JP4762852B2 - Method for evaluating the concentration of components in the thickness direction of metal samples by spark discharge emission spectrometry - Google Patents

Description

  The present invention relates to a method for evaluating a change in a component concentration in a thickness direction of a metal sample, and more particularly to a method for evaluating a change in a component concentration in a thickness direction of a metal sample quickly and accurately using spark discharge emission analysis. is there.

  Metal materials such as iron and steel are shipped after finishing the performance and shape as final products through hot rolling treatment, cold rolling treatment, annealing treatment, surface treatment and the like after adjusting the components in the steel making process. Among these, in the heat treatment process represented by the annealing treatment process, the component elements contained in the metal material change into various forms and affect the properties of the final product. For example, C is fixed in the form of TiC precipitates using component elements such as Ti in steel that is soluble in acid and uniformly dissolved in the base metal element to improve the processing characteristics and strength. Like IF steel and electromagnetic steel that uses MnS, AlN, etc. as inhibitors to control grain growth, the precipitation form and concentration distribution of the constituent elements in the steel are important in determining the final product characteristics. .

  In particular, in thin plate products, in order to precipitate the desired precipitate and control the size of the crystal grains, in the process of performing various rolling treatments and heat treatments, or various surface treatments such as providing a plating layer on the surface, Concentration gradients of various component elements are generated in the thickness cross section of the thin plate, which affects the quality of the final product. Therefore, it is important to evaluate the concentration gradient of the component elements in the thickness cross section of the thin plate in terms of manufacturing and quality control such as optimization of process control conditions. For this reason, it is necessary to separate and quantify the component elements that affect the final product characteristics, and to optimize the final product characteristics by controlling the production conditions of the precipitation state and concentration distribution of these component elements. is there.

  Conventionally, the step chemical analysis method has been mainly used as a method for measuring the distribution of the concentration of component elements in the thickness cross section of a thin metal plate. In this method, as shown in FIG. 1, the metal sheet is melted from the surface to a predetermined thickness with chemicals (this is sometimes called chemical stepping), and this dissolution process is performed sequentially to obtain a plate thickness after melting. A plurality of samples having different values are prepared. These samples with different plate thicknesses were analyzed for various metal elements and non-metallic elements such as N using ICP emission spectroscopic analysis and Kjeldahl distillation, respectively. The concentration distribution in the plate thickness direction of the thin metal plate can be obtained from the difference in the component concentration in the dissolved solution between a plurality of samples having different thicknesses. Such a chemical analysis method is a method with high quantitative accuracy as a measurement absolute value of a component concentration. However, since a plurality of samples having different plate thicknesses are prepared by dissolution processing, a large amount of valuable samples are consumed. Since only one analysis value can be obtained in each analysis, the time until the measurement data is obtained is as long as one week per component element, which is very expensive in terms of cost.

On the other hand, the component concentration analysis method for the sample surface and the plate thickness cross section includes glow discharge spectrometry (GDS), X-ray photoelectron spectrometry (XPS), secondary ion mass spectrometry (SIMS), electron probe X-ray micro area An analyzer (EPMA), Auger electron spectrometry (AES), and the like are known (see, for example, Non-Patent Document 1 and Patent Document 2). However, when measuring the component concentration change of the thickness cross section of a thin metal plate of a thickness of several mm to 0.2 mm, the actual metal sample of interest,
1) The measurement area (several nm to several tens of μm) is too narrow for the target range.
2) Except SIMS, component analysis of trace amount (<0.1%) is impossible,
3) Fewer elements can be measured simultaneously
4) Sample preparation, measurement and evaluation take time.
5) The measuring device itself, the measurement fee is very expensive,
There were practical problems such as.

In view of the problems of these conventional analysis methods, the present inventor performed a spark discharge many times on a metal sample using a spark discharge emission analysis method. By analyzing several hundred pulses, a method has been proposed in which the number of inclusions, particle size, content, or average particle size can be determined according to a predetermined formula (see, for example, Patent Document 1).
In addition, in the spark discharge emission analysis, the present inventors also confirmed that inclusions are ionized, atomized and contribute to light emission after being subjected to selective discharge, but are finely dispersed in the base material (for example, (See Patent Document 3). That is, at the beginning of the spark discharge in the spark discharge emission analysis of a metal sample, the inclusions are subjected to selective discharge to give high spectral line intensity, but after several hundred pulses, the inclusions present in the surface layer of the metal thin plate, etc. Most of them are subjected to selective discharge and are repeatedly melted and solidified to be finely dispersed in the base material. As a result, when the number of spark discharges is several hundred pulses or more, the spatial resolution in the plate thickness direction of the metal sample deteriorates due to the discharge mixing phenomenon of the component elements during such spark discharge, and the component concentration in the plate thickness cross section of the metal sample In order to evaluate the above, there remains a problem in measurement accuracy.

