JPH0949795A - Method and device for directly analyzing molten metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To directly analyze a component of a molten metal by a method wherein a component of a steam right above a surface of a molten metal is analyzed by means of atomic absorption spectroscopy. SOLUTION: An emission light from a light source 4 is emitted passing through an emission passage 1 and is received by a light receiving passage 2 passing through a steam band right above a surface of a molten metal. Tip sections of both of the emission passage 1 and light receiving passage 2 are provided in a probe 3 and the faces of the tips are opposed to each other. An aperture section 31 is provided to a bottom end of the probe 3 and a gas introduction entrance 32 is to an upper section. A spectroscope 5 connected to the light receiving passage 2 is connected to a light measuring passage 6 which is connected to an arithmetic unit 7. A component of the steam right above the surface of the molten metal is analyzed by the arithmetic unit 7 by means of the atomic absorption spectroscopy so that the component of the molten metal is directly analyzed based on the result.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for directly analyzing a molten metal by using atomic absorption spectrometry and immediately determining the component concentration.

[0002]

2. Description of the Related Art As a direct analysis method for molten metal, direct emission spectroscopic analysis is carried out in which a high-density pulse energy is applied to the molten metal to excite the contained element to cause it to emit light for spectral analysis.
A fine particle generation direct analysis method has been proposed in which fine particles are generated from a molten metal, and the fine particles are conveyed to an analyzer and analyzed.

However, these analytical methods have problems in sensitivity and long-term stability and have not been put to practical use.

On the other hand, as a method for analyzing metals, there is an atomic absorption method which utilizes the fact that excited atoms absorb light having a wavelength peculiar to the element, as opposed to the above-mentioned light emission method. In this method, an aqueous solution in which a metal is dissolved is used as a sample, which is atomized while being sent to a heating zone of a predetermined temperature by a certain amount, and the atomization zone is irradiated with light having a wavelength peculiar to the element to be analyzed, Obtain the analytical value from the absorbance. Since only light of a specific wavelength is used, it is only necessary to measure light in a limited narrow wavelength range, which is a method with essentially no disturbance factors and which can perform measurement with essentially high accuracy.

Conventionally, proposals have been made to apply the atomic absorption method, which is an essentially high-precision analysis method, to direct analysis of molten metal. For example, in Japanese Patent Laid-Open No. 63-186131, a probe is inserted into a molten metal, a measuring cell is provided above the probe, and an inert carrier gas is sent from the lower part of the probe toward the measuring cell to melt the molten metal. Disclosed is an apparatus of a system in which metal vapor in the vicinity of the surface is sent to a measurement cell by this carrier gas, where elements heated by heating means to 1200 ° C. or higher and vaporized again during transportation are vaporized to measure atomic absorption. There is.

[0006]

However, in the above-mentioned method, since the apparatus is complicated, such as injecting an inert gas and heating means in addition to the probe, the apparatus cannot be used in a harsh environment where high temperature and dust are filled. There is a problem that it is difficult to install, remove or maintain.

The present invention has been made to solve these problems, and provides a technique for directly analyzing molten metal using a device having a simple structure, easy handling, and stable even in a harsh environment. Is what you are trying to do.

[0008]

The above object is a method for directly analyzing an element in a molten metal by using atomic absorption spectrometry, which comprises irradiating a vapor band near the surface of the molten metal with irradiation light to obtain the vapor. This is achieved by a method for direct analysis of molten metal, characterized in that the light passing through the band is processed by atomic absorption spectrometry to determine the concentration of components in the molten metal.

The vicinity of the surface of the molten metal is filled with vapor from the metal, and the components of this vapor are in equilibrium with the components of the molten metal. Therefore, by measuring the concentration of the components in the vapor zone, the components in the molten metal can be measured. The concentration can be determined. In addition, if it is near the surface of the molten metal, the components are not solidified and a heater is unnecessary, and it is not necessary to convey steam to the heater.

In addition to the straight line path connecting the irradiation point and the light receiving point with one straight line,
There is a reflection path in which the irradiation light is irradiated toward the surface of the molten metal, is once reflected by the surface of the molten metal, passes through the vapor band again, and then is received. When the area of the molten metal surface is limited, the use of the reflection path makes it convenient to increase the absorbance because it passes through the vapor zone twice, and the apparatus is simple and compact.

