Core Tip: The spiral tube, also called spiral steel tube or spiral welded tube, is a low carbon structural steel or a low alloy structural steel strip rolled into a tube blank at a certain angle of the helix (called the forming angle), and then the tube seam is welded. Made of, it can produce large diameter steel pipes with narrow strips.

1. Fake and inferior steel pipes are prone to folding. Folding is a variety of fold lines formed on the surface of steel pipes. Such defects often run through the longitudinal direction of the entire product. The reason for the folding is that the inferior manufacturer pursues high efficiency, the amount of pressing is too large, and the ear is generated, and the next rolling causes folding, and the folded product is cracked after bending, and the strength of the steel is greatly reduced.

2. The surface of the counterfeit steel pipe often has a pockmark phenomenon, and the pockmark surface is a defect that the irregularity of the steel surface is irregular due to the serious wear of the groove. Due to the pursuit of profit by shoddy steel pipe manufacturers, the most frequent rolling mill rolling is exceeded.

3. The surface of the fake steel pipe is prone to scarring. There are two reasons for this: (1) The material of the fake steel pipe is uneven and has many impurities. (2) The guide equipment of the fake inferior material manufacturer is simple and easy to stick steel. These impurities are easy to cause crusting after biting the roller.

4. The surface of the fake inferior material is prone to cracks because the billet is an adobe, and the adobe has many pores. The adobe is cracked by the action of thermal stress during the cooling process, and cracks occur after rolling.

5. Fake and inferior steel pipes are easy to scratch, because the equipment of the fake and inferior steel pipe manufacturers is simple, easy to produce burrs and scratch the surface of the steel. Deep scratches reduce the strength of the steel.

6. The counterfeit steel pipe has no metallic luster and is light red or similar to pig iron. The reason is two points. 1. The blank is adobe. 2, the temperature of the fake inferior material rolling is not standard, their steel temperature is measured by visual inspection, so that it can not be rolled according to the specified austenite area, the performance of the steel naturally cannot meet the standard.

7. The cross-fabricity of the inferior steel pipe is thin and low, and the phenomenon of filling and dissatisfaction often occurs. The reason is that the manufacturer has to achieve a large negative tolerance, the amount of pressing of the first few passes of the finished product is too large, the iron type is small, and the hole type is not full.

8. The cross-section of the counterfeit steel pipe is elliptical. The reason is that the manufacturer has to reduce the amount of the two rolls in front of the finished roll in order to save material. The strength of the rebar is greatly reduced, and it does not meet the standard of the rebar dimensions.

9. The composition of high-quality steel is uniform, the tonnage of the cold-shearing machine is high, the end face of the cutting head is smooth and tidy, and the fake inferior material is often poor in material, and the end face of the cutting head often has a phenomenon of falling meat, that is, unevenness and no metallic luster. And because the fake inferior products manufacturers have fewer heads, big ears will appear at the head and tail.

10. The fake steel pipe material contains many impurities, the density of the steel is small, and the size is too bad, so in the absence of the vernier caliper, it can be weighed and checked. For example, for rebar 20, the national standard specifies a maximum negative tolerance of 5%. At a fixed length of 9 M, its single theoretical weight is 120 kg. Its minimum weight should be: 120X (l-5%) = 114 kg. The actual weight of a single root is less than 114 kg, which is a fake steel because its negative tolerance exceeds 5%. In general, the effect of the phasing weighing will be better, mainly considering the problem of cumulative error and probability theory.

11. The inner diameter of the fake steel pipe fluctuates greatly, the reason

1 steel temperature instability has yin and yang surface.

2 The composition of steel is not uniform.

3 Due to the simplification of the equipment, the foundation strength is low and the rolling mill has a large bounce. There will be a large change within the same week, and such a steel bar is unevenly stressed and easily broken.

12. The trademarks and printing of quality pipes are relatively standardized.

13. The three-diameter steel pipe has a diameter of 16 or more, and the distance between the two trademarks is above IM.

14. The longitudinal reinforcement of the counterfeit steel rebar is often wavy.

15. Because there is no driving, the shoddy steel pipe manufacturers are loosely packed and have an oval shape on the side.

Concerned about surprises

Label: Identification method of inferior spiral tube

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