JP2000338039A - Method and apparatus for analyzing molten metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To magnify a measuring concn. range by adjusting the wavelength of laser beam at a position shifted from the center position of the absorption wavelength of an element to be analyzed by a specific value. SOLUTION: Laser beam of which the wavelength is adjusted to a position shifted from the center position of the absorption wavelength of an element to be analyzed by 0.001-0.03 mm is used and guided to the vicinity of the surface of a molten metal to be passed through a molten metal vapor layer to measure the change in the intensity of laser beam caused by the passage. A relational expression of the change quantity of intensity and the concn. of a component element in a metal is preliminarily calculated and the concn. of the element to be analyzed is calculated from the measured change quantity of intensity by using the relational expression. Herein, the absorption spectrum by the element to be analyzed has width with respect to the wavelength of light because the temp. or the like of an absorbing substance thereof exerts effect. That is, the change of intensity by absorption is max. in the center wavelength of absorption and reduces along with shift quantity at a wavelength position shifted from a center wavelength.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an analysis technique for rapidly analyzing constituent elements in a molten metal.

[0002]

2. Description of the Related Art Online analysis of molten metal is strongly required to control the refining process of the metal. However, the environment in which molten metal is measured and analyzed is inferior at high temperatures and dust, and there is a large engineering problem to cope with such an environment. Therefore, practical use of online analysis has hardly been made.

In general, as a highly reliable analysis method for analyzing the composition of a metal, an atomic absorption method is known for a sample in which a metal is decomposed with an acid or the like to form a solution. A proposal has been made to apply the atomic absorption method, which is essentially a highly accurate analysis method, to the direct analysis of molten metal. As such a proposal, for example, Japanese Patent Application Laid-Open No. 09-0497
No. 95 discloses a method and apparatus for direct analysis of molten metal, and Japanese Patent Publication No. 09-500725 discloses a direct chemical analysis method for molten metal. These techniques irradiate the metal vapor layer on the surface of the molten metal with light of a specific wavelength (atomic absorption line wavelength), measure the absorptivity of light absorbed by the vapor layer, and determine the component elements in the molten metal. Is determined.

However, in the method described in the above-mentioned literature, in which the vapor of a molten metal is directly analyzed by atomic absorption spectrometry, the amount of generated metal vapor cannot be controlled, so that the concentration range of measurement is narrow. The disadvantages of the above appear remarkably. Hereinafter, this will be described.

[0005] The measurement principle of the atomic absorption method is to determine the amount or concentration of an analytical element in a sample based on the atomic absorption phenomenon according to the following equation (1).

A = μCL …………………………………… (1) (where A: intensity change due to light absorption (= −log (I /
I _o )), (I / I _o ); light intensity ratio, I; light intensity after light absorption, I _o : light intensity before light absorption, μ; extinction coefficient (wavelength-specific), C; L; length of vapor layer) As can be seen from the above equation (1), the light intensity ratio (I / I _o ) rapidly decreases with an increase in the amount or concentration C of the element to be analyzed. If the light intensity ratio (I / I _o ) is too small, influences due to light other than the absorbed light and variations in measured values with a measuring device appear. As a result, concentration measurement becomes difficult. Thus, there is an upper limit on the amount or concentration C of the analysis element.

Therefore, in order to widen the range of the measured amount or the concentration, one or more of the terms μ, C and L are reduced based on the equation (1). For example, in the atomic absorption method of a solution, a sample solution is diluted to lower the amount or concentration C of an element to be analyzed, or the angle with the optical axis of an atomization section (burner) is changed to shorten the vapor layer length L. Thus, it is possible to extend the measurement concentration range.

[0008]

However, in the measurement of molten metal during smelting, the concentration C of the generated vapor layer is determined by the smelting conditions and the content in the molten metal, and cannot be controlled. Therefore, in order to widen the measurement concentration range, either the vapor layer length L or the extinction coefficient μ must be reduced. It is difficult to reduce the length L of the vapor layer because there is a large engineering problem to stably maintain the thickness of the vapor layer at an appropriate small value. Also, it is difficult to reduce the absorption coefficient μ because there is not always an absorption line having μ corresponding to the measured concentration range. For example, as an atomic absorption line of Mn (manganese), there is only a line of 279 nm as a line having a large absorption coefficient μ and a line of 403 nm as a line having a small μ. In Mn concentration measurement, 403n having a small coefficient μ
When the molten steel temperature is 1600 ° C., the Mn concentration C in the vapor layer is high even when the absorption line of m is used.
Even if it is very short, about m, the absorption by the vapor layer is too strong. Therefore, the above-mentioned light intensity ratio becomes 1% or less with respect to Mn having a concentration of 0.1%, and Mn having a concentration of 0.1% or more cannot be measured.

Further, in the method of focusing on the surface of a molten metal described in Japanese Patent Application Laid-Open No. 9-500725, it is difficult to put the molten metal surface into practical use. If the surface of the molten metal is stationary, it behaves like a mirror,
The reflection of the light projected thereon reaches the designed reflection position, and the reflection intensity is sufficiently high. However, in a state where the surface fluctuates and a wave is generated, it is only intermittent that the reflection direction returns to the designed reflection position. Further, the reflection intensity is very small as compared with the stationary surface reflection. that is,
This is because the reflection surface is not a parallel surface but a curved surface, and the reflection angle is widened according to the curvature, so that the illuminance (light intensity density) at the measurement position is reduced. Such a problem does not occur if a stationary surface is made, but it is difficult to make a stationary surface in the smelting process. Even if a probe for light irradiation is used, a stationary surface cannot be formed because the surface of the molten metal fluctuates as a result of flowing Ar or nitrogen gas to inactivate the atmosphere inside the probe.

On the surface of the molten metal, it is very difficult to keep the thickness of the vapor layer constant because of the flow of the molten metal, the heat convection of the vapor layer, and the generation of dust.
During the measurement, the thickness of the vapor layer varies. Therefore, it is necessary to correct this variation.

Further, since molten metal is generally at a high temperature (for example, about 1600 ° C. for molten steel), the molten metal itself emits radiant light. The radiated light is continuous light from ultraviolet to infrared, and naturally includes light having a wavelength at which atomic absorption is to be measured. Since the temperature of the molten metal changes every moment, the radiant light from the surface of the molten metal also changes every moment. Therefore, in the method described in Japanese Patent Application Laid-Open No. 9-500725, the amount of light actually measured is the sum of the amount of light after atomic absorption and the amount of radiation light of the same wavelength, and the true atomic absorption It is not possible to detect only the amount of the subsequent light. In this case, if the radiated light fluctuates during the refining, it is apparent that the light amount of the light after the atomic absorption has fluctuated.

