JPH11166922A - Method for quantitatively analyzing organic additive in stainless steel acid-cleaning liquid and method for acid-cleaning stainless steel using same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for quantitatively analyzing organic additives in a stainless steel acid-cleaning liquid for capable of speedily quantitatively analyzing an acid-cleaning accelerator containing an organic compound having mercapto groups and an organic compound having disulfide bonds added to an acid-cleaning liquid for stainless steel by a simple method and a method for acid-cleaning stainless steel using the same method. SOLUTION: An organic additive preferably containing an organic compound having mercapto groups and/or an organic compound having disulfide bonds in a non-oxidizing acid-cleaning liquid for stainless steel is oxidized with permanganic acid ions, and determination is performed on the basis of the amount of consumed permanganic acid ions. Or the above-mentioned organic additive is oxidized with nichrome acid ions, and determination is performed on the basis of the amount of generated Cr<3+> in a method for quantitatively analyzing an organic additive in a stainless steel acid-cleaning liquid and a method for acid-cleaning stainless steel using the same method for quantitative analysis.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for quantitatively analyzing an organic additive used for pickling stainless steel and a method for pickling stainless steel using the same. More particularly, the present invention relates to a method for pickling stainless steel. The present invention relates to a method for quantitatively analyzing an organic additive for promoting washing and a method for pickling stainless steel using the same.

[0002]

2. Description of the Related Art In a manufacturing process of a stainless steel sheet,
Dissolve the iron by immersing it in an acid such as sulfuric acid or hydrochloric acid to remove the scale and dechromized layer present on the surface of the steel sheet annealed after hot rolling or hot rolling, or to smooth the surface irregularities Pickling is performed.

On the other hand, in recent years, the types of stainless steel having high corrosion resistance have increased, and the pickling ability has been insufficient in the conventional pickling method from the viewpoint of improving productivity. On the other hand, attempts have been made to increase the pickling rate by adding an additive which is a pickling accelerator to a pickling solution. It is said that inorganic sulfur and thiosulfuric acid are effective as a pickling accelerator in a sulfuric acid pickling solution.

Further, a water-soluble organic sulfur compound having a mercapto group or a disulfide bond promotes sulfuric acid pickling of stainless steel (see Japanese Patent Application Laid-Open No. 9-228081). In this case, when an organic sulfur compound containing a mercapto group is added to a pickling solution that is a solution containing a high concentration of acid and metal ions (in the case of a stainless steel pickling solution; mainly iron ions and chromium ions), In addition to the added compound having a mercapto group (hereinafter also referred to as RSH), a compound having a disulfide bond (hereinafter, also referred to as RSSR or a disulfide compound) generated from the compound by a chemical reaction which proceeds in an acid washing solution, disulfide ( RS (= O) S (= O) R),
And mercapto-desulfurized / hydrogenated compounds (RH)
(Japanese Patent Application No. 9-75591).

Since the concentration of the pickling accelerator gradually decreases in the pickling solution and the pickling effect decreases, it is important to control the concentration appropriately. As a method for analyzing the above-mentioned group of compounds derived from the organic compound added initially, the present inventors have previously proposed a quantitative analysis method based on the integrated value of the signal of the ¹ H-NMR spectrum (Japanese Patent Application Flat 9-75591
issue).

The above-mentioned method is an excellent method which enables appropriate concentration control of an organic additive such as a pickling accelerator.
Since it is an advanced analyzer, development of a simpler analysis method has been desired. Therefore, the present inventors subsequently proceeded with further research, quickly and easily quantitatively analyze the above-mentioned organic compound in a pickling line, and can reflect the analysis result in the concentration control of the pickling accelerator. The quantitative analysis method of organic additives in pickling solution of stainless steel was studied.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a simple and rapid quantitative analysis of a pickling accelerator containing an organic compound having a mercapto group or a disulfide bond added to a pickling solution for stainless steel. It is an object of the present invention to provide a method for quantitative analysis of an organic additive in a pickling solution of stainless steel and a method for pickling stainless steel using the same.

