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

Tetsu-to-Hagané Vol. 76 (1990), No. 9

  • The Present Status and Future Outlook of Refractories as a Ceramic Material

    pp. 1403-1413

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    1. High Productivity Operation at Chiba No.4 Sinter Plant Tetsu-to-Hagané Vol.76(1990), No.5
    2. Progress of Metal Powder Injection Molding Tetsu-to-Hagané Vol.76(1990), No.5
    3. Estimation of Deterioration of Coke Strength by CO2 Reaction Tetsu-to-Hagané Vol.76(1990), No.5
  • Elasto-plastic Models for Evaluating γ Value of Clad Sheets and Dual-Phase Steels

    pp. 1414-1422

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  • Electrocthemistry of Semiconductors

    pp. 1423-1436

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  • Microtribology and Its Measuring Techniques

    pp. 1437-1442

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  • New Disinfection Method by Electrodialysis Using Ion-exchange Membranes

    pp. 1443-1448

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  • Corrosion and Protection of Reinforcing Steel in Concrete

    pp. 1449-1457

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  • High Productivity Operation in a Large Blast Furnace

    pp. 1458-1465

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    At the high productivity operation of Keihin No. 2 BF (4052 m3, blown in 1979), taking into account the limit of five limited factors (fluidization of burden materials at throat, flooding of dropping liquid below cohesive zone, heat flux ratio, traveling time of burden in furnace and flame temperature at tuyere nose), the appropriate operational diagram with oxygen enrichment and humidity addition has been introduced and estimated. According to this diagram, the steps to increase the productivity have been planned and carried out with the increase of oxygen enrichment and humidity addition simultaneously.
    In order to increase the productivity, the increase of blast volume was considered to be more effective than the decrease of coke rate. Therefore, following five countermeasures against the improvement of permeability in furnace have been carried out.
    1. Increase in strength and size of coke
    2. Decrease in fine ratio of burden materials
    3. Improvement of burden distribution controllability by repairing the throat profile
    4. Burden distribution control aimed at U-type pattern (sharp central flow with strong peripheral flow)
    5. Changes in tapping procedures corresponding to the high productivity operation.
    As a result, the high productivity operation over 2.4 t/m3/d has been continued in Keihin No. 2 BF since June of 1989. Especially, the maximum productivity 2.69 t/m3/d (10900 t/d) was recorded in August of 1989.
  • Circumferential Balance Control in Blast Furnace by Hot Blast Control Valves

    pp. 1466-1473

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    NKK jointly with Asahi Glass Co., Ltd. have developed a Hot Blast Control Valve (HBCV) which can control the flow rate at each tuyere. 19 HBCVs out of 38 tuyeres were installed in Keihin No. 2 BF in 1986. Through various test operations, innovative technologies for blast furnace operation have been developed. This paper reports the circumferential balance control of stock line levels.
    (1)At the proper block with closed HBCVs, the coke consumption amount at the tuyere decreases, however the burden descending rate at the throat becomes faster. Applying these phenomena, it is Possible to control the circumferential balance of SL levels.
    (2)The simple stand-alone method, where the HBCVs at the block with higher SL level are closed based on the average SL levels during the past definite period of time, had sometimes put into disorder, and it was impossible to continue a stable control of SL levels.
    (3) For further stable control, Successive Alleviative Integration (SAINT) method has been developed, taking account of their interferences of each HBCV opening, dead time and integral action of changes in valve opening.
    (4)The test operation in Keihin No. 2 BF showed that it is extremely effective for the improvement of furnace conditions and decrease of Si content in hot metal to control the circumferential balance of SL levels on the SAINT method.
  • Evaluation of Gas Temperature by Using Vibrational-rotational Spectrum of Carbon Monoxide

