Tetsu-to-Hagane
Online ISSN : 1883-2954
Print ISSN : 0021-1575
ISSN-L : 0021-1575
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Volume 56, Issue 2
Displaying 1-23 of 23 articles from this issue
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  • The Effect of Firing Atmosphere on Pelletizing
    Sougo SAYAMA, Yoshinobu UEDA
    1970 Volume 56 Issue 2 Pages 145-155
    Published: February 01, 1970
    Released on J-STAGE: October 12, 2010
    DOIhttps://doi.org/10.2355/tetsutohagane1955.56.2_145
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    The influence of firing atmosphere on phisical properties of fired iron are pellets was investigated in a bench scale.
    Pellets were made from one of six kinds of natural iron ores or three kinds of artificial iron ores.
    Pure nitrogen, pure oxygen, mixture of nitrogen and oxygen in various rate, and others, were used as the firing atmosphere.
    The results obtained are as follows;
    (1) The crushing strength of limonite pellet became weak as the oxygen content in firing atmosphere was higher. The crushing strength of magnetite pellet was low when fired in the atmosphere containing 10% oxygen, and that of hematite pellet was almost independent of firing atmosphere.
    (2) Physical properties of pellets fired in atmosphere of steam, carbon dioxide or nitrogen were mostly the same.
    (3) Higher oxygen content in the firing atmosphere tends to give higher porosity for all the pellets tested.
    (4) When CaCO3 was added to the ore, the bonding mechanism was seemed to be complicated.
    (5) The results show that the crushing strength and chemical composition of pellets are influenced by the firing atmosphere. This indicates thavan adequate knowledge of the effect of firing atmosphere for each irono re is necessary in order to improve the pellet quality.
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  • Reduction Velocity of Iron-Oxide Pellet by CO Gas Accompanied with Carbon Deposition
    Masahiko TANIGUCHI, Toshihiko KUBO, Iwao MUCHI
    1970 Volume 56 Issue 2 Pages 156-161
    Published: February 01, 1970
    Released on J-STAGE: October 12, 2010
    DOIhttps://doi.org/10.2355/tetsutohagane1955.56.2_156
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    In order to determine the reduction velocity of hematite pellet by CO gas, experiments of the reduction were conducted by use of thermobalance over the range of temperature where carton deposition might take place simultaneously. The rate constant of the reduction was determined, and the value of activation energy was obtained as 18.51kcal/mol.
    It was found also that the moles of deposited carbon increased with the increase in temperature for the case below 600-650°C, but the moles decreased gradually for the case beyond these temperatures.
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  • Reaction Kinetics of Carbon Deposition Accompanied with Reduction of Iron-Oxide Pellet by CO Gas
    Masahiko TANIGUCHI, Iwao MUCHI
    1970 Volume 56 Issue 2 Pages 162-168
    Published: February 01, 1970
    Released on J-STAGE: October 12, 2010
    DOIhttps://doi.org/10.2355/tetsutohagane1955.56.2_162
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    On the reaction of carbon deposition during the reduction of hematite pellet by CO gas, the reaction mechanism in which the catalytic action of iron carbide was taken into account was proposed, and on the basis of this mechanism an equation of reaction velocity was presented.
    Rate constants of carbon deposition were determined experimentally, and it was found that the moles of deposited carbon calculated from the equation of reaction velocity were in good agreement with those obtained experimentally for the case below 650°C.
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  • Effect of the Change in Parameters on the Longitudinal Distributions of Process Variables, the Production Rate and the Carbon Ratio in Blast Furnace
    Jun-ichiro YAGI, Iwao MUCHI
    1970 Volume 56 Issue 2 Pages 169-177
    Published: February 01, 1970
    Released on J-STAGE: October 12, 2010
    DOIhttps://doi.org/10.2355/tetsutohagane1955.56.2_169
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    Rate constants of indirect reduction of iron ores by CO and of solution loss, heat transfer coefficient between gas and solid particles, over-all heat transfer coefficient for heat loss from furnace wall and fractional prereduction of iron ores are considered as the parameters in this work. On the basis of the mathematical model of blast furnace process reported previously, the variations of the production rate of pig iron, the carbon ratio and the longitudinal distributions of process variables caused by the changes of the parameters mentioned above are calculated with the aid of a digital computer (HITAC 5020 E).
