厚断面球墨铸铁件组织与性能分析

Microstructure and Mechanical Properties in Heavy Section Spheroidal Graphite Cast Iron

浇注了厚大断面球墨铸铁试块,借助光学显微镜、扫描电子显微镜、能谱仪及拉伸试验机分析了厚断面球墨铸铁件表面及心部的微观组织和力学性能,探讨了其形成机理。结果表明,现有试验条件下近表层区域凝固速度快,石墨球数量较多、球径较小,中心或热节部位石墨畸变严重,为减少或抑制石墨畸变,微合金化的同时还应强化冷却;Mg、Sb、S及RE等的化合物是球状石墨核心的主要组成物,这些元素在石墨球周围的富集使各个面或方向的生长趋于球形;凝固速度对试块中各位置的抗拉强度和屈服强度影响不同,其断裂为石墨与基体处形成裂纹不断扩展所致。

Abstract： A heavy section spheroidal graphite cast irons block was prepared. And the morphology features in spheroidal graphite cast irons castings were analyzed by using optical microscope, scan electronic microscope, energy spectrometer and tensile tester. The mechanical properties of spheroidal graphite cast iron with heavy section were discussed. The results show that the solidification rate at surface is fast, resulted in a gradual increase in number of graphite nodules and an decrease in graphite size under the current experimental conditions, and the graphite was serious distortion in the center section or hot spot. Micro- alloying and cooling systems should be applied at the same time to reduce or inhibit chunky graphite in heavy section spheroidal graphite cast iron castings. The compounds ofMg, Sb, S and RE elements is the main composition of spheroidal graphite core, and their enrichment around spheroidal graphite make each surface or the direction of the growth tends to be spherical. The effect of solidification rate in each position on the tensile strength and yield strength was different, fracture of graphite and the matrix is formed due to the continued expansion of cracks.