Journal of the Japan Institute of Metals and Materials
Online ISSN : 1880-6880
Print ISSN : 0021-4876
ISSN-L : 0021-4876
Volume 29 , Issue 12
Showing 1-21 articles out of 21 articles from the selected issue
  • Masao Honma, Sougorho Morita, Katsunobu Yamaya
    1965 Volume 29 Issue 12 Pages 1131-1136
    Published: 1965
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    Metallographic studies have been performed on the structures of weld metal and the heat-affected zone of 13% chromium martensitic stainless steel. The heat-affected zone was obtained by single bead welding, in which a single bead 10∼12 cm in length was placed on a 13% chromium stainless steel plate of 200×75×20 mm3. The isothermal austenitization diagrams (T-T-A diagram, Time-Temperature-Austenitization diagram) were determined for two specimens differently pre-heat treated. The specimen was heated in a salt bath, followed by rapid quenching in water, and then the T-T-A diagram was obtained from changes in hardness (Hv) and in matrix structure.
    The results may be summarized as follows: (1) In the specimen heated at 1050°C for 30 min and then oil quenched, the heat-affected zone is shaply divided into two parts; one is heated over the Ac1 point and the other is tempered at a lower temperature than the Ac1 point. This is characterized by hardness. (2) The hardness of the heat-affected zone approaches that of base metal by a short-time annealing at 700°C, but the chromium carbide is aggregated in the heat-affected zone. (3) By rapid heating and cooling, the 13% chromium stainless steels with varying carbon contents show a different hardness and an almost identical Ac1 point. The hardness curve exhibits a peak at a maximum heating temperature. (4) From the T-T-A diagrams of the specimens differently treated, it is clear that, in the rapid heating and quenching, a very short holding time is sufficient for hardening when the specimen is heated up to a specified temperature. (5) As to the different pre-heat treatment of the 13% chromium martensitic stainless steel, the austenitization time of the specimen that received only solid solution treatment is shorter than that of the annealed specimen.
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  • Taichi Kamijo
    1965 Volume 29 Issue 12 Pages 1137-1141
    Published: 1965
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    Slip rotations occurring during rolling are considered to be due to a triaxial stress system, in which the three stresses are σ, a compressive stress normal to the rolling plane, −nσ, a tensile stress parallel to the rolling direction and (1−n)⁄2·σ, a compressive stress parallel to the transverse direction. If the direction cosines of each stress axis with respect to the slip plane normal and slip direction are represented, the total resolved shear stress acting on the slip system is given by: τ=σ{cosφ_1 cosλ_1+(1-n)/2 ·cosφ_3 cosλ _3-n cosφ_2 cosλ_2}.
    In case of the triaxial stress system where two compression axes exist, displacements of the rolling plane normal in a standard stereographic projection will depend on the ratio of component of resolved shear stresses owing to the two compressive stresses. When the effect of the tensile stress can be ignored, the trarsverse compressive stress causes the transverse direction to move to the slip plane normal and the normal compression rotations lead the rolling plane normal towards the slip plane normal. In consequence, the displacements of the rolling plane normal will be composed of those which arise from two compressive stresses.
    When a lateral spread occurs at cosφ3cosλ3<0, it will be necessary to operate the slip system which accommodates the lateral spread. In case that cosφ3cosλ3 is nearly zero, the slip rotations on the triaxial stress system will be consistent with that on the biaxial stress system, since the effect of the transverse compressive stress can be ignored.
    It can be concluded that the three stress axes should be considered to act together in order to investigate the texture development from slip rotations occurring during rolling.
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  • Muneo Oka
    1965 Volume 29 Issue 12 Pages 1141-1147
    Published: 1965
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    The sub-structures of the martensite in a quenched Ti-Mo alloy have been investigated by means of transmission electron microscopy, and also the microhardness and X-ray measurement have been made. The results are as follows:
    (1) In X-ray and electron diffraction patterns of the quenched Ti-6%Mo alloy, the spots due to the α-phase (h.c.p.) were found, but the spos due to the β-phase (b.c.c.) or ω-phase (hexagonal) were not.
