Ultrasonic Evaluation of Microstructure in Pipe Steels

• Author / Creator

  Kennedy, Jacob R

• Traditionally in pipeline steels and welds, ultrasonic testing (UT) has been used for crack and/or flaw detection. The work presented in this Thesis explores the use of this technique to characterize the microstructure of pipe steels. Ultrasonic velocity calculations, for shear and longitudinal waves, done with the stiffness tensor of a 1050 steel showed that shear velocity exhibits a greater difference between structures such as ferrite, mixed ferrite-pearlite, and martensite, than longitudinal velocity. Experiments were carried out, through thickness skelp investigation of L80 and X70 steels, annealing of interstitial free steel and structure variation in L80, 4130 and 5160. The ultrasonic velocity and attenuation of shear and longitudinal waves were measured through the thickness of L80 and X70 pipe skelps and did not vary significantly. XRD was performed through the thickness as well. Interstitial free steel was ultrasonically tested at room temperature after different annealing times. Both shear and longitudinal ultrasonic velocity changed as recrystallization progressed, while attenuation changed during grain growth. Structure variations after heat treatment in L80, 4130 and 5160 all showed a decrease in ultrasonic shear wave velocity in martensite when compared with mixed structure of ferrite and pearlite, confirming the velocity calculation results. The longitudinal velocity did not vary with structure. The attenuation of both shear and longitudinal waves also decreased in martensite compared with mixed ferrite-pearlite. Both shear and longitudinal ultrasonic waves had properties which varied with different structural properties and had the potential to be useful tools in microstructural characterization. The ultrasonic shear velocity showed a decrease from ferrite-pearlite (3268 m/s) to martensite (3207 m/s) as did the longitudinal attenuation (0.25 dB/mm for ferrite-pearlite and 0.17 dB/mm for martensite)

• Subjects / Keywords

  • L80
  • Pipe
  • Steel
  • Microalloyed steel
  • Ultrasonic
  • X70

• Graduation date

  Spring 2015

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3N08S

• 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.