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

Tetsu-to-Hagané Vol. 65 (1979), No. 9

  • Behavior of Alkali Compounds in the Sintering Process

    pp. 1355-1364

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    Alkali compounds in sinter mix have an important effect upon blast furnace practice and gas cleaning work of sinter plant.
    In order to clarify the behavior of alkali compounds in the sintering process, some fundamental experiments were made on chlorine roasting of alkali compounds. Experiments were carried with an electric furnace and small sintering pot using mixtures of alkalifeldspar as alkali source, NaCl and CaCl2 as chloline source and in some cases, FeS as sulphur source.
    The main results obtained are as follows:
    (1) It was found that formation of volatile alkali compounds increased in proportion to the amount of chlorine in raw materials.
    (2) Sulphides in raw materials had an effect to retsrain voltalization of alkali compounds.
    (3) Volatilization of alkali compounds into waste gas was remarkable at the last stage of the sintering process.
    (4) Volatile alkali compounds consisted of alkali chloride, mainly KCl and alkali sulphate, (Na, K) 2SO4 as a minor component.
  • Mathematical Model of Blast Furnace Considering the Degradation of Coke by Gasification

    pp. 1365-1374

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    The reaction rate of solution loss with CO2 gas was measured under the conditions which are corresponding to those in the blast furnace. It is represented by the following equation.
    where R=reaction rate
    k1, k2, k3=reaction rate constant
    PCO, PCO2=Partial pressure of carbon monoxide and carbon dioxide
    f (Dp), h (SL) =corrective term
    From the results of the experiments and the dissection of blast furnace, a mathematical model of blast furnace was made by presuming the degradation of coke by gasification.
    This model is used for discussing what kind of effects the coke properties have on the blast furnace operation.
  • Analysis of Residual Stresses in Hot-Rolled H-shapes

    pp. 1375-1382

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    The generating mechanism of residual stresses in hot rolled H-shapes is studies to estimate the magnitude of residual stresses through numerical methods. A method for computation of the internal stresses from the temperature distribution throughout the cooling process is reported. The following results are obtained.
    (1) The magnitude and the distribution of residual stresses are estimated through a simplified twodimensional model using the finite difference methods, The computed distributions of temperature during caoling and the residual stresses agree well with the experimental results.
    (2) The principal cause for the formation of residual stresses is the large temperature difference between the flanges and the web during cooling. The maximum amount of difference (T1-T3) max. between the temperature at the flange-center and the web-center during cooling is the main factor to decide the magnitude of residual stresses.
    (3) Shapes geometry has a large effects on magnitude of residual stresses. When the shape is geometrically similar, the larger shape has larger residual stresses. When the width and height is the same, the H-shapes with smaller t1/t2 has larger residual stresses. t1/t2 is the ratio of thickness of web (t1) and that of flange (t2).
    (4) The effects of initial temperature difference (T1-T3) on the residual stresses is very large. When the initial temperature difference is large, the residual stresses becomes large.
    However, the level of initial temperatures has little effects on residual stresses when teh temperature difference is fixed.
  • Control of Residual Stresses in Hot-Rolled H-shapes

    pp. 1383-1390

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    (1) Residual stresses in Hot-rolled H-shape are caused by the inhomogenity of thermal distribution. Especially, temperature difference between web and flanges during cooling are important factores. Therefore, following methods are found to be effective to control and reduce the magnitude of residual stresses.
    (a) Forced cooling on the outside surfaces of flanges during cooling.
    (b) Cooling on cooling bed keeping the web vertical or flange horizontal.
    (c) Heating of the web after cooling.
    (2) Destructive and non-destructive methods are applied to measure the residual stress distribution. The measured residual stresses on the flanges have different distribution depending on the measuring methods but have similar distributions on webs.
    This is mainly due to the different measurable depth of each methods. X-ray and magnetic methods, for example, measure the mean stresses only in the thin layer of the surface.
    In order to get the stable measurement to monitor and control residual stresses non-destructively it is desirable to measure on the web.
  • Effect of Residual Stresses in H-shapes on the Performances

    pp. 1391-1399

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    In hot rolled H-shapes residual stresses are generated during cooling due to the different cooling rate between the web and flanges. The residual stresses in beams and colums are reported to have bad effects on the performances of beams. In this paper the following effects of residual stresses in H-shapes are studied.
    (1) Cracking on flame-cutting (Initiation and propagation of brittle cracks in web after flamecutting)
    (2) Deflection of T-shaped beams cut from H-shapes
    (3) Deterioration of bending performance
    It is found that the residual stresses give bad effects on the items mentioned above. However, the beams in which the residual stresses are reduced by the forced cooling on flange are improved in these performances.
    (a) Deflection of T-shapes becomes very small on cutting H-shapes along web center
    (b) Bending performance becomes similar to that of the ideal H-beams which have no residual stresses
    It also becomes clear that the initiation of micro-cracks can not be prevented on flame-cutting, even if a small magnitude of residual stresses exists. The micro-cracks, however, do not propagate when the residual stresses are small.
  • Effects of the Intercritical Rolling on Structure and Properties of Low Carbon Steel

