Large-diameter welded pipe is the pipe welds, raw materials are mainly steel sheet and strip, large diameter straight seam welded steel pipe is used, the higher productivity of the kinds of steel, more used in more low-cost steel products one. Large diameter spiral welded steel pipe is used, compared to the straight pipe joints, mechanical strength of the products is relatively high, to save raw materials, but the production is slow. The product is widely used in water engineering, petrochemical industry, chemical industry, power industry, agricultural irrigation, urban construction, is one of the products of China's 20 key development. For the transport of liquids: water supply, drainage. For gas transportation: gas, steam, LPG. For structural purposes: as piling pipe for bridges; piers, roads, pipes and other building structures.
In the large-diameter steel pipe welding process, the most commonly used is welded steel pipe, which is mainly used for oil drilling and machinery manufacturing stove pipe can be used as water-gas pipe, large diameter welded pipe for high pressure gas transmission, etc.; spiral welded pipe for oil and gas, piles, piers, etc. seamless steel pipe and welded steel pipe is lower than cost, high production efficiency. Longitudinal simple production technology, high production efficiency, low cost, rapid development. spiral strength than the straight seam welded pipe is generally pipe, can narrow the billet production of large diameter pipe, you can use the same width of the billet production of different pipe diameters, but with a straight seam pipe compared to the same length, the weld length of 30 to 100%. and lower production rate, so the smaller diameter pipe is mostly a straight seam welded, large diameter spiral welded pipe is mostly used.
According to different methods can be divided into arc welding pipe, high or low frequency electric resistance welded pipe, gas pipe, stove pipe, Bundy tubes. According weld shape can be divided longitudinally and spirally welded pipe welded steel refers to steel or steel bending round, square, etc. and then welded into shape, the surface of the steel pipe seams welded steel pipe production process simple, high production efficiency, variety specifications, less capital equipment, but generally lower than the intensity of seamless steel tubes. since the 1930s, along with the rapid development of high-quality steel rolling production, and improve the welding and inspection technology, continuous improvement of weld quality, welded steel pipe increasing number of varieties and specifications, and in more and more areas instead of seamless pipe.