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Yamada W.,Mathematical Science and Technology Research Laboratory | Tanaka K.,Materials Characterization Research Laboratory
Nippon Steel Technical Report | Year: 2013

The solidification structure of the coating layer in hot-dip Zn-11%Al-3%Mg-0.2%Si coated steel sheet was studied by metallographic examinations together with the calculation of a phase diagram based on Thermo-Calc. The observation exhibited that the solidification structure is a combination of the Zn/Al/MgZn2 ternary eutectic structure, the primary fcc-Al phase and the MgZn2 phase, which is different from the predicted one under an equilibrium state in the sense that meta-stable MgZn2 instead of stable Mg2Zn11 was observed under the present condition. Excluding the Mg2Zn11 phase from the equilibrium phase diagram, the metastable phase diagram was calculated and excellent agreement was obtained between the calculation and the experiment in terms of the solidification structure of the coating layer. The small amount of Ti addition to the coating bath was confirmed to lead to the formation of fine dendrite structure. Detailed EBSD observation revealed that TiAl3 acts as heterogeneous nucleation sites of the primary fcc-Al. Source


Kanehashi K.,Materials Characterization Research Laboratory
Nippon Steel Technical Report | Year: 2011

It is important to analyze structure of slag and mold flux in the steel-making process with complicated multi-component systems from the viewpoint of appropriate management of the process and their effective use. Nuclear magnetic resonance (NMR), a nuclide specific method, is a powerful tool for structural analysis of slag with complicated structure. We have developed in situ high temperature NMR technique for analysis of melt structure and dynamics up to 1,500 degrees Celsius and some information have been obtained: (1) an averaged coordination number around Al increases with elevating temperature and (2) atomic-scale motion is closely related to macroscopic viscous flow. Source


Fujioka Y.,Materials Characterization Research Laboratory
Nippon Steel Technical Report | Year: 2011

I tried to apply the Infrared emission spectroscopy to identify the organic substances on the non-smooth or non-flat metallic surface. The organic substances like oils, fats and coating materials play an important role to enhance the lubricant property just like a processing property of steel and to protect it from corrosion. An organic substance on the flat metallic materials like a steel plate can be analyzed by the spectroscopic analysis that uses reflection method. But, the organic substances on non-flat materials like a fiber, wire rod, ball and powder must be removed and then preceded to various analyses. On the other hand, this infrared emission spectroscopy method can practice contactless analysis of the organic substances getting infrared spectral information just by heating up the target samples and references without any pre-treatment. And this emission is isotropic; therefore it can easily detect the organic substances of the non-flat surface of the metallic surface with limited influence of the surface shape of a material. This method is very simple and easy to expand in application. Source


Kimura M.,Materials Characterization Research Laboratory
Nippon Steel Technical Report | Year: 2012

The magnetization of iron depends on its crystal orientation. Electrical steel is a material whose magnetic property is dramatically improved by controlling the orientation of iron grains in the steel. In its manufacturing process, the process in which grains exceeding 10 mm in size are formed from grains tens of microns in size is especially important. On the other hand, implementing an atomic-level observation of the behavior of a catalyst in the actual environment requires a sophisticated observation technique. Therefore, knowledge of catalyst behavior is still insufficient. This has been one of the obstacles to efficient development of catalysts. Concerning the process in which the state of the active noble metal in the catalyst changes according to the change in composition of engine exhaust fumes, Nippon Steel succeeded in performing in situ observation of the process within tens of milliseconds. Source


Hayashi S.-I.,Materials Characterization Research Laboratory
Nippon Steel Technical Report | Year: 2012

The steel industry is now in the midst of global competition. From the standpoint of developing a new steelmaking process to impart denser and more complex structures to steel products, characterization technology that enables researchers to understand every phenomenon involved in the process on the basis of fundamental principles has become indispensable. The STEM was also applied to study the behavior of grain boundary segregation of trace amounts of boron, which is important from the standpoint of understanding the mechanism of improving the hardenability of high-strength steels used for ocean structures. It permits determining the types and spatial arrangement of the atoms that exist in the tip of the specimen, and its lateral resolution is 0.2 nm or less. Thanks to positron microscopy developed recently, however, the application of the technique is expanding, as in the observation of plastic deformation-induced defects in iron-copper alloys. It is expected that our technique will make it possible to obtain information about the distribution and density, etc. of dislocations and precipitates. Source

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