Austenitic stainless steel with high strength and hydrogen sulfide stress corrosion cracking resistance and preparation method of austenitic stainless steel
By optimizing the composition and microstructure in austenitic stainless steel, combined with vacuum arc smelting, solid solution treatment, cold rolling and tempering treatment, the problem of stainless steel being easily corroded in H2S environments is solved, and high-strength and anti-corrosion and cracking properties are achieved, which is suitable for high-performance materials requirements in oil and gas fields.
Patent Information
- Application Number
- CN202510477374.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-16
- Publication Date
- 2025-06-13
AI Technical Summary
Existing stainless steels are prone to stress corrosion and cracking of hydrogen sulfide in oil and gas mining environments containing H2S, resulting in economic losses and safety accidents. Traditional materials are costly and insufficient in strength.
A high-strength austenitic stainless steel that resists stress corrosion cracking with high strength, the components of which include C, Si, Mn, Ni, Cr, Mo, B and Cu were developed. It was prepared by vacuum arc smelting, solid solution treatment, cold rolling and tempering treatment to form a microstructure of 80~95% austenitic and 5~20% martensite.
It achieves high strength and anti-corrosion and cracking properties of stainless steel, with a yield strength of no less than 110 ksi, and is suitable for the production of oil well pipes and meets the needs of oil and gas field development and transportation.
Smart Images
Figure CN120138508A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of stainless steel design and preparation, and particularly relates to an austenitic stainless steel with high strength and resistance to hydrogen sulfide stress corrosion cracking and a preparation method thereof. Background Art
[0002] Energy is closely related to the development of human society. In recent years, the energy resources exploited in the shallow and middle traditional exploration fields have gradually been unable to meet the growing living and working needs. Therefore, the exploitation of oil and gas is tending towards deep oil and gas reservoirs with rich reserves at high temperature, high pressure, and high corrosiveness. As the exploitation environment becomes more severe, the requirements for material performance are more stringent. Since traditional carbon steel and low alloy steel can no longer withstand high-corrosion application scenarios, and in addition, as the exploitation depth increases, the steel for oil well pipes also has to bear the axial tensile stress of its own weight and the circumferential stress of deep gas pressure; in summary, the complex exploitation working condition environment urgently requires high-performance materials.
[0003] Ultra-low-carbon supermartensitic stainless steel has excellent welding performance and is widely used in the petroleum industry. However, the application of high-strength martensite is affected by hydrogen embrittlement, especially in the exploitation environment containing H 2 2S gas, and the application of supermartensitic stainless steel is restricted. Standards indicate that martensitic stainless steel can only be used under the condition that the H 2 2S partial pressure is less than 10 kPa. The use of duplex stainless steel in acidic oil fields has a long history, but this duplex stainless steel contains a large amount of high-value Cr, Ni, Mo alloying elements, making its cost expensive, and due to its low strength, the diameter needs to be increased when reaching the use conditions, resulting in higher use costs.
[0004] The high corrosion resistance and easy processing characteristics of austenitic stainless steel are widely used in the oil and gas field. Its relatively high work hardening rate and diverse strength and toughness means provide more possibilities. In the oil and gas exploitation environment containing H 2 2S, the oil casing is prone to hydrogen sulfide stress corrosion cracking during use, which will cause significant economic losses to the oil field and also result in serious safety accidents. Therefore, developing stainless steel with good resistance to hydrogen sulfide stress corrosion cracking has important research significance and application value. Summary of the Invention
[0005] To solve the existing technical problems, the present invention aims to meet the requirements of a seamless steel with high strength, high toughness, and resistance to hydrogen sulfide stress corrosion cracking, whose yield strength is not less than 110 ksi, that is, the yield strength is not less than 750 MPa, its austenitic structure is stable, and at the same time, the stainless steel has high strength and resistance to hydrogen sulfide stress corrosion cracking performance.
[0006] The present invention provides an austenitic stainless steel with high strength and resistance to sulfide stress corrosion cracking. The composition elements and mass percentages of the austenitic stainless steel are as follows: C: 0.01 - 0.08%, Si: 0.10 - 0.50%, Mn: 0.20 - 0.80%, Ni: 4.00 - 10.00%, Cr: 10.00 - 18.00%, Mo: 1.00 - 5.00%, B: 0.001 - 0.010%, Cu: 1.50 - 5.00%, and the balance is Fe element and inevitable impurities.
[0007] Preferably, the microstructure of the austenitic stainless steel consists of 80 - 95% austenite and 5 - 20% martensite.