Yuhei Uhira, Shosodo, "Chemical Analysis", 1993, p. 254 JP-A-4-238250 Japanese Patent Laid-Open No. 11-160257 JP 2004-163400 A

  Therefore, in view of the above-described problems of the prior art, the present invention aims to provide a method for quickly and accurately evaluating the component concentration of a plate thickness cross section of a metal sample using a spark discharge emission spectrometry. To do. Another object of the present invention is to provide a method for preparing a metal sample using an inclined polishing process for improving the measurement resolution of the component concentration of the plate thickness cross section of the metal sample using the spark discharge optical emission spectrometry. .

This invention solves the said subject, and the summary of the invention is as follows.
(1) A thin metal sample with a thickness of 0.5 mm or less, which is an object to be measured, is fixed to a support base, the surface of the metal sample is preliminarily polished , and then the metal sample is left on the sample stage. Then, a block sample for heat removal is placed as a holding table on the metal sample, and adjacent analysis points along the surface inclination direction in which the thickness of the metal sample is reduced by using a spark discharge optical emission analysis method. Spark discharge that analyzes the emission spectrum obtained from each analysis point while moving the analysis point so that it does not overlap, and obtains the concentration of the specific component corresponding to each thickness of the metal sample from the emission intensity of the wavelength corresponding to the specific component a thickness direction component density evaluation method of the metal sample by emission spectroscopy, spark discharge frequency per the analytical point and 10 to 2000 times, the spark discharge emission spectroscopy, characterized in that the spark discharge frequency is 500Hz or less Thickness direction component density evaluation method by the metal sample.
(2) The metal by spark discharge emission analysis according to (1) above, wherein the analysis point on the surface of the metal sample is moved by horizontally moving a fixed position of the metal sample on the sample stage. Sample thickness direction component concentration evaluation method.
(3) from the average value of the emission intensity of the corresponding wavelength to a particular component of each emission spectrum obtained from the previous SL min析点, and wherein the determination of the concentration of a specific component in the thickness of the metal sample corresponding to the analytical point The method for evaluating the concentration of components in the thickness direction of a metal sample by spark discharge emission spectrometry as described in (1) or (2) above.
(4) The thickness direction component concentration evaluation method of a metal sample by spark discharge emission analysis according to any one of (1) to (3), wherein the spark discharge frequency is 100 Hz or less.

According to the present invention, in the spark discharge emission analysis, the metal sample surface is inclined with respect to the sample back surface by inclined polishing or the like so that the plate thickness of the metal sample is gradually reduced in advance, and the analysis is performed in the surface inclination direction of the sample. By measuring the emission spectrum while moving the points, the component concentration analysis in the plate thickness direction can be performed simultaneously in multiple elements quickly and with high accuracy in a shorter analysis time than in the conventional chemical analysis method.
By applying the method of the present invention to the evaluation of changes in the concentration of components in the thickness cross section of a thin metal sheet, such as invasion, concentration, and purification of various component elements in the annealing process in the manufacturing process of a thin sheet such as steel, the quality of the product It is possible to evaluate the manufacturing process quickly and accurately, and to appropriately control the manufacturing process conditions of the product based on the result, which is an extremely valuable invention in industry.

In the present invention, the metal sample to be subjected to spark discharge emission analysis is a metal material separated for product quality evaluation from the manufacturing process of various metal products. In the present invention, the plate thickness is particularly about 0.2 to 5 mm. Measurement of the plate thickness cross-sectional concentration distribution of the metal sample is a preferred object. The metal of the metal sample is not particularly limited, such as pure iron, steel, aluminum, copper, titanium, stainless steel, silicon wafer, and indium.
In addition, after manufacturing a thin plate product among metal samples, various surface treatment materials such as an annealing separator are applied to the surface of the thin plate and a glass film is chemically formed on the surface by heat treatment. The formed thin steel plate and the surface-treated steel plate in which the surface of the thin plate is subjected to electrical or chemical plating surface treatment are also objects of the present invention.

Embodiments of the present invention will be described below with reference to the drawings.
The evaluation of the concentration of the specific component in the thickness direction of the metal sample in the present invention is performed by subjecting the surface of the metal sample to be measured to a slanted surface in advance, and then using the spark discharge emission spectrometry, the surface slope in which the metal sample is thinned. Spectral analysis of the emission spectrum obtained from each analysis point while moving the analysis point so that adjacent analysis points do not overlap each other along the direction, and from the emission intensity of the wavelength corresponding to the specific component to each thickness of the metal sample The concentration of the corresponding specific component is obtained.

  FIG. 2 shows an example of an embodiment of a method for slant polishing the surface of a metal sample as a measurement object using a surface grinder. In the following explanation, the two-dimensional direction on the surface of the surface plate (parallel to the sample surface before processing) is the X direction and the Y direction, the sample surface tilt direction is the X direction, and the direction perpendicular to the X direction is the Y direction. And the normal direction of the surface of the surface plate is the Z direction.

