Concentration detection method and concentration detection device

Abstract

Provided is a method for detecting an Fe2+ ion concentration and / or an Fe3+ ion concentration in an acidic solution for pickling a material to be rolled, wherein the Fe2+ ion concentration and / or the Fe3+ ion concentration is determined on the basis of: a relational expression (1) of the Fe2+ ion concentration which is a function of an electrical conductivity EC, a specific gravity d, and a hydrochloric acid concentration in the acidic solution; a relational expression (2) of the Fe3+ ion concentration which is a function of the electrical conductivity EC, the specific gravity d, and the hydrochloric acid concentration in the acidic solution; a relational expression (3) of an oxidation reduction potential ORP which is a function of the Fe2+ ion concentration, the Fe3+ ion concentration, and the hydrochloric acid concentration in the acidic solution; and the electrical conductivity EC, the specific gravity d, and the oxidation reduction potential ORP which are measured of the basis of the acidic solution during pickling.

Description

[Technical Field]

[0001] The present invention relates to the pickling of metallic materials, in particular ferrous materials. [Background technology]

[0002] Pickling is a process in which metal materials are immersed in an acid solution such as hydrochloric acid or sulfuric acid to clean and remove oxide films, rust, and other substances adhering to the surface. Examples of metal materials that can be subjected to pickling include cold-rolled steel sheets, hot-rolled steel sheets that are used to roll cold-rolled steel sheets, and hot-rolled steel sheets that are the final product. In addition to immersion in an acid solution, pickling can also be performed by spraying the acid solution. The composition of the acid solution is adjusted to ensure high pickling efficiency. However, as pickling continues, the composition of the acid solution, particularly the acid concentration, changes over time, reducing the effectiveness of the pickling. Therefore, the acid concentration is adjusted during the pickling process.

[0003] For example, Patent Document 1 discloses that when controlling the acid concentration of an acid solution used in a pickling facility, the density, temperature, and conductivity of the acid solution are continuously measured to determine the hydrochloric acid concentration and the iron chloride concentration. More specifically, the hydrochloric acid concentration and the iron chloride concentration, i.e., the Fe ion concentration, are derived, the results are continuously output, the hydrochloric acid concentration value is compared with a target value, and the amount of acid solution to be added is determined so that the difference between the two becomes zero. In addition, Patent Document 2 discloses a method for maintaining a constant pickling power and 3+ It is mentioned that the ion concentration should be maintained at 1 g / liter to 300 g / liter. 2+ It is proposed to oxygenate and reoxidize the ions, maintaining a redox potential between 0 and 800 mV, measured between a platinum electrode placed in the acid solution and an Ag / AgCl reference electrode. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-313979 [Patent Document 2] Patent No. 4186131 Summary of the Invention [Problem to be solved by the invention]

[0005] During pickling, the Fe ions contained in the acid solution, especially Fe 3+ The concentration of ions affects the pickling ability. However, although Patent Document 1 mentions the Fe ion concentration, 2+ ions and Fe 3+ There is no disclosure of the specific concentration of the ions, and two valence states (Fe 3+ ,Fe 2+ ) is not even taken into consideration. In addition, Patent Document 2 discloses that the acid solution used for pickling contains Fe 2+ ions and Fe 3+ Although the existence of Fe ions is disclosed, there is no disclosure of the specific concentrations of both. 2+ ions and Fe 3+ Achieving the correct concentration of ions is difficult. Therefore, the present invention aims to eliminate the Fe actually contained in the acid solution during pickling. 2+ ions and Fe 3+ ions, especially Fe 3+ The object of the present invention is to provide a detection method capable of quickly detecting the concentration of an ion. [Means for solving the problem]

[0006] The Fe contained in the acid solution used to pickle the rolled material of the present invention 2+ ions and Fe 3+ The method for detecting the concentration of one or both of the ions is as follows: The electric conductivity of the acid solution, EC, is a function of the specific gravity, d, and the concentration of hydrochloric acid. 2+ The ion concentration relationship (1) and The electric conductivity of the acid solution, EC, is a function of the specific gravity, d, and the concentration of hydrochloric acid. 3+ The ion concentration relationship (2) and Acid solution Fe 2+ Ion concentration and Fe 3+ The relationship between the oxidation-reduction potential (ORP) and the concentration of hydrochloric acid is given by equation (3). The electrical conductivity EC, specific gravity d, and oxidation-reduction potential ORP measured from the acid solution during pickling, Based on Fe 2+ Ion concentration and Fe 3+ Determine one or both of the ion concentrations.

