1. High-quality spiral steel pipes have standardized trademarks and markings.

2. High-quality spiral steel pipes have uniform composition, are cut using high-tonnage cold shearing machines, and have smooth and regular cut ends. Inferior materials, due to poor raw materials, often have uneven cut ends with missing material, lacking metallic luster. Furthermore, because manufacturers of inferior materials cut fewer ends, large burrs may appear at the beginning and end.

3. Inferior spiral steel pipes often have a pitted surface. This pitting is caused by severe wear of the rolling groove, resulting in irregular unevenness on the steel surface. Because manufacturers of inferior spiral steel pipes seek profit, they often exceed the rolling groove’s maximum allowable length.

4. Inferior spiral steel pipes are prone to surface scaling.

5. 6. Substandard spiral welded steel pipes are prone to surface cracking because the billet is made of clay, which has many pores. During cooling, the clay billet is subjected to thermal stress, causing cracks that appear after rolling.

7. Substandard thick-walled spiral welded steel pipes are easily scratched because the equipment used by manufacturers is rudimentary, easily producing burrs that scratch the steel surface. Deep scratches reduce the strength of the steel.

8. Substandard spiral welded steel pipes lack metallic luster and are pale red or similar in color to pig iron.

9. For spiral welded steel pipes with a diameter of 16mm or more, the distance between the two threads is more than 1m.

10. The longitudinal ribs of substandard spiral welded steel often have a wavy shape.

11. Because manufacturers of substandard spiral welded steel pipes do not have overhead cranes, their packaging is relatively loose. 11. The transverse ribs of substandard spiral steel pipes are thin and low, often appearing incomplete. This is because, to achieve maximum negative tolerance, the manufacturer uses excessive reduction in the first few passes, resulting in smaller molds and incomplete filling of the die.

12. The cross-section of substandard spiral steel pipes is elliptical. This is because, to save material, the manufacturer uses excessive reduction in the first two passes of the rolling mill. This significantly reduces the strength of the threaded steel and does not meet the standard dimensions for threaded steel.

13. Substandard spiral steel pipes contain many impurities, have lower steel density, and exhibit severe dimensional deviations. Therefore, in the absence of calipers, weighing is necessary for verification.

14. The inner diameter of substandard spiral steel pipes fluctuates significantly.

15. Substandard spiral steel pipes are prone to folding. Folding refers to various zigzag lines on the surface of the spiral steel pipe, a defect that often runs longitudinally throughout the entire product. The reason for folding is that defective manufacturers pursue high efficiency and reduce the amount of material too much, which causes ears to form. When the material is rolled in the next rolling process, folding will occur. Folded products will crack after bending, and the strength of the steel will drop significantly.