JPH0815153A - Method and apparatus for laser emission spectroscopic analysis - Google Patents

Abstract

PURPOSE:To obtain a method for laser emission spectroscopic analysis in which the analysis is performed while regulating the distance between the point of a laser irradiation lance and the surface of a molten sample automatically and an apparatus used for effecting the method. CONSTITUTION:The surface of a molten sample 2 is irradiated with a laser light LB through a lance 1 to produce a plasma P. The light emitted from the plasma P is then subjected to spectroscopy to produce a spectral line SP and the intensity thereof is measured in order to analyze the elements contained in the molten sample 2. In such method for laser emission spectroscopic analysis, the surface of the molten sample 2 is additionally irradiated with an ultrasonic wave and the reflected wave thereof is detected in order to measure the level of the molten sample 2 thus sustaining a constant distance between the point of the laser irradiation lance 1 and the surface of the molten sample 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser emission spectroscopic analysis method and an apparatus therefor, and more specifically, it automatically adjusts the distance between a laser irradiation lance tip and the surface of a melt sample such as molten metal which is a sample to be analyzed. However, the present invention relates to a method for analysis and an apparatus for performing the method.

[0002]

2. Description of the Related Art As a method for emission spectroscopic analysis of elements in a molten material such as molten metal, for example, manganese, carbon, sulfur, phosphorus in molten steel, a part of the molten metal has been conventionally collected and rapidly solidified. There are known ones that analyze a so-called solid sample made by utilizing discharge phenomena such as arc, spark, and glow, and one that uses high-frequency induction plasma. However, these methods are inconvenient because the analysis time is long and inconvenient to obtain the component information immediately in the refining process online, and the research and development of the method for direct emission spectroscopic analysis on the sample in the molten state have been actively conducted. Has proposed a method using arc discharge, spark discharge, oxygen fire point, laser, or the like.

Among them, the laser emission spectral analysis method is disclosed in Japanese Patent Application Laid-Open No. 58-219439.
It has attracted attention as an online continuous analysis method for components in molten metals such as hot metal, molten steel and hot dip galvanizing, and in molten materials such as molten slag. The reason is that it has an advantage that the lower limit of quantification is lower than that of arc discharge, spark discharge, oxygen fire point and the like.

However, in the laser emission spectroscopic analysis method,
In order to keep the energy density of the irradiation laser and the intensity of the emitted spectral lines constant, that is, in order to improve the analysis accuracy,
It is very important to adjust the distance between the laser irradiation lance (hereinafter referred to as “lance”) and the surface of the melt sample. Conventionally, during analysis, laser oscillation and analysis /
There is a drawback that it is necessary to stop the measurement and visually measure and adjust the distance. For example, in the hot dip galvanizing operation of steel sheets, the zinc bath is continuously replenished due to the consumption of the plating solution over time, and the plating bath surface changes continuously. It was necessary to keep the distance between the two constant, and the analysis work was very complicated.

[0005]

DISCLOSURE OF THE INVENTION The present invention solves the problems of the above-mentioned prior art, and laser emission spectroscopy for analyzing while automatically adjusting the distance between the lance tip and the surface of a melt sample such as molten metal. It is an object of the present invention to provide an analytical method and a device that can be used for carrying out the method.

[0006]

In order to achieve the above-mentioned object, the inventor has focused on automatically adjusting the above distance using a non-contact type distance measuring device. Adopted the total. As a non-contact distance measuring device, there are some that use light in addition to sound waves, but the optical distance meter requires a device with too good accuracy because of its short response time.
This is a disadvantage in that it is costly to manufacture. In order to achieve the above purpose, since the response speed by sound waves is sufficient,
In the present invention, an ultrasonic range finder is selected.

