Metallurgical and Materials Transactions A

, Volume 36, Issue 7, pp 1793–1805 | Cite as

Correlation of rolling condition, microstructure, and low-temperature toughness of X70 pipeline steels

  • Byoungchul Hwang
  • Young Min Kim
  • Sunghak Lee
  • Nack J. Kim
  • Jang Yong Yoo


Correlation of rolling conditions, microstructure, and low-temperature toughness of high-toughness X70 pipeline steels was investigated in this study. Twelve kinds of steel specimens were fabricated by vacuum-induction melting and hot rolling, and their microstructures were varied by rolling conditions. Charpy V-notch (CVN) impact test and drop-weight tear test (DWTT) were conducted on the rolled steel specimens in order to analyze low-temperature fracture properties. Charpy impact test results indicated that the energy transition temperature (ETT) was below −100 °C when the finish cooling temperature range was 350 °C to 500 °C, showing excellent low-temperature toughness. The ETT increased because of the formation of bainitic ferrite and martensite at low finish cooling temperatures and because of the increase in effective grain size due to the formation of coarse ferrites at high finish cooling temperatures. Most of the specimens also showed excellent DWTT properties as the percent shear area well exceeded 85 pct, irrespective of finish rolling temperatures or finish cooling temperatures, although a large amount of inverse fracture occurred at some finish cooling temperatures.


Acicular Ferrite Pipeline Steel Bainitic Ferrite Polygonal Ferrite Retain Austenite 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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Copyright information

© ASM International & TMS-The Minerals, Metals and Materials Society 2005

Authors and Affiliations

  • Byoungchul Hwang
    • 1
  • Young Min Kim
    • 1
  • Sunghak Lee
    • 1
    • 2
  • Nack J. Kim
    • 1
    • 2
  • Jang Yong Yoo
    • 3
  1. 1.the Center for Advanced Aerospace MaterialsPohang University of Science and TechnologyPohangKorea
  2. 2.Materials Science and EngineeringPohang University of Science and TechnologyKorea
  3. 3.the Plate Research GroupTechnical Research Laboratories, POSCOPohangKorea

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