JP5359244B2 - Method for analyzing precipitates and / or inclusions in a metal sample - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an analyzing method for separating the deposit or the like (especially being &le;1 &mu;m in size) present in a metal sample without losing the same to precisely analyze the deposit or the like by size. <P>SOLUTION: The remainder of the metal sample is extracted out of an electrolyte during or after electrolysis, and the extracted metal sample is subsequently directly immersed in a dispersible solution to peel the adhered deposit or the like into an aqueous solution type dispersing medium to thereby obtain the highly dispersed deposit or the like. The deposit or the like present in the metal sample is extracted without being lost and flocculated to precisely perform the analysis of the deposit or the like by size, and also the analysis of the deposit or the like by form. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an analysis method for accurately analyzing, for example, the composition and particle size distribution of precipitates and / or inclusions in a metal sample.

  Precipitates and / or inclusions (hereinafter sometimes referred to as precipitates) present in a metal sample may vary depending on the form, size, and distribution of material properties such as fatigue properties, hot And significantly affects cold workability, deep drawability, machinability, and electromagnetic properties. Taking steel as an example, in particular, in recent years, techniques for improving the characteristics of steel products using fine precipitates and the like have remarkably developed, and accordingly, control of precipitates and the like in the manufacturing process has become stricter.

  As a representative example of steel products in which control of precipitates and the like is important, precipitation strengthening type high strength steel can be mentioned. There are various sizes and compositions of precipitates contained in this precipitation-strengthened high-strength steel sheet, but those that improve the characteristics of the steel sheet, those that deteriorate the characteristics, or that do not contribute to the characteristics Can be classified. Therefore, in order to produce an excellent steel sheet, it is important to stably generate beneficial precipitates and suppress the generation of harmful or irrelevant precipitates.

  In general, the interests of precipitates and the like on the properties of the steel sheet are closely related to the size of the precipitates and the like, and fine precipitates and the like contribute to higher strength of the steel sheet. Recently, steel sheets with high strength using nano / sub-nanosize precipitates have been developed. Therefore, it can be said that it is important in optimizing the component design and manufacturing conditions of the steel sheet to grasp the amount and composition of precipitates by size in the submicron to nano-size region.

  On the other hand, a technique for extracting and quantifying precipitates and the like in steel materials has been developed and disclosed on the basis of evaluating the total amount of precipitates and the like for a long time.

  Non-Patent Document 1 includes an acid decomposition method, a halogen method, an electrolysis method, and the like, and it is shown that the electrolysis method is excellent particularly when a precipitate is targeted. However, since the electrolysis method shown in Non-Patent Document 1 focuses on collecting and collecting precipitates in a liquid by filtration, that is, analyzing the total amount of precipitates, You can't get results about size. Furthermore, in the method of Non-Patent Document 1, in a material containing very small precipitates or the like, the agglomeration effect does not sufficiently work, and some precipitates or the like leak from the pores of the filter. There is also a problem.

  In Patent Document 1, as a method of chemically extracting non-metallic inclusions in steel materials and analyzing them by size, steel samples in an electrolytic bath are stored in a polytetrafluoroethylene net and specified. A method of separating and recovering precipitates and the like that are larger than this size is disclosed.

  Patent Document 2 discloses a technique for preventing separation of precipitates and the like by performing filtration while applying ultrasonic waves to the precipitates extracted in a liquid.

  Since the precipitates and the like tend to agglomerate in the liquid basically as the particle size becomes smaller, the method described in Patent Document 1 causes aggregation in the liquid depending on the particle size of the precipitates, and the pore size of the filter. Smaller precipitates and the like will also be collected. Therefore, it is clear that the analysis results by size are inaccurate. In the case of inclusions having a size of 50 μm to 1000 μm, which is the subject of Patent Document 1, there is no particular problem. In the case of precipitates having a size of 1 μm or less, more desirably 200 nm or less), they are likely to easily aggregate in a liquid and are not suitable for practical use.

  In Patent Document 2, similarly to Patent Document 1, coarse precipitates having a size of 1 μm or more that are easy to disaggregate are targeted, and generally the lower limit of sieving is 0.5 μm (see Non-Patent Document 2). Thus, it is difficult to apply to precipitates in the sub-micron to nano-sized region.

