JPH06337245A - Emission spectrochemical analysis - Google Patents

Abstract

PURPOSE:To utilize an analyzing method as a method for managing and analyzing adapted, for example, for an iron steel process, etc., in which contents of an N component, an O component and/or a C component in a solid sample to be analyzed can be rapidly and accurately measured. CONSTITUTION:A method for emission spectrochemically analyzing a solid sample to be analyzed and placed on a sample base 12 by discharging between an analyzing surface of the sample 13 and electrodes 15 oppositely disposed on the analyzing surface, spectrally analyzing a generated spectrum from components in the sample 13 comprises the steps of correcting spectra according to concentrations of N2 gas, O2 gas and CO2 gas existing in an atmosphere to be discharged, and deciding contents of an N component, an 0 component and/or a C component in the sample 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical emission spectroscopic analysis method, and more particularly to an optical emission spectroscopic analysis method mainly used for the analysis of trace components in the steel industry.

[0002]

2. Description of the Related Art In recent years, with the diversification of steel types, the improvement of quality, and the progress of steelmaking processing technology, the amounts of trace components, especially nitrogen, oxygen and carbon components contained in steel have been strictly controlled. Although technology has advanced, on the other hand, quantitative analysis of the above-mentioned trace components has become important as a proof of these technologies.

Further, since the steel making and refining processes are on-line operations, it is necessary that the analysis of the trace components is carried out quickly and accurately, and the analysis results are promptly fed back to the steel making and refining processes.

Conventionally, the following methods have been known as methods for analyzing trace components in steel. First, regarding a chemical analysis method for a trace component, for example, as a C component analysis method, a small amount (0.5 to 3 g) of a sample is collected from a solid sample and analyzed by a combustion method such as a weight method or a gas volume method. There is a small amount (0.5
~ 1g) sample is taken by wet method (steam distillation neutralization titration method, steam distillation bispyrazolone absorption spectrophotometry, steam distillation indophenol absorption spectrophotometry) or dry method (inert gas transfer-melt heat conduction method) There is a method of analysis.

On the other hand, as an analytical method capable of simultaneously analyzing these trace components, there is an emission spectroscopic analysis method in which a solid sample is cut and polished, and the polished surface of the sample is discharged to emit light to analyze its spectrum.

The former chemical analysis method has the advantage that high accuracy can be obtained, but has the disadvantage that the sample preparation is complicated and the analysis requires a long time.

On the other hand, the emission spectroscopic analysis method has an advantage that analysis can be carried out quickly, and further, the accuracy of analysis has been improved with the recent progress of the technology such as electronic technology.

Therefore, for the analysis of trace components in steel in the control analysis of the steelmaking process, in which a high degree of analytical precision and a rapidness of analysis are essential requirements, an emission spectroscopic analysis method satisfying such essential requirements is widely used. It is being used.

[0009]

However, when the above-mentioned emission spectroscopic analysis method is applied to an actual manufacturing site, if the analysis time is different, the N existing in the atmosphere inside the light emission stand is different.
_Since the concentrations of ₂ gas, O ₂ gas and CO ₂ gas are different,
There is a problem that the intensity of the emission spectrum corresponding to the N component, the O component, and the C component in the solid sample to be analyzed is influenced by the emission spectrum due to the N ₂ gas or the like, and an error occurs in the analysis value.

The present invention has been made in view of the above problems, and eliminates the influence of the emission spectrum due to N ₂ gas, O ₂ gas and CO ₂ gas which deteriorates the accuracy of analysis at the time of emission spectrum analysis. It is an object of the present invention to provide an emission spectroscopic analysis method capable of maintaining high analysis accuracy.