[0008] The present invention also provides a preparation method for an austenitic stainless steel with high strength and resistance to sulfide stress corrosion cracking. The preparation method includes: Step 1: Melting to obtain an ingot according to the above composition elements and ratio, and forging it into a square billet; Step 2: Subjecting the square billet to solution treatment, and obtaining an austenitic stainless steel sheet after cold rolling; Step 3: Tempering the austenitic stainless steel sheet to obtain an austenitic stainless steel with high strength and resistance to sulfide stress corrosion cracking.
[0009] Preferably, a vacuum arc melting is used to obtain the ingot in Step 1.
[0010] Preferably, the solution treatment in Step 2 includes putting the square billet into a box furnace, holding it at 1000 - 1050 °C for 4 h, and water - cooling it to room temperature.
[0011] Preferably, the cold rolling process in Step 2 is to perform cold rolling at room temperature on the solution - treated square billet on a rolling mill, and the cold rolling reduction is 50 - 75%.
[0012] Preferably, the tempering process in Step 3 is to put the austenitic stainless steel sheet into a box furnace, hold it at 600 - 750 °C for 10 - 60 min, and air - cool it.
[0013] Compared with the prior art, the present invention has the following beneficial effects: The austenitic stainless steel with high strength and resistance to sulfide stress corrosion cracking prepared by the present invention has a yield strength of not less than 110 ksi, its austenite structure is stable, and at the same time, the stainless steel has high strength and resistance to sulfide stress corrosion cracking. The prepared austenitic stainless steel can be widely used in the production of oil well pipes resistant to sulfide stress corrosion, meeting the relevant requirements of oil and gas field development and transportation. Brief Description of the Drawings
[0014] Figure 1It is the EBSD contrast image of the austenitic stainless steel with high strength and resistance to hydrogen sulfide stress corrosion cracking provided by Embodiment 1 of the present invention.
[0015] Figure 2 It is the microstructure of the fine grain region observed by TEM of the austenitic stainless steel with high strength and resistance to hydrogen sulfide stress corrosion cracking provided by Embodiment 1 of the present invention. Among them, (a) is the TEM bright field image of this fine grain region, and (b) is the HRTEM image of the Cu-rich precipitation phase.
[0016] Figure 3 It is the element distribution result of the fine grain region of the austenitic stainless steel with high strength and resistance to hydrogen sulfide stress corrosion cracking provided by Embodiment 1 of the present invention. Among them, (a) is the TEM bright field image of the fine grain region, (b) is the Cu element distribution map, and (c) is the Ni element distribution map. Detailed implementation manners
[0017] In order to make the objectives, technical solutions and advantages of the embodiments of the present disclosure clearer, the technical solutions of the embodiments of the present disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present disclosure, rather than all of the embodiments. Based on the described embodiments of the present disclosure, all other embodiments obtained by those skilled in the art without creative efforts also fall within the scope of protection of the present disclosure.
[0018] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those skilled in the art to which the subject matter of the present disclosure belongs. It will be further understood that terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the specification and the relevant art, and will not be interpreted in an idealized or overly formal form unless otherwise clearly defined herein.
[0019] Referring to "embodiments" herein means that the specific features, structures or characteristics described in connection with the embodiments can be included in at least one embodiment of the present application. The phrase "embodiments" appearing in various positions in the specification does not necessarily refer to the same embodiment, nor are they independent or alternative embodiments mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.
[0020] An austenitic stainless steel with high strength and resistance to hydrogen sulfide stress corrosion cracking provided by the present invention, the composition elements and mass percentages of the austenitic stainless steel are as follows: C: 0.01 - 0.08%, for example, it can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%; Si: 0.10 - 0.50%, for example, it can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%; Mn: 0.20 - 0.80%, for example, it can be 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%; Ni: 4.00 - 10.00%, for example, it can be 4.0%, 5.0%, 6.0%, 7.0%, 8.0%, 10.0%; Cr: 10.00 - 18.00%, for example, it can be 10.0%, 11.0%, 12.0%, 13.0%, 14.0%, 15.0%, 16.0%, 17.0%, 18.0%; Mo: 1.00 - 5.00%; B: 0.001 - 0.010%, for example, it can be 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%; Cu: 1.50 - 5.00%, for example, it can be 1.5%, 2.0%, 3.0%, 4.0%, 4.3%, 4.5%, 4.8%, 5.0%; the balance is Fe element and inevitable impurities.
