JP6943264B2 - A method for collecting inclusions and / or precipitates in a metal sample, a method for analyzing inclusions and / or precipitates in a metal sample, and an electrolytic solution. - Google Patents

Description

The present invention relates to a method for collecting inclusions and / or precipitates present in a metal material, particularly a steel material, a method for analyzing the collected inclusions and / or precipitates, and electrolysis used at the time of collection. Regarding liquid. In particular, a collection method for collecting the content of chemically unstable inclusions and / or precipitates that are difficult to extract by a normal electrolytic extraction operation, and an analysis method capable of quantifying the content. , And the electrolytic solution used at the time of collection.

The inclusions and / or precipitates (carbides, nitrides, sulfides, oxides, etc.) present in the steel material have a great influence on the quality characteristics of the steel material depending on their existence form, chemical composition, particle size and amount. Affect. Therefore, it is extremely important to know the amount of inclusions and / or precipitates in order to control the shipment of steel products, evaluate quality characteristics, or improve the manufacturing process.

In order to quantify inclusions and / or precipitates, it is necessary to extract and separate inclusions and / or precipitates from the iron matrix in the steel material. Due to recent advances in refining technology and heat treatment technology, the types of inclusions and / or precipitates contained in steel materials have diversified, and have become finer and smaller as the cleanliness of steel materials has improved. Therefore, the method for extracting and separating precipitates and / or precipitates is to extract and separate precipitates and inclusions having various chemical compositions while maintaining their presence in the steel material without decomposition or dissolution. Is required.

As a method for extracting inclusions and / or precipitates, a method of performing electrolysis in a non-aqueous solvent-based electrolytic solution is common. As the non-aqueous solvent-based electrolytic solution, an electrolytic solution using an alcohol containing a supporting electrolyte such as lithium chloride or tetramethylammonium chloride as a solvent is used. As a typical electrolytic solution, for example, 10% acetylacetone-1% tetramethylammonium chloride-methanol (hereinafter, AA-based electrolytic solution), 4% methyl salicylate-1% salicylate-1% tetramethylammonium chloride-methanol (hereinafter, hereinafter). , MS-based electrolyte), 10% maleic anhydride-2% tetramethylammonium chloride-methanol (hereinafter, MA-based electrolyte), etc. are described in Non-Patent Document 1, and among them, AA-based electrolyte is general-purpose. Widely used in.

However, the method of performing electrolysis in a non-aqueous solvent-based electrolytic solution may not be able to extract correctly because inclusions and / or precipitates dissolve or decompose during the electrolysis. Examples of such chemically unstable inclusions and / or precipitates include CaO, CaS, MnS and the like.

By the way, it is known that Ca-based inclusions such as CaO and CaS are dissolved by a small amount of water contained in an alcohol solvent. Therefore, Non-Patent Document 2 proposes a method of analyzing CaO-based inclusions by performing an extraction operation in a glove box in an Ar atmosphere using anhydrous methanol.

On the other hand, Patent Document 1 is chemically unstable when an excess of organic compounds (acetylacetone, tetramethylammonium chloride) contained for the purpose of forming a complex with iron ions among the components in the non-aqueous solvent type electrolytic solution is present. Focusing on the dissolution of various inclusions and / or precipitates, a method for electrolytic extraction with an electrolytic solution having a reduced content of organic compounds is disclosed.

Japanese Unexamined Patent Publication No. 2004-301605

Iron and Steel, 76 (1990) 483. Iron and Steel, 82 (1996) 1017.

Since the method of Patent Document 1 does not pay attention to the amount of water in the electrolytic solution, it cannot be an effective measure when extracting Ca-based inclusions. Further, since the method of Non-Patent Document 1 is an extraction operation in a glove box, the work load is large and equipment is required, and the versatility is poor.

The present invention has been made in view of the above circumstances, and is a method for collecting and analyzing chemically unstable inclusions and / or precipitates in a metal sample without dissolving them, and in a metal sample. It is an object of the present invention to provide an electrolytic solution capable of collecting chemically unstable inclusions and / or precipitates without dissolving them.