  In the present invention, as a method of performing the slant polishing of the metal sample, as shown in FIG. 2, for example, a numerical control (NC) surface grinder and an adjusting table 5 for adjusting the tilt of the metal sample 2 can be used. Normally, a numerically controlled (NC) surface grinding machine is used for surface grinding so that the average thickness of the metal sample is uniform, and the metal sample is fixed on the surface plate by a magnetic force. In order to set the cutting conditions, the distance (Z direction) between the grinding wheel 1 and the metal sample 2 was measured in μm in advance, and the working range of the surface grinding wheel on the sample surface (X direction, Y direction) was determined. Thereafter, the metal sample can be polished to a desired thickness by subjecting the sample 2 to surface grinding while polishing with the rotating grindstone 1 only for the cutting depth that defines the sample surface layer.

  In the present invention, using this numerical control (NC) surface grinder, as shown in FIG. 2, the metal sample 2 fixed to the support base 3 by the adjustment base 5 is adjusted to a predetermined inclination and the surface of the surface plate 4 is adjusted. After fixing to the surface of the metal sample repeatedly while moving the grinding wheel 1 in the X-axis and Y-axis direction horizontal to the surface plate surface and the Z-axis direction perpendicular to the surface plate surface 4 as described above, It is possible to obtain a metal sample 2 whose surface is inclined so that the thickness of the metal sample is continuously reduced.

In addition, when polishing with a thin metal sample 2 tilted using the adjustment table 5, the rigidity of the metal sample 2 is low, so that the sample 2 can be easily bent and the accuracy of planar polishing may be reduced. . For this reason, it is preferable to reinforce the strength of the metal sample 2 by fixing the back surface of the metal sample 2 and the surface of the support base 3 using spray glue, double-sided tape or magnetic force.
In addition, when a plurality of metal samples 2 having different thicknesses are inclined and polished, a support base 3 having a plurality of thicknesses can be created in order to reinforce the strength of the metal sample 2 according to the plate thickness of the metal sample 2. preferable.

  Further, as the adjustment table 5 for adjusting the metal sample 2 fixed to the support table 3 to a predetermined inclination, a part of the metal sample to be measured is cut and the adjustment table 5 is shown in FIG. By fixing it on the surface plate 4, it is possible to easily incline the thinness of the metal sample 2 to be measured. The inclination of the metal sample 2 can be adjusted by preparing a plurality of support bases 3 having different thicknesses and adjusting the thickness of the support base 3.

The thickness of the thinner end of the surface of the metal sample 2 in the inclined polishing direction (the right end of the metal sample 2 in FIG. 2) is the purpose of measuring and evaluating the component concentration by spark discharge emission spectrometry. It is preferable to adjust the thickness of the metal sample 2 to be adjusted.
However, if the thickness of the thin end of the inclined metal sample 2 becomes too thin, the metal sample becomes brittle and deforms when the metal sample 2 is peeled off from the support 3 after the inclined polishing. As a result, the smoothness of the surface of the metal sample 2 is reduced, and as a result, the analysis point on the surface of the metal sample 2 is insufficiently sealed with an inert argon gas when performing spark discharge emission analysis, resulting in poor emission. It becomes easy. In addition, if the thickness of the thin end of the metal sample 2 becomes excessively thin, the spark discharge emission analysis penetrates to the back surface of the metal sample 2 and is affected by oxides and impurity components. The analysis information is mixed up to a large component on the back surface of the sample, and there is a possibility of giving an abnormal analysis value.

  According to the examination results of the present inventors, the thickness of the thinner end portion (the right end portion of the metal sample 2 in FIG. 2) in the surface inclination direction of the metal sample 2 in the inclined polishing is the same as that before the inclined polishing. By reducing the average thickness of metal sample 2 to 1/2 or less, it is possible to prevent a decrease in the smoothness of the surface of the metal sample due to a decrease in strength at the end of the thinner metal sample, and spark discharge emission analysis In doing so, it was confirmed that abnormal analysis due to mixing of components on the surface of the back surface of the sample due to penetration to the back surface of the metal sample 2 could be prevented. The component concentration in the thickness direction in the case of a metal sample whose concentration on the front and back sides is almost the target, based on the thickness center (1 / 2t) of the metal sample, is determined by spark discharge emission analysis. By measuring and evaluating the concentration of components at the maximum depth up to 1/2 of the average thickness of the metal sample before the above-mentioned inclined polishing, the concentration distribution of the entire thickness of the metal sample can be evaluated stably and accurately. Can do.

