Austenitic stainless steel and seamless tube thereof, and preparation method and application of seamless tube

Abstract

The invention relates to the technical field of stainless steel and manufacturing thereof, in particular to austenitic stainless steel and a seamless tube thereof, and a preparation method and application of the seamless tube. The austenitic stainless steel provided by the invention comprises the following chemical components in percentage by weight: less than or equal to 0.06% of C, less than or equal to 1.0% of Si, less than or equal to 0.025% of P, less than or equal to 0.015% of S, 4.5%-7.0% of Mn, 21.5%-23.5% of Cr, 12.5%-14.5% of Ni, 1.5%-3.0% of Mo, 0.2%-0.4% of Nb, 0.2%-0.4% of V, 0.2%-0.5% of N and the balance of Fe. And the balance of Fe and other inevitable impurities. According to the austenitic stainless steel, three strengthening mechanisms of solid solution strengthening of N, precipitation strengthening of Nb and V carbonitride and grain refining are utilized, so that the prepared austenitic stainless steel has better flexibility, strength and the like in a room-temperature use environment, and can still keep good mechanical properties in high and low-temperature environments; and the problem of material selection in an extreme use environment at present is solved.

Description

Technical Field

[0001] The invention relates to the technical field of stainless steel and its manufacturing, and in particular to austenitic stainless steel and its seamless pipe, and a preparation method and application of the seamless pipe. Background Art

[0002] Stainless steel has excellent mechanical properties such as corrosion resistance, flexibility and impact resistance, and some users hope to use these excellent mechanical properties of stainless steel to achieve corresponding usage goals in many extreme usage environments (especially ultra-high and low temperature environments). However, traditional austenitic stainless steel materials and their products are difficult to maintain high mechanical properties in extreme usage environments.

[0003] Among them, the specific reasons for the performance degradation of traditional austenitic stainless steel materials mainly include: in high temperature environment, the grains of traditional austenitic stainless steel are easily promoted by high temperature and grow, and the coarsening caused by grain growth will reduce the tensile strength and creep resistance of austenitic stainless steel, and reduce its mechanical properties at high temperature; in low temperature environment, traditional austenitic stainless steel is prone to brittle fracture and other phenomena, resulting in its flexibility and impact resistance. It is difficult to meet the corresponding use requirements.

[0004] Therefore, there is an urgent need for an austenitic stainless steel that is resistant to high and low temperatures, has high strength and high toughness, which not only has better mechanical properties than traditional austenitic stainless steel materials at room temperature (generally 23°C), but also maintains better mechanical properties than traditional austenitic stainless steel materials in high and low temperature environments. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide an austenitic stainless steel to solve the material selection problem in the current extreme use environment. The austenitic stainless steel can have better mechanical properties than traditional austenitic stainless steel at both room temperature (23°C) and high temperature environment (650°C), and still have higher strength and toughness at low temperature environment (-269°C).

[0006] The present invention is achieved through the following technical solutions.

[0007] An austenitic stainless steel, characterized in that the chemical composition by weight percentage is: C≤0.06%, Si≤1.0%, P≤0.025%, S≤0.015%, Mn: 4.5%~7.0%, Cr: 21.5%~23.5%, Ni: 12.5%~14.5%, Mo: 1.5-3.0%, Nb: 0.2%~0.4%, V: 0.2%~0.4%, N: 0.2%~0.5%; the balance is Fe and other inevitable impurities.

[0008] Among them, C is often regarded as a harmful element in austenite because it forms a high-chromium Cr 23 C6 causes local chromium depletion in the steel, thereby reducing the corrosion resistance of the steel, especially the intergranular corrosion resistance. Therefore, the C content is strictly limited in the present invention.

[0009] Si can improve the ability to form oxide film on the surface of austenitic stainless steel and improve the corrosion resistance of the alloy. At the same time, Si can reduce the stacking fault energy of steel, increase dislocation slip resistance, and make deformation twins easier to form, thereby increasing the strength of steel. However, excessive Si may affect the organizational structure and mechanical properties of steel, so its dosage needs to be controlled.

