微量砷对灰铸铁组织和性能的影响

在铸造灰铸铁件时,由于某些生铁中含有As等微量元素,铸件易产生大量的裂纹或显微裂纹,导致铸件报废.利用中频无芯感应炉熔炼不同As含量的铁液并制备试样,用XTB-1金相显微镜观察不同As含量对铸件的石墨形态和基体组织的影响,用WES型液压万能试验机测定抗拉和抗弯强度,同时详细考察了铸造性能.结果表明:As会促进过冷石墨和珠光体基体的形成.过量的As会导致网状碳化物的生成,加剧磷共晶的偏析以及增加铸件的激冷深度和收缩率,从而导致应力集中和热裂,是铸件产生裂纹的主要原因.在生产工艺中,应采取措施使铸铁中As含量控制在0.010％以下,并通过孕育处理等措施改善铸件的组织,提高力学性能.

Effects of Microelement As on Structure and Properties of Gray Cast Iron

For some pig iron used to produce gray castings has microelement As,a great deal of cracks or microcracks are prone to forming,which results in reject of castings.Iron melts with different As contents were smelted by using mid-frequency coreless induction furnace and test samples were prepared.The effects of As on the graphite morphology and microstructure of castings were investigated by using metallographic microscope(XTB-1).WES hydraulic universal test machine was applied to test the tensile and bend strength.Castability of the samples was also studied.The result shows that As can promote forming of supercooling graphite and pearlite,but excessive As resulted in the formation of network carbide,aggravated the segregation of phosphide eutectic and enhanced the chill depth and shrinkage rate of castings,thereby resulted in serious stress concentration and hot tearing,which are the main reasons of cracks forming.In the practical production,the As content of cast iron must be controlled less than 0.010%,and the mechanical property can be increased by improving the metallographic structure of casting by some measures,such as inoculation.