JP2532941B2 - Emission spectroscopy - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an emission spectroscopic analysis method for analyzing and quantifying sample components according to their existing forms in a sample.

[0002]

2. Description of the Related Art For quality control during a metal refining process, it is necessary to quantitatively analyze various elements in a metal according to their existing forms in the metal. There are compound forms such as oxidation and sulfide, and alloy forms in which a simple element is dispersed in a metal. Conventionally, there is a chemical method that separates and analyzes the sample according to the form by various decomposition methods to quantify the component elements by dividing them into a dispersed state and a compound state such as nitride, oxide, etc. It was not valid for control analysis in.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to enable quantitative analysis of each element in a sample according to the existing form by using emission spectroscopy.

[0004]

[Means for solving the problems] The average concentration A of each component element in the whole sample is obtained from the emission line light intensity for each discharge by a calibration curve, and the following specific discharge for each component element is obtained from the emission line light intensity data for each discharge. From each specific discharge for each component element, the average concentration of the component in each discharge region is determined by the calibration curve, and the average concentration A of the element in the entire sample is subtracted from the average concentration. , An approximate value X ′ of the concentration of the element as the compound state in the specific discharge region, and the true concentration X of the element as the compound state in the specific discharge region, the true concentration as the dispersion state of the element in the region Is defined as Y, and X = X'-KiY Y = A-KsX is obtained as a solution of simultaneous equations, where Ki and Ks are correction coefficients. The average value Xm of X for each specific discharge was multiplied by (specific discharge count) / (total discharge count) to calculate the average concentration of the element as a compound in the entire sample. Here, the specific discharge is referred to in paragraph 0006.
As described above, one discharge is transmitted to a region containing grain boundary inclusions.
Discharge in the case of, for example, a certain discharge region
Is determined to contain inclusions such as oxides of certain elements.
Discharge, the discharge becomes a specific discharge.

[0005]

Function: The discharge diameter of one pulse in spark discharge emission analysis is 3
It is about 0 micron. What is obtained by one discharge is the average concentration of each component in this discharge region, and the average average value of each discharge in multiple discharges is the concentration of each component as a whole sample. Ingredients that make non-metallic compounds such as oxides in the metal, some exist as alloy components in the metal, the other part is an oxide or nitride, these non-metallic compounds, It is precipitated as inclusions in the crystal grain boundaries of the metal, and the size varies depending on the inclusions.
For example, the metals Al and Ca in steel are solid-dissolved in Fe, but the oxides are (Al ₂ O ₃ , CaO) and the size is about 5 μm and scattered as inclusions. Therefore,
The spectral intensities of Al and Ca obtained for each spark discharge include the oxide within the discharge diameter,
Not included, or varies significantly depending on its size. The reason is that Al in a solid solution state is dispersed in the metal at a low concentration, and when there are no inclusions in the discharge region, the proportion of Al in the discharge region is small, and therefore The emission line intensity is low, and the change in emission line intensity with each discharge is small,
When inclusions are present in the discharge, the inclusions have a high degree of Al integration, so that the proportion of Al in the discharge region is large, and the bright line light intensity of Al appears significantly. The change in size occurs in proportion to the amount of inclusions present, and the difference in the obtained spectral intensities is several times to several tens of times. Further, if there is an oxide such as Al in the discharge region, naturally bright line light of oxygen also appears.

For example, when the emission line intensity of oxygen is detected in one discharge, it is determined that the discharge region of the discharge contains an oxide, and the component elements Al and C in the discharge are included.
By determining whether or not the bright line light intensity of a is larger than the average intensity of each component element over the entire sample, it is possible to determine which component element the oxide is. When it is determined that inclusions such as oxides of a certain element are contained in the region of one discharge in this way, the discharge is named a specific discharge. Next, from the relationship between the emission line light intensities of oxygen and the component element to be oxidized, the oxide is quantitatively determined as follows.

