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

Tetsu-to-Hagané Vol. 74 (1988), No. 8

  • Recycle of Metallic Resources

    pp. 1519-1525

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  • A Starting Point of Physical Chemistry in Powder Metallurgy

    pp. 1526-1534

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  • Recent Development of Cooling Technology in Japanese Steel Industry/Revision of the Methods for Atomic Absorption Spectrochemical Analysis of Iron and Steel

    pp. 1535-1545

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  • A Numerical Analysis of Heat and Fluid Flow on Arbitrarily Shaped Region

    pp. 1546-1553

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    It is difficult to conform the discretization points to boundaries of the arbitrarily shaped region on the finite difference method of rectangular coordinate system. In this study the discretization method based on Gauss's divergence theorem is improved to deal with the arbitrarily shaped region in Eulerian method, and the present method is able to use the effective numerical techniques that have been developed on rectangular coordinate system.
    As numerical examples, steady heat conduction problem is calculated and compared with the solution of FEM, and some trials are made on analysis of problems in incompressible fluid flow. The present method is found to be useful to solve numerically partial differential equations derived from mass, heat and momentum balances.
  • Effects of CaO and SiO2 on the Rate of H2 Reduction of Dense Wustite and the Morphology of Product Iron

    pp. 1554-1561

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    Effects of CaO and SiO2 on the rate of H2 reduction of dense wustite were investigated in the temperature range of 6001000°C.
    The morphology of product iron by H2 reduction is classified into three types; dense iron with coarse pores, dense iron with few pores, and sponge iron with many fine pores. The reduction rate is closely related to the morphology of product iron. Difference of morphology of product iron was investigated in terms of the nucleation of iron, the manner of its growth and the morphology on the cross section of iron nucleus formed on the surface of wustite in the early stage of reduction.
    In the reduction of pure wustite, dense iron with coarse pores was obtained at higher temperature. It appears that pores in the dense iron layer were produced as a result of difference in specific volume between iron and wustite and sintering process of iron.
    In the reduction of wustite containing CaO, porous iron was produced inside the iron nucleus in the early stage of reduction at all the temperatures examined. From the observation of iron nuclei, it was suggested that the presence of CaO in wustite accelerated the chemical reaction between H2 and wustite surface.
    In the reduction of wustite cotaining SiO2, iron nuclei on the wustite surface were very small and did not show any further growth. Subsequent reduction occured only with the increase in the number of iron nuclei. The morphology of product iron layer was sponge iron with many fine pores except for the reduction at 700°C.
  • Effect of Blast Conditions on the Raceway of the Blast Furnace

    pp. 1562-1568

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    The raceway in front of tuyere of the blast furnace has been studied on an experimental furnace by means of penetration measurements, temperature measurements and gas composition survey. At the end of experiment, raceway is filled with light alumina particles carried by blast and is quenched with nitrogen gas. Then, profiles of the raceway, amounts and properties of coke in the raceway have been measured. The effects of operating variables such as amount of fuel injection, oxygen enrichment and blast temperature on the distribution of temperature and composition of gas have been studied.
    As the change of reaction condition around the raceway, it results in movement of position where reaction of coke takes place. It causes change of gas volume distribution and disintegrated coke particle distribution. Then profile of raceway and path of gas in the furnace are affected.
    In this way, the mechanism of shrinkage of raceway in the case of fuel injection which sometimes has been observed in the commercial furnace operation, is explained.
  • Combustion of Carbonaceous Materials in the Raceway of Experimental Furnace

    pp. 1569-1576

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    The raceway in front of tuyere of the blast furnace has been studied on an experimental furnace by means of raceway measurements, temperature measurements and gas composition survey. At the end of experiment, raceway is filled with light alumina particles carried by blast and is quenched with nitrogen gas. Then, profiles of the raceway, amounts and properties of coke in the raceway have been measured. The effects of coke properties on the reaction around the raceway have been studied using various kind of carbonaceous materials such as charcoal, pitch coke, carbon brick, formed coke and so on. It was shown that temperature of raceway is ruled by reactivity of coke. The temperature in the raceway is explained by assuming competitive reaction of blast against carbonaceous materials such as coke and CO gas in the furnace. As the results of observation of coke texture which is sampled from raceway, preferential reaction seems to take place between oxidizing gas and reactive component of coke texture. Fine coke powder, which is consisted mainly of inert component, is detached from coke in use of some kind of materials such as carbon brick where inert components are bound by small amount of reactive component. Accumulation of fine coke powder around the raceway prevents normal gas flow in the furnace.
  • Solubilities of CaO, MgO, SiO2 and 2CaO·SiO2, and Ferric-Ferrous Equilibrium in FetO-(CaO+MgO)-(SiO2+P2O5) Phosphate Slags

