How to distinguish poor quality seamless steel tubes

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How to distinguish poor quality seamless steel tubes

How to distinguish poor quality seamless steel tubes

1. Fake steel tubes are prone to folding.

Folding is various fold lines formed on the surface of steel pipes. This kind of defect often runs through the entire longitudinal direction of the product. The reason for the folding is that the fake and shoddy manufacturers are pursuing high efficiency, the reduction is too large, and ears are generated. When the next rolling is performed, folding occurs. The folded product will crack after bending, and the strength of the steel is greatly reduced.

 

2. The appearance of fake and inferior steel pipes is often pitted.

The ramie surface is a defect of irregular unevenness on the surface of the steel due to the serious groove wear. Because the manufacturers of fake and inferior steel pipes are pursuing profits, they often appear to be rolling the most.

 

3. The surface of fake and inferior steel pipes is easy to produce scars.

There are two reasons for this: (1). The material of fake and inferior steel pipes is not uniform, and there are many impurities. (2). The guide equipment of the fake and inferior materials manufacturers is simple and easy to stick to steel. These impurities are easy to scar after they bite the roller.

 

4. The surface of the fake and inferior materials is prone to cracks, because the billet is adobe, and the adobe has many pores. During the cooling process, the adobe is cracked due to thermal stress and cracks are formed after rolling.

 

5. The fake and inferior steel pipes are easy to be scratched because the manufacturers of the fake and inferior steel pipes are rudimentary and prone to burrs and scratches on the steel surface. Deep scratches reduce the strength of the steel.

 

6. The fake and inferior steel pipe has no metallic luster and is light red or a color similar to pig iron. There are two reasons for this. Its billet is adobe. 2. The rolling temperature of fake and inferior materials is not standard, and their steel temperature is measured by visual inspection. In this way, rolling cannot be performed according to the specified austenite region, and the performance of the steel cannot naturally meet the standards.

 

7. The cross bars of fake and inferior steel pipes are thin and low, and the phenomenon of full dissatisfaction often occurs. The reason is that in order to achieve a large negative tolerance, the reduction of the first few passes of the finished product is too large, the iron type is too small, and the hole type is not full.

 

8. The cross section of the fake and inferior steel pipe is oval. The reason is that in order to save material, the reduction of the first two passes of the finished roll is too large. The strength of this rebar is greatly reduced, and it does not meet the standard of the rebar external dimensions.

 

9. The composition of high-quality steel 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 materials, the end face of the cutting head often loses meat, that is, uneven, and there is no metallic luster. And because fake and inferior materials manufacturers have fewer cuts, big ears will appear at the head and tail.

 

10. The material of the fake and inferior steel pipe contains many impurities, the density of the steel is small, and the size difference is serious, so it can be weighed and checked without a vernier caliper. For example, for the rebar 20, the national standard specifies a maximum negative tolerance of 5%, and its single theoretical weight 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 the single root weighed is less than 114 kg, it is a fake steel because the negative tolerance exceeds 5%. Generally speaking, the effect of phase weighing is better, and the problems of cumulative error and probability theory are mainly considered.

 

11. The internal diameter of the fake and inferior steel pipe fluctuates greatly due to the following reasons: l, the temperature of the steel is unstable and has a positive and negative surface. 2. The composition of steel is not uniform. 3. Due to the simple equipment and low foundation strength, the bouncing of the rolling mill is large. There will be large changes within the same week, such uneven reinforcement tends to cause fracture.

 

12. The trademarks and printing of high-quality tubes are relatively standardized.

 

13. For large threads with a diameter of 16 or more, the spacing between the two trademarks is above IM.

 

14. Inferior steel rebars often have wavy longitudinal bars.

 

15. Fake and inferior steel pipe manufacturers are loosely packed because they do not have traffic.