Magnetite-based pellets with large amounts of the additives olivine, calcite and quartzite were isothermally reduced in a tubular furnace to study and describe the reaction behaviour of the additive minerals in the pellets. The reduction was thermodynamically set to yield wüstite at three different temperatures: 900, 1000 and 1150°C. The mineralogical phases that had formed before and after reduction were studied by Scanning electron microscope and X-ray diffraction. The pellets with the different additives were different already before reduction due to different reaction behaviour during induration: The results showed that it was possible to identify the main reactions during reduction for pellets with all three additives. All but the very small quartzite particles remained unreactive in reducing atmosphere until they began to form a fayalitic melt at 1000°C. The calcium ferrites of the pellets with calcite reacted to form a porous calciowüstite already at 900°C. In the pellets with olivine, the magnesium, which had constrained into magnesioferrite pockets after induration, redistributed into the entire iron oxide structure at 900°C and also reacted with silica at 1000°C. The olivine core which had not reacted during induration did not appear to react in reducing conditions at temperatures of 1150°C and below. These reaction mechanisms have indicated a potential to reduce the required amounts of additives in the pellets.

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Microwave heating was applied to metal titanium powders at high oxygen partial pressure (10⁻⁵ atm) and the partial pressure of exhaust-gas were measured using an oxygen sensor made of solid electrolyte. During the application of the heating, the pressure decreased to an order of 10⁻¹⁰ atm and quickly increased to an order of 10⁻⁵ atm and then oxygen emission peaks were observed. Furthermore, the nitriding mechanism was discussed for Ti₁₄O₁₃ model in terms of quantum chemistry. The quantum-chemical simulation showed that Ti–O bonding of titanium oxide is anti-bonding and consists of 3d orbital. The orbital becomes steady state by removing an oxygen atom from the model.

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A growing attention has been paid to development of ‘athermal glass’, which is a material showing no temperature dependence in its optical path length and is expected to be used in optical devices for the optical fibre transmission system. The athermal characteristic is usually evaluated using the dependence of optical path length (S) on temperature (T) expressed by the following equation:

where l, n and α are the geometrical length, refractive index and linear coefficient of thermal expansion of a sample, respectively. In the present work, the refractive index and liner coefficient of thermal expansion have been determined for silicate glasses containing titanium oxides in the temperature range from room temperature to about 673 K, respectively, using ellipsometry and the apparatus with image analysis equipment. The values of nα and temperature coefficient of n ranged from 1.289×10⁻⁵ to 3.345×10⁻⁵ K⁻¹ and from 0.270×10⁻⁵ to 1.467×10⁻⁵ K⁻¹, respectively, depending on the glass composition. As a consequence, it has been found that additions of titanium oxides do not have good effects on the athermal characteristic. However, only 80SiO₂–5TiO₂–15Na₂O (on a mole basis) glass has shown almost the same degree of athermal characteristic as SiO₂ glass, and it is suggested that 80SiO₂–5TiO₂–15Na₂O glass has more advantages in practice due to its lower melting temperature than SiO₂.

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The tapping process is an important step in the silicon and ferrosilicon production process. Tapping is simply how to transfer the melt from the furnace into the ladle. The tapping process has always been a challenging industrial operation where the metal flow rate is influenced by many different phenomena. In this present work we present a model for the tapping of the submerged arc furnaces. Using the model the effects of furnace crater pressure, metal height and permeability of the different internal zones have been studied. The model is based on computational fluid dynamics (CFD) where the geometry is taken from industrial furnace geometry. The internal zones with individual permeabilities are defined based on information from furnace excavations. From the model we extract new information about the process and explain phenomena which control the tapping flow rate. It was found a very good agreement between the model predictions and industrial measurements.

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The (001) surface of nonstoichiometric wüstite (Fe_0.94O) grown by the floating zone technique was investigated using STM, LEED and AES. Two distinctive structures, i.e., the dents arrangement and the FeO(001)–c(4×2) reconstructed structure coexist on the terrace after annealing at 1073 K in the ultrahigh vacuum (UHV) system. On the other hand, the only dents exist after annealing at 1273 K. The dent is the Fe vacancy pair in the rocksalt-type FeO(001)–(1×1) matrix, which is the exposed P′ phase of the defect cluster due to nonstoichiometry.

