KR100603426B1 - Method and Apparatus for Analyzing Vaporized Metal - Google Patents

Abstract

Laser light is passed through the vapor layer of the molten metal, and the concentration of analyte elements contained in the molten metal is measured from the intensity change of the laser light passing through the vapor layer. The wavelength of the laser light is adjusted from the center position of the absorption wavelength of the analysis element to the position of 0.001 to 0.03 nm deviation. It is possible to widen the measured concentration range.

Description

Method for analyzing molten metal and its apparatus {Method and Apparatus for Analyzing Vaporized Metal}

The present invention relates to a method and an apparatus for quickly analyzing a component element in a molten metal.

On-line analysis of molten metals is highly required to control the smelting and refining processes of the metals. However, the environment for measuring and analyzing molten metal is poor due to high temperature, dust, and the like, and due to the large engineering problems to cope with such an environment, practical use of on-line analysis is hardly realized.

In general, an atomic absorption method is known for a sample in which a metal is decomposed into an acid or the like as a highly reliable analysis method for analyzing the composition of a metal. In addition, a proposal has been made in which the atomic absorption method, which is an analysis method having high precision, is applied to the direct analysis of molten metal. Such proposals include, for example, a direct analysis method and apparatus for molten metals described in Japanese Patent Application Laid-Open No. 09-049795, and a direct chemical analysis method for molten metals described in Japanese Patent Application Laid-Open No. 09-500725. 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 absorbance of the light absorbed by the vapor layer, and determine the concentration of the component element in the molten metal.

However, in the method of analyzing the vapor of molten metal using the direct atomic absorption method described in the above document, since the amount of generated metal vapor cannot be controlled, the drawback of the atomic absorption method that the measurement concentration range is narrow is remarkable. . This will be described below.

The measuring principle of the atomic absorption method is to determine the amount or concentration of analytical elements in a sample based on the absorption of atoms according to Equation (1) below.

A = μC L ........................ (1)

(Where A; intensity change due to absorption (= -log (I / Io)), (I / Io); light intensity ratio, I; light intensity after absorption, Io; light before absorption Intensity, μ; extinction coefficient (property dependent on wavelength), C; amount or concentration of analyte, L; vapor layer length

As can be seen from Equation (1), the light intensity ratio (I / Io) decreases rapidly with an increase in the amount or concentration C of analytical elements. If the light intensity ratio (I / Io) is too small, the influence of light other than the absorbed light and the deviation of the measured value in the measuring device occur. As a result, concentration measurement becomes difficult. There is an upper limit to the amount or concentration C of such analyte.

And in order to widen the range of a measured quantity or a density | concentration, based on Formula (1), lowering any one or more of each term of (micro), C, L is performed. For example, in the atomic absorption method of the solution, the sample solution is diluted to lower the analyte element or concentration C, or the angle of the atomizer (burner) is changed to shorten the vapor layer length L. The measurement concentration range can be widened.

However, in the measurement of molten metal during smelting, the vapor layer concentration C to be produced is determined by the smelting conditions and the content rate in the molten metal and cannot be adjusted. For this reason, to widen the measurement concentration range, neither the vapor layer length L nor the extinction coefficient mu should be made small. It is difficult to reduce the vapor bed length L because of the large engineering problems for stabilizing and maintaining the vapor bed thickness at an appropriate small value. In addition, it is difficult to reduce the extinction coefficient μ because it is not limited to the case where there is an absorbing ray having mu corresponding to the measurement concentration range. For example, as the atomic absorption line of Mn (manganese), only a line of 279 nm exists as a line having a large extinction coefficient μ, and a line of 403 nm exists as a line having a small μ. In the Mn concentration measurement, even if a 403 nm absorption line with a small coefficient μ is used, when the molten steel temperature is 1600 ° C., since the Mn concentration C in the vapor layer is high, even if the vapor layer L is made very short by about 1 mm, Absorption too strong For this reason, the light intensity ratio mentioned above also becomes 1% or less with respect to Mn of 0.1% of concentration, and Mn of 0.1% or more of concentration cannot be measured.

Moreover, in the method of focusing on the molten metal surface described in the above-mentioned patent publication 9-500725, practical use on the molten metal surface which actually flows is difficult. If the surface of the molten metal is a stationary surface, it exhibits the same behavior as the mirror surface, and the reflection of the light projected thereon reaches a design reflection position, and the reflection strength is sufficiently strong. However, in the state where the surface is rocking and undulating, it is only intermittent that the reflection direction returns to the design reflection position. Moreover, the reflection intensity is also very small compared to the stationary surface reflection. This is because the reflecting surface becomes a curved surface rather than a parallel surface, and as a result, the reflecting angle is widened along the curvature, and as a result, the illuminance (density of light intensity) at the measurement position is reduced. Making the stop face does not cause such a problem, but it is difficult to make the stop face in the smelting process. In addition, even when a probe for light irradiation is used, in order to inactivate the atmosphere inside the probe, as a result of flowing Ar or nitrogen gas, the surface of the molten metal fluctuates, and thus a stop surface cannot be formed.

In addition, on the surface of the molten metal, it is very difficult to keep the thickness of the vapor layer constant at all times because of the flow of molten metal, tropical flow of the vapor layer, dust generation, and the like, and the thickness of the vapor layer varies during measurement. Therefore, it is necessary to correct this variation.

In addition, since molten metal is generally high temperature (for example, about 1600 ° C in molten steel), the molten metal itself emits radiant light. This radiant light is continuous light from ultraviolet to infrared, and naturally contains light of a wavelength for which atomic absorption is to be measured. Since the temperature of the molten metal changes from time to time, the radiance from the molten metal surface also changes from time to time. 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 light having the same wavelength as this, and only the amount of light after true atomic absorption can be detected. There is no number. In this case, when the radiant light fluctuates during refining, at first glance, it appears that the amount of light after 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 (active amount) and the vapor pressure (saturated vapor pressure) in the molten metal of the element. Since the saturated steam pressure is a function of temperature, if the temperature of the molten metal is constant, the concentration of the element in the molten metal is obtained from information obtained by atomic absorption method (= steam amount). In the method described in Japanese Patent Laid-Open No. 9-500725, the temperature of the molten metal is kept constant and measured. However, in the smelting process that requires concentration measurement, the temperature of molten metal generally fluctuates, and in steel refining, the temperature may fluctuate more than 100 ° C. The amount of steam fluctuates according to the temperature change of the molten metal. For example, the amount of Mn vapor generated in the molten steel at 1600 ° C. changes about 4% with respect to the temperature change at 5 ° C. Therefore, in order to perform high precision analysis, the temperature of molten metal must be measured with the precision of 5 degrees C or less, and the measured value of a vapor amount must be corrected. In order to perform high temperature measurement with high accuracy, the use of a platinum-rhodium-based thermocouple is optimal, but it is necessary to place the temperature measurement position just below the laser irradiation surface, and application is quite difficult. In particular, in a situation where a probe is used for atmosphere control or the like, it is also difficult to bring the measurement position directly below the irradiation surface.

