JPS6220499B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention performs direct emission spectroscopic analysis of small metal samples, which cannot be analyzed by currently available solid-state emission spectrometers due to shape and size limitations, while melting them at high temperatures. METHODS AND APPARATUS.

In the metal manufacturing industry, it is essential to analyze the main components and trace components contained in metals and alloys for manufacturing process control and product quality control.
Solid-state emission spectrometry methods, such as those specified in JIS KO116-1965, are utilized. In this optical emission spectrometry method, a high voltage is applied between a metal sample piece and a counter electrode to cause spark discharge or arc discharge, and the excitation light from each vaporized component is separated into spectra. This is a method for determining component content. The shape of the target analysis sample is subject to certain restrictions due to the structure of the device that causes the discharge. usually,
It is necessary to have a flat surface with a diameter of 15 mm or more, and it is difficult to analyze smaller bulk samples, cut samples taken with a shaper or drill, or powder samples. These small-sized samples are usually dissolved into a solution using a mineral acid or the like, and then analyzed by various analytical methods such as spectrophotometry, atomic absorption spectroscopy, or solution emission spectroscopy. These analytical methods have many problems, such as being complicated and time-consuming to operate and prone to individual errors, so there is a strong demand for the development of new analytical methods and devices that can directly analyze small metal samples simply and quickly. Ta.

In view of these problems, the present invention has carried out research and development for direct emission spectroscopic analysis of small-shaped metal samples, and has developed a method that includes: high-frequency induction heating melting, high energy, secondary heating, solution collection and transportation of evaporated fine particles, and plasma-excited luminescence. The present invention has led to the provision of a new analytical method and device that is simple, rapid, and has excellent quantitative accuracy, based on the basic principle of spectroscopic analysis. Prior inventions related to the present invention include Japanese Patent No. 1051683, ``Method and Apparatus for Producing Ultrafine Powder,'' and this invention is an invention for obtaining as much fine powder as possible from the same metal. The present inventors have researched techniques to rapidly generate metal fine particles from a different analysis sample each time, and to stably and efficiently transport the fine particles important for analysis to an analyzer, and to analyze the components contained in metals. This is a newly invented analysis system for plasma emission analysis.

The present invention will be described in detail based on embodiments of the present invention shown in the drawings. The device of the present invention can analyze sample 3.
A particulate generator 1 that heats and melts and evaporates as particulates, a particulate transport pipe 15 that transports particulates with an inert gas, a particulate collection pipe 20 that collects particulates in a particulate solution, and a particulate matter that excites the particulates to emit light. The main component is a plasma emission spectrometer 39 that performs spectroscopic detection to determine the content of various components in the sample.

The particle generator 1 includes a refractory crucible 4 that accommodates an analysis sample 3, a cylindrical tube 2 for particle generation that accommodates the analysis sample 3 in an almost airtight state, and a high-frequency generator set on the outer periphery of the cylindrical tube 2 at a position corresponding to the height of the crucible 4. An induction heating device 6, a secondary heating device 7 inserted at an inclination angle of up to 45° from a position perpendicular to the center of the molten metal surface, and a crucible 4 placed in a predetermined position inside the cylindrical tube 2 in a sealed state. A crucible setting device 8 with a cooling mechanism that can be used as a counter electrode to the secondary heating source, and a device 39 that keeps the inside of the cylindrical tube 2 in an inert atmosphere and analyzes evaporated fine particles.
The carrier gas supply device 13 for conveying the gas to the This particulate generator 1 is connected to a particulate collection pipe 20 via a transport gas distribution device 17 by particulate transport pipes 15 and 15'.
0 is connected to an analyzer 39 via a particle collection solution injection pipe 25.

The small metal sample piece 3 placed in the refractory crucible 4 is melted in a short time by the high frequency induction heating device 6, and the sample is maintained in a molten state. Next, the surface of the molten metal of the sample is heated by a secondary heating source, and sample 3 is evaporated as fine particles. Evaporation of fine particles occurs with high-frequency induction heating or plasma arc heating alone, but high-frequency induction heating quickly melts the sample and maintains the molten state, and then evaporates fine particles using a secondary heating device with high energy. This method ensures the evaporation of difficult-to-evaporate components in the sample, increases the amount of evaporation, and narrows the particle size distribution of evaporated particles, improving quantitative accuracy and shortening analysis time. Contribute. The time required to evaporate the sample as fine particles and analyze it is usually a short time of several minutes, so the high-frequency heating for dissolving the sample and the secondary heating for evaporating the sample as fine particles are the same as when the high-frequency heating is stopped after the sample has been dissolved. There are methods to evaporate the fine particles using only secondary heating, or to evaporate the fine particles by performing both heating at the same time.First, the sample is melted by high-frequency induction heating to a molten state, and then the fine particles are evaporated by high-frequency induction heating. An appropriate method was to lower the electric current to such an extent that stirring of the molten metal did not occur, and to evaporate the fine particles by secondary heating.

