WO2017162160A1 - Steel for hydrogen sulfide stress corrosion cracking resistant martensitic stainless steel oil casing pipe, and oil casing pipe and production method therefor - Google Patents

Abstract

A steel for a hydrogen sulfide stress corrosion cracking resistant martensitic stainless steel oil casing pipe, and an oil casing pipe and production method therefor. The steel comprises, in mass percent, chemical elements: 0<C≤0.05%, Si: 0.1-0.2%, Mn: 0.20-1.0%, Cr: 11.0-14.0%, Ni: 4.0-7.0%, Mo: 1.5-2.5%, N: 0.001-0.10%, V: 0.03-0.6%, and Al: 0.01-0.04%, with the balance being Fe and other inevitable impurities.

Description

Steel, oil casing for martensitic stainless steel oil casing resistant to hydrogen sulfide stress corrosion cracking and manufacturing method thereof Technical field

The invention relates to a metal, an oil casing and a manufacturing method thereof, in particular to a steel for a martensitic stainless steel oil casing, an oil casing and a manufacturing method thereof.

Background technique

With the gradual depletion of easily exploitable energy sources, the mining range is increasingly concentrated in high temperature and high pressure environments, H ₂ S with a partial pressure of 0.01 MPa, and a highly corrosive environment with high concentrations of CO ₂ and Cl ⁻ coexisting. In addition, since many oil and gas resources are located in relatively cold areas, temperatures can reach minus 20 ° C or even lower during winter season operations. For such an environment, high-alloy products are generally required to meet corrosion resistance requirements, such as super martensitic stainless steel. Super martensitic stainless steel has excellent corrosion resistance in high temperature and high concentration CO ₂ and Cl ^- environment, but its application in H ₂ S containing environment is limited.

The publication number is CN1729306, and the publication date is February 1, 2006. The Chinese patent document entitled "High-strength martensitic stainless steel excellent in carbon dioxide gas corrosion resistance and sulfur sulfide stress corrosion cracking resistance" discloses a Markov The body stainless steel has a yield strength of 860 MPa or more, and the chemical element mass percentage thereof is: C: 0.005 to 0.04%, Si: 0.5% or less, Mn: 0.1 to 3.0%, P: 0.04% or less, and S: 0.01% or less. Cr: 10 to 15%, Ni: 4.0 to 8%, Mo: 2.8 to 5.0%, Al: 0.001 to 0.10%, and N: 0.07% or less, the balance being Fe and other unavoidable impurities; It also satisfies: Mo ≥ 2.3-0.89Si + 32.2C, and the metal structure is mainly composed of tempered martensite, carbide precipitated during tempering, and Laves phase or σ equivalent intermetallic compound which is finely precipitated during tempering. The steel grade has a high strength characteristic, but the applicable partial pressure of H ₂ S is 0.003 MPa or less.

The publication number is CN1582342, and the publication date is February 16, 2005. The Chinese patent document entitled "Martensitic Stainless Steel" discloses a martensitic stainless steel having a chemical element mass percentage of C: 0.01-0.1%. Cr: 9-15%, N: 0.1% or less, and the amount of carbide present at the old austenite grain boundary in the steel is 0.5% by volume or less. The steel grade has economical characteristics in martensitic stainless steel and has good resistance to CO ₂ corrosion, but the applicable partial pressure of H ₂ S is only 0.0003 MPa.

In view of this, it is desirable to obtain a steel material for oil casing, an oil casing made of the material, and a manufacturing method thereof, which can be used for H ₂ S having a partial pressure of 0.01 MPa and a high concentration of CO ₂ , Cl ^- Coexisting in oil and gas wells of crude oil or natural gas in a highly corrosive environment, and in this environment can meet the corresponding corrosion resistance and mechanical properties.

