随想
Takuo ANDO
pp. 1103-1104,1246
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Tetsu-to-Hagané Vol.53(1967), No.9
Tetsu-to-Hagané Vol.41(1955), No.1
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ONLINE ISSN: | 1883-2954 |
PRINT ISSN: | 0021-1575 |
Publisher: | The Iron and Steel Institute of Japan |
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Takuo ANDO
pp. 1103-1104,1246
Readers Who Read This Article Also Read
Tetsu-to-Hagané Vol.53(1967), No.9
Tetsu-to-Hagané Vol.41(1955), No.1
Munekazu OHMI, Tateo USUI, Yoshiro MATSUMOTO, Yoshikazu MASUYAMA
pp. 1105-1113
Abstract
Mass transfer from a naphthalene sphere in a circular tube under steady and pulsating air flow at room temperature is investigated by measuring the loss in weight or the decrease in dimension of the body after a given time. Because of small mass-transfer rate, there is little difference between the results with and without the resistance due to the rate of gas flow. Under the pulsating flow, however, the resistance is taken into consideration, because air and C10H8 gas may be mixed enough. Comparison of these results with theoretical ones reported previously gives the following experimental expression:
Sh=2+ [ (0.58) 4+ (0.38z0.4) 4] 1/4Sc1/3Rep1/2, where Sh=2γ0kf/D, z= (aω/U∞) 3/2 (a/γ0) 1/2, Sc=υ/D, Rep=2γ0U∞/υ (a, amplitude; D, diffusivity; kf, mass-transfer coefficient; γ0, radius; U∞, free stream velocity; υ, kinematic viscosity; ω, angular frequency). As z=0, this expression agrees with the experimental one for steady flow mass-transfer.
The experimental results of half sphere and local mass-transfer show that the acceleration effect of pulsating flow on the mass transfer is remarkable in the dead-water region of the sphere, where the mass transfer is small under steady flow.
Yoshiyasu TAKADA, Mitsuo SUMITO, Nobuo TSUCHIYA, Kyoji OKABE
pp. 1114-1123
Abstract
The circulation behaviour of Fe, Mn, Si, Mg, Zn, Na, K, S, and Cl in blast furnace is studied. The compounds of circulating elements and the region of the circulation are quantitatively estimated by thermodynamic calculations using gas compositions measured by the vertical probes at a working blast furnace. The probable vapour pressures of circulating species are quantitatively estimated by the mass spectrometric analysis of Knudsen effusates from pig iron, slag, and coke.
Kazuo AMANO, Koin ITO, Hiroshi SAKAO
pp. 1124-1132
Abstract
The decarburization rates of liquid iron have been measured in the vavious Ar-CO-CO2 mixtures by using the levitation technique. The concentrations of carbon and oxygen change mostly along the carbonoxygen line in equilibrium with Ar-CO-CO2 mixture under the condition that the oxide film is not formed on the surface of liquid iron. The reaction finishes at a concentration determined by PCO2/PCO. The rate has been analyzed by assuming that the mass transfers between the two phases determine the overall reaction rate. The following rate equation has been obtained under the condition of nC·nO=constant; -nc=PCO2-PCO*PCOS/KInC/RT/kg {1+ (1+PCOS/KIIγ) (PCO*/KIIInC2) } At the high concentration of carbon the decarburization rate is regarded to be controlled by the mass transfer in the gas boundary layer. The rate is gradually reduced, because the resistance of the mass transfer in the metal boundary layer increases and the driving force of the reaction decreases as the concentration of carbon becomes lower. The iron droplet exploded due to the formation of the oxide film on the surface at the high partial pressure of CO2. For a short period at the beginning, the rapid reaction occurs to reduce both the concentrations toward the equilibrium line of PCO+PCO2, in Ar-CO-CO2 mixture. The reaction can be satisfactorily explained by the mechanism that C-O degassing and decarburization take place at the same time during this stage.
