JP2000297390A - Continuous pickling method and continuous pickling apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To raise the acid concn. in pickling liquid held in pickling vessels to a prescribed value while suppressing the acid concn. in the pickling liquid from the last pickling vessel to 12% or less. SOLUTION: A predicted value of the acid consumption in the pickling liquid held in a third vessel 11c and the last vessel 11d of a continuous pickling apparatus 10 at the pickling time is calculated with a control unit 14. On the basis of the calculated prediction value, acid liquid supplying quantities into the third vessel 11c and the last vessel 11d are decided and the acid liquid is supplied from an acid liquid supplying system 12. Then, the acid concns. in the pickling liquid held in the third vessel 11c and the last vessel 11d supplied with the acid liquid are continuously measured with an acid concn. continuous measuring instruments 13c, 13d, respectively. On the basis of the continuous measured values of the acid concns., the acid liquid is supplied into the third vessel 11c and the last vessel 11d from the acid liquid supplying system 12 so that the acid concns. of the pickling liquid held in the third vessel 11c and the last vessel 11d correspond to each of the target values, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous pickling method and a continuous pickling apparatus, and more particularly to, for example, a continuous pickling method for removing scale formed on the surface of a steel strip after hot rolling. The present invention relates to a pickling method and a continuous pickling apparatus.

[0002]

2. Description of the Related Art As is well known, oxide scale is generated on the surface of a hot-rolled steel strip. This scale is generally removed by performing pickling in which the steel strip is continuously immersed in a pickling solution such as hydrochloric acid. This pickling is usually performed using a continuous pickling apparatus having about 3 to 5 pickling tanks.

FIG. 4 is an explanatory view schematically showing a continuous pickling apparatus 1 having four pickling tanks 2a to 2d. As shown in the figure, the first tank 2a, the second tank 2b, and the third tank 2c of the continuous pickling apparatus 1
And pickling is performed by continuously passing the steel strip 3 through the fourth tank (final tank) 2d. Each pickling tank 2a-2d
The pickling liquid contained in the steel strip 3 gradually decreases due to the reaction with the steel strip 3 and the removal by the steel strip 3. Therefore, in the continuous pickling apparatus 1, an acid solution is supplied from the acid solution supply device 4 to the final tank 2d, and the acid solution transport pipes 5a to 5c provided between the adjacent pickling tanks 2a to 2d are used. The pickling liquid is sequentially transported from the pickling tank on the downstream side to the pickling tank adjacent on the upstream side. And the first tank
The pickling liquid overflowing from 2a is sent to the collecting device 6 to be collected and reused.

In the continuous pickling apparatus 1, since the pickling solution is circulated between the pickling tanks 2a to 2d in this manner, the acid concentrations of the pickling solutions contained in the pickling tanks 2a to 2d are different. For example, the final tank 2d
In the first tank 2a, it is about 3%. In the second tank 2b and the third tank 2c, the concentration is intermediate between the final tank 2d and the first tank 2a.

In the continuous pickling apparatus 1, in order to determine the supply amount of the acid solution to the final tank 2d, it is necessary to measure at least the acid concentration of the pickling liquid contained in the final tank 2d. But,
With the conventional acid concentration measurement technology, the acid concentration of the pickling solution cannot be measured in a short time. For example, when the acid concentration of the pickling solution contained in the final tank 2d is measured using a known titration analyzer, it takes about 15 minutes for one sampling from the introduction of the reagent to the output of the data. For this reason, the supply of the acid solution to the final tank 2d is greatly delayed, and during this time, pickling failure occurs transiently in the steel strip.

In order to compensate for the inability to measure the acid concentration of the pickling solution in a short time, for example, Japanese Patent Application Laid-Open No.
No. 73 discloses an invention in which the supply amount of an acid solution is calculated by calculation based on the dimensions and materials of a steel strip without measuring the acid concentration of the pickling solution. Each invention has been proposed in which the supply amount of the acid solution is calculated by calculation based on the measured value of the thickness of the steel strip before and after the pickling without measuring the acid concentration of the pickling solution. According to these conventional techniques,
The acid concentration of the pickling solution contained in the pickling tank (the last tank 2d in the continuous pickling apparatus 1 in FIG. 4) to which the acid solution is supplied can be controlled to a target value.

[0007]

However, these conventional techniques cannot increase the acid concentration of the pickling liquid contained in the pickling tank other than the pickling tank to which the acid liquid is supplied. It is not possible to improve the productivity of the pickling step including the continuous pickling apparatus 1, that is, to improve the pickling speed.

