Hot-rolled coil plate for oil casing and manufacturing method thereof

Abstract

The invention relates to a hot-rolled coil plate for an oil casing and a manufacturing method thereof. The hot-rolled coil plate comprise, by mass percent, 0.10 to 0.21 of C, 0.10 to 0.25 of Si, 1.0 to 1.50 of Mi, 0.010 to 0.020 of Al, less than or equal to 0.020 of P, no more than 0.010 of S, 0,012 to 0.045 of Nb, 0.005 to 0.020 of Ti, and the balance Fe and inevitable impurities. The tensile strength Rm is more than or equal to 655Mpa, the yield strength Rt 0.5 is 379-552Mpa, the elongation A50% is more than or equal to 24, and the hardness HV10 is less or equal to 248. The manufacturing method includes:LF refining, the S being less than or equal to 0.004%; RH refining, subjecting the molten steel to Ca treatment; slab continuous casting, the temperature being in a range from 1527 DEG C to 1547 DEG C, and the casting speed being less than or equal to 1.2m / min; slab heating, the temperature being in a range from 1150 DEG C to 1230 DEG C; roughing mill group rolling, the final temperature being in a range from 750 DEG C to 920 DEG C; laminar cooling; and coiling. The hot-rolled coil plate for the oil casing has low yield ratio and good welding performances, and no subsequent thermal treatment is needed.

Description

technical field [0001] The invention relates to a hot-rolled coil for oil casing and a manufacturing method thereof, that is, a hot-rolled coil for oil casing of K55 steel grade and a manufacturing method thereof. Background technique [0002] Oil casing is the lifeline to keep oil well running. It is mainly used to support the well wall during drilling and after completion, so as to ensure the drilling process and the normal operation of the entire oil well after completion. Due to different geological conditions, the downhole stress state is complex, and the tensile, compressive, bending and torsional stresses act comprehensively on the pipe body, which puts forward higher requirements on the quality of the casing itself. Once the casing itself is damaged for some reason, It may lead to the reduction of production of the entire well, or even scrapping. [0003] According to the strength of the steel itself, the casing can be divided into different steel grades, namely J5...

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Problems solved by technology

[0016]2) Chinese patent, application number 200910048199.4, application publication number CN 1O1845583A, "Steel for oil casing and its manufacturing method"; C content is 0.31-0.35%, and Selectively add Mo0.05-0.35%. Compared with the patent application number 200610027021.8, carbon-manganese steel is also used, but there are differences in composition and hot rolling process, and the carbon content is high, which affects welding performance.

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