Tetsu-to-Hagané
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ONLINE ISSN: 1883-2954
PRINT ISSN: 0021-1575

Tetsu-to-Hagané Vol. 60 (1974), No. 2

  • 分析と人

    pp. 167-168

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  • Study on the Reduction of Iron Oxide Powder

    pp. 169-176

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    This study is related to the solid-gas reaction. The focus is placed on the relationship between specific surface area and the deposition of carbon in CO, CO2 gas atmosphere, and the mechanism of sintering process of reduction powders is also studied.
    The results are as follows.
    1) Change of specific suface area of reduced powders is dependent on the reduction temperature.
    2) The rate of deposition of carbon on the powder reduced at low temperature (500°C, 600°C) is larger than that reduced at high temperature (800°C, 900°C).
    3) The correlation between the weight of deposite carbon and the specific suface area is found.
    4) The sirtering of reduced powder proceeds through fiber material of 2-5μ in length.
  • On the Experimental Study of Tuyer Model Ablation and Its Heat Transfer Analysis

    pp. 177-183

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    Through the examination of blast furnace tuyers failed and replaced by new one, it was found that 43% of the failure occured at upper wall, 45% at lower wall, 12% at side wall and 73% at outer wall of tuyer. The ablated failure occured at the upper and lower part of outer wall and edge wall of tuyer, and the failure of this type exceeded almost 80% of the total failures.
    The experimental studies of ablation failure of the blast furnace tuyer were made by the model tuyers of wall thickness 15mm which made from Cu, PBC, BS materials and the cooling water velocity was kept to 3-4m/sec at the inner surface of model tuyers, and molten iron was poured onto the side wall of model tuyers.
    On the basis of the experimental ablation data of model tuyers, the heat transfer simulation model of ablation was established, in which the heat transfer coefficients were determined by the results of electronic computer calculations.
    By this heat transfer simulation model, the cooling water velocity must be over 13m/sec by the consideration of burn-out data already published by MCADAMS.
    Further, an investigation was also made on the effects of thickness of tuyer wall and its thermal conductivity effect on the ablation speed of tuyer.
  • Optical Absorption Spectra of Quenched Glassy Slags Containing Iron Oxide

    pp. 184-191

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    Liquid slags composed of Na2O-SiO2-Fe2O3, Na2O-P2O5-Fe2O3, and CaO-SiO2-Al2O3-Fe2O3 have been equilibrated with various oxygen pressures at 1250°C, 950°C, and 1500°C, respectively. After quenching, the glassy solid slag has been polished on the both sides and the optical absorption spectra have been measured with an optical spectrometer.
    A strong charge transfer band and five absorption peaks have been observed. The five peaks are inter preted to be due to electron transitions from the ground state of 6A1g to 4T2g (D), 4A1g-4Eg (G), and 4T2g (G)(these three are attributed to 3d electrons of Fe3+) and from the ground state to 5Eg (octahedralsymmetry) and to 5T2g (tetrahedral symmetry);(these two peaks are attributed to 3d electrons of Fe2+).
    From the peak positions, it is deduced that oxygen anions are located around a ferric cation in the tetrahedral symmetry in Na2O-SiO2-Fe2O3 slags and in the octahedral symmetry in Na2O-P2O5-Fe2O3 slags and around a ferrous cation in both tetra- and octa-hedral symmetries in the all slags studied.
    The position of the edge of the observed charge transfer bands shifted to the lower energy position with the increase of the Fe2O3 addition, oxygen pressure, and the basicity. From the edge shift, it seems that the charge transfer band is essentially due to electron transitions between the ferric cation and oxygen anion.
    The reproducibility of the peak position was within 50cm-1 (0.006eV) and the relative error in the molar extinction coefficient was estimated to be ±15%.
  • Liquid Steel Refining in the Ladle with Non-Oxidising Synthetic Slag

    pp. 192-205

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    The steel-refining method by Ar-gas bubbling into liquid steel from the bottom of the ladle has been reported. But under the existence of normal slag containing much FeO in the ladle, so much effect can not be expected because of reoxidation of liquid steel by the slag.
    Two kinds of nonoxidising synthetic slags were made and applied to low C-Al killed steel. After the complete slag-off from the furnace, heats were tapped and synthetic slag (s-slag) was added into the ladle under the condition of Ar-bubbling.
    The effect of kinds of s-slags and lining-materials was studied and the following results were found.
    1) If the FeO content of slag in the ladle reduced under 2%, liquid steel was purified and total oxygen reached less than 40 ppm. Large inclusions (≥100μ) were also eliminated.
    2) Loss of sol. Al in liquid steel was caused not only by slag but also by lining material. Relative contribution of lining-material to sol. Al loss became higher by the case of s-slag treatment than by normalslag. It can be suppressed, however, by using high Al2O3 content lining-material.
    3) The velocity of sol. Al loss was controlled by diffusion of oxygen in slag.
  • Determination of Solidifying Shell Thickness of Continuously Cast Slab by Rivet Pin Shooting