The present inventor investigated a method for extracting inclusions and / or precipitates without dissolving them in an electrolytic extraction operation. As described above, the Ca-based inclusions are dissolved in the electrolytic solution during the electrolytic operation because of the slight amount of water contained in the methanol solvent even if the electrolytic solution is a non-aqueous solvent-based electrolytic solution. Has been reported. Therefore, in order to reduce the influence of this moisture, a method of using dehydrated methanol (referred to as dehydrated methanol) and a glove box was examined in accordance with the method described in Non-Patent Document 2.

First, two steel materials having the composition shown in Table 1 having a composition of 30 mm × 40 mm were sampled, the surface was ground and washed with acetone to prepare a test piece. The electrolytic solution was a 10% AA-based electrolytic solution, and one of them was prepared using normal methanol which was not dehydrated, and the electrolytic solution was subjected to an electrolytic operation in an atmospheric atmosphere (condition A). On the other hand, an electrolytic solution was prepared using dehydrated methanol, and an electrolytic operation was performed in a simple glove box in an Ar atmosphere (condition B). The electrolysis conditions were constant current electrolysis. After the completion of electrolysis, under both conditions A and B, the test piece was immediately taken out from the electrolytic solution, immersed in clean methanol prepared separately, and ultrasonically shaken to cause inclusions adhering to the surface of the test piece and After peeling off the / or precipitate to extract inclusions and / or precipitate in methanol, the test piece was taken out and the weight loss was measured. The methanol from which inclusions and / or precipitates were extracted and the electrolytic solution after electrolysis were filtered with a filter, and the amount of Ca as Ca-based inclusions contained in the collected extraction residue was analyzed three times. (Mean value) and standard deviation were analyzed. The analysis results (mean value of Ca amount, standard deviation σ and relative error CV) are shown in Table 2.

The result of condition B has a higher quantitative value of Ca-based inclusions. That is, under condition B, although there is an effect of reducing the dissolution loss by removing water, the accuracy of repeated analysis is poor, and it cannot be said that it is sufficient for quantification. It was presumed that this was because the amount of dehydration of the solvent methanol was not constant for each electrolytic solution, or the amount of water contained in the solvent methanol was not constant due to humidity, the temperature of the electrolytic solution, and the like.

Therefore, as a method for more stable electrolytic extraction, the present inventor has diligently studied a method that is not affected even if water remains in methanol. As a result, by adding an excessive amount of a compound containing a metal element constituting an inclusion and / or a precipitate to be analyzed to the electrolytic solution in advance, even if water remains in the electrolytic solution, the inclusion is present. We came up with the idea that the dissolution of substances and / or precipitates could be prevented.

Using the steel material shown in Table 1, CaS was added to the electrolytic solution under Condition A until precipitation occurred, and then the excess CaS precipitated was removed by filtration to prepare a saturated electrolytic solution. The same electrolytic extraction operation as in Condition A was performed except that this electrolytic solution in which CaS was saturated and dissolved in a small amount of water contained in the electrolytic solution was used (Condition C). The amount of Ca as a Ca-based inclusion contained in the extraction residue was quantified. The results are also shown in Table 2. The quantitative values of Ca-based inclusions increased further, and the variability in the iterative analysis decreased. Therefore, it can be said that Condition C was able to prevent dissolution during the electrolysis operation and analyze the amount of Ca-based inclusions.

