RU2599474C1 - High corrosion resistance pipe - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to production of oil pipes. To increase corrosion resistance of metal pipes in media containing hydrogen sulphide (at partial pressure H₂S of up to 1.5 MPa) and carbon dioxide (at partial pressure of CO₂ of up to 0.1 MPa) both simultaneously and separately, and to provide ultimate strength not less than 655 MPa, yield point of 552 to 758 MPa and resistance to impact loads at minus 60 °C not less than 70 J/cm² pipes are made from steel containing, wt%: carbon 0.15-0.25, silicon 0.15-0.35, manganese 0.40-0.70, chrome 0.70-1.50, molybdenum 0.10-0.30, vanadium 0.03-0.08, aluminium 0.015-0.050, sulphur not more than 0.010, phosphorus not more than 0.015, nitrogen not more than 0.012, copper 0.15-0.35, nickel not more than 0.30 (or 0.30-0.70), iron and unavoidable impurities - balance.

EFFECT: high corrosion resistance of metal pipes.

2 cl, 4 tbl

Description

The invention relates to the field of metallurgy, and in particular to the production of oil-grade tubes, which can be operated both under normal conditions and in wells with corrosive media containing hydrogen sulfide (H ₂ S) and carbon dioxide (CO ₂ ).

It is known to manufacture pipes in a corrosion-resistant version from steels with different chromium contents, which can conditionally be divided into two groups according to the chromium content: up to 1% and more than 1%.

The first group of pipes (chromium content up to 1%) relates to a hydrogen sulfide-resistant version and is made of steel with the following element content (wt.%):

15XFA - carbon 0.13; manganese 0.52; silicon 0.27; chrome 0.57; molybdenum 0.02; sulfur 0.007; phosphorus 0.013; aluminum 0.042; vanadium 0,048 [Metallurgy and heat treatment, No. 2 (656), 2010. p. 9-14];

32HG - carbon 0.32; manganese 0.72; silicon 0.27; chrome 1.02; molybdenum 0.01; sulfur 0.006; phosphorus 0.008; aluminum 0.02 [Engineering practice, No. 11-12, 2011. p. 18-21];

26KHMFA-2 - carbon 0.26 / 0.27; manganese 0.62 / 0.58; silicon 0.24 / 0.24; chromium 0.94 / 0.89; molybdenum 0.53 / 0.52; nickel 0.09 / 0.14; copper 0.013 / 0.20; sulfur 0.004 / 0.006; phosphorus 0.010 / 0.006; aluminum 0.01 / 0.02; vanadium 0.04 / 0.04; niobium 0.003 / -; titanium 0.005 / - [Metallurgy and heat treatment, No. 5 (623), 2007. p. 18-22] / [Engineering practice, No. 11-12, 2011. p. 18-21].

The disadvantage of using these steels for the production of pipes is the low resistance to peptic corrosion in environments containing dissolved carbon dioxide, the local corrosion rate reaches 8 mm / year, a low operating range for the partial pressure of carbon dioxide (0.01-0.05 MPa) is recommended.

The second group of pipes (chromium content more than 1%), designed for use in aggressive environments containing hydrogen sulfide and carbon dioxide, is made of steel with the following content of elements (wt.%): Carbon 0.1-0.35; chrome 1.0-6.0; molybdenum 0.4-1.0, after normalization and double tempering [US Pat. RF №2368836, publ. 09/27/2009].

The disadvantage of using this steel for pipe production is a low margin in terms of strength properties, it is possible to achieve a strength group Ε in accordance with GOST 633-80 (tensile strength of at least 689 MPa and yield strength of at least 552 MPa), as well as heat treatment in three stages leads to loss of productivity due to the repeated loading of thermal equipment in the conditions of a serial in-line process of manufacturing pipes.

