Petroleum case pipe with high strength and toughness and producing method thereof

Abstract

The invention discloses a petroleum casing pipe with high obdurability and a method for making the same. The invention aims to provide a petroleum casing pipe with high obdurability which can meet the mining conditions of deep wells or ultra-deep wells in the oil field and a method for making the same. The compositions in percentage by weight of the petroleum casing pipe are: 0.22 to 0.35 percent of C, 0.17 to 0.30 percent of Si, 0.45 to 0.60 percent of Mn, 0.80 to 1.10 percent of Cr, 0.70 to 1.10 percent of Mo, 0.015 to 0.040 percent of Al , less than 0.20 percent of Ni, less than 0.20 percent of Cu, 0.070 to 0.100 percent of V, less than 0.050 percent of Nb, less than 0.0015 percent of Ca, less than 0.010 percent of P, less than 0.003 percent of S, the balance being Fe. The petroleum casing pipe of the invention adopts a quenched and tempered steel of Cr-Ni-Mo-V alloy system. An ultra-fine lath is obtained after the steel is heat-treated. A certain amount of austenitic toughness phases are distributed dispersedly on a martensite matrix, which improves the obdurability of the steel so as to adapt to bear the outside squeezing load and the axial load brought by the deep wells or the ultra-deep wells.

Description

Technical field [0001] The invention belongs to the technical field of seamless steel pipe manufacturing in the metallurgical industry, and particularly relates to a petroleum casing with ultra-high strength and toughness suitable for deep wells or ultra-deep wells and a production method thereof. Background technique [0002] With the increase of oil and gas field drilling depth and the increase of temperature and pressure, the geological environment of fixed wellhead oil casing service has undergone significant changes, and the mechanical conditions used have also changed accordingly. The external squeezing load and The axial load is getting higher and higher. The high-quality petroleum casing such as V125 specified by the American Petroleum Institute standard generally adopts Cr-Mo-V series alloy steel. Due to the complicated smelting, rolling and heat treatment processes of this steel petroleum casing, the alloy composition and manufacturing process are improper , Will cause ...

AI Technical Summary

Problems solved by technology

[0004] However, the current steel grades used in oil casings contain high impurities such as sulfur and phosphorus, and the metal structure contains flaky inclusions. The uneven flow of the metal during the rolling process results in inconsistent mechanical properties in the horizontal and vertical directions.

Moreover, in the current oil casing production method, the quenching medium in the heat treatment process is water, which is easy to cause cracking. At the same time, due to the unreasonable piercing and rolling process, heat treatment process and straightening method, the best The strength and toughness of the casing match, and cause excessive residual stress, and the geometric dimension accuracy of the casing is poor, which directly affects the ability of the product to resist collapse.