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1. Fake and inferior steel pipes are easy to fold.
Folding is a kind of broken line formed on the surface of steel pipe. This defect often runs through the longitudinal direction of the whole product. The reason for folding is that the fake and inferior manufacturers pursue high efficiency, press down too much, produce ears, fold when the next rolling, folded products will crack after bending, and the strength of steel decreases greatly.
2. The appearance of fake and inferior steel pipes is often hemp-faced.
The flake surface is a defect of irregular concave and uneven surface of steel due to serious groove wear. Because the fake and inferior steel pipe manufacturers want to pursue profits, rolling grooves often exceed the standard.
3. Scars are easily formed on the surface of fake and inferior steel pipes.
There are two reasons:
(1) The quality of fake and inferior steel pipes is not uniform and there are many impurities.
(2). The guide equipment of fake and inferior material manufacturers is simple and easy to stick to steel. These impurities bite the roll and cause scarring easily.
4. Cracks are easy to occur on the surface of fake and inferior materials. The reason is that the billet is adobe and there are many air holes in the adobe. During the cooling process, the adobe is subjected to thermal stress, resulting in cracks, and there are cracks after rolling.
5. Fake and inferior steel pipes are easy to scratch. The reason is that fake and inferior steel pipe manufacturers have poor equipment and are liable to produce burrs and scratch the surface of steel. Deep scratch reduces the strength of steel.
6. Fake and inferior steel pipes have no metallic luster and are light red or similar to pig iron. There are two reasons:
(1) Its billet is adobe.
(2) The rolling temperature of fake and inferior products is not standard, and their steel temperature is measured by visual method, so that they can not be rolled according to the prescribed austenite region, and the properties of steel can not meet the standard naturally.
7. The transverse bars of fake and inferior steel pipes are thin and low, and the phenomenon of filling is often unsatisfactory. The reason is that in order to achieve large negative tolerance, the manufacturer has a large reduction in the front of the finished products, a small iron profile and a unsatisfactory filling of the pass.
8. The cross-section of the fake and inferior steel pipe is elliptical, because in order to save material, the reduction of the first two passes of the finished roll is too large. The strength of this kind of screw steel decreases greatly, and it does not meet the standard of the shape and size of the screw steel.
9. The composition of high-quality steel is uniform, the tonnage of the cold shear is high, and the end face of the cutting head is smooth and neat, while the fake and inferior materials, due to the poor material quality, often have the phenomenon of meat loss on the end face of the cutting head, that is, uneven, and no metallic luster. And because the products of fake and inferior material manufacturers cut little, big ears will appear at the end.
10. The fake and inferior steel pipe material contains many impurities, the density of the steel is small, and the dimension is excessive. Therefore, without vernier calipers, it can be weighed and checked. For example, for screw steel 20, the national standard stipulates that the maximum negative tolerance is 5%, and the theoretical weight of a single screw is 120 kg at a fixed length of 9M. Its minimum weight should be 120 X (l-5%) = 114 kg. If the actual weight of a single screw is smaller than 114 kg, it is fake and inferior steel. The reason is that its negative tolerance exceeds 5%. Generally speaking, the effect of integer phase weighing is better, mainly considering the problem of cumulative error and probability theory.
11. The internal diameter of fake and inferior steel pipe fluctuates greatly because of the reasons.
(1) The temperature of steel is unstable with Yin and yang.
(2) The composition of steel is not uniform.
(3) Because of poor equipment and low foundation strength, the spring of rolling mill is large. There will be a big change in the same week, such steel bar stress is not uniform and easy to fracture.
12. Trademarks and prints of quality management are relatively standardized.
13. Large threads with diameters of more than 16 for three steel pipes. The spacing between the two trademarks is above IM.
14. The longitudinal bars of spurious and inferior steel are often wavy.
15. Fake and inferior steel pipe manufacturers do not drive, so the packing is relatively loose. The side is oval.
