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

Tetsu-to-Hagané Vol. 60 (1974), No. 9

  • 自主技術の開発

    pp. 1259-1260

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  • Intraparticle Temperature of Iron-Oxide Pellet during the Reduction

    pp. 1261-1270

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    Intraparticle temperatures of the porous iron-oxide pellets having about 30% porosities during the gaseous reduction were measured by a thermocouple embedded into the center of the sample and the reduction rates of the similar samples were observed by a thermo-gravimetric method. Those intraparticle temperatures reflected that the reduction of iron-oxide was a multi-stage successive reaction and the variations of the temperatures with the progress of reduction corresponded to the reaction rates and heats of each reduction step.
    To predict theoretically such a temperature variation, the rate equations of the chemical reaction and the heat transfer were developed on the basis of the multi-interface unreacted core model. The calculated variations of the temperature by these equations adopting appropriate rate parameters coincided fairly well with the experimental results.
    Further, the errors of the rate parameters by ignoring the heat transfer resistances in the analysis of the experimental data of reduction were discussed from the theoretical calculation for the single step reduction. The exact values regarding the chemical reaction rate constant can be obtained but the considerable deviations may arise about the intraparticle effective diffusivity.
  • Pressure Drops in Parallel-Packed Beds with Two Kinds of Particles

    pp. 1271-1282

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    Pressure drops and gas flow in parallel-packed beds with two kinds of particles have been theoretically and experimentally studied.
    Gas flow behaviors in this sort of the bed can not be interpreted by means of simple theories only for the axial velocity of gas.
    Even with the axial insulation with a partitioning glass tube, the parallel-packed bed yields the lateral cross-flow within a thicker distributer. Also, the cross flow generally exists in the parallel-packed bed, so far as the flow resistance of the distributer is finite. In both cases the pressure drop lies between the values calculated theoretically on the parallel and series models of gas flow.
    Taking account of the existence of the cross-flow in the bed, a lumped parameter-model is proposed and the experimentally observed behaviors of the pressure drop are reasonably explained.
  • Axial Dispersion and Residence Time Distribution of Spherical Particles in Rotary Kiln

    pp. 1283-1288

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    Residence time distributions of particles in a horizontally rotating cylinder were theoretically and experimentally studied. A mathematical model of the axial dispersion of particles was analytically solved and the following expression for their residence time distribution was obtained:
    Dimensionless Peclet number as a function of variances in residence time distribution was given as fol-lows:
    Measurements were based on an impulse response method of tracers into spherical alumina particles stream through a rotary cylinder which is made of vinyl chloride resin.
    An empirical correlation among Peclet number, operational conditions, and geometrical factors was determined:
    Upon examinations of effects of the revolution rate on the axial dispersion coefficient, it was shown that the latter was directly proportional to the former.
  • The Reduction Process and Reducibility of Chromite with Carbon

    pp. 1289-1298

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    In the present work, various chrome ores and relatively pure chromites separated from them were reduced with powdered graphite over a temperature range of 1050° to 1400°C under a flow of argon.
    The results obtained are as follows:
    1) Roughly speaking, the reduction process of natural chromite consisted of the following three stages:
    2) The reduction products of the 1st stage were metallic iron and cementite, while the chromium-bearing product, (Cr, Fe), C3, was produced after the beginning of the 2nd stage.
    3) Of the constituents of chromite, iron oxide had the strongest influence on its reducibility. At tem peratures below about 1200°C, the porosity of chromite particles was also of great interest, and porous chromite was reduced more easily than compact chromite.
    4) At temperatures above 1300°C, a considerable portion of SiO2 contained in chrome are was reduced.
    5) The gangue minerals such as forsterite and enstatite retarded the reduction of chromite at temperatures below 1250°C, but accelerated it at higher temperatures.
  • The Effect of Al, B, Ge, Ta, Sn and Zr on the Solubility of Hydrogen in Liquid Iron

    pp. 1299-1309

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    The solubility of hydrogen in liquid iron alloys has been studied by Sieverts' method at the temperature range from 1548° to 1672°C and under an atmospheric pressure of hydrogen. The solubility of hydro-gen in liquid iron decreases by the addition of B, Ge, Al, Sn, and Ta, and increases by the addition of Zr.
    Interaction parameters at 1600°C are:∂log fAlH/∂[%Al]=0.0107……[%Al]<10.
    ∂log fBH/∂[%B]=0.058……[%B]<2.5
    ∂log fGeH/∂[%Ge]=0.0109……[%Ge]<10.
    ∂1og fTaH/∂[%Ta]=0.0017……[%Ta]<25.
    ∂log fSnH/∂[%Sn]=0.0057……[%sn]<7.
    ∂log fZrH/∂[%Zr]=-0.0088……[%Zr]<2.
  • Deoxidation of Continuously-Cast Low-Carbon Steel for Cold-Sheet

