JPH0238901B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention collects fine particles evaporated from the surface of molten metal and transfers them to an emission spectrometer equipped with a plasma excitation source installed at a remote location. The present invention relates to a method and apparatus for analyzing the content of various components in molten metal in real time online by transporting it with a flow of inert gas such as Ar.

In order to manage operations such as metal refining and steel manufacturing processes, it is necessary to analyze as quickly as possible to understand the component content, and to take appropriate measures based on the results. As described above, the present invention is a technology for directly analyzing molten metal, and is used in the fields of manufacturing process control analysis and quality control analysis in the steel industry, non-ferrous metal manufacturing industry, and the like.

(Prior Art) Spark emission spectroscopy, which targets block samples obtained by sampling and solidifying molten metal, is often used for manufacturing process control analysis in the metal manufacturing industry. However, in recent years, especially in the steel industry, online real-time technology that directly targets molten metals such as molten iron and molten steel has become available for faster manufacturing process control or operational management of new manufacturing processes such as multi-stage refining steelmaking methods. There is a strong need to develop analytical methods for this.

For the above purposes, molten metal has been used until now.
A method of pulverizing the powder using a special atomizer using Ar gas and performing emission spectroscopic analysis (BISRA Annual
Report: 78 (1966), 65, 78 (1967), 35 (1968))
Various methods have been studied. However, none of these methods have ever been actually put into practical use at manufacturing sites, and have only been attempted on a laboratory scale. The present inventors also applied a method of performing emission spectroscopic analysis by evaporating fine particles representative of the composition of the molten metal by irradiating the molten metal with electrical discharge such as a plasma arc or spark, or with a laser beam, etc. 201154
No. 1, patent application No. 58-30879), and filed a patent application. These inventions require a constant distance between the molten metal surface and the heating source device such as the tip of a spark discharge electrode, and are effective when the molten metal level fluctuates relatively slowly, but when the molten metal level fluctuates rapidly. In some cases, various measures must be taken to suppress fluctuations.

(Purpose of the invention) In developing a more practical direct analysis device for molten metal at actual manufacturing sites, it is important that the manufacturing site
Consideration must be given to the fact that the measurement environment is extremely poor, including high temperatures, vibrations, and dust. Therefore, precision measuring instruments such as spectrometers and detectors that can cause problems under adverse measurement environments must be installed in a building away from the location where molten metal is present. Molten metal can be evaporated as fine particles by electrical discharge, but if possible, it is necessary to evaporate the fine particles by a simple method, such as collecting fine particles that naturally evaporate due to the high heat of the molten metal itself. There is. Under these circumstances, the present invention aims at online real-time analysis in manufacturing process control analysis of molten metal, and collects fine particles that evaporate on the surface of molten metal.
The object of the present invention is to provide a practical analysis method and apparatus for easily and quickly analyzing various components contained in molten metal by transporting the molten metal with an inert gas flow to an emission spectrometer having a plasma excitation source.

(Configuration, operation, and embodiments of the invention) The configuration and operation of the present invention will be explained based on an example of an apparatus for implementing the present invention shown in FIG. FIG. 1 shows an example in which the molten metal used is molten steel in a processing ladle in a steelmaking process. The device of the present invention
It mainly consists of a container 8 containing Ar gas, a particle collection tank 1 immersed in molten steel 2, a particle transport pipe 9, and a high frequency inductively coupled plasma emission spectrometer 10. The particulate collection tank 1 is a cylinder made of a heat-shockable fireproof material such as boron nitride or graphite, and has an Ar gas introduction pipe 3 and a particulate discharge pipe 5 attached to the top, and a bottom part for taking in molten steel. It is hollow. Therefore, when the particulate collection tank 1 is immersed in the molten steel 2, it becomes a closed container having a space for the particulate evaporation chamber 7 inside.
Ar gas in the Ar gas container 8 is introduced into the Ar gas introduction pipe 3 at a constant flow rate measured by a flow meter,
Ar gas is supplied from an Ar gas inlet 4 provided at the top of the particle evaporation chamber 7. Molten steel 2 in particulate evaporation chamber 7
The fine particles of molten steel evaporated from the surface of the molten steel are carried by Ar gas to the fine particle exhaust port 6 of the fine particle exhaust pipe 5 provided at the upper part of the fine particle evaporation chamber 7. The gas for transporting particulates is regulated due to the stability of the plasma flame of the plasma analyzer, and gases other than Ar are
Inert gases such as N ₂ and He are suitable. The development of a plasma flame that uses air is currently underway, and if this technology is perfected, it will be possible to use atmospheric air instead of inert gas.