[0008]

When an organic sulfur compound having a mercapto group is added as a pickling accelerator, various compounds are formed in a sulfuric acid pickling solution as described above. As a result, it was clarified that, among these compounds, those that effectively work to promote the pickling were thiol (RSH) and disulfide compound (RSSR).

[0009] Further, as a result of analyzing the stainless steel sulfuric acid pickling solution during the pickling of stainless steel by using the above-described quantitative method based on the integrated value of the signal of the ¹ H-NMR spectrum, the pickling active ingredient was pickled. It was found that most of the liquid was present in the form of a disulfide compound. Therefore, it was found that it was sufficient to know the concentration of the disulfide compound when evaluating the concentration of the pickling accelerator.

However, there is no known method for analyzing a trace amount of a disulfide compound in an aqueous solution in which a high concentration of a metal ion and an acid are dissolved. The present inventors have conducted intensive studies on the quantification of trace disulfide compounds. As a result, the following method (A) or (B) was used to determine whether an acid containing an organic compound having a mercapto group and / or a disulfide bond added to a stainless steel pickling solution. The washing accelerator can be quantitatively analyzed in a simple manner and quickly, and it has been found that it is effective to adjust the concentration of the organic compound in the pickling solution based on the obtained quantitative analysis result. The present invention has been reached.

Method (A): The organic additive in the pickling solution is extracted and separated, preferably using an organic solvent, and the resulting extract is oxidized in concentrated sulfuric acid with permanganate ions. A quantitative analysis of the disulfide compound based on the amount of permanganate ion consumed when the disulfide compound is oxidized to the sulfonic acid compound in the above oxidation process.

Method (B): The organic additive in the pickling solution is extracted and separated preferably using an organic solvent, and the obtained extract is oxidized with dichromate ions. The disulfide compound is quantitatively analyzed based on the amount of Cr ³⁺ generated in the above oxidation process.

[0013] The present invention relates to a method for accelerating pickling of stainless steel when pickling stainless steel using a pickling solution containing an acid compound containing an organic compound having a mercapto group and / or a disulfide bond in a sulfuric acid solution. Provided are a method for quantitatively analyzing an organic additive in a stainless steel pickling solution and a method for pickling stainless steel using the same, which enable simple and rapid quantitative analysis of the effective concentration of the agent.

That is, a first invention is a method for quantitatively analyzing an organic additive in a non-oxidizing pickling solution for stainless steel, wherein the organic additive in the pickling solution is permanganate ion. A quantitative analysis method for an organic additive in a stainless steel pickling solution, characterized in that the organic additive is quantified based on the amount of permanganate ion consumed by oxidation. A second invention is a method for quantitatively analyzing an organic additive in a non-oxidizing pickling solution for stainless steel, wherein the organic additive in the pickling solution is oxidized with dichromate ions to form the organic additive. It is a quantitative analysis method of an organic additive in a pickling solution of stainless steel, characterized in that it is determined based on the amount of Cr ³⁺ .

In the second aspect of the present invention, it is preferable to use the visible absorption spectrum intensity when quantifying the organic additive in the pickling solution based on the amount of Cr ³⁺ generated. In the first invention and the second invention described above, at the time of quantification of the organic additive, an organic solvent is previously added to the pickling solution, and an organic compound is extracted and separated. It is preferable to provide for the quantitative analysis.

In the first and second aspects of the present invention, the organic additive may be an organic compound having a mercapto group (—SH group) and / or a disulfide bond (—SS—).
It is preferably used as a quantitative analysis method for an organic additive in a stainless steel pickling liquid, which is an organic additive containing an organic compound having the following. A third invention is a method for pickling stainless steel using a non-oxidizing pickling solution to which an organic additive is added as a pickling accelerator, wherein the organic additive has a mercapto group (-SH group). Using the organic additive containing an organic compound and / or an organic compound having a disulfide bond (-SS-), the organic additive in the pickling solution is quantitatively analyzed by the method according to the first or second invention. A method for pickling stainless steel, characterized by adjusting the concentration of an organic compound in the pickling solution based on the obtained quantification result.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is further described below in the order of (1) a pretreatment method for a sample pickling solution, (2) a quantitative analysis method using permanganate ions, and (3) a quantitative analysis method using dichromate ions. This will be described in detail. (1) Pretreatment of sample pickling solution: First, an organic solvent is added to the sample pickling solution to extract organic compounds in the pickling solution.

