灰铁刹车盘裂纹的失效分析

Analysis on Cracking Failure of Gray Cast Iron Brake Disk

为了解决刹车盘在服役过程中存在表面裂纹的问题,对此进行了失效分析。结果表明:石墨形态为A形石墨+C形石墨,A型石墨占90%,石墨长度3级,硬度为223 HB均符合技术要求;基体组织为铁素体+珠光体,在刹车盘表面的石墨周围,存在片层状珠光体组织,硬度为347 HB;刹车盘工作时,表面温度较高,温度梯度较大,在高温下形成了应力和应变集中,导致出现了疲劳裂纹并沿垂直摩擦力的方向朝工件纵深发展,这是裂纹产生的根本原因。改进措施是安装缓速器,经过验证,解决了刹车盘表面早期开裂的问题。

The main purpose of this paper was to solve the problem of surface cracks in the service process of brake disc.Results showed that the graphite morphology was A-shaped graphite+C-shaped graphite,and type A graphite accounted for 90%.The length of graphite was grade 3,and the hardness of 223 HB,meeting the technical requirements.The microstructures of the matrix were ferrite(F)+pearlite(P).Around the graphite on the surface of the brake disc,there were lamellar pearlite structures with a hardness of about 347 HB.When the brake disc was working,the surface temperature was higher and the temperature gradient of the workpiece was larger.At high temperature,stress and strain were concentrated,which resulted in fatigue cracks.Cracks developed along the direction of vertical friction to the depth of the workpiece,and this was the root cause of cracking failure.The improvement measure was to install a retarder.After verification,the problem of early cracking on the surface of brake disc was solved.