JP2007178321A - Evaluation method of macrosegregation due to emission spectral analysis - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an evaluation method of macrosegregation due to emission spectral analysis capable of rapidly grasping segregation state, while ensuring poor analytical precision by rationalizing the size of an analytic lattice point or the number of analyzing points. <P>SOLUTION: In the evaluation method of macrosegregation, a cast piece sample wherein a cut surface passing through the center part of a cast piece is cut and moved so that an electrode, which generates spark discharge, successively corresponds at least three unidimensional or two-dimensional analyzing lattice points on the cut surface of the cast piece sample. At the respective analytic lattice points, spark discharge, comprising a plurality of pulses accompanying preparatory, is produced through the window part of a mask, to which a window with a diameter 1-5 mm of an inscribed circle is provided and emission spectral analysis using the spark discharge as the light source is performed. Macrosegregation is evaluated quantitatively by quantitatively analyzing the concentrations of a trace amount components in steel at each of the analytic lattice points. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for quantitatively and rapidly evaluating macrosegregation that is likely to occur in a high carbon steel containing 0.5% by mass or more of carbon, such as a tire cord and a high carbon chromium bearing steel. In particular, the present invention relates to a useful method for evaluating the macrosegregation by emission spectroscopy.

  In the high carbon steel as described above, since the temperature range in which solid and liquid coexist during solidification is wide, central segregation in which trace elements in the steel such as C, S, and P are concentrated occurs at the center of the slab. easy. This center segregation is a segregation with a larger scale (macrosegregation) than segregation (microsegregation) caused by solute distribution in the dendritic tree part of the slab, and the diameter of the segregation is several to several at the stage of the slab. It may reach 10 mm.

  If the degree of central segregation is poor, such as when the segregated particle size is large or the concentration of trace components in the segregated particles is extremely high, serious quality problems may be caused. For example, in steel for tire cords, there is a case where a copper wire breakage occurs during wire drawing. Also, in bearing steel, depending on the heat treatment conditions in the subsequent process, giant carbides may be generated at the center segregation part, and the rolling fatigue life of the product may be significantly reduced.

  Even when center segregation occurs in the slab, this center segregation does not always occur continuously in the casting direction of the slab, and often occurs intermittently. In the inspection of product samples after rolling the slabs into thin strips, segregation may not be detected depending on the sample collection position even for products manufactured from slabs that have center segregation. If the representativeness is not ensured, there is a risk that the material in which the center segregation occurs is overlooked, and the material is shipped for a use that is strict in the center segregation.

  However, in the slab stage before rolling, it is possible to evaluate the degree of center segregation only by investigating a slab sample that is relatively short (about several hundred mm) in the casting direction.

  For this reason, when manufacturing high carbon steel with strict center segregation, a slab sample is collected for each slab in order to reliably detect a steel material with a poor degree of center segregation and prevent shipment. The actual situation is that the center segregation of slabs is evaluated and selected by methods such as macroprinting, (2) drill analysis, and (3) EPMA (electron probe X-ray microanalyzer). It is.

  However, in these methods, as shown below, it is difficult to evaluate the center segregation quickly and quantitatively, and the segregation that should have been able to be repaired to some extent in the subsequent process cannot be repaired. There was a problem that a long time was required until the abnormality of the operation was discovered, and a large amount of defect loss might be generated by continuing the casting with the abnormality in the meantime.

[Macro print method]
In this method, the cut surface of the slab is polished, and the segregated part is corroded with a corrosive liquid such as picric acid, which is preferentially corroded. In this method, the state of occurrence of segregation is visualized by a method such as copying the ink remaining in the corroded portion onto cellophane paper. This macro print method is effective in that it can grasp the segregation of the entire slab sample, but the concentration of the resulting print depends on the state of corrosion and polishing, and it is difficult to quantify the segregation. is there. Further, in addition to the time taken for cutting and polishing the slab, it also takes time for the slab to be corroded.

[Drill analysis method]
In this method, a macro print is taken from a longitudinal section of a slab, a center segregation region is specified, a chip sample is taken from a large number of analysis points on the center segregation region by a drill having a diameter of about 5 mm, and each analysis is performed. This is a method for quantitatively evaluating the degree of segregation by analyzing the trace element concentration in a chip sample of a spot by a combustion-infrared absorption method or an ICP (inductively coupled plasma) emission analysis method. This method has the advantage that the degree of segregation can be quantitatively evaluated. However, in order to determine the chip collection position, the position of the center segregation is specified in advance by acid corrosion or microprinting, and then the chip is collected. Since the analysis is performed after that, it takes a longer time than the macro print method until an evaluation result is obtained.

