本研究是透過兩種非破壞檢測，滲液探傷及磁粉探傷，檢驗大型低合金鎳鉻鉬鑄鋼件的切割試片，分析其中的鑄造缺陷之分佈。進一步透過電子顯微鏡觀察缺陷形貌並歸類之，並以電腦模擬凝固所得之參數探討缺陷的形成原因。
結果顯示，存在於此鑄鋼件中的三種主要缺陷是：縮孔、裂痕以及夾雜物。縮孔出現在局部凝固時間較長且硬度較低的部位，以鑄鋼上半部較嚴重，而裂痕則出現在鑄鋼外側頸部，裂痕以及縮孔出現之位置均伴隨大量的夾雜物。彎曲試驗，可以反應出鑄件中缺陷的嚴重性，含缺陷較多的鑄鋼件部位其彎曲強度明顯劣化，而衝擊試驗中，破斷面反應出破裂的起源即為縮孔。

In this research, distribution of casting defect has been examined and studied by non-destructive testing (NDT) which were included penetrant testing (PT) magnetic particle testing (MT) on sectioned specimens of large scale low alloy carbon steel. Further, scanning electron microscope can be used to observe the defect morphologies for classify the defect types. Figure out formation of defects based on computer simulation.
The results show that the defects have been classified into three main types, include shrinkage, crack and inclusion. In some particular regions were suffered from shrinkage and cracking damage, shrinkages were more severe in the upper portion of casting and corresponding to the longer solidification time and lower hardness value. Cracks were found presented in neck of casting. These two types of defect were accompanied with large amount of inclusion. Through the bending test, it was found that the mechanical performance was decreasing due to the presence of defects in tested specimen, casting part with more defects decreasing the mechanical performance sharply, fracture surfaces of Charpy specimens showing that the origin of failure is shrinkage porosity.

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