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

Tetsu-to-Hagané Vol. 61 (1975), No. 7

  • Dimensionless Groups on a Countercurrent Reduction of Iron Ore

    pp. 909-916

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    The reduction of iron are particles is a gas-solid reaction and therefore the unreacted core modelis often applied. Material balances on a unit surface area are calculated in bothgas and solid phases.The residence time of are is normalized by a theoretical reducing time, and it isnamed Ot. Thecontact time of reducing gas is also normalized by a theoretical contact time, and it is named Gc. These two dimensionless groups Ot and Gc are very advantageous to understand the phenomena incountercurrent reductions.
    Utilization coefficient diagrams are calculated by these two dimensionless parameters. These diagramsare shown by three variables, these are the reduction temperature, are sort, and reducing gas species.Other conditions, such as the gas flow rate, reducing gas fraction, are size, are weight on the bed, descending speed of ore, reaction rate constant, and so on are included in the two parameters. Bycalculating Gc and Ot from some conditions in the countercurrent reduction, the utilization coefficient and final reduction degree are decided from one of these diagrams.
  • On the Hydrogen and Carbon Contained in the Volatile Matter of Metallurgical coke

    pp. 917-924

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    A fundamental study on the dependency of hydrogen and carbon contents in the volatile matterof coke on temperature and particle size has been carried out.
    The results obtained are as follows
    1) Small size coke (or coke breeze) contains more hydrogen in volatile matter than large sizecoke.
    2) The degree of volatilization of hydrogen depends on both of temperature and particle size, butthe effect of the former is more remarkable.
    3) Main elemental components in the volatile matter are hydrogen and carbon, and the C/H ratiovaries from 2.0 in case of small size coke to 2.6 in case of large size coke.
    4) Experimental formula expressing the dependency of the hydrogen volatilization on temperature and particle size are obtained.
  • Reduction Rate of Iron-Oxide Pellets Under Heating Series

    pp. 925-934

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    Based on the fact that gas diffusibility (De/DH2-H2O) of reduced iron depends on its reduction temperatures remarkably, a mathematical model of diffusion rate through shell layer of reduced iron under heating series was presented.
    This model was examined by reduction experiments which were carried out in isothermal conditions and heating series using ferric oxide pellet. By analyzing the rates of isothermal reduction by the unreacted core model, parameters of chemical reaction constant kr and intraparticle diffusivity De were estimated as functions of reduction temperature.
    The reduction rates under heating series were calculated by using a model in which the above parameters were substituted. Those calculated results agreed well with the experimental results.
  • A Mathematical Model of Blast Furnace Based on the Assumption of Uniform Distribution of Burdens and Gas

    pp. 935-947

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    A new mathematical model of the blast furnace has been developed for estimating the effect of the coke reactivity on the operational results of the experimental blast furnace in Institute of Industrial Science, University of Tokyo.
    The furnace volume above the tuyere level is divided into three regions, namely, “indirect reduction”, “direct reduction” and “meltscontaining” by two isotherms, and the temperatures of which are considered to be determined by the coke reactivity and by the melting point of metal, The model is made up of the stagedheat balance on the regions and a rate equation of indirect reduction expressing the topochemical progress of two interfaces. Heat of reaction is included in the water equivalent of condensed phases and “heat level” of the furnace is represented by the coke temperature at the tuyere level.
    It is estimated from the calculation that coke consumption in the experimental furnace might be reduced by 119kg/t-metal, of which 33 kg/t-metal can be attributed to the reactivity, be the use of petroleum coke differing from metallurgical coke in several properties besides reactivity.
    The model can also be applied to the investigation of the effect of natural gas injection on coke rate and replacement ratio in a commercial furnace. The calculated coke rate and CO-utilization coincide well with the operational results.
  • A Mathematical Model of Blast Furnace Considering Uneven Distribution of Burdens and Gas

