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ONLINE ISSN: 1883-2954
PRINT ISSN: 0021-1575
Publisher: The Iron and Steel Institute of Japan

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Tetsu-to-Hagané Advance Publication

Development of Defect Detection Algorithm for Surface Inspection System Using Twin Illumination and Subtraction Technique

Hiroaki Ono, Masami Tate, Takahiko Oshige, Yukinori Iizuka

Abstract

Surface inspection of steel products is very important for quality assurance. Many automatic in-line surface inspection systems using the camera technique have already been installed in sheet production lines. However, automatic surface inspection of steel products such as steel pipes and thick plates has not advanced because the entire product surface is covered with uneven mill scale, and it is difficult to distinguish the pattern of the mill scale from defects with concave-convex shapes in images of the camera.

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Development of Defect Detection Algorithm for Surface Inspection System Using Twin Illumination and Subtraction Technique

Ductile Fracture Prediction During Metal Forming Using an Ellipsoidal Void Model and Some Other Models

Kazutake Komori

Abstract

This paper reviews studies on the prediction of ductile fracture during metal forming using an ellipsoidal void model and some other models proposed by the author and some relevant studies. Section 2 discusses the research on the theory of voids for predicting ductile fracture during metal forming. Section 3 summarizes the simulation method for predicting ductile fracture during metal forming using the ellipsoidal void model, and Section 4 summarizes the simulation result on the ductile fracture prediction during metal forming using the ellipsoidal void model. Section 5 shows the applicability of the ellipsoidal void model and the simulation result on the ductile fracture prediction during metal forming using some other models.

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Ductile Fracture Prediction During Metal Forming Using an Ellipsoidal Void Model and Some Other Models

Hydrogen Embrittlement Properties of Rapid Tempered High-Si Steel and Effects of the Carbide and Retained Austenite on Its Properties

Manami Sunako, Masataka Mizumoto, Azusa Ooi, Eiji Tada

Abstract

Automotive suspension springs are required to be high-strength and lightweight, and currently have a maximum strength of 2000 MPa. In addition, they must have high resistance to hydrogen embrittlement in the service environment. From previous researches, Si addition or rapid tempering improve the hydrogen embrittlement resistance of low alloy steel. In this study, we investigated the hydrogen embrittlement properties of steel samples with different Si contents and tempering rates and the effects of the fine iron carbides and retained austenite on its properties for 2000 MPa suspension spring steel. JISSUP7 (2.0Si) and SAE9254 (1.4Si) spring steels were tempered at different tempering rates by induction (IH) and furnace heating (FH) methods. Four-point bending tests under corrosion cycles were performed on these steels, and the time to failure was measured. The results show that the 2.0Si-IH steel with higher Si content and higher tempering rate has the longest fracture life and highest resistance to hydrogen embrittlement, even with relatively high diffusible hydrogen content. The size and volume fraction of iron carbides and retained austenite were evaluated by TEM, EBSD, and synchrotron XRD, and the 2.0Si-IH steels were found to have the smallest size and the highest volume fraction of fine iron carbides Fe2-3C(e) and the highest amount of retained austenite. It is considered that the fine iron carbides of Fe2-3C(e) work as hydrogen trap sites and that their high dispersion suppresses dislocation movement. They suppress hydrogen accumulation in stress concentrated areas and are expected to improve resistance to hydrogen embrittlement.