[0011]

In order to achieve the above object, an emission spectroscopic analysis method according to the present invention is directed to an analysis surface of a solid sample for analysis mounted on a sample stage and an electrode arranged to face the analysis surface. In the emission spectroscopic analysis method in which a discharge spectrum is generated by analyzing the components in a solid sample by analyzing the generated spectrum, the concentration of N ₂ gas, O ₂ gas and CO ₂ gas existing in the atmosphere to be discharged It is characterized in that the content of N component, O component and / or C component in the solid sample is determined by correcting the spectral spectrum.

[0012]

According to the above-mentioned emission spectroscopic analysis method, discharge is generated between the analysis surface of the solid sample for analysis placed on the sample table and the electrode arranged opposite to the analysis surface, and the generated spectrum is dispersed. In an emission spectroscopic analysis method for analyzing components in a solid sample, N ₂ gas and O ₂ existing in an atmosphere to be discharged
The spectral spectrum is corrected by the concentrations of the gas and the CO ₂ gas, and the N component, O component and / or C in the solid sample is corrected.
Since the contents of the components are determined, the N component, the O component and / or the C component in the solid sample are not affected by the concentrations of the N ₂ gas, O ₂ gas and CO ₂ gas existing in the atmosphere to be discharged. The content of is measured quickly and accurately.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an emission spectroscopic analysis method according to the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic view showing the main part of an emission spectroscopic analysis apparatus used in the method according to the embodiment. In the figure, 11 indicates a light emission stand.

The end of the light emission stand 11 which constitutes the emission spectroscopic analysis device is formed so as to project obliquely downward with respect to the horizontal plane, and the sample table 12 is disposed on the upper surface of the projecting part.
A sample stand hole 12a is formed in the center of the sample 2. On the upper surface of the sample table 12, a solid sample 13 for analysis is arranged in close contact with the sample table 12 so as to close the sample hole 12a, and the solid sample 13 for analysis is placed on the solid sample 13 for analysis. A sample retainer 14 is provided on the table 12 for closely contacting and fixing.

On the other hand, inside the light emitting stand 11, the counter electrode 1 is provided at a position facing the sample stand hole 12a with a predetermined interval.
5 are provided, and the counter electrode 15 and the sample table 12 are provided.
A condenser lens 16 is arranged on the opposite side of the position where the above are arranged. The counter electrode 15 is connected to a power source 21, and the power source 21 is connected to a computer 22 via a control line.

Further, in order to keep the atmosphere inside the light emitting stand 11 at a constant gas atmosphere, gas introducing tubes 17a and 17b are connected near the condenser lens 16 and near the counter electrode 15, respectively, and the tip of the sample table 12 is connected. A gas exhaust pipe 18 is connected near the side. Further, a gas concentration analysis pipe 19 is connected to the light emitting stand 11 in order to analyze a gas component in the atmosphere to be discharged.
9 is connected to a gas concentration measuring device 20, and a light emitting stand 11
It is possible to analyze the gas components and their concentrations.

Using the emission spectroscopic analyzer configured as described above, the emission spectroscopic analysis of the N component, the O component and / or the C component in the analytical solid sample 13 is performed as follows.

First, the solid sample 13 for analysis is placed in the sample holder hole 12.
It is placed on the sample table 12 so as to close a, and the analysis solid sample 13 is pressed by the sample holder 14 to bring the analysis solid sample 13 into close contact with the sample table 12. After the solid sample 13 for analysis is set on the sample table 12 in this manner, the gas introduction pipe 17a
Alternatively, an Ar gas having a purity of 99.999 vol% or a He gas having a purity of 99.999 vol% is introduced from the gas introduction pipe 17b at a flow rate of, for example, 13 liter / min, and the atmosphere for discharging is set to the atmosphere of the gas. After the elapse of a predetermined time, the gas in the atmosphere for discharging is introduced into the gas concentration measuring device 20 by using the gas concentration analysis pipe 19, and the concentration of the gas component in the atmosphere for discharging is analyzed. The gas concentration measuring device 20 actually comprises a gas chromatography device and an infrared absorption measuring device. The gas chromatography device analyzes the concentrations of N ₂ gas and O ₂ gas, and the infrared absorption measuring device measures the CO ₂ gas concentration. analyse.