On the other hand, the amount of vapor of each element generated above the molten metal is proportional to the concentration (activity) of the element in the molten metal and the vapor pressure (saturated vapor pressure). Since the saturated vapor pressure is a function of the temperature, if the temperature of the molten metal is constant, the concentration of the element in the molten metal can be obtained from the information (= vapor amount) obtained by the atomic absorption method. In the method described in Japanese Patent Application Laid-Open No. 9-500725, the measurement is performed while keeping the molten metal temperature constant. However, the temperature of the molten metal generally fluctuates in the smelting process requiring concentration measurement, and may fluctuate by 100 ° C. or more in steel smelting. The steam amount fluctuates due to such a temperature change of the molten metal. For example, the amount of Mn vapor generated from molten steel at 1600 ° C. changes about 4% with respect to a temperature change of 5 ° C. Therefore, in order to perform high-precision analysis, the temperature of the molten metal must be measured with an accuracy of 5 ° C. or less to correct the measured value of the amount of steam. Although the use of a platinum-rhodium-based thermocouple is optimal for performing high-temperature measurement with high accuracy, it is necessary to place the temperature measurement position directly below the laser irradiation surface, which is quite difficult to apply. In particular, in a situation where a probe is used for atmosphere control or the like, it is more difficult to set the measurement position immediately below the irradiation surface.

In the method described in Japanese Patent Application Laid-Open No. 9-500725, the light intensity is measured after separating the received light using a monochromator or a polychromator.
However, in this method, there is also a problem that the measurement sensitivity is insufficient because the amount of light is attenuated due to a slit or the like at the time of spectral separation.

[0014]

According to the present invention, a laser beam is passed through a vapor layer of a molten metal, and the concentration of an analysis element contained in the molten metal is measured from a change in the intensity of the laser beam passing through the vapor layer. Molten metal analysis method, wherein the laser beam is 0.001 from the center of the absorption wavelength of the element to be analyzed.
And a method wherein the wavelength is tuned to a position shifted by 0.03 nm.

Further, according to the present invention, the vapor layer in the vicinity of the surface of the molten metal containing one or more analysis elements is shifted from the center position of the absorption wavelength of the analysis element in accordance with the measured concentration range of the analysis element. A measurement light having a wavelength center position at a position and a reference light having a wavelength that does not cause atomic absorption are superimposed and passed on the same optical path, and the intensity of the measurement light component and the intensity of the reference light component of the passed light are measured. And measuring a concentration of an analysis element in the molten metal from a known relationship between an intensity ratio of a measurement light component and a reference light component, a vapor layer thickness, and a molten metal temperature. A method is provided.

In the present invention, the shift amount of the center wavelength of the measurement light is determined by setting the absorbance (= -log (light intensity after light absorption / light intensity without light absorption)) at the maximum value of the measurement concentration range to 2.5. It is preferable to set the value to the following value and less than twice the wavelength half width of the atomic absorption line of the analysis element.

In the present invention, the wavelength half width Z of the measurement light is represented by X where X is the wavelength half width of the atomic absorption line of the analysis element and Y is the shift amount of the center wavelength of the measurement light.
It is preferable to satisfy the relationship of <(2X−Y).

Further, in the present invention, the measurement light whose wavelength center position is shifted from the center position of the atomic absorption line of the main component element of the molten metal according to the absorption sensitivity and the wavelength center position for the analysis element are shifted. The measurement light and the reference light having a wavelength that does not cause the atomic absorption are superimposed on the same optical path and passed through the vapor layer on the surface of the molten metal, and the intensity of both the measurement light component and the reference light component of the passed light The intensity ratio between the measurement light component and the reference light component corresponding to the main component element of the transmitted light and the known relationship between the measurement light component and the reference light component corresponding to the analysis element It is preferable to correct the vapor layer thickness.

Further, in the present invention, the wavelength of the measuring light is monitored during the analysis, and the deviation between the central position of the atomic absorption line and the central position of the measuring light wavelength is measured. It is preferable to correct the light absorption sensitivity of the measurement light component of the light passing through the vapor.

In the present invention, it is preferable that the measurement light and the reference light are turned on / off by using a chopper, and the light intensity at the time of off is corrected as background light intensity from the molten metal.

Further, in the present invention, it is preferable to measure the intensity of the reflected light after irradiating the surface of the molten metal with the measuring light and the reference light and reflecting the reflected light and passing the reflected light through the vapor layer.

Further, in the present invention, it is preferable that the measuring light and the reference light be applied to a region of 5 mmφ or more on the surface of the molten metal.

Further, in the present invention, it is preferable to use measurement data when the reflected light intensity of the reference light is equal to or higher than a threshold value for the density measurement.

In the present invention, the reflected light is received by an optical fiber, and the received reflected light is passed through a band-pass filter having a passing wavelength including an atomic absorption line wavelength of an analysis element and a passing wavelength width of 5 nm or less. It is preferable to select the wavelength and measure the total amount of light after passing through the band-pass filter.

In the present invention, the measuring light and the reference light to be irradiated are laser light, and the intensity of the measuring light and the reference light after the reflected light has passed through the band-pass filter falls within the wavelength band passing through the band-pass filter. It is preferable to adjust the irradiation light intensity so as to be 10 times or more the radiation light intensity of the molten metal.

In the present invention, it is preferable that the main component element of the molten metal is iron and the analysis element is manganese.

Further, according to the present invention, a plurality of laser light sources whose wavelength, half width and intensity of the emitted laser light are variable, means for measuring the wavelength and intensity of the laser light, and a plurality of laser light sources are provided. An optical system that superimposes a plurality of laser lights having different emitted wavelengths on the same optical path, a chopper that turns on and off the laser light superimposed on the same optical path at a constant cycle, and an end portion installed near the molten metal, and the same An optical fiber that guides the laser light superimposed on the optical path to the vicinity of the molten metal, an optical system for irradiating the laser light emitted from the optical fiber to a range of 5 mmφ or more on the surface of the molten metal, and a light receiving unit is installed near the molten metal. One or a plurality of light receiving optical fibers for receiving the reflected light from the molten metal surface and guiding the light to the light detecting portion, and the reflected light guided by the light receiving optical fiber. A high-pass filter and / or a low-pass filter that separates the laser light into wavelength regions that include the wavelength of each laser light, and a narrow wavelength region that includes the wavelength of each laser light from the reflected light that has passed through the high-pass filter and / or the low-pass filter. And a photodetector that measures the total amount of light after passing through the bandpass filter, a unit that measures the temperature of the molten metal, and a computing device that computes the measured result. A metal analyzer is provided.

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

The analysis method according to the present invention includes a step of passing a laser beam through a vapor layer of a molten metal, a step of determining a change in intensity of the laser beam caused by the passage of the vapor layer, Measuring the concentration of the analysis element to be analyzed.

As the laser light, a laser light whose wavelength is adjusted to a position shifted from the center position of the absorption wavelength of the analysis element by 0.001 nm to 0.03 nm is used. The laser light is guided to the vicinity of the surface of the molten metal, passes through the molten metal vapor layer, and the intensity change of the laser light due to the passage is measured. A relational expression between the intensity change amount and the concentration of the component element in the metal (unit is, for example, wt%) is obtained in advance, and the concentration of the analysis element is obtained from the intensity change amount measured using this relational expression. In addition, the measurement of the intensity change may be performed by comparing the laser beam intensity before and after the passage, or by measuring only the laser beam intensity after the passage after preparing the calibration curve. In addition, the intensity change amount may be the measured intensity itself, the ratio between the state where the vapor layer is negligible or negligible and the state where the vapor layer is present, or the absorption change in the same optical system. A ratio with light that does not occur may be used. Also,
These values may be themselves or a logarithm of these values.

