High-temperature-resistant ultrahigh-strength collapse-resistant oil casing and manufacturing method thereof

Abstract

The invention discloses a high-temperature-resistant ultrahigh-strength anti-collapse petroleum casing pipe, which contains Fe and inevitable impurities, and also contains the following chemical elements in percentage by mass: 0.2 to 0.3 percent of C, 0.1 to 0.4 percent of Si, 0.8 to 1.5 percent of Mn, 1.5 to 2 percent of Cr, 1 to 1.5 percent of Mo, 0.1 to 0.3 percent of W, 0.03 to 0.1 percent of Nb, 0.10 to 0.20 percent of V, 0.02 to 0.05 percent of Ti, 0.0015 to 0.005 percent of B, 0.01 to 0.05 percent of Al and 0.001 to 0.004 percent of Ca. The invention further discloses a manufacturing method of the high-temperature-resistant ultrahigh-strength anti-collapse petroleum casing pipe, which comprises the following steps: smelting and continuously casting to obtain a pipe blank; heating and perforating; rolling and tension reducing; heat treatment: quenching and tempering; and hot straightening.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of steel and its manufacturing method, and more particularly to a kind of oil casing and its manufacturing method. BACKGROUND

[0002] Oil and gas exploitation ultra-deep string needs to bear high temperature, high pressure and other physical load, especially in the middle, deep thick high pressure salt layer (high pressure formation) section casing needs to use higher collapse resistance.

[0003] When the well depth reaches 6000 meters or more, the bottom hole temperature can exceed 180℃, the strength of the material at this temperature will decrease, the external pressure and internal pressure strength of the casing will decrease significantly, which can easily lead to casing failure under the pressure of the formation. Therefore, for high-strength pipe used in complex high-temperature environment, high-temperature strength is particularly important. In order to ensure the safety of production and use, the casing used in deep well and ultra-deep well has high requirements for high-temperature strength and collapse resistance at high temperature. In the prior art, there are some oil casings:

[0004] For example: CN106319367A, published on January 11, 2017, entitled "125ksi high strength and toughness oil casing for SAGD method to exploit heavy oil and its manufacturing method" discloses a kind of 125ksi high strength and toughness oil casing for SAGD method to exploit heavy oil and its manufacturing method, which has a yield strength of not less than 800MPa at 350℃ environmental temperature. At the same time, it has strong external extrusion deformation resistance, and the actual collapse resistance is higher than API calculation value by more than 56%, which meets the requirements of SAGD method to exploit heavy oil. However, the above patent document is only used for 4000 meters or less heavy oil development, and the strength is low, which cannot be applied to 6000 meters or more deep well.

[0005] For example: CN104264045A, published on January 7, 2015, entitled "A kind of heat-resistant high-strength casing steel and its preparation process" discloses a kind of heat-resistant high-strength casing steel and its preparation process, and the chemical composition is as follows: C: 0.10-0.25; Si: 0.10-0.30; Mn: 0.70-1.30; Hf: 0.05-0.30; B: 0.001-0.006; Mo: 0-0.20; W: 0-0.25; Nb: 0-0.15; Ta: 0-0.20; Ti: 0-0.18; Zr: 0-0.18; RE: 0.01-0.20; P: ≤0.008; S: ≤0.004; the rest is Fe. The above patent document adds Nb, W, Hf, Mo and RE elements, has heat-resistant and high-strength performance, and uses hot-rolled plate + welded pipe + tension reducing process. SUMMARY

[0006] One of the purposes of the present application is to provide a high-temperature-resistant and ultra-high-strength anti-collapse oil casing, which has ultra-high strength, good high-temperature strength and high-temperature anti-collapse performance, and can meet the requirements of high strength and anti-collapse of oil well pipes in deep and ultra-deep oil and gas fields.

[0007] In order to achieve the above-mentioned purpose, the present application provides a high-temperature-resistant and ultra-high-strength anti-collapse oil casing containing Fe and inevitable impurities, and further containing the following chemical elements with mass percentage as follows:

[0008] C: 0.2-0.3%, Si: 0.1-0.4%, Mn: 0.8-1.5%, Cr: 1.5-2%, Mo: 1-1.5%, W: 0.1-0.3%, Nb: 0.03-0.1%, V: 0.10-0.20%, Ti: 0.02-0.05%, B: 0.0015-0.005%, Al: 0.01-0.05%, Ca: 0.001-0.004%.