    (2) In the quenched specimens, the needle-shaped markings found by optical microscopy were observed as the banded martensites (α-phase) by transmission electron microscopy. Besides, a large number of small lenticular martensites were observed in the other regions in a greater part of the specimen. The hardness of this specimen was about 337 VHN on the average.
    (3) The lattice defects in the banded martensites were {10\bar11} transformation twins and dislocations on (0001) planes. And there were two kinds of the banded martensites: one contained only dislocations and other dislocations and transformation twins, and the latter was more frequently observed than the former.
    (4) The lattice parameters of the martensite in Ti-6%Mo alloy a=2.928, c=4.665, ca=1.593 were obtained by the X-ray measurement.
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  • Hiroyasu Funakubo, Gaston Collette, Nobuhiko Iwao, Yoshiki Gunji
    1965 Volume 29 Issue 12 Pages 1148-1152
    Published: 1965
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    Nous avons servi les éprouvettes du fer pur monocristallin complet en forme de lame et l’appareil, inventé par l’un des auteurs, qui est en plus amélioré pour permettre mesurer les valeurs de frottement intérieur jusqu’à la contrainte maximum de 1.5 g/mm2 ou 1.8×10−7. Les résultats obtenus par cet essai nous out montré les remarques importants comme les suivants.
    (1) un fort caractère dépendant des valeurs de frottement intérieur à la faible contrainte maximum de l’ordre de 1.5 g/mm2.
    (2) jusqu’à la contrainte de quelques dixaines de g/mm2, les valeurs de frottement intérieur varient en linaire et reversible avec la variation des contraintes de cisaillement maximum appliquées.
    (3) au dessus de cette contrainte de cisaillement maximum, la variation de valeurs de frottement intérieur linaire à la contrainte de cisallement maximum n’est plus valable, nous constatons la relation irreversible entre ces deux facteurs.
    (4) en ce qui concerne le point transitoire de ces deux domaines, nous avons marqué que cette valeur se situe dans le domaine de la contrainte de l’ordre de 40 g/mm2.
    (5) le caractère dépendant, la valeur du point transitoire et le module de cisaillement dépendent fortement à l’orientation cristallographique des éprouvettes.
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  • Tadayoshi Takahashi, Iwao Hagiwara
    1965 Volume 29 Issue 12 Pages 1152-1159
    Published: 1965
    Released: April 04, 2008
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    On the segregation of a steel or alloy ingot, the effect of stirring during the process of solidification appears to be an important factor to clarify the segregation phenomenon. In the present investigation on Al-Cu alloy, stirring was carried out by means of the method hydro-dynamically known as Taylor’s vortex flow, where the inner cylinder of the two concentric cylinders are rotated in the molten alloy. The inner cylinder was especially water cooled so that the solidification can grow from the wall of the inner cylinder to the outer region of the ingot. The results are as follows:
    By the stirring, the time for completion of solidification was remarkably increased.
    The negative segregation was observed between the inner and outer regions of the ingot, and the normal segregation was observed in the outer region of the ingot.
    The columnar crystals were developed exceedingly; this is the finding that has never been expected.
    The degree of undercooling was somewhat lower than in the case of the stational solidification.
    The thickness of diffusion layers calculated by the usual (plain interface) formula of effective distribution coefficient has no relation to the hydro-dynamically calculated thickness of the laminar layer.
    Nevertheless, the effective distribution coefficient was independent of the freezing rate, and only by a function of the mean flow rate of a molten alloy, U, it can be expressed as follows:
    (This article is not displayable. Please see full text pdf.)
    These experimental results were explained well with a theoretical analysis of turbulent mixing diffusion in the trasitional solidification layer.
