The defects on the outer surface of a seamless steel pipe are mainly the following:
1. Fold outside. The reasons for the formation are: poor quality of raw materials, mechanical scratches, and cracks in the metal surface during the deformation process.
2. Surface indentation (pits, scars). The reasons are: the surface of the tool is sticky metal, the surface of the seamless steel pipe is sticky to foreign matter, and metal blocks or other foreign materials are left in the hole type.
3. Ears, tweezers and green lines. The reasons for the formation are: the tools used are unreasonable, improper adjustments, hole-type asymmetry, or improper size of incoming materials.
4. External abrasions. The cause of the formation is that foreign objects scratch the surface of the seamless steel pipe.
5. Point (face). Mainly due to tool wear and oxide scales.
