Nippon Steel (Germany)

We report a new process which promises high critical current density in oxide superconductors. The process consists of three stages. Firstly a YBa 2 Cu 3 O x sample is rapidly heated and quenched from the Y 2 O 3 plus liquid region. Subsequently the quenched sample is reheated to the Y 2 BaCuO 5 plus liquid region, and then slowly cooled with a temperature gradient in flowing oxygen. The process enables us to grow a superconducting phase unidirectionally and to suppress the second phase intrusion, leading to the production of well textured YBa 2 Cu 3 O x which yields a high J c value in the presence of magnetic fields. It is also found that Bean's critical state is realized in such high J c samples.

In order to clarify the grain size dependence of mechanical stability of austenite, deformation-induced martensitic transformation behavior was investigated on uniaxial tensile deformation in a metastable austenitic stainless steel (Fe–16%Cr–10%Ni) with the grain size controlled from 1 to 80 μm. In addition, crystallographic characteristics of deformation-induced martensite were analyzed by means of the EBSD (electron backscattering diffraction) method to discuss the variant selection rule. It was found that mechanical stability of austenite is independent of its grain size, although thermal stability of austenite is remarkably increased by grain refinement. Some special martensite variants tend to be selected in an austenite grain on the deformation-induced martensitic transformation (near single-variant transformation), and this results in the formation of a texture along tensile direction. This suggests that the most advantageous variants are selected in the deformation-induced martensitic transformation to release tensile strain and leads to the grain size independence of mechanical stability of austenite.

COURSE50 (CO2 ultimate reduction in steelmaking process by innovative technology for Cool Earth 50) carried out COG and reformed COG (RCOG) injection operation trials at LKAB’s experimental blast furnace in Luleå in cooperation with LKAB and Swerea MEFOS. Operation trials were successfully carried out. Input of C in both COG and RCOG injection periods decreased comparing the base period, because of increase in H2 reduction instead of C direct reduction that is a huge endothermic reaction. However poor penetration depth of injected gas from shaft tuyere made furnace efficiency worse. Hot top gas injection increased temperature of top gas and upper part of the furnace. Efficiency of hot top gas injection was not clear as sinter degradation did not occur in the base period.

The 150 year history of the Japanese steel industry dates from the first western blast furnace, which was built by T. Ohashi in 1857. Modern blast furnace operation at integrated steel works in Japan started in 1901 with the first blow-in of Higashida No. 1 blast furnace at Yawata Steel Works. Throughout the prewar and postwar periods, the steel industry has supported the Japanese economy as a key industry which supplies basic materials for social infrastructure and development.After the period of recovery following the destruction caused by World War II, Chiba Works of Kawasaki Steel Corporation (now JFE Steel Corporation) was built and began operation in 1953 as the first integrated steel works in the Keiyo Industrial Region after the war. During Japan’s period of high economic growth, many coastal steel works with large blast furnaces having inner volumes of more than 3000 m3 and even 5000 m3 were built to enable efficient marine transportation of raw materials and steel products. Japanese steel makers introduced and improved the most advanced technologies of the day, which included high pressure equipment, stave cooler systems, bell-less charging systems, etc. As a result, Japanese steel works now lead the world in low reducing agent rate (RAR) operation, energy saving, and long service life of blast furnaces and coke ovens.Following the Oil Crises of the 1970s, the Japanese steel industry changed energy sources from oil to coal and implemented cost-oriented operation design and technology. In 2012, the Japanese steel industry produced approximately 80 million tons of hot metal from 27 blast furnaces, including large-scale furnaces with inner volumes over 5000 m3. During this period, the industry has faced many economic and social challenges, such as the high exchange rate of the yen, oligopoly in the mining industry, global warming, and the surge in iron ore and coal prices driven by the rapid growth of the BRICs. The industry has successfully responded to these challenges and maintained its international competitiveness by developing advanced technologies for pulverized coal injection, expanded use of low cost iron resources, recycling for environmental preservation, and CO2 mitigation.In this paper, the prospects for ironmaking technologies in the coming decades are described by reviewing published papers and looking back on the history of developments in ironmaking during the last 100 years.

The red scale, which is one of the major defects on hot-rolled Si added steel sheets, is reproduced 6xperimentally. On the basis of detailed observation of the scale properties, we propose the mechanism of formation of the red scale. Imcomplete descaling of FeO prior to hot rolling causes red scale formation even in Si-free steels, since the reaction from FeOto Fe304and red Fe203 is largely accelerated by the breakage of the FeO scale, In Si-added steels, descaling is quite difficult to perform, becausethe eutectic compound of FeO/Fe.SiO* is formed at the scale/steel interface and penetrates irregularly into both upper FeOand lower steel sides. auite high strength of the eutectic compound, even just below the solidus temperature of 11 73'C, can also make it difficult to descale.

