Large Diameter LSAW pipe wall thickness with its big, good material, process stability, becoming the first choice for large domestic and foreign oil and gas pipe project. In the large-straight seam submerged arc welded pipe welded joints, weld and heat affected zone is most likely to produce a variety of imperfections the welded undercut, porosity, slag, lack of fusion, lack of penetration, weld, burn welding cracks is the main form of welding defects, and are often the origin of so straight seam submerged arc welded pipe quality accidents.
Quality control measures: 1, before welding quality control 1) First, make a good quality of raw materials, after passing inspection before being officially entered the construction site, and resolutely put an end to the use of substandard steel 2) followed by the. management of welding materials. Check whether the welding materials for qualified products, storage and baking system whether to perform, whether to issue a weld surface clean and free of rust, electrode coating is intact, with or without mildew. 3) Once again, clean weld zone management. Cleaning QA weld zone, without water, oil, rust and dirt oxide film, which is to prevent external weld defects produced an important role. 4) Select the appropriate welding method should be implemented first test welding, after welding principles. 2, welding quality control 1) according to welding procedure specifications wire and flux review is correct, to prevent misuse of welding wire and flux caused by the quality of the accident. 2) to supervise welding environment, take appropriate measures after welding when welding environment is not good (temperature below 0 ℃, relative humidity greater than 90%) should be. 3) before the expected first test welding groove dimensions, including space, blunt edge, and whether the angle and the wrong port meet the technical requirements. 4 ) in the submerged arc welding process inside and outside the selected welding current, welding voltage, welding speed and other parameters are correct. 5) supervision of personnel in the submerged arc welding inside and outside welded steel pipe full advantage of the end plate arc length , strengthen the efficiency of the welding arc when the inner and outer plates, which helps to improve the quality of welding the pipe ends. 6) supervision of personnel in the welding slag welding whether they are first cleaned, whether you've completely processed joint groove at whether there is oil, rust, slag, water, paint and other contaminants.