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Thermodynamic interaction of chromium on aluminum in liquid Fe–Cr–Al alloys was studied by measuring the effect of chromium on the solubility product of AlN in liquid Fe–Cr–Al–N alloys containing chromium up to 26 mass% by the metal–nitride–gas equilibration technique in the temperature range from 1873 to 1973 K. Aluminum nitride formed in the melt was identified as a pure solid stoichiometric AlN. As the chromium content increases in the melt saturated with AlN, the critical nitrogen solubility increases significantly, while the aluminum solubility decreases. Using Wagner's formalism, the present results were thermodynamically analyzed to determine the first- and the second-order interaction parameters between chromium and aluminum given as follows:
e_Al^Cr = 0.0122±0.00028 r_Al^Cr = 0 (1873−1973 K, Cr≤26 mass%)

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Directly reduced iron is an imperative burden for EAF (electric arc furnace) to make good quality and special steel. As an alternative of direct reduction processes, an innovative coal-based direct reduction of composite binder magnetite pellets in grate-rotary kiln has been developed at Central South University and put into operation. A study of the direct reduction behaviors of composite binder magnetite pellets was carried out in a simulating coal-based grate-rotary kiln process in this paper. Preheated pellets made of magnetite concentrate and composite binder and fired oxide pellets containing bentonite as binder were directly reduced using non-coking coal as reductant in a tube furnace, and their reduction behaviors have been demonstrated by measuring reducibility, variations of compress strength, porosity, phases changes and micro structure under XRD, SEM and optical microscopy. It is shown that preheated pellets possess much better reducibility than fired oxide pellets. Superior reducibility of preheated pellets should be ascribed to their higher effective diffusivity due to higher porosity. The compressive strength of preheated pellets climbs quickly after reducing for 30 min and achieve a high value at the end of reduction, leading to smooth and intact metallized pellets whereas the compressive strength of metalized pellets from reducing of fired pellets is much lower, more cracks and fractures being formed. The preheated pellets possess self-curing function because of the multiple functions of composite binder, eliminate cracks and fractures and keep pellets intact during reducing, depressing reduction degradation and preventing accretion in rotary kiln.

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The behavior of phosphorus in the solid state pre-reduction and dephosphorization treatment processes of high phosphorus iron ore by mechanical crushing and screening methods were investigated in the present work. The reduction behavior of high phosphorus iron ore by carbonaceous materials was evaluated as a function of reduction temperature, reduction time and carbon mixing ratio. Most of the phosphorus compounds were not reduced in the low temperature reduction process of high phosphorus iron ore and remained as oxides in the gangue phases. The gangue phase size increased from 5 μm order before pre-reduction up to 20–30 μm after pre-reduction, and most of the phosphorus was still concentrated in the gangue phases even when the degree of sintering and agglomeration of the phases proceeded with increasing the reduction temperature. The dephosphorization treatment of the pre-reduced iron ore by mechanical crushing and screening methods was evaluated as a function of the initial reduction condition, screen size, and the mechanical property of the reduced iron ore phase.

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The drainage of the hearth plays an important role for the operation of the ironmaking blast furnace. An undisturbed extraction of the produced molten materials from the hearth is a prerequisite of a smooth operation of the high-temperature region, and a good mixing of liquid iron and slag in the taphole and runner helps desulfurize the iron. The flows of molten iron and slag in the blast furnace taphole have not received much attention, even though several investigators have studied the hearth drainage phenomena. In the present paper a two-fluid model of the taphole flow, based on an assumption of full stratification of the two liquids, is developed, and coupled with a simple material balance for the furnace hearth. Furthermore, the pressure loss of the liquids in the dead-man in front of the taphole inlet is considered. Simulations with the model are applied to illustrate how different factors affect the drainage, liquid levels and taphole flow. It is demonstrated that the in-furnace conditions play an important role for the flows and the flow distribution between iron and slag. The effects of key variables, such as coke-bed voidage and coke size, are illustrated and conclusions concerning their impact on the drainage are drawn.