Based on the above knowledge, in the present invention, in the case of a metal sample in which the concentration distribution on the front surface side and the back surface side thereof is almost the object with respect to the plate thickness center (1 / 2t) of the metal sample, in the present invention, the metal is obtained by spark discharge emission analysis. In order to stably and accurately evaluate the concentration distribution of the entire plate thickness of the sample, the thin end in the surface tilt direction of the metal sample obtained by the above tilt polishing (the right end of the metal sample 2 in FIG. 2) It is preferable that the thickness of the metal sample is equal to or less than half of the average thickness of the metal sample 2 before the above-described inclined polishing.
In addition, the present inventors, by the above method, while maintaining the strength and flatness of the metal sample well, a thin metal sample with a plate thickness of up to 0.5 mm, and further with a plate thickness of up to 0.2 mm. A thin metal sample can be slanted and polished, and as a result, it has been confirmed by spark discharge emission analysis that the concentration distribution of the entire thickness of the metal sample can be stably and accurately evaluated.

In addition, the method of performing the slant polishing so that the thickness of the end portion where the plate thickness in the surface tilt direction of the metal sample obtained by the above slant polishing is thinner is equal to or less than ½ of the average thickness of the metal sample before the above slant polishing. By adjusting the thickness of the adjustment table 5 shown in FIG. 2 to be 1/2 or more of the average thickness of the metal sample, it is possible to adjust the inclination of the metal sample and implement the desired inclined polishing by a simple method. It becomes.
In addition, if you want to analyze the interface between the surface treatment layer and the steel of a metal sample with an alloy plating layer, tinting layer, etc. on the surface layer of the steel plate, the desired polishing depth within the surface treatment layer thickness range can be obtained. By installing a dummy plate having a corresponding thickness, desired inclined polishing can be performed by a simple method.

The present invention is based on the premise that component analysis on the surface of a metal sample is performed using a generally known spark discharge optical emission spectrometry (for example, Agne “Latest Steel State Analysis”, 1979, page 107). In the spark discharge emission analysis method, a pulse voltage is applied from an electrode facing the metal sample surface in an inert atmosphere, and a vapor jet ejected from the metal sample surface collides with Ar ions to generate spark discharge plasma. From the wavelength and intensity of spark discharge light emission, the number of discharges, and the like, the content of components in metal samples, the content of inclusions, and soluble substances are determined for each form.
An example of an embodiment of a method for measuring and evaluating the component concentration in the thickness direction of a metal sample by spark discharge emission spectrometry will be described with reference to FIG.

FIG. 4 schematically shows a spark discharge emission spectrometer as an example of an embodiment of the present invention.
As shown in FIG. 4, the metal sample that has been subjected to the above-described slant polishing process, that is, the metal sample 2 whose thickness is continuously reduced in the inclined direction of the surface is set on the sample stage of the emission spectroscopic analyzer. Desirably, a stable discharge can be obtained when the metal sample 2 is pressed with a block sample having a smooth surface sufficiently thick in order to enhance the sealing performance of argon gas and prevent light emission failure. Under an inert gas atmosphere, a voltage is applied between the metal analysis sample 2 and the electrode 7 using the discharge device 8 to cause a spark discharge from 1 to several thousand pulses at the analysis point. Each emission spectrum thus obtained is guided into the spectroscopic unit 30 through the condenser lens 9 and the slit 10 and is split by the diffraction grating 11. The spectral spectrum 12 is simultaneously received by the detector 13 for each wavelength corresponding to the specific component, and the emission spectral line intensity for each pulse corresponding to the specific component is integrated for a certain period of time by the photometric device 14 and the arithmetic processing unit 15, and then digitally Performs constant-time integral photometry, which is converted into signal values and measured.

  Of the emission spectrum intensity for each pulse, the base material component received at the same time as the specific component, for example, steel, if the intensity of the spectral line of iron is abnormally weak, the discharge is defective, the emission position is shifted, or the sample Since it is a discharge failure to the crack part etc. on the surface, in order to remove this, by applying the internal standard method using the base material component strength as a trigger for each discharge, the emission failure data is appropriately cut, The analysis accuracy of components can be improved.

  There are various spark discharge conditions such as normal spark, arc spark spark, combined spark, etc., but it is normal spark discharge luminescence to select the discharge form based on the criteria of analyzing the target element with high sensitivity. It is the same as the judgment standard in the analysis method.

  In a normal spark discharge spectroscopic analysis, a preliminary discharge is performed to remove impurities adhering to the sample surface before measuring the emission spectrum. In the present invention, if the sample surface is clean, it is not necessary to perform preliminary discharge. In normal spark discharge optical emission analysis, the discharge becomes stable if the number of preliminary discharges is increased. However, in the case of component analysis of the surface of a metal sample subjected to the above-mentioned inclined polishing, the minimum thickness of the metal sample is as small as 1 mm. If this is not the case, even if the number of preliminary discharges is increased unnecessarily, analysis information may not be obtained simply by penetrating the plate thickness. Therefore, it is desirable that the number of preliminary discharges is at least zero pulse and at most about 500 pulses per analysis point. More preferably, it should be stopped at 50 pulses or less.