The organic solvent used here is preferably a polar solvent and an organic solvent which separates into two phases with water, for the purpose of extracting the water-soluble organic compound. Further, the organic solvent must be an organic solvent from which metal ions mainly composed of iron ions, chromium ions and nickel ions dissolved in the pickling solution are not extracted. Further, since the organic solvent is evaporated and removed in a later operation, the organic solvent is desirably an organic solvent having a boiling point that is not too high and can be easily evaporated and removed.

As the solvent satisfying the above conditions, preferably, for example, diethyl ether, methyl ethyl ketone and the like can be used. In addition, at the time of extraction, it is preferable to previously saturate the sample solution (aqueous phase) with an inorganic salt in order to improve the extraction rate. This is due to the effect of salting out.

The inorganic salt in this case is not particularly limited as long as it has high solubility in water and contains highly charged ions. Preferably, the inorganic salt is sodium sulfate, ammonium sulfate, or a combination thereof. Can be used. Next, the operation of collecting the organic phase, transferring it to another container, and extracting the organic compound again from the remaining aqueous phase with an organic solvent is repeated, for example, three times.

The extracts are combined and the extraction solvent is evaporated off. In this case, it is desirable not to perform heating in order to prevent air oxidation of the disulfide compound. If the extraction solvent remains, the solvent is oxidized by permanganate ions or dichromate ions, causing an error. Therefore, the solvent must be completely removed.

In consideration of these conditions, it is preferable to use diethyl ether as the extraction solvent because it can be easily removed by evaporation at room temperature. (2) Quantitative analysis method using permanganate ion: Sulfuric acid is added to the sample after removing the organic solvent obtained by the above pretreatment method of the sample pickling solution, and a permanganate solution such as an aqueous solution of potassium permanganate having a known concentration. The concentration of the disulfide compound is determined by titration with an aqueous solution containing an acid ion.

Here, if the sulfuric acid concentration is not kept sufficiently high during the titration, the oxidation-reduction reaction does not proceed completely and MnO ₂ precipitates during the titration, which is not preferable. That is,
It is preferable to add a fixed amount of concentrated sulfuric acid to the sample from which the extraction solvent has been removed and titrate the sample. The reaction of permanganate ion oxidizing the disulfide compound is slower than the oxidation of, for example, hydrogen peroxide or oxalic acid.

This is particularly noticeable near the equivalence point. For accurate quantification, a hot plate,
Heating with a hot water bath or the like is preferred. The heating temperature is not particularly limited, but if the temperature is too high, there is a possibility that the disulfide compound is decomposed, and if the temperature is too low, the reaction requires time, and it is difficult to determine the end point. 50 ~
Preferably it is in the range of 80 ° C.

The reaction in which permanganate ion oxidizes a disulfide compound to a sulfonic acid compound is represented by the following reaction formula.
The amount of the disulfide compound can be determined from the amount of permanganate ion represented by (1) and consumed in the titration.

[0026]

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FIG. 1 shows the results of an investigation on the relationship between the amount of dithiodiacetic acid and the amount of permanganate ion consumed in the titration. From the inclination of the straight line in FIG. 1, it was found that the reaction of the reaction formula (1) progressed quantitatively. (3) Quantitative analysis method using dichromate ion: The sample after removing the organic solvent obtained by the pretreatment method for the sample pickling solution described above was subjected to dichromate ion such as aqueous potassium dichromate solution under sulfuric acid condition. An aqueous solution containing
Based on (2), the disulfide compound is oxidized to a sulfonic acid compound.

