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

Tetsu-to-Hagané Vol. 62 (1976), No. 9

  • 自主管理活動の意議

    pp. 1149-1150

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  • Experimental Studies on Burnout of Tuyere

    pp. 1151-1158

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    Molten iron is poured on the upper side of test piece which section closely resembles to blast furnace tuyere section currently in use. The lower side is cooled by forced circulation of water passing the horizontal rectangular channel. Specimens are oxygen free high conductivity copper (OFHC), 99.7% cast copper, 99.97% aluminum, rolled brass plate, aluminum bronze, mild steel and titanium. A transitional phenomena until burnout were observed and the effect of principal factors on the burnout heat-flux has been investigated. The results obtained are as follows.
    (1) In the case of OFHC, the burnout temperature of molten iron is higher as the velocity of cooling water is increased.
    (2) The values of burnout heat-flux are larger as the velocity of cooling water is higher and under the same water velocity, burnout heat-flux values increase with the rise of subcooling temperature.
    (3) In the case of OFHC, the influence of specimen wall thickness on the burnout heat-flux is negligible if the velocity of cooling water is high.
    (4) Experimental equation obtained is as follows:
    qBO=A×ΔTsub×V0.45
    A is constant with given material.
    A=1.75×103×λ0.64+5.6×Tm-2.4×103.
    Where
    λ: Thermal conductivity, kcal/m hr °C
    Tm: Melting point, °C
    ΔTsub: Subcooling temperature of cooling water, °C
    V: Velocity of water, m/sec
  • Measurement of Interdiffusivities of Components in Molten Iron and Slags by Electrochemical Method

    pp. 1159-1168

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    Galvanic cells to determine the interdiffusivity of two components in molten iron and slag were developed, using stabilized zirconia as an electrolyte, because it had been proved that local equilibrium held throughout the cell at high temperature. After getting a thermodynamic equilibrium in the cell, the oxygen potential and / or chemical potential of slag components at the electrode was changed rapidly by changing the gas phase or supplying a constant current to the cell. Accompanied EMF change was measured as a function of time. The interdiffusivity was determined from the time dependency of the EMF. The results are as follows;
    DO2 in 70 mol% PbO-SiO2
    DO2=8.3 exp (-26×103/RT) cm2/ sec 1000-1250°C
    DO2 in 40 wt% CaO-40 wt% SiO2- 20 wt% Al2O3
    DO2=4.5 exp (-3.3×103/RT) cm2/ sec 1300-1430°CDSiO2-CaO in 38-42 wt% CaO-42-38 wt% SiO2-20 wt% Al2O3
    DSiO2-CaO=4.5×103 (-78.4×103/RT) cm2/ sec 1340-1460°C
    DAl2O3-CaO in 45-55 wt% CaO-55-45 wt% Al2O3
    DAl2O3-CaO=1.25×109 (-125.5×103/ RT) cm2/ sec 1450-1500°C
    DO in Fe
    DO= (1.9±0.7) ×10-4 cm2/ sec at 1550°C
    x

    Readers Who Read This Article Also Read

    1. Estimation of Quasibinary Interdiffusivities in Multicomponent Slags for Iromaking and Steelmaking Tetsu-to-Hagané Vol.62(1976), No.14
  • On the Excess Viscosity of Liquid Alloys and the Atomic Interaction of Their Constituents

    pp. 1169-1178

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    An expression describing the excess viscosity of liquid binary alloys has been derived by use of some basic physical quantities, in order to estimate the viscosities of liquid alloys which are considered to be one of the most important properties in metallurgical processes, as follows;
    Δη= (x1η1+x2η2) [-5x1x212) 2/x1σ21+x2σ22+2 {√1+ (x1x2m1-√m2) 2/ (x1m1+x2m2) 2-1} -0.12x1x2Δu/kT]
    where, Δη: excess viscosity (cP), x: atomic fraction (x1+x2=1), η: viscosity of pure liquid metal, σ: diameter of the sphere (ionic radius after Pauling), m: atomic mass (m= M/NO, M: atomic weight, N0: Avogadro number), Δu: interchange energy (ΔH=x1x2NOΔu, ΔH: integral enthalpy of mixing), k: Boltzmann constant, T: absolute temperature. And the subscripts 1 and 2 refer to the components.
    In the square bracket of the above equation, the first and the second terms show hard part and the third term represents soft part of friction constant for viscous movements.
    Values calculated from the above equation for the excess viscosity of various liquid binary alloys coincided qualitatively with their experimental data, and in particular, for regular or nearly regular solutions, an excellent agreement has been found between those calculated and experimentally observed.
  • On the Rates of Nitrogen Absorption and Desorption in Liquid Iron