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In ladle refining operations, a plume eye is the area of the bath surface that is not covered with slag, due to bubbling gas, and this area is the most important in slag–metal reactions. In contrast, in vacuum degassers, most of the surface area is not covered with slag, and in this case, the bubble rising area at the bath surface is important for gas–metal reactions. This area is referred to as the “bubble eye area” in this paper. To evaluate the bubble eye size, and its effect on the surface reaction rate, water model experiments were carried out. The plume eye size was measured by changing the thickness of a polystyrene particle layer, which was added to the surface as a slag layer. The bubble eye size was estimated by extrapolating the plume eye size to the value calculated for a polystyrene layer thickness of zero. The volumetric mass transfer coefficient of the surface reaction was measured at various size of plume eye. The volumetric mass transfer coefficient at the bubble eye area was evaluated by extrapolating the mass transfer coefficient at the plume eye area to the value calculated for a plume eye size equal to the bubble eye size. It was concluded that the size of the bubble eye is influenced by the gas flow rate through each nozzle, whereas the volumetric mass transfer coefficient at the bubble eye area is influenced by the bubble eye area and the bubble rising velocity.

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Chunky graphite is a particular form of graphite degeneracy that appears in the centre of large iron castings, with a well-defined transition from the outer unaffected area and the inner affected one. All previous works that looked for macrosegration to explain the phenomenon concluded that there are no significant composition differences between the inner and outer parts of such castings. This was challenged again because the analytical methods generally used for chemical analysis are not efficient for low-level elements. Accordingly, an ICP-MS procedure has been developed and validated to replace the usual ICP-OES method. Together with the usual methods for analysis of C, S and Si, this ICP-MS procedure has been applied to characterize chemical heterogeneities in a large block with chunky graphite in its centre, and to a standard part for comparison. It could be concluded that no macrosegregation has built up during the solidification process of the block investigated, i.e. that chunky graphite appearance is not related to any composition changes at the scale of the cast parts, in particular of elements known to affect graphite shape such as Ce, Mg, Sb, S, ···.

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A fatigue sensor called “smart stress-memory patch” has been presented to evaluate the fatigue damage of infrastructures as bridges and ship. In this study, the smart stress-memory patch was applied to the steel bar to estimate the stress amplitude and the cyclic number. Firstly, the fatigue test of the steel bar with attached sensor was carried out and the fatigue crack growth behavior of the sensor was investigated. Secondly, the stress distribution of the sensor was calculated by using the finite element method to evaluate a complex strain transfer from the steel bar. Finally, the possibility of measurement for the stress amplitude and the cyclic number by using smart patch was evaluated. The fatigue crack growth rate of the attached sensor was decreasing with the crack growth. Especially when the stress amplitude was large, the crack growth rate decreased dramatically with the crack growth. The analysis of stress distribution shows that the size of plastic zone around crack tip decreases with the crack length and the load subjected to the sensor is similar to that of the uniform displacement testing. In addition, the modified stress intensity factor based on the uniform displacement testing is proposed to correct the shape effect of the attached sensor on crack growth behavior. Appling the modified stress intensity factor to the principle of smart patch, it was demonstrated that the stress amplitude and the cyclic number of the steel bar could be estimated from the crack lengths of two sensors.

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Regulating molten steel level in continuous casting is difficult, because it suffers from various disturbances, among which the bulging disturbance is the most prominent. Moreover, as the casting speed increases in continuous casting, the phase lag due to the system delay increases. In this paper, we propose a disturbance observer with time-delay compensation to eliminate the bulging disturbance in the presence of system delay. We tested the proposed method using a 1 : 1 scale hardware simulator and confirmed that the method successfully decreased the bulging disturbance effect from the molten steel level.

