Abstract: In response to the weld cracking failure in a high-pressure steam turbine inlet system, this paper made an analysis from such aspects as metallographic microstructure morphology, fracture morphology, composition distribution and so on. Meanwhile, coupling with the results of physical and chemical properties tests, it identified the mechanism leading to the occurrence and expansion of the weld cracks. Andthe main causes of weld cracking were considered to be, in descending order, high-temperature creep, fatigue damage, excessive stress, low weld toughness, and weld defects. Aiming at the above causes of weld cracking, prevention strategies such as optimizing the stress distribution of the turbine inlet system, improving the welding and heat treatment process, strengthening operation control, adopting advanced testing technology, optimizing inspection and so forth have been adopted, which haveeffectively controlled the operational safety risks of high-pressure steam turbines.

Key words: girth weld, crack failure, creep, welding technology, risk