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Volume 21, Issue 4
Displaying 1-4 of 4 articles from this issue
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Shiro Kohara, Kiyohiko Tatsuzawa1974 Volume 21 Issue 4 Pages 91-97
Published: August 25, 1974
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSThe influence of powder types on the properties of sintered bodies was investigated on iron powders. Four types of iron powders, i.e., reduced-, atomized-, electrolytic-, and carbonyl iron powder, were used.
The relationship between mechanical properties and the porosity was obtained. In the high density region, the observed data fit the exponential relation expressed by the form,
S=S 0exp(-bP)
where S is the tensile strength (or hardness), S 0, that of bulk material, P, the porosity, and b, an empirical constant. In the low density region, however, the observed data did not fit the exponential relation, but increased abruptly as it was calculated by Knudsen. The appreciable difference of the strength among the powder types was observed in the whole region. The value of b in the above expression determined in this experiment, regarding as it is independent of temperature, ranged from 3.7 to 4.5. The effect of the grain size on the tensile strength of sintered body was also studied for the carbonyl iron powder. An equation representing the tensile strength of sintered carbonyl iron powder was determined as follows,
S=27.0G-12exp(-3.7P)[kg/mm2]
where S is the tensile strength in kg/mm2, G, the grain size in mm, and P, the porosity.View full abstractDownload PDF (1847K) -
Yuji Muramatsu, Kiyoshi Tamura1974 Volume 21 Issue 4 Pages 98-102
Published: August 25, 1974
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSIn order to produce titanium sheets by the powder rolling method, the various factors for the production of the sheet were examined. Some mechanical and corrosion properties of the sheet were also examined.
The results obtained are summarized as follows:
(1) For a given roll diameter (300 mm), a satisfying green sheet was obtained under the rolling conditions: that is roll gap of 0-0.1 mm, and roll speed of 6 r.p.m..
(2) The densification of the green sheet was small during sintering except initial stage of sintering. The density of the sheets sintered at 1300°C for 60 min was the order of 4.0 g/cm3, which corresponds to 88% of the theoretical density. Therefore, these sheets were porous and brittle.
(3) The oxygen content of the sintered sheet was in the range of 0.1%-0.13%. This content was not influenced by the experimental sintering temperatures, times and atmospheres.
(4) The density of sintered sheet increased markedly with cold-reduction, and after 50% reduction of thickness it reached the theoretical density.
(5) The mechanical and corrosion properties of the sheet depend on final annealing variables, especially annealing temperature. These properties comparable to the wrought titanium were obtained when the sheet was annealed at a temperature over 1000°C.View full abstractDownload PDF (2672K) -
Michio Watanabe, Yoji Awano, Atsushi Danno, Seiji Onoda, Takashi Kimur ...1974 Volume 21 Issue 4 Pages 103-107
Published: August 25, 1974
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSIn order to clarify deformation and densification behaviors of porous preforms in sinterforging, effects of preform density, forging temperature and forging pressure on the cracking and densification were investigated, using Fe-0.5C powder preforms.
In hot upsetting between two flat dies, there was no significant difference in deformation behavior between powder preforms and wrought steel billets, except that the former showed the tendency to crack at lower strain. Mean density of the sinterforged specimens increased with increasing preform density and forging temperature. Density distribution in the sinterforged specimen was quantitatively obtained by means of X-ray photoanalysis. In case of hot upsetting, the densification of the specimen proceeded from the core where punch pressure was high and also lateral' material flow was large. Density distribution was made to be more homogeneous by reducing the cooling effect of the die. In hot repressing, it was observed that the densification proceeded from the upper part of the specimen.View full abstractDownload PDF (1476K) -
Hisashi Suzuki, Kozi Hayashi, Yamamoto Yamamoto, Kazuo Miyake1974 Volume 21 Issue 4 Pages 108-111
Published: August 25, 1974
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSStrengthening phenomena of hot-isostatic alloy pressed WC-10%Co alloy (H.I.P. alloy) were investigated mainly by means of direct observation of the defect structures (appearing in the so-called white spot on fracture-surface), which are thought to have acted as the origin of fracture, and by comparing with the results of normally vacuum-sintered alloy (N.S. alloy). Results obtained were as follows:
(1) Slight changes in the mean grain size of WC, the composition and distribution of the binder phase, etc., were observed in H.I.P. alloy. But these changes were considered to have no relation to the strength-increase in H.I.P. alloy.
(2) It was made clear that the strengthening mechanism of H.I.P. alloy was directly related to the disappearance of a small number of large pores (which usually exist in N.S. alloy). However, it was shown here that a sharp increase in strength was not always visualized due to H.I.P., because it was usual that some large WC grains were contained in the structure.
(3) The strength level which would be obtained in H.I.P. alloy was suggested to be comparable to the level obtainable in N.S. alloy.View full abstractDownload PDF (3189K)
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