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

Tetsu-to-Hagané Vol. 55 (1969), No. 2

  • Change of the Slag Composition in Tobata No1 BF

    pp. 101-111

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    Chemical and mineral composition of samples taken from the peripheral region of the blast furnace at the belly, bosh and tuyere level was examined. In the small lumps from the belly three kinds of primary slag were found, which were considered to correspond to FeO-Al2O3-SiO2, K2O-Al203-SiO2 and CaO-K2O-Al2O3-SiO2, coexisting with the spinel, FeO·(Fe, Al) 2O3, in molten state. Bosh slag which remained in or separated from metallic iron granules consisted only of the CaO-K2O-Al2O3-SiO2 system. Most of the belly and bosh slags bad greater amount of K2O, Al203 and SiO2 than the final slag. The role of minor constituents in ascending gas, i. e. vapors of potassium cyanide and silicon mono-oxide and dusts of some aluminum compounds, is discussed in relation to the process of primary slag formation.
  • The Change of Properties of the Charge Materials in a Blast Furnace Shaft

    pp. 112-122

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    The burden material samples taken from the three levels of the Tobata No1 BF shaft were classified in sinter, hematite are (Swaziland), magnetice ores (Chilli and Dungun) and so on. The size distribution, degree of reduction and microstructure of them were also examined. Large increases of smallparticles (-5mm) of the iron ores were observed in the sample from the level of 3m bellow the stock line and the mixing ratio of the ores from the level of 8m bellow was close to the proportion of the used ores in operation. The bursting of iron are is considered to be related with the both reduction and turbulent mixing in the shaft. It was found that the silicate glass matrix of sinter became rich in CaO and poor in Al2O3 during reduction and the calcium ferrite transformed into the spinet of FeO-Fe2O3-Al2O3 system. The effect of the composition change of sinter on the softening is discussed.
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    Readers Who Read This Article Also Read

    1. 表面処理・その他 Tetsu-to-Hagané Vol.52(1966), No.11
    2. Kinetic Study of the Decarburization of Liquid Iron Tetsu-to-Hagané Vol.52(1966), No.12
    3. II 連続鋳造の凝固について Tetsu-to-Hagané Vol.56(1970), No.4
  • Mathematical Model of Oxygen Top Blowing Converter

    pp. 122-132

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    In order to predict the variations of the process variables caused with the progress of blowing oxygen in LD converter, mathematical model for oxygen absorption accompanied by the simultaneous reactions in connection with carbon, silicon and iron existing in the neighborhood of cavity in steel bath has been developed in this work.
    By use of this model, the changes of temperatures and compositions of steel bath and waste gas, and those of evolution rate of waste gas can be estimated.
    Numerical calculations based on this model under various operating conditions have been conducted with the aid of digital computer (HITAC 5020E), and from comparison of estimations with empirical results obtained by other investigators in LD converter of 150 t the authors have believed that this model may be used for prediction of behaviors of process variables.
  • Floating Zone-Refining of Iron in the Atmosphere of H20-H2-02 Gas Mixture

    pp. 133-138

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    Zone-refining of iron was tried with the oxidization refining. The original material was vacuummelted iron. The atmosphere of zone-refining was the wet or dry hydrogen. The results obtained are summarized as follows:
    (1) Zone-refining in dry hydrogen was not effective.
    (2) Zone-refining in wet hydrogen was effective and the value of electrical resistivity ratio ρRT/ρ4.2°k of 123 was obtained after one pass refining.
    (3) Materials coated with CaO-SiO2 oxide mixture was zone-refined in wet hydrogen and the ratio ρRT/ρ4.2°k became to the value of 157, showing the highest purity in the present study.
    (4) From (2) and (3), it is supposed that the purification of iron is dependent upon the oxidation refining.
    (5) Non-metallic inclusions were included in the vacuum melted iron but removed effectively during zonerefining.
    (6) Zone-refined iron in wet hydrogen had very low lower yield stress of 13.2 kg/mm2 and very low amount of increment of flowstress due to work hardening of 2.5 kg/mm2 during the strain of 5 to 10 per cent.
  • Oxide Inclusions in 18-8 Stainless Steel Deoxidized with Aluminium

