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A Comparative Analysis on Microstructure and Fracture Mechanism of X100 Pipeline Steel CGHAZ Between Laser Welding and Arc Welding

  • Xiaonan Qi
  • Hongshuang DiEmail author
  • Qian Sun
  • Xiaonan WangEmail author
  • Xiaming Chen
  • Yuan Gao
  • Zhenguang Liu
Article
  • 22 Downloads

Abstract

The objective of this study is to compare and contrast the differences in microstructure and fracture mechanism between CGHAZ of laser welding and submerged arc welding in X100 pipeline steel. The single-pass welding thermal simulation test of laser welding and submerged arc welding was carried out in MMS-200 thermal simulation test machine using self-made fixtures. The results indicated that the microstructure of laser welding CGHAZ and submerged arc welding CGHAZ was lath martensite and granular bainite, respectively. The impact energy of laser welding CGHAZ was 27 J, and the fracture mode was ductile fracture; the impact energy of submerged arc welding CGHAZ was 7.7 J, and the fracture mode was brittle fracture. The nucleation and propagation mechanism of cracks in different welding modes was established. Microcracks nucleated at the position of dislocation accumulation and remained austenite suppressed crack nucleation in laser welding CGHAZ. The nucleation site was at the M–A constituents in submerged arc welding CGHAZ. The main crack of laser welding CGHAZ was formed by one or a small number of microcracks. The main crack in submerged arc welding CGHAZ was formed by a large number of microcracks. The difference between crack nucleation and propagation mechanism is the reason why the impact energy of laser welding CGHAZ is higher than of submerged arc welding CGHAZ.

Keywords

fracture mechanism microstructure pipeline steel toughness welding thermal simulation 

Notes

Acknowledgments

This research was supported by the Natural Science Foundation of China (51775102). Professor R. D. K. Misra acknowledges continued collaboration with the Northeastern University by providing guidance in language as an honorary professor.

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Copyright information

© ASM International 2019

Authors and Affiliations

  1. 1.The State Key Laboratory of Rolling and Automation of Northeastern UniversityShenyangChina
  2. 2.School of Iron and SteelSoochow UniversitySuzhouChina
  3. 3.School of Materials Science and EngineeringJiangsu University of Science and TechnologyZhenjiangChina

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