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Volume 52, Issue 7
July
Displaying 1-12 of 12 articles from this issue
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Paper
Paper
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Takahiro Ohkubo, Takahito Akita, Hirobumi Shibata, Susumu Niwa, Katsuh ...2005 Volume 52 Issue 7 Pages 489-494
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSN-doped titanium dioxide (TiO2) particles were prepared by metallothermic reduction (MTR) method and their photocatalytic activities under UV and visible light irradiation were investigated. The mixture composed of anatase-type TiO2, Mg and NaN3 was calcined at 600°C in nitrogen atmosphere for 1 hour. Although two types of TiO2 particles, with low and high crystallinity, were used as starting materials, both obtained particles kept anatase-type crystalline and XPS spectra of them had peaks assigned to Ti-N bond. The absorption onset of the particles prepared from TiO2 with low crystallinity shifted significantly from UV region to visible one. This N-doped TiO2 particles had photocatalytic activity against oxidative degradation of gaseous 2-propanol even under visible light (>440 nm) irradiation.View full abstractDownload PDF (605K) -
Takahiro Ohkubo, Takahito Akita, Hirobumi Shibata, Susumu Niwa, Katsuh ...2005 Volume 52 Issue 7 Pages 495-499
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSTiO2 samples doped by B were prepared by the calcination of TiB2 in the air condition and metallothermic reduction (MTR) of TiO2 with Mg and B2O3 which were calcined in the Ar condition. As a result, we found that we could effectively dope B atoms to TiO2 samples by these methods, which were characterized by X-ray photoelectron spectroscopy of the 1 s orbital for B. These samples also show the photocatalytic activity for the oxidation of 2-propanol under the visible-light irradiation.View full abstractDownload PDF (459K)
Special Issue: P/M Automotive Parts Improvements from Capability, Functionality and Economical Efficiency Point of View
Summarization
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Akira Fujiki2005 Volume 52 Issue 7 Pages 502
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSDownload PDF (94K)
Memorial Lecture of JSPM Award
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Yoshikazu Seki2005 Volume 52 Issue 7 Pages 503-510
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSOne of the most important subjects in the P/M manufacturing is productivity of compacts. There are two processes that are controlling productivity in P/M manufacturing. (1) Discharging of powders from the hopper. (2) Filling of powder into the die cavity.
To evaluate the discharging characteristics of powders, the simplified discharging equipment was designed to measure the critical discharging diameter of iron based pre-mixed powder. The critical discharging diameter showed good relation to flow patterns of powders in the hopper.
In the die filling process, the air release from the die cavity was found to be important phenomena. “Agitating-shoe” which can accelerate the air release from the die cavity was able to increase the filling rate and decrease the weight variation of compacts compared to a conventional feed shoe.View full abstractDownload PDF (876K) -
Yoshinobu Takeda2005 Volume 52 Issue 7 Pages 511-518
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSAlong with growth of conventional PM (Powder Metallurgy) industry, advanced PM technologies like wrought PM aluminum alloys, super plastic super alloy, mechanically alloyed ODS alloys seemed attractive for the industry to have further growth. New materials and processes that fit to Japanese automotive and appliance industries have been developed inspired by the advanced PM technologies.
PM Al-Si-X alloys that adapt to iron and steel structure were developed. For improved economics and NNS (Near Net Shape) formability, encapsulation-free Powder Extrusion process and coining type Powder Forging process were developed. Based upon these technologies, more functional new materials than simple structural materials were also developed, for example light weight heat sink and high performance engine cylinder liners.View full abstractDownload PDF (2494K)
Rapid Communication
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Hiroyuki Takamiya, Mikio Kondoh2005 Volume 52 Issue 7 Pages 519-523
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSWe have developed a new compaction process which realized very high green density of iron powder. The crucial key of the process is the discovery of the die wall lubricant, Lithium stearate, which works at around 423 K under applied compaction pressure of 600 to 2,000 MPa. The process applied to titanium powder and showed excellent results. The mechanical properties showed equivalent to wrought titanium with good enough Net shape capability.View full abstractDownload PDF (1169K)
Paper
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Akira Fujiki, Tomonori Miyazawa, Mitsushi Oyanagi, Hiroki Fujitsuka, H ...2005 Volume 52 Issue 7 Pages 524-529
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSSintered materials have been widely used for valve seat insert (VSI) for automotive engines. They have possessed high flexibility in their alloying design to increase their performance in heat and wear resistance in comparison with that of conventional wrought steel and cast alloys. Especially several high cobalt containing sintered materials are used as exhaust valve seat insert materials because it's high wear and heat resistant properties. Recently, the circumstance of exhaust valve seat inserts has become sever due to A/F ratio (Air/Fuel ratio) of recent engines are set to leaner than that of conventional. This trend is aim to reduce exhaust gases and fuel consumption. On the other hands, the reduction use of high environmental burden materials such as cobalt has also been continually needed. And cobalt is expensive, reduce cobalt content is good for economy of these materials. This paper reports the development and the application detail of cobalt-free, lead-free and environmentally friendly exhaust valve seat insert.View full abstractDownload PDF (1257K) -
Satoshi Sunada, Kazuhiko Majima, Takeshi Matsuda2005 Volume 52 Issue 7 Pages 530-536
