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

Tetsu-to-Hagané Vol. 69 (1983), No. 2

  • Present Status of Underwater Welding Technology

    pp. 187-195

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  • Crack Depth Measurement with High Accuracy by Ultrasonics

    pp. 196-202

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  • 先進国及び主要国の粗鋼生産・製法別構成推移/製管の歴史(6)-UOE製管法の進歩-/訪中所感

    pp. 202-202,341

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  • The Full Scale Burst Test of Large Diameter, High Pressure Gas Pipelines

    pp. 203-209

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  • On Simultaneous Dephosphorization and Desulphurization of Pig Iron with CaO-CaCl2 Fluxes

    pp. 210-219

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    Characteristics of CaO-CaCl2 fluxes were studied in order to develop a new refining process of hot metal which would enable the production of steelmaking slag to decrease from the standpoint of environmental issues and improvement of controllability of LD process. Conditions of simultaneous dephosphorization and desulphurization of hot metal were investigated based on electrochemistry of the slag-metal system.
    The results are summerized as follows:
    1) Larger distribution ratios of sulphur and phosphorus of the flux to the metal are necessary for simultaneous dephosphorization and desulphurization of hot metal from equilibrium and kinetic considerations.
    2) Anodic reaction of phosphorus removal from the iron saturated with carbon is coupled with the cathodic reaction of sulphur removal, in the case of using a flux with large sulphide and phosphate capacities such as CaO-CaCl2. But additional oxidizers are necessary to attain effective dephosphorization.
    3) CaO-CaCl2 was found to have many excellent characteristics such as larger phosphate as well as sulphide capacities than those of conventional slags, extremely low viscosity like water, low melting point and the small rate of vaporization.
    4) High alumina brick is hardly attacked by CaO-CaCl2 but high zirconia brick is eroded remarkably.
  • State of Sulphur in a Synthetic Blast Furnace Slag and Relation between Segregation of Sulphur and Morphology of Primary Phase

    pp. 220-227

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    State of sulphur in a synthetic blast furnace slag was investigated by visible and infrared absorptions, electron spin resonance (ESR) of ferric ion and S Kα X-ray emission spectroscopy. Morphology of primary phase and relation between sulphur segregation and morphology of primary phase were investigated by scanning electron microscope observation and X-ray microanalysis. From chemical shifts of S Kα X-ray emission spectra it was indicated that sulphur in the synthetic blast furnace slag are in the forms of S6+ and S2-ions under weak (PO2≅10-3 atm) and strong(PO2≅10-8 atm) reducing conditions, respectively. The results of optical absorption and ESR measurements supported the fact that strong interaction between ferric and sulphur ions in the reducing condition is not attributed to Fe3+-S2- interaction but to simple oxidizing effect of sulphur. Morphology of primary phase, in most cases, was spherical. Segregation of sulphur was not always detected in primary phase.
  • Cold Model Study of Characteristics in LD Converter with Bottom Blowing

    pp. 228-237

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    Cold model experiments have been conducted to evaluate the influences of flow rate of bottom-blown gas, number and configuration of tuyeres, bath depth and top blowing conditions on mixing characteristics arid splash behavior in top blowing converter with bottom blowing.
    In such shallow bath as that in LD converter, mixing rate depends mainly upon flow rate of bottom-blown gas, and is not strongly influenced by other factors.
    Splash behavior is determined, however, by top blowing conditions.
    Combined blowing can be optimized when ca. 10% of total oxygen is blown from the bottom, the balance being blown from the top with lance situated higher than normal.
    Efficiency of utilization of the energy of top-blown gas for the mixing of the bath is considered to be much smaller, about one tenth, of that of bottom-blown gas.
  • New Application of RH Degassing Technology in Ladle Metallurgy

