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Volume 37, Issue 8
Displaying 1-13 of 13 articles from this issue
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Shigeaki Takajo1990 Volume 37 Issue 8 Pages 1125-1131
Published: November 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe creation of high quality steel powders greatly contributes to the improvements of sintered components. A new family of low alloy steel powders has been developed to meet the requirements of heavy duty structural components mainly for the automobile industry. Composite-type alloyed steel powders containing 2%Cu or 4%Ni1.5%Cu-0.5%Mo consist of iron particles to which alloying elements are finely diffusion-bonded. The powders attain the homogeneity of sintered microstructures while maintaining the compressibility of a pure iron powder. A prealloyed steel powder containing 1.0%Ni-0.3%Cu-0.2%Mo has been designed to achieve high strength after heat-treating high density sintered compacts. The sintered materials remain soft before heat treatment and are effectively densified by repressing.View full abstractDownload PDF (1503K) -
Toshio Shimoo, Masaki Sugimoto, Kiyohito Okamura1990 Volume 37 Issue 8 Pages 1132-1137
Published: November 25, 1990
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSIn relation to the synthesis of SiC powder, the mechanism of the pyrolysis of polycarbosilane-SiO2 mixture was investigated. Using mixtures with various mass ratio of polycarbosilane to Si02, the reaction rate was determined by thermogravimetry at temperatures from 1773 K to 1973 K under an argon atmosphere.
The content of SiC in the powder obtained by the pyrolysis of polycarbosilane is 57%. The addition Of SiO2 to polycarbosilane increases the content of SiC. The powder of 83% SiC was prepared from the mixture containing 15%Si02 at 1973 K.
Si02 powder reacts with amorphous carbon in polycarbosilane to produce SiO and SiC. It is considered that the reaction rate is controlled by the chemical process at the surface of Si02 particle.View full abstractDownload PDF (2293K) -
The Relationship between Contact Distance of Particles and Shrikage of Compacts in SinteringHidetsugu Yagi, Yuzo Mori, Takashi Ide1990 Volume 37 Issue 8 Pages 1138-1142
Published: November 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe mechanism of volume reduction of the sintered compact using spherical copper powders was studied. The spherical copper powder was sieved so that the particle size was 53-45μm, compacted at specific density of 0.61, and sintered at 1223 K for 10.8 ks or 21.6 ks. The amount of volume reduction was measured by the Archimedes' method, and the volume reduction ratios were calculated from the above data. On the other hand, the volume reduction ratios were calculated from the neck radius under the assumption that the neck grew by the cons-tant-radius-interpenetration mechanism and the rearrangement did not occur in the sintering. The experimental value and calculated values of the volume reduction ratios were in good agreement with each other. It was clarified that the volume of the sintering compact reduced in accordance with the assumption of the calculation of the volume reduction ratio in this specific density.View full abstractDownload PDF (346K) -
Masao Morishita, Hiroshi Kawatani, Akira Shimamoto, Nobuyasu Kawai, To ...1990 Volume 37 Issue 8 Pages 1143-1147
Published: November 25, 1990
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSA corrosion-and wear-resistant alloy for plastic shaping machines was developed by powder metallurgy including a HIP (Hot Isostatic Pressing) process. The results were obtained as follows:
(1) The composition of the new alloy was Ni-17.5 mass%Cr-24.0 Mo-3.6 B-2.9 Si-1.0 Cu. A reaction sintering method was applied to produce the new alloy. Ni-Mo-Si-Cu alloy powder and CrB powder were reaction sintered by the HIP process. CrB particles were transformed into M3B2 particles during HIP.
(2) The corrosion resistance of the new alloy was 6, 45 and 100 times superior to that of centrifugal cast alloy, respectively, and almost the same as that of Hastelloy C. It was concluded that the high corrosion resistance of the new alloy was due to the addition of Cu which inhibited the preferential corrosion of the matrix by a electrochemicalcell corrosion mechanism.
(3) The wear resistance of the new alloy was 3 times superior to that of centrifugal cast alloy and 150 times superior to that of Hastelloy C. This high wear resistance of the new alloy was due to fine dispersion of M3B2 particles.
(4) The new alloy was reaction sintered and bonded to the inner surface of steel cylinder body. This bimetallic cylinder can be used for plastic shaping machines.View full abstractDownload PDF (2365K) -
Takeshi Kaneko1990 Volume 37 Issue 8 Pages 1148-1156
Published: November 25, 1990
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSThe effect of the heat treating time is investigated to improve the mechanical properties of W-Ni-Fe heavy alloys. These alloys were annealed in the temperature at 400-1200°C in vacuo for annealing time range 1-24 h after cold-worked by swaging treatment. It is confirmed that the values of tensile strength, yield strength and hardness are increased, but the elongation is decreased by heat treatment in vacuo after swaging in the temperature at 600°C for 5 h. However, the tensile strength, yield strength and hardness are decreased, and also the elongation is increased in the temperature at 1200°C for 3 h.
