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Volume 18, Issue 3
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[in Japanese]1971 Volume 18 Issue 3 Pages 83-88
Published: September 25, 1971
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSDownload PDF (4504K) -
Haruo Kubota, Akio Hara1971 Volume 18 Issue 3 Pages 89-94
Published: September 25, 1971
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSIt is said that the hot pressing gives better properties to WC-Co alloys than the cold presssinter method. At present time, graphite is mainly used as the die material for the hot pressing of WC-Co alloys. In this paper, the carbon impregnation to the sintered body which is caused by the contact of the powder (sintered body) and the graphite die was studied. The results obtained are as follows.
(1) The layer depth of carbon impregnation increased parabolically with the increase of keeping time. However, it was assumed that the carbon impregnation which results in the excess carbon precipitation does not to occur during heating and also at the initial stage of keeping time, but assumed to begin to occur after the.sintering is completed. (2) The layer depth of carbon impregnation increased with an increase of hot press temperature. (3) The layer depth of carbon impregnation depended upon the property of the graphite used for the die. (4) The hot press pressure did not have a definite relation to the layer depth of carbon impregnation, but was affected by the behavior of metal which was squeezed from the die and other factors. (5) The metal which was squeezed from the die during hot pressing was mainly composed of cobalt and the WC content involved in it was by far lesser than that corresponding to Co-WC eutectic.View full abstractDownload PDF (3095K) -
Effect of the Forming Pressure on SinteringOsamu Yamaguchi, Shigeo Shimomura1971 Volume 18 Issue 3 Pages 95-99
Published: September 25, 1971
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe effects of the forming pressure on the sintering between PbO and PZT were investigated with a thermal dilatometer, an electron microscope and the measurement of the isothermal shrinkage and the electro-mechanical coupling coefficient.
The extent of the expansion and the shrinkage on heating depended on the forming pressure. The forming pressure gave the influence to the rearrangement stage, but not to the solution-reprecipitation and the grain growth of PZT which proceeded under nearly the same process. The good values for the physical properties (sintered density, apparent porosity, and water absorbing ratio) were attained with increase in the forming pressure. In case of the hydrostatic press, better values were obtained than in case of the usual forming method. It was found that there exists a close relation between the sintered density and the electro-mechanical coupling coefficient and also the latter was based on the polarizing conditions.View full abstractDownload PDF (1576K) -
The Formation of PZT and the Sintering under the Atmosphere of OxygenOsamu Yamaguchi, Yasuo Ohashi1971 Volume 18 Issue 3 Pages 100-104
Published: September 25, 1971
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSThis paper dealts with the investigation about the formation of PZT and about its sintering under an atmosphere of oxygen in regard to the non-stoichiometry with an excess PbO (massicot, β-PbO).
The results obtained are as follows.
(1) The formation of PZT increased under the atomosphere of oxygen, and the reason could be explained in terms of Hedvall's effect.
(2) The heating behavior of the excess β-PbO in the starting powder was described as;
in oxygen: β-PbO-β-PbO+intermediate phase (570-720°C)→a-PbO
in air: β-PbO→β-PbO+α-PbO→β-PbO+α-PbO+intermediate phase (700-730°C)→α-PbO
(3) The temperature at which a liquid phase appeared on heating agreed with that at which all of the excessive β-PbO in the starting powder were converted into α-PbO.
(4) The dielectric constant of specimens sintered under the atmosphere of oxygen had a higher value than that of specimens obtained in the air.View full abstractDownload PDF (1403K)
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