WO2010125892A1 - 鉄鋼中酸素分析方法 - Google Patents
鉄鋼中酸素分析方法 Download PDFInfo
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- WO2010125892A1 WO2010125892A1 PCT/JP2010/056014 JP2010056014W WO2010125892A1 WO 2010125892 A1 WO2010125892 A1 WO 2010125892A1 JP 2010056014 W JP2010056014 W JP 2010056014W WO 2010125892 A1 WO2010125892 A1 WO 2010125892A1
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- sample
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- steel
- arc plasma
- oxygen
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 62
- 239000010959 steel Substances 0.000 title claims abstract description 62
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 title claims abstract description 59
- 239000001301 oxygen Substances 0.000 title claims abstract description 59
- 229910052760 oxygen Inorganic materials 0.000 title claims abstract description 59
- 238000000034 method Methods 0.000 title claims abstract description 20
- 238000004458 analytical method Methods 0.000 claims abstract description 80
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 11
- 238000004140 cleaning Methods 0.000 claims abstract description 11
- 229910002804 graphite Inorganic materials 0.000 claims abstract description 10
- 239000010439 graphite Substances 0.000 claims abstract description 10
- 238000003754 machining Methods 0.000 claims abstract description 9
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims abstract description 8
- 239000011261 inert gas Substances 0.000 claims abstract description 7
- 238000010438 heat treatment Methods 0.000 claims abstract description 6
- 238000010521 absorption reaction Methods 0.000 claims abstract description 5
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims abstract description 4
- 229910002092 carbon dioxide Inorganic materials 0.000 claims abstract description 4
- 239000001569 carbon dioxide Substances 0.000 claims abstract description 4
- 229910002091 carbon monoxide Inorganic materials 0.000 claims abstract description 4
- 238000002844 melting Methods 0.000 claims abstract description 3
- 230000008018 melting Effects 0.000 claims abstract description 3
- 238000009832 plasma treatment Methods 0.000 claims description 15
- 238000011282 treatment Methods 0.000 claims description 14
- 238000012545 processing Methods 0.000 abstract description 15
- 238000007781 pre-processing Methods 0.000 abstract 1
- 239000000523 sample Substances 0.000 description 105
- 238000007670 refining Methods 0.000 description 14
- 239000007789 gas Substances 0.000 description 6
- 238000004519 manufacturing process Methods 0.000 description 6
- 238000005516 engineering process Methods 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 238000009628 steelmaking Methods 0.000 description 5
- 238000005498 polishing Methods 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 3
- 238000007796 conventional method Methods 0.000 description 3
- 238000002955 isolation Methods 0.000 description 3
- 238000002203 pretreatment Methods 0.000 description 3
- 238000005336 cracking Methods 0.000 description 2
- 238000005520 cutting process Methods 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 238000010405 reoxidation reaction Methods 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 239000003463 adsorbent Substances 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000538 analytical sample Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000011088 calibration curve Methods 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000012159 carrier gas Substances 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- 239000013068 control sample Substances 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000004868 gas analysis Methods 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 239000001307 helium Substances 0.000 description 1
- 229910052734 helium Inorganic materials 0.000 description 1
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical group [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000006213 oxygenation reaction Methods 0.000 description 1
- 238000003672 processing method Methods 0.000 description 1
- 238000004080 punching Methods 0.000 description 1
- 238000010926 purge Methods 0.000 description 1
- 239000012925 reference material Substances 0.000 description 1
- 238000004904 shortening Methods 0.000 description 1
- 238000004544 sputter deposition Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000010301 surface-oxidation reaction Methods 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
- 230000004580 weight loss Effects 0.000 description 1
Images
Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
- G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
- G01N21/3504—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light for analysing gases, e.g. multi-gas analysis
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
- G01N1/34—Purifying; Cleaning
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
- G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
- G01N21/3563—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light for analysing solids; Preparation of samples therefor
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/20—Metals
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/20—Metals
- G01N33/202—Constituents thereof
- G01N33/2022—Non-metallic constituents
- G01N33/2025—Gaseous constituents
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
- G01N1/286—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q involving mechanical work, e.g. chopping, disintegrating, compacting, homogenising
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
- G01N1/40—Concentrating samples
- G01N1/4022—Concentrating samples by thermal techniques; Phase changes
Definitions
- the concentration of elements contained in the sample is determined.
