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Volume 44, Issue 5
Displaying 1-17 of 17 articles from this issue
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Takatsugu Amano, Yasuyuki Murata, Daigo Sugiyama, Noboru Wada, Koji Ki ...1997 Volume 44 Issue 5 Pages 411-415
Published: May 15, 1997
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSDebinding process as well as carbon in alloy powder has great effects on carbon content in final products using MIM process.
This paper describes the behavior of carbon and oxygen in debinding and sintering process by varing amount of graphite addition in AISI 4600 steel compounds.
The results are summarized as follows:
(1) Proper amount of carbon and oxygen in compounds makes possible to progress their removal by CO reaction in sintering process.
(2) Graphite addition to AISI 4600 steel compounds enables the control of carbon and oxygen content in fmal products under proper debinding conditions.View full abstractDownload PDF (268K) -
Daigo Sugiyama, Yasuyuki Murata, Takatsugu Amano, Noboru Wade, Koji Ki ...1997 Volume 44 Issue 5 Pages 416-421
Published: May 15, 1997
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSThe expectation has been wide-spread that MIM keeps a good possibility of being an advanced powder processing technique. So far various kinds of studies have been reported for optimization of MIM process, however, there still remain several subjects to be discussed. Especially, it is the most important issue to control the amount of elements in the final products such as the carbon and oxygen. Therefore we have made a basical research about the behavior of those elements in SUS304L steels during debinding and sintering process. In this study, by varying the sintering atmosphere (vacuum pressure) and debinding temperature, we analyzed the carbon and oxygen contents in each step of heat treatment, and successfully made clear the guidlines of ruling reaction as follows;
1)In the vacuum sintering process for SUS304L steels, the removal of carbon and oxygen from the compacts progresses under the dominant reaction below;
2C(residual carbon)+O2(in furnace and gained as oxides) → 2CO↑
2)The carbon and metal oxidation are enhanced over about 1200K. As the oxygen pressure is higher, metal oxidation becomes more dominant.
3)During the vacuum sintering, the decrease of carbon content down to approximately 0.05mass% accelerates metal oxidation remarkedly.View full abstractDownload PDF (350K) -
Hisashi Arakawa, Yoshihisa Ohashi1997 Volume 44 Issue 5 Pages 422-426
Published: May 15, 1997
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSX-ray CT scanners are able to measure density distributions in materials without destruction. Since removal of binder causes density change, debinding behavior for alumina powder compacts was evaluated using one of the scanners. In the thermal debinding processes for these compacts, the decrease in average CT value, which corresponds to the overall decrease in X-ray energy penetrated through a compact, was found to be proportional to the decrease in density. The coefficient between the average CT value change and the decrease in density was unique under deferent debinding temperatures and deferent density distributions. Therefore, the binder losses in each cross section in compacts can be estimated by measuring changes in CT value of each section. Thus the binder losses in compacts which had density deference in the axial direction were examined. It was revealed that in the case that a compact is placed with higher density in an upper portion while debinding, the binder loss in a lower portion tends to be less than the other cases.View full abstractDownload PDF (1223K) -
Hideki Nakayama, Katsuyoshi Yamagami, Hideki Kyogoku, Shinichiro Komat ...1997 Volume 44 Issue 5 Pages 427-431
Published: May 15, 1997
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe effect of characteristics of powder on mechanical properties of sintered SUS304L compacts made by injection molding was investigated. The specimens were made by injecting the mixture of water atomized or gas atomized powder and a polyamide binder into a metallic mold. The compacts were debound in air and sintered in vacuum at the various temperatures between 1573K and 1673K for 7.2ks. The relative densities of the sintered gas atomized powder compacts were higher than those of the sintered water atomized powder compacts. Some amount of oxide was found to exist in the microstructure of sintered water atomized powder compacts. The tensile strength and elongation of sintered gas atomized powder compacts were higher than those of sintered water atomized powder compacts mainly because of their relatively higher densities. The highest density of all was 70%. On the other hand, the proof stress and hardness of the sintered water atomized powder compacts were higher because of the existence of oxides.View full abstractDownload PDF (3977K) -
Hideshi Miura, Rie Toyofuku, Takeharu Baba, Tadatoshi Honda1997 Volume 44 Issue 5 Pages 432-436
Published: May 15, 1997
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSRecently, it has been well-known that various materials produced by metal injection molding(MIM) process show the excellent mechanical properties which are normally evaluated by the static rupture test such as tensile test. However, the assesment of the dynamic rupture properties such as fatigue strength is more important for the practical machine parts.
