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Volume 23, Issue 5
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[in Japanese]1976 Volume 23 Issue 5 Pages 157-162
Published: August 05, 1976
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSDownload PDF (2862K) -
Hisashi Suzuki, Teruyoshi Tanase, Fumio Nakayama1976 Volume 23 Issue 5 Pages 163-166
Published: August 05, 1976
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSIt is well known that the strength of WC-Co low carbon cemented carbide decreases with precipitation of Co3W, when the alloy is annealed at about 800°C. The present study was undertaken to reveal the reason of the strength decrease, in relation to the structural defects which would act as a fracture source. The WC-10 and 20% Co low carbon two-phase alloys (mean grain size of carbide, about 1.2 μ) were annealed at 800°C for up to 15 hr, and used as specimens. After the transverserupture test had been performed according to the Japanese Industrial Standard, measurements of the sort, dimension and location of the defects were made on the fracture surface.
Results obtained were as follows. (1) It was shown that the sort, dimension distribution and average dimension of the defects as a fracture source didn't vary by the precipitation treatment, that is, neither the development of new defects nor the growth of the pre-xisting defects took place. (2) The strength of the sound matrix (σ0) decreased by the treatment. Thus, it became clear that the strength decrease was resulted from the decrease of σ0 only. (3) However, further investigation is needed to make clear the machanism of the decrease of σ0.View full abstractDownload PDF (1724K) -
Hidenori Kuroki, Yoshiaki Senga1976 Volume 23 Issue 5 Pages 167-171
Published: August 05, 1976
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSThe purpose of the present study is to derive an equation which gives the specific work for fracture in tension of sintered iron. Electrolytic iron powder was pressed into compacts with the density range of 5.8-7.5 g/cm3, and sintered at 1200°C for 1 hr in hydrogen.
The volume increased in the amount of 4-5% before fracture, but was regarded as constant for the following calculation. True stress-true strain curves were approximated by an equation, a=A⋅εn, where n was 0.33. This value of n was independent of as-sintered density and considered to be equal to that of cast materials with the same matrix.
Based on the above conditions, the specific work for fracture, Wfr, of sintered iron was given by the following equation,
Wfτ=σnfr⋅(1+efr)⋅1n(1+efr)⋅(n+1)-1.
Where arfr was ultimate tensile strength and efr was elongation.
The following relation between the charpy shelf value I.V. and Wfr was proposed;
I.V.∝Wfr⋅x.
Where, x was the width of the deformed zone adjacent to the fracture surface. This value was supposed to become greater with the increase of the work hardening exponent n and to be independent of the as-sintered density.View full abstractDownload PDF (396K) -
Masanori Yoshikawa, Takashi Sasaki, Toshio Asaeda1976 Volume 23 Issue 5 Pages 172-177
Published: August 05, 1976
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe purpose of this study is to investigate the production process of carbon fiber/alumina composite materials and to examine the properties of the materials.
The composites can be produced by hot-pressing mixtures of fibers and powders. During hotpressing, fibers are cut if the modulus of elasticity of fibers is high, compaction pressure is high and hot-pressing temperature is low. The composites indicate lower bending strengths than those of sintered alumina, but have better thermal shock resistances. The composite containing 18% fibers has the best thermal shock resistance in this study. The mechanical and physical properties of composites are; the density ratio is 96.2%, bending strength 17.4 kg/mm2, coefficient of thermal expansion 15×10-6, thermal conductivity 0.097J/cm·sec·°C and electrical resistivity 50 ohm-cm.View full abstractDownload PDF (3037K) -
Tadaaki Sugita, Miyoshi Tanaka1976 Volume 23 Issue 5 Pages 178-183
Published: August 05, 1976
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe machining performances of three types of cutting tools in light machining of the sintered iron compacts, which are sintered alumina containing titanium carbide, cemented carbide and cermet, have been discussed in this short note. Also, the performance of each tool was evaluated in the continuous cutting condition by turning and in the intermittent cutting condition by face milling. Consequently, the experimental results have indicated that the sintered alumina containing titanium carbide was superior to the other tools from the viewpoint of tool life.View full abstractDownload PDF (2412K)
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