A 125Ksi steel grade hydrogen sulfide corrosion resistant oil well pipe and a preparation method thereof

Abstract

The invention discloses a 125Ksi steel grade hydrogen sulfide corrosion resistant oil well pipe and a preparation method thereof, belonging to the technical field of metal materials, and solving the problem that the strength and toughness and hydrogen sulfide corrosion resistance of the oil well pipe in the prior art cannot be improved at the same time. The components of the 125Ksi steel grade hydrogen sulfide corrosion resistant oil well pipe include, by mass percentage: C: 0.10% to 0.20%, Si: ≤0.50%, Mn: 0.3% to 0.8%, V: 0.10% to 0.20%, Mo: 0.20% to 0.50%, Ni: 1.0% to 1.5%, Cr: 1.5 to 2.0%, Cu: 1.0 to 2.0%, Als: ≤0.05%, P: ≤0.010%, S: ≤0.003%, and the balance is Fe and unavoidable impurities. The oil well pipe of the invention has good strength and toughness and strong resistance to hydrogen sulfide stress corrosion.

Description

Technical Field

[0001] The invention relates to the technical field of metal materials, and in particular to a 125Ksi steel grade hydrogen sulfide corrosion resistant oil well pipe and a preparation method thereof. Background Art

[0002] About one-third of the world's oil and gas fields contain hydrogen sulfide. In the development of sulfur-containing oil and gas fields, when ordinary oil well pipes are used for mining, H 2 Under the combined action of H2S gas, oil well pipes often fail due to stress corrosion cracking, which can lead to the scrapping of oil well pipes or even the entire well. 2 S leakage will also cause great damage to animals, people and the ecological environment around the wellhead. Therefore, sulfur-resistant pipes must be used for the exploitation of sulfur-containing oil and gas fields. With the development of deep wells and ultra-deep wells, the service environment of oil well pipes is becoming more and more severe, which requires oil well pipes to have higher strength and toughness, as well as certain corrosion resistance. At present, the highest sulfur resistance level of 110Ksi can no longer meet the use requirements, and the development of 125Ksi sulfur-resistant oil well pipes is imperative. 125Ksi is the highest level of sulfur-resistant oil well pipes in the API standard. With the increase of strength, the material is more and more sensitive to corrosion. It is a major challenge to ensure high strength of the material while having excellent corrosion resistance.

[0003] At present, many studies are trying to develop 125Ksi steel grade sulfur-resistant oil well pipes. However, it is difficult to meet the requirements of strength and toughness while taking into account H2 resistance. 2 S corrosion, especially difficult to pass the assessment of NACETM0177-2005 standard A solution. In addition, the process flow of some oil well pipes in research is long and the production efficiency is low. Therefore, it is necessary to consider the chemical composition and process to develop oil well pipes with excellent resistance to hydrogen sulfide corrosion and good strength and toughness and their preparation methods to ensure the safe and reliable use of oil well pipes in sulfur-containing deep wells. Summary of the invention

[0004] In view of the above situation, the present invention aims to provide a 125Ksi steel grade hydrogen sulfide corrosion resistant oil well pipe and a preparation method thereof, which can at least solve one of the following technical problems: (1) the strength and toughness and hydrogen sulfide corrosion resistance of the existing oil well pipe cannot be improved at the same time; (2) the existing oil well pipe has a complex process and low production efficiency.

[0005] The purpose of the present invention is mainly achieved through the following technical solutions:

[0006] On the one hand, the present invention provides a 125Ksi steel grade hydrogen sulfide corrosion resistant oil well pipe. The components of the 125Ksi steel grade hydrogen sulfide corrosion resistant oil well pipe include, by mass percentage: C: 0.10%-0.20%, Si: ≤0.50%, Mn: 0.3%-0.8%, V: 0.10%-0.20%, Mo: 0.20%-0.50%, Ni: 1.0%-1.5%, Cr: 1.5-2.0%, Cu: 1.0-2.0%, Als: ≤0.05%, P: ≤0.010%, S: ≤0.003%, and the balance is Fe and unavoidable impurities.

