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Volume 40, Issue 12
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[in Japanese]1993 Volume 40 Issue 12 Pages 1142
Published: December 15, 1993
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSDownload PDF (72K) -
Hideya Imamura1993 Volume 40 Issue 12 Pages 1143-1148
Published: December 15, 1993
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSOne of the advantages of atomization is to be eazy for making spherical metal powders. This paper presents three examples of spherical atomized powders developed; bronze powders for sintered metal filters and dry bearings, copper-lead alloy powders for steel-backed bearings and self-fluxing alloy powders for thermal spraying.
First, the improvements on the air-and gas-atomization equipments used for the production of spherical powders are described, and then, the manufacturing process, powder characteristics in each application and the problems in the mass production of metal powders by atomization are reviewed.View full abstractDownload PDF (4544K) -
Tomio Satoh, Kunio Okimoto, Shin-ichi Nishida1993 Volume 40 Issue 12 Pages 1149-1153
Published: December 15, 1993
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSIn the centrifugal atomization method, a mass ratio of rapidly solidified prealloy powder to raw material, i.e. a yield rate is remarkably affected by various producing conditions. In order to get the high yield rate, it is very important that a wettability between the rotating disk and the molten metal is superior and that a formation of exces-sive deposited layer on the disk is prevented. The effects of rotating speed of disk and ejecting position of molten metal from the disk center on the formation morphology of the deposited layer have been investigated in the production of rapidly solidified Al-base prealloy powder. The following results are obtained. Though the formation morphology is little affected by the rotating speed of disk, it is significantly influenced by the ejecting position. Deviating the ejecting position from the disk center is effective in preventing the formation of excessive deposited layer. The authors have stably accomplished more than 80 % yield rate of Al-l OMg-0.8Zr prealloy powder using the Mo thin sheet disk.View full abstractDownload PDF (2925K) -
Kohmei Halada, Hiroo Suga, Kazumi Minagawa1993 Volume 40 Issue 12 Pages 1154-1159
Published: December 15, 1993
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSEight different alloy powders, Al-14%Si, Al-4%Si, A1-4.5%Cu, Zn-22%Al, Sn-15%Cu, Cu-50%Zn, Zn-20%Sn and Zn powder, were atomized by a centrifugal atomization to observe the solidified structure. Excepting Zn and Cu-50%Zn, powders had equiaxed dendric structures. However, the secondary dendrite arm spacings of powders were different from the calculated ones by using Ranz-Marshall's equation. Zn particle had facetted surfaces composed of {00.1} plane, which is known to be formed to the direction of solid growth. These results suggested that undercooled solidification occurred instead of isothermal solidification from the surface.View full abstractDownload PDF (3978K) -
Kohmei Halada, Kazumi Minagawa, Kennichi Chiba, Johan de Bie1993 Volume 40 Issue 12 Pages 1160-1165
Published: December 15, 1993
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSZn-22%A1 alloy was atomized by the method of gas atomization, water atomization and centrifugal atomization with various atomizing conditions; to compare the solidified microstructure of obtained powders. Centrifugally atomized powder, gas-atomized powder and water-atomized coarse spherical powder had equiaxed dendrite structure. While the secondary dendrite arm spacings depended on the size of the powder particle, they had no dependence on the kind of atomizing method nor on the conditions, i.e. atomizing temperature and cooling gas. This suggests that the depth of undercooling is more important than the heat loss into atmosphere to determine the solidified structure. Water atomized finer or irregular powder did not have clear structure. This suggests that more rapid solidification occurred in water atomization.View full abstractDownload PDF (2676K) -
Kazumi Minagawa, Kohmei Halada, Kenichi Chiba1993 Volume 40 Issue 12 Pages 1166-1169
Published: December 15, 1993
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSTwo types of probes were used to detect different kinds forces existing in the jet of a high pressure water atomizer. The straight type probe was used for detecting shear force, while notch type for concentrated force, which were created by the flow of the water jet.