[0009] Further, in the high-temperature-resistant and ultra-high-strength anti-collapse oil casing according to the present application, the mass percentage of each element is as follows:

[0010] C: 0.2-0.3%, Si: 0.1-0.4%, Mn: 0.8-1.5%, Cr: 1.5-2%, Mo: 1-1.5%, W: 0.1-0.3%, Nb: 0.03-0.1%, V: 0.10-0.20%, Ti: 0.02-0.05%, B: 0.0015-0.005%, Al: 0.01-0.05%, Ca: 0.001-0.004%; the balance is Fe and other inevitable impurities.

[0011] The mechanical properties of the oil casing are the key to the safety of the pipe string, so the toughness and strength of the casing at room temperature are required to be high, and the yield strength and anti-collapse strength at high temperature are also required to be high. In the present application, the inventors adopt the composition design of medium-low carbon + CrMoW + NbV. Since Cr, Mo and W elements can significantly improve the high-temperature mechanical properties of the material, but are easy to react with C to form Cr 23 C6 and Mo2C carbides, thereby reducing the toughness of the material. To solve the contradiction between toughness and high-temperature performance, the inventors add more Nb and V elements, which form MC type carbides with C elements at high temperature, which can hinder the dislocation slip of the material at high temperature, thereby improving the high-temperature performance of the material. At the same time, the content of residual C elements is reduced, which reduces the formation of Cr 23 C6 and Mo2C carbides, so that Cr and Mo elements exist in the form of solid solution, thereby improving the toughness and high-temperature performance of the material.

[0012] Specifically, the design principles of each chemical element in the high-temperature-resistant, ultra-high-strength, and anti-collapse oil casing according to the present application are as follows:

[0013] C: In the high-temperature-resistant, ultra-high-strength, and anti-collapse oil casing according to the present application, the C element is a carbide-forming element, which can improve the strength and high-temperature mechanical properties of the steel. When the mass percentage content of the C element is lower than 0.2%, the hardenability of the steel will be reduced, thereby reducing the strength of the steel; however, when the mass percentage content of the C element is higher than 0.3%, the segregation of the steel will be significantly deteriorated, thereby also causing the reduction of the toughness of the steel. Therefore, in order to achieve the high toughness requirement of the oil casing, the mass percentage content of the C element in the high-temperature-resistant, ultra-high-strength, and anti-collapse oil casing according to the present application is controlled to be between 0.2% and 0.3%.

[0014] Si: In the high-temperature-resistant, ultra-high-strength, and anti-collapse oil casing according to the present application, the Si element is dissolved in ferrite, which can improve the yield strength of the steel. However, when the mass percentage content of the Si element is too high, the workability and toughness of the steel will be deteriorated; when the mass percentage content of the Si element is lower than 0.1%, the oil casing will be easily oxidized. Therefore, in the high-temperature-resistant, ultra-high-strength, and anti-collapse oil casing according to the present application, the mass percentage content of the Si element is controlled to be between 0.10% and 0.40%.

[0015] Mn: In the high-temperature-resistant, ultra-high-strength, and anti-collapse oil casing according to the present application, the Mn element is an austenite-forming element, which can improve the hardenability and high-temperature mechanical properties of the steel. In the steel system according to the present application, when the mass percentage content of the Mn element is less than 0.8%, the hardenability of the steel will be significantly reduced, thereby reducing the proportion of the martensite in the steel and further reducing the strength of the steel; when the mass percentage content of the Mn element is greater than 1.5%, the microstructure segregation in the steel will be significantly increased, thereby reducing the toughness of the steel. Therefore, in the high-temperature-resistant, ultra-high-strength, and anti-collapse oil casing according to the present application, the mass percentage content of the Mn element is controlled to be between 0.8% and 1.5%.

[0016] Cr: In the high-temperature-resistant, ultra-high-strength, and anti-collapse oil casing according to the present application, the Cr element is an element that strongly improves the hardenability and a strong precipitate-forming element, which can improve the strength of the steel and the high-temperature mechanical properties of the steel. However, when the mass percentage content of the Cr element is higher than 2%, coarse M 23 C6 precipitates will be easily precipitated at the grain boundaries, thereby reducing the toughness. When the mass percentage content of the Cr element is lower than 1.5%, the high-temperature mechanical properties cannot be significantly improved. Therefore, in the high-temperature-resistant, ultra-high-strength, and anti-collapse oil casing according to the present application, the mass percentage content of the Cr element is controlled to be between 1.5% and 2%.