Summary of the invention

One of the objects of the present invention is to provide a steel for martensitic stainless steel oil casing which is resistant to hydrogen sulfide stress corrosion cracking, and the stainless steel can be used to obtain a martensitic stainless steel oil casing resistant to hydrogen sulfide stress corrosion cracking, the oil jacket The tube can be used in oil wells and gas wells of crude oil or natural gas in a highly corrosive environment with a partial pressure of 0.01 MPa of H ₂ S and a high concentration of CO ₂ , Cl ^{− ,} etc., and can meet the corresponding corrosion resistance in the environment. And mechanical performance indicators.

Based on the above object, the present invention provides a steel for martensitic stainless steel oil casing which is resistant to hydrogen sulfide stress corrosion cracking, and has a chemical element mass percentage of 0<C≤0.05%, Si:0.1-0.2%, Mn: 0.20 to 1.0%, Cr: 11.0 to 14.0%, Ni: 4.0 to 7.0%, Mo: 1.5 to 2.5%, N: 0.001 to 0.10%, V: 0.03 to 0.6%, Al: 0.01 to 0.04%, and the balance is Fe and other inevitable impurities.

In the present technical solution, other unavoidable impurities are mainly S, P and O.

In order to achieve the above object, the inventors conducted intensive studies on the composition, heat treatment conditions, metallographic structure, and hardness of martensitic stainless steel against sulfide stress corrosion cracking. It was found that a small amount of secondary martensite was formed during a tempering process, and the secondary martensite was transformed into the inverted austenite by lowering the temperature and formed at a lower temperature. The stability of the inverted austenite is improved, thereby reducing the hardness of the steel (can be reduced to below 27HRC), and ensuring the excellent resistance to sulfide stress corrosion cracking of the steel under the partial pressure of hydrogen sulfide of 0.01 MPa. Further, by adding V (preferably satisfying V:(C+N)=2:1 to 8:1, wherein V, C, and N respectively represent the mass percentage of the corresponding element), vanadium carbonitride is precipitated during the tempering process. The interstitial effect of carbon and nitrogen atoms in the crystal structure is reduced, and the impact toughness at a temperature of -20 ° C is improved.

The present invention has been completed based on the above findings. The main design principle of each chemical element in the steel for martensitic stainless steel oil casing which is resistant to hydrogen sulfide stress corrosion cracking according to the present invention is as follows:

C: C is an austenite forming element in martensitic stainless steel. By increasing the C content, the percentage of austenitizing of stainless steel at a high temperature can be increased, and then martensite at room temperature can be obtained, thereby increasing the strength. However, when the C content is too large, the corrosion resistance of the stainless steel is lowered and the toughness is lowered. In order to secure the desired strength, the C mass percentage is preferably 0.003% or more, but when it is 0.05% or more, the toughness and the corrosion resistance are liable to lower.

Si:Si is an important deoxidizer in the steelmaking process, but Si has the risk of promoting the formation of σ phase and ferrite phase in stainless steel with high Cr content, and the toughness and corrosion resistance of σ phase and ferrite relative to stainless steel. Performance has an adverse effect. Therefore, the Si mass percentage is limited to 0.1 to 0.2%.

Mn: Mn can increase the strength of the stainless steel. In the present invention, in order to ensure that the produced oil sleeve has the required strength, the mass percentage of Mn is not less than 0.2%. However, when the mass percentage of Mn exceeds 1.0%, the toughness decreases. Therefore, the mass percentage of Mn is limited to the range of 0.2 to 1.0%, preferably 0.2 to 0.5%.

Cr:Cr is an important element for improving the corrosion resistance of stainless steel. The addition of Cr enables the surface of stainless steel to form a corrosion-resistant passivation film even in the air, improving the CO resistance of the produced oil casing under high temperature environment. ₂ corrosion performance. In order to obtain a CO ₂ corrosion resistance having a temperature of 150 ° C or more, the mass percentage of Cr in the stainless steel of the present invention is not less than 11.0%. On the other hand, if the mass percentage of Cr exceeds 14.0%, the risk of ferrite precipitation increases, which adversely affects the hot workability and corrosion resistance of the product. Therefore, the mass percentage of the defined Cr is in the range of 11.0 to 14.0%, preferably 11.5 to 13.5%.

