In various areas of production (industry, energy, construction, manufacturing of metal, disposal) applies profiled pipe of steel. A considerable proportion of the total volume of a rectangular semifinished tube. The product range of steel produced by steel mills, is extremely wide. It is very important to be able to correctly choose the form, range profile to the specific design conditions of manufacture, to be able to quickly and correctly calculate the weight and dimensions.
Key Features and purpose
Profiled tube - a hollow metal body having different cross section. There are two basic methods for producing such pipes:
- cold or hot hood (rolling);
- electric welding.
One of the most popular sections is a rectangle. It is much more complicated in terms of the geometry of the circle and processing methods. But rectangular tube compared with a round analogue has a marked advantage. The structure made of such pipes, has higher flexural rigidity characteristics. This allows copes with high transverse loads.
Steel rectangular profiles are manufactured in accordance with GOST 8645-68 "rectangular steel tubes. Gauge ". Pipe sizes must meet the requirements of this document.
Steel composition, physical and mechanical properties determine the standards relating to the methods of manufacture:
- GOST 10704-91 "electrically welded steel tubes."
- GOST 10707-80 "... cold-steel electric."
- GOST 9941-81 "... seamless cold- and warm-deformed corrosion-resistant steel."
For pipes used in construction, adopted another GOST - 30245-2003. It differs from a primary standard over a wide range of geometric dimensions. Thus, the maximum cross section profile for use in industrial / civil engineering is 400x200 mm. The standard prescribed all the basic requirements for the production, labeling, packaging, transportation, semi-finished products, acceptance, storage and quality control.
Electro articles manufactured from the steel strip (strip) of different thicknesses by winding on a drum, and rolling. Tubular workpiece connected by different welding techniques (arc, induction, laser, plasma). The final manufacturing step profile with right angles - calibration shape. Weld quality in accordance with the requirements of GOST is checked by inspection.
Range of products. Calculating the weight of pipes
8645 standard requirements is determined that the rectangular steel pipe may have dimensions of 15x10 mm to 230h100 mm. The minimum cross-sectional area - the 15x10 tube with a wall thickness of 1 mm - 0.443 cm2. The highest rate in diameter have, oddly enough, the pipe is not very large:
- 196h170 mm - 113.24 cm2;
- 180h145 mm - 107.13 cm2.
This is due to their very large wall thicknesses - 18 and 20 mm, respectively.
The standard defines the limits external dimensions for articles of deviations produced according to different precision classes:
- Elevated - hot - ± 1,25%; cold rolled and welded - 30 mm - ± 0,25 mm, 30-50 mm - ± 0,3 mm and over 50 mm - ± 0,8%.
- Normal - hot - ± 1,50%; cold rolled and welded - 30 mm - ± 0,30 mm, 30-50 mm - ± 0,40 mm, over 50 mm - ± 0,8%.
Semi-finished products are also certified by the moment of inertia, the degree of concavity and convexity. Furthermore, the thickness deviation of the wall electric-products can not be more than 10%. For products obtained by hot or cold deformation, that of 12.5%. Maximum torsional - no more than 2 degrees, the curvature of - not more than 2 mm per running meter of length. GOST strictly controlled as the moment of resistance and the weight of one meter of semifinished products of various sections and wall thicknesses.
Weight Profiling products with the presence of angles made for the subsequent compulsory calculation of structural strength. The weight of one square meter of the metal tube is calculated by the formula:
m = ro / 7850 * 0.0157 * S * (P - 2.86 * S) * L,
where 7850 kg / m³ - steel density. Furthermore, for the calculation requires data on the pipe section (a and b), the wall thickness S. Length L in the formula is the default size of 1 m. The change of this parameter is carried out if necessary to know the weight profile measured length of the segment. For the convenience of working with mathematical values in GOST included weight table 1 m rectangular shaped tube.
Car with right angles is considered to be thin-walled, if the outer diameter to the wall thickness does not exceed 0.025. Considered standard rectangular profile with an aspect ratio of 0.5, thick-walled - 0.1.
High-quality semi-finished products are manufactured with rounded corners. The optimal radius is a value equivalent to twice the thickness of the wall of the product. The practical application in the industrial production of semi-finished products obtained overestimation of the radius. This process has two objectives:
- Facilitate construction.
- Cheaper estimate installation.
Despite the outward beauty and elegance, the design of semi-finished products with the lowest possible angle of curvature is much heavier than the standard versions. From the viewpoint of mechanics required search golden mean: a metal structure bearing characteristics reduces the use of pipes as with large and ultra-small angle with curvatures.
Scope of the rectangular pipes
A wide assortment of semi-finished products with a right angle possible to substantially increase the list of areas in industrial production in which they have been successfully applied:
- Production of frame structures.
With varying the sectional walls sizes dimensional segment can substantially increase the degree of strength of the erected buildings. The rectangle is very popular in building dlinnoprolotnyh structures - warehouses, hypermarkets, sheds, greenhouses, conservatories, sports complexes.
- Construction of railing and fencing.
Ease of installation of stainless steel products makes them popular for decorative purposes. Due to its excellent anti-corrosion properties of the rectangular tube can be operated in the open air for several decades.
Recently, rectangular tubular members of steel are widely used in relatively new sectors:
- Installation of automotive designs.
Low weight and excellent mechanical properties make steel products of various sizes with right angles in the automotive industry.
- Production of metal furniture carcass.
Of a thin rectangle in large numbers assembled metal parts of various items of furniture for the schools and universities - tables, chairs, desks, shelves.
The basic material for the manufacture of such structural elements are stainless steel and AiSi304 AiSi316. They are characterized by high thermal stability, low corrosion and prone to abrasion. The big plus is the presence of a number of different options for finishing of prefabricated steel structures.
Advantages and disadvantages of rectangular steel profile
There are some features of the finished product labeling based on their mechanical properties. For profiles, in the nomenclature of which is present letter A, regulated only by the mechanical properties. When the marking is present in letter, it is necessary strict observance of both mechanical and chemical properties. Rectangular profiles are also tested for impact strength after artificial aging treatments have become. The presence of the marking letters D says that the semi-finished products have passed hydraulic tests.
Marking rectangular semis shall comply with GOST 7566-94, include the following information:
- information about the manufacturer;
- identification and profile length;
- heat number;
- weight;
- OTC mark.
Pipes right angles to be used during the manufacture of communications water. Moreover there is a clear scientific explanation: due to less internal volume through the meter rectangular conduit pumped significantly less liquid than using circular segment. Furthermore, profile stainless pipes unable to counteract considerable internal loads. Therefore, the scope of the round and square profiles clearly demarcated.
Comparison of steel rod of similar cross-section shows that the weight is much greater than that of the hollow dimensional segment with right angles. Consequently, the structure assembled from hollow rectangular tube, have a significantly lower overall weight and greater efficiency at comparable strength indicators. It presents no particular difficulties machining process a rectangular profile. His cutting takes much less time than the separation of part of the solid profile (rod).