- the present invention relates to a highly accurate and rapid oxygen analysis method that can be applied to a series of steps of analyzing and reflecting the analysis result in the component adjustment operation of the molten steel.
- the concentration of the contained element can be analyzed quickly and accurately during the refining process in the steelmaking process for producing steel having the desired performance by adding various elements, appropriate components will be based on the analysis results. By performing the adjustment, it becomes possible to manufacture steel having stable performance at low cost and low environmental load.
- the oxygen concentration in steel is several ppm to several hundred ppm, and in order to accurately analyze the oxygen concentration in such a concentration range, the only oxygen analyzer that uses the heating-melting-infrared absorption method in an inert gas is the only principle.
- the only oxygen analyzer that uses the heating-melting-infrared absorption method in an inert gas is the only principle.
- a sample is prepared by machining from a steel ingot to a predetermined size, and then chemical polishing, electrolytic polishing, grinder or file is used for the purpose of removing the oxide film on the sample surface. It was necessary to perform pretreatment such as grinding.
- pretreatment such as grinding.
- Such processing and pretreatment are as follows: (1) The operation is complicated and time-consuming. (2) The degree of removal of the oxide film varies depending on the sample, treatment, and operator, and the analytical value varies.
- Patent Document 1 discloses a trace oxygen analysis method in which the total analysis time from sample pretreatment to analysis is 3 minutes by performing preheating at a low temperature to remove the oxide film on the sample surface.
- the reproducibility of the belt polishing treatment in the pretreatment and the deoxidation reaction in the preheating is not high, the analytical value varies, and therefore there is a problem that the analytical accuracy is not necessarily improved as compared with the conventional method.
- it takes time to machine into a sample shape applicable to belt polishing it cannot be applied as an oxygen analysis method for molten steel during refining.
- Patent Document 2 discloses a method and apparatus for analyzing trace amounts of oxygen in a metal, characterized in that a sample is dropped from a pretreatment chamber directly into a heating chamber having a graphite crucible for analysis.
- inert gas sputtering is applied as a pretreatment method, after introducing the sample into the pretreatment chamber, the gas is replaced with a sputterable atmosphere, and thus it takes time to evacuate to high vacuum once.
- the publication does not disclose analysis time including pretreatment, but it is apparent that it cannot be applied as an oxygen analysis method for molten steel during refining.
- Japanese Patent Laid-Open No. 06-148170 Japanese Patent Laid-Open No. 10-073586 JP 2002-328125 A Japanese Patent Laid-Open No. 10-311782
- the error must be within ⁇ 2 ppm for steel with an oxygen content of 50 ppm or less.
- the error is preferably within ⁇ 1 ppm.
- Time required for analysis The time (hereinafter referred to as “required analysis time”) from when the steel ingot sample is received, through sample processing and pretreatment for cleaning, until the oxygen concentration is determined by analysis is 5 Less than a minute. Preferably it is 4 minutes or less.
- an object of the present invention is to provide a highly accurate and quick method for analyzing oxygen in molten steel that satisfies the above requirements.
- the present inventor combined a simple and rapid sample processing method with a rapid and highly reproducible sample pretreatment method and a highly accurate analysis method, and further optimized each condition.
- the present inventors have found a highly accurate and rapid oxygen analysis method applicable to oxygen analysis of molten steel during refining, and have completed the following present invention.
- vacuum arc plasma treatment is performed under conditions that the degree of vacuum at the start of arc plasma discharge is 5 Pa to 35 Pa and the arc plasma output current is 15 A to 55 A
- the steel ingot taken from the molten steel is machined so that the height is 1.5 mm or more and 7 mm or less and the ratio of surface area S to volume V (S / V) is 1.05 or more and 1.30 or less.
- a small piece obtained in this manner was used as a sample, and the arc plasma discharge was applied to the sample a total of 4 times or less and the total treatment time was 0.2 seconds or more and 1.2 seconds or less. Without contact with the atmosphere, directly heated at a temperature higher than the temperature at the time of analysis, after cleaning, the steel oxygen analysis method characterized by introducing into the graphite crucible which was waiting down the temperature to analyze.
- a solidified ingot is collected from molten steel in the middle of refining, a sample for component analysis is prepared by machining, the element concentration contained in the sample is analyzed, and the analysis result is referred to Highly accurate and quick oxygen analysis that can be applied to a series of processes to be reflected in the component adjustment operation of molten steel becomes possible.
