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

Tetsu-to-Hagané Vol. 72 (1986), No. 10

  • Production of Pure Copper Castings, such as Tuyere and Lancenozzle, Used in the Iron and Steel Industry

    pp. 1481-1487

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  • Recent Trend of Warm Forging Technology

    pp. 1488-1497

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  • Mechanics of Fracture of Amorphous Metallic Materials

    pp. 1498-1506

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  • Laser Surface Modifications

    pp. 1507-1512

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  • Promotion of the Carbothermic Reduction of Chromium Ore by the Addition of Borates

    pp. 1513-1520

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    The effect of sodium and calcium salts on the carbothermic reduction of chromium ores has been studied. Among the additives such as chlorides, carbonates, fluorides and borates, the borates was found to have the strongest promoting effect on the reduction.
    The rate of reduction increased remarkably with an increase in the amount of added borates, but their addition of more than 1 wt% was less effective. The effect was much more significant in the reduction step of MgCr2O4 component of chromite than that of the FeCr2O4 component. It was found that the borates facilitated the diffusion of ionic species particularly in Al2O3-containing chromite and the grain growth of metal produced.
    Na2B4O7 slightly promoted the Boudouard reaction, but CaB4O7 retarded it. Based on the effect of CaB4O7, it was examined which of the Boudouard reaction or the reduction of chromite with CO gas mainly controlled the carbothermic reduction of synthetic chromites and chromium ores. The results were in good agreement with those from the kinetic analyses in the previous paper.
  • Characteristics of Reduction and Oxidization Cyclic Process by Use of αFe2O3 Medium

    pp. 1521-1528

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    The reduction of metallic oxides with the reducing gas and recyclic use of the metallic oxides were investigated as an elemental study of looping combustion process newly developed for efficient utilization of thermal energy(i.e., the three stages of combustion: steam-reforming of fuel at low temperature, reduction of metallic oxides at low temperature by the reformed product, and oxidization of metal or partially reduced metallic oxides at high temperature).
    αhematite(Fe2O3) was chosen as a metallic oxide. The reduction and oxidization rates were measured at various temperatures. Hydrogen-water vapor mixtures and air were used in the reduction and oxidization processes, respectively.
    In the case of Fe2O3_??_Fe cycle, the oxidization rate remarkably decreased with the number of reduction and oxidization repetitions at 1 173K, while the reduction rate was unchanged.
    In the case of Fe2O3_??_Fe1-yO cycle, both reduction and oxidization rates were unchanged under repetitions of reduction at low temperature(973K) and oxidization at high temperature(1 253K) as well as at the same temperature as that for Fe2O3_??_Fe cycle(1 173K).
    It was found that αhematite has a bright prospect as a reaction medium at reduction and oxidization stages in the looping combustion process.
  • Reduction Behavior of Sinter under Blast Furnace Conditions

    pp. 1529-1536

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    The authors developed a blast furnace inner-reaction simulator(BIS) which can simulate the behavior of reducing, softening, and melting of iron bearing materials in a blast furnace. BIS is an advanced equipment of the BORIS furnace developed by IRSID. The reduction behavior of sinter under the blast furnace conditions was investigated by BIS on two typical temperature profiles ofen found in the blast furnace, i.e. profile A having a considerably long thermal reserve zone of 1 000°C and profile B having two stage thermal reserve zones of 600°C and 1 000°C.
    The reduction degradation behavior, reduction behavior, the change of the pore structure in the reduction process, and the effect of the temperature profile on them were clarified.
    The feature of reduction behavior in the blast furnace is that the reduction degree is at a low value of 30% at the end of the thermal reserve zone of 1 000°C and that the reduction rapidly proceeds in the high temperature range below the thermal reserve zone. This reduction behavior indicates that the reducibility in the high temperature range is important as the reduction property of sinter.
  • Combustion Rate of Coke at Different Existing States Prepared by Fine Alumina

    pp. 1537-1544

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    The combustion rate of coke in the course of iron are sintering is one of the important factors which govern the temperature pattern in the sintering bed and resulting properties of the produced sinter in the blast furnace. It has been pointed out by Hida et al. that there are some kinds of existing states of coke in the sinter raw mixture, such as S, C and P types, and the existing states remarkably influenced the rate of coke combustion.
    In this study, some quasi-granules, which were modeled S and P types, were prepared by using coke and alumina particles. The effects of melt formation and reduction and reoxidation of iron oxide, which occurred at the shell layer of the granules, on the coke combustion can be neglected. The combustion rates of coke in the bed packed with dense alumina spheres were measured by a sintering simulator system. On the other hand, a mathematical model for these coke combustions was developed by the application of the unreacted-core model. The calculated results of the combustion rates were compared with measured ones, in order to derive the combustion equations of the coke. The computed results and measured data, such as combustion rates and bed-temperatures, agreed fairly well at various preheating temperatures.
  • Development of Prediction System for Unusual State in Blast Furnace

