JPS59157539A - Direct analyzer of molten metal in deep layer by fine particle generating plasma emission spectrochemical method - Google Patents

Abstract

PURPOSE:To analyze directly molten metal constituents simply and rapidly at an operating working site by taking in the deep layer part of the molten metal under a probe through a refractory cylinder and introducing the fine particle evaporated and generated by a spark discharge to an analyzer together with inert gas. CONSTITUTION:The molten metal in the deep layer is taken in under the probe 1 by lowering the refractory cylinder 39, the spark discharge is performed between a counter electrode 8 and a sample electrode 17 while blowing gaseous Ar. The evaporated and generated ultrafine particles are sent to a plasma torch 29 together with gaseous Ar, and are excited and emitted to measure each constituent content. Thus the molten metal constituent in the deep layer can be analyzed directly, simply and rapidly in working site.

Description

Detailed Description of the Invention The present invention applies a high voltage between the surface of the molten metal and a counter electrode to cause electrical discharge such as sparks to evaporate ultrafine particles representative of the component composition in the molten metal. and repeat this in the previous section 1. Direct emission spectroscopy of molten metal is carried out using an inert gas flow to analyze the content of various components in the molten metal in real time online. This relates to an analytical device.

Spark emission spectrometry analysis of sampled and solidified block samples is often used for manufacturing process control in the metal manufacturing industry. However, in recent years, especially in the steel industry, for faster manufacturing process control or operational management of new manufacturing processes such as multi-stage refining and smelting methods,
There is a strong demand for the development of online real-time analysis methods that directly target molten metals such as hot metal and molten steel.

At this size, molten metal is pulverized using a special atomizer using A and R gases and then analyzed using 5 emission spectroscopy (BISR).
A, Anna] Report: '78 (1
966), 65°78 (1967), 35 (1
Research and development has been attempted using various methods such as 968)). However, none of these three methods has ever been put to practical use in a manufacturing site, and all have only been attempted on a laboratory scale.

In order to realize a direct analysis device for molten metal that can be put to practical use at actual manufacturing sites, the manufacturing site must first be exposed to high temperatures, vibrations, and
The fact that the measurement environment is extremely poor due to dust must be taken into consideration. Precision measuring instruments such as spectrometers and detectors, which can cause problems in such poor measurement environments, should be installed away from the location where molten metal is present, and molten metal should be transported as a fine powder using electrical discharge, etc. Such methods are promising.

The present invention is a method for stably generating ultrafine particles having a narrow particle size distribution range of 0.1/zm or less from molten metal.

Preventing fine particles from adhering to the inner wall of the conveyor pipe and reducing the length of several 1.0 m.
We have conducted research and development focusing on how to efficiently transport long-distance materials and how to introduce them into analytical equipment, and we have now provided a practical new analytical equipment that can be analyzed easily, quickly, and with high precision and sensitivity. .

By the apparatus according to the embodiment of the present invention shown in FIG.

The details of the present invention will be explained.

41 The device of the present invention can be roughly divided into a fine particle generation probe 1, a vertical position i-joint device 20 of the probe that is linked with a hot water level gauge 38, and an attached large cylinder 39 that takes molten metal from deep layers into the lower part of the probe. Spark discharge device IB, particulate transport pipe 22
．． It consists of a carrier gas distribution device 24 and an optical emission spectrometer 37 having a plasma excitation source. Particulate generation probe l.

A high voltage is applied between the molten metal 13 and the counter electrode 8 to cause a snoke discharge to locally maintain the molten metal in a superheated state at a higher temperature, thereby vaporizing fine particles representing the composition of the metal in the form of smoke. It is the part that does the work. The counter electrode 8 is suitably a round bar with a small diameter of about 2 to 5 diameters with a pointed tip, and the suitable material is tungsten, which is a high melting point metal with little wear and tear due to evaporation.

The conical shape of the tip is important for evaporating fine particles at a constant rate.

The gap between the tip of the counter electrode 8 and the surface of the molten metal 13 is 5 m1.
ll, when the spark discharge is blown, it is about 1. Pulse discharge is repeated within the range of Ommφ, the discharge column 14 is also formed stably, the amount of evaporated particles is always stable, and good analytical results can be obtained. Even if the hot water level fluctuated somewhat, a discharge column 14 was always formed from the tip of the counter electrode, and fluctuations in the amount of evaporation of fine particles could be suppressed to a very small amount. When the electrode gap is set to 5m, m, ±
Even if the hot water level fluctuated by 2 m or 2 m, the fluctuation in the amount of fine particles produced could be suppressed to within a factor of 5.