In this study, the behavior of fatigue properties for a stainless steel (SUS316L) produced by MIM process were investigated taking the process conditions and microstructures into account. The fatigue strength of hydrogen sintered steels were higher than that of the vacuum sintered steels. This seemed to be due to the difference of pore distribution in the surface and inside between the hydrogen and vacuum sintered steels. Both tensile and fatigue strength of hydrogen sintered steels which had still not the full density were equivalent to those of the wrought steels. This result indicates that the MIM process is applicable to high performance machine structural parts required high static and dynamic strength as well.View full abstractDownload PDF (3894K) -
Hideshi Miura, Katsunori Hasama, Takeharu Baba, Tadatoshi Honda1997 Volume 44 Issue 5 Pages 437-442
Published: May 15, 1997
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSMetal injection molding(MIM) process is hoped to be an advanced powder processing technique for the attributes of the near net shape forming the high density, high performance, and complicated parts. However, there remains the issue that the shape and volume of MIM compacts are still limited because of the shape deformation during debinding and sintering.
In this work, as one of new approaches to improve the above problems in MIM process, joining of MIM parts by using the exuded wax during solvent debinding has been attempted to produce the larger, more complicated andfunctional parts by combination of the different materials such as iron and stainless steel. On the solvent debinding, the deformation was prevented from covering the couple of compacts with Al2O3 powder. As the solvent debinding temperature increased, the binder removal and bonding property were increased. For the combination of the same materials(Fe/Fe, SUS304L/SUS304L, SUS410C/SUS410C) and different materials (SUS304L/SUS410C), the joining properties after sintering depended on the solvent debinding temperature, that is, high joined strength was obtained at high temperature.View full abstractDownload PDF (4695K) -
Takeharu Baba, Tadatoshi Honda, Hideshi Miura1997 Volume 44 Issue 5 Pages 443-447
Published: May 15, 1997
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe homogeneous microstructure has been utilized preferably for the P/M materials such as machine structural parts required high strength. For the low alloy steels such as AIS14600 produced by Metal Injection Molding (MIM) process, however, the static fracture strength such as tensile strength of mixed elemental powder compacts which showed the fine heterogeneous microstructure was superior to that of homogeneous prealloyed powder compacts in our previous studies. Therefore, the effect of microstructure on the dynamic fracture strength such as fatigue strength of injection molded 4600 steels by MIM process using prealloyed and mixed elemental powders were investigated in this study.
The heat treated compacts using prealloyed powder showed the fine homogeneous tempered martensitic microstructure. On the other hand, the mixed elemental powder compacts heat treated showed the fine heterogeneous microstructure, which consisted of tempered martensitic matrix and retained martensite or austenite phases caused by the segregation of Ni added alloying element. The fatigue strength of the latter were about 100MPa higher than that of the former. Thus the fine heterogeneous microstructure seemed to contribute to improve not only the static but also the dynamic fracture strength. This result indicated that the MIM technique is more effective route for manufacturing high performance low alloy steel compacts using mixed elemental powder.View full abstractDownload PDF (5296K) -
Tei Ieki, Kiyotaka Katoh, Akihiro Matsumoto, Takami Masui, Kunisuke An ...1997 Volume 44 Issue 5 Pages 448-452
Published: May 15, 1997
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSTensile properties of sintered Ti compacts prepared by metal injection molding process were investigated. Powder materials used for this study were pure Ti powders, whose average particle sizes were 13μm and 23μm. After debinding, the green compacts were sintered at various temperatures for 7.2ks in vacuum (10-3Pa order). Then the green compacts were placed in a case with Al2O3 powders or BN powders to compare the oxygen contents in the sintered Ti.