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Hydrogen Embrittlement Properties of Rapid Tempered High-Si Steel and Effects of the Carbide and Retained Austenite on Its Properties

Estimation Method of Whiteline Intensity of Platinum Compounds at L3 Edge XANES and the Oxidation Number Using a Laboratory-type Spectrometer

Takashi Yamamoto, Kazunori Miyamoto

Abstract

Pt L3 edge XANES spectra of various kinds of platinum compounds were recorded using a laboratory-type X-ray absorption spectrometer. In order to investigate precision and the accuracy for oxidation state analysis of platinum species with a simple method, the white line intensity was evaluated by least squares fitting using four kinds of profile functions (Gaussian, Lorentzian and two types of pseudo-Voigt functions) and one arctangent function for continuum state. Differences in estimated values and the deviations depending on the type of profile function adopted were discussed. White line intensity could be determined easily and reproducibly using pseudo-Voigt function where a fraction of Lorentzian function is variable. The relationship between oxidation number of Pt compounds and white line area obtained by pseudo-Voigt method are the most preferable. The height of the white line for divalent compounds varies greatly in some cases, and then it is inappropriate to apply the height to estimation of the oxidation number of unknown samples. The changes in platinum species of silica supported Pt(NH3)4Cl2 of a catalyst precursor during air calcination was examined by in-situ XANES. The platinum species exist as divalent species up to 473 K, and changed to zero-valent between 473 and 573 K. The present in-situ laboratory XAFS experiment and the oxidation state analysis is consistent with SR XAFS studies by other research group.

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Estimation Method of Whiteline Intensity of Platinum Compounds at L3 Edge XANES and the Oxidation Number Using a Laboratory-type Spectrometer

Polarization X-Ray Fluorescence Analysis by Milliwatt X-ray Tube

Jun Kawai, Toshihide Kato, Susumu Imashuku

Abstract

X-ray spectra scattered to 90°were measured for various scatterers of 5-mm thick B4C, acrylic, titanium, iron, zirconium, and lead plates, and their combinations such as B4C(5 mm thick) on acrylic plate (1 or 5 mm thick). The degree of polarization was estimated from the observed X-ray spectra at 0°and 90°. Using the best scatterer as an X-ray polarizer for each samples, polarization X-ray fluorescence (XRF) spectra of various samples such as cabtyre cable, book cover made of synthetic-resin, and steel making slag, compared with non-polarization XRF spectra. Toxic elements in some samples were more sensitive for polarized XRF, while other samples were more sensitive for non-polarized XRF. The reasons for such contradicted experimental results were discussed. Most of the measurements were performed by 15 mW X-ray tube power for polarization XRF, and by 3 mW for non-polarized XRF. The meanings of lowest power XRF measurements in the literature were also discussed. This kind of low power experiments may open the possibility of easy way of experiments, and non-invasive XRF analysis for cultural heritage.

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Polarization X-Ray Fluorescence Analysis by Milliwatt X-ray Tube

In-situ Observation of the Environmental Resistance of Pure Iron Using Hydrogen and Oxygen Sensors in the Environment Simulating Hydrogen Combustion

Michihisa Fukumoto, Hiroki Takahashi

Abstract

The environmental resistance of pure iron was evaluated with oxygen and hydrogen sensor installed after the oxidation furnace. The amount of introduced oxygen was precisely controlled by oxygen pump-sensor at the front stage of the oxidation furnace and the reaction with hydrogen was analyzed. As a result, when oxygen was supplied, a reaction between hydrogen and oxygen occurred, but when sufficient oxygen was not supplied, a hydrogen-vapor environment was created and oxidation was not accelerated. However, when the amount of supplied oxygen was excessive, the environment became oxygen-steam environment and the oxidation was accelerated. At that time, it was clarified that the oxidation by oxygen was dominant under the oxygen-water vapor environment, and the mass gain increased. In addition, the border of the region dominated by oxygen oxidation and that by steam oxidation was clarified by precisely controlling the amount of supplied oxygen by the oxygen pump sensor.

