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

Tetsu-to-Hagané Vol. 65 (1979), No. 8

  • Dissolution of Solid Cr2O3 into Liquid Fe-Cr-C Alloys with CO Evolution

    pp. 1131-1139

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    A kinetic study has been carried out on the dissolution of Cr2O3 into liquid iron by immersing a rotating solid Cr2O3 cylinder into Fe-10%Cr-C alloys at 1580°C. The initial carbon concentration is 0.3-1.4% and the rotational speed is 55-1800rpm. At the initial carbon concentration of 0.3%, dissolution rate increases with increasing rotational speed. On the other hand, at higher carbon contents, the dissolution rate is determined substantially by the extent of CO evolution. It is shown that the dissolution rate is controlled by the rate of mass transfer of oxygen across the boundary layer in the metal at the solid-melt interface.
  • Dispersion of Gas Injected into Liquid Metal

    pp. 1140-1148

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    A study on dispersion of gas injected into mercury has been made by using an electroresistivity probe technique. The column diameter was 7 or 10 cm and the depth of the mercury bath was 10-70cm. Nitrogen was blown through a single nozzle (O. D. ×I. D. =1.0×0.6, 0.7×0.2, 0.4×0.24cm) into the bath. The gas flow rate was 50-1330 (cm3/s, 1 atm). Measurements were made for the size of bubbles formed at the nozzle and rising in the bath. It was found that the empirical correlation obtained previously for the size of bubbles formed at nozzles in lower gas flow rates was applicable to estimate the size of bubbles in the present gas flow rates. The volume-surface mean diameter of the bubble swarm in mercury increased with increasing the superficial gas velocity. An equation was obtained to describe the effects of liquid physical properties on the average size of bubbles in the swarm. The equation was used to estimate the average size of bubbles rising in molten iron.
  • The Effect of Carbon on the Composition of the Eutectic Conjugation in the Fe-Mn-S System and the Equilibrium of Sulfides in Solid Steels

    pp. 1149-1158

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    The effect of carbon on the eutectic conjugation of liquid, iron crystal, and (Mn, Fe) S in the Fe-Mn-S system was investigated in the range from the maximum temperature of eutectic line to peritecto-eutectic temperature. The effect of carbon and silicon on the composition of (Mn, Fe) S in <iron- (Mn, Fe) S> conjugation was also studied from 1450°C to 950°C. The results are as follows:
    (1) The temperature of eutectic line is lowered and the eutectic line is dislocated towards the iron corner in the Fe-Mn-S diagram, as the carbon content of the iron crystal increases.
    (2) The addition of carbon increases the manganese content of the iron crystal and (Mn, Fe) S in the eutectic conjugation, and decreases the sulfur content of the former.
    As the temperature falls, both the tendencies of (1) and (2) gradually decay and are not recognised at all below 1250°C.
    (3) The four-phase conjugation <liquid iron-liquid sulfide-iron crystal- (Mn, Fe) S> results from the intersection of the eutectic line with the miscibility gap, when the carbon content of the iron crystal exceeds 0.25%.
    (4) The lower the temperature and the higher the manganese content of the iron matrix, the higher is the manganese content of (Mn, Fe) S in <iron- (Mn, Fe) S> conjugation. The composition of (Mn, Fe) S is hardly affected by the carbon and silicon contents of the iron matrix.
  • Deoxidation of Silicon Killed Steel by the Flux Injection

    pp. 1159-1166

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    Deoxidation flux powder is injected into a silicon killed steel bath in a 200 ton ladle. The results obtained are as follows:
    (1) Injection of CaO-Al2O3-SiO2 flux powder lowers the total oxygen content to the same level as RH-degassed steel.
    (2) The flux injection of 2 kg/t steel is good enough for this deoxidation.
    (3) The quality of flux-injected products is the same as RH-degassed ones.
    (4) The oxygen probe measurement reveals that the flux does not contribute to the reduction of oxygen content dissolved in molten steel. This fact is also proved by flux injection with different silica contents.
    (5) The E.P.M.A. observation shows that oxide inclusions are caught by the flux powder and their rising speed up to the bath surface increases.
    (6) Based on the above-mentioned phenomena, a simple deoxidation model is proposed which explains well the change of chemical compositions of oxide inclusions during the early stage of flux injection.
  • Dephosphorization of Molten High Chromium Steel with CaC2-CaF2Flux