- This makes it possible to adjust the refining conditions according to the oxygen concentration of the molten steel, and in particular, high-grade steels such as line pipe steels and bearing steels, whose performance is governed by the abundance, form, and composition of inclusions in the steel. Leads to stable manufacturing.
- FIG. 1 schematically shows a steel oxygen analyzer according to the present invention.
- vacuum arc plasma treatment was selected as a sample pretreatment method that was quick and highly reproducible.
- the preparation method and apparatus for a sample for analyzing an in-metal component disclosed in Patent Document 3 may be applied.
- a sample can be inserted into the sample pretreatment apparatus 1 that has been previously kept in vacuum through the isolation valve 4 through the isolation valve 4 with almost no change in the degree of vacuum. Thereafter, the oxide film on the sample surface is removed in a few seconds by vacuum arc plasma treatment.
- the sample shape is limited to a cylinder or a block (cuboid). Since the sample is placed on the sample stage and processed, the surface in contact with the sample stage is not processed. Therefore, it is necessary to invert the sample for processing. That is, it is necessary to discharge at least twice for one sample. When the number of discharges increases, the sample is heated for a long time, and once the oxide film is removed, the sample surface is oxidized again. Therefore, in order to remove the oxide film on the sample surface reliably, accurately and with good reproducibility, and to ensure the analysis accuracy required for the refining operation, it is necessary to perform an arc plasma treatment under the following conditions.
- Vacuum degree 5 Pa or more and 35 Pa or less.
- the sample surface oxide film removal reaction by the vacuum arc plasma is promoted as the degree of vacuum is higher, but if it exceeds 35 Pa, the reoxidation reaction accompanying the increase in the sample temperature becomes remarkable, which is not preferable. On the other hand, if it is lower than 5 Pa, the oxide film removal reaction itself does not proceed, which is not preferable. There is therefore an optimum degree of vacuum. It is more preferable to have a pressure control mechanism for controlling the opening and closing of the vacuum exhaust valve and the gas introduction valve so that the degree of vacuum is maintained at a constant value during processing.
- Arc plasma output current 15A or more and 55A or less.
- Processing time As will be described later, the total processing time is 0.2 seconds or more and 1.2 seconds or less for one sample.
- the total number of treatments for one sample is 4 or less.
- the treated sample is finally put into the graphite crucible through the pretreated sample inlet 5 arranged in the analyzer 2 without being brought into contact with the atmosphere.
- the sample pretreatment chamber and the sample inlet of the analyzer are connected by a connecting tube 8 whose inside is replaced with vacuum or an inert gas.
- Ar is preferable from the viewpoint of reliably replacing the gas in the connecting pipe in consideration of the specific gravity difference with air and preventing reoxidation of the sample after processing, and from an economical viewpoint.
- the pretreated sample is dispensed and then transferred to a separate oxygen analyzer.
- the sample pretreatment device 1 and the oxygen analyzer 2 are arranged vertically above and below, and freely fall in the connecting tube 8 to transfer the sample. That is, an apparatus configuration as shown in FIG. 1 was adopted.
- the oxygen analyzer 2 is disposed at a position close to the floor surface, and cleaning inside the analyzer 2 hinders the maintenance work of the apparatus such as replacement of the impurity adsorbent in the gas. Therefore, the entire apparatus incorporated in the gantry 6 is placed on the lifter 7 so that it can be raised and lowered, and the entire apparatus is raised during the work to ensure workability.
- the driving method of the lifter 7 is not particularly limited. However, since the weight of the entire apparatus is considerable, an automatic hydraulic type is preferable from the viewpoint of operability. Moreover, it is desirable to cover the movable part of the lifter 7 with a stretchable material and to have a structure in consideration of safety so that an operator is not caught.
- sample pretreatment device 1 and the oxygen analyzer 2 are connected in preparation for the case where the connected oxygen analyzer 2 cannot be used due to a failure or when a preprocessed sample waiting for analysis is analyzed by another oxygen analyzer.
- An outlet 9 for a pretreated sample is provided in the middle of the tube 8.
- the height (thickness) produced by cutting the steel ingot collected from molten steel is 1.5 mm or more.
- a punched cylindrical piece is used as a sample for a slice of 7 mm or less.
- an analysis sample adjustment method and apparatus disclosed in Patent Document 4 may be applied.