In the method described in Japanese Patent Application Laid-Open No. 9-500725, the light intensity is measured after spectroscopy of light received using a monochromator or a polychromator. However, this method also causes a problem of insufficient measurement sensitivity because the amount of light is attenuated by slits or the like during spectroscopy.

An object of the present invention is to provide a method for analyzing molten metal which can broaden the measurement concentration range.

According to the present invention, a molten metal analysis method for passing a laser light through the vapor layer of the molten metal, and measuring the concentration of the analysis element contained in the molten metal from the change in the intensity of the laser light passing through the vapor layer, the laser light is analyzed A method is provided wherein the wavelength is adjusted to a position shifted from 0.001 to 0.03 nm from the center position of the absorption wavelength of the element.

In addition, according to the present invention, a wavelength at a position in the vapor layer near the surface of the molten metal containing one or a plurality of analytical elements is shifted from the center position of the absorption wavelength of the analytical element corresponding to the measurement concentration range of the analytical element. The measurement light having the center position of and the reference light having a wavelength that does not generate atomic absorption are allowed to pass through the same optical path, and the intensity of the measurement light component and the reference light component of the passed light are measured. The molten metal analysis method is provided by measuring the concentration of analyte elements in the molten metal, based on a known relationship between the intensity ratio of the light source and the reference light component, the vapor layer thickness, and the temperature of the molten metal.

In the present invention, the value of the deviation amount of the central wavelength of the measurement light is 2.5 or less as the absorbance (= -log (light intensity after absorption) / (light intensity without absorption)) at the maximum value of the measurement concentration range. In addition, it is preferable to set it to the value less than twice the width of the wavelength half value of the atomic absorption line of an analysis element.

In the present invention, if the wavelength half width Z of the measurement light is X, the wavelength half width of the atomic absorption line of the analysis element is X and the amount of deflection of the center wavelength of the measurement light is Y, where Z <(2X-Y). It is desirable to satisfy the relationship of.

In the present invention, there is provided a measurement light in which the wavelength center position is shifted corresponding to the absorbance sensitivity from the center position of the atomic absorption line of the principal component element of the molten metal, the measurement light in which the wavelength center position for the analysis element is shifted, and the atom A reference light having a wavelength that does not generate light is superimposed on the same optical path and passed through a vapor layer on the surface of the molten metal to measure the intensity of both measured light components and the reference light component of the light that passes, and correspond to the main component elements of the passed light. It is preferable to correct the vapor layer thickness from the known relationship between the intensity ratio of the measurement light component and the reference light component and the intensity ratio of the measurement light component and the reference light component corresponding to the analysis element.

Further, in the present invention, the wavelength of the measurement light is monitored during the analysis, the amount of deviation between the center position of the atomic absorption line and the center position of the wavelength of the measurement light is measured, and the absorption of the measurement light component of the vapor passing light is measured from the measurement amount. It is desirable to correct the sensitivity.

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

In the present invention, it is preferable to measure the intensity of the reflected light after the measurement light and the reference light are irradiated on the surface of the molten metal to reflect the light and pass through the vapor layer.

Moreover, in this invention, it is preferable to irradiate a measurement light and a reference light to the area | region of 5 mmphi or more of the molten metal surface.

Moreover, in this invention, it is preferable to use the measurement data when density | concentration of the reflected light intensity of a reference light is more than a threshold.

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

In the present invention, the measurement light and the reference light to be irradiated are laser light, and the intensity of the measured light and the reference light after the reflected light passes through the band pass filter is the radiant light intensity of the molten metal in the wavelength range passing through the band pass filter. It is preferable to adjust irradiation light intensity so that it may become 10 times or more.

Moreover, in this invention, it is preferable that the main component element of a molten metal is iron, and an analyte element is manganese.

Further, according to the present invention, a plurality of laser light sources whose wavelengths, half widths and intensities of the emitted laser light are variable, means for measuring the wavelengths and intensities of the laser light are different from the wavelengths emitted from the plurality of laser light sources. An optical system for superimposing a plurality of laser lights on the same optical path, a chopper for turning on and off the laser light superimposed on the same optical path at regular intervals, and an end portion of the laser light superimposed on the same optical path Optical fiber for guiding near the molten metal, an optical system for irradiating laser light emitted from the optical fiber to a range of 5 mmφ or more of the molten metal surface, and a light receiving unit is installed near the molten metal to receive the reflected light from the molten metal surface. One or a plurality of light receiving optical filters to guide the detection unit and the reflected light guided by the light receiving optical filter, respectively, From the high pass filter and / or low pass filter which separates into the wavelength range containing the low light wavelength, and the reflected light after passing through the high pass filter and / or low pass filter, the narrow wavelength area containing the wavelength of each laser beam is divided. And a band pass filter to be separated, a light detector for measuring the total amount of light after passing through the band pass filter, a means for measuring the temperature of the molten metal, and a computing device for calculating the measured result. Is provided.

1 is an explanatory diagram of the principle of the present invention.

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

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

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

FIG. 5 is a diagram showing an example of a molten metal analysis result in Examples. FIG.

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

FIG. 7 is a diagram showing an example of time series measurement results of molten metal analysis in Examples. FIG.

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

The analysis method according to the present invention includes a step of passing a laser light through a vapor layer of molten metal, a step of obtaining a change in intensity of laser light generated by the passage of the vapor layer, and a method for analyzing an analyte contained in the molten metal from the intensity change. The process of measuring the concentration is included.                 