    pp. 1167-1175

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    The appropriate conditions for dephosphorizing 18% Cr molten steel in a crucible with CaC2CaF2 flux and the method to make the slag harmless were investigated in a 100kg induction furnace.
    (1) When the initial [C%] is 0.5-1.8%, the degree of dephosphorization is high (50-80%) . The influence of the initial [C%] is explained by consideration of the amount of the remained CaC2 and the ratio of (CaC2) / (Ca).
    (2) The suitable CaF2% in the flux is about 10% when the temperature of molten steel is between 1 580°C and 1650°C.
    (3) The slag after dephosphorization should be oxidized until (CaC2%) becomes under 0.1% to prevent the generation of PH3. For the purpose, two methods were investigated. One is to vapourize phosphorus from the slag by oxygen blowing. The other is to separate the slag from the dephosphorized steel, and subsequently to oxidize the slag in contact with plain carbon steel.
  • On the Dissolution of δ-ferrite into Austenite in Continuously Cast Slabs of 18-8 Stainless Steel

    pp. 1176-1185

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    Dissolution of δ-ferrite into austenite in the annealing temperature range of 1050 to 1250°C for 18-8 (SUS304) stainless steel continuously cast slabs has been studied experimentally together with numerical calculation of diffusion model.
    (1) Secondary dendrite arm spacing (SII) increased approximately linearly with the distance from slab surface. δ content as cast did not increase linearly. At 1/4 thickness of slabs, it had minimum point which may be caused by reheating in the slab making process.
    (2) At the early stage of annealing, 6 content increased. It was explained by diffusion model.
    (3) The logarithm of dissolution rate decreased approximately linearly with decreasing δ content except the initial and final stages of annealing. Apparent activation energy was about 60 kcal/mol, which was nearly the same as the activation energy for diffusion in γ-phase.
    (4) The relation between δ content and log (t/S2II), where t is virtual annealing time which is compensated by addition of modified reheating time in the slab making process, is nearly the same at any SII on the same temperature. The calculated result agrees with these relations except the final stage of annealing, where the dissolution rate of the experiment is slower than the calculation.
  • Effect of Transformation Induced Plasticity on the Press Formability of 18%Ni Maraging Steels

    pp. 1186-1193

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    The effect of transformation induced plasticity on the press formability has been experimentally investigated at various temperatures and strain rates for 18% Ni maraging steels. The results obtained are as follows.
    (1) The best formability is obtained at 225°C (498 K) for 210kg/mm2 class maraging steel and 275°C (548 K) for 245 kg/mm2 class one under various formability tests as deep-drawing, stretching, burring and bending.
    (2) The forming limits of the formability tests mentioned above agree relatively well with the values from the Forming Limit Diagram (F.L.D.) which represents the forming limit at two dimensional stress states. However, when the work-piece is subject to strain gradient or is restricted by tool as in the case of burring test, the forming limit is higher than the value from the F.L.D.
    (3) The effect of strain rate on the forming limit is not recognized experimentally in the almost all stress states expect for uniaxial stress state in the F.L.D. This phenomenon depends on that the heat of deformation transfers to the tool rapidly, when the work-piece is in contact with the tool.
  • Effects of Laves Phase on the Properties of Ti and Nb Stabilized Low C, N-19%Cr-2%Mo Stainless Steel Sheets

    pp. 1194-1203

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    An investigation has been made of the effects of the annealing conditions and its cooling rates on the Charpy impact value and the mechanical properties of Ti and Nb stabilized low C, N-19%Cr-2%Mo stainless steel sheet. The main results obtained in this paper are as follows:
    (1) The precipitation of Laves phase has a great influence upon the mechanical properties of this steel sheet. Its structure is determined as MgZn2 (C14) type (Fe, Cr) 2 (Mo, Nb, Ti) Laves phase using electron and X-ray diffraction techniques and electron probe microanalysis. The lattice constants obtained are a0=4.78 Å, c0=7.84 Å and c0/a0=1.64. The orientation relationship between Laves phase and matrix is determined as (0001) Laves// (110) α, [1120] Laves// [111] α. The precipitation rate of Laves phase reaches the maximum at 700°C and its dissolution occurs over 900°C.
    (2) Laves phase is formed at grainboundary and then in matrix during cooling. Large Laves phase at grainboundary shifts the ductilebrittle transition temperature to higher one. The large amount of Laves phase degrades the room temperature ductility of cold rolled and annealed sheet and enhances its strength very much. The degradation of these mechanical properties can be overcome by rapid cooling.
    (3) When the effect of cold reduction on the mechanical properties of cold rolled and annealed sheet is examined between 0 and 92%, a peculiarly rapid precipitation of Laves phase is observed at 20% cold reduction and its mechnical properties are severely degraded because of the rapid precipitation.
    (4) The optimum properties of cold rolled and annealed sheet are obtained by the following conditions: Hot rolled sheet is annealed at 950°C and cooled rapidly. Cold reduction is more than 80% in order to improve r value. Cold rolled sheet is annealed at 920°C and cooled rapidly.
    x

