RU2763722C1 - SULPHUR-RESISTANT PIPE FOR A PETROLEUM BOREHOLE ATTRIBUTED TO THE KILOPOUND/INCH2 (862 MPa) STEEL STRENGTH CLASS, AND METHOD FOR MANUFACTURE THEREOF - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to the field of metallurgy, namely, to a sulphur-resistant pipe of the 125 kilopound/inch² (862 MPa) strength class for petroleum boreholes. The pipe is made of steel consisting of the following chemical elements, wt.%: C: 0.20 to 0.30, Si: 0.1 to 0.5, Mn: 0.2 to 0.6, Cr: 0.30 to 0.70, Mo: 0.60 to 1.00, V: 0.10 to 0.20, Nb: 0.01 to 0.06, Ti: 0.015 to 0.035, W: 0.20 to 0.60, Al ≤ 0.1, N ≤ 0.008, the rest Fe and unavoidable impurities. The microstructure of the pipe constitutes tempered sorbite.

EFFECT: manufactured pipes exhibit high strength and resistance to hydrogen sulphide corrosion under impact of stresses.

9 cl, 5 tbl, 8 ex

Description

The technical field to which the invention belongs

The present invention relates to an oil well pipe and a method for manufacturing the same, and more particularly relates to a sulfur-resistant oil well pipe and a method for manufacturing the same.

State of the art

With the exhaustion of oil and natural gas sources, the exploitation and development of oil and natural gas fields are developing towards the use of deep wells and ultra-deep wells. Accordingly, the environment in oil and natural gas wells exhibits conditions of increased pressure, increased temperature, and increased corrosion, and in particular, oil and natural gas contain hydrogen sulfide corrosive environment, which brings to the fore increased requirements regarding strength and resistance to hydrogen sulfide stress corrosion of oil well pipe materials.

Document Specification for Casing and Tubing of the American Petroleum Institute (API Spec 5CT) , there are four types of standard classes strength steel serostoykoy pipe, characterized tensile yield strength of 80 kp / ⁱⁿ² (i.e., 551 MPa), 90 kp / inch ² (i.e., 620 MPa), 95 kp / ⁱⁿ² (i.e., 655 MPa) and 110 kp / ⁱⁿ² (i.e., 758 MPa), while a standard of the American petroleum Institute (API) serostoykie pipe characterized by a higher tensile yield strength, such as 125 kp / ⁱⁿ² (i.e., 862 MPa), were not included due to the not yet existing maturity level scientific and industrial technology. For low alloy steel, strength and stress-induced hydrogen sulfide corrosion resistance are a pair of conflicting performance characteristics due to the significant reduction in stress-induced hydrogen sulfide corrosion resistance with increasing strength. In order to provide both strength and sulfur resistance, only expensive high-alloy stainless steel or nickel-based alloy above 13Cr can currently be used, while low-alloy steels are rarely used. Currently, mass production and use serostoykih pipes for oil wells belonging to the class of strength of steel 125 kp / inch ² (862 MPa), have not been realized both domestically and abroad, and in existing patents material strength is also improved for sulfur resistance score.

A Chinese patent document having a publication number of CN 103160752A and a publication date of June 19, 2013, titled "High-strength seamless steel pipe with excellent low-temperature toughness and manufacturing method thereof", discloses a high-strength seamless steel pipe having excellent low-temperature toughness. The main components of the steel pipe are: C: 0.15% - 0.20%, Si: 0.20% - 0.30%, Mn: 0.20% - 0.50%, P: ≤ 0.010%, S : ≤ 0.003%, Cr: 0.6% - 0.8%, Mo: 0.4% - 0.7%, Ni: 1.0% - 1.4%, Nb: 0.01% - 0.035% and varieties of Al: 0.01% - 0.05%. Pipe for an oil well, relating to the class of strength of steel 125 kp / ² inch (862 MPa) is obtained by the use of the system Cr - Mo - Ni. Despite a significant improvement in the toughness for the pipe and the achievement of an impact fracture work at -60°C of 40 J or more, there is no guarantee of sulfur resistance.

The Chinese patent document having the publication number CN 103966524A and the publication date of August 6, 2014 and entitled "Sulfide stress cracking resistant tubing and casing and production method thereof" discloses tubing and casing resistant to sulfide stress cracking. The main components of tubing and casing are: C: 0.12% - 0.20%, Si: 0.15% - 0.40%, Mn: 0.30% - 1.00%, P: ≤ 0.015%, S: ≤ 0.010%, Cr: 0.50% - 1.60%, Mo: 0.60% - 1.20%, Ni: 0.50% - 2.0%, Nb: 0.02 % - 0.08%, Ti: 0.005% - 0.015%, Al: 0.01% - 0.10%, Ca: 0.001% - 0.01%, B: ≤ 0.001% and N: 0.005 - 0.03 %. As a result of optimizing the content of Cr, Mo, Ni and Nb and reducing the content of C, the ratio between the average concentration of Cr and the average concentration of Fe in the M ₂₃ C ₆ type carbide, the M ₃ C type carbide, and the carbide in the structure the tempered martensite is controlled within a certain range to obtain, thereby, steel grade 125 klb/in ² (862 MPa) tubing and casing having a fine and uniform tempered martensite structure.

Accordingly, it is desirable to obtain related to the class of strength of steel 125 kp / inch ² (862 MPa), a pipe for oil wells, which is characterized by high strength and excellent resistance to hydrogen sulfide corrosion under stress and can be widely used in fields such as the exploitation of oil deposits and natural gas in a hydrogen sulfide environment.

Disclosure of the essence of the invention

One of the objectives of the invention is to provide a 125 klb/in ² (862 MPa) steel grade sulfur resistant oil well pipe which is characterized by high strength and excellent resistance to hydrogen sulfide stress corrosion corrosion and can be widely used in fields such as exploitation of oil and natural gas fields in an environment containing hydrogen sulfide.

