Numerical simulation of different types of voids closure in large continuous casting billet during multi-pass stretching process

Large continuous casting billet always contain void defects which may adversely affect the mechanical properties and safe performance of final products. The void must be completely eliminated during hot forging process. In this paper, different types of void defects in large billet are showed and analyzed. It is found that the voids have different geometry, orientations and positions. Using finite element (FE) software DEFORM 3D, a FE model was developed to investigate the void closure in large continuous casting billet during multi-pass stretching process. The wide die heavy blow forging (WHF) method which has been proved to be an effective method to eliminate void defects was adapted during the stretching process. Then, the stretching processes of various sizes of billets which contained different kinds of void defects were simulated. The closure processes of different kinds of void defects were obtained. The critical forging ratio for large billets from Φ500mm to Φ1000mm was obtained as 2.40. In addition, the void closure evaluation index is analyzed, and the critical value for the closure of all voids is 0.87. The work in this paper is verified by actual production, which illustrates that the simulation results and the proposed criterion in this research are reliable.