Effect Of Microstructure On Mechanical And Fine-blanking Properties Of Carbon Steels

Fine-blanking is a precise forming technique that can produce highquality components with accurate size and clear blanking surface.In the fine-blanking process,material has a crucial influence on the blanking quality.Up to now,the research works on fine-blanking are mainly based on experimental work or macro scale fine-blanking simulation according to material's macro properties.The research is still rare on studying the effect of microstructure on fine-blanking property from micro scale.In the present work,both macro and micro scale models are generated by representative volume element(RVE)approach.A macro-micro multiscale simulation is employed to explore the microstructural effect on material's mechanical and fine-blanking properties with related fineblanking tests.The content and conclusions are shown as follows:1)Macro and micro scale models are generated by RVE approach based on the typical microstructure of carbon steels for fine-blanking.The models can simulate the microstructure features such as cementite size,fraction,carbide banding in cold rolled spheroidizing annealed steels and pearlite in hot rolled steels.2)The effect of microstructure features on material's macro mechanical property is studied from micro scale with the tension and shear load on RVE models of spheroidized carbon steel.The “GND” layer is introduced into the interface to simulation the dislocation accumulation and particle decohesion at interface.The results show that the damage of material begins earlier with increased particle size and fraction as well as the existence of carbide banding.Under the shear load,the crack path is parallel to the shear direction and results in smooth fracture surface.While the crack path will be changed by carbide banding,the fracture surface is then unsmooth.3)The effect of material and blanking clearance is studied by real fineblanking test as well as macro scale simulation on various C15 E and 42CrMo4 sheets with different microstructures.When blanking clearance is increased,the blanking quality will be deteriorated and the fracture band fraction goes up.In addition,when severe carbide banding or large-sized pearlite remain in microstructure,the fine-blanking teeth may be torn.4)The microstructure deforming behavior in fine-blanking process is realized with meso scale RVE submodels that are incorporated into the center of the fine-blanking shear zone.The results show that when the particle fraction increases or carbide banding exists in submodels,the damage of material will be accelerated.And cracks will appear along the severe carbide banding zone.If there are lamellar pearlites in microstructure,they will be extended along the shear direction and cut down into small pieces.From the SEM observation of microstructure in the shear zone,the simulation results are substantiated.