Study On The Surface White Layer And Plastic Strain Of Hard Turning Hardened Steel

In the machining of bearing steels,hard turning has gradually become the mainstream processing method,compared with grinding,it has higher processing efficiency and processing flexibility,and is more suitable for workpieces with relatively complex shapes,dry cutting saves the use of cutting fluid and is also environmentally friendly.But on the other hand,dry cutting lacks lubrication in the cutting process,workpieces and tools with high hardness are in contact with each other,and local high-temperature,high-pressure and high-phase transitions cause corresponding changes in the surface material and corresponding microstructure of the workpiece.And under certain conditions,the surface layer will produce a layer that is only a few microns thick,with hard and brittle physical properties,and a white structure that appears under an optical microscope,white layer.Due to its hard and brittle performance,the appearance of the white layer will greatly reduce the life of the workpiece.For the situation described above,the main research content of the article includes the following:(1)The first part: The analysis of the formation of the white layer on the bearing steel under different cutting conditions.The experiments were carried out under normal cutting conditions and cryogenic conditions,and the morphology and microscopic crystalline structure of the white layer were observed by metallographic microscopy,SEM,and XRD observation conditions.The results were analyzed to study the effect of severe plastic deformation on the formation of white layers.(2)The second part: the critical value of plastic deformation for white layer formation under cryogenic processing conditions.We use inkjet or lithography to capture cuttings and workpiece materials using a dual-frame camera at very low cutting temperatures.The corresponding strains are calculated by digital correlation processing techniques,so that the critical value of plastic deformation under this working condition can be traced back.(3)The third part: through the finite element modeling analysis,under the same conditions,the comparison of the temperature field and stress field under normal cutting and cryogenic conditions.The material constitutive model and the adaptive mesh model are introduced to save time and improve the computational efficiency.The reliability of the experimental results is verified by comparing the simulation results with the actual experimental results.Near-surface strains agree with simulation experiments,The surface strain simulation results can be equated with actual results.