Steel rectangular pipes - technical information and
At the mention of the pipeline, to the mind first comes a product of circular cross section, which is used when laying plumbing, sewage and heating. But demand and pipes, the shape of which differs from the circle, in particular rectangular. In order to choose the right pipe, it is useful to familiarize yourself with regulatory requirements and labeling rules.

general information
Square and rectangular sections are never used for plumbing or heating systems. The advantages of a square pipeline become apparent when installing, for example, the frame of any structure.
When doing all the work with your own hands, you can note several advantages at once:
- low weight;
- high strength;
- excellent torsion resistance;
- speed of installation;
- elegant appearance.

In addition, the flat surface is also practical. It can easily be attached to the surface of the wall, and when installing, for example, a railing, the top of a profile pipe is much more difficult to install.
Normative base
Production of the profile pipeline is performed by passing the pipe through a series of rollers, which give it the desired shape. In this case, the compliance of the final product with the sizes specified in the assortments is rather strictly controlled.

As for the regulatory documents, you can select a whole “bunch” of standards containing comprehensive information on the standard sizes of the profile pipeline:
- GOST 8645-68, GOST 8645-86 and GOST 8645-82 - these documents indicate the requirements and sizes of steel rectangular pipes;

- GOST 8639-68, and GOST 8639-82 on a range of steel rectangular pipes contain basic information on square sections;

- GOST 30245-03 - in it you can find data on the pipeline, both square and section in the form of a rectangle. In addition, it contains requirements for the strength of the weld.
Steel Rectangular Piping
In this case, attention should first be paid to the width and height of the product, as well as the wall thickness. In addition, you need to understand that the corners are rounded, therefore, the radius of curvature is also controlled.
Note! Rounding at the corners of the pipeline - a necessary measure. If the corners were not rounded, then during torsional deformation in these places stress concentrations would be observed, which jeopardizes the stability of the structure.
GOST 8645-82 on a rectangular steel pipe extends to electrowelded as well as hot and cold rolled pipes. According to the assortment sizes can be in the range from 15x10 mm to 180x150 mm.
And if the minimum dimensions can be used except for a railing, the height of the pipeline more than 10 cm allows you to use it already as an element of the supporting structure.

Rectangular steel pipes according to GOST 8645-86 must meet the same requirements as specified in the standard of 82 years. The differences are more cosmetic and relate to the requirements for compliance with specified geometric dimensions.
According to this standard, special dimensions can be produced, in agreement with the customer, its diameter can be from 28x25 mm to 196x170 mm. As for the radii of curvature, the general rule is that the radius should not exceed twice the thickness of the metal.
Note! In some cases, the radius can be increased to triple the thickness of the metal. But prior approval with the customer is required.
GOST 8645-68 for a steel rectangular tube gauge contains the same information, only the sizes differ slightly. According to this document, the standard dimensions remain the same, and as for special sizes, they are in the range from 28x25 mm to 230x100 mm.

The marking of the pipeline contains comprehensive information not only on the dimensions of the section, but also on the material from which it is made.
Marking is slightly different depending on the length, such options are possible:
- 90x40x4 GOST 8645-68 / V10 GOST13663-86;
- 90x40x4x6000 GOST 8645-68 / V10 GOST13663-86;
- 90x40x4x1250cr GOST 8645-68 / V10 GOST13663-86.
The decoding instruction is the same in any case - from left to right are indicated: the geometric dimensions of the section and GOST, according to which the pipe was produced, also indicated the length of the pipeline or the multiplicity of the length, in the denominator - the type of steel and the standard to which it corresponds.
The example shows the following sizes:
- in the first case, a steel rectangular pipe according to GOST 8645-68 has a cross section of 90x40 mm in size, and a wall thickness of 4.0 mm, unmeasured length, steel B10;
- all the same, but the length is 6.0 m;
- geometrical dimensions remain the same, but the length is a multiple of 1.25 m.
Note! The moment of resistance, and other static characteristics are calculated based on a wall thickness of 1.5 mm. Considering that the thickness of the metal can reach 15-18 mm, if serious loads are planned, it is better to recalculate these characteristics based on the actual dimensions of the wall.
Square pipeline
GOST 8639-68 for a range of steel rectangular pipes is more correct to call the standard for a square pipe, because the height and width of the section are equal. Sizes, of course, differ from the rectangle, the minimum size is 10x10 mm, and the maximum size is 180x180 mm. In addition, it is possible to produce special sizes - from 32x32 mm to 65x65 mm.

