某轧辊直径由840 mm减少到780 mm时发生断裂,未达到其正常使用寿命,采用化学成分分析、断口分析、金相检验以及硬度检测等方法对轧辊断裂原因进行了分析。结果表明：轧辊辊颈与辊身交界处的表面存在微裂纹是导致其发生断裂的根本原因;由于套密封环时操件不当使得该处的表层显微组织发生淬火,形成薄且脆的淬火组织,加之该处为应力集中处,从而导致该处产生微裂纹;已经形成的微裂纹在轧辊工作时所承受压力和扭转力的作用下,由于应力集中裂纹尖端不断向轧辊中心扩展,当裂纹达到一定深度后,辊颈处无法承受外力的作用时便会发生瞬间失稳扩展,导致轧辊断裂。

A roller which hadn’t reached its normal lifetime fractured when its diameter reduced from 780 mm to 780 mm. Means such as chemical compositions analysis,fracture analysis,microstructure examination and the hardness test were used to analyze the fracture reason of the roller. The results show that there were micro cracks at the junction surface of roller body and roller neck,which was the main reason for the fracture. Thin and brittle quenching microstructure formed at this position because of the improper handling during seal ring covering process. Additionally,this position was just right the stress concentration zone,so micro cracks produced. Under the common action of the pressure and torsion stress,the formed micro cracks propagated to the center of the roller due to the stress concentration. As the crack depth increased to a certain value,fracture of the roller happened.