High-strength oil casing resistant to carbon dioxide corrosion and manufacturing method thereof

Abstract

The application discloses a high-strength oil casing pipe with carbon dioxide corrosion resistance, which contains Fe and inevitable impurities, and additionally contains the following chemical elements: C: 0.10-0.20%, Si: 0.10-0.80%, Mn: 0.10-1.50%, Cr: 3-5%, Mo: 0.10-0.70%, Al: 0.01-0.10%, V: 0.10-0.20%, Ni: 0.1-1.0%, Ce: 0.002-0.01%, and La: 0.002-0.01%. Correspondingly, the application also discloses a manufacturing method of the high-strength oil casing pipe with carbon dioxide corrosion resistance. The oil casing pipe with super-high strength and excellent carbon dioxide corrosion resistance can be obtained through reasonable chemical element component design.

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] In the development of oil and gas, corrosion problem often leads to great economic losses, and even disastrous consequences.Currently, many oil fields have serious CO2 corrosion problems.

[0003] Although a large number of researches have been carried out at home and abroad, 13Cr steel, high corrosion-resistant Ni-based alloy and other materials have been developed, but the above-mentioned materials contain a large amount of Cr, Ni, Mo and other valuable metal elements, resulting in a substantial increase in the cost of steel pipes.

[0004] In the prior art, most of the alloy steels for resisting CO2 corrosion (or simultaneously resisting CO2+H2S+Cl- comprehensive corrosion) are medium alloy or high alloy component systems such as 13Cr, and the strength is relatively low, which cannot reach more than 110 ksi steel grade.

[0005] For example, the Chinese patent document with publication number CN101899621A and publication date December 1, 2010, entitled "3Cr Seamless Steel Pipe and Its Manufacturing Method", has the chemical composition of C: 0.1-0.2%, Si: 0.1-0.5%, Mn: 0.3-0.8%, Cr: 2-4%, Mo: 0.3-0.6%, Ti: 0.0024-0.024%, Al: 0.01-0.04%, P≤0.03%, S≤0.03%, and the balance of Fe and unavoidable impurities, adopts quenching and tempering heat treatment process, and realizes yield strength ≥552 MPa, i.e. 80 ksi.

[0006] For another example, the Chinese patent document with publication number CN103602903A and publication date February 26, 2014, entitled "High-strength Anti-carbon Dioxide Corrosion Oil Well Pipe and Its Manufacturing Method", has the chemical composition of C: 0.30-0.42%, Si: 0.10-1.0%, Mn: 0.80-1.5%, Cr: 0.5-1.5%, V: 0.21-0.4%, Al: 0.01-0.10%, N: 0.031-0.05%, P≤0.015%, S≤0.005%, and the balance of Fe and unavoidable impurities, V / N ratio is controlled at 6-11, adopts normalizing process, and the mechanical properties reach more than 95 ksi steel grade. SUMMARY

[0007] One of the purposes of the present application is to provide a high-strength oil casing with resistance to carbon dioxide corrosion, which has super high strength and excellent resistance to carbon dioxide corrosion by reasonable chemical element composition design.

[0008] In order to achieve the above-mentioned purpose, the present application provides a high-strength oil casing with resistance to carbon dioxide corrosion, which contains Fe and inevitable impurities, and further contains the following chemical elements with mass percentage as follows:

[0009] C: 0.10-0.20%, Si: 0.10-0.80%, Mn: 0.10-1.50%, Cr: 3-5%, Mo: 0.10-0.70%, Al: 0.01-0.10%, V: 0.10-0.20%, Ni: 0.1-1.0%, Ce: 0.002-0.01%, La: 0.002-0.01%.

[0010] Correspondingly, the present application also provides a high-strength oil casing with resistance to carbon dioxide corrosion, which contains the following chemical elements with mass percentage as follows:

[0011] C: 0.10-0.20%, Si: 0.10-0.80%, Mn: 0.10-1.50%, Cr: 3-5%, Mo: 0.10-0.70%, Al: 0.01-0.10%, V: 0.10-0.20%, Ni: 0.1-1.0%, Ce: 0.002-0.01%, La: 0.002-0.01%; the balance is Fe and other inevitable impurities.