- the ratio S / V of the surface area S to the volume V calculated from the diameter and height of the sample bottom should satisfy the following formula (1). It is necessary to ensure a simple shape.
- an oxygen analyzer based on the operating principle of heating and melting in an inert gas-infrared absorption method was selected as a highly accurate method for analyzing oxygen in steel.
- a graphite crucible serving as a sample holder and a sample deoxidation reagent (carbon) supply source is used.
- a so-called “blank” process is performed in which only the crucible is heated in advance at a slightly higher temperature than during the analysis.
- the “blank” treatment can reduce the influence of oxygen, carbon monoxide or carbon dioxide generated from the graphite crucible changing the analytical value.
- a crucible that is, a sample is usually heated to a temperature of about 1800 ° C. to 2200 ° C.
- the heating may be performed at a temperature that is 100 ° C. or more higher than the temperature at the time of analysis and for 15 seconds or more.
- the analysis sample obtained by machining and previously weighed was subjected to vacuum arc plasma treatment and inserted into the oxygen analyzer as it was without being brought into contact with the atmosphere.
- the shape of the analysis sample (S / V: 1.07 to 1.60) was used. However, the latter sample was used only for preparing a calibration curve. After weighing the sample, it was pretreated with a sample pretreatment apparatus capable of vacuum arc plasma treatment (Estec Co., Ltd., model: AP1), and then the sample was transferred in an Ar purge atmosphere. (Model: TCH-600), and the oxygen concentration in the sample was analyzed.
- the applied power during crucible “blank” treatment and analysis was 5.0 kW (equivalent to about 2200 ° C.) and 4.0 kW (equivalent to about 2000 ° C.), respectively, and the average of the two measurements was taken as the analysis value. did.
- the vacuum arc plasma treatment was performed by [O] analysis with the other conditions unified as follows, except for the investigation conditions that were specifically refused.
- Vacuum arc plasma discharge time GS-3c was used as a sample, and oxygen analysis was performed on the sample subjected to the treatment while changing the vacuum arc plasma discharge time.
- discharge was implemented only for the same time with respect to the sample front and back, respectively.
- the total discharge time was 0.2 seconds or more and 1.2 seconds or less, the error was within ⁇ 2 ppm, and the analysis accuracy satisfying the requirements was obtained. Since the sample temperature after the treatment was particularly high at 1.4 seconds or more, it is considered that the sample surface was reoxidized.
- Arc plasma output current GS-3c was used as a sample, and oxygen analysis was performed on the sample subjected to the treatment by changing the output current in the vacuum arc plasma treatment.
- the error was ⁇ 2 ppm or less, and the analysis accuracy satisfying the requirements was obtained.
- Sample shape Samples having different shapes and oxygen-containing concentrations were prepared, subjected to vacuum arc plasma treatment under standard conditions, and then analyzed for oxygen concentration. Separately, samples collected from the vicinity of the same steel ingot as much as possible were subjected to the conventional method, that is, the sample surface was polished with a file, and then subjected to oxygen analysis, and the analytical values obtained were compared as the content concentration.
- the ratio S / V of the surface area S to the volume V of the sample is within the range of the present invention, that is, 1.05 or more and 1.30 or less, the content concentration is in good agreement and the error is within ⁇ 2 ppm. Analysis accuracy that meets the requirements was obtained.
- Example 2 A steel ingot taken from the molten steel was prepared and subjected to oxygen analysis under the standard conditions described in Example 1. The results are summarized in Table 7.
- Condition 1 is the case where the sample surface collected from the steel ingot by machining is subjected to oxygen analysis after being polished by a conventional method, that is, from a steel ingot, but it takes a long time for sample processing and pretreatment. The time required does not meet the requirements.
- the time required for the analysis will slightly increase or decrease depending on the analysis equipment (manufacturer, model) and the detailed settings of the analysis conditions. However, the analysis time can be shortened by exchanging the crucible in advance and baking it. The effect of the invention is not impaired.