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSIn this experiment, three kinds of sintered SUS304 stainless steels (P/M stainless steels) whose porosity ratios were 17.06 (compressed at 392 MPa), 11.78 (compressed at 588 MPa) and 8.75% (compressed at 784 MPa) were used. The dissolution behavior of these sintered SUS304 stainless steels in the aqueous solution composed of H2SO4 and NaCl were examined compared with that of the conventionally processed SUS304 stainless steel (I/M specimen). All of the P/M SUS304 specimens showed almost linear increment of corrosion mass loss against reaction time and the specimen with higher porosity ratio showed more mass loss, while the I/M specimen showed evidently much less mass loss than any P/M specimens. The reactivation ratio for the P/M SUS304 specimen was higher than the I/M SUS304 specimen and it increased almost linearly with increasing porosity ratio. In the case of 72 ks of reaction time, the charge transfer resistance, Rct, is highest in the specimen compressed at 785 MPa, while it is lowest in the P/M specimen compressed at 392 MPa. In the longer region than 144 ks, all of the three P/M specimens show the almost constant Rct value of 200 Ω. These Rct tendencies well correspond to the time dependence curve of mass loss.View full abstractDownload PDF (815K) -
Satoshi Sunada, Kazuhiko Majima, Syuichi Ishida, Koki Kanno, Yoshinobu ...2005 Volume 52 Issue 7 Pages 537-543
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSThe green SUS304 stainless steel powder compacts were prepared by the conventional die and warm die compaction. Then they were sintered at 1393 K, 1473 K and 1523 K in three kinds of atmospheres, i.e. N2 gas, Ar gas and vacuum, and their corrosion behavior were investigated by the electrochemical procedure. Both mass losses of the specimens prepared by conventional compaction or warm compaction decreased almost linearly with an increase in sintered density ratio. The data points, however, fall on two different straight lines. The measurement of electrochemical reactivation ratio was carried out by the newly developed method in this study, and it was confirmed that the reactivation ratio of the specimen sintered in N2 gas was lower than those of the specimens sintered in Ar or vacuum. This result suggests that the specimen sintered in N2 gas has less corrosion resistance than those sintered in Ar or vacuum.View full abstractDownload PDF (1371K) -
Satoshi Sunada, Kazuhiko Majima, Syuichi Ishida, Koki Kanno, Yoshinobu ...2005 Volume 52 Issue 7 Pages 544-550
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSThe conventional die (C/C) and warm die compaction (W/C) were applied to prepare the green powder compacts of SUS304 and SUS316 stainless steels. These green compacts were sintered at 1393 K, 1473 K and 1523 K in three kinds of atmospheres, i.e. N2 gas, Ar gas and vacuum, and some of the sintered compacts thus obtained were subjected to shot peening treatment. Both mass losses of the SUS304 and SUS316 sintered specimens prepared by W/C process decreased almost linearly with an increase in sintered density ratio. The data points, however, fell on two different straight lines, and it was recognized that the corrosion resistance of SUS316 sintered specimen was better than that of SUS304 sintered specimen. The reactivation ratios of the SUS304 sintered specimens prepared by C/C process were about 30% and about 58% respectively for without shot peening and with shot peening treatment, which indicates that the corrosion resistance could not be improved by the shot peeing treatment. And it was also confirmed that this reactivation ratio could not be improved by shot peening process on both the SUS304 and SUS316 sintered specimens prepared through the W/C process.View full abstractDownload PDF (839K) -
Satoshi Sunada, Takahisa Yamamoto, Kazuhiko Majima, Norio Nunomura2005 Volume 52 Issue 7 Pages 551-561
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSMaterials used for this experiment were three kinds of Type 304 stainless steels: the first one was made by the conventional wrought process (I/M), the second one was made by conventional powder metallurgy process (P/M) and the third one was made by Metal Injection Molding process (MIM). Using these three stainless steel specimens the corrosion behavior of them were investigated in the aqueous solution (2.5 kmol/m3H2SO4+0.2 kmol/m3NaCl) through potentiodynamic polarization curve measurement and electrochemical impedance spectroscopy (EIS). In EIS measurement, a natural electrode potential with perturbation AC potential, amplitude of which was 10 mV was applied to the specimen, and analyzing frequency range was from 100 kHz to 1 mHz. Both the potentiodynamic polarization curve and the Nyquist plot curve of MIM specimen were similar to I/M specimen. These curves of P/M specimens were differed greatly from those of MIM and I/M specimens. Therefore it might be suggested that MIM process is quite suitable to improve the corrosion resistance. On the other hand, time constants of P/M and MIM specimens are similar, but they differed remarkably from that of I/M specimen, which is considered to be due to the remained pores in P/M and MIM specimens.View full abstractDownload PDF (1345K)
Rapid Communication
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Norimitsu Hirose, Junichi Asami, Akira Fujiki, Kazuya Oouchi2005 Volume 52 Issue 7 Pages 562-565
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSIn the same sintering and heat-treated conditions, the effects of partially alloyed and prealloyed powders with the different contents of alloying elements and compacting pressure on the Young's modulus (E) and Poisson's ratio (ν) of sintered low alloy steels were investigated. The values of E and ν depended mainly on the porosity (P) controlled by compacting pressure, and those values were affected slightly by the alloy powder types. The relations of P to E and ν were described as the following equations: E=E0(1-kE · P)2 and ν=0.034(1-kν · P)2+0.267, where E0 was the value of E at P=0, and kE and kν were experimental constants that depends on the alloy powder types and sintering temperature.View full abstractDownload PDF (699K)
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