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

Tetsu-to-Hagané Vol. 74 (1988), No. 10

  • Recent Development of Bearing Steel in Japan

    pp. 1889-1894

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  • Present and Future of Cooling Technology

    pp. 1895-1900

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  • Magneto-optical Memory Disk

    pp. 1901-1908

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  • Recent Developments in Telecommunication Outside Plants and Newly Facing Problems

    pp. 1909-1915

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  • Development of an Advanced Technique for Reducing the SiO2 Variation in Fine Ore Bed

    pp. 1916-1922

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    It is very important for reducing the fluctuation of sinter qualities to decrease the SiO2 variation of the fine are bed in sinter feed. In order to reduce the variation, a new bed monitoring system and an advanced bed stacker which controls the segregation of a stocked pile have been developed and applied to the actual plants.
    The results obtained from these activities are as follows;
    1) The SiO2 variation is very remarkable at the bed reclaiming stage between fine ore bed and sinter pallet.
    2) The SiO2 variation can be estimated by the longitudinal and cross sectional bed model.
    3) The SiO2 variation of bed cross section (σW) is about seven times as large as in logitudibal bed direction (σL), and is related with the variation of sinter (σS).
    4) It is effective for reducing the variation to adopt the advanced bed stacker. The variation can be reduced to half compared with result of the conventional system.
    5) About 3 to 5% of returned fine and 3 to 4 kg/t of coke consumption can be reduced by introducing both the new monitoring system and the advanced bed stacker.
    6) The SiO2 variation of sinter (σS) can be reduced from 0.060.09 wt% to O.040.05 wt% by introducing this system.
  • Effect of Horizontal Gas Flow on Liquid Dropping Flow in Two-dimensional Packed Bed

    pp. 1923-1930

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    The effect of horizontal gas flow on liquid dropping flow in the two-dimensional packed bed was studied through cold model experiments. Liquid flow region enlarged and moved in the direction of the gas flow during its descent. Both displacement and dispersion of the liquid flow augmented with increase of gas flow rate and liquid flow rate.
    A mathematical model of the liquid dropping flow was developed, in which the packed bed is simulated with a flow network whose unit mesh size corresponds to a particle diameter. Relations of superficial velocity of gas and liquid to transit probability and turbulent diffusion ratio of liquid drops which predominate their transit paths were determined on the basis of the experimental results.
    The results of the mathematical simulation were in good agreement with the experimental results.
  • Phosphorus Distribution between Mn-Si Melts and CaO-SiO2-MnO-CaF2 Slags

    pp. 1931-1938

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    Experiments were carried out to investigate the equilibrium distribution ratio of phosphorus (LP) between CaO-SiO2-MnO-CaF2 melts and carbon saturated Mn-Si alloy as a function of oxygen partial pressure, alloy and slag compositions at 1300°C. The results demonstrate that LP increases with increasing the basicity of slag, silicon concentration and oxygen partial pressure. In order to understand quantitatively the effect of silicon concentration on LP, the phosphorus activity coefficient in Mn-Si alloys was measured and the interaction parameter, εPSi in Mn at 1300°C was found to be 10.7.
    The CaO equivalent of MnO for dephosphorization was found to be 0.4 ± 0.1 in terms of weight percent.
    By measuring the manganese activity in Mn-Si alloy, the activity coefficient of MnO in the range of the present slag composition was calculated to be in the range of 0.42 to 0.62.
    The critical oxygen partial pressure between the stability of phosphate and phosphide in this slag system was about 10-18.4 atm at 1300°C.
    x

    Readers Who Read This Article Also Read

    1. Oxidation Dephosphorising Method of Molten Steel Containing Chromium Tetsu-to-Hagané Vol.74(1988), No.2
    2. Thermodynamics of Phosphate and Phosphide in BaO-BaF2 Melts Tetsu-to-Hagané Vol.71(1985), No.6
  • Dephosphorization and Desulfurization Equilibria between Liquid Iron Containing Cr and BaO-Cr2O3-FetO Slags

    pp. 1939-1945

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    Phosphorus and sulfur distribution between MgO-saturated BaO-Cr2O3-FetO (-BaF2) slags and liquid iron containing Cr ([%Cr]= 016) has been measured in the temperature range from 1550 to 1650°C. The refining limit of dephosphorization in steel containing Cr and hot metal was discussed by using the values for phosphate capacity CP (=(%P)/[aP·aO5/2]). Thermodynamic analysis indicates that the phosphorus partition ratio increases with carbon up to a critical value and decreases beyond that.
  • Effects of Rotation and Electro-magnetic Stirring on Penetration of Hollow Ingots in ESR Core Remelting Process

