Spiral molded large-deformation-resistant submerged-arc welding pipe and manufacture method thereof

Abstract

The invention discloses a spiral molded large-deformation-resistant submerged-arc welding pipe and a manufacture method thereof. A large-deformation-resistant hot rolled coil plate is unrolled and straightened, a welding groove is respectively machined on two sides of the plate, then the plate is placed into a spiral steel pipe molding unit to be molded and bent into a pipe shape gradually, the submerged-arc welding process is adopted to conduct welding pipe welding, and the welding pipe is subjected to following treatment such as hole enlargement, detection, hydraulic test and ultrasonic detection to form a product. The submerged-arc welding pipe has low yield ratio, larger even elongation, high deformation hardening exponent and Round-House type stress-strain curve under the premise that the welding pipe meets the requirement for high strength and high flexibility. The welding pipe is mainly applied to regions such as frozen earth zones, landslide zones, earthquake zones and the like where geological movement happens easily, serves as a steel pipe in oil and gas delivery pipes which can bear large deformation and stress, and ensures safe service of the pipes.

Description

Technical field: [0001] The invention belongs to the field of oil pipelines, and relates to a welded pipe used in the field of oil and gas pipelines and a manufacturing method thereof, in particular to a spiral-formed large-deformation-resistant submerged arc welded pipe and a manufacturing method thereof. Background technique: [0002] In recent years, with the development and mining of natural gas extending to remote areas such as deserts, polar regions, and oceans, long-distance pipelines not only have to pass through areas with complex geological and climatic conditions such as tundra, landslides, and earthquakes, but also in areas with complex geological and climatic conditions. During the service period, the steel pipe is deformed due to ground subsidence and movement, and may bear huge deformation and stress. Therefore, from the perspective of technological progress and pipeline safety, new and higher requirements are put forward for welded pipes and pipe fittings to ...

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Problems solved by technology

Chinese patents 201010251848.3, 201010550557.4 and 201110223978.0 all produce large deformation longitudinal submerged arc welded pipes through JCOE or UOE forming process. For the current pipeline construction in my country, spiral welded pipes are mainly used, and large deformation resistant welded pipes adopt spiral forming submerged arc welding process. not involved

2) From the perspective of welding process, the welding method of spiral welded pipe and straight seam steel pipe is the same, but there will inevitably be a lot of T-shaped welds in the field girth welding of straight seam welded pipes, and the welding residual stress at the T-shaped welds is relatively large , the weld metal is often in a three-dimensional stress state, increasing the possibility of cracks

[0008] In order to ensure the dimensional accuracy of the steel pipe and improve the internal stress distribution of the steel pipe after welding, the straight seam welded pipe generally requires full-scale expansion of the steel pipe, which is pre-strained in the production of the steel pipe, which increases the deformation of the steel pipe and reduces The pre-strain of the steel pipe makes the deformation ability of the pipe body worse, which has an adverse effect on the performance of the large-deformed steel pipe

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