    pp. 139-144

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    The experiments are aimed to investigate the effects of aluminum content in 18Cr-8Ni-0.9Mn-0.4/0.8Si-Fe stainless steel upon the compositions and the amount of the oxide inclusions and upon their deformation by hot-and cold-rolling. The starting material is the ingot of 10 kg which is prepared in the induction furnace under argon atmosphere. The concentration range of aluminum are from 0.007 to 0.1%. The microscopic examination is used to determine the amount and the size of the oxide inclusions in ingots and their length after rolling. The compositions of inclusions are determined by a X-ray microanalyser and the crystallographic structure is examined by the electron-diffraction method.
    The following results are obtained.
    (1) The relation between the concentrations of aluminum and oxygen in molten steel is in well agreement with that of the equilibrium experiments. It is represented by the following equation.
    (2) As for the ingots containing less than 0.03%Al, the oxide inclusions are Mn-silicate and their amount decreases rapidly with increasing aluminum content. On the other hand, as for the ingots containing more than 0.03%Al, the oxide phase is alumina and the amount dcreases slightly with increasing aluminum content.
    (3) Mn-silicate is plastically deformed by hot-rolling, but in case of cold-rolling after hot-rolling of the ingots it is crushed and arranged in a dotted line in metallic matrix. Alumina is neither deformed nor crushed by hot-and cold-rolling.
  • Influence of Sulfur on Hardness and Notch Toughness on Tempering of Mild Steels Quenched from High Temperature

    pp. 145-150

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    The changes in hardness and notch toughness with tempering of mild steels (10 mm∅), water-quenched fromhigh temperatures above 1200°C, were studied with particular reference to the effect of sulfur content.
    The results obtained were as follows;
    (1) On tempering at temperatures above 500°C, it was observed that the resistance to softening increaseswith increasing sulfur content. This effect of sulfur was found to be dependent on the solid-solution hardeningof ferrite, caused by the increase of solubility of sulfur.
    (2) It was shown that the relation between quenching temperature and hardness tempered at a temperatureabove 600°C corresponds approximately with the relation between the temperature and solubility sulfurin austenite.
    (3) Sulfur dissolved in the matrix acted to reduce the notch toughness in the mild steel containinghigher sulfur.
    (4) Mild steels quenched from high temperature were superior in notch toughness to Ni-Cr steels containing similar amount of sulfur.
  • The Effect of Tempering on the Delayed Fracture Characteristics of Low-Alloy Steels

    pp. 151-161

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    The influence of tempering on the delayed fracture characteristics in 0.1N HCl solution, the initiationand propagation behavior of cracks in delayed fracture and the hydrogen embrittlement characteristics in-tensile tests have been studied in metallurgical view point for several low-alloy steels with the difference in, carbon content and tempering behavior.
    In general, the delayed fracture strength ratio (fracture strength at 30hr in life divided by static strength)-varied depending on the hardness of the steel, and showed almost constant value of 0.85 in all steels with thehardness up to Hv 350 and rapidly decreased the value with increase in hardness above Hv 350.
    Contradictorily to the general aspects described above, an abnormal increase appeared in the delayed.fracture strength ratio for the steel tempered at about 250°C, independently on the hardness of the steel.
    This phenomenon shifted to the higher tempering temperature as silicon content in the steel was increased.Considering the stabilizing effect of silicon on epsilon carbides, it is supposed that the phenomenon is attributedto the precipitation of epsilon carbides.
    The cracks in delayed fracture initiated at the prior austenite grain boundaries, but the propagation pathdiffered according as the tempering condition of the steel. It has been observed that the cracks propagatedat the prior austenite grain boundaries in the steels tempered in the temperature range of primary temper-brittleness (500°F embrittlement), and mainly propagated across the interior of the grains the steelstempered in the temperature out of the range of primary temper-brittleness.
    From the results of the electron microscopic observation of the precipitation behavior of carbides, ithas been observed that cementites precipitated in a line at the prior austenite grain boundaries in the specimenof which crack in delayed fracture propagated along the grain boundaries. The delayed fracturestrength of these steels were inferior to those cracks propagated across the interior of the grains.
    The dependence of the degree of hydrogen embrittlement, which was indicated as the decrease of the reductionof area in tensile test for the steel dipped in 0.1N HCl solution, on the tempering temperature was in goodagreement with that of the delayed fracture strength in the same solution. This fact suggests that themicrostructure of the steel contributed in the same way to both of the delayed fracture strength and the hydrogen embrittlement.
    x

