Welded Steel Pipes

Date:2024-08-07Tags:Welded Steel Pipes, LSAW welded pipes, SSAW welded pipes

1.What is welded steel pipe?

Welded steel pipes, also known as welded pipes, are made by curling and forming steel plates or strips and then welding them together, usually to a fixed length of 6 meters. The production process of welded steel pipes is simple, highly efficient, with many varieties and specifications, and requires less investment in equipment, but their general strength is lower than that of seamless steel pipes. They are widely used in projects such as hydroelectric power stations, municipal drainage pipelines, and drinking water transportation. In specific manufacturing and applications, welded pipes are generally divided into two types according to the welding method: LSAW welded pipes and SSAW welded pipes.

Welded Steel Pipes

2.What are the types of welded steel pipes?

Since the 1930s, with the rapid development of high-quality strip steel continuous rolling production and the advancement of welding and inspection technology, the quality of welds has been continuously improved, and the varieties and specifications of welded steel pipes have increased day by day. So how to classify welded steel pipes?
According to different welding methods, they can be divided into arc welded pipes, high-frequency or low-frequency resistance welded pipes, gas welded pipes, furnace welded pipes, Bondi pipes, etc.


According to the shape of the weld, they can be divided into straight seam welded pipes and spiral welded pipes. Among them, spiral seam welded steel pipes are divided into automatic submerged arc welded steel pipes and high-frequency welded steel pipes. Most of the smaller diameter welded pipes use straight seam welding, while large diameter welded pipes mostly use spiral welding.


According to the purpose, they are divided into general welded pipes, galvanized welded pipes, oxygen-blown welded pipes, wire casings, metric welded pipes, roller pipes, deep well pump pipes, automobile pipes, transformer pipes, electric welded thin-walled pipes, electric welded special-shaped pipes and spiral welded pipes. General welded pipes are used to transport low-pressure fluids. Made of Q195A, Q215A, and Q235A steel. It can also be made of other soft steel that is easy to weld. Steel pipes must undergo water pressure, bending, flattening and other tests, and have certain requirements for surface quality. Usually the delivery length is 4-10m, and it is often required to be delivered in a fixed length (or multiple lengths). The specifications of welded pipes are expressed in nominal diameter (mm or inches). The nominal diameter is different from the actual diameter. Welded pipes are divided into ordinary steel pipes and thickened steel pipes according to the specified wall thickness. Steel pipes are divided into threaded and non-threaded according to the form of the pipe ends.


LSAW welded pipes: Generally, these are medium-diameter welded pipes with outer diameters ranging from DN15 (1/2 inch) to DN150 (6 inches). The LSAW welding process is simpler than the spiral welding process, has lower welding costs, and is more efficient. However, the weld seam is in the same parallel line, resulting in lower tensile strength. Therefore, straight seam welding is only suitable for producing medium-diameter welded pipes.

SSAW welded pipes: Generally, these are large-diameter welded pipes with outer diameters ranging from DN200 (8 inches) to DN600 (24 inches). The SSAW welding process can use steel plates of the same width to produce welded pipes of different diameters. However, the process is more complicated, and the spiral weld seams are longer than the straight seams for the same length of welded pipe, resulting in higher production costs and lower productivity. Therefore, spiral welding is commonly used for producing large-diameter welded pipes. Additionally, the spiral weld seam has higher tensile strength, ensuring the bearing capacity of large-diameter welded pipes.


3.Theoretical calculation method of welded pipe weight

The theoretical calculation method of welded pipe weight has a formula to follow; the theoretical weight of steel pipe per meter (steel density is 7.85kg/dm3) calculation formula: W=0.02466 (D-S)/S; where: W represents the theoretical weight of steel pipe per meter, unit: kg/m; D represents the nominal outer diameter of the steel pipe, unit: mm; S represents the nominal wall thickness of the steel pipe, unit: mm.
Welded steel pipes are widely used in the modern construction industry. However, the quality standards they need to meet vary based on the environment and geographical location where they are used. The standards for welded steel pipes in the construction industry are as follows:

GB/T3091-1993 (Galvanized Welded Steel Pipes for Low-Pressure Fluid Conveyance): Mainly used for conveying water, gas, air, oil, and heating hot water or steam and other general lower-pressure fluids and other purposes. The representative material is Q235A grade steel.

GB/T3092-1993 (Galvanized Welded Steel Pipes for Low-Pressure Fluid Conveyance): Mainly used for conveying water, gas, air, oil, and heating hot water or steam and other general lower-pressure fluids and other purposes. The representative material is Q235A grade steel.

GB/T14291-1992 (Welded Steel Pipes for Mine Fluid Conveyance): Mainly used for mine compressed air, drainage, and shaft gas drainage using straight seam welded steel pipes. The representative materials are Q235A and B grade steel.

GB/T14980-1994 (Large Diameter Electric Welded Steel Pipes for Low-Pressure Fluid Conveyance): Mainly used for conveying water, sewage, gas, air, heating steam, and other low-pressure fluids and other purposes. The representative material is Q235A grade steel.

GB/T12770-1991 (Stainless Steel Welded Pipes for Mechanical Structures): Mainly used for machinery, automobiles, bicycles, furniture, hotel and restaurant decoration, and other mechanical parts and structural components. The representative materials are 0Cr13, 1Cr17, 00Cr19Ni11, 1Cr18Ni9, 0Cr18Ni11Nb, etc.

GB/T12771-1991 (Stainless Steel Welded Pipes for Fluid Conveyance): Mainly used for conveying low-pressure corrosive media. The representative materials are 0Cr13, 0Cr19Ni9, 00Cr19Ni11, 00Cr17, 0Cr18Ni11Nb, 0017Cr17Ni14Mo2, etc.

We use cookies to offer a better browsing experience, analyze site traffic, and personalize content. By using this site, you agree to our use of cookies.

Accept
Decline