  Patent Document 3 discloses a technique for separating precipitates and the like of 1 μm or less by filtration by ultrasonic vibration using an organic filter having a pore diameter of 1 μm or less. However, as in Patent Documents 1 and 2, aggregation separation of fine precipitates of 1 μm or less by ultrasonic waves is impossible.

Non-Patent Document 3 discloses a technique in which precipitates and the like in a copper alloy are extracted and filtered twice with filters having different pore diameters, and the precipitates and the like are classified according to size. However, the problem relating to the aggregation is not solved, and precipitates or the like smaller than the pore diameter of the filter are collected, giving an error to the analysis result by size.
JP 59-141035 A Japanese Patent Laid-Open No. 56-10083 JP 58-119383 A Japan Iron and Steel Institute "Steel Handbook 4th Edition (CD-ROM)" Volume 4 Volume 2 3.5 Agne “Latest Steel Analysis” 58 1979 The Japan Institute of Metals “Materia” Vol. 45, No. 1, p. 52, 2006

As described above, the conventional technology has a problem such as aggregation, and the precipitates in the sub-micron to nano-sized region (particularly, a size of 1 μm or less, more preferably a size of 200 nm or less) are classified by size. There is no technology that makes this analysis practical and accurate.
The present invention has been made in view of such circumstances, and precipitates and the like (especially, a size of 1 μm or less) present in a metal sample are extracted without loss and agglomeration. Provides an analysis method for accurately analyzing each form.

Below, the background that led to the completion of the present invention will be described. In the present invention, precipitates and / or inclusions may be collectively referred to as precipitates.
The electrolytic extraction method disclosed in Non-Patent Document 1 shown in FIG. 5 is a method that can stably extract precipitates and the like in steel by dissolving an iron matrix. It is regarded as a standard method (hereinafter referred to as standard method). And the patent documents 1-3 mentioned above and the nonpatent literature 2-3 are based on this standard method. However, the conventional methods including the standard method have various problems as described above. Therefore, the present inventors have intensively studied to invent a method that is not confined to the conventional standard method. The obtained findings are shown below.

  First, the problems of the above-described conventional method will be summarized. A fundamental problem is that methanol having low dispersibility such as precipitates is used as a dispersion medium such as precipitates. And it is speculated that this has hindered analysis by size of particularly fine precipitates. That is, since Patent Documents 1 to 3 and Non-Patent Documents 1 to 3 use methanol having a low dispersibility as a dispersion medium for precipitates or the like, even if a physical action such as ultrasonic waves is given, the size is 1 μm or less. The precipitates and the like are aggregated, and once aggregated, it is considered impossible to completely separate the aggregates.

  Therefore, in order to solve the aggregation problem, attention was paid to the dispersion of precipitates and the like. As a result, it has been found that dispersibility can be imparted to precipitates and the like including precipitates having a size of 1 μm or less by chemical action with an aqueous dispersion medium (hereinafter sometimes referred to as a dispersible solution). .

  However, since the main component of the electrolytic solution is methanol having low dispersibility, it is necessary to transfer the precipitate or the like to the dispersible solution in order to impart dispersibility to the precipitate or the like. For this purpose, a solid-liquid separation operation for separating precipitates and the electrolytic solution is required. Therefore, the “filtration” operation used as a solid-liquid separation means is performed to collect the precipitates dispersed in the electrolyte and the precipitates extracted in the dispersion medium, which are used in the standard method. As a result, it was found that a part of the precipitates (particularly fine ones having a size of nano / sub-nanometers of 200 nm or less) was lost by filtration.

  Based on this result, further investigations were made to obtain other solid-liquid separation means other than the above-described standard method. As a result, it was found that almost all precipitates and the like remained attached to the steel sample during and / or after electrolysis. This is a completely new knowledge that has not been obtained in the past, and based on this knowledge, solid-liquid separation can be easily realized if the remainder of the steel sample is taken out of the electrolyte during and / or after electrolysis. Then, by combining the above findings for solving the aggregation problem, it is possible to extract precipitates and the like in a dispersive solution that is completely different from the electrolytic solution. The above adhesion phenomenon is presumed to be caused by an electrical action between the steel sample and precipitates during and / or after electrolysis.