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New cylindrical bone implants containing elongated pores interconnected as open pores were fabricated by an electron beam melting (EBM) method using Ti–6mass%Al–4mass%V ELI powder (mean particle diameter, 65 μm). New bone formation in the elongated pores of the implant and preferential arrangement of biological apatite c-axis were confirmed along the long bone axis by microbeam X-ray diffraction. Bone mass and preferential degree of biological apatite c-axis, which were considered a bone quality parameter, decreased with the distance from the edge of the implant along the longitudinal bone axis because of a stress-shielding effect. Although clear interconnections between new bones appeared through the implant with elongated pores parallel to the bone axis, the defective portion was not covered with new bone in the absence of the new implant.

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High strength low alloy steel in direct quenched and tempered condition was welded using gas shielded arc welding process at different welding heat inputs. The austenite grain size adjacent to fusion line was measured in order to calculate the apparent activation energy Q_app for grain boundary movement, the time exponent n and the kinetic constant K. The austenite grain size in heat affected zone was evaluated using these calculated parameters, and was compared with the austenite grain size measured in real heat affected zone of joint. The microstructure changes in heat affected zone were studied. Results indicated that the calculated parameters can be used to the predication of austenite grain size in heat affected zone area heated to a temperature of above 1100°C. The prediction results have a good agreement with measurement, while calculation at low temperatures was poor.

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Bainite lath nucleated WithIN Grain (BWING) has been clarified to be greatly effective for the increase in both strength and toughness. The nucleation of BWING has been enhanced by the introduction of inclusion into austenite, which would act as nucleation site for BWING. However, the inclusion itself would be brittle and at the interface between inclusion and matrix, high density of dislocations are apt to be accumulated under deformation, inducing cleavage at the interface. As density of inclusion increases, steel would be strengthened, but brittle. Therefore, the introduction of dislocation network, that is, Small-Angle Dislocation Network (SADN) into austenite is tried in the present work. SADN would be stable in the high temperature region such as in austenite, because pinned dislocation existed in SADN would prevent the bow-out of dislocations through absorbing point defects. The formation of SADN in austenite, which act as nucleation site for BWING, was clarified experimentally. The bainite lath neighbor to the nucleated one might be formed under relaxing the stress field around the nucleated one and/or inclusion. It was analyzed that the average size of Aggregates of bainite Laths having nearly Parallel Slip systems between neighboring bainite laths (ALPS) corresponds to that of dimples on fracture surface. The process for ductile fracture is offered based on the crystallographic analysis using transmission electron microscopy.

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In 0.1% Mn–added 3% Si–Fe alloys, the total number of {110} grains increased with increasing bulk sulfur content and with decreasing heating rate. This is contrary to that in Mn-free alloys. During isothermal annealing, the segregation concentration of sulfur for the initial time range was lower in the alloy containing 95 ppm sulfur than that in the other alloy containing 25 ppm sulfur. Also the maximum segregation concentration of sulfur appeared at a later time in the former. Such an annealing texture development and a segregation behavior can be attributed to the MnS precipitation and the subsequent dissolution into the matrix.

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A novel method has been discovered for controlling the crystallographic orientation of body-centred cubic crystals of iron. The process allows the cube faces of the crystals to align with the major surface of the polycrystalline sample in sheet form. Such a texture is advantageous in terms of its magnetic properties and has been a long-standing goal for research on electrical steels. The mechanism controlling the favourable orientation obtained is associated with the fact that the cube faces are elastically compliant so that the texture can develop in a manner consistent with minimization of strain energy. For the same reason, the presence of surface oxide which modifies the elastic modulus of metal surface stifles the development of the correct texture. The new process is demonstrated to lead to a dramatic increase in the magnetic flux density and a reduction in iron losses. It also involves a remarkably shorter processing time than conventional texture control in electrical steels.