    pp. 1545-1551

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    For the efficient and stable blast furnace operation, the FLAG (Fine Lookout of Abnormal Gradient) system which can predict the unusual conditions at its earlier stage and direct the proper countermeasure, has been developed in NKK Fukuyama works.
    This system is included in the operation control computer system at No.2 blast furnace and has the following features.
    (1) Prediction indices ; these can detect the distinctive patterns of the sensor information which correspond to the process of the unusual states.
    (2) Usage of voice annunciator for the direction of the action ; It makes possible to deal with the abrupt change of the furnace condition.
    (3) Determination system for the threshold value of judgement ; It can maintain the prediction accuracy and can make it simple to introduce this system to the other blast furnace.
    This system has been contributing to stabilize the blast furnace operation.
  • Dispersion of Gas Injected into Liquid Metal

    pp. 1552-1559

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    The measurement of the distribution of gas holdup in nitrogen injection into mercury was made by using an electroresistivity probe technique and high speed data processing system. On the basis of the measurement near an orifice or nozzle, two regimes of gas flow are distinguished: bubbling and jetting. In the jetting regime, the gas jet issuing from the tuyere into mercury becomes very thin and rises rapidly. The radial distribution of gas holdup expands with increasing vertical distance due to entrainment of the surrounding liquid. The transition of flow behavior from jet to plume occurs about 3040 mm above the tuyere under the present experimental conditions.The effect of bath depth on the gas holdup is discussed.
    The upward flow of gas-liquid mixture in the plume zone is analyzed on the basis of macroscopic mass and momentum balances. The calculated results of plume radius and gas holdup are compared with the experimental results. It is presumed that the circulating flow in the bath affects the dispersion of bubbles.
  • The Rate of Oxidation of Phosphorus and Silicon in Liquid Iron by Molten Slags

    pp. 1560-1566

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    The rates of oxidation of phosphorus and silicon in liquid iron by steelmaking-type slags were examined at temperatures from 1 540 to 1 670°C in an induction furnace. The results obtained were analyzed on the basis of a coupled reaction model.
    The results showed that the silicon in the iron was rapidly oxidized after the slag addition, and the content of silicon decreased below 0.01% within one minute. A part of phosphorus was oxidized together with the oxidation of silicon. Thereafter, the dephosphorization of liquid iron occurred gradually.
    The kinetic analysis showed that the value of apparent mass transfer coefficient in the slag, ksρs, , was calculated to be 0.0027 to 0.0061 g/cm2s when the value in the liquid iron, kmρm was given as 0.36 to 0.47 g/cm2s. When the values of overall mass transfer coefficients, KP and KSi, were calculated from the above data by the equations (5) and (7), respectively, it was found that the silicon transfer was controlled mainly by the diffusion step in the metal, while the transport in the slag played an important role for the phosphorus transfer.
  • Superplastic Behaviour of Powder-Consolidated and Rolled Mod.IN-100 Sheet

    pp. 1567-1574

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    The powder of nickel-base superalloy Mod. IN-100 has been consolidated by hot isostatic pressing and recrystallized by rolling up to 80% at 1 123 K and subsequent annealing at 1 423 K. The superplastic behaviour of alloy sheets prepared by above processing has been investigated in the temperature range of 1 223-1 423 K and over a range of strain rates from 2.5×10-4 to 2.5×10-2 s-1.
    The Inσ vs. Inε curves were obtained and it was shown that the conditions obtaining the maximum strain-rate sensitivity index m changed from the constant strain rate at temperatures above 1 323 K to the constant flow stress below 1 323 K, so that the Inσ vs. Inε curves were possible to divide into six regions according to the deformation behaviour.
    x