[0010] Both P and S are regarded as harmful elements in steel, wherein P easily causes segregation and cold brittleness, while S easily causes hot brittleness, so both are strictly controlled in the present invention.

[0011] Mn is a good deoxidizer and desulfurizer, which can improve the strength and hardness of steel. In austenitic stainless steel, the addition of Mn helps to expand the austenite zone and improve the hardenability of steel. However, too high Mn content may also reduce the corrosion resistance of steel, especially the resistance to pitting and intergranular corrosion.

[0012] Cr is one of the most important alloying elements in austenitic stainless steel, and its main function is to improve the corrosion resistance of steel. It can increase the solubility of carbon and reduce the depletion of chromium, thereby improving the intergranular corrosion resistance of steel. However, when the Cr content is too high, on the one hand, it will cause it to react with C to form carbides, affecting the mechanical properties of the steel, and on the other hand, it will greatly increase the manufacturing cost, so its dosage needs to be controlled.

[0013] Ni is one of the main elements that stabilize the austenite structure in austenitic stainless steel. The addition of nickel can significantly improve the plasticity and toughness of steel, while ensuring that the steel has good corrosion resistance. However, too high a Ni content can easily lead to a decrease in the critical carbon content for intergranular corrosion in steel, thereby increasing the intergranular corrosion sensitivity of the steel. In extreme use environments, the possibility of attenuation of the mechanical properties of the steel will increase significantly, so its dosage needs to be controlled.

[0014] The main role of Mo in austenitic stainless steel is to expand its application range and improve the corrosion resistance of steel in reducing media. Mo can also improve the pitting and crevice corrosion resistance of steel. However, when its content is too high, it will reduce the mechanical properties of steel such as flexibility in low temperature environments, so its dosage needs to be controlled.

[0015] Nitrogen in austenitic stainless steel can improve the strength and hardness of steel while maintaining good plasticity and toughness. Nitrogen can also expand the austenite zone and improve the hardenability of steel. However, the addition of nitrogen requires strict control of process conditions to avoid the formation of defects such as nitrogen pores in the steel; and too high a nitrogen content may lead to a decrease in the toughness of the steel.

[0016] The core of the present invention lies in the addition of Nb and V and the control of their dosage.

[0017] Specifically, in order to achieve the characteristics of high and low temperature resistance, high strength and high toughness of the austenitic stainless steel, the present invention mainly relies on the solid solution strengthening of N, the precipitation strengthening of Nb and V carbonitrides and the fine graining.

[0018] Nb and V in the formula are the most commonly used microalloying elements. In steel, their main function is to combine with C and N elements to form carbonitrides. The fine dispersed carbonitrides formed can pin the grain boundaries, so in high temperature environments, they can inhibit the growth of austenite grains; and carbonitrides can also have a precipitation strengthening effect on austenitic steel. This ensures that austenitic stainless steel still retains good mechanical properties in high temperature environments.

[0019] At the same time, the atomic radius of Nb atoms is larger than that of Fe atoms. In addition to existing in the form of precipitated phases, Nb atoms can also exist in the matrix as substitutional solid solution atoms, and they are easily segregated on dislocation lines, exerting a strong drag on dislocation climb, which makes the Nb element alone have a strong grain refinement effect, thereby strengthening the steel; the V element has a large solubility in austenitic stainless steel. Generally, adding V elements to N-containing steels can combine V elements with free N elements in the steel to generate V (C, N), thereby increasing the precipitation strengthening effect of N elements and ultimately improving the strength and toughness of the steel, while the excess V elements can be dissolved in the Mn element and will not affect the performance of the steel. The above combination of these two elements ensures that austenitic stainless steel can obtain better mechanical properties at room temperature. Therefore, under low temperature conditions, even if its performance partially decays, it can still maintain better mechanical properties than traditional austenitic stainless steel and meet the requirements for material performance under the corresponding environment.

