Analytical Approach to Elimination of Surface Micro-Defects in Forging

Initial surface micro-scratches due to cropping, rolling or handling change that cause crack or lap defects during forging and reduce the quality of forged products. Elimination of surface micro-defects in forging is pressing problem in forging industry. A new method of finite element analysis featuring effective meshing and an adaptive remeshing system is applied to clarify the mechanism of the formation or the disappearance of surface micro-defects in forging. V-shaped and rectangular scratches on the surface of billet are simulated under the axisymmetric assumption and the basic deformation of scratch during upsetting and the influence of friction on the deformation of micro-defects are discussed. Shallow V-shaped scratch on the top surface of billet tends to disappear and deep scratch becomes lap defect during upsetting. Defects are more likely to disappear under low friction. It is possible to predict that an initial surface micro-scratch on the billet remain or not as a defect after forging.