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

Tetsu-to-Hagané Vol. 69 (1983), No. 7

  • Materials for Energy Saving of Automobile

    pp. 721-727

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  • Current and Future Problems in Corrosion Fatigue Research

    pp. 728-736

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  • Report of the Activity of Joint Research Committee on Heat Transfer in Reheating Furnaces

    pp. 737-738

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  • Determination of Young's Modulus and Poisson Ratio of Lump Ores

    pp. 739-745

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    Mechanical properties of iron ores are measured under the compression test.
    The results obtained are as follows:
    (1) Young's modulus of iron ores is proportional to the apparent specific gravity respectively. And the Young's modulus of the hematite shows considerably higher than that of the magnetite.
    (2) Young's modulus of iron ores can be expressed as a straight line, independent of the ore brand, when it is indicated against the porosity.
    (3) Poisson ratio of hematite and magnetite is 0.24 and 0.33 respectively.
    (4) There is a remarkable difference of Young's modulus between pellet and iron ore.
  • Smelting Reduction of Composite Pellet of Iron Ore with Coke by Arc Plasma

    pp. 746-752

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    The possibility of direct steelmaking utilizing smelting reduction of iron ore by coke was investigated by using argon plasma jet as a heat source. Coke powder was included in an iron ore pellet for the promotion of reduction and the weight of pellets charged ranged from 1.2 to 3.8 kg. The typical composition of metals obtained with the slag containing 23%Fe and 0.0020.005%P is 0.5%C, 0.2%S and 0.018%P, the process being accompanied by the significant gaseous desulfurization and dephosphorization. This may be attributed to the carrying effect of gaseous species of S and P by CO which vigorously evolves on the very rapid reduction of iron ore at high temperatures due to plasma heating, and to good contact between ore and coke in pellets. The addition of flux such as CaO and CaF2 improved the final composition of metals to yield 0.15%C, 0.003%P and 0.05%S.
  • Behavior of Penetration of Solid Particle into Liquid Metal

    pp. 753-759

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    The present study has been made to obtain fundamental knowledge on the mechanism of contact of particles with liquid metal during powder injection. A spherical body was dropped onto a stagnant mercury bath and the behavior of the penetration of the sphere was recorded by a high speed cinecamera. The spheres tested were of glass, sapphire, stainless steel, and hastelloy B (diameter =0.159 0.953 cm).
    The sphere impinging the liquid surface makes a cavity. Then the sphere jumps up from the surface of the cavity when the entry velocity is lower than a critical one. At higher entry velocities, however, the impinging sphere dips into the liquid while the cavity disappears; shortly afterward the sphere rises back to the surface with a mercury film. Based on the measurement of the jumping height of the sphere and the time during which the sphere is immersed in the liquid, the critical entry velocity for the particle penetration into the liquid has been determined.
    Taking into account the inertia of the liquid surrounding the sphere and the cavity formation, one has given a new model describing the penetrating behavior of the sphere into the liquid. The experimental results are well explained by the theoretical calculation. It is shown that the cavity formation plays an important role in the mechanism of contact of particles with liquid metal.
  • Dephosphorization of Fe-Mn-C Molten Alloys

    pp. 760-766

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    The dephosphorization of Fe-Mn-5%C-0.1%P melts containing 4 to 27% of manganese was studied by using K2CO3-KF, K2CrO4-KF, and K2CO3-KCl fluxes. As a result, 75% of phosphorus was removed from Fe-16%Mn-5%C-0.1%P melt by 70%K2CO3-30%KF at 1250°C with 2% of manganese loss, for example. The 50%K2CrO4-50%KF flux was as effective for the dephosphorization below 20% of manganese as 70%K2CO3-30%KF but the manganese loss was less than in the latter case.
    The phosphate capacity defined as (%PO43-Pp2-1/2·PO2-5/4 was estimated for various fluxes and that of the K2CO3-KF flux, 1026 was found to be far greater than those of conventional slags.
  • Estimation of Oxygen and Nitrogen Absorption of Molten Steel during Tapping from Converter

    pp. 767-774

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    The amounts of nitrogen and oxygen absorbed during tapping from the converter are estimated. The mass transfer coefficient in the liquid phase during tapping becomes large as 0.1.0.2 cm/s, due to the violent agitation of molten steel in the ladle. Absorption efficiencies of nitrogen by air entrainment, ηE, and through the surface of tapping stream, ηst, decrease with increasing oxygen content in the molten steel. Although the amounts of nitrogen and oxygen absorbed during tapping are practically independent of the tilting rate, the heat size, and the profile of the converter, they decrease with decreasing tapping height and somewhat increase with increasing slag depth in the converter. It is also estimated that those amounts increase with decreasing tapping hole diameter and with increasing its length.
    A nomograph for the estimations of oxygen and nitrogen absorptions by the gas entrainment and also through the surface of tapping stream was proposed. The estimated amounts of nitrogen absorbed during tapping agreed well with the values reported in the literature.
  • Direct Stainless Steelmaking by AOD Process with Top Blowing from Molten Fe-Ni and Fe-Cr Materials