Tomoo TAKENOUCHI, Koreaki SUZUKI
pp. 1133-1142
Abstract
In order to produce steels with ultra low sulfur and phosphorus, some experiments were done to clarify the influence of slag composition on the desulfurization and dephosphorization rates. The results obtained were summarized as follows:
(1) Large rate constants for desulfurization and dephosphorization were obtained by using slags which contained Na2O, B2O3, Na2B4O7 or K2O in CaO-CaF2 base and had great reaction ability as well as fluidity.
(2) Simultaneous reaction of desulfurization and dephosphorization became possible for steels containing some oxygen, with the use of these slags.
(3) Because of the strong erosive effect of these slags, refractories should be selected according to the slag composition.
Readers Who Read This Article Also Read
Tetsu-to-Hagané Vol.64(1978), No.3
Tetsu-to-Hagané Vol.64(1978), No.8
Tetsu-to-Hagané Vol.64(1978), No.10
Hiroyuki NOMURA, Kazumi MORI
pp. 1143-1152
Abstract
In order to clarify the mechanism of blowhole formation, an experimental study has been made of unidirectional solidification of iron for carbon contents of the melt of 0.01 to 0.40% at a solidification rate of about 5mm/min. Critical composition for blowhole formation has been determined. Above 0.15% carbon the critical oxygen concentration is almost constant (0.0025%), while it increases with decreasing carbon content below 0.15%. A macroblowhole originates from a small blowhole formed in the interdendritic area. A model based on the equilibrium solidification suggests that the small blowhole is formed without supersaturation of carbon and oxygen in the interdendritic liquid. The growth of blowholes which proceeds at oxygen contents below the critical concentration is accounted for by the model of steady growth of cyclindrical blowholes.
Kazuo YAMANAKA, Yasuya OHMORI
pp. 1153-1161
Abstract
The aluminum nitride precipitation in austenite and its effect on the hardenability of low-carbon-1/2 moly bdenum boron-treated steels has been investigated. The results are as follows:
(1) The precipitation of BN occurs under non-equilibrium condition in the case of shorter austenitizing time and consequently lowers hardenability. Such non-equilibrium BN precipitates transform to AlN with increasing the austenitizing time, resulting in the recovery of hardenability.
(2) The recovery of hardenability is due to the increase of the soluble boron content accompanied by the formation of AIN.
(3) The orientation relationship between AlN and austenite is given as:
[0001] AlN// [110] γ-Fe growth direction
(1120) AlN// (111) γ-F
(1100) AlN// (112) γ-Fe
The degree of misfit is very small along the [0001] AlN (// [110] γ-Fe) direction, leading to the preferential growth of AIN along this direction.
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Tetsu-to-Hagané Vol.64(1978), No.3
Tetsu-to-Hagané Vol.64(1978), No.8
Tetsu-to-Hagané Vol.64(1978), No.10
Kazuo YAMANAKA, Yasuya OHMORI
pp. 1162-1170
Abstract
Temper embrittlement and fracture behavior of Fe-C and Fe-C-Ni-Cr alloys doped with P were studied by means of grain boundary etching technique, Charpy impact tests, and low temperature tensile tests.
Grain boundary etching behavior with respect to aging time seems to correspond to the cementite precipitation at the grain boundaries together with the change of the grain boundary concentration of P. Temper embrittlement does not occur only by the grain boundary segregation of P, but needs the coexistence of alloying elements such as Ni or Cr.
Brittle fracture in temper embrittled alloys is initiated by the formation of grain boundary cracks followed by the crack propagation without arresting. Therefore, Griffith's crack such as a pearlite colony crack is not assumed to exist in the fracture of temper embrittled alloys.
Shigeo NOMURA, Masayoshi HASEGAWA
pp. 1171-1178
Abstract
The existence of clusterings of platelet tangled dislocations in 304 steel, produced at the grain boundary or internal interfaces by the precipitation of atomic hydrogen, was demonstrated by the transmission electron microscope. Futhermore macroscopic phenomena caused by this microscopic hydrogen defects were observed in hydrogenated stainless steel, that is, 1) the increase of flow stress 2) anomalous behavior of recovery process in hydrogen embrittlement 3) anomalous increase of intergranular corrosion loss.
