Vol.5 No.1 2012

Research paper−25−Synthesiology - English edition Vol.5 No.1 pp.25-36 (Jun. 2012) various structural components such as those for automobiles. The industrial oxygen analysis method has not yet been established for Mg, and the evaluation is currently done by methods that are neither precise nor accurate, such as microscopic observation of casting surface of the sample or visual inspection of oxides from the CT scan image. This is a barrier against building the recycling system, and it makes increasing the Mg use in products more difficult.In Mg with high oxygen affinity, the oxidation of surface tends to occur readily in the process of fabricating or being used as the structural component. Therefore, in the recycling of reuse parts and scraps produced in component fabrication process as raw material, monitoring of oxygen content and the oxide removal process based on the evaluation results are essential. However, the lack of the oxygen analysis method that can be employed at production fields is an obstacle to promoting the recycling practice.Japan has an advantage in the manufacturing technology of Mg materials and components, and particularly in both the melting and casting under oxygen shielded condition and the injection molding in semi-molten state. In these fabrication technologies, in principle, the increase in oxygen content during the process does not occur, and the components manufactured thereby are known to have low oxygen content.[5] In the international market for Mg, Japan can be positioned as the “raw-material-importing and products-exporting country.” In Korea, which is positioned similarly, there are 1 IntroductionMagnesium (Mg) is a light metal with specific gravity 1.8 g/cm3, which is one-fourth of iron (SG 7.8 g/cm3) and two-thirds of aluminum (SG 2.7 g/cm3). It is expected to have a major effect in reducing carbon dioxide when used in transportation machineries such as automobiles. The carbon dioxide emitted annually by the transportation machineries in Japan is estimated to be about 250 million ton, and 55 % thereof is dominated by private automobiles.[1] If the weight of the automobile is cut down to three quarters by reducing the weight of various structural members, the fuel consumption is expected to improve about 20 %, and the carbon dioxide emission can be reduced to 27.5 million ton (= 250 million ton x 0.55 x 0.2) for private automobiles alone.The researches for the use of Mg material that is excellent for reducing the environmental load have been done as major national policies in Europe and the United States. Some of the well-known projects are the “EUCAR Project” of EU, the “SFB390 Project” of Germany, and the “USCAR Project” of the US. However, the use of Mg per automobile is only 6 kg even in Europe as of 2005, and the use in Japan is much lower at 2 kg.[2]Mg has high oxygen affinity, and it is known that the oxygen impurities present as oxides (nonmetal inclusions) cause adverse effects on mechanical properties such as strength and fatigue life.[3][4] These prevent increase in the Mg use in - International standardization activity in parallel with R&D-A simple and reliable analysis method has been developed to measure oxygen impurity in magnesium (Mg) and its alloys. Instead of directly analyzing oxygen impurity of an analyte, a multi-step heating-up method has been invented, in which oxide, compound of oxygen impurity with metals, is first separated from an analyte and then oxygen content analysis is carried out. The oxygen analysis of the oxide has been performed by Inert Gas Fusion-Infrared Absorptiometry widely used as a method for oxygen analysis in metals. We verified that analysis with adequate accuracy can be achieved with temperature calibration of each equipment. In parallel with R&D of the analysis method, we performed international standardization activity. It has been shown that consistent data can be obtained both in Japan and Korea through our technical assistance to Korea, and a proposal to the ISO technical committee for Mg and its alloys has been submitted smoothly.An analysis method for oxygen impurity in magnesium and its alloysKeywords :Magnesium, magnesium alloy, oxygen analysis, inert gas fusion-infrared absorptiometry analysis, multistep heating procedure, international standardization[Translation from Synthesiology, Vol.5, No.1, p.25-35 (2012)]Akira Tsuge* and Wataru KanematsuResearch Institute of Instrumentation Frontier, AIST 2266-98 Anagahora, Shimoshidami, Moriyama-ku, Nagoya 463-8560, Japan *E-mail : Original manuscript received September 9, 2011, Revisions received November 15, 2011, Accepted November 22, 2011


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