Common quality problems of hot-rolled seamless pipes in the production process

The production process of hot-rolled seamless steel pipes involves multiple stages, each of which presents potential quality challenges. Union Steel Industry Co., Ltd. has summarized common quality issues and corresponding control measures to ensure product reliability.

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1. Tube Billet Defects

Defects in tube billets can significantly impact the final steel pipe quality:

Cracks: Surface or internal cracks may result from solidification defects or rolling issues during ingot or continuous casting billet production.

Inclusions: Non-metallic inclusions such as oxides and sulfides weaken the pipe’s mechanical properties.

Porosity: Internal voids reduce density and structural strength.

Segregation: Uneven chemical composition leads to inconsistent mechanical performance.

Size Deviation: Variations in diameter, length, or other dimensions can interfere with subsequent piercing and rolling processes.

Control Measures:

Select high-quality tube billets and perform rigorous inspections before processing.

2. Heating Process Issues

Proper heating is crucial for maintaining material integrity:

Uneven Heating: Causes non-uniform deformation, affecting wall thickness distribution.

Overheating/Overburning: Excessive heat leads to grain coarsening, reducing mechanical strength and causing cracks. Overburning results in severe oxidation, forming surface defects.

Control Measures:

Optimize heating parameters to ensure uniform heat distribution.

Avoid excessive temperatures to prevent oxidation and grain coarsening.

3. Perforation Defects

Perforation is a critical step in forming the pipe’s hollow structure, and various defects may arise:

Uneven Wall Thickness: Due to misaligned piercing heads or incorrect roller adjustments.

Internal and External Surface Defects:

Spiral Channel: Surface defects that reduce mechanical strength.

Ears: Surface protrusions that interfere with rolling.

Inner Folds: Internal surface defects that weaken pipe integrity.

Center Hole Deviation: Improper piercing head alignment affects straightness and wall thickness uniformity.

Control Measures:

Fine-tune piercing and roller settings to maintain consistency.

4. Rolling Process Issues

Defects introduced during rolling affect dimensional accuracy and structural integrity:

Uneven Wall Thickness: Caused by roller wear or improper adjustments.

Outer Diameter Tolerance Exceeded: Due to roller misalignment or wear.

Surface Defects:

Scratches: Reduce surface quality.

Rolling Overlap: Overlapping layers affect strength and performance.

Straightness Deviation: Pipes may bend excessively during rolling.

Control Measures:

Regularly inspect and adjust rolling equipment to maintain precision.

5. Cooling and Straightening Challenges

Issues during cooling and straightening can introduce residual stress and defects:

Uneven Cooling: Leads to residual internal stress, affecting mechanical properties.

Over-Straightening or Under-Straightening:

Over-Straightening introduces new defects.

Under-Straightening fails to correct bending deformation.

Control Measures:

Optimize cooling processes to minimize stress and maintain straightness.

6. Inspection Errors

Quality control is crucial to prevent defects from reaching end-users:

Missed Inspections: Improper inspection methods or operator errors may overlook defects.

Misjudgment: Defective pipes may be mistakenly approved or rejected, affecting efficiency.

Control Measures:

Utilize advanced inspection technology to enhance accuracy.

Implement strict quality control protocols to ensure consistency.

By identifying and addressing potential quality issues, manufacturers can ensure the production of high-performance, defect-free hot-rolled seamless steel pipes, meeting industry standards and application requirements.