After that, the solid sample for analysis 13 is heated by a heating means (not shown) so as to have a constant temperature, and when the solid sample for analysis 13 reaches a predetermined temperature, a temperature detecting device for detecting the temperature. Computer 22 (not shown)
Computer 2 which sends a signal to and receives this signal
2 sends a signal to the power supply 21, applies a voltage between the counter electrode 15 and the solid sample 13 for analysis at a predetermined timing, and discharges between the solid sample 13 for analysis and the counter electrode 15. The discharge at this time is performed by triple combined spark discharge.

FIG. 2 is a current waveform diagram of triple combined spark discharge, in which the horizontal axis represents time and the vertical axis represents current value. In triple combined spark discharge, high-power spark discharge is first performed for 15 μs, then spark discharge is performed for 20 μs, and finally arc-like discharge is performed for 120 μs. Photometry is performed during spark discharge.

The light emitted by this discharge is condensed by the condenser lens 16 and sent to a spectroscope (not shown) to select its spectral line, and its photometric value 23 is input to the computer 22.

In the present embodiment, when the N component, the O component and the C component in steel are analyzed, the N spectrum line (analysis line) is 149.2 nm and the O spectrum line is 1
30.2 nm, 165.8 nm as the spectrum line of C
As the Fe internal standard line, 287.2n
Select m. The photometry is performed using a time-resolved photometric method, and the emission intensity ratio between the spectral line of each component in the spark discharge of triple combined spark discharge and iron 287.2 nm is measured by PDA (Pulse-Height Distribution Analysis).
), And obtain the median value of the pulse distribution processed by the above method as the measurement intensity. At this time, the number of preliminary discharge pulses is set to 1000 and the number of PDA photometric pulses is set to 150.
Set to 0 pulse.

In the computer 22, the intensities of the spectral lines corresponding to the N, O and C components in the steel sample obtained by the above-mentioned method are determined by the N ₂ gas and O ₂ gas in Ar gas and He gas. The correction process is performed based on the CO ₂ gas concentration and the CO ₂ gas concentration. The method will be described below.

The content Wi of the i component in the steel can be basically obtained by the following formula 1.

[0026]

[Equation 1]

Net emission intensity I _i (N) of the above-mentioned i component
Is expressed by the following formula 2 from the peak emission intensity I _i (P) of the i component and the background emission intensity I _i (B) of the i component measured by the emission spectroscopic analyzer.

[0028]

[Equation 2]

Here, the background emission intensity I _i (B) of the i component in the equation (2) is N ₂ gas and O in the atmosphere to be discharged.
It is affected by the concentrations of ₂ gas and CO ₂ gas. Considering its influence, the background emission intensity I of the i component is
_i (B) can be expressed by the following formula 3 as a function of the concentrations of N ₂ gas, O ₂ gas and CO ₂ gas in the atmosphere to be discharged.

[0030]

[Equation 3]

The constants a, b, c and d in the above equation 3 can be obtained by the following method.

An example will be described in which the atmosphere for discharging is Ar gas and the i component in the steel sample to be analyzed is the N component. First, an atmosphere for discharging is prepared so as to be an atmosphere containing no gas other than Ar gas such as N ₂ .
A steel sample having a known content of N component is prepared, and its peak emission intensity I _i (P) is measured. The above experiment is repeated several times for steel samples having different N component contents, and the relationship between the N component content in the steel samples and the peak emission intensity I _N (P) of the N component is plotted in a graph.