    pp. 1310-1324

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    In order to develop continuouslydassy-cast steels for cold rolled sheet, the deoxidation of liquid steel has beenstudied.
    Deoxidizers of the series of Al-Si-Mn can be basically used satisfactorily for the purpose. Especiallythe cold rolled steel sheet of the composition of C=0.03-0.07%, Si=0.03-0.07%, Mn=0-40-0.50%, andacid sol-A1≤0.008% is good enough for the view point of mechanical properties; its surface defects aresufficiently few. Moreover, non-metallic inclusions decrease by the addition of complex deoxidizers asa part of deoxidizers.
    The composition of deoxidation product is studied from the view point of chemical equilibrium.
  • Effect of the Steelmaking and Continuously-Casting Conditions on Non-Metallic Inclusion of the Steel For Cold Rolled Sheet

    pp. 1325-1336

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    In order to produce continuously-cast slabs provided for mother material of cold rolled sheet, liquid steels were deoxidized with deoxidizers of Al-Si-Mn system. Non-metallic inclusions of manganesesilicate and alumina were studied with reference to its steelmaking and casting conditions.
    The results are as follows.
    (1) To reduce the amount of manganese-silicate inclusion,
    (a) keep the (blow-off [C]×(T-Fe)) higher,
    (b) keep the yield of silicon added as deoxidizers at tapping more than 95%,
    (c) furnish tundish-dam, and
    (d) keep the casting speed higher.
    (2) To reduce the amount of alumina,
    (a) keep the blow-off carbon content higher,
    (b) reduce Al/Si ratio of the deoxidizers added at tapping,
    (c) keep the blow-off temperature higher, and
    (d) keep the casting speed higher.
    As stated above, steelmaking conditions have a strong connection with the non-metallic inclusions. Therefore, the main source of inclusion is considered to deoxidation products.
  • Applications of Master Cooling Curve

    pp. 1337-1343

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    The estimation of hardness distribution curves of the cross section of steel bars quenched was made fromthe master cooling curves of coolants and CCT diagrams of steels. These results were in good agreement with the measured hardness distribution curves for respective steels. The results based on the master coolingcurve was compared with those by Lamont's method and Wever-Rose's method. In consequenceof this comparison, it was found that the method of the master cooling curve was excellent in accuracy andin the range of application for different types of steels and coolants. The critical diameters could be alsoderived from the master cooling curves and CCT curves. This result was in better agreement with thepractical results than that of the Grossman's method.
  • The Study of Structural Change due to Abrading in Carbon Steel

    pp. 1344-1352

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    In Carbon steel, quenching method is used frequently to obtain the wear resistibility of sliding surface because of its convenience. However it can be considered that the structural change due to frictional heating under severe sliding condition have not a little influence on wear behavior.
    Then in this paper, the structural change of quenched and tempered S45C carbon steel due to abrading was studied in a point of view of hardness change and microstructure, and moreover the relation between the structural change and wear behavior was discussed.
    Main results obtained for quenched materials were as follows.
    1) As sliding load increased, the hardness just under sliding surface decreased, and the minimum point that appeared in hardness distribution curve in the vicinity of sliding surface shifted to deep point decreasing its value.
    2) It was found that the martensite in the vicinity of sliding surface disappeared and spheroidal cementit precipitated under heavy sliding load.
    3) Wear resistibility was very favorable when sliding load was slight, however the effect of quenching became weak extremely due to softening of surface layer when sliding load was heavy.
    4) When the material which was softened by abrading was abraded again, the wear decreased under heavy sliding load, but increased under light sliding load.
    Above results indicate that the hardening method by quenching is available only when the sliding condition is always mild.
  • The Effect of Impurity Elements on Transition Temperatures and 475°C Embrittlement of Ferritic Stainless Steels

    pp. 1353-1362

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    The brittle-to-ductile transition curves of a series of ferritic stainless steels containing carbon, nitrogen, silicon or manganese, respectively, were determined, and also the effect of aging at 475°C on the transition curves of high purity ferritic stainless steels was discussed.
    The main results obtained were as follows:
    (1) In 18% chromium steels, at the 0.002% carbon and 0.004% nitrogen levels, the indicated transition temperature is found to be 85°C However, there is a remarkable increase in transition temperature and a decrease in upper shelf energy, as carbon or nitrogen content increases. The effect on transition temperature and upper shelf energy is attributed to the exsistence of solute carbon or nitrogen atoms and the dispersed carbide or nitride precipitates.
    (2) Addition of aluminium as stabilizer is effective in lowering transition temperature.
    (3) Silicon and manganese additions tend to raise transition temperature.
    (4) In high purity 18% chromium steel aged at 475°C the upper shelf energy decreases, but the transition temperature has little change.
    (5) In 0.05% nitrogen-18% chromium steel aged at 475°C, the upper shelf energy decreases, and the transition temperature is shifted toward higher temperatures.
    (6) The hardness increase with the aging time for high purity 18% chromium steel is less than for 0.05% nitrogen-18% chromium steel.
    (7) These phenomena caused by aging at 475°C must be depended on the precipitation of chromium rich bcc phase and chromium nitrides.
  • Precipitation Hardening and Magnetic Properties of Fe-Ni-Al, Fe-Ni-Ti and Fe-Ni-Co-Mo Maraging Steels