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In-situ Observation of the Environmental Resistance of Pure Iron Using Hydrogen and Oxygen Sensors in the Environment Simulating Hydrogen Combustion

Properties and Effectiveness of the High Phosphate Slag Fertilizer

Masayuki Tani, Rintaro Kinoshita, Kazumitsu Onishi, Hideki Ikemoto, Jun Wasaki, Yohey Hashimoto, Toshiya Harada, Hiroshi Hirata, Shohei Kakimoto

Abstract

High phosphate slag fertilizer (SHP) contains phosphorous, calcium, magnesium and silicon, expected to be effective in supplying plant nutrients and improving soil acidity. We clarified the characteristics and effects of the SHP as a fertilizer. Nippon Steel Corporation prepared the SHP prototypes by concentrating phosphorus through high-temperature processing. Five types (SHP12, SHP15, SHP18-1, SHP18-2, SHP27-2) were examined through dissolution test, pot cultivation experiment, and evaluation of improving effect on soil acidity. The SHP12 was insoluble in water but soluble in various acids and most SHP contained more than 95% of acid-soluble phosphate and silicate. Above-ground growth and phosphate uptake of spinach was higher in the SHP12 plot than in no-phosphate, ammonium phosphate and fused phosphate plots, indicating that phosphorus in the SHP12 could be absorbed more easily than the common phosphate fertilizers. Above-ground growth and phosphate uptake of wheat was also high in the SHP12 and SHP15 plots, which was comparable to ammonium phosphate plot. However, the SHP27-2 had little effect as a phosphate fertilizer. The SHP12 and SHP15 could be expected to supply calcium and silicon as well as phosphorous. Although most SHP showed the same ability to improve soil acidity as calcium carbonate, it might be necessary to avoid excessive increase in soil pH depending on the soil condition and the ability of SHP. We can conclude that if the composition of the SHP is optimized, it can be used as a fertilizer with multiple effects depending on soil types, nutrient status, and crop types.

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Properties and Effectiveness of the High Phosphate Slag Fertilizer

Effects of Retained Austenite upon Softening during Low-temperature Tempering in Martensitic Carbon Steels

Shohei Uranaka, Misa Takanashi, Takuya Maeda, Takuro Masumura, Toshihiro Tsuchiyama, Yuzo Kawamoto, Hiroyuki Shirahata, Yukiko Kobayashi, Ryuji Uemori

Abstract

The effects of retained austenite upon softening during low-temperature tempering at 373 K were investigated using martensitic carbon steels with and without retained austenite. To increase the amount of retained austenite, 10 mass% Ni was added to the base carbon steel (Fe-0.3C alloy). During tempering, the hardness decreased more rapidly in the Ni-added steel containing 6 vol.% retained austenite than in the base steel without retained austenite. Analyses of the microstructure and the carbon content in the solid solution (i.e., the solute carbon concentration) revealed that the retained austenite tended to suppress carbide precipitation and significantly reduced the solute carbon concentration in the martensitic matrix. We demonstrated that retained austenite acts as an effective absorption site for solute carbon in the martensitic matrix; however, the partitioned carbon is unevenly localized near the martensite/austenite interface, owing to the poor diffusivity at 373 K.

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Effects of Retained Austenite upon Softening during Low-temperature Tempering in Martensitic Carbon Steels

Mechanism of Formation of Aluminum-containing Carbide Layers on Carbon Steel by Al Pack Method

Daichi Fujisaki, Shigenari Hayashi, Suzue Yoneda

Abstract

The effect of C content in steels on the formation of an Al-containing carbide layer by an Al pack method at 980℃ was investigated. The continuous layer consisting of an outer β-FeAl and inner Fe3AlC layers was formed on Fe-1.2C (in wt.%) by a short process time. An α-Fe(Al) layer with Fe3AlC precipitates was formed below the β-FeAl layer on Fe-0.7C after 16 h of process, thereafter an Fe3AlC layer was formed between the β-FeAl and α-Fe(Al) + Fe3AlC layers after 25 h. The β-FeAl and α-Fe(Al)+ Fe3AlC layers were formed on Fe-0.1C, but a continuous Fe3AlC layer was not developed after longer treatment. A continuous Fe3AlC layer formed by an Al pack method was explained by carbon enrichment at the α-Fe(Al)/γ-Fe(C) interface due to an inward growth of the α-Fe(Al) layer.

