Effect of current pulsing on super 304HCu weld joints
ISSN: 1708-5284
Article publication date: 18 November 2019
Issue publication date: 20 November 2019
Abstract
Purpose
Super 304HCu super austenitic stainless steel tubes containing 2.3 to 3 (Wt.%) of copper (Cu) is used in superheaters and reheater tubings of nuclear power plants. In general, austenitic stainless steels welded by conventional constant current gas tungsten arc welding (CC-GTAW) produce coarse columnar grains, alloy segregation and may result in inferior mechanical properties. Pulsed current gas tungsten arc welding (PC-GTAW) can control the solidification structure by altering the prevailing thermal gradients in the weld pool.
Design/methodology/approach
Super 304HCu tubes of Ø 57.1 mm and the wall thickness of 3.5 mm were autogenously welded using CC and PC-GTAW processes. Joints are characterized using optical microscopy, electron microscopy, energy dispersive spectroscopy and electron backscatter diffraction (EBSD) techniques. Hot tensile properties of the weld joints were evaluated and correlated with their microstructural features.
Findings
Current pulsing in GTAW has resulted in minimal eutectic film segregation, lower volume % of delta ferrite and appreciable improvement in tensile properties than CC-GTAW joints.
Originality/value
The EBSD boundary map and inverse pole orientation map of Super 304HCu weld joints evidence the grain refinement and much frequent high angle grain boundaries achieved using weld current pulsing.
Keywords
Acknowledgements
The authors wish to express their sincere thanks to M/s Mailam India Ltd, Pondicherry, India for their financial assistance to carry out this research work through the Mailam India Research (MIR) Fellowship, M/s Salzgitter Mannesmann Stainless Tubes Italia Srl, Italy for supplying the Super 304HCu tubes required to carry out this work, The Director, Naval Materials Research Laboratory, Ambernath, Mumbai for providing the facility to carry out hot tensile testing and Dr. A. K. Lakshminarayanan, Associate Professor, SSN College of Engineering, Chennai for his help rendered in image analysis.
Citation
M., V.K. and V., B. (2019), "Effect of current pulsing on super 304HCu weld joints", World Journal of Engineering, Vol. 16 No. 6, pp. 814-822. https://doi.org/10.1108/WJE-07-2019-0207
Publisher
:Emerald Publishing Limited
Copyright © 2019, Emerald Publishing Limited