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

Tetsu-to-Hagané Vol. 69 (1983), No. 6

  • Investigation of Foundry Pig Iron and Development of Centrifugal Casting Rolls

    Juntaro HONDA

    pp. 507-522

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  • Present Status of Optical Fiber Technology and Their Application for Steel Industry

    Yutaka YOSHITANI

    pp. 523-530

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  • Microanalysis(2)

    Toshio SHIRAIWA

    pp. 531-537

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  • Measurement of Effective Thermal Diffusivity of Packed Coals during Carbonization

    Takatoshi MIURA, Kazuhiro SUGIYAMA, Jun FUKAI, Takeo TAKASHIMA, Yoshihiro IIDA, Shigemori OHTANI

    pp. 538-545

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    Abstract

    A conventional constant heating rate method (I) is applied and continuous heating method (II) is presented to the measurement of the effective thermal diffusivity of packed coals during carbonization.
    The method (II) uses nonlinear maximum likelihood estimation from the measured temperatures and permits the measurement of the thermal diffusivity under an arbitrary heating and initial conditions. Measurement error on temperature dependence of the thermal diffusivity of coals is estimated under 5% and the end effect of measuring cylindrical vessel is negligible with a ratio of the cylinder length to diameter of above 5. Measurements are made for five kinds of coals under the following experimental conditions: temperature range of 3001 100K and heating rate of 0.0170.083K/s. The effective thermal diffusivities of the each coal versus temperature for cases (I) and (II) show a similar tendency without distinction of caking coal and non-caking one: the values are almost constant until 820K and then increase rapidly. The rising of the effective thermal diffusivity shifts from low to high temperature as the fixed carbon content increases.

  • 鉄鋼製品価格の過去12年間の変動率/日本の主要資源輸入金額と輸入集中度(1981年)/アメリカの鉄道研究-レールの摩耗-

    木原 諄二

    pp. 545-545,563

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  • Kinetic Analysis of Hydrogen Reduction of Various Hematite Pellets on the Basis of the Multi-stage Zone-reaction Models

    Munekazu OHMI, Masaaki NAITO, Tateo USUI

    pp. 546-555

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    Abstract

    Hydrogen reduction of various hematite pellets (firing temperature, 1 100°1 300°C; slag content, 010 wt%; basicity, (wt% CaO) / (wt% SiO2) = 02; total porosity, 0.050.45; reduction temperature, 800°1 000°C) is analyzed by using the multi-stage zone-reaction model (MSZR1 model) and that with solid-state diffusion of oxygen dissolved in iron (MSZR2 model).
    In pellets having wüstite particles encircled with dense iron (particle E), reduction curves and boundary radii calculated by using MSZR2 model agree well with experimental data up to the final stage of reduction. In pellets having almost no particle E, such as the pellets of basicity 0.5, the results calculated by using MSZR1 model agree well with experimental data. It is quantitatively confirmed that the reduction rate in the final stage varies according to the amount and diameter of particle E and to reduction temperature.
    Expressions for chemical-reaction rate-constants and effective diffusivities are presented as functions of temperature and porosity, respectively. Moreover, the analytical method for the hydrogen reduction of any hematite pellets is proposed; reduction curves for other pellets, such as Hamersley pellet and laboratory (acid and fluxed) pellets, are estimated well by this method.