[0017] Mo: In the high-temperature-resistant ultra-high-strength anti-collapse oil casing described in the present application, Mo element mainly improves the strength and tempering stability of the steel through carbide and solid solution strengthening, and can improve the high-temperature mechanical properties of the steel. In the present application, because the carbon content is low, when the mass percentage content of Mo element is more than 1.5%, Mo element is difficult to form more carbide precipitates with C element, and the strength does not change significantly. However, once the mass percentage content of Mo element is less than 1%, the strength of the present composition system cannot reach the requirement of 140 ksi. Therefore, in the high-temperature-resistant ultra-high-strength anti-collapse oil casing described in the present application, the mass percentage content of Mo element is controlled between 1-1.5%.

[0018] W: In the high-temperature-resistant ultra-high-strength anti-collapse oil casing described in the present application, the solid solution strengthening of W element can enhance the binding force between matrix atoms, and can improve the strength of the material under high temperature environment. When the mass percentage content of W element is more than 0.3%, the strengthening effect is not obvious, and the impact toughness decreases; when the mass percentage content of W element is less than 0.1%, the high-temperature mechanical properties of the steel cannot be improved. Therefore, in the high-temperature-resistant ultra-high-strength anti-collapse oil casing described in the present application, the mass percentage content of W element is controlled between 0.1-0.3%.

[0019] Nb: In the high-temperature-resistant ultra-high-strength anti-collapse oil casing described in the present application, Nb element is a fine-grain and precipitate strengthening element in steel, which can compensate for the decrease in strength caused by the decrease in carbon content. When the mass percentage content of Nb element is less than 0.03%, its adding effect is not obvious; when the mass percentage content of Nb element is more than 0.1%, it is easy to form coarse Nb(CN), thereby reducing the toughness of the steel. Therefore, in the high-temperature-resistant ultra-high-strength anti-collapse oil casing described in the present application, the mass percentage content of Nb element is controlled between 0.03-0.1%.

[0020] V: In the high-temperature-resistant ultra-high-strength anti-collapse oil casing described in the present application, V element is a typical precipitate strengthening element, which can compensate for the decrease in strength caused by the decrease in carbon. When the mass percentage content of V element is less than 0.1%, the strengthening effect is difficult to make the material reach 140 ksi. When the mass percentage content of V element is higher than 0.2%, it is easy to form coarse V(CN), thereby reducing the toughness. Therefore, in the high-temperature-resistant ultra-high-strength anti-collapse oil casing described in the present application, the mass percentage content of V element is controlled between 0.1-0.2%.

[0021] Ti: In the high-temperature-resistant, ultra-high-strength, anti-collapse oil casing described in the present application, Ti is a strong carbonitride-forming element, which can significantly refine the austenite grains in the steel and compensate for the decrease in strength caused by the decrease in carbon content. When the mass percentage content of Ti is higher than 0.05%, coarse TiN is easily formed, which reduces the toughness of the material. If the mass percentage content of Ti is lower than 0.02%, the Ti element cannot fully react with the N element to form TiN, and the B element in the steel will react with the N element to form the brittle BN phase, thereby reducing the toughness of the material. Therefore, in the high-temperature-resistant, ultra-high-strength, anti-collapse oil casing described in the present application, the mass percentage content of Ti is controlled to be between 0.02% and 0.05%.

[0022] B: In the high-temperature-resistant, ultra-high-strength, anti-collapse oil casing described in the present application, B is also an element that can significantly improve the hardenability of the steel. In steel with low C content, B can solve the problem of poor hardenability caused by the decrease in C content. However, when the mass percentage content of B is lower than 0.0015%, the effect of improving the hardenability of the steel is not significant. When the mass percentage content of B is higher than 0.005%, BN brittle phase is easily formed, thereby reducing the toughness of the steel. Therefore, in the high-temperature-resistant, ultra-high-strength, anti-collapse oil casing described in the present application, the mass percentage content of B is controlled to be between 0.0015% and 0.005%.

[0023] Al: In the high-temperature-resistant, ultra-high-strength, anti-collapse oil casing described in the present application, Al is a good deoxidizing and nitrogen-fixing element that can refine the grains. Therefore, in the high-temperature-resistant, ultra-high-strength, anti-collapse oil casing described in the present application, the mass percentage content of Al is controlled to be between 0.01% and 0.05%.

