1984 Volume 70 Issue 2 Pages 224-231
Plug life of PRP (Press Roll Piercer) process, in which a square bloom is directly pierced and rolled simultaneously, is strongly affected by its own shape. A plug with a sharp conical top thrusts through the solid material to get galled in the earlier stage by metal flow on its surface. On the other hand, a plug with dull top or a flat top has a longer life, since it is protected by dead metal induced in front.
As for plug material, conventional tool steel for hot metal forming is durable enough, only if surface scale layer is formed before use. The product quality is also influenced by plug shape. Especially dull one is advantageous.