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

Tetsu-to-Hagané Vol. 68 (1982), No. 8

  • Continuous Coil Coating Line-The State of the Art

    pp. 895-901

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  • The Present and a View on the Production of Fibre Reinforced Metal Composite Materials

    pp. 902-910

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  • Tendencies of Bolt Steel

    pp. 911-915

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  • Present Status on the Structural Determination of Molten Ferrous Alloys and Ferrous Slags (2)

    pp. 916-922

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  • Metallic Resources Series-Zinc-

    pp. 923-929

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  • Correlation of Kinetic Parameters of High Pressure Reduction of Iron Ore Examined with φ8mm and φ60mm Fluidized Bed Reactor

    pp. 930-935

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    Fundamental data of size effect of a high pressure reactor for iron are reduction are important for commercialization of the process.
    In this paper, the correlation between kinetic parameters of pulverized iron are reduction with a microreactor (8mm in diameter) and with a fluidized bed reactor (60mm in diameter) is presented. The effect of the reduction temperature, hydrogen pressure, hydrogen flow rate and sample weight on the reduction rate are discussed on the basis of a first order reaction: In1/1-f=k·t, where f is fractional reduction, k rate parameter, and t time.
    The results indicated that reduction rate was much more influenced by hydrogen flow rate than by hydrogen pressure. The reduction rate parameters obtained with the fluidized bed reactor were lower than those with the microreactor by a factor of 0.40.6 at the same gas/ore ratio.
  • Dynamics of Burden Materials and Gas Flow in the Blast Furnace

    pp. 936-945

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    Descending behavior of burden materials and distribution of stresses in the blast furnace were studied by the use of a reduced-scale model.
    Appearance of burden descent is, macroscopically, like a plug flow at upper part of the belly and a funnel flow at the bosh. However, at the peripheral region close to the wall, a mixed zone of are and coke is formed and its dimension depends on the shaft angle and the shape factor of burden.
    Stress field is an active state in the shaft and is a passive state in the bosh. At the belly in a transitional state, the horizontal stress develops markedly.
    Particles flow into the raceway passing through a narrow part above the tuyere nose. A profile of dead coke zone estimated by a theoretical consideration of the stress field of passive state shows a good agreement with the experimental results.
    The gas permeability of a moving bed with a funnel flow is higher than that of fixed bed because of the increase in void fraction.
    x

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  • Solubility of Nitrogen in Liquid Iron and Iron Alloys Containing the Group VIa Elements

    pp. 946-955

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    The solubility of nitrogen in liquid iron was studied at temperature from 1580° to 1730°C by both the SIEVERTS' method and a sampling method. By improving the methods, the results obtained in the temperature range agreed with each other within the experimental errors. However, from the viewpoint of the temperature dependence of the solubility, the results obtained by the sampling method is more reliable on the solubility of nitrogen in liquid iron.
    The results obtained in liquid iron by the sampling method is expressed as follows:
    log K(_??_[%N]/√PN2)=-518/T-1.063±0.0004
    ΔG°=237+4.85T±0.002T (cal/g-atm).
    The study was extended to the iron alloys containing the group VIa elements at 1580°C by the sampling method. Though all elements of the group VIa were expected to decrease the solubility of nitrogen, oxygen showed the opposite effect on the solubility. The results obtained are expressed by log fjN as follows:
    log fON=-0.12[%O]<0.12%O, log fSN=0.007[%S]<4%S
    log fSeN=0.006[%Se]<4%Se, log fTeN=0.070[%Te]<0.6%Te.
  • Reduction of Molten Iron Oxide and FeO Bearing Slag with H2-Ar Plasma

    pp. 956-964

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    Reduction of molten iron oxide and FeO bearing slags with hydrogen-argon plasma was studied using a water-cooled Cu crucible. The weight of melts was 25 to 75 g, the flow rate of mixture gas was 20 l/min and DC electric power was 8.3 kW. Results obtained were as follows.
    (1) The reduction of molten iron oxides proceeds linearly with time and the reaction rate is proportional to the partial pressure of atomic hydrogen, PH. Therefore, it is considered that the rate determining step is the chemical reaction with hydrogen atoms formed by the thermal dissociation of hydrogen molecules in the plasma gas.
    (2) The rate of reduction of FeO bearing slags is lower than that of molten iron oxide and is proportional to the FeO concentration in slag. It is presumed that the reduction rate is controlled by both the chemical reaction with dissociated hydrogen at the interface and the mass transport across the boundary film of the molten slag.
    (3) The reduction of molten iron oxide and FeO bearing slag with hydrogen-argon plasma takes place only on the surface of the cavity formed by the momentum of plasma gas jet.
  • Analysis of Non-flatness of Hot Strip after Cooling

