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利用旋转弯曲疲劳试验方法对比研究了新开发的两种转向节用贝氏体型非调质钢的高周疲劳性能。结果表明,两种不同碳含量的贝氏体型非调质钢具有细小均匀的贝氏体铁素体+M-A岛组成的粒状贝氏体组织;两者具有相当的强度水平和疲劳性能,但其疲劳性能低于同等强度水平的调质钢。与锻态相比,正火处理后,试验料的抗拉强度和疲劳强度均有一定程度的降低,但屈强比和疲劳极限比明显提高。对疲劳断口的分析表明,试验料的疲劳裂纹均起源于表面基体,疲劳裂纹以准解理机制扩展。裂纹扩展速率试验表明,含碳量较低的试验料的疲劳裂纹扩展速率da/d N明显低于含碳量较高的试验料。
The high-cycle fatigue properties of two newly-developed bainitic non-quenched and tempered steels for steering knuckles were comparatively studied by using the rotating bending fatigue test method. The results show that the two types of bainitic non-quenched and tempered steels with different carbon contents have the granular bainite structure composed of fine and uniform bainitic ferrite + MA islands; both of them have considerable strength level and fatigue properties. However, Fatigue performance is lower than the same level of strength quenched and tempered steel. Compared with the as-forged condition, the tensile strength and fatigue strength of the test materials decreased to a certain extent after normalizing treatment, but the ratio of yield strength and fatigue limit increased obviously. The analysis of fatigue fracture shows that the fatigue cracks originate from the surface matrix and the fatigue crack expands with quasi-cleavage mechanism. Crack propagation rate tests show that the fatigue crack growth rate da / d N of test materials with lower carbon content is obviously lower than that of high carbon content test materials.