  • Iron-Molybdenum Phase Diagram in the Temperature Range of 1360 to 1622°C

    Yoshiyuki UESHIMA, Eiji ICHISE, Toshisada MORI

    pp. 556-563

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    Abstract

    Steelmaking temperature region of the phase diagram for Fe-Mo binary alloy was reexamined by the heat treatment and microstructure studies of the Fe-Mo alloy samples. Fe-Mo alloy samples of 30 to 88 at%Mo were annealed at temperatures 1 529 to 1 622°C and quenched into water. The heat treated samples were examined with optical microscope, EPMA and X-ray diffractometer.
    The invariant reaction between liquid, σ and Mo solid solution phases is found to be expressed as
    σ (56 at %Mo) = Liq. (38 at %Mo)+(Mo) (75 at %Mo), at 1610°C,
    where values in the parentheses are the composition of the respective phase. This result is in good agreement with the results obtained in the previous studies namely Knudsen cell mass spectrometric measurement of the activities in the Fe-Mo binary alloys and Knudsen cell mass spectrometric thermal analysis of the Fe-Mo binary alloys.
    A revised Fe-Mo binary alloy phase diagram is proposed on the basis of the present results along with the above mentioned previous results.

  • Bubbling-jetting Phenomena in Powder Injection into Liquid

    Yasuhisa OZAWA, Katsunori SUZUKI, Kazumi MORI

    pp. 564-569

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    Abstract

    To know the effect of injecting powder with gas on the bubbling-jetting transition. an experimental study has been made on powder injection into a liquid. The gas-powder mixture was injected into a water bath through a nozzle of 0.2cm in I. D. and 2cm in O. D. installed at the vessel bottom. The powders used were glass beads of 105149μ, 177210μ, and 350420μ. The mixture jet behavior was photographed by a high speed cinecamera. The injecting pressure at the entrance to the nozzle was measured.
    It was found that injecting powder with gas produced a drastic effect on the bubbling-jetting transition. The critical gas flow velocity for the initiation of jetting, which in the case of gas injection was just equal to the sonic velocity, decreased in gas-powder injection with increasing powder to gas mass ratio. This decrease in the critical gas flow velocity was found to become more extensive for powders of smaller size. These findings could be ascribed to the fact that the velocity of sound of gas-solid mixtures decreases with increasing the mass ratio and this decrease in the sonic velocity becomes more extensive for powders of smaller size.

  • Mixing Phenomena in a Torpedo-ladel Affected by Gas Injection

    Hiroshi TSUKAMOTO, Shigenori MATSUNAGA, Katsumi KAWATA

    pp. 570-574

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    Abstract

    For the purpose of improving the efficiency of desulfurization in the gas injection process of torpedo-car, experimental study was carried out by use of cold model. Test lance was inserted into the water in the torpedo-car model. The intensity of mixing was expressed by the mixing time required for the homogenization of a tracer. The mixing time was measured by phenolphthalein method by varying following parameters, i. e. injected gas flow-rate, immersed lance nozzle depth, number of nozzle orifices, and position of lance nozzle relative to the vessel. As the results of this study, it was made clear that these four parameters affected the mixing intensity in torpedo-ladle.

  • Measurement of Equilibrium between Fe-Cr Alloys and CO-CO2 Mixtures by Levitation Technique

    Koin ITO, Nobuyuki TERABE, Hiroshi SAKAO

    pp. 575-581

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    Abstract

    Investigations were made of the equilibrium between levitated droplets of Fe-Cr alloy (<18%Cr)and CO-CO2 gas mixtures at a temperature range from 1 700 to 1 950°C and of the solubility product of chromium oxide in the melt at 1 800°C. Experimental results were discussed on the assumption that the values of eCC, eOC and eOO recommended by the 19th Committee of the Japan Society for the Promotion of Science are applicable in the present temperature range. The following conclusions are drawn :
    log K1(=log PCO2/PCO · ao) =8 440/T-4.60
    logK2 (=log P2CO/PCO2·aC) = -7870/T+ 6.90
    logK3 (= log PCO/aC · ao) =570/T+ 2.30(17001950°C)
    logKCr(=loga2Cr·a3O)=-1.376
    eCrO = -0.032
    eCrC= -0.018
    eCrCr=0.002(1800°C)

