Vol.2 No.2 2009

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Research paper : Energy savings in transportation systems by weight reduction of their components (M. Sakamoto et al.)−127−Synthesiology - English edition Vol.2 No.2 (2009) 5 Current state of practical use and R&D・Casting material and billet for plastic formingThe materials for plastic forming must be highly clean and have the highest quality possible, and the quality of the material in the most upstream position greatly affects the quality and cost of the plastic formed products. We transferred the molten metal refining technology by reduced pressure method to three material supplier companies, and is engaging in usage development and mass production of high-quality, low-cost billet materials. We selected multiple companies as material manufacturers to ensure stable supply of the material. One company was capable of an integrated mass production system from billet manufacturing to extrusion, while another company was a casting company capable of multi-type low-volume production, and we aimed for a flexible production system considering the future demand for machinery structure components. The photographs on top right and left center in Fig. 9 show the plastic forming billet in rod form.・Casting materialSince the noncombustible alloy does not burn readily in the atmosphere, casting is possible at low cost in the casting process where metal is melted and then solidified in a mold. Therefore, we are working on R&D for casting technology for various machinery components with the aforementioned casting companies. Casting itself can be done in a similar manner as aluminum, and it should be specifically mentioned that green sand casting in the atmosphere is possible in the case of AZ91-based noncombustible alloy. However, since the noncombustible alloy has poor flow property compared to ordinary alloys due to its special solidification structure, and also since solidification occurs rapidly due to its low heat capacity compared to aluminum and casting iron, the problems in casting methods and their conditions are not entirely solved. In actual practice, technology, experience, and know-hows must be accumulated. However, it has definite cost advantage, and application to various machine parts are expected in the future. Figure 11 is an example of the shelf support that was selected for use in the state-of-the-art Shinkansen car. It is made of die-cast noncombustible alloy AZX912, and this is the first time in the world for a magnesium component to be used in a railroad vehicle.・Hot extruded shape materialsLong products with complex but uniform cross section like the aluminum window frame can be mass-produced efficiently, by applying pressure to the metal and pushing it through a perforated die. The extruded materials that are easily formed into shapes with complex cross sections or hollow interiors are basic industrial materials. Since the noncombustible magnesium alloy can be fabricated easily into shapes by the hot extrusion process, usage development is being conducted by the aforementioned billet company and the aluminum extrusion specialist company. Currently, as the first practical application of noncombustible magnesium shape, the specialist company created a product in the form of a square pipe to be used as gate bars for the ETC (Electronic Toll Collection) system at the expressway toll gates. There was a demand for weight reduction, as there were many cases where the shaft of the conventional aluminum bar broke due to the increased frequency of opening and closing of the gate bar. Initially, CFRP was used, but from the perspectives of product price and recycling after exchanging with a new bar, it was changed to the noncombustible magnesium alloy product. It was not merely a replacement of aluminum for further weight reduction, but this was an interesting and illustrative example of a material alternative where high specific strength and recyclability were the key considerations.・Hot forged materialForging is done by beating a simple-shaped metal material to improve strength and reliability. By forging using a mold, parts with uniform quality can be mass-produced, and it is an important processing technology in industry. Forging of noncombustible magnesium alloys is more difficult compared to other alloys, because cracks occur readily unless the temperature and speed of the process are finely controlled. However, in forged materials with fine recrystallized structure by preliminary hot extrusion processing, the forgeability improves dramatically and high speed forming using a hammer forger is possible. Therefore, even if the addition of preliminary extrusion increases the number of steps, there may be advantage in terms of total cost for Fig. 10 Core research system for processing technology of noncombustible magnesium alloy by public research institution collaboration.Fig. 11 Luggage shelf support made of noncombustible magnesium alloy (AZX912).Promotion Council forIndustrial TechnologyKyushu Region WorkshopStudy Group on NoncombustibleMg Alloy ProcessingCastingtechnologyWeldingtechnologyPressmoldingtechnologyMachiningtechnologySurfacetreatmenttechnologyFunctionadditiontechnologyParticipatingprefecturesOitaFukuokaAISTFukuokaAISTAIST(Fukuoka)●AISTSagaFukuokaKumamotoKagoshimaKumamotoSagaWall

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