JPH0367170A - Analysis method for trace amounts of carbon, sulfur, and phosphorus in metal samples - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for rapidly quantitatively analyzing carbon, sulfur, phosphorus, etc. in metal acid J'+.

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

[Junto technology] To manage operations such as metal refining and steel manufacturing processes, we collect samples from molten metal, analyze them to understand the component content as quickly as possible, and take appropriate actions based on the results. There is a replacement. 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, sulfur, and phosphorus are important components that determine quality, especially in steel manufacturing.

For example, as a method for quantitatively analyzing trace carbon,
There is a ``method for determining carbon in metals'' disclosed in Japanese Patent No. 6-10251. In this method, a metal sample is heated in a hydrogen stream, and the carbon in the sample is produced as methane, which is then extracted. The extracted methane is transported by a hydrogen stream and burned together with hydrogen gas at the end of the pipe, and the JA element ionized by the combustion is detected and quantified. However, in this method, the metal sample must be made into particles of 40 to 50 μm, and it takes time to prepare the sample. In addition, the sample must be heated for a long time (1 hour in the example described in the above publication). Therefore, it has been difficult to feed back the results of one analysis to the manufacturing process for operational management. In addition,
As a method for quantifying trace amounts of sulfur, JP-A-56-1025
There is a "method for determining sulfur in metals" disclosed in Publication No. 2. This method also requires a long time to quantify sulfur.

To solve this problem, for example, there is a method for rapidly analyzing carbon and sulfur disclosed in Japanese Unexamined Patent Publication 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.

Furthermore, as a method for rapidly analyzing carbon, sulfur, and phosphorus, there is a technique disclosed in Japanese Patent Application Laid-Open No. 60-233538. In this analysis method, energy is applied to the analysis sample by spark discharge, arc discharge, plasma arc discharge, or laser beam irradiation in an inert gas atmosphere mixed with hydrogen gas or a hydrogen gas atmosphere. It excites the carbon, sulfur, and phosphorus components contained in the water and transforms them into gaseous hydrides. Then, these hydrides are introduced into a hydrogen flame, the emission intensity or conductivity of each element is measured, and the content of each element in the sample is determined.

[Problems 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. 60-233538, the arc is generated in an inert gas atmosphere mixed with hydrogen gas or in a hydrogen gas atmosphere, which makes the arc unstable. It was not possible to obtain high sensitivity. 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 aims to investigate carbon and sulfur in metal samples.

The purpose of this invention is to provide an analysis method that can quantify phosphorus on the order of pp+uppm.

[Means for Solving the Three Problems] The method of analyzing trace amounts of carbon, sulfur, and phosphorus in a metal sample according to the present invention heats the surface of the metal sample in an inert gas stream to evaporate the metal sample components. The generated particulates are sent to a filter by an inert gas flow and collected, and the inert gas flow is stopped and the collected particulates are heated. Next, hydrogen gas is supplied to the heated fine particles to generate gaseous hydrides of carbon, sulfur, or phosphorus in the sample, and the gaseous hydrides are flowed into a gas concentrator where they are concentrated and the hydrogen gas is discharged. Replace with inert gas. Then, the concentrated gaseous hydride is sent to a gas analyzer using an inert gas stream, and the gaseous hydride is quantified. Trace carbon, sulfur, and phosphorus may all be analyzed simultaneously, or any one or two of these elements may be analyzed.

To create an inert gas stream, an inert gas source is supplied to the filtered seal from an inert gas source. Argon, rhium, nitrogen gas, etc. are used as the inert gas. The inert gas airflow should be sufficient to blow the generated particulates to the filter1.The first stage of heating the sample surface needs to rapidly heat the sample surface to evaporate the particulates. Because of its high energy density, it is used for things with high energy density, such as spark discharge, arc discharge, plasma beam irradiation, and laser beam irradiation. 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 2 as large as possible.For laser beam irradiation, the area is small, but for spark discharge, for example, 8
mmφ, plasma arc discharge can heat a wide area of 15ma+φ.

The filter uses a filter paper made of heat-resistant LA fiber such as glass fiber. To heat the fine particles (Nt) attached to the filter paper, for example, an electric heater is used.

