| About this Abstract |
| Meeting |
2023 AWS Professional Program
|
| Symposium
|
2023 AWS Professional Program
|
| Presentation Title |
Correlation Between the Coarse and Fine Grain Haz Hardness of Pipeline Girth Welds |
| Author(s) |
Alejandro Hintze Cesaro, Greg Lehnhoff, Eric Willet |
| On-Site Speaker (Planned) |
Alejandro Hintze Cesaro |
| Abstract Scope |
Analysis of recent pipeline girth weld failures, occurring predominantly in X70 pipeline girth welds using
shielded metal arc welding (SMAW), has identified the weld heat affected zone (HAZ) softening as a possible
contributing factor as it relates to low tensile strain capacity and strain localization at the girth welds. The
authors suggest that some of the current recommended practices to mitigate the softening of the HAZ can
exacerbate the maximum CGHAZ hardness, and that a deeper understanding of the relationship between
hard and soft HAZs may aid in the development of strategies and welding practices to mitigate both
challenges.
This work analyzes the HAZ properties through hardness maps of different pipeline steels with different
chemical composition and wall thickness, welded with different arc weld processes. For each weld, the
cross sectional specimen was vertically divided into different regions representing the cap, fill and hot &
root passes. Hardness values of the CGHAZ and softened zones were estimated for each pass and analyzed
with respect of the steel properties and welding parameters.
The study revealed that there is a strong linear correlation between the hard and soft regions of the HAZ
within a weld pass independent of the chemistry (Pcm) and the welding parameters used. The
microstructures in the hard and soft zones are used to rationalize this correlation. The hardness results also
corroborate that there is an effect of subsequent welding passes on the final hardness of the HAZ of previous
passes.
The combined hard and soft HAZ responses are also evaluated relative to pipeline industry standards and
recommended practices that place limits on the minimum and maximum hardness in the HAZ. The study
illustrated that efforts to improve local strain capacity by controlling HAZ softening should be studied in
tandem with efforts to improve weld toughness by controlling maximum HAZ hardness. |
| Proceedings Inclusion? |
Undecided |