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Mechanism of Formation of Aluminum-containing Carbide Layers on Carbon Steel by Al Pack Method

Effect of Cu on Solidification Microstructure and Solidification Process in High Carbon High Speed Steel Type Cast Alloy

Yuki Tanaka, Ryohei Nishino, Kazunori Kamimiyada, Kohei Morishita, Hirofumi Miyahara

Abstract

Effect of copper on solidification microstructure and solidification process were investigated for high carbon high speed steel type alloys (Fe-2.0%C-5%Cr-5%Mo-5%V-0~7.5%Cu in mass%). The microstructure of all as-cast specimens with different copper content is dendrite consisting mainly of primary γ, MC-γ eutectic and M2C-γ eutectic. In the copper-free specimen, the shape of dendrite is granular (or equiaxed), while in the copper added specimens, it is columnar, and the columnarization trend become more pronounced with increasing the amount of copper content. Furthermore, the secondary dendrite arm spacing decreased with increasing amount of copper content. The volume fraction of primary γ dendrite gradually decrease and MC-γ eutectic gradually increase with increasing of the amount of copper content. While the volume fraction of M2C-γ eutectic is approximately constant regardless of the amount of copper content. The concentrations of chromium, molybdenum and vanadium within microstructure were approximately constant regardless of the amount of copper content in any microstructures. While the concentration of copper within microstructure was higher in order of dendrite, MC-γ eutectic and M2C-γ eutectic compared with any copper content, and its order corresponds to the solidification prosses. These results suggest that copper tends to remain in the solid phase (that is dendrite) rather than redistribute to the liquid phase during solidification.

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Effect of Cu on Solidification Microstructure and Solidification Process in High Carbon High Speed Steel Type Cast Alloy

Effect of Presence or Absence of a Screw for Fixing Specimen on Rebound Hardness Test by Using Hammer with Vickers Indenter

Takeru Hashiguchi, Kenji Matsuda

Abstract

For manufacturers, rapid and accurate quality control of materials and products in the field is essential for improving competitiveness. Rebound hardness testing is one of the fundamental material tests expected to meet this requirement. However, it has been known that many factors affect rebound hardness which may cause the fluctuation in the measured value. In order to elucidate the effect of the fixing method of the specimen, the coefficient of restitution of a hammer using a Vickers indenter was compared with and without bolting the specimen to the base. The motions of the hammer and the specimen were measured simultaneously using two laser Doppler vibrometers and were also numerically analyzed using an elastoplastic finite element method. It has been clarified that, in the case of without bolting, the restitution coefficient is decreased compared to with bolting. The decreasing tendency becomes larger as the impact point moves away from the specimen center. The rebounding behaviors of the hammer and the specimen without bolting can be reproduced with a numerical model in which an appropriate elastic film is inserted between the specimen and the base. The numerical results show that the hammer impact causes rigid body motion in the specimen, which consumes hammer energy, resulting in a decrease in the coefficient of restitution. The range in which the coefficient of restitution can change is also evaluated by assuming a simple two-body collision model.

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Effect of Presence or Absence of a Screw for Fixing Specimen on Rebound Hardness Test by Using Hammer with Vickers Indenter

On-line Multi-gas Concentration and Temperature Measurement Technology Using Tunable Laser Absorption Spectroscopy

Takahiro Kamimoto, Yoshihiro Deguchi

Abstract

In the measurement of iron and steel processes, the measurement of temperature concentration distribution is very important for the analysis and control of in-furnace phenomena in order to obtain in-furnace information. However, thermocouples and gas sampling methods are used, but since they are contact and point measurements, they disturb the measurement field, require modification of equipment and piping, have low time response (10 Hz), and are affected in accuracy (20% or more) by environmental fluctuations. This report describes the development of a technology for simultaneous measurement of multiple components such as O2, CO, and CO2 concentrations in a furnace, acquisition of a spectral database necessary for measurement using various calibrators, adjustment of the optical axis when installing a sensor with a large laser beam path length (several tens of meters), and development of a technology for adjusting the optical axis by feeding back the laser beam position in real time to prevent optical axis fluctuations during equipment operation. We have developed a technology to adjust the optical axis by feeding back the position of the laser beam in real time when the optical axis fluctuates during the operation of the equipment.