[0020] In summary, the good performance of the austenitic stainless steel in the present invention is the product of the combination of three strengthening mechanisms: solid solution strengthening of N, precipitation strengthening of Nb and V carbonitrides, and grain refinement.

[0021] In a second aspect, the present invention provides an austenitic stainless steel seamless pipe, which is prepared from the above-mentioned austenitic stainless steel.

[0022] As a further improvement of the present invention, the average grain size of the austenitic stainless steel seamless pipe is grade 8 or above.

[0023] Fine-grained steel can maintain high strength at high temperatures because grain boundaries hinder dislocations and cracks, allowing the fine-grained structure to more effectively disperse thermal stress at high temperatures and prevent the seamless pipe from softening. The fine-grained structure can also reduce the occurrence of steel creep and maintain the dimensional stability of the seamless pipe. At the same time, the proportion of the steel in the present invention inhibits the growth of its grains in a high-temperature environment, which enables the seamless pipe to maintain the above-mentioned performance advantages in a long-term high-temperature environment.

[0024] Fine-grained steel exhibits better toughness at low temperatures, which is due to the hindering effect of grain boundaries on crack propagation. Fine-grained structure can reduce the occurrence of brittle fracture at low temperatures and improve the impact resistance of seamless pipes. For some seamless pipes that need to withstand corrosive media at low temperatures, fine-grained steel can more effectively prevent the penetration and diffusion of corrosive media and improve the low-temperature corrosion resistance of seamless pipes.

[0025] As a further improvement of the present invention, the tensile strength R of the austenitic stainless steel seamless pipe at room temperature is m ≥800MPa, yield strength R p0.2 ≥400MPa.

[0026] As a further improvement of the present invention, the tensile strength R of the austenitic stainless steel seamless pipe at 650°C is m ≥500MPa, yield strength R p0.2 ≥250MPa.

[0027] As a further improvement of the present invention, the tensile strength R of the austenitic stainless steel seamless pipe at -269°C is m ≥1600MPa, yield strength R p0.2 ≥1200MPa.

[0028] As a further improvement of the present invention, the austenitic stainless steel seamless pipe is prepared into an impact sample with a size of 10×10×55 mm. Under a low temperature environment of -269°C, the impact absorption energy KV2≥80J and the lateral expansion value LE≥0.53mm of the impact sample.

[0029] The above-mentioned performance data of austenitic stainless steel pipes in extreme high and low temperature environments indicate that the austenitic stainless steel pipes can still maintain good mechanical properties, sufficient strength, reliability and safety, and can meet the use requirements of austenitic stainless steel pipes in corresponding environments.

[0030] In a third aspect, the present invention provides a method for manufacturing an austenitic stainless steel seamless pipe, characterized in that the method is used to manufacture the above-mentioned austenitic stainless steel seamless pipe, and comprises the following steps: S1. smelting according to the above-mentioned austenitic stainless steel formula to obtain molten steel, and die casting and forging the molten steel to obtain a round tube blank; S2. hot extruding the round tube blank to prepare a rough tube; S3. performing several consecutive cold workings on the rough tube to prepare an intermediate tube, wherein heat treatment of the tube is arranged between the several cold workings; S4. cold working the intermediate tube to prepare a finished tube, and finally heat treating the finished tube.

[0031] As a further improvement of the present invention, in S3, the deformation amount of the intermediate tube in a single cold working process is 20-80%; and in S4, the deformation amount of the finished tube in cold working process is 15-40%.

[0032] The intermediate pipe undergoes a large amount of cold deformation during the manufacturing process, which can achieve the effect of cold deformation strengthening, help strengthen the microstructure of the intermediate pipe, and improve the mechanical properties of the material, such as strength, hardness and wear resistance. This strengthening effect helps the smooth progress of subsequent processing and improves overall production efficiency and product quality. Compared with the intermediate pipe, the finished pipe undergoes a smaller amount of cold deformation in the later stage of manufacturing because the seamless pipe is close to the final form at the finished product stage. Excessive cold deformation may introduce unnecessary stress and defects, affecting the dimensional accuracy and surface quality of the product. Therefore, controlling the cold deformation of the finished pipe within a reasonable range can ensure the stability and reliability of the product.

