淬火-分配工艺对高强钢疲劳失效的影响

高强钢是目前应用最广泛的一类钢铁材料。为提高抗疲劳失效性能,对贝氏体高强钢采用淬火-分配(quenching-partitioning,简称QP)热处理,采用岛津USF-2000型超声波疲劳试验机(频率为20kHz)进行超声波疲劳振动试验。经过QP热处理后的贝氏体高强钢的抗拉强度和超高周疲劳强度分别为1 688和875 MPa,疲强比(疲劳强度/抗拉强度)达到0.52。通过扫描电镜、透射电镜观察发现,经QP处理的钢产生大量的膜状的残留奥氏体。通过XRD测量可知,残留奥氏体的体积分数为22%,残留奥氏体中的碳质量分数为1.2%。疲劳结果表明,残留奥氏体对疲劳裂纹有阻碍作用,可有效提高钢的抗疲劳性能。

Effect of quenching-partitioning process on fatigue failure of high strength steel

High strength steel is one of the most widely used steel materials. In order to improve the fatigue performance of the bainite high strength steel，the quenching and partitioning（Q&P）heat treatment was applied，and the SHIMADZU USF-2000 type ultrasonic fatigue testing machine（20 kHz）was used in the ultrasonic vibration fatigue test. The tensile strength and the super high cycle fatigue strength of the bainitic high strength steel after the quenching and partitioning (Q&P) heat treatment were 1 688 and 875 MPa，respectively，and the σw9/Rm was 0.52. By the scanning electron microscopy and transmission electron microscopy，it was found that a large amount of film-like retained austenite was produced in the steel treated by the Q&P process. The XRD measurement showed that the volume fraction of the retained austenite was 22%，and the carbon mass fraction was 1.2%. The fatigue results showed that the retained austenite had an effect on the fatigue crack resistance and can effectively improve the fatigue resistance of steel.