JPH11316220A - Method and apparatus for high-accuracy analysis of trace element in metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a method and an apparatus in which a trace element in a metal can be analyzed simply, quickly, with high accuracy and with high reliability by a method wherein an inert-gas sputtering treatment is executed to the surface of a sample inside a preliminary treatment chamber in an inert-gas atmosphere and a contamination on the surface of the sample is removed. SOLUTION: An inert-gas sputtering treatment is executed to the surface of a sample 2 inside a preliminary treatment chamber 4 in a inert-gas atmosphere, and a contamination part on the surface of the sample 2 is removed. Argon is used as an inert gas. The sample 2 is set as the side of a cathode, and the inside wall 5 on preliminary treatment chamber 4 is used as an anode. The argon which is ionized by a glow- discharge sputtering operation under a decreased pressure is made to collide with the surface of the sample 2 at high speed, and the sputtering treatment is executed. The sample 2 whose surface contamination is removed by the sputtering treatment is moved directly to a reaction chamber 15. That is to say, the sample 2 is shifted to the reaction chamber 15 without being brought into contact with the air or the like. In the reaction chamber 15, the sample 2 is heated or reacted in the flow of a carrier gas. A trace element is gasified, and it can be detected by a detecting device 32 so as to be determined quantitatively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for high-precision analysis of trace elements in metals.
The present invention relates to an analysis method and an apparatus capable of quantifying carbon and sulfur easily, quickly and with high precision as compared with conventional analysis methods and apparatuses.

[0002]

2. Description of the Related Art Trace elements in metals, particularly oxygen in steel,
Since nitrogen, carbon, and sulfur greatly affect material properties such as ductility and workability, accurate quantitative analysis is required. Particularly, in recent years, with the purifying of steel, these trace elements in steel have become more important, and a highly accurate, quick and simple analysis method and analyzer have been demanded.

[0003] However, as the purity of steel has increased, it has become extremely important for accurate analysis to reliably remove contaminants on the sample surface before analysis. For example, in the case of oxygen analysis, an accurate analysis value cannot be obtained unless organic substances or carbon dioxide adsorbed on the surface or surface oxides due to a surrounding atmosphere such as the atmosphere are removed in advance. Therefore, in recent years, inert gas melting used as a trace oxygen analysis method in steel
In the infrared absorption method, an electrolytic polishing method using an acid or the like or a chemical polishing method has been reported as a pretreatment method for removing a contaminated portion on a sample surface.

For example, Japanese Patent Application Laid-Open No. Sho 60-18759 discloses that a sample for analyzing oxygen in steel is accommodated in a reaction tube, and a reducing gas is introduced into the reaction tube.
A method for pretreating a specimen for oxygen analysis in steel, characterized in that the specimen surface is subjected to a reduction treatment by heating the specimen to 500 ° C. or higher in the reducing gas atmosphere.

[0005] However, even if the surface adhesion contamination is removed by the above method, the sample surface is contaminated again by the sample washing or reoxidation during the period from the pretreatment to the measurement by the analyzer. Therefore, an error occurs in the quantitative analysis at the ppm level or lower. Especially on a clean iron surface, adsorption and oxidation of the atmosphere easily occur instantaneously,
There is a strong need for measures to remove contaminated parts.

In order to solve this problem, Japanese Patent Laid-Open Publication No. Hei 3-15
No. 0462 discloses a method in which a sample is electrolytically polished as a pretreatment when a trace amount of oxygen in steel is extracted by heating, and preheating is performed at a temperature of 1200 ° C. or more and 1400 ° C. or less before oxygen amount measurement. Japanese Patent Application Laid-Open No. 6-148170 discloses a method for analyzing trace amounts of oxygen in steel, which is characterized in that a steel sample surface is ground using a grinder, a file, or the like.
There is disclosed a method for analyzing trace amounts of oxygen in steel, wherein a trace amount of oxygen in the sample is extracted by heating and preheating is performed at a temperature of 1400 ° C. or less.

[0007] Also, the Journal of the Iron and Steel Institute of Japan, CAMP-IS
IJ Vol. No. 5 (1992) -440 discloses a method of removing carbon adhering to a surface by heating at 450 ° C. for 10 minutes. A method for removing contamination on the surface of a sample by sputtering in a processing vessel under a clean low-pressure gas by discharge and transferring the sample to an analyzer as it is to analyze trace elements.