Ni: Ni expands the austenite region and improves the corrosion resistance and toughness of stainless steel, especially the ability to resist stress corrosion cracking under high temperature conditions. In order to obtain this effect, the mass percentage of Ni is defined to be not less than 4.0%. However, Ni is also a relatively expensive alloying element, and in the case where the mass percentage of Ni in the stainless steel of the present invention exceeds 7%, an austenite phase in which strength cannot be controlled by heat treatment occurs in the structure, and the strength is lowered. Therefore, the mass percentage of Ni is limited to be in the range of 4.0 to 7.0%, preferably 4.5 to 6.5%.

Mo: Mo is an element that increases the resistance of stainless steel to Cl ^- pitting, especially in high temperature environments above 150 °C. In the present invention, the mass percentage of Mo is not less than 1.5%. However, Mo is a noble metal element, and in the present invention, if the mass percentage of Mo exceeds 2.5%, a large amount of ferrite is formed, which adversely affects the hot workability and corrosion resistance of the product. Therefore, the mass percentage of Mo is limited to the range of 1.5 to 2.5%, preferably 1.8 to 2.3%.

N: N is an element for improving the pitting resistance of stainless steel, and N as an austenite forming element can increase the martensite ratio of the stainless steel of the present invention and thereby increase the strength. In order to achieve this effect, the present invention limits the mass percentage of N to not less than 0.001%. However, when the mass percentage of N exceeds 0.10%, nitride is easily formed to lower the toughness. Therefore, the mass percentage of N is limited to the range of 0.001 to 0.10%.

V: V is an important microalloying element, which can generally be pinned by carbonitride precipitation. Refine the grain and increase the strength. In the present invention, it is also found that the addition of V can precipitate vanadium carbonitride during the tempering process, thereby reducing the interstitial interaction of carbon and nitrogen in the crystal structure of the steel, reducing the hardness of the steel and improving the low temperature (such as -20). Impact toughness at °C). In order to achieve this effect, it is necessary to limit the mass percentage of V to not less than 0.03%. On the other hand, if the mass percentage of V exceeds 0.6%, the toughness is lowered.

Al: Al is added as a deoxidizer in the smelting process, and in order to achieve the effect of deoxidation, the mass percentage of Al is not less than 0.01%. However, when the mass percentage of Al exceeds 0.04%, the toughness decreases. Therefore, the mass percentage of the defined Al is in the range of 0.01 to 0.04%.

O: O is an inevitable impurity and exists as an oxide in steel, which adversely affects the hot workability, impact toughness and corrosion resistance of steel. Therefore, the mass percentage of the defined O is 0.004% or less.

P: P is an unavoidable impurity and is a harmful element which lowers the corrosion resistance against CO _{2 at a} high temperature, and has an adverse effect on hot workability. If the mass percentage of P exceeds 0.03%, the corrosion resistance performance cannot meet the high temperature environmental requirements. Therefore, the mass percentage of the definition P is in the range of 0.03% or less, preferably 0.015% or less.

S: S is an unavoidable impurity and is a harmful element which causes a decrease in hot workability while adversely affecting impact toughness. If the content of S exceeds 0.01%, the steel pipe cannot be manufactured normally. Therefore, the mass percentage of S is limited to 0.01% or less, preferably 0.005% or less.

The invention can produce a martensitic stainless steel oil casing resistant to hydrogen sulfide stress corrosion cracking by using stainless steel based on the above scheme, and the oil casing can be used for H ₂ S with a partial pressure of 0.01 MPa and a high concentration of CO ₂ and Cl. ^- coexisting in oil and gas wells of crude oil or natural gas in a highly corrosive environment, and has excellent resistance to sulfide stress corrosion cracking, high temperature corrosion resistance to carbon dioxide and chloride ions, and excellent low temperature impact toughness in this environment. At the same time, it also has a yield strength of 95ksi, which meets the corresponding corrosion resistance and mechanical properties.

