JP3229561B2 - Method for pickling stainless steel and method for analyzing organic compounds in stainless steel pickling solution used therefor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for pickling stainless steel and a method for analyzing organic compounds in a stainless steel pickling solution used in the pickling method. The present invention relates to a method for pickling stainless steel using an added non-oxidizing pickling solution, and a method for analyzing organic compounds in the stainless steel pickling solution used in the pickling method.

[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 called 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.

A water-soluble organic sulfur compound having a mercapto group or a disulfide bond promotes the pickling of stainless steel with sulfuric acid (Japanese Patent Application No. 8-28803). However, according to the study results of the present inventors, when these pickling accelerators are used, the pickling effect of the pickling solution decreases over time,
This was due to a decrease in the concentration of the pickling accelerator in the pickling solution, and it was found that proper management of the concentration of the pickling accelerator in the pickling solution was important.

However, a small amount of a water-soluble organic sulfur compound having a mercapto group or a disulfide bond contained in a stainless steel pickling solution which is an aqueous solution containing a high concentration of an acid and metal ions mainly composed of iron ions and chromium ions. The analytical method has not been established. As a method for detecting a trace amount of an organic sulfur compound having a mercapto group, for example, a method utilizing color development by a reaction between a tetrazolium salt and a mercapto group (JP-A-64-68660), a method using an Ellman's reagent (Arch) .Biochem.Biophys., 82,70-77
(1959)), a method using a fluorescent labeling agent (for example, Ana
l. Chem., 56, 2461-2464 (1984), Talanta, 32, 167-169 (19
85)) and other methods are known.

However, these methods are intended to analyze mercapto compounds in biological samples or foods, and are used in a high-concentration aqueous sulfuric acid solution containing a large amount of metal ions such as iron ions and chromium ions. It cannot be applied directly to the analysis of trace amounts of organic sulfur compounds present. Further, the above method cannot detect an organic sulfur compound having a disulfide bond.

As the compound containing a mercapto group used as an acid pickling accelerator, a compound having a relatively small molecular weight is used. It is known that such compounds to be analyzed can be analyzed by gas chromatography (for example, "Handbook of Analytical Chemistry", Japan Society for Analytical Chemistry (1991)).

It has been considered that the use of gas chromatography makes it possible to analyze an organic sulfur compound having a disulfide bond. However, as a result of the study, the present inventor has found that, when the analysis is performed by gas chromatography, a disulfide bond is cleaved during the analysis, and a reaction in which a mercapto group is generated proceeds.

Therefore, gas chromatography is unsuitable for analyzing a sample containing both a compound containing a mercapto group and a compound containing a disulfide bond. As described above, several methods for analyzing organic sulfur compounds containing a mercapto group are known, but an industrially useful method for analyzing a trace amount of organic sulfur compounds in a pickling solution has not yet been established. .

[0010]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art and provides a method for pickling stainless steel capable of appropriately controlling pickling conditions, and a method for pickling stainless steel. It is an object of the present invention to provide a method for analyzing an organic compound in a pickling solution of stainless steel obtained.

[0011]

The first invention is a method for pickling stainless steel using a non-oxidizing pickling solution as a pickling solution. A stainless steel characterized in that the added organic compound in the liquid and / or the organic compound generated by the organic compound during pickling are quantified, and the concentration of the organic compound in the pickled liquid is adjusted based on the obtained quantification result. This is a method of pickling steel.

The first invention is preferably applied to a method for pickling stainless steel wherein the added organic compound is an organic compound having a mercapto group and / or an organic compound having a disulfide bond. In the first invention, it is preferable that the quantification method is a quantification method based on an integrated value of a signal of a ¹ H-NMR spectrum.

According to a second aspect of the present invention, an organic compound added to a non-oxidizing pickling solution for stainless steel and / or an organic compound produced by the pickling during the pickling is integrated with a signal of ¹ H-NMR spectrum. This is a method for analyzing an organic compound in a pickling solution of stainless steel, characterized in that it is quantified based on the following formula. The second invention is preferably applied to a method for analyzing an organic compound in a stainless steel pickling liquid, wherein the added organic compound is an organic compound having a mercapto group and / or an organic compound having a disulfide bond.

