RU2564191C2 - Pipe from steel resistant to corrosion in medium of hydrocarbon and carbon dioxide - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: pipe is made from steel containing the following, wt %: carbon 0.21-0.28, silicone 0.15-0.45, manganese 0.50-0.95, chrome 0.80-1.30, molybdenum 0.25-0.45, nickel not more than 0.50, copper not more than 0.30, aluminium 0.015-0.050, sulphur not more than 0.010, phosphorus not more than 0.015, nitrogen not more than 0.012, vanadium 0.03-0.08 or boron 0.001-0.004 and titanium not more than 0.045, and iron and inevitable impurities are the rest.

EFFECT: achieving the required corrosion resistance of pipes in media containing hydrogen sulphide and carbon dioxide at provision of ultimate strength of not less than 655 MPa and yield point of 552 to 826 MPa.

2 cl, 3 tbl

Description

The invention relates to the field of metallurgy, in particular to the manufacture of pipes for oil and gas production, which can be operated both under ordinary conditions and under conditions of corrosive attack from the produced fluid in the presence of hydrogen sulfide (H ₂ S) and carbon dioxide (CO ₂ ) .

Tubes are known in hydrogen sulfide-resistant performance of strength groups L80S, C90S according to API Spec 5CT / ISO 11961 made of steel grade 26KHMFA-2 with the following content (wt.%): Carbon 0.26; manganese 0.62; silicon 0.24; chromium 0.94; molybdenum 0.53; nickel 0.09; copper 0.013; sulfur 0.004; phosphorus 0.010; aluminum 0.01; vanadium 0.04; niobium 0.003; titanium 0.005 [Metallurgy and heat treatment, No. 5 (623), 2007, p. 18-22].

The disadvantage of using this steel composition for the manufacture of pipes is that hardenability with a content of at least 90% martensite in the microstructure, which is one of the criteria for ensuring corrosion resistance according to API Spec 5CT / ISO 11961, is achieved only up to a wall thickness of 21 mm, as well as an increase the cost of the pipe made from this composition, due to the expensive alloying with molybdenum.

Closest to the claimed invention is a steel pipe having the following ratio of components (wt.%):

carbon 0.31-0.34, silicon 0.30-0.45, manganese 0.75-0.95, niobium 0,045-0,100, vanadium 0.001-0.080, boron 0.002-0.004, aluminum 0.005-0.006, titanium 0.010-0.045, chromium 1.10-1.50, sulfur 0.001-0.045, phosphorus 0.001-0.045, nitrogen no more 0.012, nickel no more 0.50 copper no more 0.20; rest iron;

when the content of the sum [chromium] + [vanadium] + [niobium] equal to 1.15-1.70% (US Pat. RF No. 2352647, publ. 04.20.2009).

The disadvantage of this composition is that it can be used only for pipes in the usual version, the composition is not applicable for corrosive conditions from environments containing hydrogen sulfide and carbon dioxide. In addition, boron in an amount of 0.002-0.004% has a negative effect on hardenability with an increase in austenitization temperature due to an increase in its solubility and the release of an excess boron-containing phase along austenite grain boundaries, which leads to a decrease in the viscoplastic properties in a high-strength state due to the embrittling effect of the boron-containing phase at the grain boundaries. And the introduction of strong carbide-forming elements, such as vanadium 0.001-0.080%, niobium 0.045-0.100%, requires elevated heating temperatures during austenitization.

The technical problem to which the claimed invention is directed is to provide corrosion resistance of pipe metal in environments containing hydrogen sulfide (at a partial pressure of H ₂ S up to 2 atm) and carbon dioxide (at a partial pressure of CO ₂ up to 1 atm), with achievement of the level of strength properties (tensile strength of at least 655 MPa and yield strength of 552 to 826 MPa), corresponding to strength groups L80, C90, T95, C110 according to domestic regulatory standards and the international standard API Spec 5CT / ISO 11961 (acceptance levels PSL-1, 2, 3).

This result is achieved in that the pipe is made of steel that is resistant to corrosion in an environment containing hydrogen sulfide and carbon dioxide containing carbon, silicon, manganese, chromium, molybdenum, nickel, aluminum, sulfur, phosphorus, nitrogen, boron, titanium, iron and inevitable impurities, contains components in the following ratio (wt.%):

carbon 0.21-0.28 silicon 0.15-0.45 manganese 0.50-0.95 chromium 0.80-1.30 molybdenum 0.25-0.45 nickel no more 0.50 copper no more 0.30 aluminum 0.015-0.050 sulfur no more 0.010 phosphorus no more 0.015 nitrogen no more 0.012 boron 0.001-0.004 titanium no more 0,045 iron and inevitable impurities rest

however, it has a tensile strength of at least 655 MPa and a yield strength of 552 to 826 MPa.

Also, this result is achieved by the fact that the pipe is made of steel resistant to corrosion in an environment containing hydrogen sulfide and carbon dioxide containing carbon, silicon, manganese, chromium, molybdenum, nickel, copper, aluminum, sulfur, phosphorus, nitrogen, vanadium, iron and inevitable impurities, contains components in the following ratio (wt.%):

carbon 0.21-0.28 silicon 0.15-0.45 manganese 0.50-0.95 chromium 0.80-1.30 molybdenum 0.25-0.45 nickel no more 0.50 copper no more 0.30 aluminum 0.015-0.050 sulfur no more 0.010 phosphorus no more 0.015 nitrogen no more 0.012 vanadium 0.03-0.08 iron and inevitable impurities rest

however, it has a tensile strength of at least 655 MPa and a yield strength of 552 to 826 MPa.

