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

Tetsu-to-Hagané Vol. 57 (1971), No. 3

  • 成長と島国根性

    pp. 463-464

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  • Study on the Reduction of Magnetite Pellets Containing Anthracite

    pp. 465-484

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    A study was made of the influence of firing atmosphere (CO2-N2, N2, and CO-N2) on the reduction of magnetite pellets containing anthracite. Phase change during the firing was investigated by X-ray diffraction method and microscopic observations. The results are as follows.
    1) The finer the particles of are and anthracite were, and the more content of anthracite in initial pellet was, the faster the reduction proceeded.
    2) Fayalite was found in the outside layer of magnetite pellets which were fired in CO2-, N2 atmosphere.
    3) The amount of residual carbon in pellets decreased rapidly during the first 30 min of firing in every atmosphere, but the decrease was most rapid in CO2-N2 atmoshere.
    4) It was found in microscopic observations that reduction of are particles in pellets proceeded topochemically.
    5) Decrepitation and lamellar structure of metallic iron were found in some of are particles in pellets fired.
    6) Cementation of metallic iron was observed in pellets fired in N2and CO-N2atmosphere.
  • Heat Flux of in Plates during Cooling by Boiling Water

    pp. 485-497

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    Boiling curves for water cooling of high temperature materials were obtained. Surface temperature and heat flux were calculated from measured temperatures in the test material (copper) by means of extrapolation based on the finited difference equation of heat conduction. Boiling curves were obtained in following cases:
    1. low pressure water jet cooling,
    2. high pressure water jet cooling,
    3. water spray cooling.
    Effects of water flow rate, water temperature and water pressure were studied. Cooling processes for ultrasonic inspection and water quench of steels plates were calculated from the boiling curves and compared with the measured results. Errors due to the measuring method of boilingcurve were studied.
  • On Floating Zone Melting of High Purity Iron

    pp. 498-504

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    A study was made of the refining conditions for obtaining high purity iron from re-electrolytic iron by the floating zone melting technique. The main results obtained are summarized as follows:
    (1) The effect of the specimen diameter on the zone refining was not recognized in a range from 5 to 25 mm dia.
    (2) The later the travelling rate or the more the number of passage was, the greater the zone refining effect was.
    (3) A multiple zone refining which was alternately melted in dry H2 and wet H2 wasvery effective, and after seven zone passes in dry H2, wet H2 and vacuum the specimen showed the lowest value of resistance ratio (R4.2°K/R295°K=1/210).
    (4) From the zone refined specimen, only Co, Cu, Ni and Si were detected as the remained metallic impurities. O and N were effectively removed by zone melting in dry H2and wet H2, but C was hardly removed even in wet H2.°(5) The overlap method was found to be effective technique, as compared with an usually zone re fining method, for multiple zone refining to protect “melt in” or diffusion of impurities from the unpuri fied section adjacent to the starting end.
  • Effect of Casting Conditions on the Formation of Large Non-Metallic Inclusions in Top-Poured Killed Steel Ingots

    pp. 505-532

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    Experiments have been carried out to clarify the effect of casting conditions on the formation of large nonmetallic inclusions in the top poured killed steel. Tapping and pouring temperatures are closely related with the appearance of macroscopic inclusions. Pouring temperature is particularly important. Being poured at low temperatures, ingot contains many macroscopic inclusions, whose diameter is larger than hundred microns, at the bottom equiaxed zone. Being poured at high temperatures, ingot has few macroscopic inclusions. In the case of adequate refinings, the main sources of macroscopic inclusions are airoxidation products and eroded refractories during a pouring. It is unfavourable that sources of inclusions are formed at the last stage of casting practice when molten steel temperature falls. Without air-oxidation and erosion of refractories, few macroscopic inclusions are formed even in the ingot poured at low temperatures. This shows that dissolved oxygen alone cannot form macroscopic inclusions which cause ultrasonic defects. In the case of silicon killed ingots, inclusions are globular manganese silicate containing a little alumina, and are almost in equilibrium with molten steel in composition. In case of aluminium killed one, on the other hand, inclusions just inside the surface of a ingot are globular aluminium-manganese-silicate, which are not in equilibrium with steel and differ from the large high alumina inclusions at the bottom equiaxed zone.
  • Effect of Niobium Addition on Austenite Grain Size in Steels