    pp. 965-973

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    To analyze non-flatness caused by the edge wave of hot strip after cooling, a numerical method for the prediction of temperature and thermal stress has been developed by taking phase transformation into consideration. It is confirmed that temperatures during cooling and residual stresses calculated by the present method agree well with the measured ones. On the bases of the present method, the occurrence of the edge wave in thin and wide hot strip (3.24×2173mm) has been studied.
    The results obtained are as follows;
    (1) The edge wave occurs when compressive residual stress at edge part becomes greater than the critical buckling stress.
    (2) The residual stress becomes low when the distributions of finishing temperature and of cooling rate after rolling in transverse direction of hot strip are small. Water cooling of hot strip at later stage of run-out table and high coiling temperature are benificial to decrease the residual stress.
    (3) The most effective measures of preventing the edge wave formation is to cool strip uniformly in transverse direction by controlling the distribution of water supply after rolling.
  • Effect of Water Flow Rate on Cooling Capacity of Laminar Flow for Hot Steel Plate

    pp. 974-981

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    An experiment to examine the cooling process of a hot steel plate by the laminar water flow was carried out and the effect of the water flow rate on the cooling capacity was analytically discussed on the basis of the experimental results. The main points clarified here are as follows:
    (1) The vertical distance between a nozzle exit and a cooled plate surface has almost no significant effect on the cooling capacity.
    (2) The increase of the water flow rate results in the improvement of the cooling capacity. However, both the cooling capacity and the growth in black zone become saturated with the increase of the flow rate.
    (3) The saturation of the cooling capacity is considered to be correlative to that of the growth in the black zone diameter.
  • Precipitation Behavior of Nitride and Its Effect on Creep Properties of Carbon Steel

    pp. 982-988

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    Precipitation process of nitride and its effect on creep properties of a carbon steel for high temperature use were studied. A hydrogen extraction method was used for the determination of mobile nitrogen concentration at creep testing temperatures. The results obtained are as follows;
    1) It is confirmed that the method is effective to extract mobile nitrogen which has close relationship with creep properties.
    2) From isothermal annealing curves of mobile nitrogen as a function of time, the order of chemical reaction, γ in -df/dt=fγk (f: fraction of nitrogen unprecipitated, t: time, k: reaction rate constant) is found to be about two and apparent activation energy for precipitation of nitride coincides with that of diffusion of silicon in α-iron. This suggests that the precipitation is controlled by diffusion of silicon.
    3) The creep curves consist of two steady-state stages. Transition times from the first to the second correspond with marked reductions in mobile nitrogen. This correspondence and transmission electron microscope observation indicate that the end of fresh precipitation of nitride on dislocation may be primarily responsible for the increase of creep rate and the transition.
  • Study on the Propagating Shear Fracture of Line Pipes by the Partial-gas Burst Test

    pp. 989-997

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    In order to evaluate the crack arrestability of line pipes to the propagating shear fracture, the partialgas burst test was carried out on many line pipes of varied notch ductility, sizes and test conditions. A method to estimate the fracture energy of test pipes was established and the required notch ductility to line pipes against the propagating shear fracture of actual pipelines was introduced.
  • Evaluation of Brittle Fracture Strength of Circumferentially Notched Round Bar under Axial Load

    pp. 998-1007

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    The brittle fracture initiation characteristics of circumferentially notched round bar, CNRB, subjected to the axial load have been investigated theoretically and experimentally using JIS-SCM 440 and SMn 443 steel bars. The curve showing the relationship between net section stress at fracture, a and temperature, T, has two regions macroscopically. One is called Region I where σn, F diminishes with decreasing T, and the other is Region II where σn, F is nearly constant irrespectively of T. The effect of diameter, D, and notch depth, c, on σn, F in Region I can be evaluated on the basis of the linear elastic fracture mechanics. σn, F at the transition temperature from Region I to II, σn, TR, is a little higher than the general yieding stress level of CNRB analyzed with the aid of finite element method. σn, TRYY: yield stress) shows little change with D and strength of materials, and rises with an increase in relative notch depth, 2c/D. σn, F in Region II can be approximately estimated from the experimental equation relating between σn, TRY and 2c/D. Finally, a procedure is proposed to evaluate the brittle fracture strength of CNRB subjected to axial load.
  • Precipitation in the Austenite and Its Effect on Strength and Toughness in 10Ni-18Co-14Mo Maraging Steel