Hydrogen gas is supplied to the heated fine particles t from a pressurized hydrogen gas source passed through a filter. , the amount of hydrogen gas supplied is the same as the one required for analysis due to the recoil from the heated particles.
t of gaseous hydride is generated at a flow rate sufficient to send the previously generated gaseous hydride to the gas concentrator.

For concentrating the generated gaseous hydrides, conventional cold traps, concentrating columns, etc. are used.

Molekieran Lube (registered trademark for synthetic fluorite), activated carbon, and others are used as adsorbents in the concentration column.

Alcon, helium, nitrogen gas, or the like is used as an inert gas to replace hydrogen gas and send the concentrated gaseous hydride to the gas analyzer.

A gas analyzer for determining concentrated gaseous hydrides is equipped with a detector or analyzer such as a semiconductor gas sensor, a hydrogen flame ionization detector, a flame photometric detector, or an inductively coupled plasma emission analyzer. A water-collecting flame ionization detector is used to detect carbon, and a flame photometric detector is used to detect sulfur and phosphorus.

Note that the metal sample may be in a solid or molten state. The solid metal sample used is in the form of a plate or block. For example, in the steel manufacturing process, molten steel in a converter is sampled using a sub-lance, and a sample is prepared using a sample preparation machine into a disk with a diameter of 30 mm.

[Function] □ By heating the surface of the sample to a high temperature, fine particles consisting of metal sample components evaporate. The village diameter of fine particles is 0,0
It is about 1 to 0.1 μm. The fine particles generated by evaporation are carried to the filter by the inert gas flow and collected on the filter. The heated granules-f are very active and when hydrogen gas is supplied, the metal sample components react with the hydrogen gas to form gaseous hydrides. That is,
Carbon in the metal sample reacts with hydrogen to form methane ((:114
), sulfur becomes hydrogen sulfide (II25), and phosphorus becomes phosphine (pH, +1).The composition of the mixed gas consisting of the generated gaseous hydride is substantially the same as that of the original analysis sample. Equal.The generated gaseous hydride flows into the gas concentrator together with the hydrogen gas stream and is concentrated there.Since the hydride is in a gaseous state, it can be easily concentrated in the gas concentrator.Concentration The gaseous hydride thus obtained is transported by an inert gas to a gas analyzer and analysed.Since the gaseous hydride is concentrated, it is analyzed with high sensitivity and accuracy.

[Example] Hereinafter, as an example, a case 1ξ in which fine milk carbon, sulfur Zti, and carbon dioxide in a steel sample are simultaneously determined will be described.

FIG. 1 schematically shows an example of the L analyzer R for carrying out the method of the present invention.

The lower part of the cylindrical discharge chamber II is made of heat-resistant insulating material PI, and a counter electrode 12 made of tungsten is vertically attached thereto. The top of the chamber 11 serves as a mounting area for the analysis sample S. A spark discharge type fi+3 is connected to the counter electrode 12. In addition, there is piping at the bottom of the discharge chamber 11! An argon gas phone \17 and a gas purifier 18 are also connected via 9.

A filter 2 is connected to the top of the discharge chamber 11 via a pipe 21.
5 is connected. The filter 25 includes a filter paper 26 made of glass fiber Mt and an electric heater 27. In addition, a valve 23 is provided in the pipe 21, and a hydrogen gas cylinder 28 and a gas cleaner N29 are connected thereto via the pipe 30.
is connected.

A gas concentrator 32 is connected to an outlet pipe 31 of the filter 25 . The gas concentrator 32 consists of a cold trap and is cooled! It includes an fI 33 and a cooling pipe 34 inserted therein. The cooling jfI 33 is filled with liquid nitrogen 35. Cooling pipe 34 of gas concentrator 32
Since the condensation temperature of methane, hydrogen sulfide and phosphine flowing into the tank is higher than that of liquid nitrogen, they are cooled by liquid nitrogen and condensed.

On the other hand, since the condensation temperature of hydrogen gas is lower than that of liquid nitrogen, it passes through the cooling pipe 34 as it is. A sheathed heater 37 controlled by a temperature controller 36 is installed along the cooling pipe 34. After removing the cooling HI 33, the cooling pipe 34 is heated by the sheathed heater 37 to vaporize the condensed hydride.

A switching valve 41 is provided on the outlet pipe 40 of the gas concentration bag W32. One outlet of the switching valve 41 is connected to a gas analyzer 44 via a pipe 42, and the other outlet is open to the atmosphere.

