How to identify fake and inferior steel pipes:
1. Fake and inferior thick-walled steel pipes are prone to folding. Folds are various fold lines formed on the surface of thick-walled steel pipes. This defect often runs throughout the longitudinal direction of the product. The reason for folding is that shoddy manufacturers pursue efficiency and the reduction 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 steel will be greatly reduced.
2. Fake and inferior thick-walled steel pipes often have pitted surfaces on the surface. Pockmarking is an irregular uneven defect on the steel surface caused by severe wear of the rolling groove. As manufacturers of shoddy thick-walled steel pipes pursue profits, groove rolling often exceeds the standard.
3. The surface of fake thick-walled steel pipes is prone to scarring. There are two reasons: (1). The material of fake and inferior 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 thick-walled steel pipes 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 steel pipes are easy to scratch. The reason is that the equipment of the fake and inferior thick-walled steel pipe manufacturers is simple and easy to produce burrs and scratch the surface of the steel. Deep scratches reduce the strength of steel.
6. Fake and inferior thick-walled steel pipes have no metallic luster and are light red or similar in color to pig iron. There are two reasons. One is that its blank is adobe. The second is that the rolling temperature of fake and inferior steel products is not standard. Their steel temperature is measured by visual inspection. In this way, rolling cannot be carried out according to the specified austenite area, and the performance of the steel will naturally not meet the standards.
7. The transverse ribs of fake and inferior thick-walled steel pipes are thin and low, and they often appear to be underfilled. The reason is that to achieve a large negative tolerance, the reduction amount of 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 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 steel is uniform, the tonnage of the cold shear machine is high, and the end face of the cutting head is smooth and neat. However, due to poor material quality, the end face of the cutting head of fake and inferior materials often has the phenomenon of 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 thick-walled 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 standard stipulates that the maximum 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: 120X (l-5%) = 114 kg, weighing If the actual weight of a single piece is less than 114 kilograms, it is fake steel because its negative tolerance exceeds 5%. Generally speaking, the effect of phase-integrated weighing will be good, mainly considering the issues of cumulative error and probability theory.
11. The inner diameter of fake and inferior thick-walled steel pipes fluctuates greatly because of: 1. The unstable steel temperature has a yin and yang side. ②. The composition of steel is uneven. ③. Due to the crude equipment and low foundation strength, the rolling mill has a large bounce. 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 thick-walled steel pipes are relatively standardized.
13. For large threads with a diameter of 16 or more for three steel pipes, the distance between the two trademarks is above IM.
14. The longitudinal bars of shoddy steel rebar are often wavy.
15. The fake and inferior thick-walled steel pipe manufacturers have no operation, so the packaging is relatively loose. The sides are oval.
Welded pipe process flow: uncoiling – flattening – end shearing and welding – looper – forming – welding – internal and external weld bead removal – pre-correction – induction heat treatment – sizing and straightening – eddy current Inspection – cutting – hydraulic inspection – pickling – final inspection – packaging
Post time: Dec-26-2023