The absorption spectrum of the element to be analyzed has a width with respect to the wavelength of light because the temperature of the absorbing substance affects the absorption spectrum. That is, the intensity change due to light absorption is maximum at the light absorption center wavelength, and decreases with the amount of shift at a wavelength position shifted from the center wavelength. That is, by shifting the wavelength position of the laser beam used for measurement from the absorption center wavelength, it is possible to reduce the intensity change due to the absorption of the analysis element.

FIG. 1 shows an example of a change in transmitted (detected) light with respect to incident light when the wavelength position of the laser light used for measurement is shifted. When the wavelength position of the laser beam is matched with the center position of the atomic absorption wavelength, the transmitted light is almost eliminated and the light cannot be detected, whereas the transmitted light can be detected by shifting the wavelength. It turns out that it becomes.

The amount by which the wavelength is shifted is adjusted according to the concentration of the analysis element (element to be measured) and the type of the atomic absorption line. If the absorbance (= -log (light intensity after light absorption / light intensity without light absorption)) at the maximum value of the measurement concentration range exceeds 2.5, the sensitivity on the high concentration side is reduced and accurate measurement becomes difficult. .
Therefore, the shift amount is set so that the absorbance at the maximum value of the measurement concentration range is 2.5 or less. More preferably, the shift amount is set so that the absorbance at the maximum value of the measurement concentration range becomes 2 or less. In this way, the change in absorbance with respect to the concentration can be made linear in the measured concentration range. Also, since absorption does not occur if the shift is too large, the upper limit of the shift amount is set to less than twice the wavelength half width of the atomic absorption line. More preferably, the upper limit of the amount of shift is set so that the absorbance at the maximum value of the measurement concentration range is 0.5 or more. This is because if the absorbance is less than 0.5, the sensitivity in the entire range of the measured concentration is insufficient.

As described above, the concentration range of the element which can be measured by the atomic absorption method can be greatly expanded. By accurately controlling the wavelength of the laser beam and shifting it from the center wavelength of the analysis element, it is possible to set an appropriate change in intensity due to light absorption according to the concentration of the analysis element.

As the light source light that enables such measurement, continuous light can be separated by a spectroscope to extract light of a target wavelength, and the extracted light can be used as the light source light. However, the use of a laser is appropriate due to the light intensity. In particular, a so-called tunable laser that can arbitrarily adjust the oscillation wavelength position is suitable.

However, not all wavelength tunable lasers are suitable, and it is required that the wavelength width of output light be small. As the wavelength width increases, the proportion of light that deviates from the absorption width increases. That is, since the amount of light that is not absorbed (light that becomes the background of light measurement) increases, the change in light intensity with respect to the change in density becomes small, thereby deteriorating measurement accuracy.

By defining the wavelength width of the output light (light source light) serving as the measurement light as follows, it is possible to limit the ratio of the light that is not absorbed and maintain good measurement accuracy. That is, assuming that the wavelength half width of the atomic absorption line of the analysis element constituting the high-temperature molten metal is X, and the deviation amount of the center wavelength of the measurement light from the center position of the atomic absorption line is Y, the central wavelength of the measurement light is Is preferably Z <(2X−Y).

This will be described with reference to FIG. When the wavelength distribution of the absorption spectrum of the element to be analyzed can be considered to be a Gaussian distribution, the relationship between the standard deviation σ and the half width X, which is a guide for the spread, is X = 2.35σ. Generally, assuming that the intensity at the center of the Gaussian distribution is 1, the half-width of 2 from this center
The intensity at a position twice (2X = 4.7σ) apart is 10 ⁻⁵ . That is, the absorbance at this wavelength position is 10 ⁻⁵ with respect to the absorbance at the center wavelength, and even if the sample concentration increases and the absorbance at the center wavelength becomes 100 or more, it is considered that there is almost no absorption at this wavelength position. Wavelength range.

On the other hand, it can be considered that the measurement light has a Gaussian distribution having a center wavelength at a position shifted by Y from the center position of the atomic absorption line of the analysis element and a variance of the half width Z and the standard deviation σ. At a wavelength position (Y + Z) further deviated from the center wavelength Y by a half width (Z = 2.35σ) or more, the amount of the measurement light is reduced to 1%, and even if this amount of light remains without being absorbed by the element to be analyzed, it is affected. Is small.

Accordingly, the half width (wavelength width) of the measurement light is equal to the half width (Z = 2.35) from the center wavelength Y of the measurement light.
σ) It is preferable that the distant wavelength position (Y + Z) is located inside the wavelength position (2X) distant from the center of the absorption spectrum by twice the half-value width. It is determined that the effect is small. That is, Y + Z
<2X. From this, Z <2XY is derived.

The measurement light and the reference light having a wavelength that does not cause atomic absorption are superimposed on the same optical path by using an optical filter that reflects or transmits light according to the characteristics of the wavelength, and the vapor on the surface of the high-temperature molten metal is vaporized. Pass through layers.

On the surface of the molten metal, not only the light absorption by the vapor layer but also the light attenuation due to the generation of dust, etc. To correct this effect, the ratio with the reference light which does not cause atomic absorption is used. It is necessary. As the reference light, light having a wavelength close to the wavelength of the measurement light without light absorption by the vapor layer is desirable.

The light intensity of the measurement light component and the reference light component of the light that has passed through the vapor layer is detected by spectral separation using an optical filter that reflects or transmits light according to wavelength characteristics. A reference light intensity ratio (R: measured light intensity / reference light intensity) is obtained from the obtained light intensities of the respective wavelengths, and from the intensity ratio (R0) in a state where there is no or very small and negligible vapor layer. Is obtained (R / R0). At this time, the logarithm (= -log (R / R0)) of the reciprocal of the intensity ratio change is defined as the absorbance (A). This absorbance can be expressed as a function of the concentration of the analytical element (measurement component) in the molten metal, the temperature of the molten metal, and the thickness of the vapor layer. Therefore, by correcting the temperature of the molten metal and the thickness of the vapor layer, the concentration of the analysis element in the molten metal can be obtained.

First, a method of correcting the thickness of the vapor layer will be described. The measurement light for measuring the main component element of the molten metal is passed through the vapor layer on the surface of the high-temperature molten metal as the same optical path as the measurement light for the analysis element and the reference light. The light that has passed through the vapor layer is spectrally separated using an optical filter, and the light intensity of each of the main component element measurement light, the analysis element measurement light, and the reference light is detected. A reference light intensity ratio (R _IS ) of the main component element and a reference light intensity ratio (R) of the analysis element are obtained from the obtained light intensities, and the respective ratios in a state where there is no or very little vapor layer and can be ignored The amounts of change from the intensity ratios (R _IS 0, R 0) are determined. The logarithm of the reciprocal of the change in the intensity ratio (= −log (R _IS
/ R _IS 0)) and determine the main component element absorbance (A _IS ).