There was a certain region in the water jet having higher concentrated force. In this region, peak value was attained.This region was comparable to the active zone.View full abstractDownload PDF (180K) -
Kenichi Chiba, Kazumi Minagawa, Kohmei Halada, Takeshi Nakata1993 Volume 40 Issue 12 Pages 1170-1173
Published: December 15, 1993
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSImage analyzation was applied to investigate the relation between size and shape of particles and also the effect of water pressure upon the shape of atomized powders. The particle shape was evaluated by an index called the shape factor which is a ratio between the area and the perimeter. It was found that most of the produced powder had shape factor values higher than 0.5. As the particle size increased, shape factor distribution had a tendency to broaden and the mode to decrease. Higher water pressure resulted in more irregularity, but beyond intermediate water pressure, the shape factor values only differed slightly.View full abstractDownload PDF (221K) -
Hideo Okuyama, Satoru Ohno, Kazumi Minagawa, Kohmei Halada1993 Volume 40 Issue 12 Pages 1174-1178
Published: December 15, 1993
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSA ordered mixture was prepared by a coating of Ni ultrafine particles (average diameter DAva= 80 nm) onto a Pb particle (DAVe= 50 um), and elution behaviors of molten Pb from the ordered mixture were examined by a high-temperature microscope and a scanning electron microscope during heat treatment at various heating rates (1->1500 K/min) in flowing 5%H2-Ar.
The elution of molten Pb through Ni coatings occurred just above the melting point of Pb in all heating rates. However, solidified morphology of eluated Pb changed markedly with the heating rate as follows: droplet-like (10-20 μm, 1 K/min), column-like (0.5-2 μm, 10-100 K/min), and fiber-like (10-20 nm.>1500 K/min), crystals, respectively. From these results, it is presumed that the network formed by sintering of Ni ultrafine particles exists on the surface of the Pb particle.View full abstractDownload PDF (3505K) -
Yoshiro Arami, Tadashi Koyama, Osamu Iwatsu1993 Volume 40 Issue 12 Pages 1179-1184
Published: December 15, 1993
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSAl2O3 or Y2O3-dispersion strengthened nickel powders were prepared by mechanical alloying of carbonyl nickel powder with Al- or Y-alkoxide for various time in the air atmosphere followed by heat-treating in a hydrogen atmosphere at 873K. The changes in the properties of the powder of each system with milling time were investigated. The results obtained are summarized as follows: 1) In both Ni-Al2O3 and Ni-Y2O3 systems, the sinterability of the powders obtained once became worse with the milling time in the early stages of the milling, and thereafter it became better with the milling time. 2) The change in the sinterability of the powder corresponded to that in the loss of the matrix hardness due to sintering, in which the larger the loss of the matrix hardness was, the better the sinterability became. 3) The powder in Ni-A12O3 system was superior in the sinterability to that in Ni-Y2O3 system in which the dispersoid in the matrix had more thermal stability and consequently the loss of the matrix hardness due to sintering was less than in Ni-Al2O3 system.View full abstractDownload PDF (6312K) -
Junichi Hojo, Fumio Hongo, Tatsuhiko Kuga1993 Volume 40 Issue 12 Pages 1185-1189
Published: December 15, 1993
