JPH0150854B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is most commonly used in the metal manufacturing industry, etc., and instead of solid-state emission spectrometry that targets a sample piece of a fixed shape, it can be used to analyze sparks without taking a sample piece. The present invention relates to an emission spectroscopic analysis method and apparatus in which a sample is evaporated as fine particles by electric discharge or the like and directly analyzed.

In the metal manufacturing industry, analysis of the main components and trace components contained in metals and alloys is essential for the manufacturing process of metals and alloys or for quality control of products. For this analysis, a high voltage is applied between the metal sample piece and the counter electrode to cause a spark or arc discharge, and each component in the sample is determined from the spectral line intensity of the excitation light based on each vaporized component. Solid-state emission spectrometry, which determines the content of , is most commonly used.

However, this analysis method is subject to certain limitations on the sample shape due to the structure of the device that generates the discharge, and the sample size is usually 15 mmφ.
A sample piece with a flat surface equal to or greater than that must be prepared.

However, in the metal manufacturing process, when cutting out a sample piece requires considerable effort and time,
It is often difficult to collect sample pieces, such as when it is desired to avoid sample collection for products as much as possible, or when a quick online analysis is required during the manufacturing process. For these reasons, there is a strong demand for the development of a new analytical device that can easily and quickly directly analyze metal plates, square timbers, bars, etc. without collecting samples for analysis. There is also a similar demand for emission spectroscopic analysis of ceramics, minerals, etc., which uses a laser or the like as an excitation source instead of an electric discharge such as a spark.

In view of this need, the present invention vaporizes an analysis sample as fine particles using a spark, arc, plasma arc, laser, electron beam, etc. as a heating source,
Based on the basic principle of long-distance transport using inert gas and plasma emission spectroscopic analysis, we provide a new analytical method and device that allows for direct, simple, rapid, and highly accurate analysis without collecting sample pieces. be.

The present invention will be explained in detail based on the embodiment of the present invention shown in FIG.

FIG. 1 shows a case in which spark discharge is used as an evaporation heating source for generating fine particles for a metal material.

The device of the present invention can be roughly divided into a particle generator 2,
It is basically constructed of a carrier gas flow rate switch 6, a particle transport pipe 9, a carrier gas distribution device 11, and a plasma emission spectrometer. The particle generator 2 applies a high voltage between the surface of the analysis sample 1 and the counter electrode 4 to generate a spark discharge, heats the sample surface locally to a high temperature, and evaporates the particles representative of the composition of the sample in the form of smoke. This is the part that functions to Usually, the counter electrode 7 is a tungsten round rod with a sharp tip and a diameter of about 2 to 5 mm.This is used as the positive electrode, and the sample electrode 5, which is brought into contact with the sample surface by a spring mechanism, is used as the negative electrode, and is connected to the spark discharge device. do.

Spark discharge conditions affect the analysis accuracy, that is, the precision of particle generation, but the conditions that lower self-induction and increase the discharge current value, for example, self-induction 10 μH, capacitance 3 μF, resistance 1 Ω, voltage 1000 V, frequency 200 Hz.
The discharge conditions were appropriate.

The main body of the particle generator 2 is made of a cylinder 21 made of an insulating heat-resistant material such as boron nitride or fluorine resin. The bottom of the cylinder 21 is open, and a disk 22 made of fluorine-based heat-resistant insulating resin or rubber is attached to the end face. By pressing the cylinder 21, it comes into close contact with the surface of the sample 1 and removes the external The atmosphere is shut off, and the small space chamber 3 inside the cylinder 21 is in a sealed state.

The counter electrode 4 is attached to the top of the cylinder 21 so as to face the sample surface, and the distance between the tip of the counter electrode and the sample surface is usually constant in the range of 5 to 10 mm. The setting accuracy of the electrode spacing must be kept within ±2 mm; if this range is exceeded, the amount of fine particles produced will fluctuate and the analysis accuracy will decrease. The inside of the cylinder 21, where the lower part of the counter electrode 4 is located, has a diameter of 10 to 15 mmφ and a height of 30 mm.
A small space chamber 3 is dug in which a certain amount of spark discharge occurs.