[0007] In the concentration detection method of the present invention, preferably, the relational expression (3) of the oxidation-reduction potential ORP is 2+ Ion concentration and Fe 3+ It is expressed as a linear combination of the logarithm of the ion concentration and the concentration of hydrochloric acid.

[0008] The concentration detection method of the present invention preferably comprises a first measuring step and a relational equation establishing step. The first measurement step is Unknown concentration of Fe 2+ ions and Fe 3+ For each of several types of acid solutions containing ions and with different concentrations of hydrochloric acid, the electrical conductivity EC, specific gravity d, oxidation-reduction potential ORP, and Fe 2+ Ion concentration and Fe 3+ The ion concentration is measured. The relational equation construction step is The Fe is calculated from the electrical conductivity EC and specific gravity d measured in the first measurement step and the known concentration of hydrochloric acid. 2+ The relationship (1) for predicting ion concentration, The Fe is calculated from the electrical conductivity EC and specific gravity d measured in the first measurement step and the known concentration of hydrochloric acid. 3+ The relationship (2) predicts the ion concentration, Fe measured in the first measurement step 2+ Ion concentration and Fe 3+ The relationship (3) for predicting the oxidation-reduction potential (ORP) from the ion concentration and the known concentration of hydrochloric acid is is identified by multiple regression analysis.

[0009] The concentration detection method of the present invention preferably includes, after the relational equation establishment step, an acquisition step, a second measurement step, and a calculation step. The obtaining step obtains the acid solution during pickling. In the second measuring step, the electrical conductivity EC, specific gravity d, and oxidation-reduction potential ORP of the obtained acid solution are measured. The calculation step calculates Fe based on the electrical conductivity EC, specific gravity d, and oxidation-reduction potential ORP measured in the second measurement step, and the relational expressions (1), (2), and (3). 2+ Ion concentration and Fe 3+ Calculate the ion concentration.

[0010] The relational equation building step preferably includes the steps of: The objective variable of equation (1) is Fe 2+ The explanatory variables are the ion concentration, the electrical conductivity EC and specific gravity d measured in the first measurement step, and the known concentration of hydrochloric acid. The coefficients of each explanatory variable are calculated. The objective variable of equation (2) is Fe 3+ The explanatory variables are the ion concentration, the electrical conductivity EC and specific gravity d measured in the first measurement step, and the known concentration of hydrochloric acid. The coefficients of each explanatory variable are calculated. The objective variable of the relational expression (3) is the oxidation-reduction potential (ORP), and the explanatory variable is the Fe measured in the first measurement step. 2+ Logarithm of ion concentration and Fe 3+ The coefficients of each explanatory variable are calculated, including the logarithm of the ion concentration and the logarithm of the known concentration of hydrochloric acid.

[0011] The coefficients of the explanatory variables in the relational equation (3) in the relational equation establishment step are preferably determined taking into account the concentration of hydrochloric acid in the pickling tank at the start of pickling.

[0012] The Fe contained in the acid solution used to pickle the rolled material of the present invention 2+ ions and Fe 3+ The ion concentration detection device is an information acquisition unit that acquires information about the measured values ​​of the electrical conductivity meter, specific gravity, and oxidation-reduction potential of the acid solution; Based on the electrical conductivity, specific gravity, and redox potential obtained in the characteristic acquisition section, Fe 2+ Ion concentration and Fe 3+ and a calculation unit for calculating one or both of the ion concentrations.

