Ultrahigh-strength tubing and casing resistant to hydrogen sulfide corrosion and method for manufacturing same

Abstract

Disclosed in the present invention are ultrahigh-strength tubing and casing resistant to H2S corrosion. The tubing and casing contain Fe and inevitable impurities, and also contain the following chemical elements: C: 0.15-0.28%, Si: 0.1-0.5%, Mn: 0.2-0.5%, Cr: 0.4-0.8%, Mo: 0.8-1.5%, V: 0.15-0.3%, Nb: 0.05-0.15%, W: 0.2-0.6%, Al: 0.01-0.05%, Ce: 0.002-0.006%, and 0<O≤0.002%, wherein the mass percentage content of Ce and O also satisfies Ce / O: 1-3.5. Accordingly, further disclosed in the present invention is a method for manufacturing the ultrahigh-strength tubing and casing resistant to H2S corrosion. In the present invention, by means of reasonable chemical element composition design, the tubing and casing having both ultrahigh strength and excellent resistance to H2S stress corrosion can be obtained.

Description

Ultra-high strength oil casing resistant to hydrogen sulfide corrosion and manufacturing method thereof Technical Field

[0001] The present invention relates to a steel material and a manufacturing method thereof, in particular to an oil casing and a manufacturing method thereof. Background Art

[0002] Most of the oil and gas formations currently being developed contain H2S, which is buried deep, typically between 6,000 and 9,000 meters. With the increasing development of sulfur-containing oil and gas wells and the continuous increase in oil and gas drilling depths, there is a growing demand for sulfur-resistant pipes with steel grades of 110-130 ksi and above to meet the tensile and internal pressure strength requirements of casing strings in the development of deep, highly sour oil and gas fields.

[0003] Therefore, in the seamless pipes disclosed in the prior art, different technical means are used to improve the hydrogen sulfide stress corrosion resistance of steel.

[0004] For example, Japanese patent document No. JP2004332059A, published on November 25, 2004, and entitled “Low Alloy Steel”, proposes improving hydrogen sulfide stress corrosion resistance by reducing amorphous inclusions.

[0005] For example, Japanese patent document JP2005350754A, published on December 22, 2005, and entitled "LOW ALLOY STEEL FOR OIL WELL TUBE HAVING EXCELLENT SULFIDE STRESS CRACKING RESISTANCE," proposes a technology for controlling dislocation density and hydrogen diffusion coefficient to improve the hydrogen sulfide stress corrosion resistance of 125ksi steel-grade sulfur-resistant pipes.

[0006] Summary of the Invention

[0007] One of the purposes of the present invention is to provide an ultra-high strength oil casing and tubing resistant to H2S corrosion, which can obtain an oil casing and tubing having both ultra-high strength and excellent H2S stress corrosion resistance through reasonable chemical element composition design.

[0008] To achieve the above object, the present invention provides an ultra-high strength oil casing and tubing resistant to H2S corrosion, which contains Fe and unavoidable impurities, and further contains the following chemical elements in the following mass percentages:

[0009] C: 0.15~0.28%, Si: 0.1~0.5%, Mn: 0.2%~0.5%, Cr: 0.4~0.8%, Mo: 0.8~1.5%, V: 0.15~0 .3%, Nb: 0.05~0.15%, W: 0.2~0.6%, Al: 0.01~0.05%, Ce: 0.002~0.006%, 0<O≤0.002%;

[0010] The mass percentages of Ce and O also satisfy Ce / O: 1 to 3.5.

[0011] Accordingly, the present invention also provides an ultra-high strength oil casing and tubing resistant to H2S corrosion, wherein the mass percentage of each element is as follows:

[0012] C: 0.15-0.28%, Si: 0.1-0.5%, Mn: 0.2%-0.5%, Cr: 0.4-0.8%, Mo: 0.8-1.5%, V: 0.15-0.3%, Nb: 0.05-0.15%, W: 0.2-0.6%, Al: 0.01-0.05%, Ce: 0.002-0.006%, 0<O≤0.002%; the balance is Fe and other inevitable impurities;

[0013] The mass percentages of Ce and O also satisfy Ce / O: 1 to 3.5.