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSMetal coatings of SiC and TiC particles were carried out by chemical plating techniques. The ceramics particles were activated with SnCl2 and PdCl2 solutions. Amorphous Ni-P alloy coat-ing was deposited from NiCl2 solution using NaH2PO2 as reducing agent. The coating amount decreased when the amount of suspended powder and the particle size were too small. Although fine.ceramics particles were agglomerated after plating, metal phase was distributed within the agglomerates. Crystalline Ni coating was deposited from NiSO4 solution by high pressure H2 reduction using an autoclave. By the H2 reduction plating, MoOx coating was also deposited from ammonium molybdate solution, and WOx coating from ammonium tungstate solution. They were converted to Mo and W coatings by H2 reduction at 1000°C and subsequently to Mo2C and WC coatings by CH2 carburization at 1000-1100°C.View full abstractDownload PDF (3590K) -
Junichi Hojo, Yasunori Ishizaka1993 Volume 40 Issue 12 Pages 1190-1193
Published: December 15, 1993
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe formations of molybdenum silicides from various reaction systems were investigated in Ar or Ar+H2 atmosphere at 1200-1400°C in order to produce fine MoSi2 powder. The direct reaction of Mo and Si powders produced MoSi2 by heating at 1300-1400°C. However, the product was hard agglomerates. The reduction of molybdenum oxide with SiC formed mainly Mo5Si3C and Mo5Si3, and the
amount of MoSi2 was small. The carbothermal reduction of molybdenum oxide and silica gave MoSi2 powder at 1400°C. The reaction was stimulated in Ar+H2 atmosphere compared with Ar atmosphere. The agglomeration of particles was weak, and the primary size was 0.5-2 μm.View full abstractDownload PDF (2991K) -
Shigeru Ito, Kazuharu Yoshida, Nobuyuki Koura, Kazuo Akashi1993 Volume 40 Issue 12 Pages 1194-1199
Published: December 15, 1993
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSIn order to nitride aluminum chips with 2 mm in size, the mixtures of aluminum chips and atomized powder of aluminum were caused to react with nitrogen. Nitriding of aluminum chips was completely accomplished at 1000°C by adding Y(NO3)3⋅6H2O to the mixture with 40% of chip content. The mixture with 50% of chip content was also completely nitrided by heating at 1300°C. Furthermore, adding Y(NO3)3⋅6H2O, Al chips without atomized powder were able to be nitrided up to 70% of conversion. The conversion of this product was increased up to 97% by nitriding again.
The atomized powders soaked up the melt of Al chip to make a lump of Al at 900°C. In general, the formation of Al lump makes nitriding difficult. However, yttrium which existed between Al grains in the lump seemed to transport nitrogen atoms. Therefore, the nitriding rate is enhanced in the initial stage to generate a large amount of reaction heat enough to evaporate Al or Al2O vapor, which causes the rapid nitriding in vapor phase.
The products contained about 0.8 wt% of oxygen. The oxygen content tends to decrease with the increase in Al chips in raw materials.View full abstractDownload PDF (1893K) -
Kenji Tanaka, Isamu Inada, Kiichi Minai1993 Volume 40 Issue 12 Pages 1200-1207
Published: December 15, 1993
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSKenji Tanaka, Isamu Inada and Kiichi Minai : Developments in Submicron Grinding of BaTiO powder by Ball Milling and its applications.
Submicron grinding of BaTiO3, powder was studied by a ball mill with small balls of 0.75mmt to 30mmφ . BaTiO3 clinker, which was obtained by calcining an equimolor mixture of TiO2 and BaCO3 was preground to 1.8 am.
Submicron grinding of the BaTiO3 powder was possible by ball milling with several mmφ balls. For a ball diameter of 2mm, the specific surface area was maximumized.
Effect of specific gravity of balls was studied by a ball mill with 2mmφ and 5mmφ balls. It was shown that submicron grinding of BaTiO3 powder was possible in short time. The higher the specific gravity of ball, the higher the effect of grinding was.