The gist structure of the present invention based on the above examination results is as follows.
[1] An electrolysis step of electrolyzing a metal sample in an electrolytic solution and
A collection step in which inclusions and / or precipitates adhering to the rest of the metal sample after the electrolysis step are separated, filtered, and collected.
In the method of collecting inclusions and / or precipitates containing
A method for collecting inclusions and / or precipitates in a metal sample, wherein the electrolytic solution contains a compound containing a metal element constituting the inclusions and / or precipitates to be collected.
[2] The method for collecting inclusions and / or precipitates in a metal sample according to [1], wherein the electrolytic solution is a non-aqueous solvent-based electrolytic solution.
[3] The method for collecting inclusions and / or precipitates in a metal sample according to [1] or [2], wherein the amount of the compound containing a metal element contained in the electrolytic solution is a saturated amount.
[4] An analytical step for analyzing the inclusions and / or precipitates collected by the method for collecting inclusions and / or precipitates in the metal sample according to any one of [1] to [3]. A method for analyzing inclusions and / or precipitates in a metal sample, including.
[5] An electrolytic solution used when a metal sample is electrolyzed in an electrolytic solution, and inclusions and / or precipitates adhering to the rest of the metal sample after the electrolysis are separated, filtered and collected.
An electrolytic solution containing a compound containing a metal element constituting an inclusion and / or a precipitate to be collected.
[6] The electrolytic solution according to [5], wherein the electrolytic solution is a non-aqueous solvent type electrolytic solution.
[7] The electrolytic solution according to [5] or [6], wherein the amount of the compound containing a metal element contained in the electrolytic solution is a saturated amount.

According to the present invention, chemically unstable inclusions and / or precipitates in a metal sample can be collected without being dissolved, and the collected substances can be observed with an electron microscope or the like, or X. By acquiring a line diffraction pattern, the size distribution and structure of inclusions and / or precipitates can be evaluated. Furthermore, the abundance can be quantified by analyzing this collected material. Further, by electrolyzing the metal material using the electrolytic solution of the present invention, even chemically unstable inclusions and / or precipitates in the metal sample can be accurately collected without being dissolved in the electrolysis. can do. As a result, the relationship between the quality of steel products and the existence state of inclusions can be accurately known, and a great effect can be expected in material design and process condition determination.

Next, the present invention will be specifically described. The following description shows a preferred embodiment of the present invention, and the present invention is not limited to the following description.

The method for collecting inclusions and / or precipitates in a metal material of the present invention includes an electrolysis step in which a metal sample is electrolyzed in an electrolytic solution, and inclusions and / or precipitates adhering to the rest of the metal sample after the electrolysis step. It comprises a collection step of separating, filtering, and collecting an object, and is characterized in that the electrolytic solution contains a compound containing metal elements constituting inclusions and / or precipitates to be collected. do. Furthermore, inclusions and / or precipitates collected more by the collection method of the present invention can also be analyzed by an analysis step. Each procedure will be described below.

First, in the electrolysis step, the metal sample is electrolyzed in the electrolytic solution. Any metal material to be measured in the present invention can be used, but it should be applied to steel materials from the viewpoint of industrial applicability of the information obtained by the evaluation method of the present invention. Is valid.

Specifically, as a sample preparation, a metal sample to be analyzed is cut and ground to obtain a test piece, washed with acetone or the like, and then the weight of the test piece is measured.

Next, by electrolyzing the test piece in the electrolytic solution, only the solid solution element in the metal sample is dissolved together with the matrix. It is preferable to use a non-aqueous solvent-based electrolytic solution as the electrolytic solution because it can be applied relatively stably to many inclusions and / or precipitates. As the non-aqueous solvent-based electrolytic solution, in addition to the AA-based electrolytic solution, an MS-based electrolytic solution, an MA-based electrolytic solution, or the like can be used.

In the present invention, the electrolytic solution used in the electrolytic step contains a compound containing metal elements constituting inclusions and / or precipitates to be collected (hereinafter, the compound is simply referred to as a drug). For example, when the inclusions and / or precipitates to be collected contain CaS and CaS as main components, steel slag or continuous casting powder (main component CaO) may be used as the chemicals to be contained, and CaS, CaO, CaCO ₃ , At least one of the commercially available reagents of _{CaSO 4} and Ca (OH) _{2 may be selected.} When the inclusions and / or precipitates are mainly composed of CaS and CaS, even if the inclusions and / or precipitates are complex inclusions in which MnS is compounded or composite inclusions in which oxides such as alumina are compounded, the chemical contains Ca. If so, it can be analyzed. The steel materials shown in Table 1 were subjected to an electrolytic extraction experiment by adding _{CaO, CaCO 3} , CaSO ₄ , and Ca (OH) _{2 to the electrolytic solution instead of CaS under the condition C, but CaS was contained.} The analysis results were almost the same as those in the case of.