    pp. 1400-1409

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    Recovery and recrystallization behavior of ferrite during and after intercritical roiling have been investigated in low carbon steel, using laboratory mill. The results obtained are as follows:
    (1) Dynamic recrystallization of ferrite occurs in the intercritical rolling with such a high reduction as about 80 per cent.
    (2) Dynamically recovered ferrite structure formed during the intercritical rolling is very stable as compared with that formed in the rolling below Ar1.
    (3) Fine ferrite-pearlite structure is obtained from austenite worked in the intercritical range. Making use of these beneficial effects of the intercritical roiling, strong and tough steel can be produced by heating at reduced temperature, followed by the rolling both in the lower temperature range of austenite and subsequent intercritical range where the fraction of transformed ferrite is less than that of non-transformed antenite. It is also necessary, for this purpose, that the rolled products are air cooled or heat treated at the temperature below Ar1. The total molling meduction being kept same, the properties of steel obtained by intercritical multipass rolling are nearly equivalent to those obtained by single pass rolling.
  • Relation between Hot Ductility and Grain Boundary Embrittlement of Low-Carbon Killed Steels

    pp. 1410-1417

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    The hot ductility of low-carbon killed steels has been studied by the hot tensile tests, microscopic observations and the fracture surface observations.
    The ductility during cooling after solution treatment at 1350°C decreased remarkably in the temperature range between 700 and 800°C and the fracture surface showed the intergranular ductile fracture accompanied with AIN or MnS precipitates. This loss of ductility is related to the formation of the primary ferrite along the austenite grain bondaries and the precipitation of AIN or MnS particles at the grain boundaries, and becomes very large when it occursconcurrently. The intergranular ductile fracture can be induced by the micro-void coalescence nucleated at the grain boundary precipitates as the result of strain concentration at the film-likeprimary ferrite formed along the austenite grain boundaries.
  • Recrystallized and Quenched Structures of 3Cr-0.8C Steel Having Dendritic Segregation

    pp. 1418-1424

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    An ingot of 3% Cr-0.8% C steel having dendritic segregation was made by uniaxial freezing method. Specimens were cut from the ingot parallel to the freezing direction. They were heated at 1100 or 1200°C for 30min and hot-rolled to 10, 25 or 40% reduction and directry quenched, or 40% reduction and held for 10s after hot rolling and then quenched. The rolling direction was parallel to the freezing directlon. After rolling and quenching, specimens were annealed at 1200°C for 24 or 48h. The effect of rolling and anneallng on homogenization of dendritic segregation was examined. The microstructure were observed at vertical section of the freezing direction. The results obtained are as follows;
    (1) Dynamic and static recrystallization or grain growth were observed associated with hot rolling. These phenomena occured almost independent of the microsegragation in the specimen.
    (2) Martensitic quenched structure also formed independent of the microsegregation. Especially, lenticular martensite plates were extended to a large plate as if there is no influence of the concentration fluctuation.
    (3) Since the recrystallization associated with hot rolling refined the austenite grain size, some kinds of improvement of mechanical properties of the steel would be expected. The recrystallization, however, seemed to be not so effective to homogenization of segregation and it is less effective than the long time annealing at high temperature.
  • Mechanical Properties of High Strength Low Alloy Steel Controlled Rolled at Austenite and Ferrite Two Phase Regions

    pp. 1425-1433

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    Changes in strength and toughness in conjunction with controlled rolling in austenite and ferrite two phase region were investigated.
    The results are summarized as follows.
    (1) Strength increased with the lowering of rolling temperature and the raising of rolling reduction in two phase region. This strengthening will be attributed to dislocation hardening and minimizing the subgrain and cell size in warm worked ferrite grains.
    (2) Toughness is dependent on the rolling temperature at two phase region. Good toughness can be obtained by the rolling at temperatures where recovery and recrystallization of warm worked ferrite are recognized. But Charpy transition temperature is raised by rolling bellow these temperatures.
    (3) The prior hot rolling just above Ar3 temperature is effective to supress the rise of Charpy transition temperature, even though the final rolling is carried out at temperature where no recovery occurs in deformed ferrite grains.
    Because it promotes the separations which appear on fractured Charpy specimens. So in this case high strength and good toughness can be obtained.
    x

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  • Microstructure, Magnetic Permeabiiity and Electric Resistivity of High Manganese-Chromium-Nickel Steel