    Readers Who Read This Article Also Read

    1. Heat Transfer Phenomena in Immersion Cooling of Heated Steel Plate and Influence of Water Stirring on Heat Transfer Tetsu-to-Hagané Vol.64(1978), No.1
    2. 第97回講演大会討論会講演概要 Tetsu-to-Hagané Vol.65(1979), No.2
    3. 第95回講演大会討論会講演概要 Tetsu-to-Hagané Vol.64(1978), No.2
  • Effects of Chemical Composition and Heat Treatment on Mechanical Properties of Carburized Steels

    pp. 1204-1212

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    The tensile, Charpy impact bending, rotating bending fatigue, and impact bending fatigue tests on some carburized steels were performed in order to investigate the effect of chemical composition in steel and of heat treatment after carburizing on mechanical properties.
    The results obtained are summarized as follows:
    (1) The steel with re-quenching after direct quenching (specimen B) had superior properties of strength and ductility to the steel with direct quenching only (specimen A) in both tensile and Charpy impact tests. On the other hand, the fatigue strength of specimen A was higher than that of specimen B under both impact bending fatigue and rotating bending fatigue.
    (2) For these fatigue tests, the highest fatigue strength was obtained in the steel containing about 0.25% carbon. It was also found that these strength were improved by addition of Cr, Mo, and Ni.
    (3) In the impact fatigue tests, there was no clear difference in the number of blows to crack initiation for both specimen A and B. For each carburized steels, the crack propagation rate was decreased with the growth of crack at first, and then the rate was increased gradually with increasing number of blows and, finally, the specimen was led to the rupture with higher propagation rate of crack, that is, the three different stages were distinguished in the process of crack propagation. The crack propagation rate of specimen A was lower than that of specimen B for every stage to the rupture.
  • Hydrogen Damage of Nickel-Base Heat Resistant Alloys

    pp. 1213-1221

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    The damage of nickel-base heat resistant alloys exposed to hydrogen at higher temperature and pressure was investigated. Tested materials were mainly Inconel 600, Hastelloy X and nickel. Main results obtained are as follows:
    1) Inconel 600 solution treated exhibited embrittlement due to the occluded hydrogen.
    2) Hastelloy X solution treated did not exhibit embrittlement.
    3) Nickel exhibited the irreversible damage although it was completedly dehydrogenated.
    4) Stress concentration enlarged the susceptibility to embrittlement. Hastelloy X which did not show embrittlement in a smooth type specimen was also embrittled when stress was concentrated.
    5) Embrittlement depended on Ni content and materials with higher Ni content exhibited the irreversible damage.
    6) The susceptibility to hydrogen embrittlement of Inconel 600 and Hastelloy X increased when they were aged and carbides were precipitated on grain boundaries. This effect could be explained by hydrogen trapping.
  • Influence of Martensite-Austenite Constituent on Toughness of Heat-Affected Zone of High-Strength Weldable Structural Steels

    pp. 1222-1231

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    A study has been made of the cause of heat-affected zone (HAZ) embrittlement from the metallurgical point of view. The special emphasis has been placed on the clarification of the role of martensite-austenite (M-A) constituent. A synthetic weld-thermal-cycle technique has been applied to various high-strength steels in order to simulate the coarse-grained HAZ over a wide range of welding heat input/cooling time.
    In each steel, an initial increase in cooling time results in a microstructure change from martensite to a mixed structure of martensite and lower bainite, which lead to an increase in HAZ toughness. Further increase in cooling time causes microstructure to change from the mixed structure to upper bainite, which is accompanied with a marked degradation in HAZ toughness.
    A close correlation is found between HAZ toughness and the amount of M-A constituent, whereas the effect of austenite grain size or fracture facet size is only capable of explaining less than 30 percent of loss in HAZ toughness. The deteriorating effect of the constituent is evaluated to be 8°C/volume percent of M-A constituent in terms of V-notch Charpy FATT.
    Characteristics of an extremely low carbon steel have also been examined with satisfactory results due to its minimized tendency to the formation of M-A constituent.
    x

