JPH0943150A - Method for measuring composition and particle size distribution of inclusion of metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To quickly and accurate measure the compositions and particle size distributions of inclusions scattered in a metal by finding the intensity values of the inclusions by dividing the intensity values of emission spectral lines obtained at every spark and converting the intensity values into particle sizes on the basis of the data of a standard sample. SOLUTION: By causing spark discharge, for example, 1,000 times between a sample 2 set in a light emitting section 20 and a counter electrode 3, spectral lines dispersed 7 at every spark discharge are received by means of a photomultiplier (detector) and the light emitting intensities of metallic elements (Al, Si, Mn, etc.) and oxygen are measured while the intensities are time-resolved into those of a metallic part and those of a nonmetallic inclusion part. An arithmetic processor 5 ranks the measured light emitting intensities of the metallic elements by converting the intensities into particle sizes by using a calibration curve plotted in advance by using standard samples having known particle size distributions and finds the compositions and particle size distributions of the inclusions by integrating obtained data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring the composition and particle size distribution of non-metallic inclusions (hereinafter referred to as inclusions), and in particular, inclusions that are dispersed and present in a metal material by using emission spectroscopy. It relates to a measurement technique suitable for a quality control test and inspection for identifying and evaluating a metal material.

[0002]

2. Description of the Related Art Steel materials such as cast slabs have inclusions of various compositions inside, and the composition and particle size of the inclusions greatly affect the quality of the steel material, especially the composition and particle size. Is important to identify and evaluate. Especially for steel products such as wire shafts, bearing materials and deep drawing materials
If there are many relatively large inclusions of m or more in the steel,
Cracks tend to occur starting from the inclusions, and the fatigue properties of the product are significantly reduced. Therefore, high cleanliness is required for these steel products, and it is necessary to accurately and promptly grasp and evaluate the composition and grain size distribution of inclusions in the steel in each step of the steelmaking stage.

As a commonly used evaluation method for the existence state of inclusions in steel, there is a microscopic test method defined in JIS G 0555. This method involves visually observing the sample material that has been mirror-polished with a microscope, but it takes one or two days to prepare and measure the sample, which is not quick and is a visual sensory test. There is a drawback that it is difficult to identify the composition of inclusions. In recent years, an image analysis method using a computer has been developed and is being applied to the microscope test method to accelerate the measurement. However, it takes time to prepare a sample as in the conventional method, and polishing flaws and dusts are required. The drawback that measurement errors are likely to occur due to the adherence of is still unsolved.

As another evaluation method, inclusions are separated from steel by a chemical analysis method and evaluated, such as a bromine-methanol method and a warm nitric acid method. However, these methods have a problem that they are not suitable for analyzing and evaluating a large amount of various manufactured steel materials in a large amount because they use the conventional so-called chemical analysis method and are therefore quick. In addition, electronic probe microanalyzer (EP
There is also a method of evaluating inclusions in steel using MA), but this method also requires complicated procedures such as operation with an electronic probe and various arithmetic processes, and therefore lacks swiftness of measurement and a large amount of test material. Was unsuitable for processing.

Therefore, in order to rapidly evaluate the inclusions in a large amount of steel materials, several methods for measuring inclusions in steel using emission spectroscopy have been conventionally proposed (for example,
"Iron and steel" vol. 73 (1987) S969, S97
0, and "CAMP-ISIJ" vol. 7 (199
4) 1292, 1293, etc.). Also, Japanese Patent Application Laid-Open No. 4-238
The publication No. 250 measures, in a time series, about 0 to several hundreds of pulses at the initial stage of discharge, among emission pulses obtained by discharge, and measures an emission pulse corresponding to an intensity range defined in the obtained emission pulses. As a method, a method for determining the number of inclusions in the metal, the diameter, the content, and the average diameter based on a predetermined formula is disclosed.