[0021] In some embodiments of the present invention, adding Cr and Ni elements increases the corrosion resistance of the austenitic stainless steel and improves the hydrogen embrittlement resistance. Ni and Cu elements enhance the stability of the austenite, making it mainly austenite-based. In addition, the Cu element added in the present invention, on the one hand, is used to precipitate a Cu-rich phase in the fine grain region of the stainless steel, and the precipitation region is concentrated at the grain boundaries and within the martensite grains, improving the overall strength of the stainless steel. On the other hand, the solid solubility of the Cu element in the austenite phase is much greater than that in the martensite and ferrite phases. During the service of the austenitic stainless steel, a copper-containing passive film is formed on the surface of the pipe, preventing hydrogen from entering the stainless steel pipe and further improving the hydrogen sulfide stress corrosion cracking resistance of the austenitic stainless steel.
[0022] In some embodiments of the present invention, the microstructure of the austenitic stainless steel consists of 80 - 95% austenite and 5 - 20% martensite; that is, the microstructure is an organization with austenite phase as the matrix and a small amount of martensite phase as the second phase.
[0023] A preparation method of an austenitic stainless steel with high strength and resistance to hydrogen sulfide stress corrosion cracking provided by the present invention, the preparation method includes, Step 1: Obtain an ingot by vacuum arc melting according to the above composition elements and ratios, and forge it into a square billet. In some embodiments of the present invention, the process of forging the ingot into a square billet is carried out using existing conventional methods for forging, and it is only necessary to forge it into a square billet, and the method is not limited.
[0024] Step 2: Place the square billet in a box furnace for solution treatment, keep it at 1000 - 1050 °C for 4 h, cool it to room temperature with water, and obtain an austenitic stainless steel sheet after cold rolling; among them, the cold rolling is carried out at room temperature on a rolling mill, and the cold rolling reduction is preferably 50 - 75%, for example, the cold rolling reduction can be 50%, 55%, 60%, 65%, 70%, 75%.
[0025] Step 3: Place the austenitic stainless steel sheet in a box furnace for tempering treatment, at a temperature preferably of 600 - 750 °C, for example, the temperature can be 600 °C, 630 °C, 650 °C, 700 °C, 730 °C, 750 °C; preferably keep it warm for 10 - 60 min, for example, it can be 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, and air-cool to obtain an austenitic stainless steel with high strength and resistance to hydrogen sulfide stress corrosion cracking.
[0026] In some embodiments of the present invention, by implementing cold rolling at room temperature, in the matrix of the austenitic stainless steel, some unstable retained austenite with lower Ni or Cu content undergoes martensitic transformation, and the martensite generated by the transformation will further enhance the overall strength of the austenitic stainless steel, and at the same time provide nucleation sites for the formation of reverse austenite during the subsequent tempering process; through the tempering treatment, part of the martensite will be reversed into reverse austenite, so that the microstructure of the finally formed austenitic stainless steel contains 80 - 95% austenite and 5 - 20% martensite.
[0027] The following further illustrates the present invention through specific embodiments.
[0028] Example 1
[0029] An austenitic stainless steel with high strength and resistance to hydrogen sulfide stress corrosion cracking in this example is composed of the following components by mass percentage: C: 0.05%; Si: 0.3%; Mn: 0.65%; Cr: 15.00%; Ni: 8.00%; Mo: 2.00%; Cu: 3.00%; B: 0.003%; the balance is Fe element and unavoidable impurities.
[0030] The preparation process of a high-strength austenitic stainless steel resistant to hydrogen sulfide stress corrosion cracking in this embodiment is as follows. According to the mass percentage of the components of the target steel, a 50-kg steel ingot is obtained by vacuum arc melting. After cutting off the riser, the steel ingot is forged into a square billet with dimensions of 80×80×1200 mm. Subsequently, the square billet is placed in a box furnace for solution treatment at 1000 °C for 4 h, and then water-cooled to room temperature to obtain a tissue that is free of shrinkage cavities and porosity and is uniform and dense. Subsequently, the solution-treated square billet is cold-rolled at room temperature on a rolling mill with a reduction of 50%. The cold-rolled sheet is annealed at 600 °C for 1 h and then air-cooled to obtain a high-strength austenitic stainless steel resistant to hydrogen sulfide stress corrosion with an austenite content of 92%.
[0031] Figure 1 is the EBSD contrast image of a high-strength austenitic stainless steel resistant to hydrogen sulfide stress corrosion cracking in this embodiment. The tissue consists of austenite in the coarse-grained region, reverse austenite in the fine-grained region, and a small amount of martensite.
