JPH0354461A - Quick analysis of trace of carbon and sulfur in metallic sample - Google Patents

Abstract

PURPOSE:To rapidly determine carbon and sulfur on a ppm order by collecting fine particles composed of metallic sample components by a filter and oxidizing and burning the same to form gaseous oxides and concentrating the same to determine carbon and sulfur. CONSTITUTION:The surface of a metallic sample S is heated by the spark discharge of an electrode 3 to evaporate fine particles. The fine particles are carried by the gas stream from an inert gas (Ar) supply source 2 to be supplied to a filter 4 and collected on filter paper 5. The fine particles are heated by an electricx heater 6 and burnt in the presence of O2 supplied from an oxygen supply source 7 to form oxides. That is, C in the fine particles is changed to CO2 and S therein is changed to SO2. Since these oxides are in a gaseous state, they can be easily conc. by a concn. column 8. CO2 is introduced into a hydrogen flame ionizing detector through a gas reducing apparatus to be detected with high sensitivity. SO2 is detected by a flame luminous intensity detector. The respective detection signals are sent to a data processing part and the contents of carbon and sulfur in the sample S are calculated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an analytical method that can rapidly quantify trace amounts of carbon and sulfur in metal samples.

This invention is utilized in the field of manufacturing process control analysis and quality control analysis in the steel industry or various non-ferrous metal manufacturing industries.

[Prior art] Metal refining. To manage operations such as steel-making processes, it is necessary to collect samples from molten metal, analyze them to determine the component content as quickly as possible, and take appropriate actions based on the results. For example, in a steel manufacturing process, the time from sample collection to obtaining analytical results is typically 5 to 6 minutes. Highly accurate and rapid analysis is also required for product verification. Among the components to be analyzed, carbon and sulfur are important components in determining quality, especially in steel manufacturing.

As a method for rapidly analyzing the above-mentioned carbon and sulfur, there is a technique disclosed, for example, in Japanese Patent Application Laid-open No. 157541/1983. In this analysis method, the surface of a molten metal is heated by spark discharge in an inert gas stream to evaporate and generate fine particles made of metal components. The generated fine particles are then pneumatically conveyed through a transport tube to an emission spectrometer, and multiple elements including carbon and sulfur are simultaneously quantified by emission spectrometry.

Further, as another method for rapidly analyzing carbon and sulfur, there is a technique disclosed in Japanese Patent Application Laid-Open No. 61-65154. In this analysis method, a spark discharge is applied to the analysis sample in an inert gas atmosphere mixed with oxygen gas. By providing energy from arc discharge, plasma arc discharge, or laser beam irradiation, carbon and sulfur components contained in the analysis sample are excited and converted into gaseous oxides. Then, these oxide gases are introduced into a hydrogen flame, and the ionic current of the carbon component and/or the emission intensity of the sulfur component are measured to determine the content of each element in the sample.

[Problem M to be Solved by the Invention] Recently, as products have become more sophisticated, high-grade steel materials containing trace amounts of high-purity metals, such as carbon, have been developed. For this reason, there is a demand for analyzing carbon and the like on the order of ppm. In addition, in order to use the analysis results for manufacturing process control and quality control, online analysis is required and the analysis must be completed in a short time.

However, in the rapid analysis method disclosed in JP-A-59-157541, fine particles are subjected to emission spectroscopic analysis in an inert gas stream, and high sensitivity cannot be obtained. Furthermore, in the rapid analysis method disclosed in JP-A No. 81-65154, since the arc is generated in an inert gas atmosphere mixed with oxygen gas, the arc becomes unstable, and it is difficult to obtain high sensitivity similar to the above-mentioned rapid analysis method. I couldn't. Therefore, with these conventional rapid analysis methods, it has been impossible to rapidly quantify carbon and sulfur on the order of ppm.

Incidentally, the spark emission spectroscopy has a short analysis time but lacks sensitivity, and the combustion-infrared absorption method has an excellent sensitivity but has the problem of requiring a long analysis time.

Therefore, this invention reduces carbon and sulfur in metal samples to pp.
The purpose is to provide an analysis method that can rapidly quantify on the order of m.

[Means for Solving the Problems] The rapid analysis method for trace amounts of carbon and sulfur in a metal sample of the present invention heats the surface of the metal sample in an inert gas stream to generate fine particles made of metal sample components. The generated particulates are collected by a filter, and the collected particulates are oxidized and burned to produce gaseous oxides. Then, the gaseous oxide is concentrated, and then one or both of carbon and sulfur in the concentrated gaseous oxide is quantified.

