厚大球墨铸铁件正火后不同层深的组织和硬度

Microstructure and Hardness of Different Layers of Heavy Section Nodular Iron after Normalizing

研究了正火处理工艺对厚大断面球墨铸铁不同层深组织和性能的影响。详细介绍了试验研究方法,研究结果表明:对于壁厚为250 mm的铸件,正火处理后同一位置不同层深处的硬度偏差较小,壁厚对铸件不同层深处的热理效果影响不大;热处理后不同位置同一层深处硬度均匀性较好;随着层深增加,试验铸件心部石墨球数量明显减少,石墨有开花的趋势;随着层深增加,珠光体体积分数没有变化,珠光体片间距增大,硬度降低明显。

The influence of normalizing treatment on microstructure and properties of heavy section nodular iron was investigated.The experimental and investigating methods were introduced in detail.The result of investigation showed:for castings with a wall thickness of 250 mm,the hardness deviation of different layers in the same position after normalizing treatment was small,and the wall thickness had little effect on the heat treating effect of different layers of castings.After heat treatment,the hardness uniformity of the same layer was quite good in different positions.With the increase of the depth of the layer,the number of graphite nodules in the heart of the test castings decreased obviously,and the graphite had the tendency of exploding.With the increase of layer depth,the volume fraction of pearlite did not change,the spacing of pearlite layers increased,and the hardness decreased obviously.