FIG. 3 is a graph showing the relationship between the content of the N component in the steel sample and the peak emission intensity I _N (P). The straight lines A, B, C and D show the emission intensity in the discharge atmosphere. It is shown. The straight line A indicates the above-mentioned purity of 99.999vo.
It is a line connecting the plots of the peak emission intensity I _N (P) in 1% Ar gas, and the emission intensity when the content of the N component is 0, that is, the intersection of the vertical axis and the straight line A is The background emission intensity I _N (B) in this case is obtained. In the Ar gas, X (N ₂ ) = X (O ₂ ) = X (CO ₂ ) = 0, and the background emission intensity I _N (B) of the N component described above from Equation 3 becomes the value of d, From FIG. 3, d = 0.31.

Next, the straight line B is the same as in the case of the straight line A for the Ar gas containing only 1 ppm of CO ₂ gas.
6 is a graph showing the relationship between the content of components and the peak emission intensity I _N (P), showing the background emission intensity I in this case.
_N (B) is 0.28 when calculated in the same manner as in the case of A.
In this case, X (N ₂ ) = X (O ₂ ) = 0, so when substituting into Equation 3, the result is as shown in Equation 4 below.

[0035]

[Equation 4]

Similarly, A containing N ₂ gas and O ₂ gas
The background emission intensity I _N (B) is also observed for the r gas system.
Then, by substituting into Equation 3, the following Equation 5 and Equation 6 are obtained.

[0037]

[Equation 5]

[0038]

[Equation 6]

In this way, the constants a, b, c, d can be obtained, and as a result, the equation (3) is expressed by the following equation (7).

[0040]

[Equation 7]

Similar to the above method, the background emission intensity I corresponding to the equation (3) is also applied to the O and C components.
The formula for _i (B) can be found. Although the derivation of Equation 7 has been described with reference to FIG. 3, it can be obtained by using a regression equation in a computer.

The net emission intensity I _i (N) of the i component of the equation 2 can be obtained by using the formula of the background emission intensity I _i (B) of the i component thus obtained. Therefore, the calibration curve constant k of the equation 1 can also be obtained.

As described above, the relationship between the content of the i component in the steel sample and the intensity of the emission spectrum corresponding to the i component and the concentrations of N ₂ gas, O ₂ gas and CO ₂ gas in the atmosphere to be discharged. A formula is obtained, which enables correction taking into consideration the concentrations of N ₂ gas, O ₂ gas, and CO ₂ gas in the atmosphere to be discharged, and more accurate N, O, and C components in a steel sample. Can be obtained.

Next, the results of actual analysis of the N, O and C components in a steel sample using the above method will be described below.

First, Ar gas was used as a gas atmosphere for discharging, and a predetermined N ₂ gas and O were added in the atmosphere for discharging.
Ar gas having a concentration of ₂ gases was introduced, sampling was performed from the gas concentration analysis pipe 19, and N ₂ gas and O ₂ gas were analyzed by a gas chromatography device. In this case, a 3 m long molecular sieve 5A type was used for the separation column of the gas chromatography device, a heat conduction cell was used for the detector, and the separation column temperature was 70 ° C. and the detector temperature was 70 ° C. as analysis conditions. ℃, the detector current is 70
mA, sampling interval is 5 minutes and sampling amount is 2
The measurement was performed under the condition of milliliter.

FIG. 4 is a gas chromatograph showing an example of the results obtained by the above measurement, in which the ordinate represents the signal of the detector (arbitrary unit) and the abscissa represents the retention time.

As shown in FIG. 4, under the above conditions, O ₂
The gas peak and the N ₂ gas peak were clearly separated from each other, and the respective components could be quantified by performing an analysis by a usual method using the above-mentioned conditions.

[0048] Similarly the CO ₂ concentration by nondispersive infrared absorption method using the infrared absorption measuring device, could be quantified by using an infrared absorption peak of CO ₂ in the 4.3 [mu] m.

The concentrations of N ₂ gas, O ₂ gas and CO ₂ gas in the atmosphere gas to be discharged by the above method were quantified, and the emission spectroscopic analysis of the steel samples for analysis whose components were already known was conducted. A formula corresponding to the formula 7 is obtained for the C component, and from this, the content of the i component in the steel corresponding to the formula 1 described above, the intensity of the emission spectrum corresponding to the i component, and the N in the atmosphere to be discharged. ₂ gas, O ₂ gas and CO
The relational expression with the concentration of _two gases was obtained.

