Quality defects in seamless steel tubes such as internal folds, delamination, inclusions, through-cracks, porosity, severe wall thickness unevenness, bulges, and deep scratches (>30μm) cannot be repaired.
These defects are internal structural damage or structural failures that directly affect the pressure-bearing capacity and safety of the steel tube, and cannot be eliminated through surface treatment. For example:
1. Internal folds and delamination: Originate from stress concentration during perforation or inclusions in the tube blank, leading to wall delamination, which is highly susceptible to propagation and rupture under high pressure.
2. Inclusions and porosity: Disrupt material continuity, forming stress concentration points, easily triggering crack propagation.
3. Through-cracks: Penetrate the tube wall; even if repaired by welding, it will introduce new stress sources, and repair and use are strictly prohibited.
4. Severe wall thickness unevenness and bulges: Caused by uncontrolled rolling, cannot be corrected, and pose an explosion risk.
5. Deep scratches (>30μm): These are prone to developing into fatigue cracks under alternating loads, and are considered high-risk defects, especially in high-pressure systems.
⚠️ According to GB/T 8163-2023, seamless steel pipes used for transporting flammable or toxic media are not permitted to undergo any form of defect repair. If the above-mentioned defects are found, the entire pipe must be scrapped to ensure project safety.