In the present invention, after performing spark discharge emission analysis at a specific analysis point on the surface of the metal sample that has been subjected to the above-described slant polishing processing, the set position of the sample stage of the metal sample is changed, and the surface of the metal sample becomes thin After moving the analysis points so that adjacent analysis points do not overlap with each other along the tilt direction, the specific component corresponding to each thickness of the metal sample is sequentially repeated by performing the same spark discharge emission analysis as described above. Can be determined.
When moving the analysis points on the surface of the metal sample, the specific components between the adjacent analysis points due to spark discharge emission undergo selective discharge and are repeatedly melted and solidified by preventing the adjacent analysis points from overlapping each other. This prevents the mixing phenomenon that is finely dispersed in the base material, prevents the measurement accuracy of the specific component concentration corresponding to each thickness of the metal sample from being reduced, and the component concentration with high measurement resolution in the thickness direction of the metal sample. Can be measured.

  In addition, the number of spark discharges per analysis point also increases with the increase in the number of spark discharges, so mixing of components in the plate thickness direction of the metal sample occurs, and the resolution in the plate thickness direction tends to decrease. In order to improve the resolution of the metal sample in the plate thickness direction by analysis, it is desirable to reduce it as much as possible. The number of spark discharges (hereinafter sometimes referred to as the number of discharge pulses) is preferably equivalent to a minimum of 10 pulses and a maximum of 2000 pulses per analysis point. At 10 pulses or less, the intensity fluctuation is severe due to the inclusion selective discharge phenomenon that is likely to occur in the early stage of discharge, and it is difficult to obtain a highly stable analysis result. In addition, when a discharge of 2000 pulses or more is performed, the depth range of 20 to 50 μm from the sample surface is sputtered in a normal spark discharge, so that the measurement resolution of the component concentration in the thickness direction of the metal sample deteriorates. It becomes. More preferably, by suppressing the number of spark discharges to about 500 to 1200 pulses, it is possible to provide an optimum point at which both the resolution in the depth direction and the stability of the analysis value can be achieved.

  As for the spark discharge frequency per analysis point, the amount of heat generated by the discharge per unit time with the increase of the spark discharge frequency cannot be removed in time by the block sample installed on the top of the sample. Mixing of components in the thickness direction occurs and the resolution in the plate thickness direction is reduced, and penetration of the plate thickness due to melting is likely to occur. In order to prevent thick penetration, it is desirable to reduce the spark discharge frequency as much as possible. As for the spark discharge frequency, in a normal spark discharge emission spectrometer, there are many types selected from 100, 200, 333, and 500 Hz as the main discharge frequency, but it is desirable that the spark discharge frequency be 500 Hz or less. When the spark discharge frequency exceeds 500 Hz, it is not in time to remove heat with the block sample placed on the sample to be analyzed for the amount of heat generated at the time of discharge, and mixing of components in the thickness direction of the metal sample is likely to occur. In addition, as a spark discharge type, light normal elements such as C, N, S, O, and P are analyzed with higher sensitivity by using a high power spark discharge type that increases the voltage, current, etc. from the normal normal spark conditions. In this case, preferably, by suppressing the spark discharge frequency to 100 Hz or less, it is possible to provide an optimum point at which both resolution in the depth direction and stability of the analysis value can be achieved.

By using the spark discharge emission analysis of the present invention, the component concentration analysis method of the plate thickness cross section of the metal sample and the metal sample subjected to the inclined polishing suitable for this, the conventional chemical analysis method and the conventional surface and cross section analysis method Compared to
[1] A concentration distribution in a wide measurement area (thickness 200 μm to 500 μm) can be obtained.
[2] Not only metal elements such as Al and Ti but also light elements such as C, N and S can be detected with high sensitivity.
[3] Multiple elements can be measured simultaneously at the same location.
[4] The time required for sample preparation, measurement and evaluation is very quick, within a few hours.
[5] As a measuring device, a spark discharge emission spectrometer installed in the metal refining industry can be used.
[6] Compared to conventional chemical analysis and surface analysis methods, it is superior in time, accuracy and cost.
Thus, it is possible to provide a method having a very high industrial utility value.

Next, preferable polishing conditions when performing slant polishing processing (plate thickness cross section polishing) of a metal sample suitable for arc discharge emission analysis in the present invention will be described with reference to FIG.
As described above, when measuring the concentration of component elements in the plate thickness direction of a metal sample that has been previously subjected to inclined polishing using spark discharge emission analysis, the adjacent analysis on the surface of the metal sample that has been subjected to inclined polishing. When the dots overlap, a specific phenomenon between adjacent analysis points due to spark discharge emission undergoes selective discharge and repeats melting and solidification, resulting in a mixing phenomenon that is finely dispersed in the base material, resulting in the thickness of the metal sample The measurement resolution of the specific component concentration corresponding to is reduced. Therefore, in order to improve the measurement resolution of the component concentration in the plate thickness direction of the metal sample, it is premised that the adjacent analysis points on the surface of the metal sample subjected to the inclined polishing process do not overlap each other.