As laser light, the laser light whose wavelength was adjusted to the position shifted 0.001-0.03 nm from the center position of the absorption wavelength of an analysis element is used. This laser light is guided in the vicinity of the surface of the molten metal, passed through the molten metal vapor layer, and the change in intensity of the laser light due to passage is measured. The relation between the intensity change amount and the concentration of component elements in the metal (unit: wt%, for example) is obtained in advance, and the concentration of the analytical element is determined from the intensity change measured using this relation. In addition, the intensity change may be measured by comparing the laser light intensities before and after the passage, or may be performed by measuring only the laser light intensity after passage after preparing the calibration curve. In addition, the intensity change may be measured intensity itself, or may be a ratio between a negligible state in which there is no or very small vapor layer and a state in which a vapor layer exists, and light that does not generate light absorption entering the same optical system. The ratio of may be sufficient. In addition, these values themselves may be sufficient, and the number of these values may be sufficient.

The absorption spectrum due to the analyte element has a width with respect to the wavelength of light because the temperature of the absorbent material or the like is affected. In other words, the intensity change due to absorption is maximum at the absorbed center wavelength, and decreases with the amount of deviation at the wavelength position away from the center wavelength. In other words, by shifting the wavelength position of the laser light used for measurement from the absorption center wavelength, the intensity change due to the absorption of analytical elements can be reduced.

FIG. 1 shows an example of the change of the transmitted (detected) light with respect to the incident light when the wavelength position of the laser light used for the measurement is shifted. When the wavelength position of the laser light coincides with the center position of the atomic absorption wavelength, it is understood that the transmitted light can be detected by shifting the wavelength while the transmitted light is almost absent and the light cannot be detected.

The amount to shift the wavelength is adjusted by the concentration of the analytical element (the element to be measured) and the type of atomic absorption beam. If the absorbance (= -log (light intensity after absorption) / (light intensity without absorption)) at the maximum value of the measured concentration range is higher than 2.5, the sensitivity at the higher concentration side is lowered, making accurate measurement difficult. Therefore, the amount shifted so that the absorbance at the maximum value of the measurement concentration range is 2.5 or less is set. More preferably, the amount shifted so that the absorbance at the maximum value of the measured concentration range becomes 2 or less is set. In this way, the change in absorbance with respect to the concentration can be made linear in the measurement concentration range. In addition, since the absorption does not occur if it is too deflected, the upper limit of the amount to be deflected is set to a value less than twice the width of the half wavelength of the atomic absorption line. More preferably, the upper limit of the amount to be deflected 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 measurement concentration range is insufficient.

As described above, the concentration range of the element that can be measured by the atomic absorption method can be greatly expanded. By precisely controlling the wavelength of the laser light and shifting it from the central wavelength of the analysis element, it is possible to set the intensity change by appropriate absorption in accordance with the analysis element concentration.

As a light source light which enables such a measurement, it is also possible to spectroscopy continuous light with a spectroscope, to extract the light of a target wavelength, and to take out the light as light source light. However, the use of lasers in light intensity is suitable. In particular, so-called wavelength tunable lasers that can arbitrarily adjust the oscillation wavelength position are suitable.                 

However, not all wavelength tunable lasers are suitable, and it is required that the wavelength width of the output light is small. If the wavelength width is large, the ratio of light beyond the absorption width increases. In other words, the amount of light that is not absorbed (the light that becomes the background of the optical measurement) becomes large, so that the change in the light intensity with respect to the concentration change becomes small, resulting in poor measurement accuracy.

By defining the wavelength width of the output light (light source light) to be the measurement light as follows, it is possible to limit the ratio of the light that is not absorbed and to maintain the measurement accuracy satisfactorily. That is, if the width of the half wavelength of the atomic absorption line of the analytical element constituting the hot molten metal is X and the amount of deflection of the central wavelength of the measurement light from the center position of the atomic absorption line is Y, the half value at the center wavelength of the measurement light is Y. It is preferable that width Z is Z <(2X-Y).

This will be described with reference to FIG. When the wavelength distribution of the absorbance spectrum of an analyte element is Gaussian distribution, the relationship between the standard deviation (sigma) and the half width X which is a guideline of the expansion is X = 2.35σ. In general, when the intensity of the center of the Gaussian distribution to 1, the strength at 2 times the half-value width (2X = 4.7σ) position away from the center 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 is high and the absorbance at the center wavelength is 100 or more, the wavelength region is considered to have almost no absorbance. do.

On the other hand, the measurement light can be regarded as forming a Gaussian distribution of a variance of half width Z and standard deviation σ having a center wavelength at a position shifted by Y from the center position of the atomic absorption line of the analysis element. At the wavelength position (Y + Z) shifted more than half the width (Z = 2.35σ) at the center wavelength Y, the amount of measured light is reduced to 1% and the effect is small even if this amount of light remains unabsorbed by the analyte. .

Therefore, as the half width (wavelength width) of the measurement light, the wavelength position (Y + Z) separated by half the width (Z = 2.35σ) from the center wavelength Y of the measurement light is 2 of the half width at the center of the absorption spectrum. It is preferable to be located inward from the wavelength position 2X away, and it is judged that the influence of the light remaining without being absorbed is small in this way. That is, Y + Z <2X. This leads to Z <2X-Y.

The measurement light and the reference light having a wavelength that does not generate atomic absorption are superimposed on the same optical path by using an optical filter that reflects or transmits light by the characteristics of the wavelength, and passes it through a vapor layer on the hot molten metal surface.

On the surface of the molten metal, not only light absorption by the vapor layer but also light attenuation due to dust generation and the like, it is necessary to use a ratio with reference light that does not generate atomic absorption in order to correct this effect. As reference light, light absorption by the vapor layer is absent and light having a wavelength close to the wavelength of the measurement light is preferable.

The light intensity of the measurement light component and the reference light component of the light passing through the vapor layer is spectroscopically detected using an optical filter that reflects or transmits the light according to the wavelength specification. The reference light intensity ratio (R: measured light intensity / reference light intensity) is obtained from the light intensities of the respective wavelengths obtained, and the amount of change from the intensity ratio R0 in the absence or very small negligible vapor layer (R / R0) Obtain At this time, the logarithm of the reciprocal of the intensity ratio change amount (= -log (R / R0)) is taken as the absorbance (A). This absorbance can be expressed as a function of the concentration of the analyte element (measurement component) in the molten metal, the temperature in the molten metal, and the thickness of the vapor layer. Therefore, the temperature of the analysis element in the molten metal can be obtained by correcting the temperature of the molten metal and the thickness of the vapor layer.