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On-line Multi-gas Concentration and Temperature Measurement Technology Using Tunable Laser Absorption Spectroscopy

Effect of P Addition on the Corrosion Resistance of Steels Before and After Rust Formation

Chihiro Hayama, Mariko Kadowaki, Yoshiharu Murase, Hideki Katayama, Toru Hara, Yuka Hara, Hikari Watanabe, Isao Shitanda, Masayuki Itagaki

Abstract

This paper presents the effect of P addition on the corrosion resistance of steels before and after rust formation. Electrochemical measurements and surface analysis of P-containing steels (Fe-0.5 mass% P, Fe-1.0 mass% P, and Fe-1.5 mass% P) were conducted to analyze the contribution of P to their initial corrosion resistance before rust formation. The results showed that the initial corrosion resistance of the steel was worse with higher P content. According to the surface analysis conducted by SEM/EDS, more P-segregations at grain boundaries existed with higher P content. Based on the results of polarization measurements, it was considered that these P-segregation became the initiation sites of localized corrosion, resulting in the decrease in the initial corrosion resistance.

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Effect of P Addition on the Corrosion Resistance of Steels Before and After Rust Formation

Development of Novel Protic Ionic Liquid Gels Applied for CO2 Separation Materials

Kenta Matsumoto, Takeru Sunada, Yuki Murata, Tomohiro Yoshida, Yuki Morita, Hiroaki Okamoto

Abstract

Ionic liquids are salts, and their melting points were less than 100 ºC under atmospheric pressure. In particular, ionic liquids, which melting point of them were less than room temperature under atmospheric pressure, have been researched in recent decades. Ionic liquids are well-known to designer’s solvents since configuration of cation and anion are easily to change then specificity is exhibited. In this work, novel protic ionic liquids (PILs) which are applied for CO2 sorption materials have been synthesized using aromatic amine such as alkylpyridine derivatives and N,N-dimethylaniline and bis(trifluoromethanesulfonyl)amide due to co-existing proton conductivity and hydrophobicity. Synthesized PILs exhibited hydrophobicity since 1-octanol–water partition coefficients were more than 0. Also, their ionic conductivities were approximately 10-3 S cm-1 at room temperature, and their mechanism of ionic conduction were different one compared with general electrolyte solution due to high viscosities. In addition, several PILs were high selectivity for CO2 sorption compared with N2. Furthermore, PILs gelatinized with bis[4-(1H,1H,2H,2H-tridecafluorooctyl)phenyl] terephthalates due to improvement of mobility. Some of gel–sol transition temperatures of 5wt% gels were approximately 100 ºC. The driving force of gelation with ionic liquids might be an entropy driven. Sorption selectivity for CO2 and N2 were similar one before and after gelation.

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Development of Novel Protic Ionic Liquid Gels Applied for CO2 Separation Materials