[0014] There are many factors that affect the material's resistance to hydrogen sulfide stress corrosion. Among them, the carbides formed by alloying elements can play a precipitation strengthening role and act as hydrogen traps to reduce the diffusion of hydrogen in the steel, which is beneficial to improving the resistance to hydrogen sulfide stress corrosion. The interface between the precipitate and the matrix is ​​the main hydrogen trap point. Therefore, the smaller the size of the precipitate, the more interfaces per unit volume, the more hydrogen can be captured and dispersed. Larger carbides such as Cr 23 C6 and other inclusions tend to precipitate at grain boundaries and lath boundaries, becoming diffusion channels for hydrogen, accelerating the diffusion of hydrogen in the steel and causing it to accumulate at crack-sensitive points. In addition, Al2O3 inclusions in the steel are also sensitive points to hydrogen damage, and crack sources are easily formed near such inclusions.

[0015] Based on this, in the technical solution described in the present invention, on the one hand, by adding W alloy, the strength of the material is improved through its precipitation strengthening and solid solution strengthening effects, and the generated W2C carbides are dispersed in the crystal, which can increase the amount of hydrogen captured and reduce the sensitivity of sulfide stress corrosion cracking. On the other hand, the Cr content is reduced to inhibit the growth of larger carbides such as Cr 23C6 and other inclusions tend to precipitate at grain and lath boundaries, reducing the number of sites susceptible to hydrogen damage. Furthermore, the present invention incorporates the element Ce, which reacts with large inclusions such as Al2O3 in the steel, changing their shape and size. After vacuum degassing (VD), these large inclusions float up and are removed, leaving smaller and more regularly shaped CeAlO3 and composite inclusions in the steel, thereby improving resistance to sulfide stress corrosion cracking.

[0016] Specifically, the design principles of the chemical elements in the H2S corrosion resistant ultra-high strength oil casing of the present invention are as follows:

[0017] C: In the ultra-high-strength H2S corrosion-resistant oil casing described in the present invention, C is an important element to ensure strength and hardenability. When the C content in the steel is less than 0.15%, it is difficult to achieve the strength of 125ksi steel grade. When the C content in the steel is too high, quenching cracks are likely to occur, and the coarse carbides M at the grain boundaries will also increase. 23 The precipitation tendency of C6 affects the anti-sulfur performance. Therefore, the mass percentage of the C element is controlled between 0.15 and 0.28% in the present invention.

[0018] Si: In the H2S corrosion-resistant ultra-high-strength oil casing described herein, Si is introduced into the steel by the deoxidizer. A Si content exceeding 0.5% significantly increases the steel's cold brittleness. Below 0.1%, the deoxidizing effect is reduced. Therefore, the present invention controls the Si content to between 0.1% and 0.5%.

[0019] Mn: Mn has beneficial effects such as expanding the austenite phase, increasing hardenability, and refining grain size. However, Mn content above 0.5% is prone to segregation during solidification, leading to component segregation in the steel and affecting its sulfur resistance. Furthermore, to ensure deoxidation and increase hardenability, the Mn content in the steel must be maintained above 0.2%. For this reason, the mass percentage of Mn in the H2S corrosion-resistant ultra-high-strength oil casing of the present invention is controlled between 0.2% and 0.5%.

[0020] Cr: In the ultra-high strength oil casing resistant to H2S corrosion of the present invention, Cr is an element that improves strength and hardenability, and can effectively improve the corrosion resistance of steel. However, it should be noted that the Cr content in the steel should not be too high, as excessive Cr content will cause coarse Cr to precipitate at the grain boundaries during tempering. 23 C6 carbides are not conducive to hydrogen sulfide stress corrosion resistance. Based on this, the present invention controls the mass percentage of Cr element to between 0.4 and 0.8%, for example, between 0.50 and 0.80%.

[0021] Mo: Mo improves strength, tempering stability, and hardenability, while also enhancing the material's corrosion resistance. Mo contents above 1.5% lead to the precipitation of coarse carbides, which is detrimental to hydrogen sulfide stress corrosion resistance. Mo contents below 0.8% make it difficult to achieve a 125 ksi steel strength grade during high-temperature tempering. Therefore, in the H2S corrosion-resistant ultra-high-strength oil casing of the present invention, the mass percentage of Mo is controlled between 0.8% and 1.5%.