[0007] In a possible design, the components of 125Ksi steel grade hydrogen sulfide corrosion resistant oil well pipe include, by mass percentage: C: 0.12% to 0.20%, Si: 0.1% to 0.40%, Mn: 0.35% to 0.8%, V: 0.12% to 0.20%, Mo: 0.25% to 0.50%, Ni: 1.0% to 1.5%, Cr: 1.5 to 2.0%, Cu: 1.0 to 2.0%, Als: ≤0.05%, P: ≤0.010%, S: ≤0.003%, and the balance is Fe and unavoidable impurities.

[0008] In a possible design, in the composition of the 125Ksi steel grade hydrogen sulfide corrosion resistant oil well pipe, Ni / Cu is controlled to be greater than 0.5.

[0009] In a possible design, the room temperature structure of the oil well pipe is a tempered troostite matrix with dispersed and refined second phases distributed in it.

[0010] The present invention also provides a method for preparing a 125Ksi steel grade hydrogen sulfide corrosion resistant oil well pipe, which is used to prepare the above 125Ksi steel grade hydrogen sulfide corrosion resistant oil well pipe, comprising:

[0011] Step 1, smelting and pouring to obtain a casting blank or an ingot;

[0012] Step 2, subjecting the billet or ingot to high temperature homogenization treatment, performing piercing hot rolling, and cooling to obtain a rough pipe;

[0013] Step 3: After quenching the rough pipe, tempering is performed to obtain a 125Ksi steel grade hydrogen sulfide corrosion resistant oil well pipe.

[0014] In one possible design, step 3 includes:

[0015] S301, quenching: heat the rough pipe to above the austenitizing temperature and keep it warm, then quench it to room temperature;

[0016] S302, tempering: put the steel pipe into the tempering furnace and heat it up to 650-680℃, keep it warm for 2-3 hours and then air-cool it to room temperature to obtain oil well pipe resistant to hydrogen sulfide corrosion.

[0017] In a possible design, in S301, the rough pipe is heated to 880-920°C and kept warm for 0.5-2h.

[0018] In a possible design, in step 1, a converter, an electric furnace or an induction furnace is used for smelting, and continuous casting is used to produce billets or mold casting is used to produce ingots.

[0019] In a possible design, step 2 includes: heating the billet or ingot to 1100-1200° C. in a heating furnace, and keeping it at 1100-1200° C. for 2-3 hours, and performing piercing hot rolling and cooling after taking it out of the furnace to obtain a rough pipe.

[0020] In a possible design, in step 2, water spray cooling is used after hot rolling to form a rough pipe with a uniform and fine bainite structure.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] a) The oil well pipe provided by the present invention ensures that the room temperature structure of the oil well pipe is a tempered troostite matrix with dispersed and refined second phases distributed on it by precisely controlling the mass percentage of elements such as C, Mn, Ni, Cu, V, and Cr in the steel, and combining the quenching + tempering process. Under the dual effects of environmental stress and hydrogen sulfide, the semi-coherent relationship between the fine second phase precipitation and the matrix boundary can serve as a hydrogen absorption trap, and the dispersed precipitation phase ensures that the absorbed hydrogen atoms do not aggregate to form hydrogen molecules, thereby effectively improving the hydrogen sulfide stress corrosion resistance of the substrate. Therefore, the oil well pipe of the present invention has both high toughness and good hydrogen sulfide stress corrosion resistance while ensuring a high strength level, ensuring that the steel of the present invention can have excellent comprehensive performance.

[0023] b) The present invention controls the preparation method to obtain a microstructure in which a dispersed and refined second phase is distributed on a tempered bainite matrix, thereby obtaining an ideal combination of room temperature strength and toughness and hydrogen sulfide stress corrosion resistance; only by heat treatment within the composition, steps and temperature range of the present invention can the strength and toughness of the oil well pipe of the present invention be matched and both reach the required range.

[0024] c) The preparation method of the oil well pipe of the present invention is simple, has a short process, high production efficiency, low cost, economy, practicality, good strength and toughness, and strong resistance to hydrogen sulfide stress corrosion.

[0025] d) The oil well pipe prepared by the composition and method of the present invention has good comprehensive mechanical properties, including yield strength ≥863MPa, tensile strength ≥900MPa, elongation ≥15%, and impact energy at 0°C ≥100J. The oil well pipe can pass the test of NACETM0177-2005 standard A solution.

