JP6332639B2 - Hot metal removal Se treatment method - Google Patents

Description

The present invention relates to a hot metal removal Se treatment method, and more specifically, it is possible to efficiently and accurately control the Se concentration in hot metal by quantitatively analyzing the Se concentration in hot metal with high accuracy. The present invention relates to a hot metal removal Se treatment method. Note that removing Se processing method of hot metal of the present invention is to have groups Dzu the analysis of Se concentration in the molten iron stage, it means a method of treating de Se, also includes de-Se treatment with subsequent hot metal stage.

In recent years, as the demand for higher quality (higher functionality and improved reliability) for steel products increases, reduction of impurities contained in steel is desired. In particular, when Se is contained even in a very small amount in steel, it has a great adverse effect on weldability, HIC resistance, and SCC resistance, and therefore, reduction of Se content has become an important issue (for example, patents). Reference 1). Se that is included in the iron and steel products, the are those most are derived from raw materials such as iron ore and coke, during the hot metal exiting from the blast furnace, which contains a relatively large number of Se. Therefore, in order to improve the quality of steel products, it is required to reduce the Se content to less than 0.0002 mass% (2 massppm), desirably to a very small amount of 0.0001 mass% (1 massppm) or less in the hot metal stage. It is done. In the following, mass% is also simply expressed as “%”, and massppm is also simply expressed as “ppm”.

As a de-Se treatment method for removing Se in steel, Patent Document 1 discloses slag in which CaO is a main component, basicity (CaO / SiO ₂ ) is 1 or more, and total Fe concentration is 1.5% or less. And the molten steel are brought into contact with each other and Se in the molten steel is absorbed by the slag and removed by a slag-metal reaction. However, in the above-mentioned Patent Document 1, only a value of 0.001% (10 ppm) is displayed for the Se concentration after the de-Se treatment. This is presumably because the conventional Se concentration analysis method could not quantify the Se concentration of 0.001% or less.

  In general, atomic absorption analysis and inductively coupled plasma mass spectrometry are used for quantitative analysis of trace components in iron or steel. As for the analysis method of Se by the former atomic absorption analysis method, JIS G1257-20 (2013) of Non-Patent Document 1 describes "Iron and steel-Atomic absorption analysis method-Part 20: Selenium determination method-Electric heating method". It is prescribed as However, the lower limit of quantification of this method is 0.0002%, and this analysis method cannot be applied to Se concentrations less than that.

On the other hand, the latter inductively coupled plasma mass spectrometry method is more sensitive than the atomic absorption spectrometry method. Further, by developing an analyzer equipped with a quadrupole mass spectrometer, the lower limit of quantification of 0.0001% It has become possible to analyze to a concentration of (1 ppm) or less. However, when the Se concentration is quantified using the inductively coupled plasma spectrometer, ⁸⁰ Se having the largest natural abundance ratio among Se isotopes is diatomic ions of Ar ( ⁴⁰ ) used in the plasma source. Ar ⁴⁰ Ar ⁺ ) has the same mass number, and ⁷⁸ Se, which has the next highest natural abundance, has the same mass number as ³⁸ Ar ⁴⁰ Ar ⁺ and has the same spectrum. There is a problem that it is difficult to quantify accurately (this phenomenon is generally called “spectral interference”). Therefore, in recent years, an inductively coupled plasma mass spectrometer having a collision / reaction cell provided in front of a quadrupole mass filter has been developed as a countermeasure against the above-described spectrum interference.

In addition, when analyzing trace components in metal materials such as iron and steel, if the solution to be dissolved with acid, including matrix metal (Fe), is analyzed, interference caused by spectral interference of matrix metal (this phenomenon) Is generally referred to as “matrix effect” or “matrix interference” ), and it is still difficult to analyze with high accuracy. There is also a problem of clogging at the sample introduction part.