    pp. 533-546

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    The effects of niobium in steels on austenite grain size and its coarsening behaviour were investigated in relation to the precipitation of niobium carbonitride. The main results may be summarized as follows:
    1) The grain refining effect of niobium in steels is mainly atributable to the retardening effect of Nb (CN) precipitates on the growth of the initial austenite grains formed just after α-γ, transformation.
    2) Onisothermal treatment, the coagulation of Nb (CN) precipitates causes the abnormal grain growth when steels were austenitized from super saturated state of Nb (CN) and some fractions of Nb (CN) precipitated preferably in austenite grain boundaries. On the other hand, when Nb (CN) had precipitated in equilibrium before the austenitization, on subsequent austenitization, the abnormal growth hardly occurs and grains gradually grow holding relatively fine grain sizes in a long period of time. In former case, the starting time of the abnormal growth becomes longer with increase in Nb contents up to a certain contents. When niobium increases over this contents, however, the time becomes shorter again. This may be due to the fact that when niobium increases over a certain extent, the amounts of fine Nb (CN) decrease, which precipitates secondarily during the isothermal treatment and inhibits effectively the abnormal growth.
    3) These two types of the grain growth can reasonably be explained from an analysis based on the grain growth theory proposed by HILLE
  • Effect of Vanadium, Wolfram, and Boronon High-Temperature Strength of 25%Cr-28%Ni-2%Mo Heat Resisting Steels with High Nitrogen

    pp. 547-565

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    On the 25%Cr-28%Ni-2%Mo austenitic heat-resisting steel containing up to 0.67% nitrogen, 2% vanadium, 5.7% wolfram, and 0.05% boron, the high temperature strengths were investigated by tensile creep rupture testing and short time tensile testing, and the correspondence of these properties with the microstructure of the steel was discussed.
    Addition of nitrogen to the steel containing vanadium and boron increases not onlythe short time tensile strength at the temperature up to 700°C, but also remarkably the 1000 hr rupture strength at 700°C.
    The 25% Cr-28%Ni-2%, Mo steel, added with nitrogen, wolfram, and boron, has showed the most excellent creep rupture strength in the range of the present work that was carried out at both the temperature of 700°C and 800°C; for example, the steel containing 5.7% wolfram, 0.05% boron, and 0.67% nitrogen has showed 26.5 kg/mm2 of 1000 hr rupture strength at 700°C. Further, in the lower range of nitrogen con tent, the 700°C-1000 hr rupture strength of the steel was increased by about 9 kg/mm2due to the addition of 5% wolfram and 0.05% boron, and this value corresponds to about 100% increase of the strength com paring to that of wolfram-boron free steel.
    With addition of boron to this type of steel, the high temperature ductilities have been improved remarkably, but the creep rupture strength has not so much.
  • Precipitation of Aluminium Nitride during Recrystallization of α-Iron

    pp. 566-574

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    An investigation has been made on the precipitation of AlN in vacuum melted iron wires, contAlNing 0.003, 0.036 and 0.072 pct Al, solution-treated at 1 200°C, cold reduced to 70 pct and isothermally annealed in the range 500°C to 700°C. To determine the behaviour of AlN in αiron, the technique of low frequency internal friction measurement was employed. Separation of the Snoek peaks observed by this technique allows accurate determination of the amounts of dissolved carbon and nitrogen in solution. The results obtAlNed were summarized as follows:
    (1) In specimens initially contAlNing 0·003 pct Al, purified and nitrided to 0·018 or 0·052 pct and subjected to a solution treatment, increased the amount of dissolved nitrogen during isothermal annealing at 600°C after cold reduction. In specimens carburized to 0·012 or 0·019 pet, the dissolved carbon tended to decrease to the solubility limit by the same heat treatment.
    (2) It made a little difference in the behaviour of AlN precipitation during isothermal annealing whether AlN particles were completely dissolved in γiron by a solution treatment at 1200°C or undissolved partially. In both cases, when annealed at 600°C, however, AlN precipitation occured during the recovery and in the early stage of recrystallization and the recrystallization was retarded.
    (3) On annealing the nitrided specimen at 700°C, recrystallization preceded the precipitation of AlN.
    It was found that pre-precipitation clustering of AlN at dislocations and subboundaries in deformed by αiron preheat-treatment for 20 hr at 500°C prior to 700°C annealing did significantly affect the recrystallization process due to promoting AlN precipitation and decreasing the recrystallization rate.
  • The Effect of Tellurium on Properties of Steels

    pp. 575-588

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    Steels containing Te are generally used for free cutting steels. But the effect of Te on mechanical properties and mechanism of grain growth retardation by Te are not well knownyet.
    The authors have studied the influence of Te on impact properties, tensile properties and austenite grain size of common structural steels at various temperatures.
    Tellurium compounds were identified by X-ray diffraction with electrolytically extracted residues and by analysis of the compounds using electron probe X-ray microanalyzer.
    The state of dispersion of telluride was examined by autoradiography using 125m Te isotope.
    The obtained results are as follows.
    (1) Addition of Te to the steels lowered remarkably the transition temperature in Charpy impact test and increased yield point.
    (2) Te raised coarsening temperature of austenite grain and in the case of the combined addition of Te and such grain refining element as Al, Nb or Ti, the coarsening temperature was such higher than that in the case of the separate addition of Al, Nb or Ti.
    (3) Tellurium compounds were identified to be FeTe and MnTe and it was found by autoradiography using RI Te that they dispersed uniformly in the matrix.
  • Machinability of Calcium Deoxidized Steel

