1. The appearance is often pockmarked. Pockmarked surface is the defect of irregular unevenness on the surface of seamless steel pipe due to severe wear of the rolling groove. Because manufacturers of fake and inferior seamless steel pipes want to pursue profits, it often happens that the groove rolling exceeds the standard. the
2. The surface is prone to scabbing. There are two reasons:. The material of fake and inferior seamless steel pipes is uneven and there are many impurities. The guides and guards of fake and inferior material manufacturers are poorly equipped and easy to stick to steel. These impurities are prone to scarring after biting into the roll.
3. Easy to fold. Folding is a variety of fold lines formed on the surface of seamless steel pipes, and this defect often runs through the longitudinal direction of the entire product. The reason for the folding is that the fake and inferior manufacturers pursue high efficiency, and the reduction is too large, resulting in ears, and the folding will occur in the next rolling process. The folded product will crack after bending, and the strength of the thick-walled seamless steel pipe will drop greatly. .
4. Scratch easily. The reason is that the fake and inferior material manufacturers have poor equipment, which is prone to burrs and scratches on the surface of seamless steel pipes. Deep scratches reduce the strength of the seamless steel pipe. the
5. prone to cracks. The reason is that its blank is adobe, and the adobe has many pores, and the adobe is subjected to thermal stress during the cooling process, resulting in cracks, and there are cracks after rolling. the
6. No metallic luster. It is light red or similar to pig iron for two reasons. Two, its blank is adobe. 2. The rolling temperature of counterfeit and inferior materials is not standard. Their steel temperature is measured visually, so they cannot be rolled according to the specified austenite area, and the performance of seamless steel pipes cannot meet the standard naturally.
7. The cross section is elliptical. The reason is that in order to save materials, the reduction amount of the first two passes of the finished roll is too large, the strength of this kind of rebar is greatly reduced, and it does not meet the standard of rebar shape.
8. The transverse ribs are thin and low. The phenomenon of dissatisfaction often occurs. The reason is that in order to achieve a large negative tolerance, the reduction of the first few passes of the finished product is too large, the iron mold is too small, and the pass is not full. the
9. The composition of high-quality seamless steel pipes is uniform. The tonnage of the cold shearing machine is high, and the end face of the cutting head is smooth and neat. However, due to the poor quality of the fake and inferior materials, the end face of the cutting head often has the phenomenon of meat loss, that is, unevenness and no metallic luster. Moreover, because the products of fake and inferior material manufacturers have fewer heads, big ears will appear at the head and tail. the
10. The inner diameter fluctuates greatly. The reason is; 1. The steel temperature is unstable and has yin and yang sides. 2. The composition of steel is uneven. 3. Due to poor equipment and low foundation strength, the rolling mill has a large bounce. There will be a large change in the inner diameter within the same week, and such steel bars are prone to fracture due to uneven stress.
11. The material contains many impurities. The density of steel is relatively small, and the size is seriously out of tolerance, so it can be weighed and checked without a vernier caliper. For example, for rebar 20, the national standard stipulates that the maximum negative tolerance is 5%, and its single theoretical weight is 120 kg when the length is 9M, and its minimum weight should be: 120 X (l-5%) = 114 kg , The actual weight of a single piece weighed out is less than 114 kg, which is a fake and inferior seamless steel pipe, 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.
If there are any deficiencies in the above points, please add them. We welcome you to discuss knowledge about steel pipes and make progress through continuous exchanges.
