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Volume 25, Issue 6
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[in Japanese]1978 Volume 25 Issue 6 Pages 185-192
Published: September 25, 1978
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSDownload PDF (2211K) -
Kiyoaki Akechi, Zenshiro Hara1978 Volume 25 Issue 6 Pages 193-197
Published: September 25, 1978
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSValues of electric resistance and power input as a function of sintering time were calculated by using wave shapes of current and voltage measured during resistance sintering of titanium powder, and the resistance sintering process was analyzed. The results are as follows.
(1) Contribution of Joul's heat generated from two main sources in the resistance sintering (i.e., the one heat source is the titanium particle itself, and another is the contact areas between the particles) has been quantitatively explained.
(2) In the earlier stage of resistance sintering, the compact is chiefly heated by an electric current passing through the contact areas between the particles. In the intermediate stage, the heat is generated both within the particle itself and at the contact areas between the particles. In the later stage, the specimen is heated only by a current passing through the particle itself whose resistance can be estimated from the bulk resistivity of titanium at elevated temperatures. (3) Owing to positive temperature coefficient of resistance, an increase in resistivity of metal with in-creasing temperature gives rise to homogenize and to stabilize the process of resistance sintering.View full abstractDownload PDF (370K) -
Kiyoaki Akechi, Zenshiro Hara1978 Volume 25 Issue 6 Pages 198-201
Published: September 25, 1978
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSInfluences of sintering condition, particle size, alloying powders on the resistance-sintering process of titanium powder were analyzed.
The change of electric resistance during sintering depends upon the set up current level, applied pressure, particle size, pretreatment of powder and addition of alloying powders of Mo, Cr, and Al. The electric resistance at the same period becomes smaller when the set up current level, pressure and particle size become larger and also the oxygen content of the powder lowers. Addition of Mo or Cr powder to Ti powder decreases the electric resistance during sintering but addition of Al powder increases it.View full abstractDownload PDF (290K) -
Teruhisa Watanabe, Teruo Shimizu, Hiroyuki Endo1978 Volume 25 Issue 6 Pages 202-206
Published: September 25, 1978
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSSintered bronze bearing specimens having various permeabilities within the range of 0.6-60 × 10-3 darcys were prepared for measurements of the sliding noise using a resting apparatus which was designed by us. The specimens were made from atomized bronze alloy powders having three kinds of particle size of 200/250, 250/350, 350/400 mesh by controlling the intercommunicating porosity of bearing specimens in 6, 9, 12, 15, 18 and 21 vol% during compacting, sintering and sizing processes.
The results obtained were as follows;
With the decrease of permeability from about 60 × 10-3 darcys, the sliding noise also decreased gradually and came to a minimum level at a certain value of permeability, which was about 2 × 10-3 darcys in this study. However, when the specimens having smaller values of permeability than the certain value were driven. the sliding noise rather showed a tendency of increase with decreasing permeability.
And on causalities in the above results, they were able to be explained by considering the effects of permeability upon the mechanism of self-lubrication of Sintered porous bearings.View full abstractDownload PDF (1839K) -
Fumihiro Ueda, Hidekazu Doi, Yoshio Fujiwara, Hiroaki Masatomi1978 Volume 25 Issue 6 Pages 207-212
Published: September 25, 1978
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSIn order to elucidate the effect of strain rate on high temperature deformation and fracture properties of cemented carbides, bend tests were carried out at 1000°C on WC-(6-20)%O Co alloys with several WC particle-sizes; the strain rates were varied by from 3 × 10-4 to 10-1/min. The results obtained are as follows:
(1) With the decrease of strain rate, the transverse rupture strength (T.R.S.) in general decreases whereas the fracture strain increases. (2) The drop of T.R.S. and the increase of fracture strain mentioned in (1) become more pronounced with decreasing WC particle-size and/or Co content. (3) At high strain rates (≥10-1/min), T.R.S. becomes a function of the contiguity of carbide particles; T.R.S. generally increases with increasing the contiguity. (4) The drop of T.R.S. with decreasing strain rate is inversely propational to the logarithm of mean free path of Co phase.
The mechanisms of the deformation and fracture of the alloy at 1000°C were discussed.View full abstractDownload PDF (3020K) -
1978 Volume 25 Issue 6 Pages e1
Published: 1978
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSDownload PDF (12K)
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