  From the above knowledge, in the present invention, the remainder of the metal sample is taken out from the electrolytic solution during or after electrolysis, and then the taken-out metal sample is directly immersed in the dispersive solution to remove the deposited precipitates and the like in the aqueous solution system. It was possible to obtain highly dispersed precipitates and the like by peeling off into the dispersion medium.

The present invention has been made based on the above findings, and the gist thereof is as follows.
[1] An electrolysis step of electrolyzing a metal sample, and the remainder of the metal sample after the electrolysis is immersed in a solution that is different from the electrolytic solution used for the electrolysis and has dispersibility, and deposits in the metal sample and Soaking step for extracting inclusions and / or deposits and / or inclusions dispersed in the dispersible solution are sprayed and monodispersed in the gas phase, introduced into a classifier, and collected separately by particle size. Analyzing the precipitates and / or inclusions extracted into the solution by size, and analyzing at least one of the precipitates and / or inclusions sorted by size; And a method for analyzing precipitates and / or inclusions in a metal sample.
[2] The method for analyzing precipitates and / or inclusions in a metal sample according to [1], wherein an electrostatic classification method is used as the classifier.

  In the present invention, the “size” representing the size of inclusions, etc. means that the major axis and the minor axis are long when the cross section of the precipitate is substantially circular, and long when the cross section is rectangular. The short side of the side and the short side refers to a precipitate having a size of 1 μm or less, such as a precipitate having a short diameter or a short side of 1 μm or less. In addition, precipitates and / or inclusions may be collectively referred to as precipitates.

  According to the present invention, precipitates and the like existing in a metal sample (especially, a size of 1 μm or less, more preferably a size of 200 nm or less) are extracted without loss and agglomeration, and the precipitates are analyzed by size. Furthermore, the analysis according to the form can be performed with high accuracy.

  In the analysis method of the present invention, precipitates and the like (especially, a size of 1 μm or less, more preferably a size of 200 nm or less) in a metal sample are extracted into a solution having dispersibility. It is possible to prevent the precipitates and the like from agglomerating and extract the precipitates and the like as they are in the metal sample.

  In addition, since a dispersible solution for extraction different from the electrolytic solution can be selected arbitrarily, a dispersible solution suitable for precipitates and the like can be used.

  By these, it becomes possible to accurately analyze precipitates by size, and it is possible to provide industrially useful inventions such as quantification by size and accurate particle size distribution, which were impossible in the past. .

Hereinafter, the method for analyzing precipitates in a metal sample of the present invention will be described in detail.
In the method for analyzing precipitates in a metal sample of the present invention, an electrolysis step of electrolyzing a metal sample and the remaining part of the metal sample after electrolysis are made into a solution having dispersibility that is different from the electrolytic solution used for the electrolysis. Immersion step of immersing and extracting precipitates and / or inclusions in the metal sample, and spraying and monodispersing the precipitates and / or inclusions dispersed in the dispersible solution and introducing them into the classifier Then, the precipitates and / or inclusions extracted into the solution are separated according to size by being separately collected according to particle size, and at least one of the precipitates and / or inclusions separated according to the size. An analysis step for analyzing the above.

  Especially, this invention analyzes each deposit etc., after classifying a deposit etc. according to magnitude | size using a classifier. That is, precipitates in a metal sample are extracted and dispersed in a dispersible solution, and after being monodispersed using a spray-type aerosol generator while contained in the dispersible solution, the electrostatic classifier is used. By introducing and charging, and changing the voltage applied to the electrodes to move the charged particles in the classifier, the precipitates and / or inclusions are classified according to size, and then the classifier according to the applied voltage. It is characterized by analyzing precipitates that have passed through the slit. By having these characteristics, it is possible to quantify the precipitates in the steel by particle size or shape.

  The above operating procedure will be described separately as one embodiment of the present invention, until the dispersible solution is optimized and until the precipitates in the steel sample are quantified by size according to the dispersible solution. . FIG. 1 shows an operation flow in the case of optimizing the dispersible solution, and FIG. 2 shows an operation flow in the case of quantifying the precipitates and the like in the steel sample by size.

