The Hole Evolution Behavior During Hot Rolling Of Casting GCr15 Ring

Ring type parts are widely used in the manufacturing areas and industrial fields,and the forming and manufacturing of it plays a very essential role in the equipment's operating life,reliability and stability.Ring type parts often use hot rolling technology to process.Hot ring rolling is an advanced seamless ring parts rotary plastic forming process.Hot ring rolling of as-cast ring blank is a ring using cast billet hot rolling forming process of a short-ring forming new technology.However,the casting ring often exists slag,shrinkage defects,which affect the quality of the final ring.Therefore it is essential to eliminate and control hole defects during the hot ring rolling process.Based on the theory of plastic mechanics,damage mechanics and the theory knowledge of ring rolling,through the simulation and experimental validation,the theoretical analysis and numerical fitting,the hole evolution behavior of GCr15 cast ring in the hot rolling process of evolution has been studied,which providing some reference for thermal rolling process to eliminate and control hole defects.In this paper,firstly,based on Abaqus platform,GCr15 casting ring hole hot rolling three-dimensional thermal coupling model had been established.The hole geometrical morphology and its impact area deformation state in hot rolling process had been studied.It is find that the the hole change from circular to elliptic,advanced and abnormal change and ultimately closed.The degree of closure and the equivalent plastic strain step change.The triaxial stress degree almost periodic changes.Subsequently,by the single variable method and a plurality of finite element simulation,the influence factors that the hole geometry and position such as the round hole size,hole location in the ring,the ratio of the major axis than the minor axis in the oval-shaped holes and the orientation of oval-shaped holes which affecting GCr15 cast ring hole defects evolution are studied.Then,the influence factors that the main hot rolling process parameters(driven roller speed,feed rate,friction coefficient and temperature)are studied,too.First of all,the smaller the hole diameter,length of axis ratio,the orientation and the distance within the inner and outer ring,the smaller the closure time and the equivalent plastic strain.Secondly,the influence of the main hot rolling process is small.In GCr15 as-cast ring blank setting different sizes,different positions,different depth of holes,GCr15 casting ring hole hot rolling experiments had been conducted in the model HRM350 vertical CNC hot ring rolling machine,through different deformation and different driven roller feeding speed,different initial temperature.The hole size had been measured and compared to simulation,the reliability of the simulation model had been confirmed by the hot rolling experiment.According to the reverse thinking and hot rolling ring process basic deformation law,the hole evolution behavior in the hot rolling process can be simplified as the asynchronous rolling and multichannel time characteristic of the rolling process.According to the mechanical damage relations between far-field stresses and microstructure within the material,the average rate of change of spherical void volume formula had been deduced.the analytical formulas between far-field stress and internal holes evolution is deduced.Based on the simulated data,the relation between the finally long axis length of hole and rolling deformation curve with the void evolution impact factors had been fitted.