气流纺杯轴承磨损失效的分析与机理探讨

Failure Analysis of Rotor Bearing for OE Spinning Machine and Wear Mechanism

本文从宏观、微观及轴承润滑等角度出发,对具有高速、轻载和高精度特征的气流纺杯滚动轴承的磨损失效进行了分析与机理探讨,认为这种轴承磨损失效是粘着磨损和磨粒磨损的结果,而不是接触疲劳破坏所致。作者指出,在稳定磨损阶段也还存在着一些导致过渡急剧磨损阶段形成的不利因素,其在运转过程中被迫紧急刹车时,由于轴承受力突然增大和润滑脂膜破裂,造成摩擦界面温度急剧升高而使滚动元件的表层组织软化,润滑脂也随之逐渐丧失润滑能力,摩擦界面亦变得粗糙不平,比膜厚下降而发生了微凸体间的频繁接触,由此引起的粘着现象是造成气流纺杯滚动轴承磨损失效最主要的原因;由于轴承壳腔内的旧润滑脂无法取出,脂中所含的金属磨屑硬粒子在不断增多,其在高速滚动体发生滑动摩擦的瞬间会对材料表面造成擦伤或犁沟,这是导致滚动轴承磨损失效不可忽视的另一因素。

High speed rotor bearing widely used in many industrial areas is an impotant component of open end spinning machine.This bearing has the characteristics of high speed (36000-5000 r/min, the number of DN is 5×105-8×106mm·r/min),low load(contact stress is about 1600 MPa)and high precision (the clearance of new bearings is about 8-12 μm) . This paper mainly analyses the failure type and wear mechanism of the rotor bearing for material choice, design and manufacture of the bearing.Most metal elements of the bearing are made from GCr15 steel and are treated with normal heat-treatment. After analysing surface morphology of hundreds of rotor bearings and measuring their radial clearance with the aid of stereomicroscopy, SEM and other measuring methods, it was found that the main failure of the rotor bearing is resulted from adhesive wear and abrasive wear. The clearance of the failure bearing is larger than that of the new bearing , besides the wear trace, no fatigue symptoms are found. In order to study the main wear type and mechanism, authors observed and measured sectional micro-hardness,surface micro-structure, lubrication state and grease film thickness and surface roughness.The results are as follows:The micro-asperities are often in contact one another in the initial stage of wear. As the micro-asperities are gradully worn away, the surface roughness becomes smoother. Therefore, the contact of the micro-asperities is seldom taken place and the bearing comes into the stable stage of wear.At this stage the rotor bearing is in the best working condition. The longer the table stage of wear, the longer the life of the bearing.But there are some unfavorable factors which make friction surface rough, such as the vibration of the bearing system caused by dynamical unbalance, the lubrication system of the bearing in which the grease is only added into and never taken out from, the brake structure which presses a force from one side of the running axle to, let spiale stop when brake is needed. Under the condition of high running speed, those unfavorable factors may also cause the friction surface to rub severely each other in the stable stage of wear and make the friction surface rough again; the friction of the rough surface produces much friction heat, which will raise the temperature of the friction surface, soften the surface micro-structure, make the grease lose gradually its ability of lubrication, decend the ratio of film thickness, therefore, aggravate wear of the rotor bearing and eventually lead the rotor bearing to fail early. According to the further observation and analysis of the surface mopho-logy and the wear particles, it has been proved that adhesive wear and abrasive wear are the main failure types of the rotor bearing.