JP2008292169A - Apparatus and method for monitoring refining - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To continuously monitor refining at analyses of molten metals in a refining container by solving the problem of analysis interruptions due to interferences by slag and their solidification to a tuyere for analysis. <P>SOLUTION: The tuyere 1 for analysis is passed through a refractor 14 at the side wall of the refining container, has one end open to the outside of the refining container and the other end open to the inside of the refining container, and is provided in such a way that an inside opening part of the refining container may be at a location lower than the surface 5 of molten metals and that an outside opening part of the refining container may be at a location higher than the surface 5 of molten metals at refining. A laser beam is irradiated to the surface M of molten meals to be analyzed at the same level as the surface 5 of molten metals in the refining container formed in the tuyere for analysis to observe light emission. It is possible to easily secure the surface M of molten metals to be analyzed not covered with slag in the tuyere 1 for analysis, prevent the adhesion of metals to the tuyere, and stably, continuously perform laser emission analysis. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention is for measuring chemical components in molten metal in real time in a metal refining process. In particular, it is applicable to monitoring of secondary refining such as converter (primary refining) and RH in steel refining.

Hereinafter, iron refining will be described as an example. In refining steelmaking, it is necessary to continuously measure the components. In the converter, O ₂ is blown up from the lance and then blown from the bottom of the furnace to decarburize and at the same time de-P and S are being promoted. To decarburize, it is effective to continue blowing O ₂ , but when the carbon concentration falls below 0.3% from 4% of pig iron, the blown O ₂ is used for oxidation of iron. As a result, iron loss (production of FeO) increases. At the end of blowing, it is necessary to reach the target C concentration and temperature, but in the situation where FeO is generated, the C concentration cannot be achieved. Further, the increased FeO reacts with the refractory, causing the refractory to melt and increase the cost. It is necessary to continuously measure the components during blowing in response to the problem of inadequate of the above components and refractory melting. On the other hand, as a method of measuring components in a spot manner, there is a sublance method, a sample is taken from molten steel immediately before the end of blowing, and the C concentration is determined by emission analysis, but the amount of information is extremely small, It is difficult to achieve the target C concentration and temperature with high accuracy, and it is extremely difficult to control the iron loss (FeO) to be small. In view of the current situation as described above, a technique for continuously measuring components is required.

  Next, regarding the secondary refining technology, for example, the case of mass production degassing equipment (RH) will be described. RH's main goal is decarburization. It is important to understand the behavior of the C component in the degassing process, especially by ending the process when the target C concentration is reached, avoiding wasteful use of steam when evacuating, Cost reduction is possible. For this purpose, continuous component measurement is required, and the following two methods have been generally adopted.

  One is to measure the CO concentration in the exhaust gas during processing, and subtract the amount of carbon discharged from the C concentration at the start of processing to estimate the carbon during processing, but the accuracy is not necessarily high. The other method is to collect a sample of molten steel close to the ladle surface and quickly analyze it with an emission analyzer. Component analysis such as C and other Mn is possible, but samples are collected in batches. In addition, since the processing is performed by an analysis device at a location away from the degassing apparatus, it is a drawback that it is impossible to quickly follow the component change in the degassing process.

  As described above, in the converter and degassing apparatus that support mass production of steelmaking, it is impossible to grasp the component change every moment during the process, which is a problem to be solved.

  As countermeasures for these problems, development of a method for irradiating molten steel with laser and utilizing excitation light emission according to the component contained in the molten steel for analysis of the component has been advanced. In this method, there are two methods for irradiating the molten steel with laser. Method (I) is a method of irradiating a laser from above the molten steel, and the other method (II) pierces the refractory holding the molten steel and irradiates the molten steel from the tuyere. Is the method.

The method (I) is disclosed in, for example, Patent Documents 1 to 3, and the method (II) is disclosed in Patent Document 4.
JP 2002-174631 A JP-A-8-219993 Japanese Laid-Open Patent Publication No.7-190933 Japanese Unexamined Patent Publication No. 60-231141

  In the above method (I), there is slag on the molten steel, and it is necessary to remove the slag and directly irradiate the molten steel with laser. However, in general, the thickness of the slag is about 100mm in the ladle, and there is a thickness of about 1m in the converter, even though it contains gas. It was difficult.