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Abstract
Description
酸素含有量50ppm以下の鋼に対して、誤差が±2ppm以内に収まること。好ましくは誤差が±1ppmに収まること。
鋼塊試料を受け取ってから、試料加工、清浄化前処理を経て、分析により酸素濃度が判明するまでの時間(以下、「分析所要時間」と称する。)は、5分以下。好ましくは4分以下。
そこで、本発明は、上記の要求を満たす高精度かつ迅速な精錬途中の溶鋼の酸素分析方法を提供すること目的とする。
図1に本発明の鉄鋼中酸素分析装置を模式的に示す。本発明で組み合わせる要素技術の内、迅速かつ再現性の高い試料前処理方法として、真空アークプラズマ処理を選択した。例えば、特許文献3に開示された金属中成分分析用試料の調整方法及び装置を適用すればよい。予め真空に保った試料前処理装置1内に、隔離バルブ4を介して、真空度をほとんど変化させることなく、処理前試料投入口3から試料を挿入することができる。その後、真空アークプラズマ処理により、試料表面の酸化皮膜を数秒で除去する。該装置では、試料を自動搬送するため、試料形状を円柱またはブロック(直方体)に限定する。試料は、試料台に載置して処理するため、試料台と接する面は処理されない。そこで、試料を反転させて処理する必要がある。つまり、ひとつの試料に対して、少なくとも2回は放電する必要がある。放電回数が増えると、試料が長時間加熱されることになり、一旦、酸化皮膜除去された試料表面は再び酸化されてしまう。したがって、試料表面の酸化皮膜を確実、正確かつ再現性良く除去し、精錬操業上必要とされる分析精度を確保するため、下記の条件でアークプラズマ処理する必要がある。
なお、処理時に真空度が一定値に保持されるよう、真空排気バルブとガス導入バルブの開閉を制御する圧力制御機構を有することがなお好ましい。
(3)処理時間:後述するように、ひとつの試料に対して、合計の処理時間は0.2秒以上1.2秒以下とする。
処理後の試料は、大気と接触させることなく、分析装置2に配置した前処理済試料投入口5を通じて、最終的に黒鉛るつぼに投入する。試料前処理チャンバーと分析装置の試料投入口は真空または不活性ガスで内部を置換した連結管8で連結する。不活性ガス種としては、空気との比重差を考慮して、連結管内を確実にガス置換して、処理後の試料の再酸化を防止する観点、さらには経済的な観点から、Arが好ましい。特許文献3に開示された装置構成では、前処理済試料は払い出された後、別置きの酸素分析装置に移送される。しかし、本発明の目的では迅速性が要求されることから、試料前処理装置1と酸素分析装置2を、それぞれ鉛直上下に配置し、連結管8内を自由落下させて、試料を移送する方法、すなわち図1のような装置構成を採用した。
この理由は現時点で十分解明できていないが、電極形状などアーク処理部の形状に依存して、アークプラズマの空間分布において効率的な処理に好適な位置が限定されることに対応しているものと推察される。
日本鉄鋼認証標準物質(JSS)の鋼中ガス分析用管理試料GS-3c(含有濃度[O]:34.6ppm)、GS-5c(含有濃度[O]:125ppm)を機械加工して、円柱形状の分析試料(S/V:1.07~1.60)とした。ただし、後者の試料は検量線作成のみに使用した。重量を秤量した後、真空アークプラズマ処理可能な試料前処理装置(エステック株式会社製、型式:AP1)で前処理した後、Arパージ雰囲気で試料を移送し、酸素分析装置(LECO株式会社製、型式:TCH-600)に投入し、試料中の酸素濃度を分析した。なお、るつぼの「空焼き」処理時および分析時の印加電力はそれぞれ5.0kW(約2200℃相当)、4.0kW(約2000℃相当)とし、2回の測定値の平均を分析値とした。また、真空アークプラズマ処理は、それぞれ、特に断った各調査条件を除き、他の条件を以下のように統一して[O]分析を行った。
処理時間:0.4秒
出力電流:30A
合計処理回数:2回(試料表裏面に対して各1回)
なお、真空アークプラズマ処理において、試料に対して放電を実施する前に、試料を待避させた状態で放電させる、「クリーニング放電」を実施した。クリーニング放電の条件は、上記放電条件に準じた。
試料としてGS-3cを用い、真空アークプラズマ放電開始時の真空度を変えて当該処理を施したものについて酸素分析を行った。その結果、5Pa以上35Pa以下の真空度において、誤差は±2ppm以内となり、要求を満たす分析精度が得られた。
試料としてGS-3cを用い、真空アークプラズマ放電時間を変えて該処理を施したものについて酸素分析を行った。なお、放電は試料表裏面に対して、それぞれ同じ時間だけ実施した。その結果、合計放電時間が0.2秒以上1.2秒以下において、誤差は±2ppm以内となり、要求を満たす分析精度が得られた。1.4秒以上では処理後の試料温度が特に高かったことから、試料表面が再酸化したものと考えられる。