For a standard sample, the correlation between the emission line intensity of each element and the concentration of each component element by the chemical analysis of the sample is examined by emission spectroscopic analysis, and a calibration curve is prepared in advance. The average concentration of each component element in the entire sample is determined from the intensity by the above calibration curve, and this is designated as A. Then, for example, a bright line of oxygen is detected in a certain discharge,
At the same time, if the emission line intensity of one component element, such as Al, shows a strong intensity deviating from the Al emission line intensity in many discharges, it is a specific discharge of Al,
It is determined that the discharge has flown into a region containing Al ₂ O _3, and the average concentration of Al in that region can be obtained from the above calibration curve. This Al concentration is in the form of dispersed or solid solution Al.
Is the average concentration of the entire Al including Al and Al in the form of Al ₂ O ₃ . Therefore, from this average concentration,
Subtracting the average concentration of l, that is, the above A, indicates the concentration of Al in the compound form of this specific discharge region, that is, Al ₂ O ₃ . Let this be X '. However, in reality, in one specific discharge region containing Al ₂ O ₃ , the area of the Al dispersed state portion is reduced by the area of the Al ₂ O ₃ state. The bright line light intensity is lower than the average intensity of the Al bright line light obtained from all the discharges in one analysis. Therefore, a corrective calculation is performed as a first approximation from the concentration X ′ of the dispersed Al and the Al ₂ O ₃ state Al assumed above to obtain the correct Al ₂ O ₃ concentration X.

Compound-type Al ₂ in the specific discharge region
Since the first approximate concentration of Al as O ₃ overestimates the concentration of Al solid solution in the same region as described above, the true concentration X of compound Al in this specific discharge region is X = X You can put it as'-KiY. Here, Ks and Ki are Al ₂ O ₃
Since it can be determined in advance by comparing the emission spectroscopic analysis and the compound analysis of an actual sample containing, the first term on the right side of each equation in this simultaneous equation is the first approximation of the first approximation obtained from the actual measurement of the sample. Since it is known at each concentration and the coefficients Ks and Ki are also known, this simultaneous equation can be solved for X and Y.

Since X obtained in this way is the concentration of compound Al in each specific discharge region for Al, A
The concentration of compound-type Al in all specific discharges for 1 can be obtained. The concentration of compound-type Al in the entire sample can be obtained by multiplying the average concentration of compound-type Al by (specific discharge number) / (total discharge number) for Al.

[0010]

FIG. 1 shows an embodiment of the present invention. 1 is sample 3
In the discharge chamber for spark discharge, the inside is filled with argon gas. Reference numeral 2 is a discharge circuit that generates a pulse voltage for spark discharge. A counter electrode 4 is applied with a high-voltage pulse from the discharge circuit 2 between the counter electrode 3 and the sample 3 to perform spark discharge between the electrode 3 and the sample 3. A spectroscope 5 has a vacuum inside. Reference numeral 6 is an entrance slit for extracting a parallel light beam traveling in a fixed direction from the spark light generated between the counter electrode 4 and the sample 3. Reference numeral 7 is a diffraction grating that disperses the spark light. 8
Denoted at 11 are exit slits, which are arranged at the emission line positions of the respective elements on the spectrum image plane of the diffraction grating 7, and only the spark light passing through the exit slits 8 to 11 is incident on the photomultipliers 12 to 15. To do so. 16-
19 is a single pulse integrator, which is a photomultiplier 12
The bright line light intensity signals detected in ~ 15 are integrated for each discharge unit. Reference numeral 20 denotes a switching device that sequentially and individually transmits the values (single data) integrated by the single pulse integrators 16 to 19 to the A / D converter 21. The A / D converter 21 converts the received single data into a digital signal. 22 is a memory,
Single data is stored in time series for each element, and other data can also be stored. Microcomputer 23
Controls the above-mentioned units and calculates measured values from the data in the memory.

Spark discharge is repeatedly performed between the sample 3 and the counter electrode 1,000 to several thousand times, and the emission intensity of each element for each discharge is measured as shown in FIGS. In this figure, the height of the vertical bar at the same position on the time axis of each element is the output signal of the single pulse integrators 16 to 19 in FIG. 1, and represents the intensity of each bright line light in one discharge. The obtained emission line intensity data of each element is stored in the memory 22 in time series. From the data in this memory, if the emission line intensity of oxygen in the same discharge is taken as the horizontal axis and the emission line light intensity of the component element (eg, Al or Ca etc.) is taken as the vertical axis, one point is determined for each discharge, When this point is recorded for the discharge of, it is distributed as shown in FIG.
A correlation curve of the emission line light intensity between oxygen and the constituent element can be obtained. The correlation curve is approximated by a quadratic curve. This curve is broken at point P. The emission line intensity of oxygen corresponding to this point P is not due to the emission line intensity of oxygen, but is due to stray light of the spectroscope at that position and dissolved oxygen that is uniformly dispersed throughout the sample. It corresponds. The bright line light intensity of the component element at point P corresponds to the concentration of the component element in the dispersed state. Therefore, from the component element emission line light intensity at this point, using the calibration curve prepared in advance with a standard sample with few inclusions, the content% of the dispersion state of the component element is
Ask for. This is called Sol.