    pp. 206-216

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    A rivet pin shooting technique was attempted to investigate the effect of operational factors (cooling intensity by water spraying, superheat of steel and withdrawal rate) on the structure of solidifying front and case morphology. In this technique, steel pins were shot from Drivit gun into moving continuously case slabs. From the results obtained by applying the new technique above mensioned, solidification rate was determined and the effects of cooling intensity by water spraying on the solidification were elucidated. The measurement of secondary arm spacings of dedrites indicated that solidification rate was accelerated at the bottom end of liquid pool.
  • Effect of Copper Addition on the Recrystallization Texture of Low Carbon Steel Sheet

    pp. 217-225

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    In a low carbon steel containing 0.56% Cu and 0.054%C, a recrystallization texture similar to that of aluminium killed steels is obtained by a process in which the hot strip is austenitized at 950°C for 30 min, quenched into water, cold-rolled to 70% reduction and finally annealed at 700°C for 3hrs with a heating rate of 100°C/hr. The main preferred orientation in the recrystallization texture is {111}‹110›.
    The intensity of the {111}‹110› component after the final annealing strongly depends on the heating rate. The sharp {111}‹110› preferred orientation does not develope in a similar steel containing 0.56% Cu and 0.008%C, showing that the carbon content has a critical effect on the development of the {111}‹110› oriented recrystallized grains.
  • Reverse Transformation of Low-carbon Low Alloy Steels

    pp. 226-238

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    The process of formation of austenite has been studied in low-carbon low alloy steels. The specimens with acicular structures such as martensite, bainite or tempered martensite are heated at temperatures between Ac1 and Ac3. The structual changes in these specimens during heating are observed in detail.
    The main results are as follows.
    1) Austenitizing processes are divided into two stages. In the first stage globular austenites are formed accompanying the dissolution of cementite. Acicular austenites are as well formed at an early stage.
    2) In the second stage a globular austenite is formed by the coalescence of the acicular austenite grains and those formed in the both stages grow to form extended austenite grains.
    3)γ′ transformation prevails in a boron containing steel.
    Based on these results, it is proposed that the reverse transformation are mainly controlled by the rate of recrystallization of austenite.
    x

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  • Effects of Phosphorus Addition on the Precipitation Behavior of Carbides and the Age Hardening Properties in Austenitic Heat Resisting Steels

    pp. 239-257

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    The effects of phosphorus addition on both the precipitation behavior of M23C6 carbides and the quench sensitivity of the age hardening properties have been investigated in 21Cr-12Ni austenitic heat resisting steels containing carbon up to 0.3%.
    It is found that in P containing steels the higher aged hardness is obtained and this is not affected by the cooling rate after solution heating. According to the transmission electron microscopy, this quench rate insensitivity of the aged hardness is revealed to be attributed to the fact that in these steels the matrix precipitation of carbides occurs and the dispersion of carbides is not affected by the cooling procedures unless carbides are pre-formed during cooling. On the other hand, the pre-formed precipitates which have been formed during both slower cooling from the solution temperature and heating up to aging temperatures affect appreciably the dispersion of carbides formed during the subsequent aging.
    In directly aged specimens of P containing steels heterogeneous precipitation occur above a certain critical aging temperature. It is suggested that the existence of the critical temperature at which the precipitation mode of carbides changes from matrix-to heterogeneous-precipitation is based on the easilr growth of precipitates associated with dislocations at higher temperature.
    On the basis of the above results, the role of phosphorus in M23C6 carbide precipitation is discussed.
  • Kinetic Study of the Interrelation among Three Types of γ→α Martensite Transformation in Iron Alloys

    pp. 258-268

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    The γ-α martensitic transformation in iron alloys can be classified into three types: type IA (packet), 1ype IB (lenticular), and type II (isothermal) transformations.
    The interrelation among these three types of transformation were investigated using the equation of thermal nucleation rate, and the following conclusions were drawn from the obtained results.
    (1) Using the idea of temperature dependence of the activation energy ΔW, it could be shown that the athermal transformation is an extreme case of isothermal transformation.
    (2) Assuming the temperature dependence of ΔW is high enough in the calculation, the type I transformation can be obtained, whereas type II appears when the temperature dependence of ΔW becomes progressively smaller in the lower temperature range. The larger the value of autocatalytic factor c, the more burst-like transformation occurs. Physical metallurgical meaning of c can be discussed from the results of this study and also previous works by other researchers.
    (3) It is also shown that the magnitudes of ΔW and v (mean size of martensite lath) markedly shift the transformation temperature range, while they do not appreciably influence the transformation rate.
    (4) Taking into account the temperature dependence of the critical resolved shear stress and that of the shear modulus of alloys, behaviours of those three types of transformation can be explained qualitatively in terms of the temperature dependence of the activation energy.
  • Effects of the Aged Structure and the Prior Austenite Grain Size on Fracture Toughness of 18Ni Maraging Steels

