J55-grade low-yield-ratio steel for electric resistance welding casing pipe and manufacturing method of J55-grade low-yield-ratio steel

Abstract

The invention discloses J55-grade low-yield-ratio steel for an electric resistance welding casing pipe and a manufacturing method of the J55-grade low-yield-ratio steel. The J55-grade low-yield-ratio steel comprises chemical components including, by weight percent, 0.090%-0.128% of C, 0.10%-0.35% of Si, 1.02%-1.25% of Mn, smaller than or equal to 0.015% of P, smaller than or equal to 0.008% of S, 0.01%-0.03% of Nb, 0.010%-0.030% of Ti, 0.30%-0.40% of Cr, 0.02%-0.06% of Als, smaller than or equal to 0.008% of N and the balance Fe and inevitable elements. The method is characterized in that a continuous casting sheet billet is heated to 1160-1200 DEG C through a heating furnace, and the final rolling temperature in the first stage is larger than 980 DEG C; the rolling starting temperature in the second stage ranges from 980 DEG C to 1020 DEG C, and the final rolling temperature ranges from 810 DEG C to 865 DEG C; laminar flow intermittent cooling is adopted for a rolled steel strip, and the cooling speed ranges from 12 DEG C/s to 18 DEG C/s; and coiling is conducted at the temperature ranging from 590 DEG C to 680 DEG C. The J55-grade low-yield-ratio steel has the beneficial effects that the carbon content is relatively low, and weldability and the impact toughness are good; and a proper number of Cr alloy is added, the safety of a steel pipe is good, and it is ensured that the yield strength and the tensile strength meet the standard requirement.

Description

technical field [0001] The invention relates to a steel for straight seam electric resistance welded oil casing (ERW / HFW for short) and a manufacturing method thereof, in particular to a J55 grade ERW oil casing steel with a low yield ratio in APISPEC5CT and a manufacturing method thereof. Background technique [0002] Oil casing is one of the most commonly used oil-specific pipes in oil fields. The annual demand is about 800,000 to 1 million tons, accounting for more than 40% of the total steel used in the oil industry. It is an indispensable construction in oil and gas field drilling operations. Material. 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. In particular, J55 grade ERW casings have mostly replaced traditional seamless pipes. Seam steel pipe. [0003] APISpec5CT stipulates that the yield strength of J55 grade ...

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Problems solved by technology

[0018] The present invention aims at the technical problems existing in the current production of J55 grade ERW oil casing steel, such as high C content, high yield strength, low tensile strength, general weldability, impact toughness and formability, etc., and provides a direct Steel for seam resistance welding oil casing and its manufacturing method, especially low yield ratio J55 grade ERW oil casing steel with good weldability, impact toughness and formability, and its manufacturing method

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