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

Tetsu-to-Hagané Vol. 61 (1975), No. 11

  • Reduction of Molten Iron Ore with Solid Carbon

    Kenji TAKAHASHI, Masayoshi AMATATSU, Tanekazu SOMA

    pp. 2525-2530

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    Abstract

    The reduction processes of molten iron ore with solid carbon have been studied. The reduction rates of iron oxide pellets with graphite crucible have been obtained by measuring CO gas volume-rate under the atmosphere. The experimental temperature was in the range of 1330 to 1570°C.
    The following results were obtained.
    (1) At the temperature of 1330°C, it was observed that the reduction process of iron oxide pellets proceeded in semi-liquid state.
    (2) Above the temperature of 1400°C, it was observed that the reduction processes were two steps; first step was gaseous reduction from hematite to wustite and second step was direct reduction of molten wustite by solid carbon.
    (3) The reduction rates in liquid state were independent on the oxygen concentration in molten iron ore. The apparent activation energy of reduction rates in liquid state was obtained about 56 kcal/mol.

  • Study of Lime-Slurry Injection into Blast Furnace

    Kikuo TAJIMA, Yoshiteru JOMOTO, Yuji KANAYAMA, Yoshio OKUNO, Noboru OKAMOTO

    pp. 2531-2543

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    Abstract

    The effects of injection of lime-oil slurry through the tuyeres were studied with the use of modelling instruments, and full scale tests of injection into blast furnace were carried out at Muroran Works, Nippon Steel Corp., Japan.
    Following results were obtained.
    (1) Degree of sulphur distribution coefficient between pig iron and slag under the condition of an operating blast furnace was only 20-40% compared with the equilibrium to be obtained.
    (2) Sulphur content of pig iron drops was reduced rapidly in fluidized lime fines. Lime fines reacted mostly in melted zone of materials so that those slag basicity was increased. The dropping temperature of melted materials, however, did not rise in proportion to injection rate of lime, when the parts of the amount of lime in the burden materials charged into the furnace top were replaced beforehand by the equivalent amount of injected lime fines.
    (3) Lime-oil slurry injection tests through all the tuyeres of Muroran No. 1 blast furnace showed that 25% of sulphur content of pig iron was reduced at the lime injection rate of 20 kg/t-p, and permeability of the melting zone was improved without producing the viscous slag.

  • Estimation of Melting Parameters of a Large ESR Furnace Based on Limiting Solidification Rate

    Noboru MASUKO, Nobuo SANO

    pp. 2544-2551

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    Abstract

    Summarizing the results of previous investigations on ESR furnaces with ingot diameter from 2 to 60 cm. the empirical equations to express the relations between ingot diameter (D: cm) and various melting parameters have been derived. According to these findings ingot diameter. electrode diameter. slag depth and melting rate are selected as basic parameters. and the dependencies of all other melting parameters on ingot diameter are determined by the former four.
    The thermal balance between the cooling capacity and the heat release on solidification being taken into account. it is shown that the limiting condition D·u<1.9 cm2/sec (u: solidification rate cm/ sec) must be satisfied for larger ESR ingots. This means that the solidification rate should be in inverse proportion to ingot diameter when it exceeds 100 cm. while the rate is constant (=0.01 cm/sec) for smaller ingots.
    Accordingly, the melting rate will increase with ingot diameter linearly rather with its square as expected. At the same time the energy consumption (kWh/kg) will begin to increase beyond the optimum ingot diameter. which suggests that the excessive scale-up of an ESR furnace might not be favorable from the viewpoint of thermal economy.

  • Fractographic Features of Notch Root Region in Delayed Fracture in Water

    Tatsu FUJITA, Tadamiti SAKAI, Yoshiro YAMADA

    pp. 2552-2560

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    Abstract

    A delayed fracture test has been made on SNCM8 steel tempered at 490°C (σY=127kg/mm2) in distilled water at 80°C using self-stressed WOL specimens. The results obtained are as follows :
    1) Crack initiation time is almost identical with the total delayed fracture time in the case of conventional notched specimen.
    2) Prevailing dimple pattern is observed in delayed fracture surface under higher applied stress, consisting with the fracture surface in air, while intergranular cracking is observed under lower stress. This trend agrees with the cases of delayed fracture in hydrogen gas and in distilled water with zinc anode.
    3) Stretched zone is observed both in the tensile fracture and the delayed fracture. The width of stretched zone is proportional to (KIC/σY) 1.91 for the tensile fracture, while it is proportional to (KIC/σY) 1.13 for the delayed fracture if σY does not vary in the case and 127 kg/mm2 is applied. This indicates that the apparent decrease of flow stress σY should take place during the delayed fracture test. But the effect of hydrogen cannot be estimated because this material shows large stress relaxation.
    4) On the basis of Hahn and Rosenfield's relationship between KIC, and tensile properties, it is estimated that the apparent considerable decrease of the true fracture strain of material near notch root combined with the apparent decrease of flow stress σY, occurs in the delayed fracture in the water.