    pp. 1577-1584

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    Equilibrium phosphorus distribution between slag and liquid iron has been studied at a temperature range from 1300 to 1680°C. The slag systems studied were of FetO-P2O5-MxOy(MxOy = CaO, MgO, SiO2) saturated with MxOy crucible, and of FetO-P2O5-CaO-MxOy(MxOy=MgO, SiO2) saturated with MxOycrucible to clarify the effect of the added oxides on the phosphorus equilibrium and the approximate validity of the regular solution model for the phosphate slags.
    Among the results obtained, this paper shows the results concerning the solubility of the crucible materials to the phosphate slags studied and ferric-ferrous ratio in equilibrium. It was confirmed that the mole fraction of ferric oxide in the phosphate slags could be estimated by an assumption of the regular solution model within an error of ± 0.015.
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    Readers Who Read This Article Also Read

    1. Phosphorus Distribution between Liquid Iron and MgO Saturated Slags of the System CaO-MgO-FeOx-SiO2 Tetsu-to-Hagané Vol.67(1981), No.16
  • Distribution of Oxygen between Liquid Iron and FetO-(CaO+MgO)-(SiO2+P2O5) Phosphate Slags

    pp. 1585-1592

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    Equilibrium phosphorus distribution between slags and liquid iron has been studied at the temperature range from 1300 to 1680°C in order to examine the approximate validity of the regular solution model for phosphate slags. The slag systems studied were of FetO-P2O5-MxOy(MxOy= CaO, MgO, SiO2) ternary and of FetO-P2O5 -CaO-MxOy(MxOy= MgO, SiO2) quaternary.
    In continuation of our previous paper concerning the solubility of the crucible materials and ferric-ferrous equilibrium, the present paper shows the results of oxygen distribution between slags and metal. As the results, it was confirmed that the regular solution model was satisfied for all the experimental results, and the interaction energies concerning phosphate ion, αCa2+-P5+, αMg2+-P5+ and αSi4+-P5+ were determined.The iron oxide activity and oxygen content in metal could be estimated within the accuracy of±10% by the model.
  • Interaction between Gas and Liquid Caused by Jet Streams Blown to a Liquid Surface

    pp. 1593-1600

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    Studies were made of the depression, splashing of liquids and bath movement caused by jet streams impinging vertically on the surface of bath. Majority of them was performed by means of compressed air-water system except for splashing which was done by the use of various liquids.
    The depth of a cavity was not contradictory to the previous knowledge. The diameter of a cavity was dependent not only lance height but also jet momentum, which was described by momentum number through dimensional analysis.
    Generally, an increase in jet momentum or a decrease in lance height resulted in an increase in splashing to the maximum. However, beyond a certain critical value the amount of splashing decreased. A good correlation was observed between the ratio of the amount of splashing to that of jet stream and momentum number. The direction of splashing was mostly dependent on the profile of a cavity estimated from its depth and diameter.
    The ratio of the momentum of bath movement to that of jet stream was found to be proportional to 0.13th power of momentum number. This phenomenon could be explained by an introduction of the mechanism that the momentum transferred from jet to bath is proportional to the area of a cavity and jet velocity at the cavity surface.
  • Process for Enhancing Undercooling of Molten Steel

    pp. 1601-1608

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    A process has been developed to enhance the undercooling of molten carbon steel, by controlling the heterogeneous nucleation catalysts with addition of rare earth metal (REM). Molten steel of substantial mass, processed for the enhanced undercooling, was easily undercooled even with comparatively smaller cooling rates. A chemical analysis showed that REM components didn't exist in the ingot with REM addition except for the surface layer of the ingot. Furthermore, the number of nonmetallic inclusions decreased due to REM addition. It is considered that inclusions, which are active as nucleation catalyst, are attracted to the inner wall of alumina crucible used for the experiment by interreaction between REM components in the melt and the crucible wall and the active catalysts are removed from melt.
    The microstructure of specimens after solidification was investigated in relation to the degrees of undercooling and recalescence. In the specimen solidified with significant amount of recalescence, nondendritic structure of homogeneous matrix with precipitated graphite particles was observed. On the other hand, dendrite morphology was observed in the specimen solidified with little amount of recalescence even though the melt was highly undercooled.
  • Effect of Molten Steel Flow on the Surface Solidification Phenomena of Ingots

