Abstract
Influence of plug shape on surface properties of hollow shell and on plug life was investigated on a press roll piercing (PRP) test mill by piercing test billets with artificial defect. Tool shape had an effect on tool life. Plugs with a sharp head (C type) had a poorer life than those with a head of egg bottom shape (N type). Hollow shells pierced by N type plug showed good surface qualities on outer and inner surface. Stable loads in piercing process were observed by using N type plug. However, mandrel thrust load by N type plug was larger than that by sharp head plugs. As far as porosity defects in a CC-billet were concerned, it was observed that the larger the radius of curvature of plug tip became, the more reduction in defects was attained due to forging effect. Additionally, the relationship between metal flow and plug shape in PRP process was explained by experimental results.
