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ONLINE ISSN: 1883-2954
PRINT ISSN: 0021-1575

Tetsu-to-Hagané Vol. 80 (1994), No. 12

  • Numerical Simulation of Combustion

    pp. 871-877

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    Readers Who Read This Article Also Read

    1. Development of "In-situ" Observation System for Oxide Films Formed during Thermal Oxidation Using Raman Spectroscopy Tetsu-to-Hagané Vol.81(1995), No.6
    2. Sintering Process Usiug Pisolite Lumpy Ore as Hearth Layer Tetsu-to-Hagané Vol.80(1994), No.4
    3. Rist Operating Diagram(I) Tetsu-to-Hagané Vol.79(1993), No.9
  • Direct Induction Skull Melting of Electrical Conducting Materials Using Crucible with Insulating Coat and Its Heat Conduction Analysis

    pp. 878-883

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    A direct induction skull melting process, in wihch a water-cooled induction coil is directly used as a crucible, enjoys an advantage of non-contamination from the crucible together with high energy efficiency. The applications of this process, however, are limited to the materials with electrical insulating property in solid state. The aim of this study is to extend the applicable materials of the process and to melt and hold the materials with electrical conducting property in solid state such as metals and semiconductors by coating a insulating film on the coil surface. In order to clarify a theoretical base of the process, electric and magnetic fields and a temperature one are simultaneously analyzed by taking account of the differences of electrical and thermal conductivities in solid and liquid states. Experiments demonstrate the feasibility of the process for a stainless steel and a silicon which indicate the electrical conducting property in solid state and clarify the validity of the theoretical results. It is found that the conditions of the smaller thermal conductivity, the higher heat transfer coefficient and the lower magnetic frequency, can provide the wider range of the magnetic field to form the stable skull.
  • Modeling of Gas and Liquid Flow in Two Dimensional Packed Bed and Analysis of Dropping Zone in Blast Furnace

    pp. 884-889

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    A mathematical model of liquid dropping flow in a two-dimensional packed bed was developed, in which distribution of liquid generating points, wall and impermeable region have been considered. The model was combined with the gas flow model in order to analyze the phenomena in the dropping zone in a blast furnace.
    The influence of gas and liquid flow rate on the liquid flow was examinèd through cold model experiments and the simulation results were validated by the experimental results.
    On the basis of the simulation, liquid flow distribution in the blast furnace becomes uniform through dropping to the furnace bottom. Flooding tends to occur just below the cohesive layer.
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    1. 討論会集録 Tetsu-to-Hagané Vol.55(1969), No.6
    2. Sintering Process Usiug Pisolite Lumpy Ore as Hearth Layer Tetsu-to-Hagané Vol.80(1994), No.4
    3. Development of "In-situ" Observation System for Oxide Films Formed during Thermal Oxidation Using Raman Spectroscopy Tetsu-to-Hagané Vol.81(1995), No.6
  • The Effect of Oxygen Content on the Formation Behavior of Sulfides of MnS System and the Machinability of Low Carbon Resulphurized Steel

    pp. 890-895

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    Study was made to clarify the effect of oxygen content on the formation behavior of sulfides of MnS system and the machinability of resulphurized free-machining steel and the mechanism of the effects of oxygen.
    In the case of high oxygen heats about 0.02mass%O, the solid oxides rich with MnO are formed at the early stage of solidification and these oxides facilitate the heterogeneous nucleation (H. N.) on MnS crystallization. This leads the enlargement of MnS inclusions and decrease of the amount of FeS solution in MnS inclusions. In the case of low oxygen heats less than about 0.01mass%O, there aren't so many oxides which act as the site of H. N. that MnS forms at final solidification. Thereby MnS inclusions are small and the amount of FeS solution in MnS inclusions increases.
    Increase of oxygen content improves the surface roughness of plunge cutting and drill life as formerly reported. The mechanism of effect of oxygen content on the machinability is estimated as follows. The difference in oxygen content affects the morphology, size and deformability of MnS inclusions. These changes in MnS inclusions have effects on the behavior of formation and falling of built-up-edge and the friction between chip and tool, through the deformation behavior of MnS inclusions in front of the top of tool.
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    1. Thermodynamics of Copper Dissolution into MnO–SiO2–MnS Inclusion System ISIJ International Vol.49(2009), No.2
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    3. Effect of Oxide Inclusions on MnS Precipitation in Low Carbon Steel Tetsu-to-Hagané Vol.75(1989), No.3
  • Estimation of a Region with Solidification Structure Refined by Reduction in Semi-solid State through Solidification and Strain Analysis of a Cast

