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

Tetsu-to-Hagané Vol. 65 (1979), No. 13

  • The Latent Hydraulic Property of Granulated Blast Furnace Slag by Various Activators

    pp. 1825-1829

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    The latent hydraulic property of granulated blast furnace slag was studied by measuring the rate of heat liberation and the amount of combined water. The experiments were performed using different kinds and amounts of activators. Three activators, lime, gypsum+lime, and sodium hydroxide, promoted remarkably the hydration of slag.
    A small amount of lime or portland cement was used in super sulfated slag cement, as an activator together with calcium sulfate. It was found that the only small portion of slag hydrated when the amount of lime was too little, and that the reaction rate became very slow when too much lime existed.
    On the basis of these results, it will be interesting to study the above reaction in detail for the purpose of clarifying the kinetics and the mechanisms of the hydration of super sulfated slag cement, which may lead to the wider utilization of granulated blast furnace slag.
  • Numerical Analysis on the Gas-Phase Mass Transfer between an Impinging Jet of Gas and a Liquid Iron

    pp. 1830-1837

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    Theoretical studies have been made on the flow of gas and the mass transfer in the system with the immobile gas-liquid interface, in order to discuss the mass transfer between an impinging jet of gas and a liquid iron.
    The upwind difference scheme has been used for formulation of the finite differential equations of the velocity of gas and the concentration of diffusing gas. The solutions of these finite differential equations have been obtained by the relaxation method. And also. the local and average Sherwood numbers have been calculated from above solutions.
    Flow pattern visualized by tracer has been considerably similar to calculated one. The calculated values of average Sherwood number under various Schmidt and Reynolds numbers have been consistent with experimental ones obtained in the previous paper. An example of the absorption rate of nitrogen into liquid iron has been shown for the case in which the rate of absorption is controlled by mass transfer in gas phase.
  • Dephosphorization Reaction by Sodium Carbonate and Sodium Sulfate

    pp. 1838-1847

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    Reactions of Na2CO3or Na2SO4with iron, carbon and phosphorus, respectively were studied in the temperature range between 1200 and 1400°C by the use of iron, graphite and magnesia crucibles. The reaction between Na2SO4and iron was much more active than that between Na2CO3and iron, but the reaction between Na2CO3and carbon was considerably violent compared with that between Na2SO4and carbon. Reactions of Na2CO3and Na2SO4. with phosphorus (Fe-18%P alloy) were determined as follows;
    Na2CO3 (1) + 4/5 P =Na2O (1) +2/5 P2O5 (1) + C
    Na2SO4 (1) + 4/5 P = 2/3 Na2O (1) + 2/5 P2O5 (1) + 1/3 Na2S (1) + 2/3 SO2
    The dephosphorization and the desulfurization of carbon-saturated iron (0.2 %P, 0.05 %S) were also investigated at 1 250°C by the Na2CO3-Na2SO4 flux. From the chemical composition in flux analyzed before and after experiments, the degree of the dephosphorization and the desulfurization and the evaporation loss of sodium and sulfur were obtained as a function of the flux composition. Thus the degree of the dephosphorization was almost independent of the flux composition. With increasing the Na2SO4concentration, the degree of the desulfurization, the evaporation loss of sodium and iron yield decreased, but its loss of sulfur decreased with increase in the Nam2CO3concentration. The evaporation loss of sodium decreased with increasing the P2O5 concentration in slag.
    x