[0026] Other features and advantages of the present invention will be described in the following description, and part of them will become obvious from the description, or will be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the written description, claims, and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0028] Figure 1 This is a microstructure diagram of the oil well pipe of Example 1 of the present invention;

[0029] Figure 2 This is a microstructure diagram of the oil well pipe of Example 2 of the present invention;

[0030] Figure 3 This is a microstructure diagram after quenching of Example 5 of the present invention;

[0031] Figure 4 This is a microstructure diagram after quenching of Example 6 of the present invention;

[0032] Figure 5 This is a microstructure diagram of Example 5 after tempering of the present invention;

[0033] Figure 6 This is a microstructure diagram of Example 6 of the present invention after tempering. DETAILED DESCRIPTION

[0034] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used to illustrate the principles of the present invention together with the embodiments of the present invention.

[0035] The invention provides a 125Ksi steel grade hydrogen sulfide corrosion resistant oil well pipe. The components of the 125Ksi steel grade hydrogen sulfide corrosion resistant oil well pipe include, by mass percentage, C: 0.10%-0.20%, Si: ≤0.50%, Mn: 0.3%-0.8%, V: 0.10%-0.20%, Mo: 0.20%-0.50%, Ni: 1.0%-1.5%, Cr: 1.5-2.0%, Cu: 1.0-2.0%, Als: ≤0.05%, P: ≤0.010%, S: ≤0.003%, and the balance is Fe and inevitable impurities.

[0036] The following is a detailed description of the effects and dosage of the components in the present invention:

[0037] C: C is an element that expands the austenite phase region and has a strong solid solution strengthening effect. When the C content is low, the steel hardness is insufficient; when the C content is too high, the product hardness is high, and the toughness and welding performance are poor. C combines with V to form nano-scale VC particles, forming a precipitation strengthening effect; because Cr is a strong carbide forming element, it is easy to form Cr with carbon in the matrix. 23 C 6 Cr 7 C 3 In addition, if the C content in the matrix is ​​high, it will consume the amount of Cr alloy elements in the matrix, reduce the alloying effect, and reduce the corrosion resistance of the material. Therefore, the C content in the present invention is controlled at 0.10% to 0.20%.

[0038] Si: Si is a deoxidizer in steelmaking and has a solid solution strengthening effect, but excessive silicon is not good for the toughness and hydrogen sulfide corrosion resistance of steel. In the present invention, the content of Si is controlled to be ≤0.50%.

[0039] Mn: Mn can exist in a solid solution state, or enter cementite to replace a part of Fe atoms, play a role in solid solution strengthening, and can also form sulfides. At the same time, Mn elements gather in austenite, which can improve the stability of austenite and is an important toughening element. However, when the C and Mn contents in steel are too high at the same time, banded structure will be formed, which increases the sensitivity to hydrogen sulfide stress corrosion. Therefore, the Mn content in the present invention is controlled at 0.3% to 0.8%.

[0040] Cr: Cr is a carbide-forming element and an important corrosion-resistant element. It can also strongly improve hardenability. In quenched and high-temperature tempered quenched and tempered steel, Cr can improve the corrosion resistance of the steel and ensure comprehensive mechanical properties. In the present invention, the Cr content is controlled at 1.5% to 2.0%.

[0041] Ni: Ni is an austenite-forming element and one of the most commonly used and effective corrosion-resistant elements. The addition of Ni improves the hot working properties and corrosion resistance of the material, improves toughness through solid solution, and especially significantly reduces the cold brittle transition temperature. A certain proportion of Ni / Cu can also prevent defects caused by Cu during continuous casting and improve the surface quality of the ingot, so the Ni content is controlled in the range of 1.0% to 1.5%.

[0042] Mo: Mo is similar to Cr and is also an element that expands hardenability. In the continuous cooling process, Mo also delays the transformation of austenite to bainite. Mo has a strong affinity with C and is a carbide-forming element, which reduces the content of solid-solution C and enhances the ability to resist SSCC. In the quenched and tempered steel that is quenched and tempered at high temperature, the alloy carbides formed by Mo and C are precipitated, which plays a secondary hardening role, improves the tempering resistance, and ensures that the carbon (interstitial phase compound) in the matrix α is fully precipitated. In addition, in the present invention, through the effective combination of Cr-Mo, the Cr element improves the hardenability of the steel during the quenching process, the strength of the steel is improved, and the toughness is reduced. The Mo element improves the tempering stability of the steel during the high-temperature tempering process, thereby ensuring that the steel has a certain toughness and that the steel has good comprehensive mechanical properties at a higher strength. In the present invention, the content of Mo is controlled to be 0.20% to 0.50%.

