Study on fatigue property and microstructure characteristics of welded nuclear power rotor with heavy section

摘要

The fatigue property and microstructure characteristics of the welded joint for nuclear power rotor with heavy section, were systematically reported in this paper. The welded joint microstructure is inhomoge-neous for NiCrMoV rotor made by narrow gap submerged arc welding (NG-SAW), which could affect the properties in different zones of welded joint. As one of the important indicator to evaluate the running performance of welded rotor, the fatigue crack propagation behavior of the base metal (BM), weld metal (WM) and heat affected zone (HAZ) was comparatively studied. It was found that the fatigue crack propagation threshold (ΔK_(th)) of BM was higher than that of WM and HAZ as stress ratio (R) was 0.1, but ΔK_(th) was very close to each other as R increased. The microstructure, revealed by an optimized corrosive process, was granular bainite in WM and tempered martensite in HAZ, leading to their approximately equivalent resistance of fatigue crack propagation with BM. The experimental results showed that fatigue properties of welded joint for NiCrMoV rotor with heavy section could meet the design requirement, and also push NG-SAW into manufacturing large size rotor.