The effect of fine grinding of BaTiO3 powder and additives was investigated. Slurry prepared from the BaTiO3 powder and additives were sheeted with a doctor blade system. The microstructures of the green and sintered body were analyzed by SEM and XMA. Fine grining caused an improvement in sheet formation and subsequent sintering. An increase in grinding time resulted in a decreasing porosity of the green sheet and an increasing density of the sintered body.View full abstractDownload PDF (2444K) -
Kenichi Shimosaka, Hidehiko Kobayashi, Takashi Mitamura1993 Volume 40 Issue 12 Pages 1208-1213
Published: December 15, 1993
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSPreparation conditions and formation process of ZrC/Al2O3 composite powders from the ZrO2-Al-carbon black or ZrO2-CH4 system were examined. The ZrC/Al2O3 fine composite powders were prepared from the former system by heating the powder mixture of ZrO2:Al:C molar ratio=3:4:3 at 950°-1000°C for 1h. The formation process of the ZrC/Al2O3 Composite powders was composed of three main reactions: (i) the reduction of ZrO2 With Al and the formation of Al2O3, (ii) the formation of Al3Zr With Zr and Al, and (iii) the decomposition of Al3Zr with carbon black and the formation of ZrC. The process (i) was interfered by the process (ii). Al4C3 was not formed by the process (m). On the other hand, in case of the ZrO2-Al-CH4 system, preparation of ZrC/Al2O3 composite powder was difficult because of Al2C3 and ZrC were formed by reaction between Al3Zr and CH4. For the preparation of the ZrC/Al2O3 composite powder, it was most important to suppress the formation of Al4C3 by controlling the reactivity between Al and carbon source.View full abstractDownload PDF (1410K) -
Preparation of Z=0 Sialon (Si3N4)Chitake Yamagishi, Noboru Miyata, Junichiro Hakoshima, Keizo Tsukamoto ...1993 Volume 40 Issue 12 Pages 1214-1217
Published: December 15, 1993
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSThe reaction mechanism of Si2-ZAlzOzN8-z(Z=O, Si3N4) that was synthesized by carbothermal reduction and nitridation in SiO2-C system was investigated on basis of the results of weight change, CO content, XRD analysis and thermodynamic calculation. It was suggested that Si3N4 was formed by following reactions.
SiO2+C→SiO(g)+CO(g), SiO(g)+C+2N2→Si3N4+CO(g)……………(at low temperature)
Si02+CO(g)→SiO(g)+CO2(g), 3SiO(g)+3CO(g)+2N2→Si3N4+CO(g)…(at high temperature)
SiC was formed at temperature above 1550°C. It was suggested that the formation of SiC occurred by following reactions.
Si3N4+3SiO2→6SiO(g)+2N2, SiO(g)+2C→SiC+CO(g)View full abstractDownload PDF (271K) -
Preparation of Z=0.5-1.0 SialonChitake Yamagishi, Tatsuya Shiogai, Kazuyoshi Minamisawa, Takayoshi Is ...1993 Volume 40 Issue 12 Pages 1218-1222
Published: December 15, 1993
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSThe SiO2-Al2O3-C system with Si/Al ratios corresponding to the compositions of Z=0.5 and Z=1.0 in β-sialon, was heated in flowing nitrogen, and the processes of carbothermal reduction and nitridation were investigated. Al2O3 promoted the reaction of the carbothermal reduction and nitridation. In this system, the SiO4-tetrahedoron near the AlO4-tetrahedoron of amorphous aluminosilicate or mullite, was easily reduced and SiO(g) was formed at low temperature. Then, the unknown product with the chemical composition of Si6AlO6N5 was formed by the reaction in SiO(g)-Al2O3-C-N2(g) system. In the next stage, Si6AlO6N5 was reduced by CO and nitridated by N2(g). β-sialon was formed via these reactions. At temperature above 1550°C, β-sialon was reduced to amorphous Si3N4. Finaly, the amorphous Si3N4 was reduced and carbureted to forming SiC.View full abstractDownload PDF (1162K) -
Chitake Yamagishi, Tatsuya Shiogai, Norikazu Sashida, Keizou Tsukamoto ...1993 Volume 40 Issue 12 Pages 1223-1227
Published: December 15, 1993
Released on J-STAGE: July 12, 2010
JOURNAL FREE ACCESSThe fluidized bed furnace was designed and produced to synthesize β-SiAlON by carbothermal reduction. The parameters necessary for the design of furnace were decided by the chemical engineering calculation and the experiment. From the synthesis of β-SiAlON using the furnace, the rate of reaction could be distinguished three stages which included rate determining step by the film coefficient of mass transfer. Moreover, the rate of a synthetic reaction and the phase composition of the product were influenced the granular diameters and the Z value of raw material.View full abstractDownload PDF (228K) -
Kazumi Minagawa, Kenichi Chiba, Kohmei Halada1993 Volume 40 Issue 12 Pages 1231-1237
Published: December 15, 1993
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSRelationship between the condition of the high pressure water jet and the produced powder was investigated to understand the mechanism of fine powder production by high pressure water atomization. The water flow rate and the slit width of water nozzle were directly measured in three different initially set nozzle configurations under various water pressures (up to 80MPa). Also, the suction pressure above the conical water jet and the staticpressure difference of the jet interior were investigated.
