Abstract: On the basis of the traditional C-Mn-Si steel,the microstructure and mechanical properties of the experimental Q&P steel after on-line one-step quenching and partitioning treatment were studied by metallographic microscope,scanning electron microscope and tensile test.The effect of partitioning time on the microstructure and properties of the steel was also discussed.The results show that the experimental steel structure consists of lath martensite and retained austenite.With the increase of partitioning time,a small amount of bainite is formed,and the retained austenite content first rises and then falls,and the lath structure of martensite is gradually blurred and softened;the tensile strength and yield strength are gradually reduced,and the elongation first increases and then decreases.The best comprehensive performance is achieved under the partitioning time of 30 s,the tensile strength is 989 MPa,the elongation is 23.5%,and the product of strength and elongation is 23.24 GPa·%.

Key words: partitioning time, Q&P steel, retained austenite, microstructure, properties