Hot rolled profile pipes
The control of the dimensional characteristics of the profile pipes is extremely important because they are used for the construction of metal structures, and any deviation from the norms can affect the strength of the building or structure. A non-standard pipe can behave unpredictably - weaken the structure or, at best, increase the estimated mass of the structure. Designers in the design of metal structures are based on the standard dimensions laid in GOSTs for profile pipes. If the dimensional characteristics do not coincide, then all design calculations will be incorrect and a fatal error can be made. Therefore, the size and control over them determine the very existence of metal structures. 
Dimensional parameters of the pipe, i.e.its height, width, radius of curvature, wall thickness, etc. depend on the method of production of this product. Industrial metallurgical production uses only three technological processes, which are used for the production of profile tube products.
- Hot deformation of a conventional round tube.
- Cold deformation of a round tube with subsequent heating to relieve the stress of the metal.
- Sheet metal forming with joint welding.
The process method affects the wall thickness, the calibration method, for other dimensional characteristics.
According to GOST at the output of the production we have a pipe with a square section, the dimensions of which should not exceed 60 mm. If it is a pipe with a rectangular cross section, then its height should correspond to 60 mm. The assortment according to GOST 8645-68 for rectangular pipes defines up to two tens of standard sizes. A similar amount is contained in GOST 8639-82 for pipes with a square cross-section. For one and the other standard, the typical dimensions of the section will fluctuate within the limits of 60x60 to 230x100 mm. 
Further GOST 8639-82 specifies what should be the thickness of the walls of the profile pipes. The minimum thickness is 4 mm, the maximum is 14 mm. The length of a measuring segment is also a parameter specified in the standards, moreover, it does not depend on which final product should be produced. The minimum length is 4 m and the maximum length is 12.5 m.
Cold-rolled pipes
At the exit, the finished cold rolled profile pipes have more subtle characteristics than the hot version. Dimensional characteristics are the cross-section of the walls, their thickness is much smaller. According to GOST for cold rolled pipes, the faces of the section are equal to at least 10 mm and not more than 120 mm, ie from 10х10 to 120х120 mm. GOST 8639-82 has 17 standard sizes that meet these requirements, and GOST 8645-68 has 16 standard sizes. Cold-rolled pipes can have a wall thickness of 1 mm and higher to 8 mm. Therefore, the conclusion suggests that if a product is required without a joint and with thin walls, it is necessary to acquire a cold-rolled profile. The length of the measuring segments ranges from 4.5 m to 11 m. Non-limiter segments can be a minimum of 1.5 m and a maximum of 9 m. 
Welded profile pipes
The physical characteristics of products produced by this technology are no different from seamless analogs, except that the weld can reduce the rigidity of the pipe by 5-10%.These products can be made with walls 1-5mm thick and at the same time with impressive dimensions of 10x10 to 100x100.The length can also be measured and immeasurable. Measured from 5 to 9 m, immeasurable from 1.5 to 9 m. 
The welding method allows you to obtain not only square products, but also oval and rounded. The dimensions of the welded profile pipes are determined by GOST 8642-68.According to him, the oval sections are 16x10 mm to 90x32 mm with a wall thickness of not more than 2.5 mm and not less than 1 mm.