[0028]

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Here, the amount of potassium dichromate must be greater than the oxidation equivalent of the disulfide compound. Although the sulfuric acid concentration is not particularly limited, a higher acid concentration is preferable because the reaction proceeds rapidly, and the sulfuric acid concentration in the sample solution after the addition of the potassium dichromate solution should be about 0.1 to 5M. preferable.

The reaction rate of the above reaction formula (2) is low under room temperature conditions, and it is preferable to heat the sample solution to 50 ° C. or higher by a hot plate, a hot water bath or the like. The upper limit of the heating temperature is not particularly limited, but if the temperature is too high, the disulfide compound may be decomposed, and the temperature of the sample solution is preferably 80 ° C or lower.

The amount of the disulfide compound can be determined from the amount of Cr ³⁺ ions generated according to the reaction formula (2).
It is preferable to use a visible absorption spectrum for the quantification of Cr ³⁺ ions. The visible absorption spectrum of Cr ³⁺ ion is 580n
Although it exhibits an absorption maximum near m, dichromate ions and organic sulfur compounds and sulfonic acid compounds formed by oxidizing the organic sulfur compounds do not show absorption at this wavelength.

Therefore, by measuring the absorbance around 580 nm, the amount of Cr ³⁺ ions can be obtained,
As a result, the disulfide compound can be quantified. FIG. 2 shows the results of investigation on the relationship between the concentration of dithiodiacetic acid in the sample solution and the absorbance of the sample solution after oxidation with dichromate ions. The analysis conditions in FIG. 2 are as follows.

(A) Sulfuric acid concentration in sample solution after addition of potassium dichromate solution: 0.50 M (b) Potassium dichromate addition concentration: 8.35 mM (c) Measurement wavelength: 590 nm (d) Optical path length: 1 cm From the slope of the straight line 2, it was found that the reaction of the reaction formula (2) progressed quantitatively.

The method for quantitatively analyzing the organic additive in the stainless steel pickling solution of the present invention has been described above. The organic compound having a mercapto group and the organic compound having a disulfide bond in the present invention are preferably The following compounds are exemplified. (1) Organic compound having a mercapto group: The organic compound having a mercapto group in the present invention preferably has a mercapto group and further has a carboxyl group and / or a hydroxyl group.

Preferred examples of the organic compound include mercaptoacetic acid, mercaptoethanol, and mercaptosuccinic acid. The organic compound has a hydrogen atom of a carboxyl group of the organic compound before being mixed with an acid,
It may be substituted with an alkali metal such as Na or K or an alkaline earth metal such as Ca or Mg.

(2) Organic compound having a disulfide bond: The organic compound having a disulfide bond in the present invention preferably has a disulfide bond and further has a carboxyl group and / or a hydroxyl group. As the organic compound, the following general formula (3)
, (4), and one or more organic compounds selected from aromatic compounds such as dithiosalicylic acid represented by the following formulas (5) and (6). .

[0037] _{S 2 (C n H 2n COOH} ) 2 ......... (3) S 2 (C n H 2n OH) 2 ......... (4) Equation (3), (4), n 10 Represents an integer selected from
More preferably, n is preferably an integer selected from 1 to 5.

[0038]

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[0039]

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The fats represented by the above general formulas (3) and (4)
As the aliphatic compound, S_Two(CH_TwoCOOH)_Two(Dithiodiacetic acid),
S_Two(CH_TwoCH_TwoCOOH)_Two(Dithiodipropionic acid), S_Two(CH_TwoCH
_TwoOH) _Two(Dithiodiethanol) is preferably exemplified.
The aromatic compounds represented by the formulas (5) and (6) are
It may have a substituent such as a kill group.

In the present invention, the hydrogen atom of the carboxyl group of the compound represented by the general formulas (3) and (5) before mixing with an acid is an alkali metal such as Na or K or Ca,
It may be substituted with an alkaline earth metal such as Mg. As described above, the organic compound having a mercapto group in the present invention,
Preferred examples of the organic compound having a disulfide bond have been described, but two or more kinds may be used in combination.