The secondary heating device is a plasma arc gun shown in Figure 1, but spark or arc discharge devices,
High-energy heating sources such as laser beam oscillators can be used. The secondary heating source is used to heat the surface of the molten metal to a higher temperature to promote evaporation, but the method of irradiating the molten metal surface with the heating source greatly affects the evaporation efficiency of the metal. In particular, the irradiation angle to the molten metal surface and the distance from the molten metal surface are important. FIG. 1 shows an example in which the molten metal surface was irradiated from directly above. In order to maintain the molten metal surface in a superheated state and to efficiently transport the evaporated particles to the analyzer,
The most effective method was to irradiate high energy from a secondary heating source directly above the center of the molten metal surface in the crucible. However, if the secondary heating device is so large that it is difficult to install it above the small cylindrical tube 2, irradiation can also be applied from within an angle of inclination of up to 45° around the vertical position to the center of the molten metal surface. . However, if the irradiation is performed at a position inclined at an angle of 45° or more relative to the vertical position, that is, at an angle close to horizontal to the molten metal surface, the high temperature overheating of the irradiation position of the molten metal surface by the secondary heating source tends to become uneven. It is inefficient, and in the case of a plasma arc, the plasma flame is reflected in the opposite direction from the hot water surface, making it difficult to transport the evaporated particles to the analyzer, as they are scattered along with this flow. The distance from the molten metal surface to any of the above-mentioned secondary heating sources must be maintained at their optimum position. This is to efficiently maintain the molten metal surface in a superheated state, and because the purpose of the present invention is not to collect and manufacture evaporated fine particles, but to continuously transport and analyze them, evaporation is carried out at a constant rate. This is because it is necessary to ensure that Since the evaporation heating time is short, no fluctuations in the hot water level occur during that time, but the hot water level position for each analysis sample must be kept constant.
In the present invention, the position of the secondary heating source and the setting position of the crucible are kept constant, and the weight of the sample introduced into the crucible is controlled to be constant, so that the position of the hot water level is constant and the distance between the secondary heating source and the hot water level is constant. I ran.

The crucible 4 is suitably made of alumina, magnesia, carbon, or the like, which is resistant to corrosion at high temperatures. Although it is not necessary when a laser beam is used as the secondary heating source, when an arc or plasma arc is used, a crucible 4 with a copper electrode 5 attached to the bottom is used. Since the plasma emission spectrometer 24 has a high detection sensitivity, the amount of sample to be analyzed can be as small as several grams, and therefore a small crucible 4 is sufficient. Since the evaporation and analysis of the analysis sample are completed in a short period of several minutes, the sample conversion operation by the crucible setting device 8, which sets the analysis sample in the cylindrical tube 2 for generating fine particles, must be performed quickly and easily. In the embodiment of the present invention, as the easiest example, a sample exchange method was adopted in which the crucible setting device 8 on which the crucible 4 was placed was moved up and down. The crucible setting device 8 is a vertically elongated device made of copper or the like with excellent thermal conductivity and electrical conductivity, and a cradle 9 is attached to the middle of the crucible setting device. The inside of the cylindrical tube 2 can be kept in a sealed state by pressing upward against the tube 2. Further, a cooling water supply pipe 10 and a cooling water discharge pipe 11 are attached to the crucible setting device 8 to cool the copper electrode at the bottom of the crucible 4 and the setting device 8 itself. Further, when a spark, an arc, or a plasma arc is used as a secondary heating source, the crucible setting device 8 also serves as a counter electrode for them. A carrier gas blowing pipe 12 is attached to the pedestal 9 of the crucible setting device 8, and a carrier gas supply device 13 equipped with a gas flow rate regulator 14 is connected to this pipe. Melting of analysis samples by high-frequency induction heating and evaporation of fine particles by a secondary heating device are usually carried out in an atmosphere of inert gases such as Ar, He, and N ₂ to prevent metal oxidation reactions. This is done by blowing in an active gas. Therefore, the evaporated fine particles are diluted by the carrier gas, but as the dilution ratio increases, detection by the analyzer 39 becomes difficult. For this purpose, it is necessary to make the space in which the particles are generated as small as possible. That is, the cylindrical tube 2 is of a small diameter and is as close as possible to the outer diameter of the crucible 4 installed inside the tube. A suitable material for the cylindrical tube 2 is quartz glass or the like, which has excellent thermal conductivity and heat resistance.

