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Vol.43, No.6, 424 ~ 433, 2005
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| Title |
| Mechanical Behavior : Analysis of Fracture Toughness in Transition Temperature Region of Two API X70 Pipeline Steels |
| 신상용 Sang Yong Shin , 황병철 Byoung Chul Hwang , 김상호 Sang Ho Kim , 이성학 Sung Hak Lee |
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| Abstract |
| This study is concerned with the analysis of fracture toughness in the transition temperature region of API X70 pipeline steels according to ASTM E1921 standard test method. Two kinds of steels were fabricated by varying finish rolling temperatures, and their microstructures and mechanical properties were examined. Elastic-plastic cleavage fracture toughness, Kjc was determined by 3-point bend tests, using precracked Charpy V-notch (PCVN) specimens, and then the measured Kjc values were interpreted by the 3-parameter Weibull distribution. Relationship between Jc, critical distance, reference temperature in the transition region, and plane strain fracture toughness were discussed on the basis of the cleavage fracture behavior in the transition temperature region. Fractographic observation indicated that the critical distance from a precrack tip to a cleavage initiation site linearly increased with increasing the critical J (Jc) value. The steel rolled in the single phase region had lower plane strain fracture toughness and higher reference temperature than that rolled in the two phase region because of the higher volume fraction of martensite-austenite constituents and the larger effective grain size. |
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| Key Words |
| API X70 pipeline steel, ASTM E1921 standard test method, Elastic-plastic cleavage fracture toughness, Weibull distribution |
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