JPS61212761A - Quick analysis of carbon in metal sample - Google Patents

Abstract

PURPOSE:To enable simple and quick analysis on the content of carbon in a metal sample, by exciting the carbon contained in the metal sample by a spark discharge in an inert gas atmosphere containing an oxygen gas to measure the concentration of gas components. CONSTITUTION:An apparatus is mainly composed of a CO gas generating section 1, a power source 2 for spark discharge, a control section 3 for inert gas such as Ar gas, a gas sampling section 4 and a detector section 5. After the setting of a analysis sample 6 at the CO gas generating section 1, an Ar gas runs to the route of a high-purity Ar gas cylinder 9, a flowmeter 11a, a solenoid valve 12a, a gas feed pipe 13, a discharging chamber 8, a gas transport pipe 14 and a solenoid valve 12c. Discharge out atmospheric air left in the discharging chamber 8 while triggering a spark discharge preliminarily. Then, with the preliminary discharging kept up, the atmospheric gas is switched over to an oxygen-mixed Ar gas. Moreover, after fine particles 2 therein being fed is removed with a fine particle filter 15, the CO gas generated in the discharge chamber 8 fills a gas weighing meter 16 and is discharged out of the system while being fed to a detector section 5 with the Ar gas as carrier gas.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a method for simply and quickly separating carbon contained in metal samples, and is applicable to manufacturing processes in the steel industry or various non-ferrous metal manufacturing industries. It is used in the fields of management analysis and quality control analysis.

(Prior Art) In operational management of metal refining processes, etc., it is necessary to analyze as quickly as possible to understand the component content, and take countermeasures based on the results. Highly accurate and rapid analysis is also required for product verification, and carbon in particular is an important component in determining quality in the steel manufacturing process.

There are various methods for analyzing carbon in metal samples, including combustion infrared absorption method (JIS G 1211-1981 method for determining carbon in iron and steel) and emission spectrometry method (JIS G 125
3) is a typical analysis method for iron and steel.

The former is a method in which a cut metal sample is burned in an oxygen stream to convert carbon contained in the sample into carbon dioxide, and its absorption in the infrared region is measured to determine the carbon content. The latter method involves applying a high voltage between the surface of a block-shaped metal sample and a counter electrode such as tungsten to generate a spark discharge.The generated excitation light is separated using a spectrometer, and the intensity of the emission spectral lines of carbon is used to determine the content of the sample. This is a method to find the content rate.

Since the former is a combustion method, the sample to be analyzed must be in the form of cutting chips. Therefore, in process control analysis in the metal refining process, cutting powder is collected again from a block sample after collecting molten metal and solidifying it. have to,
The latter method, which has the disadvantage of being time-consuming and impractical, is a practical method that targets block samples and can simultaneously analyze multiple elements including carbon in a short time. However, in order to prevent interference between the spectral lines of each element emitting light at the same time, it is necessary to analyze the emission spectrum with a high resolution of 1 angstrom or less. Therefore, the spectrometer is large and the analyzer occupies a large space, and since the spectrometer is a precision optical device, it must be installed in a place where room temperature changes are small, vibrations do not occur, and there is little dust. The price of analysis equipment also becomes very high.

Therefore, even though it is not possible to analyze multiple elements at the same time as with conventional emission spectroscopy, it is possible to analyze just carbon, which is important for refining metals, easily and quickly.Moreover, there are no strict installation restrictions, and it is an inexpensive analysis method. equipment is often desired.

(Problems to be Solved by the Invention) The present invention is provided for this purpose and is completely new in terms of method and principle. In other words, carbon, which is a major element that has an important effect on quality evaluation such as the mechanical strength of metals, can be analyzed easily, quickly, with high sensitivity, and with high performance, while also being able to analyze installation environment constraints such as temperature changes, vibrations, and dust. The cost of the equipment is low. In addition, it has features that are superior to conventional methods, especially in terms of high-sensitivity analysis, which is essential for the production of high-purity metals, which has become important in recent years.

(Means for solving the problem) The present invention excites carbon contained in a metal sample by spark discharge in an inert gas atmosphere containing oxygen gas, converts carbon into gas components such as carbon monoxide, and generates hydrogen. This method uses a flame ionization detector to measure the concentration of gas components and easily and quickly analyze the carbon content in metal samples. Regarding this method and principle, the present inventor had already filed a patent application in 1983.
88583.