The initiation sites of microcracks due to hydrogen embrittlement in austenitic stainless steel were grain boundaries or carbide interfaces, and these were the sites of hydrogen defects. The propagation process of the microcracks by hydrogen embrittlement depended on the austenitic stability to martensite transformation under tensile stress, and the interfaces of martensite lath provided the most preferential path of microcracks.
Masakuni FUJIKURA, Tetsuo KATO
pp. 1179-1188
Abstract
The effects of Ni content and grain size on the athermal and deformation-induced martensitic transformations in 18-8 austenitic stainless steels have been examined. Furthermore, their deformation characteristics, especially 0.2% proof stress (0.2PS) and flow stress at sub-zero temperatures have also been examined in terms of austenite stability. The results are as follow:
(1) Ms and Md temperatures are depressed with increasing Ni content. Ms temperatures of commercial alloys are about 130K lower than those of high-purity alloys with low interstitials. The effect of grain size on Md is larger than that of Ms.
(2) The amount of athermal martensite formed at 77°K is analysed according to Magee's equation. There seems a good agreement between observed and calculated values when grain size is 115μ. In case of smaller grain size with 36μ, however, calculated values are larger than observed ones. This disagreement may comes from the differences of Ms and the nucleation frequency at Ms.
(3) The content of deformation-induced χ' and ε' martensite depends on Ni content and tensile temperature.
(4) The change of transformation mode from γ→ε'→α'to γ→α' is observed with increasing Ni content and tensile temperature, which can be understood in terms of stacking fault energy and chemical driving force (ΔGγ→α').
(5) Inverse dependence on temperature of 0.2% proof stress (0.2PS) does not occur in this study. The temperature dependence of 0.2PS of untransformed stable austenite is about 2.7 times larger than that of of 0.2PS of unstable austenite in which martensitic transformation intervenes before yielding of austenite.
(6) The flow stress of unstable austenite e. g. 18Cr-9Ni alloys at 93K does not follow the simple law of mixture of austenite and martensite.
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Tetsu-to-Hagané Vol.64(1978), No.1
Tetsu-to-Hagané Vol.65(1979), No.7
Tetsu-to-Hagané Vol.64(1978), No.11
Hiroyuki TSUKUI, Yutaka TOGASHI, Takashi MITAMURA
pp. 1189-1198
Abstract
An investigation was made of oxide inclusions in 19Cr-9Ni stainless steel weld metal which was produced using a electrode covered with lime-titania.
2MnO·SiO2 (tephroite), MnO·SiO2 (rhodonite), FeO·Cr2O3 (chromite), FeO·Ti2O3, Cr23C6, TiC, and TiN were identified by the X-ray analysis of the residue separated from the weld metal by ultrasonic agitating dissolution method using 14% I2-CH3OH solution.
The inclusion particles extracted were classified according to the size (5 μ over and under) by ultrasonic sieving method, and observed by optical microscope.
Typical inclusion particles over 5 μ were analyzed by electronprobe X-ray microanalyzer.
It was found that inclusion particles over 5 μ were mainly spheroidal MnO·SiO2, 2MnO.SiO2, angular SiO2, massive SiO2, plate-like SiO2, rod-like Al-silicate, needle-like TiN, and stringer-like Ca-phosphate.
Inclusion particles less than 5 μ amount to about 90% of oxide inclusions, and they contain mainly Mnsilicate, FeO·Cr2O3, and FeO·Ti2O3, the size of which was 1 μ or under.
