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Ball Clevis for Pole Line Hardware is made of ferritic ductile iron, and the castings have serious casting defects such as poor spheroidization, shrinkage porosity, and porosity. The existence of these defects will directly reduce the mechanical properties of the material. The metallographic analysis also found that there are a large number of cracks of different lengths on the surface and inside of the failed double-joint bowl casting. The cracks all originated from the surface branched and linearly expanded inward along the grain boundary, with obvious corrosion cracks. Characteristics. Scanning electron microscope observation and analysis results show that the galvanized layer on the surface of the double bowl head is not dense, and there are channels for external air intrusion. The cracks in the bowl head matrix all originate from the defects and intergranular cracks on the surface of the casting, and there are generally shallow intergranular cracks under the surface galvanized layer.
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