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    3. Crack Generation in Blast Furnace Slag Bearing High Titanium by Microwave Cyclic Heating ISIJ International Vol.47(2007), No.2
  • On the Simultaneous Dephosphorization and Desulfurization of CarbonSaturated Iron by Sodium Carbonate and Sodium Sulfate Flux

    pp. 1848-1857

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    The effect of the temperature, silicon and manganese in carbon-saturated iron (0.1% P, 0.05% S) on the dephosphorization and the desulfurization was studied by the use of the 2Na2CO3-Na2SO4 flux. The degree of the dephosphorization and the desulfurization considerably decreased and the evaporation of sodium increased with increasing temperature. As a result of the flux consumption for the oxidation of silicon, their degree was found to remarkably decrease, but manganese in metal was found to gradually decrease. The reversion of phosphorus and sulfur was observed after the end of the flux addition, but the extent of their reversion decreased when silica was present in the flux.
    The behavior of the dephosphorization and the desulfurization obtained by the 2Na2CO3·Na2SO4 flux was compared with those by the Na2CO3 flux and the 2Na2CO3·Fe2O3 flux. The degree of the dephosphorization was almost same, but the remarkable evaporation of phosphorus was observed according to the acceleration of CO formation by the reduction of iron oxide with carbon in metal. This evaporation was also observed in the 2Na2CO3·Na2SO4 flux, but its extent decreased with increasing the P2O5 and the SiO2 concentration in slag.
  • On the Dephosphorization of Carbon-Saturated Iron by Calcium Sulfate Flux

    pp. 1858-1867

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    The effect of temperature (1250-1450°C), silicon and manganese in carbon-saturated iron (0.1% P, 0.05% S) on the dephosphorization was studied by using the flux of the CaSO4-CaCO3system. It was found that CaSO4, although it is in solid state, has the strong dephosphorizing power. The following dephosphorization reaction was derived from the results of EPMA analysis for the dephosphorized reaction products;
    7/2CaSO4 (s) +2P= 3CaO·P2O5 (s) +1/2CaS (s) +1/3SO2No effect of the oxidation of silicon on the degree of the dephosphorization and no reversion of phosphorus and sulfur were observed, but the remarkable sulfur increase in metal was found as a result of the reactions of CaSO4with carbon, phosphorus and silicon. To use this flux for the dephosphorization of hot metal, all efforts were made to prevent such sulfur absorption by adding CaF2, Na2CO3and CaC2.
  • Influence of Ingot Design on the Homogeneity and Soundness in Large Flat Ingots

    pp. 1868-1877

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    Influence of shape, dimensions, and hot-topping conditions of 23 to 90 ton large flat ingots on the occurrence of heterogeneities such as channel-type and centerline segregations and centerline loose structure has been made clear to optimize the design of HSLA steel ingots for extra-heavy plates.
    Critical values of local solidification rate and local cooling rate for the formation of the channel-type segregation have been evaluated with the aid of heat-transfer calculation on these ingots. A speculative model for the later stage of solidification has also been presented which gives reasonable interpretation of the formation of the centerline heterogeneities characteristic in these large flat ingots.
  • Hydration Behavior of LD Slag at Autoclave Test

    pp. 1878-1886

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    An investigation was made of hydration behavior of LD slag in autoclave test for evaluating expansion potential of it. The results obtained are as follows:
    (1) Hydration degree of LD slag by autoclave test was expressed by the following empirical formula for generally used conditions. W= 0.02p0.63t0.34d-0.47f0.70
    W: hydration degree (%) p: steam pressure (kg/cm2)
    t: treatment time (h) d: mean particle size (mm)
    f: free lime content (%)
    (2) Hydrating mineral phases of slag and hydrates were not dependent upon the autoclave test condition. Hydration of LD slag was caused substantially by lime solid solution and unassimilated lime. In some cases, disintegration, though a little in quantity, caused by unassimilated magnesia was observed. Reaction products consisted mainly of Ca (OH) 2and also of CaCO3and Mg (OH) 2.
    (3) Evaluation of expansion potential of LD slag in autoclave was able to be made under any condition tested in this experiment. The most effective test condition was selected to have sufficient amounts of hydration and easy operation. Differences in expansion potential of LD slags could be determined by any of three measurements: volume expansion measurement using block specimen briquetted, disintegration measurement, and weight increase measurement.
  • Effect of Cu Content on the Hardenability, Strength and Toughness of Ni-Cr-Mo-V Steels

