An iron-nickel-chromium alloy oil casing and its manufacturing method

Abstract

The present invention relates to a steel for an iron-nickel-chromium alloy oil casing, wherein the steel comprises the following chemical components, by weight, less than or equal to 0.03% of C, less than or equal to 0.015% of P, less than or equal to 0.01% of S, less than or equal to 0.5% of Si, 0.5-2.0% of Mn, 27-29% of Ni, 26-28% of Cr, 3-4% of Mo, 1.5-3% of Cu, 0.1-0.3% of Al, 0.001-0.10% of N, 0.001-0.02% of Nb, 0.001-0.02% of V, 22.8-30.8 of G, and the balance of Fe, wherein G meets the following formula: G=30N+Ni+Cu-2(Cr-26)-5(Mo-3)-7Si-3Al. A manufacturing method for the oil casing comprises: carrying out smelting with an electric arc furnace or an argon-oxygen decarbonization furnace; carrying out casting to obtain an ingot, and carrying out electroslag remelting and forging to obtain a hot extrusion billet, wherein a pre-heating temperature of the hot extrusion billet is 950-1180 DEG C, and an ingot billet thermal insulation time is 1-5 minutes per cm of an ingot billet thickness; immersing the extruded pipe billet material in water, and cooling to a temperature of less than 50 DEG C; and carrying out a solid solution treatment at a temperature of 1050-1150 DEG C, wherein a pipe billet material thermal insulation time is 1-5 minutes per mm of wall thickness, and the total amount of intermetallic compounds, carbides and nitrides in the alloy microstructure after solid solution treatment does not exceed 1%. The oil casing has excellent pitting corrosion resistance and excellent stress corrosion resistance.

Description

technical field [0001] The invention relates to an oil casing, in particular to an iron-nickel-chromium alloy oil casing and a manufacturing method. This kind of oil casing has a single austenite structure, in which the number of precipitates such as intermetallic compounds, carbides and nitrides is ≤1%. It has high mechanical properties and good stress corrosion resistance, and can be used in high acid oil and gas fields. mining development. Background technique [0002] With the continuous increase of energy demand and the continuous reduction of exploitable oil and gas resources, the exploitation of oil and gas resources has to turn to deep wells, ultra-deep wells and highly corrosive wells. This type of oil and gas well is characterized by high temperature, high pressure, and high CO 2 、H 2 S partial pressure, containing elemental sulfur and high salinity. In order to meet the production and development needs of such oil and gas wells, more and more ultra-high alloy ...

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Problems solved by technology

These alloys can be used in high temperature, high pressure, high CO 2 、H 2 Production of S partial pressure and high salinity oil and gas wells, but the Ni content in it is more than 30%, the alloy cost is high, resulting in high oil field production costs

[0004] U.S. Patent No. 4,840,768 discloses an iron-nickel-chromium alloy that can be used as oil well pipe fittings, which has good corrosion resistance, but the composition disclosed in this patent has a high C content, which is easy to form carbides, and a high Si content, which promotes the formation of harmful phases. Precipitation, it is more difficult to control the metallographic structure of the alloy

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