[0008]

However, the method disclosed in Japanese Patent Application Laid-Open No. 3-150450 removes an oxide layer formed on the surface after electrolytic polishing only by removing surface oxygen due to the remaining electrolytic polishing liquid. Can not do,
The method described in Japanese Patent Application Laid-Open No. 6-148170 is to reduce and remove the surface oxygenates formed during the grinder grinding by the reaction with C in the crucible. However, the reduction reaction hardly occurs before dissolving the sample. Even if it occurs, there is a problem that it is limited to only the portion that comes into contact with the crucible, and it is not possible to expect the removal of contamination by a reduction reaction on the entire sample surface.
Furthermore, the method of removing oxygen from the surface by heating at 450 ° C. for 10 minutes has a problem that the analysis accuracy is reduced due to the graphitization of organic substances during low-temperature heating and the decarburization of the outermost surface layer in steel.

On the other hand, although the method described in Japanese Patent Application Laid-Open No. 6-148170 does not have the above-mentioned problems, the sample placed on the sample stage is cleaned or rotated or inverted on the sample stage to clean the back surface. In addition, there is a problem that the operation becomes complicated, uniform removal of surface contamination becomes difficult, and rapid processing cannot be performed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks of the conventional method and apparatus for analyzing trace amounts of oxygen in metals, and has as its object to provide means for analyzing trace elements in metals simply, quickly, with high accuracy, and with high reliability. And

[0011]

In order to solve the above-mentioned problems, the present invention provides a method for analyzing trace elements in a metal by subjecting a sample surface to an inert gas sputtering process in a pretreatment chamber in an inert gas atmosphere. And removing a contaminated portion on substantially the entire surface of the sample at substantially the same time, and directly transferring the sample after the completion of the sputtering process to a reaction chamber to quantify a trace element. In this case, it is preferable that the inert gas sputtering treatment is performed by holding the sample at a point by means of a conductive sample holder, so that the analysis of trace elements in a metal can be performed with higher accuracy and speed.

The present invention also provides a pretreatment chamber for removing a surface contaminated portion of a sample by inert gas sputtering using the above-described apparatus for analyzing a trace element in a metal, a sample from which the surface contaminated portion has been removed in the pretreatment chamber. A reaction chamber for gasifying trace elements therein, and a detection device for analyzing and quantifying gas introduced from the reaction chamber, and the pretreatment chamber,
An openable sample inlet is provided at the upper part, and an openable shutter is provided at the lower part which is openable to the reaction chamber, and a power supply for sputtering and an inert gas source are connected. Further, in the above apparatus, it is preferable that the pretreatment chamber has a sample holder that supports the sample at a point and maintains the sample on the cathode side, and an inner surface wall maintained on the anode side. Is performed with high precision. The present invention is particularly suitable for the determination of trace elements such as oxygen, nitrogen, carbon and sulfur in steel.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the drawings, taking analysis of trace elements in steel as an example. FIG. 1 shows an analyzer according to the present invention used for analyzing oxygen or nitrogen in steel, and FIG. 2 shows an example of an analyzer according to the present invention used for analyzing carbon or sulfur in steel. As shown in the above example, in the analysis in the present invention, a pretreatment for removing the contaminated portion on the sample surface and a two-stage treatment for transferring the pretreated sample to the reaction chamber without recontamination and analyzing the sample are respectively performed. Pretreatment chamber 4 and reaction chamber 15
It is performed separately.

In the preliminary processing chamber 4, the surface of the sample 2 is subjected to an inert gas sputtering process to remove contaminated portions on the surface of the sample. As an inert gas, argon was used. The sample 2 was used as a cathode side, and the inner wall 5 of the pre-treatment chamber 4 was used as an anode. Do. The pressure and voltage of the gas may be selected so that contamination on the sample surface can be removed within a predetermined time.

In the above sputtering, gas sputtering is performed simultaneously over almost the entire surface of the sample,
The contaminated portion on the sample surface is removed almost simultaneously. Thus, the contaminated portion can be quickly and uniformly removed without performing a complicated operation such as reversing the sample on the sample table, and the analysis time can be further reduced and the accuracy can be improved. Specifically, it can be performed by point-supporting the sample 2 by the conical support rod 20. Further, it is possible to take a means such as supporting the sample by its apex or ridge. In short, when supporting the sample, the area of the support that covers the sample should be as small as possible. Although depending on the required analysis accuracy, there is no practical problem if the area of the support bar 20 or the like covering the sample surface is approximately 10% or less of the entire sample surface.

The sample from which surface contamination has been removed by the above sputtering is directly transferred to the reaction chamber 15. That is,
It is moved to the reaction chamber 15 without being exposed to the atmosphere or the like. For this purpose, a slide valve type shutter 26 is provided between the pretreatment chamber 4 and the reaction chamber 15, and the atmosphere between the two chambers is made equal in pressure. Then, the shutter 26 is opened to drop the sample 2 into the reaction chamber. What should I do?

