The nuances of the rolling process of profile pipes.
This product belongs to a special grade of rolled metal, which is used in the process of assembling various metal structures. Its distinctive feature is considered to be an oval or multi-sided cross-section profile. Most often, it occurs either square or rectangular. 
Naturally, in transport systems or in a conventional pipeline, profile pipes clearly can not be used. They have insufficient capacity, as well as low resistance to internal pressure. Their production from ribbon strip, does not provide for the formation of a qualitative and reliable docking seam.
Profile pipes are also oval shaped, and their rolling is divided into welded and seamless pipes that are tempered( after the formation of the profile, the internal stress is removed) or released without the final temperature treatment.
To put it more briefly, there are so many varieties of this product that they created several GOSTs. For example, the square pipes and their parameters determine the normative document GOST 8639-82.In such documentation it is indicated that the dimensions of thick-walled and thin-walled profile pipes can not be more than 180х180mm. At the largest of them the wall thickness should be from 8 to 14mm. The smallest, is rolled square section and has a face of 1 cm, and 1 mm thick wall.
All these values significantly influenced the technology of longitudinal deformation of profile rolled products. After all, you see, it's hard to bend a hollow beam 18x18cm, the wall thickness of which is almost 1.5cm.
Rolling, as a matter of fact takes an idea at a rolling mill. The machine has the form of a pyramid of 3 cylinders( 1 bottom and 2 top).Cylinders, which are located at the bottom, are called rollers. They are responsible for transportation. The upper roller is designed to deform the profile pipe.
The rolling process is very simple: the pipe needs to be laid on the lower pair of the above mentioned rollers and the area that is left between them by the upper cylinder is pressed. Due to the pressing force, which is transported to the upper roll, the pipe gradually bends, thus deforming the longitudinal profile. The deformation zone can spread along the entire length of the product if the feed is turned on. Naturally, a long product can not be deformed in one pass. Thanks to roller machines, it is possible to form even a looped profile. 
Rollers are of several types. For example, roller sheet benders can not cope with profile pipes, so they are used only for deformation of sheet products. As a finished product made with this machine, you can see various troughs, troughs, etc.
Machines with three rollers are used for both sheet deformation and deformation of pipes. The power of the machine depends on the clamping force generator. If it is a hydraulic drive, it will be possible to bend even the T-beam. But if the equipment is a conventional clamp with a third roller, its performance will be below average. 
Machines on four rollers are considered the most powerful. They can form not only an arc, but also a circular profile. This type of machine has a mechanical drive, which significantly complicates the design and increases power consumption. However, the result is worth it. They are used in the production of profile pipes.