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Estimation of fracture toughness of X65 and X70 steels by DWTT

X65 및 X70강 가스배관의 DWTT 및 파괴인성평가

  • Cho, Ye-Won (Division of Advanced Materials Engineering, Hanbat National University) ;
  • Song, Young-Ho (Division of Advanced Materials Engineering, Hanbat National University) ;
  • Kim, Jeong-Min (Division of Advanced Materials Engineering, Hanbat National University) ;
  • Kim, Woo-Sik (Korea Gas Corporation) ;
  • Park, Joon-Sik (Division of Advanced Materials Engineering, Hanbat National University)
  • Received : 2012.03.28
  • Accepted : 2012.06.27
  • Published : 2012.06.30

Abstract

DWTT (Drop Weigh Tearing Test) is one critical method that can exhibit the fracture properties of line pipe steel, since it estimates the properties with real pipe steel. In this study, the ductile portion, inverse fracture ratio and absorbed energy of API X65 and X70 line pipe steels were estimated with temperature variation. Both steels showed that the ratio of ductile area and absorbed energy were decreased with respect to decreasing the test temperature. However, while the ductile fracture behavior exhibited until $-40^{\circ}C$ for the X70 steel, but it showed until $-30^{\circ}C$ for the X65 steel. The fracture properties were discussed with respect to test temperatures.

실 배관을 평가하는 DWTT (Drop Weight Tearing Test)의 파괴인성 값은 실 배관의 파괴인성 값 및 연성취성천이 온도를 예측할 수 있는 실험방법이므로, 최근 DWTT의 값에 대한 중요성이 증가되고 있다. 본 연구에서는 API X70과 API X65 라인파이프강의 DWTT 후의 온도에 따른 연성파면율, 역파면율, 흡수에너지와 온도 $-60^{\circ}C$~상온)와의 관계를 비교분석 하고자 하였다. X65과 X70의 값에서 마찬가지로 연성파면율 및 흡수에너지는 온도가 낮아질수록 함께 낮아지는 경향을 보였으며, X70의 경우에는 $-40^{\circ}C$ 까지 연성파괴를 보이는 반면, X65는 $-30^{\circ}C$ 까지 연성파괴를 보였다.

Keywords

References

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