  • Gaseous Desulphurization from Metallurgical Slags

    Toshisada MORI, Akira MORO-OKA, Haruo KOKUBO

    pp. 582-588

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    Abstract

    Gaseous desulphurization from molten synthetic CaO-SiO2-Al2O3 slags some of which contain CaF2and iron oxides was examined under the gas atmosphere the oxygen content of which was 100, 30, 10 or 0.1%, the total pressure being 1.1 to 1.2 atm. The basicity of the slags was 1, 2 or 3, and sulphur was contained as sulphide, sulphate or both in the initial slags. Each of these slags weighing 2 to 12 g was put in a platinum or alumina boat and heated to 1 550°C for 20 to 120 min under the gas flow of ca. 2l /min. Initial desulphurization rate of sulphide sulphur was higher in a higher oxygen pressure of the atmosphere and about 80% of sulphur was removed in 10 min under a pure oxygen atmosphere. Ferric iron accelerated the desulphurization of sulphide sulphur, and its effect was evident in the atmosphere of a low oxygen pressure. Desulphurization rate of sulphide sulphur showed the trend to be enhanced with the increase in basicity. The rate of desulphurization from sulphate bearing slag was high under the atmosphere of low oxygen pressure and was enhanced by the addition of ferrous iron. Chemical equations for the gaseous desulphurization were presented both for the acidic and basic slags separately. It was found that sulphide sulphur was gradually oxidized to sulphate under an oxidizing atmosphere. Fundamental knowledge was suggested for the effective gaseous desulphurization by the injection of oxygen, neutral or reducing gas into slags.

  • Development of Refractories for Hot Metal Treatment

    Haruya NAGAI, Takayoshi SATOH

    pp. 589-595

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    Abstract

    Unburnt brick, consisting of several elements including graphite which has excellent chemical and volume stability, was developed for use as refractories in torpedo cars. Through actual application, it has been ascertained that this brick can withstand both oxidative and basic materials used in the course of hot metal treatment.

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    3. Strength and Ductility of Ferrite-Bainite-Martensite Steels Tetsu-to-Hagané Vol.72(1986), No.15

  • Effect of Recirculating Flow Rate of Molten Steel in Refining Processes

    Yu-sheng HSIEH, Yoshio WATANABE, Shigeo ASAI, Iwao MUCHI

    pp. 596-603

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    Abstract

    A mathematical model is developed to evaluate quantitatively the effects of circulatory flow rate in the refining processes. In the model the circulatory flow rate is only one adjustable parameter. By use of the mathematical model, the concentration profiles of C and Si are simulated in LD converters with different capacities, a Q-BOP and electric furnace, and furthermore the circulatory flow rates are determined for these plants.
    The relations between the circulatory flow rate and the gas blowing rate in LD converter are theoretically discussed on the basis of the results of the water model experiments, for determining the "mixing time".
    Hitherto, a factor (ISCO) which was proposed to explain the oxidation reactions in the refining processes have been induced from the model of this paper.

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    3. New Application of RH Degassing Technology in Ladle Metallurgy Tetsu-to-Hagané Vol.69(1983), No.2

  • Development of Casting Process for Ladle Relining

    Kiyomi TAGUCHI, Masaaki NISHI, Noriaki MORISHITA, Hiroshi MIHASHI, Shigeo YOSHINO

    pp. 604-610

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    Abstract

    In recent years, operating conditions of steel making process have become very severe to ladle lining refractories. Meeting with such conditions, a development have been made on a new lining process for ladle, CL-L process (Cast Lining of Ladle). This process has been in regular use in large steel ladles.
    It is a process in which materials added with a small amount of water are charged uniformly through a cone chute and revoluting chute, given fluidity by a former with vibrators and cast to form a uniform monolithic lining. In order to reduce the curing time, this method equips the heat curing equipment.
    Introducing this method, the ladle life has risen by 3 to 45% and the specific refractory consumption has reduced by 11 to 22% in comparison with the slinger process.

