Effect of Post-Weld Heat Treatment on Toughness of Heat-Affected Zone of Grade 91 Steel

B. Silwal, L. Li, A. Deceuster, B. Griffiths

Research output: Contribution to journalArticlepeer-review

108 Scopus citations

Abstract

The impact toughness of the heat-affected zone (HAZ) for Grade 91 steel welds has been experimentally investigated. The as-welded multipass HAZ has a significant scatter in toughness, due to variations in the Charpy notch location and the path of fracture propagation. The cross-weld Charpy specimen gives a toughness value that can be attributed to contributions by the weld metal, various HAZ regions, and the base metal. The microstructure evolution of various HAZ regions during postweld heat treatment (PWHT) has been investigated and used to explain the toughness changes. A 760° for 2 h PWHT can significantly increase the cross-weld toughness of the HAZ. The measured weld HAZ toughness can be understood using a linear additive model that employs as the inputs the toughness values of various HAZ regions reproduced on the Gleeble® The toughness of the coarse-grained heat-affected zone (CGHAZ) recovers the slowest as a function of increasing PWHT temperature, and remains low until a 730° heat treatment. To guarantee an adequate HAZ toughness, a PWHT of at least 730° is recommended. Postweld heat treatment above the A C1perature will result in the formation of fresh martensite, which decreases the toughness and increases the hardness of all HAZ regions. Postweld heat treatment 20° below the AC1 temperature for 2 h has produced the highest toughness and lowest hardness of all HAZ regions.
Original languageAmerican English
JournalWelding Journal
Volume92
StatePublished - Mar 1 2013

Keywords

  • Grade 91 steel
  • Heat-affected zone
  • Post-weld heat
  • Toughness
  • Treatment

DC Disciplines

  • Engineering

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