That is, in order to increase the pickling speed of the continuous pickling apparatus 1, the supply amount of the acid solution to the final tank 2d to which the acid solution is supplied is increased, and the acid solution is accommodated in each of the pickling tanks 2a to 2d. It is necessary to increase the acid concentration of the pickling solution to be used. However, when the acid concentration of the pickling liquid in the final tank 2d exceeds about 12%, the vapor pressure of the hydrochloric acid, which is the pickling liquid, increases, and the consumption of hydrochloric acid by evaporation in the final tank 2d increases. The cost required for this increases significantly. For this reason, the acid concentration of the pickling liquid contained in each of the pickling tanks 2a to 2c other than the final tank 2d cannot be increased, and the pickling speed cannot be improved.

An object of the present invention is to increase the acid concentration of the pickling liquid contained in each pickling tank while minimizing the evaporation of the pickling liquid from the pickling tank to which the acid liquid is supplied. And to provide a continuous pickling method and a continuous pickling apparatus that can improve the productivity of pickling. Another object of the present invention is to provide such a continuous pickling method and a continuous pickling apparatus without modifying existing continuous pickling equipment as much as possible.

[0010]

According to the present invention, there is provided an acid pickling solution for pickling a pickling solution contained in at least two pickling tanks among a plurality of pickling tanks constituting a continuous pickling apparatus. Is calculated based on the pickling conditions at the time of pickling, and based on the calculated predicted value, the supply amount of the acid solution to each of the two or more pickling tanks is determined, and the acid solution is supplied. The acid concentration of the pickling liquid contained in each of the two or more pickling tanks supplied is continuously measured, and based on the continuously measured values of the measured acid concentration,
A continuous pickling method characterized by controlling the supply amount of an acid solution to two or more pickling tanks so that the acid concentration of the pickling liquid stored in each of the two or more pickling tanks matches a target value. It is.

In the continuous pickling method according to the present invention,
(i) the two or more pickling tanks include at least a final pickling tank; (ii) a continuous pickling apparatus, wherein the pickling liquid contained in the downstream pickling tank is adjacent to the pickling tank on the upstream side. A continuous pickling apparatus of a type that sequentially overflows to the pickling tank, or a continuous pickling apparatus of a type that sequentially transports the pickling liquid stored in the pickling tank on the downstream side to the pickling tank adjacent to the upstream side, (iii) ) A continuous measurement value of the acid concentration is measured using at least continuous output values from a densitometer disposed in a pickling liquid circulation channel provided in each of two or more pickling tanks. Is exemplified. In particular, in the case of this paragraph (iii), the continuous measurement value of the acid concentration is the continuous output value from each of the thermometer and the conductivity meter arranged in the pickling tank or the pickling liquid circulation channel. Is further exemplified.

Further, from another viewpoint, the present invention provides an acid pickling tank comprising two or more pickling tanks constituting a continuous pickling apparatus and supplying an acid solution to the two or more pickling tanks. Acid supply system, an acid concentration continuous measuring device for continuously measuring the acid concentration of each of the pickling liquids contained in the two or more pickling tanks, and the acid contained in the two or more pickling tanks, respectively. The predicted value of the acid consumption during the pickling of the washing solution is calculated from the pickling conditions during the pickling, and the acid solution supply amount is determined based on the calculated predicted value to supply the acid solution to the acid solution supply system. A signal is output and, based on the continuous measurement of the acid concentration output from the acid concentration continuous measuring device after the acid solution is supplied from the acid solution supply system to the two or more pickling tanks, two or more acids are measured. An acid solution supply signal is output to the acid solution supply system so that the acid concentration of the pickling solution stored in each of the washing tanks becomes the target value. A continuous pickling apparatus, characterized in that it comprises a combination of a control device for.

In the continuous pickling apparatus according to the present invention, (i)
v) the two or more pickling tanks include at least a final pickling tank;
(v) A continuous pickling apparatus in which a pickling solution contained in a downstream pickling tank overflows sequentially to an adjacent pickling tank on the upstream side, or a pickling tank on the downstream side. It is a continuous pickling apparatus of a type that sequentially transports the contained pickling liquid to an adjacent pickling tank on the upstream side, and (vi) a continuous acid concentration measuring apparatus,
A main body connected to the pickling tank and provided in a part of the flow path of the pickling liquid taken out of the pickling tank; a density meter for measuring the density of the pickling liquid flowing inside the main body; Or a thermometer that measures the temperature of the pickling solution in the pickling tank, a conductivity meter that measures the conductivity of the pickling solution in the flow path or the pickling tank, and the measurement results of the density, thermometer, and conductivity meter, respectively. And a calculation device for calculating the acid concentration of the pickling solution flowing through a part of the flow path based on the above.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a continuous pickling method and a continuous pickling apparatus according to the present invention will be described below in detail with reference to the accompanying drawings. In the following description of the embodiment, a case where the pickling liquid is hydrochloric acid and a continuous acid concentration measuring device 13 shown in FIG.

FIG. 1 is an explanatory view schematically showing a configuration of a continuous pickling apparatus 10 of the present embodiment. As shown in FIG. 1, the continuous pickling apparatus 10 includes pickling tanks 11a to 11d and an acid solution supply system.
12, a continuous acid concentration measuring device 13c, 13d, and a control device 14. Hereinafter, these components will be sequentially described.