[0033] As a further improvement of the present invention, in S3 and S4, the temperature of the heat treatment is ≥1060° C. Heat treatment of seamless pipes after cold working can restore the performance of austenitic stainless steel, eliminate internal stress in seamless pipes, improve the surface quality of seamless pipes, improve the processing performance of seamless pipes, refine the grains of austenitic stainless steel and stabilize the size of seamless pipes, etc. These beneficial effects jointly promote the improvement of seamless pipe quality and processing efficiency.

[0034] In a fourth aspect, the present invention provides an application of the above-mentioned austenitic stainless steel seamless pipe in a pressure vessel or a reactor. The pressure vessel is usually used to store solutions such as liquid nitrogen, so it is an extremely low-temperature use environment for the seamless pipe; and the reactor is usually used for high-temperature heating reaction, so it is an extremely high-temperature use environment for the seamless pipe.

[0035] The beneficial effects of the present invention include: (1) By controlling the type and content of the raw materials, austenitic stainless steel with good flexibility, strength and other mechanical properties at room temperature and high and low temperature environments can be prepared, so that the austenitic stainless steel can meet the requirements of material properties in different use environments; (2) The seamless pipe prepared by using the austenitic stainless steel in the present invention has the above-mentioned excellent mechanical properties, and can therefore be used in equipment including pressure vessels with low-temperature use environments and reactors with high-temperature use environments. The austenitic stainless steel seamless pipe has great market promotion and application value. DETAILED DESCRIPTION

[0036] The present invention is further described in detail below based on implementation cases.

[0037] In order to make the purpose, technical scheme and advantages of the present invention more clear, the present invention is further described in detail in combination with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] Embodiment 1: A method for preparing an austenitic stainless steel seamless pipe with a size of φ7.0×0.6 mm, specifically comprising the following steps: S1. Mix the raw materials according to the formula of austenitic stainless steel, and the target chemical composition of the final austenitic stainless steel is: C: 0.04%, Si: 0.85%, Mn: 5.5%, P: 0.023%, S: 0.015%, Cr: 22.0%, Ni: 12.7%, Mo: 2.3%, Nb: 0.2%, V: 0.3%, N: 0.4%; Fe balance. Melt the raw materials to obtain molten steel, and use the traditional die casting method to obtain ingots, and forge the ingots to obtain round tube embryos; S2. hot extruding the round tube blank at 1200°C to obtain a rough tube; S3. The rough pipe is subjected to six consecutive cold workings, with the deformation of a single cold working pass being 30%. The pipe is heat treated at 1070°C between the six cold workings to obtain an intermediate pipe; S4. The intermediate tube is cold worked with a deformation amount of 20% to obtain a finished tube. Finally, the finished tube is heat treated at 1080° C. to complete the preparation of the austenitic stainless steel seamless tube.

[0039] Embodiment 2: The difference between this embodiment and embodiment 1 is that, in this embodiment, the target chemical composition of the final austenitic stainless steel is: C: 0.04%, Si: 0.90%, Mn: 5.0%, P: 0.022%, S: 0.013%, Cr: 22.6%, Ni: 12.5%, Mo: 1.9%, Nb: 0.3%, V: 0.2%, N: 0.5%; Fe balance.

[0040] Embodiment 3: The difference between this embodiment and embodiment 1 is that, in this embodiment, the target chemical composition of the final austenitic stainless steel is: C: 0.05%, Si: 0.88%, Mn: 6.0%, P: 0.023%, S: 0.014%, Cr: 22.3%, Ni: 13.4%, Mo: 2.6%, Nb: 0.4%, V: 0.4%, N: 0.36%; Fe balance.