[0024] Ca: In the high-temperature-resistant, ultra-high-strength, anti-collapse oil casing described in the present application, Ca can purify the steel liquid, promote the spheroidization of MnS, and improve the fracture toughness. When the mass percentage content of Ca is too high, coarse non-metallic inclusions are easily formed. Therefore, in the high-temperature-resistant, ultra-high-strength, anti-collapse oil casing described in the present application, the mass percentage content of Ca is controlled to be between 0.001% and 0.004%.

[0025] Further, in the inevitable impurities in the high-temperature-resistant, ultra-high-strength, anti-collapse oil casing described in the present application: N≤0.008%, P≤0.015%, S≤0.003%.

[0026] In the above technical solution of the present application, N, P and S are all harmful impurity elements. In order to obtain steel with better performance and quality, the content of N, P and S should be as low as possible if the technology permits.

[0027] Furthermore, the microstructure of the high-temperature resistant, ultra-high-strength, and crush-resistant oil casing of the present invention comprises tempered sorbite and retained austenite with a volume ratio of less than 1%.

[0028] Furthermore, the grain size of the high-temperature resistant, ultra-high-strength, and crush-resistant oil casing described in this invention is grade 7-8.

[0029] In this invention, the grain size of steel also has a significant impact on the high-temperature performance of the material. Grain coarsening improves the high-temperature mechanical properties of the material and enhances its creep resistance, but it reduces its toughness. Therefore, it is necessary to comprehensively consider the impact of coarsening design on the overall mechanical properties of the material. By optimizing the hot rolling and heat treatment processes to control the grain size range to level 7-8, the casing can simultaneously possess good high-temperature performance and good toughness indicators to meet the requirements of ultra-deep well conditions.

[0030] Furthermore, the high-temperature resistant, ultra-high-strength, and crush-resistant oil casing of the present invention satisfies at least one of the following properties:

[0031] The yield strength at room temperature is 965-1240 MPa, the tensile strength is ≥1034 MPa, the elongation is ≥20%, and the transverse Charpy impact energy at 0℃ is ≥100 J.

[0032] The yield strength at 250℃ decreases by no more than 9% compared to the yield strength at room temperature, and the crush resistance at 250℃ decreases by no more than 7% compared to the crush resistance at room temperature.

[0033] The creep rate at 250℃ is ≤1.5×10-7% / s.

[0034] Another objective of this invention is to provide a method for manufacturing a high-temperature resistant, ultra-high-strength, and crush-resistant oil casing. This method can produce a high-temperature resistant, ultra-high-strength, and crush-resistant oil casing with ultra-high strength, good high-temperature strength, and high-temperature crush resistance.

[0035] To achieve the above objectives, the present invention provides a method for manufacturing a high-temperature resistant, ultra-high-strength, and crush-resistant oil casing, comprising the following steps:

[0036] Smelting and continuous casting to obtain tube blanks;

[0037] Heating and perforation;

[0038] Rolling and tension reduction;

[0039] Heat treatment: Quenching + tempering; where the quenching temperature is 900~930℃ and the holding time is 30~60min; the tempering temperature is 650~700℃ and the holding time is 50~80min.

[0040] Thermal straightening.

[0041] Furthermore, in the smelting and continuous casting steps of the manufacturing method described in this invention, the continuous casting speed is controlled to be 1.8 to 2.4 m / min.

[0042] Furthermore, in the heating and piercing steps of the manufacturing method described in this invention, the heating is carried out to a homogenization temperature of 1220–1280°C, and the piercing temperature is 1160–1240°C.

[0043] Furthermore, in the rolling and tension reduction steps of the manufacturing method described in this invention, the final rolling temperature is controlled to be 940–1000°C, and the tension reduction temperature is controlled to be 880–930°C.

[0044] Furthermore, in the hot straightening step of the manufacturing method described in this invention, the hot straightening temperature is controlled to be 500–550°C.

[0045] The high-temperature resistant, ultra-high-strength, and crush-resistant oil casing and its manufacturing method described in this invention have the following advantages and beneficial effects:

[0046] The high-temperature resistant, ultra-high-strength, and crush-resistant oil casing of this invention has ultra-high strength, good high-temperature strength, and high-temperature crush resistance, which can meet the high strength and crush resistance requirements of deep and ultra-deep oil and gas fields for oil well casings.