The gas analyzer 44 includes a chamber 45 and three SnO semiconductor gas sensors 46 arranged within the chamber. The three semiconductor gas sensors 46 are selected to have component selectivity for methane, hydrogen sulfide, and phosphine, respectively. The semiconductor gas sensor 36 is connected to a data processing section 47 including a signal processing circuit (not shown) for amplification, calculation, etc.

Here, a method for simultaneously quantifying trace amounts of carbon, sulfur, and phosphorus in an analysis sample using the apparatus configured as described above will be described. The analysis sample was obtained by preparing a small disk shape of 30n+m in diameter from molten steel collected in a converter using a well-known sample preparation machine.

An analysis sample S is placed on the top of the discharge chamber 11 so as to close the opening at the top of the discharge chamber 11 . In order to keep the discharge chamber 11 airtight, a jig (not shown) holds the analysis sample S pressed against the top of the discharge chamber 11 via a heat-resistant resin O-ring I5. Analysis sample S and counter electrode] 2 includes the cathode of the spark discharge power supply 13 and 11! Connect each pole.

Also, by switching the switching valve 23, the argon gas bomb 17 is switched to the discharge chamber 11. Piping 21. Switching valve 23° filter 25. Piping 31. Argon gas is passed through the cooling pipe 34, piping 40, and switch #-41 of the gas concentrator R32, and the gas remaining in these devices and piping is discharged and removed. Further, the switching valve 41 is switched to allow argon gas to flow into the chamber 45 of the gas analyzer 44, and gas, atmosphere, etc. remaining in the chamber 45 are discharged and removed.

Next, after the pre-flushing is completed as described above, argon gas is again circulated from the discharge chamber 11 to the outlet of the switching valve 41. The flow rate of argon gas is 0.
5 n/a+in. In this state, a high voltage is applied between the surface of the analysis sample and the tip of the counter electrode 12 to cause electrical spark discharge.

The spark discharge conditions are: the spark discharge circuit constant is self-induction lOμH1, the capacitance is 3μF, the resistance is 0Ω, and the voltage is 100
OV, the frequency is 100 to 400 Hy, and the interelectrode gap is about 4 to 6IIlo1. By spark discharge.

Each element in the sample, such as iron, manganese, silicon, carbon, sulfur, and v4, is excited, but they mutually form particles within a very short time. This particle is 0. These are extremely fine ultrafine particles with a diameter of about 1 μm, 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 fine 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 41 is closed, and the filter paper 26 to which the fine particles have adhered is heated by the electric heater 27. and,
The switching valve 23 is switched to supply hydrogen gas from the hydrogen gas cylinder 28 to the filter 25.

Carbon in the analysis sample reacts with hydrogen to form methane, sulfur to hydrogen sulfide, and phosphorus to phosphine. In this embodiment, the heating temperature of the filter 25 is 800°C.

Heating time is 60 seconds. In addition, the flow rate of hydrogen gas is 3
00 mIt/min.

Gaseous hydride (C14°H2
S, P3H) flows into the cooling pipe 34 of the gas concentrator 32 and is condensed there. Hydrogen gas is discharged from the switching valve 41. In addition, fine particles such as iron, manganese, silicon, etc.
The gaseous hydride remains attached to the filter paper 26 and remains in the filter 25. When the gaseous hydride condenses, the switching valve 23 is switched,
Cooling pipe 34 with argon gas from argon gas horn 9
The hydrogen gas remaining in the cooling pipe 34 and the piping before and after it is discharged through the switching valve 41. When the hydrogen gas has been discharged, the switching valve 41 is switched to communicate the cooling pipe 34 with the chamber 45 of the gas analyzer 44, and the cooling top 33 is removed. The cooling pipe 34 is then heated by the sheathed heater 37 to vaporize the condensed hydride.

The vaporized gaseous hydride flows into the chamber 45 of the gas analyzer 44 and is detected by the semiconductor gas sensor 46.

