Finite-Element Analysis of Cylindrical-Void Closure by Flat-Die Forging

Voids in a bloom produced by continuous casting are cylindrical in shape and located along the longitudinal direction. In the present study, the closure phenomenon of these voids by flat-die forging was investigated by the rigid-plastic finite-element analysis and experiments using plasticine specimens. The void closure was found to progress through contraction followed by collapse, and to be completed as the effective strain at the location of the void reached a certain value. The value was found to be dependent on the aspect ratio of the cross section of a void, but not on the size of the void. The relationship between the effective strain and the aspect ratio was established by which the closure of such a void with any aspect ratio can be predicted in terms of the effective strain in uniaxial forging. Compared to biaxial forging, uniaxial forging was found to be far more effective for the void closure in a bloom.