  Therefore, as a method for solving the problems of the matrix effect described above, with regard to steel materials, an ion exchange method for extracting trace components other than the matrix by bringing a hydrofluoric acid acidic solution in which a sample is dissolved into contact with an ion exchange resin. Is disclosed in Patent Document 2. However, no example has been reported so far in which the ion exchange resin separation method is used for Se analysis in steel. Note that, as described above, a method in which a solution in which a sample is dissolved is directly analyzed by inductively coupled plasma mass spectrometry is hereinafter referred to as “solution introduction method”. )

JP-A-62-017116 Japanese Patent Application Laid-Open No. 07-043353

JIS G1257-20 (2013): "Iron and steel-Atomic absorption analysis method"

  As described above, the conventional method for analyzing trace components in steel is not sufficient for the analysis of Se concentration of less than 0.0002% in terms of the lower limit of quantification, and therefore the Se concentration in hot metal is reduced to 0. It could not be applied to de-Se treatment which is reduced to less than 0002%. For this reason, in the prior art, the necessity of de-Se treatment, the amount of de-Se agent added, and the determination of de-Se treatment conditions such as treatment time had to be carried out by prediction.

  The present invention has been made in view of the above-mentioned problems of the prior art, and its purpose is to accurately analyze the Se concentration of less than 0.0002% contained in the hot metal, thereby removing the Se from the hot metal. A method of demetallizing hot metal that optimizes the conditions so that the Se concentration after hot metal pretreatment is reliably controlled to be less than 0.0002% and can prevent an increase in cost due to the addition of excessive desemination agent. It is to propose.

  Inventors repeated examination about the method of analyzing the Se density | concentration in hot metal accurately using inductively coupled plasma mass spectrometry for the solution of the said subject. As a result, instead of the conventional solution introduction method in which the solution in which the hot metal sample is dissolved is used as an object of analysis, Se in the solution in which the hot metal sample is dissolved is extracted as a hydride, and hydride generation in which this is analyzed— By using inductively coupled plasma mass spectrometry, the adverse effect of the “matrix effect” can be avoided, and the Se concentration in the hot metal can be quantitatively analyzed with high accuracy. Therefore, this hydride generation-inductively coupled plasma mass spectrometry method can be performed. It was found that the Se concentration in the hot metal can be controlled to less than 0.0002% by applying to the hot metal removal Se treatment, and the present invention was completed.

  That is, the present invention analyzes the Se concentration of a sample taken from at least one stage of hot metal before hot metal pretreatment, during hot metal pretreatment and after hot metal pretreatment, and based on the analysis value of the Se concentration, In a hot metal de-Se treatment method for determining the necessity of de-Se treatment or subsequent de-Se treatment conditions, the Se concentration is analyzed by hydride generation-inductively coupled plasma mass spectrometry. Se processing method.

  The hydride generation-inductively coupled plasma mass spectrometry method in the hot metal de-seed treatment method of the present invention includes an acidic solution process in which a sample collected from hot metal is thermally decomposed with an acid to form an acidic solution, and the acidic solution conversion A reducing agent and hydrochloric acid are brought into contact with the acidic solution obtained in the step, Se in the acidic solution is used as Se hydride gas, and Se hydride gas generated in the hydrogenation step is inductively coupled with plasma mass. It is characterized by having a Se concentration analysis step for introducing Se into the analyzer and quantifying the Se concentration.

  Further, the hot metal de-Se treatment method of the present invention uses one or more selected from sodium borohydride, lithium aluminum hydride, lithium triethylborohydride, hydrazine and hydroxylamine as the reducing agent. Features.

  Further, the hot metal de-se treatment method of the present invention is characterized in that the de-Se target concentration is less than 0.0002 mass%.

  According to the present invention, the Se concentration in a sample taken from at least one stage of hot metal before, during and after hot metal pretreatment is analyzed by hydride generation-inductively coupled plasma mass spectrometry. Since the Se concentration can be grasped with high accuracy, the Se concentration after the hot metal preliminary treatment can be controlled with high accuracy. In addition, according to the present invention, the Se concentration in the molten iron is accurately grasped, and the subsequent de-Se treatment conditions are determined. Therefore, the de-Se treatment conditions are optimized, and excessive addition of the de-Se agent is suppressed. In addition, it is possible to reduce the time for removing Se. Furthermore, according to the present invention, the Se concentration in the hot metal can be controlled to a very small amount, which contributes to the improvement of the quality of steel products.