[Pickling tanks 11a to 11d] This continuous pickling apparatus 10
Has four pickling tanks 11a to 11d. The pickling tank 11a is a first tank, the pickling tank 11b is a second tank, the pickling tank 11c is a third tank, and the pickling tank 11d is a final tank.

The steel strip 15 to be pickled is supplied to a first tank 11a and a second tank 11a.
11b, the third tank 11c and the final tank 11d in this order.
It is immersed in the pickling liquid stored in ~ 11d. Then, the steel strip 15 that has left the final tank 11d is sent to the next step.

In the continuous pickling apparatus 10, the pickling liquid contained in the downstream pickling tank sequentially overflows to the pickling tank adjacent on the upstream side. That is, the pickling liquid contained in the final tank 11d overflows to the third tank 11c,
The pickling liquid contained in 11c overflows to the second tank 11b, and the pickling liquid contained in the second tank 11b overflows to the first tank 11a. Then, the pickling solution overflowing from the first tank 11a is sent to a collecting device (not shown) to be collected and reused. The pickling tanks 11a to 11d of the present embodiment include:
The configuration is as described above.

[Acid Solution Supply System 12] The continuous pickling apparatus 10 of the present embodiment has an acid solution supply system 12. The acid solution supply system 12 of the present embodiment includes a third tank acid solution supply device 12c that supplies an acid solution to the third tank 11c, and a final tank acid solution supply device 12d that supplies an acid solution to the final tank 11d. Is done. Third tank acid solution supply device 12c
In addition, the final tank acid solution supply device 12d is connected to an acid solution supply source (not shown) via an electromagnetic diaphragm valve 16. The diaphragm valves 16 provided in the third tank acid solution supply device 12c and the final tank acid solution supply device 12d, respectively.
Are connected to the control device 14 described below,
The opening degree of the valve is controlled by the acid solution supply signal output from the control device 14. Thereby, the third tank acid solution supply device 12c
And the supply amount of the acid solution from the final tank acid solution supply device 12d to the final tank 11d is individually controlled.

In this embodiment, the acid solution is supplied to the third tank 11c and the final tank 11d.
b and also the first tank 11a, the third tank acid solution supply device 12c
Alternatively, an acid solution supply device similar to the final tank acid solution supply device 12d may be provided to supply the acid solution individually. The acid solution supply system 12 of the present embodiment is configured as described above.

[Continuous Acid Concentration Measurement Apparatus 13c, 13d] In this embodiment, the third tank 11c is provided with a continuous acid concentration measurement apparatus 13c, and the final tank 11d is provided with a continuous acid concentration measurement apparatus.
13d is provided. Since the acid concentration continuous measurement device 13c and the acid concentration continuous measurement device 13d are the same, the following description will be made using the acid concentration continuous measurement device 13d as an example.

FIG. 2 shows a continuous acid concentration measuring apparatus according to this embodiment.
It is explanatory drawing which shows the internal structure of 13d. The broken arrows in FIG. 2 indicate the flow of the pickling solution. As shown in FIG. 2, the acid concentration continuous measuring device 13d is a cylinder having a part of a circulation channel 18d for continuously flowing the pickling solution pumped from the final tank 11d in one direction by a pump 17d. Acid concentration continuous measurement device main body
19d, a density meter 20d, a thermometer 21d, and a conductivity meter 22d for continuously measuring the pickling liquid flowing through a part of the circulation channel 18d.

The main body 19d of the apparatus for continuously measuring acid concentration in this embodiment has a cylindrical shape and has a structure in which a pickling liquid as a sample can be continuously flowed from the final tank 11d and returned to the final tank 11d. It is sufficient if it is provided, and it is not limited to a specific structure.

The material of the acid concentration continuous measuring device main body 19d may be any material having an acid resistance such that it is not eroded by the pickling solution. In this embodiment, the material is made of polypropylene. Also,
A part of the circulation flow path 18d formed inside the acid concentration continuous measurement device main body 19d is formed in a straight shape with a reduced flow velocity portion such as an elbow as much as possible. As a result, the occurrence of clogging due to a decrease in the flow of the pickling liquid inside the acid concentration continuous measuring device main body 19d is suppressed as much as possible.

