During the operation of a supercritical boiler in a certain power plant
it was found that the T91/TP347H dissimilar steel welded joint at the outlet of the high-temperature reheater had fractured
causing a boiler leak. A series of tests were conducted on the failed welded joint
including macroscopic morphology observation
chemical composition analysis
metallographic examination
and hardness testing. Combined with the operating conditions and historical fault history of the boiler
a comprehensive analysis was made of the failure causes of the dissimilar steel welded joint. The results showed that poor weld formation and unqualified welding quality were the direct causes of the joint cracking; the large chemical composition difference and uneven performance of the dissimilar steel joint itself
under long-term high temperature and stress
led to element migration
resulting in a decline in interface performance
which is the fundamental reason for the cracking of the welded joint; the deep peak shaving and frequent start-stop peak shaving of the unit further accelerated the generation of cracks. Based on the failure cause analysis
and drawing on the management standards and practical experience of dissimilar steel welded joints
subsequent maintenance inspection and metal supervision strategy optimization suggestions were put forward
which can provide a reference for the management of dissimilar steel welded joints in similar power plants.
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