It is a figure which shows the structural example of Se analyzer used for this invention. It is a figure which shows an example of the analytical curve of Se produced using the hydride generation | occurrence | production-inductively coupled plasma mass spectrometry.

  The hot metal discharged from the blast furnace is transferred to the steelmaking process using a torpedo car or hot metal ladle, and then charged into the converter using a special ladle called a charging pan. As a pretreatment technique for hot metal before being charged into the converter, a method of injecting a desulfurizing agent, a dephosphorizing agent, etc. into the torpedo car or hot metal ladle, or a refractory made of hot metal contained in the hot metal ladle. There is known a KR (Kanbara Reactor) method in which a cross blade (impeller) is inserted and a desulfurizing agent or a desulfurizing agent is added while rotating at high speed in the center of the pan.

Accordingly, the inventors focused on the hot metal preliminary treatment and studied a de-Se treatment method for reducing the Se concentration in the hot metal to less than 0.0002%. Specifically, pre-pre-processing in the molten iron pretreatment, analyze Se concentration in molten iron in at least one stage after the pre-process and pre-treatment, and have groups Dzu on the analysis result, subsequent de Se treatment It was studied to determine the necessity (de Se treatment condition) such as the necessity, the amount of deSe agent introduced when performing the de Se treatment, and the treatment time.

  However, in order to carry out the above-described de-Se treatment, it is necessary to analyze the Se concentration in the hot metal with high accuracy. Therefore, the inventors have further studied a method for analyzing Se concentration in molten iron with high accuracy by using inductively coupled plasma mass spectrometry. As a result, instead of the conventional solution introduction method in which the solution in which the hot metal sample is dissolved is used as an object of analysis, Se in the solution in which the hot metal sample is dissolved is extracted as a hydride, and hydride generation in which this is analyzed— By using inductively coupled plasma mass spectrometry (hereinafter, simply referred to as “hydride generation method”), it is possible to avoid the “matrix effect” and to quantitatively analyze the Se concentration in hot metal with high accuracy. I found out.

Hereinafter, the hydride generation method which is the Se concentration analysis method of the present invention will be described.
First, in the hot metal de-se treatment method of the present invention, it is necessary to collect a sample for analysis from the hot metal in at least one stage before, during and after the hot metal pretreatment process. The method for collecting the analytical sample from the hot metal is not particularly limited. For example, the method defined in Annex 3 of JIS G0417 can be used. According to this method, the sample for analysis can be obtained very easily by crushing the molten sample collected with a spoon or the like onto a clean iron plate and solidifying it with a hammer or the like to a size of about 1 to 2 mm. Can be obtained.

Next, an analytical sample of hot metal collected as described above is weighed, and is subjected to an acid solution step by thermally decomposing with an acid to form an acid solution, and a reducing agent and hydrochloric acid are added to the acid solution obtained in the acid solution step. A hydrogenation step in which Se in an acidic solution generates Se hydride gas (gas), and Se concentration analysis in which the Se hydride gas generated in the hydrogenation step is analyzed to quantify the Se concentration The Se concentration in the molten iron sample is analyzed using hydride generation-inductively coupled plasma mass spectrometry with a process.
Hereinafter, each step will be described.

<Acid solution process>
An analytical sample collected from the hot metal is weighed and then thermally decomposed with an acid to obtain an acidic solution containing Se. Examples of the acid used for dissolving the sample include hydrochloric acid, nitric acid, hydrofluoric acid (hydrofluoric acid), sulfuric acid, perchloric acid, and a mixed acid in which two or more of the above acids are mixed. Good. As specific dissolution conditions, for example, when a mixed acid of hydrochloric acid and nitric acid is used, it is preferable to use an acid obtained by mixing 1 ml of nitric acid and 8 ml of hydrochloric acid with respect to 0.3 mg of the molten iron sample. Further, the acid concentration may be appropriately adjusted by adding pure water to the mixed acid. The heating temperature is not particularly limited as long as the sample can be completely decomposed, but is preferably in the range of 50 to 300 ° C. If the temperature is lower than 50 ° C., it takes a long time to dissolve the sample. On the other hand, if the temperature exceeds 300 ° C., usable instruments and devices may be restricted, or the solution may be bumped. .

