缸体缸盖铸件的材料性能问题——车用中小型发动机灰铸铁缸体缸盖铸件生产工艺(4)

On Properties of Gray Iron for Cylinder Block and Head Castings——Casting Production Technology of Gray Iron Cylinder Block and Head for Medium-Small Vehicle Engine(Ⅳ)

叙述如何改善灰铸铁的综合性能,认为提高灰铸铁强度的途径主要是:(1)高温熔炼;(2)常规元素成分的选择;(3)恰当的孕育;(4)合金化。要降低铸铁的缩松倾向,最根本的措施是采用高的碳当量,尽量发挥石墨化膨胀的作用,并且要:(1)控制合理的孕育量;(2)优化合金化的方法;(3)适当降低铁液浇注温度;(4)快速高温熔炼,减少铁液氧化。指出铸铁的加工性能取决于断屑的难易和硬质相的分布状态;对Mn、S以及一些微量元素对加工性能的影响进行了讨论。

How to improve overall properties of gray iron was described.The measures to increase the strength of gray iron are as follows： a） hi-temperature melting; b） optimizing contents of normal elements; c ）inoculating properly; d） alloying. In order to reduce shrinkage tendency of gray iron, it＇s the basic measure to adopt high carbon equivalent and make full use of graphitization expansion, and besides, following measures are also necessary： a） controlling rational inoculant amount; b） optimizing alloying process; c） decreasing pouring temperature properly; d） melting fast and with high temperature to reduce iron melt oxidation. It＇s pointed out that the machinability of cast iron depends on whether its chips are easy to be broken or not and depends on the distribution morphology of its hard phase. The influence of manganese and sulphur contents, as well as some trace elements on machinability was discussed.