DEGRADATION OF MECHANICAL PROPERTIES OF CrMo CREEP RESISTANT STEEL OPERATING UNDER CONDITIONS OF CREEP

摘要

Mechanical properties of a steam tube made of CrMo creep resistant steel are analysed in this contribution after up to 2,6?10~5 hours service life in creep conditions at temperature 530 °C and calculated stress level in the tube wall 46,5 MPa. During service life there were in the steel gradual micro structure changes, first pearlite spheroidization, precipitation, coaugulation and precipitate coarsening. Nevertheless the strength and deformation properties of the steel (R_e, R_m, A_5, Z), and the resistance to brittle fracture and the creep strength limit, were near to unchanged after 2,1?10~5 hours in service. The steam tube is now in service more than 2,6?10~5 h.