In order to achieve the above object, the invention provides a class related to the strength of steel 125 kp / ² inch (862 MPa) serostoykaya pipe for an oil well, consisting of the following description of chemical elements in the expression level of their quantities by mass percentage:

C: 0.20 - 0.30%, Si: 0.1 - 0.5%, Mn: 0.2 - 0.6%, Cr: 0.30 - 0.70%, Mo: 0.60 - 1.00%, V: 0.10 - 0.20%, Nb: 0.01 - 0.06%, Ti: 0.015 - 0.035%, W: 0.20 - 0.60%, Al ≤ 0.1 %, N ≤ 0.008%, while the remainder is Fe and other unavoidable impurities.

The design principles for each chemical element in serostoykoy pipe for an oil well, relating to the class of strength of steel 125 kp / ² inch (862 MPa), is as follows:

C: Carbon (C) is an important element for providing strength and hardenability. At a relatively low C content, it is difficult to guarantee the presence of strength or to avoid the formation of precipitates of pro-eutectoid ferrite, thus adversely affecting the sulfur resistance. On the other hand, at an excessively high level of C, hardening cracks easily occur, and at the grain boundary, the tendency to precipitate coarse-grained carbide M ₂₃ C ₆ (mainly (Fe, Cr, Mo, Mn) ₂₃ C _{6 )} , in which the content Fe and Cr is relatively high, while the content of Mo and Mn is relatively low, and the Fe : Cr : Mo : Mn ratio is close to 60 : 10 : 6 : 1), thus adversely affecting sulfur resistance. Therefore, the inventors impose restrictions on the level of mass percentage of C in the class relating to the strength of steel 125 kp / ² inch (862 MPa) serostoykoy pipe for oil wells of the present invention, the value in the range of 0.20 - 0.30%, preferably 0.21 - 0 .25%.

Si: Silicon (Si) is an element introduced into steel when using a deoxidizer. When the Si content exceeds a value of 0.5%, the tendency towards cold brittleness of the steel will increase significantly. At a content level of less than 0.1%, the deacidification effect will be adversely affected. Therefore, the inventors impose restrictions on the level of mass percent Si content related to the class of strength of steel 125 kp / ² inch (862 MPa) serostoykoy pipe for oil wells of the present invention, the value in the range 0.1 - 0.5%, preferably 0.2 - 0 ,4%.

Mn: Manganese (Mn) is also an element introduced into steel when using a deoxidizer. Mn has the beneficial effect of expanding the region of the austenite phase, increasing hardenability and grain refinement. However, Mn segregates easily during solidification, resulting in an obvious banded structure in the final product. Due to the obvious differences in hardness and precipitation phase between the streaky structure and the matrix, the sulfur resistance of the steel will be adversely affected. Therefore, it is necessary to limit the Mn mass percentage level to 0.6% or less. In addition, in order to have a deoxidation effect, it is necessary to limit the Mn mass percentage level to 0.2% or more. Therefore, the inventors impose restrictions on the level of mass percentage of Mn in the class relating to the strength of the steel of 125 kp / ² inch (862 MPa) serostoykoy pipe for oil wells of the present invention, a value in the range of 0.2 - 0.6%, preferably 0, 3 - 0.5%.

Cr: Chromium (Cr) is an element for improving strength and hardenability, and is favorable for improving anti-corrosion resistance. However, an excessively high level of Cr will lead to precipitation of coarse grained Cr ₂₃ C ₆ carbide at the grain boundary during tempering, which is not conducive to stress corrosion resistance. Therefore, the inventors impose restrictions on the level of mass percentage of Cr in the class relating to the strength of the steel of 125 kp / ² inch (862 MPa) serostoykoy pipe for oil wells of the present invention, the value in the range of 0.30 - 0.70%, preferably 0.4 - 0 .6%.

Mo: molybdenum (Mo) is an element for improving strength and hardenability, and is favorable for improving anti-corrosion resistance. The formation of precipitates of Mo carbide during high temperature tempering improves tempering resistance. Therefore, sufficient Mo must be added to ensure that strength and high temperature tempering resistance are present. However, Mo is a noble element and will greatly increase costs. At the same time, an excessively high level of Mo will lead to coarse carbide precipitation, which is not conducive to stress corrosion resistance. Therefore, the inventors impose restrictions on the level of the weight percent Mo content related to the class of strength of steel 125 kp / ² inch (862 MPa) serostoykoy pipe for oil wells of the present invention, a value in the range of 0.60 - 1.00%, preferably 0.65 - 0 .85%.

V: Vanadium (V) is an effective grain refining element that exhibits the effect of precipitation hardening and improvement of high temperature tempering resistance. V provides a reduced dislocation density during high temperature tempering, which favors the formation of fine VC precipitates. Fine-grained precipitates of VC are good hydrogen atom traps and can improve resistance to hydrogen sulfide stress corrosion. However, an excessively high level of V will cause temper brittleness, which adversely affects the toughness of the steel and reduces the resistance to hydrogen sulfide stress corrosion of the steel. Therefore, the inventors impose restrictions on the level of mass percentage of V in the class relating to the strength of the steel of 125 kp / ² inch (862 MPa) serostoykoy pipe for oil wells of the present invention, a value in the range of 0.10 - 0.20%, preferably 0.13 - 0 .17%.

Nb: Niobium (Nb) is an effective grain-refining element. Grain refinement is beneficial for improving the strength, toughness and resistance to hydrogen sulfide stress corrosion corrosion of the steel. Therefore, the inventors impose restrictions on the level of mass percentage of Nb element in the class relating to the strength of the steel of 125 kp / ² inch (862 MPa) serostoykoy pipe for oil wells of the present invention, the value in the range of 0.01 - 0.06%, preferably 0.02 - 0.04%.

