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Study on Fracture Behavior of Mild Steel Under Cryogenic Condition

연강(Mild Steel)의 극저온 파괴 거동에 대한 실험적 연구

Choi, Sung Woong;Lee, Woo IL
최성웅;이우일

  • Received : 2015.08.21
  • Accepted : 2015.12.09
  • Published : 2015.12.31

Abstract

Considering for plants and structure under extreme conditions is required for the successful design, especially temperature and pressure. The ductile-brittle transition temperature (DBTT) for the materials under extreme condition needs to be considered. In this study, A-grade mild steel for the LNG carrier and offshore plant was examined by performing low-temperature Charpy V-notch (CVN) impact tests to investigate DBTT and the fracture toughness. The absorbed energy decreased gradually with the experimental temperature, which showed an upper-shelf energy region, lower shelf energy region, and transition temperature indicating DBTT. In addition, the fracture surface morphologies of the mild steels indicated ductile fractures at the upper-shelf energy level, with wide and large-sized dimples, whereas a brittle fracture surface, where was observed at the lower-shelf energy level, with both large and small cleavage facets. Based on the experimental results, ductile brittle transition temperature was estimated in about $-60^{\circ}C$.

Keywords

A-grade mild steel;CVN;DBTT;Ductile fracture;Brittle fracture

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