JP5298810B2 - Method for quantifying precipitates and / or inclusions in metal materials - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for quantifying fine nanometer-sized precipitates and the like in a metal material by size. <P>SOLUTION: The method for quantifying a precipitate and the like in a metal material includes: an electrolysis step of electrolyzing a metal sample in an electrolytic solution; an immersion step of immersing a remaining part of the metal sample extracted from the electrolytic solution in a dispersive solution; a separation step of filtering the precipitate and the like separated in the dispersive solution by a filter at least once; and a quantification step of quantifying a focused element content of the precipitate and the like captured by the filter. The relationship between the electrolyzed quantity and the quantified focused element content is determined by repeatedly performing the electrolysis step to the quantification step while changing the electrolyzed quantity of the metal sample in the electrolysis step. The focused element content of the precipitate and the like, when the electrolyzed quantity is extrapolated to 0, is determined to be the focused element content of the precipitate and the like having a size larger than a size defined from a filter hole size. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a method for quantifying precipitates and / or inclusions (hereinafter referred to as precipitates) in a metal material, and more particularly to a method for quantifying fine precipitates having a nanometer size by size.

  Precipitates and the like present in a metal material have a great influence on various properties of the material, such as mechanical properties and electromagnetic properties, depending on the form, size, and distribution. In particular, in the field of steel, in recent years, techniques for improving the properties of steel materials using precipitates and the like have been remarkably developed, and accordingly, control of precipitates and the like in the manufacturing process has become important.

  Generally, precipitates and the like contained in steel materials include those that improve properties, those that degrade properties, or those that do not contribute to properties, depending on the size and composition, in order to produce steel materials with desired properties. It is important to stably generate precipitates having a certain size and composition. For example, in precipitation-strengthened high-tensile steel sheets, fine precipitates are generated to increase the tension of the steel sheet. Has been done. Therefore, there is a strong demand for a method capable of specifying and quantifying elements contained by size for precipitates of nanometer to submicrometer size.

  Non-Patent Document 1 includes acid decomposition method, halogen method, electrolysis method, etc. as techniques for quantifying precipitates and the like in steel materials, and in particular, the electrolysis method performed by the procedure shown in FIG. 1 is excellent. It is shown that. In this electrolysis method, a filter is used as a solid-liquid separation means for recovering precipitates separated in the electrolytic solution by dissolving the iron matrix in the electrolytic solution, and relatively small aggregates and relatively large aggregates. Combined with blockage of filter holes due to deposits, etc., that is, due to blockage of filter holes due to relatively large precipitates, etc., relatively small aggregates etc. aggregated on the filter and cake filtered (deposited deposits) The filtration mechanism in which the filter itself functions as a filter is further functioned, and all precipitates and the like are collected. Therefore, although it is possible to quantify the total amount of precipitates and the like, it is not possible to obtain knowledge regarding the size of the precipitates and the like.

On the other hand, several techniques for quantifying precipitates by size are proposed based on the method described in Non-Patent Document 1, all of which are used to eliminate aggregation of precipitates and cake layers (on the filter). The main purpose is to prevent the formation of deposits. For example, in Patent Document 1, nonmetallic inclusions in steel materials are chemically separated into liquid, and during filtration, ultrasonic waves are effectively applied using a metal filter to eliminate aggregation of nonmetallic inclusions. And a technique for separating non-metallic inclusions according to size in order to prevent formation of a cake layer. However, the technique of Patent Document 1 is an effective method for coarse non-metallic inclusions of several micrometers or more, but there are problems in applying it to extremely fine precipitates of nanometer to submicrometer size. is there. This is because finer particles exhibit stronger agglomeration properties in liquids, so that aggregation can be eliminated even when ultrasonic waves are applied to aggregates such as precipitates of nanometer to submicrometer size. This is because it is difficult and there is no metal filter having filter holes of nanometer to submicrometer size in order to sufficiently exert the effect of ultrasonic waves. Patent Document 2 discloses a technique that uses an organic filter having a filter pore diameter of 1 μm or less and applies ultrasonic vibration to separate precipitates of 1 μm or less. However, in the technique of Patent Document 2, as in Patent Document 1, it is difficult to eliminate aggregation of fine precipitates of 1 μm or less using ultrasonic waves. In addition, unlike metal filters, organic filters are not sufficiently propagated and reflected by ultrasonic waves, so the clogging of filter holes cannot be eliminated by ultrasonic vibration, and a cake layer is formed on the aforementioned filter. Thus, the precipitates according to the filter pore diameter are not separated. Non-Patent Document 2 discloses a technique for separating precipitates and the like in a copper alloy according to size by using filters with different filter pore diameters and performing filtration twice. However, even the technique of Non-Patent Document 2 does not solve the problems related to the aggregation of precipitates and the formation of a cake layer, and cannot be quantified by size.
Japanese Patent Publication No.53-37595 JP 58-119383 A Japan Iron and Steel Association "Steel Handbook 4th Edition (CD-RM)" Vol. 4, 2 3.5 The Japan Institute of Metals “Materia” Vol. 45, No. 1, p. 52 (2006)

