Directing against the causes leading to a lot of concentrated fractures occurred on the low-pressure last-stage blades of 2Cr12MoV steel in N135-13.24/535/535 units

a test analysis has been carried out.Results of test show that the main cause is due to the reinforcement technolgical process of said blades having been unsuitably selected or unstrictly controlled

the reinforced zone at steam-inlet side of the low-pressure last-stage blades due to fully quenched

a hardened zone being formed

and having higher stress in the phase-changed structure.For this

it is recommended that the manufacturer should perfect the high frequency quenching process for partial reinforcement of the said blades

such as adopting laser treatment etc.

so as to avoid occurrence of fractures on the blades.