150 m ³ / hr or less, and the side nozzle satisfies the formula (2). Is installed. As a result, along with the replenishment of the acid solution, the acid solution injected from the side nozzle blocks the flow of the acid solution generated following the movement of the steel strip, and the laminar flow state changes to a turbulent state, destroying the boundary layer. The pickling efficiency can be increased.

[0081] In the horizontal pickling apparatus according to claim 3 of the present invention, a fresh acid or a recovered acid and an oxidation inhibitor or an acid inhibitor containing an oxidation inhibitor are added to a circulation tank other than the most downstream in a circulation tank other than the most downstream. Install the piping system to be charged and control the acid concentration in each circulation tank to perform pickling. As a result, similarly to the uppermost and lowermost circulation tanks, the variation in the acid concentration in the other circulation tanks can be reduced, and the pickling efficiency can be increased. In addition, due to the efficiency of pickling, the scale removal time is shortened and the time for exposing the base steel to the steel strip surface is shortened, but the pickling accelerator containing an oxidation inhibitor or an oxidation inhibitor together with new or recovered acid is used. By adding the steel, it is possible to prevent the ground iron from dissolving after removing the scale of the extra steel strip, and to prevent the surface roughness of the steel strip due to peracid washing.

[0082] In the horizontal pickling apparatus according to claim 4 of the present invention, an intermediate spray is provided between the inlet nozzle and the outlet nozzle of each pickling tank and the side nozzle. This makes it possible to obtain an acid solution having a substantially constant acid concentration over the entire area of the pickling tank, and it is possible to increase the pickling efficiency.

[0083] The horizontal pickling apparatus according to claim 5 of the present invention is provided with an acid solution heating facility for heating the acid solution supplied to the pickling tank and a heating device for the acid solution stored in the circulation tank. This makes it possible to raise the temperature of the acid solution before being supplied to the pickling tank by an amount corresponding to the amount of heat removed by the steel strip in the pickling tank. Can be increased.

As described above, the horizontal pickling apparatus of the present invention can reduce the integral value of the thickness of the boundary layer in the pickling tank, secure the optimum acid concentration or the optimum acid solution temperature, and increase the pickling efficiency. be able to. In addition, the surface roughness of the steel strip can be prevented, and stable steel strip surface quality can be ensured.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view of a horizontal pickling apparatus according to claim 1 of the present invention.

FIG. 2 is a schematic explanatory view of the vicinity of an outlet nozzle and an inlet nozzle of a pickling tank of the horizontal pickling apparatus according to claim 1 of the present invention.

FIG. 3 is a schematic explanatory view around a side nozzle of a pickling tank of a horizontal pickling apparatus according to claim 2 of the present invention.

FIG. 4 is an overall explanatory view of a horizontal pickling apparatus according to claim 3 of the present invention.

FIG. 5 is a graph showing variations in the acid concentration of each circulation tank when a horizontal pickling apparatus according to claim 3 of the present invention and a conventional horizontal pickling apparatus are used.

FIG. 6 is a schematic explanatory view of a horizontal pickling apparatus according to claim 4 of the present invention.

[Figure 7] Near the side nozzle position (1) and near the intermediate spray (2)
In the graph showing the relationship between the elapsed time and the acid concentration, (a) is a case using a conventional horizontal pickling apparatus, (b) is a diagram using a horizontal pickling apparatus according to claim 4 of the present invention It is.

FIG. 8 is a schematic explanatory view of a horizontal pickling apparatus according to claim 5 of the present invention.

FIG. 9 is a graph showing a line speed required for descaling for each test material when the horizontal pickling apparatus of the present invention and a conventional horizontal pickling apparatus are used.

FIG. 10 is a graph showing a relationship between an angle between an acid solution injected from a nozzle and the surface of a steel strip, an acid solution flow rate, and a region with good pickling efficiency.

FIG. 11 schematically shows a result of a visual observation of an acid solution flow in a pickling tank of a horizontal pickling apparatus without a side nozzle, wherein FIG. 11 (a) is a plan view and FIG. It is sectional drawing.

FIG. 12 schematically shows a result of a visual observation of an acid solution flow in a pickling tank of a horizontal pickling apparatus having a side nozzle but having a poor installation angle, and FIG. 12 (a) is a plan view and FIG. b) is a sectional view of the side nozzle.

