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Volume 24, Issue 8
Displaying 1-5 of 5 articles from this issue
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Akio Kato, Fumihiro Tokunaga1977 Volume 24 Issue 8 Pages 219-222
Published: December 25, 1977
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSFormation of iron oxide powders by spray-pyrolysis technique from the ethanol solution of several Fe salts, mainly of nitrates, was investigated to elucidate the effects of reaction conditions on the properties of products. The reaction was carried out by spraying . the solution into a reactor heated by an electric furnace.
α-Fe2O3 powders obtained from Fe nitrate at 600°-1200°C became finer and less porous withincreasing reaction temperature. The particles were finer than 1μ at 1200°C. By changing the solution to air ratio, one can obtain the iron oxide powders which are composed mainly of α-Fe2O3, γ-Fe2O3, and Fe2O4 or FeO. The kind of iron salt gave a considerable effect on the shape and size of iron oxide particles produced: The oxalate and lactate gave hollow particles of α-Fe2O3.View full abstractDownload PDF (3001K) -
Hisasuke Takeuchi1977 Volume 24 Issue 8 Pages 223-227
Published: December 25, 1977
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSIn order to prepare closely packed mixtures for hot isostatic compaction, the flowing properties and blending conditions of gas-atomized steel powders were investigated. Being liable to size-segregation, spherical particles show a marked heterogeneity during the flow in a glass vessel.
A magnetization treatment was tried to make the flowable steel powders attractive to each other, for varying their flow rates. Mixtures of attractive particles could be homogenized, when stirred in a certain range of flow rates.
This enabled to prepare the closely packed mixtures without segregation, having apparent density of up to 75 per cent, whereas the values of untreated powders ranged from 63 to 65 per cent. The high density mixtures were compacted by hot isostatic pressing and the homogeneity of their structures was microscopically confirmed.View full abstractDownload PDF (2576K) -
Hisasuke Takeuchi, Shinsuke Morimoto1977 Volume 24 Issue 8 Pages 228-231
Published: December 25, 1977
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSPartial pressures of the gases evolved during vacuum sintering or degassing treatment of some alloy powders were measured by use of a mass-spectral analyser. A mixture of tungsten carbide and cobalt, water- and gas-atomized high speed steel powders, powdery carbonyl nickel, tungsten and zirconium hydride were respectively heated in a vacuum, the extracted gases being analysed stepwise at temperatures up to 1000°C.
The distinctive features in the results are as follows:
(1) WC-Co compacts and high speed steel powders evolve carbon dioxide at 300-600°C, and carbon manoxide at 500-1000°C.
(2) Carbonyl nickel noticeably evolves carbon dioxide.View full abstractDownload PDF (256K) -
Hisashi Suzuki, Teruyoshi Tanase, Fumio Nakayama, Koji Hayashi1977 Volume 24 Issue 8 Pages 232-235
Published: December 25, 1977
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe transverse-rupture strength of conventional WC-10%Co high carbon two-phase alloys (mean grain size is about 1.4μ) was measured as a function of width (w) or thickness (t) of the specimen. Then, the observed strength was examined in relation to the structural defects which appeared on the fracture surfaces as a fracture source.
Results obtained were as follows. (1) The increase of w or t resulted in the decrease of strength, showing the so-called volume effect. (2) The strength decrease was accompanied by the increase of the average defect (or source) dimension, and by that of the average distances from the tension surface and also from the span center to the defect. It was also accompanied by the change in the sort of defects. Thus, the volume effect as above was considered not to be simply related to usually cited risky volume, but to be related to the volume containing a defect which actually acts as a fracture source. (3) The effect of specimen-volume on the strength of conventional cemented carbide could not be satisfactorily explained by Weibull's equation.View full abstractDownload PDF (303K) -
Tetsuro Yamaguchi, Tamotsu Ishii, Akira Mochizuki1977 Volume 24 Issue 8 Pages 236-241
Published: December 25, 1977
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSEffects of small amount of various oxides on the magnetostrictive properties of magnetite were studied with a view of enhancement of the magnetic properties of materials. The specimens were sintered at temp-eratures from 1150 to 1200°C in the atmosphere of CO2 gas by the conventional powder metallurgical technics. It has been clarified that the substitution of cobaltous ions for ferrous ions leads to an enhan-cement of magnetostrictive properties (the increase of the saturation magnetostriction), and the addition of a small amount of TiO2 results in the increase of the resistivity and also the reduction of the eddy current loss. Furthermore, it has been confirmed that the addition of Si02 results in the formation of homogeneous specimens with high density, fine grain size and favourable mechanical strength.
A procedure for preparing the magnetostrictive vibrator of good performance is given after considering the effect of additives on the properties of magnetite.View full abstractDownload PDF (2986K)
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