Identification method for counterfeit and inferior thick walled seamless pipes

Release time：2023-12-06    Click：41

1. Fake and inferior thick walled seamless steel pipes are prone to folding. Folding refers to various creases formed on the surface of thick walled seamless steel pipes, which often run through the longitudinal direction of the entire product. The reason for the occurrence of folding is due to the pursuit of high efficiency by inferior manufacturers, which leads to excessive pressing and the generation of ears. Folding occurs during the next rolling process, and the folded product will crack after bending, resulting in a significant decrease in the strength of thick walled seamless steel pipes.

2. Fake and inferior thick walled seamless steel pipes often have pitting on the surface. Pitted surface is a defect caused by severe wear of the rolling groove, resulting in irregular unevenness on the surface of thick walled seamless steel pipes. Due to the pursuit of profit by manufacturers of fake and inferior thick walled seamless steel pipes, it is common for groove rolling to exceed the standard.

3. The surface of fake and inferior thick walled seamless steel pipes is prone to forming scars. 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 steel, and these impurities can easily cause scars when they bite the rolling mill.

4. The surface of fake and inferior materials is prone to cracking because their raw materials are adobe, which has many pores. During the cooling process, the adobe is subjected to thermal stress, resulting in cracks that appear after rolling.

5. Counterfeit and inferior thick walled seamless steel pipes are prone to scratches due to the crude equipment of the manufacturer, which can easily produce burrs and scratch the surface of the thick walled seamless steel pipes. Deep scratching reduces the strength of thick walled seamless steel pipes.

6. Fake and inferior thick walled seamless steel pipes have no metallic luster and appear in a light red or pig iron like color. There are two reasons for this: firstly, their billet is adobe. 2. The temperature for rolling fake and inferior materials is not standard, and their steel temperature is visually measured, which makes it impossible to roll according to the specified austenite area, and the performance of thick walled seamless steel pipes cannot meet the standard.

7. The transverse reinforcement of counterfeit thick walled seamless steel pipes is thin and low, often resulting in insufficient filling. The reason is that the manufacturer, in order to achieve a large negative tolerance, presses the first few layers of the finished product too much, the iron shape is too small, and the hole shape is not fully filled.

8. The cross-section of counterfeit thick walled seamless steel pipes is elliptical. The reason is that the manufacturer, in order to save materials, has a large amount of pressure on the first two rolls of the finished product, which greatly reduces the strength of this type of threaded steel and does not meet the standards for the external dimensions of threaded steel.

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 the poor material quality, the cut end face of fake and inferior materials often has the phenomenon of falling flesh, which is uneven and lacks metallic luster. Moreover, due to the limited cutting of counterfeit and inferior products by manufacturers, large ears may 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 low, and the size is severely out of tolerance. Therefore, without a vernier caliper, it can be weighed and checked. For example, for threaded steel 20, the national standard specifies a maximum negative tolerance of 5%. When the length is 9M, its theoretical weight per piece is 120 kilograms, and its minimum weight should be 120 X (l-5%)=114 kilograms. If the actual weight of a single piece measured is smaller than 114 kilograms, it is a fake and inferior thick walled seamless steel pipe, because its negative tolerance exceeds 5%. Generally speaking, the overall weighing effect will be better, mainly considering the issues of cumulative error and probability theory.

11. The inner diameter size of fake and inferior thick walled seamless steel pipes fluctuates greatly due to:; l. The steel temperature is unstable with yin and yang sides. 2. The composition of steel is uneven. 3. Due to the rudimentary equipment, low foundation strength, and high bounce of the rolling mill. There may be significant changes in the inner diameter within the same week, which can cause uneven stress on the steel bars and lead to fracture.

The trademark and printing of high-quality materials are relatively standardized.

13. For three thick walled seamless steel pipes with a diameter of 16 or more, the spacing between the two trademarks should be above IM.

14. The longitudinal bars of forged thick walled seamless steel pipes and threaded steel pipes often exhibit a wavy shape.

15. The manufacturer of fake and inferior thick walled seamless steel pipes has loose packaging due to the lack of crane operation. Oval shaped on the side