In the construction of long-distance pipelines, pipeline pipes account for a large proportion. Generally, pipeline pipes account for 35% to 40% of the total investment in investment projects. How to choose pipelines with reasonable prices and excellent performance is particularly important. Reasonable selection of pipelines has a very important impact on saving construction investment, facilitating construction, and safe operation of the pipeline system. Gas pipeline straight seam steel high frequency resistance welded steel pipe, spiral submerged arc welded steel pipe, straight seam submerged arc welded steel pipe. The diameter range of limited frequency straight seam electric welded steel pipes is generally limited to domestic steel pipes below Φ406.4mm, and the largest diameter in Japan has reached Φ508mm. For large-diameter pipes, there are two types: spiral submerged arc welding and straight seam submerged arc welding. Due to many shortcomings in the pipe forming process and characteristics of spiral welded pipes, the proportion of spiral welded pipes in long-distance pipelines is gradually declining. In other countries, especially many European countries, the use of spiral submerged arc welded pipes as main line pipes has been banned. Longitudinal submerged arc welding is widely used in long-distance oil and gas pipelines due to its unique advantages. Its advantages are as follows.
(1) No unwinding process is required, and there are few indentations and scratches on the base material.
(2) The incision is staggered, the diameter and circumference are easy to control, and the welding quality is excellent.
(3) There is basically no residual stress after the pipe expansion stress is eliminated.
(4) Since it is a straight weld and the weld is shorter, the probability of defects is smaller.
(5) After diameter expansion, the geometric accuracy of the pipe is improved, which greatly facilitates on-site welding.
(6) The weld is straight and has little impact on the quality of the anti-corrosion coating material.