Thiosulfate ion was used as a substitute for hydrogen sulfide (H2S) to simulate stress corrosion cracking (SCC) of corrosion-resistant alloys (CRAs) and sulfide stress cracking (SSC) of high-strength, low-alloy steels. Several SCC tests using a variety of stress application techniques showed the brine containing thiosulfate exhibited similar severity to brine containing H2S in regard to SCC when plastic strain was applied to the CRAs. Materials that exhibited SCC susceptibility in brine containing thiosulfate agreed well the SCC susceptibility of those in brine containing H2S. Types 304 (UNS S30400) and 316L (UNS S31603) stainless steels and duplex stainless steel exhibited in both environments. However, high-nickel austenitic alloys such as alloys 904L (UNS N08904) and 825 (UNS N08825) did not. A10−3 to 10−2 mol/l S2O32− addition in 20% NaCl aqueous solution at 353 K corresponded to H2S of 0.1 to 1 MPa at 473 K. The SSC susceptibilities of high-strength, low-alloy steels in a 10−3 mol/l S2O32− + 5% NaCl + 0.5% acetic acid solutions were close to those in NACE Standard TM0284-86 solution (substitute ocean water saturated with 0.1 MPa H2S). Results suggested the possibility of using thiosulfate ion as an alternative to H2S.

The testing method for delayed fracture has not been standardized yet. The quantitative evaluation method is necessary to develop low alloy high strength steels with higher delayed fracture resistance. The sustained load tests under cathodic hydrogen charging condition have been investigated considering the severity of the actual environment. The delayed fracture and hydrogen absorption behavior have also been investigated especially in 0.5C-0.3Mn-lCr-0.7Mo0.03Nb-0.3V-low P-low S steels.The maximum hydrogen permeation coefficient, 0.1μA/cm, has been determined at the lowest pH=3.5 realized in the local environment such as in a crevice. The sustained load tests using notched round bar specimens have been carried out under cathodic hydrogen charging condition corresponding to 0.1μA/cm. The results show that this steel has the enough resistance to delayed fracture as 1.3GPa grade-high strength bolts. Although the apparent diffusible hydrogen content is much higher than 1.1GPa grade-JIS SCM440 steel, this steel absorbs the diffusible hydrogen evolved at more than 200°C in thermal analysis. It has been clarified that this diffusible hydrogen evolved at elevated temperatures has no relation with hydrogen embrittlement. Therefore, the susceptibility for embrittlement would be lower in this steel because of the uniform carbides dispersion and the decrease in the internal strain due to the high temperature tempering.

Metal complexes emitting thermally activated delayed fluorescence based on intra-ligand charge transfer and enhanced by metallization were synthesized. Organic light-emitting diodes using a thermally stable zinc complex processed by vacuum vapor deposition achieved an external quantum efficiency of nearly 20%.

Dextran-magnetite complex (DM) is a colloidal sol of subdomain magnetite particles (i.e. a 'magnetic fluid'). The specific absorption rate of DM in an AC magnetic field is much higher than those of multidomain ferrite particles due to its different mechanism of heat generation. We designed two DM-containing embolic materials (a DM/Lipiodol emulsion and a DM/degradable starch microsphere suspension) to heat target tissues with the use of an external AC magnetic field. In vitro experiments showed that the heat-generating capacity of DM was not reduced in these mixtures. When these materials were injected into the renal arteries of Japanese white rabbits, they both achieved embolization of the artery and selective heating of the embolized kidney by exposure to a 100 kHz AC magnetic field of approximately 15,000 A/m. Histological examination showed a homogeneous distribution of DM in the embolized kidney. These results suggest the possibility of using DM-containing embolic materials for inductive hyperthermia.

1 ) Naoetsu Re- Clad materials are more useiul than uniform materials in manycases since they have characteristics of both materials.

