FeMnC계 TWIP 압연강의 미세조직 및 열처리 특성 연구

Abstract

The purpose of this study was to analyze microstructural changes and evaluate the mechanical properties of TWIP steel subjected to variations in heat-treatment, in order to identify optimal process conditions for enhancing the mechanical performance of TWIP steel. For this purpose, a homogenization heat treatment was conducted at 1200 ℃ for 2 hours, followed by hot rolling with reduction ratio 40 % at temperature exceeding 1100 ℃ and cold rolling with reduction ratio 91 %. Annealing heat-treatment is achieved using a muffle furnace in the range of 600 ℃ to 1000 ℃. The microstructure characterization was performed with an optical microscope, scanning electron microscope, X-ray diffraction, EBSD and EPMA. Mechanical properties are evaluated using micro Vickers hardness, tensile test, and ECO index (UTS × Elongation). Additionally, to examine cryogenic temperature characteristics, a Charpy impact test was performed at –196 °C and a tensile test was performed at –170 °C. The specimens annealed at 900 ℃ and 1000 ℃ experienced a significant decrease in hardness and strength due to decarburization in the vicinity of the surface. Consequently, the decarburization phenomenon was closely related to the heat treatment process and mechanical properties of TWIP steel, and the effect of the microstructure change during annealing heat-treatment.