However, the place where hot metal, molten steel, and hot dip galvanizing bath are analyzed online is usually at a high temperature and the ambient temperature fluctuates greatly. Therefore, when the above distance was actually measured with an ultrasonic range finder, there was a change in the ultrasonic velocity due to a change in ambient temperature. That is, even if the ambient temperature on the molten sample fluctuates by about 100 ° C., the speed of the ultrasonic wave fluctuates, and as a result, the apparent measurement distance fluctuates. The energy density of the laser was different, and the analysis value of the laser emission spectroscopic analysis was changed. Therefore, the inventor made diligent efforts to correct the above-mentioned temperature fluctuation, and considered the correction method described later to complete the present invention. That is, the present invention irradiates the melt sample surface with laser light through a laser irradiation lance and measures the intensity of a spectral line obtained by dispersing the emission of the generated plasma to measure in the melt sample. In the laser emission spectroscopic analysis method for analyzing the contained elements, the melt sample surface is separately irradiated with ultrasonic waves, the reflected wave is detected to measure the melt sample surface height, and the laser irradiation lance tip is used. Is a laser emission spectroscopic analysis method characterized in that the distance between the melt sample surface and the melt sample surface is kept constant. Further, according to the present invention, the distance L between the laser irradiation lance tip and the melt sample surface is automatically kept constant within L ± 0.05 L. But also
The laser emission spectral analysis method according to claim 2, further comprising: correcting a change in ultrasonic velocity due to a change in ambient temperature above the surface of the melt sample.

The present invention, which is an apparatus that can be used for implementing the above method, provides a laser emission spectroscopic analysis apparatus comprising a laser oscillator, a laser irradiation lance having a condenser lens inside, a spectroscope, a photometer, and a computer. An ultrasonic wave generator / receiver for measuring the height of the melt sample, a calculation means for obtaining a correction amount of the lance position for laser irradiation based on the measured value, and the lance is automatically moved up and down based on the calculation result. A laser emission spectroscopic analysis device is characterized in that it is provided with a raising and lowering means.

The present invention is also the laser emission spectroscopic analyzer according to claim 4, characterized in that a moving mechanism for the condenser lens is provided in place of the moving means for the lance position. The laser emission spectrum analyzer according to claim 4 or 5, wherein the emission spectrum analyzer is provided with a temperature detector and an arithmetic means for correcting the velocity fluctuation of the ultrasonic wave based on the temperature measurement value. is there.

In this case, the ultrasonic transmitter / receiver and the temperature detector may be directly attached to the lance or may be separately provided at fixed positions. The present invention is used for online analysis of molten steel, molten metal such as hot dip galvanizing, molten slag and other molten materials, and is particularly preferably used for online analysis of molten materials in which the molten metal surface and / or the ambient temperature fluctuates. . In addition to the hot dip galvanizing and the like, the present invention can be suitably used for on-line analysis of molten steel in advanced secondary blowing such as RH vacuum degassing of molten steel.
This is because even if the molten steel temperature changes due to vacuum suction or the molten steel temperature decreases due to the lack of a heat source and the ambient temperature changes,
This is because the present invention can deal with those variations.

Further, the present invention can be preferably used for on-line analysis of hot metal in hot metal gutter of blast furnace and online analysis at blast furnace slag or converter slag processing site. The hot metal flowing through the hot metal gutter can be analyzed by the present invention in the same manner as described above even if the amount of hot metal changes with time and the level and temperature of the molten metal change That is why.

In particular, the reason why the present invention is suitably used for analysis of a melt is that in the case of a melt, even if a laser emission spectroscopic analysis, which is a kind of destructive inspection, is applied, it is possible to scratch a solid such as a steel plate. This is because the problem of turning on does not occur.

[0013]