  As described above, in the prior art, there is a problem of agglomeration of precipitates and the formation of a cake layer, and precipitation of nanometer to submicrometer size (particularly, size 1 μm or less, more preferably size 200 nm or less). Things cannot be quantified by size.

  This invention is made | formed in view of this situation, and makes it a subject to provide the method of quantifying the nanometer-sized fine deposits etc. which are contained in a metal material according to magnitude | size.

  The electrolytic extraction method disclosed in Non-Patent Document 1 shown in FIG. 1 is a method capable of stably recovering precipitates in steel, etc. by dissolving an iron matrix. It is regarded as a standard method for quantification (hereinafter referred to as standard method). Patent Documents 1 and 2 described above 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.

  To sort out the problems of the above-mentioned standard method, methanol that has low dispersibility with respect to precipitates, etc. is used as a dispersion medium for separated precipitates, etc., and a filter that is easy to close is suitable for total recovery. It is presumed that there was a fundamental problem in that the separation of fine precipitates and the like by size was hindered. In other words, since methanol, which has low dispersibility with respect to precipitates, is used as a dispersion medium, fine precipitates easily agglomerate, and even if a physical action such as ultrasonic waves is applied, the aggregation is completely eliminated. In addition, if a filter that easily closes is used, agglomerated precipitates close the filter pores and a cake layer is easily formed. It is thought that it becomes difficult to sort precipitates by size.

  Accordingly, the present inventors first examined a dispersion medium such as precipitates in order to eliminate aggregation of precipitates and the like, and found that electricity by an aqueous dispersion medium (hereinafter referred to as a solution having dispersibility) was used. It has been found that dispersibility can be imparted to precipitates having a size of 1 μm or less by chemical action.

  However, since the main component of the electrolytic solution used in the standard method is methanol with low dispersibility, in order to impart dispersibility to the precipitate, etc., the precipitate is changed from the electrolytic solution to a solution having dispersibility. It is necessary to move. For this purpose, a solid-liquid separation operation for separating the precipitate and the electrolytic solution is required. Therefore, according to the conventional standard method, as a solid-liquid separation means that is performed to recover the precipitates in the electrolytic solution and the precipitates separated in the dispersion medium (specifically methanol). When the “filtration” operation was performed, it was found that some of the precipitates (particularly, sub-nanometers having a size of 200 nm or less to fine ones having a nanometer size) may be lost by the filtration.

  Based on this result, in order to obtain solid-liquid separation means other than the conventional standard method, further examination was performed using steel samples. As a result, it was found that almost all precipitates and the like remain attached to the steel material sample during and / or after electrolysis. This is a completely new knowledge that has not been obtained so far. From this knowledge, solid-liquid separation can be easily realized if the remainder of the steel material sample is taken out from the electrolyte during and / or after electrolysis. Then, by combining the above findings for solving the aggregation problem and separating the precipitates in the dispersible solution, the aggregation of the precipitates can be eliminated. Although details of this adhesion phenomenon are unknown, it is presumed to be due to the electrical action of the steel material sample and precipitates during and / or after electrolysis.

  In this manner, precipitates and the like attached to the steel material sample are highly dispersed by an electrochemical action in a solution having dispersibility, whereby aggregation of the precipitates and the like can be eliminated. As a result, as in Patent Documents 1 and 2, it is no longer necessary to apply the physical action of ultrasonic waves in a solvent (including water and methanol) during filtration, which hinders the use of ultrasonic waves. It is also possible to apply a filter having a fragile material or structure or a non-aqueous solvent-soluble filter that has prevented the use of methanol.

  In the present invention, the scope of the present invention is not limited to the case of analyzing only the deposits and the like attached to the remainder of the metal sample. That is, in addition to precipitates and the like attached to the remainder of the metal sample, analysis results such as precipitates contained in the electrolytic solution for some reason can be added. Thereby, the analysis value may be more accurate.

