某E355钢冷拔油缸管内表面存在较密集的点状缺陷。采用宏观观察、化学成分分析、非金属夹杂物分析、金相检验、扫描电镜和能谱分析等方法对油缸管表面出现点状缺陷的原因进行了分析。结果表明：E355钢冶炼工艺控制不当造成硫含量偏高，从而形成较多含硫A类非金属夹杂物，破坏了冷拔油缸管表面钝化膜，在A类非金属夹杂物四周形成空洞，而酸洗过程操作不当造成过酸洗形成了点蚀，最终导致冷拔油缸管内表面形成点状缺陷。

The inner surface of a cold drawing cylinder tube of E355 steel had dense spot defects. The causes of spot defects on the surface of cylinder tube were analyzed by means of macroscopic observation, chemical composition analysis, non-metallic inclusion analysis, metallographic examination, scanning electron microscope and energy spectrum analysis. The results show that the improper smelting process control of E355 steel resulted in the high sulfur content, which resulted in the formation of more sulfur-containing A-type non-metallic inclusions, the destruction of the passivation film on the surface of the cold drawn cylinder tube, the formation of cavities around the A-type non-metallic inclusions, and the improper pickling process resulted in the formation of pitting corrosion due to over pickling, which eventually led to the formation of pitting defects on the inner surface of the cold drawn cylinder tube.