Method (II) has no problem with the above method (1) because there is no slag in the molten steel, but there are tuyere installed in the molten steel, so that a large amount of molten steel is not inserted and hardened. It is necessary to apply a pressure higher than the static pressure of the molten steel by flowing gas through the tuyere. As the gas to be blown, an inert gas such as Ar or N ₂ is usually selected, but the tip of the tuyere is cooled by the sensible heat of the gas, and the metal is likely to grow and adhere. Because this metal was attached, when the molten steel side was viewed from the entrance side of the tuyere, the molten steel surface corresponding to the cross-sectional area of the tuyere could not be seen. Even if it irradiates, sufficient irradiation area cannot be obtained. As a result, there is a problem that the components contained in the molten steel cannot be accurately determined because sufficient excitation light emission cannot be obtained.

  The present invention solves the practical problems inherent in each of the above methods (I) and (II), eliminates slag, and does not cause metal adhesion, so that the analysis hot water has a sufficient area. An object of the present invention is to provide an apparatus and method for refining monitoring by laser emission analysis that stably secures a surface and is stable and accurate.

The gist of the present invention for solving the above problems is as follows.
(1) It penetrates the refractory on the side wall of the smelting vessel, one end opens to the outside of the smelting vessel, and the other end opens to the inside of the smelting vessel. A refining vessel provided with an analysis tuyere at a position lower than the molten metal surface and having an opening on the outside of the refining vessel located at a position higher than the molten metal surface; An ablation laser oscillator for vaporizing and atomizing a part of the molten metal by irradiating a molten metal surface of the molten metal formed inside the mouth, and a selective excitation laser oscillator for resonantly exciting the element to be analyzed, A refining monitoring device comprising at least an optical fiber for transmitting light emission generated on the molten metal surface, a spectroscopic analyzer, and a light amount detector for measuring laser-induced fluorescence.
(2) The refining monitoring apparatus according to (1), wherein an observation nozzle including a gas inlet, a gas outlet, and an electromagnetic valve is inserted into the analysis tuyere.
(3) The refining monitoring apparatus according to (2), wherein at least the innermost side of the observation nozzle is a stainless steel pipe.
(4) The refining monitoring device according to any one of (1) to (3), wherein the analysis tuyere has a taper in which the inner diameter on the inner side of the refining vessel is larger than the inner diameter on the outer side of the refining vessel.
(5) The refining monitoring apparatus according to any one of (1) to (4), wherein the refining vessel is a converter, and the molten metal is one or both of hot metal and molten steel.
(6) The refining monitoring apparatus according to any one of (1) to (4), wherein the refining vessel is a secondary refining degassing vacuum tank, and the molten metal is molten steel.
(7) The refractory on the side wall of the smelting vessel penetrates, one end of which opens to the outside of the smelting vessel, and the other end opens to the inside of the smelting vessel. On the surface of the molten metal formed inside the tuyere for analysis provided so that the opening on the outside of the refining vessel is at a position higher than the surface of the molten metal. A refining monitoring method comprising measuring a chemical component concentration in a molten metal by spectroscopically analyzing light emission generated by irradiating an ablation laser for vaporizing and atomizing a part.
(8) The refractory on the side wall of the smelting vessel passes through, one end of which opens to the outside of the smelting vessel, and the other end opens to the inside of the smelting vessel. The ablation laser is applied to the molten metal surface formed inside the tuyere for analysis provided so that the opening on the outside of the refining vessel is at a position higher than the molten metal surface. After irradiating and evaporating and atomizing a part of the molten metal, the amount of emitted light emitted by irradiating a selective excitation laser having a wavelength that matches one of the resonance wavelengths of the element to be analyzed is converted into an electric signal by a light amount detector. A refining monitoring method characterized in that the chemical component concentration in the molten metal is measured by converting the electric signal intensity into electric power and measuring the electric signal intensity by electric transmission.

  According to the present invention, an analysis hot water surface not covered with slag can be easily secured, and no metal deposit on the tuyere is generated, so that stable and continuous laser emission analysis can be performed. Thereby, shortening of refining time can be achieved and it can contribute to reducing variable costs, such as gas, water vapor, and refractory.

Hereinafter, the present invention will be described in more detail.
First, issues related to slag elimination will be described. In order to eliminate slag, it is effective to install a weir in the molten steel. Incorporating this concept, the shape of the analysis tuyere 1 is as shown in Fig. 1, and the location of the tuyere D (in the refining vessel located above the opening of the analysis tuyere 1 inside the refining vessel) The side surface) serves as a weir, and a hot water surface M without slag can be formed in the analysis tuyere 1. The position of the molten metal surface M is the position of the primary meniscus which is the same as the molten metal surface level 5 of the molten steel (molten metal 6).

