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在大断面球铁件生产中,有时会发现很多大黑点,其部位常在铸件冷却最慢的地方,它的宏观断口特征(图1)是近似呈球形的黑色斑点,在显微镜下观察大黑点时,其基体为铁素体组织,在铁素体的基体上嵌着珊瑚状石墨(如图2),它严重地降低球铁的机械性能,因此它是球铁的一种缺陷。为此有必要研究它的形成机理,以便消除此种缺陷,提高大断面球铁件的质量。
In the production of large-section nodular iron parts, sometimes many large black spots are found, the parts of which are often the places where the casting cools most slowly. Its macroscopic fracture features (Figure 1) are approximately spherical black spots observed under a microscope Black spots, the matrix of ferrite, ferrite matrix embedded in coral graphite (Figure 2), it seriously reduces the mechanical properties of ductile iron, it is a defect of ductile iron. Therefore, it is necessary to study its formation mechanism in order to eliminate such defects and improve the quality of large-section ductile iron pieces.