  • Martensitic Transformation and Plastic Deformation in 18-14 Stainless Steel Single Crystals

    Yakicki HIGO, Tsutomu MORI, Tadahisa NAKAMURA

    pp. 2561-2578

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    Abstract

    Relations between martensitic transformation and plastic deformation have been studied using single crystals of 18%Cr-14%Ni austenitic stainless steel. The Ms temperature for γ→α transformation decreases with plastic deformation due to slip. It has been found that the morphology and the crystal orientation relationships between the martensites and γ have close relations to the slip systems which have been active during plastic deformation. When the martensitic transformation occurs during plastic deformation, the plastic deformation is concentrated in bands parallel to {111} planes of γ and the negative temperature dependence of the yield stress is noted. This is associated with the γ→ε transformation. The above plastic bands are parallel to the most stressed {111} <211> shear system of γ to induce the γ→ε lattice change. The occurrence of the γ→χ transformation results in a decrease in the easy glide strain and in a high strain hardening in the stage II deformation.

  • Effect of Cementite Distribution in Low Carbon Steel on Hydrogen Attack

    Shigeo NOMURA, Masayoshi HASEGAWA

    pp. 2579-2588

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    Abstract

    Hydrogen attack of low carbon steels with 0.003-0.15%C heated at 380°C in 200 atm hydrogen was investigated with reference to the change of distribution of Fe3C carbide in the steel. The susceptibility of the steels with carbides precipitated continuously at grain boundary to hydrogen attack was larger than the steels with carbides precipitated dispersively in the matrix. Many voids and micro-cracks were observed at the hydrogen-attacked intergranular fracture surface with a scanning electron microscope. The gas evolvedfromthe hydrogen-attackedfracture surface consisted of H2 and CH4 by gas chromatography. Non-diffusible molecular hydrogen and methane which couldn't be removed with the dehydrogenation at 250°C for 3 hr in vacuum, increased with increase of carbon con tent and internal defects. It is suggested from these results that hydrogen attack is caused with the voids which are produced with molecular hydrogen or methane trapped at grain boundary carbide.

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  • Improved Toughness of Weld Fussion Zone by Fine TiN Particles and Development of a Steel for Large Heat Input Welding

    Shogo KANAZAWA, Akira NAKASHIMA, Kentaro OKAMOTO, Ken KANAYA

    pp. 2589-2603

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    Abstract

    The improvement of toughness of weld fusion zone has been made by converting the microstructure from coarse intermediate stage structure to fine ferrite-pearlite in large heat input welding processes such as one side submerged arc welding, electro gas welding and consumable nozzle electroslag welding.
    Following results have been obtained from intensive investigation on effects of TiN upon austenite grain size, transformation behavior and toughness at weld fusion zone:
    (1) Fine TiN particles prevent the coarsening of austenite grains. Austenite grain diameter dr at 1400°C can be expressed by the equation, dr = K (r/f) where r=mean particle diameter of undissolved TiN at 1400°C, f=volume fraction of undissolved TiN smaller than 0.05 μ in diameter at 1400°C. The increase of the amount of TiN particle smaller than 0.05 μ undissolved at 1400°C gives rise to the decrease of austenite grain size.
    (2) Aggregation of fine TiN particle accelerates the formation of ferrite during cooling. The transformation products are thus further refined.
    (3) As a result unit facet diameter of brittle fracture which closely coincides with {100} plane becomes small. Thus the thoughness of fusion zone in large heat input welding is greatly improved.
    (4) The fusion zone of commercial 60 kg/mm2 grade steel has proved to be improved by utilization of fine precipitates of TiN both in large and small heat input welding.