Further, the flow rate of the pickling liquid flowing through a part of the circulation channel 18d is controlled by a density meter 20d, a thermometer 21d and a conductivity meter 22d.
d In order to maintain the accuracy of each measurement, it is desirable that it be 2 m / sec or less. Inside the acid concentration continuous measuring device main body 19d of the acid concentration continuous measuring device 13d of the present embodiment, a lower circulation channel 18d is formed at substantially the same height as the discharge pipe 23d. As a result, the pickling solution pumped by the pump 17d temporarily stays in the vicinity of the bottom in the acid concentration continuous measuring device main body 19d as shown by the broken arrow in the figure, and then flows to the discharge pipe 23d. It is led. For this reason, the acid concentration continuous measurement device 19 of the present embodiment
In d, the flow rate of the pickling liquid flowing through the circulation passage 18d is
From the viewpoint of the measurement accuracy of the thermometer 20d, the thermometer 21d and the conductivity meter 22d, it is possible to easily set and manage the flow velocity to 2 m / sec or less, which is a desirable flow rate, thereby improving the measurement accuracy. In the present embodiment, the dimensions of each part of the acid concentration continuous measuring device main body 19d are set such that the flow rate of the pickling solution is 1 m / sec.

In this embodiment, the density meter 20d includes:
A known differential pressure sensor type densitometer having two detectors 20d-1 and 20d-2 was used. Two detectors 20d-1 and 20d-2
In order to ensure the desired density measurement accuracy,
At least 500m distance d ₁ of a portion of the formation direction of the d
The main body 19d is installed at a substantially central body in the longitudinal direction of the main body 19d of the continuous acid concentration measuring device so as to be m.

Further, in the installation of the detection unit 20d-1, 20d-2 is a projection amount d ₂ of diverter with respect to the direction (horizontal direction in FIG. 2) perpendicular to the flow direction of the pickling solution, and set as small as possible It is. Thereby, the stagnation of the pickling liquid in the branch part is suppressed, and the clogging of the pickling liquid is reliably prevented.

In this embodiment, a known platinum resistor type thermometer is used as the thermometer 21d. A known electromagnetic induction type conductivity meter was also used as the conductivity meter 22d. Both the thermometer 21d and the conductivity meter 22d are installed at the bottom of the acid concentration continuous measuring device main body 19d so that the measurement can be performed at a part of the outlet side of the circulation channel 18d.

In the present embodiment, both the thermometer 21d and the conductivity meter 22d are provided with the acid concentration continuous measuring device main body 19d.
d. This is because the measurement error can be reduced as much as possible by arranging both the thermometer 21d and the conductivity meter 22d near the density meter 20d. However, thermometer 21d,
The conductivity meter 22d is not necessarily the acid concentration continuous measurement device main body 19d.
You do not need to place them. Thermometer 21d, conductivity meter 22d,
The temperature and conductivity of the circulating pickling liquid should be measured by installing the inside of the final tank 11d or in a pipe or the like constituting the circulation flow path 18d between the final tank 11d and the acid concentration continuous measuring device main body 19d. It may be. In this case, the values of the temperature and conductivity near the installation portion of the density meter 20d and the thermometer 21d and the conductivity meter 22d
Deviations from the measurement data at the installation portion of the thermometer 21d and the conductivity data at the installation portion of the conductivity meter 22d may be corrected using these deviations. Thereby, the measurement error can be reduced as much as possible without disposing the thermometer 21d and the conductivity meter 22d near the density meter 20d.

In this embodiment, the acid concentration continuous measuring device 13d is installed near the outer wall surface of the final tank 11d. The acid concentration continuous measuring device 13d allows the pickling liquid contained in the final tank 11d to flow in one direction by a pump 17d installed near the final tank 11d. Thereby, the acid concentration continuous measuring device 13d
Can continuously measure the density, temperature and conductivity of the pickling liquid.

As described above, as the density meter 20d, the thermometer 21d and the conductivity meter 22d used in the acid concentration continuous measuring device 13d of the present embodiment, all known industrial instruments having a high track record of use are used. For this reason, the acid concentration continuous measuring device 13d of the present embodiment can accurately and accurately determine the density, temperature, and conductivity of the pickling liquid.

Further, the acid concentration continuous measuring device 13 of the present embodiment
In the vicinity of d, based on the density continuously measured by the density meter 20d, the temperature continuously measured by the thermometer 21d, and the conductivity continuously measured by the conductivity meter 22d, An arithmetic unit (not shown) that calculates the acid concentration of the pickling solution
Is installed. The arithmetic unit continuously calculates the acid concentration of the pickling solution. The calculation result by this calculation device is input to the control device 14 described later.

It should be noted that the acid concentration continuous measuring device 13 of the present embodiment
"Continuous measurement" by d means, for example, measurement at a measurement pitch that is extremely short as compared to the measurement pitch (about 15 minutes) when using a known titration analyzer, for example,
It refers to acid concentration measurement where the measurement pitch is 1 minute or less, preferably 10 seconds or less.

The acid concentration continuous measuring device 13 of the present embodiment
In d, the acid concentration continuous measurement device main body 19d is a cylindrical single tube type. Therefore, the following effects (i) to (vii) can be obtained.

(I) The shape of the circulation channel 18d is made as straight as possible, and the distance d ₂ is set as small as possible. This prevents the pickling solution from staying in the circulation flow path 18d, particularly in the vicinity of each of the density meter 20d, the thermometer 21d, and the conductivity meter 22d, and allows the pickling solution to flow continuously.