BACKGROUND/AIMS: Dextran magnetite complex (DM) is a colloidal suspension of subdomain magnetite particles ('magnetic fluid'). It has been reported that DM generates a great amount of heat in an AC magnetic field. MATERIAL AND METHODS: In this experimental study on Japanese white rabbits, a new treatment modality for liver tumors was examined in which the tumor is selectively heated with an intravascularly administered DM-containing embolic material followed by external application of an AC magnetic field. RESULTS: The heat generation of DM in vitro was found to be more than 3-fold greater than that with magnetite particles of 40-micron diameter. As a DM-containing embolic material, we developed a DM/Lipiodol emulsion. When DM/Lipiodol emulsion was injected into the hepatic arteries of the rabbits following VX2 tumor transplantation into the liver, embolization of the artery and selective heating of the embolized liver were successfully attained following exposure to a 100-kHz AC magnetic field of approximately 15000 A/m. Histological examination of the embolized liver disclosed that DM had accumulated in the hypervascular, viable part of the tumor. CONCLUSION: These results demonstrate the potential feasibility of using a DM-containing embolic material for targeted hyperthermia of liver tumors.

Lath-shaped upper bainite structures play a very important role in many high-strength steels (HSSs) and ultra high-strength steels (UHSSs). Although bainite transformation is strongly affected by the initial structure, the effect of the second phase in a multi-phase structure is yet to be clearly understood. It is significant for the advancement of UHSS to study this effect. The aim of this study is to clarify the effect of martensite, which forms before bainite, in Fe-0.2C-8Ni alloy. The bainite transformation from an austenite and martensite dual-phase structure is faster than that from single-phase austenite and the nucleation of bainitic ferrite laths are accelerated around martensite. This effect of martensite on bainite kinetics is equivalent to that of polygonal ferrite when their volume fractions are almost the same. This suggests that the boundary between martensite and austenite is a prior nucleation site of bainitic ferrite. Martensite also affects the crystallographic features of bainite. The orientations of bainitic ferrite laths tend to belong to the same block with martensite adjacent. This tendency intensifies with an increase of the transformation temperature of bainite, resulting in the formation of huge blocks consisting of bainitic ferrite and martensite laths at high temperatures (693K and 723K). In contrast, at a low temperature (643K), bainitic ferrite laths belong to same packet as martensite and have several orientations. This change of crystallographic features with transformation temperature can explain with the driving force of the nucleation of bainitic ferrite.

Increasing the Al2O3 content in the blast furnace slag, the blast furnace operations tend to make troubles such as excess accumulation of molten slag in the blast furnace hearth and increasing pressure drop at the lower part of the blast furnace. So, it will be important to keep good slag fluidity at the blast furnace operations such as, drainage of tapping and keeping good permeability.In order to clarify the effect of high Al2O3 slag fluidity on the blast furnace, high Al2O3 slag (20%) test operations of experimental blast furnace have been carried out. Investigation results of the test operation are as follows;1) Slag MgO improves the hearth drainage rate at high Al2O3 slag operation.2) Permeability of the dripping zone is improved by decreasing slag CaO/SiO2, at high Al2O3 slag operation of the blast furnace.3) It was verified that the slag drainage phenomena were able to described by the fluid model.4) The optimum composition of high Al2O3 slag of the blast furnace is high MgO and low CaO/SiO2.

As a fundamental study to clarify the agglomeration and coalescence of alumina inclusions in molten steel from the viewpoint of interfacial chemical interactions, it has been experimentally verified for the first time that significant agglomeration force is exerted between alumina particles in aluminum deoxidized molten steel by using a newly established experimental method. In this method, the agglomeration force exerted between alumina particles in molten steel is directly measured separately from the effect of molten steel flow. In addition, it has been quantitatively demonstrated that the contact angles measured between aluminum deoxidized molten steel and an alumina plate are larger than those between the molten iron-oxygen alloy and the alumina plate, which have already been measured by other researchers. Moreover, it has also been indicated by analyzing the actual measurement values of agglomeration force with an interaction model taking contact angles and interfacial properties into consideration that the agglomeration force between the alumina particles in aluminum deoxidized molten steel derives not from the van der Waals force but from the cavity bridge force occurring due to molten steel, which is unlikely to wet the alumina particles. Meanwhile, it has been assumed that the agglomeration force on spherical alumina inclusions in aluminum deoxidized molten steel calculated on the basis of the interaction model according to the cavity bridge force is greater than the buoyant force and drag force, and the alumina inclusions once coming into contact are therefore not prone to be simply dissociated even under molten steel flow. Thus, they maintain the agglomeration state and are subsequently sintered and form comparatively solidly bonded alumina clusters.

