Quenching-partitioning-tempering(Q-P-T)process were applied to a quenched carbide-free bainite/martensite(CFB/M)multiphase steel 40Mn2Si2Cr and its effect on the mechanical properties was studied.The results showed that the partitioning time of Q-P-T treatment can be increased greatly to 90min or even longer.The tensile strength,elongation and product of strength and elongation(PSE)of the experimental steel can achieve 1 650MPa,about 20%and over 33GPa·%,respectively.The significant increase of partitioning time and excellent mechanical properties could be related to the CFB microstructure introduced in the quenching process during the Q-P-T treatment. Quenching-partitioning-tempering (QPT) process were applied to a quenched carbide-free bainite / martensite (CFB / M) multiphase steel 40Mn2Si2Cr and its effect on the mechanical properties was studied. The results showed that the partitioning time of QPT treatment can be increased greatly to 90min or even longer. tensile strength, elongation and product of strength and elongation (PSE) of the experimental steel can achieve 1 650MPa, about 20% and over 33GPa ·%, respectively. significant. Partitioning time and excellent mechanical properties could be related to the CFB microstructure introduced in the quenching process during the QPT treatment.