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Effect of decarburization heat treatment and chromium addition on intergranular embrittlement of SA-106 carbon steel was investigated by scanning Auger electron spectroscopy analysis on fracture surface. Optical microscopy, scanning electron microscopy, transmission electron microscopy with energy dispersive spectroscopy analyzer and tensile test were performed to clarify the change in microstructure and mechanical properties due to decarburization heat treatment and 0.3–0.4 wt% chromium addition. The experimental results showed that decarburization heat treatment reduced the bulk carbon contents up to 40 mass ppm and caused the low temperature fracture mode to change from cleavage to intergranular under ultra high vacuum. It was also found that the decarburization heat treatment and chromium changed the shape and size of cementite in pearlite and formed the stable Cr-rich precipitates in the grain boundary which had an influence on the phosphorus segregation in the grain boundary. The tensile properties of SA-106 steels also changed due to the decarburization and chromium addition. Considering the direct and indirect effect of residual tensile stress imposed on SA-106 feeder pipes in heavy water reactor during manufacturing and installation, cautions should be taken in the effect of increased phosphorus segregation due to such various causes as tensile stress, decarburization heat treatment and chromium addition on the intergranular embrittlement of SA-106 feeder pipes in heavy water reactors.

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The temperature dependence of austenite nucleation behavior was investigated in an ultralow carbon 13%Cr–6%Ni martensitic stainless steel. The martensitic structure was partially reversed to austenite by heat treatment at different temperature in (austenite+ferrite) two-phase region. With increasing the reversion temperature, the shape of austenite grains tend to be changed from acicular to granular, and their nucleation site is changed from lath boundaries to prior austenite grain boundaries. The transition of nucleation site was discussed in terms of energetics by considering the increases in interfacial energy and elastic strain energy by formation of an austenite nucleus. The calculation results suggested that lath boundary is more preferential nucleation site rather than prior austenite grain boundary because the increment of elastic strain energy is reduced with lowing the reversion temperature.

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In this study, acoustic emission behavior of a tool steel during fracture toughness tests was investigated. Selected steel (AISI D2 cold-work tool steel) was heat treated at 5 different conditions (austenitized at 1010°C and tempered at 0, 300, 450, 525 and 575°C) and its properties were characterized using standard metallographic examinations, hardness and tensile tests. Compact specimen testing according to ASTM standard E 399 and acoustic emission technique were used to determine the fracture toughness value (K_IC) and fracture process. Determination of fracture toughness using AE technique was carried out according to classical and two modified methods. Results showed that: (a) by increasing tempering temperature, plain strain fracture toughness (K_IC) values and the fraction of ductile fibrous fracture increase except at 525°C when tempering process leads to secondary hardening, (b) fracture toughness values determined, using AE technique is lower than standard ASTM E399, (c) estimation of K_IC values, using modified methods (AECR and AEER), is more accurate in comparison with the classical AE method and (d) the effect of tempering temperature on AE characteristics during fracture toughness test is similar to its effect on hardness.

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Steel is the most widely used material in the world and numerous studies analyzing the material flow of steel have been conducted for Japan, Asia and the world. While top-down and bottom-up approaches have been employed in material flow analysis and steel stock accounting, the applicability of these approaches is largely dependent on data availability. To overcome this problem of limited data, we proposed a method for estimating steel stock based on satellite images. Previous studies have shown that satellite images of nighttime lights are closely correlated with human activities, such as electricity consumption, CO₂ emissions, and GDP, etc., which are also linked to the amount of steel stock. Therefore, in this study, images of nighttime lights were used in conjunction with land cover data to estimate the building and civil construction steel stock in Japan and other Asian countries. We initially performed the analysis for each prefecture of Japan and then applied the combined result to Japan, China, South Korea and Taiwan. Building steel stock was highly correlated with urban nighttime lights, while the steel stock used for civil construction structures was more closely correlated with total nighttime lights.

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The Utility of Stock hypothesis, which assumes that an in-use stock of constructional material is a function of GDP, was formulated and a clear correlation between the world steel stock and the world GDP led to the estimation that the world demand for iron ore (primary iron) depends not on the volume of GDP but on the variation of GDP, as already reported. In this study, the world steel stock in use is computed. Sensitivity analyses are conducted to show the effect of lower reliable data such as the usage period (lifetime) of iron-containing final products. Clear correlation is found between the in-use steel stock and the steel stock. Hence, the Utility of Stock hypothesis is verified.

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