    pp. 1434-1439

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    In order to investigate the austenitic steel with the non-magnetic characteristics, microstructures, mechanical properties, magnetic permeability and electric resistivity of manganese-chromium-nickel steels with much amount of manganese as an austenitizing element have been examined. The results obtained are as follows.
    It was found that composition range showing stable austenite phase lays on the higher content side of the line connecting approximately 10Mn-10Cr and 20Mn-0Cr in Mn-Cr-1%Ni phase diagram. This composition range moved to the line connecting approximately 20Mn-10Cr and 23Mn-0Cr in the case of cold rolled steel plate. High toughness and magnetic permeability (μ) under 1.01-1.02 were obtained in the steel with complete austenite phase. Magnetic permeability markedly increased by small amount of martensite in austenite phase. Therefore, it is necessary that nonmagnetic steel have complete austenite phase. The relationship between electric resistivity (ρ) and alloying element; manganese, chromium, nickel, silicon in austenite phase, can be written as ρ=1.27 [%Mn] +0.66 [%Cr] +1.62 [%Ni] +5.90 [%Si] +36 (μΩ-cm). From the above results, 25Mn-5Cr-1Ni steel may be selected as an optimum composition from the view points of stable austenite, high toughness, non-magnetism and suitable electric resistivity.
  • Compressive Yield Strength and Fracture of High-carbon, High-vanadium Iron Alloys

    pp. 1440-1447

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    The present study was undertaketn to clarify the compressive yield strength and fracture of high-carbon, high-vanadium iron alloys. Compressive testing and microscopic examination were carried out on high-carbon, high-vanadium iron alloys prepared by melting and by welding-overlay-methods, in order to study the effect of size and distribution of vanadium-carbide on the compressive strength of the alloy. Vanadium-carbide in the materials was controlled from 21 to 55% in volume and from 26μm to 100μm in diameter. The measurement of the mechanical properties was performed using a specially designed apparatus on specimens tempered at various temperatures.
    The results obtained were as follows:
    (1) On the compressive state, cracks in large carbides are not propagated to matrix whereas shear cracks are initiated in matrix and grow up to the fracture.
    (2) Yield strength is a little influenced by the amount of vanadium-carbide.
    (3) Compressive yield strength does not depend upon the carbide size, even if the carbide size varied from 26μm to 100μm.
    (4) Yield strength is increased linearly with increase in the hardness of specimen and maximum strength is increased in proportion to the amount of vanasium-carbide.
  • Spectrophotometric Determination of trace amount of Cobalt in Iron and Steel by Extraction with Nitroso-R Salt

    pp. 1448-1454

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    In order to determine the trace amount of Co in iron and steel, the formation of the chelate of nitroso-R salt and Co [Co-NRS] and the extraction of this chelate into a chloroform solution with amines were studied.
    Co-NRS chelate was formed at pH 5-7 in the presence of sodium citrate and extracted quantitatively into a chloroform solution by adding tri-n-octylamine [TOA]. The absorbance of Co-NRS chelate in TOA-chloroform solution should be measured at a wave length of approximate 550nm to avoid the reagent blank. NRS chelates of other elements could be decomposed completely by adding H2SO4 into a color developing solution and under this condition the fourteen elements coexisted in iron and steel did not interfere in the determination of Co.
    The coefficients of variation as the reproducibilities of this method were 1.2% and 2.1% for 0.23% and 0.03% in Co content respectively and the analytical results of the standard samples agreed well with their corresponding certified values. Because of the simplicity of the analytical procedures, the present method was suitable for the routine analysis.
  • Dissolution Rate of Graphite into Liquid Iron

    pp. 1455-1456

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    Experiments on the dissolution of a graphite-rod into liquid Fe-C alloy were made in order to discuss the mass-transfer in the inductively stirred liquid iron.
    Average mass-transfer coefficient obtained from the change of concentration of carbon in liquid iron with time, does not almost depend upon temperature, but depends upon the power of the furnace.
    Local mass-transfer coefficient obtained from the change in diameter of the rod, varies with the position of the rod, the frequency and the power of the furnace.
    From these results, it seems that the flow conditions of liquid iron vary with the above electro-magnetic factors.
  • An Autoradiographic Study for Revealing the Solidification Structure of 17Cr Steel

    pp. 1457-1459

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    It was not satisfactorily elucidated that the casting structure of 17Cr stainless without any other elements has either dendritic morphology or not.
    Because difference between liquidus and solidus temperature was small, it was considered that the difference of solute concentrations between primary and final solidified crystals was very small.
    Therefore, the dendritic structure has not be easily confirmed by a few conventional etching method utilizing common etching agents. But, using radioactive nuclide as indicator, even small amount of solute could be detected by autoradiography.
    The present report has assured that the dendritic structure of Fe-17% Cr added very small amount of radioactive sulfur-35 was observed on the autoradiograph.
  • Measurement of Dynamic Fracture Toughness of 13% Cr Cast Stainless Steel by Instrumented Charpy Test

    pp. 1460-1461

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    Instrumented Charpy impact test has many excellent features to measure the fracture toughness of materials. Several problems derived from conducting this method are presented and a very convenient procedure to measure the J integral value of 13% Cr cast steel is introduced.
  • Current Problems of Steelplant Refractories

    pp. 1462-1474

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  • Recent Progress in Production and Consolidation Technology of Steel Powders

    pp. 1475-1482

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  • Advanced Special Welding Process

    pp. 1483-1492

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  • Reheating Furnace with Waste Gas Jet Preheating Equipment for Saving Energy

    pp. 1493-1501

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  • (論文) 純鉄単結晶板の深絞り性と張出し性

    pp. 1502-1503

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  • 抄録

    pp. 1504-1507

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