The sample transferred to the reaction chamber is heated or reacted in a stream of a carrier gas (Ar, He, O _2, etc.) depending on the purpose of analysis to gasify the trace elements, and this is converted to an appropriate gas. It is detected and quantified by the detection device 32. For example, oxygen is measured in a graphite crucible using Ar or He as a carrier gas and the generated CO gas by an infrared absorption method. Nitrogen is subjected to heat treatment using He as a carrier gas, and the generated N ₂ gas is quantified by a heat conduction measurement method. Carbon or sulfur is burned in a magnetic crucible using oxygen gas as a carrier gas, and the generated CO or SO ₂ gas is quantified by an infrared absorption method.

As shown in FIGS. 1 and 2, a pretreatment chamber 4 is provided in an analyzer for performing the above-described analysis method. The pretreatment chamber 4 is configured so that argon is introduced from the argon gas source 6 via the valve 8 until the argon sputtering is completed, and exhausted through the valve 12 by the exhaust pump 10. The pre-processing chamber 4 has a sample inlet 24 which can be opened and closed at an upper portion, and a slide valve type shutter 2 which can be opened and closed and which communicates with the reaction chamber at a lower portion.
6 is provided. Argon is guided to the reaction chamber 15 through the switching valve 28, and can be used as a carrier gas.
Further, in order to facilitate opening and closing of the shutter 26, the atmosphere pressure of the pretreatment chamber and the reaction chamber can be equalized by using argon.

A sample holder 20 for supporting the sample 2 is provided in the pre-processing chamber 4 so as to be able to advance and retreat, so that the sample 2 can be gripped or opened. This sample holder 20 charges the sample negatively (-).
Power supply 2 for sputtering, made of conductive material
2 cathodes. On the other hand, the inner wall 5 of the pretreatment chamber
Is connected to the anode of the sputtering power supply 22 via a conducting wire.

Therefore, the sample inlet 2 of the pretreatment chamber 4
4 is opened, the sample 2 is set on the sample holder 20, the slide valve type shutter 26 is closed, argon gas is introduced from the valve 8, the exhaust pump 10 is operated, and an argon atmosphere of a predetermined pressure is set. When a high voltage is applied between the inner wall 5 of the pretreatment chamber 4 and the sample 2 from the power supply 22 for use, a glow discharge occurs between the two, and the sample 2
Is cleaned by sputtering with the generated argon ions. At this time, if the sample holder 20 is formed in a conical shape with a sharp tip as shown in the figure, the sample 2 is supported at a point, and the contamination removal by sputtering is performed simultaneously on the entire surface of the sample. As described above, the means for supporting the sample 2 does not matter as long as the area of the supporting means covering the sample surface is sufficiently small, for example, 10% or less.

The reaction chamber 15 is configured according to the element to be analyzed. For analysis of oxygen or nitrogen, a graphite crucible 16 and a power supply 30 for heating the same are provided inside. For analysis of carbon and sulfur, a magnetic crucible 17 is provided, and a high-frequency power supply 31 is provided for heating a sample. In the present invention, the upper part of the reaction chamber 15 is connected to the pre-processing chamber 4 via a shutter 26, and the carrier gas is supplied to the pre-processing chamber 4 and the reaction chamber 1 via a switching valve 28.
5 is introduced. The carrier gas is Ar or He gas for oxygen analysis, He gas for nitrogen analysis, and O ₂ gas for carbon or sulfur analysis. In addition, when Ar gas is used as a carrier gas for oxygen analysis, the He introduction pipe in FIG. 1 is not required.

In transferring the sample 2 to the reaction chamber 15 using the apparatus of the present invention, the switching valve 28 is operated to operate the reaction chamber 1.
The reaction chamber 15 and the pretreatment chamber 4 are filled with an argon gas or a carrier gas so that the atmosphere and pressure of the pretreatment chamber 5 and the pretreatment chamber 4 are the same, the shutter 26 is opened, the sample holder 20 is retracted, and the sample 2 Is dropped into the reaction chamber 15. Next, the shutter 26 is closed, and the switching valve 2
8 to allow the carrier gas to flow,
Alternatively, the gas extracted by heating the sample 2 by the high-frequency power supply 31 is guided to a detection device 32 (here, an infrared absorption device or a heat conduction measurement device) and quantified.

According to the above configuration, the sample 2 from which impurities such as oxygen on the surface have been removed by sputtering falls directly from the pretreatment chamber 4 into the reaction chamber 15 without being exposed to air, and undergoes an analysis operation. For example, in the case of trace oxygen analysis in steel, the sample directly falls into the reaction chamber 15 having the graphite crucible 16 and the reaction chamber 15
The temperature is raised to 00 to 2,500 ° C., and all trace amounts of oxygen are reduced by carbon and quantified by an infrared absorption device known as CO gas.

