Effects of finish rolling temperature on inverse fracture occurring during drop weight tear test of API X80 pipeline steels

Hyo Kyung Sung, Seok Su Sohn, Sang Yong Shin, Sunghak Lee, Nack J. Kim, Seung Hwan Chon, Jang Yong Yoo

Research output: Contribution to journalArticle

20 Citations (Scopus)

Abstract

In this study, drop-weight tear tests (DWTT) were conducted on API X80 pipeline steels fabricated with different finish rolling temperatures in order to analyze abnormal fracture appearance, i.e., inverse fracture, occurring in the region impacted by a hammer. Area fractions of fracture modes were measured from fractured DWTT specimens, and the measured data were analyzed in relation to microstructures, DWTT absorbed energy, and strain hardening of the hammer-impacted region. As the finish rolling temperature decreased, the volume fraction of fine-grained acicular ferrite increased, while that of large-grained upper bainite or granular bainite decreased. According to the DWTT results, the absorbed energy tended to increase with increasing volume fraction of acicular ferrite (with decreasing finish rolling temperature). A large area of inverse fracture of cleavage type was found in the hammer-impacted region of the steels fabricated with high finish rolling temperatures, but the area fraction of inverse fracture was reduced in the steels fabricated with low finish rolling temperatures. Since the area fraction of inverse fracture was closely related with strain hardening of the hammer-impacted region, it could be successfully reduced by lowering strain hardening and by promoting the formation of acicular ferrite via low finish rolling temperatures.

Original languageEnglish
Pages (from-to)181-189
Number of pages9
JournalMaterials Science and Engineering A
Volume541
DOIs
Publication statusPublished - 2012 Apr 15
Externally publishedYes

Keywords

  • API X80 pipeline steels
  • Acicular ferrite
  • Drop-weight tear tests
  • Finish rolling temperature
  • Inverse fracture

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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