1. Fake and inferior thick-walled seamless steel pipes are prone to folding. Folds are various fold lines formed on the surface of thick-walled seamless steel pipes. This defect often runs throughout the longitudinal direction of the product. The reason for folding is that shoddy manufacturers pursue high efficiency, and the reduction amount is too large, resulting in ears. Folding will occur during the next rolling process. The folded product will crack after bending, and the strength of the thick-walled seamless steel pipe will be greatly reduced.
2. Fake thick-walled seamless steel pipes often have pitted surfaces on the surface. Pockmarking is an irregular uneven defect on the surface of thick-walled seamless steel pipes caused by severe groove wear. As manufacturers of shoddy thick-walled seamless steel pipes pursue profits, groove rolling often exceeds the standard.
3． The surface of fake thick-walled seamless steel pipes is prone to scarring. There are two reasons: ① The material of fake and inferior thick-walled seamless steel pipes is uneven and contains many impurities. ② The guide equipment of fake and inferior material manufacturers is simple and easy to stick to steel. These impurities can easily cause scarring after biting the rollers.
4． The surface of fake and inferior materials is prone to cracks because its raw material is adobe, which has many pores. The adobe is subject to thermal stress during the cooling process, causing cracks, and cracks appear after rolling.
5. Fake and inferior thick-walled seamless steel pipes are easy to scratch. The reason is that the equipment of the fake and inferior material manufacturers is simple and easy to produce burrs, which can scratch the surface of thick-walled seamless steel pipes. Deep scratches reduce the strength of thick-walled seamless steel pipes.
6． Fake thick-walled seamless steel pipes have no metallic luster and are light red or similar in color to pig iron. There are two reasons. ① Its blank is adobe. ② The rolling temperature of fake and inferior steel pipes is not standard. Their steel temperature is measured by visual inspection. This makes it impossible to roll according to the specified austenite area. Naturally, the performance of thick-walled seamless steel pipes cannot meet the standards.
7. The transverse ribs of fake and inferior thick-walled seamless steel pipes are thin and low, and they often appear to be underfilled. The reason is that to achieve a large negative tolerance, the manufacturer’s reduction in the first few passes of the finished product is too large, the iron shape is too small, and the hole pattern is not filled.
8. The cross-section of the fake thick-walled seamless steel pipe is oval. The reason is that to save materials, the manufacturer uses a larger reduction amount in the first two passes of the finished roller. The strength of this kind of rebar is greatly reduced, and it does not meet the overall dimensions of the rebar. standards.
9. The composition of high-quality thick-walled seamless steel pipes is uniform, the tonnage of the cold shear machine is high, and the cut end face is smooth and neat. However, due to poor material quality, the cut-end face of fake and inferior materials often has meat loss, that is, it is uneven and has no metallic luster. And because the products produced by 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 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%. When the fixed length is 9M, the theoretical weight of a single rod is 120 kg. Its minimum weight should be 120 X (l-5%) = 114 kg. If the actual weight of a single pipe is less than 114 kilograms, it is a fake thick-walled seamless steel pipe because its negative tolerance exceeds 5%. Generally speaking, the effect of phase-integrated weighing will be better, mainly considering the issues of cumulative error and probability theory.
11. The inner diameter size of fake thick-walled seamless steel pipes fluctuates greatly due to the following reasons: ① Unstable steel temperature has Yin and Yang sides. ②The composition of steel is uneven. ③Due to crude equipment and low foundation strength, the rolling mill bounces greatly. There will be large changes in the inner diameter within the same week. Such uneven stress on the steel bars will easily lead to breakage.
12. The trademarks and printing of high-quality materials are relatively standardized.
13. For thick-walled seamless steel pipes with large threads with a diameter of 16 or more, the distance between the two trademarks is above IM.
14. The longitudinal bars of the rebar in fake thick-walled seamless steel pipes are often wavy.
Post time: Jan-04-2024