  Next, as a measure against the solidification / clogging of the tuyere, in order not to blow a large amount of gas, the molten steel 6 is not subjected to static pressure, that is, the molten steel head pressure at the analysis position is set to zero. is required. As shown in FIG. 1, the state is that the meniscus position in the tuyere 1 is the same position as the hot water surface 5 inside the refining vessel body.

  As described above, the tuyere structure as shown in FIG. 1 can solve both the problems of slag removal and tuyere blockage. That is, as shown in FIG. 1, the refining vessel of the present invention is provided with an analysis tuyere 1 that obliquely penetrates the refractory 14 on the side wall, and an opening inside the refining vessel of this analyzing tuyere 1 Is provided at a position lower than the molten metal surface 5 of the molten metal 6 during refining. By doing in this way, when the molten metal 6 to be smelted is poured into the smelting vessel, the analysis hot water surface M not covered with the slag is formed in the middle of the analysis tuyere 1.

  There are two problems in operation from the fact that the surface position of the molten metal 6 changes. First, the amount of molten metal varies with each charge, and the tuyere length is determined so that the amount of change of the molten metal 6, that is, the change of the meniscus can be accommodated.

  Next, since the refractory in the smelting vessel melts down, the hot metal surface position and the meniscus may change to the lowering side even with the same amount of molten metal. In order to cope with this, the setting position of the tuyere brick is changed according to the increase in the number of times the refining vessel is used. That is, when the method of exchanging the tuyere is effective, the number of times the smelting vessel is used is low, and the refractory melts little, the tuyere is set at position H (high position), and the smelting vessel Can be dealt with by setting a tuyere at position L (low position).

  In order to prevent the metal from solidifying at the meniscus portion inside the tuyere, it is desirable that the molten metal side of the tuyere 1 (the inner side of the refining vessel) is tapered so that it is slightly wider. As a result, the hot molten metal 6 always enters the tuyere 1. For this purpose, it is not necessary that the tuyere 1 has a taper over the entire length of the tuyere 1, and it is only necessary that the portion of the tuyere 1 where a meniscus can be formed has a taper. Of the total length of the tuyere, the length of the tapered portion is L (mm), and the difference between the maximum tuyere inner diameter and the minimum tuyere inner diameter is Δd (mm), Δd / L is 1/50 or more 3 / 50 or less is desirable. Here, Δd is suitably from 10 mm to 30 mm.

  In the analysis tuyere 1 of the present invention, the molten metal 6 does not leak out of the refining vessel due to gravity, so that the flow rate is large enough to counter the static pressure of the molten metal 6 as in the case of bottom blowing tuyere. There is no need to blow gas into the tuyere 1. However, when carbon or the like is included in the analysis target element, it is necessary to replace the inside of the tuyere with an inert gas such as Ar in order to prevent contamination from air. An observation nozzle 7 is inserted into the analysis tuyere 1, and the gas introduced from the gas blowing port 12 by opening the electromagnetic valve 10 is introduced from the molten metal side opening of the observation nozzle 7 into the tuyere. It blows out toward the analysis hot water surface M inside, fills the inside of the tuyere 7, and then escapes from the exhaust port 13 to the outside of the refining vessel. The opening on the molten metal side of the observation nozzle 7 is positioned at an appropriate distance above the analysis molten metal surface M, for example, a distance of 100 to 300 mm in consideration of fluctuations in the amount of molten metal injected and fluctuations in the molten metal surface during refining. It is desirable.

  During charging and discharging of the molten metal 6, inert gas is blown into the tuyere so that no slag or molten metal 6 is inserted. At this time, the exhaust-side electromagnetic valve 11 is closed, the gas introduction-side electromagnetic valve 10 is opened, and a gas such as Ar is blown in at a required flow rate.

  The circumferential arrangement in the wall of the smelting vessel is determined in consideration of the replacement of the tuyere 1 in addition to considering the position of the molten metal surface 5 in the hot metal charging and the outgoing steel of the molten metal 6. There is a need. Now consider the case of a converter as a refining vessel with reference to FIG. First, the trunnion positions 100 and 101 have a converter tilting device, so it is very difficult to replace the tuyere and cannot be used in the actual machine. Therefore, it is considered which of the steel output side 102 and the charging side 103 is advantageous. If tuyeres 1 are set on the outgoing steel side 102, the tuyere 1 may be in direct contact with high-temperature molten steel during the outgoing steel and is difficult to employ. On the other hand, on the charging side 103, the tuyere 1 comes into contact with the low temperature hot metal, but when the converter is tilted about 45 ° from the vertical direction and the hot metal is charged, the hot metal does not enter the tuyere. It is effective to adopt the tuyere position at an intermediate position between the trunnion position and the charging side position, more specifically, a position 35 to 45 ° from the trunnion in the horizontal plane including the trunnion. It has been found.