    According to the calculated results, the reduction of iron ores proceeded rapidly in a lower part of furnace when the value of activation energy relating to the rate constant of indirect reduction was large, and the production rate of pig iron, Wp, increased and the carbon ratio, Cr, decreased with the increase in this activation energy.
    Both Wp and Cr were not affected so much by the rate constant of solution loss, but the longitudinal distributions of process variables in a lower part of furnace were influenced considerably by the change of this constant.
    The value of heat transfer coefficient between gas and solid particles, hp, influenced remarkably on the temperature distributions and the rates of reduction and melting of iron ores. And, Wp increased and Cr decreased with the increase in the value of hp.
    It was found that the linear variations of Wp and Cr were caused by the change in the value of over-all heat transfer coefficient for heat loss from furnace wall, and that Wp proliferated and Cr decreased exceedingly with the increase in fractional prereduction of iron ores.
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  • On the Desulfurization in the Basic Oxygen Converter
    Masataka YOSHII, Masayoshi ICHINOHE
    1970 Volume 56 Issue 2 Pages 178-185
    Published: February 01, 1970
    Released on J-STAGE: October 12, 2010
    DOIhttps://doi.org/10.2355/tetsutohagane1955.56.2_178
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    An analysis was done on the mechanism of desulfurization in the Basic Oxygen Converter, and the following results were obtained.
    (1) Desulfurization as gas phase is less than 10% of total input sulfur, and is not considered to be a main process of desulfurization in the Basic Oxygen Converter. Almost all of desulfurization proceeds through slag-metal reactions.
    (2) Behaviour of sulfur in metal during blowing is governed by the rate of lime slagging, and sulfur partition ratio between slag and metal ((S%)/[S%]) is generally influenced by the slag basicity.
    (3) In some cases, increase in (FeO) content in slag increases (S%)/[S%] ratio, but this does not means the direct reaction between [S] and (FeO). Increase in (FeO) in slag accelerates the lime slagging rate and thus, increases the basicity and the quantity of the slag.
    Therefore, it is important to accelerate the lime slagging and to operate under high basic slag during blowing for improving desulfurization of metal. However, because the remarkable desulfurization is not expected during blowing, it is nesessary to decrease the input sulfur by using pre-treated low sulfur hot metal and low sulfur fluxing materials for producing low sulfur steel.
    Considering sulfur contents in metal charge, flux and desulfurizing reactions in the furnace, it is estimated that the lower limit of sulfur content of produced steel is 0.002% under operations using 15% scrap and 0.001% under the all hot metal operations.
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  • On the Relation Between Iron Oxide in Molten Slag and Oxygen in Molten Steel at LD Converter
    Shinji TSUDA, Takami IKEDA, Katsukiyo MARUKAWA
    1970 Volume 56 Issue 2 Pages 186-193
    Published: February 01, 1970
    Released on J-STAGE: October 12, 2010
    DOIhttps://doi.org/10.2355/tetsutohagane1955.56.2_186
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    The relation between iron oxide in molten slag and oxygen in molten metal in 160 t LD converter are studied, and the main results obtained are as follows.
    (1) During the period between end point and tapping the oxygen content in molten metal changes in a range of ±150ppm in low carbon steel (0.04%-0.08%C).
    (2) This change of oxygen in molten metal depends on the total FeO content of molten slag. When the total FeO content in slag is high, oxygen content in metal increases between end point and tapping. On the other hand, when the total FeO content is low, the oxygen content decreases.
    (3) At the end of oxygen blowing the slag temperature is higher than that of metal. The difference in temperatures seems to be over 50°C. This difference, however, vanishes during the period between the end point and tapping. This decrease of slag temperature after the end of blowing reduces the oxidizing potential.