    pp. 1474-1479

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    The new technique for estimating gas temperature at more than 1000°C was developed based on quantum mechanics. The spectrum of gas at the fixed temperature in the experimental furnace was observed. Carbon monoxide was chosen as a "probe" gas for the examination. The gas was monitored by an infrared optical sensor with Fourier Transform Infrared Spectrometer ( FTIR ). Zinc selenide lens and KRS-5 infrared optical fiber were set in a water cooled probe. The shape of the P-branch in vibrationalrotational spectrum of carbon monoxide was examined as an index for temperature and partial pressure. The evaluation of temperature ranging from 1000 to 1550°C was possible by using the shape analysis of spectrum at PCO = 0.31.0 atm.
  • Dephosphorization and Decarburization of High Carbon Iron Melts by Sodium Carbonate

    pp. 1480-1487

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    In order to get a basic knowledge concerning dephosphorization of hot metal by soda ash, the behavior of phosphorus and carbon in metal and gases evolved during the reaction was examined.
    Sodium carbonate explosively reacted with liquid iron containing 3 5% carbon. Gaseous material evolved by the reaction was only carbon monoxide.
    When sodium carbonate was added to liquid 4%carbon-0.2%phosphorus-iron, dephosphorizing reaction rapidly occurred within the first few minutes. While, decarburizing reaction began at around the period when dephosphorization was almost completed. Only a small amount of carbon dioxide gas evolved early in the experiment, gaseous material evolved over a run was mainly carbon monoxide.
    It was presumed from the relation between the amounts of carbon monoxide gas evolved and phosphrus removed that the dephosphorizing reaction of high carbon iron melt can be expressed as follows ;
    5Na2CO3 + 2P = 5Na2O + P2O5 + 5CO
    The reactions ofdephosphorization and decarburization were retarded by the addition of sodium disilicate together with sodium carbonate.
    It was found that the phosphate capacity of high sodium carbonate flux was very low compared with those of Na2O- SiO2 fluxes.
  • Interfacial Oxygen Potential in Phosphorus Reaction between Iron Oxide Containing Slag and Molten Iron of High Carbon Concentration

    pp. 1488-1495

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    Oxygen potential at slag-metal interface, PO2*, is determined from the experimental results of the authors' previous study on phosphorus reaction kinetics between high carbon concentration iron melt and iron oxide containing slag. The PO2* value is calculated on the assumption that quasi-equilibrium is attained when transition in the phosphorus reaction occurs from dephosphorization to rephosphorization.
    The oxygen potential at the slag-metal interface, PO2, is obtained as 10-16 10-15 atm. PO2* increases with increasing Fe3+/(Fe2+ + Fe3+ ) in the slag phase or the partial pressure of oxygen in the atmospheric gas, while PO2* decreases with the increase in the rotating speed of mechanical stirrer. The oxygen potential in the slag bulk, PO2, is calculated on the basis of regular solution model, and is found to be 2 or 3 orders of magnitude greater than PO2* at the slag-metal interface. Comparison is made between the PO2* values determined from the data of the experimental study and those obtained from mathematical model calculation which simulates the simultaneous reactions of phosphorus and carbon. Fairly good agreement between the two is obtained.
  • Behavior at Under-film Corrosion Tips of Zn-Fe Alloy Coated Steel Sheets

    pp. 1496-1503

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    Under-film corrosion behavior of Zn-Fe alloy coating in the tip of corrosion was investigated using the atmospheric exposure test. The better correlation between chlorine penetration distance and paint exfoliation width from scribe was recognized. The formation of deteriorating coating layer due to chlorine ions attacking of coating is an important factor controlling the paint adhesion of zinc alloy coated steel sheets.
    The durability of coating against chlorine penetration was affected by the coating weight and total zinc weight in the coating. Zn-Fe (10 20% ) alloy coating had better durability against chlorine ion attacking than pure Zn coating because of the difference of coating itself corrosion behavior between these coatings. The effect of Zinc phosphate film was not mainly the controlling factor of durability against chlorine penetration.
  • Influence of Stress on Low Temperature Sensitization of SUS304 Stainless Steel