13μm powders enabled to sinter at lower temperature than 23μm powders, so the Ti compact sintered at 1298K had 0.2% offset yield stress of 485 MPa, modulus of elasticity of 101 GPa and tensile elongation of 18%. The tensile elongation was influenced by the oxygen content in sintered Ti. The oxygen content increased with sintering temperature when the green compacts were sintered in a case with Al2O3 powders. But, when BN powders were used instead of the Al2O3 powders, the oxygen content changed hardly by sintering temperature. Consequently the tensile elongation was improved drastically.View full abstractDownload PDF (2625K) -
Akira Sugiyama, Keizo Kobayashi, Kimihiro Ozaki, Kenji Miwa1997 Volume 44 Issue 5 Pages 453-457
Published: May 15, 1997
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe composition of Fe-18mass%Cr-18mass%Ni alloy powder were prepared by mechanical alloying (MA) of three kinds of elemental powders. The MA powder became homogeneous by milled for 360ks. The hardness of powders MAed after 360ks were about 700Hv. The MA powder was consolidated by pulse current sintering (PCS) method at 1073K. The microstructure of this sample was fine and the hardness was about 400Hv. The sample consolidated by using powders milled in N2 gas atmosphere contained much y phase. But the sample made by using powders milled in Ar gas atmosphere contained much a phase. Because the phase of powders as MA is almost a, the α -> γ transformation was occurred during heating of sintering. N2 surpresses the γ ->α transformation during cooling.View full abstractDownload PDF (1501K) -
[in Japanese]1997 Volume 44 Issue 5 Pages 460
Published: May 15, 1997
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSDownload PDF (82K) -
Keizo Takeuchi, Toshiaki Terada1997 Volume 44 Issue 5 Pages 461-465
Published: May 15, 1997
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe production amount of sintered P/M parts have been increased year by year, because of their good productivity for the parts with complicated shape, and their good flexibility for material design. However, after 1993, the increase ratio of P/M production in Japan have shown a drop by business recession. Under such serious condition, more studies and developments are needed in order to expand the use of P/M parts. In this report, we introduce a few topics that P/M parts will be given higher quality and cost performance, and suggest the necessity of activating R&D on P/M parts for automotive applications from user's point of view.View full abstractDownload PDF (1438K) -
Hiroyuki Endo1997 Volume 44 Issue 5 Pages 466-469
Published: May 15, 1997
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThere are two major trends of PM material development. The first is PM products application to the structural parts of automobiles which were originally made of conventional cast iron, carbon steel or alloyed steel.The PM materials were improved based on the alloyed material design, optimum manufacturing process and conditions to obtain comparable mechanical properties with them. The second is unique PM materials having heat and wear resistant properties utilizing PM advantage of flexibility in alloy elements and microstructures. It is understood that there is getting no economical advantage of the PM materials for the former application unless any further new development concept implemented.