Ti: Titanium (Ti) is also an effective grain refining element and exhibits an N-fixing effect. However, an excessively high level of Ti will lead to the formation of coarse TiN inclusions, which is unfavorable for the stress hydrogen sulfide corrosion resistance of the steel. Therefore, the inventors impose restrictions on the level of Ti in mass percentage relating to the class of strength of steel 125 kp / ² inch (862 MPa) serostoykoy pipe for oil wells of the present invention, a value in the range of 0.015 - 0.035%, preferably 0.015 - 0.025%.

W: Tungsten (W) can greatly improve the hardenability and mechanical properties of steel. W can also improve the tempering resistance of the steel so that when the level of Mo in the steel increases, non-coarse-grained carbide M ₂₃ C ₆ and KSI carbide (mainly (Fe, Mo, Cr) ₃ C carbide) are additionally formed, where the ratio of Fe : Mo : Cr is close to 10 : 4 : 1), and fine-grained and homogeneous precipitates of MC carbide (mainly WC, VC or (Mo, V)C carbide, where the Mo : V ratio in the carbide (Mo, V)C is close to 1 : 1). In addition, W can cause the steel to still exhibit relatively high strength after high temperature tempering or after a long tempering time, thus greatly reducing the dislocation density and improving the stress corrosion resistance of the steel. The beneficial effect of W is not apparent when adding a small amount of W, while adding an excessively large amount of W will increase the cold brittleness of the steel. Therefore, the inventors impose restrictions on the level of mass percentage of W in the class relating to the strength of steel 125 kp / ² inch (862 MPa) serostoykoy pipe for oil wells of the present invention, the value in the range of 0.20 - 0.60%, preferably 0.25 - 0 .45%.

Al: aluminum (Al) is an essential element for steel deoxidation, so it is not possible to completely avoid introducing Al into the steel. However, if the Al content exceeds the value of 0.1%, this will have an adverse effect on the steel casting process. Therefore, the inventors impose restrictions on the level of mass percentage of Al in the class relating to the strength of the steel of 125 kp / ² inch (862 MPa) serostoykoy pipe for oil wells of the present invention, the value was 0.1% or less, preferably in the range of 0.01 - 0.03%.

N: Adding N to steel can effectively improve the strength and hardness of steel. However, the addition of N will result in segregation for the steel at the grain boundary, resulting in a decrease in the stress corrosion resistance of the steel. Therefore, the inventors impose restrictions on the level of mass percentage of N in the class relating to the strength of the steel of 125 kp / ² inch (862 MPa) serostoykoy pipe for oil wells of the present invention, the value is 0.008% or less. Due to the inevitability of avoiding contact between steel and air during the smelting and casting processes, an unlimited reduction in the level of N content will significantly increase the production cost of smelting. The weight percentage level of N may be limited to a value in the range of 0.002-0.008%, preferably 0.003-0.005%.

In addition, in the 125 klb/in ² (862 MPa) steel strength grade of the sulfur-resistant oil well pipe of the present invention, the elements Cr and Mo satisfy the relationship: 2.4 ≤ [Cr%] + 3[Mo%] ≤ 3.5.

In the technical solution of the invention to provide demonstrations relating to the class of strength of steel 125 kp / inch ² (862 MPa) serostoykoy pipe for oil wells invention excellent resistance to hydrogen sulfide corrosion under stress and at the same time in order to avoid the formation of precipitates of large size phase, due to excessively high levels of Cr and Mo, which is not conducive to the formation of resistance to hydrogen sulfide corrosion under the stress of steel, the inventors as a result of the study found that the elements Cr and Mo must satisfy the ratio: 2.4 ≤ [Cr%] + 3[Mo %] ≤ 3.5, where Cr and Mo, respectively, represent their respective mass percentage levels, and the values inserted into the ratio defined above should be the values preceding the percent symbols, for example, at a mass percentage level of Cr 0 .45% and the level of mass percentage of Mo 0.75% of the value that e are substituted into the ratio are 0.45 and 0.75 respectively, the calculation is thus carried out according to the following: [Cr%] + 3[Mo%] = 0.45 + 3 × 0.75 = 2.7.

In addition, related to the class of strength of steel 125 kp / inch ² (862 MPa) serostoykoy oil well pipe according to the invention, including those other unavoidable impurities the amount of S is 0.004% or less, the amount of P is 0.015% or less, and the amount of O is 0.01% or less.

In the technical solution of the invention, other unavoidable impurities mainly include S, P and O. S is a harmful element in steel, and its presence has an adverse effect on the corrosion resistance, hot workability and toughness of the steel, so the S content should be as low as possible. The invention limits the level of the mass percentage of the elements in S serostoykoy pipe for an oil well, relating to the class of strength of steel 125 kp / ² inch (862 MPa), the value is 0.004% or less, preferably 0.001% or less. P is also a detrimental element in steel, and its presence adversely affects the corrosion resistance and toughness of the steel, so the level of P should also be as low as possible. The invention limits the level of the weight percent content of the element F in serostoykoy pipe for an oil well, relating to the class of strength of steel 125 kp / ² inch (862 MPa), the value is 0.015% or less, preferably 0.01% or less. O is an element that reduces the corrosion resistance and toughness of steel. An excessively high O level means a high level of inclusions. Therefore, the level of O content in steel must be strictly controlled. The present invention limits the level of the mass percentage of the element O in serostoykoy pipe for an oil well, relating to the class of strength of steel 125 kp / ² inch (862 MPa), the value is 0.01% or less, preferably 0.005% or less.

Furthermore, serostoykaya pipe for an oil well, relating to the class of strength of steel 125 kp / ² inch (862 MPa), has a fully tempered microstructure structure sorbitol. As Applicant's studies show, the retained bainite structure and the quenched martensite structure during heat treatment are detrimental to stress corrosion resistance, while the tempered sorbitol structure is superior in stress corrosion resistance. In order to have a full sorbitol structure after tempering, during the quench heat treatment to obtain a fully quenched martensite structure, sufficient quenching speed and temperature must be provided.