However, when the tip of the counter electrode is made into a cross section of a round bar or the cross section of the pipe of the particle introduction tube 3 is used directly as the tip of the electrode,
A stable discharge column is not formed.

In particular, when fluctuations occur in the hot water level, the discharge column moves,
It becomes impossible to obtain reproducibility of the amount of evaporation of fine particles.

Analysis accuracy was extremely reduced.

For these reasons, the particle introduction tube 3 is used as a conductor for the counter electrode 8, but the counter electrode for spark discharge is fixed at the tip of the introduction tube 3. There are several methods for fixing this, but as shown in FIG. Insert vertically.

6- A suitable method is to open the particulate introduction lower and fix it with screws 9 or the like.

The particulate introduction tube 3 is made of steel or copper and has an inner diameter of 2 to 3 m, with a small diameter on the order of mφ, and its upper portion is fixedly held at the top of the cooling cylinder 2 via a heat-resistant insulating material. The outside of the particulate introduction tube 3 is coated with a four-sided heat insulating tube 4 made of alumina, magnesia, etc., but holes are formed inside the cooling cylinder 2 so that a slight gap 5 is formed concentrically around the outer circumference. An inert gas supply pipe such as Ar is attached to the upper part of this gap 5.

The lower part is connected to a gas outlet 10.

The cooling cylinder 2 itself is equipped with a mechanism capable of being cooled by air cooling or water cooling in order to prevent heating of the molten metal due to side radiation heat. A cylinder 11 made of an insulating refractory material such as boron nitride is attached around the lower part of the cooling cylinder 2, and the lower end is immersed in the molten metal 6 to form a small chamber 12 inside.

An electrode holder part 6 with a counter electrode 8 attached to the lower end of the particle introduction pipe 3 protrudes from the small space chamber 12, and the tip of the counter electrode 8 is perpendicular to the molten metal body 13. Opposed to each other, the electrodes are set at regular intervals in the range of 5 to 50 m, and a particulate introduction lower opens downward at only 2' part of the tip of the counter electrode.

Gas outlet]-〇 is located at the top of the small space chamber 12,
It should be located above the particulate introduction lower part.

Suitable for efficient introduction of evaporated fine particles.

A high voltage is applied between the tip of the counter electrode 8 and the molten metal surface 13 to cause a spark discharge, and the evaporated ultrafine particles of the molten metal are carried by the Ar gas flow discharged from the Ar gas outlet 10 and are transferred to the counter electrode. 8. The particles are quickly transported to the fine particle introduction lower located directly above the tip.

The small space chamber 12 has a diameter of 30 m, mφ, and a height of 30 m, m.
The volume is small, and the diffusion of evaporated particles occurs at <<.

It is efficiently introduced into Roma at the same time as it is generated.

The inert gas blown into the small space chamber 12 is necessary to expel the atmosphere in the small space chamber 12 to create an atmosphere conducive to spark discharge, and to transport the generated particulates to the analyzer.

The type of gas affects the particle size and amount of fine particles generated.
Ar, He, Ar-H2, etc. are used, but 1
Generally, Ar gas is suitable. In order to prevent the dispersion of the generated fine particles, it is necessary to make the space chamber in which the discharge occurs [-2] as small as possible;
The molten metal surface is likely to be cooled by the blown Ar gas. Introductory tube 3 with fine particles
The temperature i of the Ar gas passing through reaches several hundred degrees, but the Ar gas blowing in the present invention is preheated by a heat exchange effect before it is supplied through the gap 5 made on the outer wall of the introduction pipe 3. Cooling of the molten metal surface can be prevented.

Further, the ultrafine particles produced by evaporation have a property of immediately adhering to the inner wall of the tube when the temperature of the inner wall is low, making it difficult to quantitatively transport the fine particles. Alternatively, the number of particle transport pipes 22],
In order to clean the particulates that adhere and remain inside the pipe, which tends to occur when the pipe is long like Om, it is necessary to intermittently apply high pressure and blow Ar gas at high speed. For these purposes, the particulate introduction pipe 3 installed in the cooling cylinder 2 is not cooled by directly contacting the cooling cylinder 2, but is 1 inch. For efficient contact, it is necessary to have a concentric double tube structure with a narrow gap on the outside of the particle introducing tube 3.

