Cr-Mo-V鋳鋼経年劣化材の評価

概要

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Cr-Mo-V cast steel is being used widely for steam turbine castings, since it possesses superior elevated temperature properties. Recently, however, the degradation of material properties of these castings bas been not noticed after long-term service at high temperature and high pressure environments. In this study, the metallurgical and mechanical characteristics of long-term degraded Cr-Mo-V castings Were investigated, and a method to estimate the degree of deterioration was examined. The main results obtained are summarized as follows: (1) Reduction in mechanical strength after long-term service is considered to be caused by the carbide growth and the recovery of microstructure. (2) Although grain boundary is subjected to reversible temper embrittlement after service, the toughness can be restored by the de-embrittlement procedure. (3) The long-term degraded material showed low creep rupture strength and low ductility, because creep cavities were easily formed. The de-embrittled material showed the same behavior. (4) Anodic polarization measurement by which SACM can be observed was found to be a suitable method to detect the material property change after long-term service.
社団法人日本材料学会の論文
1986-03-15