Kumamoto-shi, Japan
Kumamoto-shi, Japan

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Kitahara H.,Kumamoto University | Yada T.,Kumamoto University | Hashiguchi F.,Kumamoto University | Hashiguchi F.,Kyushu Yanagawa Seiki Co. | And 2 more authors.
Surface and Coatings Technology | Year: 2014

Wire-brushing was applied under varying conditions to surfaces of AZ31B Mg alloy sheets for the purpose of grain refinement. The microstructure, mechanical properties and corrosion resistance of the wire-brushed Mg sheets were investigated. The thickness of the maximum deformed areas from the wire-brushed surfaces were about 20. μm, and the deformed areas near the surfaces each consists of nanocrystals and ultrafine grains. A nanocrystalline surface layer consisted of equiaxed nanocrystals smaller than 100. nm, with the smallest mean grain size being 68.2. nm. The mean grain size in the nanocrystalline layer depended on the feed speed rather than the pressing load of the wire-brushing. Powdery Mg debris, which were produced at the surface of the sheet during wire-brushing, moved several millimeters during the wire-brushing. The 0.2% proof stress and tensile strength slightly increased after the wire-brushing, although the elongation decreased. The corrosion resistance of the wire-brushed sheet was approximately 4 times higher than that of the starting sheet. © 2012 Elsevier B.V.

Koya E.,Honda Corporation | Suzuki T.,Honda Corporation | Nakagawa M.,Honda Corporation | Fujimoto G.,Kyushu Yanagawa Seiki Co. | And 2 more authors.
SAE Technical Papers | Year: 2013

Using sand cores, the weld-able, hollow die-cast parts have been developed. For casting, the transition flow filling method is applied to reduce gas containment and to minimize damages to the core. In designing the products, the newly developed core stress prediction system by melt pressure distribution and the newly developed in-product gas containment prediction system have been applied. The hollow die-cast frame made by the new method attains a 30% increase in rigidity and 1kg reduction of weight. Copyright © 2003 SAE International and Copyright © 2003 Society of Automotive Engineers of Japan, Inc.

Koya E.,Honda R&D Co. | Fukuda Y.,Honda R&D Co. | Kitagawa S.,Honda R&D Co. | Murakami M.,Kyushu Yanagawa Seiki Co. | And 2 more authors.
SAE International Journal of Passenger Cars - Mechanical Systems | Year: 2015

When using aluminum for vehicle body parts to reduce weight, the high pressure die casting (HPDC) is widely applied due to its adaptability to thin-wall products, near-net-shape castability, and short casting cycle time. Since a hollow construction is advantageous to increase stiffness of body parts, there has been a need of development of techniques for casting of hollow parts by HPDC. So far, hollow casting by HPDC has been realized for small parts using sand cores. When applying that method to large parts, however, it is necessary to increase filling speed. When the filling speed is increased, the core tends to break. In this project, we have developed a method to estimate changes of pressure distribution when filling molten metal by the casting simulation in order to analyze damages to the core. Through the analysis, we discovered occurrence of impulsive pressure waves. Furthermore, the impulsive changes of molten metal pressure have been confirmed through the precise measurement of molten metal pressure. On the basis of the aforementioned findings, we have established a method to prevent core damage by controlling impulsive pressure waves by modifying the flow path. With the newly-developed method applied, the filling speed is increased by 1.5 times more than that of the conventional casting method for small parts, thus realizing casting of large hollow parts by HPDC. Copyright © 2015 SAE International.

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