The thickness of the vapor layer is corrected by the ratio (A / A) between the absorbance of the analysis element (A) and the absorbance of the main element (A _IS ).
A _IS ) can be obtained by setting the absorbance after correcting the vapor layer thickness of the element to be analyzed. For the main component element and the analysis element, the previous equation (1) of the light absorption phenomenon is established. Accordingly, by taking the ratio of the absorbances of both elements, the fluctuation term of the vapor layer thickness (length) L is eliminated, and can be expressed as a function of the concentration of the analyzed element.

The center position of the wavelength of the measurement light with respect to the main component element of the molten metal can be shifted from the center position of the atomic absorption line of the main component element in accordance with the absorption sensitivity of the atomic absorption of the main component element. desirable. The reason is that if the center position of the wavelength of the measurement light and the center position of the atomic absorption line are the same, the signal becomes small and the S / N deteriorates when the absorption sensitivity is high. In addition, as will be described later, the measurement accuracy is further improved by monitoring the wavelength of the measurement light during the measurement and correcting the change in the absorbance due to the change in the wavelength.

Next, a method for correcting the temperature of the molten metal will be described. The amount of vapor of each element generated on the surface of the molten metal is proportional to the concentration (activity) of the element in the molten metal and the vapor pressure (saturated vapor pressure). The saturated vapor pressure can be expressed as a function of the temperature of the molten metal. Therefore, based on the saturated vapor pressure of the analytical element at the standard temperature T0 ° C. of the molten metal (P0) and the saturated vapor pressure of the main component element (P _IS 0), each saturated vapor pressure at the temperature T ° C. at the time of measurement is obtained. (P (T), _PIS (T)) (P0
/ P (T), P _IS 0 / P _IS (T)), and using this, the absorbance (A and A _IS ) is corrected. For the change of the saturated vapor pressure at each temperature, literature values may be used.

At this time, the wavelength tunable laser is required to have a sufficiently small wavelength width of the output light, to be able to accurately set the center position of the wavelength, and to have no change over time in the wavelength position. Ideally, there is no change in the wavelength position over time, as described above, since the absorbance sensitivity is a function of the light source light wavelength position. However, if the laser installation environment (especially temperature change) is to be strictly controlled, the laser structure Various difficulties arise, such as making each part unchanged, and it is difficult to achieve in practice. As a countermeasure, the wavelength position is changed in advance to determine the wavelength dependence of the light absorption sensitivity, and in online measurement of gas, the amount of light absorption is measured while monitoring the wavelength of the emitted laser light. The on-line analysis of gas components in a realistic situation becomes possible by correcting the change online to determine the gas component amount.

FIG. 3 shows an example of the configuration of an apparatus for carrying out the present invention. In FIG. 3, a laser beam emitted from a laser light source 1 is applied to a metal vapor layer 4 on the surface of a molten metal 3 through an optical system 2. The laser beam that has passed through the metal vapor layer 4 is guided to a photodetector 6 through an optical system 5, and the intensity is measured.

As the optical systems 2 and 5, it is preferable to use optical fibers. By doing so, the laser light source 1, the photodetector 6, and the like can be arranged separately from the surface of the molten metal 3.

The laser light source 1 is a tunable laser whose wavelength can be set to an arbitrary value. Since the center position of the absorption wavelength of the analysis element is described in a literature or the like, the emission wavelength is set to be shifted from the center position by 0.001 nm to 0.03 nm.

The optimum shift amount of the wavelength can be obtained as follows. First, the wavelength dependence of the change in the absorption intensity is checked in advance. That is, after preparing the measurement system, the concentration of the target analysis element of the molten metal 3 is measured at several points by changing the wavelength of the laser beam. Then, the position of the laser wavelength at which the laser light intensity after absorption by the metal vapor 4 is considered to be the most appropriate is found. Or
In the atomic absorption analysis of a solution sample using an ordinary atomic absorption spectrometer, the laser light source of the present analysis system is used as a light source, and the wavelength dependence of the change in absorption intensity is checked in advance. Next, for the molten metal 3 having a small analytical element concentration,
The measurement is performed at the center position of the absorption wavelength of the analysis element, and the measurement limit at this center position is determined. Then, an appropriate wavelength for the measurement concentration range is determined from the result of the investigation on the wavelength dependence of the change in the absorption intensity performed in advance.

Further, since the intensity change due to light absorption changes depending on the half-width of the emission wavelength, the sensitivity can be made more appropriate by changing the wavelength width as well as the wavelength shift amount.

The laser light may be only the light having the absorption measurement wavelength of the element to be measured, but may also include the absorption wavelength of another analysis element and the reference light not absorbed by the analysis element. . By irradiating these lights simultaneously, the light intensity can be measured for each analysis element.

Further, in order to stabilize the vapor layer 4, the optical systems 2 and 5 may be arranged in the probe, and the inside of the probe may be set to an inert gas atmosphere.

Further, a spectroscope or a band-pass filter may be provided before the photodetector 6. By doing so, it is possible to measure only the intensity of the light of the target wavelength and reduce the influence of the heat radiation of the molten metal 3 and the stray light from the illumination.

Further, the optical systems 2 and 5 are arranged so that the surface of the molten metal 3 is treated as a reflecting mirror for the laser beam.
May be arranged. That is, the laser beam emitted from the optical system 2 may pass through the vapor layer 3 near the surface and be reflected on the surface of the molten metal 3 before entering the optical system 5.

FIG. 4 shows an example in which an optical system is arranged so that the surface of the molten metal 3 is treated as a reflecting mirror for laser light. In FIG. 4, laser light emitted from laser light sources 1a (for analysis element analysis), 1b (for main component element measurement) and 1c (for reference light) is converted into an optical filter (high-pass filter) 8a in a condensing optical system 7. To 8c to be the light of the same optical path. This light is introduced into the irradiation optical fiber 11 a through the lens 9 and transmitted to the vicinity of the molten metal 3. The chopper 10 is arranged immediately before the chopper 10 is introduced into the optical fiber 11a. The light 20 emitted from the tip of the optical fiber 11a passes through the irradiation optical system 22, then passes through the vapor layer 4, and is irradiated on the surface of the molten metal 3. The light 21 reflected on the surface of the molten metal 3 passes through the vapor layer 4 again, and is transmitted through the light receiving optical fiber 11b. The light emitted from the light receiving optical fiber 11b passes through the lens 12, is converted into parallel light, passes through optical filters 13a and 13b (high-pass filter), is divided into respective laser light wavelengths, and then passes through the band-pass filters 14a and 14b. Then, the intensity is measured by being guided to the photodetectors 6a and 6b.
The measured intensity of each wavelength is the temperature information from the molten metal temperature sensor 16, the laser wavelength information from the wavelength measuring device 19 measured for the laser light of the laser light source,
The laser output power information from the laser light source measured by the beam sampler 17 and the photodetector 18 is sent to the arithmetic unit (calculator) 15.

From this information, the correction of the laser power fluctuation, the fluctuation of the laser output wavelength, the fluctuation of the vapor layer thickness, and the correction of the temperature are performed by the arithmetic unit 15 to obtain the concentration of the analysis element in the molten metal. be able to.

