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Vol.41, No.5, 279 ~ 288, 2003
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| Title |
| Analysis of Abnormal Fracture Appearance in Drop-Weight Tear Test of a High-Toughness Line-Pipe Steel |
| 황병철 Byoung Chul Hwang , 이성학 Sung Hak Lee , 김영민 Young Min Kim , 김낙준 Nack J Kim , 유장용 Jang Yong Yoo , 우종수 Chong Soo Woo |
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| Abstract |
| In this study, various types of drop-weight tear test (DWTT) were conducted on a high-toughness line-pipe steel in order to investigate abnormal fracture appearance occurring in the region impacted by a hammer. A pressed notch or a chevron notch was introduced into DWTT specimens, some of which had a back slot designed to decrease the inverse fracture area. After the DWTT, percent shear area, 85% shear appearance transition temperature, area of inverse fracture surface, hardness and work hardening exponent of the hammer-impacted region were measured. The results indicated that the shear area of the pressed notch DWTT specimens was larger than that of chevron notch DWTT specimens. In the hammer-impacted region of all the DWTT specimens, abnormal inverse fracture having a cleavage fracture mode appeared, and its area fraction was correlated well with Vickers hardness and work hardening exponent(n) measured by an indentation test. The formation of this inverse cleavage fracture raised the fracture propagation transition temperature by decreasing the shear area measured in accordance of the API 5L3 specification, which was confirmed by relating to the Charpy V-notch test data of pre-strained steel specimens. |
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| Key Words |
| High-toughness pipeline steel, Abnormal fracture appearance, Drop-weight tear test, DWTT, API 5L3 specification, Acicular ferrite |
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