    pp. 1008-1015

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    When a thermomechanical treatment (TMT) was applied to a 350 kgf/mm2 grade 10Ni-18Co-14Mo maraging steel containing a large amount of Mo, the austenite grain size was refined to below 10μm, but precipitation in the austenite occurred during TMT, leading to a detrimental effect on toughness before aging. This study was carried out to show the precipitation characteristics during TMT and accelerated precipitation behavior by hot-working, and then to investigate the relationship between the change in microstructure and mechanical properties. To evaluate the effect of hot-working on precipitation behavior, a continuous cooling treatment without working (CCT) was also carried out.
    The results are as follows:
    1) Precipitation in the austenite did not occur during CCT with a cooling rate of 4.2°C/s corresponding to that of TMT. 2) When the cooling rate during CCT was reduced to 0.42°C/s, precipitation occured along the grain boundaries in the 10Ni-18Co-14Mo steel. 3) When applying the TMT, precipitation occurred after sixth pass and with further increase in pass number the amount of precipitates increased greatly. 4) These precipitates were identified as the intermetallic compound of molybdenum and titanium sulfide. 5) Toughness before aging was drastically reduced by the presence of these precipitates. 6) It is difficult to detect the detrimental effect of the precipitates from the change of tensile properties and fracture toughness after aging.
    x

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  • Grain Growth in Dual-Phase Steel

    pp. 1016-1023

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    The grain growth characteristics of dual-phase steels have been investigated using 3%Si-0.3%Cr-0.020.13%C steels which are composed of α- and γ-phases at 300°C.
    The grain growth in single-phase region proceeds by grain boundary migration, and the relation between mean radius r and annealing time t is described as follows,
    (r)2-(r0)2=k2·t……(1)
    In the case of dual-phase steels, the grain growth is in need of diffusion of alloying elements, because the chemical composition of α- and γ-phases differs each other. The grains of the minor phase grow slowly in a mode of Ostwald ripening, while the grain boundaries in the major phase migrate under a restriction of pinning by the minor phase grains. It follows as a consequence that the grains of both the phases grow slowly, obeying the following equations,
    (r)3-(r0)3=k3·t……(2)
    (r)4-(r0)4=k4·t……(3)
    In the α-rich dual-phase steels, the growth rate is controlled by volume-diffusion in the α-phase, and the growth law is expressed by eq. (2). In the γ-rich dual-phase steels, however, boundary-diffusion is predominant than volume-diffusion in the γ-phase, and the growth law is expressed by eq. (3).
  • Oxide Dispersion Strengthened Nickel and Nichrome by Means of the Spray-dispersion Method

    pp. 1024-1031

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    WO3, Al2O3, ZrO2, Y2O3 or ThO2-dispersed nickel and nichrome were produced by the "Spray-Dispersion Method", and their mechanical properties were studied. The main results obtained are summarized as follows:
    1) The addition of 1.6 pct. niobium as a "controlling element" was effective in lowering the oxide particle size in nickel. The mean diameter of ThO2 particles in nichel containing 1.6 pct. niobium reached to about 60 nm.
    2) 20 pct. of chromium in nickel also decreased the oxide particle size, and the addition of 0.8 pct. niobium in nickel-20 pct. chromium alloy decreased the mean diameter of Al2O3 particles to 79 nm.
    3) Tensile strengths at room temperature of oxide spray-dispersed nickels increased with the volume fraction of oxide particles and their increments were maintained even at 1073 K. In the case of oxide spray-dispersed nichromes, their incroments of tensile strength at room temperature were small, but those were multiplied at higher temperature.
    4) The fine oxide particles contributed to an increase of creep rupture strength, and this tendency became more pronounced toward longer time. 1273 K-1000 h creep rupture strength of 2 vol pct. ThO2 spray-dispersed nickel and 3.8 vol pct. Al2O3 spray-dispersed nichrome, for instance, were 47 Mpa and 19 Mpa, respectively.
    5) The oxidation resistance at high temperature of oxide spray-dispersed nickel and nichrome was improved as compared with non-dispersed ones.
    From these results, the oxide dispersion strengthened nickel-base heat-resisting alloy has been able to produce by the "Spray-Dispersion Method".
  • JIC Fracture Toughness of Nuclear Reactor Pressure Vessel Steels in Transition and Upper Shelf Regions