When the molten metal surface fluctuates and undulates, the waves occur randomly and move in random directions. And the curvature of the wavefront also changes from moment to moment. When light is applied to a point on such a metal surface, the direction in which the light is reflected and returned is also random. Therefore, when the measurement time is finite, the reflected light from a specific point on the molten metal surface may never reach the light receiving section. However, since the wavefront change occurring at another point away from this specific point also occurs at random, the probability that the reflected light from that point also does not reach the light receiving unit is very small. Therefore, by increasing the number of reflection points, the expected value of the number of times that the reflected light reaches the light receiving unit increases. In other words, for the laser beam irradiation on the molten metal surface, see Table 9-5.
In contrast to the method of focusing on the melted surface described in No. 725, the larger the area of the irradiated portion is, the more the number of times of reaching the light receiving section increases.

Many waves generated on the surface due to fluctuations of the molten metal surface have a radius of curvature of about 1-2 mm, and the waves propagate to form complicated irregularities on the surface. Focusing on one of the convex portions, when the convex portion is irradiated with light and reflected light from one point in the convex portion is received, reflected light from another portion of the convex portion other than the portion very close to that point Is not received. In order to increase the number of times of light reception, it is an essential condition that the other concave and convex portions are irradiated with laser light so that the reflected light from other convex or concave portions can be received. The number of light receptions can be increased by irradiating light to at least the same width as the convex part before and after the convex part of interest as such a concave and convex part.

Since the typical size of the protruding portion is 1-2 mm in width, irradiating an area having an equal width before and after that means that the irradiation area of the laser beam is 5 mmφ in actual work. That is all. By defining such an irradiation area, the measurement is made extremely effective.

Since the reflection efficiency is not constant as described above, it is impossible to determine whether the change (decrease) in the amount of measurement light received is due to absorption or a change in reflection efficiency due to fluctuation. Therefore, it is essential for the measurement to compensate for the change in the reflection efficiency by irradiating and measuring the comparison light simultaneously with the measurement light and taking the ratio. The comparison light is light for comparison in which the optical path and the irradiation area are completely the same so that the change in the reflection efficiency becomes equal to the measurement light even at an arbitrary short time.

Regarding the method of measuring the received light intensity, the measurement accuracy is improved by measuring the light intensity in each short period and using the signal only when the intensity of the reflected light is equal to or higher than the threshold value for the density measurement. Most of the signal having a low reflected light intensity is only radiated light, and the amount of absorbed light cannot be measured accurately. Therefore, by using a signal only when the intensity of the reflected light (especially the reflected light of the reference light) is equal to or higher than the threshold for the density measurement, the S / N is improved, and the analysis accuracy is further improved.

The radiation emitted by the molten metal itself is as follows:
It is separated from the measuring light as follows. That is, the irradiation of the laser light is interrupted at a constant cycle, and the radiation light (I
measured _f), the difference between the measured light intensity at the time of laser irradiation (I _r) and measured at the Blocked radiant light intensity _{(I f) (I r -I} f), regarded as the intensity of the reflected light only the laser . The intensity of the atomic absorption can be accurately measured based on the measured intensity of the reflected light.

When the radiated light fluctuates with time,
Cut off the laser beam irradiation at regular intervals, and
Measuring the radiated light at the time of the
Take into account. That is, the light intensity (I_r),
And the radiated light intensity (I_f1,
I_f2), The radiation light intensity at the time of laser cutoff (= (I
_f1+ I_f2) / 2), the difference in light intensity (I_r− (I_f1+ I_f2) /
Find 2). This difference in light intensity is determined only by the reflected light of the laser.
And the intensity of atomic absorption is measured. do this
This enables accurate correction of radiation light. laser
-The cycle of blocking light irradiation is 1 to 1000 Hz.
Range is desirable.

In order to cut off the laser light at a constant period in order to measure only the radiant light from the molten metal, a rotary interrupter (hereinafter referred to as a chopper) before irradiating the laser light to the surface of the molten metal. Let it pass. Irradiation and interruption of laser light are performed alternately, and the total light of laser reflected light and radiation light is measured at the time of irradiation, and only radiation light is measured at the time of interruption. This makes it possible to easily measure the true laser reflected light. At this time, the laser light cutoff time is
It needs to be longer than the optical measurement time. For example, when the optical measurement time is a cycle of 0.002 seconds, the laser cutoff is set to 0.
It is desirable that laser irradiation be about 02 seconds and 0.08 seconds (period 0.1 seconds). It should be noted that the cutoff time and the irradiation time do not necessarily have to be the same, and when the measurement including the fluctuation of the radiated light can be sufficiently performed during the cutoff, the irradiation time may be increased in order to improve the measurement accuracy of the laser reflected light. desirable. In this way, even if only a simple band-pass filter and a photomultiplier (photomultiplier) are installed in the spectrophotometer that splits the light from the molten metal, the radiated light can be measured accurately.

Since the radiated light from the molten metal is continuous light, as a method of easily measuring, the total light of the reflected light and the radiated light is separated by a spectroscope, and the light having a wavelength very close to the wavelength of the incident laser light is measured. By measuring the radiation light, the radiation light having the same wavelength as the laser light may be estimated.

Further, the relationship between the radiation light of a specific wavelength such as infrared rays and the radiation light of the reflected measurement light is determined in advance, and only the radiation light of the specific wavelength is measured, whereby the radiation of the same wavelength as the laser light is obtained. Light may be estimated.

As a method of detecting the reflected light, there is a method of measuring the light intensity by dispersing the received light using, for example, a monochromator or a polychromator. However, in this method, the light quantity is attenuated due to a slit or the like at the time of spectral separation, so that the measurement sensitivity is insufficient. Therefore, the received light is
After passing through a band-pass filter having a passing wavelength including a reflected light wavelength and a passing wavelength width of 5 nm or less to select a wavelength, light detection is performed using the total amount of light as a signal. For example, 1 mm
A light-receiving optical fiber with a diameter of about φ is attached to receive the reflected light from the surface of the molten metal, and the light emitted from the other end of the optical fiber is converted into parallel light by a lens. After passing through, the total amount of light is guided to a photomultiplier tube (Photomaru), and the light intensity is measured. By doing so, the measurement sensitivity can be improved. At this time, it is desirable that the wavelength to be measured is included in the half width of the bandpass filter, and that the half width is as small as possible.

Further, light after atomic absorption by a molten metal analysis element, light after atomic absorption by a main component element, reference light, etc.
When a plurality of reflection measurement lights are on the same optical path, the laser light is separated using an optical filter that reflects a specific wavelength range and transmits another specific wavelength range with respect to the incident light at 45 degrees, and further focuses on the measurement wavelength. After passing through a band-pass filter having a wavelength, the light may be guided to a photomultiplier (photomultiplier), and the intensity thereof may be measured.

When the temperature of the molten metal becomes high, the radiated light becomes large, and it becomes difficult to detect the reflected light from the surface of the molten metal.
Therefore, the intensity of the irradiation light is adjusted so that the intensity of the reflected light to be detected becomes 10 times or more that of the radiation light. In particular, since the intensity of the reflected light of the wavelength absorbed by the vapor layer is reduced by the absorption, the intensity of the incident light is adjusted so that the intensity of the reflected light when not absorbed is at least 100 times that of the radiated light. It is desirable to adjust.

