고인성 API X70 라인파이프강의 파괴특성 : Ⅲ. Drop-Weight Tear Test 시 발생되는 역파면에 대한 연구 Ⅲ. Inverse Fracture Occurring during Drop-Weight Tear Test = Fracture Properties of High-Toughness API X70 Pipeline Steels

다국어 초록 (Multilingual Abstract)

This study is concerned with the effects of microstructure on inverse fracture in the hammer-impacted region during drop-weight tear test(DWTT) of three high-toughness API X70 pipeline steels. Pressed notch or Chevron notch DWTT and Charpy V-notch impact test were conducted on the rolled steel specimens, and the results were discussed in comparison with the data obtained from tensile and Charpy impact tests of pre-strained specimens. In the hammer-impacted region of the DWTT specimens, cleavage-type inverse fracture appeared, and its fracture area was correlated well with upper shelf energy (USE) obtained from the Charpy impact test and with microstructure. The steel specimens having higher USE or having coarse polygonal ferrite had the larger inverse fracture area than those having lower USE or having fine acicular ferrite because of the larger compressive pre-strain induced by work hardening of the hammer-impacted region. These results were confirmed by relating to the Charpy impact test data of pre-strained steel specimens.
(Received January 19, 2004)