    (4) As a consequence, the oxidizing potential of slag becomes lower than that of metal at tapping. In the smelting of low carbon steels, this phenomenon is observed in approximately one third of the heats, but scarcely in medium and high carbon steels.
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  • On the Mineral Composition and the Microscopic Structure of Ingot Scums and Oxide Inclusions Appeared in the Bottom-and Top-Teeming Ingot
    Hiroshi NAGAYAMA
    1970 Volume 56 Issue 2 Pages 194-211
    Published: February 01, 1970
    Released on J-STAGE: October 12, 2010
    DOIhttps://doi.org/10.2355/tetsutohagane1955.56.2_194
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    In order to investigate the source of oxide inclusions in steel by mineralo-chemical method, mineral composition and microscopic structure of ingot scums and oxide inclusions, appeared in some bottom-and top-teeming ingots produced in our plant, were investigated.
    The results were summarized as follows.
    1. In bottom-teeming ingot scums, many kinds of constituent mineral, mainly composed of FeO-MnO-Al2O3-SiO2 system with a small quantity of slag mineral, were found. It is characteristic that a large quantity of α-quartz as silica mineral were observed.
    2. Oxide inclusions in the bottom-teeming ingot were rich in Al2O3 compared with ingot scums, and consist of aluminate minerals (CaO·6Al2O3, MgO·Al2O3) with a small quantity of silicate matrix.
    3. In top-teeming ingot scums, many kinds of constituent mineral, originated from slag, refractories, deoxidation products etc. were found. It is characteristic that a large quantity of α-cristobalite were observed instead of α-quartz as silica mineral.
    4. Mineral composition and microscopic structure of oxide inclusions in the top-teeming ingot were similar to that in the bottom-teeming ingot. However, in macroscopic inclusions, three typical forms, -(1) multi-component silicate (spinel, corundum and α-cristobalite with a fine crystal matrix mainly composed of CaO-Al2O3-SiO2 system), (2) silicious silicate, (3) special type (chrome spinel) were observed.
    5. Spinel (MgO·Al2O3), a main constituent mineral of oxide inclusions, was observed regardless of Aldeoxidation in the ladle. Moreover, in the top-teeming ingot, crystal growth of it was observed comparatively remarkable, coagulating with matrix minerals mainly composed of CaO-Al2O3-SiO2 system.
    6. On the basis of these investigation, the source of oxide inclusions was discussed.
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  • On the Mechanism of Formation of the Inverted V Segregates in Killed Steel Ingots
    Kiichi NARITA, Masayuki TANIGUTI
    1970 Volume 56 Issue 2 Pages 212-229
    Published: February 01, 1970
    Released on J-STAGE: October 12, 2010
    DOIhttps://doi.org/10.2355/tetsutohagane1955.56.2_212
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    The mechanism of formation of the “inverted V” segregation in killed steel ingots was investigated by means of the autoradiographic technique. The results obtained can be summarized as follows:
    1) An inverted V segregation occurs in the transitional solidification zone, when liquid enriched with solute in the interdendritic region which commonly forms microsegregation begins to move upwards owing to the gravitational force. Then it grows gradually to a larger segregation.
    2) The inverted V segregation occurs in the transitional solidification zone, but grows mainly in the boundary region between the transitional zone and the liquid bulk.
    3) The solute concentration inside the interted V segregation diminishes gradually as it grows larger, but this concentration appear again at the final stage of the solidification.
    4) The process of the growth of the inverted V segregation is rather the confluence and spread of the liquid which is already enriched with the solute than the enrichment or accumulation of the solute at the socalled solidification front or interface.
    5) Thus the inverted V segregation is not formed as a result of the solute enrichment at the solidification front, but rather the solute is ejected and enriched at the solidification front through the formation of the inverted V segregation.