Further, when the radiated light is large, the ratio of the reflected light to the radiated light becomes small, and the measurement accuracy of the reflected light is deteriorated. It is desirable to shield at least a part.

The necessity of the correction for the temperature change of the molten metal and the correction method are as described above. The temperature measurement of the molten metal may be performed by calculating a relational expression between the intensity of the radiated light of a specific wavelength and the temperature of the molten metal in advance and calculating the measured value of the intensity of the radiated light of the specific wavelength. Further, instead of the radiation light intensity of the specific wavelength, a ratio of the intensity of the radiation light of two specific wavelengths may be used. The radiation light intensity may be measured by separately installing a measuring device, or may be obtained by using the light amount measured when the measurement light is blocked by the chopper.

The method of the present invention is a method for measuring a system such as molten steel in which the main component is iron and the analysis element is Mn (manganese). In conventional atomic absorption spectrometry, M
When the n concentration is 0.2 wt% or more, the absorption is saturated and measurement is impossible, but by using the method of the present invention, it is possible to measure even when the Mn concentration in molten steel is 2 wt%.

The molten metal analyzer according to the present invention will be described. FIG. 4 shows an example of the apparatus. In FIG. 4, laser light emitted from laser light sources 1a (for measuring an analysis element), 1b (for measuring a main component element) and 1c (for a reference light) is converted into an optical filter (high-pass filter) 8 in a focusing optical system 7. Through the same optical path. As the laser light source, a laser light source whose wavelength, half width and intensity of the emitted laser light are variable is used. Light with the same optical path,
The light is introduced into the optical fiber 11a through the lens 9 and transmitted to the vicinity of the molten metal. In order to measure the radiation light from the molten metal, the laser light is passed through the chopper 10 immediately before being introduced into the optical fiber 11a. Light emitted from the tip of the optical fiber 11a passes through the irradiation optical system 22, passes through the vapor layer 4, and is irradiated on the surface of the molten metal 3. The irradiation optical system 22 adjusts the distance between the end face of the fiber 11a and the lens by a fine adjustment mechanism for the lens position attached to the lens, and irradiates the surface of the molten metal 4 with laser light as parallel light or divergent light. I have. The light reflected on the surface of the molten metal 3 passes through the vapor layer 4 again and is transmitted through the light receiving optical fiber 11b. This optical fiber may be one or a plurality. The light emitted from the light receiving optical fiber 11b passes through the lens 12 to become parallel light, passes through optical filters 13a and 13b for separating wavelength ranges, is divided into respective laser light wavelengths, and then is passed through bandpass filters 14a to 14c. , And guided to photodetectors 6a to 6c for measuring the total amount of light, and the intensity is measured.
The measured intensity of each wavelength is the temperature information from the molten metal temperature sensor 16, the laser wavelength information from the wavelength measuring device 19 measured for the laser light of the laser light source,
The information is sent to the arithmetic unit 15 together with information on the laser output power from the laser light source measured by the beam sampler 17 and the photodetector 18.

From the information, the correction of the laser power fluctuation, the fluctuation of the laser output wavelength, the fluctuation of the vapor layer thickness, and the correction of the temperature are performed by the arithmetic unit 15, and the concentration of the analysis element in the molten metal is obtained. be able to.

Using the apparatus shown in FIG. 4, laser output power correction, laser output wavelength correction, vapor layer thickness correction, and temperature correction are performed in advance to obtain the absorbance of the analysis element and the concentration of the analysis element in the molten metal. By obtaining a relational expression (calibration curve) with (for example, wt%), highly accurate analysis can be performed.

[0079]

EXAMPLES (Example 1) The Mn concentration in the molten metal was measured using the measuring apparatus shown in FIG.

The molten metal 3 was produced by melting 5 kg of molten steel in a carbon crucible in a high frequency melting furnace. Then, Mn was added to the molten steel in an amount equivalent to 0 to 1 wt% in concentration in the molten steel.
Mn measurement was performed at a molten steel temperature of 1600 ° C.

The tunable laser used for the measurement was output as follows. That is, the Ti sapphire laser was excited by the second harmonic oscillation light (0.53 nm) of the YAG laser to obtain continuous wavelength laser light. Then, the second harmonic of this continuous wavelength laser light was oscillated by adjusting the wavelength, and output as a tunable laser. The adjustment of the oscillation wavelength is performed by adjusting the atomic absorption wavelength of Mn to 403.3.
It shifted by 0.001 nm centering on 07 nm. The energy of the outputted laser beam was 10 mW, and the half-width at wavelength was 0.002 nm.

As the optical system, two optical fibers (2 for laser light input and 5 for laser light reception) were used. One end of the laser light input fiber 2 was placed at a position where laser light from the laser light source 1 was condensed. The other end of the light-entering fiber 2 was put in a probe and placed together with the probe near the molten steel surface. The inside of the probe was filled with nitrogen gas in order to prevent oxidation due to air mixing. In the probe, light emitted from the light-receiving fiber 2 passed through the vapor layer 4 and was then sent to one end of the light-receiving optical fiber 5. The other end of the light receiving optical fiber 5 was placed in the entrance slit of a 50 cm evert type spectroscope. The light reaching the entrance slit was split by a spectroscope and the intensity was measured by the photodiode 6.

Using the above system, the wavelength of the laser beam was shifted, and the relationship between the Mn concentration in the molten steel and the change in intensity due to light absorption was measured for each shift amount. FIG. 5 shows an example of the measurement result. As is clear from FIG. 5, when the wavelength of the laser beam is set to the center of the wavelength of the absorption line of Mn,
At a concentration of 0.2 wt% or more, a change in intensity change due to light absorption could not be measured. However, by shifting the wavelength of the laser light from the center of the absorption line wavelength of Mn by 0.005 nm or more, it was possible to sufficiently measure the intensity change due to light absorption even at a Mn concentration of 1 wt%.

As described above, the measurement sensitivity can be controlled by controlling the wavelength position of the laser beam according to the present invention. As a result, the narrowing of the measurement range, which is a defect of atomic absorption spectrometry, has been eliminated, and the use of atomic absorption spectrometry for molten metal analysis has become more versatile.

Example 2 The Mn concentration in the molten metal was measured using the measuring device shown in FIG.

The molten metal 3 was prepared by melting 5 kg of molten steel in a carbon crucible in a high frequency melting furnace and adding Mn to the molten steel in an amount equivalent to 0 to 1.5 wt% in the molten steel. . Measuring temperature 1550 ° C to 1650 ° C
It went in the range of.

The laser light source 1a for measuring an analytical element in the apparatus shown in FIG.
(53 nm) to excite a Ti sapphire laser into continuous wavelength laser light, and a wavelength tunable laser that oscillates by adjusting the wavelength of the second harmonic of the continuous wavelength laser light. The oscillation wavelength was adjusted to 403.313 nm, which was shifted from the center of the atomic absorption wavelength of Mn (403.307 nm) by 0.006 nm. The wavelength half width of the laser was 0.002 nm, and the output was 10 mW.