  Moreover, in this drill analysis method, since the average concentration of the cylindrical region having a length also in the depth direction of the sample is measured, compared with the EPMA method to be described later and the mapping method of the cut surface, the analysis result is thinned. The analytical sensitivity for small segregated grains is low. In order to avoid such inconvenience, if the drill diameter is reduced or the cutting depth is reduced to increase the sensitivity, the amount of chips that can be collected from one analysis point is insufficient and the analysis accuracy is reduced. Problems arise. If the area of one analysis point is reduced, it is necessary to increase the number of analysis points. However, if the number of analysis points is increased, there is a problem that the time required for analysis for the evaluation of the entire sample becomes long, and there is a limit.

[EPMA method]
This method uses mapping analysis by an electron beam probe X-ray microanalyzer. In this method, if the entire surface of the slab sample is inspected, there is an advantage that the macro view of segregation can be grasped and the result can be quantified. However, since the beam diameter used in the EPMA method is extremely small compared to the segregation particle size of macro segregation such as center segregation, in order to evaluate macro segregation, analysis must be performed on an extremely large number of analysis points. For example, in order to analyze a wide area such as a slab sample cross section of 50 mm × 250 mm, a long analysis time of 20 hours or more is required. Further, if the inspection area is reduced in order to shorten the analysis time, there is a problem that the representativeness with respect to the inspection result is reduced and large segregated grains are missed.

  Recently, an analysis method called OPA (Original position statistic distribution analysis) has been developed for various conventional technologies as described above, and examples applied to the evaluation of macro segregation of slabs have been reported (for example, non-patents). Reference 1). Although the details of this method have not been clarified so much, it is an analytical apparatus equipped with a polychromator and a sample moving stage, and is applied by emission spectroscopy which is characterized by a short analysis time. This is a mapping analysis technique aimed at evaluating the segregation and the distribution of inclusions.

In ordinary emission spectroscopic analysis, in order to obtain sufficient analysis accuracy, a large number of discharges of several hundred times or more are used after a preliminary discharge as a light source for emission analysis, whereas the OPA method is used. So, in order to ensure the speed of analysis, single pulse discharge without preliminary discharge is used. If segregation can be accurately evaluated by such a method, the OPA method can be expected as a useful method capable of evaluating macrosegregation quickly and quantitatively.
The third international conference on continuous casting of steel in developing countries, IRON & STEEL SUPPLEMENT 2004 Vol.39, p.310

  However, in the OPA method as described above, it has been reported that even if the same slab sample is used, the distribution of segregation varies depending on the type of element to be measured. On the other hand, in the above-described drill analysis method, the segregation distribution state is less dependent on the type of element to be measured, such that the segregation degree of S is high at analysis points with high C concentration. . That is, the segregation evaluation result by the OPA method is different from the segregation evaluation result by the drill analysis method.

  This situation arises because the OPA method emphasizes the rapidity of analysis, and as a light source for emission analysis, single pulse discharge without preliminary discharge is used, and sufficient analysis accuracy can be secured. It is thought that it is based on not. In other words, although there is a possibility that central segregation can be quickly evaluated by performing component analysis at a plurality of points in a sample using the principle of emission spectroscopy, the OPA method has a problem in terms of analysis accuracy. is there. That is, the above-described OPA method has a problem that the analysis accuracy is slightly lowered because importance is attached to the quickness of the analysis.

  By the way, the disconnection during the wire drawing process in the steel for tire cords occurs mainly due to segregated grains having a diameter of about 5 to 15 mm at the slab stage. In recent years, however, the patenting process during wire drawing has been omitted, and direct drawing has been directed to increase the degree of processing per heat treatment. The number of cases judged to be increasing is increasing. For example, based on the steel material diameter and the segregated particle size of the portion where the disconnection occurred, a disconnection may occur due to a small segregated particle having a segregated particle diameter of about 3 mm, which was calculated backward in the slab stage having a cross-sectional size of 380 mm × 600 mm. It is necessary to reliably detect such small segregated grains.

