Quenching And Partitioning Treatment Of35CrMnSi And Stability Of Retained Austenite

Quenching and partitioning is to heat the steel to a certain temperature, then quenching the steel to a temperature (QT) between Ms and Mf, is obtaining a hybrid organization of Martensite and a certain amount of untransformed austenite. Then in a heat preservation temperature which is greater than or equal to PT, the carbon transforms from Martensite to austenite without diffusion, thereby increasing the untransformed Austenite stability in the cooling process of the next. Finally, by quenching to room temperature, the organization of Martensite and retained austenite, will gain high strength and toughness. Heat treatment of quenching and partitioning applied in treatment of35CrMnSi, can make35CrMnSi get good plasticity and toughness, and avoid the tempering brittleness caused by traditional process of quenching-tempering process.This research explores the detailed experimental method of quenching and partitioning applied in treatment of35CrMnSi. This research also explores the tensile ability and impact ability of35CrMnSi after quenching and partitioning process, and explores the function of residual Austenite in35CrMnSi under the effects of tensile, impact. This research exhibits deep cryogenic treatment in order to determine whether the35CrMnSi organization can stably exist in the practical application under deep cryogenic circumstance.For quenching and partitioning treatment on35CrMnSi steel, after a series of experiments, the proper process is:880℃austeniting for8min, quenching at200℃for10s,400℃distributioning for180s.35CrMnSi steel after quenching and partitioning treatment of the proper process as described is composed of hybrid organization of martensite and residual austenite, the content of retained austenite in steel is up to7.9%(vol.%). Its tensile strength is1500MPa, elongation is18.56%, strong plastic product is up to27.84GPa%, and is respectively-8%,100%,93%higher than the sample without Q-P process.In order to research the practical application under deep cryogenic circumstance of35CrMnSi steel after quenching and partitioning treatment, we create an atmosphere of-20℃～-80℃for different time, using alcohol-liquid mixture in cryogenic, and then use the XRD diffraction method to measure the content of retained austenite. The result shows that after quenching and partitioning treatment, residual austenite in35CrMnSi steel retains good thermal stability.