FIG. 6 shows an example of the result of measuring the change in the light absorption sensitivity of Mn depending on the laser wavelength position using this laser light source. As is clear from FIG. 6, a peak of the light absorption sensitivity was obtained at an atomic absorption wavelength of Mn of 403.307 nm.

The laser light source 1b for measuring main component elements of the apparatus shown in FIG. 4 employs the tunable laser described above to adjust the oscillation wavelength to around the atomic absorption wavelength center (386 nm) of Fe which is the main component of the molten metal. What was done was used. The power of the laser was 10 mW.

A blue semiconductor laser having an oscillation wavelength of about 430 nm was used as the reference light laser light source 1c in FIG.

The laser irradiation optical system uses three types of laser light, which are arranged in a positional relationship of 90 degrees, and optical filters 8a to 8c described later are arranged at the intersections of the laser light, and three types of laser light are used. The laser light was on the same optical path. That is, the laser light from the laser light source 1a was reflected by the optical filter 8a, and then crossed at 90 degrees with the laser light from the laser light source 1b. At this intersection, an optical filter 1b that transmits light of 403 nm (light source 1a) and reflects light of 386 nm (light source 1b) for 45-degree incident light was placed. In this way, the laser beams from the light sources 1a and 1b have the same optical path. Next, the laser light from the light sources 1a and 1b having the same optical path is transmitted to the laser light source 1c.
At 90 degrees with the laser beam from At this intersection, light of 403 nm (light source 1a), 386 nm (light source 1
The optical filter 8c that transmits the light of b) and reflects the light of 430 nm (light source 1c) was placed. Thus, 403n
A situation was created in which the laser light of m (light source 1a), 386 nm (light source 1b) and the laser light of 430 nm (light source 1c) had the same optical path. In this way, the three types of laser beams having the same optical path were condensed by the lens 9 and introduced into the optical fiber 11a having a diameter of 0.3 mm. Laser light to optical fiber 1
It was passed through a rotary chopper 10 just before it was placed in 1a.
The opposite end face of the optical fiber 11a is fixed with a connector, and the distance between the lens 22 and the end face of the fiber 11a is adjusted by a mechanism for finely adjusting the position of the lens 22 to convert the laser beam into parallel light 20 and then irradiate the molten steel surface. did. The irradiation diameter on the molten steel surface was 5 mmφ.

The light receiving optical system is an optical fiber 11b.
Only, and optical filters 13a and 13b were used as spectral systems. That is, a light receiving optical fiber 11b having a diameter of 1 mm was attached near the molten steel surface, and the reflected light 21 from the molten steel surface was received. The light emitted from the other end of the optical fiber 11b was converted into parallel light by the lens 12, and then introduced into the optical filter 13a to be separated. The optical filter 13a
This is a filter that transmits light of 430 nm (light source 1 c) and reflects light of 403 nm (light source 1 a) and 386 nm (light source 1 b) for 45-degree incident light. The reflected laser light was further separated by the optical filter 13b.
The optical filter 13b has 403n for 45 degree incidence.
m (light source 1a) is transmitted and 386 nm (light source 1b)
Is a filter that reflects light. The laser light of each measurement wavelength separated in this manner is passed through band-pass filters 14a to 14c each having a half-value width of 2 nm centered on each wavelength and guided to photomultiplier tubes (photomultipliers) 6a to 6c. It was measured in units of 2 ms. The measurement was performed for 2 seconds and 1000 data were collected.

The temperature was measured using a Pt-Rh thermocouple 16. The relationship between the temperature immediately below the surface of the molten steel and the temperature at the temperature measurement position was measured in advance using a Pt-Rh-based thermocouple, and a relational expression was obtained.

The cycle of the chopper 10 is 100 ms,
The interruption was repeated for 25 ms and the irradiation was repeated for 75 ms. As described above, the light intensity when cut off by the chopper 10 is radiation light. The average value of the radiated light intensity when the light was blocked was obtained in a time series, and as described above, the radiated light intensity during the reflected light measurement was obtained by averaging the radiated light intensity before and after the reflected light measurement. . The true reflected light intensity was obtained by subtracting the radiation light intensity thus calculated from the measured value at the time of the reflected light measurement. This was determined for each of the reference light and the measurement light.

FIG. 7 shows an example of the reflected light obtained by blocking with the chopper 10 for the reference light and the light for Mn measurement.

Regarding the absorbance data, the data at the timing when the reference light intensity is higher than 50% when the reference light intensity is arranged in the order of the intensity is regarded as valid data. The intensity ratio (R) between the average value of the Mn measurement light and the reference light at these timings and the average ratio of the Mn measurement light and the reference light when the laser light is received without passing through the molten steel surface. Intensity ratio (R0)
And the logarithm of the reciprocal thereof (= −log (R / R
0)) was taken as the absorbance of Mn. The absorbance of Fe, which is a main component, was determined in the same manner.

The temperature of the molten metal 3 was corrected using the literature value of the change in vapor pressure with reference to the absorbance of Mn and Fe at a vapor pressure of 1600 ° C.

The thickness of the vapor layer 4 is corrected by calculating the absorbance ratio between Mn and Fe.
The absorbance was used.

FIG. 8 shows an example of the relationship between the Mn absorbance thus measured (actually, the ratio to the Fe absorbance) and the Mn concentration in the molten steel. As is clear from FIG. 8, by implementing the present invention, the correlation between the Mn absorbance and the Mn concentration in the molten steel is improved, and the Mn concentration analysis can be performed with high accuracy.

Since the measurement in this example was a short time, the output wavelength of the laser beam was stable and did not change. However, during the actual long-term measurement, the laser output wavelength changes. When the laser output wavelength changes, high-precision analysis is possible by correcting the absorbance using an example of the change in absorbance depending on the wavelength position as shown in FIG.

[0101]

As described above, the atomic absorption spectrometry is excellent as a method for analyzing molten metal due to its ease of engineering, but the conventional atomic absorption spectrometry has greatly limited the applicable concentration range. However, in the present invention, the restriction has been eliminated and the method has become a general-purpose analysis method. In the present situation where other molten metal analysis methods have hardly been put into practical use due to engineering problems, the molten metal analysis method according to the present invention is the analysis method with the lowest hurdle for practical use. By implementing the present invention, the effect of improving the process control of metal refining, such as energy saving and quality improvement, is very large.

[Brief description of the drawings]

FIG. 1 is an explanatory view of the principle of the present invention.

FIG. 2 is an explanatory diagram of the principle of the present invention.

FIG. 3 is a diagram showing an example of a molten metal analyzer according to the present invention.

FIG. 4 is a diagram showing another example of the molten metal analyzer according to the present invention.

FIG. 5 is a view showing an example of a molten metal analysis result in the example.

FIG. 6 is an explanatory diagram of the principle of the present invention.

FIG. 7 is a diagram showing an example of a time-series measurement result of molten metal analysis in the example.