  In general, the smaller the size of analysis grid points and the greater the number of analysis points, the more segregation can be grasped. On the other hand, while maintaining the analysis accuracy of each analysis grid point, If the number is increased, the time required for the entire analysis becomes longer, and there is a problem that the speed cannot be ensured.

  From this point of view, considering the technologies that have been proposed so far, it is insufficient as a technology that satisfies any of the required characteristics when viewed as a technology that quickly evaluates segregation while ensuring analysis accuracy. In fact, the establishment of such technology is desired.

  The present invention has been made to solve the above-described technical problems in the related art, and its purpose is to achieve good analysis accuracy by optimizing the size of analysis grid points and the number of analysis points. It is an object to provide a macro-segregation evaluation method by emission spectroscopic analysis which can quickly grasp the segregation state while ensuring the above.

  The macro-segregation evaluation method of the present invention that has achieved the above object is to cut a slab sample whose cut surface passes through the center of the slab, and an electrode that generates spark discharge is the primary on the slab sample cut surface. The slab sample is moved so as to sequentially correspond to three or more analysis grid points in the original or two-dimensional, and the window of the mask with the inscribed circle diameter of 1 to 5 mm at each analysis grid point Through this part, a spark discharge consisting of a number of pulses accompanied by a preliminary discharge was generated, an emission spectroscopic analysis was performed using this spark discharge as a light source, and the concentration of trace components in steel at each analysis lattice point was quantitatively analyzed. The point is that the segregation is evaluated quantitatively.

  In the method of the present invention, prior to the emission spectroscopic analysis, preliminary emission spectroscopic analysis is performed in a state where the window portion of the mask at each spectral lattice point is larger than the above, and the segregation degree in the analysis result is determined in advance. If the emission spectroscopic analysis according to the present invention is carried out only in the region exceeding the threshold value, it is effective in shortening the time required for analysis and performing quick analysis.

  In the method of the present invention, by optimizing the size of the analysis lattice points and the number of analysis points in the emission spectroscopic analysis, an evaluation method capable of quickly grasping the segregation status while ensuring good analysis accuracy can be established. This method is extremely useful as a method for evaluating the segregation degree of steel materials.

  The present inventor has further studied from the viewpoint of measuring the size of the analysis lattice points and the optimization of the number of analysis points by using the principle in the emission spectroscopic analysis method described above. As a result, when the segregation was evaluated according to the procedure as described above, it was found that the above object was achieved brilliantly, and the present invention was completed.

  Hereinafter, the configuration and operational effects of the present invention will be described in more detail based on the drawings. FIG. 1 is an explanatory view showing a configuration example of an apparatus for carrying out the method of the present invention, in which 1 is a slab sample whose segregation degree is evaluated, 2 is a refractory for a mask, and 3 is a spark discharge. Electrodes for use, 4 for a spectrometer (polychromator), 5 for an amplifier and an A / D (analog / digital) converter, 6 for a computer, and 7 for an industrial robot.

  In such an apparatus, the slab sample 1 is cut so that the cut surface passes through the central portion (the portion where segregation is expected to exist), and is moved one-dimensionally or two-dimensionally (hereinafter referred to as the following) by the industrial robot 7. It is configured so that it can be called “moving stage”. This slab sample 1 is configured such that the analysis lattice point (region where segregation is analyzed) of the cut surface opposes the spark discharge generating electrode 3 and the analysis lattice point can be analyzed. . The mask refractory 2 is provided with a window (not shown) whose size can be adjusted, through which spark discharge composed of a plurality of pulses accompanied by preliminary discharge is generated. Then, in the analysis grid of the slab sample, emission spectroscopic analysis using spark discharge as a light source is performed by the spectrometer 4, and the result is input to the computer 6 via the amplifier and the A / D converter. Based on the input data and movement information by the industrial robot 7, emission spectroscopic analysis data at each analysis grid point is processed.

  In carrying out the present invention using the above-mentioned apparatus, it is necessary to appropriately control the size of the analysis grid point on the slab sample. The size of the analysis grid point is determined by spark. About the spot to form, it showed by the length of the short side in the rectangular lattice point area | region which it inscribes. For example, when the shape of the area of the analysis grid point is a square, the diameter of the inscribed circle coincides with the length of one side of the square.