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  • Masanobu Miyake, Tadao Sano
    1965 Volume 29 Issue 12 Pages 1160-1164
    Published: 1965
    Released: April 04, 2008
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    Using a rotating cylinder method, a kinetic study has been made on the dissolution of 54.6%Cu-44.0%Ni and 87.1%Cu-11.9%Ni alloys in liquid Bi. The solution rates of the solid specimens were measured at 500°C and at constant rotational speeds in the range of 0∼1000 rpm. The results show that the dynamic solution rates for Ni- and Cu-component of the alloys conform to the same reaction law which was applied to the dissolution of these alloys under a static condition. It was also found that the solution rate constants of both components increased remarkably with the increasing rotational speed of the specimens up to 500 rpm, but above 500 rpm each value of the solution rate constant has a tendency to approach the respective costant value. From these results, the dissolution mechanism was schematically discussed in comparison with that of pure Ni and Cu in liquid Bi.
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  • Akira Moriyama, Iwao Muchi
    1965 Volume 29 Issue 12 Pages 1165-1171
    Published: 1965
    Released: April 04, 2008
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    The rate of gaseous oxidation of carbon in molten iron was analysed in consideration of the overall reaction process comprising of the chemical reaction and diffusion in the gaseous film.
    A mechanism of the chemical process involving the dissociative adsorption of oxygen was proposed and the rate equations of decarburization were derived theoretically. Rate equations given in thie work agreed well with many experimental data obtained by other investigators.
    The numerical equations of both the rate constant k1 of the dissociative adsorption and the gas-phase mass-transfer coefficient kf were obtained as in Eqs. (18) and (19), respectively.
    The rate-determining steps of the reaction of decarburization were discussed in relation to the surface area of a metal bath and the flow rate of a gaseous oxidant.
    And, it was found that the interfacial chemical process became more dominant with the decrease in the surface area and the increase in the flow rate of gas.
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  • Masao Ibaraki, Hirofumi Yoshimura
    1965 Volume 29 Issue 12 Pages 1171-1176
    Published: 1965
    Released: April 04, 2008
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    The effect of lattice defects in the deformed austenite of Cr-Ni steel on the strengthening by ausforming was investigated by means of the micro-hardness test, and optical and transmission electron microscopy.
    (1) The micro-hardness test showed that the austenite strain-hardened remarkably by up to about 20%-ausforming, beyond this, it reached a constant hardness level. The ausformed martensite did not harden so much by up to 20%-ausforming, beyond this, it hardened rapidly. (2) Numerous fine parallel and crossed striations in the 10%-ausformed austenite were observed by optical microscopy, and they were confirmed as ε-phase and deformation twins by transmission electron microscopy. It was observed that the martensite plate originated from these lattice defects and formed along or across them. The orientation relationships among austenite, ε-phase and martensite were (111)γ\varparallel(0001)ε\varparallel(011)α′ and [10\bar1]γ\varparallel[11\bar20]ε\varparallel[1\bar11]α′. (3) In the case of the martensitic transformation from the austenite which contained the ε-phase, both austenite and ε-phase could be transformed to a martensite, and the ε-phase would act as a transitional phase in the martensitic transformation without being inherited into the martensite as a kind of lattice defects of martensite. (4) The deformation twins in the austenite have a possibility of leaving the {110}α interface in martensite. (5) In the case of 30%-ausforming, the austenite did not contain the ε phase and deformation twins but dislocations, and the martensite contained only dislocations. Both martensite and austenit were high in dislocation density. (6) The non-ausformed martensite had dislocations with only one kind of Burgers vector, and the ausformed martensite had dislocations with two or more kinds of Burgers vector. The dislocation density was very high in the ausformed martensite. (7) From the above results, it can be considered that lattice defects contributing to the increasing of dislocation density and to the strengthening of ausformed martensite are dislocations in the ausformed austenite.