The application was filed as "Method and apparatus for rapid analysis of carbon and sulfur components in metal samples."

The difference between the present invention and the prior invention is that when a spark discharge is applied to a metal sample, the atmospheric gas is first changed to a high-purity inert gas that does not contain impurities such as oxygen gas to preliminarily generate the spark discharge. The point is that the production of -carbon oxide gas is stabilized by allowing the spark to flow, then switching the atmospheric gas to an inert gas containing oxygen and continuing to cause spark discharge. In an inert gas atmosphere containing oxygen, spark discharge does not normally fly, and the amount of evaporation of each element becomes a diffusion discharge, which reduces the amount of carbon monoxide produced or makes it unstable, resulting in poor quantitative accuracy. However, this problem was solved by switching the atmospheric gas mentioned above.

(Structure, operation, and embodiments of the invention) Based on the example of the apparatus for implementing the present invention shown in FIG. 1, the structure 8 and operation of the present invention will be explained. It is mainly composed of a discharge power supply section 2, an inert gas control section 3 such as argon gas, a gas sampling section 4, and a detection section 5. - The carbon oxide gas generating section 1 is provided with a counter electrode 7 made of tungsten or the like facing the analysis sample 6, and forms a small volume discharge chamber 8 provided with an inert gas supply port and a discharge port. The counter electrode 7 is held by a heat-resistant insulating material and is insulated from the 1 analysis sample 6. The cathode and the anode of the spark discharge power supply device 2 are connected to the 0 analysis sample 6 and the counter electrode 7, respectively. A high voltage is applied to these two electrodes to generate a spark discharge between the surface of the analysis sample 6 and the tip of the counter electrode 7, thereby exciting and vaporizing each element in the analysis sample. Appropriate conditions for spark discharge are those that provide good reproducibility of the excitation of each element.For example, the spark discharge circuit constant is self-induction 104H, capacitance 3F, resistance 0Ω, voltage tooov, frequency 100~ 400Hz
.

When general low-pressure spark discharge conditions with an interelectrode gap of about 4 to 6 mm were used, the sensitivity and accuracy of the quantitative results were excellent.

The gas control unit 3 includes a high-purity argon gas pump 9, a high-purity argon gas pump 10 mixed with oxygen gas of about 0.001 to 0.1z, and a flowmeter 11a with a needle valve.

ttb, electromagnetic valves 12a, 12b, etc., which switch the flow path and control the flow rate of argon gas and oxygen-mixed argon gas.First, after setting the analysis sample 6 in the -carbon oxide gas generation section l, the first The route indicated by the arrow in the figure, that is, the high-purity argon gas pump 9, the flow meter 11a, the solenoid valve 12a, the gas supply pipe 13, the discharge chamber 8, the gas conveyance pipe 1
4 and the solenoid valve 12c path for 10 to 20 minutes.
Flowing at a flow rate of 1/sin to discharge and remove the atmosphere remaining in the discharge chamber 8, and to preliminarily blow a spark discharge.
This preliminary discharge is performed in order to prevent this from occurring, since if the discharge is started from the beginning with oxygen-mixed argon gas, a normal spark discharge will not be obtained and the accuracy of carbon analysis will deteriorate. In addition to stabilizing the discharge state, the purpose is to remove any traces of carbon contamination on the surface of the sample.

Next, the atmospheric gas is switched to oxygen-mixed argon gas without stopping this preliminary discharge. That is, an oxygen mixed argon gas pump 10, a flow meter 11b, a solenoid valve 12b, a supply pipe 13
, discharge chamber8. Oxygen-mixed argon gas is flowed at a flow rate of 0.5 to 3 M/m'in through the paths of the conveying pipe 14, the solenoid valve 12C, the particulate filter 15, and the gas metering pipe 16 to cause the spark discharge to flow. Switching is a feature of the present invention, but a patent application filed in 1973 that does not involve gas switching
i3-188583.

The analytical precision (coefficient of variation) of steel samples containing 0.2FH carbon was compared 10 times. As a result, the coefficient of variation of the present invention is 0.85%.
Analysis accuracy was significantly improved compared to 3.7z.

