For the installation of various metal constructions are widely used pipe. As a rule, it is round or square products. In order to make a correct calculation of the loads on structural elements, it is necessary to know what is stronger - the usual round tube or profiled tube of square section. Knowing the maximum load on the structural element, it can be very accurately determine which profile is more appropriate for use in the installation process.
Tensile round and square profiles
Guests for square and round tubes regulate a variety of processes:
- physical properties of surfaces.
- mechanical properties of compounds.
- procedure for transformation (bending, torsion, hoods, etc.).
Conditions of bending profile can be different. Also, different and the data on the outer diameter stainless and carbon tubes.
If bending is performed with bulk material heating methods or filling hollow spaces, the outer diameter should be not less than 3,5DN (nominal diameter). For pipe bending machines, this value is 4DN. Deviation from the requirements of GOST 494/90 and 617/90 permitted if the decrease of the wall thickness of the bend is not more than 15%. In this case it is possible to reduce the nominal data to calculate the flexural strength of the profile.
Compare the level of strength of the hollow square and circle of the steel it makes it part of the technical mechanics studies the resistance of various materials. When calculating the flexural strength index are used two formulas:
- The calculation of the length of the bent parts.
L = 0,0175 * r * α + Ι,
Where
r - the radius of the bending profile, mm.
α - the desired bending angle, about.
I - distance 100/300 for the equipment, holding the workpiece.
- Calculation of the bending portion.
U = π * α / 180 * (r + DH / 2),
Where
α - angle of bend, about.
r - bending radius mm.
DH - outer diameter.
Calculation of the profile of the pipe ends after the determination of the voltage values calculated in accordance with Hooke's law:
H = Μ / W,
Where
Μ - degree of bending force feedback axis.
W - bending resistance along the line.
For calculation purposes it is imperative to take into account a measure of body inertia in rotation - the moment of inertia. For the same thickness of the walls of hollow tubes of different cross sections and specific tyazhosti bending force to a square in 1,181 times greater than for a circle. But inertia radius of the circular pipe is greater than square. Therefore, it is less durable.
Circle or square
Hollow metal (steel or aluminum) cores square and round cross-sections are widely used in construction and manufacturing of metal structures. The hollow profile has a much smaller, compared with the bar, by weight. As the carrier element square metallic structure is more convenient than a circle. It is easier to install. Two dimensional square profile segment can be joined by welding, in contrast to the circle. The flat surface square profile provides better contact with various hinged elements (polycarbonate, various kinds of pressed hardboard insulation, etc.).
And the presence of stiffeners to successfully use the square in a place where there are the highest loads. If the bending force directed at 90about to the face profile, the bending resistance in the same way anywhere in the tube. Bending load is strongest at the edges of the profile. Central is part of a much more stable. Closed cross sectional profile also provides high torsional strength. This allows the use of square tube for mounting a variety of complex structures:
- arches arch type.
- roofs with steep slopes.
- ribbed domes.
Calculation shaped tube shows that the structure reliability is directly proportional to the material of which it is made. Concrete is much safer wood, but much inferior to steel. The fact is that when it is used it is very difficult to mount runs. holes drilled in concrete for anchors will not provide the required strength. In metal profile compared with other materials many advantages. And the square - the same advantages over the circle.
For example, when the restrictive device structures (fences) optimum pitch racks - 2.5m With frequent gusty winds it. should be reduced to 2 m If the height of 1.5-2.0 m to design the optimal size of a square with a wall thickness of 2 mm -. 40x40 or 60x60 mm. As used material - for metal profiled tube of carbon steel or low alloy steel (GOST P 54157-2010). When mounting the pipe can be used broader constructions sizes from 50x50 to 200x200 mm.
Field of the use of square tubes is much wider than round. This is due to the fact that they have higher degree of interaction with the planes having symmetric surface. Clearly defined sectors in which such a pipe section shall not apply:
- production of frame structures.
- transport of gaseous substances.
- water supply and sewerage.
The profiled tube is not suitable for the pipeline due to the fact that the calculated, unlike circular, resisting substantial bearing loads. Due to the presence of the angular velocity of gases and liquids pumping inside the square tube is much smaller than the inside circular.
Manufacturing square profile
In theory, to produce a square pipe, it is enough rolling machines, with the necessary dimensions molding profile. The circle is rolled to obtain a square. But in terms of the quality of products the technology is completely unacceptable, as the mechanical characteristics of the pipes differ significantly from the required GOST worse. For the release profile of an industrial scale requires a set of complex technological equipment.
Tubes, which subsequently will be used for installation of metal, should be significantly stronger, and therefore dispensed on a complete production cycle. It includes five successive operations:
- Processing steel strip (strip).
- Welding of circular cross-section of the workpiece.
- Profiling.
- Quality control of finished products.
- Heat treatment.
Cutting the strip is carried in a special unit. The tape is wound onto a rotating drum. Continuous profile rolling is performed to the winding machine is not idle. After welding, the molding passage and the emulsion mill machining, the workpiece receives a normal circular shape.
The next step is the production of profiling:
- rounding preform throughout dyne profile.
- four-party crimping.
The resulting preform is subject to separation into measured lengths. During the entire process of machining the workpiece must be cooled by water.
To ensure the durability of welded square profile is critical to have a smooth and high-quality weld. He should definitely be inspected for leaks. Furthermore, to complete a square production process necessary to carry out the method of flaw detection by the eddy currents. With the help of the identification of possible defects:
- inner shell.
- high voltage weld location.
The final stage of checking the quality of the finished product is a visual inspection. Profiles are subject to rejection with irregularities and other mechanical damage. Reducing the number of defects contributes bulkhead pinch rolls.
The line for the production of steel profile consists of the following units:
- decoiler console for processing a metal sheet.
- forming mill.
- welding assembly and machine for the cut seam edge.
- cooling section.
- the shaping mill.
- Knife for the dimensional cutting.
for production of profiled pipe line can be automatic and semi-automatic. Shafts on standard lines have a rectangular shape.