  • Effects of Vanadium and Niobium on Long Period Creep Rupture Strength of 12 Percent Chromium Heat Resisting Steel Containing Molybdenum and Boron

    Norio TAKAHASHI, Toshio FUJITA

    pp. 2604-2616

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    Abstract

    The effects of vanadium and niobium were investigated in order to improve the creep rupture strength of 12% Cr heat resisting steel. The results obtained are as follows:
    1) The creep rupture strength of 12% Cr heat resisting steel is increased by additions of vanadium and niobium. Additions of vanadium and niobium result in precipitation hardening.
    2) The optimum amounts of vanadium and niobium depend on creep rupture test condition. When tested at 600°C for 100 hr 0.18% V and 0.15% Nb are the optimum amounts. When tested at 600°C for 10000 hr 0.24% V and 0.15% Nb are the optimum amounts. Thus, it seems that the longer the testing time, the higher is the optimum amount of vanadium.
    3) It has been observed in an electron microscope that coalescence of precipitated carbide particles are retarded by additions of vanadium and niobium.

  • Relation between the Phase Transformations and the Magnetic, Physical and Mechanical Properties in 18Ni 350 Grade Maraging Steels

    Yasuo KIMURA, Katsuyuki UCHIBORI, Kazunori TOKOROF, Hiroyuki MOTOKAWA

    pp. 2617-2628

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    Abstract

    The behavior of the martensite→austenite and austenite→martensite transformations in maraging steels containing 17.5%Ni, 12.5%Co, 4%Mo and 0-2.5%Ti has been studied by magnetic, dilatometry, and differential thermal analyses.
    The martensite→austenite transformation during heating occurs in two successive stages in 17.5Ni-12.5Co-4Mo-Ti maraging steels with 0-1.3%Ti, but in one stage in a 17.5Ni-12.5Co-4Mo-2.5Ti maraging steel.
    The reversion temperature shifts to higher temperatures as the titanium content is increased. Austenite reversed in the first stage is stable down to the liquid nitrogen temperature. However austenite reversed in the second stage transforms partially to martensite during cooling to room temperature, depending on the chemical composition of steels.
    While the ferromagnetic to paramagnetic transformation always coincides with phase transformation on heating, they differ slightly on cooling. The Curie temperature of austenite reversed on heating is around 120-270°C, depending on the titanium content and elevated temperature.
    The tensile strength increases with the increase of titanium content in steels, but the ductility decreases. The density increases as the volume of reverted austenite increases.

  • Microstructures and Mechanical Properties of Sintered and Hot-Forged High-Carbon High-Vanadium Tool Steels

    Hisashi ANDO, Akira OKAYAMA, Ko SOENO

    pp. 2629-2638

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    Abstract

    Microstructures of steel powders containing 3.79 to 6.62% C, 16.48 to 37.55% V and 1% Cr, atomized by spraying water or argon gas, have been investigated. Vanadium carbides are uniformly distributed in the powders containing up to 5% C and 25% V. However, coarse spheroidal vanadium carbides are distributed with more than 5% C and 25% V.
    Tool steels containing 3.4 to 4.4% C, 14 to 18% V, 2.7 to 3.2% Cr, 2.3 to 4.1% Mo, 4.7 to 9.7% W and 6.3 to 8.6% Co have been made by sintering water-atomized alloy powders in a vacuum and hot-forging to investigate their microstructures, heat-treatment, and mechanical properties. It is observed that fine vanadium carbides, the total volume per cent of which is about 40%, are uniformly distributed. Grinding is relatively easy in the tool steels as well as in the conventional high speed steel bar stock of JIS SKH 57. Furthermore, it is concluded that the tool steels hardened by quenching and tempering have a high hardness, high transverse rupture strength, and high notch-toughness because of the uniform distribution of fine carbides. Their cutting tool life is also greatly increased.

  • The Influence of Composition on Surface Reactivity of Cold Rolled Steel Sheet

    Shoji SHIMADA, Shigeyoshi MAEDA, Takatoshi EGAWA

    pp. 2639-2649

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    Abstract

    The effects of elements as Mn, S, and O in steel sheets on rusting tendency and the properties of the phosphate coatings formed thereon have been studied by using pure iron and low carbon rimmed steel sheets to which controlled amounts of these elements had been added.
    The rate of rusing of base sheets is determined by the “pack rust test” and the humidity cabinet test, and the resistance to blistering of the laquered phosphated sheets is examined by the salt spray test.
    The chemical reactivity of the steel surface is affected considerably by the presence of these elements; the rate of rusting increases substantially with increases of precipitated MnS and MnO, and the ability to form protective phosphate films increases with increase of total Mn content.
    The above results can be ascribed to the property of MnS to accelerate iron dissolution anodically in both rusting and phosphating. While manganese in solid solution serves as a cathodic dipolarizer in phosphating. Manganese oxide has an effect since its precipitation during hot rolling changes the equilibrium of Mn and S in austenite and therefore favours precipitation of fine MnS during subsequent annealing.

