巻号一覧
22 巻, 5 号
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Yoshiki Oshida1975 年 22 巻 5 号 p. 147-153
発行日: 1975/08/25
公開日: 2009/05/22
ジャーナル フリーIn the present investigations an application of the superplastic phenomena to the sintering of pure iron and cast iron powder has been demonstrated.
In the characteristic contraction-cycle number curves there exists the typical break point for both the powders; i.e. the curve is becoming to be saturated within a zone before that point is reached and the curve finally goes on the linear relationship after the point. The present author would call the former zone to be a sintering zone and the latter a condensing zone., Incidentally the superplastic behavior of the latter has been recognized to be resemble to that of the fused materials.
From the experimental fact that the tensile tests of products sintered within only five minutes have shown the same or higher strength than that of fused materials, it could be suggested that the present application might be able to shorten the sintering period in the conventional process.抄録全体を表示PDF形式でダウンロード (1353K) -
鴻野 雄一郎, 大矢根 守哉1975 年 22 巻 5 号 p. 154-159
発行日: 1975/08/25
公開日: 2009/12/04
ジャーナル フリーIn order to make sure the optimum density of the preform, which was prepared from electrolytic copper powder, the quantity of the closed pores, the impact strength and the required pressure for forging of the preform were examined.
The quantity of the closed pores in the preform was constant up to the relative density of 0.85 and began to increase rapidly at 0.85. Above 0.85, almost all of the pores became closed ones. The impact strength of the preform increased with increasing density but decreased rapidly at the density of 0.83 and beyond 0.85 increased again.
The required pressure for forging of the preform was calculated using the basic equations for plastic deformation of porous metals which were proposed by the authors previously. The calculated results showed that the lower the density of the preform, the higher the final forging pressure.
As a result, it was concluded that the optimum value of the density of the preform used in this work was about 0.8. And, in general, this optimum density may exist in the preform prepared from other metallic powders than electrolytic copper ones.抄録全体を表示PDF形式でダウンロード (1751K) -
鈴木 寿, 林 宏爾, 山本 勉1975 年 22 巻 5 号 p. 160-166
発行日: 1975/08/25
公開日: 2010/07/12
ジャーナル フリーThe impact strength of WC-Co cemented carbide was studied in relation to the microstructural defects acting as a fracture source. The WC-10%Co and WC-20%Co two-phase alloys having mean grain size of about 1.7μ, were vacuum-sintered and ground with diamond wheel for obtaining the specimen without notch (the dimension; about 4×4×48 mm). The impact strength test was done at room temperature using a Charpytype impact machine (capacity; 0.4 kg⋅m, span; 40 mm). The impact strength, impact-transverse-rupture strength, stress-strain curve in impact test, and the dimension and location of the defect appearing on the ruptured surface were measured. The correlations between these values were examined, comparing with the result (in static-transverse-rupture test) previously reported.
The results obtained were as follows: 1) Such defects as residual micropores or coarse WC grains were found to act as a source of impact fracture, in the same way as they were in static-rupture test. However, the true impact strength (It) didn't directly correlate to the dimension of defects (2a). 2) Then, a close correlation was found between It and σIm (impact-transverse-rupture strength), and also between σIm⋅f and √a: therefore, It can be expressed by the following equation.
It-1/2⋅f-1=(l/18E)-1σIo-1+2{(l/18E)-1σIo-1ρI-1/2}×√a
(where f; a function of the location of the defect, l; span, E; Young modulus of the alloy; σI0, the impact-trans-verse-rupture strength of the matrix around the defects, ρI; the effective crack radius of the defects). Thus, it was made clear that It was directly controlled by the dimension and location of the defects, the same as in the static-transverse-rupture strength. 3) By decreasing the 2a value down to about mean grain size, the It value of cemented carbide would sharply increase in particular in the alloy with comparatively low Co contents, because the defect size is apt to increase as the cobalt content decreases.抄録全体を表示PDF形式でダウンロード (4058K) -
鈴木 寿, 林 宏爾, 寺田 修1975 年 22 巻 5 号 p. 167-172
発行日: 1975/08/25
公開日: 2009/05/22
ジャーナル フリーIt has been previously reported by the present authors that the transverse-rupture strength of WC-Co cemented carbide could clearly be explained based on the analysis of the structural defects retained in the alloy, because the strength is usually controlled by the defects. The present work is related to the same subject as above for titanium carbide base cermets. The TiC-(10-30)%Mo-(20-40)%Ni and p(5-70%WC)-(15-20)%Ni alloys with mean grain size of about (1.2-2.6)μ and 2.5μ, respectively, were vacuum-sintered and used as specimens.
The results obtained were as follows: 1) It was confirmed that the strength of these alloys was also directly controlled by the dimension and location of the defects (residual micropore and coarse carbide grain). 2) In each alloy, the calculated external stress (σd) which operated at the defects when the fracture was initiated" correlated so strongly to the dimension of defects (2a), that the linear relation was found between σd-1 and √a. However, the strength (σO) of the matrix (free from defects) obtained in each alloy from the extrapolated value of the straight line to the vertical axis, was found in the range from about 230 to 290 kg/mm2 (according to JIS), which was very much lower than the value of about 800 kg/mm2 in conventional WC-10%Co alloy. 3) Thus, it was made clear that the transverse-rupture strength of the present titanium carbide base cermets would not exceed the value of about 250 kg/mm2 at room temperature, even though the strength increases as the defect size decreases. Discussion as to the lower value of σO in the cermet has been given.抄録全体を表示PDF形式でダウンロード (3314K) -
山口 修, 大牧 七郎, 竹岡 清, 清水 澄1975 年 22 巻 5 号 p. 173-175
発行日: 1975/08/25
公開日: 2009/05/22
ジャーナル フリーOsamu Yamaguchi, Hichirô Ômaki, Kiyoshi Takeoka, Kiyoshi Shimizu: Thermal and Mechanical Properties of Titanium Dioxide (TiO2) Prepared by Alkoxy-Method.
Brookite, the metastable titanium dioxide under ordinary pressure, was produced by heating amorphous TiO2 prepared from the alkoxide in the temperature range from 300°C to 500°C. This amorphous TiO2 was converted into ruffle through brookite by grinding.抄録全体を表示PDF形式でダウンロード (1252K)
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