According to the present invention, the surface of a melt sample such as a molten metal is irradiated with a laser beam through a laser irradiation lance, and the intensity of a spectral line obtained by dispersing the emission of the generated plasma is measured. In the laser emission spectroscopic analysis method for analyzing the elements contained in the melt sample, the melt sample surface is separately irradiated with ultrasonic waves, the reflected wave is detected to measure the melt sample surface height, and The distance between the laser irradiation lance tip or the condenser lens inside the lance and the melt sample surface is kept constant. Specifically, the distance L is automatically set to L ± 0.0.
The accuracy of analysis was remarkably improved as compared with the conventional method because the temperature was changed to 5 L or less and the change in the temperature of the atmosphere was detected to correct the fluctuation of the ultrasonic velocity due to the change in the temperature of the atmosphere. Further, in the present invention, in a laser emission spectroscopic analyzer comprising a laser oscillator, a laser irradiation lance having a condenser lens inside, a spectroscope, a photometer, and a computer, an ultrasonic wave for measuring the melt sample height is used. A generator / receiver, an arithmetic means for obtaining a correction amount of the lance position for laser irradiation based on the measured value, and an elevating means for automatically moving the lance up and down according to the arithmetic result are provided. Further, instead of the moving means for moving the lance position, a moving mechanism for moving the condensing lens position may be provided, or the laser emission spectroscopic analyzer may be provided with a temperature detector and a speed variation of ultrasonic waves based on the temperature measurement value. Since the correction means is provided, the above method can be smoothly performed by one operator, and the analysis time and labor can be reduced.

In this case, the reason why L is limited to within ± 0.05 L is that, within this range, the molten metal surface does not largely deviate from the position (commonly called beam waist) where the laser focused diameter is the minimum. Therefore, the fluctuation of the laser energy density is small. Further, the reason why the correction is necessary will be specifically shown below. The ambient temperature is from T ₀ = 1600 ° C. to T
_This is an example of the case where the temperature fluctuates to ₁ = 1530 ° C. and L = 1500 mm. The speed of sound at each temperature is C ₀ = 8
67.76 m / sec, C ₁ = 851.40 m / sec
Therefore, the round trip time of the ultrasonic wave is t ₀ = 3.4.
57 msec, t ₁ = 3.524 msec.

Therefore, when calculation is performed using the sound velocity at T ₀ = 1600 ° C., at T ₁ = 1530 ° C., L is apparently observed as L ₁ = 1529 mm, and 29
A correction for mm is necessary. Therefore, according to the present invention, when the ambient temperature changes, the true distance L is obtained by the following equation according to the flow of FIG. 4, and the lance position or the position of the condenser lens in the lance is automatically adjusted. .

L _T = (a√T / 2t) × 1000 mm where L _T : true distance at temperature T (K), t: round-trip time (sec) of ultrasonic wave at temperature T, a: below constant In the examples, the contents of the present invention will be described in detail with reference to FIGS.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an overall configuration diagram showing an example of an apparatus used for carrying out a laser emission spectral analysis method according to the present invention. In FIG. 1, 1 is a lance, 2 is a molten metal sample,
Reference numeral 3 is an ultrasonic wave generator / receiver, 4 is an ultrasonic wave measuring device, 5 is a temperature detector, 6 is an arithmetic means, and 7 is an elevating means.

While confirming the position of the lance 1 by using the ultrasonic wave generator / receiver 3, the elevating means 7 is used to install the lance 1 at a predetermined position. Therefore, when the laser light LB is output from the laser light oscillator 11, the laser light LB is condensed by the condensing lens 8 and is applied to the molten metal sample 2 to be analyzed. At this time, plasma P is generated on the surface of the molten metal sample 2, and the continuous spectrum SP emitted by the plasma P is divided into the characteristic spectral lines of each element through the spectroscope 9 and analyzed.

However, when the surface height of the molten metal sample 2 fluctuates during the analysis, a change in the round-trip time of the ultrasonic wave is detected by the ultrasonic wave generator / receiver 3, and the ultrasonic wave measuring device 4 and calculation means are used. Feedback to the elevating means 7 via 6 and the lance 1
Is automatically installed at the optimum position. Similarly, when the temperature of the atmosphere fluctuates during the analysis, it is detected by the temperature detector 5,
The correction is performed by the calculation means 6, and the lance position is controlled by the information. Thereby, the distance between the lance 1 and the surface of the molten metal sample 2 can be maintained at a predetermined distance. The lance 1 may be a so-called immersion lance type, which is soaked in the molten metal sample 2.
Further, the calculating means 6 also has a function of adjusting the position of the condenser lens with respect to a change in the distance between the condenser lens and the surface of the molten metal sample and a correction calculation with respect to a temperature change. Further, the position adjustment by the raising / lowering method of the lance can be optionally switched to the position adjusting method of the condenser lens in the lance in the present invention.