  Next, the Se-containing acidic solution obtained in the acidic solution forming step is introduced into a hydride generation-inductively coupled plasma mass spectrometer. FIG. 1 shows an example of a hydride generation-inductively coupled plasma mass spectrometer used in the present invention. The analyzer includes a hydride generator 1 that performs a hydrogenation step of generating Se hydride gas from the Se-containing acidic solution, and a step of performing mass analysis by ionizing the generated Se hydride gas in plasma. The inductively coupled plasma mass spectrometer 2 is used.

<Hydrogenation process>
The hydride generator 1 includes a sample solution supply line 3 that supplies an Se-containing acidic solution, a carrier gas supply line 4 that supplies a carrier gas, a reducing agent supply line 5 that supplies a reducing agent, and a hydrochloric acid solution supply line 6. The Se-containing acidic solution is introduced into the hydride generator 1 through the sample solution supply line 3, and the solution is brought into contact with the reducing agent introduced from the reducing agent supply line 5 and the hydrochloric acid solution introduced from the hydrochloric acid supply line 6. To reduce Se to form a hydride of Se (H ₂ Se). Since the Se hydride H ₂ Se is a gas (gas), it is guided to the inductively coupled plasma mass spectrometer 2 by the carrier gas (argon gas) supplied from the carrier gas supply line 4.

  Here, as the reducing agent, one or more selected from sodium borohydride, lithium aluminum hydride, lithium triethylborohydride, hydrazine and hydroxylamine can be used. The amount of the reducing agent added is preferably 2 to 10 times the molar amount of Se contained. When the amount of the reducing agent added is less than twice the amount of Se hydride (gas) generated, the amount may decrease. On the other hand, if the amount exceeds 10 times, there is a possibility that problems such as concern about contamination from reagents and excessive reaction by-product gas such as hydrogen may occur.

  The hydrochloric acid added together with the reducing agent is a kind of reducing agent and plays a role of promoting the generation of Se hydride. In order to acquire the said effect, it is preferable to set it as the range of 0.5-6.0 mol / L. If the hydrochloric acid concentration is less than 0.5 mol / L, the generation of Se hydride may be insufficient. On the other hand, hydrochloric acid with a high concentration exceeding 6.0 mol / L requires care in handling. is there.

  As acids used with the reducing agent, oxidizing acids such as nitric acid and perchloric acid oxidize +4 valent Se to +6 valence, which may hinder the generation of Se hydride (gas). Is not preferable. In addition, since sulfuric acid increases the viscosity of the solution, it may cause physical interference when measured with an inductively coupled plasma mass spectrometer. Since hydrofluoric acid erodes the glass, special equipment is installed in the measuring instrument. Neither is desirable because it is necessary. Therefore, it is desirable to use hydrochloric acid in the present invention.

  In addition, since the optimum concentration of the reducing agent and hydrochloric acid varies depending on the hydrogenation apparatus, the reagent used, and the like, an experiment is performed in advance to obtain the optimum concentration of the reducing agent and hydrochloric acid that generate Se hydride. It is desirable. The concentration is preferably adjusted using pure water from the viewpoint of avoiding adverse effects on the analysis accuracy due to impurities.

<Se concentration analysis process>
Next, the Se hydride gas guided to the inductively coupled plasma mass spectrometer 2 by the carrier gas is ionized in a high-temperature argon plasma, and Se mass analysis is performed.
The inductively coupled plasma mass spectrometer 2 is provided with an interference suppression device such as a collision / reaction cell in front of the quadrupole mass filter in order to avoid “spectral interference” due to the above-described argon polyatomic ions or the like. It is preferable to use one.

