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

Tetsu-to-Hagané Vol. 75 (1989), No. 8

  • The Purification of Rare Earth Metals Using Solid State Electrotransport

    pp. 1237-1246

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  • Superplasticity of Ferrous Alloys and Steels

    pp. 1247-1257

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  • Development and Application of High Strength Superplastic Aluminium Alloys

    pp. 1258-1266

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  • Quantitative Evaluation of Effects of Defects and Non-metallic Inclusions on Fatigue Strength of Metals

    pp. 1267-1277

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  • Development of Oxygen Blast Furnace Process with Preheating Gas Injection into Upper Shaft

    pp. 1278-1285

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    A new blast furnace process has been developed which blows normal temperature oxygen in place of the hot blast through the tuyeres and injects preheating gas into the upper shaft.
    For the development of this process, mathematical model simulations and operation tests with an experimental blast furnace were done. The test operation was so stable that this process was technically verified to be consistent as an ironmaking process. The pulverized coal was injected up to the ratio of 0.94 kg-coal/Nm3-oxygen. The high productivity of 5.1t/dm3 was realized. According to the analysis of measurements during the operation and dissection results, this process has been verified to have the following characteristics; (1) The preheating gas injection lowers the heat flow ratio and raises the temperature in a whole section of the furnace. (2) The gaseous reduction takes place fast at relatively low temperature region and the content of the boudouard reaction is low. (3) The silicon content in metal is lower than that in the hot blast.
    The lower limit of the fuel rate was estimated 530 kg/t for a commercial blast furnace.
  • Silicon Transfer Estimated by the Raceway Data

    pp. 1286-1293

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    The mechanism of silicon transfer in the blast furnace was examined through fundamental experiments, chemical analyses of metal and slag drips taken from the end of raceway during operation and measurements of PO2 at the same place.
    The (FeO) content in slag averages about 15wt% and oxygen partial pressure PO2 averages 10-12 atm at the end of raceway.
    These data imply that siliconization reaction via SiO gas from coke ash and slag occurs chiefly in the zone above and below tuyere level, respectively.
    Slag-metal reaction occurs chiefly in the zone below tuyere level and desiliconization reaction proceeds until (FeO) content in slag is reduced to about 0.2wt %.
    In the hearth, the slag-metal reaction, i.e. Si+2(FeO)=SiO2+2Fe, changes from desiliconization to siliconization reaction and [Si] content in metal approaches [Si]eq, at (FeO)=0.2wt %.
    If the [Si] content of dripping metal is more than [Si]eq at (FeO)=0.2wt% or (FeO) content in slag is more than 0.2wt%, siliconization reaction does not occur any more.
    The measured [Si] content agrees with the above equilibrium one in many blast furnaces. In some blast furnaces, however, the measured values are lower than the equilibrium ones. It is indicated that hot metal is tapped before the above equilibrium one is reached in these cases.
  • Atomization of Molten Metal by Use of Electromagnetic Force

    pp. 1294-1299

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    A new atomization process is proposed in which molten metal is atomized by electromagnetic energy instead of kinetic one produced by fluid impingement or disk rotation in the conventional atomization processes. This electromagnetic atomization process was tested to clarify characteristics of atomizing molten metal. It was found that a crucial operation factor is a contacting condition of molten metal with an electrode. In order to control the condition, a delay time controller unit was developed and incorporated in the electromagnetic atomization process. It is noticed that this controller works well to produce the better uniform size particles than those of conventional atomization processes.
    A linear relation between the impulse which is defined as the product of the imposed electromagnetic force and the period of current passing, and the momentum which is defined as the product of the mass and the velocity of splashed particle, is found by use of experimental data and this fact is explained from a theoretical view point.
  • Effect of Stirring Force by Bottom Blown Gas and Partial Pressure of CO in It on Characteristics of Metallurgical Reaction in a Converter

    pp. 1300-1307

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    Experiments were carried out in 5 t converter using five kinds of gases as a bottom blown gas in order to quantitatively evaluate the contributions of stirring force and dilution of PCO by bottom blown gas to characteristics of metallurgical reactions in a converter. On the basis of the experimental results, a new reaction model was proposed, which enables us to reasonablly explain the metallurgical reactions in a converter with bottom blown gases.
    The results obtained are summarized as follows;
    1) Independently of sort of bottom blown gas, oxygen concentration dissolved in steel decreases as increasing the gas flow rate of bottom blown gas.
    2) Taking into consideration oxygen transfer from metal to slag, the model can reasonablly explain the phenomena that concentrations of carbon and oxygen reduce to those in equilibrium with less than 1.0 atm of CO.
    3) The amount of oxygen transfer from metal to slag increases with increasing the stirring force by bottom blown gas and decreasing carbon concentration in molten steel.
    4) The effect of dilution of PCO on behavior of oxygen concentration in steel and (%T. Fe) in slag is considered to be small. Hence, the decreases of. oxygen and (%T. Fe) in IOD(Inert and Oxygen Gases Decarburization) mode result from the increase of stirring intensity by inert gas blown from bottom.
    x