[0012] Generally, in order to improve the CO2 corrosion resistance of the material, a certain amount of Cr element is usually added to form a dense corrosion film to protect the base material, but the Cr element is easy to combine with the C element to form carbide C 23C6 and C7 C3, unable to form a Cr(OH)3 corrosion film with anion selectivity, so the present application adopts a low carbon composition design, reduces the content of Cr carbide to promote the formation of Cr-rich corrosion film, improve the stability of the corrosion film, thereby improving the corrosion resistance. At the same time, Ce and La elements are added, on the one hand, they have strong affinity with O, S and other elements, can deeply deoxidize, form rare earth compounds to facilitate smelting and impurity removal, thereby reducing the content of coarse inclusions, preventing the formation of pitting pits at the location of large inclusions, on the other hand, rare earth reduces the crystallization supercooling degree, resulting in microstructure refinement during solidification process, rare earth modification, forming uniform and dispersed fine rare earth inclusion particles, which can act as a second phase nucleation core, and can also produce grain boundary pinning effect, which is beneficial to grain refinement and improvement of comprehensive performance. In addition, through the multi-element micro-alloying composition design of V, Ni, Nb, the present application can achieve a high yield strength of 140 ksi, improve the corrosion resistance while improving the collapse resistance of the casing, thereby significantly improving the service life of the casing.

[0013] Specifically, in the high-strength carbon dioxide corrosion-resistant oil casing described in the present application, the design principles of each chemical element are as follows:

[0014] C: In the high-strength carbon dioxide corrosion-resistant oil casing described in the present application, C is the main solid solution strengthening element, which can improve the strength of the steel, but excessive content will worsen segregation and reduce toughness, and the formation of carbides will damage the corrosion resistance, therefore the C content is controlled to be 0.10-0.20%.

[0015] Si: In the high-strength carbon dioxide corrosion-resistant oil casing described in the present application, Si is a deoxidizer, which has a strong solid solution strengthening effect on ferrite, improves hardenability, temper resistance and yield strength, but excessive content will worsen the toughness and processability of the steel, therefore the Si content is controlled to be 0.10-0.80%.

[0016] Mn: In the high-strength carbon dioxide corrosion-resistant oil casing described in the present application, Mn is one of the important alloying elements, which strongly improves the hardenability of the steel and promotes the formation of martensite to ensure the strength, but excessive content has the adverse tendency of promoting grain coarsening and segregation, therefore the Mn content is controlled to be 0.10-1.50%.

[0017] Cr: In the high-strength carbon dioxide corrosion-resistant oil casing described in the present application, Cr is the main alloying element for improving corrosion resistance, and can also increase the hardenability of the steel, therefore the Cr content is controlled to be 3-5%.

[0018] Mo: In the high-strength oil casing resistant to carbon dioxide corrosion according to the present application, Mo has a strong ability to suppress the transformation of austenite to pearlite, can suppress temper brittleness, forms special carbides in a dispersed distribution at a higher tempering temperature, and improves strength, and based on this, the Mo content is controlled to be 0.10-0.70%.

[0019] Al: In the high-strength oil casing resistant to carbon dioxide corrosion according to the present application, Al is mainly used for deoxidization and grain refinement, has a large solid solution strengthening effect, and based on this, the Al content is controlled to be 0.01-0.10%.

[0020] V: In the high-strength oil casing resistant to carbon dioxide corrosion according to the present application, V is a strong carbide and nitride forming element, improves the temper resistance of the steel and has a strong secondary hardening effect, has a very strong solid solution strengthening effect when dissolved in ferrite, but a high V content easily forms coarse V(C, N) and impairs toughness, and therefore the V content is controlled to be 0.10-0.20%.