Further, in the steel for martensitic stainless steel oil casing of the present invention, V:(C+N)=2:1 to 8:1 is also satisfied, wherein V, C, and N respectively represent the mass percentage of the corresponding element ( For example, when the V content is 0.1%, the value corresponding to V substitution in the formula should be 0.1 instead of 0.001) to achieve the aforementioned better effect of lowering the hardness.

Preferably, in the steel for martensitic stainless steel oil casing according to the present invention, Mn is 0.2 to 0.5%.

Preferably, in the steel for martensitic stainless steel oil casing described in the above or above, 0.003% < C ≤ 0.05%.

Another object of the present invention is to provide an oil casing which can be used for a crude oil or natural gas in a highly corrosive environment in which a partial pressure of 0.01 MPa of H ₂ S and a high concentration of CO ₂ , Cl ^- and the like coexist. In oil wells and gas wells, the corresponding corrosion resistance and mechanical properties can be met in this environment.

Based on the above object, the present invention provides an oil casing which is obtained by using a martensitic stainless steel oil casing of any of the above aspects.

Further, the oil casing of the present invention has a yield strength of more than 655 MPa, and has the ability to withstand hydrogen sulfide stress corrosion cracking in an environment in which the partial pressure of hydrogen sulfide reaches 0.01 MPa.

Further, the oil casing of the present invention has a yield strength of more than 655 MPa, and has the ability to resist hydrogen sulfide stress corrosion cracking in an environment where the partial pressure of hydrogen sulfide reaches 0.01 MPa, and the -20 ° C low temperature toughness impact work. More than 100J.

It is still another object of the present invention to provide a method of manufacturing the above oil casing.

Based on the above object, the present invention provides a method of manufacturing an oil casing of any of the above aspects, which comprises the steps of:

(1) manufacturing a tube blank;

(2) rolling the tube blank into a seamless steel pipe;

(3) Heat treatment of seamless steel pipes according to the following steps:

(3a) quenching to form a martensite structure;

(3b) First tempering: heating the seamless steel pipe to the T1 temperature for the first tempering, T1 is 600 ° C - 670 ° C;

(3c) Second tempering: a second tempering at T2 temperature, T2 = T1 - 40 °C.

In the method for manufacturing the oil casing of the present invention, in the step (1), a conventional melting method such as a converter, an electric furnace, a vacuum induction furnace, or the like may be used, and the tube blank is produced by continuous casting, ingot casting, and the like; In the step (2), the tube blank can be rolled into a seamless steel pipe of a predetermined size by a conventional Mannesmann tube rolling machine; the first tempering in the step (3b) is to ensure that the stainless steel tube has Excellent low temperature impact toughness. After the first tempering, inverted austenite is formed at the martensite lath boundary. Partially inverted austenite will undergo martensite transformation during the cooling process due to the higher temperature formed, forming secondary martensite. The second tempering in the step (3c) can help the transformation of the secondary martensite formed in the first tempering to form a new inverted austenite, reduce the hardness of the steel, and improve the sulfurization under the hydrogen sulfide resistant environment. Material stress corrosion cracking ability and impact toughness.

Further, in the above method of manufacturing the oil casing, in the step (3a), the seamless steel pipe is to be It is heated to a temperature above AC3 for quenching, and then cooled to below 100 °C.

In the above embodiment, if the heating is performed below AC3, the stainless steel of the present invention cannot be sufficiently austenitized, so that a sufficient martensite structure cannot be obtained during the cooling process, so that the strength of the steel pipe is lowered, and then the back is reduced. The toughness obtained by fire treatment is insufficient.

Preferably, in the method for manufacturing the oil casing, in the step (3a), the seamless steel pipe is heated to a temperature above AC3, below 1000 ° C, and then seamlessly cooled at a cooling rate of 10-100 ° C/min. The steel pipe is cooled to below 100 °C.