In order to obtain the effect of suppressing the dissolution of inclusions and / or precipitates, it is preferable to contain the drug in the electrolytic solution to at least a saturated amount. To allow the electrolytic solution to contain the drug to a saturated amount, the electrolytic solution is added while stirring well until the drug precipitates, and the precipitated drug is removed by a filtration operation. As will be described later, when collecting inclusions and / or precipitates, the electrolytic solution may be directly filtered, so it is important to ensure that the precipitated drug is removed. Depending on the combination of the electrolytic solution and the drug, it may take a long time for the drug to dissolve. Therefore, it is desirable to ensure that the state is saturated (referred to as saturated electrolytic solution).

Next, an electrolytic solution containing metal elements constituting inclusions and / or precipitates to be collected is placed in an electrolytic cell, and constant potential electrolysis or constant current electrolysis is performed using the test sample as an anode. The amount of electrolysis depends on the purpose of extraction and is not particularly limited, but for the purpose of quantitative analysis, it usually dissolves in an amount of about 0.5 to 1.0 g. It is preferable to increase the amount of dissolution by electrolysis as the sample has a stricter cleanliness requirement.

Next, after electrolyzing a predetermined amount of the metal sample, inclusions and / or precipitates extracted by the electrolysis operation are separated from the test sample, filtered and collected. The inclusions and / or precipitates to be analyzed are adsorbed on the surface of the test sample after electrolysis. After removing the test sample from the electrode and gently pulling it out of the electrolytic solution, the test sample after electrolysis is subjected to ultrasonic shaking in methanol to bring the inclusions to be analyzed into methanol from the surface of the test sample and the inclusions to be analyzed. / Or the precipitate is separated, filtered and collected.

For collection, use a filter with a pore size of about submicron so that filtration leakage does not occur, and collect by a general filtration operation such as suction filtration. Large-sized inclusions and / or precipitates may fall off from the surface of the test sample into the electrolytic solution during the electrolytic operation, which causes an error in the analysis / analysis. Therefore, the electrolytic solution after electrolysis is also filtered and collected.

Enclosures and / or precipitates collected on the filter should be washed with clean methanol. If cleaning is not performed, the chemical containing Ca dissolved in the electrolytic solution adheres to the surface of the metal sample, inclusions, and precipitates after electrolysis, and if this is not cleaned and removed, a positive error will occur. Because. The dissolution of inclusions and / or precipitates by washing with methanol described above is at a level that can be ignored in the collection method of the present invention and the quantitative analysis described later.

The collected material obtained by the collecting method of the present invention may be analyzed according to the purpose of evaluation. In the case of quantitative analysis, after decomposing inclusions and / or precipitates by a method such as acid decomposition or alkaline melt decomposition, elemental analysis is performed by ICP emission spectroscopy, atomic absorption spectrometry, or the like. When observing inclusions and / or precipitates which are collectibles with an electron microscope, they can be observed after vapor deposition of carbon or the like is performed on the collectibles to impart conductivity.

Hereinafter, the present invention will be specifically described with reference to Examples, but these do not limit the scope of the present invention.

Hereinafter, as Example 1, an example in which the content of calcium (Ca) -based inclusions in the steel sample is analyzed will be specifically described.

The steel materials having the chemical compositions shown in Table 3 are analyzed by the following analysis methods (the method of the present invention and the comparative method) after cutting two types of steel plates into 30 mm × 40 mm, grinding and cleaning the surface. rice field.

[Method of the present invention]
10 g of CaS powder reagent (manufactured by Tokyo Chemical Industry Co., Ltd.) was added to 300 ml of a 10% AA-based electrolytic solution. When it was stirred well, it was not observed that it was dissolved in the electrolytic solution more than the added amount. Therefore, the mixture was allowed to stand overnight until the next day. Then, the undissolved CaS reagent precipitated on the bottom of the electrolytic solution was removed by a filtration operation, and about 0.5 g was subjected to constant potential electrolysis using a steel sample whose weight was measured in advance with a balance as an anode. After completion of electrolysis, the sample is gently pulled out of the electrolytic solution, transferred to another container containing about 100 ml of methanol, and subjected to ultrasonic shaking to remove inclusions and / or precipitates adhering to the sample surface. It was separated from the metal sample. When the surface of the sample exhibited a metallic luster, ultrasonic shaking was stopped, the sample was taken out of the container, washed with methanol, and then dried. After drying, the sample weight was measured with a balance and subtracted from the sample weight before electrolysis to obtain an accurate electrolysis weight.

