| H13 steel is characterized by high strength,high toughness,high hardenability and good resistance to thermal softening.Therefore,it is widely used in the production of various types of hot working dies,such as forging dies,extrusion dies,and die-casting dies,which are typical difficult-to-cut materials.The development and application of NC machining technology shorten the development cycle of the mold.Determining reasonable tool structure and cutting parameters is an important part of NC machining technology,which not only affects the machining efficiency,but also directly affects the machining quality.Therefore,it is of great theoretical significance and application prospect to study its cutting mechanism and tool structure optimization.Based on the analytical modeling and numerical modeling of machining process,the material model parameters identification,cutting mechanics analysis,residual stress prediction and tool structure innovation optimization design of H13 steel are studied in this paper,the main contents are as follows:The finite element model of orthogonal cutting is established to reveal the influence of model parameters and workpiece material performance parameters on cutting force.Based on the cross-platform rapid pre-processing parametric modeling,the constitutive model of workpiece is regarded as the optimization problem of simulation.The error of measuring cutting force and simulation cutting force is used as the adaptive function value to optimize the constitutive parameters.The inverse identification method of constitutive parameters based on joint simulation is proposed,and it is applied to the identification of constitutive parameters of typical difficult-to-machine material die steel H13 and titanium alloy Ti-6Al-4V.The effectiveness of the method is verified by comparing with the cutting force experiment.An analytical model of orthogonal cutting force of H13 steel considering the influence of shear zone,friction zone and ploughing zone is established,combined with the common relationship between the division shear-zone model and the unequal division shear-zone model,the multi-physical field calculation method of the first deformation zone is proposed,the distribution characteristics of shear velocity,shear strain rate,shear strain,shear stress and temperature in the main shear zone are analyzed with the variation of cutting parameters,the model correctly reflects the distribution characteristics of temperature and stress in the shear zone and is consistent with the two-dimensional finite element model.The influence of cutting parameters and tool geometry angle on tool-chip contact is divided into four states,based on the equivalent cutting edge,the oblique cutting force prediction model is established to reveal the interaction mechanism of tool geometry(edge radius,nose radius)and tool angle(main cutting edge angle,inclination angle and rake angle)on cutting force components,respectively,then,in order to better reflect the reliability of the cutting mechanical model,a three-dimensional milling mechanical model is established,and the influence of milling parameters on the milling process force is expounded,the correctness of the model is verified by experimental observation of milling force.Through the analysis of the thermal-mechanical coupling effect on the cutting surface,combined with the Hertz rolling and sliding contact model and the elastic-plastic loading and unloading principle,the analytical model of residual stress on the surface of H13 steel in orthogonal cutting considering the combined effect of mechanical load and thermal load was established.The influence of cutting parameters(cutting speed,cutting thickness)and tool parameters(edge radius,rake angle)on residual stress distribution was discussed,and the correctness of the model was verified by the residual stress observed by X-ray method.Based on Python,the secondary development of ABAQUS cutting simulation model is carried out to realize parametric modeling of arbitrary shape of tool rake face,and the optimal rake face shape corresponding to different cutting thickness is obtained,the segmented design concept of rake face shape,length of transition zone between rake face and edge radius and edge radius are proposed.In order to expand the application range of fixed tool structure under different feed rates,the normalized optimization function of cutting force is established according to the segmented design concept,and the optimized tool is obtained by designing the rake face structure based on the existing turning tool structure.The optimized tool entity was prepared by powder metallurgy pressing method,and the comprehensive cutting performance experiment was carried out,and then it was concluded that the optimized turning tool reduces the cutting force and surface roughness,reduces the plastic deformation of the chip,and reduces the tool-chip contact and chip adhesion of the rake face.Based on the three-dimensional finite element model of milling,the point cloud coordinate data corresponding to the wear area of the rake face of the milling cutter are obtained,the tool design method based on the crater shape is proposed,the spline smoothing,surface construction and boolean operation are used to design the microgroove based on the crater shape on the rake face of indexable insert,a new tool entity was prepared based on powder metallurgy,The comparative experiment of tool wear was carried out,and the change process of milling force and milling tool temperature was analyzed.The wear mechanism of micro-groove milling cutter was revealed.It was found that the micro-groove milling cutter reduced the degree of oxidative wear of the cutter by reducing the maximum temperature of the cutter,and improved the life of the cutter.The effect of tool geometry angle and cutting parameters on turning/milling force and residual stress on workpiece surface is expounded by establishing theoretical model of cutting H13 steel.Based on numerical modeling,the innovative optimization design of tool rake face is carried out.The turning / milling positionable blade for H13 steel is developed,and the comprehensive cutting performance of the new tool is explored.The research results can provide theoretical support and scientific basis for improving machining technology of die steel,optimizing the machining parameters and the Structure of tool rake face. |
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