Thermal Deformation Of Hardened Steel Partition Affect The Microstructure And Mechanical Properties

Quenching and Partitioning (Q&P) is a heat treatment to fabricate complex microstructure of martensite and retained austenite, steel treated by Q&P process can obtain the mechanical properties of high strength combine with good ductility. In this paper, a new heat treatment of hot compress deformation plus Q&P was studied base on a low alloy steel, the microstructure and harness were characterized. The purpose of this paper is to study a process of obtaining steels with high strength and high performance.Gleeble-3800hot simulation machine was employed to study the process of hot compress deformation plus Q&P on CrNi3Si2MoV steel, the OM, SEM, TEM, XRD, and Vickers hardness were used to characterize the microstructure and mechanical properties. The results show that:Compared with the samples treated by Q&P process, the volume fraction of retained austenite and hardness of those treated by process of hot compress deformation plus Q&P both increase, it is include that the process of hot deformation plus Q&P is an effective method to obtain steels with high strength and high performance. With the decreasing of deformation temperature, the microstructure of steel refinement, the volume fractions of retained austenite first increase and then decrease, the hardness of steel gradually increasing. With the increasing of deformation amount, both the hardness and the volume fractions of retained austenite increase firstly and then decrease, the maximum volume fractions of retained austenite of17.22%was obtained under the deformation temperature of750℃and deformation amount of30%. The dynamic recrystallization occurred when the deformation amount exceed50%at750℃, which induced the microstructure become finer greatly, and both the hardness and the volume fractions of retained austenite decrease. With the increasing of quenching temperature under the same deformation condition, both the amount and the size of fresh martensite increase, and the volume fractions of retained austenite increase firstly and then decrease, the hardness decrease gradually, the decreasing of matrix induce the decreasing of hardness. Hot deformation strengthen steel, and the dislocation accelerate the partitioning of carbon atom from initial martenite into untransformed austenite, cause the increasing of volume fractions of retained austenite and hardness。...