  Next, as a result of repeated investigations on the problem of the formation of the cake layer, the inventors have reduced the density of precipitates separated from the metal sample during electrolysis with respect to the same area of the filter to pass through, Focusing on the fact that the clogging of the metal sample is less likely to occur and the formation of the cake layer is suppressed, and that the density of the precipitate separated from the metal sample and the amount of electrolysis of the metal sample have a positive correlation, It was found that the precipitates and the like can be quantified by size by using the quantitative value when the amount of electrolysis is extrapolated to 0 by obtaining the relationship with the quantitative results such as. The details will be described below.

  When a solution containing precipitates and the like not aggregated is filtered with a filter having a predetermined filter pore size, ideally, the precipitates collected by the filter according to the filter pore size and the size of the precipitates, etc. It should be separated into precipitates and the like passing through the filter. However, in practice, precipitates and the like that should pass through may be collected by the filter due to the blockage of the filter holes. This is a cross-linking phenomenon that occurs when a single precipitate, etc., larger than the filter pore diameter cannot completely close one filter pore (the moving particles in the liquid are blocked and overlapped at the opening of the filter pore and its surroundings). This is probably due to the formation of arches. That is, a cake layer is formed by this cross-linking phenomenon, and precipitates having a size smaller than the filter pore diameter are also collected by the filter. Therefore, even if the precipitates collected by the filter are quantified, the precipitates having a size larger than the filter pore diameter are not quantified. Similarly, the precipitates that should pass through the filter are collected by the filter due to the filter hole clogging, so even if the precipitates in the filtrate that has passed through the filter are quantified, the size is smaller than the filter hole diameter. This does not mean that the amount of precipitates etc. was quantified.

Now, if the amount of electrolysis m of the metal sample is increased by Δm and filtered through a filter with a new amount of electrolysis (m + Δm), the effect of the filter hole clogging on the precipitates etc. present in the amount of electrolysis Δm It is significantly larger than the case. Therefore, in an ideal case where the filter layer is not clogged and the cake layer is not formed, the quantitative result of precipitates, that is, the content of the element of interest should be constant regardless of the amount of electrolysis. the amount (m + Δm) content C _{m + Delta] m} of the aimed element in is greater than the content of C _m of the target element in the electrolyte quantity m. Conversely, if the amount of electrolysis m is reduced by Δm and filtered with a new electrolysis amount (m-Δm), the formation of the cake layer is suppressed, and the content of the element of interest in the new electrolysis amount (m-Δm) C _m−Δm is smaller than the content C _{m of the} element of _interest in the electrolysis amount m. Therefore, as shown in the following formulas (1) and (2), when the amount of electrolysis m is set to 0, an ideal case where the filter layer is not blocked and the cake layer is not formed is achieved, and the content ratio of the element of interest Will be obtained.

here,
R _m : Weight of the element of interest collected in a filter having a predetermined filter pore size when the amount of electrolysis is m,
F _m : Weight of the element of interest that has passed through a filter having a predetermined filter pore size when the amount of electrolysis is m,
C _Rm : Content of the element of interest obtained from precipitates collected in a filter having a predetermined filter pore size when the amount of electrolysis is m (the total composition of the sample is set as a reference (= 1)),
C _Fm : Content of the element of interest obtained from precipitates in the filtrate that passed through a filter having a predetermined filter pore size when the amount of electrolysis is m (the total composition of the sample is set as a reference (= 1)),
C _R : the content of the element of interest contained in precipitates having a size larger than the size defined by the filter pore size of the predetermined filter in the sample (with the total composition of the sample as the reference (= 1)),
C _F : Content ratio of the element of interest contained in precipitates having a size less than the size defined by the filter pore size of the predetermined filter in the sample (with the total composition of the sample as the reference (= 1)),
It is. Here, the size defined from the filter hole diameter means not the nominal filter hole diameter but the minimum size of precipitates or the like actually collected by the filter hole diameter.

  However, since the amount of electrolysis cannot actually be reduced to zero, the amount of electrolysis m is varied to quantify the content of the element of interest in the precipitates and the like, and the amount of electrolysis m and a filter with a predetermined filter pore diameter are captured. Find the relationship with the content of the element of interest contained in the collected precipitates, etc. or the precipitate passed through the filter, and extrapolate the amount of electrolysis to 0 to obtain the content, then the element of interest contained in the precipitate, etc. The content of can be quantified.