Here, the collision / reaction cell interference suppression mode includes a collision mode and a reaction mode.
The former Korijo Nmo over de is or dissociated by colliding with the collision cross-sectional area than the analyte element ions is large polyatomic ions (interfering ions) and collision gas, selected analyte element ions by or de-energized Is a mode that suppresses spectral interference by analyzing automatically, for example, by introducing a collision gas into the cell and colliding with polyatomic ions Ar ₂ ⁺ (mass number 80) that are interference ions to reduce energy, ⁸⁰ Se ⁺ having a high energy is selectively analyzed. As the collision gas, helium or hydrogen can be used.

On the other hand, in the latter reaction mode, the target element ions and reaction gas are reacted to form ions with a mass number different from the interference ions, and the spectrum interference is selectively analyzed by selectively analyzing the ions with different mass numbers. In this mode, for example, oxygen is supplied as a reaction gas into the cell and reacted with ⁸⁰ Se ⁺ to react with ⁸⁰ Se ¹⁶ O ⁺ or ⁷⁸ Se ⁺ to form ⁷⁸ Se ¹⁶ O ^+. By analyzing, interference of Ar ₂ ⁺ (mass number 80 or 78) is excluded.

  In addition to the use of the collision / reaction cell, a method of suppressing the generation of polyatomic ions of argon by adjusting the plasma output (RF power) is also effective as a method of suppressing spectral interference. This method may be used alone or in combination with a collision / reaction cell.

In addition, the Se to be analyzed includes ⁷⁴ Se (natural abundance ratio of 0.9 at%, the same shall apply hereinafter), ⁷⁶ Se (9.4 at%), ⁷⁷ Se (7.6 at%) as isotopes existing in nature. , ⁷⁸ Se (23.8 at%), ⁸⁰ Se (49.6 at%) and ⁸² Se (8.7 at%). Of these isotopes, those having any mass number may be analyzed, but in terms of analysis sensitivity, it is preferable to target ⁸⁰ Se and ⁷⁸ Se having a large abundance ratio. Alternatively, a plurality of Se having different mass numbers may be simultaneously measured, and an analysis value of an isotope that can be measured with the highest accuracy among them may be used as a measurement value.

  Here, when performing quantitative analysis of trace components by the hydride generation method, from the viewpoint of avoiding adverse effects due to impurities, the reagent to be used is an ultra-high purity standard for analysis, an electronic industry standard, or It is preferable to use the same or higher purity. The pure water used for dilution or the like is distilled or ion-exchanged, and is preferably A4 grade (ultra pure water) as defined in JIS K0557 “Water used for water and wastewater tests”.

  Also, the carrier gas for introducing the generated Se hydride (gas) into the inductively coupled plasma mass spectrometer, the argon gas used for the plasma gas, the auxiliary gas, and the like are high-purity argon gas, specifically, the purity is high. It is preferable to use a high purity argon gas of 99.9 vol% or more. This is because the plasma becomes unstable when a gas other than argon is introduced into the analyzer.

  Furthermore, the micro-scaling of the measurement sample can reduce the size of the container used for acid decomposition of the sample and adjustment of the acid concentration, and reduce the amount of reagent used, thereby reducing contamination from the reagent and the container. it can. Further, in order to increase the representativeness of the measurement sample, a macro-scaling that increases the amount of the measurement sample may be attempted, and it is preferable to find an optimum scale in a preliminary experiment in advance.

Next, an example of creating a calibration curve necessary for quantitative analysis of Se concentration in a hot metal sample will be described.
Se-containing standard solution (for atomic absorption manufactured by Kanto Chemical Co., Inc.), hydrochloric acid (for electronic industry manufactured by Kanto Chemical Co., Ltd.), and ultrapure water collected from Millipore ultrapure water production equipment as dilution water are mixed in a specified ratio. The Se concentration was 0% (blank solution), 1 × 10 ⁻⁶ % (0.01 ppm), 3 × 10 ⁻⁶ % (0.03 ppm), 5 × 10 ⁻⁶ % (0.05 ppm) and 1 × ¹⁰ -5% by adjusting a standard solution of 5 stages of (0.10 ppm), co Region / back and forth quadrupole mass filter provided with hydride generation of reaction cell - inductively coupled plasma mass spectrometer (Agilent Technologies, Inc. Ltd., using a Agilent 8800), were subjected to mass analysis of ^Se having a mass number of 80 in the collision gas mode using hydrogen as collision gas ⁽⁸⁰ Se). The standard solution was measured three times for each solution.