[0013] The concentration detecting device of the present invention preferably includes a measuring unit. an electrical conductivity meter for measuring the electrical conductivity of the acid solution; a hydrometer for measuring the specific gravity of the acid solution; and an oxidation-reduction potentiometer for measuring the oxidation-reduction potential of the acid solution.

[0014] The calculation unit in the present invention preferably includes: The electric conductivity of the acid solution, EC, is a function of the specific gravity, d, and the concentration of hydrochloric acid. 2+ The ion concentration relationship (1) and The electric conductivity of the acid solution, EC, is a function of the specific gravity, d, and the concentration of hydrochloric acid. 3+ The ion concentration relationship (2) and Acid solution Fe 2+ Ion concentration and Fe 3+ The relationship between the oxidation-reduction potential (ORP) and the concentration of hydrochloric acid is given by equation (3). The electrical conductivity EC, specific gravity d, and oxidation-reduction potential ORP measured from the acid solution during pickling, Based on Fe 2+ Ion concentration and Fe 3+ Determine one or both of the ion concentrations. [Effects of the Invention]

[0015] According to the present invention, during pickling, the Fe actually contained in the acid solution is 2+ ions and Fe 3+ ions, especially Fe 3+ The concentration of ions can be detected quickly. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 3 is a flowchart showing the procedure of a concentration detection method according to the embodiment. [Figure 2]1 is a table showing actual measured values ​​of detected concentrations of acid solutions used to construct a relational expression according to an embodiment. [Figure 3] This is a graph showing the relationship between the calculated values ​​obtained by substituting the measured values ​​shown in the table in Figure 2 into the estimation formula that forms the basis of the relational equation and the measured values. The upper row relates to the hydrochloric acid concentration [H+], and the lower row relates to the Fe2+ ion concentration [Fe2+]. [Figure 4] The upper graph shows the relationship between calculated and measured values ​​for Fe3+ ion concentration [Fe3+], and the lower graph shows the standard deviation of various concentrations. [Figure 5] FIG. 1 is a diagram illustrating an example of an acid pickling facility capable of performing a concentration detection method according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, Fe according to the embodiment will be described. 2+ ions and Fe 3+ The ion concentration detection method and the concentration detection device will be described. 2+ ions and Fe 3+ When there is no need to distinguish between these ions, they are sometimes collectively referred to as Fe ions.

[0018] [Concentration detection procedure: See Figure 1] In this embodiment, the acid solution being pickled is obtained, its characteristics are measured, and the Fe ion concentration is calculated based on the measurement results. For this purpose, a relationship between the characteristics and the Fe ion concentration is established in advance. In other words, as shown in FIG. 1 , this embodiment involves two steps: a preparatory step AP for establishing the relationship, and a monitoring step MN for calculating the Fe ion concentration. The monitoring step MN can calculate the amount of additive to be added to the acid solution to maintain the pickling performance based on the detected Fe ions. The acid solution in this embodiment is primarily composed of hydrochloric acid.

[0019] 1 shows the preparation step AP and the monitoring step MN executed consecutively, but the present invention is not limited to this. After the relational expression is constructed in the preparation step AP, the monitoring step MN can be executed independently using the relational expression thus constructed, without the preparation step AP.

[0020] [Outline of the preparatory step AP] The advance preparation step AP includes a step (S101) of acquiring a relationship between the characteristics of the acid solution and the Fe ion concentration, which is necessary for constructing a relational equation, and a step (S103) of constructing the relational equation based on the acquired relationship. More specific details will be described below.

[0021] [Relationship acquisition step (S101)] Fe 2+ ion concentration, Fe 3+ The following equations (1) to (3) were developed to estimate the concentration of Fe ions and oxidation-reduction potential (ORP). 2+ ion concentration ([Fe 2+ ]) and Fe 3+ ion concentration ([Fe 3+ ]) and the detected results can be quickly reflected in the pickling process being performed. In this embodiment, this is referred to as being able to be reflected online or being able to respond online.