In the above embodiment, it is preferable to perform heating in a temperature range of 1000 ° C or lower because the austenite structure grows when the quenching heating temperature is higher than 1000 ° C, and the impact toughness is further deteriorated.

detailed description

The steel, oil casing and the manufacturing method thereof for the hydrogen sulfide stress corrosion cracking resistant martensitic stainless steel oil casing according to the present invention will be further explained and explained below with reference to specific embodiments. However, the explanation and description are not correct. The technical solution of the invention constitutes an undue limitation.

Examples 1-16 and Comparative Examples 1-8

The oil casings in the above examples and comparative examples were prepared by the following steps:

(1) manufacturing a tube blank: casting molten steel corresponding to each of the examples and comparative components in Table 1 into a round ingot;

(2) Rolling the tube billet into a seamless steel tube: using a small rolling mill to make the round ingot perforated tube into a steel tube and then air-cooling to make a seamless steel tube with an outer diameter of 73.02 mm and a wall thickness of 7.01 mm;

(3) Heat treatment of seamless steel pipes according to the following steps:

(3a) quenching: heating the seamless steel pipe to a temperature above AC3, below 1000 ° C, and then cooling the seamless steel pipe to below 100 ° C with a cooling rate of 10-100 ° C / min or more to form a martensite structure;

(3b) The first tempering: heating the seamless steel pipe to the temperature of T1 for the first tempering, T1 is 600 ° C - 670 ° C, holding time 40 min;

(3c) Second tempering: a second tempering at T2 temperature, T2 = T1 - 40 ° C, holding time 40 min.

Table 1 above lists the mass ratio of each chemical element of the steel for oil casing of the examples and the comparative examples, and the value of the formula V: (C+N), in which V, C, and N respectively represent the corresponding elements Percentage of mass. The underlined values in Table 1 indicate that the values are outside the scope of the invention.

Table 2 lists the specific process parameters of the manufacturing methods of the examples and comparative examples and the performance test results of the examples and comparative examples.

Table 2

In the above Table 2, Comparative Examples 1-4 correspond to the steel species components of Comparative Examples 1-4 in Table 1, respectively, and Comparative Examples 5-8 correspond to the masses of the chemical elements using Examples 1-4 in Table 1, respectively. The distribution ratio, in order to prove the influence of the process on the effect of the present invention, the manufacturing method of Comparative Examples 5-8 did not implement the step (3c).

In Table 2 above, the performance test results are from the following tests:

(1) Strength test: The prepared seamless steel pipe is processed into an API curved sample, and the average is obtained after testing according to the API standard, and YS (yield strength) and TS (tensile strength) are obtained.

(2) Impact toughness test: The impact toughness is characterized by Charpy V-type impact absorption work, and the V-type impact specimen with a volume of 5*10*55 (mm) is taken on the seamless steel pipe, and the test temperature is -20 °C. According to the AGB/T229 standard, the average is taken and converted to 10*10*55 (mm) full size according to the API5CT standard to obtain the impact toughness at -20 °C.

(3) Hardness test: The hardness test of the cross section of the seamless steel pipe was carried out by a Rockwell hardness tester at a test temperature of -20 ° C, and the average of the three hardness points was obtained to obtain a hardness at -20 ° C.

(4) Corrosion test: The seamless steel pipe sample was immersed in a liquid at 150 ° C in an autoclave, the partial pressure of CO ₂ was 6 MPa, the concentration of Cl ^- was 100000 mg / L, the flow rate of liquid was 1 m / s, and the test time was 240 h. The weight of the sample before and after the test was calculated to obtain a uniform corrosion rate.

(5) SSC (constant load sulfide stress corrosion cracking) test: The SCC test is carried out according to the method A in the GB/T 4157-2006 standard using a stress ring tester. Using a 0.01 MPa H ₂ S gas (the balance being CO ₂ ) and a saturated 25% NaCl solution (pH 4.0), the test temperature was 24 ° C, the test cycle was 720 hours, and the stress test was performed with a minimum specified yield strength of 85%. Each of the examples was tested using three samples, and the samples were inspected after the end of the test period. The results are shown in Table 2, where "√" indicates no crack and "×" indicates crack.