The small space chamber 3 has an inert gas supply port 7 such as Ar and a particulate discharge port 8, but is in a sealed state that is reliably isolated from the atmosphere. The particulate discharge pipe 23 is a pipe containing the counter electrode 4, and its end is connected to the particulate transport pipe 9, and the other end is located slightly above the tip of the counter electrode 4 and serves as a particulate discharge port 8. Ar
The gas is sent into the small space chamber 3 from the supply port 7 provided in the outer peripheral gap of the particle exhaust pipe 23, and the generated particles are discharged to the particle exhaust port 8.

The structure and positional relationship of the gas supply port 7 and the particulate discharge port 8 are appropriate for efficiently discharging particulates from the small space chamber with less diffusion. Ar gas uses a pressure reducing valve, an on-off valve, and an on-off valve to change the flow rate intermittently.
The gas is fed into the gas supply port 7 from the gas flow rate switch 6, which is comprised of a flow rate regulator or the like. Switching the gas flow rate is necessary for transporting fine particles, but
Details will be described later.

As described above, the particle generating device 2 is small, lightweight, and portable, and can be carried to the location where the analysis sample 1 is present and analyzed by pressing it against the surface of the sample.

In FIG. 1, spark discharge is used as a heating source for vaporizing the sample into fine particles, but arc discharge, plasma arc, laser beam, electron beam, etc. can be used as the heating source. These are used depending on the purpose, such as the type of sample to be analyzed and the analysis position in the depth direction from the sample surface.

The particulates introduced into the particulate discharge port 8 are carried by the Ar gas flow through the particulate transport pipe 9 to the carrier gas distribution device 11 . Unlike the case where fine particles are simply generated, the present invention allows evaporated fine particles to be constantly and stably delivered to the analyzer together with a carrier gas at a constant flow rate.
0, and an efficient particle transport technology is required. In particular, it is important to prevent fine particles from adhering to and remaining on the inner wall of the conveying tube as much as possible and to remove the remaining particles.

When utilizing the present invention for manufacturing process management and product check analysis, the plasma emission spectrometer must be housed in an air-conditioned building;
Due to the measurement environment such as vibration and dust, the number of fine particles is small.
Must be transported over a long distance of 10m. As the transport distance becomes longer, fine particles tend to remain attached to the inner wall of the transport pipe, causing fluctuations in the fine particle concentration in the transport gas and contamination, making it impossible to obtain accurate analysis values.

The fine particles generated by spark discharge on steel materials are very fine spherical particles of 0.1 μm or less, but they tend to adhere to the inner wall of the pipe when they are transported at low speeds, especially when they come into contact with low-temperature parts. It has the property of becoming easier. Further, fine particles attached to the inner wall of the pipe have a property that they can be easily peeled off by blowing gas on them within a short period of time after attachment. Therefore, the fine particles generated in the small space chamber 3 are transported through the transport pipe 9 by supplying Ar gas at a high flow rate. In order to increase the flow rate of the carrier gas, it is appropriate to use a thin tube with a diameter of about 2 to 5 mm, and to suppress adhesion, it is appropriate to attach a heating device 10 to the outer wall of the tube for constant heating.

Even if such measures are taken, it is impossible to reliably prevent fine particles from remaining attached, and a removal operation is required. As a result of various experiments, fine particles adhering to the inner wall of the tube can be removed by blowing Ar gas at a high flow rate rather than by blowing Ar gas at a high flow rate, then temporarily stopping Ar gas blowing or reducing the flow rate to a very low rate. Then return to high flow rate and blow in again. It has been found that by repeating these operations, it can be removed more reliably and in a shorter time.

That is, rather than keeping the Ar gas flow blown at a constant flow rate, it is more effective to change the flow rate intermittently to add a pulsating shock to the Ar gas flow. In addition, the Ar gas flow rate needs to be blown at a high flow rate at the start of the analysis in order to drive out the atmosphere remaining in the small space chamber 3. These flow rate switches of Ar gas are controlled by a carrier gas flow rate switch 6.