However, these emission spectroscopic analysis methods determine the composition and the amount of inclusions from the spectral line wavelengths and intensities of the contained elements after the light is emitted under the conditions of spark discharge according to the sample and the light is dispersed. And
The particle size of the inclusions cannot be measured, and the inclusions to be measured are limited to alumina-based inclusions.
Further, the measurement elements are only metal elements such as Al and Fe that is a matrix, and it is impossible to analyze and evaluate inclusions other than alumina, non-metal elements forming inclusions, and elements other than inclusions. Therefore, conventionally, there is no technique for quickly and accurately evaluating inclusions in steel, the inclusion composition and grain size are measured, and the results are reflected in process control.
It was difficult to obtain a desired quality steel material.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and it is possible to quickly determine the composition and particle size distribution of inclusions dispersed and present in a metal by using a spark discharge type emission spectroscopy. The purpose is to provide a method for accurate and accurate measurement.

[0008]

According to the present invention for achieving the above-mentioned object, inclusions existing in a metal sample are generated by performing a large number of spark discharges between a metal sample and a counter electrode in an inert gas atmosphere. In the emission spectroscopic analysis, while determining the content of each element in the usual data processing, the intensity value of the emission spectrum line obtained for each spark discharge, the solid solution of each element at the preset discharge time And the inclusions, the intensity value of the inclusions is converted to a particle size based on the relationship between the intensity value and the particle size obtained in advance with a standard sample, and this operation is performed every many discharges. It is a method for measuring the composition and particle size distribution of inclusions in a metal, which is characterized by repeating and integrating to determine the particle size distribution of the inclusions present in the metal. Also, the present invention
Among the constituent elements of the inclusions, it is also a method for measuring the composition and particle size distribution of inclusions in a metal in which the non-metal element is oxygen or nitrogen.

As a result, the composition and particle size distribution of the inclusions in the metal can be measured more quickly and accurately by the emission spectroscopy. Hereinafter, the content of the present invention will be described, including the circumstances leading to the invention. Since the composition of inclusions in a metallic material such as steel material affects the quality characteristics of the metallic material, under the present circumstances where it is necessary to adjust the composition with high accuracy, the metallic material is chemically analyzed to determine its composition. ,
Depending on the composition, the composition is adjusted based on experience in the steelmaking stage, or the product inspection is used to determine whether it is acceptable or not, and rejected products are eliminated. Therefore, the inventors decided to review the emission spectroscopic analysis method in order to perform treatment in a more rapid manner.

Spark discharge optical emission spectrometry is an analytical method capable of simultaneously analyzing many elements in a sample. Normally, this analysis method is used to quantify the average content of each element in the metal ingots (portions other than inclusions) of metal materials, and in order to perform accurate measurement, light emission by spark discharge Abnormal spectral line intensities are deleted from the spectral line intensity data from each of the above elements and processed. This is because the spectral line showing this abnormal intensity is considered to be because the spark discharge causes a selective discharge at the boundary between the metal and the inclusion (for example, "iron and steel" vol. .66 (1980) p1401-
1405, "Iron and Steel," vol. 73 (1987) p14
19-1424).

By the way, the emission spectrum line of Al obtained after the emission spectral analysis of the steel material is shown for each spark discharge in FIG. 1 (A) without deleting the one showing the above-mentioned abnormal intensity. The spectral line intensity of the inclusions is greater than the spectral line intensity from the. Furthermore, when these data are arranged by the appearance frequency of the emission spectrum line intensity of the metal and the inclusion, it becomes the one shown in FIG. 1 (B). FIG. 1 (C) makes this easier to understand.

Next, the inventor obtained a large number of relational data between the emission spectrum line intensity of each element and the emission time within one spark discharge period, and the obtained data are shown in FIG.
An example of inclusions of aluminum and oxygen is shown in (B).
FIG. 2C is a diagram in which these relationships are organized for convenience of understanding. According to FIG. 2 (C), in the case of metal, Al, which is a metal element, emits light at the initial stage of discharge, but O (oxygen), which is a non-metal element, hardly emits light because it is not present in the metal. I understand. On the other hand, in the case of inclusions, it is recognized that Al, which is a metal element, emits light in the latter stage of discharge, and O (oxygen), which is a non-metal element, also emits light at about the same time. This phenomenon is that there is a difference in the time until light emission due to the difference in the boiling points of the metal and inclusions,
It was speculated that this is because the size (volume) of the inclusions causes a difference in the melting and evaporation time due to the spark discharge, and when the inclusions are large, the light emission time is long.

