Abstract
This paper constitutes the failure analysis of a 24-inch diameter ‘Flange’ that had been welded to
a high-pressure gas transmission pipeline. The flange had ruptured catastrophically during the
hydrostatic test that was conducted to testify the integrity of the flange as well as that of the weld
joint. The rupture had occurred along the weld through the heat-affected-zone (HAZ) on the
flange side. The flange, which was a steel forging (of Class 600 as per ANSI Standards) made
from ~ 0.25 % carbon steel, was expected to exhibit good weldability. However, the
metallographic examination revealed that the steel had a coarse grain-size and an in-homogenous
microstructure wherein pearlite-rich regions, ~2-3 mm across in size, were sporadically
distributed in the microstructure. The coarse grain-size coupled with the presence of pearlite-rich
patches in the microstructure had locally reduced the weldability of the steel, i.e., increased its
tendency towards HAZ cracking during welding.
F. Ahmed, F. Hasan, L. Ali. (2008) Failure Analysis of a High Pressure Butt-Weld Flange, Pakistan Journal of Engineering and Applied Sciences, Volume 3, Issue 1.
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