A kind of hot-rolled steel strip for 750mpa grade coiled tubing and its manufacturing method

Abstract

The invention discloses a hot-rolled steel strip for 750MPa grade coiled tubing and a manufacturing method thereof, and relates to the technical field of steel for oil well pipelines. A hot-rolled steel strip for 750MPa-level coiled tubing of the present invention and its manufacturing method, adopting molten iron pretreatment → converter steelmaking → LF external refining → RH external refining → continuous casting → hot rolling, the weight percentage of the chemical composition in the steel : 0.12%~0.14%C, 0.3%~0.4%Si, 1.50%~2%Mn, P≤0.015%, S≤0.005%, 0.5%~0.7%Cr, 0.1%~0.4%Cu, 0.1%~0.3 %Ni, 0.2%~0.5%Mo, 0.05%~0.07%Nb, 0.04~0.05%V, 0.01~0.02%Ti, 0.02~0.035%Als; the rest is Fe and inevitable inclusions; the thickness of the hot-rolled steel strip At 3-5mm, its metallographic structure is ferrite + martensite, so as to meet the needs of hot-rolled steel strips for coiled tubing in ultra-deep wells.

Description

technical field [0001] The invention relates to the technical field of steel for oil well pipelines, in particular to a hot-rolled steel strip for 750MPa grade coiled tubing and a manufacturing method thereof. Background technique [0002] Coiled tubing (CT, Coiled tubing) is a new type of oil and gas tubing with a single length of up to several thousand meters or even tens of thousands of meters with high strength, high plasticity and certain corrosion resistance. It is wound on a reel for transportation and use. In cooperation with the coiled tubing machine, it can perform dozens of operations in oil and gas field workover, logging, drilling, completion, oil and gas transportation, etc. It has the advantages of small footprint, safe and efficient operation, low environmental pollution, and convenient transportation and installation. [0003] With the development needs of domestic ultra-deep wells and shale gas in southwest China, the number of domestic ultra-deep wells (60...

AI Technical Summary

Problems solved by technology

For example, the Chinese patent application number is: 200810040895.6, the application date is: July 24, 2008, and the authorized announcement date is: July 20, 2011, which discloses a steel for CT90 coiled tubing and its manufacturing method. The weight percentage distribution ratio of components is: C: 0.02~0.25%, Si: 0.10~0.60%, Mn: 0.50~2.0%, P≤0.015%, S≤0.005%, Cr: 0.30~1.50%, Nb: 0.02~0.13 %, Ti: 0.01-0.10%, V: 0.01-0.10%, Mo: 0.05-0.35%, Cu: 0.10-0.50%, Ni: 0.10-0.40%, Ca: 0.0010-0.0050%, Al: 0.01-0.05% , N≤0.012, the balance is Fe and unavoidable inclusions. Through smelting, casting, slab reheating, rolling, cooling, coiling and other processes, the strength has been improved, but its strength is also not enough to meet the requirements of ultra-deep well operations. At the same time, its composition design contains high V, which is unfavorable to the toughness and welding performance of the product; the yield strength ratio of the steel plate is above 0.90, and the deformability is poor, which cannot meet the repeated requirements of this type of product during operation. Plastic Deformation Requirements

[0005] Another example is the Chinese patent, the application number is: 201711324677.0, the application date is: December 13, 2017, and the authorization announcement date is: March 8, 2019, which discloses a hot-rolled steel strip for CT110 continuous pipe and its production method. Its components and wt%: C: 0.11~0.15%, Si: 0.10~0.30%, Mn: 0.90~1.30%, P: ≤0.015%, S: ≤0.0020%, Cu: 0.25~0.40%, Ni: 0.15 ~0.35%, Cr: 0.60~1.00%, Nb: 0.020~0.050%, V: ≤0.010%, Ti: 0.010~0.030%, N: ≤0.0050%, Al: 0.015~0.060%, Mo: 0.10~0.30 %, Ca: 0.0008~0.0025%, the production steps are: continuous casting into slab after converter smelting and other processes; heating the slab; rough rolling; finish rolling; The operation of ultra-deep wells also faces the risk of insufficient strength

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