    pp. 1504-1511

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    By using carbide nucleation-heat-treated SUS304 stainless steel specimens, the effect of various type of stresses applied during 500°C isothermal heat treatment on Low Temperature Sensitization (LTS) was examined. The Degree of Sensitization (DOS) was detected by means of the Electrochemical Potentionkinetic Reactivation (EPR) test and Strauss test. The main results of the study are as follows :
    1) When constant tensile stress is applied to the specimens during isothermal heat treatment, the LTS was accelerated more than unstressed specimens. The degree of acceleration was larger when the applied stress was larger. The acceleration of the LTS was also seen even when the stress less than proof stress at the test temperature.
    2) The electrochemical potentiokinetic reactivation ratio of the specimens after 100 h of the LTS test corresponded to strain rather than stress.
    3) When alternating stress was applied to the specimens during the isothermal heat treatment, the LTS was accelerated even more than when constant tensile strees was applied.
  • Effect of Quenching from γ/α Dual-Phase on Mechanical Properties of Controlled-rolled Low-carbon Boron-steels

    pp. 1512-1519

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    Effect of γ/α dual-phase quenching on the mechanical properties of controlled-rolled low C-Mn-Nb-Ti-B steels has been studied with changing quench temperature, and carbon-and manganese-contents. The steels were heated to 1050°C, then controlled-rolled to 720°C. Contolled-rolled plates were directly water-quenched after rolling. High strength has been obtained by water-quenching from the temperatures in the γ/α dual-phase range after controlled-rolling. And the strength increases with increasing quench temperature. A major strengthening factor is increase in the amount of hard-phases, that is in this case, martensite and bainite with increasing quench temperature. It is found that high toughness can be obtained by keeping the amount of ferrite more than about 40% in volume when quenching from the temperature below 600°C, although toughness has been rapidly decreased by quenching from the temperatures above 650°C.
  • Effect of Inter-pass Time in Rough Rolling Process on the Orientation Distribution in 17%Cr Stainless Steel Sheet

    pp. 1520-1527

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    Orientation distribution in the 17%Cr stainless steel rough rolled with inter-pass time of 10s (specimen A) and 30s (specimen B) respectively were investigated utilizing SEM-ECP (selected area electron channeling pattern).
    Large colonies, groups of grains with the same orientation, of {100} <011>orientation are found in the specimen A after rough rolling. It is proposed to be formed by the poor static recrystallization during rough rolling due to the short inter-pass time and the suppression effect of static recrystallization caused by the α-γ transformations immediately after the final pass of the rough rolling.
    Large ridging is observed in the cold rolled and annealed specimen A.
    The cause of the large ridging is considered to be due to the large colonies of {100} <011> orientation inherited from the rough rolled stage and scattered asymmetrically along the central line of the specimen thickness.
  • Effect of Coiling Temperature in Hot Rolling on the Mechanical Properties in 17%Cr Stainless Steel Sheet

    pp. 1528-1535

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    Effect of coiling temperature on the mechanical properties of 17%Cr stainless steel sheet containing 0.124%Al(A) and 0.013%Al(B) has been investigated.
    The yield stress and yield point elongation of the specimen A initially incerase and then decrease with increasing final annealing time when processed with coiling temperature lower than 750°C and without annealing before cold rolling. This is due to decomposition of α' during initial stage of annealing and subsequent precipitation of AlN. The yield stress and yield point elongation of the specimen A coiled at 850°C are low and remain almost the same with increasing final annealing time as no α' is present before cold rolling and AlN phase has been precipitated at coiling stage.
    In the case of specimen B, the yield stress and yield point elongation increase with increasing final annealing fime when processed with coiling temperature lower than 750°C and without annealing before cold rolling. This is due to the decomposition of α' during initial stage of annealing and no preciptation of AlN during final annealing.
  • Metallurgical Study to Develop a Production Technique with a Lowered Hot-coiling Temperature for Cold-rolled, Deep-drawable Continuous-annealed Aluminum Killed Sheet Steels