  • Phase Analysis of Zirconium in Steel

    Kazuo KAWAMURA, Shiro WATANABE, Minoru AMANO, Torao UCHIDA, Tokio SUZUKI

    pp. 2650-2659

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    Abstract

    In order to establish a method for phase analysis of zirconium in steel, an investigation was made on the chemical behavior of various zirconium compounds in steel. The results obtained are as follows:
    1) Fine ZrC and Zr sulfide particles are not quantitatively extracted by mineral acids treatment.
    2) Zirconium compounds in steel are quantitatively extracted by the potentiostatic electrolysis methods.
    3) The procedure for phase analysis of zirconium in steel is as follows:
    a) For isolation of all zirconium compounds in steel, the potentiostatic electrolysis method (30% citric acid-15% sodium citrate-1.2% KBr or 10% acetyl acetone-1% tetramethyl ammonium chloride-methanol electrolyte) is applied and the extracted residue is filtered. (Separation of metallic Zr).
    b) The extracted residue is treated by 100 ml of 10% I2-CH3OH at room temperature for 20 min and filtered (Separation of Zr sulfide and where existing Fe2Zr).
    c) The residue of b) is treated with 20 ml of HF (1+20) at 40°C for 20 min and filtered (Separation of ZrN and fine ZrC).
    d) The residue of c) is finally treated with 15 ml of HF (1+20) and 15 ml of conc HNO3 at room temperature for 30 min and filtered (Coarse precipitate of ZrC is determined from the filtrate, and zirconium oxide from the insoluble residue).
    e) Metallic zirconium is calculated by subtraction of combined zirconium fraction from the total amount of zirconium which is determined with use of a separate sample.

  • Wide Flange Beam Mill at Kimitsu Works of The Nippon Steel Corporation

    Shoshiro ISHIMORI, Makio KODAMA, Tsuneyoshi NISHI

    pp. 2660-2670

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    Abstract

    The Wide Flange Beam Mill at Kimitsu Works of The Nippon Steel Corporation started its operation in 1972. Its main features are following.
    (1) Continuous rolling of wide flange beam.
    (2) Continuous finishing line.
    (3) Automatically controlled warehouse.
    (4) Computerized production control system.

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  • Research and Development of a High Quality Wire Rod for Cold Heading and Its Mass Production

    Gennosuke ARISAWA

    pp. 2671-2677

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    Abstract

    The cold heading process is a working technique which has rapidly progressed recently, to make this technique possible, however, higher properties of materials are demanded because of the severe working condition.
    This paper describes the aspect of developing high quality wire rod for cold heading application by improving its production techniques.
    The author investigated the properties of cold headability using several testing methods which include measuring method of working load during heading.
    With these testing methods, the influence of chemical composition, hardness, macro and micro structures, and surface defects were studied.
    The basic researches on nonmetalic inclusions in steel were also carried out, and at the same time a number of test trials on production scale were carried out to make a good quality of steel for cold heading. In order to improve ingot moulds for making less segregated and cleaner steel, the solidification mechanism of molten steel was investigated by adding tracer elements, and several testing models in laboratories were carried out and a computer was also used to analize their results.
    On the other hand, we also improved rolling technique by our long experiences. The No. 7 wire rod mill was designed and manufactured by Kobe Steel Ltd. under the above mentioned improvements, and it is one of the most modern mills in the world. The No. 7 wire rod mill can produce heavy weighted, and large diameter wire rod with close tolerance and superior surface quality much more efficiently than before.

  • Studies on Plastic Working of Steel

    Isao GOKYU

    pp. 2678-2697

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  • 抄録

    小口 征男, 古川 武, 郡司 好喜, 高橋 謙治, 中西 恭二, 鈴木 健一郎, 矢野 修也, 木下 勝雄, 佐藤 隆樹, 菊池 実, 鈴木 正敏, 田中 徹, 白石 春樹, 土田 裕, 春日井 孝昌

    pp. 2698-2703

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  • © 1975 The Iron and Steel Institute of Japan

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