    pp. 775-781

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    The LD-AOD process was previously reported. This report is concerned with direct stainless steelmaking by AOD process with top blowing from molten Fe-Ni and Fe-Cr materials, which has been investigated in order to get increased saving of materials and energy. The results obtained are as follows:
    1) The steelmaking process can be simplified because of unnecessary pretreatment in the E.F. or the L.D. converter.
    2) AOD with top blowing is effective to refine high carbon (C = 3.54.5%) and high silicon (Si = 1.52.5%) molten alloys. It results in increase of the decarburization and desiliconization rate, and consequently reduces operation time and Fe-Si consumption.
    3) Although 84% of the inert gas consumed is nitrogen, the nitrogen content in the products can be controlled below 650 ppm.
    x

    Readers Who Read This Article Also Read

    1. Recent Progress of AOD Process Tetsu-to-Hagané Vol.63(1977), No.13
    2. Decarbonization Process and the Improvement of Material Property for Stainless Steel Zairyo-to-Kankyo Vol.44(1995), No.1
  • Roll Wear in Hot Strip Test Mill

    pp. 782-789

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    A small laboratory scale hot strip test mill was developed for the purpose of studying the roll wear in a hot strip mill. Using the test mill, various phenomena observed in production mills were reproduced. They were wear patterns, cracks, cat-ear wear, black film, effects of oil lubrication, and so on. The phenomena in the test mill were compared with those in production mills and utility of the test mill was discussed.
    Using the test mill, anti-wear properties of mineral oils and fatty acids were estimated. It was found that some mineral oils increased the roll wear. It was also found that stearic acid in a mineral oil had an excellent anti-wear property. The relation between anti-wear properties and lubricity was discussed. The different effects of fatty acids on the roll wear were considered to come from the enlargement of difference of their lubricity due to very long rolling length.
  • Effects of Cold Working Prior to Aging on Hydrogen-induced Cracking of 18Ni Maraging Steel

    pp. 790-797

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    Sustained load tensile testing has been made while under cathodic charging with hydrogen using notched sheet specimens of an 18% Ni maraging steel. Two kinds of specimens as to the way of processing prior to aging have been prepared; R-specimens which were cold rolled after solution treatment, and S-specimens undeformed after solution treatment. Aged S-specimens have shown characteristic delayed failure, accompanied with subcritical intergranular fracture surfaces. No. fracture has been observed below a stress called the lower critical stress, at which the local concentration stress at notch roots is found to be identical to the yield stress of the specimens.
    Cold rolling prior to aging has resulted in great suppression of hydrogen induced intergranular cracking, and the fracture lives are increased even by 70 times with rolling reductions up to 30%. The effect, however, is being saturated in the heavier reduction of 80%, where the delaminations along rolling planes have been observed. From fractographic evidence, apparent Kc has been found to decrease greatly in 5-specimens during the testing, but not remarkably in R-specimens.
    No delayed failure has been observed in 80%-rolled R-specimens when the age-hardening is confined within the strength level of conventionally treated (i.e. non-deformed and peak-aged) S-specimens.
  • Wetting Characteristics of Aluminium-killed Steel with Molten Zinc

    pp. 798-805

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    Relations between Al-enrichment to the surface layer of Al-killed steel sheets during short-time heating in an H2-N2 atmosphere and its wetting characteristics with a molten zinc were studied in connection with the surface structures of the steel sheets.
    1) The wettability of Al-killed steel sheets with the molten zinc after the reduction-heating for a short time varies depending on the Al concentration of the surface layer. It is degraded in accordance with the thickness of aluminosilicates which is formed on the surface layer.
    2) While the degree of Al-enrichment is notably increased by heating at temperatures above 800°C, the wettability does not decrease. In this case, the film consists of a defect spinel type structure of <111> oriented γ-Al2O3 which is partially substituted with Fe at the vacancy site.
    3) The degree of Al-enrichment to the surface layer varies depending on the quantity and the state of Al in the steel sheets. When Al is stabilized as AlN, the Al-enrichment by reduction-heating is significantly depressed.
    4) The wettability does not decrease after the partial oxidizing treatment which forms visible oxide films on the steel surface, followed by the reduction-heating.
  • Pine Cone Like Fracture Surface and Temper Embrittlement of 5.5%Ni Steels