[0047] In some embodiments, the high-temperature resistant, ultra-high-strength, and crush-resistant oil casing of the present invention has a yield strength of 965–1240 MPa at room temperature, a tensile strength ≥1034 MPa, an elongation ≥20%, and a transverse Charpy impact energy ≥100 J at 0℃; the yield strength at 250℃ decreases by no more than 9% compared to the yield strength at room temperature, and the crush resistance at 250℃ decreases by no more than 7% compared to the crush resistance at room temperature; the creep rate is ≤1.5 × 10⁻⁶. -7 % / s. Detailed Implementation

[0048] The following will provide further explanation and description of the high-temperature resistant, ultra-high-strength, and crush-resistant oil casing and its manufacturing method according to the present invention, with reference to specific embodiments. However, this explanation and description do not constitute an improper limitation on the technical solution of the present invention.

[0049] Examples 1-6 and Comparative Examples 1-5

[0050] The high-temperature resistant, ultra-high-strength, and crush-resistant oil casings of Examples 1-6 and the control pipes of Comparative Examples 1-5 of this invention were all prepared using the following steps:

[0051] (1) Smelting and continuous casting to obtain tube blanks: The continuous casting speed can be controlled at 1.8 to 2.4 m / min;

[0052] (2) Heating and piercing: The heat-soaking temperature can be controlled at 1220~1280℃. After heat-soaking, piercing is performed. The piercing temperature can be controlled at 1160~1240℃.

[0053] (3) Rolling and tension reduction: The final rolling temperature can be controlled at 940–1000℃, followed by tension reduction at a temperature of 880–930℃.

[0054] (4) Heat treatment: Quenching + tempering; wherein the quenching temperature is 900~930℃, and the holding time is 30~60min; the tempering temperature is 650~700℃, and the holding time is 50~80min;

[0055] (5) Hot straightening: The hot straightening temperature can be controlled at 500-550℃.

[0056] It should be noted that the chemical element composition and related process design of the high-temperature resistant, ultra-high-strength, and crush-resistant oil casings of Examples 1-6 of this invention all meet the design specifications of this invention. However, the chemical element content of the control tubes in Comparative Examples 1-4 does not meet the design of this invention, and the process parameters of Comparative Example 5 do not meet the design of this invention.

[0057] Tables 1-1 and 1-2 list the mass percentage of each chemical element in the high-temperature resistant, ultra-high-strength, crush-resistant oil casings of Examples 1-6 and the control pipes of Comparative Examples 1-5.

[0058] Table 1-1. (wt%, balance Fe and other unavoidable impurities besides N, P and S)

[0059] No. C Si Mn Cr Mo W Nb V Ti Example 1 0.2 0.2 0.8 1.5 1 0.1 0.03 0.1 0.02 Example 2 0.22 0.1 1.2 1.6 1.1 0.15 0.05 0.12 0.025 Example 3 0.24 0.3 1.3 1.7 1.2 0.2 0.04 0.15 0.03 Example 4 0.27 0.4 1.2 1.8 1.4 0.25 0.06 0.18 0.04 Example 5 0.3 0.25 1.5 2 1.5 0.3 0.1 0.20 0.05 Example 6 0.25 0.3 1.3 1.6 1.2 0.25 0.008 0.16 0.035 Comparative Example 1 0.22 0.1 1.2 2.5 1.8 0.5 0.05 0.18 0.02 Comparative Example 2 0.22 0.1 1.2 1.2 0.8 0.05 0.05 0.18 0.025 Comparative Example 3 0.22 0.1 1.8 1.6 1.1 0.15 0.15 0.28 0.03 Comparative Example 4 0.22 0.1 0.5 1.6 1.1 0.15 0.01 0.05 0.04 Comparative Example 5 0.22 0.1 1.2 1.6 1.1 0.15 0.05 0.18 0.05

[0060] Table 1-1. (wt%, balance Fe and other unavoidable impurities besides N, P and S)