[0043] V: V can refine the grains, form carbides, and play a precipitation strengthening effect. It can also improve the high-temperature tempering resistance and ensure that the dislocation density of the steel is reduced during high-temperature tempering. At the same time, the dispersed and fine VC particles precipitated during the tempering process can also act as hydrogen traps to improve the material's resistance to hydrogen-induced cracking. However, when the V content in the steel is too high, the material toughness will be significantly reduced. Therefore, the V content in the present invention is controlled to be 0.10% to 0.20%.

[0044] Cu: Cu is an austenite forming element and one of the most effective elements for improving corrosion resistance. It mainly exists in solid solution, but too high Cu content in steel will cause cracking of the ingot. Considering the matching of Cu precipitation strengthening and improving corrosion resistance, the present invention controls the copper content to 1.0% to 2.0%.

[0045] Al: Al is an essential element for deoxidation of steel, so it is impossible to completely avoid introducing Al into steel. However, when the Al content exceeds 0.1%, it will have an adverse effect on the casting process of the steel. Therefore, the inventor of this case limits the mass percentage of acid-soluble aluminum in the 125ksi steel-grade sulfur-resistant oil well pipe of the present invention to Als: less than 0.05%.

[0046] P: It is an impurity in steel, which is not conducive to weldability and toughness. The content is controlled at ≤0.010%.

[0047] S: seriously deteriorates the corrosion resistance and toughness of steel, and its content is controlled at ≤0.0030%.

[0048] In order to further improve the comprehensive performance of the above-mentioned 125Ksi steel grade oil well pipe resistant to hydrogen sulfide corrosion, the components of the above-mentioned 125Ksi steel grade oil well pipe resistant to hydrogen sulfide corrosion can be calculated by mass percentage: C: 0.12%-0.20%, Si: 0.1%-0.40%, Mn: 0.35%-0.8%, V: 0.12%-0.20%, Mo: 0.25%-0.50%, Ni: 1.0%-1.5%, Cr: 1.5-2.0%, Cu: 1.0-2.0%, Als: ≤0.05%, P: ≤0.010%, S: ≤0.003%, and the balance is Fe and unavoidable impurities.

[0049] Specifically, in the present invention, Ni / Cu is controlled to be greater than 0.5.

[0050] The present invention also provides a method for preparing the above-mentioned 125Ksi steel grade hydrogen sulfide corrosion resistant oil well pipe, comprising:

[0051] Step 1, smelting and pouring to obtain a casting blank or an ingot;

[0052] Step 2, subjecting the billet or ingot to high temperature homogenization treatment, performing piercing hot rolling, and cooling to obtain a rough pipe;

[0053] Step 3: After quenching the rough pipe, tempering is performed to obtain a 125Ksi steel grade hydrogen sulfide corrosion resistant oil well pipe.

[0054] Specifically, in the above step 1, a converter, an electric furnace or an induction furnace may be used for smelting, and continuous casting may be used to produce billets, or mold casting may be used to produce ingots.

[0055] Specifically, the role of the above step 2 is to ensure that all alloy elements are fully dissolved and exist in the matrix in the form of solid solution. Considering that the holding temperature is too high or the holding time is too long, the austenite grains will grow excessively or even overheat, affecting the final performance of the material; the holding temperature is too low or the holding time is too short, resulting in the steel being unable to be completely austenitized or the alloy elements are not fully dissolved, and the steel pipe composition is uneven, affecting the performance. Therefore, the specific steps of controlling the above step 2 include: heating the billet or ingot to 1100-1200°C in a heating furnace, and keeping it at 1100-1200°C for 2-3h, and after being taken out of the furnace, piercing hot rolling and cooling are performed to obtain a rough pipe of the required size.

[0056] Specifically, in the above step 2, water spray cooling is used after hot rolling to form a rough pipe with a uniform and fine bainite structure.

[0057] Specifically, in the above step 2, the final rolling temperature of hot rolling is above 850°C.