    pp. 948-956

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    In order to clarify the effects of radial distribution patterns of the burdens on the are reduction, heat transfer between gas and solids, and other operational results, a mathematical model taking account of an uneven radial distribution is presented.
    The blast furnace is divided annularly into center, intermediate and peripheral zones, to all of which the mathematical model presented before can be applied by assuming the plug flow and uniform distribution of gas as well as of burdens. The distribution of gas flow rate to the three zones is regarded to be so determined as that gas pressure is equal everywhere in any horizontal section of the furnace under the radially different gas permeability due to radial distribution of ore/coke ratio. The calculation is carried out so as to make the mean of coke temperatures at the tuyere level equal to a predetermined value under a given o/c distribution.
    The results of the calculation show that the increase of CO-utilization by about 1.8% and the saving of coke consumption by about 10kg/t-metal may be expected under the condition of uniform distribution in comparison with the distribution pattern in the 22th campaign of the experimental blast furnace.
  • A Study on Bonding Mechanism of Aluminum Clad Steel by Cold Rolling

    pp. 957-962

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    A number of studies on bonding mechanism of clad metals by cold rolling have been reported, but adefinite conclusion of the bonding mechanism has not yet been recognized.
    In cold clad practice, it can be thought that the factors affecting the bondability may be kind of metals, surface condition, thickness ratio of metals, temperature, relative slip, and so on.
    Several factors affecting the bond shear strength of aluminum clad steel by cold rolling were examined. Further, the temperature of the bond during rolling was measured by I. C. thermo-couple. As the result, an average temperature of about 650°C in 0.05 sec was obtained.
    From these facts it may be suggested that the bonding mechanism by cold rolling is mutual fusion of metals at contact part under high pressure and high deformation by frictional heat caused by relative slip of metals.
  • The Effect of Thermo-Mechanical Treatments on the Fatigue Strength of Type 316 Stainless Steel

    pp. 963-971

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    The fatigue strength at room temperature and microstructure of the type 316 austenitic stainless steel with and without various thermo-mechanical treatments were investigated and the test results by a ultrasonic fatigue testing machine were compared with that by a conventional tension-compression fatigue testing machine.
    The 106 cycle fatigue strength of type 316 steel increased about 30% by the tensile cold work of 30%, and moreover by the aging treatment of 30hr at 700°C after 20% cold work about a 50% increase of 106 cycle fatigue strength was obined comparing with that of the solution treated steel. These fotigue strengths, however, are a little smaller than that obtained by the treatment, 20% cold working followed by aging of 24hr at 480°C and 216hr at 700°C, which was proposed by Garofalo.
    Based on the results of the microstructural survey, it was suggested that the high dislocation density and fine and homogeneous distribution of precipitated M23C6 carbide contribute to the strengthening of the thermo-mechanical treated steels.
    The S-N curves both by ultrasonic and magnetic fatigue testing machines showed an almost similar tendency. Therefore, the advantage of ultrasonic fatigue testing machine in time-saving of the testing of type 316 steel was confirmed.
  • Toughness of High Strength Ni-Cr-Mo-V Steels Containing 1-5% Nickel

    pp. 972-990

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    A study has been made of mechanical characteristics with special reference to toughness of low carbon Ni-Cr-Mo-V structural steels containing 1-5% nickel with the intermediate stage transformed structure and tempered-martensitic structure.
    Some intermediate structures have been compared with the tempered-martensitic structure at a similar strength level, by evalution of charpy impact values, transition temper-atures and fracture toughness values and also examination of microfractograghs.
    In the intermediate structures as well as the tempered-martensitic structure of these steels, it is generally to say that the toughness is improved with increasing nickel amount though the latter structure is always superior to the former ones.
    Considerations on microfractograghs of fractured Charpy impact or slow bend specimens lead to some informations concerning the influence of microstructural factors, e. g. morphology of the precipitates and mixture of different transformation products at different temperatures, on the toughness and fracture behaviour of these steels.
  • Influence of Crystallographic Texture on the Strength and Toughness of the Controlled Rolled High Tensile Strength Steel

    pp. 991-1011

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    Fairly strong textures were found to be present in experimentally controlled rolled high tensile strength steels. The effect of such textures on the anisotropies of strength and toughness of these steels was quantitatively investigated. It was noted that the effect of textures on the anisotropies of yield stress and tensile strength could be accurately evaluated with Hosford and Backofen's method, if fine details of textures were properly taken into account by adopting the method of crystallite orientation distribution analysis developed by Roe. The anisotropy of toughness, on the other hand, was found to be qualitatively related to the distribution of {100} cleavage plane. Among the main components of the texture, which is present in those controlled rolled high tensile strength steels, {311}‹011› orientations not only enhance the difference in strength between 0°(RD) and 90°(TD) direction, but also reduce the toughness at 45°C direction, whereas {332}‹113› orientations proved to be favourable to both strength and toughness, showing weak anisotropy. Thus, further improvement in strength and toughness might be possible, if {332}‹113› orientations could be developed more preferentially.
  • Embrittlement Due to the High Temperature Solution Annealing in 18% Ni Maraging Steels

