JP2002328091A - Probe for laser emission spectrometry device for hot sample, and method for laser emission spectrometry for hot sample - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a probe for a laser emission spectrometry device for a hot sample, together with its spectrometry method, capable of protecting an optical system from a radiation heat of a sample and capable of high precision spectrometry. SOLUTION: The probe for the laser emission spectrometry device for a hot sample measures an emission spectrum from an irradiated part when the hot sample is irradiated with pulse laser beam. There are provided a probe main body of such shape as covers the part of the sample which is measured, a means for condensing the emission spectrum from the sample into a window fitted to the probe main body for taking out the emission spectrum caused by the laser beam, and a gas exhaust opening which, provided to a bottom surface of the probe main body, protects the probe main body from heat and gas-seals an analyzing part. Related to an analyzing method for the hot sample, the hot sample is irradiated with pulse laser beam while an irradiation position is moved, for continuously measuring the emission spectrum, to measure the change in concentration of target elements of at least one kind.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser emission analyzer, and more particularly to a probe for a laser emission analyzer of a high-temperature sample and a method of analyzing laser emission of a high-temperature sample.

[0002]

2. Description of the Related Art Conventionally, composition analysis of materials such as metals generally involves measurement of a sample at room temperature, including analysis of process control. However, although sufficient cooling time is sufficient, it is often more convenient to analyze a sample in a hot-rolled state for process control of a high-temperature process such as an iron making site.

[0003] For example, in management analysis of cast slabs in steel works, speeding up analysis is a problem. In recent years, in each steelworks, casting of smelted molten steel is generally performed by a continuous casting method. In this case, in addition to continuous casting of one charge of molten steel, there are many cases where charges of steel types having different components are continuously and continuously cast (separate steel types are continuously cast). When continuously casting steels of different compositions, the molten steel of the next charge is injected into the tundish (TD) before the casting of the previous charge is completed, and the molten steel of the previous charge and the remaining A portion where molten steel is mixed, that is, a so-called hot water mixing portion occurs.

[0004] The composition of the slab cast in the hot water mixing portion gradually changes, and a slab that falls outside the steel type component range of both front and rear charges is produced. Therefore, several slabs cast at a timing that seems to include the hot water mixing portion must be withdrawn from the production line and analyzed to determine whether or not they are within the specification range. In the conventional analysis method, since a specimen is collected for analysis and further adjusted, it cannot be analyzed in a production line.

[0005] Therefore, these slabs cannot be directly conveyed to the next step including so-called direct rolling. As a result of analysis, some were discarded as nonstandard waste material,
Alternatively, it is a steel material having a component specification of another standard, but this slab is reserved during the grading and distribution judgment after the analysis value is obtained, and if it is long, a retention period of 3 to 4 days is required. Needless to say, this time is wasted in the manufacturing process. In addition, logistics costs such as labor for securing a storage place and transportation are increased, and thus the productivity of steel products is reduced, which is one of the causes of an increase in manufacturing costs.

Therefore, there is a demand for a technique capable of performing analysis on a slab production line without changing the production process. In this case, what is required for the analysis is that there is no need for sampling, and that a sample at a high temperature of 400 to 700 ° C. can be analyzed. From this viewpoint, for example, there is a method of directly analyzing a joint of a slab by a laser induced plasma (laser ICP) method disclosed in Japanese Patent Application Laid-Open No. 9-68499. This method is to irradiate the laser on both the top and bottom cut surface of the slab cast and cut by the continuous casting method,
The particles (steam) of each component element generated at this time are guided by an induction plasma (IC
It is introduced into P) for luminescence analysis. This method
It is quick enough to complete one analysis in about 30 seconds, and can be used to analyze red-hot samples.

[0007] However, it is difficult to maintain the ICP torch at the casting site, which is a poor environment, and an expensive ICP apparatus is required. Further, the apparatus becomes large. Therefore, it is essential to completely shield the analysis point of the sample from the external atmosphere, and a smooth sample surface is required so that the sample surface and the particle transfer tube can be in close contact with each other. This has the disadvantage that the reliability of the analysis values due to the so-called memory effect is insufficient.

On the other hand, there is a laser emission analysis method as a method capable of solving the above-mentioned disadvantages. The high-temperature specimen is directly irradiated with a pulsed laser, and the light emitted in the generated plasma is transported to a spectroscope for spectral analysis. In order to perform this, a movable analysis probe for taking in the light emitted by contacting the high-temperature specimen is required. The inventors have
A probe for laser emission analysis that does not require sampling is disclosed in Japanese Patent Application No. 2000-138291. However, this probe is intended for use on a cold sample such as determining the cause of a scratch on a steel plate, and cannot be used when measuring a high-temperature sample. The reason is that, when the probe is brought close to the high-temperature sample, the radiation heat causes breakage of the lens and mirror inside the probe and deviation of the optical axis.

