低温石墨化退火对低钼、低镍球墨铸铁组织和力学性能的影响

对含钼0.25%,含镍0.2%~0.8%的球墨铸铁进行低温石墨化退火,测试了其力学性能,并对显微组织和冲击断口进行观察和分析.结果表明:添加少量钼和镍后铸态球墨铸铁中铁素体含量增加,冲击韧度提高50%以上,强度和硬度下降;进行低温石墨化退火后球墨铸铁中珠光体逐渐转变成铁素体,与铸态相比冲击韧度有大幅度提高,冲击吸收功最多增加500%,冲击断口存在较多的撕裂岭和少量韧窝;此外,添加钼和镍后,不同的退火工艺下试样的力学性能参数比较稳定,波动小.

Effects of Low Temperature Graphitization Annealing on Microstructure and Mechanical Properties of Nodular Cast Iron with Low Nickel and Molybdenum

The mechanical properties of ductile iron samples containing 0.25% molybdenum and 0.2%~0.8% nickel were tested after being annealed at a low graphitization temperature. The microstructure and impact fracture were observed and analyzed. The ferrite content of ductile iron was increased after adding a small amount of molybdenum and nickel. Consequently, the impact toughness was increased by more than 50% while the strength and the hardness were decreased. The pearlite in the ductile iron was gradually transformed into ferrite after low temperature annealing. The impact toughness was increased substantially and the impact absorbed energy was increased to 500% compared with cast ductile iron samples. Many tearing ridges and dimples were found on the impact fracture through SEM observation. The mechanical properties in different annealing parameters were relatively more stable with a smaller fluctuation after molybdenum and nickel were added.