Furthermore, serostoykoy oil well pipe belonging to the class of strength of steel 125 kp / ² inch (862 MPa), the value K _1SSC, which is resistant to H ₂ S-corrosion under stress is 27.5 MPa · m ^1/2 or more.

Accordingly, another object of the present invention is to provide a method for fabricating the above serostoykoy oil well pipe belonging to the class of strength of steel 125 kp / ² inch (862 MPa). The manufacturing method is characterized by low costs. As a result of appropriate design of the process obtained serostoykaya pipe for an oil well, relating to the class of strength of steel 125 kp / ² inch (862 MPa) characterized by high strength and excellent resistance to hydrogen sulfide corrosion under stress.

In order to achieve the above object, the present invention proposes a method for manufacturing the above sulfur resistant oil well pipe belonging to the steel grade 125 ksi / ² (862 MPa), including the steps:

(1) obtaining a pipe blank;

(2) perforating and hot rolling a pipe blank to obtain a pipe made by a piercing mill;

(3) cooling the pipe made by the piercing mill by real-time controlled cooling; and

(4) carrying out a single heat treatment during quenching and tempering as a result of quenching and tempering: where the quenching temperature at the quenching stage is Ac3 + (30 - 50°C), and where Ac3 (°C) = 910 - 203[C%] ^1/2 + 44.7[Si%] + 104[V%] + 31.5[Mo%] + 13.1[W%] followed by water quenching where the water quench rate is ≥ 30° C / sec, and the tempering temperature at the tempering stage is in the range of 680 - 700 ° C, and after that air cooling.

In the manufacturing method according to the invention, in step (1), in some embodiments, first, smelting is carried out in an electric furnace, then the molten steel after smelting is cast into an ingot, and then the ingot is forged or rolled to obtain a tube blank. In step (3), in some embodiments, the hot-rolled piercing-machine pipe rapidly passes through an annular cooler having a water-cooling nozzle, and the piercing-machine pipe is cooled by a controlled real-time cooling, with controlled maintenance of pressure and water flow for the nozzle and conveying speed on a roller table for a pipe made on a piercing mill. At a certain cooling rate and a certain cooling temperature after rolling, a uniform and fine-grained bainite structure is obtained. The goal of obtaining a bainite structure as a result of controlled cooling is to obtain a sufficient amount of austenite nucleation particles for subsequent heating during quenching. The more carbides there are, and the more dispersed the carbides are in the steel prior to quenching, the finer and more uniform the austenite grains formed by heating during quenching will be, and the finer and more uniform will be the microstructure of tempered sorbitol formed by heating during quenching. tempering, thus resulting in stronger resistance to hydrogen sulfide stress corrosion corrosion of the steel. In the case of non-use of controlled cooling after rolling, the resulting microstructure will be ferrite and pearlite (with some bainite present). The structure of ferrite and pearlite belongs to the lamellar structure, and the distribution of carbide is not dispersed, while the carbide of the bainite structure is basically uniformly dispersed. At stage (4), in some embodiments, after heating the cooled pipe made on the piercing mill to Ac3 + (30 - 50 ° C), the temperature is maintained at the quenching stage for 0.5 - 1 hour, and then quenching is carried out in water ; and at the tempering stage, a hardened pipe made on a piercing mill is tempered in a tempering furnace at 680–700°C and held for 1.5–2.5 hours, and then air cooled to obtain the tempered sorbitol structure.

In addition, as it should be noted, in step (4) in the quenching step, it is necessary to provide a quenching rate of ≥ 30° C./sec to obtain a complete martensite structure after quenching. The full martensite structure can be converted to a fully tempered sorbitol structure in a subsequent tempering process. As the study shows, the structure of the tempered sorbitol is characterized by the best resistance to hydrogen sulfide stress corrosion. However, at low quench rates, some bainite structures will form. The bainite structure will not undergo the transformation of tempered sorbitol during the subsequent tempering process, which ensures that the tempered structure is converted into tempered sorbitol and residual bainite. The structure of the residual bainite is an effective hydrogen atom trap due to its high hardness and high dislocation density, which is unfavorable in terms of resistance to hydrogen sulfide stress corrosion of the material.

In addition, as it should be noted, in step (4) in the quenching step, the quenching temperature is Ac3 + (30 - 50°C), where Ac3 (°C) = 910 - 203[C%] ^1/2 + 44 .7[Si%] + 104[V%] + 31.5[Mo%] + 13.1[W%], and where C, Si, V, Mo, and W, respectively, are their respective weight percentage levels content, and the values substituted into the ratio defined above should be the values preceding the percent symbols, for example, at the mass percentage level C 0.25%, the mass percentage level Si 0.21%, the mass percentage level V 0, 11%, a Mo mass percentage level of 0.75%, and a W mass percentage level of 0.45%, the values that are substituted into the ratio are 0.25, 0.21, 0.11, 0.75, and 0.45, the calculation is therefore carried out according to the following: Ac3(°C) = 910 − 203[C%] ^1/2 + 44.7[Si%] + 104[V%] + 31.5[ Mo%] + 13.1[W%] = 910 - 203 × 0.25 ^1/2 + 44.7 × 0.2 1 + 104 x 0.11 + 31.5 x 0.75 + 13.1 x 0.45 = 858.8.

In addition, in the manufacturing method of the invention, the bainite structure is obtained by controlled cooling after rolling. A sufficient amount of austenite nucleation particles can be obtained by subsequent heating in quenching, and the grain size of the original austenite is refined. The austenite is completely converted to quenched martensite during quench cooling, and the quenched martensite is completely converted to tempered sorbite during subsequent tempering heat treatment. A fine-grained and uniform bainite structure is obtained using a cooling process controlled in real time. In the manufacturing method of the invention, a fine grain structure can be obtained after only one quenching and tempering heat treatment, so that a 125 klb/in ² (862 MPa) sulfur resistant oil well pipe of the invention is obtained. Compared with the prior art, in which the grains are refined by two or more times of quenching and tempering heat treatment to improve the strength of the steel and the performance stability of hydrogen sulfide stress corrosion resistance, the manufacturing method of the invention significantly reduces costs.