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  • Effect of the Molten Surface Vibration on the Cast Structure of Ingots and Controlling the Structure
    Atsumi OHNO, Hiroshi SODA
    1970 Volume 56 Issue 2 Pages 230-238
    Published: February 01, 1970
    Released on J-STAGE: October 12, 2010
    DOIhttps://doi.org/10.2355/tetsutohagane1955.56.2_230
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    The authors have already proposed that most of the crystallites which form an equiaxed zone originate at the initial stage in the upper part of the growing interface, then fall along the interface to the bottom. The present work using vibrations and agitation on the molten metal in the mold, clearly confirmed the above mechanism. The molten surface vibration at the initial stage of solidification is very important for controlling the ingot structure. Several pouring methods were applied to aluminum-0.2% copper alloy ingot casting: top pouring, bottom pouring, pouring with pencil ring gates, and pouring into a tilting mold. The resulting macrostructures showed that the pouring process which produces violent wave action at the point where molten surface touches the side of the solid shell is most effective for the formation of a fine equiaxed structure. In addition, the pouring temperature should be as low as possible.
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  • Mechanical Properties of Super Giant H Shapes
    Shoichi NAKANISHI, Toshiaki HAZE, Tsuguo FUKUDA
    1970 Volume 56 Issue 2 Pages 239-251
    Published: February 01, 1970
    Released on J-STAGE: October 12, 2010
    DOIhttps://doi.org/10.2355/tetsutohagane1955.56.2_239
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    Although super giant H shapes are used progressively in the field of skyscraper construction, in recent Japan mechanical properties in each positions of H shapes have not clearly been reported. In this paper, their mechanical properties were examined by tension tests and Charpy impact tests respectively.
    The deformation behaviours of H spapes was estimated by rolling of Plasticine model, and the differences of mechanical properties in each position of H shapes were considered to be caused by the difference of degree of deformation.
    The results are as follows:
    (1) There were not marked differences in yield strength and tensile strength at any position, while elongation decreased linearly with increasing strain by rolling.
    (2) Impact properties near the surface region were higher than near the center of H shapes.
    This tendency was affected by not only the deformation behaviour but also the thermal history of the process of H shapes making.
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  • Diffusion of Sulfur in Gamma Iron
    Akihiko HOSHINO, Toru ARAKI
    1970 Volume 56 Issue 2 Pages 252-257
    Published: February 01, 1970
    Released on J-STAGE: December 22, 2010
    DOIhttps://doi.org/10.2355/tetsutohagane1955.56.2_252
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    Study on the diffusion behaviour of sulfur in pure iron in the temperature range from 950°C to 1 250°C, was carried out by means of radiotracer. A thin film of radioactive sulfur was deposited as a diffusion source on iron specimens by heating with ferrous sulfide in vacuum sealed capsule.
    The surface residual radioactivity counting method was applied to determine the coefficients of volume diffusion and of grain boundary diffusion.
    As a result, the volume diffusion coefficient of sulsur in pure iron is given by: Dv=1.7 exp (-53000/RT) cm2/sec. The measured grain boundary diffusion coefficient below 1100°C follows the rule that was determined for grain boundary diffusion in alpha iron. However, the grain boundary diffusion of sulfur above 1100°C is more rapid and temperature dependence may be given by: Dgbδ=1.1×10-5 exp (-23000/RT) cm3/sec., where δ is grain boundary width.
    Microscopic observation shows that rod-like sulfide precipitates appear in the crystal grain after cooling from the diffusion temperature above 1 200°C.
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  • Yield and Flow Stress of Iron Alloys Containing 1, 3 and 5 Per Cent Nickel
    Tadahisa NAKAMURA, Tsuneaki SAKAKI
    1970 Volume 56 Issue 2 Pages 258-265
    Published: February 01, 1970
    Released on J-STAGE: December 22, 2010
    DOIhttps://doi.org/10.2355/tetsutohagane1955.56.2_258
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    Iron-1, 3 and 5 per cent nickel alloys were melted paying attention to have the same chemical composition except nickel. Most studies were performed on the lower yield stress as the function of testing temperature, cross head speed and grain diameter, and on the measurement of the elastic constants. The results obtained were as follows:
    1) When tests were performed at room temperature with the cross head speed of 0.5 mm/min, the lower yield stress was raised by 8.5 kg/mm2 with increasing the nickel concentration from 1 to 5 per cent. This crement was caused by raising the frictional strees for the dislocation motion.