  The present invention was made based on the above knowledge, an electrolysis step of electrolyzing a metal sample in an electrolytic solution, an immersion step of immersing the remainder of the metal sample taken out of the electrolytic solution in a solution having dispersibility, A separation step of filtering the precipitate separated into the dispersible solution at least once with a filter, and a quantification step of quantifying the content of the element of interest contained in the precipitate collected in the filter And changing the amount of electrolysis of the metal sample in the electrolysis step, repeating from the electrolysis step to the quantification step, obtaining the relationship between the electrolysis amount and the content of the quantified element of interest, and setting the electrolysis amount to 0 The content rate when extrapolated is the content rate of the element of interest contained in precipitates having a size greater than the size defined from the filter pore diameter of the filter It provides a method of quantifying a precipitate or the like of the genus material.

  The present invention also separates an electrolysis step of electrolyzing a metal sample in an electrolyte solution, an immersion step of immersing the remainder of the metal sample taken out of the electrolyte solution in a solution having dispersibility, and the solution having dispersibility. A separation step of filtering the deposited precipitates etc. once or more with a filter, and a quantification step of quantifying the content of the element of interest contained in the precipitates etc. that have passed through the filter, and in the electrolysis step, The amount of electrolysis was changed and the electrolysis step to the quantification step were repeated to determine the relationship between the amount of electrolysis and the content of the quantified element of interest, and the content when the amount of electrolysis was extrapolated to 0 Providing a method for quantifying precipitates in metal materials characterized by the content of the element of interest contained in precipitates having a size less than the size defined by the filter pore size To.

  In the quantification method of the present invention, it is preferable to use a filter having a straight hole and a porosity of 4% or more in the fractionation step. Here, the straight hole means a filter hole penetrating the filter surface with a certain opening shape. Moreover, it is preferable to quantify the deposits and the like adhering to the remainder of the metal sample in the quantitative step. Furthermore, in the immersion step, the solution having dispersibility preferably has an absolute value of zeta potential of 30 mV or more with respect to the precipitate to be quantified.

  According to the present invention, fine precipitates and the like (especially, a size of 1 μm or less, more preferably a size of 200 nm or less) present in a metal material can be separated without loss and aggregation, so It can be quantified separately. The result obtained by the quantification method of the present invention provides new knowledge about various properties of the metal material, and provides useful suggestions for elucidating the cause of defective products and developing new materials.

  The characteristic of the quantitative method of the present invention is that the remainder of the metal sample to which the deposits and the like after electrolysis are attached is immersed in a solution having dispersibility and separated without agglomerating the deposits and the like attached to the sample, The purpose is to separate and quantify precipitates and the like separated in a solution having dispersibility by a filter. Therefore, taking a steel sample as an example, a procedure for optimizing a dispersible solution for separating precipitates and a procedure for separating and quantifying separated precipitates with a filter will be described in detail below. .

1) Optimization procedure for a solution having dispersibility Fig. 2 shows an operation flow for optimizing a solution having dispersibility. Optimization of the solution having dispersibility is performed according to steps (1) to (6) shown in FIG. 2, and in each step, the following is specifically performed.
Step (1): A steel material is processed into an appropriate size to obtain a sample for electrolysis.
Step (2): A solution different from the electrolyte and having dispersibility is prepared separately from the electrolyte for separating 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 solution having dispersibility will be described later.
Step (3): Electrolyze a sample by a predetermined amount. Here, the predetermined amount is set as appropriate, and is an amount capable of performing zeta potential measurement and elemental analysis described later. Electrolysis can be performed by an electrolysis apparatus 7 as shown in FIG. The electrolyzer 7 includes a fixing jig 2 for the sample 1, an electrode 3, an electrolyte solution 6, a beaker 4 for containing the electrolyte 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 sample 1 is connected to the fixing jig 2 and immersed in the electrolytic solution 6. The electrode 3 is immersed in the electrolytic solution 6 and is disposed so as to cover the surface of the sample 1 immersed in the electrolytic solution 6. It is most convenient to use a permanent magnet as the fixing jig 2 for the normal steel material sample. However, since the permanent magnet may come into contact with the electrolytic solution 6 and dissolve, a platinum plate is used in the portion 2a in FIG. Similarly, the electrode 3 uses a platinum plate in order to prevent dissolution by the electrolytic solution 6. Electrolysis of the sample 1 is performed by supplying a charge from the constant current power source 5 to the electrode 3. Since the amount of electrolysis of the sample is proportional to the amount of coulomb, it is determined by the electrolysis time if the current is constant.
Step (4): Remove the sample left unelectrolyzed from the electrolyte and immerse it in the solution with dispersibility prepared in step (2) to disperse the deposits adhering to the sample. Separate into solution. At this time, ultrasonic waves are applied while the sample is immersed in the dispersible solution in order to more efficiently separate the deposits and the like adhering to the sample and separate them into the dispersible solution. It is preferable. And although a sample is taken out from the solution which has dispersibility, when taking out, it is preferable to wash | clean a sample with the same solution as the solution which has dispersibility.
Step (5): Measure the zeta potential of the dispersible solution from which the precipitates and the like after step (4) are separated.
Step (6): If the absolute value of the zeta potential measured in step (5) is less than 30 mV, change the type and concentration of the dispersant and repeat steps (2) to (6). On the other hand, it is assumed that a solution having dispersibility is optimized when the absolute value of the zeta potential reaches 30 mV or more.