The scanning electron micrographs of the fracture surfaces show that heat treatment strengthens mainly the interface between tungsten-matrix phase boundaries and W-W grain boundaries.View full abstractDownload PDF (3760K) -
Yoshihiro Tada, Teisuke Sato, Isao Tsutsui1990 Volume 37 Issue 8 Pages 1157-1162
Published: November 25, 1990
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSAn aluminum alloy, 2024, has been mechanically alloyed with nickel to investigate the effects of three process control agents, i.e., zinc stearate, amorphous carbon and graphite, on milling process and powder characteristics. In milling aluminum powders, some process control agent must be used so that a balance between cold welding and fracturing is obtained. Zinc stearate has turned out to be a suitable additive for controlling milling processes. The influences of process control agents on mechanical property were assessed in tensile tests of extrudates of the mechanically alloyed powders. It was found that carbon and graphite gave good tensile strengths both at ambient temperature and at elevated temperatures. Although zinc stearate gave good room temperature tensile strengths, it was not so effective to improve elevated temperature strengths. It was found that the combined addition of process control agents offered a way to comply with various demands; for example, good control characteristics of milling process with excellent high-temperature strengths on the extrudates were achieved by a combined addition of zinc stearate and carbon.View full abstractDownload PDF (350K) -
Takeji Hachisuka1990 Volume 37 Issue 8 Pages 1163-1170
Published: November 25, 1990
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSSimultaneous addition of WC and HfC to TiC-TiN-Mo2C-Cr3C2 composite ceramics was attempted to broaden application field of composite ceramics based on TiC-Cr3C2 system for cutting tool materials. Compacts of the multicomponent ceramics consisting of 40%TiC-15%TiN-4%Mo2C-25%WC-8%HfC-8%Cr3C2 in weight percentage, contained about 1% of metallic impurities of iron group outside the proper components, were sintered at temperatures up to 1600°Cfor 2 hr in a vacuum of 10-4mmHg.
The compacts showed distinguished sinterability similar to TiC-TiN-Mo2C-Cr3C2 composite ceramics: those were attained complete densification by means of sintering at temperature somewhat above 1350°C.
It was confirmed that the same mechanism in densification was taken place in both composite ceramics. Namely, Mo2C was dissolved in TiC in the form of cubic ζ-MoC as a solute readily and preferentially at the temperature up to about 1100°C, resulting formation of (Ti⋅Mo)C solid solution. Preferential formation of the solid solution was promoted dissolution of other components, viz. WC, TiN and Cr3C2, into itself during sintering, which played an important role as the main driving force of densification, especially dissolving of TiN in the final stage of densification.
Metallic impurities in the multicomponent composite ceramics were fully dissolved at temperature up to 1400°C into low-chromium carbides, which have been formed in sintering process as well as in TiC-Cr3C2 system.
The dissolution mechanism of hexagonal WC into TiC in the form of cubic β9-WC phase as a solute was also discussed.View full abstractDownload PDF (6850K) -
Carbide: SiC, WC and TiCShigeru Ito, Kuniaki Miyazaki, Seiki Sato, Nobuyuki Koura, Noboru Yone ...1990 Volume 37 Issue 8 Pages 1171-1176
Published: November 25, 1990
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSCr-Carbides (SiC, WC and TiC) composites were prepared by HIP technique. Although the chromium is easy to react with the carbides at high temperature, the fractions of reactions were controlled below 27% at 800°C using the carbide powders having large grain sizes of 25-110 μm. The dense and pore free composites with the compositions of Cr-5 wt% Carbide and Cr-10 wt%SiC, 20 wt%WC, 10 wt%TiC were obtained at 800°C (at 900°C for Cr-TiC) for 30 min, applying 50-200 MPa and 200 MPa, respectively. The thickness of reaction layers around SiC, WC and TiC grains were measured to be about 5.3 μm, 5.8 μm and 2.8 μm, respectively. In the Cr-WC composite, the growth rate of the reaction layer largely decreased with an increase in HIPing pressure. The activation volume of the reaction was calculated as 80 ml/mol, which is larger than that of metalmetal composite. The Cr-Carbide composites exhibited excellent wear resistances, which were also increased under higher HIPing pressure.View full abstractDownload PDF (1985K) -
Nobujiro Tsuchiya, Masahide Fukuda, Tsuyoshi Nakai, Hisashi Suzuki1990 Volume 37 Issue 8 Pages 1177-1180
Published: November 25, 1990
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSHigh carbon WC-(10, 20)mass%Co micro-grained alloys containing no Cr3C2 or 5.0 mass%Cr3C2 in binder, were prepared by solid-phase sintering, that is, vacuum sintering at 1473-1553K and then HIP-treatment at 1523 K. Some properties such as microstructure and mechanical properties were studied. It was found that the alloys prepared by solid-phase sintering, for instance, sintering at 1523K for 10.8ks and then HIP-treatment, reached full density and showed excellent mechanical properties. As to the transverse-rupture strength, the alloys, having grain size of 0.5-0.6 μm, exhibited the value so high as about 3.5 GPa or more, independent of binder content or Cr3C2 addition. It was noted that WC grains recrystallized during solid-phase sintering.View full abstractDownload PDF (3822K) -
Masao Komai, Yoshihiko Isobe, Ken-ichi Takagi, Tadao Watanabe1990 Volume 37 Issue 8 Pages 1181-1186
Published: November 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSEffects of Co content on the phase formation and the mechanical properties of Mo2FeB2 base hard alloys were studied in Fe-5B-44.4Mo-XCo alloys with six levels of Co content from 0 to 10 mass%. The transverse rupture strength (TRS) and hardness of the alloys depend strongly on their microstructure which varies significantly with Co content. TRS keeps about the value of 2.0 GPa up to 5 mass% Co; it then decreases drastically at 7.5 mass% Co and increases slightly again at 10 mass% Co. On the other hand, hardness keeps approximately 83 RA up to 5 mass% Co, thereafter, it increases to 87.5 RA with increasing Co content. X-ray diffraction results indicate that the changes of TRS and hardness from 7.5 mass% Co up are attributed to the formation of a new boride phase which is considered to be Mo(Fe, Co)B.
