Development of functional materials by ECAE and subsequent heat treatment

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To obtain materials for micro screw which was high strengthened plane carbon steel with ductility, a cold ECAE (equal channel angular extrusion) process and following heat treatment were conducted. Grain refinement with grain size less than him was achieved by repeated ECAE process and tensile strength was increased. After ECAE process, low temperature, short time heat treatment, by which tensile strength become lower and total elongation increased, was carried out.In FY 2005, SWCH18A (0.16%C with spheroidizing treatment) which is usually used as a material of screws and S15C were used in investigation. Both materials were ECAE processed to 4 passes via route C at room temperature. ECAE Processed specimens were annealed at 600 ℃ in several periods, then ductility were improved. Manufacturing micro screw was conducted to specimen after heat treated and succeed in producing micro screw.In FY 2006, Different carbon contained steels, S25C, S35C and S45C were selected. Materials were ECAE processed to 4 passes via route C at room temperature. ECAE Processed specimens were annealed at 600 ℃ in several periods, then ductility were improved. Producing micro screw was conducted by the cold header, that was design to manufacture micro screw, made by nakashimada co. ltd.The results of producing micro screw, whether it was possible or not, was used for judging of formability in enhanced materials fabricated by deformation and heat treatments. These obtained knowledge were reflected in the optimization for combination of thermo-mechanical process.