    pp. 1012-1027

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  • ffect of Alloying Elements on the Mechanical Properties of High Strength Cast Steels for Roll Use

    pp. 1028-1053

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    (I) The effects of further additions of Ni, Cr, V and Nb on the mechanical properties at room and elevated temperatures of conventional Ni-Cr-Mo cast steel material (SNI) have been investigated.
    The following results were obtained:
    (1) Vanadium addition improves the elongation and reduction of area of Ni-Cr-Mo cast steel at elavated temperatures.
    (2) Interaction effect of chromium with nickel improves the toughness and strength of the cast steel.
    (3) Niobium addition decreases the toughness.
    (4) The addition of 0.4% V, 0.75% Cr and 0.5% Ni to the conventional Ni-Cr-Mo cast steel used for roll is effective in increasing the fatigue strength and toughness and this new material seems to be suitable for slabbing and heavy plate rougher mill roll.
    (II) The effects of further addition of 3.0% Ni and reduction of 0.1% C to the new material at room and elevated temperatures have been investigated and the following results were obtained:
    (I) 0.4%C-1.25%Cr-4.0%Ni-0.5%Mo-0.4%V cast steel has higher tensile and fatigue strength (Δδβ=23kg/mm2, Δδw106=8kg/mm2) than new 0.5%C-1.25%Cr-1.0%Ni-0.5%Mo-0.4%V cast steel has.
    (2) The individual effects of chromium and nickel on the toughness are small, but the interaction effect of these two elements seems to improve the toughness under the temperature of 100°C.
  • Effects of Cold Drawing and Hot Dip Aluminizing on Stress Corrosion Cracking of 18-8 Stainless Steel Wire

    pp. 1054-1062

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    A study was made of the effects of cold drawing and hot dip aluminizing on stresscorrosion cracking (SCC) of 18-8 stainless steel wire. SCC tests were carried out in boiling 42% MgC12 solution.
    The main results are summarized as follows:
    (1) The effect of cold drawing before annealing on the SCC susceptibility was almost negligible.
    (2) The effect of cold drawing after annealing on the SCC susceptibility varied with the applied stresses. When applied stress was lower than 10kg/mm2, increased susceptibility was observed in a specific range of cold drawing. The maximum susceptibility appeared at 16% in cold drawing.
    (3) The increased susceptibility was accompanied by the formation of ε′ martensite, whereas greater cold drawing beyond the susceptible range induced the formation of α′ martensite. The observed facts suggest the different effect of ε′ and α′ martensite on the development of SCC.
    (3) The increased susceptibility was accompanied by the formation of ε′ martensite, whereas greater cold drawing beyond the susceptible range induced the formation of α′ martensite. The observed facts suggest the different effect of ε′ and α′ martensite on the development of SCC.
    (4) When susceptibility was increased by cold drawing, cracks propagated transgranularly to certain depth and then converted to intergranularlyl.
    (5) Hot dip aluminizing was beneficial in preventing austenitic stainless steel wire from SCC.
  • Indirect Determination of Phosphorous in Iron and Steel by Atomic Absorption Spectrometry

    pp. 1063-1068

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    An atomic absorption spectrometric study was carried out to establish fundamental conditions in the indirect determination of phosphorus in iron and steel. This method involves the extraction of phosphomolybdate (heteropolyacid H3PO4·12Mo03) complex with butyl acetate and the measurement of absorbance of the molybdenum in the extract.
    The interference from iron and other elements such as Mn, Ni, Cr, Cu, Mo, Co, As, and W was found to be uninfluential, while the influence of V and Ti was not avoidable if they are over 5mg and 0.5rng respectively.
    The results obtained were satisfactory for the determination of phosphorus in iron and steel. The coefficient of variation was 3.56% or 1.55% for 0.011% or 0.052% phosphorus respectively.
  • Recent Trend of Research and Manufacturing Technique of Refractories for Steel Industry

    pp. 1069-1077

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  • Theoretical Studies of Rolling Made Great Contribution to Rapid Progress of Iron and Steel Industry in Japan

    pp. 1078-1087

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  • 抄録

    pp. 1088-1094

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