Irreversible defects in seamless steel tubes must be scrapped entirely. Repair through welding, diameter expansion, or other methods is strictly prohibited to ensure safe operation under high pressure, high temperature, or corrosive conditions.
I. Handling Principles
1. Immediate Isolation: Once defects such as internal folds, delamination, inclusions, through-cracks, porosity, severe wall thickness unevenness, bulges, or deep scratches (>30μm) are confirmed to be irreparable, the steel tube should be immediately removed from the qualified product pool to prevent misuse.
2. Marking and Recording: A clear scrap mark (such as "×" or "scrap") should be made on the defective tube, and the defect type, location, and batch information should be recorded to facilitate tracing the production process.
3. Centralized Disposal: Scrapped steel tubes should be stored in a designated area to avoid confusion with qualified products. They can then be recycled as scrap steel.
II. Standards Applicable
According to the national standard GB/T 8163-2023 "Seamless Steel Pipes for Transporting Fluids,"
1. Seamless steel pipes used for transporting flammable or toxic media are not permitted to undergo any form of defect repair. Any structural defects found must result in immediate rejection.
2. Furthermore, industry standards for petrochemicals, boilers, and pressure vessels (such as SH/T 3405 and GB 150) also explicitly require that steel pipes with internal defects must not be used in pressure-bearing equipment to ensure the inherent safety of the system.
III. Recommendations for Further Improvement
To reduce the occurrence of such defects, it is recommended to optimize from the source:
1. Strengthen the quality inspection of pipe blanks to eliminate subcutaneous porosity, inclusions, and other original defects;
2. Optimize piercing and rolling process parameters to prevent internal folds and delamination;
3. Regularly calibrate testing equipment to ensure that the sensitivity of ultrasonic and eddy current testing systems meets standards.