    Readers Who Read This Article Also Read

    1. Strength and Toughness of 9Ni-Cr Steels in the Temperature Range from 77 to 4.2K Tetsu-to-Hagané Vol.72(1986), No.10
    2. 21世紀の頭脳労働の坦手 Tetsu-to-Hagané Vol.71(1985), No.7
    3. Monitoring of the Hydrogen Permeation Behavior in Pipeline Tetsu-to-Hagané Vol.71(1985), No.8
  • Effects of Visco-elastic Properties of Core Resin on Loss Factor and Acoustic Characteristics of Composite Damping Steel Sheets

    pp. 1575-1581

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    A study has been made of the effect of resin intermediate layer(core resin) on the damping characteristics of composit damping steel sheets (CDS). The efforts have been focussed on the following three points.
    (1) Effect of mechanical characteristics of core resin on loss factor of CDS.
    (2) Comparison of loss factors obtained by different method of measurement, i.e. the shape of test piece, the boundary condition, and method of acceleration.
    (3) Relation between loss factor and sound pressure level in two dimensional material accelerated.
    Above studies have resulted in the following four points.
    (1) Adoption of CDS is effective countermeasure against vibration or noise.
    (2) Loss factors obtained by different method of measurement will differ because of different mode of vibration.
    (3) Materials which have different elastic moduli will vibrate in differnt mode, even if they have same shape and the order of resonance is same.
    (4) Not only tanδ, but also elastic modulus of core resin is important mechanical characteristics to loss factor of CDS.
  • Effect of Phosphorus on Phosphatability and Perforation Corrosion Resistance of Ultra-low Carbon Steel Sheet

    pp. 1582-1589

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    The influence of phosphorus on both the phosphatability and perforation corrosion resistance of ultra low-carbon Al-killed steel sheets were investigated. Results are summarized as follows;
    (1) Phosphorus in ultra low-Carbon steel sheets was beneficial in refining the grain and increasing the coverage area of a phosphate layer on the steel surface. The steel sheet containing 0.07 wt% phosphorus has excellent phosphatability.
    (2) Phosphorus in steel accelerated the pickling rate of the steel in acid solutions. The rest potential of P-containing steels in a zinc phosphating bath moved to noble direction more rapidly than the steels without phosphorus. This fact means that the former shows the higher formation rate of the phosphate layer than that of the latter. The effect is possibly caused by the depolarization due to phosphorus in steel.
    (3) The increase in the phosphorus content of steel reduced the weight loss of both bare cold-rolled steel sheets and phosphated ones in cyclic corrosion tests. The addition of phosphorus to steel improved perforation corrosion resistance. This effect was more pronounced in phosphated steel sheets.
    (4) Phosphorus in steel also improved perforation corrosion resistance after painting.
  • Liquid Phase Diffusion Bonding of a Nickel-base Oxide Dispersion Strengthened Alloy MA 754

    pp. 1590-1597

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    The ODS alloy(MA754) produced by mechanical alloying was joined by a Liquid phase diffusion bonding method under a low compressive stress using an amorphous insert ribbon metal with small thickness. Microstructural features, concentration of alloying elements and mechanical properties of bonded area were examined.
    1) Dispersed Y2 O3 particles coagulated at the bonded interface in the process of isothermal solidification. However, the amorphous ribbon of insert metal with elements to lower the melting point produced a sound structure without any voids.
    2) The rate of interface diffusion between the insert metal and the base metal was influenced by the element added to lower the melting point of insert metal.
    3) The fractured position of specimens tested in tension was changed to base metal position at elevated temperatures. The transition temperature depended on the element added to lower the melting point of insert metal.
    4) The creep rupture life at 982°C of bonded alloy was more than 85% of that of the base metal.
  • Change in the Austenite Grain Size Due to Temperature Cycling

    pp. 1598-1604

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    The effects of number of temperature cycles, heating-cooling rate and applied stress on the austenite grain size were studied in SCM415 steel.
    (1) The austenite grain size of specimens subjected to temperature cycling approaches almost a constant value regardless of the initial grain size. However, the effect of applied stress(4 kgf/mm2) on the final austenite grain size is hardly observed.
    (2) The initial grain size of 13 μm of the specimens tends to become the fine austenite grain size of 5 μm after three temperature cycles through austenite _??_ ferrite + bainite transformation. This value of grain size is the same as that attained through austenite _??_ martensite transformation.
    (3) The austenite grain size becomes smaller in the case of the larger heating or cooling rate. The effect of cooling rate on grain refinement is larger than that of heating rate.
    (4) In the case of the large initial grain size, the austenite grain size tends to become smaller after one cycle. In the case of the small initial grain size, the austenite grain size tends to become larger during austenization. Therefore the austenite grain size approaches almost a constant value through the repeated temperature cycling.
  • Effect of Grain Boundary Precipitates on High Temperature Creep Properties of Ni-2OCr-Nb-W Alloys