[0022] V: V is an effective grain-refining and precipitation-strengthening element, improving resistance to high-temperature tempering and ensuring low dislocation density during high-temperature tempering. The resulting fine VC phase acts as a hydrogen trap, enhancing resistance to hydrogen sulfide stress corrosion. However, it is important to note that the V content in the steel of this invention should not be too high, as excessive V content can lead to temper brittleness and reduce the steel's stress corrosion resistance. Therefore, in the H2S corrosion-resistant ultra-high-strength oil casing of this invention, the mass percentage of V is controlled between 0.15 and 0.3%.

[0023] Nb: Nb is an effective grain-refining element. The Nb precipitates formed in the austenite region refine the grains, positively impacting the steel's strength, toughness, and sulfur resistance. In the H2S-corrosion-resistant oil casing of the present invention, the mass percentage of Nb is controlled between 0.05 and 0.15%.

[0024] W: In the ultra-high-strength oil casing and tubing resistant to H2S corrosion described in the present invention, W is one of the core elements. It exists in the steel in the form of solid solution and precipitation. The precipitated phase can be dispersed and evenly distributed in the steel, which has a good precipitation strengthening effect, can improve the high-temperature tempering resistance and improve the strength of the material. However, when the W content is too high, the precipitated phase is easy to coarsen, forming hydrogen-induced cracking sensitive points. When the W content is too low, the strengthening effect is insufficient and it is difficult to achieve the 125ksi strength level. Therefore, the mass percentage of the W element is controlled between 0.2% and 0.6%.

[0025] Al: Al is an essential element for steel deoxidation, so its inclusion in steel cannot be completely avoided. However, the Al content in steel should not be too high. When the Al content exceeds 0.05%, it has an adverse effect on the casting process, etc. Therefore, the present invention controls the Al content to 0.01-0.05% by mass.

[0026] Ce: In the H2S corrosion-resistant ultra-high-strength oil casing described herein, Ce purifies the molten steel, modifies inclusions, and strengthens the steel through precipitation. Ce readily combines with elements such as O and S at high temperatures to form high-melting-point oxides, sulfides, and sulfur oxide particles. Furthermore, Ce has a significant modifying effect on hard inclusions such as Al2O3. When the Ce content in the molten steel is above 20 ppm, it modifies the steel, generating smaller composite inclusions of CeAlO3 + CaS. Combined with the fact that large inclusions are almost completely removed by floating after VD treatment, the size of inclusions in the steel is significantly reduced, significantly improving the casing steel's toughness and resistance to hydrogen sulfide stress corrosion cracking (SSC). However, excessive Ce content can form brittle, hard iron-rare earth intermetallic compounds, reducing the material's SSC resistance. Furthermore, excessive Ce addition can easily cause nozzle clogging, leading to casting difficulties. Therefore, the Ce content in the present invention is controlled between 0.002% and 0.006% by weight.

[0027] In addition, in the ultra-high-strength H2S corrosion-resistant oil casing described in the present invention, while controlling the mass percentage of a single chemical element, it is also necessary to control the Ce / O ratio to meet the following conditions: 1 to 3.5. This is because the O element in the steel can form large-sized Al2O3 inclusions with the Al element. These large-sized inclusions act as strong hydrogen traps in a hydrogen sulfide environment, easily leading to hydrogen sulfide stress corrosion cracking. Through research, the inventors have found that when the ratio of the added Ce content to the O content reaches 1 or above, Ce can form granular CeAlO3 inclusions, thereby refining the inclusions and avoiding the harmful effects of large-sized Al2O3 inclusions. However, when the ratio of the Ce content to the O content exceeds 3.5, the casting process becomes difficult. Therefore, the mass percentages of the Ce and O elements are controlled to meet the relationship: 1≤Ce / O≤3.5.

[0028] Furthermore, in the ultra-high strength oil casing and tubing resistant to H2S corrosion of the present invention, the mass percentage of each chemical element may further satisfy at least one of the following conditions:

[0029] C: 0.18~0.25%;

[0030] Cr: 0.4~0.7%;

[0031] Mo: 0.9~1.2%;

[0032] V: 0.18~0.25%;

[0033] Nb: 0.05~0.1%;

[0034] W: 0.2~0.5%;

[0035] Al: 0.015~0.04%;

[0036] Ce: 0.002~0.005%.

[0037] Furthermore, among the inevitable impurities in the H2S corrosion resistant ultra-high strength oil casing of the present invention: S≤0.002%, P≤0.01%, and N≤0.008%.

[0038] Furthermore, S≤0.0015%, P≤0.008%, and N≤0.007%.