In addition, in the manufacturing method of the invention in step (3), the cooling rate is controlled at a value in the range of 10 - 30°C/sec, and the final cooling temperature is controlled at a value of (Bs ± 30)°C, where the bainitic transformation temperature is (Bs) = 830 - 270[C%] - 90[Mn%] - 70[Cr%] - 83[Mo%], and air cooling is carried out after completion of the real-time controlled cooling.

In the manufacturing process according to the invention, in step (3), the cooling rate is controlled in a range of 10 - 30°C/sec, since an excessively high cooling rate will result in the bainite structure not being obtained, while an excessively low cooling rate will lead to the formation of perlite. In addition, as it should be noted, the bainite transition temperature is Bs = 830 − 270[C%] − 90[Mn%] − 70[Cr%] − 83[Mo%]. In the ratio, C, Mn, Cr, and Mo, respectively, represent their respective mass percentage levels, and the values inserted into the ratio defined above should be the values preceding the percent symbols, for example, at a mass percentage level C of 0.25 %, Mn mass percentage level of 0.53%, Cr mass percentage level of 0.45%, and Mo mass percentage level of 0.75%, the values that are substituted into the ratio are, respectively, 0.25, 0.53 , 0.45 and 0.75, the calculation is thus carried out according to the following: Bs = 830 - 270[C%] - 90[Mn%] - 70[Cr%] - 83[Mo%] = 830 - 270 x 0.25 - 90 x 0.53 - 70 x 0.45 - 83 x 0.75 = 621.1.

In addition, in the manufacturing method of the invention, in step (2), the pipe blank is heated to 1050-1250°C and kept for 1-3 hours, and then subjected to perforation and hot rolling to obtain a pipe made by a piercing mill.

In addition, in the manufacturing method of the invention in step (2), the final rolling temperature of hot rolling is controlled to be 900° C. or more to ensure that the piercing pipe has a full austenite structure at the end of final rolling, and to ensure the transformation of austenite into a bainite structure during a subsequent cooling process controlled in real time.

In addition, in the manufacturing method of the invention, in step (3), air cooling is carried out using a cooling rack after completion of real-time controlled cooling.

In comparison with the prior art serostoykoy pipe for an oil well, relating to the class of strength of steel 125 kp / ² inch (862 MPa), and a method for manufacturing the present invention is characterized by the following further favorable effects:

(1) As a result of proper formulation of the composition, the 125 klb/in ² (862 MPa) steel grade sulfur resistant oil well pipe of the invention is low cost, and exhibits relatively high strength and excellent resistance to hydrogen sulfide stress corrosion corrosion, and can be widely used in areas such as the exploitation of oil and natural gas fields in a hydrogen sulfide environment.

(2) A method relating to the class of strength of steel 125 kp / ² inch (862 MPa) serostoykoy oil well pipe according to the invention significantly reduces the cost of production resulting from the optimized design of the process and provides a yield strength in tension (R _t0,7 ) of the obtained serostoykoy oil well pipe belonging to the class of strength of steel 125 kp / inch ² (862 MPa) is 125 kp / ⁱⁿ² (i.e., 862 MPa) or more, and the value of K _1SSC, which is a resistance to H ₂ S-corrosion under stress of 27.5 MPa * m ^1/2 or more.

Implementation of the invention

Serostoykaya pipe for an oil well, relating to the class of strength of steel 125 kp / inch ² (862 MPa), and a method of production of the present invention will be further explained and described using specific examples below, but the explanation and description does not impose unduly limits of technical solution of the present invention.

Examples 1-6 and Comparative Examples 1-10

In Tables 1 - 1 and 1 - 2 lists the weight percent levels of chemical elements belonging to the class of strength of steel 125 kp / ² inch (862 MPa) serostoykih for oil well pipes of Examples 1 - 8 and Comparative Examples 1 - 10. Examples 7 and 8 are characterized by optimized compositions.

Table 1 - 1.

(% (mass), the remainder is Fe and unavoidable impurities other than P, S and O)

Number C Si Mn P S Cr Mo V Nb Example 1 0.25 0.21 0.53 0.013 0.003 0.45 0.75 0.11 0.03 Example 2 0.2 0.49 0.37 0.012 0.001 0.69 0.61 0.16 0.01 Example 3 0.29 0.12 0.2 0.014 0.002 0.31 0.95 0.19 0.05 Example 4 0.26 0.35 0.59 0.011 0.001 0.52 0.8 0.14 0.02 Example 5 0.24 0.29 0.28 0.009 0.002 0.66 0.94 0.18 0.04 Example 6 0.28 0.42 0.44 0.012 0.003 0.38 0.82 0.17 0.03 Example 7 0.21 0.2 0.5 0.009 0.001 0.41 0.85 0.15 0.02 Example 8 0.24 0.4 0.3 0.011 0.002 0.51 0.75 0.17 0.04 Comparative Example 1 0.25 0.35 0.36 0.011 0.002 0.42 0.76 0.13 0.04 Comparative Example 2 0.23 0.41 0.39 0.013 0.001

0.77

0.04 Comparative Example 3 0.27 0.32 0.27 0.009 0.002 0.41 0.62 0.13 0.05 Comparative Example 4 0.22 0.39 0.41 0.008 0.001

0.96 0.15 0.03 Comparative Example 5 0.24 0.35 0.33 0.012 0.002 0.32

0.12 0.04 Comparative Example 6 0.21 0.3 0.42 0.011 0.002 0.35 0.74 0.13

Comparative Example 7 0.26 0.47 0.52 0.008 0.001 0.52 0.71

Comparative Example 8 0.26 0.35 0.59 0.011 0.001 0.52 0.8 0.14 0.02 Comparative Example 9 0.26 0.35 0.59 0.011 0.001 0.52 0.8 0.14 0.02 Comparative Example 10 0.26 0.35 0.59 0.011 0.001 0.52 0.8 0.14 0.02

Table 1 - 2.