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  • Yoshio Baba
    1965 Volume 29 Issue 12 Pages 1177-1182
    Published: 1965
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    Experiments have been carried out to investigate the influence of addition of Cr (0.01∼0.2 at%), Mn (0.01∼0.3 at%) and Zr (0.01∼0.2 at%) to Al-2.5 at% (6.0 wt%) Zn alloy upon the pre-precipitation or clustering phenomenon.
    The results are as follows:
    (1) The rate of clustering of Zn atoms is reduced by the addition of Cr, Mn and Zr, but general features of pre-precipitation in these ternary alloys are not different from those in Al-2.5 at%Zn binary alloy since these third elements in the above-mentioned range do not interact with Zn atoms.
    (2) The decrement in the rate of clustering of Zn atoms increases in the order of Mn<Cr<Zr, particularly by the addition of Mn 0.2∼0.3 at%, Cr 0.1∼0.2 at% and Zr 0.03∼0.2 at% which is characterized by the existence of the second phases.
    (3) This effect can be more reasonably explained in terms of the increase in boundary area by grain refining and in dislocation density by remaining of dislocations introduced by plastic deformation which could act as sinks to cause the decrease in the concentration of quenched-in vacancies, rather than the binding energy between an atom of the third elements and a vacancy which is greater than that between a Zn atom and a vacancy.
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  • Genjiro Mima, Masaharu Yamaguchi
    1965 Volume 29 Issue 12 Pages 1182-1189
    Published: 1965
    Released: April 04, 2008
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    The deformation behavior of an aged iron-chromium alloy at 470°C has been investigated by means of measurements of electrical resistivity and electron microscopic observations, in order to make clear the embrittlement of the iron-chromium alloy aged at 475°C.
    The electrical resistivity of the aged iron-40 wt% chromium alloy which were measured at the liquid nitrogen temperature increased with increasing aging time.
    The deformation substructure of the slightly deformed brittle specimens remarkably differs from the slightly deformed ductile specimens, in the former deformation twins were directly observed by transmission electron microscopy and dislocations were streight although by no means smooth. In the latter dislocations showed a rather irregular form and irregular tangles were observed scatteringly.
    The specimens aged for a long time at 470°C fractured generally by cleavage with a few isolated regions of intergranular fracture and many twin traces were observed at the fracture surface.
    Deformation twins observed in the aged and slightly deformed specimens seem to be closely related to the embrittlement of the aged iron-chromium alloy.
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  • Shozo Yoshioka, Yutaka Nakayama, Taichiro Ito
    1965 Volume 29 Issue 12 Pages 1189-1194
    Published: 1965
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    The behavior and distribution of dislocations at the easy glide of Cu-15 at%Al single crystals have been investigated by means of the dislocation etching technique. Etching an undeformed crystal has revealed random dislocation forests having the density of 5×106/cm2 and well-developed subboundaries. Because of the low stacking fault energy in this alloy, dislocations tend to be retained in their slip planes. Hence, a definite slip direction can be assigned to each array of dislocation etch pits. Secondary slips are detected at the very early region of the easy glide, which are thought to arise from the vicinity of the primary slip bands. As the deformation proceeds, the width of the primary slip bands grows and the region between the primary slip bands decreases. The narrower the region between slip bands, the more extensive the secondary slip activated there. Secondary slips are also detected in the interior of the wide primary slip band. Dislocation densities on the primary slip system and secondary systems are measured from the etch pit density, and it is found that at the end of the easy glide the dislocation density on the primary slip system is much higher than that on secondary slip systems.
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  • Shozo Yoshioka, Yutaka Nakayama, Norio Hosokawa
    1965 Volume 29 Issue 12 Pages 1194-1200
    Published: 1965
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    The secondary defects introduced by quenching of Al-Zn alloys were investigated by means of transmission electron microscopy, with particular attension to the effect of the quenching rates and the solute concentrations.
    Two different methods of quenching were employed in this experiments. One was a fast quenching at the quenching rate of 1×104 deg C/sec, and the other a slow quenching at the rate of 1×103 deg C/sec.