The electrolytic solution after electrolysis was suction-filtered using a nucleo-pore filter having a pore size of 0.2 μm. Then, the methanol from which the residue of inclusions and / or precipitates adhering to the sample after electrolysis was extracted was also filtered on the same filter and collected. The collected residue (inclusion) was placed in a platinum crucible together with the filter paper and incinerated using a gas burner. After allowing to cool, 1 g of sodium carbonate and 1 g of sodium tetraborate were added to the crucible, and the mixture was heated again with a gas burner to melt and decompose the collected residue. When the decomposition was completed, the heating was stopped, and after allowing to cool, the crucible was immersed in a beaker containing about 50 ml of (1 + 1) hydrochloric acid, and extraction was performed with an acid on a hot plate at 200 ° C. After the volume of the solvent after extraction was adjusted to 100 ml, the Ca concentration was determined by an ICP emission spectrophotometer and divided by the electrolytic weight to calculate the content of Ca inclusions in the steel.

[Comparison method]
Constant potential electrolysis was performed using a 10% AA-based electrolytic solution in 300 ml of an electrolytic solution to which CaS was not added. The electrolysis conditions and the conditions for separation, filtration, collection, and analysis after electrolysis are the same as in the method of the present invention.

For the method of the present invention and the comparative method, a series of operations from electrolysis to quantification was repeated four times, and the average value and standard deviation of the contents of Ca inclusions were determined.

The results are shown in Table 4.

From Table 4, it can be said that in the method of the present invention, the amount of Ca is high, and the analysis can be performed without eroding the amount of Ca even when compared with the amount of Ca in Table 3. On the other hand, in the comparative method, the amount of Ca varies widely, and the value is lower than that of the amount of Ca in Table 3, so it is judged that lysis loss has occurred, and compared with the method of the present invention. It can be said that it is inferior.

By using the method of the present invention, even chemically unstable inclusions and / or precipitates in a metal sample can be accurately collected without being dissolved in electrolysis, and the amount of Ca-based inclusions can be accurately collected. Can be analyzed highly.

Claims (7)

An electrolysis process in which a metal sample is electrolyzed in an electrolytic solution and
A collection step in which inclusions and / or precipitates adhering to the rest of the metal sample after the electrolysis step are separated, filtered, and collected.
In the method of collecting inclusions and / or precipitates containing
A method for collecting inclusions and / or precipitates in a metal sample, wherein the electrolytic solution contains a compound containing a metal element constituting the inclusions and / or precipitates to be collected. The method for collecting inclusions and / or precipitates in a metal sample according to claim 1, wherein the electrolytic solution is a non-aqueous solvent-based electrolytic solution. The method for collecting inclusions and / or precipitates in a metal sample according to claim 1 or 2, wherein the amount of the compound containing a metal element contained in the electrolytic solution is a saturated amount. In a metal sample, comprising an analysis step of analyzing the inclusions and / or precipitates collected by the method for collecting inclusions and / or precipitates in the metal sample according to any one of claims 1 to 3. Method for analyzing inclusions and / or precipitates. An electrolytic solution used when a metal sample is electrolyzed in an electrolytic solution, and inclusions and / or precipitates adhering to the rest of the metal sample after the electrolysis are separated, filtered and collected.
An electrolytic solution containing a compound containing a metal element constituting an inclusion and / or a precipitate to be collected. The electrolytic solution according to claim 5, wherein the electrolytic solution is a non-aqueous solvent-based electrolytic solution. The electrolytic solution according to claim 5 or 6, wherein the amount of the compound containing a metal element contained in the electrolytic solution is a saturated amount.