    2) The rate of work hardening of iron-1 to 5 per cent nickel alloys at room temperature was in the same range of 1.2 kg/mm2/0.01 true strain.
    3) The lower yield stress at -196°C was decreased by 8.8 kg/mm2, when the nickel concentration increased from 1 to 5 per cent. This decrement was due to lowering of the frictional stress.
    4) The cross head speed dependence of the lower yield stress was diminished by the addition of nickel.
    5) The flow stress was increased in the same way as the lower yield stress when the testing temperature was lowered from room temperature to -196°C.
    6) The interaction energy between an edge dislocation and a nickel atom by the size misfit effect was calculated as -0.012 ev, and that between a screw dislocation and a nickel atom by the modulus misfit effect was as -0.007 ev. The solution hardening observed at room temperature was considered to be due to these interaction mechanisms.
    7) The rigidity modulus of iron-nickel alloys was decreased by about 5-5 per cent when nickel concentration increased from 0 to 5 per cent. It is supposed that the change of the cohesive force which causes the decrease of the rigidity modulus brings about the diminution of the Peierls force, which is one of the factors of the solution softening observed at low testing temperature.
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  • Precipitation Phenomena in High Strength Steels in Which Elements of IVa, or Va Family in the Periodic Table are Added Together with Elements of VIa Family
    Shogo KANAZAWA, Akira NAKAJIMA, Kentaro OKAMOTO, Tokio SUZUKI
    1970 Volume 56 Issue 2 Pages 266-276
    Published: February 01, 1970
    Released on J-STAGE: October 12, 2010
    DOIhttps://doi.org/10.2355/tetsutohagane1955.56.2_266
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    It is reported in this paper that the combined addition of 0.03% Nb and 0.55% Mo in quenched and tempered steel has shown such a high strength increase that can not be deduced from the present knowledges.
    It is also investigated whether there is any other combination effects between elements of VIa or Va family and elements of VIa family in the periodic table, as in the case of Nb and Mo.
    1. It is found that Nb-Mo added steels have the largest combination effect, Ti-Mo, Zr-Mo and Nb-Cr steels have a slight effects, and Ti-Cr, Zr-Cr, Nb-W steels have none of the combination effect.
    2. The reason why such combination effect occurs has been investigated. It is found that, in the case of combination having such effective combination effect, a large number of, and a great amount of cubic duplex carbide particles of IVa or Va element containing VIa element in it precipitate in the course of tempering, and it is infered that such duplex carbides result in the great combination effect of the steel.
    3. The extraction method of Nb or V precipitates from steels is investigated, and it is found that the best is the (1+1) HCl aq. extraction method.
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  • The Role of Rust Layers on the Corrosion Process of Steels in the Atmosphere
    Hideya OKADA, Yuzo HOSOI, Hiramitsu NAITO
    1970 Volume 56 Issue 2 Pages 277-284
    Published: February 01, 1970
    Released on J-STAGE: October 12, 2010
    DOIhttps://doi.org/10.2355/tetsutohagane1955.56.2_277
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    An electrochemical investigation has been made of the corrosion process of the steels rusted in the atmos-phere, in order to reveal the role of the rust in the atmospheric corrosion.
    The cathodic reaction of the rusted steel is found to be mainly consisted of the reduction of FeOOH (brownrust) to Fe3O4 rather than the reduction of dissolved oxygen, and the anodic reaction is the dissolution, of iron.