    pp. 1179-1188

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    The rates of nitrogen absorption and desorption of levitated iron droplets have been measured. This study made it clear that the rate of reaction of gas with liquid iron is determined by the mass transfers between two phases. The following equation was obtained in accordance with the two film theory.
    -nN=km (nN-√ αnN+ (α/2) 2+ (neN) 2+ α/2)
    where α= kmRTK2N/ 2kgf2
    Applying this equation to various experimental conditions, the following became clear. The reaction is first-order when there exists no gas boundary layer, for example, the nitrogen absorption from pure nitrogen gas injection. The reaction is between first- and second-order when there are two boundary layers, for example, the nitrogen desorption into pure argon gas. Oxygen which is a surface active element, retards the reaction rate because it decreases the effective surface area. This influence disappeared at about 2 100°C. Other alloying elements change the value of a affecting the activity of nitrogen in liquid iron.
  • Determination of Changes of the Dissolved Oxygen Content after Silicon Deoxidation by the Use of the Radioactive Silicon

    pp. 1189-1198

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    Changes of the dissolved oxygen content after deoxidation with 0.1 % and 0.42 % silicon have been determined by fixing the oxygen as the radioactive SiO2 with the radioactive silicon (silicon-31) previously charged in the sampler and counting radioactivity of the inclusions extracted from the sample.
    In both cases, the dissolved oxygen content decreases rapidly below the equilibrium value, and then increases gradually to reach it.
    The mechanism of the silicon deoxidation has been discussed from the viewpoint that such changes of the dissolved oxygen is due to the non-uniform distribution of silicon formed in liquid iron immediately after silicon addition.
    The conclusions are as follows:
    (1) In the regions where the silicon contents are high, SiOx (x<2) is produced, owing to the fast rate of reaction between silicon and oxygen, and the oxygen contents decrease to lower value than the equilibrium one.
    (2) The minimum of the dissolved oxygen attained immediately after silicon addition is regarded as a mean oxygen content at the time when silicon and oxygen dissolved uniformly in the melt.
    (3) The oxygen content increases again by the reaction SiO2 (crucible) = Si+2 O and the deoxidation processes such as growth of the deoxidation products and adhesion of them to the crucible wall are rate controlled by this reaction.
    (4) The composition of SiOx is not widely different from that of SiO2.
  • Effects of Natural Convection on Solidification Processes in Experiments Conducted by the Use of Cold Systems

    pp. 1199-1208

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    A study of the effects of natural convection on solidification processes under the various casting conditions has been made by the use of KCl solutions as the solidification system.
    Experimental results show that the increase in the teeming temperature causes the increase in the velocity of natural convection taking place along the solidification front and the increase of this velocity results in the acceleration of the removal rate of superheats in the liquid pool and also increase of the deviations of the liquidus and solidus planes from a vertical plane. Furthermore, it has been found that within the range below an eutectic concentration, as the concentration of KCl solution increases, the mean maximum velocity in the natural convection becomes faster and also the deviations of the liquidus and solidus planes from a vertical plane increase, but the mean maximum velocity is not so much affected by the change of temperature in the colling box.
    Moreover, it has been observed in the solidification experiments of the distilled water that the bubbles rising along the solidification front accumulate on the solidification front near the point of boundary-layer separation which moves upward with the progress of solidification process.
  • Effect of Dispersion State of TiN on the Austenite Grain Size of Low-Carbon Low Alloy

    pp. 1209-1218

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    The effect of TiN particles in low-carbon low-alloy steels on the austenite grain size was studied in relation to the dissolution, coalescence, and reprecipitation. Main results are summarized as follows.
    (1) Ostwald ripening was observed in the process of coalescence of TiN particles.
    (2) Main factors controlling the austenite grain size were the volume fraction (f) and the mean size of TiN particles (r). A linear relationship between the diameter of austenite grain and the mean distance of TiN particles (r/f) was obtained. The experimental relationship could be explained by a simple model proposed in this study.
  • Effects of Ni Content and Austenite Phase on Low Temperature Toughness and Embrittlement Behaviour of Fe-26% Cr Alloys

    pp. 1219-1228

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    The effects of Ni content and microstructure on the embrittlement of Fe-26% Cr alloys containing up to 10% Ni by reheating at a temperature range of 400 to 750°C were investigated. Furthermore, mechanical properties at low temperatures of ferritic alloys in annealed conditions were also investigated and the following results were obtained.
    (1) The addition of Ni to high Cr ferritic alloys promoted the occurrence of deformation twinning during tensile test.
    (2) The fracture of Fe-26% Cr ferritic alloy tested at- 196°C occurred without any plastic deformation, but the alloy containing 6% Ni exhibited a good ductility and strength due to the work- hardening effect of deformation twins.
    (3) The peaks of embrittlement by reheating were observed at 450, 500 and 750°C in case of the ferritic alloy annealed at 1000°C, while the embrittlement peaks of the two phase alloy were observed at 500 and 750°C.
    (4) The embrittlement of the ferritic alloy appeared within short heating times in comparison with the phase alloy that produced the embrittlement after long heating times. The causes of embrittlement observed at 750°C were different each other.
  • Strengthening and Toughening of 280kg/mm2 Grade Maraging Steel through Control of Microstructure

