发动机缸套用球墨铸铁的组织与铸造工艺研究

Study on Microstructure and Casting Process of Ductile Iron for Engine Cylinder Liner

针对一种断面尺寸较大、壁厚较厚的QT400-15缸套铸件,通过合理设计化学成分,采用球化和孕育工艺处理,使其组织均匀和性能达标。控制反球化作用因子K_(1)在1附近,选用低稀土Lamet 6124球化剂。采用冲入法球化结合多次复合孕育的处理工艺,使石墨球更圆整、更细。其球化级别达到2级以上,石墨大小达6级左右,球化率和石墨大小都满足性能要求。将珠光体区域和大断面铸件最后凝固区容易析出的碳化物和不规则形状的石墨控制在了合理范围之内。最终在大铸件上多处取样测试,满足抗拉强度>400 MPa、伸长率>15%的力学性能要求。

Aiming at a cylinder liner casting made of QT400-15 with large section size and thick wall thickness,the uniform microstructure and performance of the casting can be guaranteed by reasonable chemical composition design and spheroidization and inoculation process treatment.In terms of the composition design,it is ensured that the anti spheroidization factor K_(1) was around 1.The low rare earth Lamet 6124 spheroidizing agent was selected,and the treatment process of multiple composite inoculation with the impact spheroidization method and cabasi inoculant was adopted to ensure that the graphite balls were more rounded and finer.The spheroidization level reached above level 2,and the graphite size reached about level 6.Both the spheroidization rate and the graphite size met the performance requirements.The carbides and irregular graphite that were easy to precipitate in the pearlite area and the final solidification area of large section castings were controlled within a reasonable range.Finally,multiple samples were taken on large castings for testing,meeting the requirements of tensile strength>400 MPa and elongation>15%.