Therefore, the inventors have performed selective discharge to the inclusions, and have a difference in the content of the same element between the inclusions and the metal,
It was judged that the composition and particle size of the inclusions can be measured by focusing on the difference in the intensity of the emission spectrum line and the difference in emission time due to the time difference in the emission phenomenon due to their physical properties. That is, as shown in FIG. 2B, the emission spectrum line intensities of the elements forming the inclusions are simultaneously measured to identify the type (composition) of the inclusions, and further, the spectral line intensities of the inclusions are identified. It was considered possible to infer the particle size of the inclusions from the degree of.

A specific measurement example is shown in FIG. 3. 60 μmsec from the start of light emission (in this case, the start of spark discharge).
60μ when the photometry can be divided by time
The emission intensity of the front (bare part) by msec and 60 μms
The emission intensity after ec (inclusion part) is shown by Al. From FIG. 3, an abnormal emission intensity hardly appeared in the early stage of discharge (before 60 μmsec), and in the latter stage of discharge (60 μm).
It was confirmed that an even higher emission intensity appears after (sec).

FIG. 4 shows the emission spectrum line intensities of inclusion forming elements in the order of discharge. According to FIG. 4, from the spectral line intensity indicated by the symbol (c), Al ₂ O ₃
The presence of inclusions can be identified, and the inclusion of Al ₂ O ₃ —Si—MnO—CaO can be identified from the spectrum line intensity indicated by the symbol (f), and Si-M can be identified from the spectrum line intensity indicated by the symbol (a).
It can be seen that the inclusion of nO and the presence of Al ₂ O ₃ alone can be identified by the code (c).

Next, the emission intensity of each element in FIG. 4 was converted into a frequency distribution of emission intensity and appearance frequency by the same arithmetic processing as in FIG. 1 (B). Then, the emission intensities are ranked stepwise and used as an index representing the particle size of inclusions. For that purpose, emission spectroscopic analysis is performed using a standard sample in which the composition and particle size of inclusions are known in advance, and The luminescence intensity of the element is obtained, and the luminescence intensity is ranked stepwise so as to correspond to the particle size, and these ranked luminescence intensities are used as the reference value of the particle size. That is, a standard curve is used to prepare a calibration curve regarding the relationship between the emission intensity of each element and the particle size, and the calibration curve is converted into the particle size in comparison with the actually measured emission intensity. Finally, the data of all discharges are integrated and the composition of inclusions and particle size distribution are determined by the frequency of appearance.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 6 schematically shows an apparatus for measuring the composition and particle size distribution of inclusions in steel by the spark discharge emission spectroscopy according to the present invention. that is,
A light emitting unit 20 including a discharge device 1, an analysis sample (also an electrode) 2, and a counter electrode 3, a diffraction grating 7 for splitting an emission spectrum line into a characteristic spectrum line of each element, and a spectrum line for each element A spectroscope 30 including a detector (photomultiplier) 6 for detecting, a photometric device 4 for performing a photometric process by converting the analog amount of the spectral line emitted at each spark discharge into a digital signal, and a composition from the spectral line intensity. It is composed of an arithmetic processing unit 5 for identification and conversion into a particle size distribution. In addition, the arithmetic processing unit 5 has a terminal 9 (C
RT, printer, keyboard, etc.) are also attached.

In the emission spectroscopic analyzer shown in FIG. 6,
The sample 2 is installed in the light emitting unit 20, and the start-up command is issued from the terminal device 9 to automatically start the emission spectroscopic analysis and output the measurement result to the terminal device 9. First, a spark discharge is performed 1000 times between the sample 2 and the counter electrode 3, and a spectral line separated for each spark discharge is received by a photomultiplier, and a metal element (Al, Si, Mn, Ti, Ca) is received. And the emission intensity of O (oxygen) are time-resolved into a bare metal part and inclusions, and photometry is performed respectively. The emission intensity obtained at that time is as illustrated in FIG. The emission spectrum of the ingot is determined by using the emission intensity of O as an index of the inclusion. When the emission intensity of O is at the same level as that of the intrusion, the presence of the emission is detected. Since it is not regarded as an object, the emission intensity of the metal element is not measured.

