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Volume 27, Issue 7
Displaying 1-6 of 6 articles from this issue
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Hidenori Kuroki1980 Volume 27 Issue 7 Pages 213-218
Published: September 25, 1980
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSRadial and axial spring-backs of electrolytic iron powder compacts (φ10 ×h 10 mm) were determined. After the dewaxing at 600°Cfor 30 min and the sintering at 1100°C for 60 min in cracked-ammonia, the dimensional change of the compacts were measured.
The spring-back of the compacts containing zinc stearate increased with the pressure in both directions. The axial spring-back increased with the content of zinc stearate.
The dimensional change in the axial direction by sintering was a shrinkage which appeared to com-pensate a part of the porosity formed by the spring-back. While it was a dilation in the radial direction.
In the axial direction, there exists an obvious relationship between the spring-back and the dimensional change by sintering. But not in the radial directionView full abstractDownload PDF (449K) -
Mitsuo Takahashi, Haruki Sato, Yoshio Kawasumi1980 Volume 27 Issue 7 Pages 219-222
Published: September 25, 1980
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSA new process for the production of copper-coated MoS2 powder is developed through numbers of technical researches for the coated powder production that would be available as raw materials in the powder-metallurgy. The process mainly consists of making activated surface on fine MoS2 powder and plating copper on it by substitution.
The sintered bronze bearing which contains a small quantity of this copper-coated MoS2 powder improves a considerable frictional performance. Strength of sintered bronze bearing added this copper-coated MoS2 powder by 10% is fully enough. This new type of sintered bronze bearing which contains copper-coated MoS2 powder (50% Cu) by 5% can be commercially produced.View full abstractDownload PDF (2739K) -
Kiyoaki Akechi, Zenshiro Hara1980 Volume 27 Issue 7 Pages 223-228
Published: September 25, 1980
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSMixtures of titanium powder and alumina or carbide (SiC, TiC or WC) powder were resistance-sintered. Up to 2vol% alumina, 10vol% SiC, 20vol% TiC and 20vol% WC, sound compacts were obtained, and with increase of volume fraction of alumina or carbide, the elongation decreased and the hardness and the electrical resistance of specimens increased. When the volume fraction was 1 vol% alumina or 2 vol% carbides, the maximum tensile strength (alumina 102 kg/mm2, carbides 83-86 kg/mm2) was obtained. Influence of volume fraction of added particles on the various properties was discussed in relation to dispersion behavior of added particles and a reaction between titanium and alumina or carbide.View full abstractDownload PDF (5002K) -
Hisashi Suzuki, Koji Hayashi, Wan Jae Lee1980 Volume 27 Issue 7 Pages 229-233
Published: September 25, 1980
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe activation energy in bending creep up to 2 hr in WC-Co alloy was investigated at 900-1000°C as a function of cobalt and carbon contents, triple carbide contents, carbide grain size and domain size of binder phase.
It was found that the activation energy increased with decreasing cobalt content and increasing amount of additional triple carbide, and it was almost in no relation to the other factors such as carbon content, carbide grain size, etc. It was suggested that the creep deformation of cemented carbides was generally controlled by an atomic diffusion at carbide-carbide interfaces as well as the diffusion in binder phase.View full abstractDownload PDF (342K) -
Sachio Oki, Kusuhiko Sakagami, Toshihiko Akiyama, Keiichiro Shoji1980 Volume 27 Issue 7 Pages 234-239
Published: September 25, 1980
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSUsing three kinds of Cr containing powders, vacuum sintered Cr-steel specimens of different porosity were prepared. The transformation behavior and hardenability of these specimens were investigated by means of dilatometric method. The results obtained are as follows:
1) The difference of porosity had no effect on the feature of CCT diagram and the critical cooling rate.
2) Different features of CCT diagram were mainly due to the Cr distribution caused by the use of different Cr containing powders.
3) From the relation between critical cooling rate and ideal critical diameter after Grossmann, it was concluded that the hardenability of sintered steels was not inferior to that of wrought steels in the experimental conditions of present investigation.View full abstractDownload PDF (1765K) -
Shuji Wanikawa, Tohru Takeda1980 Volume 27 Issue 7 Pages 240-246
Published: September 25, 1980
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSIn order to improve mechanical properties of sinter-forged Cr bearing low alloy steel, effects of primary sintering of preforms and secondary sintering after forging on mechanical properties were examined for spherical powder having the porous surface layer (CP) and conventional P/M steel powder of under 100 mesh size (FP). Results were summarized as follow:
1) Oxygen contents of CP and FP preforms were 50-60 and 100110 ppm respectively at the primary sintering temperature of 1250°C for 60 min.
2) At the forging temperature of 1100°C, the densities of both CP and FP sinter-forged steels were saturated at the forging pressure of 9 t/cm2.
3) The impact strength of CP sinter-forged steels was influenced by the mean free path of small pores, as well as oxygen content.
4) The secondary sintering plays an important role for increasing the impact strength of both CP and FP sinter-forged steels. With increasing sintering temperature, residual pores became spherical and impact strength increased. The impact strength of the sinter-forged steels sintered under the secondary sintering conditions (for example at 1250°C for over 30 min) was located in the range of 13.5-15 kg-m/cm2. while those of CP and FP sinter-forged steels (without the secondary sintering) were 8-9 and 8.5-9.5 kg-m/cm2 respectively.
5) Tensile strength and hardness of both CP and FP sinter-forged steels were not influenced by the sintering conditions.View full abstractDownload PDF (4720K)
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