某热轧厂在进行穿孔操作过程中,一支顶头仅穿孔50次就发现其表面存在凹陷缺陷,将其与穿孔200次仍完好的顶头进行了理化检验及对比分析.结果表明:顶头氧化层出现游离块状铁素体,导致该区域组织松散、硬度降低,进而致使顶头出现凹陷缺陷而失效.

During the process of punching in a hot rolling plant,concave defect was found on the surface of a piercing plug which was used for only 50 times.The piercing plug was compared with another intact one used for 200 times from the aspects of physical testing and chemical anslysis.The results show that the structure became loose and the hardness declined due to the granular ferrite existing in the oxidation layer,which led to the concave defect on the surface of the piercing plug.