    pp. 1363-1372

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    Precipitation hardening, tensile properties, and D. C. magnetic properties of Fe-(5-20)% 1.57)%Al, Fe-(5-20)% Ni-(0.5-4.8)%Ti, and Fe-(8-18)% Ni-10% Co-5% Mo maraging steels were investigated.
    Maximum hardness produced by aging at 475 C were measured as a function of additional amount of aluminium or titanium. In the nickel range from 10 to 20%, titanium addition is more effective in hardening than aluminium addition is. However, in 5% nickel level, aluminium addition is more helpful in age-hardening.
    It is considered that a meta-stable phase is formed in aging the Fe-18% Ni-l0% Co-5% Mo and Fe-14% Ni-10% Co-5% Mo maraging steels at 425°C Precipitation hardening produced by aging the Fe-10% Ni-10% Co-5% Mo and Fe-8% Ni-10% Co-5% Mo maraging steels at 425°Cis markedly decreased. Accordingly, it is implied that either meta-stable phase is not formed or is slightly formed in aging at 425°C
    Small amounts of pearlite structure formed by the cellular precipitation reaction are found in the Fe-5% Ni-1.57% Al maraging steel aged at 475°Cfor 50 hr and 100 hr. Except the Fe-5% Ni-1.57% Al maraging steel, the pearlite cellular structure is not found in the Fe-Ni-Al maraging steels, aged at 475°C nearly to their maximum hardness.
    Considerable drop in toughness is often observed in the Fe-Ni-Ti maraging steelsage-hardened at 475°C to hardness over about Hv; 450. Molybednum addition is effective in suppressing the drop in toughness. The upper limit of the tensile strength of the Fe-Ni-Al maraging steels aged at 475°Cis about 140 Kg/mm2. Regarding the Fe-Ni-Al, and Fe-Ni-Ti maraging steels having tensile strength less than about 140 kg/mm2, no difference in elongation is found in tensile test.
    Magnetic properties of the maraging steels depend mainly on their chemical compositions. On comparing coercive force and magnetic induction at the same hardness level, the magnetic properties of the Fe-Ni-Al maraging steels are softest and those of the nickel maraging steels containing cobalt and molybdenum are hardest.
  • Effect of B on Delayed Fracture in Heat-Affected Zone in 80kg/mm2 Class High Tensile Strength Steel

    pp. 1373-1379

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    This paper showed the effect of B on the delayed fracture of high strength steels. As the result of many cold cracking tests in welding (Tekken-type etc.), three characteristic facts were indicated. Firstly, B is very effective in preventing cold cracking. Secondly, B segregates at austenite grain boundaries in heat affected zone. Thirdly, diffusion of hydrogen becomes slower when B segregates at austenite grain boundaries. From these facts it is thought that the diffusion of hydrogen to stress-concentrated region is suppressed by B in heat affected zone and thus B is beneficial in preventing cold cracking and makes steels insensitive to cold cracking.
  • Investigation for Emission Spectroscopic Analysis of Chip-Briquetted Steel Products

    pp. 1380-1388

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    This paper deals with an investigation of a chip-briquette method for eliminating the effect of microst ructure and segregation in the emission spectroscopic analysis of low carbon steel products. In the method, when the chips for analysis are obtained from rolled steel product by sawing, its microstructure, having been passed through any process of heat treatment, are transformed intensely into similar fine grains. And by mixing of chips before briquetting for analysis, sample uniformity at the size of analytical spot is made better. Consequently, it is possible to eliminate their effects in the analysis. The analytical results of various low carbon steel products are improved.
  • Solution by Simulator of the Temperature Changes of Slab in Continuous Casting

    pp. 1389-1394

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    Using an electric simulator for the solidification of slab, the change and distribution of slab temperature concerning both conventional mould and continuous casting were obtained. Experimental results made clear the effect of the time of air-gap occurrence and the effect of the coefficient of heat transfer of the boundary between slab and mould.
    In the case of continuous casting, the temperature change during solidification process was clarified; the temperature of slab surface dropped rapidly in a mould after pouring, then rose owing to air-gap occurence, followed by dropping again as secondary cooling, subsequently the temperature rose due to air-cooling in the following step.
    Accordingly, using such a simulator, the change and distribution of slab temperature can be obtained easily under different casting conditions.
  • On the Sliding Wear Mechanisms of Cast Iron

    pp. 1395-1408

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  • 抄録

    pp. 1409-1417

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