[0032] Figure 2 are the TEM bright-field image and HETEM characterization of the Cu-rich phase of a high-strength austenitic stainless steel resistant to hydrogen sulfide stress corrosion cracking in this embodiment. Among them, the fine-grained region consists of reverse austenite and martensite. At the same time, Cu-rich precipitates can be found inside and at the grain boundaries of the martensite.
[0033] Figure 3 is the SEM image of a high-strength austenitic stainless steel resistant to hydrogen sulfide stress corrosion cracking in this embodiment. Among them, Cu and Ni elements are enriched inside the austenite grains, indicating that Cu and Ni elements are austenite stabilizing elements in the present invention. Since the austenite content in the present invention is 92%, it shows that these two elements have extremely high solid solubility in the matrix.
[0034] Through the mechanical property experimental data in Table 1, the mechanical properties of the steel in this embodiment meet the requirements of the 110 ksi level. An anti-SCC experiment is carried out. The anti-hydrogen sulfide stress corrosion is carried out according to the NACE TM0177-2016 standard using Method A. Under a constant load of 80% * 750 MPa (110 ksi level), the specimen does not crack after 720 hours, and at the same time, no SSC cracks are visually observed under a 10-fold magnifying glass.
[0035] Example 2
[0036] A high-strength austenitic stainless steel resistant to hydrogen sulfide stress corrosion cracking in this embodiment is composed of the following components by mass percentage: C: 0.05%; Si: 0.3%; Mn: 0.65%; Cr: 15.00%; Ni: 8.00%; Mo: 2.00%; Cu: 3.00%; B: 0.003%; the balance is Fe element and inevitable impurities.
[0037] In this embodiment, the preparation process of a high-strength austenitic stainless steel resistant to hydrogen sulfide stress corrosion cracking is as follows. According to the component mass percentages of the target steel, a 50-kg ingot is obtained by vacuum arc melting. After cutting off the riser, the ingot is forged into a square billet with dimensions of 80×80×1200 mm. Subsequently, the square billet is placed in a box furnace for solution treatment at 1000 °C for 4 h, and then water-cooled to room temperature to obtain a non-porous, non-shrinkage cavity, uniform and dense structure. Subsequently, the solution-treated square billet is cold-rolled at room temperature on a rolling mill with a reduction of 75%. The cold-rolled sheet is annealed at 720 °C for 10 min and then air-cooled to obtain a high-strength austenitic stainless steel with a mixed structure of austenite and martensite phases. Compared with the stainless steel in Example 1, the difference in the structure is the difference in the relative contents of austenite and martensite phases. In this embodiment, the austenite content is 81%.
[0038] Based on the mechanical property experimental data in Table 1, the mechanical properties of the steel in this embodiment meet the requirements of the 125 ksi grade. For the SCC resistance test, for the hydrogen sulfide stress corrosion resistance, according to the NACE TM0177-2016 standard, Method A is adopted. Under a constant load of 80% * 850 MPa (125 ksi grade), the specimen does not crack after 720 hours, and at the same time, no SSC cracks are visually observed under a 10-fold magnifying glass.
[0039] Example 3
[0040] A high-strength austenitic stainless steel resistant to hydrogen sulfide stress corrosion cracking in this embodiment is composed of the following components by mass percentage: C: 0.05%; Si: 0.3%; Mn: 0.65%; Cr: 15.00%; Ni: 8.00%; Mo: 2.00%; Cu: 4.50%; B: 0.003%; the balance is Fe element and inevitable impurities.
[0041] In this embodiment, the preparation process of a high-strength austenitic stainless steel resistant to hydrogen sulfide stress corrosion cracking is as follows. According to the component mass percentages of the target steel, a 50-kg ingot is obtained by vacuum arc melting. After cutting off the riser, the ingot is forged into a square billet with dimensions of 80×80×1200 mm. Subsequently, the square billet is placed in a box furnace for solution treatment at 1000 °C for 4 h, and then water-cooled to room temperature to obtain a non-porous, non-shrinkage cavity, uniform and dense structure. Subsequently, the solution-treated square billet is cold-rolled at room temperature on a rolling mill with a reduction of 50%. The cold-rolled sheet is annealed at 600 °C for 1 h and then air-cooled to obtain an austenite-based high-strength austenitic stainless steel resistant to hydrogen sulfide stress corrosion. Compared with the stainless steel in Example 1, the difference in the structure is the difference in the relative contents of austenite and martensite phases. In this embodiment, the austenite content is 94%.
