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Volume 22, Issue 7
Displaying 1-6 of 6 articles from this issue
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Kunio Okimoto, Tomio Sato, Toshio Yamakawa1975 Volume 22 Issue 7 Pages 205-212
Published: November 05, 1975
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSEffect of some conditions on the coefficient of lateral pressure was experimentally investigated by using the various metal powders. These conditions were a powder's kind, particle shape, particle size distribution, manufacturing process of powders and particle surface state. Range of compacting pressure was from zero to 60 kg/mm2. Powders used were thirteen kinds, that was, lead, tin, zinc, aluminium, copper, iron, bronze, titanium, nickel, cobalt, chrome, manganese and tungsten. The coefficient of lateral pressure was showed in relation to green density.
It was found that the coefficient of lateral pressure of soft metal powders was larger than that of hard metal powders. In the case of same kind's powders, the effect of particle shape on the coefficient of lateral pressure was recognized, and the coefficient of lateral pressure of spherical powders was smaller than that of irregular powders.View full abstractDownload PDF (2328K) -
Kunio Okimoto, Tomio Sato, Toshio Yamakawa1975 Volume 22 Issue 7 Pages 213-219
Published: November 05, 1975
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe effects of zinc stearate in compaction of metal powders are experimentally investigated in the aspects of apparent density, flow rate, coefficient of friction between the die and green compacts, mechanical strength of green compacts, coefficient of lateral pressure, consolidation equation, and density distribution of compacts. The zinc stearate is used as the powder lubricant and also die lubricant.
The results obtained are as follows:
1) When the zinc stearate of 0.1-2.0% is added, the apparent density of metal powders is increased, and when more than 2% this is decreased conversely.
2) The effect of die lubricant on the decrease of friction coefficient is far superior to that of powder lubricant on it.
3) The coefficient of lateral pressure is little affected by adding the zinc stearate.
4) When the zinc stearate is used as a powder lubricant, the mechanical strength of the powder compacts is decreased.View full abstractDownload PDF (461K) -
Kanji Kawaguchi, Mitsuo Kawai1975 Volume 22 Issue 7 Pages 220-225
Published: November 05, 1975
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSOxidation resistance of sintered SUS304 stainless steel and the effect of calorizing were studied.
The results obtained are summarized as follow:
1) Oxidation resistance of sintered compacts at 500°C and 700°C increases with increasing of relative density.
2) Oxidation resistance at 900°C of sintered compacts with relative density of 96-98% is superior to that of other sintered compacts and of the specimens from molten metal.
3) Oxidation resistance of sintered compacts is improved by calorizing.
4) Bending strength of sintered compacts decreases very slightly after being oxidized.View full abstractDownload PDF (4894K) -
Hisashi Suzuki, Koji Hayashi, Masahide Fukuda, Teruyoshi Tanase, Fumio ...1975 Volume 22 Issue 7 Pages 226-231
Published: November 05, 1975
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSThe WC-(10, 20, 30)%Co alloys were minutely vacuum-sintered, so that the defect acting as a fracture source in each alloy might almost consist of coarse WC grains smaller than about 20μ. Two sorts of cooling rates after sintering, about 15°and 0.5°C/min, were adopted in the temperature range from 1360°to 1300°C for 10%Co alloy, 1350°to 1300°C for 20%Co alloy and 1340°to 1300°C for 30%Co alloy, respectively. Two sorts of specimens different in cooling rates in each alloy were ground with a diamond wheel, and transverse-ruptured according to JIS. After the test, the dimension (2a) and location of coarse WC grains as a fracture source were measured on the ruptured surface.
The results obtained were as follows: 1) The average transverse-rupture strength (σm), and also the external stress (σd) corresponding to σm were always higher in rapidly cooled specimen (R-specimen) than in slowly cooled specimen (S-specimen). 2) The 2a of R-specimen was generally smaller than that of S-specimen, showing that of an anomalous grain growth of WC also occurred during the time of cooling specimens, when the cooling rate was decreased. 3) The distance from the tension surface to the defect (Δt) of R-specimen was larger in 10%Co alloy than that of S-specimen. However, the difference in Δt was hardly observed in (20, 30)%Co alloys. It was found in a slowly cooled 30% Co alloy that the location of the defect was always on the domain boundary of binder phase. 4) The increase in Δm and σd due to increasing cooling rate was considered to be affected mainly by the increase in the strength of WC-Co matrix including that of the domain boundary, and partially by the changes in 2a and Δt.View full abstractDownload PDF (1773K) -
Osamu Yamaguchi, Hichiro Omaki, Kiyoshi Takeoka, Kiyoshi Shimizu1975 Volume 22 Issue 7 Pages 232-237
Published: November 05, 1975
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSThe sintering process of titanium dioxide derived from alkoxide was investigated by means of dilatometry, X-ray diffraction, electron microscopy and the measurement of isothermal shrinkage. 1) Titanium oxide (anatase, +brookite) prepared by calcining the as-prepared material at low temperatures (300°-500°C) was highly sinterable. The sintering process was composed of two stages: a rapid shrinkage at 400°to 680°C and a gradual shrinkage above 900°C. The sintered bodies as high as 98% of the theoretical density were obtained by heating at 1400°C.
2) The sintering mechanisms were studied at the temperatures ranging from 450°Cto 680°C. At 450°C to 550°C, the process was expressed with the linear relation between log (shrinkage) and log (time) with a slope of unity, and was thought to be the rearrangement process of primary particles. This process was followed by the process with a different slope due to volume diffusion. The activation energies were about 9.6 kcal/mol for the rearrangement process and 116.7 kcal/mol for the volume diffusion, respectively. At 550°to 680°C, no shrinkage was observed except for the initial rapid shrinkage due to the rearrangement process.
3) In the sintering of rutile prepared by calcining at 800°C, the rearrangement process was also predominant at the initial stage followed by grain boundary diffusion. The apparent activation energy for the latter was about 78 kcal/mol.View full abstractDownload PDF (3715K) -
Masakazu Hakomori, Takashi Yamaguchi, Hiroshi Kuno1975 Volume 22 Issue 7 Pages 238-243
Published: November 05, 1975
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSEffects of mixing method of raw material powders on the formation and sintering of PZT ceramics have been studied. Raw material mixtures were prepared both by conventional wet ball-milling and partial precipitation methods. The latter consists of precipitating PbCO3 in a suspension containing TiO2 and ZrO2. Techniques employed are dilatometry, X-ray diffraction analysis and electron microscopy.
It is shown that the formation depends on the mixing method. Thus, for ball-milling method, PbZrO3 was not detected as a separate phase throughout the course of PZT formation, whereas for the precipitation mixing, PbZrO3 was detected. Dense sintered bodies were not obtained from partial precipitation mixtures even with additives. For ball-milled mixtures, however, addition of Pb2Nb2O7 and MnCO3 caused an abrupt densification at a certain temperature. The observed differences in the formation and sintering of PZT could possibly be attributed to the state of aggregation of reactant powder particles. Results with mixtures prepared by modified mixing methods, together with those by electron microscopy, supported the point of view.View full abstractDownload PDF (1472K)
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