Welded steel pipes, also called welded pipes, are steel pipes made by welding steel or strip steel after crimping. Welded steel pipes have simple production process, high production efficiency, many varieties and specifications, and less equipment, but their general strength is lower than seamless steel pipes. Since the 1930s, with the rapid development of high-quality strip continuous rolling production and the advancement of welding and inspection technology, the quality of welds has been continuously improved, and the variety and specifications of welded steel pipes have increased, and they have replaced non-products in more and more fields. Seam the steel pipe. Welded steel pipes are divided into straight seam welded pipes and spiral welded pipes according to the form of welds.
The billet used for welded steel pipe is steel plate or strip steel, which is divided into furnace welded pipe, electric welding (resistance welded) pipe and automatic arc welded pipe due to different welding processes. Because of its different welding forms, it is divided into two types: straight seam welded pipe and spiral welded pipe. Because of its end shape, it is divided into round welded pipe and special-shaped (square, flat, etc.) welded pipe. Welded pipes are divided into the following varieties due to their different materials and uses: General welded pipes
GB/T3091-2001 (galvanized welded steel pipe for low pressure fluid transportation). Mainly used to transport water, gas, air, oil, heating water or steam and other generally lower pressure fluids and other purposes. Its representative material is: Q235A grade steel.
GB/T14291-2006 (Welded steel pipe for mining fluid transportation). Mainly used for straight seam welded steel pipes for mine pressure, drainage and shaft gas discharge. Its representative material is Q235A, Grade B steel. GB/T14980-1994 (Large diameter electric welded steel pipe for low pressure fluid transportation). It is mainly used to transport low-pressure fluids such as water, sewage, gas, air, heating steam and other purposes. Its representative material is Q235A grade steel.
GB/T12770-2002 (stainless steel welded steel pipe for mechanical structure). Mainly used in machinery, automobiles, bicycles, furniture, hotel and restaurant decoration and other mechanical parts and structural parts. Its representative materials are 0Cr13, 1Cr17, 00Cr19Ni11, 1Cr18Ni9, 0Cr18Ni11Nb, etc.
GB/T12771-1991 (stainless steel welded steel pipe for fluid transportation). Mainly used to transport low-pressure corrosive media. Representative materials are 0Cr13, 0Cr19Ni9, 00Cr19Ni11, 00Cr17, 0Cr18Ni11Nb, 0017Cr17Ni14Mo2, etc.
In addition, welded stainless steel pipes for decoration (GB/T 18705-2002), stainless steel welded pipes for architectural decoration (JG/T 3030-1995), large diameter electric welded steel pipes for low-pressure fluid transportation (GB/T 3091-2001), and Welded steel pipes for heat exchangers (YB4103-2000).
Longitudinal welded pipe has simple production process, high production efficiency, low cost and rapid development. The strength of spiral welded pipes is generally higher than that of straight seam welded pipes. A narrower blank can be used to produce welded pipes with larger pipe diameters, and a billet with the same width can be used to produce welded pipes with different pipe diameters. However, compared with the straight seam pipe of the same length, the weld length is increased by 30-100%, and the production speed is lower.
Therefore, most of the smaller diameter welded pipes use straight seam welding, and the large diameter welded pipes mostly use spiral welding.
Supplement: The welded pipe is welded with strip steel, so its status is not as high as that of a seamless pipe.