    pp. 1609-1616

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    The molten steel poured into the water cooled copper mold was rapidly solidified by changing the filling time. From the measurement of the temperature change in the copper mold, heat flux was calculated. Temperature distribution in the copper mold was simulated and predicted, and the primary dendrite arm spacing was calculated by use of the dendrite growth theory. Heat flux in the copper mold increased with time and reached a maximum value and then decreased gradually due to the formation of the air gap. The shorter was the filling time into the copper mold, the greater was its maximum value. The reason for this is that Nusselt number as a function of Reynolds number increases and extractive rate of heat increases with decreasing of the filling time. Therefore, it is found that the shorter is the filling time, the thicker is the initial solidification layer and the finer is the microstructures. By the modeling of the dendrite arm spacing based on TRIVEDI'S growth theory, the arm spacing was found to be mainly influenced by the temperature gradient.
  • Effects of Hot Rolling Temperature and Solute Carbon on Drawability of Hot Rolled in Ferrite Region and Annealed Sheet Steel

    pp. 1617-1624

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    The effects of the solute carbon content during hot rolling and the hot rolling temperature in ferrite region on the recrystallization texture and Lankford value of extra low carbon sheet steels were studied. The conclusions are as follows :
    1) With the addition of Ti or Nb effective in raising the recrystallization temperature of the extra low carbon steel, the hot rolled texture becomes nealy the same as the cold rolled one even though the rolling temperature is 700800°C. The effects of the hot rolling temperature in ferrite region on the hot rolled and hot rolled-annealed textures of interstitial free steel seet are small.
    2) Solute carbon content during hot rolling is one of the most important factors that affect the recrystallization texture. When decreased the solute carbon content during hot rolling by carbide (TiC, NbC) precipitation, recrystallization texture of {554} <225> orientation is developed after annealing. That is nealy the same as the cold rolled and annealed texture. The r value of 1.9 was obtained by hot rolling with lubrication using solute carbon free steel.
  • Effect of Central Segregation on Drawability of High-carbon Steel Wire Rod Manufactured from Continuously Cast Blooms

    pp. 1625-1632

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    A study has been made on the microstructure of the central segregation zone in wire rod and its fracture process for the purpose of improving the drawability by reducing central segregation in high-carbon steel wire rod manufactured from continuously cast blooms. (1) In the central segregation zone of wire rod, a kind of duplex segregation which consists of segregation plateau and microsegregation peaks was observed. This type of segregation is considered to originate from the macrosegregation in cast blooms. (2) The fracture which occurred during wire drawing was initiated from the martensite stringers or proeutectoid cementite networks on the microsegregation peaks formed on the segregation plateau. The propagation of fracture was governed by the width of the segregation plateau. (3) A dominant factor governing wire drawability is the width of the segregation plateau, that is, the width of the macrosegregation spots in cast blooms.
  • Formation Mechanism of Goss Texture in Hot Rolled 3% Silicon Steel

    pp. 1633-1640

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    A formation mechanism of Goss texture in 3% silicon steel hot band has been studied using a slip rotation theory of a single crystal proposed by the author. At first an orientation change during cold rolling has been predicted by this theory in the midplane of the single crystal with the initial orientation having <110> axis parallel to the transverse direction of rolling. Experimental results obtained here have supported this prediction. Then a new kind of stress in the vicinity of the sheet surface during hot rolling has been assumed by adding a friction stress between roll and sheet surface to the stress used in the above prediction of the orientation change in the midplane. The formation and the stability of Goss orientation during hot rolling have been explained using this theory and this new kind of simple stress as a phenomenon in the vicinity of the surface of single crystal sheet with the orientation of <110> //TD. At the same time this theory has suggested the stability and the formation of {112} <111> orientation besides Goss orientation in the surface layer of hot band.
  • Effect of Prior Austenite Grain Size on High Temperature Creep Properties of a Cr-Mo-V Steel

    pp. 1641-1648

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    The creep tests for the specimens with the various prior austenite grain sizes (10, 26, 52 and 106 μm in diameter) have been carried out at 650°C-617 kgf/mm2 to investigate the effect of the prior austenite grain size on high temperature creep properties of a 1Cr-1Mo-1/4V steel.
    The minimum creep rate decreased linearly with increasing prior austenite grain diameter up to 50 μm.This increase in the creep resistance was proportional to the decrease in the volume fraction of the recovered zone along the prior austenite grain boundaries. In the specimen with prior austenite grain diameter larger than 50 μm, however, the creep resistance did not follow the linear increase with the grain diameter, because of the formation of large cracks at higher stress, and the marked increase in the recovered zone width at lower stress due to the microstructural inhomogeneity.
    The prior austenite grain size should be controlled to be below 50 μm in diameter to optimize the creep resistance of a Cr-Mo-V rotor steel for the long term service.
  • Reversion Process of Deformation Induced Martensite to Austenite in Metastable Austenitic Stainless Steels