[0021] Ni: Ni has a certain solid solution strengthening effect and can improve corrosion resistance, in the high-strength oil casing resistant to carbon dioxide corrosion according to the present application, Ni, in combination with Cr and Mo, can improve the thermal strength and corrosion resistance of the steel, and based on this, the Ni content is controlled to be 0.1-1.0%.

[0022] Ce, La: In the high-strength oil casing resistant to carbon dioxide corrosion according to the present application, trace amounts of Ce and La are added for grain refinement and improvement of toughness, but a high content easily forms coarse oxides or sulfides, and therefore the Ce and La contents are each controlled to be 0.002-0.01%.

[0023] Further, in the high-strength oil casing resistant to carbon dioxide corrosion according to the present application, the mass percent content of each chemical element can further satisfy at least one of the following:

[0024] Si: 0.1-0.4%;

[0025] Mn: 0.2-1.0%;

[0026] Mo: 0.4-0.6%;

[0027] Al: 0.01-0.04%;

[0028] Ni: 0.1-0.5%;

[0029] Ce: 0.002-0.008%;

[0030] La: 0.002-0.005%.

[0031] Further, the high-strength oil casing with carbon dioxide corrosion resistance according to the present application further contains 0 < Nb ≤ 0.15 wt%.

[0032] Nb has strong solid solution strengthening effect and can refine grains, and trace addition can increase the strength of the steel without affecting the plasticity and toughness, based on which, in some embodiments of the present application, the content thereof is controlled to be 0 < Nb ≤ 0.15 wt%.

[0033] Further, in the inevitable impurities of the high-strength oil casing with carbon dioxide corrosion resistance according to the present application: P ≤ 0.015%, S ≤ 0.008%, N ≤ 0.008%.

[0034] Further, P ≤ 0.012%, S ≤ 0.005%, N ≤ 0.006% are controlled.

[0035] In the technical solution described above in the present application, P, S and N are all harmful impurity elements, among which, P and S segregate seriously in the steel and are not conducive to plasticity and toughness. N has no significant strengthening effect, forms nitrides to damage the strengthening effect of micro-alloy elements, and easily causes aging hardening phenomenon of low-carbon steel, thereby reducing plasticity and toughness. Therefore, in order to obtain steel with better performance and higher quality, the content of P, S and N should be reduced as much as possible under the condition of technology.

[0036] Further, in the high-strength oil casing with carbon dioxide corrosion resistance according to the present application, the microstructure matrix thereof is tempered sorbite.

[0037] Further, in the high-strength oil casing with carbon dioxide corrosion resistance according to the present application, the grain size thereof is above grade 10.

[0038] Further, in the high-strength oil casing with carbon dioxide corrosion resistance according to the present application, the percentage of large-size inclusions with an average diameter greater than 5 μm in the total inclusions is < 6%.

[0039] Further, in the high-strength oil casing with carbon dioxide corrosion resistance according to the present application, the content of Cr in the corrosion product film is higher than 13 wt%.

[0040] Further, the high-strength oil casing with carbon dioxide corrosion resistance according to the present application has the performance that: the yield strength is 965-1173 MPa, the tensile strength is ≥ 1034 MPa, and the 0 ℃ transverse Charpy impact energy is ≥ 80 J.

[0041] Further, the high-strength oil casing with carbon dioxide corrosion resistance according to the present application has a uniform corrosion rate ≤ 2.5 mm / a under the corrosion environment condition of temperature 60 ℃, CO2 partial pressure 1 MPa and NaCl concentration 20 g / L.

[0042] Correspondingly, another object of the present application is to provide the manufacturing method of the high-strength oil casing with carbon dioxide corrosion resistance, which has a simple process and low production cost.

[0043] In order to achieve the above object, the present application provides the manufacturing method of the high-strength oil casing with carbon dioxide corrosion resistance, which comprises the following steps:

[0044] (1) smelting and continuous casting to obtain a pipe blank;

[0045] (2) heating, piercing, rolling, sizing;

[0046] (3) quenching: the quenching temperature is 880-920℃, and the water quenching is performed after the heat preservation for 30-60min;

[0047] (4) tempering: the tempering temperature is 550-650℃, and the heat preservation time is 45-75min.