Fine particles generated in the form of smoke from the analysis sample 3 melted in the refractory crucible 4 usually move upward onto the surface of the molten metal due to convection caused by heat, and then diffuse into the surroundings. If the purpose is to collect evaporated fine particles as a powder, some loss due to diffusion is not a problem, but in the present invention, which analyzes the amount of components in a sample, it is necessary to collect the total amount of evaporated fine particles or a stable constant amount at all times. A proportionate amount must be delivered to the analyzer together with the carrier gas. This point is very different from the case where evaporated fine particles are collected and manufactured, and a more efficient fine particle transport technology is essential. Although methods such as blowing a carrier gas from an oblique direction close to horizontal to the molten metal surface and sending the fine particles to the opposite horizontal direction are possible, the purpose of this method is to quantitatively convey the fine particles, which is essential in the present invention. in case of,
The most efficient method is to carry the fine particles that are generated from the molten metal surface and rise directly upwards, and quickly carry them away by carrying them in the flow of carrier gas that flows directly above the molten metal surface, before they diffuse to the surroundings. , was appropriate. That is, the particulate transport pipe 15 should be installed vertically and directly above the surface of the molten metal in the crucible 4 at a constant distance. The shape of the opening of the transport tube 15 is suitably a cylindrical tube with a diameter smaller than the inner diameter of the crucible 4, or one whose tip expands into a conical shape close to the outer diameter of the crucible. The carrier gas is blown in from the blowing pipe 12 to maintain an inert atmosphere inside the cylindrical pipe 2.
Since the outlet is not a particulate transport port, gas flows toward the opening through the vicinity of the molten metal surface. The fine particles generated by the secondary heating source and raised from the surface of the molten metal are drawn into the flow of the carrier gas and are sent to the port of the carrier pipe at a constant dilution ratio. When the secondary heat source is applied from directly above the molten metal, it is appropriate to use a structure in which the transfer port 14 is a cylindrical tube concentrically surrounding the heat source. When irradiating with the secondary heat source from an oblique direction, it is preferable to provide the opening of the transport pipe 15 directly above the irradiation center plane. Even when using a plasma arc gun 7, etc., if the angle of installation is within 45° from the vertical position to the molten metal surface, it will be affected by the intensity of plasma irradiation. In normal cases, the particles will be diffused to some extent by the plasma flame, but they will be carried by the carrier gas airflow and will almost certainly reach the carrier pipe 15 directly above.
sent to. The inner wall of the cylindrical tube 2 and the particle transport tube 15 are heated to a considerably high temperature by the high-temperature molten sample, so that particles are difficult to adhere to. If fine particles are diffused and suspended in the cylindrical tube 2, they must be removed before proceeding to the analysis of the next sample, which becomes very complicated, but with this method, fine particles are generated from the molten metal surface. Since the rising flow is surrounded by a kind of air curtain-like carrier gas flow, diffusion of fine particles is unlikely to occur, so there is no need to worry about it.

The evaporation rate and particle size of fine particles are greatly influenced by the pressure of the evaporating atmosphere, the heating temperature, the type of atmospheric gas, and the like. If the atmosphere is reduced in pressure, the evaporation rate will increase and a larger amount of fine particles can be obtained. Therefore, if it is necessary to increase the amount of fine particles generated, although it is not shown in the explanatory diagram of the example,
The inside of the cylindrical tube 2 for particle generation is first evacuated and filled with Ar.
A method is adopted in which an inert gas such as the like is introduced and maintained in a reduced pressure state to generate fine particles, which are then returned to atmospheric pressure and transported to an analysis device. The particle size of the fine particles is important because it affects the quantitative accuracy when analyzed by the emission spectrometer 39 that uses plasma as an excitation source, and in particular, it is necessary to make the particle size as small as possible and narrow the particle size distribution. When the fine particles generated in a steel sample by the apparatus of the present invention were investigated by electron microscopy, they were found to be extremely fine particles with a diameter of approximately 0.1 μm or less, the width of the particle size distribution was also relatively narrow, and plasma emission was observed. It was ideal for spectroscopic analysis. The most suitable conditions for obtaining evaporated fine particles with a fine particle size were to lower the pressure of the generated atmosphere, to not raise the heating temperature too high, and to use Ar, which has a small atomic weight, as the atmospheric gas. The method of installing the openings of the particulate transport pipe 15 of the present invention at regular intervals just above the surface of the center of the molten metal is such that coarse particles caused by splash generated by a secondary heating source such as a plasma arc fall due to their own weight. It was also found to be effective in adjusting the particle size of the particles so that they do not reach the conveying pipe 15.