  Further, the position of the tuyere 1 provided in the RH vacuum tank is preferably provided on the downcomer pipe side where the riser side is more stable because the splash blows up and the molten metal surface fluctuation is large.

Next, a method for observing light emission by irradiating the analysis hot water surface M with a laser will be described.
The laser oscillated from the ablation laser oscillator 28 is reflected by the mirror 22, passes through the optical window 9, passes through the observation nozzle 7, and is irradiated onto the analysis hot water surface M. Here, the laser is condensed by the lens 23 so as to be focused on the analysis surface M. Laser-induced plasma 8 is generated on the analysis surface M by the energy of the laser, and the emission of atoms emitted from the plasma 8 travels in the direction opposite to the laser in the observation nozzle 7 and passes through the optical window 9. Reflected by the mirror 20, condensed on the light receiving end 25 of the optical fiber 26 by the lens 24, guided to the spectroscopic analysis device 27 by the optical fiber 26, and measured by the spectroscopic analysis device 27. From the spectrum intensity, the concentration of this element is determined using a calibration curve determined in advance.

  After a delay time of 10 to 150 μs from the ablation laser pulse, the selective excitation laser 29 oscillates from the selective excitation laser 29 and is reflected by the mirror 21, then passes through the optical window 9 and passes through the observation nozzle 7 for analysis. The hot water surface M is irradiated. The selective excitation laser is irradiated while being tuned to a wavelength that resonates with the analysis target element. The laser-induced fluorescence travels in the observation nozzle 7 in the opposite direction to the laser, passes through the optical window 9, is reflected by the mirror 19, and is converted into an electrical signal having a strength proportional to the amount of light by the light amount detector 30. The electric signal is transmitted to the measuring device 32 through the electric wire 31, and is measured and recorded. From the electric signal intensity measured in this way, the concentration of this element is determined using a calibration curve determined in advance.

  Since the analysis tuyere 1 obliquely penetrates the furnace wall having a thickness of about 1 m, the analysis tuyere 1 has a length of 2 m, and the observation nozzle 7 inside thereof has a length of 1 to 1.5 m. For this reason, the solid angle for directly observing the light emission on the analysis hot water surface M is small. Therefore, the present inventors have found that the use of a stainless steel tube as the observation nozzle through which light emission passes improves the light emission observation efficiency. This is considered to be because light emitted at a solid angle larger than the solid angle observed directly is detected because the light passes through while being reflected by the inner wall of the stainless steel tube. A stainless steel tube is most suitable as an inexpensive material that has such reflection characteristics and can be used stably at high temperatures. It is more preferable if the inner surface of the stainless steel tube is subjected to electrolytic polishing or the like and the roughness is small.

The ablation laser is a pulsed laser that is focused and irradiated so that the energy density and the peak power density on the surface of the analytical solution are approximately 5 J / cm ² or more and 0.3 GW / cm ² or more, respectively. There must be. The most commonly used laser for this purpose is a Q-switched pulse Nd: YAG laser, with a pulse time half width of 5 to 15 ns, a pulse energy of 100 to 1000 mJ, and a pulse repetition of 10 to 50 Hz being generally marketed. Yes.

  As the selective excitation laser, a titanium sapphire laser, a dye laser, an optical parameter oscillator (OPO), or the like can be used.

  As the optical fiber 26 for transmitting the laser emission, an optical fiber having a fused silica core is suitable.

  The ablation laser oscillator 28 and the selective excitation laser oscillator 29 can be installed at a position independently from the refining vessel and can be transmitted to the entrance of the analysis tuyere 1 by spatial propagation or optical fiber propagation. Alternatively, the laser oscillators 28 and 29 may be installed integrally with the analysis tuyere 1.

  The spectroscopic analyzer 27 may be fixed at a place where it can be connected by an optical fiber length of 5 to 20 m.

