Currently, many spiral steel tube manufacturers produce pipes that do not meet the standard surface requirements despite the continuous production of spiral tubes. Let's delve into the specific surface requirements for these pipes.
Although standards specify "surface smoothness" for spiral steel tubes, various factors can lead to over a dozen surface issues during production. These issues mainly include: cracks, hairlines, internal and external folds, roll-breaks, internal and external straight lines, delamination, scars, pits (pockmarks), scratches, internal and external spiral marks, blue lines, corrective depressions, roller marks, etc.
Among the aforementioned surface issues, some pose severe risks to the performance indicators of spiral steel tubes and are considered critical issues, such as cracks, internal and external folds, roll-breaks, delamination, scars, dents, and bulges. Other issues have relatively minor impacts on the pipes' performance and are classified as conventional issues, including pockmarks, blue lines, scratches, slight internal and external straight/spiral marks, corrective depressions, and roller marks.
Even though some very minor conventional issues with negligible impact on the practical use of spiral tubes may be tolerated, standards impose strict limitations on the depth and length (size) of these issues.
For critical surface issues on spiral tubes, methods like cutting or grinding are employed to eliminate them completely. When grinding is performed on pipes where it is allowed, the depth of the ground area and the shape of the grinding points must adhere strictly to the standards. To further enhance the surface quality of spiral tubes, processes such as shot blasting (or sandblasting), sanding, or machining may also be applied to the inner and outer surfaces of the tubes.