    pp. 1887-1895

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    The effect of Cu content on the hardenability, strength and toughness of Ni-Cr-Mo-V steels has been investigated. The results obtained are summerized as follows:
    (1) The hardenability of Ni-Cr-Mo-V steels remarkably increases with increasing Cu content. The Ms temperature and bainite transformation temperature become lower, and the each critical cooling rate to form bainite or ferrite decreases with increasing Cu content. The bainitic structure is obtained even at a cooling rate of 15 °C/h in quenching.
    (2) The tensile strength of the quenched and tempered steel changes little with increasing Cu contents but the notch toughness remarkably increases. The notch toughness of 2.8% Ni-Cr-Mo-V steels containing Cu exhibits the larger value than that of 3.7% Ni-Cr-Mo-V steels containing Cu, at a slow cooling rate in quenching and after tempering. This is thought to be caused by high susceptibility to temper embrittlement in the higher Ni-containing steels. The temper embrittlement can be reduced by Cu ad dition.
    (3) The improvement of hardenability and the reduction of temper embrittlement are possible by addition of Cu to 2.8% Ni-Cr-Mo-V steels. The steels containing Cu are able to have higher notch toughness than that of 3.7% Ni-Cr-Mo-V steels for large steel forgings.
  • Low Temperature Toughness of Carbon free-11Ni-Mo Steels

    pp. 1896-1905

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    The effects of micro-structures and molybdenum alloying on the low temperature toughness have been investigated in carbon-free 11%Ni- 0 to 4%Mo steels reheated below each Af temperature after double normalizing. In spite of very low content of C, N, P, S, and other impurities in these steels, temper embrittlement appeared in reheating or slow cooling in the range of 450°to 525°C. To inhibit this embrittlement the following two methods were shown effective. One was using substructures which had a small amount of fresh martensite and the other was alloying of 1% molybdenum. There was the optimum molybdenum content, because at higher contents age-hardening and solution hardening by this element became the enevitable cause of the low temperature brittleness. Further, it was concluded that the 1% molybdenum steel having a small amount of fresh martensite showed excellent properties in both strength at room temperature and toughness at -196°C. This steel is expected to have a good toughness also at temperatures below -196°C.
  • The Effects of Ni and Co on Microstructures and High Temperature Properties of 10Cr-2Mo Heat Resisting Steels

    pp. 1906-1915

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    Addition of nickel up to 3% and cobalt to 2% have been made to lowC-10Cr-2Mo-0.1V-0.05Nb steel and the effects on mechanical and high temperature-properties were examined. Microstructures were also investigated by transmission electron microscopy. Results obtained are as follows;
    (1) Increasing the nickel content up to 1% improves both creep rupture properties and tempering resistance but high nickel addition has a deleterious effect on them.
    (2) The low nickel steels exhibit the maximum tempering resistance when they are normalized at 1 100°C, but high nickel steels have almost the same long time tempering resistance though they are normalized at various temperatures.
    (3) Cobalt addition has no significant effects on creep rupture properties and tempering resistance.
    (4) Increasing the nickel content gives rise to a significant increase in the ultimate tensile strength but progressive decrease in ductility.
    (5) Their creep properties are clearly related to Ac1 temperature. According to the micrographic examination, the coagulation of the carbide is retarded but recovery of matrix is accelerated in the temperature range from 550°C to Ac1.
  • As-rolled Dual Phase Steel with Good Ductility and High Strength