Further, the first or second invention is directed to a method for pickling stainless steel using a non-oxidizing pickling solution that is an aqueous solution containing sulfuric acid, an aqueous solution containing hydrochloric acid, or an aqueous solution containing sulfuric acid and hydrochloric acid. Alternatively, it is preferably applied to a method for analyzing an organic compound in a pickling solution of stainless steel.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. For example, in the case of a sulfuric acid pickling solution, a stainless steel pickling solution is a high concentration acid having a sulfuric acid concentration of 200 g / L or more in a fresh liquid state, and is often heated to increase the pickling ability. .

In addition, hydrogen is generated because the melting of the steel sheet is progressing. In such a solution, the organic sulfur compound containing a mercapto group or a disulfide bond causes various chemical reactions, and a compound having a different chemical structure from the original compound may be generated. Therefore, when examining the analysis method of the pickling accelerator, first, it is necessary to know what chemical change the added pickling accelerator undergoes in the pickling solution.

In the pickling of stainless steel plates, the present inventors use a sulfuric acid pickling solution to which an organic compound having a mercapto group is added, extract the organic compounds in the used pickling solution, and conduct nuclear magnetic resonance analysis. As a result of examination using (NMR) method, gas chromatography-mass spectrometry (GC-MS) method, the following became clear. That is, when a compound having a mercapto group is added to a non-oxidizing pickling solution, that is, a sulfuric acid pickling solution that generates hydrogen due to a metal dissolution reaction, it is initially added to a pickling solution after use. In addition to a compound having a mercapto group (hereinafter, also referred to as RSH), a compound having a disulfide bond formed from the compound by a chemical reaction which proceeds in an acid washing solution (hereinafter, also referred to as RSSR or a disulfide compound), a disulfide (RSH). (= O)
S (= O) R) and a compound (RH) in which the mercapto group was desulfurized and hydrogenated were found.

Further, even when a disulfide compound (RSSR) is added to a non-oxidizing pickling solution, RSH and RS (= O) S (= O) R or RH corresponding to the RSSR must be present. I found It was also found that RSH and RSSR were easily converted to each other in a non-oxidizing pickling solution.

These facts indicate that in pickling of stainless steel using a non-oxidizing pickling solution such as a sulfuric acid pickling solution or a hydrochloric acid pickling solution, a compound containing a mercapto group is added as a pickling accelerator. In addition, it shows that even if the corresponding disulfide compound is added, an equivalent pickling accelerating effect appears. It was also found that the concentration of the group of compounds changed with time during the pickling of the steel sheet, and that the concentration of the group of compounds did not change over time after the steel sheet was pulled out of the pickling solution. .

The above findings suggest that pickling of stainless steel using a non-oxidizing pickling solution to which an organic compound for accelerating pickling, such as an organic compound having a mercapto group or an organic compound having a disulfide bond, is added. The added organic compound in the washing solution, the organic compound is quantified the organic compound generated at the time of pickling, it is important to adjust the concentration of the organic compound in the pickling solution based on the obtained quantitative results, Also,
It indicates that there is no point in analyzing the pickling accelerator in the pickling solution unless the group of compounds is analyzed in addition to the initially added compound.

Furthermore, the present inventor has conducted intensive studies on a method for simultaneously analyzing the above-mentioned various compounds in the present examination process, and as a result, it has been found that the concentration of each component can be quantified from the integrated value of the signal of ¹ H-NMR spectrum. The present inventors have found that this is possible and have led to the present invention. According to the analysis method of the present invention, since the sample is not heated in the course of the analysis, each component can be analyzed simultaneously while maintaining the composition of the sulfur-containing compound group contained in the sample.