Fine particles of molten steel evaporate from the surface of the molten steel due to the high heat of the molten steel itself. On the other hand, in plasma emission spectrometry that analyzes these fine particles, the finer the particle size and the narrower the particle size distribution range, the better the excitation efficiency in the plasma and the more stable the emission intensity can be obtained. , the sensitivity becomes better. Therefore, it is necessary to collect particles suitable for plasma emission spectroscopic analysis as the target of analysis, and for this reason, the installation positions of the Ar gas inlet 4 and the particle outlet 6 in the particle evaporation chamber 7 are limited. Near the molten steel surface, large particles scattered from the molten steel and large particles formed by agglomeration of evaporated fine particles exist, but the particles that evaporate and float several tens of millimeters above the molten steel surface are fine particles with a diameter of several hundred millimeters or less. The particles have excellent uniformity. For example, if the Ar gas inlet 4 is placed approximately 80 mm away from the molten steel surface and the particulate discharge port 6 is provided 5 to 10 mm above the molten steel surface, molten steel fine particles containing large particles mixed with fine particles will be collected. , the analysis accuracy decreases. If the Ar gas inlet 4 and particulate outlet 6 are installed in the opposite direction, the blown Ar gas will cause a temperature drop on the surface of the molten steel, reducing the amount of particulate evaporation, and making it difficult to obtain a stable amount of evaporation, resulting in a decrease in analysis accuracy. A problem arises.

In Figure 2, a preheated particle collection tank 1 is immersed in molten carbon steel existing in a ladle, and particles are collected by changing the height of the Ar gas inlet 4 from the surface of the molten steel. This figure shows the results of measuring the luminescence intensity of each element in the fine particles by transporting them to the plasma emission spectrometer 10. Although influenced by the vapor pressure of each element, the amount of evaporated fine particles decreases as the Ar gas inlet 4 approaches the hot water surface. In addition, a decrease in quantitative accuracy was also observed. These phenomena are thought to be caused by the temperature drop caused by the molten steel surface being cooled by the injected Ar gas. From the above results, the Ar gas inlet 4 and the particulate discharge port 6 need to be installed in the upper part of the particulate evaporation chamber 7 at a predetermined distance from the surface of the molten steel 2 and at approximately the same height. The distance from the molten metal surface varies depending on the type of molten metal, the inner diameter of the particulate collection tank 1, the Ar gas flow rate, etc. In the case of Fig. 2, the target was molten steel at 1600℃, using a particle collection tank with an inner diameter of approximately 50 mmφ, and an Ar gas flow rate of 0.6/min. 6
The appropriate height from the scene was about 40 to 80 mm.

The particulate discharge pipe 5 is connected to a plasma torch 11 of an analyzer 10 through a transport pipe 9 such as a stainless steel pipe. The particles in the particle evaporation chamber 7 are moved to the particle outlet 6 by the introduced Ar gas at a constant flow rate.
from there to the plasma torch 11. A stainless steel pipe with an inner diameter of 4 mmφ and a length of 40 m is used for the conveyance pipe.
When the Ar gas flow rate was 0.6/min, the internal pressure in the particle evaporation chamber 7 was approximately 150 mmH ₂ O, and the molten metal level dropped by approximately 2 cm, but the molten steel particles reached the plasma torch 11 after approximately 18 seconds. However, by integrating the emission intensity for about 10 seconds, we were able to obtain analytical results with good reproducibility for each element. Although a small amount of fine particles remain on the inner wall of the transport tube, after one analysis, which takes about 30 seconds, is completed, the switching valve 14 installed just before the plasma torch 11 is switched to switch the Ar
By blowing Ar gas from the gas container 8' at a flow rate of 10 to 20/min into the particle evaporation chamber 7 through the conveying pipe 9, the remaining particles could be removed. At the same time, the molten steel in the particulate evaporation chamber 7 is removed from the same chamber, and new molten steel in the ladle is taken into the evaporation chamber 7 by switching the switching valve 14 to return to the original analysis state. By such a method, online analysis of the refining process of molten steel in the processing pot can be easily performed.