It's a trench, if you keep emitting electrical discharge for a long time.

Since some of the evaporated particles adhere to the tip of the counter electrode 8, a method is used in which the polarity is intermittently reversed and discharge is performed to evaporate and remove the attached particles. but,
For long-term continuous analysis.

The counter electrode will need to be replaced. This replacement must be done quickly, but in the present invention, the counter electrode 8 and the particle introduction tube 3
By integrating the cooling cylinder 2, there is an advantage that it can be replaced quickly by simply removing the fixture on the upper part of the cooling cylinder 2 and pulling it upward.

A problem with directly analyzing molten metal is that the level of the molten metal fluctuates dramatically, and it is rare for the level to remain static. That is, the purpose of analysis to know the component content is process control of metal manufacturing, so direct analysis during the manufacturing process is necessary, and the molten metal level during the manufacturing process is usually not stable. Taking steel manufacturing as an example, the amount of hot metal ICL flowing from the furnace into the gutter changes from time to time, and the subsequent dephosphorization, desulfurization, decarburization, etc. During the treatment, the water level fluctuates violently, indicating a boiling state. Even if the analysis is carried out by mechanical means or by selecting a relatively stable period, the gap between the tip of the counter electrode 8 and the molten metal surface 13 when fine particles are evaporated and generated by spark discharge is usually small. Since it is necessary to keep the temperature below lOrnm and IJ, measures against fluctuations in the hot water level are essential.

Therefore, in the present invention, as shown in FIG. 1, a hot water level detector 38 is installed facing the surface of the molten metal 13 to constantly detect the hot water level, and this detection signal is used to detect the fine particles holding the counter electrode 8. A method was adopted in which the gap between the counter electrode and the molten metal 1B1 was maintained at a constant interval by operating the vertical position adjustment device 20 that moves the cooling cylinder 2 of the production probe up and down.

The hot water level detector uses capacitance No. 1. ! ! etc., is suitable, and it is fixedly held on the particle generation probe 1 or the supporting frame 19 of the probe. The upper part of the probe can be accessed using a zoN knee motor and a screw jack as the drive source for vertical movement of the probe l. Small level fluctuations on the surface of the hot water.

By immersing the refractory cylinder 11 in molten metal to form the small space chamber 12, it disappears considerably, but the level meter 38
The level detection accuracy is over 10.5mm, and the speed at which the detection signal is converted into one-tone downward movement is also fast.

According to this method, the gap between the electrodes is always 5 rr + η1 ± 1
It is possible to adjust the size to 1 mm, stably generate fine particles, and perform analysis with good accuracy.

Another major problem in direct analysis of molten metals is that
These are the removal of slag floating on the surface of the molten metal and the intake of deep molten metal into the fine particle generation probe. Usually, slag is floating on the surface of the molten metal, and an oxide film is formed on the surface of the molten metal, and it is necessary to remove these and expose the surface of the molten metal for analysis. Furthermore, the composition of the molten metal directly under the slag layer is often different from that of the molten metal in the deeper layer due to the influence of the slag-metal reaction, so it is necessary to eliminate the slag and also analyze the molten metal in the deeper layer. There is.

In the present invention, as shown in FIG. 1, a particulate generation probe 1 and a liquid level gauge 38 are enclosed, and a cap 41 made of a material having a melting point equal to or lower than that of the target molten metal is covered at the lower end. A method was adopted in which a refractory cylinder 39 for slag shielding was infiltrated into the molten metal 13. magnesia, alumina.

A lifting device 40 is attached to the top of the cylinder 39 made of a refractory material such as boron nitride, and before the start of analysis, the refractory cylinder 39 is lifted above the molten metal in the same way as the particulate generation globe 1. but.

First, the slag shielding refractory cylinder 39 is lowered.

The slag is removed by passing through the slag layer 42, and the molten metal 13
let it penetrate inside.

The cap 4 attached to the bottom is melted by the molten metal 13, and the molten metal in the deep layer is taken into the refractory cylinder 39. After this, particulate generation probe 1
Start analysis by lowering -.

After the analysis is completed, the refractory cylinder 39 is pulled up together with the particle generation probe 1, and the lower ends of the three refractory cylinders are placed.

Attach a new cap 41 and wait for the next analysis 13- do.

