Research On The Simulation Of Forging Process For Oblique Tee Forgings Used In Generator Set

As one connecting part of main steam pipe for generator set,large oblique tee works in the environment of high pressure,high temperature and alternating stress for long time.The capacity of generator set is improving day by day,the temperature and pressure of the environment are increasing,then it comes to high requirements for the combination property of oblique tee.Because the traditional processing for produce oblique tee can not meet the requirements,such as casting then machining or welding,the whole forging process for oblique tee was came up.Based on DEFORM-3D,the related models were built,the upsetting,drawing,outline forming and inner bores forming were simulated to acquire the reasonable parameters.It is essential to providing the theoretical basis to the actual production.The main objective of upsetting and drawing is to get large forging ratio and eliminate some defects of casting.It is important to control the reduction ratio during upsetting,reasonable reduction ratio leads to a three-dimensional compressive stress in center.The field of three-dimensional compressive stress is bigger with bigger reduction ratio when the height-diameter ratio is set.It will cause cracks in center and lateral surface when the reduction ratio is too big.The stress and strain distribution in center affected by tool width ratio and reduction ratio.The size of three-dimensional compressive stress field will increase when the tool width ratio and the reduction ratio is increasing.The strain distribution is inhomogeneous along the center axis when billet is drawing,it looks like the sinusoidal curve.Change the position of the anvil in the next step can improve the strain homogeneity along the center axis.Because of the irregular shape of large oblique tee,it can be produced by free-forging process with V-anvil and wide flat anvil.Compare the strain and stress distribution of different square billet produced by different forging process,an ideal forging process for the square billet forming could be find.The reasonable reduction ratio along the diagonal of the square billet can lead to the regular shape of the both ends of main pipe.More over,It can also lead to the strain stability of the branch and main pipe wall along axis.Because of the deep inner bores and irregularity of oblique tee,only deep hole punching can be used for forming the inner bores.The cylinder of H0/D0=2.5 which can be inscribed in the main pipe of the oblique tee was researched.The minimum d/D was found by researching on the punching load,the maximum d/D was found by researching on the shape change of the cylinder.As the diameter was less than the target size after hole punching,the hole need to be expanded.By analyzing the change of shape,strain distribution and the damage value,It could be found the smaller d/D when punching lead to the smaller shape change and the more stability of strain distribution,but the edge of the holes would craze easier.The results of this simulation can provide the theoretical basis for the process design of large oblique tee,can optimize the experimental parameter,and guide the manufacture of large oblique tee better.