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The more affordable cost compared to seamless products and the continuous improvement of welding technologies contributes to the growing popularity of welded pipes, which today account for up to half of all pipe products.
The operational characteristics of seam pipes are determined by the production technology and the steel grade used.
Production technology of welded pipes
For the production of welded pipes, carbon, alloy and stainless steel, sheet or rolled steel are used. The production technology involves welding the edges of the workpiece, the molding of which is performed by cold or hot deformation. Products can have a straight or spiral seam.
Production of products with a straight longitudinal seam is regulated by GOST 10704-91. Straight-seam pipes are made of steel sheets bent to the shape of the final product. To obtain a particularly large diameter structure, two sheets with a limited width are welded. Accordingly, it will have two longitudinal seams.
According to the current standards, straight-seam pipe products are produced:
- with a diameter of 10-1420 mm;
- with a wall thickness of 1-32 mm. (Pipes with a diameter of less than 426 millimeters can have a measured or non-measured length)
Production of products with a spiral seam, obeys GOST 8696-74. They are made of rolled steel:
- with a diameter of 159-2520 mm;
- with a wall thickness of 3.5-25 mm;
- 10-13 meters long.
The advantages of spiral welding include the ability to produce pipes with a diameter of up to 2.5 meters, with a wall thickness-to-diameter ratio that can be more than 100. In addition, with a sufficiently high accuracy of execution, the production of pipes with a spiral seam involves the use of less complex equipment than for products with a straight seam.
Welding methods
In the production of suture pipes, the following technology can be used::
- furnace welding. It involves heating the steel sheet in a tunnel furnace, up to a temperature of 1400 degrees, with subsequent deformation on a forming and welding machine;
- electric welding. It is used in the production of large-diameter thin-walled pipes made of cold-rolled billets;
- welding in a protective gas environment. It is used in the production of stainless and high-alloy steel pipes. Welding in a protective environment prevents carbidization of alloying elements, which worsens the quality of joints. Both gas and electric welding can be used.
Advantages and applications
The undoubted advantage of welded pipes over seamless ones is a more affordable cost, due to less expensive and faster production. In addition, seam products made of sheet or rolled steel have a uniform wall thickness. Moreover, the technology makes it possible to obtain a pipe with a significantly larger diameter than that of solid-drawn products.The presence of a seam can be attributed to the weakness factor of suture products, however, the improvement of welding technologies gradually deprives it of relevance.
Suture pipe products are successfully used in the oil and gas and energy industries, construction and utilities. And stainless steel products are used in the food, pharmaceutical and light industries.