The evaporated particulates are carried by the blown inert gas and enter the transport gas distribution device 17 through the transport pipe 15, and then pass through the transport pipe 15' again to the particulate collection pipe 20.
However, it is an important issue here that the particles do not remain attached to the inner walls of the conveyor pipes 15, 15', the distribution device 17, etc. When simply collecting the same evaporated fine particles, a small amount of residue is not a problem, but when analyzing fine particles to determine the amount of components in the original sample as in the present invention, it is difficult to transport the particles due to the attached residue. This may cause the concentration of fine particles in the gas to fluctuate or cause contamination of the next analysis sample, making it impossible to obtain accurate analysis values. When evaporated fine particles are conveyed in a slow, quiet flow or when the temperature decreases during conveyance, aggregation among the fine particles and adhesion to the wall surface tend to occur. Therefore, the diameters of the transport pipes 15, 15' are made as small as possible to increase the flow rate of the transport gas, the transport gas distribution device 17 is also made small, and heaters 16 are attached to these parts to heat them as shown in the figure. Do the following.
In addition, it has been found that evaporated fine particles once attached to the inner wall of the tube can be easily peeled off by blowing gas within a short time after attachment. Control valve 1
It was also effective to use the method of increasing the flow rate of the carrier gas and removing it by automatic switching operation in step 4.

The carrier gas distribution device 17 is a particulate collection pipe 2 that once diffuses the particulates sent in together with an inert gas from the transport pipe 15 in a space to make them more uniform.
The function is to adjust the flow rate of the carrier gas introduced into the system to an optimum value or to exclude coarse particles from the system, but these functions can be omitted if they are not necessary. The distribution device 17 has a heater 16 on the outer periphery.
Particle transport pipe 15 is a small diameter cylindrical pipe equipped with
is inserted from the side wall with the tube end facing upward, and the outlet side conveyor tube 15' is inserted into the conveyor tube 1 from the upper part of the cylindrical tube.
The carrier gas exhaust pipe 18 is installed vertically at a constant interval so as to face the end of the cylinder 5, and a carrier gas discharge pipe 18 equipped with a flow rate control valve 19 is installed at the bottom of the cylindrical pipe. Each of these tubes is a thin tube with a diameter of 10 mm or less. Coarse particles and distributed fine particles are discharged from the system through the bottom discharge pipe 18 together with excess carrier gas, and the remaining fine particles are discharged from the conveyor pipe 15' together with a constant flow rate of carrier gas.
The particles are introduced into the particle collection tube 20 through the .

The particulate collection tube 20 is a small diameter cylindrical tube with a solution supply tube 24 connected to a solution storage tank 22 and a constant flow pump 23 at the top, and a solution discharge tube 21 at the bottom.
A particle transport pipe 15' and a solution injection pipe 25 are attached to the side or top. The particulate collection tube 20 functions to collect particulates sent through the transport pipe 15' into a solution and introduce the collected particulates into the analyzer 39. There are several methods for collecting fine particles.
A method of injecting the solution into the collection tube 20 and then introducing it from the transport pipe 15' for a certain period of time to collect it. Generally, a method of continuously collecting fine particles can be adopted. The former has the advantage of being able to concentrate the fine particles, and the latter has the advantage of being able to transport the fine particles to an analyzer a certain distance away without causing any adhesion or residue by making the collecting tube 20 a long tube. Suitable solutions are those that do not interfere with plasma emission spectroscopy and are effective in dispersing fine particles, and suitable are aqueous solutions and organic solvents such as isopropyl alcohol and methyl isobutyl ketone. Further, in order to increase the dispersion effect, it is appropriate to attach an ultrasonic oscillator to the collection tube 20 or to use a dispersant together.

The fine particles collected in the solution are introduced into the analyzer 39 through the solution injection tube 25. The analyzer 39 may be an atomic absorption spectrometer or the like, but a solution emission spectrometer that can quantify multiple components simultaneously is most suitable. Among solution emission spectroscopy, the high frequency inductively coupled plasma emission spectrometer 39 is suitable because it has excellent quantitative accuracy and sensitivity. This device 39 includes an atomization device 26 connected to the solution injection tube 25, a sample introduction tube 27 connected to the atomization device, a plasma gas supply tube 28,
A plasma torch 30 consisting of a cooling gas supply pipe 29, a high frequency generator 31 attached to the upper part of the torch, a condensing lens 33 for the emission spectrum of the particulate component excited and emitted in the plasma section 32, a reflecting mirror 35, and a diffraction grating. Spectrometer 3 consisting of 36
4. Consists of a detector 37 that measures the spectral line intensity of each component, a content rate calculation device 38, and the like. Particulate collector 2 in which particulates are dispersed and collected
The solution in 0 is sucked through the solution injection tube 25 by the Ar gas blown into the atomization device 26 and atomized, and since the fine particles are fine particles with a particle size of 0.1 μm or less, they are injected into the plasma from the sample introduction tube 27. The sample is introduced into a torch 30 and excited to emit light, and the amount of each component in the sample is measured.

