Controlling the size, number, and composition of secondary inclusions is vital in the production of high-quality steels. In this study, experimental and computational investigation of the relationship between secondary inclusion formation in Fe-36mass%Ni alloy and cooling rate was carried out. Assuming the case of large ingots, solidification experiments using various cooling rates (0.17 to 128 K/min) were employed and the size, number, composition, and distribution of inclusions were analyzed by SEM-EDS automatic inclusion analysis. Like previous studies, inclusion number density increased with increasing cooling rate, while inclusion size decreased with increase of cooling rate. On the contrary, oxide inclusion area fraction was found to have little relationship with the cooling rate and was instead found related with oxygen content of the sample. As a new attempt to investigate the relationship between microsegregation and secondary inclusion formation, a combination of SEM-EDS analysis and EPMA mapping analysis was carried out. By superimposing information of microsegregation and inclusions, it was found that high-Al₂O₃ inclusions formed during the early stage of solidification, whereas low-Al₂O₃ inclusions formed during the later stage of solidification. These findings suggest that Al₂O₃ inclusions formed in the early stage of solidification reacted with the remaining Si-enriched liquid steel and changed into low-Al₂O₃ inclusions. Experimental results were also confirmed by thermodynamic calculations. Present work made it possible to understand deeper the relationship between microsegregation and secondary inclusion formation.

To improve the prediction accuracy of oil quenching distortion, the transformation plasticity coefficient was determined by oil quenching experiment on the steel sheet and numerical simulations. The cooling curve of the steel sheet during oil quenching and the deflection after quenching were measured under three experimental conditions. In the first condition, austenitic stainless steel sheet was quenched into cold quenching oil for confirmation of the validation of the temperature prediction results by the numerical simulation. In the second condition, chromium molybdenum steel sheet was quenched into cold quenching oil for confirmation of the validation of the latent heat predicted by the numerical simulation. By fitting the results of the numerical simulation to the deflection of the sheet in this experiment, the transformation plasticity coefficient in the martensitic transformation of the chromium molybdenum steel was determined to be 21 x 10^-5 MPa^-1. In the third condition, chromium molybdenum steel sheet was quenched into semi-hot quenching oil to verify the accuracy of the prediction of heat treatment distortion using the determined transformation plasticity coefficient. The error in the deflection of the sheet after oil quenching using the determined transformation plasticity coefficient was reduced to 6% from 64% (the previous report). The accuracy of distortion prediction was improved by changing the specimen morphology used in oil quenching experiments from bars to sheets.

During hot stamping, Zn oxidation occurs on the surfaces of Zn-coated steel sheets such as galvanized iron and galvannealed sheets. In order to elucidate the effect of Al in the Zn coating layer on the Zn oxidation, the present study investigated the amount of ZnO formed on the Zn-coated steel sheets with and without Al addition to the coating layer. The amount of ZnO was found to decrease upon Al addition. The microstructural analysis of the Zn-coated steel sheets with Al addition revealed that the added Al became the ZnAl₂O₄ layer at the interface between the ZnO layer and Zn coating layer after hot stamping. As a result, Zn oxidation is considered to be suppressed by the presence of the ZnAl₂O₄ layer.

The purpose of this report is to compare the coating structure and corrosion mechanism of newly developed Zn-19%Al-6Mg-Si with conventional Zn-Al-Mg alloy coating Zn-11%Al-3%Mg-0.2%Si. In past papers the corrosion resistance of Zn-Al-Mg alloy coating layers was mainly discussed based on analysis methods that focus on one aspect of early corrosion stage. However, this report focuses on the changes in the corrosion mechanism until the end of the coating lifespan and picks up the factors of the coating layer that contribute to corrosion resistance.

The results of the corrosion cross section images of the Zn-Al-Mg alloy coating layer after cyclic corrosion test suggested that corrosion of the coating layer progresses selectively in each phase, which means each phase has its own electrochemical potential. Considering the differences in the corrosion mechanisms of these two coated steel sheets, it was suggested that the phase proportion of the coating layer and the unique potential determine the corrosion resistance of the coating layer.

