Currently, the demand for natural gas is increasing as a result of high world energy consumption and rising environmental awareness. As the exploration of natural gas field is expanding towards remote regions, long distance pipelines have been developed. The economical, environmental, and safe movement of gas to the marketplace requires that transmission pipelines designed to operate at high pressure should possess adequate strength and improved toughness over a variety of temperature ranges.
The purpose of this research was to investigate the effect of submerged arc welding (SAW) parameters on the quality and mechanical properties of X80 steel, which was supplied by IPSCO Inc., Regina. The welding was performed using single and double wires and different speeds (16.93, 19.69, 25.4, 29.63 and 33.87mm/s). The weld quality was evaluated using non-destructive testing methods (NDT) such as visual inspection, radiography, and ultrasonic test. The weld bead characteristics were studied using weld geometry measurements. The relationship between the microstructures and mechanical properties of weld deposits was studied by means of hardness measurements, Charpy V-notch test, lateral expansion measurements, tensile test, optical metallography, image analysis, scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDS).<p>It was found that there was a limit to which welding speed could be increased without the weld suffering from severe defects such as lack of penetration and undercut. The use of more than one welding wire improved the maximum welding speed at which good weld quality was maintained. Increasing the welding speed resulted in changes in the weld microstructure through the formation of higher percentage of fine acicular ferrite (AF) grain structure and a reduction in the amount of grain boundary ferrite (GBF) in the weld metal. Changing weld speed also reduced the size of the heat affected zone (HAZ). All of this resulted in improved the mechanical properties of the welded joints.
| Identifer | oai:union.ndltd.org:USASK/oai:usask.ca:etd-08312007-140407 |
| Date | 11 September 2007 |
| Creators | Farhat, Hanan Alsharef |
| Contributors | Yannacopoulos, Spiro, Yang, Qiaoqin, Oguocha, Ikechukwuka N., Hertz, P. Barry, Dolovich, Allan T. |
| 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-08312007-140407/ |
| 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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