[0042]

The present invention will be described more specifically below with reference to examples. (Example 1) Dithiodiacetic acid (: dithiodiglycolic acid) (HOOCCH ₂ SSCH ₂ COOH) (reagent) as a pickling accelerator was added to a sulfuric acid pickling solution to which no pickling accelerator was added. 2.00mM
A solution was prepared so that

To 1 mL of the obtained solution was added 0.5 g of sodium sulfate (anhydrous) to dissolve as much as possible, and then 1 mL of diethyl ether was added to the solution to extract components in the solution. After repeating the above extraction with diethyl ether a total of three times, the solvent of the extract was removed by evaporation at room temperature, and concentrated sulfuric acid was added to the residue.
0.5 mL was added. Next, to the residue to which the above-mentioned concentrated sulfuric acid was added, an appropriate amount of a 20 mM aqueous potassium permanganate solution was added by a micropipette, and titration was performed.

Near the end point, a 4 mM aqueous solution of potassium permanganate was used so that the amount of potassium permanganate added could be adjusted to a smaller amount. The point at which the pink color of potassium permanganate did not disappear even after heating at 80 ° C. for 1 minute was regarded as the end point. The concentration of dithiodiacetic acid (: dithiodiglycolic acid) in the sample was determined from the amount of consumed potassium permanganate.

The results obtained are shown in Table 1. As shown in Table 1, the concentration in the sulfuric acid washing solution and the concentration obtained by the analysis were in good agreement, and the repetition accuracy was also good.

[0046]

[Table 1]

Example 2 A solution was collected from a sulfuric acid pickling solution in use by adding mercaptoacetic acid as a pickling accelerator (mercaptoacetic acid was changed to dithiodiacetic acid in the pickling solution). The titration with potassium permanganate was performed in the same procedure as in Example 1. From the consumed amount of potassium permanganate, the concentration of dithiodiacetic acid in the sample solution was determined using the equivalence relation shown in the above-mentioned reaction formula (1).

The same sample solution was analyzed by NMR (nuclear magnetic resonance analysis) method (Japanese Patent Application No. 9-75591). The analysis by the NMR method was performed as follows. That is, 2 g of sodium sulfate (anhydrous salt) was added to 2 mL of the collected sample solution to saturate, and then extracted with 10 mL of diethyl ether.

7 mL of the extract was taken out and the solvent was removed by evaporation at room temperature. Next, 700 μL of heavy water is added to the remaining liquid to dissolve it, and a heavy aqueous solution of dimethyl sulfoxide of known concentration (70.4 mM) is added.
20 μL was added, and the ¹ H-NMR spectrum was measured. Dithio diacetic acid in the ¹ H-NMR spectrum _{(HOOCCH 2 SSCH 2 COOH),} HOOC
CH ₂ S (= O) S (= O) CH ₂ COOH and acetic acid (CH ₃ COOH) signals were observed.

Next, a quantitative value was obtained from the area of each signal and the area of the signal of dimethyl sulfoxide added as a reference. Table 2 shows the obtained results. As shown in Table 2, the results of the KMnO ₄ titration method were in good agreement with the NMR method. Also, the repeatability is good and the relative standard deviation is 1.5
~ 3.4%.

[0051]

[Table 2]

(Example 3) A solution was collected from a sulfuric acid pickling solution in use to which mercaptoacetic acid was added as a pickling accelerator (mercaptoacetic acid was changed to dithiodiacetic acid in the pickling solution). 4 g of sodium sulfate (anhydrous) was added to 8 mL of this solution to dissolve as much as possible, and then 10 mL of diethyl ether was added to the solution to extract components in the solution.

7 mL of the extract was collected and the solvent was evaporated off at room temperature. Sulfuric acid and an aqueous solution of potassium dichromate were added to the obtained residue to make the total amount 4 mL. This solution was placed in a vial with a cap and heated on a hot plate at 80 ° C. for 30 minutes to cause a reaction.

