摘要
Abstract
The groove type clamp of the BOP water fire protection system in a nuclear power plant broke during service.The causes of clamp fracture were analyzed using macroscopic observation,chemical composition analysis,hardness testing,metallographic examination,scanning electron microscopy and energy spectrum analysis.The results show that the Mn element content in the clamp was relatively high,and the casting cooling rate was fast,which resulted in a significant increase in the pearlite content in the microstructure of the matrix,and the formation of a large number of hard and brittle structures such as ledeburite and lamellar primary carbides,which made the material hardness significantly higher than the standard requirements,and the plasticity and toughness significantly decreased.At the same time,there was uneven wall thickness in the clamp,and stress concentration was easily formed at the thin-walled corner,where cracks initiated and continuously propagated,ultimately leading to brittle fracture of the clamp.关键词
沟槽式卡箍/QT450-12球墨铸铁/脆性断裂/显微组织/硬度Key words
groove type clamp/QT450-12 ductile iron/brittle fracture/microstructure/hardness分类
通用工业技术