[0048] Further, in the step (1) of the manufacturing method, the overheat degree of the molten steel is controlled to be ≤30℃ during the casting process, and the continuous casting speed is controlled to be ≤2.0m / min.

[0049] Further, in the step (2) of the manufacturing method, the heating is performed to the soaking temperature of 1200-1250℃, and the heat preservation is performed for 100-300min.

[0050] Further, in the step (2) of the manufacturing method, the piercing temperature is controlled to be 1150-1250℃.

[0051] Further, in the step (2) of the manufacturing method, the finish rolling temperature is controlled to be 900-1000℃.

[0052] Further, in the step (2) of the manufacturing method, the sizing temperature is controlled to be 850-950℃.

[0053] The high-strength oil casing with carbon dioxide corrosion resistance and the manufacturing method thereof have the following advantages and beneficial effects:

[0054] The high-strength oil casing with carbon dioxide corrosion resistance has a low-carbon composition design, and appropriate Cr elements, Ni, Mo, V, Ce and La elements are added, so that the produced oil casing has high strength and excellent corrosion resistance.

[0055] In some embodiments, the high-strength oil casing with carbon dioxide corrosion resistance has a yield strength of 965-1173MPa, reaches 140ksi, a tensile strength ≥1034MPa, and a 0℃ transverse Charpy impact energy ≥80J, and has excellent mechanical properties.

[0056] In some embodiments, the high-strength oil casing with resistance to carbon dioxide corrosion has a uniform corrosion rate of ≤2.5 mm / a under the corrosion environment conditions of temperature 60℃, CO2 partial pressure 1 MPa, and NaCl concentration 20 g / L, and thus has excellent resistance to carbon dioxide corrosion. BRIEF DESCRIPTION OF DRAWINGS

[0057] Figure 1 Figure 2 is a microstructure photograph of the oil casing of Example 1 under an optical microscope.

[0058] Figure 2 Figure 3 is a microstructure photograph of the oil casing of Example 1 under a scanning electron microscope.

[0059] Figure 3 Figure 4 is a microstructure photograph of the oil casing of Comparative Example 1 under a scanning electron microscope. DETAILED DESCRIPTION

[0060] The high-strength oil casing with resistance to carbon dioxide corrosion and the manufacturing method thereof described in the present application will be further explained and described below in conjunction with specific examples and the accompanying drawings of the specification, however, the explanation and description do not constitute undue limitations on the technical solutions of the present application.

[0061] Examples 1-18 and Comparative Examples 1-5

[0062] The high-strength oil casing with resistance to carbon dioxide corrosion of Examples 1-18 is prepared by the following steps:

[0063] (1) Smelting: smelting is performed by primary smelting, secondary refining, and vacuum degassing, and the tapping temperature can be 1600-1700℃.

[0064] (2) Continuous casting: round billets are prepared by a continuous casting process, and the superheat of the molten steel is controlled to be ≤30℃, and the continuous casting speed is controlled to be below 2.0 m / min.

[0065] (3) The round billet is heated to the soaking temperature of 1200-1250℃ in a ring heating furnace, and then is pierced, and the piercing temperature is 1150-1250℃.

[0066] (4) Rolling: after piercing, continuous rolling is performed, and the finish rolling temperature is controlled to be 900-1000℃.

[0067] (5) Sizing: after short-time heating in a heating furnace, sizing is performed, and the sizing temperature is controlled to be 850-950℃.

[0068] (6) Quenching: after heating to 880-920℃ and holding for 30-60 min, water quenching is performed.

[0069] (7) tempering: tempering temperature is 550-650℃, holding time is 45-75 min.

[0070] It should be noted that the chemical element content of Comparative Examples 1-5 does not conform to the design of the present application.