[0022] For example, titration analysis, a quantitative analysis method that measures the amount of a chemical substance using a chemical reaction, can be used to determine the amount of [Fe 2+ ] and [Fe 3+However, titration analysis requires a considerable amount of time, so it is difficult to say that the analysis results can be reflected online. In particular, titration requires processes such as replenishing the titrant, sampling the sample, and diluting it, so automatically obtaining the detection results places a heavy burden, including equipment requirements. Therefore, in this embodiment, an estimation formula was developed on the premise that the results can be reflected online.

[0023] Therefore, each estimation formula is based on the characteristics of the acid solution that can be quickly detected, and these characteristics lead to the unknown [Fe 2+ ] and [Fe 3+ ] in the acid solution. 2+ ] and [Fe 3+ ] is the unknown concentration ([H + ]) are also involved. Therefore, there are three unknowns: [Fe 2+ ], [Fe 3+ ] and [H + In order to obtain the solution of [], we used the estimation formulas (1) to (3) consisting of simultaneous equations with three unknowns.

[0024] In addition to being able to rapidly detect acid solutions, [Fe 2+ ], [Fe 3+ ] and [H + As the properties related to the above, electrical conductivity (EC), specific gravity (d) and oxidation-reduction potential (ORP) were selected, and the following estimation formulas were created: 2+ and Fe 3+ This assumes a potential relationship of

[0025] <Estimation formula> Fe 3+ +e - =Fe 2+ …Formula (0) [Fe 2+ ]=A*EC+B*EC 2 +C*d+D*d 2 +E*[H + ]+F …Formula (1) [Fe 3+ ]=G*EC+H*EC2 +I*d+J*d 2 +K*[H + ]+L …Formula (2) ORP=M*Ln[Fe 2+ ]+N*Ln[Fe 3+ ]+O*Ln[H + ]+P …Formula (3) EC: Electrical conductivity (S / m), d: Specific gravity (g / cm 3 ) ORP: Oxidation-reduction potential (mV) [Fe 2+ ]:Fe 2+ Ion concentration (mol / L) [Fe 3+ ]:Fe 3+ Ion concentration (mol / L) [H + ]:HCl concentration (mol / L) A~L: Constant M~P: Variables depending on T-HCl (assumed as a quadratic function of T-HCl)

[0026] The hydrochloric acid (HCl) contained in the acid solution before being used for pickling is consumed by the pickling, but some remains in the form of hydrochloric acid without being consumed, and this is sometimes called free hydrochloric acid (HCl). + When steel is pickled in an acid solution that is primarily hydrochloric acid, the consumed hydrochloric acid appears in the form of iron chloride (FeCl2, FeCl3) compounds. The sum of these is T-HCl (total hydrochloric acid).

[0027] In order to confirm the accuracy of the above estimation formula, acid solutions with various concentrations were prepared, and total hydrochloric acid (T-HCl), free hydrochloric acid (HCl), Fe 2+ ion, Fe 3+ The ion concentrations were measured (first measurement step). The measured values ​​were compared with the values ​​calculated using the estimation formula. Figure 2 shows the measured values ​​of the prepared acid solution, which were measured and detected using the titration method. The concentration of hydrochloric acid (HCl) in Figure 2 is a known quantity, while the others are unknown quantities. The comparison results are shown in Figures 3 and 4. The calculated values ​​are close to the measured values, and it was confirmed that the estimation formulas consisting of formulas (1) to (3) are suitable for practical use. Here, Fe 2+ ion, Fe 3+ An acid solution with an unknown ion concentration was used, but Fe 2+ ion, Fe 3+ The accuracy of the estimation formula can also be confirmed by using an acid solution with a known ion concentration.

[0028] [Relational equation construction step (S103)] Next, for the estimation formula consisting of formulas (1) to (3), constants are determined to construct a relational equation. Multiple regression analysis was used to determine the constants. The constructed relational equations are essentially the same as the estimation formulas, so they will be referred to as relational equations (1) to (3) except when it is necessary to distinguish between the two.