FIG. 2 shows a calibration curve obtained by obtaining a linear regression equation by the least square method from the relationship between the Se concentration of the standard solution and the measured intensity (ion count value) of ⁸⁰ Se. When the coefficient of determination (square of correlation coefficient R) of this regression equation was obtained, it was 0.999, and it was found that the Se concentration and the measured intensity of ⁸⁰ Se had a very good correlation and were effective as a calibration curve. .
In addition, when blank measurement was performed 10 times for a blank solution with a Se concentration of 0% and the Se concentration was quantified from the calibration curve, the standard deviation σ was 7 × 10 ⁻⁹ % (7 × 10 ⁻⁵ ppm). It was. From this, the detection limit (lower limit) of Se concentration defined by 3σ in the hydride generation method of the present invention is 2 × 10 ⁻⁸ % (2 × 10 ⁻⁴ ppm), and the lower limit of quantification defined by 10σ is 7 It becomes * 10 <^-8> % (7 * 10 < ^-4 > ppm).
From the above results, it was found that by using the hydride generation method of the present invention, it is possible to measure with sufficiently high accuracy even at a Se concentration of less than 0.0002% (2 ppm).

The above calibration curve is obtained when ⁸⁰ Se having a mass number of 80 is subjected to mass spectrometry. However, ⁷⁸ Se having a mass number of 78 or a polyatomic molecule of Se and oxygen ( ⁸⁰ Se ¹⁶ O ⁺ or ⁷⁸ Se). Even when mass analysis of ( ¹⁶ O ⁺ ) is performed, it has been confirmed that the determination coefficient (R ² ) of the calibration curve is 0.999 or more, and the Se concentration can be analyzed at the same lower limit as the above.

  Note that the hydride generation method used in the present invention has a feature that the measurement time of one sample is about 1 minute and that a plurality of elements can be measured simultaneously. Since it takes a long time and almost one day is required as a whole, it is difficult to feed back the analysis result directly to the hot metal desemination process of the hot metal sampled.

  However, Se in hot metal originates from the hot metal raw material, mainly coke and iron ore, and since the variation in the type and mixing ratio of coal and iron ore of the coke raw material is relatively small, Se in hot metal Concentration fluctuations also occur in a relatively long cycle, and if the difference is about one day, the fluctuation amount is small. Therefore, even if the Se concentration in the hot metal discharged from the blast furnace is periodically measured and the result is applied to the subsequent de-Se treatment, the Se concentration in the hot metal can be estimated with sufficiently high accuracy. .

Therefore, the measurement of Se concentration is performed on de-Se pretreatment of molten pig iron, and have groups Dzu on the results, subsequent principal soon de Se processing tapping is the hot metal, dosage of leaching Se agents, processing time, etc. The de-Se processing conditions are determined. For example, samples before and after de-Se treatment are collected from various hot metal with different chances of brewing, Se concentration is analyzed, and the relationship with de-Se treatment conditions (de-Se agent input, treatment time, etc.) the database of, thereto to have based Dzu preferably determined de Se processing conditions described above.

  In addition, the measurement of the Se concentration is not limited to the hot metal before the de-Se treatment, for example, during the de-Se treatment or after the de-Se treatment, and depending on the result, Subsequent hot metal removal Se conditions may be determined, necessity of removal Se processing in the next steelmaking process, or removal Se conditions may be determined.

