蠕墨铸铁组织性能均匀性研究

Homogeneity Research on Microstructure and Properties of Vermicular Graphite Cast Iron

蠕墨铸铁是制造高功率发动机机体及气缸盖等部件的理想材料。缸盖等部件属于结构复杂且壁厚不均匀铸件。为此，本文通过对阶梯件的蠕墨铸铁组织性能测试，研究壁厚对蠕铁组织性能的影响。通过金相分析发现：试样壁厚在10-50mm范围内，随着壁厚的增加，蠕化率陡增后缓慢增加。壁厚不同，试样各部位的冷却速率不同，冷速越快，蠕化衰退时间越短，球状石墨不能充分衰退为蠕虫状石墨，蠕化率降低，铁素体数量越少。通过力学性能测试发现：随着壁厚由10mm增加到50mm，抗拉强度先降低后基本不变，伸长率逐渐增大，硬度对壁厚敏感性小，变化不大。

Vermicular graphite cast iron is an ideal material for manufacturing high power density engine and cylinder head parts, which has complex structure and uneven thickness section. Therefore, the influences of thickness on the microstructure and mechanical properties were studied by testing the properties. The results show the vermicularizing increases sharply and then increases gradually with the thickness increasing. The different parts of sampling has different cooling rate and different wall thickness .The fading time decreases with the cooling rate increasing, and spheroidal graphite can not fully fade to compacted graphite, so the vermicularizing and the amounts of ferrite decrease. The mechanical properties tests result show that the tensile strength sharply decreases first and then basically unchanges with the wall thickness increasing; the elongation gradually increases. The hardness changes small, and is insensitive to the wall thickness.