| The ultra-fine acicular ferrite/bainite compound microstructures were obtained by proper chemical composition design and optimizing Thermo Mechanical Control Process technology (TMCP). The microstructure and mechanical experiments, including tensile and impacting tests, were conducted. The results indicated that the flattening and refinement of austenite grain was the main factor to the change of mechanical performance, such as impacting energy. The size of bainitic bundle less than 1 µm and the average flattening thickness of austenitic grain less than 5 µm were obtained. Meantime its tensile strength Rm was above 1000 MPa, total fracture elongation A is greater than 14%, and Charpy notched impact energy AKV reached above 120 J at a temperature of 30 below zero (-30 °C). |
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