    pp. 1536-1543

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    Metallurgical factors realizing low temperature coiling of hot-rolled bands for producing deep-drawable continuous-annealed Al-killed sheet steels have been investigated in order to improve yield and productivity. The following proposal is given: the control of chemical composition such as i) C ≤0.02%, ii) Mn≤0.15%, and iii) Al ≥0.05%, and the choice of iv) low slab reheating temperature below 1150°C. The conditions i) and ii) contribute to the coarsening of cementite particles in hot-rolled bands and to the reduced amount of Mn-C complex during annealing, while the condition iii) contributes to the promotion of AIN precipitation in hot-rolled bands. These are considered to play a significant role in ameliorating r-value of the final products. Furthermore the condition iv) not only has an effect of improving formability, but also contributes to the prevention of hot-shortness caused by S. The effective mechanisms are discussed concerning the influence of C and Mn contents on the cementite coarsening in hot-rolled bands.
    On the basis of the knowledge obtained by the laboratory investigation, a mill test was carried out and it was confirmed that the proposal ensures a high and uniform r-value through the whole length of a coil employing the low temperature coiling.
  • Effect of W/Ta Ratio on Hot Corrosion of Nickel-base Superalloy Single Crystals in Combustion Gas Stream

    pp. 1544-1551

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    Burner rig tests of nickel-base superalloy single crystals with various W/Ta ratio (W + Ta = 7at%) were carried out at 900°C for 7h in combustion gas flowing at Mach 0.5, prepared from 5ppm NaCl - containing air and 0.5% sulfur-containing fuel. The hot corrosion tests revealed that the alloys with higher W/Ta ratio were severely attacked. The cross sections of these alloys with high W/Ta ratio were characterized by a thin oxide layer, while that of the alloy with the lowest W/Ta ratio was characterized by a continuous aluminum oxide layer covered by a thick NiO layer. The hot corrosion behavior seems to depend primarily on W content rather than on Ta content ; the difference in hot corrosion behavior was explained by acidic fluxing of NiO and Al2O3 due to dissolution of tungsten oxide.
  • Effect of Cathodic Protection on Fretting Fatigue of High Strength Steels in Seawater

    pp. 1552-1558

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    The effect of cathodic protection on the fretting fatigue of high strength steels in synthetic seawater was studied. The fretting fatigue life in seawater under freely corroding condition was much shorter than that in air. Using cathodic protection, the fretting fatigue life in seawater was greatly increased, and became longer than that in air, and the lower the frequency, the longer the life. The improvement in fretting fatigue life by cathodic protection resulted mainly from the increase in crack propagation life not influenced by fretting. This increase was probably caused by crack closure effect of calcareous deposits produced under the cathodic potential employed. In stainless steel used to compare with the high strength steels, the fretting fatigue life in seawater under freely corroding condition was almost the same as that in air.
  • Development of the System for Automatic Crystallographic Orientation Analysis by Electron Channelling Pattern

    pp. 1559-1566

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    Electron Channelling Pattern (ECP) is useful for determination of the precise orientation of individual grain observed under a scanning electron microscope. It is necessary to analyse a large number of crystals to obtain crystallographic information which is useful to understand and control the properties of various materials.
    However, previously reported ECP methods required a laborious work and/or expertness.
    In order to save time and labor, in this study, ECPS are recorded to hard disks linked to the personal computer, followed by orientation analysis by image-processing (image enhancement, Hough transformation, detection of lines, etc.), which leads to automatic determination of the crystallographic orientation.
    The functions of the present system are summarized as follows ;
    (1)The achievement rate of automatic drawing-and-analysis in the routine work is more than 95%(about 2300 grains analysed).
    (2)240 images are handled over one night (16h) with no operator (4min/image).
    (3) ECP images, which are hard to analyse automatically due to broadness, can be easily treated by manual method (1 min/image).
    The development of this system has achieved decrease in labor. Furthermore, even unpracticed person can easily operate it.
    In the future, completely automatic ECP analysis without any operator will become possible by attaching an automatic specimen-displacing stage to the ECP/SEM.
  • 俵賞を受賞して

    pp. 1572-1573

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