If the analysis diameter φ (mm) or the number of analysis points n (pieces) of the spark discharge and the maximum polishing depth t (mm) of the metal sample are determined in advance, the target measurement resolution r (mm) in the spark discharge emission analysis The polishing conditions for ensuring the thickness, that is, the polishing conditions for the polishing length L (the length of the line segment AC along the inclined surface) (mm) or the inclination angle θ (rad) are determined using the following <1> equation it can.
In FIG. 3, the range of the thickness d (mm) of the metal sample (before polishing) and the maximum polishing depth (after polishing) t (mm) of the metal sample is (d / 2) ≦ t <d, the target The measurement resolution r in the plate thickness direction of the metal sample is assumed. The number of analysis points n is defined as n = t / r from the relationship between the polishing depth t and the measurement resolution r in the plate thickness direction, and is determined when the maximum polishing depth t and the measurement resolution r are determined in advance. It is.

Under this condition, the polishing length L (the length of the line segment AC along the inclined surface) (mm) is such that the discharge diameter φ between adjacent analysis points in the inclination direction of the metal sample surface after the inclined polishing process does not overlap. Therefore, it is necessary to satisfy the relationship of the following formula <1>.
AC ≧ n × φ = (t × φ / r) ……… <1>
Assuming that the position of the minimum polishing depth position A (polishing start position) after polishing and the maximum polishing depth position C is point D before polishing corresponding to point C, the above formula <1> The polishing length L (mm) is indicated by a line segment AC in FIG. 3, and the inclination angle θ (rad) after polishing is indicated by an angle formed by the line segments AD and AC.
The polishing length L (mm) is adjusted by changing the position of the inclination angle θ (rad) and the minimum polishing depth position A (polishing start position).
sinθ = t / L ≦ (t / nφ) ……… <2>
θ ≦ asin {t / (nφ)} ………. <3>
The required AD length is
L × cosθ ≧ nφ × cos {asin (t / nφ)} ……… <4>
Since the analysis score n is an integer, the analysis score n is obtained from the following formula <5> by rounding it up to an integer using the function of roundup (x, 0).
n = roundup {n, 0} = roundup {(t / r), 0} ……… <5>
When the above formula <5> is substituted into the above formula <4>, the polishing length L is determined.
L × cosθ ≧ roundup {(tφ / r), 0} × cos {asin (r / φ)} ……… <6>
In the present invention, the thickness of the metal sample is as thin as about 0.2 to 5 mm, and the inclination angle of the inclined polishing process is small (θ → 0), so cos θ → 1, which can be approximated by the following formula <7>.
L ≧ n × φ = (t × φ / r) ……… <7>

  From the above, as the polishing conditions for ensuring the target measurement resolution r (mm) in the spark discharge optical emission analysis, the polishing length L (inclination) in the inclined polishing process of the metal sample is satisfied so as to satisfy the above formula <7>. It is preferable to adjust the condition of the length (mm) of the line segment AC along the surface (mm) or the inclination angle θ (rad).

  In order to satisfy the above formula <7>, the condition of the polishing length L (length of the line segment AC along the inclined surface) (mm) or the inclination angle θ (rad) in the inclined polishing processing of the metal sample is, for example, In case of plate thickness d = 0.23mm, analysis diameter φ = 5mm, polishing depth t = 0.138mm (60%), depth direction resolution r = 10μm (from t, r the number of analysis points n = 14 points) The condition of the above formula <7> is L ≧ 70 mm, and the target measurement resolution r (mm in the spark discharge optical emission analysis is obtained by subjecting the metal sample to the slant polishing process so that the polishing length L is 70 mm or more. ) Can be secured.

  Similarly, in the case of plate thickness d = 0.50 mm, analysis diameter φ = 5 mm, polishing depth t = 0.30 mm, depth direction resolution 10 μm (from t, r, the number of analysis points n = 30), The condition of the above formula <7> is L ≧ 150 mm, and the target measurement resolution r (mm) in the spark discharge optical emission analysis is obtained by slant polishing the metal sample so that the polishing length L is 150 mm or more. Can be secured.

Before a sample subjected to inclined polishing under the above conditions is subjected to a spark discharge optical emission spectrometry, it is necessary to carefully peel the inclined polished sample from the sample support. For example, after placing alcohol or organic solvent on the edge of the sample, push a sharp cutter blade into the gap between the sample and the support, and then remove the liquid that dissolves adhesives such as alcohol and organic solvent. The sample can be easily peeled off by repeatedly putting it in the gap between the support bases.
Since there is a possibility that an adhesive or the like remains in the obtained sample, the light element (C, N) is obtained by cleaning and drying the entire sample again using an alcohol or an organic solvent. , S) contamination can be prevented.