    Readers Who Read This Article Also Read

    1. 表面処理・その他 Tetsu-to-Hagané Vol.52(1966), No.11
    2. Kinetic Study of the Decarburization of Liquid Iron Tetsu-to-Hagané Vol.52(1966), No.12
    3. II 連続鋳造の凝固について Tetsu-to-Hagané Vol.56(1970), No.4
  • Creep Rupture Strength of 18Cr-12Ni-3Mo Austenitic Heat Resisting Steel Containing Nitrogen

    pp. 161-173

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    In order to develop the high strength heat resisting steel served at temperatures above 600°C, the effectsof C and Nb contents and heat treatment on creep rupture strength of 18Cr-12Ni-3Mo austenitic steelcontaining 0.15%N were investigated.
    Creep rupture strength was given as a function of Nb/(C +N)(atomic per cent ratio) irrespective of Cand Nb contents and reached maximum at Nb/(C+N) =0.3-0.5. Moreover, creep rupture strengthincreased with increasing solution treatment temperature, which was due to the solid solution hardeningof Nb (C, N) and the grain growth of austenite.
    As results, the steel with nominal composition of C0.1, Si0.8, Mn1.5, Cr18, Ni12, Mo3, Nb0.7, N0.15, B 0.02% was developed. 10000 hr creep rupture strength of this steel was 20kg/mm2 at 650°C, 13-5 kg/mm2 at 700°C and 9.8 kg/mm2 at 750°C. It was concluded that this favourable creep rupture strength for long time up to 750°C is mainly due to the excellent structural stability.
    x

    Readers Who Read This Article Also Read

    1. 表面処理・その他 Tetsu-to-Hagané Vol.52(1966), No.11
    2. Kinetic Study of the Decarburization of Liquid Iron Tetsu-to-Hagané Vol.52(1966), No.12
    3. II 連続鋳造の凝固について Tetsu-to-Hagané Vol.56(1970), No.4
  • Changes of Microstructures and Mechanical Properties of Type 321 and 347 Austenitic Steels after Long Aging

    pp. 174-183

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    18-8 series stainless steels, which being used widely for big boiler plants recently, reveal some changes ofmechanical properties during their use at high temperature, resulting fromthe changes of structures, i. e., precipitation of carbide particles and their coalescence.
    Type 321 and 347 stainless steels were aged for up to 10000 hr at approximate service temperature in useof 650°C. The changes of structure, especially, the changes of observed shapes of precipitated carbides, were examined by optical and electron microscopies and those of mechanicalproperties were also investigated.
    As results, precipitated carbides had many shapes, i. e., massive, fiborid, dendric, net-like and rod-likeM23C6 and spheroidal TiC on the grain boundaries and fine spheroidal TiC, needle-like TiC and fine spherroidalM23C6 within the grains in type 321 steel, and also massive and spheroidal carbides (NbC) onthe grain boundaries and spheroidal and massive carbides (M23C6+NbC), rosettes of NbC and needle-likecarbide within the grains in type 347 steel. The Charpy impact value at room temperature and the creeprupture strength at 650°C of both steels became lower owing to long time aging.
    x

    Readers Who Read This Article Also Read

    1. 表面処理・その他 Tetsu-to-Hagané Vol.52(1966), No.11
    2. Kinetic Study of the Decarburization of Liquid Iron Tetsu-to-Hagané Vol.52(1966), No.12
    3. II 連続鋳造の凝固について Tetsu-to-Hagané Vol.56(1970), No.4
  • Effect of Tin Crystal Orientation on the Corrosion of Tin Plate

    pp. 184-189

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    For the purpose of improving the corrosion resistance of tin plate, the effect of tin crystal orientation onthe corrosion was investigated by electrochemical methods.
    The results obtained are as follows:
    1. In a 6g/l citric acid solution, the corrosion rate of tin depended on the exposed crystal plane, that is, .the rate decreased with orientation of the single crystal plane according to the order;(001)>(011)>(110), (010).
    2. When two single crystals of tin with different orientations were made a galvanic cell, the more closelypacked plane became a cathode and was protected by the other of more loosely packed crystal.
    3. In order to improve the corrosion resistance, it is necessary that the orientations of plated tin crystals. should be all alike and they should be those of more closely packed planes.
  • The Study on the Isolation of Oxide Inclusions in Rimmed Steel by Using Alcoholic-Iodine Solution Containing Na-Methylate

