A kind of Cr alloyed steel for electric resistance welded oil casing and its manufacturing method

Abstract

The invention provides a Cr alloying electric resistance weld petroleum casing pipe steel and a manufacturing method thereof. The steel comprises the following chemical components: 0.15%-0.20% of C, 0.10%-0.35% of Si, 0.90%-1.15% of Mn, less than or equal to 0.020% of P, less than or equal to 0.008% of S, 0.010%-0.030% of Ti, 0.08%-0.28% of Cr, 0.02%-0.06% of Als, less than or equal to 0.008% of N, and the balance Fe and inevitable elements. The manufacturing method includes: smelting, continuous casting, rolling, cooling, and reeling. The heating temperature of a continuous casting sheet billet is 1100-1200DEG C. The rolling adopts two-stage control. In the first stage, the initial rolling temperature is 1050-1150DEG C, the final rolling temperature is higher than 970DEG C, and the accumulative deformation is more than 60%. In the second stage, the initial rolling temperature is lower than 990DEG C, the final rolling temperature is 780-850DEG C, and the accumulative deformation is above 70%. A rolled steel strip is cooled to 570-640DEG C at a cooling rate of 10-15DEG C / s and is subjected to reeling. The metallographic structure of the steel is ferrite-pearlite, and the pearlite volume content is 6%-40%. According to the invention, a Cr alloying design is adopted, and adding of Nb and V precious alloys is unnecessary. By controlling rolling, cooling and reeling processes, the steel plate can meet the requirements of the API SPEC 5CT standard on a J55 grade steel pipe.

Description

technical field [0001] The invention belongs to the field of manufacturing ERW (ERW, Electric Resistance Weld, high-frequency resistance welding) casing steel, in particular to a Cr alloyed resistance welding oil casing steel in APISPEC5CT and a manufacturing method thereof. Background technique [0002] Oil casing is one of the most commonly used petroleum-specific pipes in oil fields. It consumes a lot of money and costs a lot. It is an indispensable construction material in oil and gas field drilling operations. Compared with seamless pipes, ERW casings have significant advantages such as uniform wall thickness, high dimensional accuracy, good perforation performance, strong collapse resistance, and low cost. Medium and low steel grade ERW casings are replacing traditional seamless pipes. Steel Pipe. [0003] APISpec5CT stipulates that the yield strength of J55 grade steel pipe is between 379-552MPa, the tensile strength is ≥517MPa, and the elongation is ≥24%. [0004] ...

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Problems solved by technology

For example, "A method for producing J55 steel grade oil casing steel based on electric furnace thin slab continuous casting and rolling process" publication number CN1884787A, "A low-cost oil casing steel and its production method" publication number CN101200791A, "high strength toughness J55 Petroleum casing steel and its production method" public number CN101210299A, both use Nb and Ti compound addition; "A vanadium alloyed straight seam resistance welding oil casing steel and its manufacturing method" public number CN1019994057A uses V and Ti compound addition ; Using Nb, Ti or V, Ti compound addition, the cost of the alloy is high, and the Nb microalloyed steel often causes problems such as transverse cracking of the billet angle in actual production; "A kind of steel for oil casing, high-frequency welding oil Casing and its manufacturing method” public number CN101928877A, “hot-rolled strip for straight seam welding oil casing and its production method” public number CN101033525A, “low-alloy high-strength steel for manufacturing J55 grade welded oil casing” public number CN1924061A adopts One of Nb or V or Ti is strengthened, and the single addition of Nb or V or Ti is strengthened, and the yield strength of the produced steel strip is low. Considering the decrease in strength caused by the Bauschinger effect during pipe making, the strength of the final steel pipe is difficult to meet the standard requirements.

The steels for longitudinal seam welding oil casing disclosed above meet the requirements of the J55 steel strip specified by the American Petroleum Institute APISpec5CT, but they all have the problems of low strength or high cost of precious alloys

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