Abstract: A ratchet fracture accident of driving shoveling blade was analyzed by means of chemicalcomposition analysis, fracture analysis, metallographic examination and hardness distribution testing of carburizedlayer.The analysis results indicated that the main fracture reason of the ratchet was overheating.Carbon eliminatedat the surface of ratchet and grain was growing and coarsening because of overheating and then quenching cracks wereproduced at the surface of ratchet.Ratchet bore excess impact and then fracture formed on the surface of ratchet.