  If the thickness of the sample is sufficiently thick and there is no fear of penetrating the plate thickness by spark discharge, it can be used for analysis while being in close contact with the sample support, but the plate thickness is penetrated by spark discharge. If there is a possibility, the adhesive substance that exists between the sample and the support base when it penetrates may cause contamination to light elements and does not show a clean value. It is desired to peel off.

  When performing spark discharge optical emission analysis, it is preferable to use a block sample having a smooth surface with a sufficiently thick plate as the holding table after the sample is left on the sample table. This is because when the sample is discharged as it is, since the plate thickness is thin, if it is penetrated, air entrainment occurs in the analysis chamber, causing a light emission failure. Also, by using a block sample with a thickness of about 10 to 30 mm, preferably a block sample made of a material with good thermal conductivity such as Cu, or a block sample with a cooling mechanism, the heat at the time of spark discharge applied to the inclined polishing sample is blocked. Removes heat, minimizes the progress of melting in the plate thickness direction, improves the resolution in the plate thickness direction, and makes the entire slant polished sample smooth and in close contact with the analytical sample holder. It also has the role of preventing abnormal discharge due to leakage of argon in the analysis chamber where the discharge is performed.

  Next, examples of the present invention will be described. The conditions of the examples are one example of conditions adopted for confirming the feasibility and effects of the present invention, and the present invention is limited to this one example of conditions. Is not to be done. The present invention can adopt various conditions as long as the object of the present invention is achieved without departing from the gist of the present invention.

(Example 1)
An alumina coating was applied to the surface of Si: 3%, Mn: 0.08%, S: 0.03% steel to prevent seizure, and a sample with a thickness of 0.5 mm that had been annealed at 1100 ° C. for 48 hours was slant polished.
Polishing conditions at the time of plate thickness, polishing thickness, and resolution at this time are shown below.
When plate thickness d = 0.50mm, inclination angle φ = 5mm, and polishing depth t = 0.50mm, resolution in the depth direction is 40μm (from t, r, the number of analysis points is n = 13), and the polishing length L is The metal sample was polished under conditions satisfying the above condition <7>, that is, a polishing length L = 65 mm satisfying L ≧ 65 mm (<7>). Under this polishing condition, the ratio (L / d) between the polishing length L and the plate thickness d is 130 times.
The obtained slant polished sample was subjected to spark discharge emission spectrometry, n = 13 points, a discharge diameter of 5 mmφ, and slanted polished surfaces were juxtaposed to obtain S emission intensity at each point. In this case, a calibration curve of S concentration was prepared in advance using a standard sample with known S concentration, and the obtained S emission intensity was converted from the calibration curve into S concentration. The analyzed points were performed twice at the same polishing depth position. The obtained results are shown in FIG. The plate thickness is plotted on the horizontal axis and the S concentration is plotted on the vertical axis. As a result, the process of purifying sulfur from the surface layer by annealing was clarified.

It has been found from many experiments so far that the sulfur content in the sample disappears as a gas body such as H ₂ S from the surface layer, but the theoretical calculation is more advanced for the S concentration distribution inside the sample. Thus, although there were very few experimental results for accurately grasping the actual analysis value, it became possible to obtain the sulfur concentration distribution quickly and accurately by using the present invention.

(Example 2)
An alumina coating was applied to the surface of Si: 3%, Mn: 0.08%, S: 0.03% steel to prevent seizure, and a sample having a thickness of 0.23 mm was annealed at 1100 ° C. for 48 hours, and was slant polished.
Polishing conditions at the time of plate thickness, polishing thickness, and resolution at this time are shown below.
Thickness d = 0.23mm, analysis diameter φ = 5mm, polishing depth t = 0.138mm (60%), depth resolution = 10μm or less, number of analysis points n = 15, polishing length L is 80mm or more In this way, the metal sample was slant polished.
The obtained slant polishing sample was subjected to spark discharge emission analysis, and the number of analysis points was n = 15, the discharge diameter was 5 mmφ, and the slant polishing surfaces were juxtaposed to obtain N emission intensity at each point. In this case, in order to detect N with high sensitivity, a high power spark was selected as the spark discharge condition. When the discharge frequency is implemented at a normal 333 Hz, as shown in the middle row of FIG. 6, the heat removal by the block sample placed on the sample is not in time, and the analysis value is obtained because it penetrates the plate thickness with 500 pulse discharge. Can't get. When the high power spark is stopped and the normal normal spark discharge mode is performed at the normal 333 Hz, the penetration of the plate thickness is avoided as shown in the lower △ in FIG. 6, but the light emission intensity of the target light element N is extremely weak. Therefore, it becomes impossible to obtain an analytical value of 100 ppm or less. Therefore, when the high power spark discharge mode and the discharge frequency are set to 100 Hz, it is confirmed that it is possible to prevent the penetration of the plate thickness as shown in the upper part ◎ of FIG. did.

