steam turbine rotor steel 28CrMoNiV

 

 

LIU Zhong hua1, HE Cheng1, LIU Jing wei2, XV Wei3,

 HUANG Shu qiu3, FANG Zhang fa2, SONG Si yuan1

 

(1. Hangzhou Steam Turbine ＆ Power Group Co., Ltd., Hangzhou 310016, China;

 

2. Hangzhou Steam Turbine Co., Ltd., Hangzhou 310003, China;

 

3. Hangzhou turbine casting & forging Co., Ltd., Hangzhou 310006, China)

 

 

Abstract: Aiming at the problems of how to assess the FATT of industrial steam turbine rotor steel 28CrMoNiV correctly, the impact absorbing energy and percentage of brittle fracture surface of rotor steel at different temperatures were measured by impact test, the change of fracture morphology were studied by using SEM, and these experimental results were fitted by using Boltzmann function, then the FATT of rotor steel were assessed correctly. Meanwhile, the factors affecting FATT were summarized; the effects of chemical component, microstructure and grain size on the FATT of rotor steel were investigated. The results indicate that the fracture morphology of 28CrMoNiV steel is gradually changed from dimple to cleavage fracture with decreasing temperature, the FATT of rotor steel (-52℃) is less than technical standard requirements obviously (≤85℃).The strictly controlled chemical component, small and homogeneous tempered sorbite grain, high density dislocation and sub grain boundary in acicular ferrite which achieved by advanced smelting and hot working technology, are the main reasons for the increase of impact toughness and decrease of FATT of rotor steel.

 

Key words: industrial steam turbine; rotor; 28CrMoNiV; impact toughness; FATT; fracture morphology