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

Tetsu-to-Hagané Vol. 63 (1977), No. 2

  • ファインケミカルと鉄

    pp. 199-200

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  • Rate of Air-Oxidation of Graphite Sphere Heated in the Temperature 800-1070°C

    pp. 201-206

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    Rates of the air-oxdation of a graphite sphere heated in the temperature range between 800 and 1070°C were studied. At higher temperatures more than 850°C the reaction was controlled by the gas-film diffusion and the abserved rates of the reaction well coincided with the theoretical prediction. In the heating at 850°C the progress of reaction was affected by the chemical reaction and the intraparticle diffusion processes.
  • Reduction Behavior of Chromite with Carbon in Various Atmospheres and with Flowing CO Gas

    pp. 207-216

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    Relatively pure chromite from the South Africa was reduced with graphite powder in the atmospheres of CO, Ar, and a vacuum, and the differences in the reduction behavior were investigated. Then, the reduction with flowing CO gas was also studied to compare with the former.
    The results are as follows:
    1) The reduction process of the chromite with graphite consisted of the following three stages in every atmosphere used:
    (Mg, Fe) (Cr, Al, Fe) 2O4→ (Mg, Fe) (Cr, Al) 2O4→Mg (Cr, Al) 2O4→MgAl2O4+MgO
    2) In the 1st and 2nd stages, the reduction rate was about the same for CO and Ar atmospheres, while it was much lower in vacuum. On the contrary, in the 3rd stage the rate was the highest in vacuum, followed by Ar, and finally by CO atmospheres.
    3) Below 1100°C, carbon deposition was observed during the reduction with graphite in the CO atmosphere and with flowing CO gas.
    4) The amount of carbon dissolved in metal by carburization during the reduction with flowing CO gas increased with temperatures up to 1200°C, but decreased above 1250°C.
    5) The reduction with the flowing CO gas was much slower with graphite. The reduction in this process indicated a preference of the iron oxide over the chromic oxide.
  • Effect of Charging Methods, Furnace Design and Liquid Surface on Gas Flow in Blast Furnace

    pp. 217-226

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    Gas flow model in packed column with distributions of particle diameter, void ratio and temperature has been studied. This paper shows a newly developed model which can simulate the gas flow in blast furnace more precisely. In this model the gas source by chemical reaction, blast furnace profile, charging sequence, stock line profile and liquid surface were taken into consideration.
    Concerning the upper part of the blast furnace, several charging methods were evaluated using two indices; channeling factor and index of ore by gas. Besides. the effect of stock line profile was theoretically solved. Concerning the lower part of the blast furnace, the inclination of the liquid surface was calculated under the influence of gas permeability, liquid level and blast volume. With respect to the whole part of the blast furnace the optimum blast furnace profile was discussed from the view point of pressure drop.
  • Behavior of Nitrogen in Plasma Jet Melting

    pp. 227-235

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    Nitrogen absorption in plasma jet melting of iron was studied by using A-N2 and A-H2-N2 mixtures. The electric power supplied was 20kVA (DC), the total pressure inside a melting furnace was 30 Torr, and nitrogen partial pressure was less than 5×10-2 Torr. Under these conditions nitrogen gas was almost completely dissociated in plasma jet. Little bublles were visually observed.
    The obtained results were summarized as follows.
    (1) Nitrogen solubility of liquid iron (nitrogen concentration in a steady state) is found to be approximately 100 times as great as the one expected from thermodynamical equilibrium at 2000°C. The solubility increases in proportion to the square root of nitrogen partial pressures. Sulfur increases the solubility.
    (2) It may be concluded from these results that the solubility is determined by the rates of absorption and desorption reactions occurring on the melt surface; that is, N+??=N (ad) =N+?? at the are spot and 2N+2??=2N (ad) =N2+2?? on the rest surface, where ?? is the vacant site on the surface and N (ad) the adsorbed nitrogen.
    (3) Hydrogen in the mixture decreases the solubility of nitrogen. This effect of hydrogen can be explained by that in a boundary layer adjacent to the melt surface, nitrogen atom is converted to hydrogennitride such as NH, NH2 or NH3.
  • Study of Decarburization Process of Inductively Stirred Fe-C Melts