    pp. 806-814

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    Pine cone like fracture surfaces ("pine cone") were observed in Charpy and compact tension specimens of cryogenic Ni steels containing retained austenite when temper embrittled and broken in a brittle manner. 5.5Ni steels, especially those bearing no molybdenum, were severely embrittled on slow cooling from the final tempering, and their fracture surfaces were mainly composed of "pine cone". Microscopic observations and various mechanical tests were performed to elucidate the characteristics of this fracture surface.
    It was found that "pine cone" is a kind of intergranular fracture surfaces and produced by fracture along P segregated α'/γ interfaces which formed at prior austenitic grain boundaries and its roughness is not caused by precipitates but the reverted austenites at grain boundaries. Intercritical heat treatment promoted austenite formation at grain boundaries and enhanced the roughness of "pine cone" and suppressed "pine cone" fracture. It was also found that the reverted austenite was not stably present on "pine cone" fracture surface through Mössbauer spectroscopy nevertheless reduced susceptibility to temper embrittlement.
  • Grain Refinement and Tensile Properties of 17.5Ni Maraging Steels with High Strength

    pp. 815-820

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    Solution-treatment temperature and the refinement of austenite grains by solution-treatment after cold working have been investigated for 17.5Ni-12.5Co-Mo maraging steels with and without titanium. Titanium contents were 1.7 and 2%, and molybdenum content varied from 3.9 to 6.5%.
    Optimum solution-treatment temperature rises with the increase in molybdenum or titanium content. When the solution-treatment after cold working is applied to the maraging steels which were previously solution-treated at relatively low temperatures, austenite grains are possible to be refined considerably.
    Tensile properties after maraging in the temperature range 500° to 560°C have also been investigated for 17.5Ni-12.5Co-5.4Mo-2Ti and 17.5Ni-12.5Co-6.2Mo-1.7Ti maraging steels, the austenite grains of which were refined by solution-treatment after cold working. Maximum tensile strengths obtained are about 280 kgf/mm2 for the 17.5Ni-12.5Co-5.4Mo-2Ti steel and about 270 kgf/mm2 for the 17.5Ni-12.5Co-6.2Mo-1.7Ti steel. Because of fine austenite grains, the materials are ductile even in high strength level.
  • The Crystal Structures of Oxide Films and Their Effect upon Corrosion Resistance of Bright-annealed SUS 434 Ferritic Stainless Steel

    pp. 821-828

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    In the previous paper, 1) it has been reported that the crystal structures of oxide films formed on the surface of bright-annealed type 430 ferritic stainless steel depend on the bright-annealing conditions and chemical composition, especially Mn and Si contents of the steel, and influence the corrosion resistance of the steel to dilute sulphuric acid.
    This paper deals with the influence of oxide films formed on the surface of type 434 steel upon the corrosion resistance to dilute sulphuric acid, when bright-annealed under various treating conditions.
    The results obtained are as follows;
    Despite that SUS 434 contains Mo as an important element to improve the corrosion resistance, oxidation behaviour of the steel (Si : 0.45%, Mn : 0.52%, Mo : 0.99%) in H2-H2O atmospheres with dew points of -10° to -40°C at temperatures of 800° and 900°C is almost same as that of type 430 containing same contents of Mn and Si. The crystal structures of oxide films formed on the surface of the steel, when treated in the atmospheres with dew points of -10° to -30°C at 900°C, are mainly MnCr2O4 and SiO2. With increasing dew point in this range, the formation of inner oxide layer is promoted and SiO2 precipitates in the substratum near the interface between oxide film and substratum. On the contrary, with decreasing dew point, SiO2 precipitates densely and forms an external oxide film with MnCr2O4.
    The corrosion resistance behaviour of bright-annealed SUS 434 can be explained by the variation of the microstructure and thickness of the oxide films formed under the varied treating conditions.
  • Effect of Austenite Grain Size on Stress Corrosion Cracking Behavior of 25Cr-6Ni-2Mo Duplex Stainless Steel

    pp. 829-836

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    The effect of γ grain size on stress corrosion cracking (SCC) behavior of a 25Cr-6Ni-2Mo duplex stainless steel was studied by means of constant load method in boiling 42%MgCl2 solution. The main results obtained are as follows:
    (1) On heating at 950 or 1050°C, the growth of γ grain was nearly proportional to one-half power of holding time and SCC susceptibility increased with the grain growth of γ. By preparatory heating at 1150 or 1300°C before the final heat treatment of 0.5 h at 950°C, γ grain was coarsened remarkably and SCC susceptibility was increased up to that of SUS304.
    (2) On isothermal aging at 475°C for long time, SCC susceptibility of the microduplex structure decreased remarkably as compared with that of the coarser structure. In the coarser structure, deformation twin formed easily in α by applied stress after aging, and it should be directly connected with the initiation of cracks. In the microduplex structure, however, did not form.
    (3) In both of the microduplex and coarser structure, the cracks propagated preferentially in α and the interface of α and γ similarly to the case of non-aging, and the crack restraining effect was observed in γ.
  • Influence of Alloying Elements on the Susceptibility of Austenitic Stainless Steels to Chloride Stress Corrosion Cracking

