| The mold is an important basic process equipment in advanced manufacturing industry,and cutting technology is one of the key technologies in mold manufacturing,which directly reflects the manufacturing level of mold.Due to the structural characteristics and functional requirements,large covering molds are often made of multi-hardness materials.After remanufactured repairing,the molds will also appear heterogeneous materials with changes in hardness.The surface consistency of workpiece,tool life and cutting rate will be greatly affected if this kind of variable hardness material is cut with the machining technology of single hardness material.In order to improve machining quality,reduce production cost and improve machining efficiency,it is of great theoretical significance and practical value to study machining performance considering the effect of material hardness.In this thesis,the cutting performance of variable hardness die steel is explored by finite element simulation method and test method.To sum up,the main research contents are as follows:(1)The cutting simulation model of splicing hardness material of Cr12 MoV is established considering the effect of plough cutting.The effects of cutting speed and feed speed on chip morphology and the effects of material hardness on cutting stress,cutting temperature,material equivalent plastic strain and material damage are investigated.The multi-objective optimization of cutting parameters is carried out by using matrix analysis method with the abrupt cutting force value and material removal rate as the evaluation indexes.And the correctness of the optimization results was verified.(2)The Cr12 MoV laser cladding part is chosen as the research object,and the hardness distribution regular of material is explained from the perspective of microstructure.Based on the hardness distribution,the hypocycloid simulation model of milling with variable hardness is established.From the cutting heat,cutting force,residual stress,the influence of parameters including material hardness distribution,cutting speed,cutting depth,feed speed on cutting performance is studied by single factor analysis method.The cutting mechanism of variable hardness material is revealed.(3)Milling test is carried out on the Cr12 MoV laser cladding parts,and thecutting vibration performance,surface morphology and surface roughness of the substrate area and the cladding area were compared and analyzed.The influence of cutting speed and feed speed on the roughness of substrate area and cladding area is studied.Aiming at the workpiece surface consistency and cutting efficiency,the cutting speed and feed speed are optimized,and the correctness of the optimization results is verified.The research results will provide reference and guidance for the process formulation of remanufacturing machining. |
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