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Classification and characteristics of seamless steel pipe structure

Views: 0     Author: Site Editor     Publish Time: 2021-02-03      Origin: Site

The seamless steel pipe structure currently used in the project can be classified according to the cross-sectional shape, structural form and manufacturing method. According to the cross-sectional form, seamless steel pipe structure can be divided into three types: round pipe structure (CHS), square (rectangular) pipe structure (RHS) and other shapes.

Due to the nature of appearance and stress performance, round tube structure and square tube structure are widely used. According to the structural form, the seamless steel tube structure can be divided into four types: grid (reticulated shell), truss, frame and seamless steel tube concrete structure. The structure of seamless steel pipe refers to the form in which round pipes and square pipes are used as components, and the pipes are connected by intersecting welding.

According to the production method, seamless steel pipe structure can be divided into three types: hot-rolled seamless steel pipe structure, cold-rolled seamless steel pipe structure, and welded seamless steel pipe structure. The wall thickness of hot-rolled seamless steel pipe is relatively thick and the production cost is high, while the wall thickness of cold-rolled seamless steel pipe is relatively thin.

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The characteristics of the structure of round pipe and square (rectangular) seamless steel pipe are as follows: both round pipe and square (rectangular) section have the characteristics of biaxial symmetry, and the cross-section centroid and shear center coincide; The moment of inertia is the same for each axis, which has outstanding advantages as a bending and compression member; closed section, high torsional rigidity, and local stability of the plate, especially the circular tube section, the polar axis distribution of the section is uniform, and the torque resistance is special; Concise and smooth, the rods can be directly welded to the same point without the gusset plate to save steel.

The seamlessness of the steel pipe is mainly completed by tension reduction, which is a continuous rolling process of hollow base material without mandrel.

Seamless steel pipes are hot rolled, while seamless steel pipes are cold drawn. Production technology of seamless steel pipe: The seamless steel pipe is mainly completed by tension reduction, which is a continuous rolling process of hollow base material without mandrel.

Under the premise of ensuring the welding quality of the main pipe, the welded pipe tension reducing technology is to heat the entire welded pipe to above 950 degrees Celsius, and then roll it into various outer diameters and walls by a tension reducer (the tension reducer has 24 passes). For thick finished pipes, the hot-rolled steel pipes produced by this technology are substantially different from the usual high-frequency welded pipes. After being heated by a heating furnace, the metallographic arrangement and mechanical properties of the weld and the parent body can be consistent. In addition, after multiple passes, the rolling and automatic control of the tension reducer make the dimensional accuracy of the steel pipe (especially the roundness and wall thickness accuracy of the pipe body) better than similar seamless pipes.

Many of the developed fluid pipes and boiler pipes have used welded pipe seamless technology. With the development of society, domestic hot-rolled welded pipes have gradually replaced seamless pipes.

How to distinguish between the two? First of all, welded pipes are usually fixed length, and are usually 6 meters, 9 meters or 12 meters. There are very few seamless steel pipes with fixed-length, because the fixed-length ex-factory price increases very much. It can be seen from the cross-section of the tube head, if there is rust, wipe it clean. If you look closely, you will find the welding area. Third, if it is pickled, it will be remarkable.

The expression of the diameter of large-diameter thick-walled steel pipes should meet the following requirements:

1. For pipes such as steel pipes (galvanized or non-galvanized) and cast iron pipes for water gas transportation, the pipe diameter should be expressed by the nominal diameter DN;

2. For seamless steel pipes, welded steel pipes (straight seam or spiral seam), copper pipes, stainless steel pipes and other pipes, the pipe diameter should be expressed by outer diameter × wall thickness;

3. For pipes such as reinforced concrete (or concrete) pipes, clay pipes, acid-resistant ceramic pipes, cylinder tile pipes, etc., the pipe diameter should be expressed as the inner diameter d;

4. For plastic pipes, the pipe diameter should be expressed according to the product standard method;

5. When the design uses the nominal diameter DN to represent the pipe diameter, there should be a comparison table between the nominal diameter DN and the corresponding product specifications. The specifications of rigid polyvinyl chloride pipes for building drainage are represented by de (nominal outer diameter) × e (nominal wall thickness) (GB5836.1-92) The specifications of polypropylene (PP) pipes for water supply are represented by de × e (nominal outer diameter × Wall thickness).

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