That is, since the cap 4 is used as a consumable item, it needs to be easy to replace, but it is sufficient to attach it by slightly fitting it into the lower end of the cylinder 39. This cap 4 is melted by the molten metal 13 and becomes the subject of analysis, but since the amount of the cap 41 is small compared to the total amount of molten metal taken into the refractory cylinder 39, it hardly becomes a problem. , use a material that does not contain the component to be analyzed as much as possible.

In order to reduce the amount of cap that penetrates into the molten metal and to increase the mechanical strength of the cap, a refractory cylinder 3 is used.
An effective method was to cover the bottom of the 9 with fireproof material, make a small hole in the center, and cover the outside with a cap. According to the above method of the present invention, slag can be sufficiently eliminated;
The collection of deep molten metal was also successful.

There are various methods for converting the molten metal 13 into fine particles, but in the method of atomizing using a spray action using a high-speed Ar gas flow, as in the above-mentioned cited document, the diameter of the generated fine particles is 10 to 10.
Because the particle size is about 100 μm or more, it is difficult to transport over a long distance due to the large particle size, and the wide particle size distribution causes large fluctuations in emission intensity when excited and emitted, resulting in poor analytical accuracy. There is a problem. In the method of superheating evaporation by irradiating a DC arc or arc column with a plasma arc converged by the pinch effect of water cooling,
The interelectrode gap between the counter electrode and the molten metal surface is ], ~2
Unless the distance between the particles is kept short, on the order of mm, evaporation of fine particles will not occur beyond a certain amount, and so-called selective evaporation will occur, in which the evaporation of components with low vapor pressure takes priority, and the molten metal It is difficult to stably produce fine particles with a representative composition.

The method using laser irradiation has the advantage of being applicable to non-conductive materials, but continuous lasers such as CO2 lasers have little evaporation potential, so a giant pulse laser has to be used, but it can evaporate several tens of times per second. Since high power irradiation is not possible, this method is also not suitable for extremely accurate on-line analysis.

As a result of our detailed research into the suitability of the energy source for vaporizing and producing the bath molten metal as fine particles,
Spark discharge was selected as the optimal method. That is,
A rod-shaped electrode 17 made of carbon or a high-melting point metal immersed in the molten metal 13 serves as a sample electrode and a cathode, and the upper end of the particle introduction tube 3 is connected to a counter electrode 8 whose tip is placed on the surface of the molten metal 13 with a slight gap. Using the terminal 16 that has been reached as an anode, it is connected to a spark discharge device 18, and a high voltage is applied to both poles to generate a spark discharge, thereby vaporizing the molten metal] and 3 as fine particles.

In order to evaporate and transport molten metal as fine particles and analyze the amount of various components contained in the molten metal, it is particularly important to stably generate fine particles that represent the contained components.
The way each discharge constant in spark discharge is set also has an influence. Self-induction 1.0 μn - capacitance 3/zF - resistance 1 Ω, voltage 1000 V.
F, OΩ, arc-like spark discharge set at 700 V (looking at the discharge current waveform, the former has a peak current value of 20 OA-holding time of 3゜μS, the latter each has a peak current of 20 OA and a holding time of 3゜μS, respectively,
The results of repeated analysis of each component by generating fine particles for steel phase loss under surface discharge conditions of 4.00 μS) were -0,
The coefficient of variation of the analytical value of 50% Sl is 2.5 for the former.
%, the latter contains 1.6% and 104% of Mn, respectively, of 38%.

], 2.6%, and 0.30%, respectively.
%.

Results such as 14.2% were obtained.

That is, as described above, spark-like spark discharge is more suitable than arc-like spark discharge for stably evaporating each component in the molten metal as fine particles. Regarding the discharge frequency, a range of 50 to 800 Hz was investigated, and it was found that a frequency of 200 Hz or higher, which has a large number of discharges per unit time, is advantageous in terms of analysis accuracy.

In the present invention, which aims at component analysis in molten metal,
Unlike the case where fine particles are simply generated, the evaporated fine particles must be constantly and stably sent to the analyzer 37 with a constant flow rate of carrier gas, and a more efficient fine particle conveying technique is required. In the present invention, the fine particles evaporated from the surface of the molten metal 13 and rising in the vertical direction from one end of the tip 17 of the counter electrode 8 are diffused to the surroundings by 1E.
Ar gas blows out from the lower end 1o of the Ar gas blowing pipe 5 and flows into the opening 7 at the lower end of the particulate introduction pipe 3.
We adopted a method of rapidly transporting it away in the r gas flow.