[0039] In the above technical solution of the present invention, P, S, N, and O are all harmful impurity elements. In order to obtain steel with better performance and higher quality, the content of P, S, N, and O should be reduced as much as possible if the technology permits.

[0040] Furthermore, the microstructure matrix of the H2S corrosion resistant ultra-high strength oil casing of the present invention is tempered troostite.

[0041] Furthermore, the H2S corrosion resistant ultra-high strength oil casing of the present invention has W2C carbides dispersed in the crystals.

[0042] Furthermore, the number of alloy precipitates with a diameter of 200 nm or more in the microstructure of the ultra-high strength oil casing resistant to H2S corrosion of the present invention is ≤5 / 100 μm. 2 , for example 1 to 5 per 100um 2 .

[0043] As mentioned above, the larger alloy precipitates, such as Cr 23 C6 is easy to precipitate at the grain boundary and lath boundary, becoming a diffusion channel for hydrogen, accelerating the diffusion of hydrogen in the steel grade and causing it to gather at crack sensitive points. Therefore, the present invention controls the number of alloy precipitates with a diameter of more than 200nm to ≤5 / 100μm. 2 .

[0044] Furthermore, the ultra-high strength oil casing and tubing resistant to H2S corrosion of the present invention has CeAlO3 inclusions and CeAlO3+CaS composite inclusions.

[0045] Furthermore, in the H2S corrosion resistant ultra-high strength oil casing of the present invention, the sizes of CeAlO3 inclusions and CeAlO3+CaS composite inclusions are both ≤6 μm.

[0046] Furthermore, the performance of the ultra-high strength oil casing resistant to H2S corrosion of the present invention meets the following requirements: yield strength ≥ 862MPa, impact energy at 0°C ≥ 120J, and H2S stress corrosion resistance meets K 1SCC Value ≥ 25MPa*m 1 / 2 .

[0047] In some embodiments, the yield strength of the H2S corrosion resistant ultra-high strength oil casing of the present invention is 862-930 MPa.

[0048] In some embodiments, the H2S corrosion resistant ultra-high strength oil casing of the present invention has an impact energy of 120-160 J at 0°C.

[0049] In some embodiments, the H2S corrosion resistant ultra-high strength oil casing of the present invention has an H2S stress corrosion resistance that meets K 1SCC The value is 25~30MPa*m 1 / 2 .

[0050] In some embodiments, the ultra-high strength oil casing and tubing resistant to H2S corrosion of the present invention is not broken after being loaded with 80% of the nominal yield strength according to NACE TM0177 standard A method D solution for 720 hours.

[0051] Accordingly, another object of the present invention is to provide a method for manufacturing the above-mentioned ultra-high strength oil casing and tubing resistant to H2S corrosion, which has a simple process and low production cost.

[0052] In order to achieve the above object, the present invention proposes a method for manufacturing the above-mentioned ultra-high strength oil casing and tubing resistant to H2S corrosion, which comprises the following steps:

[0053] (1) smelting and continuous casting to obtain tube blanks;

[0054] (2) Heating, perforating, rolling, and sizing;

[0055] (3) Quenching: The austenitizing temperature is 880-920°C, and the temperature is kept for 30-60 minutes, for example, 40-60 minutes, and then quenched;

[0056] (4) Tempering: The tempering temperature is 690-720℃, the holding time is 50-80min, and then air cooling.

[0057] Furthermore, in step (1) of the manufacturing method of the present invention, the superheat of the molten steel is controlled at 40° C. to 50° C. during the casting process, and the continuous casting speed is controlled at 1.5 to 1.8 m / min.

[0058] The addition of Ce in this invention increases the viscosity of the molten steel and reduces its fluidity. Therefore, to ensure the fluidity of the molten steel and prevent blockage caused by nozzle buildup during the casting process, it is preferable to maintain a high superheat and a low continuous casting speed. Therefore, in a preferred embodiment of the present invention, the superheat of the molten steel is controlled at 40-50°C, while the continuous casting speed is reduced to 1.5-1.8 m / min.

[0059] Furthermore, in step (2) of the manufacturing method of the present invention, heating is performed to a soaking temperature of 1200 to 1280°C.

[0060] Furthermore, in step (2) of the manufacturing method of the present invention, the perforation temperature is controlled to be 1150-1250°C.

