Welded pipe is a common pipe in the gas pipeline, the diameter of more than 426mm (or 508mm) of the welded pipe is generally referred to as large-diameter welded pipe, in accordance with the welding into pipe mode, can be divided into spiral welded pipe and straight seam welded pipe two. Straight seam welded pipe is the hot rolled coil after forming machine, to make the steel coil deformation into a smooth cylindrical shape, using the skin effect of high-frequency currents and the proximity effect or the arc welding under the flux layer, the edge of the tube is heated and melted and fused under the action of a certain extrusion force, which is cooled by the final cooling molding. One of the Tube billet edge using high-frequency current melting is known as high-frequency straight seam welded pipe (ERW), using arc melting is called straight seam submerged arc welded pipe (LSAW).
The main raw material of longitudinal welded pipe is low carbon steel hot rolled coil, hot strip, in petroleum, metallurgy, construction, coal, port, machinery and other industries are widely used in oil and gas transportation, low pressure water gas transportation, mine fluid transportation, belt conveyor idler, automobile transmission shaft and so on. Welded steel pipe, also known as welded pipes, is made of steel plate or steel after crimping molding welded steel pipe. Welded steel pipe production process is simple, high production efficiency, variety specifications, equipment, less capital, but the general strength of less than seamless steel tube. Since the 1930s, with the rapid development of high quality strip continuous rolling and the progress of welding and inspection technology, the quality of welding has been improved continuously, the variety specification of welded steel pipe is increasing, and the seamless steel pipe is replaced in more and more fields.
Welded steel pipe is divided into straight seam welded pipe and spiral welded pipe in the form of weld seam. Welded steel pipe used in the blank is steel or strip, because of its different welding process is divided into furnace welded pipe, welding (resistance welding) pipe and automatic arc welded pipe. Because of its different forms of welding are divided into straight seam welded pipe and spiral welded pipe two kinds. Because of its end shape is divided into circular welded pipe and shaped (square, flat, etc.) welded pipe.
Welded pipe due to its different materials and uses are divided into the following varieties: gb/t3091-1993 (Galvanized welded steel pipe for low pressure fluid conveying). Mainly used for conveying water, gas, air, oil and heating hot water or steam and other general low pressure fluids and other uses of the tube.
Its representative material q235a grade steel. gb/t3092-1993 (Galvanized welded steel pipe for low pressure fluid conveying). Mainly used for conveying water, gas, air, oil and heating hot water or steam and other general low pressure fluids and other uses of the tube.
Its representative material is: q235a grade steel. gb/t14291-1992 (mine fluid conveying welded steel pipe). Mainly used in mine pressure, drainage, shaft discharge gas with straight seam welded steel pipe. Its representative material q235a, B grade steel. gb/t14980-1994 (large diameter welded steel pipe for low pressure fluid conveying). Mainly used for conveying water, sewage, gas, air, heating steam and other low-pressure fluids and other uses.
Its representative material q235a grade steel. gb/t12770-1991 (stainless steel welded steel pipe for mechanical structure). Mainly used in machinery, automobiles, bicycles, furniture, guesthouses and hotel decoration and other mechanical parts and structural parts.
Its representative material 0cr13, 1cr17, 00cr19ni11, 1cr18ni9, 0cr18ni11nb and so on. gb/t12771-1991 (stainless steel welded steel pipe for fluid conveying). Mainly used for conveying low pressure corrosive medium.
Representative materials for 0cr13, 0cr19ni9, 00cr19ni11, 00cr17, 0cr18ni11nb, 0017cr17ni14mo2 and so on. Straight seam welded pipe production process simple, high production efficiency, low cost, rapid development. The strength of spiral welded pipe is generally higher than that of straight seam welded pipe, it can produce welded pipe with larger pipe diameter with narrower billet, and can produce welded pipe with different pipe diameter with same width. However, the weld length increases 30~100% and the production speed is lower compared with the straight seam tube of the same length. As a result, the smaller-caliber welded pipe mostly uses the straight seam welding, the large diameter welded pipe mostly uses the spiral welding.