    Readers Who Read This Article Also Read

    1. Q-BOP導入の頃の思い出 Tetsu-to-Hagané Vol.76(1990), No.11
    2. Measurement of Oxygen Potential and Temperature in Liquid Slag, Metal and Gas Phase of Q-BOP Converter by Oxygen Concentration Cell Tetsu-to-Hagané Vol.68(1982), No.2
    3. III.川崎製鉄(株)の場合 Tetsu-to-Hagané Vol.76(1990), No.11
  • Effect of Surface Active Element on the Initial Solidification Structure of Stainless Steel Ingot

    pp. 1308-1315

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    18-8 stainless steel ingots which are added with surface active elements, Bi, Sn, Te are cast with the water cooled copper mold at the pouring speed of 10 mm/s. Transverse and longitudinal microstructures in the vicinity of the surface of ingots are observed. The solidification microstructures become fine and the effect of rapid quenching increases with increasing the amount of the surface active element. Primary dendrite arm spacing is about 50μm at the 50μm from the surface of ingot which is not added with the surface, active element, but arm spacing is about 10μm in the case of 0.0055 mass %Bi addition. Corresponding cooling rate are 1×102 and 3×103K/s, respectively.From temperature distribution in the water cooled copper mold, heat flux are calculated. The maximum value of heat flux in the mold increases and appears soon, when the surface active element is added.It is seemed that by the addition of the surface active element wettability increases, therefore heat transfer coefficient between molten steel and mold increases. Furthermore, the surface active element seems to have the effect of increase of nucleation rate.
  • Discussion on Residual Stress and Camber after Longitudinal Cutting in Steel Plates

    pp. 1316-1323

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    Camber or in-plane warping of plates after longitudinal cutting occasionally becomes a problem, because it is very difficult to correct the deflection. In particular, the slit camber is large for steel plates by controlled rolling or cooling. As the slit camber is related to the residual stress, we carried out thermal stress analysis on the cooling process of steel plates. Then we considered a one-dimensional longitudinal stress state, thermoelastic-plastic material and stress relaxation. We examined the effect of controlled rolling (CR) and controlled cooling (On-Line Accelerated Cooling, abbreviated to OLAC) on the camber.
    The outline of result obtained is as follows.
    (1) Stress just after non-uniform deformation in ordinarily controlled rolling with the finishing temperature of 680-780°C causes the residual stress of maximum 100 MPa at room temperature. Therefore, the influence of rolling condition on the slit camber cannot be ignored.
    (2) The type of controlled rolling which generates tensile residual stress in the edge of width, reduces the slit camber caused by non-uniform cooling during OLAC.
    (3) Optimum value of masked edge for reducing the slit camber is 50-100 mm for 30 mm thickness.
    (4) Lower initial temperature or higher end temperature in controlled cooling reduces residual stress and its slope, which results in smaller slit camber.
  • Effect of Polyacrylonitrile (PAN) and Acrylic Emulsion (AE)-addition on the Properties of Insulating Coating for Non-oriented Electrical Steel Sheets

    pp. 1324-1331

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    In order to improve the characteristics of an insulating coating, addition of PAN and AE as resin components was investigated.
    The results were as follows.
    In the insulating coating with PAN and AE film defects such as fine crater were not found. On the contrary the coating without PAN easily formed film defects.
    It is supposed that PAN remains as particles even at drying temperature because of its high melting point and as a result, water which causes film defects vaporizes and escapes easily from the interior of the coating.
    A proper composition of PAN was found to be 25-75wt% of resin in the coating. Addition of PAN in this composition range, improves the corrosion resistance, TIG weldability, the interlaminar resistance, etc. of the coating.
    Poor punchability was perceived by single application of PAN, however excellent punchability was obtained by PAN/AE mixture.
  • Effects of Ni and Mo on Critical Conditions for Crevice Corrosion of Low Alloy Titanium

