控轧控冷中碳非调质钢的高周疲劳性能

 采用中碳非调质钢制造的轴类等零件常承受交变载荷，因而对钢材疲劳性能具有高的要求。为了评估控轧控冷工艺生产的非调质钢棒材的疲劳性能，利用旋转弯曲疲劳试验机研究了一种常用的钒微合金化中碳非调质钢38MnVS及对比钢38MnS的高周疲劳性能。结果表明，与38MnS钢相比，38MnVS钢中铁素体体积分数增加，组织明显细化；相分析表明约有54%的钒处于M（C，N）相中，且尺寸小于10 nm的M（C，N）粒子质量分数为32%，这些细小粒子的析出强化增量约为116 MPa。38MnVS钢的疲劳极限较38MnS钢提高了62 MPa，提高幅度约为18%；疲劳极限比从38MnS钢的0.43提高到38MnVS钢的0.48。M（C，N）相的析出强化及组织细化是38MnVS钢较38MnS钢具有优异疲劳性能的主要原因，但其疲劳性能仍低于锻态非调质钢。根据试验结果及文献数据，给出了预测铁素体＋珠光体型非调质钢疲劳极限的简便方法。

High-cycle fatigue properties of controlled rolling and cooling microalloyed medium-carbon forging steels

Most engineering components made of microalloyed medium carbon steels experience cyclic loading in serve，and thus high fatigue performance is also required. In order to evaluate the fatigue behavior of microalloyed medium carbon steel manufactured through controlled rolling and cooling process，high-cycle fatigue properties of a commonly used V-microalloyed medium carbon forging steel 38MnVS and a medium carbon forging steel 38MnS for comparison were studied by using rotating bending fatigue test. The results show that the ferrite fraction is increased and the microstructure is refined for the 38MnVS steel compared with that of the 38MnS steel. Physical-chemical phase analysis of the 38MnVS steel shows that about 54% V of the total V in the steel is tied up in the M（C，N） precipitates，while the mass percent of fine particles （less than 10 nm） is about 32% and the corresponding yield strength increment is about 116 MPa. There is an increase of about 62 MPa of fatigue limit，i.e. a relative increase of about 18%，of the 38MnVS steel compared with that of the 38MnS steel. The fatigue limit ratio increased from 0.43 for the 38MnS to 0.48 for the 38MnVS steel. It is revealed that the precipitation strengthening of fine M（C，N） particles and microstructure refining are primarily responsible for the enhanced fatigue property of the 38MnVS steel though it is still lower than that of the as-forged medium carbon steel. A simple method of estimating the fatigue limit of ferritic-pearlitic medium carbon steel is proposed based on the results of this study and those in the literature.