The material mainly used for high-temperature bolts on large-capacity thermal power units is 12% Cr steel

but it has been discovered in application that the said steel had problems

such as the hardness value decreasing rapidly

the impact value being lower

and the impact index of C-422 bolts of 12% Cr steel hasn't standard can be based on

etc.

having serious phenomenon of demobilization in a short period.For these

though a series of ageing test without stress

the relationship among property of mechanics

structural state

ageing time

and ageing temperature of the bolts has been determined

and the varying regularity of structural property for 12% Cr martensitic heat-resistant stainless steel bolts under condition of ageing without stress being preliminarily given

and recommendations being put forward for supervision of high-temperature bolts made from 12% Cr martensitic heat-resistant stainless steel after operation.