A preferred method for data processing of atomic absorption spectrometry will be described below. In addition to the wavelength of the line spectrum of the element to be analyzed, the irradiation light always contains the wavelength of the line spectrum of the main constituent element of the analysis sample. This is to cope with fluctuations in measurement conditions such as the temperature of the molten metal, which will be described later.

For light received through the vapor band,
A spectroscopic measurement is performed to obtain the difference between the intensity of the irradiation light and the intensity of the light passing through the vapor band at the center position and background position of each of the line spectra for the element to be analyzed and the main constituent element. Then, by calculating the logarithm of the ratio of the difference in light intensity at the center position of the line spectrum and the difference in light intensity at the background position, the absorbance of each of the analysis target element and the main constituent element of the analytical sample is calculated, and each of the line spectra The difference between the light intensity at the center line position and the light intensity at the background position is obtained, and the absorbance for the element to be analyzed and the main constituent element is obtained by the logarithm of the ratio of the difference in these light intensities. This is because the received light includes noise other than irradiation light (referred to as background light), for example, noise of ambient light such as light emitted from molten metal or sunlight, and is excluded. In particular, since the present invention collects light near the surface of the molten metal, the amount of light emitted from the metal cannot be ignored.

The removal of noise will be described with reference to FIG. The graph is the line spectrum measured by a spectroscope with sufficiently high resolution, the thick solid line is the line spectrum measured through the vapor band, and the thin line is the line spectrum contained in the irradiation light. It is in a state in which the absorption of light has not occurred.

The center position of the line spectrum is the wavelength λ and
Corresponding to constant elements, the foot position λ_bIs background
It is a place. The intensity of the central position is I with irradiation light.₀In Although,
The measurement light passing through the vapor band is not absorbed by the measurement element.
It has fallen to I. Background position intensity
Is the intensity of the light that is not the object of measurement. _0b
However, with the measuring light I_bIt is.

That is, the measurement light is subjected to spectroscopic measurement, the light intensities at both the center position and the background position of the spectrum are measured, and the absorbance excluding the influence of the background light is obtained by the equation (1).

[0016]

[Equation 1]

Using the absorbance thus obtained, the ratio between the absorbance of the element to be analyzed and the absorbance of the main constituent elements (hereinafter simply referred to as the absorbance ratio) is then determined. Then, the calculated absorbance ratio is converted into the component concentration based on the calibration curve.

In the present invention, the measurement is performed in a bad environment. In addition to the ambient light described above, the dust is also exposed, and the dust changes the irradiation light amount and the received light amount. Moreover, the position of the molten metal surface also fluctuates, and the temperature of the vapor zone is not controlled. The measured amount of received light is affected by these disturbance factors.

The reason for using the ratio is to deal with these disturbance factors. When measuring the absorbance for two elements,
Although the measured values are obtained under the same influence of the disturbance factors, the influence of the disturbance factors can be canceled by taking the ratio of these measured values.

An apparatus for carrying out the above-described analysis method will be described. The device consists of a light source, an irradiation optical path for guiding the irradiation light from the light source, a light receiving path in which the front end surface of the irradiation optical path is spaced apart, and a spectroscope connected to the other end of the light receiving path. A photometer for measuring the emitted light and a calculation device for calculating the photometric result are provided.

The light source is a light source of irradiation light containing the wavelength of the line spectrum of the element to be analyzed and the main constituent element, and a composite hollow cathode lamp can be used.

The irradiation path is an optical path for guiding the irradiation light to the vapor band near the metal surface, and the light receiving path is an optical path for receiving the light transmitted through the vapor band and guiding it to the spectroscope. Although the optical path can be formed by using a prism, a reflecting mirror, a lens, or the like, the use of an optical fiber is preferable because the configuration of the device is simplified.

It is necessary to maintain a fixed positional relationship between the irradiation light path and the tip of the light reception path so that the irradiation light is received through the vapor band. Therefore, the tips of the irradiation light path and the light receiving path are provided in the probe, and the molten metal whose surface is exposed is introduced into the probe through the opening at the lower end. Further, an inert gas introducing port is provided above the probe to prevent the chemical change of the exposed surface as an inert atmosphere in the probe.

When the front end surface of the irradiation light path and the front end surface of the light reception path are opposed to each other, the irradiation light passes through the vapor band and is directly received.