    The type, size and density of secondary defects were sensitive to the quenching rates and the solute concentrations. The types of secondary defects observed in quenched Al-Zn alloys were the Frank sessile loop, prismatic loop, helical dislocation and black spot defect. Frank sessile loops were observed only in pure Al by the fast quenching and in the alloys containing less than 1.9 at%Zn by the slow quenching. Helical dislocations were observed in the alloys containing above 7.0 at%Zn by the fast quenching but in alloys of more than 1.6 at%Zn by the slow quenching. Black spot defects were found in the alloys containing above 0.5 at%Zn by the fast quenching and in alloys of more than 7.0 at%Zn by the slow quenching. Judging from the various experimental results, the black spot defects found in the quenched Al-Zn alloys were thought to be the three dimensional vacancy clusters.
    The initial vacancy concentrations estimated roughly from the size and density of secondary defects in the quenched alloys were much larger than in pure Al. This may indicate that the presence of Zn in Al lowers the activation energy to form a vacancy.
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  • Ishoshi Kawashima, Kenzi Tokiwa
    1965 Volume 29 Issue 12 Pages 1201-1205
    Published: 1965
    Released: April 04, 2008
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    The application of the fluorescent X-ray analysis of iron and steel for the efficient daily work to more kinds of impurity element and to a wider range of each amount than usual was studied. The calibration curves of 21 alloying and residual elements (Si,P,S,Ti,V,Cr,Mn,Fe,Co,Ni,Cu,As,Zr,Nb,Mo,Ag,Sn,Sb,Ta,W,Pb) were made out for 61 NBS and BS standard samples of cast iron, white iron, carbon steel, low alloy steel, stainless steel, tool steel and high temperature iron alloys. The results showed that each element could be determined with the error of less than 10% when the concentration was more than 0.001%. The influence of the coexisting elements on the determination of one element was discussed.
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  • Koin Ito, Kokichi Sano
    1965 Volume 29 Issue 12 Pages 1205-1209
    Published: 1965
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    We studied the rates of sulfur transfer between H2S-H2 mixtures and molten iron. Empirical rate equations of sulfurization and desulfurization were compared with Eq. (9) which was derived from the 2-film theory. As a result, the following equations were obtained from Eq. (9):
    (This article is not displayable. Please see full text pdf.)
    The value of KG calculated from the data of desulfurization was of the same order at that obtained from rates of sulfurization. The activation energy of sulfurization was found to be 4.7±1.2 kcal/mole. Accordingly, in the transference of sulfur between gas and molten iron, the transfer of sulfur in both of boundary layers at the gas- and liquid-sides might be thought to be the rate determining steps. Furthermore, it was shown theoretically that the effect of the additional element, X, on the rate of desulfurization of molten iron is proportional to the influence of X on the activity of sulfur, fSx. On the basis of the present results, we considered the means of measurement for the equilibrium of the reaction, H2(g)S=H2S(g).
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  • Hideo Sugawara, Saburo Shimodaira
    1965 Volume 29 Issue 12 Pages 1210-1215
    Published: 1965
    Released: April 04, 2008
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    Exposure corrosion tests were made on mild steels in the precincts of the Sendai railway station, in the suburbs of Sendai city and in the laboratory. The atmospheric corrosion rates depend not only on the composition of steels but also on the quantities of oxygen and sulphur dioxide on the steel surface. In the present laboratory experiment, mild steels containing various amounts of copper and sulphur were tested in the atmospheres of different relative humidity and concentration of sulphur dioxide at 30°C. Corrosion products were identified by diffuse reflection spectra and an electron diffraction method. γ-FeOOH was observed in all the atmospheres, while α-FeOOH was in large quantities detected in the atmosphere containing sulphur dioxide. But neither sulphate, sulphide nor compounds of copper was detected in the rusts. The electrochemical behavior of mild steels in 5%H2SO4 containing sulpher dioxide was examined by a potentiodynamic method. Both anodic and cathodic polarizations were decreased in the presence of sulphur in steel or sulphur dioxide in the aqueous solution. Sulphur in steel or sulphur dioxide in the aqueous solution reacted as cathodic depolarizers. By the addition of copper to steels, the corrosion rates were clearly decreased in the H2SO3 solution, while the corrosion rates were increassed by the increase of sulphur content in steels.