    pp. 896-901

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    It is well known that solidification structure is made finer by reduction in semisolid state. The object of this research is to clarify the condition of occurrence of such a process quantitatively and to make it possible to estimate the size of the refined region in cast products. We made experiments in which cast pieces were reduced in semisolid state. We also analysed the distribution of temperature, fraction of solid and strain in the thickness direction of cast pieces. The results obtained from these experiments and/or analyses are as follows.
    (1) The solidification structure of the region refined by reduction is equiaxed and transformed into globular austenite, while that of the other part, columnar dendritic or equiaxed with regular size, is transformed into columnar austenite.
    (2) The portion of refined region becomes larger as average fraction of solid and/or reduction ratio increase. Precisely, the condition of refining is expressed with the following equation in terms of local solid fraction and local compressive strain.
    fs≤0.75ε0.132
    (3) By use of the above quantitative relations for refining, it becomes possible to estimate the fined region in cast pieces.
  • Determination of Calcium in Steel by Secondary Ion Mass Spectrometry

    pp. 902-907

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    The possibility of applying the Secondary Ion Mass Spectrometry (SIMS) to the determination of bulk Ca of low concentration was studied. Ca containing iron alloys of 2.1 to 210 ppm Ca which is determined by wet analysis, a NBS standard sample (53 mass ppm Ca) for instrumental analysis and 40Ca+ ion doped iron samples (10 and 2000 mass ppm at peak concentration) were analyzed by SIMS.
    Analyzing the area of 500×700gμm2 with O2+ primary ion and measuring over 10 spots each sample, one can obtain generally less than 30% for the relative standard deviation of the ion intensity of 40Ca+ normalized with matrix 57Fe+ ion. Analysis of all the three type of samples gave a good linear corelation between relative ion intensity of 40Ca+ and bulk Ca concentration. Under the condition of this work, the relative sensitivity coefficient of Ca to Fe was given 50 and the analytical limit of Ca determination was estimated 0.5 mass ppm Ca.
  • Formulation of Flow Stress of Nb Added Steels by Considering Work-hardening and Dynamic Recovery

    pp. 908-913

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    Flow stress of Si-Mn steel and Nb added steels measured under the usual hot deformation conditions for the rolling of steel plates was formulated by taking strain hardening and dynamic recovery into consideration. The functions derived include variables of deformation conditions such as deformation temperature, strain and strain rate and metallurgical factors such as austenite grain size and Nb concentration. The calculated stress-strain relations and the stress-dislocation density relations show good correlation with experimental data. The increase in flow stress by Nb addition is due to the additional effects of the increase in strain hardening rate and the decrease in dynamic recovery rate leading to a high level of dislocation density just after deformation.
  • Formulation of the Decrease in Dislocation Density of Deformed Austenite Due to Static Recovery and Recrystallization

    pp. 914-919

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    Decrease in dislocation density (ρ) in deformed austenite of Si-Mn steel and Nb added steels due to static recovery and recrystallization has been investigated. By comparing the flow stress measured at the second pass of a double compression test and the fraction of recrystallized austenite of the specimen quenched a certain time after deformation, the change in ρ due to static recovery has been separated from the total change of ρ. The change in ρ due to static recovery has been formulated as functions of the concentration of Nb(Nb%), deformation conditions and time after deformation. The recovery process is mainly controlled by the climbing of deslocations in the case of higher deformation and holding temperature(DT) and lower Nb%, while it is mainly controlled by the annihilation of dislocations with opposite Burgers vectors in the case of lower DT and higher Nb%. Recovery is retarded by an increase in austenite grain size, a decrease in DT and an increase in Nb%.
  • Effect of Dislocation Density in an Unrecrystallized Part of Austenite on Growth Rate of Recrystallizing Grain

    pp. 920-925

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    The growth rate of recrystallizing austenite grains of Si-Mn steels and Nb added steels after hot deformation was investigated by measurement of the fraction of recrystallized austenite and recrystallized austenite grain size. The fraction of recrystallized austenite(Xcr) at which the mechanism of recrystallization changed from nucleation and growth (NG) to site saturation (SS) was formulated as a function of Nb concentration and deformation conditions.According to the increase in deformation temperature and strain, Xcr increases while the increase in Nb in solution decreases Xcr.
    The growth rate of recrystallizing austenite was also formulated as a function of strain energy (Fv) and Nb concentration. Strain energy, Fv is calculated with the dislocation density decreasing due to static recovery during holding time after deformation by the method shown in the previous reports. The growth rate decreases rapidly after deformation due to the decrease in Fv and is obviously restrained by Nb addition.
  • Effect of Metallurgical Variations on Hydrogen Attack Resistance in C-0.5Mo Steel

    pp. 926-931

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    A large number of C-0.5Mo steel equipments have been subjected to successful operation in petroleum and petrochemical industries. However, recent hydrogen attack incidents below the Nelson chart limitation have been pointed out that metallurgical variation makes an important role to affect the hydrogen attack resistance. Under the circumstances, five cases of actual damaged samples taken from reactors and heat exchangers were investigated in metallurgical view points. X-ray diffraction analysis revealed abnormal carbide precipitation with M23C6 in all of the actual damaged samples. As a result of laboratory examinations, these abnormal carbides of M23C6 were recognized to precipitate in a limited heat treatment condition with slow cooling rate from austenitizing temperature, which resulted in the deteriorated resistance. At the same time, effects of tempering temperature for the base metal were examined by autoclave test. Methane bubble formations of the base metal were apparently facilitated with the higher tempering temperatures. These unique variations in the resistance were discussed in relation to bubble formation sites and effect of free carbon in the ferrite matrix.
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  • Grain Oriented Silicon Steel Sheet with TiN Film Characterized by Ultra-low Iron Loss