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Tetsu-to-Hagané Vol.64(1978), No.9
ISIJ International Vol.32(1992), No.4
Tetsu-to-Hagané Vol.64(1978), No.11
Koji YAMAGUCHI, Kenji KANAZAWA, Susumu YOSHIDA
pp. 1199-1208
Abstract
There are three effects, mechanical, environmental, and creep effects, on the low-cycle fatigue life of Type 321 stainless steel at high temperatures. At intermediate temperature such as 450°C, the strain rate dependence of the fatigue life is due mainly to the mechanical effect caused by the cyclic strain hardening, because the fracture mode is transgranular and creep and environmental effects seem to be negligible. At higher temperatures above 600°C, the strain rate dependence of the fatigue life is due mainly to the change of the fracture mode from a transgranular type to an intergranular type with decreasing the strain rate. This intergranular fracture mode, composed of smooth, grain boundary facets, is similar to the creep fracture mode of wedge type cracking. The wedge type crack seems not to propagate without the oxidation effect, because it is said that in vacuum test the strain rate dependence of the fatigue life is hardly observed and the fracture mode is rather transgranular. Therefore, in this case the main damaging factor is the environmental effect. On the other hand, in hold time test in tension intergranular facets covered with small dimples are observed. This intergranular fracture mode is similar to the creep fracture mode of void type cracking. The void type crack seems to propagate without being influenced by oxidation, because it is said that the hold time effect is observed even in vacuum test. In void type intergranular cracking, creep effect, that is, creep-fatigue interaction exists.
Shoichi MATSUDA, Shoichi SEKIGUCHI, Hideaki KAGEYAMA
pp. 1209-1218
Abstract
In relation to clarifying the cause of the scattering of energy absorbed in Charpy transition temperature range, a study was made of finding the cleavage crack initiation site. Main results were as follows.
1) The cleavage crack always initiated at the pearlitic second phase independently of the energy level absorbed in Charpy test. Heterogeneity such as inclusions and so on did not contribute to the cleavage crack initiation.
2) The cleavage microcracks initiating at the effective grain larger than mean size could grow to final fracture, while the microcracks initiating at the smaller effective grains could not propagate.
3) Frequency of cleavage microcrack initiation was very small. It was one or two cracks per area of 0.4mm2 of ductile fracture surface. On the basis of experimental results described above, statistical analysis was made. It may be concluded that Gaussian distribution of effective grain size was the direct cause of the scattering cf energy absorbed in Charpy test.
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Tetsu-to-Hagané Vol.64(1978), No.1
Tetsu-to-Hagané Vol.65(1979), No.7
Tetsu-to-Hagané Vol.64(1978), No.11
Hisashi ANDO, Akira OKAYAMA, KO SOENO, Hisasuke TAKEUCHI
pp. 1219-1225
Abstract
Green and tap densities of atomized high speed steel powders (JIS SKH 57) are measured. The shapes of the powders are spherical in gas atomization and irregular in water atomization. The densities are lower in the water-atomized powders than in the gas-atomized ones. Pulverization of the water-atomized powders increases the densities. Compacting press also increases the densities of the water-atomized powders. However, the densities of the water-atomized powders are difficult to approach to the tap density of the gasatomized powders.
Hot isostatic pressing, 113 MPa is applied at 1150°C in order to sinter densely the water-atomized powders, gas-atomized powders, and their mixture. Transverse rupture strength have been investigated in the dense specimens subjected to heat-treatment for hardening. The strength level of the specimens produced by using the water-atomized powders is much higher than that of the specimens produced by using the gas-atomized powders. It is also observed that adding the gas-atomized powders to the water-atomized powders causes the decrease in strength level.
Strength level is greatly increased by hot isostatic pressing and subsequent hot forging. However, the strength level of the dense specimens of the gas-atomized powders can not be increased satisfactorily without destroying the spherical forms by giving a great forging ratio.
Takesada SASAKI, Hiroshi ENDO, Tadahumi HONDA, Yoshimasa ZAMA
pp. 1226-1235
Hisao SUZUKI, Jiro OHNO
pp. 1236-1245
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Tetsu-to-Hagané Vol.64(1978), No.1
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Tetsu-to-Hagané Vol.64(1978), No.11
伊藤 伍郎
pp. A135-A158
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Tetsu-to-Hagané Vol.64(1978), No.1
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田中 良平
pp. A179-A198
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Tetsu-to-Hagané Vol.64(1978), No.1
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Tetsu-to-Hagané Vol.64(1978), No.11
高橋 愛知
pp. A91-A114
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Tetsu-to-Hagané Vol.64(1978), No.1
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