(Ii) The pickling liquid flows continuously in the circulation channel 18d. For this reason, segregation of the pickling liquid in the circulation channel 18d is prevented, and a plurality of types of pickling liquid separately collected can be accurately measured under the same conditions.

(Iii) Since the pickling solution is constantly flowed by the pump 17d, both the maintainability and the internal cleanability of the acid concentration continuous measuring device main body 19d are significantly improved, and continuous measurement can be performed while eliminating clogging of the pickling solution. It can be carried out.

(Iv) Since the density, temperature and conductivity of the pickling solution are continuously measured, the acid concentration of the pickling solution can be continuously measured. With this, this acid concentration continuous measurement device
By combining 13d with, for example, feedback control on the acid concentration of the final pickling tank of a continuous pickling facility, or feedback control and feedforward control,
It is also possible to automatically control the acid concentration in the final pickling tank continuously and with high accuracy.

(V) The acid concentration continuous measuring device 13d has an extremely simple external shape as shown in FIGS.
For this reason, there is a high degree of freedom in installation in, for example, a continuous pickling facility.

(Vi) The inside of the continuous acid concentration measuring device 13d has a simple internal structure as shown in FIG. For this reason,
The flow rate of the pickling liquid flowing through the circulation channel 18d can be easily set and controlled to be 2 m / sec or less, which is a desirable flow rate from the viewpoint of the measurement accuracy of the density meter 20d, the thermometer 21d, and the conductivity meter 22d. . Therefore, the acid concentration continuous measurement device 13d
Is easy to maintain the measurement accuracy.

(Vii) Since the acid concentration continuous measuring device 13d has a simple structure, it can be easily installed near the pickling tank. For this reason, the length of the pipe constituting the circulation flow path 18d for diverting the pickling solution from the pickling tank can be shortened as much as possible. As a result, the time loss between the time when the pickling solution leaves the pickling tank and the time when it reaches the acid concentration continuous measuring device 13d and is measured can be reduced as much as possible. For this reason, the acid concentration continuous measurement device 13d can suppress a decrease in control accuracy.

In this embodiment, the continuous acid concentration measuring devices 13c and 13d are provided in the third tank 11c and the final tank 11d, respectively. However, as shown in FIG. A measuring device 13b is provided, and if necessary, a first tank
A continuous acid concentration measuring device 13a may be provided in 11a, and these output values may also be input to the control device 14. The continuous acid concentration measuring devices 13c and 13d of the present embodiment are configured as described above.

[Control unit 14] Continuous pickling apparatus of this embodiment
10 has a control device 14. This control device 14 is a third tank
Acid consumption during pickling of the pickling solution contained in 11c,
The acid consumption of the pickling solution contained in the final tank 11d during pickling is calculated using an approximate expression. Third tank 11
The prediction calculation of the acid consumption in each of c and the final tank 11d is based on the material and dimensions of the steel strip 15, the passing speed, the acid solution composition, the acid solution temperature, and the It is performed based on pickling conditions at the time of pickling, such as dimensions, but is not limited to a specific means. The prediction calculation may be performed by a known means.

For example, when the amount of reduction per unit area (hereinafter, referred to as “pickling weight loss value”) is approximated by a linear equation with respect to time, the pickling time and the pickling weight loss value are calculated. The relationship is proportional. FIG. 3 is a graph showing an example of this relationship.

As shown in the graph of FIG. 3, the relationship between the pickling time and the pickling weight loss value is a linear relationship starting from the origin O. That is, the pickling weight loss value m ₁ at the time t ₁ passing through the first tank 11 a, the pickling weight loss value m ₂ at the time t ₂ passing through the second tank 11 b, and the acid value at the time t ₃ passing through the third tank 11 c. Both the washing loss value m ₃ and the pickling loss value m _{4 at} time t ₄ when passing through the final tank 11 d are on the same straight line, and after the time t ₄ at which the pickling is completed, the pickling weight loss value Becomes constant. The slope of this straight line indicates the pickling speed, and is defined by the material of the steel strip 15 to be pickled and the pickling conditions (temperature, composition, etc. of the pickling solution).

Therefore, the amount of acid consumed in each of the pickling tanks 11a to 11d depends on the time required to pass through each of the pickling tanks 11a to 11d, the slope of the straight line in the graph of FIG.
It is obtained as a value multiplied by the dimension (width) of
In this way, the consumption of the pickling solution in each of the pickling tanks 11a to 11d can be calculated. Note that, as in the present embodiment, the relationship between the pickling time and the pickling weight loss value is not approximated by a straight line, but as shown by a dashed line in FIG. 3, an S-shaped curve close to the actual pickling curve is used. By approximation, the acid consumption in each of the pickling tanks 11a to 11d can be calculated with higher accuracy.