According to the present invention, the time required for analysis from inserting an analysis sample into a particle generator to generating particles and determining the content of each component in the sample is within about 5 minutes, and requires almost no manual effort. can be easily analyzed without In terms of quantitative accuracy, we were able to obtain good results comparable to those of spectrophotometric analysis, which involves dissolving the sample in mineral acid and requires a complicated and time-consuming operation. As explained above, the present invention has made it possible to perform simple and rapid direct emission spectroscopic analysis of small-sized metal samples, for which direct emission spectroscopic analysis has been difficult until now. In addition, in solid-state emission spectroscopy analysis using spark, arc, or glow discharge that targets block samples with a certain shape, in addition to the sample shape limitations, problems such as the metal structure and each component in the sample due to the heat treatment history of the sample have also been encountered. We were also able to solve problems such as a decrease in quantitative accuracy due to segregation.

The present invention enables easy, quick, and highly accurate measurement of each component contained in metal materials, which is essential for process control or quality control in the metal manufacturing industry, without being affected by sample shape, metal structure, or component segregation. The present invention provides a new analytical method and device for analysis, making a significant contribution to this field.

[Brief explanation of the drawing]

The drawings are explanatory diagrams of embodiments of the present invention. 1: Particulate generator, 2: Cylindrical tube for particulate generation, 3: Analysis sample, 4: Refractory crucible, 6: High frequency induction heating device, 7: Secondary heating device, 8: Crucible setting device, 15, 15': Particulates Transport pipe, 17: Transport gas distribution device, 20: Particulate collection pipe, 24: Solution supply pipe, 25: Solution injection pipe, 26: Atomization device,
30: Plasma torch, 34: Spectrometer, 39: Plasma emission spectrometer.

Claims (1)

[Claims] 1. A small metal sample piece is melted in a refractory crucible placed in a small-volume closed container by high-frequency induction heating of a primary heat source, and the sample is placed directly above or directly above the center of the surface of the molten metal. Vaporized metal fine particles are generated by energy irradiation from a high-energy secondary heating source from a position within a tilt angle range of up to 45 degrees around the vertical position, and the vaporized metal fine particles are blown into the sealed container. The particles are transported by a carrier gas through a particle transport tube to a particle collection tube equipped with a particle collection solution supply device, dispersed and collected in the solution in the particle collection tube, and the particle collection solution is injected. The excitation light is introduced into the plasma emission section of the emission spectrometer through the tube, atomization device, and introduction tube, and the excitation light generated in the plasma emission section is separated by the spectrometer of the emission spectrometer to obtain the spectral lines of each component. A direct dissolution emission spectroscopic analysis method for small metal samples, which is characterized by measuring the amount of each component contained in an analysis sample from the intensity. 2. A small refractory crucible to hold the analysis sample, a closed cylindrical tube with a small diameter and a vertical length that immediately surrounds the outer periphery of the refractory crucible, and a high frequency as a primary heating source installed on the outer periphery of the cylindrical tube in proportion to the height of the crucible. Induction heating device, for high-energy irradiation to generate evaporated metal fine particles, attached to the cylindrical tube at a position directly above the center of the molten metal surface in the crucible, or at an angle of inclination of up to 45°C around the position directly above it. a secondary heating device, a particulate carrier gas supply device equipped with a flow rate regulator and having an inlet at the bottom or top of the cylindrical tube; A crucible setting device that also serves as a counter electrode for the secondary heating device and is capable of keeping the cylindrical tube in a sealed state; one end opens vertically directly above the center of the molten metal surface in the crucible; A particulate generator comprising a particulate transport pipe connected to the particulate collection pipe described below; an end of the particulate transport pipe, a particulate collection solution supply device, a discharge pipe for the solution, and a particulate collection solution injected into the plasma light emitting device described later. a particulate collection tube consisting of a container fitted with a particulate collection solution injection pipe for the purpose of A plasma emission spectrometer comprising: an atomizer having a plasma excitation source, a plasma light emitting device having a plasma excitation source, a spectrometer, a detector, a component content calculation device, etc.; Spectroscopic analyzer.