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Vol.42, No.4, 329 ~ 338, 2004
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| Title |
| Fracture Properties of High-Toughness API X70 Pipeline Steels 3. Inverse Fracture Occurring during Drop-Weight Tear Test |
| 황병철 Hwang Byeong Cheol , 김양곤 Kim Yang Gon , 이성학 Lee Seong Hag , 김낙준 Kim Nag Jun , 유장용 Yu Jang Yong |
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| 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) |
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| Key Words |
| High-toughness pipeline steel, Inverse fracture, Drop-weight tear test, DWTT, API RP 5L3 specification |
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