[0029] For the estimation formula (1), the objective variable is [Fe 2+ ] and the explanatory variables are EC,EC 2 ,d,d 2 ,[H + ] and perform multiple regression analysis to determine the constants. For the estimation formula (2), the objective variable is [Fe 3+ ] and the explanatory variables are EC,EC 2 ,d,d 2 ,[H + ] and perform multiple regression analysis to determine the constants. For the estimation formula (3), the objective variable is ORP, and the explanatory variable is Ln[Fe 2+ ],Ln[Fe 3+ ],Ln[H + ] and perform multiple regression analysis to determine the constants.

[0030] To make the constants in equation (3) dependent on T-HCl, samples with the same T-HCl are grouped together, and the constants in equation (3) are calculated for each group. Then, a bifurcated curve is fitted to the horizontal axis to represent the correlation between the constants and T-HCl, and the T-HCl dependence of the constants is displayed. In the examples of Figures 2 to 4, specifically, the T-HCl concentrations of 4.74 mol / L, 5.38 mol / L, and 6.02 mol / L are divided into Group 1, Group 2, and Group 3. A constant is calculated by multiple regression analysis for Group 1 with a concentration of 4.74 mol / L, a constant is calculated by multiple regression analysis for Group 2 with a concentration of 5.38 mol / L, and a constant is calculated by multiple regression analysis for Group 3 with a concentration of 6.02 mol / L. Then, the dependence of the constant on the T-HCl concentration can be expressed as a digraph curve.

[0031] [Overview of Monitoring Step MN] Once the relational expressions (1) to (3) have been established by the above-described advance preparation step AP, the monitoring step MN can be executed. The monitoring step MN includes step S201 of measuring the electrical conductivity EC, specific gravity d, and ORP (oxidation-reduction potential) of the acid solution undergoing pickling, and step S203 of calculating the concentration by substituting the obtained measured values ​​into the relational expressions.

[0032] [Measurement step S201] The electrical conductivity EC, specific gravity d, and ORP are measured by any measuring means (second measuring step). Electrical conductivity EC can be measured, for example, using a known electrical conductivity meter using the "alternating current two-electrode method" or "electromagnetic induction method." The alternating current two-electrode method is a method of measuring the magnitude of the current flowing between a pair of electrodes sandwiching a solution (acid solution). The electromagnetic induction method is a method of measuring the magnitude of the induced current generated between a pair of coils sandwiching a solution. The specific gravity d can be measured by a known hydrometer such as a hydrometer using a floating scale or a hydrometer using a load cell. ORP can be measured with an oxidation-reduction potentiometer, typically connecting a potentiometer between a platinum electrode and a reference electrode.

[0033] [Calculation step S203] Once the electrical conductivity EC, specific gravity d, and ORP are measured, they are substituted into the relational expressions (1) to (3) to perform calculations. First, the measured electrical conductivity EC and specific gravity d are substituted into equations (1) and (2). From equation (1), [Fe 2+ ] and [H + ] is obtained as the correlation equation (4), and [Fe 3+ ] and [H + ], the correlation equation (5) is obtained.

[0034] [Fe 2+ ]=A*EC+B*EC 2 +C*d+D*d 2 +E*[H + ]+F …Formula (1) [Fe 3+ ]=G*EC+H*EC 2 +I*d+J*d 2 +K*[H + ]+L …Formula (2) [Fe 2+ ]=r1*[H + ] …Formula (4) [Fe 3+ ]=r2*[H + ] …Formula (5)

[0035] Once correlation equations (4) and (5) are obtained, substitute equations (4) and (5) and the measured ORP into equation (3). Then, ORP and Ln[H + ] correlation equation (6) is obtained. ORP=M*Ln[Fe 2+ ]+N*Ln[Fe 3+ ]+O*Ln[H + ]+P …Formula (3) ORP=Ln[H + ] …Formula (6)