The TRS drop and the hardness increase at 7.5 and 10 mass% Co are attributed to the increase of area frac-tion of the boride phases from 0.66 to 0.78 associated with the formation of the new Mo(Fe, Co)B boride phase.
Moreover, the TRS drop at 7.5 mass% Co is also caused by coalescence of the boride grains, namely Mo2FeB2 and Mo(Fe, Co)B, and coarsening of the Mo2FeB2 grains, and a small increase of the TRS at 10 mass% is due mainly to the re-improved dispersion of Mo(Fe, Co)B boride particles despite its lager grains.View full abstractDownload PDF (3146K) -
DrillingEiichi Sentoku, Mikito Kumagai, Yoshio Fujimura1990 Volume 37 Issue 8 Pages 1187-1192
Published: November 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSIn recent years, many glass ceramics with various kinds of properties have appeared on the market. These ceramics are used for a few mechanical and electronic parts. Glass ceramics consisting of fiuor-phlogopite can be machined with tight tolerance using conventional metalworking equipment and tools. The purpose of this paper is to study the shape of drill edge and to find the mechanism of chipping on drill key hole in cutting with high efficiency. The chipping size was discussed upon both examination in drilling and analysis with the finite element method. The tests of drilling mica-ceramics were performed with twist drill of high speed steel by milling.
The main results obtained are as follow: (1) Cutting of high speed and feed had an important effect on chipping size of drill key hole. (2) The tip angle of 90°on drill resulted in small chipping size. (3) The worn tool increased chipping on machining surface. (4) A large thrust in drillingincreased chipping of exit side on hole.View full abstractDownload PDF (1189K) -
Sil Mook Lim, Yasushi Nakamura1990 Volume 37 Issue 8 Pages 1193-1198
Published: November 25, 1990
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSEquilibrium experiments were performed to determine thermally stable ranges of BaO⋅2FeO⋅8Fe2O3 (W) and BaO⋅FeO⋅7Fe2O3 (X) under various oxygen pressures. Ferrous contents of W and X compounds increas-ed with increasing temperature and with decreasing oxygen pressure. No significant changes in saturation magnetization were observed with variation of ferrous contents of W and X compounds. Upper and lower limits of the stablility ranges for W and X compounds were found to be expressed as follows:
(1) W compound; W=Magnetite+Liq. RTlnPo2=-1030×103+578T(1622-1728 K), 2W+O2=2M (BaO⋅Fe2O3)+6Fe2O3 RTlnPo2=-444×103+255T (1448-1622K)
(2) X compound; X=W+Liq. RTlnPo2=-967×103+553T (1587-1697K), 2X=W+M (BaO⋅6Fe2O3) RTlnPo2=-682×10;3+402T (1510-1633K)
Here, Po2: the oxygen pressure in atm unit, T: temperature in K unit, and R: 8.3145J/mol⋅K.View full abstractDownload PDF (406K) -
Masato Imamaura, Kazuhiko Miyamoto, Jie Wei, Takeo Nakagawa1990 Volume 37 Issue 8 Pages 1199-1202
Published: November 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSA permeable metal-ceramic mold is made by the oxidization sintering of slurry cast material. First, slurry casting is performed for transprinting of master pattern. Though enough strength is obtained by the expantion of iron-oxide transformation, the surface roughness becomes worse.
To improve this surface quality, the variation of mixing ratio and of sintering conditions is performed. As a result, it is experimentally confirmed that metal-ceramic mold having 30% fine carbonyl iron powder and 70% mullite powder sintered at 500°C is satisfied for both strength and surface requirements.View full abstractDownload PDF (2682K)
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