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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Q&P)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Q&P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Q&P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。
High-strength steel is currently the most widely used type of steel materials. In order to improve the anti-fatigue failure performance, quenching-partitioning (Q & P) heat treatment of bainitic high strength steel was carried out, and the ultrasonic fatigue vibration test was carried out by using the Shimadzu USF-2000 ultrasonic fatigue testing machine (frequency of 20 kHz). The tensile strength and super high cycle fatigue strength of the bainitic high strength steel after Q & P heat treatment were 1 688 and 875 MPa respectively, and the fatigue ratio (fatigue strength / tensile strength) reached 0.52. Scanning electron microscopy and transmission electron microscopy revealed that the Q & P-treated steels produced a large amount of residual austenite in the film form. The XRD measurement revealed that the volume fraction of retained austenite was 22% and the mass fraction of carbon in retained austenite was 1.2%. Fatigue results show that retained austenite has an inhibitory effect on fatigue cracks, which can effectively improve the fatigue resistance of steel.