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

Tetsu-to-Hagané Vol. 66 (1980), No. 14

  • 大学の窓から

    pp. 2021-2022

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  • Decomposition of Sodium Carbonate and Its Mixture with Silica by Heating and Carbon-Reduction

    pp. 2023-2031

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    The decomposition rate of Na2CO3 melts in the temperature range from 1 200 to 1 700°C under argon atmosphere was measured by using a thermobalance. Significant weight loss of the melt was observed adove 1 300°C. The rate at a steady state was given as ω=9.66 × 102 exp (- 58 600/RT) (g/cm2·). The reaction scheme was concluded from this equation to be Na2CO3(l)→ Na2O(l) + CO2(g), Na2O(l) → 2Na (g) + 1/2O2(g). The rate-determining step was the diffusion of reaction products in argon.
    The reduction of premelted Na2CO3-SiO2 mixtures with graphite at about 1 200°C was examined. Residual Na2CO3 in the premelted mixture was completely decomposed by the reaction: Na2CO3(l) + 2C(s) → 2Na(g) + 3CO(g). No substantial reduction was observed for sodium metasilicate, Na2O· SiO2, dissolved in the premelted mixture. Excess Na2O over 1 mol per 1 mol SiO2 was decomposed by carbon: Na2O(l) + C(S) → 2Na(g) + CO(g). Dense fume rising in the reaction furnace was observed during the reaction with graphite. This fume would be originated from the sodium vapour produced as the reaction product in the above reaction.
    Some experimental results were presented on the removal of carbon dissolved in liquid iron by Na2CO3-SiO2 mixtures.
  • The Standard Free Energies of Dissolution of Phosphorus Gases in Liquid Iron

    pp. 2032-2039

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    The ratio of the vapor pressures of P(g) and P2(g) above Fe-P alloys were determined by a combination of a mass spectrometer and a Knudsen cell. The effused vapors from Knudsen cell were collected onto target plates and the amounts of phosphorus in the deposits on the target plates were determined by a secondary ion mass spectrometer. The vapor pressures of P(g) and P2(g) were calculated from these results, and the following values for the standard free energy changes were obtained.
    P(g) = P (%) ΔG°= - 95.3 + 1.55 × 10-2 T (±2.2) kcal/mol
    1/2 P2 (g) = P (%) ΔG°= - 37.7 + 0.13 × 10-2 T (±1.1) kcal/mol
    P(g) = 1/2 P2(g) ΔG°= - 57.6 + 1.42 × 10-2 T (±1.1) kcal/mol
    (1-3 wt% P, 1 590-1 650°C)
  • Shape Control Mechanism of Nonmetallic Inclusions in Steel by Calcium Treatment

    pp. 2040-2049

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    Hydrogen induced crackings in line pipe steels are caused even by very fine, elongated inclusions. In order to prevent these crackings, calcium treatment of molten steel has been developed. Sulfur in steel can be reduced to about 10 ppm and both oxide and sulfide inclusions are modified to be globular by calcium treatment.
    In this paper, the distribution of elements and the shape, composition and distribution of inclusion in the calcium treated commercial steel were investigated to clarify the shape control mechanism of nonmetallic inclusions.
  • Separate Recovery of Iron and Phosphorus from BOF Slags by Using Fe-Si Alloys

    pp. 2050-2057

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    The recovery of iron from BOF slags by reduction is one of the most effective ways of its utilization. However, phosphorus which is simultaneously reduced dissolves in liquid iron almost completely.
    The present work was undertaken to seek the possibility of the separate recovery of iron and phosphorus from BOF slags.
    The experiments were carried out using a plasma furnace under the conditions that BOF slags were reduced by carbon powder in coexistance of Fe-Si alloy bath where silicon presumably enhances the activity of phosphorus.
    More than 95% of iron and phosphorus were removed from the slags. While iron was recovered by Fe-Si alloy, the substantial amount of reduced phosphorus was removed to gas phase as P2 gas. It is likely to be CO gas explosively generated on the reduction of iron oxide in slag that has great effect on the gaseous dephosphorization.
  • Effects of Strain-aging and Welding on Embrittlement of Cold-worked Structural Steel Plates

    pp. 2058-2066

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    COD tests were conducted on JIS-SM41B, -SM50B and -SM58Q steel plates in order to examine the effect of strain-aging on embrittlement of these steels. Hot straining embrittlement phenomenon was also studied on weld joints of cold worked steel plates. Finally the bending radius allowable in cold working of structual steels was examined on the basis of COD test results.
    The main results obtained are as follows:
    (1) Strain-aging strongly affects the brittle fracture behavior and shifts the COD transition curve toward the higher temperature range. Fibrous crack initiation at the crack tip and its slow growth, on the other hand, are not strongly affected by strain-aging if the prestrain is limited up to 10%.
    (2) The amount of the shift of COD transition curve toward the higher temperature range due to strain-aging is in good accordance with the prediction based on the Tetelman's critical fracture stress theory.
    (3) The COD value at the hot straining embrittled zone near the weld joint of cold worked steel plate is nearly equal to that of the steel plate which is strained and then aged at 250°C for one hour.
    (4) The critical bending radius allowable in cold working can be calculated using the COD test results, and it is 4.57.3 times as large as the plate thickness.
  • Development of A New Test Method for Chloride Stress Corrosion Cracking of Stainless Steels and Its Application to That of Type 316 in Dilute NaCl Solutions