    pp. 236-245

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    A kinetic study of the decarburization process in a state of high oxygen blowing density which is similar condition in commercial converters has been done by blowing O2-N2 gas mixture of 0.12-0.48Nm3/min into the inductively well stirred Fe-C melts of about 50kg.
    The results obtained are as follows: (i) the oxygen efficiency for decarburization is low in general, namely 40-50%; (ii) the maximum rate of decarburization is influenced markedly by partial pressure of oxygen, flow rate and lance height; (iii) temperature dependence of the decarburization rate is relatively small; (iv) a large amount of spit is created near the fire spot from the start of blowing and boiling occurs with decrease of carbon contents, thus the reaction surface moves gradually into bath; (v) the temperature of fire spot depends on partial pressure of oxygen.
    Finally, a qualitative model of the behavior of oxygen has been proposed on the basis of the experimental results.
  • Investigation of Decarburization Process Based on a Mathematical Model Considering Flow and Reactions in Bath

    pp. 246-255

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    A mathematical model taking the flow and reactions in bath into consideration has been developed in order to investigate the decarburization process quantitatively. This model is able to simulate well the variation of process variables.
    The knowledges obtained from process analysis in this study are as follows: (i) the low value of oxygen efficiency for decarburization is due to the low value of absorption efficiency of oxygen, namely 50-60%, which is further caused by the relatively large resistance of mass transfer in gas phase; (ii) the fire spot occupies the area corresponding to the width of gas jet; (iii) the variation of exhaust gas composition is primarily determined by the division of unabsorbed oxygen between the combustion of CO gas and the oxidation of scattered droplets of liquid iron.
    Finally, the self-acceleration of decarburization in commercial converters has been pointed out.
  • Solidification Structure and Segregation in Austenitic Stainless Steel Containing Phosphorus

    pp. 256-264

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    This paper describes an experimental study made of the solidification structure and the segregation in austenitic stainless steels containing phosphorus.
    Small melts were unidirectionally solidified to simplify the freezing process. The cooling curves were also obtained in 300kg ingots to compare the solidification structure with unidirectionally solidified ingots.
    The results obtained are as follows:
    1) The secondary dendrite-arm spacing in the columnar crystal zone in the unidirectionally solidified ingots was influenced by the average cooling rate during solidification and phosphorus content. The ralation between the secondary dendrite-arm spacing and the average cooling rate in the above mentioned ingots was applicable to the 300kg ingots.
    2) The primary dendrite-arm spacing in the columnar crystal zone was also influenced by the average cooling rate. but the result obtained from the unidirectionally solidified ingots was not applicable to the 300kg ingots.
    3) Microsegregations around the primary and the secondary dendrite arms in the unidirectionally solidified ingots were determined by an electron probe microanalysis. The degress of microsegregation of phosphorus, chromium, and molybdenum increased with a decrease of the cooling rate.
    4) An inverse segregation was found in a 300kg ingot. It should have resulted from the solidification shrinkage in a wide mushy zone formed in the ingot.
  • On Activity of Iron Oxide in Basic Steelmaking Slags