If optical fibers are used for the irradiation light path and the light receiving path, and the tip surfaces thereof are arranged so as to point to a point above the opening on the probe center line and below the inside of the probe, the molten metal surface is aligned with this point. At this time, the irradiation light passes through the vapor band and is reflected at this one point, and the reflected light passes through the vapor band again and enters the light receiving path. With this structure, the probe has a simpler shape and is slender, can be easily handled even in a bad environment, and is durable.

[0026]

EXAMPLE A direct analysis was performed on high chromium steel, carbon steel and hot dip galvanizing baths during refining.

Embodiment 1 FIG. Direct analysis of chromium was performed on high chromium steel during refining.

The analyzer used is shown in FIG. In the figure, 1 is an irradiation optical path, and 2 is a light receiving path, each of which is composed of an optical fiber, and the tips thereof are both arranged in the probe 3 and the tip surfaces face each other. The other end of the irradiation light path 1 is connected to the light source 4,
The other end of the light receiving path 2 is connected to the spectroscope 5.

An opening 31 is provided at the lower end of the probe 3, and a gas inlet 32 is provided above the probe 3.

The spectroscope 5 is connected to the photometer 6, and the photometer 6
Is connected to the computing unit 7. First, Ar gas is introduced from the gas introduction port 32 to create an inert atmosphere in the probe 3,
The molten metal was introduced from the opening 31 by inserting the probe 3 into the molten metal whose surface was exposed from above.
Then, the probe 3 was fixed to a depth where the surface of the molten metal was located above the opening 31 and below the tip of the irradiation light path 1 and the tip of the light receiving path 2. Ar from the gas inlet 32
The gas was always introduced, and the gas was discharged from the gas outlet 33 to prevent the contamination of the tip surfaces of the irradiation path 1 and the light receiving path 2 and the oxidation of the vaporized component.

As the light source 4, an Fe-Cr composite hollow cathode lamp (lamp current 30 mA) was used.

A Passengerunge type spectroscope was used for the spectroscope 5, and a photomultiplier tube was used for the photometer 6. The center positions of the line spectra are 380 nm (Fe) and 268 nm (C, respectively).
r), the background position is 382 nm (Fe), 27
It is 0 nm (Cr).

The light intensity at the above-mentioned position was sent to the arithmetic unit 7, the respective absorbances were calculated by the equation (1), and further converted into analytical values by the calibration curve from the ratio of the absorbances of Fe and Cr.

The measurement was carried out continuously for molten steels having different Cr concentrations, but in order to compare the direct analysis value by this method with the chemical analysis value, a sample was drawn during the measurement. A comparison between the direct analysis value at the time of drawing and the chemical analysis value of the drawn sample is shown in FIG.

In the figure, the vertical axis represents the direct analytical value, the horizontal axis represents the chemical analytical value at the same interval, and the analytical value at the same time point is represented by a white circle. The direct analytical value and the chemical analytical value are in good agreement. ing.

Example 2. For carbon steel during refining, Mn
A direct analysis of

The reflection path type probe shown in FIG. 2 was used. An optical fiber is arranged so that the tip ends of the irradiation optical path 1 and the light receiving path 2 face downward and point toward one point in the center of the probe.
Irradiate by aligning the position of the molten metal surface with this one point,
The irradiation light was made to pass through the reflection path.

In the figure, the distances between the tip end surfaces of the optical fibers of the irradiation light path 1 and the light reception path 2 and the reflection points are equal, but they need not be equal. For example, it is possible to increase the irradiation area by far apart the tip end surface of the optical fiber of the irradiation optical path 1.

The atmosphere adjustment in the probe, the spectroscopic method and the photometric method are described in Example 1. Is the same as The conversion to analytical value is Fe
And the center position of Mn line spectrum, that is, 380 nm (F
e), each absorbance is calculated from the light intensity at 252 nm (Mn) and the background position, that is, 382 nm (Fe), 150 nm (Mn) by the formula (1), and the ratio of the two is converted into an analytical value by the calibration curve. It was

Example 1. Similarly to, the comparison between the direct analysis value and the chemical analysis value is shown in FIG. The direct analysis value and the chemical analysis value are in good agreement.

Example 3. Hot dip galvanizing bath Pb
A direct analysis of

The center position of the line spectrum is 283 nm (P
b), 214 nm (Zn), background position is 28
It is 1 nm (Fe) and 212 nm (Mn). Others are the same as the second embodiment.

A comparison between the direct analysis value and the chemical analysis value is shown in FIG. The direct analysis value and the chemical analysis value are in good agreement.