(% (mass), the remainder is Fe and unavoidable impurities other than P, S and O)

Number Ti W Al O N [Cr%] + 3[Mo%] Example 1 0.022 0.45 0.06 0.009 0.006 2.7 Example 2 0.032 0.58 0.09 0.005 0.005 2.52 Example 3 0.015 0.21 0.04 0.002 0.007 3.16 Example 4 0.033 0.36 0.07 0.004 0.006 2.92 Example 5 0.019 0.25 0.06 0.007 0.005 3.48 Example 6 0.034 0.41 0.08 0.008 0.002 2.84 Example 7 0.025 0.21 0.01 0.004 0.003 2.96 Example 8 0.019 0.45 0.03 0.003 0.005 2.76 Comparative Example 1 0.031

0.06 0.003 0.004 2.7 Comparative Example 2 0.028 0.32 0.04 0.002 0.003 2.58 Comparative Example 3 0.032 0.36 0.06 0.008 0.006 2.27 Comparative Example 4 0.019 0.27 0.07 0.005 0.002 3.6 Comparative Example 5 0.021 0.62 0.05 0.003 0.004 3.47 Comparative Example 6 0.013 0.32 0.06 0.006 0.008 2.57 Comparative Example 7 0.036 0.38 0.08 0.007 0.008 2.65 Comparative Example 8 0.033 0.36 0.07 0.004 0.006 2.92 Comparative Example 9 0.033 0.36 0.07 0.004 0.006 2.92 Comparative Example 10 0.033 0.36 0.07 0.004 0.006 2.92

Note that in the table, Cr and Mo in the ratio [Cr%] + 3[Mo%], respectively, represent their respective mass percentage levels, and the values inserted into the ratio defined above must be the values preceding the percent symbols.

Belonging to Class strength steel 125 kp / inch ² (862 MPa) serostoykie oil well pipe of Examples 1 - 8 and Comparative Examples 1 - 10 produce using the following further steps (see Table 2 - 1 and Table 2 - 2 in relation to specific process parameters).

(1) The levels of chemical elements in tables 1 to 1 and 1 to 2 are the mass percentage levels of chemical components after smelting using an electric furnace. The molten steel after smelting is cast in the form of an ingot, and then subjected to rolling to obtain a pipe billet ϕ 300.

(2) The tube billet is heated to 1050 to 1250°C and held for 1 to 3 hours, and then it is subjected to piercing and hot rolling to obtain a tube produced in a piercing mill, where the final rolling temperature for hot rolling is controlled to values of 900°C or more.

(3) Real-time controlled cooling is carried out on a piercing-machine-produced pipe whose temperature after hot rolling is in the single-phase austenite temperature region. The real-time controlled cooling device is an annular cooling device having a water cooling nozzle. The annular nozzle ensures uniform cooling of the steel pipe around the circumference. The intensity of cooling is controlled in a controlled manner based on the pressure and flow rate of water for the nozzle and the conveying speed on the roller table for the pipe made on the piercing mill. The conveying roller table uses the pipe in an inclined position to keep the pipe made by the piercing mill rotating as it passes through the throw ring, thus preventing production difficulties due to pipe bending during the cooling process. The cooling rate is controlled at a value in the range of 10 - 30°C, and the final cooling temperature is controlled at a value of (Bs ± 30)°C, where the bainite transition temperature is Bs = 830 - 270[C%] - 90[ Mn%] - 70[Cr%] - 83[Mo%]. Air cooling when using a refrigerator rack is carried out after the completion of cooling, controlled in real time. As it should be noted, the bainite transition temperature is Bs = 830 - 270[C%] - 90[Mn%] - 70[Cr%] - 83[Mo%], where C, Mn, Cr and Mo, respectively, represent their respective weight percentage levels, and the values substituted into the ratio defined above must be the values preceding the percent symbols.

(4) One-time quenching and tempering heat treatment is carried out as a result of quenching and tempering at the quenching stage, the quenching temperature is Ac3 + (30 - 50°C), and where Ac3 (°C) = 910 - 203[C%] ^{1 /2} + 44.7[Si%] + 104[V%] + 31.5[Mo%] + 13.1[W%], and the holding time at the temperature is in the range of 0.5 - 1 hour, and after this is carried out quenching in water, where the rate of quenching in water is ≥ 30°C/sec; and at the tempering stage, the tempering temperature is in the range of 680 - 700°C, and the holding time at the temperature is in the range of 1.5 - 2.5 hours; and then air-cooling is carried out to obtain a 125 klb/in ² (862 MPa) steel grade sulfur-resistant oil well pipe having a specification of ϕ200.03*10.92. As it should be noted, in the ratio Ac3(°C) = 910 − 203[C%] ^1/2 + 44.7[Si%] + 104[V%] + 31.5[Mo%] + 13.1 [W%] C, Si, V, Mo, and W, respectively, are their respective weight percentage levels, and the values substituted into the ratio defined above must be the values preceding the percent symbols.

Tables 2 - 1 and 2 - 2 lists specific parameters of the process for manufacturing methods relating to the class of strength of steel 125 kp / ² inch (862 MPa) serostoykih for oil well pipes of Examples 1 - 8 and Comparative Examples 1 - 10.

