About the development of longitudinal submerged arc welded pipe

At present, pipelines are mainly used for long-distance oil and gas transportation. Pipeline steel pipes used in long-distance pipelines mainly include spiral submerged arc welded steel pipes and straight seam double-sided submerged arc welded steel pipes. Because the spiral submerged arc welded pipe is made of strip steel and its wall thickness is limited, the improvement of steel grade is limited by the heat treatment of the material. In addition, there are some insurmountable shortcomings of spiral submerged arc welded pipe, such as long weld, large residual stress and poor reliability of weld. With the increasing requirements for oil and gas transmission steel pipes, they are no longer used in densely populated areas and areas with high reliability requirements, and large-diameter straight welded pipes are gradually replacing spiral welded pipes.

With the development of oil exploitation to the depths of the ocean, the pipeline laying on the seabed is affected by the combined forces of pressure, impact force and bending force, and the phenomenon of flattening still appears, which is the weak link of spiral welded pipe. In order to improve the pipeline transportation capacity and ensure the submarine pipeline to develop towards thick wall, the submarine pipeline mostly adopts straight welded pipe. Therefore, compared with spiral welded pipe, straight welded pipe has higher dimensional accuracy and easier repair welding, so from this aspect, straight welded pipe is also the first choice.

 Coal slurry and slurry pipeline need to use straight welded pipe, and the pipeline transportation is "pasty". Pipeline transportation is the upward direction. Because the weld excess height of spiral welded pipe is spiral, which has great resistance to coal slurry, and the pipe needs a large wall thickness, it is inclined to adopt straight welded pipe.

3. Machinery, construction, chemical industry and other industries need straight welded pipes. At present, the inner hole of valve seat is machined after forging in mechanical industry, which is labor-consuming, time-consuming and material-consuming. If thick-walled straight seam welded pipe is used, it will be much more economical. In addition, due to the requirements of mechanical properties of anti-flattening, only straight welded pipes are used for building pipes; Straight welded pipe is also expected to be used for chemical pipes.