    pp. 1946-1953

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    The ESR core remelting process has been attractive for manufacturing of large monoblock ingots or composite ingots, but it has not been put into a practical use. The reason may be that the peripheral penetration depth of a shell was not uniform.
    In this paper, to overcome this problem, effects of shell rotation and electro-magnetic stirring on the shell penetration were studied. The results were as follows.
    (1) The periphral penetration depth was made much uniform by applying shell rotation or magnetic stirring.
    (2) Under the same remelting conditions, the penetration depth became smaller by applying rotation or magnetic stirring.
    (3) Rotation or magnetic stirring resulted in increase of the electrode melting rate.
    (4) By applying the phenomena described in (3) and by combining the shell rotation speed appropriately, the shell penetration depth was made almost uniform both along the peripheral direction and longitudinal direction.
  • The Mechanism of Dust Generation in Converter

    pp. 1954-1961

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    A study was made on the mechanism of dust generation by the investigation of dust behavior in top and bottom blowing converter. The results are summarized as follows:
    (1) Dust in converter is formed by the condensation of fume on the surface of bubble bursting particle.
    (2) Weight ratio of bubble bursting particle included in total weight of dust is larger in early stage of blowing and decreases with blowing time. Therefore it is considered to be effective for decreasing dust weight to form slag as early as possible in the blowing period and to decrease the temperature of hot spot area by oxygen jet in the middle and final stage of blowing.
  • Development of Ladle Arc Refining Process

    pp. 1962-1969

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    In order to meet the recent demands for higher quality steels and rationalization in manufacturing processes, the ladle refining technology has advanced remarkably.
    Kakogawa works installed the ladle refining furnace (LF) in January 1986 for the stable production of high-grade steel and to decrease the thermal burden in the LD converter. This equipment is capable of arc heating, strong top agitation, and slag skimming. Furthermore, combining this equipment with the existing hot metal pretreatment and RH degassing equipment has made possible the production of low phosphorous and sulfur content steel.
    Also, the production technology of clean steels such as steel tire-cord has been established by making the shape control of non-metallic inclusions through the ladle slag refining.
  • Mechanical and Thermal Characteristics in Cold Rolling by Using Drawing Type Rolling Mill

    pp. 1970-1977

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    Mechanical and thermal characteristics in cold rolling have been evaluated as the first step of lubrication study. Through experimental and theoretical works, the following conclusions have been obtained.
    (1) Pressure distribution was calculated by using the theory of differential work-roll rolling. The relation between the neutralpoint in the lower work roll and the rolling torque was obtained. Based on the computed results, the applicability of the equation of a practical friction coefficient μ=τ/(R·P) was made clear.
    (2) With respect to the temperature rise of strip and roll surface, the measured data by contact thermocouple method was in good agreement with the calculated results by plastic and frictional works in the absence of heat transfer between roll and strip.
    (3) Multi-thermocouple method was developed to investigate the temperature distribution in the roll. With the aid of boundary element method, this sensor could provide reliable estimation of temperature rise at the interface between roll and strip.
  • On the Ability of Simulation Testing Machine for Lubricant in Cold Rolling Developed Newly

    pp. 1978-1985

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    The purpose of this study is to obtain a better understanding of the possibility of using the newly developed simulation testing machine by the author in order to evaluate the lubricity and the anti-seizure property of lubricant in cold sheet rolling. The friction coefficient used for evaluating the lubricity of lubricant is given by,
    μ= T/P
    where T is the back tension, P the rolling load and α the contact angle. It is possible to evaluate the friction coefficient in operation mill by the simulation testing machine, based on the evaluation of the friction coefficients obtained by the different tesing machines.
    The surface of the upper roll and the rolled workpiece were inspected after rolling with emulsion oil of tallow. In the simulation tesing machine, the friction pick up could be reproduced. It was confirmed that the friction pick up was the same as that occured in actual mill. The anti-seizure property of lubricant could be simulated from the limitation lines of friction pick up obtained by the simulation testig machine.
  • Systematic Evalation of Effect of the Lubricity on Composition and Additive in Mineral-base Oils in Cold Sheet Rolling