    In the case of low alloy steels alloyed suitably for atmospheric corrosion resistance, both anodic and cathodic reactions are remarkably suppressed by the formation of protective rust layer after exposure to the atmosphere for more than about 3.5 years. Ancdic reaction is prevented due to masking of active sites on the steel surface by the formaticn of dense arnorplicus iron oxide layer and cathodic reaction is suppressed by increasing difficulty in the reduction of FeOOH.
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  • The Functions of Nb and Mo, and the Effects of V, Zr, Y and Ce on the High Temperature Properties of 10M6N Type Alloys, and the Grain Boundary Reaction
    Heitaro YOSHIDA, Kisaburo KOIKE, Renpei YODA
    1970 Volume 56 Issue 2 Pages 285-299
    Published: February 01, 1970
    Released on J-STAGE: October 12, 2010
    DOIhttps://doi.org/10.2355/tetsutohagane1955.56.2_285
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    The effect of Mo, Nb, Y, Ce, Zr and V on the high temperature properties of 10M6N type alloys and the grain boundary reaction (G. B. R.) occurred in this type alloys were examined.
    Results obtained are as follows:
    1) Addition of Nb causes such effects as (a) refinement of grain size, (b) increase of hardness in solution, (c) increase of tensile strength and deformation resistance at high temperatures, (d) suppression of age hardening accompanying the grain boundary reaction, (e) improvement of the properties against softening, (f) improvement of creep rupture time and elongation and so on. These are mutually related.(F) is chiefly due to (d) and (e), and also is considered to be partially due to the dispersion strengthening with Nb (C, N), from (b) and (c).
    2) The improvement of creep rupture time by addition of Mo is due to (a) solution strengthening, (b) improvement of creep rupture elongation by strengthening in grain boundary.
    3) G.B.R. tends to occur at a tripple point and also at the regions where two twins meet each other or where a grain and a twin meet each other. G. B. R. is accelerated by stress.
    4) Addition of Y and Ce to 10M6N alloy and that of Zr and V to 10M6NB alloy do not remarkably im-prove the creep rupture properties of these alloys.
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  • Effect of Heat Treatment on the High Temperature Properties of High Manganese Heat Resisting 10M6N Type Alloys
    Heitaro YOSHIDA, Kisaburo KOIKE, Renpei YODA
    1970 Volume 56 Issue 2 Pages 300-310
    Published: February 01, 1970
    Released on J-STAGE: October 12, 2010
    DOIhttps://doi.org/10.2355/tetsutohagane1955.56.2_300
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    Effect of heat treatment on the high temperature properties of high manganese heat resisting 10M6N alloy and 10M6NB alloy (10M6N type alloy containing a small amount of boron) were examined.
    Results obtained are as follows:
    1) These two alloys show more intense age hardenability, more excellent creep rupture life and poorer rupture elongation, as solution temperature becomes higher. It is probably considered to be due to the fact that the finer precipitates tend to distribute. Especially, creep rupture strength in 1000 hr at 700°C of 10M6NB alloy solution treated at 1300°C, is improved up to about 30 Kg/mm2, which belongs to the strongest group in Ni-Cr austenitic steels. Its rupture elongation is about 20%, and the creep rupture strength of notched specimen is higher than that of smooth specimen. That is, the high temperature strength of the alloy can be improved by this heat treatment, still keeping enough ductility.
    2) Creep rupture strength becomes inferior, as the aging process proceeds in pre-aging after solution treatment. This is considered to be due to two functions; the first, carbon and nitrogen dissolved in the matrix precipitate as carbide and nitride, and so, solution strengthening becomes inferior, because of deconcentration of these two elements and the second, precipitates formed in pre-aging treatment more easily grow and coagulate in the process of creep rupture testing. Consequently this type alloys are preferred to be used as solution treatment.
