蠕化率对蠕墨铸铁高周疲劳性能的影响

Effect of Vermicular Graphite Rate on High Cycle Fatigue Properties of Vermicular Cast Iron

对不同蠕化率的蠕墨铸铁进行了室温轴向拉压的疲劳试验,对显微组织进行了观察,对拉伸性能进行了测试,研究了高周疲劳性能及疲劳断裂机理研究了。结果表明,随着蠕化率的升高,蠕墨铸铁的抗拉强度和条件疲劳极限下降。当珠光体含量在87%左右,蠕化率从53.9%升高至92.62%时,石墨团簇直径从330μm增加到730μm,抗拉强度从665 MPa降低到440 MPa,减小了34%,疲劳极限从223 MPa降低到160 MPa,减小了28%;蠕墨铸铁的裂纹是在石墨处或脱粘处开始萌生并沿团簇扩展,珠光体对裂纹扩展有阻碍作用;石墨团簇是疲劳寿命的主要影响因素,石墨团簇越小,分布越均匀,疲劳寿命越高。

The fatigue tests of vermicular graphite cast iron with different vermicular rate under axial tension and compression at room temperature were carried out. The microstructure was observed, the tensile properties were tested, and the high cycle fatigue properties and fatigue fracture mechanism were studied. The results show that the tensile strength and conditional fatigue limit of vermicular graphite cast iron decrease with the increase of vermicular graphite rate. When the pearlite content is about 87% and the vermicular graphite rate increases from 53.9% to 92.62%, the diameter of graphite cluster increases from 330 μm to 730 μm, the tensile strength decreases from 665 MPa to 440 MPa, which decreases by 34%;the fatigue limit decreases from 223 MPa to 160 MPa, which decreases by 28%. The crack of vermicular graphite cast iron germinates at the graphite or debonding place and propagates along the cluster, and the pearlite hinders the crack growth. The graphite cluster is the main influencing factor of fatigue life. The smaller the graphite cluster is, the more uniform the distribution is and the higher the fatigue life is.