夹杂物尺寸对60Si2CrVA高强度弹簧钢的高周疲劳性能的影响

Effect of Inclusion Size on High-Cycle Fatigue Behavior of High Strength Spring Steel

利用旋转弯曲疲劳实验,研究了3种商业生产的60Si2CrVA弹簧钢的高周疲劳破坏行为。结果表明,虽然实验料的氧含量相同,但由于钢中夹杂物尺寸的差异,使其高周疲劳性能存在明显差异。随着夹杂物尺寸的减小,实验料的疲劳寿命和疲劳强度均逐渐提高。夹杂物最为粗大的D-60料(平均夹杂物尺寸фin≈44.4μm),疲劳S-N曲线连续降低,疲劳断裂主要起源于钢中的粗大夹杂物,传统的疲劳极限消失;夹杂物最为细小的A-60料(фin≈15.4μm),疲劳断裂主要起源于表面基体,存在传统的疲劳极限。对于在低应力幅、高循环周次(约大于106)下,内部夹杂物引起的疲劳破坏,在夹杂物周围往往存在粗糙的粒状区域。

The high cycle fatigue fracture behavior of three heats commercial spring steels 60Si2CrVA were studied by using rotating bar two-point bending fatigue machine in the high-cycle regime up to 10^7 cycles. The experimental results indicated that there i＇s significant difference in the fatigue properties of steels, with same oxygen content. Further investigation revealed that this difference is mainly caused by the difference in inclusion size. That means, both fatigue life and fatigue strength increase with decreasing inclusion size. For D-60, in which the average inclu- sion size is 44.4μm the S-N curve displays a continuous decline without conventional limit and fatigue failures originated mainly from large oxide inclusions. For A-60,which has the smallest inclusion size of about 15.4 μm, all the fatigue cracks except two did not initiate from inclusions but from specimen surface and there was conventional limit. In the case of internal inclusion-induced fracture at cycles beyond 1 ×10^6 , inclusions were found inside the fish-eye and granular bright facets （GBF） were observed in the vicinity of inclusions.