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为了改善球墨铸铁的低温冲击性能,研究了不同镍含量对铸态球墨铸铁组织性能的影响和镍含量为0.6%退火态球墨铸铁的组织和低温冲击性能。结果表明:不同镍含量下球墨铸铁铸态显微组织均为铁素体+石墨球+少量珠光体组成,随着镍含量在0.0%~0.6%之间的增加,铁素体晶粒逐渐细小,石墨球亦逐渐细小圆整,且数量增多,镍含量为0.8%时,石墨球化率和均匀性下降。随着镍含量的增加,珠光体的含量增加,球墨铸铁的硬度和抗拉强度逐渐提高,屈服强度先升高后下降,而伸长率却总体呈下降趋势。镍含量为0.6%的球墨铸铁经760℃加热,零保温,随即以5℃/min冷却速度降温到620℃后出炉空冷后,得到了铁素体+石墨球组织,冲击试样在-60℃下仍然属于韧性断裂,冲击功仍高达13.2 J,能够满足工程机械零部件在较低温下工作冲击韧性的需求。
In order to improve the low temperature impact properties of ductile iron, the effects of different nickel contents on the microstructure and properties of as-cast ductile iron and the microstructure and low temperature impact properties of ductile iron with annealed nickel content of 0.6% were studied. The results show that the as-cast microstructures of ductile iron are all composed of ferrite + graphite balls + a small amount of pearlite with different nickel contents. With the increase of nickel content from 0.0% to 0.6%, the ferrite grains gradually become smaller , Graphite balls gradually small and round, and the number increased, the nickel content of 0.8%, graphite ball rate and uniformity decreased. With the increase of nickel content, the content of pearlite increased, the hardness and tensile strength of ductile iron gradually increased, the yield strength first increased then decreased, while the elongation decreased overall. The ductile iron with a content of 0.6% of nickel was heated at 760 ℃ and zero-insulated, then cooled to 620 ℃ with a cooling rate of 5 ℃ / min and then cooled with air to obtain a ferrite + graphite ball structure. The impact specimen was sintered at -60 ℃ Under the still belongs to the ductile fracture, the impact energy is still as high as 13.2J, able to meet the needs of engineering machinery parts working impact toughness at lower temperatures.