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  • Yotaro Murakami, Hiroyuki Yoshida, Yasushi Ikai
    1965 Volume 29 Issue 12 Pages 1215-1221
    Published: 1965
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    For the purpose of investigating the effects of annealing, deformation and additional elements on the susceptibility of stress corrosion cracking of α-brass in ammonical environment, stress corrosion tests were carried out by bending or elongating by a lever-system type apparatus and an Instron type tensile-testing-machine. Commercial high-purity 70:30 brass with or without additional elements, such as Be,Y,Si and Mischmetall, were stress corroded. During the tests, the measurements of electric resistance and stress relaxation were carried out to trace the crack initiation and propagation.
    It has been found that the time to failure, its stress dependence and the modes of cracks are very sensitive to deformation and annealing before tests. The alloys containing 0.1 at% Misch-metall or 1.0 at%Si have good resistance against stress corrosive conditions. Additional elements have effects mainly on the crack propagation. The fact that pre-strained specimens are much susceptible to trans-granular cracking may correspond to the dislocation distributions.
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  • Hideo Abe
    1965 Volume 29 Issue 12 Pages 1221-1226
    Published: 1965
    Released: April 04, 2008
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    The hot-strip of a 3% silicon-iron has a pronounced preferred orientations (112)[\bar110] and (100)[011]. On heating the hot-strip, lenticular carbides precipitate at temperatures lower than 400°C, and precipitates along the subboundaries and grain boundaries are observed on heating at 600°∼1000°C, while the grain boundary migration and disintegration of the texture occur on heating at 1000°C. After the two stages of cold-rolling separated by an intermediate annealing, an approximate (111)[11\bar2] orientation is developed from the (112)[\bar110] orientation contained in the hot-strip. The process of the secondary recrystallization or the effect of dispersed inclusions on the inhibition of the normal grain growth can be altered remarkably by heat-treatments prior to the cold rolling process. The results suggest the importance of the solution-treatment of MnS during the hot-rolling process. It is found that the grains after primary recrystallization are elongated parallel to the rolling direction, which are similar to the “pancake structure” in Al-killed low carbon steel.
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  • Kazuaki Iijima
    1965 Volume 29 Issue 12 Pages 1227-1233
    Published: 1965
    Released: April 04, 2008
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    Static torsional properties of hardened steels were determined in relation to austenitizing temperature, austenitic grain size, carbon content and subzero treatment in order to provide a guide for heat treating of steels used in a low temperature tempered state, such as some tool steels, case hardening steels and urtra high strength steels.
    Four plain carbon steels and three low alloy steels were used in the experiment.
    (1) The torsional properties of hardened steels, such as torsion strength, plastic torsion angle and absorbed energy required for breaking, are affected markedly by the austenitizing temperature. The utmost degree of torsional strength, plasticity and toughness is obtained when they are austenitized just above the critical temperature, and it extremely decreases as the temperature increases.
    However, the plasticity and the toughness and sometimes the strength start to increase again from a certain austenitizing temperature and the maximum values are obtained in hardened steels when they are austenitized at about 900°C.
    When the temperature is over the degree, which coinsides, with the overheating temperature accompanying abrupt austenitic grain coarsening, these properties decrease.
    (2) The effect of carbon content on these properties is also prominent. The greatest degree of strength, plasticity and toughness is obtained in hardened 0.2 to 0.3%C steel, and it decreases extremely as the carbon content increases. But when the content is over about 0.6%C, the properties again increase, showing a maximum at about 1.0%C, decreasing as the carbon content increases.