Viscosity Measurement of CaO-SiO2-FexO Foaming Slag at 1673 K

Yoshiyuki Egashira, Noritaka Saito, Kunihiko Nakashima

Abstract

Foaming slag generated in the steelmaking process, especially in hot-metal pretreatment and electric arc furnaces, is a gas-liquid coexistent fluid with CO gas generated by the interfacial reaction between slag containing iron oxide and hot metal or carbonaceous materials. In addition, it is essential to understand the flow behavior of foaming slag during slag-tapping and the sedimentation behavior of iron particles, which affects iron yield, and to expand our knowledge of the viscosity of gas-liquid coexisting fluids for CFD modeling of these phenomena. In the present study, the apparent viscosity of a foaming slag was systematically investigated, which was generated by reacting CaO-SiO2-FexO slag with Fe-C alloy and varying the composition, gas phase ratio, and shear rate of the slag. By adding Fe-C alloy powder to the slag, bubbles were continuously generated in the molten slag, and foaming slag suitable for viscosity measurement could be prepared. It was found that the higher the amount of Fe-C alloy powder, the larger the gas phase ratio of the foaming slag due to an increase in the number of bubbles generated. The relative viscosity of the foaming slag was found to increase with the gas phase ratio. The higher the rotation speed, the smaller the relative viscosity of the foaming slag indicating shear-thinning characteristics. The relationship between shear rate and shear stress calculated from the viscosity of the foaming slag did not show general non-Newtonian fluid behavior.

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Viscosity Measurement of CaO-SiO2-FexO Foaming Slag at 1673 K

Terminal Settling Velocity of Particle in Suspension

Shin-ichi Shimasaki, Shigeru Ueda, Noritaka Saito

Abstract

In the steel making process, most slags and fluxes often contain solids phase such as CaO. It is well known that the suspension in which solid phase are suspended has higher viscosity than that of pure matrix liquid. Therefore, it is expected that the viscosity of slag containing solid phase will increase. In this study, terminal settling velocity of particle in suspension has been measured. The suspensions consist of silicone oil matrix and polyethylene beads, and the settling particles are bearing balls made of stainless steel. As a result of the higher viscosity of suspension, the terminal settling velocity of bearing ball becomes slower than that in pure silicone oil. It was clarified that the retardation of the terminal velocity and the increasing of drag coefficient depend only on the volume fraction of solid phase (the polyethylene beads) of the suspension, and it is independent of the size of the suspended beads and the viscosity of the matrix liquid. A correlation equation for predicting the drag coefficient of particles in suspension was proposed.

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Terminal Settling Velocity of Particle in Suspension

Interaction Coefficients of Mo, B, Ni, Ti and Nb with Sn in Molten Fe-18mass%Cr Alloy

Koga Hori, Kengo Kato, Hideki Ono

Abstract

Increasing the utilization of steel scrap is strongly required for reducing CO2 emission in iron- and steel-making processes. In steel scrap recycling, the content of tramp elements in steel (such as copper and tin) inevitably increases. Accordingly, it is important to understand the thermodynamic characteristics of relevance to the accumulation of tramp elements in molten steel. The values of the interaction coefficients of Mo, B, Ni, Ti, and Nb with Sn in molten iron were reported previously. However, little is known about the interaction coefficients of alloying elements with tramp elements in molten high-chromium steel. In this work, the interaction coefficients of Mo, B, Ni, Ti, and Nb with Sn in the molten Fe–18mass%Cr alloy were measured at 1873 K by a chemical equilibration technique that uses the liquid immiscibility of the Fe–18mass%Cr alloy and Ag, yielding the following results:

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Interaction Coefficients of Mo, B, Ni, Ti and Nb with Sn in Molten Fe-18mass%Cr Alloy

Gas Pressure Measurement Beneath of Oxide Scale during High-temperature Oxidation of Steel

Ryoto Okumura, Yuto Adachi, Yasumitsu Kondo

Abstract

Blistering occurs when oxide scale swells during oxidation at steel high temperatures.Blistered scale causes surface defects when steels are rolled. An assumption has been proposed that the pressure of CO and CO2 gas generation beneath the scale causes blisters. This study the qualitative measurements of the gas pressure beneath the oxide scale were tried.A stainless tube was set in order to connect to the beneath the scale during oxidation.Positive pressures were confirmed beneath oxide scale. Also gas permeability through FeO mono-layer scale was obtained.