    pp. 238-247

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    A new process has been developed as a result of R & D effort to investigate and establish the feasibility of applying degassing technology to the molten steel to produce steels with low concentration of phosphorus, sulphur, oxygen and hydrogen.
    The VOF process (namely Vacuum-Oxygen-Flux Process) consists basically of the following steps; (1) desulphurization during tapping of molten steel from an LD converter, (2) transferring the desulphurized liquid steel to a ladle during which slag is removed from the molten bath, (3) heating the molten steel in the RH vessel, (4) adding the flux of 1 : 1 mixture of lime and fluorite into an RH vacuum vessel for further desulphurization, degassing and deoxidation of the molten steel.
    The new development has made it possible to reduce the sulphur content of steel down to approximately 0.002 percent, phosphorus content to 0.015 percent, oxygen content to 0.002 percent and hydrogen content to 0.00015 percent.
  • Effects of Mould Oscillation Conditions on Oscillation Marks of Stainless Steel Casts

    pp. 248-253

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    Oscillation marks formed on the surfaces of continuously cast stainless steel slabs are one of the factors that hinder the use of unconditioned slabs. Therefore, the effects of mould oscillation conditions on oscillation marks have been investigated using a Continuous Caster Mould Simulator.
    Following results have been obtained through the experiments.
    1) A crescent-shaped extended surface is formed in the valley of an oscillation mark on a SUS 304 solidified shell and an unusual solidified structure is generated in the upper part of this extended surface. The unusual solidified structure is found to be a layer of Ni-segregation.
    2) When the negative strip ratio is positive, the shorter the heal time ((θh), the shallower the oscillation mark depth.
    3) Oscillation marks are formed even at θh-0 and when the negative strip ratio is negative, the shorter the stroke, the shallower the oscillation mark depth.
    x

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    1. Fundamental Study and Its Application of Surface Defects of Powder Cast Strands Tetsu-to-Hagané Vol.67(1981), No.8
  • A Theoretical Study of the Cooling of a Disk by an Impinging Jet of Water

    pp. 254-261

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    Theoretical studies were made to discuss the mechanism of unsteady heat transfer in the system used in the previous experiments, in which a disk of mild steel is cooled at 373K by an impinging jet of water.
    Four models were discussed concerning the convective heat transfer in the liquid, those of which are unsteady-state model (A), quasi-steady-state model (B), steady-state and constant heat flux model (C) or constant wall temperature model (D).
    First, distributions of temperatures in the fluid and solid, local heat fluxes and local Nusselt numbers at the fluid-solid interface were computed by model A and B. It was found that the results of model A were consistent with those of model B except initial stage of cooling, and that the calculated temperatures in the solid were consistent with observed ones.
    Secondly, distributions of temperatures in the solid were computed by model C and D. Model C showed a suitable agreement with calculated ones by model A and B, and observed ones, while model D showed lower temperature than observed ones. From these results, it seemed sufficient to use model C for estimation of temperature in the solid.
  • Cooling Characteristics and Heat Transfer Coefficients during Water-spray Cooling of Hot Steel Plate

    pp. 262-267

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    Water-spray cooling is widely applied to forced cooling of hot steel products. A number of problems, however, still remain to be solved, including heat transfer mechanism, cooling ability, the difference of heat transfer coefficient values between the upper and lower surfaces of a horizontally placed wide plate on which spray is impinged, the effect of scale deposit on heat transfer, and so on.
    In order to investigate heat transfer phenomena and cooling abilities of water-spray cooling, plate specimens of carbon steels with dimension of 22.5 to 51mm×550mm×1 000mm, heated at about 630°C, have been water-sprayed. The main results obtaind are as follows:
    (1) In the water-spray cooling of the upper and lower surfaces of a horizontally placed specimen with the same water flux W, the value of the heat transfer coefficient α on the upper surface is higher than that on the lower surface in the region of test conditions.
    (2) The maximum values of α of the upper and lower surfaces exist in the surface temperature of about 200°C.
    (3) The following equation is applicable for describing the quantitative relation of specimen surface temperature θs [°C] and W[l/m2 · min] with α [kcal/m2·h·°C].
    α= A·W0.8 · 10B·θs
    where, A and B are constant.
  • Heat Transfer Coefficients in the Surface Temperature Range of 400 to 800°C during Water-spray Cooling of Hot Steel Product