[0058] Specifically, the specific steps of the above step 3 include:

[0059] S301, quenching: heat the rough pipe to above the austenitizing temperature and keep it warm, then quench it to room temperature;

[0060] S302, tempering: put the steel pipe into the tempering furnace and heat it up to 650-680℃, keep it warm for 2-3 hours and then air-cool it to room temperature to obtain oil well pipe resistant to hydrogen sulfide corrosion.

[0061] Specifically, in the above S301, quenching is to heat the rough pipe to above the austenitizing temperature and keep it warm for a period of time to ensure that all the micro-alloying elements are dissolved into the matrix, and then quench it to room temperature to obtain a complete martensitic structure, and the alloying elements are fully dissolved. Considering that the temperature is too high or the insulation time is too long, the austenite grains will grow excessively or even overheat, affecting the final performance of the material; the insulation temperature is too low or the insulation time is too short, resulting in the inability to completely austenitize the steel or the insufficient solid solution of the alloying elements, and the composition of the steel pipe is uneven, affecting the performance. Therefore, the rough pipe is heated to 880-920℃ (the heating rate is controlled to be 4-40℃ / S) and kept warm for 0.5-2h.

[0062] Specifically, in the above S302, the heating temperature of the tempering process is lower than the austenite transformation temperature, so the process is mainly the tempering transformation of martensite into fine troostite structure, while dispersed and refined second phase particles of various types, such as VC, MoC, ε-Cu, etc., are precipitated in the matrix.

[0063] Specifically, in the above S302, the steel pipe is placed in a tempering furnace and the temperature is raised to 650-680° C. at a heating rate of 4-40° C. / S.

[0064] Specifically, in the above S302, the room temperature structure of the oil well pipe resistant to hydrogen sulfide corrosion is a dispersed and refined second phase distributed on the tempered troostite matrix. Under the dual effects of environmental stress and hydrogen sulfide, the semi-coherent relationship between the fine second phase precipitation and the matrix boundary can serve as a hydrogen absorption trap, and the dispersed precipitation phase ensures that the absorbed hydrogen atoms do not aggregate to form hydrogen molecules, thereby effectively improving the hydrogen sulfide stress corrosion resistance of the substrate.

[0065] Specifically, the second phase includes MC, M 23 C 6 、M 7 C 3 Etc., for example, VC, MoC, ε-Cu, etc.

[0066] Specifically, the grain size of the room temperature structure of the above-mentioned hydrogen sulfide corrosion resistant oil well pipe is less than 30 μm, for example, 20 to 28 μm.

[0067] Specifically, in the above S302, the mechanical properties of the oil well pipe resistant to hydrogen sulfide corrosion are as follows: yield strength of 863MPa or more (e.g. 870-950MPa), tensile strength of 950MPa or more (e.g. 970-1100MPa), elongation of 15% or more (e.g. 17%-22%), 0°C impact energy ≥100J (e.g. 110J or more, e.g. 112-160J), and passing the assessment of NACETM0177-2005 standard A solution. The oil well pipe of the present invention has excellent hydrogen sulfide stress corrosion resistance while reaching the 125Ksi steel grade strength and toughness level.

[0068] The hydrogen sulfide corrosion resistant oil well pipe of the present invention reaches the one-tenth principle, that is, the value of the 0°C impact energy of the hydrogen sulfide corrosion resistant oil well pipe of the present invention exceeds one-tenth of the yield strength value.

[0069] The preparation method of the oil well pipe of the invention is simple, has short process, high production efficiency, low cost, economy, practicality, good strength and toughness, and strong resistance to hydrogen sulfide stress corrosion.

[0070] Examples 1-4

[0071] Embodiments 1-4 of the present invention provide a 125Ksi steel grade hydrogen sulfide corrosion resistant oil well pipe and a preparation method thereof. The components of the steel in embodiments 1-4 include, by mass percentage, C: 0.10% to 0.20%, Si: ≤0.50%, Mn: 0.3% to 0.8%, V: 0.10% to 0.20%, Mo: 0.20% to 0.50%, Ni: 1.0% to 1.5%, Cr: 1.5 to 2.0%, Cu: 1.0 to 2.0%, Als: ≤0.05%, P: ≤0.010%, S: ≤0.003%, and the remainder is Fe and unavoidable impurities.