As shown in FIG. 1, an inert gas is supplied from an inert gas supply source 2 to a sealed portion 1 leading to a filter 4 to control the inert gas flow. Use argon, helium, nitrogen gas, etc. as an inert gas. The inert gas flow has a flow rate sufficient to transport the generated particulates to the filter 4. Since it is necessary to rapidly heat the sample surface to evaporate fine particles, the means for heating the sample surface are those with high energy density, spark discharge, and arc discharge. Plasma beam irradiation, laser beam irradiation, etc. are used. FIG. 1 illustrates an electrode 3 that forms a spark discharge. Plasma beam irradiation may be of either a transfer type or a non-transfer type. In order to collect sample components uniformly, it is desirable to make the heating area as large as possible.The area for laser beam irradiation is small, but for spark discharge, for example,
mmφ, and plasma arc discharge can heat a wide area of 15 mmφ.

The filter 4 uses filter paper 5 made of heat-resistant fibers such as glass fibers. The fine particles adhering to the filter paper 5 are heated by an electric heater 6, and oxygen is supplied from an oxygen supply source 7 to burn them.

A concentration column 8 is used to concentrate gaseous oxides generated by combustion. Molecular sieves (registered trademark for synthetic fluorite), activated carbon, and others are used as adsorbents in the concentration column.

A detector or analyzer 9 such as a hydrogen flame ionization detector, a flame photometric detector, or an inductively coupled plasma emission analyzer is used to quantify the condensed gaseous oxide. A flame ionization detector is used to detect carbon, and a flame photometric detector is used to detect sulfur.

Note that the metal sample may be in a solid or molten state.

[Function] By heating the surface of the metal sample to a high temperature, fine particles consisting of the metal sample components evaporate. The particle size of the fine particles is 0,0
It is about 1 to 0.1 μm. Particulates generated by evaporation are carried to the filter by the inert gas flow and collected on the filter. The particulates are very active, and when oxygen is supplied, or when the filter is heated and oxygen is supplied, the particulates burn to form oxides. That is, through oxidation, carbon changes to carbon dioxide gas, and sulfur changes to sulfur dioxide gas. Since oxides are in a gaseous state, they can be easily concentrated using a concentration column. Since gaseous oxides are concentrated, they can be quantitatively analyzed with high sensitivity and precision.

[Example 1] Quantitative analysis of trace carbon in a steel sample will be described below as an example.

FIG. 2 schematically shows an example of a trace carbon quantitative analysis apparatus for carrying out the method of the present invention.

The bottom of the cylindrical discharge chamber 11 is made of a heat-resistant insulating material, and a counter electrode 12 made of tungsten is vertically attached thereto. The top of the discharge chamber 1l serves as a mounting portion for the analysis sample S. The counter electrode 12 has a spark discharge power source l.
3 is connected. Further, an argon gas cylinder 17 and a gas purifier 18 are connected to the bottom of the discharge chamber I1 via a pipe 19.

A filter 25 is connected to the top of the discharge chamber l1 via a pipe 21.
is connected. Filter 25 is glass fiber filter paper 2
6 and an electric heater 27 are built in. Also, piping 2
1 is provided with a switching valve 23, where a switching pipe 30 is connected.
An oxygen gas cylinder 28 and a gas purifier 29 are connected via.

The outlet side of the filter 25 is connected to a gas concentrator 34 via a pipe 32.
is connected. The gas concentrator 34 is a copper oxide column 35
, molecular sheep force ram 40 and electric heater 42
It is equipped with A switching valve 38 is attached to the piping 37 on the outlet side of the copper oxide column 35. One outlet of the switching valve 38 is connected to the molecular sieve power ram 4 via a pipe 39.
0, and the other outlet is open to the atmosphere. A switching valve 44 is attached to the outlet piping 4l of the molecular sieve force ram 40. The switching valve 38 and the switching valve 44 are in communication via a pipe 45. The switching valve 44 is connected to an argon gas pump 4 via a pipe 48.
6 and a gas purifier 47 are connected.

A gas reduction device 54 is installed in the piping 50 on the outlet side of the switching valve 44.
Or it is not connected. The gas reduction device 54 converts carbon dioxide into methane using hydrogen gas using nickel as a catalyst.

