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

Tetsu-to-Hagané Vol. 48 (1962), No. 12

  • 教職27年の今日を想う

    pp. 1549-1550

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  • Study on Combustion Zone in a Blast Furnace

    pp. 1551-1557

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    By using an experimental blast furnace of which the inner volume is 04m3 and the diameter of hearth is 440mm, the effects of some factors on the combustion zone in front of the tuyeres were investigated. The results obtained were as follows:
    (1) On increasing the temperature of blast, the temperature in front of tuyeres was raised uniformly, while the CO2 content was decreased.
    (2) On enriching oxygen into blast, the temperature in front of tuyeres was raised, and its rate was more than that of the temperature of blast. The extent to which CO2 exsisted was very small.
    (3) On adding moisture into blast, the temperature in front of tuyeres dropped considerably.
    (4) In combination with enrichment of oxygen and addition of moisture, the state of the combustion zone in front of the tuyeres could be approached to that of normal operation.
    (5) When the size of coke was too small, the temperature at the lower part of the bosh was little changed. But the temperature of the upper part of the bosh was raised.
    (6) When the diameter of tuyeres was small and the velocity of blast in tuyeres were increased, the temperature at the center of hearth and the lower part of the bosh was raised.
    (7) On increasing the blast volume, the temperature in front of tuyeres was raised slightly.
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  • Construction and Operation of the Open Hearth Furnace with a Brick Hearth

    pp. 1557-1562

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    Steel makers have hoped since earlier years for operating the furnace always with a stabilized hearth. It has been dominantly considered that the magnesite stamp method is the best for the hearth construction of a basic open hearth furnace, but even the hearth which is made by this method is necessary to be repaired periodically in the later half period of one furnace campaign owing to the damage of a hearth. Now the author tried to construct them with bricks instead of stamped magnesite for the improvement in these failure and the results obtained were as follows;
    (1) The, following points which had been anxious problems in the past were improved:
    a) Penetration of molten steel through the clearance between bricks.
    b) Floating up of hearth bricks.
    c) The spalling of hearth bricks.
    (2) With this method, it was possible to continue the operation twice as long as magnesite stamped hearth.
    (3) By this method, it was possible to operate with lower cost than the magnesite stamp method.
    (4) The production was increased during one campaign because the hearth repairing hours had been shortened.
  • Study on the Electrolytic Isolation of Carbide from Steel

    pp. 1562-1569

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    The present paper deals with the technique for the electrol ytic isolation of carbide from steel, without decomposition and contamination, by using the Koch -Sundermann method and others.
    The results obtained are as follows.
    (1) In order to dissolve all the matrix metal, the surface electric potential of steel mussetbtl oe wer than the hydrogen potential.
    (2) In the case of dissolving in a partly passive state of steel surface, it is not desired to isolate the carbide at a too low current density. On the other hand if steel is dissolved in an active state, it need to isolate at a current density as low as possible.
    (3) The residues isolated electrolytically must be dried and weighed under the cona dithioignhvs aocf uum and a high temperature.
    (4) Copper or its compounds are contaminated in the residues isolated electrolytically from the low-alloy steel containing copper. (Cu content is 022%). When this copper included is separated from the residues by using KCN solution, part of carbide also tends to be decomposed.
    It is found that using the ammonium solution, this copper can be separated from the residue isolated eleotrolytically in 5% Na-citrate+1.2% KBr solution.
  • On the Equilibrium Relations between Iron and Exothermic Atmospheres Converted from Propane

    pp. 1569-1574

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    Carburizing or oxidizing equilibrium relations between solid iron and exothermic atmospteres of CO-0O2-H2-H2O system which were converted from a mixture of propane and air by partial burning through a catalyzer chamber were studied by thermodynamic calculations and chemical analysis. The results obtained were summarized as follows.
    In the converted atmospheres, CO2 and H2O contents were increased and CO and H2 contents were decreased by raising the mixing ratio of air to propane at a constant temperalure. After heated with iron, CO and H2O contents in an atmosphere converted at constant air ratio were increased and CO2 and H2 contents were decreased by raising heating temperature so as to approach the equilibrium condition of water-gas reaction. The calculated values of CO/CO2 ratio in the exothermic atmospheres in equilibrium with iron were approximately in good agreement with the experimental values obtained from analysis of effluent gas from the heating furnace.
    The carbon potential of the single phase, either ferrite or austenite, in exothermic atmospheres was decreased by raising the ratio of air to propane and by increasing temperature at a constant air ratio. In general, the carbon potential of iron in exothermic atmospheres was very low.
    It was found that oxidation of iron in exothermic atmospheres converted at an air ratio higher than 16-17 (when cooled at 18° after converted at 1000°) was nearly independent of heating temperature in the range between 800°C and 1000°C.
  • Effects of Aluminum Nitride on the High-Temperature Ductility and on the Welding Crack of Low-Carbon Steel