  • Decarburization of Na2CO3 Pre-refined Hot Metal in LD Converter

    Satomi YAMAMOTO, Hidetake ISHIKAWA, Masatoshi KUWABARA, Ichiro KOKUBO, Mutsuo NAKASHIMA, Toshihiro KOSUGE

    pp. 611-617

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    Abstract

    Decarburization of desiliconized, dephosphorized and desulphurized (pre-refined) hot metal was studied. The pre-refined hot metal (45 T) was charged in LD converter (75 T/heat) and oxidized with top blown oxygen. Since [P] and [S] contents of hot metal had been reduced to the specified concentration range for those elements, the flux (lime) was not used. The amount of slag formed at the turn down was less than 5 kg/t. s and the thickness of slag on the steel bath was estimated to be 5 mm.
    The metallurgical characteristics of decarburization without the use of flux were summarized as follows.
    1) High efficiency (97%) of oxygen used for the oxidation of elements (C, Si, Fe, etc) was kept throughout the whole blowing period even in the production of low carbon steel.
    2) Very low concentrations of [N] and [H] at turn down were obtained (less than 10 and 2 ppm, respectively).
    3) Iron yield of heat was improved by 0.37%.
    4) The amount of dust evolved during the blowing was the same as that of the ordinary heats. The iron content of the dust was 10% higher than that of the ordinary heats.
    5) Bath temperature was raised at the rate of 120°C/ [%C] during the decarburization.

  • A New Electrode-type Mold Level Meter in Continuous Casting Machines

    Hiroshi IMADA, Yoshitaka NIMURA, Hideki YOKOYAMA, Yasuo SUZUKI, Shinzo IIDA, Yukio OZAKI

    pp. 618-624

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    Abstract

    This paper is concerned with a new electrode-type mold level meter to be used in the mold of continuous casting machines, and with a mold level control system. The principle of this meter is as follows : the electric resistance of flux on molten steel in the mold is detected by the electrode of the level meter. The displacement of the electrode is controlled in such a way that the resistance, which is equivalent to the distance between the electrode and the molten steel surface, has a constant value. Hence the electrode smoothly follows the movement of the free surface of the molten steel. Therefore the mold level can be detected by measuring the electrode displacement. This level control system was analyzed through the use of a simulation model.
    The performance of the electrode-type level meter is as follows: (1) maximum range of use: 500 mm, (2) maximum follow-up control speed : 70 mm/s and (3) response time: 1 sec.
    Even in the case of applying the electro-magnetic stirring in the mold, it has been confirmed that the electrode-type level meter can perform so well as to keep the change of molten steel level within ±5 mm under the automatic operation.

  • Chemical State of Phosphorus Segregated at Grain Boundaries of Iron

    Kenji ABIKO, Shigeru SUZUKI, Hiroshi KIMURA

    pp. 625-630

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    Abstract

    Determination of the chemical state of phosphorus segregated at grain boundaries of iron is important to discuss mechanisms of the grain boundary decohesion by phosphorus. X-ray photoelectron spectroscopy (XPS) analysis and the scanning Auger electron spectroscopy (AES) analysis were performed to determine the chemical state of segregated phosphorus.
    Specimens of iron containing various amount of phosphorus (0.05 to 15.6 wt%) were fractured under a vacuum better than 6 × 10-11 Torr. The clean ultra-high vacuum allows a prolonged XPS analysis (10h) which is necessary for a small amount of phosphorus segregated at grain boundaries. The spectra were compared with those from an Fe3P specimen, and the chemical state of the segregated phosphorus was determined to be the same as phosphorus in Fe3P. This result supports the grain boundary decohesion mechanism proposed by Losch, who considers the segregated phosphorus atoms to form a strong binding with surrounding iron atoms and the iron-iron binding neighboring the phosphorus to be weaken.
    The shape of AES of phosphorus in solid solution varies with the concentration of phosphorus, but that of phosphorus at grain boundaries is independent of the phosphorus concentration and same as that of phosphorus in Fe3P. Importance of the variation of the shape in the AES quantitative analysis of segregated phosphorus is discussed.