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

carbon 0.14-0.23,

silicon 0.14-0.40,

manganese 0.50-0.90,

niobium 0.02-0.08,

vanadium 0.05-0.17,

aluminum 0,020-0,050,

titanium 0.005-0.030,

chrome 0.60-1.10,

sulfur not more than 0.010,

phosphorus no more than 0.015,

nitrogen not more than 0.010,

nickel no more than 0.30,

copper no more than 0.30,

calcium 0.0010-0.0030,

oxygen no more than 20ppm,

hydrogen no more than 2ppm;

the rest is iron and inevitable impurities;

with the chromium equivalent Cr _eq = [Cr] + 2 · [Mo] + 5 · [V] + 1.5 · [Nb] + 1.5 · [Ti] equal to 1.6 ≤ Cr _eq ≤ 2.5 (US Pat. RF №2437954, publ. 12/27/2011).

The disadvantage of this composition in the manufacture of oil range pipes is the low resistance to peptic corrosion in environments containing carbon dioxide, the possibility of their use only in environments with a ratio of Pco ₂ / Rn ₂ s≤20, which leads to corrosion damage under the influence of hydrogen sulfide (hydrogen delamination, sulfide stress corrosion cracking) with a small proportion of the development of carbon dioxide corrosion. In addition, the positive effect of chromium, copper and nickel on the corrosion resistance of pipes against carbon dioxide corrosion is not fully realized due to their low content in this chemical composition.

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 1.5 MPa) and carbon dioxide (at a partial pressure of CO ₂ up to 0.1 MPa) as simultaneously and separately with the achievement of the level of strength properties (tensile strength of at least 655 MPa and yield strength of 552 to 758 MPa), corresponding to strength groups N80 type Q, L80 type 1, R95 (K, E, L) according to domestic regulatory standards and international standard API Spec 5CT / ISO 11961, and resistance to impact loads at minus 60 ° С not less than 70 J / cm ² .

This result is achieved in that the pipe of increased corrosion resistance, made of steel containing carbon, silicon, manganese, chromium, molybdenum, vanadium, aluminum, nickel, copper, iron and inevitable impurities, contains components in the following ratio (wt.%):

carbon 0.15-0.25

silicon 0.15-0.35

manganese 0.40-0.70

chrome 0.70-1.50

molybdenum 0.10-0.30

vanadium 0.03-0.08

aluminum 0.015-0.050

sulfur not more than 0.010

phosphorus no more than 0.015

nitrogen no more than 0.012

copper 0.15-0.35

nickel no more than 0.30

iron and

unavoidable impurities rest,

however, it has a tensile strength of at least 655 MPa and a yield strength of 552 to 758 MPa, impact resistance at minus 60 ° C of at least 70 J / cm ²

Also, this result is achieved in that the pipe of increased corrosion resistance, made of steel containing carbon, silicon, manganese, chromium, molybdenum, vanadium, aluminum, nickel, copper, iron and inevitable impurities, contains components in the following ratio (wt.%) :

carbon 0.15-0.25

silicon 0.15-0.35

manganese 0.40-0.70

chrome 0.70-1.50

molybdenum 0.10-0.30

vanadium 0.03-0.08

aluminum 0.015-0.050

sulfur not more than 0.010

phosphorus no more than 0.015

nitrogen no more than 0.012

copper 0.15-0.35

nickel 0.30-0.70

iron and

unavoidable impurities rest,

at the same time, it has a tensile strength of at least 655 MPa and a yield strength of 552 to 758 MPa, and shock resistance at

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

Carbon (0.15-0.25) allows you to provide the required level of strength properties as a result of tempering with tempering, the maximum limit of 0.25% avoids excessive formation of the carbide phase and significant structural stresses, which negatively affects the resistance of the metal in hydrogen sulfide-containing media.

Manganese (0.40-0.70) provides strength in addition to the deoxidizing effect of steel. With the introduction of manganese more than 1.0%, the viscoplastic properties deteriorate and the corrosion resistance of the steel decreases because more than 0.80% is possible the formation of segregation heterogeneity of the metal.

Chromium (0.70-1.50) has a positive effect on increasing hardenability, especially in the presence of carbide-forming elements such as molybdenum and vanadium due to an increase in its content in solid solution during austenitization. Also, chromium has a positive effect on resistance against peptic carbon dioxide corrosion due to the formation of a protective layer at the metal-medium interface.

