1. Shoddy thick-walled seamless steel pipes are prone to folding. Folding is a variety of fold lines formed on the surface of thick-walled 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. 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.
2. Fake and inferior thick-walled seamless steel pipes often have pockmarks on the surface. A pockmarked surface is a defect of irregular unevenness on the surface of thick-walled seamless steel pipe due to severe wear of the rolling groove. Because manufacturers of fake and inferior thick-walled seamless steel pipes want to pursue profits, it often happens that the groove rolling exceeds the standard.
3. The surface of fake and inferior thick-walled seamless steel pipes is prone to scarring. There are two reasons: a. The material of inferior thick-walled seamless steel pipe is uneven and there are many impurities. b. The guides and guards of fake and inferior material manufacturers are poorly equipped and easy to stick to steel. These impurities are easy to produce scarring after biting the roll.
4. Cracks are easy to occur on the surface of fake and inferior materials. The reason is that it blank is in Adobe, and Adobe has many pores. During the cooling process, the adobe is subjected to thermal stress and cracks occur. After rolling, there are cracks.
5. Fake and inferior thick-walled seamless steel pipes are easy to scratch. The reason is that the manufacturers of fake and inferior materials have poor equipment, which is easy to produce burrs and scratch the surface of thick-walled seamless steel pipes. Deep scratches reduce the strength of thick-walled seamless steel pipes.
6. Shoddy thick-walled seamless steel pipes have no metallic luster, are light red, or have a color similar to pig iron, for two reasons. a. Its blank is Adobe. b. The rolling temperature of counterfeit and inferior materials is not standard, and their steel temperature is measured visually, so rolling cannot be carried out according to the specified austenite region, and the performance of thick-walled seamless steel pipes naturally cannot meet the standards.
7. The horizontal ribs of fake and inferior thick-walled seamless steel pipes are thin and low and often appear to be full and unfulfilled.
8. The cross-section of fake and inferior thick-walled seamless steel pipes is elliptical. The reason is that to save materials, the reduction in the first two passes of the finished roll is too large. standard.
9. The composition of the high-quality thick-walled seamless steel pipe 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 inferior material, 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.
10. The material of fake and inferior thick-walled seamless steel pipes contains many impurities, the density of the 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 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, If the actual weight of a single piece weighed is less than 114 kg, it is a fake thick-walled 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.
11. The inner diameter of fake and inferior thick-walled seamless steel pipes fluctuates greatly because of: a. The temperature of the steel is unstable and there are Yin and Yang sides. b. The composition of the steel is not uniform. c. 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.
12. The trademark and printing of high-quality materials are more standardized.
13. Three thick-walled seamless steel pipes with large threads with a diameter of 16 or more, and the distance between the two trademarks is above 1M.
14. The longitudinal reinforcement of fake and inferior thick-walled seamless steel pipe rebar is often wavy.
Post time: Jun-30-2023