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Gas Pressure Measurement Beneath of Oxide Scale during High-temperature Oxidation of Steel

A Method for the Analysis of Chromium at Sub-μg L−1 Level Using a Portable Total Reflection X-ray Fluorescence Spectrometer

Rihoko Miyazaki, Kosei Oikawa, Shinsuke Kunimura

Abstract

In this study, total reflection X-ray fluorescence (TXRF) spectra of dry residues of 10 μL, 100 µL, 200 µL, and 400 μL droplets of a solution containing 10 μg L−1 of Cr on hydrophobic film coated sample holders were measured by a portable TXRF spectrometer, and these spectra were compared. The net intensity of the Cr Kα peak per the concentration of Cr in the sample solution (counts / μg L−1) increased with an increase in the volume of a droplet of the sample solution. This was because the mass of Cr in the dry residue increased with an increase in the volume of a droplet of the sample solution. This enhancement in the net intensity of the Cr Kα peak per the concentration of Cr led to a significant improvement in the detection limit expressed as the concentration of Cr. Detection limits for Cr obtained from the measurements of the dry residues of 10 μL, 100 µL, 200 µL, and 400 μL droplets of the sample solution were 2.1 μg L−1, 0.30 μg L−1, 0.13 μg L−1, and 0.09 μg L−1, respectively. Measuring the dry residue of a large volume droplet of a water sample would be useful for the analysis of trace elements in the sample.

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A Method for the Analysis of Chromium at Sub-μg L−1 Level Using a Portable Total Reflection X-ray Fluorescence Spectrometer

Settling of Particle in Foaming Slag

Shin-ichi Shimasaki, Shigeru Ueda, Noritaka Saito, Kenji Katoh

Abstract

In the steelmaking process, molten slag is foamed through gas injection and gas generation reactions, and molten iron droplets get mixed and trapped in the slag. A settling velocity of an iron droplet in the foaming slag are very important, because a residence time of an iron droplet in the slag is directly calculated the settling velocity. According to the previous research, the settling velocity is expected to be slower than in regular non-foaming slag. However, it has yet to be quantitatively clarified. This study measured the settling velocities of particles through a foaming liquid of glycerin-water solution. A dimensionless correlation equation for particle settling velocity in the formed liquid was proposed by conducting a dimensional analysis of the experimental data. Using the obtained equation, we have predicted the settling velocity of iron particles in the foaming slag. It was clarified that the settling velocity of iron particles is highly affected by a volume fraction of gas phase in the foaming slag. There is a certain threshold for the velocity, and the velocity abruptly became zero when it falls below that threshold.

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Settling of Particle in Foaming Slag

Rapid Identification of Crystal Structure of Alumina Scale on Heat-resistant Alloy

Susumu Imashuku

Abstract

Identifying a crystal structure of alumina (Al2O3) scale is critical for evaluating the performance of heat-resistant alloys because α-Al2O3 is stable and protective against high-temperature oxidation and corrosion but θ- and g-Al2O3 provide poor oxidation resistance. Conventional methods to identify crystal structures of Al2O3 scales are time-consuming. Herein, the author proposes a method to rapidly identify crystal structures of Al2O3 scales on β-NiAl by obtaining their cathodoluminescence (CL) spectra. α-, θ-, and g-Al2O3 can be identified by detecting a sharp peak at 695.8 nm and 686.3 nm, and a broad peak at around 700 nm, respectively, in CL spectra. Concentrations of α-, θ-, and g-Al2O3 scales can be determined roughly from intensities of these peaks. This method can be applied to areas ranging from the millimeter to micrometer scale, and the acquisition time for the CL spectra was less than 10 s. The results indicate that obtaining CL spectra contributes to the identification of crystal structures of Al2O3 scales on heat-resistant alloys and a reduction in time to evaluate the performance of heat-resistant alloys.

