AP1000接管段检测不合格原因分析

The Analysis on the Disqualification Reason for AP1000 Nozzle Belt

材质为SA-508 Gr.3Cl.1的核反应堆压力容器锻件AP1000容器法兰接管段,经锻后正回火处理,在超声检测时发现多处严重超标缺陷。利用扫描电子显微镜、能谱仪、图像分析仪等检测手段进行取样分析,对试样进行低倍断口观察、金相组织检验,利用SEM和EDS对断口的微观形貌和成分进行进一步的分析,结合锻造工艺,确认缺陷性质为白点。其形成原因是由于生产过程中控氢不严使得钢中含有大量氢并发生聚积,在内应力作用下形成裂纹,最终导致检验不合格。通过改善工艺条件,达到消除白点提高产品质量的目的。

The nuclear reactor pressure vessel AP1000 flange nozzle belt forging made by material SA-508 Gr. 3Cl.1 has found many super indications during the UT after the post forging normalizing and tempering. The detection methods such as scanning electron microscope（ SEM）,energy disperse spectroscopy（ EDS） and image analyzer are used to analyze the test specimen,and observe the fracture of test specimen through the macroscopic examination,and inspect the metallographic structure. The SEM and EDS are used to analyze the microstructure and composition of fracture further,and combined with forging process,the result show that the nature of the indication is flaking. The reason for the formation of flaking is the lax control of hydrogen during manufacturing which cause a lot of hydrogen accumulates in the steel,and form the crack by the inner stress,and ventually lead to the inspection unquanlified. The process conditions are improved to achieve the purpose of eliminating the flaking and eventually improve the quality of forgings products.