In this work, five different hot-rolled steel strips with different microstructures were produced through different microalloying design and adjusting final coiling temperature. The relationship between microstructure and mechanical properties, especially fatigue limit, was analyzed in detail. The results showed that the steels with mainly quasi-polygonal ferrite and pearlite have a similar yield strength as the steels with acicular ferrite and martensite, but they are higher than the DP (ferrite + martensite) steels that are strengthened by the second martensite phase. This is probably because the yield strengths of fine ferritic steels are further enhanced by the precipitation strengthening mechanism of nano-sized particles. Under the present experimental conditions, the fatigue limit is proportional to yield strength rather than tensile strength. It is also found that the precipitation strengthening mechanism is more beneficial to improving the fatigue stress than the strengthening mechanism by introducing martensite, although all these steels have the same fatigue crack initiation mode.

在这项工作中，通过不同的微合金设计和调节最终卷取温度，生产出了五种不同的具有不同组织的热轧钢带。详细分析了显微组织与力学性能之间的关系，特别是疲劳极限。结果表明，主要为准多边形铁素体和珠光体的钢与具有针状铁素体和马氏体的钢具有相似的屈服强度，但它们比被第二马氏体相强化的DP（铁素体+马氏体）钢高。这可能是因为细晶粒铁素体钢的屈服强度通过纳米颗粒的沉淀强化机理而进一步提高。在目前的实验条件下，疲劳极限与屈服强度而不是抗拉强度成正比。还发现尽管所有这些钢都具有相同的疲劳裂纹萌生模式，但析出强化机制比通过引入马氏体强化机制更有利于改善疲劳应力。