전${\cdot}$후방 압출 제품의 유동 결함에 관한 연구

The study on the flow defect of cold combined forward-backward extrusion product

This paper presents a study of cold combined forward-backward extrusion product. The case of product with thin wall in piercing process occur defects of deformation and breakdown during piercing process and the center web of product with thin thickness cause flow defect. Such defect is made by the difference of material flow. Methods of the material flow control in the two directions and forming process to remove this flow defect is proposed. The effectiveness of the proposed methods is examined by comparison experiment and finite element simulation.