Straight seam high frequency (ERW) welding and induction welding is divided into two forms of two welding contacts, hot rolled coil as raw material, through pre-bending, continuous forming, welding, heat treatment, sizing, straightening, Short weld, high dimensional accuracy, uniform wall thickness, surface quality, the advantages of pressure, but the disadvantage is that only the production of small diameter thin-walled tubes, easy to produce gray spot welding, incomplete fusion trench-like corrosion defects. At present, city gas, crude oil and other oil products transport a wider range of applications.
The volume of the SSAW tube is the same as the tube forming angle at its center (adjustable) to form a weld that is welded into a spiral with the same specifications for producing steels of various diameters and adapting to a wider range of raw materials , The main coal seam can avoid stress, stress is better, the disadvantage is poor geometry, the length of the straight seam weld is longer than the length of the tube, easy to produce cracks, porosity, slag inclusions and other welding defects, weld, weld stress tension state. Generic Design Code for Oil and Gas Pipelines Spiral submerged arcs are only available in Class 3 and Class 4 areas. This process will increase the foreign raw material steel, the welding shape, in addition, lean pre-welding and post-weld cold expansion, the quality close to the UOE pipe, there is no such process is the direction of plant improvement. "The East" is still used in the traditional production process, but the pipe end has been expanded denied the United States in Japan and Germany, the general spiral welded pipe, the main consideration should not be used spiral pipe spiral; Canada and Italy part of the use of spiral welded pipe, spiral welded pipe , Russia, has developed a very strict additional conditions, due to historical reasons, the majority of domestic backbone still use spiral welded pipe.
LSAW is a veneer for raw materials, high pressure plate (roll) in the mold or molding machine, the use of double-sided submerged arc welding and production expansion. Its complete product specifications, good weld toughness, good ductility, good uniformity, compactness, with a large diameter, high wall thickness, high pressure, low temperature, corrosion-resistant and so on. When constructing high-strength, high-toughness, high-quality long-distance oil and gas pipelines, most of the large-diameter thick-walled pipes required are straight seam submerged arcs. According to API standards, LSAW pipe is the only designated applicable for large-scale oil and gas pipelines in urban areas with high density, sea and dense population such as Grade 1 and Grade 2 areas.