    pp. 1229-1238

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    In order to strengthen and toughen 280kg/mmm2 grade maraging steels, the effects of solution and aging treatments on the microstructure, tensile properties and fracture toughness have been investigated, and metallurgical factors affecting the strength-toughnesss balance have been discussed.
    Tensile ductility is strongly dependent upon prior γ grain size. Unstable fracture under low stresses occurs due to the decrease in ductility above a critical grain size, which depends on the strength level and fracture toughness of the steel. On the other hand, the fracture toughness is independent upon prior γ grain size but strongly dependent upon undissolved precipitates. The presence of undissolved precipitates can greatly lower the fracture toughness. Therefore, a simultaneous improvement of ductility and toughness would be obtained in the fine grained martensite structure without undissolved precipitates. Three special treatments, which consist of complete solution treatment of undissolved precipitates and grain refinement, have been proposed by utilizing the difference of metallurgical factors affecting the ductility and toughness respectively. Simultaneous improvements of the ductility and toughness for the higher strength level of 13 Ni-15 Co-10 Mo steel are obtained by a special thermomechanical treatment.
  • On the Dissolution of Spheroidized Carbides into Austenite in 0.8%C and 0.8% C-Cr Steels

    pp. 1239-1248

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    Dissolution of spheroidized carbides into austenite was studied in 0.8% C steels containing 0, 2 and 5% Cr. M3C carbides was observed in 0.8% C and 0.8% C-2% Cr steels and M7C3 in 0.8% C-5% Cr steel. It was found that the larger particles required longer times for dissolution into austenite than smaller ones. Marked acceleration of carbides dissolution was also observed with increasing austenitizing temperature.
    Activation energies of dissolution of carbides into austenite were obtained to be 90 kcal/mol in 0.8% C steel and 80 kcal/mol in 0.8% C-Cr steels. The variation of mean particle size of dissolving carbides was calculated under the assumption of diffusion model. From these results it was concluded that the dissolution of carbides into austenite would be controlled by diffusion of Cr atoms in 0.8% C-Cr steels.
  • Strengthening of 18%Ni Maraging Steels by Cold Rolling after Pre-aging and Re-aging

    pp. 1249-1255

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    Thermomechanical treatments for improving tensile strength of 18% Ni maraging steels have been investigated. The thermomechanical treatments applied to the 210kg/ mm2 and 245kg/mm2 grades maraging steels include a) cold rolling and aging, b) cold rolling in preaged conditions with and without subsequent re-aging at about 500°C.
    Increases in strength produced by cold rolling and aging are given as a function of the reduction in thickness. The tensile strength in the transvers direction reaches to a peak and then decreases because of the drop in elongation.
    The increase in strength produced by cold rolling in the pre-aged conditions is small. However, the tensile strength is greatly increased by the subsequent re-aging. The tensile strength in the transverse direction is remarkably improved by a thermomechanical treatment including preaging at 500°C, cold rolling, and re-aging at about 500°C.
  • The Relation of Structure to Drawability of Hypereutectoid Steel Wire Rods

    pp. 1256-1264

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    In order to improve the drawability of hypereutectoid wires used for sewing machine needles and card cloths, suitable structure for them have been studied. The various structures of hypereutectoid steel wires are obtained by various heat treatment processes they are drawn by continuous drawing machine. These processes are lead patenting after usual heating or rapid heating and a combined heat treatment of quenching in oil and lead patenting.
    The fittest structure of the hypereutectoid steel wire for drawing is composed of residual granular cementite after austenitizing and fine pearlite. This structure is obtained by the next process; the steel wire is quenched in oil after heating and then patented in a lead bath at 580°C after rapid heating to 900°C.
  • On Industrial Applications of Oxygen Concentration Cells

    pp. 1265-1277

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  • Report of the Instrumentation Committee and the Weighing and Measuring Subcommittee of the Joint Research Society of ISIJ

    pp. 1278-1286

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    [in Japanese]
  • Report of the Quality Control Committee and the Mechanical Testing Subcommittee of the Joint Research Society of ISIJ

    pp. 1287-1294

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  • 「水素-アルゴンプラズマによる鉄および鉄クロム合金の脱炭および脱窒」に対する討論

    pp. 1295-1296

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  • 抄録

    pp. 1297-1303

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