Further, around the high-temperature sample, water vapor and contaminants existing in the atmosphere are heated by the high-temperature sample to become a gas, and the detection intensity and accuracy of emitted light are reduced. Further, generation of gas mainly affecting the analysis value of light elements such as carbon and sulfur also occurs. In the composition analysis of a high-temperature sample, the analysis accuracy is required more than the determination of the cause of the flaw. Therefore, it is necessary to eliminate such components that hinder the analysis from the analysis surface or to control the components to a certain amount or less. However, in the above-mentioned probe, the emission of the atmospheric gas is only from a part of the laser irradiation part, which is enough to keep the plasma by the laser constant, but when analyzing a sample having an unevenness of 2 to 10 mm on the surface, In some cases, these contaminant gases may be caught in the probe and cannot be completely eliminated or controlled.

[0010]

SUMMARY OF THE INVENTION The present invention relates to an apparatus for irradiating a high-temperature sample with a pulse laser beam and quantifying the chemical composition of the sample from an emission spectrum emitted from the high-temperature sample. An object of the present invention is to provide a probe for a laser emission analyzer for a high-temperature sample and a method for analyzing laser emission of a high-temperature sample, which enable protection of an optical system and high-precision analysis.

[0011]

SUMMARY OF THE INVENTION The present invention discloses a specific probe structure which can solve the above-mentioned problems, and the gist thereof is as follows. (1) A probe for a high-temperature sample laser emission analyzer for irradiating a high-temperature sample (7) with a pulse laser beam (3) and measuring an emission spectrum (13) from an irradiation unit (14), 7) A probe body (1) having a shape covering the part to be measured (15), a window (16) attached to the probe body, and a window for extracting the emission spectrum by the pulsed laser light. A means (8) for condensing an emission spectrum from a high-temperature sample, and a gas outlet (6) provided on the bottom surface of the probe main body for protecting the probe main body from heat and gas-sealing the analysis section (10). ), A probe for a high-temperature sample laser emission analyzer. (2) The high temperature sample is irradiated with a pulsed laser beam while moving the irradiation position, and the emission spectrum is continuously measured, thereby continuously measuring the concentration change of one or more elements. Laser emission analysis method for a high-temperature sample. (3) The laser emission analysis method for a high-temperature sample according to (2), wherein the high-temperature sample is a cast piece. (4) The laser emission analysis method for a high-temperature sample according to (2) or (3), wherein the probe according to (1) is used.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG. First, the analysis probe 1 is brought into contact with the high-temperature sample 7. The high-temperature sample is irradiated with the pulsed laser light 3 emitted from the pulsed laser oscillator 2, and the emitted light emission spectrum 13 is introduced into the spectroscope 4 via the optical fiber 5 for analysis.

The pulsed laser beam used for the emission analysis may be one capable of evaporating and scattering a metal component or a non-metal component on the surface of a high-temperature sample and emitting the same. For this reason, the spire output of the pulse laser is 1MW or more,
Desirably, it is 120 MW or less. If the output of the spire is lower than 1 MW, it is difficult to obtain sufficient emission intensity of the analysis element. Considering rapid chemical composition analysis, 20MW
It is desirable that this is the case. If a pulse laser having a strong spire output of 120 MW or more is used, the atmosphere before reaching the sample surface is broken down, and the components of the sample cannot be emitted. It is advantageous to increase the number of laser pulses as much as possible in order to shorten the analysis time.

As described above, when analyzing a high-temperature sample, the probe for an analyzer receives heat from radiation from the high-temperature sample and thermally deteriorates the probe. Further, the analysis atmosphere is deteriorated by the gas generated by the reaction of the atmospheric gas or water on the surface of the high-temperature sample, and the concave mirror 8 for condensing the emitted light provided inside the probe main body for condensing the emitted light. The optical system such as the lens 9 for condensing the emitted light is contaminated. Contamination of the optical system causes damage and also causes variation in the analysis value of the high-temperature sample.

In order to solve these problems, an inert gas such as argon is blown onto the sample surface between the probe and the sample so as to prevent air or pollutant gas from being trapped in the probe, and the analysis atmosphere is maintained at a constant level. Cool the sample surface. To achieve this, about four cooling atmosphere control gas outlets 6 are provided on the bottom surface of the probe main body. At this time, the flow rate of the analysis atmosphere and the inert gas for cooling is desirably maintained at 200 to 1000 ml / min for each outlet. Furthermore, at the same time as securing the escape port for the inert gas, the distance between the sample and the probe main body is always kept constant, and the positional relationship between the probe main body and the laser irradiation site of the sample is fixed at three or four points. A support foot 12 is provided.
In order to reduce the variation in the analysis, it is necessary to always collect the emission spectrum from the sample by the pulsed laser irradiation with the same optical path length. In this case, it is preferable that the thickness be 1 to 5 mm, which can eliminate the backlash and efficiently collect the emitted light.

Further, when the composition analysis is required during the cooling step, particularly when the high-temperature sample is a slab, the target high-temperature slab may be cooled while moving sequentially.
In this case, the analysis may be performed while moving the analysis probe at a relative speed of about 20 cm / sec or less with the slab.