[0041] Embodiment 4: The difference between this embodiment and embodiment 1 is that, in this embodiment, the size specification of the austenitic stainless steel seamless pipe is φ15.0×1.6 mm.

[0042] Embodiment 5: The difference between this embodiment and embodiment 1 is that, in this embodiment, the size specification of the austenitic stainless steel seamless pipe is φ28.0×2.4 mm.

[0043] Comparative Example 1: The difference between this comparative example and Example 1 is that in this comparative example, the target chemical composition of the final austenitic stainless steel is: C: 0.04%, Si: 0.85%, Mn: 4.0%, P: 0.023%, S: 0.015%, Cr: 22.0%, Ni: 12.7%, Mo: 2.3%, Nb: 0.2%, V: 0.3%, N: 0.4%; Fe balance.

[0044] Comparative Example 2: The difference between this comparative example and Example 1 is that in this comparative example, the target chemical composition of the final austenitic stainless steel is: C: 0.04%, Si: 0.85%, Mn: 8.0%, P: 0.023%, S: 0.015%, Cr: 22.0%, Ni: 12.7%, Mo: 2.3%, Nb: 0.2%, V: 0.3%, N: 0.4%; Fe balance.

[0045] Comparative Example 3: The difference between this comparative example and Example 1 is that in this comparative example, the target chemical composition of the final austenitic stainless steel is: C: 0.04%, Si: 0.85%, Mn: 5.5%, P: 0.023%, S: 0.015%, Cr: 22.0%, Ni: 12.7%, Mo: 2.3%, Nb: 0.14%, V: 0.3%, N: 0.4%; Fe balance.

[0046] Comparative Example 4: The difference between this comparative example and Example 1 is that in this comparative example, the target chemical composition of the final austenitic stainless steel is: C: 0.04%, Si: 0.85%, Mn: 5.5%, P: 0.023%, S: 0.015%, Cr: 22.0%, Ni: 12.7%, Mo: 2.3%, Nb: 0.46%, V: 0.3%, N: 0.4%; Fe balance.

[0047] Comparative Example 5: The difference between this comparative example and Example 1 is that in this comparative example, the target chemical composition of the final austenitic stainless steel is: C: 0.04%, Si: 0.85%, Mn: 5.5%, P: 0.023%, S: 0.015%, Cr: 22.0%, Ni: 12.7%, Mo: 2.3%, Nb: 0.2%, V: 0.16%, N: 0.4%; Fe balance.

[0048] Comparative Example 6: The difference between this comparative example and Example 1 is that in this comparative example, the target chemical composition of the final austenitic stainless steel is: C: 0.04%, Si: 0.85%, Mn: 5.5%, P: 0.023%, S: 0.015%, Cr: 22.0%, Ni: 12.7%, Mo: 2.3%, Nb: 0.2%, V: 0.52%, N: 0.4%; Fe balance.

[0049] Comparative Example 7: The difference between this comparative example and Example 1 is that in this comparative example, the target chemical composition of the final austenitic stainless steel is: C: 0.04%, Si: 0.85%, Mn: 5.5%, P: 0.023%, S: 0.015%, Cr: 22.0%, Ni: 12.7%, Mo: 2.3%, Nb: 0.2%, V: 0.3%, N: 0.17%; Fe balance.

[0050] Comparative Example 8: The difference between this comparative example and Example 1 is that in this comparative example, the target chemical composition of the final austenitic stainless steel is: C: 0.04%, Si: 0.85%, Mn: 5.5%, P: 0.023%, S: 0.015%, Cr: 22.0%, Ni: 12.7%, Mo: 2.3%, Nb: 0.2%, V: 0.3%, N: 0.56%; Fe balance.

[0051] Comparative Example 9: The difference between this comparative example and Example 1 is that in this comparative example, the target chemical composition of the final austenitic stainless steel is: C: 0.04%, Si: 0.85%, Mn: 5.5%, P: 0.023%, S: 0.015%, Cr: 22.0%, Ni: 12.7%, Mo: 2.3%, Nb: 0.19%, V: 0.55%, N: 0.4%; Fe balance.