    pp. 265-274

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    Studies were made on a calculation method of the iron oxide activity in basic multi-components steelmaking slag.
    The studies have revealed:
    1) Among previously proposed calculation methods, there is no generalized one being capable to calculate the iron oxide activity range of multi-component slag. The methods proposed by ELLIOTT et al and HERAHY-MENKO et al are reliable to calculate the iron oxide activity to some extent and the equilibrium oxygen content in metal can be calculated with a standard deviation of about 200ppm; the oxygen content is in equilibrium with the slag that has a high basicity and (% FetO) of more than 5%.
    2) On the assumption that the molten slag dissociates completely to the ionic species, effects of calculation methods of ionic fraction assuming various ionic species of the iron oxide on the iron oxide activity are discussed.
    As the result, a new calculation method on iron oxide activity has been interoduced by authers
    log assuming that iron oxide is dissociated to the species Fe2+, Fe3+ and O2-, and utilizing the calculation method on ionic fraction proposed by FLOOD et al. This calculation method is available to determine average oxidation potential of slags.
    3) When (CaF2) content is less than 80%, (CaF2) component in the slag increase the iron oxide activity and increase the equilibrium oxygen content in the metal by about 200ppm compared to that in metal, which is equilibrium with the slag free from (CaF2)
  • Calorimetric Study of Heat of Mixing of Copper Alloys at 1120°C

    pp. 275-284

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    An isothermal calorimeter was newly designed and constructed to measure the heats of mixing of alloys, in expectation of expansion of the study at steelmaking temperatures.
    The calorimeter consists of a cylindrical molybdenum heater with slit, calorimeter block, and isothermal jacket made of beryllia, which is a good thermal conductor. In order to check the accuracy of the constructed calorimeter, copper alloys were applied to measure the heats of mixing under low An isothermal calorimeter was newly designed and constructed to measure the heats of mixing of alloys, in expectation of expansion of the study at steelmaking temperatures.
    The calorimeter consists of a cylindrical molybdenum heater with slit, calorimeter block, and isothermal jacket made of beryllia, which is a good thermal conductor. In order to check the accuracy of the constructed calorimeter, copper alloys were applied to measure the heats of mixing under low pressures of argon (0.1-5.0mmHg) at 1120°C. The temperature of the isothermal jacket was. controlled within+0.1C at 1200°C. and the difference of the temperature inside the isothermal jacket was negligible. As socalled “Newton's law of cooling” is valid for heat transfer form the calorimeter block to the isothermal jacket, the obtained data can be calibrated reasonably.
    The maximum heat of mixing of the Cu-Ag and the Cu-Sn systems were 970 and-1430cal/g·atom respectively, and the heats of mixing of the Cu-Si system were exothermic up to 0.2 atomic fraction of silicon.
    The error in the heats of mixing was estimated approximately as ±8%.
  • Deformation Behaviours of a 0.16% Carbon Steel in the Austenite Range

    pp. 285-293

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    High temperature tensile deformation of a 0.16% carbon steel was studied over a wide range of strain rates from 1.43sec-1 to 2.73×10-5sec-1 in the austenite (γ) range. The shape of the true stress-true strain (σ-ε) curve showed a sharp maximum or regular oscillation in the low strain region and then reached to a steady state deformation in the higher strain region. With a given initial grain size, D0, the σ-ε curve is expressed solely in terms of the first maximum flow stress, σM, or Z in the following equation. σM which is independent of D0 can be correlated with temperatuer, T, and strain rate, ε, approximately by the following deformation equation;
    in which n (=5.4) and Q (=68.5kcal/mol) are nearly equal to those obtained in creep experiments. The energy value is almost the same as the activation energy for self-diffusion in the γ phase of the 0.16% carbon steel.
    The austenite grain size (D) in the deformed structure is unchanged in the high strain region. D is a function of σM or Z in the above equation and is independent of the actual D0 and T or ε. From these results and the metallographic observations reported previously, it is considered that the high temperature deformation of the 0.16% carbon steel in the γ range is controlled by the dynamic recrystallization process assisted by the diffusion of atoms.
    The mono-peak stress type curve is observed when the grain size decreases with deoformation (D0>D), and the oscillated stress type curve appears when the grain size increases with deformation (D0<D). It is concluded, therefore, that whether the observed σ-ε curve shows a peak stress type or an oscillated stress type depends on the relative difference between the initial grain size, D0, and the dynamically recrystallized grain size, D. This suggests that the shape of σ-ε curves is dependent on not only Z but also D0 and the change in the shape with Z and D0 is explained qualitatively in terms of the nucleation and growth model applied to the dynamic recrystallization.
  • Strengthening of Steel by Spray-Dispersion of Fine Oxide Particles