[0061] Furthermore, in step (2) of the manufacturing method of the present invention, the finishing rolling temperature is controlled to be 880-940°C.

[0062] Furthermore, in step (2) of the manufacturing method of the present invention, the sizing temperature is controlled to be 840-910°C.

[0063] The H2S corrosion resistant ultra-high strength oil casing and its manufacturing method of the present invention have the following advantages and beneficial effects:

[0064] The ultra-high-strength H2S corrosion-resistant oil casing of the present invention can control the amount of large-sized alloy precipitates by controlling the reasonable ratio of alloy elements, and at the same time modify the inclusions to reduce the size of the inclusions, thereby obtaining an oil well pipe with both ultra-high strength and H2S stress corrosion resistance.

[0065] The ultra-high strength oil casing resistant to H2S corrosion of the present invention reaches 125ksi steel grade, its yield strength is ≥862MPa, the impact energy at 0℃ is ≥120J, and the H2S stress corrosion resistance meets K 1SCC Value ≥ 25MPa*m 1 / 2 And NACE TM0177 standard A method D solution loading 80% nominal yield strength for 720h without fracture.

[0066] The H2S corrosion-resistant ultra-high-strength oil casing of the present invention can be used for the exploitation of oil and natural gas containing hydrogen sulfide in ultra-deep wells above 9,000 meters, and has very important practical significance. DETAILED DESCRIPTION

[0067] The ultra-high strength oil casing and tubing resistant to H2S corrosion and the manufacturing method thereof according to the present invention will be further explained and illustrated below in conjunction with specific embodiments. However, such explanation and illustration do not constitute an undue limitation to the technical solution of the present invention.

[0068] Examples 1-6 and Comparative Examples 1-8

[0069] The H2S corrosion resistant ultra-high strength oil casings of Examples 1-6 and the comparative oil casings of Comparative Examples 1-8 were all prepared by the following steps:

[0070] (1) According to the chemical composition shown in Table 1, smelting, ladle furnace (LF) refining, VD furnace vacuum treatment and continuous casting are carried out to obtain tube billets: wherein pure Ce or Ce alloy is added to the molten steel in the LF furnace and VD furnace process, and argon blowing is performed to calm the steel for more than 5 minutes before continuous casting; during the casting process, the superheat of the molten steel is controlled at 40-50°C, and the continuous casting speed is 1.5-1.8 m / min.

[0071] (2) Heating: Heat to an even temperature of 1200-1280°C.

[0072] (3) Perforation: Control the perforation temperature to 1150-1250℃.

[0073] (4) Rolling: Control the final rolling temperature to 880-940℃.

[0074] (5) Sizing: Control the sizing temperature to 840-910°C to obtain pipe.

[0075] (7) Quenching: austenitizing temperature is 880-920℃, keep warm for 40-60min and then quench;

[0076] (8) Tempering: The tempering temperature is 690-720℃, the holding time is 50-80min, and then air cooling.

[0077] It should be noted that the chemical element composition and related process design of the H2S corrosion resistant oil casing of Examples 1-6 of the present invention meet the design specification requirements of the present invention. However, the chemical element content of Comparative Examples 1-8 does not meet the design requirements of the present invention.

[0078] Table 1 lists the mass percentages of the chemical elements in the H2S corrosion resistant oil casings of Examples 1-6 and the comparative oil casings of Comparative Examples 1-8.

[0079] Table 1. (wt%, the balance is Fe and other inevitable impurities except P, O, N, S)

[0080] Table 2 lists the specific process parameters of the H2S corrosion resistant ultra-high strength oil casing of Examples 1-6 and the comparative oil casing of Comparative Examples 1-8 in the above process steps.

[0081] Table 2.

[0082] The H2S corrosion resistant ultra-high strength oil casing of Examples 1-6 and the comparative pipes of Comparative Examples 1-8 were sampled and tested, and the test results are listed in Table 3. The relevant test process is as follows:

[0083] (1) Microstructure observation: After polishing, the sample was observed for inclusions using an optical microscope. The microstructure of the test sample was analyzed using an EVO MA25 scanning electron microscope and a JEM 2100F transmission electron microscope. The type of carbide was determined by analyzing the electron diffraction spectrum of the carbide, and the size of the carbide was measured using a transmission electron microscope. The size of the inclusion was determined by a scanning electron microscope, and the type of inclusion was determined by energy dispersive spectrometer (EDS) analysis. The diameter and number of the alloy precipitates were determined using a scanning electron microscope.