Table 2 - 1

Number Stage (2) Stage (3) Heating temperature (°C) Holding time at temperature (hour) Final rolling temperature (°C) Cooling rate (°C/sec) Bs Final cooling temperature (°C) Example 1 1240 2.5 960 sixteen 621.1 642 Example 2 1100 3.0 920 22 643.8 620 Example 3 1200 2.0 950 thirty 633.2 650 Example 4 1050 3.0 910 25 603.9 606 Example 5 1210 1.5 943 12 615.8 625 Example 6 1190 1.2 972 23 620.1 592 Example 7 1200 2.5 915 twenty 629.1 620 Example 8 1180 1.5 921 25 640.3 645 Comparative Example 1 1220 2.0 935 25 637.6 610 Comparative Example 2 1150 2.5 918 28 650.0 663 Comparative Example 3 1100 2.3 935 eighteen 652.6 625 Comparative Example 4 1230 2.5 930 26 603.6 616 Comparative Example 5 1180 3.0 942 21 626.0 640 Comparative Example 6 1120 3.0 910 25 649.6 613 Comparative Example 7 1230 1.5 980 24 617.7 622 Comparative Example 8 1200 2.5 950 / 603.9 / Comparative Example 9 1220 2.0 960 25 603.9

Comparative Example 10 1180 2.0 940 eight 603.9 610

Please note: in the table Bs = 830 - 270[C%] - 90[Mn%] - 70[Cr%] - 83[Mo%], where C, Mn, Cr and Mo in the ratio, respectively, represent their respective the mass percentage levels, and the values to be substituted into the ratio defined above, must be the values preceding the percent symbols.

Table 2 - 2

Number Stage (4) Hardening stage Holiday stage AC3 (°C) Hardening temperature (°C) Holding time at temperature (hour) Quenching speed in water (°C/sec) Holiday temperature (°C) Holding time at temperature (hour) Example 1 858.8 900 1.0 35 695 2.0 Example 2 884.6 920 0.6 40 690 2.5 Example 3 858.5 890 0.8 45 700 1.5 Example 4 866.6 900 0.5 32 685 2.0 Example 5 875.1 910 0.6 36 695 1.5 Example 6 870.2 905 1.0 43 690 2.0 Example 7 871.0 905 1.0 35 695 2.0 Example 8 875.6 910 0.8 40 690 2.0 Comparative Example 1 863.8 900 0.6 35 680 2.0 Comparative Example 2 867.7

0.5 40 695 1.5 Comparative Example 3 856.6 895 1.0 thirty 690 2.5 Comparative Example 4 881.6

0.5 35 685 1.5 Comparative Example 5 879.9

0.8 36 700 2.0 Comparative Example 6 871.4

1.0 33 680 2.5 Comparative Example 7 877.7 910 0.5 35 695 2.0 Comparative Example 8 866.6 900 0.8 35 690 2.0 Comparative Example 9 866.6 900 1.0 40 695 1.5 Comparative Example 10 866.6 900 1.0 35 690 2.0

Please note: in the table Ac3(°C) = 910 − 203[C%] ^1/2 + 44.7[Si%] + 104[V%] + 31.5[Mo%] + 13.1[W% ], where C, Si, V, Mo, and W in the ratio, respectively, represent their respective weight percentage levels, and the values substituted into the ratio defined above must be the values preceding the percent symbols.

Performance tests were carried out on the 125 klb/in ² (862 MPa) steel grade sulfur resistant oil well pipes of Examples 1 to 8 and Comparative Examples 1 to 10. Tensile testing at ambient temperature was performed in accordance with document GB/T 228.1-2000 standard. The hydrogen sulfide stress corrosion test is carried out in accordance with NACE standard TM0177-2005 D (solution A). The test results are listed in Table 3.

Table 3

Number Tensile test at ambient temperature Resistance to hydrogen sulfide stress corrosion Tensile yield strength R _t0.7 (MPa) Tensile strength R _m (MPa) K _1SCC (MPa * m ^1/2 ) Example 1 908 965 28.9 Example 2 930 984 28.2 Example 3 887 939 29.5 Example 4 955 998 27.8 Example 5 901 954 29.0 Example 6 933 986 28.6 Example 7 895 943 31.1 Example 8 910 960 30.0 Comparative Example 1 867 924 25.3 Comparative Example 2 890 952 25.6 Comparative Example 3 923 976 24.6 Comparative Example 4 948 999 23.8 Comparative Example 5 926 992 24.7 Comparative Example 6 915 972 24.9 Comparative Example 7 916 968 25.1 Comparative Example 8 931 983 25.3 Comparative Example 9 902 963 25.6 Comparative Example 10 928 985 26.5

As can be seen from the table 3, relating to the class of strength of steel 125 kp / inch ² (862 MPa) serostoykie oil well pipe of Examples 1 - 6 characterized by tensile yield strength of 125 kp / inch ² or more (i.e. , 862 MPa), and the value of K _1SSC representing resistance to hydrogen sulfide corrosion under stress, component 27.5 MPa * m ^1/2 and more. Examples 7 and 8 are related to the class of strength of steel 125 kp / ² inch (862 MPa) serostoykie pipe, characterized preferred compositions and demonstrate value K _1SSC, component more than 30 MPa · m ^1/2, which indicates better resistance to hydrogen sulfide stress corrosion.

Level W content related to the class of strength of steel 125 kp / ² inch (862 MPa) serostoykoy oil well pipe of Comparative Example 1 is excessively low, leading to a decrease serostoykosti.

The levels of both Cr and V in the 125 klb/in ² (862 MPa) steel grade sulfur resistant oil well pipe of Comparative Example 2 are excessively low, resulting in a reduction in the amount of the dispersed precipitate phase and an imperceptible effect grinding grains, which leads to a decrease in sulfur resistance.

The amount of Cr + 3Mo in the 125 klb/in ² (862 MPa) steel grade sulfur resistant oil well pipe of Comparative Example 3 is excessively small, resulting in a decrease in the corrosion resistance of the steel in an acidic environment, resulting in a decrease in sulfur resistance.