[0061] No. B Al Ca N P S Example 1 0.0015 0.01 0.001 0.004 0.008 0.0005 Example 2 0.002 0.04 0.003 0.005 0.008 0.0007 Example 3 0.003 0.05 0.004 0.006 0.01 0.0015 Example 4 0.004 0.03 0.0025 0.007 0.011 0.001 Example 5 0.005 0.02 0.0035 0.008 0.012 0.002 Example 6 0.0025 0.025 0.002 0.0055 0.007 0.003 Comparative Example 1 0.002 0.04 0.003 0.005 0.008 0.0007 Comparative Example 2 0.002 0.04 0.003 0.005 0.008 0.0015 Comparative Example 3 0.002 0.04 0.003 0.005 0.01 0.001 Comparative Example 4 0.002 0.04 0.003 0.005 0.011 0.002 Comparative Example 5 0.002 0.04 0.003 0.005 0.012 0.003

[0062] Table 2 lists the specific process parameters of the high-temperature resistant, ultra-high-strength, crush-resistant oil casings of Examples 1-6 and the control pipes of Comparative Examples 1-5.

[0063] Table 2.

[0064]

[0065] Samples were taken from the high-temperature resistant, ultra-high-strength, and crush-resistant oil casings of Examples 1-6 and the control pipes of Comparative Examples 1-5, and microstructure analysis was performed. The results are listed in Table 3. The relevant testing procedures are described below:

[0066] Grain size rating: The grain size of steel shall be rated in accordance with the provisions of GB / T 6394.

[0067] Microstructure: The microstructure of Examples 1-6 and Comparative Examples 1-5 was observed under an optical microscope after polishing.

[0068] Table 3 lists the microstructure test results of the high-temperature resistant, ultra-high-strength, and crush-resistant oil casings of Examples 1-6 and the control pipes of Comparative Examples 1-5.

[0069] Table 3.

[0070] No. Microstructure Grain size (grade) Example 1 0.8% retained austenite, remainder tempered sorbite 7 Example 2 0.9% retained austenite, remainder tempered sorbite 7.5 Example 3 0.6% retained austenite, remainder tempered sorbite 8 Example 4 0.7% retained austenite, remainder tempered sorbite 8 Example 5 0.5% retained austenite, remainder tempered sorbite 7.5 Example 6 0.4% retained austenite, remainder tempered sorbite Comparative Example 1 0.8% retained austenite, remainder tempered sorbite 7.5 Comparative Example 2 0.9% retained austenite, remainder tempered sorbite 8 Comparative Example 3 0.6% retained austenite, remainder tempered sorbite 8 Comparative Example 4 0.7% retained austenite, remainder tempered sorbite 7.5 Comparative Example 5 0.5% retained austenite, remainder tempered sorbite 6

[0071] As can be seen from Table 3, the microstructure of the high-temperature resistant, ultra-high-strength, and crush-resistant oil casings of Examples 1-6 prepared by the present invention is tempered sorbite and retained austenite with a volume ratio of less than 1%, and their grain size is between 7 and 8.

[0072] In addition, samples were taken again from the high-temperature resistant, ultra-high-strength, and crush-resistant oil casings of Examples 1-6 and the control pipes of Comparative Examples 1-5, and tested. The test results are listed in Tables 4-1 and 4-2. The relevant test procedures are as follows:

[0073] Tensile test: Tensile properties at room temperature are tested according to GB / T 228.1-2000 standard.

[0074] Impact test: The impact energy test at 0℃ was conducted according to GB / T 229-2007 "Metallic Materials Charpy Pendulum Impact Test Method".

[0075] Yield strength at 250°C: Yield strength at 250°C is determined according to ASTM E21-09 standard.

[0076] Crushing resistance at 250°C: Crushing resistance at 250°C was tested according to ISO / TR10400-2008 standard.

[0077] Creep rate: The creep test shall be conducted in accordance with GB / T 2039.

[0078] Tables 4-1 and 4-2 list the performance test results of the high-temperature resistant, ultra-high-strength, and crush-resistant oil casings of Examples 1-6 and the control pipes of Comparative Examples 1-5.

[0079] Table 4-1.

[0080]

[0081] Table 4-2.

[0082]

[0083] As can be seen from Tables 4-1 and 4-2 above, the high-temperature resistant, ultra-high-strength, and crush-resistant oil casings of Examples 1-6 prepared using the present invention exhibit yield strengths between 965 and 1240 MPa at room temperature, tensile strengths greater than 1034 MPa, elongation greater than 20%, and transverse Charpy impact energy greater than 100 J at 0℃. Furthermore, the yield strength of the high-temperature resistant, ultra-high-strength, and crush-resistant oil casings of Examples 1-6 at 250℃ decreases by no more than 9% compared to their yield strength at room temperature, and their crush resistance at 250℃ decreases by no more than 7% compared to their crush resistance at room temperature. The creep rate is also less than 1.5 × 10⁻⁶. -7 With a strength of % / s, it possesses high strength and fracture toughness, which can meet the high strength and anti-crushing requirements of deep and ultra-deep oil and gas fields for well pipes.