    pp. 294-302

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    A new technique has been developed to make dispersion strengthened steels, i. e., oxide particles are sprayed into steel streams. The mechanical properties of the steel with dispersed aluminum oxide or zirconium oxide has been studied.
    The main results obtained are summarized as follows:
    (1) For fine dispersed aluminium oxide or zirconium oxide of less than 1200Å in particle size, the hardness of the steel increases with their volume fraction, but little change occurs in the hardness of the steel for the osides of 1700 to 2600Å in particle size.
    (2) Both of the 0.2 pct. proof stress and tensile strength increase with a volume fraction for fine dispersed oxides of less than 1200Å in particle size.
    (3) The increment of the 0.2 pct. proof stress is proportional to the reciprocal of the planar interparticle spacing in this case, and this fact supports Orowan's by passing mechanism. The work hardening behabior of this steel can be explained by the theory of Fisher-Hert-Pry or Ashby.
    (4) An increase in transition temperature (Tr E) and a decrease in maximam absorbed energy are observed as a volume fraction of particles increases. By the observation of the fracture surface, it is obvious that the existence of finer particles has little effect on ductile fracture surface.
    (5) From these results, it is found that the steels are strengthened by spray-dispersion of oxides of below 2 volume pct..
  • Improvement in Microstructure and Toughness of Large Heat-Input Weld Bond Due to Addition of Rare Earth Metals and Boron in High Strength Steel

    pp. 303-312

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    For the purpose to improve the weld bond toughness through ferrite grain refinement in 40-60kg/mmmm2 tensile strength steels, the effects of various alloying elements on the grain structure and notch toughness in the weld bond were investigated. Of the alloying elements investigated, small additions of both rare earth metal (REM) and boron (B) were found to accelerate the formation of fine ferrite grains inside prior austenite grains, resulting in a remarkable improvement weld bond thoughnss.
    The main results obtained are summarized as follows:
    (1) The optimum concentration range of REM and B are 0.020-0.040% and 0.0020-0.0035%, respectively.
    (2) With an increase of BN content, the number of fine ferrite grains increases remarkably.
    (3) The amount of BN re-precipitated during welding thermal cycle is larger in REM-B steel than in B steel.
    (4) Spherical inclusions are frequently observed in the center of ferrite grains or adjacent to them and many of them identified as Ce2O2S and BN.
    (5) According to the observation by IMMA, the location of B+-images is in good accordance with that of both Ce+-and N+-images.
    By the use of commercial heats of REM-B steel, brittle fracture tests were conducted and good results were obtained.
  • Estimation of Kca Value of Brittle Crack Arrest from Instrumented Charpy Test by a Modified Notch Specimen

    pp. 313-320

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    To utilize the advantage of Charpy impact test, a study was made of the empirical correlation between crack arrest test, such as DWTT and temperature gradient ESSO test, and instrumented Charpy test by a modified notch specimen. Main results were as follows.
    1) Fracture initiation resistance was reduced in the order of the V-notch, the fatigue-notch, the fatigue-notch after embrittlement by an electron beam welding and the V-notch after embrittlement by the welding (EBV-notch).
    2) The lowest temperature where 100% shear fracture occurred in the EBV-notch Charpy test (EBVTrs=100) coincided with DWTT 85% SATT.
    3) Kca value deduced from instrumented Charpy test by EBV-notch specimen almost coincided with Kca value obtained from temperature gradient ESSO test.
  • Influence of Manufacturing Conditions of Steel Substrate on Corrosion Resistance of Phosphated and Electropainted Steel Sheets

