Major defects in seamless steel pipes

Seamless steel pipes are widely used in industries such as petroleum, chemical, power, and construction due to their strength, durability, and reliability. However, defects that arise during production or processing can severely impact pipe quality, performance, and safety.

To ensure seamless steel pipes meet strict industry standards, it is important to understand the common defects, their causes, and effective prevention methods. Below, we explore the eight major defects found in seamless steel pipes.

1. Folds in Seamless Steel Pipes

Appearance: Linear or spiral irregularities on the inner or outer surface, which may be continuous or discontinuous.
Causes: Poor raw material quality, inherent folds in billets, surface inclusions, severe scratches or cracks, sharp corners at grinding areas, or excessive stretching during post-drawing.
Prevention: Use high-quality raw materials, carry out strict inspections, and ensure careful grinding before further processing.

2. Cracks in Seamless Steel Pipes

Appearance: Linear or spiral cracks, typically 1 mm or deeper, found on the pipe surface.
Causes: Subsurface bubbles or inclusions in hot-rolled billets, cracks or deep pitting before drawing, or longitudinal scratches and abrasions during hot rolling or cold drawing.
Prevention: Improve billet quality, strengthen inspection and grinding, and reduce pitting, scratches, and abrasions during cold drawing.

3. Scratches on Seamless Steel Pipes

Appearance: Longitudinal grooves or streaks on the pipe surface, sometimes raised instead of recessed.
Causes: Internal billet scratches, residual oxide scale, die adhesion, uneven hardness of dies, chipping, hammer head defects, or poor mold finish.
Prevention: Enhance billet surface preparation, use high-strength and high-hardness molds, and ensure a smooth mold finish to minimize scratching.

4. Pits on Seamless Steel Pipes

Appearance: Localized depressions scattered across the surface, either periodic or irregular.
Causes: Scale or hard particles pressed into the surface during drawing or straightening, flaking of surface scale, or improper straightening operations.
Prevention: Remove surface scale and contaminants, maintain clean equipment and lubricants, and regularly check straightening machines for roller misalignment, worn grooves, or improper angles.

5. Roughness on Seamless Steel Pipes

Appearance: Small dot-like pits or rough patches on the surface.
Causes: Poor pickling, thick oxide scale after annealing, improper straightening, or rusting from humid storage environments.
Prevention: Control pickling operations, prevent excess oxide scale formation, and store pipes in dry, ventilated areas to avoid rust-related pitting.

6. Spotting on Seamless Steel Pipes

Appearance: Water spots or rust spots visible after storage or processing.
Causes: Contact with water or moisture without timely drying. Water spots appear shallow, while prolonged exposure leads to rust spots that may corrode the surface.
Prevention: Keep pipes dry during processing and storage, ensure proper ventilation, and avoid prolonged contact with corrosive moisture.

7. Warping in Seamless Steel Pipes

Appearance: Thin flakes on the inner or outer pipe surface, partially detached from the metal base.
Causes: Poor steel quality, subsurface bubbles exposed during cold drawing, scale warping during hot rolling, or deep transverse pits.
Prevention: Improve steel quality, remove surface scale before drawing, and ensure billets are defect-free before processing.

8. Scabbing in Seamless Steel Pipes

Appearance: Thin, irregular flakes or lumps adhered to the pipe surface that resist peeling.
Causes: Failure to remove folds, scale warping, or other surface defects during early stages of processing.
Prevention: Conduct thorough inspection, remove surface defects promptly, and ensure billets are properly prepared before drawing.

Conclusion

Seamless steel pipe defects—such as folds, cracks, scratches, pits, roughness, spotting, warping, and scabbing—can greatly reduce product quality and service life. By understanding their causes and implementing preventive measures, manufacturers can enhance production efficiency, ensure product reliability, and meet stringent industry standards.

For buyers and project managers, choosing suppliers who enforce strict quality control and inspection procedures is the best way to guarantee seamless steel pipes free from these common defects.