    pp. 1649-1656

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    The reversion process of martensite (α') to austenite (γ) was investigated using 15.62%Cr-9.83%Ni(16-10) and 17.62%Cr-8.78%Ni(18-9) steels with metastable austenitic structure by means of transmission electron microscopy and magnetic analysis. The steels used almost transform to lath α' from γ by 90% cold rolling, and reverse to γ again by the following annealing at temperature above about 900 K. But, the reversion processes are greatly different in the two steels. The difference is clear for 923 K isothermal annealing after 90% cold rolling. The results are as follows :
    (1) For 16-10 steel, α' reverses to γ during heating up to 923 K by a martensitic shear transformation.The γ structure contains high density of dislocations and traces of α' block which was induced by cold rolling. During annealing at 923 K, the reversed γ is refined to 0.5 μm in grain size by a recovery process, that is, the formation of dislocation cells and subgrains.
    (2) For 18-9 steel, α' reverses to γ during annealing at 923K by a diffusional nucleation-growth process.
    (3) The reversion process of α' to γ is greatly dependent on the composition of steels and annealing temperature. The increase in Cr content and the decrease in Ni content lead to the increase in martensitic shear transformation temperature, resulting in an occurrence of a diffusional nucleation-growth process.
  • Solid State Bonding of Superplastic δ/γ Duplex Stainless Steels with Similar and Dissimilar Ferrous Materials

    pp. 1657-1664

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    Solid state bonding of superplastic δ/γ duplex stainless steels with similar and dissimilar ferrous materials has been studied by means of hot compressive bonding test at temperatures ranging from 1073 to 1573 K in the N2 atmosphere. By using the superplasticity of duplex stainless steels, good bonding, in which the specimen is fractured in the base metal by room temperature tensile test, can be obtained in significantly short time, e.g., the critical time for the bonding at 1373 K under a compressive stress of 19.6 MPa was 120 s in the case of similar bonding of as-hot rolled 25%Cr-7%Ni-3%Mo duplex stainless steels.In the vicinity of the bonding interface, fine microstructure is observed, indicating dynamic recrystallization due to superplastic deformation. The bonding ability is hardly deteriorated by increasing the surface roughness up to 100 μm or by mixing O2 up to 0.5% in the N2 atmosphere, because of the easy adhesion or of easy breakage of the oxide film formed on the bonding interface. Bonding of the duplex stainless steels with other non-superplastic materials such as austenitic, ferritic stainless and low carbon steels can also be obtained. By using the superplastic duplex stainless steel sheets as insert materials, non-superplastic steels can easily be joined. The critical bonding time largely depends on the superplasticity of the insert materials such as the kind of steel or the prior treatment.
  • Formulation of Stress Waveform and Frequency Effects on Fatigue Crack Growth Rate of Steel in Sea Water

    pp. 1665-1672

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    The fatigue crack growth of steel in sea water is influenced by various factors, such as loading condition, environmental and metallurgical variables. In this report, the effects of waveform and frequency of cyclic loading on corrosion fatigue crack growth rate have been studied for a 660 MPa tensile strength steel in synthetic sea water. Used waveforms are triangular, trapezoidal, and positive-and negative-saw tooth, and frequencies ranged from 0.017 Hz to 0.83 Hz. The results show that da/dN at a certain ΔK is affected only by the rise time, Trise, in each load cycle. Furthermore, the relation between the crack growth rate per Trise, (da/dt)rise, and the increasing rate of K in Trise, (dK/dt)rise, is linear on log scales, and the coefficient is described as a function of ΔK. Consequently, the da/dN has been formulated with ΔK, Trise and (dK/ dt)rise as follows.
    da/dN=∫Trise c1exp(-c2/(ΔK-c3))(dK/dt)c4 rise dt
    This formulation uniformly describes the effects of both waveform and frequency. In addition, the formula can express even the effect of changing (dK/dt)rise in a cycle.
  • マク・マスター大学の集中講座と討論会に参加して

    pp. 1673-1678

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  • 常温超電導材料の開発計画/図書案内/取り越し苦労か/論文査読をうけて思うこと

    pp. 1678-1678,1686

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