Influence of modern melting techniques on the creep behaviour of heavy‐section components of 1% CrMoV steels

Abstract

By following new paths in steel metallurgy the quality of heavy‐section components of 1% CrMoV steels, such as turbine rotors for fossil‐fired steam‐power plants, has been continuously improved. The objective of this paper is to study the influence of modern steel‐making processes on creep behaviour at 500 and 550°C using specimens taken from the rim and core zones of turbine rotors manufactured during the past ten years. While an influence of the steel‐making process on creep‐rupture strength could not be established, the creep‐rupture strength and the creep strength for 1% creep strain were found on average to be 20% higher than the recommendations of SEW 555. In the VCD‐treated melts a creep strain of 1% was achieved earlier (time factor 2 to 3) than in melts treated otherwise. Particularly the VCD‐treated melts are characterised by high creep ductility (reduction of area after creep rupture). But also the other melts were found to achieve a higher creep rupture ductility than in the past. This is mainly due to a lower content of residual elements as well as optimised heat treatment.

Creep and Fatigue Behavior in Micro-alloyed Steels – A Review

“…Evidences of long term embrittlement after cavity formation has been result of degradation of microstructure by creep exposure. Favourable creep behavior in 15CrMoV 5 10 has been ascribed to high amount of Mo, which has been present both as solid solution and deformation induced carbides at dislocation [1,2].…”