Use of active shielding gases to optimize the weld metal microstructure
- SINTEF Materials Technology, Trondheim (Norway)
- Colorado School of Mines, Golden, CO (United States). Center for Welding and Joining Research
The microstructure and properties of a structural steel weld metal are dependent on both its composition and thermal experience. With different welding heat input, preheat, plate thickness, and joint geometry, a given steel can exhibit a variety of different microstructures, from ferrite to martensite. One of the compositional variables that strongly influence steel weld metal microstructure and mechanical properties is the weld metal oxygen content. As the weld metal oxygen content increases, a change in microstructure occurs. At low concentrations of oxygen ferrite with aligned or non-aligned second phases may become predominant; slightly higher oxygen levels may result in the formation of the desired acicular ferrite; and further increase in the oxygen content promotes the formation of grain boundary ferrite. Bead-in-groove gas metal arc welding experiments were performed on HSLA steel coupons using three different welding wires and two heat inputs. A total of seventeen different argon-based shielding gas mixtures were used. Complete metallographic and chemical analyses were carried out to evaluate the weld specimens. A parameter defined as the shielding gas oxygen equivalent was developed in order to express the effects of the shielding gas composition on weld metal chemical composition and microstructure. The results showed that the shielding gas oxygen equivalent strongly influenced the pyrometallurgical reactions that occurred during welding, giving rise to significant changes in weld metal chemical composition, and thus, weld metal microstructure.
- OSTI ID:
- 205440
- Report Number(s):
- CONF-950695-; ISBN 0-7918-1309-6; TRN: IM9615%%220
- Resource Relation:
- Conference: International conference on offshore mechanics and arctic engineering, Copenhagen (Denmark), 18-22 Jun 1995; Other Information: PBD: 1995; Related Information: Is Part Of OMAE 1995 -- Proceedings of the 14. international conference on offshore mechanics and arctic engineering. Volume 3: Materials engineering; Salama, M.M. [ed.] [Conoco, Inc., Ponca City, OK (United States)]; Toyoda, Masao [ed.] [Osaka Univ., Suita, Osaka (Japan)]; Liu, S. [ed.] [Colorado School of Mines, Golden, CO (United States)]; Santos, J.F. dos; Kocak, M. [eds.] [GKSS, Geesthacht (Germany)]; Patterson, E.A. [ed.] [Univ. of Sheffield (United Kingdom)]; Berge, S. [ed.] [Univ. of Trondheim (Norway)]; Stacey, A. [ed.] [Health and Safety Executive, London (United Kingdom). Offshore Safety Div.]; PB: 600 p.
- Country of Publication:
- United States
- Language:
- English
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