The technical result provided by the selected ratio of individual chemical elements in steel is determined by the following factors.

Carbon (0.21-0.28) is regulated when alloying steel with manganese, chromium, molybdenum, boron under conditions of quenching in water to avoid the appearance of quenching cracks.

Manganese (0.50-0.95) provides high strength in addition to the deoxidizing effect of steel. With the introduction of manganese more than 1.0%, the visco-plastic properties deteriorate and the corrosion resistance of the steel decreases.

Chromium (0.80-1.30) has a positive effect on increasing hardenability, which is manifested with a certain minimum content in steel, usually in the range from 1.10% to 1.50%. Chromium has an even greater effect in the presence of strong carbide-forming elements, such as molybdenum, titanium, vanadium, due to an increase in their content in the solid solution during austenitization. Also, chromium has a positive effect on resistance against peptic carbon dioxide corrosion due to the enrichment of corrosion products and the formation of a protective layer at the metal-medium interface.

Molybdenum (0.25-0.45) is introduced in the specified amount, based on the fact that when complexed with boron additives, the amount of molybdenum required is less than is usually required to ensure the strength and visco-plastic properties of the products during quenching and low-temperature tempering. The lower limit of 0.25% of the content is due to the requirements of the international standard API Spec 5CT / ISO 11961 to ensure corrosion resistance in environments containing hydrogen sulfide.

Boron (0.001-0.004) has a positive effect on the hardenability of steel. When the boron content exceeds 0.005%, the viscoplastic properties of steel deteriorate due to the release of an excess boron-containing phase along the austenite grain boundaries. Thus, the optimal doping range for boron is 0.001-0.004%.

Titanium (0.015-0.045) fixes nitrogen in steel in the form of nitrides and ensures the presence of boron in the active form, that is, in the solid solution during quenching, which is required to achieve high hardenability. To obtain these effects, titanium must be added at least 0.005%. An upper titanium limit is necessary to prevent the formation of large nitrides in the structure.

Vanadium (0.03-0.08) contributes to the grinding of the grain structure and hardening of steel due to the formation of finely dispersed carbides and nitrides.

The content in the steel of strong carbide and nitride forming elements: vanadium and titanium above the stated standards can lead to a decrease in corrosion resistance due to the possible formation of coarse inclusions along grain boundaries. It is also impractical to apply complexly in one composition more than two strong carbide and nitride forming elements.

Under the conditions of the Sinarsky Pipe Plant, pipes were manufactured with the ratio of components known and proposed in the invention.

The results of industrial production of the proposed pipe in comparison with the known pipes (including the prototype) are shown in table 1 — chemical composition options, table 2 — mechanical properties, and table 3 — corrosion resistance assessment.

As can be seen from the results of the study, the achieved level of mechanical properties and high resistance to sulfide corrosion attack (SCRN) in environments containing hydrogen sulfide at a partial pressure of 1.5-2.0 atm, pipes from the proposed compositions make them effective after heat hardening by means hardening and tempering for strength groups C90, T95 (second option) and up to a maximum strength group C110 (first option) in accordance with domestic regulatory documents and the international standard API Spec 5C T / ISO 11961 in hydrogen sulfide resistant design. Also, the results of assessing the overall corrosion rate in environments containing carbon dioxide at a partial pressure of 1 atm confirm the applicability of the proposed compositions for use in conditions complicated by the presence of a small amount of dissolved carbon dioxide of not more than 500 mg / l.

The proposed solution of complex alloying of steel with molybdenum in amounts of 0.25-0.45% and boron allows to reduce the cost of pipes to 20% in comparison with the known solution for the use of steel pipes with a molybdenum content of 0.50-0.65%.

Claims (2)

1. Corrosion resistant pipe in an environment containing hydrogen sulfide and carbon dioxide, made of steel containing carbon, silicon, manganese, chromium, molybdenum, nickel, copper, aluminum, sulfur, phosphorus, nitrogen, boron, titanium, iron and inevitable impurities, characterized in that it is made of steel containing components in the following ratio, wt.%:
carbon 0.21-0.28 silicon 0.15-0.45 manganese 0.50-0.95 chromium 0.80-1.30 molybdenum 0.25-0.45 nickel no more than 0.50 copper no more than 0.30 aluminum 0.015-0.050 sulfur no more than 0,010 phosphorus no more than 0.015 nitrogen no more than 0,012 boron 0.001-0.004 titanium no more than 0,045 iron and inevitable impurities rest
however, it has a tensile strength of at least 655 MPa and a yield strength of 552 to 826 MPa. 2. A pipe resistant to corrosion in an environment containing hydrogen sulfide and carbon dioxide, made of steel containing carbon, silicon, manganese, chromium, molybdenum, nickel, copper, aluminum, sulfur, phosphorus, nitrogen, vanadium, iron and inevitable impurities, characterized in that it is made of steel containing components in the following ratio, wt.%:
carbon 0.21-0.28 silicon 0.15-0.45 manganese 0.50-0.95 chromium 0.80-1.30 molybdenum 0.25-0.45 nickel no more than 0.50 copper no more than 0.30 aluminum 0.015-0.050 sulfur no more than 0,010 phosphorus no more than 0.015 nitrogen no more than 0,012 vanadium 0.03-0.08 iron and inevitable impurities rest
however, it has a tensile strength of at least 655 MPa and a yield strength of 552 to 826 MPa.