NDLI: The Effect of Inclusions on the Fracture Toughness of Local Brittle Zones in the HAZ of Girth Welded Line Pipe

Content Provider	The American Society of Mechanical Engineers (ASME) Digital Collection
Author	Moore, Philippa Nicholas, Joanna
Copyright Year	2013
Abstract	A programme of testing and research has been carried out to deliberately identify the causes of, and measure the fracture toughness of, potential local brittle zones (LBZs) in the heat affected zone (HAZ) of girth welds in a 20mm thick API 5L X70 grade pipe. This involved determining the most susceptible test temperature and notch location within the HAZ of two different welds by Charpy testing to define the T40J. Subsequent fracture toughness testing of a large set of fracture mechanics specimens notched into this region and tested at a low temperature based on T40J was able to achieve occasional low fracture toughness results. Post-test metallography identified that the inclusions in the parent metal affected the risk of brittle fracture initiation in two ways; firstly large and clustered inclusions acted as local brittle zones and/or fracture initiation sites; secondly, the large inclusions had reduced the effect of grain boundary pinning, as would be expected from well-dispersed smaller inclusions. This then resulted in significant grain coarsening in the HAZ fusion line, which could also act as a low toughness fracture initiation region. The inclusion types were chemically analysed, and recommendations were made to the steel producer in order to further improve the fracture toughness of the X70 pipe at increasingly lower temperatures.
Sponsorship	Ocean, Offshore and Arctic Engineering Division
File Format	PDF
ISBN	9780791855355
DOI	10.1115/OMAE2013-10729
Volume Number	Volume 3: Materials Technology; Ocean Space Utilization
Conference Proceedings	ASME 2013 32nd International Conference on Ocean, Offshore and Arctic Engineering
Language	English
Publisher Date	2013-06-09
Publisher Place	Nantes, France
Access Restriction	Subscribed
Subject Keyword	Grain boundaries American petroleum institute Temperature Fracture mechanics Brittle fracture Metals Metallography Risk Fracture (materials) Brittleness Steel Fracture toughness Fracture (process) Welded joints Heat Pipes Testing Low temperature
Content Type	Text
Resource Type	Article

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