That is, the first invention is a method for pickling stainless steel using a non-oxidizing pickling solution as the pickling solution,
It is characterized in that the added organic compound in the pickling solution and / or the organic compound generated by the organic compound during pickling are quantified, and the concentration of the organic compound in the pickling solution is adjusted based on the obtained quantification result. This is a method for pickling stainless steel.

The first invention is preferably applied to a method for pickling stainless steel in which the added organic compound is a sulfur-containing organic compound for the purpose of accelerating the pickling rate. The first invention is preferably applied to a method for pickling stainless steel in which the added organic compound is an organic compound having a mercapto group and / or an organic compound having a disulfide bond.

Further, in the first invention, it is preferable that the quantification method is a quantification method based on an integral value of a signal of ¹ H-NMR spectrum. The second invention is
Quantifying the added organic compound in the non-oxidizing pickling solution for stainless steel and / or the organic compound generated by the organic compound during pickling based on the integrated value of the signal of the ¹ H-NMR spectrum. This is a method for analyzing organic compounds in a stainless steel pickling solution.

The second invention is preferably applied to a method for analyzing an organic compound in a stainless steel pickling solution in which the added organic compound is a sulfur-containing organic compound for the purpose of accelerating the pickling rate. Further, the second invention is preferably applied to a method for analyzing an organic compound in a stainless steel pickling solution in which the added organic compound is an organic compound having a mercapto group and / or an organic compound having a disulfide bond.

That is, a preferred embodiment of the second invention is a compound having a mercapto group dissolved in a non-oxidizing pickling solution such as a sulfuric acid solution, a compound having a disulfide bond,
Provided is a method for simultaneously quantitatively analyzing products obtained during pickling, such as sulfoxide and compounds having a structure in which a CS bond of these sulfur-containing compounds is cleaved and a sulfur atom is replaced by a hydrogen atom, using ¹ H-NMR.

In the present invention, the mercapto group (-SH
Organic compounds having a disulfide bond (-SS)
As the additional organic compound having-), the following compounds are preferably exemplified, but the present invention is not limited to the following organic compounds. [1]: an added organic compound having a mercapto group; examples of the added organic compound having a mercapto group in the present invention include:
More preferably, it preferably further has a carboxyl group and / or a hydroxyl group.

This corresponds to the carboxyl group of the organic compound,
Hydroxyl groups are caused by OH caused by oxides on the metal surface
This is considered to be because hydrogen gas is easily separated from the steel sheet surface because of its good affinity with the base group and the COOH group, thereby promoting the dissolution reaction. Preferred examples of the organic compound include mercaptoacetic acid, mercaptoethanol, and mercaptosuccinic acid.

In the present invention, the hydrogen atom of the carboxyl group of the compound before mixing with an acid may be replaced with an alkali metal such as Na or K or an alkaline earth metal such as Ca or Mg. . Further, in the present invention, two or more of the above compounds may be used in combination as the additional organic compound.

[2]: Additional organic compound having a disulfide bond; The additional organic compound having a disulfide bond in the present invention more preferably further has a carboxyl group and / or a hydroxyl group.
This is because, similarly to the above [1], since the carboxyl group and the hydroxyl group of the organic compound have good affinity for OH groups and COOH groups caused by oxides and the like existing on the metal surface, hydrogen gas is applied to the steel sheet surface. This is considered to facilitate the dissolution reaction by facilitating the dissolution reaction.

As the organic compound, the following general formula (1):
It is preferable that the organic compound is one or more organic compounds selected from the aliphatic compounds represented by (2) and aromatic compounds such as dithiosalicylic acid represented by the following formulas (3) and (4). _{S 2 (C n H 2n COOH} ) 2 ····· (1) S 2 (C n H 2n OH) 2 ······· (2) Equation (1), in (2), n is Indicates an integer selected from 1 to 10,
More preferably, n is preferably an integer selected from 1 to 5.