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  • Influence of γ→α' Transformation on Low-cycle Fatigue Behavior in Austenitic Stainless Steels

    Kazuo HOSHINO, Kouji MUKAI

    pp. 631-640

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    Abstract

    In this paper, the influence of γ→α' transformation on strain-controlled low cycle fatigue behavior of austenitic stainless steels was studied in the temperature range from room temperature to -162°C. Low cycle fatigue life of stable steel was longer than that of unstable one. In unstable steels, fatigue life decreased with increase of volume of α'-phase induced in cycling test.
    A discussion was made on cyclic hardening behavior by γ→α'transformation. It was shown that harmful effect of α'-inducement on low cycle fatigue life was attributed to strengthen cyclic hardening and fatigue life was represented as a function of amount of cyclic hardening.

  • A Simple Method for Charpy Impact Test at Liquid Helium Temperature

    Toshio OGATA, Keijiro HIRAGA, Kotobu NAGAI, Keisuke ISHIKAWA

    pp. 641-646

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    Abstract

    A simple and reliable method for Charpy impact test at liquid helium temperature has been established.
    An impact specimen has been inserted into the capsule which is composed of grooved polystyrene foam plate. Liquid helium has been transferred to the capsule during testing. The experimental results are as follows :
    ( 1) The specimen temperature drops to 4.2 K in about 60 seconds and the temperature gradient in the specimen is negligible.
    (2) Liquid helium consumption is less than one litter per each test.
    (3) The error in the absorbed energy due to the capsule is negligible.

  • Fracture Mechanics Approach to Evaluate the Effect of Thickness on Fracture Toughness in Heavy Sectioned Steel

    Yukito HAGIWARA, Shiro MIYAMOTO

    pp. 647-654

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    Abstract

    In order to develop an estimation method of the fracture toughness in heavy sectioned A533B steel from small size specimen with reduced thickness, the effects of specimen thickness and side groove on fracture toughness have been investigated.
    An increase in side groove depth clearly lowers the resistance to ductile crack propagation. This is due to the fact that side groove restrains the formation of shear lip. On the other hand, the slow crack growth initiation toughness is independent of side groove depth. In the case of brittle failures, the fracture toughness is nearly constant irrespective of side groove depth. This fact is confirmed by fractographical examination of stretched zone size on fracture surfaces. It is seen from these results that the fracture toughness for full thickness can not be estimated by using the results obtained in small specimens with side groove.
    A model is proposed to evaluate effect of specimen thickness on fracture toughness in terms of fracture mechanics. Fracture toughness of thick plate is estimated from this model using the fracture toughness values of ordinarily notched small specimens with reduced thickness. The predicted values are in good agreement with experimental results of full thickness specimens.

  • The Effect of Cooling Rate from Austenitizing Temperature on the Microstructure and Toughness of the 0.4C-5Cr-Mo-V Hot Work Alloy Tool Steel

    Toshio OKUNO

    pp. 655-662

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    Abstract

    The effect of quenching rate from austenitizing temperature on the microstructure and toughness of the 0.4C-5Cr-Mo-V hot work alloy tool steel was investigated.
    (1) As the quenching rate decreases, plane strain fracture toughness and charpy impact value after tempering to HRC 44 are reduced gradually.
    (2) The microstructural changes corresponding to the above behavior of toughness can be summarized as follows.
    ( a ) Formation of upper bainite and increasing of its volume ratio to martensite.
    ( b ) Increasing of width of bainite grain, compared with that of martensite lath, and increasing of particle size and tendency of connected distribution of carbide precipitating along bainite grain boundaries compared with carbide precipitating along martensite lath boundaries.
    ( c ) Increasing of density of extremely fine carbide precipitates.
    ( d ) Increasing of the effective grain size.
    ( e ) Transition of bainite configuration from lath to granular type, and increased tendency of carbide precipitation along the grain boundaries of bainite and prior austenite.
    The decrease of quenching rate reduces upper bainite toughness through microstructural changes as (b)→(e) in sequence.
    (3) Fatigue crack propagation rate are somewhat increased by the formation of upper bainite. This corresponds to the increased distribution density of extremely fine carbide precipitates in tempering of upper bainite.