  The inventor examined the influence of the size of the analysis grid point on the analysis sensitivity using the apparatus as described above. First, the analysis sensitivity was investigated for segregation with a segregation particle diameter of φ5 mm or φ3 mm by changing the inscribed circle diameter of the analysis lattice point. The result is shown in FIG. The analysis sensitivity is the analysis sensitivity when the segregation degree of the segregated grains can be correctly evaluated when the size of the grid points is sufficiently small (for example, 1 mm or less) when the center of the circular segregated grains and the square analysis lattice points coincide. As 1, the relative analytical sensitivity indicating how much relative output can be obtained is shown.

  Even if there are no segregated grains, there is a variation in concentration due to microsegregation. Therefore, in order to detect segregated grains with certainty, it is necessary to secure this relative analytical sensitivity of 0.3 or more. is there. For segregated grains of φ5 mm, which are normally considered harmful, if the inscribed circle diameter of the analysis lattice point is controlled to 5 mm or less, a sensitivity of 80% or more can be secured and segregated grains can be reliably detected. I understand. In addition, even for minute segregated grains with a diameter of 3 mm, which are considered harmful in steel for steel cords drawn by direct rolling, if the inscribed circle diameter of the analysis lattice point is 5 mm or less, the relative analytical sensitivity can be increased. 0.3 or more can be secured, and minute segregated grains can be reliably detected. However, since it is necessary to detect smaller segregated grains in order to cope with further strengthening of steel for tire cords in the future and further direct rolling, in order to cope with such a situation, It is preferable to control the inscribed circle diameter of the analysis grid point to 3 mm or less.

  On the other hand, the inventor also investigated the relationship between the number of analysis points necessary for analyzing the entire 50 mm × 250 mm region of the slab sample and the inscribed circle diameter of the analysis grid point. The result is shown in FIG. If the accuracy per analysis grid point is maintained, the time required for analysis will be approximately proportional to the number of analysis points. However, if the inscribed circle diameter of the analysis grid point is less than 1 mm, the required analysis grid points increase rapidly. In addition, it is difficult to realize rapid analysis while maintaining the analysis accuracy of each analysis grid point.

  As is clear from these results, in order to detect segregated grains efficiently and reliably with as few analysis points as possible, it is effective to make the size of the analysis lattice points substantially coincide with the size of the smallest segregated grains that are harmful. In order to achieve both analysis accuracy and rapidity, it is necessary to set the inscribed circle diameter of the analysis grid point to 1 to 5 mm.

  In addition, prior to performing the emission spectroscopic analysis as described above, the size of the window portion of the mask at each analysis lattice point is larger than the above (a state larger than the diameter of the inscribed circle when analyzing later). Preliminary emission spectroscopic analysis is performed, and only in a region where the degree of segregation in the analysis result exceeds a predetermined threshold (for example, a region where the degree of segregation is 1.1 or more), the light emission as described above It is also useful to perform a spectroscopic analysis, which can shorten the time required for analysis and perform a quick analysis (see Example 3 below).

  Characteristics of the method of the present invention and the prior art when the conditions are changed (quantitative analysis, analysis value representative of each analysis grid point, rapid analysis, whether or not segregated particles having a diameter of 3 to 5 mm can be detected) Are shown in Table 1 below. The evaluation criteria for characteristics are as follows. Table 1 below also shows the cases where the requirements defined in the present invention are not satisfied.

[Quantitative analysis]
○: A numerical value indicating the degree of segregation is obtained.
X: Only a pattern is obtained and quantitative numerical data cannot be obtained.

[Analysis value representativeness of each analysis grid point]
○: The analysis result of each analysis grid point shows an average value of the whole analysis grid point, and represents the segregation degree of each analysis grid point.
×: The analysis result of each analysis grid point is the analysis result of the point where a spark happens to occur in the analysis grid, and if it hits an inclusion in the steel, an abnormal value is shown. It does not represent the degree of segregation (only one pulse in the case of OPA method).

