Abstract
In this study, fracture toughness in the transition temperature region of three API X70 line pipe steels rolled in the two-phase (α + γ) region was analyzed in accordance with the ASTME1921- 05 standard test method. Elastic-plastic cleavage fracture toughness (KJc) was determined by three-point bend tests, using precracked Charpy V-notch specimens, and then the measured KJc values were interpreted by the three-parameter Weibull distribution. The fracture toughness test results indicated that the master curve and the 98 pct con.dence curves explained the variation in the measured fracture toughness values well. Reference temperatures obtained from the fracture toughness tests as well as index temperatures obtained from the Charpy impact tests were lowest in the steel cooled at 500 °C, which did not contain brittle martensite and had a small e.ective grain size. In this steel, the absence of martensite led to the higher resistance to cleavage crack initiation, and the smaller e.ective grain size led to the higher possibility of crack arrest, thereby resulting in the best overall fracture properties.
Original language | English |
---|---|
Pages (from-to) | 1012-1021 |
Number of pages | 10 |
Journal | Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science |
Volume | 38 |
Issue number | 5 |
DOIs | |
State | Published - May 2007 |
Externally published | Yes |
Funding
This work was financially supported by the National Research Laboratory Program of the Ministry of Science and Technology of Korea. The authors thank Professor Nack J. Kim, Dr. Byoungchul Hwang, and Dr. Young Min Kim, POSTECH, for their help with the fracture toughness testing.