FIG. 2 shows the relationship between the time and the intensity ratio (Al / Zn) of the emission spectrum line when the Al concentration in the hot dip galvanizing bath was continuously analyzed. As is apparent from FIG. 2, when the lance position is automatically controlled within 1 ± 0.05 L by the method according to the present invention, the analysis value is constant, while the lance position is visually aligned according to the conventional method. It can be seen that the fluctuation of the analysis value is large in the case of. The intensity ratio of the emission spectrum line obtained in FIG. 2 is converted into Al concentration using the calibration curve shown in FIG. 3 prepared using a standard sample in advance. If the intensity ratio and the calibration curve are similarly created for the other elements, the change with time of the concentration of each element can be continuously obtained. According to the present invention, the analysis work conventionally performed by three people is
It was reduced to a name.

[0021]

As described above, according to the present invention,
An ultrasonic wave is generated by irradiating an ultrasonic wave on the surface of a molten material sample such as molten metal using an ultrasonic wave generator / receiver, detecting the reflected wave, and further detecting the temperature change in the atmosphere Since the fluctuation of the velocity is corrected, the distance L between the laser irradiation tip or the condenser lens and the melt sample surface can be automatically kept constant within L ± 0.05 L (5%). We were able to improve the analysis accuracy. As a result, it was possible to analyze the melt sample without interrupting the analysis work as before, and the efficiency of the analysis work was improved.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an example of an apparatus for carrying out a laser emission spectral analysis method according to the present invention.

FIG. 2 is an analysis example in which aluminum in a hot dip galvanizing bath is continuously analyzed by a laser emission spectral analysis method according to the present invention and a conventional method.

FIG. 3 is a diagram showing an example of a calibration curve of a standard sample.

FIG. 4 is a flow defining a procedure for temperature correction.

[Explanation of symbols]

 1 Lance 2 Melt Sample 3 Ultrasonic Wave Generator / Receiver 4 Ultrasonic Measuring Device 5 Temperature Detector 6 Computing Means 7 Elevating / Means 8 Condensing Lens 9 Spectrometer 10 Photometric Device 11 Laser Oscillator LB Laser Light P Plasma SP Spectrum

Claims (6)

[Claims] 1. A melt sample surface is irradiated with a laser beam through a laser irradiation lance, and the intensity of a spectrum line obtained by dispersing the emitted light of the generated plasma is measured to be included in the melt sample. In the laser emission spectroscopic analysis method for analyzing the element to be generated, the melt sample surface is separately irradiated with ultrasonic waves, the reflected wave is detected to measure the melt sample surface height, and the laser irradiation lance tip and A laser emission spectral analysis method, characterized in that the distance between the melt sample surfaces is kept constant. 2. The laser emission spectral analysis method according to claim 1, wherein the distance L between the laser irradiation lance tip and the melt sample surface is automatically kept constant within L ± 0.05 L. 3. The laser emission spectroscopic analysis method according to claim 2, wherein fluctuations in ultrasonic velocity due to changes in ambient temperature above the surface of the melt sample are corrected. 4. A laser emission spectroscopic analyzer comprising a laser oscillator, a laser irradiation lance equipped with a condenser lens inside, a spectroscope, a photometer, and a computer. It is characterized in that a receiver, an arithmetic means for obtaining a correction amount of the laser irradiation lance position based on the measured value, and an elevating means for automatically moving the lance up and down according to the arithmetic result are provided. Laser emission spectroscopy analyzer. 5. The laser emission spectroscopic analyzer according to claim 4, further comprising a moving mechanism for moving the condenser lens, in place of the moving means for moving the lance position. 6. The laser emission spectroscopic analyzer is provided with a temperature detector and an arithmetic means for correcting the velocity fluctuation of the ultrasonic wave based on the temperature measurement value.
Alternatively, the laser emission spectral analyzer according to item 5.