Study On Effects Of Q&P Treatment Processes On Microstructure And Properties Of 0Cr13Ni5MoN And 0Cr13Ni5MoCuN Martensitic Stainless Steel

Super martensitic stainless steels have good weldability,higher strength,excellent corrosion resistance and plasticity and toughness,so it is widely used for petroleum pipeline,hydraulic turbines and water conservancy project.In this paper,we present a newly heat treatment process,namely quenching and partitioning,which can improve the comprehensive mechanical properties of super martensitic stainless steels.In this paper,we research super martensitic stainless steels based on 0Cr13Ni5MoN and 0Cr13Ni5MoCuN.with the help of laser scanning confocal microscope(LSCM),X-ray diffraction(XRD),transmission electron microscope(TEM)and tensile testing machine,we research the impact quenching and partitioning on super martensitic stainless steels from austenitizing temperature,quenching temperature,partitioning temperature and partitioning time.Finally,we confirm the optimalizing quenching and partitioning heat treatment process.The conclusion was obtained as follows:1.After treated by quenching and partitioning,the microstructure of super martensitic stainless steels is mixture of martensite and retained austenite.Different quenching and partitioning heat treatment process will lead different proportion of martensite and retained austenite.Martensite is composed of lath and twined martensite,while retained austenite is in forms of film and bulk.2.Austenitizing temperature,quenching temperature,partitioning temperature and partitioning time will have an important affect on properties of steels.Austenitizing temperature affects the degree of solution of carbide and nitride,which further affects Ms;Quenching temperature will decide the content of lath martensite and have impact on the content and morphology of austenite.Partitioning temperature and partitioning time have affect on diffusion of carbon and nitrogen atom,which has impact on the stability of austenite and the last content of austenite.3.The optimalizing quenching and partitioning heat treatment process of 0Cr13Ni5MoN:austenitizing at 950? for 30min,quenching temperature at 30?,partitioning temperature at 480? for 60min,under the heat treatment process,the steel of 0Cr13Ni5MoN receives the best the comprehensive mechanical properties:Rp0.2=1037MPa,Rm=1346MPa,A=25.9%,Akv=75J,Rm×A=34861MPa·%.4.The optimalizing quenching and partitioning heat treatment process of OCr13Ni5MoCuN:austenitizing at 960? for 30min,quenching temperature at 20?,partitioning temperature at 480? for 60min,under the heat treatment process,the steel of OCr13Ni5MoCuN receives the best the comprehensive mechanical properties:Rp0.2=1103MPa,Rm=1396MPa,A=25.5%,Akv=80J,Rm×A=35598MPa·%.5.After copper element added to 0Cr13Ni5MoCuN,Yield strength and ultimate strength are improved,while elongation has no change.The reason are as follows:copper are soluted into lath martensite and retained austenite after quenched.Cu can precipitate ?-Cu in the steel of 0Cr13Ni5MoCuN during partitioning.But the increase degree of Yield strength and ultimate strength is small,whose reasons may be lack of more copper in the steel of 0Cr13Ni5MoCuN.