[0024]

FIG. 3 shows the result of analyzing the surface of the sample 2 after subjecting the surface of the sample 2 to argon sputtering by Auger electron spectroscopy. The horizontal axis represents the electron energy level and the vertical axis represents the Auger differential spectrum. As is clear from FIG. 3, almost no oxygen is observed in the surface layer portion of Sample 2 after sputtering, indicating that the contamination by the oxide film has been completely removed.

As a comparative example, FIG. 4 shows the results of analysis by Auger electron spectroscopy in the depth direction after leaving the sample pretreated in the same manner as described above in the air for 1 minute. FIG. 4 shows that a high value of oxygen was detected, indicating that the sample surface was reoxidized by exposure to the atmosphere. Thereby, it was confirmed that an error of about 1 ppm occurs in the oxygen analysis value.

Although the embodiment of the present invention has been described with respect to a method and an apparatus for high-precision analysis of trace oxygen in steel, it is apparent that the above-described method and apparatus can be applied to metals other than steel. In that case, an analyzer including a reaction chamber can be appropriately selected depending on the metal to be analyzed and the element to be analyzed, and can be combined with the pretreatment chamber according to the present invention.

[0027]

The present invention relates to the analysis of trace elements in metals,
The inert gas sputtering phenomenon was used to simultaneously remove contaminated parts from the entire surface of the sample, and this was directly introduced into the reaction chamber.Therefore, there was no risk of re-contamination, and the determination of trace oxygen in metals was performed with high accuracy. Can be performed quickly. Further, by utilizing the present invention, it becomes possible to accurately know the influence of trace elements in a metal, which can significantly contribute to the development of a high-purity material in the future.

[Brief description of the drawings]

FIG. 1 is an example of a schematic diagram of an apparatus for analyzing trace oxygen or nitrogen in steel according to the present invention.

FIG. 2 is an example of a schematic view of an apparatus for analyzing trace carbon or sulfur in steel according to the present invention.

FIG. 3 is a result of analyzing a sample processed according to the present invention by Auger electron spectroscopy.

FIG. 4 shows the result of analysis by Auger electron spectroscopy after leaving the sample in the air for 1 minute after the pretreatment according to the present invention.

[Description of Signs] 2: Sample 4: Pretreatment chamber 5: Inner wall 6: Argon gas source 8, 12: Valve 10: Exhaust pump 15: Reaction chamber 16: Graphite crucible 17: Magnetic crucible 20: Sample holder 22: Sputtering Power supply 24: Sample inlet 26: Shutter 28: Valve 30: Heating power supply 31: High frequency power supply 32: Detector

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI G01N 31/00 G01N 1/28 G (72) Inventor Hisao Yasuhara 1 Kawasaki-cho, Chuo-ku, Chuo-ku, Chiba City, Chiba Prefecture In the laboratory (72) Inventor Makoto Shimura 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Research Institute Co., Ltd. (72) Inventor Kenji Yasuhiko 6-27-9 Takamori, Izumi-ku, Sendai, Miyagi Prefecture 72 Inventor Yukitoshi Morimoto 3-9-23 Nishigotanda, Shinagawa-ku, Tokyo Inside Japan Analyst Co., Ltd.

Claims (5)

[Claims] 1. A step of subjecting a sample surface to an inert gas sputtering process in a pretreatment chamber in an inert gas atmosphere to substantially simultaneously remove contaminated portions on substantially the entire surface of the sample, and And directly quantifying the trace elements by directly transferring the trace elements to the reaction chamber. 2. The method according to claim 1, wherein the inert gas sputtering treatment is performed by supporting the sample at a point with a conductive sample holder. 3. The method according to claim 1, wherein the trace element is oxygen, nitrogen, carbon or sulfur in steel. A pretreatment chamber for removing a surface contaminated portion of the sample by inert gas sputtering, a reaction chamber for gasifying a trace element in the sample from which the surface contaminated portion has been removed in the pretreatment chamber; A detection device for analyzing and quantifying a gas introduced from the chamber, wherein the pretreatment chamber is provided with an openable sample inlet at an upper portion, and an openable shutter which communicates with the reaction chamber at a lower portion, and a sputtering device. A high-precision analyzer for trace elements in metals, which is connected to a power supply and an inert gas source. 5. The pretreatment apparatus according to claim 4, wherein the pretreatment chamber has a sample holder for supporting the sample at a point and maintaining the sample on the cathode side, and an inner wall maintained on the anode side. High-precision analyzer for trace elements.