汽车齿轮轴用钢SCM440H扭转疲劳寿命及断裂特征分析

Analysis on the Torsion Fatigue life and Fracture Characteristics of SCM440H Steel for Automobile Gear Shaft

通过试验测定汽车齿轮轴用钢SCM440H扭转疲劳寿命，拟合扭转疲劳S-N的曲线，并采用扫描电镜（SEM）对疲劳断口进行观察、分析。结果表明，显微组织为回火索氏体的SCM440H钢扭转疲劳极．限约为253MPa；不同切应力幅下的扭转疲劳断口呈现典型的韧性断裂特征，疲劳断口裂纹源处没有明显的析出物，试样材质及栽荷因素可能共同影响到最终的扭转疲劳试验结果。

The torsion fatigue life of SCM440H steel for automobile gear shaft was determined by testing, and the torsion fatigue S - N curve was matched, moreover the observation and analysis on the fatigue fracture was carried out by SEM. The results show that, for SCM440H steel with the microstructure of tempered sorbite, its torsional fatigue limit is about 253 MPa; and under the different shear stress range, the torsion fatigue fracture all appears the typical ductile fracture characteristics, there is no obvious precipitates at fatigue crack source, and the sample material and load factor can influence the final results of torsion fatigue test.