Since the small space chamber 12 in which the particles are generated has no outlet other than the opening 7 of the particle introducing tube 3, they are drawn into the Ar gas flow and are always passed through the opening 7 of the introducing tube 3 at a constant dilution ratio.
sent to. In order to form an Ar gas flow that stably sends fine particles to the opening 7 without disturbing the discharge of the discharge column 14 formed by the tip of the counter electrode 8 and the surface of the molten metal, it is necessary to The outlet 1° at the lower end of the tube 5 is wider than the opening 7 at the lower end of the particle introduction tube 3.
It should be located slightly at the top.

The particles introduced into the particle introduction tube 3 are carried by the -Ar gas flow and are conveyed to the carrier gas distribution device 24 through the particle transfer tube 22 connected by the insulating connector 21, as in the present invention. When analyzing fine particles, it is important to prevent 18- fine particles from adhering to and remaining on these inner walls. Since the fine particle introduction tube 3 is heated by the high heat of the molten metal, the fine particles are difficult to harvest and there is no problem, but the conveyance tube 22 is long.

As the temperature drops, adhesive residue tends to occur. As a result, the concentration of particulates in the carrier gas fluctuates and contamination occurs, making it impossible to obtain accurate analytical values.

Therefore, the diameter of the transport pipe 22 is made as small as possible to increase the flow rate of the transport gas. As shown in the drawing, a heating device 23 is installed to heat the surface constantly, or fine particles once attached can be easily peeled off within a short period of time, so a method such as cleaning by blowing carrier gas at a higher speed is adopted. did.

The carrier gas distribution device 24 once diffuses the fine particles sent by the carrier gas from the carrier pipe 22 in a small space to further make the particles uniform. In order to obtain the optimum flow rate of the carrier gas introduced into the plasma torch 29, the carrier gas is distributed by discharging a certain portion out of the system. Alternatively, particles that have become particularly coarse due to agglomeration progressing while they are being transported are removed from the system and subjected to particle sizing to send only fine particles to the plasma torch 29.

The distribution device 24 is a small-diameter cylindrical tube with a heating device 23 attached to its outer periphery.The particle conveyance tube 22 is inserted through the side wall and the tube end opening 25 is directed upward, and the particle supply tube 26 is conveyed from the top of the two cylindrical tubes. At a constant distance from the tube end opening 25,
A discharge pipe 27 equipped with a flow regulator 28 is mounted on the bottom of the cylindrical tube mounted oppositely. These three tubes.

Coarse particles, excess particles, and carrier gas are all discharged from the system through the bottom exhaust pipe 27 through thin tubes with a diameter of 1-Omrnφ or less, and the remaining particles are discharged together with a constant flow rate of carrier gas.
It is introduced into the supply pipe 26.

The particle supply pipe 26 is connected to the plasma excitation emission spectrometer 3
Connected to 7. The introduced particles are transferred to the particle supply pipe 26, as shown in the figure. The high-temperature A generated by the high-frequency generator 52 is carried into the triple-pipe plasma torch 29 consisting of the plasma gas supply pipe 30 and the cooling gas supply pipe 31.
It reaches the r plasma section 33 and is excited to emit light. The excitation light is separated into spectra by a spectrometer 34, and the intensity of each spectral line is measured by a detector 35 consisting of a photomultiplier tube or the like and a component content calculation device 36 to quickly determine the content of each component in the molten metal. It will be done. Analyzer 37 that excites fine particles to emit light
Although a high-frequency inductively coupled emission spectrometer is most suitable for this purpose, other types of plasma excitation emission spectrometers such as arc discharge or atomic absorption spectrometers can be used.

The analysis operation of the apparatus of the present invention will be briefly described.

First, three slag shielding fire suppressing cylinders are lowered into the molten metal 13 through the slag layer 42 by the lifting device 40. The camp 41 at the tip is melted and the molten metal 13 at the deep layer is taken into the cylinder 39. Next, the support frame 19
The particle generating probe 1 attached with a drive source 20 is lowered toward the surface of the molten metal 13 while blowing Ar gas into the Ar gas blowing tube 15. Ar
Ar gas is blown out from the gas outlet 10, and the lower end of the fire tube 11 is melted 2 while expelling the atmosphere inside the fire tube 11.
1- Immerse in the molten metal 13 and seal the small space chamber 12.