[0052] Comparative Example 10: The difference between this comparative example and Example 1 is that in this comparative example, the target chemical composition of the final austenitic stainless steel is: C: 0.04%, Si: 0.85%, Mn: 5.5%, P: 0.023%, S: 0.015%, Cr: 22.0%, Ni: 12.7%, Mo: 2.3%, Nb: 0.49%, V: 0.17%, N: 0.63%; Fe balance.

[0053] Performance testing: The grain size, room temperature tensile strength, room temperature yield strength, high temperature tensile strength at 650°C, high temperature yield strength at 650°C, low temperature tensile strength at -269°C, low temperature yield strength at -269°C, and low temperature impact properties (including impact absorption energy and LE) at -269°C of the austenitic stainless steel seamless pipes prepared in the above Examples 1 to 5 and Comparative Examples 1 to 10 were tested, and the test results are shown in Table 1.

[0054] Table 1 Performance test results At room temperature, the tensile strength and yield strength of austenitic stainless steel seamless pipes are required to reach 800 MPa and 400 MPa respectively to meet the use requirements; at 650°C, the tensile strength and yield strength of austenitic stainless steel seamless pipes are required to reach 500 MPa and 250 MPa respectively to meet the use requirements; at -269°C, the tensile strength and yield strength of austenitic stainless steel seamless pipes are required to reach 1600 MPa and 1200 MPa respectively, and the impact absorption energy reaches ≥80 J and LE reaches ≥0.53 mm to meet the use requirements.

[0055] Comparing the relevant performance test results of Examples 1 to 3, it can be found that when placed within the target chemical composition percentage range defined by the present invention, the three strengthening mechanisms of solid solution strengthening of N, precipitation strengthening of Nb and V carbonitrides, and fine graining can be coordinated with each other, so that austenitic stainless steel has good mechanical properties at room temperature and high and low temperature environments, and can meet the corresponding use requirements. At the same time, combined with Examples 4 to 5, it can be seen that the improved austenitic stainless steel in the present invention can retain the above-mentioned beneficial effects after being prepared into seamless pipes of different sizes, so it can be applied to corresponding instruments with different requirements for seamless pipe size specifications.

[0056] By comparing Comparative Examples 1 to 2 and 6 with Example 1, it can be found that both Comparative Examples 1 and 6 have relatively low Mn contents, but there are differences between the two. Comparative Example 1 mainly caused the problem that too high a content of N was difficult to dissolve into the matrix. Although part of the N was combined with Nb and V, the N content was still high, so structural defects such as pores were generated in the steel; while in Comparative Example 6, the V content was too high, which easily formed a block of V element segregation in the steel matrix, thereby causing a sharp drop in the mechanical properties of the steel. In Comparative Example 2, the excessively high Mn content resulted in N being dissolved into the Mn element and unable to form effective NbN and VN strengthening phases, which did not work on the fine grain strengthening and precipitation strengthening of the steel. Therefore, under high and low temperature use environments, the mechanical properties of the steel were difficult to meet the corresponding use requirements.

[0057] By comparing Comparative Examples 3 to 5 with Example 1, it can be found that the Nb content or V content of the steel in Comparative Examples 3 and 5 is too low, resulting in a decrease in the mechanical properties of the steel in some use environments. This is mainly due to the low content of Nb and V, the strengthening phases of NbN and VN with strengthening effects are only formed in small amounts or cannot be formed, there is no strengthening phase on the austenite grain boundary, and the pinning effect cannot be achieved. The strengthening mechanism of the steel finally manufactured is mainly solid solution strengthening, without fine grain strengthening and precipitation strengthening, resulting in the grain size of the steel unable to reach level 8 or finer, and ultimately causing the mechanical properties of the prepared steel to decrease in various use environments.