    Readers Who Read This Article Also Read

    1. Thermal Cycle Test of High Strength Steels and Steel Plates for Low Temperature Service Tetsu-to-Hagané Vol.58(1972), No.2
  • Effect of Titanium and Nitrogen on Toughness of Heat-Affected Zone of Steel Plate with Tensile Strength of 50kg/mm2 in High Heat Input Welding

    pp. 1232-1241

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    A study has been made of the effect of titanium and nitrogen on heat-affected zone (HAZ) toughness in one-sided submerged arc welding by using 30 mm thick steel plate with tensile strength of 50kg/mm2. The distribution of TiN particles in the steel plates and welding thermal cycle specimens simulated the HAZ, was observed in relation to the toughness.
    The HAZ toughness exhibits the highest value at approximately 0.015% titanium, which also gives the finest distribution of TiN particles in the HAZ regardless nitrogen content. The optimum nitrogen content for the toughness is about 0.0050%, although the number of TiN particles increases with increasing nitrogen. The degradation of the toughness in the range of more than about 0.0050% nitrogen can be explained by the increase of free nitrogen harmful to toughness. By means of controlling the amounts of titanium and nitrogen in the optimum range, the fine distribution of TiN particles can be attained, which enables the production of steel plates for high heat input welding in conventional steel making process without special precaution.
  • Prestrain and Its Effect on Low Temperature Toughness of Fe-Cu Alloys

    pp. 1242-1249

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    Slow bend test for standard Charpy V notched specimens and tensile test for notched small specimens (30mm×4mm×1mm), were carried out over a range of low temperatures to investigate the effect of prestrain on the low temperature toughness of Fe-Cu alloys by changing the quantity of prestrain and prestraining temperatures.
    Prestraining of 1 to 6% at room temperature increased ratio of fracture stress (σF) to 0.2% offset stress (σ0.2) over 1 at 143K for notched tensile specimens of aged Fe-1.7%Cu alloy (650°C ×25h) and the prestrained notched specimens were cleaved after macroscopically plastic deformation. Any prestrain at 153K, however, decreased the ratio of σF to σ0.2 to less than 1 at 143K and the specimens were cleavage fractured with macroscopically elastic deformation. Energy transition temperature in slow bend test of Fe-1.1%Cu alloy of as solution-treated did not change with 4% prestrain at room temperature but increased 77K with 40% cold roll at 273K. Energy transition temperature of aged Fe-1.1%Cu alloy (650°C×25h), however, decreased 25K with 4% prestrain at room temperature but increased 30 K with 40% cold roll at 273K.
  • Trends of Technology in Nonferrous Pyrometallurgy

    pp. 1250-1263

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  • 日本鉄鋼技術の現状と将来

    pp. 1264-1272

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  • Recent Development of Non-Destructive Inspection and Its Problems

    pp. 1273-1279

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  • 中国の技術近代化について

    pp. 1280-1282

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  • “International Conference on Machinability Testing and Utilization of Machining Data (Oak Brook) ”

    pp. 1283-1284

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  • 抄録

    pp. 1285-1289

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    x

    Readers Who Read This Article Also Read

    1. Heat Transfer Phenomena in Immersion Cooling of Heated Steel Plate and Influence of Water Stirring on Heat Transfer Tetsu-to-Hagané Vol.64(1978), No.1
    2. 第97回講演大会討論会講演概要 Tetsu-to-Hagané Vol.65(1979), No.2
    3. 第95回講演大会討論会講演概要 Tetsu-to-Hagané Vol.64(1978), No.2
  • 第98回講演大会討論会講演概要

    pp. A117-A132

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  • 第98回講演大会討論会講演概要

    pp. A133-A148

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  • 第98回講演大会討論会講演概要

    pp. A149-A172

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    x

    Readers Who Read This Article Also Read

    1. Heat Transfer Phenomena in Immersion Cooling of Heated Steel Plate and Influence of Water Stirring on Heat Transfer Tetsu-to-Hagané Vol.64(1978), No.1
    2. 第97回講演大会討論会講演概要 Tetsu-to-Hagané Vol.65(1979), No.2
    3. 第95回講演大会討論会講演概要 Tetsu-to-Hagané Vol.64(1978), No.2
  • 第98回講演大会討論会講演概要

    pp. A173-A196

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  • 第98回講演大会討論会講演概要

    pp. A197-A220

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