[0084] (2) Tensile test: The room temperature tensile property test is carried out according to GB / T 228.1-2000 standard, and the yield strength is measured.

[0085] (3) Impact test: The 0℃ impact energy test is carried out in accordance with GB / T 229-2007 “Charpy pendulum impact test method for metallic materials”.

[0086] (4)K 1SCC Value determination: The test was carried out according to the D method in the NACE TM0177-2016 standard.

[0087] (5) Sulfur resistance test: The sulfur resistance test was performed according to the A method in the NACE TM0177-2016 standard using D solution loaded with 80% nominal yield strength (862 MPa) for 720 h.

[0088] Table 3 lists the test results of Examples 1-6 and Comparative Examples 1-8.

[0089] Table 3.

[0090] As can be seen from Table 3, the yield strength of the H2S corrosion resistant oil casing of Examples 1-6 of the present invention is ≥870MPa, the impact energy at 0°C is ≥140J, and the H2S stress corrosion resistance meets the K 1SCC Value ≥ 26.5MPa*m 1 / 2 Moreover, the NACE TM0177 standard A method D solution is loaded with 80% nominal yield strength for 720 hours without breaking.

[0091] Sampling and observation of the H2S corrosion resistant oil casing of Examples 1-6 revealed that their microstructure matrix was tempered bainite, with W2C carbides dispersed within the grains, CeAlO3 inclusions, and CeAlO3+CaS composite inclusions. The CeAlO3 inclusions and CeAlO3+CaS composite inclusions were small in size, all less than 6 μm. In addition, the number of alloy precipitates with a diameter of 200 nm or more was ≤4 / 100 μm.2 .

[0092] The chemical element compositions of Comparative Examples 1 to 8 do not conform to the design specifications of the present invention, but their processes are substantially consistent with the requirements of the present invention.

[0093] In Comparative Example 1, the carbon content in the steel is lower than the requirement of the present invention, so the strength does not meet the 125 ksi steel grade requirement, and the performance test of NACE TM0177 standard A method is unqualified.

[0094] In Comparative Example 2, the carbon content in the steel is higher than the requirement of the present invention, resulting in a large number of alloy precipitates with a diameter of more than 200 nm, which reduces the sulfur resistance.

[0095] In Comparative Example 3, the Mo and V contents in the steel are lower than the requirements of the present invention, resulting in the strength failing to meet the 125 ksi steel grade requirement, and the performance test of Method A of NACE TM0177 standard is unqualified.

[0096] In Comparative Example 4, since the Mo and V contents in the steel are higher than the requirements of the present invention, a large number of alloy precipitates with a diameter of more than 200 nm are formed, which reduces the sulfur resistance and impact resistance.

[0097] In Comparative Example 5, since the steel does not contain W and the Cr content is higher than the requirement of the present invention, a large number of alloy precipitates with a diameter of more than 200 nm are formed, and the sulfur resistance is unqualified.

[0098] In Comparative Example 6, since the W content in the steel is higher than the requirement of the present invention, a large number of alloy precipitates with a diameter of more than 200 nm are formed, and the sulfur resistance and impact properties are unqualified.

[0099] Since the steel of Comparative Example 7 does not contain Ce, the inclusions are large in size and the sulfur resistance is unqualified.

[0100] In Comparative Example 8, since the Ce / O ratio in the steel is higher than the requirement of the present invention, a large number of alloy precipitates with a diameter of more than 200 nm are formed, the size of the inclusions is large, and the sulfur resistance is unqualified.

[0101] It can be seen that by adopting the technical solution described in the present invention, an oil casing with both ultra-high strength and H2S stress corrosion resistance can be obtained.

[0102] It should be noted that the combination of the various technical features in the present invention is not limited to the combination described in the claims of the present invention or the combination described in the specific embodiments. All technical features described in the present invention can be freely combined or combined in any way unless there is a contradiction between them.

[0103] It should also be noted that the embodiments listed above are merely specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and similar changes or modifications made therefrom that can be directly derived from or easily conceived by those skilled in the art based on the disclosure of the present invention are intended to fall within the scope of protection of the present invention.