Vanadium composite electrogalvanized (Zn-V hydroxide) steel sheets were prepared by electroplating using a horizontal flow cell. The structure of Zn-V plating layer depended on the flow rate of electrolyte and the current density, and the performance of Zn-V steel sheets depended on the structure of plating films. The Zn-V plating films composed of two-phase structure without cracks showed the high corrosion resistance and high adhesion. The two-phase layer consisted of the field oriented fiber and non-field oriented texture. The field oriented fiber phase was mainly composed of metallic Zn, and the non-field oriented phase was mainly formed from the amorphous V compound. The V compound in the non-field oriented phase seems to be formed by the hydrolysis reaction of V ions due to pH increase in cathode layer according to hydrogen evolution during Zn-V plating. The Zn-V steel sheets had a black and low-gloss appearance compared to the conventional electrogalvanized steel sheet (EG). Since the V compound in the non-field oriented texture was black and the field oriented texture formed the surface roughness, the lightness and gloss of the Zn-V steel sheets decreased with increasing V content in plating films.

Main application of steelmaking slag is a base course material. In order to utilize slag as a base course material, it is necessary to have various characteristics in the criteria, and the modified California Bearing Ratio (CBR) value which evaluates the performance as a base course material is an important index in comparison with other competitors. Although it is expected that various factors such as properties and granularity affect CBR characteristics and compaction properties, the particle properties and granularity of steelmaking slag is different on each refining process which produce steelmaking slag. In addition, until now, X-ray CT measurement for slag base course material and effect of particle property have not been examined. Therefore, in this study, measurement of the internal phenomena of the steelmaking slag base course material by micro-focused X-ray CT and various measurement were carried out. It was revealed that the particle strength of porous particles is lower than that of dense real particles regardless of particle size and the subbase bearing capacity did not differ as much as the particle strength difference. In addition, from the mechanism by which the stress propagates and elastic finite element analysis by using X-ray CT, it was considered that the distribution of the stress was changed by the dispersion of the particle strength of each grain, and it affected the property of base course material which was the integral value of the effective stress.

In this study, we develop a high-speed, high-resolution vision system that enables real-time measurement of deflection displacement distribution in cranes with long beam structures. It can measure dynamic displacement distribution with sub-pixel accuracy in real time by executing digital image correlation for 4096×904 images at 100fps. Millimeter-level deflections at tens of points on a crane are measurable with the position of its moving load when a camera is tens of meters away from the crane. The trolly of a crane indicates the load position, and our system can also analyze deflection influence lines at all points on the crane as speed-invariant features that indicate its structural property. The effectiveness of our vision-based displacement measurement is demonstrated by showing experimental results for (1) a 1-m-length belt conveyor, and (2) an unloader crane with a 98-m beam structure operating in ironworks.

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.

The authors developed a new surface inspection system using the twin illumination and subtraction technique, which emphasizes only concave-convex defects while canceling the pattern of the mill scale covering these types of steel products. An optical approach to enhance the detection performance of this system was already reported in connection with the development of a steel plate surface inspection technology. This paper discusses the development of a new image processing technique to detect defects from obtained images in order to satisfy the conditions of introducing automatic inspection systems at steel production lines. Concretely, a high-speed bright-dark pattern detection algorithm using expansion and conjunction processing was developed, and improved the processing speed by 22.6 times relative to the conventional simple method. An effective new original feature, overlap ratio of bright parts, was also developed, resulting in a 5.15 % improvement in the classifier concordance rate relative to that without the proposed features. The developments described above have realized automatic surface inspection systems suitable for introduction in steel production manufacturing processes.

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.

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 Fe_2-3C(e) and the highest amount of retained austenite. It is considered that the fine iron carbides of Fe_2-3C(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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Although the initial corrosion resistance was worse with higher P content, the long-term corrosion resistance was better with higher P content. According to the results of atmospheric exposure tests at Miyakojima and the surface analysis of rust layers, P was incorporated into the rust layer, and it promoted the protective ability against corrosion.

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.

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:

The results show that the values of the interaction coefficients of M with Sn in the Fe-18mass%Cr alloy are smaller than those for molten iron, which were measured in the previous work, except for titanium. The interaction coefficients of M with Sn in Fe and Fe–18mass%Cr alloy were estimated based on a regular solution model. The estimated interaction coefficients of B, Ni, and Ti with Sn in molten iron and Ni and Ti with Sn in the molten Fe–18mass%Cr alloy reasonably agree with the measured values.

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.

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.

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.