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      • HARVEST
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      Effects of multiple wires and welding speed on the microstructures and properties of submerged arc welded X80 steel

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      Date
      2007-09-11
      Author
      Farhat, Hanan Alsharef
      Type
      Thesis
      Degree Level
      Masters
      Metadata
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      Abstract
      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).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.
      Degree
      Master of Science (M.Sc.)
      Department
      Mechanical Engineering
      Program
      Mechanical Engineering
      Supervisor
      Yannacopoulos, Spiro; Oguocha, Ikechukwuka N.
      Committee
      Yang, Qiaoqin; Hertz, P. Barry; Dolovich, Allan T.
      Copyright Date
      September 2007
      URI
      http://hdl.handle.net/10388/etd-08312007-140407
      Subject
      SAW
      HSLA
      Speed
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      • Graduate Theses and Dissertations
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