Claims

1. An ultra-high strength oil casing and tubing resistant to H2S corrosion, containing Fe and inevitable impurities, characterized in that: It also contains the following chemical elements in the following mass percentages: C: 0.15~0.28%, Si: 0.1~0.5%, Mn: 0.2%~0.5%, Cr: 0.4~0.8%, Mo: 0.8~1.5%, V: 0.15~0 .3%, Nb: 0.05~0.15%, W: 0.2~0.6%, Al: 0.01~0.05%, Ce: 0.002~0.006%, 0<O≤0.002%; The mass percentages of Ce and O also satisfy Ce / O: 1 to 3.

5.

2. The ultra-high strength oil casing and tubing resistant to H2S corrosion according to claim 1, characterized in that: The mass percentage of each element of the ultra-high strength oil casing is: C: 0.15-0.28%, Si: 0.1-0.5%, Mn: 0.2%-0.5%, Cr: 0.4-0.8%, Mo: 0.8-1.5%, V: 0.15-0.3%, Nb: 0.05-0.15%, W: 0.2-0.6%, Al: 0.01-0.05%, Ce: 0.002-0.006%, 0<O≤0.002%; the balance is Fe and other inevitable impurities; The mass percentages of Ce and O also satisfy Ce / O: 1 to 3.

5.

3. The H2S corrosion resistant ultra-high strength oil casing according to claim 1 or 2, characterized in that: The mass percentage of each chemical element of the ultra-high strength oil casing further satisfies at least one of the following items: C：0.18～0.25％； Cr：0.4～0.7％； Mo: 0.9~1.2%; V：0.18～0.25％； Nb: 0.05-0.1%; W：0.2～0.5％； Al：0.015～0.04％； Ce: 0.002~0.005%.

4. The H2S corrosion resistant ultra-high strength oil casing according to claim 1 or 2, characterized in that: Among the unavoidable impurities: S ≤ 0.002%, P ≤ 0.01%, N ≤ 0.008%.

5. The H2S corrosion resistant ultra-high strength oil casing according to claim 1 or 2, characterized in that: The microstructure matrix of the ultra-high strength oil casing is tempered troostite.

6. The H2S corrosion resistant ultra-high strength oil casing according to claim 1 or 2, characterized in that: The ultra-high strength oil casing has W2C carbides dispersedly distributed in the crystal.

7. The H2S corrosion resistant ultra-high strength oil casing according to claim 1 or 2, characterized in that: The number of alloy precipitates with a diameter of more than 200 nm in the microstructure of the ultra-high strength oil casing is ≤5 / 100 μm 2 .

8. The H2S corrosion resistant ultra-high strength oil casing according to claim 1 or 2, characterized in that: The ultra-high strength oil casing has CeAlO3 inclusions and CeAlO3+CaS composite inclusions.

9. The ultra-high strength oil casing and tubing resistant to H2S corrosion according to claim 8, characterized in that: The sizes of CeAlO3 inclusions and CeAlO3+CaS composite inclusions are both ≤6μm.

10. The H2S corrosion resistant ultra-high strength oil casing according to claim 1 or 2, characterized in that: The performance of the ultra-high strength oil casing meets the following requirements: yield strength ≥ 862MPa, impact energy at 0°C ≥ 120J, and H2S stress corrosion resistance meets K 1SCC Value ≥25MPa*m 1 / 2 .

11. The method for manufacturing the H2S corrosion resistant ultra-high strength oil casing according to any one of claims 1 to 10, characterized in that: It includes the steps of: Smelting and continuous casting to obtain tube billets; Heating, perforating, rolling and sizing; Quenching: austenitizing temperature is 880-920℃, keep warm for 30-60min and then quench; Tempering: The tempering temperature is 690-720℃, the holding time is 50-80min, and then air cooling.

12. The manufacturing method according to claim 11, characterized in that: In step (1), during the casting process, the superheat of the molten steel is controlled at 40°C to 50°C, and the continuous casting speed is controlled at 1.5 to 1.8 m / min.

13. The manufacturing method according to claim 11, characterized in that: In step (2), heating is performed to a soaking temperature of 1200 to 1280°C.

14. The manufacturing method according to claim 11, characterized in that: In step (2), the perforation temperature is controlled to be 1150-1250°C.

15. The manufacturing method according to claim 11, characterized in that: In step (2), the final rolling temperature is controlled to be 880-940°C; and / or In step (2), the sizing temperature is controlled to be 840-910°C.

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