First, the correction method of the thickness of a vapor layer is demonstrated. The measurement light for measuring the main component element of the molten metal is passed through the vapor layer on the surface of the hot molten metal in the same optical path as the measurement light for the analysis element and the reference light. The light passing through the vapor layer is spectroscopically detected using an optical filter to detect the respective light intensities of the principal component element measurement light, the analysis element measurement light, and the reference light. From the obtained light intensities, the reference light intensity ratio (R _IS ) of the main component element and the reference light intensity ratio (R) of the analysis element are obtained, and the respective intensity ratios (R _IS 0, R0 in the absence of or very small vapor layer) are negligible. Obtain the amount of change from). Similarly to the analytical element, the logarithm of the reciprocal of the intensity ratio change amount (= -log (R _IS / R _IS 0)) is also obtained for the main component element as the main component absorbance (A _IS ).

The correction of the vapor layer thickness can be performed by using the ratio (A / A _IS ) of the absorbance (A) of the analysis element to the absorbance (A _IS ) of the main component element as the absorbance after the correction of the vapor layer thickness of the analysis element. For the main component element and the analytical element, the formula (1) of light absorption phenomenon is established. Thus, by taking the ratio of absorbance to both elements, the variation term of the vapor layer thickness (length) L is eliminated and can be expressed as a function of the analyte element concentration.

Moreover, it is preferable that the center position of the wavelength of the measurement light with respect to the main component element of a molten metal shifts from the center position of the atomic absorption line of the said main component element corresponding to the absorption sensitivity of the atomic absorption of the said main component element. This is because if the wavelength center position of the measurement light and the center position of the atomic absorbing ray are the same, the signal becomes small and the S / N becomes bad when the absorbance sensitivity is high. In addition, as will be described later, the measurement accuracy is further improved by measuring the wavelength of the measurement light during measurement and measuring while correcting the variation in absorbance due to the change in the wavelength.

Next, the correction method of the temperature of molten metal is demonstrated. The amount of vapor of each element generated on the surface of the molten metal is proportional to the concentration (active amount) and vapor pressure (saturated vapor pressure) in the molten metal of the element. Saturated vapor pressure can be expressed as a function of the temperature of the molten metal. Therefore, on the basis of the saturated steam pressure (P0) of the analytical element at the standard temperature T0 ° C of the molten metal and the saturated vapor pressure (P _IS O) of the main element, the respective saturated vapor pressures (P ( _{T), P iS (T)} ) with non-(P0 / P (T), to obtain a _{P iS 0 / P iS (T} )), and using this correction the absorbance (a and a _iS). The change of the saturated steam pressure at each temperature may use a literature value.

In this case, the wavelength tunable laser is required to have a sufficiently small wavelength width of the output light, to accurately set the center position of the wavelength, and to have no change in wavelength position over time. Since the absorbance is a function of the light source wavelength position, it is ideal that there is no change over time in the wavelength position as described above. However, in order to strictly manage the laser installation environment (particularly the temperature change), Various difficulties arise, such as no change, and are difficult to achieve in reality. As a countermeasure, the wavelength dependence of the absorbance is determined by changing the wavelength position in advance, and in the on-line actual measurement of the gas, the absorbance amount is measured while monitoring the wavelength of the laser light emitted, and the change in absorbance sensitivity due to the variation of the wavelength position is obtained online. By calculating the amount of the component in the gas by correcting it, it is possible to analyze the component in the gas in realistic situations.

3 shows an example of an apparatus configuration for implementing the present invention.

In FIG. 3, the laser light generated from the laser light source 1 is irradiated to the metal vapor layer 4 on the surface of the molten metal 3 through the optical system 2. The laser light passing through the metal vapor layer 4 is guided to the photodetector 6 through the optical system 5 and the intensity is measured.

As the optical systems 2 and 5, it is preferable to use optical fibers. In this way, the laser light source 1, the photodetector 6, and the like can be separated from the surface of the molten metal 3 and arranged.

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

The optimum amount of deflection of the wavelength can be obtained as follows. First, the wavelength dependence of the change in absorbance intensity is examined in advance. That is, after making a measurement system, several points are measured by changing the wavelength of a laser beam to the density | concentration of the analytical element made into the objective of molten metal (3). Then, the position of the laser wavelength where the laser light intensity after absorption by the metal vapor layer 4 is considered to be the most appropriate is found. In addition, in the atomic absorption analysis of a solution sample using a conventional atomic absorption spectrometer, the laser light source of this analysis system is used as a light source, and the wavelength dependence of the absorption intensity change is investigated beforehand. Next, the molten metal 3 having a small analysis element concentration is measured at the center position of the absorption wavelength of the analysis element, and the measurement limit at this center position is obtained. Then, an appropriate wavelength for the measurement concentration range is obtained from the results of the investigation on the wavelength dependence of the absorbance intensity change already performed.

In addition, since the intensity change due to absorption changes with the half width of the wavelength of the light emission wavelength, the sensitivity can be more appropriate by changing not only the wavelength deviation but also the wavelength width.

The laser light may be light of the absorption wavelength of the element to be measured, but may include absorption wavelengths of other analysis elements and reference light not absorbed by the analysis elements. By irradiating these lights simultaneously, the light intensity can be measured for each analysis element.

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

In addition, a spectrometer or a band pass filter may be provided in front of the photodetector 6. By doing in this way, only the intensity | strength of the light of a target wavelength can be measured, and the influence from the heat radiation light or illumination of the molten metal 3 can be reduced.

In addition, the optical systems 2 and 5 may be arranged so that the surface of the molten metal 3 is treated as a reflecting mirror for laser light. In other words, the laser light emitted from the optical system 2 may pass through the vapor layer 4 near the surface and be reflected on the surface of the molten metal 3 to enter the optical system 5.