As can be seen from the above Table 2, the oil casings of Examples 1-16 have a strength of YS of 655 MPa or more, satisfying the requirements of 95 ksi steel grade, and the impact toughness of -20 ° C is more than 100 J, and the hardness is below 27 HRC, and is contained at 150 ° C. The uniform corrosion resistance is excellent in the environment of CO ₂ and high Cl ^- concentration, and the SSC test results under the test conditions of 24 ° C also show no sulfide stress corrosion cracking, which is better than the corresponding performance of the oil casing in Comparative Examples 1-8. It has the remarkable advantages of high toughness and high corrosion resistance, and can be used in oil wells and gas wells of crude oil or natural gas under strong corrosive environment where the partial pressure reaches 0.01 MPa of H ₂ S and high concentration of CO ₂ , Cl ^- etc. Corresponding corrosion resistance and mechanical properties are met in this environment.

It is to be noted that the above is only specific embodiments of the present invention, and it is obvious that the present invention is not limited to the above embodiments, and there are many similar variations. All modifications that are directly derived or associated by those of ordinary skill in the art are intended to be within the scope of the invention.

Claims (10)

1. A steel for martensitic stainless steel oil casing resistant to hydrogen sulfide stress corrosion cracking, characterized in that the chemical element mass percentage thereof is:

   0<C≤0.05%, Si: 0.1 to 0.2%, Mn: 0.20 to 1.0%, Cr: 11.0 to 14.0%, Ni: 4.0 to 7.0%, Mo: 1.5 to 2.5%, N: 0.001 to 0.10%, V : 0.03 to 0.6%, Al: 0.01 to 0.04%, and the balance is Fe and other unavoidable impurities.
2. The steel for martensitic stainless steel oil casing according to claim 1, which further satisfies V:(C+N)=2:1 to 8:1, wherein V, C, and N respectively represent the quality of the corresponding element. percentage.
3. The steel for martensitic stainless steel oil casing according to claim 1 or 2, wherein Mn is 0.2 to 0.5%.
4. The steel for martensitic stainless steel oil casing according to claim 1 or 2, wherein 0.003% < C ≤ 0.05%.
5. An oil casing made of steel for a martensitic stainless steel oil casing according to any one of claims 1 to 4.
6. The oil cannula according to claim 5, wherein the yield strength is greater than 655 MPa, and it has the ability to withstand hydrogen sulfide stress corrosion cracking in an environment in which the partial pressure of hydrogen sulfide reaches 0.01 MPa.
7. The oil casing according to claim 5, wherein the yield strength is greater than 655 MPa, and it has the ability to resist hydrogen sulfide stress corrosion cracking in an environment where the partial pressure of hydrogen sulfide reaches 0.01 MPa, and the temperature is -20 ° C. The tough impact energy is greater than 100J.
8. A method of manufacturing an oil cannula according to any of claims 5-7, comprising the steps of:

   (1) manufacturing a tube blank;

   (2) rolling the tube blank into a seamless steel pipe;

   (3) Heat treatment of seamless steel pipes according to the following steps:

   (3a) quenching to form a martensite structure;

   (3b) First tempering: heating the seamless steel pipe to the T1 temperature for the first tempering, T1 is 600 ° C - 670 ° C;

   (3c) Second tempering: a second tempering at T2 temperature, T2 = T1 - 40 °C.
9. The method of manufacturing an oil cannula according to claim 8, wherein in the step (3a), the seamless steel pipe is heated to a temperature equal to or higher than AC3 to be quenched, and then cooled to 100 ° C or lower.
10. A method of manufacturing an oil casing according to claim 9, wherein in said step (3a) In the middle, the seamless steel pipe is heated to a temperature above AC3, below 1000 ° C, and then the seamless steel pipe is cooled to below 100 ° C by a cooling rate of 10-100 ° C / min.