The fine particles introduced into the plasma torch 11 are excited and emit light at the high temperature of the plasma, and the emitted light is transmitted to the spectrometer 1.
2, the emission intensity of each element is simultaneously measured by a detector 13 such as a photomultiplier tube set at each wavelength position, and the emission intensity of multiple elements in the molten steel is simultaneously measured.
Rapid analysis can be performed. According to the present invention, C, P, S, Si, Mn, which are contained in trace amounts as impurities in molten steel,
Simultaneous analysis of most elements such as Ni and Cr, except for O, N, and H gas components, was possible. The emission spectrometer 10 is suitably an emission spectrometer having a plasma excitation source. Currently, a high-frequency inductively coupled plasma emission spectrometer that uses Ar plasma is most suitable from the viewpoint of good analysis accuracy and ease of handling.

Fine particles resulting from natural evaporation do not necessarily represent the chemical composition of the original molten metal due to the vapor pressure of each element. A notable example is Mn, which has a low vapor pressure, for example, when the Mn content in molten steel is 1.
%, the Mn content in naturally evaporated fine particles is approximately
20%. Therefore, it is difficult to directly determine the content of each element in the molten metal from the emission intensity of each element in the fine particles obtained by a plasma emission spectrometer. Therefore, we first prepared molten metal in which the content of each element was changed in stages,
Based on the content of each element in this molten metal, we investigated the correlation with the luminescence intensity of each element in the evaporated fine particles,
Create a calibration curve in advance. For the emission intensity of each element, the integrated intensity over a certain period of time may be used as is, but in the case of molten steel, which is the main component of molten metal, it is better to quantify it by using the ratio of the integrated emission intensity of Fe to the integrated emission intensity of the element of interest. Improves accuracy. Further, the temperature of the molten metal affects the amount of evaporation of the fine particles, and the higher the bath temperature, the easier the evaporation becomes, but the content ratio of each element in the fine particles also changes. Therefore, if the bath temperature changes in the manufacturing process of the target molten metal, the correlation between the content of each element and the luminescence intensity when the bath temperature is changed is investigated and created in advance. Use a standard calibration curve. That is, the content of each element can be determined with high accuracy by correcting the slope of a calibration curve created for molten metal at a certain temperature using the bath temperature. However, in the refining process of steelmaking, the fluctuation in molten steel temperature is very small, and it is around 10 degrees for molten steel at 1600 degrees Celsius, and in such cases, it is almost necessary to correct the analytical values of each element due to bath temperature. do not have.

(Effects of the Invention) As explained above, the present invention eliminates the complicated operations such as sampling, cooling solidification, cutting, and pretreatment such as polishing that have been conventionally performed when analyzing the components contained in molten metal samples. It is possible to perform direct analysis quickly and accurately without having to carry out the analysis, and it is extremely effective for operational management of metal refining and steelmaking processes.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of the apparatus according to the present invention, and Figure 2 shows the correlation between the distance of the tip of the Ar gas introduction tube from the molten steel surface and the concentration of each element in the fine particles evaporated from the molten steel surface in the apparatus of the present invention. It is a figure showing the result of investigation. 1... Particulate collection tank, 2... Molten metal, 3...
Ar gas inlet pipe, 4... Ar gas inlet, 5... Particulate discharge pipe, 6... Particulate discharge port, 7... Particulate evaporation chamber, 8... Ar gas container, 9... Particulate transport pipe, 10... ...High frequency inductively coupled plasma emission spectrometer, 11... Plasma torch, 12... Spectrometer, 13... Detector.

Claims (1)

[Claims] 1. The open bottom of a container is immersed in molten metal to form a sealed space, and an inert gas is introduced into the space from the top of the container to prevent fine particles that evaporate and float above the surface of the molten metal. The fine part is discharged from the upper part of the container by the inert gas, and the fine part is transported and introduced into a plasma emission spectrometer to measure the luminescence intensity of each element in the fine particle, and to determine the concentration of each element in the molten metal. Features of evaporated particulate recovery molten metal analysis method. 2. Particulate collection by installing an inert gas inlet and a particulate outlet at almost the same height on the upper part a certain distance from the molten metal surface, and immersing the open bottom part in the molten metal to seal it. What is claimed is: 1. An evaporated particulate recovery molten metal analysis device comprising: a tank; and a plasma emission spectrometer connected to a particulate discharge port of the particulate collection tank via a particulate transport pipe.