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

Tetsu-to-Hagané Vol. 65 (1979), No. 10

  • Influence of Alkali on the Coke Properties

    pp. 1509-1516

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    Experiments were conducted on the influence of alkali on the coke properties and the following results were obtained.
    (1) The rate of solution loss reaction is dependent appreciably upon the adsorbed alkali in coke ash.
    (2) There is little possibility that the alkali attacks the specific coke texture selectively.
    (3) It seems that alkali acts as catalysis for solution loss reaction.
    (4) The remarkable gasification of coke with alkali degrades the coke properties and makes worse the gas permeability.
    (5) Control of the gasification of coke by solution loss reaction is an effective method for preventing the degradation of coke.
  • Properties of Cold and Hot Pressed Briquets Made of Reduced Ore Powder

    pp. 1517-1525

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    The rednced ore powder for sample was prepared by reducing Hamersley hematite ore with pressurized hydrogen gas at about 900°C in a pilot plant for fluidized bed reduction. The cold and hot pressed briquets were produced from the meduced ore powder using a die at various temperatures.
    The influences of compacting load at various temperatures On the crushing strength, density, and rate of reoxidation with a mixture of oxygen and nitrogen gas at 250°C to 800°C were investigated.
    The following results were obtained.
    1) To obtain the briquets of high crushing strength and high density, it was desirable to use reduced ore powder above the reduction degree of about 90%.
    2) The maxinum rate of reoxidation of briquets was observed at about 400°C, and the reason for this became evident.
    3) Hot pressing at 500°C tO 600°C under lower compacting load than that of cold pressing was effective for obtaining high crushing strength of briquets.
    4) The reoxidation rate of briquets was controlled by a parabolic law and decreased with increased density of briquets.
    5) Sintering of briquets at temperatures of 800°C to 1100°C for 4hrs was not effective for the increase in density.
  • Investigation on the Profile of Softening-Melting Zone in the Dissected Blast Furnace

    pp. 1526-1535

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    In order to clarify the function of softening-melting zone in a blast furnace, a mathematical model, by which the gas volume rate distribution through coke slits between softening-melting layers above “roots” can be calculated, is devised. Calculated results with Hirohata No. 1 blast furnace show that the greater part of bosh gas flow through the coke slits in lower softening-melting zone, and that the softening and melting-down volume of every softening-melting layer is proportional to the coke slit gas volume rate just under that layer.
    It is considered that the irregular shape of “root” softening-melting layers in Hirohata No. 1 blast furnace was mainly caused by the difference of blast volume rate at every tuyere.
    And also, from the relationship among the slit gas distribution, pressure drop and position of top softening-melting layer and inner or outer sides of softening-melting zone, which is calculated by the above mentioned mathematical model, a desirable profile of softening-melting zone is proposed.
  • Investigation of Melt-down of Softening-Melting Zone in Blast Furnace

    pp. 1536-1543

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    Melt-down mechanism of softening-melting layers in Hirohata No. 1 BF (blast furnacc) is examined. As the results with the upper part of “root” (the lower part of softening-melting zone, the end of which contacts with the furnace wall), heat of fusion is considered to depend on the reduction rate (R.R.) of softening-melting layer. The values are about 3×103kcal/t-softening-melting layer with R.R. -50%, 8×103kcal/t with R.R. -70% and 31×103kcal/t with R.R. >70%. From these values and calculated melt-down volume at “root” of Hirohata No. 1 BF, heat transfer coefficient for melt-down of “root” is obtained. By applying the relation to the estimated softening-melting zone in Kimitsu No. 3 BF, melt-down volume agrees approximately with the heat transfer quantity. Melt-down of inverse V-shaped softening-melting zone is concluded to occur by this mechanism.
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    Readers Who Read This Article Also Read

