1. Fake and inferior steel is prone to folding. Folds are various fold lines formed on the surface of the steel, and this defect often runs through the longitudinal direction of the entire product. The reason for the folds is that the counterfeit and inferior manufacturers pursue high efficiency, and the reduction amount is too large, resulting in ears, and folding occurs during the next rolling. The folded products will crack after bending, and the strength of the steel will be greatly reduced.
2. The appearance of fake and shoddy steel often has a pockmarked surface. The pitted surface is the irregular unevenness on the surface of the steel due to the serious wear of the rolling groove. Due to the pursuit of profit by manufacturers of counterfeit and inferior steel products, groove rolling often exceeds the standard.
3. The surface of fake and inferior steel is prone to scarring. There are two reasons: 1. The material of fake and inferior steel is uneven and there are many impurities. 2. The guide and guard equipment of the fake and inferior material manufacturers are simple and easy to stick to the steel. These impurities are prone to scarring after biting the roll.
4. The surface of fake and inferior materials is prone to cracks. For more CNC programming knowledge, pay attention to the WeChat public account (NC programming teaching), because its blank is adobe, and the adobe has many pores, and the adobe is subjected to thermal stress during the cooling process. Cracks occur after rolling.
5. Fake and inferior steel is easy to be scratched, the reason is that the fake and inferior material manufacturers have simple equipment, which is easy to produce burrs and scratch the surface of the steel. Deep scratches reduce the strength of the steel.
6. The fake and inferior steel has no metallic luster and is light red or similar to pig iron. There are two reasons for it. The blank is adobe.
7. The rolling temperature of fake and inferior materials is not standard, and their steel temperature is measured visually, so that the rolling cannot be carried out according to the specified austenite area, and the performance of the steel will naturally fail to meet the standard.
8. The horizontal bars of the fake and inferior steel are thin and low. For more CNC programming knowledge, pay attention to the WeChat public account (NC programming teaching), and there is often a phenomenon of dissatisfaction. The reason is that in order to achieve a large negative tolerance, the reduction amount of the first few passes of the finished product Too large, the iron type is too small, and the hole type is not full.
9. The cross-section of the fake and inferior steel is oval. The reason is that in order to save materials, the reduction amount of the first two passes of the finished roll is too large. .
10. The composition of high-quality steel is uniform, the tonnage of the cold shearing machine is high, and the end face of the cutting head is smooth and tidy. However, due to the poor material of the fake and inferior material, the end face of the cutting head often has the phenomenon of falling meat, that is, unevenness and no metallic luster. And because the products of the fake and inferior material manufacturers have less cutting heads, there will be big ears at the head and tail.
11. The material of fake and inferior steel contains a lot of impurities, the density of the steel is too small, and the size is out of tolerance, so it can be weighed and checked without a vernier caliper. For example, for rebar 20, pay more attention to the WeChat public account (NC programming teaching) for more CNC programming knowledge. The national standard stipulates that the maximum negative tolerance is 5%. When the fixed length is 9M, its single theoretical weight is 120 kg, and its smallest The weight should be: 120 X (l-5%) = 114 kg. If the actual weight of a single piece is less than 114 kg, it is fake and inferior steel, because its negative tolerance exceeds 5%. Generally speaking, the effect of whole phase weighing will be better, mainly considering the problem of cumulative error and probability theory.
12. The inner diameter of the fake and inferior steel fluctuates greatly, the reason is: l. The steel temperature is unstable and there are yin and yang sides. 2. The composition of steel is not uniform. 3. Due to the simple equipment, more NC programming knowledge should pay attention to the WeChat public account (NC programming teaching), the foundation strength is low, and the rolling mill bounces greatly. There will be a large change in the inner diameter within the same week, and the uneven stress of such a steel bar is prone to fracture.
13. The trademark and printing of high-quality materials are relatively standardized.
14. For large threads with a diameter of more than 16 steel materials, the spacing between the two trademarks is above IM.
15. The longitudinal bars of the fake and inferior steel rebar are often wavy.
16. Since the manufacturers of fake and shoddy steel do not have traffic, the packaging is relatively loose, and the side is oval.