In order to investigate mechanism of suspected linear defects indication in radiographic inspection of narrow gap welds in a nuclear power plant,microstructure and micro-hardness of the welds with suspected linear defects were studied by means of scanning electron microscopy and atomic probe.Causes of formation of micro-pores in microstructure were discussed,and distribution of micro-pores was characterized by porosity rate.The results showed that suspected linear defects were not true welding defects.Microstructure of the welds with suspected linear defects was austenite matrix and δ ferrite,and δ ferrite content was the same in different regions.Porosity rate of weld with suspected linear defects was about 0.06%,higher than that of the zone without suspected linear defects,0.03%.Therefore,difference of porosity rate in microstructure was the main reason for suspected linear defects in radiographic inspection,and the difference did not affect microhardness.This study provided a new way to evaluate suspected linear defects in radiographic inspection.
关键词
核电厂/主管道/窄间隙焊接/射线检验/疑似线性缺陷
Key words
nuclear power plant/main pipe/narrow gap welding/radiographic inspection/suspected liner defects
维普
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