[0084] It should be noted that the combination of the technical features in this case is not limited to the combination methods described in the claims of this case or the combination methods described in the specific embodiments. All technical features described in this case can be freely combined or combined in any way, unless they contradict each other.

[0085] 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 thereto are those that can be directly derived or easily conceived by those skilled in the art from the content disclosed in the present invention, and should all fall within the protection scope of the present invention.

Claims

1. A high-temperature resistant, ultra-high-strength, and crush-resistant oil casing, containing Fe and unavoidable impurities, characterized in that... It also contains the following chemical elements in the following percentages by mass: C: 0.2-0.3%, Si: 0.1-0.4%, Mn: 0.8-1.5%, Cr: 1.5-2%, Mo: 1-1.5%, W: 0.1-0.3%, Nb: 0.03-0. 1%, V: 0.10-0.20%, Ti: 0.02-0.05%, B: 0.0015-0.005%, Al: 0.01-0.05%, Ca: 0.001-0.004%.

2. The high-temperature resistant, ultra-high-strength, and crush-resistant oil casing as described in claim 1, characterized in that, Its elemental mass percentage content is as follows: C: 0.2-0.3%, Si: 0.1-0.4%, Mn: 0.8-1.5%, Cr: 1.5-2%, Mo: 1-1.5%, W: 0.1-0.3%, Nb: 0.03-0.1%, V: 0.10-0.20%, Ti: 0.02-0.05%, B: 0.0015-0.005%, Al: 0.01-0.05%, Ca: 0.001-0.004%; balance Fe and other unavoidable impurities.

3. The high-temperature resistant, ultra-high-strength, and crush-resistant oil casing as described in claim 1 or 2, characterized in that, In unavoidable impurities: N≤0.008%, P≤0.015%, S≤0.003%.

4. The high-temperature resistant, ultra-high-strength, and crush-resistant oil casing as described in claim 1 or 2, characterized in that, Its microstructure matrix includes tempered sorbite and retained austenite, which accounts for less than 1% of the volume.

5. The high-temperature resistant, ultra-high-strength, and crush-resistant oil casing as described in claim 1 or 2, characterized in that, Its grain size is grade 7-8.

6. The high-temperature resistant, ultra-high-strength, and crush-resistant oil casing as described in claim 1 or 2, characterized in that, Its performance satisfies at least one of the following: The yield strength at room temperature is 965-1240 MPa, the tensile strength is ≥1034 MPa, the elongation is ≥20%, and the transverse Charpy impact energy at 0℃ is ≥100 J. The yield strength at 250℃ decreases by no more than 9% compared to the yield strength at room temperature, and the crush resistance at 250℃ decreases by no more than 7% compared to the crush resistance at room temperature. Creep rate at 250℃ ≤ 1.5 × 10 -7 % / s.

7. The method for manufacturing the high-temperature resistant, ultra-high-strength, and crush-resistant oil casing as described in any one of claims 1-6, characterized in that, It includes the following steps: Smelting and continuous casting to obtain tube blanks; Heating and perforation; Rolling and tension reduction; Heat treatment: Quenching + tempering; where the quenching temperature is 900~930℃ and the holding time is 30~60min; the tempering temperature is 650~700℃ and the holding time is 50~80min. Thermal straightening.

8. The manufacturing method as described in claim 7, characterized in that, During the smelting and continuous casting steps, the continuous casting speed is controlled at 1.8–2.4 m / min.

9. The manufacturing method as described in claim 7, characterized in that, In the heating and piercing steps, the temperature is heated to a homogenization temperature of 1220–1280°C, and the piercing temperature is 1160–1240°C.

10. The manufacturing method as described in claim 7, characterized in that, During the rolling and tension reduction steps, the final rolling temperature is controlled at 940–1000℃, and the tension reduction temperature is controlled at 880–930℃.

11. The manufacturing method as described in claim 7, characterized in that, In the hot straightening step, the hot straightening temperature is controlled at 500-550℃.

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