중공 튜브 성형을 위한 만네스만 천공기의 개발 및 유한요소법을 이용한 공정변수 설계

Development of Rotary Tube Piercing Machine and Parametric Study on Design Variables using Finite Element Analysis

Typical seamless tube production methods are an extrusion and a rotary tube piercing. The rotary piercing process is more competitive than the extrusion process form view point of productivity, quality, and flexibility. It consists of twin rolling mills, a pair of disc or flat guides, and a plug. Twin rolling mills are skewed with proper angles in two directions. A round billet is progressively fed forward and rotated due to the rotation of twin rolling mills. Internal crack initiation and growth at central area of the billet are gradually progress because of the repeating actions of tension and rotation. Design variables in the rotary piercing rolling process are the feed angle, the cross angle, the reduction ratio, and the position of plug. In this work, a rotary tube piercing machine was developed and parametric studies on design variables were carried out using finite element analysis. The Brozzo ductile fracture criterion was utilized to determine an internal crack initiation.