Method for manufacturing X70 steel-level large deformation-resistant longitudinally submerged arc welding pipe

Abstract

The invention discloses a method for manufacturing X70 steel-level large deformation-resistant longitudinally submerged arc welding pipes, which is applied to the manufacture of special welding pipes for oil and gas transmission. In the method, a controllable rolled steel plate is used, wherein the controllable rolled steel plate has a ferrite-bainite double-phase metallurgical microstructure and contains the following chemical components: 0.04 to 0.07 percent of C, 1.60 to 1.85 percent of Mn, 0.15 to 0.30 percent of Si, not more than 0.003 percent of S, not more than 0.010 percent of P, 0.15 to 0.30 percent of Ni, not more than 0.020 percent of Ti, 0.015 to 0.040 percent of Al, 0.010 to 0.065 percent of Nb, not more than 0.006 percent of N, not more than 0.30 percent of Cu, 0.10 to 0.25 percent of Cr, and not more than 0.0005 percent of B. The method comprises the following steps: (1) milling edges of the steel plate; (2) pre-bending bended edges; (3) performing JCO forming; (4) pre-welding joint seams; and (5) performing finish-welding on the inner and the outer sides of the joint seams. The method is applied to the manufacture of large-deformation-resistant welding pipes which are used in seismic belts, frozen soil areas, landslide area and other areas with high risk of deformation. The method has the advantages as follows: in the JCO forming process, the local deformation amounts and straight edge sizes of the steel plate in different rolling passes are analytically acquired according to the width, thickness and strength of the steel plate and the size of a die so as to determine the rolling passes and ensure uniform deformation at all parts of the steel plate after forming; and in the diameter expansion process, the minimum diameter expansion amount is determined according to the size and shape of the formed steel pipe, so as to ensure the size, shape and physiochemical properties of the steel pipe after diameter expansion.

Description

technical field [0001] The invention relates to a method for manufacturing a welded pipe, in particular to a method for manufacturing an X70 steel grade anti-large deformation straight seam submerged arc welded pipe. Background technique [0002] As an important energy source, oil and natural gas account for an increasing proportion in my country's energy structure, and the demand is strong. Using long-distance pipelines to transport oil and gas from production sites to users is a safe, efficient and economical method, and has become the main way of onshore oil and gas transportation. With the continuous increase of oil and gas demand for my country's economic development, my country's oil and gas pipeline network construction will usher in a new round of peaks in the next five to ten years. [0003] During pipeline construction, since the pipeline passes through permafrost zones, landslide zones, earthquake zones and goaf subsidence zones, it may bear huge deformation and ...

AI Technical Summary

Problems solved by technology

At present, my country cannot independently produce this kind of X70 large-deformation-r...

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