Abstract: A low-carbon steel with Cu addition was heat-treated by direct quenching， Q&P (quenching and partitioning) and tempering processes. The mechanical properties and impact toughness of the test steel were investigated by universal testing machine and drop weight impact testing machine. The microstructure was characterized by SEM (scan electron microscope)， EPMA(electron probe microanalysis)， XRD (X-ray diffraction) and TEM (transmission electron microscope). The results show that the phenomenon of dynamic carbon partitioning from martensite to retained austenite in the continuous cooling process is observed and the impact toughness of test steel is improved by Q&P process and tempering process. The test steel has a good comprehensive mechanical properties: the product of tensile strength and elongation， the tensile strength， the total elongation and the impact toughness at room temperature are 20GPa%，1400MPa， 14% and 40J， respectively. The test steel based on dynamic carbon partitioning mechanism can meet the requirement of hot-stamping process and can be used as an excellent hot stamping steel with high product of strength and elongation.

Key words: dynamic carbon partitioning, retained austenite, hot press forming, product of strength and elongation, impact toughness