Influence of welding heat input on notch ductility of microalloyed high strength steels for use offshore
- Cranfield Inst. of Tech. (United Kingdom)
A number of high strength microalloyed steels with yield strengths of 500--560 MPa were welded using submerged arc welding at heat inputs in the range 1.5--6kJ/mm and thicknesses ranging from 25mm to 60mm. The coarse HAZ region of each weld was tested using Charpy V notch specimens to determine its notch ductility. The test program was supplemented by an extensive post-test metallographic assessment program to correlate microstructural features with either enhanced or reduced performance. Although in general the heat affected zone ductility decreased as the welding heat input increased, the extent of the decrease varied considerably with steel type and composition. Some steels retained excellent notch ductility even after welding at high heat inputs such as 6kJ/mm whereas others could not be recommended for use at heat inputs above 1.5/J/mm. The greatest reduction in notch ductility took place in the coarse grained HAZ region adjacent to the fusion line. Microstructures containing large quantities of M-A particles were found to have very low notch ductility. The highest notch ductility performance was associated with the formation of a finite bainitic subgrain size which did not necessarily correlate with a fine prior retained austenite grain size. The brittle subcritically reheated or intercritically reheated coarse grained regions exerted a greater influence on resulting notch ductility than the supercritically reheated much tougher finer grained HAZ regions. It`s considered more important to attempt to reduce the grain size din the brittle regions than to attempt to further reduce the grain size in the tougher regions. The results from this work demonstrate that certain types of high strength steel have great potential for use in offshore construction. They retain their excellent notch ductility even after high (6kJ/mm) heat input welding which means that in addition to their weight saving advantages, they also offer benefits in welding fabrication economics.
- OSTI ID:
- 33204
- Report Number(s):
- CONF-930641-; ISBN 0-7918-0785-1; TRN: IM9518%%25
- Resource Relation:
- Conference: OMAE `93: 12th international conference on offshore mechanics and arctic engineering, Glasgow (United Kingdom), 20-24 Jun 1993; Other Information: PBD: 1993; Related Information: Is Part Of OMAE 1993: Volume 3, Part A -- Materials engineering; Salama, M.M.; Toyoda, Masao; Liu, S.; Dos Santos, J.F.; Kocak, M.; Williams, J. [eds.]; PB: 434 p.
- Country of Publication:
- United States
- Language:
- English
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