电站给水泵液力偶合器勺管断裂原因分析

Analysis on Cracking Cause of Scoop Tube for Water Feeding Pump Fluid Coupling of Power Station

某电站1号机组2号给水泵液力偶合器勺管在运行中发生断裂,采用宏观分析、化学成分分析、力学性能试验、金相显微分析及扫描电镜断口分析等手段对断裂原因进行了分析。结果表明,该勺管锻造退火后未进行正火处理,组织中遗传了大量魏氏组织和网状铁素体等不良组织,使其材质脆化,强度降低;后续进行的调质处理又在局部区域产生了淬硬马氏体并伴随淬火裂纹;当勺管运行中因发生卡涩弯曲等而承受较强应力时,淬火裂纹迅速失稳扩展,进而引发勺管整体断裂。对此提出加工过程中应严格执行工艺,锻造退火后及时进行正火处理来消除不良组织,以获得组织和性能良好的材料等建议。

The fluid coupling scoop tube of No.2 water teedmg pump was broken when unit 1 was running. The cracking cause of scoop tube was investigated by means of macroscopic analysis, chemical composition analysis, mechanical property analysis, microstructure examination and SEM analysis. The result showed that scoop tube was not treated by normalizing treatment after forge annealing, so lots of reticulate α-ferrites and widmanstaten structure produced which lead to friable. Besides, the quenched structure and quenching cracks generated because of modified treatment in local area. The quenching cracks extended rapidly lead to scoop tube was broken when powerful bending stress was applied to it. So treatment technology should be executed strictly. In order to acquire good microstructure and properties of material, it is needed to execute normalizing treatment after forge-annealing Key words： fluid coupling; fracture of scoop tube; heat treatment; quenching cracks