The water flow rate and the configuration of the water nozzle increased comparably as the water pressure increased, but the suction pressure formed a peak. The shape and size of powders change up to the value of water pressure where the peak suction pressure appeared. The characterization of powders did not change considerably when atomized in the water pressure which exceed the value of Peak suction pressure.View full abstractDownload PDF (3296K) -
Eiichi Sentoku, Tsutomu Naka1993 Volume 40 Issue 12 Pages 1238-1241
Published: December 15, 1993
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSMachinable ceramics consisting of fluor-phlogpite can be machined with tight tolerance using conventional metal working equipment and tools. In recent years, it was clear that the machining surface of these ceramics is formed as a small fracture. The cutting mechanism of precise machining is related to a small fracture mechanism of ceramics. The purpose of this paper is to study the fracture mechanism of machinable ceramics. An investigation into the fracture mechanism was carried out on a newly developed fracture device.
The main results obtained are as follows: (1) The cracks for fracture grew roughly in three stages, and then a large AE signal generated. (2) A fracture model for machinable ceramics was suggested using grown-up cracks. (3) The fracture energy of per unit area was estimated to be 40 J/m2.View full abstractDownload PDF (2749K) -
Susumu Sakuragi, Takuya Sasaki, Yutaka Yamada, Mamoru Ishihara, Mamoru ...1993 Volume 40 Issue 12 Pages 1242-1245
Published: December 15, 1993
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe effects of sintering temperature on the mechanical properties of high speed steels were investigated. The test specimens were formed by injection molding techniques using SKII51 water atomized powders mixed with organic binder. After thermal debinding under vacuum condition, the specimens were sintered at the temperatures between 1518K and 1538K for 3.6ks under the reduced pressrure at 400 Pa of nitrogen gas, then quenched and double tempered at 833K for 5.4ks. The following results are obtained :
1) The density of sintered specimen is increased with the sintering temperature. The density is also saturated at 1528K.
2) Vickers hardness and transverse rupture strength are increased with the sintrering temperature, and the specimen sintered at 1528K showed the hardness of 820Hv and the strength of 3630MPa. The strength is decreased above the sintering temperature of 1533K because of the precipitation of coarse carbides at the grain boundaries.View full abstractDownload PDF (4628K) -
Tetsuo Kato, Tomio Kono, Makoto Kawamura, Yasuo Nakajima1993 Volume 40 Issue 12 Pages 1246-1252
Published: December 15, 1993
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSChange of magnetic properties in direct and alternating fields by forming and sintering condition was studied for the three alloy powders of Fe-12.5Cr, Fe-16Cr and Fe-17Cr-1Mo. The change of different tendency between the relative permeability of direct and alternating fields was observed depending on the condition of forming pressure and sintering temperature. The increase in sintered density occurs with the increase of forming pressure and the rise of sinterig temperature, and the magnetic properties in the direct magnetic field were improved with that. On the contrary, the relative permeability in alternating field indicates a change of increase and then decrease with rise of the sintering temperature. This phenomenon is dependent on the change of the electrical reistivity originated in the porosity in the material. Fe-12.5Cr alloy shows the best magnetic properties in direct and alternating magnetic fields of the three tested alloys. The suitable control of forming and sintering condition as to be 7.0-7.2 g/cm2 in sintered density is important in order to obtain the high magnetic property in alternating field.View full abstractDownload PDF (491K)
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