Reshearch On The Grain Refinement And Work Hardening Of Cold Roll-beating

Cold roll-beating is a new type of green forming method,which has the advantages of low forming cost,high quality of parts,high material utilization rate,etc.It has wide application prospects in aerospace,transportation,equipment manufacturing and other industrial fields.During the cold roll-beating process,plastic deformation,dislocation proliferation and grain boundary deformation will occur in the crystal inside the material,which directly affects the macro mechanical properties of the final formed part.Based on the theory of crystal plasticity and the characteristics of the cold roll-beating process,this paper studies the law of grain deformation and work hardening of shaped parts,aiming to reveal the establishment of a quantitative relationship between the grain deformation and work hardening.According to the metal plasticity theory,analyze the plastic deformation and work hardening mechanism of the material crystal in cold roll-beating;based on DEFORM-3D,the finite element model of the cold roll-beating process at the macro and meso scales is established,and the material in the forming process is analyzed flow transfer law;through the finite element simulation of the material grain size change of the cold roll-beating process,the grain change process and evolution law of different forming regions of the shaped part are obtained;cold roll-beating experiments were carried out to analyze the metal flow and metallurgical structure deformation characteristics of the formed parts.Through the measurement and analysis of the grain size in different forming areas,the correctness of the finite element model and its analysis results were verified.Through the metallographic micro system and micro hardness analysis technology,the work hardening behavior of the cold roll-beating process was studied.The metallographic structure changes and flow characteristics in different areas of the shaped part are analyzed,and the distribution rule of the grain size of the shaped part along the tooth surface is obtained.Based on this,the surface hardening law of the formed parts under different process conditions was studied,and the distribution characteristics and change rules of the surface hardening degree,depth of hardening of the cold roll-beating parts,tooth top,tooth surface and tooth bottom different areas were obtained.The Hall-Petch relationship and prediction model between the grain size of the formed parts and the work hardening are established,and the prediction results are in good agreement with the experimental results.