[Rapid analysis]
○: Analysis time for one slab sample (50 mm x 250 mm) is within 20 hours x: Analysis time for one slab sample (50 mm x 250 mm) exceeds 20 hours

  Among the materials of bearing steel, a material that is particularly strict in segregation is subjected to a soaking diffusion treatment over about 20 hours after casting. If it is found that the segregation degree of the slab is abnormal before the soaking diffusion treatment is completed, there is a possibility that the soaking diffusion treatment time can be extended and relieved. However, steel materials that have been found to be abnormal after the soaking and diffusion treatment must be dropped or discarded. When the previous soaking diffusion process is completed and the soaking furnace is opened, casting of the next bearing steel is started. If it becomes clear that the previous casting was abnormal before the start of casting, it is possible to prevent the abnormality from occurring again in the next casting by correcting the abnormality of the equipment. For this reason, the reference time for analysis is 20 hours.

[Possibility of detecting segregated grains having a diameter of 3 to 5 mm]
○: It has an analytical sensitivity capable of reliably detecting segregated grains having a diameter of 3 to 5 mm.
×: Segregated grains having a diameter of 3 to 5 mm may be missed.

  Hereinafter, the effects of the present invention will be described more specifically by way of examples. However, the following examples are not intended to limit the present invention, and any design changes in accordance with the gist of the preceding and following descriptions are technical aspects of the present invention. It is included in the range.

[Example 1]
A sample of a cross section of a carbon steel ingot with a carbon content of 0.8% by mass is collected, and the slab sample is moved along a straight line passing through the center of the slab so that the C concentration at multiple points can be quantified. And an emission analysis using a spark discharge as a light source. At this time, the number of analysis points was changed to 1 to 7, and the analysis was performed. In addition, the used agglomerated material is not subjected to center segregation countermeasures, and the degree of center segregation is poor.

  The segregation degree analysis results when the number of analysis points is 1 or 2 are shown in FIGS. 4 and 5 (relationship between the distance from the center of the slab and the segregation degree [Cmax / C0]), respectively. Further, the results of the analysis of the degree of analysis when the number of analysis points is 3 or 7 are shown in FIGS. 6 and 7 (relationship between the distance from the center of the slab and the degree of segregation [Cmax / C0]), respectively. The degree of segregation represents the ratio between the maximum concentration Cmax in the carbon concentration and the carbon concentration C0 of the molten steel sample collected in the tundish when casting the slab. These results can be considered as follows.

  Even when the number of analysis points is 1 or 2 (FIGS. 4 and 5), it can be determined that the degree of segregation is high, but in these cases, the distribution of the degree of segregation cannot be grasped, and the maximum value of the degree of segregation. Therefore, the representativeness of the measurement result regarding the maximum segregation degree is not sufficient.

  In contrast, when the number of analysis points is 3 (FIG. 6) or 7 (FIG. 7), the maximum value (peak value) of segregation sparseness can be grasped from the segregation degree distribution, and the center segregation. It can be seen that a representative evaluation is possible. From these facts, in order to evaluate the center segregation of a slab whose center segregation has been improved by continuous casting, it is desirable to conduct analysis on a larger number of points. If so, the accuracy can be ensured.

[Example 2]
For tire cord steel that has a carbon content of 0.82% by mass and is drawn directly, a longitudinal section sample including the central axis is collected from the slab, and the position of central segregation is determined by the macro print method. The slab sample was placed on a moving stage so that the sample was repolished and analyzed along the specified center segregation line, and line analysis was performed by an emission analysis method using a spark discharge as a light source. At this time, a high-speed light emission excitation power source that discharges about 400 times per second was used as a spark power source, and a polychromator was used for spectroscopic analysis. The analysis was performed by sequentially moving the slab sample in one direction with respect to the fixed spark discharge electrode so that the electrode was about 4 mm away from the longitudinal section of the slab sample.

  Further, a refractory mask having a square window opened was used so that, for each analysis lattice point, the sparks jumped only to a 3 mm × 3 mm square region of the slab cross section. At each analysis grid point, signals corresponding to individual sparks were taken into a computer and integrated, and the trace element concentration at that analysis grid point was calculated. When flying a spark, sometimes the spark will fly to the refractory mask, but if you use the emission analysis results for the spark that hit the refractory mask, an analysis error will occur, so you can handle each spark. On the basis of the analysis result, it was automatically determined whether the spark hit the slab sample or the fire mask, and the analysis result was integrated only for the spark hit the slab sample. The measurement was carried out for 50 analysis grid points at a pitch of 4 mm, and the segregation of a region having a length of about 200 mm was evaluated.