FIG. 13 is a view schematically showing a result of visual observation of an acid solution flow in a pickling tank of a horizontal pickling apparatus having a side nozzle and an installation angle satisfying a condition of the present invention, and FIG. The plan view and the figure (b) are sectional views of the side nozzle portion.

FIG. 14 is a schematic explanatory view of a conventional dip type pickling apparatus.

FIG. 15 is a schematic explanatory view of a conventional horizontal pickling apparatus.

16 is a view as viewed in the direction of arrows HH in FIG. 15.

FIG. 17 shows the relationship between the boundary layer thickness in the tank longitudinal direction of the jet stirring type pickling apparatus, and FIG. 17 (a) is an enlarged sectional side view of the pickling layer of the jet stirring type pickling apparatus; The figure is a graph showing the relationship between the length in the tank longitudinal direction and the thickness of the boundary layer.

[Explanation of symbols]

 1, 141, 151 Pickling tank 2, 2a, 2b, 2c, 152 Circulation tank 3, 144 Acid solution 4, 81, 153 Pump 5, 154 Heating device 6, 155 Inlet nozzle 7, 156 Outlet nozzle 8, 157 Side nozzle 9, 42a, 42b, 42c, 158 Conduit 10, 145, 159 Steel strip 11, 160 Ringer roll 12, 161 Tank bottom brick 13, 162 Skid 41a, 41b, 41c Acid concentration meter 43 Acid supply tank 61 Middle Spray 82 Heat exchanger 142 Partition 143 Cover 146 Support roll 147 Squeeze roll 148 Rinse tank 163 Waste acid

Claims (5)

[Claims] Claims 1. An inlet nozzle and an outlet nozzle for spraying an acid solution on the inlet and outlet sides of a pickling tank on the surface of a steel strip to be transported in contact with an acid solution under tension. A side nozzle that injects the acid solution from the tank, a shallow pickling tank provided with a skid at the bottom of the tank, a circulation tank that supplies the acid solution to the pickling tank, and an acid solution from the circulation tank. In the horizontal pickling apparatus provided with a piping system for supplying the inlet nozzle, the outlet nozzle, and the side nozzle, a distance between the inlet nozzle, the outlet nozzle, and the surface of the steel strip is 100 mm or more, and the inlet nozzle and the outlet nozzle. Angle between the acid solution injected from the side nozzle and the steel strip surface (θ1)
Is at least 5 °, the acid solution flow rate (Q1) from the inlet and outlet nozzles is 150 m ³ / hr or less, and the inlet and outlet nozzles are installed so that the following formula (1) is satisfied. A horizontal pickling apparatus. (Equation 1) 2. The distance between the side nozzle that sprays the acid solution from the side and the steel strip surface is 100 mm or more, and the angle (θ2) between the acid solution sprayed from the side nozzle and the steel strip surface is 5 ° or more. The acid solution flow rate (Q2) from the side nozzle is 150 m ³ / hr or less, and the following (2)
2. The horizontal pickling apparatus according to claim 1, wherein a side nozzle is provided so as to satisfy the formula. (Equation 2) 3. A new acid or a recovered acid and an oxidation inhibitor or an acid inhibitor containing an oxidation inhibitor are charged into a lowermost circulation tank of a horizontal pickling apparatus having a plurality of pickling tanks connected in series. In a continuous horizontal pickling device that sequentially supplies the acid solution containing the antioxidant stored in the circulation tank in a cascade to the upstream circulation tank, a new horizontal circulation tank along with the lowest circulation tank is newly installed. Install a piping system for supplying acid or recovered acid and oxidation inhibitor or pickling accelerator containing oxidation inhibitor, and in each circulation tank, pick up new acid or recovered acid and oxidation inhibitor or oxidation inhibitor containing oxidation inhibitor. 3. The horizontal pickling apparatus according to claim 1, wherein the pickling is performed to control the acid concentration, and pickling is performed. 4. An inlet nozzle and an outlet nozzle for injecting an acid solution to the surface of the steel strip on the inlet side and the outlet side of each pickling tank, and an acid solution is injected from the side of each pickling tank to the surface of the steel strip. An intermediate spray is installed between the side nozzle and the side nozzle.
4. The horizontal pickling apparatus according to any one of 1 to 3. 5. An acid solution heating system is provided in an acid solution supply system for supplying an acid solution to an acid washing tank, and a heating device for the acid solution stored in a circulation tank is provided. 5. The horizontal pickling apparatus according to any one of 4.