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非调质钢常用来代替调质钢制造用于疲劳设计的运动部件，因而改善其疲劳性能十分重要。对于铁素体-珠光体型非调质钢，由于存在软相铁素体，其疲劳疲劳裂纹基本上萌生于试样表面的铁素体/珠光体边界，并优先沿着铁素体/珠光体边界扩展。因此，强化铁素体、改善铁素体的分布状态和组织细化是改善其疲劳性能的关键。进一步的研究结果证实，具有粗大的网状铁素体-珠光体组织或粗大贝氏体组织的非调质钢的疲劳性能较差，而具有细小、均匀的铁素体-珠光体组织的非调质钢则具有良好的疲劳性能。在热锻态，微合金化元素V因具有明显的析出强化和组织细化作用而能够明显地改善铁素体-珠光体型非调质钢的疲劳性能。与调质回火马氏体组织不同，氧含量对铁素体-珠光体组织的疲劳性能没有明显的影响。总之，组织精细控制的铁素体-珠光体型非调质钢的疲劳性能可达到调质钢的水平。

It is increasingly demanded to improve the fatigue properties of medium-carbon microalloyed forging steels which are increasingly used to replace conventional quenched and tempered (QT) medium-carbon steels for the manufacture of fatigue design components. For ferrite-pearlite steel, owing to the existence of soft phase of ferrite, it is revealed that fatigue crack preferentially initiated and propagated along the ferrite/pearlite boundary in the early stage of fatigue crack propagation. Therefore, the fatigue property of ferrite-pearlite type microalloyed forging steel could be improved by increasing ferrite strength through precipitation strengthening and controlling the distribution of ferrite and refining microstructure. Further investigation shows that ferrite-pearlite steel with film-like ferrite along coarse prior austenite grain boundary and pearlite microstructure or coarse bainite microstructure has lower fatigue property. However, ferrite-pearlite steel with much fine and uniform ferrite and pearlite microstructure has higher fatigue property. Microalloying element V can significantly improve the fatigue properties of ferrite-pearlite steel mainly through precipitation strengthening and grain refining mechanism in as-forged condition. Unlike that of tempered martensite structure, there is little effect of oxygen content on the fatigue properties of ferrite-pearlite steel. In conclusion, the fatigue properties of microstructure carefully controlled ferrite-pearlite steel could be as high as that of QT steel.