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Volume 26, Issue 8
Displaying 1-6 of 6 articles from this issue
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Junjiro Takekawa, Yoshimichi Masuda1979 Volume 26 Issue 8 Pages 277-282
Published: November 26, 1979
Released on J-STAGE: July 12, 2010
JOURNAL FREE ACCESSThe triaxial compaction tests were made on a spherical atomized copper powder and an angular alpha alumina powder, which are both very hard to be formed by means of the conventional die or isostatic compactions. The shearing effect of the stress difference in this method on the forming and compacting of these powders was studied on the basis of the experimental results of the densification and the particle morphology on these compacts. The results obtained are as follows:
1) On the atomized copper powder, the shearing effectively exercised to induce plastic deformation and frictional welding of the particles and considerably lowered the compressive stress for the forming as compared with those in the conventional methods.
2) The effect on the forming of the alpha alumina powder was only to facilitate rearrangement and interlocking of the particles. For the forming of this sort of powder consisting of the particles with poor plastic deformability, the triaxial compaction was less advantageous.View full abstractDownload PDF (4999K) -
Masaru Yokota, Akira Hara, Mototsugu Ohata, Hiroyasu Mitani1979 Volume 26 Issue 8 Pages 283-288
Published: November 26, 1979
Released on J-STAGE: July 12, 2010
JOURNAL FREE ACCESSA more developed differential equation of penetration of liquids into porous bodies has been derived, and the solution has been obtained on some reasonable assumptions for simplification. The validity of the solution was also discussed by comparing with the experimental results:
The rigid solution of penetration of liquids into porous bodies was given as
t=η⋅T2⋅h∞/Cs⋅P⋅Rp2⋅p⋅g∞σn=2 1/n(h/h∞)n,
and when n=2, the approximate solution was
h=2/T(Cs⋅p⋅γ⋅cosθ∞/η⋅Rp)1/2⋅t1/2,
where h and t; height of liquid penetrated at time t, η, γ and ρ; viscosity, surface tension and density of liquid, respectively, Rp; hydraulic radius, T; tortuosity, Cs; shape factor ofvoids, p; porosity, θ∞; equilibrium contact angle of liquid against solid, h∞; equals to 2⋅γ⋅cosθ∞/Rp⋅ρ⋅g.
From the comparison of theoretical considerations with experimental results it was confirmed that the first rigid solution might be available to the entire range of penetration of liquids into porous bodies and the second approximate solution was only available to the early stage of the penetration process.View full abstractDownload PDF (3008K) -
Shuji Wanikawa, Tohru Takeda1979 Volume 26 Issue 8 Pages 289-293
Published: November 26, 1979
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSIn order to improve compressibility and compactibility of Cr bearing low alloy steel powder, spherical powder with controlled amount of surface oxide layer were prepared by water atomization and reduced in hydrogen atmosphere so as to make the surface of particles porous. Influence of preparing conditions on properties of powder were examined. Results were summarized as follows.
1) For obtaining a good compressibility and compactibility, effective oxygen contents of as-atomized powder were of 1-3 wt %.
2) To make the surface of spherical particle porous and controll rattler's value below 3%, maximum reducing temperature of 0.5, 1 and 2% Cr steel powders under the constant time of 60 min was of 900, 950 and 1050°C respectively.
3) Oxygen contents of reduced powder were 0.12-0.25 wt % when the reduction temperature is higher than 800°C.
4) 0.5 and 2% Cr steel powder containing 20100 mesh particles of about 60% showed the green density of 7.1 and 7.0 g/cm3 respectively, when pressed at 5 ton/cm2.View full abstractDownload PDF (1325K) -
Hisashi Suzuki, Koji Hayashi, Wan Jae Lee, Yutaka Kubo1979 Volume 26 Issue 8 Pages 294-298
Published: November 26, 1979
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe effect of tantalum carbide or titanium carbide addition on the short-time creep-rupture strength of WC-Co alloy was studied at 700-900°C in relation to the carbon content, carbide grain size and the domain (or grain) size of binder phase of the alloy.
The results are as follows. At temperatures above about 800°C, the creep-rupture strength of tantalum carbide and/or titanium carbide contained alloys increased with increasing amount of those carbides. The observed increase in the creep-rupture strength of tantalum carbide contained alloy was found to be mainly due to the increased domain size, and that of titanium carbide contained alloy, due to the effect of increased strength of carbide skelton in addition to the increased domain size.View full abstractDownload PDF (1949K) -
Masasuke Takata, Keiichi Katayama, Satoshi Ishihara, Hiroaki Yanagida1979 Volume 26 Issue 8 Pages 299-303
Published: November 26, 1979
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSThe effects of simultaneous addition of Al2O3 and Li2O upon the sensor properties of porous zinc oxide sintered bodies have been investigated by resistivity measurements with various surrounding gas atmosphere and scanning electron microscopic observation. The microstructure having large surface area and the appropriate high resistivity obtained by simultaneous addition of Al2O3 and Li2O showed high sensitivity for inflammable gases at high temperatures 350-500°C and for humidity at low temperatures 25-150°C.View full abstractDownload PDF (2401K) -
Tadahiko Watanabe, Kenji Ishibai1979 Volume 26 Issue 8 Pages 304-309
Published: November 26, 1979
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSThis paper describes the effect of binder on properties of TiB2 based cermets. The used binders are Ni4B3, Co-Cr-B alloy, WB, Mo, NbB, Tall, NiB, CrB, CoB, AlB2, TaB2, AlB2-Ni·P, TaB2-Ni·P, CrB2-Ni·P, ZrB2-Ni·P W-Ni·P, and Mo-Ni·P. The results are as follows:
1) Ni4B3 and NiB are good binders for TiB2 based cermets. Binding phase of TiB2-NiB sintered compact contains NiB, Ni4B3 and unknown phase. This Ni4B3 may combine with TiB2 particle.
2) TiB2-10%CrB2-1%Ni·P sintered compact has the bending strength of 40-56kg/mm2 and is almost free of pores. It is likely that Ni·P acts an important parts of good sintering.
3) TiB2-10%CoB and TiB2-5%Mo-1%Ni·P sintered compact has the bending strength of 50-60kg/mm2.View full abstractDownload PDF (4013K)
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