First, in FIG. 1, (1) to (6) are shown as operation procedures for optimizing the dispersible solution conditions. According to Figure 1,
(1) First, a steel material is processed into an appropriate size to obtain a sample for electrolysis.
(2) On the other hand, a dispersive solution different from the electrolytic solution and having dispersibility is prepared separately from the electrolytic solution for extracting precipitates and the like. Here, in order to disperse the deposits and the like adhering to the surface of the electrolysis sample in the dispersible solution, the amount of liquid less than half of the electrolyte is sufficient. The dispersant for the dispersible solution will be described later.
(3) Electrolyze a sample by a predetermined amount. Note that the predetermined amount is set as appropriate, and as an example, in FIG. 1, the predetermined amount is set to be measurable when used in a zeta potential measuring device.

FIG. 3 is an example of an electrolysis apparatus used in the electrolysis method. The electrolysis apparatus 7 includes an electrolysis sample fixing jig 2, an electrode 3, an electrolytic solution 6, a beaker 4 for containing the electrolytic solution 6, and a constant current power source 5 for supplying current. The fixing jig 2 is connected to the anode of the constant current power source 5, and the electrode 3 is connected to the cathode of the constant current power source 5. The electrolytic sample 1 is connected to the fixing jig 2 and held in the electrolytic solution 6. The electrode 3 is immersed in the electrolytic solution 6 and disposed so as to cover the surface of the sample for electrolysis (mainly the portion immersed in the electrolytic solution 6). For the fixing jig 2, it is most convenient to use a permanent magnet in the case of steel. However, since it will be dissolved by contact with the electrolytic solution 6 as it is, even if a platinum plate is used for the portion easily contacting with the electrolytic solution 6, 2 a between the sample 1 for electrolysis in the case of FIG. 3. good. Similarly, the electrode 3 uses a platinum plate in order to prevent dissolution by the electrolytic solution 6. Electrolysis of the sample 1 for electrolysis is performed by supplying a charge from the constant current power source 5 to the electrode 3. Since the amount of electrolysis of steel is proportional to the amount of charge, the amount of electrolysis can be determined by time if the amount of current is determined.
(4) The sample piece for electrolysis remaining without being electrolyzed (dissolved) is removed from the electrolysis apparatus and immersed in the dispersible solution prepared in (2) above, and precipitates and the like are extracted into the dispersible solution. Here, it is preferable to irradiate ultrasonic waves while being immersed in the dispersible solution. By irradiating with ultrasonic waves, the deposits and the like adhering to the sample surface can be peeled off and extracted into the dispersible solution more efficiently. Next, the sample from which the precipitates and the like are peeled off from the surface is taken out from the dispersible solution. In addition, when taking out, it is preferable to wash | clean a sample with the same solution as a dispersible solution. In addition, it is preferable that a dispersible solution is a composition which has electroconductivity and does not contain as much as possible what remains as a solid, when a solvent is vaporized. If it remains, select a solid that is as fine as possible. In addition, when using a sonic spray or a spray type for the spray system of (8), it is not necessary to limit a solvent to what has electroconductivity.
(5) The zeta potential of the dispersible solution containing precipitates and the like prepared in (4) above is measured.
(6) When the absolute value of the zeta potential measured in the above (5) is less than 30 mV, the above (2) to (6) are repeated by changing the type and / or concentration of the dispersant. On the other hand, when the zeta potential reaches 30 mV or more, the dispersant and concentration at that time are determined as the optimum conditions of the dispersible solution with respect to the target precipitate and the operation is terminated. In FIG. 1, the zeta potential was measured, and when the zeta potential reached 30 mV or more, the dispersant and concentration at that time were determined as the optimum conditions for the dispersible solution with respect to the target precipitate, etc. In this case, the precipitates and / or inclusions may be sufficiently dispersed with little aggregation when collected in the dispersible solution. As a means for selecting and determining the dispersible solution, the zeta potential may be used. It is not limited to measurement. Next, in FIG. 2, (7) to (11) are shown as operation procedures for dividing and quantifying the precipitates and the like in the steel sample by size using the dispersible solution. According to FIG. 2, (7) the same dispersive solution determined by (1) to (6) in FIG. 1 and newly optimized in the same manner as (1) to (4) in FIG. In addition, precipitates or the like that are actually analyzed are extracted.
(8) The solution in which the precipitate is dispersed is sprayed to evaporate the solvent, thereby generating monodispersed fine particles. Spraying is not limited as long as it is a technique that can generate fine droplets. However, in the case of contrasting fine precipitates on the order of μm or less, the following method that can form fine droplets should be used. Is desirable. A thermospray method in which a solution dispersed in a conductive solvent is introduced into a heated capillary and sprayed, and a sample is introduced into the capillary in the same way as a thermospray, but charging is performed by applying a high voltage to the capillary and installing a counter electrode. There are an electrospray method for generating a droplet, a sonic spray method in which a sample is introduced into a capillary and sprayed by a sonic gas flow. By these methods, the precipitate can be separated from the solvent in a monodispersed state and introduced into the gas phase.
(9) The precipitate monodispersed in the gas phase by the above method is introduced into an electrostatic classifier. The produced monodisperse fine particles are transported by using the gas (argon, nitrogen, air, etc.) used in (8) as it is or by replacing it with a gas suitable for a classifier.
(10) The precipitate is fractionated by size using a classifier. An electrostatic classifier is a system that classifies particles according to the electric mobility of the particles, and the electric mobility is inversely proportional to the particle size. Therefore, by adjusting the voltage of the electrode inside the electrostatic classifier, only particles having a specific mobility, that is, precipitates having a specific particle size, move toward the electrode, pass through the slit of the classifier, It becomes possible to take out.
(11) Analyze the precipitates obtained by the above operation and sorted according to size.
Although the quantification method is not particularly specified, it is usually made into a solution by acid decomposition or melting, or a combination method thereof, followed by wet chemical analysis such as volumetric method and spectrophotometry, atomic absorption method, ICP emission analysis method, ICP The constituent elements are quantified by instrumental analysis such as mass spectrometry. When the amount of the precipitate is large, it can be quantified by fluorescent X-ray analysis after being formed into briquettes or glass beads.
The above procedure may be used when analyzing a precipitate composition having a specific particle size, but the following procedure is further added when determining the composition by particle size of the entire precipitate.
(i) Connect a particle counter to the electrostatic classifier and measure the particle size distribution of the precipitate.
(ii) Combine the results of (11) and (i) to calculate the elemental composition of each particle size fraction in the entire precipitate. This method is used when the type and density of precipitates can be almost specified.
If the type of precipitate cannot be specified, the following method is used.
(iii) In the process of spray vaporizing the precipitate dispersion solution obtained in (7), the amount of sample introduced into the sprayer is measured, and the quantitative value of the collected precipitate is calculated without particle size fractionation.
(iv) The quantitative value obtained in (11) / the quantitative value obtained in (iii) × 100 (%) is the precipitate content in the specific particle size fraction of the entire precipitate.
(v) The total amount of precipitates is determined by a conventional precipitate analysis method (for example, electrolytic extraction / alkaline melting-acid dissolution / ICP emission spectrometry).
(v) × (iv) / 100 can be converted into the precipitate content of a specific particle size. Then, by selecting these methods according to the purpose, it becomes possible to quantify the precipitates by particle size and shape.