  • Elastic-plastic Fracture Toughness in Nodular Cast Iron

    Kazuhiko KURIBAYASHI, Teruo KISHI, Paritud BHANDHUBANYONG, Masanori ITO, Takateru UMEDA, Yasuo KIMURA

    pp. 663-670

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    Abstract

    In the nodular cast iron and the compacted vermicular cast iron with a ferrite matrix, the elasticplastic fracture toughness JIC was evaluated by means of acoustic emission, electric potential and Rcurve method based on ASTM E 813. Jin (AE) and Jin (EP), estimated from rapid increasing points in cumulative number of AE events and electric potential difference respectively, correspond with a small amount of crack extension in the mid-thickness of specimen. Jin (R), on the other hand, estimated from R-curve method, corresponds with an appropriate amount of crack extension which is nearly equal to 2δc. In the present analysis, JIC was optimized from Jin (R).
    Dependence of JIC on graphite nodularity n was represented by
    JIC=62-14.7 (n-1/2-n3/2) (kJ/m2)
    using the critical condition of void coalescence that R=X where R is a mean radius of voids developed around graphite nodules and X is an inter-nodule spacing, respectively.

  • Manufacturing Technology and Material Properties of Large Size Austenitic Stainless Steel Forgings

    Keizo OHNISHI, Hisashi TSUKADA, Komei SUZUKI, Kunio TESHIROGI, Hisashi KAGA, Mikio KUSUHASHI, Ikuo SATO

    pp. 671-677

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    Abstract

    The effects of grain size, cooling rate, and chemical composition (especially carbon content) on tensile properties, intergranular corrosion resistance and ultrasonic attenuation were studied to establish manufacturing conditions of large size austenitic stainless steel forgings. Based on these fundamental studies, large size products such as disk and flange forgings were manufactured and the verified results proved their homogeneity, excellent quality, and good manufacturing performance.

  • High Temperature Oxidation Behavior of Chromium Ferritic Stainless Steels

    Hisao FUJIKAWA, Junichiro MURAYAMA, Nobukatsu FUJINO

    pp. 678-685

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    Abstract

    The relation between the effects of C, N, Cr and Si contents on the oxidation resistance and the metallurgical structure of 1117%Cr steels has been studied at temperatures lower than 1 000°C. C and N have very harmful effects, and Cr and Si have very beneficial effects. It has been found, however, that their effects depend on the austenitic phase precipitates at the oxidation temperature, that is, the appearance of the austenitic phase has harmful effect against the oxidation resistance. It is suggested that decreasing C and N contents or adding stabilized elements such as Zr, Ti and Nb is effective against the oxidation resistance. Among the stabilized elements, Zr is beneficial, but Ti and Nb are not very effective. Difference of their behaviors depends on the stability of their carbides and nitrides at 1 000°C. Because Zr compound does not decompose at 1 000°C, the austenitic phase does not precipitate, whereas Ti or Nb compound decomposes at 1 000°C and the austenitic phase precipitates in Ti- or Nb-containing steel. The steel containing high C and the steel containing Nb or Ti have austenitic phases mainly around the grain boundaries at 1 000°C. It has been found that the unusual oxidation phenomenon occurs from the precipitation sites of austenitic phase, of which Cr content is less than that of ferritic phase that is determined by means of optical microscope, EPMA, IMMA and so on.

