Manufacturing method for X120 steel-level spiral seam hidden arc welding tube

Abstract

The invention discloses a manufacturing method for an X120 steel-level spiral seam hidden arc welding tube. The contents of various chemical components of the spiral seam hidden arc welding tube are optimally designed and a trace B element is added. The manufacturing method comprises the following steps: uncoiling; flattening; milling edges; pre-bending; molding; internally welding and externallywelding, or pre-finishing welding; layering a mother plate; performing ultrasonic flaw detection on a welding joint and X-ray flaw detection on the welding joint; expanding a tube end; testing a water pressure; performing ultrasonic flaw detection on the welding joint; performing X-ray flaw detection on the tube end; chamfering the tube end; and checking an end-product. The strength of the high-intensity spiral seam hidden arc welding tube manufactured by using the method is greatly increased, the molding stability in manufacturing process is greatly increased and the production cost is efficiently lowered.

Description

technical field [0001] The invention relates to a spiral seam submerged arc welded pipe and its manufacturing technology, which is used as an oil and gas transportation pipe, especially a manufacturing method of a high-strength X120 steel grade spiral seam submerged arc welded pipe. Background technique [0002] The spiral submerged arc welded pipe is made by helically bending the steel coils according to a certain radius of curvature and then welding them together along the gap between the butt joints of the steel plates. Because the spiral seam submerged arc welded pipe has the advantages of low investment and many types of production, it has become the most widely used steel pipe manufacturing method in China. However, due to the limitations of its forming method and the relatively low strength of steel pipes for a long time, there are few productions of high-strength steel pipes. At present, the steel used in the steel pipe produced by the spiral seam submerged arc weld...

AI Technical Summary

Problems solved by technology

The current production method still has many problems in the production of high-strength spiral submerged arc welded pipes. The main manifestations are: as the strength of the steel increases, the deformation of the steel strip in the former, especially the edge of the strip on the delivery side, is insufficient. At the same time, the edge trimming process commonly used at present will also cause the under-flange phenomenon of the plate edge. If it is not corrected in the subsequent process, pouting, tightness inside the forming seam and looseness outside the forming seam, wrong edge, etc. will easily occur during the production process. Defects can even cause fatal defects such as weld micro-cracks; problems such as crescent bends in the coil itself significantly affect the forming stability of the steel pipe, making the circumference and ellipticity of the steel pipe change greatly, and the shape of the steel pipe cannot be effectively guaranteed. Dimensional stability has a certain impact on the on-site butt joint construction of steel pipes; with the improvement of steel grades, especially X120 ultra-high-strength steel grades, it is more sensitive to the control of stress concentration and residual stress; in addition, with the increase of steel strength , making the welding process more difficult, how to control the structure and performance of the welded joint is also a key issue that needs to be solved

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