The distance between the tip of the counter electrode 8 and the surface of the molten metal 13 is automatically adjusted to a predetermined distance by the hot water level gauge 38 and the bottom position adjustment device 20, and by operating the spark discharge device 18, the distance between the sample electrode 17 A high voltage is applied between the counter electrode 8 to generate a spark discharge.

The evaporated particles are transferred to the particle introduction pipe 3. The gas is fed into a plasma torch 29 via a transport pipe 22 and a gas distribution device 24, and is excited to emit light.The content of each component is measured from the integrated emission intensity value for about 10 seconds. After the analysis is completed, Ar gas is intermittently blown at high pressure from the Ar gas blowing pipe 15 of the particulate generation probe 1 to wash off the particulates adhering to the inner wall of the particulate transport pipe 22, etc.

Next, at the time when it became necessary to pull up the refractory cylinder 39 and the particulate generating globe 1 from the molten metal and analyze it again,
Next, the probe 1 is lowered into the refractory cylinder 39 with a new cap attached to its tip, and the above operation is repeated to perform one analysis. The particle size and particle size distribution of the generated fine particles are
In the method of analysis using excited light emission in plasma, it is particularly important because it has a large effect on the quantitative accuracy22-1.The fine particles generated in molten steel using the device of the present invention are approximately 0.1 μm in size.
J, V, lower extremely fine particles with an average particle size of 0.
For 0511m, 0.04~0.06/rm
The width of the particle size distribution is also narrow so that about 70% or more falls within the range of .

It was ideal for plasma emission spectroscopy.

As explained above, according to the present invention, components contained in a molten metal sample can be directly analyzed quickly and accurately without performing operations such as sampling.

It is extremely effective for operational management of metal refining and steel manufacturing processes.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the entire apparatus according to an embodiment of the present invention, and FIG. 2 is an explanatory diagram of the tip of the fine particle generating glove. 1: Particle generation probe 2: Cooling tube 3: Particle introduction pipe 5, ], 5
: A, r gas injection pipe 8: Counter electrode l]-: Fireproof cylinder 12: Small space chamber 13: Sample electrode
17: Sample electrode] 8 Varnish spark discharge, device 20 Nibro one vertical position adjustment device 22: Particle transport tube 24: Carrier gas distribution device 29
: Plasma torch 37 : Plasma emission spectrometer 38 : Hot water level meter 39 Fireproof cylinder for Nislag shielding

Claims (1)

[Scope of Claims] A round bar counter electrode with a circular tip is attached vertically to the lower end facing the surface of the molten gold layer, an opening for introducing fine particles is provided just above the counter electrode, and a fine particle transport pipe is provided at the upper end. A small-diameter, vertically elongated particulate introduction tube that also serves as a conductor for the counter electrode, and a particulate introduction tube arranged concentrically around the outer periphery of the particulate introduction tube, with a supply port at the top and a discharge port at the bottom end. Through an inert gas blowing pipe, a cooling cylinder containing and holding the inlet pipe and having a cooling structure around it, and a cooling cylinder around the lower part of the cooling cylinder, the lower end of which is immersed in molten metal during analysis, A particle generation probe consisting of a refractory tube installed to form a small hermetically sealed chamber; 2. A spark discharge device in which the upper part of the particle introduction tube is used as an anode and the sample electrode immersed in molten metal is connected as a cathode. ; Facing the molten metal surface, the above-mentioned particulate generation probe 1 - In conjunction with the detection signal of the hot water level meter fixed to the supporting frame of the probe, the electrode gap between the tip of the counter electrode and the molten metal surface is adjusted. A vertical position adjustment device that functions to control the desired dimensions and is attached to a part of the same probe; contains the above-mentioned particulate generation probe and surface level gauge, and has a metal with a melting point equal to or lower than that of the target molten metal at the bottom. A refractory cylinder for slag shielding; a refractory cylinder for slag shielding; a refractory cylinder for slag shielding; A carrier gas distribution device consisting of a small container to which is attached an end part of a particulate transport pipe connected to the upper end, a lower end part of a particulate supply pipe to the plasma light emitting device, and a discharge pipe for excess carrier gas; A direct analysis device for molten metal, characterized in that it is mainly composed of an emission spectrometer consisting of a light emitting device having a plasma excitation source such as a high-frequency inductively coupled plasma, a spectrometer, a detector, etc.