Next, using the steel samples of which the contents of N component, O component and C component are unknown, the concentrations of N ₂ gas, O ₂ gas and CO ₂ gas in the atmosphere to be discharged by the above method were determined. The background emission intensity I _i (B) was obtained from the value, and finally the contents of N component, O component and C component in the steel sample were obtained. Table 1 shows the obtained analytical values and the accuracy of repeated analysis of the analytical values. Further, as a comparative example, Table 1 also shows the results obtained by the conventional method of quantifying only the emission intensity without correcting the concentrations of N ₂ gas, O ₂ gas and CO ₂ gas in the Ar gas atmosphere. The analysis was repeated 5 times every hour. In addition, the content of the analysis sample in Table 1 and Table 2 is the analysis value of each component obtained by the chemical analysis. In this case, the impulse melting thermal conductivity method is used as the analysis method for the N component, and the impulse is used as the analysis method for the O component. Fusion infrared method, C
The high-frequency combustion infrared method was used as the analysis method.

[0051]

[Table 1]

As is clear from Table 1, according to the analysis method of the embodiment, it is possible to analyze each of the N component, the O component and the C component with higher accuracy as compared with the case of the conventional analysis method. It was

He gas, which has a higher excitation efficiency than Ar gas, was used as the atmosphere gas, and the content of the C component was not determined. The N and O components in the steel sample were the same as in the case of Ar described above. Was determined. Table 2 shows the analytical values obtained and the accuracy of repeated analysis of the analytical values. The analysis was repeated 5 times every hour.

[0054]

[Table 2]

As in the case of Table 1, according to the analysis method of the example, both the N component and the O component could be analyzed with higher accuracy as compared with the case of the conventional analysis method.

[0056]

As described in detail above, in the emission spectroscopic analysis method according to the present invention, the analysis surface of the solid sample for analysis placed on the sample table and the electrode arranged opposite to the analysis surface are provided. In an emission spectroscopic analysis method in which the components in a solid sample are analyzed by discharging the generated spectrum and analyzing the generated spectrum, the spectrum according to the concentrations of N ₂ gas, O ₂ gas and CO ₂ gas present in the atmosphere to be discharged. Of the N component, the O component and / or the C component in the solid sample for analysis is determined, the N ₂ gas, the O ₂ gas and the CO ₂ gas present in the atmosphere to be discharged are It is possible to measure the content of the N component, O component and / or C component in the solid sample for analysis quickly and accurately without being affected by the concentration. For example, a suitable management analysis method in a steel process or the like. Analysis of the present invention as The law can be utilized.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a main part of an emission spectroscopic analyzer used in a method according to an example of the present invention.

FIG. 2 is a current waveform diagram of triple combined discharge.

FIG. 3 is a graph showing the relationship between the content of N component in a steel sample and the peak emission intensity I _N (P), showing straight lines A, B, C,
D shows the light emission intensity in the atmosphere for discharging.

FIG. 4 is an example of a gas chromatograph obtained when N ₂ gas and O ₂ gas in an atmosphere gas to be discharged are analyzed by gas chromatography.

[Explanation of symbols]

 12 sample stage 13 solid sample for analysis 15 counter electrode

Claims (1)

[Claims] 1. An electric discharge is made between an analysis surface of a solid sample for analysis mounted on a sample stage and an electrode arranged opposite to the analysis surface, and the generated spectrum is dispersed to analyze the components in the solid sample. In the emission spectroscopic analysis method, the spectral spectrum is corrected according to the concentrations of N ₂ gas, O ₂ gas and CO ₂ gas existing in the atmosphere to be discharged, and the N component, O component and / or C in the solid sample is corrected. A method for emission spectroscopic analysis, which comprises determining the content of a component.