    pp. 268-274

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    Heat transfer coefficients (α) of water-spray cooling in the region of steel surface temperature (θs) 400 to 800°C are numerically expressed as a function of θs and impinged water flux (W), by using published water-spray cooling data (7 papers, 112 data) measured with scale-coated steel specimens by many researchers. In the region of θs : 400 to 800°C and W: 10 to 2 000 l/m2 · min, αw is represented by the following equation,
    αw=2.292 × 108 · W0.616θs 2.445
    where αw is value of α without radiation heat transfer, [αw] being kcal/m2· h ·°C.
    In addition, are discussed features of exponents of W and θs, comparison of the above equation with other researchers' one, α in the film boiling region, and α calculation methods for θs between 125°Cand about 1 200°C.
    x

    Readers Who Read This Article Also Read

    1. Numerical Modeling for Cooling Process of a Moving Hot Plate by a Laminar Water Curtain ISIJ International Vol.29(1989), No.11
    2. Study on the Water Spray Cooling of Steel Plate at High Tempeature Tetsu-to-Hagané Vol.54(1968), No.14
  • Surface Roughness Caused by Hot Deformation in a Duplex-phase Stainless Steel

    pp. 275-282

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    Surface roughness caused by hot deformation in a 22.5Cr-6.25Ni steel with ferrite/austenite (δ/γ) duplex structure has been studied by using a Gleeble hot tensile machine. The results obtained are as follows :
    ( 1 ) Two types of surface roughness were observed to occur during hot tensile deformation; Type A : the isotropic severe surface roughness formed in the case of pre-heating in the δ-single phase region (_??_ 1 250°C), and Type B : ridging-like wrinkles along the rolling direction formed in the case of preheating in the δ-γ duplex phase region.
    ( 2 ) The surface roughness was found to depend on deformation temperature and prior thermal history especially in the case of Type A. The degree of surface roughness increased with either increasing pre-heating temperature or decreasing deformation temperature. Such observations can be explained in terms of the δ grain coarsening and the precipitation behavior of γ phase.
    ( 3 ) The surface roughness of the specimen pre-heated in the δ-single phase region increased by the deformation in δ-γ duplex phase region where γ grains precipitated continuously along δ grain boundaries in comparison with the deformation in the δ-single phase region.
    ( 4 ) The δ-matrix precipitation of γ grains during long time holding in the δ-γ duplex phase region reduced the surface roughness.
  • Effect of Hot Rolling on Mechanical Properties of Extra Low Carbon Cold Rolled Steel Sheet Containing Niobium

    pp. 283-290

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    Effects of hot rolling conditions on the mechanical properties of extra low carbon cold rolled steel sheets containing niobium have been investigated. The mechanical properties of this steel depend on the hot working conditions and heat history after hot rolling, and the former effect is stronger than the latter. Hot rolling with high reductions, high speeds or low finishing temperatures (≥Ar3) improves the Lankford-value and the ductility of cold rolled and continuously annealed steel sheets. The reason can be explained as follows. When carbo-nitride precipitation is accelerated through the hot rolling with the above conditions, the grain size of the hot rolled sheets becomes amaller and the density of fine carbo-nitrides precipitating after hot rolling decreases extremely. The smaller grain size of hot rolled sheets contributes to the improvement of Lankford-value. The low density of fine carbo-nitrides in hot rolled sheets increases the ductility of cold rolled and rapidly heated steel sheets.
  • Tensile Properties of 245 kgf/mm2 Grade 18Ni Steel Maraged after Ausaging

    pp. 291-297

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    A study has been made on the precipitation behavior in the austenite region of an 18Ni 245kgf/mm2 grade maraging steel. Because of relatively high titanium content, considerable precipitation-hardening is observed in ausaging. Tensile properties of the maraging steel preaged in the austenite region and maraged have also been investigated. The considerable increase in maximum tensile strength after an isothermal maraging is found in the maraging steel preaged in the austenite region. The maraging steel preaged at 550°C shows high tensile properties with good ductility after maraging. However, the maraging steel preaged at 600°C and maraged is less ductile because of relatively coarse precipitates formed at the austenite grain boundaries.
  • Effects of Boron and Nitrogen on Fracture Toughness of Boron treated 0.35%C Steels Tempered at Low Temperature