Further, the controller 14 controls the third tank 11c and the final tank 11d based on the predicted values of the acid consumption in the third tank 11c and the final tank 11d calculated in this way.
The supply amount of the acid solution to each is determined. And the control device
The unit 14 outputs an acid solution supply signal to the diaphragm valve 16 of the acid solution supply system 12 to supply a required amount of the acid solution to each of the third tank 11c and the final tank 11d.

Further, the control device 14 supplies the acid solution from the third tank acid solution supply device 12c to the third tank 11c and supplies the acid solution from the final tank acid solution supply device 12d to the final tank 11d. An acid solution supply signal is output again to the acid solution supply system 12 based on the continuous measurement of the acid concentration output from the concentration measuring devices 13c and 13d, and the acid solution is stored in the third tank 11c and the final tank 11d, respectively. Fine adjustment is made so that the acid concentration of the pickled solution matches the target value.

The control device 14 of this embodiment is configured as described above. Next, four pickling tanks 11a to 11d, an acid solution supply system 12, an acid concentration continuous measuring devices 13c and 13d, and a control device 1
4 and the continuous pickling apparatus 10 of the present embodiment,
The situation of pickling is described with reference to FIG.

[Estimation Calculation of Acid Consumption] Pickling is performed on the steel strip 15 by the continuous pickling apparatus 10 shown in FIG. Here, the controller 14 calculates the predicted value of the acid consumption of the pickling liquid stored in the third tank 11c and the final tank 11d based on the aforementioned pickling conditions input from the pickling line controller 24. Is calculated.

Here, regardless of the type of prediction calculation, the calculated value always has an error with respect to the actual acid consumption. Therefore, in the present embodiment, as will be described later, the error is reduced as much as possible by controlling the supply amount of the acid solution using a continuous measurement value of the acid concentration.

[Supply of Acid Solution Based on Calculated Value] Next, the controller 14 calculates the acid consumption of the pickling solution contained in the third tank 11c and the final tank 11d, respectively, as predicted in this manner. The supply amount of the acid solution to each of the third tank 11c and the final tank 11d is determined.

Then, the controller 14 outputs an acid solution supply signal to the diaphragm valves 16 and 16 of the third tank acid solution supply system 12c and the final tank acid solution supply system 12d, respectively. Each of them is supplied with the determined supply amount of the acid solution.

[Continuous Measurement of Acid Concentration] After the determined supply amount of the acid solution is supplied to each of the third tank 11c and the final tank 11d, the third tank 11c is continuously measured by the acid concentration continuous measuring apparatus 13c. The acid concentration of the pickling liquid stored in the final tank 11d is continuously measured by the acid concentration continuous measuring device 13d while the acid concentration of the pickling liquid stored in the pickling liquid 11c is continuously measured. These continuous measurements are sent to the controller 14.

[Supply of Acid Solution Based on Continuous Measurement Results] In the control device 14, these continuous measurement values and the target value of the acid concentration of the pickling solution stored in the third tank 11c and the final tank 11d, respectively. Is determined. Then, the control device 14 controls the diaphragm valves 16 of the third tank acid solution supply system 12c and the final tank acid solution supply system 12d so that this deviation becomes zero.
An acid solution supply signal is output to 16 and the third tank 11c and the final tank
11d The supply amount of the acid solution for each is controlled.

Thus, the third tank 11c and the final tank 11d
The error in the prediction calculation result of the supply amount of the acid solution to each is corrected, and the acid concentration of the pickling solution contained in the second tank 11b as well as the third tank 11c and the final tank 11d is quickly adjusted to the target value. And it can be approached accurately.

In the present embodiment, the acid solution is supplied not only to the final tank 11d but also to the third tank 11c, as described above, because the pickling liquid contained in the third tank 11c and the second tank 11b is supplied. This is for increasing the acid concentration to approach the target value. Therefore, in this embodiment in which the fourth tank is the final tank 11d, the final tank
The acid solution was supplied to the tank 11d and the third tank 11c.
In the case of a continuous pickling apparatus in which the tank is the final tank, it is desirable to supply an acid solution to each of the final tank and the third tank.

In this embodiment, the supply of the acid solution based on the result of the continuous measurement is performed not only in the final tank 11d but also in the third tank 11c.
The acid concentration of the pickling liquid contained in the third tank 11c can be increased to approach the target value without increasing to more than 12%. For this reason, the acid concentration of the pickling liquid contained in the third tank 11c can be increased to approach the target value while preventing the pickling liquid from evaporating from the final tank 11d. For this reason, each pickling tank
Pickling of the steel strip 15 can be performed by fully exhibiting each of the pickling abilities of 11a to 11d. Therefore,
According to the present embodiment, the overall productivity of the continuous pickling apparatus 10 can be improved.

