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基于发动机缸体在铸造成形后放置过程中出现异常锈斑且人工打磨后反复出现的问题,对缸体表面产生异常锈斑的原因进行了分析研究。通过对锈斑表面和截面两个方向研磨及显微观察发现,在每一异常锈斑的浅表面均存在着大小不等的夹渣。进一步的扫描电镜观察及能谱分析发现,这些夹渣是Ba、Ca、Al、S等外来元素的富集区。分析认为,二次孕育残存在铸件表面并与外界空气相连的夹渣起到了吸潮的作用,使冷芯砂中水分以及空气中的水分子聚集在夹渣附近,并与基体中的铁碳元素发生电化学反应导致了表面异常锈斑的产生。
Based on the problem that the engine block appears abnormal rust during the setting process after casting, and recurred after manual grinding, the cause of the abnormal rust on the surface of the cylinder block is analyzed. Through the grinding and microscopic observation of the rust spot surface and the cross section in both directions, it is found that slag inclusions of different sizes exist on the shallow surface of each abnormal rust spot. Further scanning electron microscopy and energy spectrum analysis found that these slag inclusions are the enrichment regions of Ba, Ca, Al, S and other foreign elements. The analysis shows that the secondary entrapment remnant in the casting surface and connected with the outside air slag play a role in moisture absorption, cold core sand water and water molecules in the air gathered in the vicinity of slag, and the matrix of iron and carbon Elemental electrochemical reactions lead to the generation of abnormal surface rust.