The sampling section 4 includes a solenoid valve 12C1, a particulate filter 15, a gas measuring tube 18, and the like. When spark discharge is performed under argon gas flow, each element such as iron, carbon, manganese, silicon, sulfur, and phosphorus in the steel sample is excited, but they mutually form particles within a very short time. . These particles are extremely fine ultrafine particles of about 0.01 pm.
Although it depends on the circuit constants of the spark discharge, its composition is close to that of the original steel sample. However, if high-purity argon gas is mixed with oxygen gas and spark discharge is performed in the same way as above, found that iron, manganese, silicon, etc. in steel samples form ultrafine particles, but the moment carbon is excited, it reacts with oxygen to produce oxide gases of carbon monoxide and carbon dioxide. . The main component of the produced gas was carbon monoxide gas. The carbon monoxide gas generated in the discharge chamber 8 is filtered through a particulate filter 15 to remove particulates 2 such as iron, which are sent along with the carbon monoxide gas, and then passed through a gas metering tube 1B consisting of a thin tube with a switching valve that has a constant capacity of about 1 to 5 cc. filled and discharged from the system. The carbon monoxide gas filled in the metering tube 1B is sent to the detection section 5 using argon gas supplied from another pump as a carrier gas by operating the switching valve.

The detection unit 5 includes a gas reduction device 17. It is composed of a hydrogen flame ionization detector (FID) 1B, a data processing device 19, and the like. The FID detector 18 is a detector commonly used in gas chromatographs, and uses a hydrogen flame as an excitation source to ionize an analytical component and measure the ion current. - Carbon oxide and carbon dioxide gases are FID
Since the detector cannot measure directly, a gas reduction device 17 heated with a nickel catalyst is installed in front of the FID detector. - Carbon oxide and carbon dioxide are reduced to methane and FI
D and detected with high sensitivity. The detection signal is sent to the data processing unit 19, the detected peak height or peak area 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. .

If a gas component separation column is attached between the gas metering tube 1B and the gas reduction device 17, carbon monoxide and carbon dioxide will be separated and detected in about 3 minutes. Since no interfering gas components were detected, the installation of a separation column is not absolutely necessary; therefore, if a separation column is not used, - carbon oxides and trace amounts of carbon dioxide produced are both removed from the gas reduction device. Since the gas is reduced to methane by 17, the contents of both gas components can be measured in a short period of about 40 seconds using FID.

Fig. 2 shows an example of a calibration curve created by analyzing carbon in a steel standard sample, with the flow rate of oxygen (40 ppm) mixed argon gas during spark discharge being 21/1n, and the sampling amount of -carbon oxide generation gas being lsf. Indicated. As shown in Fig. 2, according to the present invention, trace amounts of carbon in steel samples are
It can be easily and accurately quantified within minutes.

(Effects of the Invention) As explained above, the present invention has the advantage that the target element to be analyzed is carbon, compared to the case of using optical emission spectrometry, which rapidly analyzes carbon in metals for blow-shaped samples, which has been adopted up to now. Although the measurement environment for the analyzer is limited to vibrations, temperature changes, dust, etc., there are loose constraints on the measurement environment for the analyzer, and the equipment price is low at about 115 0. It is a non-destructive method with short laboratory time and excellent quantitative sensitivity. It is useful as a rapid analysis and targets carbon, which is the most important element for quality evaluation of metals such as steel, titanium, aluminum, copper, etc., so it is extremely effective for operational management of metal refining and manufacturing processes. .

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the configuration of an apparatus for implementing the present invention. FIG. 2 is an example of a calibration curve created by analyzing carbon in a steel standard sample using the method of the present invention. Note that the numbers in FIG. 1 indicate the following. DESCRIPTION OF SYMBOLS 1...-carbon oxide gas generation part, 2... power supply part for spark discharge, 3... atmospheric gas control part, 4... gas sampling part, 5... detection part, 6... analysis Sample, 7
Counter electrode, 8 Spark discharge chamber, 9 Argon gas cylinder, 10 Oxygen mixed argon gas cylinder, 15 Particulate filter, 16 Gas measuring tube, 17... Gas reduction device, 18...Hydrogen flame ionization detector.

Claims (1)

[Claims] In an analysis method for determining the carbon component content in a sample using gas components generated by spark discharge on the surface of a metal sample, the spark discharge is first performed preliminary in an inert gas atmosphere. After stabilizing the sample surface condition and discharge condition, spark discharge is performed in an inert gas atmosphere containing a trace amount of oxygen, and carbon gas components such as carbon monoxide generated are reduced to methane. A method for rapid analysis of carbon in a metal sample, characterized by introducing the carbon into a hydrogen flame and measuring the ionic current of the carbon component to determine the carbon content.