    pp. 589-600

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    In order to clarify the machinability of calcium deoxidized 0.45% carbon steel, the effect of chemical composition on the machinability was investigated in turning and drilling.
    Experimental results in turning with carbide tool showed that the tool wear depends on contents of aluminum, calcium and sulfur in steel, and it is suppressed when the content of sulfur is more than 0.035% and that of aluminum is less than 4.3 times of calcium content in steel.
    In this case, a thin oxide layer containing some sulfide phase is always found on the tool face and it is supposed that this prevents the tool wear.
    In drilling with high speed steel tool, higher sulfur content in steel is favorable for tool life. But no effect of aluminum or calcium is observed.
  • Automatic Nondestructive Inspection for Surface Defects of Hot Rolled Round Steel Bars

    pp. 601-613

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    The fluorescent magnetic particle method is usually used for inspection of surface defects of hot rolled steel bars. However, in this method, the evaluation is not quantitative and the judgement of harmful defect depends on the skill of inspector, and moreover the inspection rate is very low.
    To improve these drawbacks and to develope an automatic inspection in production line, the present autors have studied the eddy current inspection method and a new automatic magnetic inspection method using semi-conductor elements.
    Some characteristics of eddy current test coil have been investigated and a high sensitive coil newly designed clearly detects a surface defect whose depth is 0.3 mm.
    Eddy current inspection is suitable for detection of surface single or short defects such as shells and roll marks.
    An automatic magnetic inspection method has been developed for detection of long defect. In this method Sony magnetodiode (SMD) is used to detect leakage flux from surface defect of bar which is magnetized by a. c. magnetic field.
    The inspection system based on this new method is able to detect harmful seam and crack without descaling process. A seam of 0.1 mm depth is easily detected and inspection rate is 30-40 T/H for bars of 50-100 mm diameter.
    This system is taking the place of fluorescent magnetic particle inspection method.
    The combined method of eddy current inspection and leakage magnetic flux detection is possible to detect all kinds of surface defect in production line automatically.
  • Hot Corrosion of Some Heat Resisting Alloys by V2O5-Na2SO4-NaCl Mixtures

    pp. 614-622

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    The accelerated attack in an atmosphere contaminated with vanadate, sulphate, and halide which is often found in alloys for gas turbine or marine diesel has been examined by means of crucible test. Six different materials used for turbine blades or valves were tested in this investigation. Samples partly immersed in mixtures of vanadium pentoxide and sodium sulphate and/or sodium chloride were heated in air at temperatures of 700 and 800°C, and weight losses were determined after descaling. The results obtained are as follows:
    (1) Mixtures of Na2SO4+0.5-70% NaCl and V2O5+10-40%(Na2SO4+NaCl) were the most corrosive for these materials.
    (2) At lower temperatures, all alloys were resistant to attack by Na2SO4/NaCl but above about 750°C, they were subject to severe effects. These reactions occurred only in the reducing environments.
    (3) In the V2O5/Na2SO4 environment, there was a considerable attack for S 590, LCN 155, SUH 3, and SUH 31 at even 700°C.
    (4) LCN 155 and YA2B were the most corrosion-resistant alloys in the Na2SO4/NaCl environment, but they were subject to some intergranular attack.
    CRK 22 and YA2B have a comparatively good corrosion resistance in V2O5/Na2SO4mixtures.
  • Coulometric Determination of Sulphur in Steel

    pp. 623-628

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    By varying analytical conditions in quantitative coulometric determination of sulphur in steel, was established a method by which a favorable reproducibility can be obtained.
    Furthermore, a standardizing method of the apparatus was examined and the accuracy could be im proved for wider quantitative range. The outline is as follows:
    1. Analytical conditions sample weight: 0.5-1.0g O2 flow: 1500 ml/min combustion time: 6 min CO2expelling time: 4-5 min combustion accelerator: Sn 0.5g or Sn 1.0g+Fe 0.5g (high sulphur steel)
    2. Reproducibility By the use of an SO2, SO3adhesion preventing equipment, the reproducibility is found to be favorable in both successive and interval test, δ-being 0.0007% in the case of carbon steel containing 0.04-4% sulphur.
    3. Accuracy A favorable accuracy in quantitative scope between 0.001 and 0.300% S was obtained after standardi zation of the equipment by high sulphur steel (0.300%) to reduce the influence of unelectrolyzed remain ing count.
  • World's Coking Coal and Iron Ore Situation as Seen from Japanese Steel Iudustry

    pp. 629-645

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  • On Continuous-Continuous Casting of Steel

    pp. 646-655

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  • State Analysis of Steel

    pp. 656-672

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  • 抄録

    pp. 673-686

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