When the hot metal preliminary treatment is performed using the KR method in which the impeller is rotated and mechanically stirred in the hot metal contained in the hot metal ladle, No. 1 with different chances of unloading from the blast furnace. Samples before and after hot metal pretreatment and after hot metal pretreatment are collected from the hot metal of 1 to 5 by the method specified in Annex 3 of JIS G0417, and the sample for Se concentration analysis is prepared. Got ready. Here, the above “difference in ironing” means that the hot metal raw materials are different and the hot metal components are also different (hereinafter the same).
Next, the sample for Se concentration analysis was weighed and thermally decomposed with hydrochloric acid and nitric acid to obtain an acidic solution, and then the hydride generation-inductively coupled plasma mass spectrometer shown in FIG. 1 (manufactured by Agilent Technologies; Agilent 8800). Was used to quantitatively analyze the Se concentration. The hydrochloric acid and nitric acid used in the preparation of the acidic solution were for the electronics industry manufactured by Kanto Chemical Co., and the pure water used for the concentration adjustment was ultrapure water manufactured by Millipore ultrapure water manufacturing equipment. .
In addition, the quantitative analysis of Se concentration was carried out using the above acidic solution, 2.0 w / v% sodium borohydride-0.5 w / v% sodium hydroxide aqueous solution and 1.5 M / L hydrochloric acid solution, and purity as a carrier gas. A high purity argon gas of 99.9 vol% is introduced into the hydride generator 1 shown in FIG. 1 to generate Se hydride gas, and the Se hydride together with the carrier gas has a collision / reaction cell. The sample was introduced into the quadrupole inductively coupled plasma mass spectrometer 2 and quantitatively analyzed for the Se concentration.
In addition, Kanto Chemical Co., Ltd. atomic absorption was used for the sodium borohydride, Kanto Chemical special grade reagent was used for sodium hydroxide, and Kanto Chemical Co., Ltd. electronic industry was used for hydrochloric acid.
The RF power of the inductively coupled plasma mass spectrometer is 1500 W, and the argon gas used as the carrier gas, plasma gas, and auxiliary gas is a high-purity argon gas with a purity of 99.9 vol%, and each flow rate is 1 0.7 L / min, 15.0 L / min, and 0.9 L / min.
The collision / reaction cell was set to the following two modes.
<Korijo Nmo over de>
Hot metal No. About 1-3, hydrogen gas is introduce | transduced into a cell as collision gas at 7 mL / min, and the mass of ⁸⁰ Se (mass number 80) is measured with a detector.
<Reaction mode>
Hot metal No. For 4 and 5, oxygen gas was introduced into the cell as a reaction gas so that the volume concentration was 30 vol%, and ⁸⁰ Se oxygen polyatomic molecule ⁸⁰ Se ¹⁶ O ⁺ (mass number 96) was generated. Is measured with a detector.
In addition, the quantification of the Se concentration was performed using the ⁸⁰ Se calibration curve (calibration curve correlation coefficient R ² : 0.999, lower limit of quantification: 7 × 10 ⁻⁸ %) prepared in advance by the method described above, and It was carried out by an absolute calibration curve method using a calibration curve of SeO ⁺ (correlation coefficient R ^{2 of} calibration curve: 0.999, lower limit of quantification: 8 × 10 ⁻⁸ %). The hot metal sample was analyzed for Se concentration by the “iron and steel-atomic absorption analysis method” (conventional method) defined in JIS G1257-20 (2013).

The results of measuring the Se concentration are shown in Table 1 by comparing the method of the present invention with the conventional method.
As can be seen from Table 1, in the conventional method, the Se concentration of less than 0.0002% (2 ppm) in the hot metal could not be measured because it was below the lower limit of quantification. Therefore, in the conventional method, the effect of the removal Se process by the KR process cannot be determined, and the removal Se process condition cannot be optimized.
On the other hand, in the hydride method of the present invention, all hot metal samples can be sufficiently quantified even with a trace Se concentration of less than 0.0002% (2 ppm), so the hot metal de-Se treatment conditions are optimized, It becomes possible to stably control the Se concentration in the hot metal to less than 0.0002% (2 ppm).
Furthermore, from the comparison of the Se concentration before and after the KR treatment in the method of the present invention, it can be seen that the KR treatment is effective as a de-Se technique.

