Causes and Preventive Measures of Fracture of Straight-Line Walking Spool of Excavator

Surface of straight-line walking spool for excavator adopted carburization-quenching treatment, after service for a period of time, fatigue fracture occurred at oil holes. Through Macro observation, scanning electron microscopy and energy spectrum analysis, metallographic examination and hardness test and other methods, the reason for spool fracture were analyzed. The results showed that the failure form of spool was low-stress and high-cycle fatigue fracture under tension-compression load. The fracture was mainly related to sharp corner effect of hole edge caused by improper design, the surface damage caused by abnormal grinding and network carbide formed by poor carburization. Through finite element simulation, it was found that transverse load had a significant effect on the size and distribution of stress at circular hole. The edge rounding could effectively reduce stress concentration and reduce sharp corner effect.