[0032]

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[0033]

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The aliphatic compounds represented by the general formulas (1) and (2) include S ₂ (CH ₂ COOH) ₂ (dithiodiacetate) and S ₂ (CH ₂ CH ₂ COOH) ₂ ( Dithiodipropionic acid) and S ₂ (CH ₂ CH ₂ OH) ₂ (dithiodiethanol) are preferred. Also, the above equation
The aromatic compounds represented by (3) and (4) may have a substituent such as an alkyl group.

Also, in the present invention, the hydrogen atom of the carboxyl group of the compound represented by the above general formula (1) or (3) before mixing with an acid is changed to an alkali metal such as Na or K or Ca,
It may be substituted with an alkaline earth metal such as Mg. The preferred examples of both the added organic compound having a mercapto group and the added organic compound having a disulfide bond in the present invention have been described above, but two or more of these may be used in combination.

Hereinafter, the present invention will be described more specifically. First, an organic solvent is added to a 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 capable of two-phase separation from 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 cannot be 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, for example, diethyl ether, methyl ethyl ketone, or the like can be preferably used.

In the 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, but it is preferable to use sodium sulfate, ammonium sulfate, or a combination of both. it can.

After the organic compound in the pickling solution is extracted with an organic solvent and separated into two phases with water, a certain amount of the organic phase is collected, and the extraction solvent is removed by evaporation. At this time, the extracted analysis target components include compounds that do not have a very high boiling point, so that they are prevented from volatilizing.Also, to prevent the oxidation of the mercapto group and the thermal decomposition of the disulfide compound, heating should be performed as much as possible. It is desirable to avoid.

In consideration of the various conditions described above, in the present invention, it is more preferable to use diethyl ether as the extraction solvent. This is due to the fact that diethyl ether can be easily removed by evaporation at room temperature. Next, a deuterium solvent is added to the sample from which the extraction solvent has been removed to prepare a solution for ¹ H-NMR measurement.

The deuterium solvent used at this time is necessary for ¹ H-NMR measurement, but is not particularly limited as long as it can dissolve the extracted organic components and is miscible with water. Note that the latter condition is because the extract contains water. As the deuterium solvent, heavy water, methanol-d3, acetone-d6 and the like can be used.

[0042] In the present invention, the signal area value of ^{1 H-NMR (: 1 H} -NMR integral values of the signal spectrum) for performing quantitated using a concentration in the solution for the ¹ H-NMR measurement It is necessary to add a substance which becomes a standard of the above. For this purpose, a known amount of an organic compound is added to the measuring solution. The compound used as the internal standard is not particularly limited as long as it is soluble in a polar solvent such as water or methanol and the ¹ H-NMR signal is not close to the compound to be analyzed.

As such a compound, preferably,
For example, dimethyl sulfoxide, acetonitrile, and the like can be used. For each signal belonging to the analysis target component of the ¹ H-NMR spectrum obtained by the measurement,
The concentration of each component is determined from each signal area and the signal area of the compound added as a reference.

[0044]

The present invention will be described below in more detail with reference to examples. Example 1 In a sulfuric acid aqueous solution (sulfuric acid concentration: 240 g / L), the concentration of mercaptoacetic acid as a compound having a mercapto group was adjusted.
4.8 mM was added, and a stainless steel plate was immersed in the obtained aqueous sulfuric acid solution at a liquid temperature of 80 ° C. for 1 hour.

Next, 2 mL of the aqueous sulfuric acid solution after the immersion was collected, saturated with 2 g of sodium sulfate (anhydrous salt), and extracted with 10 mL of diethyl ether. 7 mL of the extract was taken out and the solvent was evaporated off at room temperature. Next, 700 μL of heavy water was added to the remaining liquid to dissolve it, and 20 μL of a dimethyl sulfoxide heavy aqueous solution having a known concentration (70.4 mM) was added, and ¹ H-NMR spectrum was measured.