A hydrogen flame ionization detector 56 is installed on the outlet side of the gas reduction device 54.
is connected. Flame ionization detector (FID) 5
6 is a detector commonly used in gas chromatographs, which ionizes analytical components using a hydrogen flame as an excitation source.
Measure the ionic current.

Since carbon dioxide cannot be measured by the flame ionization detector 56, a gas reduction device 54 in which a nickel catalyst is heated as described above is placed in front of the flame ionization detector 56. The carbon dioxide gas is separated into methane and introduced into the hydrogen flame ionization detector 56, where it is detected with high sensitivity. The detection signal is sent to the data processing unit 59, where the peak height or peak area of each component is determined, and the carbon content in the steel sample is calculated based on a calibration curve determined in advance using a steel standard sample. be done. A gas vent 57 is connected to the outlet side of the hydrogen flame ionization detector 56.

Here, a method for analyzing trace carbon in an analysis sample using the apparatus configured as described above will be described. The analysis sample was obtained by preparing molten steel collected in a converter into a small disk shape with a diameter of 30+ nm using a well-known sample preparation machine.

The analysis sample S is placed on the top of the discharge chamber 1l so as to close the top opening of the discharge chamber II. In order to keep the discharge chamber II airtight, the analysis sample S is held in a pressed state with a jig (not shown) via a heat-resistant resin O-ring 15. The # electrode and the anode of the spark discharge power supply device 13 are connected to the analysis sample S and the counter electrode 12, respectively.

While setting the analysis sample S as described above, the switching valve 38 is set so that the argon gas flows along the broken line in FIG.
．． 44. Then, the switching valve 23 is switched to open the argon gas cylinder 17, the discharge chamber 1], the piping 21, the cut frame fr-23, the filter 25, and the piping 32. Argon gas is passed through the copper oxide column 35, piping 37, and switching valve 38 to exhaust and remove the atmosphere remaining in these devices and piping. Also, from the argon gas cylinder 46 to the piping 48, the switching valve 44, the piping 41, the molecular sieve force ram 40. Piping 39. Switching valve 38, piping 45.
Argon gas is also made to flow through the switching valve 44, piping 50, gas reduction device 54, and hydrogen flame ionization detector 56, and the atmosphere remaining in these devices and piping is discharged and removed.

Next, after the pre-flushing is completed as described above, argon gas is again circulated from the discharge chamber l1 to the outlet of the switching valve 38. The flow rate of argon gas is 0.
5IL/min. In this state, a high voltage is applied between the surface of this analysis sample and the tip of the counter electrode l2,
Produces an electrical spark discharge.

The spark discharge conditions are: the spark discharge circuit constant is self-induction 10μH, #% capacitance 3μF, resistance 0Ω, and the voltage is IO
OOV, frequency is 100 to 400 Hz, and interelectrode gap is about 446 mm. Iron in the sample is removed by spark discharge. manganese. Silicon, carbon. Elements such as sulfur and phosphorus are excited, but they form particles together within a very short time. These particles are extremely fine ultra-fine particles of about 0.01 μm in size, and their composition is close to that of the original steel sample, although it depends on the circuit constant of the spark discharge.

The generated particles are carried to the filter 25 by the argon gas flow and adhere to the filter paper 26 of the filter 25. Next, the switching valve 23 is closed, the switching valves 38 and 44 are switched so that the gas flows along the solid line in FIG. Then, by switching the switching valve 23, oxygen gas is supplied from the oxygen gas cylinder 28 to the filter 25. As a result, the carbon in the particles is combusted, most of which becomes carbon dioxide gas, and some of which becomes carbon monoxide gas, and the sulfur becomes sulfur dioxide gas, and these gaseous oxides flow into the gas concentrator 34.

In addition, iron, manganese, silicon, etc. are also oxidized, and fine particles of these oxides remain attached to the filter paper 26 as they pass through the filter 25.
remain in the Among the gaseous oxides that have flowed into the gas concentrator 34, carbon monoxide gas is oxidized to carbon dioxide gas in the copper oxide column 35. Carbon dioxide gas and sulfur dioxide gas are adsorbed by the adsorbent (molecular sieve) of the molecular sieve force ram 40.