[0058] However, the Nb content of the steel in Comparative Example 4 is too high. During the smelting and manufacturing process of the material, a large amount of Nb element segregation is easily formed. The segregation of the Nb element has a great influence on the mechanical properties of the material, which is reflected in the decrease of the toughness of the steel, etc., especially in the low-temperature use environment, the mechanical properties of the steel are more significantly degraded.

[0059] By comparing Comparative Examples 7-8 with Example 1, it can be found that too little N element cannot form sufficient strengthening phase with the Nb content and V in the matrix, which leads to a significant reduction in the low-temperature impact performance of the steel, and too low N content will also cause the material to easily form high-temperature ferrite during the smelting process. Excessive N element leads to the formation of NbN and VN strengthening phases, but still has a relatively high retention of N and forms structural defects such as pores in the steel, resulting in a decrease in various mechanical properties of the steel.

[0060] In comparative examples 9-10, the ratio of Nb, V and N is completely destroyed, so that various effects on the properties of steel caused by excess or small amounts of various elements are mixed, thereby reducing the mechanical properties of the steel in various use environments and making it difficult to meet the corresponding use requirements.

[0061] Finally, it should be noted that the above implementation cases are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned implementation cases, those skilled in the art should understand that they can still modify the technical solutions recorded in the aforementioned implementation cases, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the implementation cases of the present invention.

Claims

1. An austenitic stainless steel, characterized in that: The chemical composition by weight percentage is: C≤0.06%, Si≤1.0%, P≤0.025%, S≤0.015%, Mn: 4.5%~7.0%, Cr: 21.5%~23.5%, Ni: 12.5%~14.5%, Mo: 1.5-3.0%, Nb: 0.2%~0.4%, V: 0.2%~0.4%, N: 0.2%~0.5%; the balance is Fe and other inevitable impurities.

2. An austenitic stainless steel seamless pipe, characterized in that: The stainless steel is prepared from the austenitic stainless steel described in claim 1.

3. The austenitic stainless steel seamless pipe according to claim 2, characterized in that: The average grain size of austenitic stainless steel seamless pipe is grade 8 and above.

4. The austenitic stainless steel seamless pipe according to claim 2, characterized in that: Austenitic stainless steel seamless pipe at 650 ℃, tensile strength R m ≥500MPa, yield strength R p0.2 ≥250MPa.

5. The austenitic stainless steel seamless pipe according to claim 2, characterized in that: Austenitic stainless steel seamless pipe at -269 ℃, tensile strength R m ≥1600MPa, yield strength R p0.2 ≥1200MPa.

6. The austenitic stainless steel seamless pipe according to claim 2, characterized in that: The austenitic stainless steel seamless pipe is prepared into an impact sample with a size of 10×10×55 mm. The impact sample has an impact absorption energy KV2≥80J and a lateral expansion value LE≥0.53mm under a low temperature environment of -269°C.

7. A method for manufacturing an austenitic stainless steel seamless pipe, characterized in that: The method for manufacturing the austenitic stainless steel seamless pipe according to any one of claims 2 to 6 comprises the following steps: S1. The various components of the austenitic stainless steel are smelted to obtain molten steel, and the molten steel is molded and forged to obtain a round tube embryo; S2. The round tube embryo is hot extruded to prepare a rough tube; S3. The rough pipe is subjected to several consecutive cold workings to prepare an intermediate pipe, wherein heat treatment of the pipe is provided between the several cold workings; S4. cold processing the intermediate tube to obtain a finished tube, and finally heat treating the finished tube.

8. The method for manufacturing austenitic stainless steel seamless pipe according to claim 7, characterized in that: In the S3, the deformation amount of the intermediate tube in a single cold working process is 20-80%; in the S4, the deformation amount of the finished tube in a cold working process is 15-40%.

9. The method for manufacturing an austenitic stainless steel seamless pipe according to claim 7, characterized in that: In S3 and S4, the temperature of the heat treatment is ≥ 1060°C.

10. Use of the austenitic stainless steel seamless pipe according to any one of claims 2 to 6 in a pressure vessel or a reactor.

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