試料としてGS-3cを用い、真空アークプラズマ放電回数を変えて該処理を施したものについて酸素分析を行った。なお、放電は試料表裏面に対して、それぞれ同じ回数だけ実施した。その結果、合計4回以下では、誤差が±2ppm以下となり、要求を満たす分析精度が得られた。
試料としてGS-3cを用い、真空アークプラズマ処理における出力電流を変えて該処理を施したものについて酸素分析を行った。その結果、15A以上55A以下の範囲において、誤差は±2ppm以下となり、要求を満たす分析精度が得られた。
試料としてGS-3cを用い、真空アークプラズマ処理後、酸素分析装置へ投入するまでに、試料を保持する雰囲気を変えたものについて酸素分析を行った。その結果、処理後の試料を大気と接触させた場合、誤差は±2ppmを越え、要求を満たす分析精度は得られなかった。
形状、酸素含有濃度の異なる試料を準備し、標準条件で真空アークプラズマ処理した後、酸素濃度を分析した。別途、同じ鋼塊のできる限り近傍から採取した試料を、従来の方法、すなわち試料表面をヤスリで研磨した後、酸素分析に供して得られた分析値を、含有濃度として比較した。
(実施例2)
溶鋼から採取した鋼塊を準備し、実施例1で記載した標準条件で酸素分析した。その結果を表7にまとめて示す。
3 処理前試料投入口 4 隔離バルブ
5 前処理済試料投入口 6 架台
7 リフター 8 連結管
9 前処理済試料途中取出口
Claims (1)
- 鉄鋼試料を黒鉛るつぼに入れて不活性ガス中で加熱融解し、発生した一酸化炭素または二酸化炭素のいずれかひとつあるいは両方の赤外線吸収度から該試料中の酸素濃度を測定する方法であって、
該試料表面の酸化皮膜を除去、清浄化する前処理として真空アークプラズマ処理をアークプラズマ放電開始時の真空度を5Pa以上35Pa以下かつ、アークプラズマ出力電流を15A以上55A以下とする条件下において、
溶鋼から採取した鋼塊に対して、高さ1.5mm以上7mm以下、表面積Sと体積Vの比(S/V)が1.05以上1.30以下となるように機械加工して得た小片を試料とし、
前記アークプラズマ放電を前記試料に、合計4回以下であって、かつ合計処理時間として0.2秒以上1.2秒以下施した後、
該試料を大気と接触させることなく、直接、分析時の温度よりも高い温度で加熱、清浄化した後、分析する温度に下げて待機させた黒鉛るつぼへ投入することを特徴とする鉄鋼中酸素分析方法。
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JPH06148170A (ja) | 1992-11-13 | 1994-05-27 | Nkk Corp | 鉄鋼の微量酸素分析方法 |
JPH1073586A (ja) | 1996-08-30 | 1998-03-17 | Kawasaki Steel Corp | 金属中微量酸素の分析方法および装置 |
JPH10311782A (ja) | 1997-05-12 | 1998-11-24 | Stec Kk | 分析試料の調整方法及びその装置 |
JP2000193657A (ja) * | 1998-12-25 | 2000-07-14 | Horiba Ltd | 試料中の酸素分析方法および装置 |
JP2002328125A (ja) | 2001-05-02 | 2002-11-15 | Stec Kk | 金属中成分分析用試料の調整方法及び装置 |
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JP2003181679A (ja) * | 2001-12-13 | 2003-07-02 | Mitsubishi Heavy Ind Ltd | 溶接方法、被覆物の除去方法、被覆物除去装置 |
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JPH06148170A (ja) | 1992-11-13 | 1994-05-27 | Nkk Corp | 鉄鋼の微量酸素分析方法 |
JPH1073586A (ja) | 1996-08-30 | 1998-03-17 | Kawasaki Steel Corp | 金属中微量酸素の分析方法および装置 |
JPH10311782A (ja) | 1997-05-12 | 1998-11-24 | Stec Kk | 分析試料の調整方法及びその装置 |
JP2000193657A (ja) * | 1998-12-25 | 2000-07-14 | Horiba Ltd | 試料中の酸素分析方法および装置 |
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