The initial stage of solidification for continuous casting is very important in optimising the surface quality of steel. It is well known that hypo-peritectic steel has problems with longitudinal cracking due to shrinkage resulting from the δ→γ transformation. High speed continuous casting, with a speed range of 4-5 m/min, suffers from the same problem. For a round-shaped billet caster, the shape of the mold cross section is at a disadvantage with regard to longitudinal cracking. In this study, mild cooling mold powders were developed in order to improve the surface quality of high speed casting slabs and round-billets. The results can be summarized as follows; 1) High CaO/SiO2 ratio mold powder with a high solidification temperature is most suitable for a slab caster. 2) Low CaO/SiO2 ratio mold powder with a high solidification temperature is most suitable for a round billet caster. 3) The effect of radiation in liquid powder film is bigger than solid powder film.

A computer model which predicts complex precipitation behavior quantitatively in Nb-Ti bearing steel has been developed on a theoretical basis. The solubility and composition of the complex precipitates, and the chemical driving force of the precipitates from supersaturated austenite are estimated by means of thermodynamic analysis of regular solution composed of four-binary compounds. The change in dislocation density which acts as a nucleation site during hot working is calculated by using dislocation theory. And the time dependence of volume fraction and the particle radius of strain induced precipitation are also predicted on the basis of classical nulceation theory. In order to estimate the effect of deformation on nucleation, the change in elastic energy of dislocation with nucleation is calculated.Experimental results showed that combination of Nb and Ti addition, decreased the solubility of carbonitrides and accelerated the precipitation rate from supersaturated austenite because of the formation of complex precipitates. Such experimental results are in good agreement with the prediction by the present model. And both the acceleration of precipitation rate and the refinement of precipitates particles due to hot deformation are also quantitatively explained.

Work roll life of hot rolling mills is strongly affected by roll material. Recently, high-carbon high speed steel rolls have been developed to improve further work roll life.

The recently developed I-P-Z model is modified in order to analyze the observed enhanced permeation of hydrogen that occurs in the presence of hydrogen sulfide during cathodic hydrogen charging of iron. The modification accounts for the fact that the energy of adsorption becomes coverage dependent at the higher coverages and affects the hydrogen evolution reaction (HER) in the presence of H2S. Charging experiments were performed on Ferrovac E–iron membranes 0.5 mm thick using a Devanathan–Stachurski cell in deaerated, pre-electrolyzed solutions made from 0.1 M HClO4 and 0.1 M NadO4 with pH values of 1 and 2. The transfer coefficient, α, exchange current density, i0, thickness-dependent absorption-adsorption rate constant, k″, recombination rate constant, k3, surface hydrogen coverage, θH, and discharge rate constant, k1o were obtained by application of the model to the experimental results. As a result, the role of H2S has been clarified. While θH is increased in the presence of H2S, the overpotential, η, is decreased consistent with an observed increase in a, and the increased H entry is found to be the result of a decreased k3 as well as the increased α. In addition, a very important relationship has been derived that will enable the calculation of the absorption, kabs, and adsorption, kads, rate constants from the electrochemical permeation results for different membrane thicknesses.

Development in sheet steels has progressed in strong relation with automotive industry in Japan. To meet the requirements from automotive industry, various types of sheet steels including high and ultra high strength steel sheets have been developed. Progresses in three types of steel series will be discussed by checking the historical facts and technologies and their contributions. Introductions of interstitial free (IF) steel and continuous annealing system are the important events in mild steel developments for panels. Extensive work on finding the optimum mixtures of hard and soft phases to improve elongation of steels contributed to improve the crashworthiness of autobodies. Continuous annealing system also played an important role in producing these advanced high strength steels. Precipitation is used in a particular way which is to scavenge solute carbon and nitrogen and to prevent coarse cementite particle precipitation. It is also worth to point out that the collaborative activities particularly strong in Japan between steel manufacturers and auto companies have affected the progress in advanced sheet steels.

The rust layers formed on weathering and mild steels by atmospheric corrosion in an industrial region for a quarter of a century have been characterized by means of observation of the reflection behaviour of polarized light, scanning electron microscopy, infrared transmission, X-ray diffraction and Raman spectroscopy, and electron probe microanalysis.It was found that the protective and stable corrosion product which covered the surface of weathering steel mainly consisted of α-FeOOH (ferric oxyhydroxide). The protective rust layer contained a considerable amount of Cr, and was composed of densely packed rust particles in contrast with the rust layer formed on the mild steel. The fact that the protective rust layer was mainly composed of α-FeOOH can reasonably be interpreted in terms of the transformation process of a corrosion product formed by the atmospheric corrosion of steels.