Economical low-yield-ratio steel for pipe fittings for oil and gas transmission and method for producing economical low-yield-ratio steel

Abstract

The invention discloses economical low-yield-ratio steel for pipe fittings for oil and gas transmission and a method for producing the economical low-yield-ratio steel. The economical low-yield-ratio steel comprises from 0.09% to 0.16% of C, from 0.20% to 0.40% of Si, from 1.00% to 1.39% of Mn, from 0.01% to 0.04% of Nb, from 0.005% to 0.018% of Ti, from 0.01% to 0.04% of V, from 0.008% to 0.035% of Als, from 0% to 0.20% of Mo, from 0% to 0.30% of Ni, from 0% to 0.30% of Cu, from 0% to 0.25% of Cr, the balance iron and inevitable impurities, wherein the total content of the Nb, the V and the Ti is lower than or equal to 0.09%, and the total content of the Mo, the Ni, the Cu and the Cr is lower than or equal to 0.40%. After the economical low-yield-ratio steel is subjected to heat treatment, the yield strength of the economical low-yield-ratio steel for the pipe fittings can be higher than 490MPa or 560MPa, the tensile strength of the economical low-yield-ratio steel can be higher than 670MPa or 720MPa, the yield ratio of the economical low-yield-ratio steel is lower than 0.80, the impact toughness of the economical low-yield-ratio steel at the temperature of minus 46 Celsius degrees is not lower than 80J, and technical requirements of X70-grade steel for pipe fittings and X80-grade steel for pipe fittings are met completely.

Description

technical field [0001] The invention belongs to the technical field of low-carbon micro-alloy steel, and in particular relates to an economical low-yield ratio pipe fitting steel for oil and gas transportation and a production method thereof. Background technique [0002] Pipe fittings are important structural parts in pipelines that change direction, reinforce and strengthen, mainly including tees, bends and heads, etc. A large number of pipe fittings are required in the construction of long-distance pipelines. With the development of pipeline transportation towards high pressure and large diameter, the requirements for the strength, toughness and weldability of pipe fittings have been continuously improved, and higher requirements have been put forward for the comprehensive quality of steel for pipe fittings. [0003] At present, the production of oil and gas pipe fittings generally needs to undergo heat treatment and forming. Therefore, it is required that the steel for p...

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Problems solved by technology

[0007] To sum up, the research on economical low-yield-ratio pipe fitting steels in the prior art is still insufficient.

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