1. Substandard steel pipes are prone to folding.

Folding refers to various zigzag lines that form on the surface of steel pipes; this type of defect often runs along the entire length of the product. The cause of folding is typically due to substandard manufacturers pursuing high efficiency, resulting in excessive reduction during rolling, which creates "ears." When the material undergoes the next rolling pass, these "ears" transform into folds. Products with such defects are prone to cracking after bending, significantly reducing the steel's strength.

2. Substandard steel pipes often exhibit a rough, pitted surface appearance.

Surface pitting is a defect characterized by irregular, uneven protrusions on the steel surface, caused by severe wear of the rolling grooves. Unfortunately, substandard steel pipe manufacturers, driven by profit motives, often exceed the permissible limits in groove rolling.

3. Substandard steel pipes are prone to forming scars on their surfaces.

There are two reasons: (1) The substandard steel pipe material has uneven composition and contains many impurities. (2) Manufacturers of counterfeit materials often use rudimentary guide devices, making it easy for steel to stick to the rollers. These impurities, once embedded in the rolls, tend to cause scale formation.

4. Substandard materials are prone to cracking on their surfaces because their billets are made of raw clay, which contains numerous air pockets. As the clay billets cool, these inherent weaknesses become more pronounced.

During the process, cracks are generated due to thermal stress, and after rolling, these cracks become visible.

5. Counterfeit and substandard steel pipes are prone to scratching, as these manufacturers typically use rudimentary equipment that easily produces burrs, damaging the surface of the steel material. Deep scratches can significantly reduce the strength of the steel.

6. Counterfeit and substandard steel pipes lack metallic luster, appearing instead with a pale red hue or a color resembling pig iron. There are two main reasons for this: first, their billets are made from raw, unrefined material; second, the rolling temperature of these counterfeit materials is not properly controlled—instead, the steel temperature is estimated by eye. As a result, they cannot be rolled within the specified austenitic temperature range, naturally leading to subpar material performance that fails to meet industry standards.

7. The transverse bars of substandard steel pipes are thin and poorly formed, often resulting in incomplete filling. This occurs because manufacturers, aiming to achieve significant negative tolerances, tend to apply excessive rolling reductions during the initial stages of production, leading to smaller die sizes and insufficient metal flow into the final pass.

8. The cross-section of substandard steel pipes is elliptical because manufacturers, in an effort to save materials, have set the reduction levels too high during the first two passes before the finishing roll. As a result, the strength of this rebar is significantly reduced, and it also fails to meet the standard dimensions for rebar profiles.

9. High-quality steel boasts uniform composition and features a high-tonnage cold shear machine, resulting in smooth and neatly cut head ends. In contrast, substandard materials—due to their inferior quality—often exhibit material loss at the cut ends, leading to uneven, bumpy surfaces that lack metallic luster. Additionally, because manufacturers of counterfeit or low-grade materials typically produce fewer cuts, the head and tail sections often end up with large "ears" or protrusions.

10. Inferior-quality steel pipes often contain high levels of impurities, resulting in a lower steel density and significant deviations from the specified dimensions. Therefore, if a dial caliper is unavailable, you can verify the material by weighing it against the standard specifications. For instance, for 20mm threaded steel bars, the national standard mandates a maximum negative tolerance of 5%. When the fixed length is 9 meters, the theoretical weight of a single bar should be 120 kilograms. Consequently, the minimum acceptable weight would be: 120 × (1 - 5%) = 114 kilograms. If the actual weight measured for a single bar falls below 114 kilograms, it indicates that the steel is substandard, as its negative tolerance exceeds the permitted 5% limit. Generally speaking, weighing an entire batch yields more accurate results, primarily because it accounts for cumulative errors and considers probabilistic factors.

11. The inner diameter dimensions of substandard and counterfeit steel pipes fluctuate significantly due to the following reasons: 1. Unstable steel temperature, resulting in uneven heating on different sides. 2. Non-uniform composition of the steel material. 3. Limited equipment and weak foundation, leading to substantial springback in the rolling mill. As a result, the same pipe may exhibit considerable variation within a single circumference, causing uneven stress distribution and increasing the risk of fracture.

12. The trademarks and markings on the high-quality pipes are all quite standardized.

13. For large threads with a diameter of 16 mm or more on the three steel pipes, the spacing between the two trademarks is at least 10 mm.

14. The longitudinal bars of substandard and counterfeit steel rebar often appear wavy.

15. Fake and substandard steel pipe manufacturers, lacking overhead cranes, tend to pack their products loosely, resulting in oval-shaped sides.