利用数码相机、光学显微镜、扫描电镜以及能谱仪等仪器, 对某参与钢管轧制后失效报废的限动芯棒进行了解剖分析, 对失效芯棒的各种表面缺陷进行了观察和分类, 并探讨了缺陷产生的原因。结果表明: 限动芯棒经过轧制后产生的表面缺陷主要有片状脱落、网状裂纹、沟状缺陷和环状裂纹等, 高温氧化和高温磨损是限动芯棒表面失效的主要原因; 在轧制初期, 芯棒头部和中部表面的镀铬层被磨损, 随后形成氧化膜, 氧化膜在压力、摩擦力及热应力的作用下发生起泡乃至开裂、脱落; 裂纹首先从表面萌发, 逐渐向芯棒心部扩展、交汇, 在摩擦或内应力的作用下极易脱落, 甚至形成大面积的严重磨损; 芯棒表面的网状缺陷或大面积的氧化膜剥落进一步恶化, 裂纹逐渐变宽, 伴随着表层的块状脱落, 形成了较深的磨损沟, 并且在高温、润滑剂以及腐蚀液的作用下, 沟状缺陷的内表面发生氧化, 这些氧化皮的破裂和脱落加速了裂纹的扩展和局部脱落, 因此当限动芯棒表面出现沟状缺陷时, 意味着其失效速度将明显加快。

By means of digital camera, OM, SEM, and EDS, a scrapped retained mandrel after steel tube rolling was dissected. The surface defects of the scrapped retained mandrel were observed and classified, the cause for each kinds of defect was discussed. The results show that the surface defects of the scrapped retained mandrel consisted of flaking, map cracking, trench defect, and annular crack, etc. High temperature oxidation and high temperature wear were main reasons for the formation of these defects. The chromium coating at the end and the middle part of the retained mandrel were worn at the initial stage of the rolling. Then the oxidation film formed. The oxidation film blistered, crazed and then fell off. The cracks generated from the surface, expanded and met. They fell off because of friction and inter stress, and then heavy wear formed. With the deterioration of the map cracking, oxidation film, cracks and the drop of the mandrel, the wear trench formed. When trench defect appeared at the surface of the retained mandrel, the failure would be sped up.