(Example 1)
The analysis tuyere 1 shown in FIG. 1 was attached to the charging side of the 150-ton converter 40. The overview is shown in FIG. The analytical tuyere 1 shown in FIG. 3 has a taper over a length of 500 mm on the molten metal side, the inner diameter on the molten metal side is 40 mm, the inner diameter on the molten metal side is 500 mm, and the inner diameter on the iron skin side is 30 mm. did. The opening on the molten metal side was about 1800 mm from the bottom of the furnace so that the analytical hot water surface M was generated inside the tuyere during refining. When the furnace was upright (during refining), the angle between the vertical direction and the center line of tuyere 1 was about 30 °. As shown in FIG. 2, the mounting position of the tuyere 1 in the horizontal direction when the furnace was upright was mounted at a position of about 40 ° from the trunnion.

  Inside the tuyere, a stainless steel tube with an inner diameter of 7.5 mm was installed, and an observation nozzle 7 surrounded by a mullite tube was inserted around the tube.

  At the time of hot metal charging, the electromagnetic valve 11 was closed, the electromagnetic valve 10 was opened, and Ar gas was blown into the tuyere to prevent the hot metal from entering the tuyere.

  After the hot metal is charged, the furnace 40 is erected, the electromagnetic valve 11 is opened, and Ar gas is blown into the observation nozzle 7 at a flow rate of 100 to 200 NL / min. The atmosphere was purged.

  A Q-switched pulsed Nd: YAG laser (pulse energy 200 mJ, pulse repetition 10 Hz) is irradiated onto the analysis surface M in the tuyere, and then tuned to a resonance wavelength of carbon (C) of 193.09 nm (titanium sapphire laser) The light emission generated by irradiating was measured with the light quantity detector 30, and the electric signal was transmitted with the electric wire 31 and observed and recorded with the measuring device 32. An oscilloscope was used as a measuring device.

  Further, the light emission generated by irradiating the Q switch pulse Nd: YAG laser was transmitted to the spectroscopic analyzer 27 by the optical fiber 26 having a length of 20 m, and the light emission intensity of manganese (Mn) was monitored by spectroscopic analysis.

  The C concentration was determined using a relationship (calibration curve) between the known C concentration measured in advance and the output voltage of the light quantity detector 30. The Mn concentration was determined using the relationship (calibration curve) between the known Mn concentration measured in advance and the Mn emission peak intensity.

  FIG. 5 shows changes in C and Mn concentrations measured by the above method from the middle of blowing. The thick solid line and the thin solid line in FIG. 5 indicate the C and Mn concentrations measured at intervals of 30 seconds by the method of the present invention, respectively. Further, ● and ○ indicate the C and Mn concentrations obtained by analyzing the sampled molten steel by the spark emission analysis method, respectively.

  As shown in FIG. 5, if the refining monitoring apparatus and method of the present invention are used, the analysis tuyere 1 is not blocked by the solidification of the molten metal and the analysis is not hindered. It was possible to measure the concentration.

(Example 2)
The analysis tuyere 1 shown in FIG. 1 was attached to the downcomer side of the RH vacuum chamber 41. An overview is shown in FIG. The analysis tuyere 1 has a taper over a length of 500 mm on the molten metal side, the inner diameter on the molten metal side is 40 mm, and the inner diameter on the 500 mm iron side from the opening on the molten metal side is 30 mm. The height of the opening on the molten metal side (H1 in FIG. 4) was set to about 150 mm so that a simulated molten metal surface M was generated inside the tuyere when the molten steel was refluxed.

  Inside the tuyere, a stainless steel tube with an inner diameter of 7.5 mm was installed, and an observation nozzle 7 surrounded by a mullite tube was inserted around the tube.

  With the electromagnetic valves 10 and 11 both closed, the ascending and descending tubes of the vacuum chamber were immersed in the molten steel in the ladle 42, evacuation was started, the molten steel was refluxed, and vacuum refining was started.

  A Q-switched pulse Nd: YAG laser (pulse energy 200 mJ, pulse repetition 10 Hz) is irradiated to the analysis hot water surface M in the tuyere, and then a wavelength tunable laser (titanium sapphire laser) tuned to a resonance wavelength of C of 193.09 nm. The emitted light was measured by the light quantity detector 30 and the electric signal was observed and recorded with an oscilloscope.

  The C concentration was determined using the relationship (calibration curve) between the known C concentration measured in advance and the output voltage of the light amount detector.

  FIG. 6 shows the transition (solid line) of the C concentration measured by the method described above. The black circles in Fig. 6 indicate the C concentration determined by the combustion infrared absorption method of the sampled molten steel.

  From FIG. 6, if the refining monitoring apparatus and method of the present invention are used, the analysis is not hindered by the slag of the ladle hot water surface or the clogging due to the solidification of the molten metal at the tuyere 1 for analysis. It has been shown that the concentration of components in metals can be measured.