  • Influence of Various Factors on the Elevated Temperature Ductility of 18Cr-12Ni Austenitic Stainless Steels

    Yoshihiro UEMATSU, Kazuo HOSHINO

    pp. 686-693

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    Abstract

    Effects of chemical composition, cleanliness, grain size and morphology of grain boundary carbide on the tensile ductility of 18Cr-12Ni austenitic stainless steels have been studied in the temperature range of 500°1 000°C. Metallurgical factors which are concerned with the ductility drop in this temperature range have been discussed. The results obtained are as follows.
    (1) The combined addition of carbon and nitrogen to 18Cr-12Ni steel causes a serious ductility drop resulted from the intergranular fracture in the temperature range of 600°900°C. Decreasing cleanliness and increasing grain size decrease the ductility in the temperature range.
    (2) The ductility sensitively varies with distribution condition of carbides precipitated at grain boundaries. High dense precipitation of small carbides harms the ductility.
    (3) Nitrogen retards the dynamic restoration process during deformation at the elevated temperatures. The deformed substructure in nitrogen bearing steel seems to have planar arrays of dislocations. The ductility drop may be concerned with the combined effect of the harmful precipitation condition and the nonhomogeneity of deformed substructure.

  • Effect of Chemical Composition on Physical Properties of Nonmagnetic High Manganese Steel and Its Processing Condition

    Chiaki OUCHI, Yohji KOHSAKA, Masahiro UEDA

    pp. 694-702

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    Abstract

    For the purpose of lowering the thermal expansion coefficient of high manganese austenitic steel, the effects of carbon and manganese content on the thermal expansion coefficient from O to 100°C were investigated. The permeability after cold working and electrical resistivity were measured in these steels. These physical properties were also investigated after addition of various alloying element such as Si, Cu, Ni, Cr, Mo, Co, and Al in 0.25%C-25%Mn (or 21%Mn) based steel. The decrease of carbon content and the increase of manganese content markedly reduced the thermal expansion coefficient. The addition of ferrite forming elements did not result in increase of permeability, but electrical resistivity was markedly increased with addition of Si or Mo in 0.25%C-25%Mn steel. Particularly, the mechanism controlling the thermal expansion coefficient of high manganese austenitic steel is discussed by making reference to existing theories.
    Hot ductility and strengthening due to controlled rolling in high manganese austenitic steel were studied to establish the optimum processing condition.

  • Identification of the Precipitates in Maraging Steels by Non-aqueous Electrolyte Extraction Method

    Yasutaka OKADA, Jyo ENDO, Tsuyoshi NAKAYAMA

    pp. 703-710

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    Abstract

    Many works with respect to precipitates in maraging steels have been presented. However, the precipitates at the peak-aging condition (the maximum tensile strength level) have hardly been identified due to their very fine shape, complicated multi-phase precipitation, and similar crystal structures.
    Fine precipitates formed at peak-aging condition were extracted by a non-aqueous electrolyte extraction method. The chemical composition and the crystal structure of the extracted residue were analyzed by the ICP analysis and electron diffraction analysis, respectively. As the result, fine precipitates formed at the various aging processes (under aging, peak aging, and over aging conditions) of the maraging steels were identified. The change of the precipitates in the various alloy series of maraging steels with aging time at 500°C are as follows :
    1) Ni-12.5Co-6Mo-1.2Ti steels :
    The precipitation of Ni3Ti and FeMo was confirmed. In 17.5%Ni steel, Ni3Mo was identified at the peak-aging condition.
    2) Ni-12.5Co-6Mo steels :
    It was confirmed that FeMo precipitated at the start and then Ni3Mo did. The precipitation of Ni3Mo was accelerated by the increase of nickel concentration.
    3) Ni-12.5Co-1.2Ti steels :
    Only Ni3Ti was confirmed. This precipitates was very fine and needle-like shaped.

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  • 大島高任の高炉とヒュゲェニン著「大砲鋳造法」

    芹沢 正雄

    pp. 711-712

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  • 抄録

    永田 眞資, 月橋 文孝, 片田 康行, 曽田 裕二, 金澤 健二, 山口 弘二, 望月 俊男

    pp. 718-720

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  • © 1983 The Iron and Steel Institute of Japan

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