  By the above method shown in FIG. 1 and FIG. 2, the analysis result regarding the composition according to the size of the precipitate or the like is obtained. Based on the obtained analysis results, knowledge about various properties of the steel material can be obtained, and useful information can be obtained for elucidating the cause of defective products and developing new materials.

  The present invention can be applied to analysis of various types of precipitates in steel, and is particularly suitable for steel materials containing a large amount of precipitates having a size of 1 μm or less, and having a size of 200 nm or less. This is more suitable for steel materials containing a large amount of precipitates.

  In addition, it supplements about the dispersible solution in said (2) here. As described above, there is no clear method for extracting fine precipitates having a size of 1 μm or less (particularly, size of 200 nm or less) as a well-known technique without aggregation in a solution. Therefore, an attempt was made to obtain knowledge about the dispersible solution by sequentially testing the products in which the dispersant was made into an aqueous solution. As a result, regarding the kind and concentration of the dispersant, no clear correlation was obtained between the composition and particle size of the precipitates, the density of the precipitates in the liquid, and the like. For example, as an aqueous dispersion, sodium tartrate, sodium citrate, sodium silicate, potassium orthophosphate, sodium polyphosphate, sodium polymetaphosphate, sodium hexametaphosphate, sodium pyrophosphate and the like are suitable. It was found that addition exceeding the concentration has an adverse effect on the dispersion of precipitates and the like.