[0017]

Next, the present invention will be described with reference to FIG. The present embodiment was carried out in a process called a rotary cooling floor 17 in which a slab 7 (a prismatic bloom) cast by successive castings of different steel types moves while rotating so as to be uniformly cooled. The rotation of the slab 7 is usually performed at 90 ° intervals in about 30 seconds, and the total cooling process time is about 20 minutes.

The cross section of the slab 7 conveyed to the cooling floor 17 is in a state of being cut out by a cutter or the like, usually has irregularities of about several mm, and the surface is covered with an oxide layer of about 1000 μm. ing. The chemical composition in this oxide layer is different from the bulk composition of the target slab and needs to be removed, but before the analysis operation, pre-irradiation with the pulse laser used for analysis until the bulk surface comes out Can be removed. The pulse laser having the above-mentioned peak output can be sufficiently removed by irradiation of 100 to 200 pulses.

After exposing the bulk surface of the slab, it is irradiated with the above-mentioned laser, and the chemical composition of the slab is quantitatively evaluated by integrating the emission spectrum intensity at this time. The relationship between the emission spectrum intensity and the composition of the slab may be determined in advance using a steel standard sample or the like. In this way, the composition of the slab is changed to 3
The analysis can be performed in a short time within 0 seconds. If further analysis reliability is required, this may be repeated a plurality of times for the same slab sample. The analysis result is recorded on a spectrometer-controlled personal computer or the like immediately after the analysis operation is completed. After the analysis is completed, the analysis probe is retracted, and when the next slab comes to a standstill, the slab is again moved to the slab and brought into contact with the slab to perform the analysis.

The method of the present invention was used to analyze the mixture of hot water and the good material of a slab in which two types of molten steel having different components were continuously cast. Table 1 shows the analysis results of typical components together with the results of conventional sampling analysis. The analysis results showed good agreement between the two, and the analysis results obtained in 3 to 4 days were obtained within 30 seconds according to the present method. In addition, from the results of multiple experiments of the same cross section by the present method, the relative standard deviation (variation) is within approximately 15%.
Sufficient reliability of this determination method was confirmed. As a result, it was shown that the slab grading according to the present method was sufficiently possible.

[0021]

[Table 1]

[0022]

According to the present invention, the chemical composition of a high-temperature sample at 300 to 700 ° C. or higher can be determined with high accuracy without complicated adjustment by laser emission analysis. Is extremely valuable.

[Brief description of the drawings]

1A and 1B are a cross-sectional view and a bottom view of an example of a probe according to the present invention, wherein FIG. 1A is a side view, and FIG.
It is X sectional drawing.

FIG. 2 is a schematic diagram showing an example of an embodiment of an analysis method belonging to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Probe main body 2 ... Pulse laser oscillator 3 ... Pulse laser beam 4 ... Spectroscope 5 ... Optical fiber 6 ... Cooling and atmosphere control gas outlet 7 ... High temperature sample, cast piece 8 ... Concave mirror for condensing emitted light 9 ... Emission light focusing lens 10 ... Analyzing unit (laser plasma) 11 ... Analyzing atmosphere and inert gas for cooling 12 ... Support foot for fixing probe 13 ... Emission spectrum 14 ... Irradiation part of pulsed laser light 15 ... Measurement of high temperature sample Part 16: Probe body window 17: Rotating cooling floor

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Eisai Anzai 12 Nakamachi, Muroran, Hokkaido Inside Nippon Steel Corporation Muroran Steel Corporation (72) Inventor Koichi Watanabe 12 Nakamachi, Muroran, Hokkaido Nippon Steel Corporation F-term in Muroran Works (reference) 2G020 BA02 BA05 BA15 CA01 CB23 CD14 2G043 AA01 BA01 BA03 BA07 CA05 EA10 FA05 GA04 GB01 HA01 HA03 HA05 JA01 KA08 KA09 LA01 MA03

Claims (4)

[Claims] 1. A pulse laser beam (3) applied to a high temperature sample (7).
And the emission spectrum (1)
3) A probe for a high-temperature sample laser emission analyzer for measuring 3), comprising: a probe body (1) having a shape covering a measured portion (15) of a high-temperature sample (7); and a window ( 16) means for condensing the emission spectrum from the high-temperature sample toward the window for extracting the emission spectrum by the pulsed laser light; and (8) protecting the probe body from heat and analyzing the probe body. A gas emission port (6) provided on the bottom surface of the probe main body for gas-sealing (10). 2. A method for continuously measuring a change in concentration of one or more elements by irradiating a high-temperature sample with a pulse laser beam while moving an irradiation position and continuously measuring an emission spectrum. A method for laser emission analysis of a high-temperature sample, characterized in that: 3. The method according to claim 2, wherein the high-temperature sample is a cast piece. 4. The laser emission analysis method for a high-temperature sample according to claim 2, wherein the probe according to claim 1 is used.