[0071] Table 1 lists the mass percentage of each chemical element of the high-strength carbon dioxide corrosion resistant oil casing of Examples 1-18 and the comparative oil casing of Comparative Examples 1-5.

[0072] Table 1. (wt%, the balance is Fe and other inevitable impurities except P, S, N)

[0073]

[0074]

[0075] Table 2 lists the specific process parameters of the high-strength carbon dioxide corrosion resistant oil casing of Examples 1-18 and the comparative oil casing of Comparative Examples 1-5 in the above process steps.

[0076] Table 2.

[0077]

[0078]

[0079]

[0080] The high-strength carbon dioxide corrosion resistant oil casing of Examples 1-18 and the comparative pipe material of Comparative Examples 1-5 are sampled respectively, and the statistics of large-size inclusion particles with an average diameter of >5 μm and the grain size measurement are carried out, and the test results are listed in Table 3.

[0081] Table 3.

[0082]

[0083] As can be seen from Table 3, the grain size of each embodiment of the present application is above 10 levels, and the percentage of large-size inclusions with an average diameter of >5 μm in the total inclusions is <6%. The grain size level of Comparative Examples 4 and 5 is lower than 10 levels, and the percentage of large-size inclusions is also much higher than that of the embodiments of the present application.

[0084] In addition, Figure 1 The microstructure photograph of the oil casing of Example 1 of the present application under an optical microscope is shown. As can be seen from Figure 1 , the microstructure of Example 1 at room temperature is tempered sorbite structure.

[0085] Figure 2The microstructure of the oil casing of Example 1 under a scanning electron microscope is shown. It can be seen from the microstructure of Example 1 that a small amount of fine dispersed carbides are distributed. Figure 2

[0086] The microstructure of the oil casing of Comparative Example 1 under a scanning electron microscope is shown. It can be seen from the microstructure of Comparative Example 1 that there are a large number of coarse carbides, which are not conducive to corrosion resistance. Figure 3 Figure 3

[0087] In addition, the high-strength carbon dioxide corrosion-resistant oil casing of Examples 1-18 and the comparative pipes of Comparative Examples 1-5 are respectively sampled for mechanical property testing and corrosion resistance testing, and the test results are listed in Table 4. The relevant test processes are as follows:

[0088] The room temperature tensile property test is carried out according to the standard GB / T 228.1-2021 “Metallic Materials-Tensile Testing-Part 1: Method of Tensile Test at Room Temperature”.

[0089] The V-shaped impact sample is processed, and the 0℃ impact property test is carried out according to the standard GB / T 229-2020 “Metallic Materials Charpy Pendulum Impact Test Method”.

[0090] The corrosion piece is sampled and processed according to the standard JB / T 7901-1999 “Metallic Materials Laboratory Uniform Corrosion Immersion Test Method”, and the test is carried out in a high-temperature high-pressure kettle under the corrosion environment conditions of temperature 60℃, CO2 partial pressure 1MPa, NaCl concentration 20g / L, rotating speed 1m / s, and test period 168h, the uniform corrosion rate is calculated, and the cross section of the corrosion piece is analyzed by SEM+EDS.

[0091] Table 4 lists the test results of the high-strength carbon dioxide corrosion-resistant oil casing of Examples 1-18 and the comparative oil casing of Comparative Examples 1-5.

[0092] Table 4.

[0093]

[0094]

[0095] As can be seen from Table 4, the yield strength of the high-strength carbon dioxide corrosion-resistant oil casing of Examples 1-18 of the present application is higher than 965MPa, the tensile strength is higher than 1034MPa, and the 0℃ transverse Charpy impact energy is greater than 80J. At the same time, in the test corrosion environment, the Cr content in the corrosion product film of each example of the present application is higher than 13wt%, and the uniform corrosion rate is lower than 2.5mm / a.

[0096] ​​Comparative Examples 1 to 5 are not in accordance with the design requirements of the present application in terms of chemical element content, and their corrosion resistance is worse than that of the present application, and their mechanical properties are also not good.