  In FIG. 2, 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 analysis method, there is no problem if the precipitates are sufficiently dispersed without agglomerating in the dispersible solution. Therefore, the optimization index of the dispersible solution is limited to the zeta potential. It is not something. Details of the dispersible solution and the zeta potential will be described later.

2) Classification and quantification procedure of separated precipitates Fig. 4 shows an operation flow for separating and quantifying the separated precipitates by size according to their size. The separation and quantification of precipitates and the like are performed according to steps (7) to (10) shown in FIG. 4, and the following is specifically performed at each step.
Step (7): Using the solution having dispersibility optimized in the operation of FIG. 2, the precipitates and the like are separated into the solution having dispersibility by the same steps (1) to (4) as in FIG. In step (3), the coulomb amount is set so that the amount of electrolysis of the sample becomes a predetermined amount of electrolysis Wn.
Step (8): The dispersible solution containing precipitates and the like is filtered using a filter having a predetermined filter pore diameter D, and the precipitates collected by the filter and the precipitates and the like that have passed through the filter are acidified. After dissolution, the element of interest is quantified, and the contents of the element of interest contained in the precipitate collected by the filter and the precipitate passed through the filter, C _R n and C _F n are obtained.
Step (9): The operations of steps (7) and (8) are repeated with an electrolysis amount Wn + 1 different from the electrolysis amount Wn to obtain C _R n + 1 and C _F n + 1. The amount of electrolysis to be changed is at least 2 levels, preferably 4 levels.
Step (10): The relationship between Wn and C _R n or C _F n obtained by the above operation is formulated by regression calculation, and the amount of electrolysis Wn is 0, that is, the amount of electrolysis Wn is extrapolated to 0 _CR or C _F is obtained, and the content of the element of interest contained in precipitates having a size greater than or equal to the size D defined by the filter pore diameter, the size less than the size D defined by the filter pore size, respectively. The content of the element of interest contained in the precipitates of Note that linear regression calculation is sufficient for regression calculation, but higher-order regression calculation can also be applied.

  The quantification method of the present invention described above can be applied to quantification of precipitates in various metal materials, and is particularly suitable for steel materials containing a large amount of precipitates having a size of 1 μm or less, It is more suitable for steel materials containing a large amount of precipitates having a size of 200 nm or less.

3) About the solution having dispersibility The solution having dispersibility in the above step (2) will be supplemented. Currently, there is no dispersible solution that can be separated without agglomerating fine precipitates having a size of 1 μm or less. Therefore, when examining an aqueous solution of a dispersant used for particles having a size of 1 μm or more, the type and concentration of the dispersant, the composition and size of the precipitate, and the density of the precipitate in the solution, No clear correlation was obtained. For example, as the dispersant, sodium tartrate, sodium citrate, sodium silicate, orthophosphoric potassium, sodium polyphosphate, sodium polymetaphosphate, sodium hexametaphosphate, sodium pyrophosphate and the like are suitable. The knowledge that precipitates and the like aggregate when the concentration is exceeded was obtained. From the above, when optimizing a solution having dispersibility, the type and concentration of the dispersant are appropriately optimized according to the properties and density of precipitates or the subsequent quantification method.

  The reason for using the zeta potential as an index for optimizing a solution having dispersibility is that when an aqueous solution containing a dispersant as described above is used, there is a close correlation between the surface charge of the precipitate and the dispersibility. In addition, it was found that the optimum dispersive solution conditions (such as the type of dispersant and the appropriate concentration of addition) can be determined by grasping the surface charge state using a zeta electrometer. In other words, the smaller the precipitates and the like, the easier it is to agglomerate in the liquid. By adding an appropriate dispersant at an appropriate concentration, charges are applied to the surface of the precipitates and repel each other, preventing aggregation. It is thought that it is done. From this result, it is easy to use the value of zeta potential as an index when determining the type and concentration of the dispersible solution, but it is surely the optimum dispersive solution conditions (type of dispersant and appropriate It seems desirable from the point that it is possible to determine the added concentration and the like. As a result of repeated studies, the developers have found that the zeta potential is preferably as large as possible from the viewpoint of dispersing precipitates and the like. Furthermore, in the quantification of precipitates and the like, it was found that if an absolute value of about 30 mV or more was obtained, agglomeration could be prevented and the quantification of precipitates or the like could be performed.