    1. Heat Transfer Phenomena in Immersion Cooling of Heated Steel Plate and Influence of Water Stirring on Heat Transfer Tetsu-to-Hagané Vol.64(1978), No.1
    2. 第97回講演大会討論会講演概要 Tetsu-to-Hagané Vol.65(1979), No.2
    3. 第95回講演大会討論会講演概要 Tetsu-to-Hagané Vol.64(1978), No.2
  • Estimation of Lower Limit of Fuel Rate in Blast Furnace by Mathematical Model

    pp. 1544-1552

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    For the purpose of estimating the fuel rate in case that operating conditions of a blast furnace are given. a mathematical model has been developed. This model was built based upon the method which was used by Muchi et al. and the data which were taken from the recent dissection of blast furnaces were adopted, by taking account of the softening-melting zone, the melts dropping through a dead man, and the reduction of silicates by gas-metal reactions.
    With the aid of this model, the fuel rate was estimated based upon the operating conditions at No. 3 blast furnace of Kimitsu Works in March, 1975. By comparing the calculated fuel rate and the actual one, the usefulness of this model has been confirmed. Further, the fuel rate has been estimated making use of the data set at a boundary condition and compared with the theoretical fuel rate which was derived by Nakatani et al.
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    Readers Who Read This Article Also Read

    1. Heat Transfer Phenomena in Immersion Cooling of Heated Steel Plate and Influence of Water Stirring on Heat Transfer Tetsu-to-Hagané Vol.64(1978), No.1
    2. 第97回講演大会討論会講演概要 Tetsu-to-Hagané Vol.65(1979), No.2
    3. 第95回講演大会討論会講演概要 Tetsu-to-Hagané Vol.64(1978), No.2
  • Operation of Blast Furnace at the Condition of Low Fuel Rate

    pp. 1553-1560

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    At No. 3 blast furnace of Kimitsu Works, a test operation was planned to foresee the lower limit of fuel rate (the target was 430kg/t-Pig) mainly by controlling the softening-melting zone in the furnace. As a result of the operation, the new record of fuel rate 431kg/t-Pig was attained in March, 1975.
    Based on the result of the test operation, the technique to lower fuel rate was investigated and the lower limit of fuel rate to be attained in next 10 years (about 400kg/t-Pig) was estimated by use of mathematical model. The technique for attaining this fuel rate is mainly in the improvement of raw material properties.
  • Blowhole Formation in Fe-N System under Reduced Pressures

    pp. 1561-1570

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    The blowhole formation in the Fe-N system during solidification under the reduced pressures has been studied by using a levitation melting apparatus. Molten irons containing various nitrogen contents were cast into the copper mold under various reduced pressures. Blowholes were evaluated by the radiographic inspection and the examination of sectioned portions of the ingot.
    The results are summarized as follows:
    1) The contents of nitrogen for blowhole formation are decreased by reducing external pressure at solidification and are approximately 25% lower than the equilibrium solubility of nitrogen at the melting point of iron and furthermore are propotional to square root of the irexternal pressures in the range of 1 atm. to 10 torr, However, below 10 torr. external pressures, the critical nitrogen contents for blowhole formation are independent of their external pressures and take almost a constant value of 40 ppm.
    2) The growing process of blowholes is discussed from the point of view of the amount of gas available from the enriched layer of solute at the solid-liquid interface during solidification.
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    Readers Who Read This Article Also Read

    1. Heat Transfer Phenomena in Immersion Cooling of Heated Steel Plate and Influence of Water Stirring on Heat Transfer Tetsu-to-Hagané Vol.64(1978), No.1
    2. 第97回講演大会討論会講演概要 Tetsu-to-Hagané Vol.65(1979), No.2
    3. 第95回講演大会討論会講演概要 Tetsu-to-Hagané Vol.64(1978), No.2
  • Influence of Alloying Elements on the Formation of “A” Segregates in Steel Ingot