    pp. 298-307

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    Effects of boron, nitrogen, and controlling factors on fracture toughness KIC of boron-treated 0.35%C steels tempered at low temperature were investigated.
    1) KIC linearly increased with a value of β=34.0 B-13.3N, where B and N are boron and nitrogen contents (wtppm), respectively. Aluminium content gave little effect on KIC.
    2) Concentrations of boron and nitrogen in solution in austenite in equilibrium with BN and Fe2B were calculated from solubility products in the iron-boron-nitrogen systems.
    3) High content or concentration in solution of boron resulted in higher KIC because of suppression of both decohesion at inclusion-matrix interface and intergranular fracture. Quasi-cleavage like cracks were observed in steels having high content or concentration in solution of nitrogen, and KIC was reduced. However, effect of nitrogen on KIC was less than that of boron.
    4) Optimum amounts of boron and nitrogen required for high KIC were found from the iron-boron nitrogen equilibrium phase diagram.
  • Fracture Toughness Behavior and Its Analysis on Nuclear Pressure Vessel Steels

    pp. 308-315

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    A drop weight JId testing machine has been developed successfully, by which the multiple specimen J resistance curve test technique can be applied to measure the fracture toughness. In this study, the use of a small size round compact tension (RCT) specimen for measuring the fracture toughness JIc or JId of the nuclear pressure vessel steels is recommended and confirmed for the surveillance tests.
    The static and dynamic fracture toughness of ASTM A508 C 1.2, A508 C 1.3 and A533 Cr.B C 1.1 steels in the wide range of temperature including the upper shelf have been measured and their behavior has been analysed. The fracture toughness behavior under various strain rates and in a wide temperature range can be explained by the behavior of stretched zone formation preceding the crack initiation. The scatter of KJ values in the transition range is caused by the amount of crack extension contained in the specimens. In this paper, the method to obtain the fracture toughness equivalent to the KIc from the KJ value is also presented.
  • Improvement of Toughness of Weld Portion of 3.5% Ni Steel Pipes for Low Temperature Service Produced by UOE Process

    pp. 316-325

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    Studies on welding method, consumables and heat treatment in the laboratory and mill production test have been conducted to produce 3.5% nickel steel UOE-pipes suitable to be used for around -100°C service by the following process, namely, (A) normalized plates→UOE (inside : SAW/ outside : MIG)→pipe SR and (B) as rolled plates→UOE (SAW)→pipe QT. The manufacturing procedure has been established by UOE process.
    (1) To weld pipe A using the wire of 1.6Mn-3.1Ni-Ti-B steel with the high current MIG process can give the high toughness to the weld metal and HAZ in both as welded and stress-relieved condition.
    (2) The optimum condition for the rapid heating cycle in a short time in pipe B is to quench at 950°C and temper at 630°C for 6 min. The hardness and toughness of weld metal and HAZ are improved by quenching and tempering.
    (3) Based on the above studies in the laboratory, both types of pipe A and B meeting with the standard of ASTM A671-CF71 and A333 Gr.3 have been developed and manufactured in the mill production scale.
  • Emission Spectrochemical Determination of Boron in Steels with Pulse Height Distribution Analyzer

    pp. 326-332

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    The method for rapid determination of total, acid soluble and insoluble boron was established by using emission spectrochemical apparatus equipped with pulse height distribution analyzer. By using the analyzer, emission intensity can be expressed as different level intensity of pulse height distribution. It was made clear that soluble and insoluble boron had different contribution degree to each intensity and that this contribution degree varied at different pre-spark. Therefore, it is necessary for accurate determination of boron that this contribution degree should be corrected by using two intensities, of which contribution degrees are different. It was found on this two intensities method that total and soluble boron corresponded well to 50% intensities at zero pre-spark and at 2 000 pre-spark and that insoluble boron corresponded well to 70% intensity at zero pre-spark and 50% intensity at 2 000 pre-spark.
  • 教師と教科書の中の鉄鋼

    pp. 333-334

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  • 抄録

    pp. 338-341

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