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Volume 26, Issue 7
Displaying 1-6 of 6 articles from this issue
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[in Japanese]1979 Volume 26 Issue 7 Pages 235-243
Published: September 25, 1979
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSDownload PDF (1640K) -
Characterization of α-Fe2O3 PowdersTakeshi Nomura, Takashi Yamaguchi1979 Volume 26 Issue 7 Pages 244-249
Published: September 25, 1979
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSIn order to study sintering of powders with special reference to the effect of powder characteristics, eight kinds of a-Fe2O3 powders were characterized by powder densities and particle sizes. Techniques used are SEM and mercury porosimetry, and different methods for particle size determination were used. The aggregation states were evaluated by the Hausner ratio (tap density/apparent density), the compaction ratio (pressed density/apparent density), sedimentation density, and pore structure of pressed bodies. Marked differences were seen between the powders containing hard aggregated particles and those composed of soft agglomerates. Hard aggregates produce larger pores and wider pore size distributions in compacts, while soft agglomerates give uniform pore size distributions of compacts.View full abstractDownload PDF (1695K) -
Sintering Behavior of α-Fe2O3 PowdersTakeshi Nomura, Takashi Yamaguchi1979 Volume 26 Issue 7 Pages 250-253
Published: September 25, 1979
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSEffects of powder characteristics on the sintering of eight kinds of commercial a-Fe2O3 powders have been studied with special reference to the aggregation state by constant-rate heating method. Techniques used are dilatometry, mercury porosimetry, and photomicroscopy. It is shown that the temperature at which densification starts is well correlated with the primary particle size, while the fired density, with the size ratio of pore to primary particle. A striking difference in the sintering behavior was observed between the powders containing hard aggregated particles and those composed of soft agglomerates. Hard aggregates have deleterious effects not only on the sintering of compacts but also on the microstructure of sintered bodies.View full abstractDownload PDF (1517K) -
Moriya Oyane, Kunio Okimoto, Tomio Sato1979 Volume 26 Issue 7 Pages 254-258
Published: September 25, 1979
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSFor the purpose of obtaining sintered products of complicated shapes or of a shape which is lengthening in compression direction, joining of short compacts of a simple shape is studied, and in particular the feasibility of infiltration method is investigated. Torsional strength of the joined compacts are examined, and compared with that of the conventional compacts.
The results obtained are as follows:
(1) Both joining of the pre-formed compacts and strengthening of the base metal can be carried out in one process.
(2) The torsional strength of the compacts joined by the infiltration method can compete with that of compacts infiltrated by usual way. This result does not depend on whether the preforms are made of green compacts or sintered ones.View full abstractDownload PDF (1418K) -
Moriya Oyane, Kunio Okimoto, Tomio Sato1979 Volume 26 Issue 7 Pages 259-264
Published: September 25, 1979
Released on J-STAGE: July 12, 2010
JOURNAL OPEN ACCESSTensile strength, impact value, ductility, hardness distributions and strain distributions for the joined products by means of infiltration method are investigated. The mechanism of the joining is also studied. The result obtained are as follows:
(1) In the case of impact value and ductility, the joined compacts are a little inferior to the conventional compacts infiltrated in usual way. But the tensile strength is as good as that of the conventional ones.
(2) The joined compacts possess a uniform hardness distribution, therefore the deformation patterns in the products obtained by the compression with grooved dies is similar to that in the conventional infiltrated compacts.
(3) Strengthening of the joined compacts can be established by the following process; first the iron skeletons are joined between their contact faces and subsequently the infiltration occurs. So that, in order to increase the strength of joined prooducts, the two conditions must be satisfied in the manufacturing process; these are possible by the so-called low-speed heating and short-time infiltration.View full abstractDownload PDF (4989K) -
Takeshi Sadahiro1979 Volume 26 Issue 7 Pages 265-269
Published: September 25, 1979
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSCracks emanating from the corners of Vickers indent, can be employed to determine the crack resistance of cemented carbides. Crack resistance was measured as a function of structural variables and compositions of cemented carbides.
Results obtained were as follows: (1) The crack resistance of WC-Co alloys was observed to be correlated to the thickness of Co phase and the hardness of the alloys, independent of Co content,
WC grain size, carbon content and hot isostatic pressing treatment.
(2) The crack resistance of alloys involving addition carbides, was correlated to the thickness of
Co phase, and this relation was influenced by the content and composition of the addition carbides.
(3) In comparison with the parameters of fracture mechanics, the crack resistance which can be easily measured was evaluated as the toughness of cemented carbides.View full abstractDownload PDF (309K)
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