Effect Of Pulsed Magnetic Field Treatment On Mechanical Properties And Fatigue Life Of 20Cr2Ni4A Steel

With the development of science and technology,the performance of mechanical parts has put forward higher requirements.The mechanical properties of the part are the most important performance during the service of the part.The fatigue life of the part determines the effective working time of the part.In most mechanical parts,the stress concentration introduced in the production process is the root cause of its failure.Existing methods for improving the mechanical properties and fatigue strength of parts by changing stress have many disadvantages.The pulsed magnetic field enhancement technique places the pre-stressed specimen in an applied pulsed magnetic field for magnetization.Pulsed magnetic field strengthening technology reduces the residual stress of materials and has many advantages such as short time-consuming,no temperature rise,convenient operation,clean and pollution-free.Therefore,it is very urgent to study the influence of pulsed magnetic field strengthening technology on the mechanical properties and fatigue life of metal materials.In this paper,the commonly used alloy steel 20Cr2Ni4 A is taken as the research object.The pulse magnetic treatment is used to study the change of residual stress of materials after pulsed magnetic treatment.The mechanical properties and fatigue life have also been explored.The research results are as follows:(1)In this paper,the pulsed magnetic field strengthening tester is first built.Through the investigation of pulse magnetic treatment on material modification and pulse magnetic processing equipment,a pulse magnetic field generating machine was designed,and a prototype of pulse magnetic field strengthening testing machine was built.The equipment foundation was laid for the later research.(2)The magnetic domain structure and dislocation structure of 2Cr2Ni4 A material before and after the magnetization treatment of the pulsed magnetic field were observed by Magnetic Force Microscope and Transmission Electron Microscope.The changes were studied.It is found that after a certain parameter of pulse magnetic treatment,the magnetic domain structure of the material changes from labyrinth domain to sheet domain,and dislocation tissue undergoes dislocation proliferation,entanglement and dislocation slip.(3)The residual stress and yield strength of 20Cr2Ni4 A materials were studied by X-ray Diffraction residual stress tester and universal tensile tester.These properties of the material before and after the pulsed magnetic treatment were tested.Through the study,the change of the residual stress of the material in different states by pulsed magnetic treatment was found.(4)Fatigue life is one of the most important indicators to measure the performance of mechanical parts.In this paper,the fatigue properties of 20Cr2Ni4 A materials before and after pulsed magnetic treatment were studied by universal tensile fatigue testing machine.The research mainly on three aspects of material three-point bending fatigue life,material tensile fatigue life and gear bending fatigue life.