[0097] It can be seen that the oil casing with both super-high strength and carbon dioxide corrosion resistance can be obtained by using the technical scheme of the present application.

[0098] It should be noted that the combination of the technical features in the present case is not limited to the combination in the claims or the combination in the specific embodiments, and all the technical features disclosed in the present case can be freely combined or combined in any way, unless contradictory to each other.

[0099] It should also be noted that the above-mentioned embodiments are only specific embodiments of the present application. Obviously, the present application is not limited to the above-mentioned embodiments, and similar changes or modifications made on the basis of the disclosure of the present application are directly derived or easily conceived by those skilled in the art, and should all fall within the scope of protection of the present application.

Claims

1. A high strength oil casing resistant to carbon dioxide corrosion, characterized by, each of which has a mass percentage content of: C: 0.10-0.20%, Si: 0.10-0.80%, Mn: 0.10-1.50%, Cr: 3-5%, Mo: 0.10-0.70%, Al: 0.01-0.10%, V: 0.10-0.20%, Ni: 0.1-1.0%, Ce: 0.002-0.01%, La: 0.002-0.01%; the balance being Fe and other unavoidable impurities; the performance of which satisfies: yield strength of 965-1173 MPa, tensile strength ≥1034 MPa, 0℃ transverse Charpy impact energy ≥80 J, and uniform corrosion rate under the conditions of temperature 60℃, CO2 partial pressure 1 MPa, and NaCl concentration 20 g / L is ≤2.5 mm / a.

2. The high strength, carbon dioxide corrosion resistant oil casing of claim 1 wherein, the mass percentage content of each chemical element further satisfies at least one of the following: Si: 0.1-0.4%; Mn: 0.2-1.0%; Mo: 0.4-0.6%; Al：0.01～0.04％； Ni: 0.1-0.5%; Ce: 0.002-0.008%; La: 0.002-0.005%.

3. The high strength, carbon dioxide corrosion resistant oil casing of claim 1 wherein, It also contains 0 < Nb ≤ 0.15 wt%.

4. The high strength, carbon dioxide corrosion resistant oil casing of claim 1 wherein, Among the unavoidable impurities: P ≤ 0.015%, S ≤ 0.008%, N ≤ 0.008%.

5. The high strength, carbon dioxide corrosion resistant oil casing of claim 1 wherein, The microstructure matrix thereof is tempered sorbite.

6. The high strength, carbon dioxide corrosion resistant oil casing of claim 1 wherein, The grain size thereof is above 10 levels.

7. The high strength, carbon dioxide corrosion resistant oil casing of claim 1 wherein, The percentage of large-size inclusions with an average diameter greater than 5 μm in the total number of inclusions is < 6%.

8. The high strength, carbon dioxide corrosion resistant oil casing of claim 1 wherein, The Cr content in the corrosion product film thereof is higher than 13 wt%.

9. The method of producing a high-strength carbon dioxide corrosion resistant oil casing according to any one of claims 1 to 8, characterized by, It comprises the steps of: (1) smelting and continuous casting to obtain a pipe blank; (2) heating, piercing, rolling, sizing; (3) quenching: quenching temperature is 880-920℃, holding for 30-60 min, and then water quenching; (4) tempering: tempering temperature is 550-650℃, holding time is 45-75 min.

10. The production method according to claim 9, wherein In step (1), the overheat degree of molten steel during casting is controlled to be ≤30℃, and the continuous casting speed is controlled to be below 2.0 m / min.

11. The production method according to claim 9, wherein In step (2), heating to soaking temperature 1200-1250℃, holding for 100-300 min.

12. The production method according to claim 9, wherein In step (2), the piercing temperature is controlled to be 1150-1250℃.

13. The production method according to claim 9, wherein In step (2), the finish rolling temperature is controlled to be 900-1000℃.

14. The production method according to claim 9, wherein In step (2), the sizing temperature is controlled to be 850-950℃.

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