[0046]¹Mercaptoacetic acid (HS
CH_TwoCOOH), dithiodiacetic acid (HOOCCH) _TwoSSCH_TwoCOOH), HOOC
CH_TwoS (= O) S (= O) CH_TwoCOOH and acetic acid (CH_ThreeCOOH) Signa
Was recognized. Next, the area and base of each signal
Area of signal of dimethyl sulfoxide added as standard
From Table 1, the quantitative values shown in Table 1 were obtained.

As shown in Table 1, when the compound having a mercapto group was added to the pickling solution, the compound (RSH) having a mercapto group initially added was reduced, the compound having a disulfide bond (RSSR), and a large amount were added. It was found that acetic acid was produced. The fact that the combined amount of RSH and RSSR is reduced in a relatively short time reduces the effect of accelerating pickling.According to the present invention, it is possible to appropriately control the concentration of the pickling accelerator. Was.

[0048]

[Table 1]

(Example 2) To a sulfuric acid pickling solution containing no pickling accelerator, 2-mercaptopropionic acid as a compound having a mercapto group was added so as to have a concentration of 5 mM, and the resulting sulfuric acid pickling solution was obtained. A stainless steel plate was immersed therein at a liquid temperature of 80 ° C. for 1 hour. Next, the same operation as in Example 1 described above was performed, and the ¹ H-NMR spectrum was measured.

In the obtained ¹ H-NMR spectrum, signals of 2-mercaptopropionic acid, disulfide of 2-mercaptopropionic acid and propionic acid were recognized.
Next, quantitative values shown in Table 2 were obtained from the area of each signal and the area of the signal of dimethyl sulfoxide added as a reference. As shown in Table 2, when the compound having a mercapto group was added to the pickling solution, the compound (RSH) having a mercapto group initially added was reduced, and both the compound having a disulfide bond (RSSR) and propionic acid were reduced. It was found that a large amount was formed.

The decrease in RSH + RSSR concentration reduces the effect of accelerating pickling. According to the present invention, it is possible to appropriately control the concentration of the pickling accelerator.

[0052]

[Table 2]

As described above, according to the present invention, iron,
A compound having a mercapto group (RSH), a compound having a disulfide bond (RSSR), and a group of compounds formed from these compounds during pickling in a pickling solution of stainless steel in which metals such as chromium and nickel are dissolved, It has become possible to carry out quantitative analysis simultaneously and easily while maintaining the form.

As a result, according to the present invention, the concentration of the pickling accelerator can be controlled appropriately, and the pickling conditions can be controlled appropriately.

[0055]

According to the present invention, an organic additive such as a compound having a mercapto group and a compound having a disulfide bond in a stainless steel pickling solution, and a group of compounds formed from these compounds during pickling, Simultaneous and easy quantitative analysis can be performed while maintaining the compound form.

As a result, according to the present invention, it is possible to appropriately control the concentration of an organic additive such as a pickling accelerator, which is of great industrial significance.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-8-333692 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C23G 1/08 G01N 24/08

Claims (5)

(57) [Claims] 1. A method for pickling stainless steel using a non-oxidizing pickling solution as a pickling solution , wherein the pickling solution after the start of pickling is used.
Then , the added organic compound in the pickling solution and / or the organic compound generated by the organic compound during pickling is quantified,
A method for pickling stainless steel, comprising adjusting the concentration of an organic compound in the pickling solution based on the obtained quantitative results. 2. The method for pickling stainless steel according to claim 1, wherein the added organic compound is an organic compound having a mercapto group and / or an organic compound having a disulfide bond. 3. The method for pickling stainless steel according to claim 1, wherein the quantification method is based on an integrated value of a signal of a ¹ H-NMR spectrum. 4. An organic compound added in a non-oxidizing pickling solution for stainless steel and / or an organic compound produced by pickling of the organic compound is quantified based on an integrated value of a signal of ¹ H-NMR spectrum. A method for analyzing organic compounds in a pickling solution of stainless steel, characterized by comprising: 5. The method for analyzing an organic compound in a stainless steel pickling solution according to claim 4, wherein the added organic compound is an organic compound having a mercapto group and / or an organic compound having a disulfide bond. .