1. Counterfeit rectangular tubes are prone to folding. Folds are various fold lines formed on the surface of rectangular tubes. This defect often runs through the entire longitudinal direction of the product. The reason for the folding is that counterfeit manufacturers pursue high efficiency and the amount of pressing is too large, resulting in ears. Folding occurs during the next rolling process. The folded product will crack after bending, and the strength of the steel will be greatly reduced.
2. Counterfeit rectangular tubes often have pockmarks on the surface. Pockmarks are irregular and uneven defects on the surface of steel caused by severe wear of the rolling groove. Since counterfeit rectangular tube manufacturers want to pursue profits, the rolling groove often exceeds the standard.
3. Counterfeit rectangular tubes are prone to scarring on the surface. There are two reasons: (1). The material of counterfeit rectangular tubes is uneven and contains many impurities. (2). The guide equipment of the counterfeit manufacturer is simple and easy to stick to the steel. These impurities
4. The surface of the counterfeit material is prone to cracks. The reason is that its blank is adobe, which has many pores. The adobe is subjected to thermal stress during the cooling process, resulting in cracks. After rolling, there are cracks.
5. The counterfeit rectangular tube is easy to scratch. The reason is that the equipment of the counterfeit rectangular tube manufacturer is simple and easy to produce burrs, which scratch the surface of the steel. Deep scratches reduce the strength of the steel.
6. The counterfeit rectangular tube has no metallic luster and is light red or there are two reasons. Second, its blank is adobe. The rolling temperature of the counterfeit material is not standard. Their steel temperature is visually measured, so it cannot be rolled according to the specified austenite area, and the performance of the steel naturally cannot meet the standard.
7. The transverse ribs of the counterfeit rectangular tube are thin and low, and the phenomenon of insufficiency often occurs. The reason is that the manufacturer has a large negative tolerance, and the pressure of the first few passes of the finished product is too large.
8. The cross section of the counterfeit rectangular tube is elliptical. The reason is that in order to save materials, the manufacturer has a large amount of pressure reduction in the first two passes of the finished product roller. The strength of this threaded steel is greatly reduced, and it does not meet the standard of the threaded steel appearance size.
9. The composition of high-quality steel is uniform, the tonnage of the cold shearing machine is high, and the end face of the cut head is smooth and neat. However, due to the poor material quality, the end face of the cut head of the counterfeit material often has the phenomenon of meat loss, that is, unevenness, and no metallic luster. Moreover, due to the small number of cut heads of the manufacturer's products, large ears will appear at the head and tail.
10. The material of the counterfeit rectangular tube contains many impurities, the density of the steel is low, and the size is out of tolerance. In the absence of a vernier caliper, it can be weighed and checked. For example, for rebar 20, the national standard stipulates that the maximum negative tolerance is 5%. When the fixed length is 9M, its theoretical weight of a single root is 120 kg. Its minimum weight should be: 120 X (1-5%) = 114 kg. If the actual weight of a single root is less than 114 kg, it is fake and inferior steel. Generally speaking, the whole weighing effect will be better, mainly considering the cumulative error and probability theory.
11. The inner diameter size of fake and inferior rectangular tubes fluctuates greatly. The reasons are: 1. The steel temperature is unstable and there are positive and negative sides. 2. The composition of the steel is uneven. 3. Due to the simple equipment, low foundation strength, and large bounce of the rolling mill. There will be a large change in the same week. Such steel bars are unevenly stressed and prone to fracture.
12. The trademarks and printing of high-quality pipes are relatively standardized.
13. The spacing of rectangular tubes with a diameter of more than 16 is above IM.
14. The longitudinal reinforcement of fake and inferior steel rebars is often wavy.