4 shows an example in which an optical system is arranged so that the surface of the molten metal 3 is treated as a reflector for laser light. In Fig. 4, the laser light generated from the laser light source 1a (for analysis element measurement), 1b (for main component element measurement) and 1c (for reference light) is used as an optical filter (high pass filter) in the condensing optical system 7 ( It is set as the light of the same optical path using 8a-8c). The light is introduced into the irradiated optical fiber 11a through the lens 9 and transmitted to the vicinity of the molten metal 3. The chopper 10 is arranged just before the optical fiber 11a is introduced. The light 20 from the tip of the optical fiber 11a passes through the vapor layer 4 after passing through the irradiation optical system 22 and is irradiated onto the surface of the molten metal 3. The light 21 reflected from the surface of the molten metal 3 passes through the vapor layer 4 again and then passes through the light receiving optical fiber 11b. The light from the light receiving optical fiber 11b becomes parallel light passing through the lens 12, and is divided into respective laser light wavelengths through the optical filters 13a and 13b (high pass filter), and then a band pass filter ( After 14a and 14b, they are guided to photodetectors 6a and 6b to measure the intensity. The intensity of each wavelength measured is the temperature information from the temperature sensor 16 of the molten metal, the laser wavelength information from the wavelength meter 19 measured with respect to the laser light of the laser light source, and the beam sampler 17 and the light. The laser output power information from the laser light source measured by the detector 18 is sent to the computing device (calculator) 15.

From this information, correction of the laser power fluctuation, correction of the laser output wavelength fluctuation, correction of the vapor layer thickness fluctuation, and temperature correction can be performed by the computing device 15 to obtain the concentration of analytical elements in the molten metal.                 

When the molten metal surface swings and the wave is generated, the wave randomly occurs and moves in a random direction. Moreover, the curvature of the wave surface also changes every time. When light is irradiated to any point on such a metal surface, the direction in which the light reflects and returns is also random. Therefore, when the measurement time is limited, the reflected light from a specific point of the molten metal surface may never reach the light receiving portion. However, since the wavefront changes occurring at other points away from this particular point also occur randomly, the probability that the reflected light from that point also does not reach the light receiving portion 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 portion increases. That is, instead of focusing on the molten surface described in Japanese Patent Application Laid-Open No. 9-500725 for laser light irradiation onto the molten metal surface, the number of times reaching the light-receiving portion is increased by increasing the area of the irradiated portion.

Waves generated on the surface due to the fluctuation of the molten metal surface have a radius of curvature of about 1 to 2 mm, and they propagate to cause complicated irregularities on the surface. In the case of paying attention to one of the convex portions, when the light is irradiated to the convex portion to receive the reflected light from any point in the convex portion, the convex portion from another portion of the convex portion except for the vicinity of the pole Reflected light is not received. In order to increase the number of times of receiving light, it is essential to irradiate the laser light to the other uneven portions so as to receive the reflected light from the other convex portion or the concave portion. By taking the same width as that of the convex portion at least before and after the convex portion noted as such an uneven portion, and increasing the number of light receptions can be achieved by irradiating light in the range of the width.                 

Since the typical size of the convex portion is a width of 1 to 2 mm, irradiating more than a region having the same width before and after it means that the irradiation region of the laser light is 5 mmφ or more in actual work. By specifying such an irradiation area, the measurement becomes very effective.

In addition, since the reflection efficiency is not constant in this manner, it is not possible to determine whether the change (decrease) in the amount of light received by the measurement light is due to absorption or the change in reflection efficiency due to shaking. Therefore, it is essential for measurement to compensate for the change in reflection efficiency by irradiating and measuring the comparison light simultaneously with the measurement light and taking the ratio thereof. The comparison light is a comparison light in which the optical path and the irradiation area are all the same so that the change in the reflection efficiency is the same in the measurement light and at any minute time.

Regarding the method for measuring the received light intensity, the measurement intensity is improved by dividing the light intensity every short time and using the signal only for the concentration measurement when the intensity of the reflected light is equal to or greater than the threshold value. For signals with low reflected light intensity, most of them are only radiant light, and the amount of light absorption cannot be accurately measured. Therefore, by using the signal only when the intensity of the reflected light (particularly the reflected light of the reference light) is equal to or greater than the threshold value, the S / N is improved and the analysis accuracy is further improved.

The above-mentioned radiant light generated by the molten metal itself is separated from the measurement light as follows. That is, the irradiation of the laser light is cut off at regular intervals to measure the radiant light (I _f ) at the time of blocking, and the difference between the measured light intensity (I _r ) at the laser irradiation and the radiant light intensity (I _f ) measured at the blocking ( I _r -I _f ) is regarded as the intensity of only the reflected light of the laser. The intensity of atomic absorption can be accurately measured by the intensity of the reflected light measured in this way.

In the case where the radiant light fluctuates in time, the irradiation of the laser light is interrupted at regular intervals, the radiant light at the time of blocking is measured as follows, and the change over time of the radiant light intensity is taken into account. That is, the radiation intensity at the time of laser cutoff (= (I _f1 + I _f2 ) calculated from the light intensity I _r at the time of laser irradiation and the radiation intensity (I _f1 , I _f2 ) at the time of laser blocking before and after From / 2), the difference in light intensity (I _r- (I _f1 + I _f2 ) / 2) is obtained. The intensity of atomic absorption is measured by considering this difference in light intensity as the intensity of only the reflected light of the laser. In this way, accurate radiation can be corrected.

As for the period which interrupts irradiation of a laser beam, the range of 1-1000 Hz is preferable.

To block the laser light at regular intervals to measure only the radiant light from the molten metal, it is passed through a rotary breaker (hereinafter referred to as a chopper) before the laser light is irradiated onto the molten metal surface. Irradiation and blocking of laser light are alternately performed, and at the time of irradiation, the light which combined the laser reflection light and the radiation light is measured, and at the time of blocking, only the radiation light is measured. By doing so, the true laser reflected light can be easily measured. At this time, the interruption time of the laser light needs to be longer than the optical measurement time. For example, when the light measurement time is a period of 0.002 seconds, the laser cutoff 0.02 seconds, the laser irradiation 0.08 seconds (cycle 0.1 seconds) is preferable. Note that the cutoff time and the irradiation time do not necessarily have to coincide. When the measurement including the fluctuation of the radiant light is sufficiently performed during the blocking, it is preferable to increase the irradiation time in order to improve the measurement accuracy of the laser reflected light. In this way, even if only a simple band pass filter and a photomultiplier (photomultiplier) are installed in the spectrophotometer for spectroscopic light from the molten metal, the radiant light can be measured accurately.