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  • Effect of Carbon on the High Temperature Properties of Type 304 and 316 Austenitic Steels (Study of Stainless Steels for Fast Breeder Reactor)
    Heitaro YOSHIDA, Renpei YODA, Kisaburo KOIKE, Kunihiko MATUO
    1970 Volume 56 Issue 2 Pages 311-330
    Published: February 01, 1970
    Released on J-STAGE: October 12, 2010
    DOIhttps://doi.org/10.2355/tetsutohagane1955.56.2_311
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    As the pipe materials for nuclear fuel cover in fast reactor, type 304, 347 and 316 austenitic stainless steels are used. In future plutonium carbide for nuclear fuel and liquidus sodium for coolant would be used. As the result pipe materials for nuclear fuel cover are carburized, and it would become a problem whether high temperature properties are affected.
    From this standpoint, in this paper we investigated the effect of carbon on high temperature properties of type 304 and 316 austenitic steels.
    Results obtained are as follows:
    When these alloys are solution treated at 1150°C, (1) solution hardness:(2) deformation resistance at 900°C, 1000°C and 1100°C:(3) tensile strength and yield strength at room temperature, 600°C, 700°C and 800°C tend to increase nearly in proportion to carbon content, but (a) recrystallization temperature:(b) 10000 hr creep rupture strength at 600°C, 700°C and 800°C show maximum at about 0.2% carbon content.
    It is believed that such behaviour of (a) and (b) are due to excellent solution hardening and precipitation hardening, because residual carbide particles in the alloy containing carbon more than 0.2% cause precipitates to form around it in heating at high temperature, and cause solution strengthening and precipitation strengthening to lower.
    But, when solution temperature is 1200°C, the maximum of creep strength is obtained at a higher amount of carbon than 0.3%, and the effect for improvement of strength is a little, further the ductility lowers.
    Therefore, the upper limits of carbon content and solution temperature are considered to be about 0.2% and 1150°C respectively.
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  • The Effect Alloying Elements on the Properties of SUH 31 Alloy
    Yoshizumi NISHI, Yoshimichi MATSUMOTO, Kanoo KIKUCHI, Hitoshi IIDA
    1970 Volume 56 Issue 2 Pages 331-341
    Published: February 01, 1970
    Released on J-STAGE: October 12, 2010
    DOIhttps://doi.org/10.2355/tetsutohagane1955.56.2_331
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    For valve alloys are required higher tensile strength, creep-ruptuer and fatigue strength at elevated temperatuers and high resistance to accelerated corrosion, by sodium, sulfur and vanadium in fuel. SUH 31 alloy has been developed as the most suitable alloy for exhaust valve.
    We have tested the effects of alloying elements of Cr, Mn, Si, Nb and B of SUH 31 alloy.
    The rusults obtained are as follows:
    1. Short time tensile strength increased by 2.0-7.0 kg/mm2 higher than SUH 31 alloy by adding a small amount of N and 6.0-8.0% Mn instead of Ni. There was no change in the tensile properties by increasing Cr to about 19% and by varyng Si between 1.0% and 3.0%.
    2. Creep-rupture strength increased remarkably by adding both B and N, but reduced by adding Cr, Mn and C respectively.
    3. Cr was an effective element for the hot corrosion resistance. The optimium Cr content was about 19.0%. Si did not show a good effect on hot corrosion resistance by any immersion crucible tests at 800°C, but at 900°C. Replacement of Ni by Mrs ga ie a good effect for the test in synthetic ash containing 20 wt of Na2SO4.
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  • Influence of Dissolved Oxygen on the Stress Corrosion Behavior of 18Cr-8Ni Austenitic Stainless Steel
    Ryohei TANAKA, Kyuya NAGASAKI, Tingkwei Hsu
    1970 Volume 56 Issue 2 Pages 342-350
    Published: February 01, 1970
    Released on J-STAGE: October 12, 2010
    DOIhttps://doi.org/10.2355/tetsutohagane1955.56.2_342
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    In order to study the behavior of oxygen dissolved in corrosives which has been reported to influence the stress corrosion cracking of austenitic stainless steels, the specimens of the steel were stressed and exposed to 42% MgCl2 solution or 40% FeCl2 solution under nitrogen or normal atmosphere, and the change in ductility and hardness during corrosion, and fracture time were measured.