Molybdenum (0.10-0.30), when combined with chromium, increases the corrosion resistance in hydrogen sulfide-containing media and provides a sufficient level of viscoplastic properties, including at low temperatures, by suppressing the segregation of harmful impurities (sulfur, phosphorus, etc.) at the boundaries grains.

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 more than two strong carbide and nitride forming elements (such as vanadium, niobium, titanium, etc.) is impractical, as this can lead to a decrease in corrosion resistance due to the possible formation of coarse inclusions at the grain boundaries, and their transition to solid the solution requires high austenitization temperatures, which is non-technological.

Copper (0.15-0.35) has a direct effect on the protective properties of corrosion products by the formation of a dense layer of oxides during oxidation of the metal surface, which serves as a barrier to the further penetration of aggressive media to the metal, and does not have a visible effect on the level of mechanical properties. With an increase in copper content of more than 0.35%, the likelihood of its negative influence during hot pressure treatment, associated with the formation of surface cracks, increases.

Nickel (0.30-0.70) increases the protective properties of the metal against corrosion due to its tendency to passivation and enrichment of the metal-medium interface, which allows it to be used along with chromium to increase resistance against ulcerative carbon dioxide corrosion.

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 manufacturing are shown in table 1 - chemical composition options, table 2 - assessment of contamination by non-metallic inclusions, table 3 - mechanical properties and table 4 - assessment of corrosion resistance.

As can be seen from the results of the study, the achieved level of mechanical properties and corrosion resistance in environments containing hydrogen sulfide and carbon dioxide, after quenching with tempering, make it possible to recommend the proposed pipes for use in a corrosion-resistant design. The results of tests for corrosion resistance against carbon dioxide corrosion, carried out using an autoclave installation, which allows you to accurately simulate the conditions of the well by creating high pressures and temperatures, confirm the resistance of the proposed pipes under conditions of excess pressure of carbon dioxide and the applicability of this solution to increase corrosion resistance in environments with a partial pressure of carbon dioxide up to 0.1 MPa. Also, the proposed pipes achieved a high level of impact strength at a negative test temperature of minus 60 ° C (KCV _-60 180-261 J / cm ² ), which is required for cold-resistant performance in relation to the conditions of the Northern regions of oil and gas production.

Claims (2)

1. The pipe increased corrosion resistance made of steel containing carbon, silicon, manganese, chromium, molybdenum, vanadium, aluminum, sulfur, phosphorus, nitrogen, nickel, copper, iron and inevitable impurities, characterized in that it is made of steel, containing components in the following ratio, wt.%:
carbon 0.15-0.25 silicon 0.15-0.35 manganese 0.40-0.70 chromium 0.70-1.50 molybdenum 0.10-0.30 vanadium 0.03-0.08 aluminum 0.015-0.050 sulfur no more than 0,010 phosphorus no more than 0.015 nitrogen no more than 0,012 copper 0.15-0.35 nickel no more than 0.30 iron and inevitable impurities rest,
wherein the pipe has a tensile strength of at least 655 MPa, a yield strength of 552 to 758 MPa, and impact resistance at minus 60 ° C of at least 70 J / cm ² . 2. A pipe of increased corrosion resistance made of steel containing carbon, silicon, manganese, chromium, molybdenum, vanadium, aluminum, sulfur, phosphorus, nitrogen, nickel, copper, iron and inevitable impurities, characterized in that it is made of steel, containing components in the following ratio, wt.%:
carbon 0.15-0.25 silicon 0.15-0.35 manganese 0.40-0.70 chromium 0.70-1.50 molybdenum 0.10-0.30 vanadium 0.03-0.08 aluminum 0.015-0.050 sulfur no more than 0,010 phosphorus no more than 0.015 nitrogen no more than 0,012 copper 0.15-0.35 nickel 0.30-0.70 iron and inevitable impurities rest,
wherein the pipe has a tensile strength of at least 655 MPa, a yield strength of 552 to 758 MPa, and impact resistance at minus 60 ° C of at least 70 J / cm ² .