Toughness of CG HAZs of welds in Q T steels
- Univ. of Coimbra (Portugal). Faculty of Science and Technology
- Univ. of Porto (Portugal). Faculty of Engineering
Heat-affected zones of steel welded joints show a gradient of microstructures from the fusion line to the unaffected base metal, which makes the evaluation of notch toughness by COD testing difficult, since crack front samples show different types of microstructure. The region of low toughness may be completely missed and misleading results can be obtained. A buttering technique can be used to produce a relatively straight fusion line, thereby simplifying the COD fatigue notch location. This technique was used to produce specimens with variable amounts of coarse grain heat-affected zone (CGHAZ) in quenched and tempered (Q T) steel welded joints and to study the influence of heat input. Weld thermal simulation was used to establish a relationship between microstructure and toughness. The increase of heat input increased the phase transformation temperatures and the volume fraction of coarse upper bainite instead of lower bainite and low-carbon martensite in welds and simulated specimens. These phase transformations were accompanied by a drastic reduction of hardness and notch toughness in CGHAZ with increasing heat input, which was attributed to changes in the microstructure. The results also show that HAZ toughness tends to decrease with an increase in the proportion of brittle zone sampled by the COD test.
- OSTI ID:
- 6987411
- Journal Information:
- Welding Journal (Miami); (United States), Journal Name: Welding Journal (Miami); (United States) Vol. 73:9; ISSN 0043-2296; ISSN WEJUA3
- Country of Publication:
- United States
- Language:
- English
Similar Records
HAZ fracture properties of Ti-microalloyed offshore steel in as-welded and simulated condition
Fracture characteristics of HAZ-double edge notched weld joints with mechanical undermatching