    pp. 837-844

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    The influence of alloying elements on the susceptibility of austenitic stainless steels to chloride stress corrosion cracking has been investigated by means of 8 months' exposure test of spot-welded specimens at the interface of air and sodium chloride solution with 1000 ppm Cl- or 21000 ppm Cl- at 80°C.The occurrence of stress corrosion cracking has been clearly detected on the cross section of the specimen. Both 18Cr-10Ni stainless steel and 18Cr-18Ni stainless steel showed susceptibility to stress corrosion cracking in spite of the decrease in the amount of carbon, nitrogen, phosphorous and sulphur, or the addition of small amount of titanium, niobium, zirconium, vanadium, and tungsten. The addition of 2 wt percent of copper, however, made the steels immune to chloride stress corrosion cracking, while the addition of silicon and molybdenum by 2 wt percent had no effect to its protection.
  • Effect of Recrystallization on Damping Capacity and Mechanical Properties of Sintered Ferritic Fe-16.5Cr and Austenitic Fe·25Cr-20Ni Alloys

    pp. 845-852

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    The effect of the fine recrystallized grains by annealing on the damping capacity was investigated by using of powder alloys. After sintering ferritic Fe-16.5%Cr powder and austenitic Fe-25%Cr-20%Ni powder were rolled 40%, 60% and 80% and annealed at various temperature heated for 1 h, the damping capacity, the hardness and the tensile properties for these specimens were measured at room temperature. Only sintering austenitic Fe-25%Cr-20%Ni powder rolled 80% and annealed at 820°C indicated good results that the internal friction Q-1 was 1.0 × 10-2, the ultimate tensile strength σB was as high as high tensile steel, 69 kgf/mm2 and the total elongation δ was 18.7% in spite of powder alloy.
  • Some Properties of Platelike Carbides Generated by the Rolling Contact Fatigue

    pp. 853-860

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    A study has been made on the characteristics of the platelike carbides formed under the rolling track during the thrust type rolling fatigue tests. By EPME analysis, chemical shift measurements by EPMA of C-K bands, and electron microscope observations, the platelike carbides are found to be cementites and ε carbides formed independently at a ratio of 1 to 1.
    EPMA analysis shows that concentrations of Mn and Cr in the platelike carbides are the same as in the matrix. The platelike carbides, cementites or εs carbides, are etched dark by alkaline sodium picrate in similar tone. When heated to 800°C, the platelike carbides dissolve into the matrix as the spheroidized cementites do.
  • Effects of Vacuum Carbon Deoxidation, Extra Low Sulfur Content, and ESR Process on the Quality of Cr-Mo-V Rotors

    pp. 861-867

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    In order to improve the quality of the central axial part of CrMoV steel rotors, the investigations were performed on the rotors made of conventional Si-killed steel, extra low sulfur Si-killed steel, vacuum carbon deoxidized (VCD) steel, and electroslag remelted (ESR) steel.
    From the comparison of sulfur prints of the end cross sections of the rotors, an inprovement in the segregation pattern was observed in the rotor made by applying VCD and the reduction of segregates was found in the rotor made of extra low sulfur steel.
    The rotor manufactured from ESR ingot showed the best result; in addition to finding no spot in sulfur print, there was no indication in the magnetic particle test of the axial bore in the magnetizing condition of 700 ampers per inch of the bore diameter. Some indications were detected, however, in the condition of 300 amperes per inch on the rotor made of Si-killed steel.
    These results have been discussed in the light of the current concepts on segregation.
  • Fatigue Crack Propagation Properties and ΔKth for Several Structural Steel Plates

    pp. 868-873

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    The fatigue crack propagation properties and ΔKth of three kind of ferrite-pearlite steels (SS41, SM41, and SM50A) and five kind of martensitic steels (SM58Q, 5.5%Ni, A553A, HT80, and SCM435) have been investigated at varying stress ratios (-10.8) by using an automatic method of continuously decreasing stress intensity factor with crack propagation. The correlation between mechanical properties and fatigue crack propagation properties is not clear. The scattering of fatigue crack propagation properties and ΔKth of these steels is within the factor of two. This scattering is smaller than the distribution induced by the different stress ratios.
  • 釜石製鉄所と香村さん/鉄は国家/しんかい2000と鉄鋼材料

    pp. 874-879

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  • 抄録

    pp. 884-886

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