Numerical Simulation Of Forging Technology Of Ball Valve Core Based On Hollow Billet

As a key component of oil and gas equipment,the valve core of large diameter ball valve has bad working environment,high requirements on product quality and service life,and is traditionally forged from solid billet.The use of hollow billet can realize the short process manufacturing,and can save steel,reduce energy consumption,in line with the national green manufacturing strategy development trend.The research on forging technology of ball valve core with hollow billet has certain theoretical and production guiding significance.Different from the solid billet which can be removed by punching process,the metallurgical defects in the hollow billet cannot be removed and can only be solved by forging process.Therefore,the cavity closure inside the hollow billet has become the focus of industry research.In this paper,the closure of the cavity in the hollow billet is studied by using DEFORM3 D simulation software.Firstly,the material(Q345E steel)model was established,and the V function was obtained by increasing the coefficient k on the basis of the T function criterion of the ratio of volume energy rate to plastic energy rate.Then,the change rule of V function of each point in the upsetting process during the closing process was analyzed.The results show that all parameters have obvious abrupt changes at the moment of cavity closure,and the hydrostatic strain rate representing constant volume is not0.Compared with the traditional criterion of void closure,it is concluded that the V function has obvious salience in the judgment of void closure.The pre-forging process of the hollow billet includes upsetting and drawing.The pre-forging process of the ball valve core is determined by studying the amount of pressure required during the forging of the hollow billet.It is concluded that the combination of upsetting and drawing is more favorable to the closure of defects by using V function to judge the closure of cavities under different forging modes.At the same time,the upsetting process of hollow billet with core shaft is adopted because of the instability in the process of upsetting which will affect the subsequent forging.It can be seen from the simulation results that the critical closure of the void decreases,and the critical pressure reduction required for the closure of the void increases with the increase of the ratio of height to thickness,but the maximum is less than 40%,which provides a reference for the pre-forging process of the ball valve core.Through the research on the whole forging process of ball valve core,it is found that the core structure is improved well after upsetting.At the same time,after the elongation,the whole workpiece is basically recrystallized,the percentage of recrystallization of the whole workpiece is significantly increased,and the grain is obviously refined.The forging process parameters of ring forging were determined by analyzing the forging permeability of ring parts,which indicated that the forging parts had good forging permeability and the whole workpiece was formed well under the calculated technological parameters.