鉄のセミソリッド鋳造プロセスの現状

概要

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Recent advance of semi-solid processing has been reviewed, in particular, focusing on iron casting and product quality. Firstly, fluidity of cast iron slurry is discussed with the data of slurry viscosity and cavity filling ability. It is pointed out that process design should be done with fraction solid of slurry less than 0.3 to 0.4 and with sufficient slurry stirring. Next semi-solid casting with pressurization (SSCP) is discussed based on the authors research. Using inclined cooling plate, cast iron slurry is poured into metal mold, followed by pressurization on the cast surface. Cast sample obtained shows sound one without porosity and gives reasonable mechanical properties and solidification structure with fine globular graphite after proper heat treatment. For example, tensile strength 700 to 800 MPa with elongation value 4 % and Vickers hardness value 520 to 650 are obtained using mold preheated at 300°C. Pressurization following the casting produces fine cementite phase in the cast sample which is disintegrated easily to form graphite particles. Semi-solid casting has a big prospect for its development in real process. However more vigorous study is needed to optimize process parameters including casting design and to overcome cost problems.
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