    pp. 2067-2076

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    Tapered Double Cantilever Beam specimen with artificial crevice has been designed to clarify SCC behaviors of Type 316 stainless steel in dilute NaCl solutions. This specimen has two dimensional characteristics, which mean that both mechanical and chemical parameters are independent of the specimen thickness. The former is stress intensity, KI and the latter is repassivation potential of crevice, ER. SCC tests have been conducted potentiostatically in 3, 0.3, and 0.03% NaCl solutions at 80°C under KI constant condition.
    Cracking occurs at the crevice bottom only when the bottom surface is dissolving at potentials more noble than ER and Ki is over KISCC, 1314kgf/mm3/2. Bulk NaCl concentration has no significant influence on KISCC and iII, crack growth rate in the region II where i is independent of KI. Cracking occurs at potentials between -0.23 and -0.18 V (SCE) in 3% NaCl, and between -0.11 and +0.10 V in 0.03% NaCl solution. The lower limit of the potential range for cracking is the potential just more noble than ER in each solution and the upper corresponds to the potential where the dissolution rate at the crevice bottom is equal to iII.
  • Fluorescent X-ray Analysis of Iron Content in Iron Ores by Glass Bead Technique

    pp. 2077-2085

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    Fluorescent X-ray analysis of iron contents in iron ores by glass bead technique has been theoretically studied. Calculation has been made on FeKα fluorescent X-ray intensity in Fe-O binary sample and in Fe-O-impurity ternary sample in various fusion procedures by means of theoretical formulas for fluorescent X-ray intensity.
    The results are as follows:
    1. In the comparison of characteristics of various fusion procedures, the intensity decreases, the derivative of calibration curve increases and matrix effect decreases with X-ray absorption of glass bead. For example, in the procedure in which lanthanum oxide is used as reagent, matrix effect is low and lanthanum oxide is useful as heavy absorber, while vanadium oxide has a little effect as heavy absorber and matrix effect is not low.
    2. In the procedure in which sodium tetraborate is used as flux, calibration curve for iron-oxygen binary system sample is made, and FeKα intensity is calculated for iron-oxygen-impurity ternary system samples when impurity is substituted with oxygen in iron-oxygen binary system sample.
    Theoretical correction factors are derived from the change of FeKα intensity. It is shown in experiments that these correction factors have an effect on analysis of iron content.
  • On the Effect of Combined Water on Iron Content Determination in Fluorescent X-ray Analysis of Iron Ores by Glass Bead Technique and on SiO2, CaO Content Determination

    pp. 2086-2094

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    There has been problems on fluorescent X-ray analysis of iron ores by glass bead technique. Of these, the influence of combined water on the analysis of total iron content and the influence of coexistent elements on the analysis of SiO2 and CaO contents have been theoretically studied. In the glass bead procedure in which sodium tetraborate is used as fusing flux, calculation is made on the intensity of FeKα, SiKα and CaKα.
    The results are as follows :
    (1) In the glass bead which is prepared without calcination of iron ore sample with combined water, FeKα intensity increases as combined water is lost out of the system by fusing and heating. For example, Goethite (Fe2O3·H2O) which has 10.1% combined water is analysed more by about 0.5% T. Fe in the calibration curve of Fe-O binary system sample.
    (2) In the analysis of SiO2 and CaO, the intensities of SiKα and CaKα do not change largely when coexistent iron oxide is substituted with other impurities, that is, the influence of coexistent element is little.
    (3) Analytical experiments for JSS standard sample show that the theoretical results of (1) and (2) described adove agree well with experimental ones.
  • Dephosphorization of High Carbon Ferrochromium Particle by Na2CO3, Na2SO4 and K2CO3 Fluxes

    pp. 2095-2099

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    High carbon ferrochromium particles weighing 3 g were tested for dephosphorization by sodium carbonate, sodium sulfate, potassium carbonate and their mixtures in the temperature range 730 to 1 200°C in a nickel crucible. 60% of phosphorus was removed from the samples with 0.3 mm in diameter using the flux of 0.5 to 0.8 g.
    Diffusion of phosphorus in the solid metal was found to be rate-determining. The carbonates and sulfate oxidized, pulverized ferrochromium particles and enhanced dephosphorization. The optimum temperatrue was 1 000 to 1 100°C, but rephosphorization occured at higher temperatures following the initial dephosphorization due to the vaporization and the decomposition of the fluxes. The dephosphorization capability was in the order of sodium sulfate, potassium carbonate and sodium carbonate. Phosphorus in the fluxes was water-soluble and recovered completely. Inert atmosphere prevented ferrochromium from oxidation.
  • Reduction and Dephosphorization of Molten Iron-oxide with Hydrogen-Argon Plasma

    pp. 2100-2105

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    Iron oxide (Whyalla ore) of 300 700 g charged in a water-cooled iron vessel was melted down by argon plasma, and then reduced by plasma of 10 50% H2-Ar mixtures. The flow rate of mixture was 10 l/min and the electric power was 15 kW. The result showed that the reduction degree of iron oxide was determined as a linear function of the ratio of hydrogen amount used to the weight of iron oxide charged. The utilization efficiency of hydrogen for the reduction reaction was found to be 50 70%, which was higher than the equilibrium values for H2-H2O-Fe-FexO system below 3 000°K. Such a high efficiency would result from strong reactivity of hydrogen atom which was formed by the thermal dissociation of hydrogen molecule in the plasma.
    Phosphorus behaviour during the reduction of molten iron oxide containing P2O5, CaO, SiO2, and Al2O3 was examined. The calculation of material balance for phosphorus indicated that phosphorus was transferred out of the reactor. The amount of phosphorus transfer was found to increase exponentially with respect to the reaction time. The transferred amount decreased with increasing value of CaO/(SiO2+Al2O3) ratio.
  • Creep and Fatigue at Elevated Temperature

    pp. 2106-2118

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  • Fundamental Study on Isolation and Determination of Carbide in Steels

    pp. 2119-2138

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  • 良い英文を書くために

    pp. 2139-2140

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  • 抄録

    pp. 2149-2154

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