Since the radiant light from the molten metal is continuous light, as a method of easily measuring, by spectroscopically spectroscopy the light of the reflected light and the radiant light and measuring the radiant light of the wavelength near the incident laser light wavelength, You may estimate the radiant light of the same wavelength.

Further, for example, the relationship between radiation of a specific wavelength such as infrared rays and radiation of reflected measurement light may be obtained in advance, and only the radiation of this specific wavelength may be measured to estimate radiation of a wavelength such as laser light.

As the detection method of the reflected light, there is a method of spectroscopy of light received using, for example, a monochromator or a polychromator and measuring the light intensity. However, this method lacks measurement sensitivity because the amount of light is attenuated by slit or the like during spectroscopy. Therefore, the received light is passed through a bandpass filter whose pass wavelength includes the reflected light wavelength and the pass wavelength width is 5 nm or less, and after selecting the wavelength, the total amount of light is detected as a signal. For example, a light-passing optical fiber having a diameter of about 1 mmφ is installed 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, the total amount of light is guided to a photomultiplier and the light intensity is measured. By doing in this way, a measurement sensitivity can be improved. At this time, the wavelength measured within the half width of the band pass filter is included, and the half width is preferably as small as possible.

In addition, when a plurality of reflection measurement lights, such as light after atomic absorption by a molten metal analysis element, light after atomic absorption by a main component element, and reference light, are in the same optical path, a specific wavelength range is reflected and is different from 45-degree incident light. The specific wavelength range may be used for spectroscopic laser light spectroscopy, pass through a bandpass filter having the measurement wavelength as the center wavelength, and then guide the photomultiplier to measure the intensity thereof.

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

In addition, when the radiant light is large, the ratio of the reflected light to the radiant light is small, and the measurement accuracy of the reflected light is deteriorated. Therefore, at least a part of the surface of the molten metal is preferably shielded so as not to detect the radiant light from the molten metal.

The necessity and correction method for the temperature change of the molten metal are as described above. The temperature measurement of the molten metal may be performed by calculating a relational expression between the radiant light intensity of a specific wavelength and the temperature of the molten metal in advance, and calculating it from the measured value of the radiant light intensity of this specific wavelength. In addition, instead of the specific light intensity, the ratio of the light intensity of two specific wavelengths may be used. The radiant light intensity may be measured by separately providing a measuring device, or may be calculated using the amount of light measured when the measurement light is blocked by the chopper.

The method of the present invention is a method of measuring a system such as molten steel whose main component is iron and whose analytical element is Mn (manganese). In the conventional atomic absorption method, absorption is saturated at a Mn concentration of 0.2 wt% or more in molten steel, and measurement is impossible. However, even when the Mn concentration in molten steel is 2 wt%, it can be measured.

A molten metal analyzing apparatus according to the present invention will be described. 4 shows an example of the apparatus. In Fig. 4, the laser light generated from the laser light source 1a (for analysis element measurement), 1b (for main component element measurement) and 1c (for reference light) is used as an optical filter (high pass filter) in the condensing optical system 7 ( Through 8), light of the same optical path is used. As the laser light source, a laser light source having a variable wavelength, half width and intensity of laser light to be emitted is used. The light having the same optical path is guided through the lens 9 to the optical fiber 11a and transmitted to the vicinity of the molten metal. In order to measure the radiant light from the molten metal, the chopper 10 is passed just before guiding the laser light to the optical fiber 11a. The light 20 from the tip of the optical fiber 11a passes through the irradiation optical system 22, passes through the vapor layer 4, and is irradiated onto 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 of the lens position provided on the lens, so that the laser light is applied to the surface of the molten metal 4 as parallel light or divergent light. We do with mechanism that we can check. The light reflected from the surface of the molten metal 3 passes through the vapor layer 4 again and is transmitted through the light receiving optical fiber 11b. One or more optical fibers may be provided. The light from the light receiving optical fiber 11b passes through the lens 12 to become parallel light, passes through the optical filters 13a and 13b separating the wavelength region, and is divided into respective laser light wavelengths, and then a band pass filter. After 14a-14c, it guides to the photodetectors 6a-6c which measure the total light quantity, and intensity is measured. The intensity of each wavelength measured is the temperature information from the temperature sensor 16 of the molten metal, the laser wavelength information from the wavelength meter 19 measured with respect to the laser light of the laser light source, and the beam sampler 17 and the light. The laser output power information from the laser light source measured by the detector 18 is sent to the computing device 15.

From this information, correction of the laser power fluctuation, correction of the laser output wavelength fluctuation, correction of the vapor layer thickness fluctuation, and temperature correction can be performed by the computing device 15 to obtain the concentration of analytical elements in the molten metal.

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, and the absorbance of the analysis element and the concentration of the analysis element in the molten metal (e.g., wt% By obtaining the relational expression (calibration line) with), high-precision analysis is possible.

(Example 1)

The Mn concentration in the molten metal was measured using the measuring apparatus shown in FIG.

The molten metal (3) was made by melting 5 kg of molten steel in a carbon crucible by a high frequency melting furnace. Then, Mn was added in the molten steel at a concentration of 0 to 1 wt% in the molten steel. Mn measurement was performed at the molten steel temperature of 1600 degreeC.

The wavelength tunable laser used for the measurement was output as follows. That is, Ti sapphire laser was excited by the 2nd high frequency oscillation light (0.53nm) of YAG laser, and it was set as the wavelength continuous laser light. Then, the second high frequency of the wavelength continuous laser light was oscillated by adjusting the wavelength and output as a wavelength tunable laser. The oscillation wavelength was adjusted by shifting the atomic absorption wavelength of Mn in units of 0.001 nm with respect to 403.307 nm. The energy of the output laser light was 10 mW and the wavelength half width 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 incident light fiber 2 was placed at a position to focus the laser light from the laser light source 1. The other end of the light receiving fiber 2 was placed in a probe and placed near the molten steel for each probe. The probe was filled with nitrogen gas in order to prevent oxidation due to mixing of air. In the probe, the light from the light receiving fiber 2 passed through the vapor layer 4 and was 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 incident slit portion of the 50 cm Evert type spectrometer. The light which reached the incident slit part was spectroscopically measured by the spectroscope, and the intensity | strength was measured by the photodiode 6.