  As described above, in the present invention, the dispersible solution is not particularly limited as long as the precipitate and / or the inclusions are dispersed without agglomeration when the precipitate and / or the inclusion is in the solution. In determining the dispersible solution, the type and concentration of the dispersible solution are appropriately optimized according to the properties and density of the precipitates or the subsequent analysis method.

  The precipitates were analyzed according to the procedures (1) to (9) shown in FIG. 1 and FIG. In addition, although the specific conditions of each operation are as showing below, this invention is not restrict | limited to the following specific conditions.

  Titanium-added steel was used as a metal sample. Its chemical composition is C: 0.05 mass%, Si: 0.05 mass%, Mn: 1.3 mass%, P: 0.01 mass%, S: 0.002 mass%, Ti: 0.04 mass%, Nb: 0.01 mass%, N: 0.0035 mass%.

For electrolysis, about 300 ml of 10 vol% acetylacetone-1 mass% tetramethylammonium chloride-methanol solution was used as an electrolytic solution, and constant current electrolysis was performed at 20 mA / cm ² .

  After electrolysis, the remainder of the metal sample taken out from the electrolyte solution was immersed in a 0.01% sodium hexametaphosphate aqueous solution as an acidic solution, and the precipitate was peeled and dispersed from the sample surface layer by ultrasonic penetration.

  This was introduced into an electrospray nebulizer at a sample flow rate of 10 μl / min, and microdroplets were generated at a capillary voltage of 2 kV. Air was used as the carrier gas, and fine particles generated by removing the solvent from the fine droplets were introduced into the electrostatic classifier at 2 L / min. Precipitates of 0.01 μm or more and less than 0.05 μm, 0.05 μm or more and less than 0.1 μm, or 0.1 μm or more and less than 0.2 μm were fractionated with an electrostatic classifier and electrostatically collected on a glass plate.

The precipitate collected on the glass was ultrasonically stripped in a small amount of methanol, then alkali-melted with Na ₂ O ₂ -LiBO ₄ , the molten salt was dissolved in hydrochloric acid, and the contained components were quantified by ICP mass spectrometry.

The total amount of precipitates in steel was also quantified by the same method, and the elemental analysis value for each particle size fraction was converted to the content in steel.
The obtained results are shown in FIG. From FIG. 4, it can be seen that the analysis according to the size of the precipitates (particularly, the size of 1 μm or less) present in the metal sample can be performed with high accuracy.

It is a figure which shows the flow of dispersible solution optimization operation as one Embodiment which concerns on this invention. It is a figure which shows the flow of the quantitative analysis according to magnitude | size as one Embodiment which concerns on this invention. It is a figure which shows typically the structure of the electrolyzer used with the analysis method of inclusions etc. of this invention. Example 1 It is a figure which shows the analysis result of the inclusion content according to magnitude | size in Al, Ti, Nb, Mo, and Mn. Example 1 The flowchart of the standard method currently disclosed by the nonpatent literature 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electrolytic sample 2 Electrolytic sample fixing jig 3 Electrode 4 Beaker 5 Constant current power source 6 Electrolytic solution 7 Electrolytic device

Claims (2)

  An electrolysis step of electrolyzing a metal sample and the remainder of the metal sample after the electrolysis are immersed in a solution different from the electrolytic solution used for the electrolysis and having dispersibility, and precipitates and / or intervening in the metal sample A soaking step for extracting a substance, and spraying the precipitates and / or inclusions dispersed in the dispersible solution to monodisperse them in the gas phase, introduce them into a classifier, and collect them separately according to particle size. An analysis step for separating the precipitates and / or inclusions extracted into the solution according to size and analyzing at least one of the precipitates and / or inclusions separated according to the size. A method for analyzing precipitates and / or inclusions in a metal sample.   2. The method for analyzing precipitates and / or inclusions in a metal sample according to claim 1, wherein an electrostatic classification method is used as the classifier.

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