    pp. 1032-1039

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    The JIC fracture toughness of the nuclear reactor pressure vessel steel and its heat-treated steel, which wa s simulated to one embrittled by the neutron irradiation, has been evaluated by the electrical potential method in the range from transition to upper shelf regions. The results obtained are summarized as follows:
    (1) The difference of transition temperatures between as received and heat treated steels at 41 J of absorbed energy in Charpy V-notch impact (CVN) test is nearly the same as the temperature shift of 100 MPa√m level in the fracture toughness, regardless of the specimen size at the transition region.
    (2) At upper shelf region, the percent decrease of the fracture toughness is much more than that of the CVN absorbed energy.
    (3) From the fact mentioned above, it is proposed to use two test methods as the new surveillance test practice. One is the CVN test for the transition region, and another is the JIC fracture toughness test for the upper shelf region.
    (4) The electrical potential method can be the candidate technique to detect the onset of crack initiation for the irradiated material in the JIC test from the view point of less specimen and technical difficulty.
  • Application of D. C. Electrical Potential Method for Measurement of J-R Curve by a Single Specimen

    pp. 1040-1045

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    The fracture toughness tests at temperatures from -60°C to 100°C are conducted to develop the new method for the generation of the fracture resistance curve (J-R curve) by a single specimen. The three-point bend specimens with several configurations made of four kinds of nuclear reactor pressure vessel steels are used and the crack extention is measured by the d. c. electrical potential method during testing. From the results obtained, the following conclusions can be drawn:
    (1) The relation between the potential difference (V0V)/V0 and the ratio of crack extention (a0a)/a0 is a very little bit scattered regardless of the specimen size, type of steels or testing temperatures, when the specimen configurations are kept as the similar figure. Where, a0, Δa, V0 and ΔV respectively denote the initial crack length, the amount of crack extention, the initial potential and the amount of potential difference. This relation is named here as the master curve.
    (2) Then, the J-Δa relation (J-R curve) can be developed using the load-deflection record by a single specimen through the above mentioned master curve.
  • Microstructural Alteration and Flaking due to Rolling Contact

    pp. 1046-1053

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    It is well known that microstructural alteration such as a dark etching constituent (D. E. C.) and a white etching constituent (W. E. C.) occurs on the area adjacent to the rolling surface due to rolling contact fatigue. Specimens taken from high carbon chromium bearing steel were fatigue tested in the thrust type rolling fatigue testing machine for these experiments to investigate into microstructural alteration.
    The D. E. C., W. E. C. and plate-like carbides were observed among which the plate-like carbides were found out most closely related to the flakings in the specimens for the thrust type tester and observed under approx. 80% of the flakings. Their hardness was up to 1300 of HV. Some plate-like carbides formed perpendicular both to the rolling surface and to a tangent to the rolling track with the plate surfaces and others formed parallel to the rolling surface.
    The plate-like carbides formed during fatigue testing had higher carbon concentration than that of the matrix, which indicates a considerable amount of carbon diffused to generate the plate-like carbides during the test.
  • Effect of Nickel on Strengthening and Toughening of 13% Cr Cast Stainless Steel by Quenching from (α+γ) Temperature Range

    pp. 1054-1062

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    Strengthening and toughening of a 13%Cr cast stainless steel added with Ni by heat treatment is studied. In this work, low temperature quenching treatment (L) from (α+γ) range, in the intermediate stage between usual quenching and tempering, is applied. Then, the effects of Ni content and retained austenite on the low temperature toughness are investigated. The heat treated samples are compared by V-notched Charpy impact test, dynamic fracture toughness test and static tensile test.
    It is shown that the steel with higher Ni content has the better low temperature toughess, and that the L treatment improves the toughness of the 13%Cr cast steel. Improvement of the low temperature toughness due to the L treatment becomes larger in the higher Ni content steel. It is also shown that the stable and fine retained austenite improves the toughness and the ductility at low temperature. This may be due to the transformation induced plasticity of the retained austenite.
  • 抄録

    pp. 1069-1072

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  • 曲がりやすい鉄と鋼/木を見て森を見ない!

    pp. 1072-1072,1126

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