    pp. 1605-1612

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    Creep properties and microstructure of Ni-20Cr-Nb-W alloys containing variable amounts of niobium and tungsten were investigated at 900 and 1 000°C, focusing on a role of grain boundary precipitates. The alloys with higher niobium content, in which the Widmanstätten type β-Ni3Nb phase precipitates after its precipitation at grain boundaries, showed a relatively small minimum creep rate at 900°C accompanied by the degradation of rupture elongation. The effect of the time lag between the in-grain and grain boundary precipitations of the β-phase on the creep resistance of the alloys was evaluated by observing their creep rate-time curves. When the tungsten content of a Ni-20Cr-3Nb-13W alloy increased up to 17 wt%, marked improvement of creep properties was found under lower stress levels and it is strongly correlated to the grain boundary precipitation of the α2W-phase which occurs after that of the β-phase. It is concluded that the grain boundary precipitation strengthening effect due to such dual phases as β and α2 is one of most effective methods for improving the creep strength.
  • Strength and Toughness of 9Ni-Cr Steels in the Temperature Range from 77 to 4.2K

    pp. 1613-1620

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    The temperature dependence of the strength and toughness was measured for quench-and-tempered 9%Ni steels containing 0.5% Cr and 1.0% Cr which were quenched with the cooling rate simulated to heavy plate, and a commercial 9%Ni steel in the temperature range from 77 to 4.2 K. The yield strength of the three steels increased monotonically and reached the same value with decreasing temperature down to 20 K. Below 20 K, anomal change in yield strength was observed. The Charpy impact tests showed a decrease in the absorption energy and an increase in the brittle area on fracture surface in 9Ni-0.5Cr and 9Ni-1.0Cr steels at the temperature between 77 and 40 K, but below 40 K, only a slight change in the absorption energy and no apparent ductile-brittle transition temperature. The commercial 9%Ni steel showed a full ductile fracture mode in the whole temperature range tested.
    The fracture toughness test (J ingegral test) of the three steels showed the clear ductile and brittle transition and a low energy brittle fracture below 30 K. The nil-ductility temperature and the ductile and brittle transition temperature are almost the same among three steels, but KIC(J) values are different. The 9Ni-1.0Cr steel showed a relatively high K IC (J) value especially in the brittle fracture range.
    x

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    2. 21世紀の頭脳労働の坦手 Tetsu-to-Hagané Vol.71(1985), No.7
    3. Monitoring of the Hydrogen Permeation Behavior in Pipeline Tetsu-to-Hagané Vol.71(1985), No.8
  • Effect of the Amount of Austenite Precipitated on the Charpy Absorbed Energy for Ductile Fracture of 9% Ni Steel

    pp. 1621-1628

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    An investigation was made on the effect of the amount of austenite precipitated on the Charpy absorbed energy for ductile fracture of high toughness 9% Ni steel. The main results obtained are as follows:
    (1) As slab reheating temperature and finish-rolling temperature are raised; the Charpy absorbed energy for ductile fracture increases.
    (2) As slab reheating temperature and finish-rolling temperature are raised, the amount of austenite precipitated decreases.
    (3) The Charpy absorbed energy for ductile fracture has a good relation with the amount of austenite precipitated.
    (4) The fraction of area of dimples smaller than one μm increases with an increase in the amount of austenite precipitated.
    (5) The Ni content measured at the bottom of dimples smaller than one μm by micro Auger analysis is as much as that of austenite.
    (6) The above results indicate that the austenite precipitated decreases the Charpy absorbed energy for ductile fracture through the formation of dimples smaller than one μm.
  • Analysis of Raw Materials for Iron and Steel with X-ray Computed Tomographic Scanner

    pp. 1629-1636

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    X-ray computed tomographic scanner (CTS) recently reported for iron and steel analysis by one of the present authors, has been applied in this paper to raw materials for iron and steel, especially iron ore sinter, in a series of study on application of computed tomographic scanner to non-medical purposes.
    High-voltage X-ray tube (max 420 kV, 3 mA) with an iron filter of 7 mm thickness was studied and used for high quality of tomographic images. Raw materials showed higher X-ray transmission than iron and steel and the total measuring time was shortened to 6 min. (data acquisition: 5 min, data processing: 1 min, total measuring time of iron and steel: 11 min)
    The images of iron ore sinter, taken by CTS were found to be well agreed with those observed by an optical microscope after cutting and polishing the sinter.
    Using the mini-computer and the displayer of CMA (Computer aidded Micro Analyzer), CTS data of the sinter were furthermore processed in order to obtain the quantitative information of pores and residual iron ores.
    It is concluded that CTS is a new apparatus suitable to analyze raw materiales for iron and steel.
  • Development of Cross Rolling Mill

    pp. 1637-1640

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  • インドネシアでの技術協力を終えて/材料連合フォーラムの活動

    pp. 1646-1652

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  • 抄録

    pp. 1663-1665

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  • 主要先進国の科学技術研究費

    pp. 1666-1666

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