Oxygen as a welding parameter to fine tune structural steel weld metal microstructures
- Colorado School of Mines, Golden, CO (United States); and others
One of the compositional variables which strongly influences steel weld metal microstructure and properties is the weld metal oxygen content. Increasing the weld metal oxygen concentrations promotes the formation of grain boundary ferrite (GBF). With low oxygen content, intragranular products such as acicular ferrite and ferrite with aligned second phase (FS) may become predominant. Continuous cooling transformation curves of structural steel weld metals show that variations in weld metal oxygen content can alter the onset of austenite decomposition and ferrite nucleation. Gas metal arc welding experiments were carried out using E70S-6, and E70S-7 electrodes with Mn/Si ratios equal to 2, 1.6, and 2.5, respectively. Multiple binary and ternary argon gas mixtures which contained from 1 to 8 vol% O{sub 2}, and from 1 to 25 vol% CO{sub 2} were used in these experiments. The heat inputs ranged from 1.2 to 1.8 kJ/mm. Complete metallographic and chemical analyses were carried out to evaluate the specimens. In this study, the quantitative relationship between weld metal microstructure (light microscopy) and the shielding has oxygen content was determined. The results showed that it is possible to quantitatively predict the extent of changes in shielding has oxygen content to cause a specific microstructural shift. Based on the experimental results, a three-dimensional microstructural map was established to relate microstructure to O{sub 2} and heat input. With known microstructure and heat input, controlled variations in shielding gas oxygen content can shift a microstructure from low AF to high AF to maximize the weld metal microstructure.
- OSTI ID:
- 115487
- Report Number(s):
- CONF-9404233-; TRN: 95:002927-0065
- Resource Relation:
- Conference: 75. American Welding Society (AWS) annual meeting, Philadelphia, PA (United States), 10-15 Apr 1994; Other Information: PBD: 1994; Related Information: Is Part Of 75th Diamond anniversary American Welding Society annual meeting; PB: 273 p.
- Country of Publication:
- United States
- Language:
- English
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