1. The shoddy thick-walled seamless steel pipe is prone to folding. Folding is a variety of fold lines formed on the surface of thick-walled seamless steel tubes, which often extend throughout the longitudinal direction of the 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. When the next rolling occurs, the folding occurs, and the folded product is cracked after bending, and the strength of the thick-walled seamless steel pipe is greatly reduced.
2. The surface of the shoddy and thick-walled seamless steel pipe often has a pockmark phenomenon. The pockmark is a defect caused by the irregular wear of the thick-walled seamless steel pipe due to the serious wear of the groove. Due to the pursuit of profit by shoddy and thick-walled seamless steel pipe manufacturers, the most frequent rolling mill rolling is exceeded.
3. The surface of the shoddy and thick-walled seamless steel pipe is prone to scarring. There are two reasons for this: 1. The shoddy thick-walled seamless steel pipe is uneven in material and has many impurities. 2. The fake inferior material manufacturer’s guiding equipment is simple and easy to stick steel. These impurities are easy to produce 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. The shoddy thick-walled seamless steel pipe is easy to be scratched because the equipment of the fake inferior material manufacturer is simple, easy to produce burrs, and scratches the surface of the thick-walled seamless steel pipe. Deep scratches reduce the strength of thick-walled seamless steel tubes.
6. The shoddy thick-walled seamless steel pipe has no metallic luster and is light red or similar to pig iron. The reason is two points. 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 thick-walled seamless steel pipe naturally cannot meet the standard.
7. The transverse ribs of the shoddy thick-walled seamless steel pipe are 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 shoddy thick-walled seamless steel pipe is elliptical, because 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 conform to the outer dimensions of the rebar. Standard.
9. The quality of the high-quality thick-walled seamless steel pipe 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: 120 X (l-5%) = 114 kg. The actual weight of a single root is less than 114 kilograms, which is a shoddy thick-walled seamless steel pipe 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 shoddy thick-walled seamless pipe fluctuates greatly because of the reason; l, the steel temperature is unstable and there is a yin and yang surface. 2. The composition of steel is not uniform. 3. Due to the simplistic equipment, the foundation strength is low, and the rolling mill has a large bounce. There will be a large change in the inner diameter in the same week, and such a steel bar is unevenly stressed and easily broken.
12. The trademarks and printing of high-quality materials are relatively standardized.
13. Thick-walled seamless steel pipe with a diameter of 16 or more, the distance between the two trademarks is above 1m.
14. The longitudinal reinforcement of the shoddy thick-walled seamless steel pipe rebar is often wavy.
15. The fake and thick-walled seamless steel pipe manufacturers have loose packaging because they do not have driving. The sides are oval.