[0072] The method for preparing the steel of Examples 1-4 comprises:

[0073] (1) Using converter steelmaking and casting to make tube blanks;

[0074] (2) Using seamless tube forming technology, the tube blank is heated to 1150°C, kept at a constant temperature for 2 hours, then taken out of the furnace, pierced and rolled, and after leaving the rolling mill at 950°C, water spray cooling is used to form a rough tube;

[0075] (3) The cooled rough pipe is heated to 900°C at a heating rate of 5°C / S, kept at this temperature for 1 hour, and then quenched to room temperature; then the steel pipe is placed in a tempering furnace and heated to 660°C with the furnace at a rate of 5°C / S, kept at this temperature for 2 hours, and then air-cooled to room temperature to obtain an oil well pipe resistant to hydrogen sulfide corrosion.

[0076] The specific compositions of the oil well pipes of Examples 1-4 are shown in Table 1 below. The microstructures of the oil well pipes of Examples 1 and 2 after tempering are shown in Table 1 below. Figure 1 and 2 The microstructures of the oil well pipes of Examples 1-4 are shown in Table 2, and the mechanical properties of the oil well pipes are shown in Table 3 below.

[0077] Table 1 Chemical composition of oil well pipes of Examples 1-4

[0078] Serial number C Si Mn Cu Ni Cr V Mo P S Example 1 0.12 0.23 0.8 1.5 1.1 1.85 0.12 0.4 0.009 0.0026 Example 2 0.12 0.25 0.7 1.7 1.0 1.64 0.15 0.3 0.007 0.0020 Example 3 0.15 0.30 0.5 1.8 1.3 1.56 0.17 0.4 0.010 0.0012 Example 4 0.18 0.28 0.4 1.7 1.2 1.72 0.20 0.3 0.008 0.0028

[0079] Table 2 Microstructure of Examples 1-4

[0080]

[0081]

[0082] Table 3 Mechanical properties of Examples 1-4

[0083]

[0084] Embodiment 5-6

[0085] Embodiments 5-6 of the present invention provide a 125Ksi steel grade hydrogen sulfide corrosion resistant oil well pipe and a preparation method thereof. The components of the steel in Embodiments 5-6 include, by mass percentage: C: 0.15%, Si: 0.20%, Mn: 0.5%, V: 0.18%, Mo: 0.40%, Ni: 1.0%, Cr: 2.0%, Cu: 2.0%, Als: 0.03%, P: 0.008%, S: 0.0020%, and the balance is Fe and unavoidable impurities.

[0086] The method for preparing the steel of Examples 5-6 comprises:

[0087] (1) Use converter steelmaking and continuous casting to produce tube billets;

[0088] (2) Using seamless tube forming technology, the tube blank is heated to 1130°C, kept at a constant temperature for 2.5 hours, then taken out of the furnace, pierced and rolled, and cooled by spraying water after leaving the rolling mill at 930°C (final rolling temperature) to form a rough tube;

[0089] (3) First, the cooled rough pipe was heated to 900℃ at a heating rate of 5℃ / S and 40℃ / S, kept at this temperature for 1h, and then quenched to room temperature; then the steel pipe was heated to 660℃ at a heating rate of 5℃ / S, kept at this temperature for 2h, and then air-cooled to room temperature. The specific heat treatment process is shown in Table 4.

[0090] The microstructure of Example 5 after quenching is as follows: Figure 3 As shown, the microstructure of Example 6 after quenching is as follows Figure 4 As shown, the final microstructure of Examples 5-6 is as follows Figure 5 and6 The microstructure of Examples 5-6 is shown in Table 5, and the mechanical properties are shown in Table 6 below.