When the above-mentioned general low-pressure spark discharge is applied to a steel sample, about 1 μg of the steel sample is excited and vaporized by one pulse of discharge. When a frequency of 200Hz is adopted,
Approximately 12 mg of sample is evaporated per minute, and all IOppm of carbon, sulfur, and phosphorus in a steel sample, for example, is collected on the filter. Depending on the above hydrogen gas flow rate and heating conditions,
Methane gas of about 0.01 Nmffi is generated. Methane, hydrogen sulfide and phosphine formed by reduction with hydrogen are concentrated and their concentration is considerably higher when carried away with argon gas. For example, if the argon gas meteor after methane gas concentration is 100111 IL/min, the concentration of methane in the argon gas will be about 1100 pp. The detection concentration of the semiconductor gas sensor 46 is even lower, lp
The concentration of pm is a stationary concentration with a sufficient margin. Therefore, the quantitative sensitivity of the final method is extremely high, and 10
An extremely small amount of carbon of about pp11 can be sufficiently quantified. The same applies to sulfur and phosphorus. Further, according to the present invention, analysis can be performed within a short time of about 1.5 minutes after setting the analysis sample S in the reaction chamber 1.

When the analysis of one sample is completed, argon gas is passed through the equipment and piping as described above, and the evaporated particles, gaseous hydrides, etc. of the analysis sample remaining therein are discharged and removed.

Note that the filter paper 26 of the filter 25 was replaced approximately every 30 analyses.

Hereinafter, an example has been described in which carbon, sulfur, and phosphorus in a sample are simultaneously determined using an f-conductor gas sensor silo, but the concentration of any one of these elements may also be determined. Further, a detector or an analyzer other than a semiconductor gas sensor may be used as the gas analyzer 44. For example, these elements may be quantified using an emission spectrometer. Inductively coupled plasma emission analyzer (1 (: +
1), since the inductively coupled plasma emission analyzer detects nitrogen gas, a gas other than nitrogen gas, such as argon gas, is used as the inert gas. Furthermore,
When quantifying carbon, a flame ionization detector (FI
D) can also be used. Hydrogen flame ionization detector is
A detector commonly used in gas chromatographs, which uses a hydrogen flame as an excitation source to ionize analytical components and measure the ion current.

The carbon is reduced to methane and introduced into a flame ionization detector, where it is detected with high sensitivity. A flame photometric detector (FPD) can also be used to perform quantitative analysis of f&yellow or phosphorus. Flame photometric detectors are selectively sensitive to phosphorus and sulfur compounds, with maximum emission intensities at wavelengths around 400 nm for sulfur and around 530 nm for phosphorus. Therefore, selection is made using a J-interference filter that passes through this wavelength range, and the intensity of each spectrum is measured using a photomultiplier tube. Based on the calibration curve determined in advance using a steel standard sample, the content of sulfur or phosphorus can be determined from the measured spectral intensity.
is calculated.

Although the present invention has been explained 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 steel samples.

[Effects of the Invention] According to the present invention, although the elements to be analyzed are limited to carbon, sulfur, and phosphorus, these elements can be rapidly quantified on the order of ppn+. In addition, since the main elements of carbon, sulfur, and phosphorus, which are the most important elements for quality evaluation of metals, are analyzed, it is highly effective in controlling operations such as refining and manufacturing processes of two metals.

[Brief explanation of drawings]

FIG. 1 is an apparatus configuration diagram schematically showing an example of an apparatus for carrying out the method of the present invention. 11...Discharge i chamber, 12...Counter electrode, +3-...
Source for spark discharge, 17...Argon gas cylinder, 23-...Switching valve, 25...Filter, 28...
・Hydrogen gas cylinder, 32-...Gas concentrator, 34...
・Cooling pipe, 35...Liquid nitrogen, 41...Switching valve,
44... Gas analyzer, 46-... Semiconductor gas sensor, 47... Data processing unit, S... Analysis sample.

Claims (1)

[Claims] 1. In a method of heating the surface of a metal sample in an inert gas stream to evaporate the metal sample components and quantifying carbon, sulfur, and phosphorus in the fine particles generated by the evaporation, the fine particles are filtered by the inert gas stream. The inert gas flow is stopped and the collected particles are heated. Hydrogen gas is supplied to the heated particles to generate gaseous hydrides of carbon, sulfur, or phosphorus in the sample. The gaseous hydride is flowed into a gas concentrator to be concentrated, and the hydrogen gas is discharged and replaced with an inert gas.The concentrated gaseous hydride is sent to a gas analyzer using an inert gas stream, and the gaseous hydride is A method for analyzing trace amounts of carbon, sulfur, and phosphorus in metal samples, characterized by quantitative determination.