How to identify the shoddy seamless pipe?

Seamless pipe is a steel pipe made of whole round steel perforated without welded seams on the surface. According to its production process, it can be divided into cold drawn seamless tubing, hot-rolled seamless pipe, extruded pipe, top pipe, etc., all of which have their own process regulations. It is widely used in pipelines for transporting oil, natural gas, gas, water and certain solid materials, etc.

With the popular application of seamless pipe in the construction industry, its quality is prone to problems, so how to identify the shoddy seamless pipe?

1. Shoddy seamless pipe easy to fold
 
Folding is a variety of folding lines formed on the surface of the seamless pipe, and this defect often runs longitudinally throughout the product. The reason for folding is due to the pursuit of high efficiency by shoddy manufacturers, the amount of press down is large, generating ears, and the next rolling produces folding, and the folded product will crack after bending, and the strength of the wall seamless pipe drops greatly.

2. Shoddy seamless pipe appearance often pockmarked phenomenon
 
The pockmarked surface is a defect caused by the serious wear of the rolling groove to cause irregular unevenness on the surface of the seamless pipe. As the shoddy seamless pipe manufacturers want to pursue profits, there is often an overrun of the rolling groove rolling.

3. The surface of the shoddy seamless pipe is prone to scarring. There are two reasons for the scars: firstly, the fake pipes are made of uneven materials with too many impurities; secondly, the inferior equipment tends to stick to the steel, and when some impurities enter the machine, it leaves scars on the surface of the seamless pipe.

4. The surface of the shoddy seamless pipe is easy to produce cracks, the reason is that its billet is adobe, adobe has many pores, and cracks are produced during the process of cooling due to the thermal stress, and cracks are formed after rolling.

5. Shoddy seamless pipe is easy to scratch, the reason is that the shoddy seamless pipe manufacturer's equipment is rudimentary, easy to produce burrs, scratching the surface of the seamless pipe. Deep scratches reduce the strength of the seamless pipe.

6. Shoddy seamless pipe without metallic luster, light red or similar to the color of pig iron. The main reason is that the rolling temperature is not standard. The temperature of these pipes is measured manually rather than mechanically, so they cannot be rolled in the austenite zone and their performance is not up to standard.

7. The cross-section of the shoddy seamless pipe is oval. In order to save materials, some manufacturers intentionally increase the rolling depression, which causes a decrease in strength and cannot meet the requirements of seamless pipe specification.

8. The diameter error of the shoddy seamless pipe is large. There are three reasons for this phenomenon: first, the steel temperature is unstable; second, the steel composition is not uniform; third, the equipment lags and the mill bounces more. Due to these reasons, the inner diameter of the steel pipe becomes larger, the stress is not uniform and easy to fracture.

9. High-quality seamless pipe has uniform composition, high tonnage of cold shear, smooth and neat cutting head end, while the shoddy material often has the phenomenon of flesh dropping on the cutting head end due to poor material, i.e., uneven and uneven, and no metallic luster. And because of the shoddy seamless pipe manufacturer's product cutting head less, the head and tail will appear big ears.

10. Shoddy seamless pipe material contains more impurities, the density of steel is small, and the size is super poor, so in the absence of vernier calipers, it can be weighed to check. For example, for rebar 20, the national standard stipulates that the maximum negative tolerance is 5%, and its single theoretical weight is 120 kg at a fixed scale of 9M, and its minimum weight should be: 120 X (l-5%) = 114 kg, and the actual weight of a single weighing out is smaller than 114 kg, which is a shoddy seamless pipe.

Article source: https://article-realm.com/article/Finance/22466-How-to-identify-the-shoddy-seamless-pipe.html