    pp. 1571-1580

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    In order to investigate the influence of alloying elements, Ni, Cr, Mo and V on the occurrence of “A” segregates and dendrite structure, simulation tests for “A” segregates were made using 14kg ingot solidified horizontally and unidirectionally.
    The solute-enriched phenomenon, investigated by taking samples from the solidification front, was discussed in connection with the influence of alloying elements.
    The results obtained are summarized as follows:
    1) Adding 1% Mo to plain carbon steel made “A” segregates eliminate and made the solute-enriched liquid distribute homogeneously to form fine structure.
    2) Ni, Cr and V did not have a great influence on “A” segregates and dendrite structure, but Cr made “A” segregates eliminate a little and V made them increase a little.
    3) The cooling rate of the solidification front in the solid-liquid zone decreased as the solidification proceeded and consequently shifting the solidification front to higher solid fraction side made the solute concentration increase.
    4) The reason that “A” segregates are eliminated by adding 1% Mo is caused by suppressing a shift of the solidification front to higher solid fraction side. which means that there does not occur the solute enrichment enough to form the segregates at the solidification front.
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    1. 日本鉄鋼協会第91回講演大会講演大要 Tetsu-to-Hagané Vol.62(1976), No.4
    2. Heat Resisting Alloys for Gas Turbines Tetsu-to-Hagané Vol.62(1976), No.1
    3. 日本鉄鋼協会第98回講演大会講演概要 Tetsu-to-Hagané Vol.65(1979), No.11
  • The Elimination Mechanism of “A” Segregates of Steel Ingot

    pp. 1581-1588

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    The mobility of the interdendritic liquid metal under the solid-liquid state was measured by means of sucking out the liquid to a vacuum chamber when Si or Mo contents of materials were varied in order to discuss the elimination mechanism of “A” segregates such as by lowering Si content or adding Mo. The results obtained are summarized as follows:
    1) Amounts of metal sucked decreased as solid fraction increased. An abrupt increase of the fluidity resistance of low Si material occurred in lower solid fraction side than that of high Si material, and this effect is particularly characteristic of low alloy steels with Ni, Cr, Mo and V.
    2) These phenomena could not be explained only by the viscosity or density difference of the movable liquid in dendrite array. Consequently it should be explained by the difference of dendrite array when the solidification front was being formed in the solid-liquid zone.
    3) These effects of Si and Mo can be explained by the following mechanism; i. e. the solidification front is formed in lower solid fraction side when Si is lowered or Mo is added, and then a driving force for floatation of the solute-enriched liquid metal will not be great enough to form the segregates as the concentration of interdendridc liquid at the solidification front does not become great.
    Thus, the elimination mechanism of “A” segregates can be concluded to be caused by a shift of the solidification front to lower solid fraction side because of change in dendrite array.
  • Transformation and Mechanical Properties of Low Carbon-High Mn-Mo Steel by Controlled Rolling

    pp. 1589-1597

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    A study was made of the effect of controlled rolling on austenite to ferrite or bainite decomposition, and also on the resultant mechanical properties. Several laboratory heats of 0.05C-1.9Mn-0.25Mo-0.06Nb steel were used with emphasis on the role of austenite forming elements such as carbon and manganese and that of ferrite forming elements such as silicon, molybdenum and vanadium. Controlled rolling were carried out after heating slabs at temperatures of 1100°C and 920°C.
    The results can be summarized as follows.
    1) Fine duplex microstructures of ferrite plus bainite, or ferrite plus martensite, were obtained by controlled rolling, resulting in an excellent combination of toughness and tensile strength above 70kg/mmmm2.
    2) By applying controlled rolling, the austenite to ferrite transformation was accelerated, while the austenite to bainite transformation was shifted to lower temperature range. Thus, the separation of the above two transformations was accompanied by the increased volume fraction of ferrite, and by the decreased volume fraction of martensite or bainite. However, the obtained hardness was increased.
    3) Similar separation of the transformations could also be achieved by increasing silicon content.
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  • Recrystallization of the Austenite Transformed Reversely and Structure of Martensite in 18Ni Maraging Steel

    pp. 1598-1606

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    A recrystallization of austenite during heating at the temperatures above Af was investigated in the solution-treated and the 50% rolled 18 Ni maraging steels. The characteristics of martensite structure formed from the unrecrystallized austenite was also studied. The main results obtained are as follows:
    1) Just after the α′-γ transformation, the austenite structure (i. e., prior austenite boundary) of the starting materials is inherited into the reverted austenite in non-deformed and 50% rolled specimens. The reverted austenite is recrystallized to a finer grain size by heating it for longer time or at higher temperatures.
    2) In the case of non-deformed materials, the reverted austenite grain boundary is the preferential nucleation site of recrystallization. On the other hand, in the 50% rolled materials, the recrystallization occurs finely and uniformly in the reverted austenite grain. Owing to such a difference of recrystallization behavior, a deformation prior to heating enhances the refinement of austenite grain.
    3) During the cycle of α′→γ→α′ transformation, the structure memory effect of martensite (packet and block structures) is observed provided martensites are formed from the unrecrystallized austenite. However, the width of martensite laths formed from the unrecrystallized austenite is fine in comparison with that formed from the recrystallized austenite.
    x

