1. Shoddy steel pipe prone to fold. Fold is formed on the surface of a variety of steel fold, this defect often throughout the product's longitudinal direction. The reason is due to shoddy factory folded pursuit of high efficiency, reduction is too large, resulting in the ears, it creates a rolling fold down when the product will crack when folded bending, the strength of steel big drop. 2. Ma often shoddy steel pipe outer surface phenomenon. Pock is due to the groove worn steel surface irregularities caused serious irregularities defects. Because of shoddy steel pipe manufacturers to pursue profits, often the most excessive rolling groove. 3. Shoddy steel surface is easy to produce scarring. There are two reasons: (1). Shoddy steel material uneven impurities. (2). Shoddy material manufacturers guides poorly equipped, easy to stick steel, easy to produce scarring after these impurities roll bite. 4. Too shoddy material surface is easy to crack, because it's blank adobe, adobe many pores, adobe in cooling Process due to thermal stress, cracks, crack after rolling there. 5. Shoddy steel easily scratched because of shoddy steel pipe manufacturers poorly equipped, prone to glitches, scratches steel surface. Deep scratches reduce the strength of steel. 6. No shoddy steel metallic luster, pale red color of pig iron or similar reasons two two, its stock is adobe. 2, inferior-rolling temperature is not standard, they are visually steel temperature, so the region can not be prescribed by austenite rolling, properties of steel naturally not compliance. 7. Shoddy

According to the production method: Pipe according to production methods can be divided into two categories: seamless steel pipe and pipe joints, pipe joints referred to as straight pipe joints. 1. seamless steel pipe according to production methods can be divided into: hot-rolled seamless pipe, cold drawn pipe, precision steel tubes, thermal expansion tubes, cold spinning tube and squeeze tubes. Seamless steel pipe with high-quality carbon steel or alloy steel, hot-rolled, cold-rolled (pull) of the points. 2. welded steel pipe because of different welding process is divided into stove pipe, welded (ERW) pip

Rolled steel rolling process for the continuation of the process and reducing fixed. Steel rolling is a process of moving together by steel and mandrel in multiple racks, steel deformation and movement as well as by common action rolls and mandrel. Mandrel can be free floating, that is, thanks to the forward movement of the metal drive; it can be limited to acting, that is a given mandrel speed of movement, limiting their freedom