[0091] Table 4 Heat treatment process of Examples 5-6

[0092] Serial number Heating speed / ℃ / S Quenching holding temperature / ℃ Tempering temperature / ℃ Example 5 5 900 660 Example 6 40 900 660

[0093] Table 5 Microstructure of Examples 5-6

[0094]

[0095] Table 6 Mechanical properties of Examples 5-6

[0096]

[0097] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A 125Ksi steel grade hydrogen sulfide corrosion resistant oil well pipe, characterized in that: The components of the 125Ksi steel grade hydrogen sulfide corrosion resistant oil well pipe include, by mass percentage: C: 0.10% to 0.18%, Si: ≤0.50%, Mn: 0.3% to 0.8%, V: 0.12% to 0.20%, Mo: 0.20% to 0.50%, Ni: 1.0% to 1.5%, Cr: 1.56% to 2.0%, Cu: 1.0% to 2.0%, Als: ≤0.05%, P: ≤0.010%, S: ≤0.003%, and the balance is Fe and unavoidable impurities; The preparation method of the 125Ksi steel grade hydrogen sulfide corrosion resistant oil well pipe comprises: Step 1, smelting and pouring to obtain a casting blank or an ingot; Step 2, subjecting the billet or ingot to high temperature homogenization treatment, performing piercing hot rolling, and cooling to obtain a rough pipe; Step 3, quenching the rough pipe and then tempering it to obtain 125Ksi steel grade hydrogen sulfide corrosion resistant oil well pipe; The step 2 comprises: heating the billet or ingot to 1100-1200° C. in a heating furnace, and keeping the billet or ingot at 1100-1200° C. for 2-3 hours, and performing piercing hot rolling and cooling after the billet or ingot is taken out of the furnace to obtain a rough pipe; In the step 2, after hot rolling, water spray cooling is used to form a rough pipe with a uniform and fine bainite structure; The room temperature structure of the oil well pipe is a tempered troostite matrix with a dispersed and refined second phase distributed on it; the second phase includes MC, M 23 C6, M7C3; the grain size of room temperature structure is less than 30μm; The mechanical properties of oil well pipes resistant to hydrogen sulfide corrosion are as follows: yield strength 870-950MPa, tensile strength above 950MPa.

2. The 125Ksi steel grade hydrogen sulfide corrosion resistant oil well pipe according to claim 1 is characterized in that: The components of the 125Ksi steel grade hydrogen sulfide corrosion resistant oil well pipe include, by mass percentage, C: 0.12%-0.18%, Si: 0.1%-0.40%, Mn: 0.35%-0.8%, V: 0.12%-0.20%, Mo: 0.25%-0.50%, Ni: 1.0%-1.5%, Cr: 1.56%-2.0%, Cu: 1.0%-2.0%, Als: ≤0.05%, P: ≤0.010%, S: ≤0.003%, and the balance is Fe and unavoidable impurities.

3. The 125Ksi steel grade hydrogen sulfide corrosion resistant oil well pipe according to claim 1, characterized in that: In the composition of the 125Ksi steel grade hydrogen sulfide corrosion resistant oil well pipe, Ni / Cu is controlled to be greater than 0.

5.

4. A method for preparing 125Ksi steel grade hydrogen sulfide corrosion resistant oil well pipe, characterized in that: The method for preparing the 125Ksi steel grade hydrogen sulfide corrosion resistant oil well pipe according to any one of claims 1 to 3 comprises: Step 1, smelting and pouring to obtain a casting blank or an ingot; Step 2, subjecting the billet or ingot to high temperature homogenization treatment, performing piercing hot rolling, and cooling to obtain a rough pipe; Step 3, quenching the rough pipe and then tempering it to obtain 125Ksi steel grade hydrogen sulfide corrosion resistant oil well pipe; The step 2 comprises: heating the billet or ingot to 1100-1200° C. in a heating furnace, and keeping the billet or ingot at 1100-1200° C. for 2-3 hours, and performing piercing hot rolling and cooling after the billet or ingot is taken out of the furnace to obtain a rough pipe; In the step 2, water spray cooling is used after hot rolling to form a rough pipe with a uniform and fine bainite structure.

5. The preparation method according to claim 4, characterized in that: The step 3 comprises: S301, quenching: heat the rough pipe to above the austenitizing temperature and keep it warm, then quench it to room temperature; S302, tempering: put the steel pipe into the tempering furnace and heat it up to 650-680℃, keep it warm for 2-3 hours and then air-cool it to room temperature to obtain oil well pipe resistant to hydrogen sulfide corrosion.

6. The preparation method according to claim 5, characterized in that: In the S301, the rough pipe is heated to 880-920°C and kept warm for 0.5-2h.

7. The preparation method according to claim 4, characterized in that: In the step 1, a converter, an electric furnace or an induction furnace is used for smelting, and continuous casting is used to produce billets or mold casting is used to produce ingots.

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