In the above measurement, a flexible optical fiber and a probe with an inert gas introducing pipe may be attached to the furnace, and the shape of the probe is simple. Was also easy to handle.

Furthermore, in the first embodiment. In the probe used in
Although the tip ends of the irradiation light path 1 and the light reception path 2 are curved until they become horizontal, this limits the shortening of the probe diameter. By using a mirror together, the curvature of the tip can be omitted or the radius of curvature can be reduced. FIG. 3 shows an example using a mirror, in which mirrors 11 and 12 are installed near the tip of an optical fiber.

[0046]

As described above, according to the present invention, since the component concentration in the molten metal is obtained by measuring the atomic absorption by the vapor band just above the surface of the molten metal, a simple apparatus can be used. The stable direct analysis of molten metal can be performed even in a bad environment with dust and vibration at high temperature. Furthermore, the background light is removed by obtaining the light intensity at the center line position and the background position of the measurement spectrum, and the analysis value is obtained from the ratio of the absorbance of the element to be analyzed and the absorbance of the main constituent element Since the influence of fluctuations is reduced, accurate analysis results can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing an outline of an apparatus used in an embodiment of the invention.

FIG. 2 is a conceptual diagram of a probe showing an arrangement of optical fibers used for a reflection path in an embodiment of the invention.

FIG. 3 is a conceptual diagram showing another arrangement of the optical fiber and the structure of the tip.

FIG. 4 is a light intensity graph for explaining the position of a line spectrum.

FIG. 5 is a diagram showing a relationship between a direct analysis value of Cr and a chemical analysis value obtained in Examples.

FIG. 6 is a diagram showing a relationship between a direct analysis value and a chemical analysis value of Mn obtained in Examples.

FIG. 7 is a diagram showing a relationship between a direct analysis value of Pb and a chemical analysis value obtained in Examples.

[Explanation of symbols]

 1 irradiation optical path 2 light receiving path 3 probe 4 light source 5 spectroscope 6 photometer 7 arithmetic unit 31 opening 32 gas inlet

Front Page Continuation (72) Inventor Tadashi Mochizuki, 1-2 Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Inventor Akiko Sakashita 1-2, Marunouchi, Chiyoda-ku, Tokyo Nihon Steel Pipe Co., Ltd. In-house (72) Inventor Yoshito Iwata 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Nihon Steel Pipe Co., Ltd.

Claims (5)

[Claims] 1. A method for directly analyzing an element in a molten metal by using atomic absorption spectrometry, which comprises irradiating a vapor band near the surface of the molten metal with irradiation light and atomically absorbing light passing through the vapor band. A method for direct analysis of molten metal, characterized in that the concentration of a component in the molten metal is obtained by processing by an analytical method. 2. Irradiation light is irradiated toward the surface of the molten metal,
The light reflected by the surface of the molten metal after passing through the vapor zone and again passing through the vapor zone is processed by atomic absorption spectrometry.
A method for direct analysis of a molten metal as described. 3. Irradiation light containing the wavelength of the line spectrum of the element to be analyzed and the wavelength of the line spectrum of the main constituent element of the analytical sample is used, and irradiation is carried out at the center position and background position of each of the line spectra. Analyze the element to be analyzed by obtaining the difference between the light intensity and the light intensity of the light that has passed through the vapor band, and then calculating the logarithm of the ratio of the light intensity difference at the center position of the line spectrum to the light intensity difference at the background position. Calculate the absorbance of each of the main constituent elements of the sample, and then use these absorbances to find the ratio between the absorbance of the element to be analyzed and the absorbance of the main constituent element, and then find the concentration of the component in the molten metal based on this ratio. The method for direct analysis of molten metal according to claim 1 or 2, characterized in that. 4. A light source, an irradiation optical path for guiding the irradiation light from the light source, a light receiving path in which the front end surface of the irradiation optical path is spaced apart from the front end surface of the irradiation light path, and the other end of the light receiving path is connected. A spectroscope, a photometer for measuring the dispersed light, and a computing device for computing the photometric result.The irradiation optical path and the tip of the light receiving path are provided in the probe, and the probe is at the lower end of the probe. A direct analyzer for molten metal having an opening for introducing the molten metal and having an inert gas inlet at the top. 5. The irradiation optical path and the receiving optical path are both optical fibers, and these optical fibers are arranged with their tip faces toward a point in the lower center of the probe.
The molten metal direct analyzer described.