    pp. 932-937

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    An improvement in the iron loss in grain oriented silicon steel sheet was investigated for TiN ceramic coating produced by ion plating on polished silicon steel sheets. The influence of the coating conditions on magnetic properties was also investigated, relating to the thickness, bias voltage, coating temperature, tension, vacuum pressure and reactive N2 gas used for TiN ceramic coating by the hollow cathode discharge (HCD) method.
    The experimental results obtained are summarized as follows.
    (1) The magnetic flux density B8(T) of silicon steel sheets with a thin TiN film increases moderately to 0.0040.015T, while the iron loss W17/50 (W/kg) is improved dramatically to 0.11-0.23W/kg.
    (2) The iron loss in the TiN-coated silicon steel sheet by the HCD method is most improved under the coating conditions of (a) the thickness above 0.7μm, (b) bias voltages in the range of-50 to-100V, (c) coating temperatures in the range of 573 to 673K, (d) tensions in the range of 0.9 to 5MPa, (e) vacuum pressures above 0.3Pa, and (f) reactive N2 gas above 150SCCM.
    (3) The domain structure of the chemically polished and TiN-coated areas inside a single giant secondary Goss grain changed drastically, showing four to six narrow wall spacings from an original 180° main domain with large black and white wall spacings elongated in the rolling direction.
  • Effects of Insoluble Carbide on Microstructure and Hardness of Martensitic Stainless Steels

    pp. 938-943

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    The Effects of insoluble carbide on the microstructure and hardness of martensitic stainless steels were investigated in 12%Cr-(0.10.4%)C steels. In high carbon steels, carbide does not dissolve into austenite fully at a solution treatment temperature around 1300K and the insoluble carbide affects the mechanical properties of martensite at room temperature. By means of hardness testing in specimens solution-treated at different temperatures (T;K), the solubility of carbon in austenite ([C];mass%)was given by the equation ; log [C]=-6100/T +4.1. The relation between volume fraction of insoluble carbide (F;vol%) and carbon content of steels (C;mass%) was given by the equation ;F=20(C-[C]) by taking the densities of carbide and martensite into consideration. The contribution of insoluble carbide was added to the hardness of martensite matrix, so that the hardness of martensitic steels with insoluble carbide (Hv*) was represented by the equation ; Hv*=25+1250√[C]+500(C-[C])
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  • Effect of Minor Alloying Elements on the Mean Thermal Expansion Coefficient of Fe-36% Ni Invar Alloy

    pp. 944-949

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    The effects of single addition (C, B<0.02%, Al<0.1%, others<0.5%) of various minor alloying elements such as C, Si, Mn, Cr, Mo, Cu, Nb, Ti, V, Al, W and B in 36%Ni base alloy on thermal expansion and Curie temperature (Tc) were investigated.
    The results obtained are as follows :
    (1) Thermal expansion coefficient between 30°C and 100°C (α30100°C) increases with increase in the content of all these alloying elements. The magnitude of the effect of alloying elements on α30100°Cwas evaluated quantitatively. α300400°Cincreases also with increase in the content of these alloying elernents except B and Cu.
    (2) It is found that α 30100°C of 36%Ni alloys with Tc lower than that of the base alloy tends to decrease with rise in Tc. On the other hand α30100°C of the alloys with Tc higher than that of the base alloy tends to increase with rise in Tc.
    (3) Relation between α 30100°C and the mean number of valence electrons per atom (e/a) is classified into 3 groups which depend on number of valence electrons of alloying elements. α30100°C in each group has good relation to e/a.
  • Thermal-Elasto-Plastic Analysis on Occurrence of Liquid Zinc Induced Cracking in Bridge Girder under Hot-Dip Galvanizing

    pp. 950-955

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    The aim of the present study is to clarify the mechanical behavlor of a bridge girder during hot galvanizing. The mechanical behavior is analyzed using finite element method (FEM) analysis in which the constitutive equation is given by Bodner's viscoplastic model. The mechanism of zinc induced cracking is also discussed in detall. A shape and size parameter, Rσmax. is proposed and discussed. Rσmax is the ratio of the maximum compressive thermal stress to the elastic buckling stress of the panel and is related to zinc induced cracking. The parameter Rσmax correlates well with the final tensile strain calculated by FEM analysis. Critical strain for crack initiation, εc, was obtained from bending tests and from FEM analysis for several steels. Each value of Rσmax at crack initiation was estimated from comparison with the final tensile strain and εc. The estimated critical value of Rσmax is nearly the same as the critical value of Rσmaxobtained by calculation of the transition from non-cracking to cracking behavior of bridge girders.
  • Advancement in Steel Production Technologies and Its Future Issues

    pp. N598-N605

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