Effect of Stress Field on Closure of Center Defects in Symmetric Rolling and Asymmetric Rolling of Round Billets

Although the closure of defects at the center of billets on rolling such billets is an important subject, a method of quantity evaluation for such closure has not yet been clarified. Therefore, to establish a method for such quantity evaluation, we study such defects using experiments and finite element analysis including asymmetric rolling, especially with respect to the integration of the hydrostatic stress Gm. The results showed that stress was widely distributed, as determined in the experiment and in the FEM analysis of rolling at the edge around an artificial central hole in which defects were simulated. Therefore, it was suggested that, to evaluate the behavior of defect closure, the size of defects and the shape of the grooved roll used should be taken into account. [doi:10.2320/matertrans.P-M2014837]