The wavelength of the laser light was deflected using the above system, and the relationship between the Mn concentration in the molten steel and the intensity change due to absorption was measured for each deflection amount. An example of the measurement result is shown in FIG. As can be seen from Fig. 5, when the wavelength of the laser light was adjusted to the center of the absorption wavelength of Mn, the change in intensity change due to absorption at the Mn concentration of 0.2 wt% or more could not be measured. However, by shifting the wavelength of the laser light by 0.005 nm or more from the center of the absorption line wavelength of Mn, the intensity change due to absorption was sufficiently measured even at 1 wt% of Mn.

As described above, according to the present invention, the measurement sensitivity can be controlled by controlling the wavelength position of the laser light. As a result, the narrowness of the measurement range which is a defect of the atomic absorption method is eliminated, and the use of the atomic absorption method in the molten metal analysis method has become more general.

(Example 2)

The concentration of Mn in the molten metal was measured using the measuring apparatus shown in FIG.

As the molten metal 3, 5 kg of molten steel was melted in a carbon crucible by a high frequency melting furnace, and Mn was added in a molten steel at a concentration of 0 to 1.5 wt% in molten steel. The measurement was performed in the range of molten steel temperature of 1550 degreeC-1650 degreeC.

In the laser light source 1a for analytical element measurement of the apparatus of FIG. 4, a Ti sapphire laser is excited by the 2nd high frequency oscillation light (0.53 nm) of a YAG laser, and it is set as wavelength continuous laser light, The wavelength tunable laser which oscillated by adjusting a wavelength with respect to a 2nd high frequency wave was used. The oscillation wavelength was adjusted to a wavelength of 403.313 nm which was shifted by 0.006 nm from the Mn atomic absorption wavelength center (403.307 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 absorbance sensitivity of Mn by the laser wavelength position using this laser light source. As can be seen from FIG. 6, a peak of absorbance sensitivity was obtained at an atomic absorption wavelength of 403.307 nm of Mn.

As the laser light source 1b for measuring the main component elements of the apparatus of FIG. 4, the above-described tunable laser was used to adjust the oscillation wavelength to near the center of the atomic absorption wavelength (386 nm) of Fe as the main component of the molten metal. The power of the laser was 10 mW.

In addition, a blue semiconductor laser having an oscillation wavelength of around 430 nm was used as the laser light source 1c for the reference light of FIG.

In the optical system for laser irradiation, an optical filter 8a to 8c, which will be described later, is disposed at the intersection of the laser beams at a position of 90 degrees, and the three laser beams are routed to the same optical path. It was. That is, after reflecting the laser light from the laser light source 1a with the optical filter 8a, it intersected with the laser light from the laser light source 1b by 90 degree | times. At this intersection, an optical filter 8b was disposed in which light at 403 nm (light source 1a) was transmitted and light at 386 nm (light source 1b) was reflected with respect to the incident light at 45 degrees. In this way, the laser light from the light sources 1a and 1b was the same optical path. Next, the laser light from the light sources 1a and 1b set to the same optical path was crossed at 90 degrees with the laser light from the laser light source 1c. The optical filter 8c which transmits the light of 403 nm (light source 1a), the light of 386 nm (light source 1b), and reflects the light of 430 nm (light source 1c) was arrange | positioned at this intersection. In this way, the laser beam of 403 nm (light source 1a) and 386 nm (light source 1b) and the laser light of 430 nm (light source 1c) became the same optical path. In this manner, three kinds of laser light having the same optical path were collected by the lens 9 and introduced into the optical fiber 11a having a 0.3 nm diameter. The rotary chopper 10 was passed just before the laser light was put into the optical fiber 11a. The reflective side end surface of the optical fiber 11a is fixed with a connector, and the distance between the lens 22 and the optical fiber 11a end surface is adjusted by a mechanism for finely adjusting the position of the lens 22 so that the laser light is parallel light. After making it into (20), it irradiated to the molten steel surface. The irradiation diameter to the molten steel surface was 5 mmφ.

As the light receiving optical system, only the optical fiber 11b was used, and the optical filters 13a and 13b were used as the spectrometer. That is, the light receiving optical fiber 11b of diameter of 1 mm (phi) was provided in the vicinity of 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 guided to the optical filter 13a for spectroscopy. The optical filter 13a is a filter that transmits light at 403 nm (light source 1c) to 45-degree incident light, and reflects light at 403 nm (light source 1a) and light at 386 nm (light source 1b). The reflected laser light was also spectroscopically analyzed by the optical filter 13b. The optical filter 13b is a filter which transmits light of 403 nm (light source 1a) to 45 degree incident light, and reflects light of 386 nm (light source 1b). The laser beams of the spectroscopic measured wavelengths are then passed through bandpass filters 14a to 14c having half widths of 2 nm each having the wavelength as the center wavelength, and guided to the photomultiplier 6a to 6c. The strength was measured in units of 2 m seconds. The measurement was performed for 2 seconds to collect 1000 data.

Temperature measurement was measured using a Pt-Rh-based thermocouple (16). The relationship between the temperature just below the molten steel surface and the temperature at the temperature measurement position was measured using a Pt-Rh-based thermocouple and a relational expression was obtained.

The cycle of the chopper 10 was set to 100 m seconds, and repeated 25 m seconds of cutoff and 75 m seconds of irradiation. As described above, the light intensity when blocked by the chopper 10 is radiant light. The average value of the radiant light intensity at the time of blocking was calculated | required in time series, and as mentioned above, the radiant light intensity at the time of reflected light measurement was calculated | required and averaged the radiant light intensity at the time of blocking before and after reflected light measurement. From the measured value at the time of reflected-light measurement, the calculated intensity of the reflected light was subtracted and the true reflected light intensity was obtained. This was calculated | required about each of reference light and measurement light.

7 shows an example of the reflected light cut off by the chopper 10 with respect to the reference light and the light for Mn measurement.

Regarding the absorbance data, when the reference light intensities are arranged in the order of the intensity, the data at the timing of becoming at least 50% or higher is regarded as valid data. Intensity ratio R between the average value of Mn measurement light and reference light at these timings, and intensity ratio R0 between the average value of Mn measurement light and reference light when laser light is received without passing through a molten steel surface. ), And the reciprocal number (= -log (R / R0)) was taken as the absorbance of Mn. The absorbance was similarly calculated | required about Fe which is a main component element.