    pp. 1575-1581

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    Effects of aluminum nitride (A1N) precipitates on the high-temperature ductility and on the welding crack at heat-affected zone were investigated. Small tensile test pieces were made of the steels containing different amounts of aluminum and nitrogen (Table 1 and 2), and were drawn at 500-1000°C The specimens of C. T. S. (controlled thermal severity) test Fig.
    1) were used for the investigation of the welding crack at the heat-affected zone. (1) The high-temperature ductility of low-carbon steel as cast is decreased extremely by the addition of aluminum (Fig. 2 and 3). The ductility of low-carbon steel at a temperature lower than 800°C is higher than the one of medium-carbon steel.
    2) The ductility during rapid-cooled from 1350°C of low-carbon steel as cast or as forged is decreased at a temperature higher than 850°C by the addition of aluminum (Fig. 5). The ductility of it during slow-cooling from 1350°C is not decreased by the addition of aluminum unlike the ductility of medium-carbon steel (Fig. 4). The ductility without preheat-treat ment of low-carbon steel as forged is decreased at a temperature higher than 850°C by the addition of aluminum.
    3) Presumably there is a relation between the decrement of the high-temperature ductility of low-carbon steel by the addition of aluminum and the morphology of aluminum nitride in the steel (Photo. 1 and 2).
    4) In the heat-affected zone directly under weld-deposit of the steel containing more aluminum and nitrogen, the precipitates of aluminum nitride scatter undissolved by welding heat. The precipitates in the steel containing less aluminum and nitrogen are dissolved in the heat-affected zone by welding heat. The aluminum nitride precipitates which exist dispersedly undissolved by welding heat in the heat-affected zone seem to promote the transformation during cooling after heated by welding heat, and consequently the welding crack in the heat-affected zone (Photo. 3) is decreased by the addition of large quantities of aluminum and nitrogen.
    5) Presumably there is a relation between the increment of the welding crack in the heataffected zone by the addition of aluminum up to 0.01-0.02% and the decrement of the hightemperature ductility by the addition of aluminum. It is considered that the hot crack in the heat-affected zone initiates on account of the decrement of the high-temperature ductility by the precipitation of aluminum nitride, and that consequently the cold crack in the heataffected zone is increased with the hot crack as its starting point.
    6) The welding cracks in the heat-affected zone observed in the steel as cast are much more than those in the steel as forged, and are not decreased by the addition of great quantities of aluminum unlike with the steel as forged. This phenomenon seems to be based on the fact that the ductility at high temperature is decreased by formation of the line of aluminum nitride precipitates and the network of sulphide inclusions.
  • Effects of Composition and Structural Conditions on Corrosion Resistance of Cr-Ni Stainless Steels

    pp. 1581-1586

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    In the previous report (Tetsu-to-Hagane, 48 (1962) 6, p. 776), the anthors reported the effect of Ni and Mo content on structures of Ni-Cr stainless steels and the effects of structures on mechanical properties.
    This paper describes the effects of structures, mainly those of δ ferrite on corrosion resistance to nitric acid and sulfuric acid and also describes the relation between corrosion potential in both acids and compositions and structural conditions.
    Precipitatipn of chromium carbide and decomposition of δ ferrite to σ phase resulted in an increase in corrosion rate in nitric acid.
    Corrosion resistance to sulfuric acid was increased with Mo content while that of specimens aged at 750°C was decreased with increasing Mo content when excess molybdenum was added.
    It seems that δ ferrite had a bad effect on corrosion resistance to sulfuric acid. Potential of δ ferrite was higher than that of matrix in nitric acid but was lower than that of matrix in sulfuric acid.
  • On the Aged Structure of Heat-Resisting Alloy A286 and Its Fracture Process at Elevated Temperature

    pp. 1586-1591

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    Relations of aged structures to the fracture process in the heat-resisting alloy A286 were studied by means of microscopic observation on the ruptured specimens at 650°C. The effect of melting procedures and natures of rupture tests on the fracture process also was investigated. The results obtained in the present experiment were summarized as follows:
    Contributions of the surface between G phase and grain boundary to crack nucleation were significant. Although the contributions were also recognized with η phase, the contributions. from η phase were less important than those from G phase. Intergranular precipitates such as TiC and Laves phase had no essential effect on the propagation of crack so long as these precipitates had no continuous arrangement.
    Difference between creep rupture and tensile rupture was notable, that is, nucleation and. propagation of crack was less structure-sensitive in the case of tensile rupture, while crack was much correlated with G phase, η phase, grain boundary and so on in the case of creep rupture.
    Effect of melting procedure on the fracture process was remarkable, that is, the resistance to crack nucleation and propagation was more increased with the vacuum-melted alloy than with the air melted one. It was supposed that the phenomena as abovementioned might be due to an existence of boron atoms which had come into the solution from the crucible during the melting process.
  • Effect of Pretreatment on Austenite Grain Size of Steel

    pp. 1592-1600

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  • Fuel Injection into the Blast Furnace

    pp. 1601-1620

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    x

    Readers Who Read This Article Also Read

    1. Effect of Magnetite (Fe2+ source) on Initial Liquid Formation in Sintering Process Tetsu-to-Hagané Vol.103(2017), No.6
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  • 抄録

    pp. 1621-1625

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  • 鉄鋼ニューズ

    pp. 1629-1630

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  • 特許記事

    pp. 1631-1633,1628

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