    pp. 1916-1925

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    The purpose of the present study is to investigate the main manufacturing and microstructural features of as-rolled dual phase (DP) steels, characterized by a combination of excellent ductility, formability, and high strength.
    It was revealed by a laboratory simulation that the DP steel with required properties could be obtained, when a suitable combination of chemical compositions and rolling conditions was chosen. That is, 0.05% C-1.5%Si-1.6%Mn-0.5%Cr-0.25%Mo steel, 0.05%C-1.5%Si-2.2%Mn-0.20%Mo steel or 0.05%C-2.1%Si-2.4%Mn steel should be finish-rolled just above Ar3 point and coiled below 600°C.
    From the investigation of transformation behavior by dilatometric test and micro-segregation analysis by EPMA, the mechanism for generating the DP structure is considered as follows: Silicon is so effective for polygonal ferrite to be formed quickly and easily even under an accelerated cooling by water spray on a runout table, and at the same time carbon is enriched in the untransformed austenite portion. Most of the austenite transforms to martensite at the range of temperature lower than 300°C even under slow cooling after coiling, due to the increased hardenability attained by the enriched carbon and the presence of molybdenum, chromium, manganese, etc. in solution.
    The constituents of untempered martensite and high volume fraction of polygonal ferrite bring about the same mechanical properties in as-rolled DP steels as in heat-treated DP steels. For example, yield ratio of the former is as low as that of the latter.
    Also, a retained austenite was observed in as-rolled DP steels by transmission electron microscopy and, from an X-ray diffraction technique, the volume fraction was found to be 1-3%.
  • Intergranular Segregation and the Resultant Embrittlement in P-doped 2.25 wt% Cr Steels with Variations in Mo and C Contents

    pp. 1926-1935

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    In P-doped 2.25 wt% Cr steels with variations in Mo and C contents, isothermally aged (embrittled) at 773 K for times up to-1 000 h, the intergranular segregation and embrittlement behavior has been examined by means of Auger electron spectroscopy and instrumented Charpy impact tests. C, Cr, and Mo, together with P, segregated to the grain boundaries, but their segregated concentrations were believed to vary widely in different grain boundary facets. In contrast to the enrichment of the intergranular P concentration, depletion of the grain boundary C concentration was found during the first step of aging. In addition to the retardation effect of Mo on the segregation to grain boundaries of P, it also had an effect of suppressing the decrease in intergranular fracture strength due to P-segregation (“Direct strengthening effect”). The brittle fracture load (Lf) vs. temperature diagrams were divided into the lower temperature region (Region I) where Lf was independent of test temperature and aging time, and the higher temperature region (II) where Lf increased rapidly with test temperature, and also a further brittle region (III) which was specific to the high C steels. The transition temperature from region I to II was very sensitive to aging time in one steel but was not so in the other steel. The reason for this has been discussed.
  • Effect of Microstructure on Charpy Impact Properties in 80kg/mmm2 Grade Low Carbon High Tensile Strength Steel

    pp. 1936-1945

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    The Charpy impact properties of an 80kg/mmm2 grade low carbon high tensile strength steel were examined using an instrumented Charpy impact testing machine in the temperature range from -196 to 80°C with the V-notch half size specimens austenitized at 900, 1 000, and 1 100°C for 30 min followed by water quenching and tempering at 650°C for 1 h.
    The austenite grain size (dA) and the packet size (dP) of martensite lath bundle were 19 and 8.1 (in case of austenitizing at 900°C), 67 and 21 (1 000°C), and 150 and 93 μm (1 100°C), respectively.
    The crack initiation energy (E1), the propagation energy (Er), and the total energy (Et) were calculated from the load-deflection record and the transition behavior of these values was examined.
    The lower austenitizing temperature with the finer austenite grain size provided the higher value of upper shelf energy and the lower transition temperature. The Hall-Petch relation was recognized between the energy transition temperature and the inverse of root of dA and dP; ΔTrdA-1/2= -18 and ΔTrdP-1/2= -9.8°C/mm-1/2, respectively.
    The micro-fractography by S. E. M. revealed that the propagation of brittle crack in the low temperature range proceeded on (100) α in the cleavage mode with localized shear deformation in a packet.
    The refined grain of austenite (2.4 μm) could be obtained by the up-quenching method. This material resulted in the excellent resistance to brittle fracture because of the long total path of crack through packets.
    The apparent dynamic fracture toughness was related to the value of crack initiation energy per unit area in ligament under notch.
    The lateral expansion quantity was linear with the absorbed energy in the temperature range lower than the transition temperature, and the upper limit value of lateral expansion quantity in the relation may be considered as a characteristic.
    x

