High-performance low-carbon microalloy steel SEW (hot stretch-reducing electric welding) expansion casing and manufacturing method thereof

Abstract

The invention relates to a high-performance low-carbon microalloy steel SEW (hot stretch-reducing electric welding) expansion casing and a manufacturing method thereof. The expansion casing comprises the following chemical components in percentage by mass: 0.10-0.25% of C, 0.12-0.30% of Si, 0.60-1.50% of Mn, no more than 0.010% of P, no more than 0.005% of S, 0.05-0.5% of Nb+V+Ti and the balance of Fe and inevitable impurity. The manufacturing method comprises the following steps: (1) performing FFX molding and HFW welding on a high dimensional precision controlled low-carbon microalloy steel TMCP hot rolled coil to manufacture an HFW welded tube; (2) quickly heating the HFW welded tube to 900-1100 DEG C in an intermediate-frequency induction heating mode, then performing hot mechanical rolling and hot stretch reducing to obtain a tube blank having a required size, and optimizing a welding seam structure to ensure that the welding seam structure is almost the consistent with the base material, thus realizing physical seamless treatment; (3) performing overall special heat treatment on the whole tube blank subjected to hot rolling and reducing, thus ensuring that the whole tube is consistent in structure and property; and (4) performing hot straightening, nondestructive flaw detection and in-tube sandblast derusting treatment, machining tube end screw threads, and inspecting, thus finally forming the expansion casing.

Description

technical field [0001] The invention belongs to the technical field of oil well pipe manufacturing, and in particular relates to a high-performance low-carbon microalloy steel SEW (Hot Stretch-reducing Electric Welding, hot tension reducing electric resistance welding) expansion sleeve and a manufacturing method thereof. Background technique [0002] Expansion casing is a special oil-specific pipe. Generally, the expansion pipe string lowered into the well is permanently plastically deformed by hydraulic or mechanical means, and expands about 10-30% in the diameter direction. It provides a new and effective solution to problems such as drilling and drilling, and has many incomparable advantages such as optimizing the wellbore structure, reducing drilling costs, saving operating time, quickly restoring production, and increasing single well production. It is considered to be the 21st century oil drilling industry One of the revolutionary technologies in mining industry. my c...

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Problems solved by technology

For example, the Chinese patent application number 200910187461.3 uses seamless steel pipe as the expansion pipe, and its out-of-roundness index of the outer diameter is less than 2%, which is far lower than the outer diameter of the welded pipe stipulated in the SY / T5989-2012 "Straight Seam Resistance Welding Sleeve" standard. Diameter out of roundness ≤ 0.50%, due to strain concentration when the casing expands, the outer diameter out of roundness and wall thickness unevenness of the casing will deteriorate on the original basis, resulting in uneven deformation during the expansion process, resulting in The residual stress in the hoop direction reduces the collapse strength of the pipe body. In severe cases, the wall thickness of the pipe section is thinner and even cracks. Therefore, the initial wall thickness unevenness and out-of-roundness of the expansion sleeve should be stricter than API and other standards; The Chinese patent application number is 201010144992.7. The chemical composition of the steel for HFW expansion pipes contains Si content as high as 1~2.5%, which is extremely unfavorable to welding, and it is easy to form welding defects such as gray spots, which significantly reduces the toughness of the weld seam and causes the weld seam to be damaged during the expansion process. At the same time, the ratio of Mn to Si ω(Mn) / ω(Si) should be ≥ 5 to ensure that the oxides are easily discharged during welding; the Chinese patent application number is 201110301303.8, and the steel used for the expansion tube is made of high alloy Material, the content of Mn and Cr in its chemical composition is as high as 10~26% and 1~10% respectively, not only the raw material cost is high, but also the HFW weldability of the material is poor

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