    pp. 1332-1337

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    Critical conditions to repassivate growing crevice corrosion in terms of electrode potential, ER, temperature, TR, and NaCl concentration, CNacl, R, were determined for metal/metal-crevice of ASTM Grade 12 (G 12 Ti) and Ti-x (=0?2%)Ni-y(=0?0.4%) Mo alloys.
    G 12 Ti with 0.8%Ni and 0.3% Mo has more noble ER values than commercially pure Titanium (C.P. Ti)and this tendency is more enhanced in lower concentrations of NaCl solutions. G 12 Ti is predicted to be resistant to crevice corrosion in solutions containing as high as 9% NaCl at 100°C, which is markedly high-er than 1% NaCl or less as the highest concentration for C. P. Ti to be resistant at the temperature.
    ER value for Ti-x Ni-y Mo alloy depends almost on Ni content. Sufficiently noble value of ER is attained for the alloys with Ni contents over 0.2%. The beneficial effect of Ni could be explained from formation of Ti2Ni which works as Pd does in Ti-0.15 Pd alloy.
    CNaCl, R depends not only on Ni content but also on Mo content. It decreases with increasing Mo content in the range from 0 to 0.1?0.2%, above which CNaCl, R increases with increasing Mo content. This shows beneficial effect of Mo combined with Ni. Based on the results of Ti-x Ni-y Mo alloy, characteristics of G 12 Ti are found to be accounted for approximately through its contents of Ni and Mo.
  • Stress Corrosion Cracking Behavior of Martensitic Stainless Steels under Static Load in High Temperature High Purity Water

    pp. 1338-1345

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    Stress corrosion cracking behavior of martensitic stainless steels is evaluated as a function of tempering temperature by means of three points bending SCC tests in high purity water at 70-288°C. Stress corrosion cracking initiates at small corrosion pits or crevice corrosion and SCC susceptibility increases with increasing hardness of the steel. Threshold SCC stress is about 300 MPa for the steel with hardness of HV 430 and equal to yield strength for that of HV 300. No susceptibility is detected for the steels of which HV are less than 270 with an exception of the steel of high Ni content. SCC susceptibility increases with increasing water temperature and increasing hardness of steels. Chromium plated steel and high Ni steel show higher SCC susceptibility than the unplated steel and lower Ni steel, respectively. Low C and low Ni steel in fully annealed conditions exhibits no SCC susceptibility even in long term exposure test for 5 000h in high purity water at 288°C.
  • Improvement in the Long Term Creep Rupture Strength of SUS 316 Steel for Fast Breeder Reactors by Nitrogen Addition

    pp. 1346-1353

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    Improvement of creep fatigue property of structural materials for fast breeder reactors. In order to im-prove the resistance to creep fatigue of SUS 316 steels, the effects of nitrogen, carbon, and molybdenum on creep properties have been investigated, under the concept that creep fatigue endurance is correspond to creep rupture ductility. Creep rupture tests and slow strain rate tensile tests were conducted at 550°C and extensive microstructural works were performed. The strengthening by nitrogen is much greater than carbon. Moreover, while carbon reduces rupture ductility, nitrogen does not change it. The addition of carbon results in coarse carbide formation on grain boundaries during creep, but with nitrogen very fine Fe2Mo particles precipitate on grain boundaries. The difference between the effects of nitrogen and carbon on creep properties is arise from the different morphology of precipitation. Strengthening by molybdenum brings about a slight decrease in rupture ductility. On the basis of these results, 0.01%C-0.07%N-11%Ni-16.5%Cr-2%Mo steel is selected as a promising material for fast breeder reactors. This steel has higher rupture ductility and strength than SUS 316 steel. It is also confirmed that this steel has a higher resistance to creep fatigue.
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    Readers Who Read This Article Also Read

    1. Relationship between Creep Rupture Elongation and Time-to-Rupture in Type 304 and 316 Stainless Steels Tetsu-to-Hagané Vol.75(1989), No.12
    2. Effect of Aging on Microstructures and Mechanical Properties of High Nitrogen Austenitic Stainless Steel Tetsu-to-Hagané Vol.93(2007), No.3
    3. ステンレス鋼 Tetsu-to-Hagané Vol.61(1975), No.4
  • The Growth of γ' Precipitates in Nickel-base Superalloy

    pp. 1354-1361

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    The growth behaviour of γ' (L12) -phase precipitates in Inconel X-750 type Ni-base alloy has been investigated mainly by micro-Vickers hardness test and transmission electron microscopy. The precipitating phase was observed to be spherical especially at the early stage of aging time and to be ordered fcc γ' phase, likely pointed out previously.
    The hardness of specimens aged in various conditions closely related to the size of γ' precipitates.
    The growth kinetics of γ' precipitates followed the predictions of Lifshitz-Slyozov-Wagner (LSW) theory of diffusion controlled growth at all aging temperatures. The activation energy for the growth of γ' precipitates was estimated to be 281 kJ/mol which was nearly similar to those of diffusion of solute atoms in Ni and Ni-base alloys. This would also suggest that the growth of γ' in Inconel X-750 type alloy follows the Ostwald ripening of diffusion-controlled growth. The actual particle size distribution of γ' was somewhat different from the distribution predicted by the LSW theory.
  • Effect of Residual Stress on Fatigue Strength of Induction Hardened Specimens of a Medium Carbon Steel