In this embodiment, the continuous acid concentration measuring devices 13c and 13d are provided in the vicinity of the third tank 11c and the final tank 11d of the existing continuous pickling device.
The output signals from c and 13d are sent to the controller 14,
The present invention can be implemented by only partially changing the software of the control device 14. For this reason, the existing continuous pickling equipment can be implemented as little as possible. As described above, according to the present embodiment, it is possible to reduce both the defect rate and improve the productivity without significantly improving the conventional production equipment.

[0060]

EXAMPLES The present invention will be described more specifically with reference to examples. Using the continuous pickling apparatus 1 shown in FIG. 1 (the capacity of each of the pickling tanks 13a to 13d: 50 m ³ , the temperature of the pickling liquid: 90 ° C.), the continuous pickling method according to the present invention and the continuous pickling Using the washing method, the steel strip 15 was pickled for one month. In the pickling using this type of continuous pickling apparatus, usually, almost all various changes in the operating conditions occur during one month of the operating period in the present embodiment, so that the usefulness of the present invention is evaluated. That's enough time to do it.

In the example of the present invention, the controller 14 uses the material of the steel strip 15 and the pickling conditions (the temperature and the acid concentration of the pickling solution) based on a first-order approximation formula previously determined for each steel type. 3 tanks
The consumption of the pickling liquid contained in each of the final tank 11c and the final tank 11d is estimated and calculated, and based on the result, the third tank 11c and the final tank 11d are each supplied with an acid. On the basis of the continuous measurement values from 13c and 13d, the third tank acid solution supply system is set so that the acid concentration of the pickling liquid contained in each of the third tank 11c and the final tank 11d is 12 ± 0.5%. 12c and final tank acid solution supply system 12d
Each of the diaphragm valves 16, 16 was on / off controlled.

On the other hand, in the comparative example, the acid was supplied only to the final tank 11d, and the acid solution overflowed by the supply was supplied to the third tank 11c.
, And sequentially transported to the second tank 11b, and the waste acid is removed from the first tank 11c, and the acid concentration of the pickling liquid contained in the final tank 11d is reduced.
The on / off control of the diaphragm valve 16 of the final tank acid solution supply system 12d was controlled to 12 ± 0.5%.

In both the present invention example and the comparative example, pickling was performed by increasing the sheet passing speed to such an extent that no descaling failure was generated by the judgment of the operator. And the second tank 11b
-The range of change in the acid concentration of the pickling solution contained in each of the final tanks 11d, the rate of descaling failure occurrence, and the productivity were measured. The results are summarized in Table 1.

[0064]

[Table 1]

As is clear from Table 1, according to the present invention, the acid concentration of the pickling liquid contained in each of the pickling tanks 11a to 11d was increased and stabilized within a range not exceeding the target value. Thereby, the descaling defect occurrence rate was significantly reduced, and the productivity was also significantly improved.

(Modification) In the description of the embodiment and the examples, a continuous pickling apparatus having four pickling tanks was used. However, the present invention is not limited to this form, and is similarly applied to a continuous pickling apparatus having a plurality of pickling tanks.

In the description of the embodiments and examples,
The case where the acid consumption of the pickling liquid stored in the third tank and the final tank is predicted and an acid liquid is supplied to these pickling tanks is taken as an example. However, the present invention is not limited to this mode.
The acid consumption of the pickling liquid contained in the pickling tanks other than the tank and the last tank may also be predicted, and the pickling tank may be supplied with the acid solution. Thereby, the acid concentration of the pickling liquid contained in each pickling tank can be controlled with higher accuracy.

In the description of the embodiments and examples,
The case where the acid concentration continuous measurement device shown in FIG. 2 was used was taken as an example. However, this is merely an example of the acid concentration continuous measurement device, and the present invention is not limited to the acid concentration continuous measurement device shown in FIG. The present invention is not limited to the acid concentration continuous measuring device shown in FIG. 2, but may be any acid concentration continuous measuring device capable of continuously measuring the acid concentration of the pickling solution contained in the pickling tank. Can be applied.

In the description of the embodiments and examples,
A continuous pickling apparatus in which an acid solution was supplied to at least the final tank was used. However, the present invention is not limited to this mode, and is similarly applied to a continuous pickling apparatus in which an acid solution is not supplied to the final tank.

In the description of the embodiments and examples,
A continuous pickling apparatus of a type in which the pickling solution contained in the pickling tank on the downstream side was sequentially overflowed to the pickling tank adjacent on the upstream side was used. However, the invention is not limited to this form,
The same applies to a continuous pickling apparatus having a plurality of pickling tanks. For example, as shown in FIG. 4, the present invention is similarly applied to a continuous pickling apparatus of a type in which a pickling liquid contained in a downstream pickling tank is sequentially transported to an adjacent pickling tank on the upstream side. You.

Further, in the description of the embodiments and examples, the case where the acid solution is hydrochloric acid is taken as an example. However, the present invention is not limited to this form, and is equally applicable to any acid solution such as sulfuric acid that can perform a pickling treatment on a steel plate.