    pp. 1986-1992

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    The purposes of the study are to evaluate the lubricity and the anti-seisure property of O/W emulsion and to examine the effect of various additives and saponfication value on these properties in cold sheet rolling, using the simulation testing machine developed by the present auther.
    The lubricity is evaluated by the coefficient of friction (μ= T/P+α) and anti-seisure property is evaluated by maximum roll speed or maximum reduction in a non-metal pick up region.
    The results obtained are as follows: (1) In rolling oils with an oiliness agent, the rolling oil with stearic acid is excellent in the lubricity and the anti-seisure property.
    (2) In rolling oils with a EP-agent, the rolling oil with dialkylphosphite is excellent in the lubricity and anti-seisure property. (3) In rolling oils mixed mineral oil with fat, the break in the curves of coefficient of friction versus saponification value is recognized.
  • Development of High-Cr Roll for Hot Strip Mill with Superior Resistance to Surface Deterioration and to Spalling of Outer Shell

    pp. 1993-2000

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    In recent years, High-Cr cast iron work rolls have been used at front finishing stands in many hot strip mills instead of Adamite rolls.
    We researched and investigated heat treatment to improve the resistance to surface deterioration and centrifugal casting to improve the resistance to spalling of outer shell.
    According to the above, our findings are as follows:
    In case of 2.8%C-18%Cr roll,
    (1) Precipitation of secondary carbide with high wear resistance and martensitization of matrix with high hardness are obtained by destabilizing heat treatment at more than 1000°C.
    (2) Regarding to melting bond structure of roll with High-Cr outer shell and spheroidal graphite cast iron core, the roll cast with intermediate layer between outer shell and inner core is sounder than the conventional roll.
    This intermediate layer improve the mechanical property and minimize the residual stress.
    (3) This type of High-Cr rolls have been used in the actual rolling and we found the clear effects of improved resistance to surface deterioration and to spalling of outer shell.
  • Effect of Molybdenum Content on Creep-rupture Strength and Toughness of 9% Chromium Ferritic Heat Resisting Steels Containing V and Nb

    pp. 2001-2008

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    The effect of molybdenum content on creep-rupture properties and room-temperature toughness of high chromium ferritic heat resisting steels was investigated. Molybdenum content was varied from 1 to 2 wt%. In order to obtain 9Cr-Mo-V-Nb ferritic steels with both high creep-rupture strength and superior toughness, the amount of delta ferrite was controlled below 25%, and the optimum tempering condition and mechanical properties after simulated welding have been investigated. The influence of molybdenum content on creep-rupture strength and Charpy absorbed energy was investigated with respect to the ratio of delta ferrite to tempered martensite, the precipitates, and the microstructures.
    Charpy absorbed energy of the 0.05C-9Cr-1Mo-0.15V-0.05Nb steel tempered at 800°C and then heated at 600 650°C for 104 h was as high as 20 30 kgf-m. By contrast, Charpy absorbed energy of 0.05C-9Cr-2Mo-0.15V-0.05Nb steel was reduced to about 4 kgf-m after heating at 600 650°C for 104 h. It is considered that the steel of 1Mo shows superior toughness because of its low carbon content and a single phase of martensite. It was concluded that combination of superior creep-rupture strength and toughness can be obtained by optimum heat treatment for the 9Cr-1Mo-V-Nb steel containing 0.05 wt%C.
  • Creep-induced Grain Boundary Damage and Creep Properties of SUS 304

    pp. 2009-2016

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    For the purpose of evaluating creep damage, systematic study of creep damage was performed, particularly for grain boundary creep damages by SEM observation and density change measurements. Three different kinds of grain boundary creep damages leading to creep fracture were observed. They are cracks formed at triple points at higher loading stress, grain boundary cavities at medium stress and cracks at sigma/austenite interface at lower stress. Both the grain boundary cavities and the cracks at sigma/austenite interface comence to form at comparatively low creep strain (0.1-0.6%) at the steady-state creep stage (t/tr:0.2-0.4).The increasing feature of cavity volume with creep time corresponds to the creep curves. Precipitation of AIN associated with sigma phase on grain boundary leads to early formation of the cracks at their interface. In this case, the volume of the cracks increases considerably in the accelerating creep stage and constitutes a main component of the creep strain. The rapid increase in the volume causes the transition from the steady-state to the accelerating creep stage.
  • Effect of Heat Treatment on Fracture Toughness of 0.85%C-3% Cr Roll Steel

