필거다이 수명향상을 위한 재연삭 다이 특성 평가

The property of zirconium alloy tube is well known to be influenced by pilgering and its tooling; thus the control of its microstructure and mechanical property in the final tube product for nuclear fuel applications is a major concern of tube manufacture. It is obvious that the cold pilgering process is one of the key processes controlling the quality and the characteristics of the tubes manufactured, i.e. nuclear zirconium alloy tube in KEPCO NF. Cold pilgering is a rolling process for forming metal tubes in which diameter and wall thickness are reduced in a number of forming steps, using ring dies at outside of the tube and a curved mandrel at inside to reduce tube cross sections by up to 90 percent［1］. The OD size of tube is reduced by a pair of dies, and ID size and wall thickness is controlled simultaneously by mandrel During the cold pilgering process, both tools are the critical components for providing qualified tube. The Development of our own pilger die and mandrel has been a significantly important in the zirconium tube manufacturing and a major goal of KEPCO NF. The objective of this study is to evaluate the life time of reground pilger die for increasing life time of virgin pilger die through several times of regrinding. Therefore, the comparison of the slip factor and mechanical properties of pilger die made of AISI 52100 material was made in this study.