After cooling to room temperature, use a visible spectrophotometer at 590 nm.
Was measured for absorbance. Next, the dithiodiacetate concentration in the sample solution was determined using the above-described relational expression shown in FIG.
Further, the same sample solution was analyzed by the NMR method in the same manner as in Example 2 described above.

Table 3 shows the results obtained. As shown in Table 3, K ₂ Cr ₂ O ₇ oxide - results of absorption spectrometry are in good agreement with the NMR method.

[0056]

[Table 3]

As described above, according to the present invention, it is possible to analyze a disulfide compound in an aqueous solution simply and quickly without using a special analyzer, and for example, a metal such as iron or chromium is dissolved. The above compounds in the stainless steel pickling solution can be easily and accurately quantified, and in the pickling process of the stainless steel, an appropriate concentration control of the pickling accelerator in the pickling solution can be performed.

When the method of the present invention is used, an organic compound having a mercapto group (: thiol) in an aqueous solution can be analyzed in the same manner as the disulfide compound. in this case,
The reaction with permanganate ion or dichromate ion is represented by the following reaction formula (7) or (8), and is shown in FIG.
Alternatively, although the slope of the straight line corresponding to FIG. 2 is different, the analysis operation may be performed similarly.

[0059]

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[0060]

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[0061]

According to the present invention, a disulfide compound or an organic compound having a mercapto group in an aqueous solution (:
Thiol) can be easily and quickly quantitatively analyzed. Therefore, the present invention can be used for quantitative analysis of a sulfur-containing pickling accelerator added to a pickling solution of stainless steel.

As a result, according to the present invention, in the pickling process of stainless steel, it is possible to appropriately control the concentration of the organic sulfur additive which is a pickling accelerator in the pickling solution, and its industrial significance is large. .

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the amount of dithiodiacetic acid in a sample solution and the amount of permanganate ion consumed in titration.

FIG. 2 is a graph showing the relationship between the concentration of dithiodiacetic acid in a sample solution and the absorbance of the sample solution after oxidation with dichromate ions.

Claims (6)

[Claims] 1. A method for quantitative analysis of an organic additive in a non-oxidizing pickling solution for stainless steel, wherein the organic additive in the pickling solution is oxidized with permanganate ions and consumed. A method for quantitative analysis of organic additives in a pickling solution of stainless steel, wherein the method is quantified based on the amount of permanganate ions. 2. A method for quantitatively analyzing an organic additive in a non-oxidizing pickling solution for stainless steel, wherein the organic additive in the pickling solution is oxidized with dichromate ions to produce Cr. A quantitative analysis method for an organic additive in a stainless steel pickling solution, characterized in that the amount is determined based on the amount of ³⁺ . 3. The stainless steel according to claim 2, wherein a visible absorption spectrum intensity is used when quantifying the organic additive in the pickling solution based on the amount of the generated Cr ^3+. Method for quantitative analysis of organic additives in pickling liquid. 4. When quantifying the organic additive, an organic solvent is previously added to the pickling solution to extract and separate an organic compound, and the obtained extract is subjected to the quantitative analysis. The method for quantitatively analyzing an organic additive in a pickling solution of stainless steel according to claim 1. 5. The stainless steel according to claim 1, wherein the organic additive is an organic additive containing an organic compound having a mercapto group and / or an organic compound having a disulfide bond. Method for quantitative analysis of organic additives in pickling liquid. 6. A method for pickling stainless steel using a non-oxidizing pickling solution to which an organic additive has been added as a pickling accelerator, wherein the organic additive has an organic compound having a mercapto group and / or a disulfide. Using an organic additive containing an organic compound having a bond, the organic additive in the pickling solution is quantified by the quantitative analysis method according to any one of claims 1 to 4, and the acid is determined based on the obtained quantitative result. A method for pickling stainless steel, comprising adjusting the concentration of an organic compound in a washing solution.