Study on the Microstructure and Mechanical Properties of Submerged Arc Welded X80 Steel

  • Not Applicable

  • Author / Creator
    Zakaria, Syed Md
  • It is difficult to join high strength alloy steel which are produced by thermo mechanical controlled processing and get overmatched properties on the welds and heat affected zone (HAZ) when submerged arc welding (SAW) is used as joining process. Circumferential welds made in the mill to join shorter pipes into longer lengths generally employ SAW as this process offers excellent production rate. In this study two types of X80 steel plates (both 10.22 mm thick) with different carbon contents (0.06 wt% C versus 0.03 wt% C) were used. SAW was used to join the steel plates using varying heat inputs (from 1.5 to 2.25 kJ/mm) by varying the current. Charpy V-notch (CVN) results indicate that the higher carbon steel welds have better HAZ toughness than those with the lower carbon steel at all test temperatures (from 22 to -60ºC). At higher temperatures the mode of fracture was found to be ductile in nature, whereas at lower temperatures (close to -40ºC) both ductile and brittle behaviour were observed. Hardness results indicate that there is initial softening in the fine grain heat affected zone (FGHAZ) regions and hardening occurs predominantly in the coarse grain heat affected zone (CGHAZ) regions. Also, both steels demonstrate comparable results in that hardness in the HAZ decreases as the heat input increases. The transverse weld tensile specimens gave a good indication of ultimate strength; however, the degree of overmatching could not be resolved using transverse weld tensile testing, because of the limitation in measuring tensile properties of smaller individual regions (weld metal, CGHAZ and FGHAZ).

  • Subjects / Keywords
  • Graduation date
    Spring 2012
  • Type of Item
  • Degree
    Master of Science
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.