Submerged arc welding (SAW) is often the method of choice in pressure vessel fabrication. This process features high production rates, welding energy and/or welding speed and requires minimal operator skill. The selection of appropriate parameters in SAW is essential, not only to optimize the welding process in order to maintain the highest level of productivity, but also to obtain the most desirable mechanical properties of the weld.<p>
The focus of this study was to investigate the effect of welding speed on the properties of SA516 Grade 70. Plates of SA516 Gr. 70 steel 17 mm x 915 mm x 122 mm were submerged arc welded with a welding current of 700 A and welding speeds of 15.3, 12.3 and 9.3 mm/s. Following the welding; strength, microstructure, hardness and impact toughness of the specimens were examined. Charpy impact testing was performed according to ASTM E 23 on specimens notched in the weld metal (WM) and in the heat-affected zone (HAZ), to measure the impact toughness. Fractography was performed on broken specimens using optical and scanning electron microscopy in order to correlate the mechanisms of fracture with the impact toughness values.<p>
The highest hardness values were in the coarse-grained HAZ followed by the WM with the lowest hardness in the parent metal (PM). The HAZ had higher impact toughness than the WM and PM for all welding speeds. The slowest welding speed (9.3 mm/s) obtained complete penetration and therefore produced the most visually sound weld. The fastest welding speed (15.3 mm/s) had the narrowest HAZ and showed good ductile-to-brittle transition behaviour for both the WM and HAZ specimens, but produced incomplete penetration defects. Welding speed had little affect on the notch toughness of the HAZ with only a 9 J rise in upper shelf energy and an 8 °C drop in the impact transition temperature (ITT) with increased welding speed from 9.3 to 15.3 mm/s. However, for the WM, there was a 63 J drop in the upper shelf energy but also a 41 °C improvement of the ITT between the 9.3 and 15.3 mm/s welding speeds.
| Identifer | oai:union.ndltd.org:USASK/oai:usask.ca:etd-01152010-000801 |
| Date | 19 January 2010 |
| Creators | Hall, Alicia M. |
| Contributors | Oguocha, Ikechukwuka, Yannacopoulos, Spiro, Yang, Qiaoqin, Odeshi, Akindele, Sumner, David |
| Publisher | University of Saskatchewan |
| Source Sets | University of Saskatchewan Library |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://library.usask.ca/theses/available/etd-01152010-000801/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Saskatchewan or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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