(1) Pockmarking on the surface: Pockmarking is an irregular uneven defect on the steel surface caused by severe wear of the rolling groove. Because manufacturers of fake and inferior square steel tubing pursue profits, groove rolling often exceeds the standard;

(2) Cracks are easy to occur: the reason is that the blank is made of adobe, which has many pores. The adobe is subject to thermal stress during the cooling process, causing cracks, and cracks appear after rolling;

(3) No metallic luster: It is light red or a color similar to pig iron. There are two reasons: first, the blank is adobe, and second, the rolling temperature of the fake and inferior materials is not standard. It is through visual inspection, so it cannot be austenitic according to the regulations. If the body area is rolled, the performance of the square and rectangular tube will naturally not meet the standard;

(4) Folding is easy to occur: Folding is a variety of fold lines formed on the surface of steel, and this defect often runs through the entire length of the product. The reason for folding is that manufacturers pursue high efficiency and the reduction is too large, resulting in ears. Folding will occur during the next rolling process. The folded product will crack after bending, and the strength of the steel will be greatly reduced;

(5) The surface is prone to scarring: There are two reasons: first, the fake and inferior steel material is uneven and has many impurities; second, the manufacturer’s guide equipment is simple and easy to stick to the steel. These impurities can easily cause scarring after biting the roller;

(6) Easy to scratch: The reason is that the equipment of the fake and inferior square and rectangular pipe manufacturers is simple, and it is easy to produce burrs and scratch the surface of the steel. Deep scratches reduce the strength of steel;

(7) Large fluctuations in inner diameter size: The reason is that l. The steel temperature is unstable and has Yin and Yang sides. 2. The composition of steel is uneven. 3. Due to the crude equipment and low foundation strength, the rolling mill bounces greatly. There will be large changes in the inner diameter within the same week. Such square and rectangular tubes are prone to breakage due to uneven stress.