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LSAW steel pipe is a kind of API steel pipe, it use single steel plate as material, and put the steel plate into the mode or the molding machine to make a tube, and use double side submerged arc welding methods and expanding production form to produce. The product specifications are wide range, the welds toughness, ductility, uniformity and denseness are good, it also has some good features: large diameter, wall thickness, high pressure, low temperature corrosion resistance. When works are building high-strength, high-quality and long-distance oil and gas pipelines, the large diameter seamless LSAW steel pipe are mostly needed.
By molding methods, the LSAW steel pipe can be divided into several kinds:
1. UOE steel pipe, when the single welded steel pipe edge is pre-curved, by U shape, O shape, the welding, outside welding, mechanical cooling, expanding and other processes to produce.
2. JCOE steel pipe
3. HME steel pipe: Use the mandrel bar rolling method to form according to the “C-C-O” mode, and cold expanding after welding.
SAW (submerged arc welding containing electro slag surfacing) is using electric arc burn under the solder layer and weld. It has high welding productivity, stable welding quality, and no arc and little smoke, so it can be the main method that used to make pressure vessels, pipe manufacturing, box beams and some other important steel structures. Although there have been many efficient, high quality new welding methods, but submerged arc welding applications has not any impact.
From the point of view that the share of deposited metal weight for many welding methods, SAW is about 10%, and didn't change for many years. When the wire is determined (usually depending on the steel welding), the supporting use of flux is the key material. It affects the mechanical properties of the weld metal directly, especially the low-temperature toughness and plasticity, crack resistance, soldering defect rate and welding productivity rate. The wire and flux weight ratio is wire: flux = 1.1:1.6, it depends on the type of welded joints, the flux types, welding parameters to make. Compared with the melting flux, agglomerated flux amount is more savings, and it's about 20% less.
