蠕化率对蠕墨铸铁热疲劳行为的影响

Effects of Vermicularizing Rate on Thermal Fatigue Behavior of Vermicular Graphite Iron

采用V型缺口试样,通过对试样反复加热冷却,研究了不同蠕化率(55%、70%、90%)对蠕墨铸铁热疲劳行为的影响。结果表明,随着蠕化率的增加,蠕墨铸铁的抗热疲劳性能先升高后降低,当蠕化率为70%时,蠕墨铸铁抗热疲劳性能最佳。不同蠕化率,蠕墨铸铁的裂纹萌生和扩展机制具有显著差异。当蠕化率90%时,在V型缺口裂纹萌生明显,主裂纹沿着蠕虫状石墨生成二次裂纹,最后V型缺口凹陷成崩塌趋势;而蠕化率70%和55%时,V型缺口附近裂纹明显减少,仅在球状石墨尖端部位和基体组织产生少量微小裂纹,且裂纹没有明显扩展,产生裂纹倾向低,V型缺口凹陷未形成崩塌。

The influence of different vermicularizing rates(55%,70%,90%)on thermal fatigue behavior of vermicular graphite cast iron was studied by heating and cooling and V-notched sample.The results show that the thermal fatigue resistance of vermicular graphite cast iron increases first and then decreases with the increase of vermicular graphite.When the vermicularizing rate is 70%,the thermal fatigue resistance of vermicular graphite cast iron is the best.The mechanism of crack initiation and propagation of vermicular graphite cast iron is significantly different with different vermicularizing rates.When the vermicularizing rate is 90%,the V-notched crack is obviously initiated,and the main crack generated a secondary crack along the vermicular graphite.Finally,the V-notched form a collapse trend.However,when the creep rate is 70%and 55%,the cracks near the V-notched are significantly reduced,and only a small number of tiny cracks are generated in the tip of the spheroidal graphite and the matrix,and the cracks do not expand significantly,with a low tendency to generate cracks,and the V-notched depression does not form collapse.