Shielding gas oxygen equivalent in weld metal microstructure optimization

Journal Article · Mon Jul 01 04:00:00 EDT 1996 · Welding Journal

OSTI ID:276576

Onsoeien, M I ^[1]; Liu, S; Olson, D L ^[2]

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1. SINTEF Materials Technology, Trondheim (Norway)
2. Colorado School of Mines, Golden, CO (United States). Center for Welding and Joining Research

One of the compositional variables that strongly influence low-carbon structural steel weld metal microstructure and mechanical properties is the weld metal oxygen content. As the weld metal oxygen content varies, a change in microstructure occurs. At low concentrations of oxygen, ferrite with aligned or nonaligned second phases may become predominant, slightly higher oxygen levels may result in the formation of the desired acicular ferrite, and further increases in the oxygen content to promote the formation of grain boundary ferrite. The start of austenite decomposition and ferrite nucleation are very sensitive to variations in the amount of oxygen present in the weld metal. Thus, in gas metal arc welding, adjusting the shielding gas oxygen potential provides a means of controlling the weld metal oxygen content. 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 17 different argon-based oxygen and carbon dioxide shielding gas mixtures was used. Complete metallographic and chemical analyses were carried out to evaluate the weld specimens. Sub-size Charpy V-notch toughness testing was performed on selected welds.

• OSTI ID: 276576
• Journal Information: Welding Journal, Journal Name: Welding Journal Journal Issue: 7 Vol. 75; ISSN 0043-2296; ISSN WEJUA3
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CONTROLLED ATMOSPHERES
GAS METAL-ARC WELDING
LOW ALLOY STEELS
MECHANICAL PROPERTIES
MICROSTRUCTURE
PROCESS CONTROL
WELDED JOINTS