    pp. 2017-2024

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    Fracture process of band-type spalling which often occurs on the barrel surface of cold rolling work rolls, is known to be controlled by the fracture toughness KIC of the roll steel in many cases. In order to study the factors improving the KIC value, fracture toughness tests were carried out on the test pieces which were taken from the actual roll of 0.85%C-3%Cr steel, and were quenched and tempered in several conditions.
    The main results obtained are as follows:
    (1) KIC values were highly dependent on the hardness. In the same hardness level, the higher the austenitizing temperature was, the higher the KIC value became, and as for the subzero treatment, non-subzero steel gave higher KIC values.
    (2) In comparison between fully quenched steel and slack quenched steel containing some lower bainite in its structure, the latter gave higher KIC values.
  • Effect of Co, Mo and Ti Contents on Mechanical Properties of 18Ni Maraging Steels

    pp. 2025-2032

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    Effects of alloy composition on the mechanical properties of 18Ni-Co-Mo-Ti-Al maraging steels have been studied by means of tensile tests, optical and electron microscopy, and fractography, in order to examine the possibility of saving Co and Mo contents without sacrifice of the mechanical properties.
    It was found that Co does not play an important role in precipitation hardening when the addition of Mo is less than 2%, while an addition of above 2% Mo is indispensable to prevent the formation of coarse precipitates of Ni3Ti along prior austenite grain boundaries, and to obtain a uniform distribution of the fine precipitates. Increase in Mo contents beyond 5% is detrimental for reduction of area and notch tensile strength because of the presence of undissolved coarse particles of Fe2Mo.
    Ti is the most important element for precipitation hardening the Co free maraging steel.
    As a result the 18Ni-2Mo-2Ti-0.1Al maraging steel showed mechanical properties equivalent to the conventional 18Ni maraging steel.
    x

    Readers Who Read This Article Also Read

    1. Strengthening and Toughening of Maraging Steel of Over 280 kg/mm2 Tetsu-to-Hagané Vol.64(1978), No.5
    2. Grain Size Dependence of Fracture Toughness in an Ultrahigh Strength Maraging Steel Tetsu-to-Hagané Vol.69(1983), No.1
  • Estimation and Measurement for pH of High Pressure and High Temperature Sour Environments

    pp. 2033-2040

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    A new technique for estimating the pH of concentrated aqueous solutions in equilibrium with high pressure H2S and CO2 at elevated temperature was proposed. Based on the thermodynamic investigation for solution properties, the following equation was obtained.
    pH=-logγH + {(K1, HKH, HPH2S2±H2S)1/2 + (K1, CKH, CPCO22±CO2)1/2}
    The physico-chemical parameters in the equation were calculated by PBILC (Principle of Balance of Identical Like Charges) proposed by COBBLE et al. or assumed to be identical with those for HCl + NaCl aqueous solutions. The calculation of the pH of high temperature and high pressure sour environments was enabled by using this equation.
    A Nb-doped TiO2 semiconductor electrode of n-type was well applied to measure the pH of the environments and underwent no interference with NaCl, H2S and CO2. The measured pH values agreed well with those estimated by the newly proposed technique at the temperature up to 473 K and at partial pressures of H2S and CO2 up to 4 MPa. It was ascertained by pH measurements for HCl + NaCl aqueous solutions at elevated temperatures that the assumption made for physicochemical parameters in the pH estimation was valid.
  • Determination of the Nitrogen as Nitride in Steel by Alkali Fusion-Coulometric Titration Method

    pp. 2041-2046

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    The alkali fusion-coulometric titration method has been studied for the determination of nitrogen as nitride in steel.
    (1) The procedure, which has been established by using nitride reagent, is as follows.
    a) The nitride reagent is fused by molten alkali (450°C) containing water vapor.
    b) Nitrogen in the reagent is extracted as ammonia with carrier gas (Ar) and the ammonia is determined by the coulometric titration method.
    All nitrides excepting Cr2N, ZrN can be determined by this method.
    (2) This method was applied for the determination of nitrogen in the residues extracted by 15%I2-methanol decomposition method for steel.
    The results are as follows.
    a) The determination is completed within 20min.
    b) Nitrogen blank of this method is very small. (0-2μg)
    c) The trace amount of nitrogen as nitride can be determined with excellent precision. (N=7ppm C.V.=45%)
  • MITのMaterials Scienceにおける教育と研究

    pp. 2047-2049

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  • 風が吹けば容器屋がもうかる?/魚釣りと新素材

    pp. 2057-2057,2060

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