[0036] For correlation equation (6), we apply a calculation method to back-calculate the values ​​that should be substituted to derive a specific calculation result, and obtain [H + ] is obtained. + ] and correlation equation (4) and correlation equation (5), [Fe 2+ ] and [Fe 3+ ] can be obtained. The above series of steps determines the concentration of hydrochloric acid in the acid solution [H + ] and Fe2+ Ion concentration [Fe 2+ ] and the correlation equation (4) with the hydrochloric acid concentration in the acid solution [H + ] and Fe 3+ Ion concentration [Fe 3+ ] and the correlation equation (5) between the oxidation-reduction potential (ORP) and Fe in the acid solution. 2+ Ion concentration [Fe 2+ ] and ion concentration [Fe 3+ ] and hydrochloric acid concentration [H + ] and based on the relation (3), Fe 2+ ions and Fe 3+ It shows that the concentration of one or both of the ions can be determined.

[0037] The [Fe 2+ ] and [Fe 3+ ] is used to calculate the amount of acid components, such as hydrochloric acid (HCl) and hydrogen peroxide (H2O2), needed to maintain the pickling performance (Figure 1, S205). Based on the calculated amounts, hydrochloric acid (HCl), hydrogen peroxide (H2O2), etc. are added to the acid solution. These additives are usually added in the form of an aqueous solution. This addition can be performed by an operator using the calculated values, or it can be done automatically by a dosing device based on the calculated values.

[0038] [Pickling equipment: Figure 5] Next, with reference to FIG. 5, a pickling apparatus 1 capable of implementing the concentration detection method according to this embodiment will be described. The pickling device 1 continuously pickles a long metal strip MS while dissolving [Fe in the acid solution AS]. 2+ ] and [Fe 3+ ] is detected online. The pickling equipment 1 detects the detected [Fe 2+ ] and [Fe 3+ ], additives such as hydrochloric acid (HCl) and hydrogen peroxide (H2O2) are automatically added to the acid solution AS in the pickling tank 2.

[0039] The pickling apparatus 1 includes a pickling tank 2 that stores an acid solution AS, and a plurality of rollers 4 that support the metal strip MS so that it is immersed in the stored acid solution AS are provided at appropriate intervals. The pickling tank 2 is divided into four areas by, for example, three partitions 3A, 3B, and 3C.

[0040] The pickling apparatus 1 includes a main control unit 10 and a sub-control unit 20. The main control unit 10 and the sub-control unit 20 are configured by computer devices.

[0041] The main control unit 10 controls the [Fe 2+ ] and [Fe 3+ The main control unit 10 detects the amount of additive to be added to the acid solution and calculates the amount of additive to be added to the acid solution based on the detection result. The main control unit 10 transfers information about the calculated amount of additive to the sub-control unit 20. For this purpose, the main control unit 10 holds the above-mentioned relational expressions (1) to (3) and executes calculations to obtain the above-mentioned correlation expressions (4) and (5). The main control unit 10 also obtains correlation expression (6) based on the obtained correlation expressions (4) and (5) and relational expression (3). Furthermore, the main control unit 10 obtains [Fe 2+ ] and [Fe 3+ The specific procedure for this is as described above. The main control unit 10 corresponds to an example of the information acquisition unit and the calculation unit of the present invention.

[0042] The sub-controller 20 charges the additive into the pickling tank 2 based on the information on the amount of the additive transferred.

[0043] The pickling apparatus 1 includes measuring instrument units 15A, 15B, 15C, and 15D as measuring sections immersed in the acid solution AS in each region of the pickling tank 2. Each measuring instrument unit 15A, 15B, 15C, and 15D includes at least an electrical conductivity meter, a specific gravity meter, and an oxidation-reduction potential meter. Each measuring instrument is immersed in the acid solution AS so as to perform its respective measurement. Each measuring instrument unit 15A, 15B, 15C, and 15D is connected to the main control unit 10, which acquires information on the electrical conductivity EC, specific gravity d, and oxidation-reduction potential ORP measured by each measuring instrument unit. This information may be acquired continuously or at predetermined time intervals. Upon acquiring the electrical conductivity EC, specific gravity d, and oxidation-reduction potential ORP, the main control unit 10 calculates [Fe 2+ ] and [Fe 3+ Follow the steps in order to obtain ].