Samples for Se concentration analysis were collected by the method defined in Annex 3 of JIS G0417 from the A to C three types of hot metal before the hot metal pretreatment process, which differed from the blast furnace, and the same apparatus and method as in Example 1 Was used to quantify the Se concentration in each hot metal sample. The measurement conditions in the inductively coupled plasma mass spectrometer were set to the collision mode, and hydrogen gas was introduced into the cell as a collision gas.
As a result, the Se concentration before the hot metal treatment was hot metal A: 0.0003% (3 ppm), hot metal B: 0.0005% (5 ppm), and hot metal C: 0.0002% (2 ppm).
Next, when the hot metal contained in the hot metal ladle is subjected to the Se removal process by the KR method, the hot metal having the same ironing chance is assumed to have the same Se concentration. In order to make the concentration 0.0001% or less, 10 kg of de-Se agent (CaO) per 1 ton of hot metal is added to the hot metal bath surface, and after mechanical stirring for a predetermined time, a sample for Se concentration analysis is collected from the hot metal. Then, the Se concentration in each hot metal sample was quantified under the same conditions as those of the sample before the pretreatment described above. Here, the “salting chance is the same” means that the hot metal raw materials are the same and the hot metal components can be regarded as substantially the same.

As a result, the Se concentration in the hot metal after the above-mentioned desemination treatment was as follows: hot metal A: 0.00003% (0.3 ppm), hot metal B: 0.00007% (0.7 ppm) and hot metal C: 0.00002% ( 0.2 ppm), and in all cases, the target Se concentration: 0.0001% (1 ppm) or less is achieved.
In addition, the effect of the Se removal agent depends on the Se concentration in the hot metal. Even with the same amount of the Se removal agent, the higher the Se concentration before the treatment, the larger the Se removal effect, and the goal of the Se removal is In the case of 0.0001% (1 ppm) or less, when the Se concentration before de-Se is 0.0003% (3 ppm) or less, the input amount of 10 kg of de-Se agent (CaO) per 1 ton of hot metal is excessive and reduced. It turns out that there is room for.
Therefore, accumulated actual data de Se treatment as described above, the de-Se processing criteria created have groups Dzu on the accumulated data, de-Se processing or in pretreatment processes in hot metal, de-Se processing subsequent step By applying to, the Se concentration in the hot metal can be stably controlled to an extremely small amount of less than 0.0002%.

  The technique of the present invention is not limited to the hot metal desemination process, but can also be applied to desemination process in other metal materials.

1: Hydride generator 2: Inductively coupled plasma mass spectrometer 3: Sample solution supply line 4: Carrier gas supply line 5: Reductant solution supply line 6: Hydrochloric acid solution supply line

Claims (3)

Analyze the Se concentration of a sample collected from at least one stage of hot metal before hot metal pretreatment, during hot metal pretreatment, and after hot metal pretreatment, and based on the analysis value of the Se concentration, the necessity of subsequent deSe treatment Alternatively, in a hot metal de-Se treatment method for determining subsequent de-Se treatment conditions,
The Se concentration is obtained by subjecting a sample collected from hot metal to an acid solution by thermally decomposing it with an acid, and contacting the acidic solution obtained in the acid solution step with a reducing agent and hydrochloric acid to form an acid solution. Having a Se concentration analysis step of quantifying Se concentration by introducing Se hydride gas generated in the hydrogenation step into an inductively coupled plasma mass spectrometer A method for removing Se from hot metal, characterized by analyzing by generation-inductively coupled plasma mass spectrometry. As the reducing agent, sodium borohydride, de Se processing molten iron according to claim 1, lithium aluminum hydride, lithium triethylborohydride, characterized by using one or more selected from among hydrazine and hydroxylamine Method. 3. The hot metal de-Se treatment method according to claim 1 or 2 , wherein the de-Se target concentration is less than 0.0002 mass%.

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