Hot-rolled steel strip for CT90 level continuous pipe and production method of hot-rolled steel strip

Abstract

A hot-rolled steel strip for a CT90 level continuous pipe comprises chemical components including, by weight percent, 0.05%-0.10% of C, 0.10%-0.30% of Si, 0.40%-0.90% of Mn, smaller than or equal to 0.015% of P, smaller than or equal to 0.0020% of S, 0.25%-0.40% of Cu, 0.15%-0.35% of Ni, 0.50%-1.00% of Cr, 0.10%-0.20% of Mo, 0.020%-0.050% of Nb, smaller than or equal to 0.010% of V, 0.010%-0.030% of Ti, smaller than or equal to 0.0050% of N, 0.015%-0.060% of Al, 0.0008%-0.0025% of Ca and 0.0008%-0.0015% of B. A production method comprises the steps that a cast ingot is heated after smelting and ingot casting; rough rolling is conducted; finish rolling is conducted; cooling is conducted in three stages; and after a steel roll is rolled, the steel roll is placed in a thermal insulating wall to be subjected to slow cooling. Through adding of the B, the content of the C is reduced, structure segregation of the steel is improved, and it is ensured that the HIC resisting and SSCC resisting performance is qualified; through composite adding of the Cu and the Ni, the hot shortness of the Cu is improved; staging controlled cooling is conducted, regulation and control over a complex phase structure are achieved, and the yield ratio of the steel strip is reduced.

Description

Technical field [0001] The invention relates to pipeline steel and a production method thereof, in particular to a hot-rolled steel strip for CT90 grade coiled pipe and a production method thereof. Background technique [0002] Coiled tubing is a new type of tubing used in the oil drilling industry. Flexible steel pipes with a length of several kilometers to tens of thousands of meters are coiled on the tube coil. The coil is opened from the tube coil during operation. After the operation is completed, it can be coiled again on the tube coil. use. Compared with traditional oil well tubing, coiled tubing operation is more flexible, and has the advantages of working under pressure, continuous lifting, small equipment volume, fast operation cycle, and low cost. [0003] After searching, the Chinese patent application No. 200710168545.3 document discloses "a high-plasticity coiled tubing steel and its manufacturing method". After analysis, its Cr content is relatively low, and the coi...

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Problems solved by technology

[0003] After searching, the Chinese patent application number is 200710168545.3, which discloses "a steel for high plastic coiled tubing and its manufacturing method". After analysis, its Cr content is relatively low, and the hardenability and corrosion resistance of coiled tubing are relatively low. Poor; due to the addition of 0.15-0.30% Cu without adding Ni at the same time, there is hot brittleness; its alloy content is relatively low, and the strength similar to this patent is achieved through a low cooling temperature, and its low-temperature toughness is relatively poor

[0004] The Chinese patent application number is 200810040895.6, which discloses "a CT90 steel for coiled tubing and its manufacturing method". Due to the high content of C and Mn, serious segregation will occur in the steel strip, and high-frequency resistance welding Hook-shaped crack defects also appear in the pipe-making process; at the same time, its composition design contains high V, which is unfavorable to the toughness and plasticity of the steel strip; its yield ratio is above 0.90, and the deformability is poor, which is not conducive to the fatigue performance of the steel pipe

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