  At each analysis grid point, about 10 seconds were taken for movement, Ar replacement, preliminary discharge, and integration, and the line analysis with 50 analysis points was completed in about 9 minutes after setting the sample. Among the obtained 50 carbon concentrations, the degree of segregation was quantitatively evaluated by the above [Cmax / C0]. At this time, after approximately 3 seconds of preliminary discharge at each analysis point, about 1000 pulses of sparks were discharged uniformly in the analysis area of 3 mm × 3 mm, and the analysis results were accurate and representative. The analysis time was significantly reduced compared with the conventional drill analysis method while ensuring sufficient.

[Example 3]
About the steel for bearings whose carbon content is 1.0 mass%, the longitudinal cross-section sample containing a slab center axis | shaft was extract | collected, and the segregation degree was evaluated by implementing a two-step secondary mapping analysis. An industrial robot was used to move the slab sample. In the first mapping analysis, the size of the window of the refractory mask that limits the flight range of the spark at each analysis grid point is 10 mm × 10 mm, and the 50 mm × 200 mm region of the slab sample is 5 × 20 = 100 (location). The segregation degree of each analysis grid point was evaluated by dividing into the analysis grid points. Analysis lattice of carbon segregation degree [Cmax / C0] obtained by the first mapping analysis exceeds 1.1 and within 100 divisions, the carbon segregation degree [Cmax / C0] is within the third position from the highest A second mapping analysis was performed on the points.

  In the second mapping analysis, the size of the window of the refractory mask that limits the range where the sparks fly at each measurement point is 3 mm × 3 mm, and the center position of the analysis grid point in the first mapping analysis is the center, The analysis was performed on a total of 25 analysis lattice points of 5 points at the top and 5 points at the left and right at 4 mm intervals.

  At this time, the segregation degree is not determined by two-step mapping analysis, but by using a fine refractory mask having a window size of 3 mm × 3 mm from the beginning and analyzing the entire region of 50 mm × 200 mm at intervals of 4 mm. evaluated. As a result, the required number of analysis points is 600, and the analysis time required for 10 seconds for one point analysis is 100 minutes.

  On the other hand, in the two-stage two-dimensional mapping as described above, the analysis time for one grid point is reduced to 100 points in the first stage, 75 points in the second stage, and 175 points in total. If it is 10 seconds, the required analysis time can be suppressed to about 30% compared to the case of one-step analysis, and more rapid segregation evaluation can be performed.

It is explanatory drawing which showed the structural example of the apparatus for implementing this invention method. It is a graph which shows the relationship between analysis grid point size and segregation grain detection sensitivity. It is a graph which shows the relationship between an analysis grid point size and the number of required analysis points. It is a graph which shows the segregation degree analysis result when an analysis score is 1. It is a graph which shows the segregation degree analysis result when an analysis score is two. It is a graph which shows an analytical analysis result when an analysis score is three. It is a graph which shows an analytical analysis result when an analysis score is seven.

Explanation of symbols

1 slab sample 2 refractory material for mask 3 electrode for generating spark discharge 4 spectrometer (polychromator)
5 Amplifier and A / D converter 6 Computer 7 Industrial robot

Claims (2)

In evaluating macro segregation of slabs,
Cut out a slab sample whose cut surface passes through the center of the slab,
The slab sample is moved so that the electrode for generating the spark discharge sequentially corresponds to one or more three-dimensional analysis grid points on the slab sample cut surface,
At each analysis grid point, a spark discharge consisting of a plurality of pulses accompanied by a preliminary discharge is generated through the window portion of the mask with a diameter of the inscribed circle of 1 to 5 mm,
Perform emission spectroscopic analysis using this spark discharge as the light source,
By quantitatively analyzing the trace component concentration in steel at each analysis grid point,
A macro-segregation evaluation method by emission spectroscopic analysis, characterized by quantitative evaluation of macro-segregation.   Prior to performing the emission spectroscopic analysis of claim 1, preliminary emission spectroscopic analysis is performed in a state where the size of the window portion of the mask at each analysis lattice point is larger than the above, and the segregation degree in the analysis result is The macro-segregation evaluation method, wherein the emission spectroscopic analysis according to claim 1 is further performed only in a region exceeding a predetermined threshold value.

Images