[0044] The pickling apparatus 1 is equipped with injection nozzles 25A, 25B, 25C, and 25D for injecting additives into the respective regions of the pickling tank 2. The additives are injected into the acid solution AS stored in the pickling tank 2 from the injection nozzles 25A, 25B, 25C, and 25D in response to instructions from the sub-controller 20.

[0045] The [Fe 2+ ] and [Fe 3+ The actual measurement information regarding [ ] is transferred to the sub-controller 20. This transfer of the actual measurement information may be performed continuously or at predetermined time intervals.

[0046] The sub-controller 20 controls the amount of [Fe 2+ ] and [Fe 3+ The sub-control unit 20 has reference information regarding [Fe 2+ ] and [Fe 3+When actual measurement information regarding the amount of additives transferred to the sub-controller 20 is received, it compares the actual measurement information with the reference information to determine actual difference information. The sub-controller 20 holds reference difference information for this difference, compares the actual difference information with the reference difference information, and if the actual difference information is greater than the reference difference information, determines that additives need to be added. The sub-controller 20 also has tanks that store various additives, and issues instructions to add the required amounts of additives from the injection nozzles 25A, 25B, 25C, and 25D.

[0047] [effect] As described above, according to the concentration detection method of this embodiment, by constructing the relational expressions (1) to (3), which are simultaneous equations with three unknowns, [Fe 2+ ] and [Fe 3+ ] can be detected online. According to the pickling equipment 1 to which this detection method is applied, [Fe 2+ ] and [Fe 3+ In addition to being able to detect the amount of acid in the acid solution AS, the additive is automatically added based on the detection results. Therefore, the pickling device 1 can maintain the pickling performance of the acid solution AS without relying on human labor.

[0048] According to the embodiment described above, [Fe 2+ ] and [Fe 3+ Based on the above-mentioned relations (1) to (3), [Fe 2+ ] and [Fe 3+ ] can also be finally obtained. Furthermore, in the pickling apparatus 1, the main control unit 10 and the sub-control unit 20 have been described as being separate units, but they may also be an integrated control unit. Furthermore, in the pickling apparatus 1, an example has been described in which a measuring device unit (measurement unit) and a charging nozzle (charging unit) are provided for each of the divided regions of the pickling tank 2, but it is also possible to provide a single measurement unit and a single charging unit in the pickling tank 2. In this case, the measurement unit and the charging unit may be provided close to each other or at a distance from each other. [Explanation of symbols]

[0049] 1. Pickling equipment 2 Pickling tank 3A, 3B, 3C Shiqie 4 ローラ 10 Main Control Department 15A, 15B, 15C, 15D measuring machine ユニット 20 Deputy Control Department 25A, 25B, 25C, 25D put in ノズル AS acid solution MS Metal ストリップ

Claims

1. Fe contained in the acid solution used to pickle the rolled material ２＋ ions and Fe ３＋ 1. A method for detecting the concentration of one or both of ions, comprising: Fe, which is a function of the electrical conductivity EC, specific gravity d, and concentration of hydrochloric acid of the acid solution ２＋ The ion concentration relationship formula (1) and Fe, which is a function of the electrical conductivity EC, specific gravity d, and concentration of hydrochloric acid of the acid solution ３＋ The ion concentration relationship (2) and The Fe in the acid solution ２＋ Ion concentration and Fe ３＋ The oxidation-reduction potential ORP is a function of the ion concentration and the concentration of hydrochloric acid. the electrical conductivity EC, specific gravity d, and oxidation-reduction potential ORP measured from the acid solution during pickling; Based on Fe ２＋ + ion concentration and Fe ３＋ Determine one or both ion concentrations A concentration detection method comprising:

2. In claim 1, The relational expression (3) of the oxidation-reduction potential ORP is Fe ２＋ + ion concentration and Fe ３＋ It is expressed as a linear combination of the ion concentration and the logarithm of the concentration of hydrochloric acid. A concentration detection method comprising:

3. In claim 1 or claim 2, Unknown concentration of Fe ２＋ ions and Fe ３＋ For each of the plurality of acid solutions containing ions and having different concentrations of hydrochloric acid, the electrical conductivity EC, specific gravity d, oxidation-reduction potential ORP, and Fe ２＋ Ion concentration and Fe ３＋ a first measuring step of measuring an ion concentration; From the electrical conductivity EC measured in the first measurement step, the specific gravity d, and the known concentration of the hydrochloric acid, Fe ２＋ The above-mentioned relation (1) for predicting the ion concentration; From the electrical conductivity EC measured in the first measurement step, the specific gravity d, and the known concentration of the hydrochloric acid, Fe ３＋ The above-mentioned relation (2) for predicting the ion concentration; The Fe measured in the first measuring step ２＋ Ion concentration and the Fe ３＋ Ion concentration and The relationship (3) for predicting the oxidation-reduction potential ORP from the known concentration of hydrochloric acid. and a relational equation construction step for identifying the above by multiple regression analysis. A concentration detection method comprising:

4. In claim 3, a second measuring step of measuring the electrical conductivity EC, specific gravity d, and oxidation-reduction potential ORP of the acid solution during pickling; Based on the electrical conductivity EC, the specific gravity d, and the oxidation-reduction potential ORP measured in the second measuring step, and the relational expressions (1), (2), and (3), Fe ２＋ Ion concentration and Fe ３＋ and a calculation step for determining the ion concentration. A concentration detection method comprising:

5. In claim 3, The relational equation construction step The objective variable of the relational expression (1) is Fe ２＋ the electrical conductivity EC and the specific gravity d measured in the first measurement step, and the known concentration of hydrochloric acid are included as explanatory variables, and a coefficient of each explanatory variable is calculated; The objective variable of the relational expression (2) is Fe ３＋ the electrical conductivity EC and the specific gravity d measured in the first measurement step, and the known concentration of hydrochloric acid are included as explanatory variables, and a coefficient of each explanatory variable is calculated; The objective variable of the relational expression (3) is the oxidation-reduction potential ORP, and the Fe measured in the first measurement step is used as the explanatory variable. ２＋ The logarithm of the ion concentration and the Fe ３＋ Calculate the coefficients of each explanatory variable, including the logarithm of the ion concentration and the logarithm of the known concentration of hydrochloric acid. A concentration detection method comprising:

6. In claim 5, The coefficient of the explanatory variable in the formula (3) can be calculated by taking into account the concentration of hydrochloric acid in the acid solution at the start of pickling. A concentration detection method comprising:

7. Fe contained in the acid solution used to pickle the rolled material ２＋ ions and Fe ３＋ An ion concentration detection device, an information acquisition unit that acquires information about measured values ​​related to the electrical conductivity, specific gravity, and oxidation-reduction potential of the acid solution; Based on the electrical conductivity, the specific gravity, and the oxidation-reduction potential acquired by the information acquisition unit, ２＋ Ion concentration and Fe ３＋ a calculation unit for calculating one or both of the ion concentrations, The calculation unit A relational expression (1) of the Fe 2+ ion concentration, which is a function of the electrical conductivity EC, specific gravity d, and concentration of hydrochloric acid of the acid solution; A relational expression (2) of the Fe 3+ ion concentration, which is a function of the electrical conductivity EC, specific gravity d, and concentration of hydrochloric acid of the acid solution; A relational expression (3) of the oxidation-reduction potential ORP, which is a function of the Fe 2+ ion concentration, the Fe 3+ ion concentration, and the hydrochloric acid concentration of the acid solution; the electrical conductivity EC, specific gravity d, and oxidation-reduction potential ORP measured from the acid solution during pickling; Calculate either or both of the Fe 2+ and Fe 3+ ion concentrations based on the above. A concentration detection device characterized by:

8. In claim 7, an electrical conductivity meter for measuring the electrical conductivity of the acid solution; a hydrometer for measuring the specific gravity of the acid solution; and a redox potential meter for measuring the redox potential of the acid solution. A concentration detection device characterized by:

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