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Volume 16, Issue 8
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[in Japanese], [in Japanese]1970 Volume 16 Issue 8 Pages 329-337
Published: April 25, 1970
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSDownload PDF (582K) -
Kaoru Kase, Hiroshi Itô, Yasuo Mihashi1970 Volume 16 Issue 8 Pages 338-344
Published: April 25, 1970
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe formation of powders in an electric discharge with heavy current through a metallic wire in the atmosphere was studied, and the characteristics of the resulting powder were examined.
The results obtained were as follows.
(1) The powders obtained at the optimum conditions had a wide particle size distribution. Coarse particles were spherical similar to atomized ones.
(2) With increasing discharging voltage, particles of molybdenum powder became fine. As for tungsten, the above mentioned tendency was not confirmed with X-ray diffraction line breadth alone.
(3) In the atmosphere, metallic powder was collected mainly in an acryl case, and the particle size had a wide distribution.
However, in a vacuum cleaner, the ultra fine oxide powder (aerosol) was mainly collected.
(4) The alloy powder was formed easily from alloy wire by wire-explosion method.
(5) As for molybdenum, with increasing discharging voltage, the latice spacing increased.View full abstractDownload PDF (3954K) -
Mikio Yokohama, Takeshi Sadahiro1970 Volume 16 Issue 8 Pages 345-350
Published: April 25, 1970
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSIn order to evaluate the thonghness of cemented carbides, the influence of surface finishing on crack length at vickers indetations was studied.
The results are as follows.
(1) Grinding introduces deformed surface layer. The heavier the grinding, the shorter the crack length. The increase in crack length resulting from polishing is caused by the removal of the surface layer produced in grinding.
(2) Annealing at temperatures about 800°C removes the damage produced in grinding and polishing. Crack length in a given alloy reaches a maximum if the specimens are annealed after polishing.
(3) This maximum crack length should be used in evaluating parameters for the crack resistance of an alloy.
The crack resistance, which is independent of the indentation load and of the hardness of the alloy serves to evaluate the toughness of cemented carbides.View full abstractDownload PDF (1616K) -
Teiko Obuchi, Teruhisa Watanabe1970 Volume 16 Issue 8 Pages 351-355
Published: April 25, 1970
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSThis report covers the discussions on the relations between the movement of liquid metal infiltrating into the sintered iron skeleton and the several factors which rule the movement of the liquid. The results are as follows :
1) A general equation on the hydrodynamics of the liquid infiltrating, into the skeleton was obtained:
where,
V=21/4⋅S⋅Φ1/4⋅Pr3/4⋅(γL⋅cosθ/ηL)1/2⋅t1/2
V : volume of the liquid (cm3)
S : area of the infiltrated surface (cm2)
Φ : permeability of the skeleton (cm2)
Pr : porosity of the skeleton
γL : surface tention of the liquid (g/sec2)
θL : contact angle
ηL : viscosity of the liquid (g/cm. sec)
t : time(sec)
2) Experiments were made on the, infiltrating of liquid silver into the iron skeletons of constant dimensions, and the relations between the volume of the infiltrated liquid (V) and several factors (t, Φ, Pr, and γL⋅cosθ/ηL) in the above equation were discussed.
(a) Most exponents of t for many specimens were between 3/10-5/10, a littie smaller than 1/2 given in the above equation.
(b) The exponent of Φ were nearly 1/4, the same as that in the above equation.
(c) The exponent of Pr could not be obtained definitely because it is difficult to prepare the iron skeletons with constant Φ value. But it seems that the effect of Pr on V is quite considerable.
(d) The higher the infiltrating temperature, the better was the infiltrating ability into the skeleton. This might be explained by the increased contribution of the term(γL⋅cosθ/ηL)1/2 as effectuated by the temperature rise.View full abstractDownload PDF (340K) -
Teiko Obuchi, Teruhisa Watanabe1970 Volume 16 Issue 8 Pages 356-361
Published: April 25, 1970
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe present report is concerned with experiments on the infiltrating phenomena of silver, copper and 10%tin-bronze infiltrants into sintered iron skeletons made of three types of iron powders ; that is, (A) electrolytic iron powder made by crashing the electrolytic iron plates, (B) ore reduced iron powder made by crashing the carbon-reduced magnetite ore, (C) mill-scale reduced iron powder made by crashing the carbon-reduced mill-scale of rimmed steel. The results of the experiment can be summarized as follows :
1) In the case of silver, which shows no alloying reaction with iron :
a) With the complexity of the forms of the iron powders, the pore structures of the skeletons increases in complexity, and consequently the liquid silver decreases in infiltrativity. Infiltration can be performed by using, in the decreasing order of the degree of infiltrativity, (A), (C) and (B) powders.
b) The process of infiltrating liquid silver into the skeletons can generally be divided into the following two stages : that is, first the liquid spreads over the surface of the skeleton, and then penetrates into the skeleton. This tendency is most marked when (A) is used. However, the low compactibility of this powder is liable to cause hair cracks in the surface layer of the skeleton.
c) Adding a small amount of tin, which shows alloying reaction with both iron and silver, to the iron skeletons, fairly increases the infiltrativity of silver into the skeleton.
2) In the cases of copper and 10%tin-bronze, which show mutual alloying reaction with iron, their infiltrativity is very high. However, insufficiency in the volume of the liquid in relation to the porosity of the skeleton is liable to cause the liquid to prefer to penetrate into finer pores of the skeleton, leaving pores unpenetrated.View full abstractDownload PDF (6438K)
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