In this example, the transport tube used had an inner diameter of 3 mmφ and a length of 40 m. After pressing the particle generator 2 against the sample surface 1, Ar gas was blown in at 15 l/min for 15 seconds.
Next, switch to 5l/min and start spark discharge.
The first 10 seconds are a preliminary discharge, and then the plasma emission intensity of the particles generated by the discharge for 10 seconds is measured as an integral value. Immediately after that, switch the Ar gas flow rate to 15l/min and blow in for 3 seconds, then
Stop the Ar gas flow rate for 2 seconds, then increase it again to 15 l/min for 3 seconds.
Blow in for seconds. This procedure was repeated three times to ensure that the remaining fine particles in the tube were removed. As a result, Si, Mn, and
It was possible to analyze trace components such as P and S in a short time and with high precision.

The carrier gas distribution device 11 once diffuses the fine particles sent by the carrier gas from the carrier pipe 9 in a small space to further make them uniform. plasma torch 15
In order to obtain the optimum flow rate of the carrier gas introduced into the system, the carrier gas is distributed by discharging a certain portion out of the system.
Alternatively, while being transported, particles that have become coarse due to progressing aggregation are removed from the system, and particle size separation is performed to send only fine particles to the plasma torch 15.

The distribution device 11 is a small-diameter cylindrical tube, and the conveying tube 9 is inserted from the side wall, the tube end opening faces upward, and the particle introduction tube 14 is attached to this opening so as to face each other at a constant distance from the top. A discharge pipe 12 equipped with a flow rate regulator 13 is attached to the bottom of the pipe. These three pipes are all thin tubes with a diameter of 10 mm or less, and coarse particles, excess fine particles, and carrier gas are discharged out of the system from the bottom discharge pipe 12, and the remaining fine particles are sent to the inlet pipe 14 along with a constant flow of carrier gas. be introduced.

The particle introduction tube 14 is connected to a plasma emission spectrometer 20 . The introduced fine particles are carried to the plasma torch 15, and the high temperature plasma part 1
6 and is excited to emit light. The excitation light is a spectrometer 17
a detector 18 consisting of a photomultiplier tube;
The component content calculation device 19 measures the intensity of each spectral line, and the content of each component in the sample can be quickly determined.

Although a high-frequency inductively coupled emission spectrometer is most suitable as the analyzer 20 for exciting the particles to emit light, other types of plasma-excited emission spectrometers such as arc discharge or atomic absorption spectrometers can be used.

As explained above, according to the present invention, the components contained in various samples can be directly analyzed quickly and accurately without performing any sampling or other operations, and is particularly effective for manufacturing process control of metals and product check analysis. is large.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of an embodiment of the present invention. 1...Analysis sample, 2...Particle generator, 3...
...Small space chamber, 4...Spark counter electrode, 5...Sample electrode, 6...Carrier gas flow rate switch, 7...Gas supply port, 9...Particle exhaust port, 9...Particle transport pipe, 10... ... Heating device, 11 ... Carrier gas distribution device, 14 ... Particle introduction tube, 15 ... Plasma torch, 20 ... Plasma emission spectrometer.

Claims (1)

[Claims] 1. A sample surface located at the bottom of a small space formed by blocking the atmosphere is locally heated to a high temperature with energy selected from sparks, plasma arcs, lasers, electron beams, etc. to generate fine particles. The fine particles are transported through a long thin tube to a plasma emission spectrometer using an inert gas, and the amount of each component in the sample is measured from the emission intensity of each wavelength. Immediately after completion of the process, the inert gas is blown into the tube at a high flow rate, then stopped, and the fine particles remaining on the inner wall of the tube are peeled off and removed by repeating the process of blowing in at a high flow rate, and the next sample is analyzed. A long-distance particle transport plasma emission spectroscopic analysis method characterized by: 2 At the top, a heating device using energy selected from spark, plasma arc, laser, electron beam, etc. is installed with the tip facing the sample surface, and a particulate carrier gas supply port and particulate discharge port are connected to the flow rate switch. and a small-diameter elongated device having one end connected to the above-mentioned particle discharge port and the other end connected to the carrier gas distribution device; a particle transport pipe; a carrier gas distribution device that is attached to the end of the transport pipe, a particle introduction pipe, and a surplus gas discharge pipe equipped with a flow rate regulator; a plasma that connects the distribution device with the particle introduction pipe; What is claimed is: 1. A plasma emission spectrometer for long-distance transport of fine particles, characterized in that it is comprised of an emission spectrometer.