    Readers Who Read This Article Also Read

    1. Heat Transfer Phenomena in Immersion Cooling of Heated Steel Plate and Influence of Water Stirring on Heat Transfer Tetsu-to-Hagané Vol.64(1978), No.1
    2. 第97回講演大会討論会講演概要 Tetsu-to-Hagané Vol.65(1979), No.2
    3. 第95回講演大会討論会講演概要 Tetsu-to-Hagané Vol.64(1978), No.2
  • The Effect of Silicon on the Brittle Fracture of Ferritic-Pearlitic Steels

    pp. 1607-1613

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    The effect of silicon on the brittle fracture characteristics of ferritic-pearlitic steels has been investigated by means of both Charpy impact and double cantilever beam tests.
    Although the increase of silicon content largely raised the Charpy impact transition temperature at the same pearlite colony size, the brittle fracture propagation-arrest properties determined by the DCB test was not affected by silicon content. Since the Charpy transition temperature was closely related to the temperature for cleavage fracture initiation obtained by the fatigue notched COD test, the brittle fracture initiation properties is expected to be deteriorated by increasing silicon content. Such brittle fracture characteristics were in quite good agreement with the temperature dependence of lower yield stress.
  • Development of On-Line Analysis System for Concentration of Chromic Acid in Chromate Treatment Process

    pp. 1614-1619

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    An application of electric conductivity method was investigated in order to develop an on-line analysis system of the concentration of chromic acid in three kinds of chromate treatment baths of the galvernizing process. As the results, it was found that the additions such as colloidal silica, amine, and stynated polymer gave little influence to electric conductivity, which varied however by temperature in the chromate treatment bath. Reasonable correlation was recognized between the concentration of CrO3 and electric conductivity for the process operation data by correcting the effect of temperature. An example of automatic control system suitable to apply to practical process was proposed. The proposed system consists of electric conductivity meter, liquid-level meter, electromagnetic vales and so on.
  • Determination of Hydrogen in Liquid Steel by Use of Evacuated Quartz Tube Sampler with Stainless Steel Lining

    pp. 1620-1629

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    A new sampling method has been developed for the determination of hydrogen in liquid steel. The sampler employed is a newly designed evacuated one which consists of an outer quartz tube and a well fitted inner tube of degassed austenitic stainless steel.
    In the new procedure developed, liquid steel is aspirated directly from the steel bath in industrial operation into the inner stainless steel tube, quenched in water, and treated in the same way as in the conventional rapid-quench methods. The sample as kept in the stainless steel tube is analyzed for hydrogen by the vacuum hotextraction method.
    Comparative investigations of the newly developed sampler with the conventional evacuated quartz tube sampler have revealed that the former gives increasingly higher analytical results than the latter does as the hydrogen content in liquid steel increases. It has been confirmed that the stainless steel tube in the new sampler prevents loss of hydrogen from the aspirated sample, and accordingly more accurate results are obtained.
    Furthermore, some problems of sample preparation and blank determination which occurred in the analytical procedure of the new method have been investigated and a satisfactory procedure has been established.
  • Progress in Methods of Surface and Interface Analysis and Their Application to Iron and Steel Research

    pp. 1630-1641

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  • 原子力製鉄用Ni-Cr-Mo-W系耐熱合金の諸特性

    pp. 1642-1643

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  • Development of Sumitomo High Toughness Process (SHT) for Low Temperature Service Steels

    pp. 1644-1650

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    x

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  • ‘Iron and Steel’ and ‘Metal Progress’

    pp. 1651-1654

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  • 抄録

    pp. 1655-1660

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