The correction of the temperature of the molten metal 3 was corrected by reference to the values of the absorbances of Mn and Fe at a vapor pressure of 1600 ° C. using the literature values for the temperature change of the vapor pressure.

The correction of the vapor layer 4 thickness calculated the absorbance ratio between Mn and Fe, and the absorbance ratio was taken as the Mn absorbance after the vapor layer 4 thickness correction.

An example of the relationship between the Mn absorbance (substantially the ratio of Fe absorbance) measured in this way and the Mn concentration in molten steel is shown in FIG. As can be seen from Fig. 8, by the present invention, the correlation between Mn absorbance and Mn concentration in molten steel is good, and Mn concentration analysis can be performed with high precision.

In addition, since the measurement in this Example was a short time, the output wavelength of the laser light was stable and there was no change. However, the laser output wavelength changes during the actual long time measurement. When the laser output wavelength is changed, high accuracy analysis is possible by correcting the absorbance using an example of the change in absorbance due to the wavelength position as shown in FIG.

Claims (14)

delete A measurement light having a center position of the wavelength in a vapor layer near the surface of the molten metal containing at least one analyte element, which is shifted from the center position of the absorption wavelength of the analysis element corresponding to the measurement concentration range of the element; Passing a reference light having a wavelength that does not generate atomic absorption in the same optical path in a superimposed manner; And Measuring the intensity of the measured light component and the intensity of the reference light component of the light that has passed; And Measuring the concentration of analyte elements in the molten metal from a known relationship between the intensity ratio of the measured light component and the reference light component, the vapor layer thickness, and the temperature of the molten metal; Made of The deviation of the central wavelength of the measurement light is a value at which the absorbance at the maximum value of the measurement concentration range (= -log (light intensity after absorption) / (light intensity in the absence of absorption)) is 2.5 or less, and also the measurement concentration. A method for analyzing molten metal, wherein the absorbance at the maximum value of the range is set to a value of 0.5 or more. delete The method of claim 2, The wavelength half width Z of the measurement light satisfies the relationship of Z <(2X-Y) when X is the wavelength half width of the atomic absorption line of the analysis element as X and the amount of deflection of the central wavelength of the measurement light is Y. Method for analyzing molten metal A measurement light in which the wavelength center position is shifted from the center position of the atomic absorption line of the main component element of the molten metal corresponding to the absorbance sensitivity, the measurement light in which the wavelength center position for the analysis element is shifted, and the wavelength which does not generate the atomic absorption Passing the reference light in the same optical path and passing it through the vapor layer on the surface of the molten metal; Measuring the amount of light passing through the intensity of the light component and the intensity of the reference light component; Measuring the concentration of analyte elements in the molten metal from a known relationship between the intensity ratio of the measured light component and the reference light component, the vapor layer thickness, and the temperature of the molten metal; And Correcting the vapor layer thickness from a known relationship between the intensity ratio of the measurement light component corresponding to the main component element of the passing light and the reference light component and the intensity ratio of the measurement light component corresponding to the analysis element and the reference light component; Made of The deviation of the central wavelength of the measurement light is a value at which the absorbance at the maximum value of the measurement concentration range (= -log (light intensity after absorption) / (light intensity in the absence of absorption)) is 2.5 or less, and also the measurement concentration. A method for analyzing molten metal, wherein the absorbance at the maximum value of the range is set to a value of 0.5 or more. The method of claim 2, Monitoring the wavelength of the measurement light during the analysis, measuring the amount of deflection between the center position of the atomic absorption beam and the center position of the wavelength of the measurement light, and correcting the absorbance of the measurement light component of the vapor passing light from the measured amount of deflection; Analysis method of molten metal, characterized in that. The method of claim 2, A method of analyzing molten metal, comprising the step of turning on / off the measurement light and the reference light using a chopper and performing a background correction using the light intensity at the time of off as the radiant light intensity from the molten metal. The method of claim 2, The process of measuring the intensity of the measurement light component and the intensity of the reference light component is characterized by measuring the intensity of the reflected light after the measurement light and the reference light is irradiated and reflected on the molten metal surface to pass through the vapor layer. Way. The method of claim 8, The method for analyzing molten metals, wherein the measurement light and the reference light are irradiated to the molten metal surface by irradiating the measurement light and the reference light to a region of 5 mmφ or more on the surface of the molten metal. The method of claim 8, A measurement method for molten metal, wherein measurement data when the reflected light intensity of the reference light is equal to or greater than the threshold value is used for concentration measurement. The method of claim 8, The reflected light is received by the optical fiber, and the received reflected light is passed through a band pass filter whose pass wavelength includes the wavelength of the atomic absorption beam of the analysis element and whose pass wavelength width is 5 nm or less, and the wavelength is selected. An analysis method of molten metal, characterized in that for measuring the total amount of light. The method of claim 11, The measurement light and the reference light to be irradiated are laser light, so that the intensity of the measured light and the reference light after the reflected light passes through the band pass filter is 10 times or more the radiant light intensity of the molten metal in the wavelength band passing through the band pass filter. An analysis method of molten metal, characterized in that the irradiation light intensity is adjusted. The method of claim 2, A method for analyzing a molten metal, wherein the main element of the molten metal is iron and the analytical element is manganese. Analysis device for molten metal consisting of the following configuration: A plurality of laser light sources of varying wavelength, half width and intensity of the emitted laser light; Means for measuring the wavelength and intensity of the laser light; An optical system overlapping a plurality of laser lights having different wavelengths emitted from the plurality of laser light sources with the same optical path; A chopper for turning on and off laser light superimposed on the same optical path at a predetermined cycle; An optical fiber having an end portion installed near the molten metal and guiding the laser light superimposed on the same optical path near the molten metal; An optical system for irradiating laser light emitted from the optical fiber to a range of 5 mmφ or more of the molten metal surface; One or more light-receiving optical fibers which are provided in the vicinity of the molten metal and receive light reflected from the molten metal surface and guide the light-detecting portion; A high pass filter and / or low pass filter for separating the reflected light guided by the light receiving optical fiber into a wavelength region including the wavelength of each laser light; A band pass filter for separating a narrow wavelength region 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 light detector for measuring the total amount of light after passing through the band pass filter; Means for measuring the temperature of the molten metal; And Computing device that calculates the measured result.

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