FIG. 8 is a diagram showing an example of a molten metal analysis result in the example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Laser light source 1a ... Laser light source (for analysis element analysis) 1b ... Laser light source (for main component element measurement) 1c ... Laser light source (for reference light) 2,5 ... Optical system 3 ... Molten metal 4 ... Metal vapor layer 6a , 6b, 6c photodetector 7 focusing optical system 8a, 8b, 8c optical filter (high-pass filter) 9 focusing lens 10 chopper 11a irradiation optical fiber 11b light receiving optical fiber 12 ... optical filters (high-pass filters) 14a, 14b, 14c ... band-pass filters 15 ... arithmetic unit 16 ... temperature sensors 17 ... beam samplers 18 ... photodetectors 19 ... wavelength measuring instruments 20 ... measurement light and reference light 21 ... reflected light 22 ... irradiation optical system

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Takanori Akiyoshi 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Japan Inside the Kokan Co., Ltd. (72) Inventor Jun Junno 1-2-1-2, Marunouchi, Chiyoda-ku, Tokyo Japan Inside the Honko Tube Co., Ltd. (72) Inventor Ikuhiro Sumi 1-2-1, Marunouchi, Chiyoda-ku, Tokyo, Japan Inside Nippon Kokan Co., Ltd. (72) Inventor Ryo Kawabata 1-2-1, Marunouchi, Chiyoda-ku, Tokyo, Japan F term in the company (reference) 2G059 AA01 BB08 CC03 EE01 EE02 EE12 FF08 GG01 GG03 GG06 HH02 HH03 HH06 JJ02 JJ11 JJ17 JJ24 KK01 KK02 KK03 MM01 MM03 MM05 MM12 NN01 NN02 NN05

Claims (14)

[Claims] 1. A method for analyzing a molten metal, comprising passing a laser beam through a vapor layer of a molten metal, and measuring a concentration of an analysis element contained in the molten metal from a change in intensity of the laser beam passing through the vapor layer. A method wherein the wavelength of the laser light is adjusted to a position shifted from the center of the absorption wavelength of the analysis element by 0.001 to 0.03 nm. 2. A vapor layer near a surface of a molten metal containing one or a plurality of analysis elements, wherein a wavelength center position is shifted from a center position of an absorption wavelength of the analysis element according to a measurement concentration range of the analysis element. And the reference light having a wavelength that does not cause atomic absorption is superimposed and passed on the same optical path, and the intensity of the measurement light component and the intensity of the reference light component of the passed light are measured. A method for analyzing a molten metal, comprising: measuring a concentration of an analysis element in a molten metal from a known relationship among an intensity ratio of a reference light component, a vapor layer thickness, and a temperature of the molten metal. 3. The amount of shift of the center wavelength of the measurement light is such that the absorbance (= -log (light intensity after light absorption / light intensity without light absorption)) at the maximum value of the measurement concentration range is 2.5 or less. Value and the half-width at half maximum of the atomic absorption line of the analytical element
3. The method according to claim 2, wherein the value is set to less than twice. 4. The wavelength half width Z of the measurement light is defined as Z <(2X−Y), where X is the wavelength half width of the atomic absorption line of the analysis element and Y is the shift amount of the center wavelength of the measurement light. 4. The method according to claim 2, wherein the relationship is satisfied. 5. A measurement light in which a wavelength center position is shifted from a center position of an atomic absorption line of a main component element of a molten metal according to an absorption sensitivity; a measurement light in which a wavelength center position for the analysis element is shifted; The reference light having a wavelength that does not cause atomic absorption is superimposed on the same optical path and passed through the vapor layer on the surface of the molten metal, and the intensity of both the measured light component and the reference light component of the passed light is measured and passed. From the known relationship between the intensity ratio of the measurement light component corresponding to the main component element of the light and the reference light component and the intensity ratio of the measurement light component and the reference light component corresponding to the analysis element, the vapor layer thickness is determined. 5. The method according to claim 2, wherein the correction is performed.
7. The method for analyzing molten metal according to the above item. 6. Monitoring the wavelength of the measuring light during the analysis,
3. The method according to claim 2, wherein a deviation amount between the center position of the atomic absorption line and the central position of the measurement light wavelength is measured, and the absorption sensitivity of the measurement light component of the vapor passing light is corrected based on the measured deviation amount. 6. The method for analyzing molten metal according to any one of claims 5 to 5. 7. The apparatus according to claim 2, wherein the measuring light and the reference light are turned on / off using a chopper, and the light intensity at the time of off is corrected as background light intensity as radiation light intensity from the molten metal. 2. The method for analyzing molten metal according to claim 1. 8. The method according to claim 2, wherein the measuring light and the reference light are applied to the surface of the molten metal, reflected and passed through the vapor layer, and then the intensity of the reflected light is measured.
7. The method for analyzing molten metal according to the above item. 9. The measuring light and the reference light are applied to the surface of the molten metal 5
9. Irradiation is performed on an area of not less than mmφ.
The described molten metal analysis method. 10. The molten metal analysis method according to claim 8, wherein the measurement data when the reflected light intensity of the reference light is equal to or higher than a threshold is used for concentration measurement. 11. A reflected light is received by an optical fiber,
The reflected light received is passed through a band-pass filter having a passing wavelength including the atomic absorption line wavelength of the element to be analyzed and having a passing wavelength width of 5 nm or less, selecting a wavelength, and measuring the total amount of light after passing through the band-pass filter. The molten metal analysis method according to any one of claims 8 to 10, wherein: 12. The measuring light and the reference light to be irradiated are laser light, and the intensity of the measuring light and the reference light after the reflected light has passed through the band-pass filter is determined by the radiation of the molten metal in the wavelength band passing through the band-pass filter. The molten metal analysis method according to any one of claims 8 to 11, wherein the irradiation light intensity is adjusted so as to be 10 times or more the light intensity. 13. The method for analyzing a molten metal according to claim 1, wherein the main component element of the molten metal is iron, and the analysis element is manganese. 14. A plurality of laser light sources having variable wavelengths, half-widths and intensities of laser light to be emitted, means for measuring the wavelength and intensity of the laser light, and different wavelengths emitted from the plurality of laser light sources. An optical system that superimposes a plurality of laser beams on the same optical path, a chopper that turns on and off the laser beams superimposed on the same optical path at a constant period, and a laser whose end is installed near the molten metal and that is superimposed on the same optical path An optical fiber for guiding light to the vicinity of the molten metal; an optical system for irradiating the laser light emitted from the optical fiber to a range of 5 mmφ or more on the surface of the molten metal; One or a plurality of light receiving optical fibers that receive the reflected light and guide the light to the light detection unit, and the reflected light guided by the light receiving optical fiber are separated into respective lasers. A high-pass filter and / or a low-pass filter that separates into a wavelength range including the wavelength of the laser light, and a band that separates a narrow wavelength range including the wavelength of each laser light from the reflected light after passing through the high-pass filter and / or the low-pass filter. A molten metal analysis comprising: a pass filter; a photodetector that measures the total amount of light after passing through the bandpass filter; a unit that measures the temperature of the molten metal; and a calculation device that calculates the measured result. apparatus.