Abstract: Effect of different normalizing cooling rate on the creep rupture property of 2.25Cr-1Mo steel was studied by means of SEM and creep testing machine. The results show that the extrapolated creep strength σ₁₀⁴ under 530 ℃ of the 2.25Cr-1Mo steel normalized with air, 30 ℃/min and 5 ℃/min cooling rate are all about 120 MPa. The creep rupture strength decreases conspicuously when the cooling rate drops to 1 ℃/min, the main reason is a large number of big size particles precipitated on the interface of ferrite and bainite, which results in the occurrence of creep holes. Meanwhile, a large number of proeutectoid ferrite appears, which leads to the strength of the matrix decrease and can not effectively hinder cracks to propogate, thus the creep rupture property decreases.

Key words: 2.25Cr-1Mo steel, creep rupture property, bainite, ferrite