A welded steel pipe is a steel pipe which is welded and formed by a steel strip or a steel plate and deformed into a circular shape or a square shape, and has a joint on the surface. The welded steel pipe has simple production process, high production efficiency, many varieties and specifications, and less equipment, but the general strength is lower than that of seamless steel pipe. 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 welded joints has been continuously improved, the variety specifications of welded steel pipes have been increasing, and more and more fields have replaced Seam steel pipe.
According to different welding methods, it can be divided into arc welded pipe, high frequency or low frequency electric resistance welded pipe, gas welded pipe, furnace welded pipe, Bondi pipe and so on. According to the shape of the weld, it can be divided into straight welded pipe and spiral welded pipe.
Electric welded steel pipes are used in oil drilling and machinery manufacturing. Furnace welded pipe can be used as water gas pipe, etc., large diameter straight seam welded pipe is used for high pressure oil and gas transportation, etc.; spiral welded pipe is used for oil and gas transportation, pipe pile, pier and so on. Welded steel pipes have lower cost and higher production efficiency than seamless steel pipes. Straight seam welded pipe has simple production process, high production efficiency, low cost and rapid development. The strength of the spiral welded pipe is generally higher than that of the straight welded pipe. It is possible to produce a welded pipe with a larger diameter by using a narrow blank, and it is also possible to produce a welded pipe having a different pipe diameter with a blank of the same width. However, compared with the straight pipe of the same length, the weld length is increased by 30 to 100%, and the production speed is low. Therefore, most of the smaller diameter welded pipes are straight seam welded, and the large diameter welded pipes are mostly spiral welded.
The blanks used for welded steel pipes are steel plates or strip steels, which are divided into furnace welded pipes, electric welding (resistance welded) pipes and automatic arc welded pipes due to different welding processes. Due to the different welding forms, it is divided into straight seam welded pipe and spiral welded pipe. steel pipe manufacturers,Because of its shape, it is divided into round welded pipes and special-shaped (square, flat, etc.) welded pipes. Welded pipes are divided into the following varieties due to their different materials and uses:
GB/T3091-1993 (galvanized welded steel pipe for low pressure fluid transport). It is mainly used to transport water, gas, air, oil and heating water or steam and other general pressure fluids and other uses. It stands for material Q235A grade steel.
GB/T3092-1993 (galvanized welded steel pipe for low pressure fluid transportation). It is mainly used to transport water, gas, air, oil and heating water or steam and other general pressure fluids and other uses. Its representative material is: Q235A grade steel.
GB/T14291-1992 (mineral fluid transport welded steel pipe). It is mainly used for straight seam welded steel pipes for mine pressure, drainage and shaft discharge. It represents the material Q235A, B grade 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 uses. It stands for material Q235A grade steel.
GB/T12770-1991 (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. It represents materials 0Cr13, 1Cr17, 00Cr19Ni11, 1Cr18Ni9, 0Cr18Ni11Nb, and the like.
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, and the like.