The high and medium pressure rotor of a 300 MW subcritical unit in a power plant has been running for 45 490 hours

application for shutdown due to shaft vibration exceeding standard

it was found by inspection that rotor stress relief groove cracking failure.By means of fracture analysis.physical and chemical properties test

structural dimension test and stress simulation calculation

the

failure causes were analyzed from the properties of materials and the influenue of structure.The main cause of failure for the high and medium pressure rotor stress release slot processing size and design

there is a big deviation make stress concentration factor increases

which make the unit start-stop or load change in the process of alternating stress peak value increases

more than the yield strength of material

which in the high and medium pressure rotor surface au raw fatigue stress release crack

then extending from the early cracking failure.Through the analysis

the factors affecting the failure of high and medium pressure rotors are obtained

so as to guide the measures that should be taken during the inspections and operation of the same type rotors

so as to avoid the occurrence of major equipment accidents.