1. Pre-hardening steel is not annealed before quenching;
2, high hardness, attention to hardness and toughness is contradictory body, looking for a reasonable balance zone;
3, uneven hardness, workpiece hardness deviation is not only poor polishing effect, stress;
4, quenching, overheating, resulting in coarse grains, decarbonization serious, martensite coarse, coarse crystal fracture, toughness, plastic low;
5, the lack of tempering, resulting in residual stress, in the subsequent processing or production environment stress superposition, stress is greater than the fatigue strength of steel;
6, quenching after tempering or temper insulation time is insufficient, over burning, resulting in process defects, heating or cooling too fast, quenching cooling media selection, cooling temperature is too low, cooling time is too long.