  From the above, when determining the type and concentration of the dispersible solution for separation of precipitates, etc., it is preferable to use the zeta potential value as an index. The absolute value of the zeta potential is preferably 30 mV or more.

4) Filters The filter in step (8) above is supplemented. In the size separation of precipitates and the like, which are the main subject of the present invention, it is possible to reliably separate precipitates and the like that are larger than the size defined from the filter pore diameter and precipitates that are less than the size defined from the filter pore diameter. is necessary. For this purpose, it is preferable that the filter has a porosity of 4% or more and the filter hole has a straight hole. This is because if the porosity is less than 4%, the pores are likely to be clogged with coarse particles or aggregated particles, and if the filter pores are not straight holes, the separation resolution by the size of precipitates etc. tends to decrease. It is. As an example of the method for calculating the porosity, the following equation (3) is available.
Porosity = (filter volume-filter weight / specific gravity) / filter volume x 100 (%) (3)

  According to the procedures of steps (1) to (6) shown in FIG. 2, the relationship between the titanium content in the precipitates and the zeta potential was examined. Specific conditions for each operation are as follows, but the present invention is not limited to the following specific conditions.

  Carbon steel added with titanium containing C: 0.09%, Si: 0.12%, Mn: 1.00%, P: 0.010%, S: 0.003%, Ti: 0.18%, N: 0.0039% by mass% The electrolysis apparatus shown in FIG. 3 was used for electrolysis in about 300 ml of 10% AA electrolyte (10 vol% acetylacetone-1 mass% tetramethylammonium chloride-methanol). Then, the carbon steel remaining after the electrolysis is immersed in an aqueous solution of sodium hexametaphosphate (hereinafter referred to as SHMP) whose concentration is changed to 7 levels within a range of 0 to 2000 mg / l which is a dispersible solution, and precipitates The zeta potential at each concentration was measured with a zeta potentiometer. As a result, as shown in FIG. 5, it can be seen that the absolute value of the zeta potential increases as the concentration of SHMP increases. Note that even when a sodium pyrophosphate aqueous solution was used as the dispersible solution, the same tendency as in FIG. 5 was obtained. Thus, it can be seen that the zeta potential can be controlled by the type and concentration of the dispersant.

  Next, using a filter having a straight hole and a porosity of 47% obtained by electron microscope observation and a filter pore diameter of 100 nm, the operations of steps (7) to (9) in FIG. The titanium content (ratio to the whole steel) in precipitates having a size defined by As a result, as shown in FIG. 6, when the absolute value of the zeta potential is less than 30 mV, the smaller the absolute value of the zeta potential, the more the precipitates are agglomerated, and the titanium content in the precipitates apparently increases. When the absolute value of the zeta potential is increased to 30 mV or higher, the titanium content in the precipitates becomes constant and the dispersibility of the precipitates is good.

  In the quantification method of the present invention, there is no problem as long as the precipitates are sufficiently dispersed without agglomerating in the dispersible solution. Therefore, as an index of optimization of the dispersible solution, zeta The potential is not limited.

  The carbon steel ingot containing titanium having the composition shown in Table 1 is divided into two parts, sample P and sample Q. Sample P is heated at 1200 ° C for 60 minutes and then cooled with water, and sample Q is 1200 ° C. After heating for 60 minutes, it was hot-rolled at a finishing temperature of 930 ° C. and heated to 630 ° C. for 60 minutes. When both samples were observed with an electron microscope after the treatment, precipitates of titanium nitride and titanium carbide as shown in Table 2 were confirmed. Large titanium nitride and titanium carbide with a size of 1 μm or more observed in both samples are produced during the solidification process of the steel and do not melt even at a high temperature of 1200 ° C. it can. On the other hand, the fine titanium carbide having a size of about 10 nm observed only in the sample Q is not observed in the sample P that is heated at 1200 ° C. for 60 minutes and then water-cooled. It can be considered that it was produced during heating for a minute.