The obtained results are shown in FIG. The plate thickness is plotted on the horizontal axis and the N concentration is plotted on the vertical axis. As a result, it became clear that N was purified from the surface layer by annealing.
It has been found from many experiments so far that the N content in the sample disappears as a gas body from the surface layer. However, the theoretical calculation was preceded by the actual analysis of the N concentration distribution inside the sample. Although there were very few experimental results for accurately grasping the values, it was possible to obtain a nitrogen concentration distribution quickly and accurately by using the present invention.

  In order to obtain depth resolution similar to that of the present invention by the conventional chemical analysis method, prepare 10 to 20 samples prepared under the same conditions and dissolve them from the surface by chemical analysis according to thickness. Thus, the element must be analyzed from the resulting solution or the remaining sample must be analyzed chemically. The time required for this would be about a week to a little less than a month, even if estimated to be small. In contrast, in the method of the present invention, the time required for sample preparation is about 1 hour, and the time required for spark discharge emission analysis is about 1 minute per analysis point, including evaluation analysis of analysis data, In less than about 2 hours, it became possible to evaluate the concentration change of all elements accurately and quickly.

The method of obtaining the cross-sectional concentration in a steel sheet by a chemical analysis method using step cutting in the prior art will be described. A method for producing a slant polishing sample for spark discharge emission in an example and a slant polishing sample by a surface grinder will be described. The example which demonstrated the relationship between the inclination angle at the time of carrying out the inclination grinding | polishing of a metal sample, the emission analysis area, the frequency | count of emission analysis, polishing depth, and sample thickness is shown. The schematic diagram of a spark discharge emission spectrometer is shown. An example in which a change in S concentration in a cross section of a sample obtained by annealing a 0.5 mm-thick magnetic steel sheet in Example 1 and purifying S content from the surface layer is analyzed according to the present invention will be shown. The example of the spark discharge (QV) trace by the discharge conditions and discharge frequency in Example 2 is shown. An example in which the cross-sectional N concentration distribution of the annealed sample having a thickness of 0.23 mm in Example 2 was analyzed at a discharge frequency of 100 Hz is shown.

Explanation of symbols

1 Grinding wheel
2 Sample
3 Support stand
4 Surface plate
5 Height adjustment stand
6 Cutting allowance
7 electrodes
8 Discharge device
9 Condensing lens
10 slits
11 Diffraction grating
12 Spectral spectrum
13 Detector
14 Metering device
15 Arithmetic processing unit
20 Light emitter
30 Spectrometer
40 Data processing section
A Minimum polishing depth position after polishing
The back of the BA point
C Maximum polishing depth position after polishing
D Position corresponding to point C before polishing
E Center thickness line
L Polishing length (Line AC)
d Thickness of metal sample before polishing (mm) (Line AB)
n Number of analysis points
r Measurement resolution in the plate thickness direction (mm)
t Maximum polishing depth (line segment DC)
θ Inclination angle before polishing (angle of line segment AC and line segment AD)
φ Emission analysis diameter of spark discharge (mm)

Claims (4)

After fixing a thin metal sample with a thickness of 0.5 mm or less, which is an object to be measured, to a support base and pre-tilting the surface of the metal sample in advance, the metal sample is left on the sample stage. A block sample for heat removal is placed on the metal sample as a holding stand, and the adjacent analysis points are not overlapped along the surface inclination direction in which the thickness of the metal sample is reduced by using a spark discharge emission analysis method. By analyzing the emission spectrum obtained from each analysis point while moving the analysis point to the point, and using the spark discharge emission analysis to obtain the concentration of the specific component corresponding to each thickness of the metal sample from the emission intensity of the wavelength corresponding to the specific component A thickness direction component concentration evaluation method for a metal sample,
The number of spark discharges per analysis point is 10 to 2000 times,
The spark discharge frequency is 500 Hz or less, the thickness direction component concentration evaluation method of a metal sample by spark discharge emission analysis.   The thickness direction of the metal sample according to claim 1, wherein the analysis point on the surface of the metal sample is moved by moving a fixed position of the metal sample on the sample stage in a horizontal direction. Component concentration evaluation method. Claim that the average value of the emission intensity of the corresponding wavelength to a particular component of each emission spectrum obtained from the previous SL min析点, and obtains the concentration of a specific component in the thickness of the metal sample corresponding to the analytical point 3. A method for evaluating a concentration of components in a thickness direction of a metal sample by spark discharge emission analysis according to 1 or 2. The said spark discharge frequency is 100 Hz or less, The thickness direction component density | concentration evaluation method of the metal sample by the spark discharge emission analysis of any one of Claims 1-3 characterized by the above-mentioned.