    pp. 189-195

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    The method for the complete isolation of the oxide inclusions from rimmed steel was studied. The results obtained are as follows.
    (1) In the case of using the generally applied alcoholic-iodine method, only a part of the oxide inclusions can bc isolated from rimmed steel.
    (2) In the case of using the newly developed method using iodine-methanol solution containing a small amounts of Na- alcoholate, the oxide inclusions can be almost isolated from rimmed steel.
    (3) The oxide inclusions present in rimmed steel consist mainly of (Mn, Fe) O, which is enriched with manvanese.
  • Study on Determination of Low Content of Carbon in Steels by Non-aqueous Titration

    pp. 196-203

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    An attempt has been made to study the non-aqueous titrimetric analysis of low content of carbon insteels. The procedure studied is as follows. The carbon dioxide, which is evolved by the combustion of sample in oxygen stream at 1350°C, is absorbed into monoethanolamine solution and titrated with the standard solution of tetra-n-butylammonium hydroxide, thus the carbon content being obtained. The experimental results showed that the present method is simple, rapid, and of good reproducibility, that is, coefficients of variation were 7.31% and.1.62% as for the samples of carbon contents of 0.0011% and 0.0043%, respectively.
    As the blank value is as small as about 4μg all through the procedure, this method can be applied to analysis of very low content of carbon (about 5μgC).
  • On Fluorescent X-Ray Analysis of Phosphor and Sulphur in Steels

    pp. 203-208

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    Analysis of phosphor and sulphur in steels by bluorescent X-ray was studied. For furnace control, they can be analysed simultaneously with elements of high atomic number, using tungsten target tube. Effects of crystal, collimator, setting condition of pulse height analyser, and others were studied, and precision of 0.0016% at 0.007% P and 0.0011% at 0.007% S was obtained. Heat treatments of samples have no affect on X-ray intensity and 0.001% of differece in sulphur is measured between rolled or forged samples and cast samples. The working curves of phosphor and sulphur were studied, and overlapping of Mo on SKα was corrected simply. Accuracy obtained in analysis of carbon-and low alloy-steels was 0.0023% for sulphur and 0.0017% for phosphor.
  • Application of a Fast Neutron Activation Method to the Control of Oxygen Content in Iron and Steel Making Process

    pp. 209-215

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    The determination of oxygen content in steel by the fast neutron activation method was investigated.
    The results are as follows.
    (1) The characters of this method are the rappidity and non-destructivity in the determination of oxygen content in steel.
    (2) The analytical values for the oxygen content between 0.1-0.001% by this method were in good agreement with those by the vaccum fusion method.
    (3) The reproducibility of this method was about ±7% in the standard deviation.
    (4) In the analysis of the oxygen content in molten steel, “the direct sampling method” was determined as the most reliable from the results of the test in which the values of sampling errors were compared between various sampling methods. It is neccesary that the oxide film formed on the sample surface is ground off before shaping it.
  • Determination of Mn, Cu, Ni, Cr, Mo, V, Ti and Al in Steel by Atomic-Absorption Spectrophotometry

    pp. 216-221

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    An accurate, precise and rapid method has been presented for the atomic absorption spectrophotometric determination of Mn, Cu, Ni, Cr, Mo, V, Ti and Al in steel.
    The sample is dissolved in acid. The solution prepared to volume and aliquot is subjected to the atomic absorption analysis of Mo, V, Ti and Al by nitrous-oxide acetylene flame and other elements by air acetylene flame referring to the calibration curves.
    Influenced by large amounts of Fe and other elements, the determination of Cr and Mo should be done in the presence of the suppressor, NH4Cl for Cr and K2SO4 for Mo.
    On the determination of Ti, Al was added both for the enhancement of sensitivity and the suppression of other elements.
    The apparatus employed was a Nippon Jarrell- ash AA-I type with a water cooling fish tail burner having a solot 0.4mm by 50mm.

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