(Invention example)
Using the electrolysis apparatus shown in FIG. 3, the currents of sample P and sample Q in which such precipitates and the like are generated are adjusted so that the amount of electrolysis is about 0.1 g in about 300 ml of 10% AA-based electrolytic solution. Constant current electrolysis was performed at a density of 20 mA / cm ² . The electrolyzed sample was immersed in 50 ml of a 0.05% by mass SHMP aqueous solution having dispersibility, and the precipitate adhered to the sample surface was separated into the SHMP aqueous solution by applying ultrasonic vibration. At this time, the zeta potential of the SHMP aqueous solution from which precipitates and the like were separated was measured and found to be about -32 mV. The SHMP aqueous solution from which precipitates and the like were separated was filtered using a filter A having a filter pore diameter of 100 nm, a straight hole, a porosity of 4%, and a porosity of 47%, and then filtered. The collected precipitates and the filtrates obtained by drying the filtrate are heated and dissolved in a mixed solution of nitric acid, perchloric acid and sulfuric acid, and then the respective precipitates are analyzed by ICP emission spectrometry. The absolute amount of titanium in the same was quantified. This titanium absolute amount was divided by the amount of electrolysis, and the titanium content in the precipitate collected in the filter and in the precipitate passed through the filter was determined.

  The same operation was performed by changing the amount of electrolysis of the sample to 0.2 g, 0.3 g, and 0.5 g. The relationship between the amount of electrolysis and the titanium content in the precipitates collected in the filter, and the amount of electrolysis and the filter The relationship with the titanium content in the precipitates that passed through was determined.

  Approximate the relationship between the amount of electrolysis and the titanium content in the precipitates for each of the obtained precipitates, and obtain the titanium content when the amount of electrolysis is 0 g. From the filter pore diameter collected in the filter The titanium content in the precipitates and the like having a size not less than the size defined and the titanium content in the precipitates and the like having a size less than the size defined from the filter pore diameter that passed through the filter. Here, the titanium content is expressed in ppm by mass, and is a value when the total composition including Fe of the sample is 100% by mass.

(Comparative example)
The sample after electrolysis was processed in the same manner as the invention example except that pure water with low dispersibility was used instead of the SHMP aqueous solution and only the filter A was used. The titanium content in precipitates and the like having a size greater than or equal to the size of the precipitate and the titanium content in precipitates and the like having a size less than the size defined from the filter pore diameter that passed through the filter were determined. The zeta potential of pure water from which precipitates and the like were separated was measured and found to be about -0.1 mV. The titanium content here is expressed in ppm by mass, and is a value when the total composition including Fe of the sample is 100% by mass.

  7 and 8 show the relationship between the amount of electrolysis and the titanium content in the precipitates collected in the filter, and the amount of electrolysis and the filter passing through the filter, in the sample P having only a precipitate of 1 μm or more in size. The relationship with the titanium content rate in the deposited precipitate etc. is shown. From the results of these figures, the titanium content in the precipitates etc. collected in the filter and the titanium content in the precipitates etc. that passed through the filter are both invention examples and comparative examples having different filter porosity. It can be seen that there is no difference between the two, and that even if the amount of electrolysis is changed, it is constant. Therefore, it can be considered that the titanium content in these precipitates and the like is quantified by size. In addition, since the filter pore diameter is 100 nm, in the sample P having only precipitates having a size of 1 μm or more, the titanium content in the precipitates passing through the filter should be 0 mass ppm, but according to the result of FIG. That is supported.

  9 and 10, in the sample Q having precipitates having a size of 1 μm or more and precipitates having a size of about 10 nm, etc., the amount of electrolysis and the titanium content in the precipitates collected by the filter And the relationship between the amount of electrolysis and the titanium content in the precipitates and the like that have passed through the filter. From the results of FIG. 9, in the inventive examples having different porosity of the filter, the titanium content in the precipitates collected in the filter when the amount of electrolysis is 0 g is not different depending on the porosity, and is shown in FIG. It can be seen that the titanium content in the precipitates of sample P and the like is almost the same. This supports the inference that precipitates with a size of 1 μm or more are generated during the solidification process of steel, and the titanium content in the precipitates by the method of the present invention is classified according to the size of the precipitates. It shows that it can be quantified. Further, from the results of FIG. 10, in the invention examples having different porosity of the filter, the titanium content in the precipitate etc. that passed through the filter when the amount of electrolysis was 0 g was almost the same with no difference due to the porosity. It can be seen that the titanium content in the precipitates and the like can be determined by the size of the precipitates by the method of the present invention.

  From the above, it can be concluded that, in the method of the present invention, if the filter pore size is appropriately selected, precipitates and the like can be quantified by an arbitrary size. In particular, as in the case of the invention example using the filter A with a low porosity, the titanium content varies depending on the amount of electrolysis, and it is suggested that the cake layer is formed due to the blockage of the filter holes. Even if it exists, the characteristic is that the fixed_quantity | quantitative_assay according to the magnitude | size of deposits etc. is possible.