The figure showing the structure of the analysis tuyere and analyzer of this invention The figure explaining the tuyere mounting position for horizontal analysis of the converter Device configuration diagram with the analysis tuyere and analyzer of the present invention attached to the converter Device configuration diagram with the analysis tuyere and analyzer of the present invention attached to the RH vacuum chamber The figure which shows the result of having continuously measured the density | concentration of Mn and C in converter refining by this invention The figure which shows the result of having continuously measured the density | concentration of C in RH vacuum degassing by this invention

Explanation of symbols

1: analysis tuyere
2: Refining container iron skin
3: inner wall of refractory refractory
4: Inside the refining vessel
5: Molten metal surface
6: Molten metal
7: Observation nozzle
8: Laser induced plasma
9: Optical window
10,11: Solenoid valve
12: Gas inlet
13: Exhaust port
14: Refractory container side wall refractory
19: Laser-induced fluorescence reflection mirror
20: Laser emission reflecting mirror
21: Selective excitation laser reflection mirror
22: Ablation laser reflection mirror
23: Lens
24: Laser-emitting condenser lens
25: Optical fiber receiving end
26: Optical fiber
27: Spectroscopic analyzer
28: Ablation laser oscillator
29: Selective pump laser oscillator
30: Light intensity detector
31: Transmission line
32: Measuring equipment
33: Slag
40: Converter
41: RH vacuum chamber
42: Ladle
43: Rise pipe
44: Downcomer
100,101: Trunnion side
102: Steel exit side
103: charging side
104,105: Mounting position for analysis tuyere
M: Analytical hot water

Claims (8)

  It penetrates the refractory on the side wall of the smelting vessel, one end opens to the outside of the smelting vessel, and the other end opens to the inside of the smelting vessel. A refining vessel provided with an analysis tuyere at a low position and the opening on the outside of the refining vessel is located at a position higher than the surface of the molten metal, and during refining, inside the analysis tuyere An ablation laser oscillator for vaporizing and atomizing a part of the molten metal by irradiating a laser on a molten metal surface to be formed, a selective excitation laser oscillator for resonantly exciting an analysis target element, and the molten metal surface A refining monitoring device comprising at least an optical fiber for transmitting emitted light generated thereon, a spectroscopic analyzer, and a light amount detector for measuring laser-induced fluorescence.   2. The refining monitoring apparatus according to claim 1, wherein an observation nozzle including a gas inlet, a gas outlet, and an electromagnetic valve is inserted into the analysis tuyere.   3. The refining monitoring apparatus according to claim 2, wherein at least the innermost side of the observation nozzle is a stainless steel pipe.   4. The smelting monitoring apparatus according to claim 1, wherein the analysis tuyere has a taper in which the inner diameter on the inner side of the smelting container is larger than the inner diameter on the outer side of the smelting container. The refining monitoring apparatus according to any one of claims 1 to 4, wherein the refining vessel is a converter, and the molten metal is one or both of hot metal and molten steel. The refining monitoring apparatus according to any one of claims 1 to 4, wherein the refining vessel is a secondary refining degassing vacuum tank, and the molten metal is molten steel.   It penetrates the refractory on the side wall of the refining vessel, one end opens to the outside of the refining vessel, and the other end opens to the inside of the refining vessel. During refining, the opening inside the refining vessel is lower than the molten metal surface A part of the molten metal on the surface of the molten metal formed inside the analysis tuyere provided so that the opening on the outside of the smelting vessel is at a position higher than the surface of the molten metal. A refining monitoring method characterized in that the chemical component concentration in a molten metal is measured by spectroscopic analysis of light emission generated by irradiation with an ablation laser for vaporization and atomization.   It penetrates the refractory on the side wall of the refining vessel, one end opens to the outside of the refining vessel, and the other end opens to the inside of the refining vessel. During refining, the opening inside the refining vessel is lower than the molten metal surface Ablation laser is applied to the molten metal surface formed in the tuyere for analysis, which is located at the position and the opening on the outside of the smelting vessel is higher than the molten metal surface. After evaporating and atomizing a part of the molten metal, the amount of emitted light generated by irradiating a selective excitation laser having a wavelength that matches one of the resonance wavelengths of the element to be analyzed is converted into an electric signal by a light amount detector. A refining monitoring method, wherein the concentration of chemical components in the molten metal is measured by measuring the electric signal intensity by electric transmission.

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