    pp. 269-283

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    A study has been made of the effects of the aged structure and the prior austenite (γ) grain size on plane strain fracture toughness (KIC) of 18 Ni 300 and 350 grade maraging steels. The relationship between KIC and tensile properties or Chrpy V notch absorbed energy (CVN) has been also investigated. KIC is strongly affected by the structure aged at different temperatures. It is found that Kic of the specimen with high temperature aged structure is superior to those with low temperature aged and overaged structures, and the factors which affect KIC of the three different aged structures are discussed. KIC is scarcely affected by the prior γ grain size. This phenomenon is in contrast to those of tensile ductility and CVN which markedly decrease with increasing the prior γ grain size.
    Therefore, any relationship between KIC and tensile properties or CVN can not be observed. This may be due to the change of the fracture mode, with increasing the prior Therefore, any relationship between KIC and tensile properties or CVN can not be observed. This may be due to the change of the fracture mode, with increasing the prior γ grain size, from dimple in the grain to dimple along the prior γ grain boundaries or quasi-cleavage. grain size, from dimple in the grain to dimple along the prior γ grain boundaries or quasi-cleavage.
  • On the Combination of Tensile Strength and Ductility of High Tensile Strength Cold Rolled Steel Sheets and the Metallurgical Factors

    pp. 284-295

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    Aiming at the use for the inner and the outer steel panels of the automobiles on which the safety of the rider should be considered as the first importance, various high tensile strength cold rolled steel sheets have been developed. A trial has been carried out to find what strengthening mechanism is the best for the combination of strength and ductility (n-value and the total elongation).
    The following results were obtained:
    1) The combination of the strength and ductility can be ranked as follows from the best to the worst; Substitutional solution hardening>Grain boundary hardening>Precipitation hardening This ranking well coincides with the work hardening behavior.
    2) In the substitutional solution hardening type, a collinear distribution of dislocations is dominantly observed and the work hardening still increases at a large tensile strain.
    3) In the grain boundary hardening type, more cell substructures and less structures of collinear distribution of dislocations are formed than in the substitutional solution hardening type.
    4) In the precipitation hardening type, most of dislocations often have interactions with the uniformly distributed fine precipitates in the matrix and the strain increases forming dislocation loops at an early stage of tensile strain. Thus, work hardening is fairly large at the early stage of strain but soon saturates without forming clear cell substructions at the late stage of tensile strain.
    5) The poor combination of strength and ductility of the precipitation hardened steels by the usual treatment is much improved up to a level of the grain boundary hardening type by taking a special treatment, i. e. 950°C×1hr pre-heating before cold rolling and causing the precipitating particlescoalesce and distribute heterogeneously. This improvement coincides with the result of the transimission electron micro - scopic obserbation that the microstructure after deformation resembles that of the grain boundary hardening type.
  • Review of Current Application of ESR and its Products

    pp. 296-303

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    In the past 20 years, there were some developments of vacuum metallurgy and, at each time, every special metallurgical process was to meet the demand of customers for better quality and its improved mechanical property.
    Studies have been made in this paper as to the most current development in this field, i. e., Electro-Slag Remelting process, as one of the special metallurgical processes following up the trend of vacuum metallurgy.
    ESR process has spread rapidly all over the world recently but it is still under development and one can not state with an absolute certainty what reasons could lead to the large scale technical application of this process without exact knowledge of the individual application.
    Several important technical and economical reasons for applying this process should be known in the steel industry so that one can understand its advantage without any arbitrary decision.
  • Recent Advances in the Mechanism of Hydrogen Embrittlement

    pp. 304-316

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    Readers Who Read This Article Also Read

    1. III圧延材の矯について Tetsu-to-Hagané Vol.60(1974), No.2
    2. III圧延材の矯について Tetsu-to-Hagané Vol.60(1974), No.2
  • 抄録

    pp. 317-322

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  • 高炉燃焼帯の挙動

    pp. A1-A6

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  • III圧延材の矯について

    pp. A23-A34

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    x

    Readers Who Read This Article Also Read

    1. III圧延材の矯について Tetsu-to-Hagané Vol.60(1974), No.2
    2. Recent Advances in the Mechanism of Hydrogen Embrittlement Tetsu-to-Hagané Vol.60(1974), No.2
  • III圧延材の矯について

    pp. A35-A42

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    x

    Readers Who Read This Article Also Read

    1. III圧延材の矯について Tetsu-to-Hagané Vol.60(1974), No.2
    2. Recent Advances in the Mechanism of Hydrogen Embrittlement Tetsu-to-Hagané Vol.60(1974), No.2
  • II鋼の破壊靭性

    pp. A43-A58

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  • V鉄その他BCC金属のクリープと格子欠陥

    pp. A59-A70

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  • 鉄鋼精錬における界面現象

    pp. A7-A22

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