球墨铸铁经等温淬火形成贝氏体状铁素体和奥氏体两相混合基体组织,可以得到高强度和良好的韧塑性。球铁等温淬火存在的问题之一是冷却速度会随壁厚增大而减小,因而难以使工件整个断面组织转变为贝氏体。解决这个问题,可以考虑添加合金元素或者加大冷却速度。但添加大量合金元素不仅使成本提高,而且可能出现偏析,导致性 Ductile iron isothermal quenched to form bainitic ferrite and austenite two-phase mixed matrix structure, can be high strength and good toughness. One of the problems with isothermal quenching of ductile iron is that the cooling rate will decrease as the wall thickness increases, so it is difficult to transform the entire cross-sectional structure of the workpiece into bainite. To solve this problem, you can consider adding alloying elements or increase the cooling rate. However, adding a large amount of alloying elements not only increases the cost, but also may cause segregation, leading to sexual