    pp. 1362-1369

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    The effect of residual stress on fatigue strength of a medium carbon steel was investigated. Specimens were induction hardened and subsequently reheated in three conditions to give them various distributions of residual stress. Fatige limit was improved by reheating in a condition compared with as induction hardened. Residual stress after the heat-treatments was compressive around the surface of the specimens, and varied to tensile stress in the inner unhardened region. A method to estimate fatigue limit from the total stress which is the sum of the residual stress and applied stress was proposed.
  • Discussion by Stress Analysis and Material Strength of Broken Rolls of Large Sized Backup Rolls with a Center Bore

    pp. 1370-1377

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    Breaking accidents which started at the center bore face of the journal of large sized backup rolls were experienced. To settle these problems, the working stresses inflicted on the center bore face of the backup roll was analysed by the three-dimensional photoelastic method. The fatigue strength of the test pieces taken from the core part of the journal and the residual stresses were also investigated. The main results obtained are as follows:
    1) Though the repeated tensile stresses were inflicted on the center bore face of the journal, they were not so large. It is thought that the main cause of the fracture in question was the residual tensile stresses there.
    2) The fatigue strength in the core part of the journal was equivalent or less than the fatigue strength of the sharp notched test pieces.
    3) It was concluded that the breaking accidents from the center bore face could be prevented by giving the residual compressive stresses on the bore face.
  • Relation between the Procedures of Hot Water Quenching and Mechanical Properties of High Carbon Steels

    pp. 1378-1385

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    The article has proved the possibility of replacement of lead patenting in wire production from two respects of theory and practice, and pointed out that lead patenting in wire production should be not considered isothermal quenching operation, while ought to be visualized as continuous cooling heat treatment. The development of hot water quenching for wires and the relevent deta were evaluated, and so the reason was discussed that the hot water quenching of wires could not be expaned. A new procedure of hot water quenching was invented by theoretical analyse and a great of experiments, in which wires heated to 1 1931 223 K are first immersed in hot water for a certain time ( > 2/3 total boiling time), and then taken from the hot water, transferred to a brittleproof furnace at 773873 K and cooled in air after austenite has decomposed. The results obtained in laboratory and wire production have confirmed enough that the new operation can ensure the quality of hot water quenched wires to keep up with or to exceed the average levels attainable with lead patented wires.
  • Influence of Austenitizing Temperatures on Microstructures and Mechanical Properties of Hot Water Quenched Steel Wires

    pp. 1386-1393

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    A new process of hot water quenching from low austenitizing temperature was explored for steel wires. It is pointed out that the operation of lead patenting of steel wires at high heating temperature (1 1931 223 K) is not a optimising process. Higher austenitizing temperatures of lead patenting are caused by lower cooling power of lead liquid. The possibility using lower austenitizing temperatures in patenting of steel wires was proposed by means of theoretical analysis. The effect of austenitizing temperature on mechanical properties and microstructures of the hot water quenched steel wires was studied in detail. Austenitizing temperature of steel wires during patenting can be reduced to conventionally used heating temperature (Ac3+20?30K) in heat treatment by enhancing the cooling rate. When performing single-step hot water quenching in pure boiling water, the strength and ductility are arised with a increase in austenitizing temperature ; when the austenitizing temperature exceeds a certain valure (Tm), brittle fracture of wires would be occur for producing martensite. Tm is a lowest austenilizing temperature, at which mechanical properties obtained by hot water quenching is similar to that of lead patented steel wire, under a given cooling rate, and Tm of various diameters of steel wires falls with increasing the cooling rate. A new technique-Complex Water Bath Processing has been developed, which can make the heating temperature reduce to 1073?1093 K for intermediate heat treatment (normalizing) and to 1093?1123 K for final heat treatment (patenting) in wire production. The quality of the complex water bath processed wires can fully attain the level of lead patented wires, and the strengths of wires in diameter of more than 5 mm φ may be even higher than that for lead patented wires.
  • 誌上討論

    pp. 1394-1395

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  • 技術の脆弱化を回避しよう

    pp. 1414-1414

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