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Volume 25, Issue 2
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[in Japanese]1978 Volume 25 Issue 2 Pages 35-43
Published: March 25, 1978
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSDownload PDF (5613K) -
Tadahiko Watanabe, Katsushige Nakazono1978 Volume 25 Issue 2 Pages 44-48
Published: March 25, 1978
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSThis paper describes the thermal-distribution of TiB2-Ni-P sample by sintering with a direct electric current used various graphite mould and hollow graphite disk.
1) By examining the influence of the clearance between graphite die body and punch, the specific resistance, and the thickness of die body on the thermal-distribution of sample, the mechanism how electric current passed through graphite die body and sample was studied. It was known as the result that the clearance resistance exerts a most influence on the electric current flow or on the thermal-distribution of sample.
2) By using the graphite die and the clearance of 0.01-0.03 mm, the thermal-distribution of sample was kept uniformly in the vacuum, but was not uniform in the air.
3) By inserting the hollow graphite disks between sample and punchs, the sample temperature was kept to be uniform even in the air. Because the electric current was dispersed from the center to radial direction of the disks.View full abstractDownload PDF (351K) -
Kazuhiko Majima, Hiroyasu Mitani1978 Volume 25 Issue 2 Pages 49-54
Published: March 25, 1978
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSTo conclude our studies for the sintering in mixed powder compacts of Fe-Cu-C ternary system, the authors investigated the mechanical properties of Fe-(0- 10)%Cu-(0-1.0)%C ternary sintered compacts in relation to the addition of copper and graphite.
The results obtained were summarized as follows:
(1) The dividing ridge connecting the maximum points of hardness makes a line between the point of 4.0%Cu without graphite which corresponds to Fe-Cu binary eutectoid, and the point of 6.0%Cu with 1.0%C corresponding to Fe-Cu-C ternary eutectoid. The dividing ridge of tensile strength, however, is nearly perpendicular to the axis of copper content and passes the point of 4.0%Cu independent of graphite addition. On the other hand, the elongation becomes lower with increasing copper and graphite contents; the elongation of Fe-Cu-1.0%C ternary sintered compacts containing more than 6.5% Cu is less than 1.0%.
In order to produce a good quality of sintered copper steel, the proper compositions of copper and graphite are considered to be 0.51.0%C and 26.0%Cu, respectively.
(2) For the specimen of Fe-4.0% Cu-C ternary sintered compacts containing up to 1.0% C, a similar improvement of mechanical properties to the wrought copper steel was made due to the precipitation of e phase which occurs during annealing between 400'-500'C after being waterquenched from 910°C ×15 min.View full abstractDownload PDF (2456K) -
Masaru Kobayashi, Atsuya Kamada, Ryoji Iwamura, Tadao Hayasaka1978 Volume 25 Issue 2 Pages 55-61
Published: March 25, 1978
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe mechanical properties of sintered steel are improved by the combination of surface densification which is brought about by surface-working (extruding or rolling), and full annealing. The summarized results are as follows.
(1) In the case of extruding, the most effective reduction in area to improve the mechanical properties of sintered steel is about 11%.
(2) In the case of rolling, the mechanical properties of sintered steel are improved in the condition of smaller one pass reduction and larger amount of total reduction using the rolls of smaller diameter. The flexure strength increases from 75 to 125 kg/mm2, the limit of flexure increases from 0.7 to 1.5 mm and the fatigue strength increases from 12 to 17 kg/mm2, in the condition of 7.5 mm roll diameter, 0.02 mm one pass reduction and 0.2 mm total reduction, which was the best condition in the experiment.
(3) The improvement of mechanical properties of sintered steel in bending stress field may be due to the reasons that a proper density distribution is given by the cold surface-working (the density is almost theoretical at the surface layer and smaller inside) and that the flattened holes are spheroidized by the full annealing.View full abstractDownload PDF (4499K) -
Observations an Peculiar Structures Appearing around Fracture Source in WC-Co Base Cemented CarbidesHisashi Suzuki, Koji Hayashi, Teruyoshi Tanase, Fumio Nakayama1978 Volume 25 Issue 2 Pages 62-65
Published: March 25, 1978
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSPeculiar fracture sources and related surface structures formed around fracture sources in WC-Co, WC-TiC(TaC)-Co and WC-VC-Co alloys were examined by scanning electron micrography.
It was found that: (1) In a WC-Co alloy, a flat region or a stepped region appearing around the carbide defects with the size less than about 8, um, would closely be related to the domain (or grain) bounda-ry of binder phase. The stepped region formed in high cobalt alloys seems to lower the strength of the alloy. (2) In a WC-TiC(TaC)-Co alloy, a stepped defect formed by the addition of a small amount of TiC(TaC) is found to be a sort of pore with irregular shape. (3) In an ultra fine grained WC-VC-Co alloy, a peculiar source would be a region having densely distributed micropores.View full abstractDownload PDF (3681K) -
Hisashi Suzuki, Teruyoshi Tanase, Fumio Nakayama, Koji Hayashi1978 Volume 25 Issue 2 Pages 66-68
Published: March 25, 1978
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe transverse-rupture strength (am) of conventional WC-(10, 20)%Co alloys was examined in the temperature range from room temperature to -196°C in comparison with WC-(10, 20)%Ni alloys ac-cording to the Japanese Industrial Standard (JIS). The strength was analyzed in relation to the structural defects acting as a fracture source.
In each type of the alloys, the sort, dimension and location of the defects as a fracture source were not changed, but the values of ao and p (ao, strength of the sound alloy around the defect; ρ. usual meaning in brittle fracture) increased and decreased, with decreasing temperature respectively. In WC-Co alloys, however, the temperature dependence of these values was remarkable. For instance, the value of ao was higher at each temperature when the binder content was kept constant. The value of ?? m of each type of alloys changed with test temperatures in the same way as that of σo.View full abstractDownload PDF (211K)
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