[0042] Based on the mechanical property experimental data in Table 1, the mechanical properties of the steel in this embodiment meet the requirements of the 110 ksi grade. The SCC resistance test was carried out. For the resistance to hydrogen sulfide stress corrosion, according to the NACE TM0177-2016 standard, Method A was used. Under a constant load of 80% * 750 MPa (110 ksi grade), the specimen did not crack after 720 hours, and at the same time, no SSC cracks were visually observed under a 10-fold magnifying glass.
[0043] Comparative Example 1 An austenitic stainless steel in this comparative example is composed of the following components by mass percentage: C: 0.08%; Si: 0.3%; Mn: 0.65%; Cr: 15.00%; Ni: 8.00%; Mo: 2.00%; Cu: 1.00%; Nb: 0.05%; the balance is Fe element and inevitable impurities.
[0044] The preparation process of a high-strength austenitic stainless steel resistant to hydrogen sulfide stress corrosion cracking in this embodiment is as follows: According to the component mass percentage of the target steel, a 50-kg steel ingot was obtained by vacuum arc melting. After cutting off the riser, the steel ingot was forged into a square billet with dimensions of 80×80×1200 mm. Subsequently, the square billet was placed in a box furnace for solution treatment at 1050 °C for 4 h, and then water-cooled to room temperature to obtain a uniform and dense structure without shrinkage cavities and porosity. Subsequently, the solution-treated square billet was cold-rolled at room temperature on a rolling mill, and the reduction of the rolling mill was 80%. The cold-rolled sheet was annealed at 700 °C for 30 min and then air-cooled to obtain a stainless steel with a mixed structure of austenite and martensite phases, in which the austenite content was 86%.
[0045] Based on the mechanical property experimental data in Table 1, the mechanical properties of the steel in this embodiment meet the requirements of the 110 ksi grade. The SCC resistance test was carried out. For the resistance to hydrogen sulfide stress corrosion, according to the NACE TM0177-2016 standard, Method A was used. Under a constant load of 80% * 750 MPa (110 ksi grade), the specimen cracked after 720 hours.
[0046] Table 1 Summary Table of Mechanical Property Tests
[0047] The above-given embodiments are the preferred examples for implementing the present invention, and the present invention is not limited to the above embodiments. Any non-essential addition or replacement made by those skilled in the art based on the technical features of the technical solution of the present invention falls within the protection scope of the present invention.
Claims
1. A high-strength austenitic stainless steel resistant to hydrogen sulfide stress corrosion cracking, characterized in that: The constituent elements and mass percentages of the austenitic stainless steel are: C: 0.01-0.08%, Si: 0.10-0.50%, Mn: 0.20-0.80%, Ni: 4.00-10.00%, Cr: 10.00-18.00%, Mo: 1.00-5.00%, B: 0.001-0.010%, Cu: 1.50-5.00%, and the remainder is Fe element and unavoidable impurities.
2. The high-strength austenitic stainless steel resistant to hydrogen sulfide stress corrosion cracking according to claim 1, characterized in that: The microstructure of the austenitic stainless steel consists of 80-95% austenite and 5-20% martensite.
3. A method for preparing high-strength austenitic stainless steel resistant to hydrogen sulfide stress corrosion cracking, characterized in that: The preparation method comprises: Step 1, smelting to obtain a steel ingot according to the constituent elements and proportions of claim 1, and forging it into a square billet; Step 2: subjecting the square billet to solution treatment and cold rolling to obtain an austenitic stainless steel sheet; Step 3: Tempering the austenitic stainless steel plate to obtain high-strength austenitic stainless steel that is resistant to hydrogen sulfide stress corrosion cracking.
4. The method for preparing a high-strength austenitic stainless steel resistant to hydrogen sulfide stress corrosion cracking according to claim 3, characterized in that: In step 1, vacuum arc melting is used to obtain a steel ingot.
5. The method for preparing a high-strength austenitic stainless steel resistant to hydrogen sulfide stress corrosion cracking according to claim 3, characterized in that: The solution treatment in step 2 includes placing the billet in a box furnace, keeping it at 1000-1050° C. for 4 hours, and cooling it to room temperature with water.
6. The method for preparing a high-strength hydrogen sulfide stress corrosion cracking resistant austenitic stainless steel according to claim 3, characterized in that: The cold rolling process in step 2 is to cold roll the solution treated billet on a rolling mill at room temperature, with the cold rolling amount being 50-75%.
7. The method for preparing a high-strength austenitic stainless steel resistant to hydrogen sulfide stress corrosion cracking according to claim 3, characterized in that: The tempering process in step 3 is to place the austenitic stainless steel plate into a box furnace, keep it at 600-750° C. for 10-60 minutes, and air cool it.