[0072]

As described above in detail, according to the present invention, the acid concentration of the pickling liquid contained in each pickling tank is reduced while the evaporation amount of the pickling liquid from each pickling tank is suppressed as much as possible. , Both of which can be raised to approach the target value,
It has become possible to provide a continuous pickling method and a continuous pickling apparatus capable of improving the productivity of pickling without modifying existing continuous pickling equipment as much as possible. The significance of the present invention having such an effect is extremely remarkable.

[Brief description of the drawings]

FIG. 1 is an explanatory view schematically showing a configuration of a continuous pickling apparatus according to an embodiment.

FIG. 2 is an explanatory diagram showing an internal structure of the continuous acid concentration measuring device of the embodiment.

FIG. 3 is a graph showing an example of the relationship between the pickling time and the pickling weight loss value.

FIG. 4 is an explanatory view schematically showing a conventional continuous pickling apparatus having four pickling tanks.

[Explanation of symbols]

 10 Continuous pickling equipment 11c Third tank 11d Final tank 12 Acid solution supply system 13c, 13d Acid concentration continuous measurement device 14 Controller

Claims (9)

[Claims] 1. A pickling method according to claim 1, wherein the pickling solution contained in each of two or more of the plurality of pickling tanks constituting the continuous pickling apparatus is estimated at the time of pickling. The amount of the acid solution supplied to each of the two or more pickling tanks was determined based on the calculated predicted value, the acid solution was supplied, and the acid solution was supplied. The acid concentration of the pickling liquid contained in each of the two or more pickling tanks is continuously measured, and based on the continuous measurement values of the measured acid concentrations, A continuous pickling method characterized by controlling the amount of the acid solution supplied to the two or more pickling tanks so that the acid concentrations of the stored pickling solutions all coincide with target values. 2. The continuous pickling method according to claim 1, wherein the two or more pickling tanks include at least a final pickling tank. 3. The continuous pickling apparatus according to claim 1, wherein the pickling liquid contained in the downstream pickling tank is successively overflowed to an adjacent pickling tank on the upstream side, or a downstream pickling apparatus. 3. The continuous pickling method according to claim 1, wherein the continuous pickling apparatus is a type of a continuous pickling apparatus that sequentially transports the pickling liquid contained in the washing tank to an adjacent pickling tank on the upstream side. 4. The continuous measurement value of the acid concentration is at least a continuous output value from a densitometer disposed in a pickling liquid circulation channel provided in each of the two or more pickling tanks. The continuous pickling method according to any one of claims 1 to 3, wherein the method is used and measured. 5. The continuous measurement value of the acid concentration is obtained by using a continuous output value from each of a thermometer and a conductivity meter arranged in the pickling tank or the pickling liquid circulation channel, The continuous pickling method according to claim 4, which is measured. 6. An acid pickling tank constituting at least two of a plurality of pickling tanks constituting a continuous pickling apparatus; an acid liquid supply system for supplying an acid liquid to each of the two or more pickling tanks; An acid concentration continuous measuring device for continuously measuring the acid concentration of the pickling liquid contained in each of the above pickling tanks; and at the time of pickling the pickling liquid contained in each of the two or more pickling tanks. A predicted value of the acid consumption is calculated from the pickling conditions at the time of the pickling, an acid solution supply amount is determined based on the calculated predicted value, and an acid solution supply signal is output to the acid solution supply system. In addition, based on a continuous measurement of the acid concentration output from the acid concentration continuous measuring device after the acid solution is supplied from the acid solution supply system to the two or more pickling tanks,
A control device for outputting an acid solution supply signal to the acid solution supply system is provided in such a manner that the acid concentration of each of the acid solutions contained in the above-mentioned acid tanks coincides with the target value. And continuous pickling equipment. 7. The continuous pickling apparatus according to claim 6, wherein the two or more pickling tanks include at least a final pickling tank. 8. The continuous pickling apparatus according to claim 1, wherein the pickling liquid contained in the downstream pickling tank is sequentially overflowed to the pickling tank adjacent to the upstream side, or a downstream pickling apparatus. The continuous pickling apparatus according to claim 6 or 7, wherein the continuous pickling apparatus is of a type in which the pickling liquid contained in the washing tank is sequentially transported to an adjacent pickling tank on the upstream side. 9. The acid concentration continuous measuring device, comprising: a main body connected to the pickling tank and provided in a part of a flow path of a pickling liquid taken out of the pickling tank; A density meter for measuring the density of the flowing pickling liquid; a thermometer for measuring the temperature of the pickling liquid in the flow path or the pickling tank; and a conductivity of the pickling liquid in the flow path or the pickling tank. And a calculating device for calculating an acid concentration of a pickling liquid flowing through a part of the flow path based on the measurement results of the density, the thermometer, and the conductivity meter, respectively. Claim 6
The continuous pickling apparatus according to any one of claims 1 to 8.