    pp. 321-327

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    Corrosion resistance of phosphated and electropainted steel sheets has been investigated. Low carbon Alkilled steels containing 0.09% Sb and 0.04% Mo were used.
    The higher the cold reduction and the annealing temperature of the steel substrates, the greater the corrosion resistance after painting. The corrosion resistance depends on the density of pohosphate nuclei which is mainly affected by the texture and the oxide film thickness appearing in the specific manufacturing condition: that is, the higher the axis density of (111) parallel to the rolling surface, or the thinner the oxide film thickness, the higher the density of phosphate nuclei. It has been observed that the texture of steels also influences the anodic dissolution rate of the phosphate crystals during the electropainting. However, since the dissolution is less than 20% of the total amount of the phosphate film, it results in only minor effect on corrosion resistance.
  • Potential Dependence of Stress Corrosion Cracking Mode of 18Cr-10Ni Stainless Steel in MgCl2 Solution

    pp. 328-337

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    The effect of the MgCl2 concentration-potential relationship on the transgranular stress corrosion cracking (TGSCC) and intergranular stress corrosion cracking (IGSCC) of solution treated and sensitized 18Cr-10Ni-0.15C stainless steel was investigated in 15 to 35% MgCl2 solutions at 80°C under the stress of 25kg/mmmm2. The effect of applied stress on SCC mode of sensitized 18Cr-10Ni-0.15C stainless steel was also studied.
    Only the TGSCC occurred in the solution treated 18Cr-10Ni-0.15C stainless steel when the concentration of MgCl2 was above 30%, and the potential range of SCC was widened with an increase of MgCl2 concentration. The MgCl2 concentration-potential range for TGSCC or mixed types of SCC of sensitized 18Cr-10Ni-0.15C stainless steel was almost the same with that for TGSCC of the solution treated one. The potential range in which only the IGSCC occurred was just below that of TGSCC in the case of sensitized 18Cr-10Ni-0.15C stainless steel, and this potential range became wider with a decrease of MgCl2 concentration.
    It was found that the fracture shifted from TGSCC to IGSCC with an increase of applied stress in the same environmental condition.
    The anodic polarization curves of 6 to 18Cr-10Ni and 18Cr-10Ni-0.15C steels were measured. The mechanisms of TGSCC and IGSCC were also discussed.
  • Chemical Analysis of Metallic Chromium and Iron Contained in Semi-reduced Chromium Pellet

    pp. 338-344

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    Chemical analysis of metallic chromium and iron contained in semi-reduced pellet produced in ferrochromium factory was studied. Metallic Cr and Fe form complex carbide which is easily dissolved in concentrated H2SO4. However, when acid concentration was high, higher analytical values of Cr and Fe were obtained because of the dissolution of Cr and Fe from unreacted chromite ore which was contained in the semireduced pellet. H2SO4 (1+3) was most suitable to fully recover metallic Cr and Fe preventing the dissolution of chromite. Another important point was to put a condensation cooler over a beaker to maintain constant volume and concentration of acid during heating period. The boiling point of H2SO4 (1+3) was kept to 111°C. Under this condition being maintained for 30 minutes, the best result was obtained. The proposed method had no bias among four laboratories and precision of the method was as follows; for metallic Cr, the standard deviation was 0.15% to mean value of 13.6%. for metallic Fe, the standard deviation was 0.20% to mean value of 11.0%.
  • Aqueous Corrosion of Ferrous Materials at Elevated Temperature

    pp. 345-360

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  • 第3回鉄鋼オートメーション国際会議出席報告

    pp. 361-366

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  • 第2回鉄鋼工学セミナー報告

    pp. 367-369

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  • 抄録

    pp. 370-376

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  • 第93回講演大会討論会講演概要

    pp. A1-A16

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  • 第93回講演大会討論会講演概要

    pp. A17-A32

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  • 第93回講演大会討論会講演概要

    pp. A33-A56

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  • 第93回講演大会討論会講演概要

    pp. A57-A68

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  1. blast furnace
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