Next, in the arithmetic processing unit 5, the emission intensity of each of the photometric metal elements is ranked as a particle size by using the calibration curve prepared in advance by a standard sample having a known particle size distribution. The composition and particle size distribution of inclusions were obtained by integrating these data. The calibration curve is
A large number is required for each composition of inclusions.

[0020]

EXAMPLE FIG. 7 (A) is an example of the alumina-based inclusions in the bearing steel obtained by the composition and particle size distribution measuring method according to the present invention, which was obtained from a calibration curve prepared in advance on the X-axis. Particle size,
The frequency of appearance of inclusions is plotted on the Y-axis, and the particle size distribution of the alumina inclusions is shown. On the other hand, FIG. 7B shows the particle size distribution obtained from the same sample by the conventional microscopic examination method.

As is clear from FIGS. 7 (A) and 7 (B), the results obtained by the measuring method according to the present invention are in good agreement with the results obtained by the microscopic examination method. The composition and particle size distribution of the product can be accurately measured. In the measurement by the method according to the present invention, the time required from the start to the end of measurement is about 20 seconds, and the adjustment time of the sample is about 5 minutes or less.
Compared with one or two days, the time is significantly shortened, and it is possible to sufficiently meet the demand for speedy evaluation of inclusions.

[0022]

As described above, according to the present invention, the composition and particle size distribution of inclusions in a metal can be measured quickly and accurately. In addition, since the method according to the present invention can be attached to a multi-element simultaneous quantitative emission spectroscopic analyzer, it is possible to analyze and evaluate inclusions at the same time as component analysis for operation management, and improve efficiency of test work. It also has a great effect on improving the yield in the refining process and reducing the manufacturing cost.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the number of discharges and emission line intensity, where (A) shows emission intensity in the order of discharge, (B) shows appearance frequency distribution of the emission intensity, and (C) shows (B). The figure is shown schematically.

FIG. 2 is a diagram showing a relationship between a time (light emission time) during which light is emitted by one discharge of Al and O (oxygen) and light emission intensity;
(A) is a diagram schematically showing a light emission behavior of a bare metal portion, (B) is a light emission behavior of inclusions, and (C) is a diagram schematically showing (B).

FIG. 3 is a diagram showing the relationship between the emission intensity of the bare metal portion and the inclusion portion and the number of times of light emission when Al is separated into a bare metal portion and inclusions at each emission (60 μmsec after light emission).

FIG. 4 Inclusion-forming elements (O, Al, Si, Mn, C
It is a figure which shows the relationship between the discharge order and light emission intensity of a).

FIG. 5 is a calibration curve showing the relationship between emission intensity and particle size of inclusions.

FIG. 6 is a diagram showing an outline of an emission spectroscopic analysis apparatus embodying the present invention.

FIG. 7 is a result of actually measuring a particle size distribution of inclusions in bearing steel, (A) is a method according to the present invention, and (B) is a conventional microscope test method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Discharge device 2 Sample 3 Counter electrode 4 Photometric device 5 Data processing device 6 Detector 7 Diffraction grating 8 Slit 9 Terminal device 20 Light emitting part 30 Spectrometer

Claims (2)

[Claims] 1. In an inert gas atmosphere, spark discharge is performed a large number of times between a metal sample and a counter electrode, and when the inclusions present in the metal sample are analyzed by emission spectroscopy, each data is processed by ordinary data processing. In addition to determining the content of the element, the intensity value of the emission spectrum line obtained for each spark discharge is divided into a solid solution component and an inclusion component of each element at a preset discharge time, The intensity value of the substance is converted into a particle size based on the relationship between the intensity value and the particle size obtained in advance with a standard sample, and this operation is repeated every many discharges, and the inclusions present in the metal are integrated after integration. A composition of inclusions in metal and a method for measuring particle size distribution, characterized by defining a particle size distribution. 2. The composition and particle size distribution measuring method of inclusions in a metal according to claim 1, wherein the non-metal element among the constituent elements of the inclusions is oxygen or nitrogen.