In this paper, existing concerns for PM materials to be more widely applied to the automobiles and future trend of their development are mentioned focusing on iron base materials.View full abstractDownload PDF (1196K) -
Kuniaki Ogura1997 Volume 44 Issue 5 Pages 470-474
Published: May 15, 1997
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe average weight of powder metallurgy (PM) parts per car was 6.6kg in 1995 in Japan. This report describes tasks for increasing the average weight and the state of development of raw powders as it relates to those tasks. (1) To improve basic properties of parts, new powders for control of microstructure of PM material by alloying and heat-treatment, , and densification by new compacting and sintering methods are continuing to be developed. (2) For higher value-added PM parts, pre-mixed segregation-free powders have been developed. (2)-1 New raw powders to stabilize feeding into the cavity of the forming die and a new compacting technique are expected, and will contribute to improved stability of PM part quality and dimensional accuracy. (2)-2 Powder with AC magnetic properties is under development to add functional performance to PM parts. (3) To reduce production costs by improving productivity, powders which will make it possible to omit machining, heat-treatment, and similar processes after sintering are being developed.View full abstractDownload PDF (342K) -
Tadatoshi Honda1997 Volume 44 Issue 5 Pages 475-482
Published: May 15, 1997
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe use of sintered ferrous components in automotive applications has been increasing. At the same time, fatigue properties are becoming more and more important in the application for PM structural parts. Therefore, it is important in the future to add fatigue data to conventional materials data for sintered materials used in dynamically stressed components. This paper reviews the following factors influencing fatigue properties of sintered ferrous materials.
(1) Relation between matrix and pore structures
(2) Post-sintering treatment (heat-treatment, surface working, etc)
(3) Crack propagation rate and stress intensity factor
(4) Statistical analysis of fatigue strength and fatigue lifeView full abstractDownload PDF (503K) -
Yuichi Itou, Mikio Kondoh, Kazuyoshi Ogawa, Yoji Awano, Akira Manabe1997 Volume 44 Issue 5 Pages 483-486
Published: May 15, 1997
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSA method of predicting fatigue strengths using fracture mechanics on noched components of ferrous sintered materials is investigated. By applying Lukas's formula for evaluation of AK and a intrinsic crack model for small crack propagation on notched components, a simple formula for predicting fatigue limits was derived. This method requires three material properties: the fatigue limit of smooth specimen, the threshold stress intensity range for long crack, and the threshold value of the effective stress intensity. For experimental verification, a notched specimen for fatigue tests as sintered was designed, and fatigue tests were conducted with notched specimens of ferrous sintered materials with two different pore sizes. The predicted fatigue limits are comparatively in good agreement with the experimental results.View full abstractDownload PDF (1828K) -
Mikio Kondoh, Shigehide Takemoto1997 Volume 44 Issue 5 Pages 487-491
Published: May 15, 1997
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSDimensional tolerance of P/M parts is improved by uniformly filling powders in a die cavity. In this study, the moving behavior of the powders filled into a rectangular die cavity during the pullback or shaking of a feed-shoe has been investigated using a newly devised visual apparatus. It is clarified that the powder behavior in the feedshoe movement during powder filling is divided into three regions; where the powders move as rolling, where the powders slide, and where the powders do not slide with the movement of the feed-shoe. As the width of the cavity becomes thinner, the powders are more difficult to move; therefore, the none-sliding region increases. When shaking of the feed-shoe is repeated, the moving distance of powders in a vertical direction becomes larger, and the filling density increases. However, the increasing moving distance of powders is greatly affected by the width of the die cavity.View full abstractDownload PDF (2893K) -
Katsushi Kusaka, Tomio Kohno, Takashi Furuya1997 Volume 44 Issue 5 Pages 495-500
Published: May 15, 1997
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSThe objective of the present work is to develop plastic bonded Alnico magnet for high-quality electronic display or other applications. Here Alnico powders were produced by water-atomization (W/A) instead of cast-crushing method as usual. When W/A Alnico powder was held in the range 1000-1100K for a few minutes and then aircooled, the magnetic properties was wholly improved: practically, 2%Co- and 24%Co-bearing Alnico powders showed the coercive force (Hcj) of more than 6000e and 9000e, respectively. Subsequently, plastic bonded magnet, when press-compacted, showed the maximum energy products (BH)max : 0.45MGOe for 2%Co and 0.67MGOe for 24%Co (packing factor: approximately 65%). As a whole, W/A Alnico powder is of almost the same magnetic properties and further, is expected to be less costy as compared with cast-crushed one.View full abstractDownload PDF (1215K)
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