    The results obtained are summarized as follows:
    (1) In 42% MgCl2 solution without dissolved oxygen, the stress corrosion cracking occurred both in case of whole immersion specimen or half immersion specimen.
    (2) It was concluded that the dissolved oxygen is necessary for pitting to occur in high temperature sodium chloride solution, but, after the initial pit forms, the crack propargation may depend on hydrogen embrittlement which is resulted from the phenomenon that low pH FeCl, is filled in the pit by electrochemical reaction.
    (3) The stress corrosion mechanism seemed to be illustrated from the standpoint of crevice corrosion mechanism, and consequently it was concluded that not oxygen but hydrogen plays an important role in stress corrosion cracking processes.
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  • Some Studies for Increasing the Extraction Velocity and the Extraction Rate of Nitrogen on the Determination of Nitrogen in Steel by Vacuum Fusion Method
    Yoshihiko ABE, Shintaro TAKAZAWA
    1970 Volume 56 Issue 2 Pages 351-359
    Published: February 01, 1970
    Released on J-STAGE: October 12, 2010
    DOIhttps://doi.org/10.2355/tetsutohagane1955.56.2_351
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    To establish a method for determining the nitrogen in steels by vacuum fusion method, de-gassing speed was measured in connection with physical and chemical properties of carbon-saturated melt, and it was found that the speed was promoted by the existence of the precipitation of graphite in the spheroidal form and by the co-existence of pretty amounts of volatile elements in melt.
    Practical techniques available for determing oxygen and nitrogen simultaneously were, subsequently, studied by applying the above significant effects, and the results are summarized as follows:
    1. Ce is effective as a spheroidal graphite-forming element when empty crucible is used for each analysis.
    2. Sb is desirable as a volatile element, in which the degassing takes place through the mechanism of gas bubbles, especially when the element is put in a capsule.
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  • The Determination of Microgram Amount of Sulfur in Pig and Cast Iron with Pararosaniline
    Hiroshi HARA, Jiro YAMADA, Kimio SUGIMOTO, Masaru YAMAGUCHI, Haruhisa ...
    1970 Volume 56 Issue 2 Pages 360-365
    Published: February 01, 1970
    Released on J-STAGE: October 12, 2010
    DOIhttps://doi.org/10.2355/tetsutohagane1955.56.2_360
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    A method which is rapid and highly sensitive is described for the determination of microgram quantities of sulfur in pig and cast irons.
    The sample is burned at 1450°C in a stream of oxygen. The sulfur is converted-to sulfurdioxide, which is absorbed into 0.2 M Na2HgCl4 solution, and determined photometrically with P-rosaniline and formaldehyde at 560 Mil after 20 min standing.
    Vanadium pentoxide is used as a combustion aid.
    The limit of identification of sulfur in this method is 0.05 μg per ml.
    Time for analysis is about 30 min.
    The reproducibility of analytical results by the proposed method as coefficient of variation is 4.1% for carbon steel (0.011%S).
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  • The Equilibrium between Vanadium and Oxygen in Liquid Iron
    Kiichi NANITA, Sinji KOYAMA, Fumikazu KAWAGUCHI
    1970 Volume 56 Issue 2 Pages 366-367
    Published: February 01, 1970
    Released on J-STAGE: October 12, 2010
    DOIhttps://doi.org/10.2355/tetsutohagane1955.56.2_366
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    The equilibrium between vanadium and oxygen in liquid iron is examined. As the results, it is recognized that VO is formed as the deoxidation product in liquid iron containing vanadium more than 4-5% at 1550°C-1650°C.
    In such case the chemical reactions and the equilibrium constants are represented as follows;
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  • Erratum to : 1969 Perspective of Production and Technique of Iron and Steel in Japan
    1970 Volume 56 Issue 2 Pages N36
    Published: 1970
    Released on J-STAGE: October 12, 2010
    DOIhttps://doi.org/10.2355/tetsutohagane1955.56.2_N36
    JOURNAL OPEN ACCESS
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