    Readers Who Read This Article Also Read

    1. Heat Transfer Phenomena in Immersion Cooling of Heated Steel Plate and Influence of Water Stirring on Heat Transfer Tetsu-to-Hagané Vol.64(1978), No.1
    2. 第97回講演大会討論会講演概要 Tetsu-to-Hagané Vol.65(1979), No.2
    3. 第95回講演大会討論会講演概要 Tetsu-to-Hagané Vol.64(1978), No.2
  • Irradiation Effects in Iron Whisker

    pp. 1946-1952

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    An investigation was carried out on the formation and recovery of radiation defects of iron whiskers irradiated by Rikkyo University reactor (TRIGA 11 type) and Kyoto University Reactor (KUR).
    Iron whiskers produced by hydrogen reduction of liquid iron halide salt were irradiated to a fission neutron dose of-1016 n/cmm2 (>1.28 MeV) at 19±1°K and the electrical resistivity changes (Δρ) were measured during irradiation.
    It was shown that Δρ was proportional to neutron dose (φt) in the present dose range, and the defect formation velocity (i. e. dΔρ/dφt) varied with direction of neutron incidence.
    On the basis of the present study it is suggested that the direction dependence of (dΔρ/dφt) is due to that of threshold energy.
    On the other hand some whiskers have been isochronally annealed after irradiation and mechanical properties, for instance upper yield stress, were measured using an Instron type tensil machine at -196°C.
    Annealing after neutron irradiation was found to cause a softening effect on iron whiskers; the upper yield stress remained unchanged on annealing temperature up to 330°C and then recovered steadily until it returned to the unirradiated value at 500°C.
    It is presumed that softening of iron whiskers is attributed to aggregation of point defects such as dislocation loops.
  • Crevice Corrosion Test Method for Stainless Steel

    pp. 1953-1962

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    Study was carried out for the purpose of finding laboratory crevice corrosion test method necessary for the development of sea water resistant stainless steels. The test results obtained are as follows:
    (1) Pitting potentials or immersion test in ferric chloride solution could not evaluate the corrosion resistance of stainless steels to sea water, in which crevice corrosion is prevalent on stainless steels.
    (2) A new laboratory crevice corrosion test method was developed which consisted of immersing crevice test specimen in an aerated solution with 3%NaCl, 1/20 M Na2SO4, and activated carbon. Activated carbon was mixed into the solution with the weight ratio of 2 parts of activated carbon to 5 parts of the solution. The test results obtained by this method were correlated well with the immersion test results in sea water.
    (3) The role of activated carbon on the crevice corrosion of stainless steels was to enhance the cathodic reduction of oxygen by increasing active cathodic site on the outer surface of crevice test specimen. Accordingly, the corrosion potential of stainless steel in the test solution having approximately the same pH value as that of sea water changes to the potential nobler than Vcrev. (the initiation potential for crevice corrosion), and then crevice corrosion occurs in shoter period compared with field test in sea water.
  • Man and Robot

    pp. 1963-1971

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    x

    Readers Who Read This Article Also Read

    1. Heat Transfer Phenomena in Immersion Cooling of Heated Steel Plate and Influence of Water Stirring on Heat Transfer Tetsu-to-Hagané Vol.64(1978), No.1
    2. 第97回講演大会討論会講演概要 Tetsu-to-Hagané Vol.65(1979), No.2
    3. 第95回講演大会討論会講演概要 Tetsu-to-Hagané Vol.64(1978), No.2
  • 中国金属学会1978年年会 (北京)

    pp. 1972-1975

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  • 抄録

    pp. 1976-1981

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