Note! In the assortment, some sizes are bracketed, which means that this size is considered recommended for most tasks. Value for money and maximum efficiency.
Also, as in the case of a rectangular section, the magnitude of the corner radius is normalized. In general, the radius should not be less than double the thickness of the metal. And only for size 60x60x4 mm an exception can be made and the radius can be increased to threefold wall thickness (but this requires the consent of the customer).
In addition, both standards contain fairly stringent requirements for the geometry of the product itself, not only the dimensions of the section, but also the curvature and angle deviation from 90 are strictly controlled? etc.
For example, an electrowelded rectangular steel pipe according to GOST 8369-68 must comply with the following requirements:
- the deviation of the wall thickness from the norm depends on the production method, so for the seamless rolled products the thickness of the metal should not differ from the range data by more than + 12.5% or -15%, the electric welded pipeline - ± 10%, and for the cold-drawn - 12.5 %;
- especially compliance with the form affects the work under load, so the deviation of the angle between the walls should not exceed ± 1.5 ?;
- maximum curvature should not exceed 1 mm per 1 m length, this parameter is easy to verify with your own hands;
In addition, restrictions are put forward on such parameters as a tie (implied by the concavity of the sides), the length of the finished product, etc.
Current regulatory requirements
If in the past the main characteristics of square and rectangular pipelines were normalized by different documents, then the GOST 2003 combined the sizes of these two types of sections. This somewhat facilitates the work with the document.
GOST 30245-03 for a steel rectangular pipe gauge consists of 2 tables, the 1st shows the standard sizes of square pipes, and the 2nd for rectangular pipes.
Compared to the documents listed above, the sizes vary slightly:
- for a square section, the minimum dimensions are 40x40 mm, and the maximum dimensions are 300x300 mm;
- in the case of a rectangle, the dimensions are in the range from 50x25 mm to 400x200 mm.

As for the length, then according to GOST 30245-2003 it can be equal to 6.0, and the maximum is set at 13.0 m (but only with the consent of the customer). For mass production, a size range of 6.0 - 12.0 m is used.
The difference from the standards of previous years is also noticeable in the requirements for geometry. Also attention is paid to the strength of the weld, the rules of marking, storage, etc.
Criterias of choice
It is important to be able to work with the product mix. That is, knowing the purpose of the structure and having on hand a table with standard sizes (as well as static characteristics of the section), you need to be able to choose the option you want. And if during the laying of water supply or sewage throughput was of decisive importance, in the case of a profile pipeline, attention should be paid to the structural strength, the price is also taken into account.

The main requirement is that only elastic deformation is allowed (that is, after the load is applied, the structure will return to its original position, and with its long-term application, the deformation does not increase). If the calculation is carried out independently, then the nature of the deformation (bending, axial compression, torsion) must be taken into account; GOST pipes will be needed to determine the static characteristics of the section.

It is unlikely that someone will want to calculate the design independently, and not everyone will be able to. In this situation, you can use the tables, which indicate the approximate sizes for a specific type of load.
Finally
In order not to be mistaken when choosing a rectangular pipe, you need to understand the regulatory documentation and at least roughly imagine the conditions of operation of the structure. There are a lot of standards issued for profile pipes, the information contained in this article will allow you to navigate them.
The video in this article shows the use of a shaped pipe as a frame for a future structure.