Both the Cr content and the Cr + 3Mo value in the 125 klb/in ² (862 MPa) steel grade sulfur resistant oil well pipe of Comparative Example 4 are excessively high, resulting in a significant increase in the amount of the coarse precipitate phase. in steel, which leads to a decrease in sulfur resistance.

The levels of both Mo and W in the 125 klb/in ² (862 MPa) steel grade sulfur resistant oil well pipe of Comparative Example 5 are excessively high, resulting in a significant increase in temper resistance and an increase in hardness by cold for steel, which leads to a decrease in sulfur resistance.

The levels of both Nb and Ti in the 125 klb/in ² (862 MPa) steel grade sulfur resistant oil well pipe of Comparative Example 6 are excessively low, resulting in a reduction in the amount of the dispersed precipitate phase and an imperceptible effect grinding grains, which leads to a decrease in sulfur resistance.

All levels of V, Nb and Ti in pertaining to the class of strength of steel 125 kp / inch ² (862 MPa) serostoykoy pipe for oil wells of Comparative Example 7 are excessively high, which results in an increase in the number of coarse inclusions and phase precipitates in the steel , which leads to an obvious decrease in sulfur resistance.

The pipe blank of the 125 klb/in ² (862 MPa) steel grade sulfur resistant oil well pipe of Comparative Example 8 is not subjected to a controlled real-time cooling process after hot rolling, resulting in obtaining a coarse-grained and uneven structure after a single heat treatment during quenching and tempering, which leads to a decrease in sulfur resistance.

The pipe blank of the 125 klb/in ² (862 MPa) steel grade sulfur resistant oil well pipe of Comparative Example 9 is not subjected to a controlled real-time cooling process with a final cooling temperature outside the range (Bs ±30)°C after hot rolling, and the pipe billet is unable to realize bainitic transformation, resulting in a coarse and uneven structure after quenching and tempering heat treatment once, resulting in a decrease in sulfur resistance.

For the 125 klb/in ² (862 MPa) steel grade sulfur resistant oil well pipe of Comparative Example 10, due to the low cooling rate in the real-time controlled cooling, a mixed structure of pearlite and bainite is formed, and thus , grain refinement after a single heat treatment during quenching and tempering is imperceptible, which leads to a decrease in sulfur resistance.

As it should be noted, the restrictive part in the scope of protection of the present invention is not limited by the embodiments presented in this application document. The scope of protection of the present invention may include all prior art that is not inconsistent with the solution of the present invention, including the following, but not limited to: prior patent documents, prior public publications, prior public use case, and the like.

In addition, the methods of combining technical features in the present application are not limited by the methods of combining described in the claims or specific embodiments. All technical features described in this application can be freely combined or combined in any way, unless there is a contradiction between them.

As should also be noted, the foregoing is merely illustrative of specific embodiments of the invention. As is obvious, the present invention is not limited to the above embodiments, but has many such variations. All variations that are directly produced or conceived by those skilled in the art from this disclosure are intended to fall within the scope of the present invention.

Claims (15)

1. Steel-grade 125 ksi/ ² (862 MPa) sulfur-resistant oil well pipe, consisting of the following chemical elements when expressed in terms of mass percentage level: C: 0.20 - 0.30%, Si: 0.1 - 0.5%, Mn: 0.2 - 0.6%, Cr: 0.30 - 0.70%, Mo: 0.60 - 1.00%, V: 0.10 - 0.20%, Nb: 0.01 - 0.06%, Ti: 0.015 - 0.035%, W: 0.20 - 0.60%, Al ≤ 0.1 %, N ≤ 0.008%, while the remainder is Fe and unavoidable impurities, while the microstructure of the oil well pipe corresponds to the tempered sorbitol. 2. The pipe according to claim 1, in which the elements Cr and Mo satisfy the ratio: 2.4 ≤ [Cr%] + 3[Mo%] ≤ 3.5. 3. The pipe according to claim 1, in which among the mentioned inevitable impurities S ≤ 0.004%, P ≤ 0.015% and O ≤ 0.01%. 4. The pipe according to claim 1, wherein the K _{1SSC value} , which is H ₂ S stress corrosion resistance, is 27.5 MPa*m ^1/2 or more. 5. A method of manufacturing related to the class of steel strength 125 klb/in ² (862 MPa) sulfur-resistant pipe for an oil well according to any one of paragraphs. 1 - 4, including stages: (1) obtaining a pipe blank; (2) piercing and hot rolling a pipe blank to obtain a pipe made by a piercing mill; (3) cooling said pipe by real-time controlled cooling; and (4) carrying out a single heat treatment of the specified pipe in the form of quenching and tempering, while the temperature of the specified pipe at the stage of quenching is Ac3 + (30 - 50°C), where Ac3 (°C) = 910 - 203[C%] ^{1/ 2} + 44.7[Si%] + 104[V%] + 31.5[Mo%] + 13.1[W%], and said pipe is cooled during quenching in water at a rate of 30°C/s or more , wherein the temperature of said pipe at the tempering stage is 680 - 700°C, and said pipe is cooled during tempering in air. 6. The method according to claim 5, wherein in step (3) the cooling rate is controlled at a value in the range of 10 - 30°C/s and the final cooling temperature is controlled at a value of (Bs ± 30)°C, where the bainitic transformation temperature is (Bs)=830-270[C%]-90[Mn%]-70[Cr%]-83[Mo%], and air cooling is carried out after completion of real-time controlled cooling. 7. The method according to claim 5, wherein in step (2) the pipe blank is heated to 1050 - 1250°C and held for 1 to 3 hours, and then subjected to piercing and hot rolling to obtain a pipe made on a piercing mill. 8. The method according to claim 7, wherein in step (2), the final rolling temperature of the hot rolling is controlled to be 900° C. or more to ensure that the piercing pipe has a fully austenitic structure at the end. final rolling. 9. The method according to claim 6, wherein in step (3) air-cooling is carried out using the cooling rack after completion of the real-time controlled cooling.