  On the other hand, in the comparative example, as shown in FIG. 9, the titanium content in the precipitates collected in the filter is significantly higher than that in the invention example, and as shown in FIG. The titanium content in the precipitate and the like that has passed through is almost zero. This is because the electrolyzed sample was immersed in pure water with low dispersibility, so that precipitates and the like aggregated and became coarse, and fine precipitates and the like of around 10 nm were collected by the filter. Therefore, in the comparative example, it is not possible to perform quantification by size of precipitates and the like.

3 is a diagram showing an operation flow of an electrolysis method described in Non-Patent Document 1. FIG. It is a figure which shows an example of the operation flow which optimizes the solution which has the dispersibility which is this invention. It is a figure which shows typically an example of the electrolysis apparatus used with the determination method of precipitates etc. which are this invention. It is a figure which shows an example of the operation flow of quantification methods, such as a precipitate which is this invention. It is a figure which shows the relationship between the sodium hexametaphosphate aqueous solution density | concentration and the absolute value of zeta potential. It is a figure which shows the relationship between the absolute value of zeta potential, and the titanium content rate in a precipitate. It is a figure which shows the relationship between the amount of electrolysis in the sample P, and the titanium content rate in the precipitate etc. which were collected by the filter. It is a figure which shows the relationship between the amount of electrolysis in the sample P, and the titanium content rate in the precipitate etc. which passed the filter. It is a figure which shows the relationship between the amount of electrolysis in the sample Q, and the titanium content rate in the precipitate etc. which were collected by the filter. It is a figure which shows the relationship between the amount of electrolysis in the sample Q, and the titanium content rate in the precipitate etc. which passed the filter.

Explanation of symbols

1 sample
2, 2a Fixing jig
3 electrodes
4 Beakers
5 Constant current power supply
6 Electrolyte
7 Electrolyzer

Claims (5)

An electrolysis step of electrolyzing a metal sample in an electrolyte solution;
An immersion step of immersing the remainder of the metal sample taken out of the electrolyte in a solution having dispersibility;
A separation step of filtering precipitates and / or inclusions (hereinafter referred to as precipitates) separated into the solution having dispersibility one or more times through a filter;
A quantitative step for quantifying the content of the element of interest contained in the precipitate or the like collected in the filter,
The amount of electrolysis of the metal sample is changed in the electrolysis step, and the steps from the electrolysis step to the quantification step are repeated to obtain the relationship between the electrolysis amount and the content of the quantified element of interest, and the electrolysis amount is extrapolated to 0. The content of the target element contained in a precipitate having a size greater than or equal to the size defined by the filter pore diameter of the filter. Quantification method;
Here, the size defined from the filter hole diameter means not the nominal filter hole diameter but the minimum size of precipitates or the like actually collected by the filter hole diameter. An electrolysis step of electrolyzing a metal sample in an electrolyte solution;
An immersion step of immersing the remainder of the metal sample taken out of the electrolyte in a solution having dispersibility;
A separation step of filtering precipitates and / or inclusions (hereinafter referred to as precipitates) separated into the solution having dispersibility one or more times through a filter;
A quantitative step for quantifying the content of the element of interest contained in the precipitate or the like that has passed through the filter,
The amount of electrolysis of the metal sample was changed in the electrolysis step, and the steps from the electrolysis step to the quantification step were repeated to obtain the relationship between the electrolysis amount and the content of the quantified element of interest, and the electrolysis amount was extrapolated to 0 Quantification of precipitates and the like in a metal material, characterized in that the content rate is the content of the element of interest contained in precipitates or the like having a size less than the size defined by the filter pore diameter of the filter Method;
Here, the size defined from the filter hole diameter means not the nominal filter hole diameter but the minimum size of precipitates or the like actually collected by the filter hole diameter.   3. The method for quantifying precipitates and the like in a metal material according to claim 1 or 2, wherein a filter having straight holes and a porosity of 4% or more is used in the fractionation step; The term “filter hole” refers to a filter hole penetrating the filter surface with a certain opening shape.   4. The method for quantifying precipitates and the like in a metal material according to claim 1, wherein in the quantification step, precipitates and the like adhering to the remainder of the metal sample are quantified.   In the immersion step, the solution having dispersibility is characterized in that the absolute value of the zeta potential with respect to the precipitate to be quantified is 30 mV or more, in the metal material according to any one of claims 1 to 4, Quantitative method for deposits, etc.

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