Next, the molecular sieve column 40 is heated to 340° C. by the electric heater 42, and the switching valve 38 is switched so that the gas flows along the solid line in FIG. When argon gas is supplied from the argon gas bombay 6 to the molecular sieve column 40, concentrated carbon dioxide gas and sulfur dioxide gas are desorbed from the adsorbent. The released carbon dioxide gas and sulfur dioxide gas are transferred to the switching valve 38 and piping 4.
5, the waste reduction device 5 via the switching valve 44 and piping 50
4 and is introduced into a hydrogen flame ionization detector 56. Carbon dioxide gas is reduced to methane gas, which is detected by a hydrogen flame ionization detector 56, and a data processing section 59 calculates the carbon content in the steel sample.

When the analysis of one sample is completed, as described above, argon gas is passed through the equipment and piping to wash away the evaporated particles, gaseous oxides, etc. of the analysis sample remaining therein. Note that the filter paper 26 of the filter 25 was replaced approximately every 30 analyses.

The quantitative analysis of carbon in a sample has been described above, but in order to simultaneously quantify sulfur, for example, a distribution valve is provided between the switching valve 44 and the hydrogen flame ionization detector 56 in the above apparatus. A flame photometric detector (FPD) is then connected to one outlet side of the distribution valve. In other words, the carbon analysis line and the sulfur analysis line are placed in parallel. A flame photometric detector measures an emission spectrum obtained by causing an analytical component to emit light using a hydrogen flame as an excitation source. Flame photometric detectors have high sensitivity selectively for phosphorus and sulfur compounds, but sulfur has a wavelength that exhibits maximum intensity around 400 nm, so selection is performed using an interference filter that passes this wavelength range well. , measure each spectral intensity with a photomultiplier tube. The sulfur content in the steel sample is calculated from the measured spectral intensity based on a calibration curve determined in advance using a steel standard sample.

When the aforementioned general low-pressure spark discharge is applied to a steel sample, one pulse of discharge reduces the steel sample's approximately tALg.
is excited and evaporates. When a frequency of 200 Hz is employed, approximately 12 mg of the sample is evaporated per minute, and for example, all of the 10 ppm of carbon and sulfur in the steel sample is collected in the filter. The carbon dioxide gas and sulfur dioxide gas produced by oxidative combustion are concentrated in the column, and when they are desorbed and released by the carrier gas, their concentration becomes quite high, so that extremely small amounts can be quantified. Therefore, the provisions of this Act M
The sensitivity is extremely high, and trace amounts of carbon and sulfur of about 10 ppm in steel can be sufficiently determined. Further, if necessary, it is also possible to measure only one of carbon and sulfur. According to this invention, analysis can be performed in a short time of about 1 minute after setting the sample in the oxide generating section.

Although the above description has been made using a steel sample as an example, the present invention can also be applied to various non-ferrous metals, minerals, ceramics, etc. in addition to iron samples.

[Effects of the Invention] According to the present invention, although the elements to be analyzed are limited to carbon and sulfur, these elements can be rapidly quantified on the order of ppm. In addition, since the analysis targets the main elements of carbon and sulfur, which are the most important elements for quality evaluation of metals, etc., it is extremely effective for operational management of metal refining and manufacturing processes.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an apparatus for carrying out the present invention, FIG. 2 is a block diagram schematically showing an apparatus for quantifying trace carbon, and FIG. 3 is a drawing showing the flow of gas in a gas concentrator. DESCRIPTION OF SYMBOLS 1... Sealed part, 2... Inert gas source, 3... Electrode, 4... Filter, 5... Filter paper, 6... Electric heater, 7... Oxygen supply source, 8 ...Concentration power ram, 9...
・Quantitative analyzer, 1l...discharge chamber! 2...Counter electrode,
13... Spark discharge power supply, l7... Argon gas cylinder, 23... Switching valve, 25... Filter,
2 8-...Oxygen gas cylinder, 34...Gas concentrator,
35...Copper oxide column, 3 8-...Switching valve, 40
...Molecular sieve power ram, 42...Electric heater, 44...Switching valve, 46...Argon gas cylinder, 54...Gas reduction device, 56...Hydrogen flame ionization detector, S- ...Analysis sample.

Claims (1)

[Claims] 1. In a method in which the surface of a metal sample is heated in an inert gas stream to evaporate the metal sample components, and the fine particles generated by the evaporation are quantitatively analyzed for carbon and sulfur, the fine particles are collected using a filter. A method for rapid analysis of trace amounts of carbon and sulfur in a metal sample, which comprises: generating gaseous oxides by burning the fine particles, concentrating the gaseous oxides, and then quantifying the concentrated gaseous oxides.