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Rapid Identification of Crystal Structure of Alumina Scale on Heat-resistant Alloy

Estimation of Flow Properties and Process Simulation on Multiphase Melts

Yoshihiko Higuchi, Shin-ichi Shimasaki, Shigeru Ueda, Noritaka Saito

Abstract

In the process of steelmaking refining, slag used in the preliminary treatment of molten iron or the converter is a multiphase melt. It contains solid particles that cannot dissolve entirely from the raw materials and gas bubbles generated through reactions, thus making it a multiphase molten material with dispersed components. The flow characteristics of the suspensions, foams, and emulsions significantly affect the separation of iron particles in the slag and the behavior of slag discharge. Multiphase melts typically behave as non-Newtonian fluids, so the evaluation, focusing on viscosity, is crucial to understanding their flow characteristics. This report reviews recent advances in slag visualization techniques for understanding the flow of multiphase molten materials. The results are as follows:

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Estimation of Flow Properties and Process Simulation on Multiphase Melts

Rupture of Thin Film of Surfactant Solution Due to Penetration of Spherical Particle

Kenji Katoh, Tatsuro Wakimoto

Abstract

We experimentally investigated the rupture conditions of a thin film of an aqueous surfactant solution when a spherical particle with a finite falling velocity penetrates the film. When the sphere passes through the film, the film wraps around the sphere, and a gas layer is maintained between the film and the spherical surface. When the velocity of the sphere is small, perforation occurs in the wrapping film below the equator of the sphere and the contact line moves along on the sphere surface. The energy instability occurs at a certain position of the contact line on the sphere surface, leading to rupture of the entire thin film. As the sphere velocity is increased, the perforation of the wrapping film occurs above the equator. In this condition, the probability of thin film rupture increases, since the perforation of the wrapping film immediately leads to rupture of the entire film. The motion of the gas between the thin film and the spherical surface was considered analytically from the balance between surface tension and viscous force. According to the result, the velocity condition above which the wrapping thin film could exist beyond the equator of the sphere was evaluated.

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Article Title

Rupture of Thin Film of Surfactant Solution Due to Penetration of Spherical Particle

Measurement of Bubble Size Distribution and Generation Position of Bubbles Generated during Smelting Reduction of Iron Oxide-containing

Ko-ichiro Ohno, Taiga Eguchi, Tatsuya Kon

Abstract

Slag foaming is a phenomenon caused by the generation of CO bubbles due to the reaction between iron oxide in slag and carbon in pig iron. The purpose of this study is to explore the controlling factors of slag foaming by observing the bubble formation behavior caused by the chemical reaction between iron oxide and Fe-C alloy in slag. 0.06 g of Fe-C alloy was charged to the bottom of the BN crucible, and 6.0 g of slag (SiO2:CaO:Fe2O3 = 40:40:30) was charged on top of it. The crucible was placed in an infrared image heating furnace, and the temperature was rapidly raised to 1370°C at a rate of 1000°C/min in a N2 stream, then held for a predetermined time and rapidly cooled. After rapidly cooling, the internal structure of the sample was observed using a high-resolution X-ray CT device. The spherical equivalent volume is calculated based on the number of bubbles observed and their equivalent circle diameter, and the relationship between the volume ratio of small bubbles in the slag volume and the distance from the bottom of the crucible is calculated, and the bubble density and volume ratio are calculated. It was suggested that the value tends to increase as the distance from the bottom of the crucible increases.

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Measurement of Bubble Size Distribution and Generation Position of Bubbles Generated during Smelting Reduction of Iron Oxide-containing

Hydrodynamic Behavior of Sphere Penetrating into Water Bath Covered with Oil Layer

Satoshi Hasui, Yoshihiko Higuchi

Abstract

To meet the increasing demand for low-impurity steel products, powder top blowing has been applied to the steelmaking process. Powder reagents penetrating deeper into the molten metal lead to longer resident time and higher efficiency of refining. Many studies have been performed on the basis of cold model experiments with a single liquid phase for clarifying the penetration behavior of the particle. However, the effects of the second liquid phase have been reported little whereas molten slag often exists on the surface of molten metal in the steelmaking process.

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Hydrodynamic Behavior of Sphere Penetrating into Water Bath Covered with Oil Layer

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