    (3) These properties are generally decreased by subzero treatment, and each maximum state of properties, especially that of plasticity, obtained by austenitizing at about 900°C or by a carbon content of about 1.0%, almost disappear. It suggests that the ductile retained austenite would be available in some degrees improving the plasticity, toughness and also strength of hardened steels.
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  • Minoru Tanaka, Jô Yamamoto
    1965 Volume 29 Issue 12 Pages 1233-1239
    Published: 1965
    Released: April 04, 2008
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    Some microstructural observations at elevated temperatures in vacua (10−5 mmHg) have been studied on the A1 transformation and grain growth of austenite for mild steel, and also on the tempering for the Si-Cr-V tool steel.
    The results obtained in this study are summarized as follows:
    (1) In heating of the mirror polished mild steel, the grain boundary of ferrite reveals faintly at 300°∼400°C, and then becomes clearly at 600°∼700°C. The grain boundaries of austenite can be slightly detected anywhere in ferrite grains at 730°∼750°C and then become clearly at higher temperatures following the fade-away of boundaries of ferrite grains.
    (2) On the grain growth of austenite for mild steel, coalescence of some of the grains occurs with the decrease in the total area of grain boundaries. The boundaries of austenite reveal clearly in a rectilinear shape after a prolonged heating at a high temperature.
    (3) When austenite grains are cooled, ferrite grains reveal at random in austenite grains below 700°C. The structure of pearlite, however, cannot be observed in this step. The reason of this behaviour is presumed that cementite will be graphitized at the surface layer of the test piece. Because there are many black spots in the metallographic polished and etched surface after cooling, and the normal microstructure can be observed in the lower parts of the test piece whose surface was removed about 0.05 mm in thickness.
    (4) On tempering for the quenched Si-Cr-V tool steel, any surface changes cannot be observed up to 170°C. However, the surface relief can be detected on the etched surface at about 200°C due to the initiation of the decomposition of residual austenite. At about 550°C, this surface relief turns into a smooth wavy surface which precipitated many small carbides. These observed hot stagemicrostructures on tempering agree with the results of dilatation tests.
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  • Susumu Morioka, Yoshinobu Sawada, Katsuhisa Sugimoto
    1965 Volume 29 Issue 12 Pages 1240-1246
    Published: 1965
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    Effects of Al2O3 on the anodizing of SAP in 15% H2SO4 aqueous solutions were studied by comparing the results obtained with the data for pure aluminum of different purity (99.99%Al and 99.49%Al). The specimens used were SAP 26 (1.2%Al2O3), SAP 45 (4.6%Al2O3), SAP 61 (8.0%Al2O3), SAP 82 (12.7%Al2O3).
    Al2O3 contained in SAP gives remarkable effects on the anodic oxidation, and the results obtained are summerized as follows: (1) In the constant voltage anodizing, the leakage current density decreases with the increasing Al2O3 content of SAP, and the bath voltage increases for the constant current density anodizing. (2) In the constant current density anodizing, the bath voltage-time curves of SAP containing a small amount of Al2O3 show critical voltages, but not for the specimens of a high Al2O3 content. (3) In the constant voltage anodizing, the thickness of the anodic oxide films decreases with the Al2O3 content of SAP. However, no remarkable effect of the Al2O3 content was observed for the constant current density anodizing. (4) Oxide films formed on SAP containing a large amount of Al2O3 are dark grey or black in color when the specimen is anodized under a high current density. (5) There is no relation between the corrosion resistance of anodic oxide films of SAP and its Al2O3 content. (6) From the electron microscopic observation, it was found that pores observed on the anodic oxide films of pure Al are gradually diminished as the Al2O3 content increases, and that the surface of the films becomes smooth.
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  • 1965 Volume 29 Issue 12 Pages 1246
    Published: 1965
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    Please see pdf. Wrong:(203), (203), (203) Right:(213), (213), (213)
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