Next, referring to FIG.
As shown in, the appearance frequency distribution curve of the bright line light intensity is obtained,
A discharge corresponding to the emission line intensity of oxygen in an appropriate range centered on the most frequent value, for example, ± σ, was extracted, and the average value of the emission line intensity of the component elements in each extracted discharge was determined, and created with a standard sample. Using the calibration curve of the constituent elements, the average concentration of the constituent elements in the discharge region containing the inclusions is determined. This is designated as Tl. In the above, the data in the range of ± σ is used, although there are various amounts of inclusions included in one discharge region. This is because the concentration of the component in the compound form is required.

The emission line intensity of the component element used at this time includes the emission line intensity of the same element in the oxide state as the emission line intensity of the component element in solid solution form. The element concentration is separated into a solid solution state and a compound state. First
As the next approximation, a value obtained by subtracting Sol obtained in the previous stage from Tl is used, and this is referred to as Insol. The correction coefficients obtained by the chemical method are Ks and Ki, respectively, and the true concentration of Al in the compound state is X and the true concentration of Al in the dispersed state is Y.
Then, Y = Sol-KsX X = Insol-KiY By solving the above simultaneous equations, the contents of inclusions and component elements can be obtained.

[0014]

According to the present invention, the bright line light intensities of the component element and the non-component element are measured for each discharge, and the component element is determined from the correlation between the bright line light intensity of the component element and the bright line light intensity of the non-component element. Since it has become possible to quantify the content of iron and the content of inclusions, quantitative analysis can be performed quickly, and high quality control in the refining process has become possible.

[Brief description of drawings]

FIG. 1 is a block diagram of one embodiment of the present invention.

FIG. 2 is an explanatory diagram of data in the above embodiment.

FIG. 3 is a correlation curve diagram of the emission line light intensities of the component element and the non-component element in the above example

FIG. 4 is an appearance frequency distribution diagram of emission line light intensities of non-component elements in the above-described example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Discharge chamber 2 Discharge circuit 3 Sample 4 Counter electrode 5 Spectrometer 6 Entrance slit 7 Diffraction grating 8-11 Exit slit 12-15 Photomultiplier 16-19 Single pulse integrator 20 Switcher 21 A / D converter 22 Memory 23 Microcomputer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mamoru Yamaji 1850 Minato, Wakayama City Sumitomo Metal Industries, Ltd. Wakayama Works (56) References JP-A-4-294258 (JP, A) JP-A-5-79982 (JP , A) JP-A-3-138548 (JP, A)

Claims (1)

(57) [Claims] 1. The average concentration A of each component element in the entire sample is obtained from the emission line light intensity for each discharge by a calibration curve, and the following specific discharge for each component element is searched from the emission line light intensity data for each discharge: From each specific discharge for each component element, the average concentration of that component in each discharge region is obtained by the above calibration curve, and the average concentration A of that element of the entire sample is subtracted from the average concentration to determine the following The approximate value X ′ of the concentration of the element as the compound state in the discharge region is obtained, and the true concentration X of the element as the compound state in the specific discharge region and the true concentration of the element as the dispersed state in the region are set as Y. , X = X'-KiY Y = A-KsX Obtained as a solution of simultaneous equations, where Ki and Ks are correction coefficients. The average value Xm of X for each specific discharge is multiplied by (specific discharge number) / (total discharge number) to calculate the average concentration of the element as a compound state in the entire sample. Emission spectroscopy analysis method. The specific discharge is a discharge in which the emission line of oxygen and the emission line intensity of one component element, for example, Al are simultaneously detected at a certain value or more in a certain number of discharges, and the discharge is a specific discharge of Al. The discharge is judged to have flown into a region containing the Al oxide Al ₂ O ₃ .